Schulthess Clinic Zürich Shoulder Instability Registry: a local registry for multimodal data collection and enhanced care.

PURPOSE: The Shoulder Instability Registry (SIR) was established in 2019 to systematically capture and monitor outcomes following surgical treatment of shoulder instability (SI). The aim of this cohort profile is to describe the purpose, design, data structure and baseline characteristics of the SIR, and to outline how the registry supports longitudinal assessment of safety, functional recovery, quality of life and patient-reported outcomes after surgical treatment of SI. PARTICIPANTS: The registry includes all patients treated surgically for SI. Data collection includes medical history of instability, surgical techniques and intraoperative findings. Clinical assessments include range of motion, instability-specific tests, hyperlaxity signs, Constant Score, subjective shoulder value and SI-specific scores such as the ROWE Score and the Western Ontario Shoulder Instability Index. Radiological evaluations included initial and follow-up imaging via X-rays and CT to assess bony lesions and SI-related arthropathy, as well as MRI for soft tissue injuries. Data are documented preoperatively, at 6 months and at 24 months postoperatively. Although the SIR is an observational cohort rather than a randomised clinical trial, treatment effectiveness is evaluated through longitudinal changes in validated patient-reported outcomes, clinical performance measures and imaging findings. FINDINGS TO DATE: Between January 2019 and December 2024, 668 patients have been registered (mean age 31 years, 82% men, mean body mass index of 25). According to the American Association of Anesthesiology (ASA) Classification, 66% of patients were classified as ASA I, 33% as ASA II and only 1% as ASA III. 69% of admissions were due to accidents and 31% due to illness. Mean surgery duration was 75 min, and the median hospital stay was 2 days. 38% of patients were insured privately and had general insurance in 62%. 85% of cases were treated arthroscopically, and 15% were treated openly. Baseline clinical scores showed a mean Constant Score of 77 points, mean subjective shoulder value of 49%, mean ROWE Score of 46 points and mean Western Ontario Shoulder Instability Index of 53. Based on Gerber's classification, 68% of cases were type B2, 29% B3, 2% B5 and fewer than 2% were classified as B4 or B1. 85% of cases suffered from anterior instability, while only 13% experienced posterior instability, the remaining 2% showed multidirectional instability. Among posterior cases, Moroder's classification identified 58% as type B2, 19% as A2, 7% as A1, 6% as B1, 6% as C1 and 4% as C2. Regarding osteochondral lesions, 20% showed none, 31% showed a glenoid defect, 54% showed a Hill-Sachs lesion and 13% showed a cartilage defect. Scheibel's classification identified glenoid defects as type 3a in 38% of cases, type 2 in 24%, type 1a in 13% of cases, type 3b in 11%, type 1b in 8% and type 1c in 5% of cases. Positive Gagey and Walch signs were observed in 29% and 27% of cases, respectively. Dislocations presented as primary events in 24% of cases, while 76% were recurrent. Surgical interventions included 459 (70%) Bankart repairs, 6 Bankart plus repairs (<1%) and 108 (16%) Remplissage procedures for soft tissue stabilisation. Bony reconstructions included 52 fragment fixations (8%), 41 coracoid transfers (6%) and 87 iliac crest bone grafts (13%). Additional pathologies were addressed in 533 cases (81%), while 38 cases required revision surgery. FUTURE PLANS: We will continue prospectively enrolling and monitoring patients that receive surgical treatment of SI. There are no current plans to halt the data collection in the near future, thereby consistently increasing the number of patients in the registry. A larger availability of data will additionally allow us to apply machine learning modelling and develop risk-prediction tools with the goal of aiding surgical decision making.