The incidence of Perthes' disease in Southwest Scotland.

We have investigated the annual incidence of Perthes' disease in Dumfries and Galloway (Southwest Scotland), in relation to the population density and socio-economic status. The incidence of Perthes' disease in rural Scotland is comparable with that in urban areas (15.4 per 100,000). There was a direct association between the incidence of Perthes' disease and deprivation scores, with the highest incidence in the most deprived areas. A higher incidence of Perthes' disease was noted in areas with a lower population density compared with those with a higher density. We found no correlation between population density and deprivation scores for individual electoral wards within the region.

Radiographic and non-invasive determination of the hip joint center location: Effect on hip joint angles

A localizacao do centro de rotacao do quadril e importante na analise dos dados cinematicos da marcha. Metodos acurados para localizacao do centor de articulacao envlovem tecnicas invasivas e de alto custo. O objetivo deste trabalho foi obter angulos no quadril durante a marcha, usando quatro metodos nao-invasivos de estimar o centro de rotacao do quadril, e comparar com angulos obtidos usando tecnica radiografica QPR. Dez sujeitos sadios, entre 57 e 73 anos de idade, participaram do estudo. As tecnicas nao-invasivas usam distancias entre proeminencias osseas localizadas na pele e no quadril para estimas o centro de rotacao do quadril. As radiografias no plano frontal obtidas usando o OPR fornecem com precisao a localizacao do centro de rotacao do quadril nas direcoes medio-laterais e proximo-distais. O metodo mais acurado de estimar a localizacao do centro de rotacao do quadril foi determinado o ponto medio de uma limha conectando a espinha iliaca direita anterior-superior e a sinfise pubica, e movendo essa linha 2 cm inferiormente. Essa tecnica estimou o centro de rotacao do quadril 0,7 cm medial e 0,8 cm superior a sua localizacao, como determinado pela tecnica do QPR. Os angulos obtidos no quadril durante ciclo da marcha usando esse metodo gerou erros inferiores 2º em cada plano, quando comparado com o QPR. O s resultado deste estudo indicam que esse metodo nao-invasivo e de baixo custo e valido para estimar o centro de rotacao do quadril em estudos de analise de marcha.

Investigation of an outbreak of gastroenteritis caused by Norwalk-like virus, using solid phase immune electron microscopy.

In February 1993, 95 persons (47 patients and 48 staff members) were affected by an hospital outbreak of viral gastroenteritis. Using direct electron microscopy (EM) the causative agent was identified as a small round structured virus. This was confirmed as a Norwalk-like virus using solid phase immune electron microscopy (SPIEM). Of 94 stool samples examined, 12 (13%) samples containing small round structured viruses (SRSV) were SPIEM positive for Norwalk-like virus. A further 25 (27%) samples contained small round featureless virus (SRFV) identified by direct EM and were negative on SPIEM. The illness was characterized by preceding influenza-like symptoms in 76% of cases followed by vomiting (76%), diarrhoea (79%) and abdominal pain (79%). One fatality was recorded. The outbreak lasted for 15 days, with a peak incidence of new cases amongst patients and staff occurring on day 5. It was controlled through a combination of ward closures, patient cohorting, suspension of duties for affected staff and disinfection procedures. Difficulties were encountered in the education of staff and in the implementation of environmental control measures. Screening of hospital catering services and a case control study, carried out among affected staff members, failed to identify a foodborne source. Consumption of tap water in the hospital was commoner among affected staff members than among controls, but this did not reach significance (P = 0.1).

The effect of segment parameter error on gait analysis results.

The extent to which errors in predicting body segment parameters (SP) influence biomechanical analysis of human motion is unclear. Therefore, the current study quantitatively evaluated the differences in SP estimates using literature predictive functions and computed the effect of SP variation on the kinetic output of walking. For a group of 15 young males, significant differences (P<0. 05) were observed between SP estimates for the leg and thigh using the literature predictive functions, with mass and moment of inertial values differing by more than 40%. Using kinematic and ground reaction force data collected for each subject while walking, inverse dynamic analysis was performed iteratively to compute hip forces and moments while simultaneously varying SP values over nine intervals within +/-40% of a baseline value. SP variations were found to significantly affect (P<0.05) most of the kinetic estimates produced, particularly those taken during the swing phase. However, the magnitude of these effects was generally less than 1% of body weight. The data from the current study allows researchers to estimate the errors in kinetic measures due to SP variation. The results also indicate that the accuracy of SP prediction should be of concern in biomechanical research particularly for open chain and high acceleration activities. Further study is necessary to identify the importance of SP variation on other motion skills.

Hip moments during level walking, stair climbing, and exercise in individuals aged 55 years or older.

