Disorders of the Acromioclavicular and Sternoclavicular Joints

Ovid: OSE Sports Medicine

Editors: Schepsis, Anthony A.; Busconi, Brian D.
Title: OSE Sports Medicine, 1st Edition
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III – Upper Extremity > 20 – Disorders of the Acromioclavicular and
Sternoclavicular Joints

Disorders of the Acromioclavicular and Sternoclavicular Joints
Mark J. Lemos
Kelton Burbank
Jennifer Taniguchi
The acromioclavicular (AC) and sternoclavicular (SC)
joints serve as the primary links in the suspension of the upper
extremity from the axial skeleton. Despite its requisite strength, the
AC joint is one of the most commonly injured structures in the athletic
population, particularly in young males involved in collision sports.
It is also susceptible to overuse injury in the overhead athlete. More
than 60 different procedures have been described to treat these
injuries, indicative of the lack of consensus historically. More
recently, however, the treatment of AC joint pathology has evolved
dramatically, especially with the introduction of arthroscopic
techniques. This chapter will first describe the anatomy and
biomechanics of the AC joint to clarify the complex pathophysiology of
injuries to this area. This will facilitate an understanding of the
diagnosis and treatment options, which are then reviewed.
Anatomy and Biomechanics
The AC joint is a diarthrodial joint formed by the
distal clavicle and the medial facet of the acromion with an extremely
variable orientation. A fibrocartilaginous disk of variable size,
shape, and composition resides within the joint. A complete disk is
seen in less than 10% of the general population. The frequency with
which it is found decreases dramatically with age; nevertheless, it
becomes nonfunctional in most individuals after about age 40.
The AC joint first appears at 3 to 5 years of life. The
clavicle, which is one of the first bones to ossify, appears first at
intrauterine week 5. It increases in diameter via intramembranous
ossification. Two epiphyses, one on the medial end and one on the
lateral end, contribute to the longitudinal growth via enchondral
activity. The medial epiphysis is responsible for the majority of this
growth, appearing at about age 18 and fusing between ages 22 and 25.
The lateral epiphysis is less consistent and is often mistaken for a
fracture in young adults. The acromion has between 2 and 5 ossification
centers that appear at puberty. They fuse by age 25. Failure of any of
these apophyses to fuse is known as an “os acromiale,” which can also
be mistaken for a fracture.
The AC joint has a relatively thin capsule, which is
supported by the strong AC ligaments, as well as the fascia from the
deltoid and the trapezius muscles. The superior,


inferior, anterior, and posterior AC ligaments provide resistance to horizontal translation (Box 20-1).
Of these, the superior ligament is the strongest, providing 56% of the
resistance to horizontal translation of the clavicle in serial
sectioning studies, followed by the posterior ligament, which provided
25%. The insertion of these ligaments on the clavicle averaged about
1.5 cm from the AC joint. This is important when considering distal
clavicle resection for AC joint arthrosis (Fig. 20-1).

Figure 20-1
The AC joint is supported by the capsule, AC ligaments, and the CC
ligament. (From Oatis CA. Kinesiology: The Mechanics and Pathomechanics
of Human Movement. Baltimore: Lippincott Williams & Wilkins, 2004.)
The coracoclavicular (CC) ligaments—the conoid and the
trapezoid—which provide resistance to vertical displacements, further
stabilize the AC joint. The more lateral trapezoid is a broad ligament
that runs obliquely from the superior surface of the coracoid process
to the inferior aspect of the clavicle about 1 cm medial to the AC
joint. The more medial conoid ligament is conical in shape and arises
along the posteromedial side of the coracoid process. It inserts
posteriorly along the undersurface of the clavicle at the junction of
the lateral and middle thirds. Both are posterior to the insertion of
the pectoralis minor on the coracoid. There is often a bursa separating
these two limbs of the CC ligament. The average distance between the
coracoid and the clavicle is 1.1 to 1.3 cm, which is important in the
diagnosis of complete disruptions of the joint. Sectioning studies have
shown the importance of these ligaments is a function of both the
direction and the magnitude of the deforming force.
The coracoacromial (CA) ligament runs from the lateral
aspect of the coracoid to the undersurface of the acromion. Its
function in the stability of the AC joint was originally thought to be
important; however, more recent studies imply that it does not have a
significant role with forces at or equal to 70 N. It is an important
secondary glenohumeral stabilizer, particularly in the presence of a
complete rotator cuff tear.
The AC joint has 6 degrees of freedom in allowing motion
in the anterior/posterior and superior/inferior planes. Originally,
studies by Inman (1944) hypothesized 20 degrees of motion at the AC
joint, with forward elevation and abduction of the arm and 40 degrees
of clavicular rotation in total. This led many to the conclusion that
arthrodesis of the AC joint would limit motion of the shoulder.
Subsequent work by Rockwood and Kennedy and Cameron (1954) demonstrated
“synchronous scapuloclavicular rotation.” Thus, as the clavicle rotates
upward, the scapula rotates simultaneously downward. There is 40 to 50
degrees of clavicular rotation but only 5 to 8 degrees at the AC joint.
The majority of the rotation occurs at the SC joint.
Injuries to the AC joint are very common in the athletic
population. In an early study, Thorndike and Quigley (1942) noted AC
joint injuries in 223 of 578 (39%) athletes with shoulder injuries.
Since then, AC joint injuries have been reported to be one of the most
common traumatic injuries in rugby, football, ice hockey, skiing,
cycling, and snowmobiling. Overuse injuries of the AC joint are also
commonly seen in players of golf, baseball, and tennis. AC injuries are
much more common in males than females (5 to 10:1) and in young adults.
In a review of dislocations of the shoulder complex, dislocations of
the glenohumeral joint occurred in 85%, the AC joint in 12%, and the SC
joint in 3% (Cave, 1958). However, incomplete injuries are twice as
common as complete injuries. As the population ages (and more
specifically the athletic population), there will likely be an increase
in acute injuries to the AC joint in older individuals as well as an
increase in AC joint arthrosis, which has been correlated with previous
traumatic injury.

