Peer-reviewed veterinary case report
How femur deformity affects kneecap slipping in dogs
By Lee, Jiyun et al.·Published in BMC veterinary research·2020·Department of Veterinary Surgery, South Korea·View original on PubMed →
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Original publication title: Biomechanical analysis of canine medial patellar luxation with femoral varus deformity using a computer model.
- Species:
- dog
Plain-English summary
A Beagle with medial patellar luxation (MPL), where the kneecap slips out of place, was studied to understand how a specific leg deformity (femoral varus) affects this condition. The research found that when the angle of the leg bone was 103 degrees or more, the kneecap began to luxate, or dislocate, during movement. This suggests that dogs with this degree of deformity may need a surgical procedure called distal femoral osteotomy (DFO) to correct the alignment and prevent further issues. While the findings provide useful insights, they should be considered carefully in real-life cases.
People also search for: dog kneecap slipping treatment · Beagle patellar luxation surgery · femoral varus deformity in dogs
Abstract
BACKGROUND: Femoral varus deformities complicating the realignment of the quadriceps muscles are frequently associated with medial patellar luxation (MPL) in dogs. Therefore, distal femoral osteotomy (DFO) is recommended in dogs affected with severe MPL and a distal femoral varus deformity. The presence of an anatomic lateral distal femoral angle (aLDFA) of ≥ 102° has been anecdotally recommended as an indication for performing corrective DFO in large-breed dogs. However, the effect of a femoral varus deformity on MPL has not been scientifically evaluated. We aimed to evaluate the influence of a femoral varus deformity on MPL using a finite element method based computer model. Three-dimensionally reconstructed computed tomographic images of a normal femur from a Beagle dog were deformed using meshing software to create distal varus deformities. A total of thirteen aLDFAs, including 95°, 98° and 100°-110°, were simulated. The patellar positions and reaction force between the patella and trochlear grooves were calculated for all finite element models under constant rectus femoris muscle activation. RESULTS: The patella was displaced medially from the trochlear groove at an aLDFA of ≥103°. With an aLDFA of 103° to 110°, the reaction force was equal to zero and then decreased to negative values during the simulation, while other models with aLDFAs of 95°, 98°, and 100°-102° had positive reaction force values. The patella began to luxate at 24.90 seconds (sec) with an aLDFA of 103°, 19.80 sec with an aLDFA of 104°, 21.40 sec with an aLDFA of 105°, 20.10 sec with an aLDFA of 106°, 18.60 sec with an aLDFA of 107°, 15.30 sec with an aLDFA of 108°, 16.60 sec with an aLDFA of 109°, and 11.90 sec with an aLDFA of 110°. CONCLUSION: Severe distal femoral varus with an aLDFA of ≥103° caused MPL when other anatomical factors were controlled. Thissimplified computer model provides complementary information to anecdotal cutoffs for DFO, hence it should be applied to clinical patients with caution.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/33272258/