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Biomedical subjects

F Löer

Publications and source records attributed to F Löer.

At least 19 recordsLinked to original sources
PubMed2007

[Structural femoral head allografts in revision surgery of loosened acetabular cups].

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.

Acetabulum↗
PubMed2006

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.

Aged↗
PubMed2005

[A comparison of the antiresorptive effects of bisphosphonates and statins on polyethylene particle-induced osteolysis].

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.

Animals↗
PubMed2003

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.

Adult↗
PubMed2001

[Intraoperative Doppler ultrasound of the femoral vein for maintaining venous patency in hip joint prosthesis implantation].

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.

Aged↗
PubMed2001

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.

Adult↗
PubMed1999

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.

Adult↗
PubMed1998

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.

Biomechanical Phenomena↗
PubMed1998

[Possibilities for static and dynamic stabilization of the spine in lesions of the anterior and posterior ligament complex].

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.

Adult↗
PubMed1998

Laminectomy and functional impairment of the lumbar spine: the importance of muscle forces in flexible and rigid instrumented stabilization--a biomechanical study in vitro.

Laminectomy is the accepted treatment for spinal canal stenosis in cases where conservative treatment has failed. Opinions diverge on the resulting clinical instability and the necessity of instrumented stabilization. The present biomechanical study was performed to determine the functional impairment following laminectomy and the stabilizing effect of flexible and rigid devices. This was the first time that the effects of agonist and antagonist intersegmental lumbar muscle forces acting on intact, unstable and instrumentally stabilized functional spinal units have been investigated. Six human cadaveric lumbar spines were tested in a spine tester. The coactivation of agonist and antagonist muscle forces resulted in increased stability under the load conditions of bending and rotation; a slight increase in the range of motion was noted during flexion. The functional impairment following laminectomy was corrected by ligamentoplasty and by means of muscle forces. Ligamentoplasty appears to be an alternative to decompression with spondylodesis, especially in patients with well-developed muscles.

Biomechanical Phenomena↗
PubMed1994

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.

Chromium↗
PubMed1991

Systemic effects of implanted prostheses made of cobalt-chromium alloys.

Systemic effects of Co-Cr alloy/polyethylene hip joint prostheses were investigated using instrumental neutron activation to determine the concentrations of up to 16 elements. First, in a prospective study whole blood and serum taken from 10 patients from 1 day before to 90 days after implantation were analyzed. Secondly, in a retrospective study whole blood and serum from 23 patients who had had prostheses in place for up to 18 years were analyzed. For comparison, normal trace element levels in humans were determined by analyzing whole blood and serum from 21 patients. Finally, various tissues and organs from two decreased implant patients were analyzed and compared with normal concentrations obtained from the analysis of five "normal" patients without implants. In agreement with other recent investigations, our analyses of normal serum, whole blood, tissues, and organs show that most previously defined "normal" trace element concentrations were too high, chiefly owing to contamination and insufficient blanks. A detailed discussion shows that for many elements the ranges of normal concentrations have to be revised. This conclusion is of particular importance with respect to the sometimes conflicting earlier reports of systemic effects of metal prostheses. In the work reported here, both the prospective and the retrospective investigations of serum and whole blood showed massive Co enrichments as a consequence of implant corrosion. The data show a wide range of individual burdening, ranging from practically no effect to the most extreme values. The analyses of tissues from the vicinity of the implants in the two deceased implant patients showed strong local effects of Co, Cr, Zr, and Hf, the latter two elements originating from the X-ray contrast media in the bone cement. The analyses of organs revealed significant Co and Cr enrichment in several tissues and organs. Consequently, it can be seen that implant corrosion is not an occurrence of merely local significance, but one that affects the trace element status of the entire organism.

Bioprosthesis↗
PubMed1991

[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].

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.

Aged↗
PubMed1989

[The tensile strength of various osteosyntheses of the unstable major trochanter. An experimental study].

Eight of the prevalent techniques for performing osteosynthesis of the greater trochanter were compared to determine the stability of each. In an experimental setup, the reaction to deformation in the osteotomy cleft as a result of increasing tension stress was determined and analyzed in the femora of 22 corpses. The strain tolerance was not only dependent on the particular form of osteosynthesis but also on the technical details. Our study on the reaction to deformation showed that even low levels of tension stress caused significant dislocation in the osteyomy cleft despite an intact osteosynthesis. The results permit conclusions to be drawn that will contribute to the improvement of surgical technical details as well as postoperative treatment.

Biomechanical Phenomena↗
PubMed1984

Trace element burdening of human tissues due to the corrosion of hip-joint prostheses made of cobalt-chromium alloys.

Using instrumental neutron activation analysis, the concentrations of 18 elements were studied in human articular capsule and fascia lata before and after application of total endoprostheses of the hip joint made of cobalt-chromium alloys. Tissues from the vicinity of the implant showed extreme burdening by corrosion products (Co, Cr, Ni), as well as by Zr, Hf, and Ba from the bone cements. Tissues more distant from the implants exhibited lower, but still significant burdening. Moreover, some essential trace elements not contained in the implant materials were changed in the tissues after implantation. In order to clarify the dissolution of alloy constituents in biological media, the passivation of cobalt-chromium alloy was investigated by tracer techniques using Ringer's solution as a simple model of the body fluids. The passivation process lasted for more than 1 month and was accompanied by a selective dissolution of the alloys constituents in the order Ni greater than Co approximately Fe greater than Mo greater than Cr. A comparison of the tissue analyses with the corrosion experiments demonstrates that the distribution patterns of the corrosion products in the tissues are influenced by both the corrosion process and the biochemical properties of the corrosion products.

Adult↗