[Characterisation of the impact and features of trampoline park-related injuries]. / Die spezifischen Auswirkungen und Merkmale von Trampolinpark-assoziierten Verletzungen.

INTRODUCTION: Numerous studies have described indoor trampoline park (ITP)-related injury patterns, but they have shown heterogeneous results. No such study has been performed in Germany to date. The aim of this study was to analyse the specific trampoline-related injury patterns found in our population. METHODS: This retrospective study included patients suffering from ITP-related injuries between 1 October 2016 and 30 April 2018. 258 patients were included in the analysis. Patients were categorised depending on different variables including age, sex, site of injury, diagnosis, length of admission and treatment using SPSS. RESULTS: In the 19-month study period, 258 patients with ITP-related injuries were recruited. Single ITP-related injuries were diagnosed in 250 (96.9 %) patients. The median age of this group was 22 years (IQR 15-28). 126 (50.4 %) injuries were suffered by men and 124 (49.6 %) by women. 168 (67.2 %) injuries occurred in the lower extremity. Sprains (n = 114, 45.6 %) and fractures without joint dislocation (n = 59, 23.6 %) were the most common diagnoses. Males suffered significantly more often from injuries of the upper extremity (26.2 vs. 9.7 %; p = 0.010), while females most commonly suffered from injuries of the lower extremity (79.8 vs. 54.8 %; p < 0.001). 45 (18 %) patients required hospital admission and twenty-five (10.0 %) patients required surgery. Eight (3.1 %) patients suffered from injuries in more than one anatomic location. CONCLUSIONS: ITP-related injuries were more prevalent in adults compared with children. The lower limb was the most affected anatomic location in all ages. The pattern of the injuries was heterogeneous, and their respective treatment represents a major challenge for traumatology surgeons.

Stimulation of trigeminal afferents improves motor recovery after facial nerve injury: functional, electrophysiological and morphological proofs.

Recovery of mimic function after facial nerve transection is poor: the successful regrowth of axotomized motoneurons to their targets is compromised by (1) poor axonal navigation and excessive collateral branching, (2) abnormal exchange of nerve impulses between adjacent regrowing axons, and (3) insufficient synaptic input to facial motoneurons. As a result, axotomized motoneurons get hyperexcitable and unable to discharge. Since improvement of growth cone navigation and reduction of the ephaptic cross talk between axons turn out be very difficult, we concentrated our efforts on the third detrimental component and proposed that an intensification of the trigeminal input to axotomized electrophysiologically silent facial motoneurons might improve specificity of reinnervation. To test our hypothesis we compared behavioral, electrophysiological, and morphological parameters after single reconstructive surgery on the facial nerve (or its buccal branch) with those obtained after identical facial nerve surgery but combined with direct or indirect stimulation of the ipsilateral infraorbital (ION) nerve. We found that in all cases, trigeminal stimulation was beneficial for the outcome by improving the quality of target reinnervation and recovery of vibrissa! motor performance.

Reconstruction of a Bryan and Morrey type I capitellar fracture in a sawbone model with four different fixation devices: an experimental study.

BACKGROUND: We evaluated 4 different fixation devices for the reconstruction of a standardised Bryan and Morrey capitellar shear fracture in a sawbone model. Outcome measurements were the quality of reduction, time for reconstruction and stability. METHODS: 80 standardised Bryan and Morrey type I fractures were created for 5 different orthopaedic surgeons in 80 sawbones. Each surgeon reconstructed 16 fractures with 2mm K-wires, 3mm Herbert screws, 2.7 mm AO screws and 2.2mm fine-threaded wires (Fragment Fixation System: FFS). 4 fractures were allocated to each method with a standardised reconstruction procedure. Quality of reduction and time for reconstruction were measured after definitive fixation. Biomechanical testing was performed using a shear loading model with the application of monocyclic or polycyclic stress to the reconstructed capitulum. RESULTS: There was no difference in the quality of reduction with the different fixation devices. Herbert and AO screw fixation was slower than the other implants (p<0.05). No difference in the time for reconstruction was observed with K-wires and FFS. Failure load was less for K-wires compared to FFS, Herbert screws and AO screws (p<0.05). With polycyclic loading, residual deformation was higher with K-wire reconstruction compared to FFS, Herbert screws and AO screws (p<0.05). CONCLUSION: When using four different fixation devices, the fixation of standardised Bryan and Morrey type I fractures in the sawbone model differs when it comes to the time needed for reduction, but not in the quality of reduction. Stability was the same for the implants used, except for the K-wires. There is no argument in favour one of the screw implants over another in clinical use.

