FOREWORD PRESERVATION UNICOMPARTMENTAL KNEE SYSTEM

Transcription

1 Surgical Technique

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3 FOREWORD PRESERVATION UNICOMPARTMENTAL KNEE SYSTEM Our surgeon design team first implanted the Preservation Unicompartmental Knee System in The system was developed with over 100 years combined unicompartmental knee replacement experience. In its design, our objective was to develop specialist instruments and a new concept of specific technique that allowed the surgeon to achieve accurate, reproducible alignment and balance for long-term clinical results. Since its launch, this technique has evolved with the experience of our designing surgeon team and is incorporated into this Surgical Technique manual. Appropriate implant alignment and articulation, as well as flexion and extension space balancing must be achieved to obtain optimal results. The relatively small working area available for unicompartmental surgery means that the cementing technique is also critical to long term fixation. If these fundamentals are respected, excellent outcomes can be achieved with early return of function, outstanding range of motion, and a very high level of patient satisfaction. The clinical results to date have been enlightening and rewarding. With 5 years of clinical experience, we continue to follow hundreds of patients enjoying ongoing clinical success with the Preservation Unicompartmental Knee. We believe the implant will continue to perform well for years to come. The Preservation Design Group Dr. Dave Dalury - Baltimore, USA Dr. Dave Fisher Indianapolis, USA Dr. James McAuley London, Canada Dr. Wolfgang Herzberg Hamburg, Germany Dr. Greg Keene Adelaide, Australia Dr. Ed Newman Christchurch, New Zealand Dr. Gerry Engh Arlington, USA

4 CONTENTS Contents 1 Introduction 2 Templating 3 Approach and Exposure 5 Tibial Jig Alignment 7 Proximal Tibial Resection 10 Extension Gap 12 Flexion Gap 13 Alignment and Femoral Resection 14 Femoral Sizing and Rotation 15 Femoral Chamfer Cuts 18 Trial Reduction 19 Femoral Fin Slot 21 Femoral Peg 22 Tibial Keel Preparation 23 Component Trial 24 Cementing Preparation 25 Cementing the Tibial Components 26 Cementing the Femoral Component 30 Possible Flexion/Extension Gap Adjustment 32 Implant Product Codes 33 Instrument Product Codes 35 1

5 INTRODUCTION PRESERVATION UNICOMPARTMENTAL KNEE SYSTEM Precise Alignment The exposure for the Preservation Unicompartmental Knee System leaves the patella in its natural position over the femoral condyles and avoids disruption of the extensor mechanism. Varus/valgus alignment The key to precise varus/valgus alignment is the approach to femoral resection. For the Preservation Unicompartmental Knee System, the distal femoral cut is made with the leg in extension, with the cutting block resting on the resected tibia. This allows the surgeon to assess the joint for natural balance and alignment with the patella close to it s normal position, before the final cut is made. True component to component alignment Adjustment to medial/lateral alignment at the trial stage ensures that the femoral and tibial component are truly aligned for optimum articulation, throughout the range of motion. Preserved Natural Balance Preventing over correction The joint balance is checked in natural alignment to ensure even load distribution across the joint, using the Preservation Unicompartmental Knee System distal cutting block and shims. This avoids over correction of the unaffected compartment. Restores Joint Function Established articulating geometry The Preservation Unicompartmental Knee System J curve sagittal geometry, with its anterior kick-back, provides good coverage of the femoral condyle. This allows smooth, pain free kinematic patella function. Its coronal profile is curved to optimise bearing contact, avoiding edge loading in varus or valgus lift off. Optimal, intra-operative bearing selection to suit each patient The Preservation Unicompartmental Knee System offers a range of all-polyethylene, modular fixed and mobile bearing options, to suit the needs of each patient. GUR 1020 Cross-linked bearing material GUR 1020 cross-linked, closed foil pack sterilised polyethylene is used in the Preservation Unicompartmental Knee System for its resistance to oxidation and wear. Keeled tibial fixation The keel design ensures the tray or bearing is mechanically stable on the tibial plateau. It also adds strength to the tibial component and allows a minimum bearing thickness of 7 mm for the all-polyethylene option. Balanced flexion and extension The flexion and extension gaps are checked before any femoral cuts are made. This allows fine adjustments to be made to balance the knee. Joint line restoration Positioning the implant based on a joint line reference with the distal femoral cutting block allows good function throughout gait. Indications Unicompartmental Knee Replacement (UKR) is indicated for patients with osteoarthrosis that is isolated to the medial or lateral tibial-femoral compartment. In these cases, the remaining opposite compartment articular cartilage is physically and biomechanically intact and capable of bearing normal loads. In very young and active patients, a high tibial osteotomy may still remain the treatment of choice for advanced single compartmental disease. Contraindications UKR is contraindicated for patients with inflammatory arthritis, significant chondrocalcinosis of the articular surface, advanced involvement of the other compartments or a significant extra-articular deformity. 2

6 TEMPLATING +5 mm 7 mm tibial component New Joint Line 3 mm 4 mm tibial resection Joint Line -5 mm -10 mm Joint Line 3 mm 4 mm tibial resection Anterior posterior X-ray and template Figure 1 Figure 2 X-ray Templating Templating the Anterior/Posterior (A/P) X-ray will indicate the amount of tibia to be resected (Figure 1). The lateral X-ray is used to determine the size of the femoral component and the angle of the posterior tibial slope. It is recommended that each patient is X-ray templated prior to the procedure. Anterior Posterior Template: Tibia The A/P template is placed over the A/P X-ray with the thick red horizontal line 2 mm above the lowest point of the superior tibial bone on the non-arthritic side (Figure 2). This indicates the new joint line on the arthritic side. Select the thinnest tibial prosthesis that will remove the defect. The minimum thickness of a fixed bearing all-polyethylene is 7 mm. A fixed bearing modular metal backed or mobile bearing minimum thickness is 9.5 mm. This thickness will determine the tibial resection. If the gap from the joint line to the lowest point of the worn side is 3 mm, then only 4 mm of tibia is resected. If there has been greater wear of the tibia and a thicker tibial component is necessary, simply adjust the measurements accordingly. This predicted tibial resection must be checked intra-operatively before tibial resection. 3

