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.
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
Aims. Fixation of osteoporotic proximal humerus fractures remains challenging even with state-of-the-art locking plates. Despite the demonstrated biomechanical benefit of screw tip augmentation with bone cement, the clinical findings have remained unclear, potentially as the optimal augmentation combinations are unknown. The aim of this study was to systematically evaluate the biomechanical benefits of the augmentation options in a humeral locking plate using finite element analysis (FEA). Methods. A total of 64
Aims. Proximal humeral fractures are the third most common fracture among the elderly. Complications associated with fixation include screw perforation, varus collapse, and avascular necrosis of the humeral head. To address these challenges, various augmentation techniques to increase medial column support have been developed. There are currently no recent studies that definitively establish the superiority of augmented fixation over non-augmented implants in the surgical treatment of proximal humeral fractures. The aim of this systematic review and meta-analysis was to compare the outcomes of patients who underwent locking-plate fixation with
Introduction. The main symptoms in multiple myeloma are the result of skeletal destruction mainly the vertebral column. The current treatments for multiple myeloma include radiotherapy and chemotherapy but unfortunately it is still incurable. However, the symptoms and quality of life of these patients can be improved by
Hip fractures constitute the most debilitating complication of osteoporosis with a steadily increasing incidence in an aging population. Intramedullary nailing of osteoporotic proximal femoral fractures can be challenging because of poor implant anchorage in the femoral head. Recently,
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. Materials and Methods. A total of 60 lumbar vertebrae were divided into six groups:
PLS submitted to instant pull-out and fatigue-resistance testing
(groups A1 and A2, respectively), TPS submitted to instant pull-out
and fatigue-resistance testing (groups B1 and B2, respectively)
and PLS augmented with 2 ml polymethylmethacrylate, submitted to
instant pull-out and fatigue-resistance testing (groups C1 and C2,
respectively). The PPF and normalized PPF (PPFn) for bone mineral density
(BMD) were compared within and between all groups. Results. In all groups, BMD was significantly correlated with PPF (r =
0.83, p < 0.001). The PPFn in A1 was significantly less than
in B1 (p = 0.006) and C1 (p = 0.002). The PPFn of A2 was significantly
less than in B2 (p < 0.001) and C2 (p < 0.001). The PPFn in
A1, B1, and C1 was significantly greater than in A2 (p = 0.002),
B2 (p = 0.027), and C2 (p = 0.003). There were no significant differences
in PPFn between B1 and C1, or between B2 and C2. Conclusion. Pedicle lengthening screws with
We have developed a hollow perforated cannulated screw. One or more of these was implanted percutaneously in 11 patients with an osteolytic metastasis in the femoral neck and multiple metastases elsewhere. They were supplemented by one or two additional standard 6.5 mm cannulated screws in nine patients. Polymethylmethacrylate bone cement was injected through the screw into the neck of the femur using small syringes, as in vertebroplasty. The mean amount of cement injected was 23.2 ml (17 to 30). Radiotherapy was started on the fourth post-operative day and chemotherapy, on average, was resumed a day later. Good structural stability and satisfactory relief from pain were achieved in all the patients. This technique may be useful in the palliation of metastases in the femoral neck.
