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Flexor Tenorrhaphy Tensile Strength: Reduction by Cyclic Loading

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  • Wakefield Orthopaedic Clinic

Abstract and Figures

The integrity of the repair is critical to maintain coaptation of the severed flexor tendon end until healing has advanced sufficiently. In our hospital, we use a modified Savage repair (four-strand Adelaide technique) using 3-0 Ethibond (Ethicon, Somerville, NJ, USA) for acute flexor tenorrhaphy and an active postrepair mobilization protocol. To explain the apparent differences between the theoretical and actual repair strength of a multistrand repair in a single tension test and the reduced strength of a repair subjected to cyclic loading, we compared single and cyclical tensile loading with different suture in vitro configurations of 3-0 Ethibond (Ethicon, Somerville, NJ, USA; one, two, and four strands) and an ex vivo four-strand repair of freshly divided porcine tendon to calculate the ultimate tensile strength (UTS). Mechanical testing was repeated 15 times with both single tensile and cyclical loading for each suture configuration and porcine repair. In the in vitro model, the presence of a knot in a single strand reduced the UTS by 50%. The stiffness of a knotted strand was substantially less than the unknotted strand but became identical after cyclical loading. There was no statistical significance of the UTS between single and cyclical loading with different numbers of strands in this model. In the ex vivo four-strand porcine repair model, there was a significant reduction in UTS with cyclical loading, which equated to the number of strands times the strength of the knotted strand. This discrepancy can be explained by the change in stiffness of the knotted strand after cyclical loading and has important implications for previous studies of suture tendon repair using single tensile loading where the UTS may have been overestimated. We believe that cyclical loading is more representative of physiological loading after acute flexor tendon repair and should be the testing model of choice in suture tenorrhaphy studies.
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ORIGINAL ARTICLE
Flexor Tenorrhaphy Tensile Strength: Reduction
by Cyclic Loading
In Vitro and Ex Vivo Porcine Study
C. E. R. Gibbons &D. Thompson &M. J. Sandow
Received: 2 July 2008 / Accepted: 31 October 2008 / Published online: 17 December 2008
#American Association for Hand Surgery 2008
Abstract The integrity of the repair is critical to maintain
coaptation of the severed flexor tendon end until healing
has advanced sufficiently. In our hospital, we use a
modified Savage repair (four-strand Adelaide technique)
using 30 Ethibond (Ethicon, Somerville, NJ, USA) for
acute flexor tenorrhaphy and an active postrepair mobiliza-
tion protocol. To explain the apparent differences between
the theoretical and actual repair strength of a multistrand
repair in a single tension test and the reduced strength of a
repair subjected to cyclic loading, we compared single and
cyclical tensile loading with different suture in vitro
configurations of 30 Ethibond (Ethicon, Somerville, NJ,
USA; one, two, and four strands) and an ex vivo four-strand
repair of freshly divided porcine tendon to calculate the
ultimate tensile strength (UTS). Mechanical testing was
repeated 15 times with both single tensile and cyclical
loading for each suture configuration and porcine repair. In
the in vitro model, the presence of a knot in a single strand
reduced the UTS by 50%. The stiffness of a knotted strand
was substantially less than the unknotted strand but became
identical after cyclical loading. There was no statistical
significance of the UTS between single and cyclical loading
with different numbers of strands in this model. In the ex
vivo four-strand porcine repair model, there was a
significant reduction in UTS with cyclical loading, which
equated to the number of strands times the strength of the
knotted strand. This discrepancy can be explained by the
change in stiffness of the knotted strand after cyclical
loading and has important implications for previous studies
of suture tendon repair using single tensile loading where
the UTS may have been overestimated. We believe that
cyclical loading is more representative of physiological
loading after acute flexor tendon repair and should be the
testing model of choice in suture tenorrhaphy studies.
