Abstract
PurposeInstability and fractures may result from tensioning errors during reverse total shoulder arthroplasty (RTSA). To help understand tension, we measured intraoperative glenohumeral contact forces (GHCF) during RTSA.MethodsTwenty-six patients underwent RTSA, and a strain gauge was attached to a baseplate, along with a trial glenosphere. GHCF were measured in passive neutral, flexion, abduction, scaption, and external rotation (ER). Five patients were excluded due to wire issues. The average age was 70 (range, 54–84), the average height was 169.5 cm (range, 154.9–182.9), and the average weight was 82.7 kg (range, 45.4–129.3). There were 11 females and 10 males, and thirteen 42 mm and 8 38 mm glenospheres.ResultsThe mean GHCF values were 135 N at neutral, 123 N at ER, 165 N in flexion, 110 N in scaption, and 205 N in abduction. The mean force at terminal abduction is significantly greater than at terminal ER and scaption (p < 0.05).ConclusionsThese findings could help reduce inappropriate tensioning.
Highlights
Reverse total shoulder arthroplasty (RTSA) has become a widely used treatment for a variety of conditions, including cuff-tear arthropathy [5], pseudoparesis due to massive rotator cuff tear [29], fracture [7], rheumatoid arthritis [35], revision of failed total shoulder arthroplasty [33], and osteoarthritis with glenoid wear [17]
Sixteen RTSAs were performed for cuff-tear arthopathy, 1 for irreparable rotator cuff tears, 1 for proximal humeral malunion, 1 for glenohumeral arthritis, and 1 for rheumatoid arthritis
The most important finding of this study was that softtissue glenohumeral contact forces were at their lowest during scaption and external rotation (ER), and at their greatest during abduction
Summary
Reverse total shoulder arthroplasty (RTSA) has become a widely used treatment for a variety of conditions, including cuff-tear arthropathy [5], pseudoparesis due to massive rotator cuff tear [29], fracture [7], rheumatoid arthritis [35], revision of failed total shoulder arthroplasty [33], and osteoarthritis with glenoid wear [17]. Recurrent prosthetic instability accounts for a large percentage of these complications in some studies [9, 11, 14]. The etiology of recurrent RTSA instability may be multifactorial, but one factor often cited is inadequate soft-tissue tension [9, 16, 20, 31]. In his groundbreaking article, Grammont coined the term “global decoaptation,” and described the situation as recurrent instability due to lack of sufficient deltoid tension [16, 19]. Intraoperative assessment of soft-tissue tension remains subjective to this day, with no reproducible method of assessment
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