2. Biodegradable implants are derived by transforming
compounds that are present in nature to structural
plastics.
Organic molecules are polymerized to form strong
fibers and solid compounds.
When these polymers are implanted in patients,
they degrade and are eliminated from the body in a
period of time.
3. history
The first biodegradable material was made from
animal intestines and used as a suture material by
Galen in 175 BC.
The first usage of these materials in
orthopaedic surgery was in 1984 by Rokkanen for the
treatment of internal fixation of ankle fractures .
4. materials
Widely used biodegradable materials include
polyglycolic acid (PGA),
poly-L- lactic acid (PLLA),
poly-DL-lactic acid (PDLLA), PGA/trimethylene
carbonate compolymers (PGA/TMC),
poly-p-dioxanone (PDS) and
poly-beta-hydroxybutyric acid (PBHBA).
5. Biodegradable materials need to be hydrolytically
labile and sturdy, at least for a period of time.
To meet these requirements, they are produced by the
“self-reinforcing” (SR)technique .
The biodegradation process takes from one to 6
months starting around 6 onth post op.
This period depends on contact with body
fluids,temperature, motion, molecular weight, crystal
form and geometry of material, and the tissue that is
implanted.
6. biodegradation
begins with the polymer chains being broken into
smaller fragments by hydrolysis--- molecular weight
of the implant decreases --- the mechanical strength
decreases allowing subsequent mechanical
fragmentation and absorption of the implant to begin.
Actual mass loss of the implant occurs through the
release of soluble degradation products,
--phagocytosis by macrophages and histiocytes,
intracellular degradation and finally, metabolic
elimination through the citric acid (Krebs) cycle to
carbon dioxide and water, which are expelled from
the body via respiration and urine.
7. Clinical applications
The mechanical properties of the materials permit
them to be used with metaphyseal and peri-articular
fractures where the loading is relatively low.
For treating small-bone fractures such as ankle
fractures .
Not suitable for comminuted and unstable fractures.
8. Clinical applications
Another suitable anatomic area for application is the
elbow joint, for fixing fractures of the radial head,
olecranon, capitellum and distal humerus.
Comminuted fractures --- not good candidates .
Also #s of the distal radial styloid, patella, glenoid
fossa and acetabulum; osteochondral fractures in the
knee, tibial plateau, phalanx, calcaneus and talus; and
also hallux valgus surgery.
Screws or rods may also be used for epiphyseal #s.
9. Clinical applications
Other uses--- as interference screws in knee ligament
surgery;
for the promotion of osteogenesis in bone defects;
for the slow release of antibiotics and
growth factors; as an antiadhesive
membrane for preventing adhesions in flexor tendon
surgery;
as a matrix for cells in cartilage, bone or connective
tissue engineering.
10. Maintenance of alignment and fixation of bone fractures,
osteotomies, arthrodeses or bone grafts (OTPSTM Pin)
• Maintenance of reduction and fixation of cancellous bone
fractures, osteotomies or arthrodesis of the upper extremity,
ankle and foot (OTPSTM Ankle)
• Bone graft & fragment containment, cement restriction in
total joint arthroplaties, protective barrier for bone graft harvest
sites (OTPSTM Mesh)
• Fixation of non-comminuted diaphyseal fractures of the
metacarpal, proximal phalangeal middle phalangeal and
osteotomies (OTPSTM Hand/Mini)
11. advantages
main advantage of biodegradable implants---
secondary operation for removal not necessary, in
contrast to metallic implants, which need to removed
because of osteopenia, corrosion and irritation of
adjacent tissues.
As biodegradable implants degrade, they lose
strength and this puts loading of bone--- prevent
bone resorption.
Will not interfere wth radiological imaging.
12. disadvantages
Disadvantage ---expensive, having less strength than
metals, tissue reactions, causing osteolysis around the
implant and sterile draining sinuses.
most cases, the symptoms of the tissue reaction are
subclinical and pass unnoticed, but in some patients a
clinically manifest inflammatory foreign-body
reaction ensues.
synovitis when implant is put intra articularly
13. Danger of adverse tissue reaction more if the rate of
implant degradation produces more debris particles
than the tissue is able to tolerate. greatest risk when
the gross geometry of the implant is rapidly lost.
(Böstman and Pihlajamäki 2000, Middleton and
Tipton 2000)
typically manifest in the latter stages of implant
degradation i.e. 6-12 months post operatively. In
children, the tissue reactions appear to be quite rare
(2.1 % of cases with polyglycolide implants) and
always mild in character (Rokkanen et al.
14. rate of bacterial infections not related to the implant
material, same after implantation of metal and
biodegradable materials. (Sinisaari 2004)
In studies concerned with polylactide implants, the
adverse tissue reaction rate has usually been lower
than with polyglycolide
All implants cause tissue response but this varies
radically
15. Phases of Degradation
Phases of Degradation of Amorphous Biodegradable
Implants and Tissue Reactions According to Pistner et
al.47
1. healing phase: Unchanged implant, development
of a fibrous capsule with a high amount of fibroblasts
2. Latency phase : Unchanged implant, fibrous
capsule gets thinner with less cells and more fibers or
direct implant contact to bone
16. 3. Protracted resorptive phase :Mainly central
degradation of the implant, development of cracks,
mild to moderate cellular response with invasion of
macrophages and foreign-body giant cells
4. Progressive resorptive phase : Progressive
disintegration of the implant with a severe tissue
response (macrophages, foreign-body giant cells)
5. Recovery phase :No polymer remnants detectable,
development of scar tissue or osseous replacement of
the former implant site
17. Table 2. Classification of Osteolysis (O)
According to Hoffmann et al. and Weiler et
al.46,69
Osteolysis Radiological Findings
O-0 None
O-1 Mild
O - 2 Moderate
O-3 Severe
O-4 Disturbed healing
No osteolytic changes visible
Mild Osteolytic changes at the
implant site (osteolysis 1 mm or
larger than implant diameter)
Moderate Cystic-like extended
osteolysis (osteolysis 3 mm or
larger than implant diameter
Severe Confluence of osteolysis
into a resorption cavity (if more
than 1 implant is used)
Disturbed healing Fracture
displacement, fragment
sequestration, or healing failure
of soft tissue due to osteolysis .
