Click here to load reader
Upload
tim-alexander
View
216
Download
0
Embed Size (px)
Citation preview
SHOULDER
Novel single-loop and double-loop knot stitch in comparisonwith the modified Mason–Allen stitch for rotator cuff repair
Stephan Frosch • Gottfried Buchhorn • Anja Hoffmann • Peter Balcarek •
Jan Philipp Schuttrumpf • Florian August • Klaus Michael Sturmer •
Hans Joachim Walde • Tim Alexander Walde
Received: 13 June 2013 / Accepted: 30 March 2014
� Springer-Verlag Berlin Heidelberg 2014
Abstract
Purpose In rotator cuff repair, strong and long-lasting
suturing techniques that do not require additional implants
are needed. This study examines the ultimate load to failure
and the Young’s modulus at the suture–tendon interface for
a novel single-loop knot stitch and double-loop knot stitch.
These values are compared to those of the modified
Mason–Allen stitch.
Methods Twenty-four infraspinatus muscles with tendons
were dissected from porcine shoulders (twelve Goettingen
minipigs). The preparations were randomly allocated to
three groups of eight samples. Load-to-failure testing of the
single-loop knot stitch, the double-loop knot stitch and the
mMAS were performed using a Zwick 1446 universal
testing machine (Zwick-Roell AG, Ulm, Germany).
Results The highest ultimate load to failure for the three
techniques occurred with the double-loop knot stitch with a
median value of 382.2 N (range 291.8–454.2 N). These
values were significantly higher than those of the single-
loop knot stitch, which had a median value of 259.5 N
(range 139.6–366.3 N) and the modified Mason–Allen
stitch, which had a median value of 309.3 N (range
84.55–382.9 N). The values of the single-loop knot stitch
and the modified Mason–Allen stitch did not differ sig-
nificantly. Regarding the Young’s modulus, no significant
differences were found between the double-loop knot stitch
with a median value of 496.02 N/mm2 (range
400.4–572.6 N/mm2) and the modified Mason–Allen stitch
with 498.5 N/mm2 (range 375.5–749.2 N/mm2) with
respect to the stiffness of the suture–tendon complex. The
median value for the Young’s modulus of the single-loop
knot stitch of 392.1 N/mm2 (range 285.7–510.6 N/mm2)
was significantly lower than those of the double-loop knot
stitch and modified Mason–Allen stitch.
Conclusion This in vitro animal study demonstrated that
both the single-loop knot stitch and the double-loop knot
stitch have excellent ultimate load-to-failure properties
when used for rotator cuff repair. The introduced single-
loop knot stitch and double-loop knot stitch offer an
alternative to other common used stitch techniques in
rotator cuff repair.
Keywords Rotator cuff repair � Modified Mason–Allen
stitch � Biomechanical study � Ultimate load to failure �Shoulder � Stitch strength
Introduction
Reduction in high failure rates in rotator cuff repair is of
outmost clinical relevance as failures of 39 % in cases of
isolated supraspinatus tears and up to 94 % in cases of
massive rotator cuff tears have been reported [8, 14, 15].
Rotator cuff failure after repair most often occurs during
the early post-operative period while load transmission
mainly depends on fixation of the suture–tendon interface
[2, 27]. In addition to rupture of the thread, anchor dislo-
cation and knot malfunction, failure of the suture–tendon
Hans Joachim Walde: deceased.
S. Frosch (&) � A. Hoffmann � P. Balcarek �J. P. Schuttrumpf � F. August � K. M. Sturmer �H. J. Walde � T. A. Walde
Department of Trauma Surgery, Plastic and Reconstructive
Surgery, University Medicine Gottingen, Robert Koch Straße 40,
37075 Gottingen, Germany
e-mail: [email protected]
G. Buchhorn
Department of Orthopedics, University Medicine Gottingen,
Robert Koch Straße 40, 37075 Gottingen, Germany
123
Knee Surg Sports Traumatol Arthrosc
DOI 10.1007/s00167-014-2976-7
interface causes early rotator cuff failure [3, 10, 12, 13, 16].
