Influence of physico-chemical material characteristics on staphylococcal biofilm formation--a qualitative and quantitative in vitro analysis of five different calcium phosphate bone grafts.

Various compositions of synthetic calcium phosphates (CaP) have been proposed and their use has considerably increased over the past decades. Besides differences in physico-chemical properties, resorption and osseointegration, artificial CaP bone graft might differ in their resistance against biofilm formation. We investigated standardised cylinders of 5 different CaP bone grafts (cyclOS, chronOS (both ß-TCP (tricalcium phosphate)), dicalcium phosphate (DCP), calcium-deficient hydroxyapatite (CDHA) and α-TCP). Various physico-chemical characterisations e.g., geometrical density, porosity, and specific surface area were investigated. Biofilm formation was carried out in tryptic soy broth (TSB) and human serum (SE) using Staphylococcus aureus (ATCC 29213) and S. epidermidis RP62A (ATCC 35984). The amount of biofilm was analysed by an established protocol using sonication and microcalorimetry. Physico-chemical characterisation showed marked differences concerning macro- and micropore size, specific surface area and porosity accessible to bacteria between the 5 scaffolds. Biofilm formation was found on all scaffolds and was comparable for α-TCP, chronOS, CDHA and DCP at corresponding time points when the scaffolds were incubated with the same germ and/or growth media, but much lower for cyclOS. This is peculiar because cyclOS had an intermediate porosity, mean pore size, specific surface area, and porosity accessible to bacteria. Our results suggest that biofilm formation is not influenced by a single physico-chemical parameter alone but is a multi-step process influenced by several factors in parallel. Transfer from in vitro data to clinical situations is difficult; thus, advocating the use of cyclOS scaffolds over the four other CaP bone grafts in clinical situations with a high risk of infection cannot be clearly supported based on our data.

Biofilm formation by staphylococci on fresh, fresh-frozen and processed human and bovine bone grafts.

Biofilm formation is a multi-step process influenced by surface properties. We investigated early and mature biofilm of Staphylococcus aureus on 4 different biological calcium phosphate (CaP) bone grafts used for filling bone defects. We investigated standardised cylinders of fresh and fresh-frozen human bone grafts were harvested from femoral heads; processed humanand bovine bone grafts were obtained preformed. Biofilm formation was done in tryptic soy broth (TSB) using S. aureus (ATCC 29213) with static conditions. Biofilm density after 3 h (early biofilm) and 24 h (mature biofilm) was investigated by sonication and microcalorimetry. After 3 h, bacterial density was highest on fresh-frozenandfresh bone grafts. After 24 h, biofilm density was lowest on freshbone grafts (p < 0.001) compared to the other 3 materials, which did not differ quantitatively (p > 0.05). The lowest increase in bacterial density was detected on fresh bone grafts (p < 0.001). Despite normal shaped colonies, we found additional small colonies on the surface of the fresh and fresh-frozen samples by sonication. This was also apparent in microcalorimetric heat-flow curves. The four investigated CaP bone grafts showed minor structural differences in architecture but marked differences concerning serum coverage and the content of bone marrow, fibrous tissue and bone cells. These variations resulted in a decreased biofilm density on freshand fresh-frozenbone grafts after 24 h, despite an increased early biofilm formation and might also be responsible for the variations in colony morphology (small colonies). Detection of small colony variants by microcalorimetry might be a new approach to improve the understanding of biofilm formation.

[An unexpected case of lower left-side abdominal pain. Acute reactivation of chronic osteomyelitis]. / Eine unerwartete Ursache von linksseitigen Unterbauchschmerzen. Akute Reaktivierung einer chronischen Osteomyelitis.

