Wook-Cheol Kim

Effect of early axial dynamization on tibial bone healing: a study in dogs.

Early axial dynamization and its effect on experimental tibial bone healing was compared with healing under rigid fixation in a time-sequenced manner using dogs. An external fixator that could be rigidly locked or set to allow free axial movement while preventing bending and shear was used. Both tibias were osteotomized and externally fixed, leaving a gap between bone ends of 2 mm. At 1 week, one side was dynamized, whereas the other side was kept rigidly locked as a control. Dogs were euthanized at 1 day and 1, 3, 5, 8, and 11 weeks after dynamization. The outcome measures were static and dynamic load-bearing, periosteal callus development, new bone formation, callus tissue composition, and mechanical strength. Load bearing was higher on the dynamized limbs during standing for the first 5 weeks and during gait for the first 3 weeks after dynamization compared with the controls. Maximum periosteal callus size was reached faster and was distributed more symmetrically on the dynamized side. The periosteal callus area decreased at 12 weeks on the dynamized sides, but there was no significant change in the area on the control sides. Endosteal new bone formation and bone density decreased between 9 and 12 weeks only on the dynamized sides. The dynamized side showed a significantly higher torsional stiffness at 6 weeks than did the controls. There were no significant differences between dynamized and control tibias at other times. Maximum torque also tended to be higher on the dynamized sides at the same time. Early axial dynamization appeared to accelerate callus formation and remodeling and to provide higher mechanical stiffness during early stages of bone healing.

Biomechanical monitoring of healing bone based on acoustic emission technology.

Acoustic emission testing is a well-established method for assessment of the mechanical integrity of general construction projects. The purpose of the current study was to investigate the usefulness of acoustic emission technology in monitoring the yield strength of healing callus during external fixation. Thirty-five patients with 39 long bones treated with external fixation were evaluated for fracture healing by monitoring load for the initiation of acoustic emission signal (yield strength) under axial loading. The major criteria for functional bone union based on acoustic emission testing were (1) no acoustic emission signal on full weightbearing, and (2) a higher estimated strength than body weight. The yield strength monitored by acoustic emission testing increased with the time of healing. The external fixator could be removed safely and successfully in 97% of the patients. Thus, the acoustic emission method has good potential as a reliable method for monitoring the mechanical status of healing bone.

Effects of alternating current electrical stimulation on lengthening callus.

Limb lengthening by the callotasis method has been clinically applied to patients who suffered from limb length inequality, micromelia, angular deformation and partial bone defect on long bones. However, this technique was time consuming and led to various complications, such as infection at the pin insertion sites, limitation of the range of motion in adjacent joints, muscular weakness and peripheral neuroparalysis. This study was undertaken to investigate whether alternating current electric (AC) stimulation could shorten the maturation period during callotasis. The tibiae of 20 immature male Japanese white rabbits were osteotomized and fixed with external lengthener (Orthofix M100; Orthofix Srl, Bussolengo, Italy). The experimental schedule lasted 5 weeks consisting of 1 week for the latency period, 2 weeks for distraction and 2 weeks for maturation. Twenty rabbits were equally divided into two groups: the control group and the electrical stimulation (ES) group. The control group was not stimulated with an AC stimulator. The ES group was stimulated for 5 weeks just after osteotomy. The obtained results revealed radiologically, electrophysiologically and histologically that AC stimulation accelerated the maturation of lengthened callus and that it could shorten the time course of callus lengthening.

Assessment of distraction callus in rabbits by monitoring of the electrical impedance of bone

Background and purpose Evaluation of distraction callus is important for determination of the optimal time for removal of external fixation. We attempted to determine whether there might be a relationship between the electrical impedance of bone and callus maturation, with a view to using impedance as a way of knowing when to remove a fixator. Methods We applied an external lengthener to the right tibia of 24 rabbits and performed distraction at 1 mm/day for 10 days. Radiographs were taken and measurement of overall impedance between fixation pins was performed weekly after distraction. At weeks 2, 4, 6, and 8 after distraction (n = 6 each), resistivity of the bone to electrical conductivity was measured before killing. Cross-sectional area of the conduction pathway in callus and maximum bending stress were measured after excision of the tibia. Results The overall impedance increased statistically significantly from 1 to 6 weeks after completion of distraction. The resistivity of bone decreased over 4 weeks and the cross-sectional area of callus decreased significantly over 6 weeks, while the maximum bending stress increased significantly over the same time. We observed a negative correlation between the cross-sectional area of callus and maximum bending stress. Interpretation The impedance values, which are related to changes in electrical conductivity and the conduction pathway, increased due to the changes in the cross-sectional area of callus, despite the reduction in bone resistivity. Since the cross-sectional area of callus was correlated with maximum bending stress and the impedance values increased with the callus-remodeling process, we suggest that temporal increases in overall impedance reflect callus maturation.

