Stefan Andereya

A Prospective Multicenter Study on the Outcome of Type I Collagen Hydrogel–Based Autologous Chondrocyte Implantation (CaReS) for the Repair of Articular Cartilage Defects in the Knee

Background: The Cartilage Regeneration System (CaReS) is a novel matrix-associated autologous chondrocyte implantation (ACI) technique for the treatment of chondral and osteochondral lesions (Outerbridge grades III and IV). For this technology, no expansion of the chondrocytes in a monolayer culture is needed, and a homogeneous cell distribution within the gel is guaranteed. Purpose: To report a prospective multicenter study of matrix-associated ACI of the knee using a new type I collagen hydrogel (CaReS). Study Design: Case series; Level of evidence, 4. Methods: From 2003 to 2008, 116 patients (49 women and 67 men; mean age, 32.5 ± 8.9 years) had CaReS implantation of the knee in 9 different centers. On the basis of the International Cartilage Repair Society (ICRS) Cartilage Injury Evaluation Package 2000, the International Knee Documentation Committee (IKDC) score, pain score (visual analog scale [VAS]), SF-36 score, overall treatment satisfaction and the IKDC functional status were evaluated. Patient follow-up was performed at 3, 6, and 12 months after surgery and annually thereafter. Mean follow-up was 30.2 ± 17.4 months (range, 12-60 months). There were 67 defects of the medial condyle, 14 of the lateral, 22 of the patella/trochlea, and 3 of the tibial plateau, and 10 patients had 2 lesions. The mean defect size was 5.4 ± 2.4 cm2. Thirty percent of the defects were <4 cm2 and 70% were >4 cm2. Results: The IKDC score improved significantly from 42.4 ± 13.8 preoperatively to 70.5 ± 18.7 (P < .001) at latest follow-up. Global pain level significantly decreased (P < .001) from 6.7 ± 2.2 preoperatively to 3.2 ± 3.1 at latest follow-up. There also was a significant increase of both components of the SF-36 score. The overall treatment satisfaction was judged as very good or good in 88% by the surgeon and 80% by the patient. The IKDC functional knee status was grade I in 23.4%, II in 56.3%, III in 17.2%, and IV in 3.1% of the patients. Conclusion: Matrix-associated ACI employing the CaReS technology for the treatment of chondral or osteochondral defects of the knee is a safe and clinically effective treatment that yields significant functional improvement and improvement in pain level. However, further investigation is necessary to determine the long-term viability and clinical outcome of this procedure.

BMP-2 Incorporated in a Tricalcium Phosphate Bone Substitute Enhances Bone Remodeling in Sheep

Bone morphogenetic protein-2 (BMP-2) is a well-known osteoinductive protein, which requires a carrier for local application. As an alternative to the previously described carriers, an in situ hardening, resorbable, and osteoconductive β-tricalcium phosphate cement (TCP) is tested. Trepanation defects in the bovine distal femoral epiphysis are filled with a composite consisting of TCP and 200 μg rhBMP-2 per cm3 TCP, autologous bone graft, pure TCP, or left empty. A radiological follow-up is performed after 7 weeks and 3 months. The sheep are euthanized and bone samples are analyzed by microradiography, histology, and histomorphometry. Microradiography and histology show similar results for pure TCP and the composite. The defects are filled with trabecular bone and newly formed bone is in close contact with the remaining TCP-particles. The majority of the cement is resorbed, in the composite group the amount of remaining cement particles is reduced. Defects treated with autologous bone graft are filled completely, while untreated defects shows only a small amount of bone originating from the rim of the defect. Histomorphometry of the defects treated with pure TCP shows a significantly increased bone content in comparison to defects treated with the composite or autologous bone graft. Analysis of the remaining cement particles shows significantly less cement in the TCP/rhBMP-2 group in comparison to pure TCP. The sum of bone and cement content in the rhBMP-2 group shows amounts comparable to the calcified structures found following autologous bone grafting. The addition of rhBMP-2 to the TCP leads to faster remodeling of the defect comparable to autologous bone graft, while defects treated with pure TCP are not completely remodeled.

