Xuhua Lu

A Validated Finite Element Analysis of Facet Joint Stress in Degenerative Lumbar Scoliosis

OBJECTIVEnTo develop modified finite element models to simulate degenerative lumbar scoliosis (DLS) based on the normal lumbar spine model and to investigate the facet joint force of the DLS.nnnMETHODSnA 3-dimensional finite element model of a normal lumbar spine was modified to simulate 3 different Cobb angles conditions (12.3°, 22.2°, and 31.8°). The stresses on the facet joint were calculated on both sides (right and left) of the each vertebra. Changes of stress and asymmetry in contact forces between facet joints in the development of DLS were quantitatively analyzed to better understand the development of DLS and the biomechanical forming mechanism.nnnRESULTSnThe results show that asymmetric responses of the facet joint forces exist in various postures and that such effect is amplified with larger curve. When the Cobb angle was smaller, the convex side of the facet joints suffered larger force. When the Cobb angle was larger than 20°, the concave side of the facet joints suffered larger force. In the axial-rotation cases, the facet joint compression is less often located on the ipsilateral side than the contralateral side at the same level.nnnCONCLUSIONSnWith the asymmetric loading, facet joints compressive deformation appears on the concave side, and it decreases in the effect of the facet joints to limit the vertebral rotation and listhesis. Asymmetric loading on facet joint contact forces accelerates asymmetry in the lumbar spine.

Comparison of Clinical Outcomes of Posterior C1-C2 Temporary Fixation Without Fusion and C1-C2 Fusion for Fresh Odontoid Fractures.

BACKGROUNDnPosterior C1-C2 temporary-fixation technique can spare the range of motion (ROM) of the atlantoaxial joint after odontoid fracture healing. However, few studies analyze the difference in clinical outcome between this technique and posterior C1-C2 fusion technique for new odontoid fracture.nnnOBJECTIVEnTo verify whether the clinical outcome of the posterior C1-C2 temporary-fixation technique is superior to that of the posterior C1-C2 fusion technique in the treatment of a new odontoid fracture.nnnMETHODSnTwenty-one of 22 patients who underwent posterior C1-C2 temporary fixation of an odontoid fracture achieved fracture healing and regained motion of the atlantoaxial joint. The functional outcomes of these 21 patients were compared with that of a control group, which consisted of 21 randomly enrolled cases with posterior C1-C2 fixation and fusion. The differences between the 2 groups in the visual analog scale score for neck pain, neck stiffness, Neck Disability Index, 36-Item Short Form Health Survey, and time to fracture healing were analyzed.nnnRESULTSnSignificantly better outcomes were observed in the temporary-fixation group for visual analog scale score for neck pain, Neck Disability Index, and neck stiffness. The outcomes in the temporary-fixation group was superior to those in the fusion group in all dimensions of the 36-Item Short Form Health Survey. There were no significant differences in fracture healing rate and time to fracture healing between the 2 techniques.nnnCONCLUSIONnFunctional outcomes were significantly better after posterior C1-C2 temporary fixation than after fusion. Temporary fixation can be used as a salvage treatment for an odontoid fracture with an intact transverse ligament in cases of failure of, or contraindication to, anterior screw fixation.

Application of Unilateral C2 Translaminar Screw in the Treatment for Atlantoaxial Instability as an Alternative or Salvage of Pedicle Screw Fixation

OBJECTIVEnTo analyze the clinical outcomes of our experience with the unilateral C2 translaminar screw technique and evaluate its feasibility as an alternative or salvage of the pedicle screw.nnnMETHODSnEleven consecutive adult patients with atlantoaxial instability who underwent hybrid fixation techniques using unilateral translaminar screw combined with contralateral C2 pedicle screw and bilateral C1 LMS via posterior arch from January 2010 to December 2013 were retrospectively investigated. The surgical techniques and treatment procedures were described, and clinical symptoms, neurologic function, and imaging appearance were evaluated.nnnRESULTSnThe average age in our series was 40.9 years. No vascular or neurologic injuries occurred. No hardware failure or breach of C2 lamina or pedicle was observed in postoperative radiographs or computed tomography scans. Good bone union was achieved in all patients. There were no cases of screw pullout or pseudarthrosis.nnnCONCLUSIONSnPatients with variant vertebral artery or osseous anomaly are good candidates for the hybrid translaminar screw technique as an alternative to or salvage of C2 pedicle screw.