Evaluating Bone Union of Distal Radius Fractures by Measuring Impedance Values

The measurement of impedance is a noninvasive and simple quantitative technique for evaluation of fracture healing. Fractures of the distal radius are the most common long bone fractures, accounting for approximately 20% to 25% of all acute fractures. External fixators have been applied clinically to treat unstable distal radius fractures. The evaluation of radiological findings and clinical signs are current standard methods and are effective in assessing fracture union of the distal radius, but these methods are dependent on subjective elements. For the objective methods, previous studies have shown that measurement of bone mineral density, ultrasound, quantitative computed tomography, and acoustic emission are useful in evaluating bone union. However, due to the complexity and high radiation dose associated with these methods, are seldom used clinically. This study was undertaken to examine the correlation between bone union and impedance at the site of digital radius fractures treated with an external fixator, using an alternating current electrical stimulator and a digital oscilloscope.

Experience of bone bridge resection and bone wax packing for partial growth arrest of distal tibia.

Two patients with a partial growth arrest of the distal tibia were treated by bone bridge resection and bone wax packing technique. Their average age at the time of surgery was 7 years, both had been injured in an accident, and each had been treated with percutaneous pinning and a plaster cast. Unfortunately, partial growth arrest of the distal tibia occurred, and the ankle varus deformity gradually progressed. About 1 year after initial treatment, bone bridge resection and bone wax packing were performed. The average follow-up period was 80 months. There was no reformation of the bone bridge or recurrence of deformity, and gradual improvements in clinical and radiographic findings were observed. Although fat is typically used as an interpositional material after bone bridge resection, there are problems with its use, including a lack of hemostasis and the absence of intrinsic stability. Bone wax is readily available and commonly used in medical applications to control bleeding. It is considered a useful plug, it is inexpensive, and it is not associated with complications.

Usefulness of epiphyseal quotient measurement on magnetic resonance images for outcome prediction in patients with early-stage Legg-Calve-Perthes disease.

To investigate the usefulness of epiphyseal quotient (EQ) measurement for outcome prediction in patients with Legg–Calvé–Perthes disease (LCPD), magnetic resonance (MR) imaging was performed in 26 patients with unilateral LCPD within 6 months of the disease onset and subsequently once every 3 months. All the patients were treated conservatively in our institute between 1990 and 1999. The mean follow-up period was 80 months. Clinical outcome was evaluated based on the plain radiograms of the femoral head at the final examination according to Stulbergs classification: the patients whose outcome was class I were regarded as ‘excellent’ (excellent group), class II as ‘good’ (good group), and classes III, IV and V as ‘poor’ (poor group). The excellent group consisted of 10 patients, the good group of 12, and the poor group of four. The EQ measured on MR images (MR-EQ) decreased remarkably in the poor group chronologically, whereas there was no decrease in the excellent group and a slow decrease in the good group. The mean MR-EQ at or before the sixth month (range, 2–6 months; mean, 4.9 months) was 86.2 (range, 76.8–94.8) in the excellent group, 78.3 (57.0–93.4) in the good group, and 67.4 (57.8–74.5) in the poor group (P<0.05 among the three groups). According to our results, because all patients having an MR-EQ at or before the sixth month of 75 or higher were classified in the excellent or good groups, it is thought that the ongoing method of treatment can be continued. On the other hand, since half of the patients having an MR-EQ at or before the sixth month of lower than 75 were classified in the poor group and had a high potential for a poor outcome, it is thought that these patients require strict containment therapy, and altering the surgical procedure could be considered depending on the particular patient. It was thought that the MR-EQ is a useful predictive factor of LCPD prognosis.

