Histological Analysis Of The Newly Formed Bone Secondary To

Distraction Osteogenesis Of The Mandible In Goat

MOUKHTAR MOUSSA* and MAHMUD NASR**

*Dept. Cytology and Histology1 and Faculty of Veterinary Medicine

** Dept. Dental Surgery National Institute for laser enhanced sciences

Cairo University – Giza, EGYPT

Dr_moukhtarmoussa@hotmail.com & moneim_mahmoud@hotmail.com

Abstract: A unilateral mandibular distraction osteogenesis (DO) was performed in 16 healthy adult male goats.

The mandibular body was lengthened by gradual distraction. After 10 days of distraction periods, using a protocol

of 0-day latency and a 1-mm/day rate for 10 days, the mandible was held in external fixation for 8 weeks

consolidation. The histological features and pattern of the healing process was described after 4 and 8 weeks

consolidation. Contrary to the prevalent concept, the results indicated that bone formation in the mandible of this

model was principally via the intramembranous-type of ossification. No evidence of cartilage tissue was seen in the

gap healing. Five phases could be observed during the healing process: 1) Initial phase 2) Collagenic phase 3)

Osteogenic Phase 4) Lacuna Formation Phase, and 4) Early modeling - remodeling phase of the bony regenerate.

Key Words: distraction osteogenesis, osteodistraction, mandibular body lengthening, consolidation, osteogenic

cells, intramembranous ossification, Bone remodeling.

1 Introduction

DO is the biologic process of new bone formation

between the surfaces of bone segments that are

gradually separated by incremental traction [1]. The

traction generates tension on the skeletal and

surrounding soft tissue structures, which stimulates

new bone formation parallel to the vector of distraction

[2,3]. DO was first described by Codivilla in 1905 to

elongate the femur [1]. In 1951, Ilizarov developed a

technique for repairing complex fractures of long

bones. This technique was divided into five

sequentional periods: osteotomy, latency, distraction,

consolidation and remodeling [4, 5, 6].

When the

desired or possible length is reached, a consolidation

phase follows to allow maturation of the regenerate

after traction forces are discontinued [7].

Cope and

Samchukov [8] found zones of endochondral

ossification and transchondroid bone formation at 4

weeks of consolidation in dog mandible. In rabbit

mandible, new bone was formed in the distraction gap

(DG) by both intramembranous and endochondral

ossification [5] and by intramembranous ossification

only [6, 9]. Sawaki et al. [7] in children reported new

bone formed by intramembranous ossification with

some fibro-cartilage islands. The aim of this study was

to analyze the sequence of histological features and cell

behaviors during DO of the mandibular body.

2 Materials and Methods Sixteen adult male goats, divided into two groups, were

used in this study. They underwent unilateral

mandibular body DO using a protocol of 0-day latency

and a 1-mm/day rate for 10 days.

The mandible (in one group) was held for 4 and (in the

other group) for 8 weeks consolidation periods to allow

distraction gap regeneration. Plain radiographs were

performed before the mandibles of both groups were

harvested. Also an arteriogram had been made to show

the pattern and distribution of the inferior alveolar

artery in the distraction area. Sagittal sections of The

10 mm distraction regenerate was osteomized and fixed

in 10% buffered formalin for 24 hours. Then

decalcified in 10% EDTA for about 3 weeks before

paraffin embedding. Sections, 5 – 7 Um thick, were

cut and stained with hematoxylin and eosin and

Crossmon’s trichrome stain as outline by Bancroft and

Stevens [10].

3 Results When a fracture induced, the soft and bony

vasculatures were disrupted. A hematoma floods the

wound as a result, with many blood borne elements

providing the first population of cells at the fracture

site. As the clot was formed, platelet deposition

occurred and a fibrin scaffold developed. Too few

mesenchymal cells (Fig. 1) migrated from the

adjacent marrow and bony tissue. They

contributed to the earliest formation of the DR. In

addition, osteoclasts in the form of syncytial

consolidation of monocytes of hematological origin

were observed (Fig. 2). This stage lasted from 1 to 5

Recent Researches in Medicine and Medical Chemistry

ISBN: 978-1-61804-111-1 80

days, at which time the clot was replaced by a

granulation tissue. One week after osteotomy, the

reparative tissue was filling the DG. It was soon

reinvaded by an influx of undifferentiated cells. This

stage lasted for approximately 2 weeks.

