Use of an Ultrasonic Osteotome for Direct Removal of Beak-Type Ossification of Posterior Longitudinal Ligament in the Thoracic Spine

Abstract

Direct removal of beak-type ossification of posterior longitudinal ligament at thoracic spine (T-OPLL) is a challenging surgical technique due to the potential risk of neural injury. Slipping off the cutting surface of a high-speed drill may result in entrapment in neural structures, leading to serious complications. Removal of T-OPLL with an ultrasonic osteotome, utilizing back and forth micro-motion of a blade rather than rotatory-motion of drill, may reduce such complications. We have applied the ultrasonic osteotome for posterior circumferential decompression of T-OPLL for three consecutive patients with beak-type OPLL and have described the surgical techniques and patient outcomes. The preoperative chief complaint was gait disturbance in all patients. Japanese orthopedic association scores (JOA) was used for functional assessment. Scores measured 2/11, 5/11, 2/11, and 4/11 for each patient. The ventral T-OPLL mass was exposed after posterior midline approach, laminotomy and transeversectomy. The T-OPLL mass was directly removed with an ultrasonic osteotome and instrumented segmental fixation was performed. The surgeries were uneventful. Detailed surgical techniques were presented. Gait disturbance was improved in all patients. Dural tear occurred in one patient without squeal. Postoperative JOA was 6/11, 10/11, 8/11, and 8/11 (recovery rate; 44%, 83%, 67%, and 43%) respectively at 18, 18, 10, and 1 months postoperative. T-OPLL was completely removed in all patients as confirmed with computed tomography scan. We hope that surgical difficulties in direct removal of T-OPLL might be reduced by utilizing ultrasonic osteotome.

Keywords: Beak; Ossification of posterior longitudinal ligament; Osteotome; Surgery; Thoracic spine; Ultrasound.

Fig. 1. Ultrasonic osteotome. Various kinds of tips could be attached to the hand piece according to the purpose of surgery (A). The blade (B, left) was used for laminotomy and shaving tips (B, middle and right) were preferentially used in direct removal of ossified mass.

Fig. 2. A : The lamina was gradually cut with ultrasonic osteotome by slight pushing down its blade against lamina with a vertical motion (right blade). When inner cortical bone was cut, loss of resistance was felt (left blade) and the ostetome was not inserted beyond the depth. Then the ostetome was moved cranially and caudally along the lamina for laminotomy. B : After laminotomy, facetectomy and pediclectomy, ossification of posterior longitudinal ligament (OPLL) mass was exposed under the dura (white broken line). The ultrasonic osteotome was inserted at the base of OPLL mass and moved gradually along the OPLL mass (white curved arrow). Note that nerve root was retracted with the shaft of ultrasonic osteotome. Because the energy was not transmitted from the shaft, the osteotome could be inserted at the base of OPLL mass while retracting nerve root.

Fig. 3. Case 3. Sagittal magnetic resonance (MR) T2-weighted imaging (A), sagittally reconstructed (B), axial (C) and 3-D (D) computed tomography (CT) scan showed beak-type ossified posterior longitudinal ligament (OPLL). The level of the axial scan was marked in sagittal CT scan with a black line. Postoperative sagittally reconstructed CT scan (E) showed complete removal of OPLL mass (F, white line in E), but a small fragment was left at T7 (G, arrow, black line in E). A 3-D reconstructed CT scan showed instrumentation, removal of OPLL (H, arrow) and laminoplasty with miniplate (I).

Fig. 4. Case 4. Sagittal magnetic resonance (MR) T2-weighted imaging (A), sagittally reconstructed (B), and axial (C) computed tomography (CT) scan showed beak-type ossified posterior longitudinal ligament (OPLL). Postoperative sagittal MR imaging (D) and sagittal (E) and axial CT scans (F) showed complete removal of T-OPLL mass. The laminoplasty was performed with translaminar screws (G).