Applied Radiology

Diagnosis

Symptomatic bipartite medial cuneiform

Findings

Weight-bearing plain radiographs of the right foot showed no acute fracture or subluxation, but they did reveal a bipartite medial cuneiform (Figure 1). The patient continued to have pain despite conservative management. Magnetic resonance imaging (MRI) of the foot was performed 3 months later for further workup. The MRI showed the presence of a bipartite medial cuneiform with increased signal in the uppermost medial cuneiform (Figures 2 through 5). An os tibiale externum variant was present with no signal abnormality. No other abnormalities were noted.

Discussion

Common developmental anomalies of the foot (such as accessory and bipartite bones) are usually asymptomatic incidental radiographic findings. The medial cuneiform can sometimes present as a bipartite cuneiform, a rare developmental anomaly. The partition classically divides the bone into upper and lower halves and is best seen in the lateral view of the foot. The incidence of bipartite medial cuneiform has been reported to range from 0.33% to 2.4%.¹ Bipartitions can mimic traumatic injury² but are generally bilateral and have smooth cortical margins.³

Barlow reported the first case of bilateral bipartite medial cuneiform in a cadaver foot in the 18^th century. The incidence of bipartite medial cuneiform is 1 in 320.³ There have been only 3 reports in the literature citing bipartite medial cuneiform in a living patient as an incidental finding. Barclay⁴ reported a case of a 34-year-old male jockey with navicular fracture and an incidental medial cuneiform. The other case report was cited by Dellacorte et al³ in 1992. The bipartite medial cuneiform was detected by computed tomography that was performed to assess for fracture of the intermediate cuneiform. O'Neal et al² described the presence of a bipartite medial cuneiform in a 5-year-old boy's amputated leg.

A literature search showed only 2 reported cases of a symptomatic bipartite medial cuneiform. In 2001, Azurza and Sakellariou¹ reported a case of bipartite medial cuneiform in 34-year-old soldier with chronic left foot pain after a soccer injury. He was successfully treated with osteosynthesis. Chiodo et al⁵ presented a case of symptomatic medial cuneiform in 2002 in a 32-year-old female marathon runner with exertional left midfoot pain. Weight-bearing radiographs of the symptomatic foot revealed a bipartite medial cuneiform.

We present a case of a symptomatic bipartite medial cuneiform, which was seen on plain radiographs. MRI, as stated above, showed increased signal in the uppermost medial cuneiform and superior aspect of the inferior medial cuneiform. This suggests marrow edema, which was likely caused by a minor traumatic event and led to the symptoms in this patient. The tarsal anomaly may have allowed a relatively minor traumatic event to cause significant long-term symptoms due to altered biomechanics within the midfoot.⁶

CONCLUSION

A bipartite medial cuneiform is an uncommon anomaly that is rarely symptomatic. This type of developmental anomaly of the foot may change the biomechanics of the tarsal bones, which can allow minor injuries to cause disproportionately severe symptoms. A relatively minor acute injury can ultimately lead to chronic inflammation and long-term pain, as was the case in this patient.

1. Azurza K, Sakellariou A. 'Ostoesynthesis' of a symptomatic bipartite medial cuneiform. Foot Ankle Int. 2001;22:499-501.
2. O'Neal ML, Ganey TM, Ogden JA. Fracture of a bipartite medial cuneiform synchondrosis. Foot Ankle Int. 1995;16:37-40.
3. Dellacorte MP, Lin PJ, Grisafi PJ. Bilateral bipartite medial cuneiform. A case report. J Am Podiatr Med Assoc. 1992;82:475-478.
4. Barclay M. A case of duplication of the internal cuneiform bone of the foot (cuneiforme bipartitum). J Anat.1 932;67:175-177.
5. Chiodo CP, Parentis MA, Myerson MS. Symptomatic bipartite medial cuneiform in an adult athlete: A case report. Foot Ankle Int. 2002;23:348-351.
6. Schweitzer ME, White LM. Does altered biomechanics cause marrow edema? Radiology. 1996;198:851-853.