Template guided cervical pedicle screw instrumentation

Background: Pedicle screw instrumentation of the cervical spine, although technically challenging due to the potential risk of serious neurovascular injuries, is biomechanically favorable for stabilization purposes. Patient-specific templates are increasingly used in the thoracolumbar spine with excellent accuracy. The aim of this study was to evaluate the accuracy of cervical pedicle screw placement with patient-specific templates in a clinical setting and to report the European experience so far. Methods: Multicentric, retrospectively obtained data of twelve patients who underwent dorsal instrumentation of the cervical spine with 3D-printed patient-specific templates were analyzed. Postoperative computed tomography (CT) scans were used to evaluate pedicle perforation and screw deviations between the planned and actual screw position. Furthermore, surgical time, radiation exposure, blood loss and immediate postoperative complications were analyzed. Results: A total of 86 screws were inserted, of which 82 (95.3%) were fully contained inside the pedicle. All perforations (four screws, 4.7%) were within the safe zone of 2 mm and did not result in any neurovascular complications. Overall, median deviation from planned entry point (Euclidean distance) was 1.2 mm (0.1 - 11 mm), median deviation from the planned trajectory (Euler angle) was 4.4° (0.2-71.5°), median axial and sagittal trajectory deviation from the planned trajectory were 2.5° (0 - 57.5°) and 3.3° (0 - 54.9°), respectively. Median operative time was 168 minutes (111 - 564 minutes), median blood loss was 300 ml (150 - 1300 ml) and median intraoperative fluoroscopic dose was 321.2 mGycm2 (102.4 - 825.0 mGycm2). Overall complications were one adjacent segment kyphosis, one transient C5 palsy and one wound healing disorder. Conclusion: Patient-specific 3D-printed templates provide a highly accurate option for placing cervical pedicle screws for dorsal instrumentation of the cervical spine. Keywords: Cervical spine; Patient-specific template; Pedicle screw; Pedicle screw accuracy; Pedicle screw instrumentation; Three-dimensional model

Risk factors for wound-related complications after surgical stabilization of spinal metastases with a special focus on the effect of postoperative radiation therapy

Background!#!Advancements in the field of oncological therapies during the last decades have led to a significantly prolonged survival of cancer patients. This has led to an increase in the incidence of spinal metastases. The purpose of this study was to assess risk factors for wound-related complications after surgical stabilization of spinal metastases with a special focus on the effect of postoperative RT and its timing.!##!Methods!#!Patients who had been treated for metastatic spine disease by surgical stabilization followed by radiotherapy between 01/2012 and 03/2019 were included and a retrospective chart review was performed.!##!Results!#!Of 604 patients who underwent stabilizing surgery for spinal metastases, 237 patients (mean age 66 years, SD 11) with a mean follow-up of 11 months (SD 7) were eligible for further analysis. Forty-one patients (17.3%) had wound-related complications, 32 of them before and 9 after beginning of the RT. Revision surgery was necessary in 26 patients (11.0%). Body weight (p = 0.021), obesity (p = 0.018), ASA > 2 (p = 0.001), and start of radiation therapy within 21 days after surgery (p = 0.047) were associated with an increased risk for wound complications. Patients with chemotherapy within 3 weeks of surgery (12%) were more likely to have a wound-related surgical revision (p = 0.031).!##!Conclusion!#!Body weight, obesity and ASA > 2 were associated with an increased risk for wound complications. Patients with chemotherapy within 3 weeks of the surgery were more likely to have a wound-related revision surgery. Patients who had begun radiation therapy within 21 days after surgery were more likely to have a wound complication compared to patients who waited longer

Does time-to-surgery affect mortality in patients with acute osteoporotic vertebral compression fractures?

Introduction!#!Osteoporotic vertebral compression fractures (VCFs) are common. An increase in mortality associated with osteoporotic VCFs has been well documented. The purpose of this study was to assess the impact of time to surgery on 1-year survival in patients with osteoporotic vertebral compression fractures.!##!Methods!#!In a retrospective cohort study with prospective mortality follow-up, consecutive patients aged ≥ 60 years who had operative treatment of a low-energy fracture of a thoracolumbar vertebra and had undergone surgical stabilization between January 2015 and December 2018 were identified from our institutional database. By chart review, additional information on hospitalization time, comorbidities (expressed as ASA - American Society of Anesthesiologists Scale), complications and revision surgery was obtained. Time-to-surgery was defined as the time between admission and surgery. Mortality data was assessed by contacting the patients by phone, mail or the national social insurance database.!##!Results!#!Two hundred sixty patients (mean age 78 years, SD 7 years, range, 60 to 93; 172 female) were available for final analysis. Mean follow-up was 40 months (range, 12 to 68 months). Fifty-nine patients (22.7%) had died at final follow-up and 27/260 patients (10.4%) had died within 1 year after the surgery. Time-to-surgery was not different for patients who died within 1 year after the surgery and those who survived (p = .501). In-hospital complications were seen in 40/260 (15.4%) patients. Time-to-surgery showed a strong correlation with hospitalization time (Pearson's r = .614, p < .001), but only a very weak correlation with the time spent in hospital after the surgery (Pearson's r = .146, p = .018).!##!Conclusions!#!In contrast to patients with proximal femur factures, time-to-surgery had no significant effect on one-year mortality in geriatric patients with osteoporotic vertebral compression fractures. Treatment decisions for these fractures in the elderly should be individualized

