SEARCH · PubMed Health

Results for “Tibia”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 613 records · Page 34Linked to original sources

PubMed1996

Ipsilateral fractures of the femur and tibia: treatment with retrograde femoral nailing and unreamed tibial nailing.

Between 1989 and 1995 a total of 47 patients with 50 fractures of the ipsilateral femoral and tibial shafts without significant articular involvement were treated at Tampa General Hospital. Within this group were 24 patients with 26 fractures who were treated with intramedullary fixation of both bones using a technique of retrograde insertion of a femoral nail and unreamed insertion of an interlocking tibial nail. Information concerning the injuries, treatments, and much of the follow-up was gleaned from a trauma registry. Five of the femoral fractures (19%) and 14 of the tibial fractures (54%) were open. Associated injuries were present in 18 of the 24 patients (75%) with injuries of the pelvis, other extremities, and head being most prevalent. The average Injury Severity Score was 14 (range 9-32). The femoral nails were placed either through the medial femoral condyle (n = 14) or the intercondylar notch of the distal femur (n = 12). Twenty patients with 22 extremities had sufficient follow-up at an average of 20 months (range 4-60) postinjury to be included in the review. One patient had died, and three were completely lost to follow-up. Both fractures in 14 extremities had healed or were healing uneventfully at final review. Seven of the tibiae and three of the femora had complications after initial hospitalization. Two patients developed problems in both bones. Three patients had electrical stimulation of a tibia fracture, one of which underwent simultaneous nail dynamization. A total of 18 additional operative procedures were necessary after the primary treatment in six problematic extremities. Thirteen additional operative procedures were required in five complicated tibiae (one nail dynamization, six debridement procedures, five bone grafts, and one muscle flap) after the initial hospitalization. Five additional operative procedures were required in the three complicated femora (two nail dynamizations, one bone graft, and two exchange nailing procedures). Functional results were good or excellent in 13 of the 20 patients (65%) and 15 of the 22 extremities (68%) available at final review. No significant knee problem related to the femoral nailing technique was identified. This method of treatment can be performed using a standard radiolucent table and a single medial parapatellar incision. It is expedient and allows other procedures to be performed simultaneously in this group of severely injured patients.

Adolescent↗

PubMed1997

Intramedullary nailing of unstable diaphyseal fractures of the tibia with distal intraarticular involvement.

OBJECTIVE: To evaluate the efficacy of intramedullary nailing in diaphyseal tibia fractures with distal intraarticular involvement. DESIGN: Retrospective. SETTING: Henry Ford Hospital, a level I trauma center. PATIENTS/PARTICIPANTS: Twenty patients with twenty fractures at an average of twenty-two months of follow-up were evaluated. There were fifteen closed and five open fractures. INTERVENTION: All fractures were stabilized with lag screw fixation (with or without supplemental plates) of the intraarticular-fracture extension or ankle fracture, and intramedullary nailing of the diaphyseal tibia fracture. MAIN OUTCOME MEASUREMENTS: Time to bony union, malunion, knee and ankle range of motion, early arthrosis, and any complications of treatment were assessed. RESULTS: Nineteen fractures healed, with an average time to bony union of seventeen weeks. One nonunion after a grade IIIB open fracture required exchange nailing and healed after sixty-two weeks. Nineteen fractures had excellent alignment after healing. There were no infections. CONCLUSIONS: The indications for intramedullary nailing of unstable diaphyseal tibia fractures may be extended to include certain fractures with distal extension into the ankle joint, as well in a tibial shaft fracture occurring in combination with a noncontiguous ipsilateral ankle fracture.

Adult↗

PubMed1997

The role of fibular fixation in combined fractures of the tibia and fibula: a biomechanical investigation.

