Muscle and tendon disorders Flashcards
Tendons
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.
Characteristics of tendons that impact healing
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
Suture patterns that can be used to repair a tendon
Three loop pulley
Bunnells suture
Locking loop
Suture selection for a three loop pulley suture
Monofilament
Swaged on neddle
Slow resorption or permanent
Most commonly polypropylene (prolene)
Surgical principles of tendon repair
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
Bicipital tenosynovitis
Conditions range from complete ruptures, through partial ruptures to mild inflammation or tenosynovitis.
Bicipital tenosynovitis- signalment
Often large breed young active dogs
Bicipital tenosynovitis - history
acute or insidious onset and often chronic forelimb lameness.
Bicipital tenosynovitis - palpation
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.
Bicipital tenosynovitis - diagnosis
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
Bicipital tenosynovitis- treatment
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
Breeds affected by Biceps brachii displacement
Racing dogs - greyhounds/lurchers
Breeds affected by superficial digital flexor tendon displacement
Shetland sheepdogs
Breeds affected by quadriceps tendon displacement (patellar luxation)
Any - small breeds predisposed
Breeds affected by long digital extensor tendon displacement
Extremely rare
Tendons that sit in grooves can displace due to:
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
Clinical signs of a displaced tendon
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.
Treatment of displacing tendons
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.
Medial Displacement of the Biceps Brachii Tendon
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.
Treatment of medial displacement of the biceps brachii tendon
Involves replacing the function of the transverse humeral ligament with a smooth bone staple or wire suture.
Lateral displacement of the superficial digital flexor tendon
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.
Carpal laxity in puppies
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.
Clinical signs of carpal laxity in puppies
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.
Stressed radiography of carpal laxity in puppies
Will reveal no abnormalities
Treatment of carpal laxity in puppies
Increase exercise on firm ground
Feed correct diet
Prognosis usually good
Signs of carpal hyperflexion in puppies
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.
Treatment of capral hyperflexion in puppies
conservative, correct diet and adjust exercise as necessary.
Prognosis of carpal hyperflexion in puppies
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.
Cause of carpal hyperflexion in puppies
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?
Tendon lacerations
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.
Flexor tendon lacerations
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.
Tendon ruptures
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.
Loss of function with a biceps brachii tendon rupture
Increased flexion of shoulder with elbow extended
Loss of function with a calcaneal/gastrocnemius tendon rupture
Dropped hock, claw foot
Loss of function with a quadriceps tendon rupture
Inability to extend stifle when weight bearing
Loss of function with a digital flexor tendon tendon rupture
Knocked up/flat toes
Loss of function with a long digital extensor tendon rupture
Lameness (often avulsion injury in young dogs)
Loss of function with a triceps tendon rupture
Inability to extend elbow when weight bearing
Partial rupture of the gastrocnemius tendon
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.
Musculotendinous avulsions
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.
Possible tendon avulsions
Gastrocnemius
Quadriceps tendon
Popliteal
Long digital extensor
Digital flexor tendon
Dropped toe
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.
Knocked up toe
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.
Contractures
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.
Infraspinatus contracture
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.
Aetiology of infraspinatus contracture
trauma (repetitive or a single incident) resulting in inflammation of the tendon which heals by fibrosis and contracture.
Palpation, manipulation & radiography of infraspinatus contracture
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.
Treatment of infraspinatus contracture
severing or removing a small section of the infraspinatus tendon will resolve this problem satisfactorily.
Contracture of supraspinatus
Extremely rare
Has similar signs and treatment to infraspinatus contracture
Quadriceps contracture
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.
Signalment of quadripceps contracture
skeletally immature cats and dogs subsequent to femoral fractures.
Presenting signs of quadripceps contracture
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.
Investigation of quadripceps contracture
radiography to monitor for bony abnormalities and fracture healing.
Serology in cases that occur without any prior history of trauma.
Treatment of quadripceps contracture
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.
Prevention of quadripceps contracture
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.
Pathophysiology of quadripceps contracture
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
Prognosis of quadripceps contracture
guarded – prevention is best.
Gracilis contracture
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.
