Glenoid concavity – baseline investigation of its role for glenohumeral instability

• Applicants: Professor Dr. Jan Christoph Katthagen; Professor Dr. Jens Wermers
• Subject Area: Orthopaedics, Traumatology, Reconstructive Surgery
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 528833393

Dislocation of the shoulder joint (glenohumeral joint) often causes associated defects of the fibrocartilaginous socket rim (labrum) as well as the bony socket (glenoid). Unless defects to the labrum and glenoid are treated surgically, recurrent shoulder instability (SI) occurs in over 67 % of cases. This is considered a risk for pain, reduced quality of life, and in some cases, the development of osteoarthritis (OA). Surgical treatment to restore stability is based on soft tissue refixation of the torn labrum or bony reconstruction. The decision between these procedures is essentially made based on a critical threshold of bony defect size at the glenoid. However, recent studies show that over 26 % of patients have recurrent SI after soft tissue procedure. This high rate is concerning because many of the affected patients are young and healthy at the time of first dislocation. Defect size as a universal decision criterion for surgical treatment appears to be inadequate. To reduce the high rate of recurrent SI, future treatment choices must be made based on patient-specific characteristics rather than a critical, generalized cutoff value. Recent simulation-based studies show that concavity of the glenoid may be a determining factor for SI. The relevance of concavity has been confirmed in our own biomechanical, radiological, and clinical studies. However, in addition to concavity, retroversion, and certain rupture patterns at the rotator cuff (RC) or long head of the biceps tendon (LHB) have been identified as elementary factors for SI. The correlations have been neglected in decision making but may be a missing piece of the puzzle in patient-specific care. To improve and personalize patient care, the influence of concavity on stability, considering retroversion, needs to be further investigated in a physiological model. This model must include dynamic muscle forces to evaluate the role of concavity in the intact joint and in the presence of ruptures of the RC or LHB. The proposed project involves the development of this model by combining two established methodologies in a novel way. Dynamic muscle forces will be built up and active movements will be generated in a robot-based test bed using actuators. In addition to highly relevant baseline data on joint and muscle function, this methodology will allow the classification of concavity and retroversion for the treatment of recurrent SI, both in the intact joint and in deficient RC or LHB. Thus, the long-term goal is to reduce chronic pain, as well as improve quality of life.

• DFG Programme: Research Grants