Lumbar Instability Post-discectomy Using the Tubular vs. Classic Approach: An Observational Retrospective Study

Background The spine is an articulated structure that bears the load and mechanical stresses of its proximal segment as it traverses distally. To withstand this stress, a proper balance between bony components and soft tissue (ligaments and muscles) must be achieved. Losing the balance between these tissues initiates a degenerative and inflammatory process that alters this balance, resulting in dynamic instability, arthrosis, and discal degenerative disease. Instability develops due to the failure of intrinsic or extrinsic dynamic support. Midline approaches, compared to more paravertebral ones, have a higher probability of affecting the stabilizing tissues of the spine, predisposing it to prolonged instability and possibly requiring repair. Methods A retrospective, observational, cohort-type, comparative study was conducted in adult patients diagnosed with radiculopathy associated with a confirmed diagnosis through radiological and imaging studies, undergoing discectomy via tubular or classic approach, at our Institution from 2016 to 2023. The primary outcome was the comparison between dynamic instability in tubular discectomy and classic microdiscectomy by the differences in radiological measurements in AP (antero-posterior), lateral, and dynamic projections between the two groups. The secondary outcomes were the contrast in disc degeneration of each group through MRI and comparison of other factors (age, BMI, pain, functional scores, blood loss, and surgery duration).  Radiographic studies were measured with RadiAnt 2023 (DICOM viewer tool; Medixant, Poznan, Poland) using Cobb angles and AP movement in mm. Data was collected, managed, and all statistical calculations were made with SPSS 26 (IBM Corp., Armonk, USA). Central tendency measures were performed for all variables. The comparison between groups was performed using the Student's t-test and Mann-Whitney U test, and the comparison of stratified variables by groups and measured throughout their evolution was done using covariate linear models. Results In the 38.3-year-old average cohort, 57.1% were women, with L5-S1 being the most affected level and Pfirrmann grade VI the most frequent. The tubular discectomy technique was used in 62.9% of cases and demonstrated significantly lower intraoperative blood loss compared to the open technique, without differences in surgery duration. Preoperative group differences were limited to flexion angle (p = 0.04), while postoperative outcomes favored the tubular group, with notable improvements in Oswestry, Roland, VAS (Visual Analogue Scale), and extension angles. The tubular technique also showed superior results in the Daniels scale recovery (p < 0.001), and multivariate analysis revealed a marked reduction in vertebral translation in the tubular group (-85.7%) versus an increase in the open group (+111.4%) (p = 0.05). Conclusion There is a non-statistical trend favoring the tubular approach at two levels associated with less postoperative pain. For radiographic and MRI (Magnetic Resonance Imaging) measurements, no general difference was found when comparing the two groups preoperatively and postoperatively.