Bioartificial reconstruction of peripheral nerves using the rat median nerve model.

Different bioartificial tubes were recommended for peripheral nerve reconstruction in the past. In order to replace autologous nerve grafts this materials are still under review in different animal studies. Most of them are dealing with the rodent peripheral nerves. One very popular animal model to study different materials is the rat median nerve model. With its easy excess, simple behavioral tests and reliable long term results it is attractive to many scientists in this field. This review gives an overview about the past, current and future options in this model for bioartificial nerve tubes. It summarizes the evolution of successful implantation of different materials across short nerve gaps and demonstrates the obstacles arising from long nerve gaps and the problems associated to them.

Intrinsic and therapeutic factors determining the recovery of motor function after peripheral nerve transection.

Insufficient recovery after peripheral nerve injury has been attributed to (i) poor pathfinding of regrowing axons, (ii) excessive collateral axonal branching at the lesion site and (iii) polyneuronal innervation of the neuromuscular junctions (NMJ). The facial nerve transection model has been used initially to measure restoration of function after varying therapies and to examine the mechanisms underlying their effects. Since it is very difficult to control the navigation of several thousand axons, efforts concentrated on collateral branching and NMJ-polyinnervation. Treatment with antibodies against trophic factors to combat branching improved the precision of reinnervation, but had no positive effects on functional recovery. This suggested that polyneuronal reinnervation--rather than collateral branching--may be the critical limiting factor. The former could be reduced by pharmacological agents known to perturb microtubule assembly and was followed by recovery of function. Because muscle polyinnervation is activity-dependent and can be manipulated, attempts to design a clinically feasible therapy were performed by electrical stimulation or by soft tissue massage. Electrical stimulation applied to the transected facial nerve or to paralysed facial muscles did not improve vibrissal motor performance and failed to diminish polyinnervation. In contrast, gentle stroking of the paralysed muscles (vibrissal, orbicularis oculi, tongue musculature) resulted in full recovery of function. This manual stimulation was also effective after hypoglossal-facial nerve suture and after interpositional nerve grafting, but not after surgical reconstruction of the median nerve. All these findings raise hopes that clinically feasible and effective therapies could be soon designed and tested.

Midclavicular fracture: not just a trivial injury: current treatment options.

BACKGROUND: Conservative treatment was long recommended for midclavicular fractures because of the excellent results that were reported in the 1960's and 70's. Recently, however, the rucksack bandage has received competition from surgical treatment. The spectrum of operations ranges from classic plate osteosynthesis to intramedullary techniques and angle-stable implants. METHODS: We present and evaluate the current treatment options on the basis of a selective review of the literature. RESULTS: Recent studies have confirmed some long-held concepts and refuted others. The risk of non-union after conservative treatment was previously reported as 1% to 2% but has turned out to be much higher in selected subgroups such as in patients with severe displacement, female patients, and patients of advanced age. Furthermore, new implants and techniques have made surgery safer and more likely to result in bony union. CONCLUSION: In any case of midclavicular fracture, the type of fracture should be precisely analyzed and an individual treatment strategy should be developed in view of the patient's particular situation. Current studies show with a high level of evidence (level 1) that patients with dislocated fractures benefit from surgery.

MDCT evaluation of injuries after tram accidents in pedestrians.

