The forces in the distal femur and the knee during walking and other activities measured by telemetry.

The forces and moments in the shaft of a distal femoral replacement were measured by telemetry for a subject during different activities, and calculations were then made of the forces at the knee. The axial force showed a small peak at heel-strike followed by two main peaks during stance. In level walking, the peak axial force was between 1,487 and 1,718 N (2.

Pictorial review: ultrasonography of primary bone tumours.

We present our experience with the use of ultrasonography in the assessment of suspected primary or recurrent bone tumours of the appendicular skeleton and pelvis in 73 patients. Ultrasound can effectively assess the extraosseous component of malignant and aggressive benign lesions and those tumours arising from the surface of the bone. Periosteal reaction, cortical destruction, pathological fracture, matrix mineralization, fluid-fluid levels and involvement of the neurovascular bundle are all identified.

Possible effects of fatigue on muscle efficiency.

The efficiency of energy transduction is defined as the ratio of the work done by a muscle to the free energy change of the chemical processes driving contraction. Two examples of the experimental measurement of muscle efficiency are: (1) the classical method of Hill which measures the value during a steady state of shortening, (2) measuring the overall efficiency during a complete cycle of a sinusoidal process, which comes closer to the situation during natural locomotion. The reasons why fatigue might lower efficiency are the following.

Effects on the vertebral end-plate of uncomplicated lumbar discography: an MRI study.

The study aimed to identify and characterise changes occurring in the vertebral end-plate on MRI following uncomplicated lumbar discography. MRI was performed immediately before and within 2 h after uncomplicated lumbar discography in 20 consecutive patients undergoing the study as a precursor to possible spinal fusion. Of these, seven patients underwent a further MRI study at a mean of 72 days after discography (range 19-183 days).

Orientation of lumbar pars defects: implications for radiological detection and surgical management.

Lateral oblique radiographs are considered important for the identification of spondylolytic lesions, but these projections will give a clear view only when the radiological beam is in the plane of the defect. We studied the variation in orientation of spondylolytic lesions on CT scans of 34 patients with 69 defects. There was a wide variation of angle: only 32% of defects were orientated within 15 degrees of the 45 degrees lateral oblique plane.

The value of lumbar spine magnetic resonance imaging in the demonstration of anular tears.

Study Design: Retrospective review of magnetic resonance imaging and discography in patients investigated for low back pain before spinal fusion.

Objective: To determine the sensitivity of magnetic resonance imaging in the detection of painful anular tears manifested by the high-intensity zone.

Summary Of Background Data: Two studies have produced results showing that magnetic resonance imaging has a high specificity for the detection of painful anular tears manifested by a high-intensity zone.

Osteoid osteoma and osteoblastoma of the spine. Factors associated with the presence of scoliosis.

Study Design: A retrospective study of 44 museum cases of spinal osteoid osteoma or osteoblastoma and a meta-analysis using 421 additional cases from a review of the literature.

Objectives: To identify the factors that are associated with the development of scoliosis in these patients.

Summary Of Background Data: Painful scoliosis is a well recognized presentation of spinal osteoid osteoma and osteoblastoma and is considered to be secondary to pain-provoked muscle spasm on the side of the lesion.

Mechanical and energy characteristics during shortening in isolated type-1 muscle fibres from Xenopus laevis studied at maximal and submaximal activation.

The mechanical and energy characteristics of isolated fast-twitch muscle fibres (type 1) of Xenopus laevis in isometric- and isovelocity contractions were measured at 20 degrees C. The fibres were stimulated at either 60 Hz or 20 Hz to produce contractions at different levels of activation. The high stimulation frequency gave fused contractions, while at the low stimulation frequency tension fluctuated.

The value of lumbar spine MRI in the assessment of the pars interarticularis.

The aim of this study is to assess the ability of conventional lumbar spine magnetic resonance imaging (MRI) to demonstrate the pars interarticularis. The right and left L4 and L5 pars in 50 patients undergoing lumbar spine MRI for low back pain, with or without radiculopathy, were assessed and classified into four types. Based on their appearance, 59 (29.

Defining the use of gadolinium enhanced MRI in the assessment of the postoperative lumbar spine.

A retrospective study of case notes and magnetic resonance imaging (MRI) examinations was performed to assess the value of gadolinium enhanced MRI in the investigation of persistent back pain following lumbar spine surgery in patients who have not had a discectomy for disc herniation. Gadolinium enhancement is commonly used during MRI of patients with persistent back pain following surgery and epidural scar is frequently identified in patients who have had a previous discectomy. However the value of gadolinium enhancement in patients without previous discectomy had not been addressed.

Sagittal vertebral body fractures: magnetic resonance imaging features.

