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Osteonecrosis of the femoral head or avascular necrosis of the femoral head (HKN) is a complex disease that, without treatment, leads to infraction of the femoral head in most cases. In these cases, only replacement of the hip joint will help, although there is no clear recommendation of an arthroplasty type. In the last two decades, the treatment of primary and secondary coxarthrosis with short-shaft prostheses with different anchoring philosophies has increased. Since short-shaft fitting is a possible option especially in younger patients, the question arises about possible fittings of advanced HKN with these stem types, especially with metaphyseal anchorage. The aim of this study was to review the existing literature on the results of short stem prosthesis in HKN and to present the advantages and disadvantages of short stem prosthesis in osteonecrosis of the femoral head.This review analyzes the existing studies on short stem arthroplasty for HKN.Only a few studies exist that have analyzed clinical and radiologic outcomes of short stem replacement in HKN.The existing short- and medium-term results show mostly good outcomes. However, it is difficult to draw a general conclusion due to differences in stem design and fixation. Short stems with primary diaphyseal fixation do not show an increased risk of failed osseointegration or loosening. Constructions with primary metaphyseal fixation should undergo MRI to rule out the possibility of necrosis extending beyond the femoral neck.EINLEITUNG: Die Hüftkopfnekrose oder avaskuläre Nekrose des Hüftkopfes (HKN) ist eine komplexe Erkrankung, die ohne Behandlung in den meisten Fällen zu einer Infraktion des Femurkopfes führt. In diesen Fällen hilft nur noch ein Ersatz des Hüftgelenkes, wobei es keine eindeutige Empfehlung eines Endoprothesentyps gibt. In den letzten beiden Jahrzehnten hat die Versorgung der primären und sekundären Koxarthrose mit Kurzschaftprothesen mit unterschiedlichen Verankerungsphilosophien zugenommen. Da gerade bei jüngeren Patienten eine Kurzschaftversorgung eine mögliche Option ist, stellt sich die Frage nach möglichen Versorgungen der fortgeschritten HKN mit diesen Schafttypen, insbesondere mit einer metaphysären Verankerung. Ziel dieser Studie war es, die vorhandene Literatur zu den Ergebnissen der Kurzschaftprothese bei HKN zu überprüfen und die Vor- und Nachteile der Kurzschaftprothese bei Osteonekrose des Hüftkopfes darzustellen.Diese Übersichtsarbeit analysiert die vorhandenen Studien zur Kurzschaftversorgung bei HKN.Es existieren nur wenige Studien, die klinische und radiologische Ergebnisse bei einer Kurzschaftversorgung bei HKN analysiert haben.Die kurz- bis mittelfristigen Ergebnisse zeigen überwiegend gute Ergebnisse. Aufgrund von Unterschieden im Design der Kurzschäfte und ihrer Fixierung ist es jedoch schwierig, eine allgemeine Schlussfolgerung zu ziehen. Kurzschäfte mit primärer diaphysärer Fixierung weisen kein erhöhtes Risiko einer fehlgeschlagenen Osseointegration oder Lockerung auf. Bei Konstruktionen mit einer primären metaphysären Verankerung sollte eine MRT durchgeführt werden, um auszuschließen, dass die Nekrose über den Schenkelhals hinausragt.

No optimal therapy exists to stop or cure chondral degeneration in osteoarthritis (OA). While the pathogenesis is unclear, there is consensus on the etiological involvement of both articular cartilage and subchondral bone. Compared to original bone, the substance of sclerotic bone is mechanically less solid. The osteoproliferative effect of Mg has been shown repeatedly during development of Mg-based osteosynthesis implants. The aim of the present study was to examine the influence of implanted high-purity Mg cylinders on subchondral bone quality in a rabbit OA model. 10 New Zealand White rabbits received into the knee either 20 empty drill holes or 20 drill holes, which were additionally filled with one Mg cylinder each. Follow-up was at 8 weeks. Micro-computed tomography (µCT) was performed. After euthanasia, cartilage condition was determined, bone samples were collected and processed for histological evaluation and elemental imaging by micro-X-ray fluorescence spectrometry (µXRF). Articular cartilage collected post-mortem showed different stages of lesions, from mild alterations up to exposed subchondral bone, which tended to be slightly lower in animals with implanted Mg cylinders. µCT showed significantly increased bone volume in the Mg group. Also, histological evaluation revealed distinct differences. While right, operated limbs did not show any significant difference, left, non-operated controls showed significantly less changes in articular cartilage in the Mg group. A distinct influence of implanted cylinders of pure Mg on subchondral bone of osteoarthritic rabbits was shown. Subsequent evaluations, including other time points and alternative alloys, will show if this could alter OA progression.

Kinematic alignment is a philosophy for individual knee prosthesis implantation in a three-dimensional view. The key of the concept is to understand the femoral flexion-extension axis as the centre of a cylinder within the posterior condyles. This axis defines the knee in three dimensions over the entire range of motion. The tibia follows the femur, is balanced on the knee in extension and flexion, and shows individual laxities in flexion and deep flexion.As a consequence, limbs will be reconstructed along their constitutional leg axis, which in most patients is different to a straight hip-knee-ankle centre axis. The method aims at perfectly reconstructing the natural joint lines, which in many patients leads to the natural oblique joint lines. This results in considerable advantages, as the natural stability of the knee is restored, and native patella kinematics are maintained. From a static view, polyethylene and the implant-bone interface may be vulnerable to mechanical overloading due to altered adductor moments. However, a growing body of evidence shows that naturally oriented knee joints show a more balanced loading pattern. Moreover, dynamic gait patterns actually show the mechanism of even reduced knee adductor moments, explaining the clinical results of up to 10 years follow up.HINTERGRUND: Das kinematische Alignment ist eine Philosophie zur individuellen Knieprothesenimplantation in einer dreidimensionalen Betrachtung. Der Kern des Konzeptes ist das Verständnis der femoralen Flexions-Extensions-Achse als Zentrum eines Zylinders in den posterioren Kondylen. Diese Achse definiert das Knie dreidimensional über den gesamten Bewegungsablauf. Die Tibia folgt dem Femur, ist in Extension und Flexion auf das Knie balanciert, zeigt in Flexion und tiefer Flexion dann individuelle Laxitäten, häufig mit einer asymmetrisch lateral laxeren Einstellung als medial.Als Konsequenz zeigt sich eine konstitutionelle Beinachse, die von der klassischen mechanischen Achse abweicht. Als wesentliche weitere Konsequenz wird die natürliche Gelenklinie exakt rekonstruiert. Dieses ergibt erhebliche Vorteile, da die natürliche Stabilität des Knies wiederherstellt wird und gleichzeitig eine natürliche patellare Gleitkinematik erlaubt wird. Aktuell ist nicht gänzlich geklärt, inwieweit sich Konsequenzen aus extremer Achseinstellung und Interaktion mit Gelenklinienabweichungen ergeben. Das Polyethylen als tribologisches Material und das Implantat-Knochen-Interface sind gegenüber Überlastungen vulnerabel und bedeuten möglicherweise verkürzte Standzeiten. Der menschliche Organismus verfügt jedoch offensichtlich über dynamische Mechanismen zur Reduktion des Adduktorenmomentes mit Anpassung des Gangbildes. Klinische Erfahrungen über 10 Jahre und multiple randomisierte Studien zeigen neben dem deutlichen funktionellen Vorteil der Methode keine Hinweise auf frühzeitiges Versagen und lassen die vorsichtige Verbreitung der Methode als sinnvoll erscheinen.

