The document discusses biocomposite interference screws which are used for anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) reconstruction. The screws are composed of 70% poly-L-lactide-co-D,L-lactide (PLDLA) polymer and 30% biphasic calcium phosphate (BCP) ceramic. This composite is osteoconductive and degrades over 12-16 months, replacing the screw with new bone formation. The polymer and ceramic components, along with the screw's macro-porous design, enhance mechanical strength while promoting bone ingrowth. Studies show the biocomposite screws integrate well with bone with less inflammation compared to polymer screws alone.

1. 1Biocomposite Int. Screw | Ahmed ELSokkary
A Stronger turn in ACL / PCL Reconstruction
Orthopedic biomaterials should be aimed at engineering the material properties and degradation
characteristics to improve fixation and bony integration avoiding any adverse reactions.
BioComposite 70% PLDLA & 30% BCP
(PLDLA; 70:30 PLLA: PLDA) ---- (BCP; 60:40 HA: B-TCP)
70% Polymers (PLDLA) 30% Ceramic (BCP)
PLA exists in two isomeric forms, L-lactide (PLLA) and
D-lactide (PLDA)
Ceramics such as hydroxyapatite (HA) and Beta-
tricalcium phosphate (B-TCP)
70% PLLA 30% PLDA 60% HA 40% B-TCP
L-lactide is more
commonly found and
semi-crystalline, has a
prolonged degradation
time.
D-lactide is much less
common and amorphous.
HA is crystalline and has a
slow resorption rate on the
order of years, ideal for
maintaining structure,
but can lead to ingestion of
ceramic particulates by
surrounding tissues.
B-TCP is amorphous and
resorbs quickly, not
leaving enough time for
new bone to replace the
material in the defect site
(that define the reason of
fibrous tissue replacement
to product made from B-
TCP only )
Material Composition
BioComposite
Interference Screw
TM

2. 2Biocomposite Int. Screw | Ahmed ELSokkary
WHY…….?!
Main Properties of Biocomposite Int. Screw
70:30 PLLA: PLDA Ratio?
• Combining just these PLA isomers alone can alert
degradation time and mechanical strength.
• This ratio in our BioComposite Interference Screw
results in Retention of ½ of its tensile strength after 32
weeks and ½ of its shear strength after 45 weeks in
vitro.
• Has a degradation time of 12-16 months, compared to
PLLA: 36-60 months (in vitro).
• Completely replaced by new bone at 36 months in vivo.
• No crystalline degradation product buildup at the implant
site.
• Greatly reduces chance of osteolytic lesions frequently
seen with rapidly absorbing polymers.(PGA)
The Essential addition of BCP to PLDLA in Biocomposite screw is
Osteoconductive.
60:40 HA: B-TCP Ratio?
• Ceramics such (HA) and (B-TCP) are commonly used as
bone void filler materials (bone graft) because of their
excellent bone biocompatibility and similarity in
mineral content to natural bone.
• Combining of HA and B-TCP in 60:40 ratio would be
ideal. A new class of ceramic materials, biphasic calcium
phosphates (BCPs) Shows:
- A range of controllable resorption profiles, with
adequate degradation over HA or B-TCP alone.
- New bone formation without a fibrous interface at
earlier time points as opposed to HA or B-TCP Alone.
- Good integration between newly formed bone within
the degrading material and existing bone.
- Provides superior balance of osteoblast adhesion and
proliferation over HA or ß-TCP alone
-Higher compressive strength and Higher mechanical
strength compared to pure HA.
70:30 PLDLA: BCP Ratio?
• The ratio of polymer to ceramic in a composite material should be optimized for mechanical strength and material behavior.
Either lowering or raising the amount of polymer and/or ceramic material can affect strength at the interface by making the
screw brittle or pliable, or possibly increase resorption via acidosis. Polymer degradation that occurs too quickly can lead to a pH
drop, therefore increasing the activity of osteoclasts to resorb tissue and screw material and weaken the interface.
• Combining the inherent degradation characteristics of a biocompatible polymer with the bioactivity of a ceramic.
Note: As BCP content increases in PLDLA materials, ultimate tensile strength decreases, but is still
within range for bone fixation materials.

