The work reported in this paper encapsulates the theories and algorithms developed to drive the core analysis modules of the software which has been developed to model a musculoskeletal structure of anatomic joints. Due to local bone surface and contact geometry based joint kinematics, newly developed algorithms make the proposed modeller different from currently available modellers. There are many modellers that are capable of modelling gross human body motion. Nevertheless, none of the available modellers offer complete elements of joint modelling. It appears that joint modelling is an extension of their core analysis capability, which, in every case, appears to be musculoskeletal motion dynamics. It is felt that an analysis framework that is focused on human joints would have significant benefit and potential to be used in many orthopaedic applications. The local mobility of joints has a significant influence in human motion analysis, in understanding of joint loading, tissue behaviour and contact forces. However, in order to develop a bone surface based joint modeller, there are a number of major problems, from tissue idealizations to surface geometry discretization and non-linear motion analysis. This paper presents the following: (a) The physical deformation of biological tissues as linear or non-linear viscoelastic deformation, based on spring-dashpot elements. (b) The linear dynamic multibody modelling, where the linear formulation is established for small motions and is particularly useful for calculating the equilibrium position of the joint. This model can also be used for finding small motion behaviour or loading under static conditions. It also has the potential of quantifying the joint laxity. (c) The non-linear dynamic multibody modelling, where a non-matrix and algorithmic formulation is presented. The approach allows handling complex material and geometrical nonlinearity easily. (d) Shortest path algorithms for calculating soft tissue line of action geometries. The developed algorithms are based on calculating minimum ‘surface mass’ and ‘surface covariance’. An improved version of the ‘surface covariance’ algorithm is described as ‘residual covariance’. The resulting path is used to establish the direction of forces and moments acting on joints. This information is needed for linear or non-linear treatment of the joint motion. (e) The final contribution of the paper is the treatment of the collision. In the virtual world, the difficulty in analysing bodies in motion arises due to body interpenetrations. The collision algorithm proposed in the paper involves finding the shortest projected ray from one body to the other. The projection of the body is determined by the resultant forces acting on it due to soft tissue connections under tension. This enables the calculation of collision condition of non-convex objects accurately. After the initial collision detection, the analysis involves attaching special springs (stiffness only normal to the surfaces) at the ‘potentially colliding points’ and motion of bodies is recalculated. The collision algorithm incorporates the rotation as well as translation. The algorithm continues until the joint equilibrium is achieved. Finally, the results obtained based on the software are compared with experimental results obtained using cadaveric joints.

ABSTRACT

Background: Antidepressant effects have been demonstrated with both high-frequency left-sided repetitive transcranial magnetic stimulation (rTMS) (HFL-TMS) and low-frequency stimulation to the right prefrontal cortex (LFR-TMS). However, doubts remain about the extent of these reported treatment effects. Design and Methods: The study was a 6 week double-blind randomized sham-controlled trial of sequential bilateral rTMS (SBrTMS) in depression. The method consisted of 3 trains of LFR-TMS of 140 s duration at 1 Hz being applied daily followed immediately by 15 trains of 5 s duration of HFL-TMS at 10 Hz. Sham stimulation was applied using identical parameters, but with the coil angled at 45 degrees from the scalp resting on the side of one wing of the coil. Results: There was a significant difference in response between the two groups at the 2-week time-point (F(1,25) = 25.5, p < 0.001) and for the full duration of the study (F(5,44) = 3.9, p = 0.005). A significant proportion of the active study group met response (11/25) and remission criteria (9/25) by study end compared to the sham group (2 and 0/22). Interpretation: Bilateral rTMS treatment, involving the sequential application of both HFL-TMS and LFR-TMS, has substantial treatment efficacy in patients with treatment-resistant depression. The treatment response is clinically significant following 4–6 weeks of active treatment. Therefore this novel style of bilateral rTMS has the potential to become a substantive clinical intervention, although the study requires replication.

According to the American Cancer Society, more than 211 000 women in the USA were diagnosed with invasive breast cancer in 2005, (American Cancer Society. www.cancer.org. 2005). Nearly 65 000 of these women had postmastectomy reconstruction – a 100% increase from just over a decade ago, (American Society of Plastic Surgeons. www.plasticsurgery.org. 2005). A significant proportion of these women, will elect to undergo bilateral mastectomy for treatment and/or prophylaxis of breast cancer. Contemporary techniques provide numerous options for bilateral, postmastectomy reconstruction. Procedure selection will be based on a range of patient variables, including: availability of local, regional, and distant donor tissues for bilateral reconstruction, size and shape of the desired breasts, surgical risk, and most importantly, patient preference. Ultimately, the individualized selection of a reconstructive technique for each patient is a predominant factor in achieving a reconstructive success.

A case of Wegener’s granulomatosis (WG) presenting with hearing loss and right facial nerve palsy is reported. The definitive diagnosis was based upon clinical data and serum cANCA and AECA detection. Early assessment of WG prevented surgical facial nerve decompression to treat a chronic otitis media complication. Immunosuppressive therapy with steroids, cyclophosphamide and methotrexate was required for relief of clinical symptoms and cANCA negativity as an expression of disease remission. The effectiveness of co-trimoxazole for preventing relapses of WG is discussed.

We report a 68-year-old male with a rare case of synchronous bilateral carcinomas of the maxillary sinus. A CT scan revealed a large tumour mass that extruded from the left maxillary sinus; tissue of soft density filled the right antrum which had intact bony walls. A probe antrostomy on the right side disclosed a tumour which was diagnosed histologically as the same poorly differentiated squamous cell carcinoma as that in the left antrum. The incidence and aetiology of this disorder are presented, and its diagnosis and management are discussed.

The neurofibromatoses consist of at least two distinct autosomal dominant hereditary disorders. Neurofibromatosis type 1 (NF1) is due to a lesion on chromosome 17q. Neurofibromatosis type 2 (NF2) is caused by a defect on chromosome 22q. The hallmark of NF2 is the development, in the second and third decades, of bilateral acoustic neuromas. NF1 is characterized by the appearance of cafe-au-lait spots and neurofibromas in addition to iris hamartomas, or Lisch nodules, of the eye, during the first and second decades.

Ten families were personally studied. A total of 16 members were found to be affected with NF2. A protocol for evaluation and review of subjects and relatives of NF2 families is proposed. A team approach, coordinating the expertise of multiple specialties is recommended.

A study was undertaken on a 3.2 kilogram fresh stillborn neonate, to determine ways and means of preventing damage to the skull base.

Gruber and Rosen aural specula were inserted separately into the right nostril, to determine the degree of exposure of the choana with each. The position of the surgeon was varied (septoplasty versus tonsillectomy position), to determine on which anatomical site of the choana the surgeon's field of vision was focused.

The Gruber aural speculum, gave a completely, uninterrupted view of the choana.

In the tonsillectomy position, the entire field of vision was focused on the choana itself, whilst in the septoplasty position, one half was focused on the choana and the other half on the roof. Since the roof is part of the skill base, damage to this area can result in serious intracranial complications, such as CSF leak and meningitis.

These complications can be avoided if the surgeon uses the Gruber aural speculum for exposure and operates from a tonsillectomy position.

A patient with neurofibromatosis two (NF2) presented with bilateral acoustic neuroma. Pre-operative audiometry revealed a dead right ear and severe left-sided sensorineural hearing loss. Following surgical removal of the larger right acoustic neuroma we have documented a sensorineural improvement of 45 dB in the contralateral ear on pure tone audiometry, which as far as the authors are aware has not previously been described.