Radial head fractures are seen in 20% of elbow fractures. It may involve the radial head, radial neck or both. It may either be an isolated injury or associated with other fractures or ligamentous injury. Treatment depends on the type of fracture, amount of displacement, comminution and associated injuries. Previously radial head excision was a popular treatment, now it is being replaced by open reduction and internal fixation or radial head replacement. The assessment of these common fractures and treatment have evolved with better understanding of the anatomy and biomechanics of radial head and the development of evidence based guidelines.
Proximal radius consists of the radial head and the neck. The proximal surface of radial head is concave and articulates with the convex articular surface of capitellum. Radial head articulates with the capitellum of humerus. The rim of the radial head articulated with the lesser sigmoid notch of ulna. The radial head is elliptical in shape and the long axis is perpendicular to the lesser sigmoid notch in the position of neutral rotation of the forearm. The radial head is variably offset 60 to 280 from the long axis of the radius with the average of 16.80. The mean diameter of the radial head is 22+/-3 mm. The mean radial neck-shaft angle is 7°+/-3°
Stability to the radial head is provided by the lateral collateral ligament complex and the annular ligament. Posterolateral rotatory stability of the elbow is provided by the lateral ulnar collateral ligament and it should be protected during surgery. Lateral ulnar collateral ligament is attached to the lateral epicondyle of humerus proximally and to the ulna distally, behind the posterior attachment of annular ligament on the crista supinatoris. Annular ligament is composed of superior and inferior oblique bands. The axial stability of forearm is provided by the radio-capitellar articulation, interosseous ligament and the ligaments of the distal radioulnar ligament.
The functions of the radial head are the following.
- Motion at the elbow and forearm by articulation with capitellum and lesser sigmoid notch.
- Secondary stabilizer of elbow against valgus instability. Primary stabilizer is the medial collateral ligament.
- Axial stability of forearm along with interosseous ligament and the ligaments of the distal radioulnar joint.
- Transmits 60% of load across the elbow. Load is more in the extended and pronated position of elbow than in flexion.
Mechanism of Injury
Typically occur from a fall on the outstretched hand. Axial loading along with valgus force is thought to be important in the development of comminuted fractures. Failure of the lateral collateral ligament complex and subluxation of radial head can lead to shear fractures involving the anterolateral part of radial head. Fractures of the anterolateral lip of radius are the most common radial head fracture pattern.
Proximal radius fracture is the most common elbow fracture. It accounts for about 5% of all fractures and 20% of elbow fractures. It may be an intra-articular radial head fracture or an extra-articular fracture of the radial neck. Radial head fractures are 7 times more frequent than the radial neck fractures. The incidence in male and females is equal but the injury in males is comparatively more severe. It may be an isolated injury, but about one third are associated with other fractures or ligament injuries. About 10% of those with undisplaced fractures, 50% of those with displaced fractures and three fourth of those with comminuted fractures are associated with other elbow injuries. About 10% will have a coronoid fracture and 15-20% will have associated dislocation.
Clinical features depend on the severity of injury and the associated injury. Patients with undisplaced fracture and no associated injuries often have only minimal symptoms. More serious injuries present with pain on the lateral aspect of elbow. Those with associated injuries or dislocation present with severe pain, deformity, swelling and severe restriction of elbow and forearm movements.
Carefully look for ecchymosis and swelling of medial and lateral aspects of elbow indicating ligamentous injury. Palpate the distal humerus, medial and lateral aspects of elbow, radial head, olecranon, radial shaft, ulnar diaphysis, interosseous membrane, distal radioulnar joint, lower end of radius and the ulnar styloid. Tenderness over the forearm and ulnar styloid should alert about the possibility of an Essex Lopresti lesion. Assess the elbow movement and forearm rotation. If there is any restriction, aspirate the joint to reduce intra-articular pressure, inject local anesthetic agent and reassess the range of movement. Mechanical block to motion is an indication for surgery. Gentle assessment of the medio-lateral stability of elbow is a must as it may lead to fracture displacement. Assess the shoulder and wrist for any injury. Rule out vascular compromise, nerve injury and compartment syndrome.
