CORR Insights®: What Factors Are Associated With Postoperative Ischiofemoral Impingement After Bernese Periacetabular Osteotomy in Developmental Dysplasia of the Hip?

摘要

Where Are We Now? Ischiofemoral impingement (IFI) is an underrecognized source of hip pain, especially among recipients of offset-altering or center of rotation-altering hip procedures [2, 7, 12]. This entity was originally described among patients who have had THA in whom excessive medialization of the hip’s center of rotation or reduced offset led to a decreased distance between the lateral aspect of the ischium and the lesser trochanter of the femur, resulting in subsequent impingement [7]. Similarly, IFI can follow periacetabular osteotomy and even occur in a native joint that is anatomically predisposed to this problem [4, 7, 8]. In this issue of Clinical Orthopaedics and Related Research®, Huang et al. [5] investigated the link between preoperative and intraoperative determinants and the risk of IFI after Bernese periacetabular osteotomy for developmental dysplasia of the hip (DDH), which to this point has not been well characterized. Periacetabular osteotomy changes the orientation of the acetabulum to redistribute load on the articular cartilage, to decrease the risk of progression to osteoarthritis in patients with hip dysplasia [6, 11, 13]. However, redirection of the acetabulum cannot change the shape of the acetabulum or its total surface area. We do know, from a recent investigation by Fowler et al. [1] using reference-standard CT measurements, that periacetabular osteotomy has been associated with an average medialization of 4 mm ± 3 mm. The extent of medialization was even more pronounced among patients with a lateral center-edge angle (LCEA) of ≤ 15° (in whom the mean medialization was 6 mm ± 3 mm), a cohort that constitutes most of the patients in the investigation by Huang et al. [5] (LCEA < 20° was an inclusion criterion). However, while seemingly intuitive, the association between the extent of medialization after periacetabular osteotomy and the occurrence of IFI had not been extensively described before Huang et al.’s timely study. In addition to the substantial proportion of patients who had some degree of IFI (26%), the factors associated with IFI described by Huang et al. could be categorized into nonmodifiable and modifiable. Nonmodifiable associated factors include increasing the neck-shaft angle and a positive coxa profunda sign; the latter has a negative correlation with IFI. Conversely, medialization of the hip’s center of rotation was the sole surgeon-modifiable associated factor that could influence the development of IFI. Notably, the 1.9-mm cutoff for safe medialization, as described by the authors [5], may be a relatively conservative estimate. If viewed in the context of the average 6-mm medialization reported by Fowler et al. [1], a substantial proportion of patients undergoing periacetabular osteotomy can—and will—exhibit some degree of IFI. Based on Huang et al.’s [5] discoveries, surgeons should not ignore posterior hip or gluteal pain or discomfort after periacetabular osteotomy. This pain could originate from hip arthritis, but also could be due to IFI. A proper investigation and clinical assessment can help the surgeon in defining the source of pain and the right management. Where Do We Need To Go? The study by Huang et al. [5] provides several avenues for further investigation. Although the authors demonstrated that medialization and the neck-shaft angle are associated with the development of IFI, baseline femoral offset is yet to be explored. Furthermore, additional variables that were considered exclusion criteria in the present investigation may need further elaboration, including the effect of a concurrent femoral osteotomy, wider ranges of LCEAs, and most importantly, cutoffs of medialization in periacetabular osteotomies performed in patients without DDH. The criteria for diagnosing IFI remain relatively controversial [3, 7]. IFI is a relatively new topic, and the diagnosis starts with a clinical examination that can be supported by MRI findings and clinical tests. Therefore, c