Upland Yedoma taliks are an unpredicted source of atmospheric methane.

Landscape drying associated with permafrost thaw is expected to enhance microbial methane oxidation in arctic soils. Here we show that ice-rich, Yedoma permafrost deposits, comprising a disproportionately large fraction of pan-arctic soil carbon, present an alternate trajectory. Field and laboratory observations indicate that talik (perennially thawed soils in permafrost) development in unsaturated Yedoma uplands leads to unexpectedly large methane emissions (35-78 mg m-2 d-1 summer, 150-180 mg m-2 d-1 winter). Upland Yedoma talik emissions were nearly three times higher annually than northern-wetland emissions on an areal basis. Approximately 70% emissions occurred in winter, when surface-soil freezing abated methanotrophy, enhancing methane escape from the talik. Remote sensing and numerical modeling indicate the potential for widespread upland talik formation across the pan-arctic Yedoma domain during the 21st and 22nd centuries. Contrary to current climate model predictions, these findings imply a positive and much larger permafrost-methane-climate feedback for upland Yedoma.

The latest freshwater giants: a new Peltocephalus (Pleurodira: Podocnemididae) turtle from the Late Pleistocene of the Brazilian Amazon.

Overkill of large mammals is recognized as a key driver of Pleistocene megafaunal extinctions in the Americas and Australia. While this phenomenon primarily affected mega-mammals, its impact on large Quaternary reptiles has been debated. Freshwater turtles, due to the scarcity of giant forms in the Quaternary record, have been largely neglected in such discussions. Here we present a new giant podocnemidid turtle, Peltocephalus maturin sp. nov., from the Late Pleistocene Rio Madeira Formation in the Brazilian Amazon, that challenges this assumption. Morphological and phylogenetic analyses of the holotype, a massive partial lower jaw, reveal close affinities to extant Amazonian species and suggest an omnivorous diet. Body size regressions indicate Pe. maturin possibly reached about 180 cm in carapace length and is among the largest freshwater turtles ever found. This finding presents the latest known occurrence of giant freshwater turtles, hinting at coexistence with early human inhabitants in the Amazon.

Subsea permafrost organic carbon stocks are large and of dominantly low reactivity.

Subsea permafrost carbon pools below the Arctic shelf seas are a major unknown in the global carbon cycle. We combine a numerical model of sedimentation and permafrost evolution with simplified carbon turnover to estimate accumulation and microbial decomposition of organic matter on the pan-Arctic shelf over the past four glacial cycles. We find that Arctic shelf permafrost is a globally important long-term carbon sink storing 2822 (1518-4982) Pg OC, double the amount stored in lowland permafrost. Although currently thawing, prior microbial decomposition and organic matter aging limit decomposition rates to less than 48 Tg OC/yr (25-85) constraining emissions due to thaw and suggesting that the large permafrost shelf carbon pool is largely insensitive to thaw. We identify an urgent need to reduce uncertainty in rates of microbial decomposition of organic matter in cold and saline subaquatic environments. Large emissions of methane more likely derive from older and deeper sources than from organic matter in thawing permafrost.

[Radial head prosthesis for acute fractures]. / Radiuskopfprothese bei akuten Frakturen ­ wann und welche?

Non-reconstructible radial head fractures with concomitant injuries and resultant instability of the elbow are often treated by implantation of a radial head prosthesis. Various prosthetic designs and implantation techniques are available. Several pitfalls have to be respected during implantation. This article provides tips and tricks for successful implantation and aftercare and gives an overview of long-term outcomes and revision rates.

Evaluation of simulators for x-ray speckle-based phase contrast imaging.

