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

Yusuke Kohno, Yasuharu Nakashima, Takashi Hatano, Mio Akiyama, Masanori Fujii, Daisuke Hara, Masayuki Kanazawa, Akihisa Haraguchi, Yukihide Iwamoto

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


Cam deformity could lead to suboptimal articulation by causing secondary femoroacetabular impingement after periacetabular osteotomy; however, the inherent femoral head-neck morphology in dysplastic hips and the effect of an additional osteoarthritic deformity have not been well described. We compared femoral head-neck morphology using three-dimensional imaging of normal and dysplastic hips in pre/early (Tönnis grade 0 and 1) and advanced stage osteoarthritis (Tönnis grade 2). Using computed tomography, we measured the circumferential α-angle and head-neck offset ratio in 68 dysplastic hips and 24 normal hips. Locations of the head-neck junction were represented by the clock position. In the pre/early group, the α-angle was significantly larger at the anterosuperior and inferior aspects (1, 2, and 5–7 o'clock) and head-neck offset ratio was smaller at the anterosuperior aspect (2 o'clock) than in the control group. The α-angle was significantly larger at the anterior aspects (1–4 o'clock) in the advanced group than in the pre/early group. The maximum α-angle was most commonly found at 2 o'clock (60%, 41/68 hips) in dysplastic hips. The prevalence of cam deformity (maximum α-angle >55°) was 4.2% (1/24 hips) in the control group, 22% (11/50 hips) in the pre/early group, and 50% (9/18 hips) in the advanced group. Cam deformity, inherent in the pre/early group, was found with relatively high frequency. The higher prevalence in the advanced group reflected degeneration-modified changes. When performing periacetabular osteotomy, preoperative radiographic assessments should include the femoral head-neck junction to prevent secondary femoroacetabular impingement, especially in patients with advanced stage osteoarthritis.

Original languageEnglish
Pages (from-to)1613-1619
Number of pages7
JournalJournal of Orthopaedic Research
Issue number9
Publication statusPublished - Sept 1 2016

All Science Journal Classification (ASJC) codes

  • Orthopedics and Sports Medicine


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