Additive manufactured biodegradable poly(glycerol sebacate methacrylate) nerve guidance conduits

Entubulating devices to repair peripheral nerve injuries are limited in their effectiveness particularly for critical gap injuries. Current clinically used nerve guidance conduits are often simple tubes, far stiffer than that of the native tissue. This study assesses the use of poly(glycerol sebacate methacrylate) (PGSm), a photocurable formulation of the soft biodegradable material, PGS, for peripheral nerve repair. The material was synthesized, the degradation rate and mechanical properties of material were assessed and nerve guidance conduits were structured via stereolithography. In vitro cell studies confirmed PGSm as a supporting substrate for both neuronal and glial cell growth. Ex vivo studies highlight the ability of the cells from a dissociated dorsal root ganglion to grow out and align along the internal topographical grooves of printed nerve guide conduits. In vivo results in a mouse common fibular nerve injury model show regeneration of axons through the PGSm conduit into the distal stump after 21 days. After conduit repair levels of spinal cord glial activation (an indicator for neuropathic pain development) were equivalent to those seen following graft repair. In conclusion, results indicate that PGSm can be structured via additive manufacturing into functional NGCs. This study opens the route of personalized conduit manufacture for nerve injury repair.

STATEMENT OF SIGNIFICANCE

This study describes the use of photocurable of Poly(Glycerol Sebacate) (PGS) for light-based additive manufacturing of Nerve Guidance Conduits (NGCs). PGS is a promising flexible biomaterial for soft tissue engineering, and in particular for nerve repair. Its mechanical properties and degradation rate are within the desirable range for use in neuronal applications. The nerve regeneration supported by the PGS NGCs is similar to an autologous nerve transplant, the current gold standard. A second assessment of regeneration is the activation of glial cells within the spinal cord of the tested animals which reveals no significant increase in neuropathic pain by using the NGCs. This study highlights the successful use of a biodegradable additive manufactured NGC for peripheral nerve repair.

[A FEASIBILITY STUDY ON TRANSPOSITION OF PROXIMAL MOTOR BRANCHES FROM TIBIAL NERVE TO RECONSTRUCT DEEP FIBULAR NERVE]

OBJECTIVE

To explore the feasibility of transposition of the proximal motor branches from tibial nerve (TN) as direct donors to suture the deep peroneal nerve (DPN) so as to provide a basis for surgical treatment of high fibular nerve injury.

METHODS

Nineteen lower limb specimens were selected from 3 donors who experienced high-level amputation (2 left limbs and 1 right limb) and 8 fresh frozen cadavers (8 left limbs and 8 right limbs). The length and diameter of the three motor branches from TN (soleus, medial gastrocnemius, and lateral gastrocnemius) and the distance from the initial points to the branch point of the common peroneal nerve (CPN), as well as the length and diameter of the noninvasive separated bundles of DPN, then the feasibility of tensionless suturing between the donor nerves and the DPN bundle was evaluated. At last, part of the nerve tissue was cut out for HE and Acetylcholine esterase staining observation and the nerve fiber count.

RESULTS

Gross anatomic observation indicated the average distance from the initial points of the three donor nerves to the branch point of the CPN was (71.44 ± 2.76) (medial gastrocnemius), (75.66 ± 3.20) (lateral gastrocnemius), and (67.50 ± 3.22) mm (soleus), respectively. The three donor nerves and the DPN bundles had a mean length of (31.09 ± 2.01), (38.44 ± 2.38), (59.18 ± 2.72), and (66.44 ± 2.85) mm and a mean diameter of (1.72 ± 0.08), (1.88 ± 0.08), (2.10 ± 0.10), and (2.14 ± 0.12) mm, respectively. The histological observation showed the above-mentioned four nerve bundles respectively had motor fiber number of 2,032 ± 58, 2.186 ± 24, 3,102 ± 85, and 3,512 ± 112. Soleus nerve had similar diameter and number of motor fibers to DPN bundles (P > 0.05), but the diameter and number of motor fibers of the medial and lateral gastrocnemius were significantly less than those of DPN bundles (P < 0.05).

