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Patellofemoral Contact Pressure for Medial Patellofemoral Ligament Reconstruction Using Suture Tape Varies With the Knee Flexion Angle: A Biomechanical Evaluation
Journal Pre-proof Patellofemoral contact pressure for medial patellofemoral ligament reconstruction using suture tape varies with the knee flexion angle: A biomechanical evaluation. Yukiko Sakamoto, M.D., Shizuka Sasaki, M.D., Yuka Kimura, M.D., Yuji Yamamoto, M.D., Eiichi Tsuda, M.D., Yasuyuki Ishibashi, M.D. PII:
S0749-8063(20)30040-2
DOI:
https://doi.org/10.1016/j.arthro.2019.12.027
Reference:
YJARS 56741
To appear in:
Arthroscopy: The Journal of Arthroscopic and Related Surgery
Received Date: 13 August 2019 Revised Date:
18 December 2019
Accepted Date: 18 December 2019
Please cite this article as: Sakamoto Y, Sasaki S, Kimura Y, Yamamoto Y, Tsuda E, Ishibashi Y, Patellofemoral contact pressure for medial patellofemoral ligament reconstruction using suture tape varies with the knee flexion angle: A biomechanical evaluation., Arthroscopy: The Journal of Arthroscopic and Related Surgery (2020), doi: https://doi.org/10.1016/j.arthro.2019.12.027. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier on behalf of the Arthroscopy Association of North America
1
Title
2
Patellofemoral contact pressure for medial patellofemoral ligament reconstruction
3
using suture tape varies with the knee flexion angle: A biomechanical evaluation.
4
Yukiko Sakamoto M.D.1, Shizuka Sasaki M.D.1, Yuka Kimura M.D.1, Yuji Yamamoto
5
M.D.1, Eiichi Tsuda M.D.2, Yasuyuki Ishibashi M.D.1.
6 7
1
8
Hirosaki, Japan
9
2
10
Department of Orthopaedic Surgery, Hirosaki University Graduate School of Medicine,
Department of Rehabilitation Medicine, Hirosaki University Graduate School of
Medicine, Hirosaki, Japan
11 12
Corresponding Author:
13
Yukiko Sakamoto
14
Address: 5 Zaifu-cho, Hirosaki, Aomori 036-8562, Japan
15
TEL: +81-172-39-5083
16
FAX: +81-172-36-3826
17
E-mail: [email protected]
18
IRB information
19
This study was approved by the Hirosaki University Graduate School of Medicine Ethics
20
Committee. Reference number is "2014-229".
21 22
Running title: PF contact pressure of MPFLR with suture tape
23 24
ACKNOWLEDGMENTS
25
We would like to express our gratitude to Eiji Sasaki for helping us with data analysis. We
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also would like to thank Editage (www.editage.jp) for English language editing.
1
Title
2
Patellofemoral contact pressure for medial patellofemoral ligament reconstruction
3
using suture tape varies with the knee flexion angle: A biomechanical evaluation.
4 5
ABSTRACT
6
Purpose: The purpose of this study was to evaluate the effect of the knee flexion angle during
7
graft fixation on patellofemoral (PF) contact pressure in medial patellofemoral ligament
8
(MPFL) reconstruction using polyester suture tape and knotless anchors.
9
Methods: Nine human knees (mean age: 71.2 ± 14.2 y) were used in this study. Polyester suture
10
tape was fixed at the medial edge of the patella with two 3.5-mm knotless anchors and then to
11
the femur with a 4.75-mm knotless anchor at four different knee flexion angles (0°, 30°, 60°,
12
and 90°). A pressure sensor was used to measure the maximum contact pressure (MCP) of the
13
medial and lateral PF joints in the intact knee and in post-reconstruction knees at each knee
14
flexion angle (0°, 30°, 60°, and 90°). Each MCP was normalized to that of the intact knee. A
15
statistical comparison was made between MCP in the intact and reconstructed knees.
16
Results: The normalized MCP of the medial PF joint fixed at either 0° or 30° significantly
17
increased at 60° of knee flexion (p=0.036 and 0.042, respectively) and at 90° of knee flexion
18
(p=0.002 and 0.001, respectively). Conversely, the normalized MCP fixed at 60° and 90°
19
remained at the same level as the intact knees at all angles of knee flexion. The normalized MCP
20
of the lateral PF joint showed no significant difference at any fixation angle compared with
21
intact knees.
22
Conclusion: To avoid excessive PF joint contact pressure after MPFL reconstruction, it may be
23
best to fix polyester suture tape between 60º to 90º of knee flexion.
24
Clinical Relevance: Fixation of the polyester suture tape with a knotless anchor for MPFL
25
reconstruction should be at 60º to 90º of knee flexion to most closely restore PF joint contact
26
pressures to that of the intact knee.