Assessment of leech therapy for knee osteoarthritis: A randomized study

Background and purpose Symptomatic treatment of osteoarthritis of the knee with leeches is presently undergoing a renaissance. Previous studies have shown methodical weaknesses. In the present study patients were blinded regarding the treatment, and a control group was included to explore possible differences in various subjective clinical scores and intake of pain medication over time between leech therapy and placebo control. Patients and methods 113 patients with advanced osteoarthritis of the knee were included. The patients were randomized to a single treatment group, group I (single leech application, n = 38), a double treatment group, group II (double application, n = 35), and a control group (n = 40). The second treatment in group II took place after an interval of 4 weeks. The treatment in the control group was simulated with the help of an “artificial leech”. Results were documented with the KOOS and WOMAC scores and also a visual analog scale (VAS) for pain. Changes in the use of pain medication were monitored over 26 weeks. Results An improvement in KOOS and WOMAC scores, and also in VAS, was found in all 3 groups following treatment. These improvements were statistically significant for treatment groups I and II during the complete follow-up period. The reduction in individual requirements for pain medication was also statistically significant. The greatest improvement was seen in the group treated twice with the leeches, with a long-term reduction of joint stiffness and improved function in the activities of daily living. Interpretation Leech therapy can reduce symptoms caused by osteoarthritis. Repeated use of the leeches appears to improve the long-term results. We have not determined whether the positive outcome of the leech therapy is caused by active substances released during the leeching, the placebo effect, or the high expectations placed on this unusual treatment form.

In vitro comparison of six different matrix systems for the cultivation of human chondrocytes

SummaryIn recent years, a great variety of different matrix systems for the cultivation of chondrocytes have been developed. Although some of these scaffolds show promising experimental results in vitro, the potential clinical value remains unclear. In this comparative study, we propagated human articular chondrocytes precultivated in monolayer culture on six different scaffolds (collagen gels, membranes and sponges) under standardized in vitro conditions. Mechanical properties of the matrix systems were not improved significantly by cultivation of human chondrocytes under the given in vitro conditions. The gel systems (CaReS, Ars Artho, Germany and Atelocollagen, Koken, Japan) showed a homogeneous cell distribution; chondrocytes propagated on Chondro-Gide (Geistlich Biomaterials, Switzerland) and Integra membranes (Integra, USA) were building multilayers. Only few cells penetrated the two Atelocollagen honeycomb sponges (Koken, Japan). During cultivation, chondrocytes propagated on all systems showed a partial morphological redifferentiation, which was best with regard to the gel systems. In general, only small amounts of collagen type-II protein could be detected in the pericellular region and chondrocytes failed to build a territorial matrix. During the first two weeks of cultivation, the two gel systems showed a significantly higher collagen type-II gene expression and a lower collagen type-I gene expression than the other investigated matrix systems. Although collagen gels seem to be superior when dealing with deep cartilage defects, membrane systems might rather be useful in improving conventional autologous chondrocyte transplantation or in combination with gel systems.

Klinische Drei-Jahres-Ergebnisse der matrixgekoppelten ACT zur Behandlung osteochondraler Defekte am Kniegelenk

AIM The aim of this study was to examine the clinical results after the treatment of osteochondral defects of the knee with autologous bone grafting and matrix-supported autologous chondrocyte transplantation (ACT). METHOD In this study 13 patients with osteochondral defects of the knee (12 femoral, 1 tibial) with OCD ICRS grade IV or ICRS grade IV B were included. The osteochondral defects were reconstructed simultaneously with autologous monocortical cancellous bone cylinders or chips from cancellous bone and matrix-supported autologous chondrocyte transplantation (CaReS). Data were analysed in accordance with the ICRS criteria and the Brittberg score. Patients were followed up to 36 months after the operation. RESULTS The average age of the patients was 34.9 (16 - 47) years at the time of surgery. The size of the defect was 8.1 (3.8 - 13.5) cm(2). The subjective and objective IKDC scores, the Brittberg and the ICRS function score were statistically significantly improved during the observation time. In one patient the transplantation failed and another patient was not available for the follow-up at 36 months. The objective IKDC score and the ICRS function score increased from 0/13 (0 %) to 11/12 (91.7 %) in categories A and B, or I and II, respectively, after 3 years. At this point of time 83.4 % (10/12) of the patients voted the treatment as excellent or good. The subjective IKDC score improved from 38.4 (+/- 12.7) preoperatively to 66.1 (+/- 17.0) after 3 years. CONCLUSION The treatment of osteochondral defects of the knee with autologous bone grafting and matrix-supported autologous chondrocyte transplantation shows promising results even for larger defects. But for a final decision about this therapy the present sample size was too small. There is a need for further long-term investigation with a larger number of patients.

