[3D printing navigation template assisted pedicle screw placement for the treatment of typeâ ¡old odontoid fractures].

OBJECTIVE: To compare the safety and clinical efficacy of freehand and 3D printing navigation template assisted screw placement in patients with old odontoid fractures of typeⅡ. METHODS: Total of 38 patients with old odontoid fractures of typeⅡwere treated from November 2018 to December 2022, all of which presented as chronic neck pain. According to the different methods of screw insertion into the pedicle, the patients were divided into a navigation template group and a freehand group. In the navigation template group, there were 17 patients including 9 males and 8 females with an average age of (51.30±13.20) years old, disease duration was (22.18±7.59) months. In the freehand group, there 21 patients including 7 males and 14 females with an average age of (49.46±11.92) years old, disease duration was (19.52±9.17) months. The intraoperative blood loss, operation time, and postoperative drainage output were recorded and compared between two groups. The accuracy of screw placement was evaluated by CT scan. Before operation and 1 year after operation, cervical pain was assessed by visual analogue scale(VAS), neurological changes were evaluated by the Japanese Orthopaedic Association (JOA) score, and the degree of spinal cord injury was assessed by the American Spinal Injury Association (ASIA) injury scale. RESULTS: All patients were followed up for (25.31±1.21) months. The operation time of template group (112.00±20.48) min had significantly shorter than that of the freehand group(124.29±15.24) min(P<0.05), while there were no significant differences between two groups in terms of intraoperative blood loss, postoperative drainage, and hospital stay(P>0.05). At 1 year after operation, in template group and freehand group, the VAS [(2.88±0.86), (2.90±0.83)] and JOA [(14.94±1.82), (14.62±2.19)] improved with preoperative [VAS(4.71±0.92), (4.86±0.79) and JOA (12.18±2.30), (11.95±2.31)](P<0.05), with no significant difference between two groups (P>0.05). No significant improvement was observed in ASIA grading in either group at 1 year after operation(P>0.05), and there was no significant difference between two groups(P>0.05). The template group had significantly better accuracy of screw placement in the pedicle of the axis than the freehand group (P<0.05), while no significant difference was observed between two groups in the accuracy of screw placement in the pedicle of the atlas (P>0.05). CONCLUSION: In the treatment of typeⅡold odontoid fractures with posterior pedicle screw fixation, 3D printing navigation template screw placement can significantly shorten the operation time, achieve similar clinical efficacy as free-hand screw placement, and significantly improve the accuracy of screw placement in the pedicle of the axis.

Micro-Computed Tomography Analysis and Histological Observation of the Screw-Bone Interface of Novel Porous Scaffold Core Pedicle Screws and Hollow Lateral Hole Pedicle Screws: A Comparative Study in Bama Pigs.

OBJECTIVE: Screw loosening is a common complication of pedicle screw internal fixation surgery. This study aimed to investigate whether the application of a porous scaffold structure can increase the contact area between screws and bone tissue by comparing the bone ingrowth and screw-bone interface of porous scaffold core pedicle screws (PSCPSs) and hollow lateral hole pedicle screws (HLHPSs) in the lumbar spine of Bama pigs. METHODS: Sixteen pedicle screws of both types were implanted into the bilateral pedicles of the L1-4 vertebrae of 2 Bama pigs. All Bama pigs were sacrificed and the lumbar spine was freed into individual vertebrae at 16 weeks postoperatively. After the vertebrae were made into screw-centered specimens, micro-computed tomography analysis and histological observation were performed to assess the screw-bone interface and bone growth around and within the screws. RESULTS: We found that the bone condition around PSCPSs and HLHPSs did not show significant differences on micro-computed tomography three-dimensional reconstruction images. CT transverse views showed different bone growth inside the 2 screws. In PSCPSs, bone tissue was seen to fill the internal pores and was evenly distributed around each strut. Inside HLHPSs, bone growth was confined to 1 side of the screw and did not fill the entire cavity. Osteometric analysis showed that bone volume fraction and trabecular number, the parameters representing bone mass, were higher in PSCPSs than in HLHPSs. These differences were not statistically significant (P > 0.05). Histological observations visualized that the osseointegration within PSCPSs was superior to that of HLHPSs, and the tight integration of bone tissue with the porous scaffold resulted in a larger screw-bone integration area in PSCPSs than in HLHPSs. CONCLUSIONS: Compared with HLHPSs, PSCPSs possessing a porous scaffold core could promote bone ingrowth and osseointegration, resulting in an effective enhancement of the combined area of the screw-bone interface.

Biomechanical Properties of Novel Porous Scaffold Core and Hollow Lateral Hole Pedicle Screws: A Comparative Study in Bama Pigs.