OBJECTIVES: To determine whether adjunctive plating of the fibula with tibial fixation enhanced the stability of the construct under combined compressive and bending loads in simulated fractures of both the tibia and fibula. METHODS: Each of twelve fresh cadaveric specimens (six pairs) with an intact knee, lower extremity, and foot was mounted on the table of a materials testing machine. An intramedullary (IM) rod locked in the distal femur allowed combined compression, and flexion, valgus bending, or varus bending loads to be transmitted from the actuator of the testing machine to the knee. Three displacement measurement transducers were mounted on the tibia at anterior, posterolateral, and posteromedial positions. Intact tibial deformations under load were measured. Then, in one specimen of each pair a 2 cm osteotomy was created near the tibial midshaft, which was stabilized with an external fixator. Tibial gap displacements were measured under the following conditions: (a) intact fibula, (b) osteotomized fibula, (c) fibula fixed with a plate, (d) fibula fixed with an Enders IM nail. In the other specimen of the pair, tibial fixation was performed with an interlocked unreamed IM nail, with the same successive stages of fibular fixation. RESULTS: Osteotomy of the fibula significantly increased tibial defect motion when external fixation was used, and plating the fibula in this case significantly decreased motion. Using an Enders rod to stabilize the fibula instead of a plate, with tibial external fixation, produced smaller decreases in tibial defect site motion. With IM rod fixation of the tibia, osteotomizing the fibula had no effect on defect site motion or on its subsequent stabilization using a plate or IM rod. CONCLUSION: Plating the fibula can decrease motion across a tibial defect, but only when less rigid (i.e., external) fixation is used.

Biomechanical Phenomena↗

PubMed1997

Assessment of the AO/ASIF fracture classification for the distal tibia.

OBJECTIVES: The purpose of this study was to assess the interobserver reliability and intraobserver reproducibility of the AO/ASIF and Rüedi and Allgöwer classifications for fractures of the distal tibia, and to determine the benefit of a computed tomography (CT) scan and experience on observer agreement for several fracture characteristics, including classification. METHODS: The radiographs of forty-three fractures of the distal tibia, fourteen of which had CT scans, were assessed by groups of experienced and less-experienced observers. Each case was classified according to the AO/ASIF and Rüedi and Allgöwer systems. Several other fracture characteristics also were assessed. The kappa coefficient of agreement was calculated and used to compare the interobserver reliability and intraobserver reproducibility of the classification systems and to determine the benefit of experience and CT scans. The intraclass correlation coefficient was used to assess noncategoric data. RESULTS: Interobserver and intraobserver agreements were good when classifying fractures into AO/ASIF types and significantly better than that for the Rüedi and Allgöwer system. However, agreement was poor when classifying the fractures into AO/ASIF groups. For most assessments, the experienced group tended to have higher levels of interobserver agreement, but not intraobserver agreement. Viewing the CT scans improved agreement on the percentage of articular surface involved, but it did not improve interobserver reliability or intraobserver reproducibility for either of the classification systems. CONCLUSION: The AO/ASIF classification for fractures of the distal tibia has good observer agreement at the type level, but poor agreement at the group level. Experience tends to improve interobserver agreement, but not intraobserver agreement. Viewing CT scans does not improve agreement on classification, but it tends to improve agreement on articular surface involvement.

Ankle Injuries↗

PubMedDate not supplied

Tension wire position for hybrid external fixation of the proximal tibia.

OBJECTIVE: To compare a new configuration of proximal wires for hybrid external fixation with the standard configuration. DESIGN: Biomechanical testing of five matched pairs of fresh cadaveric tibia. INTERVENTION: The authors compared the standard tension wire configuration of the three proximal wires with a more sagittal orientation of the oblique wires. A second study compared the new configuration with two wires and an offset half-pin. A two-centimeter segmental defect was created just distal to the tibial tubercle and the tibias fixed in a Montecelli Spinelli (Howmedica, NJ, U.S.A.) hybrid frame. The constructs were biomechanically tested using an Instron servohydraulic biaxial testing machine. RESULTS: There was a significant 67 percent decrease in displacement during anterior posterior bending and a significant 40 percent decrease in displacement in posterior bending with the new configuration compared with the standard configuration (p < 0.05). The differences in stability in all other testing modes were not significant. There was no significant difference between the new configuration and the two wire and off-set half-pin configuration. CONCLUSION: We recommend anterior placement of the oblique tension wires in the proximal tibia to more effectively resist bending in the sagittal plane, which is the most common deforming force on proximal metaphyseal fractures.

