[A comparison of the antiresorptive effects of bisphosphonates and statins on polyethylene particle-induced osteolysis]. / Ein Vergleich der antiresorptiven Effekte von Bisphosphonaten und Statinen auf Polyethylenpartikel-induzierte Osteolysen.

An ongoing unraveling of the molecular mechanisms in aseptic loosening of hip arthroplasty has opened up novel potential pharmacological interventions. In this study the antiresorptive effects of the bisphosphonate zoledronate and the statin simvastatin on ultra high molecular weighted polyethylene (UHMWPE) particle-induced osteolysis were compared. Two previous studies of our group based on the murine calvarial model of UHWMPE particle-induced osteolysis were pooled to form four study groups. Animals in group I (n=14) underwent sham surgery only. In groups II (n=14), III (n=7) and IV (n=7) UHMWPE particles were implanted on the calvariae. Animals in groups III and IV were additionally treated with zoledronate (single 25 microg/kg s.c. injection) and simvastatin (120 mg/day p.o. for 14 days), respectively. After two weeks, calvaria were processed for undecalcified histomorphometry. Bone resorption was measured using Giemsa staining. Osteoclast numbers were determined using TRAP-staining. UHMWPE particle implantation resulted in a grossly pronounced osteolytic activity with significantly increased values of bone resorption (p < 0.001) and osteoclast numbers (p < 0.001). Additional treatment with zoledronate or simvastatin counteracted the particle-induced effects. A comparison of the two medical treatments revealed no statistically significant differences in bone resorption (p = 0.63) and osteoclast numbers (p = 0.41). A single dose of the bisphosphonate zoledronate decreased UHMWPE particle-induced osteolysis in a murine calvarial model as effectively as a daily treatment with simvastin. Both drug groups may have a preventive and therapeutic role as antiresorptive agents in wear particle-induced bone resorption following total joint replacement.

Decrease in particle-induced osteolysis in obese (ob/ob) mice.

There may be variability in the susceptibility of different individuals to osteolysis from wear debris, and it is not clear whether some individuals may have a genetic predisposition for a more marked osteolytic response. The purpose of this study in mice was to determine whether genetically determined obesity can alter the response to particulate debris. Polyethylene particles were implanted onto the calvaria of seven wild-type mice and seven obese mice (ob/ob). Calvaria from unimplanted wild-type and obese mice served as controls. Calvaria were harvested after 7 days, stained with toluidine blue and for tartrate-specific alkaline phosphatase, and analyzed by histomorphometry. The osteoclast number per mm total bone perimeter was 8.000+/-3.464 in wild-type animals with particles and 2.857+/-1.676 in ob/ob animals with particles (p=0.002; Fisher's PLSD). Bone resorption was 1.895+/-0.713 mm/mm(2) in wild-type animals with particles and 1.265+/-0.494 mm/mm(2) in ob/ob animals with particles (p=0.0438; Fisher's PLSD). Particles induced a diminished osteolytic response in genetically determined obese mice, suggesting that obesity may have a protective role against particle-induced bone resorption-similar to obesity and osteoporosis. These important new findings may help to stimulate clinical studies which may define criteria to better identify patients at risk to develop particle-induced osteolysis.

Importance of the intersegmental trunk muscles for the stability of the lumbar spine. A biomechanical study in vitro.

STUDY DESIGN: A biomechanical study was performed to determine the consequences of a simulation of muscle forces on the loads imposed on the functional spinal units. OBJECTIVES: No biomechanical study has investigated the effect of incorporation of agonist and antagonist muscle forces on the loading of functional spinal units. SUMMARY OF BACKGROUND DATA: Spinal disorders and low back pain are increasingly becoming a worldwide problem. Traditional conservative therapies are intended to strengthen the muscles of the trunk using a judicious regimen of physical exercises. METHODS: Eighteen whole, fresh-frozen human cadaveric lumbar spine specimens (L2-S2; average age, 53.4 years) were tested in a spine tester using pure flexion-extension, lateral bending, and axial moments. The effects of coactivation of psoas and multifidus muscles on L4-L5 mobility were simulated in vitro by applying two pairs of corresponding force vectors to L4. The segmental stability was defined by the correlation of an applied moment to the resultant deformation as shown in load-displacement curves, and the range of motion was defined as the angular deformation at maximum load. RESULTS: The coactivation of muscles was accompanied by a 20% decrease in the range of motion (i.e., a significant increase in stability) during lateral bending and axial moments. Application of flexion-extension moments and muscle coactivation resulted in a 13% increase in the sagittal range of motion. CONCLUSIONS: The action of the intersegmental agonist and antagonist muscles biomechanically increases the overall stiffness (stability) of the intervertebral joints in axial torque and lateral bending, whereas it may destabilize the segment in flexion.

