Analysis of passive tibio-femoral joint movement of Beagle dogs during flexion in cadaveric hind limbs without muscle

Depleting transforming growth factor beta receptor 2 signalling in the cartilage of itga1-null mice attenuates spontaneous knee osteoarthritis

Objectives

Integrin α1β1 protects against osteoarthritis (OA) when it is upregulated in the superficial zone of cartilage in the early stages of disease. However, the mechanism behind this protection is unknown. Integrin α1β1 moderates transforming growth factor β receptor II (TGFBR2) signalling, a critical regulator of chondrocyte anabolic activity. To this end, mice lacking integrin α1β1 have increased baseline activation of TGFBR2 signalling and overall fibrosis. The purpose of this study was to evaluate the interplay between integrin α1β1 and TGFBR2 in the development of spontaneous OA. We hypothesized that dampening TGFBR2 signalling in the cartilage of itga1-null mice would attenuate OA.

Methods

Behavioural and histological manifestations of spontaneous knee OA were measured at 4, 8, 12 and 16 months in mice with and without a ubiquitous itga1 deletion and with and without a tamoxifen-induced cartilage specific TGFBR2 depletion.

Results

Knee cartilage degeneration, collateral ligament ossification and pain responses increased with age. Itga1-null mice with intact TGFBR2 signalling developed earlier and more severe OA compared to controls. In agreement with our hypothesis, depleting TGFBR2 signalling in the cartilage of itga1-null mice attenuated OA progression.

Conclusion

Intact TGFBR2 signalling drives early and worse knee OA in itga1-null mice. This result supports the hypothesis that the increased expression of integrin α1β1 by superficial zone chondrocytes early in OA development dampens TGFBR2 signalling and thus protects against degeneration.

The effect of joint orientation on passive movement of the dog's stifle

Introduction

The cranial cruciate ligament (CCL) is one of numerous structures which determine the path of the tibia relative to the femur when passively flexing/extending the stifle of the dog. The effect of cutting the CCL on passive motion with the hind limb in different orientations, is unknown. The aim of this study was to describe passive movement of the tibia relative to the femur in dogs, with the hind limb in three different orientations, and with CCL intact and cut.

Methods

Ten cadaveric hind limbs were obtained from dogs weighing between 20 kg and 25 kg and prepared for testing in a custom-built joint testing machine. Each hind limb was tested in three different orientations with data collected, using an electromagnetic tracking system, during 2 cycles of flexion/extension with the CCL intact and cut. Each cycle was initiated with the stifle in full extension (0°) and data was collected at 0°, 20°, 30°, 40°, 45°, and 55° of stifle flexion/extension.

Results

Flexion of the stifle resulted in caudal translation and internal rotation of the tibia relative to the femur, with cranial translation and external rotation occurring during extension along the identical path. Cutting the cranial cruciate ligament did not result in significant differences in translation or rotation when the stifle was orientated to approximated the standing position of a dog.

Discussion

Isometric points at the origin and insertion of the CCL can potentially be identified in CCL deficient stifles using a technique based on passive motion of an intact stifle.

Investigation of the effects of excessive tibial plateau angle and changes in load on ligament tensile forces in the stifle joints of dogs

OBJECTIVE

To investigate the effect of an excessive tibial plateau angle (TPA) and change in compressive load on tensile forces experienced by the cranial cruciate, medial collateral, and lateral collateral ligaments (CCL, MCL, and LCL, respectively) of canine stifle joints.

SAMPLE

16 cadaveric stifle joints from 16 orthopedically normal Beagles.

PROCEDURES

Stifle joints were categorized into unchanged (mean TPA, 30.4°) and excessive (mean TPA before and after modification, 31.2° and 41.1°, respectively) TPA groups. The excessive TPA group underwent a TPA-increasing procedure (curvilinear osteotomy of the proximal aspect of the tibia) to achieve the desired TPA. A robotic system was used to apply a 30- and 60-N compressive load to specimens. The craniomedial band of the CCL, caudolateral band of the CCL, MCL, and LCL were sequentially transected; load application was repeated after each transection. Orthogonal force components were measured in situ. Forces on ligaments were calculated after repeated output force measurements as the contribution of each component was eliminated.

RESULTS

Increasing the compressive load increased tensile forces on the craniomedial and caudolateral bands of the CCL, but not on the MCL or LCL, in specimens of both groups. At the 60-N load, tensile force on the craniomedial band, but not other ligaments, was greater for the excessive TPA group than for the unchanged TPA group.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that stress on the CCL may increase when the compressive load increases. The TPA-increasing procedure resulted in increased tensile force on the CCL at a 60-N compressive load without affecting forces on the MCL or LCL.