Radiological characterisation of photon radiation from ultra-high-intensity laser-plasma and nuclear interactions.

With the increasing number of multi-terawatt (10(12) W) and petawatt (10(15) W) laser interaction facilities being built, the need for a detailed understanding of the potential radiological hazards is required and their impact on personnel is of major concern. Experiments at a number of facilities are being undertaken to achieve this aim. This paper describes the recent work completed on the Vulcan petawatt laser system at the CCLRC Rutherford Appleton Laboratory, where photon doses of up to 43 mSv at 1 m per shot have been measured during commissioning studies. It also overviews the shielding in place on the facility in order to comply with the Ionising Radiation Regulations 1999 (IRR99), maintaining a dose to personnel of less than 1 mSv yr(-1) and as low as reasonably practicable (ALARP).

Prediction of live and carcass characteristics of market hogs by use of a single longitudinal ultrasonic scan.

Live animal and carcass data were collected from market barrows and gilts (n = 119) to determine the accuracy and precision of using a single longitudinal scan, parallel to midline, in estimating body and carcass composition. Data from test pigs (n = 96) were used to develop prediction equations. Best results were obtained in predicting weight of boneless cuts (ham, loin, and shoulder), weight of lean cuts (bone-in ham, loin, and shoulder), and weight of fat-standardized carcass lean. Less accuracy was obtained in predicting ratios of all estimates on a live basis. Independent variables analyzed for the live models were live weight, sex, and ultrasonic fat depth and muscle depth at the 10th rib. Independent variables for the carcass models were the same as on the live animal; the estimators for boneless cuts (ham, loin, and shoulder) were most precise. Equations were tested against an independent set of experimental pigs (n = 23). Equations for predicting weight of boneless cuts, weight of ham and loin, and percentage of fat-standardized lean using both live and carcass measurements were most accurate, with R2 values between .78 and .87 and RSD values between 1.30 and 1.92 kg. The results of this study reinforce the potential of assessing carcass composition and value by using a single longitudinal B-mode scan on both live pigs and carcass; live weight, sex of pig, and fat depth at the 10th rib were the greatest contributors to variation.

Preliminary biocompatibility screening of several biodegradable phosphate fiber reinforced polymers.

This article describes preliminary biocompatibility screening of three degradable phosphate fibers containing K +, Ca +2/Na + and Na +/Ca +2/Al +3 ions in the polymer chain, and of several different degradable polymers reinforced with these fibers. Biodegradable phosphate fibers of calcium-sodium-metaphosphate (CSM) and sodium-calcium-aluminum-polyphosphate (NCAP) were acutely nontoxic in cellular, tissue, and whole animal evaluations, as determined by standard acute toxicity tests. Histological studies of bone implants sites fabricated from composites of copolymers of poly(E-caprolactone/L-lactide) and poly(ortho ester) reinforced with either CSM or NCAP fibers showed these composite materials to be nontoxic, with no abnormal inflammatory response. However, histological evaluation of muscle implants sites revealed the appearance of necrotic foci associated with implant sites in 12 of 22 NCAP containing composite specimens (p less than 0.05). Results of this preliminary biocompatibility screening suggest CSM fibers may be useful in reinforcing degradable polymers for production of completely biodegradable composites for implant use.

High tibial osteotomy. Use of an osteotomy jig, rigid fixation, and early motion versus conventional surgical technique and cast immobilization.

High tibial osteotomy (HTO) using conventional surgical technique and cast immobilization was compared to HTO using an osteotomy jig, rigid internal fixation, and early motion. Fifteen patients (19 knees) had conventional HTO. The mean preoperative femoral-tibial angle was 2.5 degrees of varus, and the mean postoperative angle was 6.5 degrees of valgus. Two knees were undercorrected and eight knees (42%) had associated complications. Twenty patients (21 knees) had HTO utilizing the new surgical technique and postoperative management. The mean preoperative femoral-tibial angle was 2.3 degrees varus, and the mean postoperative angle was 7.6 degrees valgus. One knee was undercorrected (less than 4 degrees valgus) and one knee (5%) had an intraoperative intraarticular fracture. High tibial osteotomy with an osteotomy jig to provide accurate correction, and rigid internal fixation to allow early motion, is an attractive alternative to conventional HTO.

Cementless total knee arthroplasty in patients over 65 years old.

