Solution blow spinning of PLLA/hydroxyapatite composite scaffolds for bone tissue engineering

Composite poly-L-lactide acid-based scaffolds with hydroxyapatite (HAp) content up to 75 wt.% were fabricated via solution blow spinning. The influence of HAp concentration on structure, wettability, mechanical properties and chemical and phase composition of the produced materials was examined. It was found that with an increase of HAp content the average fiber diameter was increased, the uniaxial strength and relative elongation were reduced, while the phase composition and surface wettability did not change. The performance of the scaffolds during implantation in the parietal bone of a rat skull for a period from 15 to 90 days was studied. The materials have shown high ability to integrate with both soft and hard tissues. It was found that scaffolds with 25 wt.% HAp content significantly enhance osteogenesis during scarification (damage) of the periosteum. Overall, the fabricated scaffolds proved to be highly efficient for replacing bone defects in long tubular bones.

[Blood Flow and Regional Blood Flow Rate in the Middle Cerebral Artery during Surgical Leg Lengthening in Patients with Congenital and Acquired Limb Shortening]

This is a comparative study of changes in blood flow rate in the popliteal artery, the arteries of bone regenerate and cerebral arteries in 45 patients with congenital and acquired diseases of the limbs at different stages of surgical lengthening of 3-15 cm shortened shin by Ilizarov method. We observed an increase in regional blood flow rate in all patients during the periods of distraction and fixation. A 25% increase in blood flow rate in the middle cerebral artery on the contralateral side was found only in patients of the first adult age with acquired limb shortening. Basing on the analysis of the reaction of cerebral arteries during a functional test with additional muscle work, we suggested that the absence of reaction in congenital diseases is caused by relative excess of somatic afferentation which results from morphological and functional immaturity of brain regulatory systems.

Experimental study of progressive tibial lengthening in dogs using the Ilizarov technique. Comparison with and without associated intramedullary K-wires

A delay in the union of bone regenerate in surgical lengthening procedures and the healing index (HI) are major factors in the quality of the results in progressive bone lengthening. Early removal of the external fixator (EF) is associated with a low rate of postoperative complications, including pin track infection, and with better muscle and joint function recovery. Addition of intramedullary wires (IMWs) to the EF led to a 9-49% decrease in the HI depending on the clinical series. We hypothesized that IMWs may accelerate the ossification process of bone regenerate and tested it in this experimental study.

METHODS

Progressive tibial lengthening of 28 mm was obtained in 12 dogs operated with the classical Ilizarov technique (group I) and in 12 dogs operated with the same technique and addition of two IMWs 1.5 mm in diameter (group II). The following criteria were assessed: HI, X-ray measurements, and histological aspect of the bone regenerate and postoperative complications.

RESULTS

The mean HI was 32.3% lower in group II than in group I. The radiological bone union criteria were observed on day 15 of the fixation period in group II versus day 30 in group I. Histology showed that maturation occurred earlier and bone cortices were thicker in group II than group I. Intramedullary ossification was present along the IMW in group II, whereas it was absent in group I. No clinical complications were observed in either group.

DISCUSSION

The presence of the IMWs clearly contributes to stimulation of the ossification processes of the bone regenerate and to acceleration of bone union. IMWs allowed an earlier removal of the external fixator for a 32% time reduction compared to cases without IMWs. In addition, new intramedullary bone formation and presence of IMWs are expected to increase the mechanical resistance of the bone regenerate.

CONCLUSION

Improvement of quantitative and qualitative criteria of bone regenerate in progressive bone lengthening with an EF combined with IMWs was demonstrated in this experimental study.

SIGNIFICANCE

Favorable results encourage the authors to continue using IMWs in addition to the EF in patients treated with long-bone progressive lengthening.

LEVEL OF EVIDENCE

II.

[Fracture healing under intramedullary insertion of wires with hydroxyapatite coating]

AIM

To study morphological features of the bone formation process in consolidation of fractures of long tubular bones in conditions of intramedullary wires insertion with bioactive calcium-phosphate coating of hydroxyapatite.

MATERIALS AND METHODS

In experimental study in dogs was simulated open comminuted tibia fracture and performed intramedullary insertion of wires with hydroxyapatite coating. Using light and electron microscopy, using X-ray electron microprobe microanalyses were studied bone regenerates in 14-360 days after surgery.

