inion compared with titanium osteosynthesis1

8/7/2019 INION COMPARED WITH TITANIUM OSTEOSYNTHESIS1

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H. Leonhardt, A. Demmricha,Mueller , R. Maia, R. Loukota, U. Eckelt

British Journal of Oral and Maxillofacial Surgery 46 (2008) 631634


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Titanium or steel osteosynthesis was usedroutinely for treatment of mandibularfractures.

Corrosion and the spread of titanium into thetissues, thermal paraesthesia, the need toremove the plate, and interference withcomputed tomograms (CT) led to the search forbiocompatible systems of osteosynthesis.


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Resorbable materials were established inmaxillofacial surgery, initially in craniofacialsurgery and then in the treatment of midfacial

fractures and orthognathic surgery.Eppley BL. Use of a resorbable fixation technique for maxillary fractures.J Craniofac Surg 1998;9:31721

Reports of the use of resorbable systems in

mandibular fractures have recently beenpublished

Laughlin RM, Block MS, Wilk R, Malloy RB, Kent JN.Resorbable plates for the fixation of mandibular fractures: aprospective study. J Oral Maxillofac Surg 2007;65:8996


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Poly-(DL)-lactide polymers are degraded byhydrolysis in vivo to -hydroxiacides and thento water and carbon dioxide.

Within the first three days after implantationmechanical stability increased, after which thebiomechanical rigidity is similar to that oftitanium plates


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The INION system is available in 3 differentsizes: 1.5 mm, 2 mm, and 2.5 mm.

The screw holes are drilled with conventionaldrills and tapped.

Placement of the plate on the lateralmandibular surface is possible using an angled

screwdriver.


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Patients with fractures of the mandibular body,from one mandibular angle to the other, wereincluded in this study.

Patients in the INION group had 37mandibular fractures (1 symphyseal, 14parasymphyseal, and 22 of the mandibularangle).

Seven patients had double fractures.

The mean time between accident and treatmentof the fracture was 2.5 days (range 0 to 12)


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In the titanium group 44 fractures were treated(21 parasymphseal and 23 mandibular angle).

Fourteen patients had double fractures.

The mean time between the fracture and theoperation was 2.3 days (range 0 to 6)

The displacement of the fractures between the

two groups was similar.


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Fractures were treated by open internal fixationunder general anaesthesia.

The miniplates were adapted to the bone andthe reduced fracture was fixed by insertingmonocortical screws according to Champysprinciples.


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Osteosynthesis was achieved with 2.0mm and2.5mm INION plates.

The plates consisted of L-polylactide,

DLpolylactide, and trimethylenecarbonate.

In the other group, only 2.0mm titaniumminiplates were used.

Any abnormality of wound healing was classedas a dehiscence.


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All patients were examined at 1 and 6 weeksafter operation.

At 6 months, there were only 17 patients in the

INION group and 21 patients in the titaniumgroup.

The median inpatient treatment time of the

patients in the INION group was 7 days(range 1 to 14), and in the titanium group 7days (range 2 to 17).


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In the INION group there were 12 objective and13 subjective disturbances of occlusion after oneweek.

All patients were treated with elastic intermaxillaryfixation (IMF) for a week, and after 6 weeks onlyone objective and two subjective malocclusionswere recorded.

After 6 months all patients had perfect occlusions.


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In the titanium group there were 6 objective and7 subjective malocclusions after a week.

These patients were treated with elastic IMF for

a week.

There were 2 objective and 4 subjectivemalocclusions after 6 weeks, but no

malocclusion could be detected objectively orsubjectively at 6 months.


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11 dehiscences were found in the INIONgroup after a week. One patient had a purulentwound infection and one a massive

haematoma. After 6 weeks only two patients had

dehiscences.


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When the 2.0mm INION plates were placedon the lateral surface of the mandible therewere only 4 dehiscences and no plate

exposures.


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In the titanium group 12 dehiscences weredetected after a week, including three woundinfections, and one haematoma.

At 6 weeks there was only one wounddehiscence and none after 6 months.


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All patients had a soft postoperative swelling aweek after operation.

At the final follow up there were 4 dense

swellings in the INION group.


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One patient treated with INION had the plateremoved after 3 weeks because it was exposed.

The fracture was already stable and no new

osteosynthesis was required.

4 exposed INION plates from the obliqueridge had to be removed between 3 and 6months, but this had no effect on the healing ofthe fracture.


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Four titanium miniplates were removed earlybecause of problems with wound healing.

The earliest was 2 weeks after operation, and a

new osteosynthesis was required.

The others were removed between 6 weeks and4 months postoperatively


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There were twice as many malocclusions in theINION group after the first week, which ispossibly related to the material itself.

