Isolated closed rupture of the flexor digitorum superficialis tendon

Sir,

We present the long-term outcome of an isolated closed rupture of the flexor digitorum superficialis (FDS) tendon of the non-dominant left ring finger in a 46-year-old male, with a delay not only in making the diagnosis but also in treating. After a minor trauma, the initial examination at another hospital was stated to be unremarkable. However, he gradually developed a flexion contracture at his proximal interphalangeal joint (PIPJ). Physical examination 5 months after injury revealed a 95° flexion contracture at the PIPJ [Figure 1] with minimal active distal interphalangeal joint flexion. A mass in the palm at the level of the distal palmar crease in line with the ring finger was palpable. A clinical diagnosis of FDS rupture was suspected and magnetic resonance imaging (MRI) confirmed the ruptured FDS tendon, which appeared to be coiled up in the palm [Figure 2].

Figure 1.

The near 90° flexion contraction at the PIP joint at the beginning of operation

Figure 2.

MRI of the left ring finger showing a ruptured FDS tendon, coiled up in the palm (single arrow shows the normal attachment of the FDS and double arrow shows the ruptured FDS tendon)

Surgical exploration revealed a coiled and ruptured FDS within a reactive pseudo-sheath [Figure 3]. The A1 pulley was released and the scarred tissue excised to isolate the FDS from the flexor digitorum profundus (FDP). Generous proximal excision of the FDS was performed so that the stump would be well away from the FDP within the carpal tunnel. This corrected the flexion contracture to 45° at the PIPJ. Next, a chevron-shaped incision was made over the volar aspect of the PIPJ. The A3 pulley was excised. The remnant of the FDS tendon was excised along with part of the volar plate, which was significantly thickened and contracted. The collateral ligaments were recessed off their attachment to the proximal phalanx and to the base of the middle phalanx. This made it possible to correct the finger to 20° short of full extension. Rehabilitative exercises were commenced on the same day with nighttime splinting, followed by an aggressive strengthening program at 4 weeks.

Figure 3.

An intraoperative photograph shows the opened reactive sheath (red arrow) exposing the ruptured FDS (black arrow) and the prominent FDP (blue arrow)

Three months later, the patient had nearly full composite flexion albeit with a 20° PIPJ flexion contracture [Figure 4a and b]. The patient was pleased with the functional outcome of his finger. However, 4.5 years later, he had an extension deficit of 60° with full flexion at the PIP and distal interphalangeal joint (DIP) joints [Figure 5a and b]. As he had no pain, he declined further care.

Figure 4.

Postoperative photographs show (a) Extension and (b) Full composite flexion at 3 months

Figure 5.

Postoperative photographs show (a) Extension and (b) Full composite flexion 4.5 years after operative treatment

While all previous reports[1–3] yielded a good functional outcome, this case underlines the significance of early identification and management of isolated FDS rupture as well as follow-up at regular intervals.