As the granulation tissue continued to organize,

endothelial cells and smooth muscle cells migrated

along the fibrin scaffold as vascular buds. They

provided the pool needed for the ongoing

replacement of cells during regeneration. As healing

progressed, ossification centers became apparent to

start an intramembranous-type of bone. They were

randomly scattered in the DR. Each center appeared as

an area of mesenchymal condensation within a

homogeneous ground substance (Fig.3).

Pronounced development occurred when fi-

broblasts differentiated from the mesenchymal cells.

They produced collagen fibers and extracellular

ground substance. Later, randomly scattered collagen

fibers were seen among the cells. Progressive

development of the collagen produced identifiable

bony specules. In the meantime, some of the

mesenchymal cells became osteoprogenitor cells and

preosteoblasts (Fig.4). Soon after, these

preosteoblasts underwent maturation and became

active osteoblasts. Each appeared as a large oval cell

with a basal spherical nucleus, basophilic cytoplasm

and a prominent large pale apical Golgi zone (Fig.4). It

seems possible that maturation of these osteoblasts

was enhanced by the presence of pre-existing

osteoclasts in the ossification centers (Fig.5).

Fig.1: Ossification center – 4 weeks consolidation.

H&E stain, 800 X

Fig.2: Syncytial condensation of monocytes to form

osteoclasts. H&E stain, 600 X

Fig.3: Ossification center – 4 weeks consolidation.

H&E stain, 300 X

Fig.4: Cell behavior during osteogenesis – 4 weeks

consolidation. H&E stain, 600 X

Fig.5: Cell behavior during osteogenesis – 4 weeks

consolidation. H&E stain, 600 X

Recent Researches in Medicine and Medical Chemistry

ISBN: 978-1-61804-111-1 81

An osteoclast appeared as a giant multinucleated cell

(Fig.6). Their nuclei varied in number, 6-15.

Their cytoplasm was "foamy" with many vacuoles. As

osteoblasts deposit initial matrix (osteoid), some of

them became entrapped in their secretion as the

future osteocyte (Fig.7). This osteoid became

mineralized after a time lag the so called osteoid

maturation period. As healing advanced, the

reparative area showed many irregular primitive

trabeculae or specules. Later on, progressive

expansion of these developing trabeculae occurred.

Formations of other new trabeculae made them

branched and united with one another to form

woven bone (Fig.8). This primitive bone enclosing

spaces filled with fibro-cellular vascular elements

which gradually transformed into marrow tissue. In

parallel with this, the peripheral zone of the

regenerate grew rapidly and thickened. It became

more organized to form the future periosteum.

Woven bone was a transient structure during the

reparative process. The early formed osteonal

canal could be seen at this stage of growth.

Gradually, the new regenerate became modeled and

remodeled, by both the osteoblasts and the

osteoclasts, to acquire the architecture of

neighboring bone. Although, newly formed bone was

achieved by the 4th weeks and became more remodeled

by the 8th weeks of consolidation, the reparative gap

did not yet attained the neighboring bony architecture.

Analysis and Cell behaviors in the Distraction

regenerate (DR):

After 4th

and 8th weeks consolidation, the new

regenerate revealed only an intra-membranous-type of

ossification which occurred simultaneously in the

following phases:

2.1 Initial phase: Examination of the newly formed DR revealed

multiple ossification centers scattered randomly in

the reparative framework. These foci could be

considered as the osteogenic forerunner in the

DG. Adjacent to the DR, the outer surface of the

edges of the DG was invested by the periosteum.

Its inner osteogenic layer was sharing actively in

invading the DR by an influx of osteoprogenitor

cells. Each ossification center appeared as an

aggregation of mesenchymal and osteoprogenitor

cells intermingled with minute blood spaces and

randomly arranged collagen fibrils. The mesenchymal

cells appeared crowded and hyperplastic, forming

mesenchymal condensations. A mesenchymal cell had

a small cell body with a few long and thin cell

processes. The nucleus was large spherical with clear

appearance. Many mesenchymal cells begun to

differentiate very rapidly into preosteoblasts. The

cells enlarged and gradually became polyhedral or

rectangular. Their processes were retained or

disappeared. Their cytoplasm stained lightly

basophilic on account of its high content of rER.

Gradually, these centers became more vascular as they

Fig.6: Osteoclast in early ossification center. H&E

stain, 800 X

Fig.7: Osteoblast entrapped in the osteoid. H&E

stain, 600 X

Fig.8: Woven bone. Crossmon's trichrome stain, 150 X

Recent Researches in Medicine and Medical Chemistry

ISBN: 978-1-61804-111-1 82

were actively invaded with numerous capillaries

derived from periosteal and endosteal. These new

capillaries were essential for the ongoing reparative

process. As these ossification foci became highly

vascular, their activity became more pronounced.

