Micro-CT evaluation of rheumatoid arthritis mouse model disease progression: Manual tracings versus semi-automated routines.

PURPOSE: The primary goal of this study was to demonstrate the value of micro-CT imaging in a rheumatoid arthritis (RA) mouse model. The secondary goal was to assess whether manual correction of the articular surface regions of interest (ROI) identification of the semi-automated methods may result in more effective assessment of bone volume and density loss. MATERIALS AND METHODS: Collagen-induced arthritis (CIA) was induced in six DBA/1J mice at 12 weeks of age and three other DBA/1J identical mice served as controls. Micro-CT images were acquired at baseline and at four, seven, and nine weeks post-induction. Disease was monitored via ROI analysis, and ROIs were first generated using semi-automated techniques. These ROIs were manually manipulated so that a variety of edge irregularities were corrected. Effort was focused on the proximal and distal humerus and the distal femur. ROI volume and density were calculated, and data were compared. A histologic analysis of the study mice was also performed after the last time frame. RESULTS: There was a significant difference between the volume data comparison between the manually manipulated data and the semi-automated routine data across all time frames and across both humeri and femurs. There was no significant difference in densities calculated in Hounsfield units across any of the time frames, humeri or femurs, except for one time frame. CONCLUSION: Our findings suggest that the manual correction technique of semi-automated data can be used to quantify and evaluate bone volume, density, and joint surface architecture changes in a RA mouse model.

Factors affecting reaction times to short anterior postural disturbances.

One source of falls in the elderly may be an inability to sufficiently adjust to transient postural perturbations or slips. Identifying useful predictors of fall potential, as well as factors that affect the ability of an individual to detect a movement of the standing support surface may provide insight into postural stability and methods to increase stability in elders. The effects of acceleration, displacement, neurological status, and age on movement detection reaction times were studied in 25 individuals--1 young adults, seven neurologically intact elderly adults, and six elders with (diabetic) peripheral neuropathy. Acceleration detection thresholds for anterior perturbations of 1, 4, and 16 mm of the support surface was previously determined for each subject via a two-alternative forced choice (2AFC) protocol, with longer (16 mm) moves yielding lower 2AFC thresholds (12-39 mm/s(2)) that varied by group. Using the acceleration threshold value determined, and 125% of that threshold (suprathreshold), reaction times to the start of the platform movement were determined for all three displacements. Reaction times to an additional superthreshold movement (4 mm at 100 mm/s(2)) were also measured. Lower acceleration values over longer moves required longer reaction times for motion detection. Reaction times were also influenced by peak energy imparted to the subject through the move. The higher prevalence of falls in the elderly and elderly diabetic may be due to slowing reaction times compounded by larger amounts of imparted energy needed for detection of a slipping event.

A virtual five-link model of the thumb.

Most researchers have modelled the thumb as three rigid links with connections of two universal joints (carpometacarpal joint and metacarpo-phalangeal joint), and a hinge joint (interphalangeal joint). Although this produces the required number of degrees of freedom, the resulting motion is not anatomically accurate. In this work, the thumb is modelled as a five-link manipulator with the virtual links connected by hinge joints-one for each degree of freedom of the thumb. The axes of the hinges are not orthogonal to one another, in the long axis of the bones or to the anatomic planes. Four static positions of hand function were analysed-key pinch, screwdriver hold, tip pinch, and wide grasp. The virtual five-link model of the thumb predicted similar muscle recruitment patterns to published EMG data. The force at the distal surface of the trapezium is between 6 and 24 times the applied load depending on the posture.

The relationship of the interosseous membrane to the axis of rotation of the forearm.

Fresh anatomic specimen forearms were studied using a mechanical device, the axis finder, to locate the axis of rotation. The relationship of the axis to the membrane was demonstrated directly using a small jig. The axis of rotation of the forearm is constant and independent of elbow flexion or extension. It runs from the center of the radial head to the center of the distal ulna. All fibers of the interosseous membrane cross the axis of rotation near their distal insertion into bone. This relationship of the ligaments to the axis of rotation is similar to those of the ankle, knee, and thumb joints. The membrane does not limit forearm rotation and can provide little stability if the bony ring is disrupted.

