Imagine this clinical scenario: in your previous practice, you performed lots of block recession trochleoplasties as part of the surgical treatment of medial patellar luxation, and you have been very satisfied with the post-operative results. However, in your new practice, the standard procedure is wedge recession trochleoplasty, and you are asked to switch to this method. Therefore, you decide to explore the evidence around whether block or wedge recession trochleoplasty results in better patient outcomes.
Three papers were critically appraised – one was a retrospective observational study, one a case series study and the third a cadaver study.
The cadaver study by Johnson et al. (2001) looked at 12 cases with 24 stifles. It described the difference in patellar depth, patellar articular contact, percentage of recessed trochlear surface area and resistance to medial patellar luxation in stifles treated with trochlear block recession or trochlear wedge recession. The study found the block technique superior to the wedge technique due to a deeper proximal patellar depth, a greater patellar articular contact in the extended stifle (P< 0.01), a larger percentage of recessed trochlear surface and a greater resistance to medial patellar luxation.
Since the study was performed on cadavers with specimens mounted in a position device, it is difficult to interpret the results in relation to live animals.
Since the study was performed on cadavers with specimens mounted in a position device, it is difficult to interpret the results in relation to live animals. Also, all dogs were large-breed dogs, and it is unclear whether the results can also be applied to small-breed dogs.
In the retrospective observational study by Rossanese et al. (2019), femoral trochleoplasty was performed in 90 stifles. It included a trochlear wedge recession in 68 stifles (76 percent) and a trochlear block recession in 22 stifles (24 percent). No significant difference in complication rates between the trochlear wedge and block technique was found.
As the study was retrospective, there are several limitations, including the fact that there were no standardised protocols to compare the techniques and that the study relies on the accuracy of the medical record entries. The study also lacks long-term follow-up.
Case series study
In the final study by Ballatori et al. (2005), only two of the dogs included had a medial patellar luxation, with both surgical approaches used on the same patient (right stifle: trochlear block recession; left stifle: trochlear wedge recession). The post-operative clinical picture was similar two to three months after surgery, but the very small sample size limits meaningful conclusions.
Overall, further studies are needed to evaluate the short-term and long-term clinical outcomes in small-breed dogs with medial patellar luxation undergoing either trochlear wedge recession or trochlear block recession.
Further studies are needed to evaluate the short-term and long-term clinical outcomes in small-breed dogs with medial patellar luxation
The cadaver study (Johnson et al., 2001) provided the most impressive implementation, with ex vivo testing of a stifle model that mimics patellar luxation, objective interobserver assessment and distinct variable measurements obtained from computed tomography. However, the results may not be applicable to live animals, and long-term effects cannot be evaluated.
Rossanese et al. (2019) found no significant difference in complication rates between trochlear wedge resection and trochlear block resection. The main limitation of this study was that it lacks long-term follow-up, so we do not know if any of the trochleoplasty techniques had a worse or more favourable outcome after several years.
In the case series by Ballatori et al. (2005), only two dogs had medial patellar luxation and with different luxation degrees in the individual hindleg. Therefore, a meaningful comparison between the treatment methods cannot be made.
On one hand, one may consider the block technique to be more physiologically or anatomically appropriate, as it creates a deeper trochlea proximally in the joint and a more profound femoropatellar contact. On the other hand, the wedge technique is less invasive and, thus, conceivably associated with a lower risk of complications.
Until future randomised controlled studies in live animals are performed, the preference and previous experiences of the veterinary surgeon should be taken into account
Until future randomised controlled studies in live animals are performed, the preference and previous experiences of the veterinary surgeon should be taken into account.