Kinematics of the Lumbo–Pelvic Complex under Different Loading Conditions

The lumbo-pelvic complex is a highly complex structural system. The current investigation aims to identify the kinematics between interacting bone segments under different loading conditions. A specimen of the lumbo-pelvic complex was obtained from a human body donor and tested in a self-developed test rig. The experimental setup was designed to imitate extension, flexion, right and left lateral bending and axial rotation to the left and to the right, respectively. The vertebra L3 was firmly embedded and load was introduced via hip joints. Using a digital image correlation (DIC) system, the 3D motions of 15 markers at different landmarks were measured for each loadcase under cyclic loading. For each loadcase, the kinematics were analyzed in terms of three-dimensional relative movements between L3 and the sacrum. The usefulness of the experimental technique was demonstrated. It may serve for further biomechanical investigations of relative motion of sacroiliac and vertebral joints and deformation of bony structures

Biomechanical comparative study of midline cortical vs. traditional pedicle screw trajectory in osteoporotic bone

Abstract Introduction In lumbar spinal stabilization pedicle screws are used as standard. However, especially in osteoporosis, screw anchorage is a problem. Cortical bone trajectory (CBT) is an alternative technique designed to increase stability without the use of cement. In this regard, comparative studies showed biomechanical superiority of the MC (midline cortical bone trajectory) technique with longer cortical progression over the CBT technique. The aim of this biomechanical study was to comparatively investigate the MC technique against the not cemented pedicle screws (TT) in terms of their pullout forces and anchorage properties during sagittal cyclic loading according to the ASTM F1717 test. Methods Five cadavers (L1 to L5), whose mean age was 83.3 ± 9.9 years and mean T Score of -3.92 ± 0.38, were dissected and the vertebral bodies embedded in polyurethane casting resin. Then, one screw was randomly inserted into each vertebra using a template according to the MC technique and a second one was inserted by freehand technique with traditional trajectory (TT). The screws were quasi-static extracted from vertebrae L1 and L3, while for L2, L4 and L5 they were first tested dynamically according to ASTM standard F1717 (10,000 cycles at 1 Hz between 10 and 110 N) and then quasi-static extracted. In order to determine possible screw loosening, there movements were recorded during the dynamic tests using an optical measurement system. Results The pull-out tests show a higher pull-out strength for the MC technique of 555.4 ± 237.0 N compared to the TT technique 448.8 ± 303.2 N. During the dynamic tests (L2, L4, L5), 8 out of the 15 TT screws became loose before completing 10,000 cycles. In contrast, all 15 MC screws did not exceed the termination criterion and were thus able to complete the full test procedure. For the runners, the optical measurement showed greater relative movement of the TT variant compared to the MC variant. The pull-out tests also revealed that the MC variant had a higher pull-out strength, measuring at766.7 ± 385.4 N, while the TT variant measured 637.4 ± 435.6 N. Conclusion The highest pullout forces were achieved by the MC technique. The main difference between the techniques was observed in the dynamic measurements, where the MC technique exhibited superior primary stability compared to the conventional technique in terms of primary stability. Overall, the MC technique in combination with template-guided insertion represents the best alternative for anchoring screws in osteoporotic bone without cement

Analysis of a Unilateral Bridging Cage for Lumbar Interbody Fusion: 2-Year Clinical Results and Fusion Rate with a Focus on Subsidence

