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A bioresorbable, mono-crystalline magnesium (Mg) ring device and suture implantation technique were designed to connect the ends of a transected anterior cruciate ligament (ACL) to restabilize the knee and load the ACL to prevent disuse atrophy of its insertion sites and facilitate its healing. To test its application, cadaveric goat stifle joints were evaluated using a robotic/universal force-moment sensor testing system in three states: Intact, ACL-deficient, and after Mg ring repair, at 30°, 60°, and 90° of joint flexion. Under a 67-N anterior tibial load simulating that used in clinical examinations, the corresponding anterior tibial translation (ATT) and in-situ forces in the ACL and medial meniscus for 0 and 100 N of axial compression were obtained and compared with a control group treated with suture repair. In all cases, Mg ring repair reduced the ATT by over 50% compared to the ACL-deficient joint, and in-situ forces in the ACL and medial meniscus were restored to near normal levels, showing significant improvement over suture repair. These findings suggest that Mg ring repair could successfully stabilize the joint and load the ACL immediately after surgery, laying the framework for future in vivo studies to assess its utility for ACL healing. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2001-2008, 2016.

Growth factors have been shown to play a critical role in enhancing tissue healing. In this study, we evaluate the effect of growth factors on cell proliferation and matrix synthesis. Fibroblasts were derived from medial collateral ligaments (MCLs) of goats and grown in culture. Basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF-BB), epidermal growth factor (EGF), and transforming growth factor ( TGF -β1) were used for the treatment of cells. It was found that bFGF, PDGF-BB and EGF significantly increased proliferation of the goat MCL fibroblasts. In addition, among these three growth factors, bFGF, at the concentration of 1.0 ng/ml, had the maximal effect on cell proliferation. Furthermore, both TGF -β1 and EGF significantly increased collagen and noncollagenous protein syntheses of goat MCL fibroblasts. The results of this study may be used as baseline data for the application of growth factors to enhance MCL healing in a goat model.

Most often we look at historic events through the lens of past achievements. The phrase - “The history books are written by the victors of wars” - applies as well to technologic innovation. Rarely do we look at the process of innovation prospectively.

The goal of this study was to determine the effects of peak knee valgus angle and peak knee abductor moment on the anterior, medial, and lateral tibial translations (ATT, MTT, LTT) in the "at risk" female knee during drop landing. Fifteen female subjects performed drop landings from 40 cm. Three-dimension knee motion was simultaneously recorded using a high speed, biplane fluoroscopy system, and a video-based motion analysis system. Valgus knee angles and knee abduction moments were stratified into low, intermediate, and high groups and peak ATT, MTT, and LTT were compared between these groups with ANOVA (α = 0.05). Significant differences were observed between stratified groups in peak knee valgus angle (p0.0001) and peak knee abduction moment (p0.0001). However, no corresponding differences in peak ATT, LTT, and MTT between groups exhibiting low to high-peak knee valgus angles (ATT: p = 0.80; LTT: p = 0.25; MTT: p = 0.72); or, in peak ATT (p = 0.61), LTT (p = 0.26) and MTT (p = 0.96) translations when stratified according to low to high knee abduction moments, were found. We conclude that the healthy female knee is tightly regulated with regard to translations even when motion analysis derived knee valgus angles and abduction moments are high.

The contribution of biomechanics to the advancement of management of ligament and tendon injuries has been significant. Thanks to Professor Y.C. Fung's writing and guidance, our field of research has done fundamental work on anatomy and biology of ligaments and tendons, developed methods to accurately determine mechanical properties, identified various experimental factors which could change the outcome measurements as well as examined biological factors that change tissue properties in-vivo. Professor Fung also gave us his quasi-linear viscoelastic theory for soft tissues so that the time and history dependent properties of ligaments and tendons could be properly described. We have further adopted Professor Fung's eight steps on methods of approach for biomechanical investigation to understand as well as enhance the treatment of ligament and tendon injuries during work or sports related activities. Examples on how to better treat the tears of the medial collateral ligament of the knee, as well as how to improve reconstruction procedures for the anterior cruciate ligament are presented in detail. Currently the use of functional tissue engineering for ligament and tendon healing is a topic of great interest. Here the use of biological scaffolds, such as porcine small intestinal submucosa, has shown promise. For the last 35 to 40 years, the field of biomechanics has made great strides in the treatment of ligament and tendon injuries, and many patients have benefited. The future is even brighter because of what has been done properly in the past. Exciting advances can be made in the field of tissue engineering through novel in-vitro culture and bioscaffold fabrication techniques. Recent technology can also allow the collection of in-vivo data so that ligament and tendon injuries can be better understood. Yet, solving new and more complex problems must still follow the stepwise methods of approach as taught by Professor Fung.

