Search PubMed⌕ Search

Biomedical subjects

L Good

Publications and source records attributed to L Good.

47 records · Page 3Linked to original sources
PubMed1993

Load and length changes in an artificial ligament substitute. 10 cases of anterior cruciate ligament reconstruction.

In 10 patients who had reconstruction of the anterior cruciate ligament, the load and length changes in an artificial ligament substitute were measured during passive knee motion. Using a special drill guide, the ligament was placed within +/- 2 mm of the normal anatomic center on the femur. With the femoral end fixed with a bicortical screw the ligament was preloaded to 40 N at the flexion angle with the shortest intraarticular ligament length, usually 45 degrees. The change in load was then registered from 90 degrees of flexion to full extension. In 2/10 cases loads of > 200 N were registered in full extension, but the mean load was 160 N. There was a higher loss of load during the first extension/flexion cycle than during the 4th cycle. The load change correlated to the length change, but the degree of length change could not predict the maximum load level. There was a large variation in load levels between different knees, even with similar ligament placements, but the least change in load and length was obtained by an anatomic placement. Isometer readings did not predict the load level in the ligament substitute, but could indicate the angle of flexion with minimum load. Therefore, the isometer can be used to control the placement of the attachment points for the substitute. After fixation, fiber settling and stretching the ligament, as well as adaptation of the tissues, will tend to reduce the load levels.

Adult↗
PubMed1991

Intercondylar notch measurements with special reference to anterior cruciate ligament surgery.

The femoral intercondylar notch width was measured in 93 patients with chronic anterior cruciate ligament (ACL) insufficiency (Group 1), in 62 patients with an acute tear of the ACL (Group 2), and in 38 fresh anatomic specimen knees (Group 3). In six of the specimen knees, further anatomic studies of the intercondylar notch were performed after tissue removal. The average intercondylar distance was 16.1 mm in Group 1, 18.1 mm in Group 2, and 20.4 mm in Group 3. All differences were highly significant. The intercondylar notch was wider in the posterior part and had no crossing bony ridges but had generally concave walls, which provided a functional shelf for the ACL to insert on the lateral side. Significant osteophyte formation and stenosis of the anterior outlet of the intercondylar notch occur early in the ACL-deficient knee. A narrow anterior outlet of the intercondylar notch without osteophytes was also found in knees with an acute ACL rupture. At reconstruction of the ACL, notchplasty should be performed concomitantly.

Anterior Cruciate Ligament↗
PubMed1990

Load tolerance, security, and failure modes of fixation devices for synthetic knee ligaments.

One weak link in synthetic ligament reconstruction of the knee is the fixation device-ligament-bone interface. In this study, a laboratory model using bovine calf bone was designed to evaluate six different fixation devices combined with either an unlooped ligament in different configurations or a looped ligament. Results are expressed in terms of maximum load to failure, elongation at the site of fixation, stiffness of fixation prior to failure, and mode of failure. When failure of the test model occurred, it was always at the ligament--fixation device interface, the fixation device--bone interface, or a combination of the two. Elongation was recorded in all modes of fixation. The most secure fixation was obtained with a cortical screw and a looped ligament, the strength and predictability being mainly dependent on bone quality. The least secure and least predictable fixation was obtained with a prototype called bucket wedge. A barbed ligament staple and an unlooped ligament also had low predictability and considerably less strength than the screw fixation but showed less sensitivity to alterations in bone quality.

Animals↗
PubMed1989

Failure of a bovine xenograft for reconstruction of the anterior cruciate ligament.

Fourteen patients with gross anterior instability had the anterior cruciate ligament reconstructed with a bovine xenograft. Major problems with swelling, pain, and synovitis were encountered in 13 patients, of whom 3 developed a synovial fistula. Histologic evidence for allergic reactions was found in 3 patients. Revisional surgery had to be performed in 10 patients because of substantial problems or rupture of the graft. At 3 years, there was only one possibly functioning graft. The 3 nonrevised patients were unstable at clinical examination. This type of reconstruction cannot be recommended for clinical use.

Adolescent↗
PubMed1989

Surgical or non-surgical treatment of acute rupture of the anterior cruciate ligament. A randomized study with long-term follow-up.

One hundred and eleven consecutive patients who had acute injuries to the knee that included rupture of the anterior cruciate ligament, as shown by physical examination with the patient under anesthesia and by diagnostic arthroscopy, were randomized to three treatment groups: simple repair of all injured structures, repair of all injured structures and augmentation of the anterior cruciate ligament with a strip of the iliotibial band, and repair of all injured structures except the anterior cruciate ligament. In all other respects, the knees were treated in an identical fashion. Of the 111 patients, 107 were re-examined forty-five months or more after operation. At the most recent follow-up, the knees that had been treated by repair and augmentation of the anterior cruciate ligament were significantly more stable and had had significantly fewer subsequent meniscal tears. Sufficient instability to necessitate late reconstruction was also less frequent in the patients who had had an augmented repair. These patients had better function of the knee and a higher level of activity than the patients in the other two groups. Sixty-four per cent of these patients who had a rupture of the anterior cruciate also had a meniscal tear, and primary care was indicated for more than 50 per cent of the tears. Therefore, we believe that early arthroscopic examination is essential for patients who have an acute rupture of the anterior cruciate ligament.

