CHAPTER 31 Ectopic Ossification About the Elbow

INTRODUCTION

Development of pathologic formation about the elbow takes on several forms including heterotopic ossification, myositis ossificans, and periarticular calcification. Heterotopic ossification refers to the formation of mature lamellar bone in nonosseous tissue. Heterotopic ossification and ectopic bone are terms that are used interchangeably for this type of bone formation. Myositis ossificans refers to abnormal formation of bone in inflammatory muscle.¹ Myositis ossificans also consists of mature lamellar bone and is distinguished from ectopic bone only by its location.

Calcification about the elbow is distinctly different from ossification. Calcific deposits typically consist of calcium pyrophosphate and do not contain mature bone. These are usually amorphous globular deposits and have no trabecular structure. Calcific deposits may occur in tendon, synovium, capsular tissue, and ligaments. Calcium deposits are most commonly seen in ligamentous tissue after elbow trauma.^10,^12,⁵¹ Elbow motion is rarely affected to any significant degree.

ETIOLOGY

TRAUMATIC CONDITIONS THAT MAY LEAD TO ECTOPIC BONE FORMATION

Thompson and Garcia ⁸⁴ documented the incidence of ectopic bone formation in a series of more than 1200 traumatic elbow conditions: 3% in simple dislocations, 20% in elbow dislocations associated with radial head fractures, and 16% in elbow dislocations associated with other fractures. Although the definition of what constitutes ectopic bone is not clear, this report does serve as a worthwhile benchmark of the relative incidence among these three injury types.

Elbow Dislocations

Patients with simple dislocations without fracture are less likely to develop ectopic bone formation than are those with associated fractures.^72,⁷³ Linscheid and Wheeler⁵¹ noted an incidence of some radiographic density in about 30% in a series of 110 elbow dislocations. True ectopic bone formed in the anterior capsule in five patients (4.5%), and most had calcification in the collateral ligaments below the medial and lateral epicondyles (Fig. 31-1). Josefsson and colleagues⁴² found true ectopic bone formation in only 1 of 52 elbow dislocations (1.6%). Periarticular calcification, however, was noted in 38 patients (76%). Eleven of the 12 patients in whom there was no evidence of periarticular calcification had sustained their dislocations before the age of 16 years.

FIGURE 31-1 Distribution of possible radiographic densities about the elbow after trauma.

(Redrawn from Broberg, M. A., and Morrey, B. F.: Results of treatment of fracture-dislocations of the elbow. Clin. Orthop. Rel. Res. 216:111, 1987.)

The incidence of ectopic bone formation increases about fivefold when an elbow dislocation is associated with a radial head fracture.⁸⁴ McLaughlin⁵⁵ listed several principles to reduce the formation of ectopic bone: (1) excision of the radial head within 24 hours of injury, (2) complete removal of the radial head with all the fracture fragments, (3) avoidance of the formation of bone dust within the operative bed at the time of radial head excision, (4) careful hemostasis, and (5) avoidance of hematoma formation. There is little scientific evidence to support these recommendations, but they seem reasonable.

Radial Head Fractures

Ectopic bone formation may also occur following isolated fractures of the radial head. Patients with Mason type III comminuted fractures are probably at the greatest risk.⁵² In a study of 60 cases, Mikic and Vukadinovic⁵⁶ noted ossification about the elbow in 32 (56%). In the 18 patients with more extensive amounts of bone, restriction of elbow motion was seen in all. In 31 (52%) of these patients, there was significant regrowth of bone at the level of resection of the radius, as noted by others.^48,⁸¹ We have observed a rather consistent pattern of ectopic bone emanating from the resected radius in this clinical circumstance (Fig. 31-2).

FIGURE 31-2 Temporal correlation of radiographic and serum alkaline phosphatase changes with clinical symptoms.

(Redrawn from Orzee, J. A., and Rudd, T. G.: Heterotopic bone formation: clinical, laboratory, and imaging correlation. J. Nucl. Med. 26:125, 1985.)

Timing of Surgical Treatment with Elbow Trauma

We have observed that patients with open injuries undergoing several surgical procedures performed during the first 7 to 14 days of injury are at particular risk (Fig. 31-3). In McLaughlin’s series of radial head fractures,⁵⁵ 12% who underwent excision within 24 hours had ectopic bone formation, compared with 38% who had delayed excision.

