Abstract: Study presents data about bone quality in patients before and after lengthening of shin by transosseous osteosynthesis method. Materials and methods: 168 patients with shortening or limb deformity, before treatment and after lengthening, underwent multislice computed tomography, with estimation of anatomical and radiological-morphological features of shin. Results: according to data of X-ray examination and MSCT, patients with diagnosed achondroplasia, congenital or acquired shortenings - have initial restructuring of meta-diaphyseal tibial bone, that worsen during lengthening. Patients with subjectively insufficient growth, radiological-morphological changes developed in knee joint during lengthening, which appeared as bone density reduction, appearence of resorption areas, architectonics change and persisted in late period in patients older 35 years. Cortical plate density of tibial diaphysis in patients with shortening of different etiology, during MSCT, was characterized by age, nosological and topographic features and is one of the important parameter of the bone quality before and during treatment stages. Maximum density is marked in the middle third of diaphysis. Density and structure of cortical plate are changed during lengthening. Severe cortical plate density reduction is up to 350 HU on the line of maternal bone and regenerate. Conclusion: bone quality in patients with different etiology of shin shortening, is determined by structure of meta-diaphyseal bone and structural and density features of cortical plate anc determine, in the greater degree, strength bone criteria changing during lengthening of shin. References 1. Aleksandrov Yu.M., Alekberov D.A., D'yachkov K.A. Rengenomorfologicheskie osobennosti dlinnykh kostey i perestroyka ikh struktury pri ustranenii deformatsii kolennykh sustavov u detey s posledstviyami gematogennogo osteomielita [Roentgenomorphological features of long bones and reorganization of their structure when correction of the knee deformities in children with hematogenous osteomyelitis consequences]. Vestnik khirurgii im. Grekova. 2014;173(2):61-65 [In Russ]. 2. Rodionova S.S., Torgashin A.N., Solod E.N. et al. Strukturnye parametry proksimal'nogo otdela bedrennoy kosti v otsenke ee prochnosti [Structural parameters of the proximal femur in the evaluation of its strength]. Vestnik travmatologii i ortopedii im. N.N. Priorova. 2014; (1):77-81 [In Russ]. 3. Bala Y, Chapurlat R., Cheung A.M. et al. Risedronate slows or partly reverses cortical and trabecular microarchitectural deterioration in postmenopausal women. J. Bone Miner. Res. 2014; 29 (2):380-388. 4. Baum T, Grande Garcia E., Burgkart R. et al. Osteoporosis imaging: effects of bone preservation on MDCT- based trabecular bone microstructure parameters and finite element models. BMC Med. Imaging. 2015; 15:22. 5. Garkavenko Yu.E., Yanakova O.M., Bergaliev A.N. Kompleksnyy monitoring protsessov osteogeneza distraktsionnogo regenerata u detey s posledstviyami gematogennogo osteomielita pri udlinenii nizhnikh konechnostey [Complex monitoring of the processes of distraction regenerated bone osteogenesis in children with hematogenous osteomyelitis consequences during the lower limb lengthening]. Travmatologiya i ortopediya Rossii. 2011;1(59):106-111 [In Russ]. 6. Gostishchev V.K., Lipatov K.V., Pisarenko L.V. et al. Prognozirovanie izmeneniy prochnosti dlinnykh trubchatykh kostey v khirurgii khronicheskogo osteomielita [Predicting changes in long tubular bone strength in chronic osteomyelitis surgery]. Khirurgiya. Zhurn. im. N.I. Pirogova. 2010;(2):4-6 [In Russ]. 7. D'yachkov K.A., D'yachkova G.V., Novikov K.I. et al. Dinamika pokazateley kostnoy plotnosti bedrennoy i bol'shebertsovoy kostey u bol'nykh posle udlineniya nizhney konechnosti [Dynamics of femoral and tibial bone density values in patients after lower limb lengthening]. Ilizarovskie chteniya: materialy nauch.-prakt. konf. [Ilizarov readings: materials of scientific-practical conference]. Kurgan. 2012; 107-108 [In Russ]. 8. Stupina T.A., Shchudlo N.A., Petrovskaya N.V. et al. Gistomorfometricheskiy analiz sustavnogo khryashcha i sinovial'noy obolochki kolennogo sustava pri metadiafizarnom udlinenii goleni: (eksperimental'no-morfologicheskoe issledovanie) [Histomorphometrical analysis of the knee articular cartilage and synovium for metadiaphyseal lengthening of the leg: (an experimental and morphological study)]. Travmatologiya i ortopediya Rossii. 2013;1:80-86 [In Russ]. 