153. HYPOESTHESIA AFTER TOTAL KNEE ARTHROPLSATY: PROSPECTIVE COMPARATIVE RANDOMISED STUDY OF A LATERAL INCISION VERSUS A MINI-MEDIAL INCISION 5657

Abstract

Purpose of the study: A medial incision for implantation of a total knee arthroplasty (TKA) offers an excellent surgical exposure while minimising the length of the skin opening. This incision however implies section of the proximal portion of the infrapatellar branch of the medial saphenous nerve, potentially associated with lateral hypoesthesia and formation of a neuroma (painful scar). We hypothesised that an anterolateral skin incision would produce less hypoesthesia and postoperative discomfort.

Material and methods: We conducted a prospective randomised study to compare the degree of hypoesthesia after a medial or lateral skin incision for the implantation of a TKA. Fifty-knees in 43 patients, mean age 65.9±8.4 years were included; 26 knees for the lateral incision and 24 for the medial. All patients had the same type of implant. Clinical results were assessed with WOMAC, KOOS and SF36. Semme-Weinstein monofilaments were applied to measure sensitivity at 13 characteristic points. Patients were assessed at six weeks and six months. The zone of hypoesthesia was delimited and photographed for measurement with Mesurim Pro9^®. Satisfaction with the surgery and the scar was noted. Data were processed with Statview^®; p< 0.05 was considered significant.

Results: The two groups were comparable preoperatively regarding age, gender, body weight, height, body mass index, body surface area, aetiology, and clinical score. Operative time, blood loss, and number of complications were comparable. The functional outcomes (WOMAC, KOOS, SF36) were comparable at six weeks and six months. Active flexion was significantly greater at six months in the lateral incision group (p=0.03). The zone of hypoesthesia was significantly smaller in the lateral incision group at six weeks (p< 0.01) and at six months (p< 0.01), as were the number of points not perceived on the filament test (p< 0.01 in both cases) while the length of the incision was comparable (p> 0.05). This was associated subjectively, with less loss of sensitivity and less anterior pain reported by the patient at six months.

Discussion: Lateral and medial incisions enable comparable functional outcomes. The lateral incision produces less hypoesthesia and less anterior pain. This improves the immediate postoperative period and facilitates rehabilitation as is shown by the gain in flexion at six months.