Experimental Analysis of Robotic Cortical Bone Specimen Drilling Performance: Effect of Cryogen.

In orthopedic surgery, precise bone screw insertion is crucial for stabilizing fractures, necessitating a preliminary cortical bone drilling procedure. However, this process can induce temperatures exceeding 70 °C due to the low thermal conductivity of cortical bone, potentially leading to thermal osteonecrosis. Furthermore, significant cutting forces and torque pose risks of tool breakage and bone damage, underlining the need for high precision and optimal processing parameters. Traditionally, drilling relies on the surgeon's experience and often results in imprecise outcomes due to inconsistent feed rates. Therefore, this study proposes the use of a 6-axis robot for controlled drilling, offering precise control over angular velocities and consistent feed rates. Additionally, explore the use of cryogenic liquid nitrogen (LN2) as a novel cooling method compared to conventional saline solutions, examining its efficacy under various cutting conditions. The results demonstrate that LN2 cooling conditions lead to a reduction in thrust and torque under specific processing conditions, and facilitate smoother chip evacuation. Additionally, LN2 significantly lowers the peak temperature around the drilling site, thus minimizing the risk of thermal osteonecrosis. Consequently, the use of a 6-axis robot provides consistent feed rates, and LN2 cooling achieves optimal processing conditions, enabling a more controlled and effective drilling process.

Cortical Trajectory versus Traditional Pedicle Screw Trajectory in Open Transforaminal Lumbar Interbody Fusion: Meta-Analysis of Complications and Clinical Outcomes.

BACKGROUND: Lumbar degenerative disease imposes a substantial burden on global health care expenditures. Transforaminal lumbar interbody fusion (TLIF) using either traditional trajectory (TT) pedicle screws or cortical bone trajectory (CBT) pedicle screws has become increasingly common. This meta-analysis evaluated outcomes and safety of open TLIF with TT compared with CBT. METHODS: PubMed, Cochrane, and Google Scholar were searched up to April 2024. The studied outcomes included complications, revision surgeries, operating room time, estimated blood loss, length of hospital stay (LOS), incision length, Visual Analog Scale, Oswestry Disability Index, and Japanese Orthopedic Association. RESULTS: This meta-analysis included 5 studies; 770 patients undergoing TLIF were included, with 415 in the CBT group and 355 in the TT group. No statistically significant differences were found in the rate of overall complications, including specific complications, rate of revision surgeries, patient-reported outcome measures, operating room time, and estimated blood loss. However, the CBT group demonstrated shorter LOS (P = 0.05) and shorter incision lengths (P < 0.001) compared with the TT group. CONCLUSIONS: TT and CBT in TLIF procedures demonstrated comparable rates of complications, reoperations, and patient-reported outcome measures. Despite similar operating room times and estimated blood loss, the CBT group exhibited shorter incision lengths and shorter LOS than the TT group. Both CBT and TT pedicle screws are safe and effective options for TLIF. There are potential benefits to CBT such as shorter incision and LOS, although TT remains an essential tool for spinal instrumentation techniques.

Comparative effectiveness of cortical bone trajectory screws and pedicle screws in the treatment of adjacent segment degeneration after lumbar fusion surgery: a systematic review and meta-analysis.