X-ray phase contrast imaging (PCI) denotes a group of highly sensitive imaging techniques that permits imaging at scales ranging from nanoscopic to the medical. Recently introduced, speckle-based imaging has seen a rapid development because of its experimental simplicity and its capability to retrieve the refraction, the scattering and the absorption of a sample using a conventional x-ray set-up. Precise simulation would permit to optimise the imaging setups for different applications, but until now works on simulation of x-ray speckle-based PCI have been very few. In this work we evaluate different simulation codes, based on Monte-Carlo, analytical ray-tracing and wave-optics Fresnel propagation. The simulation results are compared to both synchrotron and conventional imaging experiments to permits their validation. We obtain a strong similarity between simulated and experimental data. We discuss the validity and applicability of each approach.

[Extensor tendon injuries of the thumb]. / Strecksehnenverletzungen des Daumens.

Extensor tendon injuries of the thumb include lesions of the tendons of the extensor pollicis longus, extensor pollicis brevis and abductor pollicis longus muscles. The latter is practically only affected in open injuries. Open injuries require a tendon reconstruction by suture followed by immobilization in the distal and an adequate aftercare depending on the zone of injury. In distal injuries static splinting is applied, whereas proximal injuries from T4 on require a dynamic after-treatment. Different courses of the tendon of the extensor pollicis brevis muscle exist distal to the metacarpophalangeal joint and must be considered. The rare ruptures of the extensor hood at the metacarpophalangeal joint provoke an ulnar displacement of the extensor pollicis longus or both extensor tendons with concomitant lack of active extension in the metacarpophalangeal and interphalangeal joints. This injury is often misdiagnosed as a rupture of the ulnar collateral ligament of the metacarpophalangeal joint. It should be treated by refixation of the ruptured structures. Closed chronic ruptures of the extensor pollicis longus tendon go along with a defect that requires a tendon transfer or a tendon autograft.

Viscoelastic properties of the human A2 finger pulley.

INTRODUCTION: Biomechanical evaluation of the viscoelastic properties tissue deformation, stiffness, and maximum breaking load of the human A2 pulley. We hypothesized that the A2 pulleys of index, middle, and ring fingers exhibit no difference regarding the aforementioned biomechanical parameters. METHODS: Forty-one A2 pulleys of 14 upper extremities (8 body donors) were assessed. Cyclic and load-to-failure testing were performed. The biomechanical parameters tissue deformation during cyclic and load-to-failure testing, stiffness, and maximum breaking load were determined. RESULTS: No significant differences between the fingers could be detected regarding the biomechanical parameters. A significant negative correlation could be detected between stiffness and deformation of the pulley. Significant positive correlations could be identified between stiffness and maximum breaking load and between maximum breaking load and deformation of the pulleys. CONCLUSIONS: Assessment of the viscoelastic properties of the A2 finger pulley promotes precise diagnosis of pulley lesions and will help to optimize treatment.

[Revision surgery for carpal and cubital tunnel syndrome]. / Revisionseingriffe beim Karpal- und Kubitaltunnelsyndrom.

BACKGROUND: Carpal tunnel syndrome, a compressive neuropathy of the median nerve at the wrist and cubital tunnel syndrome, a compressive neuropathy of the ulnar nerve at the elbow, are the two most common peripheral nerve compression syndromes. Chronic compressive neuropathy of peripheral nerves causes pain, paraesthesia and paresis. Treatment strategies include conservative options, but only surgical decompression can resolve the mechanical entrapment of the nerve with proven good clinical results. However, revision rates for persistent or recurrent carpal tunnel syndrome is estimated at around 5% and for refractory cubital tunnel syndrome at around 19%. Common causes for failure include incomplete release of the entrapment and postoperative perineural scarring. THERAPY: Precise diagnostic work-up is obligatory before revision surgery. The strategy of revision surgery is first complete decompression of the affected nerve and then providing a healthy, vascularized perineural environment to allow nerve gliding and nerve healing and to avoid recurrent scarring. Various surgical options may be considered in revision surgery, including neurolysis, nerve wrapping and nerve repair. In addition, flaps may provide a well vascularized nerve coverage in the case of recurrent carpal tunnel syndrome. In the case of recurrent cubital tunnel syndrome, anterior transposition of the ulnar nerve is mostly performed for this purpose. RESULTS: In general, revision surgery leads to improvement of symptoms, although the outcome of revision surgery is less favourable than after primary surgery and complete resolution of symptoms is unlikely.

