Exposure for revision knee requires using the previous incision, employing the “quad snip”, the “Banana Peel”, or the tubercle osteotomy. The “quad snip” is a 45-degree incision of the proximal extensor mechanism that helps protect the distal insertion on the tubercle. The “banana peel,” is my exposure of choice and has been used extensively for revision total knee arthroplasty (TKA) for more than 20 years in my community. We retrospectively reviewed use of this technique in a cohort of 100 consecutive patients who underwent tibial-femoral stemmed revision TKA. The technique involves peeling the patella tendon as a sleeve off the tibia, leaving the extensor mechanism intact with a lateral hinge of soft tissue. A quadriceps “snip” must be done proximally to avoid excessive tension. No patient has ever reported disruption of the extensor mechanism or decreased ability to extend the operative knee. With a mean Knee Society score of 176 (range, 95–200). Post-operative motion was 106 degrees. No patient reported pain over the tibial tubercle. The “banana peel” technique for exposing the knee during the revision TKA is a safe method that can be used along with a proximal quadriceps snip and does not violate the extensor mechanism, maintaining continuity of the knee extensors. As a last resort, tibial tubercle osteotomy as described by Whiteside, is preferred for revising porous coated stemmed tibial components and is repaired with cerclage wire or cables. Keep the osteotomy fragment at least 8–10cm long leaving a lateral soft tissue attachment

Systematic surgical exposure during revision total knee arthroplasty is essential for revision surgery. Surgical exposure protects the extensor mechanism, facilitates safe implant removal and allows for accurate reimplantation of components. The pre-operative plan is critical to achieving appropriate exposure in the revision setting. Evaluating the skin and previous incisions will aid in the exposure technique selected. The key to revision total knee arthroplasty is systematic releases. Revision total knees can be exposed with a standard medial parapatellar arthrotomy, a proximal medial tibial peel, and a quad snip. This takes tension off the stiff knee, is easy to repair, and does not require limitation of rehabilitation protocols. The patella need not be everted in the revision surgery. The Banana Peel technique is very helpful for the stiff knee. The tibial tubercle osteotomy can also be utilised in patients with extreme stiffness and can aid in removal of well-fixed tibial stems. Keep the osteotomy long (8–10 cm) and leave a lateral soft tissue bridge. Other techniques such as the quadricepsplasty or V-Y turndown are rarely needed

Surgical exposure during revision total knee arthroplasty is the most essential part of the procedure. An appropriate surgical exposure protects the extensor mechanism, facilitates safe implant removal and allows for accurate reimplantation of components and appropriate soft tissue balancing. The pre-operative plan is critical to achieving appropriate exposure in the revision setting. Evaluating the skin and previous incisions and determining range of motion will aid in deciding which exposure technique is most appropriate. The key to exposure in revision total knee arthroplasty is patience. Approximately 90% of revision total knees can be adequately exposed with a standard medial parapatellar arthrotomy, a proximal medial tibial exposure, complete synovectomy and clearing of the medial and lateral gutters. The patella need not be everted in the revision setting and extreme care must be taken to protect the extensor mechanism. In cases where standard exposure techniques are inadequate or may jeopardise the extensor mechanism, a quadriceps snip may be performed. This takes tension off the stiff knee, is easy to repair and does not require limitation of rehabilitation protocols. The tibial tubercle osteotomy is utilised in patients with extreme stiffness and to aid in removal of well-fixed tibial components. General principles include keeping the osteotomy fragment long (8–10 cm) and leaving a lateral periosteal bridge and soft tissue attachment to aid in repair and healing of the fragment. Other techniques such as the quadricepsplasty or V-Y turndown may be utilised but are rarely needed

Achievement of adequate exposure in revision total knee arthroplasty is critical as it reduces the surgical time, enhances the ability for both component removal and reconstruction, and avoids devastating complications such as extensor mechanism disruption. However, this can be challenging as prior multiple surgeries and limited mobility contribute to a loss of tissue elasticity, thickened capsular envelope, and peri-articular soft tissue adhesions. A thorough pre-operative assessment of a patient's past surgical history, comorbidities, pre-operative radiographs (i.e. the presence of severe patella baja), and physical examination including range of motion, prior incisions, and soft tissue pliability are useful in determining the appropriate surgical techniques necessary for a successful revision.

