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Lymphangiosarcoma (LAS) may occur as a rare complication of primary lymphedema. A case of LAS in hereditary lymphedema of the lower extremity in a 36-year old female is reported. Despite of chemotherapy, local hyperthermia and later amputation of the extremity the patient died of progressive disease due to pulmonary metastasis. In respect to this case, the different therapeutic concepts, as reported in the literature, and their results are presented and discussed.

Background: The problem of metal sensitivity (Ni, Cr, and Co) in arthroplasty is still unsolved. To prevent the risk of allergy in cases with proved metal allergy in an epicutaneous test, a Natural Knee total knee arthroplasty, made totally from titanium (Ti-6Al-4V) and polyethylene, can be implanted. The results of this device have to be compared to the results of normal knee arthroplasty designed with a femoral component out of CrCoNi alloy. The mechanical resistance of this alloy is much higher than that of titanium, and therefore it is the standard for the femoral components of most knee-resurfacing devices., Methods: Thirty-five patients with a titanium Natural Knee were examined retrospectively after a mean follow-up of 2 years and 5 months (range 6 months to 5 years and 4 months). In comparison, 36 patients with a Genesis-I knee with a CrCoNi alloy femoral component were studied after a mean follow-up of 2 years and 4 months (range 8 months to 6 years and 2 months)., Results: In spite of the lower mechanical resistance of titanium, the Natural Knee showed better results (knee score 84.1 points, function score 77.7 points, HSS score 80.1 points, 82.9% excellent and good results) than the Genesis-I knee (knee score 80.6 points, function score 76.4 points, HSS score 76.4 points, 68.5% excellent and good results), although these differences had no statistical significance., Conclusions: The titanium Natural Knee prosthesis has proven to be a reliable knee joint replacement in the medium term.

Introduction: The two available computer-assisted surgery robotic systems consist of a preoperative planning computer workstation and an industrial robot with a high speed milling device. During the computed tomography (CT) scan of the hip and the ipsilateral knee for planning the hip arthroplasty, the patient's movements are registered by a bar that is fixed at the patient's leg along its axis. Despite the companies' claim that a high accuracy of implant position can be achieved by this method, misplacements of implants are reported in the literature., Materials and Methods: In an experimental study, a cadaver femoral bone was rotated during the CT scan strictly around this bar to simulate a rotational movement of the patient. Using the CT data, the planning of the hip stem and the following preparation of the femur by the robot was possible without detection of the patient's movements by the system. According to the system manual, the computer should stop the planning or give a warning in case of patient movement during the CT scan., Results: The postoperative CT scan of the cadaver femoral bone revealed a rotary deviation and a shift of the stem compared with the original planning, caused by the rotation during the CT scan., Conclusion: We propose using a second bar during the CT scan to detect these movements and thus avoiding misplacement of the implant.

Enchondromas are benign cartilaginous tumours and rarely transform into chondrosarcomas. Curettage is usually performed, and a low rate of complications is assumed. We analysed retrospectively data from 73 patients with enchondromas treated by curettage with respect to symptoms, therapy, complications and recurrences. All patients were treated by curettage of the tumour, in most cases followed by cancellous bone grafting. Twenty-three percent of the patients presented a complication. There were two recurrences but no malignant transformations in the follow-up period. During the same time period 29 patients with chondrosarcomas were treated, including two secondary chondrosarcomas. One had a recurrence of a benign enchondroma of the metacarpal and developed a pulmonary metastasis from a chondrosarcoma. The other was a patient with Ollier's disease who had a secondary chondrosarcoma of the radius. Malignant transformation of a solitary enchondroma to a chondrosarcoma is rare. On the other hand the complication rate of enchondroma curettage is considerable. Regular radiological follow-up of asymptomatic enchondromas may therefore be the better option.

In this retrospective study, the effect of surgical therapy on a series of 70 patients with breast cancer who were surgically treated for metastasis of the bone was evaluated. At presentation, 19 patients had one osseous lesion, 19 patients had multiple bone lesions, and 32 patients had additional visceral involvement. The surgical procedures included 60 palliative procedures, six radical resections, and four biopsies. In 14 surviving patients, the mean observation period was 35.6 +/- 40.1 months. Of the six patients with radically resected solitary bone lesions, five patients had systemic progression of the disease develop. Of the 19 patients with presumably solitary bone lesions, five currently are free of tumor. Of the 19 patients with multiple bone lesions and initially no visceral tumor spread, only two are alive. Of the 32 patients with additional visceral metastases at surgery, four are alive with the disease. For the entire group, the survival rate was 59% after 1 year, 36% after 2 years, 13% after 5 years, and 7% after 10 years. The only two independent factors that were associated with survival were the extent of the disease and the duration of symptoms from bone metastasis. These findings suggest that in orthopaedic surgery in patients with bone metastases secondary to breast cancer, wide resection is not likely to be necessary. Patients with solitary bone lesions have a 39% chance of living 5 years.

