Johannes Beckmann

Evaluation of implant position and knee alignment after patient-specific unicompartmental knee arthroplasty

Implant positioning and knee alignment are two primary goals of successful unicompartmental knee arthroplasty. This prospective study outlines the radiographic results following 32 patient-specific unicompartmental medial resurfacing knee arthroplasties. By means of standardized pre- and postoperative radiographs of the knee in strictly AP and lateral view, AP weight bearing long leg images as well as preoperative CT-based planning drawings an analysis of implant positioning and leg axis correction was performed.The mean preoperative coronal femoro-tibial angle was corrected from 7° to 1° (p<0.001). The preoperative medial proximal tibial angle of 87° was corrected to 89° (p<0.001). The preoperative tibial slope of 5° could be maintained. The extent of the dorsal femoral cut was equivalent to the desired value of 5mm given by the CT-based planning guide. The mean accuracy of the tibial component fit was 0mm in antero-posterior and +1mm in medio-lateral projection. Patient-specific fixed bearing unicompartmental knee arthroplasty can restore leg axis reliably, obtain a medial proximal tibial angle of 90°, avoid an implant mal-positioning and ensure maximal tibial coverage.

Cup positioning in THA: current status and pitfalls. A systematic evaluation of the literature

The correct determination of cup orientation in THA regarding the intraoperative as well as the postoperative assessment due to the pelvic tilt and rotation with inexact incorporation of the pelvis is uncertain. The anterior pelvic plane (APP) seems to be the most reliable reference frame and computer-assisted navigation systems seem to provide the best tool for correct implantation to date. For the intraoperative assessment of the APP, the exact determination of the bony landmarks is mandatory. For the standard plain radiography, standardized positioning of the patient and approximation of pelvic tilt by a lateral view are mandatory. An additional CT must be carried out for certain indications. More emphasis has to be given to the individuality of pelvic tilt and range of motion.

Fixation of revision TKA: a review of the literature

PurposeEarly aseptic loosening is a major complication in revision total knee arthroplasty (TKA). It is well accepted that intramedullary stems improve the anchoring of the prosthetic components; however, controversy still exists about the optimal fixation technique of the stems (cementless, hybrid, cemented).MethodsA literature review was carried out in the main medical databases from 1980 to 04/2010 to evaluate the available literature by evidence-based criteria and to analyse the results of the single studies regarding fixation technique in knee revision arthroplasty.ResultsThere are four studies regarding the cementless fixation. Eight studies reported the hybrid technique and five studies the cemented technique. Hybrid and cemented techniques are comparable regarding the survival of arthroplasties, the rate of aseptic loosening and the clinical outcome. However, most studies just show a low level of evidence (LoE III and IV), a small to medium number of cases and a short follow-up.ConclusionBased on the current literature, no final statement can be drawn regarding the optimal fixation technique in revision TKA. Future RCTs are needed to enable conclusive statements about the possible advantages and disadvantages of the single fixation techniques, although the clinical implementation often is critical.

Cell based therapy for the treatment of femoral head necrosis

ZusammenfassungDas Ziel bei der Therapie der Femurkopfnekrose des Erwachsenen ist es, den Hüftkopf zu erhalten und einen künstlichen Gelenkersatz zu vermeiden. Die Core-Dekompression bietet neben der intraossären Druckentlastung zusätzlich die Möglichkeit, bioaktive Materialien, Substanzen und Zellen in den Bohrkanal einzubringen. Hierzu zählen vaskularisierte und nichtvaskularisierte Knochentransplantate, allogene und synthetische Knochenersatzmaterialien, osteogen und angiogen wirkende Wachstumsfaktoren sowie unterschiedliche Vorläuferzellen. Insbesondere der Einsatz neuer zellbasierter Verfahren hat ein großes therapeutisches Potenzial und könnte zukünftig einen entscheidenden Fortschritt bei der Behandlung der Femurkopfnekrose bedeuten. In diesem Beitrag werden die bisherigen klinischen Erfahrungen der zellbasierten Strategien zur Therapie der Femurkopfnekrose des Erwachsenen zusammenfasst und ein eigener neu entwickelter Therapieansatz unter der Verwendung von Knochenmarkstammzellen (TRCs: „tissue repair cells“) in Kombination mit einer β-TCP-Matrix vorgestellt.AbstractThe goal of the therapy for necrosis of the femoral head in adults is the preservation of the femoral head and, therefore, avoidance of total joint replacement. Core decompression is known to reduce the intraosseous pressure and additionally provides the opportunity to introduce bioactive materials, substances and cells into the core tract. These include vascularized and non-vascularized bone grafts, allogenic and synthetic bone substitutes, osteogenic and angiogenic growth factors, as well as different progenitor cells. In particular, the use of cell-based strategies has great therapeutic potential and could play an important role in the treatment of femoral head necrosis in adults in the future. In this article, we summarize the existing clinical experience of current cell-based strategies for the treatment of femoral head necrosis in adults, and present a therapeutic approach using bone marrow stem cells (TRCs: tissue repair cells). in combination with a β-TCP matrix.

