pISSN 1598-298X / eISSN 2384-0749 J Vet Clin 34(1) : 7-12 (2017) http://dx.doi.org/10.17555/jvc.2017.02.34.1.7

Triple Tibial Osteotomy (TTO) for Treatment of Cranial Cruciate Ligament Rupture in Small Breed Dogs

Tae-Hwan Kim, Subin Hong, Heesup Moon, Jeong-In Shin, Yun-Sul Jang, Hyeonjong Choi, In-Geun Kim and Jae-hoon Lee1 Institute of Animal Medicine, College of Veterinary Medicine, Gyeongsang National University, Jinju 52828, Korea

(Received: November 23, 2016 / Accepted: February 14, 2017)

Abstract : Twelve dogs weighing less than 10 kg underwent unilateral TTO to stabilize the stifle joint with cranial cruciate ligament rupture. Surgical findings, intra-operative and post-operative complications were recorded. Radiographic examinations were performed for 8 weeks following surgery. Postoperative outcome was evaluated using a visual analogue lameness scoring system. Mean preoperative PTA (the angle created by the intersection of the tibial plateau extrapolation line and the patellar tendon) was 103.8 degrees. Mean tibial wedge angle was 16.6 degrees. Mean postoperative PTA was 92.1 degrees. Intraoperatively, fracture through the caudal tibial cortex occurred in all dogs, through the distal tibial crest cortex in 2 dogs, through the lateral tibial cortex in 2 dogs and through the fibula in 1 dog. Four-week postoperative radiographs demonstrated evidence of progressive bone union at osteotomy site and complete unions were identified at 8 week in 10 dogs. All dogs were healed in 11 weeks. Most of dogs revealed weak lameness in 4 weeks and normal ambulation in 8 weeks postoperatively except for only one dog returned in 11 weeks. Despite frequent minor complication, it appears that the TTO is an alternative procedure for management of cranial cruciate ligament rupture in small breed dogs. Key words : cranial cruciate ligament, triple tibial osteotomy, complication, small breed, dog.

Introduction don was perpendicular to the tibial plateau (10). The triple tibial osteotomy (TTO) combines three osteoto- Proximal tibial osteotomy techniques for treatment of mies made in the proximal tibia to create a partial tibial CCLR recently have gained popularity. There are two alter- wedge osteotomy caudal to a partial tibial crest osteotomy. nate concepts about how dynamic stabilization should be This procedure partially levels the tibial plateau while advan- attained with proximal tibial osteotomy. The first concept cing the tibial tuberosity and patella tendon in an attempt to was suggested by Slocum and Devine (24). This concept was neutralize femorotibial shearing forces across the stifle (5). that the joint reaction force in the stifle during weight bear- Proposed advantages of TTO over other proximal tibial ing was nearly parallel to functional the long axis of the tibia. osteotomies include the need for less radical angular changes Because of the caudo-distally sloping tibial plateau, the shear of the tibia than would be indicated in procedure’s that solely forces in the stifle joint accountable for CTT would have a level the tibial plateau or advance the tibia tuberosity, mini- relationship with the angle formed between the tibial plateau mal change to the femorotibial articulating surfaces, minimal and functional long axis of the tibia. They suggested that need for specialized implants or surgical equipment and no CTT would be removed from CCL ruptured joint by reduc- loss of tibial length (5,13). ing the tibial plateau angle (TPA) so that it was perpendicu- There is no information in the work on the surgical find- lar to the functional long axis of the tibia. The surgery ings, complications and outcome associated with the TTO in techniques to accomplish this purpose were the cranial tibial small breed dogs. The purposes of this study are to docu- wedge osteotomy (CTWO) (25) and the tibial plateau level- ment the surgical findings and complications of TTO for the ing osteotomy (TPLO) (26). The second concept is founded treatment of cranial cruciate ligament disruption in small on a biomechanical model suggested by Tepic et al. This breed dogs. concept was developed from study in human being that the joint force generated in weight bearing is parallel to patellar Materials and Methods tendon (17). It was therefore suggested that elimination CTT during weight bearing would be achieved by performing a This study was conducted under approval of ethical com- tibial tuberosity advancement (TTA), so that the patellar ten- mittee of Gyeong-sang national university laboratory animal center (Approval number: GNU-150402-D0016). The twelve dogs weighed less than 10 kg, and had a normal ambulation 1Corresponding author. on physical examination. The medical data was noted for E-mail : [email protected] breed, age, sex, weight, affected limb and meniscal tear.