Keywords Flexor .Tenorrhaphy.Cyclic loading .Stiffness
Introduction
Maintaining approximation of the severed flexor tendon
ends is critical after repair to achieve healing and there have
been multiple techniques and extensive research to identify
the optimal tenorrhaphy method [3,5,6,13]. Successful
flexor tenorrhaphy can depend on a number of factors
including the tensile properties of suture material, integrity
of each suture grasp, the type of suture repair, and the
surgical expertise available [1,9,11,12]. On the basis of
previous research in our unit, we use a four-strand single
cross grasp suture repair (Fig. 1) modified from the Savage
technique [10], and active mobilization is started as early as
possible (either the same day or day after operation) under
the care of the physiotherapist.
While the in vitro and ex vivo testing of various suture
constructs is important to identify the optimal technique,
the differences between the theoretical and actual repair
HAND (2009) 4:113118
DOI 10.1007/s11552-008-9151-x
M. J. Sandow
Department of Orthopaedics and Trauma,
Royal Adelaide Hospital, The University of Adelaide,
Adelaide, South Australia, Australia
D. Thompson
Department of Mechanical Engineering, University of Adelaide,
North Terrace,
Adelaide, 5000 South Australia, Australia
C. E. R. Gibbons (*)
Department of Orthopaedics and Trauma,
Chelsea and Westminster Hospital,
369 Fulham Road,
London SW10 9RH, UK
e-mail: cergibbons@talktalk.net
strength of a multistrand repair [10] and the apparent
reduced strength on a repair subjected to cyclic loading [4,
8] have not been explained by this previous work. Many
studies have investigated the mechanical properties of
suture repair with single tensile loading [1], but few have
compared single tensile and cyclical loading [8].
To investigate these discrepancies, we assessed the
mechanical performance of our preferred tenorrhaphy
technique during cyclic and static loading in an in vitro
and ex vivo situation. The conduct of this study was to
firstly analyze, in both single tension and cyclic loading
conditions, the mechanical properties of in vitro 30
braided polyester suture material (Ethicon, Somerville, NJ,
USA) with different strand configurations (single strand
without knot, single strand with knot, two strands with
knot, and four strands with knot) and then a four-strand ex
vivo porcine tendon repair.
Methods
The study was conducted in two parts: Firstly, an in vitro
study to test the mechanical performance of the suture
material in various configurations and secondly, an ex-vivo
study to test the performance of the multistrand repair in an
animal tendon model. A Hounsfield mechanical testing
machine (Hounsfield H25KM Universal Testing Machine,
Hounsfield Testing Equipment Ltd, Surrey, UK; Material
Testing System (MTS)) was used to measure stiffness
during cyclic loading and ultimate tensile load both for the
different suture configurations and the porcine four-strand
tendon repairs for both single tensile and cyclical loading
tests, with each particular test being repeated 15 times. A
standardized technique was used for testing both the suture
configurations and tendon repairs, with 30 Ethibond
(Ethicon, Somerville, NJ) suture. Different configurations
of single strand with and without a knot, two strands with a
knot, and four strands with a knot were tested.
The suture was attached to the testing apparatus by
means of two smooth 1 cm bars, 60 mm apart (Fig. 2). In
the tests using a closed loop (i.e., knotted two- and four-
strand knotted repairs), the strands were passed around the
bars. Where the repairs were not a closed loop (i.e., single
strand knotted and unknotted configurations), the free ends
of the two end strands were secured to the bar by multiple
wrapping and then adhesive tape over the entire wrap
(Fig. 3). Preliminary studies showed this technique of
fixation achieved no appreciable creep under the testing
conditions. A minimum of five square throws were
performed to secure the knot where used.
For the single tensile load testing, the suture config-
urations were preloaded to one Newton and then a tensile
force applied until ultimate failure. Cyclical tensile tests
were applied loading at 10 N per strand for ten cycles prior
to loading to ultimate failure. This level of submaximal
cyclic loading was chosen to eliminate the slack within the
knot prior to testing to tensile failure.
