A discrete element model to predict anatomy of the psoas muscle and path of the tendon: Design implications for total hip arthroplasty.

BACKGROUND: The accurate estimation of a muscle's line of action is a fundamental requirement in computational modelling. We present a novel anatomical muscle wrapping technique and demonstrate its clinical use on the evaluation of the Psoas muscle mechanics in hip arthroplasty. METHODS: A volume preserving, spring model to parameterize muscle anatomy changes during motion is presented. Validation was performed by a CT scan of a cadaver model in multiple positions. The predicted psoas musculotendinous path was compared with the actual imaging findings. In a second stage, psoas kinetics were compared between a conventional versus a resurfacing hip arthroplasty during gait. FINDINGS: Anatomy prediction error was found to be 2.12 mm on average (SD 1.34 mm). When applied to psoas mechanics during walking, the muscle was found to wrap predominantly around the femoral head providing a biomechanically efficient and nearly constant moment arm for flexion during the entire gait cycle. However, this advantage was found to be lost in small diameter hip arthroplasty designs resulting in an important mechanical disadvantage. The moment arm for flexion, was on average 36% (SD 0.03%) lower in the small diameter conventional hip arthroplasty as compared to the large diameter head of the hip resurfacing and this difference was highly significant. (p < 0.001). INTERPRETATION: Despite the shortcomings of an "in silico" and cadaveric study, our findings are in accordance with previous clinical and gait studies. Furthermore, the findings are strongly in favour of large diameter implant designs, warranting their further development and optimisation.

Postmortem pump-driven reperfusion of the vascular system of porcine lungs: towards a new model for surgical training.

PURPOSE: The objective of this experiment is to establish a continuous postmortem circulation in the vascular system of porcine lungs and to evaluate the pulmonary distribution of the perfusate. This research is performed in the bigger scope of a revascularization project of Thiel embalmed specimens. This technique enables teaching anatomy, practicing surgical procedures and doing research under lifelike circumstances. METHODS: After cannulation of the pulmonary trunk and the left atrium, the vascular system was flushed with paraffinum perliquidum (PP) through a heart-lung machine. A continuous circulation was then established using red PP, during which perfusion parameters were measured. The distribution of contrast-containing PP in the pulmonary circulation was visualized on computed tomography. Finally, the amount of leak from the vascular system was calculated. RESULTS: A reperfusion of the vascular system was initiated for 37 min. The flow rate ranged between 80 and 130 ml/min throughout the experiment with acceptable perfusion pressures (range: 37-78 mm Hg). Computed tomography imaging and 3D reconstruction revealed a diffuse vascular distribution of PP and a decreasing vascularization ratio in cranial direction. A self-limiting leak (i.e. 66.8% of the circulating volume) towards the tracheobronchial tree due to vessel rupture was also measured. CONCLUSIONS: PP enables circulation in an isolated porcine lung model with an acceptable pressure-flow relationship resulting in an excellent recruitment of the vascular system. Despite these promising results, rupture of vessel walls may cause leaks. Further exploration of the perfusion capacities of PP in other organs is necessary. Eventually, this could lead to the development of reperfused Thiel embalmed human bodies, which have several applications.

Improved cone-beam computed tomography in supine and prone breast radiotherapy. Surface reconstruction, radiation exposure, and clinical workflow.

BACKGROUND AND PURPOSE: Cone-beam computerized tomography (CBCT) enables three-dimensional information of the scanned region and provides soft tissue images with good spatial resolution. Our aim was to optimize image acquisition settings for prone and supine breast radiotherapy with respect to contour accuracy, clinical practicalities, and radiation dose. PATIENTS AND METHODS: CBCT images were acquired for both prone and supine anthropomorphic phantoms and a female cadaver in supine and prone set-up. CBCT protocols were investigated by altering the tube current, exposure time, range of projection views, field of view (FOV), and starting angle. For clinical practicalities, the frequency of the use of an offset CBCT isocenter was evaluated at 558 205°-CBCTs (37 patients; 13 prone and 24 supine) and 1272 360°-CBCTs (102 patients; 13 prone and 89 supine). RESULTS: Prone and supine breast CBCT images acquired with a bowtie filter, a small FOV, a range of projection views equaling 180°, a tube current of 20 mA and an exposure time of 32 ms, demonstrated adequate contour accuracy and an elimination of the offset CBCT isocenter procedure, while this occurred in 40.7 % for the old full-rotation protocol. Furthermore a 4.3-fold dose reduction was observed for the Computed Tomography Dose Index (CTDIw) compared to the preset Chest M20 protocol. CONCLUSION: The established 180° protocol demonstrated acceptable contour accuracy, eliminated the CBCT isocenter offset procedure and reduced patient radiation exposure.