CONCLUSION

All of the three motor branches from TN at popliteal fossa can be used as direct donors to suture the DPN for treating high CPN injuries. The nerve to the soleus muscle should be the first choice.

Epineurial compartments and their role in intraneural ganglion cyst propagation: An experimental study

New patterns of intraneural ganglion cyst formation are emerging that have not previously been explained in current pathoanatomic terms. We believe there are three important elements underlying the appearance of these cysts: (a) an articular branch of the nerve that connects to a nearby synovial joint; (b) ejected synovial fluid following the path of least resistance along tissue planes; and (c) the additional effects of pressure and pressure fluxes. The dynamic nature of cyst formation has become clearly apparent to us in our clinical, operative and pathologic practice, but the precise mechanism underlying the process has not been critically studied. To test our hypothesis that a fibular (peroneal) or tibial intraneural cyst derived from the superior tibiofibular joint could ascend proximally into the sciatic nerve, expand within it and descend into terminal branches of this major nerve, we designed a series of simple, qualitative laboratory experiments in two cadavers (four specimens, six experiments). Injecting dye into the outer or "epifascicular" epineurium of the fibular and the tibial nerves we observed its ascent, cross over and descent patterns in three of three specimens as well as its cross over after an outer epineurial sciatic injection. In contrast, injecting dye into the inner or "interfascicular" epineurium led to its ascent within the tibial nerve and its division within the sciatic nerve in one specimen and lack of cross over in a sciatic nerve injection. Histologic cross-sections of the nerves at varying levels demonstrated a tract of disruption within the outer epineurium of the nerve injected and the nerve(s) into which the dye, after cross over, descended. Those specimens injected in the inner epineurium demonstrated dye within this tract but without disruption of or dye intrusion into the outer epineurium. In no case did the dye pass through the perineurial layers. Coupled with our observations in previous detailed studies, these anatomic findings provide proof of concept that sciatic cross over occurs due to the filling of its common epineurial sheath; furthermore, these findings, support the unifying articular theory, even in cases wherein patterns of intraneural ganglion cyst formation are unusual. Additional work is needed to be done to correlate these anatomic findings with magnetic resonance imaging and surgical pathology.

Anterior innervation of the proximal tibiofibular joint

Mucoid cysts compressing the common peroneal nerve have been reported. Whether these cysts are schwannoma or are synovial in nature is the subject of controversy in the medical literature. To contribute to this debate, the present study was designed to detail the anterior innervation of the proximal tibiofibular joint. We dissected 10 knees of five fresh cadavers after staining the tibiofibular joint under fluoroscopic guidance. Through a lateral approach near the fibular head, the common peroneal nerve was isolated then dissected distally to determine whether it or its branches ramified over the proximal tibiofibular joint. In all 10 legs, only one collateral branch was observed on the common peroneal nerve proximal to its terminal division. This collateral sent a branch to the proximal tibiofibular joint before penetrating the tibialis anterior muscle. The articular branch coursed in a superior and posterior direction approximately 1 cm to attain the tibiofibular joint. In no specimen did the deep or superficial peroneal nerves send a twig to the tibiofibular joint. This study confirms and clarifies prior descriptions of the innervation of the anterior aspect of the proximal tibiofibular joint. It clarifies the mechanisms of compression of the common peroneal nerve by synovial cysts that originate from the proximal tibiofibular joint and provides anatomical landmarks that should facilitate complete resection of these cysts.

[Fibular nerve compression due to an unusual cause. A case report]

There are many factors causing a compression of the fibular nerve accompanied by a loss of function. We describe an unknown cause: a chronic low-grade infection after implantation of a knee endoprosthesis. Perforation of the capsule of the knee joint followed by discharge of polyethylene particles originating from the endoprosthesis. A granuloma developed which resulted in a compression of the peroneal nerve with sensomotor disabilities. Preoperatively we were not able to define the dignity of the tumour. Neurolysis was performed followed by excision of the tumour. The infection was treated by long term antibiotics without removal of the endoprosthesis. Histological examination revealed the definitive diagnosis.