Biomechanical Phenomena↗

PubMed2003

Hybrid external fixation of the proximal tibia: strategies to improve frame stability.

OBJECTIVE: To determine the specific frame construction strategies that can increase the stability of hybrid (ring with tensioned wires proximally connected by bars to half-pins distally) external fixation of proximal tibia fractures. DESIGN Repeated measures biomechanical testing. SETTING: Laboratory. SPECIMENS: Composite fiberglass tibias. METHODS: Using the Heidelberg and Ilizarov systems, external fixators were tested on composite fiberglass tibias with a 1-cm proximal osteotomy (OTA fracture classification 41-A3.3) in seven frame configurations: unilateral frames with 5-mm diameter half-pins and 6-mm diameter half-pins; hybrid (as described above), with and without a 6-mm anterior proximal half-pin; a "box" hybrid (additional ring group distal to the fracture connected by symmetrically spaced bars to the proximal rings) with and without an anterior, proximal half-pin; and a full, four-ring configuration. Each configuration was loaded in four positions (central, medial, posterior, and posteromedial). MAIN OUTCOME MEASUREMENTS: Displacement at point of loading of proximal fragment. RESULTS: The "box" hybrid was stiffer than the standard hybrid for all loading positions. The addition of an anterior half-pin stiffened the standard hybrid and the "box" hybrid. CONCLUSIONS: The most dramatic improvements in the stability of hybrid frames used for proximal tibial fractures result from addition of an anterior, proximal half-pin.

Biomechanical Phenomena↗

PubMed2004

Anatomy of the superficial peroneal nerve in relation to fixation of tibia fractures with the less invasive stabilization system.

OBJECTIVE: To examine the danger to the superficial peroneal nerve during percutaneous screw placement in the distal holes of the 13-hole proximal tibia Less Invasive Stabilization System plate in a cadaver. DESIGN: Anatomic study. SETTING: Medical school anatomy laboratory. INTERVENTIONS: Fourteen adult cadaveric lower extremities were used. A 13-hole proximal tibia Less Invasive Stabilization System plate was placed as described by the manufacturer. Dissection of the superficial peroneal nerve was performed following localization of screw holes 7 through 13 using insertion sleeves, centering sleeves, and 2.0-mm Kirschner wires passed through the insertion guide. RESULTS: The average distance from the superficial peroneal nerve to the center of holes 11, 12, and 13 was 10.0 mm (range 0-21, standard deviation 5.6), 6.8 mm (range 0-16, standard deviation 4.3), and 2.7 mm (0-11, standard deviation 3.7), respectively. In 12 of 14 legs (86%), the superficial peroneal nerve was 5.0 mm or less from the center of hole 13. The nerve was touching the guide wire at hole 11 in 1 specimen (7%), at hole 12 in 2 specimens (14%), and at hole 13 in 6 specimens (43%). In 1 specimen (7%), the guide wire pierced the superficial peroneal nerve at hole 13. CONCLUSION: These findings suggest that the superficial peroneal nerve is at significant risk during percutaneous screw placement in holes 11 through 13 of the 13-hole proximal tibia Less Invasive Stabilization System plate. Use of a larger incision and careful dissection down to the plate in this region may minimize the risk of damage to the nerve.

Bone Screws↗

PubMed1995

Unreamed interlocking nail versus external fixator for open type III tibia fractures.

