Pedicle Screw Instrumentation Research Articles

Comparative Analysis of Monoaxial and Polyaxial Pedicle Screws in the Surgical Correction of Adolescent Idiopathic Scoliosis.

Background: Although several biomechanical studies have been reported, few clinical studies have compared the efficacy of monoaxial and polyaxial pedicle screws in the surgical treatment of adolescent idiopathic scoliosis (AIS). This study aims to compare the radiological and clinical outcomes of mono- and polyaxial pedicle screws in the surgical treatment of AIS. Methods: A total of 46 AIS patients who underwent surgery to treat scoliosis using pedicle screw instrumentation (PSI) and rod derotation (RD) were divided into two groups according to the use of pedicle screws: the monoaxial group (n = 23) and polyaxial group (n = 23). Results: The correction rate of the main Cobb's angle was higher in the monoaxial group (70.2%) than in the polyaxial group (65.3%) (p = 0.040). No differences in the rotational correction of the apical vertebra were evident between the two groups. SRS-22 scores showed no significant differences according to the type of pedicle screws used. Conclusions: The use of polyaxial pedicle screws resulted in coronal, sagittal, and rotational correction outcomes comparable to those associated with the use of monoaxial pedicle screws for surgical treatment using PSI and RD to treat moderate cases of AIS.

Radiographic and clinical outcomes of robot-assisted pedicle screw instrumentation for adolescent idiopathic scoliosis.

Pedicle screw instrumentation (PSI) serves as the widely accepted surgical treatment for adolescent idiopathic scoliosis (AIS). The accuracy of screw positioning has remarkably improved with robotic assistance. Nonetheless, its impact on radiographic and clinical outcomes remains unexplored. This study aimed to investigate the radiographic and clinical outcomes of robot-assisted PSI vs. conventional freehand method in AIS patients. Data of AIS patients who underwent PSI with all pedicle screws between April 2013 and March 2022 were included and retrospectively analyzed; those with hybrid implants were excluded. Recruited individuals were divided into the Robot-assisted or Freehand group according to the technique used. Radiographic parameters and clinical outcome measures were documented. In total, 50 patients (19, Freehand group; 31, Robot-assisted group) were eligible, with an average age and follow-up period of 17.6 years and 60.2 months, respectively, and female predominance (40/50, 80.0%). The correction rates of Cobb's angles for both groups were significant postoperatively. Compared to freehand, the robot-assisted technique achieved a significantly reduced breech rate and provided better trunk shift and radiographic shoulder height correction with preserved lumbar lordosis, resulting in significantly improved visual analog scale scores for back pain from the third postoperative month. Overall, robot-assisted PSI provides satisfactory radiographic and clinical outcomes in AIS patients.

Pulmonary Function at Minimum 10 Years After Segmental Pedicle Screw Instrumentation for Thoracic Adolescent Idiopathic Scoliosis.

A prospective multi-center cohort study. This study evaluates the 10-year pulmonary function outcomes for patients with structural thoracic adolescent idiopathic scoliosis (Lenke curve types 1-4, 6) after segmental pedicle screw instrumentation. Adolescent idiopathic scoliosis with thoracic curves is associated with reduced pulmonary function preoperatively. It remains unclear how much pulmonary improvement can be obtained using pedicle screw instrumentation at long-term follow-up. Out of 64 consecutively surgically treated patients with thoracic AIS (Lenke 1-4, 6) using pedicle screw instrumentation, 50 (mean age at final FU 14.7 ± 1.9, 44 females) participated in a prospective 10-year follow-up study. They were evaluated using clinical examination, spinal radiographs, and spirometry preoperatively and at 10-year follow-up. The preoperative percentage predicted values were adjusted for the height loss caused by the scoliosis according to curve size. Preoperatively 49% (20/41) had forced vital capacity (FVC) or forced expiratory volume in one second (FEV1) below 80% of the predicted normal values representing pulmonary function impairment. Major curve correction averaged 76% (SD 9%). FVC improved from preoperative 3.29 L (SD 0.78L) to 3.87 L (0.79L) at 10-year follow-up (P<0.001). This improvement averaged 510mL (SD 560mL) in patients having both preoperative and 10-year follow-up measurements available. The percentage predicted values for FVC showed an improvement from 83% preoperatively to 86% at 10-year follow-up (P=0.048). At 10-year follow-up 38% (19/50) of the patients had FVC or FEV1 below 80% of the predicted values. FVC improved by a mean of 510ml from preoperative to 10-year follow-up in patients undergoing pedicle screw instrumentation for thoracic AIS. Despite 76% scoliosis correction and significant improvement of absolute lung volume values, more than one-third of these surgically treated otherwise healthy young adults fulfilled the criteria for pulmonary function impairment at 10-year follow-up. II.

