Sat., 10/18/08 Femur, Paper #51, 9:52 am OTA-2008
Predictors of Distal Anterior Cortex Impingement and Penetration during Intramedullary Nailing for Proximal Femur Fractures: An Analysis of Risk Factors
Jason W. Roberts, MD (n); Lev A. Libet (n); Philip R. Wolinsky, MD (n);
University of California-Davis Medical Center, Sacramento, California, USA
Background/Purpose: Distal femoral anterior cortex penetration is a complication of intramedullary nailing of proximal femur fractures. Studies have measured the femoral bow in different populations and documented the mismatch with current implants. When nailing proximal femur fractures, this mismatch can be problematic because the shaft segment is intact and cannot deform to fit the curvature of the implant. A femoral angle of incidence (AI) has been described that can be used to quantify the femoral bow on a lateral radiograph. We performed a clinical study to identify patient factors available prior to surgery that can predict an increased likelihood of an anterior nail tip position and/or cortical penetration.
Methods: After obtaining IRB approval, records of all patients treated with intramedullary nailing for a proximal femur fracture (OTA types 31A and 32.1 subgroup) at our institution over a 4-year period (January 2004-December 2007) were retrospectively reviewed. Patients who had a more distal femoral fracture or deformity, treatment with a short nail, inadequate radiographs, or pathologic fractures were excluded. The position of the distal tip of the nail was analyzed on a lateral radiograph and patients were grouped according to tip position in the anterior, middle, or posterior third of the femur. Patients in the anterior third group, in whom the tip of the nail contacted or penetrated the anterior cortex, were designated as having “cortical impingement”. Radiographs were analyzed and demographic, medical, and surgical variables were compared between the groups.
Results: 150 out of 175 patients qualified for analysis (n = 150). The distal nail tip position was in the anterior third in 71, the middle third in 75, and the posterior third in 4. 38 patients in the anterior group had cortical impingement (36 contacted the cortex and 2 perforated the cortex). The patients with an anterior third nail tip position had a higher average AI than the other patients (9.8° vs 6.9°, P <0.001). The impingement subgroup had the highest AI (10.8° vs 7.4°, P <0.001). Shorter patients (below 5’ 3”) were more likely to have an anterior nail tip position (P = 0.048). Shorter nail lengths were more common in the anterior third group (366 mm vs 388 mm, P <0.001), likely related to the increased risk in shorter patients since all nails were placed to a similar depth. The position of the starting point was also associated with distal tip position. An anterior starting point significantly decreased the likelihood of the distal tip of the nail being in the anterior third group (P <0.01) and a posterior starting point showed a trend toward a more anterior nail tip position (only eight patients had a posterior start point). No significant associations were found when comparing age, race, gender, injury mechanism, medications, nail brand, fracture type, or presence of osteoporosis.
Conclusions and Significance: While performing intramedullary nailing of a proximal femur fracture, patients at a higher risk for distal cortical penetration may be identified by their femoral AI and shorter stature. A posterior starting point may also increase this risk.
If noted, the author indicates something of value received. The codes are identified as a-research or institutional support; b-miscellaneous funding; c-royalties; d-stock options; e-consultant or employee; n-no conflicts disclosed, and *disclosure not available at time of printing.
• 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.