[Revision surgery after failed (partial-) arthrodesis of the wrist]. / Revisionen nach fehlgeschlagenen (Teil­)Versteifungen am Handgelenk.

(Partial) arthrodeses of the wrist have been proven cornerstones to treat many lesions for decades, especially in the case of revision surgery. Four-corner, scapho-trapezo-trapezoidal (STT), radio-scapho-lunate (RSL) and total wrist fusions are very common techniques in hand surgery. However, even these proven surgical procedures have significant non-fusion rates. Prior to revising a failed arthrodesis, it is essential to analyse the latter failure precisely. A technically adequate revision is only feasible when based on a correct and meticulous analysis. The understanding of the biological processes and technical aspects of the implants are the basis for solving this issue.

[Surgical treatment of carpal tunnel syndrome: open release of the flexor retinaculum and hypothenar fat flap for revision surgery]. / Operative Behandlung des Karpaltunnelsyndroms: offene Retinakulumspaltung und Hypothenarfettlappenplastik beim Rezidiv.

OBJECTIVE: Decompression of the median nerve by complete release of the flexor retinaculum and the distal antebrachial fascia. In the case of revision surgery providing of a scar-free covering of the median nerve, if necessary. INDICATIONS: Carpal tunnel release is indicated for symptomatic patients with painful paraesthesia or neurological deficits after adequate diagnostic evaluation. The hypothenar fat flap is indicated in revision surgery if a sufficient nerve bed of the median nerve is needed and to restore nerve gliding. CONTRAINDICATIONS: General operative limitations. The hypothenar fat flap is not indicated in revision surgery if median nerve irritation is not caused by surrounding scaring but other reasons like tendonitis. SURGICAL TECHNIQUE: Proximal longitudinal incision of the palm. Subcutaneous dissection and incision of the palmar aponeurosis. Careful ulnar incision of the transverse carpal ligament. Considerate release of the distal and proximal parts of the retinaculum as well as the distal part of the antebrachial fascia. Exploration of the median nerve and palpation of the carpal tunnel and resection of compressive structures, if necessary. In case of revision surgery, if required, the hypothenar fat flap is raised. The fat flap is transposed without tension palmar to the median nerve and fixed to the radial side of the carpal tunnel. POSTOPERATIVE MANAGEMENT: Early functional mobilization. Immobilization for a short period is optional. After revision surgery and hypothenar fat flap, splinting for one week is recommended.

[Dorsal plate arthrodesis of the thumb metacarpophalangeal joint]. / Die Arthrodese des Daumengrundgelenks durch Plattenosteosynthese.

OBJECTIVE: Elimination of pain or instability by arthrodesis of the thumb joint in functional position by dorsal plateosteosynthesis. INDICATIONS: Painful primary or secondary arthrosis of the thumb, nonreconstructable ulnar, radial or palmar instability, posttraumatic dislocation, defect injuries, bone tumors in the region of the thumb metacarpophalangeal joint. CONTRAINDICATIONS: Local infection of the thumb metacarpophalangeal joint area. SURGICAL TECHNIQUE: Dorsal approach to the thumb metacarpophalangeal (MP) joint, splitting of the extensor aponeurosis between the extensor pollicis longus and extensor pollicis brevis tendon. Opening of the anterior capsule and separation of the collateral ligaments, open up the joint, narrow concave and convex joint surface resections, adjustment of the arthrodesis position in 10-20° flexion and K­wire transfixation, dorsal plateosteosynthesis, fine adjustment of the flexion, axis and pronation position. Closure of the capsule and the periosteal gliding tissue over the plate, reconstruction of the extensor aponeurosis. POSTOPERATIVE MANAGEMENT: Splint for 3 weeks. Full load after 6-8 weeks. RESULTS: The dorsal plate arthrodesis of the thumb MP joint is a reliable surgical method with very good functional results.