Either direct or indirect forces can injure the AC
joint. The most common etiology is a fall onto the anterior, superior
edge of the acromion (“point of the shoulder”) with the arm in an
adducted position. This drives the acromion downward, away from the
fixed clavicle. The resulting appearance of the shoulder is secondary
to this movement, not an upward displacement of the clavicle, despite
its prominence. Injury can also occur indirectly, via a fall onto an
adducted, outstretched arm or elbow, which can cause the humerus to
translocate superiorly, forcing the humeral head up and into the
acromion. Another indirect mechanism that has been described is a
sudden downward force on the upper extremity, such as a change in the
position of a heavy load, which pulls the scapula downward. Both of
these indirect mechanisms are rare, compared with direct trauma from a
fall onto the acromion.
Figure 20-2 Classification of AC joint instability.
Pathophysiology and Classification
Tossy (1963) and Allman (1967)
originally classified AC joint injuries into types I, II, and III on
the basis of x-rays and clinical examination. This was later revised by
Rockwood (1989) to account for differences he saw within “type III”
injuries. He added types IV, V, and VI to account for these differences
(Fig. 20-2 and Table 20-1).
Trauma to the AC joint initially injures the AC
ligaments (type I). When the force continues, further energy is
absorbed by the CC ligaments (type II) and may result in even greater
displacement of the joint as these ligaments rupture


III). An even more severe injury may occur with larger forces that
result in the disruption of the deltotrapezial fascia, as well as the
ligaments (type V). If the deforming force is directed posteriorly and
is of sufficient magnitude, the clavicle can be displaced into or
through the trapezius muscle (type IV). Type VI is a subcoracoid
dislocation of the clavicle. It is associated with extreme trauma and
is rare. A type VII, which is complete dislocation of the AC and SC
joints, has been described but is extremely rare.






The AC ligaments are sprained, but intact. The CC ligaments and the deltotrapezial fascia are uninjured.
The AC joint is intact.

No obvious deformity of the shoulder girdle; pain at the AC joint with palpation and some mild swelling.
ROM of the shoulder is comfortable and full, except cross-shoulder adduction.


The AC
ligaments are torn. The CC ligaments are sprained, but intact. The
deltotrapezial fascia is typically uninjured. The AC joint is subluxed,
unstable in the horizontal plane.

prominence of the clavicle; swelling at the AC joint; pain to palpation
over the AC joint and in the costoclavicular interspace. ROM is painful.
There is some horizontal instability to the clavicle noted with testing.


The AC ligaments are torn. The CC ligaments are torn.
The deltotrapezial fascia is sprained. The AC joint is subluxed (<100%), and unstable in the horizontal and vertical planes.

The clavicle is again prominent with marked swelling.
is significant pain at rest and with palpation, ROM testing, which
usually cannot be tolerated. The clavicle feels unstable in both the
horizontal and vertical planes.


Same as type III, except the clavicle is 100% displaced posteriorly into or through the trapezius muscle.

Typically, the
patient has more pain than in type III. The displacement of the joint
may not be as apparent as in type III because it is posterior, nor does
the clavicle feel “free floating.” ROM is not tolerated well.


Same as type III, but with >100% displacement of joint in the vertical plane. The deltotrapezial fascia is torn.

Very similar to type III in presentation, except level of pain is greater and the clavicle seems to be more prominent (Fig. 20-3). Skin is likely tented.


Same as type
III, but the clavicle is displaced inferior to the coracoid process and
posterior to the conjoined tendon. This is very rare and usually the
result of severe trauma.

appears to be flatter as the clavicle is displaced downward. The
acromion is more prominent. There may be an associated neurological
injury. Careful assessment for other injuries (rib fracture,
pneumothorax, SC joint dislocation) is critical.


Complete dislocation of the AC and SC joints. It is a severe form of a type IV, with a posterior clavicle dislocation.

AC, acromioclavicular; CC, coracoclavicular; ROM, range of motion; SC, sternoclavicular.

History and Physical Examination
  • The diagnosis of an AC joint disruption is usually made by history and confirmed by physical examination and x-ray.
  • With acute traumatic injuries, the diagnosis can be obvious.
  • Classification of injury (e.g., Rockwood
    type II vs. III) and assessing for other concomitant injuries can be
    more difficult (see Table 20-1).
  • In general, palpation of the area and assessment of joint stability are important.
  • X-ray analysis is also important (see below).
  • In patients without a history of acute trauma, localization of the pathology to the AC joint can be more involved.
  • The innervation of the AC joint is provided by the lateral pectoral nerve anteriorly and the suprascapular nerve posteriorly.
  • Gerber (1998) evaluated patterns of pain
    for both AC joint and subacromial pathologies. Irritation of the AC
    joint produced pain directly over the joint, in the anterolateral neck,
    and over the anterolateral deltoid—areas that were subtly distinct from
    the subacromial irritation.
  • The cross-shoulder adduction test,
    performed with the arm elevated to 90 degrees and the elbow bent 90
    degrees, can be helpful if it produces pain localized to the AC joint
    because the arm is adducted across the chest, thereby compressing the
  • O’Brien’s test can also be helpful in differentiating AC joint pathology from soft-tissue lesions within the glenohumeral


    joint, especially the superior glenoid labrum or proximal biceps attachment.

