Distal Humerus Fractures

                        Distal Humerus Fractures
  

                                        Dr. KS Dhillon

Introduction

Fractures of the distal humerus constitute about 2% of all fractures in the adult population [1]. The overall incidence of distal humeral fractures in adults is 5.7 cases per 100,000 in the population per year. The male to female ratio is about equal. There is a bimodal age distribution with the first peak in young individuals resulting from high-energy trauma and the second peak in the elderly osteoporotic population. Two-thirds of those affected are aged 50 years or older. The incidence of these fractures is rising. 

Simple falls are the most common overall cause of the fracture, and the majority of the fractures are extra-articular or complete articular fractures [2]. 

The aim of treatment is to restore a functional elbow in the functional range of motion between 30 to 130 degrees [3]. Loss of elbow movements can severely affect activities of daily living and lead to a loss of independence, especially in elderly individuals [4]. Treatment of these fractures can be challenging due to fracture comminution, poor bone quality as well as difficulty in restoring the complex anatomy of the distal humerus [5].

Most of the distal humerus fractures used to be treated non-operatively in the past and the treatment often resulted in significant functional impairment [2]. 

However, with evolution in implant design and surgical technique, the outcome of operative treatment has improved and this has made internal fixation of the fractures as the current standard of care. The aim of surgical treatment is to restore articular congruity and bony alignment while providing rigid, stable fixation that enables early active motion [6]. 

         

Anatomy of Distal Humerus

In the coronal plane, the distal humerus is triangular in shape. It is formed by the medial and lateral columns which are linked by the articular segment as shown in Fig.1. 

The distal end of the humerus includes two smooth articular surfaces (capitulum and trochlea), two depressions (fossae) that form part of the elbow joint, and two projections (medial and lateral epicondyles). The capitulum laterally articulates with the radius; the trochlea, a spool-shaped surface, articulates with the ulna. The articular surface is in 4-8 degrees of valgus relative to the shaft and flexed 40 degrees relative to the shaft.

               

                                                        Fig 1. Anatomy of distal Humerus

Classification of Distal Humerus Fracture

The AO classification divides distal humeral fractures into three groups namely, A, B, and C with complexity and severity increasing.

Müller’s classification of distal humeral fracture is part of the AO scheme. This region is marked 13, so each type has this prefix, e.g. 13-A1.

Type Description

Type A:   Extraarticular fractures:

13-A1:    Apophyseal avulsion

13-A2:    Metaphyseal simple

13-A3:    Metaphyseal multifragmentary (comminuted)

Type B:    Partial articular fractures:

13-B1:     Sagittal lateral condyle

13-B2:     Sagittal medial condyle

13-B3:     Frontal

Type C:   Complete articular fractures:

13-C1:     Articular simple, metaphyseal simple

13-C2:     Articular simple, metaphyseal multifragmentary (comminuted)

13-C3:     Articular, multifragmentary (comminuted)

Imaging for Distal Humerus Fractures

All attempts are made to obtain good-quality radiographs. This may be difficult due to patient discomfort. The AP is taken with the elbow flexed to 40 degrees. This facilitates olecranon disengagement from the fossa which allows for better visualization of the distal humerus. The lateral images are taken with the shoulder abducted to 90 degrees and the elbow flexed to 90 degrees with the plate underneath the medial aspect of the elbow. A CT scan is useful to assess articular involvement and aid surgical planning. 

Non-Operative Treatment

Over the decades, there are only a few conflicting reports available in the literature on the outcomes of conservatively treated fractures of the distal humerus. Non-operative treatment involves splintage for pain relief followed by gentle mobilization. 

Nauth et al [7] showed that in elderly patients, those treated non-operatively were almost three times more likely to have an unacceptable result as compared to those treated operatively. Non-operative treatment is usually reserved for undisplaced fractures, for patients with dementia, and those who are not fit for anesthesia. Recently Aitken et al. reported that non-operative treatment could give a modest functional result in low-demand patients while avoiding substantial surgical risks [8].

Operative treatment 

Distal humerus fractures are commonly treated by surgery if the fracture is displaced and the patient is fit for surgery.

