Quantitative computed tomography has higher sensitivity detecting critical bone mineral density compared to dual-energy X-ray absorptiometry in postmenopausal women and elderly men with osteoporotic fractures: a real-life study.

INTRODUCTION: Dual-energy X-ray absorptiometry (DXA) is considered the gold standard for the diagnosis of osteoporosis and assessment of fracture risk despite proven limitations. Quantitative computed tomography (QCT) is regarded as a sensitive method for diagnosis and follow-up. Pathologic fractures are classified as the main clinical manifestation of osteoporosis. The objective of the study was to compare DXA and QCT to determine their sensitivity and discriminatory power. MATERIALS AND METHODS: Patients aged 50 years and older were included who had DXA of the lumbar spine and femur and additional QCT of the lumbar spine within 365 days. Fractures and bone mineral density (BMD) were retrospectively examined. BMD measurements were analyzed for the detection of osteoporotic fractures. Sensitivity and receiver operating characteristic curve were used for calculations. As an indication for a second radiological examination was given, the results were compared with control groups receiving exclusively DXA or QCT for diagnosis or follow-up. RESULTS: Overall, BMD measurements of 404 subjects were analyzed. DXA detected 15 (13.2%) patients having pathologic fractures (n = 114) with normal bone density, 66 (57.9%) with osteopenia, and 33 (28.9%) with osteoporosis. QCT categorized no patients having pathologic fractures with healthy bone density, 14 (12.3%) with osteopenia, and 100 (87.7%) with osteoporosis. T-score DXA, trabecular BMD QCT, and cortical BMD QCT correlated weakly. Trabecular BMD QCT and cortical BMD QCT classified osteoporosis with decreased bone mineral density (AUC 0.680; 95% CI 0.618-0.743 and AUC 0.617; 95% CI 0.553-0.682, respectively). T-score DXA could not predict prevalent pathologic fractures. In control groups, each consisting of 50 patients, DXA and QCT were significant classifiers to predict prevalent pathologic fractures. CONCLUSION: Our results support that volumetric measurements by QCT in preselected subjects represent a more sensitive method for the diagnosis of osteoporosis and prediction of fractures compared to DXA.

A new minimal-invasive approach for total hip replacement in sheep.

BACKGROUND: Over the last 50 years arthroplasty became the gold-standard treatment for disabling conditions of the coxofemoral joint. Variations of anterior, lateral, and dorsal incision have been applied, but as each approach requires the incision and reflection of various muscles to gain adequate exposure of the joint results are still controversial. OBJECTIVE: The purpose of this study was to develop a minimal-invasive, tissue-sparing approach in sheep with reduced risks in animal testing. METHODS: 12 mature sheep underwent hip surgery as part of a study to evaluate a hip resurfacing system. In line with the preliminary cadaveric tests a modified, minimal-invasive, musclepreserving surgical approach was sought after. RESULTS: We developed a surgical approach to the coxofemoral joint in sheep using only blunt tissue dissection after skin incision without any limitations in joint exposure or increased blood loss/duration of surgery. CONCLUSION: Even though limitations occur and femoral orientation in sheep differs from man, joint forces have similar relative directions to the bone with similar bony and vascular anatomy. Therefore, this minimal-invasive muscle preserving approach might be a safe and comparable alternative in still inevitable animal testing.

Lumbar spinal stenosis - surgical outcome and the odds of revision-surgery: Is it all due to the surgeon?

