Hand and Wrist Projects

Repair and rehabilitation of flexor tendon injury

The goal of this project is to improve the results of tendon repair by developing therapies that affect the tendon gliding surface. The underlying hypothesis is that improving the results of flexor tendon repair can be obtained by methods that minimize friction on the gliding surfaces of the tendon and sheath.

In this project, Dr. Amadio will investigate methods to preserve the beneficial effects of this novel tendon-surface modification while improving intrinsic tendon healing through a tissue-engineering approach.

The project team has three specific aims:

  • Investigate the healing of flexor tendons following the incorporation of a bone marrow-derived stromal cell-seeded, cytokine-augmented collagen patch into the repair site in an animal model in vitro
  • Investigate the effects a bone marrow-derived stromal cell tendon patch combined with surface modification on flexor tendon repair in an animal model in vivo
  • Investigate the effect of surface modification and a bone marrow-derived stromal cell patch on animal models subjected to a postponed tendon rehabilitation protocol
  • Microscopic image of a tendon surface

    Tendon surface under a scanning electron microscope (upper row with low magnification and bottom row with high magnification)

Surface modification of intrasynovial tendon for flexor allograft

The purpose of this study is to investigate the role of surface treatment, a form of tissue engineering, on the results of flexor tendon allograft surgery in an animal model.

The project team has two specific aims:

  • Characterize the gliding ability and mechanical properties of allograft intrasynovial tendons treated with cd-HA gelatin compared with autograft tendons in vitro. Lyophilization alters tendon surface morphology and increases tendon friction. Surface modification with carbodiimide-derivatized hyaluronic acid (cd-HA) gelatin reverses this adverse effect and restores the graft to its normal gliding properties.

    When tendon allografts are used in a situation where gliding of the allograft is important to subsequent clinical function, treatment of the surface with cd-HA gelatin may be beneficial.

  • Test the results in vivo in an animal model. This aim is ongoing.
  • Image of tendons and subsynovial connective tissue and a diagram of two-tendon

    Tendons and subsynovial connective tissue in human carpal tunnel (left) and initial basic model of two-tendon excursion (right)

  • Graph showing an example of displacement in the Z direction

    Example of displacement in the Z direction

Mathematical modeling of tendon, nerve and subsynovial connective tissue stress during excursion of the human carpal tunnel

This project aims to aid in the understanding of how normal and abnormal subsynovial connective tissue affect tendon function and also in identifying mechanical properties within the carpal tunnel that may predispose a person to the onset of carpal tunnel syndrome.

Joint motion and tendon excursion with respect to subsynovial connective tissue strain will be combined in this project to understand task-specific motions. Mathematical modeling will be developed for analyzing various tasks from a mechanical perspective, while at the same time merging external measures of finger motion with internal measures of subsynovial connective tissue strain.

Once the basic model is validated, a tendon model will be designed to mimic everyday tasks such as typing, playing an instrument or various repetitive hand activities.

Carpal tunnel syndrome and subsynovial connective tissue

This project is looking at whether fibrosis is a cause or merely an associated finding in carpal tunnel syndrome, a compression neuropathy of the median nerve. The laboratory has validated its model and now has a preclinical model that mimics the actual clinical evolution, though not necessarily the specific inciting cause, of carpal tunnel syndrome.

The most common pathological finding in carpal tunnel syndrome is noninflammatory fibrosis and thickening of the subsynovial connective tissue. Dr. Amadio and his team are studying various interventions directed at halting or reversing the evolution of subsynovial connective tissue fibrosis, which appears to be an important factor in the etiology and development of carpal tunnel syndrome. The team is also studying the pathogenesis of carpal tunnel syndrome in more detail.

Comparative study of the effects of growth differentiation factor 5 on muscle-derived stem cells and bone marrow stromal cells in tendon healing

The project team is biomechanically, biochemically and histologically investigating the healing strength of repaired flexor tendons with a gel patch seeded with muscle-derived stem cells and supplemented with growth differentiation factor 5 in an in vitro animal model.

The functional repair of flexor tendon injury, especially in zone two, remains a great challenge for hand surgeons. Improvements in suture materials, suture techniques and postoperative rehabilitation protocols have generally resulted in improved clinical outcomes, but many complications still occur and require better solutions. Complications include rupture at the repair site and formation of restrictive adhesions.

Growth differentiation factor 5 has been shown to improve tendon healing. If this study demonstrates the effectiveness of the combination of muscle-derived stem cells and growth differentiation factor 5 in tendon healing, it will provide a novel treatment for tendon repair that could be further explored in an in vivo model.