Sagan Michelle L, Datta Jason C, Olney Brad W, Lansford Todd J, McIff Terence E
Department of Orthopedic Surgery, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
J Pediatr Orthop. 2010 Oct-Nov;30(7):638-43. doi: 10.1097/BPO.0b013e3181efb8e2.
Procurvatum or anterior bow deformity is a potential complication after treatment of femur fractures with flexible titanium nails (FTNs). This article reports on a clinical evaluation of angulation after treating pediatric femur fractures with FTNs. The article also reports on a complementary investigation of potential causes of these deformities using a biomechanical model.
All pediatric femoral shaft fractures treated with FTNs over a 4-year period were reviewed. Fracture location, pattern, angulation, and nail shoe tip orientation were recorded from postoperative radiographs. Malunion was defined as greater than 10 degrees of angulation on the AP radiograph or greater than 15 degrees on the lateral view. As an adjunct to the clinical study, a synthetic femur model was created using midtransverse fractures. These femurs were nailed using 2 FTNs inserted so as to create constructs having the following combinations of nail shoe tip orientation: both anterior (AA), both posterior (PP), both neutral (NN), or 1 anterior and 1 posterior(AP). The resulting angular deformities noticeable upon gross inspection were then measured.
Of the 70 fractures reviewed, malunion occurred in 16 fractures, of which 11 had increased anterior bow. A majority of malunions was observed in older children with middle third of the femur fractures. They were significantly more prevalent in transverse fractures compared with all other fracture patterns. Clinically, increased anterior bowing did not occur if 1 of the nails was positioned to resist procurvatum, as seen in the lateral radiograph. Depending on nail tip orientation, the biomechanical femur fracture model showed significant differences in mean deformations after nail placement: AA had 12.6 degrees of posterior bow compared with 14.8, 3.7, and 0.3 degrees of anterior bow for PP, NN, and AP, respectively.
Anterior bowing greater than 15 degrees is the most common malunion noted in this series of femur fractures that were nailed using FTN's. We conclude that final nail shoe tip orientation influences the likelihood of anterior bow deformity. The likelihood of large anterior bowing may be reduced if at least 1 of the nails is inserted with the tip pointing in an anterior direction. LEVEL OF EVIDENCE/CLINICAL RELEVANCE: Level III.
股骨前弓畸形是使用弹性钛钉（FTN）治疗股骨骨折后的一种潜在并发症。本文报告了使用FTN治疗儿童股骨骨折后对成角情况的临床评估。本文还报告了使用生物力学模型对这些畸形潜在原因的补充研究。
回顾了4年间所有接受FTN治疗的儿童股骨干骨折病例。从术后X光片中记录骨折位置、类型、成角情况和钉帽尖端方向。畸形愈合定义为正位X光片上成角大于10度或侧位片上大于15度。作为临床研究的辅助，使用中段横行骨折创建了一个合成股骨模型。这些股骨用2根FTN进行固定，以创建具有以下钉帽尖端方向组合的结构：均朝前（AA）、均朝后（PP）、均为中性（NN）或1根朝前1根朝后（AP）。然后测量肉眼可见的由此产生的角畸形。
在回顾的70例骨折中，16例发生畸形愈合，其中11例股骨前弓增加。大多数畸形愈合发生在年龄较大的股骨中段骨折儿童中。与所有其他骨折类型相比，横行骨折中畸形愈合明显更为普遍。临床上，如侧位X光片所示，如果其中一根钉子的位置能够抵抗股骨前弓，则不会出现前弓增加。根据钉帽尖端方向，生物力学股骨骨折模型显示固定后平均变形存在显著差异：AA组有12.6度的后弓，而PP组、NN组和AP组的前弓分别为14.8度、3.7度和0.3度。
在这一系列使用FTN固定的股骨骨折中，大于15度的前弓畸形是最常见的畸形愈合情况。我们得出结论，最终的钉帽尖端方向会影响前弓畸形的可能性。如果至少有一根钉子的尖端朝前插入，则大角度前弓畸形的可能性可能会降低。证据水平/临床相关性：三级。
