Biomedical subjects

E S Grood

Publications and source records attributed to E S Grood.

82 records · Page 5Linked to original sources

PubMedDate not supplied

Reproducibility of the knee signature system.

To assess trial-to-trial, installation-to-installation, and day-to-day effects of the Knee Signature System, we studied anterior/posterior translation measurements in six normal subjects. The protocol consisted of testing both knees on 6 days with three installations per day and three trials per installation. We recorded anterior, posterior, and total anterior/posterior translation at +/- 20 and +/- 40 pounds of force at 30 degrees of flexion. Additionally, after measuring anterior/posterior translation during passive knee extension, active extension, and active extension with 15 pounds of weight at the ankle, we calculated the difference in anterior translation at 30 degrees of flexion between each of these three conditions. We analyzed the size of the effects and computed 90% confidence limits using analysis of variance. Means and 90% confidence limits for total anterior/posterior translation measured at +/- 20 pounds of force were: right knee, 6.8 +/- 2.3; left knee, 8.2 +/- 2.0; and right/left difference, 1.5 +/- 2.7 mm. Left knee translation means were significantly greater than right knee means in all tests. Day-to-day effects, while statistically significant for right and left knee measurements, showed no significant effects for right/left differences. Trial-to-trial and installation-to-installation effects were not significant for any parameter. Right/left differences during knee extension testing were smaller than for the stress test, measuring 0.1 mm or less, but confidence limits were larger, being +/- 3.7 mm for active extension-passive knee extension, +/- 1.5 mm for 15 pounds of weight at the ankle-active extension, and +/- 4.6 mm for 15 pounds of weight at the ankle-passive knee extension. Active extension produced 6.3 mm more anterior translation at 30 degrees of flexion than passive extension.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMedDate not supplied

A comparison of patellar tendon autograft and allograft used for anterior cruciate ligament reconstruction in the goat model.

Similar-sized patellar tendon autografts and fresh-frozen allografts were used to reconstruct the anterior cruciate ligament of one knee in 40 female goats. Evaluations of the reconstructions and contralateral controls at the 6-week and 6-month postoperative periods included anterior-posterior translation, mechanical properties determined during tensile failure tests, measurement of cross-sectional area, histology, collagen fibril size and area distribution, and associated articular cartilage degenerative changes. Six months after anterior cruciate ligament reconstruction, the autografts demonstrated a smaller increase in anterior-posterior displacement, values of maximum force to failure two times greater, a significant increase in cross-sectional area, a more rapid loss of large-diameter collagen fibrils, and an increased density and number of small-diameter collagen fibrils compared to the allografts. Clinical significance. More surgeons are allowing their patients to return to running and sports 6 months after anterior cruciate ligament reconstruction. While the structural and material properties of autografts and allografts at time zero are similar, in the goat model during the first 6 months they differ. The allografts demonstrate a greater decrease in their implantation structural properties, a slower rate of biologic incorporation, and the prolonged presence of an inflammatory response. At 6 months the autograft demonstrates a more robust biologic response, improved stability, and increased strength to failure values.

Animals↗

PubMedDate not supplied

The role of the lateral extraarticular restraints in the anterior cruciate ligament-deficient knee.

We measured the increases in tibiofemoral motion when lateral structures were sectioned in anterior cruciate ligament-deficient knees of 20 unembalmed cadaveric whole lower limbs. Motion was measured with a six degrees-of-freedom electrogoniometer. The lateral structures investigated were the iliotibial band and mid-lateral capsule, lateral collateral ligament, and popliteus tendon and the posterolateral capsule. Cutting the anterolateral structures increased anterior translation and internal rotation, particularly in flexion. Increases in motions were highly variable, reflecting the variation in function in the lateral collateral ligament and posterolateral structures. Cutting the lateral collateral ligament produced small changes in anterior translation and external rotation and larger increases in adduction. Cutting the posterolateral structures produced small increases in external rotation. Large increases in external rotation were found only if the lateral collateral ligament was also sectioned. The posterolateral structures act in concert with the lateral collateral ligament in restraining internal and external rotation. External rotation was affected at all flexion angles; internal rotation was affected mainly in extension. Our results can be used in the diagnosis of complex knee ligament injuries. Findings of increased anterior translation in both flexion and extension and increased internal rotation at 90 degrees of flexion are consistent with combined injury to the anterior cruciate ligament and the anterolateral structures. The anterior cruciate ligament-deficient knee with significant posterolateral compromise (posterolateral structures/lateral collateral ligament) would exhibit larger anterior translation in extension than in flexion, increased adduction, and increased external rotation in both flexion and extension.

