Long term, secondary implant fixation of Total Disc Replacements (TDR) can be enhanced by hydroxyapatite or similar osseo-conductive coatings. These coatings are routinely applied to metal substrates. The objective of this in vivo study was to investigate the early stability and subsequent bone response adjacent to an all polymer TDR implant over a period of six months in an animal model.

Six skeletally mature male baboons (Papio annubis) were followed for a period of 6 months. Using a transperitoneal exposure, a custom-sized Cadisc L device was implanted into the disc space one level above the lumbo-sacral junction in all subjects. Radiographs of the lumbar spine were acquired prior to surgery, and post-operatively at intervals up to 6 months to assess implant stability. Flourochrome markers (which contain molecules that bind to mineralization fronts) were injected at specified intervals in order to investigate bone remodeling with time.

Animals were humanely euthanized six months after index surgery. Test and control specimens were retrieved, fixed and subjected to histological processing to assess the bone-implant-bone interface. Fluorescence microscopy and confocal scanning laser microscopy were utilized with BioQuant image analysis to determine the bone mineral apposition rates and gross morphology.

Radiographic evaluation revealed no loss of disc height at the operative level or adjacent levels. No evidence of subsidence or significant migration of the implant up to 6 months. Heterotopic ossification was observed to varying degrees at the operated level.

Histology revealed the implant primary fixation features embedded within the adjacent vertebral endplates. Flourochrome distribution revealed active bone remodeling occurring adjacent to the polymeric end-plate with no evidence of adverse biological responses. Mineral apposition rates of between 0.7 and 1.7 microns / day are in keeping with literature values for hydroxyapatite coated implants in cancellous sites of various species.

Radiographic assessment demonstrates that the Cadisc L implant remains stable in vivo with no evidence of subsidence or significant migration. Histological analysis suggests the primary fixation features are engaged, and in close apposition with the adjacent vertebral bone. Flourochrome markers provide evidence of a positive bone remodelling response in the presence of the implant.

Introduction: Dural tears are one of the most frequent type of complication in posterior spinal fusion with little known about their predictors.

Method: Prospective consecutive study with an evidence level 2++ of 42 patients in the international spine registry Spine Tango, who had been treated between 05/2005 and 8/2008 with posterior spinal fusion after opening of the spinal canal. Median age was 62.7 yrs (min 12.5, max 90.5 yrs) with a female to male ratio of 2:1. In 42 of 1575 cases a dural tear occurred being the most frequent type of complication in our study sample. Multiple linear regression was performed on potential predictor-variables of the occurrence of dural tears.

Results: Hospital (p=0.02) and number of segments of fusion (p=0.018) were found to be predictors of the occurrence of dural tears in posterior spinal fusion. Number of fusions per hospital (min 25, max 526) and academic status of hospital had no influence on the rate of dural tears. Fusions of four and more segments showed an increase of the rate of dural tears by three compared to fusions of less than four segments.

Conclusion: Predictors of dural tears in posterior spinal fusion are hospital, independent of number of spinal surgeries and academic status of hospital, and number of segments of fusion. In fusions of four and more segments a threefold higher risk of dural tears in comparison to fusions of less than four segments should be taken into consideration.

Introduction: Posterior lumbar fusion, in many variations, is one of the frequently performed procedures in spinal surgery. High percentages of good and excellent results are indicated by physicians. On the other hand isolated patient-based outcomes are reported. However, little is known about correlation of these two assessment types. We aimed at their comparison.

Methods: The analysis included 567 patients from the international registry ‘Spine Tango’. 453 patients with degenerative disease and posterior lumbar fusion had preop and postop VAS separately indicating back- and leg-pain, surgery and follow up data. Mean age was 57y; female/male ratio was 52% to 48%. Remaining 114 patients with the same diagnoses and treatment had additional preop and postop Oswestry disability indices (ODI). Mean age was 61y; female/male ratio was 55% to 45%.

