157 - Radiologic Results of Total Disc Replacement in Lumbar Spine: Experien...

#157 Radiologic Results of Total Disc Replacement in Lumbar Spine: Experience of Single Institute with Minimum 5-year Follow up

Oral Posters: Lumbar

Presented by: J. Hur

Author(s):

J.-W. Hur (1)
C.-K. Park (1)
K.-S. Ryu (1)
J.-S. Kim (1)
M.-H. Shin (1)

(1) Seoul St. Mary's Hospital, Neurosurgery, Spine Center, Seoul, Korea, Republic of

Abstract

Purpose: The present study was designed to evaluate safety, therapeutic efficacy and biomechanical effects of lumbar total disc replacement (TDR) using ProDisc®-L (Synthes Spine, West Chester, PA) by analyzing clinical outcome and radiological changes at index and adjacent levels in minimum 5-year follow-up.

Methods: The patients were examined preoperatively and at 1 month, 3 month, 1 year, 2 year and 5 years postoperatively, and evaluations at each visit include patient self-assessments, physical and neurologic examinations, and radiographic evaluations.

Radiologic changes were assessed by amount of segmental translation, angular disc motion at the implanted level, lordotic curvature, height of functional spinal unit (FSU) and relative position and size of the prostheses. The magnetic resonance imaging (MRI) and CT scans were used to determine the arthritic changes of the facet joints and degenerative changes in intervertebral discs at the index and adjacent levels. Furthermore, radiographs were analyzed with regard to arthritic degeneration at the adjacent level and disc spaces were graded on a 4-point arthritic scale. These changes in radiologic findings were determined in relation to the clinical outcome, various perioperative factors, and prosthesis factors.

Results: Forty-three consecutive patients were followed up for at least 60 months (mean 86.67±11.52, range 60-120).

Postoperatively, all outcome measures (VAS scores, mean ODI, sports activity score) were significantly improved.

The height of FSU was significantly increased at postoperative 1 month (10.51±2.68 to 17.21±1.89, P=0.018) but then gradual decrements were observed until the last follow-up. (14.4±1.4 at 2-years to 13.77±2.39 at 5 years, P=0.00) The mean segmental translation was 1.43±1.65 mm at 1 month after surgery and showed significant increase to 1.92±1.46 mm at last follow-up (P=0.002).

Mean global ROM and mean segmental ROM of index segments were significantly reduced from 29.03±24.54° and 4.46±4.51° at postoperative 2 years to 17.0±18.3° and 2.1±2.4° respectively (P=0.044, 0.00) at the last visit. There were 7 (16.3%; L3-4: 1, L4-5: 3, L5-S1: 3) patients with no motion at index segment (ROM less than 0.5°) at the last visit. Among the 56 segments operated on, PFA was observed in 30.3% of index segments (17 of 56) and 10.9% (9 of 82) of adjacent segments. 3 and 5 cases of newly developed PFA were observed at index and adjacent segments respectively. All cases of PFA occurred only in those with preoperative degeneration grade 1 and there was no case showing a change in the grade at 2 or more steps or improvement. The progression of disc degeneration was observed in 6.1% and adjacent segment degeneration in 10.97% of the adjacent segments.

None of the postoperative radiological parameters included in the present study presented significant correlation with clinical outcome.

Conclusion: The study demonstrates that most of patients treated with TDR can maintain segmental motion at index level until more than 5-year after TDR although the range of motion appears to be so small, and TDR provides a good clinical outcome postoperatively regardless of motion preservation or FSU height preservation at the last follow-up. After TDR, the degenerative changes in the index and adjacent segments advanced, however these changes did not appear to exert negative influence upon clinical outcomes. A longer-term observation is warranted.