SIMITRI STABLE IN STRIDE

Transcription

1 Copyright 2016 NGD. All rights reserved Neil Embleton, B.Sc., DVM and Veronica Barkowski, DVM Helivet Mobile Surgical Services, Sundre, AB, Canada July 2016 SIMITRI STABLE IN STRIDE 1. SIMITRI STABLE IN STRIDE IMPLANT A. Implant design B. Implant testing C. Indications and contraindications 2. PREOPERATIVE PLANNING A. Patient assessment and selection B. Preoperative radiographs C. Radiographic measurements D. Implant Selection and Positioning 3. SURGICAL PROCEDURE A. Patient preparation and surgical approach B. Femoral plate contouring and implantation C. Tibial plate contouring and implantation D. Common errors to avoid 4. POST-OPERATIVE CARE A. Immediate post-operative care B. Rehabilitation program APPENDIX STIFLE RADIOGRAPHS A. Guide to preoperative radiographs for AHT s

2 Copyright 2016 NGD. All rights reserved Neil Embleton, B.Sc., DVM and Veronica Barkowski, DVM Helivet Mobile Surgical Services, Sundre, AB, Canada July 2016 SIMITRI STABLE IN STRIDE IMPLANT The Simitri Stable in Stride implant was designed to stabilize the canine stifle. This module will cover the following information: Implant design Implant testing Implant Indications contraindications 1

3 A. Implant design The cranial cruciate ligament preforms two main functions: It limits cranial translation and internal rotation of the tibia relative to the femur. As the level of disease increases within the ligament, its ability to perform these functions diminishes. This leads to progressive stifle instability, the consequence of which is increasing lameness, progressive degenerative joint disease, loss of comfortable range of motion, decrease in affected limb thigh circumference and a compensatory increase in thigh circumference of the unaffected limb. Current surgical techniques affect stifle kinematics and or alter stifle geometry. The Simitri Stable in Stride implant is a three-part modular implant with surgical grade stainless steel femoral and tibial plates and an ultra high molecular weight polyethylene articular insert. The femoral plate has a ball and stem and interdigitates with the tibial plate via a travel channel. The femoral plate is currently available as 2.7 mm, 3.5 mm small and 3.5 mm standard. A 3.5 mm broad plate is in the design stages. Each plate size has a maximum patient body weight (Table 1-1). Tibial plates are currently available in 2.7 mm (10 mm offset) and 3.5 mm (10, 13 and 16 mm offset). The small and standard 3.5 femoral plates can be used with any of the 3.5 tibial plate offset sizes. Figure 1: Simitri Stable in Stride implant. A. Femoral plate. B. Tibial plate C. articular insert. Note: Each plate has three screw holes and two, 2 mm holding pin holes for temporary implantation. The screw holes are number # 1 to # 3, the hole closest to the joint is # mm plates accept 3.5 or 4.0 mm cortical locking screws. 2.7 mm plates only accept 2.7 mm screws. 2

4 Permanent implantation is achieved via three bicortically placed locking screws of appropriate size for patient (Table 1-1). The implant is positioned on the inside of the affected limb and remains completely extracapsular. Once implanted it provides immediate and continuous translational and rotational stability while minimally affecting stifle kinematics. B. Implant Testing The Simitri Stable in Stride implant has undergone biomechanical testing, 3D computer modelling and clinical trials. Biomechanical testing of the implant was conducted using and Instron 3343 at the New Jersey Institute of Technology. Static and dynamic biomechanical tests included: Range of motion flexion/extension and axial twist Tibial thrust Wear testing Results of biomechanical tests indicated that the implant would allow for functional range of motion (flexion, extension and axial twist) within the normal canine biomechanical ranges and provide the strength required to prevent tibial thrust in the canine patient. Tibial thrust was tested out to 1000 N with no failure of the EAI. Wear testing showed structural stability through 1,000,000 cycles at 250 N with loss of stability occurring at 791,373 cycles at 350 N. Based on an in silico comparison using a 3D computer model of a 33 kg Golden retriever, stifle joint biomechanics were improved in the EAI-managed stifle compared to the CrCLdeficient stifle joint and the EAI treated CrCL deficient stifle was predicted to return ligament loads and tibial kinematics closer to the state of the intact CrCL stifle than did the TPLO managed (Bertocci et al, Vet Surg April 2016). Cadavers were used in the early stages of design and through out the testing procedure to refine the design and surgical procedure prior to beginning clinical trials. The results of the first 66 implantations will be published in the August 2016 issue of Veterinary Surgery. 3

5 C. Indications and Contraindications The Simitri stable in Stride implant is indicated as a primary treatment in dogs with: partial or complete tears of the cranial cruciate ligament partial or complete tears of the caudal cruciate ligament partial or complete tears of both the cranial and caudal cruciate ligaments The implant can be used in patients with concurrent collateral ligament injuries or luxating patella. However, these injuries must undergo a primary repair prior to implantation of the Simitri Stable in Stride implant. The Simitri stable in Stride implant is contraindicated in cases: where stifle instability is associated with either infection or neoplasia. with excessive tibial torsion. that exceed the recommended patient body weight of the implant. 2.7 mm standard 3.5 mm small and standard 3.5 mm broad Maximum patient weight 12 kg (25 lb) 34 kg (75 lb) 55 kg (120 lb) Locking screw sizes 2.7 mm only 4.0 mm screws are always used in hole #1 patients > 30 kg - assuming sufficient bone size, use 4.0 mm screws in all screw holes patients < 30 kg mm can be used in holes #2 and #3 Table 1-1 Maximum patient body weight and locking screw sizes for different implant sizes, all screws are cortical locking screws. 4

6 Copyright 2016 NGD. All rights reserved Neil Embleton, B.Sc., DVM and Veronica Barkowski, DVM Helivet Mobile Surgical Services, Sundre, AB, Canada July 2016 SIMITRI STABLE IN STRIDE PREOPERATIVE PLANNING As with all procedures, proper patient selection is an important first step in a successful procedure. To understand preoperative planning for Simitri Stable in Stride we will explain: Patient assessment and selection Preoperative radiographs Radiographic measurements Implant selection and positioning 1

7 A. Patient Assessment and Selection Prior to surgery all patients must be assessed by both physical examination and stifle radiography. The following should be kept in mind when assessing a patient prior to surgery: 1) Patients must be below the maximum allowable weight for the size of implant chosen. (see Table 2-1) 2) Patients must be free of clinical signs consistent with infection. 3) Patients must be free of any significant dental disease. 4) Patients must not be on immunosuppressive medication to the extent that it could adversely affect the outcome of the surgical procedure. 5) Patients must be free of femoral and or tibial valgus or varus deformities to the extent that they could adversely affect the outcome of the surgical procedure. 6) Patients should be free of excessive tibial torsion. 7) Owners should be fully aware of all aspects of the procedure and be prepared to follow the post operative care handout to the letter. 8) Owners should be informed of necessity to maintain dental hygiene for their pet, prior to and in the years following the procedure. 9) Review indications and contraindications for this procedure in Section 1-C. 2.7 mm standard 3.5 mm standard 3.5 mm broad 12 kg (25 lb) 34 kg (75 lb) 55 kg (120 lb) Table 2-1: Maximum weight for each implant size 2