Physician administered McNab criteria “excellent, good, fair and poor” were compared to ODI, VAS back- and leg pain and to the patients answer describing the outcome of the operation with the following options: helped a lot, helped, helped only little, didn’t help and made things worse. Then the concept of minimum clinically important difference (MCID) was applied

Results: In the “excellent” group ODI-improvement was detected for all patients, the proposed MCID was reached in 90% for ODI. According to this model 85.2% of patients reached MCID for VAS leg pain and 54.1% for VAS back pain. All patient said that the treatment helped or helped a lot

In the “good” group 86% (MCID: 51.7%) of patients improved regarding ODI, 81% (MCID: 65,7%) regarding back and 93% (MCID: 89.4%) regarding leg pain. 99% of patients said that the treatment helped a lot, helped or helped only little.

65% (MCID: 40%) of patients in the “fair” group had improved ODIs. Even in this group 88% of patients perceived the treatment as helping a lot, helping or helping only little.

Moreover in the “poor” group had 60% (MCID: 40%) of patients improved ODIs, 55% (MCID: 40%) alleviated back and 36% (MCID: 30%) reduced leg pain. But only 30% of patient stated that the treatment helped or helped only little.

Spearman correlation coefficients for ODI, VAS back, VAS leg and patient’s verbal statement on overall outcome were 0.42, 0.18, 0.27 and 0.53.

Discussion: ‘Spine Tango’ registry, to date containing more than 13.000 documented surgeries and three times more outcome datasets, provides excellent opportunities for comparison of outcomes. The analysis of patient and physician-based outcomes showed good correlation with the highest correlation coefficient for patient’s verbal statement. With this study we can state that there is strong evidence that physicians evaluation of outcome is very good corresponding with the patients’ perception of success or failure of the analyzed procedure.

Purpose: SWISSspine is a national health technology assessment (HTA) registry for ballon kyphoplasty (BKP) and total disc arthroplasty (TDA). It was initiated to evaluate the safety, efficiency and cost-effectiveness of these products. It is the first mandatory orthopaedic HTA registry of its kind in Switzerland. The aim is to generate evidence for a decision about reimbursement by the Swiss basic health insurance.

Methods: During the time between March 2005 until June 2008, 331 interventions with 391 treated levels in 320 patients have been documented. Data was collected in a prospective, observational multicenter mode. The preliminary timeframe for the registry is three years. Data collection is performed preoperative, at 6 weeks, 3 months, 6 months and 1 year followup as well as annually thereafter. Surgery and followup case report forms are administered by spinal surgeons. Comorbidity questionnaires, NASS and EQ-5D forms are completed by patients.

Results: Significant and clinically relevant reduction of back pain, improvement of quality of life and reduction of pain killer consumption was seen in the 1 year followup. Improvement of preoperative segmental kyhposis was achieved in the majority of cases. There were three symptomatic cement extrusions with radiculopathy documented.

Conclusion: BKP is a safe and effective treatment concerning pain reduction, quality of life improvement and pain killer consumption. The SWISSspine registry proved to be an excellent tool for evaluation of this new technology and its results lead to a permanent coverage of BKP by the basic health insurance.

Introduction: To date, herniated nucleus pulposus (NP) with radiculopathy and central or lateral recess stenosis are considered as contraindications for lumbar disc arthroplasty. In the present study we used data from a unique mandatory spine register, SWISSspine to investigate associations between preoperative status of NP herniated/non herniated with presence/absence of sciatica and clinical outcome

Methods: Between 3/2005 and 8/2008, 358 mono-segmental lumbar total disc arthroplasties were documented in a prospective observational multicenter mode. The data collection included peri-operative data and clinical outcomes based on NASS, EuroQol and VAS. The patients were divided into 4 groups: group I-128 patients with herniated NP with sciatica, group II-48 patients with herniated NP without sciatica, group III-74 patients without herniated NP but with sciatica and group IV-108 patients without herniated NP and no sciatica (classic indication). The groups were pair wise compared regarding 1-year postoperative VAS, EuroQol and NASS scores using ANOVA-test with Boferroni-Holm adjustment (α=0.05)

Results: The 4 groups had similar demographic characteristics. Statistical analyses showed no significant outcome differences between the classic and the other indications. For example a outcomes for group IV: NASS back pain pre-post: 72.0/31.7 EQ-5D pre-post: 0.32/0.69.

