Objective To investigate the surgical technique and efficiency of the "Cave-in" 360°circumferential decompression for thoracic spinal stenosis(TSS)with ossification of posterior longitudinal ligament(OPLL).Methods From October 2005 to October 2009,26 TSS cases with OPLL were surgically treated,including 17 males and 9 females.Nineteen cases had upper thoracic spinal stenosis(T1-4)with OPLL,while 14 of them also had ossification of ligamentum flavum(OLF).All the other 7 cases had middle and/or lower(T5-12)TSS with both OPLL and OFL.All patients had severe spinal cord compression,and preoperative Frankel Grade was B in 6 cases,C in 13 cases and D in 7 cases.All these cases were surgically treated by 360° circumferential decompression("Cave-in" technique).Firstly,posterior wall was removed to decompress thoracic spinal cord.Secondly,the residual facets and pedicles were removed and posterior 1/3 of vertebral cancellous bones were cut along pedicles at 60° angle inclination to make a "culvert".Finally,the culvert walls were pressed to collapse and the OPLL blocks were removed to achieve ventral decompression.Pedical screw fixations were performed in all patients.Results All cases had immediate postoperative neurological improvement except 2 who experienced transient postoperative neurological deterioration for 13-27 days.At the end of 6-30 months follow-up,all these patients had neurological improvement.At the last follow-up,Frankei Grade was C in 2 cases,D in 15 cases and E in 9 cases.Conclusion This "Cave-in"360° circumferential decompression removes ventral and dorsal spinal compression from the posterior approach in TSS cases.It is a direct decompression procedure,which reduces the rate of postoperative paralysis.