BACKGROUND: No-profile anterior cervical discectomy and fusion (ACDF) devices are commonplace in spinal surgery. Contained within the intervertebral margins, these devices diminish risks associated with anterior cervical plating, while also marginalizing cage migration and subsidence. However, these devices have been limited in their scope of implant material. Accordingly, a no-profile ACDF (npACDF) device supporting a machined allograft implant body with a connected load-sharing fixation interface was developed. However, it is not established in the literature whether the device supports early mechanical stability and subsequent boney fusion. The objective of this study was to assess this device in both the clinical and preclinical settings. METHODS: Biomechanical Analysis: Twenty-four functional spinal units (FSUs) were divided into 4 groups (n = 6). Each group would receive a single construct: (1) npACDF device with connected polyetheretherketone (PEEK) body, (2) npACDF with connected allograft body, (3) npACDF (allograft body) with nonconnected fixation plate, and (4) standard ACDF plate and PEEK interbody cage. FSUs were subjected to pure moment loading (flexion/extension, lateral bending, and axial rotation) via a kinematic test machine in their intact state and then following instrumentation. Vertebral motion was recorded and range-of-motion (ROM) reduction, relative to intact, was calculated.Clinical Case Series: Ten patients receiving single-level ACDF with the npACDF allograft (connected) device for the treatment of persistent cervical radiculopathy or myelopathy were retrospectively reviewed at 12 months. Radiographic and patient reported outcomes were reported. RESULTS: No differences in ROM existed between the npACDF constructs (P ≥ 0.99). Standard ACDF achieved more ROM reduction than the npACDF constructs in all directions (P ≥ 0.04). All subjects achieved fusion at 12 months. CONCLUSIONS: The npACDF allograft device supported less motion reduction in comparison to traditional plating; however, case series data suggest the device provides clinically effective stability resulting in quality radiographic fusion and pain improvement. CLINICAL RELEVANCE: This report provides both clinical and preclinical insight into a device which offers alternative design features to traditional continuous/rigid ACDF device designs.
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 Ncm 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.
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.
Learning Curve , Surgeons , Humans , Minimally Invasive Surgical Procedures , Spine/surgery
OBJECTIVE: The objective of this study was to characterize the biomechanical implications of spinous process compression, via in situ shortening of a next-generation interspinous process fixation (ISPF) device, in the context of segmental fusion. METHODS: Seven lumbar cadaveric spines (L1-L4) were tested. Specimens were first tested in an intact state, followed by iterative instrumentation at L2-3 and subsequent testing. The order followed was 1) stand-alone ISPF (neutral height); 2) stand-alone ISPF (shortened in situ from neutral height; shortened); 3) lateral lumbar interbody fusion (LLIF) + ISPF (neutral); 4) LLIF + ISPF (shortened); 5) LLIF + unilateral pedicle screw fixation; 6) LLIF + bilateral pedicle screw fixation. A 7.5-Nm moment was applied in flexion/extension, lateral bending, and axial rotation via a kinematic test frame. Segmental range of motion (ROM) and lordosis were measured for all constructs. Comparative analysis was performed. RESULTS: Statistically significant flexion/extension ROM reductions: all constructs versus intact condition (P < 0.01); LLIF + ISPF (neutral and shortened) versus stand-alone ISPF (neutral and shortened) (P < 0.01); LLIF + USPF versus ISPF (neutral) (P = 0.049); bilateral pedicle screw fixation (BPSF) versus stand-alone ISPF (neutral and shortened) (P < 0.01); LLIF + BPSF versus LLIF + unilateral pedicle screw fixation (UPSF) (P < 0.01). Significant lateral bending ROM reductions: LLIF + ISPF (neutral and shortened) versus intact condition and stand-alone ISPF (neutral) (P < 0.01); LLIF + UPSF versus intact condition and stand-alone ISPF (neutral and shortened) (P < 0.01); LLIF + BPSF versus intact condition and all constructs (P < 0.01). Significant axial rotation ROM reductions: LLIF + ISPF (shortened) and LLIF + UPSF versus intact condition and stand-alone ISPF (neutral) (P ≤ 0.01); LLIF + BPSF versus intact condition and all constructs (P ≤ 0.04). CONCLUSIONS: In situ shortening of an adjustable ISPF device may support increased segmental stabilization compared with static ISPF.
Internal Fixators , Joint Instability/surgery , Biomechanical Phenomena , Cadaver , Female , Humans , Lordosis/surgery , Lumbar Vertebrae , Male , Middle Aged , Pedicle Screws , Range of Motion, Articular , Spinal Fusion , Treatment Outcome
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 biomechanical study. OBJECTIVES: The objective of this in vitro biomechanical range-of-motion (ROM) study was to evaluate spinal segmental stability following fixation with a novel anterior cervical discectomy and fusion (ACDF) device ("novel device") that possesses integrated and modular no-profile, half-plate, and full-plate fixation capabilities. METHODS: Human cadaveric (n = 18, C3-T1) specimens were divided into 3 groups (n = 6/group). Each group would receive one novel device iteration. Specimen terminal ends were potted. Each specimen was first tested in an intact state, followed by anterior discectomy (C5/C6) and iterative instrumentation. Testing order: (1) novel device (group 1, no-profile; group 2, half-plate; group 3, full-plate); (2) novel device (all groups) with lateral mass screws (LMS); (3) traditional ACDF plate + cage; (4) traditional ACDF plate + cage + LMS. A 2 N·m moment was applied in flexion/extension (FE), lateral bending (LB), and axial rotation (AR) via a kinematic testing machine. Segmental ROM was tracked and normalized to intact conditions. Comparative statistical analyses were performed. RESULTS: Key findings: (1) the novel half- and full-plate constructs provided comparable reduction in FE and LB ROM to that of traditional plated ACDF (P ≥ .05); (2) the novel full-plate construct significantly exceeded all other anterior-only constructs (P ≤ .05) in AR ROM reduction; and (3) the novel half-plate construct significantly exceeded the no-profile construct in FE (P < .05). CONCLUSIONS: The novel ACDF device may be a versatile alternative to traditional no-profile and independent plating techniques, as it provides comparable ROM reduction in all principle motion directions, across all device iterations.
