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. 2019 Sep 25;12(3):212–223. doi: 10.1177/1758573219876921

Radial head fractures

RP van Riet 1,2,3,✉, MPJ van den Bekerom 4, A Van Tongel 5, C Spross 6,7, R Barco 8, AC Watts 9
PMCID: PMC7285971  PMID: 32565923

Abstract

The shape and size of the radial head is highly variable but correlates to the contralateral side. The radial head is a secondary stabilizer to valgus stress and provides lateral stability. The modified Mason–Hotchkiss classification is the most commonly used and describes three types, depending on the number of fragments and their displacement. Type 1 fractures are typically treated conservatively. Surgical reduction and fixation are recommended for type 2 fractures, if there is a mechanical block to motion. This can be done arthroscopically or open. Controversy exists for two-part fractures with >2 mm and <5 mm displacement, without a mechanical bloc as good results have been published with conservative treatment. Type 3 fractures are often treated with radial head replacement. Although radial head resection is also an option as long-term results have been shown to be favourable. Radial head arthroplasty is recommended in type 3 fractures with ligamentous injury or proximal ulna fractures. Failure of primary radial head replacement may be due to several factors. Identification of the cause of failure is essential. Failed radial head arthroplasty can be treated by implant removal alone, interposition arthroplasty, revision radial head replacement either as a single stage or two-stage procedure.

Keywords: elbow, radius, fracture, radial head, prosthesis, arthroscopy, instability

Introduction

Radial head fractures are common and are usually caused by a fall on the outstretched hand. Average age of patients is 45 years old.1 The incidence has been shown to be 2.5 per 10,000 per year. Radial head and neck fractures account for 0.2% of all visits to the accidents and emergency department.2 Associated injuries are found in about one-third of patients and these often dictate treatment.

The proximal radius is important for the function of the elbow and forearm. It plays an important role in maintaining stability and force transfer from the hand to the shoulder.

This article aims to describe the current knowledge of anatomy, biomechanics, classification and treatment options.

Anatomy and biomechanics of the radial head

The proximal radius consists of the radial head and the neck. The radial shaft has a nutrient artery within the intramedullary canal, with vessels for the radial head; blood supply of the head is provided by the radial recurrent and interosseous recurrent artery.3

Articular cartilage covers the concave surface as well as at least an arc of approximately 280° around the rim of the native radial head. The remaining non-articulating part with less or no cartilage is this safe zone in which plates and screws can be applied.4 This safe zone is about 133°.5

The articulating part of the proximal radius is concave, and this is accentuated, as cartilage at the periphery is thicker.6 The concave surface of the radial head articulates with the convex surface of the humeral capitellum acting as a buttress, providing stability by the concavity/compression mechanism and tensioning of the lateral collateral ligament (LCL) complex, avoiding external rotation at the ulnohumeral joint.7

The side and the rim of the radial head also articulate with the proximal ulna in the lesser sigmoid notch and with the lateral part of the trochlea (zona conoidea).8

About 60% of load across the elbow is transmitted through the radiocapitellar joint. Load in the lateral compartment is increased with the elbow extended and the forearm pronated and depends on the valgus axis of the elbow, stability and congruency of the joint.

The radial head is the secondary stabilizer for valgus after the ulnar collateral ligament injury and primary stabilizer for longitudinal stability with the interosseous membrane as a secondary stabilizer.9 The annular ligament encircles the radial head and attaches to the margins of the lesser sigmoid notch. The annular ligament stabilizes the proximal radio-ulnar joint and the radiocapitellar joint.

There is a large variation in dimensions, angles and curvatures of the proximal radius.10 The native radial head is elliptical and not perfectly round.11 Kinematics of the elbow are not significantly affected by changing the shape of the radial head, but it affects cartilage load forces through the radiohumeral joint.12 Although there is no clinical evidence to support this, this may induce degenerative changes to the elbow.13 Size and shape of the native head correlate to the contralateral side.14

Under- or overlengthening of the radiocapitellar joint should be avoided to optimize load on the cartilage of the capitellum and to reconstruct longitudinal, lateral and medial stability.15 Radiographs are not reliable.16 The lesser sigmoid notch is the most accurate and reliable landmark to determine the length of the radial head. In a cadaveric study, it was shown that the height of the radial head corresponds to the proximal edge of the lesser sigmoid notch with the forearm in neutral rotation.17

Classification

Radial head fractures range in severity from occult, non-displaced, fractures to fractures with severe displacement and comminution. Several classifications of radial head fractures have been proposed ultimately aiming to guide treatment according to the pattern of the injury.

