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Dynamic External Traction Device for PIP Joint Fracture Dislocation: Which Is The Best Model? A Comparative Cadaveric Biomechanical Analysis
Stephanie Thibaudeau, MD; Julian Diaz Abele; Mario Luc, MD, FRCSC
Plastic Surgery, McGill University, Montreal, QC, Canada

Purpose:The ideal k-wire based external distraction device for fracture dislocations of the PIP joint has yet to be identified. To date, there are no direct comparisons between different types of distraction devices in the literature.

Using a cadaveric hand model, we performed a biomechanical analysis of two devices, using one as described by Suzuki et al and the other by Hynnes & Giddins. The effect of the devices on the intra-articular width and on the force of flexion of the PIP joint was measured.

Methods: Thirty-two cadaveric fingers were used to compare a pins and rubber system with 3 and with 5 elastics per side (3E and 5E), as well as a pin system that uses no elastics (2P). Articular distraction of each device was compared using x-ray imaging. The force of flexion required to pull on the flexor digitorum profundus to flex the PIP joint to 45? and to 90? with each group was also measured.

Results: The three study groups showed statistically significant (p<0.01) articular distraction from baseline. Intra-articular spaces were 3E-AP 199%, Lat193%; 5E-AP 217%, Lat 200%; and 2P- AP 241%, Lat 183% of the pretreatment measurement space. Articular widths were 3E-AP 1.29mm, Lat 1.18mm; 5E-AP 1.41mm, Lat 1.22mm; and 2P-AP 1.46mm, Lat 1.22mm (no statistical difference between groups). Forces of flexion at 45? was 3E- 3.97N, 5E- 4.17N, and 2P- 4.87N (no statistical difference) and 3E- 11.27N, 5E- 10.29N, 2P- 14.34N at 90?.

Discussion: The three devices have similar distraction effect on the PIP joint. Resistance to joint mobility was greatest for 2P despite not attaining statistical significance. Given that all devices are equally as effective to distract the joint, the choice of device should be based on the force of flexion, ease of placement, reliability, and simplicity. Based on this, we favor 3E and 5E given that it is easier to flex, simpler to obtain precise placement of the distraction pin, and did not spontaneously disengage over the course of the study as opposed to 2P. The use of 5E over 3E provides a greater joint distraction, no increased resistance to flexion, and is just as reliable and easy to place.

Clinical relevance: This study allows clinicians to better understand the biomechanical effects of each of these devices and allows physicians make an informed decision as to the best distraction device described.

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