A surprisingly poor correlation between in vitro and in vivo testing of biomaterials for bone regeneration: results of a multicentre analysis.

New regenerative materials and approaches need to be assessed through reliable and comparable methods for rapid translation to the clinic. There is a considerable need for proven in vitro assays that are able to reduce the burden on animal testing, by allowing assessment of biomaterial utility predictive of the results currently obtained through in vivo studies. The purpose of this multicentre review was to investigate the correlation between existing in vitro results with in vivo outcomes observed for a range of biomaterials. Members from the European consortium BioDesign, comprising 8 universities in a European multicentre study, provided data from 36 in vivo studies and 47 in vitro assays testing 93 different biomaterials. The outcomes of the in vitro and in vivo experiments were scored according to commonly recognised measures of success relevant to each experiment. The correlation of in vitro with in vivo scores for each assay alone and in combination was assessed. A surprisingly poor correlation between in vitro and in vivo assessments of biomaterials was revealed indicating a clear need for further development of relevant in vitro assays. There was no significant overall correlation between in vitro and in vivo outcome. The mean in vitro scores revealed a trend of covariance to in vivo score with 58 %. The inadequacies of the current in vitro assessments highlighted here further stress the need for the development of novel approaches to in vitro biomaterial testing and validated pre-clinical pipelines.

The optimal timing of baseline radiostereometric analysis of uncemented press fit cups.

BACKGROUND AND AIMS: The baseline radiostereometric analysis (RSA) is usually performed during the first postoperative week. We investigated the micromotion of two uncemented press fit acetabular cups during the first week after total hip arthroplasty. MATERIAL AND METHODS: All study patients had unilateral osteoarthritis of the hip and received an uncemented THA combination consisting of a CLS stem and either an Allofit or an Interop acetabular cup. The study group consisted of 24 patients who underwent RSA within 1 hour after skin closure, and at 1 and 7 days after surgery. RESULTS: The upper limit of the 95% confidence interval for micromotion was less than or close to the precision of the method for all studied directions during the first week after surgery. Mean values indicate proximal and medial translation of the uncemented cup at one week. CONCLUSIONS: We found only minimal micromotion, barely above the precision limit, measured as medial and proximal translations of these uncemented cups. This indicates that the first postoperative RSA measurement following a primary THA with an uncemented press fit ace-tabular cup should be made as early as possible after the first postoperative day.

Cement augmentation in fracture treatment.

Surgical treatment of fractures close to joints, especially in osteoporotic patients, is often associated with problems to obtain adequate strength of the bone-implant construct as well as sufficient purchase for screws in the weak bone. One way to address this increasing problem is through the development of new metal implants specifically designed for fixation of fractures in osteopenic bone. An alternative strategy is to develop methods for augmentation of the weak bone that surrounds the metal implant. In most instances augmentation is achieved by using injectable cement to reinforce the bone. Conventional PMMA provides good strength but due to several drawbacks it has never gained general acceptance for fracture augmentation. More recently several injectable cements based on calcium-phosphate, calcium-sulphate or bioglass has been developed for augmentation of fractures in the extremities as well as for vertebral compressive fractures in the spine. On the basis of biomechanical studies and the clinical experience so far, cement augmentation will enable faster rehabilitation, as the strength of the cement makes it possible to allow full weight-bearing earlier than conventional metal implants alone. More clinical studies are needed in order to refine the surgical technique, develop cement types aimed for fracture treatment and define the most appropriate indications and limitations of augmentation for fracture repair. The purpose of this article is to review the possible use of augmentation as a technique in the treatment of fractures in the extremities as well as in the spine.

Resorbable cement for the augmentation of internally-fixed unstable trochanteric fractures. A prospective, randomised multicentre study.

