Intra-medullary nail insertion accuracy: A comparison of the infra-patellar and supra-patellar approach

The anatomical safe zone for intra-medullary nail insertion through the tibial plateau is small, insertion outside of this area risks damage to intra-articular structures and poor fracture reduction. The purpose of this retrospective study was to determine if the new supra-patella (SP) approach confers improved nail insertion accuracy, when compared with the standard infra-patella (IP) technique.

Two hundred cases were included in the study (SP 95, IP 105). Insertion accuracy was assessed on AP and lateral radiographic imaging, and measured as the distances between the central axis of the proximal nail and the ideal entry point.

The median distance from the ideal entry point was 4.4 mm (SP) and 5.1 mm (IP) (p = 0.046) in the coronal plane, and 4.0 mm (SP) and 3.7 mm (IP) (p = 0.527) in the sagittal plane. A narrower range in measurements was observed in the SP technique in both sagittal and coronal planes, 17.8 mm vs 28.6 mm, and 19.7 mm vs 30.3 mm respectively.

We found that the SP technique achieved significantly improved nail insertion accuracy in the coronal plane. Insertion accuracy was equivocal between the two techniques in the sagittal plane. A narrower range in entry points was observed in the SP cohort in both planes suggesting improved control in nail insertion using this technique.