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Hybrid plate-and-UHMWPE fixation for step-cut subtrochanteric osteotomy in crowe IV hip dysplasia: a finite
Askarjan Beknazarov1, Kairat Ashimov2, Olzhas Bekarissov3
1Astana Medical University, National scientific center of traumatology and orthopedics named after academician N.D. Batpenov, Astana, 010000, Kazakhstan.
Background:
Total hip arthroplasty (THA) in Crowe type IV developmental dysplasia of the hip (DDH) is technically demanding due to high dislocation, abnormal femoral morphology, and soft-tissue contractures. Subtrochanteric shortening osteotomy (SSO) is often required to restore the anatomic hip center and prevent excessive lengthening, yet the ideal osteotomy design and fixation remain controversial. The step-cut SSO offers greater rotational stability and bone contact but is technically complex and biomechanically under-evaluated. This report describes a clinical case supplemented by computational biomechanical analysis evaluating a hybrid fixation technique using a titanium plate reinforced with ultra-high-molecular-weight polyethylene (UHMWPE) tape.
Case Presentation:
In this clinical case, a 35-year-old female with bilateral Crowe IV DDH underwent staged THA with step-cut SSO at the National Scientific Center of Traumatology and Orthopedics, Astana, Kazakhstan. Approximately 4.5 cm of femoral shortening was performed per side. The osteotomy was stabilized with a locally designed titanium plate and UHMWPE tape cerclage. Both procedures were uneventful, achieving equal limb lengths, early mobilization, and complete bone union by four months. Finite element analysis (FEA) was performed to evaluate mechanical behavior under single-leg-stance loading (1000 N vertical, 200 N horizontal). The hybrid construct demonstrated favorable stress distribution: peak von Mises stress values of 137 MPa in cortical bone and 94 MPa in the plate - both below yield limits. Maximum displacement was 0.16 mm, and safety factors exceeded 2.9, confirming high rigidity. Clinically, both hips showed stable fixation, pain-free gait, and excellent functional outcomes with a Harris Hip Score of 90 for the right hip and 88 for the left hip at one-year follow-up.
Conclusions:
In this case, the combination of step-cut SSO with hybrid titanium-plate and UHMWPE-tape fixation demonstrated favorable biomechanical characteristics and successful clinical outcome. Finite element analysis supported the mechanical stability of the construct. These findings should be considered preliminary and represent a proof-of-concept observation. Further experimental and multicenter clinical studies are required to confirm the generalizability of this approach.