Background Rigid interspinous process fixation (ISPF) may serve as a minimally disruptive adjunct to lumbar interbody fusion. Previous biomechanical assessments of ISPF have demonstrated particularly advantageous outcomes in stabilizing the sagittal plane. However, ISPF has not been well characterized in regard to its impact on interbody load, which has implications for the risk of cage migration or subsidence, and sagittal alignment. The purpose of this study was to biomechanically assess in vitro the interbody load (IBL), focal lordosis (FL), and spinous process loading generated by in situ compression/distraction with a novel ISPF device capable of incremental in situ shortening/extension. Bilateral pedicle screw fixation (BPSF) was used as a control. Methods Two fresh frozen human lumbar spines were thawed and musculature was removed, leaving ligaments intact. Seven functional spinal units were iteratively tested, which involved a standard lateral discectomy, placement of a modified lateral cage possessing two load cells, and posterior fixation. BPSF and ISPF were performed at each level, with order of fixation was randomized. BPSF was first performed with maximum compressive exertion followed by 75% exertion to represent clinical application. The ISPF device was implanted at a neutral height and incrementally shortened/extended in situ in 1-mm increments. IBL and FL were measured under each condition. Loads on the spinous processes were estimated through bench-top mechanical calibration. Results No significant differences in IBL were observed, but the ISPF device produced a significantly greater change in FL compared to the clinically relevant BPSF compression. IBL, as a function of ISPF device height, expressed linear behavior during compression and exponential behavior during distraction. Conclusions The novel ISPF device produced clinically effective IBL and FL, performing well in comparison to BPSF. Additionally, incremental ISPF device manipulation demonstrated predictable and clinically safe trends regarding loading of the interbody space and spinous processes.
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. The objective of this multicenter study was to prospectively assess patients receiving single-level anterior (ALIF) or lateral (LLIF) lumbar interbody fusion with adjunctive ISPF. METHODS: This was a prospective, randomized, multicenter (11 investigators), noninferiority trial. All patients received single-level ALIF or LLIF with supplemental ISPF (n = 66) or pedicle screw fixation (PSF; n = 37) for degenerative disc disease and/or spondylolisthesis (grade ≤2). The randomization patient ratio was 2:1, ISPF/PSF. Perioperative and follow-up outcomes were collected (6 weeks, 3 months, 6 months, and 12 months). RESULTS: For ISPF patients, mean posterior intraoperative outcomes were: blood loss, 70.9 mL; operating time, 52.2 minutes; incision length, 5.5 cm; and fluoroscopic imaging time, 10.4 seconds. Statistically significant improvement in patient Oswestry Disability Index scores were achieved by just 6 weeks after operation (P < .01) and improved out to 12 months for the ISPF cohort. Patient-reported 36-Item Short Form Health Survey and Zurich Claudication Questionnaire scores were also significantly improved from baseline to 12 months in the ISPF cohort (P < .01). A total of 92.7% of ISPF patients exhibited interspinous fusion at 12 months. One ISPF patient (1.5%) required a secondary surgical intervention of possible relation to the posterior instrumentation/procedure. CONCLUSION: ISPF can be achieved quickly, with minimal tissue disruption and complication. In supplementing ALIF and LLIF, ISPF supported significant improvement in early postoperative (≤12 months) patient-reported outcomes, while facilitating robust posterior fusion.
BACKGROUND: Studies 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. METHODS: Seventy-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. RESULTS: EBL, 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. CONCLUSIONS: Study 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.
BACKGROUND: When performing hindfoot arthodeses, one goal of fixation is often to achieve compression across the joint. Traditional lag screws are applied eccentrically, providing compression more on the edge of the fusion. A new technique, using a post in one bone and a lag screw through the post to the other bone, may offer better compression across more of the joint. METHODS: There are three parts to this study comparing a post-and-screw construct to traditional lag screws. Synthetic bone models, representative of the talonavicular joint, were created and assessed for biomechanical measures of compression. Next, the post-and-screw construct was tested in cadavers, under conditions representing early weight bearing after arthrodesis surgery. Finally, 18 patients who had a talonavicular fusion with a post-and-screw construct with one surgeon were compared to the previous 18 patients fixed with traditional screws. RESULTS: In the synthetic bone model, the post-and-screw construct brought the centre of compression closer to the centre of the joint, suggesting compression was less eccentric. Neither traditional screws nor the post-and-screw construct were sufficiently strong to resist early weight bearing forces in cadaver specimens. In the clinical comparison, four patients had a painful nonunion when fixed with traditional screws, compared to none in the post-and-screw construct. CONCLUSIONS: A post-and-screw construct spreads the forces of compression more uniformly across an arthrodesis, even when placed eccentrically. Although not all the biomechanical measures were superior, the post-and-screw construct achieved higher levels of successful fusion in patients. This technology may offer improved outcomes in some clinical scenarios and deserves further study. LEVEL OF EVIDENCE: Level 3.
Arthrodesis/methods , Foot Diseases/surgery , Foot/surgery , Tarsal Joints/surgery , Adult , Aged , Aged, 80 and over , Bone Nails , Bone Screws , Cadaver , Female , Humans , Male , Middle Aged , Models, Anatomic , Pressure , Tarsal Bones/surgery , Weight-Bearing
