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. Methods. Micro-finite element (µFE) models were created from micro-CT (μCT) scans of vertebrae implanted with two types of pedicle screws (L: Ennovate and R: S. 4. ). Simulations were conducted for a 10 mm radius region of interest (ROI) around each screw and for a full vertebra (FV) where different cementing scenarios were simulated around the screw tips. Stiffness was calculated in pull-out and anterior bending loads. Results. Experimental pull-out strengths were excellently correlated to the µFE pull-out stiffness of the ROI (R. 2. > 0.87) and FV (R. 2. > 0.84) models. No significant difference due to screw design was observed. Cement augmentation increased pull-out stiffness by up to 94% and 48% for L and R screws, respectively, but only increased bending stiffness by up to 6.9% and 1.5%, respectively. Cementing involving only one screw tip resulted in lower stiffness increases in all tested screw designs and loading cases. The stiffening effect of cement augmentation on pull-out and bending stiffness was strongly and negatively correlated to local bone density around the screw (correlation coefficient (R) = -0.95). Conclusion. This combined experimental, µCT and µFE study showed that regional analyses may be sufficient to predict fixation strength in pull-out and that full analyses could show that cement augmentation around pedicle screws increased fixation stiffness in both pull-out and bending, especially for low-density bone. Cite this article: Bone Joint Res 2021;10(12):797–806

Introduction. Nucleus replacement surgery has the potential to be an early treatment option for chronic lower back pain. The surgery involves removal (nuclectomy) and replacement of the native degenerated nucleus with a material designed to restore the disc's physiological properties. Multiple techniques have been considered to perform a nuclectomy, however the advantages and disadvantages of each are not well understood. The aim of this study was to quantitatively compare three nuclectomy techniques: automated-shaver, rongeurs, and laser. Methods and results. Fifteen human vertebra-disc-vertebra lumbar specimens were split into three groups. Before and after nuclectomy axial mechanical tests were performed and T2-weighted 9.4T MRIs were acquired for each specimen. Using the automated-shaver and rongeur similar volumes of disc material were removed (2.51±1.10% and 2.76±1.39% of the total disc volume, respectively), whilst considerably less material was removed when using the laser (0.12±0.07%). Using the automated-shaver and rongeur significantly reduced the toe-region stiffness, while the linear region stiffness was significantly reduced only in the rongeur group. From the MRIs, more homogeneous cavities were seen in the center of the disc when using the automated shaver compared to rongeur, whilst laser ablation resulted in small, localized cavities. Conclusion. Results suggest that the current laser parameters are not suitable for removal of large volumes of material unless the technique is optimised for this application. Both rongeurs and automated-shavers can be used to remove large volumes of material but the reduced risk of collateral damage to surrounding tissues suggests that an automated-shaver may be more suitable. Conflicts of interest: No conflicts of interest. Sources of funding: Part of this work was funded by an Imperial College Research Fellowship for NN and an EPSRC DTP CASE Conversion Studentship for TR (EP/R513052/1)

Objectives. Understanding lumbar facet joint involvement and biomechanical changes post spinal fusion is limited. This study aimed to establish an in vitro model assessing mechanical effects of fusion on human lumbar facet joints, employing synchronized motion, pressure, and stiffness analysis. Methods and Results. Seven human lumbar spinal units (age 54 to 92, ethics 15/YH/0096) underwent fusion via a partial nucleotomy model mimicking a lateral cage approach with PMMA cement injection. Mechanical testing pre and post-fusion included measuring compressive displacement and load, local motion capture, and pressure mapping at the facet joints. pQCT imaging (82 microns isotropic) was carried out at each stage to assess the integrity of the vertebral endplates and quantify the amount of cement injected. Before fusion, relative facet joint displacement (6.5 ± 4.1 mm) at maximum load (1.1 kN) exceeded crosshead displacement (3.9 ± 1.5 mm), with loads transferred across both facet joints. After fusion, facet displacement (2.0 ± 1.2 mm) reduced compared to pre-fusion, as was the crosshead displacement (2.2 ± 0.6 mm). Post-fusion loads (71.4 ± 73.2 N) transferred were reduced compared to pre-fusion levels (194.5 ± 125.4 N). Analysis of CT images showed no endplate damage post-fusion, whilst the IVD tissue: cement volume ratio did not correlate with the post-fusion behaviour of the specimens. Conclusion. An in vitro model showed significant facet movement reduction with stand-alone interbody cage placement. This technique identifies changes in facet movement post-fusion, potentially contributing to subsequent spinal degeneration, highlighting its utility in biomechanical assessment. Conflicts of interest. None. Sources of funding. This work was funded by EPSRC, under grant EP/W015617/1