Adolescent↗
PubMed1987

Precision in reconstruction of the anterior cruciate ligament. A new positioning device compared with hand drilling.

To evaluate the precision of a drill guide for use in anterior cruciate ligament reconstruction and the reproducibility of the results, the device was tested in 30 operations (Group 1); 17 operations were done freehand (Group 2); 10 cadaver knees served as anatomic controls. The internal orifices of the bony channels in Groups 1 and 2 and the central point of the anterior cruciate ligament attachments in the cadaver group were identified on lateral radiographic views. The position of the tibial ligament attachments in the cadaver group did not differ from the orifices of the drilled channels in Groups 1 and 2. The position of the femoral attachments in the cadaver group did not differ from the orifices of the drilled channels in Group 1, but between the cadaver group and Group 2, and Groups 1 and 2, the positions of the femoral attachments differed. The hand-drilled channels were generally located too far anteriorly, and the scatter of the attachments was 1.8 times greater. The drill guide enables reproducible anatomic positioning of an anterior cruciate ligament graft.

Adult↗
PubMed1984

Some simple computational methods to improve the folding of large RNAs.

Computational methods are described which increase the efficiency of the RNA folding algorithm described by Zuker and Stiegler. Bit addressing has been used to reduce the memory requirements from 2NxN to NxN/2. The order in which the nucleotide sequence is examined internally has been altered, and some additional short arrays which carry temporary information have been introduced. These changes optimize the management of the large data arrays generated by the algorithm. The methods were developed for use with a UNIVAC 1100/82 computer. They are, however, easily adaptable to other computers; especially those with virtual memory capabilities. The analysis of sequences up to 1000 nucleotides long are relatively routine, and larger searches are also feasible. Some limitations and applications of the algorithm are also discussed.

Base Sequence↗
PubMedDate not supplied

Postural control after anterior cruciate ligament reconstruction and functional rehabilitation.

Total sagittal knee laxity and postural control in the sagittal and frontal planes were measured in 25 patients at a mean of 36 months (range, 27 to 44) after anterior cruciate ligament reconstruction and in a control group consisting of 20 uninjured age- and activity-matched subjects. Body sway was measured in the sagittal plane on a stable and on a sway-referenced force plate in single-legged stance, double-legged stance, or both, with the eyes open and closed. Postural reactions to perturbations in the sagittal and frontal planes were recorded in the single-legged stance with the eyes open. Total sagittal plane laxity was significantly greater in the anterior cruciate ligament-reconstructed knee (11.2 mm; range, 6 to 15) than in the uninjured knee (8.9 mm; range, 6 to 12) or in the control group (6.0 mm; range, 5 to 8). In spite of this, the patients, in comparison with the controls, exhibited normal postural control except in two variables-the reaction time and the latency between the start of force movement to maximal sway in the sagittal plane perturbations. This supports the hypothesis that rehabilitation, with proprioceptive and agility training, is an important component in restoring the functional stability in the anterior cruciate ligament-reconstructed knee.

Adolescent↗
PubMedDate not supplied

Sagittal knee stability after anterior cruciate ligament reconstruction with a patellar tendon strip. A two-year follow-up study.

Tibial anteroposterior displacement after anterior cruciate ligament reconstruction with a patellar tendon graft was followed prospectively for 2 years in 24 patients with an arthrometer. The femoral ligament insertion location, in a lateral projection, and the change in intraarticular fixation distance, measured with an isometer, were documented intraoperatively. Two years after surgery, the overall mean injured-noninjured difference in anteroposterior displacement was 2.0 +/- 2.3 mm. All grafts were fixed during surgery at 20 degrees of knee flexion. Patients for whom this angle coincided with the angle of minimum intraarticular fixation distance (Group I), and patients who had a femoral ligament insertion location > 2 mm anterior to the center of the normal anterior cruciate ligament attachment (Group A) showed larger tibial displacement than the other patients. An injured-noninjured difference in tibial anteroposterior displacement > or = 3 mm was classified as failure. Groups I and A failure rates were higher than for the other patients. No correlation was found between anteroposterior displacement and magnitude of the change in intraarticular fixation distance. We conclude that anterior femoral locations lead to larger sagittal play after 2 years than central or posterior locations and that the magnitude of the fixation distance is less important than the pattern.

Adult↗