It was assumed that at the rate of loading used, the
viscoelastic effect is negligible. The rate of loading used is
best defined as quasistatic and changes within this range
have negligible influence on ultimate tensile strength (UTS)
and construct stiffness. Testing at 500 mm/s would most
likely create different viscoelastic loading effects, but this
was not assessed in this study:
1. In vitro study: The initial study was to assess the in
vitro properties of the commonly used tenorrhaphy
suture, 30 Braided Polyester (Ethibond, Ethicon,
Somerville, NJ, USA), when subjected to testing in
both single tensile and cyclic loading conditions. A
single strand with and without a knot and then two- and
subsequently four-strand configurations were tested
2. Ex vivo study: Thirty porcine forefoot flexor tendons
were freshly prepared which were similar in size and
appearance to human flexor profundus tendon. The
tendons were divided with a sharp blade and a four-
strand Adelaide repair performed with 30 Ethibond
Figure 2 Photograph of a two-strand Ethibond (Ethicon, Somerville,
NJ, USA) suture configuration with knot looped around restraining
bars of Hounsfield tensile machine.
Figure 1 Illustration demonstrating four-strand Adelaide repair used
for flexor tenorrhaphy.
114 HAND (2009) 4:113118
(Ethicon, Somerville, NJ, USA). The tendon ends were
attached to securing clamps of the MTS. Fifteen single
and 15 cyclical tests before loading to ultimate tensile
strength were then applied under standardized conditions.
Using computer software, the results were extrapolated to
produce a load displacement curve for each test
The mean of both the in vitro suture tension tests and ex
vivo four-strand tendon repairs were calculated. Statistical
analysis was applied using the student ttest to compare the
single and cyclical loading tension tests for each suture
configuration or four-strand repair. Using computer soft-
ware, a curve of best fit for each test of the suture
configurations was plotted. This allowed assessment of
stiffness of the particular strand configuration by visualiza-
tion of the slope of the curve at different points.
Quantifying the stiffness is achieved by dividing the load
by the displacement (N/mm).
Results
Each suture configuration was tested to failure following
either a single tension loading or a cyclic loading sequence.
In all knotted strands, failure occurred at the site of the
knot. Quantifying the stiffness is achieved by dividing the
load by the displacement (N/mm). This is simple for linear
materials like the unknotted and perfectly secured unknot-
ted strand (i.e., a 5-mm displacement for 10 N load=2 N/
mm); however, when the knot slips, there is a nonlinear and
unpredictable initial stiffness. The stiffness is initially low
and ramps up to the unknotted equivalent stiffness.
Effect of KnotSingle Strand In Vitro Repair
The mean ultimate tensile load for a single strand 30
Ethibond (Ethicon, Somerville, NJ, USA) was 34 N under
single tensile loading and 36 N under cyclical loading
conditions (n.s. p>0.05). The presence of a knot with a
single strand reduced the ultimate tensile load by approx-
imately 50% (p<0.05) in both cyclic loading and single
tension testing groups (Fig. 4).
Number of Suture Strands
In both single and cyclical loading tests, increasing the
number of strands increased the ultimate tensile load
(Table 1). Doubling the suture strand from single strand to
double strand with knot and from double strand to four
strands with knot slightly more than doubled the ultimate
tensile load.
Single Versus Cyclical Loading
All groups were compared with single tensile and cyclical
loading. There was no statistical difference found with a
single strand, single strand with knot, and double strand
with knot with different loading tests. There was a slight
decrease in ultimate tensile load in the four-strand group
with cyclical loading (Fig. 4), but this was not significant
(p>0.05). With the four-strand tendon (ex vivo) repair,
Figure 4 Bar chart demonstrating effect of cyclic loading on in vitro
strand configurations and four-strand ex vivo porcine repair.
Figure 3 Illustration demon-
strating unknotted and knotted
single suture strand between
restraining bars.
