Using distraction forces to drive an autodistractor during limb lengthening
ABSTRACT Distraction osteogenesis can result in high forces developing in the limb. To determine and control the distraction forces (DF), a motorized distractor driven by feedback from DF was developed and used to lengthen the tibiae of 6 sheep undergoing distraction osteogenesis. The forces were measured continually, and, in 4 of the sheep, a force threshold was set, above which an increase in rate was initiated. The rate kept increasing to a set limit if forces remained above the threshold; otherwise, the rate was decreased. Radiographs were acquired biweekly, and muscle samples were analyzed from both the operated and contralateral limbs upon termination of the experiment. Results demonstrated a drop in DF associated with increased lengthening rate, attributed to separation of the callus as indicated by radiography. Histological evidence of muscle damage generally correlated with higher DF levels. There was a significant decrease in muscle fiber diameter in lengthened relative to contralateral limbs. Collectively, the results demonstrated the use of a force-driven distraction system and support the need for considering force data in regulating distraction rates to achieve optimal clinical outcomes.
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ABSTRACT: We reviewed our first 53 lengthenings performed in 45 patients with an average age of 19 years at the time of lengthening. The shortening was congenital in 16 patients, post-traumatic in 15 and had various causes in the 14 remaining. 31 femurs and 22 tibias with an average shortening of 6 and 5 cm, respectively, were lengthened 6 (2-14) cm. The aim was achieved in all but 4 patients, where lengthening had to be discontinued due to complications. Potential complications of lengthening can be numerous but, if recognized, can in most cases be dealt with during the extended lengthening procedure. 38 cases of pin-tract infections healed with antibiotics. Restricted motion in one or more joints was registered in 49 cases during lengthening; minor restriction of joint motion persisted in 14 patients. 28 cases had angular deviations during lengthening. After additional surgery all but 10 could be corrected. 4 fractures occurred after removal of the external fixator. The total number of complications was 146, and of these 76 were minor, 42 moderate and 28 severe. 36 of the 42 patients available to follow-up were satisfied with the results of the lengthening procedure.Acta Orthopaedica Scandinavica 09/1994; 65(4):447-55. DOI:10.3109/17453679408995491
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ABSTRACT: Difficulties that occur during limb lengthening were subclassified into problems, obstacles, and complications. Problems represented difficulties that required no operative intervention to resolve, while obstacles represented difficulties that required an operative intervention. All intraoperative injuries were considered true complications, and all problems during limb lengthening that were not resolved before the end of treatment were considered true complications. The difficulties that occurred during limb lengthening include muscle contractures, joint luxation, axial deviation, neurologic injury, vascular injury, premature consolidation, delayed consolidation, nonunion, pin site problems, and hardware failure. Late complications are those of loss of length, late bowing, and refracture. Joint stiffness may also be a permanent residual complication. Pain and difficulty sleeping are other problems that arise during limb lengthening, especially in the more extensive cases. Forty-six patients had 60 limb segments lengthened between 1.0 and 16.0 cm, with a mean of 5.6 cm. The average treatment time was approximately one month per centimeter for single-level lengthenings with no deformity and 1.2 months per centimeter with deformity correction. The lengthening index for double-level lengthening was 0.57 month per centimeter with no deformity and 0.90 month per centimeter with correction of deformity. In adults, the lengthening index was 1.7 months per centimeter for single-level and 1.1 months per centimeter for double-level lengthening. There were 35 problems that had to be resolved in the outpatient clinic. There were 11 obstacles that required additional operative intervention to resolve. There were 27 true complications, of which 17 were considered minor and ten were considered major complications. Of the major complications, three interfered with achieving the original goals of treatment. All three required further operative intervention to achieve the original goal. These were nonunion in one and late bowing in two. Despite these problems, obstacles, and complications, the original goals of surgery were achieved in 57 of the 60 limb segments treated. Patient satisfaction was achieved in 94% of 46 cases.Clinical Orthopaedics and Related Research 02/1990; DOI:10.1097/00003086-199001000-00011 · 2.88 Impact Factor
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ABSTRACT: Complications arising from limb-lengthening procedures such as muscle contracture, axial malalignment of the bone and traction injuries to the nerves and vessels, are often severe. Often complications arise from the build-up of forces in the biological tissues which are resisting lengthening. Little is known about the origin and magnitude of these forces, although three studies have identified the regenerate (new bone tissue) as the dominant resisting tissue. This study describes the development of a method to examine these forces. It employs load measurement devices in the structural columns of Ilizarov fixators which measure the compressive load on the frame exerted by the biological tissues. The distribution of this load between the columns of the frame, in conjunction with a transverse radiograph of the limb at the regenerate site, is used to examine the origin of the resisting force. Accuracy was determined by a laboratory simulation which found the predicted position of the force to be within 5 mm of the actual position in all four cases tested. Mean error in the total measured force was 2 N (SD, 1 N). A pilot study on a patient undergoing a 60 mm femoral lengthening revealed a peak force of 717 N originating in the Vastus Lateralis or the illiotibial tract. Negligible contribution to resistance was provided by the regenerate, contrary to that found with other studies.Medical Engineering & Physics 08/1997; 19(5):405-11. DOI:10.1016/S1350-4533(97)00010-6 · 1.84 Impact Factor