pISSN 1598-298X
J Vet Clin 31(5) :421-424 (2014)
421
Treatment of Grade IV Medial Patellar Luxation by Femoral Shortening Osteotomy in Three Small-Breed Dogs
Byung-Jae Kang, Daeun Rhew, Yongsun Kim, Seunghoon Lee, Daeyoung Yoon, Wan Hee Kim and Oh-Kyeong Kweon1
Department of Veterinary Surgery, BK21 PLUS Program for Creative Veterinary Science Research, Research Institute for Veterinary Science and College of Veterinary Medicine,
Seoul National University, Daehak-dong, Gwanak-gu, Seoul 151-742, Korea (Accepted: August 18, 2014)
Abstract : Three small-breed dogs with grade IV medial patellar luxation were presented. In all cases, patellar luxation could not be reduced by conventional surgical techniques. Femoral shortening osteotomy was performed in all dogs to correct patellar luxation. In all the dogs, the clinical condition was remarkably improved, and following surgical procedures, no complication or recurrence was presented. Femoral shortening osteotomy is an effective treatment in small-breed dogs with medial patellar luxation associated with severe skeletal deformity.
Key words : dog, femoral osteotomy, medial patellar luxation.
Introduction
Patellar luxation is a common cause of lameness in small- breed dogs, but also occurs in large-breed dogs. Medial lux- ation is much more common than lateral luxation, in every size and breed category (3). Mostly, this condition is termed congenital, since they are developed after birth, as a result of deformities that may be present at birth. The degree of clini- cal sign and skeletal condition associated with patellar lux- ation varies from mild to severe forms. Therefore, a grading system for medial patellar luxation is useful for diagnosis and therapeutic decision-making (7).
Proper alignment of the quadriceps mechanism promotes patellar function and stability. Malalignment of the quadri- ceps apparatus causes an imbalance in muscular forces, favoring patellar luxation. Medial patellar luxation is com- monly associated with the typical deformities, including coxa vara, femoral varus, genu varum, shallow trochlear sulcus, hypoplasia of the medial femoral condyle, medial torsion of the tibial tubercle, internal rotation of the tibia, proximal tib- ial varus, and internal rotation of the foot (4,5). These defor- mities move the long axis of the quadriceps muscle in the medial direction. This discrepancy leads to a strong medial tension upon the patella, during muscular contraction.
Surgical correction of medial patellar luxation is based on realignment of the quadriceps mechanism, and stabilization of the femoropatellar joint, to restore normal stifle biome- chanics, and eliminate repeated trauma to articular cartilage (2,5,8). Numerous surgical techniques, including bone recon- struction (trochleoplasty and tibial tuberosity transposition) and soft tissue reconstruction (medial soft tissue release and
lateral soft tissue tightening), have been used for the correc- tion of patellar luxation. In general, a combination of these techniques is necessary for satisfactory results. The progno- sis with grade I to III patellar luxation is mostly excellent;
but that of grade IV is guarded (5,8).
Femoral osteotomy is mainly used in large-breed dogs with grade IV medial luxation associated with severe skeletal deformity, in which patellar reduction is impossible with the conventional surgery (6,9). The distal femoral wedge osteot- omy technique has been developed and used, since the site of maximal deformity of the femur is distal. However, this tech- nique requires accurate preoperative measurement, special equipment, and training for wedge osteotomy of the femur.
The present report describes a femoral shortening osteotomy technique that is relatively easy, and does not require special equipment for the treatment of grade IV medial patellar lux- ation associated with severe skeletal deformity in small-breed dogs.
Case
Three small-breed dogs were presented, with severe hind- limb lameness by grade IV medial patellar luxation. These dogs were skeletally mature, and had clinical lameness associ- ated with medial patellar luxation. Femoral shortening osteoto- mies were performed in all cases, because conventional surgery for medial patellar luxation failed to restore patellar stability.
Case 1 was a 2-year-old neutered male Pomeranian, with a body weight of 3.3 kg. The dog used the affected limb but showed partial weight bearing, and obvious lameness (Fig 1A). Grade IV medial patellar luxation was palpable on manipulation of the stifle joint. Radiography confirmed severe skeletal deformities and medial patellar luxation (Fig 2). Sur-
1Corresponding author.
