PubMed Health⌕ Search

Biomedical subjects

W C Hayes

Publications and source records attributed to W C Hayes.

187 records · Page 11Linked to original sources
PubMedDate not supplied

Calculation of cross-sectional geometry of bone from CT images with application in postmenopausal women.

OBJECTIVE: The objectives of this study were to develop a software program that calculates bone cross-sectional area (CSA) and moments of inertia from digital images, test the computations for accuracy, and implement the software in a study of longitudinal changes in bone properties in a large group of postmenopausal women. MATERIALS AND METHODS: A program called SLICE was adapted to use computed tomography (CT) bone images as input. The main outcome variables of the resulting program, SLICE_CT, were bone CSA, areal moments of inertia, and mass-weighted moments of inertia. SLICE_CT was tested for accuracy using representative arrays of CT numbers that approximate cross-sections of cortical bone. Then the technique was applied to images from a 3 year longitudinal study of the radius in 86 postmenopausal women who underwent quantitative CT of the dominant radius at 30% the distance from the wrist to the elbow. The mean age of the subjects at entry into the study was 57 years. Images at baseline and at 3 years were analyzed, and the null hypothesis of no change in cross-sectional geometry was tested by a paired difference two-tailed t test. RESULTS: The error of SLICE_CT was < 1% with proper segmentation, using half-maximal height as the threshold. In the longitudinal study of postmenopausal women, the mean change of CSA of the radius was -1.4% (SD = 3.0%; p < 0.001). However, there was a compensatory 2.4% increase in the cross-sectional second polar moment of inertia (SD = 3.7%; p < 0.001). CONCLUSION: SLICE_CT is an accurate method with which to determine cross-sectional geometry of digital images and can be used to detect changes in cross-sectional geometry of the radius with age in postmenopausal women. The results indicate that the radius remodels to compensate for bone loss and decreasing material properties of bone associated with aging.

Bone and Bones↗
PubMedDate not supplied

A comparison of the Synthes 4.5-mm cannulated screw and the Synthes 4.5-mm standard cortex screw systems in equine bone.

OBJECTIVE: To determine risk of failure of the Synthes 4.5-mm cannulated screw system instrumentation in equine bone and to compare its application with the Synthes 4.5-mm standard cortex screw system. STUDY DESIGN: The maximum insertion torque of the cannulated and standard cortex screw systems were compared with the ultimate torsional strengths of the equipment. Pullout strength and ultimate tensile load of cannulated and standard cortex screws were also determined. SAMPLE POPULATION: Paired equine cadaver third metacarpal and third carpal bones. METHODS: Maximum insertion torque and ultimate torsional strengths were determined by using an axial-torsional, servohydraulic materials testing system and a hand-held torquometer. Pullout tests were performed by using a servohydraulic materials testing system. RESULTS: Maximum insertion torque of all cannulated instrumentation was less than ultimate torsional strength at all locations (P < .05). Maximum insertion torques of cannulated taps and screws were greater than for standard taps and screws in the third carpal bone (P < .002). Pullout strength of the cannulated screws was less than the standard cortex screws at all sites (P < .001). Cannulated screws broke before bone failure in all but one bone specimen. CONCLUSIONS: The risk of cannulated instrument or screw failure during insertion into bone is theoretically low. The relatively low pullout strength of the cannulated screws implies that the interfragmentary compression achievable is likely to be less than with standard cortex screws. CLINICAL RELEVANCE: The relatively low pullout strength of the cannulated screw suggests that its risk of failure during fracture repair is greater than with the standard cortex screw.

Animals↗
PubMedDate not supplied

Pull-out strength of suture anchors for rotator cuff and Bankart lesion repairs.

Surgical reconstructions of anterior-inferior shoulder instabilities and rotator cuff injuries require secure fixation of soft tissue to bone. Sutures are inserted directly through transosseous tunnels in current techniques, which are surgically complex and not always adequate for fixation strength. Using fresh-frozen cadaveric human specimens, our objectives were 1) to compare immediate pull-out strength of two versions of polyacetal suture anchors (wedge and rod) with conventional suture-only attachment techniques in Bankart lesion and rotator cuff repairs, and 2) to compare pull-out strength of the two polyacetal suture anchors with a metallic suture anchor. Our results indicate no significant differences in fixation strength of Bankart lesions or rotator cuff repairs using sutures only, or using wedge or rod polyacetal suture anchors (P = 0.70). Pull-out force did not differ significantly (P = 0.37) between the two polyacetal anchors. Polyacetal anchors exhibited higher pull-out forces than metallic anchors when inserted into metaphyseal regions of the tibia and significantly higher pull-out forces (P < 0.001) when inserted into metaphyseal regions with thicker cortical walls. Our results indicate that both polyacetal suture anchors provide adequate immediate fixation for soft tissue repairs in the human shoulder.