PURPOSE: To compare the efficacy and safety of cortical bone trajectory (CBT) screw and pedicle screw (PS) internal fixation in the treatment of adjacent segment degeneration (ASD) after lumbar fusion. METHODS: This study was registered on International Prospective Register of Systematic Reviews (PROSPERO) (ID: CRD42023484937). We searched PubMed, Embase, Web of Science, Cochrane Library, China National Knowledge Infrastructure (CNKI), Wan Fang Database, and Wei Pu Database by computer to collect controlled clinical studies on the efficacy and safety of cortical bone trajectory (CBT) screw and pedicle screw (PS) internal fixation in the treatment of adjacent segment degeneration (ASD) after lumbar fusion from database establishment to November 2023. Two researchers screened the literature, extracted data and evaluated the risk of bias of the included studies, recorded the authors, and sample size, and extracted the intraoperative blood loss, operation time, Oswestry disability index (ODI), Visual analogue scale (VAS), disc height (DH), hospital length stay and complications in each study. Meta-analysis was performed using Revman 5.4 software provided by Cochrane Library. RESULTS: A total of 6 cohort studies (CS) and 1 randomized controlled study with a total of 420 patients were included in this study, including 188 patients in the CBT group and 232 patients in the PS group. The CBT group had lower intraoperative blood loss than the PS group [mean difference (MD) = -129.38, 95% CI (-177.22, -81.55), P < 0.00001] and operation time was shorter than that of the PS group [MD = -1.42, 95% CI (-2.63, -0.20), P = 0.02]. Early postoperative back and leg pain improved more significantly in the CBT group [MD = -0.77, 95% CI (-1.35, -0.19), P = 0.01; MD = -0.24, 95% CI (-0.37, -0.10), P = 0.0005]. CONCLUSION: Compared with PS, CBT for adjacent segment degeneration after lumbar fusion has the advantages of less intraoperative blood loss, shorter operation time, and less back and leg pain in the early postoperative period.

Ex-vivo parametric study of laser ablation-based drilling of cortical bone.

Frequently orthopedic surgeries require mechanical drilling processes especially for inserted biodegradable screws or removing small bone lesions. However mechanical drilling techniques induce large number of forces as well as have substantially lower material removal rates resulting in prolong healing times. This study focuses on analyzing the impact of quasi-continuous laser drilling on the bone's surface as well as optimizing the drilling conditions to achieve high material removal rates. An ex-vivo study was conducted on the cortical region of desiccated bovine bone. The laser-based drilling on the bovine bine specimens was conducted in an argon atmosphere using a number of laser pulses ranging from 100 to 15,000. The morphology of the resulting laser drilled cavities was characterized using Energy dispersive Spectroscopy (EDS) and the width and depth of the drills were measured using a laser based Profilometer. Data from the profilometer was then used to calculate material removal rates. At last, the material removal rates and laser processing parameters were used to develop a statistical model based on Design of Experiments (DOE) approach to predict the optimal laser drilling parameters. The main outcome of the study based on the laser drilled cavities was that as the number of laser pulses increases, the depth and diameter of the cavities progressively increase. However, the material removal rates revealed a decrease in value at a point between 4000 and 6000 laser pulses. Therefore, based on the sequential sum of square method, a polynomial curve to the 6th power was fit to the experimental data. The predicted equation of the curve had a p-value of 0.0010 indicating statistical significance and predicted the maximum material removal rate to be 32.10 mm3/s with 95%CI [28.3,35.9] which was associated with the optimum number of laser pulses of 4820. Whereas the experimental verification of bone drilling with 4820 laser pulses yielded a material removal rate of 33.37 mm3/s. Therefore, this study found that the carbonized layer formed due to laser processing had a decreased carbon content and helped in increasing the material removal rate. Then using the experimental data, a polymetric equation to the sixth power was developed which predicted the optimized material removal rate to occur at 4820 pulses.

Efficacy and Safety of Cortical Bone Trajectory Screws versus Pedicle Screws in Lumbar Fusion: A Systematic Review and Meta-Analysis.

OBJECTIVE: A systematic review and meta-analysis was conducted to compare the efficacy and safety of cortical bone trajectory (CBT) screws and traditional pedicle screws in lumbar fusion. METHODS: Randomized controlled studies and cohort studies on CBT versus pedicle screws in lumbar fusion were searched in China Biology Medicine, China National Knowledge Infrastructure, Wanfang, VIP Database for Chinese Technical and Science Periodicals, PubMed, Cochrane Library, and Web of Science databases. The search period spanned from the establishment of the databases to December 2023. The Cochrane bias risk assessment tool and Newcastle-Ottawa scale were applied to assess the quality of the literature included. Clinical and imaging data as well as surgical outcomes, recovery, and postoperative complications were extracted from the relevant literature. RESULTS: A total of 6 randomized controlled trials and 26 cohort studies were included after screening by inclusion and exclusion criteria with a total of 2478 patients. The meta-analysis demonstrated significant discrepancies between the CBT and TPS groups in Japanese Orthopaedic Association score at 3 and 6 months and final follow-up. Moreover, the TPS group exhibited a higher Oswestry disability index at final follow-up, a greater VAS for low back pain at both 1 week and final follow-up, as well as a higher VAS for leg pain at 1 month. Differences were also noted in surgical and recovery outcomes. However, there was no significant difference between the 2 groups in postoperative complications. CONCLUSIONS: CBT and TPS have analogous safety profiles when applied to lumbar fusion, but the clinical efficacy of CBT is superior to that of TPS to some extent, and the procedure is less invasive with faster recovery.