BACKGROUND: Surgical decompression is the intervention of choice for lumbar spinal stenosis (LSS) when non-operative treatment has failed. Apart from acute complications such as hematoma and infections, same-level recurrent lumbar stenosis and adjacent-segment disease (ASD) are factors that can occur after index lumbar spine surgery. OBJECTIVE: The aim of this retrospective case series was to evaluate the outcome of surgery and the odds of necessary revisions. METHODS: Patients who had undergone either decompressive lumbar laminotomy or laminotomy and spinal fusion due to lumbar spinal stenosis (LSS) between 2000 and 2011 were included in this analysis. Demographic, perioperative and radiographic data were collected. Clinical outcome was evaluated using numeric rating scale (NRS), the symptom subscale of the adapted version of the german Spinal Stenosis Measure (SSM) and patient-sreported ability to walk. RESULTS: Within the LSS- cohort of 438 patients, 338 patients underwent decompression surgery only, while instrumentation in addition to decompression was performed in 100 cases (22.3%). 38 patients had prior spinal operations (decompression, disc herniation, fusion) either at our hospital or elsewhere. Thirty-five intraoperative complications were documented with dural tear with CSF leak being the most common (33/35; 94.3%). Postoperative complications were defined as complications that needed surgery and differentiated between immediate postoperative complications (⩽ 3 weeks post operation) and complications that needed revisions surgery at a later date. Within all patients 51 revisions were classified as immediate complications of the index operation with infections, neurological deficits and hematoma being the most common. Within this group only 22 patients had fusion surgery in the first place, while 29 were treated by decompression. Revision surgery was indicated by 53 patients at a later date. While 4 patients decided against surgery, 49 revision surgeries were planned. 28 were performed at the same level, 10 at the same level plus an adjacent level, and 10 were executed at index level with indications of adjacent level spinal stenosis, adjacent level spinal stenosis plus instability and stand-alone instability. Pre- operative VAS score and ability to walk improved significantly in all patients. CONCLUSIONS: While looking for predictors of revision surgery due to re-stenosis, instability or same/adjacent segment disease none of these were found. Within our cohort no significant differences concerning demographic, peri-operative and radiographic data of patients with or without revision wer noted. Patients, who needed revision surgery were older but slightly healthier while more likely to be male and smoking. Surprisingly, significant differences were noted regarding the distribution of intraoperative and early postoperative complications among the 6 main surgeons while these weren't obious within the intial index group of late revisions.

Local and systemic inflammation after implantation of a novel iron based porous degradable bone replacement material in sheep model.

Despite the high potential of healthy bone to regenerate, the reconstruction of large bone defects remains a challenge. Due to the lack of mechanical stability of existing bone substitutes, recently developed degradable metallic alloys are an interesting alternative providing higher load-bearing capabilities. Degradable iron-based alloys therefore might be an attractive innovation. To test the suitability of a newly-designed iron-based alloy for such applications, an animal experiment was performed. Porous iron-based degradable implants with two different densities and a control group were tested. The implants were positioned in the proximal tibia of Merino sheep. Over a period of 6 and 12 months, blood and histological parameters were monitored for signs of inflammation and degradation. In the histological evaluation of the implants` environment we found degraded alloy particles, but no inflammatory reaction. Iron particles were also found within the popliteal lymph nodes on both sides. The serum blood levels of phosphorus, iron and ferritin in the long term groups were elevated. Other parameters did not show any changes. Iron-based degradable porous bone replacement implants showed a good biocompatibility in this experiment. For a clinical application, however, the rate of degradation would have to be significantly increased. Biocompatibility would then have to be re-evaluated.

The effects of whole-body electromyostimulation (WB-EMS) in comparison to a multimodal treatment concept in patients with non-specific chronic back pain-A prospective clinical intervention study.

BACKGROUND: According to present guidelines, active exercise is one key component in the comprehensive treatment of nonspecific chronic back pain (NSCBP). Whole body electromyostimulation (WB-EMS) is a safe, and time-effective training method, that may be effective in NSCBP-patients. METHODS: In this prospective and controlled nonrandomized clinical study, two therapeutic approaches were compared. One group received 20 minutes WB-EMS per week. An active control group (ACG) received a multimodal therapy program. A third group included subjects without back pain. To all groups, the following measurement instruments were applied: Numeric Rating Scale (NRS), Oswestry Disability Index (ODI), North American Spine Society Instrument (NASS); SF 36 survey and measurements for muscular function and postural stability. In the EMS-group: T0: baseline; T1: at 6 weeks; T2: at 12 weeks and T3: at 24 weeks. In the ACG: T0 baseline and T1 after 4 weeks. RESULTS: In the intervention group, 128 patients with low back pain were enrolled, 85 in the WB-EMS group and 43 in the ACG. 34 subjects were allocated to the passive control group. The average age was 58.6 years (18-86 years). In the EMS group, the NRS (1-10) improved statistically and clinically significantly by 2 points. The ODI was reduced by 19.7 points. The NASS and most of the SF 36 items improved significantly. In the multimodal treatment group, only the muscular function improved slightly. CONCLUSION: Our data support the hypothesis that WB-EMS is at least as effective as a multimodal treatment, which is often referred to as being the golden standard. Therefore WB-EMS may be an effective and, with 20 min./week training time, very time-efficient alternative to established multimodal treatment models.

