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PubMed1991

Crossed reflex actions from group II muscle afferents in the lumbar spinal cord of the anaesthetized cat.

1. The effects of electrical activation of muscle nerves at strengths sufficient to activate group II afferents in contralateral hindlimb motoneurones have been investigated by intracellular recording from motoneurones in alpha-chloralose-anaesthetized cats in which the spinal cord was intact or transected at a low thoracic level. 2. A large proportion of the motoneurones encountered could be influenced by activation of contralateral group II afferents. With the spinal cord intact, the predominant effect of contralateral group II afferents was inhibitory in almost all motoneurones, including extensors. After spinal transection the same stimuli elicited EPSPs in extensor motoneurones and IPSPs in flexors. 3. Both with the spinal cord intact and following spinal transection, group II afferents from particular nerves had powerful effects, whereas others were without effect in most neurones and had weak effects in others. Stimulation of gastrocnemius-soleus or of the hamstring nerves was largely ineffective, evoking weak effects in a small minority of motoneurones. Stimulation of the quadriceps, tibialis anterior-extensor digitorum longus and flexor digitorum longus nerves had powerful effects and in a high proportion of motoneurones. 4. The minimal latencies of the IPSPs evoked prior to spinalization were directly comparable to those of IPSPs evoked from ipsilateral group II afferents. The possibility that the mid-lumbar region, where many neurones which mediate ipsilateral group II reflexes are located, might mediate these crossed effects is discussed.

Animals↗

PubMed2004

The human spinal cord interprets velocity-dependent afferent input during stepping.

We studied the motor response to modifying the rate of application of sensory input to the human spinal cord during stepping. We measured the electromyographic (EMG), kinematic and kinetic patterns of the legs during manually assisted or unassisted stepping using body weight support on a treadmill (BWST) in eight individuals with spinal cord injury (SCI). At various treadmill speeds (0.27-1.52 m/s), we measured the EMG activity of the soleus (SOL), medial gastrocnemius (MG), tibialis anterior (TA), medial hamstrings (MH), vastus lateralis (VL), rectus femoris (RF) and iliopsoas (ILIO); the hip, knee and ankle joint angles; the amount of body weight support (BWS); and lower limb loading. The EMG amplitude and burst duration of the SOL, MG, TA, MH, VL, RF and ILIO were related to the step cycle duration during stepping using BWST. EMG mean amplitudes increased at faster treadmill speeds, and EMG burst durations shortened with decreased step cycle durations. Muscle stretch of an individual muscle could not account for the EMG amplitude modulation in response to stepping speed. The effects on the EMG amplitude and burst duration were similar in subjects with partial and no detectable supraspinal input. We propose that the human spinal cord can interpret complex step-related, velocity-dependent afferent information to contribute to the neural control of stepping.

Adolescent↗

PubMed1996

Local bone mineral density, muscle strength, and exercise in adolescent boys: a comparative study of two groups with different muscle strength and exercise levels.

The primary objective of the present study was to evaluate the impact of physical activity and muscle strength on bone mineral density (BMD) of the tuberositas tibiae in adolescent boys. Two groups with different exercise levels were compared. The high activity group consisted of 20 subjects (age 15.9 +/- 0.3) from a junior ice hockey team. The reference group consisted of 24 volunteers (age 15.9 +/- 0.3) not training for more than 3 hours per week. The groups were matched for age, weight, and pubertal stage. BMDs (g/cm2) of the tuberositas tibiae and proximal tibia were measured using dual energy X-ray absorptiometry. Quadriceps strength was significantly higher in the high activity group (P < 0.01). Univariate correlations were measured between tuberositas tibiae BMD and pubertal stage, weight, height, BMI, fat mass, lean body mass, quadriceps strength, and hamstrings strength in the high activity group and the reference group, respectively. Quadriceps strength was estimated to be the best significant predictor of BMD of the tuberositas tibiae in the reference group. A multivariate analysis confirmed this result. In the high activity group, there was no significant predictor of BMD of the tuberositas tibiae. There was no significant difference in BMD at this site when comparing the two groups. However, five of the boys in the high activity group had a former history of Mb Osgood-Schlatter with a significantly lower BMD of the tuberositas tibiae than the rest of the boys in that group. After exclusion of these boys, the remaining 15 boys were matched against 20 boys from the reference group using the previous criteria. These 15 boys then showed a significantly higher BMD of the tuberositas tibiae (P < 0.05) but not of the proximal tibia than the 20 boys in the reference group. In conclusion, this study demonstrates site-specific increments of tuberositas tibiae BMD in adolescent ice hockey players unless they are affected by the negative effects on BMD by Mb Osgood-Schlatter. These increments seem primarily to be associated with forceful muscle contractions related to high quadriceps strength and not greater weight-bearing loading. Muscle strength seems to positively affect BMD of the tuberositas tibiae in adolescents, but only up to a certain level, above which additional muscle strength has no effect.