Multidetector computed tomography (MDCT) is especially suited for emergency diagnostics in multiple trauma patients. The objectives of this study were to investigate the types and frequencies of injuries associated with tram accidents in pedestrians. Eighteen consecutive pedestrian patients with multiple traumas after tram accidents were evaluated with MDCT in our Level I Trauma Center. The mean age in our patient cohort was 36.9 years with a range from 14-92 years. There was a trend for accident events occurring more commonly during the winter months in middle-aged men, often under the influence of alcohol. Patients were divided into two groups with unilateral or complex injury patterns. In both groups, leading diagnoses were head (83.3%) and thorax injuries (66.6%). Abdominal injuries (44.4%) were less common and mainly found in the complex injuries group. The most serious injuries occurred in the complex injuries group when the victim was caught under or between tramcars. A wide range of injuries is associated with tram accidents in pedestrians, which can be classified into two main injury patterns, unilateral and complex. The life-limiting injuries in this setting involved the head with a mortality rate of 22.2% (four patients) in our cohort.

Schwann cells overexpressing FGF-2 alone or combined with manual stimulation do not promote functional recovery after facial nerve injury.

PURPOSE: To determine whether transplantation of Schwann cells (SCs) overexpressing different isoforms of fibroblast growth factor 2 (FGF-2) combined with manual stimulation (MS) of vibrissal muscles improves recovery after facial nerve transection in adult rat. PROCEDURES: Transected facial nerves were entubulated with collagen alone or collagen plus naïve SCs or transfected SCs. Half of the rats received daily MS. Collateral branching was quantified from motoneuron counts after retrograde labeling from 3 facial nerve branches. Quality assessment of endplate reinnervation was combined with video-based vibrissal function analysis. RESULTS: There was no difference in the extent of collateral axonal branching. The proportion of polyinnervated motor endplates for either naïve SCs or FGF-2 over-expressing SCs was identical. Postoperative MS also failed to improve recovery. CONCLUSIONS: Neither FGF-2 isoform changed the extent of collateral branching or polyinnervation of motor endplates; furthermore, this motoneuron response could not be overridden by MS.

Manual stimulation, but not acute electrical stimulation prior to reconstructive surgery, improves functional recovery after facial nerve injury in rats.

UNLABELLED: The outcome of peripheral nerve injuries requiring surgical repair is poor. Recent work suggested that electrical stimulation (ES) of the proximal nerve stump to produce repeated discharges of the parent motoneurons for one hour could be a beneficial therapy if delivered immediately prior to reconstructive surgery of mixed peripheral nerves. PURPOSE: We tested whether ES has a positive influence on functional recovery after repair of a purely motor nerve, the facial nerve. METHODS: Electrical stimulation (20 Hz) was delivered to the proximal nerve stump of the transected facial nerve for 1 hour prior to nerve reconstruction by end-to-end suture (facial-facial anastomosis, FFA). For manual stimulation (MS), animals received daily rhythmic stroking of the whisker pads. Restoration of vibrissal motor performance following ES or MS was evaluated using video-based motion analysis. We also assessed the degree of collateral axonal branching at the lesion site, by counting motoneuronal perikarya after triple retrograde labeling, and estimated the quality of motor end-plate reinnervation in the target musculature. Outcomes at 4 months were compared to animals receiving sham stimulation (SS) or MS. RESULTS: Neither protocol reduced the degree of collateral sprouting. ES did not improve functional outcome and failed to reduce the proportion of polyinnervated motor end-plates. By contrast, MS restored normal whisking function and reduced polyinnervation. CONCLUSION: Whereas acute ES is not beneficial for facial nerve repair, MS provides long-term benefits.

Electrical stimulation of paralyzed vibrissal muscles reduces endplate reinnervation and does not promote motor recovery after facial nerve repair in rats.