Development of a novel biodegradable porous iron-based implant for bone replacement.

Bone replacement and osteosynthesis require materials which can at least temporarily bear high mechanical loads. Ideally, these materials would eventually degrade and would be replaced by bone deposited from the host organism. To date several metals, notably iron and iron-based alloys have been identified as suitable materials because they combine high strength at medium corrosion rates. However, currently, these materials do not degrade within an appropriate amount of time. Therefore, the aim of the present study is the development of an iron-based degradable sponge-like (i.e. cellular) implant for bone replacement with biomechanically tailored properties. We used a metal powder sintering approach to manufacture a cylindrical cellular implant which in addition contains phosphor as an alloying element. No corrosion inhibiting effects of phosphorus have been found, the degradation rate was not altered. Implant prototypes were tested in an animal model. Bone reaction was investigated at the bone-implant-interface and inside the cellular spaces of the implant. Newly formed bone was growing into the cellular spaces of the implant after 12 months. Signs of implant degradation were detected but after 12 months, no complete degradation could be observed. In conclusion, iron-based open-porous cellular biomaterials seem promising candidates for the development of self-degrading and high load bearing bone replacement materials.

[Undetected coccyx fracture in a woman with fibromyalgia]. / Unentdeckte Os-coccygis-Fraktur bei Patientin mit Fibromyalgiesyndrom.

This article presents the case of a 46-year-old woman with fibromyalgia with an undetected fracture of the coccyx. The heterogeneity of the symptoms of patients suffering from fibromyalgia including chronic widespread pain, vegetative and functional disorders, mental and physical exhaustion as well as sleep disorders can cause accidentally undetected comorbidities, especially if these are rare and predominantly present with pain as the main symptom. In the present case the reason for symptoms was detected only after 14 months of ineffective therapies and diagnostic procedures. The coccygeal pain was eliminated through a coccygectomy as ultima ratio. It should be nevertheless emphasized that patients with fibromyalgia suffer from a central pain-processing disorder. Indications for operative treatment must be very carefully considered. Surgery should only be considered in consultation with the patient and after failed conservative therapy.

Effects of Whole Body Vibration Therapy and Classic Physiotherapy on Postural Stability in People With Back Pain: A Randomized Trial.

STUDY DESIGN: This 2-step prospective randomized parallel trial evaluated postural stability in 65 back pain participants (61.6±7.9 y) and 50 nonback pain participants (61.2±8.6 y) in a first step using the MFT-S3-Check. In a second step, postural stability and questionnaires were evaluated in back pain participants before and after therapy with either whole body vibration therapy or classic physiotherapy. OBJECTIVE: The first aim was to investigate whether the MFT-S3-Check is suitable to evaluate differences in postural stability in back pain and nonback pain participants. The second aim was to evaluate the effect of whole body vibration therapy and classic physiotherapy on postural stability and the influence of depressive symptoms and pain. SUMMARY OF BACKGROUND DATA: Objective bodily measurement values in chronic back pain are rare; therefore, the evaluation of effectiveness of different therapies is difficult. METHODS: Postural stability was investigated using stability-, sensorimotor-, and symmetry indexes, in standing and seated positions with the MFT-S3-Check. The following standard questionnaires were used to investigate pain and depressive symptoms: HADS, ODI, NASS, SF-36. RESULTS: No significant difference in postural stability was found between back pain participants and the nonback pain group. None of the two training concepts in back pain participants was superior, concerning postural stability and pain. Both treatments showed positive effects, with significant improvements in postural stability in the classic physiotherapy group. Depressive symptoms had a significant correlation with pain intensity in back pain participants. CONCLUSIONS: The MFT-S3-Check could not find a significant difference in postural stability between the back pain and nonback pain group in the study setting. Postural stability improved after treatment.

Slow correction of severe spastic hyperlordosis in an adult by means of magnetically expandable rods.

