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Wheeless' Textbook of Orthopaedics

Wheeless' Textbook of Orthopaedics

C.R. Wheeless MD

URL
Wheeless' Textbook of Orthopaedics

Revision Total Knee Arthroplasty:

- Work Up of the Painful TKR: - TKR following HTO; - PreOperative Considerations: - patellar component: - if the patellar component does not appear to be causing symptoms, and if it appears to be well fixed at surgery, consider leaving it in place; - femoral component: - determine whether the joint line has been elevated: - on average the joint line is 12-16 mm above the fibula, 48-54mm below the adductor tubercle, and 25mm below the medial and lateral epicondyles; - these distances vary from person to person with shorter people tending to be at the lower end of the above given ranges; - this can be measured from the adductor tubercle to the joint line (and compared to the opposite knee) or can be measured from the tip of the fibular head to the joint line (and compared to the opposite knee); - films of the native contralateral knee or of the ipsilateral knee prior to TKA can be used to give exact measurements; - in many cases, the joint line is 2 finger breadth above the tibial tubercle; - proximal placement of the revision femoral component moves the joint line proximally, and the kinematics of knee are significantly distorted; - see: malposition of the joint line: - this also results in iatrogenic patella baja w/ inefficient quad mechanism and possible impingement of patella on prosthetic tibial spine; - it is therefore important that revision femoral component be seated distally enough to come close to restoring original level of knee joint line; - evaluation and management of bone defects - revision for stiff total knee arthroplasty (Christensen, Vail, unpublished data 1998) - 13 stiff and painful TKAs (range of motion less than 70 degrees) were revised with a posterior stabilized condylar prosthesis and evaluated after an average of 12.3 months (range, 2-25 months); - on average, the range of motion increased from 42.1 degrees pre-operatively to 85.2 degrees post-operatively; - the mean flexion contracture went from 13.8 degrees to 2.9 degrees; - 5 of 13 revisions required a quadriceps snip for exposure; - no quadriceps turndowns or tibial tubercle osteotomies were needed; - 4 of 13 patients required closed manipulation in the first month following revision surgery. - other complications included persistent stiffness, patella infera, and 2 minor wound problems. - all patients had improvement in pain and were satisfied; - Selection of Implants: - implants will be PCL sacrificing w/ medullary stems; - be prepared to add wedges to defects; - revision femoral component: - medullary stems: - addition of a stem to the component generally is desirable in all techniques used for bone defects; - stem transfers up to 30% of force from bone subtending component to point more proximally on the femur and more distally on tibia; - as noted by S.B. Haas et al, 1995, cement should be applied to the medullary surfaces but usually should not be applied to the medullary stems; - press fit stems remove less bone than cemented stems and are easier to remove should infection occur; - cementing stems causes stress shielding of the metaphysis and makes the subsequent revision more difficult - extensive soft tissue dissection on the medial and posterior aspect of tibia may be necessary to expose the proximal tibia; - reference: - V-Y quadricepsplasty in total knee arthroplasty. - thickened capsule and synovium may need to be removed; - need to recreate the recess between the medial and lateral femoral condyles; - Surgical Approach: (Surgical Approach for Primary TKR); - w/ more than one longitudinal incision, choose the more lateral incision since a larger medial flap tends to have a better blood supply; - longer incisions tend to cause less tension on the skin - if unsure, one can perform a "sham" incision through the skin and down to the fascia and then evaluate the wound healing in that location prior to performing revision TKA; - all medial and lateral dissection must be subfascial; - subcutaneous dissection will lead to wound slough; - the first goal is to evert the patella without avusing the patellar tendon from the tibial tubercle; - one must first debride scar from the suprapatellar pouch, the medial and lateral gutters, and the patellar tendon; - also consider early lateral retinacular release for optimal exposure; - lateral retinacular release will assist in eversion of the patella; - if eversion continues to be difficult, extension of the longitudinal quadriceps division proximally, debridement of tibial and patellar osteophytes, and a lateral retinacular release helps; - increased subperiosteal exposure of the proximal tibia is also helpful; - the lateral aspect should be exposed to Gerdy's tubercle (do not elevate the ITB insertion); - medial exposure elevating the superficial and deep attachments of the MCL can increase external rotation of the tibia to help patellar evesion; - many authors