Computational study of extrinsic factors affecting ACL strain during single-leg jump landing

BACKGROUND

Non-contact anterior cruciate ligament (ACL) injuries are a major concern in sport-related activities due to dynamic knee movements. There is a paucity of finite element (FE) studies that have accurately replicated the knee geometry, kinematics, and muscle forces during dynamic activities. The objective of this study was to develop and validate a knee FE model and use it to quantify the relationships between sagittal plane knee kinematics, kinetics and the resulting ACL strain.

METHODS

3D images of a cadaver knee specimen were segmented (bones, cartilage, and meniscus) and meshed to develop the FE model. Knee ligament insertion sites were defined in the FE model via experimental digitization of the specimen's ligaments. The response of the model was validated against multiple physiological knee movements using published experimental data. Single-leg jump landing motions were then simulated on the validated model with muscle forces and kinematic inputs derived from motion capture and rigid body modelling of ten participants.

RESULTS

The maximum ACL strain measured with the model during jump landing was 3.5 ± 2.2%, comparable to published experimental results. Bivariate analysis showed no significant correlation between body weight, ground reaction force and sagittal plane parameters (such as joint flexion angles, joint moments, muscle forces, and joint velocity) and ACL strain. Multivariate regression analysis showed increasing trunk, hip and ankle flexion angles decreases ACL strain (R2 = 90.04%, p < 0.05).

CONCLUSIONS

Soft landing decreases ACL strain and the relationship could be presented through an empirical equation. The model and the empirical relation developed in this study could be used to better predict ACL injury risk and prevention strategies during dynamic activities.

Characterizing In-Situ Metatarsal Fracture Risk During Simulated Workplace Impact Loading

Metatarsal fractures represent the most common traumatic foot injury; however, metatarsal fracture thresholds remain poorly characterized, which affects performance targets for protective footwear. This experimental study investigated impact energies, forces, and deformations to characterize metatarsal fracture risk for simulated in situ workplace impact loading. A drop tower setup conforming to ASTM specifications for testing impact resistance of metatarsal protective footwear applied a target impact load (22-55 J) to 10 cadaveric feet. Prior to impact, each foot was axially loaded through the tibia with a specimen-specific bodyweight load to replicate a natural weight-bearing stance. Successive iterations of impact tests were performed until a fracture was observed with X-ray imaging. Descriptive statistics were computed for force, deformation, and impact energy. Correlational analysis was conducted on donor age, BMI, deformation, force, and impact energy. A survival analysis was used to generate injury risk curves (IRC) using impact energy and force. All 10 specimens fractured with the second metatarsal being the most common fracture location. The mean peak energy, force, and deformation during fracture were 46.6 J, 4640 N, 28.9 mm, respectively. Survival analyses revealed a 50% fracture probability was associated with 35.8 J and 3562 N of impact. Foot deformation was not significantly correlated (p = 0.47) with impact force, thus deformation is not recommended to predict metatarsal fracture risk. The results from this study can be used to improve test standards for metatarsal protection, provide performance targets for protective footwear developers, and demonstrate a methodological framework for future metatarsal fracture research.

Biomechanical Comparison of 3 Medial Patellofemoral Complex Reconstruction Techniques Shows Medial Overconstraint but No Significant Difference in Patella Lateralization and Contact Pressure

PURPOSE

The purpose of this study was to investigate biomechanical differences of medial patellofemoral ligament (MPFL) reconstruction, medial quadriceps tendon femoral ligament (MQTFL) reconstruction, and a combination of these techniques to restore lateral patellar constraint and contact pressures.

METHODS

Eight fresh frozen cadaver knees were mounted to a custom jig with physiological quadriceps tendon loading. Flexion angles and contact pressure (CP) were dynamically measured using Tekscan® pressure sensors and Polhemus® Liberty 6 degree of freedom (6DOF) positioning sensors in the following conditions: 1) intact 2) MPFL and MQTFL deficient, 3) MPFL reconstructed, 4) Combined MPFL + MQTFL reconstructed, and 5) MQTFL reconstructed. Lateral patellar translation was tested using horizontally directed 30 N force applied at 30° of knee flexion. The knees were flexed in dynamic fashion, and CP values were recorded for 10°, 20°, 30°, 50°, 70°, and 90° degrees of flexion. Group differences were assessed with ANOVA's followed by pairwise comparisons with Bonferroni correction.

RESULTS

MPFL (P = .002) and combined MPFL/MQTFL (P = .034) reconstruction significantly reduced patellar lateralization from +19.28% (9.78%, 28.78%) in the deficient condition to -17.57% (-27.84%, -7.29%) and -15.56% (-33.61%, 2.30%), respectively. MPFL reconstruction was most restrictive and MQTFL reconstruction the least -7.29% (-22.01%, 7.45%). No significant differences were found between the three reconstruction techniques. Differences in CP between the three reconstruction techniques were not significant (<.02 MPa) at all flexion angles.

CONCLUSION

The present study found no significant difference for patellar lateralization and patellofemoral CP between MPFL, combined MPFL/MQTFL, and MQTFL reconstruction. All 3 techniques resulted in stronger lateral patellar constraint compared to the native state, while the MQTFL reconstruction emulated the intact state the closest.

CLINICAL RELEVANCE

Various surgical techniques for medial patellofemoral complex reconstruction can restore patellar stability with similar patellofemoral articular pressures.

Attraction of leaf hopper, Amrasca biguttulla biguttulla, and whitefly, Bemisia tabaci, toward natural essential oils in cotton

Leaf hopper, Amrasca biguttula biguttula, and whitefly, Bemisia tabaci are the most economical sucking pests of cotton (Gossypium spp.) causing stunting, shortening of internodes and transmitting plant pathogenic viruses. The management of these pests is primarily based on application of synthetic pesticides, which not only triggers resistance to insecticide molecules but also contributes to environmental pollution. We aimed to study the attraction of A. biguttula and B. tabaci toward six natural essential oils (NEOs) viz., sandalwood, basil, grapefruit, rose, clove and mint oils using yellow sticky traps under field conditions. The results showed that traps treated with sandalwood and basil oils attract significant numbers of A. biguttula and B. tabaci as compared to the other traps during the seasons 2016-2017 and 2017-2018. Further, the Attractive Index (AI) of sandalwood and basil oils to these pests were significantly higher (i.e., >1). In addition, the traps treated with sandalwood and basil oils caught relatively lower numbers of natural enemies. The GC-MS analysis specified the presence of vital attractive volatile compounds, viz., santalene, funebrene and pentadecane in sandalwood; and linalool, β-farnesene, caryophyllene and methyl eugenol in basil oil. Based on the results obtained it can be concluded that application of sandalwood and basil oils increased the attracting efficacy of sticky traps for the management of A. biguttula and B. tabaci in cotton.