Pedicle screw pullout or loosening is increased in the osteoporotic spine. Recent studies showed a significant increase of pullout forces especially for PMMA-augmentation. With application of conventional viscosity PMMA the risk of cement extravasation is associated. This risk can be reduced by using radiofrequency-responsive, ultrahigh viscosity bone cement. 11 fresh-frozen lumbar vertebral bodies (VB) from 5 cadavers were collected and freed from soft-tissue and ligaments. By DEXA scan (Siemens QDR 2000) 8 VB were identified as severely osteoporotic (BMD 0.8 g/cm3), 3 VB were above this level. Two screws (6×45 mm, WSI-Expertise Inject, Peter Brehm, Weisendorf, Germany) were placed in the pedicles. Through the right screw 3ml of radiofrequency-responsive bone cement (StabiliT® ER2 Bone Cement, DFine, Germany) were injected via hydraulic cement delivery system (StabiliT® Vertebral Augmentation System, DFine, Germany). As control group, left pedicle screws remained uncemented. After potting the whole VB in technical PMMA (Technovit 4004, Heraeus Kulzer, Germany) axial pullout test was performed by a material testing device (Zwick-Roell, Zmart-Pro, Ulm, Germany).Introduction
Method
Posterior internal fixation systems undergo internal constraints resulting in high load bearing requirement for the pedicular screw/bone interface. Only few studies deal with the impact of the vertebral augmentation on the migration of pedicular screws. In this study, the impact of the pedicular screw augmentation has been investigated under physiological load for osteoporotic vertebras. The data have been proceeded to reduce the influence of vertebral geometry, which generally leads to results devoid of statistical meaning In 8 osteoporotic vertebrae, two screws have been inserted in each vertebra: a non-augmented on one side and an augmented one on the contralateral side. Compression tests have been performed (two consecutive 50 cycles load steps -100N and 200N-) to observe the displacement of the screw’s head. Two different setups have been employed: a free connection (FC) and a blocked connection (BC). A load step is successful if the migration between two consecutive cycles tends to zero. To reduce the impact of the vertebras’ geometry, the screws’ migration have been compared contra-laterally using the migration ratio (MR). MR of vertebrae is defined as the division of the augmented screw’s migration with the non-augmented screw’s migration. All the augmented screws survived both test setups whereas the non-augmented failed the 200N FC load step. Significant differences are observable only for the highest successful load steps for each test setup: T-tests (P=0.039 and P=0.007 respectively) put into evidence that the results are statistically smaller than one. It is observable as well, that the BC induced fewer loads into the vertebrae: even non-augmented screw can withstand 200N load step. As expected, augmentation of pedicular perforated screws increases their stability in osteoporotic vertebras undergoing large physiological load. This could be explained by the fact that the presence of PMMA increases the load transfer interface improving screw/PMMA complex bearing capacity. Smaller loads induce only small differences that are not significant.
Over 85% of patients with multiple myeloma (MM) have bone disease, mostly affecting thoraco-lumbar vertebrae. Vertebral fractures can lead to pain and large spinal deformities requiring application of vertebroplasty (PVP). PVP could be enhanced by use of Coblation technique to remove lesions from compromised MM vertebrae prior to cement injection (C-PVP). 28 cadaveric MM vertebrae, were initially fractured (IF) up to 75% of its original height on a testing machine, with rate of 1mm/min. Loading point was located at 25% of AP-diameter, from anterior. Two augmentation procedure groups were investigated: PVP and C-PVP. All vertebrae were augmented with 15% of PMMA cement. At the end of each injection the perceived injection force (PIF) was graded on a 5-point scale (1 very easy to 5 almost impossible). Augmented MM vertebrae were re-fractured, following the same protocol as for IF. Failure load (FL) was defined as 0.1% offset evaluated from load displacement curves.INTRODUCTION
METHODS
The purpose of this study was to determine the effect of cement mixing time on fixation augmentation in both healthy and simulated osteoporotic canine bone. In a canine diaphyseal model, screw insertion into liquid cement achieves greater bending stiffness and resists a greater load to failure than cement inserted as a paste. Bone cement in its liquid state may provide increased structural support in the setting of an osteoporotic fracture, possibly due to increased interdigitation of the cement with the screw threads and bone. An inconsistency exists among orthopaedic surgeons with regards to the appropriate mixing time for bone cement to achieve optimal results. The purpose of this study was to determine the effect of cement mixing time on fixation augmentation in both healthy and simulated osteoporotic canine bone. In a canine diaphyseal fracture model, screw insertion into liquid cement achieves greater bending stiffness and resists a greater load to failure than insertion into cement with the consistency of a paste. Bone cement in its liquid state may provide increased structural support in the setting of an osteoporotic fracture, possibly due to increased interdigitation of the cement with the screw threads and bone. Baseline stiffness for fourteen pairs of cadaveric canine femora was determined. A transverse diaphyseal osteotomy was created and fixed using an eight-hole DC plate and 3.5 mm screws. A 1cm gap was created at the osteotomy site simulating loss of bone. In the left femora, cement was mixed for one minute (liquid) prior to injection into pre-drilled holes; in the right femora, cement was mixed for five minutes prior to injection (thick paste). In each mixing time group, seven specimens were treated with a plate and properly sized pre-drilled and tapped holes (2.5mm), and seven received over-drilled holes (3.2 mm) to simulate osteoporotic bone. Four-point bending stiffness was determined for each plated construct, and normalized to baseline stiffness. Specimens were then loaded to failure. Within the properly sized holes, there were no statistically significant differences (SSD) in bending stiffness with or without a gap. The liquid cement had a force to failure 77% greater than that of cement as a paste (p<
0.05). Within the over-sized holes, there was no SSD between liquid and paste without a gap. With a gap, liquid cement demonstrated an increased bending stiffness of 24 % (p<
0.05) and force to failure was 92% higher (p<
0.05).