Therefore, strong and lasting suture configurations are
needed in rotator cuff repair. Various studies have mea-
sured forces of the supraspinatus muscle that range from
175 to 353 N [7, 20, 21]. The infraspinatus muscle can
even endure forces up to 909 N, according to the results of
a cadaveric study by Hughes and An [20]. The modified
Mason–Allen stitch technique (mMAS) (Fig. 1) is consid-
ered to be superior to simple or mattress stitch with respect
to the initial fixation strength and shows similar biome-
chanical and clinical results when compared to double-row
fixation [18, 29, 30]. Ma et al. [29] reported an ultimate
tensile load of 246 N for the mMAS in a bovine in vitro
test. Even though the mMAS has better biomechanical and
clinical results, there remains the issue of the ultimate load
resistance of the mMAS when compared to the forces that
act on the intact rotator cuff muscles. Evidently, it is not
only the suture itself that is the weakest link but rather a
combination of several variables at the suture–tendon
interface. These variables include the orientation of the
thread, the length of contact, the number of fibres
embraced, compression of the fibre bundles, the self-cin-
ching of the knot, in addition to other variables. Previous
studies have pointed to anatomical conditions as being a
major cause of suture fixation problems [23, 31]. Since the
direction of the tendon fibres is parallel to the direction of
strain, the delicate soft tissue sheaths, which are composed
of fibre groups, are too weak to withstand the strain applied
by the thread under tension. The significant complication of
the thread cutting through these sheaths leads to elongation
and reduction in pressure within the footprint. At the
moment, a solution to this is a strain-dependent increase in
traverse compression of tendon fibres. Therefore, improved
stitch techniques to strengthen the suture–tendon interfaces
are needed. Additionally, these techniques should allow
reliable and easy application in both open and arthroscopic
approaches and not require additional implants.
The present study introduces the single-loop knot stitch
(SLKS) (Fig. 2) and the double-loop knot stitch (DLKS)
(Fig. 3) for rotator cuff repair. The rationale for these new
stitches is comprised mainly of three aspects: the knot
should not prevent the thread from compressing the fibres
of the tendon to strengthen the grip as strain increases; the
stitch should only make use of as many fibres of the tendon
as needed for secure fixation; and non-compressed fibres
are thought to be better nourished, thus supporting better
healing of the footprint.
This study focuses on the biomechanical strength of three
stitch techniques. In a tensile test, the ultimate load to failure
and the Young’s modulus were evaluated for the SLKS and
DLKS and compared with the results of the mMAS.
The hypothesis of this study is that the double-loop knot
stitch and the single-loop knot stitch are better or at least equal
to the modified Mason–Allen stitch with respect to ultimate
load to failure and the cutting of the tendon by the thread.
Materials and methods
The aim of this study was to examine performance at the
suture–tendon interface. It was determined that, due to
variations in quality of bone or suture anchors, refasteningFig. 1 Modified Mason–Allen Stitch (mMAS)
Fig. 2 Single-loop knot stitch (SLKS)
Knee Surg Sports Traumatol Arthrosc
123
the tendon at the original footprint might adversely affect
results. Thus, an in vitro study would be performed.
Sample preparation
Twenty-four porcine shoulders were harvested from twelve
Goettingen minipigs (female adult pigs at a comparable
weight and age) and stored at about -38 �C. The animals
had been previously killed for a non-related experiment,
thus no animal protection documentation was needed. Ten
hours before preparation, the shoulders were thawed at
room temperature. The infraspinatus muscle was exposed
with care to the enclosing fascia and dissected from the
protruding scapula crista. The tendon was then sharply cut
directly from its bony insertion at the tuberculum of the
humerus. The latter was inspected for regular anatomy and
discarded. All tendons were roughly 25–30 mm long and
had a cross-section of approximately 15 by 6 mm. The
preparations were then randomly allocated to three groups
of eight samples each. In each group, one of the three
suture configurations was tested. The testing began
immediately after the preparations were finished.