We undertook a prospective study comparing the unreamed interlocking nail to Hoffmann external skeletal fixation (ESF) in the treatment of 36 consecutive patients with open type IIIA and IIIB tibia fractures. The choice of interlocking nail or Hoffmann ESF was randomized, ultimately producing four different patient groups: group 1, type IIIA fractures treated by interlocking nail; group 2, type IIIA fractures treated by ESF; group 3, type IIIB fractures with interlocking nail; and group 4, type IIIB fractures with ESF. The average length of follow-up was 20.5 months. The infection rate was highest in group 3 (3 of 8). The malrotation, malunion, and nonunion rates were highest in group 4 and lowest in group 1. These results suggest the unreamed interlocking nail is a good choice for the treatment of open type IIIA tibia fractures, but not recommended for the treatment of open type IIIB tibia fractures because of the high infection rate.

Adolescent↗

PubMed1998

Muscle perfusion after intramedullary nailing of the canine tibia.

BACKGROUND: Intramedullary nailing with and without reaming leads to a reduction in cortical bone blood flow. The repair of the devascularized bone is mediated principally by the surrounding soft-tissue envelope. The objective of this study was to determine the effect on muscle blood flow of reamed and unreamed intramedullary nailing techniques. METHODS: Midshaft tibial osteotomies to create a 2.5-cm segment of devascularized tibial cortex were performed in 19 adult canines. The tibia was stabilized with a locked intramedullary nail without reaming in 9 animals and with intramedullary reaming in 10 animals. In the unreamed group, the tibia was stabilized with a loosely fitting (n = 4) or a tightly fitting (n = 5) locked nail. In the reamed group, limited reaming (n = 5) or standard reaming (n = 5) was performed. Muscle perfusion was measured in the anterior compartment musculature of the hind-limb using laser Doppler flowmetry. RESULTS: Overall muscle perfusion was greater in the reamed group than in the unreamed group at the conclusion of the nailing procedure (p = 0.0001) and at 5 weeks (p = 0.0008) and 11 weeks after nailing (p = 0.001). The degree of canal fit of the intramedullary nails and the extent of reaming before nail insertion did not further influence muscle circulation. CONCLUSION: The results of this study demonstrate that in the presence of an intact soft-tissue envelope, intramedullary reaming of the canine tibia has a major effect on increasing the circulation to the surrounding muscles. The increased extraosseous circulation may have implications for fracture healing.

Animals↗

PubMed2003

Closed fractures of the proximal tibia treated with a functional brace.

It generally is agreed that fractures of the proximal tibia, when treated with intramedullary nails, are more likely to present technical difficulties and to be associated with an increased rate of complications. This study reports on 108 closed fractures located in the proximal third of the tibia that were treated with functional braces. Nonunion occurred in 2.7% of the patients; the final displacement and shortening averaged 20% and 3.5 mm, respectively. Eighty-eight percent of the fractures healed with less than 6 degrees of angular deformity. It seems that functional braces for closed fractures of the tibia, located in its proximal third, are a viable therapeutic approach that offers satisfactory clinical and radiographic results in a high percentage of instances.

Adolescent↗

PubMed2005

The choice of intramedullary devices for the femur and the tibia in osteogenesis imperfecta.

The results of intramedullary rodding of 50 femoral and 25 tibial segments were analyzed retrospectively. The techniques of femoral rodding included single Rush rodding, dual Rush rodding and Sheffield telescoping rodding. Single Rush rods or Sheffield rods were used in the tibia. The frequencies of fractures following rodding and implant-related complications and the interval between initial rodding and rod revision were analyzed. The longevity of the rods was evaluated by survival analysis. In the femur, dual Rush rods and Sheffield rods were equally effective and both were superior to a single Rush rod with reference to each of the outcome variables. The technique of dual Rush rodding was more demanding than telescoping rodding. In the tibia, a single Rush rod was as effective as a Sheffield telescoping rod. Based on our results, a single Rush rod would be the preferred implant in the tibia while in the femur, dual Rush rods or a Sheffield telescoping rod may be preferred.

Adolescent↗

PubMedDate not supplied

Two techniques for supplementing interlocking nail repair of fractures of the humerus, femur, and tibia: results in 12 dogs and cats.

