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Polyethylene wear is a major cause of aseptic loosening of knee endoprostheses. With the aim of minimizing this mechanical wear, we stretch-modified the structure of polyethylene. From plates of UHMWPE, stretched PE samples were produced under defined conditions, and subsequently submitted to friction tests in a fluid environment (cycles 5 x 10(5), frequency 1.5 Hz, load 500 N, contact stress 10 MPa). After load testing, the stretched samples revealed a 70% reduced wear rate in comparison with non-stretched samples. Microscopic examination (light microscopy, scanning electron microscopy) showed abrasive scratches in all test samples, but only in the non-stretched specimens were signs of pitting found. Translating these results to unidirectional tractive rolling on the tibial plateau in the knee joint suggests that a significant reduction in polyethylene wear can be expected. However, further experimental investigations need to be carried out to confirm this highly promising possibility.

Aim: Low back pain ranks high among the reasons for physician office visits and is costly in terms of medical treatment. A number of studies have shown that low back pain patients have significantly lower trunk strength when compared with healthy controls. The working hypothesis at the beginning of the 1990's was that low back pain patients could be treated effectively using lumbar extension exercise., Method: 21 papers and abstracts reporting on lumbar extension training are rated. Validation was performed for each paper according to the internationally accepted system of the American Association of Spine Surgery in types A-E., Results: 1100 cases from 21 publications and abstracts dealing with lumbar extension training were evaluated. We did not find a single type A study in our search. The clinical outcome of the studies was a reduction of pain, improvement of range of motion, improvement of spinal condition and of the lumbar extension strength., Conclusion: Prospective, randomized, controlled studies with long-term results should help to delineate further the role of isolated lumbar extension exercise for the treatment of low back pain and to test the efficacy compared to other methods of care.

Aim: The pigmented vilionodular synovitis (PVNS) is a tumour like disease of unknown origin that often shows recurrence. The pathogenesis is still unknown and therefore the question of the right therapy is not resolved., Material: With a case report of a patient with recurrence after two arthroscopic synovectomies, PVNS is discussed against the background of the clinical, histological, and radiological features., Results: We performed an open synovectomy and cystic lesions in both condyles of the femur and proximal tibia were filled with homologous and autologous cancellous bone. Three months later the patient had no pain and the bone density in the former cystic lesions was appropriate., Discussion: The pathogenesis is still unknown. Diagnosis often is obtained much too late due to missing specific symptoms. PVNS occurs in local forms as well as in a diffuse growth pattern. Recurrence rates of up to 78% are very high. Besides arthroscopic and open synovectomy, the treatment with radiosynoviorthesis must be considered. Depending on the growth pattern, the tumour masses, and the affected joint, the therapy has to be chosen very carefully and sometimes different forms have to be combined if a recurrence--free result is to be achieved.

Aim: In the study we evaluated the effectiveness of intraarticular injected hyaluronic acid (Hyalart) with regard to the changes in the parameters maximal isokinetic muscle strength, total work, pain at rest, and pain under toad., Method: We examined 43 patients with osteoarthritis in both knee joints (Kellgren II or II according to X-ray) in right/left comparison. We used the isokinetic system Cybex 600 for measuring the maximal isokinetic muscle strength and the total work. We used the visual analog scale for the pain. The evaluated parameters were measured before and after a 5-week treatment phase with 5 intraarticular injections (one injection per week with 20 mg hyaluronic acid)., Results: In knees treated with hyaluronic acid the mean peak torque of the knee extensor was 57 +/- 26.15/32 +/- 19.63 Nm vs. 77.17 +/- 32.54/47.83 +/- 21.43 Nm after (p < 0.01), the mean peak torque of the knee flexor was 40.44 +/- 21.58/22.89 +/- 16.64 Nm vs. 53.55 +/- 24.26/34.05 +/- 17.37 Nm after treatment (p < 0.01) at the angular velocities of 60 degrees/s and 180 degrees/s. Significant differences (p > 0.01) between treated and untreated knee were found for total work of the extensor and flexor of the knee. The pain at rest decreased from 3.83 +/- 1.72 cm to 1.36 +/- 1.42 cm and the pain under load decreased from 7.57 +/- 1.34 cm to 3.75 +/- 1.32 cm in the treated knee group (p < 0.01)., Conclusion: The intraarticular injection of hyaluronic acid is effective and safe in the treatment of patients with gonarthrosis. The treatment resulted in a functional improvement of the knee joint and had a good pain lowering effect in patients suffering from gonarthrosis.

