PolyPIN

PolyPIN is a bioresorbable bone pin from polylactide. Metal implants are normally removed in a second operation, once the bone has healed.
This not only means additional expense, but is also stressful for the patient!

What is more, a second stay in hospital is necessary to remove the metal, involving absence from work and increased risk of complications.

The ideal osteosynthesis implant should, therefore, simply dissolve after it has fulfilled its stabilising or fixing task, without subjecting the body to an additional burden in doing so. The Polypin is such an implant.

It is a pin made of a polylactide copolymer (Poly L/D, L- Lactide 70/30). Thanks to the material it is made of and the way it is designed, it offers significant advantages.

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Indications

The PolyPIN special design is its distinguishing feature and improves its performance:

The head exerts a slight compression on the facture fragments.

The circular ribs prevent the PolyPIN from slipping.

The Polypin is available in three different diameters:

PolyPIN 1.5, length: 8 – 25 mm

PolyPIN 2.0, length: 10 – 35 mm

PolyPIN 2.7, length: 12 – 60 mm

Fractures subject to low load stresses: PolyPIN 1.5
Fixation of bony or osteochondral fragments: e.g. fractures to the heads of metacarpal bones, arthrodeses of fingers and toes, stabilising of certain finger factures, osteochondral factures or dissections eochondral fractures or dissections.

Apical fragements, osteochondral fractures or dissections: PolyPIN 2.0
Apical fragments: e.g. fractures of the radial head, fracture of the patella rim, fractures at the proximal and distal ends of the metatarsal and metacarpal bones.

Osteochondral fractures or dissections:
e.g. ankle-bone dome, femoral condyle, cancellous fragments or those subject to low stresses: e.g. layered reconstruction of fractures of the heel or acetabulum, corticocancellous grafting of chips.

Large osteochondral fragments: PolyPIN 2.7
Large osteochondral fragments: e.g. fractures of the femur head (Pipkin fractures), fractures of the malleolus (Weber A fractures), fractures of the radius, longitudinal fractures of the patella.

Material / Effect

The PolyPIN is made of polylactide, an absorbable biomaterial which has proved its worth as a material for biological implants, as shown by extensive in vitro an in vivo testing an in clinical use over several years. The special copolymer (Poly L/D, L- Lactide 70/30) has good absorption properties:

Its flexural strength remains constant for 24 weeks, which is a sufficient time for the fracture to heal, and then drops at a constant rate.

Degradation

Biological degradation takes place mainly due to hydrolysis, into lactic acid, which is a natural product of metabolism, and is subsequently metabolised into CO₂ and H₂O. Within 15 months the Polypin is completely degraded from a mechanical point of view, although it can still be detected in the form of a cylindrical fragment of the original pin.

After 18 to 21 month only fibrous cords are recognisable and after another three months the place of implant is filled with bony substance. Studies have shown that the same results are achieved both by the Polypin and a metal implant, but in the case of the Polypin no implantdependent complications arise.

Design

The PolyPIN special design is its distinguishing feature and improves its performance:

The head exerts a slight compression on the facture fragments
Circular ribs prevent the PolyPIN from slipping

The Polypin is available in three different diameters:

1.5 mm PolyPIN, length: 8 - 25 mm
2.0 mm PolyPIN, length 10 - 35 mm
2.7 mm PolyPIN, length: 12 - 60 mm

Application

Drilling
After reducing the fragments, drill a hole of the same diameter as the PolyPIN.

Diameter 1,5 mm for the PolyPIN 1.5
Diameter 2,0 mm for the PolyPIN 2.0
Diameter 2,7 mm for the PolyPIN 2.7

perpendicular to the surface of the fracture. If more than one PolyPIN is used, the drilled holes should not run parallel, but converge, to ensure secure fixation of the fragment.

Length measurement
After loosening the locking screw, insert the measuring tip of the appropriate depth gauge as far as possible to the end of the drilled hole. The depth of the drilled channel can then be determined. Tighten the locking screw. In this way, the measured length is transferred directly to the cutting guide secured at the rear. The PolyPIN is then sheared to about 1 mm less than the measured drilling depth

Shortening the PolyPIN
Push the PolyPIN head first as far as the stopper in the mounting at the rear end of the measuring device. Secure by means of the locking screw. Position the shearing head so that the arrow marked on it is visible.

Turn the shearing head in the direction of the arrow to shear the PolyPIN to the requiered length.

WARNING: Do not turn the shearing head in the opposite direction to the arrow. This could press the PolyPIN against the locking screw and cause
deformations.

Adjusting the tip of the PolyPIN
Adjust the pin using the sharpener to simplify insertion. Once the cut – off part has been removed, withdraw the pin sligthly from the depth gauge and then secure again by means of the locking screw. Then adjust sligthly using the sharpener as you would a pencil sharpener.

Impacting the PolyPIN
The respective special impacting device and a hammer must be used to insert the PolyPIN. Remove the pin from the impactor and insert the PolyPIN tip first into the casing from the rear. Insert the pin again and push it forwards slowly until the tip of the PolyPIN into the drilled hole and place the impacting device over the hole, perpendicular to the fragment surface. Make sure that the PolyPIN does not become jammed while it is being hammered in. Then carefully hammer the PolyPIN into the drilled channel until the head is below the level of the surface of the fragment.

WARNING: Oblique positioning may cause the impacting device to slip resulting in the PolyPIN being broken and the white cap for the impacting
device damaged.

Figure 1: Drilling