Compression nerveuse par pseudo-kyste mucoïde : à propos de 23 cas

PURPOSE OF THE STUDY

Mucoid pseudocysts are infrequent benign tumors which can develop on all peripheral nerves near joints. The origin of these cysts remains to be determined. We searched for arguments favoring an articular origin which would have an impact on management and risk of recurrence.

MATERIALS AND METHODS

Twenty-three patients (21 men and 2 women, mean age 38 years, age range 13-56 years) presented mucoid pseudocysts and were followed for a mean six years. The mucoid pseudocyst was located on the common fibular nerve at the neck of the fibula in 16 patients, on the tibial nerve at the knee in one, on the median nerve in one, on the ulnar nerve in one, and on the suprascapular nerve in two. Pain was local in 18 patients and irradiated to the concerned nerve territory in 20. Motor deficit was the inaugural feature in 17 patients. EMG was performed in all patients, ultrasound exploration in 15, computed tomography in 7 and magnetic resonance imaging in 10. All patients included in this series underwent surgery: pathological diagnosis of mucoid intra-neural pseudocyst was established in all. Systematic search for communication with the neighboring joint was performed in all cases.

RESULTS

An articular communication was found in 17 patients. Mean time to recovery of muscle force (scored 5) and/or normal sensitivity was seven months in 17 patients. One patient did not achieve full recovery. Three patients experienced recurrence and required tibiofibular arthrodesis.

DISCUSSION

Three theories have been proposed (cystic degeneration of schwannoma, degeneration of nerve sheath connective tIssue, and an articular origin). The articular theory appears to be the most probable. The presence of an articular pedicle in 60% of the patients, the anatomic juxtaposition between the nerves involved and neighboring joints, and occasional migration along the articular nerve as well as the cyst's mucoid content argue in favor of the articular theory. The notion of recurrence after complete minute excision is also in favor of an articular pathogenic mechanism. The diagnosis of mucoid cyst should be retained as a possibility in patients with rapidly progressive signs of nerve compression near a joint. It is important to search for articular communication before and during the surgical excision in order to limit the risk of recurrence.

The value of inching technique in evaluating the peroneal nerve entrapment at the fibular head

The peroneal nerve palsy at the fibular head is quite common but often difficult to diagnose both clinically and electrophysiologically. The purpose of this study was to evaluate the usefulness of the inching in mononeuropathy of the peroneal nerve at the fibular head. Recording from extensor digitorum brevis muscle the nerve was stimulated supramaximally at 1 cm intervals starting 2 cm distal and ending 8 cm proximal to the fibular head. Forty-six patients were examined: the inching was modified in 32 patients. In five of these the motor conduction using conventional method was normal, but the inching was normal or borderline in fourteen patients with reduced conduction velocity across the fibular head. Despite some limitations, the inching can be useful in evaluating patients with suspected palsy of the peroneal nerve at the fibular head.

Restoration of motor function of the deep fibular (peroneal) nerve by direct nerve transfer of branches from the tibial nerve: An anatomical study

Traction injuries of the common fibular (peroneal) nerve frequently result in significant morbidity due to tibialis anterior muscle paralysis and the associated loss of ankle dorsiflexion. Because current treatment options are often unsuccessful or unsatisfactory, other treatment approaches need to be explored. In this investigation, the anatomical feasibility of an alternative option, consisting of nerve transfer of motor branches from the tibial nerve to the deep fibular nerve, was studied. In ten cadaveric limbs, the branching pattern, length, and diameter of motor branches of the tibial nerve in the proximal leg were characterized; nerve transfer of each of these motor branches was then simulated to the proximal deep fibular nerve. A consistent, reproducible pattern of tibial nerve innervation was seen with minor variability. Branches to the flexor hallucis longus and flexor digitorum longus muscles were determined to be adequate, based on their branch point, branch pattern, and length, for direct nerve transfer in all specimens. Other branches, including those to the tibialis posterior, popliteus, gastrocnemius, and soleus muscles were not consistently adequate for direct nerve transfer for injuries extending to the bifurcation of the common fibular nerve or distal to it. For neuromas of the common fibular nerve that do not extend as far distally, branches to the soleus and lateral head of the gastrocnemius may be adequate for direct transfer if the intramuscular portions of these nerves are dissected. This study confirms the anatomical feasibility of direct nerve transfer using nerves to toe-flexor muscles as a treatment option to restore ankle dorsiflexion in cases of common fibular nerve injury.

