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PubMed1989

Electromyographic study of the anterior cruciate ligament-hamstrings synergy during isometric knee extension.

The purpose of this investigation was to determine the role the hamstrings group may play in augmenting passive articular mechanisms during activity in which anterior drawer force may detrimentally affect the anterior cruciate ligament (ACL). Nine male subjects performed non-weight-bearing isometric knee extension at 10% increments of maximum voluntary contraction (MVC). Electromyographic (EMG) signals were detected and recorded from the vastus lateralis, vastus medialis oblique, vastus medialis longus, and the long head of the biceps femoris. The EMG signals were rectified and integrated over 1000 ms and normalized to subject-specific values. The data were subjected to a repeated-measures analysis of variance. The results demonstrated that expected significant increases in quadriceps excitation accompanied increases in knee extensor torque. Hamstrings excitation was not found to change significantly (total change = 3.4%). It was concluded that functionally adequate knees do not require posterior drawer force in excess of that provided passively by articular structures.

Adult↗

PubMed1971

Hamstrings stretch reflex in human spasticity.

In 16 patients with spastic paralysis the hamstrings stretch reflex was found to increase as the velocity of stretch increased, and generally to subside after movement ceased. These effects are attributable to the dynamic property of the primary spindle ending. The stretch reflex commonly appeared in only the last third of the stretching movement and was maximal as the knee became fully extended. This is consistent with the static properties of the primary and secondary spindle endings, and accounts for the absence of the clasp-knife phenomenon in the spastic hamstrings. The difference in the nature of the stretch reflex in spastic flexor and extensor muscles is best explained by the differential reflex effects of group II afferent fibres which facilitate flexor motoneurones and inhibit extensor motoneurones.

Electromyography↗

PubMed1989

The role of preseason conditioning in preventing athletic injuries.

The role of preseason conditioning in injury prevention was discussed in this article. Evidence was presented that conditioning involving flexibility, cardiovascular work, and resistance training contributed to the structural integrity of the joint as well as the muscle-tendon unit. The effect these physiologic adaptions had on the prevention of injuries was investigated. Epidemiological studies were reviewed to ascertain this effect and were found to carry methodological problems that made conclusions questionable. Further epidemiological research was recommended with suggested design modifications to produce valid conclusions. Even though there is a lack of empirical evidence relating preseason conditioning to injury prevention, many studies were reviewed that showed a clear connection between many specific training techniques that are used to prevent injury. The role of flexibility and resistance training in the prevention of hamstring strains was particularly emphasized. The application of preseason conditioning toward preventing injury was then discussed. It was recommended that a preseason evaluation precede this conditioning so that the sports medicine evaluator could assess the athlete's level of conditioning. Based on the strengths and weaknesses of this evaluation a preseason conditioning program could be devised. The elements of such a program were then presented with a summary of preseason training techniques. Specificity of testing and training was recommended. The closer that athletes come to testing and training for the muscle function needed in their sport, the greater the chance of increased performance. In addition, a more specific and adequate muscle function was thought to help in the prevention of injuries.

Athletic Injuries↗

PubMed1976

The treatment of intoed gait in spina bifida patients by lateral transfer of the medial hamstrings.

The operation of lateral transfer of the medial hamstring muscles is described. Its applicating in the management of intoed gait in spina bifida is discussed, and the results of eight such operations, performed on four children, are recorded. The operation was effective in correcting the intoed gait in all; however, there was no activity in the transferred muscles in one child.

Child, Preschool↗

PubMed1992

The management of decubitus ulcers by musculocutaneous flaps: a five-year experience.

Large decubitus ulcers can be treated by using many methods, including musculocutaneous flaps. Musculocutaneous flaps provide reliable, well-vascularized cover and often can be revised in patients with secondary recurrence. We have treated 30 patients with large decubitus ulcers during a 5-year period by using musculocutaneous advancement flaps of the gluteus maximus, the hamstring muscle, and the tensor fasciae latae. There were two complications treated by debridement with flap advancement in 1 patient and the use of another flap in the second patient. Four patients developed a recurrent ulcer, which was treated by reelevation and advancement of the original flap in all patients. The general management and overall results are presented.

Buttocks↗

PubMedDate not supplied

Distal hamstring elongation in the management of spastic cerebral palsy.

Forty-nine children with spastic cerebral palsy treated by distal hamstring elongation and followed for an average of 4.4 years were reviewed. The aim of the operation was to release hamstring tightness to improve the patients' level of function and efficiency and the cosmetic appearance of their gait. Forty patients had significant improvement in gait pattern, and 18 had improved motor function. Complications included transient stiff-legged gait and exaggerated lumbar lordosis. One patient with spastic quadriceps had 15 degrees of persistent genu recurvatum.

