Lars Peter Müller

Aging of biogenic secondary organic aerosol via gas-phase OH radical reactions

The Multiple Chamber Aerosol Chemical Aging Study (MUCHACHAS) tested the hypothesis that hydroxyl radical (OH) aging significantly increases the concentration of first-generation biogenic secondary organic aerosol (SOA). OH is the dominant atmospheric oxidant, and MUCHACHAS employed environmental chambers of very different designs, using multiple OH sources to explore a range of chemical conditions and potential sources of systematic error. We isolated the effect of OH aging, confirming our hypothesis while observing corresponding changes in SOA properties. The mass increases are consistent with an existing gap between global SOA sources and those predicted in models, and can be described by a mechanism suitable for implementation in those models.

Radiation exposure to the hands and the thyroid of the surgeon during intramedullary nailing

During 41 procedures of intramedullary nailing of femoral and tibial fractures, the primary surgeon and the first assistant wore ring dosimeters on their dominant index fingers. While the average fluoroscopy time per procedure was 4.6 min, the average dose of radiation to the dominant hand of the primary surgeon was 1.27 mSv and 1.19 mSv to the first assistant. The dose limit for the extremities is 500 mSv per year, as recommended by the International Commission on Radiological Protection. Extrapolation of the mean dose of the primary surgeon and first assistant per procedure of 1.23 mSv leads to the result that the recommended dose limit of 500 mSv would only be exceeded if more than 407 intramedullary nailing procedures are carried out per year. The duration of fluoroscopy time correlated with the radiation dose to the hands of the surgeons, though it was determined by phantom measurements that the majority of radiation exposure occurred during brief exposures of the hands in the direct X-ray beam on the X-ray tube near side of the patient. In order to assess the surface doses of the thyroid gland to the primary surgeon with and without a lead shield, we performed in vitro measurements during operative procedures of the lower leg simulating different intraoperative situations under fluoroscopic control. The average registered ionizing dosage without a thyroid shield was approximately 70 times higher than with thyroid lead protection. In a previous study we found average fluoroscopy times during intramedullary nailing of the tibia and femur of 4.6 min per procedure. Extrapolation of this value leads to the result, that even when 1000 intramedullary nailings were carried out without wearing lead protection, only 13 per cent of the dose limit recommended by the International Commission on Radiological Protection for the thyroid of 300 mSv per year would be reached; by wearing the lead protection only 0.2 per cent of the recommended dose would be reached.

Mid- to long-term results after bipolar radial head arthroplasty

BACKGROUND Radial head arthroplasty is considered the treatment of choice for unreconstructable radial head fractures in the acute fracture situation. Although short-term results in the current literature are promising, replacement of the radial head remains controversial as long-term results are still missing. We report our 8.8-year results after treatment with a bipolar radial head prosthesis by Judet. MATERIALS AND METHODS In our department, 19 patients were treated with bipolar radial head arthroplasty between 1997 and 2001. Seventeen of these patients-14 men and 3 women-were examined retrospectively after 106 months (range, 78-139). Of these, 9 patients were treated primarily, 7 patients secondarily, and 1 because of a tumor. RESULTS On the Mayo Elbow Performance Score, 6 patients achieved excellent results, 10 good, and one fair. The mean DASH score was 9.8 (range, 0-34). No differences were seen between primary and secondary implantation. Flexion averaged 124° (range, 110-150°), the extension deficit was 21° (range, 0-40°), pronation 64° (range, 30-90°), and supination 64° (range, 30-90°). The following complications were seen: 2 dislocations and 8 cases of degenerative changes of the capitellum, 1 with severe erosion. Signs of ulnohumeral arthrosis were found in 12 patients. No evidence of loosening, radiolucencies, or proximal bone resorption was detected. CONCLUSION Despite major primary complications and high incidence of radiographic signs of degenerative changes after 8.8 years, mainly good clinical results were achieved with Judets bipolar prosthesis.

