Aims. To develop and internally validate a preoperative clinical prediction model for acute adjacent vertebral fracture (AVF) after vertebral augmentation to support preoperative decision-making, named the after vertebral augmentation (AVA) score. Methods. In this prognostic study, a multicentre, retrospective single-level vertebral augmentation cohort of 377 patients from six Japanese hospitals was used to derive an AVF prediction model. Backward stepwise selection (p < 0.05) was used to select preoperative clinical and imaging predictors for acute AVF after vertebral augmentation for up to one month, from 14 predictors. We assigned a score to each selected variable based on the regression coefficient and developed the AVA scoring system. We evaluated sensitivity and specificity for each cut-off, area under the curve (AUC), and calibration as diagnostic performance. Internal validation was conducted using bootstrapping to correct the optimism. Results. Of the 377 patients used for model derivation, 58 (15%) had an acute AVF postoperatively. The following preoperative measures on multivariable analysis were summarized in the five-point AVA score: intravertebral instability (≥ 5 mm), focal kyphosis (≥ 10°), duration of symptoms (≥ 30 days), intravertebral cleft, and previous history of vertebral fracture. Internal validation showed a mean optimism of 0.019 with a corrected AUC of 0.77. A cut-off of ≤ one point was chosen to classify a low risk of AVF, for which only four of 137 patients (3%) had AVF with 92.5% sensitivity and 45.6% specificity. A cut-off of ≥ four points was chosen to classify a high risk of AVF, for which 22 of 38 (58%) had AVF with 41.5% sensitivity and 94.5% specificity. Conclusion. In this study, the AVA score was found to be a simple preoperative method for the identification of patients at low and high risk of postoperative acute AVF. This model could be applied to individual patients and could aid in the decision-making before vertebral augmentation. Cite this article: Bone Joint J 2022;104-B(1):97–102

Background

We have reported an injectable L-pNIPAM-co-DMAc hydrogel with hydroxyaptite nanoparticles (HAPna) which promotes mesenchymal stem cell (MSC) differentiation to bone cells without the need for growth factors. This hydrogel could potentially be used as an osteogenic and osteoconductive bone filler of spinal cages to improve vertebral body fusion. Here we investigated the biocompatibility and efficacy of the hydrogel in vivo using a proof of concept femur defect model.

Introduction/Aim

Numerous lumbo-pelvic reconstruction methods based on posterior construct and anterior cages have been proposed for cases involving total sacrectomy and lumbar vertebrectomy. These constructs create long lever arms and generate high cantilever forces across the lumbo-sacral junction resulting in implant failure or breakage. Biomechanical studies have shown that placing implants anterior to lumbo-sacral pivot point provide a more effective moment arm to resist flexion force and improve the ultimate strength of the construct. As a result more emphasis is placed on screws in the pelvis.

We report a new and novel technique that allows for the placement of a pelvic ring construct to augment the posterior construct in a lumbo-pelvic reconstruction.

To investigate and compare the biomechanical characteristics of Bipedicular versus Unipedicular Vertebroplasty in cadaveric vertebra. Cadaveric single level vertebra were used to evaluate Bipedicular versus Unipedicular Vertebroplasty as an intervention for vertebral compression fractures. Cadaveric vertebra were assigned to two arms: Arm A simulated a wedge fracture followed by bipedicular cement augmentation; Arm B simulated a wedge fracture followed by unipedicular cement augmentation. Micro-CT imaging was performed to assess vertebral dimension, cement fill volumes and bone mineral density. All augmented specimens were then compressed under a static eccentric flexion load to failure. Pre and post augmentation failure load and stiffness were used to compare the two groups. Results suggest, when compared with actual failure strength, that the product of bone mineral density and endplate surface area gave a good prediction of failure strength for specimens in both arms. The mean cement volume fill of augmented vertebral bodies was 22.8% ± 7.21%. The bipedicular group showed a reduction in stiffness but an increase in post augmentation failure load of 1.09. The unipedicular group also showed a reduction in stiffness but showed a much greater increase in post augmentation failure load of 1.68. Preliminary data from this study suggests there is a significant reduction in stiffness following both bipedicular and unipedicular vertebroplasty. There is a significant increase in failure load post augmentation in the unipedicular group

