The regulation of tendon stem cell differentiation by the alignment of nanofibers.

Surgical treatment of tendon ruptures and lacerations is currently the most common therapeutic modality. Tendon repair in the hand involves a slow repair process, which results in inferior repair tissue and often a failure to obtain full active range of motion. The initial stages of repair include the formation of functionally weak tissue that is not capable of supporting tensile forces that allow early active range of motion. Immobilization of the digit or limb will promote faster healing but inevitably results in the formation of adhesions between the tendon and tendon sheath, which leads to friction and reduced gliding. Loading during the healing phase is critical to avoid these adhesions but involves increased risk of rupture of the repaired tendon. Understanding the biology and organization of the native tendon and the process of morphogenesis of tendon tissue is necessary to improve current treatment modalities. Screening the genes expressed during tendon morphogenesis and determining the growth factors most crucial for tendon development will likely lead to treatment options that result in superior repair tissue and ultimately improved functional outcomes.

Tendon: biology, biomechanics, repair, growth factors, and evolving treatment options.

Biomechanics of tendon injury and repair

Regaining satisfactory digital function after flexor tendon laceration and repair within the digit has long been one of the most difficult problems in hand surgery. Until the 1960s it was universally recommended that tendons divided in the digit (then referred to as “no man’s land”) should not be repaired. Bunnell taught that “it is better to remove the tendons entirely from the finger and graft in new tendons smooth throughout its length.” That dictum remained sacrosanct until the 1960s when reports by Verdan, Kleinert et al, and Kessler and Nissim challenged the concept that flexor tendons should not be repaired primarily. These investigators noted that when done correctly, immediate tendon suture would outperform secondary free tendon grafting. Armed by those encouraging reports, there was a gradual and cautious development of the concept and practice of primary flexor tendon repair. Initially, primary tendon repair was often combined with anecdotal protocols by Duran et al, Lister et al, and Strickland and Glogovac for applying varying amounts of early post-repair motion to the repaired tendons. As often happens with advances in medicine, the efforts to improve the performance of flexor tendon repairs were based almost entirely on individual experience and clinical experimentation with little or no scientific support. The last 25 years, however, have heralded an enormous amount of basic research designed to improve our knowledge of the structure of tendons, including the kinesiology, the biomechanics of their action on the joints they move, their biologic response to injury and repair, the mechanical characteristics of various tendon suture constructs, and the effect of post-repair motion stress on tendon strength and healing. These investigative efforts have given rise to improved methods of tendon repair, a greater emphasis on flexor sheath preservation and restoration, and protocols for the early application of passive and active wrist and digital motion as a means to more rapidly increase the strength and gliding of repaired tendons. The following sections will provide a concise review of some of the most important of these reports.

Development of flexor tendon surgery: twenty-five years of progress.

https://avecell.cz/4nsa9ca/uploads/2015/05/Stem-cells-in-veterinary-medicine-–-attempts-at-regenerating-equine-tendon-after-injury.pdf

Stem cells in veterinary medicine--attempts at regenerating equine tendon after injury.

▪ Abstract In this chapter, biomechanical methods used to analyze healing and repair of ligaments and tendons are initially described such that the tensile properties of these soft tissues as well as their contribution to joint motion can be determined. The focus then turns to the important mechanical and biological factors that improve the healing process of ligaments. The biomechanics of surgical reconstruction of the anterior cruciate ligament and the key surgical parameters that affect the performance of the replacement grafts are subsequently reviewed. Finally, injury mechanisms and the biomechanical analysis of various treatment techniques for various types of tendon injuries are described.

Injury and Repair of Ligaments and Tendons

Management of a partially lacerated digital flexor tendon within zone II remains controversial. To address this issue, we undertook an evaluation of the impact of tenorrhaphy on the gliding function and tensile properties of canine flexor tendons with lacerations involving either 30% or 70% of their cross-sectional area. Assessment of tendon excursion and joint rotation after 6 weeks of postoperative controlled passive mobilization failed to reveal any statistically significant benefit from tenorrhaphy on the gliding function. In fact, we demonstrated a significant negative effect of repair on tendons with 30% lacerations. Moreover, no significant differences between the structural properties or integrity of the repaired and nonrepaired tendons could be demonstrated. Thus, in light of the inherent tensile properties in these partially lacerated tendons, our data suggest that digital function of partially lacerated tendons of up to 70% of the cross-sectional area may be preserved without primary repair. However, additional work is needed to more definitively address this issue in a clinical context. (J Hand Surg 1999;24A:302–309. Copyright © 1999 by the American Society for Surgery of the Hand.)

Effects of tenorraphy on the gliding function and tensile properties of partially lacerated canine digital flexor tendons.

The purpose of this study was to compare the effect of unrestricted active versus passive mobilization on the gliding function and structural properties (ultimate load and stiffness) of repaired and nonrepaired canine flexor digitorum profundus tendons following partial laceration at 1 week. Using a radiographic method, normalized tendon gliding of the flexor digitorum profundus tendon adjacent to the metacarpal bone and total joint rotation were shown to be significantly greater in passive than in active tendons. Each group differed from their control group, however, by an average of only 5%. Both rehabilitation (active vs passive) and treatment (repair vs nonrepaired) of the partial tendon laceration significantly affected gap formation. Both active rehabilitation and repair of the laceration significantly increased gap formation compared with passive rehabilitation and nonrepair of the partial laceration. Rehabilitation did not significantly affect the normalized ultimate loads and stiffness in the passive and active groups but the nonrepair groups displayed significantly higher ultimate loads and stiffness than the repair groups.

Serena S. Chan Saw

Papers

Injury and Repair of Ligaments and Tendons

Effects of tenorraphy on the gliding function and tensile properties of partially lacerated canine digital flexor tendons.

Passive and Active Rehabilitation for Partial Lacerations of the Canine Flexor Digitorum Profundus Tendon in Zone II

Evaluation of passive and active rehabilitation and of tendon repair for partial tendon lacerations after three weeks of healing in canines