Several surgical options have been utilised to treat patients with back dominant lumbar disc disease. The purpose of our study was to compare the outcomes in patients who underwent lumbar fusion with an expandable interbody device (B-TWIN) using different surgical techniques (PLIF, TLIF or posterolateral screws alone). Observational study, retrospective analysis of prospectively collected data. Patients underwent a single level lumbar fusion. Group A: PLIF with B-Twin cage; Group B: TLIF with B-Twin cage and unilateral pedicle screw fixation and Group C: bilateral posterolateral screw fixation alone. Functional outcomes were assessed using: SF-36, Oswestry Disability Index (ODI), Distress and Risk Assessment Method scores (DRAM) and the visual analogue pain scores (VAS). There were 32 patients, 24 female and 8 male. Average age was 45 (range 33-63). Average follow up was12 months (range 2-36). Level of spinal fusion was 2 L3/4, 11 L4/5 and 13 L5/S1. Mean hospital stay was 5.8 days. VAS improved in all 3 groups A 5.83 – 5; B 8 – 4.83; C 5.71 – 2.3. ODI improved in all 3 groups A 0.5 – 0.35; B 0.51 – 0.44, C 0.42 – 0.16. There was no statistical difference on comparison of the three groups. There were no operative complications. One patient broke her interdody device during a all in the first post-operative week requiring a subsequent procedure. Lumbar interbody fusions can safely be performed using an expandable interbody device. Good functional outcomes can be achieved in the majority of well selected patients

A biomechanical study assessing compressive failure load, strength and stiffness with three different interbody device shapes was performed in human cadaveric vertebrae. The custom-made interbody devices had similar cross-sectional areas and specimens were tested with 20% or 40% coverage of indentor to endplate area. Axial compressive load was applied at 0.2mm/s to a depth equivalent to 20% of the vertebral height. The clover-leaf shaped device resulted in significantly higher failure load, strength and stiffness over the elliptical and the kidney shaped devices for both areas of coverage. The clover-leaf shaped devices extended over stronger periphery regions of the endplates and resulted in stronger interface properties. To determine if two novel interbody cage shapes, the kidney and the clover-leaf, are biomechanically superior to a standard elliptical shape of similar cross sectional area. Uniaxial compression tests with unrestricted rotations were carried out on the superior endplates of forty-eight thoracolumbar (T9-L2) vertebrae with one of three shaped indentors covering 20% or 40% of the endplate area. Compressive load was applied using a servohydraulic testing machine at 0.2mm/s, to depth equivalent to 20% of the vertebral height. Failure load, strength and stiffness were compared. The clover-leaf shaped indentors resulted in higher failure load (53% average increase), higher strength (67% average increase) and higher construct stiffness (43% average increase), and these results were significant (p< 0.05). Larger indentor coverage area of 40% also resulted in significantly higher failure loads over 20% coverage (75% average increase). Current elliptical interbody devices are placed over the central region of the endplate, which is also the weakest. A clover-leaf shaped device extended over the stronger peripheral regions of the endplates and resulted in improved bone-implant interface properties. This implant if implemented in vivo could potentially reduce implant subsidence and lead to better long-term outcomes in osteoporotic patients. The novel clover-leaf shaped indentor displayed superior bone-implant interface properties. Larger interbody devices should be used when possible to improve interface properties. Implant subsidence in osteoporotic patients could be significantly reduced with a clover-leaf shaped device, leading to better long-term outcomes. Funding: Funding from the Canadian Institutes for Health Research

Aim. To assess the safety of Zero Profile Interbody fusion (Zero P) device in Anterior Cervical Decompression and fusion (ACDF) for degenerative cervical stenosis. Method. 89 consecutive patients treated with Zero P interbody device from September 2009 to September 2012 were included in this retrospective study. Inclusion criterion: degenerative cervical stenosis with myelopathy, persistent radiculopathy after at least 3 months of failed conservative management. Exclusion criterion: Paediatric population; patients with infection, metastatic disease and trauma. There were 39 females, 50 males with mean age of 55 (ranging from 24 to 84 years). 56 (64%) had surgery at 1 level, 31 (35%) at 2 levels, 1 (1%) at 3 levels. Total number of levels operated were 121. Common levels operated were C56 (62%) and C67 (47%). Majority were operated due to radicular symptoms, 56 (64%) had radicular symptoms, 28(31%) had myelopathy and 5 (5%) Myeloradiculopathy. Results. All had a minimum of 6 months follow up (maximum 2 years). No patient had cage subsidence or extrusion. 1 had superficial infection which settled with antibiotics, 10 (11%) had dysphagia which settled in 6 to12 weeks. Conclusions. Our study demonstrates that ACDF with Zero P can be considered a safe option in management of patients with cervical degenerative stenosis. We would will also recommend a prospective randomised study as a follow on to this retrospective study. Preoperative kyphosis or lordosis did not change the outcome or make the surgical technique any more difficult, hence this implant can also be used in these circumstances. Conflicts of interest: No conflicts of interest. Sources of funding: No funding obtained