3. 3Biocomposite Int. Screw | Ahmed ELSokkary
Advantage of Biocomposite Int. Screw
2- Absorbs predictably over time 3- Little to no inflammatory response
Has a degradation time of 12-16 months, compared to
PLLA: 36-60 months, Completely replaced by new bone
at 36 months.
Compared with the well-documented inflammatory
response seen with bioabsorbable polymers, several
studies have failed to observe adverse clinical reactions with
biocomposites or have shown only a mild reaction.
Histologically, less inflammatory response was seen in
Biocomposites than with PLLA alone.
The explanation: The release of basic salts by the
degradation of the bioceramic may buffer the acidic
breakdown products of the polymers. So ceramic work as
PH buffering causes less toxicity.
4- Mineralization 5- Controlled Solubility
A statistically significant higher level of mineralization
and bone in-growth was observed in the Biocomosite
group compared to the PLLA group at 6 and 12 months in
both femur and tibia.
Molecular weight (MW) and Inherent viscosity (IV) drop
slowly and uniformly from time 0 up to 12 weeks, with
maintain mechanical strength.
Early bone formation Due to Favorable osteoconductive and bioresorbable properties within BCP. The explanation:
A- Bioactive ceramics have been studied
extensively for use as bone-graft
substitutes. Whereas bioabsorbable
polymers are surrounded by a fibrous
layer, bioactive ceramics spontaneously
form a bone-like apatite layer from
amorphous calcium phosphate on their
surface, which bonds directly to and
integrates with the bone matrix.
B- Both HA and B-TCP have
excellent osteoconductivity
because of the release of calcium
and phosphate when degraded
which encourages mineralization
and provides a scaffold for bone
growth. This degradation is
osteoclast mediated and similar to
that of normal bone.
C- The increased calcium
levels with degradation
potentiate chemotaxis and
differentiation of osteoblasts.
F- The mineral matrix may also
mimic the interactions of
osteoblasts with normal bone and
regulate intracellular signal
transduction and gene
transcription, enhancing bone
production. (In vitro studies
show amounts of human
osteoblast adhesion after 24
hours and proliferation after 48
hours)
D- Serum protein adhesion
to HA be almost 60 times
greater than adhesion to
titanium and many of these
proteins are important for
directing the differentiation of
osteoblasts.
E- Biocomposites show
increased contact area
compared with polymers.
1- Osteoconductive

4. 4Biocomposite Int. Screw | Ahmed ELSokkary
6- High strength 7- Macro and Micro porous role
Biocomposite has High tensile strength and shear
strength which prevent postoperative damage or
migration.
The combination of ceramics with biodegradable polymers
adds significant strength to the implant by virtually
eliminating stress risers while creating a macro and micro
porous matrix to aid in the bone remodeling and
replacement process. (it allows for faster resorption of the
calcium phosphate (Ca-P) components and better bony
ingrowth)8- Able to carry growth factors.
SEM: 25x Magnification
Hexalobe Driver Interface of the BioComposite Screw
9- Innovative Design
Which Prevent Intraoperative screw breakage, provide strong fixation, easer insertion.
• The material blending and binding process is optimized to
increase mechanical strength without becoming brittle, creating
a homogenous blend of the components throughout the
implant.
• A macro and micro porous structure is formed promoting cell
adhesion and proliferation.
• Unmatched thread shear and blunting resistance.
• Optimized thread form to ease insertion and maximize
soft tissue and bone fixation in cortical and cancellous
bone.
• A stepped taper design of the screw maximizes
insertion torque as the screw is fully seated.
• Material strength allows for implantation without
tapping in most circumstances.
• The cannulated hexalobe drive system enhances the screw family by providing one universal drive system for all screws
and significantly improved torsional and insertion strength. Each screw fully seats on and is completely supported along the
entire length of the driver tip.
- Mechanical Testing
Testing found that 10 mm BioComposite Delta Screws, using a hexalobe driver, had a lower cyclic displacement and higher
loads-to-failure compared to Milagro screws.
23 mm, 28 mm Full Thread,
28 mm Round Delta Tapered,
35 mm Delta Tapered Screws and
20 mm BioComposite Retro Screw

