OTA 1997 Posters - Femur Fractures

The Entry Point in Genucephalic Nailing

Gerald E. Wozasek, MD, Wolfgang A. Menth-Chiari, MD, Mehdi Mousavi, MD, Vilmos Vécsei, MD

Trauma Center, Vienna General Hospital, Medical School, Vienna, Austria

Introduction: The intercondylar starting point in intramedullary supracondylar nailing has been described in a nonarticular portion of the distal femur just anterior to the origin of the posterior cruciate ligament. Possible complications related to this entry include notch impingement, cartilage damage and femoropatellar compromise.

Purpose: The purpose of this study was to investigate the optimum entry point in relation to the femoropatellar joint, to the cruciate ligaments and to quantify the cartilage involvement.

Material: Ten pairs of fresh cadaver knee specimens with a mean age of 68 years (65-73 years) were studied. They were photographed in 90 degree flexion of the joint in orthograde view. The cartilage surfaces of the distal femur, of the femoropatellar joint and the nail entry point were measured by planimetry in this position. Hereby the femoropatellar joint was defined as the area between the roof of the intercondylar notch and the superior bone cartilage border of the femur. A 11 mm retrograde nail was inserted according to the standard operative techniques. Postoperatively all knee specimens were brought through a full range of motion.

Results: The femoral cartilage surface in orthograde view measured on the average 2948 sq mm (2895 - 3103 sq mm) and the mean femoropatellar surface averaged 751 sq mm (720 sq mm - 805 sq mm). The 11 mm nail entry point involved 16% of the femoropatellar joint and was located 5 to 7 mm anterior and central to the insertion of the posterior cruciate ligament in the cartilage surface of femoropatellar joint. The entry point caused no impingement of the cruciate ligament during knee motion.

Conclusion: Based on the findings of this study, the entry point in genucephalic nailing is located in the cartilage surface of the femoropatellar joint. This entry site is a modification to the recommendations of the described operative techniques. The nail insertion does not cause any impingement at the intercondylar notch. However, the tip of the nail has to be countersunk 1-2 mm below the articular surface to prevent retropatellar impingement.