Ectopic Ossification About the Elbow

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CHAPTER 31 Ectopic Ossification About the Elbow

Bernard F. Morrey, G. Dean Harter

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).

Traumatic Brain Injury without Elbow Trauma

In a review of 496 patients with traumatic brain injury, Garland and colleagues ^32,³³ found an incidence of periarticular bone formation in 100 joints in 57 patients (11%). Patients with spastic quadriparesis have the highest incidence of ectopic bone formation. The hip was the most common location, followed by the shoulder, elbow, and knee. Ectopic bone formation developed in 4% of the elbows. Anterior bone formation was deep to the biceps and brachialis muscles and anterior to the joint capsule, occasionally involving the entire brachialis muscle (Fig. 31-7). The posterior ectopic bone was beneath the triceps tendon in close association to the posterior capsule. In Garland’s series,³² the ectopic bone was anterior in six and posterior in 17, and eight of the elbows were completely ankylosed preoperatively. Posterolateral ectopic bone formation is the most common site of occurrence.³⁰

FIGURE 31-7 Extensive proximal radioulnar synostosis (A) treated by excision of a segment of the radius distal to the synostosis (B).

A major determinant of potential successful surgical treatment is the residual neurologic deficit. Twenty-three patients underwent resection of ectopic bone about the elbow. In general, resection should be delayed until at least 18 months after CNS injury to allow maximum functional recovery. The results of excision correlate with the neurologic classification.³² Complications include soft tissue infections and neurologic injury. Recurrence is closely associated with spasticity.³⁰

Traumatic Brain Injury with Associated Elbow Trauma

The incidence of heterotopic ossification about the elbow dramatically increases in patients with fracture-dislocations of the elbow and concomitant head injury. In one study,⁴⁶ ectopic bone developed about the elbow in greater than 90% of patients with this injury complex. Routine prophylaxis in this patient population is logical, although studies demonstrate its efficacy.

ECTOPIC BONE FORMATION IN BURN PATIENTS

Significant ectopic bone formation in burn patients is a rare occurrence. Evans ^20,²¹ listed the following risk factors: (1) the percentage area, (2) the location of the burn, (3) the length of bed confinement, (4) osteoporosis, (5) superimposed trauma, and (6) genetic predisposition. The elbow, shoulder, and hip are the most commonly involved.^20,²¹ In a study of more than 5000 cases at the U.S. Army Institute of Surgical Research, the incidence of ectopic bone formation was only 1.2%, with 82.5% of those cases involving the elbow. This is similar to the recent report of a 1.2% incidence after 1478 burns, of which the elbow is the most commonly involved joint.⁶⁷ Although several studies have reported an incidence of ectopic bone formation varying from 2 to 35 percent,^20,^21,^63,^76,⁸² the incidence of significant ectopic bone formation at the elbow that requires treatment is probably about 1%.²¹

The distribution of the ectopic bone about the elbow in the burn patient is posterior and medial along the medial border of the triceps and anterior in the plane of the brachialis from the anterior surface of the humerus to the coronoid (Fig. 31-8).²¹

FIGURE 31-8 The entire brachialis muscle has been replaced in this 30-year-old man after head injury without elbow trauma.

Evans ²¹ and others¹⁹ have noted that prevention of ectopic bone in the burn patient is best accomplished by reducing the period of bed confinement and the period of postburn hypermetabolic state through the use of early wound excision and grafting. If ectopic bone formation does occur, passive stretching of the joint should be avoided. Active range of motion exercises of the joint within a pain-free arc may continue.¹⁵

Results of excision of heterotopic ossification about the elbow in children with burns was recently reported.³⁶ All patients experienced an improvement in their arc of motion (average increase of 57 degrees), and all patients were able to reach the face and perineum after their operative procedure. No recurrent heterotopic bone was noted.

Selection criteria for excision include (1) decreased range of motion sufficient to cause functional limitations, (2) maturation of new bone confirmed on the radiograph, (3) no evidence of acute inflammation, and (4) complete healing of the skin in the area of the ectopic bone. After excision, most patients have functional range of motion arcs and recurrence is uncommon.^15,³⁹ The most common complication is ulnar nerve irritation.¹⁸

Technical factors include anterior transposition of the ulnar nerve, excision of the ectopic bone and collateral ligaments if they are ossified, and excision of the radial head when forearm rotation is limited.²⁰ In the senior author’s (Bernard F. Morrey, MD) experience, however, radial humeral involvement very rarely occurs. If the anterior aspect of the elbow is significantly scarred by third-degree burns, excision of the scarred areas with release of the contractures and excision of the ectopic bone is recommended.¹⁷ In these complex situations, plastic surgical consultation and assistance should be considered.