Adolescent↗

PubMed1987

[Current status of the therapy of anterior cruciate ligament injuries].

This review presents the current concepts in the treatment of anterior cruciate ligament (ACL) injuries. Conservative treatment emphasising strengthening of the muscles to stabilise an unstable knee is discussed. The agonistic and antagonistic functions of the hamstrings and the quadriceps muscle in relation to the ACL are described. The possible mechanisms of muscular stabilisation of the knee are discussed on a neurophysiological basis. The existence of joint specific receptors is pointed out and their reflex and perceptive functions are demonstrated. Taking this into account one can deduce a two-step mechanism of joint protection: 1) via the mechanical strength of the joint capsule and ligaments and 2) via reflex muscle contractions. It follows therefrom that in an unstable knee with a lax capsule and disturbed reflex mechanisms, strengthening of muscles alone is insufficient and cannot protect the joint from progressive deterioration. Therefore, surgical treatment is necessary for an ACL deficient knee. Our indications for ACL reconstruction are described. In addition, the existing methods of surgical replacement of the ACL are critically elucidated. In our opinion, an extraarticular repair tendon transfer as the only surgical procedure to regain stability is of only historical interest. However, extraarticular repair of the medial or lateral capsule is often a necessary additional step to restore stability of the knee. The replacement of the ACL is the crucial step. Using autogenous grafts one must consider the doubtful outcome of biological response leading to necrosis and revascularization in the transplant.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗

PubMed1979

Lateral hamstring transfer and gait improvement in the cerebral palsy patient.

A retrospective analysis of twenty-three spastic patients who underwent forty-three transfers of the semitendinosus muscle to the lateral intramuscular septum and of the semimembranosus muscle to the biceps is presented. Decreased knee-flexion deformity as well as improved walking function were achieved in 91 per cent. An unsatisfactory result was associated with complications of the procedure. Only one knee of the forty-three that were operated on showed late genu recurvatum. This procedure appears to be both effective and relatively free of late comlications.

Adolescent↗

PubMed1992

Effect of knee joint laxity on long-loop postural reflexes: evidence for a human capsular-hamstring reflex.

The onset latency and discharge amplitude of preprogrammed postural responses were evaluated in order to determine if the structure of synergistic activation could be altered by ligamentous laxity at the knee joint. Twelve subjects with unilateral and one subject with bilateral anterior cruciate ligament (ACL) insufficiency were tested while standing on a moveable platform. External balance perturbations (6 cm anterior or posterior horizontal displacements of the platform) were presented at velocities ranging from 15 to 35 cm/s. Perturbations were presented under the following experimental conditions: unilateral and bilateral stance, knees fully straight or flexed, and with ankle motion restricted or free. These stance, knee position, and ankle motion conditions were introduced to alter the stress transmitted to the knee joint during movement of the support surface. The automatic postural response was recorded from the tibialis anterior (T), quadriceps (Q), and medial hamstrings muscles (H) bilaterally. The normal response to an externally induced backward sway involved the automatic activation of T and Q at latencies of 80 ms and 90 ms respectively. Activation of the hamstrings in the non-injured extremity was not coupled with the postural response. Hamstrings are not typically involved in the correction posterior sway because H activation would tend to pull the center of mass further backwards. However, when the response in the ACL-deficient extremity was compared to the non-injured limb: (1) the automatic postural response in the ACL-deficient extremity was restructured to include hamstrings activation (100 ms latency), (2) H activation time was faster and less variable in the ACL-deficient limb, and (3) the ratio of H/Q discharge amplitude integrated over 100 ms and 200 ms from the onset of EMG activation showed a dominance of hamstring activity during unilateral stance on the lax limb. In addition, H/Q ratios integrated over 200 ms showed dominant hamstring activity in the ACL-deficient limb during bilateral stance. (4) Cross-limb comparisons showed greater normalized IEMG amplitudes for T, H, and Q during unilateral stance on the lax limb. These results suggest that a capsular-hamstring reflex is integrated into the existing structure of a preprogrammed postural synergy in order to compensate for ligamentous laxity. Furthermore, the generalized increase of response gain observed during perturbations of unilateral stance on the lax limb indicates that joint afference can modulate central programming to control localized joint hypermobility. A concept of postural control is discussed with respect to the capsular reflex, joint loading and displacement of the center of gravity.

Adolescent↗

PubMed1991

Changes in hip position modulate soleus H-reflex excitability in man.

