Rico Vannini graduated 1981 from the University of Zürich. 1987 he completed his surgical residency at The Ohio State University. For nine years he was faculty surgeon and lecturer at the University of Zürich. 1994 he became Diplomate of the European College of Veterinary Surgeons. Since 1996 he is owner of Bessy's small animal clinic, one of the largest private clinics in Switzerland. He was president of AO and ESVOT. He maintains an active interest in continuing education among others being international speaker and international chairmen of the Education Commission of AOVET. His hobbies are agility, scuba diving and cooking. He is mobile cash machine for two young adults, master of 8 dogs and food provider of a cat.

Anatomically a ligament is a band or a cord of nearly pure collagenous tissue, which unites two or more bones. Most ligaments function as collateral ligaments, which are present to a greater or lesser degree in all hinge joints. They are important stabilizers of the joints and provide proper function and joint motion.

Ligamentous injuries occur frequently in dogs and cats. Damage to ligaments most commonly occurs following severe trauma, i.e., from excessive force placed across a joint. Less commonly, ligaments may be disrupted by sharp laceration or destroyed by shearing injuries. In the distal extremities the medial collateral ligaments are more commonly injured than the lateral ones.

If external forces exceed the tensile strength of the ligament, disruption of the collagen bundles results, leading to various degrees of instability. Ligaments are very inelastic and collagen fiber bundles become permanently deranged after 10% elongation.³

Classification of Ligament Injury

 Grade 1: Ligament is stretched, but remains intact and results in no instability

 Grade 2: Partial ligament tears that leads to mild instability

 Grade 3: Complete tear that results in significant instability

Grade 1 injuries are associated with disruption of relatively few collagen fibrils and little functional compromise. This type of injury is commonly seen with mild collateral ligament injuries of the carpus and tarsus. Diagnosis of a grade 1 injury is made based on history, pain on palpation, mild soft tissue swelling at the site of injury and lack of instability. Treatment of grade 1 injuries is conservative. Initial management of grade 1 injury should include application of ice to the affected area to reduce pain, swelling and hematoma formation. A soft padded bandage might be helpful to reduce pain, control swelling and give support to the joint. Exercise should be restricted to minimal walking for 2 weeks, followed by short leash walks for additional 2 weeks. Non-steroidal antiinflammatory drugs (NSAIDs) can be considered to provide additional analgesia. Physiotherapy is highly recommended to return the animals rapidly back to full function.

Return to normal exercise is permitted after 4 weeks if resolution of clinical signs occurs and joint stability is maintained.

Grade 2 injuries have greater amount of collagen damage, resulting in functional deficits and some joint instability. Part of the ligament has been disrupted, but a portion of the ligament remains intact maintaining stability. Grossly, a portion of the ligament may appear torn or simply stretched. Increased swelling and hematoma formation is seen. Documentation of some instability can generally be accomplished by stress radiographic views. It is often helpful to compare radiographs of the abnormal to the normal joint. Depending the activity of the patient and the joint affected surgical treatment of this type of injury might be preferable, although some grade 2 injuries with mild instability can be treated successfully with conservative management.

Grade 3 injuries are associated with complete tearing of the ligament, resulting in total loss of ligament function. This leads to severe instability of the joint, which often times allows dislocation to occur. Surgical intervention is strongly recommended to increase the chance of attaining adequate stability for good joint function.

Shear wounds are associated with marked damage characterized by loss of soft tissues and bone. They require aggressive management of the wound and the bone according the guidelines for open fracture management. Often treatment of the ligament injury has to be delayed until the soft tissue condition permits. Ligament reconstruction has usually to be delayed until the wound is healthy and is beginning to develop granulation tissue.

Healing of Ligaments

Healing of the torn ligament goes through the same phases as every wound: after an initial inflammatory phase, there is 24–48 h later the proliferative phase, which is followed by the remodeling and maturation phase, that last several weeks up to 12 month after the injury. A healed ligament never reaches its initial strength anymore, but compensates with an increased cross-section and bigger volume.⁵

Primary Ligament Repair

If possible, a torn ligament should be repaired primarily with a locking-loop or 3 loop pulley suture pattern. The three loop pulley suture pattern seems to be the stronger repair for ligaments.²

A suture anchor can be used effectively for reattaching avulsed ligaments, tendons and joint capsule to bone, thus reestablishing stability to the involved joint.

