Hippolite O. Amadi

A biomechanical study of the meniscofemoral ligaments and their contribution to contact pressure reduction in the knee

The aim of this study was to test the hypothesis that the meniscofemoral ligaments (MFLs) of the human knee assist the lateral meniscal function in reducing tibiofemoral contact pressure. Five human cadaveric knee joints were loaded in axial compression in extension using a 4-degree of freedom rig in a universal materials testing machine. Contact pressures pre- and post-sectioning of the MFLs were measured using pressure sensitive film. Sectioning the MFLs increased the contact pressure significantly in the joints for two of the four measures. In addition to their known function in assisting the posterior cruciate ligament (PCL) to resist tibiofemoral posterior drawer, the MFLs also have a significant role in reducing contact stresses in the lateral compartment. Their retention in PCL and meniscal surgery is therefore to be advised.

A scapular coordinate frame for clinical and kinematic analyses

The aim of this study was to define a body-fixed coordinate frame for the scapula that minimises axes variability and is closely related to the clinical frame of reference. Medical images of 21 scapulae were used to quantify 14 different axes from identifiable landmarks. The plane of the blade of the scapula was defined. The orientations of the quantified axes were calculated. The angular relationships between axes were quantified and applied to grade the sensitivity of each axis to inter-scapular variations in the others. The volume of data required to define an axis was noted for its dependency on pathology and the three criteria were weighted according to relative importance. The two axes with the highest weighting were applied to define a body-fixed Cartesian coordinate frame for the scapula. A least square medio-lateral line through the centre of the spine root was the most optimal axis. The plane formed by the spine root line and a least square line through the centre of the lateral border ridge was the most optimal scapular plane. This body-fixed Cartesian coordinate frame is closely aligned to the cardinal planes in the anatomical position and thus is a clinically applicable, specimen invariant coordinate frame that can be used in patient-specific kinematics modelling.

A numerical tool for the reconstruction of the physiological kinematics of the glenohumeral joint

Abstract The aim of this study was to develop and test a robust approach to apply a joint coordinate system (JCS) to imaging data sets of the glenohumeral joint and to reconstruct the kinematics with six degrees of freedom (6DOF) in order to investigate shoulder pathologies related to instability. Visible human data were used to reconstruct bony morphology. Landmarks were used to define axes for body-fixed Cartesian coordinate frames on the humerus and scapula. These were applied to a three-cylinder open-chain JCS upon which the humeral 6DOF motions relative to the scapula were implemented. Software was written that applies 6DOF input variables to rotate and translate the nodes of the surface geometry of the humerus relative to the scapula in a global coordinate frame. The instantaneous relative position and orientation of the humerus for a given set of variables were thus reconstructed on the bone models for graphical display. This tool can be used for graphical animation of shoulder kinematics, demonstrating clinical assessments, and allowing further analysis of the function of tissues within the joint.

Definition of the capsular insertion plane on the proximal humerus

The aim of this work was quantitatively to establish the relationship between the plane that hosts the humeral head lateral margin (anatomical neck) and that of the capsular insertion. Eight cadaveric shoulders were used. These were dissected, exposing the humeral head margin and the root of the capsular humeral insertion to extract digitally their outlines using a mechanical 3‐d digitizer. The datasets of the digitized outlines were applied and the geometric planes they best fitted mathematically calculated. Vector analysis techniques were finally applied to the two planes to quantify the relationship between them. The humeral head margin is circular (± 2.2% of radius), having each of its outlining points on the same plane (within ± 1.5 mm.) The capsular attachment outlining points also insert on a plane (± 1.4 mm). The two planes are related to one another by an inclination of 14.5 ± 3.6°. The relationship described here would allow for in vivo prediction of humeral attachment of capsular structures by using radiological datasets of the anatomical neck. This would be useful in patient‐specific modelling to study and understand the glenohumeral ligament kinematics during clinical examinations and to plan surgical reconstructive procedures.

An optimised method for quantifying glenoid orientation

A robust quantification method is essential for inter-subject glenoid comparison and planning of total shoulder arthroplasty. This study compared various scapular and glenoid axes with each other in order to optimally define the most appropriate method of quantifying glenoid version and inclination. Six glenoid and eight scapular axes were defined and quantified from identifiable landmarks of twenty-one scapular image scans. Pathology independency and insensitivity of each axis to inter-subject morphological variation within its region was tested. Glenoid version and inclination were calculated using the best axes from the two regions. The best glenoid axis was the normal to a least-square plane fit on the glenoid rim, directed approximately medio-laterally. The best scapular axis was the normal to a plane formed by the spine root and lateral border ridge. Glenoid inclination was 15.7° ± 5.1° superiorly and version was 4.9° ± 6.1°, retroversion. The choice of axes in the present technique makes it insensitive to pathology and scapular morphological variabilities. Its application would effectively improve inter-subject glenoid version comparison, surgical planning and design of prostheses for shoulder arthroplasty.