5. 5Biocomposite Int. Screw | Ahmed ELSokkary
Disadvantage of Bio-interference Screw
Comparable with Biocomposite Screw
Amorphous PLLA - Biodegradable – Bioabsorbable
Despite their routine use, a major concern with bioabsorbable materials in surgery has been
the incidence of adverse events. Various case reports, series reports and studies in the past
years have reported complications specific to the use of bioabsorbable interference screws
intra operatively and at different time periods post operatively. Although bioabsorbable
screws promise to degrade within months up to several years after implantation, often this
does not exactly happen. In fact, other problems such as screw breakage, tunnel enlargement,
allergic or foreign body reactions, cyst or abscess formation, and delayed migration of
‘‘biodegradable’’ screws have been reported. As followed:-
1- Prolonged degradation Time
2- Intraoperative screw breakage
(damage) 7%
Prolonged degradation Time 4-5 years in vivo and
complete resorb at 7-10 years
The most common complications of using PLLA screws
in ACL reconstruction described in literature are intra
operative screw damage around 7%
3- Postoperative late damage to the
screw, intraarticular migration
4- Bony replacement of the screw doesn’t
always occur – bone tunnel widening
(Within 3-23 months) manifested by (Pain, swelling,
mechanical complain, may appear like palpable mass)
When complete reabsorption is seen, screws were not
replaced with bone but instead consisted of a partially
calcified fibrous tissue.
5- Fixation less secure
Lower mechanical strength and ligament laxity
6- Inflammation
• The accumulation of the degradation products can cause adverse reactions. Foreign-body reactions osteolytic, synovitis,
intraosseous cyst formation, intra-articular inflammatory reactions, systemic allergic response, and loose intra-articular foreign
bodies are sometimes seen.
• These reactions are thought to be due to the acidic nature of the byproducts during implant degradation. This may also interfere
with bone formation (Polymer degradation that occurs too quickly may decrease the local pH at the surgical repair site, thereby
increasing the activity of osteoclasts to resorb tissue and screw material, weaken the interface, and induce inflammation)
• Reaction rates to polylactic acid (PLA) have been reported in literature to range from 0%4to 0.04%, 0.2%, 1.2%, 3.7%, and
even as high as 16.2% and 60%.
Data compiled from June 2004 through October 2011. The following reaction rates were observed:
Bio = 12 per million implants, BioComposite = 10 per million implants By Arthrex R & D :
Material Units Sold Reactions
Bio 5,854,541 69
BioComposite 1,104,118 11

6. 6Biocomposite Int. Screw | Ahmed ELSokkary
Conclusion
BioComposite interference Screw has the same advantage of the bio-interference Screw
like Biocompatible (Amorphous PLLA) – Bioabsorbable, Nonobstructive in imaging,
Nonobstructive in subsequent surgeries, Wide range of material properties, Metal-like
mechanical properties are achievable, Positive clinical results, various degradation profiles,
Minimal damage to graft tissue, not need to revision surgery in addition to that the
properties of combining polymers (PLDLA) and BCP which is Osteoconductive ( bone
graft substitutes) has ability to completely replacement by new bone formation without
fibrous tissue , less or no inflammatory response, less degradation time, Forms a strong
dynamic interface with bone, high mechanical strength, perfect Geometry Design,
according to a lot of studies it Has no disadvantage compared with other screws. It is the
combination between the design and material which grantees: The integrity of the screw
during the insertion, the tissue regrowth, the stability of fixation.
References:
[1] “Arthrex Bio and BioComposite Implants : Post-Op Complaint Analysis,” p. 2012, 2012.
[2] Arthrex Research and Development, “Arthrex BioComposite Interference Screws for ACL and PCL
Reconstruction.”
[3] J. a. Hunt and J. T. Callaghan, “Polymer-hydroxyapatite composite versus polymer interference screws in
anterior cruciate ligament reconstruction in a large animal model,” Knee Surgery, Sport. Traumatol. Arthrosc.,
vol. 16, no. 7, pp. 655–660, 2008.
[4] S. Konan and F. S. Haddad, “A clinical review of bioabsorbable interference screws and their adverse effects in
anterior cruciate ligament reconstruction surgery,” Knee, vol. 16, no. 1, pp. 6–13, 2009.
[5] H. M. D. Pereira, V. M. Correlo, J. Silva-Correia, J. M. Oliveira, R. L. Reis CEng, and J. Espregueira-Mendes,
“Migration of ‘bioabsorbable’ screws in ACL repair. How much do we know? A systematic review,” Knee Surgery,
Sport. Traumatol. Arthrosc., vol. 21, no. 4, pp. 986–994, 2013.
[6] B. I. Screw, “BioComposite Interference Screw,” Delta.
[7] M. Suchenski, M. B. McCarthy, D. Chowaniec, D. Hansen, W. McKinnon, J. Apostolakos, R. Arciero, and A. D.
Mazzocca, “Material Properties and Composition of Soft-Tissue Fixation,” Arthrosc. J. Arthrosc. Relat. Surg., vol.
26, no. 6, pp. 821–831, 2010.
[8] K. Tecklenburg, P. Burkart, C. Hoser, M. Rieger, and C. Fink, “Prospective Evaluation of Patellar Tendon Graft
Fixation in Anterior Cruciate Ligament Reconstruction Comparing Composite Bioabsorbable and Allograft
Interference Screws,” Arthrosc. J. Arthrosc. Relat. Surg., vol. 22, no. 9, pp. 993–999, 2006.