Background
Brachial plexus birth lesions occur with an incidence of around 2.3–3.3/1000 live
births per year [[1],[2]]. Spontaneous recovery is common but as many as 25% of teenagers with a brachial
plexus birth lesion may have secondary complications, which are mostly located in
the shoulder region with the deformity, medial rotation contracture and problems with
activity of daily living (ADL; [[3]]). An untreated medial rotation contracture may lead to posterior subluxation or
dislocation since the natural history of untreated brachial plexus birth palsy with
residual weakness is progressive glenohumeral deformity due to persistent muscle imbalance.
Progressive deformity has also been found with increasing age [[4]]. Posterior shoulder dislocation can occur even before the age of one, but the etiology
of such an early lesion, which include particularly birth trauma, use of splint devices
or muscle imbalance, is still not clarified [[5],[6],[7],[8],[9]]. Recently, the frequency of the condition was reported in consecutive cases with
brachial plexus birth palsy below the age of one [[5],[6]]. As many as 8 (11/134) to 10% of the children may have a posterior shoulder dislocation
before their first birthday. However, the incidence of posterior dislocation in relation
to brachial plexus birth palsy in children below one year of age has not previously
been reported. Our aim was to determine the incidence of posterior dislocation of
the shoulder among children with an age below one and the corresponding incidence
of brachial plexus birth lesion in Malmö municipality, Sweden, during 2000–2005.
Methods
All children born at Malmö University hospital and living in Malmö municipality (mean
population of Malmö 263 550 during the study period) with signs of brachial plexus
birth palsy are referred within days for follow-up to the Unit of Child Habilitation.
The children have been followed by the same physiotherapist since 1982 (KE) and by
a child neurologist (MF). Similar treatment strategies have been adopted during these
years, i.e. prophylactic exercises against contracture [regular oral and written (schematic
drawing with instruction of specific exercises to prevent particularly shoulder contracture)
instructions to parents], regular follow-up of neurological recovery and observation
of any signs of development of medial rotation contracture. The procedures have essentially
not changed during the time period. Since 1997 most children, and since 2000 all children,
with a brachial plexus birth palsy have also been prospectively examined at regular
intervals by a hand surgeon (LD) to judge recovery of the neurological deficit of
the brachial plexus lesion and particularly any development of shoulder dysfunction
including development of contracture and signs of dislocation. A study of persistent
symptoms in teenagers with a brachial plexus birth lesion has previously been published
from Malmö [[3]]. The diagnosis of posterior shoulder dislocation was based on the history (sudden
development of impaired external rotation), a clinical examination [impaired passive
external rotation, asymmetry of the shoulder with palpable humeral head posteriorly,
shortening of the length of the upper arm and asymmetry of skin fold due to telescoping
of humerus and axillary asymmetry], conventional x-ray (all cases) and MRI/CT (one
case).
Results
During 2000–2005 21610 living infants were born at Malmö University hospital in Malmö,
Sweden. Of these, 82 children had a brachial plexus birth palsy and the children were
referred to the Child Habilitation Unit for follow up. The mean incidence of brachial
plexus birth palsy was 3.8/1000 living infants per year with a slight variation during
the six years (Figure [1]). During 2000–2005, we observed one case per year with a posterior shoulder dislocation
occurring before the age of 12 months, corresponding to an incidence of posterior
shoulder dislocation in such children with brachial plexus birth palsy of 0.28/1000
living children and year, i.e. the frequency of 6/82 (7.3%).
Figure 1 Incidence of brachial plexus birth palsy and early (age less than one year) posterior
dislocation of the shoulder per 1000 living born infants and year 2000–2005 in Malmö
municipality, Sweden. The numbers correspond to a frequency of 7.3% (six posterior
shoulder dislocations out of 82 brachial plexus birth palsies during 2000–2005).
The median birth weight of the six children was 4760 gram (min-max 4100–5340; two
boys and four girls). Shoulder dystocia was reported in all six cases. The brachial
plexus birth lesion was classified according to Narakas [one case group one (C5–C6),
four cases group two (C5, C6, C7) and one case group three (total lesion without Horner)].
In five of the cases there was a spontaneous, not always complete, recovery of neurological
function that did not require nerve reconstruction, while the child with the total
injury had surgical reconstruction. In that child the C5 and C6 roots were reconstructed
with nerve grafts at the age of four months. Posterior shoulder dislocation in the
infants was observed in the children before or at the age of 12 months (median 6.5
months; range 4–12 months). No concomitant trauma to the upper extremities was reported
among the children except an undislocated humerus fracture at the contralateral side
in one girl. All patients, except one (parents declined treatment), were operated
on to reposition the humeral head at a mean age of 8 months (range 4–12 months), usually
via an anterior exploration with reposition, resection of ligaments, shortening of
coracoid process and lengthening of the suprascapular muscle (and conjoined tendon).
In the case with total injury botulinum toxin (Botox®) was injected into the latissimus dorsi muscle peroperatively. In two patients, additional
procedures were done due to the rotation of the humeral head (rotation osteotomy)
or recurrence of the dislocation (further anterior release, subscapular release and
humerus rotation osteotomy). In all cases (except the child where treatment was denied)
the humeral head was correctly located at follow-up [mean follow-up 42 months (2–51;
one patient moved after two months)].
