Healthy tendons are critical for dogs’ joints to function properly and allow dogs to move well. In a previous blog, the functions and biology of dogs’ tendons was discussed. Please see https://www.fullstride.com.au/blog/what-is-the-anatomy-of-dog-s-tendons

Tendons, like muscles can be injured in several ways. Tendons may be injured by trauma such as traffic accidents or falls from a height resulting in a rupture or laceration or chronic inflammation from repetitive strain or overloading.

Regardless of the cause, tendons can be injured in different ways. The type of injury impacts the healing and rehabilitation approach. Tendons can be injured in the following ways:

• Laceration at the musculotendinous junction

• Laceration in the central part of the tendon

• Rupture at the insertion point with the bone

• Avulsion fracture where the tendon pulls off a piece of bone

• Contusion (The blood capillaries are ruptured causing a bruise.)

• Strain (Tendon fibres are overstretched and some fibres are ruptured which weakens the tendon.)

What are the symptoms of tendon injury in dogs?

Signs of tendon injury may include:

• Lameness – limping and not weight bearing. Lameness occurs when the tendon injury is severe and renders a joint immobile; unable to flex or extend.

• Pain or sensitivity when palpating the joint. When the injury initially occurs, the pain will be intense and decline over time.

• In less severe injuries, the joint range of motion will be limited.

• Nodules will develop along the lacerated edge of the ruptured tendon.

In the case of avulsion fractures, diagnosis by radiography is required.

What is the treatment for tendon injuries in dogs?

Depending on the severity and type of tendon injury, treatment may be conservative or require surgical intervention.

Conservative treatment may be suitable in the case of contusion and strains. This type of treatment may include an initial phase of immobilisation followed by a similar rehabilitation approach as recommended for dogs that require surgical treatment.

In cases when the tendon is ruptured, then suturing may be required to repair it. The aim of surgery is to restore the tendon’s strength and to enable it to glide smoothly within the sheath thus ensuring good joint movement.

Following surgery, canine studies have shown that rehabilitation is effective to address the following:

• Tendon adherence to the sheath surrounding tendon fibres

• Tendon excursion (stretch or elongation)

• Joint function

Canine studies have shown that passive joint mobilisation during the healing phase has a positive effect on stimulating the healing rate and restoring the strength of tendons. Other studies have shown that early, active mobilisation has an injurious effect on healing. Early, active mobilisation can increase tension along the suture line and allow a gap to form thus weakening the tendon and increasing the risk of re-rupture.

A canine study investigated the effects on controlled, passive range of motion exercises on the healing of the flexor tendon repair in dogs. The study measured the strength and gliding ability of the repaired tendon after the following post-surgical rehabilitation interventions:

1. Three weeks immobilisation with the wrist joint (metacarpal) braced at 90 degrees flexion
2. Six weeks immobilisation with wrist braced at 90 degree flexion
3. 12 weeks immobilisation with wrist braced at 90 degree flexion
4. Three weeks immobilisation followed by three week full weight bearing mobilisation
5. Three weeks immobilisation followed by three weeks partial mobilisation with the wrist braced at 90 degree flexion
6. Three week immobilisation followed by six week partial mobilisation. During the six weeks of partial mobilisation, the dog’s wrist joint was braced at 90 degree flexion for three weeks and then 45 degree flexion.
7. Three week immobilisation followed by nine weeks partial mobilisation. During the nine weeks mobilisation, the dog’s wrist joint was braced at 90 degree flexion for three weeks, then 45 degrees for three weeks and then a neutral position for three weeks.

In the groups where partial mobilisation was part of their rehabilitation protocol, the dog’s wrist and digits were manually flexed and extended for five minutes daily. The mobilisations were performed passively, that is, the dogs did not actively move their joints.

After the 12 week test period, 14 repaired tendons had re-ruptured, the majority of these occurred in the group that were allowed to return to full weight bearing, active mobilisation after three weeks. (Group 4)

Tendon strength

Tendon strength was measured for the repaired tendon and the contralateral tendon (not repaired or injured) was used as a control. The control tendons (not repaired or injured), when subjected to strength test, failed at the point at which the tendon inserted into the bone, while the repaired tendons failed at the repair site.

Of the repaired tendons, those dogs that received 9 weeks of passive mobilisation had the highest tensile strength.

This study indicates that maintaining the joint’s range of motion accelerates the rate of repair. At weeks 6 and 12, those dogs receiving passive range of motion exercises showed the largest increase in strength compared to other groups.

