Posterior Fracture-Dislocations

Read in conjunction with page on posterior dislocations. (Posterior shoulder dislocation)

Anatomy

Blood supply of humeral head:

The humeral head has a segmental blood supply, mainly derived from the ascending branch of the anterior circumflex humeral artery and its intraosseous continuation, the arcuate artery.

Many extra- and intraosseous anastomoses exist among the arteries supplying the humeral head. The most substantial extraosseous anastomoses of the anterior circumflex artery are to the posterior circumflex, thoracoacromial, and suprascapular arteries. The more significant intraosseous anastomoses are between the arcuate artery and branches of the posterior humeral circumflex artery entering the posteromedial aspect of the proximal humerus, the metaphyseal vessels, and the vessels of the greater and lesser tuberosities.

Within the humeral head, the arcuate artery supplies almost the entire epiphysis. The anterolateral ascending branch of the anterior circumflex artery enters the humeral head where the proximal end of the intertubercular groove meets the greater tuberosity. The branches of the posterior humeral circumflex artery enter the posteromedial aspect of the proximal humerus just below the articular margin. This is the reason why a fracture of the anatomic neck of the humerus, especially a displaced one, interrupts the intraosseous vascularization, resulting in avascular necrosis of the humeral head. Some vascularity of the head may be preserved if the fracture line at the medial part of the humeral neck extends distal to the entrance of the branches of the posterior humeral circumflex artery.

Classification

The three most commonly encountered fracture patterns are:

2 part fractures of the lesser tuberosity
2 part fractures of the anatomic neck
Complex three-part and four-part fractures

Posterior dislocation and 2 part fracture of lesser tuberosity

Dislocations with an undisplaced lesser tuberosity fracture can be treated in the same manner as simple posterior dislocations.

Open reduction and internal fixation is recommended if there is displacement.

The tuberosity may be fixed either anatomically or into the base of the humeral head defect if the shoulder is unstable.

Posterior fracture dislocation and Anatomical neck fracture

Treatment of posterior fracture dislocations involving the anatomical neck are complex injuries presenting several problems.

Method of reduction (open or closed)
Approach
Internal fixation or not following reduction
Viability of the head and arthroplasty

Neer recommended open reduction and internal fixation in young patients and a primary prosthetic replacement in older patients.

Closed reduction

Closed reduction for posterior fracture-dislocation risks further displacement and avascular necrosis of the humeral head.
The decision about performing closed or open reduction should be made based on the position of the humeral head, the time elapsed between the occurrence of injury and the diagnosis, and the possibility of further dissociation of the fracture.

Neer reported that adequate attachment and contact is generally found in posterior fracture dislocations to provide adequate blood supply to the head fragment. This blood supply may facilitate rapid revascularization accompanied by creeping substitution and prevent avascular necrosis.

Given these facts Neer suggested that posterior fracture dislocations should be reduced open to prevent further disimpaction of the fragment, and that preliminary attempts at closed reduction are contraindicated because of the danger of further displacement of the humeral head and disimpaction.

Nevertheless, there are many reports of patients successfully treated by closed reduction.

Based on this evidence it may be reasonable to attempt a GENTLE closed reduction under full-relaxant general anaesthesia.

Great care must be taken so as not to destroy the soft tissue hinge between the humeral head and the greater tuberosity.

Closed reduction is not worth attempting, however, if the humeral head is completely detached.

Closed reduction technique

General anaesthetic WITH muscle relaxation
Apply longitudinal traction with arm in adduction
Accompanied by direct pressure posteriorly on the head while gently internally rotating shoulder

Open Reduction

Approaches

Deltopectoral, posterior and superior subacromial approaches have been reported, with the most common being the deltopectoral approach.

The deltopectoral approach has shortcomings, however. Normal or injured soft tissue anterior to the shoulder may be further injured, and the engagement between the humeral head and the glenoid cannot be directly visualized.

The superior subacromial involves release of the deltoid from the acromion and the subacromial gliding mechanism may be disturbed.

In contrast, the posterior approach provides direct visualization of the engagement between the humeral head and the glenoid without disturbing the subacromial gliding mechanism, and also permits reduction of a completely detached humeral head. In addition, blood vessels important to the proximal end of the humerus are not exposed, which precludes the possibility of injury to these vessels.

