Primary stability of cementless threaded acetabular cups at first implantation and in the case of revision regarding micromotions as indicators

The primary stability of cementless total hip endoprosthesis is of vital importance for proximate, long-term osteointegration. The extent of micromotions between implant and acetabulum is an indicator of primary stability. Based on this hypothesis, different cementless hip joint endoprosthesis were studied with regard to their micromotions. The primary stability of nine different cementless threaded acetabular cups was studied in an experimental setup with blocks of rigid foam. The micromotions between implant and implant bearing were therefore evaluated under cyclic, sinusoidal exposure. The blocks of polymer foam were prepared according to the Paprosky defect classifications. The micromotions increased with the increasing degree of the defect with all acetabuli tested. Occasionally coefficients of over 200 mu m were measured. From a defect degree of 3b according to Paprosky, the implants could no longer be appropriately placed. The exterior form of the spherical implants tended to exhibit better coefficients than the conical/parabolic implants

Sports Activity After Short-Stem Hip Arthroplasty

Background: No data are available about the sports activity of patients with bone-conserving short-stem hip implants. Hypothesis: Patients can return to a good level of sports activity after implantation of a short-stem hip implant. Study Design: Case series; Level of evidence, 4. Methods: The sports activity level of 68 patients (76 hips) after short-stem hip arthroplasty was assessed for a minimum of 2 years after implantation. In addition to the clinical examination, a detailed evaluation of the patients’ sports pattern was obtained. Furthermore, the results were analyzed with regard to gender (female and male) and age (55 years). Results: After a mean of 2.7 years, patients showed a Harris Hip Score (HHS) of 93.6, a Western Ontario and McMaster Universities Arthritis Index (WOMAC) score of 9.5, and a University of California, Los Angeles (UCLA) activity score of 7.6, with each individual participating on average in 3.5 different disciplines after surgery compared with 3.9 before surgery. High-impact activities decreased significantly postoperatively, whereas low-impact activities increased significantly. The duration of the sports activities remained stable, while the frequency actually increased. In contrast, men participated preoperatively in more sports than women (4.3 men vs 3.3 women). However, because of a pronounced decrease in high-impact activities by men, both genders participated in an equal number of sports postoperatively (3.5 men vs 3.5 women). Finally, 45% (n = 31) reported at least one activity that they missed. Most of them were disciplines with an intermediate- or high-impact level. Conclusion: Patients with a short-stem hip implant can return to a good level of activity postoperatively. Participation in sports almost reached similar levels as preoperatively but with a shift from high- to low-impact activities. This seems desirable from a surgeon’s point of view but should also be communicated to the patient before hip replacemen

Revision of hip resurfacing arthroplasty with a bone-conserving short-stem implant: a case report and review of the literature

Introduction Suitable treatment of early failure of total hip replacement is critical in younger patients, as bone stock is lost and the functional outcome is impaired. Case presentation We report the case of a 56-year-old Caucasian woman with early failure of hip resurfacing arthroplasty. While revision is usually performed with a conventional hip implant, this case report describes for the first time a revision procedure with a bone-conserving short-stem hip implant. Conclusions Our approach allows further conservation of femoral bone stock and provides a long-term solution to the patient, which maintains the possibility of using a conventional hip implant should a second revision become necessary

Patellofemoral contact patterns before and after total knee arthroplasty: an in vitro measurement