OBJECTIVE: Screw loosening is a common complication of internal fixation of pedicle screw. Therefore, the development of a pedicle screw with low loosening rate and high biosafety is of great clinical significance. This study aimed to investigate whether the application of a porous scaffold structure can improve the stability of pedicle screws by comparing the biomechanical properties of novel porous scaffold core pedicle screws (PSCPSs) with those of hollow lateral hole pedicle screws (HLHPSs) in a porcine lumbar spine. METHODS: Thirty-two pedicle screws of both types were implanted bilaterally into the L1-4 vertebrae of four Bama pigs, with our newly designed PSCPSs on the right and HLHPSs on the left. All the Bama pigs were sacrificed 16 weeks postoperatively, and the lumbar spine was freed into individual vertebrae. Biomechanical properties of both the pedicle screws were evaluated using pull-out tests, as well as cyclic bending and pull-out tests, while the mechanical properties were assessed using three-point bending tests. The data generated were statistically analyzed using paired-sample t-tests and two independent sample t-tests. RESULTS: We found that the maximal pull-out forces before and after cyclic bending of the PSCPSs (1161.50 ± 337.98 N and 1075.25 ± 223.33 N) were significantly higher than those of the HLHPSs (948.38 ± 194.32 N and 807.13 ± 242.75 N) (p < 0.05, p < 0.05). In 800 cycles of the bending tests, neither PSCPS nor HLHPS showed loosening or visible detachment, but their maximal pull-out forces after cyclic bending tests decreased compared to those in cycles without cyclic bending tests (7.43% and 14.89%, respectively), with no statistical significance (p > 0.05 and p > 0.05, respectively). Additionally, both screws buckled rather than broke in the three-point bending tests, with no statistically significant differences between the maximal bending load and modulus of elasticity of the two screws (p > 0.05 and p > 0.05, respectively). CONCLUSIONS: Compared with the HLHPSs, the PSCPSs have greater pull-out resistance and better fatigue tolerance with appropriate mechanical properties. Therefore, PSCPSs theoretically have significant potential for clinical applications in reducing the incidence of loosening after pedicle screw implantation.

Bone resorption of vertebral bodies at the operative segment after prevail cervical interbody fusion: A case report.

BACKGROUND: We report an interesting case of bone resorption of vertebral bodies at the operative segment after Peek Prevail cervical interbody fusion. Instability of cervical vertebrae is likely to occur due to increased stress in Peek Prevail implant body for bone resorption. The finite element analysis was used to clarify the biomechanical effects of bone resorption and stress distribution in Peek Prevail implant body. METHODS: We reported the case of a 48-year-old male patient who underwent Peek Prevail cervical interbody fusion and exhibited bone resorption 1 month after the surgery in X-ray of cervical vertebra. The degree of bone resorption was aggravated 2 months after surgery. Bone resorption in 3 months was similar to that in 2 months. We established a 3D reconstruction of the surgical segment in this case using Mimics software (vision 20.0) to generate basic boss resorption model. We simulated models of bone resorption using Ansys 17.0. The stress distribution of the contact surface between the screw and bone was analyzed under 6 conditions: flexion, extension, left and right flexion, and left and right rotation. RESULTS: The loading conditions affected the stress distribution in the implant body. When bone resorption occurred, the stress distribution of the contact surface between screw and bone focus in the tip of the screw increased sharply. CONCLUSION: Bone resorption of vertebral bodies in the operative segment may be a potential complication after Peek Prevail cervical interbody fusion. Great attention must be paid when bone resorption was occurred in order to avoid screw loosening before vertebral fusion.

Video-assisted thoracoscopic surgery for Andersson lesion in ankylosing spondylitis: A case report and literature review.

RATIONALE: Andersson lesion (AL), a phenomenon initially described by Andersson nearly 80 years ago, has been the subject of extensive research and various treatment modalities. The ongoing debate surrounding the need for anterior surgery in AL cases has spurred numerous proposed approaches. Despite the demonstrated efficacy of anterior surgery in achieving fusion and stabilization, its implementation is associated with prolonged operation time and heightened intraoperative bleeding. PATIENT CONCERNS: A 32-year-old male patient presented at our hospital in February 2019 with a 2-month history of bilateral lower extremity weakness and sensory disturbances. These symptoms were exacerbated by a recent fall. DIAGNOSIS: AL conbined with ankylosing spondylitis. INTERVENTIONS: A 1-stage posterior fixation and decompression procedure was performed to ensure spinal stability, minimize deformities, and reduce surgical trauma. To achieve these goals, a 2-stage approach was employed, which included video-assisted thoracoscope-guided vertebrectomy, spinal canal decompression, and bone graft fusion. OUTCOMES: No recurrences of significant pain, limb numbness, or other symptoms were reported, ultimately leading to an improved quality of life for the patient. LESSONS: We utilized video-assisted thoracoscopic surgery technology for anterior bone graft fusion in a patient with AL to minimize the trauma of secondary surgery. However, the 3-year follow-up showed insufficient bony fusion at the fracture site. Nevertheless, the patient maintained spinal stability with posterior internal fixation and no significant kyphosis or symptoms. Thus, standalone posterior fixation may suffice for favorable clinical outcomes in patients with AL.