The outcome of peripheral nerve injuries requiring surgical repair is poor. Recent work has suggested that electrical stimulation (ES) of denervated muscles could be beneficial. Here we tested whether ES has a positive influence on functional recovery after injury and surgical repair of the facial nerve. Outcomes at 2 months were compared to animals receiving sham stimulation (SS). Starting on the first day after end-to-end suture (facial-facial anastomosis), electrical stimulation (square 0.1 ms pulses at 5 Hz at an ex tempore established threshold amplitude of between 3.0 and 5.0V) was delivered to the vibrissal muscles for 5 min a day, 3 times a week. Restoration of vibrissal motor performance following ES or SS was evaluated using the video-based motion analysis and correlated with the degree of collateral axonal branching at the lesion site, the number of motor endplates in the target musculature and the quality of their reinnervation, i.e. the degree of mono- versus poly-innervation. Neither protocol reduced collateral branching. ES did not improve functional outcome, but rather reduced the number of innervated motor endplates to approximately one-fifth of normal values and failed to reduce the proportion of poly-innervated motor endplates. We conclude that ES is not beneficial for recovery of whisker function after facial nerve repair in rats.

Manual stimulation of the orbicularis oculi muscle improves eyelid closure after facial nerve injury in adult rats.

We have shown that manual stimulation of rat whisker-pad muscles following facial-facial-anastomosis (FFA) restores normal whisking by lowering the proportion of polyinnervated motor endplates. Here we examined whether manual stimulation of the orbicularis oculi muscle (OOM) after FFA would also improve outcome. Blink responses to standardized air puffs were analyzed using video-based motion analysis. Two months after FFA, blink capacity was impaired, as indicated by a largely increased minimum distance between the eyelids after air-puff stimulation compared with intact rats (2.7 +/- 0.4 vs. 0.2 +/- 0.01 mm). Manual stimulation reduced this deficit by a factor of two (1.3 +/- 0.5 mm). The functional improvement after manual stimulation was associated with a 2-fold decrease in the proportion of polyinnervated OOM endplates (21 +/- 10% vs. 42 +/- 10% without manual stimulation, 0% in intact rats). We conclude that manual stimulation is a noninvasive and simple procedure with immediate potential for clinical rehabilitation of eyelid closure following facial nerve injury.

Manual stimulation of the suprahyoid-sublingual region diminishes polynnervation of the motor endplates and improves recovery of function after hypoglossal nerve injury in rats.

BACKGROUND: Using the rat facial nerve axotomy model, the authors recently showed that manual stimulation of denervated whiskerpad muscles reduced the posttransectional polyinnervation at the neuromuscular junctions and promoted full recovery of vibrissal whisking. OBJECTIVE: Prompted by implications for rehabilitation therapy, the authors examined whether manual stimulation of denervated supra- and infrahyoid muscles would also improve recovery after unilateral lesion on the hypoglossal nerve. METHODS: Adult rats underwent transection of the right hypoglossal nerve. Half of the animals received no postoperative treatment, and the other half were subjected to daily manual stimulation of the suprahyoid/sublingual region for 2 months. Recovery was assessed by measuring the angle of tongue-tip deviation from the midline, degree of collateral axonal branching at the lesion site (counts after retrograde labeling with 2 fluorescent dyes), synaptic input to the hypoglossal motoneurons using synaptophysin immunocytochemistry, tongue-muscles motor representation in the cerebral cortex after c-Fos immunocytochemistry, and portion of polyinnervated neuromuscular junctions. RESULTS: In animals receiving manual stimulation, the tongue-tip deviation was 37.0 +/- 49.37 degrees , whereas values in control nonstimulated rats were significantly higher (50.1 +/- 9.01 degrees ; P < .05; mean +/- SD). Improved recovery was not associated with reduced collateral axonal branching; there were also no differences in tongue-muscles representation in the motor cortex. However, manual stimulation restored the total synaptic input to levels in intact animals and reduced the proportion of polyinnervated neuromuscular junctions compared with nonstimulated animals. CONCLUSION: The data show that manual stimulation of denervated muscles improves functional outcome following peripheral nerve injury. This suggests immediate potential for enhancing clinical rehabilitation strategies.