The effects of hip flexion and extension on the ipsilateral soleus Hoffmann (H) reflex recruitment curve were studied in 11 healthy subjects. Hip flexion (50 degrees), but not hip extension (15-20 degrees), produced changes in the H-reflex. A maintained facilitation, peaking at intensities of stimulation producing a maximal H-reflex (Hmax), was observed in 6/18 sessions. Inhibition, peaking at intensities submaximal for Hmax, was seen in 7/18 sessions. In some of the latter experiments, there was also a facilitation at high intensities of stimulation (greater than Hmax). The remaining experiments were classified as showing no effect: 3 were unmodulated but 2 showed a facilitation at high intensities of stimulation (greater than Hmax). Since the knee was extended in the test position, a second series of experiments (n = 7) were carried out to determine the possible influence of stretch of the biarticular hamstrings muscle group on the soleus H-reflex by comparing the effects of hip flexion with the knee extended with those obtained when the knee was flexed, thereby relaxing the hamstrings. The results provided no evidence that the variability could be explained by differences in the relative degree of stretch on the hamstrings muscle group. There were, however, systematic variations in the shape of the corresponding control H-reflex recruitment curves between subjects: the mean slope of the rising limb of the recruitment curve was highest in those experiments showing an inhibition, intermediate in the ineffective experiments and lowest in those showing a maintained facilitation. These observations indicate that the reflex output studied was different in the three groups, possibly reflecting differences in the relative proportions of slow- and fast-twitch motor units contributing to the reflex response.

Achilles Tendon↗

PubMedDate not supplied

Hamstring tenotomies in cerebral palsy: long-term retrospective analysis.

One hundred seventeen cerebral palsy patients were followed for a mean of 3.4 years after undergoing hamstring tenotomy by proximal semimembranosus release in conjunction with distal semitendinosus and biceps femoris release. Range of motion was significantly improved 1 year after the operation and remained so for 4 years. Thirty percent of nonambulatory patients improved at least one level in activity, some at up to 12 years of age. Minor recurvatum was observed at 1 year but became nearly nonexistent after 3-5 years.

Activities of Daily Living↗

PubMedDate not supplied

Combined adductor transfer, iliopsoas release, and proximal hamstring release in cerebral palsy.

Twenty-two patients with cerebral palsy (CP) and progressive lateral migration of the hip who underwent a combined adductor transfer, iliopsoas release, and proximal hamstring release were reviewed retrospectively. The average age at surgery was 4 years 9 months, and clinical and roentgenographic follow-up averaged 21.9 and 19.2 months, respectively. Ninety-five percent of the patients demonstrated an improved range of motion. Roentgenographic analysis showed a statistically significant decrease in the migration percentage and the acetabular angle and an increase in the CE angle. We concluded that this procedure adequately addressed this complex problem, thereby limiting the number of hospitalizations and surgical procedures for this patient group. Longer follow-up will be necessary to determine if these results are maintained with time.

Adolescent↗

PubMed1989

Importance of the iliopsoas muscle in soft-tissue surgery of hip deformities in cerebral palsy children.

Twenty cerebral palsy patients who had undergone soft-tissue surgery at the hip (adductor tenotomy, medial lengthening of the hamstrings) were compared with a matched group of another 20 patients with a similar age range and findings and with additionally performed iliopsoas release, 2 or more years after surgery. Extension deficits of the hip did not improve with the addition of iliopsoas release. Internal rotation deformities showed equal improvement in both groups; the influence of the iliopsoas procedure was not significant. Adduction deformities, as documented on roentgenograms of the hip, showed significant improvement, however. Postural anomalies were not essentially influenced by iliopsoas release. Hip dislocations and subluxations, as assessed by the CE angles, were positively influenced by additional iliopsoas release; however, more effective improvement was obtained with ischiocrural elongation.

Adolescent↗

PubMed1985

Mechanics of the knee. A study of joint and muscle load with clinical applications.