Displacement of the common peroneal nerve associated with upper tibial fracture: implications for fine wire fixation

The constant anatomic position of the common peroneal nerve is relied on when performing fine wire external fixation in the upper tibia. We report the case of a sixty-two-year-old woman with a Schatzker Type V fracture of her right tibial plateau and upper-third diaphyseal fracture associated with displacement and shortening of the upper tibia. She was treated by minimal internal fixation of the intraarticular fracture and application of a Sheffield Hybrid External Fixator. During percutaneous insertion of the reference wire in the fibular head, a distal muscle twitch alerted the surgeon, and the common peroneal nerve was duly explored and found displaced forward over the fibular head, dangerously close to the wire. It is postulated that at the time of injury, the common peroneal nerve was displaced anteriorly and that despite reduction of the tibial fractures, it had failed to return to its original position. The mechanism of this was confirmed by an anatomic study on an above-the-knee amputation specimen in which the metaphyseal-diaphyseal element of the fracture was reproduced. We recommend insertion of the reference fibular wire with the knee in flexion. Open insertion of this wire, with an incision down to bone and exposure of the fibular head, is recommended in cases in which severe trauma with shortening of the upper tibia, with possible disruption of the tibiofibular joint, puts the nerve in danger of injury.

Anatomical variations of the sensory nerves to the fibular osteocutaneous flap

OBJECTIVE

To describe the anatomical relationship of the sural sensory nerve complex to the posterior crural intermuscular septum (PS), the key anatomical structure for the osteoseptocutaneous fibula skin paddle.

DESIGN

Anatomical study.

SUBJECTS

Twenty-two legs from 11 cadavers (7 females and 4 males).

RESULTS

The lateral sural cutaneous (LSC) nerve, present in 20 of 22 legs, divides into lateral and medial branches near the head of the fibula. The LSC nerve and its medial branch course away from the PS, whereas the lateral branch tends to course toward the PS. The lateral branch courses nearest to the PS at a median distance of between 4 cm proximally and 3 cm distally. The medial branch of the LSC nerve terminates approximately in the middle of the leg, and the lateral branch of the LSC nerve terminates within 7 cm below the head of the fibula. The peroneal communicating branch is thicker than the LSC nerves; however, it is further from the PS in the upper leg.

CONCLUSIONS

The LSC nerve is the most consistent and accessible donor sensory nerve in the posterior leg for harvest with the osteoseptocutaneous fibula free flap. Results of this study will assist the surgeon in harvesting a sensory nerve with the osteoseptocutaneous fibula free flap, bringing this potentially sensate flap into more common use. Arch Facial Plast Surg. 2000;2:252-255

Normal values of F wave in lower extremities of 73 healthy individuals in Iran

F wave latency has been shown to be a simple and valuable method in evaluation of proximal part of peripheral nerves. According to our previous study of F wave of upper extremity nerves (1), maximum normal F wave latency for the median nerve was 28 ms with stimulation at wrist and 25 ms with stimulation at elbow. These values for the ulnar nerve were 29 ms and 25 ms respectively. Maximum normal difference between right and left F wave latency with wrist stimulation was 2 ms for median nerve and 2.5 ms for ulnar nerve. Maximum normal difference between median and ulnar nerve F latency was 3.5 ms with stimulation at wrist. In this study we measured F wave of lower extremity nerves in 73 healthy individuals in Shiraz. Maximum normal F wave latency for tibial nerve was 55 ms with stimulation at ankle and 46 ms with stimulation at popliteal area. Maximum normal F wave latency for the peroneal nerve was 54 ms with stimulation at ankle and 47 ms with stimulation at fibular head. Mean F ratio for both nerves was 1.29 with stimulation at knee. Maximum normal difference in F wave latency between right and left lower extremities was 3.5 ms with stimulation at ankle and 3 ms with stimulation at knee for the peroneal nerve. These values were 3 ms and 2.5 ms for the tibial nerve respectively. Maximum normal difference in F wave latency between tibial and peroneal nerve was 4 ms with stimulation at ankle and 3 ms with stimulation at knee.