Osteomyelitis caused by S. aureus can be reactivated after decades. Our patient presented with an acute episode of lower left-side abdominal pain and subfebrile temperature due to a reactivation of a S. aureus osteomyelitis in the iliac bone which was initially misinterpreted as a sigma diverticulitis. Diagnosis was established by conventional radiographs as well as CT and MR scans. Harvesting the responsible germ by a bone biopsy prior to therapy is mandatory. Therapy consists of a surgical debridement combined with a long-lasting antibiotic therapy. Relapse can be found after long latency.

The histology around the cemented Müller straight stem: A post-mortem analysis of eight well-fixed stems with a mean follow-up of 12.1 years.

The aim of this study was to obtain detailed long-term data on the cement-bone interface in patients with cemented stems, implanted using the constrained fixation technique. A total of eight stems were removed together with adjacent bone during post-mortem examinations of patients with well-functioning prostheses. Specimens were cut at four defined levels, contact radiographs were obtained for each level, and slices were prepared for histological analysis. Clinical data, clinical radiographs, contact radiographs and histological samples were examined for signs of loosening and remodelling. The mean radiological follow-up was 9.6 years and all stems were well-fixed, based on clinical and radiological criteria. Contact radiographs revealed an incomplete cement mantle but a complete filling of the medullary canal for all implants. Various amounts of polyethylene particles were evident at the cement-bone interface of seven stems, with no accompanying inflammatory reaction. Cortical atrophy and the formation of an 'inner cortex' were confirmed in six of eight stems by contact radiographs and histology, but were only visible on two clinical radiographs. Our results confirm that a complete cement mantle is not essential for the survival of Müller straight stems into the mid term, and support our hypothesis that no benefit to long-term survival can be expected from modern cementing techniques.

[Pregnancy-associated osteoporosis. Differential diagnosis of "common" musculoskeletal pain during pregnancy and lactation]. / Schwangerschaftsassoziierte Osteoporose. Differentialdiagnose des "banalen" muskuloskelettalen Schmerzes in Schwangerschaft und Stillzeit.

Musculoskeletal pain during pregnancy and lactation is a common finding. Differential diagnoses range from"normal" findings to disturbances in bone metabolism and pregnancy-associated osteoporosis (PAO). Imaging options are limited due to pregnancy, and laboratory diagnostics are time-consuming. Treatment of PAO with physiotherapy, pain killers and substitution of vitamin D and calcium leads to a rapid recovery from symptoms.

Fixation and loosening of the cemented Muller straight stem: a long-term clinical and radiological review.

The original forged Müller straight stem (CoNiCr) has shown excellent ten- to 15-year results. We undertook a long-term survival analysis with special emphasis on radiological changes within a 20-year period of follow-up. In all, 165 primary total hip replacements, undertaken between July 1984 and June 1987 were followed prospectively. Clinical follow-up included a standardised clinical examination, and radiological assessment was based on a standardised anteroposterior radiograph of the pelvis, which was studied for the presence of osteolysis, debonding and cortical atrophy. Survival of the stem with revision for any reason was 81% (95% confidence interval (CI), 76 to 86) at 20 years and for aseptic loosening 87% (95% CI, 82 to 90). At the 20-year follow-up, 15 of the surviving 36 stems showed no radiological changes. Debonding (p = 0.005), osteolysis (p = 0.003) and linear polyethylene wear (p = 0.016) were associated with aseptic loosening, whereas cortical atrophy was not associated with failure (p = 0.008). The 20-year results of the Müller straight stem are comparable to those of other successful cemented systems with similar follow-up. Radiological changes are frequently observed, but with a low incidence of progression, and rarely result in revision. Cortical atrophy appears to be an effect of ageing and not a sign of loosening of the femoral component.

Estimation of the wear volume after total hip replacement. A simple access to geometrical concepts.

