The effect of implant position on bone strain following lateral unicompartmental knee arthroplasty: A Biomechanical Model Using Digital Image Correlation.

OBJECTIVES: Unicompartmental knee arthroplasty (UKA) is a demanding procedure, with tibial component subsidence or pain from high tibial strain being potential causes of revision. The optimal position in terms of load transfer has not been documented for lateral UKA. Our aim was to determine the effect of tibial component position on proximal tibial strain. METHODS: A total of 16 composite tibias were implanted with an Oxford Domed Lateral Partial Knee implant using cutting guides to define tibial slope and resection depth. Four implant positions were assessed: standard (5° posterior slope); 10° posterior slope; 5° reverse tibial slope; and 4 mm increased tibial resection. Using an electrodynamic axial-torsional materials testing machine (Instron 5565), a compressive load of 1.5 kN was applied at 60 N/s on a meniscal bearing via a matching femoral component. Tibial strain beneath the implant was measured using a calibrated Digital Image Correlation system. RESULTS: A 5° increase in tibial component posterior slope resulted in a 53% increase in mean major principal strain in the posterior tibial zone adjacent to the implant (p = 0.003). The highest strains for all implant positions were recorded in the anterior cortex 2 cm to 3 cm distal to the implant. Posteriorly, strain tended to decrease with increasing distance from the implant. Lateral cortical strain showed no significant relationship with implant position. CONCLUSION: Relatively small changes in implant position and orientation may significantly affect tibial cortical strain. Avoidance of excessive posterior tibial slope may be advisable during lateral UKA.Cite this article: A. M. Ali, S. D. S. Newman, P. A. Hooper, C. M. Davies, J. P. Cobb. The effect of implant position on bone strain following lateral unicompartmental knee arthroplasty: A Biomechanical Model Using Digital Image Correlation. Bone Joint Res 2017;6:522-529. DOI: 10.1302/2046-3758.68.BJR-2017-0067.R1.

Compressive strength after blast of sandwich composite materials.

Composite sandwich materials have yet to be widely adopted in the construction of naval vessels despite their excellent strength-to-weight ratio and low radar return. One barrier to their wider use is our limited understanding of their performance when subjected to air blast. This paper focuses on this problem and specifically the strength remaining after damage caused during an explosion. Carbon-fibre-reinforced polymer (CFRP) composite skins on a styrene-acrylonitrile (SAN) polymer closed-cell foam core are the primary composite system evaluated. Glass-fibre-reinforced polymer (GFRP) composite skins were also included for comparison in a comparable sandwich configuration. Full-scale blast experiments were conducted, where 1.6×1.3 m sized panels were subjected to blast of a Hopkinson-Cranz scaled distance of 3.02 m kg(-1/3), 100 kg TNT equivalent at a stand-off distance of 14 m. This explosive blast represents a surface blast threat, where the shockwave propagates in air towards the naval vessel. Hopkinson was the first to investigate the characteristics of this explosive air-blast pulse (Hopkinson 1948 Proc. R. Soc. Lond. A 89, 411-413 (doi:10.1098/rspa.1914.0008)). Further analysis is provided on the performance of the CFRP sandwich panel relative to the GFRP sandwich panel when subjected to blast loading through use of high-speed speckle strain mapping. After the blast events, the residual compressive load-bearing capacity is investigated experimentally, using appropriate loading conditions that an in-service vessel may have to sustain. Residual strength testing is well established for post-impact ballistic assessment, but there has been less research performed on the residual strength of sandwich composites after blast.

A large multicentre, parallel group, double-blind study comparing tenoxicam and piroxicam in the treatment of osteoarthritis and rheumatoid arthritis.

A total of 1,328 patients with osteoarthritis or rheumatoid arthritis were entered into this double-blind, parallel group study of tenoxicam and piroxicam. The patient populations were well matched. An improvement was seen in pain on moving and at night in both groups and in both indications. Stiffness was also improved by both drugs, being most marked in the rheumatoid arthritis group. The primary efficacy variable was global assessment, and this showed tenoxicam to have slightly greater effect in osteoarthritis and the reverse in rheumatoid arthritis. There were no statistically significant differences in any of these findings. There were no significant differences in tolerance ratings, although the more serious gastrointestinal events occurred in the piroxicam group.

A randomized, double-blind study to compare tenoxicam with sustained release indomethacin in osteoarthritic patients treated in general practice.

A total of 144 patients were recruited for this randomized, double-blind study to compare the efficacy and tolerance of tenoxicam and sustained release indomethacin in patients with osteoarthritis. The results show that 20 mg/day tenoxicam is equal in efficacy to, and significantly better tolerated than, 75 mg/day sustained release indomethacin. Patients receiving tenoxicam recorded significantly better global tolerance ratings (P = 0.042) and fewer adverse events than those receiving indomethacin.

The use of flumazenil as an antagonist to midazolam in intravenous sedation for dental procedures.

The efficacy of flumazenil was tested in a double-blind placebo controlled study of 40 patients undergoing dental procedures. Flumazenil recipients were less sedated at 5 and 30 min post-operatively (P less than 0.001), were better oriented at 5 min (P less than 0.001) and 30 min (P less than 0.01) and were more co-operative at 5 min (P less than 0.001) and 30 min (P less than 0.005). None of the patients in either the placebo or flumazenil groups could remember operative events. The dental surgeon felt that flumazenil made recovery in the supine position unnecessary and made post-operative monitoring easier. Flumazenil is a drug that should be included in the armamentarium of any emergency drug kit when benzodiazepines are used i.v.

The histopathogenesis of acute ulcerative gingivitis.

The present study was a preliminary histological and immunofluorescent investigation of the edge of the ulcer in acute ulcerative gingivitis. The results of this study show that the lesion is dominated by polymorphonuclear leukocytes, with plasma cells present in the deeper parts. The epithelium on the edge shows widening of the intercellular spaces with destruction of the epithelial cells, accompanied by a heavy infiltrate of PMNs. Both IgG and C3 could be demonstrated between these epithelial cells, although the present study could not establish whether this represented immune complex deposition. The histopathogenesis of AUG therefore seems to involve a PMN infiltration of the epithelium, with subsequent destruction of the epithelium, probably due to the release of hydrolytic enzymes. The presence of the PMNs within the epithelium may involve direct bacterial chemotaxis and/or the activation of complement via the classical or alternative pathways.

The effects of "autonomic drugs" on villous movement in the small intestine of the pigeon.

1. The responses of pigeon duodenal villi to intravenous injection or local application of "autonomic drugs" were studied and compared with those reported in dogs by other workers.2. Choline esters, anticholinesterases, noradrenaline, adrenaline and nicotine all stimulated villous movement in the pigeon. Similar responses to these drugs have been reported in the dog. The effects of these drugs on villous activity could be inhibited by pretreatment of the bird with suitable antagonists, although hexamethonium was ineffective in preventing the effects of nicotine. Some of the antagonists also stimulated the villi.3. Isoprenaline caused inhibition of villous movements, which could be prevented by pretreatment of the bird with propranolol. It appears that in pigeons the villi have both alpha-adrenoceptors, stimulation of which increases villous activity, and beta-adrenoceptors, stimulation of which depresses villous movements.