HAND (2009) 4:113118 115115
there was a decrease from 80 N in the single tensile loading
group to 70 N in the cyclical loading group (p<0.05).
Stiffness of Single Strand Group
For the single strand configurations (single strand with and
without knot), all 15 tests were expressed as a linear line of
best fit for a load displacement curve. The relative stiffness
of the suture material was represented by the slope of the
load displacement curve. It was found that the knotted
single strand was less stiff than a single strand (mean
stiffness=stiffness value) under tensile loading (p< 0.05;
Fig. 5); however, after cyclical loading, the single strand
and the single strand with a knot had the same stiffness
represented by the same slope on the load displacement
graph (Fig. 6).
Variance in Mean Ultimate Tensile Strength
There was found to be less variance in ultimate tensile load
with cyclical loading in all groups (Table 1).
Discussion
An active postrepair mobilization protocol places increasing
stresses on the suture construct as it is the suture material
itself which maintains the integrity of the tendon repair
until the healing is sufficiently advanced. In an effort to
improve the ultimate mechanical strength of repairs, multi-
strand techniques have been introduced. To identify the best
suture materials for tendon repair, in vitro and ex vivo
studies of suture ultimate tensile strength of different
techniques of acute flexor tenorrhaphy have previously
been described [1,2,7,9,11,12].
In the first part of this study, the mechanical strengths of
different numbers of strands of suture material was
reviewed. Savage [9] has previously shown the weakest
area being at the site of a knot. This was confirmed in our
study which showed the ultimate tensile strength of a single
suture strand to be reduced by approximately 50% with the
presence of a knot (Fig. 6). Savage and Rositano [10] also
suggested that in a multistrand repair in a frictionless
environment, each strand should share the load and the
construct should fail once the weakest strand (i.e., the
knotted strand) has exceeded its ultimate tensile. Previous
studies [8,10] have documented a discrepancy of this
simple arithmetic formula (strength of the weakest (knotted)
strand times the number of strands) with a higher measured
UTS on single tension testing being attributed to some form
of friction in the experimental system. Aoki et al. identified
that the tensile strength of a tenorrhaphy following cyclic
loading was less than the same repair under single tension
testing loads. Again, the difference is attributed to the
effects of friction in the testing system.
Our study, however, suggests that the discrepancy in the
UTS of the multistrand repair between single tension and
COMPARISON BETWEEN UNKNOTTED AND KNOTTED
CYCLIC TENSILE TEST BEHAVIOUR
0
5
10
15
20
25
30
35
40
0 2 4 6 8 10 12 14 16
EXTENSION, (mm)
LOAD, (N)
Single Strand
Single Strand with Knot
Figure 6 Load displacement curve demonstrating effect of cyclic
loading on unknotted and knotted single suture strand.
SINGLE TENSION TEST
0
5
10
15
20
25
30
35
40
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
EXTENSION, (mm)
LOAD, (N)
Single Strand with Knot
Single Strand
Figure 5 Load displacement curve demonstrating effect of single
tensile loading on unknotted and knotted single suture strand.
Table 1 In vitro 30 Ethibond (Ethicon, Somerville, NJ, USA) suture
and ex vivo four-strand tendon repair mean ultimate tensile strength
(N).
Single tensile
loading
(variance)
Cyclical
loading
(variance)
pvalue
1 strand (no knot) 34 (8) 36 (6) n.s.
1 strand with knot 16 (9) 18 (4) n.s.
2 strand with knot 39 (13) 41 (10) n.s.
4 strand with knot 90 (10) 87 (9) n.s.
4 strand tendon
repair
80 (9) 70 (6) <0.05
116 HAND (2009) 4:113118
cyclic loading can be explained by the behavior of the knot
during initial and subsequent loading. The load displace-
ment curves for a knotted and unknotted strand for both
single tensile and cyclical loading (Figs. 5and 6) were
compared. It was clear that the stiffness of the knotted
strand was substantially less than the unknotted strand
(represented by the slope of the curve) for a single tensile
test. After cyclical loading, the stiffness of the knotted
strand was identical to that of the unknotted strand, but the
UTS remained the same being 50% weaker in the presence
of a knot.