Study Design: The authors report on the clinical course of 27 consecutive patients surgically treated for solitary or multiple myeloma of the spine., Objectives: To evaluate the complications, neurologic function, life quality, and survival after decompression of the spinal cord and stabilization of the spinal column in cases of conventionally untreatable pain, neurologic impairment, or spinal instability., Summary of Background Data: The clinical outcome in patients surgically treated for multiple myeloma of the spine has not been intensively studied. Because patients with myeloma often live longer than patients with bone metastases from other malignancies, it is important that these patients be examined and treated with methods specific to their needs and not only with those typically used for patients with metastatic disease., Methods: The 27 patients had undergone the following surgical procedures: two dorsal decompressions, seven dorsal decompressions and stabilizations, 15 ventral decompressions and stabilizations, and three ventral and dorsal decompressions and stabilizations. Quality of life was measured by the Karnofsky Index, neurologic impairment according to Frankel, and survival by the Kaplan-Meier method., Results: Life quality improved from 48% before surgery to 59% 1 month after surgery and 73% in 24 survivors after the first year. Comparison of their presurgical scores with the scores obtained 1 month after surgery revealed that 18 patients had improved, five patients stayed the same, and four patients declined. After 1 year the scores of all 24 surviving patients had improved from their presurgical levels. In the 21 patients with unimpaired preoperative neurologic function, one patient developed a paraparesis as a complication of surgery, while 20 remained unimpaired until death or 1 year after treatment. All six patients with neurologic deficits improved, two of them to normal function. Pain relief was evident in 26 cases. The mean length of postoperative survival was 49.7 months. Local tumor recurrence occurred in three of 27 patients (11.1%)., Conclusion: The surgical treatment of myeloma of the spine seems to be an effective method of treatment with respect to neurologic function and life quality in selected cases.

Malignant lymphoma of bone is rare. In many cases, its diagnosis is delayed because of unspecific clinical signs and equivocal radiographs. Therapy in general is multimodal, including surgery and radio- and chemotherapy. Our objective was to demonstrate the clinical and radiological aspects of the lesion to optimize diagnostic approaches and to evaluate treatment and prognostic factors. Thirty-six patients with malignant lymphoma of bone who were surgically treated over a 15-year-period were retrospectively reviewed. Seventeen of them showed a singular bone non-Hodgkin's lymphoma (NHL) which was classified as primary lymphoma of the bone (PLB). In 13 cases, dissemination of the disease with multiple bone or visceral involvement was apparent (dNHL). Six patients suffered from bone involvement due to Hodgkin's disease (HD). Surgical treatment was indicated for diagnostic reasons or complications due to the disease. Radiation and chemotherapy were part of the oncological treatment. The patients' mean age was 57 years. The main symptom in malignant bone lymphoma in 33 patients was pain, with an average duration of 8 months. In the secondary cases, bone involvement appeared on average 57 months after the initial diagnosis. An osteolytic pattern was seen in 58% of the lesions. Soft-tissue involvement was seen in 71% of cases (PLB 80%, dNHL 73%, HD 40%) and was the primary diagnostic sign associated with this disease. The 5-year survival rate was 61% (PLB 88%, dNHL 38%, HD 50%). Multiple vs solitary bone involvement was the most significant factor in the prognosis. Extraskeletal involvement significantly decreased survival. No correlation was found between gender, age, location, or histological subtypes and survival. Bone involvement in NHL appears late in the extraskeletal disease. The clinical appearance is nonspecific, and the delay between the onset of symptoms and diagnosis is often long. One of the major radiologic signs is the existence of a soft-tissue tumor surrounding the bone with little or no bone involvement on plain films. Treatment generally is conservative, based on the stage of the disease. Local radiation with or without systemic chemotherapy should be used. The long-term survival is favorable, but dependent on the stage of the disease and the amount of bone involvement.

In principle three different types of subchondral bone cysts have been described in literature: subchondral bone cysts in osteoarthritis, subchondral bone cysts in rheumatoid arthritis and in intraosseous ganglia. However, an exact differentiation of these lesion types has not yet been defined, as there is no consensus on etiology. The aim of this study is the investigation of the etiology of cysts using finite element analysis. We assume that local cartilage lesions, i.e. the typical arthritic joint disease, can cause cysts. The results of these investigations are confirmed by clinical observations. Cartilage lesions generating stress induced microfractures may be able to explain the process of subchondral cyst formation. We assume that bone resorption is caused primarily by local overload. Moreover, local stress concentration along the border of cysts may account for their tendency to enlarge.

We treated nine consecutive patients by internal hemipelvectomy and reconstruction with custom-made megaprosthesis between 1990 and 1997. Four had a primary malignant bone or soft tissue tumour, one a recurrent benign giant cell tumour, three solitary metastatic bony lesions, and one a pelvic defect secondary to multiple revision procedures after total hip replacement. After a mean follow-up period of 62 (40-102) months five patients were still alive, including four of the eight patients with tumours. Three patients died as a result of the malignant disease, and one died of an infection related to the surgical treatment after 10-41 months. In two patients removal of the prosthesis was required due to infection, and six patients suffered various complications. One patient had an excellent outcome.