[Open reduction and plate/screw osteosynthesis of proximal phalanx fractures]. / Offene Reposition und Schrauben­/Plattenosteosynthese von Fingergrundgliedfrakturen.

OBJECTIVE: Anatomical open reduction and internal fixation using screw/plate osteosynthesis. INDICATIONS: Extra-articular fractures with clinically evident malrotation of the finger, comminution fracture and/or loss of length, which cannot be treated non-operatively; fracture instability; intra-articular fracture with step off greater than 1 mm, which cannot be treated percutaneously but openly using plate/screw osteosythesis; failure of conservative treatment. CONTRAINDICATIONS: General operative limitations. SURGICAL TECHNIQUE: Dorsal, mediolateral, or palmar approach, temporary reduction using pincers or optional Kirschner wires; screw/plate osteosynthesis for internal fixation. POSTOPERATIVE MANAGEMENT: Immediate mobilization facilitated by buddy loops for the first 4-6 weeks, prevention of edema using elastic dressing, physiotherapy. RESULTS: Open reduction and internal fixation using screw/plate osteosynthesis provides good results in combination with immediate mobilization. Nevertheless, adhesion of tendons or capsule tissue with restriction of range of motion is observed.

[Metacarpophalangeal joint replacement]. / Der Gelenkersatz der Fingergrundgelenke.

BACKGROUND: Arthroplasty of metacarpophalangeal (MCP) joints is crucial for patients with rheumatoid arthritis. Motion preserving therapies are mandatory for this joint, since loss of function of the MCP joint is detrimental. Many protheses or spacers have been introduced over the last 80 years, but most of them have been dismissed due to major complications. CURRENT PROCEDURES: Since the 1960s the Swanson spacer has been established as the reference standard for motion preserving procedures of the finger MCP joints. High fracture rates of the spacer do not seem to limit function and patient satisfaction after all. Current long-term studies show at least promising results for pyrolytic carbon protheses with respect to range of motion, survival, and revision rates in comparison to the Swanson spacer.

[Anatomy of the trapeziometacarpal joint in the context of arthroplasty]. / Anatomie des Daumensattelgelenks unter Berücksichtigung der Endoprothetik.

The thumb has a crucial role in the hand due to its position with regard to the fingers. The CMC-1 joint enables an extraordinary range of motion, since its geometry allows for opposition. The former joint may often succumb to osteoarthritis because a great range of motion in combination with large forces, small contact areas, and thorough usage are always present. Joint replacement is challenged by the great range of motion based on the necessary joint stability and the demand for sufficient pain reduction. This review highlights the anatomy of the CMC-1 joint with regard to joint preplacement solutions.

[Scaphoid pseudarthrosis : Complex reconstruction using vascularized bone grafts]. / Skaphoidpseudarthrose : Komplexe Rekonstruktionen mithilfe vaskularisierter Knochentransplantate.

The most important goals of scaphoid reconstruction in pseudarthrosis are correction of the humpback deformity, the realignment of the proximal carpal row and the bony union of the scaphoid. Therefore, in most cases bone grafting is required. To increase the healing rate and to improve vascularization, several kinds of vascularized bone grafts have been developed. Pedicled grafts are preferably harvested from the dorsal or palmar side of the distal radius with fusion rates between 27% and 100%. Free microvascular grafts can be obtained from the iliac crest and the medial or lateral femoral condyle with fusion rates between 60% and 100%. For their application microsurgical equipment and skills are required. Up to now osteochondral grafts from the femoral condyle offer the only chance for joint surface replacement by transferring part of the surface of the femoropatellar joint. The use of vascularized grafts is still a matter of controversy, since their superiority is still unproven compared to nonvascularized grafts, which also achieved 100% fusion rates in several series. They are indicated in secondary procedures after failed reconstruction and nonunion with small avascular proximal pole fragments. Since no evidence-based guidelines exist, this article provides an experience-based treatment algorithm for scaphoid nonunion with special consideration to vascularized bone grafts.

