[Percutaneous pedicle screw anchored vertebral augmentation for the treatment of Kümmell disease without neurological symptoms].

OBJECTIVE: To explore the clinical effect of percutaneous pedicle screw anchored vertebral augmentation(PPSAVA) in the treatment of asymptomatic Kümmell disease without neurological symptoms. METHODS: The clinical data of 20 patients with Kümmell disease without neurological symptoms treated with PPSAVA in our hospital from January 2019 to December 2021 were analyzed retrospectively, including 5 males and 15 females, aged 56 to 88 (74.95±9.93) years old. and the course of disease was 7 to 60 days with an average of (21.35±14.46) days. All patients were treated with PPSAVA. The time of operation, the amount of bone cement injected and the leakage of bone cement were recorded. The visual analogue scale(VAS), Oswestry disability index(ODI), vertebral body angle(VBA), anterior edge height and midline height of vertebral body were compared among the before operation, 3 days after operation and during the final follow-up. The loosening and displacement of bone cement were observed during the final follow-up. RESULTS: All the 20 patients completed the operation successfully. The operation time was 30 to 56 min with an average of (41.15±7.65) min, and the amount of bone cement injection was 6.0 to 12.0 ml with an average of (9.30±1.49) ml. Bone cement leakage occurred in 6 cases and there were no obvious clinical symptoms. The follow-up time was 6 to 12 months with an average of (8.43±2.82) months. The VBA, anterior edge height and midline height of of injured vertebral body were significantly improved 3 days after operation and the final follow-up(P<0.05), and the VBA, anterior edge height and midline height of of injured vertebral body were lost in different degrees at the final follow-up (P<0.05). The VAS and ODI at 3 days after operation and at the final follow-up were significantly lower than those at preoperatively(P<0.05), but the VAS score and ODI at the final follow-up were not significantly different from those at 3 d after operation(P>0.05). At the last follow-up, no patients showed loosening or displacement of bone cement. CONCLUSION: PPSAVA is highly effective in treating Kümmell disease without neurological symptoms, improving patients' pain and functional impairment, and reducing the risk of cement loosening and displacement postoperatively.

Effect of cervical spine motion on displacement of posterolateral annulus fibrosus in cervical spondylotic radiculopathy with contained posterolateral disc herniation: a three-dimensional finite element analysis.

BACKGROUND: Previous studies on dynamic impingement of nerve root in cervical spondylotic radiculopathy (CSR) have focused on effect of cervical spine motion (CSM) on dimensional changes of intervertebral foramen. However, there are few studies to investigate effect of CSM on displacement of posterolateral intervertebral disc until now. The present study aimed to investigate effect of CSM on displacement of posterolateral annulus fibrosus (AF) in CSR with contained posterolateral disc herniation. METHODS: A C5-C6 CSR finite element model with unilateral contained posterolateral disc herniation was generated based on validated C5-C6 normal finite element model. Forward and backward displacement distributions of posterolateral AFs in CSR model and normal model were compared. Changes in forward and backward displacement magnitudes of posterolateral AFs of the herniated side and the healthy side in CSR model, with respect to those of the ipsilateral posterolateral AFs in normal model, were compared. The comparisons were performed under flexion, extension, lateral bendings and axial rotations. RESULTS: There was no difference in deformation trend of posterolateral AF between CSR model and normal model. Bilateral posterolateral AFs mainly moved forward during flexion and backward during extension. Left posterolateral AF mainly moved backward and right posterolateral AF forward during left lateral bending and left axial rotation. Left posterolateral AF mainly moved forward and right posterolateral AF backward during right lateral bending and right axial rotation. However, with respect to forward and backward displacement magnitudes of the ipsilateral posterolateral AFs in normal model, those of the herniated side increased relatively significantly compared with those of the healthy side in CSR model. CONCLUSIONS: Flexion, lateral bending to the healthy side and axial rotation to the healthy side make posterolateral AF of the herniated side mainly move forward, whereas extension, lateral bending to the herniated side and axial rotation to the herniated side make it mainly move backward. These data may help select CSM or positions to diagnose and treat CSR with contained posterolateral disc herniation. Increase in deformation amplitude of posterolateral AF of the herniated side may also be the reason for dynamic impingement of nerve root in CSR with contained posterolateral disc herniation.

Investigating the mechanical effect of the sagittal angle of the cervical facet joint on the cervical intervertebral disc.

Background: Facet tropism is defined as the asymmetry between the left and right facet joints relative to the sagittal plane. Published clinical studies have found that facet tropism is associated with cervical disc herniation. However, the relationship between the facet orientation and the side of cervical disc herniation remains controversial. Therefore, this study used the finite-element technique to investigate the biomechanical effects of the sagittal angle of the cervical facet joints on the cervical intervertebral disc. Objective: The biomechanical effects of the sagittal angle of the cervical facet joint on the cervical disc and facet joint were investigated using the finite-element technique. Methods: The finite-element model was constructed using computed tomography scans of a 26-year-old female volunteer. First, a cervical model was constructed from C3 to C7. The model was verified using data from previously published studies. Second, the facet orientation at the C5-C6 level was altered to simulate different sagittal angles of cervical facet joints. Five models, F70, F80, F90, F100, and F110, were simulated with different facet joint orientations (70°, 80°, 90°, 100°, and 110° facet joint angles at the left side, respectively, and 90° facet joint angles at the right side) at the C5-C6 facet joints. In each model, annular fibres stress and facet cartilage pressure were studied under six pure moments and two combined moments. Results: Comparing the stress of the annulus fibres in flexion combined with right axial rotation and in flexion combined with left axial rotation in the same model, no difference in the maximum stress of the annulus fibres was noted between these two different moments in the F90 model, whereas differences of 12.80%, 8.84%, 14.95% and 33.32% were noted in the F70, F80, F100 and F110 models, respectively. The same trend was observed when comparing the maximum stress of the annulus fibres in each model during left and right axial rotation. No differences in annular fibres stress and facet cartilage pressure were noted among the five models in flexion, extension, lateral bending, left axial rotation, and flexion combined with left axial rotation in this study. However, compared with the F70 model in flexion combined with right axial rotation, the annulus fibres stress of the F80, F90, F100, and F110 models increased by 5.53%, 13.03%, 35.04%, and 72.94%, respectively, and the pressure of the left facet joint of these models decreased by 5.65%, 12.10%, 18.41%, and 25.74%, respectively. The same trend was observed in the right axial moment. Conclusion: Facet tropism leads to unbalanced stress distribution on the annulus fibres at the cervical intervertebral disc. The greater the sagittal angle of the facet joint, the greater the annular fibres stress on this side. We hypothesised that the side with the larger sagittal angle of the facet joint exhibits a greater risk of disc herniation.