have stated that this does not cause post-operative instability; - other strategies for everting the patella - "transverse quadriceps snip": - a transverse incision extending across the proximal quadriceps which extends lateral to the longitudinal incision; - w/ transverse snip, eversion of the patella is not necessary, rather it can simply be retracted to the side (hence there is no stress on the patellar tendon); - alternatively an oblique cut across the proximal quadriceps tendon angled distally; - this can be extended as far as is needed to get the patella out of the way; - when using a "snip", eversion of the patella is not necessary since it often can simply be retracted to the side (hence there is no stress on the patellar tendon); - Coonse-Adams quadriceps turndown: - if necessary, the quad snip can be extended distally to the lateral aspect of the patella to complete a quadripceps turndown; - of course, the greater the snip, the more morbidity to the patient; - w/ a full turndown, the leg should be kept in extension for at least 2 weeks postoperatively before reinitiating rehabilitation; - tibial tubercle osteotomy - begin by subperiosteally dissecting 5cm distal to the tubercle medially; - pre-drill 2-3 holes for re-attachment. - use an oscillating saw or an osteotome to create an osteotomy on the medial side of the tubercleabout 6-7cm in length, 2cm wide, and 9-10mm at its thickest point; - begin the osteotomy about 1 cm distal to the tibial plateau so the bone acn "key in" when the osteotomy is repaired and proximal migration will not occur; - leave the lateral soft-tissue hinge intact; - repair with two 6.5 or 7.3 mm screws directed around the tibial stem or with 3- 16 gauge wires; - keep cement out of the osteotomy site; - Femoral Component Removal: - remove polyethylthene liner first to improve exposure; - beware that w/ revision TKR posterior neurovascular structures may be scarred and adherent to posterior capsule & hence may be at risk for injury during bone cuts and soft tissue dissection; - in TKR revision, remove the femoral component first, unless the tibia has an obstructing central eminence; - steps in femoral component removal - expose bone-component interface; - begin with a half inch straight osteotome under the anterior flange; - use a half inch curved osteotome to free-up the interface on the medial and lateral aspects of the notch; - use a gigli saw placed under the anterior flange and pull anteriorally against the component while sawing distally until one reaches the pegs on the femoral component; - use a bone tamp and mallet to remove the component; - if the component is still fixed, the gigli saw can be placed around the posterior condyles and one can saw distally to release that interface; - well fixed porous femoral component can pose a serious problem if bone has solidly healed into porous coated pegs; - these cannot be easily reached by osteotomes or high speed burrs; - if gentle axial extraction does not free the component, make a small portal in the side of the distal femur to expose atleast part of the peg, and work around it; - Gigli saw may be useful to disrupt ingrown bone (esp anteriorly); - Tibial Component Removal: - all poly components can be removal w/ oscillating saw; - remove tibial components that are made entirely of polyethylene by sawing across interface & thru any keel, post, or pegs on component; - with the components removed, saw a thin layer of bone off the proximal tibia and distal femur, taking the cement layer with it; - a bone-metal interface can be removed w/ high speed burrs and flexible osteotomes; - following the disruption of the bone-metal interface, the axial extractor w/ its attached slap hammer can be applied; - with the components removed, saw a thin layer of bone off the proximal tibia and distal femur, taking the cement layer with it; - if an intramedullary stem remains, this can be sectioned with an osteotome and removed in pieces; - steps in tibial component removal: - expose interface with knife or cautery: - begin dividing the interface with a half inch straight osteotome; - continue with a wider osteotome or with an oscillating saw to completely disrupt the bone metal interface; - use a bone tamp or an axial extractor with a slap hammer to remove the component; - carefully remove remaining cement, irrigate bony surfaces and remove fibrous tissue; - a bone-metal interface can be removed w/ high speed burrs and flexible osteotomes; - Patellar Component Removal: - if the patellar component does not appear to be causing symptoms, and if it appears to be well fixed at surgery, consider leaving it in place; - begin by clearing the soft-tissue from the bone-implant interface with a knife or cautery; - a one-inch straight osteotome can then be used to remove the component; - do not lever the component off as this can cause patellar fx; - a metal-backed patella may require a diamond burr for removal; - medullary stems: - typically used if greater than 50 % of the distal femur or proximal tibia required grafting or if there is a