[Anatomy and pathobiomechanics of the scaphoid]. / Anatomie und Pathobiomechanik des Skaphoids.

Among the carpal bones the scaphoid (Os scaphoideum) is the most important. The most frequent fracture of the carpus is a fracture of the scaphoid bone. The frequently occurring absence of healing of these fractures as well as unhealed ruptures of the ligament complex between the scaphoid and lunate, lead to the most severe biomechanical and thus the most severe clinical changes of the wrist. The detailed anatomy of the scaphoid, blood flow, ligament attachments, injury mechanisms and pathobiomechanics are described and illustrated.

[Anatomy and biomechanics of the distal radioulnar joint]. / Anatomie und Biomechanik des distalen Radioulnargelenks.

BACKGROUND: The functionality of the upper extremity is decisively based on rotation of the forearm. The rotation depends on the extent of motion of the distal radioulnar joint. Rotation enables complete and focused usability of the hand in order to cope with daily activities. The configuration of the distal radioulnar joint has developed over millions of years of evolution. ANATOMIC CONDITIONS: The triangular fibrocartilage complex is the crucial stabiliser of the latter joint since osseous structures are limited. The palmar and dorsal radioulnar ligaments belong to this complex. The superficial and deep parts of the latter ligaments insert both centrically in accordance to the axis of rotation and eccentrically. This arrangement guarantees stability of the joint throughout pronosupination. The interosseous membrane is a further relevant stabiliser that guarantees sufficient load transmission from radius to ulna. The distal oblique bundle of the interosseous membrane is outstanding in this context. The pronator quadratus muscle is the relevant dynamic stabiliser of the distal radioulnar joint. Contraction of the muscle prevents diastasis of the joint. The deep head of the muscle is always activated during pronosupination.

[Diagnosis and treatment of degenerative disc lesions of the wrist]. / Diagnostik und Therapie der degenerativen Diskusläsion.

BACKGROUND: The triangular fibrocartilage complex (TFCC) widens the radiocarpal joint and takes part in load transmission from the carpus to the forearm. It is thereby prone to degenerative changes. The painful situation that can accompany degeneration is called ulnar impaction. DIAGNOSIS: Clinical examination helps differentiate between various causes of ulnar-sided wrist pain. Standard X­rays are needed to determine ulnar variance and stress radiographs can depict narrowing of the ulnocarpal joint space under load. MRI may prove degeneration of the TFCC itself or may indirectly confirm ulnar impaction in the presence of bone marrow edema in the ulnar head or at the proximal ulnar aspect of the lunate. TREATMENT: If conservative treatment fails to alleviate symptoms, arthroscopy may be indicated. On the one hand, this completes the diagnostic cascade, and, on the other hand, allows decompression of the ulnocarpal joint space by resection of the TFCC with partial resection of the ulnar head (wafer resection). In the case of ongoing pain, ulnar shortening sufficiently alleviates ulnar-sided wrist pain. Thereby, modern standardized operation techniques are safe enough to ensure bone healing at the osteotomy site. The aim of alleviating ulnar-sided wrist pain is mostly achieved if the correct treatment option is chosen.

[Defect coverage of fingers and thumb : Indications and treatment]. / Defektdeckung an den Fingern und am Daumen : Indikation und Therapie.

Due to the exposure of the hands in the daily routine, defect wounds of the hand are common. The injury severity varies and ranges from small fingertip defects to large soft tissue lesions with exposed tendons, nerves and vessels. The complete extent of the soft tissue defect is often only recognizable after meticulous debridement. A considerable variety of techniques for defect coverage are available to the surgeon but the actual challenge is to select the most appropriate procedure which will result in the smallest possible residual defect. This review article presents the diagnostic approaches to soft tissue defects of the hand and current treatment options.