Adolescent↗

PubMed2005

Primary stability of hamstring graft fixation with biodegradable suspension versus interference screws.

PURPOSE: During the early postoperative period, the stability of the fixation of a hamstring graft to the bone tunnel is the primary factor in limiting rehabilitation. The aim of this study was to evaluate if the initial fixation strength of a new suspension screw is comparable to that of the biodegradable interference screw fixation technique in the hamstring reconstruction of the anterior cruciate ligament (ACL). TYPE OF STUDY: Experimental laboratory study. METHODS: We evaluated the initial fixation strength of a biodegradable poly-L-lactide/tri-calcium phosphate (PLLA/TCP) screw that suspended the graft in the bone tunnel and compared it with the strength of an interference screw for fixation of hamstring grafts in ACL reconstruction using bovine knees. Single-cycle and cyclic loading tests were performed using a materials testing machine. RESULTS: The suspension screw provided a significantly higher yield load and ultimate failure load than the interference screw. There was no significant difference in the stiffness of both techniques. The typical failure mode for the suspension screw was fracture of the screw and for the interference screw it was slippage of the graft past the screw. In cyclic testing, both methods of fixation ran out to 1,000 cycles up to 250 N with a mean displacement of 2.6 mm (range, 1.8 to 3.3 mm) for the suspension screw and 4.1 mm (range, 2.3 to 6.0 mm) for the interference screw. Only the grafts fixed with the suspension screw survived a protocol with 1,000 cycles up to 400 N. CONCLUSIONS: Our biomechanical data suggest that hamstring graft fixation using a biodegradable PLLA/TCP suspension screw provides an alternative to interference screw fixation. CLINICAL RELEVANCE: Hamstring graft fixation using a suspension screw provides a reasonable alternative to interference screw fixation.

Absorbable Implants↗

PubMed1994

[The importance of neuromuscular coordination for athletic stress of the knee joint after anterior cruciate ligament injuries. A gait and locomotion analysis with EMG on treadmill].

Anterior cruciate ligament (ACL) injuries are considered of high prevalence in sports medicine and are of socio-economical relevance. Indications for operative treatment and the ability for physical activity after ACL injuries are discussed controversially. Although it is known that the ACL has neurosensory functions, no test system has been developed which takes this biological function into account. The first goal of this study was to determine the neurosensory function after ACL reconstruction, and the second goal was to develop predictive markers for functional results after surgery. 20 healthy athletes (10 male, 10 female) (control group) and twenty ACL deficient patients (10 male, 10 female) (study group) were included in a prospective, controlled study. Electromyograms (EMG) were performed under defined load conditions of the knee. Important results of our study are: 1. Previously described parameters can be reproduced with EMG techniques. Their validity was proved. Typical contraction patterns (m. quadriceps, hamstrings, m. gastrocnemius) for defined load conditions can be recorded. 2. Statistically significant differences can be shown between the control group and the study group as well as between the two legs (injured/noninjured) of the same patient in the study group. 3. The results suggest that the diminished innervation of the m. biceps femoris and m. gastrocnemius in down-ramp-running as an important parameter for ACL deficiency. 4. Distinct differences of innervation patterns of the muscles, which stabilise the knee in downramp walking suggest that despite a subjective stability, altered load conditions may result. Innervation patterns seem to vary from individual to individual. 5. Concluding from our findings, we suggest that clinical methods should be developed to allow a patient-specific assessment of physical activity.

