Introduction of innovations in joint arthroplasty: Recommendations from the 'EFORT implant and patient safety initiative'.

With the implementation of the new MDR 2017/745 by the European Parliament, more robust clinical and pre-clinical data will be required due to a more stringent approval process. The EFORT Implant and Patient Safety Initiative WG1 'Introduction of Innovation', combined knowledge of orthopaedic surgeons, research institutes, orthopaedic device manufacturers, patient representatives and regulatory authorities to develop a comprehensive set of recommendations for the introduction of innovations in joint arthroplasty within the boundaries of MDR 2017/745. Recommendations have been developed to address key questions about pre-clinical and clinical requirements for the introduction of new implants and implant-related instrumentation with the participation of a steering group, invited by the EFORT Board in dialogue with representatives from European National Societies and Speciality Societies. Different degrees of novelty and innovation were described and agreed on in relation to when surgeons can start, using implants and implant-related instrumentation routinely. Before any clinical phase of a new implant, following the pre-market clinical investigation or the equivalent device PMCF pathway, it is a common understanding that all appropriate pre-clinical testing (regulatory mandatory and evident state of the art) - which has to be considered for a specific device - has been successfully completed. Once manufacturers receive the CE mark for a medical device, it can be used in patients routinely when a clinical investigation has been conducted to demonstrate the conformity of devices according to MDR Article 62 or full equivalence for the technical, biological and clinical characteristics has been demonstrated (MDR, Annex XIV, Part A, 3.) and a PMCF study has been initiated.

Does Posterior Tibial Slope Influence Knee Kinematics in Medial Stabilized TKA?

BACKGROUND: During total knee arthroplasty (TKA), one of the key alignment factors to pay attention to is the posterior tibial slope (PTS). The PTS clearly influences the kinematics of the knee joint but must be adapted to the coupling degree of the specific TKA design. So far, there is hardly any literature including clear recommendations for how surgeons should choose the PTS in a medial stabilized (MS) TKA. The aim of the present study is to investigate the effects of different degrees of PTS on femorotibial kinematics in MS TKA. MATERIALS AND METHODS: An MS TKA was performed in seven fresh-frozen human specimens successively with 0°, 3°, and 6° of PTS. After each modification, weight-bearing deep knee flexion (30-130°) was performed, and femorotibial kinematics were analyzed. RESULTS: A lateral femoral rollback was observed for all three PTS modifications. With an increasing PTS, the tibia was shifted more anteriorly on the lateral side (0° PTS anterior tibial translation -9.09 (±9.19) mm, 3° PTS anterior tibial translation -11.03 (±6.72) mm, 6° PTS anterior tibial translation 11.86 (±9.35) mm). No difference in the tibial rotation was found for the different PTS variants. All PTS variants resulted in internal rotation of the tibia during flexion. With a 3° PTS, the design-specific medial rotation point was achieved more accurately. CONCLUSIONS: According to our findings, we recommend a PTS of 3° when implanting the MS prosthesis used in this study.

Osteogenic Differentiation of Human Adipose-Derived Stem Cells Seeded on a Biomimetic Spongiosa-like Scaffold: Bone Morphogenetic Protein-2 Delivery by Overexpressing Fascia.

Human adipose-derived stem cells (hADSCs) have the capacity for osteogenic differentiation and, in combination with suitable biomaterials and growth factors, the regeneration of bone defects. In order to differentiate hADSCs into the osteogenic lineage, bone morphogenetic proteins (BMPs) have been proven to be highly effective, especially when expressed locally by route of gene transfer, providing a constant stimulus over an extended period of time. However, the creation of genetically modified hADSCs is laborious and time-consuming, which hinders clinical translation of the approach. Instead, expedited single-surgery gene therapy strategies must be developed. Therefore, in an in vitro experiment, we evaluated a novel growth factor delivery system, comprising adenoviral BMP-2 transduced fascia tissue in terms of BMP-2 release kinetics and osteogenic effects, on hADSCs seeded on an innovative biomimetic spongiosa-like scaffold. As compared to direct BMP-2 transduction of hADSCs or addition of recombinant BMP-2, overexpressing fascia provided a more uniform, constant level of BMP-2 over 30 days. Despite considerably higher BMP-2 peak levels in the comparison groups, delivery by overexpressing fascia led to a strong osteogenic response of hADSCs. The use of BMP-2 transduced fascia in combination with hADSCs may evolve into an expedited single-surgery gene transfer approach to bone repair.