Design and radiological confirmation of 3-column cortical bone trajectory in the lumbar spine.

OBJECTIVE: The aim of this study was to design a novel lumbar cortical bone trajectory (CBT) penetrating the anterior, middle, and posterior vertebral area using imaging; measure the relevant parameters to find theoretical parameters and screw placement possibilities; and investigate the optimal implantation trajectory of the CBT in patients with osteoporosis. METHODS: Three types of CBTs with appropriate lengths were selected to simulate screw placement using Mimics software. These CBTs were classified as the leading tip of the trajectory pointing to the posterior quarter area (original CBT [CBT-O]) and middle (novel CBT A [CBT-A]) and anterior quarter (novel CBT B [CBT-B]) of the superior endplate. The authors then measured the maximum screw diameter (MSD) and length (MSL), cephalad (CA) and lateral (LA) angles, and bone mineral density (Hounsfield unit [HU] values) of the planned novel 3-column CBT screw placements. The differences in the parameters of the novel CBTs, the percentages of successfully planned CBT screws, and the factors that influenced the successful planning of 3-column CBT screws were analyzed. RESULTS: Three-column CBT screws were successfully designed in all segments of the lumbar spine. The success rate of the 3-column CBT planned screws was 72.25% (83.25% for CBT-A and 61.25% for CBT-B). From the CBT-O type, to the CBT-A type, to the CBT-B type, the LA, CA, and MSD of the novel CBT screws decreased with increasing trajectory length. The HU values of the three types of trajectories were all significantly higher than that of the traditional pedicle screw trajectory (p < 0.001). The main factor affecting successful planning of the 3-column CBT screw was pedicle width. CONCLUSIONS: Moderating adjustment of the original screw parameters by reducing LAs and CAs to penetrate the anterior, middle, and posterior columns of the vertebral body using the 3-column CBT screw is feasible, especially in the lower lumbar spine.

Ex vivo analysis of cortical microarchitecture of the distal clavicle: implications for surgical management of fractures.

BACKGROUND: Cortical thickness and porosity are two main determinants of cortical bone strength. Thus, mapping variations in these parameters across the full width of the distal end of the clavicle may be helpful for better understanding the basis of distal clavicle fractures and for selecting optimal surgical treatment. METHODS: Distal ends of 11 clavicles (6 men, 5 women; age: 81.9 ± 15.1 years) were scanned by micro-computed tomography at 10-µm resolution. We first analyzed cortical thickness and porosity of each 500-µm-wide area across the superior surface of distal clavicle at the level of conoid tubercle in an antero-posterior direction. This level was chosen for detailed evaluation because previous studies have demonstrated its superior microarchitecture relative to the rest of the distal clavicle. Subsequently, we divided the full width of distal clavicle to three subregions (anterior, middle, and posterior) and analyzed cortical porosity, pore diameter, pore separation, and cortical thickness. RESULTS: We found the largest number of low-thickness and high-porosity areas in the anterior subregion. Cortical porosity, pore diameter, pore separation, and cortical thickness varied significantly among the three subregions (p < 0.001 p = 0.016, p = 0.001, p < 0.001, respectively). Cortex of the anterior subregion was more porous than that of the middle subregion (p < 0.001) and more porous and thinner than that of the posterior subregion (p < 0.001, p = 0.030, respectively). Interaction of site and sex revealed higher porosity of the anterior subregion in women (p < 0.001). The anterior subregion had larger pores than the middle subregion (p = 0.019), whereas the middle subregion had greater pore separation compared with the anterior (p = 0.002) and posterior subregions (p = 0.006). In general, compared with men, women had thinner (p < 0.001) and more porous cortex (p = 0.03) with larger cortical pores (p < 0.001). CONCLUSIONS: Due to high cortical porosity and low thickness, the anterior conoid subregion exhibits poor bone microarchitecture, particularly in women, which may be considered in clinical practice. LEVELS OF EVIDENCE: Level IV.

