Is TTA better than lateral suture in small dogs with cruciate disease?

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Appraisal, application and reflection

There was no evidence that addressed the PICO question. In combination, two prospective clinical trial studies by Krotscheck et al. (2013) and Krotschek et al. (2016) objectively compared the long-term functional outcomes of tibial plateau levelling osteotomy (TPLO), TTA and extracapsular reconstruction (ECR) by LFS. In the 2013 study, data for normal dogs, ECR and TPLO groups were reported. Data for the control group and TTA group in the 2016 study were reported and compared to data for the control group, TPLO group and ECR (LFS) group reported in the 2013 study. Both studies were identical in design. In the 2016 study, owners with dogs suffering from naturally occurring cranial cruciate ligament disease were offered three surgical interventions, that is, TPLO, ECR (LFS), and TTA. Owners that opted for TTA were given the option to participate in the study. Inclusion criteria were a body mass greater than 15 kg, diagnosis of unilateral cranial cruciate ligament disease and absence of any other orthopaedic abnormalities. Standard TTA was performed on all dogs in the study (n=14) with standardised perioperative care. Force plate gait analysis was performed on normal control dogs and study dogs preoperatively and at 2 weeks, 8 weeks, 6 months and 12 months postoperatively. At 12 months postoperatively, the TTA group had a better functional outcome at the walk than the ECR (LFS) group and was indistinguishable from the control group. At 12 months postoperatively, the functional outcomes of the TTA and the ECR (LFS) groups were indistinguishable at the trot but inferior to the control group. The TTA group had more postoperative complications than the ECR (LFS) group. At 12 months postoperatively, the TPLO group had functional outcomes indistinguishable from the control group at both the walk and the trot, suggesting superior long-term functional outcomes of the TPLO group to both the TTA and ECR (LFS) groups. However, long-term functional outcomes of the TPLO group are irrelevant to the PICO. Although the results of the two studies suggest better long-term functional outcomes in the TTA group compared to the ECR (LFS) group, both studies excluded dogs weighing less than 15 kg, and thus the results may not be applicable to this PICO.

A study by Di Donna et al. (2015) compared objective, validated long-term functional outcomes of TTA and LFS using force plate analysis. Dogs in both groups had good to excellent outcomes but kinematic results indicated superior surgical outcome with the TTA group at 6 month follow-up. However, the conference abstract available lacked important detail on inclusion criteria and statistical inference in its methodology and did not specify whether the study population included dogs weighing below 15 kg, making it difficult to determine its evidentiary value to this PICO. It has been previously recommended that dogs weighing less than 15 kg do not require surgery. This was based on a 1984 study by Vasseur where 85.7% of dogs weighing under 15 kg were considered clinically normal after an average follow-up period of 36.6 months following conservative non-surgical management, compared to 19.3% of dogs weighing over 15 kg after an average follow-up period of 49.1 months. However, it has since been demonstrated that conservatively managed dogs develop more severe osteoarthritis in the long-term than surgically managed dogs. In view of this, surgery in one form or another is recommended (Innes, 2012; Hamilton, 2016; and Mölsä et al. 2014). The literature does not specify whether this has been demonstrated in dogs weighing under 15 kg so the relevance of this observation regarding small dogs cannot be determined.  In order to address the PICO question, the ideal study would be a blinded, randomised, controlled clinical trial (Bergh et al., 2014) addressing the specific weight class, with objective assessment of long-term functional outcomes of TTA and LFS. Mölsa et al. compared long-term surgical outcomes in dogs following surgery for cruciate ligament disease in a 2014 retrospective study. They used force plate analysis, orthopaedic and radiographic examination, and physiotherapeutic examination as objective, validated methods to measure and compare long-term functional outcomes in dogs that had undergone intracapsular, extracapsular and osteotomy techniques. The dogs that had undergone osteotomy techniques had less radiographic osteoarthritis than the dogs that had undergone intracapsular and extracapsular techniques. The low number of dogs treated with the extracapsular technique did not allow for comparison of ground reaction forces with the osteotomy and intracapsular techniques. There were no other significant differences. The limitations of the study are that it excluded dogs weighing less than 17 kg, largely focused on comparing surgically treated limbs to contralateral, healthy limbs, and compared broad surgical technique classifications namely intracapsular, extracapsular and osteotomy techniques rather than specific surgical techniques such as TTA and LFS. The study is, therefore, irrelevant to the PICO question as it excluded dogs weighing under 17 kg and the singular contributions of TTA and LFS to the findings cannot be determined.  A 2013 study by Mölsa et al. compared long-term surgical outcome and chronic pain in dogs that underwent intracapsular, extracapsular and osteotomy techniques for cranial cruciate ligament disease. The Helsinki Chronic Pain Index (HCPI) was used to evaluate chronic pain following surgery for cranial cruciate ligament disease. There were no significant differences in chronic pain indices between the different techniques. The study was carried out on a heterogenous population of dogs and does not indicate whether dogs weighing under 15 kg were included. The HCPI questionnaire used, although validated, remains subjective. This study also compared broad surgical technique classification rather than specific surgical techniques such as TTA and LFS. Progressive osteoarthritis which always develops secondary to cranial cruciate ligament disease regardless of surgical technique used to manage the condition may be responsible for chronic pain (Muir, 2018). The use of chronic pain to evaluate long-term surgical outcome is therefore limited as chronic pain may have other sources unrelated to surgery. The relevance of this study to the PICO given these limitations is therefore not possible to determine. Based on the absence of evidence, the choice of procedure between LFS and TTA should be guided by what the surgeon deems to be in the patient’s best interests.

There is currently zero evidence to base choice between performing TTA or LFS in dogs weighing under 15 kg. However, surgeons should be guided by the patient’s best interests in choosing between which of the two to perform in dogs weighing under 15 kg.

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