OTA 2012 Posters

Scientific Poster #35 Hip/Femur OTA-2012

Posterior Cruciate Ligament Injury With Retrograde Femoral Nailing: An Anatomic and MRI Study

Joshua Blomberg, MD; Christopher J. Doro, MD;
Department of Orthopaedics, University of Wisconsin School of Medicine,
Madison, Wisconsin, USA

Purpose: It has been suggested that retrograde femoral nails can cause posterior cruciate ligament (PCL) injury. The limits of reaming size proposed in the literature suggest a maximum diameter of 13 mm; however, we are unaware of any specific studies or data that support this limit. Our hypothesis is that the PCL will not be damaged to a significant degree with retrograde reaming up to 17 mm, which would be the required diameter for the largest noncustom, commercially available nail.

Methods: 20 unmatched embalmed cadaveric knee specimens with soft tissue and skin intact were obtained. The knees were stripped of all soft tissue, except for the knee capsule and ligaments. The distal femurs’ AP and lateral diameters were measured with fluoroscopy using a radiographic marker of known diameter. The femurs were then reamed in the standard manner with the Stryker T2 femoral nailing system up to 17 mm in a retrograde fashion with the use of fluoroscopy. Two methods were then used to determine the amount of disrupted PCL. First, the knees were imaged with a 3-T MRI scanner, and sequential measurements were made on the MRI digital images to determine the percentage of disrupted PCL compared to its entire footprint. The second method was photographic quantification. This involved careful dissection of the PCL from its femoral origin after marking the disrupted region. Then NIH Image J software was used to measure the area of marked disrupted PCL fibers. This was quantified as a percentage of the entire femoral origin of the PCL.

Results: Evaluation of the 20 specimens using the digital MRI measurement technique showed that a mean of 11.2% (SD 4.8%) of the femoral PCL footprint was disrupted after reaming up to 17 mm. Photographic quantification of the 20 specimens showed a mean of 9.6% (SD 3.7%) of the femoral PCL footprint was disrupted after reaming. Using paired t test analysis, the mean difference between the MRI and Image J measurements was found to be 1.6% (P = 0.026).

Conclusions: Although this was an anatomic study and not a biomechanical or clinical study, the PCL is not significantly disrupted even with very large retrograde femoral reaming. Based on the findings of this study, we feel the distal femur can be reamed up to 17 mm without concern for significant PCL injury. These data could be particularly useful in situations requiring exchange retrograde femoral nailing or in treating osteoporotic femoral shaft fractures when larger nail sizes may be required.

• 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.