The Ruptured Achilles Tendon Elongates

for 6 Months After Surgical Repair

Regardless of Early or Late Weightbearing
in Combination With Ankle Mobilization
A Randomized Clinical Trial
Pernilla Eliasson,*yz MSc, PhD, Anne-Sofie Agergaard,y§ PT, MSc, Christian Couppé,y§ PT, PhD,
René Svensson,y PhD, Rikke Hoeffner,y§ PT, Susan Warming,y§ PT, PhD,
Nichlas Warming,y MSc, Christina Holm,y MD, Mikkel Holm Jensen,y PT,
Michael Krogsgaard,|| MD, PhD, Michael Kjaer,y MD, DMSc, and S. Peter Magnusson,y§ PT, DMSc
Investigation performed at Bispebjerg-Frederiksberg Hospital, Copenhagen, Denmark

Background: Treatment strategies for Achilles tendon rupture vary considerably, and clinical outcome may depend on the mag-
nitude of tendon elongation after surgical repair. The aim of this project was to examine whether tendon elongation, mechanical
properties, and functional outcomes during rehabilitation of surgically repaired acute Achilles tendon ruptures were influenced by
different rehabilitation regimens during the early postsurgical period.
Hypothesis: Restricted early weightbearing that permits only limited motion about the ankle in the early phase of tendon healing
limits tendon elongation and improves functional outcome.
Study Design: Randomized controlled trial; Level of evidence, 1.
Methods: 75 consecutive patients with an acute Achilles tendon rupture were included. They underwent surgical repair, and tan-
talum beads were placed in the distal and proximal parts of the tendon; thereafter, the patients were randomized into 3 groups.
The first group was completely restricted from weightbearing until week 7. The second group was completely restricted from
weightbearing until week 7 but performed ankle joint mobilization exercises. The first and second groups were allowed full weight-
bearing after week 8. The third group was allowed partial weightbearing from day 1 and full weightbearing from week 5. All pa-
tients received the same instructions in home exercise guidelines starting from week 9.
Results: The rehabilitation regimen in the initial 8 weeks did not significantly influence any of the measured outcomes including
tendon elongation. Achilles tendon elongation and tendon compliance continued for up to 6 months after surgery, and muscle
strength, muscle endurance, and patient-reported functional scores did not reach normal values at 12 months.
Conclusion: Differences in rehabilitation loading pattern in the initial 8 weeks after the repair of an Achilles tendon rupture did not
measurably alter the outcome. The time to recover full function after an Achilles tendon rupture is at least 12 months.
Registration: NCT02422004 (ClinicalTrials.gov identifier).
Keywords: Achilles tendon rupture; tendon strain; tendon healing; tendon elongation; weightbearing

The Achilles tendon is the strongest tendon in the human 100,000 individuals per year, and the incidence appears
body, and yet it is susceptible to complete rupture, which to be on the rise.18,31,32,38
most frequently occurs in men 30 to 50 years of age who The ruptured Achilles tendon can be treated surgically
participate in recreational sports periodically.18,32,38 The or nonsurgically followed by a rehabilitation program
prevalence has been reported to be approximately 18 per with varying emphasis on loading. However, no consensus
is available in the literature regarding the optimal rehabil-
itation protocol, and there is considerable variation in
treatment strategies for Achilles rupture in clinical prac-
The American Journal of Sports Medicine
tice.4,34 Surgical repair of Achilles tendon ruptures is
1–11
DOI: 10.1177/0363546518781826 known to significantly reduce the risk of rerupture in the
Ó 2018 The Author(s) long term and to accelerate the return to activity compared