  • In general, a triad of point
    tenderness—positive cross-shoulder adduction test and relief of
    symptoms with an injection of a local anesthetic into the AC joint—is
    indicative of AC joint pathology.
  • Clinical features for each type are summarized in Table 20-1. See also Figure 20-3.
Figure 20-3 Physical examination findings in acute injury: type V.
Radiologic Examination
  • The assessment of the AC joint can be done well with only plain films, but special views and technique are required.
  • Because of its relatively superficial
    location, less penetration strength of the beam (approximately 50%) is
    needed compared with standard views.
  • A Zanca anteroposterior (AP) view, which
    tilts the beam 15 degrees cephalad, can visualize the AC joint better
    than a standard AP view by preventing the scapular spine from being
    superimposed on the AC joint and should be routinely performed.
    • Normal x-ray findings on a Zanca AP view
      and an axillary lateral include a joint space of 1 to 3 mm, which
      diminishes significantly with age to about 0.5 mm by age 60.
    • A space of greater than 7 mm in males and 6 mm in females is abnormal.
    • A CC distance of 1.1 to 1.3 cm is normal.
    • Although an incongruent AC joint can be
      seen in as many as 30% of controls, an increase of 25% to 50% in the CC
      distance, compared with the unaffected side, can signify complete AC
      joint dislocation.
  • An axillary lateral is critical to assess
    horizontal displacements, especially in a type IV injury, and should
    also be done routinely.
  • To assess for a coracoid fracture, the Stryker notch view is helpful if indicated.
  • Previously, stress views were recommended to differentiate type II, type III, and type V injuries.
    • These were typically done in the AP plane with a 5-lb weight attached to each arm.
    • However, several studies have questioned the efficacy of the routine use of these x-rays.
  • Of historical interest, Alexander (1949), described the lateral stress view or “shoulder-forward” view.
    • It is taken from both the uninjured and
      injured sides as a scapular Y view, with the patient thrusting his or
      her shoulders forward.
    • On the injured side, the displacement of the acromion anteriorly and inferiorly can be seen.
  • Computed tomography (CT) and magnetic
    resonance imaging are not used routinely, although each may be utilized
    as an adjuvant in more complicated situations.
  • The goals of both nonoperative and
    operative management of AC injuries are full pain-free strength and
    motion and restoration of normal anatomy and appearance.
Nonsurgical Treatment
  • Type I and II injuries are treated nonoperatively, with a sling for up to 2 to 3 weeks, ice, and nonsteroidal medications.
    • The sling is used only as needed for comfort, with gradual return to regular daily activities.
    • A type I injury is treated purely symptomatically, and the patient is usually back to unrestricted activities within 2 weeks.
    • With a type II injury, the patient is not
      allowed to do any heavy lifting, pushing, pulling, or contact sports
      for up to 8 to 12 weeks to allow the ligaments to heal.
    • Continued, unrelieved pain can be treated with an injection of steroid into the AC joint.
  • The management of type III injuries is
    controversial; however, there has been no shown benefit of surgery and
    should be treated in the same way as a type II injury with a sling use
    of up to 4 weeks for comfort.
    • When in doubt, opt for nonoperative management and treat on the basis of symptoms.
    • Many devices have been described to try to reduce the AC joint with pressure, such as braces, straps, harnesses, and casts.
    • The problems with these devices include
      skin breakdown from continuous pressure, discomfort, inconvenience,
      noncompliance, and joint stiffness.
    • Many authors use a sling for simplicity and comfort, and accept the minimal deformity of the injury.
  • In type VII injuries, the SC dislocation
    is treated nonoperatively with good results, and treatment of the AC
    joint is controversial.
  • Physeal injuries and pseudodislocation through an intact periosteal sleeve, as well as base of the coracoid


    process fractures associated with AC joint separation, can be treated nonoperatively with good results.

