BACKGROUND
Failed fusion surgery remains difficult to treat. Little published data on disc replacement surgery after failed fusion procedures exists. Our objective was to evaluate outcomes of junctional lumbar disc replacement after previous fusion surgery and to correlate outcome with radiological changes to parameters of sagittal balance.

METHODS
Out of a single-center prospective registry of 290 patients with 404 lumbar disc replacements, 27 patients had had a previous lumbar fusion operation on 1 to 4 lumbar segments and had completed a mean follow-up of 33 months (range: 18–56). We correlated the clinical outcome measures (patient satisfaction, 10-point pain score, and Oswestry Disability Index (ODI) score) to parameters of spinal sagittal alignment (sacral tilt, pelvic tilt, pelvic incidence, and lumbar lordosis).

RESULTS
Postoperative hospital stay averaged 3.3 days (range: 2–8). Previously-employed patients went back to their jobs a mean of 32 days (range: 21–42) after the procedure. At the latest follow-up, 1 of the patients considered the outcome to be poor, 3 fair, 8 good, and 15 excellent. Twenty-four patients “would undergo the operation again.” Average pain

score decreased from 9.1 ± 1.0 (SD) to 3.2 ± 2.1 (P < .01). Average ODI decreased from 50.2 ± 9.9 preoperatively to 21.7 ± 14.2 (P <= .01). We found the change in pelvic tilt to be an independent predictor of better clinical outcome by multivariate analysis (P < .05).

CONCLUSIONS
In patients with junctional failure adjacent to a previous posterolateral fusion, disc replacement at the junctional level(s), compared with osteotomy and fusion surgery, offers the advantage of maintaining segmental mobility and correcting the flat-back deformity through a single approach with less operative time and blood loss. Early- to intermediate-term results are promising. The influence of changes in spinal sagittal alignment on clinical outcome needs to be addressed in future research.

CLINICAL RELEVANCE
This is the first study on “junctional disc replacement patients” correlating clinical outcome to changes in spinal/pelvic alignment.

Key Words Lumbar disc replacement, junctional disc replacement, spinal alignment. SAS Journal. Summer 2007;1; 86–94. DOI: SASJ-2007-0006-RR

From the Department of Orthopedic Surgery, University of the Witwatersrand, Johannesburg, South Africa (Hähnle and Sweet); Linksfield Park Clinic, Johannesburg (Hähnle and Weinberg); the Department of Medicine, University of the Witwatersrand (Sliwa); the Department of Mechanical Engineering, University of Potchefstrom, Potchefstrom, South Africa (de Villiers); Southern Medical, Wpadrand, South Africa (de Villiers); and the Department of Surgery, University of the Witwatersrand (Candy).

Ulrich R Hähnle, Ian R Weinberg, and Malan de Villiers are co-developers of the Kineflex disc and shareholders in SpinalMotion, Mountain View, California.

Address correspondence and reprint requests to Ulrich Hähnle, PO Box 52040, Saxonwold 2132, Johannesburg, South Africa (email: hahnleu@mdh-africa.org).

This submission was received March 29, 2007, and accepted for publication June 15, 2007.

We would like to thank Stephanie Hanekom and Aldorin Gehring for their enthusiastic support with patient management and follow-up.

The institutional review board of the hospital where all procedures were performed (Nedcare Linksfield Hospital, Nedcare, Johannesburg, South Africa) approved this study, which was conducted in accordance with the ethical standards of the Declaration of Helsinki (2000). Informed written consent was obtained from all patients.