2.2 Collagenic phase: The intercellular spaces in the ossification center were

occupied by a ground substance containing wavy

collagen fibers. As more fibroblasts differentiated

from the mesenchymal cells, more collagen fibers

became randomly scattered within the ground

substance. They formed interlacing fibers within

which many cells were located. Moreover, many

collagen fibers coalesced together to form bundles

and became embedded in the initial secretion

(osteoid) of the newly differentiated osteoblasts to

form primitive specule or trabecula. The osteoid was in

the form of a hyaline jelly-like material. This secretion

was partially surrounding the osteoblast and was mostly extending towards the collagen bundles.

2.3 Osteogenic Phase: Osteoclast was the first bone cell observed early in the

regenerate. As the growing ossification centers

initially invaded by the osteoprogenitor cells from the

neighboring tissue, many of these cells differentiated

into preosteoblasts which soon became mature

osteoblasts. This maturation was enhanced by the effect

of the pre-existing osteoclasts. An active osteoblast

deposited the initial matrix, the osteoid amorphous

substance. This secretion was in the form of a hyaline

jelly-like material. It was given off unidirectional from

the cell end away from the nucleus. The osteoid

became mineralized after a time lag the so-called

osteoid maturation period. The osteoid was mostly

extending towards the collagen bundles in the form of

thin bars (Fig. 5) which coalesced together. This

secretion masked the collagen fibers and imparted

them a hyaline or lightly basophilic appearance.

Some osteoblasts became entrapped in their

secretion as the future osteocytes. Adjacent collagenic

bundles embedded in the osteoid with some entrapped

osteoblasts formed a specule or a trabecula of early

forming bone. Numerous osteoblasts congregated on

the surface of this newly formed bony trabecula (Fig.

9). As more osteoblasts became incarcerated within

their secretion as osteocytes, they were replaced by

newly differentiated osteoblasts at the surface of the

trabeculae. The presence of some osteoclasts attached

to the surface of the newly formed trabeculae, in

association with osteoblasts (Fig.7).This supported the

theory that these two cells are working together in a

synchronizing manner and were responsible for

normalizing the newly formed regenerate.

2.4 Lacuna Formation Phase:

The osteoblasts eventually formed a row of cells on the

surface of the developing bony specules. They

deposited their osteoid secretion. Some cells, that

failed to join the surface, became entrapped within the

newly deposited matrix at the periphery of the

trabecula (Fig.10). These trapped osteoblasts became

osteocyte when it was completely encased by matrix in

a lacuna. These first osteocytes assisted in osteonal

development and its mineralization. An osteocyte lay in

its own lacuna could contacting its neighboring

osteocytes through fine primitive canaliculi. This

contact would maintain its vitality by passing nutrients

and metabolites from the blood, regulating ion

homeostasis, and transmitting signals. Maturation of

the osteoblasts into osteocytes was marked by cellular

hypertrophy, lacunar enlargement, and the change in

the lacuna shape from ovoid to flat. More osteoblasts

became embedded within their secretion. This activity

resulted in the formation of more lacunae in which the

osteoblasts resided. The lacunae and the cells within

Fig.9: Osteoblasts congregated on the surface of the

newly formed bony trabecula. H&E stain, 800 X

Fig.10: Trapped osteoblast becomes osteocyte when

completely encased by matrix in a lacuna.

H&E stain, 800 X

Recent Researches in Medicine and Medical Chemistry

ISBN: 978-1-61804-111-1 83

them appeared flattened with their long axes parallel to

the surface of the developing trabecula. The matrix was

generally acidophilic near the surface of the trabecula.

However, some trabeculae showed a mottled

appearance due to the difference in staining properties

of both the core and the edges of the trabecula.

2.5 Early Modeling-remodeling phase:

During the consolidation period, there was continual

modeling and remodeling of the newly formed bony

trabeculae and specules. They were subjected to the

synchronizing activities of both osteoblast and

osteoclast. It is well known that the osteoblast and

osteoclast are integral parts of the bone formation.

Moreover, it was believed that the osteoclast is only

lodging in a concavity called Howship's lacuna. This

lacuna, in the present study, was not found as the

osteoclast was present in a very active form at the early

reparative phase.