Instrumentation of hypoplastic pedicles with patient-specific guides.

Hypoplastic pedicles of the thoracolumbar spine (<5mm diameter) are often found in syndromic deformities of the spine and pose a challenge in pedicle screw instrumentation. 3D-printed patient-specific guides might help overcome anatomical difficulties when instrumenting pedicles with screws, thereby reducing the necessity for less effective fixation methods such as hooks or sublaminar wires. In this study, the surgical feasibility and clinical outcome of patients with hypoplastic pedicles following pedicle screw instrumentation with 3D-printed patient-specific guides were assessed. Hypoplastic pedicles were identified on preoperative computed tomography (CT) scans in six patients undergoing posterior spinal fusion surgery between 2017 and 2020. Based on these preoperative CT scans, patient-specific guides were produced to help with screw instrumentation of these thin pedicles. Postoperatively, pedicle-screw-related complications or revisions were analyzed. 93/105 (88.6%) pedicle screws placed with patient-specific guides were instrumented. 62/93 (66.7%) of these instrumented pedicles were defined as hypoplastic with a mean width of 3.07mm (SD ±0.98mm, 95% CI [2.82-3.32]). Overall, 6 complications in the 62 hypoplastic pedicles (9.7%) were observed and included intraoperatively managed 4 cerebrospinal fluid leaks, 1 pneumothorax and 1 delayed revision due to 2 lumbar screws (2/62, 3.3%) impinging the L3 nerve root causing a painful radiculopathy. The mean follow-up time was 26.7 (SD ±11.7) months. Complications were only noted when the pedicle-width-to-screw-diameter ratio measured less than 0.62. Patient-specific 3D-printed guides can aid in challenging instrumentation of hypoplastic pedicles in the thoracolumbar spine, especially if the pedicle-width-to-screw-diameter ratio is greater than 0.62.

Experience with the utilization of new-generation shared-control robotic system for spinal instrumentation.

Robotic assistance in spine surgery is emerging as an accurate, effective and enabling technology utilized in the treatment of patients with surgical spinal pathology. The safety and reproducibility of robotic assistance in the placement of pedicle screw instrumentation is still being investigated. The objective of this study was to present our experience of instrumented spinal fusion utilizing an intraoperative robotic guidance system. We retrospectively reviewed all cases of spinal instrumentation of the thoracic and lumbo-sacral spine using the Mazor X robotic system (Medtronic Inc, Minneapolis, MN, USA), performed at our institution by one surgeon between July 2017 and June 2020. Wilcoxon Rank test was used to compare time taken to place each screw during the first 20 cases and the cases thereafter. A total of 28 patients were included. A total of 159 screws were placed using the Mazor X robotic system. The overall mean time for screw placement was 7.8±2.3 minutes and there was a significant reduction in the mean time for screw placement after the 20th case or 120 screws (8.70 vs. 5.42 min, P=0.008). No postoperative neurologic deficit or new radiculopathy was noted to occur secondary to hardware placement. No revision surgery was required for replacement or removal of a mispositioned screw. From this single-center, single-surgeon series we conclude that robot-assisted spine surgery can be safely and efficiently integrated into the operating room workflow, which improves after a learning curve of approximately 20 operative interventions. We found robot-assisted spinal instrumentation to be reliable, safe, effective and highly precise.

