Study on Effects of Bipolar Coagulation on the Swine Spinal Cord: A Histological, Thermal, and Electrical Current Analysis

BACKGROUND AND OBJECTIVE: In spinal surgery, bipolar electrosurgery requires balancing effective hemostasis with the risk of neural injury. No study has systematically correlated electrical current parameters, forceps tip temperature, and histological spinal cord injury under controlled experimental conditions, leaving evidence-based guidelines for safe bipolar use in spinal neurosurgery undefined. The objective was to quantify the relationships among applied energy, cord surface temperature, and histological injury, and to identify a temperature threshold that achieves effective hemostasis with minimal injury. METHODS: Eight adult swine underwent thoracolumbar laminectomy and durotomy. Bipolar coagulation of dorsal pial (spinal cord surface) vessels was performed using standardized forceps (3-mm intertip distance) at power settings of 10, 30, and 40 W and durations of 2 to 8 seconds, without saline irrigation. Surface temperature was measured using infrared thermography. A blinded pathologist assessed 45 spinal cord segments (29 coagulated, 16 controls). Linear regression related power, time, applied energy (total energy delivered per site, J = W × s), and temperature to lesion dimensions. Coagulation was rated effective when bleeding ceased and the target vessel was occluded. RESULTS: Applied energy was strongly associated with peak temperature (R2 = 0.670, P < .001), whereas power and time alone were not. Lesion area correlated with temperature (R2 = 0.390, P = .004), energy (R2 = 0.364, P = .006), and power (R2 = 0.280, P = .020), but not with time. Lesion extension correlated with temperature (R2 = 0.546, P < .001) and energy (R2 = 0.345, P = .008), whereas lesion depth showed no significant associations. Effective coagulation occurred at higher temperatures than ineffective coagulation (median 43.5 vs 37.6°C, P = .001). CONCLUSION: Applied energy is the primary determinant of thermal and histological effects during bipolar coagulation. A surface temperature near 40°C-approximately 40 J at the geometry tested-is a practical threshold for effective hemostasis with limited superficial injury, although deeper effects may depend on current propagation and the neurological consequences of these lesions were not assessed.