Triple tibial osteotomy for treatment of the canine cranial cruciate ligament-deficient stifle joint

Vet Comp Orthop Traumatol 6/2009

473 © Schattauer 2009Clinical Communications

Triple tibial osteotomy for treat-ment of the canine cranial cruciate ligament-deficient stifle joint Surgical findings and postoperative complications in 97 stifles

A. D. Moles1; T. P. Hill2; M. Glyde1 1Murdoch University, School of Veterinary and Biomedical Sciences, Murdoch, Australia; 2Rivergum Referral Services, Willeton, Australia

Keywords Triple tibial osteotomy, cranial cruciate ligament, stifle, canine, tibial plateau levelling

Summary Objective: To report the surgical findings and early post-operative complications of triple ti-bial osteotomy (TTO) for the treatment of cranial cruciate ligament disruption in dogs. Methods: Clinical records of 84 dogs (97 stifles) that had TTO procedures were re-viewed. Surgical findings and postoperative complications were assessed. A complication was defined as any undesirable outcome re-sulting from TTO that required further diag-nostic investigation or surgical treatment. Results: Mean tibial wedge angle was 13.6 degrees (range 10–20). Incomplete tibial crest osteotomy was achieved in 79% of TTO pro-cedures. Implants were placed in the tibial crest in 67% of stifles. Early postoperative

Correspondence to Aaron David Moles Murdoch University Veterinary Hospital Small Animal Surgery South Street Murdoch Western Australia, 6150 Australia E-mail: [email protected]

Vet Comp Orthop Traumatol 2009; 22: 473–478 doi:10.3415/VCOT-09-01-0004 Received: January 15, 2009 Accepted: May 25, 2009 Pre-published online: October 29, 2009

complications occurred in 23% of joints, and included avulsion of the tibial crest (9.1%), fracture at the distal cortical attachment of the tibial crest (6.2%), fibula fracture (4.1%), patellar tendonitis (3.1%), late meniscal in-jury (3.1%), implant complications (3.1%) and patellar fracture (2.1%). Increased pa-tient age (p = 0.023), increased wedge angle (p = 0.009) and intra-operative fracturing of the cranial tibial cortex (p = 0.017) were sig-nificantly associated with postoperative tibial crest avulsion. Implants did not prevent tibial crest avulsion. Increased patient age (p = 0.012) was significantly associated with tibial crest fracture. Clinical relevance: Tibial crest avulsion and fracture are the most common postoperative complications for TTO. Late meniscal injury is uncommon after TTO.

Introduction Triple tibial osteotomy (TTO) has recently been described as a surgical treatment for cranial cruciate ligament disruption in the dog (1). The TTO is a ‘hybrid’ proximal tibial

osteotomy that partially levels the tibial pla-teau while advancing the tibial tuberosity and patella tendon in an attempt to neutralise fe-morotibial shearing forces across the stifle. For the surgical procedure, three osteotomies in the tibia are performed to create a partial

tibial crest osteotomy. The wedge defect in the proximocaudal tibia is then closed and held in reduction with a bone plate. The result is simultaneous reduction of the tibial plateau angle and advancement of the tibial tuberos-ity such that the patellar tendon becomes per-pendicular to the tibial plateau when the stifle joint is positioned at the standing angle (�Figures 1 and 2). Proposed advantages of TTO over other proximal tibial osteotomies described for cranial cruciate ligament defi-cient stifles include the need for less radical angular changes of the tibia than would be in-dicated in procedures that solely level the ti-bial plateau or advance the patellar tendon, minimal change to the femorotibial articulat-ing surfaces, no loss of tibial length, and mini-mal need for specialised surgical equipment or implants (1, 2).

Currently there is a paucity of information in the literature on the complications and outcomes associated with the TTO pro-cedure. Bruce et al reported postoperative complications in 7/64 (10.9%) procedures, with tibial tuberosity fractures at the site of implants (n = 2) and postoperative meniscal injury (n = 2) being the most common occur-rences (1). The authors have experienced ad-ditional complications, and a higher preva-lence of postoperative complications to those previously described for the TTO procedure. The aim of this study is to report the surgical findings and postoperative complications for those dogs that underwent TTO surgery over a four-year-period at our institution.

