Active unicameral bone cysts in the upper limb are at greater risk of fracture.
OBJECTIVE
To elucidate the natural history of unicameral bone cyst (UBC) and risk factors for pathological fracture.


METHODS
14 males and 8 females (mean age, 9 years) diagnosed with UBC were reviewed. Cyst location, symptoms, and whether there was any fracture or surgery were recorded. Cyst parameters were measured on radiographs, and included (1) the cyst index, (2) the ratio of the widest cyst diameter to the growth plate diameter, and (3) the adjusted distance of the cyst border from the growth plate.


RESULTS
There were 11 upper- and 11 lower-limb cysts. 13 patients had pathological fractures and 9 did not. 20 patients were treated conservatively with limb immobilisation; 2 underwent curettage and bone grafting (one resolved and one did not). Seven cysts resolved (5 had fractures and 2 did not). The risk of fracture was higher in the upper than lower limbs (100% vs 18%, p<0.001). Fractured cysts were larger than unfractured cysts (mean cyst index, 4.5 vs. 2.2, p=0.07). Active cysts were more likely to fracture.


CONCLUSIONS
Conservative management had a 30% resolution rate. Surgery should be considered for large active cysts in the upper limbs in order to minimise the fracture risk.
Tey
Inn Kuang
IK
Department of Orthopaedic Surgery, KK Women and Children's Hospital, Level 8, Children's Tower, 100 Bukit Timah Road, Singapore 229899. innkuang@hotmail.com
Mahadev
Arjandas
A
Lim
Kevin Boon Leong
KB
Lee
Eng Hin
EH
Nathan
Saminathan Suresh
SS
D001845:Bone Cysts / Q000150:complications* / Q000000981:diagnostic imaging / Q000628:therapy*; D016025:Bone Transplantation; D002648:Child; D003475:Curettage; D005260:Female; D050723:Fractures, Bone / Q000000981:diagnostic imaging / Q000209:etiology* / Q000628:therapy*; D005598:Fractures, Spontaneous / Q000000981:diagnostic imaging / Q000209:etiology* / Q000628:therapy*; D006801:Humans; D035002:Lower Extremity; D008297:Male; D011859:Radiography; D012307:Risk Factors; D016896:Treatment Outcome; D034941:Upper Extremity