Three-dimensional morphological study of the proximal femur in Crowe type IV developmental dysplasia of the hip

Abstract

Background When performing femoral reconstruction in patients with Crowe type IV developmental dysplasia of the hip (DDH), anatomical deformity presents many technical challenges to orthopedic surgeons. The false acetabulum is suggested to influence load transmission and femoral development. The aim of this study was to describe the morphological features of dysplastic femurs in Crowe type IV DDH and further evaluate the potential effect of the false acetabulum on morphological features and medullary canal of Crowe type IV femurs. Methods We analyzed preoperative computed tomography scans from 45 patients with 51 hips (25 hips without false acetabulum in the IVa group and 26 hips with false acetabulum in the IVb group) who were diagnosed with Crowe type IV DDH and 30 normal hips in our hospital between January 2009 and January 2019. Three-dimensional reconstruction was performed using Mimics software, and the coronal femoral plane was determined to evaluate the following parameters: dislocation height, dislocation ratio, height of the femoral head (FH), height of the greater trochanter (GT), GT–FH height discrepancy, height of the isthmus, neck-shaft angle, femoral offset and anteversion of the femoral neck. The mediolateral (ML) width, anterolateral (AP) width and diameter of medullary canal of the proximal femur were measured on the axial sections. Further, canal flare index (CFI), metaphyseal-CFI and diaphyseal-CFI were also calculated. Results Compared with the normal femurs, the Crowe type IV DDH femurs had a higher femoral head, larger GT–FH height discrepancy, larger femoral neck anteversion, higher isthmus position and smaller femoral offset. Dislocation height and dislocation rate were significantly larger in the IVa DDH group (65.34 ± 9.83 mm vs. 52.24 ± 11.42 mm). Further, the IVb femurs had a significantly lower isthmus position, larger neck-shaft angle and smaller femoral neck anteversion than IVa femurs. The ML, AP canal widths and the diameter of medullary canal in both DDH groups were significantly smaller than the normal group. Dimensional parameters of IVa femurs were also narrower than IVb femurs in most sections, but with no difference at the level of isthmus. According to the CFIs, the variation of proximal medullary canal in IVb femurs was mainly located in the diaphyseal region, while that in IVa femurs was located in the whole proximal femur. Conclusions High dislocated femurs are associated with more anteverted femoral neck, smaller femoral offset and narrower medullary canal. Without stimulation of the false acetabulum, IVa DDH femurs were associated with higher dislocation and notably narrower medullary canal, whose variation of medullary canal was located in the whole proximal femur.

CORR Insights®: Assessing Leg Length Discrepancy Is Necessary Before Arthroplasty in Patients With Unilateral Crowe Type IV Hip Dislocation

“…In “Assessing Leg Length Discrepancy Is Necessary Before Arthroplasty in Patients With Unilateral Crowe Type IV Hip Dislocations” [3], the authors illuminate real differences in lower limb length and configuration in patients with the most severe hip dysplasia; that is, those with Crowe Type IV. Limb length difference, variation in femoral neck offset, and angulation at the knee have been reported [4, 5, 7, 10]; however, the true pattern of differences in the lower extremities has not been defined before this work [3]. The authors show there is variation in the patterns of length and angular differences in the lower extremities in patients with unilateral, severe dysplasia.…”

“…Limb length discrepancy can be a result of treatment. Overgrowth can be stimulated by femoral varus rotational osteotomies for hip reduction [10]. Femoral shortening may be necessary with open reduction of the hip with a delayed diagnosis, or it can be secondary to femoral head collapse from avascular necrosis [6].…”

Personalized digital simulation‑assisted acetabular component implantation in revision hip arthroplasty

“…Computer-aided technology has been successfully applied in orthopedic instrument design, materials and surgical simulation with mature technology applications (12)(13)(14). Previous studies have (15,16) used Mimics software to simulate the reconstruction of a high dislocated acetabulum, with an individualized and precise preoperative design to obtain satisfactory acetabular cup position and coverage and to avoid problems such as iliopsoas impingement. However, to the best of our knowledge, no studies have been carried out yet on computer-assisted simulation in acetabular revision.…”