Is ultrasound indicated in the diagnosis of closed avulsion injuries of the flexor digitorum profundus tendon?

Dear Sir,

We report our experience of ultrasonography in the diagnosis and management of acute closed avulsion of the flexor digitorum profundus (FDP) tendon.

Closed avulsion of the FDP tendon, often referred to as ‘rugger jersey finger’ is classically described as occurring via a hyperextension mechanism in athletes. These injuries were classified by Leddy and Packer (1977). Type I: avulsion with retraction into the palm. Type II: avulsion with or without a small bone fragment and retraction to the proximal interphalangeal joint. Type III: avulsion with a bone fragment, with retraction to the A4 pulley. Robins and Dobyns (1975) described avulsion of a bony fragment, with subsequent separation of the tendon from this fragment. This is now recognised as a type IV injury.

We have reviewed retrospectively a series of 20 consecutive patients presenting to our department between February 2006 and August 2008 each with an injury to a single digit. There were 17 men and three women with a mean age of 36 (range 16–55) years. The injury was to the ring finger in 16 patients and the little finger in four. The mechanism of injury was hyperextension in all cases, and a ‘rugger jersey’ was implicated in 13.

All 20 patients had clinical evidence of tendon rupture, and plain radiographs identified an avulsed bone fragment in four cases. Thirteen patients were referred for ultrasound. The others were listed directly for surgery after discussion with a senior hand surgeon. All the ultrasound scans were performed by one of two consultant radiologists experienced in musculoskeletal ultrasound using an Aplio SSA-700A (Toshiba) with a 12 Mhz probe or an Acuson Sequoia 512 ultrasound system (Siemens) with a 15 Mhz probe.

Ultrasonography identified one partial avulsion, four type I avulsions, five type II avulsions, and three type III. No type IV injuries were identified.

All 20 patients proceeded to surgical exploration and repair under general anaesthesia. The operative findings confirmed the clinical diagnosis of tendon avulsion in all cases. The Leddy–Packer classification as determined by ultrasound was confirmed in ten of the 13 patients. In the remaining three the tendon was found proximal to the level indicated by ultrasound.

Ultrasound scans were performed at a mean of 1.2 days (range 0–5 days) from admission. In those patients who received an ultrasound scan, the mean time from admission to surgery was 1.5 days (range 0–6 days). Eleven of the 13 scans were performed within 2 days of admission, and in ten cases surgery was performed later on the day of the scan. Patients who had surgery without a scan did so in a mean time of 1 (range 0–2) days. Seventeen of the patients were operated upon within 2 days of admission.

Ultrasound has been reported in the diagnosis of complete and partial ruptures of finger flexor tendons (Martinoli et al., 2002). The role of ultrasonography in the diagnosis and management of acute closed avulsion of the flexor digitorum profundus has not been reported.

Clinical assessment and plain radiography was very accurate in our series. Ultrasound scans did not alter management but did add a small further delay to treatment. We believe that the routine use of ultrasound in the diagnosis and management of acute closed avulsed FDP tendons is unnecessary.