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Contents lists available at ScienceDirect
Journal of Science and Medicine in Sport
journal homepage: www.elsevier.com/locate/jsams
Original research
Normative MRI, ultrasound and muscle functional MRI findings in the
forearms of asymptomatic elite rowers
Michael K. Drew a,b,c,∗ , Larissa Trease d , J.P. Caneiro e , Ivan Hooper a , Chin-Chin Ooi f,g ,
Peter Counsel h , David A. Connell h,i , Anthony A. Rice j , Emma Knight k , Gregory Hoy l ,
Gregory Lovell m
a
Department of Physical Therapies, Australian Institute of Sport, Australia
Department of Physiotherapy, Faculty of Health, University of Canberra, Australia
c
Australian Centre for Research into Injury in Sport and its Prevention (ACRISP), Federation University, Australia
d
Department of Sports Medicine, Rowing Australia, Australia
e
Department of Physiotherapy, Curtin University, Australia
f
Department of Diagnostic Radiology, Singapore General Hospital, Singapore
g
Department of Diagnostic Radiology, Monash University, Australia
h
Imaging at Olympic Park, Australia
i
Department of Medicine, Nursing and Healthcare, Monash University, Australia
j
Department of Physiology, Australian Institute of Sport, Australia
k
Department of Performance Research, Australian Institute of Sport, Australia
l
Melbourne Orthopaedic Group, Australia
m
Department of Sports Medicine, Australian Institute of Sport, Australia
b
a r t i c l e
i n f o
Article history:
Received 26 September 2014
Received in revised form 26 January 2015
Accepted 14 February 2015
Available online xxx
Keywords:
Rowing
Ultrasound imaging
Intersection syndrome
Magnetic resonance imaging
Forearm
Athletes
a b s t r a c t
Objectives: Forearm injuries are common and debilitating to elite rowers. Chronic exertional compartment
syndrome, intersection syndrome and proximal radial bone stress injuries have been documented in this
population. This paper explores the imaging findings related to these conditions in asymptomatic elite
rowers.
Design: Observational study.
Methods: 19 asymptomatic senior elite and under-23 rowers currently competing at National level or
above underwent ultrasound (US), Magnetic Resonance Imaging (MRI) and muscle functional MRI evaluation of their forearms. A comprehensive evaluation sheet identifying characteristics of bone stress,
intersection syndrome and chronic exertional compartment syndrome was utilised based on a literature
search and review by senior clinicians working with this population.
Results: Peritendinous fluid of Extensor Carpi Radialis Longus (n = 10, 53%) or Extensor Carpi Radialis
Brevis (n = 6, 32%) was a common finding on US. MRI had a higher rate of identification than US. Extensor
Digitorum (Coeff = −1.76, 95%CI −3.04 to −0.49), Flexor Carpi Radialis (Coeff = −2.86, 95%CI −5.35 to
−0.38) and Flexor Carpi Ulnaris (Coeff = −3.31, 95%CI −5.30 to −1.32), Pronator Teres (Coeff = −3.94,
95%CI −6.89 to −0.99), and Supinator (Coeff = −168, 95%CI −3.28 to −0.02) showed statistically significant
changes immediately post-exercise. Mild proximal radial marrow hyperintensity was present (n = 15,
78.9%) with three participants (15.8%) also having mild periosteal oedema of the radius.
Conclusions: Imaging findings commonly seen in symptomatic populations are observed in elite, asymptomatic rowers. Care should be taken when diagnosing bone stress injuries, intersection syndrome and
compartment syndrome on imaging findings alone. Data presented can be utilised as a normative dataset
for future case studies.
© 2015 Published by Elsevier Ltd on behalf of Sports Medicine Australia.
1. Introduction
∗ Corresponding author at: Corresponding author.
E-mail addresses: Michael.drew@ausport.gov.au, michaelkdrew@gmail.com
(M.K. Drew).
Forearm injuries in international rowers are associated with
high loss of training days.1 Of these, intersection syndrome, chronic
exertional compartment syndrome (CECS), and proximal radius
stress reaction have been recorded in an Australian population.1
http://dx.doi.org/10.1016/j.jsams.2015.02.002
1440-2440/© 2015 Published by Elsevier Ltd on behalf of Sports Medicine Australia.
