• Soo Min Cha, Hyun Dae Shin, Kyung Cheon Kim, and Jung Woo Park.
• Regional Rheumatoid and Degenerative Arthritis Center, Chungnam National University Hospital, Daejeon, Korea.
• Clin. Orthop. Relat. Res. 2014 Oct 1; 472 (10): 3166-76.

BackgroundStudies have focused on intramedullary nailing of femoral simple bone cysts but have not clarified the recurrence frequency or management of recurrent cysts. In particular, the affect of pathologic fractures on cyst healing, recurrence, and complications of treatment have not been reported.Questions/PurposesWe performed a retrospective comparative study to examine whether there were differences between simple bone cysts in the proximal femur nailed after pathologic fracture and those without pathologic fracture in terms of (1) healing time, (2) frequency and timing of recurrence, and (3) complications.MethodsFrom 1995 to 2005, 54 patients diagnosed with femoral simple bone cysts were treated and followed for a minimum of 8 years. Flexible nails were inserted in a retrograde fashion in 25 patients with fractures and 29 patients without fractures. The healing period, degree of radiographic consolidation based on the criteria of Capanna et al., recurrence frequency, and final bony abnormalities were analyzed. The mean followups were 107 months (range, 96-124 months) and 103 months (range, 96-140 months) in the groups with and without fractures, respectively. With the numbers available, a post hoc calculation showed that this study had 80% power to detect a difference of 7 months of healing time as significant with a probability less than 0.05.ResultsWith the numbers available, the mean healing period was not different between groups (25 versus 30 months in the groups with and without fractures, respectively; p = 0.16). Complete healing was observed at 19 versus 18 months, incomplete healing at 5 versus 8 months, and recurrence was observed in one and three patients in the groups with and without fractures, respectively. No differences were found in the distribution of healing grade based on the criteria of Capanna et al. A second surgery was performed using intramedullary nails in two patients with an open physis and compression hip screw fixation was performed in two patients with a closed physis. Finally, the recurrent cysts were classified as completely healed in three patients and incompletely healed in one.ConclusionsWhether a pathologic fracture had occurred before surgical treatment, intramedullary nailing of femoral simple bone cysts resulted in reliable healing, and the frequency of recurrence did not differ. Because this was a retrospective study, the optimal treatment for recurred cysts after intramedullary nailing should be further investigated through a comparative or prospective study.

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