2.5.1 Role of osteoblast:

The osteoblasts produced layer after layer of bone

inward on the surface of the developing trabecula. As

the trabeculae enlarged in size, its structure was altered

by internal reconstruction and by remodeling.

Remodeling resulted from alteration in certain areas

and deposition of new bone elsewhere.

2.5.2 Role of osteoclast:

a) Bone remodeling:

Osteoclasts were usually found in contact with the

surface of a collagenic bundle (Fig.11). Osteoclasts

refine the affected bony edges. This enhanced the

newly formed regenerate largely to retain the

architectural shape of the preexisting bone.

b) Haversian canal remodeling:

The lytic or erosion-refining effects of the

osteoclasts resulted in the formation of cylindrical

cavities or tunnels, the forerunner of the Haversian

canal (Fig. 12). The latter were lined by osteoblasts

which deposited successive bony lamellae to increase

the diameter of the canal.

c) Phagocytic activity:

Some osteoclasts acted as a giant cell. This was

illustrated by phagocytosing and digesting osteocyte

together with its surrounding bony lacuna.

Radiographic findings: The regenerate filling the distraction gap after 4 weeks

consolidation, showed a variable density when

compared with the adjacent bone segments (Fig. 13).

After 8 weeks this regenerate showed homogenous

bone densities (Fig. 14).

Fig.11: Osteoclast attached to the surface of a

newly formed bony trabecula. H&E stain,800 X

Fig.12: Haversian canal remodeling. H&E stain, 200

X

Fig.13: X-ray to show bone density of the DR – 4

weeks consolidation.

Fig.14: X-ray to show bone density of the DR – 8

weeks consolidation.

Recent Researches in Medicine and Medical Chemistry

ISBN: 978-1-61804-111-1 84

Angiographic results: After 4 weeks consolidation, the inferior alveolar artery

appeared patent and thin with remarkable decrease in

its diameter (Fig.15). After 8 weeks consolidation, it

showed a relatively thicker diameter. However, it still

had a less diameter than the normal one (Fig.16).

4 Discussion

Intramembranous ossification was the main and

only mechanism of bone formation in the distraction gap.

There was no evidence of cartilaginous tissue in the

newly formed bone. This finding was also described by

Sencimen et al. [9] in rabbits. The finding of Carter et

al. [11] that distraction was associated with cartilage

only in very small discrete regions at the periphery of

the distraction gap adjacent to the osteotomy ends is

denied by the present study. Also in agreement with

Rahn et al. [12] no inflammatory phase, no cartilaginous

intermediate, nor callus formation were found in

primary bone healing. Wornom and Buchman [13] were

of the opinion that in some instances, bone may undergo

primary healing after a fracture without a cartilage

intermediate. In rabbit mandible, Komuro et al. [5]

reported new bone formed by both intramembranous and

endochondral ossification whereas Sawaki et al. [7]

found new bone formed by intramembranous

ossification, with some fibrocartilage islands. At the

initial time of osteotomy, Ashton and Allen [14] and

Brighton [15] found precursor mesenchymal cells and

osteoprogenitor cells migrating into the gap from the

adjacent muscle, marrow and from the periosteutn.

Tonna and Cronkite [16] mentioned that these cells

contribute to the earliest formation of bone at the

fracture site. The present findingsshowed an influx of

mononuclear cells invading the reparative zone. This

was derived from the marrow, blood and deepest layer

of periosteum. These local precursor cells differentiate

into fibroblasts and osteoblasts to produce collagen and

osteoid in the gap. This finding is parallel with that of

Nemelh et al. [17]. Moreover, these pluripotential cells

differentiate into osteoblasts which underwent

cementing to the cutting edges of bone at the fracture

site. Others congregate on the surface of the newly

formed bony trabeculae. They are responsible for

depositing a new matrix. Their activity results in the

formation of small lacunae in which the osteoblast

resides to become osteocyte. In agreement with Lane et

al. [18] type-1 collagen was initially deposited to form

the framework on which mineralization occurs.