Please cite this article in press as: Drew MK, et al. Normative MRI, ultrasound and muscle functional MRI findings in the forearms of
asymptomatic elite rowers. J Sci Med Sport (2015), http://dx.doi.org/10.1016/j.jsams.2015.02.002
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2
A record of normative imaging findings in this population currently does not exist and imaging studies of forearm injuries in
this population are devoid of control groups.2–4 Therefore establishing normative imaging results in this population is imperative
to allow for better comparisons and eventually improved diagnostic procedures and statistics in this population. This may assist
clinicians to understand the pathogenesis of the three conditions.
Intersection syndrome (IS) is described as a non-infectious
inflammatory condition localised to the area at the intersection of
the first and second dorsal extensor compartments. Typical signs
and symptoms consist of tenderness on palpation, pain on wrist
movements (particularly extension), local swelling, erythema and
crepitus with flexion and extension of the wrist.2–5 The aetiology of
this condition is still under debate. A recent ultrasound study has
found peritendinous oedema and small amounts of synovial fluid
within the tendon sheaths at the point of intersection, thickened
tendons and hyperechoic nodules within the fluid related to proliferation of the synovial membrane.3 This indicates tendinopathic
processes. In a case-series (Level IV evidence), compartmental tearing between the first and second dorsal comparts has been shown
surgically with authors proposing early surgical management.6 It
is therefore plausible that intersection syndrome may be two separate pathologies that can also be coexistent; tendinopathic changes
and inter-compartmental tearing. If these changes can be imaged
it could streamline care to either surgical or conservative management. It is currently unknown whether MRI and/or ultrasound can
assess the integrity of the compartmental fascia at the intersection and whether tearing is present in asymptomatic, elite rowing
populations.
Chronic exertional compartment syndrome is a state of intermittent and reversible elevation of intra-compartmental pressure
related to exertion. It has been documented in athletes of motorcycle racing,7,8 weight lifting9 and kayaking10 and is under-reported
in the rowing literature11 when compared to recent Australian
data.12,13 The diagnostic value of MRI scans in chronic exertional
compartment syndrome of the lower leg has been shown to be
of high value.14,15 However, diagnosing CECS in rowers presents a
unique challenge due to the nature of it being a water-based sport.
The ergometer is a viable alternative to use in the replacement of
on-water rowing however, it neglects the “feathering” action (rotation of the oar to change the angle of the blade) and repetitive
gripping tasks (such as rope winding exercises) may over accentuate the feathering action. Muscle functional MRI (mfMRI) studies
have been used recently to determine the level to which a muscle
is involved in a functional task.16
The purpose of this study was to: (i) establish US imaging results
in asymptomatic elite rowers; (ii) establish MRI findings in asymptomatic elite rowers (iii) establish muscle functional MRI changes
following a set stationary ergo workload and (iv) to assess the relationship that level of competition and gender has on the imaging
findings.
2. Methods
Elite asymptomatic rowers (n = 20) competing in senior (n = 7,
male: female 4:3) and under-23 levels (n = 13, male: female, 7:6)
were recruited through the Victorian Institute of Sport during
the domestic season of competition (January, 2013). Inclusion and
exclusion criteria are presented in Table 1. This study was approved
by the Australian Institute of Sport Ethics Committee and was performed following the Declaration of Helsinki. All patients provided
written informed consent.
All participants underwent a standard radiological examination
procedure. The study design is shown in Supplementary Fig. 1. All
Table 1
Inclusion and exclusion criteria.
Inclusion criteria
Exclusion criteria
Currently competing at
National level
Full training without
restrictions or
limitations
Able to complete the
ergometer test
>18 years of age
Current injury or illness anywhere in the body
Previous history of injury to the forearm or
wrist region
Previous symptoms in the wrist such as
tightness and/or pain that required medical or
physiotherapy treatment or prevented training
Contra-indication to MRI or standard safety
procedures in accordance with standard
radiology policies
images were taken on the inside arm of sweep rowers (ipsilateral
side to the oar) and the dominant arm of scullers.
