Page 228 - WSAVA2018
P. 228

 25-28 September, 2018 | Singapore
significant abnormal shear forces after cranial cruciate rupture.
The medial meniscus however, being firmly attached
to the tibial plateau, is subject to shear force when cranial cruciate instability exists. In this situation the medial femoral condyle moves caudally on flexion and cranially on extension of the stifle joint. This movement
of the medial condyle is resisted by the caudal horn of the medial meniscus and subjects it to abnormal shear forces which ultimately results in damage. Because menisci function as stabilizing “shock absorbers” they are designed to take compressive loads but are unable to withstand shearing forces.
When using the meniscal probe to detect meniscal injuries (nearly all significant injuries occur to the caudal horn of the medial meniscus) the right-angled probe is turned flat to pass between the meniscus and the tibia. In a normal medial meniscus, the probe cannot be passed caudal to the caudal edge of the meniscus because it
is attached to the capsule. The probe is turned with the tip facing dorsally and gentle traction on the caudal horn confirms no capsular tearing when there is no luxation of the horn cranially.
The probe tip is then used on the dorsal sloped surface of the caudal horn of the medial meniscus with the tip pointing down towards the meniscus. If a bucket handle (partial circumferential) tear is present the probe tip will drop into the tear and the torn piece can be dislodged.
Significant lateral meniscal injuries are rare. The same procedure with the meniscal probe can be used on the caudal horn of the lateral meniscus however this must be done in full recognition of the completely different attachment of the lateral to the medial meniscus.
It is normal to be able to pass the probe caudally between the ventral surface of the caudal horn of the lateral meniscus and the tibia because there is no tight capsular attachment as there is on the medial side.
Bucket handle tears can be identified in the same way as for a medial meniscus however.
Small radial tears of the cranial horn of the lateral meniscus are common however these are of little clinical significance.
There are 5 key points to remember about meniscal anatomy when you are doing meniscal surgery:
· The medial and lateral menisci are different.
· The caudal meniscotibial ligament of the medial meniscus. Very commonly either a part of this liga- ment or all of this ligament needs to be transected to remove either a partial tear or a complete caudal pole tear respectively. There is no capsular attach- ment at the area of the caudal meniscotibial liga- ment; the meniscal probe can pass freely dorsal and ventral to the ligament.
· The menisco-femoral ligament of the lateral menis- cus. This is the largest of the meniscal ligaments and while normal is very different to the medial meniscus.
· The medial meniscus is firmly attached to the tibial plateau. The medial meniscus is firmly attached to the tibial plateau through peripheral attachments
to the joint capsule and the medial collateral liga- ment. The lateral meniscus has no attachment to the lateral collateral ligament and has no caudal capsular attachments. Only the cranial third of the lateral me- niscus has capsular attachments. It is this difference in attachment of the menisci that renders the medial meniscus less mobile than the lateral meniscus and explains the much higher incidence of damage to the medial meniscus in the cranial cruciate deficient stifle joint. When using a meniscal probe to inspect the menisci it is important to recognise that the capsule should be firmly attached to the entire periphery of the medial meniscus.
· Normal menisci are gloss white. Damaged menisci typically have a matt or roughened appearance and are discoloured.
Treatment of meniscal injury
Surgery is the treatment of choice for meniscal injury. Conservative treatment is not recommended due to the avascular nature of the majority of the meniscus and consequent lack of healing. Only the peripheral 10% - 15% of the meniscus has a significant blood supply. The remainder of the meniscus receives nutrition from the synovial fluid. Dogs with untreated meniscal injuries remain with significant lameness despite treatment of their cruciate disease.
It is important to assume a meniscal injury is present in all cruciate ruptures where instability is present until proven otherwise on exploratory
arthrotomy / arthroscopy. Meniscal injury has been shown to be present in dogs with cruciate instability in 30-60% of cases.
Meniscal injury is rare in dogs with early cruciate disease before instability develops. Early diagnosis of cruciate disease before instability develops is key to preventing meniscal damage and the problems associated with that.
Meniscal injury – treatment goals: Remove all of, BUT ONLY THE DAMAGED PART of the meniscus. Most commonly it is the caudal horn of the medial meniscus that is damaged.
There are three common types of meniscal injury;
· bucket handle (partial circumferential) tears · peripheral capsular detachment
· radial tears
All occur predominantly only in the caudal 1/3 of the medial meniscus between the medial collateral ligament and the caudal meniscotibial ligament.
Bucket handle tears are the most common

   226   227   228   229   230