informed consent pattella luxation lateral

[malernee]

The causes of lateral patellar luxation include:
1. Femoral external torsion
2. Femoral head and neck anteversion
3. Distal femoral Valgus
4. Lateral position of the tibial tubercle
5. Secondary, cranial medial rotary instability of the stifle.
6. External tibial torsion.
7. Proximal tibial valgus.
8. Distal tibial valgus
Patellar luxations are limb alignment problems except for the rare traumatic case. (See Bojrab's book Current Techniques in Vet Surgery for the algorithm.)


Rectangular Recession Trochleoplasty for Treatment of Patellar Luxation in Dogs and Cats

<<Vet Comp Ortho Trauma 13[1]:39-43 Feb'00 Case Report 21 Refs
K.W. Talcott; R.L. Goring; J.J. deHaan
Affiliated Veterinary Specialists, Orange Park, FL USA

Trochleoplasty is a fundamental component of surgical treatment for patients with inadequate trochlear depth associated with patellar luxation. Traditional methods of trochleoplasty include trochIear resection, chondroplasty and wedge recession trochleoplasty. Each technique has its benefits and limitations. Rectangular recession trochleoplasty (RRT) is a new technique that builds upon the strengths of its predecessors while minimizing their limitations. Rectangular recession utilizes a rectangular osteochondral autograft that is harvested from the trochlear groove and replaced into its recipient bed. Unlike wedge recession, the autograft surfaces are compressed and buttressed within the recipient bed, resulting in secure implantation of the autograft. Rectangular recession achieves maximal preservation of hyaline articular cartilage while minimizing exposure of abrasive subchondral bone. Rectangular recession can be performed on dogs and cats as small as 3 kg and has been clinically effective in treating over 100 cases of patellar luxation. [Summary]
Orthopedic Foundation for Animals
PATELLAR LUXATION REGISTRY
Overview

Categories

Classification

Medical Luxation in Breeds
Clinical Signs
Lateral Luxation in Toy and Miniature Breeds
Clinical Signs

Lateral Luxation in Large and Giant Breeds

Clinical Signs



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Overview
1. Purposes - To identify those dogs that are phenotyp~cally normal prior to use in a breeding program and to gather data on the genetic disease - patellar luxation.

2. Examination and Classification - Each dog is to be examined and classified by an attending veterinarian according to the enclosed application and general information instructions.

3. Certification - A certificate and breed registry number will be issued to all dogs found to be normal at 12 months of age or older. The OFA fee is $15.00 and no charge will be made for re-certification at a later age. The breed registry number will contain the age at evaluation and it is recommended that dogs be periodically re-examined as some luxations will not be evident until later in life.

4. Preliminary Evaluation - Evaluation of dogs under 12 months of age is encouraged if the owner desires to breed at this age. OFA will enter the information in a data bank at a fee of $10.00 for those found to be normal.

5. Dogs with Patellar Luxation - The attending veterinarian and owner is encouraged to submit all evaluations, whether normal or abnormal, for the purpose of completeness of data. There is no OFA fee for entering an abnormal evaluation of the patellar in the data bank.



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Categories

Patellar luxations fall into several categories

1.) Medial luxation; toy, miniature, and large breeds.
2.) Lateral luxation; toy and miniature breeds.
3.) Lateral luxation; large and giant breeds.
4.) Luxation resulting from trauma; various breeds, and is of no importance to the certification process.
Numbers 1, 2 and 3 are either known to be heritable or strongly suspected.




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Classification

A method of classifying the degree of luxation and bony deformity is useful for diagnosis, and can be applied to either medial or lateral luxations by reversing the medial-lateral directional references. The position of the patella can most easily be palpated by starting at the tibial tubercle and working proxi-mally along the patellar ligament to the patella.

Grade 1

Intermittent patellar luxation causing the limb to be carried occasionally. The patella easily luxates manually at full extension of the stifle joint, but returns to the trochlea when released. No crepitation is apparent. The medial, or very occasionally, lateral deviation of the tibial crest (with lateral luxation of the patella) is only minimal, and there is very slight rotation of the tibia. Flexion and extension of the stifle is in a straight line with no abduction of the hock.

Grade 2

There is frequent patellar luxation which, in some cases, becomes more or less permanent. The limb is sometimes carried, although weight bearing routinely occurs with the stifle remaining slightly flexed.

Especially under anesthesia it is often possible to reduce the luxation by manually turning the tibia later-ally, but the patella reluxates with ease when manual tension of the joint is released.

As much as 30 degrees of medial tibial torsion and a slight medial deviation of the tibial crest may exist. When the patella is resting medially the hock is slightly abducted. If the condition is bilateral, more weight is thrown onto the forelimbs.