Purpose: The aim of this study was to evaluate the biomechanical stability and the clinical and radiographic outcomes in patients undergoing transforaminal lumbar interbody fusion (TLIF) using an oblique bridging cage with a particular focus on subsidence. Methods: Finite element models were developed to compare the biomechanics of the oblique cage with conventional posterior lumbar interbody fusion and banana-shaped cages with TLIF. Additionally, a retrospective review of a prospective collected database was performed to investigate the clinical and radiologic results with a focus on the subsidence rate using an oblique polyetheretherketone (PEEK) cage with a bicortical load-bearing design. We included 87 patients with degenerative pathologic conditions of the lumbar spine who underwent TLIF. The clinical outcome was assessed using the Oswestry Low Back Pain Disability Questionnaire and the visual analogue scale. Fusion and subsidence rates were assessed radiographically. Results: The finite element models showed no differences in stability on compression or extension/flexion. The oblique cage differed in terms of the location of the maximal stresses. A total of 105 levels were fused. The level at which fusion was most frequently performed was L4–L5 (59%). The fusion rate was 93.2% after 24 months. Subsidence was found at 4 levels after the last follow-up visit (3.9%). Overall clinical outcome improvement was achieved after 24 months. Conclusion: Regarding fusion, the use of an oblique PEEK cage with a cortical load-bearing design provided highly satisfactory clinical and radiologic results after 2 years. A review of the literature suggests a lower rate of cage subsidence after lumbar interbody fusion using bridging cages rather than single cages

Empfehlungen zur Diagnostik und Therapie oberer Halswirbelsäulenverletzungen: Axisringfrakturen

In a consensus process with four sessions in 2017, the working group "upper cervical spine" of the German Society for Orthopaedics and Trauma Surgery (DGOU) formulated "Therapeutic Recommendations for the Diagnosis and Treatment of Upper Cervical Fractures", taking their own experience and the current literature into consideration. The following article describes the recommendations for axis ring fractures (traumatic spondylolysis C2). About 19 to 49% of all cervical spine injuries include the axis vertebra. Traumatic spondylolysis of C2 may include potential discoligamentous instability C2/3. The primary aim of the diagnostic process is to detect the injury and to determine potential disco-ligamentous instability C2/3. For classification purposes, the Josten classification or the modified Effendi classification may be used. The Canadian C-spine rule is recommended for clinical screening for C-spine injuries. CT is the preferred imaging modality and an MRI is needed to determine the integrity of the discoligamentous complex C2/3. Conservative treatment is appropriate in case of stable fractures with intact C2/3 motion segment (Josten type 2 and 2). Patients should be closely monitored, in order to detect secondary dislocation as early as possible. Surgical treatment is recommended in cases of primary severe fracture dislocation or discoligamentous instability C2/3 (Josten 3 and 4) and/or secondary fracture dislocation. Anterior cervical decompression and fusion (ACDF) C2/3 is the treatment of choice. However, in case of facet joint luxation C2/3 with looked facet (Josten 4), a primary posterior approach may be necessary

Subaxial Cervical Spine Injuries: Treatment Recommendations of the German Orthopedic and Trauma Society

In a consensus process during four sessions in 2016, the working group lower cervical spine of the German Society for Orthopedic and Trauma Surgery (DGOU), formulated Therapeutic Recommendations for the Lower Cervical Spine, taking into consideration the current literature. Therapeutic goals are a permanently stable, painless cervical spine and the protection against secondary neurologic damage while retaining the greatest possible amount of motion and spinal profile. Due to its ease of use and its proven good reliability, the AOSpine classification for subaxial cervical injuries should be used. The Canadian C-Spine Rule is recommended as a clinical decision rule whether to perform imaging or not. If a structural or unstable injury is suspected by patient history or clinical findings, a spiral CT scan of the cervical spine is the favoured diagnosticmodality. Conventional X-ray is reserved for patients in whom there is no dangerous mechanism of injury. MR imaging is recommended in case of unexplained neurologic deficit, prior to closed reduction and open posterior surgery and to exclude disco-ligamentous injuries. Urgency of MR imaging depends on the specific findings. CT angiography is recommended in higher-grade facet joint injuries or in the presence of vertebra-basilar symptoms. Flexion-extension imaging is recommended only as a physician-guided dynamic fluoroscopy, when an unstable lesion is still suspected. The therapeutic strategy is mainly dependent on morphologic criteria, which are described using the AOSpine classification. A0-injuries are treated conservatively. A1- and A2-injuries are treated conservatively in the majority of cases, and in single cases a gross kyphotic deformity might indicate surgical stabilisation. A3-injuries do indicate a surgical therapy in the majority of cases, but certain cases might be treated conservatively. A4-fractures as well as B- and C-type injuries are to be treated surgically. Most injuries can be treated by anterior plate stabilisation with interbody support; when a complete burst fracture is present, corpectomy and vertebral body replacement is necessary. In certain cases, an additive posterior or pure posterior instrumentation might be possible or even mandatory. In most of these cases, lateral mass screws are sufficient; when pedicle screws are applied in C3 to C6, a 3D-navigation system is recommended. Injuries in an ankylosing spine (M3-modifier) should be treated preferably from posterior with long-segment instrumentation