In-Situ Fracture Tolerance of the Metatarsals During Quasi-Static Compressive Loading of the Human Foot

Accidental foot injuries including metatarsal fractures commonly result from compressive loading. The ability of personal protective equipment to prevent these traumatic injuries depends on the understanding of metatarsal fracture tolerance. However, the in situ fracture tolerance of the metatarsals under direct compressive loading to the foot's dorsal surface remains unexplored, even though the metatarsals are the most commonly fractured bones in the foot. The goal of this study was to quantify the in situ fracture tolerance of the metatarsals under simulated quasi-static compressive loading. Fresh-frozen cadaveric feet (n = 10) were mounted into a testing apparatus to replicate a natural stance and loaded at the midmetatarsals with a cylindrical bar to simulate a crushing-type injury. A 900 N compressive force was initially applied, followed by 225 N successive load increments. Specimens were examined using X-ray imaging between load increments to assess for the presence of metatarsal fractures. Descriptive statistics were conducted for metatarsal fracture force and deformation. Pearson correlation tests were used to quantify the correlation between fracture force with age and body mass index (BMI). The force and deformation at fracture were 1861 ± 642 N (mean ± standard deviation) and 22.6 ± 3.4 mm, respectively. Fracture force was correlated with donor BMI (r = 0.90). Every fractured specimen experienced a transverse fracture in the second metatarsal. New biomechanical data from this study further quantify the metatarsal fracture risk under compressive loading and will help to improve the development and testing of improved personal protective equipment for the foot to avoid catastrophic injury.

Design and Preliminary Validation of Grasp Assistive Device for an Industrial Environment

Carpal tunnel syndrome and tendonitis are two common upper extremity cumulative trauma disorders (CTD) related to repetitive and forceful activities in industrial environments. Reducing the muscular force during activities such as the operation of a pistol grip hand tool could result in lower incidence of CTDs. The objective of this research was to reduce the muscular contribution to the grip force using an active orthosis system. A novel soft, pneumatic grasp assist device, that used a unique design of sinusoidal bellows oriented at 45 degrees, was designed to augment the users' strength during operation of pistol grip hand tool. The optimized design was fabricated using rapid prototyping. Device effectiveness was quantified by measuring muscle activity and grip force during an in vivo study of a common industrial activity. Nine subjects experienced with power tools employed by an automobile manufacturer installed 18 fasteners using a pistol grip DC tool with and without the grasp assist device. Surface electromyography (sEMG) was used to measure the activity of four muscles commonly associated with grasping. Results showed that the grasp assist significantly reduced the mean, combined, normalized muscle activity by 18% (p&lt;0.05). Muscle activation results were contextualized using the revised strain index (RSI). The grasp assist device trial yielded a significantly lower mean RSI value than the typical trial by 13% (p&lt;0.05). The study showed that using an active grasp assist orthosis could reduce the incidence of CTDs in able bodied industrial workers using DC hand tools.

The effects of pistol grip power tools on median nerve pressure and tendon strains

Objectives. Tendonitis and carpal tunnel syndrome are common cumulative trauma disorders that can occur with repetitive usage of pistol grip power tools. The role of reaction torque resulting in a forceful rotary displacement of the tool handle, as well as the role of applied grip force, is not clear in the development of these disorders. This study aimed to quantify the flexor tendon strains and median nerve pressure during a typical power tool operation securing a threaded fastener. Methods. Six fresh-frozen cadaver arms were made to grip a replica pistol grip power tool using static weights to apply muscle forces. A 5-Nm torque was applied to the replica power tool. The median nerve pressure and strains in the flexor digitorum profundus and superficialis tendons were measured using a catheter and strain gauges, at three wrist flexion angles. Results. The peak tendon strains were between 1.5 and 2% and were predominantly due to the grip force more than the transmitted torque. Median nerve pressure significantly increased with the wrist flexed versus extended. Conclusion. The results indicate that the contribution of the grip force to the tendon strain and median nerve pressure was greater than the contribution from the reaction torque.

Antioxidant, physiological and biochemical responses of drought susceptible and drought tolerant mustard (Brassica juncea L) genotypes to rhizobacterial inoculation under water deficit stress

Response of drought susceptible (DS) genotype Pusa Karishma LES-39 and drought tolerant (DT) mustard genotype NPJ-124, to rhizobacterial inoculation under water deficit stress, was compared in the present study to determine the influence of inoculants on biochemical and physiological attributes of these two different genotypes. Inoculation was observed to improve root and shoot dry weight in both the genotypes, although better results were observed in the DS genotype. There was variation in the response of the two genotypes to rhizobacterial inoculation, under water deficit stress. Significant improvement in most of the physiological and biochemical parameters including antioxidative enzyme activities of the DS genotype; with concomitant decrease in starch content, accumulation of H₂O₂ and lipid peroxidation upon inoculation of rhizobacteria was observed. In contrast, there was improvement in only few physiological and biochemical parameters in the DT genotype in response to inoculation with rhizobacteria. There was significant increase in catalase enzyme activity along with concomitant decrease in lipid peroxidation. Thus, drought susceptibility of the mustard genotypes, NPJ-124 and Pusa Karishma LES-39, determined their physiological, biochemical and antioxidative responses to rhizobacterial inoculation under water deficit stress. Expression of drought stress responsive genes belonging to ABA-dependent (RD20 and RD26) and ABA-independent (DREB2 and DREB1-2) pathways was studied in the DS genotype. Expression of DREB2 and DREB1-2 genes was considerably enhanced due to inoculation under water deficit stress; indicating that in Bacillus-mediated priming for drought stress tolerance, in this genotype, ABA-independent pathway probably played key role in enhancing tolerance to drought stress.

The effect of unloader knee braces on medial meniscal strain

BACKGROUND:

A medial meniscal tear is a common knee injury, especially following an anterior cruciate ligament injury. Decreasing the compressive force on the medial meniscus during dynamic activities using an unloader knee brace could reduce meniscal strain, effectively reducing injury risk and/or severity.

OBJECTIVES:

To investigate the efficacy of two unloader knee braces on medial meniscus strain during dynamic activities in intact & deficient anterior cruciate ligament states.

STUDY DESIGN:

Combined in vivo/in vitro study.

METHODS:

In vivo knee kinematics and muscle force profiles from a healthy individual performing single/doubleleg squats and walking motions were simulated on 10 cadaveric specimens using a dynamic knee simulator system. Simulations were performed on knees in unbraced and braced scenarios, with and without the anterior cruciate ligament. Anterior and posterior medial meniscal strains were measured.