Results and Complications
  • On radiographs, there is calcification of ligaments postinjury in 40% of patients but it does not correlate with function.
    • This occurs whether or not the patient has an operation.
    • It can be an isolated bone structure or bridge between the coracoid and clavicle.
  • The prognosis for patients with type I
    and II injuries is good, but they may be more prone to degenerative
    disease and osteolysis.
  • X-ray changes seen in the distal clavicle may include osteoporosis, osteolysis, tapering, or osteophytes.
  • Dull aches usually resolve within a year on their own.
  • If the joint is still painful, then excision of the distal clavicle can be performed.
  • Nonunion of a coracoid base fracture can be very painful.
    • This should be treated with bone graft and stabilization.
  • Neurologic injuries may occur early or late, such as brachial plexopathy.
  • Fractures of the clavicle, acromion, or coracoid can occur with the initial injury.
Surgical Treatment
  • Persistent pain in the AC joint after a
    stable type I or II injury may be due to osteolysis of the distal
    clavicle or interposed tissue, such as torn ligaments, loose cartilage,
    or meniscus.
    • This should be treated with distal clavicle excision and joint debridement.
  • With stable type I and II injuries, the CC ligament is intact and thus the AC joint is stable.
  • There is some discussion about “unstable” type II injuries.
    • These may be under diagnosed type III injuries.
  • There is also a group of patients who have increased AP instability without superior migration.
    • These do not respond well to a distal clavicle resection.
  • Operative management of acute (<6
    weeks) type III injuries is often reserved for open injuries, brachial
    plexopathy, severe type III dislocations, and rarely high-level
    overhead athletes.
  • Operative management of chronic (>6
    weeks) type III injuries is indicated for failure of nonoperative
    treatment with continued AC joint pain and instability.
  • Type IV, V, and VI injuries require early
    operative reconstruction because of the severe displacement of the
    joint, pain, and deformity.
  • Many surgical procedures have been
    described for the management of AC separations. There is controversy
    over the proper surgical technique, and no treatment has emerged as
    • These procedures can be broken down into
      five groups: excision of the distal clavicle, dynamic muscle transfer,
      reconstruction of the CC ligaments, fixation between the clavicle and
      coracoid, and fixation across the AC joint.
    • With most operative techniques, authors recommend debridement of the AC joint and repair of the deltotrapezial fascia.
Excision of the Distal Clavicle
  • This is used mainly for degenerative but stable AC joints that have failed nonoperative management.
  • The procedure can be done open (Mumford) or arthroscopically (Flatow).
    • Follow-up studies on open and arthroscopic distal clavicle excisions yield similar results, with 80% to 90% success rates.
    • Surgeons who are comfortable with
      arthroscopic techniques have the opportunity to also visualize the
      glenohumeral joint and look for undiagnosed superior labral
      anterior-posterior (SLAP) tears.
      • Berg and Ciullo noted that, of 20
        patients who had a failed distal clavicle excision with presumed
        osteoarthritis of the AC joint, 15 of these patients had superior
        labral tears on arthroscopic evaluation at repeat procedure, and 9 of
        the 15 patients improved after definitive management of this problem.
  • The patients who undergo distal clavicle
    excision should be warned about weakness of the bench press motion but
    no other significant long-term disability.
  • The amount to resect is controversial, with some authors recommending 5 to 7 mm and some 20 to 25 mm.
  • The resection should be even and the superior capsule and ligament, as well as the CC ligament should be protected.
  • Inferior osteophytes on the distal clavicle should be excised.
  • Patients with unstable AC joints and distal clavicle fractures are not good candidates for excision.
  • Using distal clavicle excision alone fails to address instability if it exists.
  • Postoperatively, the patients are placed in a sling and allowed to do active and passive range of motion.
  • They are encouraged to use the arm for everyday activities but to refrain from overhead activities until the pain has subsided.
  • At 1 week postoperatively, strengthening exercises are begun and patients are allowed to return to all activities as tolerated.
Dynamic Muscle Transfer
  • This procedure involves transferring the
    tip of the coracoid process and the attached coracobrachialis and short
    head of the biceps to the undersurface of the clavicle, fixing in place
    with a screw.
  • The muscles then act as an active depressor of the clavicle.
  • There is a risk of injury to the musculocutaneous nerve.
  • P.260
  • Another problem with this technique is
    that it reconstructs a static restraint with dynamic tissue, allowing
    motion and leading to continued pain.
Reconstruction of the Coracoclavicular Ligaments
  • In the Weaver-Dunn technique (Fig. 20-4),
    the distal clavicle is excised, and the acromial end of the CA ligament
    is transferred to the remaining distal clavicle as a reconstruction for
    the CC ligaments.
    • A problem with this technique is weak initial fixation to the clavicle, which is via sutures.
    • Another issue is that the AC joint is not anatomically reduced in this procedure.
  • These problems have been addressed by
    Morrison and Lemos via a Modified Weaver-Dunn technique, which consists
    of passing an augmentation device through the clavicle and through or
    around the coracoid, anatomically reducing the clavicle and stabilizing
    the reconstruction while the CA ligament transfer matures.
    • The augmentation device can wear through
      the bone, amputating the clavicle or coracoid, and may produce a
      foreign body response in the local tissue, leading to a hypertrophic
      scar and osteolysis.
  • The CA ligament has an important role in shoulder stability, preventing superior migration of the humeral head.
    • Lee et al. showed
      that the CA ligament also restrains anterior and inferior translations
      of the humeral head through an interaction with the coracohumeral
  • Jones and Lemos have described
    reconstructing the CC ligaments by passing a semitendinosus tendon
    autograft or tibialis anterior tendon allograft around the base of the
    coracoid and through a 6-mm drill hole in the anterior third of the
    • This has been done both in revision and primary procedures.
    • This reconstruction is augmented by
      suture fixation between the coracoid and clavicle to prevent early
      failure of the graft while it is healing.
    • Revascularization of the graft, as with
      anterior cruciate ligament reconstructions, is assumed and the graft
      may stretch out over time.
  • Lee et al.
    performed a biomechanical study on cadaveric shoulders, comparing the
    strength of the native CC ligaments with reconstructions using CA
    ligament transfer, suture repair, tape repair, and tendon grafts.
    • They found that tendon grafts had the
      same peak load as the native ligaments, were stronger than the CA
      ligament transfers and suture repairs, and were stiffer than CA
      ligament transfers.
Figure 20-4 Modified Weaver-Dunn technique for reconstruction of the CC ligaments.
Fixation between the Clavicle and Coracoid
  • The goal of this technique is to keep the
    clavicle and coracoid in a reduced position long enough to allow
    primary healing of the CC ligaments, assuming that the ligaments will
    heal at the preinjury length and strength.
  • Bosworth described placing a screw
    through the clavicle into the base of the coracoid process, which
    requires later surgical removal.
    • A stab wound is made 4 cm medial to the distal end of the clavicle.
    • A drill hole is made in the clavicle.
    • The clavicle is depressed and reduced to
      the coracoid, an awl is used to make a hole in the superior aspect of
      the base of the coracoid, and a screw is inserted.
  • Others have placed cerclage material
    around the clavicle and coracoid, such as wire or Dacron tape, which
    can lead to similar problems with the augmentation device used in the
    modified Weaver-Dunn, such as coracoid or clavicle amputation, scar,
    and osteolysis.
Fixation across the Acromioclavicular Joint
  • Fixation has been described using pins, suture, suture wires, and hook plates.
  • Any hardware, like CC screws, requires later removal at 6 to 8 weeks.
  • Usually, reconstruction of the AC or CC ligaments is also done.
  • The pin is inserted laterally to the AC joint, across the joint, and into the clavicle.
    • Alternatively, the pin can be drilled
      retrograde from the joint through the acromion, then drilled antegrade
      across the joint into the clavicle.
  • With pin fixation, there is a risk of
    breakage and migration of the pins into the lung, heart, great vessels,
    spinal cord, mediastinum, and many other vital structures, which leads
    to serious consequences, including death.
    • There is also a reported increased risk of AC arthritis.
  • Hook plates violate the joint, requires later surgical removal, have a risk of infection, and may bend or dislocate.
    • This fixation is rarely used now a result
      of the complications; however, there have been recent reports of
      bioabsorbable devices not requiring later removal.
  • More recently, several authors have discussed arthroscopic reconstruction of the AC joint.