The Mid-term Outcome of Intervertebral Disc Degeneration after Direct Vertebral Rotation in Adolescent Idiopathic Scoliosis: Magnetic Resonance Imaging-based Analysis for a Mean 11.6-year Follow-up.

A retrospective cohort study. To evaluate the mid-term effect of intervertebral disc degeneration (DD) in adolescent idiopathic scoliosis (AIS) patients who underwent pedicle screw instrumentation (PSI) and rod derotation (RD) with direct vertebral rotation (DVR). Posterior spinal fusion is a mainstay of surgical treatment in AIS, and DVR is considered a main corrective maneuver for vertebral rotation. However, the mid-term effect of intervertebral DD after DVR is still unknown in AIS. A total of 336 vertebrae for 48 AIS patients who underwent PSI and RD with DVR were retrospectively assessed for intervertebral DD. They were divided into two groups based upon intervertebral DD, defined as Pfirmann grade more than IV. The Pfirrmann grade and modic change were evaluated at the disc above the uppermost instrumented vertebra (UIV), the disc below the lowest instrumented vertebra (LIV), and the lumbar disc levels. With the 11.6 years of mean follow-up, 41.7% (20/48) of patients exhibited DD, while modic changes were observed in 4.2% (2/48) of included patients. The disc below the LIV, L4-5, and L5-S1 were significantly shown to have an increasing trend of Pfirmann grade. The preoperative thoracic kyphosis was significantly lower in the DD group (22.0°) than in the non-DD group (31.4°) (P = 0.025) and negatively correlated with DD (r = -0.482, P = 0.018). The Pfirrmann grade of L5-S1 showed a high level of correlation with DD (r = 0.604, P < 0.001). The degenerative change at the disc below the LIV, L4-5, and L5-S1 levels was observed following PSI and RD with DVR. Thoracic hypokyphosis may negatively influence intervertebral discs in AIS patients required for deformity correction. Therefore, restoration of thoracic kyphosis is important to prevent long-term DD in AIS.

Forcefully engaging rods into tulips with gap discrepancy leading to pedicle screw loosening—a biomechanical analysis using long porcine spine segments

BACKGROUND CONTEXTLong-segment pedicle screw instrumentation is widely used to treat complex spinal disorders. Rods are routinely precontoured to maximize assistance on the correcting side of the deformity, but there often exists a residual gap discrepancy between the precontoured rods and screw tulips. No previous research has investigated the diminished pullout strength of the most proximal or distal pedicle screw resulting from a mismatched rod in long-segment pedicle screw instrumentation. PURPOSEThe present study aimed to investigate the decreased pullout force of pedicle screws affected by the gap discrepancy when forcefully engaging a mismatched rod into a tulip in a normal-density porcine spine. STUDY DESIGNThe pedicle screw fixation strength under axial pullout force was compared among three different gap discrepancies between rods and tulips using long porcine spine segments. METHODSTwelve porcine lumbar vertebrae (L3–L6) were implanted with pedicle screws and rods. Screws on one side had no gap between the tulip and rod (0-mm group), while the most proximal screw on the other side had an intentional gap of 3 mm (3-mm group) or 6 mm (6-mm group). Three hours after forcefully engaging the rod into the tulips at room temperature, the set screws in all specimens were loosened, and each specimen was dissected into individual vertebrae for subsequent pullout testing. RESULTSThe control group exhibited significantly greater pullout strength (1987.68 ± 126.80 N) than the groups from different rod-tulip configurations (p<.05), with significantly greater strength in the 3-mm group (945.62 ± 97.43 N) than the 6-mm group (655.30 ± 194.49 N) (p<.05). Only 47.6% and 33.0% of the pullout strength was retained in the 3-mm and 6-mm groups, respectively, compared to the control group. CONCLUSIONSGap discrepancies between rods and tulips can significantly reduce pedicle screw pullout strength, with a correlation between decreased strength and increased gaps. Surgeons should avoid forcefully engaging mismatched rods and consider well-fitted contoured rods in spinal surgery to minimize the risk of screw loosening. CLINICAL SIGNIFICANCEThe gap discrepancy between rod and tulip significantly affected pullout strength, with greater gaps leading to reduced strength. Forcefully engaging mismatched rods into tulips in degenerative spinal surgery should be avoided to minimize the risk of early screw pullout.

