Nonunion of Clavicle Fracture

 

 

Nonunion of Clavicle Fracture

                             Dr. KS Dhillon

Introduction

About 5% to 10% of all fractures are clavicle fractures [1,2]. The incidence of clavicle fractures has increased over the past decades [3]. It is often believed that clavicle fractures are entirely benign lesions with a high rate of healing and excellent functional outcome. However, following the fracture and before the fracture heals many complications can occur. Berkheiser [4] reported nine cases of nonunion, six with brachial plexus injury, and he attributed this high complication rate to the increased energy of the initial trauma. There are other authors [2,5,6,7,8] who have also reported potential problems with these fractures.

Various criteria have been used to define a nonunion. A nonunion usually describes a fracture that has not adequately healed between 6 and 9 months following the injury. A delayed union is a fracture that has not healed after 3 to 6 months [9,10]. Some clinicians believe that a clavicle fracture is nonunited if the fracture has not adequately healed 4 months after the injury [1,8,11,12].

The nonunion rate after closed fracture treatment of a clavicle fracture is between 0.1% to 15% [2,13]. Rowe [5] and Neer [2] found a higher nonunion rate in patients treated with surgery. Non-unions can produce significant disability, such as pain, altered shoulder mechanics, and neurovascular injury.  Hence surgical treatment may be necessary to achieve union. Successful treatment of a clavicular nonunion is often a difficult task.

Anatomy, Function of the Clavicle and Nonunion

The only long bone to ossify by the intramembranous process is the clavicle. It is also the first bone to ossify in the fifth week of fetal life [14]. The ossification starts at a centrally located ossification center. Secondary centers of ossification develop at both ends of the growing bone. The medial ossification center ultimately accounts for up to 80% of the longitudinal growth [1].

The clavicle has a double curvature with a convex anterior curve medially and a convex posterior curve laterally [14]. The proximal and distal ends of the clavicle are secured firmly by strong ligaments and muscle attachments. The central section is free of protective attachments [5]. 

The sternocleidomastoid muscle creates a superior force vector medially and the weight of the arm and the pull of the pectoralis major muscle produces an inferior and medial force to the lateral clavicle [15]. During abduction of the arm, the clavicle angles upward by 30° and posteriorly by 35° and it also rotates about its longitudinal axis as much as 50° [1]. These motions produce bending moments in the coronal and sagittal planes, which are concentrated at the middle section of the clavicle [1]. The middle third of the clavicle is commonly fractured and is more prone to nonunion because anatomically the middle third of the clavicle has relatively sparse cancellous bone with few soft tissue attachments and large forces concentrated in this area [15].

The clavicle serves several important functions [14]. It acts as a rigid base for muscular attachments and it forms a strut holding the glenohumeral joint in the parasagittal plane, thereby increasing the range of motion of the shoulder joint and the range of grasp in three-dimensional space for the hand. It also increases the power of the arm-trunk mechanism above the shoulder level. The clavicle provides a protective mechanism for the brachial plexus and the vascular structures of the neck and the extremity. It also serves a cosmetic function by providing a gentle curve to the base of the neck. Fracture, loss, or shortening of the clavicle can result in significant disability. It is important to restore the continuity and normal length of the clavicle when treating a clavicular nonunion.

There are many factors that lead to a nonunion of the clavicle. These include [2,4,5,6,7,8,11,12,13,16,17,18,19,20,21]:

• Severity of initial trauma

• Marked initial displacement with shortening

• Soft tissue interposition

• Primary open reduction and internal fixation

• Refracture

• Open fractures

• Inadequate initial immobilization

• Polytrauma

The severity of the injury and resultant initial displacement of the fracture contributes to the development of nonunion [4]. Ghormley et al [6] found a nonunion in 10 of 20 cases with severe initial displacement. Manske and Szabo [12] found during surgery that 50% of their patients with displaced atrophic nonunions had trapezius muscle interposed at the fracture site, which contributed to nonunion. In a retrospective study of 242 displaced middle-third fractures, Hill et al [13] found that initial shortening of the clavicle at the fracture site of 2 or more cm had a highly significant association with nonunion.

Nonunion can develop when there is inadequate initial immobilization. Ghormley et al [6] stated that severe initial injuries and improper immobilization would appear to be the chief causes of nonunion. 

