Cortical encroachment after cephalomedullary nailing of the proximal femur: evaluation of a more anatomic radius of curvature.

OBJECTIVES

: A unique complication of using full-length intramedullary nails for pertrochanteric and subtrochanteric femur fractures is nail penetration of the anterior cortex at the distal end of the femur because of a mismatch of the anatomic femoral bow with that of currently available cephalomedullary nails (CMNs). This study was performed to determine the rate of distal femoral cortical penetration after stabilization of the proximal femur in a consecutive series of patients using a long CMN with a curvature of 180 cm and to examine the final location of the nails within the femoral canal.

DESIGN

: Retrospective chart review.

SETTING

: Level 1 trauma center with tertiary care.

PATIENTS/PARTICIPANTS: : Between June 2005 and September 2008, 271 consecutive proximal femoral fractures or impending fractures were stabilized using a specially designed CMN [pertrochanteric nail (PTN) system; Biomet, Warsaw, IN]. Fifty-seven fractures were excluded because of inadequate lateral radiographs, leaving 214 nails in 212 patients available for analysis.

INTERVENTION

: The proximal femur fractures or impending fractures were stabilized with a full-length CMN with a shaft diameter of 11 mm and a radius of curvature of 180 cm.

MAIN OUTCOME MEASUREMENTS

: Nail position was determined from the lateral radiograph, which included the minimal distance from the nail to the anterior cortex of the distal femur and the relative position of the nail within the medullary canal, at a level within 2 cm proximal to the superior pole of the patella. Based on the nail position within the distal femoral canal, the following were calculated: (1) the overall rate of distal femoral anterior cortical penetration, (2) the distribution of nail distances to the anterior cortex, and (3) the proportion of nails lying in each quarter of the space available for the nail.

RESULTS

: Four surgeries (1.9%) were performed for pathologic fracture and 22 (10.3%) for impending pathologic fracture. The remaining 188 CMNs were used to stabilize OTA Type 31A1 fractures (52 nails, 24.3%), Type 31A2 fractures (62 nails, 29%), Type 31A3 fractures (15 nails, 6.5%), and Type 32 fractures (59 nails, 27.6%). Of the 214 cases available for radiographic analysis, there was 1 case (0.47%) of distal femoral anterior cortical penetration. Of the remaining 213 CMNs, 40% of nails ended up far anterior, 48% anterior, 10% posterior, and 2% far posterior. Sixteen percent (1/6) were within 3 mm of the anterior cortex and half were within 7 mm. The average distance from nail to the anterior cortex was 8.5 mm.

CONCLUSION

: Use of a CMN with a radius of curvature of 180 cm to stabilize the proximal femur resulted in a very low rate of distal femoral anterior cortical penetration. However, most of the intramedullary nails ended up in the anterior half of the space available for the nail with 16% within 3 mm of the anterior cortex. These results highlight the importance of being aware of the complication of anterior cortical impingement and perforation during CMN insertion.

LEVEL OF EVIDENCE

: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.