Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.
2005
Volume 8
Issue 3
Topic:
Veterinary Medicine
ELECTRONIC
JOURNAL OF
POLISH
AGRICULTURAL
UNIVERSITIES
Jałyński M. , Chyczewski M. , Brzeski W. , Nowicki M. , Lew M. , Powalska D. , Sobiech P. 2005. MACROSCOPIC STRUCTURE OF BONE CALLUS AFTER USING EXTERNAL FIXATOR MACZEK IN SHEEP, EJPAU 8(3), #27.
Available Online: http://www.ejpau.media.pl/volume8/issue3/art-27.html

MACROSCOPIC STRUCTURE OF BONE CALLUS AFTER USING EXTERNAL FIXATOR MACZEK IN SHEEP

Marek Jałyński1, Mariusz Chyczewski1, Wojciech Brzeski1, Marek Nowicki1, Marcin Lew1, Dorota Powalska1, Przemysław Sobiech2
1 Department of Surgery and Roentgenology, University of Warmia and Mazury in Olsztyn, Poland
2 Department of Internal Diseases, University of Warmia and Mazury in Olsztyn, Poland

 

ABSTRACT

The studies were carried on 30 black-headed sheep. The sheep were divided into three equal groups. External fixator Maczek mini was used in all groups. In group I fixation with bone fragment pressure was applied, in group II – fixation without pressure and in group III – dynamic-axial fixation. After three months of observation, all sheep were subjected to euthanasia. Callus samples were taken to prepare longitudinal osseous microsections. An analysis of 30 profiles and osseous longitudinal microsections from three group of sheep shows a proper course of ossification in the majority of animals from groups II and III, however callus of poorer quality was observed in some animals from group I.

Key words: sheep, external fixator Maczek, bone callus.

INTRODUCTION

The quality and quantity of newly-formed bone tissue depend on numerous factors [2], including the rate and rhythm of blood supply to fragments of a fractured bone, the quality of fracture reduction (stiffness or mobility of bone fragments), unity and integrity of peristeum and endosteum, extensiveness of damage in tissue and medullary cavities with their vascularization (before and after fixation), as well as such factors as: the patient’s age, deficiencies, diet and other [17,18,19].

A properly selected fixation method and adequate mechanical conditions of fracture healing can ensure positive results of treatment within an optimal period of time. Modern fixators should enable proper immobilization of a fractured bone, as well as liquidation of rotational and lateral movements. They cannot cause soft tissue damage (blood and nerve supply) during application. In some periods of treatment they should allow axial movement of bone fragments when the limb is loaded. Newly-formed provisional callus fills the whole fracture fissure, which affects the quality of definitive callus. This kind of fixation is knows as dynamic-axial, and the newly-formed callus is characterized by high resistance. The above conditions are fulfilled by external fixation, whose rapid development could be observed recently. Many modern clip, frame and circular fixators were designed in those years. With time passing the materials used and technical solutions employed were changed, but the general principles of external fixation application remained the same: two or more osseous implants pierce fragments of a fractured bone, or are partly introduced into bone tissue, proximally and distally to the fracture. After fracture repositioning these elements are joined together above the skin, by means of different kinds of material, e.g. a steel splint, plastics, or other [8,15].

The results of technical-laboratory and experimental–clinical studies on the use of external fixator Maczek, conducted at the Department of Traumatic Surgery, Medical University in Gdańsk, show that it can be useful in the treatment of bone fractures. The present paper focuses on its influence on the macroscopic structure of callus.

MATERIALS AND METHODS

A super-mini version of external fixator Maczek was used in the experiment. It is a clip, uni- or di-planar fixator. External fixator Maczek is available in four versions: MAXI, STANDARD, MINI and SUPER-MINI. They differ only in size and weight, all are made of stainless and acid-resistant steel 2H13 and tarnamide – equivalent of polyamide [15,16].

The studies were carried out on 30 black-headed sheep of both sexes, aged ca. one year. Before the experiment they all were premedicated with xylazine at a dose of 2 mg/kg of body weight i.m. Directly before treatment they were given ketamine at a dose of 5 mg/kg of body weight i.m and propofol in the form of intravenous drip infusion (solution: 210 ml of 5% glucose and 40 ml of 1% propofol) at a dose of 0.44 mg/kg of body weight per minute.

