We present data showing predictable bone-inducing capacity of two types of tissue-bank manipulated bone allograft, which is used increasingly as biological allograft.

The first type is an in-vitro tested demineralised bone matrix (DBM) composition of human long bone, which contains lyophilised cross-linked collagenous biomaterial as a delivery system. The composition is in the form of an allograft powder that is stable at room temperature and readily rehydratable into a putty-like consistency. Its superior co-adhesive properties enable it to remain at the implant site, resisting irrigation and displacement due to bleeding. We discuss a number of cases in which successful fusion of recalcitrant long bone fractures in humans followed implantation of the DBM-collagenous biomaterial composite.

We also present data on a second type of manipulated human allograft, a reconstituted DBM with increased levels of osteogenic fractions derived from human cortical bone. The osteogenic fraction is rich in bone morphogenetic protein (BMP) and capable of inducing alkaline phosphatase activity in in vitro cultures of rat myoblast cells. Alkaline phosphatase is a well-known specific marker for bone forming activity. Thirty-four patients with persistent non-union (including partial or complete segmental defects) were treated with the BMP-collagen composite. All patients had previously been treated by internal or external fixation, cast immobilisation, and/or allogenic or autogenic bone grafting. Preoperative symptoms averaged 26 months (1 to 228). At surgery the hydrated implant was injected at the site of the defect, which was then stabilised by internal or external fixation. Early radiographs showed moderate bridging in all patients, indicating that h-BMP composite implants may be effective treatment of difficult nonunions.

Human bone morphogenetic protein (hBMP) was prepared according to a modified method (Sampath et al). Implants were prepared with 500 μg of hBMP adsorbed onto a composite matrix (1 gm of insoluble collagenous bone matrix and 200 mg of lyophilised human gelatine).

The hBMP/collagen composite was used to treat 11 women and 23 men (mean age 36 years). All patients had failed to achieve union despite previous treatment by internal or external fixation, immobilisation in a cast, and/or allogenic or autogenic bone grafting. The mean age of the nonunions was 26 months (1 to 228).

At surgery a mean of 2 gm per patient of the composite was inserted at the site of the defect, which was stabilised by internal or external fixation. Supplementary allogenic cancellous bone particles and block configured spongy bone was used in 17 patients. At follow-up 1, 8, 16 and 23 weeks postoperatively, functional results were assessed according to weight-bearing. A score of 0 was given where there was no weight-bearing, a score of 1 for weight-bearing with the assistance of two crutches, 2 for light weight-bearing with one crutch, 3 for full weight-bearing with one crutch and 4 for full weight-bearing without crutches. At a mean follow-up of 17 weeks (8 to 32), the mean score was 3.25, higher than the mean preoperative score of 2.22 and mean one-week follow-up score of 0.5. Of the five patients who suffered recurrent infection, two failed to score above 2 at 17 weeks mean.

Present results indicate that hBMP composite implants may represent effective treatment of difficult nonunions.