Zenith. Total Ankle Replacement Surgical technique

Transcription

1 Total Ankle Replacement Surgical technique

2 Contents Operative summary 4 Pre-operative planning and templating 6 Patient positioning 6 Exposure 6 Saw blades 7 Joint line definition 7 Tibial alignment jig 8 Tibial cut 8 Talar cut 9 Malleolar cut 9 Tibial sizing 10 Tibial window preparation 10 Tibial window removal 11 Tibial trial 11 Talus sizing and centring 12 Anterior talus preparation 12 Talar drill guide 13 Posterior cut 13 Talus trial 14 Mobile insert selection 14 Final implants 15 Wound closure 15 Post-operative care 15 Compatibility chart 16 Ordering information 17 Instrumentation 18 2

3 Technology Reproducibility Stability Simplification through innovation 3

4 Operative summary a. Joint line definition b. Tibial alignment jig c. Tibial cut d. Talar cut e. Malleolar cut f. Tibial sizing g. Tibial window preparation h. Tibial window removal 4

5 i. Tibial trial j. Talus sizing and centring k. Anterior talus preparation l. Talar drill guide m. Posterior cut n. Talus trial o. Mobile insert selection p. Final implants 5

6 MAGNIFICATION: 115% (1:1.15) Talar Components Size Size TEMPLATE No: REV: 01 ECR: Size Size 4 DATE: 20/April/07 Pre-operative planning and templating It is recommended that patient X-rays should be studied pre-operatively to gauge any potential difficulties and to plan for them accordingly. X-rays should include accurate anterior-posterior (A-P) and lateral standing views of the complete foot and ankle of both feet. Templating can be achieved using X-rays or digital imaging. Patient positioning The patient is placed in a supine position, with a pad under the ipsilateral buttock, to prevent uncontrolled external rotation of the foot. The foot and knee should be free for rotation and alignment. A tourniquet should be used in most cases. The patient should be draped with the knee exposed to allow alignment. Exposure The surgical exposure is in line with current practice for total ankle replacement. The recommended approach is through an anterior incision over the joint line in most cases. The incision should be approximately 10-15cm long and extend proximally to allow adequate fixation for the tibial jig. The incision may be routed laterally or medially, to accommodate a previous A-L or A-M approach. After the fascia has been incised in a longitudinal fashion, the incision is deepened between the tendon of the tibialis anteriomediola, and the extensor hallucis tendons laterally. The neurovascular bundle is protected by reflecting it laterally with the extensor hallucis longus (EHL) tendon. A complete anterior capsulectomy is performed to provide access to the ankle joint line. 6

7 It is important for soft tissue balancing to be considered at this stage. Any required ligament soft tissue releases should be made to ensure that the talus can be brought into neutral alignment in this position. It should be possible for the position of the foot to be determined. The calcaneum should be in neutral to 7º of valgus. The forefoot should be neutral so that all the metatarsal heads are lying at the same level. Note: Self-retaining retractors should be used with great care during total ankle replacement surgery and where possible should not be used at all. This is a precautionary measure against pressure necrosis which can be caused by using a self-retaining retractor in the neutral position and not removing it prior to plantar-flexion. Saw blades Saw blades of the following dimensions are recommended for use with the Zenith instruments. Oscillating saw blade: 1.27mm thick with non-offset teeth, 60mm length and 15mm width. Reciprocating saw blade: 1.27mm thick with non-offset teeth and 40mm length. These specifications have been determined by the instrumentation and allow defined accurate cuts. Note: The saw blades provided with the system may not be compatible with the power tools being used. This should be checked prior to use. Step 1. Joint line definition Having checked the alignment of the joint and released soft tissues appropriately, the level of the joint line should be determined. It is important for any osteophytes to be removed from the ankle joint line in order to provide adequate visualisation and definition of the joint line. All osteophytes impinging medially and laterally should be removed. The 2mm spacer is inserted into the joint gap so that it is held between the tibia and talus. A thicker 3mm or 4mm spacer can be used in cases of bone loss and joint deformity. 7

