Effects of Prosthetic Mismatch and Subscapularis Tear on Glenohumeral Contact Patterns in Total Shoulder Arthroplasty: A Numerical Musculoskeletal Analysis.
Prosthetic components' mismatch and subscapularis (SC) tear are determining factors for glenoid failure complication in nonconforming total shoulder arthroplasty (NC-TSA). Risk factors are linked to glenoid prosthetic loading. However, the mechanisms underlying the clinical observations remain unclear. This study assessed the combined impact of mismatch and subscapularis tear on glenoid loading. It was assumed that adequate glenoid loading was associated with minimal, but non-null, humeral head translations and contact pressure, as well as with maximal glenoid contact area, and that the center of pressure (COP) on the glenoid would have a centered displacement pattern. A numerical model was used to achieve two objectives. The first was to verify whether an optimum mismatch existed, for which failure risk would be minimal. The second was to explore the effect of subscapularis tear on the position of applied forces on the glenoid. A shoulder AnyBody musculoskeletal model was adapted to the arthroplasty context by introducing humeral head translations and contact between implants. Ten simulations were computed to compare combinations of varying mismatches (1.4 mm, 3.4 mm, 6.4 mm, 8.6 mm, and 9 mm) with two shoulder conditions (intact-muscle or subscapularis tear). Humeral head translations, center-of-pressure, contact area, contact pressure, and glenohumeral joint contact forces were numerically estimated. Mismatches between 3.4 mm and 6.4 mm were associated with the most minimal humeral translations and contact pressure, as well as with maximal contact area. Center of pressure displacement pattern differed according to shoulder condition, with an outward anterior tendency in presence of tear.
Laboratoire de recherche en Imagerie et Orthopédie (LIO), CHUM Research Centre (CR-CHUM), Local R11.322, 900 St-Denis Street, Montréal, QC H2X 0A9, Canada e-mail: lauranne.sins@gmail.com.
Lauranne
L
Sins
Orthopaedics Surgery Department, Local DR-1118-16, Centre Hospitalier de l'Université de Montréal, Notre-Dame Hospital, 1560 rue Sherbrooke, Montréal, QC H2L 4M1, Canada e-mail: p.tetreault.md@gmail.com.
Patrice
P
Tétreault
Department of Automated Production Engineering, École de technologie supérieure, 1100 Notre-Dame Street West, Montréal, QC H3C 1K3, Canada e-mail: natalia.nuno@etsmtl.ca.
Natalia
N
Nuño
Laboratoire de recherche en Imagerie et Orthopédie (LIO), CHUM Research Centre (CR-CHUM), Local R11.322, 900 St-Denis Street, Montréal, QC H2X 0A9, Canada e-mail: nicola.hagemeister@etsmtl.ca.
Nicola
N
Hagemeister
D000072228:Arthroplasty, Replacement, Shoulder / Q000009:adverse effects*; D003198:Computer Simulation; D006801:Humans; D008954:Models, Biological; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000503:physiopathology*; D017755:Prosthesis Fitting / Q000009:adverse effects; D016059:Range of Motion, Articular; D000070636:Rotator Cuff Injuries / Q000209:etiology* / Q000503:physiopathology*; D012785:Shoulder Joint / Q000503:physiopathology*; D000072227:Shoulder Prosthesis / Q000009:adverse effects; D013499:Surface Properties; D016896:Treatment Outcome