Age / Sex : 27 / M

Chief complaint: lateral ankle pain after having ankle sprain during skiing, 3 days ago

1) What is your impression?

Two weeks later, you can see the final diagnosis with a brief discussion of this case.

(Quiz는 quiz일 뿐이오니 답안은 한개만 보내주시기 바라오며, 복수의 답안을 보내주시는 분은 정답이 포함되어 있더라도 부득이 semi-correct answer로 처리토록 하겠습니다.)

Courtesy: 김옥화(Kim Ok Hwa), 인제대해운대백병원(Inje University Haeundae Paik Hospital)

Dislocations of peroneal longus and brevis tendons with type III injury of superior peroneal retinaculum

Discussion

Findings:

AP radiograph of the ankle shows a small
fleck of bone detached from
the lateral fibular margin. Axial CT
scan shows a small shell-like avulsion fracture off of lateral malleolus. Axial
T2-weighted and fat-suppressed T2-weighted MR images show the dislocated peroneal
longus tendon (PLT) and peroneal brevis tendon (PBT) from their
normal positions posterior to the lateral malleolus and the bone marrow edema in the
adjacent lateral malleolus.

Differential Diagnosis:

1.    
Subluxations
of peroneal tendons

2.    
Lateral
ankle sprain.

Diagnosis:

Dislocations
of peroneal longus and brevis tendons with type III injury of superior peroneal
retinaculum.

Discussion:

The superior peroneal
retinaculum (SPR) functions as the primary restraint to peroneal tendon
subluxation and is also a secondary restraint to anterolateral ankle
instability. It is formed from a confluence of the common peroneal sheath and
the superficial fascia of the leg. Anteriorly it attaches to and blends
together with the lateral fibular periosteum. Posteriorly it has variable
attachments to the Achilles tendon and the calcaneus. The SPR creates a
fibro-osseous tunnel for the peroneal tendons contained within their common
tendon sheath.

Injury of the SPR occurs with peroneal
dislocation through forceful ankle dorsiflexion and concomitant reflex peroneal
muscle contraction. This injury has been described in conjunction with numerous
sports activities, particularly snow
skiing. Patients with chronic injury
and recurrent tendon subluxation may present with inability to recall a
specific traumatic episode. Nontraumatic dislocations can be seen congenitally,
particularly with calcaneovalgus feet, or acquired, such as in patients with
neuromuscular disease.¹ Heel valgus may predispose to injury.

In the most common form of SPR injury
(Oden’s classification Type I), the SPR is not torn, but becomes detached from
the lateral malleolus together with stripping and elevation of the periosteum
to which it is attached, forming a false pouch. In a type II injury, the SPR is
torn near the lateral fibular margin. In a type III SPR injury, there is also
an associated avulsion fracture, which may be detected radiographically as a
small fleck of bone detached from the lateral fibular margin. Type IV injury
involves a tear of the posterior portion of the SPR. The vast majority of
injuries are Type I, without an actual tear of the retinaculum.

References:

1.    
Tjin
A Ton ER, Schweitzer ME, and Karasick D. MR imaging of peroneal tendon
disorders. Am. J. Roentgenol., Jan 1997; 168: 135 - 140.

2.    
Rosenberg
ZS, Bencardino J, Astion D, Schweitzer ME, Rokito A, and Sheskier S. MRI
Features of Chronic Injuries of the Superior Peroneal Retinaculum. Am. J.
Roentgenol., Dec 2003; 181: 1551 - 1557.