Femoroacetabular impingement is more common in military veterans with end-stage hip osteoarthritis than civilian patients: a retrospective case control study

Background: The purpose of this study was to compare the frequency of femoroacetabular impingement(FAI) between matched groups of military veterans and civilian patients with end-stage hip osteoarthritis(OA).Methods: Patients who underwent a primary total hip arthroplasty(THA) between January 1, 2015 and December 31, 2015 at a single Veteran’s Affairs Hospital were identified. Veterans were then matched 1:2 with civilian patients from our prospective outcome registry. The alpha angle and lateral center-edge angle(LCEA) were measured by a single evaluator. Independent t-tests were used to compare joint angles, and Fisher exact tests were used to compare the prevalence of cam(alpha angle ≥60°), pincer(LCEA ≥40°), or mixed-type pathologies.Results: Twenty-one veterans were matched 1:2 with civilian patients. The mean alpha angle did not significantly differ between groups(P=0.33) nor did the prevalence of cam deformities(P=0.79). The LCEAs were significantly greater in veterans than in civilians(P=0.04), and veterans also demonstrated a significantly greater prevalence of pincer and mixed-type deformities than civilians(P=0.025 and P=0.004, respectively).Conclusions: These results suggest that FAI is perhaps a more common mechanism in the progression of OA in a veteran population than in a civilian population, as pincer and mixed-type deformities were significantly more common among veterans than civilians. The forces borne by the hip during military training exceed normal physiologic conditions. In addition, the time between symptom onset and surgical correction may be 10–12 months longer for active military personnel than for civilians. The combination of increased physical demands and a protracted time to treatment highlights the need for better recognition of FAI in military members. Future studies are necessary to determine whether earlier intervention may prevent or delay the progression to end-stage OA and the need for total hip arthroplasty.