7 TEMPLATING Femoral sizing on the lateral X-ray Posterior tibial slope on the lateral X-ray Figure 3 Figure 4 Lateral Template: Femur The lateral template is positioned in the coronal plane at a right angle to the long axis of the femur (Figure 3). Align the template with the planned distal femoral cut to remove the defect. The template outline should be 1-2 mm larger than the bony margin of the X-ray, and should match the outline of the articular surface (2 mm thick). The posterior condyle of the prosthesis must not excessively overlap the superior bony margin of the adjacent posterior condyle of the femur. The posterior slope of the upper tibia should also be templated on the lateral X-ray as this is set at the time of tibial resection (Figure 4). This can vary from 0 to 15 and affects tightness of the prosthesis in flexion. A preliminary arthroscopy may also be used at an earlier stage to provide an initial assessment. 4

8 APPROACH AND EXPOSURE Figure 5 Figure 6 The Approach - Medial or Lateral Compartment An antero-medial or antero-lateral skin incision is performed. The incision should begin 1 cm proximal to the superior border of the patella. It should extend 6-10 cm distally along the edge of the patella and patella tendon, and end 2 cm distal to the joint line (Figure 5). A longer incision is advised when first starting to use the procedure or if the patient is obese. The joint capsule is entered with a parapatellar incision (Figure 6). Once the joint is exposed, a final assessment can be made of the extent of arthritic damage and the suitability of the joint for this procedure. Exposure The deep menisco-tibial layer of the medial or lateral capsule should be carefully retracted to provide good access to any tibial osteophytes and allow accurate wound closure. Any excess deep synovium is excised to provide clear sight of the joint. If required, all or part of the fat pad may also be excised to improve vision and allow inspection of the opposite compartment. Two large rake or z retractors are then introduced to maintain access to the capsule during all stages of the procedure. Retraction of skin edges should be avoided. No ligament releases should be performed as part of this procedure as this is a contraindication. 5

9 APPROACH AND EXPOSURE Tidemark Figure 7 Figure 8 In order to achieve medial-lateral (M/L) alignment and joint stability, it is vital that all osteophytes are removed from the entire medial or lateral edges of the femur and tibia (Figure 7). A retractor is used on the patella rim to draw the patella into a central position. Any significant osteophytes on the edge of the patella should also be excised. With the knee in full extension, mark the tidemark on the femoral condyle with a pen or electrocautery. This should be used as a projection of the limit of the tibia in full extension and can be used to help size the femoral component at a later stage (Figure 8). 6

10 TIBIAL JIG ALIGNMENT Anatomic axis Mechanical axis Valgus angle Tibial cutting block Joint line Ankle clamp Figure 9 Figure 10A Figure 10B Natural Alignment It will not be possible for some patients to achieve a neutral mechanical axis (Figure 9) without major soft tissue release which is a contraindication. In such cases; after osteophyte removal, spacer block insertion and achieving good collateral ligament tension, the alignment achieved should be accepted. At this stage an intra-operative assessment can be made of the femoral and tibial damage. The assessment should be used in conjunction with the pre-operative templating to decide how much tibial bone is resected. Tibial Resection - Aligning the Tibial Jig The knee is placed in 90 of flexion and the ankle clamp is attached proximal to the malleoli (Figure 10A). The midline of the tibia is approximately 3 mm medial to the transaxial midline. The lower assembly of the ankle clamp is translated medially (usually to the second vertical mark). There are scribe marks at 3 mm and 6 mm for reference, aligning to the middle of the talus. Tighten the lower front varus/valgus screw to lock (Figure 10B). The tibial cutting block is then raised to just below the level of the joint line. It is important to note that accurate alignment of instrumentation to anatomical references in the initial stages of this procedure will minimise tibial bone loss and establish accurate implant alignment. 7

11 TIBIAL JIG ALIGNMENT Intramedullary axis of the tibia Axis of the tibial alignment rod Adjust proximally to achieve varus/valgus alignment Figure 11 Figure 12 The tibial cutting block is now positioned 2 mm medial to the centre of the tibial tubercle. Medial/lateral adjustment should be made proximally to achieve varus/valgus alignment that is parallel to the transmalleolar axis (Figure 11). The medial lateral position of the cutting block is pinned and stabilised. The pin is drilled percutaneously (a stab incision is required with plastic drapes) into the tibia through the vertical slot in the rod (Figure 12). Further varus/valgus adjustment can be made at the ankle clamp if required at this stage. The A/P slope of the tibia is now set. The lower assembly is translated to bring the alignment rod parallel with the intramedullary axis of the tibia in the sagittal plane. The anterior crest of the tibia can be used as a reference proximally. In this position the tibial cutting block will dictate a 0 posterior tibial slope. 8

