Clinical signs and results of treatment in cats with patellar luxation: 42 cases (1992-2002)

OBJECTIVE: To describe clinical signs and results of treatment in cats with patellar luxation. DESIGN: Retrospective case series. ANIMALS: 42 cats in which patellar luxation had been diagnosed on the basis of results of palpation of the stifle joints. PROCEDURES: Degree of luxation was graded on a scale from 1 to 4, and severity of lameness was graded on a scale from 0 to 5. Radiographs of stifle joints were evaluated for signs of osteoarthritis. Long-term function was classified as poor, fair, good, or excellent. RESULTS: 34 cats had bilateral luxation and 8 had unilateral luxation. Only 7 (17%) cats had a history of trauma. Mean age of the cats was 3.3 years, and mean weight was 4.26 kg (9.4 lb); 26 (62%) were domestic shorthairs. Seventy-three of the 76 (95%) affected joints had medial patellar luxation. Luxation grades could be assigned to 65 joints, with grade 2 (30 joints) and 3 (22 joints) luxation being most common. Lameness grades could be assigned to 73 joints, with grade 1 lameness (27 joints) most common. Outcome was excellent for 8 of 17 joints treated without surgery and for 23 of 35 joints treated surgically. Complications attributable to surgery were reported in 8 cats. CONCLUSIONS AND CLINICAL RELEVANCE: Patellar luxation should be considered as a cause of hind limb lameness in cats. Low-grade luxation can be associated with lameness of the same severity as high-grade luxation. Surgical correction of patellar luxation in cats with grade 2 or 3 lameness can result in a favorable outcome.     

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.     

Clinical Results of Surgical Correction of Medial Luxation of the Patella in Dogs

Thirty-four dogs that had surgical correction of medial patellar luxation (MPL) in 52 stifle joints were examined after a minimum follow-up period of 1 year (median, 3.6 years). The dogs were divided into the following three groups depending on their age at the time of surgery: group 1, 3 to 6 months; group 2, 8 to 20 months; and group 3, 2.2 to 12 years. Two of the dogs in group 3 had ruptured their cranial cruciate ligament in addition to having MPL. The results were based on a clinical assessment of the animal's gait, and physical and radiographic examination of the stifle joints. Six of seven stifle joints evaluated in group 1 had radiographic evidence of moderate to severe degenerative joint disease of the patellofemoral joint, and in two of the joints recurrence of MPL was observed. Failure to maintain reduction of the patellofemoral joint was also observed in 11 of 22 (50%) and 12 of 23 (52%) of the stifle joints in groups 2 and 3, respectively. In the latter groups, mild degenerative joint disease was evident radiographically in stifle joint that had not maintained reduction. Four of the 34 dogs were consistently (n = 2) or intermittently (n = 2) lame; the two dogs that were consistently lame had cranial instability of the stifle consistent with rupture of the cranial cruciate ligament. In the latter two dogs, the cranial cruciate ligament had been intact at the time of surgery for correction of MPL.     

Proximodistal alignment of the canine patella: radiographic evaluation and association with medial and lateral patellar luxation

Objectives— To evaluate the contribution of proximodistal alignment of the patella to patellar luxation, and to evaluate the structures contributing to proximodistal alignment of the patella relative to the femoral trochlea.
Study Design— Retrospective study using a convenience sample.
Animals— Medium to giant breed dogs (n=106).
Methods— Medical records and stifle radiographs of 106 dogs were reviewed. Radiographic measurements evaluated the proximodistal alignment of the patella with respect to the femoral trochlea, distal aspect of the femur, and proximal aspect of the tibia. Measurements were compared between dogs with clinically normal stifles (controls; n=51 dogs, 66 stifles), and dogs with a clinical diagnosis of medial patellar luxation (MPL, n=46 dogs, 65 stifles) or lateral patellar luxation (LPL, n=9 dogs, 11 stifles) using ANOVA.
Results— In dogs with MPL, the ratio of patellar ligament length (PLL) to patellar length (PL) was increased, as was the ratio of the distance from the proximal aspect of the patella to the femoral condyle (A) to PL ( P <.0001). Dogs with LPL had a decreased A:PL ( P =.003) and an increased ratio of the proximal tibial length (PTL) to distal tibial width (DTW; P =.009).
Conclusions— MPL is associated with a relatively long patellar ligament and patella alta in medium to giant breed dogs. LPL is associated with a relatively long proximal tibia and patella baja. Values for PLL:PL>2.06 and A:PL>2.03 are suggestive of the presence of patella alta, whereas a value for A:PL<1.92 is suggestive of patella baja.
Clinical Relevance— Measurements of both PLL:PL and A:PL are recommended in dogs with patellar luxation, and surgical correction should be considered in those with abnormal values.     