1
2 Eliasson et al The American Journal of Sports Medicine

with nonsurgical treatments, which is why surgery has chronic tendon elongation and enhance long-term functional
been advocated by some but not all.21,35,53 Data from ani- outcome.
mal models suggest that short episodes of loading may be
beneficial for the healing tendon without inducing tendon
elongation.2 Furthermore, load on the tendon can stimu- METHODS
late the tendon cells (fibroblasts) to synthesize collagen
and other extracellular components,33 and therefore early Participants
motion of the ankle might be beneficial for the rupture
repair. Patients 18 to 65 years of age with an acute Achilles tendon
The repair sutures themselves permit the tendon to with- rupture scheduled for surgery at Bispebjerg-Frederiksberg
stand up to 550 N of force before failure,7,14,17,19 which is Hospital, Copenhagen, were recruited to participate in this
a mere fraction of the load placed on the Achilles tendon dur- randomized controlled trial. A total of 75 patients with an
ing walking (~1500 N) and running (up to 8000 N).11,12,24,25 acute Achilles tendon midsubstance rupture were included
Moreover, after only 10 cycles of low-force loading, a signifi- between August 2012 and November 2015. Patients with
cant separation of the repair site has occurred.17,30 Yet, accel- prior Achilles tendon rupture or other injuries affecting
erated rehabilitation with early loading after surgical repair their lower limb functions were excluded. Other exclusion
is commonly recommended6,43,45,54,56 in an attempt to curtail criteria included systemic diseases that potentially could
the persistent long-term muscle weakness, atrophy, dysfunc- influence tendon healing (eg, autoimmune disease, genetic
tion, and frequent incomplete return to preinjury level of connective tissue disorders), immunosuppressive treat-
sports.{ No data are available that identify how early the ment including systemic corticosteroid treatment, and
repaired tendon can withstand any given loading without inability to complete rehabilitation or follow-ups due to
sustaining structural changes that yield permanent travel distance from the hospital. All the patients were
elongation. given oral and written information about the study and
The reason for the frequently observed inadequate gave written informed consent to participate in the study.
recovery of calf muscle function remains a conundrum, Ethical approval was obtained from the regional Ethics
and although considerable attention has been focused on Committee (No. H-3-2012-060). The trial was a single-
accelerated rehabilitation and muscle strength, the length center, controlled, parallel-group study using block ran-
of the repaired Achilles tendon has attracted more atten- domization and was registered (www.clinicaltrials.gov; tri-
tion recently. It appears that the tendon may elongate al number NCT02422004). Based on tendon elongation
after both surgical and nonsurgical treatment.16,20,36 In data,20 it was estimated that a sample of n = 18 was needed
fact, the magnitude of the lengthening can be substantial in each group to detect a 3-mm difference in tendon elonga-
and has been reported to occur in the initial 6 to 12 weeks tion with 80% power, and therefore 25 patients were
after surgery.20,36,44,50 Importantly, it has been observed included in each group to account for possible dropouts.
that the clinical outcome appears to be related to the mag-
nitude of elongation, such that those with less elongation
achieved a better clinical outcome.20 This implies that Surgery and Rehabilitation
efforts to prevent elongation in the initial months after ten-
Patients were positioned prone with their feet hanging
don rupture repair may be critical.
freely at the end of the operation table. A longitudinal inci-
The aim of this project was to examine tendon elongation
sion was made slightly medial to the midline at the level of
(primary outcome), mechanical properties, and functional
the rupture. The peritendon was incised and the rupture
outcomes during rehabilitation of surgically repaired acute
identified. The surgeon sutured the tendon using the Kess-
Achilles tendon ruptures and to determine whether different
ler technique with a No. 1 Vicryl suture while attempting
rehabilitation regimens during the early rehabilitation period
to achieve an anatomic length by tightening sutures until
(0-8 weeks after surgery) influenced the outcome. We hypoth-
both feet had an equal resting position and the tendons
esized that restricted early weightbearing that allowed only
on both sides felt equally tight when the foot was manually
limited motion about the ankle in the early phase of tendon
dorsiflexed. After tendon suture, 4 tantalum metal beads
healing would yield better tissue regeneration and minimal
with a diameter of 1.0 mm were implanted with a cannula
in the tendon on either side of the rupture (2 beads in each
end) (Figure 1)49; although it cannot be ruled out that
{
References 1, 5, 16, 22, 29, 35, 37, 41, 51, 52, 55.

*Address correspondence to Pernilla Eliasson, MSc, PhD, Institute of Sports Medicine Copenhagen, Bispebjerg-Frederiksberg Hospital, entrance 8, 1st
floor, Nielsine Nielsens Vej 11, DK-2400 Copenhagen, NV, Denmark (email: pernilla.eliasson@gmail.com).
y
Institute of Sports Medicine Copenhagen, Department of Orthopedic Surgery, Bispebjerg-Frederiksberg Hospital and Center for Healthy Aging, Faculty
of Health Sciences, University of Copenhagen, Denmark.
z
Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.
§
Department of Physical Therapy, Bispebjerg-Frederiksberg Hospital, Copenhagen, Denmark.
||
Section for Sports Traumatology, Department of Orthopedic Surgery, Bispebjerg-Frederiksberg Hospital, Copenhagen, Denmark.
P.E. and A.-S.A. contributed equally to this study.
One or more of the authors have declared the following potential conflict of interest or source of funding: This study was supported by grants from
Lundbeck foundation, Nordea Foundation (Center of Healthy Aging), IOC Research Center Sports Medicine Copenhagen, Danish Medical Research Coun-
cil, and Swedish Society for Medical Research.
AJSM Vol. XX, No. X, XXXX Achilles Tendon Elongation After Tendon Rupture 3

without any load (25 repetitions, 5 times per day) begin-

ning week 3. The aim of the LWB1MOB regimen was to
provide limited mechanical stimulation without any
lengthening of the tendon. In the early weightbearing
with mobilization group (EWB1MOB group), the patients
were instructed in the currently accepted rehabilitation
regimen at Bispebjerg-Frederiksberg Hospital, which
includes partial weightbearing from day 1 and full weight-
bearing from week 5. This protocol closely resembles com-
monly accepted accelerated rehabilitation regimens.56
Similar to the LWB1MOB group, patients in the
EWB1MOB group were instructed in ankle joint range
of motion exercises. The aim of the EWB1MOB regimen
was to maximize mechanical stimulation. All patients
received the same instructions in home exercise guidelines
starting from week 9 (Table 1). Patients were allowed heel-
rise exercise after 16 weeks, jogging after 22 weeks, and
return to sports 34 weeks after surgery.

