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Biomedical subjects

J L Lewis

Publications and source records attributed to J L Lewis.

314 records · Page 18Linked to original sources
PubMedDate not supplied

Effect of anterior cruciate ligament graft tensioning direction, magnitude, and flexion angle on knee biomechanics.

The objective of this study was to determine the biomechanical effect of graft tensioning during reconstruction of the anterior cruciate ligament. We evaluated the magnitude of the tensioning force (22 or 67 N), the flexion angle at which the tension was applied (extension or 30 degrees of flexion), and the direction of application of the tensioning force (proximal, distal, or distal with a posterior force simultaneously applied to the tibia) on 10 fresh cadaveric knees. The anterior cruciate ligament was reconstructed using a bone-patellar tendon-bone graft. The graft was then temporarily fixed during the application of each of 12 combinations of tensioning variables listed above. After each fixation, graft force and joint motion were measured during anterior tibial loads. Tensioning direction and the flexion angle significantly affected graft force and joint motion, while the magnitude of the graft tensioning did not. Graft forces were greater when the tensioning was applied at 30 degrees of flexion. Compared with distal tensioning with and without posterior tibial force, graft forces with proximal tensioning were greater in extension and lower in flexion. The position of the tibia relative to the femur was posterior and externally rotated, compared with normal, for all combinations of tensioning variables in both unloaded and anterior load states.

Anterior Cruciate Ligament↗
PubMedDate not supplied

The effects of grade III posterolateral knee complex injuries on anterior cruciate ligament graft force. A biomechanical analysis.

To determine if untreated grade III injuries of the posterolateral structures contribute to increased force on an anterior cruciate ligament graft, we measured the force in the graft in cadaveric knees during joint loading after reconstruction with otherwise intact structures and in the same reconstructed knees after selected cutting of specific posterolateral knee structures. Tests were first performed on the knee with the posterolateral structures intact and then after sequential sectioning of the fibular collateral ligament, popliteofibular ligament, and popliteus tendon. The graft force was significantly higher after fibular collateral ligament transection during varus loading at both 0 degree and 30 degrees of knee flexion than it was for the same loading of the joint with intact posterolateral structures. In addition, coupled loading of varus and internal rotation moments at 0 degree and 30 degrees of flexion further increased graft force beyond that with varus force alone. The increase in graft force remained significant with additional sequential cutting of the popliteofibular ligament and popliteus tendon. We believe this study supports the clinical observation that untreated grade III posterolateral structure injuries contribute to anterior cruciate ligament graft failure by allowing higher forces to stress the graft.

Anterior Cruciate Ligament↗
PubMedDate not supplied

Noncontact anterior cruciate ligament injuries: risk factors and prevention strategies.

An estimated 80,000 anterior cruciate ligament (ACL) tears occur annually in the United States. The highest incidence is in individuals 15 to 25 years old who participate in pivoting sports. With an estimated cost for these injuries of almost a billion dollars per year, the ability to identify risk factors and develop prevention strategies has widespread health and fiscal importance. Seventy percent of ACL injuries occur in noncontact situations. The risk factors for non-contact ACL injuries fall into four distinct categories: environmental, anatomic, hormonal, and biomechanical. Early data on existing neuromuscular training programs suggest that enhancing body control may decrease ACL injuries in women. Further investigation is needed prior to instituting prevention programs related to the other risk factors.

Adult↗
PubMedDate not supplied

Phantom stock dividend plan.

The Phantom Stock Dividend Plan is a method of sharing net profits with staff in the same way a stock holder in a company receives periodic dividends. The purposes of the plan are to reward the staff for creative talents and recommendations for improvements; to involve the staff in the concept of being partially responsible for increased profitability of the practice; to encourage long-term employment; and to base increases in staff remuneration on profits rather than simply on seniority. An example of the plan is presented which can be modified to fit different practice situations.

Dental Staff↗
PubMedDate not supplied

Intraperitoneal therapy in the management of ovarian carcinoma.

The intraperitoneal administration of chemotherapeutic and biological agents as therapy of ovarian carcinoma is based on both theoretical considerations and experimental evaluations which suggest that tumor present in the cavity can be exposed to higher concentrations of certain antineoplastic drugs than can be accomplished if the agents are administered systemically. Recent clinical data have confirmed both the safety and pharmacokinetic advantage associated with this approach. Surgically defined responses have been observed in patients with small-volume residual refractory ovarian carcinoma treated with several single-agent and combination intraperitoneal therapeutic programs. While significant activity has been noted in this clinical setting, a clearly defined role for intraperitoneal treatment in the standard management of ovarian carcinoma remains to be determined.

Antineoplastic Agents↗
PubMedDate not supplied

Determination of nicarbazin in chicken tissues by liquid chromatography and confirmation of identity by thermospray liquid chromatography/mass spectrometry.

A liquid chromatographic method is described for the quantitative measurement of nicarbazin in chicken liver, fat, muscle, and skin tissues. The 4,4'-dinitrocarbanilide (DNC) portion of nicarbazin is extracted from tissues with ethyl acetate. After filtration and evaporation, the extract is purified by liquid-liquid partitioning with acetonitrile-hexane and alumina cartridge chromatography. DNC is separated and measured by reverse-phase liquid chromatography (RP-LC) with an octadecylsilyl (ODS) column and a UV detector set at 340 nm. The overall average recovery of DNC added to tissues was 83.4 +/- 3.1%. The lowest level validated in tissues by this procedure was 0.10 ppm. The limit of detection was estimated to be 0.020 ppm. This method provides a sensitive, selective, rapid, and reproducible alternative to existing purification, separation, and detection techniques, such as differential pulse polarography and colorimetry, for determination of nicarbazin in chicken tissues. Identity of DNC is confirmed by subjecting the purified extracts to thermospray-LC/mass spectrometric analysis using negative-ion detection and selected ion monitoring. Three structural-indicating ions at m/z 302, 272, and 164 are monitored in the thermospray-mass spectrum which are characteristic of the DNC molecule.

Animals↗