OTA 2012 Posters

Scientific Poster #2 Hip/Femur OTA-2012

Distal Femoral Anterior Cortical Penetration After Intramedullary Hip Nailing: Fact or Fiction?

Dan Bazylewicz, MD1; Kenneth A. Egol, MD1; Kenneth J. Koval, MD2;
1NYU/Hospital for Joint Diseases, New York, New York, USA;
2Orlando Regional Medical Center, Orlando, Florida, USA

Background/Purpose: There has been concern over distal femoral cortical abutment and penetration after intramedullary (IM) hip nailing because of the known mismatch between the anatomic femoral bow and the bow of currently used IM nails. This mismatch has resulted in IM hip nail redesign, despite a lack of any clinical series reporting the rate or scope of the problem with modern IM hip nail designs. This study was performed to determine the rate of anterior cortical abutment and penetration after nailing of proximal femur fractures in a consecutive series of patients using a nail with a radius of curvature (ROC) of 180 cm, and to determine final nail positions.

Methods: Between June 2005 and September 2008, all proximal femoral fractures or impending fractures stabilized at one institution using the Pertrochanteric Nail (PTN, Biomet) were retrospectively evaluated. Fractures were excluded only if the intraoperative or first postoperative lateral radiograph did not include an adequate lateral radiograph demonstrating overlap of the two condyles. The lateral radiographs were reviewed by a single reviewer for presence of cortical abutment and penetration as well as location within the medullary canal from anterior to posterior. Cortical penetration was defined as cortical fracture with nail location beyond the anterior distal femoral cortex. Cortical abutment was defined as nail location within 3 mm of the distal femoral anterior cortex. The space available for the nail at the superior edge of the patella was divided into four equal segments and the proportion of nails lying in each quarter of the possible space available for the nail was determined using the labels “far anterior,” “anterior,” “posterior,” and “far posterior.” Statistical analysis was performed (χ2 test, comparison of proportions, MedCalc Software) to determine whether there was any relationship between fracture type (31A, 32, pathologic) and nail location in the sagittal plane.

Results: 271 fractures were stabilized using the PTN during the time frame. 57 fractures were excluded due to inadequate imaging, leaving 214 nails in 212 patients available for analysis. 144 fractures were in women and 70 were in men. The average patient age was 74 years (range, 18-96). Four nails were used to stabilize pathologic fractures, 22 nails for impending pathologic fractures, 128 nails for an acute pertrochanteric fractures (52 OTA Type 31A1, 62 Type 31A2, 14 Type 31A3), and 60 nails to stabilize subtrochanteric fractures (OTA Type 32). Of the 214 cases available for analysis, there was 1 case (0.47%) of anterior femoral cortical penetration. Of the remaining 213 nails, 35 (16.4%) were within 3 cm of the anterior femoral cortex. Analyzed by quartiles in the suprapatellar region, 40% of nails ended up far anterior, 48% anterior, 10% posterior, and 2% far posterior. No relationship was found between fracture type and rate of penetration or cortical abutment, but nails in pertrochanteric fractures (OTA 31) were more likely to end up in the “far anterior” quarter of the available canal space compared to subtrochanteric fractures (OTA 32) (P = 0.02).

Conclusions: We found a low rate (0.47%) of distal femoral cortical penetration using an IM hip nail with a radius of curvature of 180 cm. However, the high rate of nail abutment within 3 mm of the anterior cortex (16.4%) remains a concern. 88% of nails ended in the anterior half of the distal femur, which is consistent with a mismatch between the bows of the anatomic femur and IM nail.

• The FDA has not cleared this drug and/or medical device for the use described in this presentation   (i.e., the drug or medical device is being discussed for an “off label” use).  ◆FDA information not available at time of printing. Δ OTA Grant.