Introduction: Interspinous devices have been extensively used over last decades for degenerative lumbar spine disorders. Several clinical studies have been published on short and medium-term follow-up of patients treated with interspinous devices, however, only few papers focused on the long-term outcome of these patients. This study shows the results of clinical and radiological long-term follow-up (maximum 10 years) of patients surgically treated with interspinous devices.
Methods: 80 patients (44 male) were included. They underwent implant of interspinous devices at one or two spinal levels (106 devices implanted). 35 of them (20 males) completed the follow-up (mean: 100 months; range: 44-121). Clinical evaluation was performed using Visual Analogue Scale (VAS), Oswestry Disability Index (ODI), and Zurich Claudication Questionnaire (ZCQ). Pre- and post-operative x-rays and CT were collected. Flexion/extension X-rays were also obtained at last follow-up visit, to measure segmental lordosis and range of motion (ROM). Interspinous heterotopic ossification (HO) was quantified according to Tian et al. criteria on follow-up CT scan.
Results: Mean VAS score, decreased from 8.30 to 3.50 (p<0.01) at post-operative evaluation, but it was 5.34 at last follow-up visit. Similarly, mean ODI significantly decreased at post-operative assessment (p<0.01) and it slightly increased during follow-up. 40% of patients had mild/moderate symptoms at last follow-up and 43% of patients were satisfied by treatment. In 9/35 (25.7%) cases (suffering from grade-I spondilolisthesis) interspinous devices were dislocated at last radiological evaluation. Seven of these patients underwent revision surgery. Four patients (with double level implant) had spinous process fractures. Segmental lordosis was maintained in all cases. HO was detected in 77.27% of patients, with complete interspinous bone fusion and abolition of segmental movement in 13.64% of patients.
Conclusions: Interspinous devices are associated with high rate of HO, but this is often not clinically relevant. Late complications are more frequent in patients with spondylolisthesis.
Patient Care: To know the "destiny" of interspinous devices 10 year after the implant is important to better understand the correct indication for such minimally invasive, but still controversial surgery.
Learning Objectives: By the conclusion of this session, participants should be able to:
- analyze the results of long-term follow-up of patients treated with interspinous devices for degenerative lumbar disorders.
- discuss the impact of interspinous heterotopic ossification on patients treated with the implant of interspinous devices, correlating it with clinical outcome.
- speculate the influence of interspinous device on degenerative cascade of lumbar spine over long-term follow-up.