Antero-posterior, lateral and oblique vies of the elbow should be taken with the beam centered over the radio-capitellar joint. X-rays of shoulder and forearm with wrist should be taken to rule out associated injuries. Ulna variance should be assessed to rule out axial instability on bilateral wrist x-rays taken in neutral rotation. X-rays should be carefully evaluated for associated lateral column injuries, dislocation and periarticular injuries. Identify the number, location and size or fracture fragments, assess the magnitude of displacement. Complex injuries and displaced fractures should be further assessed by CT scans. CT with 3D reconstruction is an excellent method for the evaluation of complex injuries. If ligamentous injury is suspected then MRI scan is warranted. Ultrasound scan of the forearm is helpful in detection of interosseous ligament injury.
Type I – Partial head fractures without displacement
Type II – Partial head fractures with displacement
Type III – Comminuted fractures involving the whole head
Type IV – Radial head fracture associated with an elbow dislocation (Added by Johnston).
Broberg and Morrey modification is inclusion of radial neck fractures and definition of displaced fractures as fracture displacement >2mm and fragment size >30% of the articular surface.
Mason Classification as Modified by Hotchkiss by adding treatment recommendations
I – Minimal fracture displacement, no mechanical block to forearm rotation, intra-articular displacement less than 2 mm are treated by nonoperative treatment.
II – Fracture displaced more than 2 mm or angulated, possible mechanical block to forearm rotation are treated by open reduction and internal fixation.
III – Severely comminuted fracture, with mechanical block to motion are treated by radial head arthroplasty.
IV – Radial fracture with associated elbow dislocation.
Mayo Extended Classification
Type I – Non-displaced.
Type II – Displaced more than 2 mm.
Type III- Comminuted, non-reconstructible radial head.
The Mayo extended classification then adds a suffix to the fracture type to show any associated lesion.
‘c’ – Associated coronoid fracture. ‘C’ – If operative treatment was done.
‘o’ – Associated olecranon fractures. ‘O’ – If operative treatment was done.
‘m’ for medial collateral ligament (MCL) injury. ‘M’ – If operative repair was done.
‘l’ for the lateral collateral ligament (LCL) injury. ‘L’ – If operative repair was done.
‘d’ for longitudinal distal radio-ulnar joint (DRUJ) dissociation. ‘D’ – If operative treatment done.
‘X’ added for radial head excision.
‘F’ if radial head was fixed and
‘A’ if arthroplasty was done.
Mayo Extended Classification
The factors that determine the treatment are the following.
A. Radial head fracture configuration
1. Partial or completely articular
2. Fragment size – <33% or more
3. Comminution – ❤ or more fragments
5. Displacement – <2mm or more
6. Radial neck involvement
B. Radiocapitellar alignment
C. Associated fractures and ligamentous injury
D. Block to elbow and forearm range of movement
E. Elbow or forearm instability
F. Bone quality
Indications for surgery
- Displacement more than 2mm
- Restriction of range of movement
- Elbow or forearm instability
- Open fractures
- Fragment size if less than 33% of the radial head can be excised. If more than 33% it should be fixed
- Comminution with more than 3 fragments is associated with poor outcome with ORIF. Either excise or replace
- More than 2 mm displacement is considered to be an indication for surgery
- Associated fractures of capitellum, coronoid, olecranon and distal radius need surgery
- Block to elbow movement or forearm rotation is an indication for surgery
- Elbow and forearm instability is an indication for surgery
In fracture-dislocations of elbow; fixation/reconstruction is essential to restore coronal plane stability of elbow, to reduce the reliance on ulnar collateral ligament and to prevent proximal migration of radius. The options available for treatment are non-operative treatment, fragment excision, radial head excision, arthroscopic assisted reduction and fixation, open reduction and internal fixation and radial head replacement.
