Lumbar Decompression Using the Far-Lateral Approach: Patient-Reported Outcome is Associated With the Involved Vertebral Level and Coronal Segmental Angle.

Study Design: A single-centre retrospective study of prospectively collected data.

Objective: Analyse factors associated with the patient-reported outcome after far lateral decompression surgery (FLDS) for lumbar nerve root compression using the far-lateral approach.

Summary Of Background Data: To date, no studies have investigated the influence of vertebral level, coronal segmental Cobb angle, and the nature of the compressive tissue (hard or soft) on the patient-reported outcome following FLDS.

Patients And Methods: Patients who had undergone FLDS between 2005 and 2020 were included. Coronal segmental angle (CSCA) was measured on preoperative, posteroanterior radiographs. The primary outcome measure was the core outcome measures index (COMI) score at two years' follow-up (2Y-FU). Patients who had undergone microsurgical decompression using a midline approach served as a comparator group.

Results: There were 148 FLDS and 463 midline approach patients. In both groups, there was a significant improvement in the COMI score from preoperative to 2Y-FU ( P <0.0001), with greater improvement in patients treated at higher vertebral levels than in those treated at L5/S1 ( P =0.014). Baseline COMI, American Society of Anesthesiologists grade, body mass index, and low back pain as the "chief complaint" all had a significant association with the two-year COMI score. The nature of compressive tissue showed no association with the COMI score at 2Y-FU. In the FLDS group, there was a statistically significant correlation between the preoperative CSCA and the change in COMI score preoperatively to 2Y-FU ( P <0.001). The association was retained in the multiple regression analysis, controlling for confounders. A one-degree increase in CSCA was associated with a 0.35-point worse COMI score at 2Y-FU ( P =0.003).

Conclusion: Treatment of far lateral nerve root compression showed an overall good patient-reported outcome, but with less improvement with advanced CSCA. Modified approaches and techniques might be preferable for levels L5/S1.