27 28
INTRODUCTION
29
Lateral patellar instability (LPI) is a common problem in young patients and surgical
30
treatment is often recommended.1, 2 The medial patellofemoral ligament (MPFL) is a major
31
stabilizer controlling lateral displacement of the patella,3 and it is frequently injured during
32
patellar dislocation.4, 5, MPFL reconstruction has become an acceptable treatment option6 that
33
demonstrates excellent clinical results and has a low repeat dislocation rate.7 Various graft
34
options exist for MPFL reconstruction, and the choice of graft remains the preference of the
35
surgeon; include semitendinosus, gracilis, quadriceps or adductor magnus tendons, part of the
36
patellar tendon, and allografts.8 Although autologous tendon grafts are most commonly used for
37
MPFL reconstruction, artificial ligaments have been reported as an alternative option.9, 10 MPFL
38
reconstruction using an artificial ligament entails no risk on the donor side.11 Other beneficial
39
characteristics of an artificial ligament are its stiffness and resistance to elongation. Lee et al.12
40
reported the use of synthetic material with knotless anchors for MPFL reconstruction. MPFL
41
reconstruction using polyester suture tape and knotless anchors significantly improves the
42
patient’s quality of life and results in better postoperative outcomes.12 A previous study showed
43
that MPFL reconstruction using polyester suture tape and knotless anchors was stronger than a
44
semitendinosus tendon autograft with soft anchors.13
45
One potential complication of MPFL reconstruction with an artificial ligament is
46
postoperative medial patellofemoral (PF) pain caused by an overly constrained patella. This is
47
affected by the fixation angle of the artificial ligament. It is important to maintain normal
48
patellofemoral contact pressure and to achieve reconstruction that is anatomically similar to that
49
of the intact knee. However, the optimal knee flexion angle for graft tension remains a matter of
50
debate.14-19
51
The purpose of this study was to evaluate the effect of the knee flexion angle during
52
graft fixation on PF contact pressure during MPFL reconstruction using polyester suture tape
53
and knotless anchors. It was hypothesized that the optimal fixation of the polyester suture tape
54
is 60° of flexion as reported in previous studies that used a tendon graft.20
55 56 57
MATERIALS AND METHODS Specimen preparation
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Fourteen amputated human knees from eight male and six female donors (age: 74.9 ±
59
14.1 y; range: 57-97 y) were used in this study. Informed consent was obtained from the patients
60
or their family, and the study was approved by our institution’s ethics committee. Specimens
61
with obvious knee osteoarthritis, such as grade 3 or 4 cartilage lesions, a history of knee surgery,
62
or abnormal laxity were excluded. Five specimens were excluded because those had knee
63
osteoarthritis (3 were grade 3 and 2 were grade 4). Specimens were evaluated by a senior
64
orthopaedic surgeon (PhD). The knees were stored at -20ºC and thawed at room temperature for
65
24 hours before testing. The proximal femur and distal tibia were cut approximately 150 mm
66
from the joint line. The patella, quadriceps tendon, and capsular structures around the patella
67
were left intact and the MPFL was identified. Specimens were kept moist with 0.9% saline
68
during preparation and testing. After preparing the specimens, the proximal part of the femur
69
was fixed to a custom-made mount that allowed for knee movement of 0° to 90° of knee flexion
70
(Fig. 1). A force of 50 N was continuously applied to the quadriceps tendon with a pulley
71
system to simulate physiological quadriceps function.21
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Surgical procedure
73
After the MPFL was cut at the midportion, MPFL reconstruction was performed using
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polyester suture tape (FiberTape®; Arthrex, North Naples, Florida) and knotless anchors (PEEK
75
SwiveLock®; Arthrex, North Naples, Florida).12 The central portion of the polyester suture tape
76
was fixed with two 3.5-mm knotless anchors on the patella. Fixation points were the proximal to
77
the quadrisect and the distal to the middleon the medial edge of the patella. Then, the two free
78
ends of the polyester suture tape were fixed using 4.75-mm knotless anchor on the femoral side
79
while the patella was kept in the center of the patellar groove (Fig. 2).13 The femoral fixation
80
point was determined by the insertion of the intact MPFL between the adductor tubercle and the
81
medial epicondyle. The polyester suture tape was fixed with the knee in different angles of
82
flexion (Fix 0°, 30°, 60°, or 90°) in each specimen. The MPFL had excessive tension and
83
limited patella motion over 30° of knee flexion. However, the MPFL gradually relaxed beyond
84
30° flexion6. Previous research21 indicated that MPFL reconstruction using the gracilis tendon
85
and a knee flexion angle of 60° most closely restored PF contact pressure. Based on these
86
results, the fixed angles for this study were determined to be 0°, 30°, 60°, and 90°. As reported,
87
polyester suture tape was fixed at 2 N, which is suitable for graft fixation.22, 23 After testing each
88
intact knee, MPFL reconstruction was performed with the knee a randomly assigned flexion
89
angle to avoid performing the reconstruction angle in sequence. Performing pressure
90
distributions in the same knee at different graft flexion angles might have influenced the
91
measurements performed during this study. To minimize this possibility, the sequence of knee
92
flexion angles was alternated between procedures.
93
Patellofemoral joint contact pressure
94
A pressure sensor device (K-SCAN2, 4010N; Tekscan, South Boston, MA, USA) was
95
used to measure PF joint contact pressure. The pressure sensor was inserted in the PF joint and
96
the sensors were calibrated using custom-made loading blocks before each test. The maximum
97
contact pressure (MCP) of the medial and lateral PF joints was measured for the intact knee as
98
well as for each MPFL reconstruction with knee flexion of 0°, 30°, 60°, and 90°.
99
Statistical analysis
100
All data input and calculations were performed. MCP values are shown as means and
101
standard deviations. During the power analysis, partial eta squared was calculated as 0.427 from
102
our present data, and the effect size was 0.863. A power analysis for the repeated-measured
103
analysis of variance (ANOVA) showed that we needed eight samples for each fixed group to be
104
able to reject the null hypothesis with a power of 0.80 and type I error probability of 0.05.
105
Finally, we could reject the null hypothesis with a power of 0.954. The values of MCP of each
106
MPFL reconstruction fixed at 0°, 30°, 60°, and 90° were normalized to those recorded for the
107
intact knees. Normalized MCP was compared using a repeated-measures ANOVA, followed by
108
Tukey post-hoc testing. Significance was set as p=0.05.
109 110
RESULTS
111
MCP values of the medial and lateral PF joints in the intact knees were similar at each
112
knee flexion angle, and we found no significant difference between the medial and lateral PF
113
joints (Table 1). The normalized MCP of the medial PF joint fixed at 0° and 30° was
114
significantly higher than that in intact knees in 60° of knee flexion (p=0.036 and 0.042,
115
respectively) and in 90° of knee flexion (p=0.002 and 0.001, respectively) (Table 2, Fig 3).
116
However, we found no significant difference in MCP with fixations at 60° and 90° compared
117
with the intact group. We found no significant difference in the normalized MCP of the lateral
118
PF joint in any group compared with intact group (Table 3, Fig 4).
119 120
DISCUSSION
121
During this study, we found no significant difference in the normalized MCP of the
122
medial PF joint in knees fixed at 60° and 90° compared with the intact group. These results
123
suggested that MPFL reconstruction using polyester suture tape and knotless anchors should be
124
fixed by suture tape at 60º to 90º of knee flexion.
