Preoperative Distal Motor Latency Testing and Long-Term Outcomes in Combined Lumbar Spinal Stenosis: A Retrospective Analysis of Diagnostic Discordance.

STUDY

DESIGN

Retrospective cohort study.

OBJECTIVE

To determine whether a function-guided selective decompression strategy based on preoperative distal motor latency (DML) testing can avoid unnecessary L5/S decompression without compromising outcomes in patients with combined L4/5 central and L5/S foraminal-extraforaminal lumbar spinal stenosis (LSS) and to identify predictors of poor outcomes and reoperation.

SUMMARY OF BACKGROUND DATA: In multilevel LSS, radiographic evidence of stenosis at L4/5 and L5/S is common, yet anatomic narrowing does not always reflect functional neural compromise. Although DML testing has been introduced to detect L5/S foraminal-extraforaminal involvement, its value in guiding selective decompression and outcomes in cases of structural-functional discordance remains unclear.

METHODS

We retrospectively analyzed 290 consecutive patients with radiographic evidence of L4/5 central stenosis and concomitant L5/S foraminal-extraforaminal stenosis who underwent decompression surgery with preoperative DML testing (2010-2019). All patients received L4/5 microendoscopic decompression; additional L5/S decompression was performed only when DML indicated electrophysiological L5 impairment. Patients were stratified into DML-negative (n=110) and DML-positive (n=180) groups. Postoperative Japanese Orthopaedic Association (JOA), Oswestry Disability Index (ODI), Visual Analog Scale (VAS) scores, and reoperation rates were compared. Multivariate logistic regression identified predictors of poor outcomes.

RESULTS

Adjusted JOA, ODI, and VAS scores did not differ between groups at 1 year or final follow-up. Reoperation rates were comparable. Lower preoperative JOA scores and higher leg pain VAS scores independently predicted poor outcomes, whereas DML status did not. In the DML-negative group, younger age and higher body mass index were associated with reoperation.

CONCLUSIONS

A DML-guided selective decompression strategy was not associated with inferior outcomes compared with combined decompression. These findings support a structure-function framework for surgical decision-making in multilevel LSS.

LEVEL OF EVIDENCE: Level III.