A method for experimental warming of developing tree seeds with a common garden demonstration of seedling responses.

BACKGROUND: Forest dieback driven by rapid climate warming threatens ecosystems worldwide. The health of forested ecosystems depends on how tree species respond to warming during all life history stages. While it is known that seed development is temperature-sensitive, little is known about possible effects of climate warming on seed development and subsequent seedling performance. Exposure of seeds to high air temperatures may influence subsequent seedling performance negatively, though conversely, warming during seed development may aid acclimation of seedlings to subsequent thermal stress. Technical challenges associated with in-situ warming of developing tree seeds limit understanding of how tree species may respond to seed development in a warmer climate. RESULTS: We developed and validated a simple method for passively warming seeds as they develop in tree canopies to enable controlled study of climate warming on seedling performance. We quantified thermal effects of the cone-warming method across individual pine trees and stands by measuring the air temperature surrounding seed cones using thermal loggers and the temperature of seed cone tissue using thermocouples. We then investigated seedling phenotypes in relation to the warming method through a common garden study. We assessed seedling morphology, physiology, and mycorrhizal nodulation in response to experimental cone-warming in 20 seed-source-tree canopies on the San Francisco Peaks in northern Arizona, USA. The warming method increased air temperature surrounding developing seed cones by 2.1 °C, a plausible increase in mean air temperature by 2050 under current climate projections. Notable effect sizes of cone-warming were detected for seedling root length, shoot length, and diameter at root collar using Cohen's Local f2. Root length was affected most by cone-warming, but effect sizes of cone-warming on root length and diameter at root collar became negligible after the first year of growth. Cone-warming had small but significant effects on mycorrhizal fungal richness and seedling multispectral near-infrared indices indicative of plant health. CONCLUSIONS: The method was shown to reliably elevate the temperature surrounding seed cones and thereby facilitate experimental in-situ climate warming research on forest trees. The method was furthermore shown to influence plant traits that may affect seedling performance under climate warming.

Early failure of a mobile-bearing unicompartmental knee replacement.

Concerned by a perceived high revision rate, we retrospectively reviewed the survivorship of a series of 43 cemented, medial, mobile-bearing Preservation unicompartmental knee replacements implanted during a 2-year period at a single institution. The initial post-operative AP and lateral radiographs were independently assessed to test the hypothesis that suboptimal implantation of the prosthesis was responsible for early failure. An X-ray scoring system based on the criteria for assessing the Oxford mobile-bearing unicompartmental knee replacement was devised. The components of this score included assessment of prosthesis alignment, sizing and cementation. Nine (21%) LCS Preservation mobile-bearings prostheses had required revision at a mean of 22 months post-implantation. The commonest causes for failure were pain (44%) and tibial component loosening (33%). Analysis of post-operative radiographs showed no difference (n.s.) between the compound error scores for the revised and the surviving prostheses. No particular surgical error was identifiable leading to subsequent need for revision. The high failure rates shown in this study have led us to cease using this implant. The clinical relevance of this study is that the captive running track of the LCS mobile-bearing prosthesis may over constrain the meniscal component leading to early failure.

Hip resurfacing with preservation of femoral head blood supply.

Hip resurfacing arthroplasty can be performed through anterolateral or posterior approaches. Concerns have been raised about the posterior approach due to the perceived loss ofthe crucial posterolateral blood supply to the femoral head and neck. The trochanteric 'flip' osteotomy method, pioneered by Ganz, with a blood supply conserving capsulotomy was therefore developed to allow this operation to be performed through an anterolateral incision. The repair of the trochanteric osteotomy has, however, shown an incidence of non-union and does not permit full weight bearing in the immediate post-operative period. Through our current practice we have developed a technique for hip resurfacing through an anterolateral modified Hardinge approach that does not require trochanteric osteotomy, preserves the femoral neck blood supply and allows full weight bearing in the immediate post operative-period.

Nanoindentation behavior of clay/poly(ethylene oxide) nanocomposites.

Depth-sensing nanoindentation of clay/poly(ethylene oxide) nanocomposites has shown significant differences in the mechanical behavior of the composites, depending on method of synthesis and clay content. In general, the clay/polymer nanocomposite approach can dramatically improve the hardness, stiffness, and creep resistance of the polymer. However, these improvements are dependent on the clay content. At lower concentrations, the improvements are not significant, because of an adverse effect on creep behavior.

Anterior knee pain syndrome. A review of current concepts and controversies.

Anterior knee pain syndrome is a common condition in the military population. Current management is moving away from surgery as the most effective treatment, towards prolonged specific physiotherapy to recondition the extensor mechanism, especially the Vastus Medialis Obliquus (VMO) component of the quadriceps.

External fixation of children's fractures: use of the Orthofix Dynamic Axial Fixator.

We have reviewed 48 children's diaphyseal fractures of the femur and tibia managed with the Orthofix Dynamic Axial Fixator between 1987 and 1994. The indications for external fixation included open fractures, multiple injuries, failed conservative management, and unstable fracture configurations. All fractures healed without further surgical intervention, and the incidence of serious complications was low. Although pin track sepsis was common, compromise of the fixation as a result of this occurred in only one case. We conclude that use of the Orthofix for children's fractures is a safe and effective management option.

