A noninvasive laser-guided preincision localizer for spine surgery.

Abstract

The design and utilization of a novel device for noninvasive preincision localization of the target spine segment during lumbar spine surgery is presented. The device consists of 4 low-energy laser diodes, emitting planar beams, mounted around the perimeter of a ring at right angles to each other. The beams are used to align 2 radiopaque cables hanging off the sides of the patient with the target spine segment and the radiographic source and film. The performance of the device in guiding the placement of the skin incision was prospectively evaluated in 76 consecutive patients undergoing unilateral 1-level microsurgical lumbar laminotomy. Preincision lateral radiographs obtained with the device were compared with postincision localizing radiographs in all patients. In all patients, the location of the incision guided by the final preincision radiograph was found to precisely overlie the target segment as confirmed by a postincision radiograph, the latter obtained after exposure of the underlying laminae. In no instance was it necessary to extend the incision, modify the surgical trajectory, or repeat the postincision radiograph due to improper incision placement. The device's radiopaque cables were clearly visualized on radiography as they traversed the spine image, regardless of body mass index. The initial preincision radiograph based on the surgeon's estimate of the location of the target site localized the target segment in 58 patients (76.3%) and an adjacent segment in the remaining 18 patients (23.7%). Accuracy of the surgeon's initial estimate of the target site (but not accuracy of the device) was found to be inversely associated with body mass index (p < 0.001), thickness of the subcutaneous fat layer overlying the spine (p < 0.001), and presence of transitional lumbosacral anatomy (p = 0.03). The localization device presented herein provides accurate noninvasive localization of the target spine segment and guides precise placement of the incision over the target segment during lumbar spine surgery.