Optimal insertion of halo fixation pins to maximize the rigidity of the interface between the halo pins and the outer table of the skull is important in reducing the incidence of pin loosening. An in vitro biomechanical study was performed using cadaver skulls to investigate the effects of pin location on the rigidity of this pin-bone interface. Halo pins were inserted at nine positions within a recommended “safe zone” for pin insertion. It was found that the rigidity of the pinbone interface progressively decreased as pins were inserted more superiorly on the calvaria. The rigidity of the interface did not change significantly when the location of the pins was varied in the horizontal axis. This reduction in interface rigidity associated with inserting pins more superiorly on the skull may be related to an increase in the angle of insertion of the pins with respect to the surface of the calvaria. Based on this study, a change in the technique of halo pin insertion is recommended. Pins should be placed as inferiorly as possible, close to the supraorbital ridge, to achieve the most perpendicular angle of insertion and thus the most rigid fixation. The improved rigidity obtained with perpendicular pin insertion may minimize the rate of pin loosening and other complications associated with use of the halo orthosis. (Neurosurgery 26:238-241. 1990)

For years, bioengineers and orthopedic surgeons have applied the principles of biomechanics to gain valuable information about the complex function of the anterior cruciate ligament (ACL), as well as to improve the design of replacement grafts for ACL reconstruction. New experimental tools, such as robotic testing systems and mathematical models have been used to measure the multiple degree-of-freedom (DOF) knee kinematics, in situ forces, and biomechanical properties of the ACL. This manuscript will review specific examples of how biomechanics has impacted surgical reconstruction of the ACL by improving technical factors such as graft selection, tunnel placement, initial graft tension, graft fixation, and graft tunnel healing. Evolution of the single-bundle ACL reconstruction to the more anatomical double-bundle reconstruction will be featured. Finally, the future role of biomechanics to facilitate in vivo data for further improvement of ACL reconstruction will be discussed.

The measurement of anterior or posterior tibial translation depends on the existence of a repeatable and accurate reference position of the knee from which the corresponding translation is measured.Clinical measurements of posterior tibial translation alone do not accurately reflect the laxity of posterior cruciate ligament-reconstructed knees.Controlled laboratory study.Ten human cadaveric knees were tested by using a robotic/universal force-moment sensor testing system. The reference positions and the resulting kinematics in response to a 134-N anterior-posterior tibial load were determined for the intact and reconstructed knees. Posterior cruciate ligament reconstruction was performed with the graft tensioned and fixed at two different positions: 1) 90 degrees of knee flexion with a 134-N anterior tibial load and 2) full extension with no load.Posterior cruciate ligament reconstruction with graft fixation at full extension with no load resulted in anterior shift of the reference position by 1.5 to 3.2 mm. The reconstruction resulted in an overconstrained knee with significantly decreased total anterior-posterior translation of 2.6 to 3.2 mm. However, the posterior tibial translation measured was not significantly different from that of the intact knee. Posterior cruciate ligament reconstruction with graft fixation performed at 90 degrees of flexion with a 134-N anterior tibial load resulted in kinematics similar to those of the intact knee.Posterior tibial translations that are measured clinically can be misleading because the reference position of the knee can be shifted significantly after posterior cruciate ligament reconstruction.The measurement of total anterior-posterior translation may be a more accurate way to assess kinematics of the reconstructed knee.

