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Research Papers

Pronation–Supination Motion Is Altered in a Rat Model of Post-Traumatic Elbow Contracture

[+] Author and Article Information
Chelsey L. Dunham

Department of Biomedical Engineering,
Washington University in St. Louis,
St. Louis, MO 63130
e-mail: chelsey.dunham@wustl.edu

Ryan M. Castile

Department of Mechanical Engineering and
Materials Science,
Washington University in St. Louis,
St. Louis, MO 63130
e-mail: castiler@wustl.edu

Aaron M. Chamberlain

Department of Orthopaedic Surgery,
Washington University in St. Louis,
St. Louis, MO 63130
e-mail: amchamberlain@wustl.edu

Leesa M. Galatz

Department of Orthopaedic Surgery,
Mount Sinai Hospital,
New York, NY 10029
e-mail: leesa.galatz@mountsinai.org

Spencer P. Lake

Mem. ASME
Department of Mechanical Engineering and
Materials Science,
Washington University in St. Louis,
St. Louis, MO 63130;
Department of Orthopaedic Surgery,
Washington University in St. Louis,
St. Louis, MO 63130;
Department of Biomedical Engineering,
Washington University in St. Louis,
1 Brookings Drive,
Campus Box 1185,
St. Louis, MO 63130
e-mail: lake.s@wustl.edu

Manuscript received November 30, 2016; final manuscript received April 7, 2017; published online June 6, 2017. Assoc. Editor: Eric A Kennedy.

J Biomech Eng 139(7), 071011 (Jun 06, 2017) (7 pages) Paper No: BIO-16-1487; doi: 10.1115/1.4036472 History: Received November 30, 2016; Revised April 07, 2017

The elbow joint is highly susceptible to joint contracture, and treating elbow contracture is a challenging clinical problem. Previously, we established an animal model to study elbow contracture that exhibited features similar to the human condition including persistent decreased range of motion (ROM) in flexion–extension and increased capsule thickness/adhesions. The objective of this study was to mechanically quantify pronation–supination in different injury models to determine if significant differences compared to control or contralateral persist long-term in our animal elbow contracture model. After surgically inducing soft tissue damage in the elbow, Injury I (anterior capsulotomy) and Injury II (anterior capsulotomy with lateral collateral ligament transection), limbs were immobilized for 6 weeks (immobilization (IM)). Animals were evaluated after the IM period or following an additional 6 weeks of free mobilization (FM). Total ROM for pronation–supination was significantly decreased compared to the uninjured contralateral limb for both IM and FM, although not different from control limbs. Specifically, for both IM and FM, total ROM for Injury I and Injury II was significantly decreased by ∼20% compared to contralateral. Correlations of measurements from flexion–extension and pronation–supination divulged that FM did not affect these motions in the same way, demonstrating that joint motions need to be studied/treated separately. Overall, injured limbs exhibited persistent motion loss in pronation–supination when comparing side-to-side differences, similar to human post-traumatic joint contracture. Future work will use this animal model to study how elbow periarticular soft tissues contribute to contracture.

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References

Figures

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Fig. 1

Schematic of pronation–supination motion in the rat forelimb

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Fig. 2

Schematic of the experimental method timeline and a table defining each experimental animal-injury group (lightning bolt = surgery and X = analysis time point)

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Fig. 3

(a) The biomechanical test system uses a rack and pinion gear to convert linear displacement to rotational cyclic loading of the rat elbow in pronation–supination. Specimens were secured with ulna–radius and humerus fixtures. A load cell was used to measure the axial force. (b) The test system loaded with a rat elbow.

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Fig. 4

(a) Schematic of the torque–angle loading curve with parameters quantified for pronation–supination. The light gray circles are representative data. The black line for neutral zone stiffness/length is the average of the loading and unloading curves. Average curves for each injury group and contralateral for pronation–supination in (b) IM and (c) FM. These average curves represent the mean of all the animals tested per group without the standard deviation to make the differences between curves more apparent (dashed lines = injured limb; solid line = contralateral; solid black line = control).

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Fig. 5

Total range of motion (ROM) for (a) IM and (b) FM was decreased in injured limbs compared to contralateral (CL). Neutral zone length for (c) IM and (d) FM was also decreased compared to CL (average ± standard deviation; diagonally shaded bars = injured; solid bars = contralateral; # = significantly different from control; * = significantly different from contralateral limb; p < 0.05).

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Fig. 6

Correlation between flexion–extension and pronation–supination for total range of motion (ROM) in (a) IM and (b) FM, and neutral zone length in (c) IM and (d) FM (p < 0.05)

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