A systematic approach to the ankylosed knee is critical. Most techniques are geared towards mobilization of the extensor mechanism to safely displace the patella for component exposure. The initial exposure should consist of a long skin incision, a subperiosteal medial release, and debridement of suprapatellar, medial, and lateral adhesions to the femoral condyles. A lateral capsular release can prove helpful in further mobilization of the extensor mechanism. When performing a medial parapatellar arthrotomy it's important to keep in mind further extensile exposure techniques that may be required. For example, the arthrotomy should not extend proximally into the vastus intermedius or rectus femoris in the event that a quadriceps snip technique is to be used as this can compromise the ability to repair this exposure.

Despite a large exposure and release of adhesions, sometimes the extensor mechanism remains at risk of rupture and adequate visualization cannot be obtained. In this event, extensile exposures such as a quadriceps snip, quadriceps turndown or tibial tubercle osteotomy are considered. The location of the patella often dictates the best exposure option as severe patella baja may not be overcome with a proximally based release. The quadriceps snip is most commonly used and provides improved exposure without the necessity of modifying the patient's post-operative rehabilitation. In addition, it can be extended to a quadriceps turndown which vastly improves visualization, but at the expense of needing to immobilise the knee post-operatively. A tibial tubercle osteotomy can also be used and provides excellent exposure especially in the case of severe patella baja or when removal of a cemented tibial stem is required. It preserves the extensor muscles, but risks include increased post-operative wound drainage due to limited soft tissue coverage, failure of fixation, or fracture of the tibial tubercle fragment or tibial shaft.

Exposure in revision total knee arthroplasty is critical. Fortunately, this can be reliably achieved with a systematic approach to the knee and through the use of several extensile exposures at the surgeon's discretion.

Like all surgery, if you can see it, you can usually get the job done. This is especially true for extracting well-fixed components, as iatrogenic bone loss is a serious consideration regarding the reconstruction challenge. While reasons for revision are varied, several general principles are useful to consider during the pre and peri-operative course.

Pre-operatively, forewarned is forearmed. Certain factors pre-operatively can suggest the degree of operative difficulty regarding exposure. Revisions for stiffness obviously would suggest difficulty with exposure. Revisions in knees with patellar baja are almost always challenging as the patella is difficult to evert. When revising infected knees, an exuberant synovial response can result in beefy, friable synovium that has a volume effect with decreased tissue compliance. Further, the hyperemic friable tissue bleeds easily, even with tourniquet, and is difficult to anticoagulate.

Peri-operatively, the general principles to consider are as follows: 1) Don't rush exposure. Good exposure is the result of a series of deliberate and sequential steps that safely reduce tissue volume and improvement in tissue compliance. These steps include in almost all cases: a. Extend the incision as necessary, there is no call for minimally invasive revision knee surgery; b. Tenolysis of the patellar tendon; c. Clearing of the medial and lateral gutter; d. Clearing of the flexion space; e. Clearing of quadriceps adhesions.

2) Protect the extensor mechanism, above all else. Carefully monitor the insertion of the patellar tendon when beginning to flex the knee. If an avulsion begins, back off flexion and spend more time on clearing of scar tissue, as above. If still unsuccessful, then extensile exposure should be considered, such as a quadriceps snip. Be especially careful when osteolysis is present around the tibial tubercle.

3) The most difficult area to of the knee to expose in revision surgery is the posterior lateral corner, resulting in difficulty in exposing the posterior lateral femur and the posterior corner of the tibial component. Extensile exposures do not necessarily result in complete exposure of these regions. Redoubling efforts to remove scar tissue is often more successful. Bovie dissection of soft tissue on the proximal medial tibia can assist, with extension back to the semimembranosus insertion sometimes being necessary. While adequate exposure can result because of the increased ability to externally rotate the tibia, this exposure can also destabilise the medial side of the knee, sometimes resulting in the need to add constraint. The pros and cons need to be considered on a case-by-case basis.