Follow-up Evaluation
The primary outcome was tendon elongation at rest. Second-
Figure 1. During surgery, 4 tantalum metal beads with ary outcomes were tendon strain during isometric plantar-
a diameter of 1.0 mm were implanted in the tendon on either flexion, ankle joint range of motion, maximal plantarflexion
side of the rupture (2 beads in each end). Bottom right: a cal- muscle strength, tendon cross-sectional area (CSA), muscle
ibration sphere of known diameter was placed in the image. CSA, heel-rise test, and patient-reported outcomes (Achilles
tendon Total Rupture Score [ATRS] and Victorian Institute
there might be minor migration, previous research indicate of Sport Assessment–Achilles questionnaire [VISA-A]).
that this is unlikely.49
Thereafter, the peritendon and the subcutaneous tissue
were closed with a No. 2-0 Vicryl suture, and the skin was
Tendon Elongation
closed with a No. 4-0 Nylon suture. However, the first 5 Two-dimensional radiographs were used to measure the dis-
patients in the trial had the beads implanted percutane- tance between the tantalum beads inserted during surgery
ously 1 week after surgery under ultrasound guidance. as a measure of tendon elongation. The patients were posi-
After surgery, an orthosis (Nextep Contour II Walker; Don- tioned prone with their feet in a relaxed position outside the
Joy Nordic) that inhibits ankle-joint movement was table during the radiograph. The distance between the
applied and worn for 6 weeks. To keep the foot in plantar- radiographic source and the film plate was fixed at
flexion, 3 heel wedges (2 cm each) were worn the first 4 120 cm, and the radiograph was focused perpendicularly
weeks and patients were instructed to remove 1 heel wedge on the midpoint of the Achilles tendon. Radiographs were
every week thereafter. Randomization to 3 separate reha- obtained at weeks 2, 6, 12, 26, and 52. ImageJ 1.47 software
bilitation regimens was performed postoperatively by use (US National Institutes of Health) was used to calculate the
of block randomization, with 6 in each block (see CON- distance between 2 of the 4 tantalum beads, and the same 2
SORT diagram, Figure 2). The persons responsible for beads were used at all time points. An x-ray calibration
obtaining the primary outcome data (tendon elongation) sphere of known diameter was placed in the image during
were blinded, but the persons responsible for the other radiographs, and all measured distances were calibrated
follow-up tests were not systematically blinded. All data to the diameter of the sphere in the image (Figure 1).
analysis was performed in blinded fashion.
In the late weightbearing with immobilization group
(LWB1IMMOB group), the patients were completely Tendon and Muscle Cross-sectional Area
restricted from weightbearing until week 7. Partial weight-
bearing with the use of crutches was allowed at weeks 7 to Magnetic resonance imaging (MRI) was used to assess CSA
8 and full weightbearing after week 8. The aim of the of the Achilles tendon and muscles of the triceps surae on
LWB1IMMOB regimen was to minimize tendon lengthen- the injured side at 6, 26, and 52 weeks (Sigma Horizon LX
ing. In the late weightbearing with mobilization group 1.5-T). The MRI parameters used in the tendon scans were
(LWB1MOB group), the patients were completely as follows: T1-weighted spin-echo (SE); repetition time/
restricted from weightbearing until week 7. Partial weight- echo time (TR/TE) 400/16 milliseconds; field of view
bearing with the use of crutches was allowed at weeks 7 to (FOV) 12 cm; matrix 320 3 320; slice 6 mm; and spacing
8 and full weightbearing after week 8. These patients were 2 mm. The ankle was maintained at 90° during the scan
instructed to perform ankle joint mobilization exercises by use of a high definition foot-ankle coil. The open source
4 Eliasson et al The American Journal of Sports Medicine

Operated for Achilles tendon rupture

during the study period (n = 129) Excluded (n = 54)
Enrollment
Randomized (n = 75)

Allocation

LWB+MOB (n = 25) LWB+IMMOB (n = 25) EWB+MOB (n = 25)

Follow-up 2 w
Lost to follow-up due to failures when Lost to follow-up (n = 0) Lost to follow-up due to x-ray failure (n = 2) and
implanting the beads (n = 1) • Discontinued intervention (n = 0) repeatedly failing to attend the follow-ups (n = 1)
• Discontinued intervention (n = 0) • Discontinued intervention (n = 1)

Follow-up 6 w
Lost to follow-up (n = 0) Lost to follow-up (n = 0) Lost to follow-up (n = 0)
• Discontinued intervention (n = 0) • Discontinued intervention (n = 0) • Discontinued intervention (n = 0)

Follow-up 12 w
Lost to follow-up (n = 3) Two had a re- Lost to follow-up (n = 0) Lost to follow-up (n = 0)
rupture, one had re-surgery • Discontinued intervention (n = 0) • Discontinued intervention (n = 0)
• Discontinued intervention (n = 3)
Follow-up 26 w
Lost to follow-up (n = 0) Lost to follow-up due to drop out not Lost to follow-up due to repeatedly failing to
• Discontinued intervention (n = 0) interested (n = 1) attend the follow-up (n = 1)
• Discontinued intervention (n = 1) • Discontinued intervention (n = 0)

Follow-up 52 w
Lost to follow-up (n = 0) Lost to follow-up (n = 0)
Lost to follow-up (n = 0)
• Discontinued intervention (n = 0) • Discontinued intervention (n = 0)
• Discontinued intervention (n = 0)

Analyzed
Analysed (n = 23) Analysed (n = 22)
Excluded from analysis due to missing Analysed (n = 25) Excluded from analysis due to missing
baseline value (n = 2) Excluded from analysis (n = 0) baseline values (n = 2)

Figure 2. CONSORT (Consolidated Standards of Reporting Trials) diagram. EWB1MOB, early weightbearing with mobilization;
LWB1IMMOB, late weightbearing with immobilization; LWB1MOB, late weightbearing with mobilization.

