Adjacent segment hypermobility after lumbar spine fusion: No association with progressive degeneration of the segment 5 years after surgery

Abstract

Background and purpose Increased intradiscal pressure and relative segmental hypermobility are in vitro observations supporting the idea of increased postoperative load being a reason for progressive degeneration of the free mobile segment adjacent to a lumbar fusion. These mechanisms have been difficult to confirm in clinical studies, and an alternative theory claims instead that the adjacent segment degeneration follows a natural degenerative course in patients who are predisposed. We examined 9 patients 5 years after lumbar fusion, to assess whether relative hypermobility of the segment adjacent to fusion could be correlated to progressive degeneration of the same segment.Patients and methods The 9 patients, all of whom had been treated with a lumbar fusion after a preoperative intervertebral mobility assessment by spinal RSA, were re-examined 5 years after surgery. The intervertebral translations of the vertebra proximal to the fusion were determined by RSA and compared to the mobility of the same lumbar segment before fusion. The disc height and any progressive reduction at the two levels proximal to the one fused were measured on conventional radiographs.Results Adjacent segment mobility 5 years after fusion-expressed as mean transverse, vertical, and sagittal translation of the vertebra proximal to fusionwas not significantly changed compared to the mobility measured before surgery. Increased mobility of the segment seen in 5 individual patients was not associated with progressive degeneration of the same segment or to a poor clinical outcome.

A prospective randomised study on the long-term effect of lumbar fusion on adjacent disc degeneration

“…3 Examples of one physiotherapy patient (EX) and one fused patient with pedicel fixation (PLF) without disc height decrease at long term follow up 13 years later. Arrows indicate the level adjacent to the slip-level and the fusion, respectively Table 7 The difference in pain index, DRI and ODI between fused patients with and without ASD according to 4 (range 20-54, median 27 months). They were all operated on because of unaltered symptoms from inclusion into the study.…”

“…Whereas many authors have observed ASD [7,20,29,37,39,53], several have not [4,19,28,40,45,48,49], resulting in conflicting conclusions. Furthermore, the clinical implication of a radiologically demonstrated ASD is uncertain.…”

Rigid fixation of the lumbar spine alters the motion and mechanical stability at the adjacent segment level

“…Adjacent segment disease has been reported to occur in as many as 35% of patients following spinal fusion. [3,6] Initial positive results following posterior spinal fusion often degrade over time, as adjacent mobile segments proximal and distal to the fusion degenerate. [6] Following arthrodesis at L4-L5, the most common level of fusion, adjacent disc disease additional surgery is required in approximately 15% of patients.…”

“…[3,6] Initial positive results following posterior spinal fusion often degrade over time, as adjacent mobile segments proximal and distal to the fusion degenerate. [6] Following arthrodesis at L4-L5, the most common level of fusion, adjacent disc disease additional surgery is required in approximately 15% of patients. [2,3,12] Progression of the free mobile segment next to the spinal fusion is referred to as adjacent segment disease including disc degeneration, facet joint hypertrophy, spinal stenosis, and even acquired spondylolisthesis.…”

“…Posterior lumbar interbody fusion (PLIF) is a popular lumbar arthrodesis and posterolateral graft, and fixation can be easily added to PLIF to enhance spinal stability and to induce fusion. [6][7][8][9][10][11] Alteration of the biomechanics at the junction of fused and mobile segments is thought to accelerate degeneration in adjacent motion segments. Adjacent segment disease has been reported to occur in as many as 35% of patients following spinal fusion.…”