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Oxalate retention occurs in end-stage renal failure. Regular dialysis treatment does not prevent progressive accumulation of oxalate in cases of ESRF due to primary hyperoxaluria (PH), whereas such accumulation seldom seems to occur in oxalosis-unrelated ESRF. To elucidate this issue we have measured the bony content of oxalate on biopsies of the iliac crest taken from 32 uremic patients, 7 of them with ESRF associated with PH1 (6 cases) or PH2 (1 case). Ten subjects with normal renal function and no evidence of metabolic bone disease were taken as controls. Only trace amounts levels of oxalate were detected in normal subjects and oxalate to phosphate ratio was below 3:10,000. Non-PH dialyzed patients exhibited fivefold increases in oxalate levels, which rose to 5.1 +/- 3.6 mumol/g bony tissue. Calcium oxalate was estimated to represent 0.18% of the hydroxyapatite content of bone. Oxalate amounts were neither related to pre-dialysis plasma levels of oxalate, nor with duration of dialysis treatment, suggesting that accumulation was not progressive disorder. Oxalate levels were slightly higher in patients with a low turnover osteodystrophy compared to those with a high turnover pattern. Dialyzed patients with PH had remarkable increases in oxalate levels, which ranged between 14.8 and 907 mumol/g bony tissue. Oxalate deposition appeared to be progressive in that oxalate levels were significantly related to time on dialysis. In three patients calcium oxalate was a significant fraction of the mineralized bone. The occurrence of calcium oxalate crystals affected the histomorphometric patterns, that were featured by an increase in resorptive areas and a decrease in bone formation rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Histologic findings of the bone-cement junction are presented for 10 implants in rabbits and 12 human specimens. Nondecalcified sections were made, employing embedding techniques that conserve the cement. Different time periods from operation were considered. The histological approach considers mainly the distribution of the osseous elements, with a description of the sites of new and old bone, of resorptive lacunae and of fibrous tissue. Fluorescent sequential labelling of bone tissue allowed a dynamic evaluation of the viability of bone after insertion of the cement. Histologic features may be summarized as follows: In the initial phase after PMMA implantation a zone of necrosis is present around the cement. In a second phase there is very active bone formation and remodelling in the tissue adjacent to the cement, with fibrous tissue formation. Long-term adaptive bone remodelling leads to extensive resorption of cortical bone and new bone formation producing a shell around the cement with new trabeculae radiating towards the cortex.

Three madreporic prostheses in two patients were examined to evaluate resorption and formation of the surrounding bone tissue. All three prostheses were firmly fixed and had no clinical or radiographic signs of loosening. Transverse sections were examined by scanning electron microscopy at 40 days, 11 months and 2.5 years after implantation. The findings suggest that adaptive bone remodelling varies along the length of the stem; that bone resorption and formation are related to the time after implant; and that new bone formation (woven bone) can be found very close to the madreporic surface.

The histology of bone-cement interfaces was studied by using new fixation techniques that preserve the cement, as well as sectioning the samples without decalcification. This permits histological study of the unaltered morphology, and the precise topographical distribution of fibrous tissue, bone necrosis and cellular anomalies in relation to the cement. Twelve cases of implant loosening over an average 7 year follow-up period were examined. By dynamic studies with sequential fluorescent bone labelling it was possible to evaluate precisely the extent of bone damage after the application of cement. The characteristic findings were: fibrous tissue at the bone-cement interface; bone necrosis or reduced remodelling in proximity to the cement; away from the cement, normal bone remodelling is clearly demonstrated by fluorescent labelling.

The authors investigated the tissue around a failed knee prosthesis which had a metal-on-metal bearing made of chromium-cobalt-molybdenum alloy. Histological examination and the quantitative analysis of metallic particles found in the bone marrow (by fluorescent spectrometry and laser microsound) provided a detailed picture of the quantity, nature and distribution of the wear debris. The type and nature of the tissue response to the presence of the metal particles was determined by fluorescent microscopy and microradiography.