Primäre totale Ellenbogenprothese zur Versorgung distaler Humerusfrakturen Primary Total Elbow Replacement for Fractures of the Distal Humerus

ZusammenfassungOperationszielErreichen einer stabilen und schmerzfreien Funktion durch primäre Implantation einer totalen Ellenbogenprothese bei komplexen intraartikulären distalen Humerusfrakturen älterer Patienten.IndikationenFraktur mit freien Fragmenten oder schlechter Knochenqualität, die eine stabile Osteosynthese nicht zulassen. Geschlossene, komplexe intraartikuläre distale Humerusfraktur (Typ C nach der AO-Klassifikation).Typ-A- und B-Fraktur des distalen Humerus bei Patienten mit vorbestehenden degenerativen Veränderungen, rheumatoiden Erkrankungen oder Voroperationen des Gelenks. Gute Mitarbeit des Patienten, geringer Funktionsanspruch, Patientenalter > 65 Jahre.KontraindikationenOffene Frakturen (Typ II oder III nach Gustilo-Anderson).Infizierte Wundverhältnisse, offene Weichteilverletzungen.Fehlende Mitarbeit des Patienten, hoher Funktionalitätsanspruch, Patientenalter > 65 Jahre.Paralyse des Bizepsmuskels.OperationstechnikRückenlagerung des Patienten. Dorsaler Zugang zum Ellenbogengelenk. Darstellen der medialen Anteile des Musculus triceps an der Insertion des dorsalen Humerus und der Gelenkkapsel, Abdrängen in Kontinuität mit dem ulnaren Periost und der Unterarmfaszie. Bei Entfernung des frakturierten distalen Anteils des Humerus kann der Ansatz des Musculus triceps belassen werden. Vorbereitung des Humerusschafts: Bei mehrfach frakturierten Kondylen ist eine Rekonstruktion nicht notwendig; intramedulläres Entfernen des Knochens von der medialen und lateralen suprakondylären Kante mit einer Fräse. Entfernen der Olekranonspitze. Knochenspananlagerung hinter der anterioren Lasche der humeralen Komponente. Einzementieren der humeralen und ulnaren Komponente. Nachresektion des Radiuskopfes bzw. Processus coronoideus bei Impingement der Gelenkfacetten. Transossäre Reinsertion des Musculus triceps am Olekranon.WeiterbehandlungSelbständige Bewegungsübungen. Vermeidung des Hebens von Gewichten > 5 kg, keine wiederholten Dauerbelastungen > 1 kg Gewicht und keine forcierten Bewegungen im Ellenbogengelenk, z. B. Schlagsportarten.Ergebnisse49 Totalendoprothesen wurden bei 48 Patienten (Durchschnittsalter 67 Jahre) aufgrund distaler Humerusfrakturen eingesetzt. 43 Frakturen konnten nach einem Zeitraum von 7 Jahren nachuntersucht werden. Nach der AO-Klassifikation wurden fünf Typ- A , fünf Typ-B und 33 Typ-C Frakturen behandelt. Der durchschnittliche Bewegungsumfang lag zwischen 24° und 131°. Der „Mayo Elbow Performance Score“ betrug durchschnittlich 93.Die Komplikationen aller 49 Patienten wurden anhand der Akten erfasst. 32-mal bestanden im Verlauf keine Komplikationen. Insgesamt mussten zehn Revisionseingriffe durchgeführt werden, fünfmal war im Verlauf eine Revisionsarthroplastie erforderlich.Retrospektiv kann die Totalendoprothese des Ellenbogens in der Versorgung distaler Humerustrümmerfrakturen unter strenger Berücksichtigung der genannten Indikationen empfohlen werden.AbstractObjectiveAchieving stability and pain-free function for osteoporotic intraarticular multifragmentary fractures of the distal humerus in elderly patients by primary total elbow replacement (TER).IndicationsNon-soft-tissue-attached fragments, poor-quality bone, where stable osteosynthesis is not attainable.Severely comminuted intraarticular closed type C fractures according to the AO classification with multiple small bone/cartilage fragments.In case of degenerative joint diseases and/or previous surgery in rheumatoid patients also type A and B fractures. High compliance, low demand, and old patient > 65 years.ContraindicationsType II or III Gustilo-Anderson open fractures (primary irrigation and debridement).Preexisting infection, open wounds.Younger, high-demand or noncompliant patient.Paralysis of the biceps muscle.Surgical TechniqueSupine positioning of patient. Triceps-sparing dorsal approach. Elevation of medial aspect of the triceps from posterior aspect of the humerus and capsula, reflecting the triceps in continuity with the ulnar periosteum and the forearm fascia. If removal of distal part of the humerus, the triceps insertion can be left intact. Preparation of humerus: no reconstruction of multifractured condyles; excavate bone from medial and lateral supracondylar ridges with burr. Preparation of ulna: remove tip of olecranon. Cemented humeral and ulnar components. Bone graft interposition behind anterior flange of humeral component. Resection of radial head and coronoid process, if impingement after trial reduction. Triceps reattachment transosseous through olecranon.Postoperative ManagementNo formal physical-therapy sessions. Avoid single-event weight lifting of > 5 kg and repetitive lifting of > 1 kg. Discourage playing racquets sports.Results49 acute distal humeral fractures in 48 patients (average age: 67 years) were treated with TER. 43 fractures were followed at an average of 7 years. According to the AO classification, five fractures were type A, five type B, and 33 type C. The average flexion arc at follow-up was 24–131°, the Mayo Elbow Performance Score averaged 93.Data of complications were obtained from records in all 49 patients. 32 of the 49 elbows had neither a complication nor any further surgery from the time of the index arthroplasty to the most recent follow-up evaluation. Ten additional operative procedures, including five revision arthroplasties, were required.The retrospective review supports recommendation for TER for the treatment of an acute distal humeral fracture, when strict inclusion criteria are observed.