Kinematic alignment recently became an alternative alignment option for total knee arthroplasty (TKA). Beside previous studies assessing mechanical alignment in comparison to unintentional malalignment of TKA in terms of implant survival and clinical outcome, more and more studies have focused on the direct comparison of intentional kinematic alignment with mechanical alignment of the prosthesis. In the past 5 years the number of studies with respect to kinematic alignment has risen from 11 to 91 studies.The aim of this review article is to give a narrative overview of the current literature in the debate concerning kinematic and mechanical alignment in TKA.HINTERGRUND: Das kinematische Alignment hat sich in den letzten Jahren zu einer etablierten Methode in der Knieendoprothetik entwickelt. Neben früheren Studien, welche die mechanische Ausrichtung im Vergleich zur unbeabsichtigten Fehlpositionierung der Knieendoprothese (Varus- und Valgusfehlstellung) im Hinblick auf das Implantatüberleben und das klinische Ergebnis untersuchten, konzentrieren sich immer mehr Studien auf den direkten Vergleich der kinematischen und mechanischen Prothesenausrichtung. In den letzten 5 Jahren ist die Anzahl der Studien zum kinematischen Alignment von rund 11 auf 91 Studien gestiegen. ZIEL: Das Ziel dieses Beitrags ist es, einen Überblick über die aktuelle Literaturlage hinsichtlich des kinematischen im Vergleich zum mechanischen Alignment in der Knietotalendoprothetik zu geben.

Treatment of pathologies of the central and peripheral compartment of the hip using arthroscopic assisted mini-open arthrotomy via the Smith-Petersen approach.Cam- and pincer-type femoroacetabular impingement (FAI), labral tear, loose bodies.Osteoarthritis of the hip with Tönnis classification grade ≥ 2.After mini-open approach to the hip joint via direct anterior muscular gap, the anterior capsule is split with protection of the labrum. Decompression allows the joint to be inspected using an arthroscope. Depending on the intra-articular findings, additional procedures can be performed (e.g., curettage of the cartilage, microfracturing, matrix-induced autologous chondrocyte implantation [MACI]). Cases with pincer-type FAI or labral tear can also be addressed. After partial release, the cam-type FAI can be resected using a surgical burr.Partial weightbearing for 2-6 weeks with 10-20 kg or half body weight using crutches depending on the intraoperative treatment.Radiological analysis of the pre- and postoperative X‑rays (n = 69) prove that this surgical technique is suitable to address pathologies especially FAI syndromes. The α‑angle according to Nötzli could be reduced from a mean preoperative value of 72.8° to 49.4° postoperative. In combined cam-type and Pincer-type FAI syndrome (n = 16), the lateral center-edge angle could be reduced from a mean preoperative value of 50.2° to 37.6° postoperatively. The clinical follow-up (n = 29) revealed good midterm outcomes after arthroscopic assisted mini-open arthrotomy (modified Harris Hip Score [mHHS] 84.8 points after 4.9 years [range 4.2-5.7; ±0.43]).OPERATIONSZIEL: Therapie von Pathologien des zentralen und peripheren Kompartiments des Hüftgelenks über eine arthroskopisch assistierte Mini-open-Arthrotomie via Smith-Petersen-Intervall.Femoroazetabuläres Impingement (FAI) Typ CAM und Typ Pincer, Labrumläsionen, lokale Knorpelläsionen, freie Gelenkkörper.Koxarthrose mit einem Arthrosegrad nach Tönnis ≥ 2.Nach einem minimal-invasiven direkt vorderen Zugang (Mini-open-Arthrotomie) zum Hüftgelenk erfolgt die Eröffnung der anterioren Gelenkkapsel unter Schonung des Labrums. Durch Distraktion kann mit dem Arthroskop das Gelenk inspiziert werden. Je nach intraartikulärem Befund können weitere Maßnahmen (z. B. Knorpelkürettage, Mikrofrakturierung, MACI) erfolgen. Bei FAI-Syndrom Typ Pincer oder einer Labrumläsion können diese Pathologien problemlos adressiert werden. Nach partiellem Nachlassen der Distraktion kann das Abtragen des FAI-Syndrom Typ CAM mit der Kugelkopffräse durchgeführt werden.Teilbelastung für 2 bis 6 Wochen mit 10–20 kg oder mit halbem Körpergewicht an Unterarmgehhilfen in Abhängigkeit vom intraoperativen Vorgehen.Die radiologische Analyse der prä- und postoperativen Röntgenbilder (n = 69), die aufgrund eines FAI-Syndroms operiert wurden, belegt, dass diese operative Technik gut geeignet ist, um pathologische Veränderungen zu adressieren. Der α‑Winkel nach Nötzli konnte von durchschnittlich 72,8° präoperativ auf 49,4° postoperativ reduziert werden. Bei einem kombinierten FAI-Syndrom (n = 16) wurde der LCE-Winkel von präoperativ durchschnittlich 50,2° auf postoperativ 37,6° reduziert. Die klinische Nachuntersuchung (n = 29) zeigte gute mittelfristige Ergebnisse nach Behandlung des FAIs mittels arthroskopisch assistierter Mini-open-Arthrotomie (mHHS 84,8 Punkte nach 4,9 Jahren [4,2–5,7; ±0,43]).

Femoroacetabular impingement of the hip is considered a prearthrotic deformity, which should be treated at an early state to prevent complications.This video demonstrates the arthroscopic-assisted mini-open technique for the treatment of femoroacetabular impingement of the hip. In the case presented a combined Pincer and Cam-deformity is treated with rim trimming, translabral labral refixation with two suture anchors and reconstruction of the head-neck junction.The arthroscopic-assisted mini-open technique is a safe and reproducible procedure for treatment of femoroacetabular impingement. It provides an alternative to hip arthroscopy and an additional treatment option in the portfolio of hip surgeons.

