Supra-condylar humerus fractures (SCHF) are amongst the most common fractures requiring surgical stabilisation in the pediatric age group (1). Closed reduction and percutaneous fixation with Kirschner wires (KW) is currently the standard of care (2). The number of KW used and their configuration has been the subject of much research (3, 4). The failure modes leading to loss of fracture reduction are not clear and have not been quantified. The aim of this study is to compare the mechanical stability of the opt-used configurations for various loading modes and contact interactions at the KW/bone interface.

A Gartland type-III SCHF was introduced to a fourth generation composite saw bone (Sawbones®, Vashon, Washington, USA). The model was CT scanned with a slice spacing of 0.5mm and pixel size 0.3×0.3mm. The CT data set was imported into AmiraDev (AmiraDev 5.2 Visage Imaging, Inc). A uniaxial mechanical test was conducted in order to measure the KW pullout forces from the distal humerus.

A model of the fractured humerus was constructed with the following steps: 1) manual segmentation; 2) surface generation of each fragment, and; 3) automatic volumetric grid generation for each fragment. The fracture was then virtually reduced and KWs were placed at the desired configurations (Fig 1a-b). For each configuration, a separate model was generated. Material properties were assigned to the bone-model elements according to the manufacturer's data sheet; Young's modulus E = 16GPa and E = 150MPa for the cortical and cancellous bone respectively. The KW were assigned a Young's modulus of 200GPa. Each of the models created in Amira was imported to a finite element application (Abaqus 6.9, DS-Simula) for structural analysis. For each of KW configuration four different torque forces load types were simulated (Fig 1c left): 1) a clockwise and counterclockwise torque with a magnitude of 1.5 NM (Newton/Meters); 2) a translational force with a magnitude of 30 N (Newtons) in the direction of the humerus shaft, and; 3) a shear force with a magnitude of 30 N in the direction parallel to the fracture plane. The results were normalised such that the maximum displacement for the crossed pin configuration with a coefficient of friction equal to zero (μ = 0) was used as unity for each load configuration. Similarly, for each of KW configuration four different translational forces load types were simulated (Fig 1c right): 1) a clockwise and counter clock-wise torque with a magnitude of 1.5 NM (Newton/Meters); 2) a translational force with a magnitude of 30N in the direction of the humerus shaft, and; 3) a shear force with a magnitude of 30N in the direction parallel to the fracture plane. The results were normalised as described above.

Radiofrequency (RF) ablation carries success rate of 70–90% in the treatment of Osteoid Osteoma (OO). Failures are related to incomplete ablation which might be caused by the probe’s small heating radius (0.5–0.8 cm). Water cooled tips were developed in order to prevent charring of the tip and adjacent tissues and to allow for a larger, up to 3cm ablation diameter. To our knowledge safety and efficiency of this probe in the treatment of pediatric OO were never reported. Our goal was to examine if this technique, when added to conventional RF ablation, improves the clinical results and whether it carries any additional risks in the pediatric population.

Twenty two OO patients, 15 males and 7 females, 3 years and 6 months to 18 years old, were treated using the Cool-tip™ Tyco probe in a cooled mode followed immediately by conventional RF cycle under general anesthesia, in the CT suite. Fifteen of the lesions were in the femur, 2 in the tibia and the remainder lesions were located in the humerus, talus, calcaneus, 2nd metatarsus and sacrum. The OO was intraarticular in 5 patients: femur (3), calcaneus and Talus. Follow-up period averaged 38.5 months (range 16–66 months). All patients but one had their symptoms resolved immediately following a single treatment (95.5% success rate). One patient had partial relief and underwent second successful ablation. There were one recurrence after 18 months and one superficial infection. No fractures, neurovascular complications or growth disturbances were encountered.

We conclude that the addition of a Cool-tip cycle to conventional RF ablation in children is safe, efficient and reduces the risk of recurrence without adverse effects specific to this age group. We attribute this success to the larger diameter of heat distribution occurring due to cooling of the tip and the prevention of probe and tissue charring.

We retrospectively reviewed 223 cases of supracondylar fractures of elbow treated in our hospital between the years 1996 and 2000. In 30 patients we found some degree of under-reduction of the extension element of the fracture. Twenty-two of them were evaluated close to skeletal maturity. The mean age at fracture was 5.4 years and mean follow-up was 8.2 years. The radiographic remodeling, range of elbow motion and awareness of the patients of functional limitation were evaluated. At the final follow-up17 (77%) of patients have had radiographic loss of humero-condylar angle (5 or more degrees of difference compared to an uninjured side). Eleven (50%) of the patients had limited elbow flexion, and seven (31%) of them were aware of this deficit. Most of under-reductions happened when reduction was attempted in the emergency room, or when displacement was not appreciated and a cast was applied without a reduction attempt.

The conclusions are that the patients that were left to heal with some degree of extension, have had limited end-elbow flexion and may be aware of it. Although only 3 patients felt a minor functional disability at the last follow-up the 10 patients have unsatisfactory results according the Flinn’s criteria for motion restriction. The treating surgeon must be aware of this possible outcome and be more demanding in the reduction of the extension component of a fracture. Otherwise one may expect limited elbow flexion that may be clinically significant. Although the reduction of moderately displaced fractures may seem easy, it is better done in the operating room and not in the emergency room, under general anesthesia and with radiographic control.