TNF-alpha in CRPS and ‘normal’ trauma – Significant differences between tissue and serum

&NA; Posttraumatic TNF‐alpha signaling may be one of the factors responsible for pain and hyperalgesia in complex regional pain syndromes (CRPS). In order to further specify the role of TNF‐alpha we investigated tissue (skin) and serum concentrations in three different patient groups: patients with osteoarthritis and planned surgery, with acute traumatic upper limb bone fracture waiting for surgery, and with CRPS I. Thirty patients (10 in each group) were recruited. Mean CRPS duration was 36.1 ± 8.1 weeks (range 8–90 weeks). Skin punch biopsies were taken at the beginning of the surgery in osteoarthritis and fracture patients and from the affected side in CRPS patients. Blood samples were taken before the respective procedures. Skin and serum TNF‐alpha levels were quantified by ELISA. Compared to patients with osteoarthritis, skin TNF‐alpha was significantly elevated in CRPS (p < 0.001) and fracture patients (p < 0.04). Skin TNF‐alpha in CRPS patients was higher than in patients with acute bone fracture (p < 0.02). In contrast, serum TNF‐alpha values were the same in osteoarthritis and CRPS, and lower in fracture patients (p < 0.03). Our results indicate a local but not systemic increase of TNF‐alpha in CRPS patients. This increase persists for months after limb trauma and may offer the opportunity for targeted treatment.

Carbonate-coordinated metal complexes precede the formation of liquid amorphous mineral emulsions of divalent metal carbonates

During the mineralisation of metal carbonates MCO3 (M=Ca, Sr, Ba, Mn, Cd, Pb) liquid-like amorphous intermediates emerge. These intermediates that form via a liquid/liquid phase separation behave like a classical emulsion and are stabilized electrostatically. The occurrence of these intermediates is attributed to the formation of highly hydrated networks whose stability is mainly based on weak interactions and the variability of the metal-containing pre-critical clusters. Their existence and compositional freedom are evidenced by electrospray ionization mass spectrometry (ESI-MS). Liquid intermediates in non-classical crystallisation pathways seem to be more common than assumed.

Characterization of oligomeric compounds in secondary organic aerosol using liquid chromatography coupled to electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

The components of secondary organic aerosols (SOAs) generated from the gas-phase ozonolysis of two C(10)H(16)-terpenes (alpha-pinene; sabinene) and a cyclic C(6)H(10) alkene (cyclohexene) were characterized by the use of a Fourier transform ion cyclotron mass spectrometer equipped with an electrospray ionization source operated in the negative ion mode. Reversed-phase high-performance liquid chromatography was used to achieve chromatographic separation of highly oxidized organic compounds. In addition to the well-known group of low molecular weight oxidation products (monomers; e.g. dicarboxylic acids), higher molecular weight compounds (dimers) were also detected and their exact elemental compositions were determined. In order to provide additional information for the structural elucidation of these compounds, collision-induced dissociation was applied. Based on the MS/MS spectra, two higher molecular weight products are proposed to be an ester and a peroxide. Molecular formulae calculated from the exact masses show that the SOA-compounds are heavily oxidized and this information creates the background to a discussion of potential reaction pathways for the formation of higher molecular weight compounds.

