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Results and biomechanical consideration of treatment of congenital lower limb shortening and deformity using the Ilizarov method

Morasiewicz P., Morasiewicz L., Stępniewski M., Orzechowski W., Morasiewicz M., Pawik Ł., Wrzosek Z., Dragan S.

Acta of Bioengineering and Biomechanics

2014

Vol. 16, no. 1

133--140

One of the applications of the Ilizarov apparatus is the correction of congenital shortening and deformities. Ilizarov external fixator produces biomechanical structure with surrounding tissue, which is the reason why very important is correct stability of fixator. Large distraction in the case of high value of lengthening, and large deformity corection result in shear stresses that occur additionally in the regenerate, which can potentially lead to damage of the regenerating nutritive microcirculation of bone tissue and bone fragment displacements. Our objective was to assess the results of the Ilizarov method in the treatment of congenital shortening taking into account treatment strategy and the size of the axis of lengthening and correction. Our research problems include presenting the effects of biomechanics of musculoskeletal deformations on treatment results, presenting complications and their treatment. Between 1989 and 2009, 62 patients underwent surgery to correct congenital lower limb deficiencies at our Clinic; 33 patients were followed-up. In total, there were 70 surgeries (2.12/patient). Axial correction was performed in 26 patients (78.79%). Average age at the start of the treatment was 15.58 years. Mean follow-up was 8.58 years. Mean lengthening per surgery was 3.17 cm with the lengthening index of 50.7 day/cm. Results were very good for 23 patients, good for 7 patients, satisfactory for 3 patients. Complications appeared in 24 patients, problems occurred in 74.42% of the cases, obstacles in 4.65% of cases, and true complications in 20.93% of the cases. The best results were achieved in the treatment of patients with two-stage and two-segment lengthening with a total elongation of less than 7 cm, and without correction of the axis. Congenital shortening of the lower limb should be treated comprehensively because the shortening applies to all segments, and disturbs biomechanics of all lower limb. In the case of axial correction and large amount of elongation high soft tissue forces counteract the distraction forces. Hybrid construction may help to shorten treatment time, increase fixator stability and decrease rate of complications. We suggest use of hybrid Ilizarov fixator, especially when large elongation and axis corection are planned.

Distribution of radiological density in bone regenerate in relation to cyclic displacements of bone fragments

Filipiak J., Krawczyk A., Morasiewicz L.

Acta of Bioengineering and Biomechanics

2009

Vol. 11, nr 3

3-9

We asked how bone fragment displacement could influence the distribution of radiological density in bone regenerate formed during the process of bone lengthening. The metatarsi of 21 sheep were lengthened by 20 mm by the Ilizarov method. The bone fragments were externally fixed with a specially designed ring external fixator equipped with linear actuator driver system. The test sheep were divided into three experimental groups: the G1 and G2 groups (N = 8) and the GR group (N = 5) - the reference group. In the case of sheep from the G1 and G2 groups, the lengthening was supplemented with mechanical stimulation of the regenerate in the form of cyclic bone fragment displacements (CBFDs) with the amplitudes of 1 mm (G1) and 2 mm (G1). Mechanical stimulation was applied over 30 days for 1 h per day with a frequency of 1 Hz. Eight weeks after the procedure the sheep were sacrificed in accordance with the required procedures. The analysis of the degree of bone regenerate mineralization involved the studies based on the CT scanning. The analysis of the results obtained is based on the paramenter called the degree of regenerate mineralization (RMD). The analysis of radiological density was carried out in the selected measurement areas. Such an area was located in three horizontal zones, taking into account the regenerate height, i.e. in its middle part (half regenerate length); the top part, 2 mm from the edge of the proximal fragment; and the bottom part, 2 mm from the edge of the distal fragment. The value of the RMD parameter varies significantly, depending on the bone regenerate area. The results obtained show that the CBFD = 2 mm accelerates the rate of mineralization of an eight-week-old regenerate. In the case of CBFD = 1 mm, the mineralization rate is lower by more than a dozen per cent.