4) Be judicious in the utilization of extensile exposures, and choose the exposure technique best suited for the situation. If the patellar tendon is normal, consider a simple quadriceps snip. If the knee is particularly stiff or the tibial tubercle or patellar tendon insertion is in jeopardy, then the snip can be extended into a V-Y turndown. If the patellar tendon is contracted resulting in patellar baja, then a tibial tubercle osteotomy (TTO) can be considered. Careful removal of tissue in scar tissue, as above, allows for relative external rotation of the tibia on the femur that translates the patella laterally, reducing the need for TTO. TTO can also be effective when approaching a cemented tibial stem.

Following a careful in-depth preoperative plan for revision TKR, the first surgical step is adequate exposure. The following steps should be considered: 1.) Prior incisions: due to the medially based vascular supply to the skin and superficial tissues about the knee, consideration for use of the most LATERAL incision should be made. 2.) Avoid the use of flaps which may compromise the skin and soft tissue. 3.) Exposure options can be broken down into: PROXIMALLY based techniques: medial parapatella arthrotomy, establish medial and lateral gutters, eversion or subluxation of the patella, extension of arthrotomy proximal, if unable to “mobilise” patella, consider inside out lateral release, if still unable to mobilise: QUAD SNIP, in rare instances, connect lateral release with quad snip resulting in a V-Y quadplasty, may now turn down for excellent exposure.

DISTALLY based techniques: tibial tubercle osteotomy technique described by Whiteside, roughly 8 cm osteotomy segment with distal bevel, osteotomy must be at least 1.5–2 cm thick: too thin and risk of fracture increases, leave lateral soft tissues intact, greenstick” the lateral cortex with eversion of patella, closure with wires.

Obtaining adequate exposure is key to optimising outcomes in revision total knee arthroplasty. Goals of the exposure include protecting the extensor mechanism, safe removal of the components that are in place and implantation of the revision components. Challenges to these goals include prior skin incisions, arthrofibrosis, and patella baja.

Choosing a skin incision is the first important step. The blood supply to the skin is predominantly derived MEDIALLY and thus the most LATERAL skin incision that works for obtaining exposure is selected. If skin flaps are required, they MUST be full thickness as the blood supply to the skin runs deep just over the fascial layer and partial thickness flaps risk skin necrosis. Avoid acute angles between old skin incisions of <60 degrees and skin bridges, if necessary, must be at least 6cm in width.

The work-horse of revision TKA is the medial parapatellar approach. It includes a generous medial release that allows the surgeon to externally rotate and deliver the tibia by pivoting on the extensor mechanism. An anterior synovectomy is then performed to re-establish the medial and lateral gutters followed by re-establishment of the space behind the patellar tendon to free it from the proximal tibia and finally subluxation of the patella (preferable to formal eversion). A lateral release (or peel of the soft tissue off of the lateral side of the patella) is a final step to mobilise the extensor mechanism (if required). After the components are removed, a posterior capsulectomy is performed followed by re-establishment of the flexion space behind the femur further enhances tibial exposure for both bony preparation and revision component implantation.

If the above maneuvers are performed, and exposure is still inadequate, the easiest way to improve exposure is by performing a quadriceps snip. This is an oblique, apical extension of the arthrotomy ACROSS THE PATELLAR TENDON (NOT in the muscle; it is hard to repair if performed in the muscle). It is repaired side to side with no need to alter post-operative physical therapy and heals reliably.

The V-Y Quadricepsplasty is a proximal release of the extensor mechanism; essentially perform by connecting the apical extension of the medial parapatellar arthrotomy with a lateral release across the quadriceps tendon. It is classically indicated for patients with extensor mechanism contracture where the surgeon wishes to lengthen it. It usually results in increased flexion at the expense of an extensor lag and is used rarely in contemporary practice.

