iComparison of Growth Factor and
Platelet Concentration From Commercial
Platelet-Rich Plasma Separation Systems
Tiffany N. Castillo,* Michael A. Pouliot,* MD, Hyeon Joo Kim,* PhD, and Jason L. Dragee,*1" MD
Investigation performed at Stanford University, Department of Orthopaedic Surgery,
Palo Alto, California
Background: Clinical studies claim that platelet-rich plasma (PRP) shortens recovery times because of its high concentration of
growth factors that may enhance the tissue repair process. Most of these studies obtained PRP using different separation systems, and few analyzed the content of the PRP used as treatment.
Purpose: This study characterized the composition of single-donor PRP produced by 3 commercially available PRP separation systems.
Study Design: Controlled laboratory study.
Methods: Five healthy humans donated 100 ml_ of blood, which was processed to produce PRP using 3 PRP concentration systems (MTF Cascade, Arteriocyte Magellan, Biomet GPS III). Platelet, white blood cell (WBC), red blood cell, and fibrinogen concentrations were analyzed by automated systems in a clinical laboratory, whereas ELISA determined the concentrations of
platelet-derived growth factor aB and SB (PDGF~aB, PDGF-BB), transforming growth factor B1 (TGF-B1), and vascular endothelial
growth factor (VEGF).
Results: There was no significant difference in mean PRP platelet, red blood cell, active TGF-B1, or fibrinogen concentrations
among PRP separation systems. There was a significant difference in platelet capture efficiency. The highest platelet capture efficiency was obtained with Cascade, which was comparable with Magellan but significantly higher than GPS 111. There was a significant difference among all systems in the concentrations of WBC, PDGF-aB, PDGF-pB, and VEGF. The Cascade system
'concentrated leukocyte-poor PRP, compared with leukocyte-rich PRP from the GPS 111 and Magellan systems.
Conclusion: The GPS III and Magellan concentrate leukocyte-rich PRP, which results in increased concentrations of WBCs,
PDGF-aB, PDGF-BB, and VEGF as compared with the leukocyte-poor PRP from Cascade. Overall, there was no significant difference among systems in the platelet concentration, red blood cell, active TGF-B1, or fibrinogen levels.
Clinical Relevance: Products from commercially available PRP separation systems produce differing concentrations of growth
factors and WBCs. Further research is necessary to determine the clinical relevance of these findings.
Keywords: platelet-rich plasma; growth factors; platelet-rich plasma separation system
Platelet-rich, plasma (PRP) has been recognized as a powerful adhesive and hemostatic agent since the 1970s28 and as
a potent source of autologous growth factors since the
1990s.30'35 The concentrated levels of platelet-derived
growth factor aB and BB (PDGF-aB, PDGF-BB), transforming growth factor pi (TGF-B1), and vascular endothelial
growth factor (VEGF) found in PRP are known to play
a critical role in cell proliferation, chemotaxis, cell differentiation, and angiogenesis.88
Consequently, there has been strong clinical interest in
the use of PRP as a growth factor delivery medium to aid in
tissue regeneration. Platelet-rich plasma was first recognized as an effective agent for bone and tissue repair
within the field of dentistry and oral maxillofacial surgery.15'35 Its applicability then spread to the fields of plastic surgery by demonstrating evidence of improved skin
graft wound healing.20
Within the field of orthopaedic surgery, the potential role
of PRP in enhancing the healing of bone, muscle, ligaments,
and tendons has resulted in a number of studies within virtually all the orthopaedic subspecialties. Platelet-rich
plasma has been reported to improve recovery from joint
replacement,4 spine surgery,21 and fracture healing.14'28
However, the greatest interest in PRP now appears to He
within the field of sports medicine, where recovery time
and return to play are often critical considerations in patient
care.6'16 A number of studies have reported favorable clinical
outcomes with the use of PRP in anterior cruciate ligament
reconstruction,11'26'29 as well as in the treatment of acute8
and chronic tendinopathies9'27 and muscle strains.7'17124
f Address correspondence to Jason L. Dragoo, MD, Assistant Professor, Department of Orthopaedic Surgery, Stanford University, 450 Broadway, MC 6342, Redwood City, CA 94063 (e-mail: [email protected]).
'Department of Orthopaedic Surgery, Stanford University, Palo Alto,
California.
