117 - Three-year prone transpsoas (PTP) LLIF experience: Clinical and radiographic outcomes and learnings following a consecutive 120 surgeries at a single center

Introduction
PTP is a single-position alternative to the traditional lateral lumbar interbody fusion (LLIF) technique. Most reports over the last three years since its introduction have focused on technique description, feasibility, and early outcomes, including peri-op efficiencies and immediate post-op radiographic alignment. Longer-term outcomes have been pending the maturity of this PTP experience.

Aims/Objectives
To document and report the follow-up outcomes of a novel method for single-position circumferential treatment of thoracolumbar conditions

Methods
At a single institution, all consecutive patients undergoing PTP for any indication between mid-2019 and mid-2022 were captured via prospective institutional registry to document demographic, diagnostic, and procedural details, as well as clinical (patient-reported) outcomes, and radiographic alignment measures. Retrospective database analysis identified 31 prone lateral approaches prior to proceduralization using procedure-specific positioners and retractor (PTP) and 89 proceduralized PTPs, enabling comparison across early and later cohorts. All cases used saphSSEP lumbar plexus monitoring. Pain (visual analog scale, VAS), function (Oswestry disability index, ODI), and quality of life (EQ-5D) were prospectively collected at pre-op and all post-op clinic visits. Serial radiographs were measured to calculate spinopelvic alignment parameters.

Results
The total cohort of 120 patients were 64% female, averaged 64 years (range:26-84), had a mean BMI of 31 (range:18-51), and included 27% with diabetes and 11% smokers. Diagnoses included spondylolisthesis, scoliosis, flatback, and adjacent-level degeneration. One PTP was aborted due to body habitus-related IONM challenges. In the 119 patients, 187 levels were treated (range:1-5, average:1.6/patient, 76% inclusive of L4-5), with 1-7 levels/patient of fixation, 38% with direct decompression, 8% with osteotomies, and 10% revision of prior hardware. OR time, retraction time, EBL, and LOS averaged 150 min, 17 min, 50 cc, and 2.2 days, respectively. 79% were without complication; others included 3 cage repositionings, 1 partial ALL rupture, 1 durotomy, 1 epidural hematoma, 1 posterior wound infection, 1 pseudoarthrosis. Post-op hip flexion weakness was identified in 14%, transient lower extremity weakness in 12%, and sensory deficits in 10%. Secondary surgeries included 2 adjacent-level decompressions, 1 pseudo revision, and 1 epidural hematoma evacuation. Follow-up averaged 13 months (range: 6 weeks-3 years). At last follow-up, back pain, worst-leg pain, ODI, and EQ-5D health state improved by 54%, 45%, 46, and 51% respectively. 89% said they were improved, 85% were satisfied, and 84% would elect the surgery again. 97% improved or maintained sagittal alignment with an average 6° segmental lordosis gain at PTP levels. Only intra-psoas retraction time differed between pre- and post-proceduralization; proceduralization saved a mean 3.4 min/level (p=0.0371).

Conclusion
The largest single-center PTP experience with the longest follow-up to-date shows that proceduralized PTP results in few complications, quick recovery, improvements in pain, function, and quality of life, high patient satisfaction, and improved sagittal alignment at an average 1-year and up to 3-year post-op -- outcomes consistent with this surgeon’s prior lateral decubitus LLIF experience.