Complications and Revision Rates in Minimally Invasive Robotic-Guided Versus Fluoroscopic-Guided Spinal Fusions: The MIS ReFRESH Prospective Comparative Study.

STUDY DESIGN: Prospective, multicenter, partially randomized. OBJECTIVE: Assess rates of complications, revision surgery, and radiation between Mazor robotic-guidance (RG) and fluoro-guidance (FG). SUMMARY OF BACKGROUND DATA: Minimally invasive surgery MIS ReFRESH is the first study designed to compare RG and FG techniques in adult minimally invasive surgery (MIS) lumbar fusions. METHODS: Primary endpoints were analyzed at 1 year follow-up. Analysis of variables through Cox logistic regression and a Kaplan-Meier Survival Curve of surgical complications. RESULTS: Nine sites enrolled 485 patients: 374 (RG arm) and 111 (FG arm). 93.2% of patients had more than 1 year f/u. There were no differences for sex, Charlson Comorbidity Index, diabetes, or tumor. Mean age of RG patients was 59.0 versus 62.5 for FG (P = 0.009) and body mass index (BMI) was 31.2 versus 28.1 (P< 0.001). Percentage of smokers was almost double in the RG (15.2% vs. 7.2%, P = 0.029). Surgical time was similar (skin-to-skin time/no. of screws) at 24.9 minutes RG and 22.9 FG (P = 0.550). Fluoroscopy during surgery/no. of screws was 15.5 seconds RG versus 35.4 seconds FG, (15 seconds average reduction). Fluoroscopy time during instrumentation/no. of screws was 3.6 seconds RG versus 17.8 seconds FG showing an 80% average reduction of fluoro time/screw in RG (P < 0.001). Within 1 year follow-up, there were 39 (10.4%) surgical complications RG versus 39 (35.1%) FG, and 8 (2.1%) revisions RG versus 7 (6.3%) FG. Cox regression analysis including age, sex, BMI, CCI, and no. of screws, demonstrated that the hazard ratio (HR) for complication was 5.8 times higher FG versus RG (95% CI: 3.5-9.6, P < 0.001). HR for revision surgery was 11.0 times higher FG versus RG cases (95% CI 2.9-41.2, P < 0.001). CONCLUSION: Mazor robotic-guidance was found to have a 5.8 times lower risk of a surgical complication and 11.0 times lower risk for revision surgery. Surgical time was similar between groups and robotic-guidance reduced fluoro time per screw by 80% (approximately 1 min/case).Level of Evidence: 2.

Reduction in complication and revision rates for robotic-guided short-segment lumbar fusion surgery: results of a prospective, multi-center study.

Studies evaluating robotic guidance in lumbar fusion are limited primarily to evaluation of screw accuracy and perioperative complications. This is the first study to evaluate granular differences in short and long-term complication and revision rate profiles between robotic (RG) fluoroscopic (FG) guidance for minimally invasive short-segment lumbar fusions. A retrospective analysis of a prospective, multi-center database was performed. Complications were subdivided into surgical (further subcategorized into adjacent segment disease, new-onset back pain, radiculopathy, motor-deficit, hardware failure, pseudoarthrosis), wound, and medical complications. Complication and revision rates were compared between RG and FG groups cumulatively at 30, 90 days, and 1 year. 374 RG and 111 FG procedures were performed. RG was associated with an 86.25, 83.20, and 69.42% cumulative reduction in complication rate at 30, 90 days, and 1 year, respectively, compared to FG (p < 0.001). At all follow-up points, new-onset radiculopathy and medical complications were most prevalent in both groups. The greatest reductions in complication rates were seen for new-onset back pain (88.13%; p = 0.001) and wound complications (95.05%; p < 0.001) at 30 days, new-onset motor deficits (90.11%; p = 0.004) and wound complications (85.16%; p < 0.001) at 90 days, and new-onset motor deficits (85.16%; p = 0.002), wound (85.16%; p < 0.001), and medical complications (75.72%; p < 0.001) at 1 year. RG was associated with a 92.58% (p = 0.002) reduction in revision rate at 90 days and a 66.08% (p = 0.026) reduction at 1 year. RG was associated with significant reductions in postoperative complication rates at all follow-up time points and significant reductions in revision rates at 90 days and 1 year.

Fluoroscopy time analysis of a prospective, multi-centre study comparing robotic- and fluoroscopic-guided placement of percutaneous pedicle screw instrumentation for short segment minimally invasive lumbar fusion surgery.