Discussion
In the present paper we describe six of 82 patients with brachial plexus birth palsy
who developed a posterior shoulder dislocation during the first year of life. The
incidence of a brachial plexus birth lesion was found to be 3.8/1000 live births/year
during the study period 2000–2005, with a corresponding incidence of a posterior shoulder
dislocation of 0.28/1000 live births per year. The incidence of brachial plexus birth
palsy has been reported in previous studies. It has been found to be increased in
the western world and various factors related to the occurrence of the lesion have
been defined [[1],[2],[10]]. Our incidence of brachial plexus birth lesions is somewhat higher than previously
reported. We have no clear explanation for this but it may be explained by the fact
that since 2000 we see all patients where there is a suspicion of brachial plexus
birth lesion (prospective follow up). Thus, we may include in the calculation also
patients who recover very rapidly. A posterior shoulder dislocation in children with
a brachial plexus birth lesion is known to occur, but is considered to be rare before
the age of one. The incidence of a posterior shoulder dislocation before that age
has not previously been reported. However, it may occur in as much as 8–10% of the
children with a brachial plexus birth palsy before the age of one [[5],[6],[11]], which is in accordance with our results (7.3%).
The diagnosis of posterior shoulder dislocation among our six cases was done by the
history from the parents and by clinical and radiological examinations (plain x-ray).
Unfortunately, ultrasonography of the shoulder [[12]] was not available at our hospital during the study period. MRI may show deformities
of the glenoid in as many as 9 out of 16 children during the first year of age [[13]]. We did MRI in only one case. The reason was limited MRI resources and the need
for anaesthesia during the procedure as previously pointed out by others [[7],[9]]. MRI provides important information about glenoid and articular surface. In the
present study, our aim was to confirm the posterior dislocation of the shoulder before
surgery thereby not causing any delay for surgery by waiting for an MRI.
Five of the children were operated on to reposition the humeral head, usually with
an anterior release and lengthening of subscapular muscle. Recently, arthroscopic
release has been reported with successful results even at an age below one [[8]]. In two of our cases a rotation osteotomy of the humerus was done later while in
our third case with dislocation it was more obvious that there was rotation of the
humeral head after reposition of the head. In that case an osteotomy of the humerus
was done primarily. We suggest that at time of reposition one should consider that
a retroversion of the head of the humerus is present [[11],[14]]. Such a condition can be treated immediately at time of reposition with humeral
rotation osteotomy [[11],[15]] in order to avoid a second procedure with additional anaesthesia, even if it is
more surgically demanding performing the osteotomy at the same time as the release/subscapular
lengthening according to the technique by Birch [[11]]. The advantage being that, one will avoid the possibility of the child being unable
to rotate the shoulder medially, a complication described as “play with the hands
on the affected side”.
Previously, we have not observed early posterior dislocations in infants (< 1 year),
although we have followed neurological recovery and shoulder function regularly over
the years using the same treatment strategies. We used children followed from 1997–1999
as retrospective controls but we did not find any early dislocations among those children.
However, we cannot be sure that we screened all children during that time period.
One can not rule out the possibility that the observed number of cases may be explained
by our detailed observations, increased awareness, and improved registration of the
children thereby finding six cases during the last six years.
Posterior dislocation of the shoulder in connection with brachial plexus birth lesion
has been known for 100 years [[16],[17],[18],[19],[20]]. The exact mechanisms by which the condition develops are still incompletely known,
but have been discussed in several papers (see for example [[5],[6],[8]]). We have used the same treatment strategy, and patient/parents education, to avoid
medial rotation contracture. Still we report six cases with posterior shoulder dislocation
before the age of one during 2000–2005. Have any procedures changed during the years
regarding infants and children that may explain occurrence of posterior shoulder dislocation?
Weight bearing on the affected arm during crawling may increase the force of subluxation
[[5]], but may not simply explain the phenomenon. Recommendations to parents regarding
the sleeping position of their infants have changed due to the increased risk for
sudden infant death syndrome (SIDS; [[21]]). Among the recommendations to avoid SIDS the parents are advised to let the infant
sleep in supine position. During the 1990’s a decrease in prone sleeping (decreasing
from 32% to 7%) was seen in Sweden in favour of supine sleeping position (increase
from 35% to 44%; [[21]]). Prone sleeping is actually the optimal position for prevention of medial contracture
in infants since a passive external rotation of the shoulder (with an abducted shoulder)
is stressed in that position during sleep. One may hypothesise that the crucial changes
in the sleeping position to avoid SIDS may possibly increase the risk for posterior
shoulder dislocation in infants with a brachial plexus birth palsy.
Conclusion
The incidence of posterior dislocation of the shoulder among children below the age
of one with a brachial plexus birth lesion is 0.28/1000 living infants and year (7.3%
of all brachial plexus birth lesions). Parents are carefully advised to perform exercises
aimed to avoid medial contracture and thereby a posterior dislocation, although early
MRI studies observe deformation of the glenoid [[13]]. We recommend that all children with a brachial plexus birth palsy should regularly,
particularly during the first year of life, be examined, not only for extent of neurological
recovery, but also with the purpose to early detect a posterior shoulder dislocation.
Competing interests
The author(s) declare that they have no competing interests.
Authors’ contributions
All authors contributed equally to the article.
