Association of Pectoralis Minor Tightness With the Initiation Site of Rotator Cuff Tears

Overview

This study looks at whether tightness of a small chest muscle called the pectoralis minor is linked to where rotator cuff tears begin in the shoulder. Rotator cuff tears can start on the bursal side (top surface) or the articular side (joint surface). We want to learn if people with a tighter pectoralis minor are more likely to have tears that begin on the bursal side. Adults aged 18-60 who already plan to have shoulder arthroscopy as part of their usual medical care at Gazi University Hospital may be invited. Taking part does not change their treatment. Before surgery, a trained clinician will measure shoulder posture and pectoralis minor length using simple external tools (a caliper and ruler-like square). We will also review routine shoulder X-rays and MRI scans if available. During surgery, the surgeon will look inside the joint (standard arthroscopy) and record where the tear appears to start. No extra procedures are added for research. We expect to include about 81 participants. The main question is whether people with a shorter (tighter) pectoralis minor more often have bursal-side tear initiation. Results may help doctors understand shoulder mechanics and improve prevention or rehabilitation strategies in the future. Participation is voluntary, and data will be de-identified and kept confidential. There is no direct benefit to participants, and risks are limited to the brief, noninvasive measurements performed before surgery.

Detailed Description Rationale and Objectives Pectoralis minor (PM) tightness alters scapular position (anterior tilt, internal rotation) and may increase subacromial compression. This study prospectively evaluates whether PM tightness is associated with the initiation site of rotator cuff tears (RCTs)-specifically, whether tears more often begin on the bursal side in shoulders with a shorter (tighter) PM. Design and Setting Single-center, prospective, observational study at a tertiary academic hospital (orthopaedic shoulder service). Care is not altered by participation. All surgical and imaging procedures are standard of care; research procedures are limited to noninvasive postural/PM length measurements and structured data collection. Participants Adults scheduled for routine shoulder arthroscopy for suspected/confirmed RCT may be invited. Key exclusions (summarized): prior ipsilateral shoulder surgery; acute fracture/dislocation; major-trauma RCT; cervical radiculopathy/thoracic outlet syndrome; systemic inflammatory arthropathy; barriers to consent. (Full inclusion/exclusion are listed in the Eligibility section.) Study Procedures Preoperative assessments (same-day or pre-op clinic): Pectoralis minor length (mm): Linear distance from coracoid tip to rib attachment measured with a digital caliper; three trials recorded; mean used for analysis. Scapular posture metrics: Medial scapular border-thoracic distance (mm) using calipers/ruler. Forward shoulder posture using a 300 mm square/ruler referenced to the table/chest wall. Imaging abstraction: Standard shoulder radiographs and MRI summarized (tear size/pattern, fatty infiltration grades if reported). Intraoperative assessment (standard arthroscopy): Surgeons document tear initiation site (bursal vs articular/delamination) and tear characteristics (pattern/size) using a standardized form based on video visualization. No additional portals or procedures are performed for research. Data Elements and Sources Source documents: medical records, PACS (X-ray/MRI), operative reports, arthroscopy video, and study case report forms (CRFs). Key variables: PM length (continuous, mm); posture measures; tear initiation site (primary outcome); tear size/pattern; demographic/clinical covariates (age, sex, side, symptom duration, occupation/sport, BMI if available). Registry Operations and Quality Plan Quality Assurance \& Monitoring Training/standardization: Investigators receive a 1-page landmarking guide and a brief hands-on calibration session for PM and scapular measurements. Inter-/intra-rater reliability: A random 15-patient subset will be re-measured by a second rater within the same visit; intraclass correlation coefficients (ICC, two-way random, absolute agreement) will be reported. Instrument calibration: Digital calipers checked weekly with a gauge block; records kept in a calibration log. On-site checks: Monthly coordinator audits of 10% of charts for consent presence, eligibility, and CRF completeness. Automated Data Checks Electronic CRFs include range checks (e.g., PM length 80-200 mm; posture distances 0-100 mm) and logic checks (e.g., surgery date ≥ consent date; side consistency across forms). Cross-field consistency rules (examples): if "tear initiation = bursal," then arthroscopy notes must include bursal-surface description; MRI "no tear" triggers manual review of intraop outcome. Source Data Verification (SDV) 100% SDV of primary outcome (tear initiation site) against operative video/report. 