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

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

• Costa F
• Ottardi C
• Volkheimer D
• Ortolina A
• Bassani T
• Wilke HJ
• Galbusera

• KMID: 2428109
• DOI: http://doi.org/10.3340/jkns.2018.0023

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.

Keyword

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

MeSH Terms

Decompression*
Decompression, Surgical
Humans
Iatrogenic Disease
In Vitro Techniques
Laminectomy
Lumbosacral Region
Pedicle Screws
Pliability*
Range of Motion, Articular
Spine*

Figure

• 

  Fig. 1. Decompression and stabilization procedures performed on the specimens : unilateral laminotomy for bilateral decompression at L3–L4 (UNI-1L, n=6 specimens); bone-preserving laminectomy at L3–L4 (BI-1L, n=3); unilateral laminotomy for bilateral decompression at L3–L5 (UNI-2L, n=3); bonepreserving laminectomy at L3–L5 (BI-2L, n=3). Experimental set-up used for load application and motion analysis with an optoelectronic motion analysis system (right).

• 

  Fig. 2. Schematic representation of the incremental protocol of decompression and fixation. Intact : specimens before decompression, UNI-1L : after unilateral laminotomy for bilateral decompression at L3–L4, UNI-2L : after unilateral laminotomy for bilateral decompression at L3–L5, BI-1L : after bone-preserving laminectomy at L3–L4, BI-2L : after bone-preserving laminectomy at L3–L5, fixed : after posterior fixation with pedicle screws and titanium rods at L3–L4 or L3–L5.

• 

  Fig. 3. Photographs (top) and anteroposterior radiographic projections (bottom) of specimens after bone-preserving laminectomy at L3–L4 (left) and L3–L5 (right).

• 

  Fig. 4. Statistical comparison of the range of motion (ROM) and neutral zone (NZ) between the intact specimens and those subjected to unilateral laminotomy for bilateral decompression at L3–L4 (UNI-1L), in fiexionextension, left and right lateral bending, left and right axial rotation. *A statistically significant difference (p<0.05) between the intact and the decompressed condition (n=6).

• 

  Fig. 5. Changes in the range of motion (ROM) and neutral zone (NZ) of the L3–L4 motion segment (indicated by the arrow) due to incremental decompression performed at the same level, in flexion-extension, left and right lateral bending, left and right axial rotation. The gray areas indicate the range between the maximum and minimum ROM and NZ among the three specimens, whereas the solid lines indicate the median value. Intact : specimen before decompression, UNI-1L : after unilateral laminotomy for bilateral decompression at L3–L4, BI-1L : after bone-preserving laminectomy at L3–L4, fixed : after posterior fixation with pedicle screws and titanium rods at L3–L4.

• 

  Fig. 6. Changes in the range of motion (ROM) and neutral zone (NZ) of the L3–L4 motion segment (indicated by the arrow) due to incremental decompression performed at the L3–L4 and L4–L5, in fiexion-extension, left and right lateral bending, left and right axial rotation. The gray areas indicate the range between the maximum and minimum ROM and NZ among the three specimens, whereas the solid lines indicate the median value. Intact : specimen before decompression, UNI-1L : after unilateral laminotomy for bilateral decompression at L3–L4, UNI-2L : after unilateral laminotomy at L3–L5, BI-1L : after bone-preserving laminectomy at L3–L5, fixed : after posterior fixation with pedicle screws and titanium rods at L3–L5.

• 

  Fig. 7. Changes in the range of motion (ROM) and neutral zone (NZ) of the L4–L5 motion segment (indicated by the arrow) due to incremental decompression performed at the L3–L4 and L4–L5, in fiexion-extension, left and right lateral bending, left and right axial rotation. The gray areas indicate the range between the maximum and minimum ROM and NZ among the three specimens, whereas the solid lines indicate the median value. Intact : specimen before decompression, UNI-1L : after unilateral laminotomy for bilateral decompression at L3–L4, UNI-2L : after unilateral laminotomy at L3–L5, BI-1L : after bone-preserving laminectomy at L3–L5, fixed : after posterior fixation with pedicle screws and titanium rods at L3–L5.

Reference

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