Cruciate disease Flashcards
(29 cards)
Prevalence
Common
- consider every mature dog with hindlimb lameness to have cruciate dz until proven otherwise
Most common cause of hindlimb lameness
Signalment
Breed predispositions
- rotties, labs, bull mastiff, WHWT, border terrier
Larger breeds
- more commonly a degenerative condition seen in the younger pt
WHWT
- appears to be older at presentation
Traumatic injuries
- uncommon
- hyperextension of the stifle can cause a torn cruciate
Cat
- older and often overweight
Anatomy of the stifle
Internal stability of the stifle results from the cranial and caudal cruciate, the medial and lateral menisci, collateral ligaments, joint capsule and surrounding musculature particularly the quadriceps, hamstrings (biceps femoris) and gastrocnemius.
The cranial cruciate also prevents internal rotation as well as cranial movement of the tibia / caudal movement of the femur during weight bearing.
The tibial plateau is set at an angle to the long axis of the limb.
When the animal weight bears there is a tendency for the tibia to move cranially (tibial thrust) which is counteracted by the cranial cruciate.
Tibial plateau angle (TPA)
- set by a line at right angles to the long axis of the tibia and the plateau
- the greater this angle the more strain is placed on the cranial cruciate ligament
- this might explain the grater incidence of cruciate dz in those breeds with a large TPA e.g. WHWT although recent investigations cast doubt on this suggestion
Cruciate ligament anatomy and function
Cranial cruciate: prevents cranial movement of the tibia when weight bearing and limits internal rotation - it is composed of a smaller craniomedial component and large caudolateral. It originates from the medial/intercondylar surface of the lateral femoral condyle and inserts on the intercondylar cranial tibial plateau.
Caudal cruciate: this prevents caudal translation of the tibia when weight bearing. It originates from the craniomedial aspect of the medial femoral condyle and inserts on the caudal aspect of the lateral tibial plateau/popliteal fossa.
The craniomedial component is taut in both extension and flexion, the caudolateral in extension only.
A partial tear of the cruciate (craniomedial component [most common]) results in instability in flexion only as the caudolateral part produces stability when the stifle is extended. Damage to the caudolateral component may not result in any discernible instability.
Rupture of the caudal cruciate ligament is very uncommon unless associated with stifle derangements as seen in the cat.
Meniscal cartilages - anatomy
These are 2 crescent shaped fibrocartilaginous structures that have been described as the toilet seat of the joint. They’re broader at their extremities where they have a blood supply and extensive neural network both for pain sensation and proprioception.
They function to improve the congruity of the curved femoral condyles and the flat surface of the tibial plateau.
In the cranial cruciate deficient joint the lateral meniscus moves with the tibia as it has no attachment to the lateral collateral ligament due to the presence of the tendon of origin of the popliteus muscle. The medial meniscus is attached to the medial collateral and cannot move with the tibia, therefore is prone to injury.
During any surgery these are generally examined although there is some debate about the usefulness of this. The integrity of the menisci should be maintained but torn portions are best removed.
Aetiology of cruciate disease
Multiple theories
Angle of the tibial plateau
- the steeper angle puts greater strain on the cranial cruciate and is particularly seen in breeds such as the WHWT
Autoimmune dz
Intercondylar width (distance between medial and lateral femoral condyles)
- particularly seen in the lab
- it’s postulated that iff this is narrow then the cranial cruciate is exposed to more strain (as it is squeezed between the 2)
History
- chronic lameness with sudden deterioration
- an acute injury (e.g. dog that runs down the garden after a squirrel)
- a chronic lameness
- a clicking sound may be heard (the meniscal click as the meniscus folds and unfolds)
- an unexplained lameness in the hindlimb
- beware of the bilateral case which can appear like neurological dz
Clinical presentation
Acute
- traumatic injury
- may be accompanied by other injuries such collateral ligament rupture as seen in the cat with the dislocated/deranged stifle
Acute on chronic
- degenerative changes precede a more acute rupture
Chronic
- degenerative changes within the cruciate
- particularly seen in large breeds and the most common presentation
Clinical signs
- lame and variable amounts of pain are demonstrated
- hold the limb from ground when standing
- stifle may be swollen
- presence of a medial buttress (fibrous thickening on the medial aspect of the stifle) is seen in the more chronic cases
- pain on stifle flexion
- pain in the acute phase on attempting cranial drawer
- lameness is severe at 1st (10/10) but slowly improves over the next few weeks
Cranial cruciate dz diagnosis
- hx & CS
- typical radiographic signs of degenerative changes
- 2 definitive tests which demonstrate instability in the joint are:
– cranial drawer
– tibial thrust or compression test
^ these 2 tests can be performed in the conscious animal but is occasionally better done under sedation or GA.