Spinal deformations are posture dependent. Official data from the Netherlands show that youth are encountering increasing problems with the musculoskeletal system (>40% back pain, and sport injury proneness). Prolonged sloth and slumped sitting postures are causative factors. Dutch youth are “champion sitting” in Europe. The effects of sitting on the development of posture and function of locomotion (stiffness) during growth have only been reported clearly in classic textbooks (in German) of practical anatomy and orthopaedics. Research with relevant clinical examinations is being done to understand epidemiological data on the increasing posture-dependent problems. A cohort of adolescents (15–18 years) in secondary school was assessed for sagittal postural deviations while bending. 248 children completed a questionnaire, and tests were done on neuromuscular tightness. The femorotibial angle was used to measure hamstring tightness. Measurement of the dorsiflexion of the foot was used to assess the tightness of calf muscles and Achilles tendons. All adolescents were photographed laterally while performing the finger–floor test (used to test flexibility), assessed as a knockout test: “Can you reach the floor or not?” The spinal profiles while bending were classified as abnormal arcuate or angular kyphosis. Hamstring tightness was present in 62.1% of the cohort in both legs, and in 18.2% unilaterally. Achilles tendon tightness was present bilaterally in 59.3%, and unilaterally in 19.4%. Activities with presence of stiffness (finger–floor distance), in descending order, were football, running, no sports, field hockey, tennis, dance, and gymnastics. 93.5% of the soccer players had tight hamstrings in both legs compared with none of those performing gymnastics. The correlation of the finger–floor test with tight hamstrings was 73.2%. For sagittal bending deformities, the correlation between form and function deficits cannot be made yet. 80 of 248 spines were rated by the examiners as having deformed flexion. Since Andry (1741) and at the zenith of continental orthopaedics and anatomy around 1900, the prolonged flexed positions of a young spine were indicated as being the main cause of deformity by overload and shear loads on immature discs and cartilage, preventing normal development of the discs. Nachemson proved that the intradiscal pressure in sitting adults was extremely high, so it follows that children must also be at risk. Evidence suggests that youth, generally because of their sedentary and “screenful lifestyle”, will encounter serious problems in growth, manifesting as incongruent neuro-osseous growth (Roth), serious neuromuscular tightness (being prone to injury), and spinal deformations, leading to pain

Background. The majority of adults will experience an episode of low back pain during their life. Patients with non-specific low back pain and lumbar disc degeneration (LDD) may experience spinal pain and morning stiffness because of a comparable inflammatory process as in patients with osteoarthritis of the knee and/or hip. Therefore, this study assessed the association between spinal morning stiffness, LDD and systemic inflammation in middle aged and elderly patients with low back pain. Methods. This cross-sectional study used the baseline data of the BACE study, including patients aged ≥55 years visiting a general practitioner with a new episode of back pain. The association between spinal morning stiffness, the radiographic features of lumbar disc degeneration and systemic inflammation measured with serum C-reactive protein was assessed with multivariable logistic regression models. Results. At baseline, a total of 661 back pain patients were included. Mean age was 66 years (SD 8), 416 (63%) reported spinal morning stiffness and 108 (16%) showed signs of systemic inflammation measured with CRP. Both LDD definitions were significantly associated with spinal morning stiffness (osteophytes OR=1.5 95% CI 1.1–2.1, narrowing OR=1.7 95% CI 1.2–2.4) and spinal morning stiffness >30 minutes (osteophytes OR=1.9 95% CI 1.2–3.0, narrowing OR=3.0 95% CI 1.7–5.2) For severity of disc space narrowing we found a clear dose response relationship with spinal morning stiffness. We found no associations between spinal morning stiffness and the features of LDD with systemic inflammation. Conclusions. This study demonstrated an association between the presence and duration of spinal morning stiffness and radiographic LDD features. No conflicts of interest. No funding obtained