8 B. Preoperative Radiographs Two radiographic views centered on the injured stifle are required: 1. Extended lateral with condyles superimposed (Figure 2-1; It is critical that femoral condyles are superimposed) 2. Cranial caudal view with half of the femur and half of the tibia only included in view (Figure 2-2). Figure 2-1 This is an example of a correctly positioned diagnostic extended lateral stifle radiograph. Condyles are superimposed, the radiograph is collimated to include half of the femur and tibia and a marker of known dimensions (R marker) is included in the image and has been raised to the level of the joint (in this case with a stack of gauze squares). Figure 2-2 This is an example of a correctly positioned cranial caudal radiograph. The patella is centered over the femur, half of the femur and tibia are in view, the radiograph is centered over the stifle joint and the tail has been moved out of the way of the stifle joint. The calibration marker (R marker) has been raised to the level of the stifle joint with a stack of gauze squares. Note: A second cranial caudal view centered over the tibia shaft and including the distal femur (patella) and hock joint may be useful to assess for tibial torsion (Figure 2-3). The position of the calcaneus relative to the distal tibia serves as an indication of the degree of tibial torsion. Marked tibial torsion may cause significant internal rotation of the proximal tibia during flexion of the stifle. This can be extremely difficult to manage surgically and may interfere with the correct positioning and function of the Simitri Stable in Stride implant. As radiographs may fail to diagnose some cases of tibial torsion, the patient should always be assessed intraoperatively for excessive rotation 3

9 which is characterized by the tibial plate rotating more than is allowed by the flanges of the tibial insert (i.e. 10 degrees). This is intraoperative assessment is described in Module 3 Surgical Procedure. Figure 2-3 Cropped image of distal tibia with tibial torsion. Note that the calcaneus is not centered in this image but appears to be in a lateral position, this is due to torsion of the tibial shaft. C. Radiographic Measurements Measurements obtained from the preoperative radiographs are used to select the appropriate size of implant for your patient and to aid in positioning the implant during surgery. To obtain accurate measurements the calibration marker is used to adjust for the magnification of the radiographic image. As discussed above, a marker of known dimension (in mm) must be on every radiographic image (at the level of the stifle joint) and will be used to calibrate the software used to measure the radiograph or used to adjust the measurements obtained on the radiograph. Most commercially available DICOM viewer software have measuring tools that allow you to make measurements on digital radiographs. Ideally your measuring tool should be set to measure in millimeters to one decimal place. Depending on the software used it may be possible to set the scale of the measuring tool prior to making measurements of your patient s radiograph. This will be done by measuring the image of your calibration marker on the radiograph and then entering the actual measurement of the marker in mm into the program which will then correct for the magnification on all measurement subsequently made on that radiograph (Figure 2-4). It is important to recalibrate for every new image taken. If the software cannot be calibrated the measurements obtain can be adjusted to true to scale manually by multiplying the measurements by the magnification factor (actual measurement of marker/software measurement of marker). ImageJ is a program developed by the National Institute of Health, USA available at that allows true to scale measurements to be made on a variety of digital images including JPEG. This is also convenient for measurement of digital radiographic images from referring practices. For radiographic films, measurements can either be made with a ruler on the processed films and then manually adjusted for the magnification as described above or, a digital 4

10 photo of the film can be taken and software such as ImageJ can be used to measure the digital image of the film. Figure 2-4 This is an example of how the magnification is corrected using ImageJ software. A line has been drawn across the R marker (arrow) using the ImageJ measuring tool. The marker was previously measured with a ruler and found to be 20 mm in width. By entering the Known distance (found in the Set Scale feature under Analyze), the program will automatically provide actual true to scale measurements of any line subsequently drawn on this radiograph. Note: The scale must be reset for every radiograph measured. Once a method for obtaining true to scale measurements has been established the extended lateral radiograph can be used to obtain the necessary preoperative measurements described step by step in the following pages (Figures 2-5 to Figure 2-12). 5

11 STEP 1: Find A - width of femoral diaphysis A Figure 2-5 The scale of this image was set using the width of the R marker as previously described. A sagittal line is drawn across the femoral diaphysis proximal to the supracondylar tuberosity (between arrows). Measure this line and mark the midpoint. The length of this line is A. 6

12 STEP 2: Find Y axis X Y axis Figure 2-6 A second sagittal line is drawn distal to the supracondylar tuberosity and the midpoint is found. A longitudinal line is drawn bisecting the midpoints of both sagittal lines this represents the Y axis of the distal femur. 7

13 STEP 3: Find midpoint of Blumensaat s line Figure 2-7 Find the midpoint of Blumensaat s line (prominent radiopaque line that represents the top of the intercondylar fossa). Midpoint of Blumensaat s line 8

14 STEP 4: Find B Y axis B Figure 2-8 Draw a line from the midpoint of Blumensaat s line to the distal edge of the medial condyle (parallel to the Y axis). The length of this line is B. 9

15 STEP 5: Find C - width of medial condyle C (X axis) Figure 2-9 Draw a line the intersects the midpoint of Blumensaat s line that is perpendicular to the Y axis. This represents the X axis of the medial femoral condyle and the length of this line is C. 10

16 STEP 6: Find D D Figure 2-10 Measure the distance from the Y axis to the caudal edge of the medial condyle along C (between arrows). This is measurement D. These four measurements are used to select the appropriate size of femoral plate for your patient and to position the femoral plate during surgery. 11

17 Figure 2-11 This figure summarizes the measurements made on the preoperative extended lateral radiograph. A, B, C and D aid in selection of the appropriate size of implant and B and D aid in surgical positioning of the implant. 12

18 STEP 7: Find Patient Tibial Offset Patient offset Figure 2-12 Starting approximately 50 mm distal to the proximal end of the tibia (red arrow), draw a line parallel to the medial tibial cortex. This line continues proximally and will intersect the wider proximal tibia and medial femoral condyle. A second line is drawn parallel to the first, touching the medial edge of the medial femoral condyle at the location of the white arrow as shown. The distance measured between these two lines is the patient offset in mm and will be used to select the tibial plate offset size that best fits your patient. 13

19 D. Implant Selection and Positioning The measurements obtained from the preoperative radiographs are used to find the ideal femoral ball position for each patient. By determining this position, it is possible to choose the implant that will best fit your patient. There are four key points for determining which implant fits a patient best (Figure 2-13). 1. The patient cannot exceed the maximum weight for the implant. 2. The femoral diaphysis width A must be large enough to fit the screw segment. 3. The femoral condyle width C must be large enough to fit the ball and stem segment 4. With the femoral ball in the ideal position over the medial femoral condyle, the screw segment of the implant must fit within the confines of the femoral diaphysis. The first 3 determine whether your patient is likely to fit a 2.7 mm or a 3.5 mm femoral plate (Table 2-2). The fourth ultimately determines which component best fits your patient and how the screw segment will be positioned relative to the Y axis of the femoral diaphysis. Figure 2-13 This diagram demonstrates the relationship between the patient measurements and the dimensions of the implants. D B is related to the distance from the center of the femoral ball to the center of the screw holes. The dimensions of each implant are different and are given in the Table below: Femoral Plate dimensions 2.7 mm 3.5 mm (with 10 mm tibial plate) 3.5 mm (with 13 and 16 mm tibial plates) 3.5 mm (broad) A 9 mm 10 mm 10 mm TBA B 6 mm 7.5 mm 7.5 mm TBA C 23 mm 25 mm 30 mm TBA D 18.5 mm 21.5 mm 26.5 mm TBA D minus B 12.5 mm 14 mm 19 mm TBA Weight 12 kg 34 kg 34 kg 55 kg Table 2-2 Femoral plate dimensions shown as they relate to patient measurements. The minimum patient measurements for A, B and C are shown and the patient must not exceed maximum weight. D B is related to ideal ball position and is explained below. 14