peripheral defect requiring a block, wedge, or graft; - stem lengths required for press fit are usually at least 100mm for the tibia and 100-150mm for the femur; - reaming should cease once firm resistance is encountered; - it is not necessary to have direct cortical contact, inorder to avoid excessive bone loss; - generally, stem diameter will be the same size as the reaming diameter; - once one has reached the desired stem diameter, a sleeve of that same diameter can be placed on the intramedullary rod and tibial and femoral preparation can be performed using the appropriate guides; - stems are typically press fitted. Cement is only used if press fit is not possible; - these situations may include severe osteoporosis and poor bone quality where allografting may be needed; - other situations where cement is used is to improve rotational stability; - when using cement, a distal cement plug is suggested; - Insertion of the Patellar component: - one should consider not resurfacing the patella if less than 12mm of native bone remains (fx or early loosening may result); - some suggest sewing a remnant of the patellar fat pad into the patella if it is not resurfaceable; - revision patellas are thicker to make up for lost bone and have shorter pegs; - if a primary patellar component is having its peg shortened for use in a revision situation, cut the peg with an oscillating saw away from the wound to prevent a shower of polyethylene particles; - following revision, the patellar height should be around 24-26 mm; - Reaming for Medullary Stems: - after reaming to 12 mm, continue to procede slowly by 1 mm increments; - reaming should cease once firm resistance is encountered; - it is not necessary to have direct cortical contact, inorder to avoid excessive bone loss; - generally, stem diameter will be the same size as the reaming diameter; - Insertion of Components: - its necessary to be aware of the joint line position as well as as well as flexion and extension spaces; - at this point its also necessary to evaluate and manage bone defects; - Tibial Preparation: - remove 1-2mm of bone using the intramedullary guide. - be aware of the preoperative flexion stability and ROM in choosing posterior slope; - for example, if the knee was unstable in flexion preoperatively, 0 degrees posterior slope may help reduce some of the flexion gap; - Femoral Preparation: - be aware of pre-op extension gaps as this may affect resection - choose componenet size based on AP dimensions - bone will often be deficient distally and posteriorally, so be prepared to augment these areas; - insert IM rod with appropriate sleeve and place IM cutting guide (we prefer 5 degrees of valgus); - remove 1-2mm of bone distally - perform anterior and posterior cuts; - both the anterior and posterior cuts should be parallel to the epicondylar axis; - be aware that increased external rotation will improve patellar tracking, increase the medial flexion gap and decrease the lateral flexion gap; - Insertion of the Trial Femoral Component: - use the femoral epicondyles to judge neutral rotation of the femoral component; - the posterior condyles may give a false reference point for rotation; - be prepared, to add wedges to the posterior condyles so that no gaps remain between posterior femoral components and the bone surface; - Insertion of Trial Tibial Component: - place an appropriately sized tibial component and stem and measure flexion and extension gaps - keep this component in position during femoral preparation; - typically it will be necessary to insert intra-medullary stems; - it is essential that the intra-medullary stem be inserted centrally in the medullary canal, which may or may not conform to the center of the cut tibial surface; - if there is a descrepancy between central medullary rod position and an optimally positioned tibial joint surface, the difference is made up w/ tibial wedges; - the tibial surface may have to be recut to conform to the wedges; - Attention to the Flexion Gap: - the flexion gap often ends up being larger than the extension gap; - determined by the height of the tibial surface and height of the posterior femoral condyle; - w/ a loose flexion gap, a femoral component of appropriate size is selected (which may mean that wedges may have to be added to the posterior condyles) - or decreasing increasing the trial polyethyelene component will also affect the flexion gap; - Attention to the Extension Gap: - once an adequate flexion gap has been established; - this is easier to manage the flexion gap since the extension gap can be increased or decreased simply by descreasing or increasing the height of distal femoral wedge-spacers, respecitvely; - place trial components and ensure that full extension and 90 degrees of flexion are attainable; - make sure that the patella tracks well and that the knee is stable through a full ROM; - Cement Considerations: - Cementing Technique: - apply cement to only condylar surfaces if press-fit stems are being used; - cement is applied to cut medullary surfaces, but in most cases cement is not