Introduction. Thoracic wall surgery can cause severe pain and inhibition of coughing with effects. (1) Various local anaesthetic (LA) techniques have been tried successfully to mitigate the use of opioids alone. We believe this is the first time that a serratus plane block using an epidural catheter (SABER)has been studied in anterior spinal fusion (ASF) procedures. Our aim was to ascertain how it would affect ASF compared to gold standard posterior spinal fusion (PSF) surgery. Materials and Methods. We identified 43 patients from the years 2017 to 2019. 24 had ASF and 19 had PSF. Detailed data were collected on local anaesthetic infusion (LAI) SaBER, mean pain scores(MPS), morphine, chirocaine usage and hospital length of stay (HLOS). We divided the patients into 4 groups: Short PSF (SPSF), Long PSF (LPSF), Thoracic anterior fusion (TA) and Thoracolumbar anterior fusion (TLA) surgery. 4 patients in the SPSF and 4 in the LPSF group had LAI because they had a costoplasty. All patients in the anterior group had SaBER. Results. Mean morphine usage was higher in the ASF group. Mean LA usage was lowest in the TLA and highest in the LPSF group (see table). 12 and 24 hour MPS were lower in both anterior groups compared to posterior. Mean HLOS was similar in all groups. Conclusion. Despite painful costoplasties in the anterior group, LAI enabled lower MPS overall and similar HLOS between PSF and ASF groups. Consequently, ASF (with fewer fusion levels) can replace equivalent PSF with resultant less stiffness and increased mobility. Reduction in MPS may be further improved by investigating detailed protocols whereby boluses of LA are given in addition to LAI. This may lead to morphine sparing in the anterior group as has been seen in other studies on thoracic wall procedures. (2). For any figures or tables, please contact the authors directly

Aims

The aim of this study was to investigate the incidence and characteristics of instrumentation failure (IF) after total en bloc spondylectomy (TES), and to analyze risk factors for IF.

Aims

The aims of this study were first, to determine if adding fusion to a decompression of the lumbar spine for spinal stenosis decreases the rate of radiological restenosis and/or proximal adjacent level stenosis two years after surgery, and second, to evaluate the change in vertebral slip two years after surgery with and without fusion.

The purpose of this study is to investigate what effect cross links have on scoliosis constructs and whether cross links may be used instead of pedicle screws at the apex of the deformity. The rotational stiffness of six different construct designs was investigated on scoliotic sawbone models with zero, one or two cross links. In three of the constructs the screws at the apex were removed. Testing was performed to an average torque of 3Nm and ration was detected using electromagnetic motion tracking system. The stiffness in axial rotation of all constructs increased with the number of cross links, however the difference was not statistically significant. In constructs with apical screws the stiffness increased by 3.01% and 12.9% for one and two cross links respectively. In constructs without apical screws the increase was 1.64% and 14.3% for one and two cross links respectively. The total stiffness of the construct increased with the addition of apical screws by 20%, 21.7% and 18.8% for zero, one and two cross links respectively. This increase was statistically significant using a paired t-test (p= 0.01142). On the basis of these results we conclude that the use of cross links in scoliosis correction surgery is not necessary. Pedicle screws positioned at the apex of the scoliosis curve statistically increase the stiffness in axial rotation and are therefore necessary to promote an environment suitable for bony fusion