Aims. Loosening of pedicle screws is a major complication of posterior spinal stabilisation, especially in the osteoporotic spine. Our aim was to evaluate the effect of cement augmentation compared with extended dorsal instrumentation on the stability of posterior spinal fixation. Materials and Methods. A total of 12 osteoporotic human cadaveric spines (T11-L3) were randomised by bone mineral density into two groups and instrumented with pedicle screws: group I (SHORT) separated T12 or L2 and group II (EXTENDED) specimen consisting of T11/12 to L2/3. Screws were augmented with cement unilaterally in each vertebra. Fatigue testing was performed using a cranial-caudal sinusoidal, cyclic (1.0 Hz) load with stepwise increasing peak force. Results. Augmentation showed no significant increase in the mean cycles to failure and fatigue force (SHORT p = 0.067; EXTENDED p = 0.239). Extending the instrumentation resulted in a significantly increased number of cycles to failure and a significantly higher fatigue force compared with the SHORT instrumentation (EXTENDED non-augmented + 76%, p < 0.001; EXTENDED augmented + 87%, p < 0.001). Conclusion. The stabilising effect of cement augmentation of pedicle screws might not be as beneficial as expected from biomechanical pull-out tests. Lengthening the dorsal instrumentation results in a much higher increase of stability during fatigue testing in the osteoporotic spine compared with cement augmentation. Cite this article: Bone Joint J 2016;98-B:1099–1105

Aims

Anchorage of pedicle screw rod instrumentation in the elderly spine with poor bone quality remains challenging. Our study aims to evaluate how the screw bone anchorage is affected by screw design, bone quality, loading conditions, and cementing techniques.

This review provides a concise outline of the advances made in the care of patients and to the quality of life after a traumatic spinal cord injury (SCI) over the last century. Despite these improvements reversal of the neurological injury is not yet possible. Instead, current treatment is limited to providing symptomatic relief, avoiding secondary insults and preventing additional sequelae. However, with an ever-advancing technology and deeper understanding of the damaged spinal cord, this appears increasingly conceivable. A brief synopsis of the most prominent challenges facing both clinicians and research scientists in developing functional treatments for a progressively complex injury are presented. Moreover, the multiple mechanisms by which damage propagates many months after the original injury requires a multifaceted approach to ameliorate the human spinal cord. We discuss potential methods to protect the spinal cord from damage, and to manipulate the inherent inhibition of the spinal cord to regeneration and repair. Although acute and chronic SCI share common final pathways resulting in cell death and neurological deficits, the underlying putative mechanisms of chronic SCI and the treatments are not covered in this review.

Fracture of a pedicle is a rare complication of spinal instrumentation using pedicular screws, but it can lead to instability and pain and may necessitate extension of the fusion. Osteosynthesis of the fractured pedicle by cerclage-wire fixation and augmentation of the screw fixation by vertebroplasty or temporary elongation of the fixation, allows stabilisation without sacrifice of the adjacent healthy segment. We describe three patients who developed a fracture of the pedicle in the most caudal instrumented vertebra early after lumbar spinal fusion. During revision surgery the pedicles were reduced and secured by a soft cerclage wire bilaterally. Fusion was obtained at the site of the primary instrumentation and healing of the pedicles was achieved. Cerclage wiring of the fractured pedicle seems to be safe and avoids permanent extension of the fusion without the sacrifice of an otherwise healthy segment

