Muscle and tendon disorders

Question 1

Tendons

Answer 1

Classified as dense regular connective tissues, composed of cells (fibroblasts) and collagen fibres arranged parallel to each other and embedded in a ground substance matrix (protein polysaccharides) and water.

In areas where tendons change direction or friction exists a tendon sheath or bursa exists.

Question 2

Characteristics of tendons that impact healing

Answer 2

Avascularity – poor blood supply therefore prolonged healing periods

Orientation of fibres in tendon are arranged // to the direction of major strain. Correct orientation of fibres only occurs once loading has begun

Scar formation – scars represent weak points susceptible to damage, adhesions may interfere with normal function

Muscle contraction – contraction of muscle complicates re-apposition of ends – this problem becomes more serious with time

Question 3

Suture patterns that can be used to repair a tendon

Answer 3

Three loop pulley

Bunnells suture

Locking loop

Question 4

Suture selection for a three loop pulley suture

Answer 4

Monofilament

Swaged on neddle

Slow resorption or permanent

Most commonly polypropylene (prolene)

Question 5

Surgical principles of tendon repair

Answer 5

Carry out as soon as possible to minimise contracture problems

Suture materials should be non-absorbable and monofilament e.g. prolene

The damaged tendon needs rigid support post-operatively

Question 6

Bicipital tenosynovitis

Answer 6

Conditions range from complete ruptures, through partial ruptures to mild inflammation or tenosynovitis.

Question 7

Bicipital tenosynovitis- signalment

Answer 7

Often large breed young active dogs

Question 8

Bicipital tenosynovitis - history

Answer 8

acute or insidious onset and often chronic forelimb lameness.

Question 9

Bicipital tenosynovitis - palpation

Answer 9

direct palpation of the biceps tendon is necessary in mild cases - simply checking ROM may not reveal any abnormalities.

To feel the biceps tendon extend the elbow, flex the shoulder and palpate just medial to the greater tubercle.

In a normal dog some soft tissue is just palpable under the skin, in affected animals pain may be elicited by palpation in this area or obvious thickening may be evident - compare with the other side.

Question 10

Bicipital tenosynovitis - diagnosis

Answer 10

Radiography - evidence of DJD and new bone deposition

Ultrasound - limited due to small size of tendon

MRI

Arthrography - useful to outline the tendon

Synovial fluid analysis

Question 11

Bicipital tenosynovitis- treatment

Answer 11

Initially try 6-8 weeks of strict rest and NSAIDs

Then try injection of methylprednisolone around the tendon or intra-articularly

If that fails then cut the biceps tendon close to its origin and secure it to the proximal humerus

Question 12

Breeds affected by Biceps brachii displacement

Answer 12

Racing dogs - greyhounds/lurchers

Question 13

Breeds affected by superficial digital flexor tendon displacement

Answer 13

Shetland sheepdogs

Question 14

Breeds affected by quadriceps tendon displacement (patellar luxation)

Answer 14

Any - small breeds predisposed

Question 15

Breeds affected by long digital extensor tendon displacement

Answer 15

Extremely rare

Question 16

Tendons that sit in grooves can displace due to:

Answer 16

Trauma and rupture of the retinaculum - e.g. Traumatic patella luxation can be seen in cats due to rupture of fascia lata.

Tendonitis and inflammation of the retaining ligament (eg. Transverse humeral ligament keeps biceps tendon in groove)

Conformational abnormalities (such as a shallow or angled groove) e.g. shelties with SDFT luxation have calcaneal abnormalities

Question 17

Clinical signs of a displaced tendon

Answer 17

Tendon displacements usually result in lameness.

This may be intermittent if the tendon is slipping in and out of the groove or more chronic if it is permanently displaced.

On careful physical examination it will often be possible to palpate the displacing tendon.

Question 18

Treatment of displacing tendons

Answer 18

Treatment is aimed at restoring the tendon to its normal place either by deepening the groove, or keeping the tendon in the groove by suturing soft tissues or use of a smooth staple to replace retaining ligaments.

Question 19

Medial Displacement of the Biceps Brachii Tendon

Answer 19

Most commonly seen in greyhounds, lurchers and whippets.

The tendon displaces medially out of the bicipital groove, which can be palpated when the shoulder is flexed.

On extension the tendon usually returns to the groove.

The condition may be associated with bicipital tenosynovitis.

Question 20

Treatment of medial displacement of the biceps brachii tendon

Answer 20

Involves replacing the function of the transverse humeral ligament with a smooth bone staple or wire suture.

Question 21

Lateral displacement of the superficial digital flexor tendon

Answer 21

Most commonly seen in Shetland sheepdogs.

Dogs present with pelvic lameness and owners may report hearing a clicking sound.

The point of the calcaneus is often visibly swollen (partial gastrocnemius rupture is a differential).

On careful palpation and manipulation by flexing and extending the leg it is often possible to feel the tendon moving from side to side.