BACKGROUND: As minimally invasive spine surgery becomes more widespread, concerns regarding radiation exposure to surgeons and patients alike have become a growing concern. Robotic guidance has been developed as a way to increase the accuracy of instrumentation while decreasing radiation burden. METHODS: A retrospective analysis of a large, multi-centre, prospective study comparing robotic-guided (RG) to fluoroscopic-guided (FG) (Multi-centre, Partially Randomized, Controlled Trial of MIS Robotic vs. Freehand in Short Adult Degenerative Spinal Fusion Surgeries) was performed to evaluate for differences in radiation exposure between study groups. RESULTS: RG was associated with 78.3% (p < 0.001) and 79.8% (p < 0.001) reduction in total and per screw fluoroscopy times, respectively, as compared to FG. RG was also associated with a 50.8% (p < 0.001) reduction in total operative fluoroscopy time. CONCLUSIONS: RG was associated with significantly lower fluoroscopy times compared to FG. This suggests that utilization of robotic navigation systems may result in decreased operative radiation exposure, which is a growing concern for surgeons performing minimally invasive spine surgery.

Assessment of Surgical Procedural Time, Pedicle Screw Accuracy, and Clinician Radiation Exposure of a Novel Robotic Navigation System Compared With Conventional Open and Percutaneous Freehand Techniques: A Cadaveric Investigation.

STUDY DESIGN: Cadaveric study. OBJECTIVE: To evaluate accuracy, radiation exposure, and surgical time of a new robotic-assisted navigation (RAN) platform compared with freehand techniques in conventional open and percutaneous procedures. METHODS: Ten board-certified surgeons inserted 16 pedicle screws at T10-L5 (n = 40 per technique) in 10 human cadaveric torsos. Pedicle screws were inserted with (1) conventional MIS technique (L2-L5, patient left pedicles), (2) MIS RAN (L2-L5, patient right pedicles), (3) conventional open technique (T10-L1, patient left pedicles), and (4) open RAN (T10-L1, patient right pedicles). Output included (1) operative time, (2) number of fluoroscopic images, and (3) screw accuracy. RESULTS: In the MIS group, compared with the freehand technique, RAN allowed for use of larger screws (diameter: 6.6 ± 0.6 mm vs 6.3 ± 0.5 mm; length: 50.3 ± 4.1 mm vs 46.9 ± 3.5 mm), decreased the number of breaches >2 mm (0 vs 7), fewer fluoroscopic images (0 ± 0 vs 108.3 ± 30.9), and surgical procedure time per screw (3.6 ± 0.4 minutes vs 7.6 ± 2.0 minutes) (all P < .05). Similarly, in the open group, RAN allowed for use of longer screws (46.1 ± 4.1 mm vs 44.0 ± 3.8 mm), decreased the number of breaches >2 mm (0 vs 13), fewer fluoroscopic images (0 ± 0 vs 24.1 ± 25.8) (all P < .05), but increased total surgical procedure time (41.4 ± 8.8 minutes vs 24.7 ± 7.0 minutes, P = .000) while maintaining screw insertion time (3.31.4 minutes vs 3.1 ± 1.0 minutes, P = .650). CONCLUSION: RAN significantly improved accuracy and decreased radiation exposure in comparison to freehand techniques in both conventional open and percutaneous surgical procedures in cadavers. RAN significantly increased setup time compared with both conventional procedures.

A Multicenter Radiographic Evaluation of the Rates of Preoperative and Postoperative Malalignment in Degenerative Spinal Fusions.

STUDY DESIGN: Multicenter, retrospective, institutional-review-board -approved study at 18 institutions in the United States with 24 treating investigators. OBJECTIVE: This study was designed to retrospectively assess the prevalence of spinopelvic malalignment in patients who underwent one- or two-level lumbar fusions for degenerative (nondeformity) indications and to assess the incidence of malalignment after fusion surgery as well as the rate of alignment preservation and/or correction in this population. SUMMARY OF BACKGROUND DATA: Spinopelvic malalignment after lumbar fusion has been associated with lower postoperative health-related quality of life and elevated risk of adjacent segment failure. The prevalence of spinopelvic malalignment in short-segment degenerative lumbar fusion procedures from a large sample of patients is heretofore unreported and may lead to an under-appreciation of these factors in surgical planning and ultimate preservation or correction of alignment. METHODS: Lateral preoperative and postoperative lumbar radiographs were retrospectively acquired from 578 one- or two-level lumbar fusion patients and newly measured for lumbar lordosis (LL), pelvic incidence (PI), and pelvic tilt. Patients were categorized at preop and postop time points as aligned if PI-LL < 10° or malaligned if PI-LL≥10°. Patients were grouped into categories based on their alignment progression from pre- to postoperative, with preserved (aligned to aligned), restored (malaligned to aligned), not corrected (malaligned to malaligned), and worsened (aligned to malaligned) designations. RESULTS: Preoperatively, 173 (30%) patients exhibited malalignment. Postoperatively, 161 (28%) of patients were malaligned. Alignment was preserved in 63%, restored in 9%, not corrected in 21%, and worsened in 7% of patients. CONCLUSION: This is the first multicenter study to evaluate the preoperative prevalence and postoperative incidence of spinopelvic malalignment in a large series of short-segment degenerative lumbar fusions, finding over 25% of patients out of alignment at both time points, suggesting that alignment preservation/restoration considerations should be incorporated into the decision-making of even degenerative lumbar spinal fusions. LEVEL OF EVIDENCE: 3.