There are still a high number of dissatisfied knee arthroplasty patients. This situation has not changed much for decades, despite many innovations focusing on implant longevity and higher procedural precision. In this context, there is a growing discussion on possible systematic errors made in knee arthroplasty, especially regarding the alignment philosophy of the implants.It was reported that a more anatomical alignment might result in improved patient outcome. However, current technologies have severe limitations to achieving optimized and individual alignment. In this context, the aim of this manuscript was to assess whether image-based robot-guided knee arthroplasty might represent an opportunity for achieving individualized alignment.The literature on this subject was evaluated and analyzed. Furthermore, research projects and expert recommendations were discussed.The precision of preoperative planning is higher with robotic techniques than with other computer-assisted or manual technologies. In addition, the individual soft tissue situation of the patient is taken into account and the prosthesis position is optimized. This ensures optimum soft tissue balancing and stability of the prosthesis.Modern robot-assisted systems are the mechanical bridge between imaging and patient. This technique provides objective control over the results produced with alternative alignments. This applies to both the prosthesis position itself and the resulting soft tissue balancing.

Objective: Implant infections in elective orthopedic surgery are still a clinically relevant problem with devastating consequences for the patient. Thereof results a great need for new strategies to prevent implant infections. Functionalization of implant surfaces to reduce the microbial adherence show great potential in vitro, but have to be tested in suitable models in vivo. Proper evaluation methods of the bacterial load on the implant surface are important for their evaluation. Up to now, the simultaneous assessment of the quantity and morphology of the bacterial infection in vivo was not performed. Methods: Cubic Ti90/Al6/V4-rods were inserted in the tibia of Lewis rats and infected with Staphylococcus aureus strain 36/07 in different concentrations. After 21 days, explanted implants were stained for living and dead cells. The bacterial surface colonization was analyzed by confocal microscopy and assessed semi quantitatively via two different approaches (spot method and volume method) using the software Imaris® × 64. Furthermore the bacterial morphology was evaluated. The results were compared to radiographic and histological changes. Results: The new semi quantitative CLSM evaluation to assess the bacterial biomass on implant surfaces was successfully implemented. Both methods gave equivalent results. The results of the morphologic assessment of the bacterial colonization were similar to those of the quantification. A tendency towards increasing bacterial biomass and biofilm formation on the implant surface was observed with decreasing infection concentrations. In contrast, histologic and radiographic assessment as well as the relative tibial bone weight revealed more severe changes for higher inoculation concentrations. Conclusion: In combination with the morphological assessment of the bacterial appearance this CLSM based evaluation is a suitable tool to assess the bacterial load on the implant surface. Combined with radiographical and histological evaluation of bone alterations, this model is appropriate for the evaluation of new implant surfaces.

Die interdisziplinare Zusammenarbeit von Orthopaden und plastischen Chirurgen ist in der rekonstruktiven Chirurgie der Extremitaten sowohl bei traumatologisch-orthopadischen Frakturen mit ausgedehnten Weichteilschaden als auch bei muskuloskeletalen Tumorresektionen indiziert. Der Beitrag stellt insbesondere die Rekonstruktionen nach Tumorresektionen dar, wobei die enge Zusammenarbeit bereits in der praoperativen Planung wichtig ist, um das gemeinsame Vorgehen unter besonderer Berucksichtigung ggf. notwendiger adjuvanter Therapien zu diskutieren. Je nach Lokalisation und Ausmas tumorchirurgischer Resektionen stehen zur Weichteildeckung sowie zur funktionellen Rekonstruktion verschiedene Moglichkeiten zur Verfugung. Insbesondere mussen einzeitige gegenuber zweizeitigen Verfahren abgewogen werden.

Das femoroazetabulare Impingement (FAI) und dessen Therapie haben in den letzten Jahren an Bedeutung gewonnen. Es konnte in zahlreichen Studien gezeigt werden, dass es sich um eine praarthrotische Deformitat handelt, die unbehandelt zur Koxarthrose fuhrt. Dieser Beitrag soll einen Uberblick uber die Pathologie, Diagnostik und die operativen Therapien, gerade auch im Hinblick auf den aktiven Sportler, geben. Erste eigene klinische und radiologische Ergebnisse von 91 Patienten, die durch arthroskopisch assistierte Mini-open-Arthrotomie behandelt wurden, werden vorgestellt. Sie zeigen sehr gute Ergebnisse und signifikante postoperative Verbesserungen im Hinblick auf HOOS-, WOMAC- und UCLA-Activity-Score sowie die Korrektur des α-Winkels. Diese in der Literatur vergleichsweise noch wenig beachtete Operationstechnik steht als Therapieoption zur Behandlung des FAI zur Verfugung. Die Nachbehandlung ist mit der der Huftarthroskopie gleichzusetzen.

Um die Patientenversorgung zu verbessern, werden neue, innovative Biomaterialien fur den Einsatz als orthopadische Implantate entwickelt. Ihre Langlebigkeit hangt von verschiedenen Faktoren ab, der wichtigste ist die Verschleisresistenz. Um diese zu verbessern, werden neue Biokeramiken und Implantatdesigns untersucht. Biokeramiken als Keramik-Keramik-Gleitpaarung fur den totalendoprothetischen Kniegelenkersatz weisen einen deutlich verringerten Verschleis auf. Sie sollen ihre Funktion nur fur einen bestimmten Zeitraum erfullen. Derartige Implantate losen sich sukzessive im Korper auf, demzufolge kann auf eine Zweitoperation zur Materialentfernung verzichtet werden. In den vergangenen Jahren wurden unterschiedliche, degradierbare Magnesiumlegierungen bezuglich ihrer mechanischen Eigenschaften und Biovertraglichkeit untersucht.

Biodegradable magnesium-based implants are currently being developed for use in orthopedic applications. The aim of this study was to investigate the acute, subacute, and chronic local effects on bone tissue as well as the systemic reactions to a magnesium-based (MgYREZr-alloy) screw containing rare earth elements. The upper part of the screw was implanted into the marrow cavity of the left femora of 15 adult rabbits (New Zealand White), and animals were euthanized 1 week, 12 weeks, and 52 weeks postoperatively. Blood samples were analyzed at set times, and radiographic examinations were performed to evaluate gas formation. There were no significant increased changes in blood values compared to normal levels. Histological examination revealed moderate bone formation with direct implant contact without a fibrous capsule. Histopathological evaluation of lung, liver, intestine, kidneys, pancreas, and spleen tissue samples showed no abnormalities. In summary, our data indicate that these magnesium-based screws containing rare earth elements have good biocompatibility and osteoconductivity without acute, subacute, or chronic toxicity.