RESULTS:

Two different braces each showed a significant reduction in the posteromedial meniscal strain ( p ⩽ 0.01) in an intact anterior cruciate ligament state. Neither brace mirrored this result for the anteromedial strain ( p > 0.05). In the deficient anterior cruciate ligament state, the braces had no significant effect on strain ( p > 0.05).

CONCLUSION:

Two unloader knee braces effectively reduced strain in the medial meniscus with an intact anterior cruciate ligament during dynamic activities. Neither brace made a significant reduction in strain for anterior cruciate ligament-deficient knees.

CLINICAL RELEVANCE

Unloader knee braces could be used to reduce the medial meniscus strain following meniscal surgery and during rehabilitation in patients with an isolated medial meniscus injury. However, these braces cannot be recommended for this purpose in patients with an anterior cruciate ligament deficiency.

Exploring expression patterns of PR-1, PR-2, PR-3, and PR-12 like genes in Arabidopsis thaliana upon Alternaria brassicae inoculation

In this study, we systematically examined the expression patterns of pathogenesis-related genes in model plant Arabidopsis thaliana after Alternaria brassicae inoculation using reverse transcription polymerase chain reaction(RT-PCR). Based on the results, none of the PR-1 and PR-2 like genes were induced significantly in the unwounded local or distal leaves upon A. brassicae challenge. However, only At2g14580 of the PR-1like gene showed a significant expression in wounded leave after Alternaria challenge but not in control; confirming its expression in response to A. brassicae was aided by the wounding. Among PR-3 like genes, At2g43590 showed local early expression and other PR-3 like genes showed significant distal expression after A. brassicae infection only in unwounded but not in wounded leaf samples. Although all the three PR-12 like genes were induced in local tissues, At2g26020 was the only gene showed significant induction locally as well as systemically after pathogen infection in the both with and without wounding experiments. Therefore, among the PR-1, PR-2, PR-3 and PR-12 like genes studied, At2g26020 can be the most promising candidate for the further line of research, viz, molecular characterization of its promoter to develop pathogen-inducible promoter in response to Alternaria and to develop fungus-resistant transgenics in Brassica juncea.

Dynamically tensioned ACL functional knee braces reduce ACL and meniscal strain

PURPOSE

The effectiveness of ACL functional knee braces to reduce meniscal and ACL strain after ACL injury or reconstruction is not well understood. A new dynamic knee tensioning brace system has been designed to apply an active stabilizing force to the knee. The ability of this system to reduce tissue strains is unknown. The purpose of this study was to test the ability of the dynamically tensioned brace to reduce strain in both the ACL and meniscus during rehabilitation activities.

METHODS

A combined in vivo/in silico/in vitro method was used to study three activities: gait, double leg squat, and single leg squat. Muscle forces and kinematics for each activity were derived through in vivo motion capture and applied to seven cadaveric knee specimens fitted with custom braces. Medial meniscal strain and ACL strain were measured in ACL intact, deficient and reconstructed conditions.

RESULTS

The brace lowered peak and average meniscal strain in ACL deficient knees (P < 0.05) by an average of 1.7%. The brace was also found to lower meniscal strain in reconstructed knees (1.1%) and lower ACL strain in ACL intact (1.3%) and reconstructed knees (1.4%) (P < 0.05).

CONCLUSIONS

This study supports the use of a brace equipped with a dynamic tensioning system to lower meniscal strain in ACL-deficient knees. Its use may help decrease the risk of subsequent meniscal tears in chronic ACL deficiency or delayed reconstruction. In ACL-intact and reconstructed knees, the brace may be beneficial in injury prophylaxis or in protecting the ACL graft following reconstruction. These results will aid clinicians make informed recommendations for functional brace use in patients with unstable knees.

LEVEL OF EVIDENCE

II.

Isolation and characterization of systemic acquired resistance marker gene PR1 and its promoter from Brassica juncea

Systemic acquired resistance (SAR) is an inducible defense response in plants that provides enhanced resistance against a variety of pathogens. In this regard, SAR marker gene PR1 (pathogenesis-related gene 1) was isolated from Brassica juncea and was named as BjPR1. The amino acid sequence of BjPR1 protein showed 99, 92, and 78% similarity with known PR1 proteins of Brassica rapa, Brassica napus, and Arabidopsis thaliana, respectively. Quantitative real-time PCR (qRT-PCR) analysis showed increased expression of BjPR1 gene both in local (infected) and distal (non-infected) leaves of B. juncea after Alternaria brassicae infection, whereas mechanical wounding showed expression only in local (wounded) leaves but not in distal (unwounded) leaves. Moreover, BjPR1 gene was strongly induced by salicylic acid (SA), whereas no such induction was observed following jasmonic acid (JA) or abscisic acid (ABA) treatments. To further elucidate gene regulation pattern of BjPR1, 2 kb promoter region of BjPR1 was isolated and subjected to in silico analysis which identified many potential cis-regulatory elements associated with plant defense as well as signaling pathways. The transient GUS expression analysis showed strong expression of GUS gene driven by BjPR1 promoter after SA treatment, while as ABA and JA downregulates GUS gene expression compared to control. In addition, BjPR1 promoter was significantly induced by wounding at local tissues. Hence, these results highlight the multiple role of BjPR1 gene in response to biotic and abiotic stresses. In addition, the present study also reported BjPR1 promoter as stress-specific inducible promoter that can be ideal candidate for controlling the expression of biotic stress response genes in transgenic plants.

New Adjustable Unloader Knee Brace and Its Effectiveness

Unloader knee braces are prescribed for patients with unicompartmental osteoarthritis of the knee. These braces aim to reduce pain in patients by applying a coronal moment to the knee to unload the symptomatic knee compartment. However, existing unloading mechanisms use straps that go directly behind the knee joint, to apply the needed moment. This can impinge on the popliteal artery and peroneal nerves thereby causing discomfort to the patient. Hence, these braces cannot be worn for prolonged periods of time. This research focused on developing a new knee brace to improve comfort while unloading the osteoarthritic knee. A new knee brace was developed that uses a four-point bending approach to unload the knee. In this brace, unloading can be adjusted, and the unloading mechanism is away from the joint. The new brace was tested on a cadaver specimen to quantify its capability to unload the knee compartment. The brace was also worn by a patient with osteoarthritis who subjectively compared it to his existing unloader brace. During cadaver testing, the new brace design could reduce the force exerted on the medial condyle by 25%. Radiographic images of the patient's knee confirmed that the brace unloaded the medial condyle successfully. The patient reported that the new brace reduced pain, was significantly comfortable to wear and could be used for a longer duration in comparison to his existing brace.

