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Although autologous bone grafting is widely considered as an ideal source for interbody fusion, it still carries a risk of nonunion. The influence of the intervertebral device should not be overlooked. Requirements for artificial spinal devices are to join the vertebrae together and recover the original function of the spine rapidly. Ordered mineralization of apatite crystals on collagen accelerates bone functionalization during the healing process. Particularly, the stable spinal function requires the ingrowth of an ordered collagen and apatite matrix which mimics the intact intervertebral microstructure. This collagen and apatite ordering is imperative for functional bone regeneration, which has not been achieved using classical autologous grafting. We developed an intervertebral body device to achieve high stability between the host bone and synthesized bone by controlling the ordered collagen and apatite microstructure. This was an in vivo animal study. Intervertebral spacers with a through-pore grooved surface structure, referred to as a honeycomb tree structure, were produced using metal 3D printing. These spacers were implanted into normal sheep at the L2–L3 or L4–L5 disc levels. As a control group, grafting autologous bone was embedded. The mechanical integrity of the spacer/bone interface was evaluated through push-out tests. The spacer with honeycomb tree structure induced anisotropic trabecular bone growth with textured collagen and apatite orientation in the through-pore and groove directions. The push-out load of the spacer was significantly higher than that of the conventional autologous graft spacer. Moreover, the load was significantly correlated with the anisotropic texture of the newly formed bone matrix. The developed intervertebral spacer guided the regenerated bone matrix orientation of collagen and apatite, resulting in greater strength at the spacer/host bone interface than that obtained using a conventional gold-standard autologous bone graft. Our results provide a foundation for designing future spacers for interbody fusion in human. [ABSTRACT FROM AUTHOR]

Abstract: Background context: With the increase of the elderly population, osteoporotic vertebral fractures have been frequently reported. Surgical intervention is usually recommended in osteoporotic vertebral collapse with neurologic deficits. However, very few reports on surgical interventions exist. Purpose: To compare surgical results of anterior and posterior procedures for treating osteoporotic thoracolumbar vertebral collapse with sustained neurologic deficits. Study design: Retrospective comparative study. Patient sample: Fifty patients who sustained osteoporotic thoracolumbar vertebral collapse with neurologic deficits were treated either by anterior decompression and strut graft (n=32) or by posterior decompression and pedicle screw fixation with vertebroplasty (n=18). Outcome measures: Incidence of complications, sagittal Cobb angle, spinal canal encroachment, and Japanese Orthopedic Association score. Methods: The authors retrospectively reviewed the results of a consecutive series of patients undergoing anterior decompression and strut graft or posterior decompression and pedicle screw fixation with vertebroplasty for osteoporotic thoracolumbar vertebral collapse with neurologic deficits. Operative notes, clinical charts, and radiographs were analyzed. Results: Operative time was similar between the groups, but intraoperative blood loss was significantly lower in the posterior group. All patients showed neurologic recovery. No significant difference was observed in the neurologic improvement, kyphosis correction angle, and loss of correction. Perioperative respiratory complications were found in 11 patients (34%) in the anterior group. In the anterior group, early posterior reinforcement was required in patients with very low bone density below 0.60 g/cm2 and/or in those with three segments of instrumentation for two vertebral collapses. Posterior group patients did not undergo additional surgery. Conclusions: Anterior reconstruction for osteoporotic vertebral collapse is significant because anterior elements, particularly those at the thoracolumbar junction, play a major role in load bearing. However, difficulties arise when anterior reconstruction is performed in cases with very low bone density and in those with multiple vertebral collapse. [Copyright &y& Elsevier]