Modern trends for external fixation of fractures in children: a critical review.

There is considerable controversy about the use of external fixation to manage children's fractures. The indications for external fixation are examined in the light of the available evidence in the literature. A general overview of surgical considerations, including the type of fixator, pin placement, and duration of treatment, is given with an assessment of possible complications. External fixation offers a safe and effective management option and may perhaps be the subject of randomized controlled trials in the future.

Surgical management of fractures of the acetabulum: the Sheffield experience 1976-1994.

Of 56 acetabular fractures treated in Sheffield between 1976 and 1994, 43 fractures in 40 patients underwent open reduction and internal fixation. This paper reviews the surgically managed fractures with emphasis on the quality of operative reduction and outcome, in particular the development of degenerative osteoarthritis leading to total hip replacement. A good clinical result following operative management was seen to correlate closely with a near perfect reduction; in contrast, all cases with a poor reduction underwent joint replacement in the follow-up period. The relatively few cases managed at a major referral centre in this series suggest that either the incidence of acetabular fracture is low in the area or that only a proportion of cases are referred from the surrounding district general hospitals.

Management of gunshot fractures of the extremities.

Extremity fractures resulting from gunshot trauma are frequently encountered by civilian as well as military surgeons. This paper highlights the relevant ballistic principles necessary to allow a sound appreciation of the degree of energy transfer in typical gunshot injuries that involve bone, and provides guidelines for the management of both low- and high-energy transfer wounds.

Pattern and mechanism of traumatic amputation by explosive blast.

The mechanism of traumatic amputation of limbs by explosion is presented. A survey of blast casualties from Northern Ireland revealed that amputations through joints were very uncommon--the principal site was through the shaft of the long bones. Computer modelling of a bone exposed to blast forces reinforced the hypothesis developed from the casualty survey, that the primary mechanism of the bone injury was the direct coupling of the blast wave into the tissues. The fracture occurs from the resulting axial stresses in the bone, prior to limb flailing from the gas flow over the limb. The gas flow completes the amputation. Field trials employing a goat hind limb model have confirmed the hypothesis. Having identified the mechanism, concepts to develop protective clothing may now be proposed.

Pattern of injury in those dying from traumatic amputation caused by bomb blast.

Traumatic amputation of limbs caused by bomb blast carries a high risk of mortality. This paper describes 73 amputations in 34 deaths from bomb blast in Northern Ireland. The principal aim was to determine the sites of traumatic amputation to provide a biophysical basis for the development of protective measures. Few amputations were through joints; nearly all were through the bone shafts. The most common site in the tibia was the upper third. The distribution of femoral sites resulting from car bombs differed from that characterizing other types of explosion. For car bombs the principal site of amputation was the upper third; for other types of device it was the lower third. It is concluded that flailing is not a notable contributor to limb avulsion. The pattern of amputation is consistent with direct local pressure loads leading to bone fracture; the amputation itself is a secondary event arising from the flow of combustion products.

Traumatic amputation by explosive blast: pattern of injury in survivors.

Explosive blast causes a pattern of injury including primary blast lung, secondary fragment injury and traumatic amputation of limbs. Major traumatic amputation is rare in survivors of bomb blast but common in those who die. The mechanism of such injury has not been previously determined, but must be established if protective measures are to be developed for members of the armed forces. The nature of 41 traumatic amputations in 29 servicemen who survived to reach medical care after blast injury was investigated to determine the anatomical level of amputation and the pattern of soft tissue damage. Joints were an infrequent site of amputation and the tibial tuberosity was a particularly frequent site of lower-limb severance. Comparison of the pattern of injury was made with that seen in ejecting fast-jet pilots, who frequently suffer major flailing injury; there appears to be a substantially different injury distribution. The accepted mechanism of traumatic amputation, avulsion by the dynamic overpressure, is challenged; it is suggested that the shockwave resulting from an explosion is capable of causing at least bone disruption in a limb.

Blast: injury patterns and their recording.

Exposure to explosive blast results in a variety of injuries dependent on the degree of blast loading, the relative contribution of secondary fragments and the interaction of a casualty with the surroundings. The internal and more covert injuries peculiar to blast are easily overlooked in the haste to treat the obvious external wounds which are usually much more dramatic. This paper describes the pathogenesis of blast injury and suggests how best it may be recorded.

Tattoo removal by surgery in a bloodless field.

Tattoo removal from the forearm often requires excision and split skin grafting. The authors propose the use of a bloodless field to facilitate accurate dermal peeling, to ensure complete removal of the pigment, and to reduce operative time.

Orchidopexy in a military hospital.

A retrospective analysis of 53 consecutive cases of orchidopexy performed at the British Military Hospital Munster between 1984 and 1988 showed that the average of referral for orchidopexy was 4 years 7 months and that the average age at surgery for mal/un-descended testes was 5 years exactly. Sixty-four percent of all orchidopexies were carried out before the age of 5 years; 8 percent were carried out by the age of 2 years.