The presacral retroperitoneal approach for axial lumbar interbody fusion (presacral ALIF) is not widely reported, particularly with regard to the mid-term outcome. This prospective study describes the clinical outcomes, complications and rates of fusion at a follow-up of two years for 26 patients who underwent this minimally invasive technique along with further stabilisation using pedicle screws. The fusion was single-level at the L5-S1 spinal segment in 17 patients and two-level at L4–5 and L5-S1 in the other nine. The visual analogue scale for pain and Oswestry Disability Index scores were recorded pre-operatively and during the 24-month study period. The evaluation of fusion was by thin-cut CT scans at six and 12 months, and flexion-extension plain radiographs at six, 12 and 24 months. Significant reductions in pain and disability occurred as early as three weeks postoperatively and were maintained. Fusion was achieved in 22 of 24 patients (92%) at 12 months and in 23 patients (96%) at 24 months. One patient (4%) with a pseudarthrosis underwent successful revision by augmentation of the posterolateral fusion mass through a standard open midline approach. There were no severe adverse events associated with presacral ALIF, which in this series demonstrated clinical outcomes and fusion rates comparable with those of reports of other methods of interbody fusion

Aims

The aim of this study was to compare the peak pull-out force (PPF) of pedicle-lengthening screws (PLS) and traditional pedicle screws (TPS) using instant and cyclic fatigue testing.

Objectives

Cement augmentation of pedicle screws could be used to improve screw stability, especially in osteoporotic vertebrae. However, little is known concerning the influence of different screw types and amount of cement applied. Therefore, the aim of this biomechanical in vitro study was to evaluate the effect of cement augmentation on the screw pull-out force in osteoporotic vertebrae, comparing different pedicle screws (solid and fenestrated) and cement volumes (0 mL, 1 mL or 3 mL).

Objectives

Although vertebroplasty is very effective for relieving acute pain from an osteoporotic vertebral compression fracture, not all patients who undergo vertebroplasty receive the same degree of benefit from the procedure. In order to identify the ideal candidate for vertebroplasty, pre-operative prognostic demographic or clinico-radiological factors need to be identified. The objective of this study was to identify the pre-operative prognostic factors related to the effect of vertebroplasty on acute pain control using a cohort of surgically and non-surgically managed patients.

Ventral screw osteosynthesis is a common surgical method for treating fractures of the odontoid peg, but there is still no consensus about the number and diameter of the screws to be used. The purpose of this study was to develop a more accurate measurement technique for the morphometry of the odontoid peg (dens axis) and to provide a recommendation for ventral screw osteosynthesis.

Images of the cervical spine of 44 Caucasian patients, taken with a 64-line CT scanner, were evaluated using the measuring software MIMICS. All measurements were performed by two independent observers. Intraclass correlation coefficients were used to measure inter-rater variability.

The mean length of the odontoid peg was 39.76 mm (sd 2.68). The mean screw entry angle α was 59.45° (sd 3.45). The mean angle between the screw and the ventral border of C2 was 13.18° (sd 2.70), the maximum possible mean converging angle of two screws was 20.35° (sd 3.24). The measurements were obtained at the level of 66% of the total odontoid peg length and showed mean values of 8.36 mm (sd 0.84) for the inner diameter in the sagittal plane and 7.35 mm (sd 0.97) in the coronal plane. The mean outer diameter of the odontoid peg was 12.88 mm (sd 0.91) in the sagittal plane and 11.77 mm (sd 1.09) in the coronal plane. The results measured at the level of 90% of the total odontoid peg length were a mean of 6.12 mm (sd 1.14) for the sagittal inner diameter and 5.50 mm (sd 1.05) for the coronal inner diameter. The mean outer diameter of the odontoid peg was 11.10 mm (sd 1.0) in the sagittal plane and 10.00 mm (sd 1.07) in the coronal plane. In order to calculate the necessary screw length using 3.5 mm cannulated screws, 1.5 mm should be added to the measured odontoid peg length when anatomical reduction seems possible.

The cross-section of the odontoid peg is not circular but slightly elliptical, with a 10% greater diameter in the sagittal plane. In the majority of cases (70.5%) the odontoid peg offers enough room for two 3.5 mm cannulated cortical screws.

