Research Papers

Effects of Prosthetic Mismatch and Subscapularis Tear on Glenohumeral Contact Patterns in Total Shoulder Arthroplasty: A Numerical Musculoskeletal Analysis

[+] Author and Article Information
Lauranne Sins

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

Patrice Tétreault

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

Natalia Nuño

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

Nicola Hagemeister

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

1Corresponding author.

Manuscript received February 12, 2016; final manuscript received August 23, 2016; published online November 3, 2016. Assoc. Editor: Tammy L. Haut Donahue.

J Biomech Eng 138(12), 121007 (Nov 03, 2016) (8 pages) Paper No: BIO-16-1058; doi: 10.1115/1.4034654 History: Received February 12, 2016; Revised August 23, 2016

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.

Copyright © 2016 by ASME
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Fig. 1

(a) Workflow of inverse dynamic analysis (adapted from Ref. [17]) and (b) workflow of inverse dynamic analysis with the force-dependent algorithm. q, q̇, q̈: respectively, position, velocity, acceleration of each bone segment, I(q)q̇: inertial forces and torques (vector), C(q)q̇2: centrifugal and Coriolis forces and torques (vector), G(q): gravitational forces and torques (vector), G(q): muscle moment arms (matrix), FMT: musculotendon (MT) forces (vector), R(q)FMT: torques (vector), F: joint forces, and C(q,q̇): external forces and torques applied to the body by the environment (vector).

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Fig. 2

Representation of the two components (humeral head and glenoid) placed in the shoulder model. The figure represents a 6.4 mm mismatch.

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Fig. 3

Range of humeral head translations in inferior–superior (IS) and anterior–posterior (AP) directions

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Fig. 4

Positions of contact area and center of pressure. The five mismatches are depicted, at five degrees of elevation in the scapular plane (15 deg, 30 deg, 60 deg, 90 deg, and 120 deg). For each case, the contact area for an intact-muscle shoulder (black line) and a shoulder with a subscapularis tear (gray line) are drawn. The centers of pressure are represented by the cross sign.

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Fig. 5

Contact area values at the end of elevation (maximal values)

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Fig. 6

Pattern of displacement of the center of pressure (COP) during elevation in the scapular plane. The figure shows the values for the 6.4 mm mismatch, corresponding to a combination of a medium glenoid size and a Ø51 mm humeral head size. COP position is represented in black for the intact-muscle shoulder, and in gray for the subscapularis-tear shoulder.

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Fig. 7

Glenohumeral joint reaction force and glenohumeral contact pressure at arm elevation of 90 deg




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