8 Step 2. Tibial alignment jig The two parts of the tibial alignment jig and the tibialtalar block are assembled. The shaft of the jig is aligned parallel to the longitudinal axis of the tibia and proximally aligned with the tibial tuberosity. The tibial-talar block locates over the spacer using the dedicated slot. The proximal aspect is adjusted to the correct length and then secured below the knee with a silicone strap. A-P positioning of the jig is adjusted by loosening the screw on the fixing block. Once the jig has been adjusted the screw is tightened. The M-L position of the jig can also be adjusted. This is done by sliding the fixing block medially or laterally. The medial end of the tibial cut should be aligned to the lateral edge of the medial malleolus. Note: Once the alignment of the jig is satisfactory the proximal pins are fixed to maintain its position. The foot is then brought into a 5 equinus position and secured in place by two pins distally in the talus. Step 3. Tibial cut The tibial-talar block provides three tibial cutting options. The slots are 3mm apart allowing a standard cut and +/- 3mm cuts, depending on the condition of the tibia and the amount of bone to be resected. The medial hole is drilled first to dissipate any stresses thus protecting the medial mallelous. 8

9 An oscillating blade is then used to make the tibial cut. Step 4. Talar cut The most distal slot on the tibial-talar block is used to make the talar cut. An oscillating saw is used. Note: Ensure that the foot is not moved from the neutral position in between tibial and talus cuts. The cuts must be parallel to each other when the foot is in neutral for accurate implant positioning. Step 5. Malleolar cut The tibial-talar block is removed from the jig. The tibial alignment jig should remain in place for later preparation. A vertical cut is made using a reciprocating saw in a straight line starting at the tibial distal face and ending at the medial hole that was made earlier. In order to remove the resected bone it may be necessary to extend the horizontal tibial cut laterally. Extra care must be taken to ensure that the fibula is not notched. 9

10 By undertaking the tibial and talar cuts consecutively it is easier to remove the posterior part of the talus, providing an optimal work space. Use of a laminar spreader facilitates this. Step 6. Tibial sizing The tibial sizing instrument is positioned such that the posterior lip hooks onto the posterior tibia. The correct size is read off the scale. Note: If the size indicated falls between two sizes then the tibia should be prepared for the smaller size and then up-sized if necessary. Step 7. Tibial window preparation The tibial window is prepared using the selected tibial window cutting block. This block is chosen from a range of six blocks based on the following criteria: 1. The thickness of the initial distal tibia cut. If a standard cut is made then the standard blocks should be used; if a -3mm cut is made then the -3mm block should be used; if a +3mm cut is made than the +3mm block should be used. 2. The size is measured by the tibial sizer in the A-P plane. This defines the stem of the implant. The blocks are marked for use with sizes 1/2 and sizes 3/4. 10

11 The correct block is located onto the jig and the 3.2mm drill is used to prepare the proximal radius of the tibial window. Note: A reciprocating saw is used to cut both sides of the tibial window. It is important to use the correct length of sawblade to prevent cutting bicortically. Both the block and the jig can be removed after this stage. Step 8. Tibial window removal The tibial window is removed by using the curved osteotome as a punch. Tapping the proximal end of the prepared tibial window allows the bone to be removed in one piece. It is important that this window of bone is removed and stored carefully as it will be repositioned at the end of the procedure. The tibial window is then deepened such that the stem will be in the mid-point of the tibia in both planes. Step 9. Tibial trial The tibial trial is assembled onto the handle and inserted into the tibia using a tilt and lift action. Note: Care must be taken when inserting these trials. They should not be rotated or have pressure exerted on them to avoid fracture of the medial or lateral malleolus. The tibial trial should rest on the anterior cortex of the tibia. If the trial does not fit as expected then a larger trial can be used, and excess bone can be removed until the trial fits in place. The trial impactor can be used to ensure seating of the implant. In general, down-sizing should be avoided, however up-sizing can be achieved by using a larger tibial window cutting block (following step 7). 11

