Ventral root avulsion induces dramatic loss of the affected spinal cord motoneurons. The neuroprotective effect of riluzole has been previously proven on the injured motoneurons: the vast majority of them can be rescued even when they have no possibility to regenerate their axons. In this study the number of injured motoneurons rescued by riluzole treatment and their capacity to reinnervate the denervated forelimb muscles was investigated. Surgical reconnection with a peripheral nerve graft between the affected spinal cord segment and the C7 spinal nerve was established immediately or with 1- and 3-week delay after avulsion. Avulsion and immediate reconnection of the motoneuron pool to the spinal nerve resulted in moderate reinnervation of the spinal nerve (281 ± 23 standard error of mean [SEM] retrogradely labeled motoneurons), whereas treatment of the injured motoneurons with riluzole yielded considerably higher numbers of reinnervating motoneurons (548 ± 18 SEM). Reconnection of the motor pool with the C7 spinal nerve with 1-week delay allowed fewer motor axons to reinnervate their targets in control and riluzole-treated animals (159 ± 21 vs. 395 ± 16 SEM). A clinically relevant 3-week delay in reconnection further reduced the number of reinnervating motoneurons (76 ± 22 SEM), but riluzole pre-treatment still enabled a significant number of rescued motoneurons (396 ± 17 SEM) to regenerate their axons into the C7 spinal nerve. These results show that those injured adult motoneurons that are rescued by riluzole treatment started immediately after the avulsion injury are able to reinnervate their targets even if they are provided with a conduit several weeks after the primary injury. This finding suggests that partial rescue of injured motoneurons with riluzole in patients who suffered a brachial plexus avulsion injury may provide an available pool of surviving motoneurons for late reconnection/reimplantation surgeries.

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ÖZAmaç: Bu çalışmada yaşlılarda çift kolon kırıklarında osteosenteze (plak ve vida tespiti) kıyasla kalça artroplastisi ile desteklenen aynı yöntemin (hibrid çözüm) mekanik stabilitesi karşılaştırıldı. Hastalar ve yöntemler: Çift kolon kırıkları için geliştirilen ileri sonlu eleman pelvis modelinde mekanik araştırmalar yapıldı. İncelenen simüle edilen implant kombinasyonları şunlardı: poliaksiyel vidalı ve U plaklı, halkalı, modüler asetabüler sepet; medial horizontal (linea terminalis) ve kuadrilateral kemik yüzeylerine yerleştirilen poliaksiyel vidalı plaklar; U plaklı, modüler asetabüler kap ve çeşitli ebatlarda sonlu eleman modeline (FEM) göre optimize edilen poliaksiyel vidalar. Bu modellerde yük, gerilim ve implant deformasyonuna bağlı farklı hareket paternlerinden doğan pik yük pozisyonlarındaki muhtemel kaymalar ölçüldü. Bulgular: Hibrid sistemler, piyasada bulunan implantlarda minimum deformasyona neden oldu. Tek başına konvansiyonel osteosenteze kıyasla, asetabüler kırık bölgelerinde daha az muhtemel kayma ve daha yüksek stabilite gözlendi. Mevcut ve uygun implant ebatlarına göre optimizasyon yapıldığında, stabilitede anlamlı düzeyde ilave bir artış izlendi. Sonuç: Yaşlılarda çift kolon kırıklarının tedavisinde biyomekanik modellerde osteosentez ve protez implantasyonunu içeren hibrid yöntem daha fazla stabilite sağlamaktadır.Anahtar sözcükler: Asetabüler kırık, asetabulum, sonlu eleman modeli, pelvik travma, plak osteostentezi, total kalça replasmanı. ABSTRACTObjectives: This study aims to compare mechanical stability of osteosynthesis (plate and screw fixation) alone versus the same method supplemented with hip arthroplasty (hybrid solution) for double column fractures in elderly. Patients and methods: Mechanical investigations were performed on an advanced finite element pelvis model developed for double column fractures. The following simulated implant combinations were analyzed: modular acetabular basket with a ring with polyaxial screws and U-plate; plates with polyaxial screws placed on the medialhorizontal (linea terminalis) and quadrilateral bone surfaces; modular acetabular cup with U-plates; and polyaxial screws in sizes optimized based on a finite element model (FEM). Using the models, the possible shifts in peak load positions arising in different movement patterns caused by load and tension and implant deformation were measured. Results: Hybrid systems resulted in minimal deformation of the implants already available on the market. We observed less possible shifts and greater stability in the acetabular fracture zones, compared to conventional osteosynthesis alone. Optimization with available and compatible implant sizes led to a further significant increase in stability. Conclusion: Hybrid method combining osteosynthesis and prosthesis implantation provide more stability in biomechanical models in the treatment of double column fractures in elderly.