MEGA FIX® B –

ART 19-9 06/2014/ EW-E
MEGA FIX® B –
The Bioresorbable Interference Screw
MEGA FIX® B –
The Bioresorbable Interference Screw
The ideal synthesis of:
• Mechanical strength
• Tissue compatibility
• Proven degradation
• Osseous substitution
The MEGA FIX® B screw has been designed to meet the challenges associated with modern
bioresorbable interference screws. The unique CROSSDRIVE® hex-to-tip screwdriver interface,
combined with superior material strength, ensures maximum torsion strength and simplifies
Bone-Tendon-Bone fixation as the screw starts easily. The patented MEGA FIX® B thread
design starts easily while minimizing tissue damage.
Fig. 1
Poly-(L-co-D, L-lactide) implant 15 months after implantation in an animal model. While the implant breaks down into
fragments, there is already an ingrowth of newly formed bone trabeculae (courtesy of W.B. Saunders, Arthroscopy 16:
305-321, 2000).
2 3
Bioresorbable Material – A Decisive Factor
The benefits of bioresorbability are obvious:
• Anatomic joint line fixation of soft tissue grafts
• Undistorted radiological imaging
• Uncompromised revision surgery
• Minimized risk of tissue laceration
Bioresorbable interference screws are becoming increasingly popular due to many advantages
(anatomic joint line fixation of soft tissue grafts, unimpaired check-ups – for example, MRT,
easier revision surgery). However, many of the screws available commercially are not truly
“bioresorbable” as they are made from crystalline poly-(L-lactide) (PLLA). Screws made from
this material could be removed – even after several years – in an almost unaltered form (1-3).
The raw material used to make the bioresorbable interference screw is, therefore, of crucial
importance.
Material
MEGA FIX® B is the first screw to be made from a special amorphous stereocopolymer,
poly-(L-co-D, L-lactide) 70:30). This material and, consequently, the MEGA FIX® B screw
degrades (bioresorbable) protractedly over time without adverse resorption reactions.
Histologically, this is reflected by a very thin bone-transplant interface (3).
Complete Resorption
The complete resorption of highly molecular and crystalline polylactide screws (PLLA
screws) has not yet been established. However, the MEGA FIX® B material (amorphous
stereocopolymer) has demonstrated complete resorption after approx. 18 months (following
implantation in an animal model with a 2.5 year follow-up) (3).
Osseous Substitution
Due to its amorphous polymer structure and its gradual resorption, the material of the
MEGA FIX® B allows a uniform bone ingrowth (3).
Optimal Biocompatibility
Follow-up studies have shown very good biocompatibility (Fig. 2) of the MEGA FIX® B screw
due to the optimal choice of bioresorbable material.
Fig. 2 a-c
Experimental investigation of the MEGA FIX B
screw implanted in a proximal sheep tibia (a).
There is no inflammatory reaction and a
homogeneous osseous encapsulation of the
implant (b). The very thin tissue-implant interface
indicates very good biocompatibility (c).
®
Fig. 2 a
Fig. 2 b
Fig. 2 c
4 5
Optimal Screw Design
Many interference screws have threads that are either too sharp or too blunt. Sharp threads
pose a risk of graft laceration while blunt threads cannot be inserted or are difficult to start.
In contrast to other implants, the MEGA FIX® B screw features a specially patented thread
configuration that combines both sharp and blunt threads (Fig. 3).
• Sharp Threads
Sharp threads at the tip of the screw allow for an easy and safe start of the MEGA FIX® B
screw.
• Smooth Threads
The smooth threads in the remaining screw body ensure atraumatic insertion as well as
sufficient graft fixation.
Minimized Risk of Graft Laceration
The special screw design of the MEGA FIX® B protects the graft during insertion and, at the
same time, permits reliable starting of the screw when insertion begins (Fig. 3).
Fig. 3 b
Fig. 3 a
Figs. 3 a-b
MEGA FIX® B screw design
Optimized Drive
Torsional strength during insertion has been a fundamental problem with various types of
bioresorbable screws. If a brittle, bioresorbable material is used, the screws break when
the torsion limit is exceeded. A soft material will cause the screwdriver to continue to turn
without advancing the screw.
The MEGA FIX® B screws are not only made from a special bioresorbable material
(amorphous stereocopolymer), they also deliver greater torsional stability. The precision-fit,
crosswise drive of the screwdriver (CROSSDRIVE®) was developed for this purpose (Fig. 4).
CROSSDRIVE® ensures excellent force transmission from the driver to the screw.
Comparative tests on the torsional strength of various resorbable screws showed that most
screws available commercially had a maximum torsional strength between 2 and 6 Nm (4). Of
all the screws tested, MEGA FIX® B (tested screw size 8 x 23 mm) with the CROSSDRIVE®
showed an average torsional strength of 9.2 Nm. The MEGA FIX® B screw, therefore, features
the best torsional stability (Fig. 5).
The optimized interface between the screw and the screwdriver prevents the screw from
slipping off the screw driver.
