Material and functional properties of articular cartilage and patellofemoral contact mechanics in an experimental model of osteoarthritis
Introduction
It is generally accepted that tissues of the musculoskeletal system adapt to changes in the mechanical environment (Taber, 1995). These adaptations have been best quantified in bone (Carter, 1987; Cowin, 1986; Goldstein et al., 1991; Huiskes et al., 1987) and skeletal muscle (Booth, 1982; Goldberg et al., 1975; Simard et al., 1982; Tabary et al., 1972; Vandenburgh, 1982). However, the relationship between mechanical (stress–strain) state of tissue and its growth and remodelling is largely unknown.
Articular cartilage is thought to adapt to changes in its mechanical environment (Adams, 1989; Brandt et al., 1991; Jurvelin et al., 1986; Setton et al., 1994). Perturbations of the joint mechanics through surgical removal of the anterior cruciate ligament (ACL), meniscectomy, or resection of the tibial plateau in the knee of experimental models of joint injury have been shown to produce osteoarthritic changes in the articular cartilage (McDevitt et al., 1977; Moskowitz et al., 1979; Pond and Nuki, 1973). However, the changes in the in situ mechanical properties of the articular cartilage in these joint injury models are largely unknown. Furthermore, changes in the functional properties of the joint (e.g., load transmission) associated with the alterations in cartilage properties have not been determined to date.
The purposes of this study were (1) to determine the in situ functional and material properties of articular cartilage in an experimental model of joint injury; and (2) to quantify the corresponding in situ joint contact mechanics. The cat ACL-transected knee was chosen as the experimental model (Herzog et al., 1993). Measurements in the experimental knee were made 16 weeks following ACL transection; a time when biochemical and morphological changes have occurred in the articular cartilage. Reference measurements were made in the corresponding intact, contralateral knee. It is realized that the contralateral knee may have been affected by the intervention in the experimental knee, and thus, may not represent a ‘normal’ control. However, this design approximates best the injury scenario in humans in which ACL tears typically occur unilaterally.
Section snippets
Animals and surgery
All experimental measurements were performed in adult, outbred cats (mass>3.5 kg; ). The anterior cruciate ligament was transected in the left knee using an arthroscopic approach performed by a trained clinician while the animal was deeply anesthetized (Halothane). The right knee was left intact. Following surgery, ACL transection was functionally verified using an anterior drawer test, and was further verified following sacrifice. All experimental aspects of this study were approved by the
Gross morphology
Inspection of the experimental knees revealed that all ACLs had been cut completely except for one animal in which about 25% of the ACL had been left intact. The results of this animal did not differ from the remaining animals, thus no further distinction will be made. It should be noted though, that a partial ACL transection appeared to have similar effects on cartilage growth and remodelling, as well as on patellofemoral contact properties as a complete transection.
The experimental knees
Discussion
Anterior cruciate ligament transection has been shown to lead to complete erosion of the articular cartilage in the dog knee (Brandt et al., 1991). Our work in the ACL-transected cat shows that articular cartilage growth and remodelling is similar to that observed in the dog (Herzog et al., 1993). In the early stages of adaptation following ACL transection, canine articular cartilage has been shown to increase in thickness (Adams, 1989), and its elastic modulus and permeability (Setton et al.,
Acknowledgments
This study was supported by the Medical Research Council and The Arthritis Society of Canada.
References (34)
- et al.
An asymptotic solution for the contact of two biphasic cartilage layers
Journal of Biomechanics
(1994) Mechanical loading history and skeletal biology
Journal of Biomechanics
(1987)- et al.
Trabecular bone remodelingan experimental model
Journal of Biomechanics
(1991) - et al.
A preliminary study of hindlimb loading, morphology and biochemistry of articular cartilage in the ACL-deficient cat knee
Osteoarthritis and Cartilage
(1993) - et al.
In-situ calibration of the implantable force transducer
Journal of Biomechanics
(1996) - et al.
A system for studying the mechanical properties of muscles and the sensorimotor control of muscle forces during unrestrained locomotion in the cat
Journal of Biomechanics
(1995) - et al.
Adaptive bone-remodelling theory applied to prosthetic-design analysis
Journal of Biomechanics
(1987) - et al.
Contractile properties of rat hind limb muscles immobilized at different lengths
Experimental Neurology
(1982) - et al.
Knee muscle moment arms from MRI and from tendon travel
Journal of Biomechanics
(1992) Dynamic mechanical orientation of skeletal myofibers in vitro
Developmental Biology
(1982)