Download Biomechanical Study of a Subscapularis Repair Technique

n Feature Article
Biomechanical Study of a Subscapularis
Repair Technique for Total Shoulder
Arthroplasty
Evan Lederman, MD; Jonathan Streit, MD; John Idoine, DO; Yousef Shishani, MD;
Reuben Gobezie, MD
abstract
Secure subscapularis repair is an essential element of total shoulder arthroplasty. Some surgeons prefer subscapularis peel because of ease of use, but
some evidence suggests that lesser tuberosity osteotomy provides better fixation. The authors developed a novel, through-implant repair technique and
performed a biomechanical study of its strength with cadaveric specimens.
The authors obtained 20 matched pairs of cadaveric shoulders and inserted
an uncemented short-stemmed humeral prosthesis that facilitates throughimplant repair in all specimens. For each cadaver, the subscapularis was repaired with lesser tuberosity osteotomy and standard suture technique on 1
side, and the contralateral subscapularis was repaired with a novel throughimplant suture repair and subscapularis peel technique. Displacement of the
subscapularis footprint, ultimate load to failure, and stiffness of each repair
were measured and compared between fixation groups. Mean±SD displacement of the lesser tuberosity osteotomy group was 0.75±0.94 mm at 10 cycles
and 2.24±2.76 mm at 500 cycles. Mean±SD load to failure was 612±185 N,
and mean±SD ultimate stiffness was 119±32 N/mm. No significant differences were noted between the lesser tuberosity osteotomy group and the
subscapularis peel group in mean±SD displacement at 10 cycles (1.09±1.30
mm, P=.31), mean±SD displacement at 500 cycles (2.85±2.43 mm, P=.26),
mean±SD load to failure (683±274 N, P=.31), or mean±SD ultimate stiffness
(117±37 N/mm, P=.88). In a biomechanical testing model, through-implant
subscapularis repair provided secure fixation relative to currently accepted
subscapularis repair techniques in total shoulder replacement. [Orthopedics.
2016; 39(5):e937-e943.]
T
otal shoulder arthroplasty (TSA) is
an effective treatment for glenohumeral joint arthritis in the setting of
an intact rotator cuff. Current techniques
for TSA using the deltopectoral approach
necessitate detachment of the subscapularis tendon from the humerus for placement
of the prosthesis. This may be accom-
SEPTEMBER/OCTOBER 2016 | Volume 39 • Number 5
plished by tenotomizing the subscapularis
tendon, peeling the tendon insertion away
from the lesser tuberosity, or performing
an osteotomy of the lesser tuberosity, with
refixation of the tendon insertion after the
procedure. Most surgeons restrict shoulder
motion in the postoperative period to allow
healing of the subscapularis repair. Despite
this period of rest, several clinical studies
showed that partial or complete failure of
the repair is common and likely negatively
affects the final outcome.1,2
The authors are from The Orthopedic Clinic
Association and University of Arizona (EL), College of Medicine, Phoenix, Arizona; University
Hospitals Case Medical Center (JS), Cleveland,
Ohio; and the Cleveland Shoulder Institute (JI,
YS, RG), Beachwood, Ohio.
Drs Shishani and Gobezie are previous Blue
Ribbon Article Award recipients (Orthopedics,
July/August 2016).
Drs Streit, Idoine, and Shishani have no relevant financial relationships to disclose. Dr Lederman is a paid consultant for and receives grants
and royalties from Arthrex Inc. Dr Gobezie is a
paid consultant for and receives grants and royalties from Arthrex Inc.
Correspondence should be addressed to:
Reuben Gobezie, MD, Cleveland Shoulder Institute, 3999 Richmond Rd, Ste 200, Beachwood, OH
44122 ([email protected]).
Received: May 6, 2015; Accepted: September
23, 2015.
doi: 10.3928/01477447-20160623-09
e937
n Feature Article
scapularis tenotomy, subscapularis peel,
or lesser tuberosity osteotomy to gain
access to the glenohumeral joint. The authors’ preferred technique is to perform a
subscapularis peel that involves removal
of the entire tendon from its footprint on
the lesser tuberosity.