12 Step 10. Talus sizing and centring It is important to ensure the talus component sits centrally beneath the tibia in order to restore the natural biomechanics of the ankle. Each of the talus sizers are trialled on the flat talus cut made in step 4 of the procedure. The most appropriate size is the one that fits closest to the A-P and M-L planes and also locates easily beneath the tibial window. The feeler is moved across the posterior radius of the talus sizer to confirm sizing positioning and to check for posterior osteophytes. The size selected should not overhang in A-P or M-L planes. If this does happen a smaller sizer should be selected. Once the correct talus sizer has been chosen, a pin is located through the central pin hole. The talus sizer is then removed leaving the pin in place. This pin marks the central location of the talus and hence the centre of rotation of the talus. Occasional difficulty can occur with removal of the sizer. Under these circumstances the pin can be temporarily removed and then carefully replaced. Step 11. Anterior talus preparation The anterior talus guide locates around the pin in the talus to ensure that the guide sits in the correct A-P position. Alignment with the second metatarsal is performed using the guide rod which locates at the base of the guide. This gives a guide to rotation of the talar component around a longitudinal axis. The talus guide is fixed in place using two driven pins through the pin holes. The correct reamer tool is chosen depending on the previously selected talus sizer. Each reamer directly corresponds to the four talus sizes to ensure the correct amount of bone is resected from each face depending on the size chosen. 12

13 The reamer is inserted through the introduction hole and is moved around within the guide until the anterior face has been fully resected. The guide block pin is then removed revealing the two, flat prepared surfaces of the talus, one anteriorly and one superiorly. Step 12. Talar drill guide The talar guide is placed against the prepared anterior/ superior talus. The M-L position of the peg hole is determined by aligning the pin hole directly beneath the tibal window. The block is then pinned in place. The peg holes are drilled by using the short 4.5mm drill through the anterior guide holes in the block as shown. Step 13. Posterior cut The appropriate posterior cutting block is placed against the anterior/superior talus with the pins locating into the holes. An oscillating saw is used in the slot to make the posterior cut. Note: Care must be taken not to take the cut too far and damage the posterior soft tissue. 13

14 Step 14. Talus trial The correct talus size (as defined by the talus sizer) should be trialled to ensure that the chosen implant is the best fit. Any further bone removal should be carried out at this stage to ensure that the trial implant fits perfectly. The talar impactor can be used to ensure that the trial is fully seated in direct line with the pegs. The tibial trial is then re-introduced and fully seated. Step 15. Mobile insert selection The mobile insert trial must match the size of the talus (see compatibility chart on page 16). The thickness of the mobile insert is defined by the condition of the ankle in relation to the soft tissue and ligaments, ensuring joint stability. The trial is inserted in between the trial tibia and talus. Varus/valgus tests are performed to confirm that the mobile insert and the talus remain in full contact medially and laterally. The mobile bearing must slide on the tibial component in the coronal plane. During these checks, the joint surfaces must remain in contact. Any gaps or tilting of the insert indicate instability and must be remedied by the insertion of a thicker bearing and if necessary ligament balancing procedures including lateral ligament reconstruction. With the trials in place, the ankle joint must have a good range of movement. Plantar-flexion should be up to 45 and dorsi-flexion should be up to 20. If dorsi-flexion is found to be insufficient or if there is an equinus deformity, then it will be necessary to lengthen the Achilles tendon, since this will preserve the correct ligament tension and give a satisfactory range of movement into dorsi-flexion. Do not insert a thinner mobile bearing, as this will cause instability. Do not insert a thicker mobile bearing as this will cause joint stiffness and pain. 14

15 Step 16. Final implants The final implants are placed into position and impacted until fully seated. The bone wedge is replaced in the window of the tibia, grafting it in place, if required, with small pieces of cancellous bone. Step 17. Wound closure The wound should be closed in layers with particular care taken to close the retinaculum over the tendons. Step 18. Post-operative care Patients should be mobilised initially non-weight bearing in a cast below the knee for two weeks. Once the wound is healed and providing that there are no complications, the patient can be mobilised partial weight bearing in a removable cast for a further four weeks at which point radiographs should be taken. Following satisfactory radiographs, the patient should go through a course of physiotherapy. 15