Changes of concentrations of the elements Co, Cr, Sb, and Sc in tissues of persons with joint implants.

Elevated levels of Co and Cr were found in several organs of decreased implant bearers (CoCr-alloy/polyethylene joint prostheses) by means of instrumental and radiochemical neutron activation analysis as compared to normal persons. For comparative purposes, concentrations of the elements Co, Cr, Sb, and Sc were measured in heart, kidney, liver, and spleen of the patients and normal persons. For Cr determination, a new radiochemical separation technique with sufficiently low determination limit was employed. The importance of such investigations for studying possible carcinogenic effects of corrosion products and wear particles of metallic prostheses is mentioned.

[Immune competence of human tissue lymphocytes in contact with loosened hip joint prostheses. On the topic of cellular or humoral rejection reaction as the mechanism of loosening]. / Immunkompetenz menschlicher Lymphocyten im Kontaktgewebe gelockerter Hüftgelenkendoprothesen. Zur Frage der cellulären oder humoralen Abstossungsreaktionen als Mechanismus der Auslockerung.

In several investigations rejections were accused of being a possible cause for the loosening of hip endoprostheses. Using immunocytochemical techniques we studied the number and type of lymphocytes in the tissue adjacent to loosened hip endoprostheses. Tissue samples were taken from 18 patients being reoperated for a loosened endoprostheses. Impressive lymphocyte infiltrates were found in 4 of 18 patients (22%). These infiltrates only consisted of T-cells. In the other samples only few lymphocytes were detected belonging to T- and B-lymphocyte population, respectively. In our patients T-cell mediated rejections were of minor importance for the loosening of total hip replacement. B-cell accumulations were detected in none of the samples.

Functional interest of an articulating spacer in two-stage infected total knee arthroplasty revision.

INTRODUCTION: Deep periprosthetic infection is one of the most serious complications after total knee replacement. The two-stage procedure with implantation of a temporary cement spacer and later re-implantation of a revision total knee prosthesis is an accepted procedural standard. The use of articulating spacers has been proposed to enhance ease of revision and functional results. PATIENTS AND METHODS: Twenty-three patients treated with an articulating spacer were retrospectively studied. All patients had undergone a two-stage surgery. The infected prosthesis was explanted and the femoral component was sterilized and re-implanted. On the tibial side a block of gentamicin-loaded bone cement was produced intraoperatively using specially manufactured templates. Eighteen total knee arthroplasty revisions and 5 arthrodesis were finally performed. RESULTS: A total of three (13%) re-infections occurred 5-20 months after revision total knee arthroplasty in a mean follow-up period of 47 months. Prior to re-implantation, flexion with the articulating spacer ranged between 15 and 100° (mean 68±28°). The average postoperative flexion after re-implantation of total knee replacement was 105±11°. CONCLUSION: The articulating spacer used in this study appears to be as effective as the standard procedures in terms of re-infection risk rate and postoperative range of motion recovery. LEVEL OF EVIDENCE: Level IV.

The role of [18F]fluoride positron emission tomography in the early detection of aseptic loosening of total knee arthroplasty.

