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J Korean Neurosurg Soc. 2018 Nov;61(6):680-688. doi: 10.3340/jkns.2018.0023. Epub 2018 Oct 30.

Bone-Preserving Decompression Procedures Have a Minor Effect on the Flexibility of the Lumbar Spine.

Author information

1
Department of Neurosurgery, Humanitas Clinical and Research Center, Rozzano, Italy.
2
LaBS, Department of Chemistry, Material and Chemical Engineering, Politecnico di Milano, Milano, Italy.
3
Institute of Orthopaedic Research and Biomechanics, Trauma Research Centre Ulm, Ulm University, Ulm, Germany.
4
IRCCS Galeazzi Orthopedic Institute, Milano, Italy.

Abstract

OBJECTIVE:

To mitigate the risk of iatrogenic instability, new posterior decompression techniques able to preserve musculoskeletal structures have been introduced but never extensively investigated from a biomechanical point of view. This study was aimed to investigate the impact on spinal flexibility caused by a unilateral laminotomy for bilateral decompression, in comparison to the intact condition and a laminectomy with preservation of a bony bridge at the vertebral arch. Secondary aims were to investigate the biomechanical effects of two-level decompression and the quantification of the restoration of stability after posterior fixation.

METHODS:

A universal spine tester was used to measure the flexibility of six L2-L5 human spine specimens in intact conditions and after decompression and fixation surgeries. An incremental damage protocol was applied : 1) unilateral laminotomy for bilateral decompression at L3-L4; 2) on three specimens, the unilateral laminotomy was extended to L4-L5; 3) laminectomy with preservation of a bony bridge at the vertebral arch (at L3-L4 in the first three specimens and at L4-L5 in the rest); and 4) pedicle screw fixation at the involved levels.

RESULTS:

Unilateral laminotomy for bilateral decompression had a minor influence on the lumbar flexibility. In flexion-extension, the median range of motion increased by 8%. The bone-preserving laminectomy did not cause major changes in spinal flexibility. Two-level decompression approximately induced a twofold destabilization compared to the single-level treatment, with greater effect on the lower level. Posterior fixation reduced the flexibility to values lower than in the intact conditions in all cases.

CONCLUSION:

In vitro testing of human lumbar specimens revealed that unilateral laminotomy for bilateral decompression and bone-preserving laminectomy induced a minor destabilization at the operated level. In absence of other pathological factors (e.g., clinical instability, spondylolisthesis), both techniques appear to be safe from a biomechanical point of view.

KEYWORDS:

Decompression, Surgical; Iatrogenic disease; Laminectomy; Lumbosacral region; Pedicle screws; Spine

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