All participants underwent a standard ultrasound procedure to
evaluate the intersection region. The standard assessment incorporated results from a literature search and the clinical experience
of the authors with backgrounds in sports medicine, radiology,
surgery and sonography (LT, GH, GL, OC, and DC). All ultrasound examinations were performed using a Philips iU22 (Philips
Healthcare, Bothell, WA) that was equipped with a 17.5 MHz
high resolution linear transducer. A single sonographer (OC), with
greater than 10 years of experience in musculoskeletal ultrasound,
performed the scans. Patients were seated facing the sonographer, with their forearm rested comfortably on the examination
couch, elbow in mid-flexion and the wrist in pronation. A preprogramed scanning technical protocol (with optimised scanning
parameters such as depth, frequency, focal zone and colour Doppler
setting for perfusion) was used to ensure consistency of results
obtained. Multiple transverse and longitudinal scans were acquired
at the dorsal aspect of the distal forearm and wrist, with particular attention paid to the point of the intersection region. The
anterior-posterior (AP) thickness and cross-sectional area (CSA)
of the tendons in the first and second compartments were measured. The presence of tendinopathic signs (subcutaneous oedema,
peritendinous fluid, fluid between the first and second extensor
compartments, breaching or tearing of the synovia, hypervascularity of tendons, compartment thickness at the intersection and
tendon hypoechogeneity) were observed and documented. In addition, dynamic real-time scanning with flexion–extension of the
patient’s wrist was performed and mobility of the tendons at the
level of intersection was evaluated for presence of staccato tendon
movement.
All MRI scans were taken in a single Philips Ingenia 3T scanner (Philips, Veenpluis, Best, Netherlands) using a 32 channel
phased array body coil (Invivo, Gainesville, FL, USA) with their arm
extended in a true anatomical position. The scans were obtained
from the wrist to the elbow in the axial plan at the pre-exercise,
immediate post-exercise and delayed post-exercise time points.
The scan parameters were as follows. Pre-exercise axial PD spin
fast spin echo technique (40 slices at TR 3400 ms, TE 30 ms,
12.0 cm × 12.0 cm Field of View (FOV), 512 × 512 matrix, 3.0 mm
slice thickness, 7 to 9 mm gap, ETL of 14 and 1 NSA) extending
from the distal radioulnar joint to the proximal. Pre-exercise T2
SPAIR (fat sat) axial fast spin echo technique was the same 40 slices
with a constant FOV, slice thickness and slice gap. The matrix size
was 432 × 432 and using a TR of 8500 ms, TE 50 ms, ETL of 14 and
2 NSA. The immediate post-exercise and delayed scans used the
same parameters as the pre-exercise T2 Axial SPAIR.
Muscle functional MRI (mfMRI) techniques were utilised to evaluate the effect of ergometer rowing on the forearm muscles. The
participants rested for 30 min prior to the mfMRI. This occurred
simultaneously with the ultrasound evaluation. The ergometer
protocol consisted of a standardised warm up of 3 min at a selfselected rate and wattage; following this the participant completed
Please cite this article in press as: Drew MK, et al. Normative MRI, ultrasound and muscle functional MRI findings in the forearms of
asymptomatic elite rowers. J Sci Med Sport (2015), http://dx.doi.org/10.1016/j.jsams.2015.02.002
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8 min of rowing on a stationary ergometer at 90% wattage of
their most recent 6 km ergometer test. All workloads were completed on a Concept II Rowing Ergometer (Concept2, Vermont,
USA) and utilised drag factors consistent with the Rowing Australia
policies for ergometer testing for the participant’s weight class
and gender (lightweight women = 95; lightweight men and heavyweight female = 105; heavyweight men = 115). The participants
were instructed to maintain a constant rate for the test (24–26
strokes/min). This protocol was selected to ensure that the participant had to grip the handle to provide a sufficient stimulus
to invoke MRI detectable changes. Upon completion of the test,
the participants were allowed to regain their breath and proceed
immediately into the MRI scanner for post-exercise imaging. All
participants began imaging within 2 min of completing the test.
All delayed post-exercise MRI images were taken between 60 and
90 min (mean = 73.5 min) following the ergometer test. During the
break, participants were instructed to rest quietly in a seated position and avoid any physical activity and tasks which would change
their forearm signal such as lifting bags.
After scanning, the ultrasound data was analysed by the sonographer (OC). The baseline MRIs were evaluated by two radiologists
(DC and PC) using the same standard reporting proforma as the
sonographer (Table 2). Calculation of the muscle T2 signal intensities utilised the InteleViewer program (InteleViewer, Intelerad
Medical Systems Incorporated). Regions of interest (ROI) were
identified on the T2 images at the level where the proximal
interosseous membrane became visible. The mean and standard
deviations of signal intensities were measured for each muscle.