Peroneal nerve motor conduction to the extensor digitorum brevis

Peroneal motor studies to the extensor digitorum brevis are commonly performed in electrodiagnosis. They have been investigated by many authors to derive the normal ranges for latency, amplitude, and nerve conduction velocity. Many of these studies, particularly the older ones, have methodological limitations, especially in light of modern technique and statistical applications. They often used small sample sizes. The objective of this study was to generate an expanded database of normative values for the peroneal nerve. In this study, 242 asymptomatic subjects without risk factors for neuropathy were tested, and their peroneal motor response was analyzed for latency, amplitude, area, duration, and nerve conduction velocity. Side-to-side and proximal-to-distal variation was recorded. Mean +/- 2 standard deviations (SD) and percentiles of normality are presented. Mean onset latency was 4.8 ms (SD, 0.8). Mean amplitude was 6.8 mV (SD, 2.5) and 5.1 mV (SD, 2.5) for the younger and older than 40-yr age groups, respectively. Mean nerve conduction velocity ranged from 44 to 49 m/s, depending on the demographic group (SD, 4-5). The upper limit of normal side-to-side latency variation was 1.4 ms (mean + 2 SD). The upper limit of normal drop in nerve conduction velocity from the low leg to the across knee segment was 10 m/s (mean - 2 SD) or 12% (97th percentile). The upper limit of normal amplitude difference from side to side was 61 % (at the 97th percentile), and the upper limit of normal drop in amplitude from below to above the fibular head stimulation was 25% (at the 97th percentile). The other measures are presented in the article.

Fibre composition in the interosseous nerve of the pigeon

The interosseous nerve of birds innervates a string of Herbst corpuscles located near the interosseous membrane between the tibia and fibula. Fibre composition of this nerve was assessed including both myelinated and unmyelinated axons. The diameter of the whole nerve is approximately 100 microm. Complete data were obtained for 3 nerves. The mean total number of myelinated fibres and unmyelinated axons was 2872 +/- 53. The mean number of myelinated fibres was 280 +/- 20 and that for unmyelinated axons was 2600 +/- 47. There was a broad distribution of diameters for myelinated fibres ranging from approximately 2 microm to 10 microm with a distinct peak at approximately 3-5 microm and a less prominent second peak at 6-8 microm. Similarly, myelin sheath thickness distribution showed 2 peaks, one at 0.6-0.8 microm and another at 1.4-1.6 microm. It is suggested that the group represented by the second peak innervates the Herbst corpuscles. The group of smaller myelinated fibres and the unmyelinated axons are assumed to innervate other types of receptors, some of which may be nociceptors.

Bilateral foot-drop in a patient with anorexia nervosa

We report the occurrence of bilateral foot-drop in a patient with anorexia nervosa. To the best of our knowledge this has not been reported previously. The underlying pathology was found to be peroneal nerve palsy probably related to mechanical pressure at the head of the fibula. Nutritional deficiency may also be implicated.

Giant cell tumor of the proximal fibula: surgical management

Five patients with giant cell tumor of the proximal fibula were treated with intralesional excision of the lesion, preservation of the peroneal nerve, and reconstruction of the lateral collateral ligament. At minimum 24-month follow-up there have been no local recurrences. Four patients exhibit normal function of the peroneal nerve and one has grade 4 strength of the muscles innervated by this nerve. No patient demonstrated varus instability. Marginal excision with nerve preservation and reconstruction of the ligament is a worthwhile procedure for treatment of this relatively uncommon lesion.