In 1926, Condict Cutler was one of the first to propose a classification and his treatment recommendations still hold ground today: nonoperative treatment unless the fragments block motion, prevented reduction of a dislocation, or were malunited.18

In 1949, Gaston et al. described the importance of associated lesions for the first time and recommended a different approach to treatment if the radial head was associated with an elbow dislocation.19

The most cited classification was published by Mark Mason, in 1954.20 In his original article, Mason reviewed 100 consecutive radial head fractures and their treatment. Mason described a type 1 fracture as one that either had a fissure (non-displaced) or a peripheral fracture of the rim (Figure 1), a type 2 fracture as a marginal sector fracture with displacement, and a type 3 fracture as a comminuted, displaced fracture involving the entire radial head. In 1962, Johnston added a fourth type to denote a fracture of the radial with associated dislocation (no matter the amount of displacement or comminution of the fragments).21

Figure 1.

Figure 1.

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Anteroposterior plain radiograph showing a non-displaced radial head fracture, classified as a Mason–Hotchkiss type I radial head fracture. (Courtesy of MoRe Foundation.)

Although it is commonly used, both the Mason and Mason–Johnston classifications have several shortcomings as its inter- and intraobserver reliability is only moderate, and it does not consistently guide treatment or predict prognosis.22

The Mason classification was modified by Hotchkiss to better define the need for surgical treatment. A type 2 fracture was defined as a reconstructible radial head fracture, with the presence of a mechanical block preventing movement (Figure 2). A non-reconstructable radial head fracture was defined as a type 3 fracture.23

Figure 2.

Figure 2.

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Axial CT image of a Mason-Hotchkiss type II radial head fracture. From this image it is clear that one of the displaced fragments is responsible for a block to forearm rotation. (Courtesy of MoRe Foundation.)

The modified Mason–Hotchkiss did not include associated lesions although they often determine the outcome of the treatment. van Riet et al. proposed to add a suffix to the Mason type classification of radial head fractures, to describe these associated lesions. The system was based on clinical and intraoperative observations. Only clinically significant injuries were included. The suffix denotes the articular injury (c: coronoid, o: olecranon), followed by the ligamentous injury (l: lateral collateral ligament, m: medial collateral ligament, d: distal radio-ulnar joint). For example, a type II radial head fracture with a fractured coronoid and disruption of the lateral and medial collateral ligaments is termed type II clm. This simple system allows designation of 97% of associated injuries.24

Osteosynthesis: Indication, options and limitations

Radial head fractures with a displacement of <2 mm (Mason–Hotchkiss type I) without a mechanical block for pronosupination may be treated conservatively with early range of movement exercises.25 The indication for open reduction and internal fixation (ORIF) is controversial if there is no mechanical block to movement. After a mean follow-up of 19 years, Herbertsson et al. showed satisfactory function with conservative treatment for two-part fractures with up to 4 mm displacement in the neck or up to 5 mm in the head fragment. However, there was a 12% late radial head resection rate.26–28 Other authors clearly prefer surgery in fractures with more than 2 mm displacement at the head, even in the absence of a mechanical block, to prevent later sequelae.29 At this moment, however, the evidence is not strong enough to give clear recommendations either way. There is also no conclusive data on the acceptable amount of angulation of the radial head in relation to the shaft in the literature. However, according to Akesson and colleagues the displacement at the neck should not exceed 4 mm.28

From the current literature, we can define clear indications for surgery: mechanical block after aspiration of the hematoma, two-part fractures with displacement >5 mm (head fragment) or >4 mm (neck) and fractures with comminution (>2 parts). There is no consensus on when to operate angulated radial neck fractures, but surgery is indicated in patients with a mechanical block to rotation. The decision to perform surgery is often not dictated by the radial head fracture alone. It is crucial to keep in mind that over 50% of Mason II and Mason III fractures will have associated injuries.1,24 CT scans are necessary to determine displacement, number of fragments and the presence of associated fractures. From the CT it may already be clear that ORIF may not be possible or that other fractures need to be addressed. The limitation for ORIF depends on the possibility to obtain a stable and anatomic reconstruction.30 Other options include radial head arthroplasty or radial head resection.31