This enabled visualisation and data collection of the m. Extensor Carpi Radialis Brevis (ECRB), m. Extensor Carpi Radialis Longus
(ECRL), m. Extensor Carpi Ulnaris (ECU), m. Extensor Digitorum (ED),
m. Extensor Digiti Minimi (EDM), m. Flexor Carpi Ulnaris (FCU), m.
Flexor Digitorum Profundus (FDP), m. Flexor Digitorum Superficialis
(FDS), m. Palmaris Longus (PL) (if present), m. Pronator Teres (PT), m.
Brachioradialis (BR), and m. Supinator (S). When defining the ROI,
all non-muscular tissue such as fat, fascia, bone and vessels was
avoided. This protocol is in accordance with other studies.3
Analysis was performed using Stata 13 (Version 13 IC, StataCorp, USA). To look at the relationship between the presence of
fluid in either or both ECRL and ECRB, and the level of competition
and gender, univariate logistic regression models were fitted with
presence of fluid as the response variable and competition, gender
and their interaction as explanatory variables. The mean T2 values
of signal intensity were measured in all three scans and utilised for
analysis. To look at changes in T2 signal intensity over the three
time points (baseline, immediately post-, delayed post-exercise), a
linear mixed model for each muscle was fitted with gender, competition, time and their interactions as fixed effects and participant
as a random effect to account for within participant correlation.
3
were no interactions between gender and competition and therefore removed from the model. Comparison between under-23 and
senior athletes, revealed no association between athlete group
and fluid present in ECRL (OR = 0.53, 95%CI 0.09–3.31) or ECRB
(OR = 1.17, 95%CI = 0.17–8.09) alone or in both tendons (OR = 0.29,
95%CI 0.02–3.48). Similarly, no association was found between gender and fluid present in ECRL (OR = 2.92, 95%CI 0.44–19.23) or ECRB
(OR = 1.71, 95%CI = 0.23–12.89) alone or in both tendons (OR = 2.63,
95%CI 0.22–31.35). Tendon volumes were ECRL (median = 3.2 mm,
range 2.5–3.8 mm), ECRB (median = 2.8, range = 2.0–3.3 mm), APL
(median 2.5 mm, range 1.9–3.0 mm) and EPB (median = 1.9, range
1.4–2.4 mm).
The results of the baseline MRI scans can be found in Table 2.
Mild hyperintensity of the pronator quadratus muscle was present
in 18 of 19 rowers (94.7%) on pre-exercise imaging (Sup. 3). Peritendinous fluid was observed in at least one tendon of compartment
2 in all but one participant (n = 18, 94.7%; ECRL, n = 10, ECRB, n = 6,
both ECRL and ECRB, n = 4) (Sup. 2).
Mild bone marrow hyperintensity (Sup. 4) in the proximal radius
was present in the majority of the participants (n = 15, 78.9%) with
three (15.8%) also having mild periosteal oedema. One participant
(5.3%) had foci of marrow hyperintensity in both the ulna and
radius.
In nine (47.4%) participants, there was no evidence of bicipitoradial bursal effusion with a trace of fluid in seven (36.8%) and mild
effusion in three (15.8%) (Sup. 5), respectively.
A significant random effect of participant was observed in all
linear mixed models (Coeff = 4.43, 95%CI 0.98–20.04 to 160.34,
95%CI 72.68–353.72). A significant effect of gender was observed
in ECRB (Coeff = 8.57, 95%CI 1.45 to 15.68), ECU (Coeff = 3.02, 95%CI
0.24 to 5.80), ED (Coeff = 6.19, 95%CI 1.27 to 11.12), and EDM
(Coeff = 5.35, 95%CI 1.30 to 9.43) with female participants as the
reference. There was no significant interactions in the mixed
models and therefore removed. After accounting for gender and
competition, a statistically significant decreased signal intensity
immediately following exercise was observed in ED (Coeff = −1.76,
95%CI −3.04 to −0.49), FCR (Coeff = −2.86, 95%CI −5.35 to −0.38)
and FCU (Coeff = −3.31, 95%CI −5.30 to −1.32), PT (Coeff = −3.94,
95%CI −6.89 to −0.99), and S (Coeff = −168, 95%CI −3.28 to −0.02).
