The objective of this study was to evaluate two calibration methods for the “Arthroscopically Implantable Force Probe” (AIFP) that are potentially suitable for in vivo use: (1) a direct, experimentally based method performed by applying a tensile load directly to the graft after it is harvested but prior to implantation (the “pre-implantation” technique), and (2) an indirect method that utilizes cadaver-based analytical expressions to transform the AIFP output versus anterior shear load relationship, which may be established in vivo, to resultant graft load (the “post-implantation” technique). The AIFP outputs during anterior shear loading of the knee joint using these two calibration methods were compared directly to graft force measurements using a ligament cutting protocol and a 6 DOF load cell. The mean percent error ((actual – measured)/(actual) * 100) associated with the pre-implantation calibration ranged between 85 and 175 percent, and was dependent on the knee flexion angle tested. The percent error associated with the post-implantation technique was evaluated in two load ranges: loads less than 40 N, and loads greater than 40 N. For graft force values greater than 40 N, the mean percent errors inherent to the post-implantation calibration method ranged between 20 and 29 percent, depending on the knee flexion angle tested. Below 40 N, these errors were substantially greater. Of the two calibration methods evaluated, the post-implantation approach provided a better estimate of the ACL graft force than the pre-implantation technique. However, the errors for the post-implantation approach were still high and suggested that caution should be employed when using implantable force probes for in vivo measurement of ACL graft forces.

1.
Beynnon, B. D., Howe, J. G., Pope, M. H., Johnson, R. J., and Fleming, B. C., 1991, “The Development and Initial Testing of a New Sensor to Simultaneously Measure Strain and Pressure in Ligaments and Tendons,” Proc. 1st Combined Meeting of the Orthopaedic Research Societies, Banff, Oct. 21–23.
2.
Bylski-Austrow
D. I.
,
Grood
E. S.
,
Hefzy
M. S.
,
Holden
J. P.
, and
Butler
D. L.
,
1990
, “
Anterior Cruciate Ligament Replacements: A Mechanical Study of Femoral Attachment Location, Flexion Angle at Tensioning, and Initial Tension
,”
J. Orthop. Res.
, Vol.
8
, pp.
522
531
.
3.
Fleming
B. C.
,
Beynnon
B. D.
,
Howe
J. G.
,
McLeod
W. D.
, and
Pope
M. H.
,
1992
, “
The Effect of Tension and Placement of a Prosthetic Anterior Cruciate Ligament on the Anteroposterior Laxity of the Knee
,”
J. Orthop. Res.
, Vol.
10
, pp.
177
186
.
4.
Fleming
B. C.
,
Beynnon
B. D.
,
Tohyama
H.
,
Johnson
R. J.
,
Nichols
C. E.
,
Renstrom
P.
, and
Pope
M. H.
,
1994
, “
The Determination of a Zero Strain Reference for the Anteromedial Band of the Anterior Cruciate Ligament
,”
J. Orthop. Res.
, Vol.
12
, pp.
789
795
.
5.
Glos
D. L.
,
Butler
D. L.
,
Grood
E. S.
, and
Levy
M. S.
,
1993
, “
In Vitro Evaluation of an Implantable Force Transducer (IFT) in a Patellar Tendon Model
,”
ASME JOURNAL OF BIOMECHANICAL ENGINEERING
, Vol.
115
, pp.
335
343
.
6.
Good
L.
, and
Gillquist
J.
,
1995
, “
In Vitro Correlation Between Tension and Length Change in an Anterior Cruciate Ligament Substitute
,”
Clin. Biomech.
, Vol.
10
, pp.
200
207
.
7.
Herzog
W.
,
Archambault
J. M.
,
Leonard
T. R.
, and
Nguyen
H. K.
,
1996
a, “
Evaluation of the Implantable Force Transducer for Chronic Tendon-Force Recordings
,”
J. Biomech.
, Vol.
29
, pp.
103
109
.
8.
Herzog
W.