Three approaches are most commonly used for ORIF of the radial head. The Kocher approach (posterolateral approach), which uses the interval between the anconeus and the extensor carpi ulnaris. It can be extended proximally along the lateral epicondyle and the lateral ridge to get a better exposure into the joint. This improves visibility of the radial head from 270° to 360°.32 The downside of the Kocher approach is the proximity to the lateral ulnar collateral ligament (LUCL), thus it is important to keep 1 cm of distance to the supinator crest when incising the joint capsule.23 Another popular approach is the extensor digitorum communis (EDC) split, which is very similar to the Kaplan approach. While the EDC approach splits the muscle, the Kaplan is slightly more anterior and uses the interval between the EDC and the extensor carpi radialis brevis. However, the differentiation of these two approaches is rather theoretical as it is hard to find this interval in traumatic situations. However, both approaches can be extended proximally in the same way as described for the Kocher approach above. The extended EDC split offers up to 306° of visibility of the radial head, which is significantly less than the Kocher approach.32 Compared to the Kaplan approach however, the Kocher approach exposes significantly less of the proximal radius.33 The downside of both the Kaplan and the EDC split is the proximity to the posterior interosseus nerve, which must be protected with pronation of the forearm and care must be taken when pulling on the anterior retractors. Most of the radial head fractures can be addressed through all three approaches and no clear recommendation can be made in this regard. As most of the fractures of the radial head are localized anterolaterally,34 they are usually well amenable to an EDC split or Kaplan approach, preserving the LCL complex. The choice of implant depends on the fracture configuration and the preference of the surgeon. Headless screws are typically used to fix head fragments with or without involvement of the radial neck. This can be done through any classical approach or with a minimal invasive EDC split (Figure 3). Plates are commonly used to fix radial neck fractures, but these need to be removed in up to 70% of patients.35 Some complications can be avoided by positioning the implant in the so-called safe zone. This is the area of the radial head, which is never in contact with the ulna neither in pro- nor in supination. Caputo et al. defined the save zone in relation to the distal radius between the styloid process and the Lister's tubercle.4 Another definition of the safe zone is approximately 100° centred on the equator of the radial neck in neutral position.23 Problems with plate positioning can also be avoided by using a low-profile screw fixation (Figure 4). In this technique, one or more screws are used to fix the head to the neck.36,37 This technique may be challenging but the crossing screws are able to achieve a biomechanical stability comparable to plate fixation with the advantage of less irritation and less need of implant removal postoperatively.37,38

Figure 3.

Figure 3.

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Intraoperative photograph showing radial head headless screw fixation through a minimally invasive EDC split. (Courtesy of MoRe Foundation.)

Figure 4.

Figure 4.

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(a) Preoperative radiograph showing an elbow dislocation and displaced radial head fracture. (Courtesy of MoRe Foundation.) (b) AP and (c) lateral radiographs showing low-profile screw fixation. (Courtesy of MoRe Foundation.)

Neumann et al. published a series where they reduced the head fragments with screws but did not fix the head to the shaft if the head was rotating with the shaft in forearm pro- and supination. After a mean of 7.8 years, the authors found no differences in functional outcome and healing rate when compared to plate fixation but the implant needed to be removed in 54% in the plate fixation group.39

Arthroscopic treatment of radial head and associated lesions

Arthroscopy of the elbow is a standard option in the treatment of elbow pathology. The advantages are clear, as it allows for an enhanced view, with decreased soft tissue dissection. However, it does require quite some expertise, as it is often technically more challenging. Arthroscopy offers an excellent view on the articulating surface,40 radial head fracture (Figure 5) as well as any associated lesions, such as a coronoid fracture, chondral lesions of the capitellum or trochlea. It is not uncommon to find small chondral fragments in the joint. If the LCL is avulsed, it can be reinserted arthroscopically (Figure 6).41,42 Good to excellent results of arthroscopic radial head fixation have been published in relatively small case series.43

Figure 5.