12 TIBIAL JIG ALIGNMENT Tibial stylus assembled with slotted foot A/P slope of the tibia Figure 13 Figure 14 Further anterior translation of the distal assembly will adjust this slope angle. The slope should be set to the figure determined from templating the lateral X-ray (Figure 13). One scribe on the ankle clamp equals approximately 2, dependant on leg length. The tibial stylus height is referenced to the pre-operative tibial resection templating and intra-operative assessment of the defect. The tibial stylus is inserted into the tibial cutting block using either the open or slotted foot and its tip is brought to rest on the tibial plateau (Figure 14). Vertical movement of the proximal assembly is now stabilised to fix varus/valgus and inferior/superior position. The knob on the proximal alignment rod is locked and one or two additional percutaneous pins are introduced through the bottom row of holes in the cutting block (Figure 14). The tibial stylus is then removed. 9

13 PROXIMAL TIBIAL RESECTION L-cut It is important to use the Preservation Uni saw blade L-cut guide Transverse cut Figure 15 Figure 16 The L-cut guide may be used to stabilise the reciprocating saw blade. The leading edge of the L-cut should be just medial or lateral to the anterior cruciate ligament insertion. The L-cut guide is attached to the tibial cutting block with its foot located in one of the four available tibial sizing slots (Figure 15). The aim is to allow the largest tibial prosthesis to be implanted, covering the maximum area of cortical bone in both the A/P and M/L planes. The L-cut is then taken with a reciprocating saw. The L-cut may need to be re-cut at a later stage to adjust the tibial tray position to allow for optimal prosthesis to prosthesis contact. Care must be taken to avoid over resecting the bone or weakening the anterior cruciate ligament. The transverse cut is made through the slot in the tibial cutting guide or on the open cutting surface (Figure 16). It is important to use the Preservation Uni saw blade attached to an oscillating saw for the cut. 10

14 PROXIMAL TIBIAL RESECTION Bristow retractor Graspers Vertical slot pin is removed Figure 17 In order to remove the cut tibia, first remove the vertical slot pin and then remove the tibial jig. Use an osteotome to open the saw cut to prevent the fragment from breaking so that it can be removed in one piece. Hold the bone fragment with graspers and lever out at a 30 angle with a Bristow retractor. Any bone fragments or meniscal rim should be removed from the posterior area (Figure 17). 11

15 EXTENSION GAP 2 mm distal femoral shim 7 mm Figure 18 Check Extension Gap The distal femoral cutting block is mounted onto the system handle. This is used to check the extension gap. If the distal femur is severely worn, then a 2 mm femoral shim can be used (Figure 18). This can be assessed by extending the leg. When using the 7 mm all polyethylene fixed bearing, no shims need to be added to the tibial side of the distal cutting block. When using the mobile bearing or the modular fixed bearing, the appropriate shims can be added where necessary on the tibial side. At this stage in natural alignment the tibial implant thickness, extension gap, stability of the collateral ligaments, lower leg alignment and ability to achieve full extension can be checked. If the extension gap is found to be too tight, then remount the upper portion of the tibial jig on the pins and re-cut. If the extension gap is too loose this may suggest that the tibia has been over-cut. Add the next size tibial shim for a thicker tibial prosthesis until the desired feel in extension is achieved. If the extension gap is acceptable or only slightly loose, the flexion gap can now be checked. 12

16 FLEXION GAP Femoral damage Remove the 2 mm distal femoral shim before checking the flexion gap 7 mm Figure 19 Check Flexion Gap Before checking the flexion gap, ensure that the 2 mm femoral shim is removed if used. The distal femoral cutting block and the attached tibial shims are inserted into the flexion space (Fig 19). The block should slide in and out with minimal pressure. If it does not, then remove 2 mm of bone from the posterior femoral condyle and not from the tibia. Any resection of the tibia can affect the size selection of the tibial component. 13

17 ALIGNMENT AND FEMORAL RESECTION Anatomic axis Mechanical axis Valgus angle Distal femoral cutting block Alignment guide Joint line Alignment rod Figure 20 Figure 21 Check Alignment With the leg held in full extension, the alignment guide and the extramedullary alignment rod are assembled onto the distal femoral cutting block and long leg alignment is checked (Figure 20). Proximally, the tip of the rod is aligned with the centre of the femoral head and distally over the second metatarsal. Care should be taken to avoid overcorrection at this stage. The alignment guide and the extramedullary alignment rod are now removed. The leg is maintained in extension, which stabilises the distal femoral cutting block in position. Resect Distal Femur The leg is flexed to replicate the approximate slope of the tibial resection. The angle for the distal femoral resection is determined by the posterior slope of the tibial resection. This will ensure an appropriate flexion angle for the femur. For example with a 5 distal slope, the leg is placed at approximately 5 of flexion. The system handle on the distal femoral cutting block is now removed. A Preservation Uni sawblade (1.27 mm thickness) should be used through the distal femoral cutting block slot to initiate the cut (Figure 21). To avoid capsular damage posteriorly, this cut should be completed with the distal femoral cutting block removed. Once the resected distal bone is removed, any remaining soft tissue should be cleared from the meniscal rim and posterior tibia. 14

18 FEMORAL SIZING AND ROTATION Tidemark Tidemark Distal cut Figure 22 Figure 23 Femoral Sizing and Rotation The femoral size established during pre-operative templating is checked using the femoral rotation and sizing guide. The anterior tip profile and M/L width of the guide is the same as the femoral prosthesis. The aim is to ensure a smooth transition of the patella from the trochlea onto the anterior tip of the femoral prosthesis. The M/L position is initially chosen to be centred on the condyle after osteophyte removal. The final M/L position is chosen later with the femoral trial. The tidemark, which we had previously marked in extension to match the anterior margin of the tibial articular surface, sets the A/P limit (Figures 22 & 23). 15