9. Ahmed L.A., Shigdel R., Joakimsen R.M. et al. Measurement of cortical porosity of the proximal femur improves identification of women with nonvertebral fragility fractures. Osteoporos. Int. 2015; 26 (8): 2137-2146. 10. Bala Y, Bui Q.M., Wang X.F. et al. Trabecular and cortical microstructure and fragility of the distal radius in women. J. Bone Miner. Res. 2015; 30(4): 621-629. 11. Baumgartner R., Heeren N., Quast D. et al. Is the cortical thickness index a valid parameter to assess bone mineral density in geriatric patients with hip fractures? Arch. Orthop. Trauma Surg. 2015;135(6): 805-810. 12. D'yachkov K.A., D'yachkova G.V. Remodelirovanie kosti pri udlinenii konechnosti: kolichestvennaya i kachestvennaya otsenka [Bone remodeling during limb lengthening: a qualitative and quantitative evaluation]. Zhurn. klinich. i eksperiment. ortopedii im. G.A. Ilizarova (Geniy Ortopedii). 2015; 4: 53-60 [In Russ]. 13. Nikitinskaya O.A. Rol' kortikal'noy kosti i ee mikrostruktury v prochnosti kosti [The role of cortical bone and its microstructure in bone strength]. Consilium Medicum. 2010; 12 (2): 132-135 [In Russ]. 14. Chuyko A.N., Kopytov A.A. Komp'yuternaya tomografiya i osnovnye mekhanicheskie kharakteristiki kostnykh tkaney. [Computed tomography and basic mechanical features of bone tissues] Med. vizualizatsiya. 2012;1:102-107 [In Russ]. 15. Chappard D., Bas^ M.F., Legrand E. et al. New laboratory tools in the assessment of bone quality. Osteoporos. Int. 2011; 22(8):2225-2240. 16. Chen H., Zhou X., Shoumura S. et al. Age- and gender-dependent changes in three-dimensional microstructure of cortical and trabecular bone at the human femoral neck. Osteoporos. Int. 2010;21(4):627-636. 17. Burr D.B. Bone quality: understanding what matters. J. Musculoskel. Neuronal Interact. 2004;4(2):184- 186. 18. Hernandez C.J., Keaveny T.M. A biomechanical perspective on bone quality. Bone. 2006; 39(6): 11731181. 19. Misch C.E. Bone density: A key determinant for clinical success. In: Contemporary Implant Dentistry. 2nd ed. (Ed. by C.E. Misch). St Louis: Mosby. 1999;109-118. 20. Rebaudi A., Trisi P., Cella R., Cecchini G. Preoperative evaluation of bone quality and bone density using a novel CT/microCT-based hard-normal-soft classification system. Int. J. Oral Maxillofac. Implants. 2010;25(1):75- 85. 21. D'yachkov K.A., D'yachkova G.V., Aranovich A.M. et al. Dinamika remodelirovaniya kosti u bol'nykh akhondroplaziey posle udlineniya nizhnikh konechnostey po dannym MSKT [Dynamics of bone remodeling in patients with achondroplasia after lower limb lengthening according to MSCT data]. Geniy ortopedii. 2014;4:67-71 [In Russ]. 22. Ogarev E.V., Morozov A.K. Diagnosticheskie vozmozhnosti mul'tispiral'noy komp'yuternoy tomografii v otsenke sostoyaniya tazobedrennogo sustava u detey i podrostkov [Diagnostic potentials of multispiral computed tomography in the evaluation of the hip condition in children and adolescents]. Vestnik travmatologii i ortopedii im. N.N. Priorova. 2013; 4: 68-75 [In Russ]. 23. Chang G., Honig S., Liu Y et al. 7 Tesla MRI of bone microarchitecture discriminates between women without and with fragility fractures who do not differ by bone mineral density. J. Bone Miner. Metab. 2015; 33(3): 285-293. 24. Tjong W., Nirody J., Burghardt A.J. et al. Structural analysis of cortical porosity applied to HR-pQCT data. Med. Phys. 2014;41(1):013701. 25. Wichmann J.L., Booz C., Wesarg S. et al. Quantitative dual-energy CT for phantomless evaluation of cancellous bone mineral density of the vertebral pedicle: correlation with pedicle screw pull-out strength. Eur. Radiol. 2015; 25(6): 1714-1720. 26. Griffith J.F., Genant H.K. New imaging modalities in bone. Curr. Rheumatol. Rep. 2011;13(3):241-250. 27. Gee C.S., Nguyen J.T., Marquez C.J. et al. Validation of bone marrow fat quantification in the presence of trabecular bone using MRI. J. Magn. Reson. Imaging. 2015; 42(2): 539-544. 28. Rubin G.D. Computed tomography: revolutionizing the practice of medicine for 40 years. Radiology. 2014; 273, 2 Suppl.: S45-S74. 29. D'yachkov K.A., D'yachkova G.V., Kutikov S.A. Sposob opredeleniya lokal'noy plotnosti korkovoy plastinki dlinnykh kostey [A technique for determination of the local density of long bone cortical plate]. Patent RF, No 2539424, 2015 [In Russ]. 30. D'yachkov K.A., D'yachkova G.V., Aleksandrov Yu.M. Sposob opredeleniya stepeni rezorbtsii kortikal'noy plastinki kosti posle distraktsionnogo udlineniya konechnosti [A technique for determination of the degree of bone cortical plate resorption after limb distraction lengthening]. Patent RF, No 2484772, 2013 [In Russ].