7 8 Tae-Hwan Kim et al.

Twelve dogs had unilateral TTO procedures. The mean body- operative radiograph, the TPA was defined according to the weight of dogs was 6.25 kg (range 4.6 kg to 8.6 kg). The conventional method (3,20). The patellar tendon, the patellar mean age of the dogs was 3.4 years (range 2 years to 7 tendon angle (PTA) and the correction angle (CA) were years). There were seven entire females, five entire males. defined as previously described (5,8,23). Pre-operative radio- The dogs had been fasted for about 12 hours before the graphic calculations were as follows (Fig 1). Tibial plateau operation. They were premedicated with medetomidine (0.2 (TP) was defined by estimating the position of the surface of mg/kg, administered subcutaneously (SC), Domitor®; Pfizer, the medial tibial condyle, which was slightly convex in NY, USA) together with acepromazine (0.05 mg/kg, SC, shape. The location of the tibial plateau was determined by Sedaject®; Samu Median, Seoul, Korea) and atropine (0.04 identifying the cranial and caudal points and drawing a line mg/kg, SC, Atropine®, Jeil Pham., Daegu, Korea). Cefazolin between them. The cranial most point of the medial tibial (25 mg/kg, SC, Hankook Korus Pharm Co, Seoul, Korea) condyle was visible as a small discrete step. The caudal point was used as a prophylactic antibiotic. After placement of a was the point of insertion of the caudal cruciate ligament-the catheter in the cephalic vein, general anesthesia was induced apex of popliteal notch was a useful point of reference. A with etomidate (2 mg/kg, administered intravenously (IV), line marking the cranial edge of the straight patellar liga- Etomidate-®Lipuro; B. Braun Melsungen AG, Germany) ment (PL) was drawn. Position a straight-edge cranial to the titrated to effect and administered to effect preceding tra- stifle and slide it caudally until it first touches points on the cheal intubation. Anesthesia was maintained with isoflurane patella and tibial crest. The distance between theses points (TerrellTM, Piramal Critical Care, USA) in 100 percent oxy- was the PL length. The tibial crest osteotomy (TCO) was gen via endotracheal intubation in a circle rebreathing sys- drawn with exactly the length of PL. The TCO was made tem. Normal saline was administered at 10 mL/kg/hour through parallel to the axis of the tibial shaft and was usually parallel the cephalic vein during the whole procedure. The dog’s to the cranial aspect of the tibial crest. A line was created by heart rate, body temperature, percutaneous blood oxygen sat- drawing a line perpendicular to TP starting from the proxi- uration (SpO2) and end tidal CO2 (Et CO2) was monitored mal end of PL. the correction angle (CA) was angle between during anesthesia. A circulating water blanket (Medi-Therm®, PL and the line. The angle of the tibial wedge osteotomy was Gaymar, NY, USA) with 38~39oC was used to maintain body calculated according to the currently recommended formula; temperature. wedge angle (WA) = 0.6 X CA + 7.3o (22). The central axis CCLR modeling preceded the TTO procedure. On the pre- of the wedge was located exactly halfway along the TCO. It was drawn in the central axis of the wedge as a line extend- ing caudally and perpendicularly from the TCO line at its mid-point. Surgery was performed as described by Bruce et al (5) with the minor modifications that no meniscal release proce- dures were performed (Fig 2). The dog was positioned in lat- eral recumbency with the affected leg down and parallel to the operating table, which was to explore the medial aspect of the stifle joint. Carprofen (2.2 mg/kg, PO, twice daily, Carprofen®, Zoetis, USA), cefadroxil (25 mg/kg, PO, bid, Cefaxil®; Koruspharm, Jecheon, Korea) and famotidine (0.5 mg/kg, PO, bid, Famotidine®; NELSON, Korea) were given for 7 days. Radiographs were taken immediately following surgery, 2, 4 and 8 weeks postoperatively. On the postoperative radio- graphs, the TPA and patellar tendon angle (PTA) were mea- sured (3,20). The intended wedge angle was substracted from the preoperative TPA to give the anticipated postoperative TPA. The difference between the anticipated and the achieved postoperative TPA was calculated. On radiographic examina- tion following surgery, major complications were defined as those that required further surgery or treatment. Other com- plications were considered to be minor. Visual lameness of the dogs was evaluated at stance, walk Fig 1. Preoperative surgical plan for the TTO surgery. CA is the and trot in preoperative TTO surgery, 4 weeks and 8 weeks. correction angle formed between the patellar tendon and a line Visual lameness was graded using a modified scoring sys- originating at the cranial-most aspect of the patella and perpen- tem (12): 0 = no detectable lameness (clinically sound); 2 = dicular to the tibial plateau. PTA is the angle created by the barely detectable lameness; 4 = mild lameness; 6 = moderate intersection of the tibial plateau extraspolation line and the lameness; 8 = severe lameness (carries limb when trotting); patella tendon. TPA is tibial plateau angle. PT is patellar tendon. 10 = non-weight bearing (could not be more lame). TWO is tibial wedge osteotomy. TCO is tibial crest osteotomy. The visual lameness score was measured in preoperative The dotted line bisects and is perpendeicular to the TCO. TTO surgery, 4 weeks and 8 weeks. Statistical analysis was Triple Tibial Osteotomy (TTO) for Treatment of Cranial Cruciate Ligament Rupture in Small Breed Dogs 9

