Objective: To investigate the safety and clinical efficacy of "zoning" style
laminectomy by ultrasonic bone curette in patients with severe thoracic ossification of the ligamentum flavum(TOLF). Methods: The clinical data of 36 patients with severe TOLF treated by "zoning" style
laminectomy at Department of Spinal Surgery,Zhengzhou Orthopaedic Hospital from October 2015 to October 2018 were respectively analyzed.There were 17 males and 19 females,aged(57.3±10.2)years(range:43 to 80 years).According to the anatomical characteristics of the thoracic ligamentum flavum and the pathological process of ossionization,each
decompression segment was divided into the upper 1/3 area of the lamina,the bilateral area of the ossionum flavum,the transitional area,and the area of close contact between the ossionum flavum and the spinal cord.Different surgical strategies were used for
decompression in turn.The modified Japanese Orthopedic Association (mJOA) was used to evaluate the neurological function status before and after surgery,to evaluate the surgical effect of patients,and to observe the surgical complications.Paired sample T test was used for data analysis. Results: All 36 patients successfully completed the operation,the operation time was (88.6±24.6) minutes(range:60 to 150 minutes).The intraoperative blood loss was (426.7±167.4) ml(range:250 to 800 ml).Follow-up time was (27.2±7.7) months(range:12 to 48 months).The mJOA score at the last follow-up was 9.0±1.5,which was statistically significant compared with the preoperative score 5.4±1.8 (t=13.59,P<0.01).The improvement rate of mJOA score was (65.7±22.1) %,of which 17 cases were excellent (47.2%),13 cases were good (36.1%),4 cases were normal (11.1%),2 cases were ineffective (5.6%).Ten patients had
cerebrospinal fluid leakage during the separation or removal of dural ossification and were cured after a series of comprehensive
conservative treatment.Two patients showed transient neurological deterioration,and the neurological function gradually recovered to the preoperative state after comprehensive treatment such as increasing the mean arterial pressure and using neurotrophic drugs.During the follow-up,no aggravation of neurological dysfunction and segmental
kyphosis were found. Conclusions: The ultrasonic bone curette-assisted "zoning" style
laminectomy for the treatment of severe TOLF can directly observed the position relationship between ossification of the ligamentum flavum and the spinal canal structure during the operation,and accurately guide the
surgical decompression.It has the advantages of safe operation and complete
decompression,which provides an important reference for the selection of clinical surgery.