Figure 5.

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Arthroscopic view of a radial head fracture. (Courtesy of MoRe Foundation.)

Figure 6.

Figure 6.

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Arthroscopic view showing a complete lateral collateral ligament avulsion. An anchor is placed in the lateral epicondyle to reinsert the lateral collateral ligament. (Courtesy of MoRe Foundation.)

Radial head arthroplasty for radial head fractures

Radial head arthroplasty is an effective treatment modality for comminuted radial head fractures that are unreconstructable with ORIF. Besides the configuration of the fracture, it is important to determine the presence of posterolateral instability due to injury to the lateral ligamentous complex, valgus instability due to injury of the MCL and axial instability due to an injury to the interosseous membrane, as these are reasons for radial head arthroplasty if the radial head fracture cannot be fixed. The determination of what represents an unreconstructable radial head is subjective but having more than three fragments and loss of cortical continuity of one of the fragments are negative predictors for a successful outcome after fixation.44,45 The rationale to use an arthroplasty is to achieve an effective radiocapitellar contact that will improve the stability in valgus, posterolateral and axial loading of the forearm. Bony injuries to the proximal ulna further decrease stability of the elbow and decrease the threshold for the use of an arthroplasty.46 As with other injuries to the elbow, the outcome is dependent on associated injuries, but good short-term and mid-term results are observed (Table 1).

Table 1.

Results of radial head arthroplasty after trauma by type of implant.

Author Type of implant Type/no FU (months) ROM (flexion-extension,º) Complications Results/Scores
Tarallo et al.54 Anatomical radial head 31 Mason III 30 (12–84) 13–125; mean 112 68–66 (PS) HO: 8 Lucencies: 2 Excellent: 77% Good: 10% Fair: 13%
Flinkkilla et al.55 Anatomical radial head 23 acute 53 (12–103) 117 (20–138) 5 loose (3 removed) 8 bone loss proximally Mean MEPS: 86
Levy et al.56 Anatomical radial head 19 acute 26 (3–90) 14–138 75–76 (PS) Loosening 40% (3 revised) Stress shielding 67% HO: 2 MEPS: 87
Marsh et al.57 Metallic spacer 55 evolve 8,2 years 15–137 HO: 36% Capitellar osteopenia: 2 Lucency: 45% MEPS: 91
Doornberg et al.58 Metallic spacer 27 evolve 40 20–131 73–57 (PS) Lucency: 68% 13 HO 9 Capitellar osteopenia 4 removal 4 ulnar nerve Excellent: 13 Good: 9 Fair: 3 Poor: 2
Moghaddam et al.59 Metallic spacer 75 evolve 41 16–126 70–67 (PS) 81% radiolucencies 73% HO 4 removal MEPS: 83
Allavena et al.60 Cemented bipolar 22 guepar 50 (24 min) FE Arc:100 143 (PS) Instability: 6 Ulnar neuritis: 5 Removal: 4 HO: 4 Capitellar erosion: 6 Excellent: 3 Good: 11 Fair: 3 Poor: 1
Van Hoecke et al.61 Cemented bipolar 34 judet 113 (84–174) 25–122 62–59 (PS) Capitellar erosion: 13 Significant pain: 4 1 removed Excellent: 14 Good: 1 Fair: 5 Poor: 1
Burkhart et al.62 Cemented bipolar 9 judet 68 (62 min) 21–128 75–76 º(PS) 1 revised MEPS: 92
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HO: heterotopic ossification; PS: pronosupination; MEPS: Mayo Elbow Performance Score.

Type of implants

Current prostheses include unipolar or bipolar implants, press-fit ingrowth or cemented stems and non-anatomical (spherical) or anatomical heads. Anatomical heads have similar contact areas and mean pressures as the native radial head, but this potential benefit has not been proven clinically.47 Most surgeons will choose unipolar implants for traumatic indications for the potential instability of a bipolar implant although some surgeons use them claiming better radiocapitelar tracking.48,49

Silicone implants are no longer used due to adverse effects like synovitis secondary to wear, and fragmentation.13 Modular implants are preferred because they allow for better sizing of neck height and radial head size and height and could facilitate insertion in the event of an intact LCL.50