The tensile elongation of repaired tendons receiving passive mobilisation came from the repair site which indicates that as the healing process progressed the amount of deformation at the repair site (i.e. scar tissue) decreased as the strength of the repair site increased. Tendon elongation is critical to avoiding re-injury as elongation buffers the tendon from sudden mechanical loading thereby protecting it from strain.

After six weeks of repair, dogs receiving three weeks of passive mobilisation and their wrist immobilised at 90 degrees had increased strength compared to the dogs that had their wrist braced but did not received passive mobilisation. This point in the repair process coincides with the beginning remodelling phase (6 – 8 weeks post surgery). During this phase, the degree of vascularity (formation of capillaries) slows and the synthesis of Type I collagen increases. Collagen cells organise longitudinally along the tendon’s axis to restore its strength.

12 weeks post repair those dogs that received passive range of motion exercise had an average load of 61% (repaired strength compared with control) vs 34% of dogs that were continuously immobilised.

Range of motion (tendon gliding)

In terms of range of motion, the groups that received controlled, passive mobilisation had reduced adhesions between the repaired tendon and the sheath. Reduced adhesions resulted in better gliding capability and improved joint motion. Formation of adhesions occurs during the second phase of tendon repair: cell proliferation phase. During this phase, fibroblasts are recruited, a network of capillaries are formed and components of the extracellular matrix of the tendon are organised in a random manner forming a scar like appearance.

Dogs that were immobilisation in this study, showed reduced excursion of the tendon. In the groups that were immobilised for six weeks, tendon excursion was 21% vs 61% for the control. After 12 weeks immobilisation, tendon excursion was 19% vs 58% for the control. This compares with the passive mobilisation groups that had three times better tendon excursion than the continuously immobilised groups.

Takeaway messages for tendon injury rehabilitation for dog owners

Tendon healing following a rupture is slow. In this study, it was not until 12 weeks post-surgery that significant increases in tendon strength were observed.

Controlled passive mobilisation increased the survival rate of the repaired tendon and increased the likelihood of the tendon returning to it’s pre-injury performance level. By adding tensile forces and motion at the repair site during the remodelling phase, this study showed that passive mobilisation exercises accelerates tendon healing and restores strength. In the passive mobilisation groups, after 12 weeks of rehabilitation, the tendon had regained sufficient strength to sustain the animal’s full weight and resume limited activities.

Additionally, controlled passive mobilisation during the cell proliferation phase resulted in reduce adhesions and good gliding function between the tendon and the sheath. By contrast, 12 weeks immobilisation resulted in a decrease in tendon excursion capability due to the formation of adhesions between the tendon and the sheath.

Finally, a review of animal studies on tendon repair indicate that nutritional interventions may support the healing process regardless of whether a conservative or surgical treatment approach is taken. As the extracellular matrix of tendons comprises collagen, interventions that increase collagen and protein synthesis may be effective for remodelling and rebuilding tendons. During the healing phases, up to 8 – 12 weeks post injury or surgery, diets with sufficient energy, protein (amino acids) and trace minerals will support tendon rebuilding.

In a study of rats, taurine improved tendon healing and a study with mice, showed that a diet supplemented with other amino acids including glutamine, arginine, leucine, isoleucine and valine improved skin collagen synthesis.

Similarly, supplementation with Vitamin C (a promoter of collagen synthesis) accelerated tendon healing.

In terms of trace minerals, zinc, copper and manganese play a role in collagen formation.

Healthy, strong tendons are critical for a dog’s normal joint movement. Observing our dog’s joint motion and being vigilant to signs of discomfort allows us to identify potential tendon strain and prevent a potentially severe injury occurring.

Full Stride provides remedial canine massage to assist dogs recovering from surgical tendon repair or rehabilitating following a tendon strain or contusion.

To find a qualified myofunctional therapist in your area, please see www.saena.com.au .

Image by Klaus Hausmann from Pixabay

Sources:

Curtis, L. (2016). Nutritional research may be useful in treating tendon injuries. Nutrition, 32(6), 617-619.

Echigo, R., Fujita, A., Nishimura, R., & Mochizuki, M. (2018). Triceps brachii tendon injury in four Pomeranians. Journal of Veterinary Medical Science, 80(5), 772-777.

James, R., Kesturu, G., Balian, G., & Chhabra, A. B. (2008). Tendon: biology, biomechanics, repair, growth factors, and evolving treatment options. The Journal of hand surgery, 33(1), 102-112.

Woo, S. L., Gelberman, R. H., Cobb, N. G., Amiel, D., Lothringer, K., & Akeson, W. H. (1981). The importance of controlled passive mobilization on flexor tendon healing: a biomechanical study. Acta Orthopaedica Scandinavica, 52(6), 615-622.