TABLE 1
Rehabilitation Program Guidelinesa

EWB1MOB LWB1MOB LWB1IMMOB

Orthosis weeks 0-6 x x x

3 heel wedges weeks 0-4. Remove 1 wedge per week starting week 5 x x x
Nonweightbearing Weeks 0-6 Weeks 0-6
Partial weightbearing Weeks 0-4 Weeks 7-8 Weeks 7-8
Full weightbearing Starting week 5 Starting week 9 Starting week 9
Early ankle mobilization Weeks 3-6 Weeks 3-6
Physical therapy weeks 2, 6, 12 x x x
Rehabilitation program after removal of orthosis
Range of motion (active) starting week 7 x x x
Exercise bike starting week 9 x x x
Swimming starting week 9 x x x
Stair climbing starting week 14 x x x
Heel rises and stretching starting week 16 x x x
Jogging starting week 22 x x x
Return to sport week 32 x x x

a
EWB1MOB, early weightbearing with mobilization; LWB1IMMOB, late weightbearing with immobilization; LWB1MOB, late weight-
bearing with mobilization.

software OsiriX 4.19 for MAC OS (http://www.osirix-view- procedure has been described in detail elsewhere and has
er.com) was used to analyze the MRI scans. The Achilles been shown to reduce the underestimation of CSA by
tendon CSA (Figure 3) was measured by manually outlin- 2.8% compared with using only gray scale.8
ing the tendon in the axial plane of 4 images, and a mean For the muscle CSA, 20 images were obtained distal to
was calculated. The most distal image without any visible the tibia plateau. The protocol for the axial MRI scans
calcaneus bone was defined as the starting image. To opti- was the following: T1-weighted SE; TR/TE 440/12.7 milli-
mize the measurement, both gray scale and National Insti- seconds; FOV 28 cm; matrix 256 3 256; slice 10 mm; spac-
tutes of Health color scale were used during outlining. This ing 5 mm. The lean muscle mass of triceps surae
AJSM Vol. XX, No. X, XXXX Achilles Tendon Elongation After Tendon Rupture 5

analysis was used to calculate tendon elongation by measur-

ing the distance between the tantalum beads under differ-
ent predefined loads. Elongation was measured at loads of
0, 200, and 1200 N (1200 N only at weeks 26 and 52). Strain
was calculated as change in distance between beads from
the neutral position with 0 N of force on the tendon.

Patient-Reported Outcome
Self-reported perception of disability was evaluated with
the ATRS,40,42 and the VISA-A was used to assess symp-
toms, function, and pain during sporting activities.40 These
questionnaires were completed before functional testing at
12, 26, and 52 weeks.

Functional Evaluation
Plantarflexion muscle strength was measured during max-
imal voluntary isometric contraction with ankle flexion at
0° and thereafter at 12° of plantarflexion. Strength tests
were conducted in the same custom-made rigid steel frame
used during the tendon mechanical evaluation (see above).
Four isometric contractions of approximately 8 seconds
Figure 3. Magnetic resonance imaging of the lower leg. (A) were conducted on each side. The first contraction on each
The tendon cross-sectional area is outlined. (B) Muscle side was considered a familiarization to the test, and the
cross-sectional area for soleus (1), medial gastrocnemius remaining 3 contractions were used for calculations. A ratio
(2), and lateral gastrocnemius (3). between the injured and the noninjured side was calculated.
Muscle endurance was evaluated on both sides indepen-
dently with a single-legged standing heel-rise test on
(subcutaneous and intermuscular tissue were not included a step, as previously described.51 The test was conducted
in the measurement) was manually outlined using OsiriX to the pace of a metronome with the concentric and eccentric
4.19 for MAC OS. The CSA for medial and lateral gastroc- phases each lasting 1 second. The test ended when the
nemius and soleus was measured by first determining the patient stopped due to fatigue, was unable to maintain the
axial plane where the muscle was thickest at 52 weeks and rate, or was unable to elevate at least 5 cm. MuscleLab
then manually outlining each muscle in the same plane at (Ergotest Technology) computer software and a linear
each time point (Figure 3). On average, 3 measurements encode sensor attached to the heel were used for evalua-
were made on each section. tion.51 The average height and the total work (the body
weight times total distance) in joules were used for data
analysis, and a percentage of the noninjured side was calcu-
lated. The maximum dorsiflexion range of motion was
Mechanical Testing assessed by use of the weightbearing lunge test, which is
A previously reported method to measure Achilles tendon the maximum distance away from the wall with each foot
elongation during isometric plantarflexion contraction was while the patient could still touch the wall with the
used coupled with radiography.27 Briefly, the patient was knee.28 A percentage of the noninjured side was calculated.
seated in a rigid frame with the knee flexed to 90° and the
ankle at 0°. The foot was fixed on a footplate, and a strain
gauge was attached to the footplate to register plantarflex- Statistical Analysis
ion force (in newtons). A steel bar was tightly positioned
behind the distal femur to prevent any movement. The Demographic baseline data were analyzed by use of 1-way
patient was instructed to produce plantarflexion with only analysis of variance (ANOVA). Outcome parameters were
the ball of the foot to maintain a prescribed load by visual analyzed by 2-way ANOVAs with rehabilitation regimen
feedback, and a radiograph was recorded simultaneously. (group) and time as main factors followed by Tukey multi-
A wireless transmitter (8-channel, TeleMyo 2400T G2, ple comparisons post hoc test in case of significance unless
Telemetry System; Noraxon Inc) was used for force record- otherwise noted (GraphPad Prism version 7.00 for Win-
ing. The position of the film plate was fixed relative to the dows; GraphPad Software). All analyses were performed
foot, and radiographs were recorded in the same manner as intention to treat. Results are reported as mean 6 stan-
as described for tendon elongation. The radiography dard error of the mean unless otherwise noted.
6 Eliasson et al The American Journal of Sports Medicine

