One-year follow-up data from the German Cartilage Registry (KnorpelRegister DGOU) in the treatment of chondral and osteochondral defects of the talus.

INTRODUCTION: Chondral and osteochondral lesions of the talus (OLTs) remain a challenging issue with numerous operative treatments proposed to date. The aim of this study was to evaluate 1-year follow-up data in the German Cartilage Registry (KnorpelRegister DGOU). METHODS: Among 401 patients in the database, 114 patients with a complete 1-year Foot and Ankle Outcome (FAOS) score for subscale Pain as the primary variable were included. A total of 12 different surgical treatments were performed. However, 8 techniques were carried out in negligible numbers of patients (n = 1-3), leaving 89 patients treated with the following techniques: arthroscopic antegrade bone marrow stimulation (group A; n = 32), autologous chondrocyte implantation with autologous cancellous bone grafting (group B; n = 9), matrix-augmented bone marrow stimulation (group C; n = 22), and matrix-augmented bone marrow stimulation with autologous cancellous bone grafting (group D; n = 26). Group differences and possible influencing variables such as age and sex were evaluated. Level of significance was set at p < 0.05 for all statistical tests. RESULTS: All four treatment groups showed significant improvement of the FAOS scores at 1 year postoperatively compared with their preoperative scores. No significant differences were found with respect to score changes among the groups. A positive correlation between FAOS subscale Pain improvement and defect size volume and negative correlations between increasing age and FAOS subscales Sports/Rec and QoL were found. Concomitant ankle stabilization led to greater improvement in FAOS subscales Symptoms and ADL than in patients with no stabilization. FAOS subscale Pain showed greater improvement in women than in men. CONCLUSION: All analyzed treatment options were effective for treatment of OLTs. In particular, large defects appeared to benefit from treatment. In the presence of concomitant ankle instability, a stabilizing procedure appeared to have a positive impact on the outcome.

[Recommendations for unicondylar knee replacement in the course of time : A current inventory]. / Empfehlungen zur unikondylären Schlittenendoprothetik im Wandel der Zeit : Eine aktuelle Bestandsaufnahme.

BACKGROUND: A higher patient satisfaction stands in contrast to higher revision rates of unicondylar knee joint endoprosthetics (UKE) compared to total knee joint endoprosthetics (TKE). Furthermore, old "dogmas" regarding indications and contraindications persist, which is still reflected in the significantly different case numbers. AIM: The aim of this article is to provide an overview of the current literature regarding 1. indication and contraindication (BMI, age, sport, arthrosis of other compartments, ligament status) and 2. the "eternal rival" fixed or mobile bearing for UKE. RESULTS: The choice of the right patient remains essential, even if all the old "dogmas" of contraindications have been relativized or even outdated. Arthroses of the contralateral (in medial UKE correspondingly lateral) compartment and advanced arthroses of the lateral patella facet remain the only persistent contraindications. In contrast, a high BMI, age, chondrocalcinosis, medial patella facet and a defective (but particularly functionally stable) ACL are not contraindications; however, severe obesity is responsible for a significantly higher complication rate and probably a higher rate of loosening. Rather, the experience and thus the number of UKEs of the individual surgeon is decisive for the outcome, to which the discussion about mobile or fixed inlays must also be completely subordinated. CONCLUSION: The indications for UKE can, therefore, be extended with a clear conscience on the basis of literature, and the current 1:10 UKE:TKE ratio in Germany can be shifted significantly.

Outcome after operative treatment for chronic versus acute Achilles tendon rupture - A comparative analysis.

BACKGROUND: This study compared outcomes after treatment of acute Achilles tendon (AT) rupture via percutaneous suturing, with those after chronic AT rupture treated via open reconstruction. METHODS: This retrospective study included 30 patients who underwent either percutaneous suturing for acute AT rupture (group AR, n=16) or open reconstruction for chronic AT rupture (group CR, n=14). Function was evaluated by calf muscle circumference, and endurance through isokinetic measurement and single-leg heel-rise test. Score evaluation included AT Total Rupture Score, Victorian Institute of Sports Assessment-Achilles questionnaire, and visual analogue scale pain score. Postoperative tendon thickness was measured using ultrasonography and MRI. RESULTS: Follow-up was conducted 4.97±1.79 years postoperatively. The groups were similar in age and body mass index. There was no significant difference between groups in calf circumference, isokinetic measurement, heel-rise test, and score evaluation. There was significantly less mediolateral tendon thickening in group AR compared with group CR on ultrasonography (p=0.01) and MRI (p=0.001). CONCLUSIONS: Open reconstruction for chronic AT rupture may result in comparable clinical and functional outcomes, but a thicker tendon compared with percutaneous suturing after acute AT rupture.