Authors’ Operative Technique
  • We prefer a combination of an autograft
    CA ligament transfer or a tibialis anterior tendon allograft around the
    coracoid and through the clavicle with a synthetic augmentation between
    the clavicle and the coracoid.
Incision and Exposure
  • The patient is placed in the modified beach chair position.
  • A large radiograph cassette is placed under the patient’s AC joint.
  • Routine prepping and draping of the extremity are carried out.
  • A horizontal skin incision is made, 5 cm
    long, beginning 1 cm lateral to the AC joint and taken medially along
    the anterior edge of the clavicle.
  • Similarly, a vertical skin incision just lateral to the coracoid may be used.
  • Subcutaneous flaps are developed superior
    and inferior to the AC joint to allow adequate exposure of the
    deltotrapezial fascia and distal 6 cm of clavicle.
  • The deltotrapezial fascia is incised, exposing the lateral clavicle and AC joint.
  • Next, the clavicular periosteum is
    incised along the anterior edge, and subperiosteal dissection is done,
    exposing the distal 3 cm of clavicle.
Distal Clavicle Excision
  • In cases in which the articular surfaces
    of the clavicle and acromion are normal, distal clavicle excision need
    not be performed. This is rare in our experience.
  • In most cases in which there is damage to
    the articular cartilage (or in revision cases), 5 to 8 mm of the
    lateral clavicle is resected with a sagittal bone saw.
  • This is done in line with the AC joint, slightly obliquely, from superior lateral to posterior medial.
Coracoid Preparation
  • The coracoid is identified.
  • The deltoid is split along the line of the fibers using electrocautery.
  • The CA ligament is identified and kept intact.
  • Using electrocautery, a subperiosteal
    incision is made on the superior aspect of the coracoid base, and the
    coracoid is exposed medially and laterally.
  • A looped suture passer is passed around the base.
  • An augmentation device is passed through or around the coracoid and tagged for later use.
Clavicle and Graft Preparation
  • The clavicle is identified.
  • Any sharp edges are beveled.
  • A 2 × 6 mm burr hole is placed in the
    clavicle at the junction of its anterior and middle third, 3 cm medial
    to the AC joint, and directly above the base of the coracoid.
  • Medial placement of this drill hole
    allows the graft to provide tension along the same vector as the normal
    CC ligaments, and an anatomic reduction of the clavicle can be obtained.
  • Two smaller drill holes are placed medial and lateral to the burr hole for later passing of the augmentation sutures.
  • If a CA ligament transfer is performed,
    the acromial insertion of the ligament is identified and harvested with
    a small 3 to 5 mm wafer of acromion.
  • The coracoid attachment is left intact.
  • The acromial side is sutured with a no. 2 nonabsorbable braided material.
  • This construct is then passed through the end of the clavicle.
  • The ends of the tibialis anterior allograft are secured with a no. 2 suture using a tendon suture technique.
  • Many different synthetic augmentations have been used.
  • The graft and augmentation sutures are
    placed into the previously placed suture loops around the coracoid base
    and then passed around the base of the coracoid.
  • The augmentation suture is passed through the two smaller drill holes in the clavicle.
  • The clavicle is overreduced by 5 mm to the acromion.
  • A knot is tied under tension inferior to the clavicle to prevent knot prominence.
  • The augmentation suture will provide provisional fixation while the graft reconstruction reorganizes.
  • The graft is passed through the inferior aspect of the burr hole in the clavicle and reapproximated.
  • The sutures are tied together, then supplemented with additional no. 2 sutures.
  • Residual graft tissue is excised.
  • Copious irrigation is performed.
  • The deltotrapezial fascia is carefully reapproximated with a no. 2 suture using a mattress suture technique.
  • Routine closure of the subcutaneous tissue and skin then follows.
  • A compressive dressing, sling, and swathe are applied.
Postoperative Treatment
  • The patient is placed in a sling and swathe postoperatively.
  • For activity, the patient starts gentle, active-assisted range of motion on postoperative day 1.
  • The swathe can be removed in a few days, and the sling is used for 6 weeks.
  • At 6 weeks, the patient may progress to active range of motion and strengthening.
  • No heavy lifting or pushing is allowed for 6 months.
  • Any hardware should be removed at 6 to 8 weeks.
  • Morrison and Lemos looked at 14 patients
    with minimum 2-year follow-up, with a 34 of 36 University of
    California-Los Angeles (UCLA) score.
    • Similarly good to excellent results can be obtained using allograft reconstruction.
  • Harris et al. did a cadaver study comparing various methods of reconstruction.
  • P.262
  • They found that CC slings and suture anchors provided good strength but with greater deformations.
  • Screw fixation provided good stiffness and strength but only if bicortical purchase was obtained.
  • CA transfers were the weakest, the least stiff, and required augmentation.
  • There are many complications related to
    operative treatment, including wound and bone infection, hardware
    migration or failure, erosion or fracture due to augmentation devices,
    arthritis, and recurrent pain and deformity.
  • Death from migrating pins from the AC joint to the lungs, chest, heart, and mediastinum has been described.
Other Entities
Physeal Injuries
  • Physeal injuries and pseudodislocation through an intact periosteal sleeve occur in children and adolescents.
  • Radiographs show a large increase in the CC interspace.
  • This can be a Salter Harris I or II
    injury, in which the epiphysis remains congruous with the acromion
    while the distal clavicle metaphysis is displaced.
  • The CC ligament is intact and attached to the periosteal sleeve.
  • This is treated nonoperatively with good results.
Coracoid Process Fractures
  • Coracoid process fractures, usually of the base, can occur with AC joint dislocation but are an uncommon injury.
  • Usually, the CC ligaments remain attached to the coracoid process fragment.
  • The fracture through the coracoid base allows the clavicle to become high-riding, compared with the acromion.
  • Axillary and Stryker notch views can be helpful with showing this fracture, or a CT scan can be done.
  • Both operative and nonoperative treatments have been described, with similar results.
Acromioclavicular Joint Osteoarthritis
  • Any AC joint injury can lead to posttraumatic osteoarthritis of the AC joint.
  • Osteoarthritis can also occur in conjunction with rotator cuff tears and glenohumeral osteoarthritis.
  • The patient will present with shoulder pain.
  • On physical examination, the patient will
    have tenderness to palpation over the AC joint and have pain with
    crossed-body adduction.
  • Radiographs will reveal narrowing of the AC joint, cystic changes, and osteophytes.
  • Conservative therapy is the first line of
    treatment and consists of nonsteroidal anti-inflammatory medications,
    activity modification, passive range of motion, strengthening
    exercises, iontophoresis, and ice.
  • An intra-articular steroid injection can
    also be done as both a diagnostic and therapeutic test, taking care not
    to inject the subacromial space.
  • If symptoms persist after 12 months of
    conservative treatment, then excision of the distal clavicle can be
    performed either openly or arthroscopically.
Traumatic injuries to the SC joint are rare and usually
associated with significant trauma. The spectrum of injury includes SC
subluxation and dislocation, injuries to the medial clavicular physis,
and degenerative joint arthritis. These injuries carry potential risks
due to the proximity of the great vessels and mediastinal structures
(such as the trachea and esophagus) that lie directly beneath the SC
Anatomy and Biomechanics
The clavicle forms via intramembranous ossification at
intrauterine week 5 and is the first long bone to ossify. However, the
medial clavicular physis is the last to appear, the last to ossify at
age 18 to 20 years old, and fuses with the shaft of the clavicle at age
23 to 25 years old. A complete union may not even be present until age
31. This is important to remember because an SC joint dislocation in a
young patient may actually represent a fracture through the medial
clavicle physis.
Sternoclavicular Joint
The SC joint is a diarthrodial joint. It is the only
articulation between the upper extremity and axial skeleton and, as a
result of this, almost any motion of the upper extremity is transferred
to the SC joint. The articular surfaces are covered with
fibrocartilage. The medial end of the clavicle is large, bulbous,
concave front to back, and convex vertically. It articulates with the
clavicular notch of the sternum to form a saddle-shaped joint. Less
than 50% of the clavicle articulates with the sternum, and the joint
surfaces are not congruent, leading to the least amount of osseous
stability of any joint in the body. In 2.5% of patients, the medial
clavicle has an inferior facet that articulates with the first rib. The
SC joint has motion in all planes (Fig. 20-5).
Although the SC joint is small, incongruous, and subject
forces with all movements of the upper extremity, it is rarely
dislocated because of the stout ligaments supporting it. The SC
ligaments are important in preventing downward displacement of the
distal clavicle. This includes the intra-articular disc ligament, the
costoclavicular ligament, the interclavicular ligament, and the
capsular ligament.
Intra-articular Disc Ligament
The intraarticular disc ligament originates from the
synchrondral junction of the first rib and sternum, passes through the
SC joint dividing it into two spaces, and attaches to the superior and
posterior aspects of the medial clavicle. The disc then blends in with
the capsular ligament. It is a dense fibrous structure that rarely has
a perforation