Adult↗

PubMed1988

[A new technic for arthroscopic reinsertion and augmentation of the recently torn anterior cruciate ligament].

The arthroscopic examination of every recent haemarthrosis of the knee, even in cases without clinically obvious instability has increased the number of primary diagnosed ruptures of the LCA in the last years. The most frequent lesion of the LCA was the proximal rupture. The usual methods for the operative treatment of the ruptured LCA require the opening of the knee joint and cause the weakening of hamstrings, with all disadvantages connected with these procedures. Basing on the experiences in arthroscopic surgery of meniscal lesions and the good results of alloplastic augmentation an new method of arthroscopic refixation and augmentation of the torn LCA has been developed. The use of an arthroscopic meniscal stitcher enables anatomically exact reconstruction of the torn ligament through a femoral tunnel. Augmentation by an LAD-band (Kennedy) or Trevira band (Hoechst) allows postoperative functional treatment, avoiding atrophic degeneration of muscles and loss of mobility by immobilisation. Postoperative pain is reduced to a minimum compared to conventional technics. The period of rehabilitation is considerably shortened.

Arthroscopes↗

PubMed2006

Effect of tibial tubercle elevation on biomechanics of the entire knee joint under muscle loads.

BACKGROUND: Anterior elevation of the tibial tubercle, known as Maquet procedure, is performed to reduce excessive patellofemoral contact stresses in knee joints with patellofemoral osteoarthritis and anterior pain. Previous investigations, however, have entirely focused on the likely effect of tibial tubercle elevation procedure on biomechanics of contact at the patellofemoral joint with no attention what-so-ever to associated alterations in biomechanics of the tibiofemoral joint. METHODS: Using a validated 3D nonlinear finite element model of the entire knee joint, the effect of 1.25 cm and 2.5 cm tubercle elevations on the entire knee joint biomechanics was investigated under constant quadriceps load of 411 N alone or combined with hamstrings co-activation of 205.5 N under joint angles of 0-90 degrees. FINDINGS: Results confirm the effectiveness of this procedure in reducing patellofemoral contact forces, especially at smaller flexion angles. Maximum contact stress substantially decreased at full extension but increased at 90 degrees. Substantial effects of tuberosity elevation on tibial kinematics, cruciate ligament forces, tibiofemoral contact forces and extensor lever arm were found. The posterior cruciate ligament and tibiofemoral contact forces at larger flexion angles considerably increased whereas the anterior cruciate ligament and tibiofemoral contact forces at near full extension angles decreased. Overall, the extent of changes depended on the magnitude of anterior elevation, joint flexion angle and loading considered. INTERPRETATION: Biomechanics of the tibiofemoral joint were significantly influenced by tibial tubercle elevation. Current results advocate the need for an integral view of the entire knee joint in management of various joint disorders rather than a view in which each component is considered and treated in isolation with no due attention to perturbations caused and associated consequences.

Biomechanical Phenomena↗

PubMed1986

Relative effectiveness of C primary afferent fibers of different origins in evoking a prolonged facilitation of the flexor reflex in the rat.