Free-hand technique of C7 pedicle screw insertion using a simply defined entry point without fluoroscopic guidance for cervical spondylotic myelopathy patients with C3 to C6 instrumented by lateral mass screws: a retrospective cohort study

BackgroundNowadays, both lateral mass screw (LMS) and pedicle screw were effective instrumentation for posterior stabilization of cervical spine. This study aims to evaluate the feasibility of a new free-hand technique of C7 pedicle screw insertion without fluoroscopic guidance for cervical spondylotic myelopathy (CSM) patients with C3 to C6 instrumented by lateral mass screws.MethodsA total of 53 CSM patients underwent lateral mass screws instrumentation at C3 to C6 levels and pedicle screw instrumentation at C7 level were included. The preoperative 3-dimenional computed tomography (CT) reconstruction images of cervical spine were used to determine 2 different C7 pedicle screw trajectories. Trajectory A passed through the axis of the C7 pedicle while trajectory B selected the midpoint of the base of C7 superior facet as the entry point. All these 53 patients had the C7 pedicle screw inserted through trajectory B by free-hand without fluoroscopic guidance and the postoperative CT images were obtained to evaluate the accuracy of C7 pedicle screw insertion.ResultsTrajectory B had smaller transverse angle, smaller screw length, and smaller screw width but both similar sagittal angle and similar pedicle height when compared with trajectory A. A total of 106 pedicle screws were inserted at C7 through trajectory B and only 8 screws were displaced with the accuracy of screw placement as high as 92.5%.ConclusionIn CSM patients with C3 to C6 instrumented by LMS, using trajectory B for C7 pedicle screw insertion is easy to both identify the entry point and facilitate the rod insertion.

Intraoperative lateral wall breach simulation in the cadaveric spine and the impact of thread designs of screws on pullout strength in the osteoporotic thoracic vertebrae: A biomechanical study in human cadavers.

This study aimed (1) to simulate pedicle screw pullout after intraoperative external wall perforation and (2) to assess restoration strength with different thread designs in the pedicle screw instrumentation for osteoporotic thoracic vertebrae. Twenty fresh-frozen human cadaveric thoracic vertebra bodies were prepared and divided into 4 groups: group 1, 5.5 mm × 45 mm polyaxial single thread pedicle screws (PASTS); group 2, after wall injury 5.5 mm × 45 mm PASTS; group 3, 6.5 mm × 45 mm PASTS after wall injury; and group 4: 6.5 mm × 45 mm polyaxial mixed-threaded screws after wall injury. While group 1 was the control group, groups 2, 3, and 4 were used as study groups after the lateral wall breach. All prepared screw units were placed on a universal pullout measurement testing device. The mean bone mineral density for 20 thoracic vertebrae was 0.57 ± 0.12 g/cm2 (range 0.53-0.6 g/cm2 ). The mean pullout strength was 474.90 Newtons (N) for group 1, 412.85 N for group 2, 475.4 N for group 3, and 630.74N for group 4. The lateral wall breach caused a 14.1 % decrease in average pullout strength compared with the initial screw pullout. Mixed (double)-threaded screws increased pullout strength compared to 6.5 mm screws (P=.036) Conclusion: Using a 1 mm thicker polyaxial pedicle screw or mixed (double)-threaded pedicle screw seems to increase pullout strength; however, this was statistically significant only for group 4. In the thoracic spine, the redirection possibility of the pedicle screw is limited, and augmentation with cement will not be appropriate due to the risk of wall injury-related leakage. Therefore, care should be taken to avoid violating the lateral cortex by using appropriate pedicle entry points and trajectories.