19 FEMORAL SIZING AND ROTATION Tidemark 10 Maximum rotation Anterior tip profile and M/L width are the same as the femoral prosthesis Figure 24 Figure 25 The knee is placed in 90 of flexion and the appropriate size of femoral sizing and rotation guide is positioned under the posterior condyle using the system handle (Figure 24). It is important to start with the femoral sizing and rotation guide in a neutral orientation and centrally aligned over the tibial plateau. The femoral sizing guide should reach the tide mark anteriorly. Note the shape of the sizing guide anteriorly matches the actual shape of the prostheses which assists in positioning the guide. A tibial trial or femoral spacer guide block can be temporarily located on the tibia to balance the joint. The femoral sizing and rotation guide may be rotated by a maximum of 10 to avoid overhang on the anterior aspect of the femur and ensure maximum coverage of resected bone (Figure 25). The femoral condyle should remain central to the tibial resection. This will allow the anterior aspect of the femoral prosthesis to articulate accurately in extension on the anterior aspect of the anatomically shaped tibial prosthesis. 16

20 FEMORAL SIZING AND ROTATION Curved gouge Curved gouge cut Tidemark Figure 26 Figure 27 Once in the correct position, the pin in the femoral rotation guide is pressed into the distal femur. Two holes are drilled through the guide to create a location for the femoral finishing guide (Figure 26). The system handle is then removed. The curved gouge is used to cut the profile of the anterior tip of the femoral prosthesis. The gouge cut should be made about 2 mm anteriorly to the femoral rotation guide. This will mark the extent of the anterior chamfer cut (Figure 27). 17

21 FEMORAL CHAMFER CUTS Position 1 Position 2 Introduce the femoral finishing guide Posterior femoral resection Figure 28 Figure 29 Position 1 Limit of anterior chamfer cut as previously resected by the curved gouge (tidemark) Posterior chamfer cut Anterior cut Figure 30 Figure 31 Femoral Chamfer The femoral rotation guide is removed. The system handle should be used to stabilise the femoral finishing guide whilst the chamfer cuts are made. The cuts should be performed in the following order to prevent the guide from tilting. The femoral finishing guide is inserted into the two holes in the distal femoral surface and is tapped firmly into position - as in position 1 (Figure 28). The system handle can then be moved to Position 2 of the guide, and the posterior femur is resected through the guide slot using the Preservation Uni saw blade (Figure 29). The system handle is relocated back to Position 1 and the posterior chamfer is cut (Figure 30) With the system handle removed, the anterior chamfer is cut. It is important that the anterior chamfer cut extends no further than the previous curved gouge cut (Figure 31). The anterior chamfer cut can alternatively be made using an osteotome. 18

22 TRIAL REDUCTION FIXED BEARING 2nd Impact 1st Impact Figure 32 Figure 33 Trial Reduction The leg is held in 90 of flexion. Trial the femoral component first. A femoral trial matching the final femoral rotation guide is attached to the femoral introducer, located on the distal femoral cut, and tapped into the bone. Impact the trial with the first few hits moving from posterior to anterior (Figure 32). The appropriate tibial trial is selected, corresponding to the thickness determined by the distal femoral cutting block and shims. It is placed on the resected tibia and cortical bone coverage is assessed. Components can be up or down sized as per the chart below. The fixed bearing trial can be attached to the systems handle and should insert easily using the handle system (Figure 33). Femoral Size Fixed Bearing Tibia X X 2 X X X 3 X X X 4 X X X 5 X X 19

23 TRIAL REDUCTION MOBILE BEARING Assemble the tray and mobile bearing insert. Partially advance the mobile bearing insert under the posterior femoral condyle and then push the tibial tray into position Push Figure 34 Figure 35 As with the fixed bearing, the mobile bearing size and position are critical. The largest possible trial tray for each patient should be selected and placed anteriorly on the resected tibia. This will allow the final trial mobile bearing component to be inserted easily onto the track, avoiding any contact with the anterior tibial eminence. When the final mobile bearing tray trial is in place, position the knee more valgus and flexed to about 60 to insert the mobile bearing trial component without moving the trial tray (Figure 34). If the anterior tibial eminence causes an obstruction, the excess bone should be removed using an osteotome. Joint stability and rotational alignment are again assessed in flexion and full extension (Figure 35). Reference may also be made to the flexion and extension adjustment table on Page 32. M/L position of the femoral and tibial trials are checked. 20

24 FEMORAL FIN SLOT Align the femoral trial over the centre of the tibial trial in flexion and extension Depth of femoral fin cut Diathermy mark For the mobile bearing, remove any excess bone from the tibial eminence to allow insertion of the polyethylene component. Figure 36 Figure 37 The femur should sit in the centre of the tibial trial in flexion and extension. The M/L position of both the femoral and tibial components can be adjusted at this stage. Tibial rotation can also be modified to match any femoral rotation introduced during the sizing step. It may be necessary to re-cut the L-cut to achieve this component-to-component positioning which is most important in extension. If the trial has been successful, diathermy marks are made on the tibia against the alignment marks on the tibial trial (Figure 36). The Femoral Fin Slot With successful trialing complete, the leg is held in flexion with the tibial trial in place to stabilise the femoral trial. The femoral fin slot is cut in the distal femur using a reciprocating saw down both sides of the slot of the femoral trial (Figure 37). Because the femoral fin gets deeper posteriorly, the oscillating saw should cut deeper posteriorly, although care should be taken not to over resect. 21

25 FEMORAL PEG The slot must be cut before the peg trial is used Figure 38 Figure 39 The Femoral Peg Hole The femoral drill guide is inserted into the femoral trial and the femoral component location hole is then drilled through the drill guide, using the peg drill to the depth marked on the drill (Figure 38). The drill handle is kept in line with the femur to provide correct flexion-extension. Trial Femoral Peg The femoral peg trial is now used to ensure that the fin slot and peg hole have been formed to the correct depth (Figure 39). It is important to ensure that the femoral peg trial is fully inserted, as this component may become loose during impaction. 22

