Mid- and long-term clinical results of surgical therapy in unicameral bone cysts

Abstract

Background: Unicameral (or simple) bone cysts (UBC) are benign tumours most often located in long bones of children and adolescents. Pathological fractures are common, and due to high recurrence rates, these lesions remain a challenge to treat. Numerous surgical procedures have been proposed, but there is no general consensus of the ideal treatment. The aim of this investigation therefore was to study the long-term outcome after surgical treatment in UBC.

Methods: A retrospective analysis of 46 patients surgically treated for UBC was performed for short and mid-term outcome. Clinical and radiological outcome parameters were studied according to a modified Neer classification system. Long-term clinical information was retrieved via a questionnaire at a minimum follow-up of 10 years after surgery.

Results: Forty-six patients (17 female, 29 male) with a mean age of 10.0 ± 4.8 years and with histopathologically confirmed diagnosis of UBC were included. Pathological fractures were observed in 21 cases (46%). All patients underwent surgery for UBC (35 patients underwent curettage and bone grafting as a primary therapy, 4 curettage alone, 3 received corticoid instillation and 4 decompression by cannulated screws). Overall recurrence rate after the first surgical treatment was 39% (18/46), second (17.4% of all patients) and third recurrence (4.3%) were frequently observed and were addressed by revision surgery. Recurrence was significantly higher in young and in male patients as well as in active cysts. After a mean of 52 months, 40 out of 46 cysts were considered healed. Prognosis was significantly better when recurrence was observed later than 30 months after therapy. After a mean follow-up of 15.5 ± 6.2 years, 40 patients acknowledged clinically excellent results, while five reported mild and casual pain. Only one patient reported a mild limitation of range of motion.

Conclusions: Our results suggest satisfactory overall long-term outcome for the surgical treatment of UBC, although short-and mid-term observation show a considerable rate of recurrence independent of the surgical technique.

Figure 1

Radiographic evaluation of UBC morphology. The radiographs were evaluated according to the following parameters: length (L), width (Q), width of the growth plate (EF), distance from the adjacent growth plate (d) and distance from the growth plate to the joint (GH).

Figure 2

Frequency of pathologic fractures related to localization of UBC. Fractures were significantly more often observed in patients with UBC located in the humerus (p = 0.009).

Figure 3

Frequency of active cysts related to male and female sex.

Figure 4

(a) Pathological fracture of the proximal humerus in a male patient (5 y) initially treated conservatively. (b) 5 months later, the fracture is consolidated. However, the cyst shows significant growth progression.

Figure 5

Frequency of recurrence related to preoperative classification into active and latent. Recurrence was significantly higher in patients with UBC classified as active (p = 0.025).

Figure 6

(a) 12-year-old male patient treated by curettage and bone grafting for UBC of the right proximal femur. (b) 7 month later, UBC was considered "healed" with complete consolidation of the graft.

Figure 7

(a) 6-year-old female patient initially treated by injection of methylprednisolone. The picture shows the situation before the first injection. (b) 7 months later (3 month after revision curettage and bone grafting for pathological fracture of the distal femur in the course of corticoid therapy). (c) 16 years after the initial radiograph. No aspect of UBC is remaining.

Figure 8

11-year-old male patient initially treated by curettage and homologous bone grafting. (a) Before treatment. (b) 2 months later after surgery. (c) 8 years after surgery. Some aspect of UBC is remaining, while the patient is asymptomatic.

Figure 9

Midterm outcome after 52 months for the different surgical therapies.