In this case, we present a 5-year follow-up of a 3-fault-affected primary leiomyosarcoma of the distal femur (spontaneous fracture treated by osteosynthesis; marginal resection; stump fracture after adequate trauma) with an extended local recurrence but without metastasis.

According to several reports in the last few years, desoxypyridinoline (Dpd) in urine increases significantly in cases of loosened arthroplasty. Therefore, this marker was suggested as useful in the diagnostics of implant loosening. In this study, the level of Dpd was determined in 69 patients with arthroplasty of the hip or the knee joint. Thirty-four of these patients received revision surgery following implant loosening. In 35 of these 69 patients, there were no clinical or radiological signs of loosening (control group). The mean age of the patients with loosened implants (22 women, 13 men) was 67.9 years and of the control group (22 women, 12 men) 66.9 years. In the group with arthroplastic loosening, as well as in the control group, 14 patients had increased levels of Dpd. There were 20 patients in the group with loosened arthroplasty and 19 patients in the control group that had normal levels of Dpd. The female patients had a mean Dpd level of 8.6 nmol/mmol creatinine (4.3-24 nmol/mmol creatinine) in the urine in cases of loosening and 10.1 nmol/mmol creatinine (2-33 nmol/mmol creatinine) in the control group. The male patients had a mean Dpd level of 7.8 nmol/mmol creatinine (3.2-19.2 nmol/mmol creatinine) in the urine in cases of loosening and 5.8 nmol/mmol creatinine (0.3-11.7 nmol/mmol creatinine) in the control group. In conclusion there was no significant increase in Dpd in patients with implant loosening compared with the control group. Furthermore, older patients often suffer from diseases causing increased bone resorption that may falsify the test results. We cannot confirm that Dpd is helpful in the diagnostics and screening of implant loosening.

Hyaline cartilage is thought to be unable to regenerate. All efforts so far--including autologous chondrocyte cell transplantation--to reconstruct cartilage defects in joints have not been totally convincing. However, mesenchymal cells are able to differentiate into chondrocytes under mechanical pressure conditions. In this study, an open porous resorbable two-layer "bioimplant" was constructed in which mechanical pressure was exerted onto mesenchymal cells when migrated into the open porous structure of the bioimplant. Differentiation of the cells into chondrocytes was thus induced. The bioimplants were implanted into the medial condyles of nine rabbits and left in place for eight or twelve weeks, respectively. In seven of these cases, cartilage formation was found, in contrary to the controls in which only connective tissue and bone had grown into the empty holes. The new bioimplants have proven their effectiveness in cartilage defect repair and might evolve in the future as a new alternative treatment of full thickness defects of joint surfaces.

Aims: Intralesional treatment of giant cell tumour (GCT) of the bone may result in a high rate of local recurrence. The introduction of local adjuvant therapy, such as cementation or phenolization, has lead to a significant reduction in recurrence rates. Due to the combined use of phenol and cementation in most studies, the effect of phenol alone is described in this study., Methods: Twenty primary and nine recurrent surgical procedures in 26 patients with GCT of the bone with a median follow-up of 61 months were reviewed retrospectively. The mean age was 33.5 years (range 13.5-76.5 years). Eighteen curettages and 11 resections were performed. For the curettages, a large bone window was cut followed by high speed burring and bone graft reconstruction. In 11 of 18 curettages and three of 12 resections, phenol was additionally applied., Results: Four patients showed pulmonary metastasis. Three of these four cases also experienced local recurrences. Three patients died due to metastatic disease. In total, five patients developed local recurrence (17.2%); three in the first 2 years and one after 4 years. Four of 18 curettages recurred (22.2%), compared to one of 11 resections (9.1%). Only one of 11 patients (9.1%) treated with curettage and adjuvant phenol recurred, whereas three of seven patients (42.9%) treated with curettage alone recurred., Conclusion: Phenolization is an effective and safe local adjuvant therapy for GCT. We did not observe any significant differences in recurrence rates for curettage, phenolization and bone grafting compared to most published results using cryosurgery or cementation alone. We recommend adjuvant phenolization in the treatment of GCT of the bone after careful curettage in applicable cases, regardless of whether additional cementation is used., (Copyright 1999 Harcourt Publishers Ltd.)