Due to its excellent mechanical properties, the MEGA FIX® B screw enables sufficient fixation
of bone blocks (ACL and/or PCL reconstruction with patellar tendon – BTB technique) as well
as tissue grafts (ACL and/or PCL reconstruction with the hamstring tendons).
Fig. 4 a
Figs. 4 a-b
MEGA FIX® B driver with CROSSDRIVE®.
Fig. 4 b
6 7
Fig. 5
Comparative study of torsional strength of different bioresorbable screws.
Speciﬁc Beneﬁts of MEGA FIX® B
• Extremely high torsional strength
• Optimum interface between MEGA FIX® B and CROSSDRIVE® (screwdriver)
• Minimized risk of graft damage
• High fixation strength
• Extensive area of application:
Due to its high stability and extremely high torsional strength, MEGA FIX® B is ideal for the
fixation of both tendon grafts (hamstring tendons) and bone blocks (patellar tendon – BTB)
in the tunnel.
• Complete resorption
• Bone substitution after resorption
Other indications:
• Hybrid fixation
MEGA FIX® B provides an ideal method for hybrid fixation. For femoral fixation, a
combination with other fixation techniques (e.g., fixation button, transfixation system) has
proved to be successful. For the tibial fixation of a tendon graft (e.g., hamstring tendon),
an additional backup (e.g., knot over a bone onlay, tibial button (ENDOTACK®), screw with
shim) is recommended to prevent possible loosening of the graft.
• Posterolateral reconstruction
• Biceps tenodesis
• Patellofemoral reconstruction with the semitendinosus tendon
MEGA FIX® B – The Bioresorbable Interference Screw
Screwdriver
Diameter
Length
Order no.
9 mm
23 mm
28 mm
2870923 B
2870928 B
8 mm
19 mm
23 mm
28 mm
2870819 B
2870823 B
2870828 B
7 mm
19 mm
23 mm
28 mm
2870719 B
2870723 B
2870728 B
28770 SK
6 mm
19 mm
23 mm
2870619 B
2870623 B
28760 SK
cannulated
28789 SK
8 9
28789 GW
Nitinol Guide Wire, diameter 1.1 mm, length 38.5 cm, for use with
CROSSDRIVE® Screwdrivers 28789 SK, 28770 SK and 28760 SK
28789 KW
Nitinol Guide Wire, short, diameter 1.1 mm, length 25.5 cm, for use
with CROSSDRIVE® Screwdrivers 28789 SK, 28770 SK and 28760 SK
28729 N Notcher, with fin-like blade to assist screw insertion,
working length 15 cm
28729 NM
Chisel, for creating a bone wedge in cruciate ligament
surgery, working length 13 cm
28729 NN
Bone Wedge Chisel, for creating a bone wedge in cruciate
ligament surgery, with wide handle, working length 13 cm
References
1. Martinek V.; Seil R.; Lattermann C.; Watkins S.; Fu F.:
The fate of the poly-L-lactic acid interference screw after anterior cruciate ligament reconstruction.
Arthroscopy 2001; 17: 73-76.
2. Stähelin A.; Weiler A.; Rüfenacht H.; Hoffmann R.; Geissmann A.; Feinstein R.: Clinical
degradation and biocompatibility of different bioabsorbable interference screws: A report
of six cases.
Arthroscopy 1997; 13: 238-244.
3. Weiler A.; Hoffmann R.; Stähelin A.; Helling H.; Südkamp NP.:
Current concepts: Biodegradable implants in sports medicine – The biological base.
Arthroscopy 2000; 16: 305-321.
4. Weiler A.; Windhagen H.; Raschke M.; Laumeyer A.; Hoffmann R.: Biodegradable interference screw fixation exhibits pullout force and stiffness similar to titanium screws.
Am J Sports Med 1998; 26: 119-128.
Additional References:
ENDOWORLD®
- MEGA FIX® P – The Perforated Bioresorbable Interference Screw (ART 22)
- Instruments for use in ACL Reconstruction – Semitendinosus and/or Gracilis Tendon (ART 39)
- Instruments for PCL Reconstruction (ART 40)
- Instrument Set for Anterior Cruciate Ligament Reconstruction: Double-bundle technique (ART 36)
- MEGA FIX® Composite – The Bioresorbable Composite Interference Screw (ART 41)
Doctor-to-Doctor Manual:
J. Richter, M. Imm, M. Schulz:
Double-bundle reconstruction of the ACL with screw fixation close to the joint line
DVD:
KS707: Reconstruction of the anterior cruciate ligament with the 4-fold semitendinosus tendon
KS708: Reconstruction of the anterior cruciate ligament with the quadriceps tendon
KS720: Arthroscopically controlled MPFL reconstruction
KS721: Anatomical reconstruction of the medial patellofemoral ligament (MPFL)
10 11
Notes
It is recommended to check the suitability of the product for the intended procedure prior to use.
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96152016 ART 19-9 06/2014/EW-E
KARL STORZ GmbH & Co. KG
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Phone: +49 (0)7461 708-0
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