Experimental measurements of micromotions of the cementless intervertebral disc prostheses in the cadaver bone.

BACKGROUND: Sufficient primary stability is mandatory for successful bony prosthetic incorporation. Therefore, defined micromotion values of 150 µm should not be exceeded as higher values might compromise the ingrowth of bone trabeculae to the implant surface. The aim of this study was to evaluate the primary stability of different cementless disc prosthesis in a cadaver model. METHODS: Four different implants with different anchoring and bearing concept were tested with a target level of L4/5. 26 specimens were randomly allocated to 1 of the 4 different implants with 6 speciments in each group. Two groups were formed depending on the anchoring (spikes vs. fin) and bearing concept (non-/semi- vs. constrained). Each implant was tested regarding primary stability in a hydraulic simulator allowing simultaneous polyaxial segment movements and axial loading. The measurements were recorded on the lower plate of the prosthesis. FINDINGS: The majority of the implants showed micromotion values below 200 µm in all planes. Only one prosthesis presented borderline longitudinal amplitudes that were significant higher than the other planes. Furthermore, significant differences were observed in the sagittal plane when comparing spike and keel anchoring. Spike anchoring implants showed superior tresults to keel anchoring implants (40 µm vs. 55 µm; p = .039), while the non-/semi-constrained bearing concept was more advantageous compared to constrained group (40 µm vs. 63 µm; p = .001). INTERPRETATION: Spike anchoring and non-constrained implants might provide better primary stability.

Impact of femoro-tibial size combinations and TKA design on kinematics.

INTRODUCTION: The variability in patients' femoral and tibial anatomy requires to use different tibia component sizes with the same femoral component size. These size combinations are allowed by manufacturers, but the clinical impact remains unclear. Therefore, the goals of our study were to investigate whether combining different sizes has an impact on the kinematics for two well-established knee systems and to compare these systems' kinematics to the native kinematics. MATERIALS AND METHODS: Six fresh frozen knee specimens were tested in a force controlled knee rig before and after implantation of a cruciate retaining (CR) and a posterior-stabilized (PS) implant. Femoro-tibial kinematics were recorded using a ultrasonic-based motion analysis system while performing a loaded squat from 30° to 130°. In each knee, the original best fit inlay was then replaced by different inlays simulating a smaller or bigger tibia component. The kinematics obtained with the simulated sizes were compared to the original inlay kinematics using descriptive statistics. RESULTS: For all size combinations, the difference to the original kinematics reached an average of 1.3 ± 3.3 mm in translation and - 0.1 ± 1.2° in rotation with the CR implant. With the PS implant, the average differences reached 0.4 ± 2.7 mm and  - 0.2 ± 0.8°. Among all knees, no size combination consistently resulted in significantly different kinematics. Each knee showed a singular kinematic pattern. For both knee systems, the rotation was smaller than in the native knee, but the direction of the rotation was preserved. The PS showed more rollback and the CR less rollback than the native knee. CONCLUSION: TKA systems designed with a constant tibio-femoral congruency among size combinations should enable to combine different sizes without having substantial impact on the kinematics. The rotational pattern was preserved by both TKA systems, while the rollback could only be maintained by the PS design.

Functional results after oncological scapula resections.