Suture
A high-strength, multi-strand polyethylene suture, Fiber-
Wire No. 2 � (Arthrex, Karlsfeld/Munchen, Germany), was
taken from a reel and combined with a round sharpened
solitary needle. Care was always taken to embrace com-
parable portions and to maintain a distance of 1.5 cm to the
end of the tendon. The width and thickness of the tendon in
the plane of the sutures were measured. To avoid the need
for an additional knot to anchor the ends of the threads, a
custom-made compensator device was designed. By means
of adjustable deflection rollers, the branches of the thread
were oriented parallel to the direction of tension. The
thread ends were then each clamped to a branch of the
axially centred compensator to allow for length compen-
sation in the case of single-sided suture lengthening. This
allowed both ends of the suture to be equally loaded.
Three suture techniques were tested:
1. The modified Mason–Allen stitch technique (mMAS)
(Fig. 1).
2. The SLKS (Figs. 2, 4). This stitch requires two
horizontal passes through the tissue to form a sling
with a knot that continuously tightens as tension on the
thread increases. Care was taken to ensure that the
needle did not penetrate the tendon fully, but rather
encompassed the upper, bursal portion of the cross-
section.
3. The self-cinching double-loop knot stitch (DLKS)
(Fig. 3). Two consecutive, horizontal, single-loop
stitches with knots are performed using a single thread.
This stitch is performed using the same techniques as
the SLKS, but with a mirrored second stitch; both
stitches are only half the width of a SLKS.
In contrast to the SLKS and DLKS, the mMAS enters at
the upper (bursal) side and exits at the lower side of the
Fig. 3 Double-loop knot stitch (DLKS)
Fig. 4 Macroscopic view of a single-loop knot stitch applied to the
end of a tendon; both strings of the thread enter and leave on the
bursal surface
Knee Surg Sports Traumatol Arthrosc
123
tendon, encompassing the cross-section rectangular to the
long axis of the cross-section.
Biomechanical testing
The specimens were subjected to unidirectional, continu-
ous tension to failure using a Zwick 1446 universal testing
machine (UTM) (Zwick-Roell AG, Ulm, Germany).
The protocol described by Baums et al. [4] was utilized.
In short, the infraspinatus muscle was clamped in com-
pression by the two metal brackets of a cryo-jaw [33]. Each
bracket had three traverse recesses, 5 mm deep, to be filled
with muscle tissue under compression. To achieve reliable
fixation and to prevent a slippage of the muscle, the metal
bags of the brackets were filled with pellets of dry ice
freezing the protuberances and preventing slippage. Care
was taken to only freeze the clamped part of the muscle,
while the downwards protruding tendon and suture
remained unaffected. The cryo-jaw was attached using a
cardan joint to the load cell and crossbar of the UTM; the
compensator device was mounted on the UTM base.
The data were recorded using testing software (textX-
pert V 112.1, Zwick-Roell AG, Ulm, Germany). The
elongation (precision = 0.5 mm) and load (pre-
cision = 0.1 N) were measured and displayed in a load/
elongation curve. The Young’s modulus was calculated
using a tangent to the linear portion (elastic deformation)
and was registered with the ultimate load. The maximum
possible error of traverse movement was 0.05 %. The
calibrated force transducer (maximum load 500 N) had an
accuracy of 1 % with values above 200 N.
After pre-tension to 2 N, the prepared suture complex was
axially stressed at a displacement rate of 1 mm/s until failure.
Failure was defined as an 80 % loss of the ultimate tensile
strength independent of either failure mode (suture thread
cutting through the tendon or breaking of the suture thread).