125
Few studies have investigated the effects of knee the flexion angle on PF joint pressure
126
during graft fixation. Lorbach et al.21 conducted a biomechanical study of PF joint pressure after
127
MPFL reconstruction with a gracilis tendon. Based on that study, the tendon should be fixed at
128
60º during anatomical MPFL reconstruction. Although our study differed in that we used suture
129
tape, we obtained similar results for the optimal knee flexion angle during fixation. Hopper et
130
al.24 described a method of FT-MPFL reconstruction and stated the importance of avoiding
131
excessive constraint when fixing the suture tape because excess tension leads to irritation and
132
can result in quadriceps inhibition; however, in that study, the optimal knee flexion angle during
133
graft fixation was not reported for the clinical course or the biomechanical study. Our results
134
suggested that the optimal knee flexion angle at the time of graft fixation is 60º to 90º.
135
Several previous studies have reported the optimal fixation angle during MPFL
136
reconstruction using autografts. Deie et al.14 reported that the optimal fixation angle was30° of
137
knee flexion when using a cylindrical bone plug and semitendinosus tendon graft. Kita et al.16
138
reported that 45° was the optimal fixation angle when using a double-looped semitendinosus
139
tendon. Nomura et al.9 recommended fixation at 60° when using polyester tape (Leeds-Keio
140
artificial ligament); they also used a tension spacer between the polyester tape and the femur
141
during fixation to avoid excessive tensioning.
142
knee flexion was 90° for fixation using a polyester ligament during MPFL reconstruction.
143
Because these were clinical reports, and because biomechanical studies have not been
144
conducted, the optimal knee flexion angle for MPFL reconstruction using artificial ligaments
Additionally, it was reported10 that the optimal
145
remains unknown. Patel et al.25 conducted a systematic review of the optimal knee flexion angle
146
during graft fixation and, based on the flexion angle during graft fixation, separated subjects
147
into low (0-30°) and high (45-90°) flexion angle groups; they concluded that there was no
148
difference between the two groups. However, that study included a variety of MPFL
149
reconstruction techniques, and it cannot always be said that the flexion angle at the time of
150
fixation does not affect outcomes.
151
Lorbach21 reported that with fixation at 60°, the PF joint contact pressure was
152
equivalent to that of the intact group. In our study, fixation at 60° and fixation at 90° were found
153
to be equal to that of the intact group. These results may have been affected by the
154
characteristics of the suture tape. Polyester suture tape is an ultra-high-strength tape consisting
155
of long chains of ultra-high-molecular-weight polyethylene. Because this tape does not elongate
156
over time, as compared to autografts or allografts, the polyester suture tape fixation angle may
157
need to be equal to or greater than that used for autografts or allografts. These results were
158
consistent with those of this experiment.
159
Several studies have demonstrated that the anatomical placement of the graft is critical
160
during MPFL reconstruction. Sanchis-Alfonso26 reported that the optimal graft position on the
161
femur is critical and contributes to outcomes after MPFL reconstruction. MPFL attachment
162
footprints have been well-described by cadaveric studies.27-29 Schottle et al.30 were the first to
163
report reliable radiographic landmarks for an anatomic femoral attachment during MPFL
164
reconstruction. The MPFL was identified as a thickened, bandlike condensation of tissue
165
extending from the patella to the medial femur. The location of the femoral origin of the MPFL
166
is between the adductor tubercle and the medial epicondyle (Fig 2). Dornacher31 reported that
167
anatomical double-bundle MPFL reconstruction more closely restored PF joint contact pressure
168
to that of the intact knee. Stephen et al.32 stated that the correct femoral tunnel position restored
169
normal joint kinematics and PF joint contact pressure. In this study, anatomical double-bundle
170
reconstruction was performed in the same way as reported by previous studies to reduce the
171
influence on PF joint contact pressure.
172
Limitations
173
There were several limitations to the present study that need to be mentioned. Because
174
this was a biomechanical study of amputated knees, the results may not be completely
175
transferable to clinical situations. The surrounding soft tissue may significantly influence PF
176
joint contact pressure further, even if a constant pull of 50 N was applied to the quadriceps
177
tendon to simulate physiological quadriceps tension. This study involved knees without a
178
history of disease or patellar instability, which might differ from actual clinical conditions.
179
Sensor film was fixed to the patella using multiple simple stitches, and its influence on dynamic
180
pressure distributions cannot be ruled out. Another limitation was the possibility of deviation
181
due to the surgical technique. The techniques used in this study were comparable to those used
182
in vivo to assess anatomic fixation points. It may not be possible to completely reach anatomic
183
attachment in all knees, as recently shown by Ziegler et al.,33 because this is dependent on the
184
surgeon’s experience. A slight difference in femoral and patellar tunnel placement can
185
potentially occur during reconstruction. Another limitation was that measurements of the PF
186
joint contact pressures were only obtained medially and laterally. There was no significant
187
difference in the lateral PF joint contact pressure in this study; therefor, contact pressure
188
measured in more areas of the joint should be investigated. Another limitation was that this was
189
a time-zero study that did not consider the cyclic loading. Cyclic loading may affect the stiffness
190
of suture tape and fixation strength.
191 192 193 194
CONCLUSION To avoid excessive PF joint contact pressure after MPFL reconstruction, it may be best to fix polyester suture tape between 60º to 90º of knee flexion.
195
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10. Ellera Gomes JL. Medial patellofemoral ligament reconstruction for recurrent dislocation of the patella: a preliminary report. Arthroscopy 1992;8:335-340.
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11. Shah JN, Howard JS, Flanigan DC, et al. A systematic review of complications and failures
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12. Lee PYF, Golding D, Rozewicz S, et al. Modern synthetic material is a safe and effective
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Arthrosc 2018;26:2716-2721.
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13. Tsushima T, Tsukada H, Saaki S, et al. Biomechanical analysis of medial patellofemoral
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14. Deie M, Ochi M, Adachi N, Shibuya H, Nakamae A. Medial patellofemoral ligament
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reconstruction fixed with a cylindrical bone plug and a grafted semitendinosus tendon at
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the original femoral site for recurrent patellar dislocation. Am J Sports Med
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2011;39:140-145.
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15. Han H, Xia Y, Yun X, Wu M. Anatomical transverse patella double tunnel reconstruction of
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medial patellofemoral ligament with a hamstring tendon autograft for recurrent patellar
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dislocation. Arch Orthop Trauma Surg 2011;131:343-351.