INTRODUCTION: Tumors of the scapula are rare representing only 1.6%-2.8% of all skeletal tumor localizations. Wide resection of these tumors is often necessary, and their anatomic location is the most decisive factor for the extent of the resection. Because of the importance of the shoulder girdle for all daily activities, such resections can have major functional consequences. However, only few reports with small numbers of cases are found in the literature. PATIENTS AND METHODS: We retrospectively evaluated 31 consecutive patients with scapular tumors treated surgically for aggressive benign or malignant tumors of the scapula. Patients who had received curettage only were excluded. Four of these 31 patients were lost to follow-up. In 7 of the remaining 27 patients, a total scapulectomy had to be performed, whereas all others received a partial resection. In 1 case, a partial resection and replantation after irradiation was performed. Musculoskeletal Tumor Society Scoring System (MSTS) and Toronto Extremity Salvage Score (TESS) scores were evaluated postoperatively at the time of their follow-up. RESULTS: In 16 men and 11 women, the median age was 46.2 years and the tumor entities were heterogeneous. The median follow-up time was 71 months. Three patients died during follow-up due to their tumor and 1 due to cardiac disease. We found significantly better functional results in the group with incomplete scapula resections as opposed to the scapulectomy group. We did not see a significant functional difference between the patients with benign and those with malignant lesions. Both the MSTS score with median 83.3% (range between 23% and 100%) and the TESS score with 81.6% (ranging from 20.4% to 100%) were at a satisfactory level. The preservation of the supraspinatus muscle was shown to be advantageous for better shoulder function, and younger patients also tended to have better postoperative results. CONCLUSION: The resection of scapular tumors may lead to a significant functional disability of the shoulder girdle and the affected arm in many cases. However, this is represented neither in the MSTS or TESS score nor in the overall acceptance of the patients. Only 1 patient, an artisan, had to change his job. In total, the clinical results are quite good in short- and long-term follow-up. The score results were comparable to other studies.

The Expression Levels of Toll-like Receptors after Metallic Particle and Ion Exposition in the Synovium of a Murine Model.

To date, the exact role of specific Toll-like receptors (TLRs) in regulating immune reactivity to metallic byproducts of orthopedic implants has not been fully clarified. In light of the situation, our objective in this investigation was to assess the expression levels of surface TLRs after metallic particle and ion exposure in an established animal model. Ten female BALB/c mice in each group received intra-articular injections of phosphate buffer (PBS) (control), metallic particles (MP), and metallic ions (MI), respectively. Seven days later, immunohistochemical staining was undertaken in the synovial layer of the murine knee joints using anti-TLR 1, 2, 4, 5, and 6 polyclonal antibodies. In addition to increased cellular infiltrates and a hyperplastic synovial membrane, the MP group showed significantly elevated TLR expression compared to the control group and had higher TLR 1-, 4-, and 6-positive cells than the MI group (p < 0.0167). TLR 4- and TLR 6-positive cells were significantly augmented for the MI group compared to the control group (p < 0.0167). Additionally, greenish corrosion particles found in the necrotic tissue suggested that metallic particles might release a certain level of locally toxic metallic ions in vivo.

Effects of a medical second opinion programme on patients' decision for or against knee arthroplasty and their satisfaction with the programme.

BACKGROUND: German social legislation gives patients the right to obtain a second opinion before elective surgery and defines quality criteria for reimbursement by statutory health insurances. However, the effects of second opinions before elective surgery are largely unknown. The aim of this study was to evaluate the effects of a second opinion programme in patients recommended for knee arthroplasty. METHODS: The largest statutory health insurance funds in Bavaria offered patients who had been recommended to have knee arthroplasty the opportunity to partake in a second opinion programme which consisted of an in person presentation to an experienced knee surgeon. In this cohort study, consecutive patients from this second opinion programme who signed informed consent were included from 07/10/2016 to 14/02/2020. Data were collected before and after the second opinion visit. RESULTS: A total of 141 (66%) of 215 patients who presented for a second opinion participated in the evaluation study. The second opinion physician recommended knee arthroplasty to 40% of the patients, later knee arthroplasty if the conditions worsened to 40%, and no knee arthroplasty to 20%. After receiving the second opinion 28 of 56 (41%) undecided patients preferred knee arthroplasty, 14 no knee arthroplasty, 14 remained undecided. Four of 46 patients with a preference for "arthroplasty" changed their decision to "no arthroplasty", five of 35 patients from "no arthroplasty" to "arthroplasty". The patients were more confident in their decision according to the decision confidence scale (before: 5.4 ± 3.0; after: 7.8 ± 2.5; p < 0.001). They rated their satisfaction with the second opinion programme with a mean grade of 1.35 (± 0.60) (best:1; worst:6). Logistic regression analyses showed that the recommendation of the second opinion physician for joint arthroplasty was associated with the guideline criteria radiological severity of osteoarthritis (p = 0.001) and knee-joint-specific quality of life (p = 0.041). CONCLUSION: The second opinion of an experienced knee surgeon frequently deviates from the initial recommendation for knee arthroplasty. The association of guideline criteria to the second recommendation suggests a high quality of the second opinion. From the patient perspective, the second opinion reduces uncertainties in their treatment decision.

