Prevalence and characteristics of cam-type femoroacetabular deformity in 100 hips with symptomatic acetabular dysplasia: a case control study

Abstract

BackgroundCam-type femoroacetabular deformity in acetabular dysplasia (AD) has not been well clarified. The primary purpose of this study was to determine the prevalence and characteristics of femoroacetabular deformity in symptomatic AD patients.MethodsWe retrospectively reviewed the cases of 86 women (92 hips) and eight men (eight hips) with symptomatic AD. The mean patient age was 37.9 (range, 14–60) years. All participants underwent lateral cross-table and lateral whole-spine radiographic examinations to measure the alpha angle and pelvic tilt. Pelvic computed tomography scans were used to measure femoral anteversion. The patients were classified into two groups: AD only group, containing hips with an alpha angle less than 55°; and AD with cam-type femoroacetabular deformity (AD + cam-type deformity) group, containing hips with an alpha angle greater than or equal to 55°.ResultsOf the patients with AD, 40 hips displayed additional radiographic evidence of cam-type morphology, while 60 hips had exclusive AD morphology. The patients in the AD + cam-type deformity group had significantly increased forward pelvic tilt in the standing position (p =0.023) and decreased femoral anteversion (p =0.047) compared with the AD only group.ConclusionsOur data revealed that 40% of patients with AD also had radiographic evidence of cam-type femoroacetabular deformity. Greater forward pelvic tilt in the standing position and decreased femoral anteversion seemed to be associated with the cam-type deformity in these patients. These results indicate the morphological features that are most likely to induce secondary symptoms to developmental hip dysplasia. It is suggested that the symptoms in the AD + cam-type deformity group could arise through femoroacetabular impingement (FAI) after periacetabular osteotomy, because a predisposition was present preoperatively.

The John Charnley Award: Redefining the Natural History of Osteoarthritis in Patients With Hip Dysplasia and Impingement

“…We also found that patients with cam-type FAI and concomitant low lateral center-edge angles or high Tönnis angles (both representing acetabular dysplasia) were at increased risk of osteoarthritis progression. Co-occurrence of acetabular dysplasia and FAI has been documented previously with authors positing that the combination increases the risk of intraarticular pathology [2,6,11,12,16]. Tannast and colleagues [20] recently published modified reference values for acetabular overcoverage and undercoverage based on a cohort managed with hip preservation surgery, postulating that previous cutoffs may not provide optimal accuracy.…”

Posterior Pelvic Tilt From Supine to Standing in Patients With Symptomatic Developmental Dysplasia of the Hip

“…As the dynamics of the spine–pelvis–hip construct, the pelvis is controlled by two hinges, posteriorly the lumbosacral joint and anteriorly the hip joint . Theoretically, the acetabular morphology has less impact on the sagittal tilt of the pelvis, while some studies reported that DDH patients tilt the pelvis anteriorly in standing to compensate for insufficient femoral head coverage by the dysplastic acetabulum . On the other hand, others found a posterior rotation of the pelvis occurring from the supine to the standing position .…”

“…12,13 Theoretically, the acetabular morphology has less impact on the sagittal tilt of the pelvis, while some studies reported that DDH patients tilt the pelvis anteriorly in standing to compensate for insufficient femoral head coverage by the dysplastic acetabulum. [14][15][16] On the other hand, others found a posterior rotation of the pelvis occurring from the supine to the standing position. 17 Controversy remains regarding whether compensation due to insufficient femoral head coverage is accompanied by a postural change in DDH patients.…”

High prevalence of cam deformity in dysplastic hips: A three‐dimensional CT study

“…To evaluate the femoral head‐neck junction deformity, the α‐angle and head‐neck offset ratio (HNOR) are widely used. Several studies have examined the α‐angle or HNOR in dysplastic hips using plain radiography . One study reported that an abnormal HNOR or α‐angle was found in 73.1% of dysplastic hips, whereas another study reported that cam deformity was found in 40% of dysplastic hips .…”