The source of new bone that results from various regenerative process in bone
grafts, and in particular, the orgin of new bone when osseous tissues are
transplanted into nonskeletal tissue, has been the subject of considerable interest
in recent orthopaedic literature.
The two theories of new bone formation are: 1) the osteoblastic therory proposed
by Ham (1930), and Urist and McLean(1941) which states that all new bone formation
results from osteoblasts which arise from living osseous structures such as
periosteum, endosteum, and connective tissue of the Haversian canal, either of the
host bone or of grafts, and 2) the metaplasia theory proposed by Baschkirzew and
Petrow(1912), and Levander(1938) which staes that an osteogenic substance, referred
to as an inducer or organizer which is present in the grafts, can cause indifferent
connective tissue cells to form osteoblasts which lay down new bone around bone
Urist and McLean(1952) reported that their studies of osteogenetic tissues
transplanted into the anteiror chamber of the rabbit's eye, indicated that
periosteum, bone marrow, and some of the elements of cancellous bone and of
fibrocartilagenous callus might survive and proliferate following transplantation,
and give rise to new bone directly. They supported the osteoblastic theory.
De Bruyn and Kabisch(1955) transplanted various osseous tissues into the femoral
muscle of the rabbit. They reported that the new bone developed by metaplasia of
the connective tissue surrounding the transplants and thus they supported the
The present investigation is concerned with the question whether new bone
formation by transplants originates from sepcific osteogenetic cells derived from
the transplants, or by a metaplastic process in the connective tissue surrounding
the transplant, under the influence of osteogenetic substances present in the
transplant. Observations were also made on the histological changes and the fate of
the transplants as well as the neighbouring connective tissue of the transplants.
Materials and Methods
Albino rabbits, weighing about 2 kg., were used throughout the experiment. The
autogenous transplants of the various tissues to be transferred were aseptically
removed under open drop ether anaesthesia and transplanted into the subcapsular
region of the kidney. For transplants, cortical bone and periosteum were taken from
the anterior portion of the tibia, muscle tissues taken from the quadriceps femoris
muscle, and hyaline cartilage and fibrocartilage taken from the costal cartilage
and the meniscus of the knee joint respectively. A small piece of gelfoam soaked in
a low concentration of chondroitin sulfate (Nutritional Biochemicals Corporation)
was also prepared for transplantation.
The transplants were kept in situ for periods of time varying from 2 to 20 weeks
after the transplantation. The transplants were removed with the surrounding
connective tissue and kidney, fixed in 10% formalin or Zenker's fixative,
decalcified in 5% nitric acid solution, and embedded in paraffin. The blocks were
serially sectioned 5 micra thick and the sections were stained with
Group Ⅰ: Fresh autogenous cortical bone transplantation. The bone pieces
measured about 3x2x2 mm. were removed from the anterior portion of the tibia and
transplanted. Four weeks after the transplantation the peripheral portion of the
graft underwent certain degrees of the absorption and showed an uneven bone
surface. The lacunae of the central portion of the graft were empty and no living
osteocytes were observed in them. However, lacunae of the peripheral portion
containing living osteocytes were easily found. Evidence that the newly formed bone
was deposited on the surface of the graft, was observed. Eight weeks after the
transplantation, the original graft was found to be further replaced by the newly
formed bone and showed a more progressive absorption of the graft. In addition to
the progressive absorption, evidence of an intramembranous ossification near the
graft was confirmed. Twenty weeks following the transplantation, the most
peripheral portion of the graft was replaced by newly deposited bone in which a
Haversian system and newly organized red bone marrow were observed.조
Group Ⅱ: Boiled autogenous cortical bone transplant. The bone pieces, obtained a
s Group Ⅰ, were boiled in distilled water for 30 minutes before the
transplantation. After 4 weeks the lacunae were empty and no living osteocytes were
found in them. Bone absorption of the peripheral portion of the graft was observed,
accompanied by infiltration of probable osteoclasts or giant cells and a few
leucocytes in the surrounding connective tissue. There was no positive indication
of new bone formation. Eight weeks after the transplantation, the bone absorption
of the graft had progressed further. Also, new bone formation around or in the
graft was not found.
Group Ⅲ: Fresh autogenous periosteum transplantation. A small piece of
periosteum was carefully removed from the anterior portion of the tibia and grafted
into the subcapsular site of the host kidney. Four weeks after the transplantation,
newly formed bone embedded in the dense connective tissue, which might corresponded
to the grafted periosteum, was observed. After 8 weeks the bone formation had
progressed and a Haversian system was formed in the new bone.
Group Ⅳ: Fresh autogenous hyaline cartilage transplantation. A small piece of
hyaline cartilage, measuring about 3x2x2mm. in size, carefully obtained from the
costal cartilage, was grafted. Four weeks after the transplantation, the cartilage
showed certain degrees of absorption. However new bone formation around the grafted
cartilage was not observed. After 8 weeks the grafted cartilage showed entirely
empty lacunae and matrix was heavily calcified. The absorbed peripheral portion of
the graft showed new bone formation. The new bone formation was observed in the
area of the graft where the absorption of the cartilage took place.
Group Ⅴ: Fresh autogenous fibrocartilage transplantation. A small piece of
fibrocartilage(the same size as the hyaline cartilage) was obtained from the
meniscus of the knee joint and grafted. After 4 weeks there was no evidence of
production of newly formed bone around the graft. After 8 weeks the newly formed
bone had developed around the grafted fibrocartilage.
Group Ⅵ: Fresh autogenous uncrushed muscle tissue transplantation. A small piece
of skeletal muscle taken from the quadriceps femoris, was grafted. In no
experimental case of this group there was any evidence of new bone formation.
Group Ⅶ. Fresh autogenous crushed skeletal muscle transplantation. A small piece
of skeletal muscle taken from the same place as group Ⅵ, was crushed and grafted.
In these experimental cases the absorption of the grafted muscle tissue was more
rapid than in the cases of the Group Ⅵ. As in Group Ⅵ no evidence of new bone
formation was observed.
Group Ⅶ: Transplantation of gelfoam soaked in chondroitin sulfate. Six weeks
after the trasplantation, the grafts were completely absorbed without new bone
Observations were made on the incidence of bone formations as well as on the
histological processes involved in osteogenesis following the transplantation of
autogenous transplants of fresh cortical bone, boiled bone, fresh hyaline
cartilage, fibrocartilage, and skeletal muscle. In addition gelfoam containing
chondroitin sulfate was grafted and checked for new bone formation.
1) The author obserred new bone formation 4 weeks following transplantation of
autogenous fresh cortical bone and periosteum, and 8 weeks following
transplantation of autogenous fresh hyaline cartilage and fibrocartilage.
2) In the experiment of autogenous skeletal muscle and boiled cortical bone, no
evidence of new bone formation was found in the graft. Gelfoam with chondroitin
sulfate grafts were absorbed with no new bone formation.
3) Most of the transplanted bone underwent devitailzation and degeneration, and
subsequently bone formation and bone resorption which led eventually to complete
replacement of the original transplanted bone by new bone.
4) New bone formation observed in cases of fresh autogenous cortical bone and
periosteum transplantation indicates that it is directly derived from the grafts.
This supports the osteoblastic theory.
5) However, new bone formation observed in case of hyaline cartilage and
fibrocartilage is attributed to the mechanism of induction.