18. Osseous replacement
During or following implant degradation, osseous replacement
may follow 3 different patterns:
1. There is osseous ingrowth while the implant is degrading .
This phenomenon is most desirable but has rarely been found.
it has only been reported to occur during the degradation of
PLLA-co-PDLLA (70:30) or self-reinforced PLLA/PDLLA
composite rods.50,51
2. There is osseous ingrowth in the center of the former implant
site after the implant is degraded .46
3. There is an osseous scaring of the former implant site with a
slow marginal ingrowth of new bone.This kind of replacement
has been found in cases after an osteolytic lesion has occurred
and may progress over several months or years.46
19. Classification and Treatment of Extra-articular Soft-
Tissue Reactions (EA) According to Hoffmann et al.69
Extra-articular Soft-Tissue
Reactions
Symptoms/Findings/Treatment
EA-0 None
EA-1 Mild
EA-2 Moderate
EA-3 Severe
EA-4 Bacterial
superinfection
No or subclinical reaction
Local, mild soft-tissue induration; no
treatment
Fluctuant swelling, fluid
accumulation (ultrasound), local
warmth, reddening, swelling, pain;
single or repetitive puncture
necessary
Spontaneous discharge of sinus,
primary sterile, secondary possible
bacterial contamination; debridement
and open wound treatment.
Deep soft-tissue/bone infection
following EA-2 or EA-3; extensive and
repetitive debridement
29. A prosthesis is an artificial limb, which is fitted to an
individual who has lost a limb.
A pylon is the member which provides the
connection between the residual limb (leg stump) and
the prosthetic foot.
A method of immediate post op temporary rigid
dressing.
30. Postoperative management of below-knee
amputation varies widely.
Early rehabilitation oriented immediate post op
management.
Pressure bandages do not always remain secure, tend
to apply uneven pressure and may increase stump
edema by a tourniquet effect.
Burgess and Romano (1968) recommended the use of
rigid plaster dressings immediately after operation.
31. Pylon prosthesis
Definite advantages, but there are concerns that it is
technically demanding.
Impractical in hospitals lacking an experienced
orthotist.
Air-splints, Unna paste dressings and removable rigid
dressings recommended, but
most of these also require skilled application, and are
expensive;
some do not allow either full weight-bearing or early
ambulation.
32. Removable rigid dressings (Wu et al 1979 ; Mueller
1982) shorten rehabilitation while allowing frequent
wound inspection
but they do not permit early weight bearing.
inflatable splints (Sher 1974) ---- this airbag apparatus
holds no advantage over conventional dressings.
The plaster-pylon technique --- advantages of rigid
dressings and early weight bearing.
33. Plaster technique.
At the completion of the operation,
gauze dressing is covered with a single layer of cotton
roll and a stockinette bandage.
The stump of the limb is lifted from the table using
the free end of the stockinette sleeve.
34.
35. This is a simple but important step ----prevents
tension, shear stress and any direct pressure over the
transected tibia.
A rigid plaster dressing is then applied, extending to
upper mid thigh.
After operation the patient is allowed up in a chair,
walker or with crutches depending on physical
capability.
36. If no complications the original plaster is removed
one week later for wound inspection.
change of dressing done,
A new well-moulded cast is then applied and a
copper-tube pylon is added.
37. patient is then allowed to
take partial or full weight as is
tolerated, and is encouraged
to continue to walk
throughout his hospital stay.
38. The pylon was applied on
average seven days after
operation (range 4 to 42).
The cast-pylon was changed
weekly until the stump was
ready for fitting with a
temporary prosthesis.
39. estimation of healing time ---- definition of Wu et a!
(1979) who recorded the interval between amputation
and the ordering of a temporary prosthesis.
Rehabilitation time is then defined as that between
amputation and final discharge, walking with a
temporary prosthesis.
For the pylon group, average time for healing was
40.4 days and for rehabilitation was 108.4 days.
For the soft bandage group, average healing time was
98.4 days and average rehabilitation time 200. 1 days.
40. Removable rigid dressings (Wu et al 1979 ; Mueller
1982) are reported to shorten rehabilitation while
allowing frequent wound inspection, but they do not
permit early ambulation.
inflatable splints (Sher 1974) ---- airbag apparatus
holds no advantage over conventional dressings.
41. advantages
Decreases post op edema
Promotes maturation of scar and stump.
Help to produce a non tender stump
Decreases phantom limb sensation
Early adaptation of amputation
The full length of the cast prevents knee flexion
contracture.
Stump healing and rehabilitation time decreas
42. advantages
The plaster-pylon technique advantages of an
immediate fit prosthesis, an inflatable splint device or
a removable rigid dressing,
added benefit that it does not require the services of
a prosthetist for application.
Early postoperative ambulation with full weight-
bearing is possible in most cases at one week.
In addition, the fitting of a pylon, even if the patient
cannot yet stand--- important in maintaining morale
and encouraging efforts to walk
43. advantages
The pylon allows easier transfer of patients from bed
to chair .
Facilitates nursing care, particularly of older patients.
Amputees can learn to balance and begin to walk long
before an artificial leg is available.
Early out-patient management frees expensive
hospital beds.
The materials used for plaster-pylon application are
cheap, readily available in any hospital, and can be
used by paramedical staff without specialised
training.