Indicated in undisplaced fractures and in minimally displaced (<2mm) fractures involving <33% of the head with no mechanical block to movement. Aspirate the joint under aseptic precautions, give a cuff & collar sling and start active ROM within 2-3 days once pain subsides. Avoid weight lifting and strenuous activities for 4-6 weeks. Take an x-ray at 2 weeks to rule out displacement. After 6 weeks usually functional ROM is attained, if not physiotherapy is given. Delayed excision may be needed if there are persistent pain and limitation of range of motion.
Anterior Henry approach and posterior Thomson approach allow exposure of proximal radius and the posterior interosseous nerve. Kocher approach between anconeus and extensor carpi ulnaris (ECU) is the most commonly used approach for radial head surgery. A major disadvantage of Kocher approach is inability to expose the posterior interosseous nerve (PIN). The PIN runs between the 2 heads of the supinator in close proximity to the radial neck. It is about 3.8 cm distal to the articular surface in pronation. To protect the PIN, the following steps should be taken.
- The forearm should be kept in full pronation during the procedure.
- Identify the interval between the ECU and anconeus by recognizing the fan-shaped direction of the fibers of anconeus, which are horizontal proximally and vertical distally.
- The supinator muscle should be released from its posterior edge close to the ulna.
Steps in the surgery are as following.
a) Regional anesthesia
b) General anesthesia
a) Supine position with the arm on arm board and a pillow over the interscapular area.
b) Lateral position with arm supported over a bolster
a) Lateral incision centered over the lateral epicondyle
b) Posterior midline incision in presence of other elbow injuries raising a full thickness flap
4) Deep dissection
a) Kocher approach
i) Useful for exposure of lateral and posterior parts of the radial head.
ii) Uses the interval between the anconeus and extensor carpi ulnaris (ECU).
iii) Interval between ECU and anconeus identified by diverging direction of muscle fibers, fat pad and small perforators.
iv) Elevate the ECU anteriorly off the lateral ligament complex and incise the annular ligament in the midlateral plane to avoid injury to lateral ulnar collateral ligament (LUCL). It is better to do a Z capsulotomy for better repair after plate fixation or arthroplasty.
v) Do not elevate the anconeus posteriorly to protect the LUCL.
vi) Often the LCL is ruptured and the radial head can be exposed through that gap. LCL should be repaired at the end of the procedure.
vii) If needed LCL may be released and reattached at the end of the procedure.
b) Kaplan approach
i) Useful for exposure of lateral and posterior parts of the radial head.
ii) Uses the interval between the extensor carpi radialis and extensor carpi ulnaris (ECU).
iii) Elevate the ECU posteriorly off the lateral ligament complex and incise the annular ligament in the midlateral plane to avoid injury to lateral ulnar collateral ligament (LUCL).
iv) Chance of posterior interosseous nerve palsy is reduced by keeping the forearm pronated.
c) Hotchkiss Approach
i) Exposure through the fibers of extensor digitorum communis.
ii) Useful for exposure of anterolateral lesions.
iii) Radial head exposed through the fibers of EDC.
iv) Higher chance of posterior interosseous nerve palsy, which is avoided by keeping the forearm pronated.
Open reduction and internal fixation
About 2700 of proximal radius articulates with the lesser sigmoid notch; any protruding implants in this region will cause impingement and restriction of movement. Implants that project above the articular surface should be placed in the safe zone described by Smith and Hotchkiss. It is the posterolateral quadrant of the radial head which doesn’t articulate with the lesser sigmoid notch. It is the area of head that corresponds to the area between the radial styloid and Lister’s tubercle of distal radius. Safe zone is identified by the following method.
- Keep the forearm in neutral rotation.
- Mark the mid-lateral point of the radial head.
- 450 arc anterior and posterior to the mid-lateral point is the safe zone.