TABLE 2
Patient Characteristicsa

LWB1MOB LWB1IMMOB EWB1MOB

Sex, male/female, n 19/6 19/6 22/3

Ruptured side, right/left, n 12/13 13/12 9/16
Age, y 36.0 6 1.5 36.9 6 2.2 38.8 6 1.1
Weight, kg 81.7 6 2.8 76.0 6 2.5 85.5 6 2.9
Height, cm 181 6 2 178 6 2 181 6 2
Body mass index, kg/m2 24.8 6 0.6 23.9 6 0.5 26.0 6 0.8
Days from rupture to surgery 3.5 6 0.6 3.4 6 0.4 3.4 6 0.5

a
Values are expressed as mean 6 standard error of the mean unless otherwise noted. EWB1MOB, early weightbearing with mobilization;
LWB1IMMOB, late weightbearing with immobilization; LWB1MOB, late weightbearing with mobilization.

12 LWB+MOB A
Tissue Elongation (mm)

LWB+IMMOB
10
EWB+MOB
8

0
B
6
12
26
52

6
12
26
52

6
12
26
52

Time (weeks)

Figure 4. The change in bead distance from week 2. Values

are mean 6 standard error of the mean. EWB1MOB, early
weightbearing with mobilization; LWB1IMMOB, late weight-
bearing with immobilization; LWB1MOB, late weightbearing
with mobilization.

C 4
RESULTS
Tendon CSA (cm2)

3
No significant differences were found between the groups
with respect to sex, age, body mass index, and days from 2
rupture to surgery (Table 2). The majority (97%) sustained
their rupture during sports-related activities. 1
LWB+MOB
LWB+IMMOB
EWB+MOB
0
Tendon Elongation
6
26
52

6
26
52

6
26
52

Time (weeks)
No significant interaction or group effect was found with
respect to tendon elongation, but a significant main effect Figure 5. Tendon strain measured as percentage at (A) 200 N
of time was found (P \ .0001) (Figure 4). Elongation and (B) 1200 N of tendon force. (C) Tendon cross-sectional
increased from 6 to 12 weeks (P \ .01) and from 12 to 26 area (CSA) measured by magnetic resonance imaging. Values
weeks (P \ .001) but not from 26 to 52 weeks. For strain are mean 6 standard error of the mean. EWB1MOB, early
at 200 N, no significant interaction or group effect was weightbearing with mobilization; LWB1IMMOB, late weight-
found, but a significant main effect of time was found bearing with immobilization; LWB1MOB, late weightbearing
(P \ .0001) (Figure 5A); strain decreased from 6 to 26 with mobilization.
weeks (P \ .001) but not from 26 to 52 weeks. For
1200 N, there was no significant interaction or group effect
but a significant effect of time (P \ .0001) (Figure 5B). For Muscle Strength
tendon CSA, no interaction or group effect was found but
a significant effect of time was noted (P \ .0001) (Figure For plantarflexion strength at both 0° and 12°, we found no
5C); tendon CSA increased from 6 to 26 weeks (P \ .001) interaction or group effect but a significant main effect of
and decreased from 26 to 52 weeks (P \ .001). time (P \ .001) (Table 3). Similarly, for heel-rise index
AJSM Vol. XX, No. X, XXXX Achilles Tendon Elongation After Tendon Rupture 7

TABLE 3
Plantarflexion Strength at 0° and 12° of Plantarflexion, Range of Motion, Heel-Rise Index, and Mean Heel-Rise Height

LWB1MOB LWB1IMMOB EWB1MOB P Group P Time P Group 3 Time

Plantarflexion strength 0°
26 wk 87 6 5 96 6 5 85 6 3 .08 .0001 .63
52 wk 92 6 5 105 6 5 97 6 5
Plantarflexion strength 12°
26 wk 70 6 5 76 6 5 72 6 4 .74 .0001 .76
52 wk 83 6 4 85 6 4 88 6 4
Range of motion
26 wk 58 6 4 65 6 5 65 6 6 .59 .0001 .21
52 wk 74 6 3 80 6 5 72 6 6
Heel-rise index
26 wk 52 6 4 44 6 2 44 6 4 .57 .0001 .84
52 wk 67 6 4 70 6 3 63 6 3
Heel-rise height
26 wk 69 6 5 68 6 2 61 6 5 .18 .0001 .76
52 wk 84 6 2 79 6 2 76 6 4

a
Strength data for the three groups are expressed as percentage (mean 6 standard error of the mean) of the uninjured side. Two-way
analysis of variance was conducted with rehabilitation regime (group) and time as main factors. EWB1MOB, early weightbearing with
mobilization; LWB1IMMOB, late weightbearing with immobilization; LWB1MOB, late weightbearing with mobilization.