20 Ideal Ball Position The femoral ball is ideally positioned when it is equidistant from the caudal and distal edges of the medial femoral condyle on the X axis. Therefore, the ideal ball position (mid point of ball) is B mm from the caudal edge of the condyle (Figure 2-14). Measurement B will be used during surgery to find the ideal ball position over the medial collateral ligament. Y axis Figure 2-14 The ideal ball position is represented by the red circle and is B mm from the caudal and distal edges of the medial femoral condyle. D B D B represents the distance form the center of the femoral ball to the Y axis and is used to determine which femoral plate size best fits your patient. B will be used during surgery to find the ideal ball location on the patient (Figure 2-15). The distance between the femoral ball (mid point) and the center of the screw holes is unique to each size of femoral plate (Table 2-2). For a femoral plate to fit your patient the screw segment must fit within the confines of the femoral diaphysis with the ball in its ideal position over the medial femoral condyle. The following formula will determine the distance between the center of the ideal ball position and the center of the femoral diaphysis (Y-axis) for your patient. D B = distance from center of ball to Y axis The femoral plate that most closely matches your patient s D - B will fit your patient best (Table 2-2). It may be necessary to move the screw segment (screw holes) cranial or caudal of the Y axis if D B does not exactly match one of the plate sizes. The amount of movement can be determined by subtracting D B from the plate dimension shown in Table 2-2. The amount of cranial or caudal movement available is limited by the width of the femoral diaphysis as the entire screw segment must remain with the confines of the femoral diaphysis to ensure good screw placement therefore patients with smaller 15

21 femoral diaphysis widths have less room for adjustment. The room for adjustment is roughly A width of screw segment of femoral plate. During surgery a stay suture is placed over the medial collateral ligament (MCL) to aid in positioning the distal edge of the femoral plate on the patient. A 22 gauge hypodermic needle is used to locate the proximal tibia on the cranial border of the medial collateral ligament. Using a sterile caliper or ruler a distance of B 6 mm is measured proximal to the needle and a stay suture is placed centered over the MCL. Figure 2-15 A stay suture is used to marked the edge of the femoral plate distal to the femoral ball. The hypodermic needle marks the proximal tibia, the distance from the needle to the stay suture is B 6 mm. needle Stay suture The femoral ball is 7.5 mm from the edge of the plate however we need to add back 1.5 mm to account for the articular cartilage and joint space between the tibia and the distal edge of the medial femoral condyle as seen on the radiograph. MCL 16

22 Ideal Tibial Plate Offset The two precontoured bends in the tibial plate create the offset between the articulating portion of the tibial plate and the screw segment (Figure 2-16). These bends allow the tibial plate to engage the medial side of the femoral plate at the articulation while closely engaging the tibial diaphysis through the screw segment. Tibial plates are offered in 10 mm, 13 mm and 16 mm offsets for 3.5 mm plates and 10 mm offsets for 2.7 mm plates. Measurements obtained from the cranial caudal stifle radiograph can be used with the following formula to determine the best tibial plate offset size for your patient. To be accurate the marker used to calibrate the scale must be at the level of the stifle joint above the plate. To choose the tibial plate size that best fits your patient use the following formula (see Figure 2-16): Patient offset (mm) + 7 mm = tibial plate offset A 7 mm Femoral condyle B Figure 2-16 On the left are two tibial plates with different offsets. A is the articulating segment of the tibial plate, shown with the articular insert removed and B is the screw segment. The offset of each plate is the distance between the two arrows. On the right is the expanded view of articulation of an implant demonstrating that the 7 mm accounts for the thickness of (from left to right) the soft tissues, the femoral plate and the articular insert flange which separate the medial side of the femoral condyle and the inside of the articulating segment of the tibial plate. 17

23 Choose the tibial plate offset size that best fits your patient with minimal contouring. It is important to note that 3.5 mm tibial plates come in 10, 13 and 16 mm offsets and that these will fit both the small and large sizes of 3.5 mm femoral plates (not the broad), therefore it is possible to choose both the best fitting femoral and tibial component for your patient. It is also possible to contour both the plates to fit your patient however great care must be taken to not damage the articular insert or the screw holes (eg. use locking screw plugs prior to any contouring). Selecting Femoral and Tibial Plate Size The measurements made on the preoperative radiographs are used to select the best fitting implant for your patient (Table 2-2). Example: For the radiographs shown in the previous section the patient measurements were as follows: Based on weight, this patient will need a 3.5 mm implant. Weight 26.7 kg Femoral Plate: A = 13.4 mm Based on C it is likely that the small 3.5 femoral plate (packaged with B = 7.6 mm the 10 mm tibial plate) will fit this patient. C = 25.7 mm D = 18.4 mm D B = 10.8 mm Offset = 3.1 mm + 7 =10.1 mm Based on A = 13.4 mm 10 mm (width of screw segment) there is roughly 3.4 mm of movement from the Y axis available on the diaphysis. By subtracting D B from the plate sizes we can confirm which 3.5 plate is the best fit and determine the location of the screw holes. 19 mm 10.8 mm = 8.2 mm (screw holes will not fit within confines of femoral diaphysis) Tibial Plate: 14 mm 10.8 mm = 3.2 mm (screw holes of small plate will be positioned 3.2 mm cranial of Y axis) = BEST FIT 3.5 mm tibial plates are available in 10, 13 and 16 mm offsets. Based on tibial offset of 10.1 mm the best fit for this patient is the 10 mm offset tibial plate. It is important to note that small 3.5 mm femoral plates come prepackaged with the 10 mm tibial plate, and the large 3.5 mm plates come prepackaged with the 13 or 16 mm tibial plates, however all of these femoral and tibial plates are interchangeable. Therefore, it is possible to choose both the best fitting femoral and tibial component for your patient however it may be necessary to open more than one package. 18

24 Copyright 2016 NGD. All rights reserved Neil Embleton, B.Sc., DVM and Veronica Barkowski, DVM Helivet Mobile Surgical Services, Sundre, AB, Canada July 2016 SIMITRI STABLE IN STRIDE SURGICAL PROCEDURE The following components of the surgical procedure for successful implantation of the Simitri Stable in Stride implant will be described: Patient preparation and surgical approach Femoral plate contouring and implantation Tibial plate contouring and implantation Common errors to avoid 1

25 A. Patient Preparation and Surgical Approach Figure 3-1 The surgical limb is prepped from the greater trochanter of the femur to the distal tibia using standard aseptic technique. The patient is positioned in dorsal recumbency and the limb is draped in standard fashion. Figure 3-2 A cm curvilinear incision is made on the medial aspect of the surgical limb. The incision is centered over the stifle and extends equidistant both proximally and distally. The joint is explored via arthroscopy (prior to skin incision) or via a minimal medial parapatellar arthrotomy. Damaged portions of menisci and cruciate ligaments are removed. Meniscal release is NOT required nor indicated under any circumstance. The arthrotomy is closed as per surgeon s preference. Figure 3-3 An incision is made through the conjoined tendons of the sartorius, gracilis and semitendinosus to expose the proximal tibia and medial collateral ligament. The incision originates at the level of the proximal tibia, cranial to the insertion of the sartorius (arrow) and extends distally approximately 6 cm. The incised tissues are reflected caudally, exposing the proximal tibia and medial collateral ligament. 2

