It is essential to distinguish between symptomatic- and asymptomatic radiographic acromioclavicular (AC) osteoarthritis (OA) because AC-targeted physical examinations are dubious. This study aimed to determine the diagnostic value of a preoperative AC injection in discriminating between symptomatic- and asymptomatic radiographic AC OA based on patient arthroscopic distal clavicle resection (aDCR) outcomes. Methods: Forty-eight patients who underwent aDCR for AC OA were included. Their satisfaction was objectified using a 5-point Likert scale and patient willingness to repeat the surgery. The Oxford Shoulder Score (OSS), the Subjective Shoulder Value (SSV), and the Numerical Rating Scale (NRS) were used to assess postoperative shoulder function and pain. Patients were subdivided into groups based on their good or minimal reaction to an AC injection (good reaction: ≥7 consecutive days of pain reduction, Minimal reaction: <7 consecutive days of pain reduction). Results: Twenty-seven patients had a good reaction and 21 patients had a minimal reaction to the AC injection (median follow-up, 45.0 months; range, 31.0–52.8 months). No significant differences were found in level of satisfaction (P=0.234) or willingness to repeat the surgery (P=0.861). No significant differences were found in OSS (P=0.612), SSV (P=0.641), NRS at rest (P=0.684) or during activity (P=0.422). Conclusions: This study found no significant differences between patients with a good reaction or a minimal reaction to an AC injection after aDCR surgery. The outcomes of this study seem to suggest that a distinction between symptomatic and asymptomatic radiographic AC OA is unnecessary, as all patients were equally satisfied with the outcome. Level of evidence: IV.

Acromioclavicular (AC) osteoarthritis (OA) is a frequent pathology of the shoulder in elderly patients. Drug injection plays an important role in treatment of AC OA. Literature has demonstrated excellent short-term results regarding shoulder function and pain. However, mid- to long-term results are lacking. The aim of this study was to assess the efficacy of a single intra-articular AC injection in patients with AC OA and to identify predictive factors for success. Methods: A retrospective study was performed to analyze success rate, shoulder function, and pain perception after a single intra-articular injection in patients with AC OA. Success was defined as the absence of reinterventions such as additional injection or surgery. Outcome measures were 1-year success rate and clinical outcome scores of Numeric Rating Scale (NRS) for pain, Oxford Shoulder Score, and Subjective Shoulder Value. Results: Ninety-eight patients participated in this study. At a median final follow-up of 0.8 years (interquartile range, 0–6), 57 of these patients (58%) had undergone a reintervention. The 1-year success rate was 47% (95% confidence interval, 37%–57%), with NRS at rest as the sole factor significantly associated with success. Thirty patients not requiring reintervention reported significant improvement from baseline for all reported outcome measures at final follow-up. Conclusions: AC injections offer a 1-year success rate of 47%. The AC injection produces good mid- to long-term clinical outcomes regarding shoulder function, quality of life, and pain perception in one-third of patients. Further research is essential to analyze mid- to longterm outcomes of AC injections. Level of evidence: Level IV.