After 10 years, loosening of total joint endoprostheses occurs in about 3 to 10 percent of all patients, requiring elaborate revision surgery. A periprosthetic membrane is routinely found between bone and loosened prosthesis. Further histomorphological examination allows determination of the etiology of the loosening process. Aim of this study is the introduction of clearly defined histopathological criteria for a standardized evaluation of the periprosthetic membrane. Based on histomorphological criteria and polarized light microscopy, four types of the periprosthetic membrane were defined: periprosthetic membrane of wear particle type (type I), periprosthetic membrane of infectious type (type II), periprosthetic membrane of combined type (type III), periprosthetic membrane of indifferent type (type IV). Periprosthetic membranes of 268 patients were analyzed according to the defined criteria. The correlation between histopathological and microbiological diagnosis was high (89%, p<0,001), the inter-observer reproducibility was sufficient (95%). This classification system enables a standardized diagnostic procedure and therefore is a basis for further studies concerning the etiology of and pathogenesis of prosthesis loosening.

Surgical treatment of pyogenic infections of the sacroiliac joint is indicated in cases of ineffective conservative treatment, abscess formation, septicemia, and neurological deficits. Between 1983 and 1990 in nine patients surgical treatment was performed for pyogenic sacroiliitis under this criteria. The surgical procedure included joint debridement, primary arthrodesis of the sacroiliac joint using a autologous bone graft, antibiotic therapy and postoperative immobilisation. Follow-up examination of 8 patients in average 47 months postoperatively revealed excellent functional and roentgenological results in 6 patients. Two patients suffered only from mild low-back pain, none of the eight patients demonstrated signs of a recurrent infection, one patient died due to complications of a long-lasting preoperative septicemia. Regarding these postoperative follow-up results surgical therapy including primary sacroiliac arthrodesis should be early considered, because this treatment has a low complication rate and the surgical technique is easy to perform and results are excellent or good in most of the patients.

Silicone synovitis is an important clinical entity recognized in rheumatoid patients after arthroplasties with silicone implants. It is a foreign body reaction to particulate material (silicone elastomer) characterized clinically by the re-occurrence of pain, stiffness and swelling at the site of arthroplasty after initial relief of symptoms. Whereas silicone synovitis is a rare complication in metacarpophalangeal implants, it is an important one in the wrist implant. Long-term follow-up studies have revealed that the rates of fracture and subsidence are high and that the implants deteriorate with time necessitating operative revisions in up to 50% of cases. Indications should therefore be restricted to a painful wrist in the elderly, very low demand patient with insufficient bone stock to permit total wrist arthroplasty with a metal-on-plastic design. Severe preoperative deformity and the need for use of ambulatory aids may further limit the indication. The unusual case of direct perforation of silicone particles from the wrist into the tendon sheath of the M. flexor pollicis longus inducing a tumor-like synovitis and a secondary carpal tunnel syndrome is presented. The importance of silicone synovitis and the indication at present for implantation of a silicone wrist spacer in the rheumatoid patient are discussed.

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On comparing surgical and conservative approaches in therapy for obesity it is accepted that there is a more rapid decline in body weight after surgery than by conservative measures. In contrast to widespread convictions, it has been shown that even in extreme obesity (BMI>60 kg/m²) both a meaningful and a long-lasting reduction of body weight is possible by conservative approach. There is an increasing body of evidence that bariatric surgery, especially malabsorptive and combined forms, causes endocrine disturbances and both vitamin and micronutrient deficiencies. Furthermore, alterations in drug pharmacokinetics are possible. Even bariatric surgeons have stated that surgery neither removes the chronic disease obesity nor is its final therapy.