Patient-Specific Anatomical and Functional Parameters Provide New Insights into the Pathomechanism of Cam FAI

Abstract

Background Femoroacetabular impingement (FAI) represents a constellation of anatomical and clinical features, but definitive diagnosis is often difficult. The high prevalence of cam deformity of the femoral head in the asymptomatic population as well as clinical factors leading to the onset of symptoms raises questions as to what other factors increase the risk of cartilage damage and hip pain.Questions/purposes The purpose was to identify any differences in anatomical parameters and squat kinematics among symptomatic, asymptomatic, and control individuals and if these parameters can determine individuals at risk of developing symptoms of cam FAI. Methods Forty-three participants (n = 43) were recruited and divided into three groups: symptomatic (12), asymptomatic (17), and control (14). Symptomatic participants presented a cam deformity (identified by an elevated alpha angle on CT images), pain symptoms, clinical signs, and were scheduled for surgery. The other recruited volunteers were blinded and unaware whether they had a cam deformity. After the CT data were assessed for an elevated alpha angle, participants with a cam deformity but who did not demonstrate any clinical signs or symptoms were considered asymptomatic, whereas participants without a cam deformity and without clinical signs or symptoms were considered healthy control subjects. For each participant, anatomical CT parameters (axial alpha angle, radial alpha angle, femoral head-neck offset, femoral neck-shaft angle, medial proximal femoral angle, femoral torsion, acetabular version) were evaluated. Functional squat parameters (maximal squat depth, pelvic range of motion) were determined using a motion capture system. A stepwise discriminant function analysis was used to determine

Physical impairments in symptomatic femoroacetabular impingement: A Systematic review of the evidence

“…These included squat depth, pelvic ROM, single leg balance and number of strides. 27 29-31 35 44 There were no significant between-group effects for squat depth 44 pelvic ROM, 44 or total number of daily strides 35 between individuals with FAI and controls. In addition, when assessing static balance on one leg with eyes closed, no differences were seen in individuals posthip arthroscopy compared with controls.…”

“…The method of diagnoses ranged from arthroscopic findings, 22 23 27 28 to positive clinical signs on physical examination, 24 26 29-33 to radiographic, CT or MRI diagnosis. 3 29 30 and functional performance tasks such as single leg balance, 27 squat depth and pelvic ROM, 44 and number of strides per day. 35 The reliability of physical impairment outcomes measured was reported in 7 out of the 23 studies.…”

“…27 However, when individuals posthip arthroscopy undertook a dynamic single leg squat task, significant moderate between-group effects were noted Best evidence synthesis for functional tasks provided varying evidence depending on the challenges of the activity. One highquality case-control study 27 reported significant between-group SMDs for a dynamic balance task, while the other high-quality case-control study 44 reported no significant between-group SMDs for squat depth or pelvic ROM. The remaining study was of moderate quality.…”

Can Combining Femoral and Acetabular Morphology Parameters Improve the Characterization of Femoroacetabular Impingement?

“…The control subjects with elevated (C 55°) alpha angles also showed a larger mean omega zone of 20% (95% CI, 18-22; p = 0.004) and 16% (95% CI, 13-19; p = 0.007) for 60°and 90°of flexion, respectively, compared with the patients with FAI. Furthermore, the mean omega zone at 0°a nd 30°was larger with 23% (95% CI, 19-27; p = 0.017) and 22% (95% CI, 19-26; p = 0.004), respectively, whereas the mean omega zone in patients with FAI was 18% (95% CI, [15][16][17][18][19][20][21][22] and 16% (95% CI, [11][12][13][14][15][16][17][18][19][20] (Table 3). In contrast, the omega zone was similar in both control groups at any of the flexion positions (0°p = 0.806, 30°p = 0.925, 60°p = 0.345, 90°p = 0.136).…”

“…Furthermore, morphological parameters that determine how the proximal femur and acetabulum are positioned relative to each other also play a role in FAI, as does their interaction. These parameters are acetabular and femoral version and femoral neck shaft angle [4,15]. For example, a femur with low neck-shaft angle (varus) impinges earlier on the acetabular rim with flexion-internal rotation than a femur with higher neckshaft angle (closer to 135°).…”