FIBRODYSPLASIA OSSIFICANS PROGRESSIVA

Genetic conditions may lead to ectopic ossification about the elbow. Fibrodysplasia ossificans progressiva is a rare genetic disorder characterized by progressive soft tissue ossification. The etiology is a defect in the induction of enchondral osteogenesis.⁴⁵ More than half of patients with this disorder experience ectopic bone formation about the elbow between the third and fourth decades of life. Family history and a history of prior injury causing exuberant heterotopic ossification suggests this diagnosis. Connor and Evans ¹³ and others⁷⁴ have recommended against surgical treatment. Massive amounts of ectopic bone form after surgical intervention and result in predictably poor outcomes. Avoidable factors for the precipitation of ectopic bone in these patients include local trauma, careless venipuncture, intramuscular injections, biopsy of the lumps, and operations to excise heterotopic bone.

PATHOLOGY

The histology of ectopic bone reveals that it resembles normal bone. It is similarly mineralized, and the bone matrix-forming cells produce a highly organized bone containing secondary haversian systems as evidence of bone remodeling.

CLINICAL PRESENTATION

Ectopic ossification about the elbow typically begins to develop approximately 2 weeks following the inciting event. Patients will often experience swelling, warmth, and pain.⁶⁴ Motion loss may also begin to be evident at this time. Early presentation may be confused with cellulitis, deep infection, reflex sympathetic dystrophy, and thrombophlebitis. Infection must be considered and ruled out, especially in patients who have presented with an open injury.

As the process continues, the warmth, erythema, and swelling will gradually resolve. This may be accompanied by diminishing elbow motion. Maturation of the ectopic bone is usually associated with pain resolution. Continued pain at extremes of motion is commonly caused by bony impingement, whereas midarc pain is more commonly associated with articular incongruity, arthritis, or even loose bodies. Pain must be clearly delineated because it is not a common feature of mature ectopic bone.

DIAGNOSTIC STUDIES

LABORATORY STUDIES

Several laboratory variables have been studied in an effort to identify high-risk patients. An increased incidence of the human leukocyte antigen B18 in a group of patients with central nervous system injury and paraosteoarthropathy has been reported.^31,^40,^50,^57,⁷⁸

Unfortunately, the predictive value of serum alkaline phosphatase determinations has not been consistent and the utility of the test in clinical practice is limited.^2,^28,^49,^58,⁶⁴ The test lacks specificity, and, in most cases, the ideal time to initiate prophylactic treatment may have passed. Serum alkaline phosphatase levels are not predictive of bone maturation and are no longer used to determine surgical timing.

Complete blood count with differential, erythrocyte sedimentation rate, and C-reactive protein may be helpful in eliminating infection from the differential diagnosis in patients with early presentation. Overall, however, laboratory evaluation has little benefit in the diagnosis, evaluation, and surgical timing in this disease process.

RADIOGRAPHIC EVALUATIONS

The technetium bone scan is markedly positive during the formation of ectopic bone and usually remains positive for a prolonged time (Fig. 31-9).²⁷

FIGURE 31-9 A, Third-degree burn associated with extensive ectopic bone but a normal joint. B, Surgical excision reliably restores function.

The temporal relation between positive technetium bone scans, serum alkaline phosphatase determinations, radiographs, and the clinical presentation of ectopic bone formation was well illustrated by Orzel and Rudd ⁶⁴ in a study of 50 patients with a variety of injuries (spinal cord trauma, traumatic brain injury, extremity trauma, and so forth). Both the technetium bone scan and serum alkaline phosphatase determinations were abnormal before either the clinical onset or radiographic detection of ectopic bone formation (see Fig. 31-6).

Standard plain radiographs with anteroposterior, lateral, and oblique radiographs are usually sufficient to allow diagnosis, confirm location of abnormal bone, and determine severity. Plain radiographs are also useful in the evaluation of the maturity level of ectopic ossification. In addition, plain radiographs should be carefully evaluated to evaluate elbow joint incongruity, arthritic changes, deformity, and healing of potential associated fractures. Radiographs often will show evidence of heterotopic ossification as early as 2 weeks following an injury. Radiographs must be scrutinized carefully to see the fluffy soft tissue density at this early time frame. During early formation, the heterotopic bone lacks distinct margins and trabeculation is absent. With maturity, margins become sharply defined and trabeculations develop. The typical location of heterotopic bone development in various clinical scenarios is discussed in other sections of this chapter.

CT may be helpful to provide improved localization of heterotopic bone. This study is especially helpful in the evaluation of the proximal radioulnar joint.

