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.

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.

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.

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.

[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.

[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.

[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.

[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.

[The cement free hollow hip prosthesis to reduce intramedullary pressure]. / Die zementfreie Hohlschaft-Hüftendoprothese zur Reduzierung des intramedullären Druckes.

PURPOSE: A hollow cementless femoral stem has been developed to reduce intramedullary pressure and fat embolism during implantation. METHODS: In a prospective randomized clinical study, cementless hip stems (ALPHA-FIT) were implanted in 42 patients (24 women, 18 men, mean age: 65.9 years). In Group I (n=21) a solid standard stem was used. In Group II (n=21) a modified hollow stem was implanted with vertical and longitudinal communicating drill holes opening at the implant surface. During surgery the intramedullary pressure was measured by a cannula fixed distally. RESULTS: During stem insertion the mean pressure was 82 mmHg (minimum-maximum, 12-259 mmHg) for Group I and 27 mmHg (minimum-maximum, 0-48 mmHg) for Group II. This difference was statistically significant (t-test, p < 0.00076). The pressure measured in Group II was similar to the base pressure before opening of the intramedullary canal (mean 35 mmHg; minimum-maximum, 4-72 mmHg). In both groups higher pressures were found for opening of the canal, drilling with the smallest drill size and rasping. CONCLUSION: Using the hollow prosthesis, the intramedullary pressure could be reduced significantly. The higher pressures during preparation of the femoral canal need further research.

[Size and shape of commercially available polyethylene particles for in-vitro and in-vivo-experiments]. / Grösse und Form kommerziell erhältlicher Polyethylenpartikel für In-vitro- und In-vivo-Versuche.

AIM: The longevity of total hip arthroplasty is sometimes limited by osteolysis and aseptic loosening. Aseptic loosening may be caused by the biologic reaction to polyethylene wear particles. Particles of less than 1 micro m diameter are of particular importance. These particles are not easily available for experimental use. METHOD: We performed a morphologic analysis of commercially available, very small polyethylene particles (Ceridust(R)) in order to determine the specific size distribution. We measured 1 978 particles. Size analysis was performed using an electron microscope. Particle size was described as the equivalent circle diameter (ECD). Particle morphology was described as feret ratio. In addition, Ceridust(R) particles were compared to different particles stemming from a hip simulator experiment. RESULTS: More than 35 % of the particles were less than 1 micro m in size. The particle size was 1.75 micro m +/- 1.43 micro m (median 1.42 micro m). The minimum was 0.06 micro m, the maximum was 11.06 micro m. The feret ratio was 0.58 +/- 0.17 (median 0.63). The minimum was 0.07, the maximum was 0.93. The majority of Ceridust(R) particles had a rough surface. Compared to polyethylene particles stemming from a hip simulator experiment, Ceridust(R) particles had a rougher surface, were less longitudinal, and had a more even size distribution. CONCLUSIONS: The pure, commercially available polyethylene particles analyzed here are suitable for in vitro and in vivo experiments due to their easy availability, minor costs, and large fraction of very small particles.

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.

Periprosthetic fractures with extensive bone loss treated with onlay strut allografts.

We reviewed a consecutive series of 19 patients with comminuted periprosthetic fractures, loosening of the femoral stem (Vancouver type B3) and significant loss of bone stock (Paprosky type III and IV). Sixteen porous-coated long stems and three Exeter stems, all with impaction grafting, were used. Large femoral onlay strut allografts were applied to maintain fracture reduction and improve stability. There was one early re-fracture at the tip of the femoral stem. Eighteen fractures healed without deformity and shortening. At the last follow-up at mean 3.7 (2.0-7.5) years, the mean Harris hip score was 76.4 (57.5-92.0). There was ingrowth of all strut grafts and significant augmentation of periprosthetic bone.

[Curved osteotomy technique for intertrochanteric varus surgery--an experimental and computer-assisted surgery]. / Die Rundosteotomietechnik für die intertrochantäre Varisierung--Eine experimentelle und computergestützte Analyse.