OBJECTIVE: To describe 2 devices for improving stabilization of inadequately stabilized interlocking nail (ILN) repairs of the humerus, tibia, and femur in dogs and cats. STUDY DESIGN: Prospective study. ANIMALS: Twelve client-owned dogs and cats. METHODS: Two devices to further stabilize ILN repair of inadequately stabilized diaphyseal fractures were developed. Device 1 was an axial extension for the ILN that was connected to a conventional type I external skeletal fixator (ESF) with a short connecting bar. Device 2 had hybrid ILN bolt/ESF pins that were used to lock the ILN and serve as the pins for a type I ESF. Devices were used at the initial surgery when the stability of ILN repair was considered inadequate based on palpable fracture segment movement, insufficient medullary canal filling of the ILN at the fracture site, or when the ILN was used in a buttress mode. Outcome was obtained by recheck examinations, radiography, and telephone interview. RESULTS: Device 1 was applicable to fractures of the humerus and femur, but was not used for fractures of the tibia because the ILN extension would have interfered with the stifle. No gross loosening of the ILN/ESF extension connection to the ILN occurred. Device 2 was easily placed and used in the humerus, femur, and tibia. Device 2 allowed removal of the ILN interlock to one or both main fracture segments non-invasively. Clinically, both devices added stability compared with ILN repair alone. Both devices facilitated controlled destabilization of the fracture repair as healing progressed. Complications of pin tract infection, and premature hybrid bolt/ESF pin loosening resulting in premature ESF removal each occurred in 1 patient. Four of 28 hybrid ILN/ESF pins were grossly loose at 4- or 6-week postoperative recheck examinations. Outcomes were excellent (9), good (1), fair (1), and poor (1). CONCLUSIONS: Inadequately stabilized ILN repair of fractures can be stabilized by use of either device, both of which also permit controlled destabilization of the repair during healing. Device 2 can be used when non-invasive removal of the ILN interlock is desired during healing. CLINICAL RELEVANCE: These 2 devices should be considered as alternative methods for stabilization of inadequately stabilized ILN repairs in dogs and cats, or when controlled destabilization of an ILN fracture repair is desired.

Animals↗

PubMed1997

Dynamics of neurons controlling movements of a locust hind leg. III. Extensor tibiae motor neurons.

Imposed movements of the apodeme of the femoral chordotonal organ (FeCO) of the locust hind leg elicit resistance reflexes in extensor and flexor tibiae motor neurons. The synaptic responses of the fast and slow extensor tibiae motor neurons (FETi and SETi, respectively) and the spike responses of SETi were analyzed with the use of the Wiener kernel white noise method to determine their response properties. The first-order Wiener kernels computed from soma recordings were essentially monophasic, or low passed, indicating that the motor neurons were primarily sensitive to the position of the tibia about the femorotibial joint. The responses of both extensor motor neurons had large nonlinear components. The second-order kernels of the synaptic responses of FETi and SETi had large on-diagonal peaks with two small off-diagonal valleys. That of SETi had an additional elongated valley on the diagonal, which was accompanied by two off-diagonal depolarizing peaks at a cutoff frequency of 58 Hz. These second-order components represent a half-wave rectification of the position-sensitive depolarizing response in FETi and SETi, and a delayed inhibitory input to SETi, indicating that both motor neurons were directionally sensitive. Model predictions of the responses of the motor neurons showed that the first-order (linear) characterization poorly predicted the actual responses of FETi and SETi to FeCO stimulation, whereas the addition of the second-order (nonlinear) term markedly improved the performance of the model. Simultaneous recordings from the soma and a neuropilar process of FETi showed that its synaptic responses to FeCO stimulation were phase delayed by about -30 degrees at 20 Hz, and reduced in amplitude by 30-40% when recorded in the soma. Similar configurations of the first and second-order kernels indicated that the primary process of FETi acted as a low-pass filter. Cross-correlation between a white noise stimulus and a unitized spike discharge of SETi again produced well-defined first- and second-order kernels that showed that the SETi spike response was also dependent on positional inputs. An elongated negative valley on the diagonal, characteristic of the second-order kernel of the synaptic response in SETi, was absent in the kernel from the spike component, suggesting that information is lost in the spike production process. The functional significance of these results is discussed in relation to the behavior of the locust.