Bone scans and magnetic resonance imaging (MRI) scans are not routinely needed in the evaluation of the stiff elbow. Pittinger ⁶⁸ believed that ectopic ossificationshould not be excised before 12 months after onset. This was based on the belief that excision of active ectopic bone would lead to recurrence. However, more recent studies dispute this claim. Jupiter⁴³ and McAuliffe⁵³ have shown that active ectopic ossification about the elbow can be excised without an increase in recurrence.

GENERAL PRINCIPLES OF TREATMENT

Not all ectopic bone formation about the elbow requires surgical treatment. Ectopic ossification that does not produce symptoms or interfere with the functional arc of elbow rotation should be treated without surgery. The goal of treatment is not, and should not be, normal motion. The main indication for surgical management is ectopic bone producing an arc of elbow motion that is less than functional and limits the patient’s activities of daily living or interferes with occupational or recreational pursuits. Morrey et al ⁶¹ has shown that a functional arc of motion about the elbow includes a flexion-extension arc of 30 to 130 degrees and forearm rotation of 50 degrees of pronation and supination. Ninety percent of activities of daily living can be performed within this motion arc.

Surgical expectation of the patient and surgeon need to coincide. Patients must understand the concept of a functional motion arc as well as the risk-benefit ratio. Each patient must also be committed to a rigorous postoperative therapy and splinting program.

Tomograms may be necessary to determine whether the joint surfaces are congruous. In traumatic circumstances, if the joint surfaces are not congruous, total elbow arthroplasty or distraction arthroplasty may be necessary. The maturation is judged with plain radiographs. We do not employ laboratory tests or technetium bone scans because they are of limited value for determining the timing of resection.

When considering surgical excision of heterotopic ossification about the elbow the following criteria should be considered: (1) symptomatic limitation of elbow motion; (2) healing of associated fractures; (3) congruent articular surfaces; (4) lack of severe arthritic changes; (5) soft tissue stabilization about the elbow; (6) stabilization of brain injury; (7) patient motivation and understanding of the surgical goals and postoperative regimen.

General principles include (1) excision of all motion-limiting heterotopic bone; (2) avoiding articular cartilage damage; (3) atraumatic tissue handling; (4) careful hemostasis; (5) suction drainage of the wound; (6) avoiding the creation and deposit of bone dust in the joint by the use of osteotomes rather than saws; (7) meticulous lavage; (8) avoiding neurologic injury; and (9) early postoperative range of motion. Careful preoperative planning is crucial to identify areas to be resected and the appropriate and safe surgical approach to access all involved heterotopic bone.

Timing of Surgical Treatment

The appropriate timing of surgical intervention remains controversial; however, the trend is toward earlier surgical excision of function-limiting ectopic ossification about the elbow. As previously discussed, recent articles have demonstrated no evidence of increased recurrence rates when early excision is performed.^38,^43,⁵³ Various methods of postoperative prophylaxis were used in this study (including no prophylaxis). Long surgical delays are not without risks. Severe limitation of elbow rotation is extremely disabling and persistent contracture may lead to articular cartilage destruction. Many surgeons now consider a 3- to 4-month interval adequate and proceed with surgical excision at that time. The senior author still prefers to wait at least 6 months.

A surgical delay in excess of 6 months, however, is appropriate in certain situations. Surgical delays in burn and head injuries etiologies allow soft tissue maturation and maximum neurologic recovery. The pediatric population also may benefit from prolonged observation as spontaneous resolution is known to occur.

Indications to Interpositional Arthroplasty and Total Elbow Arthroplasty

Radiographic evaluation of patients with elbow ectopic ossification should include consideration of associated elbow incongruity and arthritic changes. Joint surface incongruity could represent arthritic surface malunion or residual elbow instability. Both can lead to progressive arthritic changes about the elbow and require treatment at the time of ectopic bone excision. Malunions are best treated with osteotomy and residual instability with ligamentous repair or reconstruction as indicated.

Concomitant interpositional arthroplasty is indicated in a younger patient with coexisting articular surface damage representing greater than 50% of the joint surface.⁵⁹ This same scenario in an older patient or more sedentary patient, is probably best managed with total elbow replacement. The age cutoff for these procedures is controversial.⁶⁶

ULNAR NEUROPATHY IN ASSOCIATION WITH ECTOPIC BONE FORMATION

Late ulnar neuropathy may occur as a result of compression in the cubital tunnel from ectopic bone. Sometimes when completely encased in bone, it is further at risk if elbow motion increases while it remains tethered or compressed by the ectopic ossification. Although ulnar neuropathy from ectopic bone is most often found in the brain-injured adult,^32,^34,^47,⁸⁹ it occurs after burns⁸⁸ and trauma as well. In a 5-year period, 2.5% of the adult brain-injured population in one study developed late ulnar neuropathy.⁴⁷ Fourteen percent had a history of trauma, and 86% were found to have idiopathic heterotopic ossification associated with spasticity. Treatment consisted of ulnar nerve transposition anteriorly, with 85% of the patients having complete recovery. We completely free the nerve from the ectopic bone for a distance of 3 cm with preservation of function. Simple subcutaneous translocation of the nerve is adequate. If completely surrounded by bone, I usually release the nerve, remove the ectopic bone and replace it in its bed, or translocate the nerve if it is stretched by motion.