The story of ShapeMatch® custom-fit cutting guides for primary total knee arthroplasty (TKA) is special compared to other available techniques. First, it was the first such patient-specific instrument (PSI) on the market. Second, the underlying philosophy of kinematic alignment is unique compared to other competitors. Finally, it is the only PSI technique that has been withdrawn from the market.The objective of this paper is to summarize the history of the ShapeMatch® technology and to review the current literature regarding clinical evidence for kinematically aligned TKA.In the recent literature, faster rehabilitation, better knee function and higher patient satisfaction are described for kinematically aligned TKA compared to conventional alignment. However, there is also evidence for inaccuracies by using the PSI technology as a possible cause of treatment failures. Due to those problems, this technology was recalled from the market. As an alternative method to achieve kinematic alignment in TKA, manual as well as computer-assisted techniques are currently under development and are discussed here.

Aktuelle Techniken der Akromioklavikulargelenk (AC)-Stabilisierung adressieren primar oder isoliert einen Ersatz der korakoklavikularen (CC) Bander. Inwiefern dieses Vorgehen jedoch geeignet ist, neben der vertikalen Primarstabilitat auch die Kinematik und Stabilitat des Gelenkes in der horizontalen Ebene wiederherzustellen, ist fraglich. Die vorliegende Arbeit zeigt durch eine Ubersicht biomechanischer In-vitro-Studien Starken und Schwachen aktuell propagierter Techniken auf. So konnte biomechanisch nachgewiesen werden, dass weder isolierte korakoklavikulare (CC) noch isolierte akromioklavikulare (AC) Rekonstruktionen in der Lage sind, sowohl die Vertikal- als auch die Horizontalstabilitat des AC-Gelenkes wiederherzustellen. Dies ist unabhangig von der Verwendung neuer Implantate, Fixationstechniken („flip-button fixation“) und der Integration von Sehnentransplantaten. Analog zu den ligamentaren Stabilisatoren des intakten Gelenkes stabilisieren CC-Rekonstruktionen primar in vertikaler und AC-Rekonstruktionen primar in horizontaler Richtung. Als klinische Konsequenz ist daher neben einer detaillierten, zweidimensionalen Diagnostik der AC-Gelenkverletzungen eine an das Instabilitatsmuster angepasste operative Therapie zu fordern. Diese sollte eine bedarfsgerechte Kombination von CC- und AC-Stabilisierung beinhalten.

Sicherung der orthograden Groszehenausrichtung bei Hallux-valgus-Korrekturen. Reduktion der Funktionseinschrankung im Groszehengrundgelenk durch Verzicht auf eine mediale Kapselraffung. Hallux valgus bzw. Hallux-valgus-Rezidiv. Allgemeine Kontraindikationen der gelenkerhaltenden Hallux-valgus-Operation (z. B. fortgeschrittene degenerative Veranderungen des Groszehengrundgelenks, Osteonekrose, schmerzhafte Bewegungseinschrankungen des MTP-I-Gelenks). Medialer Hautschnitt, Darstellung der Gelenkkapsel und der Sehne des M. abductor hallucis. Distales Ablosen der Sehne und Armierung mit einem Faden. L-formige Eroffnung der Gelenkkapsel. Abtragen der Pseudexostose und Durchfuhrung der Korrekturosteotomie. Lockerer Verschluss der Gelenkkapsel in Korrekturstellung. Readaptation der Sehne des M. abductor hallucis auf der mittleren Hohe der Gelenkkapsel unter Beachtung der Rotation der Groszehe. Hautnaht. Redressierender Verband. Regelmasiger Verbandswechsel mit Anlage der redressierenden Verbande fur 4 Wochen. Belastung entsprechend der Korrekturosteotomie. Dann Tragen der Hallux-valgus-Lagerungsschiene zur Nacht fur weitere 6 Wochen und eines Zwischenzehenkeils in normalem Konfektionsschuhwerk. Passive Mobilisation des MTP-I-Gelenks ab dem 2. postoperativen Tag. Bei 30 Patienten mit einer isolierten Hallux-valgus-Deformitat erfolgte im Zeitraum von September 2007 bis Juni 2008 eine retrokapitale Chevron-Osteotomie. Der mittlere praoperative Intermetatarsal- (IM-)Winkel ergab 12,9° (11–15°). Der mittlere Nachuntersuchungszeitraum betrug 14,4 (8–17) Monate. Bei der abschliesenden Nachuntersuchung konnte bei 28 operierten Fusen (93%) eine mittlere Dorsalextension im MTP-Gelenk von 45° (40–60°) erreicht werden. Bei 2 Patienten bestand eine Dorsalextension von 20° bzw. 30°. Insgesamt ergab sich damit eine mittlere postoperative Dorsalextension von 44° (20–60°). Der IM-Winkel verringerte sich bei den Patienten um durchschnittlich 5,6° (3–7°). Bei einem Patient trat eine Wundheilungsstorung auf, die operativ saniert wurde. Es kamen keine tiefen Infektionen oder radiologische Zeichen einer Kopfchennekrose vor. Bei keinem Patienten zeigte sich postoperativ eine Hallux-varus-Fehlstellung. Bei der Frage der Zufriedenheit mit dem operativen Ergebnis gaben 20 Patienten (67%) an, sehr zufrieden zu sein. Weitere 9 (30%) waren zufrieden und 1 Patient (3%) war wegen der Wundheilungsstorung nicht zufrieden. Nochmals operieren lassen wurden sich 28 Patienten.