Various formulas have been proposed to calculate the volume of prosthetic wear from the penetration depth of the head as assessed on plain radiographs, based on idealized, three-dimensional geometrical models of a prosthetic hip. However, for most published formulas no (or no simple) derivation is available and not all of them are correct. We describe a simple geometrical model that allows for transparent derivation of equations for various components of prosthetic wear volume and compare the calculated volumes with those obtained from published equations. These components are: (1) a right generalized cylinder resulting from a linear shift of a half spherical part of the prosthetic head into the hemispherical cup, (2) an additional wedge that is "cut" from the cup and (3) the wear from an optional additional cylindrical portion of the cup. We emphasize that calculation of a three-dimensional wear volume from linear penetration depth should be based on a geometrical concept that is transparent and simple enough for clinical research, such as the one presented. The incorrect formula of Kabo et al. should be completely abandoned.

EBRA migration patterns of the Plasmacup with ceramic or polyethylene inserts: a randomised study.

AIM: In this prospective randomised study, the influence of different bearing materials on migration and wear was measured and their effect on the function of the artificial joint and the patient outcome was investigated. Mid-term results were recorded so that recommendations can be made on the use of certain bearings, which minimise wear and thus the danger of subsequent aseptic loosening. METHOD: Sixty-six patients met the inclusion criteria and were willing to take part in the study. These patients were randomised to 2 groups. All of them had total hip arthroplasty with implantation of a cementless Bicontact stem and Plasmacup using a cementless press-fit technique. Thirty-five of these patients were given a ceramic-ceramic bearing and 31 patients a ceramic-polyethylene bearing (gamma sterilised/nitrogen environment). At the most recent follow-up, they underwent detailed clinical and radiological examination and evaluation by means of the Harris Hip Score, Hannover function questionnaire and single-film X-ray analysis (EBRA). RESULTS: The overall follow-up rate was 65.2 % (43 of 66) and the mean follow-up period was 8.1 (7.1 - 9.2) years. The median Harris Hip Score at the time of follow-up was 90.1 (58.7 - 99.9) points. The average Hannover function score was 87.14 % (63.9 - 100). In 4 of 66 cases (6.1 %) there was a tendency for the Plasmacup to subsidence in the first postoperative months that was slight but detectable by EBRA; however, this stopped subsequently. This primary subsidence was independent of the chosen bearing material. No significant difference in the clinical and radiological parameters was found between the two groups. CONCLUSION: The very good results with regard to the rate of loosening confirm the press-fit cup fixation concept. The study shows a similar medium-term result for the ceramic-ceramic and ceramic-polyethylene bearing so that use of both bearings can continue to be recommended. Only long-term studies with sufficiently large numbers of patients will be able to show whether significant differences can be detected between the two slide bearings with regard to wear and migration behaviour and so that a recommendation can be given to the surgeon.

[Corrective osteotomy of post-traumatic malunions and pseudarthroses in the femur using a fork plate: a prospective analysis of 23 consecutive cases]. / Korrekturosteotomien von posttraumatischen Fehlstellungen und Pseudarthrosen im Bereich des Femurs mittels Gabelplatte: Eine prospektive Analyse von 23 konsekutiven Fällen.

INTRODUCTION: The fork plate is a further development of the AO fixed-angle blade plate, which facilitates the seeding of the angle blade. In a prospective study we evaluated the applicability of the fork plate for the correction of post-traumatic malunions and pseudarthroses in the femur. MATERIAL AND METHODS: Between 01/1993 and 12/2003 a consecutive series of 23 patients were operated due to post-traumatic malunion or pseudarthrosis of the femur with an average age of 46 years at the time of surgery. The operative procedure is analogous to the one using angle blade plates. The most important surgical step, the placement of the fork instead of the blade, is more precise thanks to stepwise control with the image intensifier. RESULTS: All preexisting malunions and pseudarthroses were corrected with the fork plate as preoperatively planned. Complications not related to the implant were found in 13%, all of which resolved without sequelae. In 87% we found a bony union of the osteotomy after 3 months, and the three remaining femora healed within an additional 2-12 months without loss of the correction achieved. CONCLUSION: In all of the cases analyzed, the fork plate proved to be of value for correction of femoral malunion and pseudarthrosis. In relation to the angle blade plate, the fork plate features a modified surgical technique with the same possible indications. As a consequence this modification provides a high level of therapeutic safety even with a small number of annual operations performed.

