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Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XLIV | Pages 37 - 37
1 Oct 2012
Lamdan R Simanovsky N Joskowicz L Liebergall M Gefen A Peleg E
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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.

Results

Torque forces: the crossed configuration was found to be almost independent of the bone-implant friction and was symmetric in terms of direction of the applied torque. The diverging configuration exhibited larger dependency on the bone-implant interface. This is especially noticed as the coefficient of friction (COF) reduced to values below μ = 0.2. Translational forces: the diverging configuration exhibited high sensitivity to reduction of the COF μ = 0. Displacement of the fracture for μ = 0 was substantially larger for the diverging configuration relative to the crossed configuration: 13.5 times and 19 times for the transverse and pullout directions, respectively. As the COF increased to values above μ = 0.5, both fixation configurations performed in a similar manner.

Stabilisation of SCHF has been the subject of numerous studies. Relative stability of the different configurations and the risk for iatrogenic ulnar nerve injury has been in the center of the debate. Crossed KW configuration was shown in some clinical studies to be more stable than two lateral KW while others demonstrated no significant difference in stability. As ulnar nerve injury may occur in up to 15.4% of surgeries even if insertion of a medial KW is performed under direct vision, utilisation of two lateral KW configurations offers the advantage of reducing this risk significantly. The main finding of this study is that for a COF exceeding a threshold level (µ = 0.2) the crossed KW configuration did not offer any mechanical advantage over the diverging lateral KW configuration. However, for very low COF values (µ<0.2) the crossed configuration exhibited improved performance when compared with divergent lateral KW (figure 1d). The data demonstrates that the KW-bone bonding has a profound effect on the stability of the fixated bone construct. This is mostly evident when distraction forces are applied but also occurs, to a lesser degree, with rotational or translational forces. This may be a clinically important consideration in the rare SCHF in children with abnormal bones and possibly more commonly, when the KW-bone bonding was compromised after multiple attempts of passing the KW through the same entry point.

We have conducted a combined in-vitro mechanical test and finite element-based simulations of a fixated SCHF with different KW configurations, under various friction conditions. Under normal bone-implant interface bonding conditions, the two diverging lateral KW configuration offers adequate mechanical stability and may be the preferred choice of SCHF fixation.


Orthopaedic Proceedings
Vol. 92-B, Issue SUPP_III | Pages 467 - 467
1 Jul 2010
Peyser A Applbaum Y Simanovsky N Safran O Lamdan R
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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.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_III | Pages 513 - 513
1 Aug 2008
Simanovsky N Lamdan R Mosheiff R Simanovsky N
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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.


Orthopaedic Proceedings
Vol. 90-B, Issue SUPP_III | Pages 512 - 512
1 Aug 2008
Eylon S Simanovsky N Porat S
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Introduction: The usual surgical treatment of valgus knee in Ellis van Creveld Syndrom (EVC), is high tibial osteotomy. However, this approach failed to achieve the expected goal of lasting correction. Based on Dr. Paley’s observations, and our previous unsuccessful treatment of valgus knee in EVC syndrome, we changed the surgical approach. The aim of the surgical treatment is to eradicate all the elements causing sever valgus knee: 1) dysplasic lateral tibial condyle, 2) progressive depression of the lateral tibial plateau, 3) short fibula, 4) short and contracted fascia lata, 5) short lateral collateral ligament and biceps femoris, 6) short lateral head of gastrocnemius, and 7) contracted lateral knee capsule and lateral retinaculum. In many aspects the pathology of Blount’s disease grade 5 or 6 is similar, but located at the medial tibia causing genu vara.

Materials and Methods: Three valgus knees of EVC syndrome and two varus knees of Blount’s disease grade 5 & 6 underwent surgical treatment by a unique surgical approach to address all pathologies which contribute to the deformity. In the cases of EVC syndrome the first stage operation included: 1) peroneal nerve release and soft tissue release including T.F.L., B.F., L.C.L., capsule and gastrocnemius, 2) arthrogram, 3) fibulectomy, 4) elevation of lateral tibial plateau with bone graft, 5) reconstruction of L.C.L. and B.F., 6) lateral release of retinacula and rerouting of patella, and 7)cast application. In the second stage operation of these cases a corrective high tibial osteotomy was performed. In the Blount’s disease knees the operative treatment was performed in one stage and included: 1) arthrogram, 2) elevation of the medial tibial plateau, 3) fibulotomy, 4) closing wedge tibial osteotomy based laterally, 5) transfer of the bony wedge under the elevated plateau and fixation.

Results: All deformities were corrected with no recurrence, and stability of the knees persisted. We had one common peroneal nerve neuropraxia that recovered and one wound dehiscence.

Conclusions: In both conditions, EVC syndrome and Blount’s disease, corrective high tibial osteotomy does not address the pathology, and recurrence is to be expected. The described surgical technique fulfills that target – eradication of the pathologic elements that lead to valgus or varus.


Orthopaedic Proceedings
Vol. 88-B, Issue SUPP_II | Pages 333 - 333
1 May 2006
Simanovsky N Leibner E Hiller N Simanovsky N
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Introduction: Pediatric ankle trauma is common, and mostly a self limiting condition, with most children recovering within a few days to one week. However, some children seem to be affected more than others and to recover more slowly, despite normal radiographs. We set out to determine the occurrence of radiographically occult fractures, using high-resolution ultrasound.

Material and Methods: Twenty consecutive, skeletally immature patients, aged from 5 to 13 years with acute ankle injury, and normal radiographs were referred for high resolution ultrasound during the first week after the injury. A follow-up radiograph, obtained 2–3 weeks after the injury, was assessed for periosteal reaction / callus formation.

Results: In 13 patients there was no ultrasonographic evidence of fracture, nor was a periosteal reaction / callus formation. Six patients had ultrasonographic evidence of small fractures of the lateral malleolus, and periosteal reaction / callus formation on the follow-up film. In one patient a subcortical compression was evident on ultrasound. In this patient, although no periosteal reaction was observed on the follow up X-ray, a small fracture line became evident.

Discussion: Small lateral malleolar fractures may be missed on standard ankle radiographs. In patients with a clinical presentation consistent with a fracture, high resolution ultra-sound is a highly sensitive and specific diagnostic tool.