Background: Rigid interspinous process fixation (ISPF) has received consideration as an efficient, minimally disruptive technique in supporting lumbar interbody fusion. However, despite advantageous intraoperative utility, limited evidence exists characterizing midterm to long-term clinical outcomes with ISPF.

Study Design: This was a systematic literature review. Objective: The purpose of this systematic literature review was to aggregate all evidence characterizing the learning curve of instrumented minimally invasive surgery (MIS) techniques in spinal surgery and summarize what, if any, consideration has been given to surgeon training and experience. Summary of Background Data: MIS techniques have become prevalent in spine surgery given the ability to diminish the intraoperative footprint, translating to quicker patient recovery, and improved long-term outcomes. However, technical demand on the surgeon can be significant, particularly during the procedural adoption (learning curve) phase. Many studies have sought to quantify the duration and severity of these learning curve phases, with the intent to characterize MIS procedural appropriateness and safety. However, while these studies are robust regarding outcome metrics, it is not well understood whether they adequately characterize surgeon training and experience. Methods: A systematic literature review was performed in the PubMed and MEDLINE databases in accordance with the PRISMA guidelines. All inclusion articles were screened for statements regarding surgeon experience/training. Statements were further classified by the types of metrics/variables utilized to establish a contextual history of experience/training. Descriptive statistics were reported. Results: Initial search criteria yielded 458 articles, 12 met final inclusion. Seven articles (58.3%) attempted a summary statement of experience which acknowledged at least one of the following metrics: total years in practice (41.7%), years/number of cases performed using the traditional/gold-standard technique (16.7%), specification of residency/fellowship training (16.7%), use/nonuse of cadaveric or course/lab training (16.7%), and/or design of operating team (8.3%). No articles considered experience as a quantitative variable in their study analyses. Conclusions: Spine MIS learning curve studies for instrumented fusion procedures provide inadequate context/characterization of surgeon experience and training. Future efforts leveraging learning curve methodology utilized in other surgical specialties would be beneficial.

BackgroundStudies have shown that a significant learning curve may be associated with adopting minimally invasive transforaminal lumbar interbody fusion (MIS TLIF) with bilateral pedicle screw fixation (BPSF). Accordingly, several hybrid TLIF techniques have been proposed as surrogates to the accepted BPSF technique, asserting that less/fewer fixation(s) or less disruptive fixation may decrease the learning curve while still maintaining the minimally disruptive benefits. TLIF with interspinous process fixation (ISPF) is one such surrogate procedure. However, despite perceived ease of adaptability given the favorable proximity of the spinous processes, no evidence exists demonstrating whether or not the technique may possess its own inherent learning curve. The purpose of this study was to determine whether an intraoperative learning curve for one- and two-level TLIF + ISPF may exist for a single lead surgeon.MethodsSeventy-four consecutive patients who received one- or two-Level TLIF with rigid ISPF by a single lead surgeon were retrospectively reviewed. It was the first TLIF + ISPF case series for the lead surgeon. Intraoperative blood loss (EBL), hospitalization length-of-stay (LOS), fluoroscopy time, and postoperative complications were collected. EBL, LOS, and fluoroscopy time were modeled as a function of case number using multiple linear regression methods. A change point was included in each model to allow the trajectory of the outcomes to change during the duration of the case series. These change points were determined using profile likelihood methods. Models were fit using the maximum likelihood estimates for the change points. Age, sex, body mass index (BMI), and the number of treated levels were included as covariates.ResultsEBL, LOS, and fluoroscopy time did not significantly differ by age, sex, or BMI (p ≥ 0.12). Only EBL differed significantly by the number of levels (p = 0.026). The case number was not a significant predictor of EBL, LOS, or fluoroscopy time (p ≥ 0.21). At the time of data collection (mean time from surgery: 13.3 months), six patients had undergone revision due to interbody migration. No ISPF device complications were observed.ConclusionsStudy outcomes support the ideal that TLIF + ISPF can be a readily adopted procedure without a significant intraoperative learning curve. However, the authors emphasize that further assessment of long-term healing outcomes is essential in fully characterizing both the efficacy and the indication learning curve for the TLIF + ISPF technique.

Introduction: Recent literature suggests that surgical fixation of elderly sacral fractures may reduce time to mobilization and ultimately self-sufficiency. However, it is unclear if predictors of success exist in this subpopulation. The objective of this study was to characterize relative change in ambulation and residential living statuses (pre-injury vs. post-surgery) of elderly patients who received surgical fixation of sacral fractures, as well as determine whether or not demographics and injury characteristics influence these findings. Methods: Fifty-four elderly patients (≥60 years old) receiving percutaneous screw fixation of sacral fractures were retrospectively reviewed. All fractures were traumatic in nature; insufficiency fractures were excluded. Patient and surgical demographic data, as well as 1-year mortality status, was reported. Primary study endpoints included relative change in patient ambulation and residential living statuses (pre-injury to post-surgery). Statistical analyses were performed to assess relative change in ambulation/living status from pre-injury to post-surgery and to determine if predictors of outcome existed. Results: Of the 54 patients who met inclusion criteria, 4 expired prior to discharge, 2 expired post-discharge, and 4 were lost to follow-up. Of those patients discharged, 95.7% regained some form of ambulation at last follow-up (mean: 22.4 ± 18.9 weeks). Of patients living independent pre-injury, 94.9% would eventually return to independent home living. Neither time-to-surgery, concomitant orthopaedic injury, Charlson Comorbidity Index, or injury mechanism were predictors of final ambulation or residential status (p ≥ 0.07). Mortality at 1-year was 11.1%. Discussion: Operative fixation supported a high rate of return to pre-injury ambulation and residential living status. However, there did not appear to be measures predictive of final functional status. Further efforts with larger, prospective cohorts are warranted.

Study Design: In vitro cadaveric biomechanical study. Objective: Biomechanically characterize a novel lateral lumbar interbody fusion (LLIF) implant possessing integrated lateral modular plate fixation (MPF). Methods: A human lumbar cadaveric (n = 7, L1-L4) biomechanical study of segmental range-of-motion stiffness was performed. A ±7.5 Nċm moment was applied in flexion/extension, lateral bending, and axial rotation using a 6 degree-of-freedom kinematics system. Specimens were tested first in an intact state and then following iterative instrumentation (L2/3): (1) LLIF cage only, (2) LLIF + 2-screw MPF, (3) LLIF + 4-screw MPF, (4) LLIF + 4-screw MPF + interspinous process fixation, and (5) LLIF + bilateral pedicle screw fixation. Comparative analysis of range-of-motion outcomes was performed between iterations. Results: Key biomechanical findings: (1) Flexion/extension range-of-motion reduction with LLIF + 4-screw MPF was significantly greater than LLIF + 2-screw MPF ( P < .01). (2) LLIF with 2-screw and 4-screw MPF were comparable to LLIF with bilateral pedicle screw fixation in lateral bending and axial rotation range-of-motion reduction ( P = 1.0). (3) LLIF + 4-screw MPF and supplemental interspinous process fixation range-of-motion reduction was comparable to LLIF + bilateral pedicle screw fixation in all directions ( P ≥ .6). Conclusions: LLIF with 4-screw MPF may provide inherent advantages over traditional 2-screw plating modalities. Furthermore, when coupled with interspinous process fixation, LLIF with MPF is a stable circumferential construct that provides biomechanical utility in all principal motions.