A new triggered electromyography test for detection of stimulus diffusion to intercostal muscles of the contralateral side during thoracic pedicle screw placement was evaluated. Experimental research was carried out in order to determine if, using this test, neural contact at different aspects of the spinal cord and nerve roots could be discriminated. Nine industrial pigs (60–75 kg) had 108 pedicle screws placed bilaterally in the thoracic spine (T8–T13). Neural structures were stimulated under direct vision at different anatomic locations from T9 to T12. Recording electrodes were placed over the right and left intercostal muscles. Increasing intensity of the stimulus was applied until muscle response was detected at the contralateral side (diffusion phenomenon). After this first experiment, the thoracic spine was instrumented. Screws were placed in the pedicle in two different positions, the anatomic intrapedicular location and with purposeful contact with the neural elements.Introduction
Methods
Various studies have demonstrated that menisci heal in the vascular region but do not heal in the avascular area. Experimental studies of the promotion of meniscal healing in the avascular area have involved the application of fibrin clot, fibrin glue to the injured area, as well as the construction of an access chanel to the vascular regiòn, all of them with poor results. The multilineage potential of adult stem cells has been characterized extensively. The adipose tissue has been described as a useful source of adult stem cells. We try to show that the use of stem cells from the adipose tissue may promete meniscal healing in the avascular area. Twelve New Zealand white rabbits with a mean weight of 3 kg were used. The medial meniscus of both knees was aproached, and was performed a longitudinal tear in the avascular area in the anterior horn with a mean length of 0.5 cm. All the tears were sutured with one vertical stitch of nonabsorbable suture. In each rabbit a solution with 1 00 000–1 000 000 stem cells from the fat was introduced in one of the knees, and the other one was used as a control. The rabbits were killed at 12 weeks, and a macro-microscopic study of the meniscus was done, and also a inmunohistochemistry study for the stem cells. The incidence of healing was better in those menisci with the stem cells solution. Three total and three partial healing was obtained in the stem cells group and none in the control group. The inmunohistochemistry showed that the stem cells were in the repair zone. We think that stem cells will be very useful in the treatment of the lesion in the avascular area of the meniscus.