We undertook a multicentre, prospective study of a series of 112 unstable trochanteric fractures in order to evaluate if internal fixation with a sliding screw device combined with augmentation using a calcium phosphate degradable cement (Norian SRS) could improve the clinical, functional and radiological outcome when compared with fractures treated with a sliding screw device alone. Pain, activities of daily living, health status (SF-36), the strength of the hip abductor muscles and radiological outcome were analysed. Six weeks after surgery, the patients in the augmented group had significantly lower global and functional pain scores (p < 0.003), less pain after walking 50 feet (p < 0.01), and a better return to the activities of daily living (p < 0.05). At follow-up at six weeks and six months, those in the augmented group showed a significant improvement compared with the control group in the SF-36 score. No other significant differences were found between the groups. We conclude that augmentation with calcium phosphate cement in unstable trochanteric fractures provides a modest reduction in pain and a slight improvement in the quality of life during the course of healing when compared with conventional fixation with a sliding screw device alone.

Variability of the pullout strength of cancellous bone screws with cement augmentation.

BACKGROUND: Orthopaedic surgeons often face clinical situations where improved screw holding power in cancellous bone is needed. Injectable calcium phosphate cements are one option to enhance fixation. METHODS: Paired screw pullout tests were undertaken in which human cadaver bone was augmented with calcium phosphate cement. A finite element model was used to investigate sensitivity to screw positional placement. FINDINGS: Statistical analysis of the data concluded that the pullout strength was generally increased by cement augmentation in the in vitro human cadaver tests. However, when comparing the individual paired samples there were surprising results with lower strength than anticipated after augmentation, in apparent contradiction to the generally expected conclusion. Investigation using the finite element model showed that these strength reductions could be accounted for by small screw positional changes. A change of 0.5mm might result in predicted pullout force changes of up to 28%. INTERPRETATION: Small changes in screw position might lead to significant changes in pullout strength sufficient to explain the lower than expected individual pullout values in augmented cancellous bone. Consequently whilst the addition of cement at a position of low strength would increase the pullout strength at that point, it might not reach the pullout strength of the un-augmented paired test site. However, the overall effect of cement augmentation produces a significant improvement at whatever point in the bone the screw is placed. The use of polymeric bone-substitute materials for tests may not reveal the natural variation encountered in tests using real bone structures.

Ion probe study of fluorine gradients in outermost layers of human enamel.

F concentrations in the outermost layers of human tooth enamel were studied with the aid of a secondary ion microanalyzer. Concentration profiles were recorded in continuous sputtering analysis from the surface down to a depth of about 0.3 micrometer. Samples previously subjected to topical fluoride treatment were compared with reference specimens. In some samples, the results were compared with those obtained at greater depths by macroscopic etching analysis.

Biodistribution of liposomal 131I-VIP in rat using gamma camera.

Vasoactive intestinal peptide (VIP), a 28 amino-acid peptide was labeled with 131I and encapsulated into liposomes. 131I-VIP or liposomal 131I-VIP was administered intravenously into the rats. The distribution was studied by a gamma camera and established by counting the radioactivity in the removed organs. The elimination half-life for the liposomal 131I-VIP in both blood and lungs was significantly longer (5.29 and 9.28 min, respectively) than that obtained after the administration of 131I-VIP (0.62 and 3.18 min, respectively). Dynamic scans using a gamma camera after the administration of liposomal 131I-VIP showed a higher uptake of the liposomal form into the lungs compared with 131I-VIP. The lack of VIP in asthmatics has been shown in previous studies. However, the clinical investigations using VIP were disappointing most probably due to the rapid degradation of the peptide in the bronchial tract. This in fact is supported by our previous study, in which we demonstrated that VIP had a half-life of 0.45 min in blood. We conclude that the encapsulation of VIP in liposomes prolongs its elimination half-life in plasma and enhances its uptake in lungs. This observation may increase the clinical use of VIP in both diagnostic and therapy.

Uvulopalatopharyngoplasty in the sleep apnea syndrome. Predictors of results.

A prospective study of 34 consecutive patients with the sleep apnea syndrome was undertaken to evaluate the effectiveness and complications of, and predictors of, results in a conservative type of uvulopalatopharyngoplasty (UPPP). At six months, 65% of the patients had a 50% or greater reduction in the number of apneas and hypopneas per hour (responders). The responders to UPPP were less severely affected preoperatively regarding apneas and hypopneas, the mean number of which (+/- SD) were 32.7 +/- 20.8 compared with 64.6 +/- 26.0. They also had a lower body mass index before UPPP (31.3 +/- 4.1 vs 36.0 +/- 7.0 kg/m2). Preoperative computed tomography and cephalometry indicated that the nonresponders had narrower upper airways. It is concluded that UPPP is the treatment of choice for mild to moderate sleep apnea syndrome, but not for severely affected, heavily overweight patients with an increased tongue width.

