The purpose of this study was to examine how pre-operative radiographic joint space correlated with intraoperative chondral damage as diagnosed during hip arthroscopy, in patients without radiographic evidence of osteoarthritis or joint space <2mm.
Patients under the age of 50 years without prior hip conditions who underwent hip primary arthroscopy had their joint space and intraoperative chondral damage compared. A narrow joint space group was defined as those in the lowest decile of the average joint space. The demographics and presence of intraarticular findings of chondral damage were compared. Additionally, receiver operator characteristic (ROC) curves were used to assess joint space as a predictor of intraarticular damage.
There were 1,892 in this analysis. The incidence of severe cartilage damage (Outerbridge III & IV) was not significantly different between the narrow and non-narrow groups. The ROC analysis for joint space at detecting chondral damage was poor. The ROC- area under the curve for joint space detecting any chondral defect (acetabular or femoral head) was 0.536 (CI = 0.506 – 0.565), with low sensitivity (0.492), specificity (0.582), negative predictive value (0.720), and positive predictive value (0.340). Spearman correlation could not demonstrate a correlation between joint space and cartilage damage (⍴Acetabular = 0.10, ⍴Femoral Head = 0.04). Interestingly, a gradual widening was observed between the medial and lateral joint spaces, with more pronounced findings in hips without damage.
The results of this study demonstrate that in patients with Tönnis 0 and 1, narrower joint space cannot predict actual intraoperative cartilage damage. However, if the lateral joint space has relative narrowing compared to the medial joint space, this may indicate acetabular cartilage damage.