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16. Kita K, Horibe S, Toritsuka Y, et al. Effects of medial patellofemoral ligament
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reconstruction on patellar tracking. Knee Surg Sports Traumatol Arthrosc 2012;20:829-837.
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17. Matthews JJ, Schranz P. Reconstruction of the medial patellofemoral ligament using a
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18. Panni AS, Alam M, Cerciello S, Vasso M, Maffulli N. Medial patellofemoral ligament
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19. Smith TO, Mann CJ, Donell ST. Does knee joint proprioception alter following medial patellofemoral ligament reconstruction? Knee 2014;21:21-27.
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20. Lorbach O, Zumbansen N, Kieb M, et al. Medial patellofemoral ligament reconstruction:
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21. Lorbach O, Haupert A, Efe T, et al. Biomechanical evaluation of MPFL reconstructions:
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Sports Traumatol Arthrosc 2017;25:2502-2510.
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22. Beck P, Brown NA, Greis PE, Burks RT. Patellofemoral contact pressures and lateral
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23. Stephen JM, Kittl C, Williams A, et al. Effect of Mmedial patellofemoral ligament
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reconstruction method on patellofemoral contact pressures and kinematics. Am J Sports
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Med 2016;44:1186-1194.
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24. Hopper GP, Heusdens CHW, Dossche L, Mackay GM. Medial patellofemoral ligament repair with suture tape augmentation. Arthrosc Tech 2019;8:e1-e5.
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25. Patel NK, de Sa D, Vaswani R, et al. Knee flexion angle during graft fixation for medial
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patellofemoral ligament reconstruction: A systematic review of outcomes and
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complications. Arthroscopy 2019;35:1893-1904.
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26. Sanchis-Alfonso. Guidelines for medial patellofemoral ligament reconstruction in chronic lateral patellar instability. J Am Acad Orthop Surg 2014;22:175-182. 27. Shea KG, Martinson WD, Cannamela PC, et al. Am J Sports Med 2018 Feb;46:363-369.
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28. Kruckeberg BM, Chahla J, Moatshe G, et al. Quantitative and qualitative analysis of the medial patellar ligaments: An anatomic and radiographic study.
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29. Shea KG, Styhl AC, Jacobs JC Jr, et al. The relationship of the femoral physis and the
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medial patellofemoral ligament in children: A cadaveric study. Am J Sports Med
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2016;44:2833-2837.
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30. Schöttle PB, Schmeling A, Rosenstiel N, Weiler A. Radiographic landmarks for femoral
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tunnel placement in medial patellofemoral ligament reconstruction. Am J Sports Med
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2007;35:801-804.
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31. Dornacher D, Lippacher S, Nelitz M, et al. Impact of five different medial patellofemoral
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ligament-reconstruction strategies and three different graft pre-tensioning states on the
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mean patellofemoral contact pressure: a biomechanical study on human cadaver knees. J
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Exp Orthop 2018;28:1-10.
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32. Stephen JM, Kaider D, Lumpaopong P, Deehan DJ, Amis AA. The effect of femoral tunnel
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position and graft tension on patellar contact mechanics and kinematics after medial
281
patellofemoral ligament reconstruction. Am J Sports Med 2014;42:364-372.
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33. Ziegler CG, Fulkerson JP, Edgar C. Radiographic reference points are inaccurate with and
283
without a true lateral radiograph: The importance of anatomy in medial patellofemoral
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ligament reconstruction. Am J Sports Med 2016;44:133-142.
285
FIGURE LEGENDS
286
Figure 1. Testing apparatus and specimen. Knee specimens were fixed to a custom-made mount
287
that allowed for 0° to 90° of knee flexion. Pressure sensors were sutured to the undersurface of
288
the patella.
289 290
Figure 2. Computed tomography (CT) image of the right knee after medial patellofemoral
291
ligament reconstruction using polyester suture tape and knotless anchors. The central portion of
292
the polyester suture tape was fixed by two 3.5-mm knotless anchors on the medial border of the
293
patella (arrow) and the two free ends of the polyester suture tapes were fixed using a 4.75-mm
294
knotless anchor on the femoral side (arrowhead). The femoral fixation point is located between
295
the abductor tubercle (AD) and medial epicondyle (ME).
296 297
Figure 3. Normalized maximum contact pressure (MCP) of the medial patellofemoral (PF) joint.
298
The normalized MCP of the medial PF joint fixed at 0° and 30° was significantly higher than
299
that in intact knees at 60° of knee flexion (p=0.036 and 0.042, respectively) and at 90° of knee
300
flexion (p=0.002 and 0.001, respectively). *p < 0.05 compared to the intact group.
301
302
Figure 4. Normalized maximum contact pressure (MCP) of the lateral patellofemoral (PF) joint.
303
The normalized MCP of the lateral PF joint showed no significant difference in any group
304
compared with the intact group.
305
TABLES
306 307
Table 1. Average values of the maximum contact pressure of the medial and lateral
308
patellofemoral joints in intact knees. Medial PF joint
Lateral PF joint
Flexion angle 2
(N/cm )
(N/cm2)
0°
9.32 ± 4.00
10.56 ± 4.48
30°
9.56 ± 2.74
10.11 ± 2.85
60°
9.43 ± 3.43
9.67 ± 3.54
90°
8.00 ± 2.78
8.44 ± 3.78
309
Joint pressures are expressed as mean ± standard deviationSD.
310
TABLE 2. Average values of the normalized maximum contact pressure of medial
311
patellofemoral joint. Flexion angle
Fix 0°
Fix 30°
Fix 60°
Fix 90°
0°
1.09 ± 0.31
1.09 ± 0.43
0.90 ± 0.17
0.82 ± 0.13
30°
1.40 ± 0.57
1.18 ± 0.28
0.97 ± 0.09
0.94 ± 0.18
60°
1.56 ± 0.56
1.55 ± 0.62
1.01 ± 0.12
0.98 ± 0.16
90°
1.69 ± 0.46
1.76 ± 0.40
1.22 ± 0.20
1.15 ± 0.23
312
Joint pressures are expressed as mean ± standard deviation (N/cm2).
313
*p < 0.05 compared with the intact group
314 315
TABLE 3. Average values of the normalized maximum contact pressure of the lateral
316
patellofemoral joint.
