CO2 laser-based dispersion interferometer utilizing orientation-patterned gallium arsenide for plasma density measurements.

A dispersion interferometer based on the second-harmonic generation of a carbon dioxide laser in orientation-patterned gallium arsenide has been developed for measuring electron density in plasmas. The interferometer includes two nonlinear optical crystals placed on opposite sides of the plasma. This instrument has been used to measure electron line densities in a pulsed radio-frequency generated argon plasma. A simple phase-extraction technique based on combining measurements from two successive pulses of the plasma has been used. The noise-equivalent line density was measured to be 1.7 × 10(17) m(-2) in a detection bandwidth of 950 kHz. One of the orientation-patterned crystals produced 13 mW of peak power at the second-harmonic wavelength from a carbon dioxide laser with 13 W of peak power. Two crystals arranged sequentially produced 58 mW of peak power at the second-harmonic wavelength from a carbon dioxide laser with 37 W of peak power.

Total hip replacement after intra-articular injection of local anaesthetic and steroid.

Intra-articular injections of steroid into the hip are used for a variety of reasons in current orthopaedic practice. Recently their safety prior to ipsilateral total hip replacement has been called into question owing to concerns about deep joint infection. We undertook a retrospective analysis of all patients who had undergone local anaesthetic and steroid injections followed by ipsilateral total hip replacement over a five-year period. Members of the surgical team, using a lateral approach to the hip, performed all the injections in the operating theatre using a strict aseptic technique. The mean time between injection and total hip replacement was 18 months (4 to 50). The mean follow-up after hip replacement was 25.8 months (9 to 78), during which time no case of deep joint sepsis was found. In our series, ipsilateral local anaesthetic and steroid injections have not conferred an increased risk of infection in total hip replacement. We believe that the practice of intra-articular local anaesthetic and steroid injections to the hip followed by total hip replacement is safer than previously reported.

Safety and efficacy of intra-articular injection of the hip.

The aim of the present study was twofold: a) to establish the therapeutic efficacy of the hip injection with marcaine and steroid; (b) to establish the safety of the procedure with respect to possible bacterial contamination at the time of passage of needle into the hip joint. Thirty-five patients with osteoarthritis of the hip were injected. All patients were admitted as day cases and the procedure was performed in a laminar flow theatre under full aseptic conditions. The hip was aspirated before injection. Aspirate and injecting needles were sent for microbiological examination. Both aerobic and anaerobic cultures were performed. All patients were followed up for three months after hip injection. Microbiology results were not revealed to reviewing clinicians. All patients were reviewed at two weeks and at twelve weeks. Thirty-three patients (94.3%) had no growth in the samples. Two cases out of thirty-five hips had a positive culture but none of the patients went on to develop clinical sepsis. Patient response for pain in the hip was graded using a 10 point visual analogue scale (VAS) with 10 point as maximum pain and 0 points as no pain. Pre-injection the patient VAS for pain was a mean value of 6.4 0.77 (median, 6). The mean value of VAS score at 2 weeks dropped to 2.6 2.7 with median of 2. This difference was highly significant (p=0.003). At 12 weeks mean VAS score was 2.7 2.5 with median value of 2 (p=001). Three patients were worse after the injection. We found the hip injection to be safe. The risk of bacterial contamination is low provided a strict aseptic protocol is observed. In this study, one third of the patients had excellent pain relief for 3 months after the injection but in two thirds of cases it failed to provide complete, long-term pain relief (> 3 months). (Hip International 2002; 4: 378-82).

The Charnley-Hastings bipolar prosthesis in femoral neck fractures - a study of dynamic motion.

Fourteen patients who had a Charnley-Hastings bipolar prosthesis inserted for a fracture of the neck of the femur underwent a fluoroscopic assessment of the prosthesis while walking on a treadmill at an average of 24 months (range 8-48 months) post-insertion. This motion was compared with static weight-bearing and non-weight-bearing motion. The area of interest was the motion at the interprosthetic junction. Previous studies of this and similar prostheses had suggested that interprosthetic motion lessened with time, as the inner bearing stiffened up. However, in this study it was found that although the interprosthetic motion during non-weight-bearing abduction was in the region of 20-30% of total abduction, the interprosthetic motion during flexion and extension in gait accounted for 70-80% of motion. We suggest this can be explained by considering the biomechanical effect of sliding friction at the metal-acetabular bone junction during weight-bearing gait, as well as the impingement of the neck on the prosthetic socket during extremes of movement. The reported superior long term results of the bipolar prosthesis over its unipolar counterparts in femoral neck fracture treatment can be explained by the delayed acetabular wear due to reduced motion, and shear forces, at the prosthetic-bone interface.

Failure of the spiral blade module of the AO unreamed femoral nail.

The treatment of subtrochanteric femoral fractures remains difficult despite the introduction of modern intramedullary nailing techniques. Accurate fracture reduction, correct siting of the proximal entry point and restoration of medial support remain essential for a successful outcome. We report a case of failure of the spiral blade module of the AO unreamed femoral nail, which may have been precipitated by incorrect siting of the entry point, resulting in poor implant positioning within the femoral head.

Spectroscopic detection of methane by use of guided-wave diode-pumped difference-frequency generation.

We report spectroscopic gas detection by the use of mid-infrared difference-frequency mixing of two diode lasers in a channel waveguide. The waveguide was fabricated by annealed proton exchange in periodically poled lithium niobate. We generated 3.43-3.73-microm tunable radiation in a single waveguide at room temperature by mixing diode lasers near 780 and 1010 nm. High-resolution spectra of methane were obtained in 2 s with electronically controlled frequency scans of 45 GHz. The use of highly efficient waveguide frequency converters pumped by fiber-coupled diode lasers will permit construction of compact, solid-state, room-temperature mid-infrared sources for use in trace-gas detection.

The value of skeletal scintigraphy in predicting the need for revision surgery in total knee replacement.

We have reviewed the results of 99mtech-netium-methylene diphosphonate (Tc-MDP) bone scintigrams performed on patients following total knee arthroplasty. In addition, 67gallium (Ga) citrate scintigrams were carried out sequentially on 29 patients. Three groups of patients were identified: those with asymptomatic knees (undergoing scans for other reasons); those with aseptic or septic loosening; and those with pain without radiologic evidence of loosening. There was good correlation between the results of the scans and the final outcome. We conclude that sequential 99mTc-MDP and 67Ga citrate scintigrams are useful for demonstrating the presence of aseptic and septic loosening in knee prostheses, and pain with a normal scan appearance is probably not due to loosening or infection.

An important complication of upper cervical spine fracture: a case report.

A case report is presented of a patient who sustained a high cervical spine fracture, the possible mechanisms of injury and details of the fracture are discussed. The patient developed bilateral vagal nerve palsies 48 h after the accident. This complication was only recognized after dysphagia and an aspiration pneumonia developed. The complication of aspiration pneumonia was preventable. Meticulous and repeated examination of the cranial nerve function in this type of injury is recommended. Normal feeding should commence only when the cranial nerve function has been shown to be normal after repeated examination.

Avoidable complications of arthroscopic surgery.

The incidence of complications from arthroscopic surgery is low. Between 1978 and 1991, 8500 arthroscopies were performed by the two senior authors (J.N. and D.R.A.D.). Several significant complications were recorded, and these are presented to show how they occurred, and how our practice of arthroscopy was subsequently modified. There were four cases of clinically detectable deep vein thrombosis of which three were associated with pulmonary embolus, three cases of haemarthrosis, two deep infections, three compartment syndromes with one case of impending compartment syndrome, six cases of instrument failure and one case of persistent synovial fistula.