placed into the medullary canal; - if stems are being cemented, consider use of a cement plug and an injection gun; - addition of antibiotics to cement: - indicated if there are additional risk factors for infection; - generally, either 600mg tobramycin or 500mg vancomycin is added per 40g bag of cement; - Addition of Antibiotics to Cement - indicated if there are additional risk factors for infection; - Complications: - infection: - may occur in 4% of patients (which is roughly 10 time higher than should occur in primary knees); - early failure: - component survivorship is roughly 80 % at 8 years; - good to excellent results occur 50-80% of the time with complications occurring 15-30%; - wound comlications should be handled aggressively with skin graft, gastrocnemius flap or free flap; - Postoperative Rehabilitation: - quadriceps snip can be rehabilitated routinely - quadriceps turndown or tubercle osteotomy requires no ROM for 2 weeks and no active extension for 2-6 weeks; Results of revision total knee arthroplasties using condylar prostheses.A comparison of primary and revision total knee arthroplasty using the kinematic stabilizer prosthesis. Hinged knee replacement in revision arthroplasty. Femoral cement removal in revision total hip arthroplasty. A biomechanical analysis. Revision knee arthroplasty in rheumatoid arthritis. Revision of septic total knee arthroplasty. Bone grafting and noncemented revision arthroplasty of the knee. Revision total knee arthroplasty. The results of revision total knee arthroplasty. Revision total knee arthroplasty for aseptic failure. Management of intraoperative femur fractures associated with revision hip arthroplasty. Results of revision total knee arthroplasty performed for aseptic loosening. Cementless reconstruction of massive tibial bone loss in revision total knee arthroplasty. Massive allografts in salvage revisions of failed total knee arthroplasties. Results of revision total knee arthroplasty associated with significant bone loss. Isolated patellar component revision of total knee arthroplasty. Reconstruction of major segmental loss of the proximal femur in revision total hip arthroplasty. Principles of bone grafting in revision total hip arthroplasty. Acetabular technique. Amputation after failed total knee arthroplasty. Revision total knee arthroplasty with use of modular components with stems inserted without cement. Mechanisms of failure of the femoral and tibial components in total knee arthroplasty. Reoperation after condylar revision total knee arthroplasty. MJ Stuart et al. CORR. Vol 286. 1993. p 168-173.

Revision Total Knee Arthroplasty:

- Work Up of the Painful TKR: - TKR following HTO; - PreOperative Considerations: - patellar component: - if the patellar component does not appear to be causing symptoms, and if it appears to be well fixed at surgery, consider leaving it in place; - femoral component: - determine whether the joint line has been elevated: - on average the joint line is 12-16 mm above the fibula, 48-54mm below the adductor tubercle, and 25mm below the medial and lateral epicondyles; - these distances vary from person to person with shorter people tending to be at the lower end of the above given ranges; - this can be measured from the adductor tubercle to the joint line (and compared to the opposite knee) or can be measured from the tip of the fibular head to the joint line (and compared to the opposite knee); - films of the native contralateral knee or of the ipsilateral knee prior to TKA can be used to give exact measurements; - in many cases, the joint line is 2 finger breadth above the tibial tubercle; - proximal placement of the revision femoral component moves the joint line proximally, and the kinematics of knee are significantly distorted; - see: malposition of the joint line: - this also results in iatrogenic patella baja w/ inefficient quad mechanism and possible impingement of patella on prosthetic tibial spine; - it is therefore important that revision femoral component be seated distally enough to come close to restoring original level of knee joint line; - evaluation and management of bone defects - revision for stiff total knee arthroplasty (Christensen, Vail, unpublished data 1998) - 13 stiff and painful TKAs (range of motion less than 70 degrees) were revised with a posterior stabilized condylar prosthesis and evaluated after an average of 12.3 months (range, 2-25 months); - on average, the range of motion increased from 42.1 degrees pre-operatively to 85.2 degrees post-operatively; - the mean flexion contracture went from 13.8 degrees to 2.9 degrees; - 5 of 13 revisions required a quadriceps snip for exposure; - no quadriceps turndowns or tibial tubercle osteotomies were needed; - 4 of 13 patients required closed manipulation in the first month following revision surgery. - other complications included persistent stiffness, patella infera, and 2 minor wound problems. - all patients had improvement in pain and were satisfied; - Selection of Implants: - implants will be PCL sacrificing w/ medullary stems; - be