Local and systemic inflammation after implantation of a novel iron based porous degradable bone replacement material in sheep model.

Despite the high potential of healthy bone to regenerate, the reconstruction of large bone defects remains a challenge. Due to the lack of mechanical stability of existing bone substitutes, recently developed degradable metallic alloys are an interesting alternative providing higher load-bearing capabilities. Degradable iron-based alloys therefore might be an attractive innovation. To test the suitability of a newly-designed iron-based alloy for such applications, an animal experiment was performed. Porous iron-based degradable implants with two different densities and a control group were tested. The implants were positioned in the proximal tibia of Merino sheep. Over a period of 6 and 12 months, blood and histological parameters were monitored for signs of inflammation and degradation. In the histological evaluation of the implants` environment we found degraded alloy particles, but no inflammatory reaction. Iron particles were also found within the popliteal lymph nodes on both sides. The serum blood levels of phosphorus, iron and ferritin in the long term groups were elevated. Other parameters did not show any changes. Iron-based degradable porous bone replacement implants showed a good biocompatibility in this experiment. For a clinical application, however, the rate of degradation would have to be significantly increased. Biocompatibility would then have to be re-evaluated.

Ceramic-on-Ceramic Bearing in Total Hip Arthroplasty Reduces the Risk for Revision for Periprosthetic Joint Infection Compared to Ceramic-on-Polyethylene: A Matched Analysis of 118,753 Cementless THA Based on the German Arthroplasty Registry.

Periprosthetic joint infection (PJI) is one of the most common complications in total hip arthroplasty (THA). The influence of bearing material on the risk of PJI remains unclear to date. This registry-based matched study investigates the role of bearing partners in primary cementless THA. Primary cementless THAs recorded in the German Arthroplasty Registry since 2012 with either a ceramic-on-ceramic (CoC) or ceramic-on-polyethylene (CoP) bearings were included in the analysis. Using propensity score matching (PSM) for age, sex, obesity, diabetes mellitus, Elixhauser comorbidity index, year of surgery and head size, we compared the risk for revision for PJI for CoC and CoP. Within the 115,538 THAs (87.1% CoP; 12.9% CoC), 977 revisions were performed due to PJI. There was a significantly higher risk for revision for PJI for CoP compared with CoC over the whole study period (p < 0.01) after 2:1 matching (CoP:CoC) with a hazard ratio of 1.41 (95% confidence interval (CI), 1.09 to 1.80) After 3 years, the risk for revision for PJI was 0.7% (CI 0.5-0.9%) for CoC and 0.9% (CI 0.8-1.1%) for CoP. The risk for revision for all other reasons except PJI did not significantly differ between the two groups over the whole study period (p = 0.4). Cementless THAs with CoC bearings were less likely to be revised because of infection in mid-term follow-up. In the future, registry-embedded studies focusing on long-term follow-up, including clinical data, as well as basic science studies, may give a deeper insight into the influence of the bearing partners.

Secondary Patellar Resurfacing in TKA: A Combined Analysis of Registry Data and Biomechanical Testing.

The German Arthroplasty registry (EPRD) has shown that different prosthesis systems have different rates of secondary patellar resurfacing: four years after implantation, the posterior-stabilized (PS) Vega prosthesis has a 3.2% risk of secondary patellar resurfacing compared to the cruciate-retaining (CR) Columbus prosthesis at 1.0% (both Aesculap AG, Tuttlingen, Germany). We hypothesized that PS implants have increased retropatellar pressure and a decreased retropatellar contact area compared to a CR design, which may lead to an increased likelihood of secondary patellar resurfacing. Eight fresh frozen specimens (cohort 1) were tested with an established knee rig. In addition, a possible influence of the registry-based patient collective (cohort 2) was investigated. No significant differences were found in patient data-cohort 2-(sex, age). A generally lower number of PS system cases is noteworthy. No significant increased patella pressure could be detected with the PS design, but a lower contact area was observed (cohort 1). Lower quadriceps force (100°-130° flexion), increased anterior movement of the tibia (rollback), greater external tilt of the patella, and increasing facet pressure in the Vega PS design indicate a multifactorial cause for a higher rate of secondary resurfacing which was found in the EPRD patient cohort and might be related to the PS' principle function.