The implants can be fixed with press-fit technique, cemented or left loose in spacer-type prostheses. Mid-term studies suggest there are no differences in the outcome of radial head arthroplasty according to the fixation.51

Current surgical technique

The current technique includes a lateral approach (limited Kocher, extensor muscle split, modified Kaplan approach). The LCL complex is assessed and if it has been avulsed it is tagged for later reattachment. Once it is determined that the radial head fragments cannot be fixed, they are removed, and resection is completed, perpendicular to the neck. This is important as it will orient the radial head replacement in line with the rotation axis of the forearm. Furthermore, it will add support to the arthroplasty, potentially decreasing motion at the bone prosthetic interface. All fragments need to be removed and assessed for correct sizing of the implant.52,53

Preparation of the shaft depends on the implant's specifications. Trial implants are assembled and trialled. Diameter, height, tracking and congruity of the radial head are dynamically evaluated under direct vision or with the help of fluoroscopy, throughout the arc of motion of the elbow in flexion, extension and pronosupination. Special care to prevent over-lengthening is critical. The lesser sigmoid notch is the most accurate and reliable to determine the length of the radial head. The height of the radial head corresponds to the proximal edge of the lesser sigmoid notch.17 Maltracking may be due to an oblique radial neck cut or a canal broached in a valgus direction. A new cut or new broaching will eliminate these problems. Once the trial is satisfactory, the definitive implant can be inserted and soft tissue is addressed as needed.

Results

References for Table 1

Tarallo et al.54

Flinkkila et al.55

Levy et al.56

Marsh et al.57

Doornberg et al.58

Moghaddam et al.59

Allavena et al.60

Van Hoecke et al.61

Burkhart et al.62

Complications

The main complications are stiffness, residual pain and instability. Stiffness is related to overlengthening or overstuffing of the joint (Figure 7), pain is mostly related to loosening or infection and persistent instability is due to failure to address other associated injuries.13

Figure 7.

Figure 7.

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Anteroposterior postoperative radiograph showing overstuffing of a radial head prosthesis with clear asymmetry of the ulnohumeral joint and loosening of a poorly fixed cemented radial head prosthesis. (Courtesy of MoRe Foundation.)

Resorption at the proximal radius is a common finding in well-fixed stems. Chanlalit et al. reported 63% of proximal stress shielding in 86 implants, regardless of the design of the stem. This is not pathological and does not lead to loosening of the stem.63

Metallic “loose-fit” prostheses may show minimal endosteal resorption, which is usually non-progressive after the first year of follow-up. Progressive endosteal resorption should be worked-up for infection. O'Driscoll and Herald have described that proximal forearm pain is the best predictor for loosening, even in the event of normal radiographs.64

Radial head overstuffing or over-lengthening may produce pain and decreased range of motion and may need secondary surgery to excise the radial head implant or revise the component. Overlengthening has also been shown to lead to capitellar erosion.65 The main reason for removal is lateral elbow pain with implant loosening (Figure 7) and has been related to numerous factors, including timing of surgery and related to surgical technique so attention to detail during surgery is recommended.66 No data is available on asymptomatic loosening. We would recommend following the patient with serial radiographs. Removal or revision of the prosthesis would be indicated if the loosening would become symptomatic or if dramatic implant or bone failure becomes adamant.

Revision radial head arthroplasty

Little is written about revision of radial head arthroplasty. The definition of failure, frequency and causes are not clear. The best estimate for revision rate of radial head arthroplasty, although difficult to quantify from the existing literature, is 2 per 100 person years of follow-up; however, many may not be reported.13

Failure of primary radial head replacement may be due to infection, peri-prosthetic fracture, implant loosening, dislocation, dis-assembly, heterotopic ossification or persistent pain.66 Stress shielding may be observed with press fit designs but has not been shown to lead to implant failure. When observed, implant loosening may be attributed to the implant design, but in many cases surgical factors predispose to early failure. These include over-stuffing, improper alignment, inadequate fixation or persistent instability, either due to inadequate soft tissue repair or inadequate management of an associated ulna fracture. Retrospective reviews have identified hospital factors, implant factors and patient factors that can lead to re-operation. These include the use of a silicone implant, younger age, fewer co-morbidities and delay to surgery.66,67 Identification of the cause of failure is essential in the successful management of symptomatic radial head arthroplasty and it is useful to have a checklist to consider (Table 2).