Operative anatomy of nerves encountered in the lateral approach to the distal part of the fibula

We dissected fifty legs from twenty-six cadavera to determine the origin and frequency of nerves that crossed the line of a lateral approach to the distal part of the fibula. A branch of the sural or common peroneal nerve, or both, that was at least one millimeter in diameter crossed the line of the operative approach in eleven legs (22 per cent) and was within five millimeters of the anterolateral border of the fibula in twenty-seven legs (54 per cent). We recommend that a meticulous operative technique be used during exposure of the distal part of the fibula to prevent paresthesias or painful neuromas resulting from the inadvertent transection of these small nerves.

Anatomic considerations of the peroneal nerve for division of the fibula during high tibial osteotomy

Twenty legs in 10 cadavers were dissected to determine the course of the deep peroneal nerve from its origin to its termination. Particular attention was paid to defining: (1) its relationship to palpable landmarks, (2) the angle of the course of its proximal portion against the long axis of the fibula, (3) distribution of the proximal branch to the extensor hallucis longus muscle, and (4) safe areas of osteotomy in the proximal fibula during high tibial osteotomy. The extensor hallucis longus was often supplied by only one branch from the deep peroneal nerve at 99.8 mm (31.7%) distally from the apex of the fibula; this seems to explain why osteotomy of the fibula at its proximal one third often causes paralysis of this muscle. The findings suggest that safe areas for osteotomy in the proximal fibula during high tibial osteotomy are located up to 20.5 mm (6.5%) distal to the tip of the fibular head and that the safe angle of a periosteal incision against the fibular neck area is 64.1 degrees.

Anatomic basis of mandibular reconstruction by free vascularised fibular graft

The free osteofasciocutaneous fibular transplant is a direct development of the free fibular bone graft used from 1983 in reconstructive surgery of the long bones. In 1989, Hidalgo was the first to publish a method of reconstruction of the mandible by composite free fibular transplants. The aim of this study was to specify the anatomy of the osteofascio-cutaneous fibular graft and particularly of the vessels to the skin. The sensory innervation of this transplant is described.

Palsy of the deep peroneal nerve after proximal tibial osteotomy. An anatomical study

Iatrogenic, isolated weakness or paralysis of the extensor hallucis longus muscle is a common complication in patients who have had a proximal tibial and fibular osteotomy. To investigate why this complication occurs, we dissected the deep peroneal nerve and neighboring structures, such as the tibia and fibula and the muscles of the leg, in twenty-nine specimens from cadavera, paying special attention to the motor branches supplying the extensor hallucis longus. Of forty-six motor nerves that were identified, eight entered the muscle from the lateral side in an area seventy to 150 millimeters distal to the fibular head; all of them ran close to the fibular periosteum. We suggest that, in some patients, the nerve supply to the extensor hallucis longus is at high risk for injury during a tibial osteotomy because of the proximity of the bone to the motor branches.

The distal course of the sural nerve and its significance for incisions around the lateral hindfoot

Twenty preserved cadaver limbs were dissected to show the distal course of the sural nerve and the number and site of origin of its branches. The mean position of the main nerve trunk was calculated at various points related to bony landmarks of the fibula and the fifth metatarsal base. Ninety-five percent confidence limits for the course of the main nerve trunk could be described. A fibula incision may damage the nerve if it extends more than 7 mm inferior to the lateral malleolar tip with the foot in equinus. Dorsolateral foot incisions may damage both the main trunk and the major anterior branch.

The "critical zones" of entrapment of the nerves of the lower limb

The author has studied, in a group of 40 dissections on cadavers of individuals of different ages, the main "critical zones" of entrapment of some terminal branches of the lumbo-sacral plexus, which include canals (fibrous, osteo-fibrous, fibro-muscular), intervals (intermuscular, fibro-muscular, musculo-ligamentous), rings (fibrous or fibro-muscular) and foramina. They provide the topographical anatomical basis for possible compressive phenomena of the nerves of the lower limb.

