In Vitro Hip Biomechanical Positioning Device Integrated with Clinical Imaging

Area of Science:

• Biomechanics
• Orthopedic Surgery
• Medical Imaging

Background:

• In vitro hip biomechanics studies are limited by the lack of radiolucent testing platforms.
• Existing methods struggle to validate joint mechanics against clinical imaging without metal artifacts.

Purpose of the Study:

• To develop a low-cost, non-ferrous, radiolucent testing fixture for hip biomechanics.
• To enable alignment of benchtop loading with International Society of Biomechanics (ISB) recommendations.
• To facilitate artifact-free validation of joint mechanics using computed tomography (CT).

Main Methods:

• A 3D-printed (tough polylactic acid - PLA) testing fixture and drill guide were developed.
• The device allowed controlled flexion-extension and internal-external rotation (IR-ER) with a torque meter.
• Twenty cadaveric hips were tested, and reliability was assessed using CT imaging and Bland-Altman analysis.

Main Results:

• The fixture demonstrated high accuracy in positioning: 1.8 ± 1.4% in flexion-extension and 7.3 ± 3.2% in IR-ER.
• Excellent reliability was found between image-based and device measurements (ICC_rotation = 0.98; ICC_flexion = 0.99).
• Exceptional repeatability (ICC ≥ 0.99) and strong clinical agreement were confirmed.

Conclusions:

• The imaging-compatible device offers a robust, standardized platform for hip biomechanics research.
• It facilitates quantitative evaluation of joint stability and surgical interventions.
• Provided CAD models enable widespread fabrication and setup.