RESULTS

It was found that around wires there is a formation of an area of active reparative bone formation and angiogenesis, bone shaped case with the properties of the conductor and inducer of osteogenesis. Fracture consolidation is carried out in the early stages of the primary type without formation of cartilage and connective tissue in the bone adhesion.

CONCLUSION

Study results testify that intramedullary wires with hydroxyapatite coating positively influence on the process and intensity of reparative bone formation in fracture healing.

[Morphological characteristics of reparative osteogenesis under the conditions of transosseous osteosynthesis and intramedullary introduction of hydroxyapatite-coated wires]

In the experiments performed on 16 dogs, an open comminuted tibial fracture was modeled, then wires with hydroxyapatite coating were inserted intramedullary, and osteosynthesis was performed using the Ilizarov fixator. Bone regenerates were studied 14-360 days after the surgery using the methods of light microscopy, scanning electron microscopy, and X-ray electron probe microanalysis. It was found that a zone of active reparative osteo- and angiogenesis was formed around the wires, as well as a bone sheath with the properties of osteogenesis conductor and inductor. Fracture consolidation occured early according to the primary type without cartilaginous and connective tissue formation in bone adhesion.

[Dynamics of acoustic properties of skin integument and hydroxyproline content during surgical treatment of congenital limb malformation]

The aim of the work was to examine mechanical and acoustic properties of the skin and collagen metabolism in patients with congenital and developmental malformation (CDM) of extremities. Acoustic tests were performed in 39 patients with forearm CDM and in 30 with leg CDM aged 4-18 years using an ASA-4 apparatus (Russia and Yugoslavia). Mean radial and ulnar lengthening was 6.4 +/- 1.0 (5.5-8) cm, tibial and fibular lengthening 5.0 +/- 1.2 (3-8) cm, and femoral lengthening 6-12 cm. Longitudinalvelocity of sound 1 and 2 months after distraction was 42.3% and 62.9% respectively higher than the preoperative value (p < 0.05). A similar increase (36.8 and 58.4% respectively) was recorded with the ASA-4 sensor in the transverse position. Acoustic inhomogeneity in the thigh skin also increased during distraction. Maximum free to protein-bound hydroxyproline ratio in blood was measured in the end of distraction (0.58 +/- 0.04) and in the beginning of fixation (0.6 +/- 0.01). Its subsequent decrease reflected structural and metabolic changes related to proliferative and biosynthetic processes in the skin, fibrillogenesis, and altered homogeneity patterns.

[Nonreconstructive revascularizing operations in limb ischaemia]

Presented herein are the findings of experimental studies substantiating interrelationship between osteogenesis and blood circulation, as well as effects of surgical interventions based on excitation of reparative regeneration of the bone and aimed at improvement of blood circulation in the extremities. Reflected also are the main indications for the use of each operative intervention concerned. Based on the clinical findings obtained by follow up of 1,477 patients operated on for limb ischaemia secondary to obliterating arterial lesions efficacy of the methods of treatment devised is demonstrated.

[Elastic stable intramedullary nailing in Ilizarov bone lengthening]

PURPOSE OF THE STUDY

Bone lengthening with the Ilizarov technique gives good results but certain disadvantages are common: possible axial deviation during lengthening, long time to bone union, risk of fracture after removal of the external fixator. Associating the Ilizarov technique with elastic stable intramedullary nailing (ESIN) commonly used in traumatology has to be evaluated. We conducted an experimental study and report results of the first clinical application.

MATERIAL AND METHODS

Eleven lengthenings of the tibia were conducted in dogs aged 1 to 4 years using an Ilizarov external fixator associated with ESIN. Lengthening started on day 1 and continued for 28 days. X-rays were obtained every week during lengthening, then at 15 and 30 days during the fixation period and 30 days after removal of the fixator. In two cases, arteriography was performed. In a pilot clinical trial, fourteen patients (8 males, 6 females) were treated with this method (1 humerus, 1 forearm, 7 femurs, 5 tibias). Mean patient age was 14 years.

RESULTS

In the experimental study, the x-rays showed rapid ossification of the regenerate which led to increased tibia length in 7 cases from 1.25 to 2 mm/day. Total bone union was observed in four dogs during the lengthening period. At day 15 of the fixation period, all tibia had fused with a good quality cortical bone and healing of the growth part of the regenerate. In three dogs, the external fixator was removed at day 15 of fixation and weight-bearing was total with the ESIN in place. No axial deviation and no skin problems were observed. The medullary artery was seen on the two arteriograms. In the clinical trial, bone union of the regenerate appeared earlier than in the Ilizarov series. The regenerate always displayed good density on the x-rays, proving intense bone activity. In three patients, the lengthening rate was increased to avoid premature bone fusion. The endosteal bone regenerate was obvious. Mean healing index was 18.6 days/cm (SD=6.2). Weight-bearing was allowed at six weeks. The desired correction was achieved in all patients and no complications were related to ESIN.