BACKGROUND: We describe a case of severe and progressive lumbar hyperlordosis (160°) in a 28-year-old female university student with cerebral palsy. Her main complaints were abdominal wall pain and increasing inability to sit in her custom wheelchair. METHOD: When deciding on our opinion about the most promising treatment strategy, we contemplated slow continued correction by means of percutaneously expandable magnetic rods (MAGEC) after the index surgery as a key component of a satisfactory correction in this severe and rigid curve. After an initial radical release and partial correction, a release and correction procedure was required for the bilateral hip flexion contracture. A final in situ posterior fusion was performed as a second spinal procedure, once the desired final correction at 66° of lumbar lordosis was achieved. RESULT: Three years after the completion of surgery, the patient has a stable clinical and radiological result as well as a solid posterior fusion on CT. CONCLUSION: This is the first case published in which percutaneous magnetic distraction was successfully used in an adult patient.

The current state of endoscopic disc surgery: review of controlled studies comparing full-endoscopic procedures for disc herniations to standard procedures.

BACKGROUND: Neuropathic pain originating from spinal disc herniations is a very common problem. The majority of disc surgeries are performed to alleviate this pain once conservative measures and targeted injections have failed. Endoscopic spinal surgery is increasingly popular because it minimizes access trauma and hastens recovery from the intervention. This clinically oriented review evaluates controlled studies that investigate the clinical results and the complications of full-endoscopic lumbar and cervical procedures for symptomatic disc herniations in comparison to a microsurgical standard procedure. This review focuses exclusively on modern, full-endoscopic disc surgery irrespective of the specific access technique (e.g., interlaminar vs. transforaminal) and irrespective of the spinal region. STUDY DESIGN: Comprehensive review of the literature. OBJECTIVE: To assess the clinical outcomes and complication rates of full-endoscopic disc surgery compared to the microsurgical standard procedures. METHODS: A PubMed and Embase search was performed, considering entries up to January 2013. All 504 results were screened and categorized. Only 4 randomized controlled trials (RCTs) and one controlled studies (CS) could finally be considered for evaluation. All 5 manuscripts were meticulously analyzed with regards to randomization mode, inclusion/exclusion criteria, clinical results, and complication rates. RESULTS: Overall, the endoscopic techniques had shorter operating times, less blood loss, less operative site pain, and faster postoperative rehabilitation/shorter hospital stay/faster return to work than the microsurgical techniques. There were no significant differences in the main clinical outcome criteria between the endoscopic and the microsurgical techniques in any of the trials. All 5 studies had fewer complications with the endoscopic technique and this was statistically significant in 2 of the studies. One study showed a lower rate of revision surgeries requiring arthrodesis with the endoscopic technique. LIMITATIONS: All 5 studies that could be considered originate from experienced investigators and all 4 RCTs came from one group. This limits the transferability of their results to surgeons less experienced in endoscopic disc surgery. CONCLUSIONS: The studies show that full-endoscopic disc surgery can achieve the same clinical results in symptomatic cervical and lumbar disc herniations as the microsurgical standard techniques. This does not appear to come at the price of higher complication rates.

Thermoelastic stress analysis to validate tibial fixation technique in total ankle prostheses - a pilot study.

BACKGROUND: Recent literature has shown a persistently high rate of aseptic loosening of the tibial component in total ankle prostheses. METHODS: We analyzed the interface between the tibial bone and tibial component with a thermoelastic stress analysis to demonstrate load transmission onto the distal tibia. In this regard, we used two established ankle prostheses, which were implanted in two human cadaveric and in two third-generation composite tibia bones (Sawbones®, Sweden). Subsequently, the bones were attached to a hydropulser and a sinusoidal load of 700 N was applied. RESULTS: Both prostheses had an inhomogeneous load transmission onto the distal tibia. Instead of distributing load equally to the subarticular bone, forces were focused around the bolting stem, accumulating as stress maxima with forces up to 90 MPa. Furthermore, we were able to demonstrate load transmission into the metaphysis of the bone. CONCLUSION: As demonstrated in this study, anchoring systems with stems used in all established total ankle prostheses lead to an inhomogeneous load transmission onto the distal tibia, and furthermore, to a distribution of load into the weaker metaphyseal bone. For these reasons, we favor a prosthetic design with minimal bone resection and without any stem or stem-like anchoring system, which facilitates a homogeneous load transmission onto the distal tibia. Thermoelastic stress analysis proved to be a fast and easy-to-perform method to visualize load transmission.