Contact states with femoral cortical bone and periprosthetic bone mineral density changes differ between traditional and newly introduced fully hydroxyapatite-coated stems.

Aims: The aim of this study was to compare the pattern of initial fixation and changes in periprosthetic bone mineral density (BMD) between patients who underwent total hip arthroplasty (THA) using a traditional fully hydroxyapatite (HA)-coated stem (T-HA group) and those with a newly introduced fully HA-coated stem (N-HA group). Methods: The study included 36 patients with T-HA stems and 30 with N-HA stems. Dual-energy X-ray absorptiometry was used to measure the change in periprosthetic BMD, one and two years postoperatively. The 3D contact between the stem and femoral cortical bone was evaluated using a density-mapping system, and clinical assessment, including patient-reported outcome measurements, was recorded. Results: There were significantly larger contact areas in Gruen zones 3, 5, and 6 in the N-HA group than in the T-HA group. At two years postoperatively, there was a significant decrease in BMD around the proximal-medial femur (zone 6) in the N-HA group and a significant increase in the T-HA group. BMD changes in both groups correlated with BMI or preoperative lumbar BMD rather than with the extent of contact with the femoral cortical bone. Conclusion: The N-HA-coated stem showed a significantly larger contact area, indicating a distal fixation pattern, compared with the traditional fully HA-coated stem. The T-HA-coated stem showed better preservation of periprosthetic BMD, two years postoperatively. Surgeons should consider these patterns of fixation and differences in BMD when selecting fully HA-coated stems for THA, to improve the long-term outcomes.

Comparison of No Tap (two-step) and tapping robotic assisted cortical bone trajectory screw insertion.

Workflow for cortical bone trajectory (CBT) screws includes tapping line-to-line or under tapping by 1 mm. We describe a non-tapping, two-step workflow for CBT screw placement, and compare the safety profile and time savings to the Tap (three-step) workflow. Patients undergoing robotic assisted 1-3 level posterior fusion with CBT screws for degenerative conditions were identified and separated into either a No-Tap or Tap workflow. Number of total screws, screw-related complications, estimated blood loss, operative time, robotic time, and return to the operating room were collected and analyzed. There were 91 cases (458 screws) in the No-Tap and 88 cases (466 screws) in the Tap groups, with no difference in demographics, revision status, ASA grade, approach, number of levels fused or diagnosis between cohorts. Total robotic time was lower in the No-Tap (26.7 min) versus the Tap group (30.3 min, p = 0.053). There was no difference in the number of malpositioned screws identified intraoperatively (10 vs 6, p = 0.427), screws converted to freehand (3 vs 3, p = 0.699), or screws abandoned (3 vs 2, p = 1.000). No pedicle/pars fracture or fixation failure was seen in the No-Tap cohort and one in the Tap cohort (p = 1.00). No patients in either cohort were returned to OR for malpositioned screws. This study showed that the No-Tap screw insertion workflow for robot-assisted CBT reduces robotic time without increasing complications.

Micro-CT, Mechanical, and Histological Examination of the Effect of Local Adjuvants on Porcine Cortical Bone Following Intralesional Curettage of Bone Tumors.

BACKGROUND AND OBJECTIVES: Curettage is the removal of a tumor from the bone while preserving the surrounding healthy cortical bone, and is associated with higher rates of local recurrence. To lower these rates, curettage should be combined with local adjuvants, although their use is associated with damage to nearby healthy bone. OBJECTIVE: The purpose of this analysis is to determine the effect of local adjuvants on cortical porcine bone by using micro-computed tomography (micro-CT) along with histological and mechanical examination. METHODS: Local adjuvants were applied to porcine specimens under defined conditions. To assess changes in bone mineral density (BMD), a micro-CT scan was used. The pixel gray values of the volume of interest (VOI) were evaluated per specimen and converted to BMD values. The Vickers hardness test was employed to assess bone hardness (HV). The depth of necrosis was measured histologically using hematoxylin and eosin-stained tissue sections. RESULTS: A noticeable change in BMD was observed on the argon beam coagulation (ABC) sample. Comparable hardness values were measured on samples following electrocautery and ABC, and lowering of bone hardness was obtained in the case of liquid nitrogen. Extensive induced depth of necrosis was registered in the specimen treated with liquid nitrogen. CONCLUSION: This study determined the effect of local adjuvants on cortical bone by using micro-CT along with histological and mechanical examination. Phenolization and liquid nitrogen application caused a decrease in bone hardness. The bone density was affected in the range of single-digit percentage values. Liquid nitrogen induced extensive depth of necrosis with a wide variance of values.

