Internal Elbow Joint Stabilizer
A recently developed novel technology to address the aforementioned shortcomings of chronic elbow instability is the internal joint stabilizer (IJS). This device is implanted subcutaneously about the elbow joint, allowing unrestricted joint motion while avoiding the complications inherent to other methods.
First developed in the early 2000’s, the latest technology on the market is based on the design created 2014. This model involved the use of a Steinmann pin (2.5mm thick metal pin) that was inserted in the distal portion of the humerus parallel to the axis of ulnohumeral rotation. The other end of the pin (on the lateral aspect of the implant) was bent in a figure-of-eight design and then secured to the ulna with use of screws (pictures below).
This internal construct allowed for un-inhibited flexion/extension and prevented motion in any other plane. This device remained in place to allow for adequate ligament healing, and then is subsequently removed with a simple procedure (usually around 6-7wks). Although removal of these implants is recommended, even with newer designs, current reports have found that about 2/3rds of patient opt to keep them in place.
Elbow Joint Stabilization
Historically, several methods of temporary stabilization have been utilized to manage chronic elbow instability. First line option involved immobilization of the elbow joint with the use of a splint or cast with the elbow in flexion a period of time sufficient for the soft tissue stabilizers to either heal or scar down (typically for a matter of several weeks).
This method was notoriously ineffective for a couple reasons. The first is that the arbitrarily flexed position of the elbow may not actually be in a position of stability. The second is that the elbow joint becomes stiff very rapidly in a matter of days, far quicker than the time required for the soft tissues to heal enough to provide adequate stability.
The surgical option in the past involved transarticular pinning (a metal pin placed across the elbow joint preventing motion). The drawback to this method is damage to the articular surface of the joint, which predisposes patients to early on set osteoarthritis.
This led to the use of external fixators, which involve metal pins inserted through the skin and into the bone both above and below the elbow joint. These pins are then connected to rods on outside of the skin. The use of hinged external fixators has been advocated, but due to difficulty of appropriately aligning the axis of rotation, preventing stiffness with early range of motion often was unsuccessful.
This led to abandoning the hinged component of the external fixator and acceptance of significant elbow stiffness. This is still often used in today’s practice, but these come at the cost of preserving joint motion, are clumsy, and pin tract infections are very common.
Elbow Joint Instability
Elbow instability can occur in the setting of a traumatic injury involving dislocation of the elbow joint, or less commonly, after surgical intervention for release of contracture or ulnohumeral synostosis (bone formation between the humerus and ulna). Elbow dislocations are the second most common joint dislocation in adults after shoulder dislocations and are the most common dislocation in children.
The elbow joint involves the articulation of three bones, the humerus, which articulates with the radius and ulna. The elbow joint is comprised of 3 primary stabilizers: ulnohumeral congruency, the medial collateral ligament (specifically the anterior bundle, which spans from the humerus to the ulna) and the lateral collateral ligament complex (ligaments on the outside part of the elbow, part of which attach the humerus to the radius).
Elbow dislocations are described as either simple (no fracture, purely ligamentous injury) or complex (concomitant fracture). Patients often experience significant pain and inability to move the elbow. Most simple elbow dislocations can be managed non-operatively by means of joint reduction, splint application for 5-10 days and active range of motion with occupational/physical therapy starting thereafter.
Recurrent instability after simple dislocations is rare (<1-2%), but often requires operative treatment to regain stability. Most complex elbow dislocation require acute surgical management in order to regain elbow stability with the intent of preventing chronic instability. Managing the unstable elbow after injury or surgical release is often difficult and requires fixation of the aforementioned primary stabilizers, as well as the secondary stabilizers (radiocapitellar joint, joint capsule, forearm muscles that originate from the bones of the elbow). When fixation of these structures fails to regain stability, there are only a few options available.
The Skeletal Dynamics IJS-Elbow is the only internal elbow joint stabilizer readily available in the United States today. A lateral approach to the elbow is utilized, typically with a 10-15cm incision. Prior to hardware implantation, any soft tissue defects can be appropriately addressed, such as ligamentous repair or radial head replacement. Once the primary and secondary stabilizers of the elbow joint have been restored, the device is then placed.
This low-profile design still incorporates a Steinmann pin inserted through the lateral side of the distal aspect of the humerus, parallel to the axis of flexion-extension of the ulnohumeral joint. The distal extension of the construct is attached to a small plate that can be fixed to the ulna with designated screws for improved stability.
Recent studies have demonstrated substantial improvement in elbow stability, with patients regaining near full motion of the elbow joint.The most common complication of the procedure is irritation from the hardware; however, this is only temporary as it is recommended that this construct be subsequently removed 6-7weeks after placement.