A novel lower bound for tip-apex distance



The cut-out of the cephalomedullary nail is among the most common post-surgery complications for intertrochanteric fractures. As a risk predictor, a tip-apex distance (TAD) below 25 mm, observed from orthogonal fluoroscopic views, is recommended in the literature. This study aims to demonstrate that TAD < 25 mm is a mathematically insufficient risk definition and to complement the TAD upper bound with an appropriate lower bound, with the introduction of a novel distance parameter, TADX, based on the orthogonal projection of the nail tip on the central femoral midline.


Through a mathematical simulation software, all the possible points that lie inside the AP and lateral views of the proximal femoral hemisphere are utilized to create a 3D grid that is sorted into geometrically safe and risk-bearing regions. Extending this methodology, TAD < 25 mm, 10 mm < TAD < 25 mm, and the ideal tip position volumes are simulated. Finally, intersection volumes are created by a combination of different candidate lower TADX bounds and TAD < 25 mm upper bound to determine satisfactory TADX limits.


Simulation of TAD-bound zones exposed that TAD is only a mathematically suitable parameter for defining the upper boundary but not the lower boundary for the optimal region. However, using a TADX lower limit creates a 3D volume that is much closer to the optimal tip region volumetrically and can still be as quickly calculated from 2D AP and lateral views.


According to the mathematical simulations, the use of a TADX lower bound of 9 mm for small, 7.5 mm for medium, and 7 mm for large femoral heads in conjunction with a TAD upper bound of 25 mm is suggested.

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  1. 1.

    Iskrant AP. The classic: the etiology of fractured hips in females. Clin Orthop Relat Res. 2010;468:1731–5.

    Article  Google Scholar 

  2. 2.

    Keene G, Parker M, Pryor G. Mortality and morbidity after hip fractures. BMJ. 1993;307:1248–50.

    CAS  Article  Google Scholar 

  3. 3.

    Nishiura T, Nozawa M, Morio H. The new technique of precise insertion of lag screw in an operative treatment of trochanteric femoral fractures with a short intramedullary nail. Injury. 2009;40:1077–83.

    Article  Google Scholar 

  4. 4.

    Baumgaertner MR, Solberg BD. Awareness of tip-apex distance reduces failure of fixation of trochanteric fractures of the hip. J Bone Jt Surg. 1997;79:969–71.

    CAS  Article  Google Scholar 

  5. 5.

    Bojan AJ, Beimel C, Taglang G, Collin D, Ekholm C, Jönsson A. Critical factors in cut-out complication after gamma nail treatment of proximal femoral fractures. BMC Musculoskelet Disord. 2013;14:1–9.

    Article  Google Scholar 

  6. 6.

    Güven M, Yavuz U, Kadioǧlu B, Akman B, Kilinçoǧlu V, Ünay K, Altıntaş F. Importance of screw position in intertrochanteric femoral fractures treated by dynamic hip screw. Rev Chir Orthop Traumatol. 2010;96:33–4.

    Google Scholar 

  7. 7.

    Baumgaertner MR, Curtin SL, Lindskog DM, Keggi JM. The value of the tip-apex distance in predicting failure of fixation of peritrochanteric fractures of the hip. J Bone Jt Surg Am. 1995;77(7):1058–64.

    CAS  Article  Google Scholar 

  8. 8.

    Wright D, Whyne C, Hardisty M, Kreder HJ, Lubovsky O. Functional and anatomic orientation of the femoral head. Clin Orthop Relat Res. 2011;469:2583–9.

    Article  Google Scholar 

  9. 9.

    Heffernan MJ, Snyder B, Zhou H, Li X. Fluoroscopic imaging overestimates the screw tip to subchondral bone distance in a cadaveric model of slipped capital femoral epiphysis. J Child Orthrop. 2017;11:36–41.

    CAS  Article  Google Scholar 

  10. 10.

    Rubio-Avila J, Madden K, Simunovic N, Bhandari M. Tip to apex distance in femoral intertrochanteric fractures: a systematic review. J Orthop Sci. 2013;18:592–8.

    Article  Google Scholar 

  11. 11.

    Mingo-Robinet J, Torres-Torres M, Martínez-Cervell C, Alonso Del Olmo JA, Rivas Laso JA, Aguado-Hernández H, Burón-Alvarez I. Comparative study of the second and third generation of gamma nail for trochanteric fractures: review of 218 cases. J Orthop Trauma. 2015;29:e85–90.