Materials and methods

The medical records of all dogs that had undergone TTO at the Murdoch University

For personal or educational use only. No other uses without permission. All rights reserved.Downloaded from www.vcot-online.com on 2013-04-15 | ID: 1000467707 | IP: 128.233.210.97

A. D. Moles et al.: Triple tibial osteotomy in 97 stifles

Vet Comp Orthop Traumatol 6/2009 © Schattauer 2009

474

Veterinary Hospital between January 2004 and December 2007 were reviewed retrospec-tively. Only dogs with complete records indi-cating signalment, gross findings in the stifle joint at the time of arthrotomy or arth-roscopy, performance of meniscectomy or meniscal release, notation of corrective angles used, and a minimum of six weeks follow-up, including radiographs, were eligible for in-clusion in the study. Dogs that underwent concurrent corrective surgery for patellar luxation were excluded. The immediate post-operative, and all subsequent follow-up radiographs for those dogs that met inclusion criteria were reviewed. For the purpose of this study, a postoperative complication was de-fined as any undesirable outcome resulting from the TTO procedure that required further diagnostic investigation or further surgical treatment. Minor wound or bandage complications were not included as these were within the acceptable range expected after any surgical technique.

All TTO surgeries were performed using a technique similar to that described by Bruce et al (1). The intra-articular structures of all stifle joints were examined by arthrotomy, arthroscopy or a combination of both. The preoperative measurements and subsequent osteotomies were based initially upon the

original surgical description (1), however during the course of the study, the formula for calculation of the angle of the wedge to be removed changed from two-thirds of the cor-rection angle (CA) to 0.6 x CA + 7 degrees (�Fig. 1). The origin of this modified formu-la has been reported (3, 4). Either a TTO os-teometera or a precut wedge templatea was used to measure the intraoperative angle for the wedge osteotomy based on the individual surgeon’s preference. Attempts were made to maintain incomplete osteotomies in all sur-geries. All closing wedge osteotomies were held in reduction using a bone plate and screws. Additional implants were also used to support the tibial crest osteotomy at the sur-geon’s discretion.

Data for all dogs meeting the inclusion criteria, including signalment, surgical find-ings and postoperative complications, were tabulated into a computer based spreadsheetb and analysis was performed. T-tests, adjusted where necessary for differences in variance, were performed to determine whether dog size, age or the TTO wedge angle removed were significantly related to the most com-mon postoperative complications. A Fishers

exact test was performed to analyse the rela-tionship between intraoperative fracturing of the distal tibial crest cortical attachment and postoperative avulsion of the crest. An odds ratio for the likelihood of tibial crest avulsion in dogs older than six years of age versus younger dogs was calculated using a Fishers exact test applied to a two-way contingency table. The cut off of six-years was determined based upon the bi-modal distribution of the ages of the dogs in our study.

Results

Triple tibial osteotomy population data

Medical records were available for 99 dogs representing 121 stifles that had undergone a TTO during the study period. Twelve dogs were lost to follow-up, two dogs failed to have follow-up radiographs, and one dog was ex-cluded from analysis due to complications arising from a concurrent medial patellar lu-xation repair that was performed at the time of the TTO. Therefore 84 dogs (97 TTO pro-cedures) satisfied the inclusion criteria. Seventy-one dogs underwent a unilateral TTO. Thirteen dogs had bilateral TTO pro-

Fig. 1 Triple tibial osteotomy: The correction angle and patellar tendon length are measured pre-op-eratively. (CA=Correction angle, PT = Patella tendon, TP = Tibial plateau). Three linear, incomplete os-teotomies are made in the proximal tibia.(TCO = Tibial crest osteotomy, WA = Wedge angle, TCFH = Ti-bial crest flexion hole). The tibial tuberosity is advanced and the tibial plateau partially levelled after re-duction of the wedge ostectomy. Note that the cranial cortical bone at the distal end of the tibial crest is flexed without fracturing (arrowheads).

