Mechanical Evaluation of Knee Ligament Allografts for Thumb Metacarpophalangeal and Finger Proximal Interphalangeal Reconstruction

Abstract

Purpose This study evaluated knee collateral ligaments for use as allografts in small joint reconstruction in the hand, specifically the thumb metacarpophalangeal (MCP) joint ulnar collateral ligament (UCL) and the index finger proximal interphalangeal (PIP) joint radial collateral ligament (RCL), and compared them to the current gold standard, tendon autograft. Methods Uniaxial tensile testing was performed on native thumb MCP UCLs and index finger PIP RCLs and 2.5-mm–diameter grafts prepared from hemi-flexor carpi radialis (hemi-FCR) tendons and knee medial collateral ligaments (MCLs) cadaveric allografts. In situ angular testing was performed in thumb MCP and index finger PIP joints. Each MCP/PIP joint was secured to a mechanical testing system and cyclically loaded. The UCL/RCL was resected and reconstructed with either an MCL or hemi-FCR. Cyclic loading was repeated, followed by angular load to failure. Results Uniaxial testing of MCL allografts demonstrated greater ultimate stress, ultimate load, and elastic modulus than hemi-FCR grafts and native UCLs/RCLs. The maximum angular deviation of the reconstructed MCP and PIP joints was not significantly different compared with the intact joint with either an MCL or hemi-FCR graft. In situ load to failure demonstrated no differences in failure torque or angular stiffness between MCPs reconstructed with a hemi-FCR and MCL allograft, whereas reconstructed PIP joints demonstrated improved angular stiffness with an MCL allograft compared with a hemi-FCR. Conclusions Medial collateral ligament allografts demonstrated improved mechanical properties compared with hemi-FCR tendon grafts during uniaxial testing, and grafts performed equivalently in in situ testing of reconstructed thumb/finger joints. Clinical relevance Prepared knee ligament allografts may provide a viable graft material for use in reconstruction of small hand ligaments. This new allograft material avoids the need to harvest a tendon autograft and has a biologic structure similar to native hand ligaments. This study evaluated knee collateral ligaments for use as allografts in small joint reconstruction in the hand, specifically the thumb metacarpophalangeal (MCP) joint ulnar collateral ligament (UCL) and the index finger proximal interphalangeal (PIP) joint radial collateral ligament (RCL), and compared them to the current gold standard, tendon autograft. Uniaxial tensile testing was performed on native thumb MCP UCLs and index finger PIP RCLs and 2.5-mm–diameter grafts prepared from hemi-flexor carpi radialis (hemi-FCR) tendons and knee medial collateral ligaments (MCLs) cadaveric allografts. In situ angular testing was performed in thumb MCP and index finger PIP joints. Each MCP/PIP joint was secured to a mechanical testing system and cyclically loaded. The UCL/RCL was resected and reconstructed with either an MCL or hemi-FCR. Cyclic loading was repeated, followed by angular load to failure. Uniaxial testing of MCL allografts demonstrated greater ultimate stress, ultimate load, and elastic modulus than hemi-FCR grafts and native UCLs/RCLs. The maximum angular deviation of the reconstructed MCP and PIP joints was not significantly different compared with the intact joint with either an MCL or hemi-FCR graft. In situ load to failure demonstrated no differences in failure torque or angular stiffness between MCPs reconstructed with a hemi-FCR and MCL allograft, whereas reconstructed PIP joints demonstrated improved angular stiffness with an MCL allograft compared with a hemi-FCR. Medial collateral ligament allografts demonstrated improved mechanical properties compared with hemi-FCR tendon grafts during uniaxial testing, and grafts performed equivalently in in situ testing of reconstructed thumb/finger joints.