Focal articular prosthetic resurfacing for the treatment of full-thickness articular cartilage defects in the knee: 12-year follow-up of two cases and review of the literature.

INTRODUCTION: The rationale of focal articular prosthetic resurfacing used as a primary arthroplasty procedure in the treatment of articular cartilage defects is still under debate. Conflicting reports raise concern about high rates of re-operations and continued development of osteoarthritis, while others have reported good outcomes. The goal of this paper is to present the long-term results of two patients with a 12-year follow-up and to report the results of a literature review. MATERIALS AND METHODS: Two patients (male, 70 years; female 63 years) with a follow-up of 12 years were reviewed. Patients were evaluated with standard radiographs to assess the progression of osteoarthritis (OA), a clinical examination including the Knee Injury and Osteoarthritis Outcome Score (KOOS) and Tegner activity scale. The literature review was performed using the search terms HemiCAP, focal, femoral, condyle, inlay, and resurfacing to identify articles published in the English language up until September 25, 2016. RESULTS: The clinical and radiographic follow-ups of the patients were 11.9 and 11.8 years, respectively. Both patients were satisfied with their outcome and would have the operation again. Comparing the first postoperative to 12-year follow-up X-rays, the radiographic results demonstrated no signs of periprosthetic loosening, preservation of joint space, and no change in the osteoarthritic stage. KOOS Scores were 86 and 83 for pain, 89 and 93 for symptoms, 88 and 100 for activities of daily living (ADL), 75 and 65 for sports and recreation, and 75 and 81 for quality of life (QOL). The Tegner activity level was 5 and 4. The literature review comprised 6 studies with 169 focal articular prosthetic resurfacing procedures in 169 patients (84 male, 85 female) with a mean age at implantation ranging from 44.7 to 53.7 years and a follow-up range of 20 months to 7 years. Five studies were classified as level 4 and one as level 3. Clinical and radiographic results showed mainly good to excellent outcomes but were different among the studies depending on the indication. Re-operation rates ranged from 0 to 23% depending on the length of follow-up. CONCLUSIONS: The results suggest that focal articular prosthetic resurfacing is an effective and safe treatment option in selected cases.

Femoral interference screw fixation of hamstring and quadriceps tendons for ACL reconstruction.

PURPOSE: This cadaveric study compares the biomechanical properties of femoral graft fixation in ACL reconstruction of either quadriceps or hamstring tendon grafts with four different interference screws. The hypothesis was that quadriceps tendon grafts provide at least equal results concerning gap formation during cyclic loading and ultimate failure load compared to hamstring tendon grafts with four different interference screws. METHODS: Eighty porcine femora underwent interference screw fixation of human tendon grafts for ACL reconstruction. Either quadriceps (Q) or hamstring (H) tendon grafts and four different bioabsorbable interference (Wolf (W), Storz (S), Mitek (M), Arthrex (A)) screws were used, resulting in 8 groups with 10 specimens per groups (WQ, WH, SQ, SH, MQ, MH, AQ, AH). Biomechanical analysis included pretensioning the constructs with 60 N for 30 s, then cyclic loading of 500 cycles between 60 and 250 N at 1 Hz in a servohydraulic testing machine, with measurement of elongation and stiffness including video measurements. After this, ultimate failure load and failure mode analysis were performed. RESULTS: No statistically significant difference could be noted between the groups regarding gap formation during cyclic loading [Cycles 21-500 (mm): WQ 3.6 ± 0.8, WH 3.9 ± 1.4, SQ 3.6 ± 0.8, SH 3.3 ± 1.5, MQ 4.3 ± 0.8, MH 4.6 ± 1.0, AQ 4.8 ± 0.8, AH 4.3 ± 1.5, n.s.], stiffness during cyclic loading [Cycles 21-500 (N/mm): WQ 72.9 ± 16.9, WH 71.6 ± 20.7, SQ 69.5 ± 23.9, SH 77.4 ± 25.1, MQ 59.6 ± 11.2, MH 48.4 ± 15.4, AQ 48.8 ± 12.7, AH 51.9 ± 22.2, n.s.], and ultimate failure load [(N): WQ 474.4 ± 88.0, WH 579.3 ± 124.2, SQ 493.9 ± 105.2, SH 576.0 ± 90.4, MQ 478.6 ± 59.0, MH 543.9 ± 119.7, AQ 480.2 ± 93.8, AH 497.8 ± 74.2, n.s.]. CONCLUSIONS: Quadriceps tendon grafts yield comparable biomechanical results for femoral interference screw fixation in ACL reconstruction compared to hamstring tendon grafts. From a clinical perspective, quadriceps tendon grafts should therefore be considered as a good option in ACL reconstruction in the future.

