Femoral Morphologic Differences in Subtypes of High Developmental Dislocation of the Hip

Abstract

Background Previous studies show the shape of the femur in developmental dislocation of the hip (DDH) becomes more abnormal with increasing subluxation. Two kinds of high dislocations associated with DDH have been observed in clinical practice, one with (Type C1) and one without (Type C2) a false acetabulum. The presence or absence of a false acetabulum in high dislocated hips is associated with different loading patterns and could influence the development and shape of the proximal femur. Questions/purposes We therefore determined whether (1) the proximal femoral shape and dimension in Type C1 and Type C2 hips differ from each other, and (2) the femur dislocated with the same height in Types C1 and C2 hips. Patients and Methods We examined the following variables on 54 proximal femurs from 54 patients with high DDH (28 Type C1 hips and 26 Type C2 hips) on AP and lateral radiographs; the ML widths of the cortical and medullary canals, height of the femoral head, height of dislocation, and height of the greater trochanter. Reproducibility of the measurements was tested by two researchers with high interobserver and intraobserver agreement.Results The proximal femur in Type C2 hips was narrower and stovepipe shaped, with a smaller flare index (2.7 ± 0.6), compared with Type C1 hips (3.5 ± 1.2). The proximal femur migrated an average of 18 mm more superiorly in Type C2 than in Type C1 hips. Conclusions Our data confirm distinctions in the shape of the proximal femur in the presence and absence of a false acetabulum. Clinical Relevance Owing to the abnormal shapes, special implants of different geometries or modular stems may be needed for reconstruction Type C2 high dislocations.

Risk of Dislocation After Total Hip Arthroplasty in Patients with Crowe Type IV Developmental Dysplasia of the Hip

“…In Hartofilakidis' study, three dislocations occurred out of 30 hips in the no false acetabulum group (10%) while there were zero out of 49 hips in the false acetabulum group (0%). This can be explained by the fact hips without false acetabulum have a worse soft tissue condition and abductor muscle strength because of a high‐riding femoral head in the gluteal musculature, and it has a more abnormal proximal femur shape caused by the lower mechanical loads.…”

Estudo radiográfico dos aspectos anatômicos do fêmur proximal dos adultos brasileiros

“…Assim, são pertinentes novas análises de como o padrão geométrico pode interferir em patologias do fêmur. [7][8][9][10] Segundo estatísticas americanas, mais de 250 mil fraturas de quadril ocorrem a cada ano e esse número deverá estar duplicado em aproximadamente 30 anos. 4 O tratamento da maioria das fraturas de fêmur é cirúrgico.…”

Results of Total Hip Arthroplasty Differ in Subtypes of High Dislocation

“…Survivorship was lower in hips without a pseudoacetabulum (p = 0.001). Although there are no other studies in the literature comparing results of THA in high dislocation subtypes, this outcome seems reasonable, because C2 type hips have more affected morphology compared with C1 type hips that may result in a higher rate of failure [13,21]. Cox regression analysis, after adjustment for confounding factors, also showed statistically significantly worse survivorship in the C2 subtype (p = 0.021) and, after adjustment for possible predictive factors, we found a statistically significant relationship of high dislocation subtype (p = 0.018) and trochanteric union (p = 0.005) with survival of THAs.…”

“…We have recognized two subtypes of high dislocation of the hip on the basis of the presence (C1 hips) or absence of a false acetabulum (C2 hips) [10]. Xu et al [21] found that the presence or absence of false acetabulum in high dislocated hips is associated with different loading patterns and that this could influence the development and shape of the proximal femur.…”