Treatment of unstable C1 semi-ring fractures with direct C1 pedicle screw fixation using a navigational template: A case report and literature review.

RATIONALE: Because of the risk of C1 to C2 instability, which would reduce the mobility of the occipito-atlanto-axis articulation, unstable C1 semi-ring fractures are typically treated with C1 to C2 or C0 to C2 fusion. The vertebral artery and spinal cord are at risk of harm during the installation of C1 pedicle screws. There is a need for a method that can maintain the occipito-atlanto-axis articulation's mobility and increase the safety of C1 pedicle screw fixation, particularly for surgeons who have less experience inserting C1 pedicle screws freehand. PATIENT CONCERNS: A 45-year-old man who had suffered a severe fall from a height of 2.5 m presented with pain in his cervical spine. Magnetic resonance imaging and computed tomography were used to diagnose unstable atlas fractures. DIAGNOSIS: According to radiographic studies, the patient had a unilateral anterior and posterior arch fracture (semi-ring fracture, Landells type II), as well as fractures and transverse ligament avulsion at the attachment site. INTERVENTIONS: We fixed the C1 directly with a pedicle screw using a navigational template. OUTCOMES: Both during and after the operation, there were no connected complications. Imaging at 12 months after surgery demonstrated that the fracture had united. The average visual analog scale score decreased from 8 before surgery to 2. LESSONS: In particular for surgeons with less experience placing freehand C1 pedicle screws, direct C1 pedicle screw fixation with the aid of a navigational template was a good option because it can preserve the mobility of the occipito-atlanto-axis articulation and improve the safety of C1 pedicle screw.

Biomechanical Properties of Novel Lateral Hole Pedicle Screws and Solid Pedicle Screws: A Comparative Study in the Beagle Dogs.

OBJECTIVE: Although pedicle screws are widely used to reconstruct the stability of the spine, screw loosening is a common complication after spine surgery. The main objective of this study was to investigate whether the application of the hollow lateral hole structure had the potential to improve the stability of the pedicle screw by comparing the biomechanical properties of the novel lateral hole pedicle screws (LHPSs) with those of the solid pedicle screws (SPSs) in beagle dogs. METHODS: The cancellous bone of the distal femur, proximal femur, distal tibia, and proximal tibia were chosen as implantation sites in beagle dogs. In each of 12 dogs, four LHPSs, and four SPSs were implanted into both lower limbs. At 1, 2, and 3 months after surgery, four dogs were randomly sampled and sacrificed. The LHPS group and SPS group were subdivided into four subgroups according to the length of their duration of implantation (0, 1, 2, 3 months). The biomechanical properties of both pedicle screws were evaluated by pull-out and the cyclic bending tests. RESULTS: The results of the study showed that no significant difference was found between LHPSs (276.62 ± 50.11 N) and SPSs (282.47 ± 42.98 N) in pull-out tests at time 0 (P > 0.05). At the same time point after implantations, LHPSs exhibited significantly higher maximal pullout strength than SPSs (month 1: 360.51 ± 25.63 vs 325.87 ± 28.11 N; month 2: 416.59 ± 23.78 vs 362.12 ± 29.27 N; month 3: 447.05 ± 38.26 vs 376.63 ± 32.36 N) (P < 0.05). Moreover, compared with SPSs, LHPSs withstood more loading cycles (month 2: 592 ± 21 vs 534 ± 48 times; month 3: 596 ± 10 vs 543 ± 59 times), and exhibiting less displacement before loosening at month 2 (1.70 ± 0.17 vs 1.96 ± 0.10 mm) and 3 (1.69 ± 0.19 vs 1.92 ± 0.14 mm) (P < 0.05), but no significant difference in time 0 and month 1 (P > 0.05). CONCLUSIONS: The pedicle screw with the hollow lateral hole structure could allow bone to grow into the inner architecture, which improved biomechanical properties by extending the contact area between screw and bone tissue after implantation into the cancellous bone. It indicated that LHPS could reduce loosening of the pedicle screws in long term after surgery.