Issue: How does the sagittal stability influence the outcome in unconstrained knee arthroplasty?, Method: In order to clarify this aspect, 76 arthroplasties (10 male, 66 female, 39x gonarthrosis, 37x rheumatoid arthritis) in 61 patients with unconstrained primary knee arthroplasty were examined with a mean follow-up of 4 years. The determined values were the HSS-Score, the Knee-Society-Score, the range of motion, the flexion contracture as well as the posterior and anterior drawer with the KT 1000. The laxity was defined as the sum of the anterior and posterior drawer., Results: The mean values measured were 2.9 mm for the anterior drawer, 1.9 mm for the posterior drawer and 4.8 mm for the laxity. The total patient population reached 81.3 points in the Knee Score, 70.9 points in the Function-Score and 80.7 points in the HSS-Score. The medium range of motion was determined as 103.5 degrees, the medium flexion contracture as 3.5 degrees. For an anterior drawer of > 6 mm and a posterior drawer of < 1 mm the results deteriorated significantly. A laxity of 8-11 mm gave the best score results., Conclusion: An anterior drawer of < 6 mm, a posterior drawer of 2-5 mm and a laxity of 8-11 mm seem to be recommendable for unconstrained knee arthroplasty.

Purpose: The aim of the present study was to measure and interpret the change of the collodiaphyseal (CCD) angle and femoral anteversion after total hip replacement., Methods: We prospectively examined 52 patients with coxarthrosis, who were treated by total hip replacement. Preoperatively and postoperatively we used a standard X-ray ap view to measure the CCD angle and computerized tomography to determine the femoral anteversion. These projected angles were converted into the real angles by using the method of König and Schult., Results: On average the preoperative real CCD angle was 128 degrees (+/- 8.9 degrees) and the postoperative angle 145 degrees (+/- 4.8 degrees), preoperatively the real femoral anteversion angle was 14.1 degrees (+/- 6.9 degrees) and postoperatively 10.8 degrees (+/- 6.2 degrees)., Conclusions: The effect of the postoperative valgisation can be explained by the given CCD angle of the used femoral stem prosthesis of 140 degrees (cemented Weller II stem) and 145 degrees (cementless CLS classic stem). It is possible that due to the valgisation and the decreased offset of the femoral stem prosthesis compared to the preoperative conditions the gluteal muscles are insufficient and overloaded. It is also known that the change of the femoral anteversion from the physiological conditions causes an increase of the torsional moment. The resulting increased interface load could possibly be a reason for loosening of the femoral stem. The conclusion can be drawn that the CCD angle and the femoral anteversion should more carefully be considered by the surgeon in total hip replacement. This could be reached by an exact implantation technique and the choice of the appropriate stem prosthesis with different CCD angles.

65 knee arthroplasties in 60 patients (5 x both sided, 49 x female, 11 x male) with a Genesis Total Knee System (54 x cemented, 6 x cementless, 4 x tibial cemented/femoral cementless, 1 x tibial cementless/femoral cemented) were evaluated according to the Knee Society Score and the HSS Score with a medium follow up of 4 years und 5 months (3 years and 4 months to 5 years and 11 months). In 48 patients the diagnosis was gonarthrosis, in 17 patients it was rheumatoid arthritis. The medium postoperative Knee Score was 80.9 points, the Function Score was 73.7 points. The HSS Score obtained 80.9 points. 87.7% of the patients were excellent or good. The Genesis Total Knee arthroplasty has proved to be reliable for osteoarthritis and rheumatoid arthritis in medium term.

This study was undertaken to determine whether there is a correlation between magnetic resonance imaging (MRI) and clinical success after reconstruction of the anterior cruciate ligament (ACL). In a prospective study, 28 patients underwent clinical and MRI examination 3 to 5 years after ACL reconstruction with either the semitendinosus tendon (n = 15) or patellar ligament (n = 13). Knee stability was assessed both clinically and by KT-1000 arthrometer testing. Magnetic resonance imaging was performed with a 0.2-T dedicated system (Artoscan, Esaote, Italy) including sagittal and oblique coronal T1 and T2-weighted images. Magnetic resonance images were evaluated by two readers with regard to signal intensity and continuity of the ACL reconstruction and presence or absence of posterior cruciate ligament buckling. Knee stability and MRI evaluation were each summarized in a 6-point score. Statistical correlation was checked with the Spearman ranked correlation for testing non-normal distributed samples. Statistical testing of all patients' results together showed a significant correlation with a prediction value of 12%, indicating no significant correlation between clinical results and MRI evaluation. Separate statistical testing of the patellar ligament and semitendinosus patients' results showed no significant correlation in either group at all. Thus, no correlation between clinical stability and MRI could be established. Magnetic resonance images after ACL reconstruction using the techniques mentioned above should be interpreted with caution, as they may not relate to the clinical function of the ligament.

Persistent pain after knee arthroplasty is often caused by aseptic loosening, implant failure, unphysiological alignment (especially of the patella), infection, scars and neuroma. In a case of a 70-year-old patient pain and swelling after knee arthroplasty persisted despite three revision procedures. Surprisingly, a non-Hodgkin's lymphoma was found in femoral bone marrow histology. A metastatic non-Hodgkin's lymphoma as cause of pain and swelling after knee arthroplasty, like in this case, is rare and has not been described up to now.