[Treatment of Osteochondral Lesions in the Ankle: A Guideline from the Group "Clinical Tissue Regeneration" of the German Society of Orthopaedics and Traumatology (DGOU)]. / Behandlung osteochondraler Läsionen des Sprunggelenks: Empfehlungen der Arbeitsgemeinschaft Klinische Geweberegeneration der DGOU.

Background: Osteochondral lesions (OCL) of the ankle are a common cause of ankle pain. Although the precise pathophysiology has not been fully elucidated, it can be assumed that a variety of factors are responsible, mainly including traumatic events such as ankle sprains. Advances in arthroscopy and imaging techniques, in particular magnetic resonance imaging (MRI), have improved the possibilities for the diagnosis of OCLs of the ankle. Moreover, these technologies aim at developing new classification systems and modern treatment strategies. Material and Methods: This article is a review of the literature. Recommendations of the group "Clinical Tissue Regeneration" of the German Society of Orthopaedics and Traumatology (DGOU) for the treatment of OCLs of the ankle are presented. The review gives a concise overview on the results of clinical studies and discusses advantages and disadvantages of different treatment strategies. Results: Non-operative treatment shows good results for selected indications in children and adolescents, especially in early stages of osteochondritis dissecans (OCD). However, surgical treatment is usually indicated in OCLs in adolescents and adults, depending on the size and location of the lesion. Various arthroscopic and open procedures are frequently employed, including reattachment of the fragment, local debridement of the lesion with fragment removal and curettage of the lesion, bone marrow-stimulation by microfracture or microdrilling (antegrade or retrograde), and autologous matrix-induced chondrogenesis (AMIC®) - with or without reconstruction of a subchondral bone defect or cyst by autologous cancellous bone grafting. Isolated subchondral cysts with an intact cartilage surface can be treated by retrograde drilling and possibly additional retrograde bone grafting. For larger defects or as salvage procedure, osteochondral cylinder transplantation (OATS® or Mosaicplasty®) or matrix-induced autologous chondrocyte transplantation (MACT) are recommended. Transplantation of so-called (osteochondral) mega grafts, such as autologous bone grafts or allografts, are used for very large osteochondral defects that cannot be reconstructed otherwise. Implantation of the so-called "small metal implants" - such as HemiCAP Talus® - is reserved for selected cases after failed primary reconstruction. Corrective osteotomies are indicated in accompanying axial malalignments. Conclusions: There are several different treatment strategies for OCLs, but clinical studies are rare and evidence is limited. Therefore, interventional studies, e.g. randomised controlled trials (RCTs), but also observational studies, e.g. based on data of the Cartilage Registry of the German Society of Orthopaedics and Traumatology (www.knorpelregister-dgou.de), are needed and are recommended by the authors.

Results of an open posterior bone block procedure for recurrent posterior shoulder instability after a short- and long-time follow-up.

