Establishment of a rat model of chronic thoracolumbar cord compression with a flat plastic screw.

Previous studies of animal models of chronic mechanical compression of the spinal cord have mainly focused on cervical and thoracic lesions, but few studies have investigated thoracolumbar injury. The specific pathophysiological mechanism of chronic thoracolumbar cord injury has not yet been elucidated. The purpose of this study was to improve animal models of chronic thoracolumbar cord compression using the progressive screw. A custom-designed flat plastic screw was implanted in the spinal cord between thoracic vertebrae 12 and lumbar 1 of rats. The screw was tightened one complete turn (0.5 mm) every 7 days for 4 weeks to create different levels of chronic spinal cord compression. Following insertion of the screw, there was a significant decline in motor function of the hind limbs, and severe stenosis of micro-computed tomography parameters in the spinal cord. Cortical somatosensory evoked potential amplitudes were reduced remarkably, and latencies were prolonged at 30 minutes after surgery. The loss of motor neurons in the gray matter was marked. Demyelination and cavitation were observed in the white matter. An appropriate rat model of chronic thoracolumbar cord compression was successfully created using the progressive screw compression method, which simulated spinal cord compression injury.

[Treatment of infected total knee arthroplasty with a self-made, antibiotic-loaded cement articulating spacer].

OBJECTIVE: To study the efficacy of self-made, antibiotic-loaded cement articulating spacer in the treatment of infected total knee arthroplasty. METHODS: The self-made molds were used to form the spacer during the operation. From March 2002 to March 2007, 22 patients with infected knee arthroplasty (10 males with 10 knees, 12 females with 12 knees) were treated with this kind of spacer in our center. The mean age of the patients was 59.6 years old (33 to 75 years old). The interval time between primary arthroplasty and first onset of infective syndrome was 6.7 months (1 to 14 months). The diagnosis was established by the clinical presentation,serum laboratory inflammatory markers (white blood cell count,erythrocyte sedimentation rate and C-reactive protein) and knee aspiration. The serum laboratory inflammatory markers were used to measure the systemic response to infection. Clinical and radiographic follow-up was regularly performed by HSS score system and X-ray. RESULTS: All the patients were followed, the average interval between debridement and reimplantation was 4.7 months (3 to 9 months) and the infection control rate was 100% after the implantation of spacer. The average follow-up duration after reimplantation was 29.8 months (10 to 64 months) and there was no recurrence of infection at the latest follow-up. The HSS score increased from 40.5+/-5.9 to 65.8+/-7.5 after the implantation of spacer, furthermore, the score reached 88.7+/-5.1 in average at the latest follow-up. The patient satisfaction rate was 95.3%. CONCLUSION: This self-made molds and spacers is a reliable approach for the management of infected knee arthroplasty with some virtues, such as providing a mobile and functional joint through the treatment course, decreasing the difficulty of reimplantation, avoiding of a long-term post-operative infusion and high effective for eradicating infection.

Effect of low-energy shock waves in microfracture holes in the repair of articular cartilage defects in a rabbit model.

BACKGROUND: Microfracture is a type of bone marrow stimulation in arthroscopic cartilage repair. However, the overall concentration of the mesenchymal stem cells is quite low and declines with age, and in the end the lesion is filled by fibrocartilage. The aim of this research was to investigate a novel method of enhancing microfracture by determining whether low-energy shock waves in microfracture holes would facilitate cartilage repair in a rabbit model. METHODS: Full-thickness cartilage defects were created at the medial femoral condyle of 36 mature New Zealand white rabbits without penetrating subchondral bone. The rabbits were randomly divided into three groups. In experimental group A, low-energy shock-wave therapy was performed in microfracture holes (diameter, 1 mm) at an energy flux density (EFD) of 0.095 mJ/mm² and 200 impulses by DolorClast Master (Electro Medical Systems SA, Switzerland) microprobe (diameter, 0.8 mm). In experimental group B, microfracture was performed alone. The untreated rabbits served as a control group. At 4, 8, and 12 weeks after the operations, repair tissues at the defects were analyzed stereologically, histologically, and immunohistochemically. RESULTS: The defects were filled gradually with repair tissues in experimental groups A and B, and no repair tissues had formed in the control group at 12 weeks. Repair tissues in experimental group A contained more chondrocytes, proteoglycans, and collagen type II than those in experimental group B. In experimental group B, fibrous tissues had formed at the defects at 8 and 12 weeks. Histological analysis of experimental group A showed a better Wakitani score (P < 0.05) than in experimental group B at 8 and 12 weeks after the operation. CONCLUSIONS: In the repair of full-thickness articular cartilage defects in rabbits, low-energy shock waves in microfracture holes facilitated the production of hyaline-like cartilage repair tissues more than microfracture alone. This model demonstrates a new method of improving microfracture and applying shock waves in vivo. However, longer-term outcomes require further study.