STUDY DESIGN
This study was a prospective study with a minimum patient follow-up of 2 years.

OBJECTIVE
The purpose of this study was to evaluate the clinical usefulness of a vertebral endplate classification system (VEYBR) in predicting outcomes following lumbar arthroplasty.

BACKGROUND
In the present study, our previously described endplate classification system was evaluated to determine its clinical usefulness in patients undergoing lumbar arthroplasty.

METHODS
The patient cohort in this study consisted of 80 patients who had been enrolled in the US FDA ProDisc (Synthes, West Chester, Pennsylvania) clinical trial. Radiographs were classified using the VEYBR classification. The preoperative categories (Types I to V) were then correlated with the patients’ visual analogue scores (VAS) and Oswestry Disability Index (ODI) scores and radiographic outcomes at an average follow-up point of 28 months.

RESULTS
The rank order of total change in VAS based on preoperative VEYBR classification was Type IV, III, I II, and V, with Type IV having the greatest improvement in VAS and Type V having the least improvement. The rank order of total change in ODI was Type IV, II, III, I, and V. We found no differences in clinical outcomes among the 5 vertebral endplate types. Type II endplates had least optimal sagittal positioning.

CONCLUSIONS
Although not statistically significant, there was a strong trend for Type V endplates to have the least improvements in VAS and Oswestry clinical outcome scores. Knowledge and use of the endplate classification system did lead to consistent implant placement across endplate classes which may indicate the usefulness of this classification system in preoperative planning, especially for physicians in the “learning curve” phase of this procedure.

LEVEL OF EVIDENCE
Case series (Level IV).

Key Words Lumbar, endplate morphology, total disc replacement, clinical and radiographic outcomes. SAS Journal. Spring 2008. 2:101–106. DOI: SASJ-2007-0119-RR

From the Department of Orthopaedics and Rehabilitation, Yale University School of Medicine (Yue, Oetgen, and Jaramillo-de la Torre); and the Department of Orthopaedic Surgery, St. Elizabeths Klinikum, Straubing, Germany (Bertagnoli)

Address correspondence to James J. Yue, MD, Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, P.O. Box 208071, New Haven, CT 06520-8071 (email: james.yue@yale.edu)

This manuscript was submitted October 14, 2007, and accepted for publication March 20, 2008.

Institutional Review Board approval was obtained from the Yale Human Investigation Committee.