Adult↗

PubMedDate not supplied

Posterior subluxations of the medial and lateral tibiofemoral compartments. An in vitro ligament sectioning study in cadaveric knees.

We report for the first time the abnormal increases in posterior subluxation of the medial and lateral tibial plateaus after sectioning the posterolateral structures and posterior cruciate ligament. We applied specific forces and moments to the knees of seven cadaveric whole lower limbs and measured the position of the tibia at which the ligaments and the geometry of the joint limited motion. Removal of only the posterolateral structures resulted in an average increase in posterior translation of the lateral tibial plateau of 8.0 mm (range, 5.7 to 10.6) at 30 degrees of flexion over the intact state (P < 0.01), but no significant increase at 90 degrees of flexion (mean, 2.7 mm). Knees with underlying physiologic cruciate ligament laxity (high anterior/posterior displacement in the intact knee) had the greatest lateral tibial plateau subluxation (P < 0.01). There was no abnormal posterior translation of the medial tibial plateau. After sectioning the posterior cruciate ligament and the posterolateral structures, statistically significant increases in posterior translation of both the medial and lateral tibial plateaus occurred at 30 degrees and 90 degrees of flexion (P < 0.01). The increase in posterior translation of the lateral tibial plateau over the intact state averaged 17.8 and 23.5 mm at 30 degrees and 90 degrees of flexion, respectively; for the medial tibial plateau this increase averaged 7.6 and 12.3 mm at 30 degrees and 90 degrees of flexion, respectively. The diagnosis of abnormal tibiofemoral rotatory subluxations requires knowledge of the anteroposterior direction and magnitude of each tibial plateau under both low flexion and high flexion knee angle positions.

Adult↗

PubMedDate not supplied

Role of the medial structures in the intact and anterior cruciate ligament-deficient knee. Limits of motion in the human knee.

We measured motion limits in human cadaveric knees before and after sectioning the anterior cruciate ligament and the medial structures. Sectioning the medial collateral ligament in an anterior cruciate ligament-deficient knee increased the anterior translation limit at 90 degrees of flexion but not at 30 degrees of flexion. The tibia displaced straight anteriorly without exhibiting the coupled internal rotation that occurred in intact and anterior cruciate ligament-deficient knees. A lateral 15 N-m abduction moment produced a coupled external rotation in the medial collateral ligament-deficient knee. This was in marked contrast to intact, anterior cruciate ligament-deficient, or combined medial collateral ligament and anterior cruciate ligament-deficient knees, in which an abduction moment produced a coupled internal rotation. Sectioning only the medial collateral ligament caused a small but significant increase in the abduction rotation limit, whereas larger increases in the abduction rotation limit occurred when the posterior oblique ligament and posterior medial capsule were cut in addition to the medial collateral ligament. Cutting the medial collateral ligament increased the external rotation limit. The increase was independent of whether the anterior cruciate ligament was intact or sectioned. Subsequent cutting of the posterior oblique ligament and posterior medial capsule further increased the external rotation limit.

Adult↗

PubMedDate not supplied

Posterior cruciate ligament reconstruction. An in vitro study of femoral and tibial graft placement.

We studied posterior cruciate ligament reconstruction in a cadaveric model using two substitutes: a 1-mm diameter flexible cable and an 11-mm diameter Achilles tendon autograft. The thin cable allowed us to study five femoral and five tibial attachments in each knee. A nearly isometric attachment was located after cutting the posterior cruciate ligament while the tibia was reduced with a 100 N anterior force. The five femoral locations studied were the isometric location and four locations centered around this isometric point. The Achilles tendon reconstruction was used with both an isometric and a nonisometric femoral site, allowing us to confirm the results with the wire cable. Posterior motion limits were measured under a 100 N posterior force in the intact, posterior cruciate ligament-deficient, and posterior cruciate ligament-reconstructed knees. We found that the restoration of knee stability in flexion depended strongly on the femoral attachment location. A femoral attachment that was nonisometric by intraoperative measurement, but within the posterior cruciate ligament anatomic footprint, most closely reproduced the intact knee's posterior motion limits. Variations in the tibial attachment site produced only minor changes in the posterior motion limits. We concluded that the proximal-distal location selected for the femoral attachment of a posterior cruciate ligament substitute was particularly important in the restoration of normal posterior motion limits.

Achilles Tendon↗

PubMedDate not supplied

Effect of intra-articular corticosteroids on ligament properties: a biomechanical and histological study in rhesus knees.