[Comparison of Clinical Effects of Cortical Bone Trajectory Screws and Traditional Pedicle Screws in Posterior Lumbar Fusion]. / è °æ¤ŽåŽè·¯èžåˆæœ¯ä¸­çš®è´¨éª¨è½¨è¿¹èžºé’‰å’Œä¼ ç»Ÿæ¤Žå¼“æ ¹èžºé’‰çš„ä¸´åºŠæ•ˆæžœæ¯”è¾ƒ.

Objective: To compare the clinical effects of cortical bone trajectory screws and traditional pedicle screws in posterior lumbar fusion. Methods: A retrospective study was conducted to analyze lumbar degeneration patients who underwent surgical treatment at our hospital between January 2016 and January 2019. A total of 123 patients who met the inclusion criteria were enrolled. The subjects were divided into two groups according to their surgical procedures and the members of the two groups were matched by age, sex, and the number of fusion segments. There were 63 patients in the traditional pedicle screws (PS) group and 60 in the cortical bone trajectory screws (CBTS) group. The outcomes of the two groups were compared. The primary outcome measures were perioperative conditions, including operation duration, estimated intraoperative blood loss (EBL), and length-of-stay (LOS), visual analog scale (VAS) score, Oswestry Disability Index (ODI) score, and interbody fusion rate. The secondary outcome measures were the time to postoperative ambulation and the incidence of complications. VAS scores and ODI scores were assessed before operation, 1 week, 1 month, 3 months, and 12 months after operation, and at the final follow-up. The interbody fusion rate was assessed in 1 year and 2 years after the operation and at the final follow-up. Results: The CBTS group showed a reduction in operation duration ([142.8±13.1] min vs. [174.7±15.4] min, P<0.001), LOS ([9.5±1.5] d vs. [12.0±2.0] d, P<0.001), and EBL ([194.2±38.3] mL vs. [377.5±33.1] mL, P<0.001) in comparison with the PS group. The VAS score for back pain in the CBTS group was lower than that in the PS group at 1 week and 1 month after operation and the ODI score in the CBTS group was lower than that in the PS group at 1 month after operation, with the differences being statistically significant (P<0.05). At each postoperative time point, the VAS score for leg pain and the interbody fusion rate did not show significant difference between the two groups. The VAS score for back and leg pain and the ODI score at each time point after operation in both the CBTS group and the PS group were significantly lower than those before operation (P<0.05). No significant difference was found in the time to postoperative ambulation or the overall complication incidence between the two groups. Conclusion: The CBTS technique could significantly shorten the operation duration and LOS, reduce EBL, and achieve the same effect as the PS technique does in terms of intervertebral fusion rate, pain relief, functional improvement, and complication incidence in patients undergoing posterior lumbar fusion.

Comparison of facet fusion rates and clinical outcomes between cortical bone trajectory screw and percutaneous pedicle screw fixation for degenerative lumbar spondylolisthesis.