prepared to add wedges to defects; - revision femoral component: - medullary stems: - addition of a stem to the component generally is desirable in all techniques used for bone defects; - stem transfers up to 30% of force from bone subtending component to point more proximally on the femur and more distally on tibia; - as noted by S.B. Haas et al, 1995, cement should be applied to the medullary surfaces but usually should not be applied to the medullary stems; - press fit stems remove less bone than cemented stems and are easier to remove should infection occur; - cementing stems causes stress shielding of the metaphysis and makes the subsequent revision more difficult - extensive soft tissue dissection on the medial and posterior aspect of tibia may be necessary to expose the proximal tibia; - reference: - V-Y quadricepsplasty in total knee arthroplasty. - thickened capsule and synovium may need to be removed; - need to recreate the recess between the medial and lateral femoral condyles; - Surgical Approach: (Surgical Approach for Primary TKR); - w/ more than one longitudinal incision, choose the more lateral incision since a larger medial flap tends to have a better blood supply; - longer incisions tend to cause less tension on the skin - if unsure, one can perform a "sham" incision through the skin and down to the fascia and then evaluate the wound healing in that location prior to performing revision TKA; - all medial and lateral dissection must be subfascial; - subcutaneous dissection will lead to wound slough; - the first goal is to evert the patella without avusing the patellar tendon from the tibial tubercle; - one must first debride scar from the suprapatellar pouch, the medial and lateral gutters, and the patellar tendon; - also consider early lateral retinacular release for optimal exposure; - lateral retinacular release will assist in eversion of the patella; - if eversion continues to be difficult, extension of the longitudinal quadriceps division proximally, debridement of tibial and patellar osteophytes, and a lateral retinacular release helps; - increased subperiosteal exposure of the proximal tibia is also helpful; - the lateral aspect should be exposed to Gerdy's tubercle (do not elevate the ITB insertion); - medial exposure elevating the superficial and deep attachments of the MCL can increase external rotation of the tibia to help patellar evesion; - many authors have stated that this does not cause post-operative instability; - other strategies for everting the patella - "transverse quadriceps snip": - a transverse incision extending across the proximal quadriceps which extends lateral to the longitudinal incision; - w/ transverse snip, eversion of the patella is not necessary, rather it can simply be retracted to the side (hence there is no stress on the patellar tendon); - alternatively an oblique cut across the proximal quadriceps tendon angled distally; - this can be extended as far as is needed to get the patella out of the way; - when using a "snip", eversion of the patella is not necessary since it often can simply be retracted to the side (hence there is no stress on the patellar tendon); - Coonse-Adams quadriceps turndown: - if necessary, the quad snip can be extended distally to the lateral aspect of the patella to complete a quadripceps turndown; - of course, the greater the snip, the more morbidity to the patient; - w/ a full turndown, the leg should be kept in extension for at least 2 weeks postoperatively before reinitiating rehabilitation; - tibial tubercle osteotomy - begin by subperiosteally dissecting 5cm distal to the tubercle medially; - pre-drill 2-3 holes for re-attachment. - use an oscillating saw or an osteotome to create an osteotomy on the medial side of the tubercleabout 6-7cm in length, 2cm wide, and 9-10mm at its thickest point; - begin the osteotomy about 1 cm distal to the tibial plateau so the bone acn "key in" when the osteotomy is repaired and proximal migration will not occur; - leave the lateral soft-tissue hinge intact; - repair with two 6.5 or 7.3 mm screws directed around the tibial stem or with 3- 16 gauge wires; - keep cement out of the osteotomy site; - Femoral Component Removal: - remove polyethylthene liner first to improve exposure; - beware that w/ revision TKR posterior neurovascular structures may be scarred and adherent to posterior capsule & hence may be at risk for injury during bone cuts and soft tissue dissection; - in TKR revision, remove the femoral component first, unless the tibia has an obstructing central eminence; - steps in femoral component removal - expose bone-component interface; - begin with a half inch straight osteotome under the anterior flange; - use a half inch curved osteotome to free-up the interface on the medial and lateral aspects of the notch; - use a gigli saw placed under the anterior flange and pull anteriorally against the component while sawing distally until one reaches the pegs on the femoral component; - use a bone tamp and mallet to remove the component; - if the component is still fixed, the