Background: Patellofemoral complications are one of the main problems after Total Knee Arthroplasty (TKA). Retropatellar pressure distribution after TKA can contribute to these symptoms. Therefore we evaluated retropatellar pressure distribution subdivided on the ridge, medial and lateral surface on non-resurfaced patella before and after TKA. Additionally, we analyzed axial femorotibial rotation and quadriceps load before and after TKA. Methods: Seven fresh frozen cadaver knees were tested in a force controlled knee rig before and after TKA (Aesculap, Tuttlingen, Germany, Columbus CR) while isokinetic flexing the knee from 20 degrees to 120 degrees under weight bearing. Ridge, medial and lateral retropatellar surface were defined and pressure distribution was dynamically measured while quadriceps muscles and hamstring forces were applied. Aside axial femorotibial rotation and quadriceps load was recorded. Results: There was a significant change of patella pressure distribution before and after TKA (p = 0.004). In physiological knees pressure distribution on medial and lateral retropatellar surface was similar. After TKA the ridge of the patella was especially in higher flexion grades strongly loaded (6.09 +/-1.31 MPa) compared to the natural knee (2.92 +/-1.15 MPa, p < 0.0001). Axial femorotibial rotation showed typical internal rotation with increasing flexion both before and after TKA, but postoperatively it was significantly lower. The average amount of axial rotation was 3.5 degrees before and after TKA 1.3 degrees (p = 0.001). Mean quadriceps loading after implantation of knee prosthesis did not change significantly (575 N +/- 60 N in natural knee and after TKA 607 N +/- 96 N; p = 0.28). Conclusions: The increased retropatellar pressure especially on the ridge may be one important reason for anterior knee pain after TKA. The trochlea of the femoral component might highly influence the pressure distribution of the non-resurfaced retropatellar surface. Additionally, lower axial femorotibial rotation after TKA might lead to patella maltracking. Changing the design of the prosthesis or a special way of patella shaping might increase the conformity of the patella to trochlea to maintain natural contact patterns

Does osteoporosis reduce the primary tilting stability of cementless acetabular cups?

Background: Cementless hip cups need sufficient primary tilting stability to achieve osseointegration. The aim of the study was to assess differences of the primary implant stability in osteoporotic bone and in bone with normal bone density. To assess the influence of different cup designs, two types of threaded and two types of press-fit cups were tested. Methods: The maximum tilting moment for two different cementless threaded cups and two different cementless press-fit cups was determined in macerated human hip acetabuli with reduced (n=20) and normal bone density (n=20),determined using Q-CT. The tilting moments for each cup were determined five times in the group with reduced bone density and five times in the group with normal bone density, and the respective average values were calculated. Results: The mean maximum extrusion force of the threaded cup Zintra was 5670.5 N (max. tilting moment 141.8 Nm) in bone with normal density and. 5748.3 N (max. tilting moment 143.7 Nm) in osteoporotic bone. For the Hofer Imhof (HI) threaded cup it was 7681.5 N (192.0 Nm) in bone with normal density and 6828.9 N (max. tilting moment 170.7 Nm) in the group with osteoporotic bone. The mean maximum extrusion force of the macro-textured press-fit cup Metallsockel CL was 3824.6 N (max. tilting moment 95.6 Nm) in bone with normal and 2246.2 N (max. tilting moment 56.2 Nm) in osteoporotic bone. For the Monoblock it was 1303.8 N (max. tilting moment 32.6 Nm) in normal and 1317 N (max. tilting moment 32.9 Nm) in osteoporotic bone. There was no significance. A reduction of the maximum tilting moment in osteoporotic bone of the ESKA press-fit cup Metallsockel CL was noticed. Conclusion: Results on macerated bone specimens showed no statistically significant reduction of the maximum tilting moment in specimens with osteoporotic bone density compared to normal bone, neither for threaded nor for the press-fit cups. With the limitation that the results were obtained using macerated bone, we could not detect any restrictions for the clinical indication of the examined cementless cups in osteoporotic bone

Die Biegestabprothese: ein experimenteller Ansatz zur metaphysären Hüftendoprothetik

The aim of our study was to develop a femoral component for total hip arthroplasty that would exclusively anchor in the metaphysis of the femoral neck. To forego trochanteric fixation, the load needs to be transferred to the metaphysis at as many points as possible. A computer simulation model suggested that an implant with a central cylinder and 16 rods aligned along a thread would be the preferable solution. To evaluate primary implantation stability, 14 fresh frozen cadaver femora were used. A special instrument set was developed to allow for centered implantation of the prosthesis without the need to dissect the greater trochanter. For our tests, we used two prototype implants: one made from titanium and the other from a CoCrMo alloy. For the measurement of micromotions at the medial proximal femur, sinusoid dynamic loading with a force between 300 N and 1700 N and a frequency of 1 Hz was employed. In a neutral position of 16 degrees adduction and 9 degrees ante-torsion, the average micronnotions measured were 119 mu m. Despite these convincing in vitro results with regards to primary stability, circular cut-out of the implant, followed by aseptic osteonecrosis, loosening might still occur in a clinical situation. Animal experiments are therefore required to further evaluate this new implant design

