Computer assisted measurement of cup placement in total hip replacement

The introduction of image guided systems in total hip replacement surgery provides the ability to plan precisely the alignment of the acetabular cup before surgery, and to perform the surgery according to the preoperative plan. Preoperative planners (interactive computer programs for surgical planning) based on three-dimensional medical images allow planning of optimal placement of implant components based on simulated implant performance. Exact measurement of the cup position during surgery allows precise placement of the cup and accurate measurement of the final position of the cup relative to the pelvis. This measurement is used to evaluate the radiographic techniques for postoperative measurement of cup alignment. Malposition of the acetabular component increases the occurrence of impingement, reduces the safe range of motion, and increases the risk of dislocation and wear. Dislocation of the implant after total hip replacement remains a significant clinical problem. Not fully understanding the interaction between pelvic orientation and final acetabular cup alignment may be one of the main contributing factors in the continued significant incidence of dislocations after total hip replacement. In this study an attempt was made to link the preoperative planning, intraoperative placement, and postoperative measurement of cup placement in total hip replacement using computer assisted techniques.     

Bilateral total hip arthroplasty comparing hydroxyapatite coating to porous-coated fixation

Intraventricular together with atrial-axis and nodoventricular discontinuity, in which various parts of the conduction system are replaced by fibrous or fatty tissue, constitute the three major pathological categories of isolated congenitally complete heart block. Intraventricular discontinuity is distinctly rare, with only two previous cases reported in the literature, one of which was associated with a familial history of heart block. The cardiac conduction systems of two cases of isolated congenitally complete heart block were serially sectioned and analyzed histopathologically. The findings were correlated with the clinical features, in particular, the family histories and maternal serum anti-Ro antibodies. Both cases, a 9-day-old neonate and an 8-year-old schoolgirl, showed a combination of nodoventricular and intraventricular discontinuity, with absence of the atrioventricular penetrating bundle, the entire right, and the proximal portion of the left bundle branch. The branching bundle was absent in the first case and replaced by fatty tissue in the second. In contrast to the commoner atrial-axis discontinuity in which the atrioventricular node itself is usually replaced by fibrous or fatty tissue with variable involvement distally, the sinus node, and in particular, the atrioventricular node were normal in both of our cases. There was no family history in either case, whereas tests for the maternal serum anti-Ro antibody were positive in the first but negative in the second case. Intraventricular discontinuity as a cause of isolated congenitally complete heart block is very rare. In our cases, it co-existed with nodoventricular discontinuity. It can be sporadic, familial, or associated with positive maternal serum anti-Ro antibodies.     

Clinical and radiological assessment of proximally coated stems in growth in total hip replacement]

Although cocaine is a powerful reinforcer, it has been reported to produce anxiety in humans and anxiogenic-like behavior in animals. The goal of this study was three-fold: (1) to determine the doses of cocaine that induce anxiogenic-like behavior in the elevated plus-maze in rats, (2) to determine if cocaine-associated contextual cues are capable of eliciting anxiogenic-like behavior in the absence of the drug, and (3) to identify possible mechanisms through which cocaine-associated cues affect behavior in the elevated plus-maze. Measurement of the amount of time that the animals spend exploring the open arms of the maze provides a sensitive index of anxiogenic-like behavior in rats. In experiment 1, rats were injected with 10 mg/kg, 20 mg/kg, or 30 mg/kg cocaine HCl or saline for 6 days. On day 6, the rats were tested in the elevated plus-maze 25 min after injection with cocaine or saline. The animals chronically treated with the three doses of cocaine exhibited a dose-dependent increase in anxiogenic-like behavior in the elevated plus-maze, compared to the saline-treated group. In experiment 2, cocaine-induced (30 mg/kg) conditioning was achieved using a simple contextual design. On the final day of the experiment (day 6), after 5 days of conditioning, the rats were exposed for 25 min to the cocaine-associated contextual cues, then placed in the elevated plus-maze. Animals that had been exposed to cocaine-associated contextual cues prior to being placed in the elevated plus-maze exhibited a significant increase in anxiogenic-like behavior compared to the control groups. However, pretreatment of the rats with the CRF antagonist, alpha-helical CRF9-41 (1 microg, i.c.v.), on the test day, prior to exposure to cocaine-associated contextual cues, attenuated the subsequent anxiogenic-like behavioral response in the elevated plus-maze (experiment 3). The results suggest that contextual cues associated with repeated treatment with 30 mg/kg cocaine are capable of eliciting anxiogenic-like behavior in the absence of the drug and that CRF mediates the expression of anxiogenic-like behaviors in the elevated plus-maze following exposure to cocaine-associated cues. The conditioned anxiogenic action elicited by cocaine-associated cues may have relevance for understanding the complex addictive nature of this drug and some of the clinical phenomena related to its use.     

