Impact of telescopic intramedullary rodding on the growth of tibia: Comparative experimental study in dogs.

INTRODUCTION: The most commonly accepted method of long bone deformity correction in children with osteogenesis imperfecta is surgical realignment with transphyseal telescopic intramedullary rodding. This approach ensures reinforcement of the bone throughout the growth period. Although longitudinal growth does occur with these implants there has been very little work carried out to calculate the effect of such factors as rod position or implant material on growth. We carried out a prospective comparative study on 12 puppies using titanium alloy telescopic tibial rods with and without hydroxyl-apatite coating. The aim of this non-randomized controlled experimental study was to assess the impact of telescopic intramedullary rodding on spontaneous growth of the tibia. MATERIAL AND METHODS: Twelve mongrel puppies aged of 5 months underwent intramedullary transphyseal rodding of the right tibia. In group I (6 dogs) a titanium telescopic rod was used, in group II (6 dogs) a titanium rod with hydroxyapatite (HA)-coated threaded end was used. The following radiological criteria were assessed before surgery and every month until age of 12 months (natural fusion of physes in dogs): length of tibia, amount of superposition of inner (male) rod into external (female) rod; alteration of anatomy in terms of joint angles (mMPTA, mLDTA, mPPTA, mADTA); positioning of threaded ends in proximal and distal epiphyses and evidence of premature growth arrest. Parameters were compared with left tibia serving as control segment. The null hypothesis was that neither rod position nor implant material altered growth. RESULTS: The transphyseal rods did not lead to irreversible epiphysiodesis in either group. In group II (HA-coated) some loss of residual length was found in all six dogs, over 7mm (5.9%) in comparison to left intact tibia. In contrast to that, in group I (titanium nail) only one animal (16.7%) demonstrated a tibia length discrepancy of 8mm (4.8%). Eccentric ( posterior) positioning of the rod in the distal epiphysis resulted in a procurvatum deformity (increased anterior distal tibial angle) in both groups. We found no failure of telescoping and no loss of fixation of threaded parts in either epiphyses. DISCUSSION: The presence of telescopic rods with HA-coated threads parts clearly contributes to inhibition of spontaneous longitudinal growth. We hypothesize that HA stimulates maturation of chondrocytes of growth plate. Our findings regarding the potential adverse effect of thread position in the distal physis demonstrate the importance of attempting to place the rod as central as possible. CONCLUSION: Titanium alloy telescopic rods did not reveal significant effect on physeal growth in puppies in comparison to HA-coated implants. Transphyseal HA-coated implants did however inhibit growth plate function with mean loss of length of 5.2% compared to the other side. Eccentric positioning of rods relative to center of physis resulted in angular deformity due to irregular growth. There were no cases of mechanical failure or loss of telescopic function with either group of titanium implant. LEVEL OF EVIDENCE: II; prospective comparative experimental study.

Long Bone Defect Filling with Bioactive Degradable 3D-Implant: Experimental Study.

Previously, 3D-printed bone grafts made of titanium alloy with bioactive coating has shown great potential for the restoration of bone defects. Implanted into a medullary canal titanium graft with cellular structure demonstrated stimulation of the reparative osteogenesis and successful osseointegration of the graft into a single bone-implant block. The purpose of this study was to investigate osseointegration of a 3D-printed degradable polymeric implant with cellular structure as preclinical testing of a new technique for bone defect restoration. During an experimental study in sheep, a 20 mm-long segmental tibial defect was filled with an original cylindrical implant with cellular structure made of polycaprolactone coated with hydroxyapatite. X-ray radiographs demonstrated reparative bone regeneration from the periosteum lying on the periphery of cylindrical implant to its center in a week after the surgery. Cellular structure of the implant was fully filled with newly-formed bone tissue on the 4th week after the surgery. The bone tissue regeneration from the proximal and distal bone fragments was evident on 3rd week. This provides insight into the use of bioactive degradable implants for the restoration of segmental bone defects. Degradable implant with bioactive coating implanted into a long bone segmental defect provides stimulation of reparative osteogenesis and osseointegration into the single implant-bone block.

Osteointegration technology in long bone defect reconstruction: experimental study.

PURPOSE: The purpose of this experimental study was to evaluate the osteointegration of a bioactive 3D-cylindrical titanium-alloy implant (bone-graft substitute) for tibial shaft defect reconstruction. METHODS: An experimental study was done in 7 mongrel dogs. Tibial shaft defect was repaired using an original titanium-alloy (Ti6Al4V) cellular cylindrical implant. with a bioactive layer of hydroxyapatite by anode microarc oxidation. Histological study (hematoxylin-eosin stain and immunohistological reaction using ostepontin polyclonal antibodies) and scanning electron microscopy (electron probe X-ray microanalysis for calcium and phosphorus saturation in the tissue matrix) were applied to assess bone tissue regeneration. RESULTS: Experimental study revealed osteoconduction starting from the endosteum of bone fragments adjacent to the bone defect and developed to the central part of the implant. In 4 weeks, graft osteointegration was achieved in all animals. Implant cells were filled with spongy bone tissue and the graft external surface was covered with a connective tissue structures similar to the periosteum ones. CONCLUSIONS: Cellular titanium bone-graft substitute with bioactive coatings placed into bone defect stimulates reparative osteogenesis and graft osteointegration.

