◊ Tendon-Ligament Affections ◊
AFFECTIONS OF THE TENDON, LIGAMENT AND TENDON SHEATH
A tendon is a dens band of fibrous connective tissue that acts as an intermediary in the attachment of muscle to bone. The chief constituents of the tendons are thick, closely packed parallel bundles of longitudinally oriented collagen. Fibroblasts (tenoblasts) are arranged in long parallel rows in the spaces between the collagenous bundles.
Gliding function of the tendon is facilitated by the presence of tendon sheath, bursa and paratenon. In areas where the tendon makes an abrupt change in course as where it crosses a joint, a tendon sheath is present. A tendon sheath is composed of parietal and visceral connective tissue layers lined with synovial cells. It forms a cavity around the tendon containing synovial fluid. A bursa is similar to a tendon sheath except that it is covers only part of the tendon circumference. Bursae are interposed between tendons and bony prominences. Paratenon is a loosely arranged areolar tissue surrounding the tendon in areas does not require a tendon sheath. This tissue is elastic and allows gliding function where sheath are not present.
The process of tendon repair consists of four overlapping phases; injury, inflammation, repair and remodeling. Numerous factors influence healing, including the nature of the injury, the tendon injured, the type of tissue surrounding the tendon at the site of the injury and the treatment. However, the result of tendon healing is a connective tissue scar rather than restoration of normal tendineous tissue. Although this scar may restore tendon continuity, the repair process does not restore normal tensile strength and elasticity. Furthermore adhesions may develop during healing and prevent gliding of injured tendon.
AFFECTIONS OF THE TENDONS AND LIGAMENTS
I-TENDONITIS & DESMITIS
Tendonitis means inflammation of the tendon while desmitis means inflammation of the ligament.
The following tendons and ligament are usually affected:
1-Superficial digital flexor tendon
2-Deep digital flexor tendon
4-Common digital extensor tendon
Tendonitis of the superficial digital flexor tendon and suspensory ligament are common in riding and race horses. The deep digital flexor tendon is mostly affected in working animal.
1-Bad conformation such as weak tendons and upright pastern
2-Bad shoeing such as short shoe
3-Improper trimming of the hoof and long toe
4-Uneven and slippery ground
5-Muddy or sandy tracks
6-Putting of animal in work too early
8-Nature of the tendon and its function
The superficial digital flexor tendons of the forelimbs are most commonly affected. This may be related to smaller cross-sectional area of the tendon and the greater stress placed on it during hyperextension of the fetlock joint as compared to the deep digital flexor tendon.
1-Overstretching of the tendons
2-Excessive load associated with falls, jumps, stumbles and sustained heavy work.
3-Parasitic infestation with onchocerca reticulata
Clinical signs: -
Tendonitis may be acute or chronic.
1-Moderate to severe lameness and the limb is held in a flexed position
2-During rest the animal points the affected limb in front the sound one with flexion of the fetlock and knee joints
3-During walking, the animal walks on the toe of the affected limb
4-Pulsation of the metacarpal or metatarsal arteries
5-Local swelling is detected along the whole length of the metacarpus/ metatarsus in cases of the superficial digital flexor tendon and is known as bowed tendon
6-In case of inflammation of the deep digital flexor tendon, a circumscribed swelling is visible on the palmar surface in the proximal third of the metacarpal region
7-In case of desmitis of the suspensory ligament the swelling is located behind the fetlock joint
8-The swollen area is hot, tender to touch and firm
1-Slight and often intermittent lameness
2-Uniform or nodular thickening at the back of the cannon region
3-Chronic tendonitis of the deep digital flexor tendon in which the inferior check ligament is involved, a circumscribed swelling is visible on the palmar surface in the proximal third of the metacarpal region. This swelling is hard and tender to touch, and knuckling over may be acquired.
2-High palmar or planter nerve block
1-Cold packs applied to the tendons (cold hydrotherapy)
2-Parenteral administration of non-steroidal anti-inflammatory drugs
3-Peritendinous injection of corticosteroid is used to minimize adhesion
4-Prolonged rest following treatment is still regarding the most important ingredient of successful tendon repair
1-Application of blister (bin-iodide of mercury) that is rubbed for 2-5 minutes on a clipped skin then covered by absorbent bandage
2-Firing and blistering and a line firing pattern is generally used with extensive lesion and point firing when changes are circumscribed. After firing a blister is applied and rubbed then absorbent bandage is applied and left for 2 weeks.