The effect of intra-articular corticosteroid injections (methylprednisolone acetate) on the mechanical properties of anterior cruciate bone-ligament-bone units was determined. Fifty-one wild rhesus animals provided 88 knee ligaments units that were loaded in tension to failure under fast strain-rate conditions. Alterations in ligament strength and load-elongation properties were found to depend upon corticosteroid dosage and time after injection. Fifteen weeks after the higher drug dosage (methylprednisolone acetate, 6 mg/kg; three injections, spaced weekly) significant decreases occurred in the maximum failure load (20%), energy absorption prior to failure (11%) and linear stiffness (11%) of the ligament unit. In contrast, only minimal non-significant alterations in ligament strength properties occurred at the higher drug usage after 6 weeks in a second group of animals. this strong time-dependence may partially explain the negative findings reported in short term studies. The higher drug dosage used is approximately 10 times an equivalent human dose on a body mass basis and indicates the ability of this class of drugs to significantly alter the mechanical properties of a ligament unity. A third group of animals received a total of two intra-articular coticosteroid injections (single injections spaced two weeks apart) at a dosage (0.6 mg/kg) equivalent to that commonly used clinically in humans. Statistically significant decreases occurred in maximum failure load (9%) and energy absorption (8%); however, this change is believed of little importance to the projected functional capacity of the ligament unit. No detectable systemic effect of the intra-articular corticosteroid injections was found on the mechanical properties of the ligament unit in the extremity opposite to that which received the drug injection. Histological examination after failure showed normal cellularity and staining characteristics of the ligament, fibrocartilage junction and underlying bone. No bone resorptive changes were observed beneath the ligament insertion site. Failure by a ligamentous mode remained the most common mechanism of specimen failure. Scanning Electron Microscopy showed failure of collagen fibers at multiple levels throughout the ligament indicative of a serial pull-apart failure process. A rich supply of vessels to the anterior cruciate ligament was demonstrated and failure of the vessels occured by a necking down process. Insofar as the results apply to humans, they infer the potential for high and frequent doses of intra-articular slightly soluble corticosteroids to produce alterations in ligament strength and function. A single intra-articular injection or one repeated at intervals of several months probably carries little risk to ligament properties.

Adrenal Cortex Hormones↗

PubMedDate not supplied

Intra-articular cruciate reconstruction. I: Perspectives on graft strength, vascularization, and immediate motion after replacement.

All of the factors discussed here hopefully will increase the success rate of future intra-articular grafts. But it should not be supposed that the ideal ACL substitution answer is immediately forthcoming. Past experience points to the inherent difficulty of any potential solution and the need to progress in a rigorous scientific manner in the evaluation of the next wave of ligament substitutes. This article reports the utilization of an immediate protective motion program to avoid the problems of postoperative stiffness and lack of knee extension. It can not be stated with certainly whether the same program can be applied to free grafts or to those obtained from other sites. However, the avoidance of these problems will significantly lessen the morbidity of intra-articular reconstruction. The utilization of a vascularized patellar tendon hopefully will add another dimension to ACL replacement.

Bone Transplantation↗

PubMedDate not supplied

Intra-articular cruciate reconstruction. II: Replacement with vascularized patellar tendon.

The patellar tendon offers a number of advantages (strength, location, bone-to-bone fixation, vascularity) as a tissue for intra-articular cruciate ligament reconstruction. The critical factor is to preserve the vascularity, thereby maintaining tendon viability and facilitating tissue remodeling. Laboratory studies on human cadaver knees were conducted to define the blood supply to the patella, and vascularity was assessed by blood flow studies in three animal species, including nonhuman primates. In humans, the patellar ligament receives blood anteriorly from the retinaculum and posteriorly from the fat pad, which is relatively smaller and less adherent than the fat pad in other animals. The medial third of the patellar tendon and its contiguous neurovascular pedicle were used in a vascularized patellar tendon reconstruction procedure. During a period of three years, reconstruction with the vascularized patellar tendon was performed in more than 100 patients. Although only 35 patients have been followed up for more than two years, the clinical results are encouraging. At present, however, the technique is not recommended for general use; the surgical procedure is demanding, and the ultimate clinical results may not warrant the extra effort required to perform the surgery as well as commit the patient to a long rehabilitation program.

Humans↗

PubMedDate not supplied

Clinical laxity tests and functional stability of the knee: biomechanical concepts.

Biomechanical studies show one or 2 ligaments provide the primary passive restraint for each plane of knee stability with the remaining ligaments having a secondary helping role. Correct interpretation of clinical laxity tests and surgical treatment of instability requires this subdivision. Functional stability of the knee is a primary treatment goal after ligament injury, but is too often short-term, relying on muscle control alone without the fine-tuning action of the ligamentous system. If there is abnormal laxity on the clinical examination, there is an increased risk for joint wear, cartilage deterioration and arthritis on a long-term basis.

Biomechanical Phenomena↗