BACKGROUND AND PURPOSE: Low bone mass of the proximal femur is a risk factor for hip fractures. Exercise has been shown to reduce bone loss in older individuals; however, the exercises most likely to influence bone mass of the proximal femur have not been identified. Net moments of force at the hip provide an indication of the mechanical load on the proximal femur. The purpose of this study was to examine various exercises to determine which exercises result in the greatest magnitude and rate of change in moments of force at the hip in older individuals. SUBJECTS AND METHODS: Walking and exercise patterns were analyzed for 30 subjects (17 men, 13 women) who were 55 years of age or older (X = 65.4, SD = 6.02, range = 55-75) and who had no identified musculoskeletal or neurological impairment. Kinematic and kinetic data were obtained with an optoelectronic system and a force platform. Results. Of the exercises investigated, only ascending stairs generated peak moments higher than those obtained during level walking and only in the transverse plane. Most of the exercises generated moments and rate of change in moments with magnitudes similar to or lower than those obtained during gait. CONCLUSION AND DISCUSSION: Level walking and exercises that generated moments with magnitudes comparable to or higher than those obtained during gait could be combined in an exercise program designed to maintain or increase bone mass at the hip.

Radiographic and non-invasive determination of the hip joint center location: effect on hip joint moments.

OBJECTIVE: To determine which of four non-invasive measures is most accurate in locating the hip joint center. BACKGROUND: The location of the joint centers must be accurately determined in three dimensions for calculation of the moments of force during gait. It is not known which of the several non-invasive methods available for location of the hip center is most accurate. DESIGN: Hip center location was determined using standardized X-rays and four non-invasive methods which utilized measured distances between bony landmarks in 10 healthy subjects. Hip moments during gait were obtained from optical tracking, force plate and anthropometric data. RESULTS: The most accurate non-invasive method of locating the hip center was by taking the midpoint of a line connecting the antero-superior iliac spine and the symphysis pubis and moving inferiorly 2 cm. Using this approach the hip center was located 0.7 cm medial and 0.8 cm superior to its true location determined using the standardized X-rays. The 95% confidence interval of the maximum error difference in moments measured between this method and the standardized X-rays ranged from -0.15 to 0.4 Nm/kg in the frontal plane, -0.03 to 0.07 Nm/kg in the sagittal plane and -0.05 to -0.03 Nm/kg in the transverse plane. CONCLUSIONS: Locating the hip center based on the distance between the antero-superior iliac spine and the symphysis pubis is a valid technique for estimating the hip center in routine gait analysis.

Axial lower-limb alignment: comparison of knee geometry in normal volunteers and osteoarthritis patients.

Osteoarthritis of the knee is associated with deformities of the lower limb and malalignment of the limb segments. Pathogenetic relationships between the two are poorly understood. Alignment was studied by standardized radiography in 167 symptomatic Canadian osteoarthritis patients, and compared with 119 healthy adult volunteers. In healthy adults overall alignment (hip-knee-ankle angle) was principally determined by distal femoral valgus (condylar hip angle) and proximal tibial-plateau varus (plateau-ankle angle): the angle between the joint surfaces (condylar plateau) was relatively constant. In osteoarthritis, disease-associated differences included condylar-plateau angles that were divergent: accentuated medial convergence in varus osteoarthritis and lateral convergence in valgus osteoarthritis. This was interpreted as change arising from focal loss of cartilage in the medial (varus osteoarthritis) or lateral (valgus osteoarthritis) compartments of the knee. The changes would contribute to increasing limb malalignment during disease progression. But differences of limb geometry also contributed to malalignment. These were the average trends: in varus osteoarthritis there was abnormal femoral geometry (lesser femoral condylar valgus), but tibial surface geometry was the same. In valgus osteoarthritis, the opposite was true: abnormal tibial geometry (lesser plateau varus), but normal femoral geometry. A possible explanation is that these abnormal knee geometries pre-exist and predispose to osteoarthritis, although it is not impossible that they (like condylar-plateau angle) change as disease progresses. Further approaches to population studies are discussed based on these findings, along with their implications for knee surgery.

Local anesthesia for postoperative pain relief after foot surgery: a prospective clinical trial.

A prospective, randomized, controlled clinical trial was set up to test whether the addition of ankle block to general anesthesia was useful in providing postoperative pain relief following forefoot surgery. Forty feet (20 treatment, 20 control) were entered into the trial and all underwent bony operations on the first ray. Pain was assessed at fixed times following the operation using pain analog scales. Analgesic consumption and wound healing were also assessed. A significant difference was found between the pain scores in the two groups at the 6-hr stage, but there was no difference in any of the other assessments. It is concluded that ankle block is a useful addition to general anesthesia for this type of surgery.

Elbow kinematics during sit-to-stand-to-sit of subjects with rheumatoid arthritis.

