Influence of preoperative leg pain and radiculopathy on outcomes in mono-segmental lumbar total disc replacement: results from a nationwide registry.

PURPOSE

Currently, many pre-conditions are regarded as relative or absolute contraindications for lumbar total disc replacement (TDR). Radiculopathy is one among them. In Switzerland it is left to the surgeon's discretion when to operate if he adheres to a list of pre-defined indications. Contraindications, however, are less clearly specified. We hypothesized that, the extent of pre-operative radiculopathy results in different benefits for patients treated with mono-segmental lumbar TDR. We used patient perceived leg pain and its correlation with physician recorded radiculopathy for creating the patient groups to be compared.

METHODS

The present study is based on the dataset of SWISSspine, a government mandated health technology assessment registry. Between March 2005 and April 2009, 577 patients underwent either mono- or bi-segmental lumbar TDR, which was documented in a prospective observational multicenter mode. A total of 416 cases with a mono-segmental procedure were included in the study. The data collection consisted of pre-operative and follow-up data (physician based) and clinical outcomes (NASS form, EQ-5D). A receiver operating characteristic (ROC) analysis was conducted with patients' self-indicated leg pain and the surgeon-based diagnosis "radiculopathy", as marked on the case report forms. As a result, patients were divided into two groups according to the severity of leg pain. The two groups were compared with regard to the pre-operative patient characteristics and pre- and post-operative pain on Visual Analogue Scale (VAS) and quality of life using general linear modeling.

RESULTS

The optimal ROC model revealed a leg pain threshold of 40 ≤ VAS > 40 for the absence or the presence of "radiculopathy". Demographics in the resulting two groups were well comparable. Applying this threshold, the mean pre-operative leg pain level was 16.5 points in group 1 and 68.1 points in group 2 (p < 0.001). Back pain levels differed less with 63.6 points in group 1 and 72.6 in group 2 (p < 0.001). Pre-operative quality of life showed considerable differences with an 0.44 EQ-5D score in group 1 and 0.29 in group 2 (p < 0.001, possible score range -0.6 to 1). At a mean follow-up time of 8 months, group 1 showed a mean leg pain improvement of 3.6 points and group 2 of 41.1 points (p < 0.001). Back pain relief was 35.6 and 39.1 points, respectively (p = 0.27). EQ-5D score improvement was 0.27 in group 1 and 0.41 in group 2 (p = 0.11).

CONCLUSIONS

Patients labeled as having radiculopathy (group 2) do mostly have pre-operative leg pain levels ≥ 40. Applying this threshold, the patients with pre-operative leg pain do also have more severe back pain and a considerably lower quality of life. Their net benefit from the lumbar TDR is higher and they do have similar post-operative back and leg pain levels as well as the quality of life as patients without pre-operative leg pain. Although randomized controlled trials are required to confirm these findings, they put leg pain and radiculopathy into perspective as absolute contraindications for TDR.