26 TIBIAL KEEL PREPARATION Diathermy mark Figure 40 Figure 41 Figure 42 Tibial Keel Preparation The tibial keel template that matches the selected tibial trial is inserted, using the system handle. This is aligned using the diathermy marks on the tibia. This is tapped into place and secured with a Specialist 2 pin (Figure 40) or laminar spreader. A keel groove is cut through the slot using the tibial keel osteotome (Figure 41). The groove can be carefully pre-cut using a oscillating saw. All resected bone must be removed from the joint. The tibial keel trial is inserted through the slot into the groove to check the correct depth of the keel has been prepared (Figure 42). 23

27 COMPONENT TRIAL C-arm Femoral introducer 7 mm Figure 43 Figure 44 Component Trial The definitive components can be trialed to ensure that the knee is placed in the appropriate position to facilitate implantation, prior to cementing. The tibial prosthesis is trialed first and gently impacted into place using the C-arm. The prosthesis and its keel should be fully seated on the tibia (Figure 43). The femoral prosthesis is attached to the femoral introducer (Figure 44), introduced to the femur and gently pushed into place using the femoral impactor. The joint is checked for alignment and stability in flexion and extension with a trial tibial bearing. The components must be removed and thoroughly cleaned prior to final insertion. 24

28 CEMENTING PREPARATION Thin layer of cement Figure 45 Figure 46 Cementing Preparation Small holes can be drilled on the prepared tibial surface and in the keel slot in order to promote the penetration of cement. The prepared tibial surface should be fully washed out using a pulse lavage, ensuring that no residual particles of bone are present in the joint space. The surface should be fully dried using surgical swabs, ensuring the prepared tibia is as dry as possible prior to cementing. A thin layer of cement can be applied to the prepared tibial surface and a small osteotome or the handle end of surgical forceps can be used to pressurise the cement into the bone. A small cylindrical shaped piece of bone cement can also be inserted into the tibial keel slot and pressurised using the same technique (Figure 45). A thin layer of cement can be applied to the prosthesis (Figure 46). 25

29 CEMENTING TIBIAL COMPONENTS ALL POLYETHYLENE Squeeze posterior to anterior All-polyethylene tibial inserter Figure 47 Figure 48 Cementing the Tibial Components The tray can be positioned by applying pressure from the posterior to the anterior side. This will extrude the cement away anteriorly from the back of the joint (Figure 47). Ribbon gauze placed posteriorly around the implant can be used to prevent cement being displaced. Remove the gauze once the tray is impacted. Alternatively a bent arthroscopy probe can be used to remove posterior cement from the edge of the prosthesis. It is important to ensure complete removal of any bone cement extruded posteriorly from the tibial component. All-Polyethylene Tibial Bearing The all-polyethylene tibial bearing is attached to the all-polyethylene tibial inserter and lowered onto the tibial resection, from posterior to anterior, forcing the cement away from the back of the joint (Figure 48). The C-arm is used to maintain pressure until the cement has fully polymerised and fully set. 26

30 CEMENTING TIBIAL COMPONENTS FIXED BEARING Figure 49 Modular Fixed Bearing The fixed bearing prosthesis tibial tray is inserted as per the all polyethylene tibial bearing technique. The recommended method is to pre-assemble the insert and tray on the back table to ensure proper seating of the insert before the tray is cemented in the patient (Figure 49). 27

31 CEMENTING TIBIAL COMPONENTS MOBILE BEARING Press trigger to grip implant Chamfers To ensure that the bearing tracks correctly, anterior and posterior bone chamfers need to be removed. Figure 50 Figure 51 Mobile Bearing An osteotome or nibbler should be used to remove anterior and posterior bone chamfers from the lateral side of the L-cut (Figure 50). With the trial component in place, full anterior and posterior mobility of the mobile bearing should be assessed. The trials are removed and the final implant selected. Cement is applied as per the all polyethylene and fixed bearing tray. The mobile bearing tray Inserter/Impactor fits into the track of the mobile bearing tray. The tray is inserted into the joint and pressure is applied to seat the implant. Maintain pressure until the cement has fully polymerised and fully set (Figure 51). 28

32 CEMENTING TIBIAL COMPONENTS MOBILE BEARING INSERTION Femoral impactor Figure 52 Figure 53 When the cement has fully set, the final bearing can be inserted onto the track. The final mobile bearing component should be inserted into the track without any interference from the anterior tibial eminence (Figure 52). Again, full anterior and posterior mobility of the final mobile bearing must be checked. If the bearing is positioned so that the joint space is opened up, the femoral prosthesis can enter more easily (Figure 53). If the bearing is too posterior, it is impossible to insert the femoral component. 29

33 CEMENTING THE FEMORAL COMPONENT Even layer of cement Femoral introducer Thin layer of cement Figure 54 Figure 55 Cementing the Femoral Component An even layer of doughy viscosity cement is applied to the accessible cut surfaces of the femur, and digitally pressurised. A small amount of cement should be placed in the peg hole and fin slot to enhance fixation. A thin layer of cement can also be applied to the posterior condyle (Figure 54). The femoral prosthesis is attached to the femoral introducer and inserted (Figure 55). The patella will need to be strongly retracted to facilitate femoral prosthesis insertion especially for a lateral approach, and the knee flexed at