This difference in the stiffness can explain the discrep-
ancy in the UTS of the four-strand tendon repair in this
study. With the ex vivo model, there was a mean decrease
from 80 N for single tensile to 70 N for cyclical loading (p<
0.05). The reduction in the stiffness gradient of the knotted
strand effectively delays the ultimate maximal loading of the
knotted strand. In a multistrand repair where there is friction
which prevents immediate equilibration of the strand tension,
the unknotted strand which has a higher stiffness strands
(i.e., the unknotted strands) will take a proportionally greater
load across the tenorrhaphy resulting in higher value of UTS
with single tensile testing. The slight redundancy within the
knot causing the reduced stiffness in that strand can be
corrected by cyclical loading such that the stiffness of a
knotted strand becomes identical to the stiffness of an
unknotted strand (Fig. 6).
In this study, cyclical loading of the ex vivo tendon
repair does reduce the mean UTS (80 N for single tensile to
70 N for cyclical) to a value that is very close to the
arithmetic formula of the knotted strand times the number
of strands (17 N×4=68 N). In a physiological situation
where cyclic loading will occur in the course of active and
passive mobilization, the stiffness of the unknotted strand
will maximize, the loading between the various strands will
be even, and the UTS will approach the weakest strand
strength times the number of strands.
This study has not investigated the presence of grasp
migration or the viscose elastic deformation of 30
Ethibond (Ethicon, Somerville, NJ, USA) which contribute
to differences in the mean UTS between the in vitro and ex
vivo four-strand models. The main difference can be
attributed to the effect of friction combined with the
variation in stiffness of the knotted and unknotted strands
in the testing model.
We conclude that the UTS of a given knotted length of
suture will be constant, regardless of single or cyclic
loading. However, the knotted strand is both the weakest
and has a lower stiffness (during initial loading) than other
strands in a multistrand repair. During single tension
testing, if the strands of a repair cannot undergo immediate
equilibration due to friction, a lower knotted strand stiffness
is evident and this leads to delayed rate of loading until
maximum loading and ultimate failure when compared to
the loading of the stiffer unknotted strands. This in turn
leads to an incorrectly elevated estimate of the likely UTS.
This discrepancy can be addressed by cyclic loading of the
construct which maximizes (or normalizes) the stiffness of
the knotted strand. This change in the knotted systems
stiffness occurs because slack within the knot cannot be
completely removed by hand during construction and is
removed during initial tensile loading. This removal of
slack within the knot during the initial loading phase
produces a reduction in system stiffness until a point where
the slack is completely removed. At this point, the knotted
system will exhibit identical stiffness to an unknotted
system; however, the knotted system will fail at signifi-
cantly lower UTS due to the knot acting as a stress raiser.
These findings are clinically important because slack
within the knot could tighten causing a gap between tendons.
The magnitude of the gap would be minimized with
increasing numbers of strands. Cyclical mechanical loading
is a more exacting technique and more closely reproduces
physiological loading of a flexor tendon repair which has
important clinical implications for previous studies
concerning strength of tendon repair. We therefore recom-
mend the use of cyclical mechanical testing techniques in the
future study of tendon repair techniques as single tensile
testing of tendon repairs may give falsely generous results
with regards to UTS. Removing the slack from the knot within
the knotted system allows more accurate measurement of the
ultimate system strength and stiffness.