A cementless total hip replacement was implanted in a 52-year-old male patient with coxarthrosis. Rapid cranial migration of the cup and ectopic ossification were subsequently observed. Five years after the original operation, revisional arthroplasty had to be performed to replace the cup. At surgery a large amount of granulomatous tissue and the tip of a deep drainage tube were found. Interposed between the polyethylene inlay and the femoral head of the prosthesis, the drain had not been visible on any of the radiographic controls. The X-ray control performed immediately after the first procedure revealed that the drain had been slung around the neck of the prosthesis stem, a procedure preferred by some surgeons. When the drain was removed, the tip must have been caught between the polyethylene inlay and the femoral head of the prosthesis. It is not clear whether the loosening of the cup was ultimately caused by the increased wear due to the presence of the drain tip. However, in light of this finding we no longer sling the drain around the prosthesis shaft, but lay it along the neck of the femoral component in the same direction as it is routed out transcutaneously.

We analyzed osseous reactions in the rabbit femoral condyle to coralline hydroxyapatite bone substitutes of various pore sizes by radiology and histology. The results were compared to bone repair of empty cavities and to integration of allografts. Spontaneous bone repair of the empty cavities took approximately 12 weeks, while integration of the cryopreserved allografts occurred after 9 weeks. However, no signs of new bone formation were found with the 200 microns pore size hydroxyapatite. In contrast, there was substantial production of bone within the 500 microns pore size implants at 12 and 26 weeks. Our results indicate that the pore size of the coralline hydroxyapatite influenced the development of bone in the implants in the cancellous bone bed of the rabbit femoral condyle. The results also show that spontaneous bone repair should be taken into consideration when the integration of implants is evaluated.

This report presents the cement-canal prosthesis. Acrylic cement is injected through the prosthesis by means of an integrated drill hole system. A second canal system within the prosthesis allows suction from the cavities, which could form in the mantle during cement injection. In an experimental study using 36 human cadaveric femora, 3 cement implantation pressures (0.5 bar, 1.0 bar and 1.5 bar) were used. A conventional cementing technique served as a control. Compared to the controls, a deeper penetration of bone cement into cancellous bone was found. Increasing cement pressure led to deeper cement penetration. The average depths of the cement layer were 2.2 mm at 0.5 bar implantation pressure, 2.9 mm at 1.0 bar and 3.9 mm at 1.5 bar. A cement mantle without voids was achieved by this technique, whereas control specimens showed a wide variability in cement defects.

Several ways for HIV inactivation in bone allografts are being discussed. These methods must be efficient, but they must not compromise biologic properties of the allografts. According to animal studies, moderate heat treatment of bone allografts in a 65 degrees C waterbath has no adverse effects on osseointegration. A clinical follow-up study of 49 patients with heat treated bone allografts was conducted. 37 patients with conventional cryopreserved allografts were included in the study as controls. Average follow-up time was 27 months. Results were evaluated by clinical and X-ray examination, using a modified radiologic score. No significant differences in the two groups were detected, except for a slight retardation in bony integration of the heat treated allografts between week 39 and 52 postoperatively. Complication rates were 11.4% vs. 10.7%. In conclusion, moderate heat treatment of bone allografts appears to be a practicable and safe method to improve safety in bone transplantation in clinical practice. In addition to the known guide lines for bone banking heat treating of allografts should be further improved in order to minimize the low remaining risk of infection which exists despite of the three months test.

A retrospective study was performed to evaluate the outcome of operative treatment of posterior cruciate ligament (PCL) lesions in 115 patients operated on between 1980 and 1989. Follow-up was possible in 89 patients at 18-124 months postoperatively (average 76 months). In 65 re-examination was possible, while 24 patients returned a questionnaire. The results of patients who were operated on in the acute state were superior to those with chronic instabilities (Lysholm 79.9 +/- 18.5 vs 64.3 +/- 22.1; Tegner 5.7 +/- 2.3 vs 4.2 +/- 2.2; instrumented posterior drawer 5.3 +/- 3.5 mm vs 5.9 +/- 3.8 mm). On the other hand, the preoperative scores of symptomatic patients with chronic instabilities (Lysholm 38.8 +/- 22.0; Tegner 2.1 +/- 1.7) were clearly lower. Extraarticular procedures (Hughston) slightly improved symptoms in posterolateral instabilities. Olecranization of the patella had no influence on the results. Interpretation of the data is difficult as there was no matched group of patients with nonoperative treatment. A reviews of the literature suggests that isolated PCL tears are best treated with conservative management. Only in cases where associated ligamentous injuries require operative treatment should PCL reconstruction be performed. Chronic posterior instabilities should be treated operatively only if the patients are severely symptomatic. However, complete restoration of knee stability was usually not achieved with the techniques presented in this paper.