Once the subscapularis is released, the
glenohumeral joint can be disarticulated
to deliver the proximal humerus into the
surgical field. Any osteophytes that distort
the native anatomy are removed with a
rongeur. Preparation of the humerus begins with an anatomic neck cut. A sound
is used to identify the humeral canal, followed by reaming and broaching until a
snug fit without toggle is achieved. The
size of the final broach corresponds to the
size of the final humeral implant.
Figure 1: The prosthesis is loaded with 6 nonabsorbable sutures, for a total of 12 suture strands
to be tied.
Figure 2: Before implantation, 2 holes are drilled
in the bicipital groove to receive the 2 sutures that
were initially passed through the lateral fin on the
prosthesis.
Figure 3: The implant is impacted into the humeral
canal, with care taken to maintain tension on the
medial suture strands so that they retain their order.
Several biomechanical studies have
been performed in an attempt to determine
the strongest method of subscapularis fixation after TSA. Despite a lack of consensus in the literature,1,3-10 lesser tuberosity
osteotomy is considered to provide the
most secure construct over the long term
because it relies on osseous healing and
does not compromise the tendon insertion
site and footprint. However, subscapularis
tenotomy and subscapularis peel procedures take less surgical time and avoid
the possibility of tuberosity nonunion.2
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Regardless of technique, many surgeons
perform subscapularis repair by passing
heavy nonabsorbable suture around the
humeral prosthesis.
The authors developed a novel TSA
design and repair technique for the subscapularis that uses the prosthesis as an
anchoring device. The authors performed
a cadaveric study of the strength of the
repair, and this report describes the technique and the results of a biomechanical
study of an uncemented humeral prosthesis that allows subscapularis repair with
multiple sutures that are passed through
the device.
Materials and Methods
Approach and Humeral Preparation
Total shoulder arthroplasty with a
suture-incorporating prosthesis is performed with the patient in the beach chair
position. A standard deltopectoral approach to the shoulder is used to provide
exposure of the subscapularis and rotator
interval. The surgeon may perform sub-
Through-implant Subscapularis Suture
Repair
After broaching, the final humeral
prosthesis is ready to be inserted. On the
back table, the prosthesis is loaded with 6
nonabsorbable sutures, for a total of 12 suture strands to be tied (Figure 1). The first
2 sutures are passed through the lateral fin
of the implant; the superior suture is blue,
and the inferior suture is tiger striped. The
remaining 4 sutures are passed through
specially designed suture holes along the
medial edge of the implant. It is important to alternate the suture color to facilitate knot tying later in the case. Before
implantation, 2 holes are drilled in the
bicipital groove to receive the 2 sutures
that were initially passed through the
lateral fin on the prosthesis (Figure 2).
The authors use the prosthesis itself as a
guide for the location of these holes and
pass the sutures with a suture passer. The
implant is then impacted into the humeral
canal, with care taken to maintain tension
on the medial suture strands so that they
retain their order (Figure 3). With the implant seated, the 8 medial suture strands
are passed through the subscapularis
tendon in a uniform fashion (Figure 4).
The authors’ preferred method is to pass
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n Feature Article
Figure 4: With the implant seated, the 8 medial suture strands are passed through the subscapularis
tendon in a uniform fashion.
the suture with an Arthrex FastPass Scorpion suture passer (Arthrex, Inc, Naples,
Florida), but free needles also can be used.
Suture Configuration
The knot tying sequence follows a
specific pattern, as shown in Figure 5.
No sutures are tied to themselves, and
each strand is tied to a different strand in
the configuration. Therefore, the sutureimplant complex does not become taut
until the final 2 knots are tied. Knot tying
is facilitated by the placement of suture
strands in the prosthesis so that strands of
the same color are tied together, as shown
in Figure 5A. The tying sequence begins
by tying the superiormost strand of the
medial 8 strands (blue) to 1 of the superior
strands from the lateral fin (also blue), as
shown in Figure 5B. Next the inferiormost
strand of the medial 7 strands (tiger stripe)
is tied to 1 of the inferior strands from the
lateral fin (also tiger stripe), as shown in
Figure 5C. Next the remaining inferior
suture from the lateral fin (tiger stripe)
is tied to the third strand from the top of
Figure 5: Initial layout of the 12 strings of sutures (A). Superior knot tying (B). Inferior knot tying (C). First
lateral to medial knot tying (D). Second lateral to medial knot tying (E). Medial row knot tying and final
knot configuration (F).
