A 38-year old patient is referred for chronic pain in lateral plantar region of the right foot.
Complaints started after running.
Fig. 1: Reformatted proton density weighted fat saturated MRI image. Striped arrow: os peroneum incorporated in the peroneal tendon. White arrow: hyperintense signal intensity localized in the peroneal tendon at the level of the os peroneum.
Painful os peroneum syndrome (POPS) is a condition usually characterized by acute fracture of the sesamoid os peroneum (or diastasis of a multipartite os peroneum), chronic partial tendon rupture, tendon chronic entrapment or even prominent calcaneal tubercle. [1] POPS is a relatively new recognized entity and still an underdiagnosed condition. Operative treatment can be performed when conservative therapy fails and pain persists. A peroneal disorder needs to be documented very excessively before an operation can safely be performed. The procedure usually consists of tendon debridement, tenosynovectomy and excision of the os peroneum (combined with removal of the hypertrophied peroneal tubercle, if present). Delayed diagnosis may lead to sequels, such as inflammation of the peroneus longus tendon, ankle instability, and peroneal compartment syndrome.
If plain radiography shows unusual accessory bony variation, US or MRI can make the differential diagnosis, and guide further therapeutic management. Radiographic differentiation between fractured os peroneum and multipartite os peroneum can be troublesome. Fracture margins appear relatively nonsclerotic in acute presentations and the bone fragments resemble fitting “pieces of puzzle”, whereas finding rounded, smooth, sclerotic borders are suggestive of multipartite os peroneum. [2] It is conceivable that remodelling of fracture fragments could give the appearance of a multipartite os peroneum. Displacement of an os peroneum fragment can be helpful in the differential diagnosis. The distracted proximal fragment in case of a fracture may be located several centimetres proximal to the calcaneocuboid joint. Assessing this displacement pattern can be useful in differentiating between an os peroneum fracture and normal distraction in multipartite os peroneum. Pain or discomfort when applying direct ultrasound transducer pressure, combined with a large gap (6 mm or more is highly suggestive for POPS) between sesamoid particles with irregular margins requires further exploration.[2] When distance is less, like our patient exhibits (2mm), chronic impingement or a healing fracture is more likely.
Sonographic diagnostic accuracy can be elevated by the presence of associated peroneus longus tendon abnormality. Posterior acoustic shadowing is only present in larger bone fragments. MRI can be helpful when mid-foot peroneus longus tendon tear is suspected. Findings on fluid-sensitive sequences like STIR or PD-fat-saturation, include tears portrayed by a risen signal-intensity, near the site of the tear, and morphologic tendon abnormalities. Other secondary findings such as hypertrophic peroneal tubercle, bone marrow oedema of the tubercle, lateral calcaneal wall or cuboid bone can occasionally be identified. [2] Our patient was treated conservatively and recuperated well.
Painful os peroneum syndrome (POPS)
This is a 37-year-old male patient presenting with chronic pain on the lateral plantar aspect of the right foot, which is related to running. On the sagittal MRI view of the right foot, a round accessory bone is observed in the lateral region of the foot, likely associated with the base of the 5th metatarsal or the cuboid bone. This suggests an accessory bone (a bony structure known as the “os peroneum”) located within or adjacent to the peroneus longus tendon.
Near this accessory bone, there are signal abnormalities within or around the tendon: on T2/PD fat-suppressed sequences, there is a high-signal band indicating local soft tissue inflammation or mild tendinous injury. The gap between the two bony fragments is approximately 2 mm, with relatively smooth edges. There is no obvious sharp fracture sign or significant displacement. No marked abnormality is noted in the local soft tissue shape, although mild edema or tenosynovitis may be suspected. There is no extensive cortical or bone marrow signal abnormality.
Considering the patient’s age, symptoms (chronic lateral plantar foot pain exacerbated by activity), and imaging findings (mildly separated os peroneum fragments with inflammatory signals around the peroneal tendon), the most likely diagnosis is: Painful Os Peroneum Syndrome (POPS), possibly accompanied by mild chronic impingement or partial tear of the peroneal tendon.
1. Conservative Treatment:
2. Functional Exercise and Rehabilitation:
3. Indications for Surgical Treatment:
4. Precautions:
Disclaimer: The above report is for reference only and cannot replace an in-person examination or professional medical advice. Specific treatment plans should be made by a clinical physician based on the patient’s individual condition.
Painful os peroneum syndrome (POPS)