    Article  Google Scholar 

  12. 12.

    Goffin JM, Jenkins PJ, Ramaesh R, Pankaj P, Simpson AH. What Is the relevance of the tip-apex distance as a predictor of lag screw cut-out? PLoS ONE. 2013;8:4–11.

    Article  Google Scholar 

  13. 13.

    Pervez H, Parker MJ, Vowler S. Prediction of fixation failure after sliding hip screw fixation. Injury. 2004;35:994–8.

    Article  Google Scholar 

  14. 14.

    Wu C, Tai C. Effect of lag-screw positions on modes of fixation failure in elderly patients with unstable intertrochanteric fractures of the femur. J Orthop Surg. 2010;18(2):158–65.

    Article  Google Scholar 

  15. 15.

    Brammar TJ, Kendrew J, Khan RJK, Parker MJ. Reverse obliquity and transverse fractures of the trochanteric region of the femur; A review of 101 cases. Injury. 2005;36:851–7.

    Article  Google Scholar 

  16. 16.

    Zhou JQ, Chang SM. Failure of PFNA: Helical blade perforation and tip-apex distance. Injury. 2012;43:1227–8.

    Article  Google Scholar 

  17. 17.

    Li S, Chang SM, Jin YM, Zhang YQ, Niu WX, Du SC, Zhang LZ, Ma H. A mathematical simulation of the tip-apex distance and the calcar-referenced tip-apex distance for intertrochanteric fractures reduced with lag screws. Injury. 2016;47:1302–8.

    Article  Google Scholar 

  18. 18.

    Cheng Y, Wang S, Yamazaki T, Zhao J, Nakajima Y, Tamura S. Hip cartilage thickness measurement accuracy improvement. Comput Med Imaging Graph. 2007;31:643–55.

    Article  Google Scholar 

  19. 19.

    Mitra A, Khadijeh B, Vida AP, Ali RN, Farzaneh M, Maryam VF, Vahid Y. Sexing based on measurements of the femoral head parameters on pelvic radiographs. J Forensic Leg Med. 2014;23:70–5.

    Article  Google Scholar 

  20. 20.

    Zhang W, Antony Xavier RP, Decruz J, Chen YD, Park DH. Risk factors for mechanical failure of intertrochanteric fractures after fixation with proximal femoral nail antirotation (PFNA II): a study in a Southeast Asian population. Arch Orthop Trauma Surg. 2020;7:20–6.

    Google Scholar 

  21. 21.

    Yam M, Kang BJ, Chawla A, Zhang W, Way LG, Xavier RPA, et al. Cephalomedullary blade cut-ins: a poorly understood phenomenon. Arch Orthop Trauma Surg. 2020;22:110–28.

    Google Scholar 

  22. 22.

    Turgut A, Kalenderer Ö, Karapınar L, Kumbaracı M, Akkan HA, Ağuş H. Which factor is most important for occurrence of cutout complications in patients treated with proximal femoral nail antirotation? Retrospective analysis of 298 patients. Arch Orthop Trauma Surg. 2016;136:623–30.

    Article  Google Scholar 

  23. 23.

    Murena L, Moretti A, Meo F, Saggioro E, Barbati G, Ratti C, et al. Predictors of cut-out after cephalomedullary nail fixation of pertrochanteric fractures: a retrospective study of 813 patients. Arch Orthop Trauma Surg. 2018;138:351–9.

    Article  Google Scholar 

  24. 24.

    Walton MJ, Barnett AJ, Jackson M. Tip-apex distance as a predictor of failure following cephalo-medullary fixation for unstable fractures of the proximal femur. Eur J Trauma Emerg Surg. 2008;34:273–6.

    Article  Google Scholar 

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Correspondence to Ismail Lazoglu.

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Omer Subasi, Lercan Aslan, Aksel Seyahi, Mehmet Demirhan and Ismail Lazoglu declare that they have no conflict of interest.

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Subasi, O., Aslan, L., Demirhan, M. et al. A novel lower bound for tip-apex distance. Eur J Trauma Emerg Surg (2020). https://doi.org/10.1007/s00068-020-01514-x

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  • Tip-apex distance
  • TAD
  • Intertrochanteric fracture
  • Proximal nailing
  • Fluoroscopy