Complications at screw removal in slipped capital femoral epiphysis treated by cannulated titanium screws.

INTRODUCTION: Various modes of fixation are proposed for the treatment of slips of the capital femoral epiphysis (SCFE). We describe our experience with the use and removal of a new, cannulated titanium screw (Asnis III, Stryker, Howmedica). PATIENTS AND METHODS: Single cannulated titanium screws had been inserted in 101 hips of 65 patients in the 3-year period from 2001 to 2003. These pins were used for in situ fixation of minor chronic slips in 41 patients and for prophylactic fixation on the contralateral side in patients with open physis in 60 patients. RESULTS: The insertion of these screws was achieved without any real problem. The mean surgical time was 25 min (13-46 min). Problems came up when we started to remove the pins. Hardware retrieval was attempted in 27 patients with 43 pins. The mean surgical time for removal was double the average time of insertion with 51 min (26-107 min). The hexagonal Allen sockets proved to be too weak to overcome the necessary torque for loosening the pin from bone and applying the reverse-cutting-force, necessary to extract the pin. Eleven patients needed extensive chiselling. Two adolescents sustained a subtrochanteric fracture 5 and 7 weeks after hardware removal. Seven pins could not be totally removed. CONCLUSION: Due to the considerable disadvantages encountered in our series we conclude that Asnis III cannulated screws should be suspended from further use in SCFE.

Subsidence pattern of a cementless straight titanium alloy femoral stem - A radiographic study with EBRA-FCA.

EBRA (Ein Bild Roentgen Analyse) is a computer-aided algorithm to assess migration of endoprosthetic components. Stem subsidence is measured in comparable radiographs, as defined by the software. Recent studies showed an improved accuracy of EBRA-FCA as compared to standard methods. For the BiCONTACT cementless femoral component, a prospective follow-up study of 250 cases has provided excellent results, with a survival rate of 97.1% after 11 years. For this migration study 93 hips with a complete radiographic follow-up (> 10 x-rays) over 120 months were included. Seventy-one stems were be measured; in 22 stems the measurement was impossible due to heterotopic ossification. Thirty-two hips (45.1%) showed initial subsidence within the first 24 months but no later, and 11 hips (15.5%) had a late onset of subsidence. In nine hips (12.7%) continuous sinking could be found. Nineteen hips (26.8%) had irregular patterns of migration. In 31.0% the overall migration was between 0.5-1mm after 120 months. Six stems (8.5%) had an absolute amount of subsidence exceeding 2mm after 120 months (one more than 3 mm). The mean subsidence was 0.2mm after three months and six months, 0.3mm after 12 months and reached 0.5mm after 10 years. EBRA-FCA is a practicable method to assess migration of the femoral component. There seems to be initial subsidence for about one half of the stems but further movements are rare, which might be a sign for osseo-integration. The radiographic findings correspond to the excellent clinical performance of this stem in long-term follow-up. (Hip International 2005; 15: 85-91).

The musculocutaneous sural artery flap for soft-tissue coverage after calcaneal fracture.

Soft-tissue defects following calcaneal fractures can be covered in a relatively easy and safe procedure. We have modified the familiar distally based sural artery flap by lifting a part of the gastrocnemius muscle. With an inferior pedicle, this musulocutaneous flap can be rotated onto the defect on the sole of the foot and on the heel. Five patients with open fractures of the calcaneus or wound necrosis after osteosynthesis were treated with this procedure. Two defects were covered uneventfully, two flaps were prepared, the rotation being done in a secondary procedure. One patient demanded further revisions, and the flap was partially lost, but the remaining defect was covered after open treatment. This new musculocutaneous sural artery flap can be used for covering even an extensive defect after calcaneal fractures and seems to be a reliable procedure. Morbidity at the donor site is low, and in the case of failure, the free flap remains an alternative.