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This study was conducted to compare the in vitro biomechanical properties of tensile strength and gap resistance of a double grasping loop (DGL) flexor tendon repair with the established four-strand cross-locked cruciate (CLC) flexor tendon repair, both with an interlocking horizontal mattress (IHM) epitendinous suture. The hypothesis is that the DGL-IHM method which utilizes two looped core sutures, grasping and locking loops, and a single intralesional knot will have greater strength and increased gap resistance than the CLC-IHM method. Forty porcine tendons were evenly assigned to either the DGL-IHM or CLC-IHM group. The tendon repair strength, 2-mm gap force and load to failure, was measured under a constant rate of distraction. The stiffness of tendon repair was calculated and the method of repair failure was analyzed. The CLC-IHM group exhibited a statistically significant greater resistance to gapping, a statistically significant higher load to 2-mm gapping (62.0 N), and load to failure (99.7 N) than the DGL-IHM group (37.1 N and 75.1 N, respectively). Ninety percent of CLC-IHM failures were a result of knot failure whereas 30 % of the DGL-IHM group exhibited knot failure. This study demonstrates that the CLC-IHM flexor tendon repair method better resists gapping and has a greater tensile strength compared to the experimental DGL-IHM method. The authors believe that while the DGL-IHM provides double the number of sutures at the repair site per needle pass, this configuration does not adequately secure the loop suture to the tendon, resulting in a high percentage of suture pullout and inability to tolerate loads as high as those of the CLC-IHM group.
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Adhesions and scar formation between flexor tendons and the surrounding tissue can currently only be prevented by mobilization oft he flexor tendon. Active treatment concepts are more favorable than passive mobilization. The main risks of flexor tendon repair are rupture of the tendon suture, gradually progressive dehiscence and inhibition of tendon gliding within the tendon sheath. Currently, there is no consensus with respect to the optimal suture technique and suture material. Nevertheless, there are some noteworthy principles, such as the use of suture material with a greater diameter, locked suture techniques, sutures with four or more strands as well as simple circular running sutures. A technically acceptable compromise, even for persons with less practice, is currently a 4-thread suture in combination with a circular running suture, which guarantees sufficient stability for active postoperative treatment without causing resistance.
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Background: Cyclic testing of flexor tendons aims to simulate post-operative rehabilitation and is more rigorous than static testing. However, there are many different protocols, making comparisons difficult. We reviewed these protocols and suggested two protocols that simulate passive and active mobilization. Methods: Literature search was performed to look for cyclic testing protocols used to evaluate flexor tendon repairs. Preload, cyclic load, number of cycles, frequency and displacement rate were categorised. Findings: Thirty-five studies with 42 different protocols were included. Thirty-one protocols were single-staged, while 11 protocols were multiple-staged. Twenty-nine out of 42 protocols used preload, ranging from 0.2 to 5 N. Preload of 2 N was used in most protocols. The cyclic load that was most commonly used was between 11 and 20 N. Cyclic load with increment of 10 N after each stage was used in multiple-staged protocols. The most commonly used number of cycles was between 100 and 1000. Most protocols used a frequency of <1 Hz and displacement rate between 0 and 20 mm/min. Interpretation: We propose two single-staged protocols as examples. Protocol 1: cyclic load of 15 N to simulate passive mobilization with preload of 2 N and 2000 cycles at frequency of 0.2 Hz.; Protocol 2: cyclic load of 38 N to simulate active mobilization, with the same preload, number of cycles, and frequency as above. This review consolidates the current understanding of cyclic testing and may help clinicians and investigators improve the design of flexor tendon repairs, allow for comparisons of different repairs using the same protocol, and evaluate flexor tendon repairs more rigorously before clinical applications.