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.     

Combination tibial plateau leveling osteotomy and transverse corrective osteotomy of the proximal tibia for the treatment of complex tibial deformities in 12 dogs

Objective: To describe a surgical technique, and outcome, for treatment of proximal tibial deformity (varus, valgus, excessive tibial plateau angle [eTPA], tibial torsion and patellar luxation) by combined tibial plateau leveling osteotomy (TPLO) and transverse corrective osteotomy. Study Design: Cases series. Animals: Dogs (n=12; 19 stifle joints). Methods: Medical records of dogs that had combination TPLO and transverse corrective osteotomy, were reviewed. Pre‐ and postoperative tibial angulation, tibial torsion, tibial plateau angle (TPA), corrective osteotomy technique, method of fixation, and complications were recorded. In hospital re‐evaluation of limb function and alignment and length of time to radiographic healing were reviewed. Long‐term outcome was assessed by visual analog scale (VAS) questionnaire and owner telephone interview. Results: Proximal tibial varus or valgus was present in 68.4%; 73.7% had eTPA; and 47.4% had both. Medial patellar luxation (MPL) was present in 57.9%, of which 47.4% had tibial tuberosity displacement. Severe tibial torsion was present in 68.4%. Mean pre‐ and postoperative TPA was 37.5° and 5.7°, respectively. The mean postoperative mechanical medial proximal tibial angle (mMPTA) and mechanical medial distal tibial angle (mMDTA) were 92.2° (range, 88–96°) and 96.1° (range, 94–101°), respectively. Postoperative surgical complications were documented in 21.0%, which included implant loosening or breakage (5.3%), seroma (5.3%), septic arthritis (5.3%), and infection of the proximal tibia (5.3%). All complications were considered major because they required additional surgery. Mean time to document radiographic healing was 10.4 weeks. In‐hospital re‐evaluation of lameness was obtained at the same time; 82.4% were not lame or had a mild lameness, 17.6% had severe lameness (2/3 with infection). The VAS evaluation revealed excellent results and owner satisfaction in all ten dogs in which long‐term follow‐up was obtained. Conclusions: Long‐term clinical outcome of combination TPLO and transverse corrective osteotomy was excellent, and had a high owner satisfaction. Healing times were comparable to standard TPLO with a similar complication rate.     

Long-term outcome of distal femoral osteotomy for treatment of combined distal femoral varus and medial patellar luxation: 12 cases (1999-2004)

OBJECTIVE: To determine long-term outcome of distal femoral osteotomy as a component of treatment for distal femoral varus and medial patellar luxation in large-breed dogs. DESIGN:Retrospective case series. ANIMALS: 12 dogs (16 stifle joints). PROCEDURES: Medical records and radiographs were reviewed to identify large-breed dogs with medial patellar luxation (grade > or = 2) and femoral varus angle > or = 12 degrees treated with distal femoral osteotomy, with a minimum follow-up (by a veterinarian) of 18 months. Signalment, weight, medial patellar luxation and lameness grade, pre- and postoperative femoral varus angle, surgical technique, time to radiographic bone union, and complications were recorded. Follow-up with owners via questionnaire was performed > 18 months after surgery. RESULTS: 16 corrective distal femoral osteotomies were performed with ancillary medial patellar luxation procedures in 12 dogs; 4 dogs had staged bilateral procedures. Mean +/- SD preoperative and postoperative femoral varus angles were 16.3 +/- 4.3 degrees and 3.9 +/- 2.5 degrees , respectively. Mean +/- SD time to radiographic union of the distal femoral osteotomy was 52.6 +/- 13 days. One dog had Kirschner wire migration from the tibial tuberosity. Patellar luxation was not detected after surgery in any dog. Mean +/- SD follow-up by a veterinarian was 1,335 +/- 410 days and by use of an owner questionnaire was 1,497 +/- 464 days. All 10 variables of owner-observed patient comfort and function were significantly improved. CONCLUSIONS AND CLINICAL RELEVANCE: Distal femoral osteotomy in combination with traditional treatment provided predictable osteotomy healing, patellar stabilization, and long-term improvement in patient comfort and function when used to treat combined distal femoral varus and medial patellar luxation in large-breed dogs.     

