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Maximum Isometric Tetanic Force Measurement of the Tibialis Anterior Muscle in the Rat

Traumatic nerve injuries result in substantial functional loss and segmental nerve defects often necessitate the use of autologous interposition nerve ...

Mayo Clinic

Frozen bone allografts are susceptible to nonunion and fracture due to limited revascularization and incomplete bone remodeling. We aim to revascularize bone allografts by combining angiogenesis from implanted arteriovenous (AV) bundles with delivery of fibroblast growth factor (FGF-2) and/or vascular endothelial growth factor (VEGF) via biodegradable microspheres. Rat femoral diaphyseal allografts were frozen at -80°C, and heterotopically transplanted over a major histocompatibility mismatch. A saphenous AV bundle was inserted into the intramedullary canal. Growth factor was encapsulated into microspheres and inserted into the graft, providing localized and sustained drug release. Forty rats were included in four groups: (I) phosphate-buffered saline, (II) FGF-2, (III) VEGF, and (IV) FGF-2 + VEGF. At 4 weeks, angiogenesis was measured by the hydrogen washout method and microangiography. Bone remodeling was evaluated by quantitative histomorphometry and histology. Bone blood flow was significantly higher in groups III and IV compared to control (p < 0.05). Similarly, bone remodeling was higher in VEGF groups. FGF-2 had little effect on allograft revascularization. No synergistic effect was observed with use of both cytokines. Delivered in microspheres, VEGF proved to be a potent angiogenic cytokine, increasing cortical bone blood flow and new bone formation in frozen allografts revascularized with an implanted AV bundle.

Revascularization and bone remodeling of frozen allografts stimulated by intramedullary sustained delivery of FGF-2 and VEGF.

Isometric tetanic muscle force has been described in a rat model to evaluate motor recovery in a segmental sciatic nerve defect reconstructions. However, to test longer nerve defects, an alternative and larger animal model is necessary. The purpose of this study is to describe and validate a technique for isometric force measurement of the tibialis anterior (TA) muscle in New Zealand rabbits. Muscle preload and electrical stimulation parameters were optimized to obtain the highest tetanic contraction bilaterally in 10 animals. Electrophysiology, muscle weight, peroneal nerve length, and histomorphometry were also analyzed. Only the peroneal nerve length and the ratio of highest muscle force/muscle weight demonstrated the equivalence between the sides. A small variability of TA muscle force and TA muscle weight was observed between the sides suggesting dominance. Optimization of electrical stimulation and preload as well as the use of correct anesthesia were fundamental to acquire the highest muscle force.

Description and validation of isometric tetanic muscle force test in rabbits.

We have previously described a means to maintain bone allotransplant viability, without long-term immune modulation, replacing allogenic bone vasculature with autogenous vessels. A rabbit model for whole knee joint transplantation was developed and tested using the same methodology, initially as an autotransplant.

Knee joint transplantation combined with surgical angiogenesis in rabbits--a new experimental model.

An effective alternative to nerve autograft is needed to minimize morbidity and solve limited-availability issues. We hypothesized that the use of processed allografts and collagen conduits would allow recovery of motor function that is equivalent to that seen after the use of autografts.

Return of motor function after segmental nerve loss in a rat model: comparison of autogenous nerve graft, collagen conduit, and processed allograft (AxoGen).

Vascularized composite allotransplantation has the potential for reconstruction of joint defects but requires lifelong immunosuppression, with substantial risks. This study evaluates an alternative, using surgical angiogenesis from implanted autogenous vessels to maintain viability without long-term immunotherapy.

Surgical angiogenesis with short-term immunosuppression maintains bone viability in rabbit allogenic knee joint transplantation.

The sciatic functional index has long been the standard method of assessing motor recovery in the rat sciatic nerve model. The relative subjective nature of the assessment has led to development of newer methods, including video gait analysis and quantitative measurement of isometric tetanic muscle force.

Functional evaluation in the rat sciatic nerve defect model: a comparison of the sciatic functional index, ankle angles, and isometric tetanic force.

