Ulnar collateral ligament (UCL) injuries are the most common reason for baseball pitchers to be out of action. The extreme forces put through the medial elbow during the pitching motion can cause damage to the UCL that ultimately requires reconstructive surgery.

Since its invention in 1974, ulnar collateral ligament reconstruction (UCLR) — commonly known as "Tommy John surgery" — has become a routine operation among pitchers, although the long-term outcomes were not clear until recently. A new study reviewed the length of career and reasons for retirement of those who had undergone UCLR, versus a control group of pitchers who had not.

What is the UCL?

The UCL is a thick band of nonelastic connective tissue found on the inner aspect of the elbow joint. It may also be known as the medial collateral ligament. It has a triangular shape to it and can be divided into three parts: the anterior bundle, the posterior bundle and the transverse ligament.

The UCL, together with the lateral collateral ligament (on the outer elbow) provide the main support to the elbow joint.

How is the UCL damaged?

The UCL can be injured either through one extreme force or lots of repetitive forces at the elbow joint — as usually occurs in baseball pitchers. The ligament is ether frayed (like a rope), stretched, partially torn or completely ruptured. In the case of pitchers, the repeated force from throwing each pitch causes degeneration in the form of tiny microtears, which become bigger and weaken the ligament until a full tear develops.

The type of force that tends to damage the UCL is known as a valgus force. The easiest way to describe this is to say it is the force that tries to push the forearm laterally (outwards). Hold your arm out straight in front of you, palm up, and imagine someone (or something!) pushing against your inner forearm, trying to push it outwards whilst the upper arm remains stable.

That force on the inner elbow is the valgus force, which can stretch and damage the UCL. Obviously in most injury situations, including pitching, this force occurs with the arm in a different position.

What is Tommy John surgery?

Tommy John surgery is the common name given to an UCL reconstruction. It got this moniker from the first recipient of the procedure, Los Angeles Dodgers pitcher Tommy John. His surgery was performed in 1974 by Dr Frank Jobe.

The number of UCLR surgeries has increased steadily since then, with more than 30 MLB pitchers undergoing the procedure every year since 2010.

The procedure involves using a tendon from elsewhere in the body to repair the injured UCL. An incision is made on the inside of the elbow joint and the damaged tendon is replaced with a tendon harvested from the forearm, hamstring, knee or foot.

The surgery procedure has been refined since its early days and no longer involves detaching any muscles or rerouting the ulnar nerve, as it once did. This has resulted in a less invasive surgery with reduced risk of complications.

What is the rehabilitation period after UCLR?

Rehabilitation following a UCLR is an extensive process that can take between eight and 16 months to complete and return to competitive pitching.

Immediately following surgery, the elbow is placed in a cast, which is fixed at 90 degrees of flexion. Initial exercises are aimed at the wrist and hand to maintain or regain full range of motion and grip strength.

Following the first week, a gradual increase in motion at the elbow is permitted and strengthening exercises are initiated with isometrics (static muscle contraction) at around week 2, followed by isotonic (with movement) exercises from week 4.

As well as rebuilding the strength in the elbow, a thorough rehabilitation program will also work on developing stability at the shoulder joint. This will help to promote proper shoulder mechanics and prevent future injuries.

Functional rehab and a return to the motion of throwing may start at around four months post-op. Click here to see an example of the rehabilitation protocol used by The Center for Shoulder, Elbow and Sports Medicine (CSES) at Columbia University Medical Center.

What are the long-term outcomes following UCLR?

The most recent study to be published on this subject comes from December's issue of the Othopaedic Journal of Sports Medicine. The aim of the study was to identify when and why MLB pitchers who have undergone UCLR surgery retire, compared to their counterparts who had not had surgery.

The study comprised 153 MLB pitchers who underwent UCLR surgery between 1974 and 2015, who have all now retired. The control group included the same number of retired MLB pitchers who were matched to the UCLR group based on sex, age, draft year and draft round.

The analysis revealed that the average time to retirement from surgery was 4.4 years, with a range of 0-26 years. 4.4 years was also the average time to retirement from the same point in their careers for the control group, with a range of 0-15 years.

The most common reasons for retirement were a decline in performance, shoulder problems and elbow problems. Interestingly, the UCLR group were more likely to have retired due to a drop in performance, whereas the control group more often retired due to shoulder and elbow injuries. This could be due to the extensive shoulder and elbow rehabilitation protocol following UCLR surgery.

Is a UCL injury likely to reoccur, and is revision surgery successful?

There does appear to have been an increase in the number of UCL revision surgeries over the last few years. Previously the rate was around 2-4 percent, although more recently the rate has been shown to be more like 10-12 percent among MLB pitchers.

The success rates of a revision surgery are lower than with the first surgery, and a rehabilitation program would need to be even more lengthy.