Triangular Index Ratio as an Alternative Method to the Alpha Angle for Defining the Presence of Cam Morphology: A Prospective Cohort Study
Authors' conclusion
Cam morphology defined by a TIR ≥1.05 at baseline is associated with the development of RHOA 10 years later.
Study context
- Population
- Dutch population aged 45 to 65 years with first-onset hip or knee pain or both presenting to the general practitioner (CHECK study); hips free of radiographic hip osteoarthritis (RHOA) at baseline (KL grade <2)
- Participants
- 1,002 participants
- Exposure
- Triangular index ratio (TIR)-defined vs alpha angle (AA)-defined cam morphology for predicting radiographic hip OA
- Outcome
- Development of RHOA (KL ≥2)
- Follow-up
- 10-year follow-up
Methodological detailslogistic regression adjusted for age, sex and BMI, 10-year follow-up
- Logistic regression adjusted for age, sex and BMI
- 10-year follow-up
Main finding
As reported in the abstract
Development of RHOA, TIR-defined cam morphology
TIR-defined cam morphology vs none, aOR
2.48
95% CI 1.38–4.46
Observational data: associations, not effects.
Further findings
| Outcome | TIR | AA |
|---|---|---|
| Predictive performance for RHOA · 10-year follow-up | ||
| PPV | 70.6%, 95% CI 59.0-80.0 | 62.3%, 95% CI 53.8-70.1 |
| Sensitivity | 7.8%, 95% CI 5.8-10.2 | 12.3%, 95% CI 9.8-15.2 |
Predictive performance for RHOA · 10-year follow-up
- PPVs and sensitivities of TIR and AA overlapped
Original publication
Triangular Index Ratio as an Alternative Method to the Alpha Angle for Defining the Presence of Cam Morphology: A Prospective Cohort Study. Arthritis Care Res (Hoboken). Published 18 May 2026. doi:10.
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