and height, no significant interaction or group effect was days for LWB1IMMOB, and 5 weeks and 2 days 6 7 days
noted, but a significant main effect of time was found (P for EWB1MOB, with no between-group differences. The
\ .0001) (Table 3). For range of motion, we found no inter- time to return to some level of sporting activity was 24
action or group effect but a significant main effect of time weeks and 2 days 6 29 days (n = 15) for LWB1MOB, 26
(P \ .001) (Table 3). All of these parameters increased weeks and 6 days 6 28 days (n = 15) for LWB1IMMOB,
from 26 to 52 weeks. The average side-to-side difference and 26 weeks and 2 days 6 19 days (n = 22) for
in plantar flexion strength was greater at 12° compared EWB1MOB. At the 52-week follow-up, 17 patients (24%)
with 0° at 26 weeks (17.6% 6 2.6%) and 52 weeks (12.6% reported that they were back to their preinjury sporting
6 2.7%) (P \ .001, paired Student t test). level. A total of 7 complications occurred in the 75 included
patients: 2 reruptures (2.7%, both in the LWB1MOB
group), 1 adhesion, 1 deep venous thrombosis, and 4 skin
Muscle Size infections. The 2 reruptures occurred due to missed steps
and falls on the injured side 7 weeks after repair in both
For the CSA of the medial gastrocnemius, there was a sig- cases.
nificant interaction (P \ .05) and time effect (P \ .0001),
but no group effect (Table 4); CSA increased from 6 to 26
weeks but not 26 to 52 weeks. For the lateral gastrocne-
mius there was no significant interaction or group effect, DISCUSSION
but a significant effect of time (P \ .0001); CSA increased
from 6 to 26 weeks but not 26 to 52 weeks. For the soleus The principal finding of this randomized controlled trial
muscle there was no significant interaction effect, but a sig- was that Achilles tendon elongation was significant and
nificant main effect of both group (LWB1MOB and continued for up to 26 weeks after surgery (Figure 4).
EWB1MOB differed, P \ .05) and time (P \ .0001); CSA Data on secondary outcomes show that the Achilles tendon
declined from week 6 to 26, but not from 26 to 52 weeks. CSA increased from 6 to 26 weeks but then decreased from
26 to 52 weeks. Tendon compliance, which was measured
as elongation during isometric contractions, also decreased
Outcome Scores over the course of a year after surgery, at which time mus-
cle strength, endurance, and patient-reported functional
No significant interaction or group effect was found for scores had not yet reached normal values. Collectively,
ATRS, but a significant main effect of time was noted these data suggest that the time to recover full function
(P \ .001) (Table 5); ATRS increased from weeks 12 to 26 after rupture is at least 1 year. Notably, our hypothesis
and from weeks 26 to 52 (P \ .01). A significant interaction was not supported since different loading patterns during
and main effect of time (P \ .0001) were found for VISA-A rehabilitation of the tendon in the initial 8 weeks after sur-
but no group effect (Table 5); VISA-A increased from weeks gery did not significantly influence the primary outcome or
12 to 26 and from weeks 26 to 52 (P \ .01). any of the measured outcome parameters.
The time to return to full-time work was 6 weeks and 2 Although considerable attention has been focused on pre-
days 6 10 days for LWB1MOB, 6 weeks and 4 days 6 11 vention of muscle atrophy and strength loss following
8 Eliasson et al The American Journal of Sports Medicine

TABLE 4
Muscle Cross-sectional Area of the Three Triceps Surae Muscles Measured Where the Muscle Was Thickesta

LWB1MOB LWB1IMMOB EWB1MOB P Group P Time P Group 3 Time

Medial gastrocnemius
6 wk 10.9 6 0.6 12.4 6 0.7 11.8 6 0.7 .32 .0001 .03
26 wk 13.3 6 0.7 12.8 6 0.8 12.8 6 0.7
52 wk 14.0 6 0.7 13.1 6 0.8 13.2 6 0.8
Lateral gastrocnemius
6 wk 5.2 6 0.4 5.5 6 0.4 5.4 6 0.4 .49 .0001 .95
26 wk 6.6 6 0.4 6.0 6 0.4 6.4 6 0.5
52 wk 6.0 6 0.4 6.2 6 0.4 6.6 6 0.5
Soleus
6 wk 21.7 6 1.2 25.0 6 1.2 24.5 6 1.3 .05 .0001 .61
26 wk 21.3 6 0.9 22.4 6 1.1 23.2 6 1.2
52 wk 22.8 6 1.0 23.1 6 1.1 23.0 6 1.1

a
Cross-sectional area for the three groups is expressed as mm2 (mean 6 standard error of the mean). Two-way analysis of variance was
conducted with rehabilitation regime (group) and time as main factors. EWB1MOB, early weightbearing with mobilization; LWB1IMMOB,
late weightbearing with immobilization; LWB1MOB, late weightbearing with mobilization.