Many cases in this grade live with the condition reasonably well for many years, but the constant luxa-tion of the patella over the medial lip of the trochlea causes erosion of the articulating surface of the patella and also the proximal area of the medial lip. This results in crepitation becoming apparent when the patella is luxated manually.

Grade 3

The patella is permanently luxated with torsion of the tibia and deviation of the tibial crest of between 30 degrees and 50 degrees from the cranial/caudal plane. Although the luxation is not intermittent, many animals use the limb with the stifle held in a semi-flexed position. Flexion and exten-sion of the joint causes abduction and adduction of the hock. The trochlea is very shallow or even flat-tened.

Grade 4

The tibia is medially twisted and the tibial crest may show further deviation medially with the result that it lies 50 degrees to 90 degrees from the cranial/caudal plane.

The patella is permanently luxated. The patella lies just above the medial condyle and a space can be palpated between the patellar ligament and the distal end of the femur. The trochlea is absent or even convex.

The limb is carried, or the animal moves in a crouched position, with the limb partly flexed.


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MEDIAL LUXATION IN TOY, MINIATURE, AND LARGE BREEDS

These luxations are often termed "congenital" because they occur early in life and are not associated with trauma. Although the luxation may not be present at birth, the anatomical deformities that cause these luxations are present at that time and are responsible for subsequent recurrent patellar luxation. Patellar luxation in these breeds should be considered an inherited disease.

Medial luxation is far more common than lateral luxation in all breeds, representing 75 to 80 percent of cases, with bilateral involvement seen 20 to 25 percent of the time.

Three classes of patients are identifiable:
CLINICAL SIGNS


1. Neonates and older puppies often show clinical signs of abnormal hind-leg carriage and func-tion from the time they start walking; these present grades 3 and 4 generally.

2. Young to mature animals with grade 2 to 3 luxations usually have exhibited abnormal or inter-mittently abnormal gaits all their lives but are presented when the problem symptomatically wors-ens.

3. Older animals with grade I and 2 luxations may exhibit sudden signs of lameness because of further breakdown of soft tissues as result of minor trauma or because of worsening of degenera-tive joint disease pain.

Signs vary dramatically with the degree of luxation. In grades I and 2, lameness is evident only when the patella is in the luxated position. The leg is carried with the stifle joint flexed but may be touched to the ground every third or fourth step at fast gaits. Grade 3 and 4 animals exhibit a crouching, bowlegged stance (genu varum) with the feet turned inward and with most of the weight transferred to the front legs. Permanent luxation renders the quadriceps ineffective in extending the stifle. Extension of the sti-fle will allow reduction of the luxation in grades I and 2. Pain is present in some cases, especially when chondromalacia of the patella and femoral condyle is present. Most animals; however, seem to show lit-tle irritation upon palpation.


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LATERAL LUXATION IN TOY AND MINIATURE BREEDS

Lateral luxation in small breeds is most often seen late in the animal's life, from 5 to 8 years of age. The heritability is unknown. Skeletal abnormalities are relatively minor in this syndrome, which seems to represent a breakdown in soft tissue in response to, as yet, obscure skeletal derangement. Thus, most lat-eral luxations are grades 1 and 2, and the bony changes are similar, but opposite, to those described for medial luxation. The dog has more functional disability with lateral luxation than with medial luxation.

CLINICAL SIGNS

In mature animals, signs may develop rapidly and may be associated with minor trauma or strenuous activity. A knock-knee or genu valgum stance, sometimes described as seal-like, is characteristic. Sudden bilateral luxation may render the animal unable to stand and so simulate neurological disease. Physical examination is as described for medial luxation.


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LATERAL LUXATION IN LARGE AND GIANT BREEDS

Also called genu valgum, this condition is usually seen in the large and giant breeds. Rudy postulated a genetic pattern of occurrence and noted Great Danes, St. Bernards, and Irish Wolfllounds as being the most commonly affected. Components of hip dysplasia, such as coxa valga (increased angle of inclina-tion of the femoral neck) and increased anteversion of the femoral neck, are related to lateral patellar luxation. These deformities cause internal rotation of the femur with lateral torsion and valgus deformi-ty of the distal femur, which displaces the quadriceps mechanism and patella laterally.

CLINICAL SIGNS

Bilateral involvement is most common. Animals appear to be affected by the time they are 5 to 6 months of age. The most notable finding is a knock-knee (genu valgum) stance. The patella is usually reducible, and laxity of the medial collateral ligament may be evident. The medial retinacula tissues of the stiffly joint are often thickened, and the foot can often be seen to twist laterally as weight is placed on the limb.