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Verklebungen und Vernarbungen zwischen Beugesehnen und Umgebung lassen sich zurzeit nur durch Bewegung der Sehne vermeiden. Günstiger als die passive Mobilisierung sind Konzepte mit aktiver Nachbehandlung. Hauptgefahren für die Beugesehnennaht sind die Ruptur der Sehnennaht, schleichende Dehiszenzen und die Behinderung der Gleitfähigkeit in der Beugesehnenscheide. Es gibt bisher keinen Konsens hinsichtlich einer optimalen Nahttechnik oder eines optimalen Nahtmaterials. Es gibt jedoch einige beachtenswerte Prinzipien wie den Einsatz von Nahtmaterial mit größerem Durchmesser, blockierenden Stichtechniken, Nahttechniken mit vier und mehr Nahtsträngen sowie umlaufenden Feinadaptationsnähten. Einen technisch akzeptablen Kompromiss – auch für den weniger Geübten – stellt zurzeit die Vierstrangnaht in Kombination mit einer fortlaufenden Feinadaptationsnaht dar. Sie gewährleistet eine ausreichende Stabilität für eine aktive Nachbehandlung ohne Widerstand.
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To study the biomechanical properties of flexor tendon repairs, static tensile testing is commonly used because of its simplicity. However, cyclic testing resembles the physiological loading more closely. The aim of the present study is to assess how the biomechanical competence of repaired flexor tendons under cyclic testing relates to specific parameters derived from static tensile testing. Twenty repaired porcine flexor tendons were subjected to static tensile testing. Additional 35 specimens were tested cyclically with randomly assigned peak load for each specimen. Calculated risks of repair failure during repetitive loading were determined for mean of each statically derived parameter serving as a peak load. Furthermore, we developed a novel objective method to determine the critical load, which is a parameter predicting the survival of the repair in cyclic testing. The mean of statically derived yield load equalled the mean of critical load, justifying its role as a valid surrogate for critical load. However, regarding mean of any determined parameter as a clinically safe threshold is arbitrary due to the natural variation among samples. Until the universal performance of yield load is verified, we recommend employing cyclically derived critical load as primary parameter when comparing different methods of flexor tendon repair.
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The aim of this study was to find out how common it is to modify standard core suture configurations in flexor tendon repair and whether the use of standard core suture configurations gives a stronger repair. A total of 16 hand surgeons or residents participated in a workshop, in which they were asked to draw the suture configurations they used and to repair a porcine tendon. The properties of the repaired tendons were measured. Seven participants used a standard core suture configuration, and nine used a modified core suture. The biomechanical properties of the repairs were not affected by modifications to the core suture. However, they were affected by the number and lengths of peripheral suture bites, type of peripheral suture and the location of the core suture knot.
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A study was made of the results of immediate repair and controlled mobilization in 156 severed flexor tendons in 68 patients occuring over an 18-month period. Eight patients with 16 tendon injuries could not be followed. Results were obtained from examinations done 6 weeks to 18 months (mean, 5.3 months) after repair. Thirty-one of the 60 patients were less than 20 years old, and 44 of the 60 were less than 30 years old. Seventy-nine (56%) of the injuries occurred in the area known as "no man's land"; 28 patients with repair of tendons in this area were rated by our standards as "excellent" or "good"--75% of patients as compared to 84.4% for the results of repair in other areas. In one fourth of the cases of severance of both tendons, because of local conditions in the wound, the superficialis was excised, but in all others it was repaired.
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A method of evaluating flexor tendon repair techniques with the use of cyclic testing is presented. This type of evaluation complements the presently used load-to-failure tests by providing more detailed information about gap formation at the repair site. During load-to-failure testing in this study, core sutures alone demonstrated initial gap formation at 0.85 kg tensile force or more; yet on cyclic testing all techniques demonstrated gap formation of 1.9 mm or greater at 0.5 kg tensile force. Thus cyclic testing demonstrated gap formation not readily apparent on load-to-failure testing. An epitenon stitch placed circumferentially around the laceration site added strength in both load-to-failure and cyclic tests, and significantly reduced gap formation regardless of the core suture technique.
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A "six strand" method of tendon repair has been used to treat 36 fingers with flexor tendon lacerations. Following surgery, active mobilisation in a protective splint was begun immediately. 63% of lacerations were in zone 2 and 27% in zone 1. 69% and 100% respectively achieved an excellent or good result using Buck-Gramcko's assessment method. 81% of all the fingers were rated excellent or good.
