Abstract
Background: An initial anterior dislocation of the shoulder becomes
recurrent in 66% to 94% of young patients after immobilization of the shoulder
in internal rotation. Magnetic resonance imaging and studies of cadavera have
shown that coaptation of the Bankart lesion is better with the arm in external
rotation than it is with the arm in internal rotation. Our aim was to
determine the benefit of immobilization in external rotation in a randomized
controlled trial.
Methods: One hundred and ninety-eight patients with an initial
anterior dislocation of the shoulder were randomly assigned to be treated with
immobilization in either internal rotation (ninety-four shoulders) or external
rotation (104 shoulders) for three weeks. The primary outcome measure was a
recurrent dislocation or subluxation. The minimum follow-up period was two
years.
Results: The follow-up rate was seventy-four (79%) of ninety-four in
the internal rotation group and eighty-five (82%) of 104 in the external
rotation group. The compliance rate was thirty-nine (53%) of seventy-four in
the internal rotation group and sixty-one (72%) of eighty-five in the external
rotation group (p = 0.013). The intention-to-treat analysis revealed that the
recurrence rate in the external rotation group (twenty-two of eighty-five;
26%) was significantly lower than that in the internal rotation group
(thirty-one of seventy-four; 42%) (p = 0.033) with a relative risk reduction
of 38.2%. In the subgroup of patients who were thirty years of age or younger,
the relative risk reduction was 46.1%.
Conclusions: Immobilization in external rotation after an initial
shoulder dislocation reduces the risk of recurrence compared with that
associated with the conventional method of immobilization in internal
rotation. This treatment method appears to be particularly beneficial for
patients who are thirty years of age or younger.
Level of Evidence: Therapeutic Level II. See Instructions
to Authors for a complete description of levels of evidence.
The shoulder is the most commonly dislocated major
joint1. The
recurrence rate after an initial dislocation ranges between 20% and
48%2-6.
However, the recurrence rate among young patients is much higher, although the
reported rates vary greatly. These rates have been reported to be 66% to 94%
in patients under the age of twenty
years4,6-8,
92% in patients between fourteen and seventeen years of
age9, and 50% to 64%
in patients younger than thirty years of
age5,10.
Why the recurrence rate is so high among young patients is unknown. Detachment
of the inferior glenohumeral ligamentlabrum complex from the glenoid, the
Bankart lesion, is found in 94% to 97% of shoulders after an initial
dislocation11-13.
If the Bankart lesion heals, recurrence is less likely. There are several
facts that suggest that the Bankart lesion has the ability to heal. First, the
shoulder never redislocates after the initial dislocation in 52% to 80% of
patients2,5,
which indicates that the Bankart lesion may have healed in these patients.
Also, recurrent dislocations spontaneously cease in 20% of patients with
recurrent
dislocations2. In
these cases, the Bankart lesion may have healed after the last dislocation.
Despite the potential healing ability of the Bankart lesion, the recurrence
rate does not depend on how long the shoulder is immobilized or how rigidly it
is immobilized7.
Furthermore, it may not depend even on whether the shoulder is immobilized or
not2,7.
A logical explanation for these findings would be that the Bankart lesion is
not well reduced in the conventional position of immobilization— i.e.,
internal rotation.
Motivated by the lack of sufficient evidence that the Bankart lesion is
well reduced by immmobilization in internal rotation, we initiated a study
with use of magnetic resonance imaging, which demonstrated that the Bankart
lesion is separated from the bone with the arm in internal rotation and is
apposed to the bone with the arm in external
rotation14. On the
basis of this observation, we hypothesized that immobilization in external
rotation would decrease the recurrence rate. In order to prove this
hypothesis, we initiated a prospective clinical study to compare patients who
had the shoulder immobilized in internal rotation with those who had the
shoulder immobilized in external rotation. The preliminary outcome of this
prospective study supported our
hypothesis15. The
purpose of the present study was to report the two-year results of this
study.