Bone marrow-derived mesenchymal stem cell transplantation does not improve quality of muscle reinnervation or recovery of motor function after facial nerve transection in rats.

Recently, we devised and validated a novel strategy in rats to improve the outcome of facial nerve reconstruction by daily manual stimulation of the target muscles. The treatment resulted in full recovery of facial movements (whisking), which was achieved by reducing the proportion of pathologically polyinnervated motor endplates. Here, we posed whether manual stimulation could also be beneficial after a surgical procedure potentially useful for treatment of large peripheral nerve defects, i.e., entubulation of the transected facial nerve in a conduit filled with suspension of isogeneic bone marrow-derived mesenchymal stem cells (BM-MSCs) in collagen. Compared to control treatment with collagen only, entubulation with BM-MSCs failed to decrease the extent of collateral axonal branching at the lesion site and did not improve functional recovery. Post-operative manual stimulation of vibrissal muscles also failed to promote a better recovery following entubulation with BM-MSCs. We suggest that BM-MSCs promote excessive trophic support for regenerating axons which, in turn, results in excessive collateral branching at the lesion site and extensive polyinnervation of the motor endplates. Furthermore, such deleterious effects cannot be overridden by manual stimulation. We conclude that entubulation with BM-MSCs is not beneficial for facial nerve repair.

Manually-stimulated recovery of motor function after facial nerve injury requires intact sensory input.

We have recently shown in rat that daily manual stimulation (MS) of vibrissal muscles promotes recovery of whisking and reduces polyinnervation of muscle fibers following repair of the facial nerve (facial-facial anastomosis, FFA). Here, we examined whether these positive effects were: (1) correlated with alterations of the afferent connections of regenerated facial motoneurons, and (2) whether they were achieved by enhanced sensory input through the intact trigeminal nerve. First, we quantified the extent of total synaptic input to motoneurons in the facial nucleus using synaptophysin immunocytochemistry following FFA with and without subsequent MS. We found that, without MS, this input was reduced compared to intact animals. The number of synaptophysin-positive terminals returned to normal values following MS. Thus, MS appears to counteract the deafferentation of regenerated facial motoneurons. Second, we performed FFA and, in addition, eliminated the trigeminal sensory input to facial motoneurons by extirpation of the ipsilateral infraorbital nerve (IONex). In this paradigm, without MS, vibrissal motor performance and pattern of end-plate reinnervation were as aberrant as after FFA without MS. MS did not influence the reinnervation pattern after IONex and functional recovery was even worse than after IONex without MS. Thus, when the sensory system is intact, MS restores normal vibrissal function and reduces the degree of polyinnervation. When afferent inputs are abolished, these effects are eliminated or even reversed. We conclude that rehabilitation strategies must be carefully designed to take into account the extent of motor and/or sensory damage.

Local stabilization of microtubule assembly improves recovery of facial nerve function after repair.

Within a recent study on the recovery of vibrissae motor performance after facial nerve repair in blind (strain SD/RCS) and sighted (strain SD) rats, we found that, despite persisting myotopic disorganization in the facial nucleus, the blind animals fully restored vibrissal whisking. Searching for the morphological substrates of this improved recovery, we compared the amount of cytoskeletal proteins in the leading edge of elongating axons between both strains. Since our results showed an enhanced expression of neuronal class III beta-tubulin in the blind rats, we wondered whether this was due to an increased synthesis or to a delayed turnover of microtubules. In the present report, we approached this question applying established pharmacological agents to the transected buccal branch of the facial nerve in sighted Wistar rats perturbing either microtubule assembly towards stabilization (enhanced polymerization with 10 microg/ml taxol) or towards increased synthesis (challenged by destabilization with 100 microg/ml nocodazole and 20 microg/ml vinblastine). Evaluation of the effect(s) 2 months later included estimation of (i) vibrissae motor performance by video-based motion analysis, (ii) the degree of collateral axonal branching by double retrograde neuronal labeling with crystals of Fluoro-Gold and DiI and (iii) the pattern of motor end-plate reinnervation (proportions of mono- and poly-reinnervated) in the largest extrinsic vibrissal muscle, the m. levator labii superioris. We found that only stabilization of microtubules with 10 microg/ml taxol reduced intramuscular axonal sprouting and polyinnervation of the motor end-plates, which was accompanied by improved restoration of function.