Comparison of modern marker proteins in serum and synovial fluid in patients with advanced osteoarthrosis and rheumatoid arthritis

Numerous studies have focused on the significance of modern marker proteins in the synovial fluid of the knee joint and in the serum both, for osteoarthritis (OA) and rheumatoid arthritis (RA). The relationship between the serum concentrations and the concentrations in the synovial fluid is still unclear. Synovial fluid and serum samples were obtained from 13 patients with advanced OA and from 8 patients with severe RA and concentrations of MMP-1, MMP-3, MMP-13, TIMP-1, COMP and MIA/CD-RAP were determined. All values were normalized against the total protein concentrations. Serum concentrations of MMP-13 in the RA-group were statistically higher than the synovial values (P<0.05). MMP-13 was the only marker protein that revealed distinct higher levels in the serum than in the synovial fluid. The study design allows only conclusions about advanced stages of RA and OA. Longitudinal investigations may provide further information about the value of MMP-13 as a potential marker to monitor the course of RA and OA.

Condensed cellular seeded collagen gel as an improved biomaterial for tissue engineering of articular cartilage.

Three-dimensional autologous chondrocyte implantation based on collagen gel as matrix scaffold has become a clinically applied treatment for focal defects of articular cartilage. However, the low biomechanical properties of collagen gel makes intraoperative handling difficult and creates the risk of early damages to the vulnerable implant. The aim of the study was to create a stabilized form of collagen gel and to evaluate its biomechanical and biochemical properties.Collagen type-I gel was seeded with human articular chondrocytes. 20 samples were subject to condensation which was achieved mechanically by compression and filtration. Control samples were left uncondensed. From both types of gels 10 samples were used for initial biomechanical evaluation by means of unconfined compression and 10 samples were cultivated under standard conditions in vitro. Following cultivation the samples were evaluated by conventional histology and immunohistochemistry. The proliferation rate was calculated and matrix gene expression was quantified by real-time PCR.The biomechanical tests revealed a higher force carrying capacity of the condensed specimens. Strain rate dependency and relaxation was seen in both types of collagen gel representing viscoelastic material properties. Cells embedded within the condensed collagen gel were able to produce extracellular matrix proteins and showed proliferation.Condensed collagen gel represents a mechanically improved type of biomaterial which is suitable for three-dimensional autologous chondrocyte implantation.

Uncemented femoral revision arthroplasty using the modular revision prosthesis MRP-TITAN revision stem.

