Background
Obstetric brachial plexus injury (OBPI) has been described as a discrete entity since
1754 [[1 ]]. The pathophysiology of the secondary deformities encountered in this population
was described succinctly in 1905 by Whitman who wrote that the large majority of internal
rotation and subluxation deformities of the shoulder in children with obstetric brachial
plexus injuries were caused by fibrosis and contractures developed as a consequence
of the neurological injury [[2 ]]. The medial rotation contracture (MRC) is the most significant secondary shoulder
deformity in children with severe OBPI, requiring surgery in more than one third of
patients whose injury did not resolve spontaneously [[3 ]].
The current surgical approach to treating persistent MRC in OBPI patients is derotational
humeral osteotomy [[4 ],[5 ],[6 ],[7 ],[8 ],[9 ],[10 ],[11 ],[12 ]] or anterior capsule release [[13 ]]. Humeral osteotomy attempts to improve the patient’s passive range of external
rotation, but ignores the bone deformity at the root of persistent MRC, and does nothing
to address the attendant subluxation of the humeral head within the glenoid fossa.
Anterior capsule release may result in excessive external rotation positioning of
the humerus with attendant loss of internal rotation and midline functioning [[13 ]].
Scapular hypoplasia, elevation and rotation (SHEAR) deformity [[14 ]] is the ultimate bony manifestation of the muscular fibrosis described by Whitman,
and is present in the majority of OBPI patients exhibiting MRC. The SHEAR deformity
must be accounted for in any surgical correction of the MRC, and humeral osteotomy
as a strategy for bony correction does not do so ([Figure 1 ]).
Figure 1 . Ten year old boy after unsuccessful humeral osteotomy with right-sided SHEAR deformity
demonstrated in 3D CT anterior view (above) and posterior subluxation demonstrated
in axial view (below).
The presentation of weakness of the deltoid and external shoulder rotators caused
by the common C5 injury seen in OBPI immediately affects growth of both the muscles
and bones. Formation of contractures and consequent asymmetric muscle action on the
developing bony elements of the shoulder results in bone deformation of the scapula
and humerus. The scapula not only elevates and rotates laterally, but also becomes
hypoplastic with flattening of the glenoid fossa and hooking of the acromion process.
The clavicle and acromion process impinge upon the humeral head due to the abnormal
positioning of the scapula and associated acromio-clavicular triangle (ACT), with
its sides defined by the clavicular shaft and the acromion process and its base by
an imaginary line connecting their medial ends. Functionally debilitating effects
include medial rotation and posterior and inferior subluxation of the humerus within
the glenoid fossa.
The abnormal migration of the scapula disrupts the normal anatomic relationships of
the humeral head, the glenoid fossa and the acromio-clavicular triangle. Impingement
of the distal acromio-clavicular triangle against the humeral head limits external
rotation of the arm and shoulder. Without addressing the joint derangement, procedures
such as humeral osteotomy are likely to fail or have significant rates of recurrence.
To our knowledge there is no published method for correcting recurrence of the medial
rotation contracture other than repeated humeral osteotomy.
A novel osseous procedure, named the “Triangle Tilt,” releases and tilts the acromio-clavicular
plane back to neutral thus relieving the impingement of the acromio-clavicular triangle
on the humeral head. The humeral head may now reposition passively into the neutral
position within the glenoid fossa. Here we report the use of this technique to treat
4 children who had undergone unsuccessful humeral osteotomies.
Methods
During a 10 month period between October 2005 and August 2006, 73 obstetric brachial
plexus patients with persistent internal rotation underwent Triangle Tilt surgery.
Four of these patients had undergone previous humeral osteotomy (performed by board-certified
pediatric orthopedic surgeons) with complete failure of the procedure. All 4 had residual
MRC with SHEAR deformity, and underwent Triangle Tilt surgery as a salvage procedure
for unsuccessful humeral osteotomy.
The presence of SHEAR deformity was determined by physical examination and confirmed
by 3D-CT (computed tomography) if possible [[14 ]]. Elevation of the scapula was estimated clinically. Scapular elevation, defined
as the percentage of scapula visible above the clavicle and caused by downward and
anterior rotation, was quantitated on a 3D-reconstruction of the CT and confirmed
the severity of the underlying SHEAR deformity.
