Factors affecting impingement and dislocation after total hip arthroplasty - Computer simulation analysis

BACKGROUND

Studies on the causes and factors affecting dislocation after total hip arthroplasty have revealed conflicting results. The purpose of this study was to evaluate the factors affecting impingement and dislocation after total hip arthroplasty, using a 3-dimensional dynamic motion analysis.

METHODS

The CT data of 53 patients (53 hips: anterior dislocation; 11 cases, and posterior dislocation; 42 cases) who experienced hip dislocation after total hip arthroplasty with posterior approach, and 120 control patients (120 hips) without dislocation were analyzed. Parameters related to implant alignment, offset and leg length were evaluated. The impingement type was also analyzed using a software.

FINDINGS

Considering implant settings affecting dislocation, patients at risk for posterior dislocation had decreased stem anteversion, combined anteversion, femoral offset, and leg length. Nevertheless, patients at risk for anterior dislocation had only lower leg length, and these patients may also be at risk for a higher incidence of recurrent dislocation. Bony impingement occurred in almost half of the cases with posterior dislocation, while implant impingement was associated with anterior dislocation. Importantly, anterior dislocation was not as common as posterior dislocation even in cases with occurrence of posterior impingement.

INTERPRETATION

Bony impingement substantially affects dislocation even in the situation where the implant position and alignment are determined by the so-called "safe zone", especially on the anterior side, while implant impingement affects anterior dislocation. The restoration of anterior offset (i.e., prescribed by the stem anteversion and femoral offset) and combined anteversion is critical for avoidance of posterior dislocation after total hip arthroplasty.

Positronium formation at 4H SiC(0001) surfaces

Positronium formation at 4H SiC(0001) surfaces were investigated upon the removal of natural oxide layers by hydrofluoric acid etching and heat treatment at 1000 K in ultra-high vacuum. Two types of positronium were observed in the positronium time-of-flight (PsTOF) measurements irrespective of conduction type and surface polarity. One type formed the major part of the PsTOF spectrum with a maximum energy of 4.7 ± 0.3 eV. This energy exceeded the theoretical value calculated with valence electrons. The PsTOF spectrum shape was different from those of metal surfaces, suggesting that the surface state electrons or conduction electrons need to be considered as the positronium source. Another positronium appeared at 1000 K in the tail of the PsTOF spectrum with a maximum energy of 0.2-0.5 eV. This thermally-assisted athermal positronium may be formed via the surface state positrons and electrons.

Coupled afterslip and transient mantle flow after the 2011 Tohoku earthquake

Modeling of postseismic deformation following great earthquakes has revealed the viscous structure of the mantle and the frictional properties of the fault interface. However, for giant megathrust events, viscoelastic flow and afterslip mechanically interplay with each other during the postseismic period. We explore the role of afterslip and viscoelastic relaxation and their interaction in the aftermath of the 2011 M _w (moment magnitude) 9.0 Tohoku earthquake based on a detailed model analysis of the postseismic deformation with laterally varying, experimentally constrained, rock rheology. Mechanical coupling between viscoelastic relaxation and afterslip notably modifies both the afterslip distribution and surface deformation. Thus, we highlight the importance of addressing mechanical coupling for long-term studies of postseismic relaxation, especially in the context of the geodynamics of the Japan trench across the seismic cycle.

Analysis of the pattern of suprahyoid muscle activity during pharyngeal swallowing of foods by healthy young subjects

We previously developed the T_P technique to discriminate between the activity patterns of skeletal muscles. In this study we aim to identify the T_P value(s) that can be used to sensitively evaluate the activity patterns of the suprahyoid (SH) muscles during swallowing. We also analyse the effect of food textural properties on the activity patterns of the SH muscle during oral and pharyngeal swallowing. Three test foods consisting of 3%, 6% and 9% of a thickening agent, Mousse-up (MU) were prepared. Their textural properties differed significantly. Swallowing of 9% MU involved a significantly longer average duration than 3% MU. The average T₅₀ value for 6% MU was significantly larger than that for 3% MU. However, the average T₂0 and T₈₀ values of the test foods did not differ. Thus, the T₅₀ value is particularly suitable for evaluating SH muscle swallowing patterns. Moreover, test foods that vary in their textural properties elicit different durations and patterns of SH muscle activity.