The aim of this study was to work out the cross-sectional imaging characteristics of desmoplastic fibroma (DF). In 3 patients with histologically proven DF, the imaging characteristics obtained with cross-sectional techniques were reviewed retrospectively. Radiographs and CT scans were available in all patients, and plain and contrast-enhanced MR examinations in 2 patients. Compared with conventional radiographs, CT allowed more accurate assessment of the extent of bone destruction including cortical breakthrough and articular invasion. Intramedullary tumor growth and soft tissue extension was best detected with MRI. Apart from heterogeneity on MR images, DF displayed nonspecific low signal intensity on unenhanced T1-weighted images and an intermediate to high signal intensity including areas of low intensity on T2-weighted images. Desmoplastic fibroma showed a distinct, inhomogeneous gadolinium enhancement. Although cross-sectional imaging features of DF are nonspecific, some MR characteristics, such as inhomogeneous contrast enhancement and the presence of low-intensity regions on T2-weighted images, are helpful in determining the differential diagnosis. Cross-sectional imaging of DF is useful for local staging of the tumor because it provides valuable information about the extent of bone destruction as well as medullary and extraosseous spread.

The aim of this study was to report results of prophylactic spinal stabilization in patients with Duchenne muscular dystrophy. There is still debate regarding the ideal instrumentation. A prospective study of a consecutive series of 31 patients stabilized with the ISOLA system from D2 to S1 will be presented. The mean follow-up was 22 months (range, 1-60 months). The evaluation of the Cobb angle and pelvic obliquity revealed the following: 1) Cobb angle: preoperation, 48.6 degrees (range, 22-82 degrees); postoperation, 12.5 degrees (range, 0-30 degrees); follow-up, 12.5 degrees (range, 0-42 degrees); and 2) pelvic obliquity: preoperation, 18.2 degrees (range, 3-40 degrees); postoperation, 3.8 degrees (range, 0-13 degrees); follow-up, 5.1 degrees (range, 0-14 degrees). Spinal stabilization with the ISOLA system was found to be a suitable treatment for scoliosis owing to Duchenne muscular dystrophy. It should be carried out after loss of ambulation as soon as a progressive curve of more than 20 degrees is documented. The complication rate was found to be high.

Fifty-one patients with septic arthritis of the knee were reviewed retrospectively. Twenty-seven patients had been treated by arthroscopic lavage and debridement, 24 patients by open arthrotomy with subtotal synovectomy. The patients were staged according to the duration of preoperative symptoms and to the intraoperative spread of the inflammatory process. With early onset of therapy (less than 5 days) and without osseous involvement arthroscopic treatment led to an effective resolution of infection with better functional results than open arthrotomy.

The transplantation of human allograft for restoration and filling of cortical bone defects is well known. Our aim was an experimental investigation of the mechanical stability of the often used femoral head spongiosa depending on the caliber and extent of the allograft. To evaluate the orientation of the trabecular structures of the femoral head and relate this data to its mechanical properties, morphometric studies were combined with mechanical tests of cancellous bone specimens. The mechanical examination of the allograft was done following the compression test according to DIN 50106. We examined 36 human unfixed hip joint spongiosa cylinders with a height of 11 mm and a diameter of 24 mm. We took three specimens from each femoral head. We compressed the allograft at a constant velocity of 0.017 mm/sec. We calculated the maximum compression strength, the yield point and the Young's modulus. We also examined 12 parallelepipedic specimens with (17 x 17 x 51 mm) for morphometric analysis and loading in the direction of the primary compressive group (PCG), as well as perpendicular loading and at an angle of 45 degrees. We found divergent mechanical stabilities. None of the femoral heads showed comparable compressive strength. There was no position dependency of the strength of the samples. No relation between optical appearance and strength was found. We found a value for the lower compressive strength, which can be used for calculation as a basic value for safe constructions. Furthermore we tested the well known dependence of strength on the direction of the trabecular structure. We found a strong relationship between strength and load direction on the preferred direction of the trabecular structure. The sole recommendation resulting from our investigations is to rely on the lowest compressive strength for all preoperative planning. Relying on higher compressive strength by using the theoretical predicted areas of higher strength is hazardous since we found no correlation between position of sampling and strength. The size of our samples is important, because of the fact that different sizes of the samples might cause different failure mechanisms in the samples. The preparation of the femoral head spongiosa should be done according to the primary compressive group of the trabecular structure.