One or more authors has. declared a potential conflict of interest: Arteriocyte, MTF Sports Medicine, and Biomet Orthopaedics provided the
personnel support and platelet-rich plasma separation system equipment
used in this study.
'The American Journal of Sports Medicine, Vol. 39, No. 2
D01: 10.1177/0363546510387517
© 2011 The Author(s)
266
Vol. 39, No. 2, 2011
involved in the present study performed the imaging
described in this work as part of interdepartmental
arrangements.
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For reprints and permission queries, please visit SAGE's Web site at http://www.sagepub.eom/joiLmalsPe:rmissions.nav
, No, 2, 2011
Comparison of Growth Factor and Platelet Concentration 267
TABLE 1
Protocols for Tested Platelet-Rich Plasma Separation Systems®
System, Company
Whole Blood
Volume, mL
Anticoagulant
Centrifuge Force, g
Centrifuge Time,
Minutes
Final Volume of
PRP, mL
18
55
26
Sodium citrate, 2 mL
ACD-A, 5 mL
ACD-A, 4 mL
1100
1100
1200
6
15
17
7.5
6.0
6.0
Cascade, MTF
GPS III, Biomet
Magellan, Arteriocyte
"Activator not used. PRP, platelet-rich plasma; ACD-A, anticoagulant citrate dextrose solution A.
However, these studies used different PRP separation
systems, with little or no characterization of the content of
the PRP used as therapy. Not only does this make it difficult
to compare the results of these studies, but it perpetuates
the lack of standardization in PRP dosing, which further
complicates the ability to interpret the literature and compare clinical findings. As discussed by Dohan Ehrenfest
et al,10 there are substantial differences in the content of
platelet concentrates produced by the various automated
and manual protocols described in the literature. One
important distinction is whether a PRP preparation is leukocyte-rich or leukocyte-poor. Because leukocytes are
known to produce VEGF34 and have antimicrobial properties,25 they may play an important role in further enhancing
the tissue repair processes, but they may also lead to
increased local inflammation.
Several studies13'19'31 have demonstrated a difference in
the platelet and growth factor concentrations in PRP produced by platelet separation systems. However, these analyses included either expensive cell separator systems not
practical for clinical use or manual protocols with unreliable reproducibility. The studies also focused on comparing
PRP platelet concentration (PC) and yield and did not analyze the difference in PRP leukocyte or fibrinogen concentrations, which are important components of PRP.
The purpose of this study was to characterize the
platelet, white blood cell (WBC), fibrinogen, and growth
factor concentrations in the PRP produced by 3 commercial PRP separation systems, using a single-donor
model.
MATERIALS AND METHODS
Participant Recruitment
After institutional review board approval was obtained, 5
healthy humans (4 men, 1 woman, 25 to 39 years old)
who were not taking medication consented to donate
100 mL of blood by venipuncture. Pour companies were
invited to participate in the study, and three (MTF Sports
Medicine, Edison, New Jersey; Biomet Orthopaedics Inc,
Warsaw, Indiana; Arterioeyte Inc, Cleveland, Ohio) agreed
to participate and provide the equipment for their respective PRP separation systems, as well as a product repreI sentative to perform sample processing. One company
(Arthrex) elected not to participate in the study, stating
internal company reasons.
Sample Collection
All participants donated blood on the same day, and each
sample was processed immediately after collection. A single technician collected 100 mL of blood from each participant using an 18-gauge arteriovenous fistula needle (JMS
SysLoc, Hayward, California). Approximately 1 mL of
whole blood was used for whole blood platelet analysis,
1.5 mL for fibrinogen analysis, 18 mL for processing
through the MTF Cascade system, 26 mL for the Arteriocyte Magellan system, and 55 mL for the Biomet GPS III
system.
Platelet Separation Systems
Whole blood samples were collected with the appropriate
ratio of anticoagulant, and each sample was simultaneously processed using the MTF Cascade, Arteriocyte
Magellan, and Biomet GPS III PRP separation systems
according to the manufacturer's protocol (Table 1) to produce PRP and, in the case of the Biomet system, plateletpoor plasma (PPP) as well. A representative from each
company performed their respective sample processing
under direct observation of the study personnel. All PRP
and PPP samples were stored at -80°C for future analysis
to determine the concentration of PDGF-ap, PDGF-pp,
active TGF-pl, and VEGF.