Fracture prevention by femoroplasty—cement augmentation of the proximal femur

The prevention of hip fractures is a desirable goal to reduce morbidity, mortality, and socio‐economic burden. We evaluated the influence on femoral strength of different clinically applicable cementing techniques as “femoroplasty.” Twenty‐eight human cadaveric femora were augmented by means of four clinically applicable percutaneous cementing techniques and then tested biomechanically against their native contralateral control to determine fracture strength in an established biomechanical model mimicking a fall on the greater trochanter. The energy applied until fracture could be significantly increased by two of the methods by 160% (53.1 Nm vs. 20.4 Nm, p < 0.001) and 164% (47.1 Nm vs. 17.8 Nm, p = 0.008), respectively. The peak load to failure was significantly increased by three of the methods by 23% (3818.3 N vs. 3095.7 N, p = 0.003), 35% (3698.4 N vs. 2737.5 N, p = 0.007), and 12% (3056.8 N vs. 2742.8 N, p = 0.005), respectively. The femora augmented with cemented double drill holes had a lower fracture strength than the single drilled ones. Experimental femoroplasty is a technically feasible procedure for the prophylactic reinforcement of the osteoporotic proximal femur and, hence, could be an auxiliary treatment option to protect the proximal femur against osteoporotic fractures. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29:1753–1758, 2011

Analysis of Bone Matrix Composition and Trabecular Microarchitecture of the Femoral Metaphysis in Patients with Osteonecrosis of the Femoral Head

Osteonecrosis of the femoral head (ONFH) usually affects young individuals. In advanced stages of ONFH, total hip replacement is the golden standard. However, survivorship after total hip replacement has been reported to be poorer in patients with ONFH compared to patients with primary osteoarthritis (OA). In radiological and histological studies, an impaired bone quality was found not only for the femoral head, but also for the intertrochanteric and metaphyseal region. We hypothesize that alterations of bone quality in the femoral metaphysis might contribute to early stem loosening. The objective of this study was to assess the gene expression levels of factors regulating bone formation and remodeling of the intertrochanteric regions and the proximal femoral canal in patients with ONFH and those with primary OA. The cellular and macromolecular composition of the bone matrix was assessed by osteocalcin immunohistochemistry, and the three‐dimensional organization of trabecular bone was characterized by µCT analysis. Gene expression of BMP‐2 is twofold higher in the proximal femur in the region of the greater trochanter of patients with ONFH compared to those with OA. The number of osteoblasts in the greater trochanter of patients with ONFH (253/mm2) is increased compared to patients with OA (156/mm2). Trabecular properties in ONFH bone are altered for bone volume (OA: 32 mm3, ONFH: 51 mm3) and structure model index (OA: 2.2, ONFH: 1.6) in the proximal femoral canal, but not in the trochanteric regions. These alterations in bone metabolism and architecture might contribute to the higher rates of stem loosening after total hip replacement in patients with ONFH, however, further experimental and clinical studies are needed to support our findings.

Leg axis correction with ConforMIS iForma (interpositional device) in unicompartmental arthritis of the knee.

Degeneration of the meniscus and the articular cartilage in unicompartmental osteoarthritis of the knee results in progressive deformity of the leg axis. It is the aim of this study to evaluate if a leg axis correction can be achieved by implanting a customised metallic interpositional device for the knee (ConforMIS iForma™). Before and after implanting a ConforMIS iForma™ knee implant, a radiological analysis of the leg axis deviation in the frontal plane was performed prospectively in 27 patients by evaluating anteroposterior single-leg stance radiographs. We achieved a sufficient leg axis correction with an average correction of 3.8° and an averaged small under-adjustment of 0.9° by inserting the ConforMIS iForma™ interpositional knee implant. Apart from the primary treatment objective of articular surface restitution the ConforMIS iForma™ knee implant can be reliably used to correct axis deformity occurring with unicompartmental osteoarthritis of the knee.RésuméLa déformation progressive du membre inférieur entraîne lorsqu’existe une arthrose mono-compartimentale un dégénérescence du ménisque et du cartilage articulaire homolatéral. Le but de cette étude est d’évaluer la correction d’axe par un implant métallique d’interposition au niveau du genou(ConforMIS iForma™). avant et après implantation de l’implant ConforMIS iForma™ une analyse radiologique prospective de la déviation des membres dans le plan frontal a été réalisée, chez 27 patients avec radiographies de face et de profil. il est possible grâce à ce matériel d’avoir une correction moyenne de 3,8° avec une hypo correction de 0,9°. compte-tenu de l’objectif que nous nous étions fixés, l’utilisation de cet implant (ConforMIS iForma™) au niveau du genou, permet d’avoir une correction fiable de l’axe lorsque l’on traite des athroses mono-compartimentales.