In this in-vivo study magnesium alloys with a rare earth composition metal (LAE442) on the one hand and cerium as single rare earth element (LACer442) on the other hand were compared. Extruded cylindrical identically machined implants of both alloys were implanted intramedullary in both tibiae of five New Zealand White rabbits each (group 1 – LAE442, group 2 – LACer442). Three months were planned as postoperative observation period with clinical and radiographical examinations. Postmortal, μ-computed tomographical and histological analyses of the tibiae were done. Although the alloys were very similar, profound differences could be found in biocompatibility. The LAE442-alloys were tolerated well. The μCT showed an even implant degradation as well as marginal new bone formation. Histologically, a good biocompatibility was seen. The rabbits with LACer442-implants had to be euthanized ahead of schedule because of massive implant intolerance due to gas formation and fast implant degradation which could be confirmed and differentiated in the radiographic, μ-computed tomographical and histological examinations. These results show that the single rare earth element cerium can not successfully substitute the rare earth composition metal in a magnesium alloy for biomedical use. In dieser in-vivo Studie wurde eine Magnesium-Legierung mit einem Seltenen-Erden-Mischmetall (LAE442) mit einer Magnesium-Legierung mit Cer als Einzelelement aus der Gruppe der Seltenen Erden (LACer442) verglichen. Identisch hergestellte stranggepresste, zylinderformige Implantate beider Legierungen wurden beidseits intramedullar in Tibiae von je funf New Zealand White Kaninchen implantiert (Gruppe 1 – LAE442, Gruppe 2 – LACer442). Der Untersuchungszeitraum sollte drei Monate betragen. Wahrend des Untersuchungszeitraumes wurden die Tiere klinisch und radiologisch untersucht. Postmortal erfolgte eine μ-computertomographische und histologische Beurteilung der Tibiae. Obwohl die Legierungen sehr ahnlich in ihrer Zusammensetzung waren, wurden fulminante Unterschiede in der Biokompatibilitat gefunden. Die LAE442-Legierung wurde sehr gut vertragen. Im μCT zeigte sich eine beginnende gleichmasige Degradation der Implantate sowie geringgradige Knochenneubildung. Die Histologie zeigte eine gute Biokompatibilitat. Die Kaninchen mit LACer442-Implantaten mussten vorzeitig euthanasiert werden da sie klinisch hochgradige Implantatunvertraglichkeiten bedingt durch Gasbildung und schnelle Implantatdegradation zeigten, welche in den radiologischen, μ-computertomographischen und histologischen Untersuchungen bestatigt wurden. Die Ergebnisse zeigen, dass das Einzelelement Cerium fur das Seltene-Erden-Mischmetall keinen adaquaten Ersatz bei der Verwendung von biodegradablen Magnesiumlegierungen darstellt.

To investigate the initial mechanical strength and the degradation behaviour with the associated changes in mechanical properties of magnesium-based osteosynthesis implants, 30 rabbits were implanted with cylindrical pins of the alloys MgCa0.8 (magnesium with 0.8 wt% calcium), LAE442 (magnesium with 4 wt% lithium, 4 wt% aluminium and 2 wt% rare earths) and WE43 (magnesium with 4 wt% yttrium and 3 wt% rare earths). The implants were inserted into the medullary cavity of both tibiae. After 3 and 6 months, each half of the animals was euthanized, respectively, and the implants were taken out. A determination of volume, three-point bending tests, scanning electron microscopy (SEM) and energy dispersive X-ray analyses as well as metallographic and μ-computed tomography examinations were accomplished. All implants were clinically well tolerated. MgCa-implants showed the least initial strength and the highest loss in volume after 6 months. SEM- and μ-computed tomography examinations revealed a pronounced pitting corrosion. Therefore, their use as degradable implant material seems to be limited. LAE442 has the best initial strength which seems to be sufficient for an application in weight-bearing bones. The degradation behaviour is very constant. However, possible unknown side effects of the rare earths have to be excluded in further investigations on biocompatibility. Considering all results of WE43, its application as osteosynthesis material for fracture repair is ineligible due to its heterogeneous and unpredictable degradation behaviour.

Chronische Instabilitaten des Akromioklavikulargelenks (AC-Gelenk) sind das Resultat ubersehener oder insuffizient behandelter akuter Luxationen. Im Unterschied zu den akuten Verletzungen ist das biologische Heilungspotential aufgrund des posttraumatischen Intervalls kompromittiert und somit die Behandlung erschwert. Die Diagnostik chronischer Instabilitaten sollte daher die differenzierte Erfassung unterschiedlicher Instabilitatskomponenten (statisch vs. dynamisch, vertikal vs. horizontal) anhand einer eigenstandigen Klassifikation (Hedtmann und Heers) beinhalten, um in eine zielgerichtete operative Therapie zu munden. Eine eigene Technik zur operativen Stabilisation wurde biomechanisch evaluiert. Die Technik beinhaltete einen modifizierten Transfer des coracoacromialen Bandes (CA-Band) in Kombination mit einer minimal invasiven korakoklavikularen Augmentation (MINAR). Die Technik ist in der Lage, das anteriore und superiore Translationsverhalten des intakten AC-Gelenkes wiederherzustellen. Allerdings bleibt die posteriore Translation gegenuber dem intakten Gelenk erhoht (127%: 3,8 mm intakt vs. 4,6 mm rekonstruiert; p

Extruded implants (2.5 mm x 25 mm) of the resorbable magnesium alloys MgCa0.8 and LAE442 were implanted into the marrow cavity of both tibiae of 10 New Zealand White rabbits. The animals were in a good general condition over the whole experimental period and showed no signs of lameness. Radiographic examinations could not reveal any generation of gas. The endosteal based bone adhesion to the implant surface was evaluated by μ-computed tomography of the right tibia. 53 % of the evaluated slices of the alloy LAE442 showed an adherence of trabecular bone. MgCa0.8 showed trabeculae (38 %), bone clasps (13 %) and -rings (9 %) that covered the whole implant surface. Beside the weight and volume loss, the cross sectional area of the implants were measured to investigate the progress of degradation. Implants of the MgCa0.8 group showed an average loss of more than half of the original implant area (2.18 mm2 ± 1.03). In contrast LAE442 implants degraded very regularly (4.7 mm2 ± 0.07). Weight and volume measurements revealed a volume loss of 64.13 % ± 15.92 in the MgCa0.8 group and a lesser volume loss of 45.63 % ± 0.89 in the LAE442. The mechanical properties were tested by a three point bending test. It showed a decrease of the maximal force of 71.2 % ± 2.88 for LAE442 implants and of 85.6 % for MgCa0.8 implants, each compared to the initial condition. Vergleich der resorbierbaren Magnesiumlegierungen LAE442 und MgCa0,8 . bezuglich der mechanischen Eigenschaften, dem Degradationsgrad und . dem Knochen-Implantatkontakt nach zwolfmonatiger Implantation im Kaninchenmodell Stranggepresste Implantate (2,5 mm x 25 mm) der resorbierbaren Magnesiumlegierungen MgCa0,8 und LAE442 wurden in die Markhohlen beider Tibiae von 10 New Zealand White Kaninchen implantiert. Die Tiere wiesen uber den gesamten Versuchszeitraum ein gutes Allgemeinbefinden auf und zeigten keine Lahmheiten. Rontgenologisch konnte keine Gasbildung festgestellt werden. Mit Hilfe von μ-computertomographischen Untersuchungen der rechten Tibiae wurde das Knochenanwachsverhalten vom Endost ausgehend an die Implantatoberflache beurteilt. 53 % der ausgewerteten Schnittbilder der Legierung LAE442 zeigten ein Anhaften trabekularen Knochens an die Implantatoberflache. Bei MgCa0,8 wurden Trabekel (38 %), Knochenspangen (13 %) und -ringe (9 %), die der gesamten Oberflache des Implantates auflagen, detektiert. Zur Ermittlung des Degradationsgrades wurde neben der Ermittlung des Gewichts- und Volumenverlustes die Querschnittsflache der Implantate vermessen. Die Implantate der MgCa0,8-Gruppe hatten im Mittel mehr als die Halfte der ursprunglichen Implantatflache verloren (2,18 mm2 ± 1,03). Die LAE442-Implantate waren hingegen sehr regelmasig degradiert (4,7 mm2 ± 0,07). Die Gewichtsmessung und Volumenbestimmung ergab innerhalb der MgCa0,8-Gruppen einen Volumenverlust von 64,13 % ± 15,92. Die Gruppe LAE442 zeigte einen geringeren mittleren Volumenverlust von 45,63 % ± 0,89. Die mechanischen Eigenschaften wurden im Dreipunktbiegeversuch gepruft und ergaben bei LAE442 einen Abfall der maximalen Kraft von 71,2 % ± 2,88, bei MgCa0,8 von 85,6 % im Vergleich zum Initialzustand.