Quantification of Platelet, WBC, Red Blood Cell, and
Fibrinogen Concentration
All whole blood, PRP, and PPP samples were sent to the
University Hospital Clinical Laboratory immediately after
collection for platelet count, WBC, red blood cell (RBC),
and fibrinogen concentration analysis. Platelet, WBC,
and RBC counts were performed using a Coulter LH780
Hematology Analyzer (Beckman Coulter, Brea, California).
Fibrinogen concentration was determined by an assay performed using a STA-R Evolution Analyzer (Diagnostica
Stago, Parsippany, New Jersey).
Quantification of Growth Factors
The PRP and PPP growth factor (PDGF-a{3, PDGF-|3B,
active TGF-pl, and VEGF) concentrations were determined
by ELISA, performed according to the manufacturer's
The American Journal of Sports Medigine
268 Castillo et al
TAELE2
Mean Platelet, Red Blood Cell, White Blood Cell, and Fibrinogen Concentration in Whole Blood,
Platelet-Rich Plasma, and Platelet-Poor Plasma
Platelet
Concentration
(X 103/(o,L)
Factor Increase
in Platelet
Concentration
Platelet Capture
Efficiency (%)
"White Blood Cells
(X 108VL)
Red Blood Cells
(X 106/|xL)
Fibrinogen
(mg/dL)
—.
51,.9 ± 24.8
— .
—
6.4 ± 2.3
15.5 ± 16.8
0.2 ± 0.1
.09
4.35 ± 0.4
0.7 ± 1.1
0.01 ± 0.02
< .0001
239.2 ± 69.0
282.4 ± 33.7
287.1 ± 53.4
.18
67,.6 ± 4.1
22..6 ± 11.8
65.5 ±19.6
< ,.0001
1.1 ± 0.2
34.4 + 13.6
11.0 ± 8.2
< .0001
0.1 ± 0.1
1.5 ± 1.7
0.5 ± 0.3
.10
283.8 ± 34.2
286.0 ± 42.7
277.4 ± 30.5
.93
Blood Product
Whole Wood
2Y3.8 ± 7.4
—
X 2.2 ± 0 .9
Platelet-rich plasma
596.7 ± 250.4
—
Platelet-poor plasma
45.2 ± 6.5
Pa
< .0001
—
Platelet-rich plasma by separation system, company
X 1.62 ± 0.1
Cascade, MTF
443.8 ± 24.7
GPS in, Biomet
566.2 ± 292.6
X 2.07 ± 1.1
X 2.8 ± 0.8
Magellan, Arteriocyte
780.2 ± 246.5
-P6
.09
.09
aFrom
6From
analysis of variance comparison of means among whole blood, platelet-rich plasma, and platelet-poor plasma.
analysis of variance comparison of means among platelet-rich plasma separation systems.
protocol (R&D Systems, Minneapolis, Minnesota). Baseline
whole blood and additional growth factor concentrations
were not analyzed in this study, to limit the required blood
draw volume for a given participant, as required by our
institutional review board. PDGF-a(3, PDGF-|5|3, TGF-(31,
and VEGF were selected for analysis because they have
been the most widely studied growth factors that play central roles in tissue repair and have consistently been
detected in elevated concentrations in pRp.13.32>38 Plateletderived growth factor is a potent chemotactic agent and regulator of cell growth and division18; TGF-pl is involved in
cell proliferation and division, apoptosis, and immune cell
regulation6; and VEGF is an important signaling factor for
angiogenesis.34 Although other growth factors found hi platelets—such as insulin-hke growth factor, fibroblast growth
factor, and epidermal growth factor—could have been studied, they have been found to have much more variable concentrations in PRP6'12 and were thus excluded from this
analysis. Moreover, insulin-like growth factor 1 concentration is affected by exercise8 and nutritional status, which
could not be controlled for ha our study population. For
each assay, PRP samples and standards were added hi
duplicate to a plate precoated with antibodies to the growth
factor being measured. Unbound substances were removed,
and an enzyme-linked polycolonal antibody was added.
After a second wash was performed, a substrate solution
was added. A stop solution was added to stop the color development. The intensity of color in each well was measured
with a spectrophotometer (SpectraMax MZe, Molecular
Devices, Sunnyvale, California) set to 450 nm and a wavelength correction of 540 nm.