connecting the two spaces. It acts to prevent medial displacement of the inner clavicle.

Figure 20-5
SC joint. (From Oatis CA. Kinesiology: The Mechanics and Pathomechanics
of Human Movement. Baltimore: Lippincott Williams & Wilkins, 2004.)
Costoclavicular Ligament
The costoclavicular ligament, also known as the rhomboid
ligament, has a twisted appearance and anterior and posterior fasciculi
with a bursa between the two. The anterior fasciculus originates from
the anteromedial aspect of the first rib and passes upward and
laterally to attach to the clavicle. The anterior fibers act as a
checkrein against upward rotation and lateral displacement of the
clavicle. The posterior fasciculus fibers are shorter, arise laterally
to the anterior fasciculus fibers on the first rib, and pass upward and
medially. The posterior fibers resist downward rotation and medial
displacement of the clavicle. The costoclavicular ligament is short and
strong, and the crossing of the fasciculi provides stability to the
joint, similar to the CC ligament.
Interclavicular Ligament
The interclavicular ligament connects the superomedial
aspect of the clavicle with the capsular ligaments and the upper
sternum and also helps to hold up the shoulder.
Capsular Ligament
The capsular ligament consists of thickenings of the
capsule anteriorly and posteriorly, and the clavicular attachment is
mainly onto the epiphysis. The capsular ligament has been shown to be
the most important ligament in preventing anterior, posterior, and
upward displacement of the medial clavicle, as well as downward
displacement of the distal clavicle.
Surrounding Anatomy
Before operating on the SC joint, it is important to
know that anatomy well because there are vital structures in this area.
Posterior to the SC joint and medial clavicle is a curtain of
muscles—the sternohyoid, sternothyroid, and scalenes—which covers the
vital structures. The vital structures include the brachiocephalic
artery, brachiocephalic vein, vagus nerve, phrenic nerve, internal
jugular vein, trachea, and esophagus. The arch of the aorta, superior
vena cava, and right pulmonary artery are also very close to the SC
joint. The anterior jugular vein also runs between the curtain of
muscles and the clavicle, and can vary in size up to 1.5 cm.
Epidemiology, Mechanism, and History
SC injuries are rare and said to account for 3% of all
shoulder injuries. Bilateral dislocations are reported infrequently. A
significant amount of force is needed to produce a traumatic
dislocation of the SC joint. This can be direct or indirect. With a
direct force to the anteromedial clavicle, the clavicle is displaced
posteriorly into the mediastinum. An indirect force to the
anterolateral or posterolateral aspect of the shoulder can lead to a
posterior or anterior dislocation of the SC joint, respectively. An
indirect mechanism is more common than direct.
Motor vehicle accidents account for 40% of SC injuries,
and sports account for 21%. The dislocation usually occurs anteriorly
because the posterior capsular ligaments are stronger than the
anterior. Atraumatic subluxation of the SC joint has been described in
individuals with generalized ligamentous laxity and in a patient with
pseudarthrosis of the first and second ribs.
History and Physical Examination
  • A patient with an SC joint injury will complain of severe pain with any movement of the arm.
  • The head may be tilted toward the injured side.
  • The injured arm will be held across the trunk and supported by the uninjured arm.
  • With a dislocation, the affected shoulder is shortened and thrust forward.
    • The pain is worse when supine.
    • With an anterior SC joint dislocation, the medial end of the clavicle is prominent and palpable anterior to the sternum.
    • With a posterior dislocation, the medial
      clavicle is posterior to the sternum, not palpable, and less prominent,
      whereas the sternum is more easily palpable.
    • With a posterior dislocation, the
      subclavian and mediastinal structures may be compressed, leading to
      venous congestion in the neck or upper extremity, breathing
      difficulties, choking sensation, decreased blood flow to the arm, and
      even hypotension and shock.
  • Clinically, it can be difficult to tell the difference between an anterior and posterior dislocation.
Radiologic Examination
  • An SC dislocation can sometimes be picked up on a routine chest x-ray.
  • Rockwood described the serendipity view, which is a 40-degree cephalic tilt view of both SC joints.