Total knee arthroplasty is successful in the treatment of degenerative, arthritic or injured joints. But the most important long term complication seems to be aseptic loosening. An inflammatory process at the bone/cement or bone/prosthesis interface leads to a severe osteolysis. Although early diagnosis is very important the standard techniques often fail. [(18)F]Fluoride ion positron emission tomography (F-PET) is an appropriate tracer paired with a modern method for the evaluation of increased bone metabolism at the bone/prosthesis interface. In this preliminary study we describe for the first time the value of F-PET in the early diagnosis of aseptic loosening. We studied 14 painful knee arthoplasties. In 6 cases the definite diagnosis was determined by surgical procedure, for 8 cases a long clinical follow-up of the least 6 months after the onset of symptoms led to the diagnosis. The F-PET scans were obtained by with an ECAT EXACT HR+ scanner with and without attenuation correction in the two-and three-dimensional mode. An intermediate or high uptake along the bone/prosthesis or bone/cement interface including either the tibial stem or the half of the femoral component was suspected to be aseptic loose. The result were compared with plain radiographs. We found a sensitivity of 100%, a specificity of 56% and an accuracy of 71%. No false negative results were detected, in 4 patients one component as false positive. The sensitivity, specificity and accuracy for the plain radiograph of the same patients were 43%, 86% and 64%, respectively. In conclusion PET seems to be a promising new method in the early diagnosis of painful TKA because of its excellent spatial solution. In combination with the bone seeking tracer [(18) F]fluoride, PET allows the detection of aseptic loosening and the differentiation to the simple synovitis. Our preliminary results suggest that F-PET could be a useful tool although we examined a small group of patients.

[Structural femoral head allografts in revision surgery of loosened acetabular cups]. / Strukturelle Femurkopfallografts in der Revisionschirugie von gelockerten Hüftendoprothesenpfannen.

BACKGROUND: Treatment of acetabular bone defects presents a great challenge in revision total hip arthroplasty (THA). Many methods of acetabular reconstruction have been described. The purpose of this study was to evaluate the midterm results of structural femoral head allografts for acetabular reconstruction. METHODS: Thirty-six patients (33 females and 3 males) with acetabular defects ranging from type 2C to type 3B according to Paprosky's classification were included in the study. In all cases acetabular defects were closed using allografts from femoral heads. In 13 cases an uncemented press-fit cup, in 17 cases a cemented polyethylene socket, and in 6 cases a Burch-Schneider antiprotrusion cage was implanted. The mean follow-up period was 84.2 months (range: 5-147). RESULTS: Four acetabular components failed. All 36 grafts were osseointegrated radiographically and formed a mechanically stable construction. The mean Harris Hip Score at the most recent follow-up was 79.8 points. The distance from the obturator line to the prosthesis head center was 3.73 cm (1.17-5.80 cm) preoperatively and 2.79 cm (0.85-4.8 cm) postoperatively (p<0.05). The distance from the teardrop figure to the prosthesis head center was 3.02 cm (1.0-5.8 cm) preoperatively and 3.25 cm (1.6-4.8 cm) postoperatively (p<0.001). CONCLUSIONS: Closure of acetabular defects of types 2C to 3B according to Paprosky's classification can be satisfactorily accomplished using femoral head allografts. These allografts may facilitate future revision surgery. Femoral heads are readily available due to widespread primary total hip replacement surgery. However, the use of structural femoral head allografts for acetabular reconstruction is cost intensive. Individual patient-related aspects, such as the function of revision arthroplasty, have to be considered when planning revision arthroplasty using femoral head allografts.

Polyethylene particle-induced bone resorption in substance P-deficient mice.

Aseptic loosening is the major cause of total joint replacement failure. Substance P (SP) is a neurotransmitter richly distributed in sensory nerve fibers, bone, and bone-related tissue. The purpose of this study was to investigate the potential impact of SP on bone metabolism in polyethylene particle-induced osteolysis. We utilized the murine calvarial osteolysis model based on ultrahigh molecular weight polyethylene (UHMWPE) particles in 14 wild-type mice (C57BL/J6) and 14 SP-deficient mice. Group 1 (C57BL/J 6) and group 3 (SP-knockout) received sham surgery, and group 2 (C57BL/J6) and group 4 (SP-knockout) were treated with polyethylene particles. Analytical methods included three-dimensional micro-computed tomographic (micro-CT) analysis and histomorphometry. Bone resorption was measured within the midline suture. The number of osteoclasts was determined by counting the tartrate-resistant acid phosphatase-positive cells. UHMWPE-particle treated SP-deficient mice showed significantly reduced osteolysis compared to wild-type mice, as confirmed by histomorphometry (P < 0.001) and micro-CT (P = 0.035). Osteoclast numbers were significantly reduced in groups 3 and 4 compared to groups 1 and 2 (P < 0.001). Unexpectedly, SP-deficient mice (group 3) showed a significantly increased absolute bone mass compared to wild-type mice (group 1) (P = 0.02). The findings of our murine calvaria model lead to the assumption that SP is a promoter in particle-induced osteolysis. The pathophysiology of aseptic loosening is complex, and neuropeptides are not solely responsible for the progress of implant loosening; however, we conclude that there could be coherence between neurotransmitters and particle-induced osteolysis in patients with aseptic loosening.