Effect of sagittal plane mechanics on ACL strain during jump landing

The relationships between non-contact anterior cruciate ligament injuries and the underlying biomechanics are still unclear, despite large quantities of academic research. The purpose of this research was to study anterior cruciate ligament strain during jump landing by investigating its correlation with sagittal plane kinetic/kinematic parameters and by creating an empirical model to estimate the maximum strain. Whole-body kinematics and ground reaction forces were measured from seven subjects performing single leg jump landing and were used to drive a musculoskeletal model that estimated lower limb muscle forces. These muscle forces and kinematics were then applied on five instrumented cadaver knees using a dynamic knee simulator system. Correlation analysis revealed that higher ground reaction force, lower hip flexion angle and higher hip extension moment among others were correlated with higher peak strain (p < 0.05). Multivariate regression analyses revealed that intrinsic anatomic factors account for most of the variance in strain. Among the extrinsic variables, hip and trunk flexion angles significantly contributed to the strain. The empirical relationship developed in this study could be used to predict the relative strain between jumps of a participant and may be beneficial in developing training programs designed to reduce an athlete's risk of injury. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1636-1644, 2016.

Can a knee brace reduce the strain in the anterior cruciate ligament? A study using combined in vivo/in vitro method

BACKGROUND AND AIM

It is unknown whether prophylactic knee braces can reduce the strain in the anterior cruciate ligament during dynamic activities.

TECHNIQUE

An athlete, who had characteristics of high anterior cruciate ligament injury risk, was chosen. A motion capture system (Optotrak Certus; Northern Digital, Waterloo, ON, Canada) was used to record dynamic trials during drop-landing activity of this subject with and without the knee brace being worn. A musculoskeletal model was used to estimate the muscle forces during this activity. A dynamic knee simulator then applied kinematics and muscle forces on a cadaver knee with and without the brace mounted on it. The anterior cruciate ligament strain was measured.

DISCUSSION

The peak strain in the anterior cruciate ligament was substantially lower for the braced (7%) versus unbraced (20%) conditions. Functional knee braces could decrease the strain in the anterior cruciate ligament during dynamic activities in a high-risk subject. However, the reduction seems to be a result of altered muscle firing pattern due to the brace.

CLINICAL RELEVANCE

Prophylactic knee brace could reduce the strain in the anterior cruciate ligament of high-risk subjects during drop-landing through altered muscle firing pattern associated with brace wear. This could help reduce the anterior cruciate ligament injury risk.

High Rotation Rate Behavior of Cervical Spine Segments in Flexion and Extension

Numerical finite element (FE) models of the neck have been developed to simulate occupant response and predict injury during motor vehicle collisions. However, there is a paucity of data on the response of young cervical spine segments under dynamic loading in flexion and extension, which is essential for the development or validation of tissue-level FE models. This limitation was identified during the development and validation of the FE model used in this study. The purpose of this study was to measure the high rotation rate loading response of human cervical spine segments in flexion and extension, and to investigate a new tissue-level FE model of the cervical spine with the experimental data to address a limitation in available data. Four test samples at each segment level from C2–C3 to C7–T1 were dissected from eight donors and were tested to 10 deg of rotation at 1 and 500 deg/s in flexion and extension using a custom built test apparatus. There was strong evidence (p < 0.05) of increased stiffness at the higher rotation rate above 4 deg of rotation in flexion and at 8 deg and 10 deg of rotation in extension. Cross-correlation software, Cora, was used to evaluate the fit between the experimental data and model predictions. The average rating was 0.771, which is considered to demonstrate a good correlation to the experimental data.

Combined in Vivo/in Vitro Method to Study Anteriomedial Bundle Strain in the Anterior Cruciate Ligament Using a Dynamic Knee Simulator

The mechanism of noncontact anterior cruciate ligament (ACL) injury is not well understood. It is partly because previous studies have been unable to relate dynamic knee muscle forces during sports activities such as landing from a jump to the strain in the ACL. We present a combined in vivo/in vitro method to relate the muscle group forces to ACL strain during jump-landing using a newly developed dynamic knee simulator. A dynamic knee simulator system was designed and developed to study the sagittal plane biomechanics of the knee. The simulator is computer controlled and uses six powerful electromechanical actuators to move a cadaver knee in the sagittal plane and to apply dynamic muscle forces at the insertion sites of the quadriceps, hamstring, and gastrocnemius muscle groups and the net moment at the hip joint. In order to demonstrate the capability of the simulator to simulate dynamic sports activities on cadaver knees, motion capture of a live subject landing from a jump on a force plate was performed. The kinematics and ground reaction force data obtained from the motion capture were input into a computer based musculoskeletal lower extremity model. From the model, the force-time profile of each muscle group across the knee during the movement was extracted, along with the motion profiles of the hip and ankle joints. This data was then programmed into the dynamic knee simulator system. Jump-landing was simulated on a cadaver knee successfully. Resulting strain in the ACL was measured using a differential variable reluctance transducer (DVRT). Our results show that the simulator has the capability to accurately simulate the dynamic sagittal plane motion and the dynamic muscle forces during jump-landing. The simulator has high repeatability. The ACL strain values agreed with the values reported in the literature. This combined in vivo/in vitro approach using this dynamic knee simulator system can be effectively used to study the relationship between sagittal plane muscle forces and ACL strain during dynamic activities.

Hydromechanical stimulator for chondrocyte-seeded constructs in articular cartilage tissue engineering applications

Mechanical stimulation is a key technique used for controlling the mechanical properties of tissue engineered articular cartilage constructs proposed for defect repair. The present study introduces a new technical method and device for ‘hydromechanical’ stimulation of tissue engineered articular cartilage constructs. The stimulation consists of simultaneous cyclic compression, frictional shear from a sliding indenter contact and direct pressurized fluid perfusion. Each of these modes of mechanical loading has been shown by other research groups to effectively stimulate tissue engineered constructs. A device for applying these conditions was designed, developed and tested. Two sets (high and low perfusion flow rates) of three experiments were performed, each with two samples subjected to hydromechanical stimulation conditions (compression and friction forces along with perfusion). Two other samples from each set were subjected to just compression and dynamic frictional shear forces, and two more were used as controls (not stimulated). The average amount of glycosaminoglycan retained in the constructs after 3 weeks ranked from low to high as follows: controls, hydromechanical conditions with the low-flow rate, hydromechanical conditions with the high-flow rate and just compression plus dynamic frictional shear. Statistically significant differences were not detected. However, future studies would focus on glycosaminoglycan production in the superficial zone, measuring the glycosaminoglycan released to the nutrient media, and address altering the hydromechanical stimulation parameters using the results of the present study as guidance, in attempts to achieve statistically significant increases in glycosaminoglycan production compared with the controls.