Animals↗

PubMedDate not supplied

The natural history and treatment of delayed union stress fractures of the anterior cortex of the tibia.

This study presents eight patients with stress fracture of the anterolateral cortex of the midshaft of the tibia. All of the patients, ranging in age from 14 to 23 years, were competitive basketball players who experienced pain while running or jumping for an average of 4.4 months before the diagnosis was made. Eight patients were treated with rest and/or pulsing electromagnetic field therapy. Although one of the patients required bone grafting procedure, all eight of these patients showed complete healing and were able to return to full activity after an average of 8.7 months of treatment. They have remained asymptomatic for an average of 14.7 months. The overall time from initial symptoms to return to competition averaged 12.5 months in this group of athletes. The results presented in this paper suggest that rest and pulsing electromagnetic field therapy may result in healing in some patients with delayed union stress fractures of the anterolateral cortex of the midshaft of the tibia. Although this injury is associated with a prolonged healing period, seven of eight patients with adequate followup in our study were able to return to competition without complications following treatment. One patient was asymptomatic for 33 months before experiencing a reinjury. In conclusion, we feel that diagnosis of stress fracture should be primary consideration in basketball players presenting with a prolonged history of pain on the anterolateral aspect of the midthird of the tibia. Once the diagnosis is made we recommend initial treatment consist of rest and external electrical stimulation for a minimum time of 3 to 6 months prior to considering surgical intervention.

Adolescent↗

PubMed1987

The role of subtalar motion and ankle contact pressure changes from angular deformities of the tibia.

It is a well known entity that fractures of the tibia heal with some component of angular deformity. Ankle and subtalar joints may compensate for small degrees of angular deformities, but the exact amount of malunion that can be accepted without development of late sequalae has yet to be determined. Two recent studies from this institution have concluded that contact changes at the tibiotalar joint tend to be greater with distal third tibial fracture deformities compared to proximal and middle with the ankle in neutral, 5 degrees dorsiflexion, and 20 degrees of plantar flexion. Anterior and posterior bow deformities produced a greater change in contact area of the tibiotalar joint than with valgus or varus deformities. This phenomena may be possibly explained by the subtalar motion in the horizontal plane which averages 23 degrees. Thus, it was the primary purpose of this paper to determine the exact role, if any, in subtalar motion on tibiotalar contact in angular deformities of the tibia. To achieve this objective the subtalar joint was transfixed thereby eliminating its perceived compensatory movement. Six cadaveric lower extremities were disarticulated at the knee joint and stripped of soft tissue preserving capsular and ligamentous structures. A custom universal joint was used to create various angulatory deformities at proximal, middle, and distal third levels of the tibia.(ABSTRACT TRUNCATED AT 250 WORDS)

Ankle Joint↗

PubMed2006

Is there evidence-based guidance for timing of soft tissue coverage of grade III B tibia fractures?

The treatment of soft tissue damage associated with severe complicated tibia fractures is a clinical challenge. A recent study of grade III B/C open tibia fractures treated by delayed soft tissue coverage resulted in 20% of patients having osteomyelitis, with a mean follow-up of only 10 months. This study prompted us to review the literature on the association of timing of soft tissue closure in complicated grade III B tibia fractures and the incidence of infections and bone union. A Medline literature search was performed focusing on evidence-based medicine with regard to the timing of soft tissue closure and patients developing bony union and complications such as osteomyelitis. It was difficult to analyze publications with rigor. It appears that the time of surgery has little influence on free-flap failure but that early aggressive debridement followed by soft tissue cover within 3 to 5 days reduces osteomyelitis and delayed bone union. A need for better designed studies is also indicated.