26 Figure 3-4 The fascial incision is extended 6 cm proximally (to arrow) between the cranial and caudal bellies of the sartorius muscle, exposing the vastus medialis musculature and underlying descending genicular artery and medial articular nerve. Bluntly undermining the sartorius musculature with a finger prior to extending the incision proximally can aid in protecting the underlying artery and nerve. Figure 3-5 Expose the distal femur starting from the proximal extent of the fascial incision and extending 40 mm distally by bluntly dissecting between the vastus medialis and pectineus tendon. The screw segment of the femoral plate will later be applied to this area. Figure 3-6 The vastus musculature is reflected cranially with an Army retractor exposing the femur. The medial collateral ligament is also visible (blue arrow). The tip of the forceps is pointing to the genicular artery and medial articular nerve. Figure 3-7 A 15 mm wide periarticular soft tissue tunnel extending from the exposed femur to the level of the distal patella is bluntly made using Mayo scissor. The tunnel is parallel to the long axis of the femur deep to the periarticular tissues, but superficial to the joint capsule. By placing the femoral plate into this tunnel the femoral component can remain in close contact with the femoral diaphysis without compressing the genicular artery and medial articular nerve. 3

27 B. Femoral plate positioning Stay suture Figure 3-8 As previously described in the Preoperative Planning Module a stay suture will be used to aid in positioning of the femoral plate in the proximal distal direction over the MCL. The measurement used for placement of the suture is B 6 mm. B was measured on the preoperative extended lateral radiograph. needle MC Figure 3-9 With the stifle in full extension, a 22 gauge needle is walked off the proximal tibia at the level of the cranial edge of the medial collateral ligament. This marks the starting point for measuring stay suture placement. Figure 3-10 Calipers, or a ruler are used to measure B 6 mm cranial to this point (see Preoperative Planning Module). An absorbable stay suture is then placed centered over the medial collateral ligament (MCL). Note: by using the cranial edge of the MCL there is less chance of iatrogenic damage to the medial meniscus.. 4

28 Figure 3-11 This picture shows the stay suture (blue arrow) centered over the MCL (white arrow). The femoral component will be inserted through the soft tissue tunnel (dashed line) in the direction of the black arrow. Figure 3-12 With the limb in full extension, the screw segment of the femoral plate is inserted into position through the soft tissue tunnel. The distal edge of the femoral plate is positioned at the level of the stay suture with the femoral ball is centered over the medial collateral ligament. The screw segment of the femoral component is positioned as parallel as possible to the Y axis of the femur. At this point you can assess the plate to determine if any additional contouring of the plate is needed. Femoral Plate Contouring The femoral component comes precontoured however, adjustments may be required to account for variations in medial femoral diaphyseal curvature as the position of the screw segment changes relative the the Y axis of the femur. The goal of contouring is to ensure the stem of the femoral ball is perpendicular to the sagittal plane of the femur/stifle (Figure 3-14 and 3-15) and parallel to the transverse plane. In other words, the stem should project medially in relation to the stifle joint without deviating cranially, caudally, distally or proximally. There are two adjustments that may be required to correct any deviation to the stem; a bend and/or a twist. Before any contouring, always engage locking screw plugs to prevent damage to the screw holes. 5

29 Precontoured Distal holding pin segment Figure 3-13 The precontoured area of the femoral plate is indicated above as well as the distal holding pin segment. Manual adjustments are made to the distal holding pin segment. A. Bend: With the femoral plate held in position as shown in Figure 3-14, observe the orientation of the stem of the femoral ball to the sagittal plane of the femur/stifle. Ideally the femoral stem should be projecting medially without proximal or distal deflection, if the ball deflects, it can be corrected with a 1-2 mm bend in the distal holding pin segment (Figures 3-15). The bend is concave for distal deflection (most common) and convex for proximal deflection (rare). Use locking screw plugs to prevent damage to screw holes. Avoid over contouring of the plate as this will cause the ball and stem segment to elevate away from the femur; this will increase the offset required for the tibial component to engage correctly. Figure 3-14 The femoral stem should be perpendicular to the sagittal plane of the femur as is seen here. Do not over contour the plate. SAGITTAL TRANSVERSE 6

30 Location of bend Figure 3-15 location of bend through distal holding pin segment of femoral plate B. Twist: As described in the Preoperative Planning Module, the screw segment of the femoral plate may need to be positioned cranial or caudal to the Y axis of the femur in order to position the femoral ball in the ideal location. The femoral plate is precontoured (twisted through distal holding pin segment) to cause the femoral stem to project medially from the stifle joint when the screw segment is centered on the Y axis (Figure 3-16). Due to the curvature of the femoral diaphysis, moving the femoral plate cranially or caudally will cause the orientation of the stem of the femoral ball to also change (Figure 3-16). The goal of the twist is to allow the screw segment to match the curvature of the diaphysis, while allowing the femoral stem to project medially (i.e. not cranially or caudally). Therefore; if the screw segment is positioned cranial to the Y axis, the screw segment must be twisted away from the ball and stem segment (decrease precontoured twist); if the position is caudal to the Y axis, then the twist is toward the ball and stem segment (increase precontoured twist)(figure 3-17 and 3-18). Locking screw plugs must be used in the screw holes to prevent damage during twisting. The use of a locking drill guide in the last hole may aid in visualizing the degree of twist needed (Figure 3-17). 7

31 cranial Figure 3-16 If the femoral plate is moved off the center of the Y axis, the femoral ball will be deflected cranially or caudally in the direction of the arrow as show. caudal Figure 3-17 The location of the twist is indicated by the red bracket. Locking screw plugs will be engaged into holes 1 and 2 prior to twisting. The direction of the twist depends on location of screw segment on femur. Twisting the drill guide away from ball decreases the precontoured twist (cranial screw segment position); twisting toward the ball decreases the twist (caudal position). Figure 3-18 Stainless steel crescent wrenches (or bending irons) are used to accurately twist the femoral component without introducing any additional bend. 8

32 Figure 3-19 After twisting and bending the femoral plate (if required), it is reinserted into the tunnel and aligned with the stay suture with the limb in full extension. Reassess the femoral ball and stem and if you are satisfied with the orientation (projecting medially), the proximal 5/64 holding pin is implanted while maintaining the plate position and compressing the femoral plate to the femur. Fine Tuning Femoral Plate Position During flexion and extension, the stay suture will remain fixed in position relative to the tibia and therefore the femoral plate will move in relation to the suture. If the stay suture travels along edge of femoral plate, the ball is in an isometric position. If the stay suture moves away from the femoral plate during flexion the femoral component is cranial to its ideal position. If the stay suture moves under the femoral component during flexion the femoral component is caudal to its ideal position. Adjustment should be made to the cranial caudal position of the femoral plate and the ball position reassessed. When the ball is as isometric as possible, the distal femoral holding pin is engaged. Perfect isometric placement is not critical as the travel channel within the articular insert allows for up to 8 mm of ball movement. Note: The femoral ball should remain within the cranial caudal limits of the MCL. If you cannot achieve a relatively isometric position over the MCL then you must reassess and adjust the proximal distal position of the femoral plate. Figure 3-20 The stay suture is on the edge of the femoral plate in flexion (and extension), therefore the femoral plate is in an isometric position. 9

33 Figure 3-21 Screws are inserted into holes 1, 2 and 3. Screw hole #1 is closest to the joint. Locking screw drill guides ensure centered placement of the screws. Screw hole # 1 is implanted first. Initially a 3.5 mm bicortically placed non locking screw is used to compress the plate to the femur. Screw holes #2 and 3 are then engaged using 3.5 or 4.0 locking screws. Finally, the cortical screw in hole #1 is exchanged for a 4.0 cortical locking screw. Note: Ensure all screws are bicortical. For 3.5 mm plates, a 4.0 cortical locking screw must be used in screw hole # 1 for all patients and if bone size will allow, in all screw holes in cases larger than 30 kg. (2.7 mm plates take 2.7 mm locking screws.) C. Tibial plate contouring and implantation Figure 3-22 With the stifle in full extension and in a neutral position (i.e. not rotated) engage the tibial insert over the femoral ball and position the plate such that the ball is located in the middle of the travel channel. The screw segment should be in close contact with the medial cortex of the tibia and aligned with the long axis of the tibia. Approximately 3-4 mm cranial to the caudal edge of the tibia. Do not engage holding pin until you confirm proximal distal position and tibial offset of tibial plate as is described below: 10