According to Robling, Castillo,and Turner [19] bone

matrix consists mainly of type-I collagen fibers

(approximately 90%) and noncollagenous proteins or

osteocalcin, (makes up 1 % of the matrix). The latter

may play a role in calcium binding and stabilization of

hydroxyapatite in the matrix and/or regulation of bone

formation. Within larnellar bone, the collagenic fibers

are forming arches for optimal bone strength. These

lamellae can be parallel to each other or concentrically

arranged. Our findings supported the view of the

interplay of the three bone cells as a team, which is

called basic multicellular unit (BMU). This BMU is a

mediator mechanism bridging individual cellular

activity to whole bone morphology [20,21,22]. Units of

the osteoclasts and the osteoblasts were activated in

sequences of both bone resorption and formation to

convert the contours of the reparative zone to the

original bony architecture [13]. Recent evidence

suggests that the normal mechanism of internal bone

resorption may occur under the influence of the mature

osteocytes. Osteocytes live in fluid-filled hollows

within the bone matrix and are interconnected by

numerous long cell extensions through microscopic

tunnels. They are believed to be the cells that sense

mechanical strain. Osteocytes respond to this strain

by sending signals that either cause new bone

formation or bone remodeling [23]. Glass, Bialek,

Starbuck and Patel [24] described that osteoblast secrets

collagenous and non-collagenous bone matrix proteins,

including type-I collagen. Osteoblasts also produce a

range of growth factors under a variety of stimuli. The

most prominent features of the osteoclast is the ruffled

Fig.15: Arteriogram – 4 weeks consolidation.

Fig.16: Arteriogram – 8 weeks consolidation.

Recent Researches in Medicine and Medical Chemistry

ISBN: 978-1-61804-111-1 85

border facing the bone matrix. Osteoclasts are able to

produce both phosphatase and protease which are

necessary to dissolve bone minerals and to activate

enzymes that break down collagen fibers. Furthermore,

the cell secretes collagenase and gelatinase-� which

are involved in bone matrix digestion [25]. Attachment

of the osteoclast to the bone surface is essential for bone

resorption. This attachment is performed via integrin

receptors, which bind to specific Arginine-Glycine-

Aspartate (RGD) sequences found in matrix proteins

[26]. This process involves transmembrane adhesion

receptors of the integrin. According to Parfitt [27] and

Weinbaum, Cowin and Zeng [28] integrins attach to

specific amino acid sequences at the surface of the

bone matrix.

Conclusion: The intramembranous type of ossification was the

main mechanism of bone reformation in the distraction

gap in mandible. No evidence of pre-existing cartilage

tissue during gap healing. The term soft or hard callus

is a surgical term and is not longer valid in the field of

histology. Apoptotic and not necrotic changes occur

during induction and healing of fracture. The role of

osteoclast is to refine the bony surface and remodeling

the newly formed bone. Both osteoblast and osteoclast

are doing their work in a synchronizing manner under

a genetic encoding which regulates their functions.

References:

[1] Codivilla A.: On the means of lengthening in the

lower limbs, the muscles, and tissues which are shortened through deformity. Clin Orthop 301, 1994, 4 – 9

[2] Ilizarov GA.: The tension-stress effect on the

genesis and growth of tissues. Part I. The influence of

stability of fixation and soft-tissue preservation. Clin

Orthop Rel Res 238, 1989, 249-281.

[3] Ilizarov GA.: The tension-stress effect on the

genesis and growth of tissues: Part 2. The influence of

the rate and frequency of distraction. Clin Orthop 238,

1989, 263–285.

[4] De Bastiani G., Aldegheri R, Renzi-Brivio L, Trivella

G.: Limb lengthening by callus distraction (callotasis).

Journal of Pediatric Orthopedics 7, 1987, 129-34.

[5] Komuro Y., Takato T., Harii K. and Yonemara Y.: The histologic analysis of distraction osteogenesis of the

mandible in rabbits. Plast Reconstr Surg 94, 1994, 152–159 [6] Liou E.J.W., Figueroa A.A. and Polley J.W.: Rapid

orthodontic tooth movement into newly distracted bone

after mandibular distraction osteogenesis in a canine

model, Am J Orthod Dentofac Orthop 117, 2000, 391–398

[7] Sawaki Y, Ohkubo H., Yamamoto H. and Ueda M.

: Mandibular lengthening by intraoral distraction using

osseointegrated implants. Int J Oral Maxillofac

Implants 11, 1996, 186-193

[8] Cope J.B. and Samchukov M.L.: Radiographic

Classification of Mandibular Bone. In Samchukov M.L.,

Cope J.B. and Cherkashin A.M.: Craniofacial distraction

osteogenesis, St. Louis: CV Mosby; 2001, 176 -183 [9] Sencimen M., Aydintug Y.S., Ortakoglu K.,

Karslioglu Y., Gunhan O. and Gunaydin Y.: Histomorphmetrical analysis of new bone obtained by

distraction. Int. J. Oral Maxillofac Surg. 36, 2007, 235-242.

