| Abstract|| |
Background: Posterior dislocation of shoulder is a rather uncommon injury that is often not diagnosed at the initial examination. However certain constant clinical signs may lead the examiner to suspect the presence of this condition. Even the routine antero-posterior roentgenogram may provide a few clues to diagnosis but the axillary view is mandatory to verify diagnosis.
Material and methods : We report a series of 15 shoulders (14 patients) with a locked posterior dislocation. Electric shock (7 patients), vehicular accident (4 patients) and epileptic seizure (3 patients) was causes of dislocation in these patients. The diagnosis was missed initially in 10 cases. An axillary radiograph confirmed the diagnosis in all. Treatment consisted of closed reduction, which was successful in 5, Neer's modification of McLaughlin procedure (transfer of subscapularis) in 6, hemireplacement arthroplasty in one shoulder and tuberosity fixation in one patient.
Results : Follow-up ranged from 1 year to 4 years. Five patients had excellent, five good, two poor and one had fair result.
Conclusion : Key to diagnosis is a high index of suspicion. The prognosis became less favorable and the therapeutic difficulties were found to be increased in direct proportion to the length of time, these lesions remain undiagnosed. With early recognisition of dislocation, prompt reduction is relatively easy. Surgical intervention is necessary for old unreduced posterior dislocations.
Keywords: Posterior dislocation of shoulder; Neer′s operation; Hemiplacement arthroplasty.
|How to cite this article:|
Thakker TH, Prabhakar M M, Patel DA. Posterior dislocation of the shoulder joint. Indian J Orthop 2006;40:24-8
| Introduction|| |
Posterior dislocation of the shoulder is rare. This rare entity creates a diagnostic trap for unwary surgeon  . It's incidence in the literature is 2.17 %  . In recent times Hawkins et al have presented a series of 41 locked posterior dislocation in 40 patients  . The posterior dislocation of the shoulder is frequently missed by the initial surgeon, leading to delayed diagnosis and treatment. The results then are far from satisfactory. We present a series of 15 posterior dislocations of shoulder in 14 patients, highlighting their problems.
| Material and Methods|| |
In the last 10 years (1992-2003) we treated 14 patients (15 shoulders) of posterior dislocation shoulder. Ten patients were male and 4 female. Right shoulder was involved in nine patients, left in four and one patient had bilateral posterior dislocation shoulder. The age ranged from 29 to 50 years (mean age 36.2 years). Of these 14 patients, 8 patients came within 3 weeks, 6 patients with in 3-6 weeks and 2 patients after 6 weeks of initial injury. Of these only four patients were referred with a diagnosis of posterior dislocation, while in ten patients (11 shoulders) some form of treatment had been attempted before they were diagnosed as posterior dislocation shoulder. The chief complaints of these patients were difficulty in combing hair, washing the face, shaving and even eating. Three patients had been treated by physiotherapy with a diagnosis of frozen shoulder. Despite physiotherapy, all of these patients had impaired external rotation of shoulder and pain. Therefore, in the majority of the patients, the primary reason for referral was functional disability. There were certain pertinent clues that allowed the diagnosis like asymmetry of shoulder, absent humeral head anteriorly, prominent bulge of head posteriorly, and prominent coracoid [Figure - 1]. Motions of the locked shoulder were limited, the average abduction was 100 degree (60 to 150) and average internal rotation deformity was 40 degree (10 to 60). No external rotation was possible. The patient kept the forearm against his chest relatively comfortably. The diagnosis was confirmed in all fifteen shoulders on axillary radiographs. Important signs on radiological diagnosis were loss of profile of humeral neck and electrical bulb sign (the humeral head takes on a rounded, more symmetrical shape on the AP view, like a light bulb due to rotation of the humerus). The humerus was internally rotated, with the articular surface facing posteriorly. vacant glenoid (space between the anterior rim and the humeral head was greater then 6 mm), and trough line (due to impaction fracture of the humeral head caused by posterior rim of glenoid and analogous to the Hill-Sach lesion-in 8 patients). Of these 15 shouldes, 6 shoulders had associated fracture of proximal humerus and one among them also had a fracture of the proximal femur of the same side. Computerized tomography scans is the surest way of diagnosis and to elucidate the changes in the humeral head and glenoid fossa. Due to financial constrains, CT scan of the shoulder could be done only in five patients.
The modality selected for the locked shoulders was decided in accordance with the duration of dislocation and the general health of patient.