Changes in the excitability of the hamstring flexor withdrawal reflex produced by conditioning stimuli applied to C-afferent fibers of different origins have been examined in the decerebrate spinal rat. In the absence of conditioning stimuli, the flexor reflex elicited by a standard suprathreshold mechanical stimulus to the toes is stable when tested repeatedly for hours. Three categories of conditioning stimuli have been used in an attempt to modify the excitability of the flexor reflex; electrical stimulation of a cutaneous (sural) nerve or a muscle (gastrocnemius-soleus) nerve at C-fiber strength; the application of mustard oil, a chemical irritant that activates chemosensitive C-afferents, to the skin or injected intramuscularly and intraarticularly; and the indirect activation of high-threshold muscle afferents by fused tetanic contractions of the tibial muscles. Conditioning stimuli of an intensity sufficient to activate C-afferent fibers result in a heterosynaptic facilitation of the flexor motoneuronal response to the standard test input, which lasts from 3 min to more than 3 hr, depending on the stimulus and the C-afferents activated. Pretreatment of the sciatic nerve with the C-fiber neurotoxin capsaicin abolishes all the postconditioning facilitations, which is an indication that it is likely that it is C-afferents that are primarily responsible for the facilitatory effects of the conditioning stimuli, although some A delta afferents may contribute. Capsaicin pretreatment does not modify the reflex response to the test stimulus. The most prolonged increase in the excitability of the flexor reflex resulted from intraarticular injections of 5 microliter mustard oil. Using the subsequent injection of lignocaine intraarticulary, it was found that the prolonged facilitation of the reflex is triggered by the afferent input generated by the conditioning stimulus and does not require an ongoing input for its maintenance. These results indicate that there is a spectrum of central changes in the stimulus response relations of the spinal cord resulting from the activation of C-fibers of different origins. The prolonged duration of some of these changes means that the peripheral activation of C-afferents will modify the functional response of the spinal cord to other inputs applied long after the conditioning input, and this may be responsible for some of the sensory and motor alterations found after peripheral tissue injury.

Afferent Pathways↗

PubMed2003

Hamstring tendon harvesting. Reviewing anatomic relationships and avoiding pitfalls.

The gracilis and semitendinosus tendons remain popular grafts for many reconstructive procedures, including anterior cruciate ligament reconstruction. Surgeons who use other grafts for ACL reconstruction should have the hamstring tendon techniques in their arsenal in the event other grafts are unavailable or undesirable. Detailed knowledge of the anatomy of the medial side of the knee is paramount to avoid potential pitfalls and ensure a successful tendon harvest.

Anterior Cruciate Ligament↗

PubMed2003

Ankle stabilization with hamstring autograft: a new technique using interference screws.

Many techniques have been advocated for the late surgical reconstruction of the lateral ankle ligament complex, including the use of hamstring tendon autografts. A new technique is described which attempts to restore anatomically the anterior talofibular ligament using hamstring autograft. The distal end of the graft is secured in a blind-ended tunnel in the talus without the need for transosseous tensioning. This is achieved with the use of the Bio-Tenodesis Screw System.

Absorbable Implants↗

PubMed1990

[Analysis of the shear force exerted on the tibia during standing on bilateral legs with knee flexion].

Biomechanical analysis of the two-dimensional models composed of roentgenographic pictures and electromyographic analysis about the shear force (Fs) exerted on tibia during standing on bilateral legs was conducted in 21 young adult males. The simultaneous contraction of the quadriceps and hamstrings was observed in all electromyograms (EMGs). Amplitude observed on EMGs of the hamstrings increased as the trunk flexion angle increased. The calculated average values of Fs were negative at every knee flexion angle; Negative value means posteriorly directed force. As the trunk flexion angle increased, posterior drawer force increased at knee flexion angles of 30 degrees and 60 degrees. The simultaneous contraction of the quadriceps and the hamstrings was considered to represent the main factor that influenced these results. The standing on bilateral legs with knee and trunk flexion was considered to be applicable in the early stages after anterior cruciate ligament reconstruction.

Adult↗

PubMed2002

Development of an indoor rowing machine with manual FES controller for total body exercise in paraplegia.

Concept 2 indoor rowing machine (Concept 2 Inc., USA) was modified for functional electrical stimulation (FES) rowing exercise in paraplegia. A new seating system provides trunk stability and constrains the leg motion to the sagittal plane. A 4-channel electrical stimulator activates the quadriceps and hamstrings in Drive and Recovery phases of the rowing cycle, respectively. Two force-sensing resistors (FSR) on the handle measure the thumb press as the command signal to the electrical stimulator. Optical encoders measure the positions of the seat and handle during rowing. To synchronize the voluntarily controlled upper body movement with the FES controlled leg movement, a novel manual control system was developed. It uses the voluntary thumb presses to control the timing of the stimulation to the paralyzed leg muscles. The manual control system was intuitive and easy to learn and resulted in well-coordinated rowing. Evaluation of the modified rower by paraplegic volunteers showed that it is effective, safe, and affordable exercise alternative for paraplegics.