317
Flexion angle
Fix 0°
Fix 30°
Fix 60°
Fix 90°
0°
1.04 ± 0.28
1.01 ± 0.26
0.81 ± 0.18
0.75 ± 0.24
30°
1.15 ± 0.27
1.07 ± 0.35
0.93 ± 0.21
0.87 ± 0.24
60°
1.12 ± 0.27
1.03 ± 0.25
1.04 ± 0.22
1.00 ± 0.13
90°
1.09 ± 0.60
0.90 ± 0.33
1.00 ± 0.18
1.04 ± 0.26
Joint pressures are expressed as mean ± standard deviationSD (N/cm2).
Figure 1.
AD
ME
Figure 2.
(%)
＊ ＊
Maximum contact pressure
200%
＊ Intact
150%
Fix 0° Fix 30° 100%
Fix 60° Fix 90° 50%
0%
0° Figure 3.
30° 60° Knee flexion angle
90°
(%)
Maximum contact pressure
200%
150%
100%
Intact Fix 0° Fix 30° Fix 60° Fix 90°
Posterior
50%
0%
0° Figure 4.
30°
60°
Knee flexion angle
90°
S0749-8063(20)30040-2
DOI:
https://doi.org/10.1016/j.arthro.2019.12.027
Reference:
YJARS 56741
To appear in:
Arthroscopy: The Journal of Arthroscopic and Related Surgery
Received Date: 13 August 2019 Revised Date:
18 December 2019
Accepted Date: 18 December 2019
Please cite this article as: Sakamoto Y, Sasaki S, Kimura Y, Yamamoto Y, Tsuda E, Ishibashi Y, Patellofemoral contact pressure for medial patellofemoral ligament reconstruction using suture tape varies with the knee flexion angle: A biomechanical evaluation., Arthroscopy: The Journal of Arthroscopic and Related Surgery (2020), doi: https://doi.org/10.1016/j.arthro.2019.12.027. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier on behalf of the Arthroscopy Association of North America
1
Title
2
Patellofemoral contact pressure for medial patellofemoral ligament reconstruction
3
using suture tape varies with the knee flexion angle: A biomechanical evaluation.
4
Yukiko Sakamoto M.D.1, Shizuka Sasaki M.D.1, Yuka Kimura M.D.1, Yuji Yamamoto
5
M.D.1, Eiichi Tsuda M.D.2, Yasuyuki Ishibashi M.D.1.
6 7
1
8
Hirosaki, Japan
9
2
10
Department of Orthopaedic Surgery, Hirosaki University Graduate School of Medicine,
Department of Rehabilitation Medicine, Hirosaki University Graduate School of
Medicine, Hirosaki, Japan
11 12
Corresponding Author:
13
Yukiko Sakamoto
14
Address: 5 Zaifu-cho, Hirosaki, Aomori 036-8562, Japan
15
TEL: +81-172-39-5083
16
FAX: +81-172-36-3826
17
E-mail: [email protected]
18
IRB information
19
This study was approved by the Hirosaki University Graduate School of Medicine Ethics
20
Committee. Reference number is "2014-229".
21 22
Running title: PF contact pressure of MPFLR with suture tape
23 24
ACKNOWLEDGMENTS
25
We would like to express our gratitude to Eiji Sasaki for helping us with data analysis. We
26
also would like to thank Editage (www.editage.jp) for English language editing.
1
Title
2
Patellofemoral contact pressure for medial patellofemoral ligament reconstruction
3
using suture tape varies with the knee flexion angle: A biomechanical evaluation.
4 5
ABSTRACT
6
Purpose: The purpose of this study was to evaluate the effect of the knee flexion angle during
7
graft fixation on patellofemoral (PF) contact pressure in medial patellofemoral ligament
8
(MPFL) reconstruction using polyester suture tape and knotless anchors.
9
Methods: Nine human knees (mean age: 71.2 ± 14.2 y) were used in this study. Polyester suture
10
tape was fixed at the medial edge of the patella with two 3.5-mm knotless anchors and then to
11
the femur with a 4.75-mm knotless anchor at four different knee flexion angles (0°, 30°, 60°,
12
and 90°). A pressure sensor was used to measure the maximum contact pressure (MCP) of the
13
medial and lateral PF joints in the intact knee and in post-reconstruction knees at each knee
14
flexion angle (0°, 30°, 60°, and 90°). Each MCP was normalized to that of the intact knee. A
15
statistical comparison was made between MCP in the intact and reconstructed knees.
16
Results: The normalized MCP of the medial PF joint fixed at either 0° or 30° significantly
17
increased at 60° of knee flexion (p=0.036 and 0.042, respectively) and at 90° of knee flexion
18
(p=0.002 and 0.001, respectively). Conversely, the normalized MCP fixed at 60° and 90°
19
remained at the same level as the intact knees at all angles of knee flexion. The normalized MCP
20
of the lateral PF joint showed no significant difference at any fixation angle compared with
21
intact knees.
22
Conclusion: To avoid excessive PF joint contact pressure after MPFL reconstruction, it may be
23
best to fix polyester suture tape between 60º to 90º of knee flexion.
24
Clinical Relevance: Fixation of the polyester suture tape with a knotless anchor for MPFL
25
reconstruction should be at 60º to 90º of knee flexion to most closely restore PF joint contact
26
pressures to that of the intact knee.