Radioiodine uptake in the head and neck.

OBJECTIVE: To report two cases of sinusitis-associated radioiodine uptake in patients with thyroid cancer and to review the reported causes of false-positive radioiodine uptake in the head and neck area. METHODS: We present the radiologic findings in two patients who had undergone treatment for papillary thyroid cancer and discuss other settings in which radioiodine uptake suggested the presence of metastatic disease. RESULTS: Radioiodine whole-body scans of two patients who had had thyroid cancer demonstrated uptake in the sphenoid and maxillary sinuses, respectively, mimicking bone or brain metastatic involvement. The thyroglobulin levels were low. Computed tomographic (CT) scanning disclosed mucosal swelling in the sinuses, consistent with sinusitis. The radioiodine uptake cleared on a follow-up scan in one case and was more localized than the CT findings in the other. Eighteen causes of false-positive radioiodine uptake in the head and neck area have been reported. On the basis of the mechanism of uptake, they can be classified into four categories: (1) physiologic uptake (ectopic thyroid tissue), (2) nonthyroidal pathologic conditions (dacryocystitis, sinusitis, sinus mucocele, sialadenitis, folliculitis, Warthin's tumor, parotid cyst, porencephaly, posttraumatic cerebromalacia, and inflammation due to dental disease or a nose ring), (3) internal retention (ectasia of the carotid artery and an artificial eye), and (4) external contamination by body secretions (sweat and nasal, tracheobronchial, lacrimal, and salivary secretions). The estimated prevalence of external contamination in the head and neck area on whole-body radioiodine scans is 0.3%. CONCLUSION: Physicians should rule out the presence of radioiodine uptake by inflamed mucosa of the paranasal sinuses, as well as various other causes of false-positive radioiodine uptake, before metastatic thyroid cancer in the head and neck area is diagnosed.

Posterior fusion for atlanto-axial subluxation in rheumatoid arthritis.

Posterior cervical fusion was performed in 34 patients with advanced rheumatoid atlanto-axial subluxation. Atraumatic surgical technique was used with local anesthesia and without skull traction. Intractable occipital rhizopathy and long-tract signs were the main indications. Anterior atlanto-axial subluxation in 28 patients was operated on with posterior fusion of C1-C2. Superior migration of the odontoid process into the foramen magnum in six patients was treated with posterior fusion of occiput C1-C2. Immediate mobilization in a plastic brace followed surgery. Average follow-up was 3 years. All patients became symptom-free, except for three who had remaining long-tract signs. Bony fusion was achieved in 17 patients; stable fibrous fusion, in 8 patients; and pseudoarthrosis, in 4 patients. There were no major postoperative complications. Five deaths occurred after 1-2 years from unrelated causes.

Medullary compression in rheumatoid atlanto-axial subluxation evaluated by computerized tomography.

CT examination of rheumatoid dislocation in the C1-C2 region was performed in 20 patients with advanced disease. The patients were classified in three grades according to the degree of medullary compression caused by the odontoid process in the extended position of the neck. Five patients showed no dural or medullary compression (grade 1), nine dural compression (grade 2), and six medullary compression (grade 3). CT grading was found to correlate best with long tract symptoms. These were present in 4/6 grade 3 and 0/5 grade 1 patients, while 3/9 grade 2 patients had long tract symptoms. Tissue attenuation values over the anterior atlanto-axial joint indicated interposing firm connective tissue in patients showing no reduction of the subluxation on extension of the neck.

Improved bone-screw interface with hydroxyapatite coating: an in vivo study of loaded pedicle screws in sheep.