Fig. 2 Six-week postoperative lateral radio-graph depicting the typical appearance of a triple tibial osteotomy healing without complication. Note mild proximal bowing of the fibula.

a Veterinary Instrumentation, Sheffield, UK b Microsoft Excel 2003: Microsoft Corporation


© Schattauer 2009 Vet Comp Orthop Traumatol 6/2009

475 Moles et al.: Triple Tibial Osteotomy in 97 Stifles

cedures with all bilateral surgeries staged a minimum of six weeks apart. The mean weight of the dogs was 35.2 kg (range 8.5 kg to 65.9 kg). The mean age of the dogs was 58.5 months (range 10 months to 143 months). There were seven entire females, 39 spayed fe-males, four entire males and 34 neutered males. The most common breeds were Rottweilers and their crosses (n = 12), Labra-dor Retrievers and their crosses (n = 12), Mastiffs and their crosses (n = 8), Golden Re-trievers (n = 7), Staffordshire Bull Terriers and their crosses (n = 7), and German Shep-herds and their crosses (n = 5). The TTO sur-gery was performed on 54 left stifle joints and 43 right stifle joints. Partial cranial cruciate ligament disruption was observed in 45 stifles (46%) and complete cranial cruciate liga-ment rupture in 52 stifles (54%). Thirty-eight stifles (39%) had gross pathological changes observed in the medial meniscus. One medi-al meniscus had a small radial tear in the cranial lip of the caudal horn and was left un-treated. Thirty-seven stifles with medial me-niscus pathology were treated by partial (n = 25), hemi- (n = 10) or total medial meniscec-tomy (n = 2) (5, 6). There were not any re-ports of lateral meniscal pathology. One dog had an axial caudal medial meniscal release performed.

Surgical findings

Eight different surgeons performed the TTO procedures reviewed in this study. Surgical experience ranged from residents and trained staff surgeons to board-registered specialist surgeons.

The mean and median recorded angles of the tibial bone wedges removed during the TTO surgery were 13.6 and 14 degrees re-spectively (range 10 to 20 degrees) (�Fig. 3).

The immediate postoperative radiographs of the 97 stifles were reviewed. In 77 TTO pro-cedures (79%), incomplete osteotomy of the tibial crest had been achieved with an intact segment of the cranial tibial cortex preserved at the flexion hole following tuberosity ad-vancement. Twenty TTO procedures had evi-dence of cranial cortex fracturing, with 18 considered to be non-displaced and two mildly displaced. Ninety-six closed wedge os-teotomies were stabilised with either a 2.7 mm or 3.5 mm Veterinary Instrumentation

tibial plateau levelling osteotomy (TPLO) platea, and one osteotomy was stabilised with a 3.5mm Securos TPLO platec. Two giant breed dogs had a second 2.7 mm DCP plate placed caudal to the TPLO plate for addi-tional stability. Additional implants were ap-plied in all 20 procedures with fracturing of the tibial crest osteotomy at the flexion hole. Additional implants were also used in 46

other procedures despite the distal cortical at-tachment of the tibial crest having been pre-served. These additional implants included a single tension band wire (n = 1), a single K-wire (n = 26), a single K-wire combined with a tension band wire (n = 5), two K-wires (n = 25), two K-wires combined with a ten-sion band wire (n = 6), three K-wires (n = 2) and a 2.7 cortical screw in lag fashion (n = 1).

Postoperative complications

Records of follow-up examinations, includ-ing six- to 12-week postoperative radio-graphs, were reviewed for the 84 dogs. Mean follow-up time was 19 weeks (range 6 to 151 weeks).

Thirty-one complications were reported in 22 stifles (23%) during the postoperative period. The complications recorded were cranioproximal displacement of the tibial crest including any related implants (n = 9) (�Fig. 4), late postoperative fracturing of the cranial tibial cortex at the level of the tibial crest flex point (n = 6), postoperative proxi-mal fibular fracturing (n = 4) (�Fig. 5), pa-tellar tendonitis (n = 3), postoperative menis-cal injury (n = 3), isolated implant related complications (n = 3) (�Fig. 6), fracturing of the apex of the patella (n = 2), and subcu-taneous abscess (n = 1). Not all complications were detected as clinical problems; some were considered incidental findings on follow-up radiographs.

Fig. 3 Histogram illustrat-ing frequency of the different wedge angles removed in the 97 triple tibial osteotomy procedures.