The toxicity of nine chlorophenols to V79 Chinese hamster cells was determined in a survival assay which gives a direct measure of reproductive cell death by measuring single-cell cloning efficiency. Quantitative analyses of the structure-activity relationships showed that the toxicity was linearly related not only to hydrophobicity, as suggested by previous mammalian-cell studies, but also to electronic (electron-withdrawing) substituent effects. The extent electronic factors were related to the toxicity was assessed apart from their influence on partition and transport. The results suggest a relationship between the toxicity and the well-known ability of chlorophenols to induce proton permeability in membranes.

A two-dimensional biomechanical model of the juvenile hip joint was developed to describe the forces acting on the capital epiphysis and the greater trochanter apophysis in the one-legged stance. Based on anatomic femur specimens of 16 children, ranging from toddlers to teenagers, and radiographic studies of 1,350 hip joints of healthy children, we showed that the apophysis of the greater trochanter is a pressure apophysis. If the muscular forces acting on the apophysis of the greater trochanter are added, the unit sum may be considered a resultant force acting from a craniolateral direction. The trochanteric resultant force near the end of the growth period is equivalent to approximately 1.7 times body weight. The trochanteric resultant force stimulates craniolateral growth of the greater trochanteric apophysis. This mechanism is responsible for the direction of the forces exerted by the hip abductors and thus the direction and magnitude of Pauwels' hip-joint resultant, and finally influences the neck-shaft angle.

The quality of the cement layer influences the long-term survival of cemented endoprostheses. However, blood and fluid laminations within the cement layer, which can form during implantation of endoprostheses, lead to the deterioration of bone cement. Since the bone cement is the weakest part in the construction consisting of prosthesis, bone and bone cement, further weakening of the bone cement should be avoided if possible. By means of in vitro studies, three different cementing techniques were tested, measuring quantitatively the amount of fluid within the cement layer after implantation. The least amount of fluid within the cement layer was found in the cement-canal technique, and the highest amount in anterograde cement injection. Retrograde cement injection led to intermediate values.

Upon implantation of a cement-canal prosthesis in the proximal femur in total hip replacement, the bone cement is injected through the prosthesis via a system of drill holes. A second system of drill holes is used in this endoprosthesis to drain the distal femoral space as well as the cavities within the cement layer which form when the cement is being injected. Since the cement pressure is sustained until the cement has cured, substantial penetration of the cement into the cancellous bone can be achieved by using low intra-medullary cement pressures. Using cadaveric human femurs, the initial stability in the trabecular intertrochanteric region was determined in pull-out experiments for three different curing cement pressures (0.5 bar, 1.0 bar and 1.5 bar). The results were compared to corresponding controls in which a conventional cementation technique was used. With respect to the contact area of the bone/bone-cement interface, the initial stability increased by the factor 2.8 (cement-curing pressure 0.5 bar), 3.7 (cement-curing pressure 1.0 bar) and 2.9 (cement-curing pressure 1.5 bar) compared to the control group.

The surface of the proximal part of a PCA endoprosthesis stem in total hip replacement is structured with small beads to provide good conditions for bone ingrowth. The distal part of the stem has a smooth surface. For the mechanical fixation concept, this means anchorage of the proximal part and free axial mobility of the distal part of the prosthesis. We present a clinical case in which bone remodeling processes finally led to complete loosening of the prosthesis. The described mechanism of loosening could be reconstructed by radiological findings, bone scan, two digital subtraction arthrographies of the hip and by evaluation of the fibrous tissue formation around the stem after explanation. In this case, after an initial period of no measureable bone reactions, distal endosteal bone and proximal radiolucent space developed without loss of contact with the prosthesis. Later, a mechanical interruption between the proximal part of the prosthesis and bone occurred. There was no loosening of the distal part of the prosthesis at this time. Despite remarkable hypertrophy of the distal femoral bone, eventually the distal part of the prosthesis loosened so that a revision arthroplasty had to be performed. The described mechanism of loosening has not be proven to pertain to all such prostheses.

When a cement canal prosthesis is used as the femoral component in total hip replacement (THR), the penetration depth of the bone cement can be varied according to the cement implantation pressure. Using experimental data which give a relation between the pressure applied to the cement at implantation and the resulting shape of the cement layer, a three-dimensional finite element study was performed to calculate the stress distribution at the bone/bone cement interface. The calculations show that the interface stresses increase with increasing depth of penetration by the cement layer. The explanation of this effect is that as the bone cement penetrates further into the cancellous bone, the cancellous bone is stiffened and can no longer act as a soft interposition between cortical bone and bone cement. From these results and from the clinical requirement that as little bone as possible be destroyed in any kind of allo-arthroplasty, we conclude that the penetration depth of bone cement into cancellous bone in THR should be minimized to the depth necessary in order to achieve sufficient initial stability of the implant. The results show that a cement-canal prosthesis meets these requirements if a cement implantation pressure of 1.0 bar is used.