Failure analysis and mechanical testing of Ti–6Al–4V modular revision hip stems

Analysis of five modular titanium hip revision stems that failed in vivo was undertaken. The average time to failure was 4.0?±?0.6 years with a range from 3.0 years to 4.9 years. The average age of the patients was 68.4?±?7.6 years with a range of 61–81 years and the average mass was 88.0?±?10.3?kg with a range of 71.7–98.9?kg. All five stems failed through fatigue just inside the taper junction between the stem and body. Microscopic analysis failed to detect any evidence of significant corrosion at the junction. Metallurgical analysis found that the material properties for the femoral stems were in agreement with typical values for Ti–6Al–4V. Mechanical testing revealed that fatigue failure would occur only with loads above 5000?N. This is far above any repetitive load that any of these stems would have undergone in vivo. Finite element analysis simulating a ‘worst case’ scenario demonstrated that a maximum tensile stress of 350?MPa would occur near the location of fracture seen on the retrieved stems. This stress is well below the fatigue limit of the titanium alloy. The exact location of the fracture in the mechanically tested components was affected by the assembly technique. It is suggested that the assembly technique could add considerable residual stress to the femoral stems causing them to fail well below the theoretical fatigue limit. Consideration for further investigation includes residual stresses within the implant secondary to assembly technique, and other unexplored factors that may lead to early fatigue failure.     

Psychological testing in educational classification and placement.

Discusses 2 main issues—overrepresentation of minorities in all types of special education classes and bias in IQ tests that allegedly underlies such placements. The author identifies implicit issues in the IQ controversy, analyzes the classification system and its effects, and gives an alternative interpretation of classification and placement data. It is concluded that it is not tests themselves but test use that leads to discriminatory placement. Reforms in assessment procedures and classification systems are suggested. (28 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heterotopic ossification in total hip arthroplasty. The influence of the approach

From 1980 to 1990, 64 cases of Lumbar canal Stenosis have been recorded and operated on at the neurosurgical clinic. The male sex is prevailing and the breakdown by age groups showed a preponderance of the age sections between 31 and 45 and 46 and 60 years. The sciatic pain was the most frequent starting symptom. As far as the physical signs are concerned, the areflexy of the tendon predominates. The saccoradiculography has established the diagnosis in most of the cases. The laminectomy associated with another technique has permitted to obtain the best result of the treatment. With the advent of the T scan, a better estimation of the lumbar canal will be possible, so as to replace the laminectomy by a more adaptable technique: the remeasurement of the lumbar canal.     

The rationale for cementless total hip replacement

Current cementing techniques of distal plugging, pulsatile water cleaning of the canal, and retrograde filling with PMMA in a low-viscous state prepared using porosity reduction techniques and then pressurized have been shown to give excellent results at 10 or more years after operation. However, physical and aging characteristics of PMMA do not guarantee that those results will hold up in the 20- to 30-year time frame. Fifteen-year experience with bony ingrowth systems indicate the development of a durable interface without PMMA, although the interface does appear more vulnerable to attack by the biologic reaction to HMWPE debris. Bone remodeling appears more favorable around proximally fixed bone ingrowth prostheses than around distally fixed prostheses. Softening of the physical characteristics of the stem tip may reduce the incidence of thigh pain. Patients with high activity potential and a life expectancy of greater than 25 years should be strongly considered for a proximally fixed bone ingrowth or ongrowth prosthesis.     

The effects of testing accommodations on students' performances and reactions to testing.

This study examined the effects of testing accommodations on students' test performances and reactions to the use of testing accommodations. Participants (N = 170) were fourth- and eighth-grade students, with and without disabilities. All students were administered, with and without accommodations, equivalent forms of widely used math and reading tests. Students completed a questionnaire to summarize their reactions to the use of accommodations. The findings indicated testing accommodations overall had a positive impact on students' individual reading and math scores. Furthermore, testing accommodations had a differential positive effect on reading scores for students with disabilities compared to students without disabilities. The relationship between students' perceptions of testing accommodations and the effects of testing accommodations on their test performances was not significant, although most students had positive perceptions of testing accommodations. Students perceived the provision of accommodations as fair for students without disabilities and more fair for students with disabilities. These findings are interpreted within a validity framework and contribute to a greater understanding of testing accommodations by integrating information concerning effects on scores and consequential effects on test-takers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The value of preoperative planning for total hip arthroplasty

To analyse the value and accuracy of preoperative planning for total hip replacement (THR) we digitised electronically and compared the hand-sketched preoperative plans with the pre- and postoperative radiographs of 100 consecutive primary THRs. The correct type of prosthesis was planned in 98%; the agreement between planned and actually used components was 92% on the femoral side and 90% on the acetabular side. The mean (+/- SD) absolute difference between the planned and actual position of the centre of rotation of the hip was 2.5 +/- 1.1 mm vertically and 4.4 +/- 2.1 mm horizontally. On average, the inclination of the acetabular component differed by 7 +/- 2 degrees and anteversion by 9 +/- 3 degrees from the preoperative plans. The mean postoperative leg-length difference was 0.3 +/- 0.1 cm clinically and 0.2 +/- 0.1 cm radiologically. More than 80% of intraoperative difficulties were anticipated. Preoperative planning is of significant value for the successful performance of THR.     