Biomechanical Evaluation of a Novel Integrated C1 Laminar Hook Combined with C1–C2 Transarticular Screws for Atlantoaxial Fusion: An In Vitro Human Cadaveric Study

OBJECTIVEnTo evaluate the acute stability of a novel integrated C1 laminar hook (H) combined with a C1-C2 transarticular screw (TAS) with established techniques.nnnMETHODSnA novel integrated C1 laminar hook was tested. Seven human cadaveric cervical spines (C0-C3) were used. The range of motion (ROM) of C1-C2 during flexion-extension, lateral bending, and axial rotation were recorded. The specimens were tested under the following conditions: intact, destabilized (using a type II odontoid fracture model), and destabilized but with internal fixation. The following screw systems were used: bilateral C1-C2 TAS combined with the Gallie (G) technique (TAS+G), C1-C2 TAS combined with a novel integrated C1 laminar hook (TAS+H), C1 lateral mass screw and C2 pedicle screws (C2PS+C1LMS), and novel integrated C1 laminar hook combined with C2 pedicle screws (C2PS+H). The TASs were always inserted after the C2PSs. The C2PS+C1LMS and C2PS+H tests were performed alternatively, as were the TAS+G and TAS+H tests.nnnRESULTSnAll fixation constructs greatly improved acute atlantoaxial stability, with no significant difference among TAS+H, TAS+G, and C2PS+C1LMS (all P > 0.05). C2PS+H showed the greatest C1-C2 ROM in axial rotation, significantly different from TAS+G, C2PS+C1LMS, and TAS+H fixation models (all P < 0.05). However, there were no significant differences between C2PS+H and the other 3 models in flexion-extension and lateral bending (all P > 0.05).nnnCONCLUSIONSnThe TAS+H technique can achieve acute stability comparable to that with the TAS+G technique for treating C1-C2 instability. The C2PS+H is a promising alternative, although it provides less stability in axial rotation than TAS+G, TAS+H, or C2PS+C1LMS.

Single anterior approach for cervical spine fractures at C5-T1 complicating ankylosing spondylitis.

OBJECTIVESnTo evaluate the outcomes of anterior approach for cervical spine fractures at C5-T1 in patients with ankylosing spondylitis (AS) and study the problems encountered in diagnosis and treatment.nnnPATIENTS AND METHODSnTen patients with AS (all males; mean age 43.7±9.4 years) underwent anterior surgeries to treat fractures at C5-T1. Skull tractions were performed on patients with fracture dislocation preoperatively. After operation, all the patients wore a cervical collar for 3 months. Plain radiographs at follow-up were reviewed. If bone fusion could not be confirmed on plain radiograph, CT scan was employed. The pre- and postoperative neurological statuses were evaluated according to the Frankel grading system. Problems encountered in diagnosis and treatments were analyzed.nnnRESULTSnThe mean follow-up was 41.2±22.7months. After operation, the displacements of fractures were significantly reduced(P<0.05). Bone fusions were observed in 9 patients at final follow-up. Frankel grades improved by 1.0±0.7 grade (P>0.05). Posterior complications occurred in four patients, including implants failure (n=1), subsidence of cage (n=1), hoarse voice (n=1) and pneumonias (n=2). The patient with implants failure required revision surgery and anterior-posterior fixation. Patient with subsidence of the titanium cage achieved bone fusion with prolonged cervical collar immobilization.nnnCONCLUSIONnThe diagnosis and treatment of cervical spine fractures at C5-T1 in AS patients are challenging, with high risk of neurological compromise and postoperative complications. The single anterior approach followed by postoperative immobilization with a cervical collar can yield acceptable results if the cases are properly selected.