Pseudoachondroplasia is an inherited skeletal dysplasia with short-limbed dwarfism and early onset of osteoarthritis. A 29-year-old pseudoachondroplastic woman presented with progressively painful hips secondary to severe osteoarthritis of both joints, so that total joint replacements were necessary to restore her mobility and quality of life. The implants inserted had to be specifically manufactured in accordance with the individual geometry and reduced bone size. In addition, the implants mechanical resistance to dynamic loading conditions had to be tested prior to total hip replacement surgery.

Purpose: In a meta-analysis of the literature we evaluated the present knowledge of the material properties of cortical and cancellous bone to answer the question whether the available data are sufficient to realize anisotropic finite element (FE)-models of the proximal femur., Material and Method: All studies that met the following criteria were analyzed: Young's modulus, tensile, compressive and torsional strengths, Poisson's ratio, the shear modulus and the viscoelastic properties had to be determined experimentally. The experiments had to be carried out in a moist environment and at room temperature with freshly removed and untreated human cadaverous femurs. All material properties had to be determined in defined load directions (axial, transverse) and should have been correlated to apparent density (g/cm(3)), reflecting the individually variable and age-dependent changes of bone material properties., Results: Differences in Young's modulus of cortical [cancellous] bone at a rate of between 33% (58%) (at low apparent density) and 62% (80%) (at high apparent density), are higher in the axial than in the transverse load direction. Similar results have been seen for the compressive strength of femoral bone. For the tensile and torsional strengths, Poisson's ratio and the shear modulus, only ultimate values have been found without a correlation to apparent density. For the viscoelastic behaviour of bone only data of cortical bone and in axial load direction have been described up to now., Conclusions: Anisotropic FE-models of the femur could be realized for most part with the summarized material properties of bone if characterized by apparent density and load directions. Because several mechanical properties have not been correlated to these main criteria, further experimental investigations will be necessary in future.

All biomaterials used for total joint surgery are subjected to wear mechanisms. Morse taper junctions of modular hip revision implants are predilection sites for both fretting and crevice corrosion, dissociation and breakage of the components. The aim of this study is to quantify wear and study metallurgical changes of Morse taper junctions of in-vitro and in-vivo loaded modular revision stems. Three modular revision stems (MRP-Titan, Peter Brehm GmbH, Germany) were loaded by a servohydraulic testing machine. The loads and conditions used exceeded by far the values required by ISO-standard 7206. The tests were performed with maximum axial loads of 3,500 N to 4,000 N over 10-12 x 10(6) cycles at 2 Hz. Additionally, the female part of the taper junctions were coated with blood and bone debris. The free length of the implant was set to 200 mm. One other MRP stem was investigated after retrieval following 5.5 years of in-vivo use. All contact surfaces of the modular elements were assessed by visual inspection, optical microscopy and scanning electron microscopy (SEM). The degree of plastic deformation of the male part of the morse taper junction was determined by contouroscopy. None of the morse taper junctions broke or failed mechanically. Corrosion and wear affected all tapers, especially at the medial side. The retrieved implant showed no cracks and the amount of debris measured only one third of that for the stems tested in-vitro. The present retrieval and laboratory investigations have proven, that the morse taper junctions of the MRP-titanium stem are stable and resistant to relevant wear mechanisms. The longevity of the junctions for clinical use is given. If an optimal taper design is selected, the advantages of modular femoral components in total hip revision arthroplasty will outweigh the possible risks.

We present the early results of 142 uncemented femoral stem revisions using the modular MRP-Titan system. There were 70 cases with marked preoperative femoral bone defects (Paprosky type 2C and type 3); and bone grafts were used in 31 cases. At a mean follow-up of 2.3 years five cases were re-revised due to dislocation and two due to aseptic loosening. The mean Harris hip score improved from 37.4 preoperatively to 92.4. In 122 cases progressive bone regeneration on X-ray was seen; and no further osteolysis was observed.