Rowe [5] found that the figure-of-eight splint is usually inadequate because the strap can slide laterally and actually increase the deformity. He used a modified half-shoulder spica to treat displaced clavicle fractures. 

Sakellarides[8] and Wilkins and Johnston[11] were of the opinion that decreased immobilization time can contribute to nonunion. They could not, however, define a significant relationship between a specific duration of immobilization and the development of nonunion. There are other studies, that have found no difference in outcomes with the various types of conservative treatment. Andersen et al [22] found no differences in union rates, functional results, alignment of fractures, and cosmetic results in patients treated with figure-of-eight immobilization and those treated with only a simple sling.

There are several studies that have cited primary operative intervention for closed fractures as a leading cause of nonunion [2,5,8,17]. Neer [2] noted a 0.1% nonunion rate in closed fractures treated conservatively and a 4.6% nonunion rate in those treated with primary open reduction and internal fixation. Rowe [5] cited a 0.8% nonunion rate with closed treatment and a 3.7% nonunion rate with surgical treatment.

More recent studies have reported a high complication rate with primary open reduction and internal fixation. Bostman et al [23] reported a 23% complication rate with primary open procedures, including nonunion in 3%, delayed union in 3%, and malunion rates in 12% of the patients.  Poigenfurst et al [24] reported four plate breakages before union and four refractures after plate removal among 102 patients treated with primary open reduction and internal fixation. Schwarz and Hocker [25] reported a 12% failure rate with primary open reduction and internal fixation of 36 clavicular fractures.

There are, however, other studies that have reported that primary open reduction and internal fixation does not necessarily predispose to nonunion of the clavicle fracture [26,27,28]. The author was of the opinion that primary open reduction and internal fixation should be done on significantly shortened and displaced fractures to prevent nonunion or malunion and the resultant disability.

There are two large studies that have pointed out the problems with nonoperative treatment of displaced fractures. Hill et al [13] in a review of 52 patients with displaced middle third fractures of the clavicle found that 15% of the patients developed a nonunion, and 31% reported unsatisfactory results. They found a significant correlation between initial shortening of 2 cm or more and nonunion and between final shortening of 2 cm or more and unsatisfactory results.

Eskola et al [16] found that 30% of patients with clavicular fractures had neurologic symptoms after the fracture healed. They also found that there was a significant correlation between shortening of more than 1.5 cm and the degree of pain.

Zenni et al [26] treated 25 clavicle fractures by open reduction and internal fixation with a threaded intra-medullary pin or wire. They had a 100% union rate with no hardware migration. Their indications for surgery included: neurovascular compromise, fracture of the distal third of the clavicle with disruption of the coracoclavicular ligament, severe angulation and comminution of middle-third fractures, the patient's inability to tolerate prolonged immobilization, and symptomatic nonunion. 

Khan and Lucas [27] obtained a 100% union rate with open reduction and internal fixation of 20 clavicle fractures. Their patients had pain relief within 20 hours of the operation, compared to 3 weeks of pain and disability in patients treated with conservative measures, as described by Rowe [5]. Their indications for surgery included: gross displacement of the fragments with soft tissue interposition, neurovascular complications, multiple injuries or coma, and severe prolonged pain.

Faithfull and Lam [28] also reported a 100% union rate with open reduction and internal fixation of 18 acute midclavicular fractures. Their indications for operation were gross displacement and comminution or shortening of more than 1.5 cm. They noted that malunion with shortening of midclavicular fractures, especially in young patients can produce disability.

In patients with floating shoulder who have clavicle fracture with a displaced scapular fracture open reduction and internal fixation is indicated [29]. In this injury, the entire superior suspension complex of the shoulder is disrupted. This results in an extremely unstable shoulder girdle, with drooping shoulder and limited range of motion [30]. Internal fixation of the clavicle restores the superior suspension complex.

Symptomatology

A careful history and physical examination is carried out to find out the type of symptoms and disability, if any, the patient is experiencing before performing surgery for a nonunion. According to Wilkins and Johnston [11] a nonunion can be asymptomatic, especially an atrophic nonunion. Their study showed that only 3 of 11 patients who had atrophic nonunions were symptomatic enough to require surgery, as compared with 16 of 22 patients who had hypertrophic nonunions. They stated that the absence of callus in an atrophic nonunion can diminish the grating and crepitation that may be responsible for pain at the nonunion site. They were of the opinion that patients with atrophic nonunions should be followed for at least 6 months before surgery is contemplated. They believe that many patients will become asymptomatic during that time interval.