Tibial Tubercle Osteotomy is a distal release of the extensor mechanism that is most useful for accessing the canal to remove long-stemmed cemented tibial components. It is a coronal osteotomy made from the medial side of the tubercle that is usually made 5–8 cm in length, tapering from approximately 1cm thick proximally to 5mm distally.

Exposure in revision total knee replacement can be quite challenging due to scar formation from one or many previous incisions. Disruption of the patellar or quadriceps tendon during revision must be avoided at all costs and many surgical maneuvers have been described to permit safe exposure in order to remove the implants during the initial stage of reconstruction. Standard maneuvers include recreation of the medial and lateral gutters, patient dissection to allow the soft tissue to stretch over time and proximal medial exposure of the tibia and release of the semimembranosis tendon insertion.

There are three specialised techniques for exposure during revision total knee replacement: the quadriceps snip as described by Insall, the V-Y quadriceps turndown as described by Coonse and Adams, and the tibial tubercle osteotomy as described by Whiteside.

The quadriceps snip is a proximal lateral extension of the medial arthrotomy used during a standard approach. It is easy to perform and can be used for most revision situations. This is should be the standard first choice for gaining exposure in revision surgery. The V-Y quadriceps turndown is quite extensile and is a combination of a lateral retinacular release connected to the proximal portion of the medial arthrotomy. Although it allows excellent exposure in revision situations, it is associated with extensor weakness and extensor lag. The Whiteside tibial tubercle osteotomy is also a versatile approach. Care should be taken to preserve a lateral periosteal sleeve, and subsequent repair with wire presents the best healing possibility. It is quite elegant in providing access to the proximal tibia to facilitate removal of a well fixed, stemmed tibial component.

Exposure in revision total knee replacement can be quite challenging due to scar formation from one or many previous incisions. Disruption of the patellar or quadriceps tendon during revision must be avoided at all costs and many surgical maneuvers have been described to permit safe exposure in order to remove the implants during the initial stage of reconstruction. Standard manoeuvres include recreation of the medial and lateral gutters, patient dissection to allow the soft tissue to stretch over time and proximal medial exposure of the tibia and release of the semimembranosis tendon insertion.

There are three specialised techniques for exposure during revision total knee replacement: the quadriceps snip as described by Insall, the V-Y quadriceps turndown as described by Coonse and Adams, and the tibial tubercle osteotomy as described by Whiteside.

The quadriceps snip is a proximal lateral extension of the medial arthrotomy used during a standard approach. It is easy to perform and can be used for most revision situations. This is should be the standard first choice for gaining exposure in revision surgery. The V-Y quadriceps turndown is quite extensile and is a combination of a lateral retinacular release connected to the proximal portion of the medial arthrotomy. Although it allows excellent exposure in revision situations, it is associated with extensor weakness and extensor lag. The Whiteside tibial tubercle osteotomy is also a versatile approach. Care should be taken to preserve a lateral periosteal sleeve, and subsequent repair with wire presents the best healing possibility. It is quite elegant in providing access to the proximal tibia to facilitate removal of a well fixed, stemmed tibial component.

Purpose

Unexpected-positive-intraoperative-cultures (UPIC) in presumed aseptic revision-total-knee-arthroplasties (rTKA) are common, and the clinical significance is not entirely clear. In contrast, in some presumably septic rTKA, an identification of an underlying pathogen was not possible, so called unexpected-negative-intraoperative-cultures (UNIC). The purpose of this study was to evaluate alpha defensin (AD) levels in these patient populations.

Background

As life expectancy increases, the number of octogenarians requiring primary and revision total knee arthroplasty (TKA) is increasing. Recently, primary TKA has become a common treatment option in octogenarians. However, surgeons are still hesitant about performing revision TKA on octogenarians because of concerning about risk- and cost-benefit. The purpose of this study was to investigate postoperative complications and mid-term survival in octogenarians following primary and revision total knee arthroplasty (TKA).

