Total shoulder arthroplasty: Downward inclination of the glenoid component to balance supraspinatus deficiency

Larrea

Camine

et al. 2013

Clinical Biomechanics

Background: The rotator cuff muscles are the main stabilizer of the glenohumeral joint. After total shoulder arthroplasty using anterior approaches, a dysfunction of the subscapularis muscle has been reported. In the present paper we tested the hypothesis that a deficient subscapularis following total shoulder arthroplasty can induce joint instability. Methods: To test this hypothesis we have developed an EMG-driven musculoskeletal model of the glenohumeral joint. The model was based on an algorithm that minimizes the difference between measured and predicted muscular activities, while satisfying the mechanical equilibrium of the glenohumeral joint. A movement of abduction in the scapular plane was simulated. We compared a normal and deficient subscapularis. Muscle forces, joint force, contact pattern and humeral head translation were evaluated. Findings: To satisfy the mechanical equilibrium, a deficient subscapularis induced a decrease of the force of the infraspinatus muscle. This force decrease was balanced by an increase of the supraspinatus and middle deltoid. As a consequence, the deficient subscapularis induced an upward migration of the humeral head, an eccentric contact pattern and higher stress within the cement. Interpretation: These results confirm the importance of the suscapularis for the long-term stability of total shoulder arthroplasty.

Section: Introductionmentioning

confidence: 99%

Importance of the subscapularis muscle after total shoulder arthroplasty

Larrea

Camine

et al. 2013

Clinical Biomechanics

“…[1][2][3] When planning a total shoulder replacement (TSR), it is essential to address the morphology of any erosion of the glenoid in order to improve implant survival. [4][5][6][7][8][9] Optimal implant shape and positioning can be difficult to achieve, especially when bony support is lacking. 10 The positioning of the glenoid component requires a precise understanding of the orientation of the glenoid surface relative to the scapula.…”

mentioning

confidence: 99%

Measurements of three-dimensional glenoid erosion when planning the prosthetic replacement of osteoarthritic shoulders

The Bone & Joint Journal

Ston

Larrea

et al. 2014

The three-dimensional (3D) correction of glenoid erosion is critical to the long-term success of total shoulder replacement (TSR). In order to characterise the 3D morphology of eroded glenoid surfaces, we looked for a set of morphological parameters useful for TSR planning. We defined a scapular coordinates system based on non-eroded bony landmarks. The maximum glenoid version was measured and specified in 3D by its orientation angle. Medialisation was considered relative to the spino-glenoid notch. We analysed regular CT scans of 19 normal (N) and 86 osteoarthritic (OA) scapulae. When the maximum version of OA shoulders was higher than 10°, the orientation was not only posterior, but extended in postero-superior (35%), postero-inferior (6%) and anterior sectors (4%). The medialisation of the glenoid was higher in OA than normal shoulders. The orientation angle of maximum version appeared as a critical parameter to specify the glenoid shape in 3D. It will be very useful in planning the best position for the glenoid in TSR. Osteoarthritis (OA) of the gleno-humeral joint is often associated with an erosion of the glenoid.

“…A scapulo-humeral rhythm of 2:1 was assumed to replicate the motion of the scapula and the correct alignment of the muscle action relative to the arm weight. Detail of this numerical musculoskeletal model and its validation can be found in technical (Terrier et al, 2007;Terrier et al, 2008b) and clinical application papers (Terrier et al, 2008a;Terrier et al, 2009aTerrier et al, , 2009bTerrier et al, 2010).…”

Section: Methodsmentioning

confidence: 99%

“…In most of the cases, this objective can be achieved for the humeral side, thanks to the third generation modular prostheses. However, for the glenoid side, because of the constraint to keep as much as possible the subcondral bone support, the articular surface is actually displaced laterally by a few millimetres (Rockwood, 2009;Terrier et al, 2009aTerrier et al, , 2009b. The thickness of current glenoid components vary from 3 to more than 15 mm (Rockwood, 2009).…”

Section: Introductionmentioning

confidence: 99%

Importance of polyethylene thickness in total shoulder arthroplasty: A finite element analysis

Brighenti

Pioletti

et al. 2012

Clinical Biomechanics

Self Cite

Background: Articular surfaces reconstruction is essential in total shoulder arthroplasty. Because of the limited glenoid bone support, thin glenoid component could improve anatomical reconstruction, but adverse mechanical effects might appear. Methods: With a numerical musculoskeletal shoulder model, we analysed and compared three values of thickness of a typical all-polyethylene glenoid component: 2, 4 (reference) and 6 mm. A loaded movement of abduction in the scapular plane was simulated. We evaluated the humeral head translation, the muscle moment arms, the joint force, the articular contact pattern, and the polyethylene and cement stress. Findings Decreasing polyethylene thickness from 6 to 2 mm slightly increased humeral head translation and muscle moment arms. This induced a small decreased of the joint reaction force, but important increase of stress within the polyethylene and the cement mantel. Interpretation The reference thickness of 4 mm seems a good compromise to avoid stress concentration and joint stuffing.