In Honor of Professor Se-Il Suk's Significant Achievements and Contributions to Pedicle Screw Instrumentation and Related Surgical Techniques in Spinal Deformity.

In Honor of Professor Se-Il Suk's Significant Achievements and Contributions to Pedicle Screw Instrumentation and Related Surgical Techniques in Spinal Deformity.

Effects of Augmented Reality on Thoracolumbar Pedicle Screw Instrumentation Across Different Levels of Surgical Experience

Objective Augmented reality (AR) is an emerging technology that may accelerate skill acquisition and improve accuracy of thoracolumbar pedicle screw placements. We quantify the relative assistance of AR compared to free-hand (FH) pedicle screw accuracy across different surgical experience levels. Methods A spine fellowship-trained and board-certified attending neurosurgeon, PGY-4 neurosurgery resident, and 2nd year medical student placed a total of 32 FH and 32 AR-assisted thoracolumbar pedicle screws in 3 cadavers. A cableless, voice activated AR system (VisAR, Novarad, Provo, UT) was paired with a HoloLens 2 headset (Microsoft Corp., Redmond, WA). Accuracy was assessed using Chi-square analysis and the Gertzbein-Robins scale (GRS). Angular error, distance error, and time per pedicle screw were also collected and compared. Results The attending had 91.6% (11/12) clinically acceptable (GSR A or B) in both FH and AR groups; the resident had 100% (9/9) FH and AR in both cases; the medical student had 72.3% (8/11) FH accuracy and 81.8% (9/11) AR accuracy. The medical student had significantly lower ideal (GRS A) FH accuracy compared to the resident (p = 0.017) and attending (p= 0.005), but no difference when using AR. FH screw placement was faster by both the attending (median 46s vs. 94.5s, p=0.0047) and resident (median 144s vs. 140s, p=0.05). Total clinically acceptable AR and FH accuracy was 90.6% (29/32) and 87.5% (28/32, p = 0.69), respectively. Conclusion AR screw placement allowed an inexperienced medical student to double his accuracy in one training session. With subsequent iterations, this promising technology could serve as an important tool for surgical training.

Increased stability due to symmetric cement volume in augmented pedicle screws? A biomechanical study.

Pedicle screw instrumentation has become "state of the art" in surgical treatment of many spinal disorders. Loosening of pedicle screws due to poor bone mineral density is a frequent complication in osteoporotic patients. As prevalence of osteoporosis and spinal disorders are increasing with an aging demographic, optimizing the biomechanical properties of pedicle screw constructions and therefore outcome after spinal surgery in osteoporotic patients is a key factor in future surgical therapy. Therefore, this biomechanical study investigated the stability of polymethylmethacrylate (PMMA)-augmented pedicle screw-rod constructions under a deviating distribution of PMMA applied to the instrumentation in osteoporotic human cadaveric vertebrae. We showed that PMMA-augmented pedicle screw-rod constructions tend to be more stable than those with non-augmented pedicle screws. Further, there appears to be a larger risk of screw loosening in unilateral augmented pedicle screws than in non-augmented, therefore a highly asymmetrically distributed PMMA should be avoided.

Intraoperative anteroposterior and oblique fluoroscopic views for detection of mediolateral pedicle screw misplacement in the lumbar spine: a randomized cadaveric study

