Fragility fractures of the sacrum occur in elderly patients with severe loss of sacral bone mass
Patients suffering from osteoporosis-associated fragility fractures of the sacrum (FFS; also termed sacral insufficiency fractures) are increasingly observed. They have typical fracture patterns with fracture lines located in the sacral ala. When treating these patients operatively, iliosacral screw loosening is not uncommon. We aimed to study the sacral bone mass in patients presenting with a FFS using 3D statistical models.
Materials and methods
3D models of averaged Hounsfield units (HU) were generated based on CT scans from 13 patients with a unilateral FFS (mean age 79.6 years; 11 females, 2 males). The control group without fractures consisted of 28 males and 32 females (mean age of 68.3 years). A virtual bone probe along the trans-sacral corridors S1 and S2 was taken.
The bone mass distribution in the fractured sacra was similar to the control group, however, with overall lower HU. Large zones of negative HU were located in the sacral ala. In the fractured sacra, the HU in the sacral ala was significantly lower on the non-injured side when comparing to the fractured side (p < 0.001) as well as compared to the non-fractured group (p < 0.001). Low bone mass was observed in sacral body S1 (40 HU) and S2 (20 HU).
The extensive area of negative HU may explain the fracture location in the sacral ala. The low HU in the sacral bodies advocates the use of trans-sacral implants or augmented iliosacral screws to enhance the strength of fracture fixation. The increased HU in the fractured ala could be explained by fracture-asssociated hemorrhage and can be used as a diagnostic tool.
KeywordsSacrum Osteoporosis Sacral insufficiency fracture Fragility fracture Pelvis Statistical model
We acknowledge the support of Dr. Karsten Schwieger. We thank Thomas Heldstab for his technical assistance. This study was partially co-funded by the TK System of the AO Foundation (Davos, Switzerland) and Depuy Synthes (Zuchwil, Switzerland).
Compliance with ethical standards
Conflict of interest
The authors do not have any further conflicts of interests.
The anonymous use of CT data was approved by local ethics committee (Landesärztekammer Rheinland-Pfalz, Mainz, Germany) for the group with fractured sacra. The non-fractured sacra were obtained from the CT database of the AO Research Institute Davos, Davos, Switzerland, registered at the “Eidgenössischer Öffentlichkeits- und Datenschutzbeauftragter”, Bern, Switzerland. All patients agreed to anonymous research use of their CT data.
- 3.Gauthier A, Kanis JA, Jiang Y, Martin M, Compston JE, Borgström F, Cooper C, McCloskey EV (2011) Epidemiological burden of postmenopausal osteoporosis in the UK from 2010 to 2021: estimations from a disease model. Arch Osteoporos 6:179–188. https://doi.org/10.1007/s11657-011-0063-y CrossRefPubMedGoogle Scholar
- 8.Linstrom NJ, Heiserman JE, Kortman KE, Crawford NR, Baek S, Anderson RL, Pitt AM, Karis JP, Ross JS, Lekovic GP, Dean BL (2009) Anatomical and biomechanical analyses of the unique and consistent locations of sacral insufficiency fractures. Spine 34:309–315. https://doi.org/10.1097/BRS.0b013e318191ea01 CrossRefPubMedPubMedCentralGoogle Scholar
- 11.Wagner D, Kamer L, Sawaguchi T, Richards RG, Noser H, Rommens PM (2016) Sacral bone mass distribution assessed by averaged three-dimensional CT models: implications for pathogenesis and treatment of fragility fractures of the sacrum. J Bone Jt Surg Am 98:584–590. https://doi.org/10.2106/JBJS.15.00726 CrossRefGoogle Scholar
- 21.Wagner D, Kamer L, Sawaguchi T, Richards RG, Noser H, Uesugi M, Ossendorf C, Rommens PM (2017) Critical dimensions of trans-sacral corridors assessed by 3D CT models. Relevance for implant positioning in fractures of the sacrum. J Orthop Res 35:2577–2584. https://doi.org/10.1002/jor.23554 CrossRefPubMedGoogle Scholar
- 22.Gras F, Gottschling H, Schröder M, Marintschev I, Hofmann GO, Burgkart R (2016) Transsacral osseous corridor anatomy is more amenable to screw insertion in males: a biomorphometric analysis of 280 pelves. Clin Orthop Relat Res 474:2304–2311. https://doi.org/10.1007/s11999-016-4954-5 CrossRefPubMedPubMedCentralGoogle Scholar
- 23.Höch A, Pieroh P, Henkelmann R, Josten C, Böhme J (2017) In-screw polymethylmethacrylate-augmented sacroiliac screw for the treatment of fragility fractures of the pelvis: a prospective, observational study with 1-year follow-up. BMC Surg 17:132. https://doi.org/10.1186/s12893-017-0330-y CrossRefPubMedPubMedCentralGoogle Scholar
- 24.Höch A, Schimpf R, Hammer N, Schleifenbaum S, Werner M, Josten C, Böhme J (2017) Biomechanical analysis of stiffness and fracture displacement after using PMMA-augmented sacroiliac screw fixation for sacrum fractures. Biomed Tech (Berl) 62:421–428. https://doi.org/10.1515/bmt-2016-0235 CrossRefGoogle Scholar
- 25.Osterhoff G, Dodd AE, Unno F, Wong A, Amiri S, Lefaivre KA, Guy P (2016) Cement augmentation in sacroiliac screw fixation offers modest biomechanical advantages in a cadaver model. Clin Orthop Relat Res 474:2522–2530. https://doi.org/10.1007/s11999-016-4934-9 CrossRefPubMedPubMedCentralGoogle Scholar
- 26.Grüneweller N, Raschke MJ, Zderic I, Widmer D, Wähnert D, Gueorguiev B, Richards RG, Fuchs T, Windolf M (2016) Biomechanical comparison of augmented versus non-augmented sacroiliac screws in a novel hemi-pelvis test model. J Orthop Res 35:1485–1493. https://doi.org/10.1002/jor.23401 CrossRefPubMedGoogle Scholar
- 27.Oberkircher L, Masaeli A, Bliemel C, Debus F, Ruchholtz S, Krüger A (2016) Primary stability of three different iliosacral screw fixation techniques in osteoporotic cadaver specimens-a biomechanical investigation. Spine J 16:226–232. https://doi.org/10.1016/j.spinee.2015.08.016 CrossRefPubMedGoogle Scholar
- 29.Henes FO, Groth M, Bley TA, Regier M, Nüchtern JV, Ittrich H, Treszl A, Adam G, Bannas P (2012) Quantitative assessment of bone marrow attenuation values at MDCT: an objective tool for the detection of bone bruise related to occult sacral insufficiency fractures. Eur Radiol 22:2229–2236. https://doi.org/10.1007/s00330-012-2472-8 CrossRefPubMedGoogle Scholar
- 40.Vivanco JF, Burgers TA, García-Rodríguez S, Crookshank M, Kunz M, MacIntyre NJ, Harrison MM, Bryant JT, Sellens RW, Ploeg H-L (2014) Estimating the density of femoral head trabecular bone from hip fracture patients using computed tomography scan data. Proc Inst Mech Eng H 228:616–626. https://doi.org/10.1177/0954411914540285 CrossRefPubMedGoogle Scholar
- 42.Pickhardt PJ, Pooler BD, Lauder T, del Rio AM, Bruce RJ, Binkley N (2013) Opportunistic screening for osteoporosis using abdominal computed tomography scans obtained for other indications. Ann Intern Med 158:588–595. https://doi.org/10.7326/0003-4819-158-8-201304160-00003 CrossRefPubMedPubMedCentralGoogle Scholar