TABLE 5
Patient-Reported Outcomes of the Achilles tendon Total Rupture Score (ATRS)
and the Victorian Institute of Sport Assessment-Achilles Questionnaire (VISA-A)a

LWB1MOB LWB1IMMOB EWB1MOB P Group P Time P Group 3 Time

ATRS
12 wk 36 6 3 31 6 3 33 6 3 .24 .0001 .23
26 wk 65 6 3 52 6 5 54 6 4
52 wk 79 6 4 77 6 3 74 6 4
VISA-A
12 wk 42 6 3 29 6 3 44 6 4 .11 .0001 .02
26 wk 73 6 3 63 6 4 65 6 4
52 wk 82 6 4 79 6 3 79 6 3

a
Scores for the three groups are expressed as mean 6 standard error of the mean. Two-way analysis of variance was conducted with reha-
bilitation regime (group) and time as main factors. EWB1MOB, early weightbearing with mobilization; LWB1IMMOB, late weightbearing
with immobilization; LWB1MOB, late weightbearing with mobilization.

Achilles tendon rupture, much less focus has been placed on earlier studies.20,36,47 To what extent loading in the first 6
the length of the tendon. Previous investigations have months influences elongation remains unknown but should
shown that the Achilles tendon elongates substantially (5- be considered since elongation may relate to the clinical out-
11 mm) in the initial 6 to 7 weeks,20,36,44,50 and some stud- come.20 For logistical and ethical reasons it was not possible
ies,36,44 but not all,20 show that the elongation appears to to measure strain or absolute length on the uninjured side,
continue up to 12 weeks (8-14 mm). However, the elongation which would have provided a within-patient control for time
appears to have halted about 1 year after rupture.20,44 Sim- that could have provided further information. The present
ilar to previous studies, the present data show that the ten- study and other studies20,36,48,49 have used tantalum beads
don elongates in the initial 6 weeks (0.8-1.9 mm) and 12 to assess tendon length, and although it cannot be ruled out
weeks (2.6-4.2 mm), albeit with somewhat smaller magni- that some migration may take place, this appears doubt-
tudes. Whether this numerically smaller elongation relates ful.49 Any migration would likely be toward less dense tis-
to suture technique or tightening during surgery remains sue (ie, toward the rupture site/repair), which would
unknown. However, the present data expand on previous result in an underestimation of resting length, and migra-
findings by showing that the tendon continues to elongate tion would not influence tendon strain values since they
(5.5-8.2 mm) up to 26 weeks after surgery. In fact, only are normalized deformation values.
approximately 50% of the total elongation takes place in In the present study, the CSA of the Achilles tendon was
the initial 3 months after surgery, and the remaining 50% 154 to 169 mm2 at the first measurement 6 weeks after
occurs in the subsequent 3 months. It is noteworthy that surgery. It was not possible to obtain an MRI to determine
the rehabilitation regimen in the initial 8 weeks does not the CSA of the contralateral side. However, it has been
appreciably influence the elongation, which corroborates reported that the tendon on the uninjured side in patients
AJSM Vol. XX, No. X, XXXX Achilles Tendon Elongation After Tendon Rupture 9