We report an unusual case of a 38-year-old physically active patient, who suffered a Ewing sarcoma during adolescence and was therefore treated with a tumor endoprostheses ex domo (replacement of distal femur and proximal tibia). Since then he had undergone a couple of surgical interventions for revision and is currently suffering from persistent pain in the leg concerned. An aseptic loosening of the tibial component was evident after radiologic examinations. Because he had suffered for so long our patient refused further surgery to retain the affected limb and he preferred amputation.We would have taken the risk of a femoral residual limb that is much too short compared with a classical above-knee amputation. In this regard we saw difficulties in exoprosthetic treatment with functional limitations that could easily have influenced the outcome negatively.Consequently, we decoupled the tibial component from the femoral one within the knee joint and thus performed a knee disarticulation leaving the femoral component.Postoperatively, we found a mostly harmonious gait pattern with a pure mechanical interim prosthesis regarding time-distance parameters, which may be even further improved with the final prosthesis. Sagittal joint angles are comparable to conventionally knee exarticulated ones.To date, no comparable case of such an alloarthroplasty, which could regain mobility with an exoprosthetic treatment has been highlighted in the literature. In the result, a knee disarticulation within the area of a knee arthroplasty leaving the femoral component is not inferior to"ordinary" knee disarticulation.

Against the background that 20 % of patients are dissatisfied after total knee arthroplasty, there is ongoing controversy about optimal alignment. In this context, orientating the prosthetic components to the natural kinematic axes of the knee appears to be an interesting new concept.The objective of this paper is to provide a critical review of the current literature and our own research data regarding the concept of kinematically aligned total knee arthroplasty with the current evidence base and potential limitations.In the recent literature faster rehabilitation, better knee function, and higher patient satisfaction are described compared to conventional alignment, even if the postoperative alignment deviates more than 3° from the mechanical axis. However, the technique may not be suitable for every patient and pathology, and further research is necessary to set the correct indication.

Interdisciplinary collaboration between orthopedic and plastic surgeons is indicated in reconstructive surgery of the extremities for both traumatic orthopedic fractures with extensive soft tissue damage and musculoskeletal tumor resection. We want to emphasize the need for close cooperation starting in the preoperative planning for reconstruction after tumor resection in order to discuss and establish a unified approach. This is particularly important to establish a joint approach with special consideration of possibly necessary adjuvant therapies. One collaborative approach is for the orthopedic surgeon to resect the tumor and the plastic surgeon to carry out the defect reconstruction for exclusive soft tissue coverage including flap surgery as well as for functional reconstruction depending on the location and extent of tumor resection. Thus, careful preoperative and postoperative communication on the precise location, extent of tumor resection and the therapy timing between the orthopedic surgeon and the plastic surgeon will allow the most effective subsequent repair of the resection site.

The ability to predict load-bearing capacity during the consolidation phase in distraction osteogenesis by non-invasive means would represent a significant advance in the management of patients undergoing such treatment. Measurements of stiffness have been suggested as a promising tool for this purpose. Although the multidimensional characteristics of bone loading in compression, bending and torsion are apparent, most previous experiments have analysed only the relationship between maximum load-bearing capacity and a single type of stiffness. We have studied how compressive, bending and torsional stiffness are related to the torsional load-bearing capacity of healing callus using a common set of samples of bone regenerate from 26 sheep treated by tibial distraction osteogenesis. Our findings showed that measurements of torsional, bending and compressive stiffness were all suitable as predictors of the load-bearing capacity of healing callus. Measurements of torsional stiffness performed slightly better than those of compressive and bending stiffness.

Femoroacetabular impingement (FAI) and its therapy has gained importance in the last decade and several studies could show that if untreated it may lead to osteoarthritis of the hip joint. In this article an overview of the pathology of FAI, the diagnosis and treatment options are presented. A closer look is taken at the treatment of elite athletes regarding the different techniques. The first own clinical and radiological results of 91 patients treated by the arthroscopically-assisted anterior mini-open approach are presented with very good results and significant postoperative improvement regarding the hip injury and osteoarthritis outcome score (HOOS), the Western Ontario and McMasters University (WOMAC) osteoarthritis index and the University of California Los Angeles (UCLA) activity score, as well as alpha angle correction. This technique which is poorly represented in the literature can be used as a treatment option for FAI. The rehabilitation program is comparable to hip arthroscopy.

PurposeNondegradable steel-and titanium-based implants are commonly used in orthopedic surgery. Although they provide maximal stability, they are also associated with interference on imaging modalities, may induce stress shielding, and additional explantation procedures may be necessary. Alternatively, degradable polymer implants are mechanically weaker and induce foreign body reactions. Degradable magnesium-based stents are currently being investigated in clinical trials for use in cardiovascular medicine. The magnesium alloy MgYREZr demonstrates good biocompatibility and osteoconductive properties. The aim of this prospective, randomized, clinical pilot trial was to determine if magnesium-based MgYREZr screws are equivalent to standard titanium screws for fixation during chevron osteotomy in patients with a mild hallux valgus.MethodsPatients (n=26) were randomly assigned to undergo osteosynthesis using either titanium or degradable magnesium-based implants of the same design. The 6 month follow-up period included clinical, laboratory, and radiographic assessments.ResultsNo significant differences were found in terms of the American Orthopaedic Foot and Ankle Society (AOFAS) score for hallux, visual analog scale for pain assessment, or range of motion (ROM) of the first metatarsophalangeal joint (MTPJ). No foreign body reactions, osteolysis, or systemic inflammatory reactions were detected. The groups were not significantly different in terms of radiographic or laboratory results.ConclusionThe radiographic and clinical results of this prospective controlled study demonstrate that degradable magnesium-based screws are equivalent to titanium screws for the treatment of mild hallux valgus deformities.