Acetals↗
PubMedDate not supplied

The biomechanics of interference screw fixation of patellar tendon anterior cruciate ligament grafts.

Twenty-seven paired human cadaveric knee specimens were used to determine the effect of surgical technique and various interference screw parameters on the pullout strength of patellar tendon femoral bone blocks. The study compared the fixation strength of endoscopically inserted and conventional "rear-entry" screws of different diameters and lengths. In all tests the most frequent mode of failure was bone block pullout from the interference screw. There was no significant difference in fixation strength between 9-mm diameter screws inserted through a conventional rear-entry technique and 7-mm diameter screws inserted through an endoscopic technique. There was no significant effect of screw length on fixation strength. The pullout force for 20-mm long screws increased on average 120% when 7-mm diameter screws were compared with 5.5-mm diameter screws. There was no significant effect of increased screw core diameter on fixation strength. There was a weak positive correlation (r2 = 0.45) between screw insertion torque and pullout force. Our measured mean pullout force for the 7-mm endoscopically inserted screws of 362 +/- 198 N represents 20.1% of the failure load of the normal young adult anterior cruciate ligament. Our data indicate that properly inserted 7-mm diameter endoscopic interference screws can provide fixation strengths of patellar tendon anterior cruciate ligament grafts equivalent to those of conventional 9-mm diameter rear-entry, outside-in screws.

Analysis of Variance↗
PubMedDate not supplied

Anterior cruciate ligament graft fixation. Comparison of hamstring and patellar tendon grafts.

This study assessed the tensile properties of hamstring and patellar tendon anterior cruciate ligament reconstructions in older cadaveric knees (age range, 48 to 79 years). Mechanical testing to failure was conducted by translating the tibia anteriorly at 1 mm/sec with the knee in 20 degrees of flexion. The strongest gracilis-semitendinosus graft fixation technique (103% of intact anterior cruciate ligament) had the tendons doubled and secured with soft tissue washers (P < 0.01). However, all reconstructions using gracilis-semitendinosus grafts were significantly less stiff than the intact anterior cruciate ligament specimens regardless of fixation technique (P < 0.01). The highest strength patellar tendon graft fixation technique (84% of intact anterior cruciate ligament) was obtained with a combination interference screw and suture technique. The difference in stiffness between a patellar tendon graft and an intact anterior cruciate ligament was not significant when interference screws were placed at both ends of the graft (P > 0.05). Both types of grafts failed most often on the tibial side. With appropriate fixation, both grafts approximated the intact anterior cruciate ligament in strength, but only patellar tendon grafts secured with interference screws were comparable in stiffness.

Aged↗
PubMedDate not supplied

The effects of donor age and strain rate on the biomechanical properties of bone-patellar tendon-bone allografts.

Over 50% of all knee injuries involve partial or complete tear of the anterior cruciate ligament. Surgical reconstruction of this ligament using an isometrically placed bone-patellar tendon-bone autograft is the current technique of choice; however, harvest of patellar tendon as a free graft can lead to increased morbidity. To address this issue, allogenic patellar tendon grafts have been introduced as alternatives to autogenic graft material. The purpose of this study was to examine effects of age and strain rate on tensile strength, modulus, and failure mode of bone-patellar tendon-bone allografts from a typical population of tissue donors. Eighty-two, fresh-frozen, bone-patellar tendon-bone allografts were harvested from 25 different donors, aged 17 to 54. Paired grafts from individual patellar tendons were assigned randomly to tensile testing at either 10% or 100% elongation per second. Tensile strength, modulus, and failure mode were not significantly different for tests conducted at these 2 strain rates. Correlations between tensile strength and age were not significant for tests conducted at either strain rate. Specimens tested at a strain rate of 100% per second exhibited weak but significant negative correlation between modulus and age, with modulus decreasing 25% over the age range examined.

Adolescent↗