An intramedullary capillary hemangioma of the spine with an underlying plasmocytoma.

BACKGROUND CONTEXT: In contrast to vertebral hemangiomas, which are very common within the general population, only 3% to 5% of patients with plasma cell dyscrasia show a single osteolytic bone lesion due to plasma cell infiltration without the evidence of generalized myeloma. The vast majority of these hemangiomas are completely asymptomatic and only discovered incidentally. In rare occasions, representing only 1% to 2% of the known lesions, a locally aggressive subtype can cause problems analogous to the ones triggered by a plasmocytoma, ranging from back pain to vertebral compression fractures to neurologic deficit, resulting from nerve root or spinal cord compression. Both entities are extensively discussed in the literature, but finding both lesions in one is rare if not described for the first time. PURPOSE: To advise colleagues that the differential diagnosis between benign and malignant vertebral tumors can be harder than expected and has to be definitely made to avoid severe consequences for the patient. PATIENT SAMPLE: A 46-year-old healthy man presented to the emergency department with an acute onset of thoracic back pain after a trivial incident. Although his medical history included no known diseases and no history of back pain, plain X-rays raised the clear suspicion of a fracture of T6 that was verified in computed tomography scans. OUTCOME MEASURES: Visual analog scale; neurologic status; tumor recurrence. METHODS: The case of the patient was evaluated retrospectively according to standard procedures, clinical outcome, and in review of the literature. RESULTS: Because there is still controversy about the best treatment (local radiation vs. operation vs. combination) of a solitary skeletal plasmocytoma, no gold standard has been established until now. Especially if a patient needs an emergency operation before all test results are obtained, each surgeon has to decide individually. CONCLUSIONS: Capillary hemangiomas can hide underlying plasmocytomas, which might demand totally different treatment strategies. Although our patient did not match the common criteria for a solitary plasmocytoma, one has to discuss whether a stand-alone decompression and biopsy would have been the emergency treatment of choice. Such a strategy would have reduced the risk of tumor spreading and would have made radiotherapy easier, whereas on the other hand requiring a secondary stabilization procedure later on.

Analysis of orthopedic surgery of bone metastases in breast cancer patients.

BACKGROUND: Breast cancer is the most common malignancy and the second leading cause of death in women. Because bone metastases are a common finding in patients with breast cancer, they are of major clinical concern. METHODS: In 115 consecutive patients with bone metastases secondary to breast cancer, 132 surgical procedures were performed. Medical records and imaging procedures were reviewed for age, treatment of the primary tumor, clinical symptoms, surgical treatment, complications, and survival. RESULTS: The overall survival of patients with metastatic breast cancer was dependent on the site and the amount of the metastases. Age was not a prognostic factor for survival. If the result of the orthopaedic surgery was a wide resection (R0) survival was significantly better than in the R1 (marginal resection - tumor resection in sane tissue) or R2 (intralesional resection) situation. Concerning the orthopaedic procedures there was no survival difference. CONCLUSION: In conclusion a wide (R0) resection and the absence of pathological fracture and visceral metastases were predictive for longer survival in univariate analysis. Age and the type of orthopaedic surgery had no impact on survival in multivariate analysis. The resection margins lost significance. The standard of care for patients with metastatic breast cancer to the bone requires a multidisciplinary approach.

Experimental evaluation of the risk of extradiscal thermal damage in intradiscal electrothermal therapy (IDET).