PURPOSE: The aim of the present study was to analyse and compare the clinical and radiological results after open posterior bone block procedure at long- (LT) and short-term (ST) follow-up. The hypothesis was that placement of a bone block at the posterior glenoid rim in a technique of extending the glenoid surface will create permanent joint stability even in cases with hyperlaxity without a clinically relevant loss of motion or increase in osteoarthritis. METHODS: Fifteen consecutive shoulders with recurrent posterior dislocation were evaluated clinically and radiologically. The Rowe score, Western Ontario Shoulder Index, Walch-Duplay score and the Constant-Murley score were used for clinical evaluation. The patients were categorized according to their follow-up period as either ST follow-up (min 12 months) or LT follow-up (min 42 months). RESULTS: The clinical results showed no significant difference between ST (9) and LT (6) with good to very good overall results in the subjective as well as the objective scores (CS, RS, WDS). At LT, most patients felt mild to minor pain under strain. The difference in pain between the groups was not significant. Active ranges of motion and strength assessments were normal in all cases. In one case, recurrent dislocations occurred after bone graft resorption 6 months post-operatively. Only one patient presented mild osteoarthritis, without further progress at follow-up. CONCLUSION: The open posterior bone block procedure can be a successful treatment option for recurrent posterior shoulder instability at ST and LT follow-up. This series showed a low rate of recurrent dislocations without development or progression of osteoarthritis. Since soft tissue procedures do not always provide satisfying results, the posterior bone block augmentation presents a reliable technique for the treatment of symptomatic posterior instability. LEVEL OF EVIDENCE: Case Series, Treatment Study, Level IV.

[The German Cartilage Registry (KnorpelRegister DGOU) for evaluation of surgical treatment for cartilage defects: experience after six months including first demographic data]. / Das KnorpelRegister DGOU zur Erfassung von Behandlungsergebnissen nach Knorpeloperationen: Erfahrungen nach 6 Monaten und erste epidemiologische Daten.

The German Cartilage Registry (KnorpelRegister DGOU) has been introduced in October 2013 and aims on the evaluation of patients who underwent cartilage repair for symptomatic cartilage defects. It represents a nation-wide cohort study which has been introduced by the working group "Tissue Regeneration" of the Germany Society of Orthopaedic Surgery and Traumatology and is technically based upon a web-based remote data entry (RDE) system. The present article describes first experiences with the registry including patient and treatment characteristics. Between October 2013 and April 2014, a total of 230 patients who had undergone surgical cartilage repair for symptomatic full-thickness cartilage defects of the knee has been included in the German Cartilage Registry from 23 cartilage repair centres. Mean age was 37.11 years (SD 13.61) and mean defect size was 3.68 cm(2) (SD 0.23). Since the introduction of the KnorpelRegister DGOU the total number of registered patients has increased steadily up to the most recent figure of 72 patients within one month. Patients were treated mainly according to the recommended therapies. The highest percentage in therapy is represented by the bone marrow stimulation techniques (55.02 %) as well as by the autologous chondrocyte transplantation (34.92 %). Unlike the patient collective in the majority of prospective randomised controlled trials, the patient population within the registry shows a high proportion of patients with accompanying pathologies, with an age of more than 50 years at the time of treatment and with unfavourably assessed accompanying pathologies such as an affection of the opposite cartilage surface or a previously resected meniscus. In summary, the technical platform and forms of documentation of the KnorpelRegister DGOU have proved to be very promising within the first six months. Unlike data from other clinical trials, the previous analysis of the patients' data and therapies reflects successfully the actual medical care situation of patients with cartilage defects of the knee joint. This analysis also provides new information on subgroups of patients that have not yet been recorded in the scientific literature. This will be part of the first analysis of clinical treatment data. An expansion of the KnorpelRegister DGOU to patients with cartilage defects of the ankle and hip joints is already decided upon and initialised.

Functional ferroic heterostructures with tunable integral symmetry.

The relation between symmetry and functionality was pinpointed by Pierre Curie who stated that it is the symmetry breaking that creates physical properties. This fundamental principle is nowadays used for engineering heterostructures whose integral symmetry leads to exotic phenomena such as one-way transparency. For switching devices, however, such symmetry-related functionalities cannot be used because the symmetry in conventional heterostructures is immutable once the material has been synthesized. Here we demonstrate a concept for post-growth symmetry control in PbZr0.2Ti0.8O3 and BiFeO3-based heterostructures. A conducting oxide is sandwiched between two ferroelectric layers, and inversion symmetry is reversibly switched on or off by layer-selective electric-field poling. The generalization of our approach to other materials and symmetries is discussed. We thus establish ferroic trilayer structures as device components with reversibly tunable symmetry and demonstrate their use as light emitters that can be activated and deactivated by applying moderate electric voltages.