Bilateral transient radial nerve palsies in an infant after cardiac surgery

Purpose: To describe the case of an infant who suffered bilateral transient radial nerve palsies after cardiac surgery.Clinical features: A one-month-old baby was found to have bilateral wrist and finger drop after the removal of splints that has been applied to the right hand for 14 days and to the right hand for six days during perioperative management of Blalock-Taussig shunt surgery. The hand splints had been applied to the forearms with adhesive silky tape to keep peripheral vascular lines in place. The patient also suffered from several episodes of cardiogenic shock, hypoxemia and generalized edema relating to cardiac dysfunction during this fine period. Given the findings of no impairment of median or ulnar nerves and brachioradial muscle, it was suspected that bandaging with adhesive tapes caused peripheral radial nerve damage at the level of posterior interosseus nerve on forearm. Diminished oxygen delivery and edema may additionally have contributed to peripheral nerve ischemia. The aforementioned neurologic symptoms resolved spontaneously after several days.Conclusion: Prolonged compression by bandaging of splints on forearm may have resulted in ischemic damage to the posterior interosseus nerve branch combined with extensor carpi radialis longus nerve branch of the radial nerve. We should attempt to reduce the frequency and duration of splinting of the extremities, especially in sedated, paralyzed babies, given the potential risk of compression neuropathy.RésuméObjectif: Décrire le cas d’un enfant qui a souffert d’une paralysie bilatérale transitoire du nerf radial à la suite d’une intervention cardiaque.Éléments cliniques: Un bébé d’un mois avait les mains et les doigts tombants après le retrait d’une attelle appliquée à la main droite pour 14 jours et à la main gauche pour six jours pendant le traitement périopératoire d’une anastomose de Blalock-Taussig. Les attelles de la main ont été appliquées avec un ruban de soie adhésif afin de maintenir en place les cathéters vasculaires périphériques. Le patient a aussi souffert de quelques épisodes de choc cardiogénique, d’hypoxémie et d’oedème généralisé relié au dysfonctionnement cardiaque pendant cette période. Comme aucune atteinte des nerfs médian ou cubital ni du muscle long supinateur n’a été décelée, on a pensé que le bandage avec le ruban adhésif avait causé une lésion périphérique du nerf radial au niveau du nerf interosseux postérieur de l’avant-bras. L’apport réduit d’oxygène et la présence d’oedème ont pu aussi contribuer à l’ischémie du nerf périphérique. Les symptômes neurologiques susmentionnés ont disparus spontanément après quelques jours.Conclusion: La compression prolongée provoquée par le bandage d’attelles à l’avant-bras a pu causer une lésion ischémique dans le territoire du nerf interosseux postérieur, et dans la zone du muscle premier radial innervé par un rameau du nerf radial. Il faut, autant que possible, réduire la fréquence et la durée du bandage des extrémités, surtout chez des bébés sous sédation et paralysés, étant donné le risque potentiel de neuropathie par compression.

Use of a Rugby Helmet Brace for Postoperative Treatment of Muscular Torticollis

Prior to 1992, our postoperative management for congenital muscular torticollis consisted of either plaster cast immobilization or no immobilization, depending on the patients age and the degree of contracture. However, some patients required further surgery and developed complications. In 1992, we produced rugby helmet braces for postoperative management. The purpose of this study was to compare the clinical results of the previous postoperative management with the results achieved using rugby helmet braces. Twenty-five children aged younger than 6 years underwent caudal partial resection of the sternocleidomastoid muscle. Twelve children aged 6 years and older underwent cranial tenotomy. These 37 patients were divided into 2 groups: no immobilization or plaster immobilization (group A; n=19) and rugby helmet braces (group B; n=18). Canales method was used for evaluation of clinical results. In group A, the results were good in 12 patients, fair in 4, and poor in 3, whereas all 18 patients in group B had good results. Two patients in group A required further surgery, and complications were observed in 5 patients. In group B, alopecia areata was observed in 1 patient.The rugby helmet brace is easy to put on and remove, providing good retention and allowing for physiotherapy. It provides a useful method of postoperative management for congenital muscular torticollis.

Dynamic Viscoelastic Properties of Cortical Bone and Callus

The dynamic viscoelastic properties of rabbit tibial cortical bone and callus were investigated. The dynamic storage modulus (G′), dynamic loss modulus (G″), and dynamic loss tangent (tan δ) were measured under tensile and compressive strain at frequencies ranging from 0.1 to 70 Hz at body temperature. The initial strain was a 2000 microstrain, and the dynamic strain was set up at a 500 microstrain in all specimens. In wet cortical bone, G′, G″, and tan δ were dependent on frequency. There were clear differences between the immature cortical bone and the mature cortical bone in the shapes of the G″-frequency curves. However, these differences of frequency dispersion were eliminated by decalcification of specimens. The frequency dispersion also changed in dry cortical bone and in thin cortical bone in which the osteon structure was destroyed. Callus specimens were excised at 2, 4, 6, 9, and 12 weeks after making cortical defects in rabbit tibiae. G’ increased as the frequency increased in all specimens. In the case of G″, the shapes of the curves after 6 weeks differed significantly from those before 4 weeks. Tan 5 of the 2-week specimens had a clear peak at 7–10 Hz, and the shape of the curve differed significantly from those of the other periods. The changes of frequency dispersion and the changes of the histological structure or the changes of ash content over the period of time coincided. However, other factors, such as changes of water content, collagen content, binding conditions between collagen and hydroxy apatite, and so on, should not be neglected.