Introduction: This prospective observational study reports on the clinical efficacy of a complete case series of patients who have had X STOP interspinous device insertion for the treatment of lumbar spinal stenosis.

Methods: 60 patients were enrolled and asked to complete the ZCQ, ODI, SF-36 and VAS questionnaire’s pre-operatively, and at 3-, 6- and 12 months post-operatively. Clinical significance with the ZCQ is accepted as improvement in 2 of the 3 domains (where the changes correspond to a mean decrease of 0.42 or 0.46 for symptom severity or physical function respectively, or there is a mean patient satisfaction score of 2.4 or less). Changes in ZCQ were measured at each time point and compared to pre-operative levels.

Results: The mean age was 70 (range 54–90), M:F 29:30. Two of the 59 patients were withdrawn due to intra-operative spinous process fracture and unrelated death. 60% underwent single level and 40% double level insertion.

The ZCQ, ODI, SF-36 and VAS were completed preoperatively and at 12 months by 54, 50, 52, 52 respectively.

Thirty-nine patients completed all questionnaires at all time points and the maximal clinical efficacy was evident 3 months post-operatively. Clinical significant improvement was maintained at the 6- and 12 month post-operative follow-ups despite a minimal loss of clinical efficacy in absolute mean values.

Overall, clinically significant response was achieved in 65%. Seventy-one per cent of double level patients and 61% of single level patients as determined by the ZCQ, had a clinically significant response. Corresponding changes were seen in VAS and ODI and SF-36.

Ten patients (18%) required caudal epidural for recurrence of symptoms and 1 patient required perifacet injections for back pain.

Conclusion: X STOP offers a safe reversible treatment for symptomatic spinal stenosis. Clinically significant improvement is present at three months and is maintained at 12 months.

Introduction: The effect of the X-STOP on sagittal kinematics and spinal canal and neural foraminal area are reported when this interspinous device is used for the treatment of neurogenic claudication.

Methods: Patients underwent Positional MRI scanning pre-operatively and 6 months post-operatively in the erect, flexed seated and extended and neutral positions. Anterior and posterior disc heights were measured on the erect images, endplate angle and the L1S1 angle on flexion and extension images at the operated and adjacent levels. Spinal canal and neural foraminal area were measured on all images. Measurements were made using the Osiris 4.17 program and statistical analysis using the Wilcoxon sign rank test.

Results: Fifty-two patients were enrolled. M:F 26:26. Single level: Double level insertion 29:20. Three patients withdrawn, one died of unrelated causes, one intra-operative spinous process fracture, one lost to follow-up.

Single Level: Spinal canal and neural foramina areas were increased in all positions with canal area significantly increased on standing (p=0.024) and sitting neutral (p=0.036). There was no significant effect on endplate angle, segmental range of movement, L1S1 angle or disc height.

Double Level: Spinal canal area was significantly increased in the cranial segment on standing (p=0.002) and extension (p=0.016) and the caudal segment in extension (p=0.016). Foraminal area was significantly increased at the right cranial (p=0.019) and caudal (p= 0.045) segments in flexion and left cranial (p=0.017) and caudal segments (p=0.004) in extension. A significant change was observed at the endplate angles in flexion (p=0.028) and extension (p=0.026) at the upper level. The L1S1 angle was significantly reduced in extension (p=0.017). The caudal anterior disc height was reduced (p=0.023). There was no significant effect on segmental range of movement or sagittal kinematics at adjacent levels.

Conclusion: X-STOP insertion has minimal effect on the sagittal kinematics of the lumbar spine but does increase canal and neural foraminal area.