Translation and validation of the German version of the foot and ankle outcome score.

PURPOSE: Outcome assessment is critical in evaluating the efficacy of orthopaedic procedures. The Foot and Ankle Outcome Score (FAOS) is a 42-item questionnaire divided into five subscales, which has been validated in several languages. Germany has no validated outcome score for general foot and ankle pathology. The aim of this study was to develop a German version of the FAOS and to investigate its psychometric properties. MATERIALS AND METHODS: Forward and backward translation was executed according to official guidelines. The final version of the FAOS was investigated in 150 patients with various foot and ankle disorders. All patients completed the FAOS, Short Form-36, numeric rating scales for pain and disability, and the Hannover questionnaire. The FAOS was re-administered after 1 week. Test-retest reliability, internal consistency, minimal detectable change, construct validity, and floor and ceiling effects were analyzed. RESULTS: Test-retest reliability and internal consistency of each subscale were excellent (intraclass correlation coefficient, 0.88-0.95; Cronbach's α, 0.94-0.98). The minimal detectable changes of each subscale were 17.1-20.8 at the individual level and 2.0-2.4 at group level. There were moderate to strong correlations between FAOS subscales and physical outcomes and low to moderate correlations between FAOS subscales and mental outcomes. Floor and ceiling effects were not present. CONCLUSION: The German version of the FAOS is a reliable and valid instrument for use in foot and ankle patients.

The influence of a single-radius-design on the knee stability.

Prostheses with single radius (SR) design were supposed to be as good as the physiological kinematic and stability of the knee. This in-vitro biomechanical study compared SR to a multiple radius (MR) design on the one hand and seven left human knee specimens were used. The SR and MR knee prosthesis where implanted with a navigation system. We measured varus/valgus deviation of the mechanical axis and the deviation of the joint-line to the epicondyle-line in different knee flexion degrees (0°, 30°, 45°, 60° and 90°) with and without 15 Nm of varus and valgus stress. Without varus/valgus-stress in all three groups (physiological knee, SR and MR prosthesis) the results were located on the varus-site. The variation of the SR was less than the MR, without being significant. Under varus and valgus stress varus/valgus axis deviation constantly grew. From 0-60° no significant deviation between the two prosthesis models was found. At 90° flexion varus/valgus deviation with the SR component was significantly (p ⩽ 0.05) smaller compared to the MR design. This in-vitro study showed that the SR prosthesis is significantly more stable in the coronal plane than the MR in higher flexion degrees. This could have an improved effect on biomechanical stability with a higher clinical function after SR-TKA.

Effects of perfusion and cyclic compression on in vitro tissue engineered meniscus implants.

PURPOSE: The purpose of this study was to investigate the influence of continuous perfusion and mechanical stimulation on bone marrow stromal cells seeded on a collagen meniscus implant. METHODS: Bone marrow aspirates from 6 donors were amplified in vitro. 10(6) human BMSC were distributed on a collagen meniscus implant. Scaffolds were cultured under static conditions (control) or placed into a bioreactor system where continuous perfusion (10 ml/min) or perfusion and mechanical stimulation (8 h of 10% cyclic compression at 0.5 Hz) were administered daily. After 24 h, 7 and 14 days, cell proliferation, synthesis of procollagen I and III peptide (PIP, PIIIP), histology, and the equilibrium modulus of the constructs were analyzed. RESULTS: Proliferation demonstrated a significant increase over time in all groups (p < 0.001). PIP synthesis was found to increase from 0.1 ± 0.0 U/ml/g protein after 24 h to 2.0 ± 0.5 (perfusion), 3.8 ± 0.3 (mechanical stimulation), and 1.8 ± 0.2 U/ml/g protein (static control, lower than perfusion and mechanical stimulation, p < 0.05). These differences were also evident after 2 weeks (2.7 ± 0.3, 4.0 ± 0.6, and 1.8 ± 0.2 U/ml/g protein, p < 0.01); PIIIP synthesis was found to increase from 0.1 ± 0.0 U/ml/g protein after 24 h to 2.9 ± 0.7 (perfusion), 3.1 ± 0.9 (mechanical stimulation), and 1.6 ± 0.3 U/ml/g protein (controls) after 1 week and remained significantly elevated under the influence of perfusion and mechanical stimulation (p < 0.01) after 2 weeks. Mechanical stimulation increased the equilibrium modulus more than static culture and perfusion after 2 weeks (24.7 ± 7.6; 12.3 ± 3.7; 15.4 ± 2.6 kPa; p < 0.02). CONCLUSION: Biomechanical stimulation and perfusion have impact on collagen scaffolds seeded with BMSCs. Cell proliferation can be enhanced using continuous perfusion and differentiation is fostered by mechanical stimulation.