Effects of cyclic loading on the tensile properties of human patellar tendon

Bone-patellar tendon-bone (BPTB) graft is a popular choice for ACL reconstruction. These grafts are subjected to cyclic loading during the activities of daily living. Significant knee laxity is observed in reconstructed knee shortly after reconstruction. The source of this laxity is not clear. The change in the tensile properties of the graft due to cyclic loading can be one of the reasons for the change in knee laxity. Twenty patellar tendons from fresh frozen cadaver knees were cyclically loaded at a stress amplitude equivalent to 33% of the failure strength of the contralateral patellar tendon for 5000 cycles at 1.4Hz. They were then tested in tension to failure. Failure properties and the low load properties such as toe-region modulus were calculated. The results were compared with those of contralateral patellar tendons that were not subjected to cyclic loading before testing to failure. Fatigue loading did not alter the failure and low load properties with the exception of failure strain which decreased by about 10% (P<.05). Cyclically loaded patellar tendons with higher tissue mass density possess higher strength, modulus of elasticity, toughness, and transition stress (P<.05). The results indicate that there is no significant change in graft properties because of cyclic loading with the above load magnitude. The change in knee laxity observed after reconstruction, hence, is not because of change in graft properties due to moderate cyclic loading. Other factors, such as plastic deformation (yielding) of the graft, might play a role in increased knee laxity after reconstruction.

The effect of intraocular pressure on chick eye geometry and its application to myopia

Myopia is characterized by an increase in axial length of the eye, but the reasons for the axial elongation are still unknown. Higher intraocular pressure (IOP) has been associated with myopia and could be involved in eye enlargement. The purpose of this study was to investigate the effect of intraocular pressure on the geometry of the chick eye and to investigate whether an increase in IOP could cause the elongation of the eye. The IOP of ten 7-day old chick eyes was raised by injecting fluid into the eyes and the resulting deformation of the eyes was measured using digital cameras. In-vitro pressure-volume curves were obtained. The axial and equatorial strains (deformation normalized to the original dimension) were calculated. Our results showed that IOP increased exponentially with increasing injected volume. About 25 D myopia could be induced by the axial elongation created with an increase in IOP by 100 mmHg. As pressure increased from 0 to 140 mmHg, the chick eye elongated in the axial direction and initially contracted in the equatorial direction. The natural tendency of chick eyes is to elongate as IOP increases and this suggests that from a mechanical perspective IOP could play a role in myopia onset and progression. The results also suggest that oblate eyes might have higher risk of developing myopia.

Age, sex, body anthropometry, and ACL size predict the structural properties of the human anterior cruciate ligament

Anterior cruciate ligament (ACL) injury continues to be at the forefront of sports injury concerns because of its impact on quality of life and joint health prognosis. One strategy is to reduce the occurrence of this injury by identifying at-risk subjects based on key putative risk factors. The purpose of our study was to develop models that predict the structural properties of a subject's ACL based on the combination of known risk factors. We hypothesized that the structural properties of the ACL can be predicted using a multi-linear regression model based on significant covariates that are associated with increased risk of injury, including age, sex, body size, and ACL size. We also hypothesized that ACL size is a significant contributor to the model. The developed models had predictive capabilities for the structural properties of the ACL: load at failure (R2 = 0.914), elongation at failure (R2 = 0.872), energy at failure (R2 = 0.913), and linear stiffness (R2 = 0.756). Furthermore, sex, age, body mass, BMI, and height were contributors (p < 0.05) to all predicted structural properties. ACL minimal area was a contributor to elongation, energy at failure, and linear stiffness (p < 0.05), but not to load at failure. ACL volume was also a contributor to elongation and energy at failure (p < 0.05), but not to linear stiffness and load at failure models. ACL length was not a significant contributor to any structural property. The clinical significance of this research is its potential, after continued development and refinement of the model, for application to prognostic studies that are designed to identify individuals at increased risk for injury to the ligament.

Microwave assisted alkali-catalyzed transesterification of Pongamia pinnata seed oil for biodiesel production

In this study, microwave assisted transesterification of Pongamia pinnata seed oil was carried out for the production of biodiesel. The experiments were carried out using methanol and two alkali catalysts i.e., sodium hydroxide (NaOH) and potassium hydroxide (KOH). The experiments were carried out at 6:1 alcohol/oil molar ratio and 60°C reaction temperature. The effect of catalyst concentration and reaction time on the yield and quality of biodiesel was studied. The result of the study suggested that 0.5% sodium hydroxide and 1.0% potassium hydroxide catalyst concentration were optimum for biodiesel production from P. pinnata oil under microwave heating. There was a significant reduction in reaction time for microwave induced transesterification as compared to conventional heating.

Automatic system for 3D reconstruction of the chick eye based on digital photographs

The geometry of anatomical specimens is very complex and accurate 3D reconstruction is important for morphological studies, finite element analysis (FEA) and rapid prototyping. Although magnetic resonance imaging, computed tomography and laser scanners can be used for reconstructing biological structures, the cost of the equipment is fairly high and specialised technicians are required to operate the equipment, making such approaches limiting in terms of accessibility. In this paper, a novel automatic system for 3D surface reconstruction of the chick eye from digital photographs of a serially sectioned specimen is presented as a potential cost-effective and practical alternative. The system is designed to allow for automatic detection of the external surface of the chick eye. Automatic alignment of the photographs is performed using a combination of coloured markers and an algorithm based on complex phase order likelihood that is robust to noise and illumination variations. Automatic segmentation of the external boundaries of the eye from the aligned photographs is performed using a novel level-set segmentation approach based on a complex phase order energy functional. The extracted boundaries are sampled to construct a 3D point cloud, and a combination of Delaunay triangulation and subdivision surfaces is employed to construct the final triangular mesh. Experimental results using digital photographs of the chick eye show that the proposed system is capable of producing accurate 3D reconstructions of the external surface of the eye. The 3D model geometry is similar to a real chick eye and could be used for morphological studies and FEA.

Tuberculous meningitis presenting as isolated interhemispheric exudates

The total number of tuberculosis cases in the world is increasing, and less common forms of tuberculous meningitis (TBM) with varying imaging manifestations are being encountered more often. We describe anterior interhemispheric variety of TBM, which has not been previously described to the best of our knowledge in the literature. Common imaging findings in these five patients include predominant involvement of the meninges in the anterior interhemispheric fissure with relatively little enhancement of the basal cisterns. Knowledge of uncommon radiological findings is vital in early diagnosis and treatment of this common disease.