The self-reinforced poly-L/DL-lactideosteosynthesis materials gain their finalstability after 3 days in place.*

*Wood GD. Inion biodegradable plates: the first century. Br J OralMaxillofac Surg 2006;44:3841


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Postoperative IMF for 3 to 5 days should beused to prevent material deformities.

Disturbances of occlusion were treated by

elastic IMF for 1 week.

Reason for the postoperative disturbances ofocclusion could be the postoperative oedema ofthe TMJ after reposition of the condylar neck orangle fractures.


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Both groups developed dehiscences andproblems with wound healing, but withincreased experience with INION plates, it

was found that adequate soft tissue closureprevents problems with healing.

Inflammation of the tissue caused by theresorbable material, as described by othergroups does not seem to be a problem whenthere is adequate soft tissue coverage.


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Degradation of the INION plates seems to beresponsible for the higher rate of long-lastingsoft tissue swellings.

Disadvantages of biodegradable materials- Incresed cost

- Breakage of screws

- More difficult operative handling- Swelling of the plate during degradation


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Characteristics of Ideal Osteofixation Devices Should be able to meet the biomechanical demands, Not cause tissue responses necessitating removal of the

device

Be easy to use and handle Be cost-effective Be compatible with radiotherapy and imaging

techniques (Edwards and David, 1996; Pietrzak et al.,1997).

Degrade in a predictable fashion Allow for safe progressive loading during each stage of

bone healing Disappear completely.


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POLYDIAXANONE

POLYGLYCOLIC ACID

POLYLACTIC ACID

SELF REINFORCED PLA

SELF REINFORCED PGA


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There are occasions when metal implants have to beremoved- palpability,- patient sensitivity,

- imaging interference or- infection, etc.

Stress shielding may result in bone atrophy andosteoporosis but a slowly degrading polymer implantslowly loads the bone therefore assisting in the healingprocess.


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High modulus of elasticity of metals comparedto bone, results in the implant retaining a largefraction of the mechanical load applied to the

bone. This is known as the stress shieldingeffect

It leads to bone resorption, implant looseningand, consequently, the need for a second

operation.


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Mechanical Aspects

The torsion strengths and stiffnesses of thebiodegradable screws are less favorable (Shetty et

al., 1997) compared with those of titanium screws. This has been reported by several authors as a

disadvantage (Shetty et al., 1997; Bahr et al., 1999).

Biodegradable polymeric screws relax when a

force is continuously applied (Shetty et al., 1997). May result in decreased fracture stability and

possible compromised fracture healing


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A polymer consists of many small repeatingunits called monomers.

Polymers consisting of only one kind of

repeating units are called homopolymers. Copolymers are formed from two or more

different repeating units.


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TMC will add ductility to Inion implants.


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The implants initially lose molecular weight,then strength and finally mass.

The implant mass usually starts to reduce at 35

weeks. As a guide the resorption times of theimplants are 2 to 4 years.


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PGA -> URINE

glycolic acid

Glyoxylate Polylactic acid H2O + CO2

Glycine lactic acid

Citric Acid CycleSerine

Pyruvate Acetyl-CoA


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The development of adverse tissue responses seems to originate from severaldifferent physiologic and chemical processes. Crystalline remnants and adecrease of pH (Taylor et al., 1994) during degradation are probablyresponsible for the adverse effects of biodegradable polymers, although thelocal tissue tolerance and the local clearing capacity seem to be importantaspects as well (Bostman et al., 1990; Pihlajamaki et al., 1992; Bergsma et al.,

1995; Matsusue et al., 1995).T

he quantity of crystalline remnants and the rateof pH decrease are partly determined by the molecular structure of thebiomaterial (Vert et al., 1992). Amorphous polymers degrade faster thancrystalline polymers, resulting in a rapid decrease in pH. Crystallinepolymers may remain in situ for decades (Pietrzak et al., 1997). A high bloodflow rate is an essential prerequisite for successful implantation ofbiodegradable fixation materials, since adequate blood flow securessufficient removal of degradation products, thereby preventing a decrease in

pH () Bostman and Pihlajamaki, 2000b). Poly DL-Lactide acid (PDLLA)implants enriched with calcium phosphates to prevent a local decrease in pHhave been investigated in rats (Heidemann et al., 2001). The control groupreceived pure PDLLA implants. The PDLLA implants enriched with calciumphosphates showed a more severe tissue response after 72 wks. The authorsconcluded that the enriched implants are not suitable for clinical use.


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Onset of infections occur later in thebiodegradable groups. Norholt et al., 2004suggested that it could be caused by the

ongoing degradation of the plates and screws The known causes of infection are loosened

screws and wound dehiscence (Cheung et al.,2004).


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All Inion implants are packaged for single useonly.

This prevents the potential cross infection riskand alleviates problems of decontamination.


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The implant body is radiolucent.

The screw holes can be seen in post operativeX-rays.


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Thank you!

inion compared with titanium osteosynthesis1

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