Taiki Nozaki1, Atsushi Tasaki2, Saya Horiuchi1, Junko Ochi1, Jay Starkey1, Takeshi Hara3, Yukihisa Saida1, Yasuyuki Kurihara1, and Hiroshi Yoshioka4
1Radiology, St.Luke's International Hospital, Tokyo, Japan, 2Orthopaedic Surgery, St.Luke's International Hospital, Tokyo, Japan, 3Intelligent Image Information, Gifu University, Gifu, Japan, 4Radiological Sciences, University of California, Irvine, Orange, CA, United States
Synopsis
Rotator cuff tear is a common cause of shoulder
pain and disability. Minimally-invasive arthroscopic rotator cuff repair is
increasingly popular for treatment of full-thickness rotator cuff tear.
However, operative outcomes are far from perfect. Postoperative re-tears are
associated with greater fatty degeneration. The purpose of this study was to
quantify the pre- and post-operative muscular fatty degeneration using a 2-Point
Dixon sequence in patients with rotator cuff tears treated by arthroscopic
rotator cuff repair. Further, we aim to assess the relationship of preoperative
fat fraction values within rotator cuff muscles between patients who experience
re-tear and those who do not.INTRODUCTION
Rotator cuff tear is a common cause of shoulder
pain and disability, and is among the most common conditions affecting the
shoulder (1). Such injuries increase with age, reducing the quality of life due
to shoulder pain and weakness with shoulder flexion and abduction. Minimally-invasive
arthroscopic rotator cuff repair is increasingly popular for treatment of
full-thickness rotator cuff tear following the introduction of innovative
arthroscopic techniques (2). However, operative outcomes are far from perfect,
with a mean re-tear rate of 26.6% at 2 years after surgery (3). Postoperative
re-tears are associated with greater fatty degeneration, larger tear size, and
advanced age. The purpose of this study was to quantify the pre- and
post-operative muscular fatty degeneration using a 2-Point Dixon sequence in
patients with rotator cuff tears treated by arthroscopic rotator cuff repair
(ARCR). Further, we aim to assess the
relationship of preoperative fat fraction values within rotator cuff muscles
between patients who experience re-tear and those who do not.
MATERIALS
AND METHODS
Fifty patients with full-thickness supraspinatus tears (18 men, 32
women; mean age, 67.0 ± 8.0 years; age range, 41-91 years) were recruited for
this study. All MR examinations were performed on a 3.0-T unit (Magnetom Verio,
Siemens AG, Erlangen, Germany) using a 4-channel flex coil. The degree of preoperative
and postoperative fatty degeneration was quantified on a 2-Point Dixon MR image
by measuring the mean signal intensity value on in-phase “S(In)” and fat image
“S(fat)” by a board-certified radiologist on the PACS system with a region of
interest (ROI) placed over supraspinatus muscle in the most lateral
oblique-sagittal section, which appears as a “scapular Y-view”(Fig.1).
Estimates of fatty degeneration were calculated with “fat fraction” values
using the formula S(Fat)/S(In) within the supraspinatus at baseline
pre-operative and post-operative 1-year follow-up MRI. In patients who had
re-tear of the supraspinatus tendon, we evaluated the tear location by
measurement of the distance from the footprint of the humeral head where suture
anchors were placed and tear length. The Mann-Whitney U test was used to
compare preoperative fat fraction values between failed repair and intact
repair groups. The paired t-test was used to compare fat fraction values
between baseline and 1-year follow-up MRI.
RESULTS
AND DISCUSSION
Of 50 patients at baseline, 30 patients had isolated non-massive
supraspinatus tears. The remaining 20 patients had massive tears. Of 50
patients, failed repair of the supraspinatus tendon was seen on postoperative
MRI in 11. The preoperative fat fraction values of the supraspinatus muscle
were statistically higher in the failed repair group compared with the intact
repair group (37.0% vs 19.5%, p<0.01, Fig.2). The postoperative fat fraction
values of the supraspinatus muscle on 1-year follow-up MRI were statistically
higher in the failed repair group compared with the intact repair group (42.8%
vs 19.3%, p<0.01). Fatty degeneration tended to progress at 1 year
post-operatively only in the failed repair group, although there was no statistical
significance (Fig.3). In patients with failed repair, the supraspinatus tear
location was 12.4 ± 4.8 mm proximal to the footprint, and the average tear
length was 20.4 ± 7.4 mm.
CONCLUSIONS
We applied a 2-Point Dixon MR sequence for the evaluation of fatty
degeneration between pre- and 1-year post-operative MRI in patients with supraspinatus
tendon tears. The preoperative fat fraction values of the supraspinatus muscle
were significantly higher in patients with failed repair compared with intact
repair. Fatty degeneration of the rotator cuff muscles did not tend to progress
in patients with intact repair on 1-year follow-up MRI, while it tended to
progress in patients with failed repair. Measurement of preoperative fat
fraction values within the rotator cuff muscles may be a viable method for
predicting post-operative re-tear.
Acknowledgements
No acknowledgement found.References
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2004;86-A(12):2764-76.
(2) Lorbach O et al. Knee Surg
Sports Traumatol Arthrosc. 2012;20(6):1003-11.
(3) McElvany
MD et al. Am J Sports Med. 2015;43(2):491-500.