Systematic Review
Prevalence of Femoroacetabular Impingement Imaging Findings in Asymptomatic Volunteers: A Systematic Review

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Purpose

The aim of this study was to determine the prevalence of radiographic findings suggestive of femoroacetabular impingement (FAI) in asymptomatic individuals.

Methods

A systematic review was performed using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies reporting radiographic, computed tomographic, or magnetic resonance imaging (MRI) findings that were suggestive of FAI in asymptomatic volunteers were included. Cam, pincer, and combined pathologic conditions were investigated.

Results

We identified 26 studies for inclusion, comprising 2,114 asymptomatic hips (57.2% men; 42.8% women). The mean participant age was 25.3 ± 1.5 years. The mean alpha angle in asymptomatic hips was 54.1° ± 5.1°. The prevalence of an asymptomatic cam deformity was 37% (range, 7% to 100% between studies)—54.8% in athletes versus 23.1% in the general population. Of the 17 studies that measured alpha angles, 9 used MRI and 9 used radiography (1 study used both). The mean lateral and anterior center edge angles (CEAs) were 31.2° and 30°, respectively. The prevalence of asymptomatic hips with pincer deformity was 67% (range 61% to 76% between studies). Pincer deformity was poorly defined (4 studies [15%]; focal anterior overcoverage, acetabular retroversion, abnormal CEA or acetabular index, coxa profunda, acetabular protrusio, ischial spine sign, crossover sign, and posterior wall sign). Only 7 studies reported on labral injury, which was found on MRI without intra-articular contrast in 68.1% of hips.

Conclusions

FAI morphologic features and labral injuries are common in asymptomatic patients. Clinical decision making should carefully analyze the association of patient history and physical examination with radiographic imaging.

Level of Evidence

Level IV, systematic review if Level II-IV studies.

Section snippets

Methods

A systematic review was performed using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines with a PRISMA checklist.9 Three independent reviewers (one board-eligible orthopaedic surgeon in sports medicine fellowship training and 2 orthopaedic surgery residents) completed the search. The search was performed on April 13, 2013 using an explicit search algorithm: (((((hip[Title/Abstract])) AND (asymptomatic[Title/Abstract]))) AND ((((radiograph[Title/Abstract])

Results

Before screening, 237 studies were identified. After applying inclusion and exclusion criteria, 26 studies remained (Table 1). These comprised 2,114 asymptomatic hips (57.2% in men and 42.8% in women) with a mean overall age of 25.3 ± 1.5 years. Of the 2,114 asymptomatic hips analyzed, approximately 33% were in athletes (most commonly collegiate football players; n = 298), army recruits (n = 244), and hockey players (n = 127). The mean alpha angle (measured on MRI and radiography) in

Discussion

The purpose of this study was to determine the prevalence of FAI and labral tears in asymptomatic individuals. The authors hypothesized that the prevalence would be low. The hypothesis was partially confirmed. The prevalence of cam deformity was 37% and the prevalence of pincer deformity was 67%. Interestingly, there was an almost 3:1 ratio of cam deformity in the athletic population compared with the nonathletes. The prevalence of labral injury was 68%. These findings should be used to assist

Conclusions

FAI morphologic features and labral injuries are common in asymptomatic patients and may have an increased presence in athletes. Clinical decision making should carefully analyze the association of patient history and physical examination with radiographic imaging.

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    See commentary on page 1205

    The authors report the following potential conflict of interest or source of funding: S.N. receives support from Össur, Stryker, AlloSource, Arthrex, Athletico, DJ Orthopaedics, Linvatec, Miomed, and Smith & Nephew and M.S. receives support from Smith & Nephew and Linvatec.

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