gms | German Medical Science

Problem: Soft tissue destruction at total knee arthroplasty surgery can be minimized by using the intact medial collateral ligament as a guide for soft balancing and as the reference datum for selecting the tibial insert thickness. This medial collateral ligament sparing technique results in precise alignment and less trauma. The paper reports the 10-year clinical experience with 1722 knees and describes the importance of femoral design in reducing lateral retinacular release rates.

Method: The procedure requires the removal of all osteophytes and preservation of the medial collateral ligament. Tightness in the lateral collateral structures is reduced by stretching. The lateral structures are released only when necessary. With varus deformity where lateral laxity may be present, the medial side is not released but the lateral muscles, are allowed to self-adjust post-operatively. Patients were studied by technicians in the laboratory using fluoroscopic x-rays to determine component position and the mechanical axis. Standardized knee rating scales including the Knee Society Scale and the Hospital For Special Surgery Scale and a modified SF 36 were included. Outcomes were measured at two and five years postoperative.

Laboratory based studies using the technique of Artesian et al. ( J. of Biomech. 1991) were used to validate the medial collateral ligament as a reliable reference datum for tibio-femoral joint spacing. Cadaveric studies measuring the patello-femoral space were used to confirm the importance of femoral component design in limiting the lateral retinacular release.(proc.Amer.Assn.Hip and Knee Surg. Dallas Nov. 9-11 2001).

Results and conclusions: 1722 arthroplasties were performed, 980 unilateral and 371 same-day, bilateral. The cruciate retaining design was used in 538 cases and 1184 involved the posterior stabilized design. The mean age of was 70 years, 59% were female. At the time of surgery, 12 knees required lateral retinacular release and an additional 10 required lateral collateral ligament release also, for a total release rate of 1.3%. No medial releases were done. The Hospital for Special Surgery Score, the Knee Society Knee and Function Scores were 88`, 81`and 84`, respectively, at two years; all showed increases at the five years and 96% of the scores graded good or excellent, only 1% graded poor. Re-operations for any reason except closed manipulation were 1.3% at ten years into the study. Sparing the MCL and recognizing the "dynamic" nature of the lateral side distinguish this soft tissue balancing technique from its predecessors. This method, avoids leg lengthening and flexion/extension mismatch by allowing the MCL to play its essential role as a reference for tibio/femoral spacing. Used together with a modern prosthesis designed to avoid pretensing the retinaculum, accurate alignment and joint spacing can be accomplished with minimal soft tissue damage.