Hip contact force and pressure in cam femoroaceteabular impingement syndrome

Abstract

Abnormal hip biomechanics associated to different hip conditions often lead to premature articular damage and malfunction. Therefore, understanding hip biomechanics is extremely important not only for assessing joint function but also for hip preservation and reconstruction surgery. In femoroacetabular impingement syndrome (FAIS), abnormal morphology and joint biomechanics can lead to articular damage and premature joint degeneration. Surgical treatment of FAIS, with adequate morphology correction and treatment of associated intraarticular pathology, significantly improves clinical outcomes, but few studies focus on the biomechanical outcome. The research on the intraoperative assessment of hip joint biomechanics is even more limited. The main motivation for this thesis is the intraoperative evaluation of femoroacetabular contact force (CF) and pressure (CP) in the arthroscopic treatment of cam FAIS. We believe that assessing post-cam resection CF and CP can aid in identifying inadequate restoration of contact biomechanics. By detecting this intraoperatively, it may be possible to correct it during the initial surgery, potentially reducing the need for revision procedures and improving outcomes. We review the relevant anatomy, joint biomechanics, and imaging techniques essential for the diagnosis and treatment of FAIS. Our original research includes a structured review of hip CF and CP, based on both in vivo and cadaver studies. Through this review, we identified that there was no specific medical device to measure hip CF or CP in hip arthroscopy, and no standardised methodology had been published for assessing contact biomechanics in arthroscopic hip surgery. Recognising these gaps in current knowledge, we designed and produced a dual-device system to measure femoroacetabular CF and the axial load applied to the thigh during arthroscopic hip surgery. Cadaver testing confirmed the functionality of these devices, and we established the surgical technique for performing these measurements using the PC initial access technique in hip arthroscopy. In further research, we compared the new devices for evaluating CF with an intracranial pressure (ICP) microsensor for assessing CP as a control device in cadavers with cam morphology. Additionally, we explore the advancements in FAIS imaging and the arthroscopic treatment of FAIS using initial access to the peripheral compartment, which has been our preferred approach. The research conducted for this thesis suggests that: First, there was no specific device or standardised methodology to access femoroacetabular contact biomechanics in arthroscopic hip surgery. Second, the dual-device system, comprising one device specifically designed to measure femoroacetabular CF in arthroscopic hip surgery and another to control the applied axial load, allows for real-time measurement of CF across different joint positions in cadaveric hip arthroscopy. Third, the described surgical technique and standardised methodology enable the measurement of the anterosuperior femoroacetabular CF in the arthroscopic cam resection. Fourth, the ICP microsensor used for CP evaluation is fragile and difficult to handle, with saturation occurring at 30º and 60º of hip flexion. At 80º of hip flexion, the anterosuperior CP was significantly lower after cam resection. Fifth, the novel hip-specific device is functional and detected a decrease in the normalised anterosuperior femoroacetabular CF after arthroscopic cam resection across all tested joint positions. At 80º of hip flexion and 15º of internal rotation, the CF decreased by 26% following cam resection. Sixth, the concept of intraoperatively assessing CF and CP offers a promising approach to verify improvements in joint biomechanics following arthroscopic cam resection. Seventh, the hip arthroscopy technique with initial access to the PC has favourable clinical outcomes (79.4% of patients achieved the MCID, and 63.8% reached the PASS for the NAHS) without an increase in complication or reoperation rates. Eight, this arthroscopic technique is versatile and can be particularly advantageous when the pathology is primarily located in the PC or when access to the central compartment is challenging. The hip-specific device for measuring CF in arthroscopy has only been used in cadaver surgery and research settings. In the future, the integration of 3D pre-operative planning, navigation, and intraoperative contact biomechanics measurement may be used in different surgical interventions, such as acetabular rim trimming, cam resection, osteotomies, and labral repair or reconstruction. The real-time data provided by navigation and contact biomechanics can be used to optimise the precision of intraoperative corrections.