Displacement is usually in a lateral direction – so the medial retinaculum has ruptured or stretched.

Treatment of choice is suture repair of the loose or ruptured retinaculum followed by external support for 4-6 weeks.

Question 22

Carpal laxity in puppies

Answer 22

This condition is seen in young puppies from 6 weeks of age.

It occurs as a result of TENDON laxity.

Several animals in the litter may be affected and lack of exercise has been implicated.

It is also seen after external coaptation in immature animals.

Question 23

Clinical signs of carpal laxity in puppies

Answer 23

Palmigrade stance

The normal amount of hyperextension in dogs is 5-10°. With hyperextension secondary to tendon laxity this can increase to 45°

Palpation is not painful.

Question 24

Stressed radiography of carpal laxity in puppies

Answer 24

Will reveal no abnormalities

Question 25

Treatment of carpal laxity in puppies

Answer 25

Increase exercise on firm ground

Feed correct diet

Prognosis usually good

Question 26

Signs of carpal hyperflexion in puppies

Answer 26

Signs are first noticed at 6 –12 wks.

Puppies may be affected uni or bilaterally and the carpus is hyperflexed, the problem can be dynamic.

No swelling or pain is present.

Question 27

Treatment of capral hyperflexion in puppies

Answer 27

conservative, correct diet and adjust exercise as necessary.

Question 28

Prognosis of carpal hyperflexion in puppies

Answer 28

dramatic improvement usually seen within 2-4 weeks

In some severely affected cases the tendon of the ulnar head or the flexor carpi ulnaris muscle needs to be sectioned proximal to its insertion on the accessory carpal bone.

Question 29

Cause of carpal hyperflexion in puppies

Answer 29

Breed predisposition – Great Danes and Dobermanns, terriers.

Cause unknown – there may be a discrepancy in tendon and bone growth with the bones growing too quickly and the tendons lagging behind?

Question 30

Tendon lacerations

Answer 30

Most common in areas where the tendon runs in a superficial position, such as the plantar or palmar aspects of the feet, and occasionally more proximally in the limb such as the calcaneal tendon.

Question 31

Flexor tendon lacerations

Answer 31

common and usually a result of cuts from glass or other sharp objects.

To protect the repair, the foot is kept in a slightly flexed position, with external coaptation for up to eight weeks after surgery to prevent excessive loading of the repair.

Question 32

Tendon ruptures

Answer 32

The weak point in a muscle is the musculotendinous junction, and this is where ruptures commonly occur.

Usually due to inco-ordinate contractions against a fixed joint.

Animals will present with a loss of function of the affected part.

Usually only mild swelling at the site of the rupture.

With careful palpation it may be possible to palpate the deficit or lack of tendon, muscle contracture often means that the ends are widely displaced.

Question 33

Loss of function with a biceps brachii tendon rupture

Answer 33

Increased flexion of shoulder with elbow extended

Question 34

Loss of function with a calcaneal/gastrocnemius tendon rupture

Answer 34

Dropped hock, claw foot

Question 35

Loss of function with a quadriceps tendon rupture

Answer 35

Inability to extend stifle when weight bearing

Question 36

Loss of function with a digital flexor tendon tendon rupture

Answer 36

Knocked up/flat toes

Question 37

Loss of function with a long digital extensor tendon rupture

Answer 37

Lameness (often avulsion injury in young dogs)

Question 38

Loss of function with a triceps tendon rupture

Answer 38

Inability to extend elbow when weight bearing

Question 39

Partial rupture of the gastrocnemius tendon

Answer 39

occasionally seen in large breeds with Dobermann Pinschers predisposed.

palpably thickened tendon, a mildly plantigrade stance and a ‘claw foot’.

can be managed by positioning the limb in extreme extension to take tension off the tendon.

A screw placed from the calcaneus into the distal tibia can be used to keep the hock extended and then a cast should be applied for 6 weeks followed by screw removal and a bandage for a further two weeks.

Alternatively a TESF is used to keep the hock extended after repair of the tendon as above.

In severe or recurrent injuries particularly if bilateral tarsal arthrodesis can be considered.

Question 40

Musculotendinous avulsions

Answer 40

usually results from an abnormal or spastic contraction of a muscle against a fixed joint.

can either be treated as musculotendinous injuries, if the avulsed fragment of bone is small, or as avulsion fractures if the bone piece is large enough to stabilise.

As the muscle is no longer fixed it is also no longer functional so animals will present with an obvious loss of function.

The presenting complaint may just be one of lameness for more minor muscles.

Presenting complaint and loss of function are similar to those seen with ruptures.

Question 41

Possible tendon avulsions

Answer 41

Gastrocnemius

Quadriceps tendon

Popliteal

Long digital extensor

Digital flexor tendon

Question 42

Dropped toe

Answer 42

Avulsion of the superficial digital flexor tendon insertion on PII.