FCR (Coeff = −2.65, 95%CI −5.26 to −0.03) and FCU (Coeff = −2.68,
95%CI −4.82 to −0.55) remained significantly decreased in signal intensity in the delayed scan. Non-significant signal intensity
increases were observed in FDS (Coeff = 1.44, 95%CI −0.99 to 3.88),
FDP (Coeff = 1.08, 95%CI −1.28 to 3.43), RB (Coeff = 1.95, 95%CI −0.26
to 4.17) and ECRB (Coeff = 0.48, 95%CI −0.88 to 1.84) immediately
following exercise. The percentage changes from the baseline in
the T2 shifts of the exercise-induced MRI changes are presented in
Table 3.
4. Discussion
3. Results
Seventeen of 19 participants completed all scans. This was the
entire eligible population. Two participants withdrew after the
immediate post-exercise scan citing work-related commitments.
No adverse events were recorded.
The results of the ultrasound scan are presented in Table 2.
No pathology was found in the first extensor compartment (APL,
EPB) of any of the participants. Peritendinous fluid was identified
around the tendons of ECRL (n = 10, 53%; male:female, 7:3) and
ECRB (n = 6, 32%; male:female, 4:2) with four participants having
fluid around both tendons (22%; male:female, 3:1) (Sup. 2). One
female participant (5%) had hypervascularity present on Doppler
examination of her ECRB, co-existing with peritendinous fluid. No
tearing of the synovia of either compartment was identified. There
This study has found that ultrasound findings are common in
elite, asymptomatic rowers. No tendon pathology was found in the
tendons of the thumb muscles. Tendinopathic changes were found
in the ECRL and ECRB tendons at the level of the intersection. No
tearing of the synovia was identified on either the US or MRI evaluations and it is unclear whether these modalities of investigation
can identify this. However, our study supports previous research3
indicating US to be an important part of the diagnostic procedure of
rowers with forearm pain. Peritendinous fluid was common on MRI
and US, with MRI showing a higher rate. Giovagorio and Miozzi3
found peritendinous oedema and small amounts of synovial fluid
within the tendon sheaths at the point of intersection, thickened
tendons and hyperechoic nodules within the fluid. Comparatively,
in our asymptomatic population we found fluid in and around the
Please cite this article in press as: Drew MK, et al. Normative MRI, ultrasound and muscle functional MRI findings in the forearms of
asymptomatic elite rowers. J Sci Med Sport (2015), http://dx.doi.org/10.1016/j.jsams.2015.02.002
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Table 2
Imaging findings for ultrasound, MRI and dynamic ultrasound.
Compartment 1†
Imaging modality
Imaging finding
Ultrasound
Thickness at wrist
APL
EPB
ECRL
ECRB
Compartment thickness at intersection
Hypertrophy
Intratendinous alterations
Peritendinous fluid
Breach or presence of tear or hole in synovium
Fluid within compartment
Hypervascularity of tendons on Doppler
Fluid between 1st and 2nd compartment at crossover
Fascial thickness between the muscle/tendons of C1/C2 at intersection
Fascial thickening
Stenosis of the compartment 2
Subcutaneous oedema
Hypertrophy
Intratendinous alterations
Peritendinous fluid
Breach or presence of tear or hole in synovium
Fluid within compartment
Stenosis of the 2nd dorsal compartment
Subcutaneous oedema
Movement
Free movement
Friction between tendons/compartments
Staccato movement
MRI
Dynamic Ultrasound
Compartment 2†
2.51 ± 0.40
1.94 ± 0.29
1.30 ± 0.10
19:0 (0%)
19:0 (0%)
19:0 (0%)
19:0 (0%)
19:0 (0%)
19:0 (0%)
18:1 (5.3%)
0.27 ± 0.05
19:0 (0%)
3.23 ± 0.38
2.71 ± 0.38
2.61 ± 0.63
17:2 (10.5%)
19:0 (0%)
7:12* (63.2%)
19:0 (0%)
18:1 (5.3%)
18:1 (5.3%)
19:0 (0%)
19:0 (0%)
19:0 (0%)
19:0 (0%)
13:6 (31.6%)*
19:0 (0%)
16:3 (15.8%)#
19:0 (0%)
Extension
0:19 (100%)
19:0 (0%)
19:0 (0%)
19:0 (0%)
19:0 (0%)
1:18 (94.7%)+
19:0 (0%)
16:3 (15.8%)#
19:0 (0%)
Flexion
0:19 (100%)
19:0 (0%)
19:0 (0%)
†
Continuous data are presented as mean ± standard deviation measured in millimetres (mm). Categorical data, no:yes, Percentages presented represent prevalence of
positive finding; APL: Abductor pollicis longus, C1: compartment 1, C2: compartment 2; EPB: extensor pollicis brevis; ECRL: extensor carpi radialis longus, ECRB: extensor
carpi radialis brevis.