Version and subluxation were measured on axial CT or MRI images. A scapular line was
drawn connecting the medial margin of the scapula to the middle of the glenoid fossa
on transverse CT or MRI (magnetic resonance imaging) images at the mid-glenoid level.
The glenoscapular angle between the scapular line and a line connecting the base of
the anterior labrum and posterior labrum was measured according to Friedman et al.
[[15 ]]. 90° were subtracted from the posteromedial quadrant angle to determine version.
The degree of humeral head subluxation was determined using the same scapular line
and a perpendicular line traversing the humeral head at its greatest diameter. The
distance of the scapular line to the anterior portion of the head and the greatest
diameter of the humeral head were measured. The ratio of these distances multiplied
by 100 determines percent subluxation.
Two of the patients were girls, ages 7.9 and 10.4 years, and 2 were boys, ages 10.4
and 11.9 years at the time of surgery. Two patients had undergone nerve surgery in
infancy. Prior to humeral osteotomy, all 4 had undergone muscle contracture release,
tendon transfers, and decompression of the axillary nerve at the quandrangular space
[[16 ],[17 ],[18 ],[19 ]]. Improvements in abduction from muscle surgery were maintained at the time of surgery.
The medial rotation posture at rest was unaddressed by humeral osteotomy and was not
responsive to additional therapy and splinting.
Shoulder movements were assessed preoperatively and postoperatively by evaluating
video recordings of standardized movements according to the modified Mallet classification
[[20 ]]. Additional measurements were made of the angle of the humerus to the trunk during
the hand-to-mouth movement (trumpeter sign) and the angle of forearm supination as
a more sensitive determination of functional ability. All assessments were made independently
of the surgeon and principal author.
Surgical Procedure
The Triangle Tilt surgery consisted most importantly of four components. First, osteotomy
separated the clavicle at the junction of the middle and distal thirds. Second, osteotomy
of the acromion process at its junction with the spine of the scapula was performed.
Then, thirdly, ostectomy of the superomedial angle of the scapula was enacted. Finally,
the extremity was splinted in adduction, 5° of external rotation and full forearm
supination (90°). Splinting was maintained for 6 weeks after which time the splint
was worn only at night for an additional 3 months.
Minor elements of the procedure included bone grafting of the acromion process osteotomy
site, and semi-rigid fixation of the clavicular osteotomy segments to prevent nonunion.
Since all four of these children had proven shoulder instability, particularly subluxation,
diagnosed by CT or positional MRI imaging, posterior glenohumeral capsulorrhaphy was
performed.
The same surgeon performed all surgical procedures (RKN).
Results
The preoperative and postoperative Mallet scores for these patients are presented
in [Table 1 ] with representative photographs in [Figure 2 ]. The follow-up periods were 4 to 14 months with two of the four patients still undergoing
nighttime splinting. There were, however, clear improvements in shoulder function
which were not previously achieved with humeral osteotomy. Mallet score before Triangle
Tilt surgery was 10, 16, 12 and 13. After surgery, these patients improved to 17,
19, 18, and 19, respectively. All four children were able to supinate to 60° or greater
and were able to bring their hands to their mouths with a trumpeter sign of less than
45° postoperatively. Before surgery, no child was able to supinate to greater than
30° and the smallest trumpeter sign angle was 70°. Forearm supination increased secondarily
to improved external rotation at the shoulder, and provided a convenient indicator
of changes in external rotation. Improvements were also noticeable in the manner in
which the arm was held at rest ([Figure 2C ] and [2F ]).
Table 1
Radiographic classifications of glenohumeral deformity
Preoperative values
Postoperative values
Patient no.
