Follow-up MRI after conservative treatment of a complete rupture of the ulnar collateral ligament

A partial or complete rupture of the ulnar collateral ligament of the
metacarpophalangeal joint of the thumb, skier*s thumb, is an often-encountered
problem. It concerns 86% of all injuries to the base of the thumb. The
estimated incidence in the US is approximately 200,000 patients per year. The
incidence in the Netherlands is not known. In the last four years, we have
diagnosed approximately 85 patients in our own hospital. Skier*s thumb is the
result of a hyperabduction trauma of the thumb. It can occur with any fall on
an outstretched hand when a thumb that is already in abduction receives an
extra valgus stress. Skier*s thumb refers to the fact that this injury is often
seen in skiers who fall while holding on to their ski poles. This type of
injury is also seen in other sports, especially those that use a stick or ball,
such as hockey or basketball. During a query in our own inner-city hospital,
only 10% of the patients had skier*s thumb due to an injury acquired during
skiing. Often, these patients also presented with a delay because their injury
occurred during a holiday, and they waited until they came back home to see
their own physician. A fall on the hand, usually from a bicycle or motorcycle
(in which the thumb gets stuck behind the handlebars), is the most common cause
of skier*s thumb in our hospital, seen in approximately 40 % of all patients.
Another sport, especially soccer or fighting, was the cause in 30%.

The ulnar collateral ligament is made up of two parts, the proper collateral
ligament (PCL) and the accessory collateral ligament (ACL). The PCL has its
origin proximal to the base of the head of the MCP-1 joint and insertion on the
volar side of the proximal phalanx. The ACL has its origin just palmar of the
PCL and runs parallel to the PCL to its insertion on the proximal phalanx.
Together they ensure the ulnar and volar stability of the base of the thumb.
However, there are other components that also take part in creating stability
in the joint. They can be divided into stati and dynamic components. The most
important dynamic component is the adductor pollicis muscle. This muscle has
its insertion
onto the proximal phalanx partly superficial to and partly deeper than the UCL.
Most of the time, the distal end of the UCL ruptures. A Stener lesion occurs
when this part gets stuck between the proximal edge of the still intact
aponeurosis of the adductor. Because this aponeurosis stands between the UCL
and the bone, it is thought that this injury cannot heal in this position.
Stener lesions occur in 64% to 87% of all complete ruptures and are usually
treated by surgical repair. If the MCP joint is in flexion, the PCL and the
dorsal capsule are taut and therefore the most important stabilizers in that
position. The reverse applies to the ACL and the volar plate, which are taut
when the MCP is in extension.

The first step in diagnostic imaging studies is to make a plain radiograph in
the AP and lateral direction to diagnose an avulsion fracture that is mostly
located on the ulnar side of the proximal phalanx. If the plain radiograph
shows no avulsion fragment but there is a clinical suspicion of skier*s thumb,
further imaging can be performed by doing an ultrasound, CT, arthrogram or MRI.
Which technique to use seems to be determined by the physician*s preference;
there are no clear guidelines about this. MRI can be seen as a gold standard
with a sensitivity of 96%-100% and specificity of 95-100%.

If no firmendpoint is found during testing, surgery is considered the best
treatment. This also applies to Stener lesions because the general idea is that
the UCL cannot heal if it is not in contact with its insertion, even though no
evidence can be found in the literature to support this notion.
Some small prospective studies have been performed that show good outcomes for
patients with a complete rupture of the UCL that had conservative treatment.
Also, operative repair, though having a high succes rate, also has a small risk
of nerve injury. This is why the UCL-trial was set up, a multicenter randomised
controlled trial, to investigate whether conservative treatment of this injury
is equal to operative repair.
In this study, we want to make a follow up MRI scan of the UCL-trial patients
that had a conservative treatment of their injury. This way, we have an
objective and easily repeatable test to assess the level of recovery of the
UCL.

To investigate what the radiological findings on MRI are after a minimum of six
months conservative treatment of a complete rupture of the ulnar collateral
ligament of the thumb.

A descriptive study, in which patients from the aforementioned UCL trial that
were randomised into the conservative treatment group, will now get a followup
MRI scan of the thumb.

Patients will have to visit the hospital once to have the MRI scan made, this
will be a maximum of 30 minutes. The MRI scan itself does not emit harmful
radiation. Risks are not thought to be present in this study.