Posterior Temporary Fixation Versus Nonoperative Treatment for Anderson–D'Alonzo Type III Odontoid Fractures: Functional Computed Tomography Evaluation of C1–C2 Rotation

OBJECTIVEnTo evaluate differences in radiologic and functional outcomes between C1-C2 posterior temporary fixation (PTF) and cephalocervicothoracic cast fixation for type III odontoid fractures.nnnMETHODSnData from 13 patients who underwent PTF and 13 cases who underwent cephalocervicothoracic cast fixation due to fresh type III odontoid fractures were reviewed retrospectively. All patients with fracture healing underwent a functional computed tomography scan at the final follow-up to evaluate the range of motion in C1-C2 rotation. Functional outcomes were evaluated in the form of visual analog scale for neck pain, neck stiffness, patient satisfaction, and Neck Disability Index. The outcomes were compared between the 2 groups.nnnRESULTSnAt the final follow up, all 26 patients achieved healing of their fractures. There were no complications associated with either treatment. The left-to-right ranges of motion of C1-C2 rotation were 41.9° ± 11.9° in the PTF group and 43.5° ± 12.0° in the cephalocervicothoracic cast fixation group. There was no statistical difference between the 2 groups regarding the C1-C2 rotation angle (P > 0.05). There also were no significant differences between 2 groups in functional outcomes evaluated by visual analog scale for neck pain, neck stiffness, Neck Disability Index, and patient satisfaction (all P > 0.05).nnnCONCLUSIONSnThe outcomes of PTF and cephalocervicothoracic cast fixation were comparable in the treatment of type III odontoid fractures. For type III odontoid fractures that cannot be managed by nonoperative fixation or anterior screw fixation, PTF may be the treatment of choice, because it spares the motion of the C1-C2 complex.

Posterior Open Reduction and Interlaminae Compression Fusion for Os Odontoideum with Atlantoaxial Dislocation.

OBJECTIVEnTo evaluate the outcome of posterior open reduction and interlaminae compression fusion using a screw-rod system combined with a structural iliac bone graft in the treatment of atlantoaxial dislocation (AAD) secondary to os odontoideum.nnnMETHODSnA retrospective study was performed on 24 patients with AAD secondary to os odontoideum. All cases were with partial reduction after skeletal traction. Intraoperative open reduction and fixation were performed with a posterior screw-rod system, followed by interlaminae compression of an autologous iliac bone graft for fusion. The modified atlanto-dental interval (MADI) was measured to assess the degree of dislocation before traction, after traction, and postoperatively. Japanese Orthopaedic Association (JOA) score, Nurick scale score, visual analog scale score for neck pain (VASSNP), Neck Disability Index (NDI) score, and neck stiffness were used to evaluate functional outcomes.nnnRESULTSnThe mean duration of follow-up was 43.0xa0±xa024.0 months. All patients achieved relief of symptoms and solid bone fusion. There were no complications associated with instrumentation and operation. At the final follow-up, the average MADI was reduced to 2.0 ± 0.8 mm (pretraction: 9.2 ± 1.1 mm; post-traction: 6.6 ± 0.7 mm; Pxa0<xa00.001). The neck stiffness was significantly relieved (Pxa0< 0.001), and function of the spinal cord manifested by the JOA score and Nurick scale score significantly improved (all P < 0.001). The NDI score and VASSNP markedly decreased (all P < 0.001).nnnCONCLUSIONSnIntraoperative open reduction and interlaminae compression fusion using a posterior screw-rod system combined with a structural iliac bone graft is a safe and effective procedure for AAD secondary to os odontoideum.

Deep surgical site infection after anterior decompression and fusion with plate fixation for cervical spondylotic radiculopathy or myelopathy.