Fifty-nine patients with spondylodiscitis (SD) of the thoracic and/or lumbar spine were followed-up clinically and radiologically [X-ray, computed tomography (CT), magnetic resonance imaging (MRI)] over a mean time of 2.2 years (1-6.5 years). All patients without abscess formation (n = 35) were treated conservatively. Out of the group with abscess formation (n = 24) 6 patients were also treated conservatively, 11 were drained under CT control and 7 were operated. At time of diagnosis, "signs of florid inflammation" were seen in 60% of the roentgenograms, in 93% of the CTs and in all of the MRls. The sensitivity to differentiate between SD with and without abscess formation was 85% by MRI and 69% by CT. "Signs of regressive inflammation" and "signs of increasing osseous consolidation", essential facts for starting remobilization, could first be seen using CT 6 weeks after onset of therapy. Using MRI these signs were seen with a considerable delay at 12 weeks. Clinically, only 3 of the 59 analyzed patients developed recurrent SD. In conclusion, MRI is the radiological method of choice for establishing the diagnosis of SD, in particular with regard to differentiating between cases with and without abscess formations. In contrast, CT is superior for performing success control after treatment. Therapeutically, conservative, minimal-invasive and operative procedures are not rival but rather complementary.

In a prospective study C-reactive protein (CRP) and interleukin-6 (IL-6) measurements were taken serially in 30 patients before and after 20 total hip arthroplasties (THR) and 10 total knee arthroplasties (TKR). There were no peri- and postoperative complications. Postoperatively the IL-6 serum concentration increased rapidly and peaked 6 h postoperatively at maximum levels (399+/-140 pg/ml). There was a mean half-life of 15 h and thereafter a rapid return to normal concentrations. In comparison, the postoperative CRP concentration rose more slowly and reached maximum levels (138+/-54 mg/l) on the second postoperative day. There was thereafter a slow descent with a mean half-life of 62 h. There was no significant difference between the patients with THR and those with TKR (P>0.05). IL-6 is therefore a superior marker for the inflammatory phase after THR and TKR.

Introduction: Early diagnosis of isthmic lumbar spondylolysis cannot always be established on plain radiographs and CT scans, only. In the case presented here, magnetic resonance imaging (MRI) showed typical bone marrow changes in T1- and T2-weighted images, even at an early stage., Case: A 11-year old female judoka complained of deep lumbar pain with local tenderness to pressure at L3 to S1. Clinically, there was no neurologic deficit. Conventional x-ray showed no abnormalities. In contrast, MRI revealed a locally ill-defined bone marrow oedema in both pars interarticularis of the 5th lumbar vertebra. This was interpreted as the typical MR-tomographic feature of occult stress fracture, which has to be seen as early evidence of isthmic spondylolysis. Complete restitution was achieved after conservative treatment., Conclusion: In early spondylolysis--presented here in form of a case report--, changes of MR signal intensity in the pars interarticularis may be detected, even before fracture lines are to be seen on plain radiographs. Further studies are necessary to confirm MRI to be the method of choice for early diagnosis.

Purpose: The hydrolytic degradation of the implant-cement interface has to be seen as the main reason for aseptic loosening of cemented total hip replacements. Therefore, a new method of conditioning the metallic surface was developed in order to achieve a hydrolytic-resistant bound stability between the implant and bone cement. Preliminary experimental data on test bodies are presented here., Method: The metallic surface of 6 pairs of cylindrical test bodies each (CoCr-alloy, circular testing surface with O 6 mm) were conditioned by the method of silicoating/silanisation to gain a covalent coupling with the applied bone cement. In order to examine the initial stability and the hydrolytic resistance of the metal-cement compound, these pairs of surface-conditioned test bodies (SCT) as well as a reference series of surface-unconditioned test bodies (SUT) were immersed for 0, 30, 90, 150 days (d) in moisture environment (physiological saline solution, 37 degrees C) after coupling with bone cement. The adhesive strength of the test bodies-(bone cement-compounds) were determined by tensile tests on an universal testing machine (Typ Z030, Zwick, Ulm) with gimbal suspension., Results: At time 0 d (that was without immersion of the test bodies) the mean maximum tensile bond strength of the SCT-cement-compounds was 39.5 MPa (SD +/- 4.7 MPa) and that of the SUT-cement-compounds 37.1 MPa (SD +/- 7.3 MPa) (p = 0.575). After immersion the tensile bond strength of the SUT-cement-compounds significantly decreased to an average of 13.5 MPa (SD +/- 2.7 MPa) (30 d), 10 MPa (SD +/- 1.7 MPa) (90 d) and 12.3 MPa (SD +/- 1.4 MPa) (150 d) (p < 0.01). In contrast, the SCT-cement-compounds showed a nearly unchanged high mechanical stability with tensile bond strength values of 37.0 MPa (SD +/- 4.9 MPa) after 30 d, 36.1 MPa (SD +/- 5.0 MPa) after 90 d und 30.2 MPa (SD +/- 4.7 MPa) after 150 d (p > 0.01)., Conclusions: With reservation as to further in vitro and in vivo investigations the increased hydrolytic stability of the metal-cement-bound of surface-conditioned CoCr-alloy test bodies promises an improvement of the long-term stability of cement total joint replacements.

