The Prevalence of Radiographic Findings of Structural Hip Deformities for Femoroacetabular Impingement in Patients With Hip Pain

Abstract

Background: Radiography is the initial imaging modality used to evaluate femoroacetabular impingement (FAI), and diagnostic radiographic findings are well-established. However, the prevalence of these radiographic findings in patients with hip pain is unknown. Purpose: The purpose was 3-fold: (1) to determine the overall prevalence of radiographic FAI deformities in young patients presenting with hip pain, (2) to identify the most common radiographic findings in patients with cam-type FAI, and (3) to identify the most common radiographic findings in patients with pincer-type FAI. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A geographic database was used to identify patients aged 14 to 50 years with hip pain between the years 2000 to 2016. The following were evaluated on radiographs: cam type: typical pistol grip deformity, alpha angle >55°; pincer type: crossover sign (COS), coxa profunda or protrusio acetabuli, lateral center edge angle (LCEA) ≥40°, Tönnis angle <0°; and mixed type: both cam- and pincer-type features. Posterior wall sign (PWS) and ischial spine sign (ISS) were also evaluated. The prevalence of each was determined. Descriptive statistics were performed on all radiographic variables. Results: There were 1893 patients evaluated, and 1145 patients (60.5%; 1371 hips; 374 male and 771 female; mean age, 28.8 ± 8.4 years) had radiographic findings consistent with FAI. Of these hips, 139 (10.1%) had cam type, 245 (17.9%) had pincer type, and 987 (72.0%) had mixed type. The prevalence of a pistol grip deformity and an alpha angle >55° was 577 (42.1%) and 1069 (78.0%), respectively. The mean alpha angle was 66.9°± 10.5°. The prevalence of pincer-type radiographic findings was the following: COS, 1062 (77.5%); coxa profunda, 844 (61.6%); ISS, 765 (55.8%); PWS, 764 (55.7%); Tönnis angle <0°, 312 (22.8%); LCEA ≥40°, 170 (12.4%); and protrusio acetabuli, 7 (0.5%). Conclusion: The overall prevalence of radiographic findings consistent with FAI in young patients with hip pain was 60.5%. Radiographic findings for mixed-type FAI were the most prevalent. The most common radiographic finding for cam-type FAI was an alpha angle >55°. The most common radiographic finding for pincer-type FAI was the COS.

Incidence of Femoroacetabular Impingement and Surgical Management Trends Over Time

“…8 The prevalence of radiographic findings consistent with FAI in a large cohort of patients presenting with hip pain was recently found to be 60.5%. 30 The percentage of patients with FAI syndrome in the present study was less than that in the studies evaluating radiographs only. This is an expected finding since it is known that many asymptomatic patients have findings consistent with FAI on radiographs alone.…”

“…8,12,15 One study reported the prevalence of radiographic parameters of structural deformity in patients with hip pain. 30 However, the clinical diagnosis of FAI syndrome requires the presence of a triad of clinical symptoms, physical examination signs, and imaging findings. 11 We are aware of 1 study that reported the incidence of true FAI syndrome, although this was in a small cohort and the radiographic parameters were not well-defined.…”

“…The prevalence of radiographic findings consistent with FAI has been evaluated more often. 8,12,15,30 A systematic review evaluated the prevalence of cam- and pincer-type FAI on radiographs in asymptomatic patients. It revealed that 37% of asymptomatic patients had cam-type findings and 67% had pincer-type findings.…”

“…A recent study reported the prevalence of radiographic findings consistent with FAI in patients with hip pain to be 60.5%. 30 However, there is a paucity of research evaluating the true incidence of FAI utilizing a triad of clinical symptoms, examination findings, and radiographic findings for diagnostic criteria in the general population. We are aware of only 1 study that has attempted to answer this question.…”

Prevalence of Morphological Variations Associated With Femoroacetabular Impingement According to Age and Sex: A Study of 1878 Asymptomatic Hips in Nonprofessional Athletes

“…52 Even so, plain radiography of the pelvis in its different projections has been the most widely used imaging method for the radiographic detection of these anatomic variations in studies with large samples. 59 The radiographic findings associated with FAI observed on plain film radiographs include the following for the camtype variant: an increased alpha angle, a pistol-grip deformity (PGD) of the femoral head-neck, a low femoral headto-femoral neck ratio (FHFNR), lateral flattening of the femoral head (LFFH; coxa recta), focal prominence of the femoral neck (FPFN), and coxa vara defined by the femoral neck-shaft angle (NSA; also called the caput-collumdiaphyseal angle). For the pincer-type variant, the findings include the following: an increased lateral center-edge angle (LCEA; Wiberg angle); a decreased acetabular index (AI; Tö nnis angle); the crossover sign (COS; figure-of-8 sign); the posterior wall sign (PWS); excessive acetabular coverage (EAC) and its variant, os acetabuli; the ischial spine sign; coxa profunda; and protrusio acetabuli.…”