Background Context: Therapeutic devices for spinal disorders, such as spinal fusion cages, must be able to facilitate the maintenance and rapid recovery of spinal function. Therefore, it would be advantageous that future spinal fusion cages facilitate rapid recovery of spinal function without secondary surgery to harvest autologous bone.Purpose: This study investigated a novel spinal cage configuration that achieves in vivo mechanical integrity as a devise/bone complex by inducing bone that mimicked the sound trabecular bone, hierarchically and anisotropically structured trabeculae strengthened with a preferentially oriented extracellular matrix.Study Design/settings: In vivo animal study.Methods: A cage possessing an anisotropic through-pore with a grooved substrate, that we termed "honeycomb tree structure," was designed for guiding bone matrix orientation; it was manufactured using a laser beam powder bed fusion method through an additive manufacturing processes. The newly designed cages were implanted into sheep vertebral bodies for 8 and 16 weeks. An autologous bone was not installed in the newly designed cage. A pull-out test was performed to evaluate the mechanical integrity of the cage/bone interface. Additionally, the preferential orientation of bone matrix consisting of collagen and apatite was determined.Results: The cage/host bone interface strength assessed by the maximum pull-out load for the novel cage without an autologous bone graft (3360±411 N) was significantly higher than that for the conventional cage using autologous bone (903±188 N) after only 8 weeks post-implantation.Conclusions: These results highlight the potential of this novel cage to achieve functional fusion between the cage and host bone. Our study provides insight into the design of highly functional spinal devices based on the anisotropic nature of bone.Clinical Significance: The sheep spine is similar to the human spine in its stress condition and trabecular bone architecture and is widely recognized as a useful model for the human spine. The present design may be useful as a new spinal device for humans. [ABSTRACT FROM AUTHOR]

Background Context: Controversy exists regarding the effects of multilevel facetectomy and screw density on deformity correction, especially thoracic kyphosis (TK) restoration in adolescent idiopathic scoliosis (AIS) surgery.Purpose: This study aimed to evaluate the effects of multilevel facetectomy and screw density on sagittal plane correction in patients with main thoracic (MT) AIS curve.Study Design: A retrospective correlation and comparative analysis of prospectively collected, consecutive, non-randomized series of patients at a single institution was undertaken.Patient Sample: Sixty-four consecutive patients with Lenke type 1 AIS treated with posterior correction and fusion surgery using simultaneous double-rod rotation technique were included.Outcome Measures: Patient demographics and preoperative and 2-year postoperative radiographic measurements were the outcome measures for this study.Methods: Multiple stepwise linear regression analysis was conducted between change in TK (T5-T12) and the following factors: age at surgery, Risser sign, number of facetectomy level, screw density, preoperative main thoracic curve, flexibility in main thoracic curve, coronal correction rate, preoperative TK, and preoperative lumbar lordosis. Patients were classified into two groups: TK<15° group defined by preoperative TK below the mean degree of TK for the entire cohort (<15°) and the TK≥15° group, defined by preoperative TK above the mean degree of kyphosis (≥15°). Independent sample t tests were used to compare demographic data as well as radiographic outcomes between the two groups. There were no study-specific biases related to conflicts of interest.Results: The average preoperative TK was 14.0°, which improved significantly to 23.1° (p<.0001) at the 2-year final follow-up. Greater change in TK was predicted by a low preoperative TK (p<.0001). The TK <15° group showed significant correlation between change in TK and number of facetectomy level (r=0.492, p=.002). Similarly, significant correlation was found between change in TK and screw density (r=0.333, p=.047). Conversely, in the TK ≥15° group, correlation was found neither between change in TK and number of facetectomy level (r=0.047, p=.812), nor with screw density (r=0.030, p=.880). Furthermore, in patients with preoperative TK<15°, change in TK was significantly correlated with screw density at the concave side (r=0.351, p=.036) but not at the convex side (r=0.144, p=.402).Conclusions: In patients with hypokyphotic thoracic spine, significant positive correlation was found between change in TK and multilevel facetectomy or screw density at the concave side. This indicates that in patients with AIS who have thoracic hypokyphosis as part of their deformity, the abovementioned factors must be considered in preoperative planning to correct hypokyphosis. [ABSTRACT FROM AUTHOR]