Fig. 4 Four-week postoperative radiograph of a tibial crest avulsion fracture. Note the osteolytic halo in the tibial tuberosity surrounding the K-wire.

c Securos Veterinary Orthopedics, Massachusetts, USA




Three of nine dogs with cranioproximal displacement of the tibial tuberosity had undergone corrective surgery to reduce and secure the avulsed tibial crest. One of these dogs required a third surgical procedure fol-lowing repeated avulsion of the crest. In the other six dogs, the tibial crest avulsion was an incidental finding on the six- to 12-week fol-low-up radiographs and the tuberosities were found to be stable on palpation at this time. In four dogs, records revealed a history of ex-acerbation of lameness in the first week after surgery. When those dogs with tibial crest avulsions were compared to the general TTO population, increased age (p = 0.023) and in-creased wedge angle (p = 0.009) were found to be significantly associated with tibial crest avulsion. Dogs older than six-years of age were five times more likely to sustain tibial crest avulsion postoperatively than younger dogs (p = 0.028, odds ratio 5.040). Intraoper-ative fracturing of the distal cortical attach-ment of the tibial crest at the flexion hole was also significantly associated with postoper-ative avulsion (p = 0.017, odds ratio = 6.1) despite implants having been applied to the tibial tuberosity at the time of the surgery in eight of the nine cases (a single K-wire [n = 3], two K-wires [n = 4], two K-wires and a tension band [n = 1]). In the case with a ten-

sion band, the implant failure was associated with pullout of the wire through the cranial cortex of the tibia. There was no apparent as-sociation between body weight and this com-plication (p = 0.339). In a number of cases, follow-up mediolateral radiographs revealed lysis of the bone surrounding the implants in the tibial tuberosity (�Figures 4, 6). There was not any clinical evidence of osteomyelitis in these cases.

Six dogs with incomplete tibial crest os-teotomies at the time of surgery were found to have sustained late postoperative fractur-ing of the distal cortical attachment on fol-low-up radiographs. Four of these dogs had cranioproximal displacement of the tibial crest. Two dogs had non-displaced fractures at the level of the tibial crest flexion hole. Only age was found to be significantly associated with this complication (p = 0.012) with older dogs being more likely to sustain late crest fractures. Interestingly, five of these dogs had implants applied to the tibial tuberosity at the time of the TTO (single K-wire [n = 2], two K-wires [n = 3]).

Three stifle joints (3/97, 3.1%) incurred postoperative meniscal damage necessitating revision surgery and partial meniscectomy. In all three cases, the dogs had recurrence of marked lameness, and in two cases a palpable

meniscal click was recorded. Revision pro-cedures and meniscectomies were performed 10 weeks, 18 weeks and 47 weeks following the original surgeries respectively. The post-operative prevalence of meniscal injury was 3/84 (3.6%) when one removes the following values: the 12 stifles that had undergone com-plete removal of the caudal horn of the medi-al meniscus during the TTO, and the one stifle that had undergone medial meniscus release.

Three dogs had primary implant related complications. Only one of these related to the tibial metaphyseal plate and screws. In this case, the tip of a proximal plate screw had penetrated the articular surface of the lateral tibial condyle necessitating removal (�Fig. 7). Poor postoperative positioning for radio-graphs had meant that this complication was not detected until the six-week follow-up. A loose K-wire was removed in one dog six weeks postoperatively; no microorganisms were cultured from this implant. In another dog, a broken K-wire was detected as an inci-dental finding on follow-up radiographs.

Pseudomonas aeruginosa were isolated from cultures of a subcutaneous abcess lo-cated deep to the surgical incision in one dog. This infection subsequently resolved with a four-week course of antibacterial therapy that was based on culture and sensitivity re-

Fig. 6 Six-week postoperative radiograph showing a fracture in the apex of the patella. Note the osteolysis of the tibial tuberosity surrounding the K-wire.

Fig. 7 Six-week postoperative radiograph showing a proximal screw which appears to penetrate the articular surface of the tibial plateau. There is severe osteoarthritis evident on the distal femur.

Fig. 5 Two-week postoperative radiograph showing a proximal fibula fracture.



© Schattauer 2009 Vet Comp Orthop Traumatol 6/2009

sults. No untoward sequelae to the infection were reported.

