Study supports rigid fixation in canine limb press models

CURRENT FULL VERSION: A new Veterinary Surgery study adds some reassurance for researchers using canine limb press models to study stifle biomechanics: rigid proximal femoral fixation still appears to be a defensible setup. In the cadaveric experiment, published online ahead of print on February 2, 2026, investigators tested whether allowing femoral flexion-extension or changing joint angulation would materially alter simulated quadriceps and gastrocnemius forces. Their conclusion was fairly clear: both fixation method and stance configuration had limited impact, and flexion-extension mobility did not substantially increase muscle loading. (pubmed.ncbi.nlm.nih.gov)

That question matters because limb press models are widely used in canine orthopedic research, especially in studies evaluating stifle stability and procedures for cranial cruciate ligament disease. But the field has also been dealing with a methods problem. A 2025 systematic review identified 23 canine limb press studies and found that joint-angle landmarks were often poorly described or inconsistent with cited methods, while key data on quadriceps, gastrocnemius, and cranial thrust forces were sparse. The reviewers argued that these knowledge gaps could help explain why ex vivo findings do not always line up neatly with in vivo assessments after surgeries such as TPLO and TTA. (pubmed.ncbi.nlm.nih.gov)

In the new study, the authors mounted 10 unpaired pelvic limbs from adult large-breed dogs in a custom limb press. The femur was tested first in a rigidly fixed position at 70 degrees to horizontal and then in a model that allowed flexion-extension. Quadriceps and gastrocnemius forces were simulated with load cells and turnbuckles, while axial loads of 10%, 20%, and 30% body weight were applied. The team also fixed the stifle and hock at angles representing mid-stance or early stance. As expected, both muscle forces increased with higher axial load. Quadriceps force was unaffected by fixation method overall, although mid-stance values were higher in flexion-extension models at 20% and 30% body-weight loads. Gastrocnemius force varied somewhat by configuration, and muscle force ratios differed by configuration, but the overall message was that these effects were limited rather than transformative. (pubmed.ncbi.nlm.nih.gov)

The paper also lands in the context of a broader research push by this group to tighten up ex vivo model assumptions. The new article cites the authors’ own systematic review as part of that effort, and related 2026 limb press work in Research in Veterinary Science has continued examining how loading conditions affect rotational stability outcomes in canine stifles. Taken together, that suggests the field is moving toward more explicit validation of model design choices, rather than treating legacy setups as interchangeable. That’s an inference based on the sequence of publications, but it is well supported by the recent literature. (pubmed.ncbi.nlm.nih.gov)

A separate recent study helps round out the broader orthopedic picture around the proximal femur, this time in a clinical rather than cadaveric setting. In a retrospective series of 10 skeletally immature dogs with diaphyseal femoral fractures treated between 2010 and 2023 using an angle-stable interlocking nail, investigators looked specifically for proximal femoral malformation both perioperatively and at skeletal maturity. They found no evidence of proximal femoral malformation during perioperative follow-up, and long-term function appeared favorable: six of nine dogs had a Canine Brief Pain Inventory score of 0, while the remaining three had low scores, with a maximum of 10 out of 100. At skeletal maturity, two dogs had bilateral coxofemoral osteoarthritis, and the only radiographic parameter that differed significantly between operated and unaffected femurs was CORONA1, which the authors interpreted as likely reflecting reduced natural femoral procurvatum rather than a clinically important deformity. Their practical takeaway was straightforward: angle-stable interlocking nails should not be considered contraindicated in juvenile canine diaphyseal femoral fracture repair on the basis of concern for proximal femoral malformation alone.

Expert commentary specific to this paper was limited in publicly indexed sources at the time of writing. Still, the most relevant industry perspective may be the authors’ own framing in the abstract: rigid fixation remains a valid approach. In practical terms, that’s a useful message for research groups that rely on repeatable, lower-complexity cadaver models and need confidence that adding proximal femoral mobility is not essential to produce interpretable muscle-force data. The juvenile fracture series adds a complementary clinical note of reassurance that interventions involving the femur do not necessarily translate into meaningful long-term proximal femoral distortion when carefully applied and followed through maturity. (pubmed.ncbi.nlm.nih.gov)

Why it matters: For veterinary professionals, this is less about changing clinical practice tomorrow and more about improving confidence in the preclinical evidence base behind orthopedic procedures. If rigid fixation does not meaningfully distort simulated muscle loading, then many existing and future limb press studies may be more comparable than feared. That could help researchers refine protocols, reduce unnecessary model complexity, and focus validation efforts on the variables that may matter more, such as load magnitude, limb angulation definitions, and reporting standards. For surgeons reading ex vivo biomechanics papers, it’s also a reminder to pay close attention to model design before translating findings into clinical expectations. And on the clinical side, the juvenile fracture data suggest that angle-stable interlocking nails can be used in immature dogs without a significant apparent risk of proximal femoral malformation, while still warranting long-term radiographic follow-up for coxofemoral changes. (pubmed.ncbi.nlm.nih.gov)

What to watch: The next step will likely be more formal validation work linking ex vivo muscle-force and stability outputs to physiologic in vivo measurements, along with clearer reporting standards for limb angulation and loading so orthopedic studies can be compared more reliably across centers. In parallel, additional outcome data in larger juvenile fracture cohorts would help clarify how often subtle alignment changes such as reduced CORONA1 matter clinically, and whether the low observed rate of long-term proximal femoral complications holds up in broader practice. (pubmed.ncbi.nlm.nih.gov)