Indications for Ulnar Nerve Transposition

Ulnar nerve transposition is frequently indicated when surgical excision of ectopic ossification is undertaken. Simple subcutaneous transposition is the procedure of choice. Submuscular transposition is undesirable in this clinical scenario due to poor muscular beds, scarring, and prior zones of injury. The most common indication for transposition is associated ulnar nerve symptoms preoperatively. Further indications include preoperative flexion of less than 90 degrees and a preoperative arc of motion less than 60 degrees.

SURGICAL TECHNIQUES

In all instances, the basic surgical strategy is to remove the ectopic bone at its narrowest portion, and with the least risk to the articulation. It is often possible to visualize the interface between normal and heterotopic bone. Avoid injury to cartilage by excising enough bone to initiate some motion and define the joint line. Once some motion is initiated, additional bone is resected as necessary.

Capsular contracture releases are also often indicated to achieve a functional arc of motion. Both anterior and posterior capsular releases may be required in addition to heterotopic bone resection. The collateral ligaments are preserved, even if calcification is seen in these structures radiographically. Ligamentous calcification is not true heterotopic ossification and rarely limits motion. The operation is not complete until near full range of motion is returned. A flexion-extension arc of 10 degrees to 140 degrees and forearm rotation arc of 60 degrees to 60 degrees should be obtained.

POSTOPERATIVE MANAGEMENT

If the process involves muscle fibers, the surgical field is treated with 700 cGy radiation. Otherwise, 75 mg indomethacin is prescribed 3 weeks before and 8 weeks after surgery. The elbow is managed with continuous motion and splints as described in Chapters 10 and 11. When motion goals are not met, manipulation under anesthesia is performed 6 weeks after surgery.

The use of postoperative radiation remains controversial. Gaur et al ³⁶ found no recurrence in children with burns as the etiology. Jupiter and Ring⁴³ found no recurrence in 17 patients in whom post-traumatic radioulnar synostoses were excised. No prophylaxis was used in either patient group. However, Jupiter and Ring⁴³ later reported on surgical treatment of complete anklyosis about the elbow and found recurrences in one third of the trauma cohort and one patient in the burn cohort. The authors now use prophylactic radiation routinely. Prospective randomized studies are needed to further define the use of this modality.

ADJUVANT TREATMENT TO PREVENT ECTOPIC BONE FORMATION

There are three main adjuvants to reduce the likelihood of ectopic bone formation after excision: (1) oral nonsteroidal anti-inflammatory agents, (2) oral diphosphonates, and (3) low-dose external beam irradiation.

Several authors have shown that indomethacin is an effective agent ^54,^71,⁷⁷ that significantly reduces the formation of ectopic bone about the hip. The recommended dosage is 75 mg daily for 6 weeks after surgery.^54,^71,⁷⁷ We typically begin the treatment 1 to 2 weeks before the surgery but have no scientific basis for this practice.

Oral diphosphonates have been used,^24,^79,⁸³ and experimental data have shown this class of drug to delay the mineralization of osteoid.⁶⁹ Unfortunately, when these drugs are discontinued, the osteoid may mineralize.^77,⁸⁰

Low-dose external beam irradiation has been shown to be an effective method of preventing ectopic bone formation about the hip after total hip arthroplasty ^3,^4,^14,⁴⁹ and following acetabular fractures.⁶ Recent studies noted effective control of ectopic bone with only 700 cGy in a single dose.^3,⁴ External beam irradiation should be delivered to the high-risk patient within 24 hours and no later than 72 hours after surgery. Delay of radiation treatments beyond 72 hours significantly reduces its effectiveness. Potential or theoretical problems of low-dose irradiation include wound healing problems and nonunion. The risk of postirradiation sarcoma is extremely rare. In the past 10 years, we have treated more than 100 patients with low-dose irradiation for control of ectopic bone formation about the elbow and hip, and we have never detected delayed wound healing that was attributable to the low-dose irradiation. When necessary, bone graft fracture sites may be shielded.²⁵ In our experience, there have been no nonunions directly attributable to the low-dose irradiation. There are more than 130 postirradiation sarcomas in the Mayo Clinic files, and none has been caused by the use of low-dose irradiation for the prevention of ectopic bone.²⁶ We have found no instance of sarcoma to have developed after doses of 3000 cGy or less.