Object: The purpose of this prospective controlled study was to evaluate possible factors that could affect postoperative segmental range of motion (ROM) after lumbar total disc replacement (TDR) using the ProDisc II prosthesis.
Methods: Thirty-two consecutive patients with intractable discogenic pain underwent lumbar TDR using the ProDisc II prosthesis, 30 of whom were followed up for at least 24 months. Segmental ROM was assessed preoperatively and every 6 months postoperatively using dynamic x-ray films. Segmental ROM at the reference level was assessed in relation to patient age, sex, body mass index (BMI), levels with implants, preoperative ROM, prosthesis size, and prosthesis position.
Results: At the last follow-up visit, mean ROM of the disc prostheses was significantly increased from 4.23 +/- 3.12 degrees to 6.81 +/- 3.76 degrees at L3-4, and from 3.66 +/- 2.47 degrees to 6.09 +/- 2.11 degrees at L4-5. Mean ROM at L5-S1, however, was decreased from 3.12 +/- 1.56 degrees to 2.86 +/- 1.26 degrees (p > 0.05). This difference in the changes in postoperative ROM between L5-S1 and the other operated levels was the only statistically significant factor (p = 0.025) among the variables related to the postoperative ROM that the authors assessed, but other factors such as patient age, sex, BMI, disc height, and the size and position of the prosthesis were not related to segmental ROM.
Conclusions: The data demonstrate that after TDR using the ProDisc II prosthesis, ROM of the prosthesis at L5-S1 is significantly lower compared with ROM at the other levels. In preserving ROM, the advantage of lumbar TDR using the ProDisc II might be minimal at L5-S1. Among the variables related to postoperative ROM, the level at which the ProDisc II prosthesis was implanted was the only one found to be statistically significant.