Many factors influence the decision to implant a knee prosthesis with or without cement. Implant retrieval studies have demonstrated that bone ingrowth into porous-coated devices is possible even in older age groups. Early clinical follow-up observations suggest that cementless total knee arthroplasty can be successful in patients over 65 years of age, and need not be reserved for younger patients.

Effect of the tibial cut on subsidence following total knee arthroplasty.

In 33 total knee arthroplasties (TKAs) using instrumentation designed to cut the tibia with 0 degree posterior slope, ten tibial components demonstrated at least 2 mm of tibial component subsidence. These subsided components were implanted onto tibiae with an average of 8 degrees +/- 2 degrees difference between the preoperative, anatomic posterior slope and their postoperative posterior slope. The remaining 23 components, without subsidence, were implanted onto tibiae cut within 2 degrees +/- 2 degrees of their anatomic slope. To help understand these clinical observations, a laboratory study was performed to compare the load carrying capacity and the stiffness of tibial subchondral bone following two types of tibial cuts: one made perpendicular to the long axis of the tibia and the other made parallel to the articular surface of the tibia. Mock tibial baseplates mounted on paired cadaver tibiae were loaded in compression and force displacement curves were recorded. Tibiae cut parallel to the surface exhibited 40% greater load carrying capacity and 70% greater stiffness than the paired tibiae cut perpendicular to the long axis. The biomechanical data of this study indicated that cutting the tibia perpendicular to the long axis results in weaker bone that may be inadequate to support a tibial component. This may explain the higher incidence of clinical subsidence if the tibial cut is not made approximately parallel to the anatomic slope.

Total knee arthroplasty. Two- to four-year experience using an asymmetric tibial tray and a deep trochlear-grooved femoral component.

The design features of an implant system can be crucial to the success of cementless total knee arthroplasty (TKA). The implant system described in this study incorporates anatomic features including an asymmetric tibial tray that is smaller laterally than medially, and a deep trochlear-grooved femoral component. Two hundred consecutive primary total knees were implanted between October 18, 1985 and January 19, 1988 and were followed prospectively. One hundred ninety-two were implanted without cement. Clinical evaluation demonstrates good or excellent results in 96%, including a mean range of motion of 122 at two to four years after arthroplasty. Routine fluoroscopic spot roentgenograms have shown no complete radiolucency in this series of patients. Bone ingrowth was predictable if morselized autograft bone was interposed between implant and host bone. Implant retrievals demonstrated uniform bone ingrowth into the porous coating, increasing to 40% of the pore volume in the tibial tray at 27 months. Restoration of the normal kinematics appears to minimize the bone-implant stress permitting bone ingrowth fixation. The results of primary cementless TKA in this series is comparable to cemented TKA with the advantage of conserving bone stock.

Bone scans after total knee arthroplasty in asymptomatic patients. Cemented versus cementless.

The natural history of bone scans after total knee arthroplasty (TKA) was studied in 26 patients with 28 cemented TKAs and 29 patients with 31 cementless TKAs. The bone scans were examined at specified postoperative intervals. Radionuclide activity of the femoral, tibial, and patellar regions was measured. Six patients who developed pain postoperatively were excluded. Bone scans immediately postoperative and at three months demonstrated increased uptake, which gradually decreased to baseline levels at ten to 12 months. Radioisotope uptake was comparable in the cemented and cementless groups, but was highly variable in individual patients and in each of the follow-up periods. A single postoperative bone scan cannot differentiate component loosening from early bone remodeling. Sequential bone scans, as a supplement to the clinical examination and conventional radiography, may prove useful in the diagnosis of TKA failure.

Endosteal bone loss after total hip arthroplasty.

Femoral endosteal bone loss has been shown to be part of the natural aging process and may be a factor in femoral component loosening following total hip arthroplasty (THA). In this study, changes in the femoral medullary canal width in 30 patients with aseptic femoral loosening following primary THA were compared with 30 matched control patients. The rate of canal expansion on the operated side was twice that of the nonoperated side and four times that of the control. After the onset of symptoms in the failure group, the rate of femoral expansion of the operated side doubled. Iliac crest biopsies showed a decrease in male patients for osteoid surface and appositional and bone formation rates when compared with literature controls. These results suggest that femoral medullary canal expansion may be a factor in femoral component loosening following THA. The increased rate of canal expansion after the onset of symptoms demonstrates the need for early surgical intervention to avoid excessive bone loss.