Relative Sensitivity of Core-Needle Biopsy and Incisional Biopsy in the Diagnosis of Musculoskeletal Sarcomas.

BACKGROUND: There is no evidence as to the diagnostic value of the two most frequently used methods of biopsies in sarcomas: Incisional or core needle biopsy. The aim of our study was to evaluate the diagnostic sensitivity of the incisional and the core needle biopsy techniques in the diagnosis of bone and soft tissue sarcomas. METHODS: We included 417 patients with a definitive diagnosis of bone or soft tissue sarcoma in whom a total of 472 biopsies had been performed. We correlated the results of the biopsies with the result of the definitive histopathological examination of the resected tumor. Dignity, entity, and grading (whenever possible) of the tissue samples were evaluated. RESULTS: A total of 258 biopsies (55%) were performed in order to diagnose a soft tissue tumor and 351 biopsies (74.4%) were core needle biopsies. The number of repeat core needle biopsies, necessitated because of inconclusive histopathological results, was significantly higher (50 vs. 5; p = 0.003). We observed no significant difference regarding dignity, entity, and grading between the 2 different types of biopsies. Only with regards to the determination of dignity and entity of chondroid tumors, incisional biopsy was superior with statistical significance (p = 0.024). CONCLUSIONS: This study represents the largest study on biopsies for bone and soft tissue sarcomas. Based only on our results, we are unable to favor one method of biopsy and found high accuracy with both methods. Considering the potential complications, the added oncological risks of incisional biopsies and the ready availability of core needle biopsies, the latter, in our assessment, represents a valid and favourable method for bone and soft tissue sarcomas.

Short versus conventional stem in cementless total hip arthroplasty : An evidence-based approach with registry data of mid-term survival.

BACKGROUND: Short-stemmed total hip arthroplasty (THA) is well established and gaining popularity in Germany. The perception that short stems may predispose to primary instability in the femur has resulted in a more thorough follow-up of younger patient cohorts than the typical uncemented THA population. To address this issue, an evidence-based approach is presented for a retrospective mid-term survival analysis of a large registry-based cohort in primary cementless THA comparing short stems with a matched group of conventional stems. MATERIAL AND METHODS: Propensity score matching (PSM, see Infobox 1) was used on 131,580 primary cementless THAs fulfilling the inclusion criteria performed between November 2012 and September 2019 and the cumulative probability of revision (CPR) of short and conventional stems for any reason, for reasons excluding prosthetic joint infection (PJI), and due to PJI were compared. RESULTS: After PSM at 1:1 balanced groups of 17,526 short stems and of 17,526 conventional stems were achieved demonstrating no significant difference for CPR for any reason and for reasons excluding PJI. Matched CPR for any reason was 2.9% (95% confidence interval, CI, 2.4-3.5%) 5 years after primary THA in the short stem and 3.1% (95% CI 2.7-3.4%) in the conventional stem group. The CPR excluding PJI was 2.2% (95% CI 1.7-2.7%) vs. 2.1% (95% CI 1.8-2.4%). In contrast, the incidence of PJI was statistically significant lower for short stems. CONCLUSION: For the considered period, there was no statistically significant survival difference in uncemented THA between comparison groups but a lower incidence for PJI in short-stem THA. Further analyses of registry data are required to rule out range of indications and late mechanical failure of short stems.

Osteoinduction within adipose tissue fragments by heterodimeric bone morphogenetic Proteins-2/6 and -2/7 versus homodimeric bone morphogenetic protein-2: Therapeutic implications for bone regeneration.