The sheep were divided into three equal groups. Osteotomy was performed on all of them under general anesthesia, immediately before osteosynthesis. External fixator Maczek mini was used in an operating room. In group I fixation with bone fragment pressure was applied, in group II – fixation without pressure and in group III – dynamic-axial fixation [3].

After three months of observation, all sheep were subjected to euthanasia. Callus samples were taken to prepare longitudinal osseous microsections. They were prepared at the Department of Histology and Embryology, Faculty of Veterinary Medicine, University of Agriculture in Wrocław. After soft tissue dissection, samples were defatted by putting them into acetone for four hours; then they were rinsed in running water for 48 hours, dried and cut up in a longitudinal plane into two equal parts. A slice 0.50 mm in thickness was cut out of one part on optical bench Simens, and ground to a thickness of 0.18-0.20 mm. Such osseous microsections were evaluated.

RESULTS

10 profiles and longitudinal osseous microsections were analyzed in group I. Lesions of fibrous connective tissue were observed, especially in the periosteal zone. Poorly-developed callus was noted there. The whole callus was well-developed, but its central part (within the medullary cavity) was not fully developed. Numerous osteolytic lesions were also observed in this group (Figure 1).

Fig. 1. longitudinal osseous microsection (fixation with pressure)

An analysis of 10 osseous microsections in group II showed the most developed callus in this kind of osteosynthesis (Figures 2 and 3). The callus was characterized by good-quality ensheathing part and central part, with a rich network of blood vessels and obliterated medullary cavity. Bone profiles and osseous microsections show that coarse-fibrous bone tissue (a provisional bone) started to transform into a compact lamellar bone (a definitive bone).

Fig. 2. longitudinal osseous microsection (fixation without pressure)

Fig. 3. longitudinal osseous microsection (fixation without pressure)

The picture of osseous microsections in sheep from group III was similar to that in group II (Figure 4), with coarse-fibrous bone tissue beginning to transform into a compact lamellar bone. However, the degree of callus development was here slightly lower than in group II.

Fig. 4. longitudinal osseous microsection (dynamic-axial fixation)

DISCUSSION

Regardless of the method applied, therapeutic management of bone fractures should include proper fracture reduction and immobilization in the period of provisional callus development and its partial transformation into definitive callus. The earlier the reduction and immobilization occur, the better final results of treatment can be expected. At the last stage of callus formation, pre-bone tissue transforms into proper bone tissue. At the beginning of this stage lysis of ensheathing and central callus takes place. Then, as a result of internal redevelopment, a coarse-fibrous plexal bone is replaced by a lamellar bone. Transformation of the trabecular bone structure is not limited to the fracture area only – it extends to farther bone segments getting ready for load [4,5,10,19]. If this stage is to be completed without disturbances, compressive and tensile forces must operate on the callus, according to the Wolf’s law. Trabeculas arranged out-of-parallel to the axis of bone loading undergo transformation. Due to the operation of forces on the bone, new trabeculas are formed on the side where the pressure is higher. On the side where the pressure lower, the bone “scaffold” disappears [10]. An irregular network of blood vessels becomes regular. In the case of spontaneous (natural) union of a fractured bone it is very important that the fracture area is continuously supplied with blood [9,14,15].

An analysis of 30 profiles and osseous longitudinal microsections from three groups of sheep shows a proper course of ossification in the majority of animals from groups II and III. Fibrous tissue proliferation was noted in some of them, with a tendency towards subperiosteal ossification. Osseous microsections of animals from groups II and III contain well-developed ensheathing and central callus, with a partly or fully obliterated medullary cavity, or a newly-formed one. The beginning of transformation of a provisional bone into a definitive one can be observed. Therefore, it may be assumed that the callus picture is similar to that of proper bone tissue. Callus of poorer quality was observed in some animals from group I. Their osseous microsections show callus with large quantities of fibrous connective tissue and numerous osteolysis lesions.

Nails of various profiles introduced into the medullary cavity cause considerable damage to blood vessels of the bone marrow and the cortical layer of the broken bone. These vessels are one of the most important elements of revascularization of the newly-formed callus [15]. After the application of round intra-medullary nails, e.g. Steimann-Gruca ones, the medullary cavity is completely filled with the nail.