16 Compatibility chart Size 1 Size 2 Size 3 Size 4 The tibial size is selected before the talus and mobile insert. Use of the tibial sizer and trial tibial component ensures that the correct sized prostheses are chosen. The talus is sized independently of the tibia and the correct size is based on intra-operative talus sizing instruments. The previously selected talus determines the size of the mobile insert as it conforms to the deep sulcus on the talus bearing surface. The thickness of the mobile insert can vary depending on the original condition of the ankle as well as the ligaments and the soft tissue surrounding it. 5, 6, 7, 8, 10, 12mm 5, 6, 7, 8, 10, 12mm 5, 6, 7, 8, 10, 12mm 5, 6, 7, 8, 10, 12mm Size 1 Size 2 Size 3 Size 4 16

17 Ordering information Talus component Tibia component Size 1 Cementless Size 2 Cementless Size 3 Cementless Size 4 Cementless Size 1 Cementless Size 2 Cementless Size 3 Cementless Size 4 Cementless Bearing UHMWPE Size 1 x 5mm Size 2 x 5mm Size 3 x 5mm Size 4 x 5mm Size 1 x 6mm Size 2 x 6mm Size 3 x 6mm Size 4 x 6mm Size 1 x 7mm Size 2 x 7mm Size 3 x 7mm Size 4 x 7mm Size 1 x 8mm Size 2 x 8mm Size 3 x 8mm Size 4 x 8mm Size 1 x 10mm Size 2 x 10mm Size 3 x 10mm Size 4 x 10mm Size 1 x 12mm Size 2 x 12mm Size 3 x 12mm Size 4 x 12mm 17

18 Instrumentation Tray mm spacer mm spacer mm spacer EM jig Tibia/talar cutting block Tibia sizer Tibia keel cutting block - size 1 / Tibia keel cutting block - size 1 / Tibia keel cutting block - size 1 / Tibia keel cutting block - size 3 / Tibia keel cutting block - size 3 / Tibia keel cutting block - size 3 / Curved osteotome Anterior talar cutting jig Anterior talar cutting jig alignment rod Talar sizer + centre guide size Talar sizer + centre guide size Talar sizer + centre guide size Talar sizer + centre guide size Anterior talar cutter size Anterior talar cutter size Anterior talar cutter size Anterior talar cutter size Posterior talus feeler Posterior talar cutting block - size Posterior talar cutting block - size Posterior talar cutting block - size Posterior talar cutting block - size Posterior talar cutting block handle Talar drill guide mm drill mm stopped drill Pin adaptor Pin set box (with pins inside) Pin puller 18

19 Tray Talar trial extractor Talar trial - size Talar trial - size Talar trial - size Talar trial - size Tibia trial - size Tibia trial - size Tibia trial - size Tibia trial - size Tibia/insert trial handle Trial insert - size 1 / 5mm Trial insert - size 1 / 6mm Trial insert - size 1 / 7mm Trial insert - size 1 / 10mm Trial insert - size 1 / 12mm Trial insert - size 2 / 5mm Trial insert - size 2 / 6mm Trial insert - size 2 / 7mm Trial insert - size 2 / 8mm Trial insert - size 2 / 10mm Trial insert - size 2 / 12mm Trial insert - size 3 / 5mm Trial insert - size 3 / 6mm Trial insert - size 3 / 7mm Trial insert - size 3 / 8mm Trial insert - size 3 / 10mm Trial insert - size 3 / 12mm Trial insert - size 4 / 5mm Trial insert - size 4 / 6mm Trial insert - size 4 / 7mm Trial insert - size 4 / 8mm Trial insert - size 4 / 10mm Trial insert - size 4 / 12mm Talar impactor Tibia impactor 19

20 The Corinium Centre Cirencester, GL7 1YJ t: +44 (0) f: +44 (0) e: Printed on 9lives 80 which contains 80% total recycled fibre and is produced at a mill which holds the ISO for Environmental Management Systems. The pulp is bleached using Elemental Chlorine Free processes Corin P No I799 Rev3 06/2009 ECR 8876 Zenith is a registered trademark of Corin