Three-Dimensional Femur Morphology Analysis for the Optimal Location of Subtrochanteric Osteotomy with an Implanted Wagner Cone Stem in Total Hip Arthroplasty for Crowe Type IV Developmental Dysplasia of the Hip

Abstract

Background This study aimed to accurately evaluate the matching of proximal and distal femoral segments and fitting of the femur–femoral stem in patients with Crowe type IV developmental dysplasia of the hip (DDH) who have undergone subtrochanteric osteotomy at different locations with an implanted Wagner cone stem to improve the rate of the bone union at the osteotomy site. Methods Three-dimensional femur morphology of 40 patients with Crowe type IV DDH was evaluated at each cross-section to determine the femoral cortical bone area. This study focused on five osteotomy lengths (2.5, 3, 3.5, 4, and 4.5 cm). The overlapped area between the proximal and distal cortical bone segments was defined as the contact area (S, mm2), and the contact area to distal cortical bone area ratio was defined as the coincidence rate (R). Three indicators were used to evaluate the matching and fitting of the osteotomy sites with the implanted Wagner cone stems: (i) higher S and R between the proximal and distal segments; (ii) the effective fixation length of the femoral stem at the distal segments being at least 1.5 cm; and (iii) osteotomy did not involve the isthmus. Results In all groups, S significantly decreased in the two proximal levels above the 0.5 cm level below the lesser trochanter (LT) compared with those below this level. In comparison, at osteotomy lengths from 2.5 to 4 cm, R significantly decreased in the three proximal levels. The optimal osteotomy levels ranged from 1.5 and 2.5 cm below the LT for an appropriately sized stem. Conclusions Subtrochanteric osteotomy at the optimal level not only ensures fitting of the femur–femoral stem but also meets the requirements of a higher S and R to ensure adequate reduction and immobilization at the osteotomy site, which may contribute to the bone union. Although the optimal osteotomy level varies with the size of the femoral stem and the length of the subtrochanteric osteotomy, the optimal osteotomy levels for an appropriately sized Wagner cone femoral stem implantation range from 1.5 to 2.5 cm below the LT.

Subtrochanteric Osteotomy in Direct Anterior Approach Total Hip Arthroplasty for Crowe IV Dysplasia—Surgical Technique and Literature Review

“…The combination of S‐ROM modular prosthesis in severe hip dysplasia patients proved more suitable for filling the femoral canal in comparison to single‐piece prostheses. This facilitated excellent torsional stability at the osteotomy site through the stabilization of the metaphyseal and diaphyseal osteotomy block 38,40 . Given the limited visual field in DAA, the modular S‐ROM system appeared to offer greater convenience in correcting abnormal femoral anteversion.…”

“…This facilitated excellent torsional stability at the osteotomy site through the stabilization of the metaphyseal and diaphyseal osteotomy block. 38,40 Given the limited visual field in DAA, the modular S-ROM system appeared to offer greater convenience in correcting abnormal femoral anteversion. The literature also reported there to be a trend towards the use of S-ROM prostheses, which is consistent with the clinical cases in this study.…”