Isolated sagittal vertebral body fractures are rare and the plain radiographic diagnosis may be difficult. We report two cases, confirmed by CT, and describe the subtle MRI features which comprised increased signal intensity only on the midline sagittal T2 weighted images. In one case, the information from MRI significantly altered the patient's management by leading to a change from surgical to conservative treatment.

Vesico-ureteric reflux in adult patients with spinal injury.

Objectives: To review the incidence, aetiology, treatment and prognosis of vesico-ureteric reflux (VUR) in patients in a regional spinal injuries centre.

Patients And Methods: A retrospective review of radiological investigations revealed 34 of 447 (8%) patients with VUR on at least one study. The notes of these patients were examined to determine their management and outcome.

Ionising radiation: are orthopaedic surgeons' offspring at risk?

The hazards of exposure to ionising radiation are well documented. Fears have been raised that occupational exposure to ionising radiation by orthopaedic surgeons may have detrimental effects on the future health of their unborn offspring. The current members of the British Orthopaedic Trainees' Association and orthopaedic consultants appointed during the last 5 years in the United Kingdom were contacted using a postal questionnaire.

Treatment of Morton's neuroma by neurolysis.

Thirty-five patients who had undergone neurolysis for Morton's neuroma were reviewed at a mean of 21.4 months. Those patients who had received diagnostic lidocaine (local anesthetic) injections as an evaluation tool before the operation did extremely well after this operation.

Telemetry of forces from proximal femoral replacements and relevance to fixation.

Two proximal femoral replacements were instrumented to enable axial forces to be determined at two sites within the prosthesis: in the main shaft and near the tip of the intramedullary stem. The goal was to measure the changes in force distribution over time, as indicated by the ratio of the two forces. Inductive coupling between a coil worn around the leg and a small implanted coil was used, both to supply power to electronic circuits sealed into a welded cavity in the prosthesis and to telemeter data from the prosthesis.

An unusual manifestation of bleeding diathesis in a patient with osteogenesis imperfecta.

We present the anaesthetic and surgical management, and post-operative course of a patient with osteogenesis imperfecta which exemplifies the problems associated with this condition. The observed petechial haemorrhagic rash is not characteristic of the bleeding tendency in osteogenesis imperfecta nor characteristic of acute disseminated intravascular coagulation. Despite potential life-threatening complications the patient made a good recovery and was discharged 3 weeks after surgery.

Survey of spinal therapeutic procedures in the United Kingdom.

The type and frequency of spinal therapeutic work being undertaken in the United Kingdom (UK) by clinicians with an interest in the surgical treatment of disorders of the spine (primary and secondary subspecialty interest) were evaluated by means of a postal questionnaire. The willingness of respondents to take part in postgraduate spinal training was determined along with issues regarding accessibility of spinal services to non-specialist physicians in the health service in the UK. The results of 450 respondents provided insight into the types of procedures taking place, for example: primary spinal decompression was regularly carried out by 76% of surgeons, while at least 20% of respondents regularly carried out 66% of the procedures surveyed.

Spinal cord monitoring in operations for neuromuscular scoliosis.

We reviewed retrospectively the role of monitoring of somatosensory spinal evoked potentials (SSEP) in 99 patients with neuromuscular scoliosis who had had operative correction with Luque-Galveston rods and sublaminar wiring. Our findings showed that SSEP monitoring was useful and that a 50% decrease in the amplitude of the trace optimised both sensitivity and specificity. The detection of true-positive results was higher than in cases of idiopathic scoliosis, but the method was less sensitive and specific and there were more false-negative results.

Radiological and clinical recurrence of giant-cell tumour of bone after the use of cement.

We have reviewed 13 operations on 11 patients using curettage and polymethylmethacrylate cement for giant-cell tumour of bone (GCT) to assess the value of radiology in the early detection of recurrence. There were four recurrences, the most specific radiological sign on plain radiography was lysis of 5 mm or more at the cement-bone interface. This preceded clinical signs by a mean of four months and was identified at a mean of 3.

A knee simulating machine for performance evaluation of total knee replacements.

A knee simulating machine is required for the design and evaluation of total knee replacements, the kinematics and the long-term wear being aspects of particular importance. There are no generally agreed design criteria, such that existing designs of simulator have a wide variety of input and constraint conditions. In this study, it was postulated that in order to reproduce physiological wear patterns, the correct kinematics is required, on the basis that the wear will be a direct function of the sliding, rolling and tractive rolling conditions at the joint surfaces.

The effects of the level of activation and shortening velocity on energy output in type 3 muscle fibres from Xenopus laevis.

We investigated the effect of shortening velocity on the efficiency of single intact slow-twitch muscle fibres (type 3) of Xenopus laevis, at different levels of activation (10, 15, 20 and 40 Hz). Fused contractions were obtained at 40 Hz stimulation. When maximal isometric force had been reached, the fibres were shortened by 10% of the fibre length (L0) at 0.