Number and Locations of Screw Fixation for Volar Fixed-Angle Plating of Distal Radius Fractures: Biomechanical Study

PURPOSE To compare the biomechanical properties of different numbers and locations of screws in a multidirectional volar fixed-angle plate in a distal radius osteotomy cadaver model. METHODS We created an extra-articular fracture in 16 pairs of fresh-frozen human cadaver radiuses. The 32 specimens were randomized into 4 groups. All fractures were fixated with a multidirectional volar fixed-angle plate. We tested 4 different screw-placement options in the distal fragment. The distal fragment was fixed with 4 locking screws in the distal row of the plate in group a, and with 4 locking screws alternately in the distal and proximal rows in group b. In group c, 3 locking screws were used in the proximal row; in group d, 7 locking screws were used, filling all screw holes in the distal and proximal rows of the plate. The proximal fragment was fixed with 3 screws. The specimens were loaded with 80 N under dorsal and volar bending and with 250 N axial loading. Finally, load to failure tests were performed. RESULTS Group d had the highest mean stiffness, 429 N/mm under axial compression, and was statistically significantly stiffer than the other groups. Group b had a mean stiffness of 208 N/mm, followed by group a, with 177 N/mm. Group c showed only a mean stiffness of 83 N/mm under axial compression. There were no statistically significant differences under dorsal and volar bending. CONCLUSIONS In this model of distal radial fractures, there was a difference regarding the stiffness and the placement of screws in the distal rows of a volar fixed-angle plate. Inserting screws in all available holes in the distal fragment offered the highest stability. Using only the proximal row with 3 screws created an unstable situation. Based on these findings, we recommend placing at least 4 screws in the distal fragment and assigning at least 2 screws to the distal row of the multidirectional screw-holes.

Die Instabilität des distalen Radioulnargelenks – Zur Wertigkeit klinischer und röntgenologischer Testverfahren – eine Literaturübersicht

The distal radioulnar joint (DRUJ) plays a tremendous role regarding the functionality of the upper extremity. Lesions of the DRUJ can limit the functionality of the upper extremity decisively. Many clinical and radiological procedures are used to diagnose instability of the DRUJ. Up to now, there has not been a general consensus concerning the standardisation of the evaluation of DRUJ instability. The TFCC (triangular fibrocartilage complex) with its ligamentum subcruentum insertions at the fovea ulnaris and at the basis of the processus styloideus ulnae is in conjunction with the membrana interossea a very important stabiliser of the DRUJ. A fall on the extended hand or a forceful wrist rotation can usually cause injuries to the stabilisers. Ulnar-sided pain, limited pronosupination and loss of grip strength are clinically apparent. Both clinical tests and radiological procedures should be judged regarding their specific efficacies. These tests have to be evaluated in comparison to the gold standard of wrist arthroscopy. Each test alone is not able to verify DRUJ instability on a regular basis. The introduction of a standardised diagnostic procedure including anamnesis and specific clinical and radiological tests should be established. The standardisation ought to be maintained strictly in order to guarantee a growing test efficacy. Finally, high diagnostic reliability is based on a thorough examination which includes complementary clinical and radiological procedures.

Hypothenar hammer syndrome in sports

Repetitive blunt trauma or single severe trauma to the hypothenar region may lead to traumatic thrombosis of the distal ulnar artery (hypothenar hammer syndrome, HHS). In the sports-related literature we found and analysed isolated cases attributed to injuries sustained during sporting activities such as baseball, badminton, handball, football, frisbee, softball, karate, weight-lifting and hockey. Further, we report the case of an amateur golf player with ischaemic symptoms of his left hand, where angiography revealed filling defects in the digital arteries associated with a corkscrew-like configuration of the distal ulnar artery. Magnetic resonance imaging (MRI) scan demonstrated, at the level of the hamulus ossis hamati, accessory fibres of m. palmaris brevis forming a sling around the ulnar artery. Treatment by resection of the ulnar artery. Treatment by resection of the thrombosed a. ulnaris segment and replacement with an autologous vein graft resulted in complete relief of symptoms. Histological sections revealed partially organized thrombi adherent to the intimal surface with fragmentation of the internal elastic membrane, indicating a traumatic genesis. As the mechanism of injury, we suspected intensive golf playing with the grip style and subsequent motions leading to pressure injury of the hypothenar area and the underlying ulnar artery. Contraction of the anomalous muscle belly may have additionally compressed the artery, slowing down the arterial flow and promoting thrombosis. In most reported cases including our own, it took a relatively long time until the cause of the disease as traumatic was found and accepted. The initial repetitive blunt or single severe trauma initiaing the HHS can easily be overlloked or ignored. After intimal damage of a. ulnaris, the beginning of symptoms may be prolonged and mislead one into thinking the cause is a collagen or vasospastic disease.