Citation Information :
Elsheikh AA, Wright J, Stoddart MT, Goodier D, Calder P. Use of the Pixel Value Ratio Following Intramedullary Limb Lengthening: Uncomplicated Full Weight-bearing at Lower Threshold Values. 2022; 17 (1):14-18.
Aims: The pixel value ratio (PVR) can be used to assess regenerate consolidation after lengthening and guide advice for full weight-bearing (FWB). This study aimed to analyse the PVR in adults having femoral lengthening, the time to FWB and compare findings with the reported values in the literature.
Materials and methods: A retrospective database review identified 100 eligible patients who underwent lengthening using the PRECICE nail (68 antegrade and 32 retrograde). The PVR was calculated in each cortex on plain radiographs at every visit. The ratio between the regenerate and an average from the adjacent normal bone was calculated and plotted against the clinical decision to allow FWB.
Results: Eighty-seven patients (58 men and 29 women) were assessed; eleven had bilateral lengthening and two patients underwent lengthening twice. The median age was 30.5 years. The underlying cause of shortening was post-traumatic in 46%, with the remaining due to a wide variety of causes, including congenital 16%, syndromic 12% and other causes. The median lengthening achieved was 45 mm, at a median of 57.5 days. The PVR increased with each visit (p <0.0001). FWB was allowed at a median of 42 days after the last day of lengthening, with PVR values of 0.83, 0.84, 0.93 and 0.84 for the anterior, posterior, medial and lateral cortex noted, respectively (average 0.85). There were no implant failures, shortening or regenerate fractures. No differences were detected between antegrade and retrograde nails or with lengthening greater or less than 45 mm. One surgeon allowed earlier FWB at median 31 days with no nail failures.
Conclusion: PVR is a valuable tool that quantifies regenerate maturity and provides objectivity in deciding when to allow FWB after intramedullary lengthening with the PRECICE nail. FWB was permitted at an earlier time point, corresponding with lower PVR values than have been reported in the literature and with no mechanical failure or regenerate deformation.
Ilizarov GA. The tension-stress effect on the genesis and growth of tissues. Part I. The influence of stability of fixation and soft-tissue preservation. Clin Orthop Relat Res 1989(238):249–281. PMID: 2910611.
Hosny GA. Limb lengthening history, evolution, complications and current concepts. J Orthop Traumatol 2020;21(1):3. DOI: 10.1186/s10195-019-0541-3.
Yin P, Ji Q, Li T, et al. A systematic review and meta-analysis of ilizarov methods in the treatment of infected nonunion of tibia and femur. PLoS One 2015;10(11):e0141973. DOI: 10.1371/journal.pone.0141973.
Sheridan GA, Fragomen AT, Rozbruch SR. Integrated limb lengthening is superior to classical limb lengthening: a systematic review and meta-analysis of the literature. JAAOS Global Res Rev 2020;4(6):e20.00054. DOI: 10.5435/JAAOSGlobal-D-20-00054.
Sheridan GA, Falk DP, Fragomen AT, et al. Motorized Internal Limb-Lengthening (MILL) techniques are superior to alternative limb-lengthening techniques: a systematic review and meta-analysis of the literature. JBJS Open Access 2020;5(4):e20.00115. DOI: 10.2106/JBJS.OA.20.00115.
Calder PR, Laubscher M, Goodier WD. The role of the intramedullary implant in limb lengthening. Injury 2017;48(Suppl. 1):S52–S58. DOI: 10.1016/j.injury.2017.04.028.
Paley D, Harris M, Debiparshad K, et al. Limb lengthening by implantable limb lengthening devices. Tech Orthop 2014;29(2): 72. DOI: 10.1097/BTO.0000000000000072.
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.
Shim JS, Chung KH, Ahn JM. Value of measuring bone density serial changes on a picture archiving and communication systems (PACS) monitor in distraction osteogenesis. Orthopedics 2002;25(11): 1269–1272. DOI: 10.3928/0147-7447-20021101-19.
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.
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.
Singh S, Song HR, Venkatesh KP, et al. Analysis of callus pattern of tibia lengthening in achondroplasia and a novel method of regeneration assessment using pixel values. Skeletal Radiol 2010;39(3):261–266. DOI: 10.1007/s00256-009-0703-0.
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.
Ryu KJ, Kim BH, Hwang JH, et al. Reamed intramedullary nailing has an adverse effect on bone regeneration during the distraction phase in tibial lengthening. Clin Orthop Relat Res 2016;474(3):816–824. DOI: 10.1007/s11999-015-4613-2.
Archer L, Dobbe A, Chhina H, et al. Inter- and Intra-observer reliability of the pixel value ratio, Ru Li's and Donnan's classifications of regenerate quality in pediatric limb lengthening. J Limb Lengthen Reconstr 2018;4(1):26. DOI: 10.4103/jllr.jllr_11_17.
Lee CS, Shim JS, Oh WH, et al. Clinical implications of pixel values in PACS (picture archiving and communications system): a comparison with dual energy X-ray absorptiometry. J Korean Orthop Assoc 1997;32(6):1450–1457. DOI: 10.4055/jkoa.1922.214.171.1240.
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.
Calder PR, McKay JE, Timms AJ, et al. Femoral lengthening using the precice intramedullary limb-lengthening system: outcome comparison following antegrade and retrograde nails. Bone Joint J 2019;101-B(9):1168–1176. DOI: 10.1302/0301-620X.101B9.BJJ-2018-1271.R1.
Iliadis AD, Palloni V, Wright J, et al. Pediatric lower limb lengthening using the PRECICE nail: our experience with 50 cases. J Pediatr Orthop 2021;41(1):e44–e49. DOI: 10.1097/BPO.0000000000001672.
Lee DH, Kim S, Lee JW, et al. A comparison of the device-related complications of intramedullary lengthening nails using a new classification system. BioMed Res Int 2017;2017:8032510. DOI: 10.1155/2017/8032510.
NuVasive Specialized Orthopedics I. The PRECICE(®) intramedullary limb lengthening system. 2011. Available from: https://atlasapi.nuvasive.com/public/ifu/documents/retrieve?get& pVersion=0046&contRep=ZNUVEP1&docId=005056867701 1EDB9CDF0046DC5EA12A&compId=LC0046-AD_ENGLISH.pdf.
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. Strategies Trauma Limb Reconstr 2020;15(2):74–78. DOI: 10.5005/jp-journals-10080-1461.
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.
Paley D, Herzenberg JE, Paremain G, et al. Femoral lengthening over an intramedullary nail. A matched-case comparison with Ilizarov femoral lengthening. J Bone Joint Surg Am 1997;79(10):1464–1480. DOI: 10.2106/00004623-199710000-00003.
Burghardt RD, Manzotti A, Bhave A, et al. Tibial lengthening over intramedullary nails: a matched case comparison with Ilizarov tibial lengthening. Bone Joint Res 2016;5(1):1–10. DOI: 10.1302/2046-3758.51.2000577.
Kristiansen LP, Steen H. Lengthening of the tibia over an intramedullary nail, using the Ilizarov external fixator. Major complications and slow consolidation in 9 lengthenings. Acta Orthop Scand 1999;70(3):271–274. DOI: 10.3109/17453679908997806.
Fischgrund J, Paley D, Suter C. Variables affecting time to bone healing during limb lengthening. Clin Orthop Relat Res 1994;301:31–37. PMID: 8156692.