27 28
INTRODUCTION
29
Lateral patellar instability (LPI) is a common problem in young patients and surgical
30
treatment is often recommended.1, 2 The medial patellofemoral ligament (MPFL) is a major
31
stabilizer controlling lateral displacement of the patella,3 and it is frequently injured during
32
patellar dislocation.4, 5, MPFL reconstruction has become an acceptable treatment option6 that
33
demonstrates excellent clinical results and has a low repeat dislocation rate.7 Various graft
34
options exist for MPFL reconstruction, and the choice of graft remains the preference of the
35
surgeon; include semitendinosus, gracilis, quadriceps or adductor magnus tendons, part of the
36
patellar tendon, and allografts.8 Although autologous tendon grafts are most commonly used for
37
MPFL reconstruction, artificial ligaments have been reported as an alternative option.9, 10 MPFL
38
reconstruction using an artificial ligament entails no risk on the donor side.11 Other beneficial
39
characteristics of an artificial ligament are its stiffness and resistance to elongation. Lee et al.12
40
reported the use of synthetic material with knotless anchors for MPFL reconstruction. MPFL
41
reconstruction using polyester suture tape and knotless anchors significantly improves the
42
patient’s quality of life and results in better postoperative outcomes.12 A previous study showed
43
that MPFL reconstruction using polyester suture tape and knotless anchors was stronger than a
44
semitendinosus tendon autograft with soft anchors.13
45
One potential complication of MPFL reconstruction with an artificial ligament is
46
postoperative medial patellofemoral (PF) pain caused by an overly constrained patella. This is
47
affected by the fixation angle of the artificial ligament. It is important to maintain normal
48
patellofemoral contact pressure and to achieve reconstruction that is anatomically similar to that
49
of the intact knee. However, the optimal knee flexion angle for graft tension remains a matter of
50
debate.14-19
51
The purpose of this study was to evaluate the effect of the knee flexion angle during
52
graft fixation on PF contact pressure during MPFL reconstruction using polyester suture tape
53
and knotless anchors. It was hypothesized that the optimal fixation of the polyester suture tape
54
is 60° of flexion as reported in previous studies that used a tendon graft.20
55 56 57
MATERIALS AND METHODS Specimen preparation
58
Fourteen amputated human knees from eight male and six female donors (age: 74.9 ±
59
14.1 y; range: 57-97 y) were used in this study. Informed consent was obtained from the patients
60
or their family, and the study was approved by our institution’s ethics committee. Specimens
61
with obvious knee osteoarthritis, such as grade 3 or 4 cartilage lesions, a history of knee surgery,
62
or abnormal laxity were excluded. Five specimens were excluded because those had knee
63
osteoarthritis (3 were grade 3 and 2 were grade 4). Specimens were evaluated by a senior
64
orthopaedic surgeon (PhD). The knees were stored at -20ºC and thawed at room temperature for
65
24 hours before testing. The proximal femur and distal tibia were cut approximately 150 mm
66
from the joint line. The patella, quadriceps tendon, and capsular structures around the patella
67
were left intact and the MPFL was identified. Specimens were kept moist with 0.9% saline
68
during preparation and testing. After preparing the specimens, the proximal part of the femur
69
was fixed to a custom-made mount that allowed for knee movement of 0° to 90° of knee flexion
70
(Fig. 1). A force of 50 N was continuously applied to the quadriceps tendon with a pulley
71
system to simulate physiological quadriceps function.21
72
Surgical procedure
73
After the MPFL was cut at the midportion, MPFL reconstruction was performed using
74
polyester suture tape (FiberTape®; Arthrex, North Naples, Florida) and knotless anchors (PEEK
75
SwiveLock®; Arthrex, North Naples, Florida).12 The central portion of the polyester suture tape
76
was fixed with two 3.5-mm knotless anchors on the patella. Fixation points were the proximal to
77
the quadrisect and the distal to the middleon the medial edge of the patella. Then, the two free
78
ends of the polyester suture tape were fixed using 4.75-mm knotless anchor on the femoral side
79
while the patella was kept in the center of the patellar groove (Fig. 2).13 The femoral fixation
80
point was determined by the insertion of the intact MPFL between the adductor tubercle and the
81
medial epicondyle. The polyester suture tape was fixed with the knee in different angles of
82
flexion (Fix 0°, 30°, 60°, or 90°) in each specimen. The MPFL had excessive tension and
83
limited patella motion over 30° of knee flexion. However, the MPFL gradually relaxed beyond
84
30° flexion6. Previous research21 indicated that MPFL reconstruction using the gracilis tendon
85
and a knee flexion angle of 60° most closely restored PF contact pressure. Based on these
86
results, the fixed angles for this study were determined to be 0°, 30°, 60°, and 90°. As reported,
87
polyester suture tape was fixed at 2 N, which is suitable for graft fixation.22, 23 After testing each
88
intact knee, MPFL reconstruction was performed with the knee a randomly assigned flexion
89
angle to avoid performing the reconstruction angle in sequence. Performing pressure
90
distributions in the same knee at different graft flexion angles might have influenced the
91
measurements performed during this study. To minimize this possibility, the sequence of knee
92
flexion angles was alternated between procedures.
93
Patellofemoral joint contact pressure
94
A pressure sensor device (K-SCAN2, 4010N; Tekscan, South Boston, MA, USA) was
95
used to measure PF joint contact pressure. The pressure sensor was inserted in the PF joint and
96
the sensors were calibrated using custom-made loading blocks before each test. The maximum
97
contact pressure (MCP) of the medial and lateral PF joints was measured for the intact knee as
98
well as for each MPFL reconstruction with knee flexion of 0°, 30°, 60°, and 90°.
99
Statistical analysis
100
All data input and calculations were performed. MCP values are shown as means and
101
standard deviations. During the power analysis, partial eta squared was calculated as 0.427 from
102
our present data, and the effect size was 0.863. A power analysis for the repeated-measured
103
analysis of variance (ANOVA) showed that we needed eight samples for each fixed group to be
104
able to reject the null hypothesis with a power of 0.80 and type I error probability of 0.05.
105
Finally, we could reject the null hypothesis with a power of 0.954. The values of MCP of each
106
MPFL reconstruction fixed at 0°, 30°, 60°, and 90° were normalized to those recorded for the
107
intact knees. Normalized MCP was compared using a repeated-measures ANOVA, followed by
108
Tukey post-hoc testing. Significance was set as p=0.05.
109 110
RESULTS
111
MCP values of the medial and lateral PF joints in the intact knees were similar at each
112
knee flexion angle, and we found no significant difference between the medial and lateral PF
113
joints (Table 1). The normalized MCP of the medial PF joint fixed at 0° and 30° was
114
significantly higher than that in intact knees in 60° of knee flexion (p=0.036 and 0.042,
115
respectively) and in 90° of knee flexion (p=0.002 and 0.001, respectively) (Table 2, Fig 3).
116
However, we found no significant difference in MCP with fixations at 60° and 90° compared
117
with the intact group. We found no significant difference in the normalized MCP of the lateral
118
PF joint in any group compared with intact group (Table 3, Fig 4).