Adult↗

PubMed1984

[Functional treatment method following patellar dislocations].

Acute, as well as recurrent, dislocations of the patella often are treated conservatively. However, an increasing number of authors are recommending early surgical treatment for primary, traumatic, as well as congenital, dislocations of the patella. The purpose of this report was to determine, which cases should be treated by operation or conservatively by a specific patellar protection program. This program includes four phases or rehabilitation: Phase I: Antiinflammatory measures (ice, compression and elevation, non steroidal medications), specific exercises (isometrics, straight leg raises with no weight, side leg raises with no weight), active range of motion, passive range of motion with no weights, flexibility of back, hip, hamstrings, quadriceps, ankle, groin and general exercises (swimming, general conditioning and opposite extremity program). Phase II: Continue isometric program, progressive-resistive program with ankle weights, continue flexibility program, lateral step-ups if terminal extension painful, eccentric isometrics if straight leg raises painful, continue swimming, may begin low resistance cycling if motion adequate. Phase III: Isotonic progressive-resistive exercise program, exercise to fatigue using weight or similar equipment (quadriceps, hamstrings, circuit exercises). Phase IV: Slow return to sports to develop specific neuromuscular skills at that sport, continued strength and endurance training. Continue weight machines and a full range of motion, running program, continued flexibility before and after athletic play.

Braces↗

PubMed2006

Decrease in anterior knee laxity by electrical stimulation of normal and reconstructed anterior cruciate ligaments.

We have investigated the changes in anterior laxity of the knee in response to direct electrical stimulation of eight normal and 45 reconstructed anterior cruciate ligaments (ACLs). In the latter, the mean time from reconstruction was 26.7 months (24 to 32). The ACL was stimulated electrically using a bipolar electrode probe during arthroscopy. Anterior laxity was examined with the knee flexed at 20 degrees under a force of 134 N applied anteriorly to the tibia using the KT-2000 knee arthrometer before, during and after electrical stimulation. Anterior tibial translation in eight normal and 17 ACL-reconstructed knees was significantly decreased during stimulation, compared with that before stimulation. In 28 knees with reconstruction of the ACL, in 22 of which the grafts were found to have detectable somatosensory evoked potentials during stimulation, anterior tibial translation was not decreased. These findings suggest that the ACL-hamstring reflex arc in normal knees may contribute to the functional stability and that this may not be fully restored after some reconstructions of the ACL.

Adolescent↗

PubMed1998

Interference screw fixation of hamstring vs patellar tendon grafts for anterior cruciate ligament reconstruction.

The present study was designed to investigate the fixation strength of a quadruple semitendinosus-gracilis graft compared with a middle-third bone-patellar tendon-bone graft using a new interference screw developed to fix hamstrings grafts for ACL reconstructions (RCL Smith & Nephew Donjoy). Five pairs of human cadaveric knees from donors with a mean age of 43 (range 33-52) years were used. One knee of each pair was randomly allocated to be reconstructed on the femoral side with a semitendinosus-gracilis graft from the same donor using RCL screw fixation. As the control, the contralateral knee was correspondingly reconstructed with a bone-patellar tendon-bone graft using the same interference screw. The grafts were pulled out at a velocity of 30 mm/s by an axially applied load using a MTS machine. The mean (SD) failure load for the bone-patellar tendon-bone graft fixations was 505 (25) N, 110% stronger than the mean failure load for the semitendinosus-gracilis graft fixations, which was 240 (47) N (P = 0.003). The stiffness for the patellar tendon-bone graft fixations was 46 (11) N/mm, 120% stiffer than the semitendinosus-gracilis graft fixations, which was 22 (11) N/mm (P = 0.01). This study shows that the interference screw principle used for ACL reconstructions with hamstrings tendons is inferior to that for bone-patellar tendon-bone reconstructions although the screw was developed especially for soft-tissue fixation in bone tunnels.

Adult↗

PubMed1999

Bone tunnel enlargement after anterior cruciate ligament reconstruction with the hamstring autograft and endobutton fixation technique. A clinical, radiographic and magnetic resonance imaging study with 2 years follow-up.

