Minimally Invasive Surgery For Direct Repair Of Lumbar Spondylolysis By Utilizing Intraoperative O-arm Based Navigation And Microendoscopic Techniques

Background Lumbar Isthmus is the connection between the superior and inferior articular process.It is a vulnerable part of the bone structure for lumbar vertebral support.Under normal condition,lumbar isthmus is a continuous bone structure.However,congenital and acquisitus conditions may cause disturbance to the continuity of lumbar isthmus.Clinically this discontinuity is named lumbar spondylolysis,which is commonly seen in general population.6% of the people who suffer from lumbar pain have spondylolysis.The incidence of this disease is up to 20% among young athletes.After the discontinuity of the lumbar isthmus occurred,the stress from supporting the spine will be concentrated at the intervertebral disc,which accelerates disc degeneration.With severe degeneration the lesion segment of the upper vertebral moves relatively forward and forms lumbar spondylolisthesis.This may cause neurological symptoms of the lower limb and raise the need for surgical intervention.Lumbar fusion could be an early surgical treatment option for lumbar spondylolysis.While being clinically proved effective,lumbar fusion surgery may bring side effects to the patient,such as partially limited motion of lumbar spine and adjacent vertebral disease,etc.The effectiveness to risk ratio of lumbar fusion surgery is fairly low,especially for younger patients or those who only have a mild degree of intervertebral disc degeneration.Therefore,scholars have invented a method in order to repair the lumbar isthmus directly.This method effectively reduces the side effects brou ght by the lumbar fusion surgery.However,all of the traditionally surgical procedures have the disadvantage of large surgical trauma and prolong postoperative recovery.Therefore,we introduce the concept of minimally invasive therapy in order to achieve better results.Objective To perform intralaminar screw direct repair of spondylolysis by using O-arm based navigation and microendoscopy,and to analyze the effectiveness and safety of minimally invasive technique for lumbar spondylolysisMethods Between February 2012 and May 2014,11 patients with lumbar spondylolysis were treated by Buck’s procedure with the aid of intraoperative O-arm based navigation and minimally invasive approach.The debridement and autograft of pars interarticularis defects was performed under microendoscopy.Among the 11 patients,7 were males and 4 were females.The average age of the patients was 28.4 years old(range: 19 to 47 years old).The average duration of their disease was 10.5 months(range: 8-23 months).No nerve symptom or sign of lower limb was observed.The radiological examinations showed single level bilateral lumbar spondylolysis without obvious disc degeneration,lumbar instability,or spondylolisthesis.Isthmic injury located at L4 in 2 cases and at L5 in 9 cases.Of the 11 patients,7 were rated as grade 2 disc degeneration,and 4 as grade 3 disc degeneration according to the modified Pfirrmann classification system.The operation time,intraoperative blood loss,and complications were recorded.The fluoroscopic examinations were performed to assess defect repair and screw position.Visual analogue scale(VAS)score was used to evaluate the improvement of low back pain.Results The average operation time was 147.6 minutes(range,126-183 minutes).The average blood loss was 54.9 mL(range,40-85 mL).Primary healing of incision was obtained.There was no complication of nerve root injury,dural tear,or infection.Three patients had pain at donor site postoperatively,and pain disappeared within 3 weeks.The average follow-up duration was 15.7 months(range,10-23 months).VAS score of low back pain was significantly decreased from preoperative 7.1±2.3 to 1.8±0.4 at last follow-up(t=13.42,P=0.01).Of the 22 isthmic bone grafting,bilateral isthmic bony fusion was achieved in 7 patients and unilateral isthmic bony fusion in 3 patients between 6-10 months(mean,7.9 months).One patient failed bilateral isthmic bony fusion,and had bony resorption.Conclusion Debridement,autograft,and percutaneous intralaminar screw fixation by microendoscopy and O-arm based navigation may provide safe and effective treatment for spondylolysis.Minimally invasive direct repair can obtain satisfactory clinical outcome.