Statistical Analysis
From quantile–quantile plots the assumption of normal dis-
tribution was not satisfied for our data. Therefore, the indi-
vidual study parameters were compared between the three
techniques using the nonparametric Kruskal–Wallis test.
Subsequent pairwise comparisons were performed using the
Mann–Whitney U test. A value of a = 5 % was determined
to indicate statistical significance. For all statistical analyses,
the software R (version 3.0, www.r-project.org) was used.
Results
The branches of the suture increased in length as the knot
tightened under tension. During pretension (2 N), the
compensator device showed minimal multidirectional
deflection. During the load-to-failure test, no further
deflections were observed, indicating concordant tension of
both branches of the thread.
Ultimate load
The highest ultimate loads were achieved with DLSK,
whereas the SLKS were inferior to the mMAS results. A
significant difference could be shown for the values of the
ultimate load comparing the DLKS to the SLKS
(p = 0.003) as well as to the mMAS (p = 0.038) (Table 1;
Fig. 5).
No significant difference (p = 0.23) was found between
ultimate load of the SLKS and the mMAS (Table 1;
Fig. 5).
Young’s Modulus
No significant differences (p = 0.83) were found between
the median value for the Young’s modulus of the DLKS
and the mMAS. The Young’s modulus for the SLKS was
Table 1 Median values of the ultimate load and the Young’s mod-
ulus of the double-loop knot stitch (DLKS), the single-loop knot stitch
(SLKS) and the modified Mason–Allen stitch (mMAS)
Ultimate load Young’s Modulus
DLKS 382.2 N (range
291.8–454.2 N)
496.0 N/mm2 (range
400.4–572.6 N/mm2)
SLKS 259.5 N (range
139.6–366.28 N)
392.1 N/mm2 (range
285.7–510.6 N/mm2)
mMAS 309.3 N (range
84.55–382.9 N)
498.5 N/mm2 (range
375.5–749.2 N/mm2)
Fig. 5 Box-whisker-plot for results of the ultimate load (DLKS
double-loop knot stitch, SLKS single-loop knot stitch, mMAS modified
Mason–Allen stitch)
Knee Surg Sports Traumatol Arthrosc
123
significantly lower when compared to the DLKS
(p = 0.03) and the mMAS (p = 0.049) (Table 1; Fig. 6).
Failure analysis
Of the 24 performed tests, 21 failed due to suture pull-out
at the suture–tendon interface. Three failures were caused
by rupture of the suture. Two ruptures from the mMAS
group and one from the DLKS group were located at the
enlacement close to the surface of the tendon. Reasons for
rupture of the suture remain unclear. Though the thread
was markedly compressed in the compensating device, no
rupture (partial or complete) was observed at this location.
No other inspected characteristic (deficiencies of the ten-
don, slippage of the thread in the clamp, failure of the cryo-
jaw) raised attention.
Discussion
The most important finding of this study is that the double-
loop knot stitch shows superior initial fixation strength
when compared to the common modified Mason–Allen
stitch and the single-loop knot stitch. The results for the
single-loop as well as the double-loop knot stitch confirm
the hypothesis of this study.
Regardless of the technique used for rotator cuff repair,
high failure rates are described in the literature [19]. Bio-
mechanical studies have demonstrated a significant differ-
ence in ultimate load to failure depending on the stitch
technique. More complex single-row stitches such as the
modified Mason–Allen stitch (mMAS) or the massive cuff
stitch (MAC) provide superior initial strength relative to
other simple stitches [26, 31]. Ponce et al. described—in a
biomechanical in vitro animal study—a correlation
between the ultimate load to failure of a stitch and the
number and configuration of sutures passing through the
tissue [31]. Two stitches through the tendon, as with the
mattress stitch, increased the ultimate load failure by 20 N
over a single stitch, such as the simple stitch. When a third
pass was introduced, as with the mMAS and MAC stitches,
an increase in 50 N was observed.
