Use of radiographic measurements in the evaluation of dogs with medial patellar luxation

This prospective study used radiographic techniques to evaluate the inclination, Norberg, quadriceps and femoral varus angles, and the patellar position in dogs with developmental medial patellar luxation. The study also compared these measurements pre- and post-operatively to determine how they were affected by surgical procedures. Eighteen dogs with unilateral or bilateral luxation were used, and 4 groups were established according to luxation grade. Except for the quadriceps angle, there was no difference among the groups preoperatively. Significant differences for the quadriceps angle were observed between Grades 1 and 3, and between Grades 2 and 3. The Norberg and femoral varus angles and the patellar position showed no changes between pre- and postoperative groups. However, measurements of the preoperative quadriceps angle and postoperative inclination angle may be useful for evaluating dogs with grade-3 luxation. Further studies using other imaging techniques are required in dogs with severe grade-4 luxation due to the difficulty in obtaining a good radiographic position.     

Pre- and postoperative radiographic and computed tomographic evaluation of dogs with medial patellar luxation

OBJECTIVE: To quantify, using radiographic and computed tomographic (CT) techniques, the effects of surgical procedures most commonly combined to treat dogs with medial patellar luxation (MPL). STUDY DESIGN: Prospective study. METHODS: Six dogs with 8 MPL were studied. Radiographs and CT of the pelvic limbs were obtained before and immediately after soft-tissue reconstruction, trochlear wedge recession, and tibial crest transposition. Radiographic measurements included angle of inclination, Norberg angle, quadriceps angle (QA), anteversion angle, ratio of the length of the patellar tendon (PT) to the length of the patella, and change in patella tendon angle. CT measurements included angle of inclination, Norberg angle, QA, anteversion angle, depth of the femoral trochlear groove, ratio of the middle femoral trochlear groove depth to the patella thickness, and tibial crest alignment. RESULTS: Conformation of the coxofemoral joint was not affected by surgery. Surgical treatment corrected the QA by 33-58%. Trochlear wedge recession was most effective in deepening the proximal trochlea by 103.5%. The ratio of the middle femoral trochlear groove depth to the thickness of the patella postoperatively resulted in 50% coverage of the patella. Tibial crest transposition resulted in caudalization of the PT by 8.5+/-3.0 degrees, with lateralization of the tibial tuberosity of 11.3 degrees. CONCLUSION: The effects of surgery for MPL can be quantified with radiographic and CT measurements. Surgical correction restored the alignment of the quadriceps and adequately deepened the femoral trochlear groove. Tibial crest transposition resulted in caudalization of the patella tendon and lateralization of the tibial tuberosity. CLINICAL RELEVANCE: These pilot data quantified the effects of surgical procedures most commonly combined to treat MPL. We hope to use these measurements to correlate surgical treatment with functional outcome and postoperative occurrence of luxation.     

Arthroscopic release of the medial femoropatellar ligament for canine medial patellar luxation

Five dogs of varying breeds and ages were presented for evaluation of medial patellar luxation that was unresponsive to conservative treatment. Arthroscopy of each affected stifle was performed, and adequacy of the femoral trochlea and patellar tracking in the trochlea were assessed. Medial femoropatellar ligament release was then performed using a bipolar radiofrequency electrosurgical system with or without a tibial tuberosity transposition. The procedure resulted in good to excellent outcomes for four dogs and a fair outcome for a fifth dog.     

Latero-distal transposition of the tibial crest in cases of medial patellar luxation with patella alta

Medial patellar luxation is defined as medial displacement of the patella from the trochlear groove. In dogs, medial luxations account for 75% of all patellar luxation cases, and are frequently associated with patella alta. Common surgical treatments for medial luxation are trochleoplasty and lateral transposition of the crest to drive the patella into the correct anatomical alignment. Postoperative complications for this procedure are estimated to be between 18-29% of cases, with up to 48% of complications involving reluxation. It was previously hypothesized that in cases of medial luxation involving patella alta, the addition of a distal component to the lateral tibial crest transposition will result in repositioning of the patella into its proper position in the trochlear groove, thus reducing the recurrence of luxation. We performed this modified procedure on 14 dogs (17 limbs) that were suffering from medial luxation combined with patella alta, and our results led to favourable clinical outcomes. This modified surgical procedure places the patella into a more normal proximo-distal anatomical position, is simple to perform, and may become common practice for surgical treatment of medial patellar luxation with an alta component.     