Discussion and Conclusion: Our analysis revealed no differences between patients with herniated NP combined with neural compression and patients with stenosis of recesses regarding pain alleviation and QoL improvement. The findings suggest that these diagnoses may not have to be considered as absolute contraindications for TDR anymore. The results of this multicenter observational study however, need to be verified in a controlled or experimental study design.

“Delta fixation” was developed to treat low-grade L5 isthmic spondylolisthesis. It involves placement of pedicle screws into L5 and from S1 through the L5/S1 disc into L5 (Fig.1). A biomechanical comparison to standard Posterior Lumbar Interbody Fusion (PLIF) with two anterior cages and pedicle screws in L5 and S1 was made. Eight fresh frozen human specimens were instrumented with both fixations and tested. Delta fixation was significantly more stable in resisting rotation. It requires less manipulation of the nerve roots and spares the cost of the fusion cages.

Our objective is to compare the stability of Delta versus PLIF fixation in the treatment of low grade isthmic spondylolisthesis

Delta fixation provides superior initial stability, and therefore is an acceptable alternative to PLIF for the treatment of low grade isthmic spondylolisthesis of L5-S1.

Symptomatic low-grade isthmic spondylolisthesis of L5 is often managed with PLIF. This procedure requires extensive manipulation of the cauda equine, posterior resection of the disc and the placement of two inter-body cages as spacers in addition to pedicle screws in L5 and S1.

Delta Fixation has been developed to provide stable fixation with less nerve root manipulation and without the use of inter-body cages. It is therefore a safer alternative method of fixation that spares the additional cost of the fusion cages.

When comparing Delta fixation to PLIF fixation the only statistically significant difference was found in axial rotation. Delta fixation had 2.05 degrees less ROM and 0.90 degrees less NZ compared to PLIF fixation with P values of 0.0052 and 0.0104 respectively. This demonstrates that the delta fixation is more stable than PLIF fixation.

Eight fresh frozen human spines were used. Matched pairs were created and block randomization used to create two groups: PLIF fixation and Delta fixation groups. The specimens were instrumented with a grade II spondylolisthesis of L5-S1, tested, and then re-instrumented with the alternative fixation and tested again. Vertical displacement, axial rotation, flexion– extension and side bending were tested using an MTS machine.

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Hyaline cartilage and immature nucleus pulposus possess similar macromolecules in their extracellular matrix, and there is no unique molecular marker to distinguish the two tissues. We show that in normal disc (fifteen to twenty-five years old), the GAG to hydroxyproline ratio (proteoglycan to collagen ratio) within the nucleus pulposus is approximately 28:1. However, the GAG to hydroxyproline ratio within hyaline cartilage of the same group is 2.5:1. This information is important in identifying stem cell conversion to a nucleus pulposus cell phenotype rather than a chondrocyte phenotype for tissue engineering of intervertebral disc.

Tissue engineering of intervertebral discs (IVDs) using mesenchymal stem cells (MSCs) induced to differentiate into a disc-cell phenotype has been considered as an alternative treatment for disc degeneration. Since there is no unique marker for disc tissue, and because cartilage and immature nucleus pulposus (NP) possess similar macromolecules in their extracellular matrix, it is currently difficult to recognize MSC conversion to a disc cell. In this study, we compare the proteoglycan to collagen ratio in the NP of normal disc to that of the hyaline cartilage of the endplate within the same group of individuals.

To distinguish between a normal NP and hyaline cartilage phenotype for tissue engineering of IVDs.

Human lumbar spine specimens were harvested from fresh cadavers, aged twelve week to seventy-nine year. Discs and endplates were examined for total collagen using the hydroxyproline assay and glycosaminoglycan (GAG) content using a standard assay.

In a mature disc with no degeneration (fifteen to twentyfive years), the GAG to hydroxyproline ratio within the NP is approximately 28:1. However, the ratio within the hyaline cartilage endplate of the same group is 2.5:1.