BACKGROUND: Fragments of subcutaneous adipose tissue that have been genetically modified to express bone morphogenetic protein-2 (BMP-2) regenerate large segmental osseous lesions in rodents. Gene-activated adipose tissue can be implanted into osseous defects without prior cell extraction and cell culture. The present study aimed to explore whether the heterodimers BMP-2/6 or BMP-2/7 exceed the osteoinductive effect of BMP-2 on adipose tissue. METHODS: In an in vitro tissue culture system, freshly harvested rat subcutaneous adipose tissue was cultivated in the presence of either BMP-2 or BMP-2/6 or BMP-2/7 at a high (200 ng/ml) and low (50 ng/ml) concentration. Gene expression analysis as well as histological and immunohistochemical methods were applied to test for osteoinduction. RESULTS: A concentration of 200 ng/ml of homodimeric BMP-2 induced osteogenic differentiation most potently, showing more calcification and a higher expression level of bone markers than both concentrations of BMP-2/6 or -2/7. A concentration of 50 ng/ml of BMP-2 was a significantly stronger osteogenic inducer than both concentrations of BMP-2/6 and the low concentration of BMP-2/7. The most potent heterodimeric driver of osteoinduction was BMP-2/7 at a high concentration, demonstrating effects similar to those of BMP-2 at a low concentration. CONCLUSIONS: Homodimeric BMP-2 evoked osteoinduction within adipose tissue more potently and at a lower concentration than heterodimeric BMP-2/6 or BMP-2/7. This result agrees well with the fact that it might be easier to translate adipose grafts activated by homodimeric BMP-2 clinically. Preclinical in vivo gene transfer studies are necessary to confirm the results of the present study.

Ceramic Coating in Cemented Primary Total Knee Arthroplasty is Not Associated With Decreased Risk of Revision due to Early Prosthetic Joint Infection.

BACKGROUND: Prosthetic joint infection (PJI) is one of the most frequent and devastating causes of short-term revision total knee arthroplasty (TKA). In vitro evidence suggests ceramic surfaces demonstrate resistance to biofilm, but the clinical effect of bearing surface modifications on the risk of PJI remains unclear. This premier registry-based study examines the influence of ceramic bearing surface coatings on the outcome in cemented primary TKA. METHODS: In total, 117,660 cemented primary TKAs in patients with primary osteoarthritis recorded in the German arthroplasty registry since 2012 were followed up for a maximum of 3 years. The primary endpoint was risk of revision for PJI on ceramic coated and uncoated cobalt-chromium-molybdenum femoral components. Propensity score matching for age, gender, obesity, diabetes mellitus, depression and Elixhauser comorbidity index, and substratification on common design twins with and without coating was performed. RESULTS: In total, 4637 TKAs (85.1% female) with a ceramic-coated femoral component were identified, 42 had been revised for PJI and 122 for other reasons at 3 years. No survival advantage due to the risk of revision for PJI could be determined for ceramic-coated components. Revision for all other reasons demonstrated a significant higher rate for TKAs with ceramic-coated components. However, the results of this were confounded by a strong prevalence (20.7% vs 0.3%) of metal sensitivity in the ceramic-coated group. CONCLUSION: No evidence of reduced risk for PJI due to ceramic-coated implants in cemented primary TKA was found. Further analysis for revision reasons other than PJI is required.

Desmoid Tumors of the Foot: A Retrospective Study of Four Patients.

BACKGROUND: Desmoid-type fibromatosis (DF) is an aggressive (myo)fibroblastic neoplasm with an infiltrative growth pattern and a tendency for local recurrence. It is rarely seen at the foot. The aim of this retrospective study was to analyze clinical presentation, therapy, and outcomes in a consecutive series of four patients with DF at the foot. METHODS: From 1994 to 2014, four patients had been surgically treated. The resection margin was marginal or even intralesional in all. One patient already had local recurrence at first presentation. The end point was either local recurrence or progression of residual disease. RESULTS: The mean patient age was 27 years. In one patient, marginal excision healed the disease. In another patient, local recurrence after marginal resection necessitated distal phalanx amputation. Two other patients showed stable disease after either adjuvant radiotherapy or treatment with nonsteroidal anti-inflammatory drugs and tamoxifen. CONCLUSIONS: If surgery is necessary, operative margins are less important than keeping function for the patient. Radiotherapy might be an option to avoid major amputation. The role of adjuvant radiotherapy is controversially discussed. A watchful wait-and-see policy seems to be justified by the published data but may be difficult for DF at the foot.

[Realistic preclinical finite element simulation in knee and hip replacements]. / Realitätsnahe Finite-Elemente-Simulation in der präklinischen Testung von Knie- und Hüftimplantaten.

