Physiological and mechanical adaptation of periarticular cancellous bone after joint ligament injury.

The relation between blood flow and bone mineral density (BMD) of periarticular bone was examined in an in vivo model of joint instability. Eighty mature New Zealand White rabbits were randomly assigned to experimental [anterior cruciate ligament transection (ACLX)], sham-operated control, or age-matched normal control groups. Experimental rabbits underwent unilateral transection of the right anterior cruciate ligament, and the nonoperated left [contralateral (Cntra)] limb was a within-animal control. BMD and blood flow to the periarticular bone in the femoral condyles were assessed in each group at 2, 4, 6, 14, and 48 wk postsurgery, using quantitative computed tomography scanning and entrapment of colored microspheres. BMD was significantly lower (5%) in the ACLX compared with Cntra limbs. Periarticular bone blood flow in the ACLX limbs was significantly greater than in the Cntra limb (29%) in the early stages (6 wk) after injury. Up to 48 wk post-ACLX, a significant correlation was found between increased blood flow and decreased BMD in the periarticular bone of the femoral condyles in the ACLX limbs. This correlation suggested that heightened blood flow may be linked to mechanisms of bone adaptation in joints after ligament injury.

Early regional adaptation of periarticular bone mineral density after anterior cruciate ligament injury.

The present study measured early-stage adaptation of bone mineral (BMD) in the periarticular cancellous bone of the canine knee (stifle) joint after anterior cruciate ligament (ACL) transection (ACLX). Regional changes in BMD in the tibia and femur were analyzed by using quantitative computed tomography (qCT) at 3 wk and 12 wk after unilateral ACLX to determine whether there were focal points for BMD changes and whether these changes occurred early after the induced knee injury. BMD decreased rapidly after ACLX, and the more pronounced response was in the femur. In the 3-wk group, there were decreases in BMD in the tibia and the femur, and these changes were significant in the posterior-medial region of the femur, which showed a decrease of BMD in the ACLX limb (-0.048 +/- 0.011 g/cm(3)). In the 12-wk group, all regions in the tibia and femur exhibited significant decreases in BMD, and the average decrease was greatest in the posterior-medial region of the femur (-0.142 +/- 0.021 g/cm(3)). The regions of pronounced periarticular cancellous BMD adaptation corresponded to observed focal cartilage defects. Early decreases in BMD in the injured knee may be related to altered loading and kinematics in the knee and may be an important link in the pathogenesis of posttraumatic osteoarthritis.

H magnetic resonance imaging of rigid polymeric solids.

Implementation of the 1H magnetic resonance single-point imaging technique has provided new opportunities for the direct imaging of rigid solids, particularly semicrystalline polymers with spin-spin relaxation times, T2*, of the order of 10 microseconds and greater. Potential applications of industrial relevance in the following areas are briefly discussed and illustrated: fabricated/processed parts, photochemical degradation, oxidation, and blend characterization.