2023 ISAKOS Biennial Congress ePoster
Influence of Graft Positioning During the Latarjet Procedure on Shoulder Stability and Articular Contact Pressure: Computational Analysis of the Bone Block Effect
Rita Martins, MEng, Lisboa PORTUGAL
Carlos Quental, PhD, Prof., Lisboa PORTUGAL
João Folgado, PhD, Prof., Lisboa PORTUGAL
Ana Catarina Ângelo, MD, Lisbon PORTUGAL
Clara Azevedo, MD, PhD, Lisbon PORTUGAL
IDMEC, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, PORTUGAL
FDA Status Not Applicable
Summary
To investigate the influence of the positioning of the bone graft on contact mechanics and glenohumeral (GH) stability due to the bone block effect, four finite element (FE) models of a GH joint, with a 20% glenoid bone defect, treated by the Latarjet procedure were developed. For the modeled conditions, the best placement of the graft lied between a lateralization of 1.5 mm and 3.0 mm.
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Abstract
Background
The Latarjet procedure is the most popular surgical procedure to treat anterior glenohumeral (GH) instability in the presence of large anterior glenoid bone defects. Even though the placement of the bone graft has a large influence on its efficacy, no clear indications exist on the best graft position. The aim of this study was to investigate the influence of the medial-lateral positioning of the bone graft on contact mechanics and GH stability due to the bone block effect.
Methods
Four finite element (FE) models of a GH joint, with a 20% glenoid bone defect, treated by the Latarjet procedure were developed. The FE models differed in the medial-lateral positioning of the bone graft, ranging from a flush position to a 4.5 mm lateral position with respect to the flush position. All graft placement options were evaluated for two separate shoulder positions. Anterior GH instability was simulated by translating the humeral head in the anterior direction, under a permanent compressive force, until peak translation force was reached. Joint stability was computed as the ratio between the shear and the compressive components of the force.
Results
The lateralization of the bone graft increased GH stability due to the bone block effect after a 3 mm lateralization with respect to the flush position, regardless of the shoulder position. No differences in GH stability were observed between the flush and the 1.5mm lateral graft position and contact pressures were always below the failure stress threshold of articular cartilage (<29.5 MPa). The increase in GH stability after the 3 mm lateralization was associated with an increase in peak contact pressure above the failure stress threshold of articular cartilage (>29.5 MPa), due to the incongruous contact between the articulating surfaces. However, whereas this high peak contact pressure was only reached after some anterior translation of the humeral head for the 3.0mm lateralization, for the 4.5 mm lateralization, this high peak contact pressure was reached even before the humeral head was anteriorly translated.
Conclusion
The sensitivity of the contact pressures to the medial-lateral positioning of the bone graft suggests a trade-off between GH stability due to the bone block effect and the risk of osteoarthritis, especially considering that an accurate and consistent placement of the bone graft is difficult in vivo. For the modelled conditions, the best placement for the bone graft lied between a lateralization of 1.5 mm and 3.0 mm with respect to the flush position.