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Theme: Inclusion and Collaboration Theme: Inclusion and Collaboration

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Biomechanical Analysis of Capsular Repair versus TFCC Ulnar Tunnel Repair
Jayson C Johnson, MD; David M Brogan, MD, MSc; Jill E Jouret, BS; Ferris M Pfeiffer, PhD
University of Missouri, Columbia, MO

Purpose: The purpose of this study was to compare the effectiveness of a peripheral capsular repair to a knotless arthroscopic trans-osseous ulnar tunnel repair in restoring distal radioulnar joint (DRUJ) stability and stiffness in the setting of a massive triangular fibrocartilage complex (TFCC) tear.

Methods: We obtained eight matched pairs of fresh frozen cadaveric forearms for testing. Each forearm was tested in supination and pronation using 3-D optical tracking devices (NDI Certus) prior to any intervention. Each specimen then underwent a diagnostic wrist arthroscopy and sectioning of the TFCC's deep and superficial fibers. All specimens were then re-tested to assess instability secondary to the tear. The TFCC was repaired with either a peripheral capsular repair (CR) using three 2-0 polydioxanone sutures or a trans-osseous ulnar tunnel repair (TR) using a 2-0 Fiberwire, and then re-tested. Statistical significance was set a p<0.05.

Results: After arthroscopic sectioning of the TFCC, all specimens were unstable with a significant increase in translation and a significant decrease in stiffness. Repair of the TFCC with TR resulted in displacement and stiffness similar to the native tissue. CR specimens were found to have significantly greater displacement and significantly decreased stiffness compared to the intact state.

Conclusions: Arthroscopic sectioning of the TFCC resulted in DRUJ instability, as measured by stiffness and ulnar translation. TR effectively restored DRUJ stability and demonstrated no significant difference in post-operative stiffness or maximal displacement when compared to the intact specimen in pronation and supination. However, the stiffness and maximal displacement of those specimens undergoing CR continued to be significantly different than the intact state, with increased displacement and decreased stiffness in both supination and pronation.

Clinical Relevance: This study provides biomechanical evidence that an arthroscopic ulnar tunnel technique can restore stability to the DRUJ after a massive TFCC tear.

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Figure1-Experimental Set-Up

The arm was mounted with pelvic screw placed in the ulna to allow for cyclical loading in the anterior to posterior direction. Instron ram loaded ulna with 5 cycles +/-40 Newtons. Optical trackers were attached to pelvic screws inserted in radius and ulna.

Title: Max Displacement

Figure2-Pronation

Maximal ulnar displacement in millimeters with the wrist in pronation. DRUJ stiffness in N/mm with the wrist in pronation.

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Figure3-Supination

Maximal ulnar displacement in millimeters with the wrist in supination. DRUJ stiffness in N/mm with the wrist in supination.

images/Paper_24741_abstract_14675_0.jpg

Figure4-Sample Force vs Displacement curve for specimen repaired with trans-osseous ulnar tunnel technique tested in supination.


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