Strategies in Trauma and Limb Reconstruction

Register      Login

VOLUME 15 , ISSUE 2 ( May-August, 2020 ) > List of Articles

Original Article

Evaluating the Utility of the Pixel Value Ratio in the Determination of Time to Full Weight-bearing in Patients Undergoing Intramedullary Limb Lengthening

Anirejuoritse Bafor, Molly E Duncan, Christopher A Iobst

Citation Information : Bafor A, Duncan ME, Iobst CA. Evaluating the Utility of the Pixel Value Ratio in the Determination of Time to Full Weight-bearing in Patients Undergoing Intramedullary Limb Lengthening. 2020; 15 (2):74-78.

DOI: 10.5005/jp-journals-10080-1461

License: CC BY-NC-SA 4.0

Published Online: 03-03-2021

Copyright Statement:  Copyright © 2020; The Author(s).


Introduction: Limb lengthening using intramedullary nails is an increasingly popular method of achieving limb length equalisation. Currently, the decision regarding when to commence full weight-bearing (FWB) remains largely subjective. Objective criteria for determining the proper timing of FWB would be helpful to limb lengthening surgeons. This study examines using the pixel value ratio (PVR) as an objective method to determine the time to FWB for patients being lengthened with an intramedullary nail. Materials and methods: A retrospective chart review of 42 patients who underwent unilateral lengthening of the femur was undertaken. The PVR of all four cortices of the regenerate bone was monitored throughout the distraction and consolidation stages to determine the ratio at the time of FWB. Results: Clinically and radiologically determined FWB was achieved at a mean time of 125.7 ± 30.1 days from surgery. The mean PVR at the time of FWB was 0.94. The medial cortex healed fastest with a mean PVR of 0.96, while the posterior cortex healed slowest with a mean PVR of 0.92. Conclusion: The PVR is a quick and reliable method to objectively assess the state of healing of the regenerate bone during distraction osteogenesis. We observed that there were no adverse effects when subjects commenced FWB when three out of the four cortices had a PVR of at least 0.93.