Participants
In January 2000, we started a randomized prospective study comparing
immobilization in internal rotation with immobilization in external rotation
at our institutes (Akita University Hospital, Tazawako Municipal Hospital,
Ogachi Chuo Hospital, and Honjo Daiichi Hospital). The preliminary results of
treatment of forty patients at these four institutes were previously
reported15. In
October 2000, we began to recruit patients from eleven other institutes
nationwide to increase the number of patients in the study. Between October
2000 and March 2004, 229 patients with an initial traumatic anterior
dislocation of the shoulder were treated at one of these institutes. The
inclusion criteria were (1) an initial anterior dislocation caused by a
substantial traumatic event, (2) presentation within three days after the
dislocation, and (3) no associated fractures of the shoulder detectable on
routine radiographic examination. Of the 229 patients, fifteen did not meet
the inclusion criteria and sixteen refused to participate in this study,
leaving 198 patients for enrollment. There were 136 male patients and
sixty-two female patients, with an average age of thirty-seven years (range,
twelve to ninety years). After routine radiographic examination
(anteroposterior, axillary, and scapular Y views), the shoulder dislocation
was reduced manually. The methods of reduction were the elevation method (101
shoulders), the Hippocratic method (twenty-two shoulders), the external
rotation method (seventeen shoulders), the Kocher method (sixteen shoulders),
the Stimson method (fourteen shoulders), and others (twenty-eight
shoulders).
The Akita University Ethics Research Committee provided ethics approval
(number 10-5). All enrolled participants gave written informed consent.
Procedures
The patients were randomly assigned to one of two groups: immobilization in
internal rotation (internal rotation group) or immobilization in external
rotation (external rotation group). Randomization was performed with use of a
random-number table created by the principal investigator (E.I.).
Co-investigators allocated the patients at their institutes with use of this
random-number table. There were ninety-four patients in the internal rotation
group (average age, thirty-seven years; range, twelve to eighty-nine years)
and 104 patients in the external rotation group (average age, thirty-five
years; range, twelve to ninety years). The demographic characteristics of
these patients are summarized in Table
I.
Immobilization in internal rotation was performed with a sling and swathe.
Immobilization in external rotation was performed with a wire-mesh splint
covered with sponge and a stockinette
(Figs. 1-A and 1-B). The
precise method for making this immobilizer was described in our previous
report15. The
shoulder was kept in adduction and 10° of external rotation. In November
2003, we started to use a prototype brace, manufactured by Alcare, Tokyo,
Japan (Figs. 2-A and 2-B). The
same immobilization position was obtained with this brace, and it was easier
to apply than the former splint-stockinette immobilizer.
In both the internal rotation and the external rotation group, the
immobilizer was supposed to be worn continuously, except when the patient took
a shower, for three weeks. At the three-week examination, we asked the
patients how many hours a day and for how long they had actually worn the
immobilizer in order to measure their compliance with the treatment protocol.
At three weeks, we instructed the patients to begin to move the arms both
passively and actively. The patients were then seen on one or two more
occasions to make sure that they regained a full range of motion. We advised
them to avoid vigorous sports activities for at least three months. The
patients were asked to visit us at six months, twelve months, and twenty-four
months after the initial dislocation. When they were unable to do so, we
interviewed them by telephone.
The primary outcome measure was a recurrent dislocation or subluxation of
the shoulder. Dislocation was defined as the humeral head being completely out
of the glenoid socket until a reduction maneuver was performed, and
subluxation was defined as the humeral head being completely or partially out
of the glenoid socket but reducing spontaneously. We asked the patients
whether they had experienced any additional dislocation or subluxation after
the immobilization. If they had, we asked them when and how the recurrent
injury occurred and whether they had returned to preinjury sports.
Statistical Analysis
The required sample size was calculated to be forty-two in each group when
alpha = 0.05 and beta = 0.2, for a ratio of effectiveness of 0.3 in the
internal rotation group and 0.6 in the external rotation group. With the
assumption that the follow-up rate was 80% and the compliance rate was 50%,
the necessary sample size was calculated to be 105 in each group. Compliance
was assessed in both groups. Those who wore the immobilizer for twenty-four
hours a day, except when they took a shower, for three weeks were defined as
being compliant. Both intention-to-treat and per-protocol analyses were
performed. The intention-to-treat analysis included both the compliant and the
noncompliant patients, whereas the per-protocol analysis included only those
who were compliant. In addition, we performed sensitivity analyses first with
the assumption that all of the patients who were lost to follow-up had
recurrent dislocations and then with the assumption that none of them had
recurrent dislocations. The rates of recurrent dislocation and of return to
sports were compared between the groups with use of the chi-square test. The
absolute and relative risk reductions were calculated. We also compared the
recurrence rate on the basis of when the immobilization was started (the
first, second, or third day). The Kruskal-Wallis test was used to compare the
recurrence rates within each group. We further analyzed a subgroup of patients
who were thirty years of age or younger because they were the group of
patients with the highest recurrence rate and thus the most important group
clinically. Significance was set at the p < 0.05 level.
