Outcomes following a 'positive' response to diagnostic intra-articular hip injection for pre-arthritic hip pain based on the level of percent pain improvement.

Diagnostic hip injections are used to confirm an intra-articular source of hip pain in adolescents and young adults in order to guide management. There is currently no data-driven consensus regarding what cutoff metric should be used to constitute a 'positive' response to injection. This study compared using either 50% or 75% immediate pain improvement to define a positive response to fluoroscopically-guided diagnostic hip injection to aid in management decision-making. Rates of surgical management and likelihood of satisfaction with care at 12+ months were then compared between the two groups. Amongst 56 hips, (mean age 18.5 (SD ± 5.2) years, 89% (50/56) female) there was no difference in the rate of progression to surgery amongst responders when using either a ≥50% or ≥75% cutoff of pain improvement (71% (29/41) versus 74% (20/27), between-group difference 3% [95% CI, -18% to 25%], P = .76). Amongst those undergoing surgery, there was no difference in patient-reported satisfaction, at 12+ months based on a ≥50% versus ≥75% pain improvement cutoff (74% (14/19) versus 69% (9/13) reporting 'satisfied' or 'very satisfied' on 5-point Likert Scale, between-group difference 4% [-27% to 36%], P = 0.78). Our findings suggest that a ≥50% cutoff could be considered a 'positive' response in a clinical setting and used to guide management decisions.