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PubMedDate not supplied

A biomechanical evaluation of tibiofemoral rotation in anterior cruciate deficient knees during walking and running.

ACL injury has been associated with increased instability of the knee in both in vitro and in vivo studies using passively applied forces. This study assessed tibiofemoral rotation after ACL injury during the functional activity of treadmill ambulation using a triaxial electrogoniometer. Isometric and isokinetic peak torques of the quadriceps and hamstrings were obtained using the Cybex II isokinetic dynamometer. Significant increases in tibiofemoral rotation were noted with increased running speed in the injured and normal knees. The degree of rotation in the injured limb did not significantly exceed that of the normal limb. Isokinetic strength of the quadriceps and hamstrings correlates significantly with the observed extent of rotation.

Adult↗

PubMed1997

Comparison of nonballistic active knee extension in neural slump position and static stretch techniques on hamstring flexibility.

Nonballistic, active range of motion exercises have been advocated as more effective than static stretching for increasing range of motion, yet no published data exist to support this claim. This study compared the effect of nonballistic, repetitive active knee extension movements performed in a neural slump sitting position with static stretching technique on hamstring flexibility. Forty healthy, adult volunteer subjects with limited right hamstring flexibility (i.e., minimum of 15 degrees loss of active knee extension measured with femur held at 90 degrees of hip flexion) were randomly assigned to one of three groups. Group 1 (static stretch) performed a 30-second stretch twice daily. Group 2 (active stretch) performed 30 repetitions of active knee extension while sitting in a neural slump position twice daily. Group 3 served as a control. Hamstring flexibility was determined by an active knee extension test before and after 6 weeks of stretching. Goniometric measurement of knee joint flexion angle was obtained from videotape recording of the active knee extension test. A 3 (group) x 2 (test) repeated measures analysis of variance and subsequent Tukey post hoc testing revealed no significant difference in knee joint range of motion gains between the static (mean = 8.9 degrees) and active stretch (mean = 10.2 degrees). Both stretch groups' knee joint range of motion improved significantly (p < .05) more than the control group. We conclude that 6 weeks of nonballistic, repetitive active knee extensions (30 repetitions, twice daily) performed in a neural slump sitting position improves hamstring flexibility in uninjured subjects, but is no different compared with static stretching (30 seconds, twice daily).

Adult↗

PubMedDate not supplied

Results of anterior cruciate ligament reconstruction in the adolescent female.

This study evaluated the functional results and complications of anterior cruciate ligament (ACL) surgery in adolescent females. We studied 22 consecutive female patients younger than 20 years who underwent arthroscopic ACL reconstruction. Average follow-up was 31 months. One hundred percent of the patients were satisfied. Seven patients returned to intercollegiate or high school sports. The mean Lysholm score was 94, and the International Knee Documentation Committee score was 40% normal, 60% nearly normal. KT-1000 arthrometer side-to-side differences were <or=3 mm in 90% of patients and between 3 and 5 mm in 10%. Quadriceps and hamstring strength was minimally decreased. One patient sustained a patella fracture. One patient changed her lifestyle because of her knee. Arthroscopic ACL reconstruction is successful in returning the female adolescent to competitive sports with a high degree of patient satisfaction and excellent functional outcome. Mild residual quadriceps and hamstring weakness may persist, however.

Adolescent↗

PubMed1998

The role of mechanical and neural restraints to joint range of motion during passive stretch.

UNLABELLED: Musculoskeletal flexibility is typically characterized by maximum range of motion (ROM) in a joint or series of joints. Resistance to passive stretch in the mid-range of motion is a function of the passive mechanical restraints to motion. However, an active contractile response may contribute resistance at terminal ROM. PURPOSE: The purpose of this study was to examine whether maximum straight leg raise (SLR) ROM was limited by passive mechanical forces or stretch-induced contractile responses to stretch. METHODS: An instrumented SLR stretch was applied to the right leg of 16 subjects ending at the point of discomfort. Torque was measured with a load cell attached to the ankle. An electrogoniometer was placed on the hip, and the knee was braced in extension. Surface electrodes were placed over the rectus and biceps femoris muscles. Following the instrumented SLR test, maximum ROM was measured goniometrically by a physical therapist using the standard SLR test (PT SLR ROM). Torque/ROM curves were plotted for each subject. RESULTS: PT SLR ROM was positively related to total energy absorbed (area under the curve) (r = 0.49, P = 0.044), negatively related to the increase in torque from 20 to 50 degrees (r = -0.81, P < 0.0001) and negatively related to energy absorbed from 20 to 50 degrees (r = -0.73, P < 0.001). Minimal stretch-induced hamstring activity was elicited (3 +/- 1% MVC), and the EMG activity was unrelated to PT SLR ROM (r = -0.06, P = 0.8). A combination of the increase in torque from 20 to 50 degrees and total energy absorbed improved the relationship to PT SLR ROM (r = 0.89, P = 0.001). Seventy-nine percent of the variability in maximum SLR ROM could be explained by the passive mechanical response to stretch. CONCLUSIONS: These data lend support to the concept that musculoskeletal flexibility can be explained in mechanical terms rather than by neural theories.