STUDY DESIGN: An in vivo sheep model with loaded pedicle screws was used, wherein each animal served as its own control. OBJECTIVES: To examine the effects of hydroxyapatite (HA) coating on the bone-to-implant interface in loaded spinal instrumentations. SUMMARY OF BACKGROUND DATA: Spinal instrumentation improves the healing rate in spinal fusion, but screw loosening constitutes a problem. HA coating of other implants has resulted in favorable effects on the bone-to-implant interface. METHODS: Nine sheep were operated on with destabilizing laminectomies at two levels: L2-L3 and L4-L5. Each level was stabilized separately with a four-screw instrumentation. Uncoated screws (stainless steel) or the same type of screws coated with plasma-sprayed HA were used in either the upper or the lower instrumentation in a randomized fashion. The animals were killed at 6 or 12 weeks after surgery. The specimens were embedded in resin, ground to approximately 10 microm, and stained with toluidine blue. Histomorphometric evaluation was carried out in a Leitz Aristoplan (Wetzlar, Germany) light microscope equipped with a Leitz Microvid unit. RESULTS: The average percentage of bone-to-implant contact after 6 weeks was 69 +/- 10 for the HA-coated screws and 18 +/- 11 for the uncoated screws (P < 0.03), and after 12 weeks 64 +/- 31 (HA-coated) and 9 +/- 13 (uncoated, P < 0.02). The average bone volume in the area close to the screw was significantly higher for the HA-coated screws at both 6 and 12 weeks. CONCLUSIONS: HA coating improved the bone-to-implant interface significantly, indicating that HA coating can become useful for improving the purchase of pedicle screws.

Functional evaluation of the spinal cord by magnetic resonance imaging in patients with rheumatoid arthritis and instability of upper cervical spine.

Thirty-four patients with atlanto-axial instability due to rheumatoid arthritis were examined with plain x-ray views and functional magnetic resonance imaging (MR), and were neurologically evaluated. Transcranial brain stimulation was performed in 25 patients. In 22 cases, the authors observed inflammatory tissue thicker than 3 mm behind the odontoid peg. The spinal canal diameter was significantly decreased in the flexed position. Nine patients showed signs of cranial migration of the axis. The diameter of the spinal cord was measured to be 7.4 mm in the neutral position, and 6.5 mm in flexion. The difference between the diameter of the neutral and flexed positions was highly significant. Twelve of the 34 patients displayed clinical signs of cervical myelopathy, and 13 showed a significant delay of central motor latency, as calculated from the motor evoked potentials. Surgical intervention, either by a posterior approach only or combined with a transoral dens and inflammatory tissue resection, is recommended in patients with progressive atlanto-axial instability, pathologic clinical and neurophysiologic findings, and a spinal cord diameter of less than 6 mm in flexion. Severe pain and cranial migration of the axis, as measured by the MRI, also justify a surgical intervention.

Stability of cemented all-polyethylene keeled glenoid components. A radiostereometric study with a two-year follow-up.

We studied the stability of cemented all-polyethylene keeled glenoid components by radiostereometric analysis (RSA) in 16 shoulders which had received a total shoulder replacement. There were 14 women (one bilateral) and one man with a mean age of 64 years. The diagnosis was osteoarthritis in eight and rheumatoid arthritis in seven. Two of the shoulders were excluded from the RSA study because of loosening of the tantalum markers. Three tantalum markers were inserted in the glenoid socket, two in the coracoid process and two in the acromion. The polyethylene keeled glenoid component was marked with three to five tantalum markers. Conventional radiological and RSA examinations were carried out at five to seven days, at four months and at one and two years after operation. Radiolucent lines were found in all except three shoulders. Migration was most pronounced in the distal direction and exceeded 1 mm in four shoulders. In ten shoulders rotation exceeded 2 degrees in one or more axes with retroversion/anteversion being most common. No correlation was found between migration and the presence of radiolucencies on conventional radiographs.

Hydroxyapatite coating improves fixation of pedicle screws. A clinical study.