Increasing pre-activation of the quadriceps muscle protects the anterior cruciate ligament during the landing phase of a jump: an in vitro simulation

We hypothesize that application of an unopposed quadriceps force coupled with an impulsive ground reaction force may induce anterior cruciate ligament (ACL) injury. This situation is similar to landing from a jump if only the quadriceps muscle is active; an unlikely but presumably dangerous circumstance. The purpose of this study was to test our hypothesis using in vitro simulation of jump landing. A jump-landing simulator was utilized. Nine cadaveric knees were tested at an initial flexion angle of 20 degrees . Each ACL was instrumented with a differential variable reluctance transducer (DVRT). Quadriceps pre-activation forces (QPFs) ranging from 25N to 700N were applied to each knee, followed by an impulsive ground reaction force produced by a carriage-mounted drop weight (7kg) that impulsively drove the ankle upward. ACL strain was monitored before landing due to application of QPF (pre-activation strain) and at landing due to application of the ground reaction force (landing strain). No ACLs were injured. Pre-activation strains exhibited a positive correlation with QPF (r=0.674, p<0.001) while landing strains showed a negative correlation (r=-0.235, p=0.032). Total ACL strain (pre-activation+landing strain) showed no correlation with QPF (r=0.023, p=0.428). Our findings indicate that elevated QPF increases pre-activation strain but reduces the landing strain and is therefore protective post-landing. Overall, there is a complete lack of correlation between "total" ACL strain and QPF suggesting that the total strain in the ACL is independent of the QPF under the simulated conditions.

Shallow medial tibial plateau and steep medial and lateral tibial slopes: new risk factors for anterior cruciate ligament injuries

BACKGROUND

The geometry of the tibial plateau has been largely ignored as a source of possible risk factors for anterior cruciate ligament injury. Discovering the anterior cruciate ligament injury risk factors associated with the tibial plateau may lead to delineation of the existing sex-based disparity in anterior cruciate ligament injuries and help develop strategies for the prevention of anterior cruciate ligament injuries regardless of gender.

HYPOTHESIS

Individuals with a shallower medial tibial depth of concavity, while having increased posteriorly directed slope of their tibial plateau, are at increased risk of suffering an anterior cruciate ligament injury compared with those with decreased posterior slope and increased medial tibial depth. Furthermore, these relationships are different between men and women.

STUDY DESIGN

Case-control study (prevalence); Level of evidence, 3.

METHODS

The medial, lateral, and coronal tibial plateau slopes as well as the medial tibial depth of concavity in 55 uninjured controls (33 women and 22 men) and 49 anterior cruciate ligament-injured cases (27 women and 22 men) were measured using magnetic resonance images. First, a preliminary t test was performed to establish any existing differences between groups. Next, a logistic regression model was developed to determine the probability of anterior cruciate ligament injury in an individual based on the measured covariates.

RESULTS

The female anterior cruciate ligament-injured cases had increased lateral tibial slope (P = .03) and shallower medial tibial depth (P = .0003) compared with the uninjured controls, while male cases had increased lateral and medial tibial slope (P = .02) and shallower medial tibial depth (P = .0004) compared with controls. The logistic regression analysis and odds ratio estimates showed that medial tibial depth is an important risk factor (odds ratio = 3.03 per 1 mm decrease in its value), followed by lateral tibial slope (odds ratio = 1.17 per 1 degrees increase in its value) in all participants. The medial tibial slope (odds ratio = 1.18 per 1 degrees increase in its value) was a risk factor only in men.

CONCLUSION

A combination of increased posterior-directed tibial plateau slope and shallow medial tibial plateau depth could be a major risk factor in anterior cruciate ligament injury susceptibility regardless of gender. Different injury risk models may be needed for men and women as other key risk factors are identified.

A new ankle foot orthosis for running

Traumatic knee injuries in automobile accidents and sports often lead to damage of the peroneal nerve. A lack of control of muscles innervated by the peroneal nerve due to this damage, results in the inability to dorsiflex and evert the foot and to extend the toes. This condition is commonly known as foot drop. Foot drop reduces the stability in the body while walking and running and may also cause injury due to lack of foot clearance during the swing phase of the gait. Traditionally, an ankle foot orthosis (AFO), comprised of a moulded sheet of plastic that conforms around the posterior calf and distally contains all or part of the calcaneous as well as the plantar foot, is used to treat foot drop. The intent of this orthosis is to dorsiflex the foot to provide clearance during the swing phase of walking and running. Traditional AFO results in increased pressures due to a decrease in dorsiflexion range of motion at the ankle and make the orthosis increasingly uncomfortable to wear. Several other existing designs of foot drop AFO suffer from similar inadequacies. To address these issues, a new AFO was developed. The device was successfully used by one person with foot drop without issues for more than one year. This new design conforms to the lower anterior shin and dorsum of the foot using dorsiassist Tamarack ankle joints to allow for greater plantar and dorsiflexion range of motion. While still limiting ankle inversion it does allow for more ankle eversion. This orthosis can be discretely worn inside shoes due to its smaller size, and can be worn for a longer period of time without discomfort.

The geometry of the tibial plateau and its influence on the biomechanics of the tibiofemoral joint

BACKGROUND

The geometry of the tibial plateau is complex and asymmetric. Previous research has characterized subject-to-subject differences in the tibial plateau geometry in the sagittal plane on the basis of a single parameter, the posterior slope. We hypothesized that (1) there are large subject-to-subject variations in terms of slopes, the depth of concavity of the medial plateau, and the extent of convexity of the lateral plateau; (2) medial tibial slope and lateral tibial slope are different within subjects; (3) there are sex-based differences in the slopes as well as concavities and convexities of the tibial plateau; and (4) age is not associated with any of the measured parameters.

METHODS

The medial, lateral, and coronal slopes and the depth of the osseous portion of the tibial plateau were measured with use of sagittal and coronal magnetic resonance images that were made for thirty-three female and twenty-two male subjects, and differences between the sexes with respect to these four parameters were assessed. Within-subject differences between the medial and lateral tibial slopes also were assessed. Correlation tests were performed to examine the existence of a linear relationship between various slopes as well as between slopes and subject age.

RESULTS

The range of subject-to-subject variations in the tibial slopes was substantive for males and females. However, the mean medial and lateral tibial slopes in female subjects were greater than those in male subjects (p < 0.05). In contrast, the mean coronal tibial slope in female subjects was less than that in male subjects (p < 0.05). The correlation between medial and lateral tibial slopes was poor. The within-subject difference between medial and lateral tibial slopes was significant (p < 0.05). No difference in medial tibial plateau depth was found between the sexes. The subchondral bone on the lateral part of the tibia, within the articulation region, was mostly flat. Age was not associated with the observed results.

CONCLUSIONS

The geometry of the osseous portion of the tibial plateau is more robustly explained by three slopes and the depth of the medial tibial condyle.

Low-load behaviour of the patellar tendon graft and its relevance to the biomechanics of the reconstructed knee

BACKGROUND

Although the linear elastic (high-load) properties of patellar tendon graft used for anterior cruciate ligament (ACL) reconstruction are studied extensively, the low-load properties of the graft, associated with the toe region of its load-deformation curve, are largely neglected. The objectives of this study were to (i) determine the properties of the patellar tendon in the low-load region and compare to that of the intact ACL, (ii) assess the extent of variability in these properties and relate them to donor factors, and (iii) establish the theoretical importance of low-load properties to the function of the reconstructed knee.