the remaining 6 medial strands (also tiger
stripe), as shown in Figure 5D. Then the
final superior suture from the lateral fin
(blue) is tied to the third strand from the
SEPTEMBER/OCTOBER 2016 | Volume 39 • Number 5
bottom of the remaining 5 medial strands
(also blue), as shown in Figure 5E. Finally, the top 2 and bottom 2 medial strands
are tensioned to tighten the construct and
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n Feature Article
Figure 7: Comparison of cyclic displacement of the
subscapularis tendon from bone after 10 cycles
and 500 cycles showed no difference between
lesser tuberosity osteotomy with standard suture
configuration and subscapularis peel with a sutureincorporating humeral prosthesis.
Figure 6: The final subscapularis repair should
have secure knots that are evenly spaced about the
tendon footprint.
Figure 9: Comparison of construct stiffness
showed no difference between lesser tuberosity
osteotomy with standard suture configuration and
subscapularis peel with a suture-incorporating humeral prosthesis.
Figure 8: Comparison of ultimate load to failure
showed no difference between lesser tuberosity
osteotomy with standard suture configuration and
subscapularis peel with a suture-incorporating humeral prosthesis.
then they are tied together. These final 2
knots break the rule of matching suture
colors, as shown in Figure 5F. The final
construct should have secure knots that
are evenly spaced about the tendon footprint (Figure 6).
Cadaveric Study
To test the strength of subscapularis repair performed with a throughimplant technique, the authors obtained
20 matched pairs of fresh frozen cadaveric
e940
shoulders with overlying soft tissues removed, an intact rotator cuff, and a potted
humerus. Cadavers were all male, with a
mean±SD age of 58.1±10.6 years and no
previous shoulder injury or surgery. An uncemented short-stemmed humeral prosthesis that facilitates through-implant repair
(Univers Apex; Arthrex) was implanted
in all specimens. Cadavers were prospectively randomized to side (right vs left) and
surgical technique (lesser tuberosity osteotomy vs subscapularis peel). For each cadaver, the subscapularis was repaired with
a lesser tuberosity osteotomy with standard
suture technique10 on 1 side, whereas the
contralateral subscapularis was repaired
with a novel through-implant suture repair
and subscapularis peel technique. Specimens that received lesser tuberosity osteotomy repair constituted the control group,
and those that received the subscapularis
peel technique and through-implant su-
ture repair constituted the experimental
group. Lesser tuberosity osteotomy repairs
were made with 4 No. 5 FiberWire sutures
(Arthrex) that were passed through bone
tunnels in the lateral bicipital groove and
around the humeral stem before implantation. The free suture tail was then passed
through the tendon with a modified MasonAllen stitch and tied over the lesser tuberosity osteotomy.11 The same technique as
described earlier was used for all throughimplant subscapularis suture repairs in the
experimental group. Using a hydraulic
testing system (Instron, Canton, Massachusetts), each specimen was cycled at 10
to 100 N for 500 cycles and then pulled
to failure at 33 mm/s. Displacement of
the subscapularis footprint was measured
from its original position after 10 cycles
and again after 500 cycles. Ultimate load
to failure of each construct was quantified,
and the mechanism of failure was documented. The stiffness of each construct
was calculated as force/displacement at
the bone-tendon junction. Statistical analysis was performed with Student’s t test to
compare mean and SD, with significance
set at alpha=0.05.
Results
Mean±SD displacement for the control
group was 0.75±0.94 mm at 10 cycles and
2.24±2.76 mm at 500 cycles (Figure 7).
Mean±SD load to failure was 612±185
N, and mean±SD ultimate stiffness was
119±32 N/mm. No significant differences
were found between the control group and
the experimental group in mean±SD displacement at 10 cycles (1.09±1.30 mm,
P=.31), mean±SD displacement at 500
cycles (2.85±2.43 mm, P=.26), mean±SD
load to failure (683±274 N, P=.31), or
mean±SD ultimate stiffness (117±37 N/
mm, P=.88) (Figures 8-9). Individual
data, including mode of failure, are shown
in Table 1 and Table 2.