Background. The rate of subsidence for lumbar fusion surgery is variable from 7- 89%. Subsidance can affect the outcome of surgery by compramising alignment, foraminal height and stability. Modic changes have been shown to affect the stiffness and strength of the vertebral end plate and shown to affect both fusion rates and clinical outcome. Ongoing laboratory investigations into the material properties of the degenerate lumbar spine show modic changes affect the end plate and trabecular bone mechanics. This study aims to bridge this basic science research into clinical practice. Methods. A retrospective analysis of all patients in two tertiary spinal centres who have undergone lumbar interbody fusion with the implantation of a ‘cage’ over the past 6 years were analysed by two independent spinal surgeons. Pre-operative MRI findings were correlated with post-operative interbody cage subsidence after 1 year. Results. A total of 108 Interbody cages were included. Comparison of demographics did not reveal and significant between group variations. Comparison made between those displaying no modic changes and those displaying any of the three modic change types revealed a significantly higher subsidence rate in those displaying modic changes (p=0.003). Subgroup analysis showed that Type 2 modic changes (n=27) had a significantly higher subsidence rate (p=0.002). Those displaying type 3 modic changes (n=7) did not have any incidents of subsidence. Conclusions. Type 2 modic changes are associated with a higher rate of Lumbar interbody cage subsidence in this study. Those displaying type 3 changes seem to be protected from interbody cage subsidence. No Conflict of Interest. Funding: Produced as part of a research grant from the Gwen Fish Trust and Action Arthritis

Statement of Purpose. The purpose of this experiment was to characterize the biomechanical properties of a minimally-invasive flexion-restricting stabilization system (FRSS) developed to address flexion instability. Background. Lumbar flexion instability is associated with degenerative pathology such as degenerative spondylolisthesis (DS) as well as resection of posterior structures during neural decompression. Flexion instability may be measured by increased total flexion/extension range of motion (ROM), as well as reduced stiffness within the high flexibility zone (HFZ, the range in which most activities occur). Flexion and segmental translation are known to be coupled; therefore increased flexion may exacerbate translational instability, particularly in DS. Method. Five cadaveric lumbar spines were tested intact; after L4-L5 destabilization including nucleotomy and midline decompression; and following restabilization with the FRSS secured to the spinous processes. Specimens were loaded in flexion (8Nm) and extension (6Nm) under 400N compressive follower preload. Flexion stiffness in the HFZ and segmental translation were also measured. Results. Destabilization increased L4-L5 flexion by 69%±31% (p<.01); decreased HFZ flexion stiffness 56%±12% (p=.01) and increased segmental translation 70%±49% from 1.5±0.4mm to 2.4±0.4mm (p<.01). With the FRSS segmental flexion was reduced by 45%±15% (p<.01); average HFZ flexion stiffness was increased by 232%±104% (p<.01); and segmental translation was reduced by 25%±9% to 1.8±0.2mm (p<.01). These values were not significantly different from the intact condition (p=.54, p=.21, p=.19). Discussion and Conclusion. The destabilization modeled here simulated degenerative and iatrogenic destabilizations often seen clinically. Implantation of the FRSS on the destabilized segments restored flexion, stiffness and translation to intact levels. The segmental coupling of translation and flexion seen in this experiment indicates that translation may be manipulated by altering flexion kinematics. The FRSS represents a novel system for treating flexion and translational instabilities

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

Aim:. To evaluate the effect of a stiffer rod in normalising thoracic hypokyphosis in adolescent idiopathic scoliosis (AIS). Methods:. A retrospective review of AIS cases performed at our institution was carried out. In order to reduce variability, the analysis included only Lenke 1 cases which had all pedicle screw constructs, with similar constructs and implant density. Cases that underwent anterior release were excluded. All cases had the same implant (Expedium 5.5, Depuy-Synthes, Raynham, USA). The rod material differed in that some cases had 5.5 titanium, whilst others had 5.5 cobalt chrome. The preoperative and postoperative sagittal Cobb angle was measured. Results:. 35 patients met the inclusion criteria. 15 had titanium rods and 20 had cobalt chrome rods. The mean fulcrum correction index was similar between groups. The preoperative coronal and sagittal Cobb was similar between the two groups. There was no statistically significant difference in the postoperative sagittal Cobb between the two groups (ANOVA one way test). Discussion:. Despite the theoretical advantage of a stiffer construct improving the sagittal profile in AIS, this study identified no such benefit despite closely matching the two groups. All pedicle screw constructs do not seem to improve the sagittal profile despite the use of a stiffer rod. Conflict of interest:. Depuy-Synthes fund a fellow in this unit. Conflict Of Interest Statement: No conflict of interest