Common reasons for juvenile neurogenic pes planovalgus are hypoxic brain damage, birth defects of the spinal canal, trauma and cerebral cancer. When symptoms persist despite conservative treatment of symptomatic pes planovalgus, surgery is indicated. Objectives of the operation are improved gait and mobilization as well as an improved basis for wearing shoes. Joint preserving and ankylosing procedures as well as combinations of both are available. The aim of this study was a retrospective comparison of the Grice/Green extra-articular arthroreisis versus the Evans calcaneal lengthening operation.Between October 2001 and October 2009 a total of 75 arthroereisis operations were performed according to Grice/Green and in the period from April 2006 to February 2010 a total of 83 calcaneal lengthening operations according to Evans. The focus of the study was on patients with an underlying neurogenic disease which resulted in 72 cases in the Grice/Green group and 70 cases in the Evans group. The average age was 14.6 ± 5.0 years in the Evans group and 10.1 ± 3.4 years in the Grice/Green group. Of the patients in the Grice/Green group 17 had infantile cerebral palsy (ICP) and 25 had other neuromuscular diseases and in the Evans group 14 patients had ICP and 28 patients had other neuromuscular diseases. The medical records, preoperative and postoperative radiographs were analyzed. In addition information was obtained on the quality of life (EQ-5D), mobility and the supply of mobility aids using a specially designed questionnaire. The radiological evaluation was based on preoperative and postoperative lateral and dorso-plantar radiographs. The follow-up time for the questionnaire was on average 54 months (range 12-109 months) for the Grice/Green group and 22 months (range 9-53 months) for the Evans group. The postoperative treatment was similar in both groups.The talometatarsal (TMT) index could be improved by surgery according to Grice/Green from - 50.2° to - 28.1° and in the Evans group a correction from - 49.6° to - 31.8° was possible. Considering the cases with severe preoperative deformities (TMT index -50°) there was a significantly greater correction of the lateral talocalcaneal (TC) angle by the method of Grice/Green. In 67 % of patients in the Grice/Green group and 57 % in the Evans group a significant improvement in terms of pain was possible. A significant improvement in gait and possible walking distance was found in 33 % of the Grice/Green group and 43 % of the Evans group and an average improvement was possible in 40 % and 43 %, respectively. The operation was considered to be very successful by 67 % of patients in the Grice/Green group and in 57 % of patients in the Evans group but the difference was not significant. In the Grice/Green group no revisions were necessary and revision was performed in two cases after surgery in the Evans group due to wound infections.Both of the processes investigated in this study are suitable for treatment of pes planovalgus. In cases of neurogenic pes planovalgus and also in extreme cases (TMT index -50°) the procedure according to Grice/Green has radiological advantages for reconstruction of the lateral TC angle.

Ligament balancing is an integral part of total knee arthroplasty and depends on correct alignment of the knee in flexion and extension. Since the mid-1970s, the concepts of releasing the medial collateral ligaments in knees with varus deformity and the lateral ligaments in knees with valgus deformity have been widely taught and practised (1, 2).

Maintaining the corrected position of the first metatasophalangeal axis. Reducing postoperative stiffness by forgoing a medial capsular shift.Hallux valgus deformities or recurrent hallux valgus deformities.Existing osteoarthritis, joint stiffness, large bone defects, osteonecrosis. General medical contraindications to surgical interventions and anesthesiological procedures.Operation under regional anesthesia (foot block) or general anesthesia. Tourniquet. Longitudinal skin incision medial over the pseudexostosis of the first metatarsal bone. Preparing the tendon of the Musculus abductor hallucis. Detaching the tendon from the capsule. Incision of the joint capsule with protection of the extensor hallucis longus tendon and the dorsal neurovascular bundle in an L-wise manner. Osteotomy of the first metatarsal bone. Lax sutures of the capsule in correct position and reattachment of the Musculus abductor hallucis tendon shifted toward distal and dorsal, regarding the rotation of the hallux.Postoperative elevation of the operated foot. Analgesia with nonsteroidal antiinflammatory drugs. Postoperative weight-bearing according to the osteotomy. Passive mobilization of the metatarsophalangeal joint. Dressing for 4 weeks postoperatively in the corrected position. Radiologic control after 6 weeks. Hallux valgus orthosis at night and a toe spreader for a further 6 weeks.A total of 30 isolated hallux valgus deformities with a mean preoperative intermetatarsal (IMA) angle of 12.9° (range 11-15°) were operated with a chevron osteotomy. The mean follow-up was 14.4 (range 8-17) months. The mean dorsiflexion at the last follow-up was 44° (range 20-60°). Only 2 patients had a dorsiflexion40°. The mean reduction of the IM angle was 5.6° (range 3-7°). One patient required wound revision. There was no infection or avascular necrosis of the metatarsal head observed in the patients. At follow-up, 20 (67%) patients were completely satisfied, 9 (30%) satisfied, and 1 (3%) was not satisfied.

Microfractures of the femoral head during implantation of the femoral components are suspected to be a cause of fractures at the implant/neck junction which represent a common failure mode in hip resurfacing arthroplasty. Callus formation observed in femoral head retrievals suggests the occurrence of microfractures inside the femoral head, which might be inadvertently caused by the surgeon during implantation. The aim of this biomechanical study was to analyse whether or not the implantation of a cementless femoral component hip resurfacing system causes microfractures in the femoral head.After the preparation of 20 paired human cadaveric femoral heads, the cementless femoral component ESKA Typ BS (ESKA Implants GmbHCo., Lübeck) was implanted on 9 specimens with an impaction device that generates 4.5 kN impaction force. On 9 specimens the femoral component was implanted by hand. One head was used as a fracture model, 1 specimen served as control without manipulation. The femoral component used for impaction was equipped with hinges to enable its removal without further interfering with the bone stock. Specimens were scanned with a microCT device before and after impaction and the microCT datasets before and after impaction were compared to identify possible microfractures.Twenty strikes per hand or with the impaction device provided sufficient implant seating. Neither the macroscopic examination nor the 2-dimensional microCT analysis revealed any fractures of the femoral heads after impaction.At least macroscopically and in the 2-dimensional microCT analysis, implantation of the cementless hip resurfacing femoral component ESKA Typ BS with 4.5 kN or by hand does not seem to cause fractures of the femoral head.

