Methods
This was a secondary analysis of prospectively collected data of patients with advanced osteoarthritis of the glenohumeral joint who had undergone TSA or HHR and had participated in previous formal studies and were followed up for up to 2 years. This study has adhered to the STROBE guidelines for observational studies and has received ethics approval from the Research Ethics Board of the Sunnybrook Health Sciences Centre.
Subjects
The inclusion criteria included age greater than 18 years, a diagnosis of advanced primary osteoarthritis or inflammatory arthritis with or without rotator cuff pathology that had not responded to conservative treatment. The exclusion criteria included inability to speak or read English, evidence of infection, underlying metabolic disease, avascular necrosis, or capsulorraphy arthropathy. Patients with primary osteoarthritis of the glenohumeral joint and an intact rotator cuff underwent TSA. Those with humeral fractures and a normal glenoid articular surface or with severe glenoid deficiency with or without cuff tear arthropathy received HHR. In addition, younger patients and those with significant medical co-morbidities underwent HHR, rather than reverse arthroplasty, as the reverse prosthesis may not be sufficiently durable in younger age group and may have higher complication rate in the presence of other medical conditions.
All patients followed a standardized rehabilitation protocol. A sling was used for two weeks with immediate active assisted mobilization following surgery. Sub-maximal isometric exercises started at four weeks post-operatively. Active exercises started at 6 weeks in lying progressing to upright position at 7 weeks. Resistive exercises involving theraband started at 8–10 weeks. Exercises related to internal rotation followed the other directions of movement with a 4-week delay to avoid strain on subscapularis.
Outcome Measures
Two patient-oriented outcome measures and a record of physical symptoms were obtained 2–3 weeks before surgery and on clinic visits at 6, 12, and 24 months after surgery. The outcome measures were the American Shoulder and Elbow Surgeon's (ASES) assessment form and the Relative Constant Murley score (RCMS). The ASES is a 100-point scale, 50 points of which are derived from patient self-report of pain on a visual analog scale and 50 points of which are computed from a formula using the cumulative score of 10 activities of daily living derived using a four-point ordinal scale. The Constant Murley score is a combined measure, containing a patient reported component (35%) and the clinical assessment of range of motion and strength (65%). The absolute score is then converted to the relative score by accounting for age and sex-related differences. Higher scores on the ASES and RCMS indicate less disability. Both measures have established validity and reliability in patients with glenohumeral osteoarthritis. Physical symptoms were measured by the physical symptoms domain of the Western Ontario Osteoarthritis Shoulder (WOOS) Index. Symptoms captured pain with movement, nagging constant pain, weakness, stiffness, grinding and impact of weather changes on pain. The score of the physical symptoms domain varied from 0 as no pain to 600 as the maximal pain and discomfort. Performance measures included active range of motion (ROM) in 3 directions (flexion, abduction, external rotation in neutral, and hand behind back) and strength in scapular plane elevation. Strength was measured with a simple tensiometer with the shoulder at 90 degrees of elevation in the plane of the scapula and the elbow extended while the clinician pulled down on the tensiometer. The maximum painfree force that the patient could resist for 5 seconds as the examiner pulled down on the device was measured. In the case of pain while holding the position, strength was given a score of zero.
Statistical Analyses
Descriptive analyses of patients' characteristics and outcome measures' summary scores were performed. This study applied a fixed occasion repeated measures design. We applied Generalized Estimating Equations (GEE) to test for differences in the surgical groups' change trajectories for each outcome measure. GEE fit population averaged panel data models. Complete data for a given outcome measure at all time-points is not required for a patient to be included in the analysis. Dependent variables were the outcome measures assessed at multiple time-points. The independent variables were surgical group (levels were TSA and HHR) and measurement occasion (levels were pre-surgery, 6, 12, 24-months); covariates were gender and age. All analyses were conducted using STATA version 13.0 (STATACorp, College Station, TX).