Aims

Vertebral body tethering (VBT) is a non-fusion technique to correct scoliosis. It allows correction of scoliosis through growth modulation (GM) by tethering the convex side to allow concave unrestricted growth similar to the hemiepiphysiodesis concept. The other modality is anterior scoliosis correction (ASC) where the tether is able to perform most of the correction immediately where limited growth is expected.

Background. Recent studies show massage is effective in reducing back pain and heat and warmth during massage increases an individual's sense of wellbeing. The Ceragem V3 automatic thermal massage bed utilises principles of thermal massage to provide a therapeutic tool for individuals with conditions including diabetes and back pain. Though the brand is well known globally and has much anecdotal evidence, little research has been done on what effect the bed has on individuals with back pain. This study aims to assess subjective experience and function of participants with back pain when using the Ceragem V3. Methods & Results. Thirty-two participants (aged 35.2±9.9 years) with back pain (including sciatica) were recruited after screening using the Red Flags and STarT Back tools. The intervention comprised nine treatment sessions over three successive weeks using an automated thermal massage bed (Ceragem V3, Korea) in automatic mode. Body charts, Patient Reported Outcome Measures (PROM) and the Roland Morris Disability Questionnaire (RMDQ) were used to measure participant pain, stiffness, discomfort and disability levels pre and post intervention. Body chart analysis for pain location showed a significant reduction in reported pain in the thoracic and lumbosacral regions (p<0.01). PROMs showed a significant reduction in the number of days back pain was experienced (p<0.000) and clinically important reductions in back pain, stiffness and discomfort (p<0.000). There was also a significant reduction in RMDQ score (p=0.000). Conclusions. Initial findings demonstrate that through a three week intervention programme, individuals show a significant improvement in back pain, discomfort and stiffness

Aims

The aim of this study was to compare the clinical and radiological outcomes of patients with early-onset scoliosis (EOS), who had undergone spinal fusion after distraction-based spinal growth modulation using either traditional growing rods (TGRs) or magnetically controlled growing rods (MCGRs).

Aims

To determine the value of scoliosis surgery, it is necessary to evaluate outcomes in domains that matter to patients. Since randomized trials on adolescent idiopathic scoliosis (AIS) are scarce, prospective cohort studies with comparable outcome measures are important. To enhance comparison, a core set of patient-related outcome measures is available. The aim of this study was to evaluate the outcomes of AIS fusion surgery at two-year follow-up using the core outcomes set.

Costoplasty remains useful in the treatment of adolescent idiopathic scoliosis, rib hump and associated chest wall deformities. However traditional costoplasty increases morbidity and blood loss. We examine the feasibility and possible effectiveness of a more conservative costoplasty using an animal model. 4 fresh half Ovine rib cages from separate animals were obtained, stored at +4 °C and warmed to room temperature before testing. Each rib cage was randomly assigned to group 1, 2, 3 or 4. Ribs 2–10 were dissected out for testing. The ribs then underwent stepwise deconstruction according to their group. Beginning at the convexity, removing first the convex cortex, then the cancellous, then the cranial and caudal cortices to leave just the concave cortex. Testing for stiffness was by three-point bending on the concave side of each rib with the rib fixed at the head of the rib and 5 cm from the resected area. The ribs were deformed at a constant rate of 0.5 mm.sec . −. 1 up to a maximum load of 9.99 kg or until fracturing. Then stress was plotted against strain to find the Young's modulus of each group and statistics carried out with an ANOVA test. The ribs in each group were as follows: Group 1= control, group 2= 30 mm long convex side cortical bone removed 10 mm from lateral tubercle, group 3= convex, cortical and cancellous bone removal and group 4= removal of convex, caudal and cranial cortices with cancellous removal. The Young's Modulus of the groups were: 1= 3.38 N-m (+/− 0.84), 2= 2.65 N-m (+/− 1.58), 3= 1.55 N-m (+/− 0.55) and 4= 0.74 N-m (+/− 0.55). Groups 3 and 4 were significantly less stiff than group 1 (p< 0.01.) No ribs in groups 1, 2 and 4 fractured under the maximum load. 5/8 ribs in group 3 fractured before the maximum load was administered. By deconstructing the rib down to only the concave side it becomes significantly more flexible by approximately 4.5 times than the control Ribs. Coupled with its increase in flexibility it still retains its ability to withstand up to 10 kg of load without fracture. It may be possible to perform a costoplasty whilst preserving ventilatory integrity. This may improve rib hump correction, and curve correction due to increased flexibility of the stiff thoracic cage