Manual stimulation of facial muscles improves functional recovery after hypoglossal-facial anastomosis and interpositional nerve grafting of the facial nerve in adult rats.

The facial nerve in humans is often prone to injuries requiring surgical intervention. In the best case, nerve reconstruction is achieved by a facial-facial anastomosis (FFA), i.e. suture of the proximal and distal stumps of the severed facial nerve. Although a method of choice, FFA rarely leads to a satisfactory functional recovery. We have recently devised and validated, in an established experimental paradigm in rats, a novel strategy to improve the outcome of FFA by daily manual stimulation (MS) of facial muscles. This treatment results in full recovery of facial movements (whisking) and is achieved by reducing the proportion of functionally detrimental poly-innervated motor end-plates. Here we asked whether MS could also be beneficial after two other commonly used surgical methods of clinical facial nerve reconstruction namely hypoglossal-facial anastomosis (HFA) and interpositional nerve grafting (IPNG) which, however, seem to have a poorer outcome compared to FFA. Compared to FFA, daily MS for 2 months after HFA and IPGN did not completely restore function but, nevertheless, significantly improved the amplitude of whisker movements by 50% compared with untreated animals. Functional improvement was associated with a reduction in the proportion of polyinnervated end-plates. MS did not reduce the extent of axonal branching at the lesion site nor the subsequent misdirected axonal regrowth to inappropriate targets. Our data show that a simple approach leading to improved quality of muscle fiber reinnervation is functionally beneficial after different types of clinically relevant surgical interventions.

Mechanical stimulation of paralyzed vibrissal muscles following facial nerve injury in adult rat promotes full recovery of whisking.

Many patients suffer lifelong disabilities after peripheral nerve injury. Insufficient recovery has been attributed to excessive axonal branching, axonal regrowth to improper targets and polyneuronal reinnervation of motor endplates. We used the rat facial nerve transection/suture model to quantify the effects of mechanical stimulation on the paralyzed whisker musculature. "Manual" stimulation involved briskly stroking the whiskers by hand in a manner that specifically mimicked normal whisker movement. "Environmental" stimulation involved enhanced whisker use as rats encountered objects in an enriched environment. Manual and environmental stimulation were also combined. Video-based motion analysis of vibrissal motor performance showed that daily manual, but not environmental, stimulation for 2 months resulted in full recovery of whisking. Polyneuronal reinnervation of motor endplates was reduced but not misdirected axonal regrowth. Our findings indicate the potential of use-specific training to enhance appropriate functional outcome after peripheral nerve injury and may be useful in a clinical rehabilitation setting.

Opposite impacts of tenascin-C and tenascin-R deficiency in mice on the functional outcome of facial nerve repair.

The glycoproteins tenascin-C (TNC) and tenascin-R (TNR) are extracellular matrix proteins involved in the development, plasticity and repair of the nervous system. Altered expression patterns after nerve lesions in adult animals have suggested that these molecules influence axonal regeneration. To test this hypothesis, we investigated adult mice constitutively deficient in the expression of TNC, TNR or both, using the facial nerve injury paradigm. Quantitative analysis of vibrissal movements prior to nerve transection and repair (facial-facial anastomosis) did not reveal genotype-specific differences, and thus impacts of the mutations on motor function in intact animals. Two months after nerve repair, recovery of vibrissal whisking was poor in wild-type mice, a typical finding after facial-facial anastomosis in rodents. Differential effects of the mutations on whisking were found: recovery of function was worse in TNC-deficient and better in TNR null mice compared with wild-type littermates. In double-knockout animals, vibrissal performance was insufficient, but to a lesser extent compared with TNC null mutant mice. Retrograde labelling of motoneurons in the same animals showed that similar numbers of motoneurons had reinnervated the whisker pads in all experimental groups precluding varying extents of motoneuron death and/or axon regeneration failures as causes for the different outcomes of nerve repair. Our results provide strong evidence that TNC promotes and TNR impedes recovery after nerve lesion. These findings are of particular interest with regard to the scanty knowledge about factors determining success of regeneration in the peripheral nervous system of mammals.