Backgroud contextPedicle screws are commonly used for posterior fixation of the lumbar spine. Inaccuracy of screw placement can lead to disastrous complications. PurposeAs fluoroscopic assisted pedicle screw instrumentation is the most frequently used technique, the aim of this study was to assess the specificity, sensitivity and accuracy of intraoperative fluoroscopy to detect mediolateral screw malpositioning. We also analyzed whether the addition of an oblique view could improve these parameters. Study designOn 12 human cadavers, 138 pedicle screws were placed intentionally either with 0 to 2 mm (75 screws), with 2 to 4 mm (six medial and 12 lateral screws) and with >4 mm (22 medial and 23 lateral screws) breach of the pedicle from Th12 to L5. MethodsThree experienced spine surgeons evaluated the screw positioning in fluoroscopic AP views and 4 weeks later in AP views and additional oblique views. The surgeons' interpretation was compared with the effective screw position on postoperative CT scans. ResultsPedicle breaches greater than 2 mm were detected in 68% with AP views and in 67% with additional oblique views (p=.742). The specificity of AP views was 0.86 and 0.93 with additional oblique views (p=<.01). The accuracy was 0.78 with AP views and 0.81 with AP + oblique views (p=.114). There was a substantial inter-reader agreement (Fleiss's kappa: 0.632). ConclusionsFluoroscopic screening of pedicle screw misplacement has a limited sensitivity. Adding an oblique view improves specificity but not sensitivity and accuracy in detecting screw malpositions. Clinical significanceWhen in doubt of a screw malpositioning, other modalities than a fluoroscopic assisted pedicle screw instrumentation such as intraoperative CT imaging or an intraoperative exploration of the screw trajectory must be evaluated.

Cement Augmentation of Pedicle Screw Instrumentation: A Literature Review.

This literature review aimed to review the current understanding, indications, and limitations of pedicle screw instrumentation cement augmentation. Since they were first reported in the 1980s, pedicle screw cement augmentation rates have been increasing. Several studies have been published to date that describe various surgical techniques and the biomechanical changes that occur when cement is introduced through the screw-bone interface. This article provides a concise review of the uses, biomechanical properties, cost analysis, complications, and surgical techniques used for pedicle screw cement augmentation to help guide physician practices. A comprehensive review of the current literature was conducted, with key studies, and contributions from throughout history being highlighted. Patients with low bone mineral density are the most well-studied indication for pedicle screw cement augmentation. Many studies show that cement augmentation can improve pullout strength in patients with low bone mineral density; however, the benefit varies inversely with pathology severity and directly with technique. The various screw types are discussed, with each having its own mechanical advantages. Cement distribution is largely dependent on the filling method and volume of cement used. Cement composition and timing of cement use after mixing are critical considerations in practice because they can significantly alter the bone-cement and screw-cement interfaces. Overall, studies have shown that pedicle screw cement augmentation has a low complication rate and increased pullout strength, justifying its universal use in patients with a suboptimal bone-implant interface.

Early Compensatory Segmental Angle Changes at L3-4 and L4-5 Following a L5-S1 Interbody Fusion for a Grade 1 Spondylolisthesis.

Retrospective study included patients who underwent a L5-S1 ALIF or TLIF with posterior pedicle screw instrumentation for grade 1 spondylolisthesis 2018-2022. To compare early reciprocal changes at the L3-4 and L4-5 adjacent levels six months after anterior (ALIF) or transforaminal (TLIF) lumbar interbody fusion at L5-S1. Degenerative and chronic isthmic spondylolistheses often result in decreased segmental lordosis at L5-S1. This can lead to lordotic overcompensation at adjacent levels to maintain spinopelvic balance. However, the fate of adjacent angles following interbody fusion is not well understood. Preoperative and 6-month postoperative measurements of segmental lordosis (L3-4, L4-5, and L5-S1), lumbar lordosis, and pelvic incidence were obtained from sagittal standing radiographs. Preliminary t-tests were performed for descriptive purposes, and multiple regression was used for hypothesis testing. Ninety-eight patients met the inclusion criteria (50 ALIF and 48 TLIF). A greater amount of lordosis achieved at L5-S1 was significantly associated with a greater reduction of segmental lordosis at L4-5 (r=-0.65, P<.001) or L3-4 (r=-0.46, P<.001) (Fig. 3A). A greater preoperative PI was associated with a greater reduction of segmental lordosis at L4-L5 (r=-0.42, P<.001) and at L3-L4 (r=-0.44, P<.001). At six months following a lumbar interbody fusion at L5-S1, greater compensatory changes with lordosis reduction are observed at the supra-adjacent L4-5 and L3-4 levels in patients achieving greater L5-S1 segmental lordosis. Additionally, preoperative pelvic incidence (PI) played a role in influencing lordotic correction.

