Introduction

During the past decade, complete or partial rupture of the cranial cruciate ligament in dogs has become one of the preeminent topics of interest in small animal orthopaedic surgery because of both the high incidence of the problem and the clinical success of Slocum's procedure to treat it. While the majority of cases are still treated by other methods, Slocum's tibial plateau leveling osteotomy (TPLO) is, by a broad consensus, a state-of-the-art repair method. In 2002, Montavon and Tepic described their technique, called tibial tuberosity advancement (TTA), which became established for clinical use in early 2004. Realising that the total joint force runs nearly parallel to the patellar ligament, those authors proposed that the same result of TPLO could be achieved by moving the tibial tuberosity cranially. After cranial advancement of the tibial insertion of the patellar ligament, the ligament is perpendicular to the tibial plateau, there is no shear component of the total joint force of weightbearing and the cruciate ligament is no longer loaded.

Clinical Experience

After having used TPLO with very satisfying results for 7 years, we began using TTA to test this new technique. A comparison of TPLO and TTA, each with the same number of consecutive cases, was carried out. To account for the learning curve, the first 85 cases of TPLO done by the author (in a series of over 700) were compared with the first 85 cases of TTA. Tibial plateau leveling osteotomy was used in 85 stifle joints of 74 dogs from March 1998 to September 1999, and TTA in 85 stifle joints in 72 dogs from May 2004 to May 2005. All operations were carried out by the author. The mean body weight of the dogs was 43.6 kg (range 15.2-81.3 kg) for TPLO and 36.6 kg (range 9.3-82.2 kg) for TTA. The mean age of the dogs was 5.5 years (range 10 months to 11 years) for TPLO and 4.2 years (range 10 months to 12 years) for TTA. The gender distribution was 38 males and 36 females for TPLO and 36 males and 36 females for TTA. Dogs of 28 breeds were used, and TPLO and TTA were performed with similar frequency in the majority of cases within a breed. Tibial plateau leveling osteotomy was carried out bilaterally in 11 dogs and TTA in 8 (at different times). Eight dogs that underwent TTA had been treated previously with TPLO in the opposite stifle, and in four dogs, the same joint had unsuccessfully undergone extracapsular fixation previously. Partial rupture of the cranial cruciate ligament was present in two cases and complete rupture in 83 in the TPLO group; in the TTA group, partial rupture was present in 29 cases and complete rupture in 56. The average tibial slope was 22.9 degrees (range 16-40 degrees) in the TPLO group and 22.0 degrees (range 16-27 degrees) in the TTA group. Meniscal release was carried out in 83 cases (98%) in the TPLO group and in 52 cases (61%) in the TTA group.

Short-term (<2 months) and long-term (>6 months) complications were recorded, as was the outcome after a minimum period of 6 months. In the TPLO group, clinical and radiographic evaluation was carried out 2 months after surgery in 71 joints (84%), more than 6 months after surgery in 38 joints (45%), and information on the remaining cases was collected via telephone after a minimum period of 6 months. In the TTA group, clinical and radiographic evaluation was carried out 2 months after surgery in 77 joints (90%), more than 6 months after surgery in 32 joints (38%), and information on the remaining cases was collected via telephone after a minimum period of 6 months.

Short-term postoperative complications in the TPLO group included one case of tibial tuberosity fracture 25 days after surgery, which was successfully revised with a tension-band wire. Long-term complications in the TPLO group included a pivot shift in a Labrador Retriever, in which malalignment was not corrected, and a sinus tract from the plate in a Rottweiler, which required plate removal 1 year later.

Short-term postoperative complications in the TTA group included three cases with failure of the fixation in the first month postoperatively due to partial avulsion of the tibial crest at the point of insertion of the fork; two of these dogs were successfully revised and one healed successfully with conservative treatment because of minimal displacement. One other case was a Dogue de Bordeaux with a partial tear of the patellar tendon, which was successfully treated with a figure-of-eight tibiopatellar cerclage wire. Long-term postoperative complications in the TTA group included one case of a very aggressive osteosarcoma in the proximal tibia of a 2.5-year-old Maremmano Shepherd Dog 3 months after surgery and three cases of subsequent meniscal pain; reoperation with meniscal release and excision of a bucket-handle tear was carried out in one case 10 months after TTA, and in two cases, surgical revision was not required. There was also one case of persistent stifle instability in a 67 kg Newfoundland with a highly positive tibial compression test and a 27 degree tibial slope; successful revision was achieved with TPLO 14 months after TTA.

Discussion

A radiographic study of the long-term progression of osteoarthrosis in both groups is still in progress. However, the preliminary results of our clinical experience confirm that both techniques are clinically effective in restoring good function in stifles with partial or complete rupture of the cranial cruciate ligament and both have a similar incidence of postoperative complications. Tibial tuberosity advancement was a less invasive procedure than TPLO and provided a faster recovery. In the present study, TTA was not carried out in cases with limb malalignment or with excessive tibial slope (>27 degrees); in such cases TPLO was employed because of its wider versatility. The failure of TTA that occurred in a heavy dog with a 27 degree tibial slope suggests that TPLO may be the preferred method of treatment in heavy dogs with a tibial slope of >25 degrees. Meniscal release remains controversial, at least in partial rupture of the cranial cruciate ligament, although subsequent meniscal tear is a risk when this procedure is omitted both in TTA- and in TPLO-treated cases. The amount of tibial tuberosity advancement in relation to the tibial morphology is not yet well defined and some uncertainty remains when planning and performing TTA; TPLO, on the other hand, is more straightforward.

References

1.  Apelt D, Kowaleski M, Boudrieau R. Effect of tibial tuberosity advancement on cranial tibial subluxation in canine cranial cruciate-deficient stifle joints: an in vitro experimental study Veterinary Surgery 2007; 36: 170-177.

2.  Montavon PM, Damur DM, Tepic S. Advancement of the tibial tuberosity for the treatment of cranial cruciate deficient canine stifle. Proceedings of the 1st World Veterinary Orthopaedic Congress ESVOT-VOS, Munich 2002, 153.

3.  Slocum B, Slocum TD. Tibial plateau leveling osteotomy for repair of cranial cruciate ligament rupture in the canine. Veterinary Clinics of North America 1993; 23: 777-795.