Aims: In this study, the subsidence of different interbody fusion devices was investigated. Hereby, the influence of different designs as well as of the preparation technique was evaluated. Methods: 3 common cervical interbody fusion devices (BAK, Novus and WING) underwent axial compression testing with 4000 cycles in a bovine spine model. The vertebral bodies were prepared in 3 different ways, taking away 0, 1 and 2 mm of the end-plate. So each fusion device was tested in each preparation group in 5 vertebrae. Every 1000 cycles, the subsidance was measured. Results: Taking away 1 and 2 mm of the endplate resulted in a strong increase of the subsidance compared to the situation with intact end-plate. In addition, the design of the interbody device had an influence onto subsidance: In case of intact endplates, the cages with rectangular supporting areas resisted better to axial compression than the cylindrical implant. When the cortical bone of the endplate was taken away, all three implants showed similar subsidance curves. Conclusions: Implants with plane supports seem to provide better stability against subsidance than cylindrical implants. During preparation, the cortical structure of the endplate should be taken care of, especially in the zone, where the implant has its bearing areas

Purpose: At present there is no reported, valid and reproducible model of degenerative spondylolisthesis for biomechanical testing of spinal implants. The purpose of this study was to create a single functional spinal unit (FSU) model that could demonstrate anterolisthesis consistent with low grade degenerative spondylolisthesis under physiologic shear loads. Method: Eight fresh-frozen human cadaveric, lumbar FSU’s were potted and secured in a custom jig for pure shear testing. The cranial segment was loaded from – 50N (posterior) to 250N (anterior) over three cycles for each of five test conditions with a 300N preload. Test conditions addressed known restraints to shear translation and were performed in the same order for all specimens, and included: intact, facet capsulectomy and bilateral two mm facet gap, bilateral four mm facet gap, nucleotomy, and annular release. Three-dimensional motion was recorded using an optoelectronic camera system. Results: Mean anterior translation at 250N for the five test conditions was 0.7 mm (95% confidence interval 0.4 to 0.9), 1.2 mm (0.9 to 1.6), 1.5 mm (1.1 to 2.0), 1.9 mm (1.4 to 2.4) and 3.1 mm (2.2 to 4.0). The mean maximum anterior translation was significantly different for each test condition with two exceptions. The four mm facet gap did not result in a significantly different maximum anterior translation compared to the two mm facet gap or the nucleotomy. There were no differences in off-axis motion (lateral or superior-inferior translation, flexion-extension, axial rotation, lateral bending) between the five test conditions. Conclusion: Anterior translation consistent with low grade degenerative spondylolisthesis was repeatedly demonstrated under physiologic shear loads using this model. All sequential destabilizations preserved anatomy critical for the application of pedicle screw constructs, interbody devices and interspinous spacers. As such, this model is appropriate for biomechanical testing of implants currently used in the treatment of low grade degenerative spondylolisthesis

Aims

Symptomatic spinal stenosis is a very common problem, and decompression surgery has been shown to be superior to nonoperative treatment in selected patient groups. However, performing an instrumented fusion in addition to decompression may avoid revision and improve outcomes. The aim of the SpInOuT feasibility study was to establish whether a definitive randomized controlled trial (RCT) that accounted for the spectrum of pathology contributing to spinal stenosis, including pelvic incidence-lumbar lordosis (PI-LL) mismatch and mobile spondylolisthesis, could be conducted.