Correction of severe adult idiopathic scoliosis posteriorly with skipped pedicle screw instrumentation and rod augmentation.

Although it is challenging to correct severe adult idiopathic scoliosis (ADIS) deformities, optimal results can be achieved by multiple asymmetric Ponte osteotomies with lower surgical risks. Skipping the apical instrumentation and using multiple rods and connectors may further facilitate the procedure. We named this method as "modular correction technique" (MCT). Sixty-two patients with severe ADIS who were treated with MCT were recruited into this study, and retrospectively evaluated. Radiographic and functional outcomes as well as pulmonary functions were examined preoperatively and at last follow-up. Main radiologic parameters were related to Cobb angles, coronal, sagittal, and shoulder balance. Scoliosis Research Society-22 questionnaire and the Oswestry Disability Index were used to evaluate clinical outcomes. Average age of the patients was 41.3 years (range: 23-65). Thirty-nine of the patients were female and 23 of them were male. Coronal Cobb angle of the main curve, shoulder balance, coronal, and sagittal balance significantly improved after the surgery. Forced vital capacity and forced expiratory volume in the first second were mildly improved after the surgery, however the improvement was not statistically significant. Postoperative clinical outcome scores improved significantly. MCT can be performed with low risk of complications and relatively low operation time and blood loss. It facilitates rod insertion and correction maneuvers. Radiologic, especially coronal balance, and functional outcomes can be improved with minimal morbidity while deterioration of pulmonary function is prevented. This technique is useful in severe but relatively flexible ADIS deformities.

Instrumented lumbar fusion in patients over 75 years of age: is it worthwhile?-a comparative study of the improvement in quality of life between elderly and young patients.

Surgical treatment of degenerative lumbar disease in the elderly is controversial. Elderly patients have an increased risk for medical and surgical complications commensurate with their comorbidities, and concerns over complications have led to frequent cases of insufficient decompression to avoid the need for instrumentation. The purpose of this study was to evaluate clinical outcome between older and younger patients undergoing lumbar instrumented arthrodesis. This is a retrospective, comparative study of prospectively collected outcomes. One hundred and fifty-four patients underwent 1- or 2-level posterolateral lumbar fusion. Patients were divided into two groups. Group 1: 87 patients ≤65 years of age who underwent decompression and posterolateral instrumented fusion; Group 2: 67 patients ≥75 years of age who underwent the same procedures with polymethylmethacrylate (PMMA) pedicle-screw augmentation. Mean follow-up 27.47 months (range, 76-24 months). Mean age was 49.1 years old (range, 24-65) for the younger group and 77.8 (range, 75-86) in the elderly group. Patients ≥75 years of age showed higher preoperative comorbidity (American Society of Anesthesiology, ASA: 1.7 vs. 2.4), and ≥2 systemic diseases with greater frequency (12.5% vs. 44.7%). No significant differences were found between the two groups in terms of postoperative complications, fusion, or revision rate. During follow-up, adjacent disc disease and adjacent fracture occurred significantly more in Group 2 (P<0.05). At the end of follow-up, there were no significant differences between the two groups in any of the clinical and health-related quality of life scores or satisfaction with treatment received. Osteoporosis represents a major consideration before performing spine surgery. Despite an obvious increased risk of complications in elderly patients, PMMA-augmented fenestrated pedicle screw instrumentation in spine fusion represents a safe and effective surgical treatment option to elderly patients with poor bone quality. Age itself should not be considered a contraindication in otherwise appropriately selected patients.

Prospective Comparison of Two Robotically Navigated Pedicle Screw Instrumentation Techniques.

