We performed a randomised, prospective trial to evaluate the use of unreamed titanium nails for femoral fractures. Of 48 patients with 50 femoral fractures 45 were followed to union; 23 with an unreamed and 22 with a reamed nail. The study was stopped early because of a high rate of implant failure.

The fractures in the unreamed group were slower to unite (39.4 weeks) than those in the reamed group (28.5 weeks; p = 0.007). The time to union was over nine months in 57% of the unreamed group and in 18% of the reamed group.

In the unreamed group 14 secondary procedures were required in ten patients to enhance healing compared with three in three patients in the reamed group. Six implants (13%) failed, three in each group. Four of these six fractures showed evidence of delayed union.

To achieve quicker union and fewer implant failures we recommend the use of reamed nails of at least 12 mm in diameter for female patients and 13 mm in males.

Using bone decalcilied with 0.6 N hydrochloric acid as an inducing agent, the inductive capacity of different soft tissue sites was investigated. Muscle and fascia regularly permitted the induction of bone, while spleen, liver and kidney suppressed bone induction. Bone formation could be induced in these organs if living autologous fascia was implanted together with the inducing agent; while bone formation was inhibited when living autologous spleen tissue was implanted with the inducing agent to normally favourable sites. The administration of systemic heparin and the diphosphonate ethane-1-hydroxyl, 1-diphosphonic acid (EHDP) suppressed bone induction.

It is suggested that for bone induction to occur in soft tissues, three conditions must be present: 1) an inducing agent; 2) an osteogenic precursor cell; and 3) an environment which is permissive to osteogenesis. The presence of osteogenic inhibitors in spleen, liver and kidney is postulated.