Several methods have been described in the literature in order to analyze migration of femoral hip implants in conventional radiographs. However, no measurements were done regarding the potential errors inherent in such unstandardized radiographs of daily routine. In order to quantify this lack of reproducibility, we carried out experimental examinations with radiographs of a hip revision prosthesis, where different variables of technical X-ray conditions and femoral positions were changed. All radiographs were analyzed with a computer-assisted processing system by different procedures. At first, the radiographs were calibrated geometrically. Then, particular reference distances between defined points of the implant and cortical bone structures were analyzed quantitatively. The error of the axial migration analysis was up to 11.11 mm concerning different femoral positions, up to 8.29 mm in the case of different source-to-film distances and up to 2.21 mm due to different lateral localizations of the central X-ray focus. Significant errors for the migration analysis in the transverse and rotational planes were only found under conditions of varying the femoral position, and not under different technical X-ray conditions. From these experimental results, we derived the following criteria to minimize failure in a quantitative radiographic migration analysis: (1) the patient's leg has to be placed into an antirotation device to ensure identical object position; (2) the same source-to-film distance has to be used; (3) the central X-ray focus has to be localized on the center of the film-cassette; (4) film-screen systems should be of the same type and size; (5) the object has to be placed in the same position as in previous radiographs. As a conclusion, only if these standardization criteria are respected in the daily routine of conventional radiographs will an effective and meaningful use of migration analysis systems be possible to prove or to exclude mechanical failure of femoral hip implants in prospective longitudinal follow-up series.

Purpose: Purpose of the study was to summarize the current scientific knowledge of the interaction between rehabilitative procedures and the periprosthetic bone remodeling processes in the early postoperative phase of total hip arthroplasties., Method: In a comprehensive review of the international literature we analysed the interdependence between osseointegration, primary implant stability, relative micromotion of implant versus bone, and joint loading forces during mobilisation or physiotherapy. Accordingly, guidelines for the rehabilitation of cemented as well as cementless hip arthroplasties were established in order to eliminate factors disturbing prosthetic integration and hence provide for the best long-term stability of the implanted prosthesis possible., Results: Osseointegration of cementless implants is impossible if relative micromotions exceed > 150 microns. Furthermore, torsional stresses (i.e. alternate climbing of stairs, rising from seated position without arm support) will destabilize uncemented femoral shaft implants. Cemented prostheses may be loaded with full body weight. Uncemented implants should be loaded only partially for at least 6 weeks. Loadings of the hip joint with more than twice the body-weight (i.e. walking without crutches, physical exercise against high resistances or long levers) are to be avoided for 3 months. The transition from the three-points walking to the two-points walking technique depends particularly on the conditions of the muscles stabilizing the hip joint., Conclusion: The rehabilitation of patients after total hip arthroplasty has to be brought into line with the changed biomechanical situation, the particulars of the implants and the individual requirements of the patients.