BACKGROUND: In 2000 the intradiscal electrothermal therapy (IDET) procedure for the treatment of discogenic pain was introduced. The technique involves the positioning of an intradiscal catheter with a temperature-controlled thermal resistive heating coil at the inner posterior annulus. The therapeutic mechanism of IDET combines the thermo-coagulation of native nociceptors and in-grown nonmyelinated nerve fibers with collagen shrinkage, stabilizing annular fissures. Thermal nerve root injuries were described with IDET. The temperature in relation to the distance from the catheter tip was investigated. The intradiscal temperature distribution during treatment with IDET was also described. OBJECTIVE: To examine the temperature distribution outside the disc near neural structures and the risk of thermal damage to nerve tissue during a correctly performed IDET procedure. STUDY DESIGN: Experimental study. SETTING: Biomechanical laboratory of an academic orthopedic surgery department. METHODS: Testing was performed on cadaveric human lumbar spines with 10 intact intervertebral discs in a circulating water bath. Five thermocouples were attached to different locations on the disc. The temperature was recorded for 26 minutes. In addition, surface temperatures were recorded using an infrared camera. For the application of IDET, we used the Electrothermal 20S Spine System by Smith & Nephew and the standard clinical protocol. RESULTS: The shape of the recorded temperature curves was quite heterogeneous. Inside the spinal canal, temperatures as high as 45.2°C were recorded for a very short time. Temperature monitoring with the infrared camera demonstrated a change in temperature clearly restricted to the nucleus of the disc. LIMITATIONS: The temperature distribution depends on the exact position of the IDET probe, which will never be 100% identical between individual experiments. CONCLUSION: This study shows that temperatures generated within the spinal canal during IDET do not appear to be high enough to cause nerve damage.

A biomechanical evaluation of the epidural neurolysis procedure.

BACKGROUND: The epidural lysis of adhesions (ELOA) procedure supposedly has a biomechanical component in addition to the targeted injection of medications into the epidural space. It is assumed that the catheters used for the ELOA procedure can release epidural scars and adhesions. OBJECTIVES: To evaluate the possible biomechanical effects of the typically used catheters and to put these effects into clinical perspective. STUDY DESIGN: Experimental study. SETTING: The biomechanical laboratory of an academic orthopedic surgery department. METHODS: Experimental setups were devised that allow for the measurement of the 3 main forces that can be exerted by manipulating a catheter in the epidural space or by injecting fluids through such a catheter: axial forces, torsional forces, and hydraulic effects. RESULTS: The maximum axial forces measured under extremely tight catheter guidance were 7 newton (N), whereas the maximum forces under conditions that more likely reflect a real treatment situation were between 1 and 2 N. The maximum torsional forces measured were 0.3 N under extremely tight catheter guidance and 0.01 N under more realistic conditions. The maximum flow that could be achieved through the typical catheter using normal saline and the maximum possible thumb pressure onto a 5 mL or a 10 mL Luer-Lock syringe was 0.48 mL/ s. Given these results and other data available to us, it appears impossible that the ELOA procedure with typically used catheters has any relevant mechanical effect. LIMITATIONS: Like with any experimental study, the realities of an in vivo situation can only be modeled to a limited degree. The main limitation of our study is that we cannot calculate, measure, or simulate neither the flow resistance between an epidural adhesion pocket and the open, local epidural space nor the flow resistance between the open, local epidural space and the larger epidural space as well as the retroperitoneal space. CONCLUSIONS: According to our findings and arguments, the ELOA procedure is predominantly a method for the highly targeted application of epidural medications and possibly also has a lavage effect. A mechanical lysis of scars or adhesions appears unlikely.

Heat distribution of polymerisation temperature of bone cement on the spinal canal during vertebroplasty.

PURPOSE: In the last 15 years, vertebroplasty and kyphoplasty have become established operative procedures for treating osteoporotic vertebral-body fractures and vertebral bodies afflicted with metastases. These procedures are quickly performed with few personnel and material resources and have a low rate of complications. However, cases of neurological impairment are reported in the scientific literature. We analysed whether potentially harmful heat is radiated/conducted by the polymerisation temperature of polymethylmethacrylate (PMMA) bone cement in the spinal canal. METHODS: We performed vertebroplasty on 25 vertebral bodies and measured the temperature distribution during polymerisation of bone cement within the spinal canal using heat probes placed in the respective areas. The vertebral bodies were located in a circulating water bath at 37°C. RESULTS: During polymerisation of the bone cement, a temperature rise was measured. The peak temperature was reached after few minutes. Temperature curves differed; a maximum temperature of up to 43.16°C was detected for a few seconds only. CONCLUSION: When vertebroplasty is performed correctly, there is no temperature development that could eventually damage the spinal cord or spinal nerves.

Intravertebral neotrabecularization as an expression of focal load transfer by a keel-design lumbar total disc arthroplasty.