34 Figure 3-23 While holding the screw segment in the position described in Figure 3-22, place stifle through a full range of motion and observe the movement of the ball within the travel channel. Adjust the proximal distal position as required to ensure that the ball travel does not exceed the limits of the travel, i.e. it should not touch the end of the channel nor should the ball enter the key hole. Femoral condyle Figure 3-24 Although the screw segment should have good contact with the medial tibial cortex, it is more important that the tibial insert should engage the femoral ball without compressing towards the femoral plate or pulling away from the femoral plate. In addition, the flanges on all sides of the tibial insert should remain in contact with (parallel to) the corresponding surface of the ball and stem segment of the femoral plate throughout flexion and extension. There should not be significant changes in this contact (distance between red arrows is the same and constant) except to allow for a normal degree of tibial rotation as is allowed by the flanges of the insert (10 degrees) and minimal varus and valgus movement. Tibial torsion may increase internal rotation beyond the limits of the implant therefore it is vital to ensure that this rotation is not exceeded. Figure 3-25 Tibial plates are available in several offsets to accommodate the difference between the width of the femoral condyles and the tibial diaphysis. Measurements obtained on the preoperative cranial caudal radiograph will aid in choosing the tibial plate offset that will best fit your patient (see Preoperative Planning Module). Fine tuning of the tibial offset may be necessary during surgery to account for individual variation in patients. 11

35 Fine Tuning Tibial Offset As described in Figure 3-24, the contact between the tibial insert and femoral plate is used to assess whether the tibial offset is correct for your patient. Incorrect contact between the plates at the articulation can lead to insert failure and/or disarticulation. If the tibial plate compresses towards the femoral plate or the top of the tibial plate angles away from the femoral plate the offset needs to be increased. If the tibial plate pulls away from the femoral plate or the top of the tibial plate angles towards the femoral plate the offset needs to be decreased. It is always best to use the precontoured tibial plate offset that best fits your patient. If your patient falls in between plate sizes, choose the smaller plate and either implant the screw segment so it does not compress the tibial cortex (locking screws permit the plate to be elevated from the bone) or bend the plate to increase the offset. It is generally easier to increase the offset than to decrease it and small changes to tibial offset can be made with plate benders however caution must be used to not damage the UHMWPE insert or the screw holes. Use screw plugs and a small bending tool. Excessive bending of the tibial plate may weaken the plate and should be avoided. Figure 3-26 Once the proximal distal position and tibial offset are corrected as described above, align the screw segment as described in Figure 3-22 and insert the distal holding pin. Reconfirm position and reduce the subluxation of the tibia prior to engaging the proximal holding pin. Avoid internal or external rotation of the tibia. Reconfirm ball travel and parallel contact between tibial insert and femoral plate before implanting screws. Figure 3-27 Locking screw drill guides are employed to ensure centered placement of all screws. Screws are inserted as per the femoral component starting with screw hole #1 (closest to joint). Initially a 3.5 mm cortical screw (or 2.7 mm screws for 2.7 mm plates) is used to very gently compress the screw segment to the tibia without causing excess compression at the articulation. Screw holes #2 and 3 are then engaged. Finally, the cortical screw in hole #1 is exchanged for a 4.0 cortical locking screw. Note: Use caution when compressing the tibial plate to not over compress. Excessive compression could lead to misalignment of the tibia and/or insert failure. 12

36 Figure 3-28 Ensure the articulation is as parallel as possible and moves as freely as possible after each screw is placed. Do not allow the engagement of the screws to alter the orientation of the articulation. Prior to closure reconfirm correct position by placing stifle through full extension and flexion. There should be no interference with full range of motion. Note: Ensure all screws are bicortical. A 4.0 cortical locking screw must be used in screw hole # 1 for all patients and if bone size will allow, in all screw holes in cases larger than 30 kg. Figure 3-29 Routine closure of the soft tissues is performed in two layers using a simple continuous pattern of an appropriate absorbable monofilament suture. The first layer is the conjoined tendons of the sartorius, gracilis and semitendinosus. The second is the subcutaneous layer. The skin is closed with surgical staples or as per surgeon s preference. Figure 3-30 Postoperative lateral and cranial caudal radiographs are taken to confirm correct implant position and bicortical screw engagement. 13

37 D. Common errors to avoid Correct positioning of the Simitri Stable in Stride implants is dependent on following the recommendations in the Preoperative Planning Module and Surgical Technique Module. Common errors that can lead to implant positioning errors include: 1. Pre-operative planning errors: Inappropriate patient selection (i.e. body weight exceeds maximum for implant selected) Incorrect (or lack of) measurement of presurgical radiographs o Condyles not superimposed o Measuring lateral instead of medial femoral condyle o Failure to account for radiographic magnification Failure to identify tibial torsion Failure to identify concurrent collateral ligament insufficiency or concurrent luxating patella 2. Surgical errors: Incision over distal femur does not extend far enough proximally to allow access to proximal screw hole (hole #3) of the femoral plate Improper placement of stay suture. o Failure to place limb in full extension while measuring and placing stay suture o Failure to measure accurately (use calipers or ruler) o Incorrect measurements obtained preoperatively Femoral component implantation is too proximal or distal (measuring error) Femoral component too caudal or cranial (femoral ball should not be cranial or caudal of the MCL) Inappropriate (over/under) contouring of the femoral and tibial plates. Inappropriate positioning of the tibial component. Failure to reduce subluxated tibia. Failure to repair concurrent collateral ligament injuries prior to implantation Failure to repair concurrent luxating patella prior to implantation Articulation not parallel during implantation (insert should be in contact with femoral plate) Femoral ball travel exceeds limits of travel channel Implanting screws before ensuring plates are in the correct position. Failure to use 4.0 mm screw in first screw hole of all patients (3.5 mm plates) Failure to use 4.0 mm screws in all screw holes of patients >30 kg (assuming bone is wide enough to accept a 4.0 mm screw) Failure to recognize and react to tibial torsion - be extremely cautious of cases with significant tibial torsion. Excessive tibial torsion can lead to significant internal tibial 14

38 rotation of the proximal tibia. Excessive tibial torsion can overwhelm the implant and this may not be evident until the implantation. 15

39 Copyright 2016 NGD. All rights reserved Neil Embleton, B.Sc., DVM and Veronica Barkowski, DVM Helivet Mobile Surgical Services, Sundre, AB, Canada July 2016 SIMITRI STABLE IN STRIDE POST-OPERATIVE CARE As with all orthopedic procedures, post-operative care and rehabilitation are important for patient comfort and return to function. Post-operative care after Simitri Stable in Stride surgery includes: Immediate post-operative care Rehabilitation program 1