Summary. Between January 2003 and October 2004,12 patients with non tuberculous spondylodiscitis were treated by radical debridment, reconstruction and stabilization. In our group 9 patients underwent posterior procedure and 3 underwent combined anterior and posterior procedures. 3 of these had fungal and 9 pyogenic infections. All the patients had appropriate antimicrobial therapy All patients had excellent to good functional results and no evidence of infection at 2 year follow-up. Introduction. Surgical treatment of nontuberculous spon-dylodiscitis of lumbar spine is challenging due to extensive bone involvement and comorbid conditions. This study is to assess the role of radical debridment followed by reconstruction and stabilization of affected segments in reducing morbidity and mortality in these patients. Methods. 12 consecutive patients were operated between January 2003 and October 2004. Patients presented with severe back pain, root compression or paraparesis.7 cases had prior spinal surgery. Blood and radiological investigations were diagnostic. All these patients underwent radical debridement, reconstruction and stabilization of affected segments done with titanium pedicular screws, titanium mesh cages, cancellous iliac crest graft. Only posterior procedure in 9 cases, combined anterior posterior in 3 cases followed by adequate and appropriate antimicrobials therapy. Follow-up ranged from 25 to 35 months. Results: 3 cases were fungal and 9 were pyogenic infection. Oswestry low back questionnaire, kirkaldy-willis criteria showed dramatic improvement of function. All the blood parameters were normalized in 3 months.1 case had dural tear which was repaired immediately,3 cases had wound exploration and lavage. No major complications were encountered. All cases showed Radiological fusion at last follow-up. Discussion: Radical debridement of necrotic material, decompression of neurological structures, create a good vascularised environment. Restoring stability compromised by either infection or prior surgery helps in healing process and reduces morbidity of patients. Significance: Reconstruction using pedicular system and interbody devices can safely be used in presence of non tuberculous infection provided debridement has been radical

Interbody fusion aims to treat painful disc disease by demobilising the spinal segment through the use of an interbody fusion device (IFD). Diminished contact area at the endplate interface raises the risk of device subsidence, particularly in osteoporosis patients. The aim of the study was to ascertain whether vertebral body (VB) cement augmentation would reduce IFD subsidence following dynamic loading. Twenty-four human two-vertebra motion segments (T6–T11) were implanted with an IFD and distributed into three groups; a control with no cement augmentation; a second with PMMA augmentation; and a third group with calcium phosphate (CP) cement augmentation. Dynamic cyclic compression was applied at 1Hz for 24 hours in a specimen specific manner. Subsidence magnitude was calculated from pre and post-test micro-CT scans. The inferior VB analysis showed significantly increased subsidence in the control group (5.0±3.7mm) over both PMMA (1.6±1.5mm, p=.034) and CP (1.0±1.1mm, p=.010) cohorts. Subsidence in the superior VB to the index level showed no significant differences (control 1.6±3.0mm, PMMA 2.1±1.5mm, CP 2.2±1.2mm, p=.811). In the control group, the majority of subsidence occurred in the lower VB with the upper VB displaying little or no subsidence, which reflects the weaker nature of the superior endplate. Subsidence was significantly reduced in the lower VB when both levels were reinforced regardless of cement type. Both PMMA and CP cement augmentation significantly affected IFD subsidence by increasing VB strength within the motion segment, indicating that this may be a useful method for widening indications for surgical interventions in osteoporotic patients

Aims

High-grade dysplastic spondylolisthesis is a disabling disorder for which many different operative techniques have been described. The aim of this study is to evaluate Scoliosis Research Society 22-item (SRS-22r) scores, global balance, and regional spino-pelvic alignment from two to 25 years after surgery for high-grade dysplastic spondylolisthesis using an all-posterior partial reduction, transfixation technique.