To study how well an anterior cruciate ligament (ACL) graft fixed at the 10 and 11 o'clock positions can restore knee function in response to both externally applied anterior tibial and combined rotatory loads by comparing the biomechanical results with each other and with the intact knee.Biomechanical experiment using human cadaveric specimens.Ten human cadaveric knees (age, 41+/-13 years) were reconstructed by placing a bone-patellar tendon-bone graft at the 10 and 11 o'clock positions, in a randomized order, and then tested using a robotic/universal force-moment sensor testing system. Two external loading conditions were applied: (1) 134 N anterior tibial load with the knee at full extension, 15 degrees, 30 degrees, 60 degrees, and 90 degrees of flexion, and (2) a combined rotatory load of 10 N-m valgus and 5 N-m internal tibial torque with the knee at 15 degrees and 30 degrees of flexion. The resulting kinematics of the reconstructed knee and in situ forces in the ACL graft were determined for each femoral tunnel position.In response to a 134-N anterior tibial load, anterior tibial translation (ATT) for both femoral tunnel positions was not significantly different from the intact knee except at 90 degrees of knee flexion as well as at 60 degrees of knee flexion for the 10 o'clock position. There was no significant difference in the ATT between the 10 and 11 o'clock positions, except at 90 degrees of knee flexion. Under a combined rotatory load, however, the coupled ATT for the 11 o'clock position was approximately 130% of that for the intact knee at 15 degrees and 30 degrees of flexion. For the 10 o'clock position, the coupled ATT was not significantly different from the intact knee at 15 degrees of flexion and approximately 120% of that for the intact knee at 30 degrees of flexion. Coupled ATT for the 10 o'clock position was significantly smaller than for the 11 o'clock position at 15 degrees and 30 degrees of flexion. The in situ force in the ACL graft was also significantly higher for the 10 o'clock position than the 11 o'clock position at 30 degrees of flexion in response to the same loading condition (70 +/- 18 N v 60 +/- 15 N, respectively).The 10 o'clock position more effectively resists rotatory loads when compared with the 11 o'clock position as evidenced by smaller ATT and higher in situ force in the graft. Despite the fact that ACL grafts placed at the 10 or 11 o'clock positions are equally effective under an anterior tibial load, neither femoral tunnel position was able to fully restore knee stability to the level of the intact knee.

Various techniques are used to produce the pivot shift phenomenon after anterior cruciate ligament (ACL) injury. In particular, the amount of applied axial tibial torque varies among examiners. Thus, the objective of this study was to determine the effect of the magnitude and direction of axial tibial torque in combination with valgus torque on the resulting knee kinematics during such a simulated pivot shift test.This was a biomechanical study that used cadaveric knees with the intact knee of the same specimen serving as a control.On 19 human cadaveric knees (age, 26 to 69 years), a constant 10-Nm valgus torque was applied at 15 degrees of knee flexion. Then, internal and external tibial torque was applied incrementally from 0 to 10 Nm and the resulting kinematics of the ACL-intact and ACL-deficient knee, as well as the in situ force in the ACL, were measured using a robotic/universal force-moment sensor testing system.In response to isolated valgus torque, the coupled anterior tibial translation for the ACL-intact and ACL-deficient knee was 1.6 +/- 2.4 mm and 8.5 +/- 4.7 mm, respectively; therefore the difference between the ACL-intact and ACL-deficient knee was 6.9 +/- 3.4 mm. With an external tibial torque greater than 5 Nm, the tibia translated up to 4 mm posteriorly for both the ACL-intact and ACL-deficient knee. Whereas, internal tibial torque greater than 1.6 Nm caused a rapid increase in coupled anterior tibial translation up to 10.2 mm in the ACL-deficient knee, while causing only a gradual increase for the ACL-intact knee. With excessive internal torque of 10 Nm, the difference in coupled anterior tibial translation was only 4.4 +/- 2.2 mm, suggesting a decrease in the sensitivity of the test. Correspondingly, the in situ force in the ACL under 10 Nm valgus tibial torque was 43 +/- 17 N, and increased up to 87 +/- 32 N as a 10-Nm internal torque was added. By applying a 3.3-Nm external tibial torque in addition to the 10-Nm valgus torque, the in situ force decreased to 21 +/- 14 N.This study showed that a minimal amount of internal torque in combination with valgus torque may be a suitable way to elicit a pivot shift from an ACL-deficient knee.

This study focuses on the application of new experimental techniques (robotic/UFS testing system), analytical tools (FEA), and physical models to the investigation of lumbar functional spinal unit structural properties.

The current study investigated the efficacy of virtual reality (VR) assisted visual feedback for improving control of voluntary movements of the cervical spine during performance of active range-of-motion maneuvers. Active range-of-motion was assessed in 10 asymptomatic volunteers, both without and with VR-assisted visual feedback of overall cervical spine rotations. 8 of the 12 secondary rotations were significantly lower (p < 0.01) with VR feedback than the corresponding secondary rotations without VR feedback. No statistically significant differences were found between the primary rotations attained without VR and with VR feedback. These results support the use of VR-based visual feedback for enabling control of in-vivo cervical spine kinematics.

