Study finds, Biomechanical Effect on the adjacent L4/L5 segm
The superior facet arthroplasty is important for intervertebral foramen microscopy. A Study was conducted to evaluate the effect of S1 superior facet arthroplasty on lumbar range of motion and disc stress of adjacent segment (L4/L5) under the intervertebral foraminoplasty.

The lumbosacrylic vertebrae (L4/S) had established and validated eight Finite Element Models (FEMs). The arthroplasty of the superior facet S1 was simulated with several approaches. Following optimization, the models were transferred into Nastran software; the L4 superior terminal was preloaded to 500 N, and a simulation of flexion, extension, lateral turn and rotation was provided with 10 N alternating meters. The L4-L5 spine was recorded for mobility (ROM) and intervertebral disc stress.

Results:
--The ROM and disc stress of L4/L5 increased with the increasing of the proportions of S1 superior facet arthroplasty.

--Compared with the normal model, the ROM of L4/L5 significantly increased in most directions of motion when S1 superior facet formed greater than 3/5 from the ventral to the dorsal or 2/5 from the apex to the base.

--The disc stress of L4/L5 significantly increased in most directions of motion when S1 superior facet formed greater than 3/5 from the ventral to the dorsal or 1/5 from the apex to the base.

The unilateral S1 superior facet arthroplasty was ultimately influenced by the ROM and district stress of L4/L5. The developing range should be less than 3/5 of the S1 higher facet joint from the ventral to the dorsal. The formation from apex to base is not encouraged.

Source: https://josr-online.biomedcentral.com/articles/10.1186/s13018-021-02540-0
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