Purpose of study: The objectives of this study were to analyze the surgical results of cervical spine injuries associated with lateral mass and facet joint fractures retrospectively and to clarify the surgical indication and treatment strategies for these injuries. Methods used: From 1991 to 1999, 30 patients including 20 lateral mass fractures and 8 facet joint fractures received surgical treatments in our institution. The average age at surgery was 46 years. The injury types according to Allen's classification were compressive-extension in 26, lateral flexion in 3, and distractive-flexion in 1 patient. All patients, except one who required osteosynthesis for the separation fracture of the lateral mass, received exclusive posterior fusion with cervical pedicle screw system. From X-rays and magnetic resonance imaging (MRI) analyses, the fractures were classified into subtypes. The translation of fractured and adjacent vertebrae in the sagittal and coronal planes, vertebral body destruction and signal changes of disc and spinal ligaments (ALL, PLL, SSL and ISL) on MRI were evaluated. The number of stabilized segments and the spinal alignment were also evaluated at follow-up. of findings: The lateral mass fractures were divided into the following four subtypes: separation fracture in 11, comminution type in 4, split type in 5 and traumatic spondylolysis in 2. The superior and inferior articular process fractures and combination of both fractures were seen in six, one and one patient, respectively. The anterior translation of fractured vertebra was demonstrated in 77% of lateral mass fractures, whereas 24% and 10% of anterior translation was observed even in cephalad and caudal adjacent vertebrae, respectively. The alignment change in coronal plane was detected in 33% of lateral mass fractures. On MRI, the signal changes in ALL and disc were demonstrated in 76% and 25% of caudal and cephalad segments adjacent to fractured vertebra, respectively. The number of stabilized segments were 1.4, 1.67 and 2 in separation, comminution and split type, respectively. The fusion was completely achieved in all patients. However, the preservation of spinal segments resulted in fusion with the mild anterior translation in six patients. Relationship between findings and existing knowledge: Little is known about the detailed fracture type of lateral mass/facet fractures, initial instability, and a frequency of soft tissue injury. This study first analyzed these parameters. Overall significance of findings: The evaluation of spinal instability as well as the assessment of soft tissue injury on initial MRI was essential for the diagnosis and treatment of lateral mass and facet fractures. We successfully saved the stabilized segments in separation fractures or fractures with mild comminution based on the adjacent disc and ligaments evaluation. However, severely comminuted lateral mass fractures with coronal plane malalignment required two-level posterior fixation. The exclusive posterior stabilization with cervical pedicle screw system provides a short fusion as well as a normal spinal alignment even in the lateral mass fractures with severe spinal instability. Disclosures: Device or drug: cervical pedicle screw. Status: not approved. Conflict of interest: No conflicts. [ABSTRACT FROM AUTHOR]

Background context Deformation of in vivo-implanted rods could alter the scoliosis sagittal correction. To our knowledge, no previous authors have investigated the influence of implanted-rod deformation on the sagittal deformity correction during scoliosis surgery. Purpose To analyze the changes of the implant rod's angle of curvature during surgery and establish its influence on sagittal correction of scoliosis deformity. Study design A retrospective analysis of the preoperative and postoperative implant rod geometry and angle of curvature was conducted. Patient sample Twenty adolescent idiopathic scoliosis patients underwent surgery. Average age at the time of operation was 14 years. Outcome measures The preoperative and postoperative implant rod angle of curvature expressed in degrees was obtained for each patient. Methods Two implant rods were attached to the concave and convex side of the spinal deformity. The preoperative implant rod geometry was measured before surgical implantation. The postoperative implant rod geometry after surgery was measured by computed tomography. The implant rod angle of curvature at the sagittal plane was obtained from the implant rod geometry. The angle of curvature between the implant rod extreme ends was measured before implantation and after surgery. The sagittal curvature between the corresponding spinal levels of healthy adolescents obtained by previous studies was compared with the implant rod angle of curvature to evaluate the sagittal curve correction. The difference between the postoperative implant rod angle of curvature and normal spine sagittal curvature of the corresponding instrumented level was used to evaluate over or under correction of the sagittal deformity. Results The implant rods at the concave side of deformity of all patients were significantly deformed after surgery. The average degree of rod deformation Δθ at the concave and convex sides was 15.8° and 1.6°, respectively. The average preoperative and postoperative implant rod angle of curvature at the concave side was 33.6° and 17.8°, respectively. The average preoperative and postoperative implant rod angle of curvature at the convex side was 25.5° and 23.9°, respectively. A significant relationship was found between the degree of rod deformation and preoperative implant rod angle of curvature (r=0.60, p<.005). The implant rods at the convex side of all patients did not have significant deformation. The results indicate that the postoperative sagittal outcome could be predicted from the initial rod shape. Conclusions Changes in implant rod angle of curvature may lead to over- or undercorrection of the sagittal curve. Rod deformation at the concave side suggests that corrective forces acting on that side are greater than the convex side. [ABSTRACT FROM AUTHOR]