ZusammenfassungOperationszielWiederherstellung eines schmerzfrei belastbaren Hüftgelenks mit einem zementfrei implantierten, rotationsstabilen, diaphysär verankerten modularen Revisionsschaft.IndikationenProthesenschaftlockerungen mit osteolytischen Knochendefekten (Defektklassifikation nach Paprosky Typ I–III). Materialversagen mit Prothesenbruch.Sub- und/oder periprothetische Femurfrakturen.Tumoren.KontraindikationenAusgedehnte Osteolysen, die eine diaphysäre Prothesenverankerung nicht erlauben.OperationstechnikTransglutealer Zugang zum Hüftgelenk. Entfernen des gelockerten Prothesenschafts und — im zementierten Fall — des Knochenzements. Entfernen des intramedullären Granulationsgewebes. Aufbohren des Markraums mit flexiblen Bohrwellen und formschlüssige, zementfreie Implantation des sternförmigen modularen Revisionsschaftes mit diaphysärem „Press-fit‘ Bei ausgedehntem metaphysären Knochendefekt Augmentation mit autogenem/allogenem Knochen.WeiterbehandlungMobilisation an zwei Unterarmgehstützen ab dem 1. postoperativen Tag. Entfernen der einliegenden Redon-Drainagen nach 48 h. Teilbelastung mit 20 kg für 6 Wochen postoperativ. Bei nativradiologisch unverändertem Prothesensitz nach 6 Wochen Steigerung der Belastung um wöchentlich 10 kg bis zur Vollbelastung unter Fortführen der Thromboseprophylaxe. Röntgenkontrollen im weiteren Verlauf nach 3, 6 und 12 Monaten. Anschließend jährliche Verlaufskontrolle.ErgebnisseUntersucht wurden 45 Patienten (n = 48 Prothesen) mit einem durchschnittlichen Lebensalter von 67,2 Jahren (min.–max. 42,4–87,4 Jahre). Die mittlere Prothesenstandzeit der Modularen Revisions Prothese MRP-TITAN-Revisionsschaft betrug 4,7 Jahre (min.–max. 1,0–9,0 Jahre). Der Harris-Hip-Score — differenziert nach den Knochendefekttypen Paprosky I–III — stieg von 25,6 präoperativ auf 71,4 postoperativ zum Zeitpunkt der letzten Nachuntersuchung (≤0,05). 32 Patienten wiesen präoperativ einen ausgedehnten knöchernen Defekt auf (≥Paprosky IIB). 44 Patienten zeigten nativradiologisch eine stabile Verankerung ohne Migration. In einem Fall wurde der Schaft (Standzeit 2,36 Jahre) bei zunehmendem axialen Einsinken (≥5 mm) gewechselt. Bei allen Patienten mit Knochentransplantation (n = 30) zeigte sich ein guter Transplantateinbau mit konsekutiver Defektregeneration. Bei sechs Patienten kam es zu postoperativen Luxationen mit nachfolgender viermaliger geschlossener Reposition. Bei zwei Patienten wurde offen reponiert und der Antetorsionswinkel des Prothesenhalses ohne Ausbau der distal verankerten Prothesenschaftkomponente korrigiert. Mechanische Versagerquote im 9-Jahres-Nachuntersuchungszeitraum: eine von 48 prospektiv untersuchten Prothesen. Überlebensrate nach Kaplan-Meier 97%.AbstractObjectiveRestoration of a painless hip joint capable of bearing weight by uncemented implantation of a rotationally stable, modular revision stem anchored in the diaphysis.IndicationsProsthetic stem loosening with osteolytic bone defects (defect classification types I–III according to Paprosky). Material failure with broken prosthesis.Sub- and/or periprosthetic femoral fractures.Tumors.ContraindicationsExtensive osteolysis preventing diaphyseal anchorage of the prosthesis.Surgical TechniqueTransgluteal approach to the hip joint. Removal of the loose prosthetic stem and, if cemented, the bone cement as well. Excision of intramedullary granulation tissue. Reaming of the medullary cavity with flexible reaming shafts and form-fit, uncemented implantation of the star-shaped modular revision stem with diaphyseal press fit. If there is extensive loss of metaphyseal bone stock, augmentation with autogenous/allogenic bone should be performed.Postoperative ManagementMobilization on two underarm crutches from the 1st postoperative day. Removal of the Redon drains after 48 h. Partial loading with 20 kg for 6 weeks postoperatively. If plain radiographs show unchanged seating of the prosthesis after 6 weeks, loading can be increased by 10 kg per week until full weight bearing is achieved; thrombosis prophylaxis is continued throughout. Radiologic checkups after 3, 6, and 12 months. After that, the patient should be checked annually.Results45 patients (n = 48 prostheses) with an average age of 67.2 years (min.–max. 42.4–87.4 years) were investigated. The average implantation time of the Modular Revision Prosthesis MRP-TITAN revision stem was 4.7 years (min.–max. 1.0–9.0 years). The Harris Hip Score for Paprosky bone defect types I–III had increased from 25.6 preoperatively to 71.4 postoperatively at the time of the final follow-up (≤0.05). Extensively defective bone was diagnosed preoperatively in 32 patients (≥Paprosky IIB). Plain radiographs showed stable anchorage without migration in 44 patients. In one case, the stem (implantation time 2.36 years) was replaced due to increasing axial subsidence (≥5 mm). Good integration of bone graft with subsequent defect regeneration was seen in all patients with bone transplant (n = 30). Postoperative dislocation occurred in six patients and required closed reduction in four cases. Open reduction was performed in two patients, whereby the external rotation angle of the prosthetic neck was corrected without dismantling the distally anchored prosthetic stem components. The mechanical failure rate over the follow-up period of 9 years was one out of the 48 prospectively investigated prostheses. Rate of survival according to Kaplan-Meier was 97%.