  1. Birch JG. A brief history of limb lengthening. J Pediatr Orthop 2017;37:S1–S8. DOI: 10.1097/BPO.0000000000001021.
  2. Ilizarov GA. Clinical application of the tension-stress effect for limb lengthening. Clin Orthop Relat Res 1990;250(250):8–26. DOI: 10.1097/00003086-199001000-00003.
  3. Iobst CA. Intramedullary limb-lengthening lessons learned. JBJS Rev 2019;7(12):e2. DOI: 10.2106/JBJS.RVW.19.00034.
  4. Kirane YM, Fragomen AT, Rozbruch SR. Precision of the PRECICE ® internal bone lengthening nail. Clin Orthop Relat Res 2014;472(12):3869–3878. DOI: 10.1007/s11999-014-3575-0.
  5. Paley D, Harris M, Debiparshad K, et al. Limb lengthening by implantable limb lengthening devices. Tech Orthop 2014;29(2):72–85. DOI: 10.1097/BTO.0000000000000072.
  6. Anand A, Feldman DS, Patel RJ, et al. Interobserver and intraobserver reliability of radiographic evidence of bone healing at osteotomy sites. J Pediatr Orthop Part B 2006;15(4):271–272. DOI: 10.1097/01202412-200607000-00007.
  7. Den Boer FC, Bramer JAM, Patka P, et al. Quantification of fracture healing with three-dimensional computed tomography. Arch Orthop Trauma Surg 1998;117(6-7):345–350. DOI: 10.1007/s004020050263.
  8. Saran N, Hamdy RC. DEXA as a predictor of fixator removal in distraction osteogenesis. Clin Orthop Relat Res 2008;466(12): 2955–2961. DOI: 10.1007/s11999-008-0514-y.
  9. Hazra S, Song HR, Biswal S, et al. Quantitative assessment of mineralization in distraction osteogenesis. Skeletal Radiol 2008;37(9):843–847. DOI: 10.1007/s00256-008-0495-7.
  10. Song SH, Agashe M, Kim TY, et al. Serial bone mineral density ratio measurement for fixator removal in tibia distraction osteogenesis and need of a supportive method using the pixel value ratio. J Pediatr Orthop Part B 2012;21(2):137–145. DOI: 10.1097/BPB.0b013e32834f04f3.
  11. Fischgrund J, Paley D, Suter C. Variables affecting time to bone healing during limb lengthening. Clin Orthop Relat Res 1994;301(301):31–37. DOI: 10.1097/00003086-199404000-00006.
  12. Skaggs DL, Leet AI, Money MD, et al. Secondary fractures associated with external fixation in pediatric femur fractures. J Pediatr Orthop 1999;19(5):582–586. DOI: 10.1097/01241398-199909000- 00005.
  13. Starr KA, Fillman R, Raney EM. Reliability of radiographic assessment of distraction osteogenesis site. J Pediatr Orthop 2004;24(1):26–29. DOI: 10.1097/01241398-200401000-00006.
  14. Li R, Saleh M, Yang L, et al. Radiographic classification of osteogenesis during bone distraction. J Orthop Res 2006;24(3):339–347. DOI: 10.1002/jor.20026.
  15. Eyres KS, Bell MJ, Kanis JA. Methods of assessing new bone formation during limb lengthening. ultrasonography, dual energy x-ray absorptiometry and radiography compared. J Bone Jt Surg - Ser B 1993;75-B(3):358–364. DOI: 10.1302/0301-620X.75B3. 8496200.
  16. Babatunde OM, Fragomen AT, Rozbruch SR. Noninvasive quantitative assessment of bone healing after distraction osteogenesis. HSS J 2010;6(1):71–78. DOI: 10.1007/s11420-009-9130-y.
  17. Powell ES, Lawford PV, Duckworth T, et al. Is callus calcium content an indicator of the mechanical strength of healing fractures? An experimental study in rat metatarsals. J Biomed Eng 1989;11(4):277–281. DOI: 10.1016/0141-5425(89)90059-9.
  18. Reichel H, Lebek S, Alter C, et al. Biomechanical and densitometric bone properties after callus distraction in sheep. Clin Orthop Relat Res 1998;357:237–246. DOI: 10.1097/00003086-199812000-00030.
  19. Chakkalakal DA, Lippiello L, Wilson RF, et al. Mineral and matrix contributions to rigidity in fracture healing. J Biomech 1990;23(5):425–434. DOI: 10.1016/0021-9290(90)90297-G.
  20. Maffulli N, Cheng JCY, Sher A, et al. Bone mineralization at the callotasis site after completion of lengthening. Bone 1999;25(3): 333–338. DOI: 10.1016/S8756-3282(99)00168-4.
  21. Aronson J, Shin HD. Imaging techniques for bone regenerate analysis during distraction osteogenesis. J Pediatr Orthop 2003;23(4):550–560. DOI: 10.1097/01241398-200307000-00025.
  22. Zhao L, Fan Q, Venkatesh KP, et al. Objective guidelines for removing an external fixator after tibial lengthening using pixel value ratio: a pilot study. Clin Orthop Relat Res 2009;467(12):3321–3326. DOI: 10.1007/s11999-009-1011-7.
  23. Sun XT, Easwar TR, Stephen M, et al. Comparative study of callus progression in limb lengthening with or without intramedullary nail with reference to the pixel value ratio and the ruli's classification. Arch Orthop Trauma Surg 2011;131(10):1333–1340. DOI: 10.1007/s00402-011-1302-9.
  24. Vulcano E, Markowitz JS, Ali S, et al. Assessment of bone healing during antegrade intramedullary rod femur lengthening using radiographic pixel density. J Am Acad Orthop Surg 2018;26(18): e388–e394. DOI: 10.5435/JAAOS-D-16-00949.
PDF Share
PDF Share

© Jaypee Brothers Medical Publishers (P) LTD.