Section of fibular nerve affects activity pattern and contractile properties of soleus motor units in adult rats

Transection of the common fibular (FIB) nerve caused an immediate reduction in the total amount of soleus (SOL) motor unit activity, which declined further during the following 10 days and then remained stable at less than half of normal values. In addition, there was an immediate reduction in median impulse rate from about 20.0 to 14.9 Hz followed by a return to normal values during the first 10 days. Short interval (3-4 ms) double discharges, occurring either in isolation or at the same regular intervals as single impulses, were observed 2-5 days after FIB nerve section in a few motor units. Brief, high frequency impulse bursts with interspike intervals of 12-16 ms were observed in a few units from the third day and until the end of the experiment (up to 31 days). It was not established whether the high frequency discharge pattern occurred only in a fixed population of the SOL motor units, or whether the units could switch between high and low frequency activity. Two months after FIB nerve section, the SOL muscle in the same leg contracted faster than normal (mean isometric twitch contraction time 29.6 ms, n = 4; vs. 38.7 ms, n = 8), contained a larger than normal percentage of type II fibres (13-36 vs. 0-0.2%) and weighed less than the contralateral SOL muscles (180 vs. 206 mg). SOL muscles (n = 4) in the opposite leg were comparable to normal SOL muscles except for a small reduction in mean isometric twitch contraction time (35.5 ms).

Late reinnervation of the rat soleus muscle is differentially suppressed by chronic stimulation and by ectopic innervation

Soleus (SOL) and extensor digitorum longus (EDL) muscles in adult rats were kept denervated for 2 months by four repeated freezes at 2-week intervals of the sciatic nerve. Reinnervation was studied in the absence or presence of chronic muscle stimulation, starting 1 month before reinnervation began. In addition, reinnervation was studied in SOL muscles where a previously transplanted fibular (FIB) nerve had formed ectopic neuromuscular junctions outside the original endplate area. After repeated freezes only, reinnervation was complete judged by tension measurements and histochemical examinations in SOL (n = 7) and EDL (n = 8) muscles. In directly stimulated muscles reinnervation was incomplete, and the force tensions evoked from indirect stimulation was on average 87 (n = 5) and 82% (n = 5) of direct muscle stimulation in SOL and EDL muscles, respectively. Of ectopically innervated SOL muscle fibres, only 26% became reinnervated in 12 muscles. Denervation and reinnervation increased the number of muscle fibres in stimulated (n = 4) and unstimulated (n = 5) EDL muscles by 18 and 15%, respectively. In stimulated (n = 4) and unstimulated (n = 7) SOL muscles, on the other hand, the number of muscle fibres remained normal. The stronger suppression of reinnervation in ectopically reinnervated compared to chronically stimulated SOL fibres indicates that reinnervation can also be suppressed by activity independent influences from the foreign nerve.

Pressure-induced changes in fibular motor nerve conduction velocity and fibularis (peroneus) tertius muscle-evoked potentials in a goat model of the downer cow syndrome

A study was conducted to determine the acceptable fibular motor nerve conduction velocity (NCV) in goats and to characterize pressure-induced changes in conduction velocity and muscle-evoked potentials (MEP). The acceptable motor NCV in the adult goat was determined to be 95.9 +/- 6.8 m/s. Limb compression in recumbent cows was modeled by application of external compression to the goat pelvic limb to increase IM pressure to a minimum of 50 mm of Hg. This pressure, when applied for a 6-hour period, caused a 30% to 100% reduction of fibular motor NCV and a 10% to 100% reduction of amplitude of MEP measured from fibularis (peroneus) tertius muscle. The reduction of motor NCV and MEP was associated with clinically evident limb dysfunction. The changes detected by the electrodiagnostic tests were proportional to the magnitude and duration of the locomotor deficits. The limb dysfunction was accompanied by muscular damage indicated by an increase of serum creatine kinase activity.

