The aim of this paper was to study the anatomical relationship between the piriformis muscle and the sciatic nerve with regard to the possibility of neurological deficit after THA. The incidence of anatomical variation of both structures is 15-30% in the literature. The authors studied 91 cadavers and found an atypical relationship in 19 cases (20.9%). In this study individual variations were found with the following frequency: The sciatic nerve exits below the piriformis muscle in 79.1% of the cases. The sciatic nerve separates into two divisions above the piriformis, one branch passing through the muscle, the other below it (14.3%). An unsplit nerve passes through the piriformis muscle in 2.2%. The nerve separates into two divisions above the piriformis, one branch exiting above the muscle and passing along its dorsal aspect, the second exiting distally below the muscle in 4.4%. The most common reasons for sciatic nerve injury in surgery of the hip joint are direct injuries, ischemia of the nerve tissue, compression or excessive distraction of the nerve, compression by bone cement, thermal damage during cement polymerization, injury during THA dislocation, compression by hematoma, bone prominence or an implanted acetabular component. According to the presented anatomical study, overstretching of the nerve itself or its branches in the area of the pelvitrochanteric muscles after their release from their origin can be another mechanism. Such overstretching can appear in the presence of some of the aforementioned anatomical variants.

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BackgroundThe foot is often affected in patients with rheumatoid arthritis. Subtalar joints are involved more frequently than ankle joints. Deformities of subtalar joints often lead to painful flatfoot and valgus deformity of the heel. Major contributors to the early development of foot deformities include talonavicular joint destruction and tibialis posterior tendon dysfunction, mainly due to its rupture.MethodsBetween 2002 and 2005 we performed isolated talonavicular arthrodesis in 26 patients; twenty women and six men. Tibialis posterior tendon dysfunction was diagnosed preoperatively by physical examination and by MRI. Talonavicular fusion was achieved via screws in eight patients, memory staples in twelve patients and a combination of screws and memory staples in six cases. The average duration of immobilization after the surgery was four weeks, followed by rehabilitation. Full weight bearing was allowed two to three months after surgery.ResultsThe mean age of the group at the time of the surgery was 43.6 years. MRI examination revealed a torn tendon in nine cases with no significant destruction of the talonavicular joint seen on X-rays. Mean of postoperative followup was 4.5 years (3 to 7 years). The mean of AOFAS Hindfoot score improved from 48.2 preoperatively to 88.6 points at the last postoperative followup. Eighteen patients had excellent results (none, mild occasional pain), six patients had moderate pain of the foot and two patients had severe pain in evaluation with the score. Complications included superficial wound infections in two patients and a nonunion developed in one case.ConclusionsEarly isolated talonavicular arthrodesis provides excellent pain relief and prevents further progression of the foot deformities in patients with rheumatoid arthritis and tibialis posterior tendon dysfunction.