34 CEMENTING THE FEMORAL COMPONENT Femoral impactor Lift off Good even pressure 40 flexion and over flexion. Figure 56 Figure 57 Figure 58 The femoral prosthesis is tapped firmly onto the femur with the impactor and excess cement is removed (Figure 56). The knee should now rest in varus (for a medial UKR) or valgus (for a lateral UKR) at about of knee flexion. This position maintains even pressure on the tibial prosthesis. If the knee is flexed over 40 while the cement sets, pressure from the insert (fixed bearing / mobile bearing) on the posterior cut and posterior chamfer will cause undesirable distal and anterior femoral lift off (Figure 57). At of flexion, pressure from the insert on the posterior chamfer and distal cut is ideal (Figure 58). Once the cement has polymerised and fully set, the joint is checked for range of movement, alignment and collateral ligament stability. The wound is closed and the procedure is complete. 31

35 POSSIBLE FLEXION AND EXTENSION GAP ADJUSTMENTS Flexion Tight Normal Loose Extension Tight Normal Loose & & Tight in Extension If the joint is tight in extension, the femoral trial is removed and the femoral distal cutting block is placed back in the joint with an appropriate sized tibial spacer to balance the ligaments. A further 2 mm is cut from the distal femur using the Preservation Uni Saw Blade. The finishing block is then relocated on the distal femur using the existing pin holes. The chamfers are re-cut and the trial reduction is repeated. 2. Tight in Flexion and Extension If the joint is tight in both flexion and extension, the tibial cutting block is replaced on the tibia. The two rows of pin holes in the jig are 2 mm apart. 2 mm more tibia should be resected and the flexion and extension gaps re-checked. By repositioning the guide, up to 4 mm can be recut from the tibia. If more bone is to be resected, the tibial stylus should be re-employed. 3. Tight in Flexion If the joint is tight in flexion then there are two options: Firstly, the femur can either be downsized using a smaller anterior cutting block. Secondly, the tibial slope can be adjusted. The tibial jig is placed on the tibia and aligned to the mechanical axis of the tibia. The saw blade is placed in the slot of the tibial cutting guide to reference the previous cut. The ankle clamp is adjusted to generate additional slope and the tibia is re-cut. 4. Loose in Flexion The gap has to be assessed by the surgeon and in some cases may be accepted as the knee will tolerate laxity in flexion much more than in extension. However if it has to be corrected, then this is done by using a thicker insert and re-cutting the distal femur to adjust the extension gap. 5. Loose in Extension This must be corrected by adding a thicker insert. If this in turn produces a tight flexion gap, the tibial slope should be increased. Laxity in extension may lead to a poor result. 6. Loose in Extension and Flexion Use a thicker tibial insert to correct this. 32

36 IMPLANT PRODUCT CODES Preservation Cemented Femoral Components Preservation Femoral Cemented Size Preservation Femoral Cemented Size Preservation Femoral Cemented Size Preservation Femoral Cemented Size Preservation Femoral Cemented Size 5 Preservation All Poly Tibias Preservation A/P Tibial RM/LL Size 1 7 mm Preservation A/P Tibial RM/LL Size mm Preservation A/P Tibial RM/LL Size mm Preservation A/P Tibial RM/LL Size 2 7 mm Preservation A/P Tibial RM/LL Size mm Preservation A/P Tibial RM/LL Size mm Preservation A/P Tibial RM/LL Size 3 7 mm Preservation A/P Tibial RM/LL Size mm Preservation A/P Tibial RM/LL Size mm Preservation A/P Tibial RM/LL Size 4 7 mm Preservation A/P Tibial RM/LL Size mm Preservation A/P Tibial RM/LL Size mm Preservation A/P Tibial RM/LL Size 5 7 mm Preservation A/P Tibial RM/LL Size mm Preservation A/P Tibial RM/LL Size mm Preservation A/P Tibial LM/RL Size 1 7 mm Preservation A/P Tibial LM/RL Size mm Preservation A/P Tibial LM/RL Size mm Preservation A/P Tibial LM/RL Size 2 7 mm Preservation A/P Tibial LM/RL Size mm Preservation A/P Tibial LM/RL Size mm Preservation A/P Tibial LM/RL Size 3 7 mm Preservation A/P Tibial LM/RL Size mm Preservation A/P Tibial LM/RL Size mm Preservation A/P Tibial LM/RL Size 4 7 mm Preservation A/P Tibial LM/RL Size mm Preservation A/P Tibial LM/RL Size mm Preservation A/P Tibial LM/RL Size 5 7 mm Preservation A/P Tibial LM/RL Size mm Preservation A/P Tibial LM/RL Size mm Preservation Fixed Bearing Inserts Preservation Fixed Bearing Insert RM/LL Size mm Preservation Fixed Bearing Insert RM/LL Size mm Preservation Fixed Bearing Insert RM/LL Size mm Preservation Fixed Bearing Insert RM/LL Size mm Preservation Fixed Bearing Insert RM/LL Size mm Preservation Fixed Bearing Insert RM/LL Size mm Preservation Fixed Bearing Insert RM/LL Size mm Preservation Fixed Bearing Insert RM/LL Size mm Preservation Fixed Bearing Insert RM/LL Size mm Preservation Fixed Bearing Insert RM/LL Size mm Preservation Fixed Bearing Insert RM/LL Size mm Preservation Fixed Bearing Insert RM/LL Size mm Preservation Fixed Bearing Insert RM/LL Size mm Preservation Fixed Bearing Insert RM/LL Size mm Preservation Fixed Bearing Insert RM/LL Size mm Preservation Fixed Bearing Insert LM/RL Size mm Preservation Fixed Bearing Insert LM/RL Size mm Preservation Fixed Bearing Insert LM/RL Size mm Preservation Fixed Bearing Insert LM/RL Size mm Preservation Fixed Bearing Insert LM/RL Size mm Preservation Fixed Bearing Insert LM/RL Size mm Preservation Fixed Bearing Insert LM/RL Size mm Preservation Fixed Bearing Insert LM/RL Size mm Preservation Fixed Bearing Insert LM/RL Size mm Preservation Fixed Bearing Insert LM/RL Size mm Preservation Fixed Bearing Insert LM/RL Size mm Preservation Fixed Bearing Insert LM/RL Size mm Preservation Fixed Bearing Insert LM/RL Size mm Preservation Fixed Bearing Insert LM/RL Size mm Preservation Fixed Bearing Insert LM/RL Size mm Preservation Mobile Bearing Tibial Inserts Preservation Mobile Bearing Insert Size mm Preservation Mobile Bearing Insert Size mm Preservation Mobile Bearing Insert Size mm Preservation Mobile Bearing Insert Size mm Preservation Mobile Bearing Insert Size mm Preservation Mobile Bearing Insert Size mm Preservation Mobile Bearing Insert Size mm Preservation Mobile Bearing Insert Size mm Preservation Mobile Bearing Insert Size mm Preservation Mobile Bearing Insert Size mm Preservation Mobile Bearing Insert Size mm Preservation Mobile Bearing Insert Size mm Preservation Mobile Bearing Insert Size mm Preservation Mobile Bearing Insert Size mm Preservation Mobile Bearing Insert Size mm Preservation Fixed Tibial Tray - Cemented Preservation Fixed Tibial Tray RM/LL Cemented Size Preservation Fixed Tibial Tray RM/LL Cemented Size Preservation Fixed Tibial Tray RM/LL Cemented Size Preservation Fixed Tibial Tray RM/LL Cemented Size Preservation Fixed Tibial Tray RM/LL Cemented Size Preservation Fixed Tibial Tray LM/RL Cemented Size Preservation Fixed Tibial Tray LM/RL Cemented Size Preservation Fixed Tibial Tray LM/RL Cemented Size Preservation Fixed Tibial Tray LM/RL Cemented Size Preservation Fixed Tibial Tray LM/RL Cemented Size 5 Preservation Mobile Bearing Tibial Tray - Cemented Preservation Mobile Bearing Tibial Tray RM/LL Cemented Size Preservation Mobile Bearing Tibial Tray RM/LL Cemented Size Preservation Mobile Bearing Tibial Tray RM/LL Cemented Size Preservation Mobile Bearing Tibial Tray RM/LL Cemented Size Preservation Mobile Bearing Tibial Tray RM/LL Cemented Size Preservation Mobile Bearing Tibial Tray LM/RL Cemented Size Preservation Mobile Bearing Tibial Tray LM/RL Cemented Size Preservation Mobile Bearing Tibial Tray LM/RL Cemented Size Preservation Mobile Bearing Tibial Tray LM/RL Cemented Size Preservation Mobile Bearing Tibial Tray LM/RL Cemented Size 5 Preservation Femoral Trials Preservation Uni Femoral Trial Size Preservation Uni Femoral Trial Size Preservation Uni Femoral Trial Size Preservation Uni Femoral Trial Size Preservation Uni Femoral Trial Size Preservation Peg Trial Femur Size Preservation Peg Trial Femur Size Preservation Peg Trial Femur Size Preservation Peg Trial Femur Size Preservation Peg Trial Femur Size 5 33