The load moment of force about the knee joint during machine milking and when lifting a 12.8 kg box was quantified using a computerized static sagittal plane body model. Surface electromyography of quadriceps and hamstrings muscles was normalized and expressed as a percentage of an isometric maximum voluntary test contraction. Working with straight knees and the trunk flexed forwards induced extending knee load moments of maximum 55 Nm. Lifting the box with flexed knees gave flexing moments of 50 Nm at the beginning of the lift, irrespective of whether the burden was between or in front of the feet. During machine milking, a level difference between operator and cow of 0.70 m - 1.0 m significantly lowered the knee extending moments. To quantify the force magnitudes acting in the tibio-femoral and patello-femoral joints, a local biomechanical model of the knee was developed using a combination of cadaver knee dissections and lateral knee radiographs of healthy subjects. The moment arm of the knee extensor was significantly shorter for women than for men, which resulted in higher knee joint forces in women if the same moment was produced. A diagram for quantifying patellar forces was worked out. The force magnitudes given by the knee joint biomechanical model correlated well with experimentally forces measured by others. During the parallel squat in powerlifting, the maximum flexing knee load moment was estimated to 335-550 Nm when carrying a 382.5 kg burden and the in vivo force of a complete quadriceps tendon-muscle rupture to between 10,900 and 18,300 N. During isokinetic knee extension, the tibio-femoral compressive force reached peak magnitudes of 9 times body weight and the anteroposterior shear force was close to 1 body weight at knee angles straighter than 60 degrees, indicating that high forces stress the anterior cruciate ligament. A proximal resistance pad position decreased the shear force considerably, and this position is recommended in early rehabilitation after anterior cruciate ligament repairs or reconstructions. The methods presented quantify muscle activity, sagittal knee joint moments and forces, enabling assessments to be made of different work postures, training exercises and joint derangements.

Adult↗

PubMed1992

Distal lengthening of the hamstrings in patients who have cerebral palsy. Long-term retrospective analysis.

One hundred and twenty-six patients who had cerebral palsy and who had been managed with distal lengthening of the hamstrings were followed for three to fourteen years so that the long-term results of the procedure could be determined. Twenty-four of sixty-two patients who could not walk before the procedure were able to walk about the house postoperatively. Mild recurvatum developed in only ten patients, and twenty-two patients had a reoperation because of recurrence. Although straight-leg raising and the popliteal angle had improved markedly at one year in all but two patients, both parameters regressed gradually over time. Of several selected variables, only limitation of straight-leg raising preoperatively was of statistical significance (p < 0.001) for the prediction of recurrence. Age, preoperative walking ability, concomitant operations, and postoperative immobilization had no significant effect on the rates of recurrence or recurvatum.

Adolescent↗

PubMedDate not supplied

[Results of surgical therapy of knee flexion contractures in patients with myelomeningocele].

This study reports the results of 98 operations for correcting knee-flexion-contractures, which were performed between 1972 and 1989 in 60 patients with myelomeningocele. 13 knees had hamstring lengthening and 85 knees had radical flexor release. In 4 patients, who had flexion-contractures of more than 50 degrees, the soft tissue release was combined with supracondylar extension osteotomy. 58 patients had additional hip-flexion-contractures and 39 patients had feet deformities. The average age at time of surgery was 8 years, 3 months. The average follow-up-period was 65 months with a minimum of 1 year and a maximum of 13 years. In 92 knees a permanent extension ability could be achieved. In 6 knees a recurrence of flexion-contracture occurred making a second surgery necessary. The main problem in the postoperative period were 13 skin necroses, which were seen mainly after an s-shaped incision. As a conclusion a perpendicular midline incision is recommended. After surgery 11 patients could be provided for the first time with an orthoses. In the remaining the upright body position or the erection of the orthoses could be improved.

Adolescent↗

PubMedDate not supplied

Serial magnetic resonance imaging of hamstring anterior cruciate ligament autografts during the first year of implantation. A preliminary study.

A prospective, observational study was performed to document the serial changes in the magnetic resonance signal of devascularized, hamstring ACL autografts during the 1st year of implantation. Twenty-one ACL deficient knees (14 chronic, 7 acute) were reconstructed. Instability developed in five knees within the first 6 months of graft implantation (24%). Magnetic resonance examinations were performed at 1, 6, 12, 24, 36, and greater than 48 weeks postoperatively (repetition time 1500, echo delay time = 50). A total of 104 scans were reviewed (average, five per knee). The ACL graft was divided into four unequal size zones for analysis. The proximal, middle, and distal thirds of the intraarticular portion of the graft and the portion of the graft within the tibial tunnel were independently analyzed. The magnetic resonance signal in each portion of the graft was graded on a scale with (I) being a normal signal, (II) greater than 50% of the total volume of the graft having a normal signal, (III) less than 50% of the graft having a normal signal, and (IV) 100% of the graft having an increased signal. The increased magnetic resonance signal of the ACL graft was observed to be regionalized and confined to the distal two-thirds of the intraarticular portion of the graft. The portion of the graft exiting the femoral tunnel and within the tibial tunnel retained a normal magnetic resonance signal. The increases in magnetic resonance graft signal were time-dependent, became well established by 3 months, and remained unchanged at 1 year. The clinical outcome could not be predicted based on the magnetic resonance signal of the graft.

Adolescent↗