PREVALENCE,ASSOCIATION WITH STIFLE CONDITIONS,AND HISTOPATHOLOGIC CHARACTERISTICS OF TIBIAL TUBEROSITY RADIOLUCENCIES IN DOGS

A tibial tuberosity radiolucency is sometimes identified on lateral radiographs of canine stifle joints, however little is known about the cause or significance. The purpose of this study was to describe the prevalence, association with other stifle conditions, and histopathologic characteristics of tibial tuberosity radiolucencies in a group of dogs. Radiographs of all canine stifle joints over 5 years were evaluated. Presence or absence of a tibial tuberosity radiolucency was recorded by an observer who was unaware of clinical status. Patient signalment and presence of other stifle joint conditions were recorded from medical records. A tibial tuberosity radiolucency was found in 145/675 dogs (prevalence = 21.5%). Statistically significant associations were identified between tibial tuberosity radiolucency and stifle condition (P < 0.0001), breed size (P = 0.011), and younger age of presentation (P = 0.001), but not with gender (P = 0.513). Dogs with a tibial tuberosity radiolucency had higher odds of having a medial patellar luxation than dogs without (OR = 9.854, P < 0.0001, 95% CI 6.422–15.120). Dogs with a tibial tuberosity radiolucency had lower odds of having a cranial cruciate ligament rupture than dogs without (OR = 0.418, P < 0.0001, 95% CI 0.287–0.609). Four canine cadavers, two with normal stifles and two with tibial tuberosity radiolucencies, underwent radiographic, computed tomographic, and histologic examination of the stifles. Computed tomography revealed a hypoattenuating cortical defect in the lateral aspect of the proximal tibial tuberosity that corresponded histopathologically to a hyaline cartilage core. Findings indicated that the tibial tuberosity radiolucency may be due to a retained cartilage core and associated with medial patellar luxation in dogs.     

Variation in position of the medial fabella in West Highland white terriers and other dogs

O bjectives : To investigate whether West Highland white terriers exhibit significant variation in the position of the medial fabella compared to both small and large breed dogs.
M ethods : Criteria for the normal location of the medial fabella on a caudocranial radiograph were established. A retrospective analysis was undertaken of a consecutive series of bilateral caudocranial stifle joint radiographs from 70 West Highland white terriers, 100 small and 100 large control dogs by three reviewers. Medial fabellar location, cruciate ligament disease and medial patellar luxation were examined within and between groups.
R esults : Abnormal medial fabellar location was identified in 70 per cent, 9 per cent and 0 per cent of West Highland white terriers, small dogs and large dogs, respectively. In the vast majority of the affected dogs, the fabella was found in a mediodistal location. Presence of concurrent cranial cruciate ligament disease or medial patellar luxation and body weight was excluded as confounding factors.
C linical S ignificance : West Highland white terriers appear predisposed to, and have a high prevalence of, an abnormal mediodistal location of the medial fabella. The authors suggest this is an incidental finding and should not be confused with true pathological fabellar displacement.     

Medial patellar luxation in the cat

The clinical features and treatment of eight cats with medial patellar luxation are described. In six cases the condition was bilateral. The luxation was surgically treated in 10 instances and four joints were treated conservatively. Patellar function following surgery was good in 90 per cent of the cases while the results of the conservatively managed joints were disappointing.     

Extended proximal trochleoplasty for the correction of bidirectional patellar luxation in seven Pomeranian dogs

Seven Pomeranians with bidirectional patellar luxation (BPL) were prospectively studied regarding aetiology and results of a new surgical technique. Radiographic evaluation of the ratio between patellar ligament length and patellar bone length revealed no differences between Pomeranians with bidirectional patellar luxation and healthy stifle joints. Functional rather than anatomic patella alta might be associated with bidirectional patellar luxation in Pomeranians. The surgical outcome of extended proximal trochleoplasty was good‐to‐excellent in 87·5% of the stifles and all dogs achieved functional recovery. There was only minimal radiographic progression of osteophyte formation at 48 weeks after surgery. To the authors’ knowledge, this is the first report on bidirectional patellar luxation in small breed dogs and its successful surgical treatment.     

