Instability in primary total hip arthroplasty with the direct lateral approach.

Instability after a total hip arthroplasty is a serious complication. Dislocation rates as much as 6.5% after posterior approaches have been reported within the past decade. For this reason, the authors use the direct lateral approach for primary and revision total hip arthroplasties. A review of the arthroplasty database yielded 1515 primary total hip arthroplasties done via a direct lateral approach in 1333 patients. These arthroplasties were done within a 10-year period and patients with followup data less than 12 months were excluded. At the most recent examination, 11.6% of the patients had a moderate or severe limp and 2.5% had severe heterotopic ossification. Only six hips (0.4%) had a dislocation or episode of instability. Three patients had more than one dislocation and required revision surgery. The results of the current study show that dislocation after primary total hip arthroplasty almost can be eliminated using the direct lateral approach. The associated risks of heterotopic ossification or limp are acceptable.

The use of the Cryo/Cuff versus ice and elastic wrap in the postoperative care of knee arthroscopy patients.

Pain and swelling, which may lead to inhibition of the extensor mechanism and ultimately a delay in rehabilitation, are common complications of knee arthroscopy. Cryotherapy is the most often used means of decreasing both knee edema and discomfort. A number of methods have been used to provide cold pressure dressings, including ice and elastic bandages. Commercial devices, such as the Cryo/Cuff, also have been developed to provide similar beneficial effects. This article describes a multicenter randomized study undertaken to determine whether the Cryo/Cuff or the ice and elastic bandage offers the greatest convenience and relief of pain. One hundred two patients between the ages of 18 and 65 scheduled to undergo knee arthroscopy were enrolled. Postoperatively, the Cryo/Cuff patients required significantly less pain medication than those patients using the ice and elastic wrap. The Cryo/Cuff patients also expressed a high level of satisfaction with the effectiveness and convenience of the therapy. There were no differences between either group in the amount of pain reported, or preoperative and postoperative examinations in regard to knee range of motion and thigh circumference. These results indicate that the Cryo/Cuff is a useful adjunct in the rehabilitation of knee arthroscopy patients.

Fracture dislocation of the tarsal navicular with medial column disruption of the foot.

A displaced fracture of the body of the tarsal navicular with isolated disruption of the talonavicular joint is a rare injury. The authors encountered one such injury in which there was no subtalar dislocation and no injury to the calcaneocuboid joint. This injury was believed to be the result of a severe abduction force with the foot in plantar flexion, rather than the previously described medial swivel dislocation, which typically involves the subtalar joint. A case history and brief review of the literature is presented.

Achilles tenodesis for calcaneus deformity in the myelodysplastic child.

Calcaneus deformity in patients with neurologic disorders leads to gait disturbances, a high incidence of osteomyelitis, cellulitis, and skin breakdown, and a major problem in the fitting of shoes of orthoses. Correction of this deformity remains a difficult challenge for the orthopedic surgeon. Twelve tenodeses of the tendo Achillis to the fibula or tibia were performed in eight patients with myelodysplasia in an attempt to control calcaneus deformity. The average age of the patients at the time of surgery was 7.4 years (range, 3.1-13.5 years) with an average follow-up period of 6.3 years (range, two to 10.9 years). The clinical examination demonstrated definite improvement in the ability to brace, prevent skin breakdown, and improve gait in all but one patient who had progressive hindfoot valgus. Roentgenographically, there was improvement in the tibiocalcaneal angle in 67%, fibular station in 58%, talar tilt in 25%, and growth of the posterior aspect of the calcaneus in 58%.

Electron paramagnetic resonance studies of membrane proteins in hepatic microsomes.

Hepatic microsomal membranes, prepared under various conditions that yield either 'intact' or 'disrupted' microsomal vesicles, have been labeled via the sulfhydryl groups of intrinsic membrane proteins using nitroxide analogs of N-ethylmaleimide. Electron paramagnetic resonance spectra revealed the presence of two dominant classes of bound label corresponding to differing degrees of immobilization, the ratio of which were quantitated using a parameter designated the 'W/S' ratio. For latent microsomes, the value of this parameter was determined to be 0.65 +/- 0.02 and was influenced by factors such as label/protein ratio, incubation period, nitroxide structure, temperature and pH. The W/S ratio was also sensitive to the degree of membrane integrity as revealed by the latency of mannose 6-phosphate activity of glucose-6-phosphohydrolase. In addition, membrane disruption resulted in a corresponding decrease in the order parameter for nitroxide-labeled fatty acids intercalated within the lipid bilayer. The W/S ratio was observed to be dependent upon the method of microsome preparation yielding values of 1.02 +/- 0.02 for 'hypertonically disrupted' vesicles and 1.28 +/- 0.02 for 'mechanically disrupted' vesicles. Microsomal marker enzymes such as cytochrome P-450 and FAD-containing monooxygenase retained significant levels of functionality following nitroxide incorporation.

Not all aromatic nitro compounds form free radicals.

One-electron reduction of the aromatic nitro-containing drug, clonazepam, by rat hepatic microsomes was found to produce a nitro anion radical which was observable by electron paramagnetic resonance (EPR) spectrometry under anaerobic conditions. It was determined that NADPH-cytochrome P-450 reductase may be the enzyme responsible for this reduction and that this free radical reacts rapidly with oxygen to produce superoxide. The vasodilator nifedipine, another aromatic nitro-containing drug, was found not to be reduced by rat hepatic microsomes to a free radical nor to stimulate superoxide production. Based on a series of experiments, we propose that the inability of nifedipine to be bioreduced to its nitro anion free radical is the result of geometric restrictions which prevent the transfer of an electron from cytochrome P-450 reductase to nifedipine.