Tissue response during monofocal and bifocal leg lengthening in patients

Abstract

The purpose of this investigation was to compare the tissue response during mono-and bifocal limb lengthening. The study includes four patients undergoing leg lengthening. All patients started out bifocally with a total diurnal distraction of 1.75 mm, but proceeded monofocally with a rate of 1 mm a day when the distal distraction was terminated due to contractures or pain. The tissue response was monitored by registration of axial force in the distraction rods. The force increased linearly during bifocal lengthening, but culminated or decreased in the period of monofocal lengthening. Average tissue stiffness, defined as the immediate force increase due to each 0.25 mm distraction increment, was significantly higher in the bifocal lengthening phase. The force decay between each distraction was significantly lower during bifocal lengthening, thus indicating decreased tissue accommodation. Details in the force registrations indicated that the soft tissue, not the regenerate, was the main contributor to the tensile force. Conclusively, the tissues at the two osteotomy sites do not lengthen independently. Bifocal lengthening exposes the entire soft tissue to large loads, resulting in increased tissue stiffness and reduced ability to adapt to the increased length. Accordingly, bifocal leg lengthening requires special attention to soft tissue adaptation.

Zugkraftmessungen beim knöchernen Segmenttransport – in vivo Untersuchungen am Menschen / Tractive Force Measurement in Bone Transport – an in vivo Investigation in Humans

“…A A 16 m Tumor US re 220 normal B A 61 m Trauma US re 72 verzögert B A 24 m Trauma OS li 95 normal E M 12 m Tumor US re 115 kritisch F F 35 m Tumor US li 83 überbrückt 7 G S 20 w Trauma US li 51 normal 3 H M 15 m Trauma US li 93 kritisch 5 J T 32 m Trauma US li 110 überkritisch K R 33 m Trauma US li 62 [1]. Aus diesen Betrachtungen folgt, daß beide Komponenten gemeinsam eher einen konstanten als einen progressiven Einfluß auf die Gesamtkraft haben.…”

Assessment of Maxillary Distraction Forces in Cleft Lip and Palate Patients

“…Twelve hours later the distraction force had fallen substantially and reaches a value slightly greater than the final force on the previous days. As the soft tissue has substantial viscoelastic behavior, these are just a transient peak force, and after distraction the force decrease exponentially (Leong et al, 1979) with an average rate of 2.3 N/h the first 3-5 h (Aarnes et al, 2002). The main finding of this study was the differential pattern of forces between the lateral segments observed in unilateral cleft lip and palate subjects.…”

“…In the present study, assessment of distraction forces did not allow differentiation between contribution from the soft tissue envelope and the regenerate. Previous investigations have suggested the soft tissue (Aarnes et al, 2002;Gardner et al, 1997), the regenerate (Aronson and Harp, 1994) or both (Gardner et al, 1998) to be the source of the tensile force. The force in the rigid external distractor is a result of the resistance in the composite tissue system, and the interpretation of the results depends on which structure provides the major resistance.…”

“…They could be reduced to decrease pain in the patient and loads on the device by performing lengthening over a greater number of steps or using dynamic equipment able to absorb these forces (Wiltfang et al, 2001). Aarnes et al (2002) has shown that in the stepwise lengthening, a total lengthening of 1 mm cause less force accumulation than a 1.75 mm elongation. The present study indicates that this is valid for the maxillary distraction as well.…”

Growth mixture model of distraction osteogenesis: effect of pre-traction stresses

“…During the process of distraction osteogenesis stress accumulation is modulated by three effects: the mechanical elongation of the gap, the intrinsic viscoelastic nature of soft tissues in the interfragmentary gap (Leong et al 1979;Simpson et al 1996;Nakamura et al 1997;Matsushita et al 1999;Richards et al 1999;Aarnes et al 2002) and the tissue growth/differentiation inside the gap.…”