Development of nonunions in the rat fibula after removal of periosteal neural mechanoreceptors

Periosteal proprioceptive nerve receptors may act as mechanoreceptors of long bones during adaptive remodeling after fracture. They may also contribute to the mechanisms of coordinated functional activity of fractured limbs and thus inhibit harmful overloading of fracture callus. The area of proprioceptive nerve receptors around the distal part of the rat fibula was stripped surgically, and a standard fracture of the fibular shaft was produced. Animals failed to unite their fractures and developed mainly atrophic nonunions. Atrophy of ununited fragments was due to osteoclastic bone resorption. Atrophy of the bone fragments was aggravated if the legs were also subjected to sciatic denervation. Sciatic denervation alone, without removal of receptors, did not interfere with the union of fractures. The results indicate that the area of proprioceptive receptors in the rat tibiofibular bone is critical for the healing of fibular fractures. Because the effect on bone healing of receptor removal was not inhibited by sciatic denervation, the effect was not transmitted through spinal pathways of the sciatic nerve. The development of nonunions could not be explained by the surgical trauma alone. Aggravation of fibular atrophy by sectioning of the sciatic nerve suggests that some neural elements are associated with the phenomenon, either directly or indirectly through neuromuscular function.

[The operative treatment of paresis of the fibular nerve caused by external compression (author's transl)]

The operative treatment of six cases of paresis of the fibular nerve caused by external compression in five patients are reported. From the intraoperative findings and the postoperative results, decompression of the fibular nerve with simultaneous neurolysis can be recommended as the optimal method for cases, which have been treated conservatively without success.

[Peripheral nerve compression by ganglionic cysts (author's transl)]

Extra- and intraneural ganglionic cysts rarely involved peripheral nerves. They are found in the neighbourhood of large joints. Intraneural cysts prefer the deep peroneal nerve and cause intermittent pain and severe nerve damage. The ulnar nerve is affected most often at the wrist. There are different types of distal motor and/or sensory ulnar palsy. Spontaneous recovery may take place and recurrences of intraneural cysts of the peroneal nerve occur after surgery.

The interaction between foreign and original motor nerves innervating the soleus muscle of rats

1. The fibular nerve was transplanted on to the soleus muscle of the rats. Interruption of the original soleus nerve then permitted cross-innervation, and subsequently, over a period of weeks, re-innervation by the original nerve. 2. Individual muscle fibres were often innervated by both the original and the foreign nerve. The original and foreign end-plates were located in separate regions of the muscle. There were no indications that the original nerve could displace or repress the foreign innervation. 3. The extent of re-innervation by the original nerve depended upon the method of denervation. A single crush of the nerve was followed by virtually complete re-innervation, even of muscle fibres already innervated by the foreign nerve. When re-innervation was delayed by resection of a segment of the nerve only muscle fibres without foreign nerve innervation were re-innervated. Denervation by a simple nerve cut gave an intermediate result. 4. Re-innervation by the original nerve can take place without measurable extrajunctional sensitivity to ACh. 5. The original end-plate region could retain high and localized sensitivity to ACh for several months despite degeneration of its motor nerve terminal and activity of the muscle fibre. 6. Established foreign end-plates were re-innervated by the foreign nerve on muscle fibres with intact original innervation. 7. The factors controlling synapse formation in skeletal muscles are discussed.

Responses of vibration-sensitive receptors in the interosseous region of the duck's hind limb

1. Responses of receptors with fibres in the interosseous nerve of the duck's leg have been studied by recording unit discharges in filaments dissected from the sciatic nerve.2. Seventy-two of the ninety-four units examined served highly phasic, vibration-sensitive mechanoreceptors in the interosseous region interpreted as being Herbst corpuscles. Receptor types for most of the other units could not be determined, but some were slowly adapting mechanoreceptors.3. Rheobase threshold values for the most sensitive vibration-receptors were similar to those of mammalian Pacinian corpuscles.4. Threshold-frequency relationships for the vibration receptors showed a wider range of low frequency cut-off values, and a greater capacity to signal high frequencies, than is the case with Pacinian corpuscles.5. Fibres of the vibration-receptors had calculated diameters ranging from 5 to 10 mum and account for the bulk of the larger fibres in the interosseous nerve.6. It is suggested that Herbst corpuscles in the legs of birds might act as a warning device by detecting vibratory disturbances of the ground or other supporting surface.