BACKGROUND CONTEXT: Cortical bone trajectory (CBT) screws have been introduced as an alternative technique for pedicle screw (PS) insertion because they have greater contact with the cortex and a greater uniaxial pullout load than traditional PS. CBT screwing can also minimize muscle dissection. However, CBT screws and traditional PSs have not yet been compared in terms of fusion rates and clinical outcomes for particular operative procedures. PURPOSE: This study aimed to assess the fusion rate and clinical outcomes of facet fusion (FF) fixed with CBT screws (CBT-FF) and to compare them with those of FF fixed with percutaneous PS (PPS-FF). STUDY DESIGN: Retrospective study. PATIENT SAMPLE: Records of 68 patients who underwent CBT-FF for single-level degenerative lumbar spondylolisthesis (DLS) with at least 1 year of follow-up were retrospectively reviewed. The control group comprised 143 patients who underwent PPS-FF under the same conditions. OUTCOME MEASURES: Computed tomography was performed to confirm fusion. Therapeutic effectiveness was assessed as a clinical outcome using the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ), Roland-Morris Disability Questionnaire (RMDQ), and visual analog scale (VAS) preoperatively and 1 year postoperatively. The rate of revision surgery was also calculated. Intraoperative blood loss was measured. METHODS: Fusion rate, clinical outcomes, revision surgery rate, and intraoperative blood loss of CBT-FF and PPS-FF were compared. RESULTS: The CBT-FF and PPS-FF fusion rates were 91.2% and 90.1%, respectively. The JOABPEQ category scores demonstrated therapeutic effectiveness in 74.5% and 77.1% of the patients for low back pain; the corresponding proportions for walking ability were 84.7% and 89.3%, respectively. No significant differences in therapeutic effectiveness were observed for any category, including the RMDQ and VAS scores for buttock and lower limb pain. Three patients required revision surgery for adjacent segment disease between 6 months and 3.5 years after CBT-FF (revision surgery rate, 4.4%), whereas the revision surgery rate for PPS-FF was 6.3% (9/143 cases). Average intraoperative blood loss was significantly less in the CBT-FF group than in the PPS-FF group. CONCLUSIONS: Both procedures were equally useful in terms of fusion rate and clinical outcomes for DLS management.

Risk Factors for Medial Breach During Robotic-Assisted Cortical Bone Trajectory Screw Insertion.

OBJECTIVE: We describe the incidence of, and identify the risk factors for, a medial breach of the pedicle wall during robotic-assisted cortical bone trajectory (RA-CBT) screw insertion. METHODS: We analyzed a consecutive series of adult patients who underwent RA-CBT screw placement from January 2019 to July 2022. To assess the pedicle wall medial breach, postoperative computed tomography (CT) images were analyzed. Patient demographic data and screw data were compared between patients with and without a medial breach. The Hounsfield units (HUs) on the L1 midvertebral axial CT scan was used to evaluate bone quality. RESULTS: Of 784 CBT screws in 145 patients, 30 (3.8%) had a medial breach in 23 patients (15.9%). One screw was grade 2, and the others were grade 1. Patients with a medial breach had a lower HU value compared with the patients without a medial breach (123.3 vs. 150.5; P = 0.027). A medial breach was more common in the right than left side (5.5% vs. 2.0%; P = 0.014). More than one half of the screws with a medial breach were found in the upper instrumented vertebra (UIV) compared with the middle construct or lowest instrumented vertebra (6.7% vs. 1.3% vs. 2.7%; P = 0.003). Binary logistic regression showed that low HU values, right-sided screw placement, and UIV were associated with a medial breach. No patients returned to the operating room for screw malposition. No differences were found in the clinical outcomes between patients with and without a medial breach. CONCLUSIONS: The incidence of pedicle wall medial breach was 3.8% of RA-CBT screws in the postoperative CT images. A low HU value measured in the L1 axial image, right-sided screw placement, and UIV were associated with an increased risk of medial breach for RA-CBT screw placement.

Biportal endoscopic-assisted cortical bone trajectory screw placement and lumbar interbody fusion.

BACKGROUND: Endoscopically assisted screw fixation with lumbar interbody fusion is rarely performed. We succeeded in implanting the cortical bone trajectory (CBT) screws under the guidance of unilateral biportal endoscopy (UBE). METHOD: We attempted endoscopically assisted screw fixation in a patient with degenerative spondylolisthesis. Through a third portal, ipsilateral CBT screws were implanted without complications. CONCLUSIONS: We successfully performed unilateral biportal endoscopic lumbar interbody fusion (ULIF) with CBT and reversed CBT screws. Compared with percutaneous pedicle screw (PPS) placement, this procedure is a minimally invasive, endoscopic alternative that allows precise screw placement.

Comparison of the clinical and radiographic outcomes of cortical bone trajectory and traditional trajectory pedicle screw fixation in transforaminal lumbar interbody fusion: a randomized controlled trial.