A high proteoglycan to collagen ratio can be used to distinguish NP cells from chondrocytes. The lower NP collagen content is probably responsible for its gelatinous nature rather than the firm texture of hyaline cartilage, and this is essential for normal disc function. This information is crucial in identifying a NP-like phenotype when MSCs are induced to differentiate into a disc cell as opposed to a chondrocyte, for tissue engineering of IVDs.

Easier patient positioning and less extensive soft tissue dissection have spurred a trend for anterior instrumentation and fusion for C-spine fracture/ dislocations. We present group of forty-six patients treated over an eighteen month period with an anterior approach. There were no permanent approach related complications, infections, hardware failures or graft displacements. One patient had worsened post-operative neurological findings. One patient required additional posterior stabilization for a missed injury. Two patients were not reducible from the front and required posterior reduction and stabilization followed by anterior instrumentation and fusion. All grafts healed within four months of the operation.

The purpose of this study was to assess the efficacy of anterior instrumentation and fusion for Cervical Spine fracture/ dislocations

Over an eighteen month period, forty-six out of fifty-two patients with C-spine injuries requiring surgical treatment were followed prospectively. All patients underwent anterior approaches to stabilize and fuse the unstable segments using tricortical bone grafting and application of an anterior plate (CSLP, Synthes). Thirty-eight patients had single level injuries treated with discectomy and fusion. Two patients had two level discecomies. Six patients underwent corpectomy and fusions for fractures of the vertebral bodies

There were no approach related complications such as recurrent laryngeal nerve injuries, oesophageal perforations, vascular injuries or strokes. One patient deteriorated neurologically. All other patients either improved neurologically or remained with their original findings. Two patients required oral antibiotics for superficial infections at the donor site. There were no spine infections, hardware loosening or graft extrusions. All bone grafts healed within four months both clinically and radiologically. Forty-one patients complained of minor or no pain after four months. Five patients continued to have moderate discomfort. One of these patients had a missed injury above his two-level fusion with gradual progression into kyphosis requiring posterior stabilization.

Halo vest immobilization and posterior stabilization for C-spine fracture /dislocations have been the treatment of choice for many surgeons. The low complication and failure rate has spurred on a gradual change towards anterior instrumentation and fusion. Our study very strongly supports this trend. We see little indication for the more invasive posterior approach given our present results.

Purpose: A preliminary biomechanical test conducted on cadaver specimens validated a new technique for vertebral bone harvesting for anterior intervertebral grafting of the lumbar spine. A cylinder of autologous bone harvested from a neighboring vertebra was used for the intervertebralimplant. The harvesting site was filled with a bone substitute. The biomechanical tests confirmed good restoration of the vertebral body structure. An in vivo study was conducted in the baboon. A block of tricalcium-phosphate (beta-TCP) impregnated with transforming growth factor beta3 (TGF-beta3) was used to fill the bone gap. The purpose of the present study was: 1) to assess the efficacy of this in vivo technique on a primate model, 2) to validate the surgical technique.

Material and methods: The retroperitoneal approach was used to operate nine baboons. Eighteen bone cylinders were harvested. The harvesting hole was left empty or filled with a 15 mm diameter beta-TCP cylinder, or with a beta-TCP cylinder impregnated with TGR-beta3. Control scans were obtained at three and six months postoperatively. The baboons were sacrificed at 6 months and the vertebral bodies were removed for histology study.

Results: There was no evidence of fracture or loss of vertebral body height. The harvesting holes left empty did not fill, while osteointegration and substantial resorption of the bone substitute was observed in the two other groups. In the group with beta-TCP impregnated with TGF-beta3 the resorption of the cylinder was more complete and signs of prevertebral neoformation of subperiosteal bone, not observed in the beta-TCP group, was observed. There was no neoformation of bone in the spinal canal or in the foramens. The scans showed progressive resorption starting three months postoperatively in the beta-TCP group impregnated with TGF-beta3.

Conclusion: The beta-TCP block used is a very good bone substitute for the primate spine. TGF-beta3 accelerates bone resorption and induces neoformation of subperiosteal bone. The new surgical technique for local harvesting of vertebral bone was validated.