E-mail: [email protected]
422 Byung-Jae Kang, Daeun Rhew, Yongsun Kim, Seunghoon Lee, Daeyoung Yoon, Wan Hee Kim and Oh-Kyeong Kweon
gical repair of medial patellar luxation was performed, using femoral shortening osteotomy with a combination of various techniques, including medial restraint release, trochlear block recession, tibial tuberosity transposition, and lateral restraint reinforcement. In brief, a lateral parapatellar approach was made to the femoral diaphysis and stifle joint. The femoral diaphysis was osteotomized, using an electric oscillating saw, and approximately 1 cm or more of bone was removed (Fig 3). The femur was then repaired with 2.0 dynamic compres- sion plate, and seven cortical screws. Patellar tracking within the trochlear groove was assessed, after application of the plate. Medial soft tissue release, trochlea block recession, tib- ial tuberosity transposition and lateral soft tissue tightening were performed as adjunctive procedures. Radiographs and physical examination results were obtained at 1, 2, 3, 5 and 8 months following surgery (Fig 4). The dog showed clinical improvement, following correction of the patellar luxation.
Patellar luxation was also absent, and remained until 8 months following surgery. Weight bearing of the affected limb was
increased, gait was improved to nearly normal, and there was no pain at the stifle joint, although subtle lameness still remained eight months after surgery (Fig 1B).
Case 2 was a 2-year-old neutered male Shih Tzu, with a body weight of 2.78 kg; and case 3 was a 1-year-old neu- tered male Toy Poodle, with a body weight of 3.48 kg. The dog of case 2 showed moderate lameness, with partial weight bearing; and the dog of case 3 was reluctant to walk, with non-weight bearing on the affected limb. The treatments in cases 2 and 3 were also successful in restoring patellar stabil- ity and satisfactory limb function, when femoral shortening osteotomy was combined with conventional surgery, for grade IV medial patellar luxation. An additional plate was placed in case 2, and a long screw was applied on the distal femur, to prevent medial deviation of the quadriceps muscle. Follow- up examination results and radiographs were obtained until Fig 1. Standing postural photograph from the dog of case 1,
before and after surgery. (A) Before surgery, the dog showed par- tial weight bearing, and reduced joint angle of the affected limb.
(B) Eight months after surgery, the weight bearing and joint angle of the affected limb was improved.
Fig 2. (A) Preoperative craniocaudal, and (B) mediolateral radio- graphic views from the dog of case 1, showing severe medial patellar luxation, and skeletal deformities.
Fig 3. Intra-operative photograph of case 1. Following (A) com- pletion of femoral shortening osteotomy, (B) a plate and screws were placed, to stabilize the femoral osteotomy.
Fig 4. (A) Craniocaudal, and (B) mediolateral radiographic views of the dog of case 1 at 8 months after surgery, revealing improved patellar reduction and stability. (C) Complete healing of the femoral osteotomy site (arrow) was observed on radio- graphs.
Treatment of Grade IV Medial Patellar Luxation by Femoral Shortening Osteotomy in Three Small-Breed Dogs 423
three months after surgery in case 2, and eight months after in case 3.
Discussion
Most medial patellar luxation can be corrected successfully by conventional surgical techniques, including soft tissue reconstructive procedures, such as medial restrain release, lat- eral restraint reinforcement and anti-rotational suture; and bone reconstructive procedures, such as trochleoplasty and tibial tuberosity transposition (2,5,8). However, in rare cases with severe skeletal deformity, conventional surgery alone cannot maintain patellar stability and satisfactory limb func- tion. In these cases, after the quadriceps mechanism is relo- cated to a more normal cranial position with conventional surgical techniques, the osteomized tibial tuberosity lies above the proximal end of the tibia, due to muscle contrac- ture. Consequently, the tibial tubercle cannot be pinned, or numerous complications may arise following surgery, includ- ing tibial tuberosity avulsion, patellar alta, delayed union at osteotomy sites, and patellar relaxation, due to strong ten- sion on the patellar ligament. Medical records of the total sti- fles operated at the Veterinary Medical Teaching Hospital of Seoul National University to correct grade IV medial patel- lar luxation using conventional surgical techniques from June of 2005 to October of 2012 were reviewed, to confirm com- plications following surgery. Complications were observed in 9 out of 28 stifles (32.14%). Tibial tuberosity avulsion was found in 4 stifles, and patellar relaxation was discovered in 5 stifles. In the present case report, we relaxed the extensor tension and allowed the tibial tuberosity to be moved distally for pinning to the tibia, using a femoral shortening osteotomy technique. The combination of femoral shortening osteotomy and conventional surgical techniques was successful in all the cases, in preventing further luxation and improving limb function. Furthermore, no postoperative complication was observed in the three dogs of the present case report.
