The Feasibility Of The Local Granular Autogenous Bone Of Interlaminar Fenestration Application In PLIF

Objective:To discuss the clinical feasibility of using the local granularautogenous bone of interlaminar fenestration and one cage with pedicle screwinstrumentation in PLIF. Methods：From January2011to December2012, theinterverterbal fusion using the local granular autogenous harvested from laminaand facet bone of interlaminar fenestration was accomplished in the Departmentof Spinal Surgery, Affiliated Hospital of Luzhou Medical College.There were107cases（52males and55females） with an average age of26to75(mean,52.8±9.0) years. There were31cases of lumbar disc herniation（LDH）,25casesof lumbar spinal stenosis（LSS）,19cases of lumbar spondyloschisis or withspondylolisthesis within II degrees（LS）,19cases of degenerative lumbarinstability syndrome（DLIS）, and13cases of discogenic low back pain（DLBP）.The cases had an average medical history of2to240（mean，69.9±70.7）monthsand there were49cases under50years old and58cases aged50and over.Unilateral interlaminar fenestration at one segment was looked as a fenestrationunit.92cases were operated with one segment and unilateral interlaminarfenestration. There were52cases at L4/5segment，including30units on the leftand22units on the right and40cases at L5S1segment，including19units on theleft and21units on the right.9cases were operated with one segment andbilateral interlaminar fenestration. There were4cases at L4/5segment，including 5units on the left and3units on the right and5cases at L5S1segment，including6units on the left and4units on the right.6cases were operated with the twosegments and bilateral interlaminar fenestration，including4units on the left and2units on the right at L4/5and3units on the left and3units on the right at L5S1.There were113segments fused and122fenestration units. The quantity andvolume of the local decompressed bone of every fenestration unit were measuredand the type of cage used intraoperative were recorded. The height of lumbarvertebral space is that of the cage recorded. The contact surface area between thegraft and the endplate and the area of endplate were measured by the computedtomography (CT) scan postoperative, by which the ratio of the two areas wascomputed. To reache30%of the contact surface area between the graft and theendplate needs the quantity and volume of bone were estimated in these casesstudied. Serial dynamic radiological X-ray follow up were done at3,612and24months, through which the status of fusion was estimated by the criteria of SUK.The CT scan was done if it hadn’t reached bony fusion or had been suspected bythe dynamic radiological X-ray at12months postoperative. The clinical effectwas evaluated at2weeks,3,6and12months by Visual Analogue Score (VAS)and Japanese Orthopedic Association（JOA）score. All the data was analyzed bystatistical package of SPSS11.5. Results： All patients were managedsuccessfully. Five patients showed the nerve root edema symptom on the leg ofdecompressed lateral,3cases showed transient muscle weakness,3cases showeddeep venous thrombosis of lower limb and7cases showed theleakage of cerebrospinal fluid after3to5days postoperative. No one showed infection of operative incision. The mean quantity and volume of the localdecompressed bone of one fenestration unit available were2.8-4.4g (mean，3.7±0.3g) and2.6-4.2cm3(mean,3.1±0.3cm3). There showed no statisticallysignificant differences compared in the quantity and volume available of the twosegments of L4/5and L5S1segment (p＞0.05). The quantity and volume availableat the fenestration unit of the different diseases showed no statistically significantdifferences. The area of the endplate measured by CT scan postoperative was592-977mm（2mean,777.4±73.9mm2）in the intervertebral space fused. The areashowed no statistically significant differences at the L4-5and L5S1segment(p＞0.05). The contact surface area between the graft and the endplate was419-654mm2(mean，519±42.3mm2) of these cases studied, including the part of Cage.The ratio of the contact surface area to the endplate was55.7-74.9percent(mean,66.9±4.3percent).There was no statistically significant differencescompared in the two segments about the ratio(p＞0.05). The area of cross sectionof the Cage was200mm2measured by the sample. The percentage of autogenousbone contact face to endplate was32.6-49.4percent (mean，41.0±3.7percent),excluding the Cage. The quantity and volume available were2.8-4.4g(mean,3.7±0.3g) and2.5-3.9cm3(mean,3.1±0.3cm3) in the cases younger than50years,and were2.8-4.8g（mean,3.8±0.3g），2.6-4.3cm3（mean,3.1±0.4cm3）in the cases50years old and over,but there showed no statisticallysignificant of the two groups divided by age.(p＞0.05). The height of Cage was8-12mm（mean,10.4±1.2mm）of the113interspaces recorded intraoperative. Theendplate area of the6mm behind the disc was measured. To reach30percent area of the endplate needs the volume and quantity were2.5cm3and3.0g by datastudied and the method of fusion. The VAS and JOA scores showed better inclinical symptoms obviously according the94cases followed up12-36months（mean,24.3±5.9months）postoperative. The scores showed statisticallysignificant between preoperative and postoperative（p＜0.05）. The VAS and JOAscores showed no statistically significant between unilatera fenestration andbilateral in the cases（p＞0.05）.The total improvement rate of JOA scores was65-100percent（mean,82.5±7.5percent）at the12months postoperative.Therewere85cases showed continuous bone trabeculae at the fusion area and theactivity less than4degrees between the vertebral bodies by dynamic x-raypicture. The fusion rate was92.9percent in the vertebral bodies. There showedno loosening and breakage of instrumentation and subsidence of the Cage.Conclusion：The difference of volume and quantity available are not obviouslyin the cases of different diseases, ages or genders at L4/5or L5S1segment inunilateral fenestration in PLIF.The the volume and quantity of every fenestrationunit were3.7g and3.1cm3. It is feasible using local granular autogenousharvested from lamina and facet bone of the unilateral interlaminar fenestrationand one cage of nanometer with pedicle screw instrumentation in PLIF. To reach30percent area of the endplate needs the volume and quantity were3.0g and2.5cm3. It is easy to estimate the volume of bone available using a5ml disposablesyringe intraoperative. The percentage of autogenous bone contact area toendplate was41.0percent using the bone available in the method of unilateralinterlaminar fenestration and one Cage in PLIF.