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The mechanical factors in tendon repair have been studied and physical principles applied to this unsolved problem. A new technique of tendon repair has been derived and tested in the laboratory. Compared to several well known techniques it has been shown to have three times the tensile strength and to allow one tenth the gap to form between the tendon ends under load. It has been designed not to constrict the blood supply of the tendon and the tests indicate that it will be strong enough to allow early active mobilisation even after inflammation has caused the tendon to soften.
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Primary flexor tendon repair will provide superior functional results at all levels of injury: the forearm, the carpal tunnel, the palm, and distal to the superficialis tendon. Repair of injuries to the flexor tendons in the fibro-osseous tunnel (distal palmar crease to the proximal interphalangeal joint crease) is a controversial subject. Flexor tendon graft is the established and accepted method of treating these injuries. Improved technique in primary tenorrhaphy in the flexor digital sheath has produced results at least equal to those with flexor tendon graft. The technique of primary flexor tenorrhaphy is described. We do not advocate or suggest that primary tendon repair is indicated in most flexor lacerations in the „no man's land“ area unless a specially trained hand surgeon capable of performing primary tenorrhaphy is available. If this surgeon is not available, the wound should be cleansed, the skin sutured, and the patient referred to a specialist for tendon graft. Ill advised attempts at primary tenorrhaphy in this region will result in contracted scarred fingers, which may at best be impossible to restore even with a staged tendon graft procedure.
Article
The performance of 50 consecutive digits in 37 patients was analyzed following flexor tendon repair in Zone II. Twenty-five digits were managed by 3 1/2 weeks of immobilization followed by a program of gradually increased motion; 25 other digits by intermittent passive motion initiated within the first 5 days with active flexion commenced at 4 1/2 weeks. Results were graded according to the percentage of return of motion at the proximal and distal interphalangeal joints. There were four ruptures in the immobilization group with no excellent results, 12% being rated good, 28% fair, and 11% poor. In the digits managed by early mobilization there were 36% excellent, 20% good, 16% fair, 24% poor; there was one rupture in this group. Early passive motion appeared to be an effective technique to improve the results of flexor tendon repairs in this area.
Article
59 dog cadaver flexor digitorum profundus tendons were repaired with one or two knots inside or outside the tendon, using two, four and six suture strands. The ultimate tensile strength and gap strengths were compared. Locating the knots outside rather than within the tendon repair site showed significantly higher ultimate tensile strength for two, four, and six strand sutures. The strength was greater in one knot than in two knot sutures; the value of the six-strand suture using the one knot outside technique was the greatest. Similarly, increased gap strength was also obtained from the one-knot-outside technique. We concluded that the knots should be located away from the tendon repair site and there should be as few as possible.
Article
A series of 233 patients with complete divisions of flexor tendons in zones 1 and 2 underwent operation following emergency admission over a period of 3.5 years. These included 203 patients with 317 divided tendons in 224 fingers injuries in zones 1 and 2 and 30 patients with 30 complete divisions of the flexor pollicis longus tendon in zones 1 and 2. All of these patients were mobilized post-operatively in a controlled active motion regimen. 13 (5.8%) fingers and five (16.6%) thumbs suffered tendon rupture during the post-operative period. Patients treated during the last year of the study were followed prospectively for a minimum period of 3 months; ten of the 16 (62.5%) fingers with zone 1 repairs, 50 of the 63 (79.4%) fingers with zone 2 repairs, all three (100%) FPL divisions in zone 1 and three of four (75%) FPL divisions in zone 2 had good and excellent results on assessment by the original Strickland criteria (Strickland and Glogovac, 1980). These results confirm the safety of this regimen as an alternative to other regimens of post-operative flexor tendon repair mobilization in zone 1 and 2 finger injuries. However, in the unmodified form used in this series, this regimen has too high a rupture rate for FPL mobilization.