Types of Glenohumeral Instability.
Last updated Thursday, February 10, 2005
Directions of instabilityWhat are anterior dislocations of the shoulder? Dislocations of the shoulder account for approximately 45% of all
dislocations. (Kazar and Relovszky, 1969) Of these, almost 85% are
anterior glenohumeral dislocations. (Cave et al, 1974) Subcoracoid
dislocation is the most common type of anterior dislocation. The usual
mechanism of injury that causes subcoracoid dislocations is a
combination of shoulder abduction, extension, and external rotation
producing forces that challenge the anterior capsule and ligaments, the
glenoid rim, and the rotator cuff mechanism. The head of the humerus is
displaced anteriorly with respect to the glenoid and is inferior to the
coracoid process. Other types of anterior dislocation include
subglenoid (the head of the humerus lies anterior to and below the
glenoid fossa), subclavicular (the head of the humerus lies medial to
the coracoid process, just inferior to the lower border of the
clavicle), intrathoracic (the head of the humerus lies between the ribs
and the thoracic cavity). (Glessner, 1961; Moseley, 1963; Patel et al,
1963; Saxena and Stavas, 1983; West, 1949) and retroperitoneal. (Wirth
et al, 1996-in press) These rarer types of dislocation are usually
associated with severe trauma and have a high incidence of fracture of
the greater tuberosity of the humerus and rotator cuff avulsion.
Neurological, pulmonary, and vascular complications can occur, as can
subcutaneous emphysema. West (West, 1949) reported a case of
intrathoracic dislocation in which with reduction the humerus was felt
to slip out of the chest cavity with a sensation similar to that of
slipping a large cork from a bottle. His patient, who had an avulsion
fracture of the greater tuberosity and no neurological deficit,
regained a functional range of motion and returned to his job as a
carpenter.What are posterior dislocations of the shoulder? Posterior dislocations may leave the humeral head in a subacromial
(head behind the glenoid and beneath the acromion), subglenoid (head
behind and beneath the glenoid), or subspinous (head medial to acromion
and beneath the spine of the scapula) location. The subacromial
dislocation is the most common by far. Posterior dislocations are
frequently locked. Hawkins and coworkers (Hawkins et al, 1987) reviewed
41 such cases related to motor vehicle accidents, surgeries, and
electroshock therapy.
The incidence of posterior dislocations is estimated at 2 per cent
but is difficult to ascertain because of the frequency with which this
diagnosis is missed. Thomas (Thomas, 1937) reported seeing only 4 cases
of posterior shoulder dislocation in 6000 x-ray examinations. The
literature reflects that the diagnosis of posterior dislocation of the
shoulder is missed in over 60 per cent of cases. (Engelhardt, 1978;
Hehne and Hubner, 1980; Mestdagh et al, 1994; Pavlov et al, 1985;
Verrina, 1975) A 1982 article by Rowe and Zarins(Rowe and Zarins, 1982)
indicates that the diagnosis was missed in 79 per cent of cases!
McLaughlin (McLaughlin, 1952) stated that posterior shoulder
dislocations are sufficiently uncommon that their occurrence creates a
"diagnostic trap."
One of the largest series of posterior dislocations of the shoulder
(37 cases) was recorded by Malgaigne (Malgaigne, 1855) in 1855, 40
years before the discovery of x-rays. He and his colleagues made the
diagnosis by performing a proper physical examination! Cooper (Cooper,
1839) stated that the physical findings are so classic that he called
it "an accident which cannot be mistaken."
Posterior dislocation may result from axial loading of the adducted,
internally rotated arm (Moeller, 1975) or from violent muscle
contraction, by electrical shock or convulsive seizures. (See
references Ahlgren et al, 1981; Carew-McColl, 1980; Fipp, 1966; Hawkins
and Hawkins, 1985; Lindholm and Elmstedt, 1980; McFie, 1976; Mills,
1974-1975; Onabowale and Jaja, 1979; Protzman, 1980; Segal et al, 1979)
In the case of involuntary muscle contraction, the combined strength of
the internal rotators (latissimus dorsi, pectoralis major, and
subscapularis muscles) simply overwhelms the external rotators
(infraspinatus and teres minor muscles). Heller et al have recently
proposed a classification for posterior shoulder dislocation. (Heller
et al, 1994) What are inferior dislocations of the shoulder? Inferior dislocation of the glenohumeral joint was first described
by Middeldorpf and Scharm (Middeldorpf and Scharm, 1859) in 1859. Lynn
(Lynn, 1921) in 1921 carefully reviewed 34 cases, and Roca and
Ramos-Vertiz (Roca and Ramos-Vertiz, 1962) in 1962 reviewed 50 cases
from the world literature. Laskin and Sedlin (Laskin and Sedlin, 1971)
reported a case in an infant. Three bilateral cases have been reported
by Murrard,(Murrard, 1920) Langfritz, (Langfritz, 1956) and Peiro and
coworkers.(Peiro et al, 1975) Nobel(Nobel, 1962) reported a case of
subglenoid dislocation in which the acromion--olecranon distance was
shortened by 1.5 inches.