Neonatal Thermoneutrality in a Tropical Climate

Sub-Saharan African countries are notably among the nations with high neonatal mortality (NNMR) and morbidity rates (WHO, 2009). A number of issues have been previously raised in the literature in attempt to define some of the factors that contribute to these such as level of illiteracy among mothers and short supply of healthcare workers (Amadi et al., 2007). However, little has been said of the impact of environmental temperature regulation on the wellness and survival of neonates in this region. The sub-Saharan Africa is well-known for its harsh climatic conditions of high sun intensity and ambient temperatures, often in excess of 35°C, coupled with societal condition of abject poverty. Nursing environment of the neonate, especially pre-terms, is a crucial factor for the maintenance of appropriate body temperature for the physiological stability of the newborn. Classical management of neonatal thermoneutrality in this region of Africa has been dominated by procedures that were handed down from industrialised societies; these being fundamentally compliant to the peculiar climatic factors and social advantages of the countries of origin. In the last decade, there has been concerted effort to scientifically investigate factors that may be subtly contributing to high neonatal mortality and morbidity in this region. These include meteorological, socio-cultural and technological factors that define the macroand micro-environments immediate to the neonate. This knowledge is fundamental for the tweaking or outright replacement of the present morbidity-high techniques. This chapter will attempt to explore these factors and their consequences, and discuss the present interventions and techniques that are coincidentally yielding improved outcome in some neonatal centres in the region. The ideas expressed in this chapter were drawn from on-thespot clinical practice experiences in a decade-on collaborative project that has involved up to 21 neonatal referral Centres across the entire geographical region of the West African state of Nigeria (Figure 1). Recent publications show that this region of African is currently far behind the United Nation’s Millennium Development Goal (MDG) target on the survival of infants, and neonatal mortality rate is steadily making this worse (Federal Ministry of Health [FMOH], 2011). Neonatal survival might not necessarily improve by the flooding of the region with ‘foreign-culture-biased’ sophisticated incubator systems that are not so easy to handle by the users despite the high pricing of these that limit their procurement by the poor countries. There is a perceived socio-cultural dimension of the work place attitude that militates against effective practice of neonatal thermoregulation. This needed to be properly addressed perhaps by the use of affordable and manageable appropriate incubation technology that the people can easily identify with.

The Impact of Recycled Neonatal Incubators in Nigeria: A 6-Year Follow-Up Study

Nigeria has a record of high newborn mortality as an estimated 778 babies die daily, accounting for a ratio of 48 deaths per 1000 live births. The aim of this paper was to show how a deteriorating neonatal delivery system in Nigeria may have, in part, been improved by the application of a novel recycled incubator technique (RIT). Retrospective assessment of clinical, technical, and human factors in 15 Nigerian neonatal centres was carried out to investigate how the application of RIT impacted these factors. Pre-RIT and post-RIT neonatal mortalities were compared by studying case files. Effect on neonatal nursing was studied through questionnaires that were completed by 79 nurses from 9 centres across the country. Technical performance was assessed based on 10-indices scores from clinicians and nurses. The results showed an increase in neonatal survival, nursing enthusiasm, and practice confidence. Appropriately recycled incubators are good substitutes to the less affordable modern incubators in boosting neonatal practice outcome in low-income countries.

Digitally recycled incubators: better economic alternatives to modern systems in low-income countries.

Abstract The need to maintain a neutral thermal environment is critical to newborn care. Aim: To investigate reasons for the insufficiency of functional incubators and develop a cost-effective technique for using electronic digital components to recycle obsolete incubators in Nigeria. Methods: Following interview of 84 clinicians and administrators in Nigerian hospitals, it was identified that inadequate funding was the main reason for lack of functional incubators. Two groups of incubator units were then created and their performance compared. Sixteen units of modern (group A) and 19 units of obsolete (group B) incubators were obtained from six hospitals. An assembly design applying independent generic components for recycling systems was specified and produced. These were sourced through the internet at competitive cost and fitted into the reconstructed panels of the obsolete systems. The functional performance of each recycled system was rigorously monitored for 6 months and graded using ten performance indices. The same indices were used to quantify group A systems. Results: The performance of the recycled incubators (group B) was found to be similar to those of modern incubators. Group Bs cost index was found to be 25% of that of group As. Conclusion: Appropriate incubator recycling is a cost-effective method of re-equipping hospitals in low-income countries.

A motion-decomposition approach to address gimbal lock in the 3-cylinder open chain mechanism description of a joint coordinate system at the glenohumeral joint

In this study, the standard-sequence properties of a joint coordinate system were implemented for the glenohumeral joint by the use of a set of instantaneous geometrical planes. These are: a plane that is bound by the humeral long axis and an orthogonal axis that is the cross product of the scapular anterior axis and this long axis, and a plane that is bounded by the long axis of the humerus and the cross product of the scapular lateral axis and this long axis. The relevant axes are updated after every decomposition of a motion component of a humeral position. Flexion, abduction and rotation are then implemented upon three of these axes and are applied in a step-wise uncoupling of an acquired humeral motion to extract the joint coordinate system angles. This technique was numerically applied to physiological kinematics data from the literature to convert them to the joint coordinate system and to visually reconstruct the motion on a set of glenohumeral bones for validation.

Development and validation of a model for quantifying glenohumeral ligament strains during function

Analysis of the function of glenohumeral ligaments (GHLs) during physical joint manipulations is hindered by an inability to adequately image these tissues during the movements. This restricts functional biomechanics studies only to the manoeuvres that may be replicated cadaverically. There is, however, a clinical imperative to be able to investigate complex manoeuvres that exacerbate symptoms but cannot be easily conducted physically in the laboratory. The aim of this study was to develop and validate an algorithm for a computer simulation model that allows the quantification of glenohumeral ligament lengths during function. Datasets of the humerus and scapula pair were segmented to provide individual surface meshes of the bones and insertion points of each glenohumeral ligament on both bones. An algorithm was developed in which the glenohumeral ligament attachment-to-attachment length was divided into two straight lines, plus an arc overlaying the spherical wrapping portions. The model was validated by simulating two classical cadaveric studies from the literature and comparing results. Predictions from the model were qualitatively similar to the results of the two cadaveric studies by a factor of 91.7% and 81.8%, respectively. Algorithm application will allow investigation of functional loading of the glenohumeral ligaments during simulated complex motions. This could then be used to provide diagnostic understanding and thus, inform surgical reconstruction.