DISCUSSION

Bone lengthening may be obtained with an intramedullary locking nail which avoids the use of an external fixator but also destroys the endomedullary circulation. Our experimental and clinical study shows that use of an ESIN does not inhibit the endosteal regenerate and seems to improve new bone formation. In many patients, the lengthening rate had to be increased to avoid premature bone fusion. When used in optimal conditions, ESIN can stimulate new endosteal and periosteal bone formation. In addition, ESIN increases shaft stability avoiding the risk of axial deviation. ESIN plays an additional role of stabilization after early removal of the external fixation.

[Dynamics of echomorphometric human crural skin characteristics during dosed stretching]

The dynamics of echo-morphometric parameters of crural skin was studied in patients with congenital shortening of lower extremity in the process of its operative elongation. It is demonstrated that dosed stretch results in increased skin thickness. After the completion of distraction, the skin thickness exceed preoperation levels by 48.7% (in patients aged 5-8 years), 20.9% (in patients aged 10-14 years) and 26.7% (in adults). Skin acoustic density after distraction termination reached the preoperation level in children and adolescents, while it was increased in adults.

[Biochemical and anatomic changes in the muscles after leg bone lengthening by the Ilizarov method]

In process of crus lengthening, following the method, given by Ilizarov G. A., with 22 adult patients have been studied the peculiarities of metabolic processes of muscle tissue of the lengthened segment as well as the muscle tissue structural changes. As the tests were used; determination of lactate dehydrogenase content and its isoenzymatic spectrum in the blood serum, the residual products of lactic and pyruvic acids glycolysis, relating to the higher indications of the internal medium of an organism; carboxylase activity detection. Energy provision of an organism was estimated according to the ATP content; anatomical state of muscles of the lengthened extremity segment and muscle tissue structure were estimated by means of contrast myography. Dynamics of biochemical indexes suggests that the sparing character of an operation, patient mobility from the first days, preservation of locomotive and supporting function contribute to prevention of metabolic disease and ensure earlier transformation of catabolic reaction to anabolic one. Carboxylase and lactate-dehydrogenase activity increase indicates the biochemical adaptation of an organism. Metabolic changes well correlate with the detected structural changes in the lengthened crus muscles.

[Significance of contrast radiography in the assessment of the state of the muscles and differential diagnosis of extensor contractures of the knee joint]

On the basis of analysis of the roentgen contrast examination of femoral muscles of the patients with extension contractures of knee joint, roentgen systematics of the muscle changes at given pathology is presented and the criteria of differential diagnosis of contractures of different types are proposed. 55 patients (125 examinations) with extension contractures of knee joint (arthrogenic, immobilizing, due to myofascio-tenodesis) of different etiology were subjected to roentgen contrast myography. As a consequence, this offered a means of objective evaluation of the muscle state and enabled one to discover the changes of muscles, specific for contractures in general as well as for each type in particular. The table of roentgenologic signs has been compiled which permits to make differential diagnosis, determine the tactics of treatment, select the type of surgical intervention on the basis of the muscle condition.

[Clinical and biochemical indicators in patients undergoing limb lengthening using Ilizarov's method]

The authors report that in 33 patients who underwent stretching of the extremity by the method of dosed distraction after G. A. Ilizarov following corticotomy there were no significant changes in a number of biochemical values (serum concentrations of general protein, albumin, urea, uric acid, glucose, cholesterol, triglycerides, magnesium, chlorides). The level of other values (alkaline phosphatase and lactate dehydrogenase enzymes, etc.) increased and sometimes exceeded the physiological limits of its age group, but did not exceed the normal limits in the population as a whole. A reliable change in the values was observed with their level being higher during the period of natural growth because of intensification of anabolic processes and growth of the mass of organs and tissues or increase in their function. A rise in serum concentrations of calcium, phosphate and hydroxyproline with the urine demonstrates in combination with the data of biphoton densimetry of the skeleton and distraction regenerate that at the same time with improved absorption of electrolytes in the intestines during distraction there was an activation of mobilization of the minerals from the intact skeleton. A problem of adequate consumption of mineral substances with the food is put forward.