We investigated the effects of hydroxyapatite (HA) coating on the purchase of pedicle screws. A total of 23 consecutive patients undergoing lumbar fusion was randomly assigned to one of three treatment groups. The first received uncoated stainless-steel screws, the second screws which were partly coated with HA, and the third screws which were fully coated. The insertion torque was recorded. After 11 to 16 months, 21 screws had been extracted. The extraction torque was recorded. Radiographs were taken to assess fusion and to detect loosening of the screws. At removal, the extraction torques exceeded the upper limit of the torque wrench (600 Ncm) for many HA-coated screws. The calculated mean extraction torque was 29 +/- 36 Ncm for the uncoated group, 447 +/- 114 Ncm for the partly-coated group and 574 +/- 52 Ncm for the fully-coated group. There were significant differences between all three groups (p < 0.001). There were more radiolucent zones surrounding the uncoated screws than the HA-coated screws (p < 0.001). HA coating of pedicle screws resulted in improved fixation with reduced risk of loosening of the screws.

Stability of internally fixed femoral neck fractures augmented with resorbable cement. A prospective randomized study using radiostereometry.

BACKGROUND AND AIMS: Internal fixation of displaced femoral neck fractures is associated with a high risk for complications such as non-union or avascular necrosis. A stable fracture fixation can improve prognosis although stability is often counteracted by weak osteoporotic bone. The aim with this study was to evaluate whether augmentation with resorbable calcium-phosphate cement could improve fracture stability during the early period after surgery as shown in biomechanical studies. MATERIAL AND METHODS: 40 ambulatory patients with a displaced femoral neck fracture were randomized to treatment with cannulated screws alone (controls) or screws combined with calcium-phosphate cement for augmentation (augmented). All patients were allowed unrestricted weight bearing after surgery. Fracture movement was measured with radiostereometry (RSA) at 1 and 6 weeks. RESULTS: At 1 week the augmented fractures had moved on average 1.9 +/- 1.0 mm while movement in the controls was 5.5 +/- 3.4 mm (p < 0.0001). The average total movement at 6 weeks was 6.9 +/- 2.9 mm and 10.9 +/- 5.1 mm, respectively (p < 0.005). Varus angulation and distal migration of the femoral head were the most common movements for both groups although augmented fractures had moved significantly less at both 1 and 6 weeks. There were no significant differences in angulation between groups around the longitudinal and transversal axes or in migration along the transverse or sagittal axes. CONCLUSION: Augmentation with calcium-phosphate cement improved the stability of internally fixed femoral neck fractures during the first six weeks after surgery, with improvement being less pronounced at six weeks compared with at one week.

Unstable trochanteric fractures augmented with calcium phosphate cement. A prospective randomized study using radiostereometry to measure fracture stability.

BACKGROUND AND AIMS: Internally fixed unstable trochanteric fractures might be difficult to retain in position during healing. Secondary displacement might lead to malunion and poor functional result. The aim with this study was to measure whether augmentation with resorbable calcium-phosphate cement could improve fracture stability as shown in biomechanical studies. MATERIAL AND METHODS: 26 ambulatory patients with an unstable trochanteric fracture were randomized to treatment with a sliding screw device alone (Controls) or the same device combined with calcium-phosphate cement for augmentation (Augmented). All patients were allowed unrestricted weight bearing after surgery. Fracture movement was measured with radiostereometry (RSA) at 1 and 6 weeks and at 6 months. RESULTS: Two patients died during the study period due to unrelated causes and another three were excluded due to technical problems with the RSA in two and concomitant illness in one. 21 patients (11 Augmented and 10 Controls) were followed according to the study protocol. At 1 week the augmented fractures had moved on average 1.9+/-1.7 mm while movement in the controls was 4.0+/-2.4 mm (p < 0.05). The average total movement from the day after surgery until 6 months, when all fractures had healed, was 7.8+/-6.2 mm for the augmented fractures and 13.2+/-4.3 mm for the controls (p < 0.05). Varus angulation was the most pronounced rotational movement for both groups although augmented fractures revealed less varus angulation compared with controls at all time points. Rotation around the longitudinal and transversal axes were small with no significant differences between treatment groups. CONCLUSION: Augmentation with calcium-phosphate cement improved the stability of unstable trochanteric fractures fixed with a sliding screw device. The improvement was most pronounced for varus angulation and lateral and distal migration of the head and neck fragment.