Most studies show that patients who have clavicular nonunions do have some form of disability. According to Olsen et al [21], atrophic nonunions do not become asymptomatic.  Pain at the site of nonunion, altered shoulder mechanics, "ptosis" of the shoulder, or a compression lesion involving the underlying brachial plexus or vascular structures can produce disability. Manske and Szabo [12] found that pain was the prominent symptom in all 10 of their patients who had a nonunion. Wilkins and Johnston [11] reported that 17 of 19 of their patients who had symptomatic nonunions had moderate to severe pain. Boehme et al [15] reported that pain was the prominent symptom in 18 of 21 of their patients with nonunion.

In the acute phase, neurologic symptoms can develop as a result of stretch injury or bone fragment compression. In the chronic phase, the neurological symptoms can result from compression from healing of the fracture with inferior and posterior displacement of the distal fragment or massive callous, or from motion of the nonunion [31-37]. Kay and Eckardt [37] reported that acute traction neuropathies most commonly involve the lateral cord of the brachial plexus. Delayed compressive neuropathies most commonly involve the medial cord. Compressive neuropathies affect the medial cord due to entrapment from hypertrophic callus in the costoclavicular space between the clavicle nonunion site above and the first and second ribs below [4]. The medial cord crosses the first rib in this area [4]. Compressive neuropathy can develop anywhere from 3 weeks to 10 years after the injury. Hence, it is important to follow the patient's neurologic status for an extended period of time [37].

Vascular complications can also develop. There are several factors that play a role in preventing vascular injury [33]. One of the factors is the direction of displacement of the fracture fragments, with the distal fragment being displaced inferiorly and anteriorly due to gravity and the proximal fragment being displaced superiorly and posteriorly into the trapezius muscle by the trapezius and sternocleidomastoid muscles. This prevents the major vascular structures from being compressed between the bone ends. The subclavius muscle and the deep cervical fascia act as barriers between the bone ends and blood vessels. Vascular injuries ranging from subclavian vein compression or thrombosis to arterial ischemia have been reported [20,31,32,33,34].

The incidence of neurovascular complications in the literature varies. In his 18 cases of nonunion Neer [2] reported no neurovascular complications. Ghormley et al [6] reported only one case of neurovascular injury in 20 nonunions. Wilkins and Johnston [11] reported 2 neurovascular complications in 33 nonunions. Sakellarides [8] had 3 neurovascular complications in 20 nonunions.

Berkheiser [4] on the other hand reported a relatively high rate of neurovascular compromise. He had 6 neurovascular complications in 9 nonunions. Connolly and Dehne [34] and Jupiter and Leffert [20] have reported high rates of neurovascular injury from nonunion: 7 of 15 nonunions and 9 of 23 nonunions, respectively. Connolly and Dehne [34] reported that nonunion of the clavicle was the most common cause of thoracic outlet syndrome.

Surgical treatment

Surgery is indicated for symptomatic nonunion of the clavicle. Pain at the nonunion site is the most frequent symptom in patients with nonunion of the clavicle. Neurovascular compromise is another indication for surgery. Other indications include extremity dysfunction due to weakness, stiffness, or ptosis.  

The surgical procedures can be divided into two main categories i.e. salvage and reconstructive [1]. Reconstructive procedures are to achieve bone union. Salvage procedures are done to alleviate symptoms or deformities without achieving bone union. 

Salvage procedures are carried out by removing a bony prominence or performing a partial or total removal of the clavicle to provide relief from pain or to release trapped neurovascular structures. Abbott and Lucas [38] were of the opinion that the middle third of the clavicle may be removed without significant disability. Rowe [5] was of the opinion that removal of the entire clavicle results in a "surprisingly good functional and cosmetic appearance". This should, however, be done only after the patient has had several unsuccessful bone-grafting procedures and is "sufficiently" disabled.

