Zachert Gregor, Rapp Marion, Eggert Rebecca, Schulze-Hessing Maaike, Gros Nina, Stratmann Christina, Wendlandt Robert, Kaiser Martin M
Department of Pediatric Surgery, University of Lübeck, Lübeck, Germany.
Department of Pediatric Surgery, Hospital of Kassel, Kassel, Germany.
Eur J Pediatr Surg. 2015 Aug;25(4):365-72. doi: 10.1055/s-0034-1376394. Epub 2014 Jun 10.
For pediatric femoral shaft fractures, elastic stable intramedullary nailing (ESIN) is an accepted method of treatment. But problems regarding stability with shortening or axial deviation are well known in complex fracture types and heavier children. Biomechanical in vitro testing was performed to determine whether two modified osteosyntheses with an additional tension screw fixation or screw fixation alone without nails could significantly improve the stability in comparison to classical ESIN.
A total of 24 synthetic adolescent-sized femoral bone models (Sawbones, 4th generation; Vashon, Washington, United States) with an identical spiral fracture (length 100 mm) were used. All grafts underwent retrograde fixation with two C-shaped steel nails (2C). Of the 24, 8 osteosyntheses were supported by one additional tension screw (2C1S) and another 8 by two screws (2S) in which the intramedullary nails were removed before testing. Each configuration underwent biomechanical testing in 4-point bending, external rotation (ER) and internal rotation (IR). Furthermore, the modifications were tested in axial physiological 9 degrees position for shifting and dynamic compression as well as dynamic load.
Both screw configurations (2C1S and 2S) demonstrated a significantly higher stability in comparison to the 2C configuration in 4-point bending (anterior-posterior, 0.95 Nm/mm [2C] < 8.41 Nm/mm [2C1S] and 15.12 Nm/mm [2S]; posterior-anterior, 8.55 Nm/mm [2C] < 12.65 Nm/mm [2C1S] and 17.54 Nm/mm [2S]; latero-medial, 1.17 Nm/mm [2C] < 5.53 Nm/mm [2C1S] and 9.15 Nm/mm [2S]; medio-lateral, 1.74 Nm/mm [2C] < 9.69 Nm/mm [2C1S] and 12.20 Nm [2S]; all p < 0.001) and during torsion (ER, 0.61 Nm/degree [2C] < 4.10 Nm/degree [2C1S] and 9.29 Nm/degree [2S]; IR, 0.18 Nm/degree [2C] < 6.17 Nm/degree [2C1S] and 10.61 Nm/degree [2S]; all p < 0.001]. The shifting in compression in 9 degrees position was only slightly influenced. The comparison of 2S versus 2C1S showed more stability for 2S than 2C1S in all testing, except the axial 9 degrees compression tests for shifting. In contrast to the 2C configuration, both modifications (2C1S and 2S) turned out to be stable in dynamic 9 degrees axial compression with a force of 100 up to 1,000 N at 2.5 Hz in 250,000 load cycles.
In this in vitro adolescence femur spiral fracture model, the stability of ESIN could be significantly improved by two modifications with additional tension screws. If transferred in clinical practice, these modifications might offer earlier weight bearing and less problems of shortening or axial deviation.
对于小儿股骨干骨折，弹性稳定髓内钉固定术（ESIN）是一种公认的治疗方法。但在复杂骨折类型和年龄较大儿童中，缩短或轴向偏差的稳定性问题是众所周知的。进行生物力学体外测试，以确定与传统ESIN相比，两种改良的骨合成术（附加张力螺钉固定或仅用螺钉固定而无髓内钉）是否能显著提高稳定性。
总共使用了24个合成的青少年尺寸股骨干模型（Sawbones，第4代；美国华盛顿州瓦申），均为相同的螺旋骨折（长度100mm）。所有标本均用两根C形钢钉（2C）进行逆行固定。在这24个标本中，8个骨合成术用一根附加张力螺钉（2C1S）进行支撑，另外8个用两根螺钉（2S）支撑，测试前取出髓内钉。每种构型在四点弯曲、外旋（ER）和内旋（IR）状态下进行生物力学测试。此外，对改良后的构型在轴向生理9度位置进行移位和动态压缩以及动态载荷测试。
与2C构型相比，两种螺钉构型（2C1S和2S）在四点弯曲（前后向，0.95 Nm/mm [2C]＜8.41 Nm/mm [2C1S]和15.12 Nm/mm [2S]；后前向，8.55 Nm/mm [2C]＜12.65 Nm/mm [2C1S]和17.54 Nm/mm [2S]；外侧向，1.17 Nm/mm [2C]＜5.53 Nm/mm [2C1S]和9.15 Nm/mm [2S]；内侧向，1.74 Nm/mm [2C]＜9.69 Nm/mm [2C1S]和12.20 Nm [2S]；所有p＜0.001）和扭转（ER，0.61 Nm/度 [2C]＜4.10 Nm/度 [2C1S]和9.29 Nm/度 [2S]；IR，0.18 Nm/度 [2C]＜6.17 Nm/度 [2C1S]和10.61 Nm/度 [2S]；所有p＜0.001）时均表现出显著更高的稳定性。9度位置的压缩移位仅受到轻微影响。2S与2C1S的比较表明，在所有测试中，2S比2C1S更稳定，但轴向9度压缩移位测试除外。与2C构型相反，两种改良构型（2C1S和2S）在2.5Hz频率下、100至1000N力、250,000次加载循环的动态9度轴向压缩中均表现稳定。
在这个体外青少年股骨螺旋骨折模型中，通过附加张力螺钉的两种改良方法可显著提高ESIN的稳定性。如果应用于临床实践，这些改良方法可能使患者更早负重，并减少缩短或轴向偏差问题。