Fig 2. TTO procedure; Three linear (TCO line and WA line) osteotomy. A. The TCO was completed with an oscillating saw (the TCO proximal end should terminate within the non-articular part of the proximal tibia, caudal to the patellar ligament insertion and cranial to the cranial edge of the meniscus). B. A saw blade was used to cut a full thickness wedge from the proximal tibia and was orientated slightly caudally to cut the caudal and caudo-lateral parts of the lateral tibia. C. The tibia wedge was closed. The plate was then fixed to the bone using cortical screws.

Table 1. Radiographic measurements (degree) Ant PO PO TPA Pre EA Pre PTA Pre TPA CA WA (mm) WA PO PTA PO TPA PTA -Ant PO TPA 1 130.3 105.0 41.0 16.2 3.0 17.0 90.7 14.9 24.0 −9.1 2 126 98.3 30.8 12.6 6.0 14.9 89.5 17.7 15.9 1.8 3 132.7 104.0 23.5 16.8 2.0 17.4 96.5 6.0 6.1 −0.1 4 134.9 103.0 27.0 15.2 4.0 16.4 92.6 11.6 10.6 1.0 5 137.4 105.5 21.0 16.2 4.0 17.0 93.3 7.9 4.0 3.9 6 132.0 98.5 13.4 12.6 2.6 14.9 91.6 6.0 −1.5 7.5 7 125.0 108.7 28.0 18.6 5.0 18.5 89.7 16.8 9.5 7.3 8 127.0 99.0 27.0 12.1 3.0 14.6 90.4 19.5 12.4 7.1 9 129.0 114.5 31.0 21.6 2.6 20.3 95.4 12.8 10.7 2.1 10 128.0 99.6 18.0 12.4 8.0 14.7 91.0 2.0 3.3 −1.3 11 131.0 107.0 26.0 17.0 2.0 17.5 92.0 9.0 8.5 0.5 12 128.3 103.0 22.0 15.1 3.0 16.4 92.0 8.0 5.6 2.4 Mean ± SD 130.1 ± 3.7 103.8 ± 4.8 25.7 ± 7.1 15.5 ± 2.9 3.8 ± 1.8 16.6 ± 1.7 92.1 ± 2.1 11.0 ± 5.4 9.1 ± 6.6 1.9 ± 4.6 Pre; Preoperative, PO; postoperative, EA; Angle of stifle joint, Ant; Anticipated, TPA; Tibial Plateau Angle, CA; Correction Angle, WA; Wedge Angle PTA; Patellar Tendon Angle performed using SPSS 21.0 (SPSS Inc, Chicago, Ill, USA). 130.1 ± 3.7o. The mean preoperative PTA was 103.8 ± 4.8o and A repeated measure ANOVA (RM-ANOVA) was used to the mean preoperative TPA was 25.7 ± 7.1o. The mean in- investigate the change from preoperative lameness. P-value tended WA was 16.6 ± 1.7o. less than 0.05 was considered to be statistically significant. On postoperative radiographs, the postoperative TPA was The results expressed with a means ± standard deviation (S.D). different from the anticipated TPA by 9.1 ± 6.6o. The mean postoperative PTA was 92.1 ± 2.1o and the mean postopera- Results tive TPA was 11.0 ± 5.4o. In ten TTO procedures (83%), incomplete osteotomy of The TTO surgery was performed on 4 left- stifle joints and the tibial crest had been achieved with an intact segment of 8 right-stifle joint. The duration of lameness before TTO sur- the cranial tibial cortex preserved at the distal end of tibia gery was 1 ± 0.5 weeks. All dogs had no gross pathological crest following tuberosity advancement. The ten closed changes observed in the medial meniscus on arthrotomy. wedge osteotomies were stabilized with 2.0 mm tibial pla- On the preoperative and the immediate postoperative ra- teau leveling osteotomy (TPLO) plate (Veterinary Instrumen- diographs, The TPA, PTA, and others were measured (Table tation, Henry schein®, Shefield, UK). In two dogs, the closed 1). The mean preoperative stifle joint extension angle was wedge osteotomies were stabilized with 2.4 mm TPLO plate 10 Tae-Hwan Kim et al.

10) in 4 weeks and normal ambulation in 8 weeks postoper- atively except for only one dog returned in 11 weeks. Discussion