Discussion
Failure of subscapularis repair negatively affects subjective and objective
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n Feature Article
Table 1
Displacement, Load to Failure, Stiffness, and Failure Mode Data for the Control Group
Specimen
Displacement at
10 Cycles, mm
Displacement at
500 Cycles, mm
Ultimate
Load, N
Stiffness,
N/mm
Failure Mode
C120430L
0.19
0.96
586.49
179.47
Bone fractured, implant pulled out
C121212R
1.00
2.67
649.88
81.42
Suture tore through tendon
C131040R
0.27
0.63
495.00
100.15
Bone fractured, implant pulled out
C131344L
0.40
0.69
450.57
84.28
Suture broke
C131420R
0.57
2.16
216.15
105.87
Knot failure
L130716R
1.36
Not applicable
832.24
111.38
Suture broke, knot failure
S131778R
0.31
0.63
663.67
213.34
Bone fractured, implant pulled out
C121966L
0.23
1.11
703.77
109.55
Bone fractured, implant pulled out
S120195R
0.54
1.98
606.97
132.44
Knot failure, bone fractured, implant pulled out
S120757R
0.34
1.32
666.91
118.42
Knot failure, suture slipped under implant
S121187R
0.64
1.95
917.21
121.61
Knot failure, bone fractured, implant pulled out
S121660R
0.89
2.68
467.25
135.53
Knot failure, bone fractured, implant pulled out
F130694R
0.21
0.58
958.44
116.45
Knot failure, implant pulled out
F140040R
0.59
3.21
835.95
87.89
Knot failure, implant pulled out
F140131L
0.97
1.30
510.85
107.96
Implant pulled out
F140134L
0.98
3.72
324.06
95.88
Knot failure, bone fractured, implant pulled out
F140214L
0.22
0.44
677.52
116.83
Knot failure, implant pulled out
F140303L
0.53
3.08
559.36
85.98
Knot failure, suture slipped under implant
C140351L
4.50
12.82
542.38
126.18
Knot failure, bone fractured, implant pulled out
C140403L
0.22
0.64
584.91
144.30
Knot failure, bone fractured, implant pulled out
Mean
0.75
2.24
612
119
SD
0.94
2.76
185
32
results after TSA. Liem et al9 performed
tenotomy with transosseous repair and
showed partial repair defects in 30% of
patients with ultrasound at a mean followup of 43 months. In addition, 25% of their
study cohort showed both subjective and
objective signs of diminished function.
Miller et al12 reported that subscapularis
rupture after TSA results in delayed rehabilitation and a possible need for additional surgery and produces inferior outcomes, even with adequate treatment. Use
of the humeral prosthesis as an anchoring
device is a novel approach. The current
biomechanical study showed that subscapularis repair through a humeral prosthesis specifically designed for subscapularis repair options allows subscapularis
peel repair to achieve equivalent strength
to lesser tuberosity osteotomy.
This study used subscapularis peel and
lesser tuberosity osteotomy as fixation
techniques in biomechanical testing. If
suture incorporation through the humeral
prosthesis could be shown to make subscapularis peel as strong as the current
gold standard of lesser tuberosity osteotomy with a nonincorporating device,
this would theoretically provide equivalent potential for healing with a simplified
surgical technique. Despite the theoretical
advantage of osseous healing after lesser
tuberosity osteotomy, the results of biomechanical and clinical studies comparing
the techniques have been mixed. Fishman
et al3 found more gapping at the repair site
SEPTEMBER/OCTOBER 2016 | Volume 39 • Number 5
with cyclic loading with the use of tenotomy rather than lesser tuberosity osteotomy to access the glenohumeral joint, with
equivalent load to failure. Krishnan et
al7 observed superior load to failure with
lesser tuberosity osteotomy compared
with tenotomy. Jandhyala et al6 showed
superior strength to belly press testing in
patients who underwent lesser tuberosity
osteotomy compared with those who underwent tenotomy during TSA. Giuseffi
et al4 found that tenotomy produced less
displacement to cyclic loading and equivalent load to failure compared with lesser
tuberosity osteotomy. Other authors8,13
found no clear superiority of 1 technique.
