ISSN:2155-9538 JBBS, an open access journal Emerging Technology for Use in Rehabilitation J Bioengineer & Biomedical Sci Research Article Open Access Chehade et al. J Bioengineer & Biomedical Sci 2011, S1 DOI: 10.4172/2155-9538.S1-004 Keywords: Tibial Osteotomy; Radiostereometric Analysis; RSA; Diferentially Loaded Radiostereometric Analysis; DLRSA; Torsion; Axial compressive load; Bone healing Introduction Traditionally, clinical assessment and conventional radiographs have been used to monitor fracture healing. Clinical assessment relies on the reported presence and level of pain during weightbearing and the manual assessment of movement at the fracture site. Conventional radiographs identify the presence of mineralized callus tissue bridging the fracture site [1] and radiological union is usually deined as the presence of three bridging cortices [2]. Although conventional radiographs give an indication of progress toward union, they provide no information about the quality of the healing bone or the mechanical properties of the construct [3-7]. Conventional radiographs are not suiciently accurate to deine an end point to healing of internally ixed fractures and fail to allow early detection of delays or failures of union [6,8-10]. Hence, their utility in supporting important clinical decisions such as optimal and safe loading during rehabilitation, or the timing of ixation removal, is severely limited [11].  Modern computed tomography (CT) has greatly improved our ability to visualize the presence or absence of bridging callus in three dimensions but still does not allow an objective quantitative assessment of mechanical properties of a healing fracture. CT is also associated with signiicant radiation exposure, limiting its use for serial assessments. he increasing use of ixation devices in modern practice to provide immediate stability to fractures further masks the clinical state of healing at the fracture site. here may be little initial pain or movement detected owing to the stability provided by the ixation even though the fracture may remain unhealed. Ultimately, however, the ixation may fail due to metal fatigue if there is insuicient load sharing between the bone and the ixation. his progression from a “load bearing” to a “load sharing” environment occurs as fracture healing progresses and there is increased bridging with new bone across the fracture ends thus reducing the potential for ixation failure. Fracture stifness relates to the interfragmentary displacement in response to a given load. Numerous studies have concluded that monitoring stifness is valuable for assessing fracture healing [11- 13]. Some studies report the use of strain gauges on plates and nails to indirectly assess healing from the reduction in load through the *Corresponding author: Mellick Chehade, Associate Professor, Level 4 Bice Building, Department of Orthopaedics and Trauma, Royal Adelaide Hospital, North Terrace, Adelaide, Australia 5000, Tel: 61 8 82225661; Fax: 61 8 8232 3065; E-mail: mellick.chehade@adelaide.edu.au Received November 03, 2011; Accepted November 21, 2011; Published November 22, 2011 Citation: Chehade MJ, Vakaci IA, Callary SA, Findlay DM, Solomon LB (2011) Differentially loaded Radiostereometric Analysis (DLRSA) in Torsion Adds Essential Information in Diaphyseal Bone Healing: the Example of a Tibial Osteotomy. J Bioengineer & Biomedical Sci S1:004. doi:10.4172/2155-9538.S1-004 Copyright: © 2011 Chehade MJ, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Abstract Background Clinical assessment and conventional imaging, which are currently used to monitor fracture healing, do not provide information on the mechanical properties of the healing construct. This limits their use in patient management decisions. Differentially loaded radiostereometric analysis (DLRSA) is a technique developed to assess the mechanical properties of healing fractures in vivo. DLRSA measures the relative micromotion of tantalum beads inserted into bone fracture fragments in response to load across the fracture site. To date, these loads have been applied axially, although in fractures ixed with devices which are highly resistant to axial loads, such as locked intramedullary nails, torsional testing may be more sensitive to healing. The aim of this study was to establish a method to investigate DLRSA using torsional loading for clinical application. Methods A device was designed and built to apply torsional loads to the tibia. The test case was an oblique plain corrective osteotomy of a tibial diaphysis stabilized with an intramedullary nail and with tantalum beads inserted into the two adjacent bone segments. Post surgical examinations were made at 2 weeks, 2, 4, and 6 months as well as 1 and 2 years. Healing was monitored with the use of plain ilm radiographs, computed tomography (CT) and DLRSA. Axial loads of 30kg and an external torsion of 5Nm were applied during DLRSA examinations and the resultant displacement and stiffness were calculated. Results Torsional DLRSA demonstrated progressive changes in angular displacements and torsional stiffness consistent with the fracture healing observed by CT. By contrast, axial DLRSA was not informative and was more relective of the stability of the ixation than healing bone. Conclusion The addition of torsional assessments to DLRSA provides an important investigative option in assessing the biomechanical properties of bone healing in vivo. Differentially loaded Radiostereometric Analysis (DLRSA) in Torsion Adds Essential Information in Diaphyseal Bone Healing: the Example of a Tibial Osteotomy M.J. Chehade 1,2 , I.A. Vakaci 2 , S.A. Callary 1,2 , D.M. Findlay 2 and L.B. Solomon 1,2 1 Department of Orthopaedics and Trauma, Royal Adelaide Hospital 2 Discipline of Orthopaedics and Trauma, University of Adelaide, Adelaide, Australia Journal of Bioengineering & Biomedical Science J o u r n a l o f B i o e n g i n e e r g i n & B i o m e d i c a l S c i e n c e ISSN: 2155-9538