Proposal for a histopathological consensus classification of the periprosthetic interface membrane.

AIMS: The introduction of clearly defined histopathological criteria for a standardised evaluation of the periprosthetic membrane, which can appear in cases of total joint arthroplasty revision surgery. METHODS: Based on histomorphological criteria, four types of periprosthetic membrane were defined: wear particle induced type (detection of foreign body particles; macrophages and multinucleated giant cells occupy at least 20% of the area; type I); infectious type (granulation tissue with neutrophilic granulocytes, plasma cells and few, if any, wear particles; type II); combined type (aspects of type I and type II occur simultaneously; type III); and indeterminate type (neither criteria for type I nor type II are fulfilled; type IV). The periprosthetic membranes of 370 patients (217 women, 153 men; mean age 67.6 years, mean period until revision surgery 7.4 years) were analysed according to the defined criteria. RESULTS: Frequency of histopathological membrane types was: type I 54.3%, type II 19.7%, type III 5.4%, type IV 15.4%, and not assessable 5.1%. The mean period between primary arthroplasty and revision surgery was 10.1 years for type I, 3.2 years for type II, 4.5 years for type III and 5.4 years for type IV. The correlation between histopathological and microbiological diagnosis was high (89.7%), and the inter-observer reproducibility sufficient (85%). CONCLUSION: The classification proposed enables standardised typing of periprosthetic membranes and may serve as a tool for further research on the pathogenesis of the loosening of total joint replacement. The study highlights the importance of non-infectious, non-particle induced loosening of prosthetic devices in orthopaedic surgery (membrane type IV), which was observed in 15.4% of patients.

[The effect of osteoprotegerin on tendon-bone healing after reconstruction of the anterior cruciate ligament: a histomorphological and radiographical study in the rabbit]. / Der Einfluss von Osteoprotegerin auf die Sehne-zu-Knochen-Heilung nach Rekonstruktion des vorderen Kreuzbandes: Eine histomorphologische und radiographische Studie im Kaninchenmodell.

AIM: Improvement of the bony incorporation of a soft-tissue graft after ACL reconstruction by local administration of Osteoprotegerin between the bone and tendon graft. METHOD: Fifteen New Zealand White rabbits underwent unilateral anterior cruciate ligament (ACL) reconstruction using an autologous semitendinosis tendon graft. We compared the effect of three OPG doses (5 microg, 50 microg, or 100 microg) at the tendon-bone interface to the controls (OPG carrier) and ACL reconstruction only. Specimens were analyzed at 3 weeks using radiology, histology and histomorphometry to investigate the effect of OPG on the bony incorporation of the tendon graft. RESULTS: Animals treated with OPG 100 microg had a significant (p = 0.007) increase in newly-formed bone around the graft compared to the control group (0.16 +/- 0.01 mm(2); 0.06 +/- 0.02 mm(2)). No significant differences were found between the controls and the other groups (tendon graft only, OPG 5 microg, and 50 microg) (p > 0.05). Bone mineral density, measured in image-pixel brightness (IPB; reference range: 0-255), along the edge of the bone tunnel was greater in the OPG 100 microg group (169.5 +/- 5.9 IPB) compared to the control group (150.3 +/- 4.3 IPB) but this was not statistically significant (p = 0.083). There was a significant decrease in the number of osteoclasts per high-power microscopic fields (HPF) lining the bone tunnel in the OPG 100 microg group compared to the control group (4.4 +/- 2.5 cells/HPF; 6.4 +/- 1.8 cells/HPF) (p = 0.022). No significant differences were found between the control group and the other groups in osteoclast numbers (p > 0.05). CONCLUSION: Since tendon-bone healing requires new bone formation and bone ingrowth around a tendon graft, OPG may improve biologic graft fixation. A potential implication could be earlier return to function or better conditions in revision surgery.