A three-dimensional analysis of pre-and post-operative running biomechanics in femoroacetabular impingement

Abstract

Femoroacetabular impingement (FAI) consists of abnormal bony formation that leads to premature contact between the femur and acetabulum during motion1. The proximal femur can be non-spherical (Cam-FAI) leading to abrasion type impacts with the acetabular rim, whereas the femoral neck can be impacted due to acetabular over-coverage-(Pincer-FAI)2,3. The bony deformities lead to pain, intra-articular damage of the acetabular labrum and hyaline cartilage, and early development of osteoarthritis (OA)1. Initial development of FAI first presents in young to middle-aged active populations via insidious groin pain and limited passive flexion, adduction, and IR (IR) (e.g. anterior impingement sign)1-3. Continued activity and maximal ranges of motion during turning, twisting, pivoting, or lateral movements may exacerbate signs and symptoms4. Persistent aggravation may result in decreased strength5,6(e.g. decreased maximal isometric hip flexion, adduction, abduction, and external rotation[ER] strength) pre-operatively compared to controls5. These findings may lead to antalgic walking gait and decreased ability to perform activities of daily living6-10. Pre-operative three-dimensional biomechanical studies involving kinematic and kinetic FAI level walking gait are controversial7-9. Kinematically, FAI patients display significantly lower peak hip extension, adduction, IR, as well as frontal and sagittal hip excursion decreases when compared to controls7. However, in another study, no significant differences were revealed in the transverse plane8. Kinetically, a single study of a mixed (i.e. Cam and Pincer) FAI patients indicated decreases in peak flexion and ER moments7, whereas other studies showed no differences 6,8,9. Though the specific effects of symptomatic FAI on gait differ between studies, every sample showed kinematic deficits. Post-operative patients reported decreased pain and improved functional abilities 6,9,11 however, gait analyses were limited. Following arthroscopic intervention, increased sagittal hip excursion on the involved hip during walking was reported, which was largely due to increased maximal flexion during walking after arthroscopic intervention 9. However, following surgical hip dislocation (SHD) hip frontal excursion decreased both pre-and post-operatively (21.1± 9.4 months), when compared to controls6. Peak hip abduction and IR external moments and peak power generation near toe-off decreased after SHD as well6. The differences in findings may be attributed to the lack of control subjects in the arthroscopic study9, and/or the increased trauma of joint, ligament, and muscle resections utilized in the SHD technique. This increased trauma may lead to larger post-operative strength deficits12, unfortunately, strength has only been evaluated pre-operatively in FAI patients, to our knowledge5. Walking gait and hip strength related changes after FAI surgery are currently debated and unknown. Additionally, FAI patient goals include the desire to return to normal walking and also vigorous activity. To our knowledge, there are no analyses of more impactful motions than walking and stair climbing 13. A longitudinal analysis of running gait in relation to hip strength may elucidate the operative efficacy in FAI patient surgery and follow-up treatment. Therefore, the purpose of this study was to examine the three-dimensional running gait kinematics and kinetics, and hip strength in pre-and 6 months post-operative FAI patients compared to controls.