Independence in mobility is dependent on the ability to rise from a chair. Elbow kinematics of subjects with rheumatoid arthritis were compared to those of subjects with no known elbow pathology. Through a case study approach, four subjects with varying elbow pathology and symptoms, were compared with a control group of 10 subjects on four kinematic variables. Results indicated that whereas the overall movement pattern was similar between the two groups, a trend toward increased deviation occurred with increased elbow involvement (as measured using the Morrey Elbow Evaluation). The total time taken to complete the task increased and the maximum velocity decreased as scores on the Morrey Evaluation decreased. When the minimum flexion angle (maximum extension) used during the activity was compared with the minimum flexion angle available, the angle used was consistently 15 degrees to 20 degrees less than that available. This possible need for a residual range raises questions about the generally accepted belief that activities require between 30 degrees to 130 degrees of flexion and 100 degrees of rotation.

An integrated procedure to assess knee-joint kinematics and kinetics during gait using an optoelectric system and standardized X-rays.

This paper describes a 3-D gait analysis system, which combines optoelectric motion tracking and a standardized X-ray procedure, to calculate the net knee-joint forces and moments of a normal subject group during walking. The optoelectric system collects kinematic data from infra-red LED markers placed at selected skin surface locations and projecting probes attached to the lower limb. A standardized X-ray procedure is used to move surface markers into their designated bony landmarks based on individual bone structure, which reduces the error caused by uncertainty of skin-surface marker locations. Based on moved-in marker information, different joint coordinate systems are proposed for kinematic and kinetic analysis of the knee joint. Normalized data of knee angles, net reaction forces and net moments from 35 young, normal subjects are presented.

A procedure to validate three-dimensional motion assessment systems.

The automation provided by computer-assisted motion-tracking systems allows for three-dimensional motion and force analysis. These systems combined with mathematical modelling are able to analyse quickly the intricate dynamics of human movement. Understanding the limitations of human motion analysis as performed by the present measurement techniques is essential for proper application of the results. It is necessary to validate the analysis system prior to subject testing. This paper provides a validation of an optoelectric motion-tracking system used in a dynamic knee assessment study. While the validation is shown with one particular system only, it is suggested that all systems used in two- or three-dimensional motion analysis should be tested similarly in the actual configuration used. Three simple mechanical representations of the human knee have been used in this validation. The first model provided an understanding of the source and behaviour of the error introduced to the accuracy of defining a vector between the recorded coordinates of two markers. The other two models investigated the effect of processing methods specific to the knee analysis project. Separating the markers by at least 180 mm is recommended to produce stable vectors. Relative joint angles could be calculated in all three planes of rotation. The error in calculating flexion and longitudinal rotation was less than 2.0 degrees, while calculating adduction introduced errors of 4.0 degrees. Force calculations were found to be within 8%. The system behaviour was found to be consistent within the calibrated volume about the force platform. Simple mechanical models combined with straightforward procedures can provide validation in terms of clinically relevant parameters.

Reliability of an optoelectric system to measure elbow kinematics.

Motion analysis of the upper extremity during functional activities has only recently become more accessible. An optoelectric system (WATSMART) was subjected to testing using first a calibration dummy and then human subjects. The mean differences between the system calculated angles and those measured with potentiometers on a calibration dummy were less than 1.6° in all three planes. The test-retest reliability of the system when measuring elbow motion of human subjects yielded acceptable repeatability for measurement of functional activities. Calculation of the least significant difference found that minimum differences from 4 to 14° in flexion and from 10 to 19° in rotation can be detected using the reported set-up and protocol.

Elbow kinematics during sit-to-stand and stand-to-sit movements.

The sit-to-stand and stand-to-sit movements of 10 healthy women (mean age 52.4 years) were subjected to a descriptive analysis that yielded a definition of phases, determination of the peak angles reached, maximum angular velocity during each movement, and the sequencing of key events. While subjects showed little intrasubject variability, intersubject variability was evident. Subjects differed in the joint angles and angular velocity recorded, but the sequence of flexion/extension and rotation events were unchanged. Changes in direction of flexion/extension and rotation tended to occur very close in time, if not at the same time.

Semiautomatic three-dimensional knee motion assessment system.

A semiautomatic three-dimensional knee motion assessment system has been developed based on an optoelectric motion tracking system connected to an IBM-compatible computer. Critical decisions made in implementing the software component of the system include the modelling of the thigh and lower leg segments, calculating the knee angles, reaction forces, and moments; the file structure used and the format of the programs used to process the data are outlined. Once the subject-specific data have been collected, the system of programs requires no other user-intervention during processing. Also, selected curve parameters are automatically extracted from the output and combined with the subject-specific data that include precision X-ray and anthropometric data, which are all added to a knee motion assessment database. The automated portion of the system frees the experimenter from data processing and allows concentration on data analysis.

Need the thumb be immobilised in scaphoid fractures? A randomised prospective trial.

Immobilisation of the thumb is widely believed to be important in the management of fractures of the carpal scaphoid. To assess the need for this, we randomly allocated 392 fresh fractures for treatment by either a forearm gauntlet (Colles') cast, leaving the thumb free, or by a conventional 'scaphoid' plaster incorporating the thumb as far as its interphalangeal joint. In the 292 fractures which were followed for six months, the incidence of nonunion was independent of the type of cast used.