119 120
DISCUSSION
121
During this study, we found no significant difference in the normalized MCP of the
122
medial PF joint in knees fixed at 60° and 90° compared with the intact group. These results
123
suggested that MPFL reconstruction using polyester suture tape and knotless anchors should be
124
fixed by suture tape at 60º to 90º of knee flexion.
125
Few studies have investigated the effects of knee the flexion angle on PF joint pressure
126
during graft fixation. Lorbach et al.21 conducted a biomechanical study of PF joint pressure after
127
MPFL reconstruction with a gracilis tendon. Based on that study, the tendon should be fixed at
128
60º during anatomical MPFL reconstruction. Although our study differed in that we used suture
129
tape, we obtained similar results for the optimal knee flexion angle during fixation. Hopper et
130
al.24 described a method of FT-MPFL reconstruction and stated the importance of avoiding
131
excessive constraint when fixing the suture tape because excess tension leads to irritation and
132
can result in quadriceps inhibition; however, in that study, the optimal knee flexion angle during
133
graft fixation was not reported for the clinical course or the biomechanical study. Our results
134
suggested that the optimal knee flexion angle at the time of graft fixation is 60º to 90º.
135
Several previous studies have reported the optimal fixation angle during MPFL
136
reconstruction using autografts. Deie et al.14 reported that the optimal fixation angle was30° of
137
knee flexion when using a cylindrical bone plug and semitendinosus tendon graft. Kita et al.16
138
reported that 45° was the optimal fixation angle when using a double-looped semitendinosus
139
tendon. Nomura et al.9 recommended fixation at 60° when using polyester tape (Leeds-Keio
140
artificial ligament); they also used a tension spacer between the polyester tape and the femur
141
during fixation to avoid excessive tensioning.
142
knee flexion was 90° for fixation using a polyester ligament during MPFL reconstruction.
143
Because these were clinical reports, and because biomechanical studies have not been
144
conducted, the optimal knee flexion angle for MPFL reconstruction using artificial ligaments
Additionally, it was reported10 that the optimal
145
remains unknown. Patel et al.25 conducted a systematic review of the optimal knee flexion angle
146
during graft fixation and, based on the flexion angle during graft fixation, separated subjects
147
into low (0-30°) and high (45-90°) flexion angle groups; they concluded that there was no
148
difference between the two groups. However, that study included a variety of MPFL
149
reconstruction techniques, and it cannot always be said that the flexion angle at the time of
150
fixation does not affect outcomes.
151
Lorbach21 reported that with fixation at 60°, the PF joint contact pressure was
152
equivalent to that of the intact group. In our study, fixation at 60° and fixation at 90° were found
153
to be equal to that of the intact group. These results may have been affected by the
154
characteristics of the suture tape. Polyester suture tape is an ultra-high-strength tape consisting
155
of long chains of ultra-high-molecular-weight polyethylene. Because this tape does not elongate
156
over time, as compared to autografts or allografts, the polyester suture tape fixation angle may
157
need to be equal to or greater than that used for autografts or allografts. These results were
158
consistent with those of this experiment.
159
Several studies have demonstrated that the anatomical placement of the graft is critical
160
during MPFL reconstruction. Sanchis-Alfonso26 reported that the optimal graft position on the
161
femur is critical and contributes to outcomes after MPFL reconstruction. MPFL attachment
162
footprints have been well-described by cadaveric studies.27-29 Schottle et al.30 were the first to
163
report reliable radiographic landmarks for an anatomic femoral attachment during MPFL
164
reconstruction. The MPFL was identified as a thickened, bandlike condensation of tissue
165
extending from the patella to the medial femur. The location of the femoral origin of the MPFL
166
is between the adductor tubercle and the medial epicondyle (Fig 2). Dornacher31 reported that
167
anatomical double-bundle MPFL reconstruction more closely restored PF joint contact pressure
168
to that of the intact knee. Stephen et al.32 stated that the correct femoral tunnel position restored
169
normal joint kinematics and PF joint contact pressure. In this study, anatomical double-bundle
170
reconstruction was performed in the same way as reported by previous studies to reduce the
171
influence on PF joint contact pressure.
172
Limitations
173
There were several limitations to the present study that need to be mentioned. Because
174
this was a biomechanical study of amputated knees, the results may not be completely
175
transferable to clinical situations. The surrounding soft tissue may significantly influence PF
176
joint contact pressure further, even if a constant pull of 50 N was applied to the quadriceps
177
tendon to simulate physiological quadriceps tension. This study involved knees without a
178
history of disease or patellar instability, which might differ from actual clinical conditions.
179
Sensor film was fixed to the patella using multiple simple stitches, and its influence on dynamic
180
pressure distributions cannot be ruled out. Another limitation was the possibility of deviation
181
due to the surgical technique. The techniques used in this study were comparable to those used
182
in vivo to assess anatomic fixation points. It may not be possible to completely reach anatomic
183
attachment in all knees, as recently shown by Ziegler et al.,33 because this is dependent on the
184
surgeon’s experience. A slight difference in femoral and patellar tunnel placement can
185
potentially occur during reconstruction. Another limitation was that measurements of the PF
186
joint contact pressures were only obtained medially and laterally. There was no significant
187
difference in the lateral PF joint contact pressure in this study; therefor, contact pressure
188
measured in more areas of the joint should be investigated. Another limitation was that this was
189
a time-zero study that did not consider the cyclic loading. Cyclic loading may affect the stiffness
190
of suture tape and fixation strength.
191 192 193 194
CONCLUSION To avoid excessive PF joint contact pressure after MPFL reconstruction, it may be best to fix polyester suture tape between 60º to 90º of knee flexion.
195
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13. Tsushima T, Tsukada H, Saaki S, et al. Biomechanical analysis of medial patellofemoral
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14. Deie M, Ochi M, Adachi N, Shibuya H, Nakamae A. Medial patellofemoral ligament
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15. Han H, Xia Y, Yun X, Wu M. Anatomical transverse patella double tunnel reconstruction of
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17. Matthews JJ, Schranz P. Reconstruction of the medial patellofemoral ligament using a
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18. Panni AS, Alam M, Cerciello S, Vasso M, Maffulli N. Medial patellofemoral ligament
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Sports Traumatol Arthrosc 2017;25:2502-2510.