    • With an anterior dislocation, the clavicle will appear to be superiorly displaced compared with the uninjured side.
    • With a posterior dislocation, the clavicle will lie inferiorly.
  • CT is the best radiographic study for evaluating SC joint injuries (Fig. 20-6).
    • It can show fractures of the medial clavicle, physeal injuries, and subtle subluxations.
    • It is important to compare the uninjured side with the injured side.
  • With chronic posterior SC dislocations, other imaging modalities have been described.
    • Dynamic ultrasound of the subclavian artery has been used to show compression of the artery during elevation of the arm.
  • Nerve conduction studies can also confirm a suspected brachial plexus neuropathy.
Classification and Treatment
Physeal Injuries
  • Because the medial clavicular physis is
    the last to ossify at age 18 to 20 years of age and fuses with the
    shaft of the clavicle at age 23 to 25 years old, an SC joint
    dislocation in a young 20-year-old may actually be a physeal injury to
    the medial clavicle.
  • Closed reduction of posterior physeal injuries should be performed if they are less than 10 days from the injury.
  • After 10 days, if there are no signs of
    mediastinal compromise, the injury should be treated symptomatically,
    because the majority of physeal injuries will heal with time without
    surgery and remodeling will eliminate any deformity.
  • If there are symptoms from pressure on
    the subclavian vessels and mediastinum—such as difficulty breathing,
    difficulty swallowing, arm swelling, or poor circulation—a closed
    reduction should be attempted, no matter how far out from the injury
    and an open reduction is indicated if there is failure of closed
  • At the time of surgery, the
    intra-articular disk and the more lateral epiphysis have been found to
    stay with the sternum and be held in place by the capsular ligament.
    • This is important to note because the epiphysis should not be excised with the intra-articular disk ligament.
Figure 20-6 A: Routine AP x-ray of posteriorly dislocated right SC joint. B:
The AP view is suggestive of a posterior dislocation. However, the CT
scan clearly demonstrates the posteriorly displaced right medial
clavicle. Note the displacement of the trachea. (From Bucholz RW,
Heckman JD. Rockwood and Green’s Fractures in Adults, 5th ed.
Lippincott Williams & Wilkins, 2001.)
Sternoclavicular Sprain or Subluxation
  • Acute sprains of the SC joint can be mild or moderate.
    • With a mild sprain, the ligaments are all intact and the joint is stable.
      • This can be painful and is treated with ice, a sling for 3 or 4 days, and then gradual use of the arm as tolerated.
    • With a moderate sprain, the joint is subluxated anteriorly or posteriorly and the ligaments may be partially disrupted.
      • This should be treated by holding the
        shoulders back with a clavicle strap to keep the joint reduced and a
        sling and swathe to prevent arm motion for 4 to 6 weeks.
  • Atraumatic subluxation of the medial clavicle usually occurs in adolescents and young adults.
    • It can be due to generalized ligamentous laxity or a pseudarthrosis between the first and second ribs.
    • This is treated nonoperatively.
    • If the patient continues to be symptomatic, a CT scan should be performed to look for any bony anomalies.
    • Surgery should be reserved for patients with persistent pain, instability, or limitation in activities of daily living.
Anterior Sternoclavicular Joint Dislocation
  • It can be difficult to differentiate between an anterior and posterior dislocation of the SC joint on physical examination only.

    • A CT scan is recommended to further evaluate SC joint injuries.
    • There is controversy over the treatment of anterior dislocations.
  • Although most acute anterior dislocations
    are unstable after reduction, it is nonetheless recommended that closed
    reduction be attempted if the patient presents less than 10 days from
    the injury (Fig. 20-7).
    • This can be done under local or general anesthesia.
    • The patient is placed supine with a 3- to 4-inch roll between the scapulae.
    • Gentle pressure over the anteriorly
      displaced medial clavicle may reduce the dislocation; however, when the
      pressure is released, the joint usually redislocates.
  • If the patient already has fusion between
    the medial clavicle physis and the clavicular shaft, then the anterior
    clavicle would be expected to have an anterior prominence of the medial
    • This does not seem to cause problems, even with heavy manual labor.
  • If the SC joint remains reduced with the shoulders held back, a figure-eight strap can be used.
    • Some authors have recommended a bulky pad over the anteromedial clavicle to hold it reduced.
    • The shoulder should be immobilized for 6 weeks, and strenuous activities should not be done until 8 weeks.
  • If the SC joint redislocates after the
    immobilization is discontinued, a figure-eight strap or sling can be
    used until the patient is comfortable.
  • Open operative procedures should not be
    done for an anterior SC joint dislocation because the complications are
    too great, end results are unsatisfactory, and the patient usually does
    fine with residual prominence.
Figure 20-7 Technique for closed reduction of the SC joint. A:
The patient is positioned supine with a sandbag placed between the two
shoulders. Traction is then applied to the arm against countertraction
in an abducted and slightly extended position. In anterior
dislocations, direct pressure over the medial end of the clavicle may
reduce the joint. B: In posterior
dislocations, in addition to the traction, it may be necessary to
manipulate the medial end of the clavicle with the fingers to dislodge
the clavicle from behind the manubrium. C:
In stubborn posterior dislocations, it may be necessary to prepare
(sterilely) the medial end of the clavicle and use a towel clip to
grasp around the medial clavicle to lift it back into position. (From
Bucholz RW, Heckman JD. Rockwood and Green’s Fractures in Adults, 5th
ed. Lippincott Williams & Wilkins, 2001.)
Posterior Sternoclavicular Joint Dislocation
  • A posterior dislocation of the SC joint requires prompt examination and reduction, either closed or open.
  • Because of pressure on the hilar
    structures, it has been associated with respiratory distress, venous
    congestion, arterial insufficiency, brachial plexus compression, and
    myocardial conduction abnormalities.
  • Damage to the pulmonary and vascular systems needs to be ruled out.
    • When indicated, aortography, pulmonary consult, and vascular consult should be obtained before reduction.
  • If the patient presents within 10 days of the injury, closed reduction should be attempted.
    • The reduction should be done as early as
      possible because there have been reports of greater difficulty reducing
      dislocations more than 48 hours from the injury.
    • Once the joint is reduced, it is almost always stable.
    • General anesthesia is usually needed because of pain and spasm.
  • There are two techniques used for closed reduction: abduction traction and adduction traction.
    • With the abduction-traction technique, the patient is placed supine with the injured shoulder near the edge of the table.
      • A 3- to 4-inch roll is placed between the scapulae.
      • The arm is abducted and lateral traction is applied.
      • The arm is then brought into extension, the clavicle reduces with an audible pop, and it is almost always stable.
      • It may be necessary to grasp the medial clavicle with one’s fingers to dislodge it from behind the sternum.
      • If this fails, then the skin is prepped
        and a sterile towel clamp or reduction tenaculum is used to grasp the
        medial clavicle and apply anterior traction, whereas lateral traction
        is applied to the arm.
  • With the adduction-traction technique, the patient is also placed supine with a 3- to 4-inch roll between the scapulae.