Incidence of meniscal injury in cats with cranial cruciate ligament ruptures

This retrospective study evaluated the incidence of meniscal injury in cats with cranial cruciate ligament (CCL) ruptures. Medical records for cats diagnosed with CCL ruptures treated by a lateral fabellotibial suture (LFS) were reviewed for signalment, history, physical examination and surgical findings. Ninety-five cats (98 stifles) met the inclusion criteria. The incidence of meniscal injuries in feline CCL deficient stifles was 67%. Isolated medial meniscal injuries were found in 55 stifles (56%), isolated lateral meniscal injuries were found in 5 stifles (5%), and lateral and medial meniscal injuries were found in 6 stifles (6%). There was no correlation between the presence of a meniscal injury and age, breed, sex, weight, duration of lameness, presence of concurrent medial patellar luxation, degree of degenerative joint disease, or presenting side of lameness. Given the high rate of meniscal pathology in cats with CCL ruptures, exploratory surgery for meniscal assessment and concurrent stifle stabilization should be considered in feline patients.     

Comparison of trochlear block recession and trochlear wedge recession for canine patellar luxation using a cadaver model

OBJECTIVE: To compare trochlear block recession (TBR) to trochlear wedge recession (TWR) with regards to patellar depth (percentage of patellar volume under the trochlear ridges), patellar articular contact, percentage of recessed trochlear surface area, and resistance to patellar luxation. STUDY DESIGN: In vitro computed tomography (CT) and biomechanical evaluation using a cadaver model. SAMPLE POPULATION: Twelve normal, large-breed canine cadavers. METHODS: Bilateral pelvic limb specimens with intact stifle joints were mounted on a positioning device. The femoral trochlear ridges were reduced to provide a standard shallow trochlea. TBR or TWR was performed to a standard depth randomly on paired specimens. CT and biomechanical evaluations were performed pre- and postoperatively in both an extended (148 degrees ) and flexed (113 degrees ) stifle position. CT images were digitized and measurements made using an image-analysis software program. Biomechanical testing consisted of applying 40 degrees of internal tibial rotation and documenting patellar luxation. RESULTS: The change in trochlear depth (depth of recession) was not significantly different between groups. In the extended stifle position (patella in the proximal trochlea), patellar depth and patellar articular contact with the recessed trochlea were significantly greater after TBR compared with TWR. The percentage of recessed trochlear surface area was significantly greater after TBR compared with TWR. In the extended position, a smaller percentage of the patellae luxated within 40 degrees of internal tibial rotation after TBR compared with TWR. CONCLUSIONS: TBR increases proximal patellar depth, increases patellar articular contact with the recessed proximal trochlea, recesses a larger percentage of trochlear surface area, and results in a greater resistance to patellar luxation in an extended position as compared with TWR. CLINICAL RELEVANCE: TBR may help limit the development of stifle DJD in dogs treated for canine patellar luxation.     

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.     

Complications associated with corrective surgery for patellar luxation in 109 dogs

OBJECTIVE: To review surgical techniques and postoperative complications associated with correction of patellar luxation in dogs. STUDY DESIGN: Retrospective study. ANIMALS: Dogs (n = 109) with patellar luxation (n = 131). METHODS: Medical records of dogs that had corrective surgery for patellar luxation were reviewed. Signalment, history, grade and direction of patellar luxation, operative technique and clinical outcomes were retrieved. RESULTS: Overall frequency of postoperative complications was 18%. Frequency of major (requiring revision surgery) complications was 13%. Frequency of patellar reluxation was 8%. Frequency of overall, major, and patellar reluxation complications was higher for dogs weighing > or =20 kg compared with those <20 kg. Frequency of overall and major complications was higher for dogs with higher grades of patellar luxation. Femoral trochlear sulcoplasty resulted in lower frequency of patellar reluxation. Tibial tuberosity transposition (TTT) resulted in lower frequency of major complications and patellar reluxation. Retinacular/capsular release resulted in higher frequency of major complications. Patient age, gender, medial versus lateral patellar luxation, left versus right hindlimb, capsular/retinacular imbrication, use of anti-rotational sutures, and whether stifle surgery had been performed previously did not significantly influence frequency of complications. CONCLUSION: TTT and femoral trochlear sulcoplasty minimize the risk of postoperative patellar reluxation and major complications. CLINICAL RELEVANCE: Information derived from this study can be used to estimate the likelihood of postoperative complications for canine patients undergoing corrective surgery for patellar luxation.     