Discussion

The TTO is an osteotomy procedure for treat-ment of cranial cruciate ligament disruption incorporating features of the TPLO pro-cedure and the tibial tuberosity advancement (TTA) procedure. A number of studies reporting signalment and complications for cases of TPLO and TTA have been published, however only a single prospective study for TTO currently exists (1, 7–13). The mean age and weight of the dogs in our study are simi-lar to those previously reported in TPLO and TTA case studies (7–11). The gender and breed distributions for our study are also similar to those previously reported for TPLO and TTA. In our study, Staffordshire Bull ter-riers were the fifth most common breed undergoing surgery for cranial cruciate liga-ment rupture. Previous TPLO and TTA studies have not included any cases that were Staffordshire Bull terriers and this may repre-sent a regional difference in our dog popu-lation.

Twenty-three percent of stifles in our study developed complications following TTO surgery. We chose to define a compli-cation as an undesirable development that required further diagnostic investigation or surgical treatment. Based on this definition, not all complications were clinically apparent at follow-up examination; some were inci-dental findings on radiographs. Our overall postoperative complication prevalence was more than twice that of a previous TTO study (10.9%) (1). This difference may be related to variations in surgeons’ experience, the post-operative instructions given to owners, and the subsequent aftercare provided at home. Previous studies have published compli-cation rates of 18.8% to 28% for TPLO and 28.8% to 31.5% for TTA (7–10, 11). Some of these studies have included intraoperative complications as well as minor postoperative bandage and wound related changes. Differ-ent definitions of short-term, long-term, and major and minor complications have been used, making it difficult to directly compare results of each study. However, if a major complication is defined as only one that requires further surgical intervention, then

our major complication rate (9%) compares favourably to the rates of 12.5% for TTA and five percent for TPLO (7, 11).

Avulsion and displacement of the tibial crest from the distal flexion point were found to be more likely in dogs older than six -years of age, and those joints with larger osteotomy angles. Age related brittleness of the bone and increased advancement of the tibial tuberosity associated with larger closing-wedge osteot-omies may account for these findings. It has been hypothesised that the increased cranial rotational lever arm created by the TTA pro-cedure provides a mechanical advantage for m. quadriceps in maintaining stifle extension (14). The TTO procedure should achieve similar mechanical advantage for the quad-riceps through tibial tuberosity advancement. In a normal stifle, equilibrium is maintained by the counterbalance of the quadriceps ver-sus the hamstring apparatus. The cranial cru-ciate ligament contains mechanoreceptors that provide proprioceptive feedback to pre-vent hyperextension of the stifle presumably by maintaining this muscular counterbalance (15). Perhaps the lack of sensory input associ-ated with cranial cruciate ligament disease, in combination with a mechanically advantaged quadriceps apparatus, allowed for an acute overload of the crest bone or implant and pro-duced subsequent failure. This theory may also explain the postoperative fracturing of the cranial tibial cortex in two dogs with non-displaced crests, as well as the patellar ten-donitis in three dogs. Different types of tibial tuberosity fractures or avulsions have pre-viously been reported with TPLO, TTA and TTO (1, 7–11, 16). Only three dogs with crest avulsions in our study underwent repeat sur-gery. It is the authors’ experience that post-operative tibial crest avulsion associated with TTO is best treated by limiting activity, and that despite causing a short-term increase in morbidity, this complication appears to have little effect on the long-term function. This opinion is similar to the findings and recom-mendations of others with regards to tuberos-ity fractures after TPLO (8).

Fracture of the apex of the patella (�Fig. 6) has also been reported after TPLO surgery (7). The authors’ of that report were unable to identify a cause for the fracture but suggested it may have been associated with patellar ten-don desmitis. The altered joint biomechanics associated with the tibial plateau levelling as-

pect of TTO may be the cause of the patellar fractures seen in our study.

Our prevalence of 3.6% late meniscal in-jury is similar to the rate of 3.1% previously reported for TTO (1). Previous studies have reported late meniscal tears associated with extracapsular stabilisation techniques for cranial cruciate ligament ruptures in 13.8% of cases (17) and after TTA in 10 to 21.7% of cases (10, 11, 18). A study comparing menis-cal release versus non-release in dogs under-going TPLO reported late meniscal tears in 6.3% of dogs regardless of meniscal treat-ment (19). Case et al reported median time to lameness due to postoperative meniscal in-jury in 26 dogs to be 146 days after initial sur-gery for cranial cruciate ligament disruption (20). The relatively short follow-up period for some dogs in our study may have underesti-mated the true occurrence of meniscal in-juries after TTO.