Risk Factors for the Occurrence of Insufficient Cement Distribution in the Fractured Area after Percutaneous Vertebroplasty in Osteoporotic Vertebral Compression Fractures.

BACKGROUND: Insufficient cement distribution (ICD) in the fractured area has been advocated to be responsible for unsatisfied pain relief after percutaneous vertebroplasty (PVP) for osteoporotic vertebral compression fractures (OVCFs). However, little is known about risk factors for the occurrence of ICD. OBJECTIVE: The present study aimed to identify independent risk factors of the emergence of ICD. STUDY DESIGN: A retrospective cohort study. SETTING: Department of spinal surgery, an affiliated hospital of a medical university. METHODS: Patients who underwent PVP for single-level OVCF from January 2012 to September 2014 and met this study's inclusion criteria were retrospectively reviewed. Associations of ICD with co-variates (age, gender, bone mass density with a T-score, amount of injected cement, cement leakage, fracture level, fracture age, fracture severity grade, and location of the fractured area) and the influence of ICD on pain relief were analyzed. RESULTS: A total of 225 patients were included. ICD was found in 26 (11.6%) patients. Fractured area located in the superior portion of the index vertebra was significantly associated with occurrence of ICD. No further significant associations between the studied co-variates and emergence of ICD were seen in the adjusted analysis. In addition, patients with ICD had significantly higher immediate postoperative visual analog scale scores of back pain compared with those with sufficient cement distribution in the fractured area. LIMITATION: Location of the fractured area and cement distribution in the fractured area could not be evaluated quantitatively. CONCLUSIONS: The incidence of ICD is higher in patients with the fractured area located in the superior portion of the index vertebra and ICD might be responsible for unsatisfied pain relief after PVP for OVCFs. KEY WORDS: Percutaneous vertebroplasty, insufficient cement distribution, fractured area, risk factor, osteoporosis, vertebral compression fracture, spine, unsatisfied pain relief, cement augmentation.

Pedicle screw fixation with kyphoplasty decreases the fracture risk of the treated and adjacent non-treated vertebral bodies: a finite element analysis.

Adjacent vertebral fractures are common in patients with osteoporotic vertebral compression fractures (OVCFs) after kyphoplasty. This finite element study was to examine whether short segment pedicle screw fixation (PSF) with kyphoplasty may decrease the fracture risk of the treated and adjacent non-treated vertebrae after kyphoplasty for OVCFs. By simulating cement augmentation with or without short segment pedicle screw fixation (PSF), two tridimensional, anatomically detailed finite element models of the T10-L2 functional spinal junction were developed. The insertion of pedicle screws into the intact vertebra apparently decreased the stress distribution of the treated vertebra in vertical compression and other load situations. The stress distribution in the bone structures of the intact vertebra adjacent to the intact-screwed vertebra was much less than that in the one adjacent to the treated vertebra. The insertion of pedicle screws into the intact vertebra greatly decreased the maximum displacement of the cortical bones and cancellous bones of the vertebrae. Our results indicated that short segment PSF with kyphoplasty may decrease the fracture risk of the treated and adjacent non-treated vertebrae in the management of OVCFs.

Biomechanical effects of cement distribution in the fractured area on osteoporotic vertebral compression fractures: a three-dimensional finite element analysis.

BACKGROUND: According to some clinical studies, insufficient cement distribution (ID) in the fractured area and asymmetrical cement distribution around the fractured area were thought to be the reasons for unrelieved pain and recollapse after percutaneous vertebral augmentation (PVA) in the treatment of symptomatic osteoporotic vertebral compression fractures. METHODS: Finite element methods were used to investigate the biomechanical variance among three patterns of cement distribution (ID and sufficient cement distribution in the fractured area and asymmetrical cement distribution around the fractured area including upward [BU] and downward [BD] cement distribution). RESULTS: Compared with fractured vertebra before PVA, distribution of von Mises stress in the cancellous bone was transferred to be concentrated at the cancellous bone surrounding cement after PVA, whereas it was not changed in the cortical bone. Compared with sufficient cement distribution group, maximum von Mises stress in the cancellous bone and cortical bone and maximum displacement of augmented vertebra increased significantly in the ID group, whereas asymmetrical cement distribution around the fractured area in BU and BD groups mainly increased maximum von Mises stress in the cancellous bone significantly. Similar results could be seen in all loading conditions. CONCLUSIONS: ID in the fractured area may lead to unrelieved pain after PVA in the treatment of symptomatic osteoporotic vertebral compression fractures as maximum displacement of augmented vertebral body increased significantly. Both ID in the fractured area and asymmetrical cement distribution around the fractured area are more likely to induce recollapse of augmented vertebra because they increased maximum von Mises stress in the cancellous bone and cortical bone of augmented vertebra significantly.