Minimally invasive unilateral versus bilateral technique in performing single-segment pedicle screw fixation and lumbar interbody fusion

Development of a Pedicle Screw Fixation Simulation Model for Surgical Training Using a 3-Dimensional Printer

OBJECTIVE

Training surgeons in pedicle screw fixation (PSF) techniques during actual surgery is limited because of patient safety, complications, and surgical efficiency issues. Recent technical developments are leading the world to an era of personalized three-dimensional (3D) printing. This study aimed to evaluate the educational effect of using a 3D-printed spine model to train beginners in PSF techniques to improve screw accuracy and procedure time.

METHODS

Computed tomography (CT) scan data were used in a 3D printer to produce a life-size lumbar spine replica of L1-3 vertebrae. Four residents performed PSF thrice. Each resident performed 18 screw fixations on both sides (6 screws per trial). The time to complete the procedure and pedicle violation was recorded.

RESULTS

The average time for the 3 procedures was 42.1±2.9 minutes, 38.8±3.3 minutes, and 32.1±2.5 minutes, respectively. Furthermore, the average pedicle screw score for the 3 procedures was 13.0±0.8, 14.5±0.6, and 16.0±0.8, respectively. As the trial was repeated, the procedure time decreased and the accuracy of screw fixation tended to be more accurate.

CONCLUSIONS

It was possible to decrease the procedure time and increase accuracy through repeated training using the 3D-printed spine model. By implementing a 3Dprinted spine model based on the patient's actual CT data, surgeons can perform simulation surgery before the actual surgery. Therefore, this technology can be useful in educating residents to improve their surgical skills.

Contralateral bridge fixation of freehand minimally invasive pedicle screws combined with unilateral MIS-TLIF vs. open TLIF in the treatment of multi-segmental lumbar degenerative diseases: A five years retrospective study and finite element analysis

Objective

To evaluate the efficacy, safety, feasibility and biomechanical stability of contralateral bridge fixation of freehand minimally invasive pedicle screws (Freehand MIPS) combined with unilateral minimally invasive surgery-transforaminal lumbar interbody fusion (MIS-TLIF) (smile-face surgery) and open TLIF for the treatment of multi-segmental lumbar degenerative diseases (LDDs).

Methods

From January 2013 to January 2016, clinical data of multi-segmental (2- or 3-level) LDDs receiving smile-face surgery or open TLIF were retrospectively collected and analyzed. The back and leg pain VAS and ODI were used to assess clinical outcomes preoperatively and postoperatively. The MacNab criteria were used to evaluate the satisfaction of patient. The disc height (DH), lumbar lordosis (LL) and segmental lordosis angle (SLA) were measured before and after surgery. We used patient's CT data to establish the finite element model of smile-face surgery and open TLIF, and analyze biomechanical stability of two methods.

Results

Smile-face surgery group showed shorter operation time, shorter incision, less blood loss, shorter hospital stay than open TLIF (P < 0.05). The back VAS in smile-face surgery group was significantly lower than that in open TLIF immediately and 3 months after surgery, and no significant difference was observed 1 year, 2 years and 5 years after surgery. There was no significant difference in the leg pain VAS and ODI between both groups after surgery. No significant difference was observed between two groups in the DH, LL and SLA. At 5-year follow-up, grade I or II fusion was achieved in 99.00% (100/101) segments of smile-face surgery group and 97.67% (84/86) segments of open TLIF group according to Bridwell system. The complication rate of open TLIF was higher than that of smile-face surgery (24.32% vs. 0%, P < 0.01). After verification, the established finite element model can accurately simulate the biological structure of lumbar spine and there was no significant difference in biomechanical stability between two methods.

Conclusions

Smile-face surgery has some advantages over open TLIF including smaller aggression, less blood loss, and lower cost, indicating that it is a good choice of treatment for multi-segmental LDDs. Both methods can achieve good biomechanical stability.

Safety and efficacy of unilateral and bilateral pedicle screw fixation for lumbar degenerative diseases by transforaminal lumbar interbody fusion: An updated systematic review and meta-analysis

Background

The purpose of this study was to compare the safety and efficacy of unilateral vs. bilateral pedicle screw fixation (BPSF) for lumbar degenerative diseases.

Methods

Electronic databases including PubMed, Web of science, the Cochrane Library, Scopus, MEDLINE, EMBASE, EBSCO were searched by computer. The deadline was set for June 1, 2022. This study included all high-quality randomized controlled trials (RCTs), prospective clinical controlled studies (PRO), and retrospective studies (Retro) that compared unilateral and bilateral pedicle screw fixation in the treatment of lumbar degenerative diseases. Revman5.3 software was used for meta-analysis after two researchers independently screened the literature, extracted data, and assessed the risk of bias in the study.