Zementfreier Femurschaftwechsel mit der Modularen Revisions Prothese MRP-TITAN-Revisionsschaft

ZusammenfassungOperationszielWiederherstellung eines schmerzfrei belastbaren Hüftgelenks mit einem zementfrei implantierten, rotationsstabilen, diaphysär verankerten modularen Revisionsschaft.IndikationenProthesenschaftlockerungen mit osteolytischen Knochendefekten (Defektklassifikation nach Paprosky Typ I–III). Materialversagen mit Prothesenbruch.Sub- und/oder periprothetische Femurfrakturen.Tumoren.KontraindikationenAusgedehnte Osteolysen, die eine diaphysäre Prothesenverankerung nicht erlauben.OperationstechnikTransglutealer Zugang zum Hüftgelenk. Entfernen des gelockerten Prothesenschafts und — im zementierten Fall — des Knochenzements. Entfernen des intramedullären Granulationsgewebes. Aufbohren des Markraums mit flexiblen Bohrwellen und formschlüssige, zementfreie Implantation des sternförmigen modularen Revisionsschaftes mit diaphysärem „Press-fit‘ Bei ausgedehntem metaphysären Knochendefekt Augmentation mit autogenem/allogenem Knochen.WeiterbehandlungMobilisation an zwei Unterarmgehstützen ab dem 1. postoperativen Tag. Entfernen der einliegenden Redon-Drainagen nach 48 h. Teilbelastung mit 20 kg für 6 Wochen postoperativ. Bei nativradiologisch unverändertem Prothesensitz nach 6 Wochen Steigerung der Belastung um wöchentlich 10 kg bis zur Vollbelastung unter Fortführen der Thromboseprophylaxe. Röntgenkontrollen im weiteren Verlauf nach 3, 6 und 12 Monaten. Anschließend jährliche Verlaufskontrolle.ErgebnisseUntersucht wurden 45 Patienten (n = 48 Prothesen) mit einem durchschnittlichen Lebensalter von 67,2 Jahren (min.–max. 42,4–87,4 Jahre). Die mittlere Prothesenstandzeit der Modularen Revisions Prothese MRP-TITAN-Revisionsschaft betrug 4,7 Jahre (min.–max. 1,0–9,0 Jahre). Der Harris-Hip-Score — differenziert nach den Knochendefekttypen Paprosky I–III — stieg von 25,6 präoperativ auf 71,4 postoperativ zum Zeitpunkt der letzten Nachuntersuchung (≤0,05). 32 Patienten wiesen präoperativ einen ausgedehnten knöchernen Defekt auf (≥Paprosky IIB). 44 Patienten zeigten nativradiologisch eine stabile Verankerung ohne Migration. In einem Fall wurde der Schaft (Standzeit 2,36 Jahre) bei zunehmendem axialen Einsinken (≥5 mm) gewechselt. Bei allen Patienten mit Knochentransplantation (n = 30) zeigte sich ein guter Transplantateinbau mit konsekutiver Defektregeneration. Bei sechs Patienten kam es zu postoperativen Luxationen mit nachfolgender viermaliger geschlossener Reposition. Bei zwei Patienten wurde offen reponiert und der Antetorsionswinkel des Prothesenhalses ohne Ausbau der distal verankerten Prothesenschaftkomponente korrigiert. Mechanische Versagerquote im 9-Jahres-Nachuntersuchungszeitraum: eine von 48 prospektiv untersuchten Prothesen. Überlebensrate nach Kaplan-Meier 97%.AbstractObjectiveRestoration of a painless hip joint capable of bearing weight by uncemented implantation of a rotationally stable, modular revision stem anchored in the diaphysis.IndicationsProsthetic stem loosening with osteolytic bone defects (defect classification types I–III according to Paprosky). Material failure with broken prosthesis.Sub- and/or periprosthetic femoral fractures.Tumors.ContraindicationsExtensive osteolysis preventing diaphyseal anchorage of the prosthesis.Surgical TechniqueTransgluteal approach to the hip joint. Removal of the loose prosthetic stem and, if cemented, the bone cement as well. Excision of intramedullary granulation tissue. Reaming of the medullary cavity with flexible reaming shafts and form-fit, uncemented implantation of the star-shaped modular revision stem with diaphyseal press fit. If there is extensive loss of metaphyseal bone stock, augmentation with autogenous/allogenic bone should be performed.Postoperative ManagementMobilization on two underarm crutches from the 1st postoperative day. Removal of the Redon drains after 48 h. Partial loading with 20 kg for 6 weeks postoperatively. If plain radiographs show unchanged seating of the prosthesis after 6 weeks, loading can be increased by 10 kg per week until full weight bearing is achieved; thrombosis prophylaxis is continued throughout. Radiologic checkups after 3, 6, and 12 months. After that, the patient should be checked annually.Results45 patients (n = 48 prostheses) with an average age of 67.2 years (min.–max. 42.4–87.4 years) were investigated. The average implantation time of the Modular Revision Prosthesis MRP-TITAN revision stem was 4.7 years (min.–max. 1.0–9.0 years). The Harris Hip Score for Paprosky bone defect types I–III had increased from 25.6 preoperatively to 71.4 postoperatively at the time of the final follow-up (≤0.05). Extensively defective bone was diagnosed preoperatively in 32 patients (≥Paprosky IIB). Plain radiographs showed stable anchorage without migration in 44 patients. In one case, the stem (implantation time 2.36 years) was replaced due to increasing axial subsidence (≥5 mm). Good integration of bone graft with subsequent defect regeneration was seen in all patients with bone transplant (n = 30). Postoperative dislocation occurred in six patients and required closed reduction in four cases. Open reduction was performed in two patients, whereby the external rotation angle of the prosthetic neck was corrected without dismantling the distally anchored prosthetic stem components. The mechanical failure rate over the follow-up period of 9 years was one out of the 48 prospectively investigated prostheses. Rate of survival according to Kaplan-Meier was 97%.