A description of the lumbar interfascial triangle and its relation with the lateral raphe: anatomical constituents of load transfer through the lateral margin of the thoracolumbar fascia.

Movement and stability of the lumbosacral region is contingent on the balance of forces distributed through the myofascial planes associated with the thoracolumbar fascia (TLF). This structure is located at the common intersection of several extremity muscles (e.g. latissimus dorsi and gluteus maximus), as well as hypaxial (e.g. ventral trunk muscles) and epaxial (paraspinal) muscles. The mechanical properties of the fascial constituents establish the parameters guiding the dynamic interaction of muscle groups that stabilize the lumbosacral spine. Understanding the construction of this complex myofascial junction is fundamental to biomechanical analysis and implementation of effective rehabilitation in individuals with low back and pelvic girdle pain. Therefore, the main objectives of this study were to describe the anatomy of the lateral margin of the TLF, and specifically the interface between the fascial sheath surrounding the paraspinal muscles and the aponeurosis of the transversus abdominis (TA) and internal oblique (IO) muscles. The lateral margin of the TLF was exposed via serial reduction dissections from anterior and posterior approaches. Axial sections (cadaveric and magnetic resonance imaging) were examined to characterize the region between the TA and IO aponeurosis and the paraspinal muscles. It is confirmed that the paraspinal muscles are enveloped by a continuous paraspinal retinacular sheath (PRS), formed by the deep lamina of the posterior layer of the TLF. The PRS extends from the spinous process to transverse process, and is distinct from both the superficial lamina of the posterior layer and middle layer of the TLF. As the aponeurosis approaches the lateral border of the PRS, it appears to separate into two distinct laminae, which join the anterior and posterior walls of the PRS. This configuration creates a previously undescribed fat-filled lumbar interfascial triangle situated along the lateral border of the paraspinal muscles from the 12th rib to the iliac crest. This triangle results in the unification of different fascial sheaths along the lateral border of the TLF, creating a ridged-union of dense connective tissue that has been termed the lateral raphe (Spine, 9,1984, 163). This triangle may function in the distribution of laterally mediated tension to balance different viscoelastic moduli, along either the middle or posterior layers of the TLF.

In vitro validation and reliability study of electromagnetic skin sensors for evaluation of end range of motion positions of the hip.

There is growing evidence that femoroacetabular impingement (FAI) is a probable risk factor for the development of early osteoarthritis in the nondysplastic hip. As FAI arises with end range of motion activities, measurement errors related to skin movement might be higher than anticipated when using previously reported methods for kinematic evaluation of the hip. We performed an in vitro validation and reliability study of a noninvasive method to define pelvic and femur positions in end range of motion activities of the hip using an electromagnetic tracking device. Motion data, collected from sensors attached to the bone and skin of 11 cadaver hips, were simultaneously obtained and compared in a global reference frame. Motion data were then transposed in the hip joint local coordinate systems. Observer-related variability in locating the anatomical landmarks required to define the local coordinate system and variability of determining the hip joint center was evaluated. Angular root mean square (RMS) differences between the bony and skin sensors averaged 3.2° (SD 3.5°) and 1.8° (SD 2.3°) in the global reference frame for the femur and pelvic sensors, respectively. Angular RMS differences between the bony and skin sensors in the hip joint local coordinate systems ranged at end range of motion and dependent on the motion under investigation from 1.91 to 5.81°. The presented protocol for evaluation of hip motion seems to be suited for the 3-D description of motion relevant to the experimental and clinical evaluation of femoroacetabular impingement.

Neuroanatomy and neurophysiology related to sexual dysfunction in male neurogenic patients with lesions to the spinal cord or peripheral nerves.

STUDY DESIGN: Review article. OBJECTIVES: The neuroanatomy and physiology of psychogenic erection, cholinergic versus adrenergic innervation of emission and the predictability of outcome of vibration and electroejaculation require a review and synthesis. SETTING: University Hospital Belgium. METHODS: We reviewed the literature with PubMed 1973-2008. RESULTS: Erection, emission and ejaculation are separate phenomena and have different innervations. It is important to realize, which are the afferents and efferents and where the motor neuron of the end organ is located. When interpreting a specific lesion it is important to understand if postsynaptic fibres are intact or not. Afferents of erection, emission and ejaculation are the pudendal nerve and descending pathways from the brain. Erection is cholinergic and NO-mediated. Emission starts cholinergically (as a secretion) and ends sympathetically (as a contraction). Ejaculation is mainly adrenergic and somatic. For vibratory-evoked ejaculation, the reflex arch must be complete; for electroejaculation, the postsynaptic neurons (paravertebral ganglia) must be intact. CONCLUSION: Afferents of erection, emission and ejaculation are the pudendal nerve and descending pathways from the brain. Erection is cholinergic and NO-mediated. Emission starts cholinergically (as a secretion) and ends sympathetically (as a contraction). Ejaculation is mainly adrenergic and somatic. In neurogenic disease, a good knowledge of neuroanatomy and physiology makes understanding of sexual dysfunction possible and predictable. The minimal requirement for the success of penile vibration is a preserved reflex arch and the minimal requirement for the success of electroejaculation is the existence of intact post-ganglionic fibres.

