Abstract
BackgroundWith the use of constrained condylar knee (CCK) prostheses, dislocation of the knee following total knee arthroplasty (TKA) with valgus deformity is rare. In our practice with such patients, however, an abnormally high dislocation rate was noted. It appeared to be associated with the extent of soft-tissue release which varied among surgeons following different sequences of release. We asked in CCK TKA with valgus deformity is releasing both the lateral collateral ligament (LCL) and popliteus tendon (PT) associated with the occurrence of dislocation.MethodsThis is a case-control study of consecutive patients with valgus deformity who underwent primary CCK TKA between July 2008 and October 2015. The cases and controls were patients with and without postoperative dislocation of the knee, respectively. The extent of the release of lateral soft-tissue structures was compared between the two groups. Other patient characteristics including age, body mass index, pre- and post-operative valgus deformity, preoperative flexion-contracture, and height of the polyethylene insert were compared as well to reduce confounding.ResultsForty-three consecutive patients with a minimum 2-year follow-up were enrolled. 9.3% (4/43) of the patients had postoperative dislocation of the knee. While the dislocated patients did not significantly differ from the controls on most characteristics, they were more likely to have both the LCL and PT released together during the surgery [100% (4/4) vs. 2.6% (1/39), P < 0.001].ConclusionReleasing both LCL and PT in CCK TKA with valgus deformity may increase the risk of dislocation, and need to be performed with some caution.
Highlights
With the use of constrained condylar knee (CCK) prostheses, dislocation of the knee following total knee arthroplasty (TKA) with valgus deformity is rare
Achieving soft-tissue balance is a critical part of total knee arthroplasty (TKA) with valgus deformity wherein the lateral structures—the lateral collateral ligament (LCL), popliteus tendon (PT), iliotibial band (ITB), and posterolateral capsule (PLC)—are often significantly contracted [1, 2]
There seems to be an open debate between two approaches regarding the following question: should LCL and/or PT be released first; or, from another perspective considering the main result of this approach, can both LCL and PT be released during the surgery? Given the primary role of LCL and PT in stabilizing the knee, most TKA surgeons would try not to [2, 4, 5, 11], yet some would [9, 12,13,14], especially when the lateral structures are tight in both knee flexion and extension during the surgery
Summary
With the use of constrained condylar knee (CCK) prostheses, dislocation of the knee following total knee arthroplasty (TKA) with valgus deformity is rare. Achieving soft-tissue balance is a critical part of total knee arthroplasty (TKA) with valgus deformity wherein the lateral structures—the lateral collateral ligament (LCL), popliteus tendon (PT), iliotibial band (ITB), and posterolateral capsule (PLC)—are often significantly contracted [1, 2] This situation often warrants an extensive release of these structures wherein both excessive and insufficient release can lead to postoperative instability of the knee [1,2,3]. In our practice with patients undergoing CCK TKA for valgus deformity, an abnormally high rate of dislocation of the knee was noted over the recent years It appeared that these failed cases did not differ significantly from the other patients on most clinical parameters, with the exception that they all had both the LCL and PT released together during the surgery. The hypothesis was that releasing both the LCL and PT together is associated with the occurrence of dislocation following CCK TKA with valgus deformity
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