Crack revision improves fixation of uncemented HA-coated implants compared with reaming: an experiment in dogs

The crack procedure is a surgical technique for preparing the implant cavity at revision of loose joint replacement components. It disrupts the neocortical bone shell that typically forms around the cavity. Using an animal model, we compared the crack technique with reaming. Twenty micromotion implants were inserted bilaterally into the knees of 10 dogs according to our revision protocol, allowing formation of a standardized revision cavity (loose implant, fibrous tissue, and sclerotic bone rim). Eight weeks later we performed revision surgery. On the control side, in which the neocortex was removed, the cavity was reamed. On the intervention side, in which the neocortex was perforated but left in situ, the cavity was cracked. For revision we used non-motioning hydroxyapatite (HA)-coated, plasma-sprayed titanium implants. Observation after revision was 4 weeks. The implants revised by the crack technique had better mechanical fixation in all mechanical parameters by the push-out test. The crack revisions also provided more new bone formation around the implants compared with the reamed revisions but had no effect on new bone ongrowth. The data suggest using this bone-sparing technique may be superior to reaming in terms of achieving improved early implant fixation of uncemented HA-coated revision implants.