The aim of this study was to describe the contrast-enhanced magnetic resonance imaging (MRI) appearance of bone tunnel enlargement detected on radiography after anterior cruciate ligament (ACL) reconstruction with semitendinosus and gracilis tendon endobutton (STG-endobutton) fixation technique. Fourteen patients with a STG-endobutton ACL reconstruction were examined 3 months (n = 1), 1 year (n = 1) and 2 years (n = 12) postoperatively. An age- and sex-matched group with a bone-patellar tendon-bone (BTB) autograft ACL reconstruction with similar follow-up was taken as control. Data on clinical examination, laxity and isokinetic muscle torque measurements, anteroposterior and lateral view radiography were obtained, and knee scores (Lysholm and Tegner) were collected. Contrast-enhanced MRI was performed in the STG-endobutton group with a 1.5-T imager. There were no statistical differences between the groups with respect to clinical findings, stability tests, or knee scores. In the STG-endobutton group the average femoral and tibial bone tunnel diameter detected on anteroposterior view radiography had increased at 2-year follow-up by 33% and 23%, respectively. On MRI the ligamentous graft itself was not enhanced by the contrast medium whereas periligamentous tissue within and around the STG graft bundles showed mild contrast enhancement. In conclusion, the MRI results suggest that enhancing periligamentous tissue accumulated in and around the STG graft associated with the tunnel expansion. In spite of the significant bone tunnel enlargement observed on the follow-up radiography the STG-endobutton knees were stable and the patients satisfied.

Adult↗

PubMed1997

Influences of strength, stretching and circulatory exercises on flexibility parameters of the human hamstrings.

The purpose of this study was to compare the effect of resistance training, static and ballistic stretching and stationary cycling on the range of motion (ROM) and end ROM torque of hip joint flexion, resting tension of the hamstrings and stretch-induced electromyographic (EMG) activity of the hamstrings. Four separate experimental groups performed either 15 min resistance training of the hamstrings (n = 12), 15 min static stretching of the hamstrings (n = 14), 15 min ballistic stretching of the hamstrings (n = 16), or 15 min stationary cycling (n = 12). A control group (n = 15) remained resting for 15 min. ROM was increased after static and ballistic stretching and after stationary cycling. ROM remained unchanged in the resistance training group as well as in the control group. End ROM torque showed a significant increase after static and ballistic stretching. Static and ballistic stretching and stationary cycling decreased EMG activity significantly. Resting tension was decreased only after stationary cycling (p < 0.1). The constancy of the muscle resting tension suggests that merely the subjects' tolerance to higher stretching strain brings about the enlargement of ROM after short-term stretching exercises. The enlargement of ROM after stationary cycling could have been caused by the poor decrease of resting tension.

Adult↗

PubMed1997

The effect of quadriceps femoris, hamstring, and placebo eccentric fatigue on knee and ankle dynamics during crossover cutting.

This study attempted to determine the effect of eccentric quadriceps femoris, hamstring, and placebo fatigue on stance limb dynamics during the plant-and-cut phase of a crossover cut. Twenty female college students (task trained) were tested. Hamstring fatigue resulted in decreased peak impact knee flexion moments (p < or = .01), increased internal tibial rotation at peak knee flexion (p < or = .05), and decreased peak ankle dorisflexion (p < or = .05). Quadriceps fatigue resulted in increased peak ankle dorsiflexion moments (p < .01), decreased peak posterior braking forces (p < or .01), decreased peak knee extension moments (p < or = .01), delayed peak knee flexion (p < or = .01), delayed peak propulsive forces (p < .01), and delayed subtalar peak inversion moments (p < or = .05). Fatigue of either muscle group produced earlier peak ankle plantar flexion moments (p < = .05) and decreased peak propulsive knee flexion moments (p < or = .05). Variables requiring further study (p < or = .1) provide discussion data. Soleus, gastrocnemius, tibialis anterior, and deep posterior compartment calf muscles serve as dynamic impact force attenuators, compensating for fatigued proximal muscles.

Adult↗