Normal hepatic vitamin-D metabolism in icteric primary biliary cirrhosis associated with pronounced vitamin-D deficiency symptoms.

The intestinal absorption and hepatic metabolism of vitamin D were studied in a woman with icteric primary biliary cirrhosis (PBC) complicated by pronounced bone pain and muscle weakness due to vitamin-D deficiency. The patient had a markedly reduced intestinal absorption of vitamin D, while the 25-hydroxylation of this vitamin was found to be normal despite the presence of longstanding icterus. The malabsorption of fat-soluble compounds secondary to the cholestasis was probably further impaired by several years of cholestyramine treatment. Administration of 1.25-(OH)2D3 increased intestinal calcium absorption, normalized serum calcium and increased bone mineral content of the proximal tibia. Furthermore, drastic improvement of muscle weakness and relief of bone pain were observed. It is recommended that repeated measurements of serum 25-(OH)D should be carried out in patients with PBC, and especially in those treated with cholestyramine. In certain vitamin D deficient patients, studies using radio-labelled vitamin D may provide clinically valuable information as to the exact site of the underlying disturbances.

Detoxification of lignocellulose hydrolysates with ion-exchange resins.

Lignocellulose hydrolysates contain fermentation inhibitors causing decreased ethanol production. The inhibitors include phenolic compounds, furan aldehydes, and aliphatic acids. One of the most efficient methods for removing inhibiting compounds prior to fermentation is treatment of the hydrolysate with ion-exchange resins. The performance and detoxification mechanism of three different resins were examined: an anion exchanger, a cation exchanger, and a resin without charged groups (XAD-8). A dilute acid hydrolysate of spruce was treated with the resins at pH 5.5 and 10.0 prior to ethanolic fermentation with Saccharomyces cerevisiae. In addition to the experiments with hydrolysate, the effect of the resins on selected model compounds, three phenolics (vanillin, guaiacol, and coniferyl aldehyde) and two furan aldehydes (furfural and hydroxymethyl furfural), was determined. The cation exchanger increased ethanol production, but to a lesser extent than XAD-8, which in turn was less effective than the anion exchanger. Treatment at pH 10.0 was more effective than at pH 5.5. At pH 10.0, the anion exchanger efficiently removed both anionic and uncharged inhibitors, the latter by hydrophobic interactions. The importance of hydrophobic interactions was further indicated by a substantial decrease in the concentration of model compounds, such as guaiacol and furfural, after treatment with XAD-8.

Influence of lignocellulose-derived aromatic compounds on oxygen-limited growth and ethanolic fermentation by Saccharomyces cerevisiae.

Phenolic compounds released and generated during hydrolysis inhibit fermentation of lignocellulose hydrolysates to ethanol by Saccharomyces cerevisiae. A wide variety of aromatic compounds form from lignin, which is partially degraded during acid hydrolysis of the lignocellulosic raw material. Aromatic compounds may also form as a result of sugar degradation and are present in wood as extractives. The influence of hydroxy-methoxy-benzaldehydes, diphenols/quinones, and phenylpropane derivatives on S. cerevisiae cell growth and ethanol formation was assayed using a defined medium and oxygen-limited conditions. The inhibition effected by the hydroxy-methoxy-benzaldehydes was highly dependent on the positions of the substituents. A major difference in inhibition by the oxidized and reduced form of a diphenol/quinone was observed, the oxidized form being the more inhibitory. The phenylpropane derivatives were examined with respect to difference in toxicity depending on the oxidation-reduction state of the gamma-carbon, the presence and position of unsaturated bonds in the aliphatic side chain, and the number and identity of hydroxyl and methoxyl substituents. Transformations of aromatic compounds occurring during the fermentation included aldehyde reduction, quinone reduction, and double bond saturation. Aromatic alcohols were detected as products of reductions of the corresponding aldehydes, namely hydroxy-methoxy-benzaldehydes and coniferyl aldehyde. High molecular mass compounds and the corresponding diphenol were detected as products of quinone reduction. Together with coniferyl alcohol, dihydroconiferyl alcohol was identified as a major transformation product of coniferyl aldehyde.