Many conduits have demonstrated potential to substitute nerve autografts; however, the influence of conduit inner diameter (ID) has never been studied as a separate parameter. This experimental study compared motor recovery after segmental nerve repair with two different ID collagen conduits: 1.5 and 2.0 mm. In addition, the conduits were analyzed in vitro to determine the variations of ID before and after hydration. Thirty rats were divided into three groups: 2.0 mm ID, 1.5 mm ID, and a control group autograft. After 12 weeks, the 1.5 mm ID group demonstrated significant increase in force (P < 0.0001) and weight (P < 0.0001) of the tibialis anterior muscle and better histomorphometry results of the peroneal nerve (P < 0.05) compared to 2.0 mm ID group; nevertheless, autograft results outperformed both conduits (P < 0.0001). Conduits ID were somewhat smaller than advertised, measuring 1.59 ± 0.03 mm and 1.25 ± 0.0 mm. Only the larger conduit showed a 6% increase in ID after hydration, changing to 1.69 ± 0.02 mm. Although autografts perform best, an improvement in motor recovery can be achieved with collagen conduits when a better size match conduit is being used. Minimal changes in collagen conduits ID can be expected after implantation.

The influence of nerve conduits diameter in motor nerve recovery after segmental nerve repair.

Processed nerve allografts have become an alternative to repair segmental nerve defects, with results comparable with autografts regarding sensory recovery; however, they have failed to reproduce comparable motor recovery. The purpose of this study was to determine how revascularizaton of processed nerve allograft would affect motor recovery. Eighty-eight rats were divided in four groups of 22 animals each. A unilateral 10-mm sciatic nerve defect was repaired with allograft (group I), allograft wrapped with silicone conduit (group II), allograft augmented with vascular endothelial growth factor (group III), or autograft (group IV). Eight animals from each group were sacrificed at 3 days, and the remaining animals at 16 weeks. Revascularization was evaluated by measuring the graft capillary density at 3 days and 16 weeks. Measurements of ankle contracture, compound muscle action potential, tibialis anterior muscle weight and force, and nerve histomorphometry were performed at 16 weeks. All results were normalized to the contralateral side. The results of capillary density at 3 days were 0.99% ± 1.3% for group I, 0.33% ± 0.6% for group II, 0.05% ± 0.1% for group III, and 75.6% ± 45.7% for group IV. At 16 weeks, the results were 69.9% ± 22.4% for group I, 37.0% ± 16.6% for group II, 84.6% ± 46.6% for group III, and 108.3% ± 46.8% for group IV. The results of muscle force were 47.5% ± 14.4% for group I, 21.7% ± 13.5% for group II, 47.1% ± 7.9% for group III, and 54.4% ± 10.6% for group IV. The use of vascular endothelial growth factor in the fashion used in this study improved neither the nerve allograft short-term revascularization nor the functional motor recovery after 16 weeks. Blocking allograft vascularization from surrounding tissues was detrimental for motor recovery. The processed nerve allografts used in this study showed similar functional motor recovery compared with that of the autograft.

The influence of vascularization of transplanted processed allograft nerve on return of motor function in rats.

The aim of this study was to evaluate the effect of vascular endothelial growth factor (VEGF) administration around the autologous nerve graft on nerve recovery in a rat model.

Effect of Vascular Endothelial Growth Factor Administration on Nerve Regeneration after Autologous Nerve Grafting.

The purpose of this study was to describe and validate a technique for measurement of isometric tetanic force (ITF) in the rabbit biceps muscle.

Validation of Isometric Tetanic Force as a Measure of Muscle Recovery After Nerve Injury in the Rabbit Biceps.

The purpose of this study was to radiographically evaluate scaphoid length and carpal parameters before and after reconstruction of nonunions with interposition vascularized medial femoral condyle (MFC) bone graft to determine if the scaphoid was overstuffed or if normal anatomy was restored and to determine the effect on ulnar carpal translocation when the volar radiocarpal ligaments were left unrepaired.

Overstuffing of Unstable Scaphoid Nonunions: A Radiographic Analysis of Carpal Parameters.

Animal models can be helpful in evaluating new surgical strategies for brachial plexus reconstruction. While several groups have already used the rabbit brachial plexus to model injury, reports conflict in anatomic detail and do not identify a nerve-muscle pair to measure motor function recovery after reconstruction. The purpose of the current study is to describe the innervations of the biceps and triceps muscles in rabbits, which are both amenable to study in brachial plexus injury models.

Guilherme Giusti

Department of Orthopedic Surgery

Mayo Clinic

Maximum Isometric Tetanic Force Measurement of the Tibialis Anterior Muscle in the Rat

Guilherme Giusti

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Orthopedic Surgery

Mayo Clinic

Maximum Isometric Tetanic Force Measurement of the Tibialis Anterior Muscle in the Rat

Department of Orthopedic Surgery