Osteopetrosis and total hip arthroplasty. Report of two cases

In a 47-year-old male cadaver the splenic artery traveled partially through the substance of the pancreas. Additionally, the pancreas was apparently large and had an unusual shape; the neck of the organ could not be differentiated; the uncinate processus was absent; two pancreatic ducts were present. The probable reason for this combined anomaly was abnormal fusion of the ventral and dorsal pancreatic buds due to different levels of origin.     

The Stanmore total hip arthroplasty. A 15- to 20-year follow-up study

An ongoing study was made of 804 primary Stanmore total hip prostheses implanted in 839 patients between 1973 and 1991. The earliest surviving implants were brought back for radiologic and clinical review in 1995 at an average of 17 years after surgery. The remainder of the patients still living were sent a questionnaire to assess their current status. Survivorship was 95% at 10 years, 85% at 15 years, and 73% at 20 years. The average Merle d'Aubigné-Postel score was excellent up until 14 years. Patient satisfaction remained high until 22 years. Overall, 10% of the prostheses had failed. The results of this study suggest that the Stanmore prosthesis is capable of producing satisfactory long-term results that compare favorably with those of other cemented prostheses.     

Expectancy effects in Rorschach testing.

Tested the hypothesis that M. E. Strauss' (see 42:6) failure to detect bias effects on Experience Balance (EB) may have been the result of his failure to account for E's Productivity (R) expectancies using 38 undergraduate Es and 85 undergraduate Ss expecting either Movement (M) or Color dominated EBs with high or low R. Expectancies were induced in writing and evidence indicated that they were learned. Only the free association portion of the Rorschach was administered. No significant effects were found. This failure to replicate previously reported effects for R led to a 2nd experiment which used 19 Es and 37 Ss, expecting either high or low R, and high or low M to test whether: (a) there had been too much information for naive Es to cope with due to E's being given expectancies for more than 1 variable; and (b) Es and Ss being peers reflected the lack of an E-S status differential thus facilitating bias effects. Again no significant effects were obtained. It is concluded that the discrepancy between these results and findings in previous studies are in keeping with the contention that bias effects are less pervasive than previously assumed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Outcome of the contralateral hip following total hip arthroplasty for osteoarthritis

Uncertainty about the generalizability of results from clinical trials is a nagging issue plaguing psychiatric research. The possible bias introduced by the use of subjects recruited from advertisements is one source of concern. Investigators question whether these subjects are representative of the types of individuals who seek treatment in clinical practice. This article compares and contrasts demographic characteristics, functional disabilities, symptomatologies, and the health beliefs and expectations of a cohort seeking treatment at a university outpatient clinic with a cohort of symptomatic volunteers recruited by advertisements. These two groups were alike in most variables; however, the clinical subjects reported more recent exposure to psychotropic medications and were more likely to indicate that they wanted psychotherapy. The symptomatic volunteers were slightly older, endorsed more psychiatric symptoms, drank more alcohol, and believed that combined pharmacology and psychotherapy would most help them. These findings suggest that the two cohorts were remarkably similar on most variables.     

Comparison of human, primate, and canine femora: implications for biomaterials testing in total hip replacement

The canine model remains an animal of choice for determining the efficacy and safety of various materials and designs used in human total hip replacement (THR). The primate also is used in orthopedic-related research for studying limb anatomy, gait, and age-related bone loss. In order to better understand the appropriateness of these animal models for human THR, external morphologies of thirty-three adult Caucasian human, sixteen adult chimpanzee, and forty-two adult greyhound femora were compared using osteometric methods. Measured parameters included anteversion angle, cervico-diaphyseal angle, femoral head offset in the frontal plane, and anterior bow profiles along the femoral diaphysis. Although some of the measured parameters were approximately similar between species (e.g., mean cervico-diaphyseal angle of humans and chimpanzees), the majority demonstrated morphologic differences that may be biomechanically significant for interpreting stress transfer across the hip (e.g., mean anteversion angle and mean normalized femoral head offset between species). Additionally, age-related changes in proximal femoral morphology and gait pattern, as well as species-related differences in local muscle and inertial forces, may result in notably different loading conditions across the hip joint of each species. Therefore, discretion must be exercised when evaluating canine or primate THR materials and designs for potential use in the human hip.