The Role of Pectoralis Minor Tightness in the Development of Rotator Cuff Tears

Overview

This study investigates whether tightness of a small chest muscle called the pectoralis minor is associated with the development of rotator cuff tears in the shoulder. Using a propensity score matched case-control design, the study compares patients with rotator cuff tears (case group, n=45) to patients with intact rotator cuffs (control group, n=45). Adults aged 18-55 with shoulder pain who are evaluated by MRI and/or shoulder arthroscopy at Gazi University Hospital may be invited. The case group includes patients found to have rotator cuff tears during arthroscopy. The control group includes patients whose rotator cuff was documented as intact by MRI and/or arthroscopy (e.g., patients treated for labral, SLAP, or instability pathology). Groups are matched 1:1 on age, sex, BMI, occupation, sportive activity and dominant side. Before surgery, a trained clinician measures shoulder posture and pectoralis minor length using simple external tools (a digital caliper and ruler-like square). For arthroscopy patients, the surgeon records general arthroscopic findings. No extra procedures are added for research. We expect to include 90 participants total. The primary hypothesis is that pectoralis minor tightness is more prevalent in patients with rotator cuff tears compared to controls. A secondary hypothesis is that tears in patients with pectoralis minor tightness more often begin on the bursal side. Results may help clinicians understand shoulder mechanics and improve prevention or rehabilitation strategies.

Rationale and Objectives Pectoralis minor (PM) tightness alters scapular position (anterior tilt, internal rotation) and may increase subacromial compression. This propensity score matched case-control study evaluates whether PM tightness is associated with the development of rotator cuff tears (RCTs) and, secondarily, whether tears in PM-tight shoulders more often begin on the bursal side. Design and Setting Single-center, propensity score matched case-control study at a tertiary academic hospital (orthopaedic shoulder service, Gazi University Hospital). 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 Case group (n=45): Patients who underwent shoulder arthroscopy performed by Prof. Dr. Ulunay Kanatli and were found to have rotator cuff tears intraoperatively. Control group (n=45): Patients presenting with shoulder pain whose rotator cuff was documented as intact by MRI and/or arthroscopy. This includes patients who underwent arthroscopy for labral, SLAP, or instability pathology without rotator cuff tear, and patients with MRI-confirmed intact rotator cuff. Matching: Propensity score matching (nearest neighbor, caliper 0.2 SD) on age, sex, BMI, and dominant side using R MatchIt package. Key exclusions: prior ipsilateral shoulder surgery; acute fracture/dislocation; major-trauma RCT; cervical radiculopathy/thoracic outlet syndrome; systemic inflammatory arthropathy; barriers to consent. 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 (ICC 0.83-0.87); three trials recorded; mean used for analysis. * Medial scapular border-thoracic distance (mm) using digital calipers (ICC 0.88-0.97). * Forward shoulder posture using a 300 mm square (ICC 0.89). * Imaging abstraction: Standard shoulder radiographs and MRI summarized. Intraoperative assessment (for arthroscopy patients): Surgeons document tear initiation site (bursal vs articular) and tear characteristics using a standardized form based on video visualization. Sample Size and Power Based on a conditional logistic regression framework: OR=3.0, alpha=0.05 (two-sided), power=0.80, with 10% dropout allowance. Total n=90 (45 case + 45 control). Statistical Analysis Plan * Software: IBM SPSS Statistics-26, R (MatchIt package) * Normality: Shapiro-Wilk test * Comparisons: Paired t-test / Wilcoxon / McNemar for matched pairs * Multivariable: Conditional logistic regression * Primary outcome: Presence of rotator cuff tear (case vs control) as a function of PM tightness * Secondary outcome: Tear initiation site (bursal vs articular) as a function of PM length in the case group * Significance level: two-sided alpha=0.05 Quality Assurance * All measurements by a single trained investigator (intra-rater reliability) * Video recordings retained for intraoperative assessment verification * Data stored on encrypted drives (KVKK compliant)