OTA 2013 Posters

Scientific Poster #26 Geriatric OTA 2013

Bone Stock Distribution Along Transsacral Corridors in the Elderly and Its Relevance to Sacral Insufficiency Fractures

Daniel Wagner, MD1,2; Lukas Kamer, MD2; Takeshi Sawaguchi, MD3; Hansrudi Noser, PhD1; Pol M. Rommens, MD2;
1AO Research Institute Davos, Davos, Switzerland;
2Department of Trauma Surgery, University Medical Center Mainz, Mainz, Germany;
3Department of Orthopedics & Joint Reconstructive Surgery, Toyama Municipal Hospital, Toyama, Japan

Purpose: With the demographic changes the prevalence of osteoporosis is increasing and as a consequence, sacral insufficiency fractures (SIFs) are becoming more common. There exist various treatment options; however, there is no established treatment concept and a lack of anatomical data to be used to optimize implant fixation. We detail the distribution of the bone stock along the transsacral corridors.

Methods: We studied intact pelvic CT scans of 64 adults (29 females and 35 males, mean age 74.3 years, standard deviation ±13). After semi-automated image segmentation a mean shape was created using techniques for 3-dimensional statistical modeling. Then all CT grey value data given in Hounsfield Units (HU) were elastically matched into the mean shape. There resulted an averaged bone stock distribution model of the sacrum. The bone stock in HU along the transsacral corridors S1 and S2 were analyzed.

Results: We observed a distinct bone stock distribution along the transsacral corridors (Figure 1). The first peak corresponded to cortical bone of the auricular surface. It was followed by a rapid decrease and a zone of minimal values, corresponding to the paraforaminal lateral zone also called "alar void". Intermediate values were observed in the vertebral body. This pattern was seen in both, S1 and S2, with generally lower values in S2. Females showed an overall diminished bone stock with mainly negative HU in the paraforaminal lateral zone. The largest difference in HU values between females and males was found in the vertebral bodies.

Figure 1: Mean values in HU (y axis) along transsacral corridors S1 (left) and S2 (right) demonstrating a distinct pattern of bone stock distribution in males (dark grey) and females (lighter grey).

Conclusion: There was a variable, distinct bone stock distribution along transsacral corridors. The paraforaminal lateral zone was identified to be the weakest spot. This may explain the typical patterns and location of SIFs corresponding to Denis zone I. These anatomical findings influence screw anchorage/fixation and may lead to a better understanding of SIFs.

• 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.