[Influence of the x-ray technique on evaluation of cup anteversion after total hip arthroplasty]. / Einfluss der Röntgentechnik auf die Beurteilung der Pfannenanteversion nach totaler Hüftendoprothetik.

AIM: Total hip arthroplasty (THA) is a standard procedure in orthopaedic surgery. Planar radiography of the implant is routinely performed to ensure that the operation has achieved the desired result. This study investigates the influence of varying the X-ray beam on the analysis of the radiograph. METHOD: Twenty-three patients were analysed after implantation of a total hip replacement. Besides a CT scan of the pelvis, symphysis- and hip-centred radiographs were available. The cup anteversion was calculated using two published algorithms. The CT-based data were the gold standard. RESULTS: Our study revealed a significant major error in the analysis of the symphysis-centred radiographs when compared with the hip-centered radiographs. Widmer's algorithm showed a significant superiority over Pradhan's formula. CONCLUSION: The best approximation of the anteversion angle was achieved using Widmer's technique by centering the X-ray beam onto the hip.

Reinforcement of deficient femur with inlay strut grafts in revision hip arthroplasty: a small series.

Failure of the femoral component due to severe loss of femoral bone is an important long-term complication of total hip arthroplasty. We treated four patients with a type IV femoral defect (Paprosky classification) because of aseptic and septic loosening. To enhance bone stock and create a stable prosthetic reconstruction we used femoral allografts as inlay strut grafts alone or combined with onlay strut grafts and impaction grafting. At a mean follow-up of 11 years all four patients presented good or excellent results with Harris Hip Score between 86 and 95 points. Radiologically, no migration of the stems were found and the struts showed signs of incorporation. Inlay strut grafts are a reliable method for bone reconstruction of deficient femoral bone stock in failed total hip replacement.

[Effects of bisphosphonates in arthroplasty]. / Bisphosphonatwirkungen in der Endoprothetik.

AIM: This study presents an overview of the general effects of bisphosphonates and in particular of their effects on different problems in joint arthroplasty. METHOD: First the chemical properties are described, then the biological effects. It is already known that bisphosphonates have effects on orthopaedic diseases and an increasing number of studies are investigating what effects can be achieved in joint arthroplasty with these substances. RESULTS: The bisphosphonates group was derived from industrial pyrophosphate which is used to prevent calcification. Bisphosphonates inhibit bone mineralisation and resorption. Several direct and indirect mechanisms are responsible for these effects. The inhibition of bone resorption is used to benefit patients suffering from various diseases causing increased bone resorption. Treatment with bisphosphonates results in greater bone density and improved mechanical bone quality. Indications for this treatment include osteoporosis, tumour-associated osseo-destruction, fibrous dysplasia and Paget's disease. Recent studies have shown that osseo-integration of metal implants is accelerated and periprosthetic bone loss, which is caused by various different mechanisms during the lifetime of an implant, can be reduced. CONCLUSION: Bisphosphonates have been an established element in the treatment of bone metabolic disorders for many years. Their use in joint arthroplasty could become increasingly important.

[Localization of the neurokinin 1 receptor in hip joints of patients with painful osteoarthritis]. / Die Lokalisation des Neurokinin 1-Rezeptors im Hüftgelenk von Patienten mit schmerzhafter Osteoarthrose.