The aim of this study is to direct attention to the specific load transfer characteristics of keel-design total disc arthroplasty (TDA) implants that may be underreported. A variety of implants for lumbar TDA are available on the market. One of the main differences between the design types of lumbar TDA implants is whether they use a keel or small spikes/ridges in order to achieve primary stability. The consequences of such design features on load transfer have not been adequately discussed. We report and discuss a case in which new intravertebral bone trabecula have appeared after double-level implantation of a keel-based TDA. We think that the mid- and long-term follow-up radiographs of patients after TDA with keel-design implants should be examined for the presence or absence of such changes. Should our case turn out to be not a singular occurrence, this might have an impact on the design of future TDA implants.

Cartilage regeneration by bone marrow cells-seeded scaffolds.

Different approaches exist for the treatment of small articular cartilage defects. Several studies show comparable results for autologous chondrocyte implantation (ACI) and microfracture. Unfortunately, the fibrocartilage resulting from microfracture has neither the structure nor the mechanical properties of hyaline cartilage, even though the adult mesenchymal stem cells, which immigrate into the defect, are supposed to differentiate into chondrocytes. This study was performed to examine the capacity of a resorbable implant made from polylactide-co-glycolide acid (PGLA)-fleece combined with autologous bone marrow cells fixed with a fibrin/thrombin-clot in the weight-bearing area of the femoral condyle of mature sheep. For this study, six defects were treated with either the PGLA-implant alone or with a combination of the implant with added fibrin glue or were left untreated to serve as controls. The animals were sacrificed after 12 weeks; the operated knees were removed and examined by measuring the covering of the defect with cartilaginous tissue and according to the score of O'Driscoll. Additional criteria such as immunolabeling for collagen II and aggrecan were included. Results showed that no improvement of the tissue quantity or quality could be achieved by increasing the cell load of the implant with cells fixed by fibrin glue.

The gel box - a testing device for the characterization of cryo- and radiofrequency lesions employed in interventional pain therapy.

BACKGROUND: Radiofrequency (RF) and cryolesioning are established methods for the therapeutic interruption of sensory nerve supply to facet joints and other painful musculoskeletal structures. The varying clinical success rates of these treatments have - among other technical issues - been attributed to the small size of these lesions combined with the limited precision in placing them. Since there are 2 different physical methods for lesioning and a wide range of probes and lesion generators available, it is likely that the lesions generated by them may be of different size. OBJECTIVES: We sought to devise an experimental setup that would allow for the reproducible and comparable evaluation of the size of cryo and RF lesions as they are being used in interventional pain therapy. METHODS: A wide range of potential media was evaluated for this purpose. Based on technical specifications, as well as on preliminary testing, a specific agar agar gel with a gel point of between 32 degrees C and 35 degrees C and a melting point of between 80 degrees C and 85 degrees C was selected for these experiments. Two different testing containers were constructed from transparent acrylic: one with a volume of 1,500 mL and the other with a volume of 12 mL. Each of them allows for the introduction of a cryo or a RF probe and 2 bundles of thermoelements into the gel volume. A water bath was used to maintain the gels at 37 degrees C and bundled, ultrafine NiCr-Ni thermoelements type K were used for measuring the isotherms. A series of RF and cryolesions were performed within these experimental setups to evaluate their suitability for the comparative testing of cryo and RF probes and generators. RESULTS: Both testing setups generated reproducible results and proved to be suitable for measuring RF as well as cryolesions. Visual observation of the lesions was better with the small testing container and rewarming / recooling after performing a cryo / RF lesion was more rapid with the smaller gel volume. LIMITATIONS: Our setup allows for the comparative measurement of RF and cryolesions, but it cannot simulate the realities within living tissue. While convection as a confounding factor was excluded by use of a gel, capillary perfusion and the specific characteristics of different tissues cannot be simulated. CONCLUSIONS: The testing setup described in this manuscript can serve for the comparative and reproducible study of RF and cryolesions that are commonly used in interventional pain therapy.

How to connect a pedicle screw construct to a Ransford Loop: technical note.

This technical note describes how a standard pedicle screw system can be connected to the 4 mm rod of a Ransford Loop. This report may be of interest for spinal surgeons who need to perform similar add-on stabilizations.