Aims

The aim of this study was to assess orthopaedic oncologic patient morbidity resulting from COVID-19 related institutional delays and surgical shutdowns during the first wave of the pandemic in New York, USA.

Fatigue fractures which originate at stress-concentrating voids located at the implant-cement interface are a potential cause of septic loosening of cemented femoral components. Heating of the component to 44°C is known to reduce the porosity of the cement-prosthesis interface. The temperature of the cement-bone interface was recorded intra-operatively as 32.3°C. A simulated femoral model was devised to study the effect of heating of the component on the implant-cement interface. Heating of the implant and vacuum mixing have a synergistic effect on the porosity of the implant-cement interface, and heating also reverses the gradients of microhardness in the mantle. Heating of the implant also reduces porosity at the interface depending on the temperature. A minimum difference in temperature between the implant and the bone of 3°C was required to produce this effect. The optimal difference was 7°C, representing a balance between maximal reduction of porosity and an increased risk of thermal injury. Using contemporary cementing techniques, heating the implant to 40°C is recommended to produce an optimum effect

We report a retrospective review of 62 consecutive patients who had a vascularised fibular transfer to reconstruct a large skeletal defect. We were particularly interested in the bone dynamics of the vascularised graft, since fractures occurred in 25% of the cases at an average time of eight months after surgery. Hypertrophy was more common when the limb was mechanically loaded; it was enhanced where the graft was not bypassed by internal fixation. The length of the graft and the use of additional bone graft material had no influence on the incidence of stress fracture or on hypertrophy. We conclude that a vascularised graft should be protected against fatigue fracture during the first year, and that a gradual increase in mechanical loading will enhance remodelling and hypertrophy

Spondylolysis occurring after a spinal fusion is considered to result from operative damage to the pars interarticularis on both sides. Fourteen cases are reported, and compared with the 23 cases which have previously been published. The defects are usually recognised within five years of fusion, and usually occur immediately above the fusion mass. Other contributory causes may be: fatigue fracture from concentration of stress; damage and altered function of the posterior ligament complex; and degenerative disc disease immediately above or below the fusion. Fusion technique is critical, since virtually all cases occurred after posterior interlaminar fusions. This complication is easily overlooked in patients with recurrent back pain after an originally successful posterior spinal fusion

Fifteen patients who limped and had early fatigue on walking caused by ischaemic necrosis after treatment for congenital dislocation of the hip had distal and lateral transfer of the greater trochanter. Nine of them in whom the predicted leg-length discrepancy was more than 3 cm also had epiphysiodesis of the contralateral leg. At skeletal maturity the limp was eliminated and walking distance was significantly improved in them all. In those who had epiphysiodesis the average leg-length discrepancy was 0.7 cm at maturity. Two of those not treated by epiphysiodesis used a heel raise of 1.5 cm. In seven cases the two operations were performed simultaneously without serious complications. This procedure is recommended at about the age of 12 years

Implants of solid sintered hydroxyapatite form very tight bonds with living bone, but are susceptible to fatigue failure. This problem can be overcome by using plasma-sprayed apatite coatings on titanium implants. A very strong bond is formed between bone and this composite material; this was studied in canine bone with plug implants, avoiding any mechanical retention. Mechanical testing showed an interface shear strength at six weeks of 49 MPa with a maximum of 64 MPa after six months. There was histological evidence of direct bonding between the apatite coating and living bone while uncoated control plugs were easily extracted. The results indicate that apatite-coated implants can form a chemical fixation with a strength comparable to that of cortical bone itself. This fixation is far stronger than that provided by current cemented or uncemented fixation techniques

