The prevalence of radiographic criteria of femoral acetabular impingement in patients undergoing hip arthroplasty surgery.

BACKGROUND: Pistol grip deformity of the proximal femur has been reported as a potential cause of hip pain and early-onset arthritis. The exact incidence of patients with osteoarthritis resulting from femoral acetabular impingement (FAI) is unknown. The purpose of this study was to explore the relationship between radiographic markers of FAI in patients undergoing hip arthroplasty.

METHODS: We retrospectively reviewed the radiographs of patients undergoing hip arthroplasty by a single surgeon over a 2-year period. The patients were divided by age, those younger than 65 years and (group A) and those 65 years and older (group B). The radiographs were evaluated for morphology consistent with FAI including an α angle >55°, crossover sign, coxa profunda, acetabular protrusio, and ischial spine sign. Three independent reviewers evaluated all the radiographs. The incidence of CAM, Pincer, and mixed deformities were compared between the 2 groups.

RESULTS: A total of 255 patients with 258 hip arthroplasties were included in this analysis. Group A was found to have a greater number of patients with CAM morphology. Linear regression analysis revealed that the α angle was greater in younger patients.

CONCLUSION: Patients undergoing hip arthroplasty exhibit a high incidence of radiographic abnormalities consistent with FAI. The CAM-type morphology occurs more frequently in younger patients with advanced arthritis requiring hip arthroplasty. This morphology is thought to cause a delaminating injury to the cartilage of the acetabulum. This study supports the notion that CAM-type morphology is a risk factor for early development of degenerative arthritis of the hip.