In order to further decrease the failure rate, the double-
row (DR) repair was introduced, which showed promising
biomechanical properties relative to single-row (SR) repair
[5, 22, 28]. However, Lorbach and Tompkins point out the
fact that in literature most DR repairs were compared to SR
repairs using simple sutures [27]. Taking into account that
SR repair using modified suture configurations shows
comparable biomechanical results to DR repair, the authors
concluded that modified SR repair is a good alternative to
DR repair techniques [27]. Moreover, literature fails to
show significant differences in the clinical results and re-
rupture rates compared with DR to SR fixation [6]. Finally,
DR fixation is more time consuming and leads to higher
implant costs [32].
Most re-ruptures occur in the early post-operative per-
iod, during the time that load is primarily transmitted via
the suture–tendon interface [24]. Since the suture–tendon
interface is the most common failure point of the repair, a
modified SR repair technique providing high initial ulti-
mate failure load without ignoring biological milieu is
desirable.
The new SLKS and DLKS introduced in this study were
created in order to meet the aforementioned criteria. The
current study was designed to examine the initial fixation
strength of the SLKS and DLKS and compare the results to
the modified mMAS as the gold standard in modified SR
repair. In a biomechanical in vitro study comparing the
ultimate load to failure of SR repair techniques (simple and
mattress stitch, massive cuff stitch, modified Mason–Allen
stitch), Ponce et al. [31] illustrated the typical failure
mechanisms for SR repair techniques. In 189 out of 192
specimens (infraspinatus tendons of sheep shoulders),
suture pullout through the tendon was the failure mode.
This failure mechanism is not surprising, given that the
tendon fibres are in line with the direction of strain. An
increase in transverse compression of the bundle fibres
decreases the splitting effect of the thread. Transverse
compression is utilized in the massive cuff stitch as well as
the mMAS, which results in superior biomechanical
properties when compared to simple stitches without
transverse compression [11, 25, 31]. The rationale for the
SLKS and DLKS is to not only provide transverse com-
pression of the tendon fibres, but to also adjust the com-
pression depending on the applied strain forces. The loop
knot, with its self-tightening property, produces increasing
Fig. 6 Box-whisker-plot for results of the Young’s Modulus (DLKS
double-loop knot stitch, SLKS single-loop knot stitch, mMAS modified
Mason–Allen stitch)
Knee Surg Sports Traumatol Arthrosc
123
compression forces that enhance tissue grip as axial stain
increases.
In the current study, the SLKS had comparable results to
the mMAS with respect to ultimate load to failure (283.5 vs
309.3 N). Furthermore, the evaluation of the DLKS showed
statistically significant superior ultimate load to failure
(382.2 N) when compared to the SLKS and the mMAS. The
Young’s moduli did not differ significantly between the
DLKS and the mMAS, thus showing inferior stiffness at the
suture–tendon interface for the SLKS when compared to the
DLKS and the mMAS. Literature shows varying ultimate
tensile strengths for the mMAS using similar biomechanical
models [4, 28, 29, 31, 34]. However, the results are not
comparable with each other, since the absolute values are
affected by the amount of encompassed tissue, different
tissue-penetrating instruments and size of the bite [31].
Enhanced transverse compression forces act on the part
of the tendon encompassed by the suture. This raises the
concern of local tendon necrosis. However, Gerber et al.
[17] demonstrated that with the mMAS these forces do not
cause long-term histological changes within the tendon and
that they are biologically tolerated.
Christoforetti et al. [9] described a significant decline of
blood flow at the tendon repair site when suture-related
compression acts on the tendon during repair. A strangu-
lation of the tissue obviously leads to reduced blood per-
fusion possibly compromising biological healing of the
defect. However, the tendon is a region of hypovascularity.
