Nikolaus Velich 1,*, Britta Vidoni 2, Eberhard Ludewig 3, Alexander Tichy 4, Eva Schnabl-Feichter 2,*
Background
Medial patellar luxation (MPL) is common in small breed dogs and frequently requires surgical correction. Two standard surgical techniques—trochlear wedge recession (TWR) and trochlear block recession (TBR)—aim to deepen the trochlear groove and stabilize the patella. Previous ex vivo studies suggest TBR may lead to fewer osteoarthritic (OA) changes due to better patellar contact. However, clinical data comparing long-term outcomes of TWR and TBR regarding OA progression are limited. This study aimed to compare these techniques using a modified OA radiographic scoring system and assess inter-observer agreement among clinicians of varying experience.
Methods
This retrospective study included 25 small-breed dogs (32 stifle joints) with grade-2 or -3 MPL treated between 2016 and 2021. Surgeries were performed using TWR (n=11) or TBR (n=21), all including tibial tuberosity transposition and various soft tissue techniques. Radiographs were taken preoperatively and at least one year postoperatively. A modified OA scoring system, evaluating 12 anatomical points, was used to assess OA progression. Three observers (radiologist, intern, surgeon) independently scored the images. Statistical analyses assessed OA score changes, inter-observer reliability, and technique differences.
Results
Both surgical groups showed significant OA progression over time, with a greater mean score increase in the TBR group (5.2 points) than in the TWR group (1.9 points). No statistically significant differences were found between the groups regarding final OA scores. Inter-observer agreement was high (ICC > 0.78), though variability was noted, particularly from the less experienced observer. The central tibial plateau was the only individual point with a statistically significant OA score increase, observed in the TBR group.
Limitations
Limitations included retrospective design, small sample size, inconsistent documentation of adjunct soft tissue procedures, and surgeon-based technique selection, which may bias outcomes. Observer variability was present despite efforts to standardize scoring. Broad follow-up durations may affect uniformity in OA progression measurement, though no correlation between follow-up time and OA score was found.
Conclusions
The study found no significant difference in OA progression between TWR and TBR for MPL correction. A modified OA scoring system demonstrated high inter-observer reliability, supporting its clinical utility. The findings highlight the complexity of surgical outcome evaluation and suggest that radiographic OA progression does not necessarily correlate with clinical outcomes. Future prospective studies with standardized protocols and functional assessments are recommended.
a) Assessment points for the OA score in the mediolateral view. The following bone prominences were evaluated: apex of the patella (1), base of the patella (2), proximal trochlear ridge (3), distal trochlear ridge (4), femoral condyle (5), caudal aspect of the tibial plateau (8), central aspect of the tibial plateau (9), popliteal surface of the femur (10), and sesamoid bones (11). The points marked in red (6 and 7) were left out of the assessment. (b) Assessment points of the OA score in the caudocranial view. The following bone prominences were evaluated: lateral tibial and femoral epicondyle (12), medial tibial and femoral epicondyle (13), and intercondylar notch (14). The point marked in red (15) was left out of the assessment.
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