Bone formation into surface phosphonylated polymeric implants.

Through the use of two animal models, the present study demonstrates the ability of phosphonylated surfaces to bind bone. In one model, surface-treated polypropylene (PP) and polyethylene (PE) were implanted in the medial cortex of the goat tibia. In the second model, surface-treated poly(ether-ether ketone) (PEEK) and carbon fiber-reinforced PEEK (CFR-PEEK) were implanted through both cortices of the goat mandible. Selected rods of all material types were microtextured using crystallization induced microphase separation, a method for the formation of continuous, open-cell microporous surfaces in thermoplastic polymers. Microtextured and smooth rods were phosphonylated, and calcium was subsequently introduced to the phosphonylated surface by incubating the samples in a saturated solution of calcium oxide. For all substrate materials tested, phosphonylation and calcium posttreatment resulted in an increased propensity for bone binding and apposition, as measured by push out test. Microtextured PP, PE, and CFR-PEEK surfaces that were further phosphonylated and calcium treated resulted in test samples with an increased interfacial strength.

Routine use of ultrasound during pregnancy.

Ultrasound technology offers valuable information when used as a diagnostic tool during a pregnancy at risk for complications. Its use has expanded greatly to uncomplicated pregnancies as a result of expectant parents' desire to see their baby or to know its gender. Many women are having ultrasounds without being given factual information regarding the purposes, risks, and/or benefits of this procedure. Decisions regarding ultrasound sonography could have a significant physical or emotional impact on the pregnancy, and informed decision making can take place only when the patient is properly educated. Issues regarding ultrasound benefits, safety, controversies, and information helpful to nurse practitioners involved in sonography are addressed in this article.

Anthropometric study of normal glenohumeral relationships.

Ninety-three cadaveric proximal humeri and matching scapulae with no evidence of shoulder disease were obtained. High-resolution roentgenograms were made. They were the digitized, and a custom computer program was used to obtain periosteal and endosteal dimensions (humeral canal width, shaft width, tuberosity offset, head offset, radius of curvature, head diameter, canal flare index, glenoid height and depth, arc of enclosure, radius of curvature, and depth of cancellous bone, among others). Statistical analyses included correlations among pairs of dimensions, regression analysis, and confidence intervals to estimate each geometric parameter. To represent the degree of conformity and constraint between the humeral head and glenoid, a conformity index (radius of head/radius glenoid) and constraint index (arc of enclosure/360) were calculated for each shoulder. Most of the parameters measured approximated a Gaussian distribution. Pairwise correlations of the geometric parameters showed that many were significantly associated at the 5% level (p < 0.05) with a high correlation coefficient (r > 0.4), meaning that the variations between the parameters were not purely random but rather they were related and that this relationship was useful in a predictive sense. With these key parameters identified, one can design components with an optimum fit or match an existing design to a patient's anatomy with a high degree of accuracy. No correlation was found between the radii of curvature for the humeral head and glenoid in either the coronal or sagittal plane or between the humeral head diameter and arc of enclosure. The mean conformity index was 0.72 in the coronal and 0.63 in the sagittal plane. Only 16% of the specimens had a conformity index greater than 0.9, indicating the radii of curvature matched. The vast majority had a more curved humeral head and flatter glenoid. Also, there was more constraint to the glenoid in the coronal versus sagittal plane (constraint index = 0.18 vs 0.13). These anatomic features help prevent superior-inferior translation of the humeral head but allow translation in the sagittal plane. This database of basic anatomic geometry defines the anatomic relationships of the proximal humerus and glenoid cavity that allow for a precise bone-implant fit and assesses the match between the shape of existing components and the patient's anatomy.

Automated scanning and digitizing of roentgenographs for documentation and research.

A comprehensive system has been developed for analyzing and reporting the results of total hip arthroplasty. The personal-computer-based system links patient demographic data with digital storage, retrieval, and analysis of roentgenographs. The system consists of a roentgenograph scanner for converting sheet film to digital data, an optical mark reader for patient data input, an archiving system with optical storage, and a physician display station for preoperative planning and postoperative evaluation. Once a roentgenograph has been digitized and stored, the image can be retrieved and manipulated in a manner not possible with the original sheet film. A selected roentgenograph can be brought to full or enlarged scale, enhanced, and overlaid with templates for preoperative planning or for postoperative measurement of changes. In addition, an intelligent database system has been developed for linking patient demographic information with the roentgenographic data. The database system employs uniform criteria and terminology and allows the retrospective study and statistical analysis of comparable cases. Three machine-readable code sheets are used: Form A, Replacement of the Hip; Form B, Hip Prosthesis Reoperation; and Form C, Follow-up. Forms A and B contain information concerning anamnesis, diagnosis, treatment, postoperative course, recovery, and discharge of the patient from the hospital. Form C provides information on physical examination, pain, mobility of the hip, walking ability, and evaluation of the results by the surgeon as well as the patient.

Finite element modeling of the glenoid component: Effect of design parameters on stress distribution.

A two-dimensional plane stress model of the natural glenoid was developed with finite element analysis to observe the stress distributions under various loading conditions. Different glenoid prosthetic designs were evaluated with the use of the finite element model in an attempt to elucidate key features for an improved design. These included a keel model, a stair-stepped model, and a wedge model. In addition to the evaluation of these designs, different interfaces were introduced to simulate various environments of the prostheses, and different material combinations were studied. Based on the finite element analysis, the following design parameters were found to be important: (1) an all-polyethylene implant appears to provide a more physiologic stress distribution for nonaxial loads if no soft tissue is present; (2) the presence of a soft-tissue layer causes higher stresses; (3) the stair-stepped and wedge models produced a more natural stress distribution compared with the keel design; and (4) screw orientation was not a significant design parameter.