In the case of open fractures the damage is still worse, because external injuries cause infections of vascularization (including periosteal) and bone tissue. It follows that only closed fractures may be treated with intra-medullary nails [2].

The use of external fixator “Maczek” does not cause additional damage to soft tissues, nerves and blood vessels during operative treatment of fractures. “Maczek” fixation enables daily wound dressing, until its complete cure.

The studies conducted by Whittlae and Russell show that tissue infection accompanying operative treatment with intra-medullary nailing and external fixation is similar. However, fracture treatment with intra-medullary nailing causes disturbances in blood supply [15]. The results of treatment may be incomparable. Good results are achieved in the case of good vascularization of the fracture area and the lowest possible pain-related irritation. The formation and consolidation of new bone fragments are more visible when the periosteum is well vascularized (King 1976). Some authors, e.g. Hauben, performing experiments on different animal species observed a fully formed bone under well-vascularized periosteum, and fibrotic callus under a non-vascularized flap.

In 1985 Burstein reported a correlation between the amount of newly-formed bone tissue and the level of blood supply. Similar results were obtained by Takato in 1986, 1988 and Romana in 1984 [15].

In contrast to intra-medullary nailing, external fixation does not cause extensive bone marrow damage. Osteogenic properties of the medulla were discovered as early as 30 years ago [1,7]. It was found that the osteogenic series of bone marrow stroma cells [1] proliferated and tended towards osteoblasts forming bone trabeculas, which was used in autogenous bone grafts [6]. Fracture healing proceeds in a smoother way thanks to such grafts, as they enable proper callus re-vascularization and medullary cavity renewal [2,11,12]. The course of the process was similar in groups II and III. In group I two cases of osteopetrosis were noted, consisting in considerable disturbances in resorption in relation to osteogenesis. Well-developed callus and bone hypertrophy in the medullary cavity were observed in this group.

The research results indicate that the callus in groups II and III was small, of good quality, uniformly distributed around fracture fissures. This suggests uniform operation of forces on the osseous walls, situated proximally and distally to the fixator body. The callus picture in group I is worse. It shows large quantities of fibrous connective tissue and callus of poorer quality.

External fixator Maczek applied to transverse fractures of tibial bones in sheep allows to obtain callus of relatively good quality. It follows that this method may be recommended for treatment of long bone fractures in animals.

CONCLUSIONS

  1. The course of fracture healing is regular after the application of external fixator “Maczek”, and the callus formed resembles proper bone tissue to a high degree.

  2. The results obtained show that three variants of external fixation may be applied, i.e. fixation with bone-fragment pressure, fixation without bone-fragment pressure and dynamic-axial fixation.

REFERENCES

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Marek Jałyński
Department of Surgery and Roentgenology,
University of Warmia and Mazury in Olsztyn, Poland
Oczapowskiego 14, 10-957 Olsztyn, Poland

Mariusz Chyczewski
Department of Surgery and Roentgenology,
University of Warmia and Mazury in Olsztyn, Poland
Oczapowskiego 14, 10-957 Olsztyn, Poland

Wojciech Brzeski
Department of Surgery and Roentgenology,
University of Warmia and Mazury in Olsztyn, Poland
University of Warmia and Mazury in Olsztyn, Poland

Marek Nowicki
Department of Surgery and Roentgenology,
University of Warmia and Mazury in Olsztyn, Poland
Oczapowskiego 14, 10-957 Olsztyn, Poland

Marcin Lew
Department of Surgery and Roentgenology,
University of Warmia and Mazury in Olsztyn, Poland
Oczapowskiego 14, 10-957 Olsztyn, Poland

Dorota Powalska
Department of Surgery and Roentgenology,
University of Warmia and Mazury in Olsztyn, Poland
Oczapowskiego 14, 10-957 Olsztyn, Poland

Przemysław Sobiech
Department of Internal Diseases,
University of Warmia and Mazury in Olsztyn, Poland
Oczapowskiego 14, 10-957 Olsztyn, Poland
email: chirwet@moskit.uwm.edu.pl

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