Evaluation of the association between medial patellar luxation and hip dysplasia in cats.

OBJECTIVE: To investigate the association between hip dysplasia (HD) and medial patellar luxation (MPL) in cats. DESIGN: Cross-sectional prevalence study. ANIMALS: 78 cats. PROCEDURE: A complete history was obtained. Cats were examined to detect MPL and HD. Radiographs of the stifle and hip joints were obtained. Hip joints were evaluated by use of Norberg angle, distraction index, and scoring consistent with that established by the Orthopedic Foundation for Animals. RESULTS: There were 43 male and 35 female cats mean age, 2.5 years). Eleven cats had clinical signs of disease in the pelvic limbs. Medial subluxation of the patella (subgrade 1) was seen in 31 of 33 cats with otherwise normal stifle joints. Medial patellar luxation was found in 45 of 78 (58%) cats, and 35 of 45 (78%) had grade-1 MPL. Bilateral MPL was seen in 32 of 45 (71%) cats. A weak association existed between MPL and HD, because cats were 3 times more likely to have HD and patellar luxation than to have either condition alone. Concurrent MPL and HD were detected in 19 of 78 (24%) cats, and HD was diagnosed radiographically in 25 of 78 (32%) cats (19 mild, 4 moderate, 2 severe). Eighteen of the 25 cats with HD had bilateral HD. CONCLUSIONS AND CLINICAL RELEVANCE: Clinically normal cats may have a certain degree of laxity in the stifle joint, evident as medial patellar subluxation (< grade 1). There is a weak association between MPL and HD, and both conditions may develop, alone or in combination, more frequently than has been reported.     

Surgical management of a pony with a traumatic medial luxation of the patella

This report describes a successful surgical repair of medial patellar luxation in a Miniature Shetland pony where manual reduction of the patella was not possible. The surgical procedure involves transection of the medial femoropatellar ligament to facilitate patellar release, the placement of a prosthetic suture to replace the lateral femoropatellar ligament and reinforcement of the lateral retinaculum by the use of a mesh implant. This is a newly described surgical technique for the rare but recognised condition of a medial luxation of the patella.     

Retrospective risk factor assessment for complication following tibial tuberosity transposition in 137 canine stifles with medial patellar luxation

This study identified risk factors for complication following tibial tuberosity transposition by retrospective examination of cases that used various surgical techniques. Records and radiographs of 113 dogs with 137 stifles undergoing tibial tuberosity transposition for medial patellar luxation were reviewed. Patient-specific factors, surgical factors, and complication information were recorded. Owners were contacted as necessary to attain a minimum of 30 days follow-up. Of 137 stifles, 59 (43%) had complications, with 24 (18%) identified as major complications. Factors significantly associated with reduced risk of complication included increased age [odds ratio (OR) 0.8] and concurrent cranial cruciate ligament rupture (OR 0.3). Factors significantly associated with increased risk of complication included large breed compared to toy breed (OR 5.5), increased weight (OR 1.3), and use of a screw for tibial tuberosity fixation (OR infinity). While significant, these associations do not imply causality and prospective study is necessary to determine the ideal fixation method for individual patients.     

