System for Limb Lengthening
The Development and Clinical Trials of the Computer-Aided System for Limb Lengthening
Tech Area / Field
- MED-DID/Diagnostics & Devices/Medicine
3 Approved without Funding
VNIIEF, Russia, N. Novgorod reg., Sarov
- Scientific and Research Institute of Traumatology and Orthopedics, Russia, N. Novgorod reg., Sarov
- Michigan State University / Department of Pediatric and Human Development, USA, MI, East Lansing\nTexas Scottish Rite Hospital for Children, USA, TX, Dallas\nUniversity of Michigan / Orthopaedic Research Laboratories, USA, MI, Ann Arbor
Project summaryThe compression-distraction osteosynthesis is one of the basic methods used in traumatology and orthopaedics. The development of the method is closely connected to the invention of a ring frame fixator by G.A. Ilizarov and discovery of the stimulating influence of a dosed distraction of tissues on bone formation, which is called distraction osteogenesis [1,2,3,4]. The distraction osteogenesis technique has gained recognition all over the world. Most intensive investigations in the field of distraction osteogenesis are currently being carried out. New modes of lengthening and more advanced external fixation devices are being developed. The necessity to develop a up-to-date measuring equipment to control tension in the biomechanical “device-patient” system, new automatic distraction devices and to fit them with a biological feedback system has always been emphasized by leading experts in the field [5,6].
The goal of this project is to optimize a “surgeon-device-patient-device-surgeon” system based on the instant objective and reliable assessment of biomechanical parameters of the system tension. The resulting computer-aided system will perform compression/distraction osteosynthesis in the limb lengthening, deformity correction, bone replacement in cases of extensive bone defects. A unique feature of the proposed system is the ability to quantitatively study the tension dynamics of the “device-patient” biomechanical system in the process of distraction osteogenesis and optimisation of biomechanical modes in the limb lengthening on the basis of the obtained findings. Correlation between biomechanical, clinical and optical densitometry findings will allow researchers to come closer to the creation of a biological “device-patient-device” feedback system making possible the use of automatic distractors as executive elements. The above complex may be used in two ways:
a.limb lengthening with discrete manual distraction at the distraction rate of 1 mm in 4 increments.
b.limb lengthening in the automatic mode with high fractional microdistraction using automatic distractors.
The development of a computer-aided system would require:
- Special wire clamps, fitted with tension transducers. They will measure the tension of wires transosseously inserted and fixed in ring frames of external fixation device.
- Distraction/compression transducers to measure forces developing in the distraction rods of the external fixation device.
- Strain transducers of Schanz screws, inserted into bone and fixed in the ring frames.
- Automatic distractors of various sizes and force performances with improved weight-dimension parameters (for tibia, femur, humerus, forearm in patients of various ages) intended for high fractional microdistraction under the assigned program. Automatic distractors will be fitted with distraction/compression transducers. A microprocessor will be able to adjust the distraction rhythm, depending on linear increments in length and dynamics of distraction forces along the three distractional rods in the feedback mode.
- A system of quoting and wireless transmission of outputs from transducers, measuring wire tension, distraction/compression force and Schanz half-pins strain.
- A system of data reception and processing in real time mode.
The system will be bench-tested. It will include calibration of transducers, adjustment of software and experimental evaluation of external fixator stiffness and error analysis.The complex will allow to determine the fixation stiffness of bone fragments and their micromobility in various phases of patient activity (supine, upright postures with limb motion in walking with crutches without load or weight bearing). Weight bearing trials will be conducted, where changes in the distraction forces, wire tension forces in dependence of weight bearing loads will be investigated. Based on the data received, calculations will be made considering formation of regenerate, its deformity and consequently, the stiffness. These studies will allow to define and sustain the degree of a necessary and sufficient stiffness of fixation (degree of micromobility between bone fragments). They will also allow to determine the stiffness of the regenerate, to select the required training condition load, and the time for appropriate removal of the device. The data on the fixation stiffness, rate and rhythm of distraction, rigidity of the regenerate will be obtained. It will be correlated with optical densitometry data reflecting qualitative and quantitative characteristics of the regenerate being formed in the course of time. The study of biomechanical data will allow to approach the possibility of applying the biofeedback in limb lengthening using automatic microdistraction. It might be based on a certain correlation between linear increment and the applied dynamics of distractional load. Clinical tests will include femur and tibia lengthening in 5 patients using manual distraction mode and 5 using automatic microdistraction mode. Results will be compared with data from contril group. Control group will consist of patients with femur and tibia lengthening made in the absence of monitoring over biomechanical parameters of the “device-patient” system, using case histories data.
