Commentary & Perspective on
"Effect of Synergistic Wrist Motion on Adhesion Formation After Repair of Partial Flexor Digitorum Profundus Tendon Lacerations in a Canine Model in Vivo"
By Chunfeng Zhao, MD et al.

Commentary & Perspective by
Matthew J. Silva, PhD*, and Richard H. Gelberman, MD*,
Department of Orthopaedic Surgery, Washington University School of Medicine, St. Louis, MO

Synergistic wrist and finger motion (wrist extension with simultaneous digital flexion and wrist flexion with digital extension) exercises have been advocated to reduce adhesion formation in the critical early period following tendon injury and repair. While synergistic wrist motion has been shown to increase tendon excursion in both human cadaver and in vivo canine studies¹, increased excursion for the reduction of adhesion formation has only recently been investigated. In a study using a canine model of complete tendon laceration followed by suture repair, we found that passive mobilization rehabilitation that incorporated synergistic wrist motion modestly reduced the incidence and severity of adhesion formation when compared with rehabilitation performed with the wrist in the flexed position². Post-mortem assessment revealed that digits in the synergistic group and those in the fixed-wrist group had similar ranges of motion, which did not differ significantly from those of the control group.

In their study, Zhao et al. used a novel approach to assess the effects of synergistic wrist motion on adhesion formation. One notable feature of their study design is the use of a partial, rather than a complete, tendon laceration model in an effort to reduce the possible confounding effects of repair-site elongation and/or rupture. They also employed a unique experimental technique to measure the adhesion and frictional forces between the tendon and its intrasynovial sheath and pulleys. Using a method previously validated in time-zero specimens³, the authors documented that at three and at six weeks following partial laceration and repair, specimens that were treated with synergistic wrist motion had decreased adhesion breaking strength compared with those treated with wrist fixation. In addition to adhesion breaking strength, the authors measured repair-site strength with use of tensile testing. Consistent with the results of our earlier study², Zhao et al. found no evidence that synergistic wrist motion altered the tensile properties of the repair site. This finding also supports the view that increased tendon motion applied postoperatively, while effective in promoting tendon gliding, does not alter the time course of tissue-healing.

The study by Zhao et al. clearly demonstrates, albeit in an animal model, that increased tendon excursion produced by synergistic wrist motion can lead to a significant reduction in adhesion formation and, most importantly, in the force required to produce gliding of the tendon in its intrasynovial sheath. Moreover, this study demonstrates that, with the exception of a tendency to increase gap formation, the use of synergistic wrist motion does not appear to have any detrimental effects on important functional outcomes. It should be noted that the positive effects of synergistic wrist motion have not been shown to be further enhanced by increasing the force applied to the tendon⁴ and that there have been no reports that support the use of higher force, active motion-rehabilitation regimens. In conclusion, Zhao et al. have provided compelling evidence that supports the clinical application of synergistic wrist motion as an effective treatment for the promotion of tendon-gliding and the reduction of adhesion formation following intrasynovial tendon injury and repair.

*In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from National Institutes of Health Grant R01 33097. None of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

References

1. Horii E, Lin GT, Cooney WP, Linscheid RL, An KN. Comparative flexor tendon excursion after passive mobilization: an in vitro study. J Hand Surg [Am]. 1992;17:559-66.
2. Silva MJ, Brodt MD, Boyer MI, Morris TS, Dinopoulos H, Amiel D, Gelberman RH. Effects of increased in vivo excursion on digital range of motion and tendon strength following flexor tendon repair. J Orthop Res. 1999;17:777-83.
3. Uchiyama S, Amadio PC, Coert JH, Berglund LJ, An KN. Gliding resistance of extrasynovial and intrasynovial tendons through the A2 pulley. J Bone Joint Surg Am. 1997;79:219-24.
4. Boyer MI, Gelberman RH, Burns ME, Dinopoulos H, Hofem R, Silva M. Intrasynovial flexor tendon repair. An experimental study comparing low and high levels of in vivo force during rehabilitation in canines. J Bone Joint Surg Am. 2001;83:891-9.