Statistical Analysis
Data were analyzed with SPSS 17.0 (SPSS Inc, Chicago,
Illinois). Difference in mean platelet, WBC, RBC, fibrinogen, and growth factor concentration among PRP separation systems was analyzed by 1-way analysis of variance
(ANOVA) and post hoc Bonferroni testing. Linear
correlations between PC and growth factor concentration,
as well as WBC and growth factor concentration, were
analyzed with Pearson correlation. Significance was set
at P < .05.
RESULTS
Each system produced 6.0 to 7.5 mL of PRP per whole
blood sample, even though the starting whole blood volume
was different from each system (55 mL for the GPS III,
26 mL for the Magellan, and 18 mL for the Cascade).
Platelet Concentration
The overall average PRP PC (596.7 X 103/jil,) was significantly higher than the baseline whole blood PC (273.8 X
W%L) and PPP PC (45.2 X 10s/|xL, P < .001; Table 2).
Analysis of variance revealed no significant difference hi
mean PRP PC among systems (P = .09). Pairwise analysis
using Bonferroni post hoc testing also confirmed that there
was no significant difference hi mean PC between any of
the systems. The mean PRP PC from the Magellan was
the highest -(780.2 X 10S/^L), followed by the GPS IE
(566.2 X 103/|xL) and the Cascade (443.8 X 103/|xL). There
was wide variability hi the factor increase in PC among
the PRP separation systems, which ranged from a 1.06- to
4.1-fold increase from baseline PC. Moreover there was a
significant difference hi platelet capture efficiency—
(volumepKp X [plateletp^MvolumewBc X [platelet^c])—
among systems (P < .0001). The highest platelet capture
efficiency was obtained with the Cascade, which was comparable with the Magellan (P = .08) but significantly higher
than the GPS HI (P < .0001).
WBC Concentration
There was no significant difference hi mean WBC concen- (
tration between whole blood and PRP (P = .06; Table 2),
but there was a significant difference in mean WBC
, No. 2, 2011
Comparison of Growth Factor and Platelet Concentration 269
TABLES
Mean Platelet-Rich Plasma Growth Factor Concentrations, ng/mLa
Separation System, Company
Cascade, MTF
GPS III, Bipmet
Magellan, Arteriocyte
Comparison, P
Among all systems (analysis of variance)
Cascade vs GPS III
Cascade vs Magellan
GPS III vs Magellan
PDGF-ap
PDGF-pp
TGF-pl
VEGF
9.7 ± 3.6
18.7 ± 12.8
34.4 ± 10.7
14.8 ± 2.5
23.1 ± 10.1
33.0 ± 8.2
0.1 ± 0.08
0.1 ± 0.08
0.2 ± 0.1
0.3 ± 0.3
2.4 ± 1.1
1.2 ± 0.8
.006
.52
.006
.08
.009
.33
.008
.20
.37
.99
.97
.54
.005
.004
.28
.12
aPDGF-ap and PDGF-f 3, platelet-derived growth factor ct|3 and PP; TGF-pl, transforming growth factor; VEGF, vasctdar endothelial
growth factor.
concentration in all PEP (15.5 X 108/puL) compared with
PPP (0.2 X 10s/|xL, P = .003). In comparing the mean
WBC concentration in PRP among all separation systems,
there was a significant difference by ANOVA (P < .001)
and pairwise analysis. The Cascade produced PRP with
the lowest mean WBC concentration (1.1 X 108/|xL), compared with that of the GPS HI (P < .001) and the Magellan
(P = .34). The GPS III produced PRP with highest mean
WBC concentration (34.4 X 103/iai>), which was significantly
higher than that of the Magellan (11.0 X 103/pi, P = .005).
) RBC Concentration
The whole blood mean RBC concentration (4.35 X 106/fiL)
was significantly higher than the mean RBC concentration
in PRP (0.7 X 106/|xL, P < .001), which was also significantly higher than the mean RBC concentration in PPP
(0.01 X 106/plj, P = .03; Table 2). All systems produced
PRP with similarly low RBC concentrations (P = .10).
.006 and P = .008, respectively) and comparable with those
of the GPS HI (P = .08 and P = .20). There was no difference
in mean PDGF-«p or PDGF-pp concentration between the
Cascade and the GPS HI (P = .52 and P = .33, respectively).