INTRODUCTION: Recent studies on osteoarthritis have focused on nociceptive substance P (SP) containing afferent nerve fibres. The effects of SP are known to be mainly mediated by the tachykinin receptor neurokinin 1 (NK1-R). AIM: The aim of the present study was to demonstrate the NK1-R in human joint tissues. METHODS: The hip joint capsule of three patients with painful hip osteoarthritis (Group 1), three patients with femoral neck fracture showing no cartilage destruction (Group 2, controls) and the soft tissue of the fossa acetabuli of Group 1 were resected during hip arthroplasty implantation. The tissue samples were cut into small blocks and immersion-fixed in Zamboni's fixative. The specimens were frozen, cut into 50 microm sections and immunostained using a standard immunohistochemical staining protocol. RESULTS: In Groups 1 and 2 the NK1-receptor was localised in the wall of venous vessels, on Schwann cells of nerve bundles and on nerve fibres. In the osteoarthritis group the staining pattern was similar but the number of NK1-bearing cell structures seemed to be enhanced. CONCLUSIONS: The present study provides the first evidence of NK1-R in the human hip joint. In patients with painful osteoarthritis the density of NK1-R-positive cell structures seemed to be increased. The localisation of the NK1 receptor on different cell types suggests multiple effects of SP in normal and osteoarthritic joints.

[Revision of failed acetabular cups with extensive structural allografts]. / Die Revision von gelockerten Hüftendoprothesenpfannen mit ausgedehnten strukturellen Allografts.

AIM: Structural allografts are used with encouraging results for revision of failed total hip arthroplasty and in the surgery of bone tumours. The aim of the present study is to describe the clinical and radiological results achieved with structural allografts in revision of a total hip arthroplasty. MATERIAL AND METHODS: 15 patients (12 female and 3 male patients) were revised with an acetabular defect situation of type 3 A or 3 B according to the Paprosky classification. Five fresh-frozen acetabula, nine distal femora and one proximal tibia were used for acetabular reconstruction. The rigid graft fixation was performed with 2 > or = AO screws. In one case a cemented acetabular ring was implanted, four cementless cups and ten cemented polyethylene acetabular components were used. The mean follow-up was 7.9 years (1.6-11.0 years). RESULTS: A stable osseointegration of fifteen transplanted structural allografts was achieved in thirteen cases. Two allografts (one aseptic loosening, one deep infection) failed to osseointegrate. In one case the migration of a cementless cup was registered. Revision surgery of this female patient was performed successfully with a cemented reconstruction ring. The mean Harris hip score at the latest follow-up was 81.4 points (70-99 points). CONCLUSION: For reconstruction of acetabular bone stock and restoration of the bone anatomy structural allografts can be recommended. The use of cementless cups in combination with structural grafts is to be evaluated as critical.

[Value of radiologic evidence for the diagnosis of the loosening of cement-fixed total prostheses of the hip joint]. / Die Wertigkeit röntgenologischer Zeichen für die Diagnose der Lockerung zementfixierter Hüftgelenktotalprothesen.

A diagnosis of loosening of cement-anchored alloarthroplasties of the hip joint is mainly based on morphological x-ray film findings. Definite signs of loosening, however, are represented by drastic positional changes or ruptures of the implant only. All other radiological signs, such as concentric or defined osseous absorptions (bordering), damage of the osseous implant bed with slight positional change, or reactive ossifications of the osseous prosthesis bed, as well as disruption of the bone cement alone, are useful only as pointers or as latent signs of loosening. It is only when several of these signs appear together in a typical constellation, that one can safely concluded that loosening has actually occurred.

[Surgical technic in femur shaft fenestration within the scope of revision operations following hip joint total endoprostheses]. / Zur Operationstechnik bei der Femurschaftfensterung im Rahmen von Revisions-Operationen nach Hüftgelenk-Totalendoprothesen.

In revision arthroplasty the loss of stability secondary to fenestration of the proximal femur reduces the loading capacity of the limb and increases the risk of postoperative fractures. Trying to improve the fenestration technique we tested the usual fenestration procedure experimentally. Besides pure axial load we investigated the torsional forces of the proximal femur in the bended hip position. We recorded the deformation under increasing load and analysed the fracture pattern. The results shows an unwarantable loss of stability in lateral or complete ventral fenestration procedures. Ventral fenestration procedures with smooth edges and intact proximal bony ring having additional prosthesis stem support presented the best mechanical results. According to the tolerated load it is possible to give guide-lines for the postoperative treatment in the cemented and cementless arthroplasty of the hip joint.

