Management of Hip Instability in Trisomy 21

Abstract

The unstable hip in Trisomy 21 presents with a spectrum of hip instability with different problems at different ages. What links this multiphase problem, in many patients, is the final common pathway of untreated instability, that of a stiff, dislocated, and often-painful hip, leading to significant functional disability. Historically, the results of treating hip instability in Trisomy 21 were variable with a notable frequency of poor results. With an improved understanding of the Trisomy 21 hip in terms of its pathoanatomy and a more contemporary surgical approach to hip reconstruction, much improved results can be expected and indeed have recently been shown. The mainstay of treatment for the habitual dislocation group presenting before 8 years of age is the femoral varus derotation osteotomy. The older group presenting with painful subluxation often show signs of secondary acetabular dysplasia and thus are best treated with redirectional acetabular osteotomy with or without the use of femoral varus derotation osteotomy. The presence of radiographic features of degenerative arthritis in the fixed dislocation group precludes the use of joint-preserving techniques for hip reconstruction, and these patients can achieve excellent results with total joint arthroplasty. The natural history, historical results, assessment, treatment, and management of complications of hip instability in Trisomy 21 are addressed in this paper.

Combining acetabular and femoral morphology improves our understanding of the down syndrome hip

“…Subjects with Down syndrome were found to have increased lateral coverage (increased VCE angle) of the femoral head by the acetabulum compared to control subjects (Table 3). This finding is somewhat in contrast to those of previous studies on subjects with Down syndrome, which had reported that these subjects tend to have dysplastic hips, with decreased lateral coverage of the femoral head by the acetabulum (Bennet et al, 1982;Kelley and Wedge, 2013;Sankar et al, 2011). The discrepancy in results could be explained by the differences in patient populations.…”

“…However, other studies had, similarly to the findings of the current study, found that Down syndrome subjects tend to have only very moderate increases in neck shaft angle (134°) (Shaw and Beals, 1992). Such differences between previous studies have been suggested to be partly due to the difficulty in standardizing these patients' positioning during X-ray acquisition (Kelley and Wedge, 2013), especially in the presence of hip rotation. In this study, the use of biplanar X-rays with three-dimensional reconstruction for the assessment of hip anatomy, which has been previously shown to decrease the effect of patient positioning bias (Melhem et al, 2016), should have allowed precise evaluation of the anatomy of the Down syndrome hip.…”

“…The discrepancy in results could be explained by the differences in patient populations. While previous studies had mostly reported on subjects with Down syndrome who had been specifically referred for management of hip subluxation or dislocation (Bennet et al, 1982;Kelley and Wedge, 2013;Knight et al, 2011;Sankar et al, 2011), the subjects in this study had not been specifically referred for hip-related complaints. Furthermore, although the mean vertical center edge angle only slightly deferred in subjects with DS compared to controls, these patients were found to have significantly more heterogeneous lateral coverage (Fig.…”

“…Hip instability is one of the most commonly occurring (1.3 to 7%) orthopedic problems (Aprin et al, 1985;Assi et al, 2018;Bennet et al, 1982;Diamond et al, 1981;Mansour et al, 2017;Shaw and Beals, 1992) in these subjects. It is a significant source of morbidity during both childhood and adulthood (Bennet et al, 1982;Diamond et al, 1981), and is especially challenging to treat (Boylan et al, 2015;Kelley and Wedge, 2013;Knight et al, 2011;Sankar et al, 2011).…”

“…While hip pathologies in non-DS subjects mostly produce anterior instability, posterior hip subluxation and dislocation have been shown to be more frequent in subjects with DS (Bennet et al, 1982;Sankar et al, 2011). Hip instability in subjects with DS has long been believed to be related to hypotonia and ligamentous laxity (Bennet et al, 1982;Hresko et al, 1993); however, recent studies based on CT scans or Xrays, in the supine position, have suggested that either acetabular retroversion or increased neck shaft angle could be responsible for the observed posterior instability, and treatment strategies have been accordingly suggested (Kelley and Wedge, 2013;Knight et al, 2011;Sankar et al, 2011). However, acetabular alignment has been previously shown to be dependent upon body positioning during imaging (Babisch et al, 2008) and studies on other populations have underlined the importance of concomitantly assessing femoral and acetabular anatomy in order to assess hip anatomy (Dorr et al, 2009;Tönnis and Heinecke, 1999).…”