40 A. Immediate Post-operative care Post operative care of the Simitri Stable in Stride patient is similar to the care provided after other cranial cruciate ligament procedures and should include: Antibiotics Analgesics (if required) and anti-inflammatories Light bandage for 24 hours (bandage from toes to above incision) Icing to begin immediately post-operative to be repeated TID while in clinic Elizabethan collar days Belly band when walking in case of fall (should not be used for support) In general patients can be discharged the day after surgery with written home care/rehabilitation instructions. Professional animal rehabilitation can also be included into the program. B. Home care/rehabilitation After implantation of the Simitri Stable in Stride implant the stifle is immediately stable and most dogs will be weight bearing at the walk within 24 hours. Rehabilitation of the muscles of the affected limb can start immediately bearing in mind the need to allow the soft tissues to heal. Owner s should be provided with written instructions for home care and rehabilitation program and informed that it takes approximately four months for dogs to fully recover and that their pet cannot be allowed any uncontrolled activity during this healing period. The follow should be recommended: Kenneling when unsupervised during first 2 months Leash control for 4 months Prevention of weight gain (or supervised weight loss program if dog is obese) Begin rehabilitation exercises the day after surgery and gradually increase in frequency and intensity Discontinue exercises and contact veterinarian if there is sudden or continuous pain Mild intermittent lameness may occur during healing however any sudden increase in lameness or non-weight bearing should be investigated by a veterinarian The following is the current at home rehabilitation program and recheck schedule provided to our clients after Simitri Stable in Stride surgery, patient reassessment is recommended at 4, 8, 12 and 16 weeks prior to progressing to the next level of rehabilitation. The following can be adapted as per surgeon and rehabilitation therapist s preferences: 2

41 Day 1-7 (Week 1) Rehabilitation Program: Weeks 1 and 2 The day your pet arrives home is a day off from rehabilitation. Your pet is permitted outside for a 5-10 minute, completely controlled leash walk as needed for relief, allowed food, water and to sleep. Ice the surgical leg (see description) as directed. Treat the following day as day 1 of the rehabilitation program. Bruising and swelling of the lower leg is normal and expected. Swelling will be at its maximum four days after the surgery and then begin to subside. Massage, passive motion exercises (10 repetitions) and surgical leg icing (15-20 minutes) are done two to three times daily (see description) Hip extension / flexion exercises (10 repetitions) are done two to three times daily (see description). Your pet will generally begin to bear weight on the surgical leg one to two days after surgery minute, slow, completely leash controlled walks, with good footing, on level ground, are encouraged up to three to four times daily for elimination (see description). Going slowly will encourage your pet to bear weight on the operated limb. Your pet can do stairs and cross slippery surfaces under control with belly band support. (see description) When unsupervised, your pet must wear the Elizabethan collar until suture/staple removal. When unsupervised your pet must be confined to a suitable kennel, or a small room. (see description) Give all medications as directed. Day 7 14 (Week 2) Apply a heat pack (see description) to the outside side of the knee joint (see description) prior to muscle massage and passive motion exercises. Continue all passive motion exercises as described for Day 1 to 7. Increase to 15 repetitions minute, slow, completely controlled leash walks, with good footing, on level ground is encouraged three to six times daily for elimination (see description). Your pet can navigate stairs under leash control without belly band support; however continue to use the belly band when crossing slippery surfaces. When unsupervised, your pet must wear the Elizabethan collar until suture/staple removal. Ice packs can be used on the surgical leg after exercise sessions When unsupervised your pet must be confined to a suitable kennel, or a small room. (see description) Give anti-inflammatory medications (NSAID s and nutraceuticals) as directed. Skin staples can generally be removed between days after surgery. Underwater treadmill exercises can begin after staple removal. 3

42 Rehabilitation Program: Weeks 3 to 8 Weeks 3 4 Your pet no longer needs to be kenneled when unsupervised but must still be confined to an enclosed area that has good footing and prevents uncontrolled exercise or vigorous play with other pets. Belly band support is no longer required. Heat, massage, passive motion exercises and icing can be reduced to twice daily. Controlled leash walks on level ground with good footing can increase to minutes three to six times daily (see description). Hip extension exercises (15 repetitions are performed twice daily). Swimming, or water walking exercises can begin (see description) Sit to stand exercises should begin on the 14th. day after surgery (see description) Continue giving anti-inflammatory medications (NSAID s and nutraceuticals) as directed. Weeks 4 8 A four week postoperative assessment is needed to assess your pet s progress before progressing to the next level of rehabilitation. Hip extension / flexion exercises (15 repetitions are performed twice daily). Swimming, or water walking exercises can continue (see description) Unlimited leash controlled walks of 30 minutes or more, with good footing, on level ground are permitted. At this time another dog can be brought along for company. (see controlled walks description) Completely controlled leash walks on hills can begin (see description). Ten sit to stand exercises daily (see description). Heat, massage, passive motion, hip extension exercises and icing can be decreased to twice per day. When unsupervised continue to confine your pet to a small enclosed area (see description) Continue giving anti-inflammatory medications (NSAID) as directed. Remember hip flexor injuries can occur at any time. They are most common 4-12 weeks after surgery. They coincide with your pet s increase in activity. Clinically your pet will hold its leg up quite high. If you suspect there is an issue, contact your veterinarian for advice. 4

43 Rehabilitation Program: Weeks 8-16 Week 8-12 An eight week postoperative assessment is needed to assess your pet s progress before proceeding to the next level of rehabilitation. Continue to monitor your pets comfort with the frequency and intensity of exercise. Slowly increase frequency and duration of completely controlled leash walks on both level ground and hills. Always ensure good footing. Hip extension / flexion exercises Swimming, or water walking exercises can continue (see description) Ten sit to stand exercises daily (see description). Passive motion exercises, heat and ice can be discontinued. Decrease the dosage of NSAID s and nutraceuticals as directed by your veterinarian. Should your pet experience any pain or discomfort with this increase in exercise, discontinue the exercise and contact your veterinarian as soon as practical Week A twelve week postoperative assessment is needed. A thorough discussion of long term NSAID usage and the program to return to full function over the next month will be covered. Decrease the dosage of NSAID s to the 10 kilogram dose. A combination of low dose NSAID s and nutraceuticals can be extremely helpful in limiting the progression of degenerative joint disease. Hip extension / flexion exercises (15 repetitions) can be decreased to once daily. Swimming, or water walking exercises can continue (see description) Supervised controlled off leash activity in an enclosed space can be initiated (see description). This activity will increase in duration and intensity over the next 1-2 months. A final sixteen week postoperative assessment is needed to discuss long term NSAID usage and the time frame for return to full function. If you have any concerns at all about your pet s recovery. Please do not hesitate to contact your veterinarian as soon as practical. 5

44 Rehabilitation Descriptions: Kennel rest/confinement: For the first two months after surgery, your pet must be confined to a suitably sized kennel when your pet is unsupervised. That means anytime you are unable to completely control your pet s activity (i.e. sleeping, eating, working, using the washroom, or when away from the home). The kennel must be large enough for your pet to stand up turn around and lie down without significantly touching the sides. If your pet has an aversion to being in a kennel, or is simply too large, please discuss this with your veterinarian so a suitable and safe alternative can be arranged. After two months your pet can be confined to an enclosed space such as a small room, with good footing, no stairs and no other pets. If you are unsure of the suitability of the space please discuss this with your veterinarian. Belly Band support: A belly band is a sling that is placed in front of the back legs and hangs 1-2 inches (2-5 cm.) below the level of the belly. The belly band should normally not touch your pet s belly. It is only to be used as a method of supporting your dog s body weight in the event of a fall. This is especially important when ascending or descending stairs and when walking across slippery surfaces. The belly band can be as simple as a thin towel. Commercial support products are available. It is generally only needed for the first week after surgery. Muscle massage: Gently, but firmly massage the muscles of the entire surgical leg for 5-10 minutes. Begin at the toes of the foot and move up the leg, be sure to include the muscles of the hip and lower back. This is done before the passive motion exercises. It helps to warm up the muscles and most dogs generally love it. Remember the muscles and joints of our legs are the same as theirs. However, if you are unsure where these muscles are or how to do the massage properly, do not hesitate to ask for assistance and instructions. Take your time and don t be afraid, you cannot cause any damage. Until the surgical staples are removed, stay away from the incision. Passive motion: Passive motion exercises should be done after the muscle massage. These exercises consist of the gentle flexing and extending of all the joints of the surgical leg. These exercises help increase the range of motion of each joint. Begin at the toes of the foot and move up the leg to include the ankle, knee and especially the hip. The muscles of the hip always tighten secondary to knee injuries. As you work on each joint, extend and flex the joint as far as possible, with your pet remaining comfortable. If possible, as you reach full extension and flexion, hold the joint in position for 3-5 seconds and release. Go very slowly, be gentle but firm, and as you progress don t be afraid to ask for just a little more. Icing process: This is particularly important for the first 7 days after the surgery. An ice pack, or a frozen bag of peas placed in a pillow case can be applied directly to and wrapped around the outside of the knee joint. Keep the ice pack away from the incision line until the sutures/staples are removed. If your pet will allow, ice packs should be left in place for minutes. The icing process should be done two to three times a day and should always be done after the passive motion exercises. It dramatically helps control inflammation and swelling. 6