Table 2.

Checklist of causes of radial head replacement failure.

Possible causes for radial head replacement failure
Infection
Instability
Implantation (technical errorsa)
Implant design
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aIncluding periprosthetic fracture.

Patients can present with persistent pain, stiffness, infection, instability of the radiocapitellar joint, ulno-humeral joint or both.66 Loss of range of movement in both the flexion extension and pronosupination axis is reported with average extension lag of 30°, with flexion up to 117°, and pronation from 58° to 52° supination on average. A common feature of those presenting with failed radial head implants is delay to initial surgery, with 55% in one series having implantation more than six weeks after the initial injury. This delayed surgery may be more technically challenging, reflected in an increased risk of overstuffing, which may go some way to account for implant failure. Although it may be that most implants are designed for use in acute trauma and cannot withstand the abnormal forces present in an elbow that has failed non-operative treatment or presents late for reconstruction. The most common reason for revision identified in a meta-analysis of published trials is painful loosening.68

Failed radial head arthroplasty can be treated by implant removal alone, interposition arthroplasty, revision radial head replacement either as a single stage or two-stage procedure, or radiocapitellar arthroplasty. In many cases, removing the implant will provide symptomatic relief and will not result in long-term instability or pain. For some patients however, implant removal will result in mechanical symptoms, pain and weakness. The cause of these symptoms may be ulnohumeral instability or more commonly longitudinal or axial instability of the radius that can result in proximal stump impingement (Figure 8). Multifragmentary radial head fractures with displacement of fragments anterior and posterior to the capitellum should raise a suspicion for a longitudinal instability particularly if the ‘lost space’ sign described by Sabo and Watts is seen, where the radial neck fracture surface is in contact with the capitellum due to proximal migration of the radius. Radio-ulnar impingement is more difficult to predict.69

Figure 8.

Figure 8.

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CT scan showing proximal radio-ulnar impingement causing scalloping of the ulna. (Courtesy of Adam C Watts, elbowdoc.co.uk)

Anticipating these problems can be challenging but review of the primary pathology is recommended before considering excision arthroplasty.

Symptomatic failure can be addressed with revision arthroplasty. The use of a long-stem cemented prosthesis improves skeletal fixation (Figure 9). In most revision cases, it is not possible to achieve perfect tracking of the radial head for a successful mono-polar implant and bipolar radial head arthroplasty is more forgiving. Additional measures may be required such a lateral ligament reconstruction if there is persistent elbow instability, or arthrolysis if the elbow is stiff from arthrofibrosis or heterotopic ossification. Two-stage revision arthroplasty is indicated in cases of infection.

Figure 9.

Figure 9.

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Anteroposterior postoperative radiograph showing a long stem-cemented bipolar radial head. (Courtesy of Adam C Watts, elbowdoc.co.uk)

Where the articular surface of the capitellum has been damaged, the surgeon may consider radio-capitellar arthroplasty. Published experience is limited and patients should be followed closely with prospective data collection.70,71 Contra-indications include active infection, and persistent longitudinal instability as the implant will be doomed to failure.

Interposition arthroplasty is usually reserved for cases where revision arthroplasty is contra-indicated, such as forearm malunion or erosion of the capitellum or lesser sigmoid notch. Anconeus pedicled autograft can be used by mobilizing the anconeus based on a proximal neurovascular pedicle, passing it beneath the LUCL and interposing between the radius and ulna or wrapping around the radial neck.72 Achilles allograft can be used as an alternative to create a cushion between the radial neck and ulna or capitellum. Anchors can be used to secure multiple layers of the graft to the ulna as a cushion and free end of the graft wrapped around the radial neck as an annular ligament (Figure 10). It is not known how durable these techniques will prove but in the short term they can provide relief of pain.

Figure 10.

Figure 10.

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Achilles allograft interposition. (Courtesy of Adam C Watts, elbowdoc.co.uk)

Acknowledgements

Part of the content of this paper was presented as an instructional course lecture at the 27th SECEC congress in Geneva 2018.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Guarantor

RvR.

Contributorship

All authors contributed equally.

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