Late Complications of the Single Level 'Interspinous U' in Lumbar Spinal Stenosis with Mild Segmental Instability

Yoon, Seong Min; Lee, Sang Gu; Park, Chan Woo; Yoo, Chan Jong; Kim, Dae Yong; Kim, Woo Kyung

Abstract

OBJECTIVE
Decompression and/or fusion have traditionally been used to treat the spinal stenosis and spondylosis. Recently, several devices for dynamic posterior stabilization have been developed in treatment of lumbar spinal stenosis and degenerative spine diseases. This special technique of dynamic posterior stabilization of the lumbar spine may be defined as a system that would alter favorably the movement and load transmission of a spinal motion segment, without the fusion. At present, the 'interspinous U' has been using as one of favor device for dynamic posterior stabilization.
METHODS
From January 2003 to November 2004, we have used the 'interspinous U' for 48 patients with lumbar spinal stenosis with mild segmental instability, after bilateral foraminotomy. All patients were checked the follow-up simple X-ray stress view after more than 12 months and evaluated the stability and the outcome of the patients.
RESULTS
The patients were consisted of 26 men and 22 women, and mean ages was 55.3 years. The average follow- up period was approximately 22 months. The clinical outcomes were evaluated as excellent 15, good 19, fair 12 and poor 2. Especially, the patient group of unsatisfactory outcome(fair and poor) mainly complained the sudden burst back pain with the position change and this symptom was aggravated more and more during follow-up periods. In the flexion/extension lateral X-ray view, the evidence of bony absorption of the spinous process at the contacting side with 'interspinous U' device was found in 15 cases and also the minor instability was seen.
CONCLUSION
'interspinous U' is harder than any other ones for dynamic posterior stabilization, it is difficult to act like the "shock-absorber" and so the power to clamp the spinous process might be weak in spacer. Our preliminary results suggest that the late complications of the 'interspinous U' device in posterior dynamic stabilization may be the bone absorption of spinous process and minor instability, that is bone-implant interface failure.