[Patellofemoral arthroplasty--results of a nation-wide survey in Germany and review of the literature]. / Patellofemorale Endoprothetik in Deutschland - eine Standortbestimmung und Uberblick über die Literatur.

BACKGROUND: Isolated patellofemoral arthroplasty is discussed controversially. The aim of this nation-wide survey in Germany and review of the literature was to determine the current status of patellofemoral arthroplasty. METHODS: A standardised questionnaire was sent to 744 German departments of orthopaedic surgery, traumatology and general surgery. In the first part, surgeons were asked general questions about their department size, case numbers of knee arthroplasties per year and non-endoprosthetic treatment of isolated patellofemoral disorders. If patellofemoral arthroplasty was conducted, parameters concerning age, gender, duration of complaints, indication for surgery, surgical approach, type of endoprosthesis used, additional surgical treatments and failures were evaluated in the second part. Furthermore we asked for the reasons if no isolated patellofemoral arthroplasty was performed. A systematic review of the literature was done including studies published until October 2007. The main inclusion criterion was the presentation of results after the implantation of a patellofemoral prosthesis for isolated patellofemoral osteoarthritis. RESULTS: A total of 225 analysable questionnaires were returned. Of 53,420 knee arthroplasties performed per year, only 195 (0.37 %) were isolated patellofemoral arthroplasties. The majority of patients (91 %) were between 40 and 80 years old. The aetiology of isolated patellofemoral osteoarthritis was believed to be idiopathic in 41 % and traumatic in 8 %. Patellofemoral dysplasia was held to be responsible in 47 % and patellofemoral instability in 4 % of the cases. The main reason for failure and surgical revision was ongoing tibiofemoral osteoarthritis of the affected knee. Negative attitude and disbelief towards the success of isolated patellofemoral arthroplasty were stated by the majority (62 %) of non-users. A lack of appropriate indications was reported by 22 % and lacking know-how by 16 %. We analysed 12 studies (459 implantations; 390 patients) in the literature review. The treatment was considered successful in 67.8 % of cases. The overall revision rate was 30.3 %. The highest failure rates were in patients with progression of tibiofemoral osteoarthritis or malalignment. CONCLUSIONS: Isolated patellofemoral arthroplasty has only low significance among surgeons performing knee arthroplasty in Germany. The majority of surgeons do not believe in the success of the procedure. Almost one third of published cases in the literature needed to be revised.

[Autologous chondrocyte transplantation in the treatment of articular cartilage lesions of the talus]. / Die autologe Knorpelzelltransplantation zur Behandlung von Knorpelläsionen am Talus.

In contrast to the knee joint, autologous chondrocyte transplantation (ACT) is rarely used for treating articular cartilage lesions in the ankle joint. Matrix-associated autologous chondrocyte transplantation (MACT) with the use of biomaterials as cell carriers has facilitated operative application and fixation within the lesion. We have gained experience in the use of two different MACT techniques. According to the Hannover scoring system for the ankle and visual analog scores, results improved significantly (p

[Microfracture technique for the treatment of articular cartilage lesions of the talus]. / Die Technik der Mikrofrakturierung zur operativen Therapie von Knorpelläsionen am Talus.