PURPOSE: To compare the clinical outcomes and radiographic outcomes of cortical bone trajectory (CBT) and traditional trajectory (TT) pedicle screw fixation in patients treated with single-level transforaminal lumbar interbody fusion (TLIF). METHODS: This trial included a total of 224 patients with lumbar spine disease who required single-level TLIF surgery. Patients were randomly assigned to the CBT and TT groups at a 1:1 ratio. Demographics and clinical and radiographic data were collected to evaluate the efficacy and safety of CBT and TT screw fixation in TLIF. RESULTS: The baseline characteristic data were similar between the CBT and TT groups. Back and leg pain for both the CBT and TT groups improved significantly from baseline to 24 months postoperatively. The CBT group experienced less pain than the TT group at one week postoperatively. The postoperative radiographic results showed that the accuracy of screw placement was significantly increased in the CBT group compared with the TT group (P < 0.05). The CBT group had a significantly lower rate of FJV than the TT group (P < 0.05). In addition, the rate of fusion and the rate of screw loosening were similar between the CBT and TT groups according to screw loosening criteria. CONCLUSION: This prospective, randomized controlled analysis suggests that clinical outcomes and radiographic characteristics, including fusion rates and caudal screw loosening rates, were comparable between CBT and TT screw fixation. Compared with the TT group, the CBT group showed advantages in the accuracy of screw placement and the FJV rate. CLINICAL TRIALS REGISTRATION: This trial has been registered at the US National Institutes of Health Clinical Trials Registry: NCT03105167.

Biomechanical evaluation of modified and traditional cortical bone trajectory technique on adjacent segment degeneration in transforaminal lumbar interbody fusion-finite element analysis.

OBJECTIVES: Modified cortical bone trajectory (MCBT) technique was proposed by our team in previous studies, but its biomechanical properties at adjacent segments have not been discussed yet. Therefore, the purpose of this study is to investigate the biomechanical properties of modified cortical bone trajectory (MCBT) technique on adjacent segment degeneration (ASD) in transforaminal intradiscal lumbar disc fusion (TLIF) compare to traditional bone trajectory (TT) technique and cortical bone trajectory (CBT) technique. METHODS: The four human cadaveric lumbar specimens were provided by the anatomy teaching and research department of Xinjiang Medical University and four intact finite element models of the L1-S1 segment were generated. For each of these, three transforaminal lumbar interbody fusion procedures with three different fixation techniques were reconstructed at the L4-L5 segment, as follows: TT-TT (TT at both L4 and L5 segments), CBT-CBT (CBT at both L4 and L5 segments), MCBT-MCBT (MCBT at both L4 and L5 segments). The range of motion and von Mises stress of the intervertebral disc of the L3-L4 and L5-S1 segments were recorded with a 400N compressive load and 7.5 Nm moments in flexion, extension, left-right bending, and left-right rotation. RESULTS: The peak ROM of the L3-L4 segment in the MCBT-MCBT group was reduced by 10.5%, 6.1%, 12.2%, 4.1%, and 1.5% in flexion, extension, left-right bending, and left rotation compared to the TT-TT group and reduced by 1.8%, 5.5%, 10.0%, 12.8%, and 8.8% in flexion, left-right bending, and left-right rotation compared to the CBT-CBT group, respectively. The MCBT-MCBT group has the lowest peak ROM of the L3-L4 segment in flexion, left bending, and right rotation, the lowest peak ROM of the L5-S1 segment in extension and right rotation, and the lowest peak von Mises stress of the intervertebral disc at the L5-S1 segment in right rotation compared to the TT-TT and CBT-CBT group. In addition, the peak von Mises stress at the L3-L4 segment was lowest and more dispersed in all motions, the MCBT-MCBT group exhibited lower peak ROM of the L5-S1 segment in flexion, extension, and right rotation, and showed lower peak von Mises stress of the disc at the L5-S1 segment in flexion, extension, and right rotation compared with the TT-TT group. CONCLUSION: The modified cortical bone trajectory technique may have a beneficial effect on reducing the incidence of ASD in the L4-L5 TLIF model compared to the traditional bone trajectory technique and cortical bone trajectory technique.