,
Hasler
E. M.
, and
Leonard
T. R.
,
1996
b, “
In-Situ Calibration of the Implantable Force Transducer
,”
J. Biomech.
, Vol.
29
, pp.
1649
1652
.
9.
Holden
J. P.
,
Grood
E. S.
,
Korvick
D. L.
,
Cummings
J. F.
,
Butler
D. L.
, and
Bylski-Austrow
D. I.
,
1994
, “
In Vivo Forces in the Anterior Cruciate Ligament: Direct Measurements During Walking and Trotting in a Quadruped
,”
J. Biomech.
, Vol.
27
, pp.
517
526
.
10.
Holden
J. P.
,
Grood
E. S.
, and
Cummings
J. F.
,
1995
, “
Factors Affecting Sensitivity of a Transducer for Measuring Anterior Cruciate Ligament Force
,”
J. Biomech.
, Vol.
28
, pp.
99
102
.
11.
Lewis
J. L.
,
Lew
W. D.
, and
Schmidt
J.
,
1982
, “
A Note on the Application and Evaluation of the Buckle Transducer for Knee Ligament Force Measurement
,”
ASME JOURNAL OF BIOMECHANICAL ENGINEERING
, Vol.
104
, pp.
125
128
.
12.
Penner
D. A.
,
Daniel
D. M.
,
Wood
P.
, and
Mishra
D.
,
1988
, “
An in vivo study of anterior cruciate ligament graft replacement and isometry
,”
Am. J. Sports Med.
, Vol.
16
, pp.
238
243
.
13.
Peura, G. D., Fleming, B. C., and Beynnon, B. D., 1995, “Measurement of Load in Soft Tissue With the Arthroscopically Implantable Force Probe,” 2nd Combined Meeting of the Orthopaedic Research Societies, San Diego, Nov. 6–8.
14.
Platt
D.
,
Wilson
A. M.
,
Timbs
A.
,
Wright
I. M.
, and
Goodship
A. E.
,
1994
, “
Novel Force Transducer for the Measurement of Tendon Force In Vivo
,”
J. Biomech.
, Vol.
27
, pp.
1489
1493
.
15.
Roberts
C. S.
,
Cummings
J. F.
,
Grood
E. S.
, and
Noyes
F. R.
,
1994
, “
In Vivo Measurement of Human Anterior Cruciate Ligament Forces During Knee Extension Exercises
,”
Trans. Orthop. Res. Soc.
, Vol.
19
, p.
84
84
.
16.
Shino
K.
,
Hamada
M.
,
Tanaka
M.
,
Matsui
Y.
, and
Doi
T.
,
1993
, “
In Vivo Direct Measurement of Load Applied to ACL Grafts
,”
Trans. Orthop. Res. Soc.
, Vol.
18
, p.
2
2
.
17.
Tohyama
H.
,
Beynnon
B. D.
,
Fleming
B. C.
,
Peura
G. D.
,
Johnson
R. J.
, and
Pope
M. H.
,
1994
, “
Evaluation of the Arthroscopic Force Probe: A Study of the Factors That Affect the Measurement of Tendon and Ligament Forces In Vivo
,”
Trans. Orthop. Res. Soc.
, Vol.
19
, p.
644
644
.
18.
Wallace
M. P.
,
Howell
S. M.
, and
Hull
M. L.
,
1996
, “
In Vivo Tension Measurements in a Double-Looped Hamstrings Graft for Anterior Cruciate Ligament Replacement
,”
Trans. Orthop. Res. Soc.
, Vol.
21
, p.
74
74
.
19.
Xu
W. S.
,
Butler
D. L.
,
Stouffer
D. C.
,
Grood
E. S.
, and
Glos
D. L.
,
1992
, “
Theoretical Analysis of an Implantable Force Transducer for Tendon and Ligament Studies
,”
ASME JOURNAL OF BIOMECHANICAL ENGINEERING
, Vol.
114
, pp.
170
177
.
This content is only available via PDF.
You do not currently have access to this content.