The postoperative circles measurement considers recurrent instability and correlates with lower outcome scores after acute, bidirectional arthroscopically assisted acromioclavicular joint stabilization.

Purpose: The circles measurement is a newly validated in vivo method to evaluate acromioclavicular joint (ACJ) dislocations, but its postoperative and clinical relevance has not been evaluated. We hypothesised that the postoperative circles measurement would capture recurrent vertical as well as horizontal instability and that it would be associated with outcome scores in patients undergoing acute, bidirectional arthroscopically assisted ACJ stabilisation.

Methods: Male patients (18-55 years) with an acute ACJ dislocation (Rockwood type V) were included retrospectively. Radiographs included a single, bilateral anteroposterior stress view and bilateral Alexander views preoperatively and postoperatively (final follow-up of minimum 2 years). Excluded were patients with previous injuries/minors/polytrauma or insufficient radiographs. The side-to-side difference (SSD) coracoclavicular distance (CCD), the degree of dynamic horizontal translation (DHT) and the SSD circles measurement as well as the ACJ instability (ACJI) and Taft (TF) score, subjective shoulder value (SSV) and Constant score were recorded at the final follow-up (minimum 2 years). The postoperative SSD circles measurement was analysed in relation to these. Statistical analysis comprised correlations and group comparisons.

Results: Fifty-six patients (mean age, 38.9 ± 10.7 years) with a follow-up of 33.0 months (range, 24-55 months) were included. The postoperative SSD circles measurement demonstrated a correlation with recurrent vertical instability (SSD CCD: r = 0.37; p = 0.006), and with recurrent horizontal instability (DHT: r = 0.46; p < 0.001). A higher postoperative SSD circles measurement was associated with lower outcome scores (SSV: r = -0.31; p = 0.021; TF score: r = -0.29; p = 0.031; ACJI score: r = -0.35; p = 0.01). The cut-off values for lower scores (p < 0.05 by stepwise group comparison) were 0 mm for the SSV (p = 0.022); 2.2 mm for the TF score (p = 0.022) and 2.7 mm for the ACJI score (p = 0.024).

Conclusions: The postoperative circles measurement reflects both recurrent vertical and horizontal instability and correlates with lower outcome scores following arthroscopically assisted ACJ stabilisation, supporting its use as a radiographic adjunct.

Level of evidence: Level IV, retrospective case series.