Study design: Retrospective outcome data analysis.
Objective: To evaluate if there is a significant difference between the midline rectus (MR) and the paramedian lateral rectus (PLR) approaches with regard to implant position for lumbar disc arthroplasty. To establish that a less than optimal implant position may influence clinical outcome.
Summary of background data: Little is known about the impact of varying surgical approaches on lumbar artificial disc implant position and clinical outcome.
Methods: Fifty-seven patients were obtained from one center participating Food and Drug Administration study for the evaluation of the lumbar Prodisc-L. Two different surgical access techniques were compared; the MR and left PLR. Two independent evaluators calculated the postoperative radiographical displacement from the midline in the coronal and sagittal planes for each of the surgical techniques. Pre- and postoperative clinical outcomes were evaluated to determine which surgical access technique was associated with better outcomes and if there was a clinical correlation with technical accuracy.
Results: The PLR approach was associated with greater malalignment of the prosthesis in both the coronal and sagittal planes compared with the MR approach. However, the difference was significant only in the sagittal plane (P = 0.021). There was no significant difference in clinical outcome for either approach (P = 0.34). Patients with >or=5 mm prosthetic displacement from the midvertebral point had significantly worse Owestry disability index scores than patients with <3 mm malalignment in both the coronal and sagittal planes regardless of the surgical approach employed.
Conclusion: The finding of a statistically significant more anteriorly displaced position in the sagittal plane of the total disc arthroplasty using the PLR approach may indicate a need to change to the MR approach. This study also demonstrates that patients with >or=5 mm prosthetic deviation from midline in either the coronal or sagittal planes had diminished clinical outcomes regardless of the approach used.