DISCUSSION
The avulsion fracture seen on the radiograph is consistent with a pseudo-Jones fracture. Alignment of the Lisfranc and Chopart joints was within normal limits. Also noted was an os naviculare, which was nontender on palpation. The
foot was placed in a functional brace and healed uneventfully.
A total of 26 bones are located in the foot: two in the hindfoot (calcaneus, talus), five in the midfoot (navicular, cuboid, three cuneiforms), and 19 in the forefoot (five metatarsals, 14 phalanges). The foot may also display sesamoid bones, including the os trigonum, os tibiale externum, os peroneum, and os vesalianum pedis.
As early as 1902, Sir Robert Jones contributed to the discussion and understanding of fractures in the fifth metatarsal after he suffered a foot injury while dancing. With advancements in radiographic imaging, clinicians are now able to accurately identify fracture location along the fifth metatarsal. This precision enables the physician to determine the various types of fifth metatarsal fractures (ie, Jones and pseudo-Jones), each of which has different treatment and prognostic implications.
A pseudo-Jones fracture, also called a tennis fracture, occurs at the proximal base of the fifth metatarsal.1 It should not be confused with a Jones fracture, which occurs transversely at the base of the fifth metatarsal, 1.5 to 3 cm distal to the proximal tuberosity. Jones fractures typically occur at the junction between the metaphyseal portion of the proximal fifth metatarsal and its adjoining diaphysis. These fractures require more aggressive management and treatment, including non-weight-bearing immobilization and/or surgery.2
Relatively more common than Jones fractures, a pseudo-Jones fracture occurs when the foot or ankle sustains an inversion injury. In the past, students have been taught that when the ankle inverts, the pull of the peroneus brevis tendon causes this avulsion fracture. However, recent evidence suggests that pull on the lateral cords of the plantar aponeurosis generates this same avulsion pattern.3 Because pseudo-Jones fractures occur in cancellous bone, the blood supply is excellent, allowing for successful and uncomplicated healing. This vascularity is not as abundantly noted with the Jones fracture, which exists in a vascular watershed area, and thus incidences of delayed union and nonunion are higher.
Patients with a pseudo-Jones fracture will report pain and tenderness over the affected area. Treatment is usually symptomatic, and patients are permitted to bear weight as tolerated.1 Such comfort measures as an elastic wrap, a functional brace, or a short-leg walking cast can be utilized.1 Radiographic evidence of union may take significantly longer than resolution of pain. The fracture typically heals by bony union or an asymptomatic fibrous union in 6 to 8 weeks.2 Surgery is needed only if significant bone displacement has occurred, which is rare. The prognosis for nondisplaced fractures is excellent.
A Jones fracture is less common than a pseudo-Jones fracture, and more problematic. Jones fractures can result when the patient generates a pivoting movement with weight transfer onto the metatarsal heads.2 Physical examination also reveals tenderness along the base of the fifth metatarsal, which makes the distinction between a Jones fracture and a pseudo-Jones fracture difficult. Nondisplaced fractures are treated with non-weight-bearing ambulation in a short-leg cast for 6 to 8 weeks;2 however, internal fixation may be indicated for patients who participate in high-demand activities. Unfortunately, because of the tenuous blood supply to the area where the fracture occurs, the rates of delayed union and nonunion are higher in patients with Jones fractures.1,2 JAAPA
Denise Rizzolo is a physician assistant at the Care Station in Springfield, New Jersey, and Assistant Clinical Professor, Pace University-Lenox Hill Hospital Physician Assistant Program, New York, New York. William Min is Chief Resident, Department of Orthopaedic Surgery, NYU Hospital for Joint Diseases in New York, New York. The authors have indicated no relationships to disclose relating to the content of this article.
Julie Vajnar, PA-C, RT, department editor
REFERENCES
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2. Fetzer GB, Wright RW. Metatarsal shaft fractures and fractures of the proximal fifth metatarsal. Clin Sports Med. 2006;25(1):139-150.
3. Theodorou DJ, Theodorou SJ, Kakitsubata Y, et al. Fractures of proximal portion of fifth metatarsal bone: anatomic and imaging evidence of a pathogenesis of avulsion of the plantar aponeurosis and the short peroneal muscle tendon. Radiology. 2003;226(3):857-865.