Objective. It is currently unknown whether human cartilage properties change during short periods of partial load bearing. We used a post-ankle fracture model to explore whether changes in cartilage morphology occur in the knee under conditions of partial load bearing.Methods. The knees of 20 patients with Weber type B and type C fractures were examined using magnetic resonance imaging. The first scan was obtained shortly (mean ؎ SD 3.2 ؎ 3.0 days) after the injury, and a second scan was obtained 7 weeks later (mean ؎ SD 50.7 ؎ 5.5 days). The morphology (mean and maximum thickness, volume, and surface area) of the patellar, tibial, and femoral cartilage was determined from coronal and axial magnetic resonance images (fat-suppressed gradient-echo).Results. Between week 0 and week 7, the crosssectional area of the quadriceps muscle was reduced by 11% (P< 0.001). Changes in the mean (؎SD) cartilage thickness ranged from ؊2.9 ؎ 3.2% in the patella to ؊6.6 ؎ 4.9% in the medial tibia. No significant change in cartilage morphology of the contralateral knee was observed.
Conclusion.Results of this study demonstrate that in a post-ankle fracture model of partial load bearing, cartilage morphology in all knee compartments is subject to significant change. Changes in the femorotibial joint exceeded those in the patella, whereas no change was observed in the contralateral knee. These findings raise the question of whether cartilage is mechanically less competent and particularly vulnerable after states of partial or complete immobilization.Quantitative magnetic resonance imaging (MRI) is a novel, but established, technique for studying cartilage morphology under physiologic and pathophysiologic conditions (1-5). Recent studies have shown that cartilage thinning occurs during aging (4), in osteoarthritis (OA) (2,6,7), after partial meniscectomy (8), and after spinal cord injury (3,9). Results from animal models have shown that cartilage morphology, composition, and mechanical properties are subject to change during immobilization (10). However, it is as yet unknown whether changes occur in human cartilage during short periods of immobilization or partial load bearing. Such information is important in the postoperative management of OA and in the context of space travel (i.e., when astronauts return to normal gravity conditions after long-term space flight). The relevant question here is whether or not cartilage properties change under conditions of partial load bearing, and, supposing that such changes do occur, whether cartilage is vulnerable to injury when normal load-bearing conditions are reestablished.In this study, we made use of the fact that patients who have undergone operative treatments of ankle fractures are subject to a 7-week period of partial load bearing. We explored the extent to which the cartilage morphology of the ipsilateral knee changed during the postoperative period in relation to the loss of cross-sectional area of the quadriceps muscle.
Bone reconstruction after resection of malignant bone tumors of the lower extremity in children and adolescents remains a challenge in limb-sparing surgery. Equal limb length at maturity and good functional outcome are the main goals of these surgeries but often are difficult to achieve. Expandable endoprostheses are available but usually require repeated operative interventions for lengthening. Moreover, as the size of the implant increases, the proportion of the implant relative to the remaining bone increases, generating a biomechanical disadvantage to the limb. The authors describe a new concept combining an endoprosthesis with a fully implantable motorized distraction nail that can be activated in gradual steps to lengthen the remaining bone by callus distraction. New high-quality bone is growing and the proportion of prosthesis length compared with leg length develops in favor of the remaining bone.
We report the case of a 22-year-old woman who underwent plate and screw fixation for a traumatic left acetabular fracture and fixation with cancellous screws for an associated femoral neck fracture. Two months later, the internal fixation became infected and was removed. This resulted in a painful high dislocation of the hip. We solved the problem with continuous soft-tissue distraction using a fully implantable motorised distraction nail in order to reduce the proximal femur prior to total hip arthroplasty. To our knowledge, this is the first time that reduction of a high dislocation of the hip has been performed using such a system.
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