Capsular closure and piriformis preservation to prevent dislocation after total hip arthroplasty through the minimal posterior approach. Comparative series of 196 patients

Purpose of the study: This study analyzes the incidence on hip dislocation of a posterior minimally invasive approach that combines the suture of the capsular joint and the preservation of the piriformis muscle. Material and methods: A first prospective series of 98 patients having undergone hip prosthesis by a posterior minimally invasive approach that combines piriformis preservation and capsular closure is analyzed regarding 7 criteria: age, weight, duration of the intervention, piriformis integrity and quality of the capsular closure at the end of the intervention, radiological position of the implants, and rate of dislocation at M12. This series is compared to another consecutive series of 98 hip prostheses performed by the same operator, by posterior access, consisting in capsular resection and cutting of the piriformis reinserted on the trochanter. Results: The two series were identical regarding patients’ age and weight. The minimally invasive surgery lasted 20 minutes more than the other intervention. In both interventions, no effect was observed on the radiological position of the implants. The rate of hip dislocation after twelve months was significantly improved by the capsular closure combined with piriformis preservation (2.9% vs 0%). Discussion: The restoration of the capsular plane has been the subject of numerous works. The techniques described had some variants, with a related rate of dislocation less than 1%. Piriformis preservation participates in the joint coaptation. This muscle is stretched out during the first step of the dislocating movement. The presented series highlights the benefit of combining a capsular flap truly suturable and the preservation of the piriformis muscle aimed at creating a ‘‘hammock’’, passive and active at the same time, at the upper posterior part of the joint, a strategic area with a high related risk of dislocation.