Schnorenberg Dissertation Abstract

Evaluation of Shoulder Complex Kinematics Pre and Post Rotator Cuff Repair and Effects of Altering Rotation Sequence

Dissertation Date:  March 31, 2022

Approximately 25% of adults in the United States will sustain a rotator cuff tear in their lifetime. Rotator cuff tears can impede one's ability to perform activities of daily living and maintain functional independence. Nearly 300,000 rotator cuff repair surgeries are performed annually and aim to decrease pain, increase range of motion, and enable return to the workforce.     

The goal of postoperative rehabilitation is to allow healing of the repaired cuff while restoring function and range of motion, but it is demanding and may require a year. However, most rehabilitation protocols are based solely on clinical experience rather than on evidence-based rationale and the optimal protocol is still being deliberated.

Despite a rapid growth in the amount of literature, re-tear rates are still being reported between 20% and 95%, and the knowledge required to improve rehabilitative planning is “seriously deficient”. A key issue is the variability in data reporting, including the presentation of post-operative data without the corresponding pre-operative data. Additionally, better knowledge of scapular and humerus kinematics could improve treatment options.

An additional concern is the methodology used for modeling the three-dimensional angles of the glenohumeral and thoracohumeral joints. The International Society of Biomechanics recommended standardized use of the YXY Euler rotation sequence. However, a recent review found less than half of the studies examined adhered to these guidelines. Research has shown that no singular sequence is accurate for all the motions of these joints, but no studies have explored the effects of all 6 Cardan sequences and the recommended YXY rotation on three-dimensional thoracohumeral joint angle calculations during upper extremity movements.

This study performs a biomechanical evaluation of individuals with rotator cuff tears pre-operatively, 3-months post-operatively, and 6-months post-operatively to elucidate the changes occurring across the rehabilitation process and when joint motions normalize. This knowledge is critical for the development of interventions to improve the post-operative recovery process, including more targeted exercises, and shortened rehabilitation time. Additionally, the effects of the YXY and 6 Cardan rotation sequences on thoracohumeral joint angle computations will be investigated during a range of shoulder postures to provide recommendations on appropriate use.


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