Bone metastases from renal cell carcinoma: patient survival after surgical treatment

<p>Abstract</p> <p>Background</p> <p>Surgery is the primary treatment of skeletal metastases from renal cell carcinoma, because radiation and chemotherapy frequently are not effecting the survival. We therefore explored factors potentially affecting the survival of patients after surgical treatment.</p> <p>Methods</p> <p>We retrospectively reviewed 101 patients operatively treated for skeletal metastases of renal cell carcinoma between 1980 and 2005. Overall survival was calculated using the Kaplan-Meier method. The effects of different variables were evaluated using a log-rank test.</p> <p>Results</p> <p>27 patients had a solitary bone metastasis, 20 patients multiple bone metastases and 54 patients had concomitant visceral metastases. The overall survival was 58% at 1 year, 37% at 2 years and 12% at 5 years. Patients with solitary bone metastases had a better survival (p < 0.001) compared to patients with multiple metastases. Age younger than 65 years (p = 0.036), absence of pathologic fractures (p < 0.001) and tumor-free resection margins (p = 0.028) predicted higher survival. Gender, location of metastases, time between diagnosis of renal cell carcinoma and treatment of metastatic disease, incidence of local recurrence, radiation and chemotherapy did not influence survival.</p> <p>Conclusions</p> <p>The data suggest that patients with a solitary metastasis or a limited number of resectable metastases are candidates for wide resections. As radiation and chemotherapy are ineffective in most patients, surgery is a better option to achieve local tumor control and increase the survival.</p

Development of a multi-component evaluation method for the energy efficiency of rack feeders

Im folgenden Beitrag wird eine auf Basis von Messergebnissen und Simulationen entwickelte Methode vorgestellt, mit der sich die Energieeffizienz eines Regalbediengerätes charakterisieren lässt. Die Methode basiert auf einer Bewertung, die sich aus verschiedenen Komponenten zusammensetzt. Die Bewertung umfasst sowohl die einzelnen Funktionen eines Regalbediengeräts als auch seine gesamte logistische Leistung.The following article presents a method developed on the basis of measurement results and simulations, which enables the rating of the energy efficiency of a rack feeder. The method is based on a rating that is composed of individual components. The assessment covers both the individual functions of an rack feeder and its overall logistical performance

In vivo evaluation of bioactive PMMA-based bone cement with unchanged mechanical properties in a load-bearing model on rabbits

Polymethylmethacrylate-based bone cements are widely used for fixation of joint replacements. To improve the long-term outcome, bioactive bone cements are aspired to advance the bone–cement interface. This study evaluated the in vivo properties of a new polymethylmethacrylate-based bioactive bone cement with addition of amphiphilic phosphorylated 2-hydroxyethylmethacrylate. Previous in vitro studies confirmed bioactive properties in cell culture, as well as unchanged mechanical properties are tests according to ISO 5833:2002. Three different variations of the cement (polymethylmethacrylate + phosphorylated 2-hydroxyethylmethacrylate, polymethylmethacrylate + phosphorylated 2-hydroxyethylmethacrylate + CaCl2 and polymethylmethacrylate + phosphorylated 2-hydroxyethylmethacrylate + CaCl2 + Na2CO3) were compared to conventional polymethylmethacrylate cement. To evaluate the properties under load-bearing conditions, a spacer prosthesis was implanted into the femoral diaphysis of 24 rabbits. Additionally, a cement plug was installed into the proximal tibia. After three months, polished sections with Giemsa surface staining were prepared. The bioactivity was determined using the bone affinity index. The sections showed a good osseointegration of the bioactive bone cement without cement cracks under load-bearing conditions. Regarding the bone affinity index, the bioactive bone cement revealed a significantly higher value in the proximal tibia (25.9–37.7%) and around the spacer prosthesis (36.8–58.9%) compared to the conventional polymethylmethacrylate cement (12.8–17.0%). The results confirm the in vivo bioactivity of this bone cement. The absence of cement cracks indicates a sufficient mechanical stability to fix prostheses with this bioactive cement, but for a final assessment long-term tests are necessary