How does a novel monoplanar pedicle screw perform biomechanically relative to monoaxial and polyaxial designs?

BACKGROUND: Minimally invasive spinal fusions frequently require placement of pedicle screws through small incisions with limited visualization. Polyaxial pedicle screws are favored due to the difficulty of rod insertion with fixed monoaxial screws. Recently, a novel monoplanar screw became available that is mobile in the coronal plane to ease rod insertion but fixed in the sagittal plane to eliminate head slippage during flexion loads; however, the strength of this screw has not been established relative to other available screw designs. QUESTIONS/PURPOSES: We compared the static and dynamic load to failure in polyaxial, monoaxial, and monoplanar pedicle screws. METHODS: Six different manufacturers' screws (42 total) were tested in three categories (polyaxial, n = 4; monoaxial, n = 1; monopolar, n = 1) utilizing titanium rods. An additional test was performed using cobalt-chromium rods with the monopolar screws only. Screws were embedded into polyethylene blocks and rods were attached using the manufacturers' specifications. Static and dynamic testing was performed. Dynamic testing began at 80% of static yield strength at 1 Hz for 50,000 cycles. RESULTS: In static testing, monoaxial and monoplanar screws sustained higher loads than all polyaxial screw designs (range, 37%-425% higher; p < 0.001). The polyaxial screws failed at the head-screw interface, while the monoaxial and monoplanar screws failed by rod breakage in the static test. The dynamic loads to failure were greater with the monoplanar and monoaxial screws than with the polyaxial screws (range, 35%-560% higher; p < 0.001). With dynamic testing, polyaxial screws failed via screw-head slippage between 40% and 95% of static yield strength, while failures in monoaxial and monoplanar screws resulted from either screw shaft or rod breakage. CONCLUSIONS: All polyaxial screws failed at the screw-head interface in static and dynamic testing and at lower values than monoaxial/monoplanar screw designs. Monoplanar and monoaxial screws failed at forces well above expected in vivo values; this was not the case for most polyaxial screws. CLINICAL RELEVANCE: Polyaxial screw heads slip on the screw shank at lower values than monoaxial or monoplanar screws, and this results in angular change between the rod and pedicle screw, which could cause loss of segmental lordosis. The novel monoplanar screw used in this study may combine ease of rod placement with sagittal plane strength.

How does thoracic kyphosis affect patient outcomes in growing rod surgery?

STUDY DESIGN: Retrospective review of a multicenter series. OBJECTIVE: This study was conducted to specifically identify the complication rate of growing rod surgery in patients with normal (10°-40°) versus abnormal thoracic kyphosis. SUMMARY OF BACKGROUND DATA: Surgical treatment options for progressive early onset scoliosis include spinal fusion versus growth-sparing techniques. The current most commonly employed growing rod technique involves short fusions at the foundation sites using either hooks or screws as anchors and placement of dual growing rods spanning the deformity. Although the coronal deformity in these patients has been studied extensively, the sagittal profile has received less attention as a possible factor in complication rates and patient outcomes. METHODS: Out of 387 patients who underwent surgical placement of growing rods, 90 patients had complete clinical and radiographical data, with 2-year follow-up after initial surgery. Patients were categorized into 3 groups on the basis of preoperative thoracic kyphosis magnitude: less than 10° (K- group), 10°-40° (N group), and more than 40° (K+ group). Patient diagnosis, demographics, surgical information, radiographical measurements, and complication types were tabulated and analyzed. A P value of <0.05 was considered significant for all statistical tests. RESULTS: The K- group experienced 27 total complications including 15 general medical complications, the N group had 20 total and 4 general complications, and the K+ group had 55 total and 22 general complications. Patients in the K+ group were 3.1 times more likely to experience a complication than those in the N group, which was statistically significant (P < 0.05). When considering all types of complications, length of follow-up, T2-T5 proximal kyphosis, postoperative Cobb angle, and rod diameter were identified as confounding variables. When the confounding variables were taken into consideration in the analysis, the odds ratios were no longer significant between the N and K+ groups. Patients in the K+ group and K- group were 2.95 and 2.89 times more likely to experience a general medical complication than those in the N group, respectively (P > 0.05). The rate of implant-related complications between the groups did not reach statistical significance, although the K+ group had the most implant complications (n = 34), including 25 rod breakages in 16 patients. Syndromic patients had 2.9 times the risk of having an overall complication when compared with the entire patient series (P < 0.05). The number of patients who experienced multiple complications was higher in the K- and K+ groups than in the N group. CONCLUSION: Patients with thoracic hyperkyphosis present even more of a challenge with respect to complications, specifically implant-related complications. Our study shows that growing rod surgery in patients with kyphosis more than 40° has significantly more general and implant complications than that in patients with normal thoracic kyphosis. Implant complications were more common in hyperkyphotic (>40°) patients and increased linearly with increasing kyphosis. The most common implant complication was rod breakage. Patients with hyperkyphotic thoracic spines, particularly syndromic patients, must be monitored closely and parents should be counseled regarding the likelihood of future adverse events.