The GPS III produced PRP with the highest VEGF concentration, which was significantly higher than that of the Cascade (P = .004) but not significantly different than that of the
Magellan (P = .12). There was no significant difference in
mean PRP VEGF concentration between the Cascade and
the Magellan (P = .28). As expected, there was no PDGFap, PDGF-pp, TGF-pl, and virtually no VEGF (0.01 ±
0.02 ng/mL) detected in the PPP produced from the GPS HI.
There was a significant positive correlation between PC
and PDGF-ap, PDGF-pp, VEGF, and TGF-pl concentration
(R = .96, .99, .75, .95, respectively; P < .01). Correlation of
PRP WBC and growth factor concentration demonstrated
a positive correlation between WBC and VEGF (R = .88,
P = .01) as well as with PDGF-pp (R = .43, P = .05), but
there was no significant correlation between WBC and
TGF-pl (R = .14, P = .51) or PDGF-ap (R = .37, P = .07).
Fibrinogen Concentration
H
Mean whole blood fibrinogen concentration (239.2 mg/dL)
did not differ significantly from the PRP or PPP mean
fibrinogen concentrations (282.4 mg/dL and 287.1 mg/dL,
respectively, P = .18; Table 2). There was also no difference
in mean fibrinogen concentration between PRP and PPP
(P = .86) or mean PRP fibrinogen concentration among
PRP systems (P = .93).
Growth Factor Concentrations
Overall there was a significant difference among PRP systems in mean concentrations of PDGF-ap (P = .006),
PDGF-pp (P = .009), and VEGF (P = .005) (Table 3). However, there was no significant difference in mean TGF-pl
concentration among any of the systems by ANOVA (P =
.37) or pairwise analysis. The Magellan produced PRP with
the highest mean PDGF-ap and PDGF-pp concentrations,
which were significantly higher than the mean PDGF-ap
and PDGF-pp concentrations produced by the Cascade (P =
>
DISCUSSION
Currently, there are more than 16 available platelet separation systems that produce differing types of platelet-rich
concentrates. It is essential to better characterize the content of PRP produced by the various commercial systems to
make more informed decisions regarding its use in the clinical setting. Although this study used a single-donor protocol in which only a few systems were concurrently tested,
all available PRP separation systems should be subject to
the same level of investigation.
The results of this study demonstrated no overall significant difference in PRP PC among the 3 studied PRP separation systems, which was a surprising finding given
that they each started with a different whole blood volume
(18 mL for the MTF Cascade system, 26 mL for the Arteriocyte Magellan system, and 55 mL for the Biomet GPS III)
and yet produced comparable volumes of PRP (6.0 to
7.5 mL). However, calculation of the platelet capture efficiency for each system explained this finding because the
270 Castillo et al
Cascade and Magellan systems, which, start with smaller
whole blood volumes, have higher platelet capture efficiencies. Consequently, the volume of whole blood required to
produce a desired volume of PRP and the ability to reliably
predict platelet capture efficiency are practical considerations for surgeons to take into account when comparing
PRP separation systems and counseling patients about
their predicted PRP content with a given system.
The most noteworthy finding in the study was the significant difference among systems in PRP WBC concentration.
The Cascade system decreased the PRP WBC concentration
6-fold when compared with whole blood, whereas the GPS
III and Magellan systems increased the PRP WBC concentration 5-fold and 2-fold, respectively. This illustrates that
the Cascade system produces leukocyte-poor PRP whereas
the GPS III and Magellan systems produce leukocyte-rich
PRP, which may explain the need for greater starting volumes of whole blood in the GPS III and Magellan systems.
The clinical implications of these differences are unknown
and merit further investigation.
Arguments can be made both for and against concentrating WBCs in PRP. It is possible that WBCs play a valuable
antimicrobial role in PRP treatment. The concentrated presence of leukocytes can provide a local environment at the
site of PRP injection with increased immunomodulatory
capability that may aid in preventing or controlling infection at the identified site of injury. This would be of theoretic advantage in clinical scenarios where PRP is used as
an adjunct treatment with invasive procedures that
increase the chance of infection (eg, anterior cruciate ligament or Achilles repair). It is also possible that WBCs
enhance PRP growth factor concentrations through thenown release of growth factors or by stimulating platelet
release of growth factors. Zimmermann et al36 found
that WBC concentration in PRP accounted for one-third to
one-half the variance of growth factor concentration. The
leukocyte-rich PRP systems (GPS III and Magellan) demonstrated significant increases in the concentrations of PDGFap, PDGF-PP, and VEGF, compared with leukocyte-poor
PRP concentration (Cascade). The significant positive correlation between WBC concentration and VEGF and PDGFPP concentrations explains some of this observed difference
in growth factor concentration between the leukocyte-rich
and leukocyte-poor systems. This finding reinforces the
observation by Zimmermann et al that WBC concentration
may account for increased growth factor concentrations in
leukocyte-rich PRP and thus be a reason to use leukocyterich PRP to optimize growth factor concentrations.