[The magnitude of forces acting on the proximal femur in various weight alleviating gait forms with reduced ground reaction forces]. / Grösse der am proximalen Femur einwirkenden Kräfte bei unterschiedlichen entlastenden Gangarten mit reduzierten Bodenreaktionskräften.

To estimate the forces of the hip during partial or non-body-weight-bearing-gait a simple mechanical principle was used. For identification of the acting muscles of the hip during the swing period Electromyography was used. In the pure swing period without ground touch, being recommended as "de-loading" for the hip, forces resulted up to 85% of body-weight. In contrast to that, partial body-weight-bearing with limb-weight (approximately 12-15% body weight) resulted in the most efficient reduction of hip forces.

[A treatment principle with questionable effectiveness in Perthes disease]. / Ein Behandlungsprinzip mit fragwürdiger Wirksamkeit bei Morbus Perthes.

The reduction of hip joint forces is a generally accepted part of the conservative treatment of Perthes disease. To reach this effect with help of splints (e.g. Thomassplint and the following models) does not seem to be efficient enough even from a clinical point of view. Theoretical considerations of former investigations of other authors point out the insufficient effect of these splints regarding the hip joint force reduction during the weight bearing phase in walking. The effect of these splints during the non-weight bearing phase in walking with regard to the hip joint forces has not been investigated so far. Therefore this paper is dealing with the forces onto the hip joint during the swinging phase of the leg with a splint, shown in a simplified, mechanical model. The results reveal significantly higher hip joint forces if the splint is used compared to the physiological forces during the swinging phase which in a static situation rise up to twice the body weight. These joint loadings are important because they occur during hip flexion and therefore cause pressure on the ventro-cranial part of the head of the femur, a region which unfortunately is often involved in Perthes' disease and therefore especially vulnerable to these forces. From a biomechanical point of view the principle of reducing the hip joint forces with splints has to be abandoned.

[Intraoperative Doppler ultrasound of the femoral vein for maintaining venous patency in hip joint prosthesis implantation]. / Intraoperative Dopplersonographie der V. femoralis zur Aufrechterhaltung des venösen Abflusses in der Hüftgelenkendoprothetik.

PROBLEM: Is the femoral vein occluded during insertion of the stem? Can thrombembolic complications be reduced by avoiding occlusion? METHODS: In a prospective randomized study 160 cemented stems were implanted from the anterolateral approach: 76 patients had conventional figure-of-four positioning of the femur, 84 patients had a modified position according to the blood flow registered by intraoperative Doppler sonography. RESULTS: 68.7% of the 84 femoral veins were completely occluded in the figure-of-four positioning. Only by reduction of this position and soft tissue release, venous flow could be demonstrated by sonography. Increased body mass index (BMI) and age correlated with occlusion (p = 0.0001 and p < 0.05). In the 84 patients no thrombembolic complication was found. In the control group 3 deep thromboses were revealed by venography (p = 0.105). CONCLUSION: Doppler sonography helps guaranteeing venous drainage. A modified leg position should be aimed at especially in increased BMI and age.

[Studies on the stability of pertrochanteric fractures following the application of various osteosynthesis techniques with special reference to torsional forces at the proximal femur]. / Untersuchungen zum Festigkeitsverhalten pertrochanterer Frakturen nach Anwendung verschiedener Osteosynthesetechniken unter besonderer Berücksichtigung der Torsionsbelastung am proximalen Femur.

Fourteen different commonly used osteosyntheses for unstable pertrochanteric fractures with medial bone defect were systematically analysed concerning their stability. For this purpose the deformation and the maximum stability of 36 surgically stabilized fractured femora from donor corpses were tested. For the experimental investigations the hip force FM was not only induced on the femora in orthograde direction but also in an inclination of 45 degrees of anteflexion of the femur as it appears during walking up stairs. As a result, all tested osteosyntheses had significantly lower maximum stability and greater deformation if the hip force was induced on the anteflexed femur in contrast to orthograde loading. From our analysis clinically important conclusions can be drawn concerning the operation techniques and the post-operative after treatment concepts.