The quality of cementation is of paramount importance for the long-term clinical outcome in cemented total hip replacement. Four "modes of failure" have been differentiated by various authors and correlated with the clinical findings. A finite element analysis was performed to simulate an ideally cemented femoral stem-type prosthesis as well as failure modes III (proximal anchorage of implant only) and IV (Distal anchorage of implant only). While failure mode III produces a stress distribution at the bone/acrylic cement interface, which is similar to the ideally cemented prosthesis, failure mode type IV leads to a hazardous rise of the interface stresses. This correlates well with the clinical findings given in the literature, thus validating the computer simulation used. Distal cementation only of a stem-type femoral component in total hip replacement should definitely be avoided.

A retrospective study of 148 combined acute knee injuries with anterior cruciate and medial collateral ligament injuries was performed. Follow-up included 115 patients, 95 of whom were personally examined two to six years postoperatively. Proximal anterior cruciate ligament ruptures were treated with reinsertion in 96 patients, in case of intraligamentous lesions (44 times), augmentation with the semitendinosus tendon was performed. Medial collateral ligament lesions were explored during the operation. Reconstruction of intraligamentous ruptures was performed with sutures (120 times). Distal lesions were refixed with Burri plate or staple. A modified Ellison procedure was routinely performed. Postoperative treatment was cast-free and included immediate physiotherapy using a functional brace. Between the two groups with anterior cruciate ligament reinsertion and augmentation, no significant differences were observed in subjective evaluation (Lysholm score 85 vs. 88), activity level (Tegner score 5.5 vs. 5.4) or anterior stability (KT 1000 at 89 N 6.6 vs. 6.1 mm displacement). A clear pivot shift sign was noted in two knees with reinsertion and in none of the augmented group. Medial stability was reestablished almost completely, independent of the site of lesion or the reconstruction technique (average valgus movement at 30 degrees flexion 0.7+ vs. 0.5+ on injured/contralateral side). We conclude that reinsertion of femoral anterior cruciate ligament ruptures will reestablish anterior stability in most cases, although semitendinosus augmentation appears to give slightly more reliable results. Medial stability is gained by the site-depending reconstruction techniques. Whether intraligamentous medial collateral ligament lesions can be left alone with only the anterior cruciate ligament being reconstructed, cannot be answered by this study.

Tetrachlorohydroquinone, a metabolite of the fungicide pentachlorophenol, induced significant dose-related increases in micronuclei in V79 Chinese hamster cells without exogenous metabolic activation. The lowest observed effective dose was 10 microM, where the relative survival was about 62%. At the highest dose tested, 20 microM, the relative survival was about 8% and the frequency of cells with micronuclei was about 6 times the solvent control frequency. The induction of micronuclei by tetrachlorohydroquinone was significantly inhibited by the hydroxyl radical scavenger dimethyl sulfoxide at 5% (v/v).

The genotoxicity of the rodent carcinogen 2,4,6-trichlorophenol (TCP) was studied without exogenous metabolic activation in V79 Chinese hamster cells. TCP did not induce mutation at the hprt locus to 6-thioguanine resistance or structural chromosome aberrations. However, it produced statistically significant, dose-related increases in hyperdiploidy and micronuclei. From these results it appears that TCP causes chromosome malsegregation as its major mode of genotoxic action.

The results of radiologic and clinical follow-up of 81 PCA (porous coated anatomie) hip joint prostheses implanted in our clinic between 1986 and 1988 are presented. One of the prostheses had to be explanted because of aseptic loosening after 2.5 years' implantation. Contrary to the fixation concept of the prosthesis, which requires both proximal osseointegration and free axial shifting of the distal part of the prosthesis, our follow-up radiographs showed proximal lysis of 2 mm and more as well as distal hypersclerosis of 3 mm and more in the form of endosteal bone formation in 70% of cases 3 years after implantation. On the basis of our data, the question whether these bone reactions will finally lead to aseptic loosening of the implant cannot be answered yet.

The use of bone allografts is often essential in orthopedic surgery. Strict donor screening, including HIV testing 3 months postoperatively, is mandatory before a transplant may be used. Yet these measures do not definitely rule out the possibility of HIV transmission, as there is a window period before infection is revealed by blood testing. Accordingly, there is a need for virus inactivation methods that can be used on bone allografts. As radiation treatment and chemical methods have a number of disadvantages, we chose a moderate heat treatment of 65 degrees C for a series of animal experiments. In 12 rabbit femoral condyles, moderate-heat-treated bone allografts were implanted into 6-mm drill holes. Twelve normal allografts and 12 empty drill holes served as controls. Radiologic and histological evaluation up to 12 weeks postoperatively revealed slow spontaneous bone remodeling from the rim to the center of the empty cavities. Normal deep frozen allografts were quickly intergrated after a short period of osteoclast reaction around the transplant, with occasional bone bridges between host and allograft. The examination of heat-treated allografts showed no differences to the controls, including morphologic aspects and the time course of osteointegration. Five zones of bone repair and osteointegration were distinguished. We conclude that thermal treatment of bone allografts has adverse effects on osteointegration in the rabbit femoral condyle. Thus, it may contribute to improving safety in human bone transplantation.

