Using synthetic bioresorbable polymers for orthopedic tissue regeneration - Durability and Reliability of Medical Polymers - page 126

cells are well differentiated and form an extracellular matrix, while inducing
an abundant formation of bone and bone marrow after one month. However,
the polymers osteoconductive capacity is still lower than long-established
bone graft implants.
tricalcium phosphate (tCP) has also been incorporated into poly( e -
caprolactone), to tailor to the desired degradation and resorption kinetics of
the polymer matrix. 65 this composite improves its biocompatibility and tissue
integration. In addition, the basic resorption products of tCP would buffer
the acidic by-products and help to avoid the formation of an unfavorable
environment for cells.
recently some biosynthetic composites have appeared, such as PCl/
periosteum composites for osteochondral defect repair. In vivo studies on
cylindrical defects created in 10 rabbits showed that PCl-based biocomposites
promote excellent subchondral bone regeneration. 66 research is currently
focused on the synthesis of PCl composites, to combine the versatility of
caprolactone together with the mechanical properties of other polymers.
as poly( e -caprolactone) is another fDa-approved polymer, PCl-Pla
copolymers are primary items of investigation.

6.3.2 Poly( p -dioxanone) (PDS)
Poly( p -dioxanone) (PDS), another polylactone, is synthesized by catalyzed
ring-opening polymerization of p -dioxanone and has gained increasing
interest in the medical and pharmaceutical fields owing to its degradation
to low-toxicity monomers in vivo. 67 this material (fig. 6.5) has about 55%
crystallinity with a glass transition temperature around -5 °C. PDS has a
lower modulus than Pla or PGa, which have a higher degree of stiffness,
and this allowed PDS to become the first degradable polymer to be used
for monofilament sutures.
PDS demonstrated no acute or toxic effects on implantation, and thus has
been used in a number of clinical applications ranging from suture materials
to bone fixation devices. 68 Johnson and Johnson orthopedics provides an
absorbable pin for fracture fixation,58 58 and bone pins have been introduced
into the market under the names orthoSorb and ethipin, respectively, in the
USa and europe. 67 In craniofacial applications, the structure of PDS has
been examined clinically in cranial vault procedures with promising results. 69
advantages include the absence of observed intracranial translocation,
acceptable aesthetic outcomes and low complication rates. nevertheless,

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6.5 Poly( p -dioxanone) (PDS).