The computer-aided system will bring more precision to the limb lengthening process, thus making a technological breakthrough. New information will help optimize and monitor the biomechanical process of the limb lengthening more effectively. The use of the computer-aided system will allow to standardize the protocols at various stages of treatment from surgery to frame removal. It will help to minimize possible tactical or technical errors. Thus, the number of complications will be considerably reduced (slow or premature consolidation, occurrence of traction pareses of the nerve trunks, development of contractures in the adjacent joints, infection of soft tissues). The fixation stiffness control system and automatic high fraction distraction will radically shorten the period of inpatient stay with overall treatment period cut by approximately 30%. Besides, the elaborated computer-aided system may be used as an appropriate tool in further investigations in the field of distraction osteogenesis.Previous work.The authors of the project is an experienced team of surgeons and engineers that has been most active in the field of designing and clinical use of external fixation apparatuses. The first-ever automatic device for the limb lengthening was designed and manufactured in The Russian Federal Nuclear Centre – All-Russian Scientific and Research Institute of Experimental Physics and clinically tested in The Nizhny Novgorod Scientific and Research Institute of Traumatology and Orthopaedics in 1979 (SU Pat. #848011). Extensive research both in the design and clinical trials of the new instruments have been undertaken by the authors within the framework of ISTC project #1711. The new apparatus differs from the existing prototypes by lighter weight and better force parameters. The apparatus displays much greater discreteness in the lengthening process (1 mm in 300 pulses), displays greater reliability and stability to tangential loads. The apparatus is fitted with transducers enabling it to control the distraction forces. Experience from these trials will lead to potential upgrade and creation of more sophisticated models for various patient-populations, ages and applications (e.g. lengthening of tibia, femur, humerus, forearm with simultaneous deformity correction). The critically expected goal of the project is a development of computerized external fixation device able to discover the biomechanical environment of the distraction osteogenesis in limb lengthening. The proposed full-scale project for the development of a computer – aided system for the distraction osteogenesis is a logical extension of the joint research effort of The Russian Federal Nuclear Center - All-Russian Scientific and Research Institute of Experimental Physics and The Nizhny Novgorod Scientific and Research Institute of Traumatology and Orthopaedics.
- Ilizarov, G. A.: Basic principles of transosseous compression and distraction osteosynthesis. Orthop. Travmatol. Protez. 32:7. 1971.
- Ilizarov, G. A.: Clinical application of the tension-stress effect for limb lengthening. Clin. Orthop. 250:27, 1990.
- Ilizarov, G. A.: The tension-stress effect on the genesis and growth of tissues: The influence of stability of fixation and soft tissue preservation. Clin. Orthop. 238:249-281, 1989.
- Ilizarov, G. A.: The tension-stress effect on the genesis and growth of tissues: The influence of the rate and frequency of distraction. Clin. Orthop. 239:263, 1989.
- Paley D. Correction of limb deformities in the 21st century. J Pediatr Orthop. 2000 May-Jun; 20(3):279-81.
- Shevtsov V.I., Popova L.А. The main perspective directions in the development and perfecting of a Ilizarov method in clinical practice //Traumatology and Orthopedics of Russia. - 1994. - N 2. - P. 18-21.