Serum interleukin 8 levels correlate with synovial fluid levels in patients with aseptic loosening of hip prosthesis

Levels of inflammatory cytokines (tumor necrosis factor alpha, interleukin [IL] 6, and IL-8) in serum from patients with osteolysis on radiographs after hip arthroplasty [osteolysis(+), n = 28], patients without osteolysis after hip arthroplasty [osteolysis(-), n = 24], and nonoperated healthy subjects [controls, n = 20] were determined. In addition, cytokine levels in synovial fluid from patients undergoing revision total hip arthroplasty (n = 14) for loosening were measured and compared with each other and with the area of osteolysis on radiographs. Serum IL-6 and IL-8 levels were significantly higher in the osteolysis(+) group than in the osteolysis(-) or the control groups. Furthermore, a significant correlation was found between the serum and synovial fluid IL-8 levels and between synovial fluid IL-8 levels and the area of osteolysis in patients undergoing revision total hip arthroplasty. Therefore, serum IL-8 levels could be a useful periprosthetic osteolysis marker.

Rotational acetabular osteotomy for hip dysplasia: 61 hips followed for 8-15 years

We operated on 54 patients (61 joints) with rotational acetabular osteotomy (RAO) due to dysplasia of the hip with pre- or early-stage osteoarthritis/arthrosis. The mean follow-up was 11 (8-15) years. The Merle d'Aubigné median score increased from 14 to 15. In 2 patients (2 joints), the score decreased from 15 to 13. Progression of arthrosis was seen in 6 joints on the radiographs at follow-up. Kaplan-Meier survivorship analysis predicted an 89% (95% confidence interval 80-99) prevention of worsening of arthrosis at 10 years. Postoperative joint congruency was a risk factor for progression of arthrosis.

Rotational acetabular osteotomy for advanced osteoarthrosis secondary to dysplasia of the hip. Results at 6-11 years postoperatively

Clinical and radiological studies were done on the results of rotational acetabular osteotomy for advanced osteoarthrosis secondary to dysplasia of 29 adult hips followed up for 6 to 11 years postoperatively (mean 8 years). Clinical evaluation by Merle d'Aubigne and Postel's system showed improvement from a preoperative mean of 12.8 to a follow-up mean of 14.8, with aggravation being observed in 8 joints. Radiologically, this procedure produced adequated improvement regarding femoral head coverage, but improvement in joint congruency could not necessarily be obtained due to joint deformity and progression of arthrosis, with aggravation of joint congruency being observed in 6 joints. The most important factor influencing the postoperative results of this procedure was postoperative joint congruency. If the postoperative joint congruency is satisfactory, with the joint congruent index being more than 6.0, progression of arthrosis can be prevented in the long term by this procedure, even in advanced cases.

[Studies on the transfer of cefotaxime into bone marrow blood]

Cefotaxime (CTX) was administered in a dose of 2 g to 20 adult patients prior to orthopaedic surgery. Samples of the bone marrow blood and the forearm venous blood were collected at 30, 60, 90 and 120 minutes after the CTX administration, and the concentration of the drug in each sample was determined. The results are described below. The mean concentration of CTX transferred into the bone marrow blood was 59.7, 28.9, 14.7 and 7.2 micrograms/ml at 30, 60, 90 and 120 minutes after the CTX administration, respectively. The mean concentration of CTX in the venous blood was 84.0, 39.1, 19.0 and 13.8 micrograms/ml at 30, 60, 90 and 120 minutes after the CTX administration, respectively. The mean ratio of the CTX concentration in the bone marrow blood to that in the venous blood was 73.9%, 71.0%, 75.1% and 51.6% at 30, 60, 90, 120 minutes after the CTX administration. From the above results, CTX is considered to be a useful antibiotic if it is administered prior to orthopaedic surgery to prevent infections.

Primary hypothyroidism associated with pituitary enlargement, slipped capital femoral epiphysis and cystic ovaries

A case of primary hypothyroidism with pituitary enlargement, slipped capital femoral epiphysis and cystic ovaries is reported. The pituitary abnormality and cystic ovaries disappeared dramatically after thyroid hormone therapy. Hip pinning was performed. The recognition of these associations may eliminate unnecessary surgery and lead to the choice of hormone replacement therapy.