Within the over-sized holes simulating osteoporotic bone, there was no difference between liquid and paste without a gap. With a gap, liquid cement demonstrated an increased bending stiffness of 24% (p<
0.05) and force to failure was 92% higher (p<
0.05). Bone cement in its liquid state may provide increased structural support in the setting of an osteoporotic fracture, possibly due to increased interdigitation of the cement with the screw threads and bone.
The augmentation of fixation with bone cement
is increasingly being used in the treatment of severe osteoporotic fractures.
We investigated the influence of bone quality on the mechanics of
augmentation of plate fixation in a distal femoral fracture model
(AO 33 A3 type). Eight osteoporotic and eight non-osteoporotic femoral
models were randomly assigned to either an augmented or a non-augmented
group. Fixation was performed using a locking compression plate.
In the augmented group additionally 1 ml of bone cement was injected
into the screw hole before insertion of the screw. Biomechanical
testing was performed in axial sinusoidal loading. Augmentation significantly
reduced the cut-out distance in the osteoporotic models by about
67% (non-augmented mean 0.30 mm ( Cite this article:
Intercalary allografts following resection of a primary diaphyseal
tumour have high rates of complications and failures. At our institution
intercalary allografts are augmented with intramedullary cement
and fixed using compression plating. Our aim was to evaluate their
long-term outcomes. A total of 46 patients underwent reconstruction with an intercalary
allograft between 1989 and 2014. The patients had a mean age of
32.8 years (14 to 77). The most common diagnoses were osteosarcoma
(n = 16) and chondrosarcoma (n = 9). The location of the tumours
was in the femur in 21, the tibia in 16 and the humerus in nine. Function
was assessed using the Musculoskeletal Tumor Society (MSTS) scoring
system and the Toronto Extremity Salvage Score (TESS). The survival
of the graft and the overall survival were assessed using the Kaplan-Meier method.Aims
Patients and Methods
Aims. The purpose of the study was to investigate whether closed intramedullary
(IM) nailing with percutaneous
Introduction and Objective. Trochanteric fractures are associated with increasing incidence and represent serious adverse effect of osteoporosis. Their cephalomedullary nailing in poor bone stock can be challenging and associated with insufficient implant fixation in the femoral head. Despite ongoing implant improvements, the rate of mechanical complications in the treatment of unstable trochanteric fractures is high. Recently, two novel concepts for nailing with use of a helical blade – with or without bone
Introduction. Spine is a common site for haematological malignancies. Multiple myeloma affects the spine in 70% of cases. New guidelines were published in 2015 to help manage spinal haematological malignancies. Despite neural compression or spinal instability, instrumentation of the spine should be avoided. Surgery carries significant risks of wound complications and more importantly delaying the definitive chemotherapy and radiotherapy.
Intramedullary nails (IMNs) are the current gold standard for treatment of long bone diaphyseal and selected metaphyseal fractures. Their design has undergone many revisions to improve fixation techniques, conform to the bone shape with appropriate anatomic fit, reduce operative time and radiation exposure, and extend the indication of the same implant for treatment of different fracture types with minimal soft tissue irritation. The IMNs are made or either titanium alloy or stainless steel and work as load-sharing internal splints along the long bone, usually accommodating locking elements – screws and blades, often featuring angular stability and offering different configurations for multiplanar fixation – to secure secondary fracture healing with callus formation in a relative-stability environment. Bone