OBJECTIVESnTo analyze the diagnosis and management of deep surgical site infection (SSI) with implant involved after anterior decompression and fusion for cervical spondylotic radiculopathy/myelopathy (CSR/CSM).nnnPATIENTS AND METHODSnData of the patients who underwent anterior cervical decompression and fusion with plate fixation due to CSR/CSM were retrospectively reviewed. Cases with postoperative deep SSI with implant involved were identified and analyzed.nnnRESULTSnA total of 1287 patients were finally included. Five patients (0.4%) were found to be with deep SSI. Bone fusion was not obtained when SSI was confirmed in each patient. Three cases were cured using one or two debridement and postoperative antibiotic therapy. Two cases with delayed diagnosis needed anterior implants removal, interbody fusion with autologous iliac bone and posterior lateral mass screw fixation at the first/second debridement. One of the two patients developed esophagus perforation after a second debridement and experienced one-month open drainage. All of the patients were cured without relapse of infection.nnnCONCLUSIONnFor early deep SSI after anterior cervical decompression and fusion, surgical debridement was effective to eradicate infection. But for cases with delayed diagnosis, anterior debridement with prophylactic implant removal and posterior reconstruction was an ideal option. Esophagus perforation complicated with multiple debridements should be paid attention to and avoided.

Multifidus Degeneration, A New Risk Factor for Lumbar Spinal Stenosis: A Case–Control Study

OBJECTIVESnTo analyze whether multifidus degeneration has a relationship with degenerative lumbar spinal stenosis (LSS).nnnMATERIALS AND METHODSnClinical data of 40 patients with LSS were analyzed retrospectively. Moreover, 40 healthy people were selected as controls. Subjects of both groups underwent a 1.5-T lumbar spinal magnetic resonance imaging scan in our hospital, and then the multifidus muscularity, fatty infiltration ratio, and bilateral asymmetry at L4/5 level on magnetic resonance imaging were measured with ImageJ software to analyze and compare the multifidus parameters between the 2 groups.nnnRESULTSnCompared with the control group, the multifidus muscularity was lower, fatty infiltration ratio was greater, and muscle asymmetry was more significant at the L4/5 level in patients with LSS, and the difference between the 2 groups was statistically significant.nnnCONCLUSIONSnMultifidus degeneration, including reduced volume, increased fatty infiltration, and bilateral muscle asymmetry, has an association with LSS.

Influence of the T1-slope on sagittal alignment of the subaxial cervical spine after posterior atlantoaxial fusion in os odontoideum

OBJECTIVESnTo analyze the effect of T1-slope (T1S) on sagittal alignment of the subaxial cervical spine after posterior C1-C2 fusion.nnnPATIENTS AND METHODSnThe data of 35 consecutive patients who underwent posterior C1-C2 fusion due to atlantoaxial instability with os odontoideum were retrospectively reviewed. Radiographic parameters, including T1S, C1-C2 angle and C2-C7 angle, were measured before operation and at the final follow-up. Patients were divided into 2 groups: high T1S group and low T1S group. Differences within and between groups in radiographic parameters and the relationships among T1S, C1-C2 angle and C2-C7 angle were analyzed.nnnRESULTSnAfter operation, C1-C2 angle was significantly enlarged (P<0.05) while C2-C7 angle reduced (P<0.05). However, significant change was not observed in T1S (P>0.05). Postoperative C2-C7 angle had a medium positive relation with both preoperative (r=0.563, P<0.05) and postoperative T1S (r=0.547, P<0.05). C1-C2 angle was negatively related to C2-C7 angle before operation (r=-0.590, P<0.05) but not after operation (r=-0.125, P>0.05). However, change of C1-C2 angle demonstrated a medium negative relation with change of C2-C7 angle after operation (r=-0.614, P<0.05). When the patients were divided into high and low T1S groups, there were significant difference in both preoperative and postoperative C2-C7 angles between 2 groups (all P<0.05) but not in C1-C2 angle, change of C1-C2 angle or change of C2-C7 angle (all P>0.05). After operation, C1-C2 angles became larger in both groups (all P<0.05). Meanwhile, although postoperative C2-C7 angle became smaller than preoperative one in both groups, statistical difference was only observed in high T1S group (P<0.05).nnnCONCLUSIONnT1S was a useful parameter to evaluate postoperative alignment of the subaxial cervical spine after posterior C1-C2 fusion. To avoid postoperative misalignment of the subaxial cervical spine, C1-C2 should be fixed in less lordosis, especially in patients with high preoperative T1S.