Prevalence of pistol-grip deformity in patients with axial spondyloarthritis

To our knowledge, the prevalence of pistol-grip deformity (PGD) has not previously been studied in patients with axial spondyloarthritis (axSpA). This study aimed to evaluate PGD prevalence in patients with axSpA and to assess its relationship with the clinical and demographic factors.

A total of 158 patients with axSpA in whom diagnosis was established according to the Assessment of SpondyloArthritis International Society criteria in rheumatology department and 193 age- and sex-matched controls admitted to the emergency room and had anteroposterior (AP) pelvic X-rays were included in the study. PGD was identified by determining the non-spherical shape of the femoral head on AP hip or pelvic X-rays.

Prevalence of PGD was significantly higher in patients with axSpA than in controls (20.3% vs. 8.8%, respectively, p=0.002). PGD was also found to be more frequent in patients with radiographic axSpA than in those with non-radiographic axSpA (26/106 [24.5%] vs. 6/52 [11.5%]); however, this difference did not reach statistical significance (p=0.056). The presence of PGD was significantly associated with the presence of hip arthritis (odds ratio [OR], 3.1; 95% confidence interval [CI], 1.2-8.7; p=0.023), ever smoking (OR, 4.5; 95% CI, 1.4-13.6; p=0.008), and male sex (OR, 38.7; 95% CI, 5.1-292.7; p<0.001) in univariate analyses. In multivariate model, ever smoking (OR, 2.9; 95% CI, 1.10-10.05; p=0.03) and male sex (OR, 27.0; 95% CI, 3.5-208.4; p=0.002) were associated with PGD.

PGD was significantly more common in patients with axSpA. Presence of PGD correlated significantly with hip arthritis, smoking, and sex. We assume that new bone formation could be the possible reason for increased PGD prevalence. Femoroacetabular impingement should be considered as a secondary cause of hip pain in patients with axSpA.