Connolly and Dehne [34], however, were of the opinion that resection of the midclavicle should be avoided because it is likely to lead to problems later. They believe that patients in general are not satisfied with the outcome or the appearance after resection. They felt that taking into account the important functional role of the clavicle and the successful reconstructive options available, an attempt should be made to achieve bone union in patients with symptomatic nonunions.

For reconstructive procedures, there is a wide array of fixation methods for the treatment of clavicular nonunions. These include external fixation [18], threaded and unthreaded pins [11,39,40], and plate and screw osteosynthesis [12,15,19,20,21,41,42,43,44,45]. 

Schuind et al [18] used a Hoffman external fixator to treat both acute fractures and nonunions. He had a 100% union rate. Two pins were placed in the medial fragment and two pins were inserted in the lateral fragment. On average, the external fixator was used for 51 days. The indications for this type of fixation were an open fracture or a septic nonunion. 

Intramedullary pin fixation with autogenous bone grafting can be used to treat clavicle nonunions. Boehme et al [15] described a technique in which the skin incision is made in the Langer line, centered over the nonunion site. After excision of the fibrous nonunion, a modified Hagie pin is inserted into the intramedullary canal. The pin is drilled out from the nonunion site through the intramedullary canal of the distal fragment. A small skin incision is made over the pin at the lateral end of the clavicle. The pin is then pulled from the clavicle until its end is at the level of the nonunion site. The fracture is then reduced, and the pin is drilled across the fracture site and into the medial fragment of the clavicle. The tip of the pin is left palpable in the subcutaneous tissue laterally. The bone graft is then placed around the nonunion site.

Using this technique, Boehme et al [15] achieved a 95% healing rate in 21 patients. Capicotto et al [40] obtained a 100% union rate with a similar procedure using Steinmann pin fixation. Boehme et al [15] stated that the advantages of using an intramedullary pin over other forms of fixation such as plate and screws included a cosmetically acceptable incision; less dissection of the soft tissues; and easy removal of the pin through a small incision under local anesthesia. Furthermore, the intramedullary pin is a load-sharing device, as compared with plates and screws, which are load-bearing devices. Therefore, osteoporosis that occurs under a plate as a result of stress shielding is less severe with an intramedullary pin, and the likelihood of refracture through osteoporotic bone after hardware removal is reduced. With this technique, however, there is a lack of rotational control with the pin [12,20]. Another disadvantage with pin fixation is the potential for pin breakage and migration, which can result in serious neurologic and pulmonary complications [46,47,48].

Connolly and Dehne [34] described a technique using Knowles pin for fracture stabilization. They believed that this technique is particularly suitable for hypertrophic nonunions. The Knowles pin is inserted from the anterior cortex of the medial fragment into the lateral fragment under fluoroscopic guidance. The Knowles pin locks against the anterior cortex and provides good fracture fixation and compression. One main advantage of this technique is that there is minimal periosteal stripping as in intramedullary pin fixation. 

The last method of fixation is plate and screw osteosynthesis. Edvardsen and Odegard [41] described a technique where debridement and trimming of the bone ends are done, a cortical bone transplant is placed posteriorly, and a metal plate placed anteriorly, and the plate is fixed to the clavicle and cortical bone transplant with screws. They achieved a 100% union rate in 6 patients with posttraumatic nonunion. With the cortical bone graft posteriorly and plate anteriorly, the construct is stable, but an extensive amount of soft tissue stripping is needed. 

Manske and Szabo [12] treated 10 nonunions with an AO dynamic compression plate and iliac crest cancellous bone graft. All the clavicles united at an average of 19 weeks after surgery. All patients had a full painless range of motion.

Jupiter and Leffert [20] reported an 89% union rate following plate fixation and bone grafting in 18 nonunited fractures of the middle third of the clavicle. The authors said that it is important to restore the normal length of the clavicle because shortening can cause abduction weakness and can increase the forces at the fracture site [16,20]. Seiler and Jupiter [42] addressed the restoration of clavicular length by using intercalary tricortical iliac crest bone grafts to treat clavicular nonunions with bony defects. Preoperatively they determined the size of the bone graft by comparing the anteroposterior radiographs of both clavicles. The nonunion site was debrided, and the medullary canals were opened medially and laterally using a drill bit. The tricortical iliac crest graft taken was 1.5 times larger than the calculated defect. The ends of the graft was trimmed to fit into the medullary canal of the fracture fragments on either side. The graft was then placed in the defect and secured to the medial and lateral fragments with a limited contact dynamic compression plate. 

