Arthroscopic Anatomy of the Dislocated Hip in Infants and Obstacles Preventing Reduction.

PURPOSE: The purpose of this study was to describe the anatomy as seen arthroscopically, the role of the labrum and its relevance in luxation and reduction procedures, and secondary changes to the cartilaginous acetabular roof and to determine the main obstacles preventing reduction of dislocated hips in infants and young children. METHODS: A specialized pediatric medial approach to hip arthroscopy was performed on 25 hip joints in 21 patients younger than 4 years of age. The arthroscopic procedure was conducted using a 2.7-mm cannulated instrument. A subadductor portal was used for the 70° arthroscope, and a high anterolateral portal served as a working portal. The anatomic findings of the individual hip joints were recorded. We examined the femoral head, the teres ligament, the transverse ligament, the acetabulum, and the acetabular labrum. The obstacles preventing reduction were successively resected. RESULTS: An arthroscopic investigation of all major structures and arthroscopic reduction was possible in 25 hip joints. A hypertrophic teres ligament was present in 23 of the 25 hips. Capsular constriction prevented reduction in 22 of the 25 hips. The acetabular labrum was not inverted in any of the examined hip joints and was also never an obstacle to reduction. Secondary changes to the cartilaginous preformed acetabular roof were present in 10 hips. CONCLUSIONS: We have shown that arthroscopy of a developmentally dislocated hip can be safely performed using the subadductor portal. Through this arthroscopic approach, we were able to identify the previously described pathologic structures-the limbus, neolimbus, pulvinar, hypertrophic teres ligament, and capsular constriction. The capsule was the most common block to reduction, followed by the teres ligament. Successful reduction can be achieved by removal of intra-articular tissues, the pulvinar, and the teres ligament, and nearly always a capsular release. The limbus and neolimbus were not factors in achieving reduction in our series. LEVEL OF EVIDENCE: Level IV, case series.