Results

Fourteen studies with a total of 1,086 patients were included. Compared with BPSF, unilateral pedicle screw fixation (UPSF) has shorter operation time and hospital time, and less blood loss and operation cost, operation time [SMD = −1.75, 95% CI (−2.46 to −1.03), P < 0.00001], hospital time [SMD = −1.10, 95% CI (−1.97 to −0.22), P = 0.01], Blood loss [SMD = −1.62, 95% CI (−2.42 to −0.82), P < 0.0001], operation cost [SMD = −14.03, 95% CI (−20.08 to −7.98), P < 0.00001], the ODI after bilateral pedicle screw fixation was lower, and the degree of lumbar dysfunction was lighter, [SMD = 0.19, 95% CI (0.05–0.33), P = 0.007], better fusion effect, fusion rate [RR=0.95, 95% CI (0.91–1.00), P = 0.04]. VAS-Low back pain [SMD = 0.07, 95% CI (−0.07–0.20), P = 0.35], VAS-Leg pain [SMD = 0.18, 95% CI (−0.00–0.36), P = 0.05], SF-36 [SMD = 0.00, 95% CI (−0.30–0.30), P = 1.00], complications rate [RR = 0.94, 95% CI (0.9154–1.63), P = 0.82], the overall difference was not statistically significant.

Conclusions

Currently limited evidence suggests that UPSF significantly reduces blood loss, significantly shortens the operative time and hospital stay, and reduces blood loss and costs. After BPSF, the ODI was lower, the degree of lumbar spine dysfunction was lower, and the fusion rate was significantly higher. The VAS, SF-36, and complications scores of the two groups were comparable, and there was no significant clinical difference.

Management of recurrent unilateral lumbar disc herniation in a single level: unilateral versus bilateral pedicle screws fixation with interbody fusion

Background

Lumbar interbody fusion procedure is a recognized surgical technique in management of a variety of lumbar pathologies including recurrent lumbar disc prolapse. Interbody fusion augmented by pedicle screw fixation has been considered to improve fusion rates and clinical outcomes. Interbody fusion is commonly associated with better fusion potentials through applying the bone graft in the load bearing, vascular position of the anterior, and middle spinal columns. However, it still remains unknown whether interbody fusion with unilateral pedicle screw fixation (UPSF) is superior to that with bilateral pedicle screw fixation (BPSF).

Aim of the work

The aim of this study is to evaluate the efficacy and safety of unilateral versus bilateral pedicle screw fixation associated with interbody fusion for the management of single level unilateral recurrent lumbar disc prolapse as regard the clinical and biomechanical results, operation time, intraoperative blood loss, and postoperative stay.

Material and methods

This observational prospective comparative study of the two groups who were operated either unilateral (group A /15 patients) or bilateral (group B/15 patients) pedicle screw fixation with interbody fusion was done. Patients were followed up for 1, 6, ad 12 months.

Results

Significant improvement in functional outcome of the two groups was noted compared to preoperatively, except in early postoperative period where the back VAS and ODI in the unilateral group was better than bilateral group. However, on further follow up, no significant difference was noticed. There was no significant difference comparing fusion rate, complication rate, and duration of hospital stay between the two groups at postoperative follow-up. There was significantly less blood loss, and significantly shorter operation time in the unilateral PS fixation group as compared with the bilateral PS fixation group in our study.

Conclusion

Our study suggested that TLIF with unilateral PS fixation was as safe and effective as that with bilateral PS fixation for the management of recurrent single level lumbar disc prolapse; it showed better clinical outcome scores of ODI and back VAS, and a significant reduction of the intraoperative blood loss as well as the operation time, without significant differences considering fusion rate, complication rate, and duration of hospital stay between the two groups at postoperative follow-up. However, BPSF with TLIF likely causes more degeneration at the cranial adjacent segment compared with UPSF techniques. Nevertheless, the long-term follow up is required to demonstrate the impact of these findings.

Biomechanical Analysis of an Interspinous Process Fixation Device with In Situ Shortening Capabilities: Does Spinous Process Compression Improve Segmental Stability?

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.

Defining the MIS-TLIF: A Systematic Review of Techniques and Technologies Used by Surgeons Worldwide

STUDY DESIGN

Systematic review.

OBJECTIVE

To date there is no consensus among surgeons as to what defines an MIS-TLIF (transforaminal lumbar interbody fusion using minimally invasive spine surgery) compared to an open or mini-open TLIF. This systematic review aimed to examine the MIS-TLIF techniques reported in the recent body of literature to help provide a definition of what constitutes the MIS-TLIF, based on the consensus of the majority of surgeons.

METHODS

We created a database of articles published about MIS-TLIF between 2010 and 2018. We evaluated the technical components of the MIS-TLIF including instruments and incisions used as well the order in which key steps are performed.

