PEEK versus Silicon Interspinous Spacer forReduction of Supradjacent Segment Degeneration followingDecompression and Short-Segment Instrumentation forDegenerative Lumbar Spinal Stenosis

A retrospective study that aims to report Adjacent Segment Degeneration (ASD) incidence and spinopelvic balance inshort lumbosacral instrumentation for degenerative lumbar spinal stenosis. Although ASD is a common complication followinglumbar fusion, the effect of an interspinous spacer (IS) in the supradjacent segment in short lumbosacral instrumented fusionand its interaction with spinopelvic balance has not been studied adequately.Methods. From 55 consecutive age-, diagnosis-, andgender-matched patients aged 60±11 years, 17 (Group R) received PEEK IS; 18 (Group S) received Silicon IS compared with 20controls (Group C) without receiving any IS. The functional outcome was evaluated with VAS and ODI. Spinopelvic balance wasevaluatedusing SVA,T12-S1LL, SS, PT, PI, and supradjacent segmentdisc heights.All spines were preoperatively balanced (SVA<40mm).Results.The follow-up averaged out to 56±11 months. VAS and ODI scores improved postoperatively in all 3 groups. SS andanterior disc height in the supradjacent free segment increased postoperatively compensatory to spinal alterations. Although 6, 4,and 5 patients from Groups R, S, and C, respectively, showed radiological progression of the preoperative degeneration grade in thesupradjacentdisc,only2,1,and2patientsinGroupsR,S,andC,respectively,developedsymptomaticASDinthe1stsupradjacentsegment solely. No additional surgery was required in any patient.Conclusion.ASD incidence in the supradjacent segment followingshort lumbar fusion did not statistically significantly differ between PEEK and Silicon IS. There was a trend towards lower ASDincidence in Silicon IS. IS reduced ASD in both1stand2ndsupradjacent segments. The authors speculate that soft stabilizationprovided by IS may be more advantageous for preventing ASD. This trial is registered withClinicalTrials.govNCT03477955