There are three surgical approaches to the distal humerus, namely the triceps reflecting, triceps splitting, and the trans-olecranon approach. The trans-olecranon approach gives the best articular exposure but it carries the risk of non-union, future need for the removal of implants, and potentially limiting any future arthroplasty. 

The triceps splitting approach has the potential to result in triceps weakness. The triceps reflecting technique spares the triceps mechanism and has the advantage of avoiding damage to the extensor mechanism. This approach, however, provides limited exposure of the articular surface.

For complex intra-articular fractures (type C), an olecranon osteotomy is usually preferred.

The aim of treatment is to obtain anatomic reduction and rigid internal fixation which will allow early mobilization. Rigid plate fixation gives better functional outcomes as compared to fixation solely with Kirschner wires or screws [9]. Plate fixation is now the standard treatment for distal humerus fractures. Although perpendicular plating was originally advocated by the AO group, parallel plating has now grown in popularity. Studies have shown that parallel plating provides better stability compared with the perpendicular locking system [10,11]. Clinical studies show there are no differences between the groups (perpendicular and parallel plates) in terms of functional outcome or complication rate [12,13]. The use of locking compression plates has been advocated for osteoporotic fractures as they provide angular stability and the head-locking mechanism potentially results in a stiffer construct [24]. 

Different length plates are used for fracture fixation to avoid a stress riser at the end of the plates and avoid the risk of a peri-prosthetic fracture. Post-operatively a back slab used for one to two weeks to protect the wound. Passive mobilization is carried out from two weeks and active mobilization after six weeks.

Despite the improvements in surgical techniques and evolution of implant designs, operative fixation of distal humerus fractures have been associated with dissatisfaction in about 15% of patients and complication rates of up to 35% [14,15]. Some of the factors that are known to affect clinical outcome include fracture comminution, reduction accuracy, fixation stability, and quality of postoperative rehabilitation [16]. 

Complications of operative treatment of distal humerus fracture

Complications can include hardware failure, fracture, malunion, non-union, infection, heterotopic ossification, elbow stiffness, ulnar neuropathy, and complications from olecranon osteotomy [17].