with Achilles tendon rupture is approximately 101 mm2,26 heel-rises, which corresponded to 75% of the uninjured side
suggesting that there was a sizable increase in CSA in the (P \ .001, data not shown) at 52 weeks. Collectively, these
present study. This increase may be related to inflamma- data show that overall muscle function in a more plantar-
tion and the repair process, in which hydrophilic proteogly- flexed position has far from recovered 52 weeks after sur-
cans and glycosaminoglycans aggregate. Whether this gery. The heel-rise index, which represents the overall
repair process affects the longitudinal direction of the ten- muscle endurance capacity of the triceps surae muscle
don remains unknown. The CSA was at a maximum at 26 group, only recovered 63% to 70% of the uninjured side
weeks and was then reduced at the 52-week follow-up, at 52 weeks, which also corresponds to previous reports.3
a temporal pattern similar to that reported by Because muscle function often does not recover fully
others.47,49,50 The CSA at 1 year after surgery was more after an Achilles tendon rupture, some attention has
than 100% larger than reported normal values for the been directed to what extent the muscle mass can recover.
Achilles tendon,26 but since we did not follow up beyond In the present study, it was not possible to obtain muscle
1 year it is unknown whether the reduction in CSA contin- CSA on the uninjured side for logistical reasons, and there-
ued. Interestingly, it has been shown that cellular activity fore our analysis is limited to changes over time. The data
measured by the glucose uptake associated with ambula- of the present study suggest that for both gastrocnemii
tion is higher in repaired than in intact Achilles tendons there is an increase over time, which is in contrast to mus-
at 3 months (63), 6 months (33), and 12 months (1.63), cle volume changes reported by others.16 Interestingly, the
indicating that tendon response to loading is not normal- same study16 showed a side-to-side difference of 15% and
ized until after 1 year.9 11% for the medial and lateral gastrocnemii, respectively,
Collagen fibrils are the principal tensile bearing struc- 18 months after surgery, indicating a practically perma-
tures of tendons,33 but the mechanism and time course of nent reduction in that muscle mass. In contrast to the gas-
fibril integration and reorganization following a rupture trocnemii, the soleus muscle mass in the present study
remain entirely unknown. The magnitude of strain at declined from weeks 6 to 26 and did not recover at 52
a low force (200 N) declined from 6 weeks to 3 months weeks, which corroborates a previously reported 18% defi-
and continued to decline up to a year, and this increased cit in muscle mass of the soleus 18 months after surgery.16
stiffness was corroborated at a higher force (1200 N). In This apparent incomplete recovery of the soleus muscle,
other words, this process of increased tendon stiffness con- which has a physiological CSA that is more than twice
tinued for at least 1 year and was independent of the mag- the size of the combined gastrocnemii,13 may also explain
nitude of loading in the initial 8 weeks. These findings are the deficit in the heel-rise index at 52 weeks (63%-70%).
in close agreement with a previous investigation.47 Intriguingly, it has been shown that an altered muscle
Whether new collagen is deposited in the healing region activation strategy may be in place after an Achilles ten-
is unknown, but the fact that the CSA decreased from 6 don rupture with a compensatory activation of flexor hallu-
to 12 months while the strain properties continued to cis longus to achieve isometric plantarflexion moment,10
improve suggests that CSA is not directly related to tensile which appears to be supported by the recent finding of
properties in the healing phase. This may also indicate compensatory hypertrophy in this muscle group 18 months
that tissue quality rather than quantity is responsible for after surgery.16 It is possible that this is a protective strat-
the increase in stiffness, which could be caused by an egy and that it may stress shield the Achilles tendon. Fur-
improved fibril organization. thermore, to what extent the timing and magnitude of
Muscle weakness can persist for a long time after sur- loading influence this altered activation is unknown.
gery# and may be present even a decade after the injury.29 The ATRS results showed that the patient’s perception
In the present study, the rehabilitation regimen in the ini- of disability improved significantly from week 26 (score
tial 8 weeks did not influence muscle strength recovery 52 52-65) to week 52 (score 74-79). Previous reports of ATRS
weeks after surgery, which reached almost normal values at the 12-month follow-up after surgery range from 61 to
(92%-105% of the uninjured side). Interestingly, the iso- 89.3,15,39,41 Importantly, healthy persons have a score
metric strength deficit in the neutral position was 8% to that approaches 100,40 and there are no meaningful
15% at 26 weeks, but this deficit was greater (24%-30%) improvements beyond 1 year, suggesting some remaining
when tested at 12° of plantarflexion. Similarly, at 52 weeks functional deficits compared with preinjury.41 It is note-
the deficit was less in the neutral position compared with worthy that at the 1-year follow-up only 24% of patients
that at 12° plantarflexion. This amplified strength deficit reported that they were back to preinjury sporting level.
in a more plantarflexed position corroborates previous The VISA-A score showed a similar pattern with an
reports.37 In addition, the current results show that the improvement from 26 to 52 weeks but did also not reach
average heel-rise height during the heel-rise test was 100%. Notably, the patient-reported outcomes were unaf-
76% to 84% of the injured side at 52 weeks, likely also fected by the difference in rehabilitation regimens. The
reflecting a muscle-tendon functional deficit in a relative overall rerupture rate (2.7%), the complication rate
plantarflexion position. However, the average heel-rise (6.7%), and the time to return to full-time work (37-46
height may be influenced by fatigue, and therefore we days) were similar to the values reported by others.3,6
also examined the heel-rise height during the first 3 Tendon fibroblasts will initiate synthesis of collagen
and extracellular matrix components in response to strain,
and a lack thereof will elevate degradation and inhibit syn-
#
References 1, 5, 16, 22, 29, 35, 37, 41, 46, 51, 52, 55. thesis.23 We therefore hypothesized that early motion
10 Eliasson et al The American Journal of Sports Medicine

(strain) without large loads (delayed weightbearing) would 12. Froberg A, Komi P, Ishikawa M, Movin T, Arndt A. Force in the Achil-
be beneficial for the rupture repair. However, basically all les tendon during walking with ankle foot orthosis. Am J Sports Med.
2009;37(6):1200-1207.
the measured outcomes were comparable in all 3 interven-
13. Fukunaga T, Roy RR, Shellock FG, et al. Physiological cross-
tion groups. Similar to other studies on the effect of reha- sectional area of human leg muscles based on magnetic resonance
bilitation (reviewed in Reference 6), the present study imaging. J Orthop Res. 1992;10(6):928-934.
focused on the initial 6 to 8 weeks. However, the results 14. Gebauer M, Beil FT, Beckmann J, et al. Mechanical evaluation of dif-
clearly suggest increased tendon elongation and stiffness ferent techniques for Achilles tendon repair. Arch Orthop Trauma
for at least 6 months after surgery, and since the healing Surg. 2007;127(9):795-799.
process as determined by metabolic activity and vasculari- 15. Hansen MS, Christensen M, Budolfsen T, et al. Achilles tendon Total
Rupture Score at 3 months can predict patients’ ability to return to
zation is elevated for 6 to 12 months after injury,9 rehabil- sport 1 year after injury. Knee Surg Sports Traumatol Arthrosc.
itation and a controlled loading paradigm may be 2016;24(4):1365-1371.
important well beyond the initial 2 to 3 months. 16. Heikkinen J, Lantto I, Flinkkila T, et al. Soleus atrophy is common
In conclusion, differences in rehabilitation loading pat- after the nonsurgical treatment of acute Achilles tendon ruptures.
tern in the initial 8 weeks after the repair of an Achilles Am J Sports Med. 2017;45(6):1395-1404.
tendon rupture did not alter the outcome. Importantly, 17. Herbort M, Haber A, Zantop T, et al. Biomechanical comparison of
the primary stability of suturing Achilles tendon rupture: a cadaver
Achilles tendon elongation and tendon compliance were
study of Bunnell and Kessler techniques under cyclic loading condi-
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