    • The arm is held adducted, whereas
      downward pressure is exerted on the shoulders, and the medial clavicle
      is levered over the first rib back into place.
  • After closed reduction, the patient should be placed into a figure-eight strap for 4 to 6 weeks.
  • If closed reduction fails, open reduction should be done for a posterior SC joint dislocation.
    • Most patients cannot tolerate the
      symptoms associated with pressure on the mediastinal structures, and
      even patients who are initially asymptomatic develop symptoms later on.
    • It is important to be totally familiar
      with the anatomy all around the SC joint. It is also recommended that a
      thoracic surgeon be available in the case of rupture of a major vessel.
  • Wirth and Rockwood recommend resection of
    the medial clavicle with maintenance, repair, or reconstruction of the
    costoclavicular ligaments to stabilize the joint. This can be done
    using suture, internal fixation across the joint, fascia lata, or
    subclavius tendon.
    • First, the medial clavicle is resected.
    • Next, two or three nonabsorbable sutures
      are placed around the remaining medial end of the clavicle and through
      the stump or scar of the costoclavicular ligaments, taking care not to
      tighten the medial clavicle down to the first rib too much.
    • If present, the capsular and intraarticular disk ligaments can also be sutured to the medial clavicle for stabilization.
    • Last, the periosteal sleeve is closed, which will stabilize the medial clavicle.
    • Metallic pin fixation should be avoided
      because these have been reported to migrate and cause serious
      complications, including death.
  • For a chronic posterior SC dislocation
    with an associated thoracic outlet syndrome, resection of the first rib
    has been performed with good success.
    • This approach avoids iatrogenic damage to
      the mediastinal structures and instability of the medial clavicle after
      resection, and leads to a cosmetic scar in the axillomammary skin
Intra-articular Disk Ligament Injury
  • This is an uncommon injury but can be
    quite disabling, and it should be considered in any patient with an
    acute or chronic injury of the SC joint.
  • A patient with an intra-articular disk
    injury will present with complaints of clicking, grating, and popping
    in the SC joint similar to a knee meniscal tear but have a stable joint.
  • CT scan and arthrography have been used in diagnosis.
  • Keep in mind that 6% of intra-articular disks are incomplete and may be read as a tear.
    • These injuries are treated conservatively with ice and rest.
  • If symptoms persist, a local injection can be done as both a therapeutic and diagnostic test.
  • If the injection relieves the symptoms,
    then the patient may benefit from an operation with an arthrotomy to
    remove the disk and resect the medial clavicle if it is degenerative,
    because this can also be a source of pain.
Degenerative Arthritis of the Sternoclavicular Joint
  • Degenerative arthritis of the SC joint results from a traumatic injury.
  • Conservative treatment with heat, anti-inflammatory medications, and rest is usually successful.
  • If the patient has persistent pain after
    6 to 12 months of conservative treatment, a local injection can be done
    as both a therapeutic and diagnostic test.
    • If the pain is relieved temporarily, then resection of the SC joint is indicated.
  • The medial clavicle is resected, being careful to leave the costoclavicular ligament intact.
  • The residual stability of the distal clavicle should be constantly checked.
  • If too much of the medial clavicle is
    resected, the patient will have recurrence of pain due to loss of
    stability of the clavicle.
  • This can lead to limited shoulder mobility, neurologic symptoms, thoracic outlet syndrome, and fatigue.
Dislocations of Both Ends of the Clavicle
  • This problem presents as an anterior dislocation of the SC joint and a posterior dislocation of the AC joint.
  • Wirth et al. reviewed 22 cases of dislocations of both ends of the clavicle.
    • Most patients with this problem have been treated conservatively with satisfactory results.
    • One patient developed a brachial plexus neuropathy treated with excision of part of the clavicle.
    • Four patients had persistent pain localized to the AC joint and were treated with AC joint reconstruction.
Nonsurgical Treatment
  • Complications related to pressure on
    hilar structures are mainly seen with posterior SC joint dislocations;
    however, there is some concern for these problems late with posterior
    physeal injuries.
  • The only complications occurring after an anterior dislocation are cosmetic deformity and late degenerative changes.
  • The incidence of complications has been reported at 25%; however, only two deaths have been reported as a result of this injury.
  • Early complications after a posterior dislocation can affect the trachea, esophagus, or great vessels.
    • These can be very serious and include
      pneumothorax, laceration of the superior vena cava, respiratory
      distress, neck venous congestion, rupture of the esophagus with abscess
      and osteomyelitis of the clavicle, fatal tracheoesophageal fistula,
      pressure on the subclavian artery, occlusion of the subclavian artery,
      heart conduction abnormalities, compression of the right common carotid
      artery, brachial plexus compression, and voice changes.
  • Late complications after nonreduced retrosternal injuries can occur in patients who were initially asymptomatic.
    • These include thoracic outlet syndrome, brachial plexopathy, subclavian artery compression, exertional


      dyspnea, and even fatal sepsis after development of a tracheoesophageal fistula.

Surgical Treatment
  • Metallic pin fixation across the SC joint
    should be avoided because these have been reported to migrate and cause
    serious complications, including death.
  • Smooth pins, threaded Kirschner pins,
    pins with bent ends, and Hagie pins have all been reported to migrate
    either intact or broken into the heart, pulmonary artery, innominate
    artery, aorta, spinal cord, breast, subclavian artery, and base of the
Allman FL Jr. Fractures and ligamentous injuries of the clavicle and its articulation. J Bone Joint Surg Am 1967;49;774-784.
Bowen MK, Nuber GW. Acromioclavicular and sternoclavicular injuries. Clin Sports Med 2003:22:301-317.
SJ, Nicholas SJ, Akizuki KH, et al. Reconstruction of the
coracoclavicular ligaments with tendon grafts. Am J Sports Med 2003;31:
Lemos MJ. The evaluation and treatment of the acromioclavicular joint in athletes. Am J Sports Med 1998;26:137-144.
MA, Rockwood CA Jr. Acute and chronic traumatic injuries of the
sternoclavicular joint. J Am Acad Orthop Surg 1996;4: 268-278.

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