Socket wear in bilateral simultaneous total hip arthroplasty.

A total of 51 patients with bilateral simultaneous Charnley total hip arthroplasties were studied for wear behavior. The mean observation time was 14.7 years. Fourteen hips had been revised during follow-up. The mean wear rate was 0.071 mm/y for left hips and 0.081 mm/y for right hips. There were considerable side differences for individual patients and little agreement between the wear measurements of left and right hips. Linear wear was increased in men, in patients with high body weight. Linear wear after hip arthroplasty is not side related.

Polyethylene wear and calcar osteolysis.

We have examined retrospectively the correlation between linear wear of the polyethylene socket and calcar height loss (osteolysis) in 266 patients with 410 total hip arthroplasties who were followed up for a minimum of 10 years. A positive correlation existed between wear and osteolysis. The correlation was stronger in patients with osteoarthrosis. Simultaneous bilateral hip arthroplasty showed no difference in the relationship between polyethylene wear and calcar height loss when comparing the right and left hip. There was poor correlation between calcar height loss and wear in patients with rheumatoid arthritis. Our findings support the theory that femoral osteolysis in the total hip arthroplasty is related to the amount of liberated particles generated by the wear of components. The poor correlation found in cases with rheumatoid arthritis could be related to suppression of the immune response in these patients.

Migration and wear of long-term successful Charnley total hip replacements.

We analysed in-vivo migration and wear over a long period of all-polyethylene acetabular cups which had not been affected by mechanical loosening. The selection criteria of regular radiological follow-up, good clinical outcome (Charnley score of 5 or 6), continued walking without crutches and no radiological signs of loosening of the acetabular cups were fulfilled by 25 Charnley total hip arthroplasties. Mean migration, measured by the Nunn method, was 0.6 mm in the medial and 0.2 mm in the cranial direction. The mean yearly rate of wear was 0.05 mm and 0.04 mm, with six and two cups having no detectable wear, as measured by the Livermore and Charnley-Cupic methods, respectively. The maximal detected wear was 3.7 mm. There were no changes in the rate of wear with time. Computerised Ein Bild Röntgen Analyse (single-image radiological analysis) measurements of 20 hips indicated plastic deformation of the cups. We conclude that long-term successful cups do not migrate and have a very low rate of wear which was not affected by ageing of the polyethylene. There was no evidence that polyethylene wear alone caused mechanical loosening of the cup but high rates of wear seem to have an adverse prognostic value in terms of the long-term survival of the prosthesis.

EBRA improves the accuracy of radiographic analysis of acetabular cup migration.

EBRA (Ein Bild Röntgen Analyse) is a new computerized method measuring migration and wear of the acetabular cup, suggested to improve measurement accuracy. We evaluated possible errors of measurement and compared EBRA with standard methods. 1. We did repeated measurements on a single radiograph using the same reference lines. The reliability of the input procedure with standard measurements was significantly better than repeated digitization with EBRA. 2. In a more clinical test, a group of 10 patients was studied. 5 radiographs were taken of the same patient on the same day. EBRA improved the reliability of repeated radiographic examination significantly for migration measurements in the vertical direction. 3. To assess the inter- and intraobserver variations, repeated measurements were performed on the clinical series of pelvic radiographs of 10 patients. EBRA was significantly better than standard methods. With EBRA, errors of wear and migration measurements could be reduced, as compared to standard methods. The major improvement with EBRA was found for migration measurements in the vertical direction.

Non-operative treatment versus tension-band osteosynthesis in three- and four-part proximal humeral fractures. A retrospective study of 34 fractures from two different trauma centers.

