101. POSTOPERATIVE FEMORAL FRACTURES OVER NAVIGATION PIN TRACTS: A COMPLICATION OF NAVIGATED KNEE SURGERY

Abstract

Purpose of the study: Navigated surgery for implantation of knee prostheses has demonstrated pertinence in terms of quality and regularity of the implantation. This technique requires insertion of rigid position captors in the bone during the operation. We report a series of five femoral fractures which occurred on the pin tracts in a consecutive series of 385 patients and analyse the causes and means of prevention.

Material and methods: This was a retrospective clinical and radiographic analysis of five patients among our consecutive series of 385 patients, who suffered fractures on navigation pin tracts.

Results: There were five femoral fractures, in four women and one man, mean age 73.2 years (65–79). The mean body mass index was 32.56 (24.15–39.45). The rate of this complication was 1.3%. The fractures occurred on average 12.6 weeks (range 7–21) after implantation of the prosthesis. The fractures were always preceded by thigh pain and occurred in a context of minor or indirect trauma. The fracture lines always started from a pin tract orifice. In four of five cases, the pins had been inserted in a diaphyseal zone and at least one was in a transcortical position. The five fractures healed with no functional sequel at last follow-up after osteosynthesis with a nail or plate and no complementary bone graft.

Discussion: The incidence of these fractures on navigation pin tracts is estimated at 1.3%. Surgeons must be aware of this complication and describe the risk to patients. These fractures occur late after the implantation, in obese patients, after an episode of thigh pain. Treatment requires stable osteosynthesis but does not compromise the knee prosthesis. These fractures are favoured by low and transcortical diaphyseal position of navigation pins. Prevention requires implantation of bicortical metaphyseal navigation pins. The development of pain in the thigh late after a knee prosthesis implantation, in a favouring context (obese patient, low diaphyseal pin orifice, transcortical tract) should suggest possible fracture requiring complete rest.