Follow-up Rate
Figure 3 shows the profile
of the trial. Of 198 patients enrolled in this study, 159 (80%) were followed
for a minimum of two years with either a direct examination or a telephone
interview. The average follow-up period was 25.6 months, ranging from
twenty-four to thirty months. Twenty-eight (38%) of the seventy-four patients
who were followed in the internal rotation group and thirty-eight (45%) of the
eighty-five who were followed in the external rotation group were
examined.
Compliance
Despite our instructions, some patients discontinued the immobilization of
the shoulder before three weeks (Table
II). Among those who continued immobilizing the shoulder for the
full three weeks, some used the immobilizer on a full-time basis (literally
full time except when taking a shower), whereas others used it on a part-time
basis (range, one to twenty hours a day). In total, thirty-nine patients (53%)
in the internal rotation group and sixty-one patients (72%) in the external
rotation group complied with the protocol. This difference was significant (p
= 0.013).
Recurrence
The intention-to-treat analysis revealed that the recurrence rate was
thirty-one (42%) of seventy-four in the internal rotation group and twenty-two
(26%) of eighty-five in the external rotation group (p = 0.033).
Immobilization in external rotation was associated with an absolute risk
reduction of 16.0% and a relative risk reduction of 38.2%.
The per-protocol analysis showed that the recurrence rate was fifteen (38%)
of thirty-nine in the internal rotation group and twelve (20%) of sixty-one in
the external rotation group (p = 0.039). Immobilization in external rotation
was associated with an absolute risk reduction of 18.8% and a relative risk
reduction of 48.8%.
When the sensitivity analysis was performed with the assumption that all of
the patients who were lost to follow-up had recurrent dislocations, the
recurrence rate was fifty-one (54%) of ninety-four in the internal rotation
group and forty-one (39%) of 104 in the external rotation group (p = 0.037).
With this assumption, the absolute and relative risk reductions associated
with immobilization in external rotation were 16.0% and 38.2%, respectively.
With the assumption that none of those who were lost to follow-up had
recurrent dislocations, the recurrence rate was thirty-one (33%) of
ninety-four in the internal rotation group and twenty-two (21%) of 104 in the
external rotation group (p = 0.061), with the absolute and relative risk
reductions being 11.8% and 35.9%, respectively.
Additional detailed data were derived with the intention-to-treat analysis.
The recurrence rates as documented with direct examination were thirteen (46%)
of twenty-eight in the internal rotation group and ten (26%) of thirty-eight
in the external rotation group. The recurrence rates as documented with a
telephone interview were eighteen (39%) of forty-six and twelve (26%) of
forty-seven, respectively. There was no significant difference in the
recurrence rate between the patients who underwent a direct examination and
those who were interviewed on the telephone in either the internal rotation
group (p = 0.54) or the external rotation group (p = 0.93). Recurrence was
experienced at various periods following the initial dislocation but mainly in
the first year: 84% of the recurrences in the internal rotation group and 82%
in the external rotation group were noted within twelve months after the
injury. The recurrence rates stratified by age are shown in
Table III. In the twenty-one to
thirty-year-old age group, the recurrence rate following immobilization in
external rotation was significantly lower than that following immobilization
in internal rotation (p = 0.037). The recurrence rates stratified by the day
on which the immobilization was initiated are shown in
Table IV. With the numbers
studied, there were no significant within-group differences. There was a
significant between-group difference in the recurrence rates associated with
immobilization on day 1 (p = 0.024) but not in the recurrence rates associated
with immobilization on day 2 or on day 3. However, the numbers of shoulders
immobilized on days 2 and 3 were small.