Cite this article: Bone Joint J 2013;95-B:536–42.

The purpose of this study was to determine whether patients with a burst fracture of the thoracolumbar spine treated by short segment pedicle screw fixation fared better clinically and radiologically if the affected segment was fused at the same time. A total of 50 patients were enrolled in a prospective study and assigned to one of two groups. After the exclusion of three patients, there were 23 patients in the fusion group and 24 in the non-fusion group. Follow-up was at a mean of 23.9 months (18 to 30). Functional outcome was evaluated using the Greenough Low Back Outcome Score. Neurological function was graded using the American Spinal Injury Association Impairment Scale. Radiological outcome was assessed on the basis of the angle of kyphosis.

Peri-operative blood transfusion requirements and duration of surgery were significantly higher in the fusion group (p = 0.029 and p < 0.001, respectively). There were no clinical or radiological differences in outcome between the groups (all outcomes p > 0.05). The results of this study suggest that adjunctive fusion is unnecessary when managing patients with a burst fracture of the thoracolumbar spine with short segment pedicle screw fixation.

Vertebral haemangiomas are usually asymptomatic and discovered fortuitously during imaging. A small proportion may develop variable degrees of pain and neurological deficit. We prospectively studied six patients who underwent eight surgical procedures on 11 vertebral bodies. There were 11 balloon kyphoplasties, six lumbar and five thoracic. The mean follow-up was 22.3 months (12 to 36). The indications for operation were pain in four patients, severe back pain with Frankel grade C paraplegia from cord compression caused by soft-tissue extension from a thoracic vertebral haemangioma in one patient, and acute bleeding causing Frankel grade B paraplegia from an asymptomatic vascular haemangioma in one patient. In four patients the exhibited aggressive vascular features, and two showed lipomatous, non-aggressive, characteristics. One patient who underwent a unilateral balloon kyphoplasty developed a recurrence of symptoms from the non-treated side of the vertebral body which was managed by a further similar procedure.

Balloon kyphoplasty was carried out successfully and safely in all patients; four became asymptomatic and two showed considerable improvement. Neurological recovery occurred in all cases but bleeding was greater than normal. To avoid recurrence, complete obliteration of the lesion with bone cement is indicated. For acute bleeding balloon kyphoplasty should be combined with emergency decompressive laminectomy. For intraspinal extension with serious neurological deficit, a combination of balloon kyphoplasty with intralesional alcohol injection is effective.

In a prospective study between August 2002 and August 2005, we studied the quantitative clinical and radiological outcome 36 months after percutaneous vertebroplasty for intractable type-II osteoporotic vertebral compression fractures which had been unresponsive to conservative treatment for at least eight weeks. We also examined the quality of life (QoL). The clinical follow-up involved the use of a pain intensity numerical rating scale (PI-NRS, 0 to 10), the Short-Form 36 (SF-36) QoL questionnaire and an anamnestic questionnaire before and at seven days (PI-NRS only), and one, three, 12 and 36 months post-operatively.

A total of 30 consecutive patients received percutaneous vertebroplasty for 62 vertebral compression fractures with a mean time between fracture and treatment of 7.7 months (2.2 to 39). An immediate, significant and lasting reduction in the average and worst back pain was found, represented by a decrease of 3.1 and 2.7 points after seven days and 3.1 and 2.8 points after 36 months, respectively (p < 0.00). Comparison of the pre- and post-vertebroplasty scores on the various SF-36 domains showed an ultimate significant increase in six of eight domains and both summary scores. Asymptomatic leakage of cement was found in 47 of 58 (81%) of treated vertebrae. Two minor complications occurred, an asymptomatic pulmonary cement embolism and a cement spur along the needle track.

Percutaneous vertebroplasty in the treatment of chronic vertebral compression fractures results in an immediate, significant and lasting reduction in back pain, and overall improvement in physical and mental health.