Biomedical subjects

James G Richards

Publications and source records attributed to James G Richards.

4 recordsLinked to original sources

PubMed2006

Concurrent surgeries are a factor in predicting success of rectus transfer outcomes.

Cerebral palsy (CP) patients exhibit a wide range of functional responses to specific surgical interventions. The variability associated with surgical outcomes within this patient population precipitates the need to determine the functional effects in advance of the surgery. Pilot studies have indicated that the application of statistical models towards predicting functional outcomes of surgery produces clinically meaningful results. The purpose of this study was to evaluate the influence of pre-operative kinematic parameters in conjunction with concurrent surgeries on rectus transfer (RT) outcomes. Gait analysis data were collected from 68 patients (94 legs) pre- and post-operatively within a year of surgery. Patients were divided into four groups. Group 1 (N=14) contained only legs experiencing a rectus transfer. Group 2 (N=30) contained legs experiencing RT and hamstring lengthening (HL). Group 3 (N=7) contained legs experiencing RT and lower leg surgeries: either Achilles lengthening (AL), or gastrocnemius lengthening (GL). Finally, Group 4 (N=43) contained legs which experienced all four surgeries (RT+HL+AL+GL) concurrently. Multivariate jackknifed linear regression was used to predict the change in knee range of motion, DeltaROM, due to surgery on a group-by-group basis. In each case, the sole significant pre-surgical variable was the range of motion. Group 1 legs had the best correlation (R=0.846) between pre-surgical ROM and DeltaROM whereas Group 4 legs had the worst correlation (R=0.661). Group 3 results were not significant. Group 1 DeltaROM were also significantly lower as a whole, than all other groups, due to a larger percentage of patients needing the surgery to change timing of flexion in swing phase. When compared to modeling without consideration of surgery, modeling by surgical group produced results with fewer outliers and better correlation coefficients. Regardless of surgical group, patients with a lower pre-surgical ROM (<40 degrees ) were more likely to experience an increase in ROM as a result of surgical intervention compared to their peers with an elevated pre-surgical ROM who were likely to see a decrease in ROM. Pre-surgical ROM therefore serves as a useful predictor of outcome in rectus transfer surgery.

Achilles Tendon↗

PubMed2006

A method for analyzing joint symmetry and normalcy, with an application to analyzing gait.

A new method for analyzing symmetry and normalcy of gait patterns is explained. This method utilizes eigenvectors to compare waveforms. The right and left limbs of a single subject are compared to determine symmetry. To determine normalcy, a single limb from a subject is compared to a normative file created from the average of healthy control subjects. The analysis method provides four measures of symmetry and normalcy: trend phase, trend symmetry/normalcy, range amplitude ratio, and range offset. The trend symmetry/normalcy is a comparison of the shapes of the waveforms for each limb. The range amplitude ratio is a comparison of the range of motion of each limb. The range offset is a comparison of the range in which each limb operates. The exact methods and clinical applications are provided.

Amputees↗

PubMed2005

Clinical applicability of using spherical fitting to find hip joint centers.

The functional or sphere-fitting method has been proposed as an alternative to the traditional predictive approach to locating hip centers based on inter-ASIS breadth. In the functional approach, the movement of a marker on the thigh is fit to a sphere whose center coincides with the hip joint center. The first objective of this study was to determine the required parameters that allow an accurate application of a sphere-fitting method. The parameters examined in this study included: (1) the range of motion in flexion-extension and abduction-adduction, (2) the specific algorithm used to fit a sphere to the data, (3) the method of placing markers on the thigh, and (4) the type of motion used to generate points, either walking or a standing leg motion (SLM) trial. This objective was addressed with a computer simulation and clinical data. The second objective was to compare the accuracy of the functional method to the traditional predictive approach in a group of nine human subjects. The location of the hip center estimates from both methods were compared to an ultrasound-determined hip center standard, and linear errors and errors along each axis were compared. Results from the computer simulation indicated that an iterative algorithm is needed, with a method using the derivative yielding slightly more accurate results. Clinical results indicated that the functional method with a standing leg motion trial produced significantly smaller errors in hip joint center estimates (1.34 cm) versus the predictive method (2.16 cm). In addition, the range of error across hips was smaller for the functional method. If high joint center accuracy is needed or in populations characterized by obesity or pelvic asymmetries, the subject specificity and independence from anatomical landmarks characteristic of the functional method would likely provide more accurate results.

Adult↗

PubMed2005

Optimal ankle axis position for articulated boots.

An articulated boot design is commonly used in skiing and skating sports because it allows sagittal plane ankle mobility while still providing critical frontal plane stability. Although articulated boots have been in use for several decades, current manufacturers of these boots differ in their articulation placement. In this study we determined an optimal position of the ankle articulation axis. We also calculated the amount of anterior skin movement that a boot tongue must account for during a full range of ankle motion. Three-dimensional kinematic data were collected and analyzed from 40 participants moving their right foot through a full range of sagittal plane motion. The calculated horizontal position of the articulation axis was found to be highly predictable from foot length (r = 0.87, standard error of estimate = 3.44 mm), while its vertical component displayed less predictability (r = 0.49, standard error of estimate = 7.46 mm). The expansion required by the boot tongue had a moderate association with foot length and low variability (r = 0.58, standard error of estimate = 0.07 mm). An accurate axis placement will minimize relative motion between the boot cuff and the ankle, reducing friction and motion resistance. An expandable tongue will accommodate full plantar flexion and reduce pressure on the anterior ankle during dorsiflexion, eliminating common pressure-related injuries.

Adolescent↗