Nine (29%) of the thirty-one patients who experienced recurrent
dislocations or subluxations in the internal rotation group and eight (36%) of
the twenty-two who did so in the external rotation group eventually underwent
surgical stabilization.
Return to Sports
Forty-nine (66%) of the seventy-four patients in the internal rotation
group and sixty (71%) of the eighty-five in the external rotation group
sustained the injury during participation in sports (p = 0.55). At the time of
the two-year follow-up, thirty-one (63%) of the forty-nine patients in the
internal rotation group and forty-three (72%) of the sixty patients in the
external rotation group had returned to sports (p = 0.35). However, only ten
(20%) of the forty-nine patients in the internal rotation group and twenty-two
(37%) of the sixty patients in the external rotation group had returned to
their preinjury sports activity level (p = 0.064).
Complications
Six (7%) of the eighty-five patients had temporary stiffness of the
involved shoulder after immobilization in external rotation. This problem
resolved within a month or two through the use of self-directed
range-of-motion exercises. No other complications related to immobilization
were reported.
Subgroup Analyses
We performed additional analyses to assess compliance, the recurrence rate
stratified by the day on which the immobilization was initiated, sports
participation, and shoulder stiffness after treatment in the subgroup of
patients who were thirty years of age or younger. The compliance rate was
seventeen (40%) of forty-two in the internal rotation group and thirty-eight
(68%) of fifty-six in the external rotation group (p = 0.007). The recurrence
rate was twenty-five (60%) of forty-two in the internal rotation group and
eighteen (32%) of fifty-six in the external rotation group (p = 0.007).
Immobilization in external rotation was associated with absolute and relative
risk reductions of 27.4% and 46.1%, respectively.
In this younger subgroup, the recurrence rates were twenty (59%) of
thirty-four when immobilization had been initiated on day 1, one of two when
it had been initiated day 2, and four of six when it had been initiated on day
3 in the internal rotation group (p = 1.0); the respective values in the
external rotation group were ten (25%) of forty, three of eight, and five of
eight (p = 0.11). The difference between the internal rotation and external
rotation groups was significant when the immobilization had been initiated on
day 1 (p = 0.003) but not when it had been initiated on day 2 (p = 0.75) or
day 3 (p = 0.87). Thirty-nine (93%) of the forty-two patients in the internal
rotation group and fifty-three (95%) of the fifty-six in the external rotation
group had a sports-related injury (p = 0.72). At the time of the two-year
follow-up, twenty-two (56%) of the thirty-nine patients in the internal
rotation group and thirty-nine (74%) of the fifty-three in the external
rotation group had returned to sports (p = 0.085). Seven (18%) of the
thirty-nine in the internal rotation group and twenty (38%) of the fifty-three
in the external rotation group returned to their preinjury level of sports
participation (p = 0.039). Two (4%) of the fifty-six patients in the external
rotation group had temporary shoulder stiffness, which had resolved by the
time of follow-up.
Immobilization in internal rotation following shoulder dislocation has been
performed for over 2000
years16.
Surprisingly, there has been no evidence that this position is optimum for the
healing of the Bankart lesion. The current study has demonstrated that
immobilization in 10° of external rotation for three weeks reduces the
relative risk of recurrence by 38.2% compared with the risk associated with
conventional immobilization in internal rotation.
The recurrence rate in the external rotation group was significantly lower
than that in the internal rotation group when the immobilization had been
started on the day of the dislocation, but there was no difference between
groups when it had been started on day 2 or 3. This suggests that the earlier
that the immobilization is started, the better the results, although the
numbers of patients who were initially treated on day 2 or 3 were quite small,
perhaps too small to allow meaningful comparisons.
Additional analyses of the subgroup of patients who were thirty years of
age or younger revealed that individuals who are younger than that age would
particularly benefit from immobilization of the shoulder in external rotation
after an initial dislocation. Again, when the immobilization had been on day
1, the recurrence rate was significantly lower in the external rotation group
than it was in the internal rotation group. Furthermore, the proportion of
patients who returned to their preinjury level of sports was significantly
higher in the external rotation group. Thus, the benefit of external rotation
immobilization was demonstrated in this clinically important group of young
patients.