The Influence of Titanium-coated Poryetheretherketone Cages in Fusion Status after Posterior Lumbar Interbody Fusion with Cortical Bone Trajectory Screw Fixation.

OBJECTIVE: Posterior lumbar interbody fusion (PLIF) with cortical bone trajectory (CBT) screw fixation (CBT-PLIF) shows potential for reducing adjacent segmental disease. Previously, our investigations revealed a relatively lower fusion rate with the use of carbon fiber-reinforced polyetheretherketone (CP) cages in CBT-PLIF compared with traditional pedicle screw fixation (PS-PLIF) using CP cages. This study aims to evaluate whether the implementation of titanium-coated polyetheretherketone (TP) cages can enhance fusion outcomes in CBT-PLIF. METHODS: A retrospective analysis was conducted on 68 consecutive patients who underwent CBT-PLIF with TP cages (TP group) and 89 patients who underwent CBT-PLIF with CP cages (CP group). Fusion status was assessed using computed tomography at 1 year postoperatively and dynamic plain radiographs at 2 years postoperatively. RESULTS: No statistically significant differences in fusion rates were observed at 1 and 2 years postoperatively between the TP group (86.8% and 89.7%, respectively) and the CP group (77.5% and 88.8%, respectively). Notably, the CP group exhibited a significant improvement in fusion rate from 1 to 2 years postoperatively (P = 0.002), while no significant improvement was observed in the TP group. CONCLUSIONS: Examination of temporal changes in fusion rates reveals that only the TP group achieved a peak fusion rate 1 year postoperatively. This implies that TP cages may enhance the fusion process even after CBT-PLIF. Nevertheless, the definitive efficacy of TP cages for CBT-PLIF remains uncertain in the context of overall fusion rates.

Multi-objective optimization of cortical bone grinding parameters based on particle swarm optimization.

Grinding is a fundamental operation in craniotomy. Suitable grinding parameters will not only reduce force damage, but also ensure grinding efficiency. In this study, the regression equations of material removal rate and grinding force were obtained based on the theory of cortical bone grinding and full factorial test results, a multi-objective optimization based on the particle swarm algorithm was proposed for optimizing the grinding parameters: spindle speed, feed speed, and grinding depth in the grinding process. Two conflicting objectives, minimum grinding force and maximum material removal rate, were optimized simultaneously. The results revealed that the optimal grinding parameter combination and optimization results were as follows: spindle speed of 5000 rpm, feed rate of 60 mm/min, grinding depth of 0.6 mm, grinding force of 15.1 N, and material removal rate of 113.8 mm3/min. The parameter optimization result can provide theoretical guidance for selecting cortical bone grinding parameters in actual craniotomy.

The silicone metacarpophalangeal joint arthroplasty: An in-vitro analysis.

BACKGROUND: Silicone is still the gold standard implant in metacarpophalangeal arthroplasty. Whereas the clinical results are acceptable, in follow-ups with >10 years, high rates of implant fracture are common, and 5 to 7% of implants required revision. This work's purpose is to analyse the hypothesis that the joint flexion amplitude has a relevant effect on bone strain level, implant stress and bone-implant micromotion, which can reflect an increase in the risk of bone resorption/fatigue failure, implant fracture and osteolysis. METHODS: To experimentally predict the cortical loading behaviour, composite metacarpals and proximal phalanges were used in intact and implanted states. A finite element model was developed to evaluate the structural behaviour of cancellous bone and implant. This model was validated by comparing cortical strain and load-displacement curve with experimental measurements. FINDINGS: Bone strain changes between the intact and the implanted states showed a load transfer effect from the cortical to the cancellous bone that increases significantly with the flexion's amplitude rise. The peak implant stress occurred in the flexion amplitudes further away from the implant neutral angle. The highest implant pistoning motion and the highest phalanx cancellous-bone strain occurred simultaneously at the maximum flexion amplitude. INTERPRETATION: Limiting joint flexion range will be helpful to reduce the strain-shielding effect on cortical bone, minimizing the overload effect on cancellous bone and decreasing the stress levels and the pistoning motion on the implant, ultimately contributing to the longevity of silicone arthroplasty.