Influence of Factors Regulating Bone Formation and Remodeling on Bone Quality in Osteonecrosis of the Femoral Head

Osteonecrosis of the femoral head (ONFH) usually affects young individuals and has a major impact on lifestyle. Notably, the pathogenetic mechanisms of osteonecrosis are unresolved and no effective treatment exists. The objective of this study was to assess the gene expression levels of factors regulating bone formation and remodeling (bone morphogenetic protein [BMP]-2, BMP-7, Runx2, osteocalcin, osteoprotegerin [OPG]) in patients with ONFH and to compare them to those of patients with primary osteoarthritis (OA). The cellular and macromolecular composition of the bone matrix was assessed by osteocalcin immunohistochemistry, and the three-dimensional organization of trabecular bone was characterized by micro-computed tomographic analysis. Our results demonstrate that gene expression of BMP-2, BMP-7, and Runx2 is elevated in patients with ONFH. We observed increased extracellular osteocalcin deposition, presumably caused by a higher number of osteoblasts in concordance with increased activity of Runx2. Constant gene expression level of OPG implies an unchanged osteoclast differentiation rate in ONFH bone. We found no significant change in bone volume, connectivity, and structural model index; further, no significant differences were detected for trabecular properties in ONFH bone. In conclusion, we have shown increased gene expression of factors regulating bone formation and remodeling in the femoral head and/or neck of patients with ONFH. Further, we observed an increase in osteocalcin immunoreactivity and osteoblast/osteocyte cell number, while no significant changes in trabecular microarchitecture were detected. This study increases our understanding of the pathophysiology and repair process following ONFH and might help in the development of new treatment strategies in the future.

Zellbasierte Therapie der Femurkopfnekrose

ZusammenfassungDas Ziel bei der Therapie der Femurkopfnekrose des Erwachsenen ist es, den Hüftkopf zu erhalten und einen künstlichen Gelenkersatz zu vermeiden. Die Core-Dekompression bietet neben der intraossären Druckentlastung zusätzlich die Möglichkeit, bioaktive Materialien, Substanzen und Zellen in den Bohrkanal einzubringen. Hierzu zählen vaskularisierte und nichtvaskularisierte Knochentransplantate, allogene und synthetische Knochenersatzmaterialien, osteogen und angiogen wirkende Wachstumsfaktoren sowie unterschiedliche Vorläuferzellen. Insbesondere der Einsatz neuer zellbasierter Verfahren hat ein großes therapeutisches Potenzial und könnte zukünftig einen entscheidenden Fortschritt bei der Behandlung der Femurkopfnekrose bedeuten. In diesem Beitrag werden die bisherigen klinischen Erfahrungen der zellbasierten Strategien zur Therapie der Femurkopfnekrose des Erwachsenen zusammenfasst und ein eigener neu entwickelter Therapieansatz unter der Verwendung von Knochenmarkstammzellen (TRCs: „tissue repair cells“) in Kombination mit einer β-TCP-Matrix vorgestellt.AbstractThe goal of the therapy for necrosis of the femoral head in adults is the preservation of the femoral head and, therefore, avoidance of total joint replacement. Core decompression is known to reduce the intraosseous pressure and additionally provides the opportunity to introduce bioactive materials, substances and cells into the core tract. These include vascularized and non-vascularized bone grafts, allogenic and synthetic bone substitutes, osteogenic and angiogenic growth factors, as well as different progenitor cells. In particular, the use of cell-based strategies has great therapeutic potential and could play an important role in the treatment of femoral head necrosis in adults in the future. In this article, we summarize the existing clinical experience of current cell-based strategies for the treatment of femoral head necrosis in adults, and present a therapeutic approach using bone marrow stem cells (TRCs: tissue repair cells). in combination with a β-TCP matrix.

Tissue concentrations of vancomycin and Moxifloxacin in periprosthetic infection in rats

Background A one-step exchange of an endoprosthesis with periprosthetic infection requires effective antibiotics at high concentrations around the endoprosthesis. We evaluated the tissue distribution of vancomycin and Moxifloxacin in a standardized in vivo model of periprosthetic infection. Methods 36 male rats with periprosthetic infection of the left hind leg, induced by a standardized procedure, received either antibiotic treatment with vancomycin or Moxifloxacin twice daily for 2 weeks, or a sham treatment. After the last administration, different tissues from each animal were evaluated for concentrations of antibiotic. Results Compared to plasma, the tissue concentrations of Moxifloxacin were higher in all tissues investigated (lung, muscle, fat, bone) and the tissue-plasma ratio of Moxifloxacin was considerably higher than that of vancomycin. The concentrations of Moxifloxacin were equally high in the infected and the uninfected hind leg, whereas the vancomycin concentrations were significantly higher in the infected leg. Interpretation The standardized model of periprosthetic infection described here can be extrapolated to different bacterial and mycotic pathogens, and also to different antibiotics or therapeutic regimes. It provides a way of correlating tissue concentrations with clinical outcome in future studies.