Spyridon D. Masouros

Biomechanics of the meniscus-meniscal ligament construct of the knee.

The menisci of the knee act primarily to redistribute contact force across the tibio-femoral articulation. This meniscal function is achieved through a combination of the material, geometry and attachments of the menisci. The main ligaments that attach the menisci to the tibia (insertional ligaments, deep medial collateral ligament), the femur (meniscofemoral ligaments, deep medial collateral ligament) and each other (the anterior intermeniscal ligament) are the means by which the contact force between tibia and femur is distributed into hoop stresses in the menisci to reduce contact pressure at the joint. This means that the functional biomechanics of the menisci cannot be considered in isolation and should be considered as the functional biomechanics of the meniscus-meniscal ligament construct. This article presents the current knowledge on the anatomy and functional biomechanics of the meniscus and its associated ligaments. Much is known about the function of the meniscus-meniscal ligament construct; however, there still remain significant gaps in the literature in terms of the properties of the anterior intermeniscal ligament and its function, the properties of the insertional ligaments, and the most appropriate ways to reconstruct meniscal function surgically.

Outcomes of IED Foot and Ankle Blast Injuries

BACKGROUND Improvements in protection and medical treatments have resulted in increasing numbers of modern-warfare casualties surviving with complex lower-extremity injuries. To our knowledge, there has been no prior analysis of foot and ankle blast injuries as a result of improvised explosive devices (IEDs). The aims of this study were to report the pattern of injury and determine which factors are associated with a poor clinical outcome. METHODS U.K. service personnel who had sustained lower leg injuries following an under-vehicle explosion from January 2006 to December 2008 were identified with the use of a prospective trauma registry. Patient demographics, injury severity, the nature of the lower leg injury, and the type of clinical management were recorded. Clinical end points were determined by (1) the need for amputation and (2) ongoing clinical symptoms. RESULTS Sixty-three U.K. service personnel (eighty-nine injured limbs) with lower leg injuries from an explosion were identified. Fifty-one percent of the casualties sustained multisegmental injuries to the foot and ankle. Twenty-six legs (29%) required amputation, with six of them amputated because of chronic pain eighteen months following injury. Regression analysis revealed that hindfoot injuries, open fractures, and vascular injuries were independent predictors of amputation. At the time of final follow-up, sixty-six (74%) of the injured limbs had persisting symptoms related to the injury, and only nine (14%) of the service members were fit to return to their preinjury duties. CONCLUSIONS This study demonstrates that foot and ankle injuries from IEDs are associated with a high amputation rate and frequently with a poor clinical outcome. Although not life-threatening, they remain a source of long-term morbidity in an active population.

A biomechanical basis for tears of the human acetabular labrum

Objective: Acetabular labral tears predominantly affect young patients and are a source of hip pain in the athlete. Four causes of the initiation of labral tears have been proposed; trauma, hypolaxity of the anterior capsule, dysplasia and bony impingement. A further cause could be reduced biomechanical properties in the area most susceptible to tears. However, no work has defined these properties. Design: 32 compressive and 32 tensile test samples were harvested from fresh-frozen cadaveric acetabula. The labrum was divided into eight areas to allow comparison around its circumference. Semiconfined compressive testing and tensile testing were performed at a displacement rate of 10 mm/min in a controlled environment of 100% humidity at 37 (SD 1)°C. Setting: Cadaveric study. Results: The mean compressive stiffness was 31.75 (SD 16.7) MPa, and the mean tensile elastic modulus was 24.7 (SD 10.8) MPa. The anterosuperior region had a significantly lower compressive elastic modulus than either of the posterior quadrants (p<0.05) and a significantly lower tensile modulus to the anterioinferior area (p<0.05). Conclusions: The biomechanical properties in the anterosuperior region may be a contributing factor to the initiation of labral tears.

Comparison of 1- and 2-knot, 4-strand, double-modified kessler tendon repairs in a porcine model.

PURPOSE To compare 1- and 2-knot, 4-strand, double-modified Kessler tendon repairs. It was our hypothesis that a 1-knot technique using an unbraided suture material would be stronger if it is possible for some movement to occur between strands on loading, redistributing forces such that the load is equally shared. METHODS Fifty-six porcine flexor tendons were allocated to either a 1- or 2-knot, 4-strand, double-modified Kessler repair, and tested by incremental cyclical loading in vitro. RESULTS The 1-knot technique was significantly stronger. Gap formation was initially greater in the 1-knot group, consistent with movement of strands, but with increasing physiological levels of applied force, there was no significant difference between the groups. CONCLUSIONS The 1-knot technique was significantly stronger than the 2-knot technique.

Tensile properties of the human glenoid labrum

Human fresh‐frozen cadaveric glenoid labrae from 16 donors were harvested and ten of these had no gross degeneration. These ten were divided into eight equal circumferential sections. Each section was cut to produce test‐samples from the core layer with a cross‐section of 1 × 1 mm. Tensile testing was performed within a controlled environment unit at 37 ± 1 °C and 100% relative humidity. Each test‐sample was precycled to a quasi‐static state to alleviate the effects of deep‐freezing, prior to final testing. The tangent modulus was calculated for each test‐sample before and after a 5‐min period of stress relaxation and at yield. The mean elastic modulus and yield stress of the glenoid labrum were 22.8 ± 11.4 and 2.5 ± 2.1 MPa, respectively. The anterosuperior portion had a lower elastic modulus and lower yield stress than the inferior portion (both P < 0.02). The pre‐stress relaxation tangent modulus was significantly lower than the post‐stress relaxation tangent modulus for all portions of the labrum. The glenoid labrum has similar tensile material properties to articular cartilage. Its elastic modulus varies around its circumference. This suggests that the labrum may encounter different forces at different positions.