PURPOSE: In conventional intertrochanteric varus osteotomy, shortening of the leg and insufficiency of the abductor muscles occur frequently. To avoid these disadvantages, a curved osteotomy is presented. METHOD: 189 intertrochanteric barrel vault and wedge osteotomies were compared. By means of digitized preoperative radiographs the varus osteotomies were planned with a computer program optimising postoperative leg length, bone contact area at the osteotomy site, femoral offset, and abductor muscle length. RESULTS: The average leg shortening was 3.9 mm (range: 0-5 mm) for barrel vault osteotomy and 13.6 mm (range: 8-22.2 mm) for the wedge technique. After correction the mean contact area at the osteotomy sites was 1731.6 mm2 (range: 1087.8-2341.8 mm2) in the barrel vault technique compared with 783.7 mm2 (range: 563.7-1249.6 mm2) in the wedge procedure (p < 0.001, t-test). Adequate femoral offset was achieved in both types of osteotomy. In all curved osteotomies the length of the abductor muscles remained nearly constant in contrast to the wedge procedure. Additional comparative experimental barrel vault osteotomies in 22 human autopsy femora with a high-speed dissecting tool and round jigs revealed a precise application of the preoperative planning. CONCLUSION: The intertrochanteric curved osteotomy provides minimum leg shortening and increased bone contact area. It can prevent an insufficiency of the abductor muscles, because shortening is minimized.

[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.

Supportive strut grafts for diaphyseal bone defects in revision hip arthroplasty.

Large femoral cortical strut allografts were used to provide structural support of the femur in 20 patients in whom uncemented, extensively porous-coated, press-fit revision femoral stems were applied. The mean followup was 4.7 years. Radiographic analysis of the patients who had revision surgery revealed that in all 20 patients, the cortical femoral strut allografts showed incorporation. Small areas of graft resorption were observed in only two patients. Seventeen of the uncemented femoral revision stems radiographically showed bone ingrowth. Three of the revision femoral stems were interpreted as being fixed only by fibrous ingrowth after early subsidence after surgery. There were no reoperations. Before surgery, all patients were unable to walk and had severe pain. At followup, all patients were ambulatory and had considerable improvement in pain relief and in their ability to walk. The mean Harris hip score after surgery was 75 (range, 57.5-92). Complications consisted of one peroneal nerve palsy, which resolved; one deep venous thrombosis; one gastrointestinal ulcer; and one case of pneumonia. Supportive cortical strut allografts represent an alternative to the use of circumferential bulk allografts and total femoral replacements in patients with large combined proximal and diaphyseal bone defects.

Intertrochanteric osteotomy with a short intramedullary locking nail.

In this study the Gamma nail was used for fixation after intertrochanteric osteotomy in osteoarthritis. In 31 patients varus, valgus and complex intertrochanteric osteotomies were stabilized. The patients were allowed full weight bearing 2 weeks postoperatively. After a mean follow-up of 25.6 (13-42) months 29 osteotomies were healed. Two patients were lost to follow-up. No femoral shaft fractures or thigh pain occurred.

[Possibilities for static and dynamic stabilization of the spine in lesions of the anterior and posterior ligament complex]. / Statische und dynamische Stabilisierungsmöglichkeiten der Wirbelsäule bei Läsionen des anterioren und posterioren Ligamentkomplexes.

Defects of the dorsal and ventral ligament complexes of the lumbar spine results to an instability of the functional spinal unit. For the prognosis of secondary instability due to disko-ligamentous injuries the functional insufficiency of the lasting scars is a larger problem than the primary loss of osseous stability with fast healing tendency. The main goal of the present biomechanical study in vitro was to demonstrate the different grades of instability in the correlation to progressive disko-ligamentous defects as well as stabilisation through dynamic and static procedures. With a transpedicular screw-ringband-system the segmental function was preserved and instability was abolished. After rigid instrumentation with a fixateur intern remained a residual range of motion due to which can result refuse to bending moments without spondylodesis in an implant failure.