Intraoperative joint load evaluation of shoulder postures after reverse total shoulder arthroplasty: a cadaveric study using a humeral trial sensor

Allan Wang, Sven Goebel, Katie Wang, Kyle Raubenheimer, Alexander Greene, Matthias Verstraete

Research output: Contribution to journalArticlepeer-review


Background: The effect of improper tension in reverse total shoulder arthroplasty (RTSA) can cause both joint looseness potentially leading to instability and dislocation and joint tightness potentially leading to limited joint motion and acromial or scapular spine stress fractures. Intra-articular load sensors offer an innovative technology providing information on real-time joint load parameters. The objective of this study is to evaluate a novel load sensor in a cadaveric RTSA model, to measure joint loads in shoulder positions required for activities of daily living (ADLs), with and without subscapularis repair. Our hypothesis is that an in situ joint load sensor can reliably measure the magnitude of joint load, and that subscapularis repair both increases joint load magnitude and improves the concentricity of the articulation at end range motion. Methods: Nine freshly frozen full body cadaver shoulders were selected for this study. All shoulders were implanted with RTSA implants with the humeral insert incorporating a wireless load measuring sensor. Three ADL postures (“across chest”, “behind back”, and “overhead reach”) were each evaluated 5 times by a single observer that was blinded to the real time loads displayed by the sensor software interface. Joint load magnitude and resultant location of the load (centroid) were recorded for each ADL posture. The subscapularis was then repaired in the native location, and the ADL posture and load measurement protocol were repeated. Results: All 3 postures demonstrated an intra-class correlation coefficient of over 0.9, indicating high repeatability of the load magnitude measured on the same specimen. Load magnitudes ranged from 5 lbf to 70 lbf “where 1lbf = .454kgf” depending on the posture and position. Subscapularis repair statistically significantly increased mean joint loads in the behind back position (P = .046) and the “overhead reach” posture (P < .001). The centroid location differed between the “behind back” and “overhead reach” postures for both radial distance (R) and angular position (θ) (P < .05). Subscapularis repair did not change R or theta for any of the three ADL postures compared to testing with subscapularis unrepaired. Discussion: Sensors placed within the trial insert can reliably measure joint loads in selected ADL postures. Subscapularis tendon repair increases the magnitude of joint load but does not appear to improve concentricity of resultant load when the shoulder is placed in ADL postures. Future work will involve sensor usage in a clinical setting to evaluate if measured joint load parameters correlate with improved clinical outcomes. Level of Evidence: Basic Science Study; Biomechanics

Original languageEnglish
Pages (from-to)36-44
Number of pages9
JournalSeminars in Arthroplasty JSES
Issue number1
Early online date22 Jul 2021
Publication statusPublished - Mar 2022


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