45 Rehabilitation Descriptions: Heat pack: A heat pack is applied to the outside of the affected knee joint and to the hip joint for 10 minutes prior to the muscle massage and passive motion exercises. For the hip joint, the heat starts on the second day after surgery. For the knee joint, the heat starts on the eight day after surgery. This warms up the area, increases blood flow and makes the muscles and soft tissues more pliable. There are commercial products available such as wheat bags and reusable gel packs. Be very cautious with this process to prevent burns. Make sure the pack is warm and not too hot (depending on the product you may have to wrap the heat pack in a towel before applying). Check it against your own skin; if it is too hot for you, then it is too hot for your pet. Never leave a pet unattended with a heat pack in place. Electric heat pads are generally too hot for pets. Hip extension / flexion exercises: While rehabilitation of the knee joint is our primary concern, the restoration of normal range of motion of the hip joint is equally as important. Due to the chronic nature of stifle (knee) injuries, hip flexure and extensor muscles undergo significant contracture (shortening) and as a result postoperative injuries to these muscles are very common. They are characterized by the patient holding the limb several inches off the ground. Hip rehabilitation exercises greatly reduce their incidence and severity. There are two exercises we will have you perform. Resistance pulls and hind limb extension / flexions. For the resistance pulls; one person sits behind the dog and places their hands around the front of each thigh (femur) at about the halfway mark, an assistant stands or sits in front and out of reach of the pet and asks the pet to move towards them (treats help). The person holding the thighs resists this movement for 3-5 seconds and then slowly releases. This very gently stretches out both hips simultaneously. For the hind limb extension / flexion exercises, have your dog either stand up or lay on its side with the surgical leg on top. Use your heat pack (see description) to warm up the hip muscles. Perform a thorough massage of the hip and lower back musculature. If you are unsure exactly where these muscles are located, please call and ask for assistance and a description of the technique. Once the hip has been warmed and massaged, gently grasp the surgical leg about midway up the thigh (femur). Gently push the surgical leg forward. This flexes the hip, hold for 3-5 seconds and release. Repeat the hip flexion process 5-10 times per session. The same process can be repeated for the hip extensions. Instead of pushing the leg forward, it is now pulled backwards. This will stretch the muscles of the hip. As you pull backwards your pet will begin to resist, when that occurs hold the leg in the extended position. Once your pet begins to relax, extend the leg a little more, hold for 3-5 seconds and then slowly release. Repeat the hip extension process 5-10 times per session. Regardless of the technique used, remember these muscles are always tight. Go slowly it may take several weeks for the hip muscles to fully loosen. Swimming / water walking exercises: After suture/staple removal, if the opportunity arises and your pet enjoys the water, aquatic therapy is excellent for your pet s recovery. Water allows your pet to use the surgical limb with a significantly reduced weight load. Ensure there is safe access for both you and your pet. Pet flotation devices are available. Have your pet walk or swim for 5-10 minutes initially and gradually increase to 20 minutes. No explosive activity is allowed. No stick throwing. 7

46 Rehabilitation Descriptions: Sit to stand exercises: These should begin on day 14 after surgery. Initially, 5 daily and with each passing week increase by an additional 5. At the six week mark you should be at 120 daily. Prior to this exercise you should warm up your dogs legs with a 5 minute figure of 8 pattern walk. Once warm, have your pet sit squarely, hold for a few seconds and then ask your pet to stand. It is critically important that your pet sits as squarely as possible. There are two methods to help your pet sit squarely. The first method involves you kneeling down or sitting directly behind your dog with you dog facing away from you. Have a leg on either side of the dog. Give the command to sit. If you notice as your pet sits that the surgical leg is moving out to the side, gently push it back underneath. The second method is to have your pet sit with the surgical leg next to a wall. As the dog sits, the wall prevents the surgical leg from moving away from underneath the body. In the early days your pet may not be able to perform this exercise properly. Go slowly it may take two to three weeks for your pet to start sitting normally. Completely controlled leash walks: These are leash walks that are meant to have your pet use its leg as soon as possible. Your pet should be comfortable throughout this process. Initially the walks should be very slow and always done on good footing. The slow pace will encourage your pet to bear weight on the surgical leg. As things progress, allow your pet to choose the walking pace. If possible have your dog walk on your left side one day and your right side the next day. This allows the dog to bear the majority of the body weight on the surgical leg one day and gives the leg a rest the next day. If your pet resists switching sides, and some do, then walk your dog in a figure 8 pattern changing direction each day. This is very important, as it encourages your pet to use the surgical leg. Four weeks after surgery, going with another dog is also very helpful. It stimulates your dog mentally and gives them something else to focus on. Please ensure that the dogs are compatible and can both be easily kept under control. Supervised controlled off leash activity in an enclosed space: Controlled off leash activity allows your pet the freedom to move at its own pace. You are able to initiate some play at this time. Go slowly at first. Ensure that there is good footing. Remember your pet should remain completely comfortable and controlled during this activity. No other pets are allowed to participate in off leash activity until after the twelve week period. Uncontrolled activity: This includes any off leash, unsanctioned, or unsupervised activity regardless of the location or duration. Your pet must remain under complete control for the first four months. Medications: Pain control medications such as tramadol are generally only needed for the first 2-3 days. Antibiotics are generally given for the first 3 days. Non-steroidal anti-inflammatories (NSAID s) are given at full lean body weight dose for the first 8 weeks and then will be tapered on the advice of your veterinarian. Nutraceuticals can work in conjunction with NSAID s in modifying joint inflammation. Unfortunately the injury your pet has sustained will cause some degree of degenerative joint disease (arthritis). Long term, low dose treatment may be necessary to slow this process. Please refer to the Long term NSAID usage handout provided. 8

47 Minor Complications: Edema: Swelling at or below the surgical site is called edema. It is usually seen during the first three to five days after surgery. It is often most visible around the ankle area. It is completely normal and fully expected. It will resolve by itself. The icing process, massage and passive motion exercises will all help to resolve edema. If it does not resolve by the 7 th day after surgery, contact you veterinarian for advice. Seroma: This is a fluid swelling at the surgical site. If it occurs, it will be located on the inside of the joint and over the implant. It may be several centimeters in diameter. It is often an indication that the patient has been licking the incision, or is being either too active or far more commonly, not active enough. It will always resolve by itself. Under no circumstances should a seroma ever be drained. The icing process, massage, passive motion exercises and controlled leash walking are all critical in minimizing seroma formation and are also very helpful in resolving this situation. If a seroma occurs, contact you veterinarian for advice. Surgical site redness: This is almost always a result of the dog licking at the incision. It is very important to allow the skin to heal. Licking, of any amount, is the number one cause of postoperative incisional inflammation, infection, skin ulceration and seroma formation. Infections can be devastating. Skin ulceration will cause a delay in rehabilitation. Do not permit your pet any access to the incision until the staples are removed. Please keep the Elizabethan cone on when needed to prevent licking and allow the incision to heal, especially when you cannot directly supervise your pet. Do not put any creams or ointments on the incision unless directed by a veterinarian. Hip Flexor injuries: These can occur at any time during the first four months of the recovery process. The injury is characterized by significant pain on extension of the hip and reluctance to use the affected limb. The pet will almost always carry the affected limb flexed and held completely off the ground. If you suspect this injury has occurred, contact your veterinarian immediately for Advice. 9

