The best method of preparation and processing of bone allografts is still under discussion. We use fresh frozen allografts in our department with no further chemical or physical processing. The use of fresh frozen allografts became subject to the restrictive European Union Directive due to the concern of a possible transmission of an infectious disease or other illness [15
]. A low risk of disease transmission remains in some cases which are described in the literature [16
]. Sufficient donor-screening is therefore essential. Except for Rh(D)-negative females of childbearing age, fresh frozen allografts are commonly transplanted AB0- and Rh-incompatible.
In the present study we found no alloimmunization in Rh(D)-incompatible transplanted recipients. With respect to other clinically relevant antigens in the Rh system (C, c, E, e) no irregular antibodies could be detected in the recipients after transplantation. However, reviewing the literature, there are some rare cases of Rh(D)-alloimmunisation after bone grafting [18
Concerning the AB0 system, the human body always naturally contains antibodies against the other blood group antigens (except genotype AB). Therefore, the detection of anti-A or anti-B alloantibodies cannot be regarded as proof of a possible alloimmunization after AB0 incompatible transplantation. However, AB0 incompatible transplantation might cause an increase of the anti-A or Anti-B titer (boostering) [20
]. Due to the retrospective design of our study, we could not investigate a possible boostering of anti-A or Anti-B alloantibodies after AB0-incompatible transplantation of bones. Stassen et al. found no irregular antibodies in patients before and after transplantation of frozen allogeneic bone in orthopaedic or maxillo-facial surgery [21
Despite the fact that we found no antibodies and according to the current standards, we still recommend transplanting only Rh(D)-negative bones to Rh(D)-negative women of childbearing age. For all other patients, our study confirms that blood-group compatible transplantation of fresh frozen allografts is not necessary in revision hip arthroplasty.
To minimize the risks of infection, allografts could be sterilized by irradiation and chemical or physical treatment. This treatment could result in a destruction of the bone matrix and subsequent reduction in strength affecting long-term graft incorporation [22
]. Despite this consideration, studies show good mid- and long-term results of treated bone grafts in revision hip arthroplasty [1
Our study revealed 100% graft remodeling and only one case of significant acetabular component migration (6 mm migration with no clinical symptoms, no surgical revision necessary) at a mean follow up of 23 months. We found radiological evidence of good allograft trabeculation as a sign of complete remodeling and integration into the recipient bone structure, even after 6 months. This rapid remodeling rate has also been demonstrated in several other studies [23
]. We have to consider, that complete remodeling does not mean complete incorporation of the graft. This could only be confirmed by biopsy and histological examination.
Acetabular reconstruction using a revision implant and allograft bone for reconstructing pelvic bone stock is a reliable method of managing acetabular defects. The question remains whether to use treated or untreated allografts in hip revision surgery as both show good clinical results. Advantages of untreated fresh frozen non-irradiated allografts are their cost effectiveness, supposed better biological quality and availability in a local bone bank. A disadvantage is the slightly increased risk of disease transmission which can be minimized by sufficient donor-screening and sterile handling.