Background

The knowledge about the common mode of failure and each period in primary and revision TKAs offers useful information to prevent those kinds of failure in each surgery. However, there has been limited report that simultaneously compared the mode of failure between primary and revision TKAs using single prosthesis.

We compared the survival rate, mode of failure, and periods of each mode of failure between primary and revision TKAs.

INTRODUCTION

As the demographic of the patient population requiring revision total knee arthroplasty (rTKA) continues to expand, varying preoperative conditions and activity levels need to be taken into consideration when analyzing postoperative outcomes. Factoring in preoperative activity levels can help manage the expectations of patients. The purpose of this study was to analyze the outcomes of low and high activity patients receiving a contemporary rTKA.

Pre-operative planning in revision total knee replacement is important to simplify the surgery for the implant representative, operating room personnel and the surgeon. Revision knee arthroplasty is performed for many different reasons and of variable complexity. Many implant options can be considered including cemented and cementless primary and stemmed revision tibial and femoral components, with posterior cruciate retention or resection, and either with no constraint, varus/valgus constraint, or with rotating hinge bearings. One may also need femoral and tibial spacers, metaphyseal augments, or bulk allograft. It is important to pre-operatively determine which of these implants you may need. If you schedule a revision total knee and ask the implant representative to “bring everything you've got, just in case,” they will have to bring a truck full of instruments and implants. The first step of pre-operative planning is to determine how much implant constraint will be needed. Survivorship of revision total knees with modern varus/valgus constrained or rotating hinge implants are not that unacceptable. Ideally to enhance longevity, the least constraint needed should be used. This requires determination of the status of the ligaments. Varus and valgus stress is applied to the knee in near full extension, mid-flexion, and ninety degrees of flexion. If instability of the knee is noted, then radiographs are reviewed to determine if component malposition or malalignment is the reason for the collateral ligament laxity. If radiographs don't show a reason, then have additional constraint available in case the knee can't be balanced with proper component position and ligament balancing. In cases other than simple revisions, the posterior cruciate ligament is usually inadequate or needs to be resected to balance the knee. Substitution for the posterior cruciate ligament is usually needed for most revisions. The second step of pre-operative planning is to review radiographs to determine the amount and location of any bone loss. Osteolysis induced bone loss is usually worse than seen on plain radiographs. If unsure, a CT scan can be of help. The presence of significant bone loss contraindicates the use of primary components and mandates the need for stemmed implants. Larger defects may warrant having metallic augments or bulk graft present. Most revision knee implants can be conservatively metaphyseal cemented with diaphyseal engaging press-fit stems. The third step of pre-operative planning is to be familiar with what implants are present. Occasionally, one may not need to revise components that are stable and well aligned. Having compatible components available may simplify the surgery. Excellent pre-operative planning will minimise the need to bring in an excessive number of instruments and implants. It will help assure that the patient has a stable revision knee and simplify the surgery for all participants

Aims. The purpose of this study was to evaluate the infection-free outcome of patients underwent revision of total joint arthroplasty (TJA) for presumed aseptic causes, with positive intra-operative cultures. Patients and Methods. A retrospective cohort study was assembled with 130 patients undergoing revision knee (21 cases) or hip arthroplasty (109 cases) for presumed aseptic causes. For all patients five to seven separate intra-operative cultures were obtained and prosthesis sonication was done. Patients were diagnosed with a previously unsuspected prosthetic joint infection (PJI) if two or more cultures were. positive or a positive prosthesis sonication. Data were reviewed for demographic details, preoperative laboratory results and culture results. The endpoint was infection-free implant survival at 24 months. Results. Patients with unsuspected PJI was 16 out of 130 (12,3%). Following revision surgery, the rate of infection-free implant survival in patients with an unsuspected PJI was 68,8% (95% confidence intervals (CI) 45,6 to 92) at two years compared. with 94,7% (95% CI 90,5 to 98,9) in patients without PJI (p = 0.001). Conclusion. Around 12% of positive cultures can be expected after TJA aseptic revision surgery; in these cases, the rate of infection-free implant survival is lower than in cases without PJI