Peripheral and spinal motor reorganization after nerve injury and repair.

Functional recovery after peripheral nerve injury depends on the amount as well as on the accuracy of reinnervation by regenerative axons. In this study, the rat sciatic nerve was subjected to crush injury or complete transection repaired by either (1) straight nerve suture, (2) crossed nerve suture of tibial and peroneal fascicles, or (3) silicone tubulization leaving a gap of 4 mm. The compound muscle action potentials (CMAP) of gastrocnemius, tibialis anterior and plantar muscles were recorded 90 days post operation to assess functional reinnervation and Fast Blue, Fluoro Gold and DiI were applied to the nerve branches projecting into these muscles to quantify morphological reinnervation. The CMAP amplitude achieved in gastrocnemius, tibialis anterior and plantar muscles was higher after nerve crush (86%, 82%, 65% of control) than after any surgical nerve repair (straight suture: 49%, 53%, 32%; crossed suture: 56%, 50%, 31%; silicone tube: 42%, 44%, 25%). The total number of labeled motoneurons, however, did not significantly differ between groups (control: 1238 +/- 82, crush: 1048 +/- 49, straight suture: 1175 +/- 106, crossed suture: 1085 +/- 84, silicone tube: 1250 +/- 182). The volume occupied by labeled motoneurons within the spinal cord was larger after surgical nerve repair than in crush or normal control animals, and fewer neurons showed abnormal multiple projections after crush (2.5%) or straight suture (2.2%) than following crossed suture (5%) or silicone tube (6%). In conclusion, nerve repair with a silicone tube leaving a short gap does not increase accuracy of reinnervation.

Altered sensory input improves the accuracy of muscle reinnervation.

PURPOSE: To improve functional recovery after peripheral nerve suture, we characterized the quality of target reinnervation in rats in which the afferent trigeminal connection to facial motoneurons had been altered. METHODS: Employing an improved lesion model and a refined mode of retrograde tracer application, we studied the accuracy of reinnervation in rats which underwent buccal-buccal nerve anastomosis (BBA) alone (group 1), BBA plus excision of the ipsilateral infraorbital nerve (ION; group 2), and BBA plus excision of the contralateral ION (group 3). This was done by comparison between the number of double-labeled motoneurons after pre-operative injection of Fluoro-Gold (FG) and post-operative injection of Fast Blue (FB) into the whisker pad muscles. RESULTS: In the first group we counted 398 +/- 80 FG+FB double labeled cells (mean +/- SD; n = 9 rats), i.e., only 27% of all motoneurons that grew axons into the whisker pad had projected to these muscles before surgery. In group 2, this value was increased marginally to 436 +/- 68 (32%). In group 3,. we counted 580 +/- 63 double-labeled neurons. This is the first morphological report demonstrating significantly improved specificity of reinnervation. Indeed, 41% of the motoneurons innervating the target in group 3 belonged to the original neuron pool. These morphological findings are supported by evidence obtained from electrophysiological recordings and behavioural studies. CONCLUSIONS: The principle finding of the present study is that a peripheral lesion to the contralateral trigeminal nerve improves the quality of reinnervation of the whisker pad musculature by its original nerve. The contralateral trigeminal lesion may trigger behavioural demand and forced overuse of the axotomized facial nerve, which may be a key issue for recovery of vibrissae rhythmical whisking after facial nerve surgery.