Femoral corrective osteotomy or realignment osteotomy has been reported in cases with severe femoral varus and/or tor- sion deformity of large-breed dogs (6,9). Multiple techniques for distal femoral corrective osteotomy have been described, including laterally based closing wedge ostectomy, medial opening wedge osteotomy, detorsional osteotomy, and radial osteotomy. However, these require accurate preoperative measurement. The assessment of limb deformities can be challenging. Plain radiography can be used to assess limb deformities, but is limited. This may result in failure to accu- rately identify all components of the deformity, and lead to suboptimal correction (6). Furthermore, surgical procedures are complex, and require special equipment and training.
Therefore, these techniques should be performed by a trained specialist, and as a results, the clinical utility of these tech- niques may be low. The femoral shortening osteotomy used
in this case report is a palliative and suboptimal procedure, rather than a corrective and optimal procedure. This tech- nique was relatively easy, without any complication follow- ing surgery; and showed satisfactory clinical improvements in all three small-breed dogs. Although this surgery can cause the differences of left and right femoral lengths and mechanical joint angles, a previous study showed that dogs could tolerate up to 20 percent shortening of the femur (1,9).
In the present case, the length of removed bone was less than 20 percent of the affected femoral length, and following sur- gery, the dogs showed satisfactory improvements of weight bearing and lameness.
In conclusion, femoral shortening osteotomy, in addition to conventional surgical techniques, was effective in the correc- tion of grade IV medial patellar luxation associated with severe deformity, and in improving patellar stability and limb function, in the present cases. In addition, this technique was relatively easy, without the need of special skill and equip- ment. This case report suggests that the use of femoral shorten- ing osteotomy in combination with conventional techniques may be considered as a convenient and appropriate method, in the cases that only conventional surgery cannot restore patellar stability, although the number of this case series is limited.
References
1. Franczuszki D, Chalman JA, Butler HC, Debowes RM, Leipold H. Post-operative effects of experimental femoral shortening in the mature dog. J Am Anim Hosp Assoc 1987;
23: 429-437.
2. Gibbons S, Macias C, Tonzing M, Pinchbeck G,McKee W.
Patellar luxation in 70 large breed dogs. J Small Anim Pract 2006; 47: 3-9.
3. Hayes A, Boudrieau R, Hungerford L. Frequency and dis- tribution of medial and lateral patellar luxation in dogs:
124 cases (1982-1992). J Am Vet Med Assoc 1994; 205:
716-720.
4. Hulse D. Medial patellar luxation in the dog. In: Disease Mechanisms in Small Animal Surgery, 2nd ed. Philadelpia, USA: Lea and Febiger. 1993: 808-817.
5. Remedios AM, Basher AW, Runyon CL, Fries CL. Medial patellar luxation in 16 large dogs a retrospective study. Vet Surg 1992; 21: 5-9.
6. Roch S, Gemmill T. Treatment of medial patellar luxation by femoral closing wedge ostectomy using a distal femoral plate in four dogs. J Small Anim Pract 2008; 49: 152-158.
7. Singleton W. The surgical correction of stifle deformities in the dog. J Small Anim Pract 1969; 10: 59-69.
8. Willauer C, Vasseur P. Clinical results of surgical correction of medial luxation of the patella in dogs. Vet Surg 1987;
16: 31-36.
9. Witte P, Scott H. Treatment of lateral patellar luxation in a dog by femoral opening wedge osteotomy using an inter- locking nail. Vet Rec 2011; 168: 243-243.
424 Byung-Jae Kang, Daeun Rhew, Yongsun Kim, Seunghoon Lee, Daeyoung Yoon, Wan Hee Kim and Oh-Kyeong Kweon
세 마리의 소형견에서 대퇴 단축 절골술에 의한 4단계 내측 슬개골 탈구의 치료 증례
강병재·류다은·김용선·이승훈·윤대영·김완희·권오경1
서울대학교 수의과대학 수의외과학교실
요 약 : 세 마리의 소형견이 4단계의 내측 슬개골 탈구로 내원하였다. 세 마리 모두에서 일반적인 기존 수술 방법으 로는 슬개골 탈구가 환납되지 않았다. 따라서 슬개골 탈구를 교정하기 위해 대퇴 단축 절골술이 실시되었다. 수술 후 에 세 마리 모두 임상 증상이 개선되었고 합병증이나 재발은 확인되지 않았다. 대퇴 단축 절골술은 심한 골격 기형과 관련된 내측 슬개골 탈구가 있는 소형견에서 효과적인 치료 방법으로 고려될 수 있다.
주요어 : 개, 대퇴 절골술, 내측 슬개골 탈구
