Tendoscopic-Assisted Repair of Complete Rupture of the Peroneus Longus Associated With Displaced Fracture of the Os Peroneum—Case Report

Case Report

A 41-year-old construction worker was hit by a metal bar on the lateral side of his left foot, causing forceful inversion. After the injury, he complained of severe pain over the lateral side of his foot and difficulty with walking. He was admitted to our department on the same day, where examination revealed diffuse swelling over the lateral aspect of his left foot with localized tenderness at the area lateral and plantar to the cuboid. He could not evert his left foot actively because of the pain (Figure 1). The power and plantar flexion range of the involved ankle and first metatarsophalangeal joint were also limited by pain. Radiograph of his left foot revealed proximal displacement of the os peroneum compared with the contralateral side (Figure 2). Ultrasound study of his left foot was suspicious for a tear of the peroneus longus tendon at the level of the cuboid. Complete tear of the peroneus longus tendon distal to the os peroneum was diagnosed by magnetic resonance imaging (MRI) (Figure 3).

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Figure 1.

Failure of active eversion of left foot (A) compared with the right (B).

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Figure 2.

Oblique radiographic view revealed proximal displacement of the left os peroneum (arrow) compared with the right side.

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Figure 3.

(A) Computed tomography revealed fracture of multipartite os peroneus with distal osseous fragment separated from the cluster of proximal fragments. Magnetic resonance imaging confirmed complete rupture of the peroneus longus tendon just distal to the os peroneum with T1 hypointense (B) and T2 hyperintense (C) fluid signal changes at the rupture site.

Tendoscopic-assisted mini-open repair of the peroneal longus tendon was performed with the patient in the lateral position with a thigh tourniquet. Peroneal tendoscopy ¹² was performed to locate the rupture site for subsequent repair. The proximal portal was made at the level of the distal fibula. A 2.7-mm, 30-degree arthroscope was introduced into the peroneal tendon sheath and advanced distally. The peroneus brevis tendon was found to be intact. The peroneus longus tendon was traced distally to locate the proximal tendon stump. It was then marked with a needle percutaneously, and the distal portal was made at this point. The 2.7-mm arthroscope was passed distally under the cuboid to locate the distal stump of the peroneus longus tendon, which was at the lateral edge of the plantar side of the cuboid (Figure 4). The distal portal was just proximal to the distal stump. ⁸ A shaver was introduced through the distal portal, and fragments of the os peroneum at both the distal and proximal stumps were resected under arthroscopic visualization. The distal portal wound was extended to 1 cm to facilitate placement of stay stitches to the ruptured tendon ends. An Ethibond No. 2 suture (Ethicon, Inc, Johnson & Johnson, Somerville, New Jersey) was weaved through the distal stump of the peroneal longus tendon with a Scorpion needle (Arthrex, Naples, Florida) through the distal portal. The proximal stump of the peroneus longus tendon was retrieved into the same wound and was weaved with an Ethibond No. 2 suture (Figure 5). The ruptured tendon ends were approximated with the 2 stay stitches tied together. Plantar flexion of the first metatarsal facilitated the application of the stay stitch to the distal stump and retrieval of the distal stump into the distal portal wound.

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Figure 4.

(A) Surface landmark of peroneus longus tendon: (x) proximal portal of peroneal tendoscopy. (B) Tendoscopic view of the peroneal tendon sheath: (1) Peroneus brevis tendon, (2) Peroneus longus tendon. (C) The proximal stump (3) of the peroneus longus tendon was marked with a needle. (D) Tendoscopic view plantar to the cuboid (4) showing the distal stump of the peroneus longus tendon (5).

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Figure 5.

The proximal (1) and distal stumps (2) of the peroneus longus tendon were retrieved to the distal portal wound.

After the operation, the ankle was immobilized in a short-leg cast for 3 weeks in eversion, followed by another 3 weeks in neutral position. Upon cast removal, the patient regained active eversion of his left ankle. A protective walking boot was used for another 6 weeks. Physiotherapy emphasizing ankle and subtalar joint mobilization was then started. There was good recovery of ankle function at 6 months after the operation. The postoperative American Orthopaedic Foot & Ankle Society (AOFAS) hindfoot scale was 90, whereas his preoperative score was estimated to be less than 30. At the last visit, 12 months after the initial injury, the patient was able to resume his highly demanding manual work. He reported occasional residual pain over the site of the repaired tendon.

Discussion

The os peroneum is a round or oval-shaped sesamoid bone located within the peroneus longus tendon in the region of the cuboid tunnel. ¹¹ It presents in its fully ossified form in around 20% of adults and is bilateral in approximately 60%.^1,11 It can have a bipartite or multipartite appearance. ¹ Common sites of peroneus longus tendon rupture are around the lateral malleolus and os peroneum, which are the 2 distinct avascular zones associated with tendinopathy. ¹⁰ A common injury mechanism is a sudden inversion followed by forceful protective eversion of a supinated foot. The rupture can occur at the osseotendinous junction or through the os peroneum itself. It has been suggested that the presence of an ossified os peroneum predisposes to rupture of the peroneus longus tendon.^7,9

Rupture of the peroneus longus tendon with or without fracture of the os peroneum is difficult to diagnose without a high index of suspicion. ⁵ Radiographic features of an acute fracture of the os peroneum are the presence of cortical discontinuity with nonsclerotic margins and a “pieces of a puzzle” appearance. ² Fragment separation more than 6 mm had a high correlation with complete rupture of the peroneus longus tendon. ² MRI is the standard method for evaluation of a peroneus longus tendon tear, with reported specificity of 100%. ² The treatment options for complete peroneus longus tendon rupture include nonoperative management, fixation of the os peroneum fracture, excision of the os peroneum with direct repair of the tendon, tenodesis of the peroneus longus to peroneus brevis tendon, and anchoring of the peroneus longus tendon to the cuboid or calcaneus.^3,4,6 No standard repair method is advised in the literature because the abnormality is rare.

In this case, we used a tendoscopic-assisted repair technique. This technique enabled us to confirm the diagnosis, assess the extent of injury, locate the exact rupture site, and retrieve and repair the tendon stumps through small arthroscopic wounds. Relative contraindications include chronic rupture of the peroneus longus tendon with preexisting distortion of the structure (eg, compound fracture of the foot or rheumatoid arthritis). In experienced hands, the wounds can be smaller and more precise, and the distal tendon stump can be retrieved with ease. Another option to help identify the site for the distal portal involves locating the proximal os peroneum fragment using fluoroscopy. With this technique, the initial proximal portal wound could be avoided. In our case, we proceeded to primary repair of the tendon since both tendon ends were retrievable for primary repair, the tendon quality was good, and the tension after the repair was optimal.

Conclusion

Displaced fracture of the os peroneum associated with complete rupture of the peroneus longus tendon is an uncommon entity. The definitive diagnosis and treatment should be determined primarily from detailed history and physical examination, together with appropriate radiological investigations. Tendoscopic-assisted repair can be a feasible operative option that carries the advantage of minimally invasive surgery.