Biomedical subjects

J W Vahey

Publications and source records attributed to J W Vahey.

6 recordsLinked to original sources

PubMed1998

Effect of proximal phalangeal fracture deformity on extensor tendon function.

Extensor lag is a common sequella of proximal phalangeal fractures. Proximal phalangeal fractures frequently lead to extensor tendon dysfunction via adhesions and phalanx malunion with angulation and/or shortening. The primary purpose of this study was to quantify the influence of proximal phalangeal angulation and shortening on proximal interphalangeal (PIP) joint extension by examining the effect of isolated proximal phalangeal bone to extensor digitorum communis tendon discrepancy on PIP joint lag. The secondary goal was to determine the reserve of the extensor digitorum communis to overcome the PIP joint lag. A proximal phalangeal bone-extensor tendon discrepancy results in either a PIP lag or a potential lag that must be compensated for by another system, such as by overpull of the extrinsic extensor or by the pull of the intrinsics. Six cadaveric middle fingers were used, proximal phalangeal malunions were simulated, and the extensor lag was measured radiographically. A linear relationship between extensor tendon lengthening and the resulting PIP lag was observed. Similarly, a linear relationship between proximal phalangeal shortening and the lag was observed. For both, the average slope was 12 degrees of lag/mm of bone-tendon discrepancy. For average apex palmar angulations of 16 degrees, 27 degrees, and 46 degrees, PIP lags of 10 degrees, 24 degrees, and 66 degrees, respectively, resulted. The extensor tendon reserve was 2 to 6 mm. The sagittal bands became tight at the limits of the extensor tendon reserve. The results of this study quantify the importance of re-establishing the bone-tendon relationship for proximal phalangeal fractures.

Cadaver↗

PubMed1995

Carcinogenicity and metallic implants.

The literature related to the carcinogenetic potential of metallic implants was reviewed. There were 20 cases described in which tumors were identified in proximity to metallic implants. These cases occurred over a 34-year period. Investigators have identified a 70% increased incidence of lymphomas and hematopoietic tumors over that in the general population in patients who had received total hip arthroplasties. Carcinogenicity theories include the potential direct toxicity of materials, the effects of surface properties, the electromotive potential created by dissimilar metals in contact, the immunologic response to implants, and finally, the sustained presence of low-grade infection. Corrosion is a well-documented phenomenon and occurs with any type of metal. The rate of formation of corrosion products and their toxicity varies with the implant composition. Toxic effects of metals, such as malignant potential and other adverse effects, have been demonstrated in animal models. The published information on this controversial and very poignant issue of metallic carcinogenesis is useful for all orthopedic surgeons.

Animals↗

PubMed1995

Fracture of the cuboid in children. A source of leg symptoms.

We report eight cases of fracture of the cuboid in seven children under four years of age, collected during a two-year period. There was no history of trauma in five of the patients. This fracture is rarely diagnosed and has probably been under-reported. Small children are poor historians and difficult to examine, and early radiographs may be normal or have only subtle abnormalities. Cuboid fracture should be considered in the differential diagnosis of limping toddlers, and a bone scan may be needed to confirm the diagnosis earlier than radiography. These fractures heal completely, without sequelae. Treatment in a short-leg walking cast is recommended, primarily for reasons of comfort.

Casts, Surgical↗

PubMed1991

Tensions in the anterior and posterior cruciate ligaments of the knee during passive loading: predicting ligament loads from in situ measurements.

Cruciate ligament tensions were predicted for anteroposterior (AP) tibial translation at 20 degrees, 30 degrees, 80 degrees, and 90 degrees of knee flexion based on in vitro measurements from six cadaver knees. A three-dimensional trigonometric equation was derived to calculate cruciate ligament tension as functions of AP force applied to the tibia and knee flexion angle (KFA). AP forces less than or equal to 150 N were applied. Ligament tension increased with applied AP force. The relationship between ligament tension and applied AP force appeared linear, but a Hotteling's T2 test failed to demonstrate a linear relationship. Tensions in the anterior cruciate ligament (ACL) attained magnitudes of approximately equal to 140 N. Tensions in the posterior cruciate ligament (PCL) attained magnitudes of approximately equal to 220 N. An analysis was performed to determine the sensitivity of ligament tension to hypothetical errors in the experimentally measured parameters used to compute ligament tension. The new method we report can be used to determine tensions in the ligaments of the knee or other joints for various loading conditions.

Adult↗

PubMed1990

An in vitro study of anterior cruciate ligament strain induced by quadriceps and hamstrings forces.

Strain in the anteromedial fibers of the anterior cruciate ligament [ACL(am)] was studied in six cadaver knees. ACL(am) strain was measured in five knees during the application of isometric quadriceps forces alone and simultaneously applied isometric quadriceps and hamstrings forces at 10 degrees increments from 0 degrees to 90 degrees of knee flexion. ACL(am) strain during muscle loading was measured with respect to the ACL(am) strain measured with the knee in its resting position (neutral or near neutral position). A sixth knee was used to investigate the reproducibility of the resting position and quadriceps-induced ACL(am) strains. The strains induced in the ACL(am) by the quadriceps were significantly greater than 0 at knee flexion angles from 0 to 40 degrees and not significantly different from 0 for 50 to 90 degrees. The ACL(am) strains induced by simultaneously applied hamstrings and quadriceps forces were not significantly different from 0 at any of the knee flexion angles tested. Simultaneously applied hamstrings and quadriceps forces significantly reduced ACL(am) strain at 10, 20, and 90 degrees of knee flexion compared to the ACL(am) strain induced by quadriceps forces alone. The hamstrings are potentially capable of both significantly reducing and negating quadriceps-induced ACL(am) strain at 10 and 20 degrees of knee flexion.

Adult↗

PubMed1987

Elastic moduli, yield stress, and ultimate stress of cancellous bone in the canine proximal femur.

Elastic moduli, yield stress and ultimate compressive stress were determined for cancellous bone from the femoral head and neck regions of the canine femur. Unconfined compression tests were performed on 5 mm cubic samples which were cut from two femurs. Elastic moduli were measured in three orthogonal directions, and the yield stress and ultimate stress were measured along the proximal-distal axis. The results from this investigation support previous assumptions that the mechanical behavior of canine cancellous bone is qualitatively similar to human cancellous bone. The canine cancellous bone was observed to be anisotropic in elastic modulus. For two thirds of the cubic specimens tested, the elastic modulus was largest in the load-bearing, proximal-distal direction. A linear relationship between yield stress and elastic modulus was observed for canine bone, as is typical of human bone. A similar linear relationship between ultimate stress and elastic modulus was observed. Thus, for canine bone as well as for human bone, failure appears to be governed by a strain level which is position independent. The yield strain of 0.0259 and ultimate strain of 0.0288 for canine bone were both less than the yield strain of 0.0395 reported for human bone.

Animals↗