RESULTS

We could identify several patterns for MIS-TLIF performance that seemed agreed upon by the majority of MIS surgeons: use of paramedian incisions; use of a tubular retractor to perform a total facetectomy, decompression, and interbody cage implantation; and percutaneous insertion of the pedicle-screw rod constructs with intraoperative imaging.

CONCLUSION

Based on this review of the literature, the key features used by surgeons performing MIS TLIF include the use of nonexpandable or expandable tubular retractors, a paramedian or lateral incision, and the use of a microscope or endoscope for visualization. Approaches using expandable nontubular retractors, those that require extensive subperiosteal dissection from the midline laterally, or specular-based retractors with wide pedicle to pedicle exposure are far less likely to be promoted as an MIS-based approach. A definition is necessary to improve the communication among spine surgeons in research as well as patient education.

Unilateral Versus Bilateral Percutaneous Pedicle Screw Fixation in Oblique Lumbar Interbody Fusion

OBJECTIVE

To compare clinical and radiologic outcomes of unilateral pedicle screw (UPS) and bilateral pedicle screw (BPS) fixations after single-level oblique lateral interbody fusion procedures.

METHODS

This retrospective study included 74 patients receiving single-level oblique lateral interbody fusion at L3-4 or L4-5 (June 2014 to June 2017). These patients were divided into BPS (n = 36) and UPS (n = 38) groups. Perioperative outcomes included operative time, blood loss, medical expenses, and complication rates. Radiologic outcomes included fusion rates and cage subsidence rates. Clinical outcomes included disability measured by the Oswestry Disability Index and pain measured by the visual analog scale.

RESULTS

The operative time was significantly shorter in the UPS group (76.2 ± 4.4 minutes) compared with the BPS group (127.0 ± 5.6 minutes, P < 0.001). There was a significant between-group difference in medical expenses ($11,044.8 ± $470.7 in UPS group vs. $15,018.4 ± $547.1 in BPS, P < 0.001). Blood loss and hospital stay did not differ between groups. Oswestry Disability Index and visual analog scale scores significantly decreased in both groups at different time points postoperatively compared with preoperatively. The UPS group had lower Oswestry Disability Index and visual analog scale scores than the BPS group at 7 days postoperatively, but no between-group difference was found after 1-month follow-up. Fusion rate was 86.8% in UPS group and 91.7% in BPS group (P > 0.05). Cage subsidence rates did not differ between groups.

CONCLUSIONS

Oblique lateral interbody fusion with UPS fixation is an effective and reliable option for single-level lumbar diseases. Compared with BPS fixation, it resulted in less blood loss, required less operative time, and had comparable effects on radiologic and clinical outcomes.

Does the Cage Position in Transforaminal Lumbar Interbody Fusion Determine Unilateral versus Bilateral Screw Placement?: A Review of the Literature

This literature review examines the relative placement of the interbody cage with respect to the unilateral screw construct to address the need for bilateral screw placement versus unilateral screw placement. Transforaminal lumbar interbody fusion (TLIF) has become a widely used technique for correcting lumbar intervertebral pathologies. This review addresses the necessity for further study on the effects of the relative position of intervertebral cage placement on the outcome of lumbar spine surgery after TLIF with unilateral pedicle screw fixation. Previous studies have addressed various factors, including posterior screw fixation, cage size, cage shape, and number of levels fused, that impact the biomechanics of the lumbar spine following TLIF. A simple survey of the literature was conducted. A search of the English literature was conducted using the keywords ‘TLIF,’ ‘transforaminal lumbar interbody fusion,’ ‘graft placement,’ ‘graft position,’ ‘cage position,’ ‘cage placement,’ ‘unilateral pedicle screw,’ ‘unilateral TLIF cage placement,’ ‘lumbar biomechanics,’ ‘lumbar stability,’ ‘lumbar fusion,’ and ‘lumbar intervertebral cage’ with various combinations of the operators ‘AND’ and ‘OR’ and no date restrictions. Seventeen articles in the English literature that were most relevant to this research question were identified. To the best of our knowledge, there are no published data addressing the effects of cage placement relative to the unilateral screw on lumbar stability in TLIF with unilateral pedicle screw fixation. Investigation of the effects of cage placement is, thus, warranted to achieve optimal clinical outcomes in patients undergoing TLIF with unilateral pedicle screw fixation.

Comparison of Minimally Invasive and Open Transforaminal Lumbar Interbody Fusion for Lumbar Disc Herniation: A Retrospective Cohort Study

Background

This cohort study compared the efficacy and safety of minimally invasive versus open transforaminal lumbar interbody fusion (Mis-TLIF versus Open-TLIF) for lumbar disc herniation with radiculopathy.