gigli saw can be placed around the posterior condyles and one can saw distally to release that interface; - well fixed porous femoral component can pose a serious problem if bone has solidly healed into porous coated pegs; - these cannot be easily reached by osteotomes or high speed burrs; - if gentle axial extraction does not free the component, make a small portal in the side of the distal femur to expose atleast part of the peg, and work around it; - Gigli saw may be useful to disrupt ingrown bone (esp anteriorly); - Tibial Component Removal: - all poly components can be removal w/ oscillating saw; - remove tibial components that are made entirely of polyethylene by sawing across interface & thru any keel, post, or pegs on component; - with the components removed, saw a thin layer of bone off the proximal tibia and distal femur, taking the cement layer with it; - a bone-metal interface can be removed w/ high speed burrs and flexible osteotomes; - following the disruption of the bone-metal interface, the axial extractor w/ its attached slap hammer can be applied; - with the components removed, saw a thin layer of bone off the proximal tibia and distal femur, taking the cement layer with it; - if an intramedullary stem remains, this can be sectioned with an osteotome and removed in pieces; - steps in tibial component removal: - expose interface with knife or cautery: - begin dividing the interface with a half inch straight osteotome; - continue with a wider osteotome or with an oscillating saw to completely disrupt the bone metal interface; - use a bone tamp or an axial extractor with a slap hammer to remove the component; - carefully remove remaining cement, irrigate bony surfaces and remove fibrous tissue; - a bone-metal interface can be removed w/ high speed burrs and flexible osteotomes; - Patellar Component Removal: - if the patellar component does not appear to be causing symptoms, and if it appears to be well fixed at surgery, consider leaving it in place; - begin by clearing the soft-tissue from the bone-implant interface with a knife or cautery; - a one-inch straight osteotome can then be used to remove the component; - do not lever the component off as this can cause patellar fx; - a metal-backed patella may require a diamond burr for removal; - medullary stems: - typically used if greater than 50 % of the distal femur or proximal tibia required grafting or if there is a peripheral defect requiring a block, wedge, or graft; - stem lengths required for press fit are usually at least 100mm for the tibia and 100-150mm for the femur; - reaming should cease once firm resistance is encountered; - it is not necessary to have direct cortical contact, inorder to avoid excessive bone loss; - generally, stem diameter will be the same size as the reaming diameter; - once one has reached the desired stem diameter, a sleeve of that same diameter can be placed on the intramedullary rod and tibial and femoral preparation can be performed using the appropriate guides; - stems are typically press fitted. Cement is only used if press fit is not possible; - these situations may include severe osteoporosis and poor bone quality where allografting may be needed; - other situations where cement is used is to improve rotational stability; - when using cement, a distal cement plug is suggested; - Insertion of the Patellar component: - one should consider not resurfacing the patella if less than 12mm of native bone remains (fx or early loosening may result); - some suggest sewing a remnant of the patellar fat pad into the patella if it is not resurfaceable; - revision patellas are thicker to make up for lost bone and have shorter pegs; - if a primary patellar component is having its peg shortened for use in a revision situation, cut the peg with an oscillating saw away from the wound to prevent a shower of polyethylene particles; - following revision, the patellar height should be around 24-26 mm; - Reaming for Medullary Stems: - after reaming to 12 mm, continue to procede slowly by 1 mm increments; - reaming should cease once firm resistance is encountered; - it is not necessary to have direct cortical contact, inorder to avoid excessive bone loss; - generally, stem diameter will be the same size as the reaming diameter; - Insertion of Components: - its necessary to be aware of the joint line position as well as as well as flexion and extension spaces; - at this point its also necessary to evaluate and manage bone defects; - Tibial Preparation: - remove 1-2mm of bone using the intramedullary guide. - be aware of the preoperative flexion stability and ROM in choosing posterior slope; - for example, if the knee was unstable in flexion preoperatively, 0 degrees posterior slope may help reduce some of the flexion gap; - Femoral Preparation: - be aware of pre-op extension gaps as this may affect resection - choose componenet size based on AP dimensions - bone will often be deficient distally and posteriorally, so be prepared to augment these areas; - insert IM rod with appropriate sleeve and place IM cutting guide (we prefer 