Fixation may be done for Mason II and selected Mason III fractures. The implants used for fixation in Mason II fractures may be conventional bone screws (2.7 mm/2.0 mm/1.5 mm), variable pitch headless compression screws small threaded Kirschner wires and absorbable pins or screws. Mason III fractures need fixation by low profile mini-fragment plate and screws, small fragment T or L plates, cross-cannulated screws or pre-contoured anatomic radial head locking plates. In comminuted fractures, it is important to avoid excessive compression by screws.
Radial head arthroplasty
In presence of severe comminution with >3 fragments, fixation may not be possible and radial head excision is done. After excision elbow and forearm stability is tested. If stable, simple excision is sufficient. Arthroplasty is indicated in presence of forearm and/or elbow instability in fractures involving >30% of the radial head which cannot be satisfactorily reduced and stably fixed.
Aim of arthroplasty is to restore the radial head height, size and radial head-neck offset to achieve radiocapitellar and axial stability of forearm. Correct sizing is essential to prevent restriction of movement due to overstuffing and instability due to under-sizing. The resected head can be used as a template for sizing. During trials, the diameter, thickness, congruency and tracking should be assessed to estimate the proper fit. Normally when the forearm is in neutral rotation, the level superior edge of articular surface of lesser sigmoid notch and the radial head will be at the same level. Under C-arm the alignment of DRUJ, ulnar variance and symmetry of lateral and medial aspects of the ulnohumeral joint should be assessed for proper sizing.
Radial head prostheses are currently available in a number of options. It may be unipolar or bipolar, cemented or uncemented and monoblock or modular. It may be round or elliptical (Anatomic). Anatomic radial head prosthesis has an elliptical shape and it should be inserted with the long axis perpendicular to the lesser sigmoid notch, while keeping the forearm in neutral rotation.
Radial head excision
Radial head excision may be partial or total. Partial excision of >25% of radial head should be avoided. It may be required in presence of significantly comminuted and displaced fractures which cannot be reconstructed. But simple excision should be done only if the elbow and the forearm are stable. Hence after excision the stability of the forearm should be assessed and if unstable the radial head should be replaced. It may be associated with pain, instability, cubitus valgus, proximal migration of radius, DRUJ symptoms, weakness of grip and ulnohumeral arthritis.
Long arm splint is given for 7-10 days. Abduction of shoulder avoided for 6 weeks if lateral collateral ligament was repaired. Once sutures are removed active assisted mobilization is started. Strengthening exercises started once there is radiological evidence of union.
Outcome depends on the type of fracture and the associated lesions. 85% to 95% good results have been reported in undisplaced fractures managed nonoperatively with early motion. In displaced fractures, surgical treatment provides significantly better results than nonoperative treatment. Radial head prosthesis restores stability when the stability is compromised, but some loss of motion and strength is common and long term results are not yet known. In type III fractures, the results of radial head arthroplasty are superior to ORIF.
Most common complication is restriction of range of movement. Degeneration of radiohumeral articulation is also common. Secondary displacement of type I fractures can occur. Nonunion is rare. Posterior interosseous nerve palsy can occur, but usually recovers. Surgical site infection may require implant removal and debridement. Heterotopic ossification can occur. Capitellar erosion may occur after radial head replacement. Instability can occur after radial head excision. Loosening, overstuffing and radial head subluxation may be seen after radial head replacement.
From the outcome studies the importance of associated fractures and ligamentous injury is now clearly understood. But present methods of assessment of instability are nonspecific and inaccurate. With more specific and precise methods to assess instability and clearer cut guidelines for treatment will make the treatment more evidence based and reproducible.
With better understanding of anatomy of proximal radius and identification of the three dimensional pathoanatomy of common fracture patterns, development of fracture specific implants are likely to provide better methods of fixation. Anatomic radial head prosthesis is already available, but their advantages over the conventional designs need long term studies.
Radial head is essential for valgus stability of elbow, axial stability of forearm and for load transfer across the elbow. Radial head fractures are the commonest of elbow fractures. They are often associated with ligamentous injury and other periarticular fractures which have significant influence over the outcome. In presence of elbow and forearm instability, the radial head should either be fixed or replaced.
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