#
2/3 has trace of fluid.
*
Fluid present in APL (n = 5) and EPB (n = 1).
+
Fluid present in ECRL (n = 7) and both ECRL and ECRB (n = 11).
*
Mild peritendinous fluid was identified in at least one tendon in C2 (ECRL n = 10, ECRB n = 6, both ECRL and ECRB n = 4).
tendon sheaths which indicates that these may be a normal finding in this population. The results of this study highlight the need
to include matched controls in future diagnostic studies. The MRI
results in the study indicate that one participant would be considered indicative of having intersection syndrome (Sup. 6) for most
radiologists evaluating a symptomatic patient and two further participants could reflect very low grade intersection syndrome (Sup.
7). If taken as false positives, this would give a false positive rate
of 5–15% based on imaging alone, although subclinical pathology
might also account for these findings. Future studies should explore
alternate imaging methodologies such as post-Gadolinium MRI to
identify findings of fluid associated with tenosynovitis from physiological fluid.
Bone stress injuries of the forearms have been documented in
Australian rowers.1 Hyperintensity of the bone marrow was a common finding in this asymptomatic elite rowing population and may
be a typical finding in this population. The high rate of mild marrow hyperintensity may be indicative of low grade subclinical stress
reaction, although ultimately comparison to a non-rowing population would be needed to test this hypothesis.
This study illustrates that the muscles ED, PT, FCR, FCU and S
exhibit significant decreases in signal intensity following the row-
Table 3
Percentage change of the T2 signal intensities of the muscle functional MRI.
Muscle
ECRB
ECRL
ECU
ED
EDM
FCU
FCR
FDP
FDS
PL
PT
RB
SUP
Baseline versus immediate
Baseline versus delayed
Mean ± SD
95% CI
Mean ± SD
95% CI
1.43 ± 11.78
−1.55 ± 11.98
−2.24 ± 10.50
−5.34 ± 9.58a
−3.12 ± 11.61
−7.45 ± 11.40a
−8.78 ± 15.56a
4.13 ± 13.39
3.25 ± 18.02
−5.66 ± 18.13
−9.63 ± 15.56a
6.70 ± 17.18
−4.46 ± 11.44a
−4.43–7.29
−7.51–4.41
−7.46–2.98
−10.10 to −0.57
−8.89–2.66
−13.12 to −1.78
−17.07 to −0.49
−2.53–10.78
−6.02–12.52
−15.70–4.38
−17.92 to −1.34
−1.84–15.24
−10.15–1.23
−3.78
−2.46
−2.39
−3.02
−1.25
−4.10
1.33
−4.41
0.65
4.07
−6.77
−5.76
−3.86
−10.79–3.22
−10.27–5.36
−7.87–3.09
−8.84–2.79
−8.03–5.52
−14.14–5.94
−17.07–19.74
−10.71–1.88
−16.94–18.24
−17.30–25.45
−15.11–1.57
−11.77–0.26
−7.96–0.24
±
±
±
±
±
±
±
±
±
±
±
±
±
12.66
14.11
9.89
10.50
12.23
18.13a
31.88a
11.37
31.76
35.37
13.81
10.87
7.40
a
Statistically significant fixed effect (P < 0.05); Baseline n = 19, delayed n = 17; CI: confidence interval; SD: standard deviation; ECRB: extensor carpi radialis brevis, ECRL:
extensor carpi radialis longus, ECU: extensor carpi ulnaris, ED: extensor digitorum, EDM: extensor digiti minimi, FCR: flexor carpi radialis, FCU: flexor carpi ulnaris, FDP:
flexor digitorium profundus, FDS: flexor digitorium superficialis, PL: palmaris longus, PT: pronator teres, RB: radiobrachialis, S: supinator.