Thirty-four patients with three- and four-part proximal humeral fractures from two different trauma centres were studied retrospectively. Sixteen were treated without osteosynthesis and compared with 18 patients treated with tension-band fixation. Fracture classification and clinical examination were made by the same persons in both groups. Most of the three-part fractures healed with good pain relief and good function in daily life but often with a loss of motion. Four-part fractures often led to pain, loss of motion and of function. Conservative treatment seemed superior to tension-band fixation for three-part fractures. Four-part fractures healed with better function and range of motion after tension-band fixation.

A modular system for cemented and cementless implantation of femoral stem prostheses.

A femoral stem [BiContact, Aesculap, Germany) has been developed which is suitable for both cemented and uncemented implantation. Thus a highly standardized procedure and a standard implant for any iritraoperative finding is available. While the cemented stems have a smooth surface, the cementless implants are proximally coated with a microporous titanium plasmaspray [Plasmapore]. The strategy based on the intraoperative choice of the surgeon to use either cemented or cementless implants after bone preparation turned out to be very successful in our institution. A consecutive series of 250 cases with cemented implantation and 250 cases with uncemented implantation was analyzed in a prospective follow-up study, Pollow-up time averaged 7 years for cemented and 6.5 years for uncemented THRs. The follow-up rate was 88.7% in cases treated with cemented stems and 93.1% in cases treated with uncemented stems. The rate of aseptic loosening was 1.2% for the cemented version and 0.4-% for the uncemented stem. Radiological loosening could be observed in another 1.2% of the cemented stems and was not to be found in the uncemented cases. Our data suggest an excellent midterm stability of both the cemented and the uncemented version of the BiContact hip system. The long-term results for both the cemented and uncemented prostheses of our series are still to be evaluated.

Radiographic assessment of cup migration and wear after hip replacement.

Methods are needed for accurate measurement of acetabular cup migration and wear after hip replacement. The EBRA (Ein Bild Röntgen Analyse) method was recently introduced as computerized method for radiographic assessment of acetabular cup migration. In this study, various standard methods for measuring migration were evaluated and compared to radiostereometry (RSA), which has proved to be highly accurate. A subroutine for wear measurement was developed and added to the EBRA method. Of the standard methods, Nunn's method was the best for migration measurement and Livermore's the best for wear measurement. Measurements with EBRA were better than the standard methods. Pelvic tilt seemed to be the main source of error in measurements. The effect of pelvic tilt was evaluated experimentally. EBRA detected and excluded tilted radiographs, the errors of measurement being smaller with EBRA than with standard methods. The precision of the input procedure, repeated radiographic examination, the intra- and interobserver errors were assessed. Apart from the digital input of the data, EBRA was better than the standard methods. Normal values concerning acetabular cup migration and wear should be obtained from long-term surviving hip replacements, without radiographic signs of loosening. No method of measurement detected evidence of changes in the wear-rate and in migration over time. EBRA showed cold-flow in some cups, but did not provide additional information in the long-term. Nunn's method for migration measurements and Livermore's method for wear are recommended in clinical practice. EBRA is more accurate and should be used for studies of new implant designs that have passed the preclinical and, preferably, radiostereometric analysis. RSA is unsurpassed and is recommended for early clinical follow-up in a limited number of patients.

Polyethylene wear in Scanhip arthroplasty with a 22 or 32 mm head: 62 matched patients followed for 7-9 years.

We measured radiographic polyethylene wear in patients with Scanhip arthroplasty and no clinical or radiographic signs of loosening. The patients were divided into 2 groups according to head sizes. 32 patients (33 hips) had an implant with a 22 mm and 30 patients (34 hips) with a 32 mm head. They were followed for 7-9 years. The groups were matched for diagnosis, sex, weight, age, and time of follow-up. The mean linear wear with a 22 mm head was 1.1 mm and with a 32 mm head 1.5 mm (p 0.004), which corresponds to a yearly wear rate of 0.15 mm and 0.18 mm, respectively. The mean difference in volumetric wear was greater, 420 mm3, as compared to 1239 mm3.