The effect of air embolization from the femoral canal on hemodynamic parameters during hip arthroplasty.

A canine laboratory and clinical study was designed to determine the effect of air embolism during hip arthroplasty. Canine femurs were pressurized with air to 250-300 mm Hg or with low-viscosity cement to 300-900 mm Hg. Pressurization with low-viscosity cement from distal to proximal with a plugged femur revealed no change in pO2, pCO2, pulmonary artery pressure, or end-tidal CO2. Air pressurization resulted in significant increases in pCO2, pulmonary artery pressure, and end-tidal CO2, and a decrease in pO2. Pressurization of the medullary canal with xenon-labeled air was used to document pulmonary embolism. In a clinical setting, two different femoral cementing techniques during total hip arthroplasty were studied to determine their effect on hemodynamic parameters associated with embolic phenomenon. Five patients had a plugged femoral canal filled from proximal to distal with a vent tube, followed by finger-packing. Three of the patients demonstrated a significant drop in pO2 and blood pressure and a rise in pCO2 and end-tidal CO2. Five other patients had their plugged femoral canals filled from distal to proximal, three with regular cement and two with low-viscosity cement, with no significant cardiopulmonary changes. The adverse cardiopulmonary effects reported during hip arthroplasty appear to be avoided by eliminating air during the cementing procedure, by filling a plugged canal from distal to proximal.

Prophylaxis with cefamandole nafate in elective orthopedic surgery.

A prospective, randomized, double-blind study was conducted to determine the efficacy of cefamandole nafate in reducing infections in general orthopedic procedures. Of 743 patients initially entered into the study, 715 (362 on cefamandole, 353 on placebo) fulfilled the requirements of the protocol. The infection rate was 1.6% for the cefamandole-treated group and 4.2% for the placebo group. In operations lasting longer than two hours, there were two infections in the cefamandole group and seven infections in the placebo group (p less than 0.05). Staphylococcus aureus and gram-negative bacilli were the common pathogens. Adverse side effects were limited to transient elevations in liver enzymes.

Combined Coventry-Maquet procedure for two-compartment degenerative arthritis.

The combined Coventry-Maquet procedure has been proposed as a means of treating dual-compartment degenerative arthritis of the knee. The procedure was investigated in a prospective study of 14 patients treated by combined high tibial osteotomy and tibial tubercle elevation. Preoperative scores averaged 50 points and scores at follow-up evaluation averaged 57 points with a modified 100-point total knee grading system. There were no excellent results, one good result, and 13 poor results. Five patients whose results were poor have since had total knee arthroplasty. The combined Coventry-Maquet procedure required too much dissection, had too high a complication rate, and yielded a minimal improvement in knee function and pain. Two-compartment degenerative arthritis should be treated by an alternative method, such as total knee arthroplasty, when surgical intervention is indicated.

Knee stability in orthotic knee braces.

The ability of six commercially available orthotic knee braces to stabilize ligamentous injuries of the knee was evaluated using fresh cadaver specimens. Anterior, valgus, and rotational forces were applied to the intact knee, after the anterior cruciate and medial collateral ligaments were cut, and after application of the knee braces. Bony displacement was measured using half pins and an external fixator applied to the tibia and femur. There was a significant difference in brace performance, most likely due to differences in brace design. Of the six braces tested, the 3D 3-Way Brace provided the greatest knee stability.

Experience with acetabular fractures.

Acetabular fractures, although relatively rare, are often serious injuries requiring complex treatment. Major associated injuries are common and the mortality rate continues to approach 20% (8). We retrospectively evaluated 38 acetabular fractures. Twenty-six fractures were treated operatively, with adequate followup available for 23. Anatomic reduction or reduction to within 3 mm was achieved operatively in 21 (81%). The average Harris hip score was 90. The five poorly reduced fractures had an average Harris hip score of 54. Twelve patients were treated nonoperatively with adequate followup available for nine. Six patients with nondisplaced or minimally displaced fracture treated nonoperatively had an average hip score of 96. Six patients had displaced fractures which failed to reduce with nonoperative treatment. Their average hip score was 59. This study reaffirms the importance of adequate fracture reduction in the treatment of acetabular injuries.