(A) Closed Reduction: Closed reduction was tried in eight patients but found to be successful in five patients only. Reduction was done by flexion and adduction of the shoulder, traction on the affected extremity and direct pressure applied from behind in an effort to push the humeral head anteriorily in to the socket. We did not attempt closed reduction in any shoulder in which dislocation was older than three weeks. After successful closed reduction, the stability of shoulder was assessed; all three shoulders were found stable. Of these 5 shoulders, three were immobilized in 20 degree external rotation with splint, while in two shoulders reduction was maintained by temporary percutaneous two K-wires inserted under image intensifier control  . In these two patients it was possible to bring the limb by the side of chest and so avoiding cumbersome external rotation position.
(B) Neer's modification of McLaughlin procedure: Six patients were treated by transfer of lesser tuberosity with attached subscapularis tendon into the defect. These six shoulders had been dislocated for fewer than six weeks. The shoulder was approached though the deltopectoral interval, lesser tuberosity was osteotomised and carefully elevated with its attached tendon of subscapularis muscle and capsule to expose glenoid fossa. Dislocation was reduced (may require some effort due to tightness of surrounding structure because of long standing dislocation)by lifting the head with finger, the bed of impression defect clearly visualized, roughened and the osteotomised portion of lesser tuberosity with its attached tendon was secured in position using either screw (five patients) or staple (one patient) [Figure - 2].
(C) Hemi replacement arthroplasty: One patient was treated by hemi replacement arthrolasty due to posterior dislocation with comminuted fracture of proximal humerus, which was not possible to fix. After hemi replacement arthroplasty, no post operative immobilization was used and early assisted range of motion exercises were commenced on third day and continued until adequate range of motion had been obtained.
(D) Tuberosity fixation: One patient was treated elsewhere for posterior dislocation with closed reduction. He also had an avulsion fracture of greater tuberosity. This fragment had been pulled up proximally under the acromion by the pull of supraspinatus muscle. This was missed initially. Through Kessel's approach, the avulsed fragment was retrieved and fixed back using tension band technique.
(E) No Treatment: Two patients, who had stiff but painless shoulders, had refused treatment.
| Results|| |
Follow-up ranged from 1 year to 4 years. The follow up included interview and physical examination as well as radiography of the affected shoulder. Criteria of assessment followed were modified from Rowe and Zarins  , 1982. It is as follows
Excellent : No pain, full range of movement, able to perform activity of daily leaving.
Good : No pain, some limitation of movements, daily activities slightly hampered.
Fair : Some degree of pain, limitation of movement, restriction of daily activities.
Poor : Pain on attempted movement, marked limitation of movement, restriction of daily activities strength & motion  .
Overall, out of 12 treated patients (13 shoulders), five had excellent, five good, two poor and one had fair result. On analyzing results according to treatment
(a) Closed reduction (5) - At 2 years follow up, these shoulders were stable and painless with full range of motion and normal function (Excellent result).
(b) Neer's procedure (6)- After the follow up of 1 to 2 years, one had excellent, three good, one fair and one had poor results [Figure - 3].
(c) Hemireplacement arthroplasty (1) - He had good result after 2-year follow-up.
(d) Tuberosity fixation (1) - Patient had fair result at the end of 2 yr. Follow up.
| Discussion|| |
Incidence of posterior dislocation is rare in comparison to anterior dislocation 2 . This can be possibly due to some features of shoulder anatomy. The scapula is angulated anteriorly approximately 45 0 on thoracic cage. This places the posterior half of glenoid fossa, behind the humeral head and acts as a buttress to prevent posterior dislocation. Acromion as well as spine of scapula also act as a resistance. The strong pectoral major reduces the impact of an anterior blow on the glenohumeral articulation  . Majority of posterior dislocations of shoulder are due to indirect force ,, .