[10] Bancroft J.D., Stevens A.: Theory and practice of

histological techniques, 3rd ed. Churchill Livingstone,

Edinburgh, 1990

[11] Carter D.R.; Beaupre G.S., Giori N.J. and Helms

J.A.: Mechanobiology of skeletal regeneration, Clin

Orthop Relat Res 355, 1998, (Suppl 1) : S 41–S 55.

[12] Rahn P. and Callinaro Ba!tensperger A.: Primary

bone healing. An experimental study in the rabbit. J.

Bone joint Surg 53A, 1971: 783-786.

[13] Wornom L. and Buchman S.R.: Bone and

cartilaginous tissue. In Wound healing, Biochemical &

clinical aspects, by K. Cohen, Diegelmann R.F. and

Lindblad W.J., Saunders Co.USA. 1992, P 356-383.

[14] Ashton, B.A .Allen and F.D, Howlelt CR. Et al:

Formation of bone and cartilage by marrow stromal

cells in diffusion chambers in vivo. Clin Orthop 151,

1980, 294-307.

[15] Brighton C.T.: Principles of fracture healing. In

Murry JA (ed): Instructional Course Lectures. St.

Louis, CV Aloshy, 1984, P 60-82.

[16] Tonna E.A. and Cronkite G.P.: The periosteum:

Autoregdiographic studies on cellular proliferation and

transformation utilizing tritiated thymidine. Clin

Orthop 30, 1963, 218-233.

[17] Nemelh C.C., M.E Bolander and C.R. Martin.:

Growth factors and their role in wound and fracture

healing. In Hunt TK, Pines E, Barbul A, et al (ed.,).

Growth Factors and Other Aspects of wound Healing.

Biological and Clinical Implication, New York, Alan

R. Liss, 1989, pp 1-17.

[18] Lane J.M., A.L. Boskey, Li WKP, et al.: A

temporal study of proteoglycans lipids and mineral

constituents in a model of endochondrial osseus repair.

Metab Bone Dis Rel Dis 1, 1979, 319 -324.

[19] Robling A.G., Castillo A.B. and Turner C.H.:

Biomechanical and molecular regulation of bone

remodeling Annual Review of Biomedical Engineering

8, 2006, 455-498

[20] Frost H.M.: Structural adaptations to mechanical

usage (SATMU): 1. Redefining Wolff's Law: The bone

modeling problem Anat Rec 226, 1990, 403–413.

[21] Parfitt AM.: Osteonal and hemi-osteonal

remodeling: the spatial and temporal framework for

Recent Researches in Medicine and Medical Chemistry

ISBN: 978-1-61804-111-1 86

signal traffic in adult human bone. J. Cell. Biochem.

55, 1994, 273–286.

[22] Parfitt AM. 2000. The mechanism of coupling: a

role for the vasculature. Bone 26: 319–323.

[23] Rubin C, Judex S, Hadjiargyrou M.: Skeletal

adaptation to mechanical stimuli in the sence of

formation or resorption of bone. J. Musculoskelet.

Neuronal Interact. 2, 2002, 264–267.

[24] Glass DA 2nd, Bialek P, Ahn JD, Starbuck M,

Patel MS, et al.: Canonical Wnt signaling in

differentiated osteoblasts controls osteoclast

differentiation. Dev. Cell 8, 2005, 751–64.

[25] Lazenby RA.: Continuing periosteal apposition.

II. The significance of peak bone mass, strain

equilibrium, and age-related activity differentials for

mechanical compensation in human tubular bones. Am.

J. Phys. Anthropol. 82, 1990, 473– 84.

[26] Garn SM.: The Earlier Gain and the Later Loss of

Cortical Bone. Springfield, IL: Charles C. Thomas, 1970

[27] Parfitt AM.: The physiologic and clinical

significance of bone histomorphomstric data. In Bone

Histomorphometry: Techniques and Interpretations, ed.

RR Recker, pp. 143–23. Boca Raton, FL: CRC Press, 1983

[28] Weinbaum S., Cowin S. C. and Zeng Y.: A model

for the excitation of steocytes by mechanical loading-

induced bone fluid shear stresses. Journal of

biomechanics 27, 1994, 339-60.

Recent Researches in Medicine and Medical Chemistry

ISBN: 978-1-61804-111-1 87