Conversely, it is possible that WBCs—namely,
neutrophils—may impede tissue recovery by increasing local
inflammation and therefore not be a desired component in
PRP treatment. Currently, there are no controlled animal
studies to discern whether leukocyte-rich PRP increases
inflammation, compared with leukocyte-poor PRP. Additionally, clinical studies are necessary to differentiate soft tissue
healing effects of leukocyte-rich versus leukocyte-poor PRP.
In general, our study had a lower mean PRP PC than
that of some studies,12>22>27>S2 especially those that used
cell separators to produce PRP. However, we had a similar
The American Journal of Sports Medicine,
mean PRP PC compared with that found in other studies
using centrifuge separation processes.2'27 Although this
may provide an interesting reference, the utility of these
comparisons is limited given that these studies used different separation systems and different platelet counting
methods. The same limitations hold true for comparing
PRP growth factor concentrations among these studies.
Our PRP samples had markedly lower concentrations of
TGF-pl than those reported in other studies. Given that
we used an ELISA for activated TGF-pl, the low TGF-pl
concentration provides evidence that there was little platelet activation. Because we did not use calcium chloride or
thrombin to activate the platelets, the low level of activation was possibly secondary to platelet exposure to shear
forces during processing.1 We chose not to activate the
PRP, because we believe that it represents a more physiologic delivery of growth factors with platelet activation
over time, as opposed to our causing release of all growth
factors with artificial chemical platelet activation.6 Interestingly, our samples contained greater PDGF-ap and
VEGF levels than those of a previous report using unactivated PRP,13 which may again indicate that some platelets
were activated by mechanical forces during processing.
The other unique finding in this study was that there
was no significant difference in PRP fibrinogen concentration among systems, as well as no difference in fibrinogen
concentration in PRP compared with whole blood or PPP.
Thus, these systems seem to produce PRP with similar concentrations of adhesive proteins and are likely to produce
similar fibrin matrices, which is an important consideration
in the application of PRP therapy. Because fibrinogen was
the only studied protein present in a substantial concentration in PPP, the only indication to save and administer PPP
would be to deliver additional fibrinogen.
The small sample size of this study limits its ability to
detect differences among systems. Nonetheless, its strength
is its use of single donors to test all systems concurrently,
where participants serve as their own controls, which helps
to minimize the potential confounding variables when making comparisons among the tested PRP systems. The lack of
a baseline whole blood growth factor concentration limited
our ability to demonstrate the magnitude of increase in
growth factor concentration in the PRP; however, this was
less important because the samples were drawn and processed from the same 5 donors simultaneously. Therefore,
the relative concentration of the growth factors should be
comparable among the different systems.
Larger future studies are necessary to further characterize the intersystem and intrasystem variability in platelet, WBC, and activated and unactivated growth factor
concentrations in the PRP extracted from commercial
PRP separation systems. Further studies are also necessary to distinguish the indications and clinical utility of
leukocyte-rich versus leukocyte-poor PRP. Ultimately, ran- ,
domized controlled clinical trials are needed to establish
the optimal PRP dosing for the treatment of orthopaedic |
injuries that may benefit from PRP therapy. However, ha^^
the design of these studies, it is critical to characterize^H
the platelet, WBC, and growth factor content of the PRP "
Vol. 39, No. 2, 2011
produced by the chosen commercial separation systems.
This will provide an accurate context for physicians to
interpret the results and thereby make informed decisions
about when to use the various PEP separation systems to
provide effective PRP treatment.
ACKNOWLEDGMENT
We thank Arteriocyte, MTF Sports Medicine, and Biomet
Orthopaedics for providing the personnel support and
platelet-rich plasma separation system equipment that
made this study possible. We are also grateful to Tracy
George, MD, and Jerrold Michaud of the Stanford Hospital
and Clinics Clinical Laboratory for performing the platelet
count and fibrinogen analysis.