Mathematics and online learning experiences: A gateway site for engineering students

This paper focuses on the preliminary design of a multifaceted computer-based mathematics resource for undergraduate and pre-entry engineering students. Online maths resources, while attractive in their flexibility of delivery, have seen variable interest from students and teachers alike. Through student surveys and wide consultations, guidelines have been developed for effectively collating and integrating learning, support, application and diagnostic tools to produce an Engineers Mathematics Gateway. Specific recommendations include: the development of a shared database of engineering discipline-specific problems and examples; the identification of, and resource development for, troublesome mathematics topics which encompass ideas of threshold concepts and mastery components; the use of motivational and promotional material to raise student interest in learning mathematics in an engineering context; the use of general and lecture-specific concept maps and matrices to identify the needs and relevance of mathematics to engineering topics; and further exploration of the facilitation of peer-based learning through online resources.

Evaluating the effect of vehicle modification in reducing injuries from landmine blasts. An analysis of 2212 incidents and its application for humanitarian purposes

INTRODUCTION Anti-vehicle (AV) mines have been laid indiscriminately in conflict areas for the past 100 years. With an indeterminate life-span they continue to pose a significant threat to the civilian population, as well as restrict the movement of people, aid and goods to vulnerable populations. The aim of this study was to analyse unique casualty data from 2212 mine incidents to determine if simple vehicle modifications can reduce fatality and injury rates from mine explosions. METHOD We analysed casualty data from the Rhodesian War (1972-1980), to assess the effects of basic vehicle modifications (V-shaped hull, increased ground clearance, widened axles, heavy vehicles and blast deflectors) on injury rates. A multinomial regression statistical model was developed for vehicle modifications and number of alterations to explore these effects. RESULTS Incident data was available on 2212 vehicle mine incidents involving 16,456 people. The overall fatality rate was 3.3% (544/16,456) and the overall injury rate was 22.7% (3741/16,456). Explosions against mine-protected vehicles resulted in a fatality rate of 1.2% (150/12,919); occupants in unprotected vehicles sustained a fatality rate of 11.4% (395/3537). The injury rate in mine protected vehicles was 22.2% (2868/12,919) compared to 24.7% in unprotected vehicles (873/3537). Utilising a multinomial logistical-regression model, we show that each design feature significantly reduced fatality rate (from 45% in unprotected vehicles to 0.8% in protected vehicles); each of these designs had a cumulative effect in fatality reduction. In isolation, blast deflectors, whilst reducing fatality rates, increased injury rates. CONCLUSIONS Our data clearly demonstrates that simple vehicle modifications can have a significant effect on reducing fatality and injury rates from AV mine explosions. Given that the modifications described were produced using commercially available vehicles with basic engineering requirements, we believe that similar processes could be employed in post-conflict environments in a cost-effective manner.

The Compressive Behavior of the Human Glenoid Labrum May Explain the Common Patterns of SLAP Lesions

PURPOSE The aim of the study was to define the normalized compressive stiffness (modulus) of the glenoid labrum around its circumference and to characterize the difference in modulus between different areas. METHODS Sixteen fresh-frozen cadaveric shoulders were harvested and dissected down to the glenoid labrum. Any specimens with significant degenerative changes were discarded, leaving 8 labra for testing. The labrum was divided into 8 segments, to allow comparison around its circumference. A uniform testing specimen was produced from each area by use of a microtome. Each specimen measured 3 x 1 mm in cross section and was 6 mm in length. Indentation testing was conducted in a controlled environment of 100% humidity at 37 degrees C +/- 1 degrees C. RESULTS We obtained 52 test samples from 8 labra. The mean modulus of the glenoid labrum was 69.7 megapascal (standard deviation, 36.2 megapascal). The anterosuperior portion of the labrum had a higher modulus than the posteroinferior portion (P = .0075). CONCLUSIONS This study has shown that the human glenoid labrums compressive behavior varies around its circumference. The greater modulus of the anterosuperior portion of the labrum supports the theory that this area is anatomically different from the rest of the labrum and resists compressive loads. CLINICAL RELEVANCE These results may explain why the common type of SLAP lesions seen show failure at the interface between the labrum and the glenoid rather than within the substance of the labrum itself.

Testing and modelling of soft connective tissues of joints: A review

There is wealth of data from experimental and numerical methods of analysing and modelling soft connective tissues of joints. In recent years, the advances in computational and technological capabilities allowed for several aspects of the function and mechanical behaviour of soft connective tissues of joints to be explored. However, the nature of soft tissue poses a great challenge in characterizing its material behaviour in a repeatable and physiologically or clinically relevant manner. This review article attempts to present, critique, and suggest experimental and numerical methods that are associated with the function and mechanical response of soft connective tissues of joints.