Demographic and radiographic factors associated with intra-articular hip cartilage injury: a cross-sectional study of 1511 hip arthroscopy procedures

Key points

1. 01Severe cam deformity (alpha angle 78 degrees or more) nearly quintupled the odds of severe acetabular cartilage injury (OR 4.82) compared to a normal alpha angle
2. 02Borderline dysplasia (lateral center-edge angle below 25 degrees) tripled the odds of severe femoral head cartilage injury (OR 3.08)
3. 03Male sex was the strongest demographic predictor for acetabular cartilage injury (OR 4.42)
4. 04Reduced joint space width raised the risk of severe cartilage damage at both the acetabulum and femoral head (ORs ranging from 2.04 to 3.19)
5. 05Specific bony deformities appear to drive specific cartilage injury patterns: cam targets the acetabulum, dysplasia targets the femoral head

How it was conducted

Design

Cross-sectional study (Level of evidence 3)

Registry

Danish Hip Arthroscopy Registry (DHAR), January 2012 to March 2018

Participants

1511 patients aged 15-50 years undergoing hip arthroscopy

Outcome variables

Acetabular cartilage injury (modified Beck grade 0-2 vs 3-4) and femoral head cartilage injury (ICRS grade 0-2 vs 3-4)

Predictor variables

Age, sex, Hip Sports Activity Scale score, alpha angle (normal / cam / severe cam), lateral center-edge angle (normal / pincer / borderline dysplasia), joint space width (normal / mild reduction / severe reduction)

Analysis

Multivariate logistic regression with all predictors entered simultaneously

What they found

• Male sex was associated with Beck grade 3-4 acetabular cartilage injury (OR 4.42, 95% CI 3.47-5.62, P less than 0.001)
• Older age (30-50 vs under 30 years) was associated with Beck grade 3-4 (OR 1.70, 95% CI 1.30-2.22, P less than 0.001) and ICRS grade 3-4 (OR 1.92, 95% CI 1.03-3.57, P = 0.041)
• Cam deformity (alpha angle 55-77 degrees) was associated with Beck grade 3-4 (OR 2.23, 95% CI 1.48-3.34, P less than 0.001)
• Severe cam deformity (alpha angle 78 degrees or more) was associated with Beck grade 3-4 (OR 4.82, 95% CI 3.14-7.41, P less than 0.001)
• Borderline dysplasia (LCEA below 25 degrees) was associated with ICRS grade 3-4 (OR 3.08, 95% CI 1.34-6.61, P = 0.004)
• Mild joint space width reduction (3.1-4.0 mm) was associated with Beck grade 3-4 (OR 2.04, 95% CI 1.58-2.64, P less than 0.001) and ICRS grade 3-4 (OR 2.63, 95% CI 1.58-4.38, P less than 0.001)
• Severe joint space width reduction (2.1-3.0 mm) was associated with Beck grade 3-4 (OR 3.19, 95% CI 1.62-6.30, P = 0.001) and ICRS grade 3-4 (OR 3.04, 95% CI 1.07-8.45, P = 0.033)
• Increasing Hip Sports Activity Scale score was associated with ICRS grade 3-4 (OR 1.13 per unit increase, 95% CI 1.00-1.27, P = 0.047)
• Pincer deformity showed a non-significant trend toward reduced acetabular cartilage injury (OR 0.67, 95% CI 0.42-1.07, P = 0.091)
• 40.4% of patients had Beck grade 3-4 acetabular cartilage injury; 4.8% had ICRS grade 3-4 femoral head cartilage injury

Limitations

• Cross-sectional design establishes association, not causation, between bony morphology and cartilage injury
• The registry lacked information on specific surgical indications, introducing potential selection bias
• Sport activity level was recorded immediately before surgery and may underestimate activity during symptom onset or skeletal maturation, an important potential confounder
• Hip morphology was assessed by plain radiographs only, which may not capture all morphological features as accurately as MRI or CT in some cases

Why it matters

For patients

Patients with hip impingement who have a large cam deformity or borderline dysplasia on X-ray are at substantially higher risk of serious cartilage damage, which may affect their surgical outcomes and long-term joint health.

For clinicians

Pre-operative alpha angle and lateral center-edge angle measurements can stratify a patient's risk of finding severe intra-articular cartilage damage at arthroscopy, informing counselling and surgical planning.

For readers

This large registry study confirms that cam and dysplastic hip shapes drive distinct cartilage injury patterns, lending support to the biological rationale for correcting these deformities before irreversible cartilage loss occurs.