Comparison Of The Two Types Of Cages Used In Posterior Lumber Interbody Fusion For The Patients With Lumbar Spinal Stenosis

Objective:To compare the clinical effects of the nanohydroxyapatite/polyamide66 cages(n-HA/PA66 cages)or polyetheretherketone cages(PEEK cages)used in posterior lumber interbody fusion(PLIF)for the treatment of lumbar Spinal Stenosis.Methods:The study was divided into 2 parts.1.A retrospective and case-control study includes 57 patients who underwent PLIF with 2 n-HA/PA66 cages or PEEK cages of lumbar Spinal Stenosis from Jan 2014 to Dec 2017 in department of orthopaedics,the first affiliated hospital of Guangzhou university of Chinese medicine.The patients’ gender,age and bone mineral density were recorded before the operations.’hen,the patients’ visual analogue scale(VAS),the Oswestry Disability Index(ODI),Cobb angle,interspace height(IH)were recorded and compared after the treatments.2.With CT scans of the lumbar spine from LI to L5 of a healthy male,a finite element model(FEM)of the intact lumbar spine was created.In the FEM of the intact lumbar spine,the 8N/m flexion,extension,bending,rotation moment with a compressive preload of 400 N were respectively imposed on the superior surfaces of the L1 vertebral body in this study for validation of the model.The intact model was modified to simulate posterior lumbar interbody fusion with 2 n-HA/PA66 cages or PEEK cages.Then Stress of cage,stress of bone graft and stress of instrumentation were calculated and compared in two modified FEM after different loads respectively.Results:57 subjects with an average of 1-years of follow-up were included of whom 24 patients using n-HA/PA66 cages and 33 patients using PEEK cages.In n-HA/PA66 cage group,10 male and 14 female,the average age was 50.29±13.13y,the average follow up time was 11.75±1.39mon.There were 12 male and 11 female,the average age was 47.09±12.87y,tne average follow up time was 47.09±12.87mon in PEEK cage group.The preoperative bone mineral density,VAS,ODI,Cobb angle and IH of n-HA/PA66 cage group were-1.08±1.13,6.17±0.87,59.83±4.90%,14.26±5.29° and 10.85±2.83mm,while-1.43 ± 0.78,6.21±0.70,59.82±4.19%,16.57±6.47°,11.10±2.74mm in PEEK cage group,respectively.There was no significant difference in baseline data between the two groups(p>0.05).The postoperative VAS,ODI,Cobb angle and IH of n-HA/PA66 cage group were 3.17±0.64、51.67±2.55%,16.29±5.49°、12.91±2.11mm at 1 week and 3.36±0.70、50.94±2.09%、18.58±6.59°、12.46± 1.42mm in PEEK cage group,respectively.The postoperative VAS,ODI,Cobb angle,IH of n-HA/PA66 cage group were 2.17±0.76、29.42±7.77%、13.95±6.38°、12.08±3.24mm at 1 year and 1.79±0.74、24.97±9.58%、17.50±7.45°、11.54±1.42mm in PEEK eage group,respectively.At the final follow-up,the bony fusion rate was 91.67 and 90.90%for the n-HA/PA66 and PEEK groups,respectively,and the subsidence rate was 12.50 and 15.15%,respectively.There was no significant difference in preoperative sagittal parameters between the two groups(P>0.05).There was a significant difference in postoperative vs preoperative VAS and ODI of both two groups(p<0.05).A FEM of the intact lumbar spine and a FEM of PLIF with 2 n-HA/PA66 cages or PEEK cages were created.The ROM of FEM of the intact lumbar spine was consistent with the previous experimental results and FEM of the intact lumbar spine was valid.Then Stress of cage,stress of bone graft and stress of instrumentation were similar in two modified FEM after different loads respectively.Conclusion:The study suggested that n-HA/PA66 cages could promote effective clinical,radiographic outcomes and biomechanical outcomes when used to treat LSS,which is similar to PEEK cages for lumbar reconstruction after PLIF.