背景:已经描述了用于肢体长度差异(LLD)的皮物理固定术的不同手术方法。虽然这些方法都是有效的,它们与发病率(疼痛和跛行)和潜在的并发症有关。微波消融是通过热能选择性地破坏生长板以治疗儿童LLD来停止生长的侵入性较小的机会。
目的:在使用体内猪模型的概念验证研究中,我们问:(1)通过CT扫描通过胫骨的长度和角度测量的胫骨生长板微波消融后2至4个月的反应持久性如何?(2)通过标准组织学染色测量的关节软骨活力是否保持了关节软骨?
方法:为了开发微波消融的体内方案,我们将微波天线放置在18只3个月大的猪的尸体后肢的胫骨近端生长板附近。为了确定合适的时间,我们在65W功率设置下,消融时间从90秒到270秒不等.切开胫骨后,我们目测评估了变色(暗示生长板破坏),包括中央生长板,但并未以破坏关节面的方式侵入骨phy。利用这些信息,然后,我们对三只活的雌性猪(3.5~4月龄)进行微波消融,以评估生理变化和反应的持久性.进行了术后MRI检查,以确保干预导致与尸体相似的空间生长板改变。随后是连续CT,用于评估对局部骨和生长的潜在影响,直到手术后2至4个月对动物实施安乐死。我们分析了LLD,角畸形,使用CT扫描对胫骨和骨畸形。通过标准组织学染色将关节软骨的可见性与对侧胫骨的可见性进行比较,通过荧光染料标记比较胫骨近端生长板的生长速率。
结果:18个尸体标本显示生长板的消融区,关节表面无视觉损伤。三只活猪在手术后没有表现出步态变化或需要明显的止痛药。每只动物都表现出生长板破坏,预期肢体缩短(0.8、1.2和1.5cm),生长板周围的骨空化。轻微的外翻骨骼角度(4º,5º,和12º)与对照胫骨相比。从组织学上与对侧胫骨的关节软骨厚度和细胞形态进行比较,未发现定性可观察到的关节软骨损伤。
结论:将微波天线放置在猪的胫骨近端生长板中,可以减缓胫骨的生长,而没有明显的疼痛和步态和功能的改变。
结论:我们的动物模型的进一步研究和改进正在进行中,包括更短的消融时间和动态消融(消融期间移动触角)以及胫骨内侧和外侧门静脉的静态消融的比较。在我们的猪模型中,这些改进以及与标准机械生长停滞的计划比较可能会导致类似的方法来消融LLD儿童的生长板。
BACKGROUND: Different surgical methods for epiphysiodesis of limb length discrepancy (LLD) have been described. Although these methods are variably effective, they are associated with morbidity (pain and limp) and potential complications. Microwave ablation is a less-invasive opportunity to halt growth by selectively destroying the growth plate via thermal energy to treat LLD in children.
OBJECTIVE: In this proof-of-concept study using an in vivo pig model, we asked: (1) What is the durability of response 2 to 4 months after microwave ablation of the tibial growth plate as measured by length and angulation of the tibia via a CT scan? (2) Was articular cartilage maintained as measured by standard histologic staining for articular cartilage viability?
METHODS: To develop an in vivo protocol for microwave ablation, we placed microwave antennas adjacent to the proximal tibia growth plate in the cadaveric hindlimbs of 18 3-month-old pigs. To determine the suitable time, we varied ablation from 90 to 270 seconds at 65-W power settings. After sectioning the tibia, we visually assessed for discoloration (implying growth plate destruction) that included the central growth plate but did not encroach into the epiphysis in a manner that could disrupt the articular surface. Using this information, we then performed microwave ablation on three live female pigs (3.5 to 4 months old) to evaluate physiologic changes and durability of response. A postprocedure MRI was performed to ensure the intervention led to spatial growth plate alterations similar to that seen in cadavers. This was followed by serial CT, which was used to assess the potential effect on local bone and growth until the animals were euthanized 2 to 4 months after the procedure. We analyzed LLD, angular deformity, and bony deformity using CT scans of both tibias. The visibility of articular cartilage was compared with that of the contralateral tibia via standard histologic staining, and growth rates of the proximal tibial growth plate were compared via fluorochrome labeling.
RESULTS: Eighteen cadaveric specimens showed ablation zones across the growth plate without visual damage to the articular surface. The three live pigs did not exhibit changes in gait or require notable pain medication after the procedure. Each animal demonstrated growth plate destruction, expected limb shortening (0.8, 1.2, and 1.5 cm), and bony cavitation around the growth plate. Slight valgus bone angulation (4º, 5º, and 12º) compared with the control tibia was noted. No qualitatively observable articular cartilage damage was encountered from the histologic comparison with the contralateral tibia for articular cartilage thickness and cellular morphology.
CONCLUSIONS: A microwave antenna placed into a pig\'s proximal tibia growth plate can slow the growth of the tibia without apparent pain and alteration of gait and function.
CONCLUSIONS: Further investigation and refinement of our animal model is ongoing and includes shorter ablation times and comparison of dynamic ablation (moving the antennae during the ablation) as well as static ablation of the tibia from a medial and lateral portal. These refinements and planned comparison with standard mechanical growth arrest in our pig model may lead to a similar approach to ablate growth plates in children with LLD.