Abstract: Background context: In the cervical spine, the combination of ossification of the ligamentum flavum (OLF) and ossification of the posterior longitudinal ligament (OPLL) is rarely seen. There have been only four cases reported in the English literature. Purpose: We describe two more cases that exhibited cervical myelopathy resulting from the combination of cervical OLF and OPLL and required surgery. A literature review with a comparative analysis between previous reports and present cases was also performed. Study design: Case report and literature review. Patient sample: Two patients with combined OLF and OPLL. Outcome measures: Preoperative computed tomography, magnetic resonance imaging, and pathological findings from operative specimens were used to confirm the diagnoses. Methods: A 76-year-old man (Case 1) presented with disturbance of gait and fine finger movement. Magnetic resonance imaging showed severe spinal canal stenosis and cord compression at the C3–C4 level. Computed tomography showed OPLL at the C2–C6 levels (segmental type) and OLF at the left C3–C4 level. The patient underwent posterior decompression and OLF resection. A 75-year-old man (Case 2) presented with sensory disturbance and muscle weakness in his bilateral upper extremities and disturbance in fine finger movements. Magnetic resonance imaging showed severe spinal canal stenosis and cord compression at the C2–C3 and C3 levels. Computed tomography showed OPLL at the C3–C7 levels (mixed type) and OLF at the left C2–C3 and C3 levels. The patient also underwent posterior decompression and OLF resection. Results: In both cases, histological examination of the surgical specimens showed osseous tissue and enchondral ossification within the ligamentum flavum, and the diagnosis in each case was OLF. After surgery, both patients'' symptoms immediately improved, and no recurrence was observed at 2 years after surgery. Conclusions: We experienced two cases of cervical myelopathy resulting from the combination of OLF and OPLL in the cervical spine. The symptoms of myelopathy were treated successfully by laminectomy and laminoplasty with OLF resection in both cases. The literature review including the present two cases revealed that cervical OLF tended to occur adjacent or close to the margin of cervical OPLL, suggesting that the increased mechanical stress at the junction of OPLL may be a causative factor. [Copyright &y& Elsevier]

Abstract: Background context: There have been some reports describing hematoma in the thoracic and lumbar ligamentum flavum, but there have been only three reports of hematoma in the cervical ligamentum flavum. Purpose: We describe another case of the ligamentum flavum hematoma in the cervical spine with a different feature of occurrence that required surgical treatment. Study design: Case report. Patient sample: Patient with ligamentum flavum hematoma in the cervical spine. Outcome measures: Preoperative magnetic resonance imaging and pathologic finding from operative specimen confirmed the diagnosis. Methods: A 69-year-old man insidiously presented with pain in his left upper arm and difficulty in left shoulder abduction. Neurologic examination demonstrated a cervical myelopathy with diffuse muscle weakness of left upper extremity and sensory disturbance. Imaging studies revealed a mass of high intense on T1-weighted images and isointense on T2-weighted images posterior to the dura at C4 lower end level. The patient underwent C4–C5 hemilaminectomy and the removal of the mass. The mass existed within the ligamentum flavum and was connected toward the pedicle like the beads of a rosary. Results: Histopathologic examination of the surgical specimen showed that the hematoma was present within the ligamentum flavum and contained macrophages that had phagocytosed red blood cells and hemosiderin. After surgery, the patients'' symptoms immediately improved, and no recurrence was observed at 2 years postoperatively. Conclusions: We reported a very rare case of hematoma in the ligamentum flavum of the cervical spine that required surgery. Because the patient was without the history of trauma, it was suggested that the use of antiplatelet drugs was responsible for the occurrence of the disease. [Copyright &y& Elsevier]