Impact of Transphyseal Elastic Nailing On the Histostructure of the Tibia in Growing Animals (Non-Randomized Controlled Experimental Study).

BACKGROUND: The use of intramedullary elastic nailing is a method of choice for prevention of complications in children with osteogenesis imperfecta. However, the morphology of the growing long bones in the conditions created was not investigated. AIM: The purpose of our experiment was to study the impact of elastic intramedullary nailing on the histostructure of long bones in their physiological growth. METHODS: Six mongrel dogs underwent intramedullary elastic transphyseal nailing of the intact tibia with two titanium wires. Six months after nailing, a light-optical microscopic and histomorphometric study of the operated and contralateral tibiae was performed. RESULTS: It was found that asymmetric lesion of the distal physis induces a decrease in the height of the distal epimetaphysis. Adaptive changes in the hyaline cartilage of both articular ends were revealed corresponding to the initial stage of chondropathy. Intramedullary nailing promotes an increase in the thickness of the compact bone and the volume of the trabecular bone. CONCLUSIONS: Elastic transphyseal nailing of the intact tibia has a shaping effect which is expressed by an increase in the volume of spongy and compact bone, adaptive changes in the hyaline cartilage. Asymmetric damage to growth zones should be avoided to prevent deformities.

Biological activity of the implant for internal fixation.

Early treatment of bone fractures was performed using implants, which are often used in the form of plates of various types, which are fixed on the bone surface (extracellular fixation) and nails that are located in the medullary canal (intracerebral fixation). The goal of this study was to investigate the features of osseointegration of implants for internal fixation (intramedullary or extramedullary) with various bioactive coating techniques. During experimental study on 20 mongrel dogs, the implant model in the form of 1.0-mm plate made of titanium alloy (Ti6Al 4V) was placed in the medullary canal (first series) or under the periosteum (second series): the plates had bioactive coating (hydroxyapatite) produced using the technology of magnetron sputtering (six animals), plasma electrolytic oxidation or microarc oxidation technology (PEO; eight animals), and composite technology (six dogs). Anatomic and histological studies have shown that the process of active osseointegration of porous implants with bioactive coating begins after 7 days: at first, granulation tissue - and then fibrous connective tissue - is formed; after 14 days, the osteogenic substrate can be found, and after 28 days, the entire implant area is covered by the lamellar bone tissue, which creates single implant-bone block. The most active formation of bone tissue is observed around implants with bioactive coating produced using the last two technologies. Low traumatic placement of porous implants with bioactive coating in the medullary canal or subperiosteally provides the stimulation of reparative osteogenesis and rapid (especially with PEO technique) osseointegration of the implant.

Bioactivity and osteointegration of hydroxyapatite-coated stainless steel and titanium wires used for intramedullary osteosynthesis.

A lot of research was conducted on the use of various biomaterials in orthopedic surgery. Our study investigated the effects of nanostructured calcium-phosphate coating on metallic implants introduced into the bone marrow canal. Stainless steel or titanium 2-mm wires (groups 1 and 2, respectively), and hydroxyapatite-coated stainless steel or titanium wires of the same diameter (groups 3 and 4, respectively) were introduced into the tibial bone marrow canal of 20 dogs (each group = 5 dogs). Hydroxyapatite coating was deposited on the wires with the method of microarc oxidation. Light microscopy to study histological diaphyseal transverse sections, scanning electron microscopy to study the bone marrow area around the implant and an X-ray electron probe analyzer to study the content of calcium and phosphorus were used to investigate bioactivity and osteointegration after a four weeks period. Osteointegration was also assessed by measuring wires' pull-off strength with a sensor dynamometer. Bone formation was observed round the wires in the bone marrow canal in all the groups. Its intensity depended upon the features of wire surfaces and implant materials. Maximum percentage volume of trabecular bone was present in the bone marrow canals of group 4 dogs that corresponded to a mean of 27.1 ± 0.14%, while it was only 6.7% in group 1. The coating in groups 3 and 4 provided better bioactivity and osteointegration. Hydroxyapatite-coated titanium wires showed the highest degree of bone formation around them and greater pull-off strength. Nanostructured hydroxyapatite coating of metallic wires induces an expressed bone formation and provides osteointegration. Hydroxyapatite-coated wires could be used along with external fixation for bone repair enhancement in diaphyseal fractures, management of osteogenesis imperfecta and correction of bone deformities in phosphate diabetes.