TTO surgery is used to change the biomechanics of the sti- fle to overcome CTT in dogs with CCLR. The TTO is prox- imal tibial osteotomy procedure incorporating features of the TPLO procedure and TTA procedures. The purpose of the TTO procedure is to reduce the PTA to 90o. The mean post- operative PTA achieved of 92.1o, compares favorably with 94.1o achieved by Bruce et al (5), with the 93.5o achieved by Renwick et al (22) and also with the 95.5o achieved using the TTA technique (10). Although the postoperative mean PTA is almost 90o, the TTO technique failed to achieve the aim of the PTA 90o. Thus, dynamic stability of the stifle cannot be assured. The mean wedge angle removed during the surgical procedures was 16.6o. This angle was slightly larger than the mean wedge angle previously reported by Bruce et al (5) of 11.5o, by Renwick et al (22) of 15.9o and by Moles and oth- ers (16) of 13.6o. The most likely examination for the differ- ences is resulted from variations in stifle joint flexion angles on preoperative wedge angle formula (16). The radiographic protocol for TTO demands the stifle to be positioned medio- laterally at flexion angle of 135o in order to determine the Fig 3. Intra-operative complications. A. In all dogs, the caudal amount of tibial tuberosity advancement involved to ensure o cortex of the tibia fractured during the TTO procedure. B. In two PTA 90 (5). This positioning is difficult to be achieved accu- dogs (No. 2 and 3 dogs), fracture through the distal end of the rately. The difficulty provides a potential cause of error in tibial crest osteotomy occurred during the procedure, requiring a determining the exact wedge osteotomy angles demanded cerclage wire. C. Proximal fibular fracture was occurred in only preoperatively and postoperative assessment of the tibial pla- one dog (No. 6 dog). D. In two dogs (No. 1 and 11 dogs), tibial teau to patella tendon angles achieved (11). This source of lateral cortex defect was occurred. inaccuracy is similar for the TTA procedure and is compara- ble to the previously reported inter-observer variability in (Veterinary Instrumentation, Henry schein®, Shefield, UK). measuring tibial plateau slopes of up to 6o (6). Supplementary implants were applied in the two procedures Bruce et al concluded that measurement of the TPA is not with fracturing of the tibial crest osteotomy at the distal end needed when performing the TTO (18). However, Renwick of tibia crest. These additional implants were a cerclage wire. and others suggested that measurement of the TPA is neces- Four different complications were detected intra-operatively sary to avoid over-correction of the TPA and also to identify (Fig 3). Meaningfully, in all dogs, the caudal cortex of the cases that may not be ideal candidates for the technique (9). tibia fractured during the TTO procedure (Fig 3A). In two In this study, the preoperative mean TPA was 25.7 ± 7.1o and dogs, fracture through the distal end