The ideal method of immobilization in external rotation has not yet been
established. First, the best position of immobilization needs to be
determined. In this study, we immobilized the shoulder in approximately
10° of external rotation. Miller et al. measured the contact force between
the Bankart lesion and the glenoid in cadaveric shoulders as the arm was
rotated from 60° of internal rotation to 45° of external
rotation17. The
contact force started to be positive as the arm passed through neutral
rotation and became maximum at the maximum external rotation of 45°. This
study suggests that the greater the amount of external rotation, the greater
the contact force. However, in our experience, the greater the amount of
external rotation, the less comfortable the patient. Therefore, we chose
10° of external rotation, which according to the study by Miller et al.
creates positive contact for healing, but we need to determine the minimum
effective amount of external rotation in future studies.
Regarding the position of immobilization, an interesting study was reported
from the United Kingdom. During arthroscopic examination, Hart and Kelly
observed that external rotation improved the reduction of a Bankart lesion
after an initial dislocation in 92% of the shoulders in their
series18. However,
they found that the best reduction was achieved with the arm in 30° of
abduction and 60° of external rotation. Thus, the best position for
immobilization, particularly in the coronal plane, needs to be studied
further.
The second factor that needs to be better elucidated is the duration of
immobilization. In this study, we immobilized the shoulder for three weeks
according to conventional recommendations regarding the duration needed to
achieve soft-tissue
healing7,19.
We thought that this would be an appropriate length of time to allow initial
healing of a Bankart lesion. Kitamura and Ikuta reported that they immobilized
the shoulder in external rotation for four weeks followed by two weeks of
immobilization in internal
rotation20. None of
their thirteen patients had experienced a recurrence at the time of a one-year
follow-up. Their report suggests that three weeks of immobilization may not be
long enough. Thus, the optimum duration of immobilization also needs to be
determined in a future study.
There are several limitations of the present study. First, the patients'
compliance with the treatment protocol was significantly better in the
external rotation group, although the patients were randomly assigned to the
groups. One might wonder why the compliance rate was higher in the external
rotation group when the device was much more cumbersome. This finding strongly
suggests that there was some bias, as this part of the study (when the
surgeons instructed the patients regarding the immobilization protocol) could
not be blinded. We and the other treating surgeons might have made a stronger
effort to ensure compliance with the external rotation immobilization than to
ensure compliance with the internal rotation immobilization. This is a
drawback of this study and one of the reasons why it was assigned a level of
evidence of II. Second, the occurrence of dislocation or subluxation was the
primary end point of the study. However, those without recurrence may or may
not have been satisfied with the shoulder because of residual symptomatic
instability. We did not include a patient-based quality-of-life assessment
such as the Western Ontario Shoulder Instability Index
(WOSI)21. Third,
this was a two-year follow-up study. According to
Rowe7, 70.5% of all
recurrent shoulder dislocations occur within the first two years and 18.7%
occur from two to five years. Further evaluation at five years or later would
be valuable.
In conclusion, immobilization in 10° of external rotation for three
weeks reduces the relative risk of recurrence of a first-time traumatic
anterior shoulder dislocation when compared with the risk associated with
conventional immobilization in internal rotation. This treatment is
particularly beneficial for those who are thirty years of age or younger.
?
Note: The authors thank the following individuals who
participated in the patient enrollment and follow-up for this study: Dr.
Shigeo Mori (Mori Orthopaedic Clinic), Dr. Akira Saito (Soma Municipal
Hospital), Dr. Akihiro Sato (Watanabe Hospital), Dr. Tomonobu Miyazawa
(Saitama Medical School Hospital), Dr. Toshihiko Hashimoto (Tokyo Women's
Medical University Hospital), Dr. Toshiharu Takazawa (Juntendo University
Hospital), Dr. Yoshiaki Kon (Niigata Saiseikai Second Hospital), Dr. Yusuke
Iwahori (Aichi Medical University Hospital), Dr. Toshiro Kotake (Mitsubishi
Kyoto Hospital), Dr. Yukihiro Okamoto (Moriyama Municipal Hospital), Dr. Kazu
Matsumoto, and Dr. Kazuhiko Wakahara (Sumi Hospital).
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