37 IMPLANT PRODUCT CODES Preservation Fixed Bearing Tibial Trials Preservation Fixed Bearing Tibial Trial Size 1 7 mm Preservation Fixed Bearing Tibial Trial Size mm Preservation Fixed Bearing Tibial Trial Size mm Preservation Fixed Bearing Tibial Trial Size mm Preservation Fixed Bearing Tibial Trial Size 2 7 mm Preservation Fixed Bearing Tibial Trial Size mm Preservation Fixed Bearing Tibial Trial Size mm Preservation Fixed Bearing Tibial Trial Size mm Preservation Fixed Bearing Tibial Trial Size 3 7 mm Preservation Fixed Bearing Tibial Trial Size mm Preservation Fixed Bearing Tibial Trial Size mm Preservation Fixed Bearing Tibial Trial Size mm Preservation Fixed Bearing Tibial Trial Size 4 7 mm Preservation Fixed Bearing Tibial Trial Size mm Preservation Fixed Bearing Tibial Trial Size mm Preservation Fixed Bearing Tibial Trial Size mm Preservation Fixed Bearing Tibial Trial Size 5 7 mm Preservation Fixed Bearing Tibial Trial Size mm Preservation Fixed Bearing Tibial Trial Size mm Preservation Fixed Bearing Tibial Trial Size mm Preservation Mobile Bearing Tibial Trials Preservation Mobile Bearing Tibial Trial RM/LL Size Preservation Mobile Bearing Tibial Trial RM/LL Size Preservation Mobile Bearing Tibial Trial RM/LL Size Preservation Mobile Bearing Tibial Trial RM/LL Size Preservation Mobile Bearing Tibial Trial RM/LL Size Preservation Mobile Bearing Tibial Trial LM/RL Size Preservation Mobile Bearing Tibial Trial LM/RL Size Preservation Mobile Bearing Tibial Trial LM/RL Size Preservation Mobile Bearing Tibial Trial LM/RL Size Preservation Mobile Bearing Tibial Trial LM/RL Size 5 Preservation Mobile Bearing Insert Trials Preservation Mobile Bearing Insert Trial Size mm Preservation Mobile Bearing Insert Trial Size mm Preservation Mobile Bearing Insert Trial Size mm Preservation Mobile Bearing Insert Trial Size mm Preservation Mobile Bearing Insert Trial Size mm Preservation Mobile Bearing Insert Trial Size mm Preservation Mobile Bearing Insert Trial Size mm Preservation Mobile Bearing Insert Trial Size mm Preservation Mobile Bearing Insert Trial Size mm Preservation Mobile Bearing Insert Trial Size mm Preservation Mobile Bearing Insert Trial Size mm Preservation Mobile Bearing Insert Trial Size mm Preservation Mobile Bearing Insert Trial Size mm Preservation Mobile Bearing Insert Trial Size mm Preservation Mobile Bearing Insert Trial Size mm MIU Instruments Femoral Rotation Guide Spacer Block 5 mm Preservation Tibial Cutting Block RM/LL Preservation Tibial Cutting Block LM/RL Preservation Tibial Stylus Preservation L-Cut Guide Preservation Alignment Guide Preservation Femoral Spacer Block - 1 mm Defect Preservation Femoral Spacer Block - 2 mm Defect Preservation Femoral Spacer Block - 3 mm Defect Preservation Tibial Spacer Block 9.5 mm Preservation Tibial Spacer Block 11.5 mm Preservation Tibial Spacer Block 13.5 mm Preservation Femoral Distal Cutting Block Preservation System Handle Preservation Femoral Rotation and Sizing Guide Size Preservation Femoral Rotation and Sizing Guide Size Preservation Femoral Rotation and Sizing Guide Size Preservation Femoral Rotation and Sizing Guide Size Preservation Femoral Rotation and Sizing Guide Size Preservation Femoral Finishing Guide Size Preservation Femoral Finishing Guide Size Preservation Femoral Finishing Guide Size Preservation Femoral Finishing Guide Size Preservation Femoral Finishing Guide Size Preservation Femoral Peg Drill Preservation Femoral Peg Drill Guide Preservation Tibial Keel Template Size Preservation Tibial Keel Template Size Preservation Tibial Keel Template Size Preservation Tibial Keel Template Size Preservation Tibial Keel Template Size Preservation Trial Keel Size Preservation Trial Keel Size Preservation Trial Keel Size Preservation Trial Keel Size Preservation Trial Keel Size Preservation MB Tray Inserter/Impactor Preservation Tibial Keel Osteotome Fixed Preservation Femoral Introducer Preservation Fixed Bearing Tibial Impactor Size Preservation Fixed Bearing Tibial Impactor Size Preservation Fixed Bearing Tibial Impactor Size Preservation Fixed Bearing Tibial Impactor Size Preservation Fixed Bearing Tibial Impactor Size Preservation Tibial Pressure Arm (C-Arm) Preservation Femoral Impactor Specialist Alignment Rod All-polyethylene Tibial Inserter inch (ø3.2 mm) Headless Steinmann Drill Pins Specialist 2 Steinmann Pin Inserter mm Drill (127 mm long) Specialist 2 Pin Remover Specialist 2 Ankle Clamp Specialist 2 Resection Guide Preservation Sawblades Uni Blade - Old Stryker 70 x 9.5 x 1.27 mm Uni Blade - New Stryker 70 x 9.5 x 1.27 mm Uni Blade - Old Zimmer 70 x 9.5 x 1.27 mm Uni Blade - New Zimmer 70 x 9.5 x 1.27 mm Uni Blade - AO/Sod 70 x 9.5 x 1.27 mm Uni Blade - 3M 70 x 9.5 x 1.27 mm Preservation Sterilisation Tray Preservation Sterilisation Tray Preservation X-Ray Templates Preservation Mobile Bearing X-ray Template Preservation Tibial Resection X-ray Template Preservation Femur and Fixed Bearing Template 34

