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Biomedical subjects

F R Noyes

Publications and source records attributed to F R Noyes.

At least 37 records · Page 2Linked to original sources
PubMed1996

Technical considerations in the management of complex meniscus tears.

Meniscal repair continues to be an important procedure in patients with meniscal tears. The orthopedic literature has recommended excision of complex tears or tears that are located in the central avascular region. For the past 13 years, the authors have repaired all meniscal tears that can be reduced anatomically and that have healthy tissue that will support the multiple sutures required for a stable repair, regardless of tear pattern or location. Correct patient selection criteria continue to be important. In all cases, the risks of complications and retear must be considered carefully and judged against the potential benefits of repair. A postoperative rehabilitation program that allows early range of motion, and progression of weight bearing is not detrimental to the healing process if the repair is stable. Close postoperative follow-up examinations are necessary to determine the incidence of meniscal symptoms; however, the absence of joint line pain, catching, locking, or effusion does not guarantee complete healing of the tear. Follow-up arthroscopy is currently the most accurate method to determine if complete or partial healing has occurred.

Adolescent↗
PubMed1996

Posterior cruciate ligament anatomy and length-tension behavior of PCL surface fibers.

The location of the most nearly isometric region of the PCL has remained a controversial issue. Our data indicate that there is an entire region close to the PCL's proximal edge that is isometric; however, the majority of the PCL is anisometric. This concurs with the work of Grood et al, Ogata and McCarthy, and Sidles et al. However, other authors believe that the posterior-proximal region of the PCL contains the most isometric fibers. These differences could be explained in part through the differences in experimental design. It is important to note that all of these studies placed the most nearly isometric area within the substance of the ligament. What is equally important to understand from all of these studies is the complex length change pattern of fibers comprising the PCL. The function of PCL fibers is not accurately described by the traditional model of an anterolateral bundle and a posteromedial bundle that have reciprocal functions. Further kinematic studies testing potential femoral attachment sites are needed to ascertain the optimal placement for PCL graft substitutes. An earlier study performed in our laboratory suggested that PCl graft placement distal to the isometric region, 4 mm from the proximal edge (within the PCL footprint), provided the most optimal position for correcting abnormal posterior translation after PCL division. We reported that isometric placement at the time of surgery would lead to incorrect positioning of the graft. We are currently investigating alternative graft configurations (eg, two-bundle and multiple-bundle grafts) to determine if PCL function can be reproduced more ideally; however, more analysis is required before definitive recommendations can be made. At present, the ideal operative procedure for PCL reconstruction requires continued biomechanical analysis followed by carefully designed clinical trials.

Humans↗
PubMed1994

The effects of 4 Mrad of gamma irradiation on the initial mechanical properties of bone-patellar tendon-bone grafts.

Pairs of frozen human patellar tendon-bone (PTB) ligament allografts were exposed to either 0 or 4 Mrad of gamma irradiation sterilization, the latter value based on recent reports suggesting higher dosage levels for adequate sterilization against the human immunodeficiency virus. All specimens were subjected to three levels of loading: lower functional loads, higher functional loads, and failure. Lower functional loads were simulated by performing in vitro static and cyclic creep tests, similar to loads that the surgeon and patient would apply before and after implantation, respectively. Higher functional loads, simulating moderate activities of daily living, were represented by the slope of the linear portion of the force-elongation curve or linear stiffness. Failure or trauma was then simulated by failing the grafts in tension at a high strain rate. We found that the irradiation treatment shortened the tendon by only 0.6 mm, which was nevertheless statistically significant (p < 0.01). By contrast, 4 Mrad did not significantly alter either static or cyclic creep (p > 0.05) at lower functional loads. Instead, irradiation produced the greatest changes during failure testing, reducing both the graft's linear stiffness by 12% (p < 0.025) and maximum force by 26% (p < 0.001). Although our data do not describe how an allograft might perform during the early healing and later collagen-remodelling phases, such in vitro studies remain important if we are to optimize allograft properties before arthroscopic anterior and posterior cruciate ligament reconstruction.

Adult↗
PubMed1994

Posterior cruciate ligament allograft reconstruction with and without a ligament augmentation device.

Twenty-five patients with posterior cruciate ligament ruptures were treated with either allograft reconstruction alone (10 patients) or with an allograft-ligament augmentation device composite (15 patients). At follow-up (mean 45 months) the results were assessed with the Cincinnati Knee Rating System. There were no significant differences between the two groups for symptoms, functional limitations, sports activity levels, or the overall rating score. The ligament augmentation device provided no benefit. In both groups, the allograft and the allograft composite restored posterior stability at lower functional knee flexion angles, but not uniformly at higher flexion angles (70 degrees). Patients with acute ruptures faired significantly better than did those with chronic ruptures because they had lower anterior-posterior displacements and fewer symptoms and functional limitations. We recommend consideration of early arthroscopic posterior cruciate ligament reconstruction for acute ruptures in active patients. An immediate knee motion program was not deleterious to graft fixation and is recommended.