Objectives: The objective of this study was to compare bone mineral density and content measurements by dual-energy x-ray absorptiometry with bone stiffness measurements as indicators of the load-bearing capacity of regenerating bone during distraction osteogenesis. Methods: The study analyzed ex vivo a set of 26 sheep bone specimens after distraction osteogenesis. Bone mineral density and bone mineral content were measured by dual-energy x-ray absorptiometry. Biomechanical parameters such as torsional, compressive, and bending stiffness were determined using a material testing system. The maximum torsional moment applied at fracture is used to determine the load-bearing capacity of the bone. Results: The correlation between stiffness measurements and the load-bearing capacity of a bone is significantly greater than the correlation between load-bearing capacity and bone mineral density and content measurements by dual-energy x-ray absorptiometry. Conclusion: The results of this ex vivo study indicate that stiffness measurements are a better quantitative indicator of the load-bearing capacity of a bone and thus of bone healing than bone mineral density and content measurements by dual-energy x-ray absorptiometry. The results of the current study do not confirm previous work that showed that there is a significant correlation between bone material quality obtained by dual-energy x-ray absorptiometry and bone strength.

In the last decade biodegradable synthetic implant materials have been established for various clinical applications. Ceramic materials such as calcium phosphate, bioglass and polymers are now routinely used as degradable implants in the clinical practice. Additionally these materials are now also used as coating materials or as microspheres for controlled drug release and belong to a series of examples for applications as scaffolds for tissue engineering. Because immense local concentrations of degradation products are produced during biodegradation, this review deals with the question whether allergic immune reactions, which have been reported for classical metallic and organic implant materials, also play a role in the clinical routine for synthetic biodegradable materials. Furthermore, possible explanatory theories will be developed to clarify the lack of clinical reports on allergy or sensitization to biodegradable synthetic materials.

Intraoperative periprosthetic femoral fractures (PFF) during the implantation of primary non-cemented total hip arthroplasties (THA) are an increasing problem. Thus, the goal of this study was to analyse the postoperative performance of primary non-cemented THA in patients with intraoperative PFFs, with respect to the patient's subjective health-related satisfaction.42 PFFs in 1216 primary THAs using the non-cemented BiCONTACT stem were monitored. Patients were compared to a control group of 42 non-cemented THA patients without intraoperative fracture complications, using the matched-pair analysis. Preoperative and after 2.2 years (0.8-3.2 years), patients were followed-up clinically and radiographically. Clinical parameters were Harris hip score, SF-36 health score, function and pain score and postoperative complications. Radiographic parameters were bone union, stem and trochanter migration. Fractures were graded using the Vancouver classification.Results showed a significant increase in both Harris hip score and motion score and a significant decrease in pain score in both groups (p0.001). The SF-36 health score increased significantly in nearly every dimension in both groups. Except for 2 patients with trochanter migrations of 25 and 20 mm, all fractures showed bony union. In 3 patients the stems subsided by 4.7 +/- 2.9 mm. The stems showed no further migration at final follow-up. 2 patients without intraoperative fractures underwent stem revision. Overall increases and postoperative complication rates were not significantly different between the groups.Mid-term THA performance and patient satisfaction are not influenced by intraoperative Vancouver A and B1 fractures during implantation of the non-cemented BiCONTACT stem compared to a collective without intraoperative fractures during implantation.

We have investigated the value of flexion osteotomy for femoral head necrosis with regard to the survival rate.We examined 40 patients who were treated by flexion osteotomy for femoral head necrosis at the Hannover Medical School in the years 1969 to 1995. The mean follow-up period was 14.1 years.The mean survival time of the flexion osteotomies was 9.6 years. In 23 of the 40 patients, it failed within 10 years after surgery, which implies a 10-year survival rate of 42.5 %. For these 23 patients, the implantation of a total hip arthroplasty (THA) became necessary after an average time of 6.6 years.Due to the poorly predictable success of the flexion osteotomy and the comparatively poor patient satisfaction, the indication for flexion osteotomy in such cases should be reconsidered.

Roentgen stereophotogrammetric analysis (RSA) is an established method for the precise measurement of implant migration. Model-based RSA (MBRSA) alleviates the need to attach tantalum markers to the prosthesis, which has prevented wider application of RSA. The goal of this study was to investigate the equivalence of both methods for the clinical measurement of implant migration. Tibial component migration was measured in 24 patients using both methods from the same set of radiographs. The maximum agreement interval, mean (+/-2 standard deviations), of the difference between both methods was modest, at 0.002 mm (0.144 mm) and -0.078 degrees (0.782 degrees ). The results suggest that MBRSA can be used interchangeably with the marker-based method and that the advantages of MBRSA do not come at the cost of a loss in accuracy.

The in vivo corrosion of magnesium alloys might provide a new mechanism which would allow degradable metal implants to be applied in musculo-skeletal surgery. This would particularly be true if magnesium alloys with controlled in vivo corrosion rates could be developed. Since the magnesium corrosion process depends on its corrosive environment, the corrosion rates of magnesium alloys under standard in vitro environmental conditions were compared to corrosion rates in an in vivo animal model. Two gravity-cast magnesium alloys (AZ91D, LAE442) were used in these investigations. Standardized immersion and electrochemical tests according to ASTM norms were performed. The in vivo corrosion tests were carried out by intramedullar implantation of sample rods of the magnesium alloys in guinea pig femura. The reduction in implant volume was determined by synchrotron-radiation-based microtomography. We found that in vivo corrosion was about four orders of magnitude lower than in vitro corrosion of the tested alloys. Furthermore, the tendency of the corrosion rates obtained from in vitro corrosion tests were in the opposite direction as those obtained from the in vivo study. The results of this study suggest, that the conclusions drawn from current ASTM standard in vitro corrosion tests cannot be used to predict in vivo corrosion rates of magnesium alloys.

In this study we present the first results of the investigation of polymer-coated titanium implants implanted in the proximal tibia and distal femora of New Zealand white rabbits. The results of DEXA scans, micro-CT, and histological analysis showed an increase of osseointegration. We suggest that controlled release kinetics after coupling of these polymers with BMP-2 can additionally increase osseointegration.

This study addresses work sharing during navigation-assisted total knee arthroplasty. Specifically, the concept is introduced of a "navigator" assistant who operates the navigation system during surgery while the surgeon concentrates on the primary steps of surgery.In a prospective study of 40 total knee arthroplasties, one group of patients was treated using the navigator concept, a second group was treated using a conventional navigation setup, and a third group was treated with conventional internal and external alignment jigs. Surgery time and outcome parameters were compared.Results show a significant difference in surgery time between the three groups. The conventional and navigator concept groups showed similar surgery times; however, the navigation group without navigation concept exhibited longer surgery time.The navigator concept represents a highly effective principle to minimize surgery time needed during navigated total knee arthroplasty.