The PCL consists of two primary bundles, the anterolateral (AL) and posteromedial (PM). The AL bundle is larger, stiffer, and has a higher ultimate load (Harner, 1995), and has been the focus of PCL replacement surgery (Clancy, 1983). However, clinical outcomes of PCL reconstruction have been unsatisfactory (Lipscomb, 1993); which has led to the question of the advancement of a double bundle procedure in hopes to more accurately reproduce the PCL (Clancy, 1998). It was therefore the objective of this study to evaluate the biomechanics of a double bundle PCL reconstruction (PCL-2), and compare these results with those obtained for the intact knee as well as a single bundle PCL reconstruction (PCL-1). To study this, a robotic/universal force-moment sensor (UFS) testing system which measures the multiple degree of freedom (DOF) knee kinematics determines the in situ force in the ligaments (or replacement grafts) in response to external loading conditions was utilized. The hypothesis was that PCL-2 would improve knee kinematics and in situ forces to those of the intact knee throughout the range of knee flexion as compared to PCL-1.

Numerical modeling of the human knee joint has been pursued by various researchers [1,2]. Several knee joint models have been reported to simulate the kinematic and dynamic response of the knee joint to external loads, which to various degrees are representative of those found in the knee’s daily function. However, experimental validation of these models has been scarcely documented. Typical validation procedures should include a comparison of computational results from numerical simulations, to those from experimental tests performed on actual human joint specimens. The loading conditions must be carefully controlled and reproduced from one testing approach to another for acceptable comparison of the knee joint responses.

Previous studies, using imaging techniques[4] and mathematical models, have predicted that loads up to 90% of body weight are transmitted across the glenohumeral (GH) joint at 90° of abduction[2, 3]. However, in comparison to weight-bearing joints like the hip and knee, there is little quantitative data describing 3-D reaction forces generated at the GH joint during active motion. This information is important to our understanding of GH joint function in both normal and pathological conditions. It can also provide an experimental validation for computational models of the GH joint.

Clinical outcomes of reconstructive surgery for injuries to the posterior cruciate ligament (PCL) of the knee have been unsatisfactory, with persistent instability predisposing patients to early degenerative joint disease [Clancy, 1983]. One explanation for these outcomes has been the high incidence (up to 60%) of associated injuries to the posterolateral structures (PLS), which include the lateral collateral ligament (LCL) and popliteus complex. Combined PCL/PLS injuries are particularly debilitating because restraints to both posterior tibial translation and external rotation are lost [Grood, 1988]. Further, PLS injuries are difficult to reconstruct due to its complex anatomy; thus, often only the PCL is reconstructed when combined injuries occur.

In-vivo biomechanical studies of cervical spine movements are useful for defining “kinematic envelopes” of motion. Data are readily available on the ranges-of-motion of the cervical spine in flexion/extension, left/right lateral bending, and left/right axial rotation [1]. There is increasing evidence that “combined movements” may also be of clinical importance [2,3,4]. In this study, we tested the hypothesis that axial rotation limits active flexion/extension of the cervical spine. We used a specially developed measurement system featuring a 3-D magnetic tracking device with virtual reality technology that enables subjects to perform combined movements that would otherwise be difficult to achieve.

The biomechanical changes in rabbit knee contractures were measured after 9 weeks of immobilization. These results were correlated with the biochemical composition of periarticular connective knee tissue of the same knees. The loss of total hexosamine correlates significantly with joint stiffness on an animal-to-animal basis. Total hexosamine also correlates with the energy required cyclicly to flex and to extend the experimental joints. Of the individual glycosaminoglycan fractions, only hyaluronic acid showed significant correlation with the biomechanical data. The possible mechanism of contracture formation was postulated based on these results.

Prostaglandin E2 (PGE2) is known to stimulate osteolysis in vitro and has been implicated in mediating bone resorption in several animal and human tumors. Little attention has yet to be directed toward local humoral control (including PGE2) of bone resorption in primary and metastatic bone tumors. For investigation of whether histologically identified areas of osteolytic or osteoblastic bone tumors differentially secrete PGE2 under in vitro conditions, culture media from explants of central and peripheral areas of tissue were sterilely collected from 13 surgical specimens of primary and metastatic bone tumors and assayed for (PGE2) radioimmunoassay. The results indicate a marked heterogeneity in the concentration of immunoreactive (I-PGE2) synthesis by tumors of different as well as similar cell type. PGE2 production was time-dependent in culture, and at 72 hours substantial increases were apparent compared to cultures of non-neoplastic fascia controls. Significantly higher levels of I-PGE2 were found in cultures derived from "bone-destructive" tumors. No difference in I-PGE2 synthesis was found between explants of peripheral versus central tissue of the same tumors. PGE2 is synthesized in culture by bone tumors characterized as destructive of bone at higher levels than "bone-forming" tumors, and this synthesis is inhibited by indomethacin.