Inferior dislocation may be produced by a hyperabduction force that
causes abutment of the neck of the humerus against the acromion
process, which levers the head out inferiorly. The humerus is then
locked with the head below the glenoid fossa and the humeral shaft
pointing overhead, a condition called luxatio erecta. The clinical
picture of a patient with luxatio erecta is so clear that it can hardly
be mistaken for any other condition. The humerus is locked in a
position somewhere between 110 and 160 of adduction. Severe soft
tissue injury or fractures about the proximal humerus occur with this
dislocation. At the time of surgery or autopsy, various authors have
found avulsion of the supraspinatus, pectoralis major, or teres minor
muscles and fractures of the greater tuberosity. (Kubin, 1964; Laskin
and Sedlin, 1971; Lynn, 1921; Middeldorpf and Scharm, 1859; Murrard,
1920; Roca and Ramos-Vertiz, 1962) Neurovascular involvement is common.
(Gardham and Scott, 1980; Lev-EI and Rubinstein, 1981; Lynn, 1921;
Meadowcroft and Kain, 1977) Lev-El and associates (Lev-EI and
Rubinstein, 1981) reported a patient who had an injury to the axillary
artery and subsequently developed a thrombus that required resection
and vein graft. Gardham and Scott(Gardham and Scott, 1980) reported a
case in 1980 in which the axillary artery was damaged in its third part
and was managed by a bypass graft using the saphenous vein. Rockwood
and Wirth found that in 19 patients with this condition, all 19 had a
brachial plexus injury and some vascular compromise before reduction.
The force may be so great as to force the head out through the soft
tissues and the skin. Lucas and Peterson (Lucas and Peterson, 1977)
have reported a case of a 16-year-old boy who caught his arm in the
power take-off of a tractor and suffered an open luxatio erecta injury.
Reduction of an inferior dislocation can often be accomplished by
traction and countertraction maneuvers. When closed reduction cannot be
accomplished, the buttonhole rent in the inferior capsule must be
surgically enlarged before reduction can occur. What are superior dislocations of the shoulder? Speed (Speed, 1942) reported that Langier, in 1834, was the first to
record a case of superior dislocation of the glenohumeral joint;
Stimson (Stimson, 1912) reviewed 14 cases that had been reported in the
literature prior to 1912. In current literature little is mentioned
about this type of dislocation, but undoubtedly occasional cases do
occur. The usual cause is an extreme forward and upward force on the
adducted arm. With displacement of the humerus upward, fractures may
occur in the acromion, acromioclavicular joint, clavicle, coracoid
process, or humeral tuberosities. Extreme soft tissue damage occurs to
the capsule rotator cuff, biceps tendon, and surrounding muscles.
Clinically, the head rides above the level of the acromion. The arm is
short and adducted to the side. Shoulder movement is restricted and
quite painful. Neurovascular complications are usually present.What are bilateral dislocations of the shoulder? Mynter (Mynter, 1902) first described this condition in 1902;
according to Honner, (Honner, 1969) only 20 cases were reported prior
to 1969. Bilateral dislocations have been reported by McFie, (McFie,
1976) Yadav, (Yadav, 1977) Onabowale and Jaja, (Onabowale and Jaja,
1979) Segal and colleagues, (Segal, Yablon, Lynch et al, 1979) and
Carew-McColl. (Carew-McColl, 1980) Most of these cases were the result
of convulsions or violent trauma. Peiro and coworkers (Peiro, Ferrandis
and Correa, 1975) reported bilateral erect dislocation of the shoulders
in a man caught in a cement mixer. Bilateral dislocation of the
shoulder secondary to accidental electrical shock has been reported by
Carew-McColl (Carew-McColl, 1980) and Fipp. (Fipp, 1966) Nicola and
coworkers (Nicola et al, 1981) have reported cases of bilateral
posterior fracture-dislocation following a convulsive seizure. Ahlgren
and associates (Ahlgren, Lorentzon and Larsson, 1981) reported three
cases of bilateral posterior fracture-dislocation associated with a
convulsion. Lindholm and Elmstedt (Lindholm and Elmstedt, 1980)
reported a case of bilateral posterior fracture-dislocation following
an epileptic seizure, which was treated by open reduction and internal
fixation with screws. Parrish and Skiendzielewski (Parrish and
Skiendzielewski, 1985) reported a patient with bilateral posterior
fracture-dislocations after status epilepticus. The diagnosis was
missed for over 12 hours. Pagden and associates (Pagden et al, 1986)
reported two cases of posterior shoulder dislocation following seizures
related to regional anesthesia. Costigan and coworkers (Costigan et al,
1990) reported a case of undiagnosed bilateral anterior dislocation of
the shoulder in a 74-year-old patient admitted to the hospital for an
unrelated problem. The patient had no complaints related to the
shoulders and was able to place both hands on her head and behind her
back.
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This resource has been provided by the University of Washington Department of Orthopaedics and Sports Medicine as general information only. This information may not apply to a specific patient. Additional information may be found at http://www.orthop.washington.edu or by contacting the UW Department of Orthopaedics and Sports Medicine.
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