Assessing the quality of asthma care provided to Medicaid patients enrolled in managed care organizations in Connecticut.

BACKGROUND: Many states have enrolled Medicaid beneficiaries in managed care organizations (MCOs). Few assessments of the quality of asthma care provided by these new programs are available. OBJECTIVE: To describe the quality of care provided to asthmatic Medicaid children enrolled in MCOs. METHODS: For this cross-sectional survey, a chart abstraction tool was developed to evaluate fulfillment of key performance measures chosen from a national guideline for asthma diagnosis and management. These measures were prescription of an inhaled anti-inflammatory medication, accomplishment of patient education, evaluation of exposure to environmental triggers of asthma, and administration of influenza vaccination. From State of Connecticut administrative databases, a random sampling of Medicaid children, ages 5 to 18 years, enrolled in four MCOs was selected. Chart entries from July 1, 1996 to June 30, 1997 were reviewed using the abstraction tool. Accomplishment of performance measures was evaluated for the total sample and for children who were high utilizers of medical services (at least one ED visit or hospitalization during the study period). RESULTS: For 80 high utilizers among 315 children, completion of performance measures was suboptimal: 46% were prescribed inhaled steroids; an action plan was outlined for 43%; evaluation of patient or family tobacco use was documented for 56%; evaluation of the presence of a pet for 43% or mite exposure for 19%; and allergy skin testing or RAST was accomplished for 15%. CONCLUSIONS: This information suggests that opportunities exist to improve the quality of care for these children.

Factors influencing mammography use among women in Medicare managed care.

This article presents findings about the mammography screening experience of Medicare members of a health maintenance organization (HMO). Based on a mail survey of 309 women, we assessed factors that may be facilitators or barriers to this service for older women. The results indicate that these respondents generally are receiving timely mammograms; over three-quarters (79 percent) reported having a mammogram in the past 2 years. Multivariate analysis showed that women who were younger (under 75 years of age), believed in the importance of screening, had been told by a physician to obtain a mammogram, and were more satisfied with their physician and more likely to report mammography use.

The status of prenatal care among Medicaid Managed Care patients in Connecticut.

Providing quality prenatal care to high-risk, pregnant adolescents represents an important challenge to health care providers and health plans. Using national prenatal care guidelines, this study sought to evaluate the quality of important processes and outcomes of prenatal care delivered to women age 21 years and younger enrolled in three health plans serving the Connecticut Medicaid population. Some important findings include 93% compliance with recommended processes of prenatal care, an 11% C-section rate, an average length of hospital stay of 4.0 days for women having a C-section, and a 10% premature delivery rate. Opportunities for improvement include 40% failing to begin prenatal care in the first trimester, 31% not receiving the recommended number of prenatal care visits, and 8% delivering a low-birth-weight infant. This study provides important descriptive information on processes and outcomes of care for pregnant adolescents within Medicaid Managed Care and also identifies opportunities for improvement.

When consultants write orders: physicians' attitudes, beliefs, and practices.

The process by which a consultation is performed may significantly impact the extent to which the content of the consultation contributes positively to patient care. The practice of consultants writing orders independent of the explicit permission of the consultation requester is a common event. A survey of 211 multispecialty physicians on the medical staff of a large, urban, Northeastern, teaching hospital about their attitudes, beliefs, and practices regarding consultation on the inpatient service reveal that the majority of respondents in all specialties were unaware of departmental or hospital policy regarding the practice of consultant order writing. Significant differences between specialties existed in the perception of the impact of consultant order writing on patient outcomes, in the practice of discussion with the primary attending prior to order writing, and in the documentation practices. The authors discuss such results and their policy implications in light of important medico-legal and ethical principles, and best practice standards.

Mental retardation and decision making: balancing autonomy and protection.

Balancing autonomy with protection in caring for patients with mental retardation remains a formidable task for many clinicians. Though historical debate has resulted in an attitude supporting increased autonomy for all patients generally, and in legislation for enhanced decision making for the developmentally disabled specifically, the operationalization of such attitudes and policies lacks sufficient attention in the literature. The authors discuss three important areas of decision making as these relate to the care of patients with mental retardation: competence, respect, and multiple stakeholders; and, offer recommendations in each area to provide clinicians with some guidance in balancing the goals of autonomy and protection in clinical care when treating people with mental retardation.