During electrical shock or seizure, there is a sudden simultaneous spasm of musculature about the shoulder. The strong internal rotators overpower the weak external rotators. The combined strength of latissimus dorsi, pactoralis major and subscapularis muscles simply overpulls infraspinatus and teres muscles. But other factors such as position of the arm and muscle weakness must also be considered , . Missed diagnosis is not uncommon in posterior dislocation of shoulder ,, . The posterior dislocation of the shoulder is the most commonly missed major joint dislocation in the body  because of rare presentation and inadequate physical examination. Also the AP X-ray may appear deceptively normal  . The axillary view is often not obtained routinely. Multiple injuries about the shoulder area prevent abduction of the arm and so, axillary view may not be obtained. In cases where abduction of shoulder is not possible Velpeau axillary view is very helpful  . In all patients with a history of seizure, electrocution or similar trauma, where external rotation of the shoulder is limited, an axillary or modified axillary view is to be added to the standard two radiographic views as routine protocol, to avoid missing a posterior dislocation ,. According to Apley, electric shock or epilepsy plus painful shoulder indicates posterior dislocation  . A high index of suspicion is needed, if this injury is not to be missed. Stableforth and Sarangi  had 50% and Hawkins et al  had 49.9% incidence of posterior dislocation associated with fracture of proximal humerus. In our series too 40% cases had dislocation with fracture. Associated fractures of the proximal humerus divert the surgeon's attention and the dislocation may not be thought of. This delays the diagnosis and makes the closed reduction difficult or impossible. We recommend that in every case of proximal humerus fracture, the possibility of a posterior dislocation as well should be kept in mind.
Ogawa and Yoshida recommend treatment for posterior dislocation of shoulder with a fracture of anatomical neck with initial open or closed reduction of the dislocated humeral head and then impaction of the fracture, with neither repositioning nor internal fixation of any of the fractured fragments  . A completely detached humeral head or bone fragments displaced more then 10 mm after reduction of the dislocated humeral head contraindicates the use of this method  . Many articles had been published since McLaughlin described his procedures in 1952  . The recommendations for treatment have ranged from no treatment to surgical treatment of all locked posterior dislocation. A decision as how a patient with locked posterior dislocation should be treated is based on the general condition and needs of patient, the duration of dislocation, the size of Impression defect and last but the most important experience of surgeon  . We did successful closed reduction in 5 shoulders, which came with in three week and had impression defect <20 % of articular surface. All 5 of them have excellent result. This can be treatment of choice when dislocation is less than three week old and defect < 20%. After reduction shoulder should be immobilized for six weeks with arm at the side with shoulder, in 20 0 external rotation. After open reduction through delto-pectoral approach  , the stability of the reduction is the next consideration. Defect greater then 20% of the head diameter may lead to redislocation. McLaughlin described an operation in which he filled the defect with subscapularis tendon [Figure - 3]. Neer modified McLaughlin procedure. He took a block of bone from the proximal humerus, including the lesser tuberosity and the attached subscapularis tendon and fixed it in the defect of the head with a screw [Figure - 2]. His method is logical as it fills the bone defect with bone. Bone to bone fixation ensures that the repair is most secure. We used this method in six shoulders of which three had good result and three patients had fair result. Four of these patients had dislocation more then three week old and two were less then three week old, in which close reduction was not successful and impression defect involves 20-45 % of articular surface. Three patients had fair result due to poor compliance at the time of physiotherapy after immobilization for six weeks. It can be treatment of choice for dislocation of more then three week old in whom closed reduction unsuccessful and defect 20 - 45 % of articular surface. We performed hemi replacement arthroplasty with Neer's prosthesis in one case. This patient came after six months with impression defect > 45 % of articular surface on axillary radiograph and CAT scan. This patient had good result at the end of two years. This is perhaps the treatment of choice for dislocation older than six months and articular surface defect. According to Gerber and Lambert the recognized options for the treatment of locked posterior dislocation of the shoulder are dependant on the size of the anteromedial defect of the humeral head  . Defect smaller then 40% of the joint surface-transfer of lesser tuberosity with its attached subscapularis tendon in to the defect, larger defectProsthetic replacement. They treated four consecutive patients of chronic locked posterior dislocation of the glenohumeral joint associated with a defect of the humeral head at least 40% of the articular surface by reconstruction of the shape of the humeral head with use of allogeneic segment of the femoral heal and considered satisfactory result in three out four patients  . Neer has given treatment guidelines for posterior dislocation of shoulder  [Table - 1].
Outcome of the treatment of posterior dislocation of shoulder depends upon several factors. Prompt diagnosis, early treatment and good rehabilitation prognosis lead to excellent to good results. Cases that came very late may need total shoulder arthroplasty or may be left alone.
| References|| |
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Tejas H Thakker
28, Shantikunj Society, Ramnagar, Sabarmati, Ahmedabad
Source of Support: None, Conflict of Interest: None
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5]
[Table - 1]