Outcomes of Arthroscopic Dynamic Anterior Stabilization With and Without Remplissage

This is a retrospective observational cohort study evaluating arthroscopic dynamic anterior stabilization using the long head of the biceps tendon (DAS-LHB) for recurrent anterior glenohumeral instability.

DAS-LHB is an arthroscopic soft-tissue stabilization procedure in which the intra-articular portion of the long head of the biceps tendon is transferred through a split in the subscapularis tendon and fixed to the anterior glenoid. In addition to repair of the anterior capsulolabral complex, the transferred tendon is intended to provide a dynamic sling effect across the anterior-inferior aspect of the glenohumeral joint. The procedure has been proposed as an option for recurrent anterior shoulder instability, particularly in patients with subcritical glenoid bone loss.

All procedures included in the study were performed by the same established two-surgeon surgical team using a standardized DAS-LHB technique, a common indication algorithm, and a common postoperative rehabilitation and imaging protocol. Both surgeons participated in every procedure.

The study includes two consecutive treatment-era cohorts. The earlier cohort underwent isolated DAS-LHB, whereas a subsequent cohort underwent DAS-LHB combined with Hill-Sachs remplissage when remplissage became part of the surgical team's treatment strategy for patients with a clinically relevant Hill-Sachs lesion. Treatment was not assigned for research purposes.

Hill-Sachs remplissage consists of arthroscopic fixation of the posterior capsule and infraspinatus tendon into the Hill-Sachs defect, thereby reducing the likelihood of engagement of the humeral-sided defect with the anterior glenoid rim. The decision to perform remplissage was based on the clinical and imaging findings and the surgical team's treatment strategy at the time of surgery.

The comparison between the earlier isolated DAS-LHB cohort and the subsequent DAS-LHB plus remplissage cohort is prespecified but exploratory. Because the two groups correspond to different treatment periods and treatment indications, the comparison will not be interpreted as a randomized or causal comparison of the two procedures. Potential differences related to treatment indication, bipolar bone-loss characteristics, calendar time, and surgical experience will be considered when interpreting between-group findings.

All surgical treatment, postoperative rehabilitation, clinical assessments, and imaging were undertaken as part of routine clinical care. The present research protocol does not assign, modify, or withhold treatment and does not require additional surgery, imaging, medication, laboratory testing, or other research-specific interventions.

Clinical information will be obtained retrospectively from existing medical records, operative reports, and available imaging studies. Relevant demographic, clinical, imaging, and surgical variables will be collected to characterize the study population and the clinical context in which DAS-LHB, with or without remplissage, was performed. Preoperative imaging will be reviewed to characterize relevant glenoid and humeral bone-loss features, including glenoid bone loss and Hill-Sachs morphology when these data are available.

Postoperative shoulder magnetic resonance imaging is part of the surgical team's routine follow-up protocol after DAS-LHB. Existing postoperative MRI examinations obtained at least 6 months after surgery will be reviewed to assess the structural status of the transferred long head of the biceps tendon and the glenoid fixation site. No MRI examination will be obtained, repeated, or modified specifically for research purposes, and no research-specific contrast administration will be performed.

Because no validated MRI classification currently exists for healing or failure of an LHB transfer to the glenoid, structural findings will be categorized according to prespecified criteria adapted from the postoperative proximal-biceps and biceps-tenodesis literature. Assessment will focus on tendon continuity, tendon position relative to the intended glenoid fixation site, tendon morphology, and the tendon-fixation interface.

The transferred tendon will be categorized as intact/healed, partially failed, or completely failed according to the predefined imaging criteria. Tendon displacement or migration beyond the prespecified threshold may be considered a form of partial structural failure even when complete tendon discontinuity is not present. This threshold is exploratory because it is extrapolated from the biceps-tenodesis literature and has not been specifically validated for DAS-LHB.

MRI studies will be reviewed by the study investigators using these prespecified criteria. No independent blinded MRI assessment is planned. Imaging findings will therefore be interpreted as an exploratory structural endpoint, and this limitation will be acknowledged in the final analysis and reporting.

The study is based on a consecutive surgical cohort in order to reduce selection bias. All eligible procedures performed during the defined study period will be screened, rather than including only patients with complete long-term follow-up or favorable clinical outcomes.

Incomplete follow-up will be specifically evaluated because differential follow-up may introduce survivorship or ascertainment bias in retrospective shoulder-instability studies. The number of participants contributing data to each analysis will therefore be reported explicitly.

Patients with and without evaluable postoperative MRI will be described separately, and available baseline characteristics will be compared to assess whether the imaging subgroup differs systematically from the overall surgical cohort. Missing clinical and imaging data will be described and will not be assumed to be missing at random.

Where routine clinical follow-up information is incomplete, additional outcome ascertainment may be performed by telephone, secure electronic questionnaire, or clinical review, subject to the authorization granted by the relevant Ethics Committee. Such contact will be limited to established clinical outcome instruments and routine clinical assessment and will not alter patient care.

The study cohort is fixed by the number of consecutive eligible procedures performed during the study period rather than by prospective recruitment. Approximately 41 patients are expected to be included, comprising approximately 25 patients from the earlier isolated DAS-LHB treatment era and 16 patients from the subsequent DAS-LHB plus remplissage treatment era.

The primary analyses will characterize postoperative clinical and functional outcomes in the overall DAS-LHB cohort. The comparison between the two treatment-era cohorts will be exploratory and hypothesis-generating, particularly for low-frequency outcomes such as recurrent instability and reoperation.

Continuous variables will be summarized using means and standard deviations or medians and interquartile ranges, as appropriate, with 95% confidence intervals. Within-participant change over time will be assessed using paired parametric or nonparametric methods according to data distribution. Categorical variables will be reported as proportions with appropriate confidence intervals.

Between-group comparisons of the earlier isolated DAS-LHB cohort and the subsequent DAS-LHB plus remplissage cohort will emphasize effect estimates and confidence intervals rather than reliance on statistical significance alone because of the limited subgroup sizes and the nonrandomized, treatment-era nature of the comparison.

No multivariable model is planned for outcomes expected to have a small number of events. Missing data will not be routinely imputed; analyses will use available complete data for the relevant endpoint, with denominators reported explicitly. The statistical analysis plan will be finalized before database lock and formal analysis.

The study is intended to provide complementary information on the clinical performance of DAS-LHB and on the postoperative structural appearance of the transferred biceps tendon. It will also provide exploratory clinical data regarding the use of Hill-Sachs remplissage in combination with DAS-LHB, while recognizing the chronological and nonrandomized nature of that comparison.

The study will be reported in accordance with applicable observational and surgical case-series reporting guidance. Ethical approval and the final determination regarding consent requirements will be documented before formal study analysis is initiated.