This study aimed to compare screw accuracy and incidence of skive between two robotically navigated instrumented techniques in posterior spine fusion surgery: manual anti-skive instrumentation with an anti-skive cannula (ASC) and the use of a navigated, high-speed drill (HSD). Over a 3-year period, consecutive patients are undergoing RNA posterior fusion surgery with either ASC (n = 53) or HSD (n = 63). Both groups met a value of approximately 292 screws in our analysis (296 ASC, 294 HSD), which was determined by a biostatistician at an academic institution. Screw accuracy and skive was analyzed using preoperative CT and intraoperative three-dimensional (3D) fluoroscopy. Among 590 planned robotically inserted pedicle screws (296 ASC, 294 HSD), 245 ASC screws (82.8%) and 283 HSD screws (96.3%) were successfully inserted (p < 0.05). Skive events occurred in 4/283 (1.4%) HSD screws and 15/245 (6.2%) ASC screws (p < 0.05). HSD screws showed better accuracy in the axial and sagittal planes, being closer to planned trajectories in all directions except cranial deviation (p < 0.05). Additionally, HSD had a significantly lower time per screw (1.9 ± 1.0min) compared to ASC (3.2 ± 2.0min, p < 0.001). No adverse clinical effects were observed. The HSD technique showed significant improvements in time and screw accuracy compared to ASC. Biplanar fluoroscopy and 3D imaging resulted in significantly lower radiation exposure and time compared to ASC. These significant findings in the HSD group may be attributed to the lower occurrence of malpositioned screws, leading to a decrease in the need for second authentication. This represents a notable iterative improvement of the RNA platform.

Does index-level pedicle screw instrumentation affect cage subsidence after vertebral body replacement? – A biomechanical study in human cadaveric osteoporotic specimens

BackgroundVertebral body replacement is a common surgical procedure for treatment of disorders associated with spinal instability. Therefore, pedicle screws are usually inserted in adjacent vertebrae for stabilization of the posterior column, however, there is lack of evidence whether implantation of index-level pedicle screws is beneficial or not. This biomechanical study aims to investigate the effect of pedicle screw instrumentation on axial stability following vertebral body replacement. MethodsUnstable fracture at L3 level was simulated in lumbar spines from six human cadaveric specimens. Then instrumentation was performed one level above / one level below index level in three specimens and further, three specimens were instrumented at index-level (L3) additionaly. Then we used a testing protocol for biomechanical evaluation of axial loading on human cadaveric lumbar spines until cage subsidence occurred. FindingsOur results show that index-level instrumented spines endured significantly higher load until cage subsidence occurred compared to non-index-level instrumented specimens (p = 0.05). InterpretationOur results demonstrate pedicle screw instrumentation at index-level vertebra should be considered when possbile as it may have a protective effect against cage subsidence in patients undergoing vertebral body replacement surgery.

Posterior instrumented correction and fusion of adolescent idiopathic scoliosis

Balanced frontal curve correction with horizontal shoulder levels, restoration of sagittal plane and vertebral derotation with afusion length as short as possible. Curves larger than 40-50° Cobb angle; furthermore age, location, degree of rotation, and sagittal plane deviation have to be considered. Posteriorly, segmental pedicle screw instrumentation with ahigh screw density (80%) and both titanium alloy and cobalt chrome rods. Freehand screw placement under consideration of both natural and deformity-induced pedicle morphology. Correction via reduction screws or instruments. Combined correction technique with rod rotation, segmental screw approximation to the generally concave rod and segmental correction of vertebral translation. Moderate concave distraction and convex compression. If needed, final in situ bending of the rods. Schwab typeI osteotomies; in rigid curves typeII osteotomies. Fusion with local bone, allogenic bone and/or bone substitutes (i.e.,tricalcium phosphate). Intraoperative placement of athoracic epidural catheter for postoperative pain control. Neurological monitoring throughout the procedure. Mobilization on postoperative day1 with focus on pain management and nutrition. Return to school after 4weeks. Physiotherapy after 3months, cycling after 3-6months, and full sport activities after 1year. Frontal curve correction of 60-80%, sufficient sagittal plane correction. Correction of rib hump 40%. Patient satisfaction is high at 95% and long-term revision rates of < 10%.