20% SDV of key predictors (PM length, posture metrics) against paper measurement sheets. Discrepancies \>2 mm or any categorical mismatch prompt corrective action and retraining as needed. Data Dictionary A structured dictionary defines each variable (name, label, unit, allowed values, derivation, normal/expected range, source document, and coding system where relevant-e.g., MedDRA for adverse events). Versioned and stored with the analysis code; any change triggers a minor version update and change log entry. Standard Operating Procedures (SOPs) SOPs cover: screening and consent; measurements; data entry; query resolution; SDV/monitoring; adverse-event reporting (see below); database lock and change management; archiving and access control. Sample Size and Power Based on a logistic-regression framework with the primary outcome "bursal-side initiation (yes/no)," assumptions were: α=0.05 (two-sided), power=0.80, baseline bursal-initiation proportion \~0.50, prevalence of PM tightness \~0.50, and an odds ratio of \~4.0 for PM-tight vs non-tight. Variance-adjusted calculations support ≈82 shoulders total, satisfying ≥10 events per predictor for the planned model. Plan for Missing Data Prevention: required-field checks at data entry; real-time prompts for missing or out-of-range values. Handling: if ≤5% missing for a covariate, complete-case analysis will be used; if \>5-20%, single-variable multiple imputation (m = 20) under missing-at-random assumptions will be applied for predictors (not for outcomes). Sensitivity analyses will compare imputed vs complete-case results. Outcome data: primary outcome (tear initiation site) is expected to be complete; any missing outcome leads to exclusion from the primary analysis and description of reasons. Statistical Analysis Plan (SAP) Descriptive analysis: Means/SD or medians/IQR for continuous variables; counts/percentages for categorical variables. Group summaries by PM-tight vs non-tight may be shown for context. Primary analysis: Binary logistic regression with tear initiation site (bursal=1, articular/delamination=0) as the dependent variable; key predictor is PM length (continuous, per-10 mm decrease) and/or PM-tightness (binary, threshold prespecified from literature or study distribution). Covariate adjustment: Age, sex, side, tear size/pattern, acromial morphology, and other prespecified clinical factors if available. Model diagnostics: Linearity (Box-Tidwell for continuous predictors), multicollinearity (VIF\<5), calibration (Hosmer-Lemeshow), discrimination (AUC with 95% CI). Sensitivity analyses: (1) Treat PM length as continuous vs categorical; (2) exclude massive tears; (3) rater-blinded subset; (4) alternative PM-tightness cut-points (±5 mm). Significance level: two-sided α=0.05 with 95% CIs; no multiplicity adjustment for the single primary endpoint. Safety/Adverse Events No investigational procedures are performed. The physical measurements are brief, external, and low-risk (possible transient discomfort). Any adverse events observed in proximity to research procedures will be recorded and reported per institutional policy. Surgical complications are part of routine care and will be documented but not attributed to research unless clearly related to the measurement process. Data Management, Confidentiality, and Access Data are recorded on coded CRFs and stored in a secure, access-controlled database. A link file that maps codes to identities is stored separately on encrypted drives. Access is role-based (PI, coordinator, analyst). Backups occur daily. Data retention follows institutional policy and national data-protection law. Dissemination/IPD Sharing: Results will be submitted for publication and conference presentation. De-identified dataset and analysis code may be shared upon reasonable request after publication, subject to applicable privacy regulations and approvals. Timeline: Anticipated start and completion dates match the Ethics approval window; enrollment begins only after registration posting and Ethics approval confirmation.