BACKGROUND: In the process of developing an implant, computer simulation involving finite element (FE) methods allows the early identification of design-related issues, thus reducing the development process to a minimum. In addition, the FE simulation is used for selecting testing combinations in order to provide the relevant authority with proof of a "worst-case" construct scenario for the subsequent experimental fatigue test. RESULTS: Research studies with FE simulations show that implant positioning may affect mechanical loads under certain circumstances and, therefore, influence the preclinical evaluation of the prostheses. DISCUSSION: Although the FE simulation currently contributes significantly to preclinical testing, a standardization of the calculation models allowing comparability of results is lacking. Furthermore, the development of new dynamic and realistic models is necessary in order to identify complex damage modes that currently cannot be reproduced experimentally. When considering everyday clinical life in particular, models that can reproduce intraoperative kinematic changes and the resulting incorrect loads of the implant, as well as address these problems by changing the position or design of the prosthesis, are necessary and would help in future.

Metaphyseal anchoring short stem hip arthroplasty provides a more physiological load transfer: a comparative finite element analysis study.

BACKGROUND: Short stem total hip arthroplasty (SHA) preserves femoral bone stock and is supposed to provide a more natural load transfer compared to standard stem total hip arthroplasty (THA). As comparative biomechanical reference data are rare we used a finite element analysis (FEA) approach to compare cortical load transfer after implantations of a metaphyseal anchoring short and standard stem in native biomechanical femora. METHODS: The subject specific finite element models of biomechanical femora, one native and two with implanted metaphyseal anchoring SHA (Metha, B. Braun Aesculap) and standard THA (CLS, Zimmer-Biomet), were generated from computed tomography datasets. The loading configuration was performed with an axial force of 1400 N. Von Mises stress was used to investigate the change of cortical stress distribution. RESULTS: Compared to the native femur, a considerable reduction of cortical stress was recorded after implantation of SHA and standard THA. The SHA showed less reduction proximally with a significant higher metaphyseal cortical stress compared to standard THA. Moreover, the highest peak stresses were observed metaphyseal for the SHA stem while for the standard THA high stress pattern was observed more distally. CONCLUSIONS: Both, short and standard THA, cause unloading of the proximal femur. However, the metaphyseal anchoring SHA features a clearly favorable pattern in terms of a lower reduction proximally and improved metaphyseal loading, while standard THA shows a higher proximal unloading and more distal load transfer. These load patterns implicate a reduced stress shielding proximally for metaphyseal anchoring SHA stems and might be able to translate in a better bone preservation.

Primary bone lymphoma: Clinical presentation and therapeutic considerations.

BACKGROUND: Primary lymphoma of bone (PBL) is a rare entity. Due to unspecific clinical signs and equivocal radiographs diagnosis may be delayed. This retrospective report of 109 PBL cases demonstrates typical aspects of the lesion. Treatment and prognostic factors are evaluated. METHODS: Retrospectively patient records were reviewed. All patients were followed for evidence of local or distant recurrence. Overall survival (OS) was used as clinical outcome. RESULTS: The median age of the 109 patients was 62.8 years. The most common symptoms were pain (76%), swelling (29%), neurologic symptoms and pathological fracture (16% each). Mean duration of symptoms was 8 months (0-197 months).19% of patients had indolent NHL subtypes, 72% aggressive NHL subtypes and 7% cases Hodgkin disease. Cyclophosphamid, doxorubicin, vincristine and prednisone (CHOP) or CHOP plus rituximab (RCHOP) were given in 88 (81%) of patients. Radiotherapy was delivered in 67 (61%) of cases. 51 (47%) patients received both. Surgical interventions were restricted to cases with complications as fractures.The 5-year OS was 66%. The 5-year OS was 66%. In the subgroup of 78 patients with aggressive NHL subtype there was a highly significant benefit for chemotherapy or chemotherapy and radiation in comparison to no treatment or radiation alone. Raised LDH, age, IPI and ECOG performance were prognostic factors. In multivariate analysis, age and raised LDH levels only kept significance. CONCLUSIONS: In our series of primary bone lymphoma, chemotherapy resulted in a better outcome than Radiotherapy alone. Long-term survival is based on the stage of the disease, favoring younger (<60 years) patients with solitary bone lesions, low level of LDH and favourable ECOG performance status and IPI scores.