FIGURE 31-3 This 26-year-old man was involved in a motor vehicle accident and sustained a dislocation of his right elbow with a proximal ulnar fracture. Open reduction and internal fixation of the ulna was done 3 weeks after his injury. He was first seen at the Mayo Clinic 4 months later with extensive ectopic bone (A). The technetium-99m scan showed marked uptake at 4 months (B), which persisted for 18 months (C).

In a study of 14 patients with fracture-dislocations of the elbow treated by either partial or complete resection of the radial head, Broberg and Morrey ⁸ reported an incidence of significant ectopic bone formation of only 9%. The single patient with significant heterotopic ossification had undergone excision of the radial head 8 days after injury, and the results of treatment were graded as fair with continued elbow pain.

The issue of delay before definitive surgery for fracture dislocation was initially emphasized by McLaughlin.⁵⁵ This opinion has been recently strengthened by the work of Ilahi and colleagues.⁴¹ Among 71 consecutive elbow injuries of various types, none developed significant ectopic bone when operated on within 48 hours. On the other hand, 8 of 24 (33%) did enounter ectopic bone formation if treatment was delayed more than 48 hours.

Post-Traumatic Radioulnar Synostosis

Cross-union from ectopic bone may be caused by fractures,^5,^11,^23,^65,^75,⁸⁵ or soft tissue injury^7,^60,⁷⁰ of the forearm. When an associated elbow injury has occurred, the synostosis may be extensive (Fig. 31-4).

FIGURE 31-4 Comminuted, compound fracture (A). Three dèbridements and fixation occurred over a 10-day period. Extensive ectopic bone developed (B).

Vince and Miller ⁸⁶ classified synostoses of the forearm by location: type I, distal third; type II, middle third; and type III, proximal third. Two of three patients with proximal synostoses who were treated surgically had unsatisfactory results because of recurrence of the synostosis. Failla and associates²² reported a series of 20 patients from the Mayo Clinic who underwent excision, with only 7 patients achieving good or excellent results and 13 patients achieving fair or poor results. The timing of synostosis excision appeared to be important, with no good or excellent results in patients operated on less than 12 months after injury or more than 3 years after injury. We use the radiographic appearance of discrete margins and mature trabeculation as the basis of when to resect the lesion. Bone scans and serum enzymes are of little value in deciding when to resect the lesion, and hence, we do not obtain these studies.

Jupiter and Ring ⁴³ subclassified type III forearm synostosis into three types based on the location of theectopic bone. Type III A ectopic ossification is located at or distal to the bicipital tuberosity, Type III B involves the radial head and/or proximal ulnar joint, and Type III C refers to a proximal radial ulnar synostosis contiguous with ectopic bone extending across the elbow to the distal humerus. Eighteen patients underwent operative excision of post-traumatic proximal radioulnar synostosis. Recurrence was seen in only one patient. The 17 patients who did not experience a recurrence regained an average of 139 degrees of forearm rotation. No significant relationship between postoperative forearm rotation and synostosis size, the use of interpositional fat, or the concomitant use of a hinged elbow distractor was identified.⁴³

The surgical treatment of proximal radioulnar synostosis has traditionally been viewed with pessimism. This view has been based on very little published data. The importance of forearm rotation to patient function is well established, and recent experience demonstrates that surgical excision is warranted and is likely to be successful.⁴³

Preoperative planning is necessary to choose the correct surgical approach to remove the entire lesion if this is deemed necessary. CT scans or tomograms can be used to define the anatomy of the synostosis.

If possible, the entire lesion must be resected, and the radius and ulna in the area of the synostosis must be contoured to allow motion without impingement. The intimate proximity of neurovascular structures may limit this resection. Ideally, a free space of at least 5 mm should be created and maintained throughout the intraoperative arc of motion. We prefer not to interpose Silastic or other foreign material, but we do translocate fat into the defect. Patients can be expected to lose about 50% of the intraoperative motion achieved. Accordingly, the surgeon should attempt to achieve at least 120degrees of combined supination and pronation intraoperatively.

An alternative surgical approach to improve forearm rotation in this difficult clinical setting is proximal radial resection as described by Kamenini and Morrey ⁴⁴ (Fig. 31-5). Indications include (1) extensive synostosis not amenable to a safe and discrete resection, (2) articular surface involvement, and (3) associated anatomic deformity. A Kocher approach is recommended to explore the synostosis and the radius distal to the synostosis. One centimeter of bone is excised from the radius, and the remaining exposed bone is covered with bone wax. Postoperative arc of forearm rotation averages 98 degrees. Reankylosis occurred at the site of resection in one patient.