Vertical patellar position in large-breed dogs with clinically normal stifles and large-breed dogs with medial patellar luxation

OBJECTIVE: To further define vertical patellar position, as measured by the ratio of patellar ligament length to patellar length (L:P), in large-breed dogs with clinically normal stifles and compare that to the L:P of large-breed dogs with medial patellar luxation (MPL). STUDY DESIGN: Retrospective study. SAMPLE POPULATION: Large-breed dogs (n = 50) with clinically normal stifle joints and 30 large-breed dogs with MPL. METHODS: Large-breed dogs with clinically normal stifle joints or MPL were identified and divided into groups (NORM and MPL, respectively). L:P values were determined for each dog by 4 observers from single lateral stifle radiographs. L:P was compared between NORM and MPL groups and 95% confidence intervals (CIs) were calculated. RESULTS: All 4 observers found a significantly higher L:P (more proximally positioned patella) for the MPL group compared with the NORM group. Overall mean (+/-SEM) L:P were: NORM, 1.71+/-0.020 and MPL, 1.87+/-0.025. The 95% CI was determined to be 1.45-1.97 for the NORM group and 1.57-2.17 for the MPL group. CONCLUSIONS: Large-breed dogs with MPL had a significantly more proximal vertical patellar position compared with large-breed dogs with clinically normal stifles. Large-breed dogs with L:P values >1.97 are considered to have patella alta. CLINICAL RELEVANCE: Proximal displacement of the patella within the femoral trochlear groove may play a role in MPL in large-breed dogs.     

The canine stifle joint II. Medial luxation of the patella

A method of assessment of cases of medial luxation of the patella for deciding the type of surgical intervention is described. The results of treatment of the cases after such an assessment indicate that, if there is no gross distortion and no deviation of the tibial tuberosity, simple lateral capsular overlap gives a satisfactory return of function, even in cases of irreducible patellar luxation.
Résumé. Les auteurs décrivent une méthode propre à évaluer les luxations médiales de la rotule en vue de déterminer la nature de l'intervention chirurgicale à pratiquer. Les résultats thérapeu-tiques obtenus sur la base de cette évaluation portent à conclure que, sauf grave déformation ou déviation de la tubérosité du tibia, le simple chevauchement capsulaire latéral permet de rétablir un état fonctionnel satisfaisant, měme dans les cas de luxation rotulaire irréductible.
Zusammenfassung. Es wird eine Methode zur klinischen Beurteilung von Fällen einer medialen Luxation der Patella zwecks Entscheidung über die Art des erforderlichen chirurgischen Eingriffs beschrieben. Die Behandlungsergebnisse in den Fällen nach einer solchen Beurteilung zeigen, dass beim Fehlen einer makroskopischen Verformung und einer Abweichung der Tuberositas tibiae die einfache laterale Kapselüberlappung eine zufriedenstellende Rückkehr der Funktion selbst in Fällen nicht reduzierbarer patellarer Luxation ergibt.     

Surgical correction of congenital medial patellar luxation in a llama

Unilateral congenital medial patellar luxation in a young llama was corrected by medial joint capsule release, tibial crest transposition, trochleoplasty, and lateral joint capsule imbrication. The techniques used were the same as described in the dog. One year after surgery, the llama was not lame, but had a valgus deformity originating at the stifle, most likely caused by lateral femoral condyle hypoplasia.     

Rotation of the femoral trochlea for treatment of medial patellar luxation in a dog

A crossbreed dog was presented with non-weight bearing on the right hindlimb and a semi-flexed stifle. Clinical examination and radiographic investigation showed a grade 3 medial patellar luxation, characterised by hypoplasia of the medial trochlear ridge. No other significant skeletal abnormalities were detected. A 180 degrees rotation of the femoral trochlea was the surgical technique chosen to treat the trochlear dysplasia, the aim being to move the normal lateral ridge to the medial side and thereby prevent patellar luxation. This technique was able to restore correct conformation of the femoral trochlea and preserve the integrity of the trochlear groove cartilage, thus potentially retarding the progression of degenerative joint disease. The dog recovered fully and postoperative radiographic examinations showed healing of the rotated trochlea with only mild signs of degenerative joint disease.