Evidence-Based Medicine↗

PubMed2003

Proprioceptors monitoring forces in a locust hind leg during kicking form negative feedback loops with flexor tibiae motor neurons.

In preparation for jumping and kicking, a locust slowly generates large forces in the femoral muscles of its hind legs and stores them in elastic distortions of the tendons and femoral cuticle. At the femoro-tibial joints, the semi-lunar processes are bent, the cuticle of the dorsal distal femur is crumpled, and the femur is expanded in a mediolateral direction. We have analysed whether these distortions are monitored by sense organs and whether the information they provide is used to limit the forces generated and thus prevent structural damage to the joint. The two sensory neurons comprising the lump receptor lie in a groove in the ventral part of the distal femur. The sensory neurons spike if force is applied to the flexor tendon when the joint is fully flexed, but not when it is extended. They also spike as the tendon of the flexor muscle slides into the ventral femoral groove when the tibia is fully flexed during the co-contraction phase of kicking. Their spike frequency correlates with the extent of bending of a semi-lunar process that provides a quantifiable measure of the joint distortions. If the tibia is not fully flexed, however, then muscle contractions still cause distortions of the joint but these are not signalled by sensory spikes from the lump receptor. The lump receptor, therefore, does not respond primarily to the joint distortions but to the movements or force in the flexor tendon. Contractions of the flexor tibiae muscle caused by spikes in individual flexor motor neurons can evoke spikes in sensory neurons from the lump receptor when the joint is fully flexed. In turn, the sensory neurons cause a hyperpolarisation in particular flexor motor neurons in a polysynaptic negative feedback loop. The lump receptor could, therefore, regulate the output of the flexor motor neurons and, thus, limit the amount of force generated during co-contraction. It may also contribute to the inhibition of the flexors at the end of co-contraction that allows rapid kicking movements to occur.

Animals↗

PubMed1996

Contributions of structure and innervation pattern of the stick insect extensor tibiae muscle to the filter characteristics of the muscle-joint system

It is shown that the low-pass filter characteristics of the musclejoint system of the femurtibia joint of the stick insect Cuniculina impigra result from co-contraction of the extensor and flexor tibiae muscles. The most distal region of the extensor muscle, which contains a high percentage of slow muscle fibres, is involved in this co-contraction. This conclusion results from the following evidence. (1) Inertial and friction forces do not affect the characteristics of the low-pass filter of the musclejoint system. (2) There is some co-contraction of the extensor and flexor muscles during sinusoidal stimulation of the femoral chordotonal organ at high stimulus frequencies. Both muscles generate tonic forces that increase with increasing stimulus frequency and also increase with time from the beginning of stimulation until a plateau is reached. (3) For the extensor muscle, this tonic force is produced by its most distal portion only. (4) Electrical stimulation of the common inhibitory motoneurone (CI1) reduces the tonic force generated in this most distal portion of the extensor muscle. Therefore, CI1 stimulation reduces the amplitude of tibial movement in response to sinusoidal stimulation of the femoral chordotonal organ at stimulus frequencies below 0.5 Hz (over this frequency range, the tibial movement amplitude is a function of the force amplitude produced by the whole extensor muscle and there is no co-contraction), but at chordotonal organ stimulus frequencies of 1 Hz and above, CI1 stimulation increases the tibial movement amplitude (in this case, movement amplitude is limited by the degree of co-contraction of the extensor and flexor muscles). With repeated chordotonal organ stimulation at higher stimulus frequencies, the tibial movement amplitude steadily decreases. This must be a consequence of increasing levels of co-contraction of the extensor and flexor muscles, since at low stimulus frequencies (no co-contraction) there is no reduction in movement amplitude during repeated stimulations. It is concluded that co-contraction of the extensor and flexor tibiae muscles prevents instability in the reflex loop in spite of the high gain necessary for the generation of catalepsy. Therefore, the mechanism described can be considered to be an adaptation to the ecological niche occupied by this animal. The contribution of the distal part of the extensor muscle to this system can be switched off by the CI1 during active movements.

Journal Article↗