For description of posterior approach in posterior fracture dislocations (click here)

Internal fixation

Spontaneous reduction of the displaced bone fragment has been reported to occur with reduction of the dislocated humeral head in posterior and anterior fracture-dislocations. This phenomenon suggests that the bone fragments are connected to each other with the soft tissue, including the periosteum, rotator cuff, and capsule. By spontaneous reposition of the greater and lesser tuberosities, pressure generated by the rotator cuff is applied to the surface of the anatomic neck fracture, leading to stabilization of this fracture. Internal fixation, therefore, is not essential to the treatment of this injury.

Internal fixation should be performed in Patients with:

A completely detached humeral head to stabilize the fragment and facilitate rapid revascularization.
Displaced bone fragments of >1 cm after reduction.

Summary of posterior dislocation with anatomical neck fracture

Attempt extremely gentle closed reduction once under full-relaxant general anesthesia.
If closed reduction is unsuccessful, immediately proceed with open reduction of the dislocated humeral head using the posterior deltoid-splitting approach.
Do not perform reposition and internal fixation for the fracture, except for in patients with a completely detached humeral head and patients with bone fragments that are displaced more than 1 cm.

Complex three-part and four-part fractures

Two, three, and four-part fractures involving the anatomic neck are treated either with reduction and internal fixation or with arthroplasty.

The treatment is determined by the age and medical status of the patient and the degree of devascularization and fragmentation of the humeral head and tuberosities.

Arthroplasty is generally favoured for multipart fractures in the elderly. In addition to the technical problems encountered when an arthroplasty is used to treat a simple dislocation, it may be difficult to judge the appropriate prosthetic soft-tissue tensioning and to obtain stable fixation of the fractured tuberosities.

Head-salvaging reconstruction is usually attempted in younger adults with good bone stock. While closed reduction techniques have been described, open reduction and internal fixation is usually preferred because it reduces the risk of iatrogenic fracture displacement.

The type of internal fixation used is determined by the complexity of the fracture. Two-part fractures may be stabilized by simple interfragmentary screws, whereas multipart fractures require more complex reconstruction with use of buttress plates, tension bands, or intramedullary fixation. Stability should be assessed following internal fixation, as adjunctive procedures may be required if there is residual instability.

Rehabilitation

After fixation in the neutral rotation position, pendulum exercise on the scapular plane are begun within 1 week. Isometric muscle-strengthening exercises are started 10 days after reduction in cases associated with only an anatomic neck fracture, and 4 weeks after reduction in cases associated with fractures of the greater and lesser tuberosities.

In all cases, active range-of-motion and isometric muscle-strengthening exercises are started 5 weeks after reduction.

References

CURRENT CONCEPTS REVIEW: C. Michael Robinson and Joseph Aderinto; Posterior Shoulder Dislocations and Fracture-Dislocations J. Bone Joint Surg. Am., Mar 2005; 87: 639 - 650.

Cicak, N. Posterior dislocation of the shoulder. Journal of Bone & Joint Surgery - British Volume. 86-B(3):324-332, April 2004

Clough, T.M.; Bale, R.S. Bilateral posterior shoulder dislocation: the importance of the axillary radiographic view. European Journal of Emergency Medicine. 8(2):161-163, June 2001.

Ogawa, Kiyohisa MD; Yoshida, Atsushi MD; Inokuchi, Wataru MD; Posterior Shoulder Dislocation Associated with Fracture of the Humeral Anatomic Neck: Treatment Guidelines and Long-Term Outcome. Journal of Trauma-Injury Infection & Critical Care. 46(2):318-323, February 1999

Goodrich, J. Allan; Crosland, Edward; Pye, Jacque. Acromion Fracture Associated With Posterior Shoulder Dislocation. Journal of Orthopaedic Trauma. 12(7):521-523, September/October 1998

Posterior dislocation of the shoulder with ipsilateral humeral shaft fracture: a very rare injury; Injury, Volume 28, Issue 2, March 1997, Pages 150-152; S. Naresh, J. A. Chapman and T. Muralidharan

Goodrich, J. Allan; Crosland, Edward ; Pye, Jacque; Acromion Fracture Associated With Posterior Shoulder Dislocation. Journal of Orthopaedic Trauma. 12(7):521-523, September/October 1998.

Munting, T.; de Beer, M. A.; Vrettos, B. C. MISSED POSTERIOR DISLOCATIONS OF THE SHOULDER. Journal of Bone & Joint Surgery - British Volume. 85-B SUPPLEMENT II:142, 2003.

Galanakis, Ioannis A. MD; Kontakis, George M. MD; Steriopoulos, Konstantinos A. MD; Posterior Dislocation of the Shoulder Associated with Fracture of the Humeral Anatomic Neck. Journal of Trauma-Injury Infection & Critical Care. 42(6):1176-1178, June 1997