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23. Stephen JM, Kittl C, Williams A, et al. Effect of Mmedial patellofemoral ligament
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Med 2016;44:1186-1194.
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24. Hopper GP, Heusdens CHW, Dossche L, Mackay GM. Medial patellofemoral ligament repair with suture tape augmentation. Arthrosc Tech 2019;8:e1-e5.
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25. Patel NK, de Sa D, Vaswani R, et al. Knee flexion angle during graft fixation for medial
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patellofemoral ligament reconstruction: A systematic review of outcomes and
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complications. Arthroscopy 2019;35:1893-1904.
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26. Sanchis-Alfonso. Guidelines for medial patellofemoral ligament reconstruction in chronic lateral patellar instability. J Am Acad Orthop Surg 2014;22:175-182. 27. Shea KG, Martinson WD, Cannamela PC, et al. Am J Sports Med 2018 Feb;46:363-369.
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28. Kruckeberg BM, Chahla J, Moatshe G, et al. Quantitative and qualitative analysis of the medial patellar ligaments: An anatomic and radiographic study.
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29. Shea KG, Styhl AC, Jacobs JC Jr, et al. The relationship of the femoral physis and the
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medial patellofemoral ligament in children: A cadaveric study. Am J Sports Med
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2016;44:2833-2837.
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30. Schöttle PB, Schmeling A, Rosenstiel N, Weiler A. Radiographic landmarks for femoral
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tunnel placement in medial patellofemoral ligament reconstruction. Am J Sports Med
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2007;35:801-804.
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31. Dornacher D, Lippacher S, Nelitz M, et al. Impact of five different medial patellofemoral
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ligament-reconstruction strategies and three different graft pre-tensioning states on the
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mean patellofemoral contact pressure: a biomechanical study on human cadaver knees. J
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Exp Orthop 2018;28:1-10.
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32. Stephen JM, Kaider D, Lumpaopong P, Deehan DJ, Amis AA. The effect of femoral tunnel
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position and graft tension on patellar contact mechanics and kinematics after medial
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patellofemoral ligament reconstruction. Am J Sports Med 2014;42:364-372.
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33. Ziegler CG, Fulkerson JP, Edgar C. Radiographic reference points are inaccurate with and
283
without a true lateral radiograph: The importance of anatomy in medial patellofemoral
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285
FIGURE LEGENDS
286
Figure 1. Testing apparatus and specimen. Knee specimens were fixed to a custom-made mount
287
that allowed for 0° to 90° of knee flexion. Pressure sensors were sutured to the undersurface of
288
the patella.
289 290
Figure 2. Computed tomography (CT) image of the right knee after medial patellofemoral
291
ligament reconstruction using polyester suture tape and knotless anchors. The central portion of
292
the polyester suture tape was fixed by two 3.5-mm knotless anchors on the medial border of the
293
patella (arrow) and the two free ends of the polyester suture tapes were fixed using a 4.75-mm
294
knotless anchor on the femoral side (arrowhead). The femoral fixation point is located between
295
the abductor tubercle (AD) and medial epicondyle (ME).
296 297
Figure 3. Normalized maximum contact pressure (MCP) of the medial patellofemoral (PF) joint.
298
The normalized MCP of the medial PF joint fixed at 0° and 30° was significantly higher than
299
that in intact knees at 60° of knee flexion (p=0.036 and 0.042, respectively) and at 90° of knee
300
flexion (p=0.002 and 0.001, respectively). *p < 0.05 compared to the intact group.
301
302
Figure 4. Normalized maximum contact pressure (MCP) of the lateral patellofemoral (PF) joint.
303
The normalized MCP of the lateral PF joint showed no significant difference in any group
304
compared with the intact group.
305
TABLES
306 307
Table 1. Average values of the maximum contact pressure of the medial and lateral
308
patellofemoral joints in intact knees. Medial PF joint
Lateral PF joint
Flexion angle 2
(N/cm )
(N/cm2)
0°
9.32 ± 4.00
10.56 ± 4.48
30°
9.56 ± 2.74
10.11 ± 2.85
60°
9.43 ± 3.43
9.67 ± 3.54
90°
8.00 ± 2.78
8.44 ± 3.78
309
Joint pressures are expressed as mean ± standard deviationSD.
310
TABLE 2. Average values of the normalized maximum contact pressure of medial
311
patellofemoral joint. Flexion angle
Fix 0°
Fix 30°
Fix 60°
Fix 90°
0°
1.09 ± 0.31
1.09 ± 0.43
0.90 ± 0.17
0.82 ± 0.13
30°
1.40 ± 0.57
1.18 ± 0.28
0.97 ± 0.09
0.94 ± 0.18
60°
1.56 ± 0.56
1.55 ± 0.62
1.01 ± 0.12
0.98 ± 0.16
90°
1.69 ± 0.46
1.76 ± 0.40
1.22 ± 0.20
1.15 ± 0.23
312
Joint pressures are expressed as mean ± standard deviation (N/cm2).
313
*p < 0.05 compared with the intact group
314 315
TABLE 3. Average values of the normalized maximum contact pressure of the lateral
316
patellofemoral joint.
317
Flexion angle
Fix 0°
Fix 30°
Fix 60°
Fix 90°
0°
1.04 ± 0.28
1.01 ± 0.26
0.81 ± 0.18
0.75 ± 0.24
30°
1.15 ± 0.27
1.07 ± 0.35
0.93 ± 0.21
0.87 ± 0.24
60°
1.12 ± 0.27
1.03 ± 0.25
1.04 ± 0.22
1.00 ± 0.13
90°
1.09 ± 0.60
0.90 ± 0.33
1.00 ± 0.18
1.04 ± 0.26
Joint pressures are expressed as mean ± standard deviationSD (N/cm2).
Figure 1.
AD
ME
Figure 2.
(%)
＊ ＊
Maximum contact pressure
200%
＊ Intact
150%
Fix 0° Fix 30° 100%
Fix 60° Fix 90° 50%
0%
0° Figure 3.
30° 60° Knee flexion angle
90°
(%)
Maximum contact pressure
200%
150%
100%
Intact Fix 0° Fix 30° Fix 60° Fix 90°
Posterior
50%
0%
0° Figure 4.
30°
60°
Knee flexion angle
90°