Tibial compression test - how to
- for the right hind place the left hand lightly over the tibia palpating the tuberosity
- with the right hand tense the gastrocnemius muscle but keep the stifle fixed
- this mimics weight bearing
- look for forward movement of the tibia
- try this with different degrees of stifle flexion
- less painful method of detecting the ruptured cruciate
Cranial drawer - how to
- for the right hind grasp the tibia with the right hand placing the thumb in popliteal fossa
- grasp the femur in the left with a finger on patella and thumb at the origin of gastrocnemius
- push gently with the right thumb
Limitations of the cranial drawer and tibial compression tests
- pain can make assessment of the stifle instability difficult
- tension or nervousness in the dog is also detrimental
- in the chronic case the periarticular fibrosis may reduce the degree of instability appreciated
- cats may dislike being restrained on their side
- sedation or GA makes assessment much easier
- tibial compression may be superior in that it elicits less pain than the cranial drawer
Radiographic signs
- can be helpful in the chronic case or when there is equivocal instability
- although degenerative changes are not diagnostic of cruciate disease they are highly suggestive
- 1st radiographic sign is a joint effusion with loss of the sub-patella fat pad
- OA changes
– periosteal new bone to the fabellae
– poles of the patella
– tibial plateau
– trochlea ridges
Tx options
- no action - conservative management
- surgical management
– alter joint mechanics or
– place an artificial ligament
Conservative management
- ~6w restricted exercise
- if the lameness is improving then can carry on, if not might consider surgery (e.g. there may be an undetected meniscal tear?)
- in the old dog with a chronic injury with marked periarticular fibrosis and OA, try a conservative approach as much of the lameness is due to the arthritis rather than the joint instability
- sx is not cheap
- use of braces to support the unstable stifle can be helpful, as can physiotherapy and weight loss in the overweight dog
Surgical management candidates
- large & athletic dogs
- small dogs with steep tibial plateau angles e.g. >30 degrees
- those with a strong index of suspicion of meniscal injury (e.g. a meniscal click on manipulation of the joint)
Tx - the artificial ligament
- always a poor 2nd
- natural ligament is a highly vascular structure with neurons that are important for proprioception
– it prevents internal rotation as well as cranial translation of the tibia/caudal movement of the femur
– it is adapted to cyclic loading and has precise points of origin and insertion
– it is not possible to reflect these points on the femur and tibia
BUT it does have its place
- in the small dog and cat
- when there are financial constraints for O
What are the options?
- fabello-tibial suture
- Arthrex tightrope technique
- Over the Top technique (from 1980s, rarely performed now)
Tx - the DeAngelis suture
- runs from the fabella to a hole drilled in the tibial crest
- roughly coincides with the orientation of the cranial cruciate ligament
- polyester suture or monofilament nylon/leader line is generally used
- there are tensioning devices and the sutures can be secured with a crimp clip
- a more recent advance on this method of management is the Tightrope technique (Arthrex) which attempts to more closely align the prosthesis to the origin and insertion of the cranial cruciate
- the suture will cheese-saw through the soft tissues of the fabello-femoral ligament, the fabello tibial suture is anchored around this ligament
- within 2-3m the stability will be lost but it is thought that the periarticular fibrosis present by this time will stabilise the joint adequately
- wire not regularly used as breaks easily
The tibial plateau angle levelling and tibial tuberosity advancement
These attempt to recreate the stability of the joint by altering the dynamics such that the cruciate ligament is no longer required.
The tibial plateau angle will be altered to a value of c.6 degree in the TPLO (tibial plateau levelling osteotomy).
Or a right angle is created with the patella tendon and plateau with the TTA (tibial tuberosity advancement).
The triple tibial osteotomy is a combination of these 2 but is rarely performed now.
The tibial plateau angle re TTA & TPLO
It determines the size of wedge or degree of rotation of the proximal fragment in the TPLO or the degree of advancement of the tibial tuberosity.
Landmarks are the tubercle of Gerdy and caudal tibial plateau, the intercondylar eminences and the centre of the talus.
The aim of the TPLO is to level the plateau so as to obliterate the cranial thrust that occurs when weight bearing.
With the TTA a right angle is created between the plateau and the patella ligament..
As a result of these 2 techniques the cranial cruciate ligament is no longer required when weight bearing.
Tibial plateau levelling (TPLO) techniques
Slocum technique with a radial cut
- special saw is required
- difficult to perform with a very marked tibial plateau angle as the bony contact is reduced
- the degree of levelling is determined by the degree of rotation
- favoured by many surgeons and is the most widely applied osteotomy
- it has special plates which accommodate a combination of compression and locking screws
Cranial closing wedge osteotomy (CCWO)
- a wedge is removed and then closed and secured with plate and cranial wire
- the degree of levelling is determined by the size of the wedge
- was the original technique
- can be used in any size of animal and is particularly useful for those with a very marked tibial plateau angle e.g. WHWT
- does put a strain on the patella ligament and results in desmitis
CORA based levelling osteotomy (CBLO)
- more recent variant of TPLO
- used a domed cut centred on the CORA (centre of rotation angulation)
- aim is to limit the caudal movement of the tibial plateau seen with the standard Slocum technique
- useful in dogs with steep tibial plateau angles and those with open growth plates
Tibial tuberosity advancement (TTA)
- falling out of favour, results appear inferior to the TPLO
- aim is to create a right angle between the plateau and the patella tendon
- with a very marked TPA it can be impossible to advance the tibial tuberosity far enough to create a right angle between the plateau and patella tendon
- when the animal weight bears the tension in the patella tendon and quadriceps prevents the tibial drawer