Stress is placed on the proximal fibula dur-ing reduction of the TTO wedge osteotomy, which sometimes causes caudal bowing of the proximal bone (�Fig. 2). This stress presum-ably led to the fibula fractures seen in our study. Fibula fracture has also been docu-mented as a complication with other tibial plateau levelling techniques (7, 8, 9, 21). This complication was not considered clinically significant in any of our cases and no attempt was made to treat it.

In most cases of tibial crest avulsion, the in-sertion of one or more K-wires alone failed to counteract proximal distractive forces and maintain reduction of the cranial segment. The use of pin fixation alone has been recom-mended with tibial tuberosity transposition procedures (6, 22). It is not known whether the addition of a tension band wire may have prevented tibial crest avulsion in our cases where only K-wires were applied. Tension band wires provide increased fixation strength and interfragmentary compression by counteracting distractive forces at sites of ten-don or ligament insertion. Bruce et al (1) have recommended the use of additional implants in the tibial crest segment during TTO only if intraoperative fracture occurs at the tibial crest flexion hole. In about half of our cases, implants were placed prophylactilly in the ti-bial tuberosity despite an intact bone bridge at the tibial crest flexion hole being maintained. However, in the light of the findings of our study, it is the authors’ opinion that insertion


of implants in the tibial crest segment is un-necessary, provided that full cortical thickness is preserved in the cranial tibia during drilling of the tibial crest flexion hole, and that in-traoperative fracturing of this cortex does not occur during tuberosity advancement. If in-traoperative fracturing of the tibial crest seg-ment does occur, then the authors recom-mend stabilisation using K-wires and a ten-sion band wire. In contrast to other proximal tibia osteotomy procedures, no bone-plate re-lated failures were seen in our study although screw penetration of the joint was a compli-cation in one case (10, 11, 21).

The average wedge angle removed during the surgical procedures was 13.6 degrees (median 14 degrees). This angle was some-what larger than the average wedge angle pre-viously reported by Bruce et al. of 11.5 de-grees (median 11 degrees) (1). The most likely explanation for this difference is the change in the formula used for the calculation of wedge angle in this study. Early in our study the wedge angle was calculated as two-thirds the correction angle (1), however based on further work by Bruce (3, 4), this formula was later revised to Wedge Angle = Correc-tion Angle x 0.6 + 7 degrees. Differences in wedge angles may also have resulted from variations in stifle-joint angles on preoper-ative radiographs. The radiographic protocol for TTO requires the stifle to be positioned mediolaterally at a standing angle of 135 de-grees in order to determine the amount of ti-bial tuberosity advancement required to en-sure the patellar tendon is perpendicular to the tibial plateau (1). This positioning is dif-ficult to accurately achieve, and so it has been recommended to take a mediolateral radio-graph of the stifle at the angle naturally achieved when the upper, contralateral limb, is extended and secured cranially with the paw at the level of the shoulder (4). This lack of standardisation of limb positioning pro-vides a potential source of error in determin-ing the exact osteotomy angles required pre-operatively as well as the postoperative assess-ment of the tibial plateau to patella tendon angles achieved. This source of inaccuracy is similar for the TTA procedure and is com-parable to the previously reported inter-ob-server variability in measuring tibial plateau slopes of up to six degrees (23).

As with any retrospective study, one of the major limitations of this study was the re-liance on the completeness of case records and owners compliance with follow-up examination. Postoperative complications needed to be objectively recorded to be in-cluded in this study. Another limitation was the relatively short term follow-up available for some of these dogs. It is possible that some dogs may have developed complications after the last follow-up that were never reported.

Triple tibial osteotomy surgery, like TPLO and TTA, is used to change the biomechanics of the stifle to overcome cranial tibial thrust in dogs suffering from cranial cruciate ligament disruption. The postoperative complications reported here are similar to those reported for other tibial osteotomy procedures, with tibial crest avulsion being the most common com-plication and late meniscal injury occurring less frequently. The proportion of dogs in our study that underwent revision surgery was comparable to those reported for other proxi-mal tibial osteotomy procedures. Further retrospective or prospective studies are required to document long-term clinical out-comes and complications for TTO.

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Triple tibial osteotomy for treatment of the canine cranial cruciate ligament-deficient stifle joint