A COMPARISON BETWEEN L4/L5 AND L5/S1 SINGLE LEVEL DISCETOMY SURGERY

Abstract

Aim: To assess surgical outcomes between discectomy at the L4/5 level and L5/S1.

Introduction: There is sound biomechanical reasoning to suspect a difference might exist between spinal levels. The L4/5 disc is more susceptible to axial torsion and is the most common site of lumbar instability. The L5/S1 motion segment is protected from torsional strain by extensive iliolumbar ligaments but more exposed to axial compressive forces.1 There appears to be a difference between the L4/L5 motion segment and the L5/S1 in outcomes of disc replacement surgery. The available literature implies a difference but does not include studies with accepted standard outcome measures.

Method: 130 patients from a single centre undergoing a single level discectomy at L4/L5 or L5/S1 for radicular pain with prospectively gathered data. Oswestry disability index (ODI), subjective walking distance, Modified Somatic Perception (MSP), Modified Zung Depression Index (MZD), Low Back Outcome Score (LBOS) and visual analogue score (VAS) were collected over an average of 56 months of follow up. Comparisons between L4/5 vs. L5/S1 levels were made with these outcome measures using student’s t-testing.

Results: There were 78 L5/S1 and 52 L4/5 discectomies identified. Pre-operative walking distance for L5/S1 patients was higher at L4/5 (455m vs. 278m; p=0.027). At 6 months a small clinical difference exists with the back function scores that achieves statistical difference (47.11 (L4/5) vs. 39.47 (L5/S1); p=0.0229). Across all other parameters, no significant difference was found to exist between both groups. There was no difference in the recurrence rate or re-operation rate. There was no difference in early and late outcomes.

Conclusions: No statistically significant difference exists between surgery at the L4/5 level and the L5/S1 level in terms of post-operative outcome. There is no clinically significant difference in outcome. Planned surgical treatment strategies should not be altered by perceptions of difference in outcome when none exists.