Subscapularis peel and tenotomy are
simple techniques that are favored by
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n Feature Article
Table 2
Displacement, Load to Failure, Stiffness, and Failure Mode Data for the Experimental Group
Specimen
Displacement at
10 Cycles, mm
Displacement at
500 Cycles, mm
Ultimate
Load, N
Stiffness,
N/mm
Failure Mode
C120430R
0.68
1.97
894.54
136.01
Suture broke, knot failure
C121212L
0.42
1.93
493.40
81.66
Suture broke
C131040L
0.60
1.97
595.94
141.99
Suture tore through tendon, knot failure
C131344R
0.13
0.23
1388.44
168.81
Suture broke
C131420L
0.36
1.64
441.48
79.19
Suture tore through tendon, knot failure
L130716L
0.38
1.54
1105.96
116.71
Suture tore through tendon, knot failure
S131778L
0.35
1.39
475.52
98.76
Bone fractured, implant pulled out
C121966R
0.27
0.37
1010.38
62.36
Suture tore through tendon
S120195L
1.32
4.23
420.84
129.79
Suture broke, implant pulled out
S120757L
1.49
2.90
1064.80
134.17
Knot failure, implant pulled out
S121187L
0.76
1.95
646.26
141.25
Suture broke, implant pulled out
S121660L
1.06
2.90
672.94
160.69
Knot failure, implant pulled out
F130694L
1.25
3.18
530.75
133.53
Suture broke, implant pulled out
F140040L
0.16
1.28
731.98
124.85
Suture broke, implant pulled out
F140131R
0.71
2.06
425.73
99.51
Knot failure, suture broke, implant pulled out
F140134R
4.94
10.08
438.38
90.38
Knot failure, implant pulled out
F140214R
0.50
1.84
741.99
84.55
Knot failure, implant pulled out
F140303R
4.38
7.21
582.04
84.56
Suture broke, implant pulled out
C140351R
1.54
6.39
490.56
70.96
Bone fractured, implant pulled out
C140403R
0.46
1.97
505.30
204.37
Suture broke, implant pulled out
Mean
1.09
2.85
683
117
SD
1.30
2.43
274
37
many surgeons for their ease of use and
because they avoid the possibility of lesser
tuberosity nonunion that may occur after
lesser tuberosity osteotomy.2 In older patients, the subscapularis tendon insertion
may have degeneration or partial tears. In
patients with surgery involving the subscapularis tendon, the insertion may have
been lateralized or compromised. This
may affect the ability to perform lesser tuberosity osteotomy or tenotomy, and peeloff can preserve maximal tendon length
and allow for repair of the tendon to the
lesser tuberosity. The authors prefer to use
subscapularis peel and have found that
it produces excellent results. However,
Ahmad et al1 showed that this technique
alters the anatomy of the subscapularis
e942
insertion, compromising the strength of
repair. Subscapularis repair with the use
of the humeral prosthesis as an anchoring
device does not produce a more anatomic
fixation, but it appears to provide better
initial strength during the healing period.
The technique, as designed, allows for dynamic equalization of tension across the
suture construct by the nature of the sliding suture holes and the practice of tying
each suture strand to a strand from another suture. This attribute is unique to this
technique and the use of this specifically
designed device. The authors use this device because it provides superior initial
fixation strength and also may reduce the
risk of tuberosity fracture with subscapularis peel. The superior initial fixation
provided by incorporating sutures through
the humeral prosthesis may reduce the
incidence of lesser tuberosity nonunion
when lesser tuberosity osteotomy is used,
but further clinical studies with advanced
imaging techniques are needed to determine whether this benefit exists. Avoiding
the devastating complication of subscapularis failure will improve patient outcomes
and reduce revision rates.
Limitations
Limitations of the study include its
short-term nature. Biomechanical studies
and short-term clinical outcome studies
do not provide information on the ultimate healing potential of this construct.
However, this study was conducted simi-
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n Feature Article
larly to other studies of subscapularis repair.4,7,10,13 Further clinical study of the
suture-incorporating humeral prosthesis
is needed to determine whether it offers
a true benefit in terms of shorter operative
time and improved patient outcomes.
Conclusion
The results of this biomechanical study
show that a through-implant suture technique allows subscapularis peel to achieve
similar strength to lesser tuberosity osteotomy in terms of displacement to cyclic
loading, ultimate load to failure, and stiffness. The authors have begun to use this
device in clinical practice and are monitoring the early outcomes of patients treated with the device to determine whether
there is a true clinical benefit when the
subscapularis is fixed with a throughimplant suturing technique.
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SEPTEMBER/OCTOBER 2016 | Volume 39 • Number 5
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