Injury is of little significance except in show breeds.

Tendon needs to be reattached using a loop of wire to capture the avulsed fragment.

Question 43

Knocked up toe

Answer 43

Avulsion of the DDFT off the flexor process of PIII or severance of the tendon will result in a knocked up toe – little clinical significance.

Treatment of choice is usually to reattach the tendon (and bone) with either a Bunnell or three loop pulley type suture through the tendon and a hole through the adjacent bone, or with a staple or screw and washer through the tendon into adjacent bone (LDE).

Some injuries can be treated conservatively (gastrocnemius origin).

If the avulsed piece of bone is large enough pin and TBW fixation can be used.

Question 44

Contractures

Answer 44

A contracture is usually a result of fibrosis.

The initiating cause may a single traumatic event or repetitive trauma which often leads to a disruption in the blood supply of the muscle.

Parasites (neospora) can also cause contractures.

Both the muscle and / or tendon may be affected.

Specific muscles are predisposed (infraspinatus, gracilis, quadriceps and digital flexor tendons) but potentially any muscle could be affected.

Question 45

Infraspinatus contracture

Answer 45

rare condition seen in working dogs.

It results in a very obvious and characteristic gait deformity.

In a normal animal the infraspinatus muscle functions to flex or extend the shoulder joint and abduct the humerus.

Therefore when muscle contracture is present as the dog tries to extend its shoulder during a stride, extension is not possible and the limb is abducted and circumducted to complete the stride.

Question 46

Aetiology of infraspinatus contracture

Answer 46

trauma (repetitive or a single incident) resulting in inflammation of the tendon which heals by fibrosis and contracture.

Question 47

Palpation, manipulation & radiography of infraspinatus contracture

Answer 47

On palpation and manipulation it is not possible to extend the shoulder

lateral radiographs may show narrowing of the joint space caudally

craniocaudal radiographs may show narrowing of the joint space laterally.

Question 48

Treatment of infraspinatus contracture

Answer 48

severing or removing a small section of the infraspinatus tendon will resolve this problem satisfactorily.

Question 49

Contracture of supraspinatus

Answer 49

Extremely rare

Has similar signs and treatment to infraspinatus contracture

Question 50

Quadriceps contracture

Answer 50

This may occur after femoral fractures in skeletally immature animals

There is a bowstring effect as the muscle contracts while the femur continues to elongate

Ultimately leads to hyperextension of the stifle (genu recurvatum)

If it is treated early then function may be preserved.

If left untreated it can be very difficult to manage and amputation may be required.

The condition is also seen with some neuromuscular conditions such as infection with neospora caninum.

Question 51

Signalment of quadripceps contracture

Answer 51

skeletally immature cats and dogs subsequent to femoral fractures.

Question 52

Presenting signs of quadripceps contracture

Answer 52

hyperextension of the affected hind limb with a reduction in / or no stifle flexion.

The quadriceps muscle may be swollen and painful or fibrous and atrophied.

Question 53

Investigation of quadripceps contracture

Answer 53

radiography to monitor for bony abnormalities and fracture healing.

Serology in cases that occur without any prior history of trauma.

Question 54

Treatment of quadripceps contracture

Answer 54

The quadriceps can be elevated from the femur and fibrous adhesions broken down around the stifle.

However contracture and stifle hyperextension will often recur.

The use of surgical elevation and a dynamic TESF seems to be the most successful treatment option.

Question 55

Prevention of quadripceps contracture

Answer 55

Achieve a stable fracture repair.

Ensure early mobility of the limb

The best chance for a successful outcome is by early treatment.

Use of a 90° / 90° flexion bandage applied postoperatively to keep the stifle flexed

If the quadriceps muscle is found to be very swollen intra operatively then the tensor fascia lata should be left unsutured to prevent further compression of the swollen muscle thus minimising more vascular compromise.

Question 56

Pathophysiology of quadripceps contracture

Answer 56

It is likely that this occurs as a result of ‘compartment syndrome’.

Swelling occurs and the fascia lata around the quadriceps is inextensible so blood supply is impeded – ischaemia occurs and the quadriceps muscle responds to this by producing fibrous tissue

Question 57

Prognosis of quadripceps contracture

Answer 57

guarded – prevention is best.

Question 58

Gracilis contracture

Answer 58

seen most commonly in middle aged German Shepherd Dogs (often working) and very rarely in other breeds.

very characteristic gait

During the swing phase of the stride the leg is carried forward with a pronounced flick where the stifle & foot are rotated inwards and the hock outwards.

may be bilateral.

In the initial stages the condition may be painful with some swelling over the gracilis, semitendinosus or semimembranosus muscles

The diagnosis is made by observation of the characteristic gait and palpation of the firm contracted gracilis muscle.

Temporary alleviation will occur by myotomy or myectomy of the muscle but the condition will always recur an average of 3 - 4 months post-operatively.