Use of a bioabsorbable implant for the repair of severed digital flexor tendons in four horses

The Pivotal Role of Stem Cells in Veterinary Regenerative Medicine and Tissue Engineering

The introduction of new regenerative therapeutic modalities in the veterinary practice has recently picked up a lot of interest. Stem cells are undifferentiated cells with a high capacity to self-renew and develop into tissue cells with specific roles. Hence, they are an effective therapeutic option to ameliorate the ability of the body to repair and engineer damaged tissues. Currently, based on their facile isolation and culture procedures and the absence of ethical concerns with their use, mesenchymal stem cells (MSCs) are the most promising stem cell type for therapeutic applications. They are becoming more and more well-known in veterinary medicine because of their exceptional immunomodulatory capabilities. However, their implementation on the clinical scale is still challenging. These limitations to their use in diverse affections in different animals drive the advancement of these therapies. In the present article, we discuss the ability of MSCs as a potent therapeutic modality for the engineering of different animals' tissues including the heart, skin, digestive system (mouth, teeth, gastrointestinal tract, and liver), musculoskeletal system (tendons, ligaments, joints, muscles, and nerves), kidneys, respiratory system, and eyes based on the existing knowledge. Moreover, we highlighted the promises of the implementation of MSCs in clinical use in veterinary practice.

An ex vivo biomechanical comparison of two suture materials and two pattern combinations for equine superficial digital flexor tendon tenorrhaphy

OBJECTIVE

To compare biomechanical characteristics of three-loop pulley (3LP) pattern versus Bunnell technique (BT) using polydioxanone (PDS) suture; to determine the influence of polyester tape (PT) versus PDS on the BT for equine superficial digital flexor tendon (SDFT) tenorrhaphy; to compare BT with PT versus 3LP with PDS.

STUDY DESIGN

Ex vivo biomechanical study.

SAMPLE POPULATION

Forty equine forelimb SDFT.

METHODS

Two experiments were performed: (1) 10 SDFT pairs were repaired with 3LP or BT using PDS; (2) 10 SDFT pairs were repaired with PDS or PT using BT. Load at failure, mode of failure, load at 2 mm gap, and gap at failure were obtained using a material testing machine.

RESULTS

In experiment 1, 3LP + PDS₁ had higher loads at failure (p < .001) and at 2 mm gap (p < .001), and smaller gap at failure than BT + PDS₁ (p = .024). In experiment 2, BT + PT₂ had higher loads at failure (p < .001) and at 2 mm gap (p = .001), and larger gap at failure (p = .004) than the BT + PDS₂ . 3LP + PDS₁ and BT + PT₂ mostly failed by suture/implant pull-through while BT + PDS failed by suture breakage. BT + PT₂ had greater load (p = .035) and gap at failure (p < .001) than 3LP + PDS_1, with no difference in load at 2 mm gap (p = .14).

CONCLUSION

The use of BT may be justified over 3LP if combined with PT. However, the larger size of the PT required stab incisions in the tendon for placement and was subjectively more difficult to place than PDS.

CLINICAL SIGNIFICANCE

The BT + PT, although the strongest among the tested repairs, would only be able to withstand 12%-24% of the load encountered by the SDFT at walk.

One health in regenerative medicine: report on the second Havemeyer symposium on regenerative medicine in horses

Regenerative medicine is commonly used in human and equine athletes. Potential therapies include culture expanded stem cells, stromal vascular fraction of adipose tissue, platelet-rich plasma, bone marrow concentrate, or autologous conditioned serum. The purpose of this manuscript is to disseminate findings from a workshop on the development of translational regenerative medicine in the equine field. Five themes emerged: stem cell characterization and tenogenic differentiation; interactions between mesenchymal stem cells, other cells and the environment; scaffolds and cell packaging; blood- and bone marrow-based regenerative medicines; clinical use of regenerative therapies. Evidence gained through the use of regenerative medicine applications in the horse should continue to translate to the human patient, bringing novel regenerative therapies to both humans and horses.

Stem Cells in Veterinary Medicine-Current State and Treatment Options

Regenerative medicine is a branch of medicine that develops methods to grow, repair, or replace damaged or diseased cells, organs or tissues. It has gained significant momentum in recent years. Stem cells are undifferentiated cells with the capability to self—renew and differentiate into tissue cells with specialized functions. Stem cell therapies are therefore used to overcome the body's inability to regenerate damaged tissues and metabolic processes after acute or chronic insult. The concept of stem cell therapy was first introduced in 1991 by Caplan, who proposed that massive differentiation of cells into the desired tissue could be achieved by isolation, cultivation, and expansion of stem cells in in vitro conditions. Among different stem cell types, mesenchymal stem cells (MSC) currently seem to be the most suitable for therapeutic purposes, based on their simple isolation and culturing techniques, and lack of ethical issues regarding their usage. Because of their remarkable immunomodulatory abilities, MSCs are increasingly gaining recognition in veterinary medicine. Developments are primarily driven by the limitations of current treatment options for various medical problems in different animal species. MSCs represent a possible therapeutic option for many animal diseases, such as orthopedic, orodental and digestive tract diseases, liver, renal, cardiac, respiratory, neuromuscular, dermal, olfactory, and reproductive system diseases. Although we are progressively gaining an understanding of MSC behavior and their mechanisms of action, some of the issues considering their use for therapy are yet to be resolved. The aim of this review is first to summarize the current knowledge and stress out major issues in stem cell based therapies in veterinary medicine and, secondly, to present results of clinical usage of stem cells in veterinary patients.

