An investigation of the inelastic behaviour of trabecular bone during the press-fit implantation of a tibial component in total knee arthroplasty.

The stress distribution and plastic deformation of peri-prosthetic trabecular bone during press-fit tibial component implantation in total knee arthroplasty is investigated using experimental and finite element techniques. It is revealed that the computed stress distribution, implantation force and plastic deformation in the trabecular bone is highly dependent on the plasticity formulation implemented. By incorporating pressure dependent yielding using a crushable foam plasticity formulation to simulate the trabecular bone during implantation, highly localised stress concentrations and plastic deformation are computed at the bone-implant interface. If the pressure dependent yield is neglected using a traditional von Mises plasticity formulation, a significantly different stress distribution and implantation force is computed in the peri-prosthetic trabecular bone. The results of the study highlight the importance of: (i) simulating the insertion process of press-fit stem implantation; (ii) implementing a pressure dependent plasticity formulation, such as the crushable foam plasticity formulation, for the trabecular bone; (iii) incorporating friction at the implant-bone interface during stem insertion. Simulation of the press-fit implantation process with an appropriate pressure dependent plasticity formulation should be implemented in the design and assessment of arthroplasty prostheses.

Cementing techniques for the tibial component in primary total knee replacement.

The optimum cementing technique for the tibial component in cemented primary total knee replacement (TKR) remains controversial. The technique of cementing, the volume of cement and the penetration are largely dependent on the operator, and hence large variations can occur. Clinical, experimental and computational studies have been performed, with conflicting results. Early implant migration is an indication of loosening. Aseptic loosening is the most common cause of failure in primary TKR and is the product of several factors. Sufficient penetration of cement has been shown to increase implant stability. This review discusses the relevant literature regarding all aspects of the cementing of the tibial component at primary TKR.

Translation of science to surgery: linking emerging concepts in biological cartilage repair to surgical intervention.

Orthopaedic surgery is in an exciting transitional period as modern surgical interventions, implants and scientific developments are providing new therapeutic options. As advances in basic science and technology improve our understanding of the pathology and repair of musculoskeletal tissue, traditional operations may be replaced by newer, less invasive procedures which are more appropriately targeted at the underlying pathophysiology. However, evidence-based practice will remain a basic requirement of care. Orthopaedic surgeons can and should remain at the forefront of the development of novel therapeutic interventions and their application. Progression of the potential of bench research into an improved array of orthopaedic treatments in an effective yet safe manner will require the development of a subgroup of specialists with extended training in research to play an important role in bridging the gap between laboratory science and clinical practice. International regulations regarding the introduction of new biological treatments will place an additional burden on the mechanisms of this translational process, and orthopaedic surgeons who are trained in science, surgery and the regulatory environment will be essential. Training and supporting individuals with these skills requires special consideration and discussion by the orthopaedic community. In this paper we review some traditional approaches to the integration of orthopaedic science and surgery, the therapeutic potential of current regenerative biomedical science for cartilage repair and ways in which we may develop surgeons with the skills required to translate scientific discovery into effective and properly assessed orthopaedic treatments.

The posterior cruciate ligament-preserving total knee replacement: do we 'preserve' it? A radiological study.

Our aims were to map the tibial footprint of the posterior cruciate ligament (PCL) using MRI in patients undergoing PCL-preserving total knee replacement, and to document the disruption of this footprint as a result of the tibial cut. In 26 consecutive patients plain radiography and MRI of the knee were performed pre-operatively, and plain radiography post-operatively. The lower margin of the PCL footprint was located a mean of 1 mm (-10 to 8) above the upper aspect of the fibular head. The mean surface area was 83 mm(2) (49 to 142). One-third of patients (8 of 22) had tibial cuts made below the lowest aspect of the PCL footprint (complete removal) and one-third (9 of 22) had cuts extending into the footprint (partial removal). The remaining patients (5 of 22) had footprints unaffected by the cuts, keeping them intact. Our study highlights the wide variation in the location of the tibial PCL footprint when referenced against the fibula. Proximal tibial cuts using conventional jigs resulted in the removal of a significant portion, if not all of the PCL footprint in most of the patients in our study. Our findings suggest that when performing PCL-retaining total knee replacement the tibial attachment of the PCL is often removed.

Caffey's disease: an unusual cause for concern.

BACKGROUND: Caffey's disease or infantile cortical hyperostosis is a rare cause of irritability, bone pain, soft tissue swelling and fever in the infant. AIMS: To review the presentation and diagnosis of an 8-week old infant with focal tenderness of the tibia. METHODS: The symptoms, signs, laboratory work-up and radiology are reviewed. RESULTS: The child presented with focal bony tenderness and pyrexia. Laboratory work-up was inconclusive. The diagnosis of Caffey's disease was made following a skeletal survey to outrule non-accidental injury, which showed similar changes of cortical thickening in the mandible as well as the affected tibia. CONCLUSIONS: With our increasing immigrant population, an increasing number of differential diagnoses must be considered when evaluating patients presenting to our emergency rooms. Caffey's disease is an unusual cause of bone pain in the infant. Symptoms and signs are subtle and the diagnosis is generally made with plain X-rays.

Total knee replacement in patients with multiple sclerosis.

Total knee replacement was performed on two patients with Multiple sclerosis. Severe hamstring spasticity was encountered in both patients in the immediate post-operative period requiring further surgery. Both patients remain ambulatory at follow-up. The disease, and its implications in patients warranting total joint replacement are discussed.

Short-term benefit of arthroscopic washout in degenerative arthritis of the knee.

Over a 4-year period, 55 consecutive knee arthroscopies were performed on 54 patients with symptomatic mild to moderate osteoarthritis. There were 30 female patients and the average patient age was 60.9 years. The average follow-up period was 29.6 months. All patients underwent diagnostic arthroscopy and washout. Further procedures including removal of loose bodies and partial meniscal resection were necessary in 19 patients. There were no significant postoperative complications. Thirty-seven patients had subjective improvement in symptoms. The average duration of benefit was 25.5 months. Arthroscopy and appropriate debridement of the degenerative knee results in significant subjective improvement. This relatively minor procedure can delay or indeed obviate the need for reconstructive surgery.

Metastatic thymic carcinoma in a digit: a case report.

Acrometastases are a rare but important clinical entity. We present the case of a 54-year-old man with a metastasis to a digit from a primary thymic carcinoma. The prognostic implications of such a diagnosis are discussed.