The authors obtained union in all 8 patients treated with this technique within 3 months of the surgery. Olsen et al [21] also emphasized the importance of re-establishing the original clavicular length. They, however,  used autologous cancellous bone graft to fill the defect rather than a tricorticocancellous graft.

Ballmer et al [49] also emphasized the importance of restoring clavicular length. They treated 37 delayed unions and nonunions of clavicle fractures with decortication, plate osteosynthesis, and bone grafts. They achieved a 95% union rate. Nine of their patients required tricorticocancellous grafts to restore clavicular length. Tricorticocancellous graft was used for clavicular shortening of more than 1.5 cm. 

Boyer and Axelrod [45] described a technique that produces shortening of the clavicle. They excised the nonunion by making cuts at 45° to the long axis of the clavicle, and they stabilized the fragments with either a pelvic reconstruction or dynamic compression plate with a lag screw. They placed cancellous bone at the nonunion site. According to the authors their technique respects AO principles for the treatment of nonunions, allows early mobilization, and minimizes morbidity at the donor site. All of their seven patients with clavicular nonunions healed and returned to normal function. A 1.5 cm was the average reduction in length. According to the authors, the resultant lack of restoration of the shoulder width proved to be cosmetically acceptable and gave excellent function.

Bradbury et al [44] compared the outcome of an AO dynamic compression plate and an AO pelvic reconstruction plate for the treatment of clavicular nonunions. They reported a 97% union rate (31 of 32 nonunions) and they found no significant differences between the two plates. They found that the reconstruction plate was much easier to contour to the sigmoid shape of the clavicle.

Mullaji and Jupiter [19] preferred a 3.5-mm low-contact-dynamic compression plate (LC-DCP). They reported a 100% union rate in six patients treated with the LC-DCP. The useful features of the LC-DCP include a structured under-surface that preserves the blood supply beneath the plate, avoidance of stress risers after implant removal, and oblique undercuts to the screw holes that allow for insertion of lag screws up to an angle of 40°. The plate is made of titanium, which is twice as flexible as steel, hence rendering it less prone to fatigue failure when used to span a defect. The LC-DCP has universal screw holes that allow compression in either direction. This permits compression of the intercalated graft to both the medial and lateral fragments.

The overall advantages of plate and screw osteosynthesis over other methods of fixation include excellent control of rotation and the ability to restore the normal length of the clavicle. According to Jupiter and Leffert [20], the apex of deformity in a clavicular nonunion is superior; therefore, a plate applied to the superior surface can act as a tension band, which enhances compression across the fracture. The disadvantages of plate fixation include the need for wider exposure and increased periosteal stripping, which can disturb the blood supply to the healing fragments. 

Rehabilitation

Postoperatively for 6 weeks the patient wears an arm sling and performs passive range-of-motion exercises with passive forward elevation limited to 90°. Six weeks after surgery the patient's range-of-motion exercises can include passive forward elevation above 90°. At 3 months or when the radiographs reveal good consolidation of the bone graft the patient can begin active forward elevation and progressive resisted strengthening exercises. Anteroposterior radiographs and anteroposterior radiographs at 15° cephalic tilt are done to assess bone healing. If the degree of healing by plain radiographs is difficult, tomograms or computed tomography scans can be done.

Conclusion

Clavicular fractures have a relatively low nonunion rate. When a nonunion occurs, it is usually symptomatic and can cause significant disability. Symptoms due to nonunion include paresthesia, pain, extremity weakness from neurovascular entrapment, crepitation at the fracture site, shoulder weakness from disturbed shoulder mechanics, and unacceptable cosmetic appearance.

There are many treatment options for a clavicular nonunion. They range from conservative management to multiple surgical procedures. If the patient is symptomatic, usually surgery is recommended. There are two broad groups of surgical options available i.e. salvage and reconstructive procedures. The emphasis is on obtaining union in an anatomic position to restore normal shoulder mechanics and provide the best possible functional outcome. Hence, reconstructive procedures are recommended. Open reduction and internal fixation with plates and screws and with intercalary bone graft is needed to achieve this goal.

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