Sterilisation by gamma irradiation in the presence of air causes free radicals generated in polyethylene (PE) to react with oxygen, which could lead to loss of physical properties and reduction in fatigue strength. Tissue retrieved from failed total hip replacements often has large quantities of particulate PE and most particles associated with peri-implant osteolysis are oxidised. Consequently, an understanding of the cellular responses of oxidised PE particles may lead to clarification of the pathogenesis of osteolysis and aseptic loosening. We have used the agarose system to demonstrate the differential effects of oxidised and non-oxidised PE particles on the release of proinflammatory products such as interleukin-1β (IL-1β), IL-6, and tumour necrosis factor-α (TNF-α) from monocytes/ macrophages (M/M). Oxidised PE particles were shown to stimulate human M/M to phagocytose and to release cytokines. Oxidation may alter the surface chemistry of the particles and enhance the response to specific membrane receptors on macrophages, such as scavenger-type receptors

The elbow flexor muscles of four men were trained using maximal voluntary isometric contractions. Thirty contractions a day were performed for five weeks. The four men and four control subjects were tested once a week: measurements of the supramaximally stimulated isometric twitch force, the time taken for the twitch force to peak and the tetanic force were carried out; simultaneously, measurements of the force of maximal voluntary isometric contraction and resistance to fatigue were made. The testing sessions produced no training effect on control subjects. Training produced a 20 per cent increase in the force of maximal voluntary isometric contraction after five weeks, but the forces of electrically evoked twitch and tetanus showed no increase. It was concluded that the increase in the force of maximal voluntary isometric contraction must be related to factors other than the force-generating capacity of the muscle fibres themselves

Aims

The aim of this study was to determine the immediate post-fixation stability of a distal tibial fracture fixed with an intramedullary nail using a biomechanical model. This was used as a surrogate for immediate weight-bearing postoperatively. The goal was to help inform postoperative protocols.

Aims

The purpose of this study was to identify the changes in untreated long head of the biceps brachii tendon (LHBT) after a rotator cuff tear and to evaluate the factors related to the changes.

1. Prosthetic acetabular cups of the Charnley and McKee-Farrar designs were cemented into cadaveric pelves using different procedures for preparing the acetabulum. 2. The torsional moments needed to loosen these cups were measured. 3. The torsional moments so measured were found to be from about four to more than twenty times higher than the frictional moments measured in independent tests on the two designs of prosthesis. 4. It is argued that late looseness of the acetabular component after total hip replacement, in the absence of infection, seems most likely to be due to thermal damage to the bone occurring at the time of polymerisation of the cement, and to subsequent bone resorption. 5. Surgical preparation of the acetabulum should include removal of all the articular cartilage and cleaning of the acetabular fossa, but the drilling of additional holes in the floor of the acetabulum seems unimportant. 6. The possibility of fatigue fracture in bone as a factor contributing to late loosening is an argument in favour of metal-on-polyethylene prostheses with their lower frictional moments, although the importance of this factor cannot be estimated

Aims

The main aims were to identify risk factors predictive of a radiolucent line (RLL) around the acetabular component with an interface bioactive bone cement (IBBC) technique in the first year after THA, and evaluate whether these risk factors influence the development of RLLs at five and ten years after THA.

The imminent introduction of the new Trauma & Orthopaedic (T&O) curriculum, and the implementation of the Improving Surgical Training initiative, reflect yet another paradigm shift in the recent history of trauma and orthopaedic training. The move to outcome-based training without time constraints is a radical departure from the traditional time-based structure and represents an exciting new training frontier. This paper summarizes the history of T&O training reform, explains the rationale for change, and reflects on lessons learnt from the past.

Cite this article: Bone Jt Open 2021;2-3:181–190.

The purpose of the work described was to find the average pressure on each of several areas of the acetabular cartilage of the cadaver hip under physiological loads. By obtaining load-deflection curves for one chosen area of cartilage, firstly with all the cartilage present and then after the successive removal of other areas, the fractions of the original load carried by the several areas were found, and hence the average pressures on those areas. Seventeen hips (age range twenty. two to eighty-seven years) were examined. Local pressures varied from zero to 3.4 times the average pressure in each hip. The highest pressures in the series (about 4 to 5 megaNewtons per square metre) were on areas of thin fibrocartilage which were identified at the zenith of certain acetabula. The results are too few to establish whether or not the pressure distribution was age-related. The higher pressures found are within the range which in other experiments has led to fatigue failure of femoral head cartilage, and it is suggested that hips in which such pressures exist under loads of three times body weight may be predisposed to osteoarthritis

