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The influence of gap size on the development of fracture union with a micro external fixator.

ABSTRACT: Increasingly, the rat femoral fracture model is being used for preclinical investigations of fracture healing, however, the effect of gap size and its influence on mechanobiology is not well understood. We aimed to evaluate the influence of osteotomy gap on osteotomy healing between the previously published extremes of guaranteed union (0.5?mm) and non-union (3?mm) using this model. A femoral osteotomy in 12-14 week old female Wistar rats was stabilised with a micro fixator (titanium blocks, carbon fiber bars) with an osteotomy gap of 1.0?mm (n?=?5), 1.5?mm (n?=?7), 2.0?mm (n?=?6). After five weeks, the left femur was retrieved. The osteotomy gap was scanned using X-ray microtomography and then histologically evaluated. The radiographic union rate (complete mineralised bone bridging across the osteotomy) was three times higher for the 1.0?mm than the 2.0?mm gap. The 1.0?mm gap had the largest callus (0.069?m³) and bone volume (0.035?m³). Callus and bone volume were approximately 50% smaller within the 2.0?mm gap. Using cadaveric rat femurs stabilised with the external fixator, day 0 mechanical assessment of construct stiffness was calculated on materials testing machine displacement vs load output. The construct stiffness for the 1.0, 1.5 and 2.0?mm gaps was 32.6?±?5.4, 32.5?±?2.4, and 32.4?±?8.3?N/mm (p?=?0.779). Interfragmentary strain (IFS) was calculated using the change in osteotomy gap displacement as measured using microstrain miniature differential reluctance transducer spanning the osteotomy gap. Increasing the gap size significantly reduced the IFS (p?=?0.013). The mean 'day 0' IFS for the 1.0, 1.5 and 2.0?mm gaps were 11.2?±?1.3, 8.4?±?1.5 and 6.1?±?1.2% respectively. A 1.5?mm gap resulted in a delayed fracture healing by 5 weeks and may represent a useful test environment for fracture healing therapy. Increasing gap size did not affect construct stiffness, but did reduce the 'day 0' IFS, with a doubling of non-union and halving of bone volume measured between 1.0 and 2.0?mm gaps.

SUBMITTER: Meeson R

PROVIDER: S-EPMC6715773 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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The influence of gap size on the development of fracture union with a micro external fixator.

Meeson Richard R Moazen Mehran M Sanghani-Kerai Anita A Osagie-Clouard Liza L Coathup Melanie M Blunn Gordon G

Journal of the mechanical behavior of biomedical materials 20190719

Increasingly, the rat femoral fracture model is being used for preclinical investigations of fracture healing, however, the effect of gap size and its influence on mechanobiology is not well understood. We aimed to evaluate the influence of osteotomy gap on osteotomy healing between the previously published extremes of guaranteed union (0.5 mm) and non-union (3 mm) using this model. A femoral osteotomy in 12-14 week old female Wistar rats was stabilised with a micro fixator (titanium blocks, car ...[more]

PMID: 31357063

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Project description:BackgroundHyperbaric oxygen therapy (HBOT) consists of intermittently administering 100% oxygen at pressures greater than one atmosphere absolute (ATA) in a pressure vessel. This technology has been used to treat a variety of diseases and has been described as helping patients who have delayed healing or established non-union of bony fractures. This is an update of a Cochrane Review first published in 2005, and previously updated in 2008.ObjectivesThe aim of this review is to assess the evidence for the benefit of hyperbaric oxygen treatment (HBOT) for the treatment of delayed bony healing and established non-union of bony fractures.Search methodsWe searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (July 2012), the Cochrane Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 7), MEDLINE (1946 to July Week 1 2012), EMBASE (1974 to 2012 July 16), CINAHL (1937 to 17 July 2012), the Database of Randomised Controlled Trials in Hyperbaric Medicine (accessed July 2012), the WHO International Clinical Trials Registry Platform (17 July 2012) and reference lists of articles.Selection criteriaWe aimed to include all randomised controlled trials comparing the clinical effects of HBOT with no HBOT (no treatment or sham) for healing of bony fractures and fracture non-unions.Data collection and analysisTwo review authors independently screened electronic search results, and all three authors independently performed study selection. We planned independent data collection and risk of bias assessment by two authors using standardised forms.Main resultsNo trials met the inclusion criteria. In this update, we identified three ongoing randomised controlled trials. Among the eight excluded studies were three randomised trials comparing HBOT with no treatment that included patients with fractures. One of these trials had been abandoned and the other two did not report on fracture healing outcomes.Authors' conclusionsThis systematic review failed to locate any relevant clinical evidence to support or refute the effectiveness of HBOT for the management of delayed union or established non-union of bony fractures. Good quality clinical trials are needed to define the role, if any, of HBOT in the treatment of these injuries. There are three randomised controlled trials underway and we anticipate these will help provide some relevant clinical evidence to address this issue in the future.

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The influence of gap size on the development of fracture union with a micro external fixator.

Publications

The influence of gap size on the development of fracture union with a micro external fixator.

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