Geometry of the femoral condyles in dogs

Ideal Anchor Points for Patellar Anti-rotational Sutures for Management of Medial Patellar Luxation in Dogs: A Radiographic Survey

OBJECTIVE

 The aim of this study was to identify the ideal anchor point for patellar anti-rotational sutures for adjunctive stabilization of medial patellar luxation in both small and large breed dogs.

STUDY DESIGN

 Retrospective radiographic survey was performed on 110 stifles from 101 dogs. Radiographs were grouped based on patient weight (≤15 kg; >15 kg) and diagnosis (medial patellar luxation, cranial cruciate ligament rupture, and normal joints). Radiographic measurements included: the proximal, middle, and distal points of the trochlear ridge, the caudal aspect of Blumensaat's line (roof of the intercondylar notch), the centre of the lateral fabella, as well as the "best-fit" centre of a circle overlying the trochlea. These landmark coordinates were used to calculate radii for comparison, and for scaling between joints.

RESULTS

 Use of the fabellar centre resulted in larger radii (corrected p <0.001) than those from the best-fit circle centre for all but one combination of patient group and trochlear end point locations. Using the best-fit circle centre, radius variation was less marked than with the fabellar centre. Significant differences in location for centres of the best-fit circle and fabella were seen across all patient categories (Pillai's trace p <0.001).

CONCLUSION

 The fabella is unlikely to be the best choice for anchoring a patellar anti-rotational suture. Use of the best-fit circle centre to place a suture anchor should be preferred to maximise suture isometry during joint flexion and extension in large and small breed dogs.

Quantifying meniscal kinematics in dogs

The dog has been used extensively as an experimental model to study meniscal treatments such as meniscectomy, meniscal repair, transplantation, and regeneration. However, there is very little information on meniscal kinematics in the dog. This study used MR imaging to quantify in vitro meniscal kinematics in loaded dog knees in four distinct poses: extension, flexion, internal, and external rotation. A new method was used to track the meniscal poses along the convex and posteriorly tilted tibial plateau. Meniscal displacements were large, displacing 13.5 and 13.7 mm posteriorly on average for the lateral and medial menisci during flexion (p = 0.90). The medial anterior horn and lateral posterior horns were the most mobile structures, showing average translations of 15.9 and 15.1 mm, respectively. Canine menisci are highly mobile and exhibit movements that correlate closely with the relative tibiofemoral positions. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1710-1716, 2018.

Femoral condyle curvature is correlated with knee walking kinematics in ungulates

The knee has been the focus of many studies linking mammalian postcranial form with locomotor behaviors and animal ecology. A more difficult task has been linking joint morphology with joint kinematics during locomotor tasks. Joint curvature represents one opportunity to link postcranial morphology with walking kinematics because joint curvature develops in response to mechanical loading. As an initial examination of mammalian knee joint curvature, the curvature of the medial femoral condyle was measured on femora representing 11 ungulate species. The position of a region of low curvature was measured using a metric termed the "angle to low curvature". This low-curvature region is important because it provides the greatest contact area between femoral and tibial condyles. Kinematic knee angles during walking were derived from the literature and kinematic knee angles across the gait cycle were correlated with angle to low curvature values. The highest correlation between kinematic knee angle and the angle to low curvature metric occurred at 20% of the walking gait cycle. This early portion of the walking gait cycle is associated with a peak in the vertical ground reaction force for some mammals. The chondral modeling theory predicts that frequent and heavy loading of particular regions of a joint surface during ontogeny will result in these regions being flatter than the surrounding joint surface. The locations of flatter regions of the femoral condyles of ungulates, and their association with knee angles used during the early stance phase of walking provides support for the chondral modeling theory.

Evaluation of varying morphological parameters on the biomechanics of a cranial cruciate ligament-deficient or intact canine stifle joint with a computer simulation model

OBJECTIVE

To investigate the influence of varying morphological parameters on canine stifle joint biomechanics by use of a 3-D rigid-body canine pelvic limb computer model that simulated an intact and cranial cruciate ligament (CrCL)-deficient stifle joint across the stance phase of gait at a walk.

SAMPLE

Data from computer simulations.

PROCEDURES

Computer model morphological parameters, including patellar ligament insertion location, tibial plateau angle (TPA), and femoral condyle diameter (FCD), were incrementally altered to determine their influence on outcome measures (ligament loads, relative tibial translation, and relative tibial rotation) during simulation of the stance phase of gait at a walk. Outcome measures were assessed for each scenario and compared between an intact and CrCL-deficient stifle joint with the sensitivity index (the percentage change in outcome measure divided by the percentage change in input parameter).

RESULTS

In a CrCL-intact stifle joint, ligament loads were most sensitive to TPA. In a CrCL-deficient stifle joint, outcome measures were most sensitive to TPA with the exception of caudal cruciate ligament and lateral collateral ligament loads, which were sensitive to FCD and TPA. Relative tibial translation was sensitive to TPA and patellar ligament insertion location, whereas relative tibial rotation was most sensitive to TPA.

CONCLUSIONS AND CLINICAL RELEVANCE

The computer model sensitivity analyses predicted that individual parameters, particularly TPA and FCD, influence stifle joint biomechanics. Therefore, tibial and femoral morphological parameters may affect the likelihood, prevention, and management of CrCL deficiency.