Background. Synthetic interbody spinal fusion devices are used to restore and maintain disc height and ensure proper vertebral alignment. These devices are often filled with autograft bone to facilitate bone bridging through the device while providing mechanical stability. Nonporous polyetheretherketone (PEEK) devices are widely used clinically for such procedures. 1. Trabecular Metal devices are an alternative, fabricated from porous tantalum. It was hypothesized that the porous Trabecular Metal device would better maintain autograft viability through the center of the device, the ‘graft hole’ (GH). Methods. Twenty-five goats underwent anterior cervical discectomy and fusion using a Trabecular Metal or PEEK device for 6, 12 or 26 weeks. The GH of each device was filled with autograft bone morsels harvested from the animal at implantation. Fluorochrome labeling oxytetracycline was administered to the animals and used to determine bone viability in the device regions. Following necropsy, the vertebral segments were embedded in poly(methyl methacrylate) sectioned and analyzed using fluorescence and backscatter electron (BSE) imaging. The percent of bone tissue present within the GH was measured as a volume percent using BSE images (Fig. 1). Results. Bone percent analysis demonstrated that there was no significant difference (p<0.05) in volume of bone tissue within the GH of the two devices at 6 and 26 weeks (Fig. 2). At 12 weeks the animals implanted with the Trabecular Metal device had significantly greater volumes of bone within the GH region. Viable bone was observed in the host bone region and periprosthetic to the implant of all PEEK (n=12) and Trabecular Metal (n=12) animals within the study, determined by the presence of fluorescent labels (Fig. 3). Viable bone was also observed in the GH region of all animals with a Trabecular Metal device. However, only 5 of 12 PEEK animals showed bone viability within the GH (2 at 12 weeks and 3 at 26 weeks). A Fisher's exact comparison of the number of animals with viable bone in the GH showed a significant difference between the two devices, p<0.05. Conclusion. Autograft viability was better maintained within the GH for the porous Trabecular Metal device compared to the PEEK device. Although the amount of bone tissue within the GH of the PEEK devices was determined to have no significant difference compared to the Trabecular Metal devices at 6 and 26 weeks, the GH bone tissue was not viable in a number of the PEEK animals at each time point. The interconnected network and high volume porosity of the Trabecular Metal device may have allowed for fluid exchange, angiogenesis and increased blood supply to the autograft morsels. The viability of the autograft morsels also played an important role in the success of bone bridging through the GH between the vertebral endplates. In this animal model it was demonstrated that the autograft bone placed within the PEEK spinal fusion device did not always remain viable after implantation, but sometimes only filled the GH and did not necessarily facilitate fusion between the vertebrae as intended

Introduction Anterior column reconstruction and fusion remains the gold standard of treatment for a number of spinal pathologies. One of the challenges of interbody fusions cages is the footprint of the cage reducing the surface area of endplate available for fusion. Biodegradable polymer implants will over time present a greater area for fusion and may help to reduce problems such as stress shielding, particulate debris and retained foreign body response. Resorbable cages have been have been prepared from a number of different materials, including inorganic composites (eg hydroxyapatite / tricalcium phosphate) and polymers (Poly L-lactide-co-D,L-lactide (PDLLA)). However all of the current options for interbody fusion have reported deficiencies or complications. The synthesis, mechanical properties, and degradation behaviour of two novel biopolymers are presented and the applicability for use as materials in interbody fusion devices is discussed. Methods Methacrylated adipic anhydride (MAA) and methacrylated sebacic anhydride (MSA) pre-polymers were synthesized by melt condensation. Conversion of the acid to the anhydride was confirmed using 1H nuclear magnetic resonance (NMR) (Bruker, Alexandria, NSW) and FT- Infrared spectroscopy (Nicolet, Waltham MA). These pre-polymers were subsequently co-polymerized with methyl methacrylate (MMA) and 0.25 wt% benzoyl peroxide at 65oC for 16hrs and post-cured at 120oC under vacuum for 2 hrs to form biodegradable networks. The co-polymerization behaviour was monitored by FT-Raman spectroscopy. The compressive mechanical properties of the polymer were determined using an Instron 5567 (Bayswater Vic.). The polymer networks were degraded in phosphate buffered saline (PBS) with various amounts of MAA and MSA. Results The formation of the pre-polymer was confirmed with the observation of NMR peaks at 5.8 and 6.2 ppm and FT-IR peaks at 1637cm-1. Copolymerization was followed with consecutive FT-IR acquisitions with 100% conversion achieved between 10 and 30 hrs depending on the ratio of MMA to MSA or MAA. Increasing the fraction of methacrylated anhydride slowed the reaction rate. The compressive strength of the MAA and MSA based copolymers was measured as a function of anhydride concentration. Compressive strength for MMA increased (90±9 to 140±10 Mpa) in an approximately linear manner for MAA concentrations from 10 to 40 wt.% but decreased markedly for MAA concentration of 45% (62±14 Mpa). The compressive strength of MSA decreased exponentially for concentrations ranging from 10 to 45 wt.% (140±18 to 39±1 Mpa). Discussion The use of poly-L-lactic acid in lumbar interbody cages has been shown to be mechanically feasible with the mechanical strength of the cage material reported to be 93 Mpa (. 1. ). The material described here has controlled mechanical properties in the required range as well as a degradation behaviour that lends itself better to spinal applications than current materials

Objectives

We performed a systematic review of the literature to determine the safety and efficacy of bone morphogenetic protein (BMP) compared with bone graft when used specifically for revision spinal fusion surgery secondary to pseudarthrosis.