Alternatively the avulsed ligament can directly secured to the bone with a screw and a spiked washer.

Augmentation/Ligament Replacement

A prosthetic ligament can be used to protect or reinforce a primary repair (augmentation) or to replace a destroyed ligament. Prosthetic ligaments, made from heavy non-absorbable suture (0–#5) are most commonly used. Occasionally strips form fascia lata or an adjacent tendon is used to reconstruct or augment an injured ligament.

They are anchored at the ligament origin and insertion using metallic suture anchors or bone tunnels. Bone tunnels are preferred over suture anchors as there is less risk of suture failure. If there is no place for a bone tunnel suture anchors are ideal. Care has to be taken, that the anchors do not penetrate or interfere with an adjacent joint. Precise ligament reconstruction is important. Starting and insertion point of the artificial ligament has to be as anatomically as possible in order to be isometric.

An isometric position is desired to decrease the chance of the ligament stretching or breaking, and to improve stability throughout the entire range of motion. If isometric suture placement is possible, novel braided sutures such as Fibrewire® are used. They have no elasticity at all and are extremely strong. There is, however, an increased risk of infection using these materials. If they are not placed isometrically they will either restrict joint motion or eventually break. Monofilament nylon has more elasticity and some creep and is ideal if isometric suture placement cannot be achieved. It is also more resistant to infection.

Transarticular External Fixation

If the soft tissues are severely compromised or if a deep infection is suspected, a transarticular external fixator is often used to immobilize the joint without reconstructing the ligament. The fixator should be maintained for 6–8 weeks if possible, however, premature fixator pin loosening often leads to earlier removal of the device. The wound is left open to heal by second intention. This stimulates granulation tissue and secondary scar tissue formation.

Arthrodesis

Occasionally primary ligament reconstruction is not possible due to extensive loss of soft tissue or has not lead to adequate function due to implant failure, undiagnosed concomitant injury or inadequate postoperative management. Arthrodesis may be indicated in these cases to achieve stability to maintain some function. This is most commonly used in tarsal, intertarsal or carpal injuries.

Postoperative Management

Concomitant use of an NSAID can be considered to provide additional analgesia as needed. Exercise should be restricted to strict confinement for 2 weeks, then short leash walks for additional 6 weeks. Leash walks should become progressively longer over the next 4 weeks, with short trots allowed if clinical function is satisfactory. Return to normal exercise is permitted after 12 weeks if resolution of clinical signs occurs and joint stability is present.

External coaptation is often necessary for 4–6 weeks postoperatively to protect the repair during the early phases of healing, especially in large or active dogs. Transarticular ESF provide better adjunctive stability and facilitate open wound management. The potential disadvantage is a marked decreased range of motion following removal of the fixator. It is therefore important to immobilize the joint at a functional weight bearing angle. Semirigid stabilization using soft-cast material is another option to support the distal extremity of the front limb.

For optimal result early controlled motion with low stress would be ideal.⁵ This is difficult to achieve in dogs.

Physical therapy of the affected joint following immobilization will usually allow return the joint to satisfactory function.

Additional options to improve healing are the use of stem cell therapy or the use of growth factors. Platelet rich plasma (PRP or ACP) can be beneficial as it is rich in TGF, vascular endothelial growth factors and platelet derived growth factors.

References

1.  Beale BS, Lewis DD. Clinical use of titanium anchors for treatment of trauma-induced joint instability in small animals. In: Proceedings of the 23rd Conference of the Veterinary Orthopedic Society. 1996:23.

2.  Berg RJ, Egger E. In vitro comparison of the three loop pulley and locking loop suture patterns for repair of canine weightbearing tendons and collateral ligaments. Veterinary Surgery. 1986;15:107–110.

3.  Bray RC, Frank CB, Miniaci A. The structure and function of diarthrodial joints. In: McGinty JB, ed. Operative Arthroscopy. Philadelphia, PA: Lippincott-Raven; 1996:119–130.

4.  Brinker WO, Piermattei DL, Flo GL. Handbook of Small Animal Orthopedics and Fracture Treatment. 2nd edition. Philadelphia, PA: W.B. Saunders; 1990:314–323.

5.  Schepsis AA, Busconi BD. Ligament healing. In: Sports Medicine. Lippincott Williams & Wilkins; 2006.