An analytical model for rotator cuff repairs

Aurora, A.; Gatica, J.E.; van den Bogert, A.J.; McCarron, J.A.; Derwin, K.A.

doi:10.1016/j.clinbiomech.2010.05.010

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Volume 25, Issue 8 , Pages 751-758, October 2010

An analytical model for rotator cuff repairs

A. Aurora
- Department of Biomedical Engineering, ND2-20, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44122, USA
- Department of Chemical and Biomedical Engineering, SH 459, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA
J.E. Gatica
- Department of Chemical and Biomedical Engineering, SH 459, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA
A.J. van den Bogert
- Department of Biomedical Engineering, ND2-20, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44122, USA
J.A. McCarron
- Department of Orthopedic Surgery, A41, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44122, USA
K.A. Derwin
- Department of Biomedical Engineering, ND2-20, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44122, USA
- Department of Orthopedic Surgery, A41, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44122, USA
- Corresponding author. Department of Biomedical Engineering, ND2-20, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44122, USA.

Received 15 December 2009; accepted 20 May 2010. published online 28 June 2010.

Abstract

Background

Currently, natural and synthetic scaffolds are being explored as augmentation devices for rotator cuff repair. When used in this manner, these devices are believed to offer some degree of load sharing; however, no studies have quantified this effect. Furthermore, the manner in which loads on an augmented rotator cuff repair are distributed among the various components of the repair is not known, nor is the relative biomechanical importance of each component. The objectives of this study are to (1) develop quasi-static analytical models of simplified rotator cuff repairs, (2) validate the models, and (3) predict the degree of load sharing provided by an augmentation scaffold.

Methods

The individual components of the repair constructs were modeled as non-linear springs, and the model equations were formulated based on the physics of springs in series and parallel. The model was validated and used to predict the degree of load sharing provided by a scaffold. Parametric sensitivity analysis was used to identify which of the component(s)/parameter(s) most influenced the mechanical behavior of the augmented repair models.

Findings

The validated models predict that load will be distributed ∼70–80% to the tendon repair and ∼20–30% to the augmentation component. The sensitivity analysis suggests that the greatest improvements in the force carrying capacity of a tendon repair may be achieved by improving the properties of the bone–suture–tendon interface. Future studies will perform parametric simulation to illustrate the manner in which changes to the individual components of the repair, representing different surgical techniques and scaffold devices, may influence the biomechanics of the repair construct.