Lateral Patellar Luxation in Miniature Horses

Bilateral luxation of the patella in four Miniature Horses was corrected by a lateral release incision and medial imbrication of the parapatellar fascia to the tendon of the sartorius muscle. Before surgery, the four horses had a grade 3 to 4 lateral patellar luxation bilaterally and had difficulty walking. Trochlear ridge hypoplasia was evident on radiographs in each horse. Follow-up information varied from 11 months to 4 years after surgery. Three horses had no patellar luxation or lameness. The other horse had a normal right stifle, but patellar luxation (grade 3) had recurred on the left.     

基于CT技术评估髌骨内脱犬骨骼畸形

本研究旨在通过计算机断层扫描(computed tomography, CT)检查探究不同症状髌骨内脱(medial patellar luxation, MPL)犬的解剖结构差异，同时对比CT和X线技术的一致性和优缺点。选用患有髌骨内脱和健康的小型犬后肢共34条，根据症状分为正常组(n=9)、MPL无症状组(n=9)、MPL有症状组(n=16),进行CT检查，通过CT图像测量滑车沟深度/髌骨厚度、髌韧带长度/髌骨长度、解剖性股骨远端解剖轴外侧角(anatomic latero-distal femoral angle, aLDFA)、股骨远端机械轴外侧角(mechanical latero-distal femoral angle, mLDFA)、股骨近端解剖轴外侧角(anatomic latero-proximal femoral angle, aLPFA)、股骨近端机械轴外侧角(mechanical latero-proximal femoral angle, mLPFA)及股骨颈干角(femoral inclination angle, FIA),并分析各组之间的差异。此外通过...     

Medial Patellar Luxation in 16 Large Dogs A Retrospective Study

Unilateral medial patellar luxation was diagnosed in 10, and bilateral medial patellar luxation in six, large and giant-breed dogs (22 stifles). Lameness occurred in five dogs after trauma or surgery, and 11 dogs had no known predisposing history. The mean age at presentation was 25 months, and the mean time from initial onset of clinical signs to diagnosis was 13 weeks. All traumatic or iatrogenic luxations (five dogs) were unilateral. Luxations presumed to be congenital were unilateral in five dogs and bilateral in six. The grades of medial patellar luxation were I (1 stifle), II (11 stifles), III (9 stifles), and IV (1 stifle). Preoperative function was good (1 dog), fair (9 dogs), and poor (6 dogs). Surgical correction was performed in dogs with grades II, III, and IV luxations (21 stifles). Complications included one wound dehiscence and trochlear wedge migration, one pin loosening, and one persistent lameness caused by lymphoplasmacytic synovitis. Long-term follow-up was available in 13 dogs (18 stifles). Function was judged by owners to be excellent in seven dogs, good in five dogs, and poor in one dog. Surgical treatment of grades II and III luxations yielded good (8 stifles) and excellent (9 stifles) results, while one grade IV luxation had a poor long-term outcome.     

Clinical presentation and surgical repair of traumatic lateral patellar luxation associated with a complete tear of the vastus medialis muscle in a neonatal Cob foal

Patellar luxation associated with traumatic injury is rare in the horse, and surgical correction has not been adequately described. This case report describes the clinical findings associated with traumatic lateral patellar luxation in a 2-day-old cob colt, and the technique used for successful surgical repair. A combination of computed tomography (CT), radiography and ultrasound was used to diagnose lateral luxation of the patella due to a complete tear of the vastus medialis muscle. All patellar ligaments were intact and no congenital abnormalities associated with the patellar luxation were present. Surgical correction of the patellar luxation was achieved using a lateral release of the patella performed by transection of the lateral femoropatellar ligament along with overlying fascia, and stabilisation of the patella by medial imbrication of the medial patellar ligament and parapatellar fascia to the distal tendon of the sartorius muscle. Radiographs at 18 weeks of age showed the patella in a normal position in a well-developed trochlear groove. At 1 year of age the foal was walking and trotting sound, with normal range of motion of the affected stifle.