Metaphyseal bone loss, due to loosening, osteolysis or infection, is common with revision total knee arthroplasty (TKA). Small defects can be treated with screws and cement, bone graft, and non-porous metal wedges or blocks. Large defects can be treated with bulk structural allograft, impaction grafting, or highly porous metal cones. The AORI classification of bone loss in revision TKA is very helpful with pre-operative planning. Type 1 defects do not require augments or graft—use revision components with stems. Type 2A defects should be treated with non-porous metal wedges or blocks. Type 2B and 3 defects require a bulk structural allograft or porous metal cone. Highly-porous metal metaphyseal cones are a unique solution for large bone defects. Both femoral (full or partial) and tibial (full, stepped, or cone+plate) cones are available. These cones substitute for bone loss, improve metaphyseal fixation, help correct malalignment, restore joint line, and permit use of a short cemented stem. The technique for these cones involve preparing the remaining bone with a high speed burr and rasp, followed by press-fit of the cone into the remaining metaphysis. The interface is sealed with bone graft and putty. The fixation and osteoconductive properties of the outer surface allow ingrowth and biologic fixation. The revision knee component is then implanted, with antibiotic-cement, into the porous cone inner surface, which provides superior fixation compared to cementing into deficient metaphyseal bone. There are several manufacturers that provide porous cones for knee revision, but the tantalum-“trabecular metal” cones have the largest and longest clinical follow-up. The advantages of the trabecular metal cone compared to allograft include: technically easier; biologic fixation; no resorption; and lower risk of infection. The disadvantages include: difficult extraction and intermediate-term follow-up. The author has reported the results of 33 trabecular metal cones (9 femoral, 24 tibial) implanted in 27 revision cases at 2–5.7 years follow-up. One knee (2 cones) was removed for infection. All but one cone showed osseointegration. Multiple other studies have confirmed these results. Trabecular metal cones are now the author's preferred method for the reconstruction of large bone defects in revision TKA

There are many challenges facing the revision knee surgeon. Bony defects, ligamentous imbalance, and difficult gap balancing scenarios are common and require practical management strategies. Typically, an implant with the least amount of constraint necessary to provide a well-aligned, well-balanced arc of motion is preferred. Constraint in implants increases the stresses on both the bearing surfaces and the bony interfaces and may result in earlier mechanical failure of the implant. Despite this fact, there are situations where one cannot rely on a simple larger polyethylene post (such as found in CCK type devices) to balance gaps. The author prefers to choose hinge-type devices in situations that demonstrate massive gap imbalance (typically huge flexion gaps), situations with deficient extensor mechanisms that can result in recurvatum stresses, or in situations of global ligamentous instability. Techniques of supporting the bony interfaces with stems and sleeves may improve the longevity of these constructs. Complications are common, including extensor mechanism problems. Multiple studies have demonstrated reasonable results of hinged implants for these challenging revision scenarios, and the hinge should remain in the armamentarium of the revision surgeon

