Effect of pre-existing adjacent segment degeneration on medium and long term prognosis after lumbar fusion

English Keywords:Adjacent segment disease  Pre-existing degeneration  Degree of canal stenosis  Disc degeneration

English Abstract:

  【Abstract】 Objectives: To analyze the effect of pre-existing adjacent segment degeneration(ASD) on the long-term prognosis after lumbar fusion, and to compare the effect of canal stenosis and the degree of intervertebral disc degeneration on adjacent segment disease(ASDis). Methods: By retrieving the medical records from January 2002 to December 2010 in our hospital with the inclusion criteria of lumbosacral fusion and at least five years follow-up, 59 patients (27 males, 32 females; mean age, 63.0±9.6 years) were enrolled, with 80.7±7.4 months(72-96 months) follow-up. Preoperative and final follow-up radiographs and MRI images were evaluated. BMI, preoperative and final follow-up ODI, JOA, VAS scores were collected. Final follow-up adjacent segment degeneration was evaluated on MRI and radiographs. Observation indexes included Pfirrman′s grades of adjacent discs, spinal stenosis, instability of segments, height of intervertebral space, osteophytes of anterior and posterior margins of vertebral bodies. The degree of pre-existing adjacent segment degeneration was evaluated by obliteration of anterior cerebrospinal fluid space and Pfirrman′s grades. If neurological symptoms of lower extremities or low back pain were aggravated during the follow-up period, the adjacent segment disease(ASDis) were diagnosed. Influencing factors were compared between ASDis group and no ASDis group. Logistic regression analysis was used to analyze the risk factors of adjacent segment disease in final follow-up. Results: In the final follow-up, ASD were found in 38 cases(38/59, 64.4%), and 9 patients(9/59, 15.3%) were diagnosed ASDis. Forty patients(40/59, 67.8%) who had no obvious pre-existing stenosis at adjacent segments were rated as grade 0, 2 patients had ASDis at final follow-up. Nineteen patients(19/59, 32.2%) had mild pre-existing stenosis at adjacent segments, which were rated as grade 1, 7 patients had ASDis at final follow-up. The incidence of ASDis was significantly different between the two groups(P=0.003). Logistic regression analysis showed that the degree of pre-existing canal stenosis and length of fusion segments were risk factors for adjacent segment lesions. Conclusions: Compared with the degeneration of intervertebral disc, more attention should be paid to the evaluation of the degree of adjacent spinal canal stenosis, especially for the presence of mild spinal canal stenosis, which will significantly increase the risk of long-term adjacent segment disease.