Abnormally high dislocation rate following constrained condylar knee arthroplasty for valgus knee: a case-control study

Abstract

Background With 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. Methods This 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. Results Forty-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]. Conclusion Releasing both LCL and PT in CCK TKA with valgus deformity may increase the risk of dislocation, and need to be performed with some caution.

Satisfactory mid-term outcomes of condylar-constrained knee implants in primary total knee arthroplasty: clinical and radiological follow-up

“…Despite the disadvantages that have been associated with increased constraint, midterm survivorship from revision for aseptic loosening was 100%, which is in line with previous studies of primary CCK that reported no cases of failure of the implants for aseptic loosening at midterm follow-up in primary TKA [13,14,17,19,23,31,33]. Our results compare favorably with those of other studies [11,15,22,[34][35][36][37] (Table 3).…”

“…The surgical technique for the implantation of a CCK implant has already been described [14,19]. All the surgeries were performed by 2 experienced knee surgeons with preference for PS implants.…”

“…Theoretical disadvantages have been addressed to an increased level of constraint including greater risk of loosening caused by the transmission of the mechanical stress to the bone-cement interface and subsequent increased polyethylene insert wear, particularly of the tibial post, leading to a higher prevalence of osteolysis [11,12,[14][15][16][17]. However, multiple studies have reported good short-to-midterm results of CCK implants in primary TKAs.…”

Modified Medial Collateral Ligament Indentation Technique in Total Knee Arthroplasty with Severe Type II Valgus Deformity

“…If medial‐lateral balance cannot be achieved, constrained prostheses must be used 4 . Although mid‐term clinical outcomes are satisfactory, the incidence rates of prosthesis loosening and instability increase 5 . In addition, comprehensive release of the lateral soft tissue results in the need for a thicker polyethylene insert, which leads to the joint line changing, and increases the possibility of common peroneal nerve injury.…”

Modified MCL Indentation Technique in Total Knee Arthroplasty With Severe Type II Valgus Deformity

“…If the medial-lateral balance cannot be achieved, constrained prostheses must be used [4]. The literature reports that although the mid-term clinical outcomes are satisfactory, the incidence rates of prosthesis loosening and instability increase [5]. In addition, comprehensive release of the lateral soft tissue resulted in utilizing thicker polyethylene insert, which would lead to the joint line changing and increase the possibility of common peroneal nerve injury.…”