The fatigue failure of bone cement, leading to loosening of the stem, is likely to be one mode of failure of cemented total hip replacements. There is strong evidence that cracks in the cement are initiated at voids which act as stress risers, particularly at the cement-stem interface. The preferential formation of voids at this site results from shrinkage during polymerisation and the initiation of this process at the warmer cement-bone interface, which causes bone cement to shrink away from the stem. A reversal of the direction of polymerisation would shrink the cement on to the stem and reduce or eliminate the formation of voids at this interface. We have investigated this by implanting hip prostheses, at room temperature or preheated to 44°C, into human cadaver femora kept at 37°C. Two types of bone cement were either hand-mixed or vacuum-mixed before implantation. We found that the area of porosity at the cement-stem interface was dramatically reduced by preheating the stem and that the preheating temperature of 44°C determined by computer analysis of transient heat transfer was the minimum required to induce initial polymerisation at the cement-stem interface. Temperature measurements taken during these experiments in vitro showed that preheating of the stem caused a negligible increase in the temperature of the bone. Reduction of porosity at the cement-stem interface could significantly increase the life of hip arthroplasties

1. Experience with a refined type of implantable electrode for the myo-electric control of externally powered prostheses is reported. 2. The electrodes are externally energised by electromagnetic induction and therefore do not contain any battery cells. The myo-potentials are transmitted in frequency-modulated form and detected by a receiver placed on the skin. The implantable electrode, measuring 5x11x4 millimetres, is encapsulated in epoxy resin. 3. Six electrodes have been implanted in the forearms of two normal subjects and two below-elbow amputees. The time of implantation ranged from three to fifteen months. Macroscopically, a fibrous capsule developed around the electrodes. Histological examination showed a capsule of granulation tissue of varying thickness with slight inflammatory reaction and foreign-body giant cells. 4. In all cases except one the signals received have been of high quality as ascertained by conventional electromyography and frequency analysis. There has been no significant deterioration in signal quality during the follow-up periods. 5. The major source of failure was fatigue fracture of the gold wires making contact with the body tissues. In one case, however, the electrode was still functioning normally at the time of removal fifteen months after insertion. 6. The patients have not been inconvenienced either by the operative procedures or by the presence of the electrodes in the tissues

1. Posterior fusion of the spine in scoliosis cannot be relied upon to maintain correction of the curve or to prevent progression of a vicious resistant curve. It can, however, hold to some extent the correction of a mobile curve and the compensation of a fixed curve. 2. Despite generally poor results as assessed radiographically, the clinical improvement is often gratifying. Most patients claim to be greatly improved: the spine feels stronger, there is less fatigue, and balance is better controlled. Moreover, visible deformity may be improved markedly even though the anatomical correction as observed radiographically is slight (Figs. l0 and 11). 3. It is believed that the true cause of relapse is that the bone formed from sliver grafts remains immature for a long time. Even when incorporated with the immature bone of the child's spine or the mature bone of the adult spine, it remains soft and resilient. When subjected to the stresses and strains of weight bearing and gravity, and then to the unnatural forces which initiated or perpetuated the scoliosis, this immature bone undergoes remodelling to Wolff's Law—like the neck of the femur after slipping of the upper femoral epiphysis. The forces that alter the grafted bone are not only lateral forces but also—perhaps more important—rotational forces. There seems to be a definite link between the degree of rotation and the amount of relapse, correction being maintained best when rotation is least

Aims

Restoration of proximal medial femoral support is the keystone in the treatment of intertrochanteric fractures. None of the available implants are effective in constructing the medial femoral support. Medial sustainable nail (MSN-II) is a novel cephalomedullary nail designed for this. In this study, biomechanical difference between MSN-II and proximal femoral nail anti-rotation (PFNA-II) was compared to determine whether or not MSN-II can effectively reconstruct the medial femoral support.