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Comparison of In Situ Forces and Knee
Kinematics in Anteromedial and High
Anteromedial Bundle Augmentation for
Partially Ruptured Anterior Cruciate
Ligament
Yan Xu,*f MD, PhD, Jianyu Liu,** MD, PhD, Scott Kramer,* Cesar Martins,* MD,
Yuki Kato,* MD, PhD, Monica Linde-Rosen,* Patrick Smolinski,* PhD, and
Freddie H. Fu,*§ MD
Investigation performed at the University of Pittsburgh, Pittsburgh, Pennsylvania
Background: High tunnel placement is common in single- and double-bundle anterior cruciate ligament (ACL) reconstructions.
Similar nonanatomic tunnel placement may also occur in ACL augmentation surgery.
Purpose: In this study, in situ forces and knee kinematics were compared between nonanatomic high anteromedial (AM) and
anatomic AM augmentation in a knee with isolated AM bundle injury.
Study Design: Controlled laboratory study.
Methods: Seven fresh-frozen cadaver knees were used (age, 48 ± 12.5 years). First, intact knee kinematics was tested with
a robotic-universal force sensor testing system under 2 loading conditions. An 89-N anterior load was applied, and an anterior
tibial translation was measured at knee flexion angles of 0°, 30°, 60°, and 90°. Then, combined rotatory loads of 7-N-m valgus
and 5-N-m internal tibial rotation were applied at 15° and 30° of knee flexion angles, which mimic the pivot shift. Afterward,
only the AM bundle of the ACL was cut arthroscopically, keeping the posterolateral bundle intact. The knee was again tested
using the intact knee kinematics to measure the in situ force of the AM bundle. Then, arthroscopic anatomic AM bundle reconstruction was performed with an allograft, and the knee was tested to give the in situ force of the reconstructed AM bundle. Knee
kinematics under the 3 conditions (intact, anatomic AM augmentation, and nonanatomic high AM augmentation) and the in situ
force were compared and analyzed.
Result: The high AM graft had significantly lower in situ force than the intact and anatomic reconstructed AM bundle at 0° of knee
flexion (P < .05) and the intact AM bundle at 30° of knee flexion under anterior tibial loading. There were no differences between
anatomic graft and intact AM bundle. The high AM graft also had a significantly lower in situ force than the intact and anatomic
reconstructed AM with simulated pivot-shift loading at 15° and 30° of flexion (P < .05). Under anterior tibial and rotatory loading,
there was a difference in tibial displacement between anatomic and high AM reconstructions and between the high AM graft and
intact ACL under rotational loading with the knee at 15° of flexion.
Clinical Relevance: Anatomic AM augmentation can lead to biomechanical advantages at time zero when compared with the
nonanatomic (high AM) augmentation. Anatomic AM augmentation better restores the knee kinematics to the intact ACL state.
Keywords: anterior cruciate ligament; augmentation; partial rupture; in situ force; biomechanics
The anterior cruciate ligament (ACL) consists of 2 functional bundles: the anteromedial (AM) bundle and the posterior lateral (PL) bundle. The 2 bundles have their
distinct femoral and tibial insertion sites and are separated by a fine septum.11'29 Each bundle contributes to
the overall biomechanical function of the ACL. Previous
studies14'25 showed that the AM bundle has higher levels
of in situ forces during knee flexion whereas the PL bundle
supports high in situ forces at 0°, 15°, and 30°
and decreases at greater angles of flexion. The PL
especially contributes to the rotational stability of the
knee at 0° to 30° of flexion; both bundles contribute to
§Address correspondence to Freddie H. Fu, MD, Department of
Orthopaedic Surgery, University of Pittsburgh Medical Center, 3471 Fifth
Avenue, Suite 1011, Pittsburgh, PA 15213 (e-mail: [email protected]).
"University of Pittsburgh, Pittsburgh, Pennsylvania.
flnstitute of Sports Medicine, Peking University Third Hospital, Beijing, China.
*Second Affiliated Hospital of Harbin Medical University, Harbin,
China.
The authors declared that they had no conflicts of interest in their,
authorship and publication of this contribution.
The American Journal of Sports Medicine, Vol. 39, No. 2
DOI: 10.1177/0363546510383479
©2011 TheAuthor(s)
272