5 degrees of valgus); - remove 1-2mm of bone distally - perform anterior and posterior cuts; - both the anterior and posterior cuts should be parallel to the epicondylar axis; - be aware that increased external rotation will improve patellar tracking, increase the medial flexion gap and decrease the lateral flexion gap; - Insertion of the Trial Femoral Component: - use the femoral epicondyles to judge neutral rotation of the femoral component; - the posterior condyles may give a false reference point for rotation; - be prepared, to add wedges to the posterior condyles so that no gaps remain between posterior femoral components and the bone surface; - Insertion of Trial Tibial Component: - place an appropriately sized tibial component and stem and measure flexion and extension gaps - keep this component in position during femoral preparation; - typically it will be necessary to insert intra-medullary stems; - it is essential that the intra-medullary stem be inserted centrally in the medullary canal, which may or may not conform to the center of the cut tibial surface; - if there is a descrepancy between central medullary rod position and an optimally positioned tibial joint surface, the difference is made up w/ tibial wedges; - the tibial surface may have to be recut to conform to the wedges; - Attention to the Flexion Gap: - the flexion gap often ends up being larger than the extension gap; - determined by the height of the tibial surface and height of the posterior femoral condyle; - w/ a loose flexion gap, a femoral component of appropriate size is selected (which may mean that wedges may have to be added to the posterior condyles) - or decreasing increasing the trial polyethyelene component will also affect the flexion gap; - Attention to the Extension Gap: - once an adequate flexion gap has been established; - this is easier to manage the flexion gap since the extension gap can be increased or decreased simply by descreasing or increasing the height of distal femoral wedge-spacers, respecitvely; - place trial components and ensure that full extension and 90 degrees of flexion are attainable; - make sure that the patella tracks well and that the knee is stable through a full ROM; - Cement Considerations: - Cementing Technique: - apply cement to only condylar surfaces if press-fit stems are being used; - cement is applied to cut medullary surfaces, but in most cases cement is not placed into the medullary canal; - if stems are being cemented, consider use of a cement plug and an injection gun; - addition of antibiotics to cement: - indicated if there are additional risk factors for infection; - generally, either 600mg tobramycin or 500mg vancomycin is added per 40g bag of cement; - Addition of Antibiotics to Cement - indicated if there are additional risk factors for infection; - Complications: - infection: - may occur in 4% of patients (which is roughly 10 time higher than should occur in primary knees); - early failure: - component survivorship is roughly 80 % at 8 years; - good to excellent results occur 50-80% of the time with complications occurring 15-30%; - wound comlications should be handled aggressively with skin graft, gastrocnemius flap or free flap; - Postoperative Rehabilitation: - quadriceps snip can be rehabilitated routinely - quadriceps turndown or tubercle osteotomy requires no ROM for 2 weeks and no active extension for 2-6 weeks; Results of revision total knee arthroplasties using condylar prostheses.A comparison of primary and revision total knee arthroplasty using the kinematic stabilizer prosthesis. Hinged knee replacement in revision arthroplasty. Femoral cement removal in revision total hip arthroplasty. A biomechanical analysis. Revision knee arthroplasty in rheumatoid arthritis. Revision of septic total knee arthroplasty. Bone grafting and noncemented revision arthroplasty of the knee. Revision total knee arthroplasty. The results of revision total knee arthroplasty. Revision total knee arthroplasty for aseptic failure. Management of intraoperative femur fractures associated with revision hip arthroplasty. Results of revision total knee arthroplasty performed for aseptic loosening. Cementless reconstruction of massive tibial bone loss in revision total knee arthroplasty. Massive allografts in salvage revisions of failed total knee arthroplasties. Results of revision total knee arthroplasty associated with significant bone loss. Isolated patellar component revision of total knee arthroplasty. Reconstruction of major segmental loss of the proximal femur in revision total hip arthroplasty. Principles of bone grafting in revision total hip arthroplasty. Acetabular technique. Amputation after failed total knee arthroplasty. Revision total knee arthroplasty with use of modular components with stems inserted without cement. Mechanisms of failure of the femoral and tibial components in total knee arthroplasty. Reoperation after condylar revision total knee arthroplasty. MJ Stuart et al. CORR. Vol 286. 1993. p 168-173.
 
 
 
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