Long-term Follow-up Study Of Intervertebral Fusion Using Single B-twin Expandable Spinal Spacer Through Microendoscopic Approach For Degenerative Disc Disease

ObjectiveTo investigate long-term efficacy of interbody fusion using single B-Twin ESSthrough microendoscopic approach for degenerative disc disease.MethodsA retrospective analysis had been made on data of34cases or38disc levelsunderwent fusion using a single B-Twin ESS by a same surgeon from Feb.2007toJan.2010. Thirty four cases, including21male and13female whose age averaged43.9years(ranged from18to65years) presented with low back pain and unilateral orbilateral lower limb numbness and pain. The course of disease was from6monthsto30years with an average of50months. All patients underwent preoperativeevaluation involving radiography (anteroposterior, lateral, flexion-extension X-rayplain films), CT and magnetic resonance (MR) imaging. the height of disc and lumbarstability was measured in the corresponding level, JOA was scored before operation.Patients underwent anteroposterior, lateral, flexion-extension X-ray plain films at3months,6months,12months and last follow-up postoperatively, ifnecessary, review by CT scan, to ascertain the B-Twin ESS’ position and healing stateof graft. The improvement rate and effectiveness was calculated based on pre-andpost-operative JOA score. Analysis were made on changes of pre-and post-operativeJOA scores and the disc height. Healing state of the bone graft in the disc space wasevaluated by Suk’s criteria. ResultsNo patients were lost in the follow-up, the follow-up time ranged from38to64months and averaged50months. JOA score were11.5±3.2preoperatively and21.3±2.7at the first week postoperatively,26.3±1.7at last follow-up, respectively.There was statistical significance between preoperative and all the postoperative JOAscores (P <0.05), and no significant difference between the last follow-up and12months postoperatively (P＞0.05). Significant improvement after surgery had beenshown in34patients with JOA improvement rate ranging from65%to96%andaveraged85%. The effectiveness according to JOA scoring at last follow-up, wereexcellent in30cases (88.2%),good in4(11.8%), the rate of excellent and good was100%.The average disc height were9.7±1.4mm preoperatively, and11.5±1.4mm at1week,9.9±1.3mm at6months postoperatively and9.5±1.4mm at final follow-up,respectively. There was statistical significance between preoperative disc height anddisc height at3months postoperatively(P <0.05), and no significantdifference between preoperative disc height and disc height at6monthspostoperatively (P＞0.05). At last follow-up, fins broken was found in6case, andsubsidence more than3mm in5cases and loose and displacement more than3mm outof the posterior edge of vertebral occurred in2cases, disc height loss morethan1.5mm was found in3cases, but all of these cases were symptom free. Adjacentdegeneration was found in2cases, one of whom needed decompression and pediclescrew fixation; the other was treated with conservative treatment. Solid unionoccurred in16cases (42.1%) and probable union in22cases (57.9%), non-union wasfound in none of all the cases by Suk’s criteria at final follow-up.Conclusion1. The long-term efficacy was satisfied in terms of pain relieve with the treatmentfor lumbar degenerative disease with fusion using single B-Twin ESS throughmicroendoscopic approach, which meet the needs of minimally invasive treatment,but the occurrence of fins broken, loosening and subsidence were relatively high. Thedesign of spacer and the solid fusion rate were needed to be improved.2. The combination of decompression microendoscopically and fixation withB-Twin expandable spacer may serve as an ideal minimally invasive procedure for decompression and fusion, and further research is needed.