Material/Methods

From July 2016 to September 2017, we recruited 37 patients suffering from lumbar disc herniation with radiculopathy. Seventeen patients underwent Mis-TLIF (Mis group) and 20 patients underwent Open-TLIF (Open group). Baseline characteristics were similar between the 2 groups before surgery. We compared postoperative clinical and radiological outcomes between the 2 groups.

Results

Compared to patients in the Open group, patients in the Mis group has significantly less intraoperative hemorrhage, drainage fluid, time to go, and hospital stay after surgery, but had longer operation times (P<0.05). These 2 groups had similar postoperative hemoglobin reduction and drain removal time. In addition, the postoperative back and leg pain and intervertebral height reduction at 3 months after surgery in the Mis group were remarkably lower than those in the Open group. There was no significant difference in postoperative Oswestry disability index (ODI) or intervertebral height change immediately after surgery and at 1 month postoperatively between the 2 groups.

Conclusions

Mis-TLIF shows some benefits in lumbar disc herniation compared to Open-TLIF in terms of intraoperative hemorrhage, drainage fluid, time to go, hospital stay after surgery, and postoperative back and leg pain.

Use of a life-size three-dimensional-printed spine model for pedicle screw instrumentation training

Background

Training beginners of the pedicle screw instrumentation technique in the operating room is limited because of issues related to patient safety and surgical efficiency. Three-dimensional (3D) printing enables training or simulation surgery on a real-size replica of deformed spine, which is difficult to perform in the usual cadaver or surrogate plastic models. The purpose of this study was to evaluate the educational effect of using a real-size 3D-printed spine model for training beginners of the free-hand pedicle screw instrumentation technique. We asked whether the use of a 3D spine model can improve (1) screw instrumentation accuracy and (2) length of procedure.

Methods

Twenty life-size 3D-printed lumbar spine models were made from 10 volunteers (two models for each volunteer). Two novice surgeons who had no experience of free-hand pedicle screw instrumentation technique were instructed by an experienced surgeon, and each surgeon inserted 10 pedicle screws for each lumbar spine model. Computed tomography scans of the spine models were obtained to evaluate screw instrumentation accuracy. The length of time in completing the procedure was recorded. The results of the latter 10 spine models were compared with those of the former 10 models to evaluate learning effect.

Results

A total of 37/200 screws (18.5%) perforated the pedicle cortex with a mean of 1.7 mm (range, 1.2–3.3 mm). However, the latter half of the models had significantly less violation than the former half (10/100 vs. 27/100, p < 0.001). The mean length of time to complete 10 pedicle screw instrumentations in a spine model was 42.8 ± 5.3 min for the former 10 spine models and 35.6 ± 2.9 min for the latter 10 spine models. The latter 10 spine models had significantly less time than the former 10 models (p < 0.001).

Conclusion

A life-size 3D-printed spine model can be an excellent tool for training beginners of the free-hand pedicle screw instrumentation.

Spinal Biologics in Minimally Invasive Lumbar Surgery

As the use of minimally invasive spine (MIS) fusion approaches continues to grow, increased scrutiny is being placed on its outcomes and efficacies against traditional open fusion surgeries. While there are many factors that contribute to the success of achieving spinal arthrodesis, selecting the optimal fusion biologic remains a top priority. With an ever-expanding market of bone graft substitutes, it is important to evaluate each of their use as it pertains to MIS techniques. This review will summarize the important characteristics and properties of various spinal biologics used in minimally invasive lumbar surgeries and compare their fusion rates via a systematic review of published literature.

Biomechanical analysis of the posterior bony column of the lumbar spine

Background

Each part of the rear bone structure can become an anchor point for an attachment device. The objective of this study was to evaluate the stiffness and strength of different parts of the rear lumbar bone structure by axial compression damage experiments.

Methods

Five adult male lumbar bone structures from L2 to L5 were exposed. The superior and inferior articular processes, upper and lower edges of the lamina, and upper and lower edges of the spinous process were observed and isolated and then divided into six groups (n = 10). The specimens were placed between the compaction disc and the load platform in a universal testing machine, which was first preloaded to 5.0 N tension to eliminate water on the surface and then loaded to the specimen curve decline at a constant tension loading rate of 0.01 mm/s, until the specimens had been destroyed.

Results

Significant differences in mechanical properties were found among different parts of the rear lumbar bone structure. Compared with other parts, the lower edge of the lamina has good mechanical properties, which have a high modulus of elasticity; the superior and inferior articular processes have greater ultimate strength, which can withstand greater compressive loads; and the mechanical properties of the spinous process are poor, and it is significantly stiffer and weaker than the lamina and articular processes.

Conclusion

These data can be useful in future spinal biomechanics research leading to better biomechanical compatibility and provide theoretical references for spinal implant materials.

Transforaminal Lumbar Interbody Fusion with Rigid Interspinous Process Fixation: A Learning Curve Analysis of a Surgeon Team's First 74 Cases

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.