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Hydroxyapatite Pin Cannulation for Management of Simple Bone Cysts

March 01, 2019

Contributors: Katsuhiro Hayashi, MD; Toshiharu Shirai, MD; Akihiko Takeuchi, MD; Hiroyuki Tsuchiya, MD; Hirotaka Yonezawa, MD; Norio Yamamoto, MD; Norio Yamamoto, MD

Simple bone cysts (SBCs) are benign bone tumors. Most SBCs occur in the first two decades of an individual’s life. SBCs commonly occur in the proximal humerus, proximal femur, and calcaneus. The management of SBCs is controversial because of poor healing rates and the invasiveness of surgery. This video details the surgical technique and pitfalls of hydroxyapatite pin cannulation for the management of SBCs. The patient is positioned supine with a towel under the left buttock. The trochanteric epiphyseal line and the femoral neck axis as well as the axis of the femur are marked. A 2-cm incision is made over the lateral side of the proximal femur. The subcutaneous tissue is incised along the same line as the skin incision with the use of an electric scalpel. The level of the fascia is then exposed. The iliotibial band as well as the fascia and fibers of the vastus lateralis are split to expose the lateral aspect of the proximal femur. A sterile 1-mL syringe is prepared, and the internal cylinder is removed. We cut the tip of the syringe to use it as a drill sleeve. The drilling point to the cyst is confirmed with the use of an image intensifier. A 2.3-mm Kirschner wire is inserted through the sleeve. The bone cortex is then drilled. Through the syringe, we confirmed the color of the cystic content, which usually ranges from a clear yellow to red. A red color often results from the cystic content being mixed with blood from drilling. Curettage is repeated several times to remove the cyst epithelial lining. Curettage near the epiphysis should be performed with the utmost care under fluoroscopic guidance to avoid epiphyseal plate damage. The curetted tissue should be submitted for biopsy. The proximal side is drilled first. A wet gauge is then prepared, and the distal side of the bone medulla is drilled with flexible Kirschner wire. Under image intensifier guidance, the trial is inserted and pin length is measured. The hydroxyapatite pin is prepared and manually shortened with the use of a sharp knife based on the measured length. The distal side of the head is trimmed with the use of Luer bone rongeurs to achieve deep and stable pin insertion. The pin is inserted along the guidewire under image intensifier guidance. Full weight-bearing and full range of motion are allowed immediately postoperatively. Sports activity is allowed 3 months postoperatively. Follow-up radiographs are obtained every month postoperatively. Hardware removal is unnecessary. We retrospectively reviewed 39 patients with a SBC who underwent hydroxyapatite pin cannulation. The mean age of the patients was 11.8 years. Of the 39 patients, 31 were male and 8 were female. Sites of the SBCs included the calcaneus (20 patients), humerus (14 patients), femur (4 patients), and pelvis (1 patient). The mean surgical time was 62.4 minutes. The mean healing period was 5.5 months. Hydroxyapatite pin cannulation was successful in 31 of the patients (79.6%); however, treatment failed in four patients (10.2%), and four patients (10.2%) experienced recurrence. The mean follow-up time was 35.7 months. Surgeons should be careful to not cause an iatrogenic fracture during the procedure. Curettage must be performed carefully near the epiphysis. Sports activity should not be allowed until sufficient bone remodeling is achieved. If a residual cyst appears to have enlarged on postoperative radiographs, revision surgery must be planned.