Clinical and Radiologic Risk Factors of Acetabular Chondral Damage in Femoroacetabular Impingement Syndrome

Abstract

Deformities suggestive of femoroacetabular impingement syndrome (FAI) are common in young adults. Since non-invasive measures like MRI provide only limited accuracy to appropriately predict acetabular cartilage damage, valid parameters indicating patients at risk to develop significant chondral defects and osteoarthritis are urgently warranted. Both reduced internal rotation and increased alpha angle have been previously shown to be associated with an increased risk of acetabular chondral injury. The objective of the present study was to investigate the association between various clinical and radiographic parameters and the severity of acetabular cartilage damage. A total of 320 consecutive hip arthroscopies performed by a single surgeon were retrospectively reviewed. Subjects were included in the study if arthroscopic surgery was performed to correct deformities causing FAI. The following exclusion criteria were defined: previous surgery, intra-articular comorbidities (e.g. synovial chondromatosis), other prearthritic deformities (e.g. significant hip dysplasia), systemic inflammatory and musculoskeletal disease, post-traumatic cartilage damage, and insufficient joint distraction to assess the central compartment. Clinical data as well as X-ray and MRI parameters were recorded. The degree of cartilage damage was classified according to Beck et al. distinguishing (0) normal cartilage; (1) softening, surface roughening, fibrillation; (2) loss of fixation to subchondral bone, carpet phenomenon; (3) delamination, frayed edges, flap; and (4) full-thickness defects. Furthermore, the distance of the damaged cartilage extending from the chondrolabral junction to the central fossa was classified as follows: (0) no cartilage damage, (1) = 0.5 cm, (2) >0.5-1.0 cm, (3) >1.0-1.5 cm, (4) >1.5-2.0 cm, (5) >2.0 cm. 193 hips of 157 patients (50 women, 107 men) with an average age of 34 years (range, 17-67) met the inclusion criteria. Proportional odds logistic regression analysis revealed the following risk factors to be significantly associated with both a higher degree (p<0.05) as well as a larger size (p<0.05) of acetabular chondral damage: male gender, higher age at the time of surgery, reduced (internal) rotation, cam-type deformity, pistol grip deformity, positive horizontal growth plate sign, larger alpha angle, larger ½ radial height/radius ratio, smaller femoral head-neck offset, and larger acetabular depth. Regression analysis failed to demonstrate a significant association between cartilage damage and duration of symptoms, moderate coxa vara or coxa valga, center edge angle, cross-over sign, ischial spine sign, coxa profunda, prominent posterior wall, linear indentation sign, herniation pits, os acetabuli, and epiphyseal torsion angle. Our study provides important information on risk factors predicting more severe cartilage injury in FAI. The results might help to identify those patients at higher risk to develop severe chondral damage and osteoarthritis.