Measures for reducing ultra-high-molecular-weight polyethylene wear in total knee replacement: a simulator study.

Abstract Wear of ultra-high-molecular-weight polyethylene (UHM-WPE) inlays is associated with aseptic loosening in total knee replacement (TKR). The aim of this study was to investigate the in vitro performance of a TKR system that combines several measures to decrease UHMWPE wear. Tests were carried out on a BPK-S Integration system (R&D, P. Brehm Chirurgie-Mechanik, Weisendorf, Germany) according to ISO 14243-1 in a knee joint simulator. Calf serum with a high protein concentration of 30 g/l was chosen as the test lubricant. PE wear was measured gravimetrically. Particle analysis was performed by scanning electron microscopy, with measurement of particle size and shape. Low mean wear rates of 1.20 mg per million cycles were found for the fixed bearing type and 2.47 mg per million cycles for the rotating-platform bearing design. Anteroposterior deflection was low. The contact areas for both types of bearings were large and showed a constant pattern throughout the test. Backside wear was obvious on rotating platforms. Particle analysis revealed equally sized and round-shaped particles in both types of bearings (fixed, 0.35 μm; mobile, 0.32 μm). In conclusion, the combination of design features and surface modifications of the BPK-S integration TKR system leads to low gravimetric UHMWPE wear. Zusammenfassung Abrieb von Ultra-High-Molecular-Weight Polyethylen (UHMWPE) gilt als eine der wesentlichen Ursachen für die aseptische Lockerung von Knieendoprothesen. Das Ziel dieser Studie ist es, das Abriebverhalten eines Knieendoprothesensystems zu untersuchen, welches verschiedene Ansätze zur Abriebsminimierung vereint. Getestet wurde das BPK-S Integration-System der Firma R&D, P. Brehm Chirurgie-Mechanik (Weisendorf, Germany), gemäß ISO 14243-1, in einem Kniesimulator. Es wurde Kälberserum mit einer erhöhten Proteinkonzentration von 30 g/l eingesetzt. Der PE-Abrieb wurde gravimetrisch bestimmt. Die Abriebpartikel wurden mittels Elektronenmikroskopie nach deren Form und Größe analysiert. Es fanden sich insgesamt geringe Abriebraten von 1,2 mg pro 1 Mio. Zyklen beim „fixed bearing”- und 2,47 mg pro 1 Mio. Zyklen beim „mobile bearing”-System. Die a.-p.-Auslenkung war gering. Die femorotibialen Kontaktflächen zeigten bei beiden ultrakongruenten Systemen keine wesentliche Veränderung über den Prüfungszeitraum. An den Inlays des „mobile bearing”-Systems fanden sich Zeichen des „backside wear”. Die Partikelanalyse zeigte vergleichbar große, überwiegend runde Abriebpartikel („fixed”, 0,35 μm; „mobile”, 0,32 μm). Zusammenfassend fand sich als Folge der Oberflächenbehandlung und des Designs des BPK-S Integration-Systems ein sehr geringer gravimetrischer Abrieb im Vergleich zu Angaben über andere, ebenfalls nach ISO 14243-1 gemessene Kniesysteme.