The current 'state of play' of regenerative medicine in horses: what the horse can tell the human

The horse is an attractive model for many human age-related degenerative diseases of the musculoskeletal system because it is a large animal species that both ages and exercises, and develops naturally occurring injuries with many similarities to the human counterpart. It therefore represents an ideal species to use as a 'proving ground' for new therapies, most notably regenerative medicine. Regenerative techniques using cell-based therapies for the treatment of equine musculoskeletal disease have been in use for over a decade. This review article provides a summary overview of the sources, current challenges and problems surrounding the use of stem cell and non-cell-based therapy in regenerative medicine in horses and is based on presentations from a recent Havemeyer symposium on equine regenerative medicine where speakers are selected from leading authorities in both equine and human regenerative medicine fields from 10 different countries.

Microangiographic Comparison of the Effects of 3 Loop Pulley and 6 Strand Savage Tenorrhaphy Techniques on Equine Superficial Digital Flexor Tendon

OBJECTIVE

The 6-strand Savage (SSS) tenorrhaphy pattern is biomechanically superior to the commonly employed 3-loop pulley (3LP); however, its effects on intrinsic tendon vasculature remain unknown. The objective of this study was to compare perfusion of intrinsic vasculature of the equine superficial digital flexor tendon (SDFT) after 3LP and SSS tenorrhaphies. We hypothesized that the SSS technique would significantly decrease vascular perfusion compared to the 3LP technique.

STUDY DESIGN

Ex vivo, randomized, paired design.

ANIMALS

Horses (n = 9) METHODS: Under general anesthesia, 9 pairs of forelimb SDFT were transected. Two tendons served as baseline control, the remainder had either SSS or 3LP tenorrhaphy performed. Horses were heparinized, euthanatized, and forelimbs perfused with barium sulfate solution were then fixed with formalin under tension. Tendons were transected every 5 mm and microangiographic images obtained. Microvascular analysis of sections proximal to, throughout, and distal to the tenorrhaphy was completed using a custom macro. Differences in vascular count were assessed using MANOVA.

RESULTS

A significant reduction in the number of perfused vessels was seen for SSS compared with 3LP at 2 locations within the tenorrhaphy (P = .039 and P = .009). The SSS technique took on average 4.7 ± 0.9 times longer to place.

CONCLUSIONS

The SSS technique causes an acute reduction in tendon perfusion compared to the 3LP, which may limit its clinical use. Further research is required to elucidate the clinical significance of this difference.

Ex Vivo Strength Comparison of Bioabsorbable Tendon Plates and Bioabsorbable Suture in a 3-Loop Pulley Pattern for Repair of Transected Flexor Tendons from Horse Cadavers

OBJECTIVE

To test the failure strength and energy of 2 bioabsorbable implants applied to transected deep digital flexor tendons (DDFT) from adult horses.

STUDY DESIGN

Ex vivo biomechanical experiment.

SAMPLE POPULATION

Twelve pairs of deep digital flexor tendons harvested from the forelimbs of fresh equine cadavers.

METHODS

Poly-L-lactic acid tendon plates were custom manufactured for application to the cylindrical surface of an adult equine deep digital flexor tendon. Twelve pairs of DDFTs were transected 2 cm distal to the insertion of the distal check ligament of the deep digital flexor tendon. One tendon of each pair was randomly selected for repair with a biodegradable plate or a 3-loop pulley method. Size 2 polydioxanone suture was used in both repairs. Repairs were tested in tension to failure, with peak force (PF) and total energy (TE) at repair failure recorded in Newtons (N) and Joules (J), respectively. A paired t-test was used for statistical evaluation with a significant level set at P< or = .05.

RESULTS

Mean+/-SD PF for failure of plated tendons (1507.08+/-184.34 N) was significantly greater than for sutured tendons (460.86+/-60.93 N). TE was also significantly greater for failure of plated tendons versus sutured tendons.

CONCLUSIONS

Plate fixation of transected cadaver DDFTs appear to have superior immediate failure strength than 3-loop pulley repairs.

CLINICAL RELEVANCE

Whereas in vivo testing is required, a bioabsorbable tendon plate may provide initial increased strength to support tendon healing and decrease external coaptation requirements.

Healing, Diagnosis, Repair, and Rehabilitation of Tendon Conditions

Management of tendon conditions can be frustrating due to difficulty with diagnosis, choice of treatment or repair technique, prolonged tissue healing, and potential for permanent compromise of limb function after surgery. This article reviews tendon healing and reported tendon conditions, focusing on bicipital tenosynovitis and common calcaneal tendon injuries. Surgical management options, research in enhancement of tendon healing, and postoperative rehabilitation are also reviewed.

Wounds of the distal limb complicated by involvement of deep structures

The authors describe the clinically relevant structures of the distal limb and the current diagnostic and treatment modalities. Specific problems include tendon laceration, septic tenosynovitis, and sep-tic arthritis of the distal joints. A detailed description of tendon repair, tendon sheath lavage, and postoperative convalescent methodology is provided. This article makes available to the reader information necessary to appropriately diagnose and treat wounds of the distal equine limb involving deep structures. Information on the overall prognosis is also provided.