The microfracture technique is an established method for treating articular cartilage lesions of the talus. Symptomatic chondral or osteochondral lesions of grade II or higher with softening or fraying of the chondral surface or an unstable rim are indications for débridement of the lesion and use of the microfracture technique. In advanced degenerative lesions, the indication must be determined critically. In a prospective study, significant (p<0.001) improvement was observed at a mean follow-up of 5.2 years (range 3.8-6.6 years) in 23 ankles. According to the Hannover scoring system, 87% of the patients were rated as excellent or good. Results for patients older than 50 years were not inferior to those for younger patients. Results for overweight patients were significantly (p=0.03) worse compared with patients of normal weight. Magnetic resonance imaging findings revealed that filling of the defect is accomplished in the majority of cases with an inhomogeneous structure of the cartilage repair tissue and a high incidence of subchondral alterations. The microfracture technique appears to be a reliable method for treating chondral and osteochondral lesions of the talus, with good outcomes in a mid-term follow-up.

Scalable multiparticle entanglement of trapped ions.

The generation, manipulation and fundamental understanding of entanglement lies at the very heart of quantum mechanics. Entangled particles are non-interacting but are described by a common wavefunction; consequently, individual particles are not independent of each other and their quantum properties are inextricably interwoven. The intriguing features of entanglement become particularly evident if the particles can be individually controlled and physically separated. However, both the experimental realization and characterization of entanglement become exceedingly difficult for systems with many particles. The main difficulty is to manipulate and detect the quantum state of individual particles as well as to control the interaction between them. So far, entanglement of four ions or five photons has been demonstrated experimentally. The creation of scalable multiparticle entanglement demands a non-exponential scaling of resources with particle number. Among the various kinds of entangled states, the 'W state' plays an important role as its entanglement is maximally persistent and robust even under particle loss. Such states are central as a resource in quantum information processing and multiparty quantum communication. Here we report the scalable and deterministic generation of four-, five-, six-, seven- and eight-particle entangled states of the W type with trapped ions. We obtain the maximum possible information on these states by performing full characterization via state tomography, using individual control and detection of the ions. A detailed analysis proves that the entanglement is genuine. The availability of such multiparticle entangled states, together with full information in the form of their density matrices, creates a test-bed for theoretical studies of multiparticle entanglement. Independently, 'Greenberger-Horne-Zeilinger' entangled states with up to six ions have been created and analysed in Boulder.

Bell states of atoms with ultralong lifetimes and their tomographic state analysis.

Arbitrary atomic Bell states with two trapped ions are generated in a deterministic and preprogrammed way. The resulting entanglement is quantitatively analyzed using various measures of entanglement. For this, we reconstruct the density matrix using single qubit rotations and subsequent measurements with near-unity detection efficiency. This procedure represents the basic building block for future process tomography of quantum computations. As a first application, the temporal decay of entanglement is investigated in detail. We observe ultralong lifetimes for the Bell states Psi(+/-), close to the fundamental limit set by the spontaneous emission from the metastable upper qubit level and longer than all reported values by 3 orders of magnitude.

Spontaneous emission lifetime of a single trapped Ca(+) ion in a high finesse cavity.

We investigate the spontaneous emission lifetime of a single trapped (40)Ca+ ion placed at different positions in the vacuum standing wave inside a high finesse cavity which is stabilized to the atomic transition. The lifetime is measured by quantum state detection after pi-pulse excitation. The result for the natural lifetime of the D(5/2) metastable state of 1161(22) ms agrees, within 1 standard deviation, with the most precise published value. We observe a reduction of the spontaneous emission lifetime of approximately 15% in the node of the vacuum field.

Deterministic quantum teleportation with atoms.

Teleportation of a quantum state encompasses the complete transfer of information from one particle to another. The complete specification of the quantum state of a system generally requires an infinite amount of information, even for simple two-level systems (qubits). Moreover, the principles of quantum mechanics dictate that any measurement on a system immediately alters its state, while yielding at most one bit of information. The transfer of a state from one system to another (by performing measurements on the first and operations on the second) might therefore appear impossible. However, it has been shown that the entangling properties of quantum mechanics, in combination with classical communication, allow quantum-state teleportation to be performed. Teleportation using pairs of entangled photons has been demonstrated, but such techniques are probabilistic, requiring post-selection of measured photons. Here, we report deterministic quantum-state teleportation between a pair of trapped calcium ions. Following closely the original proposal, we create a highly entangled pair of ions and perform a complete Bell-state measurement involving one ion from this pair and a third source ion. State reconstruction conditioned on this measurement is then performed on the other half of the entangled pair. The measured fidelity is 75%, demonstrating unequivocally the quantum nature of the process.