FIGURE 31-5 A and B, Radial head fracture with dislocation develops a typical pattern of ectopic ossification after excision. Extensive bone formation after dislocation with ligament injury (C) and displaced type II coronoid fracture (D).

CLASSIFICATION

There are several discrete clinical circumstances in which ectopic bone develops around the elbow: (1) trauma, usually fracture; (2) closed head or spinal cord injury; (3) burn injury to the extremity; and (4) genetic conditions (Box 31-1). Recently, the process has also been reported to occur after adult respiratory distress syndrome³⁷ and after orthotopic liver transplant.⁶²

BOX 31-1 Patients at Risk for Developing Ectopic Bone About the Elbow

II. Patients with Central Nervous System Injury

A. Traumatic brain injury

B. Elbow trauma in patients with traumatic brain injury

III. Burn Patients

A. Third-degree burns over 20% of total body area

B. Third-degree burns over the elbow

C. Long periods of bed confinement

IV. Patients with Genetic Conditions

A. Fibrodysplasia ossificans progressive

B. History of ectopic bone formation

Radiographically, ectopic bone is seldom seen before 3 weeks after injury or surgery, but it usually can be detected if one looks for it critically. The soft density on the radiograph can be visualized under a bright light. The extent of ectopic bone formation usually is evident by 12 weeks (Fig. 31-6). Bressler and colleagues⁹ studied the maturation process of ectopic bone in 25 CT scans. Persistent, unossified, low-density soft tissue areas were detected adjacent to mineralized areas up to 16 years after injury. In adults, after the maturation process is completed, the bone usually does not resorb. Resorption may occur in children younger than 16 years. Ectopic ossification may be classified by its anatomic formation site or its functional affect on elbow motion and forearm rotation.

FIGURE 31-6 Proximal radioulnar synostosis from radioulnar fracture.

ANATOMIC CLASSIFICATION

Ectopic bone may develop in essentially any tissue about the elbow. Common anatomic location of the abnormal bone varies with etiology. In post-traumatic situations, posterolateral elbow is most often involved. A bone bridge often develops between the lateral condyle of the humerus and the posterolateral olecranon. Bone may also fill the olecranon fossa. A second common location in traumatic cases involve the anterolateral compartment of the elbow. Anterior bone may extend from the distal humerus to the radius and ulna at the level of the bicipital tuberosity. The coronoid is frequently enlarged and blocks elbow flexion because the coronoid fossa cannot accept the volume increase.⁸⁷

Heterotopic ossification of the elbow in the burn patient is most often posteromedial. This can also occur in cases with a traumatic etiology. The cubital tunnel is often obliterated, and the ulnar nerve may be completely encased in bone.

Neurogenic ectopic ossification most commonly develops anteriorly in the flexor muscles or posteriorly in the extensors. Ossification tends to occur with the muscle and follows a single plane. This contrasts to post-traumatic situations in which multiple planes are frequently involved.^6,⁸⁷

The forearm and proximal radioulnar joint may also be involved. Discussion of this classification system is presented in the section on post-traumatic radioulnar synostosis.

FUNCTIONAL CLASSIFICATION

Hastings and Graham ³⁸ have developed the classification based on functional range of motion of the elbow and forearm rotation. Class I ectopic bone refers to the radiographic appearance of abnormal bone without any functional limitations. This should be documented because it signifies a patient’s tendency toward heterotopic bone formation. Prophylactic treatment may be warranted in these patients.

Class II refers to patients with limited range of motion. Class II is subdivided into three types. Class II A refers to limitation of motion in the flexion/extension arc, class II B is limited forearm rotation, and class II C has limitation in both planes. Patients with class III ectopic ossification have ankylosis that eliminates either elbow flexion and extension, pronation and supination, or both. This class is subdivided into three types that are identical to class II.

INCIDENCE OF ECTOPIC BONE FORMATION

ECTOPIC BONE FORMATION FOLLOWING CENTRAL NERVOUS SYSTEM INJURY

First described during the First World War,¹⁶ ectopic bone formation may occur after central nervous system (CNS) injury to the brain or spinal cord.^29,⁷² Garland and others^29,^35,⁴⁰ extensively studied the orthopedic problems encountered by patients with both traumatic brain injury and spinal cord injury (see Chapter 72).