48 Copyright 2016 NGD. All rights reserved Neil Embleton, B.Sc., DVM and Veronica Barkowski, DVM Helivet Mobile Surgical Services, Sundre, AB, Canada July 2016 SIMITRI STABLE IN STRIDE STIFLE RADIOGRAPHS The following is intended for your technical staff and reviews proper patient positioning to obtain the diagnostic stifle radiographs required for preoperative planning of the Simitri Stable in Stride procedure. 1

49 A. Preoperative Radiographs Presurgical planning is critical for the success of this surgical procedure. Measurements obtained from preoperative radiographs will provide the information required to select the appropriate size of femoral and tibial plates and to position the femoral plate during surgery. There are 5 key points for obtaining diagnostic stifle radiographs: Dogs must be sedated or anesthetized A calibration marker of known physical dimensions (in mm) must be on the plate for every image radiographed (see Figure 2-1) Radiograph one stifle at a time (mark as left or right) Center the stifle on radiograph with half of femur and half of tibia on the film Superimpose femoral condyles on the extended lateral radiograph (see and explanation in next section) Calibration Markers: All radiographic images are magnified therefore to obtain accurate true to scale measurements this magnification factor must be determined. Examples of calibration markers L or R marker with straight edge (do not use the old style clip-on combined L/R as it is difficult to tell which side is up), clipper blade, metal pins, metal ruler, commercial x-ray calibration markers are also available. Measure the marker with a ruler to the nearest millimeter (mm). Place marker near (but not on) the limb i.e. not on edge of plate, as it will be cut out of final image. Marker should be positioned at the same height above plate as widest part of joint (ie not on the plate itself). Raise up with something radiolucent eg plastic or use commercially available holders) The percentage a radiographic image is magnified can be determined by comparing the measurement of the marker on the radiographic image to the actual measurement of the marker. This can be done manually or in most cases radiograph viewing software will allow you to calibrate or set the scale prior to using measuring devices. Note: The magnification of every radiographic image is different (even when taken on the same machine) because the distance that the stifle is above the plate will vary from patient to patient. Figure 2-1: explanation of calibration markers 2

50 Two radiographic views centered on the injured stifle are required: 1. Extended lateral with condyles superimposed (Figure 1; It is critical that femoral condyles are superimposed) 2. Cranial caudal view with half of the femur and half of the tibia only included in view (Figure 2) For the extended lateral stifle radiograph the dog is positioned in lateral recumbency with the limb to be radiographed closest to the plate and the contralateral limb flexed and rotated dorsally out of the field of view (Figure 2-4). The femoral condyles are superimposed in both the cranial caudal (most important) and proximal distal directions. A calibration marker is present on the image (R marker) and it has been raised off of the plate to the level of the joint. Figure 2-2 This is an example of a correctly positioned diagnostic extended lateral stifle radiograph. Condyles are superimposed, the radiograph is collimated to include half of the femur and tibia and a marker of known dimensions (R marker) is included in the image and has been raised to the level of the joint (in this case with a stack of gauze squares). Superimposing the medial and lateral femoral condyles allows for better assessment of stifle joint pathology and is critical for obtaining accurate measurements of the medial condyle. In most cases if the affected limb is simply stretched into an extended position on the plate the condyles will not be superimposed; the medial condyle will be longer (more caudal; Figure 2-3) and the lateral condyle will be closer to the tibia (more distal; Figure 2-4). Some minor adjustments to the the limb on the plate will correct the positioning and is described below. 3

51 Figure 2-3 This radiograph is incorrectly aligned in the cranial caudal direction. The medial condyle appears longer than the lateral in this radiograph. Note the notch on the lateral condyle at the attachment of the long digital extensor tendon (arrow). To correct the cranial caudal orientation of a radiograph first determine which femoral condyle appears to be the longest. In most cases this will be the medial condyle. If in doubt the presence of a notch corresponding to the attachment of the long digital extensor tendon aids in identification of the lateral femoral condyle. To correct the alignment of the condyles the patella must be rotated towards the shorter condyle. Therefore, if the medial condyle is longer, as is seen in Figure 2-3, the patella must be rotated toward the plate. This is most easily achieved by slightly rotating the hock away from the plate either by placing a small pad under the calcaneus or by manually rotating the hock away from the plate (Figure 2-4). Take care not to lift the lower limb off the plate when rotating the hock. 4

52 Figure 2-4 Demonstration of patient being positioned for extended lateral radiograph. Arrow indicates direction of rotation of lower limb to cause patella to rotate toward plate thereby aligning the femoral condyles. Note that the lower limb is being held without lifting it. Also note that the image will be collimated to include only half of the tibia and femur, the marker will be raised to the level of the joint and hands will be covered with lead shields (or alternatively, a pad placed under the caudal hock to maintain rotation) prior to taking the radiograph. 5

53 Figure 2-5 In this radiograph the lateral femoral condyle appears to be more distal (closer to the tibia) than the medial condyle. Note notch of the long digital extensor tendon identifies the lateral condyle. To correct an extended lateral radiograph that is not aligned in the proximal distal orientation (Figure 2-5) place a pad under the coxofemoral joint of the limb being radiographed. This will change the angle of the femur so that it is more parallel to the plate and will re-align the femoral condyles in the the proximal distal direction. Note that dogs that have natural padding over the hip (i.e. overweight) will likely not require any adjustment. For the cranial caudal stifle radiograph the dog is positioned in dorsal recumbency. To obtain a true cranial caudal view of the affected stifle it is important only one stifle is radiographed at a time. Allow the dog to rotate towards the contralateral side with the contralateral limb in a relaxed position. This will cause the affected stifle to easily be held in extension with the patella centered over the distal femur without internal rotation of the lower limb. For most dogs the stifle will be raised above the plate by several inches therefore it is important to raise the calibration marker to the level of the stifle joint to adjust for the increased magnification of the stifle joint on the radiographic image. 6

54 Figure 2-6 This is an example of a correctly positioned cranial caudal radiograph. The patella is centered over the femur, half of the femur and tibia are in view, the radiograph is centered over the stifle joint and the tail has been moved out of the way of the stifle joint. The calibration marker (R marker) has been raised to the level of the stifle joint with a stack of gauze squares. Figure 2-7 To demonstrate the correct positioning of the dog for the cranial caudal radiograph this radiograph has not been correctly collimated. The affected limb is straight and the patella centered. The contralateral limb is in a relaxed position and the pelvis is tilted toward the contralateral side. By doing this it is much easier to center the patella of the limb to be radiographed. As a final position check, the patella can be palpated to ensure that it is centered directly on top of the femur prior to taking the radiograph. Note that there is no marker present on the radiograph to indicate which limb this is nor for calibration. To assess for tibial torsion a second cranial caudal view is taken with the dog in the same position as the first view but centered over the tibia shaft and including the distal 7