METHODS

The patellar tendons of 20 unpaired fresh frozen human knees (10 males and 10 females) were harvested. The central portions were trimmed, measured, and tested in tension to failure. The stress-strain curves were fitted with a bi-linear model and the graft properties were measured.

FINDINGS

The low-load region modulus of elasticity, E 0, of the patellar tendon, ranged from 49 MPa to 276 MPa in males and 63 MPa to 279 MPa in females. The strain at which the graft transitions from its low-load region to its linear elastic region (epsilon* approximately 4.6%) is on average above the strain levels experienced by the ACL during daily activities (epsilon approximately 4%). Donor sex, height and body mass were found to significantly affect some of the mechanical properties of the low-load region.

INTERPRETATION

The results suggest that the low-load region properties of the patellar tendon, not the linear elastic properties, govern the biomechanics of the tibiofemoral joint during the early healing period. Also, a wide variability of graft properties in the low-load region exists partly due to certain donor factors. Clinicians should be aware of the low-load region behaviour of the graft and its influence on time=0 behaviour of the reconstructed knee.

The human anterior cruciate ligament: sex differences in ultrastructure and correlation with biomechanical properties

The purpose of this study was to investigate the existence of sex-based differences in the ultrastructural characteristics of the human anterior cruciate ligament (ACL) as the underlying cause of differences in the structural and mechanical properties between sexes. The ACL of six male and six female cadaveric donors were randomly chosen from a pool of 10 male and 10 female ACLs that had previously been tested for their structural and mechanical properties. Eighteen tissue samples from the distal, proximal, and middle sections of the anteromedial and posterolateral bundles were analyzed by transmission electron microscopy. Female ACLs exhibited both lower fibril concentration and lower percent area occupied by collagen fibrils (p < 0.05) compared to males. There was also a difference in the fibril diameters (p < 0.05); donor age, height, body mass, and body mass index contributed significantly to this difference. In females, ACL stiffness and modulus of elasticity were highly correlated to fibril concentration (r = 0.96 and 0.97, respectively); in males ACL failure load and strength were highly correlated to percent area occupied by collagen (r = 0.96 and 0.96, respectively). These differences in ultrastructure may underlie differences in ACL properties between sexes.

Hepatobiliary scintigraphy. An effective tool in the management of bile leak following laparoscopic cholecystectomy

Bile leaks and bile duct injury has been the major postoperative complications described after laparoscopic cholecystectomy. In this study, we evaluated the role of hepatobiliary scintigraphy (HBS) in patients who underwent laparoscopic cholecystectomy, and there was a clinical suspicion of bile leak in postoperative period.

METHOD

Twenty-five patients (M/F=11:14, mean age 39+/-8 years; range 24-58 years) with suspected bile leak postlaparoscopic cholecystectomy underwent sequential HBS.

RESULTS

Thirteen patients had normal hepatobiliary scintigraphic studies. Five patients had small bile leak in gall bladder fossa with primary route of bile flow into the gut. All these 18 patients improved on conservative management alone. Significant bile leak from the cystic stump region was demonstrated in four patients. All of them were subjected to endoscopic cholangiography (ERCP), which confirmed the site of leak. All patients had stenting and sphincterotomy. One patient showed bile leak and obstruction at the lower end of common bile duct, he improved spontaneously. Another patient showed poor hepatocytes function and no excretion of radiotracer and underwent ERCP followed by hepaticojejunostomy for common hepatic duct ligation. One patient had frank bile leak in the right paracolic gutter and had to undergo hepaticojejunostomy.

CONCLUSIONS

HBS is a valuable noninvasive method of investigating possible bile leaks or other biliary disruptions in postlaparoscopic cholecystectomy patients. Negative study for significant bile leak can assure the surgeon to manage the patient conservatively. However, it cannot be relied on absolutely when determining the need for reoperation for a significant bile leak in early postoperative period.

Technetium Tc-99m ethyl cysteinate dimer brain single-photon emission CT in mild traumatic brain injury: a prospective study

PURPOSE

To explore the role of single-photon emission CT (SPECT) in initial diagnostic evaluation of patients with mild traumatic brain injury (MTBI) and to identify subgroups in which it may serve as a useful diagnostic tool.

MATERIALS AND METHODS

Patients with MTBI seen during a 14-month period were prospectively included in this study. All patients had a CT of head within 12 hours of injury and SPECT by using technetium Tc99m ethyl cysteinate dimer (Tc99m-ECD) within 72 hours of injury. Both SPECT and CT findings were compared with clinical features such as posttraumatic amnesia (PTA), postconcussion syndrome (PCS), and loss of consciousness (LOC).

RESULTS

Ninety-two patients with MTBI underwent SPECT in the study period. There were 28 children and 64 adults, with male-to-female ratio of 4.5 to 1. CT findings were abnormal in 31 (34%) and SPECT in 58 (63%). The most common abnormality was hypoperfusion in the frontal lobe(s) in adults and the temporal lobe in children. A significantly higher number of perfusion abnormalities were seen in patients with PTA (P = .03), LOC (P = .02), and PCS (P = .01) than in patients without these symptoms. Compared to CT, SPECT had a much higher sensitivity for detecting an organic basis in these subgroup, of patients (P < .05).

CONCLUSION

Tc99m-ECD SPECT can be used as a complementary technique to CT in initial evaluation of patients with MTBI. It is particularly useful in patients having PCS, LOC, or PTA with normal CT scan.

Sex-based differences in the tensile properties of the human anterior cruciate ligament

After immense amounts of research, the root cause for the significantly higher rates of anterior cruciate ligament (ACL) failure incidents in females as compared to males still remains unknown and the existing sex-based disparity has not diminished. To date, the possibility that the female ACL is mechanically weaker than the male ACL has not been directly investigated. Although it has been established in the literature that the female ACL is smaller in size, the differences in the structural and material properties of the ACL between sexes have not been studied. The aim of this cadaveric study was to determine if any sex-based differences in the tensile properties of the human ACL exist when considering age as well as ACL and body anthropometric measurements as covariates. Ten male and 10 female unpaired cadaveric knees (mean age 36.75 years) were used for this study. The geometry of the ACL (including length, cross-sectional area, and volume) was analyzed using a 3-D scanning system. The femur-ACL tibia complex was tested to failure along the longitudinal axis of the ligament in a tensile testing machine. The structural properties of the ACL as well as its mechanical properties were determined. Analysis of covariance was performed to assess the effect of sex on tensile properties. The female ACL was found to have a lower mechanical properties (8.3% lower strain at failure; 14.3% lower stress at failure, 9.43% lower strain energy density at failure, and most importantly, 22.49% lower modulus of elasticity) when considering age, ACL, and body anthropometric measurements as covariates.