• Mechanical failure-- Mechanical failure is known to occur in 7–27% of patients [18,19,20]. Risk factors for failure include bone quality, such as osteoporotic or osteopenic bone, the complexity of the fracture,  bone defects, mechanical properties of implants, and postoperative rehabilitation [21]. Poor surgical technique is another risk factor. 
• Ulnar neuropathy-- Ulna neuropathy as a complication of distal humerus fractures, preoperatively and/or postoperatively, occurs in 0% to 51% of the patients, with an average of 13% [17]. The palsy can occur either at the time of the injury or intraoperatively. It can also occur secondarily due to swelling, to scar tissue development and thickening in the fibro-osseous tunnel, or due to hardware irritation. The true incidence of ulnar nerve dysfunction after elbow injury remains unknown. It appears that anterior transposition of the ulna nerve does not decrease the development of ulnar neuropathy after internal fixation of the fracture [17]. 
• Heterotopic ossification--The incidence of heterotopic ossification (HO) after internal fixation of distal humerus fractures varies widely from 0% to 49%. However, pooled analysis of data from several studies shows an overall prevalence of 8.6% [17]. There are several risk factors for HO and these include, concomitant head and central nervous system injury, delayed internal fixation,33 use of bone graft or substitute, prolonged postoperative immobilization. A 48 hours delay in fixation can increase the rate of HO from 0% to 33%. Kundel et al reported an increase in the rate of HO from 29% to 80% when surgical treatment was delayed by more than 24 hours [22]. HO can be radiologically visible two weeks after surgery in 86% of patients who finally developed HO [23]. In some cases, HO can cause limitations in elbow motion and function, and in such patients excision of the HO may be necessary. The routine use of indomethacin for prophylaxis against HO following internal fixation of distal humerus fractures remains controversial.
• Elbow stiffness-- Elbow stiffness is the most common sequela after internal fixation of distal humeral fractures. Elbow stiffness can be often seen even after optimal stable fixation and proper rehabilitation. Some authors have reported that one-third of patients failed to get a functional range of motion in the elbow after fracture fixation [17]. Loss of elbow motion can result from intrinsic or extrinsic causes such as malunion, nonunion, incongruity of the articular surface, intra-articular and capsular fibrosis, and adhesions around the elbow callus formation, HO, prolonged postoperative immobilization, and prominent hardware [24]. Early mobilization remains the mainstay of the prevention of elbow stiffness. In some patients, surgical treatment of elbow stiffness is needed. In these patients arthrolysis and contracture release is necessary. Open release of elbow stiffness is usually more effective when HO is obstructing motion. Sometimes implants need to be removed. Sometimes refractures can occur after the removal of implants.
• Nonunion-- Nonunions after internal fixation of distal humerus fractures have been reported to be between 2% and 10% [25].  High-energy trauma, gross comminution, and poor bone stock are some of the reasons for nonunion. In elderly patients, fracture union rather than motion is the first priority, because motion can be restored later by contracture release after the fracture unites. Nonunions can severely compromise the patient’s quality of life [26]. Nonunions usually need revision of internal fixation, autogenous bone-grafting, and aggressive contracture release.
• Malunion-- Malunion is seen in about 30% of patients with distal humerus fractures. It is more common in patients with nonoperatively treated fractures as compared to operatively treated fractures. Malunions of the distal humerus are either extra-articular or intra-articular. Extra-articular malunions are treated with humeral osteotomy and fixation. Intra-articular malunions are more difficult to treat. Intra-articular corrective osteotomy is usually considered in young patients who present with moderate to severe functional disability and/or pain and secondary post-traumatic arthritis at an early stage [27]. The aim of treatment is to restore the articular anatomy in order to improve motion, relieve pain and enhance stability in active young patients. In the elderly low demand patients, a total elbow replacement is an option.
• Infection and wound complications--  The wound complications incidence after fixation of distal humerus fractures is substantial and can be associated with significant morbidity. The risk for serious wound complications after surgery is high because of soft tissue damage, relatively thin soft tissue envelope, postoperative swelling, and shear forces occurring when elbow motion is started [28].     Infection should be suspected in any patient with persistent wound discharge. Open fractures and the use of a plate to stabilize the olecranon osteotomy, are considered to be significant risk factors. Majority of wound complications can successfully be treated with debridement and primary or delayed wound closure. In some patients, myocutaneus flaps may be necessary.
• Failure of olecranon osteotomy-- Complications of olecranon osteotomy include nonunion, malunion, hardware failure, and skin irritation by prominent implants. The incidence of complications associated with olecranon osteotomy ranges from 0% to 31% [17]. The reported rate of nonunion is about 11.9% [29].

Elbow Arthroplasty

Total elbow arthroplasty (TEA) is being increasingly used for the treatment of comminuted intra-articular distal humerus fractures in the elderly patients [30]. Because of its limited longevity due to aseptic loosening, TEA is only recommended in patients with sedentary lifestyles who can comply with the post-operative rehabilitation program [5].  A study by Prasad et al showed that survivorship of the implants, with revision and definite loosening as end-points, was 89.5% at ten years in those patients who were followed for a minimum of ten years [31]. 

A study by Mansat et al [32] which analyzed the outcome of treatment of 87 patients over the age of 65 with a distal humeral fracture treated who were treated with TEA found that 63% of patients had a pain free elbow at 37.5 months follow up, 48% had a mean flexion-extension arc of at least 100º, and 79% of the patients had normal function. 

There were complications in 23% of the patients and revision surgery was necessary for 9% of the patients. 

Conclusion

Fractures of the distal humerus constitute about 2% of all fractures in the adult population. The overall incidence of distal humeral fractures in adults is 5.7 cases per 100,000 in the population per year. Distal humerus fractures are difficult to treat especially in the elderly with poor bone stock. Improvements in implant design and surgical technique have resulted in better clinical outcomes following open reduction and internal fixation of distal humerus fractures. Open reduction and internal fixation is now standard treatment for displaced fractures of the distal humerus. 

However, the open reduction and internal fixation of these fractures can be challenging and can be associated with a high rate of complications. Total elbow arthroplasty has been advocated as a treatment option for elderly patients especially in those with unreconstructable distal humerus fractures.

References

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