The axes of rotation of the knee.

Knee motion is believed to occur about a variable flexion-extension (FE) axis perpendicular to the sagittal plane and a longitudinal rotation (LR) axis. The authors used a mechanical device to locate the FE and the LR axes of six fresh anatomic specimen knees. The motion of points on the LR axis produced circular, planar paths about the fixed FE axis. Magnetic resonance (MR) images in planes perpendicular to the FE axis showed a circular profile for the femoral condyles. The FE axis is constant and directed from anterosuperior on the medial side to posteroinferior on the lateral side, passing through the origins of the medial and lateral collateral ligaments and superior to the crossing point of the cruciates. The LR axis is anterior and not perpendicular to the FE axis, the anatomic planes. This offset produces the valgus and external rotation observed with extension. The implications of two fixed offset axes for knee motion on prosthetic design, braces, gait analysis, and reconstructive surgery are profound.

A kinematic technique for describing wrist joint motion: analysis of configuration space plots.

This paper describes an experimental method for determining the minimum number of degrees of freedom of a human joint. Application of this technique to the wrist suggests that the normal, intact wrist joint uses only two degrees of freedom to move in a plane that is not aligned with the anatomic planes. The technique may be useful in identifying emerging joint pathologies and in simplifying kinematic models of joint function.

Kinematics of the ankle: a hinge axis model.

We used a mechanical method to locate the axis of rotation of the talocrural joint. A single constant axis of rotation was found just distal to the tips of the malleoli. The paths of light-emitting diodes mounted on a talar pin were recorded with time lapse photography during flexion-extension. These paths were analyzed both in the sagittal plane and in a plane perpendicular to the axis of rotation. Sagittal plane studies were distorted by perspective error. The plane used to analyze joint motion or shape must be the plane of motion. Models of the talocrural joint for gait analysis, reconstructive surgery and prosthetic design should have a single offset axis of rotation.

The use of MRI in the diagnosis of an occult wrist ganglion cyst.

Magnetic resonance imaging (MRI) has proved to be particularly useful in the evaluation of soft-tissue lesions. A case is presented in which MRI was used to diagnose an occult ganglion cyst of the wrist.

Failure to demonstrate transfer of milk prolactin into blood of milk-fed rats and calves.

Possible absorption of ingested prolactin into blood of milk-fed neonates was studied in two species by different experimental approaches. In calves, secretion of endogenous prolactin was suppressed by administration of ergocryptine. Prolactin was measured in blood plasma at 20-min intervals before and after ingestion by the calves of bovine milk or colostrum which contained prolactin. Prolactin in plasma during the 2-h period after feeding was the same as that during the 1-h period before feeding. therefore, these data failed to demonstrate any absorption of ingested prolactin into the blood of neonatal calves. Previous research showed that bovine prolactin could be transferred into rat milk by injecting it into lactating rats. Blood serum was collected from rat pups that were suckling dams previously injected with bovine prolactin. Several dosages and times of administration were used in the experimental design, and blood serum also was collected from rat pups nursing control dams. All samples were immunoassayed for bovine prolactin with reagents that crossreacted only slightly with endogenous rat prolactin. Injection of lactating dams with bovine prolactin did not increase the amount of immunoreactive bovine prolactin in the sera of suckling rat pups. These results agree with those from the calf study and indicate that ingested bovine prolactin was not absorbed intact into the blood of neonatal rats.

PIP: The transfer of bovine milk prolactin, or colostrum containing prolactin, into the blood of milk-fed neonates was investigated in calves and rats. Ergocryptine was used to suppress prolactin secretion in calves. Plasma prolactin levels 2 hours after feeding and 1 hour before feeding were similar, thus indicating the failure of neonatal calves to absorb ingested prolactin into the blood. In rats, injection of immunoreactive bovine prolactin into lactating dams did not increase the amount of immunoreactivity in the serum of suckling rat pups. The results indicate that exogenous bovine prolactin was not absorbed intact into sera of neonatal rats.