Influence of the bone block position on the tunnel enlargement in ACL reconstruction

Tunnel enlargement can appear after anterior cruciate ligament reconstruction. We investigated the influence of the bone block position of a patellar tendon autograft on the tunnel enlargement in the femur and in the tibia from two aspects. On the one hand, we examined the influence of the tunnel position in respect to the ap-diameter. On the other hand, we examined the influence of the bone block depth in respect to the joint line. In a crossover study over three years, 103 knees with primary ACL reconstruction were included. The incidence of tunnel enlargement measured on X-rays after one year was 52% (n=103) in the femur and 81% (n=103) in the tibia. The average diameter of enlargement was 1.4 mm (14%) in the femur and 2.7 mm (27%) in the tibia. No correlation between the tunnel position and the tunnel enlargement in the sagital plane could be found. However, there is a significant positive correlation between the size of tunnel enlargement and the bone block depth in the femur and in the tibia. There is an average tunnel enlargement of about 0.6 mm (6%) per 10 mm deeper bone plug depth. The relative excess length of the patella tendon favors the development of tunnel enlargement. The effect of the bone block depth on the tunnel enlargement is equal in the femur and the tibia

Acetabular reinforcement ring in primary total hip arthroplasty: a minimum 10-year follow-up

Introduction: We report the results of a titanium acetabular reinforcement ring with a hook (ARRH) in primary total hip arthroplasty (THA), which was introduced in 1987 and continues to be used routinely in our center. The favorable results of this device in arthroplasty for developmental dysplasia and difficult revisions motivated its use in primary THA. With this implant only minimal acetabular reaming is necessary, anatomic positioning is achieved by placing the hook around the teardrop and a homogenous base for cementing the polyethylene cup is provided. Materials and methods: Between April 1987 and December 1991, 241 THAs with insertion of an ARRH were performed in 178 unselected, consecutive patients (average age 58years; range 30-84years) with a secondary osteoarthrosis in 41% of the cases. Results: At the time of the latest follow-up, 33 patients (39 hips) had died and 17 cases had been lost to follow-up. The median follow-up was 122months with a minimum of 10years. Eight hips had been revised, leaving 177 hips in 120 living patients without revision. Six cups were revised because of aseptic loosening. Two hips were revised for sepsis. The mean Merle d'Aubigné score for the remaining hips was 16 (range 7-18) at the latest follow-up. For aseptic loosening, the probability of survival of the cup was 0.97 (95% confidence interval, 0.94-0.99). However, analysis of radiographs implied loosening in seven other cups without clinical symptoms. Conclusions: The results of primary THA using an acetabular reinforcement ring parallel the excellent results of these implants often observed in difficult primary and revision arthroplasty at a minimum of 10years. Survivorship is comparable to modern cementless implants. Medial migration that occurs with loosening of the acetabular component seems to be prevented with this implant. Radiographic loosening signs can exist without clinical symptom

Observation of Parametric Instability in Advanced LIGO

Parametric instabilities have long been studied as a potentially limiting effect in high-power interferometric gravitational wave detectors. Until now, however, these instabilities have never been observed in a kilometer-scale interferometer. In this work we describe the first observation of parametric instability in an Advanced LIGO detector, and the means by which it has been removed as a barrier to progress

Deformation-related volcanism in the Pacific Ocean linked to the Hawaiian-Emperor bend

Ocean islands, seamounts and volcanic ridges are thought to form above mantle plumes. Yet, this mechanism cannot explain many volcanic features on the Pacific Ocean floor and some might instead be caused by cracks in the oceanic crust linked to the reorganization of plate motions. A distinctive bend in the Hawaiian–Emperor volcanic chain has been linked to changes in the direction of motion of the Pacific Plate, movement of the Hawaiian plume, or a combination of both. However, these links are uncertain because there is no independent record that precisely dates tectonic events that affected the Pacific Plate. Here we analyse the geochemical characteristics of lava samples collected from the Musicians Ridges, lines of volcanic seamounts formed close to the Hawaiian–Emperor bend. We find that the geochemical signature of these lavas is unlike typical ocean island basalts and instead resembles mid-ocean ridge basalts. We infer that the seamounts are unrelated to mantle plume activity and instead formed in an extensional setting, due to deformation of the Pacific Plate. 40Ar/39Ar dating reveals that the Musicians Ridges formed during two time windows that bracket the time of formation of the Hawaiian–Emperor bend, 53–52 and 48–47 million years ago. We conclude that the Hawaiian–Emperor bend was formed by plate–mantle reorganization, potentially triggered by a series of subduction events at the Pacific Plate margins

Cosmic Explorer: The U.S. Contribution to Gravitational-Wave Astronomy beyond LIGO

This white paper describes the research and development needed over the next decade to realize "Cosmic Explorer," the U.S. node of a future third-generation detector network that will be capable of observing and characterizing compact gravitational-wave sources to cosmological redshifts