Acute Disease↗
PubMed1994

Use of allografts after failed treatment of rupture of the anterior cruciate ligament.

A prospective study was done of the use of allogeneic tissue to reconstruct the anterior cruciate ligament in knees in which an intra-articular or an extra-articular operation had failed. Sixty-six consecutive patients (sixty-six knees) had such an operation with use of bone-patellar ligament-bone allografts; all but one returned for follow-up evaluation twenty-three to seventy-eight months (mean, forty-two months) after the operation. A total of 235 previous operations had been performed in these sixty-six knees, including eighty-one procedures for rupture of the anterior cruciate ligament. The results of the allograft procedure were evaluated with a subjective and objective system that rated twenty factors. The anterior-posterior displacement was substantially improved in most of the patients. According to data derived from arthrometric studies and pivot-shift tests of the fifty-seven patients who were so evaluated and in whom the condition was unilateral, 53 per cent (thirty) of the reconstructed ligaments were determined to be functional; 21 per cent (twelve ligaments), partially functional; and 26 per cent (fifteen ligaments), a failure. When we calculated the rate of failure by including ten failures that had occurred within two years after the operation with the fifteen that occurred in patients who had been followed for at least two years, the over-all rate of failure was 33 per cent (twenty-five of seventy-five operations). There was significant improvement in the subjective ratings of functional limitations and symptoms (p < 0.01) and in the over-all rating score (p < 0.0001). However, there was a significant difference between the scores of the patients in whom the surfaces of the articular cartilage had appeared normal at the index operation and those of the patients in whom there had been noteworthy fissuring and fragmentation or exposure of subchondral bone. After the program of rehabilitation, which included immediate motion of the knee, a range of motion of 0 to 135 degrees was restored in all but five knees, four of which lacked only 5 degrees of this extent of flexion or extension. The results demonstrate that bone-patellar ligament-bone allografts may be used when proper autogenous tissues are not available and that symptoms and abnormal displacement were reduced in most of our patients.

Activities of Daily Living↗
PubMed1992

The correlation between anterior-posterior translation and cross-sectional area of anterior cruciate ligament reconstructions.

Total anterior-posterior translation is commonly used to assess the integrity of the cruciate ligaments and the success of reconstructive surgery. The purpose of this study was to determine, after surgical reconstruction of the anterior cruciate ligament with a biological graft, if total anterior-posterior translation correlated with graft length, cross-sectional area, or mechanical properties. These factors were investigated by analyzing data from three previous studies. These studies involved replacement of the anterior cruciate ligament in cynomolgus monkeys and goats, with free and vascularized patellar tendon autografts and both patellar tendon and anterior cruciate ligament allografts. Data were available at time periods of 6 and 12 months after surgery. We found statistically significant inverse correlations between the amount of anterior-posterior translation and cross-sectional area of a graft at the time of sacrifice. The Pearson correlation coefficients ranged from -0.966 (p < 0.002) to -0.830 (p < 0.05). We hypothesize that these correlations result from the following mechanism: the increased anterior translation reflects a slack graft; a slack graft is stress shielded by other structures about the knee; the reduced in vivo stresses on the graft modulate cellular metabolism in a way that over time produces a small cross-sectional area.

Analysis of Variance↗
PubMed1992

Cystic degeneration of the patella after arthroscopic chondroplasty and subchondral bone perforation.

Chondromalacia of the patella is frequently encountered in patients with anterior knee pain. Arthroscopic chondroplasty with perforation of subchondral bone remains a popular treatment alternative in spite of the inferior mechanical properties of the fibrocartilaginous tissue that this procedure is designed to promote. We report a case of cystic degeneration of the patella as a previously unrecognized complication following the procedure.

Adult↗
PubMed1992

Posterior tibial subluxation of the posterior cruciate-deficient knee.

Ten subjects with unilateral posterior cruciate ligament-deficient knees were studied, comparing the knee mechanics of the affected knee with the mechanics of the opposite normal knee. The static squat test was used to determine knee forces and moments through measurements made on roentgenograms. Statistically significant increases occurred in posterior translation of the tibia in all knees at high knee flexion angles, but not uniformly at low knee flexion angles. The results suggest that posterior tibial subluxation occurs in vivo during certain activities of daily living. Posterior tibial subluxation occurred in positions of knee flexion near 70 degrees, establishing a new equilibrium for the system where tibiofemoral joint compression force (approximately four times one-half body weight) remained an order of magnitude greater than tibiofemoral shear forces (approximately 10% of one-half body weight).

Adolescent↗