• Shoulder/Elbow Surgery

The shoulder is the most frequently dislocated large joint, with a prevalence of 2–8%. Recurrent dislocations and anterior instability commonly follow a primary event, particularly in young, active men. Up to 50% develop glenoid bone loss, increasing the risk of recurrence, osteoarthritis, and functional impairment. Surgical treatment of anterior shoulder instability is often recommended, especially in young patients. Several shoulder-stabilising surgeries can be performed; however, the most frequently performed surgeries are the Bankart repair and the Latarjet procedure, depending on the amount of glenoid bone loss.
Anterior shoulder instability typically occurs with the arm in abduction and external rotation. Diagnosing anterior shoulder instability is primarily based on clinical examination, often employing the apprehension-relocation test to determine the presence or absence of instability. While CT and MRI assess structural damage, they do not capture joint function and stability in instability-provoking positions or motions.
Radiostereometric analysis (RSA) enables precise assessment of glenohumeral joint (GHJ) kinematics in six degrees of freedom, including during dynamic, instability-related positions. Inertial measurement units (IMUs) quantify shoulder activity during daily life.
This PhD aimed to evaluate GHJ stability and function before and after surgical stabilisation using RSA and IMUs.
Study I showed that the Latarjet procedure stabilised the GHJ after 15% glenoid bone loss and restored kinematics under anterior load, but led to overcorrection of the humeral head position without anteriordirected loading. Study II demonstrated that the Latarjet provided greater posterior stabilisation at lower loads and higher abduction angles, whereas the Eden-Hybinette procedure was more effective at higher loads and lower abduction angles. Study III found that unstable shoulders had a more inferior and anterior humeral head contact point and increased joint laxity compared to healthy shoulders. Study IV showed that one year after the Latarjet procedure, the GHJ kinematics during apprehension resembled the healthy shoulder, with a more posterior and superior humeral head position. Study V found no differences in daily shoulder activity between injured and healthy shoulders for patients with anterior shoulder instability, pre- or postoperatively.
These five studies contribute to an enhanced understanding of the pathokinematics of anterior shoulder instability, the stabilising effects of surgical interventions and their impact on daily shoulder function in patients with glenoid bone loss. The findings highlight the potential for further exploration of GHJ kinematics in other instability conditions and surgical procedures, offering a foundation for identifying patient-specific stabilising surgeries to optimise outcomes.

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Study I: Kipp JO, Petersen ET, Thillemann TM, de Raedt S, Borgen LE, Brüel A, Falstie-Jensen T, Stilling M (2025). The Latarjet procedure may induce secondary subluxation. An experimental radiostereometric study. J Bone Joint Surg Am. 2025 Dec 3;107(23):2661-2670.
doi.org/10.2106/JBJS.25.00120.

Study II: Kipp JO, Thillemann TM, Petersen ET, de Raedt S, Borgen L, Brüel A, Falstie-Jensen T, Stilling M (2024). Evaluation of glenohumeral joint kinematics following the Latarjet and Eden-Hybinette procedures. A dynamic radiostereometric cadaver study. Journal of Orthopaedic Research.
doi.org/10.1002/jor.26028.

Study III: Kipp JO, Petersen ET, Falstie-Jensen T, Teilmann JF, Zejden A, Åberg RJ, de Raedt S, Thillemann TM, Stilling M (2024). Glenohumeral joint kinematics during apprehension-relocation test in patients with anterior shoulder instability and glenoid bone loss: A radiostereometry study on 20 patients. Bone and Joint Journal.
doi.org/10.1302/0301-620X.106B10.BJJ-2024-0419.R1

Study IV: Kipp JO, Petersen ET, Stilling M, de Raedt S, Zejden A, Åberg RJ, Falstie-Jensen T, Thillemann TM (2025). One-year follow-up of 20 patients undergoing the Latarjet procedure: A biomechanical study during an apprehension-relocation test measured with radiostereometry. Bone Joint Res. 2025 Jun 3;14(6):506-515.
doi.org/10.1302/2046-3758.146.BJR-2024-0533.R1

V: Kipp JO, Langohr DG, Petersen ET, Stilling M, de Raedt S, Falstie-Jensen T, Teilmann JF, Teeter MG, Thillemann TM (2026). Daily shoulder activity in patients with anterior shoulder instability before and after shoulder stabilizing surgery measured with inertial measurement units.