The excimer laser was thought to be an appropriate tool for the removal of bone cement without damaging the bone. However, due to its low ablation rate, its clinical use in total hip revision arthroplasty proved to be impossible. This experimental study was designed to evaluate the maximal ablation rate by adjusting the laser's parameters. Energy density, frequency, pulse duration, radiation area, quantity of pulses, and environmental conditions were varied in the experimental setup. Even with the best set of parameters the excimer laser was about ten times slower than, e.g., the carbon dioxide laser. The removal of 10 g bone cement takes about 1 h. Thus, complete cement removal by means of the excimer laser alone is not possible. However, selective application of the excimer laser in combination with other techniques could be discussed.

For an unconstrained bicondylar sledge knee prosthesis the mechanical load of the bony support is crucial. For a design of a tibial component of such a prosthesis with improved anatomical features allowing a complete cortical support of the rim of the prosthesis, a finite element study was performed. Stress reactions of the bone for different implantation modes were calculated. Irrespective of the bony support of the prosthesis, tensile stresses are always transferred at the interface prosthesis/bone into the bone. For a complete cortical support of the rim of prosthesis, the areas of tensile stress in the bone are closely related to areas of high compression stress. If there is cortical support of the prosthesis only on the medial side due to an undersized prosthesis, this is only of minor influence on the stress pattern in the bone. However, if there is cortical support of the prosthesis only on the lateral side, there are large areas of tensile stresses in the lateral compartment of the tibial plateau. However, tensile stress transfer in the tibial plateau must be regarded as unphysiologic and therefore unfavourable. Therefore, if intraoperatively complete cortical support of the prosthesis cannot be achieved a more medial cortical support of such a prosthesis should be preferred to a lateral cortical support.

Tetrachlorohydroquinone (TCHQ) and tetrachlorocatechol (TCC), two metabolites of the environmental mutagen and carcinogen pentachlorophenol, were tested without exogenous activation in V79 Chinese hamster cells for the induction of mutation at the hypoxanthine phosphoribosyl transferase (HPRT) locus to 6-thioguanine resistance (TGr) and at the Na/K-ATPase locus to ouabain resistance (OuaR). Treatment was for 24 h at 37 degrees C. TCHQ produced statistically significant increases in the frequency of TGr mutants. The lowest observed effective dose (LOED) was 20 microM, where the relative cloning efficiency was 63%. The relationship between the dose of TCHQ and the frequency of TGr mutants was approximately linear over the range of 0-60 microM with an estimated slope (+/- 95% confidence limits) of 1.1 +/- 0.3 mutants per 10(6) clonable cells per microM. At the highest tested dose of TCHQ, 60 microM, the relative cloning efficiency was reduced to 7%. In contrast to TCHQ, TCC was unable to induce TGr mutants at doses up to 120 microM. The relative cloning efficiency at this dose was 5%. Both TCHQ and TCC were unable to induce OuaR mutants. The results suggest that TCHQ is at least partly responsible for the genotoxic activity of pentachlorophenol. TCHQ can produce reactive oxygen species, which may cause large genetic damage such as deletions, resulting in mutation to TGr but not to OuaR.

Recent reports of fractures of the tibial component of total knee prostheses have raised the question of their long term endurance. The mechanical load for the tibial plateau consists of the two forces deriving from the condyles of the femur. As the collateral and crucial ligaments always allow a little play for the femoral and tibial components, the location of the load of the condyles on the tibial plateau is either on the medial or lateral side depending on minor disturbances during gait. For a tibial plateau with only little medullary anchorage this load pattern means an alternating induction of compression and tensile stresses for the underlying bone. This alternating stress pattern is discussed as a possible mechanism of aseptic loosening of such tibial components. For two cases of such aseptic loosening and consecutive fracture of the tibial plateau of a metal backed unconstrained sledge knee prosthesis the radiologic findings are demonstrated and correlated to the biomechanical mechanisms described. It is demonstrated that the structural endurance of the tibial plateau does not withstand the mechanical stresses of such a situation of aseptic loosening. In these cases further loosening or fracture of the tibial plateau results.

Limb-preserving resections require very careful indications; in particular, the criteria of oncologic radicality must be strictly considered. The functional results can be improved compared with those of ablative surgery, while the rate of relapse-free survival is the same. Surgical therapy for metastases of bone tumors should be performed by simple and safe procedures which allow for quick rehabilitation. The most important limb-preserving methods of operation in the treatment of primary and secondary malignant bone tumors are discussed and a few examples are presented.

The induction of mutation at the hypoxanthine-guanine phosphoribosyl transferase locus and cytotoxicities of 6 different chlorophenols (2,4- and 2,6-dichlorophenol, 2,4,5- and 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol) were examined in V79 Chinese hamster cells without exogenous metabolic activation. The chlorophenols were cytotoxic to V79 cells, but failed to produce significant increases in the frequency of 6-thioguanine-resistant mutants.