of the tibial crest osteot- the postoperative mean TPA was 11.0 ± 5.4o. A subgroup of omy occurred during the procedure, requiring a cerclage wire dogs was identified with below average TPAs and relative (Fig 3 B). Proximal fibular fracture was occurred in only one large CAs. In this subgroup (dog no.5, 6 and 10), advancing dog (Fig 3 C). In two dogs, tibial lateral cortex defect was the tibial tuberosity to the recommended position using the occurred (Fig 3 D). TTO procedure may have resulted in a less than 5o TPA. In We define a major complication as an undesirable develop- vitro studies of the TPLO where the TPA is reduced have ment that required further diagnostic investigation or surgi- shown loading of the caudal cruciate ligament when the TPA cal treatment. Follow-up examinations were performed for 8 is 6o or less (21,29). And an in vitro study of TTA where the weeks after TTO procedure. Post-operative major complica- TPA was unchanged showed caudal tibial translation when tion did not occurred in 8 weeks. Minor complications the PTA was less than 90o (1). Because there are no in vitro including bruising and swelling occurred in five dogs (41%). studies to assess the effect of combined TTA and TPA reduc- The dogs were healed in 2 weeks uneventfully. tion, it is logical idea that when using the TTO, if the TPA is Four weeks postoperative radiographs demonstrated evi- reduced to less than 5o, the effect of increased loading of cau- dence of progressive bone union at the osteotomy site and dal cruciate ligament is likely to be at least equal to if not fractured sites in all dogs. Eight weeks postoperative radio- greater than the loading created at the same angle in perform- graphs demonstrated radiographic union in 10 dogs (83%). In ing a TPLO (22). Thus in these three dogs (dog no. 5, 6, 10), consequence, all dogs healed in 11 weeks (100%). we reduced the TPA to 5o, as recommended for the TPLO The visual lameness score varied from 6 to 9 before TTO method (1). surgery. Ten dogs (83%) revealed weak lameness (grade 2 of The combined osteometer and saw guide is too big to Triple Tibial Osteotomy (TTO) for Treatment of Cranial Cruciate Ligament Rupture in Small Breed Dogs 11 apply on small breed dogs. So the wedge osteotomy angle was References converted into length. The difference between the antici- pated and the achieved postoperative TPA was 1.9 ± 4.6o, 1. Apelt D, Kowaleski MP, Boudrieau RJ. Effect of tibial which was the similar result achieved by Renwick et al (9). tuberosity advancement on cranial tibial subluxation in canine Fracture through the caudal tibial cortex occurred in all cranial cruciate deficient stifle joints: an in vitro experi- dogs. The tibial wedge osteotomy should be gradually closed mental study. Vet Surg 2007; 36: 170-177. by applying upward pressure on the foot. The resultant action 2. Ballagas AJ, Montgomery RD, Henderson RA, Gillette R. 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