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High prevalence of cam deformity in dysplastic hips: A three-dimensional CT study
Yusuke Kohno1, Yasuharu Nakashima1, Takashi Hatano1
1Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Insights
Cam deformity is common in dysplastic hips, increasing with osteoarthritis severity. Preoperative assessment of the femoral head-neck junction is crucial to prevent secondary femoroacetabular impingement after surgery.
Area of Science:
- Orthopaedic Surgery
- Radiology
- Biomedical Engineering
Background:
- Femoral head-neck morphology is critical in hip joint biomechanics.
- Dysplastic hips may exhibit inherent cam deformities.
- Osteoarthritis can alter femoral morphology, potentially exacerbating impingement risks.
Purpose of the Study:
- To compare femoral head-neck morphology in normal, dysplastic, and osteoarthritic hips.
- To investigate the prevalence and location of cam deformity in different hip conditions.
- To inform surgical planning for periacetabular osteotomy to prevent secondary impingement.
Main Methods:
- Three-dimensional computed tomography imaging was used.
- Circumferential alpha-angle and head-neck offset ratio were measured.
- Dysplastic hips (n=68) and normal hips (n=24) were analyzed, stratified by osteoarthritis stage.
Main Results:
- Dysplastic hips showed larger alpha-angles and smaller head-neck offset ratios compared to controls.
- Cam deformity prevalence increased with osteoarthritis severity (pre/early: 22%, advanced: 50%).
- The anterosuperior aspect (2 o'clock) was a common location for maximum alpha-angle in dysplastic hips.
Conclusions:
- Cam deformity is inherent in many dysplastic hips and its prevalence increases with osteoarthritis.
- Preoperative assessment of the femoral head-neck junction is recommended before periacetabular osteotomy.
- Addressing cam morphology may prevent secondary femoroacetabular impingement in at-risk patients.
Abstract:
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. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1613-1619, 2016.