38 INSTRUMENT PRODUCT CODES Instruments Preservation Femoral Rotation Guide Spacer Block 5 mm Preservation System Handle , 004 Preservation Tibial Cutting Block , 002, 003, 004, 005 Preservation Femoral Rotation and Sizing Guide Size 1, 2, 3, 4, Preservation Tibial Stylus , 012, 013, 014, 015 Preservation Femoral Finishing Guide Size 1, 2, 3, 4, Preservation L-Cut Guide Preservation Femoral Peg Drill Guide Preservation Alignment Guide , 022, 023, 024, 025 Preservation Tibial Keel Template Size 1, 2, 3, 4, , , Preservation Femoral Spacer Block - 1 mm, 2 mm, 3 mm Defect , 050, 052 Preservation Tibial Spacer Block 9.5 mm, 11.5 mm, 13.5 mm , , 110, 112, 208 Preservation Trial Keel Size 1, 2, 3, 4, Preservation Tibial Keel Osteotome Fixed Preservation Femoral Distal Cutting Block Preservation Femoral Introducer , 002, 003, 004, 005 Preservation Femoral Trial , 022, 023, 024, 025 Preservation Peg Trial Femur 35

39 INSTRUMENT PRODUCT CODES , 042, 043, 044, 045 Preservation Fixed Bearing Tibial Impactor Size 1, 2, 3, 4, 5 Preservation Sawblades Uni Blade - Old Stryker 70 x 9.5 x 1.27 mm Preservation Tibial Pressure Arm (C-Arm) Uni Blade - New Stryker 70 x 9.5 x 1.27 mm Preservation Mobile Bearing Tray Inserter/Impactor Uni Blade - Old Zimmer 70 x 9.5 x 1.27 mm Specialist 2 Alignment Rod Uni Blade - New Zimmer 70 x 9.5 x 1.27 mm All-polyethylene Tibial Inserter Uni Blade - AO/Sod 70 x 9.5 x 1.27 mm Specialist 2 Steinmann Pin Inserter Uni Blade - 3M 70 x 9.5 x 1.27 mm Specialist 2 Pin Remover Specialist 2 Ankle Clamp Specialist 2 Resection Guide Preservation Femoral Impactor 36