Please cite this article in press as: Drew MK, et al. Normative MRI, ultrasound and muscle functional MRI findings in the forearms of
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ing ergometer protocol. This may be related to the aerobic exercise
administered rather than the anaerobic exercises used in previous studies16,17 and is a consideration for future mfMRI study
designs. Non-significant increases in FDS, FDP, RB and ECRB were
observed immediately after exercise. FCR and FCU showed significant decreases in signal intensity in the delayed-MRI images and
this should be taken into account clinically when imaging between
60 and 90 min after ergometer rowing. Mild MRI hyperintensity of
m. pronator quadratus was seen in most of our patients, and has
been previously described as a normal finding.18
CECS is a debilitating condition for elite rowers and usually
results in an inability to row. Clinically MRI has been used to
diagnose this condition; however, these protocols have not been
evaluated in the forearm or in this population. The purpose of this
study was to establish some normative data on asymptomatic elite
rowers. Pragmatically we investigated what happens to the imaging between 60 and 90 min after exercise. This was chosen based
on previous research which has shown that exercise-induced signal intensities changes on T2 images have a half-life of 7 min with
a complete resolution between 45 min and 1 h.12 This potentially
will allow clinicians to prescribe the workload outlined in this study
at the athletes’ rowing club or nearby gymnasium prior to imaging as it would be impractical for a rower with suspected CECS
to undertake an ergometer session at the radiology clinic. In the
delayed-MRI sequence we observed that FCR and FCU decreased
in signal intensity which reached statistical significance. Clinically
care should be taken when making clinical judgements based on
the immediate scan protocols without comparison to the normative findings. Future studies are warranted to see if this decrease in
signal intensity is observed in patients suffering from CECS as an
increase would usually be expected. Clinicians should also be aware
that FDS, FDP, RB and ECRB have the potential to show increased signal intensity following exercise, although in this study the changes
were not statistically significant. This may be due to the small sample size and this is a limitation of the study. However, the magnitude
of T2 shifts seen in this study are below those observed in patients
with compartment syndrome of the leg.14
A limitation of this study is that it only evaluated asymptomatic,
elite rowers who were free of any forearm injury history and therefore may have limited generalisability to sub-elite and recreational
rowers. Furthermore, the prevalence of many of the reported findings in this study is unknown among the general population. Future
research may benefit from a wider control group containing nonrowers and symptomatic rowers. A further limitation identified
before the study was that the ergometer protocol negated the feathering action of the wrist during the rowing stroke. It is unknown
what impact this action has on the mfMRI findings and caution
should be taken when comparing the current results to post- onwater rowing images.
5. Conclusion
In ultrasound and MRI scans of the forearm in asymptomatic
athletes peritendinous fluid is often seen in the region of the intersection in asymptomatic rowers. It is important to note that all fluid
seen was of a small quantity and florid oedema may still be important clinically. Imaging findings without clinical symptoms may be
considered normal in this population. For suspected compartment
syndrome of the forearm in rowers pre- and post-exercise comparative MRI imaging may be appropriate. Post-exercise MRI should be
obtained between 60 and 90 min after activity where an increase in
compartment T2 signal may be diagnostic of CECS pathology. Bone
marrow hyperintensity interpreted as mild bone stress was a common finding in this asymptomatic elite rowing population and this
can be considered a typical finding.
5
Practical implications
• Fluid around the tendons of the intersection region is a common
finding. Both MRI and US are able to detect these. MRI showed a
higher rate of identification.
• Ultrasound allows the visualisation of tendon movements within
their sheath and these should be able to freely move without
staccato movements or limitations.
• Mild marrow and periosteal oedema was a common finding on
MRI.
• MRI of athletes with suspected compartment syndrome should
be imaged between 60 and 90 min after the stationary ergometer
protocol.
Funding
This study was funded by the Clinical Research Fund through
the Australian Institute of Sport Grant ID : C2DREW.
Acknowledgments
The authors would like to acknowledge and thank Rowing
Australia and the Victorian Institute of Sport for allowing access
to their athletes. The authors would like to acknowledge the contribution Mark Ward for his assistance with the MRI protocol and
obtaining the MRI images. The authors would also like to thank
Alice McNamara for her assistance in data collection.
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jsams.2015.02.002.
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