Hip arthroscopy has been widely accepted as a less invasive surgical technique to treat a variety of pre-arthritic conditions, ranging from FAI to labral tears, chondral lesions and loose bodies, but the role of arthroscopic surgery in the management of mild dysplastic hips is under debate [3, 13]. This is a particular subset of patients that may be both suitable for arthroscopy and periacetabular osteotomies [6].
The treatment of patients with an LCEA between 18° and 25° is nowadays controversial since there is no agreement on the critical value of LCEA where bony correction is mandatory, and arthroscopic surgery has been reported to significantly improve symptoms in borderline dysplastic hips if associated with labral repair and careful capsular closure [7, 14]. As a matter of fact, less evidence-based data are available about the outcomes of such patients, and early reports considered borderline dysplasia to be a relative contraindication for hip arthroscopy [13]. Besides, the concept of LCEA to define hips labeled as “mild” or “borderline” dysplastic seems to be simplistic, since other radiological parameters should be taken into consideration [14].
The aim of the present study was to evaluate the outcomes of hip arthroscopy in patients with borderline dysplasia (LCEA between 18° and 25°, Figs. 1 and 2). The results of our series demonstrated that hip arthroscopy can be a valuable alternative in this subset of patients, if associated with capsular suture and careful labral management.
Although a significantly larger number of osteochondral lesions have been encountered and treated in the study group (see Table 2), clinical outcomes are comparable to the control group of normal hips (LCEA greater than 25°). As it could be expected, a significantly lower rate of pincer FAI has been recorded in the study group. Besides, capsular plication was significantly more frequent in the study group (see Table 2). There was no conversion to THA in both groups.
Besides, concerns have arisen about the adequacy of LCEA in defining borderline dysplasia, because acetabular undercoverage should be evaluated in the anterior, posterior and lateral regions by using additional radiographic parameters, such as acetabular inclination angle of Tönnis, the anterior center-edge angle, the anterior wall index (AWI) and posterior wall index (PWI), and the femoral epiphyseal acetabular roof (FEAR) index [10, 11, 14, 15, 17,18,19]. As it was stated above, a thorough radiographic assessment of acetabular coverage should be implemented in the setting of hip dysplasia, because failure of arthroscopic approaches in borderline dysplastic hips may be due to an inadequate evaluation of proximal femoral anatomy. In this scenario, hips classified as “borderline” or “mild” dysplastic on the basis of the LCEA should be probably scheduled for hip arthroscopy only if other radiographic parameters (particularly the FEAR index) fall into the normal range value. In the case of multiple abnormal radiographic values, periacetabular osteotomy (PAO) can be considered.
The results of our series are in line with those of the recent literature about this topic. Domb et al. [6] demonstrated that patients with borderline dysplasia can achieve similar clinical improvements after undergoing hip arthroscopy with subsequent capsular repair. Similarly, Beck et al. [3] showed that, at least in the short term, patients with borderline dysplasia undergoing hip arthroscopy with capsular plication and careful labral management can anticipate same clinical outcomes when compared with their counterparts with normal LCEA. Finally, in a large multicenter study, Matsuda and coworkers demonstrated that LCEA did not influence outcomes of primary hip arthroscopy performed in borderline dysplastic patients [13]. Our results confirm those findings, and support the role of arthroscopy in borderline dysplasia, if capsular closure is routinely performed to avoid iatrogenic instability. This study has some relevant limitations. First of all, it is retrospective in nature and used a short-term follow-up data. Secondly, the small number of patients especially in the study group. Thirdly there is not enough statistical power.