Sex-based differences in the anthropometric characteristics of the anterior cruciate ligament and its relation to intercondylar notch geometry: a cadaveric study

BACKGROUND

A significantly higher rate of anterior cruciate ligament injuries occurs in women involved in sports activities compared to the corresponding male population. Reasons for this disparity are not well understood; however, sex-based differences in the geometry of the anterior cruciate ligament, its morphologic characteristics, and the intercondylar notch size have been cited as possible factors.

HYPOTHESES

(1) The anterior cruciate ligament in women has a shorter length, and smaller cross-sectional area and volume than that in men. (2) The female anterior cruciate ligament has a lower mass density. (3) Ligament size is proportional to notch width in both male and female populations.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Using a 3-dimensional imaging system, the authors measured the geometric parameters, including length, area, and volume, of the anterior cruciate ligaments of 10 male and 10 female donors (all Caucasian). A digital image of the frontal plane of the knee flexed at 90 degrees was used to measure notch size. After the ligament's removal from its attachment sites, its mass was measured using a digital balance. Geometric parameters, mass density, and notch size were compared based on sex. Correlation analyses between ligament size and body anthropometric characteristics, and between notch size and ligament size were performed.

RESULTS

The anterior cruciate ligament in women was smaller in length, cross-sectional area, volume, and mass when compared to that in men. No significant difference in ligament mass density was found between the sexes. Also, no differences were found in notch geometry between male and female populations. A correlation between notch size and ligament size was found for men but not for women.

CONCLUSIONS

Because the densities of female and male anterior cruciate ligaments appear to be similar, the smaller ligament size in women may contribute to their having a higher rate of ligament injuries. Anterior cruciate ligament size increases in proportion to notch width in men but not in women.

Diagnosis of ectopic gastric mucosa using 99Tcm-pertechnetate: spectrum of scintigraphic findings

We highlight the spectrum of scintigraphic findings likely to be encountered in patients with ectopic gastric mucosa with illustrative cases for each such finding. 11 children (aged 4 months to 120 months, all males) underwent (99)Tc(m)-pertechnetate scintigraphic evaluation for ectopic gastric mucosa. Functioning ectopic gastric mucosa was detected in Meckel's diverticulae in three patients, in small bowel duplications in four, in a gastric duplication in one, and in intrathoracic foregut duplication cysts in three. Ectopic functioning gastric mucosa in Meckel's diverticulum, and gastric duplication is visualized simultaneously with the stomach while in intestinal duplications tracer activity can be visualized in the dynamic sequence and even before gastric tracer visualization. In the three patients with intrathoracic duplication cysts, the functioning ectopic gastric mucosa was evident only in the delayed (99)Tc(m)-pertechnetate images, much later than the visualization of stomach activity. Therefore, acquisition of delayed images are useful when the initial images are equivocal or negative in children with intrathoracic foregut duplication cysts. In addition, we suggest a hypothesis of a possible mechanism for the uptake of pertechnetate in ectopic gastric mucosa in some patients with intrathoracic forget duplication cysts. In conclusion, a variety of scintigraphic patterns may be found in patients with ectopic gastric mucosa undergoing (99)Tc(m)-pertechnetate scintigraphy depending upon the location and size of the ectopic tissue.

The mechanical properties of the human patellar tendon are correlated to its mass density and are independent of sex

BACKGROUND

A diverse range of values for the mechanical properties of the human patellar tendon has been reported in the literature. Donor age has been excluded as a factor that causes this disparity. However, the effects of donor sex and tissue mass density on the mechanical properties of the patellar tendon have not been established. More importantly, predictors of the mechanical properties of the patellar tendon, used as grafts in anterior cruciate ligament reconstruction surgeries, are not available.

METHODS

Uniaxial tension tests were performed to determine the effects of donor sex and mass density of the tissue on the mechanical properties of twenty unpaired human patellar tendons (10 male and 10 female; age, 17-50). Mass density of the patellar tendon was determined by measuring its volume and mass.

FINDINGS

No evidence of sex-based differences in any of the mechanical properties of the patellar tendon was found. The results revealed a diverse range of mass densities extending from a low of 0.76 g/cm(3) to a high of 2.68 g/cm(3) (250% difference). Furthermore, it was determined that the ultimate tensile strength (mean=58.71 MPa), elastic modulus (mean=507.38 MPa) and strain energy density (mean=4.59 MPa) of the patellar tendon were significantly correlated to its mass density. The tensile strength and elastic modulus were significantly higher for those patellar tendons having a mass density greater than 1.67 g/cm(3).

INTERPRETATION

The mass density of the patellar tendon may be considered as an indicator of mechanical properties of the patellar tendon or graft quality.

An alternative method of anthropometry of anterior cruciate ligament through 3-D digital image reconstruction

Accurate and flexible measurements of length, area, and volume are important in evaluation of the mechanical properties of soft tissue. Although a number of contact-based and non-contact techniques have been reported in the literature, due to a variety of reasons such as cost, complexity, and low accuracy, the research community has not adopted a standardized technique. In this paper, an alternative method of measuring the geometric parameters of cadaver anterior cruciate ligament (ACL) is presented. In this method, a 3-D scan of the ACL is constructed using a simple, commercially available, scanning system. The 3-D scan is then analyzed using the 3-D Doctor Software to extract important information regarding the length, cross-sectional area, and volume of the ACL. The accuracy and repeatability of measurements obtained by this method are acceptable and comparable to existing non-contact methods. The limitation of the method is that surface concavities cannot be detected. However, the non-contact optical method, described here, has inherent advantages over the existing methods: (1) it is inexpensive; (2) it allows the determination of area at any distance along the length of the tissue of interest; (3) all relevant information including minimum area is extracted from one single application of the method; (4) the volume can be calculated with a simple additional step of length measurement although, for accurate results, condylar blockage must be minimized by coring the ACL out. The entire process of scanning takes less than 30 min. This technique has the potential to become a standard method in anthropometry of soft tissue.

Reflux in Native Kidneys Mimicking Urine Leak Postrenal Transplant

A 19-year man underwent live related renal transplantation for end-stage renal disease. He was referred for a baseline renal scan on day 4. The urine output was satisfactory and the serum creatinine showed a decreasing trend. Renal dynamic scintigraphy with technetium-99m ethylenedicysteine demonstrated radiotracer activity above the transplant kidney, suspected to be a urine leak. Postvoiding posterior, delayed images confirmed that the radiotracer activity in the anterior postvoiding images was the result of vesicoureteral reflux from the patient's native kidneys.