The highest vascularity of the rotator cuff region after
repair comes from the bursal tissue and from the bone-
tendon interface promoting fibrovascular scar formation [1,
35]. With these findings in mind, the SLKS and DLKS
encompass, in contrast to the mMAS, the bursal side of the
tendon only, without penetrating the articular side (Figs. 2,
3, 4). Therefore, the tendon fibres in direct contact with the
foot print do not experience suture compression forces.
Under these conditions, normal blood flow should be
retained, promoting a suitable environment for biological
healing at the tendon-footprint interface.
One of the limitations of this study is the use of an
in vitro animal model to investigate suture techniques for
rotator cuff repair in human beings. However, mechanical
properties of pig tendons are comparable to human tendons
and sheep infraspinatus tendons are considered to be sim-
ilar to human rotator cuff tendons in size, shape, histo-
logical parameters and mechanical properties [16, 36].
Another limitation of the present study is that the ten-
don-suture interface was tested exclusively. Other causes
of rotator cuff repair failure were not tested in this setting.
Since failure at the tendon-suture interface is the most
common reason for malfunction, the present study uses a
testing configuration that exclusively focuses on the main
failure mode and excludes other factors.
The potential clinical relevance of the results is that the
introduced single-loop and double-loop knot stitch might
be an alternative to other common used stitch techniques in
rotator cuff repair, because of its self-cinching abilities, the
small amount of tendon fibres encompassed by the suture
promoting biological healing and providing high initial
fixation strength without the need of further implants.
Conclusion
This in vitro animal study demonstrated that secure fixation
of a suture can be achieved with a transverse, self-tight-
ening knot that only engages the bursal half of the tendon.
Both the single-loop knot stitch and the double-loop knot
stitch have excellent ultimate load-to-failure properties and
offer an opportunity for better healing in rotator cuff repair.
Acknowledgments This work is published in memory of Hans
Joachim Walde, MD, who passed unexpectedly. He was an ardent
physician, a great supporter of younger fellows and a wonderful
inspiration in many other aspects of his life. His basic ideas on tendon
restoration, suture and knot characteristics, as well as training in
manual skills assisted the study described here. We owe thanks to
Klaus Jung, PhD, Department of Clinical Statistics at the University
Medical Center Gottingen, as well as the Department of Mouth—Jaw
and Facial Surgery at the University Medical Center Gottingen for the
assistance and provision of the porcine specimens.
Conflict of interest The authors declare that they have no conflict
of interest.
Ethical standards The manuscript submitted provides no conflict
with animal ethical standards. All authors listed contributed to the
study.
References
1. Adler RS, Johnson KM, Fealy S, Maderazo A, Gallo RA, Gam-
radt SC, Warren RF (2011) Contrast-enhanced sonographic
characterization of the vascularity of the repaired rotator cuff:
utility of maximum intensity projection imaging. J Ultrasound
Med 30(8):1103–1109
2. Anderl W, Heuberer PR, Laky B, Kriegleder B, Reihsner R,
Eberhardsteiner J (2012) Superiority of bridging techniques with