3-Radiation therapy using ultraviolet rays short waves and microwaves.
4-Tendon splitting: the aim of the operation is to stimulate the formation of vascularized granulation tissue into what is thought to be ischemic, degenerated core of tendon. The tendon splitting knife is inserted through the skin. With the blade held parallel to the longitudinal axis of the tendon, the tip of the knife is moved up and down in a fanlike split, perforating the peritendinous tissue on the opposite side.
5-Carbon fibers implantation: The aim of the implanted carbon fiber is not to provide mechanical strength but to provide a physical scaffold for the invading fibroblasts to grow along. Thus the subsequent collagen fibers are aligned in a manner similar to that of normal tendon rather than the haphazard organization that occurs in scar tissue following injury.
Acute cases can recover well. Chronic cases require adequate rest after treatment followed by optimum training program (about 12 months), to be improved, but normal soundness can’t be obtained
II-TENDON WOUND (Severed tendon)
It is fully discussed under topic wound
Wire cut, or any sharp object comes in contact with the flexor tendons or tendon Achillis
Clinical signs: -
Open wound at the level of the tendons with mostly severe hemorrhage. The tendon stumps can be seen with flexion and extension of the joints.
1-In fresh cases suturing should be tried
2-Cast is essential
3-Old cases are nearly hopeless
AFFECTION OF THE TENDON SHEATH
The most important tendons with tendon sheaths are
1-At the level of the carpal joint
1-Tendon of extensor carpi radialis with its sheath
2-Tendon of extensor digitorum communis with its sheath
3-Tendon of extensor digitorum lateralis with its sheath
4-Tendon of ulnaris lateralis with its sheath
5-Tendon of extensor carpi obliques with its sheath
6-Tendon of flexor carpi radialis with its sheath
2-At the level of the fetlock and pastern joints
1-Superficial and deep digital flexor tendon with their sheath
2-Common digital extensor tendon with its sheath
Tenosynovitis means inflammation of the synovial membranes of the tendon sheath, the fibrous layer of the tendon sheath is usually incorporated as well
Synovial effusion was detected without any other signs of inflammation, pain or lameness. The cause of the condition is unknown. The most common sites are tarsal synovial sheath, digital flexor tendon sheath and extensor tendon sheath. Treatment is restricted to aspiration of the synovial fluid and injection of corticosteroid then a pressure bandage is applied.
It is characterized by rapid developing of synovial effusion of the tendon sheath accompanied by signs of inflammation including hotness, pain, swelling and lameness. A marked elongated, warm, markedly fluctuating swelling appears at the palmar aspect of the fetlock joint medial and lateral to the digital flexors. Direct trauma appears to be the direct cause of the condition.
1-Cold hydrotherapy or cold packs
2-Aspiration and injection of corticosteroids
3-Parentral injection of nonsteroidal anti-inflammatory
It is characterized by presence of synovial effusion with fibrous tissue thickening of the tendon sheath. The condition is usually followed acute form.
1-Aspiration and injection of corticosteroids
2-Blistering and firing sometime is recommended
4-Septic or infectious tenosynovitis
This type occurs as a result of haematogenous infection and seen during the course of some infectious diseases. Also, punctured wound of the tendon sheath from picked up nail in the foot may be a cause.
Clinical signs: -
1-Diffuse, hot and painful swelling is seen behind the fetlock joint.
2-Severe degree of lameness
3-Increase body temperature and general bad condition of the animal
4-Multiple abscesses may be formed at the level of the swelling
1-Parentral injection of broad spectrum antibiotics
2-Aspiration of the infected synovial fluid and irrigation with antiseptic solution
3-Through and through technique is used for irrigation of the synovial sheath. Medial and lateral vertical skin incisions are performed on the palmar aspect of the fetlock joint. Another third incision is performed at the midline on the palmar aspect at the level of the pastern joint. The incisions are extended inside the tendon sheath. The contents are evacuated and the cavity is irrigated with mild antiseptic solution then local antibiotic solution is injected.