A terrible triad injury refers to a posterior dislocation of the elbow associated with radial head and coronoid process fractures.
Describe the pertinent anatomy and provide links to relevant pages
- Dislocations or subluxations typically occur as a result of a fall on an outstretched hand.
- Results in axial load and supination & valgus moments at elbow
- Soft tissue disruption proceeds sequentially in three stages from medial to lateral as displacement increases. This typical pattern of soft tissue disruption is associated with fractures of the coronoid and radial head.
- The coronoid fracture commonly consists of a transverse fracture of the tip of the coroniod that includes the anterior capsular insertion site. Less commonly the coronoid fracture is large or may primarily involve the anteromedial facet.
Stages of soft tissue injury as described by O'Driscoll:
- Stage 1:
- ulnar lateral collateral ligament disruption with or without disruption of the remaining lateral collateral ligament
- results in posterolateral rotatory subluxation that reduces spontaneously
- positive lateral pivot-shift
- Stage 2:
- Additional anterior and posterior soft tissue disruption
- elbow subluxes so that the coronoid is perched under the trochlea
- Stage 3:
- Stage 3a: Anterior band of MCL is intact. Elbow is stable to valgus stress test after reduction
- Stage 3b: Anterior band of MCL is ruptured and elbow is unstable to valgus stress after reduction
- Stage 3c: All soft tissues stripped from distal humerus; Elbow grossly unstable from 0-90 degrees, even after splinting or casting. Stable when flexed to greater than 90 degrees. If there is no associated fracture of the coronoid or radial head, displacement may be severe and sudden once the coronoid and radial head have cleared the distal humerus, leading to extensive soft tissue tearing. Typically the common flexor and extensor tendons are torn as well. However, fractures of the radial head and coronoid (terrible triad injury), when present, absorb energy in progression and the elbow dislocates and displacement (and secondary soft tissue tearing) may be less severe.
**An elbow with intact joint surfaces only requires two ligaments for stability: the ulnar lateral collateral ligament and the anterior band of the medial collateral ligament.
**Surgical repair of the anterior medial collateral ligament after an acute dislocation has not been shown to be superior to nonoperative treatment.
Describe the natural history,epidemiology and prognosis
Patient History and Physical Findings
In the setting of an elbow dislocation that has undergone a closed reduction it is imperative to test and document stability in all planes with the forearm in pronation, neutral, and supination. This will help guide treatment and rehabilitation.
Imaging and Diagnostic Studies
- AP and lateral views
- a line drawn through the long axis of the radius should intersect the capitellum on all views
- Fracture classifications:
- Radial head:
- Mason classification
- Hotchkiss modification
- Coronoid process
- Regan and Morrey
- Useful for further assessment of fractures in terrible triad injuries
Include a list with links to relevant conditions
All terrible triad injuries require surgical repair.
- Skin incisions:
- Posterior skin incision; If a medial exposure is contemplated, this incision will allow access to the medial and lateral elbow through one incision by raising flaps.
- Separate medial and lateral incisions; Medial approach will be required if a large, repairable radial head is in the way. Most repairs can be done from the lateral side.
- Lateral options:
- Extensors are elevated off the supracondylar ridge
- Kocher approach: ECU and anconeus interval
- Modified Kocher: exposure is gained through a traumatic rent in the common extensors
- EDC tendon is divided in its midline
- Medial: Between the two heads of the FCU or the over-the-top technique as described by Hotchkiss
- A standard surgical protocol should be used when treating these injuries that includes fixation or replacement of the radial head, fixation of the coronoid fracture if possible, repair of associated capsular and lateral ligamentous injuries, and in recalcitrant cases repair of the medial collateral ligament and/or adjuvant hinged external fixation . Recommended surgical steps are as follows:
- Radial head fixation or replacement
- Internal fixation:
- fractures involving less than 25% of the head, fragments that are very small or very osteoporotic and extraarticular at the radioulnar joint may be excised as ling as the elbow is stable after repair of the coronoid and collateral ligaments. If the elbow is unstable at this point, proceed with radial head replacement. Excision of the radial head without replacement is not recommended for these injuries .
- "Safe zone" for internal fixation: With the forearm in neutral rotation, bisect the anteroposterior diameter to the radial head and make a mark at this point. The safe zone extends 65 degrees anterior to and 45 degrees posterior to this mark (total arc = 110 degres)
- Over- or understuffing the radiohumeral joint by 2.5 mm or more significantly alters elbow kinematics and radiocaptiallar pressure
. Overstuffing may lead to pain and early EJD, while undersuffing increases the risk of valgus instability.
- The plane of the articular surface of the radial head is located 0.9mm proximal to the plane of the lateral articular surface of the coronoid
- A visual lateral ulnohumeral joint gap seen intraoperatively is a reliable indicator of over-lengthening greater than 2mm. Radiographic asymmetry of the medial ulnohumeral joint is insensitive for detecting over-lengthening, as incongruity of ulnohumeral joint only occurs after over-lengthening of the radius by 6mm or more.
- Coronoid fracture repair.
- If unable to fix from a lateral approach, fix through a medial approach
- Fixation options:
- Small fragments can be fixed with nonabsorbable suture (#2 or #5 nonabsorbable). A targeting guide may be used to make a drill hole(s) from the subcutaneous border of the ulna through the fracture fragment. Medial and lateral holes are made with a small drill or 0.062 K-wire. Keith needle or suture passer is used to route the suture.
- Fragments large enough to accommodate two screws can be fixed with two or more cannulated screws.
- Basal fractures may be fixed with a small plate
- Fractures involving less than 10% of the coronoid process have little effect on elbow stability and do not need repair.
- repair lateral collateral ligament
- the ligament is typically avulsed from its origin
- repair with suture anchors or transosseous suture with the elbow at 90 degrees
- MCL intact: repair LCL with forearm in pronation
- MCL injured: repair LCL with forearm in supination
- After treatment of the radial head fracture, coronoid process and LCL test elbow stability under live fluoroscopy. The elbow should remain concentrically reduced from 30 degrees to full flexion in one or more positions of forearm rotation. If this is the case, repair of the MCL is not necessary. If elbow is still unstable, repair the medial collateral ligament.
- At least one study has concluded that repair of the MCL is unnecessary.
- If elbow unstable after repairing the MCL, place the patient in a static or hinged external fixator (ulnohumeral transfixation is an option as well).
- Static ex fix must be removed within 3 weeks and hinged ex fix is removed between 3-8 weeks.
- Before leaving the OR test and document the stable arc of motion for rehabilitation purposes.
- Postoperative splinting position:
- MCL intact, LCL repaired: splinted at 90 degrees/full pronation
- MCL and LCL repaired: splint in neutral
- LCL repaired and MCL unrepaired: 90 degrees flexion and full supination
- Range of motion to begin 2-5 days postop within stable arc of motion determined intraoperatively. Include pronation/supination with elbow at 90 degrees.
- Resting splint used between exercises for 6 weeks
- Static progressive extension night splint begun at 6 weeks
- Strengthening at 8 weeks or when fractures and ligamentous repairs are secure.
Pearls and Pitfalls
Tips and problems to avoid
Include immediate postoperative care and rehabilitation
Include functional and prosthetic survivorship data as applicable
Include overview of complications