Background:. Larger breasted women are at higher risk of wearing ill-fitting breast-support garments. Failure to support breasts during everyday activity can lead to physiological conditions including back and breast pain. This study aimed to identify initial and short-term (4 weeks) biomechanical change and patient reported outcome measures (PROMS) in larger breasted women with non-specific back pain (NSBP) when wearing different breast-support garments. Methods & Results:. 20 females (Age: 32.1±9.4 years; Bra sizes: 36DD-32K) with NSBP were recruited using modified red flags screening. Participants were tested initially in their usual bra, followed by the professionally-fitted and Optifit bras, in randomised order. Pre/post assessments comprised an established bra-fit assessment, body chart analysis, frequency of wear and pain, continuous-pain intensity (SF-MPQ-2), back stiffness and discomfort, neck disability and thoracic posture in standing using 3D-movement analysis. 100% of Usual and 90% of professionally-fitted bras failed the bra-fit assessment, compared to 5% with the Optifit. Though worn the least on average, a short-term intervention with the Optifit bra resulted in significant reductions in reported thoracic pain, clinically important reductions in neck disability, back pain frequency, continuous-pain intensity, stiffness and discomfort compared to the other bras. The Optifit and professionally-fitted bras significantly reduced reported lumbosacral pain compare to the usual bra. There was no initial change in thoracic posture with the Optifit bra however, significant improvements in flexion-extension posture were seen post-intervention. Conclusions:. Following a short-term intervention, larger breasted women with NSBP appear to show some clinically important improvements. Provision of correctly fitting breast-support garments may contribute to better clinical management of NSBP in these women

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). Materials and Methods. A total of 54 osteoporotic human cadaver thoracic and lumbar vertebrae were instrumented with pedicle screws (uncemented, solid cemented or fenestrated cemented) and augmented with high-viscosity PMMA cement (0 mL, 1 mL or 3 mL). The insertion torque and bone mineral density were determined. Radiographs and CT scans were undertaken to evaluate cement distribution and cement leakage. Pull-out testing was performed with a material testing machine to measure failure load and stiffness. The paired t-test was used to compare the two screws within each vertebra. Results. Mean failure load was significantly greater for fenestrated cemented screws (+622 N; p ⩽ 0.001) and solid cemented screws (+460 N; p ⩽ 0.001) than for uncemented screws. There was no significant difference between the solid and fenestrated cemented screws (p = 0.5). In the lower thoracic vertebrae, 1 mL cement was enough to significantly increase failure load, while 3 mL led to further significant improvement in the upper thoracic, lower thoracic and lumbar regions. Conclusion. Conventional, solid pedicle screws augmented with high-viscosity cement provided comparable screw stability in pull-out testing to that of sophisticated and more expensive fenestrated screws. In terms of cement volume, we recommend the use of at least 1 mL in the thoracic and 3 mL in the lumbar spine. Cite this article: C. I. Leichtle, A. Lorenz, S. Rothstock, J. Happel, F. Walter, T. Shiozawa, U. G. Leichtle. Pull-out strength of cemented solid versus fenestrated pedicle screws in osteoporotic vertebrae. Bone Joint Res 2016;5:419–426