medial fixation on initial strength. Knee Surg Sports Traumatol
Arthrosc 20(12):2559–2566
3. Baleani M, Ohman C, Guandalini L, Rotini R, Giavaresi G,
Traina F, Viceconti M (2006) Comparative study of different
tendon grasping techniques for arthroscopic repair of the rotator
cuff. Clin Biomech 21(8):799–803
4. Baums MH, Buchhorn GH, Spahn G, Poppendieck B, Schultz W,
Klinger HM (2008) Biomechanical characteristics of single-row
repair in comparison to double-row repair with consideration of
the suture configuration and suture material. Knee Surg Sports
Traumatol Arthrosc 16(11):1052–1060
5. Baums MH, Spahn G, Steckel H, Fischer A, Schultz W, Klinger
HM (2009) Comparative evaluation of the tendon-bone interface
contact pressure in different single- versus double-row suture
Knee Surg Sports Traumatol Arthrosc
123
anchor repair techniques. Knee Surg Sports Traumatol Arthrosc
17(12):1466–1472
6. Burks RT, Crim J, Brown N, Fink B, Greis PE (2009) A pro-
spective randomized clinical trial comparing arthroscopic single-
and double-row rotator cuff repair: magnetic resonance imaging
and early clinical evaluation. Am J Sports Med 37(4):674–682
7. Chang YW, Hughes RE, Su FC, Itoi E, An KN (2000) Prediction
of muscle force involved in shoulder internal rotation. J Shoulder
Elbow Surg 9(3):188–195
8. Chillemi C, Petrozza V, Garro L, Sardella B, Diotallevi R,
Ferrara A, Gigante A, Di Cristofano C, Castagna A, Della Rocca
C (2011) Rotator cuff re-tear or non-healing: histopathological
aspects and predictive factors. Knee Surg Sports Traumatol
Arthrosc 19(9):1588–1596
9. Christoforetti JJ, Krupp RJ, Singleton SB, Kissenberth MJ, Cook
C, Hawkins RJ (2012) Arthroscopic suture bridge transosseus
equivalent fixation of rotator cuff tendon preserves intratendinous
blood flow at the time of initial fixation. J Shoulder Elbow Surg
21(4):523–530
10. Cole BJ, ElAttrache NS, Anbari A (2007) Arthroscopic rotator
cuff repairs: an anatomic and biomechanical rationale for dif-
ferent suture-anchor repair configurations. Arthroscopy 23(6):
662–669
11. Cummins CA, Appleyard RC, Strickland S, Haen PS, Chen S,
Murrell GA (2005) Rotator cuff repair: an ex vivo analysis of
suture anchor repair techniques on initial load to failure.
Arthroscopy 21(10):1236–1241
12. Cummins CA, Murrell GA (2003) Mode of failure for rotator cuff
repair with suture anchors identified at revision surgery.
J Shoulder Elbow Surg 12(2):128–133
13. Cummins CA, Strickland S, Appleyard RC, Szomor ZL, Marshall
J, Murrell GA (2003) Rotator cuff repair with bioabsorbable
screws: an in vivo and ex vivo investigation. Arthroscopy
19(3):239–248
14. Galatz LM, Ball CM, Teefey SA, Middleton WD, Yamaguchi K
(2004) The outcome and repair integrity of completely arthro-
scopically repaired large and massive rotator cuff tears. J Bone
Joint Surg Am 86-A(2):219–224
15. Gazielly DF, Gleyze P, Montagnon C (1994) Functional and
anatomical results after rotator cuff repair. Clin Orthop Relat Res
304:43–53
16. Gerber C, Schneeberger AG, Beck M, Schlegel U (1994)
Mechanical strength of repairs of the rotator cuff. J Bone Joint
Surg Br 3:371–380
17. Gerber C, Schneeberger AG, Perren SM, Nyffeler RW (1999)
Experimental rotator cuff repair. A preliminary study. J Bone
Joint Surg Am 81(9):1281–1290
18. Gerhardt C, Hug K, Pauly S, Marnitz T, Scheibel M (2012)
Arthroscopic single-row modified mason-allen repair versus
double-row suture bridge reconstruction for supraspinatus tendon
tears: a matched-pair analysis. Am J Sports Med 40(12):