Purpose: For patients with prostate cancer (CaP) the proof of osteoblastic bone metastases is decisive regarding the prognosis as well as the therapeutical concept. To evaluate the efficiency of skeletal alkaline phosphatase (SAP) as staging marker for bone metastases in prostate cancer, SAP was measured in CaP-patients with and without bone metastases compared with prostate-specific antigen (PSA) as the marker of choice till now., Method: 73 patients with histological proven, but still untreated CaP were entered into the study. After staging the patients were divided into 3 groups: group I: patients with CaP and bone metastases (n = 21), group II: patients with locally advanced CaP without bone metastases (n = 26), group III: patients with clinically localized CaP without bone metastases (n = 26). Serum concentration for SAP and PSA were determined using radioimmunassay. As reference range we defined serum concentrations for SAP < 19 ng/ml and for PSA < 100 ng/ml., Results: 71% of the patients with bone metastases (group I) showed elevated SAP and PSA serum concentrations. In contrast, patients without bone metastases (group II + III) have normal SAP-values (<19 ng/) and in 19% of the cases elevated PSA-values (>100 ng/ml). This resulted in a sensitivity and specificity of 71% and 100% for SAP and 71% and 81% for PSA. The positive predictive value for osteoblastic bone metastases was 100% for SAP and 60% for PSA., Conclusion: SAP is a useful staging marker in prostate cancer and can contribute for an early detection of osteoblastic bone metastases.

Purpose: Aseptic loosening of prostheses implants is the most common complication of hip replacement surgery and represents an increasing problem because of still rising numbers of primary arthroplasties. This study reviews the current scientific status of causes, diagnosis and therapeutical concepts on this theme in literature., Method: We analyzed 6,386 cases on aseptic hip revision arthroplasties published in the international literature and separated the results for cup and femoral components. On this basis we deduced some recommendations for the operative procedure in aseptic hip revision surgery., Results: The mean follow-up time of all studies was 6.8 years in the case of cemented and 4.0 years in the case of uncemented hip revision arthroplasty. As an average rate of rerevision, 15.1% was calculated for cemented cup revisions, 4.3% for uncemented cup revisions. Rates of aseptic loosening were 23.1% for cemented procedure, 8.8% for uncemented cup implants. Femoral revision implants showed an average aseptic loosening rate of 21.2% for cemented procedures and an average rate of rerevisions of 12.7%; uncemented procedures showed aseptic loosening in 4.4% of the cases and rerevision in 5.5%. For old, relatively immobile patients with reduced physical constitution, cemented reimplantation has still to be regarded as the method of choice. In young patients uncemented revision arthroplasty is to prefer both on the acetabular and the femoral side to achieve superior results with good long-term prognosis. Regarding the bony defects induced by loosening, bone grafting is recommended for cemented and uncemented reimplantation technique., Conclusion: In the case of aseptic hip revision arthroplasty, the therapeutical procedure has to be adapted especially to the age and general constitution of the patient as well as to the bony defects induced by prosthetic loosening. For the future, controlled studies should respect the initial condition of primary as well as revision arthroplasty in reporting the results.

Purpose: In the case of hip revision arthroplasty, cementless implants combined with bone grafts are increasingly used to reconstruct the acetabular bone stock. The study on hand reports about the results with the trabecular orientated cup implant of CopflHolz after 10 years of application., Method: A total of 256 hip revision arthroplasties were prospectively recorded with a mean follow-up period of 5.6 years. For the osseous augmentation of the acetabulum, autogenous bone was used in 227 cases, allogenic spongy bone in 15 cases and mixed bony materials in 8 cases. The clinical and radiological follow-ups were done after 3, 6, 12 months and then in 2-years intervals., Results: Within the 10 years follow-up 3 rerevisions must be done because of deep infection, 6 rerevisions because of aseptic loosening or primary instable fixation. The specific failure rate of the used cup implant amounts to 96.2% five years after revision arthroplasty, and 86.8% ten years after revision arthroplasty. Revealed from a radiological point of view, the transplanted spongiosa showed in 83.5% a complete osseous integration one year after the operation. Worse incorporation was conspicuous especially when allografts or mixed bone grafts were used. Clinically, a permanent improvement of motion, pain and walking ability was seen postoperatively. 91% of all follow-up patients were satisfied with the result of the revision arthroplasty., Conclusions: The trabecular orientated cup implant has proven itself worthy for cementless cup revision arthroplasty and will be an alternative to the cups and rings used up to now for the reconstruction of great acetabular bone deficiencies.