Both gap balancing and measured resection for TKA will work and these techniques are often combined in TKA. The only difference is really the workflow. The essential difference in gap balancing is that you determine femoral component rotation by cutting the distal femur and the proximal tibia, and then using a spacer to determine femoral rotation. I prefer measured resection because I am, for most cases, a cruciate retaining surgeon. It is not ideal to determine femoral rotation based upon a gap balancing if you retain the cruciate. It is also important to maintain the joint line, especially in cruciate retention, in order to reproduce more normal kinematics and balance the knee throughout the range of flexion and extension. It is my opinion that the soft tissue balancing is easier to do with measured resection and the workflow is easier. The sequence of cuts and soft tissue balance is different if one is a gap balancing surgeon. This is more conducive for people who are cruciate substituters, but more difficult in a varus cruciate retaining knee. In that situation, if you determine femoral rotation by gap balancing with the tibia before you have cleared the posterior medial osteophytes in the varus knee, and remove the last bit of meniscus, you could artificially over rotate the femoral component causing posteromedial laxity. The major difference is that cutting the posterior cruciate will open the flexion space and allow the surgeon easier access to the posteromedial corner of the knee before the posterior femoral cut is made. It is also important to remember that in most cases cruciate substitution surgeons will make the flexion space 2 mm smaller than the extension space to compensate for the flexion space opening when the posterior cruciate is cut. The extensor mechanism plays an important role in flexion balance and should only be tested once the patella is prepared and the patella is back in the trochlear groove. I prefer gap balancing in most revision knees as I am virtually always substituting for the posterior cruciate in that case. My technique for measured resection is to assess the character of the knee prior to surgery. Is it varus? Is it valgus? Does it hyperextend? Does it have a flexion contracture? Would the knee be considered tight or loose? I cut the distal femur first, based upon measured resection. I use anatomic landmarks to determine femoral rotation. My most consistent landmark is the transtrochlear line, which is not always from the top of the notch to the bottom of the trochlea. I will use the medial epicondyle and the posterior reference in a varus knee, but not in a valgus knee. The tibial cut, also by measured resection, is easier once the femur has been prepared. The patellar cut is also a measured resection. Having done a preliminary soft tissue balance based upon the deformity, I will then use trial components to finish the soft tissue balance. In summary, both techniques can be used successfully in a cruciate substituting knee, but measured resection, in my opinion, is preferable especially in varus arthritis when the posterior cruciate is retained

Background. One of the major concerns of hinge knees have been reported in literature is mechanical failure. Failure in the form of component fracture (2–10%) and hinge dislocation/ failure are worrisome. In addition, higher risk of aseptic loosening with hinge knee prosthesis has been attributed to stress transfer at bone cement interface. Methods. Retrospective review of clinical and radiological results of 71 consecutive patients operated at single centre using Smiles hinge knee (Stanmore implants) between 2010 and 2014. Data was collected till the latest follow up. Mechanical failure due to any reason was considered as primary end point. Radiological evidence of aseptic loosening was considered to be one of the surrogate end points. Results. Mean age at revision knee was 65.4 years (range 42 – 84). The number of previous revisions ranged from 1 – 4. Most common indications for revision were infection (n=26) and instability (n=26). Majority of patients had rotating hinge knee (n=66). Average follow-up was 31 months (range 3 – 72). Four patients died during follow-up due to medical reasons. There were no mechanical failures of implants apart from backing out of axle due to failure of circlip in 1 patient. Asymptomatic aseptic loosening of implant on femoral side was noted in 1 patient; however, there were no peri-prosthetic fractures in this series. Three patients had re-revision for infection and one for extensor mechanism subluxation. Conclusion. To our knowledge, this is the largest series till date reporting on mechanical outcomes of hinged knee implants for complex revisions. Clip failure is of concern; however there have been no other mechanical failures. Early results are encouraging, with no symptomatic aseptic loosening of implants to report

There are many challenges facing the revision knee surgeon. Bony defects, ligamentous imbalance, and difficult gap balancing scenarios are common and require practical management strategies. Typically, am implant with the least amount of constraint necessary to provide a well-aligned, well-balanced arc of motion is preferred. Constraint in implants increases the stresses on both the bearing surfaces and the bony interfaces and may result in earlier mechanical failure of the implant. Despite this fact, there are situations where one cannot rely on a simple larger polyethylene post (such as found in CCK type devices) to balance gaps. The author prefers to choose hinge type devices in situations that demonstrate massive gap imbalance (typically huge flexion gaps), situations with deficient extensor mechanisms that can result in recurvatum stresses, or in situations of global ligamentous instability. Techniques of supporting the bony interfaces with stems and sleeves may improve the longevity of these constructs. Complications are common, including extensor mechanism problems. Multiple studies have demonstrated reasonable results of hinged implants for these challenging revision scenarios, and the hinge should remain in the armamentarium of the revision surgeon