2777–2785
19. Harryman DT, II, Mack LA, Wang KY, Jackins SE, Richardson
ML, Matsen FA, III (1991) Repairs of the rotator cuff. Correla-
tion of functional results with integrity of the cuff. J Bone Joint
Surg Am 73 (7):982–989
20. Hughes RE, An KN (1996) Force analysis of rotator cuff muscles.
Clin Orthop Relat Res 330:75–83
21. Juul-Kristensen B, Bojsen-Moller F, Finsen L, Eriksson J, Jo-
hansson G, Stahlberg F, Ekdahl C (2000) Muscle sizes and
moment arms of rotator cuff muscles determined by magnetic
resonance imaging. Cells Tissues Organs 167(2–3):214–222
22. Kim DH, Elattrache NS, Tibone JE, Jun BJ, DeLaMora SN,
Kvitne RS, Lee TQ (2006) Biomechanical comparison of a sin-
gle-row versus double-row suture anchor technique for rotator
cuff repair. Am J Sports Med 34(3):407–414
23. Klinger HM, Buchhorn GH, Heidrich G, Kahl E, Baums MH
(2008) Biomechanical evaluation of rotator cuff repairs in a sheep
model: suture anchors using arthroscopic Mason–Allen stitches
compared with transosseous sutures using traditional modified
Mason–Allen stitches. Clin Biomech 23(3):291–298
24. Kluger R, Bock P, Mittlbock M, Krampla W, Engel A (2011)
Long-term survivorship of rotator cuff repairs using ultrasound
and magnetic resonance imaging analysis. Am J Sports Med
39(10):2071–2081
25. Lorbach O, Bachelier F, Vees J, Kohn D, Pape D (2008) Cyclic
loading of rotator cuff reconstructions: single-row repair with
modified suture configurations versus double-row repair. Am J
Sports Med 36(8):1504–1510
26. Lorbach O, Kieb M, Raber F, Busch LC, Kohn D, Pape D (2012)
Comparable biomechanical results for a modified single-row
rotator cuff reconstruction using triple-loaded suture anchors
versus a suture-bridging double-row repair. Arthroscopy 28(2):
178–187
27. Lorbach O, Tompkins M (2012) Rotator cuff: biology and current
arthroscopic techniques. Knee Surg Sports Traumatol Arthrosc
6:1003–1011
28. Ma CB, Comerford L, Wilson J, Puttlitz CM (2006) Biome-
chanical evaluation of arthroscopic rotator cuff repairs: double-
row compared with single-row fixation. J Bone Joint Surg Am
88(2):403–410
29. Ma CB, MacGillivray JD, Clabeaux J, Clabeaux J, Lee S, Otis JC
(2004) Biomechanical evaluation of arthroscopic rotator cuff
stitches. J Bone Joint Surg Am 86-A(6):1211–1216
30. Nelson CO, Sileo MJ, Grossman MG, Serra-Hsu F (2008) Single-
row modified Mason–Allen versus double-row arthroscopic
rotator cuff repair: a biomechanical and surface area comparison.
Arthroscopy 24(8):941–948
31. Ponce BA, Hosemann CD, Raghava P, Tate JP, Sheppard ED,
Eberhardt AW (2013) A biomechanical analysis of controllable
intraoperative variables affecting the strength of rotator cuff
repairs at the suture–tendon interface. Am J Sports Med 41(10):
2256–2261
32. Reardon DJ, Maffulli N (2007) Clinical evidence shows no dif-
ference between single- and double-row repair for rotator cuff
tears. Arthroscopy 23(6):670–673
33. Rickert M, Georgousis H, Witzel U (1998) Tensile strength of the
tendon of the supraspinatus muscle in the human. A biome-
chanical study. Unfallchirurg 101(4):265–270
34. Sileo MJ, Ruotolo CR, Nelson CO, Serra-Hsu F, Panchal AP
(2007) A biomechanical comparison of the modified Mason–
Allen stitch and massive cuff stitch in vitro. Arthroscopy
23(3):235–240
35. St Pierre P, Olson EJ, Elliott JJ, O’Hair KC, McKinney LA, Ryan
J (1995) Tendon-healing to cortical bone compared with healing
to a cancellous trough. A biomechanical and histological evalu-
ation in goats. J Bone Joint Surg Am 77(12):1858–1866
36. Yamada H, Evans FG (1970) Strength of biological materials.
Williams & Wilkins, Baltimore
Knee Surg Sports Traumatol Arthrosc
123