Subluxation
Version
% Scapula visible over clavicle
Glenohumeral deformity*
Age at surgery
Abduction
External rotation
Hand to Neck
Hand to Spine
Hand to Mouth
Hand to Mouth angle
Supination angle
Total Mallet
Abduction
External rotation
Hand to Neck
Hand to Spine
Hand to Mouth
Hand to Mouth angle
Supination angle
Total Mallet
Follow-up (months)
1
13.5
-27
N/A
III
10.4
4
1
2
2
1
120
-90
10
4
3
3
3
4
40
60
17
6
2
22.2
-24
25
III
11.9
4
3
3
3
3
70
30
16
4
4
4
3
4
10
80
19
9
3
45.7
-28
N/A
III
7.9
4
1
3
2
2
110
-90
12
4
3
3
2
4
20
35
16
14
4
59.7
-42
41
V
10.4
4
2
4
2
1
135
0
13
4
4
4
3
4
10
90
19
4
Mallet scores and functional hand to mouth and forearm supination angles in patients
who following failed humeral osteotomy recently underwent Triangle Tilt surgery. *Glenohumeral
deformity classification according to Waters [21]. N/A data not available.
Figure 2 . Pictures of 10 year old girl who had previously undergone an unsuccessful humeral
osteotomy, pre (a through c) and 6 months post (d through f) Triangle Tilt surgery.
Panels a and d show decreased trumpet sign during the hand to mouth movement. Panels
b and e show improved supination. Panels c and f show the improvement in resting arm
position.
Discussion
The developmental consequences of an obstetric brachial plexus injury, medial rotation
contracture and progressive posterior dislocation of the shoulder, have serious consequences
for shoulder function. Most commonly, the treatment method is humeral osteotomy, which
places the arm in a more functional, externally rotated position. Though this procedure
can give functional improvement, a significant proportion of children are not helped
by this salvage procedure due to the fact that it does not address the bone deformities
at the root of the progressive posterior dislocation and poor shoulder movement. The
presence of unaddressed SHEAR deformity guarantees the continued impingement of the
acromion upon the humeral head which can lead to recurrence of the debilitating internal
rotation. Only in the absence of significant SHEAR is humeral osteotomy a viable treatment
option.
The improvements possible with the Triangle Tilt surgery are clear from the preoperative
and postoperative photographs shown in [Figure 2 ]. Mallet functional scores quantitatively show the improvements of all four patients
who had previous humeral osteotomies ([Table 1 ]). One patient improved Mallet score by 3, another by 7 and the remaining two by
6 points. Satisfactory changes in function are reflected in the measured angles of
forearm supination (improvement by 150, 50, 165 and 90 degrees respectively) and flaring
of the elbow during the hand to mouth movement (80, 60, 35 and 45 degrees). Because
of the apparent pronation deformity due to MRC pre-surgically the neutral position
was inaccessible and so supination increased by more than 90° in three out of four
patients.
The degree of torsion caused by contractures around the shoulder is manifest during
surgery, and observation of how the bones respond during surgery reveals the forces
still acting on the glenohumeral joint after humeral osteotomy. When released by Triangle
Tilt, the highly abnormal bony framework around the injured shoulder and the significant
intraosseous torque results in immediate clavicular and acromial movements. Separation
of the distal acromio-clavicular triangle from the abnormal medial structures relieves
the torsion developed over time.
The clavicle is abnormally twisted due to scapular migration, and the distal and proximal
clavicle segments are intraoperatively observed to rapidly unwind after osteotomy.
Significant movement also follows osteotomy of the acromion process, with the body
of the acromion process and the medial margin of the acromion rapidly separating,
and the distal segment moving both inferiorly and posteriorly. The distal acromio-clavicular
triangle becomes normalized, and so does the humeral head through its relationship
to the lateral structures. With the release of the abnormal torque and the leveling
of the acromio-clavicular triangle, the glenohumeral axis returns towards neutral.
This improves clinical arm positioning and movement possibilities.
Conclusion
The four patients presented here demonstrate how important it is to recognize and
treat the bone deformity. If SHEAR is present, it must be accounted for in the surgical
plan. The design of the Triangle Tilt procedure aims at improving the position of
the humeral head in the glenoid fossa by eliminating the impingement occurring in
the SHEAR deformity. Long-term improved function of the shoulder is the expected consequence
of improved glenohumeral anatomy. Only months after surgery, these four patients who
had Triangle Tilt surgery to address the SHEAR as well as the medial rotation contracture
show dramatically improved function.
Competing interests
The authors declare that they have no competing interests.
Authors’ contributions
RKN conceived of the study, performed all surgeries, and edited the manuscript. MP
collected and analysed data, created figures, and edited the manuscript. SEM collected
and analysed data, and drafted the manuscript.
