Altered Walking and Muscle Patterns Reduce Hip Contact Forces in Individuals With Symptomatic Cam Femoroacetabular Impingement

Abstract

Background: Cam-type femoroacetabular impingement (FAI) is a causative factor for hip pain and early hip osteoarthritis. Although cam FAI can alter hip joint biomechanics, it is unclear what role muscle forces play and how they affect the hip joint loading. Purpose/Hypothesis: The purpose was to examine the muscle contributions and hip contact forces in individuals with symptomatic cam FAI during level walking. Symptomatic cam FAI demonstrate different muscle and hip contact forces during gait. Study Design: Controlled laboratory study. Methods: Eighteen patients with symptomatic cam FAI (nFAI = 18) were age-and BMI-matched with eighteen control participants (nCON = 18). Each participant's walking kinematics and kinetics were recorded throughout a gait cycle (ipsilateral foot-strike to ipsilateral foot-off), using a motion capture system and force plates. Muscle and hip contact forces were subsequently computed using a musculoskeletal modelling program and static optimization methods. Results: The FAI group walked slower and with shorter steps; demonstrating reduced joint motions and moments during contralateral foot-strike, compared to the CON group. The FAI group showed reduced psoas major (median = 1.1, interquartile range (IQR) = 1.0-1.5 Newton/bodyweight (N/BW)) and iliacus forces (median = 1.2, IQR = 1.0-1.6 N/BW), during contralateral foot-strike, compared to the CON group (median = 1.6, IQR = 1.3-1.6 N/BW, p = 0.004; and median = 1.5, IQR = 1.3-1.6 N/BW, p = 0.03, respectively); which resulted in lower hip contact forces in the anterior (p = 0.026), superior (p = 0.02), and medial directions (p = 0.038). The three vectors produced a resultant peak force at the anterosuperior aspect of the acetabulum for both groups; with the FAI group demonstrating a substantially lower magnitude. 4 Conclusions: FAI participants altered their walking kinematics and kinetics, especially during contralateral foot-strike as a protective mechanism, and resulted in reduced psoas major and iliacus muscle force and anterosuperior hip contact force estimations. Clinical Relevance: Limited hip mobility is not only attributed to bone-on-bone impingement, caused by the cam morphology, but could be attributed to musculature as well. Not only would the psoas major and iliacus be able to protect the hip joint during flexion-extension, athletic conditioning could further strengthen core muscles for improved hip mobility and pelvic balance.

Hip muscle atrophy in patients with acetabular labral joint pathology

“…Changes in neuromuscular function of the hip are associated with intra‐articular hip joint pathology. Recent systematic reviews (Diamond et al, ; Freke et al, ; Mayne et al, ) and research studies have examined physical impairments associated with FAI syndrome, acetabular labral pathology and chondropathology, and have found impaired hip range of motion (Kemp et al, ; Diamond et al, ), reduced hip muscle strength (Casartelli et al, ; Harris‐Hayes et al, ; Mendis et al, ; Kemp et al, ; Nepple et al, ; Diamond et al, ), impaired functional task performance (Hatton et al, ; Bagwell et al, ; Charlton et al, ; Kemp et al, ; Samaan et al, ), and altered gait biomechanics (Kennedy et al, ; Brisson et al, ; Hunt et al, ; Ng et al, ). With respect to hip muscle size, previous research has investigated size of the gluteal muscles in patients with chronic hip joint pain (Mastenbrook et al, ) and of the individual hip flexor muscles in patients with acetabular labral pathology (Mendis et al, ); however, no research to date has investigated the individual hip abductor, hip extensor, or hip external rotator muscles in this patient population.…”

Hip Radiograph Findings in Patients Aged 40 Years and Under with Posterior Pelvic Pain

“…Lateral rotation of the hip joint has been shown to cause posterior impingement of the femoral neck against the posterior acetabulum, another possible source of posterior hip pain . Studies have shown that people with acetabular retroversion walk with slow gait and smaller steps as a way of reducing hip joint forces . This is associated with hip muscle weakness .…”

“…13 When walking at heel strike, there is a low-level brief posterior joint reaction force. [57][58][59] In the normal hip, that force is directed into bony structures but with acetabular retroversion, the force would be partially distributed into tissues such as the labrum. Acetabular retroversion and FAI are known to be associated with traumatic posterior hip dislocation in athletes, indicating that during activity there can be posteriorly directed forces.…”

“…57,59 This is associated with hip muscle weakness. 59 Muscle weakness associated with normal activity has the potential of causing muscle strain if the individual increases the demands on the hip by initiating fitness activities, such as running or hiking. Thus a variety of daily activities involving periodic increases in the demands of muscular activity and in range of motion in hips with structural variations, particularly acetabular retroversion, dysplasia, and FAI can be sources of posterior hip pain, arising from the posterior acetabulum, soft tissues, and muscles.…”

Muscle activity and morphology in hip-related pain

“…Greater stride lengths and walking speed in young adults with FAI syndrome compared to controls is inconsistent with observations from cohorts with more advanced hip pathology. 208 People with hip osteoarthritis 208 and pre-surgical populations with FAI syndrome 152,252 are reported to walk with shortened stride lengths and at slower speeds compared to matched controls. The participants with FAI syndrome in this study come from a young active cohort, which may contribute to the conflicting spatiotemporal findings.…”