Adult↗

PubMedDate not supplied

The orthopaedic manifestations of Pelizaeus-Merzbacher disease in children.

Pelizaeus-Merzbacher disease (PMD) is a degenerative leukodystrophy of the central nervous system resulting in progressive spasticity and neurologic deterioration. Seitelberger (13) divided this rare disease into six types. Five patients with the type 1 and two patients with the type II form of PMD have been treated at the Children's Hospital of Eastern Ontario. Our study sought to identify the orthopaedic manifestations of PMD and to develop a common orthopaedic profile for these patients. All children with types I and II PMD developed spastic quadriparesis, truncal hypotonia, thoracolumbar scoliosis, soft-tissue contractures of the adductors and hamstrings, osteopenia, bilateral coxa valga, and associated hip dislocation.

Bone Diseases, Metabolic↗

PubMed2005

Hip strength following hamstring tendon anterior cruciate ligament reconstruction.

OBJECTIVE: The objective of this study was to determine whether there is alteration in resultant joint moment of the hip extensors and adductors after hamstring anterior cruciate ligament (ACL) reconstruction. DESIGN: Cross-sectional outcome analysis. SETTING: University sport medicine center. SUBJECTS: Fifteen subjects more than 1 year after ACL reconstruction with semitendinosus and gracilis tendons were compared with 15 matched controls with no knee injury. INTERVENTIONS: Strength testing of the hip extensors and hip adductors of both limbs. MAIN OUTCOME MEASUREMENTS: Isokinetic (50 degrees /s and 150 degrees /s) hip extensor strength test and isometric (15 degrees and 30 degrees ) hip adductor strength test. RESULTS: Hip extensors increase in strength after hamstring ACL reconstruction, evening out normal side-to-side strength differences. Hip adductor strength deficits of up to 43% are demonstrated in the ACL reconstructed subjects compared with controls. CONCLUSIONS: The identification of hip adductor strength deficits after hamstring harvest for ACL reconstruction may have important implications for both graft harvest site selection as well as postoperative rehabilitation protocols. Given the known existence of knee strength deficits after ACL reconstruction, increases in isovelocity hip extensor strength may contribute to increased lower limb strength imbalances. This may have implications for the ability of the lower limb muscles to protect the ACL graft.

Anterior Cruciate Ligament↗

PubMedDate not supplied

Outcome of medial versus combined medial and lateral hamstring lengthening surgery in cerebral palsy.

Pre- and postoperative gait analysis and static measurements from 37 children with cerebral palsy who underwent hamstring lengthening were evaluated. Significant improvements in static and kinematic measures were noted after surgery in both groups. Although the differences were not statistically significant, there was a suggestion that combined medial/lateral hamstring lengthening may provide greater improvement in popliteal angle and maximum knee extension in stance. However, there also appears to be a greater risk of knee hyperextension during gait after combined medial and lateral hamstring lengthening than after medial hamstring lengthening alone. Postoperative calf spasticity also appears to be a risk factor for postoperative knee hyperextension. Assessment of calf spasticity may be important in patients undergoing medial and lateral hamstring lengthening. Additional treatments such as bracing and/or botulinum toxin injections to the calf to control equinus and knee hyperextension may be beneficial.

Cerebral Palsy↗

PubMed1992

Further evidence against a direct automatic neuromotor link between the ACL and hamstrings.

The purpose of this experiment was to determine whether reflexive, or more broadly, automatic hamstrings excitation could be elicited during isometric, maximum effort, step increases in knee extension torque. Eight healthy subjects without lower extremity dysfunction or injury performed maximum effort isometric knee extension at 15 and 85 degrees of knee flexion in minimum elapsed time. Surface electromyography was used to record medial (semimembranosis and semitendinosis) and lateral (biceps femoris--long head) hamstrings excitation that was subsequently normalized to the excitation during maximum isometric knee flexion. To assess whether automatic hamstrings excitation was elicited, the amplitude of the EMG signals was analyzed and compared for 50 ms prior to peak knee extension torque, and three consecutive 50 ms windows following peak knee extension torque. The amplitude of the EMG subsequent to the peak knee extension torque failed to support the contention of an automatic hamstrings excitation mediated by neural circuitry from the ACL. The present results, in conjunction with previous work, suggest that a protective automatic hamstrings contraction is not normally elicited in response to conditions subjecting the anterior cruciate ligament to strain.

Adult↗

PubMed2003

Electromyographic and biomechanic analysis of anterior cruciate ligament deficiency and functional knee bracing.

OBJECTIVE: Examine the neuromuscular response to functional knee bracing relative to anterior tibial translations in vivo. DESIGN: During randomised brace conditions, electromyographic data with simultaneous skeletal tibiofemoral kinematics were recorded from four anterior cruciate ligament deficient subjects to investigate the effect of the DonJoy Legend functional brace during activity. BACKGROUND: Knee braces do not increase knee stability but may influence afferent inputs from proprioception and therefore one might expect changes in muscle firing patterns, amplitude and timing. METHODS: Hoffman bone pins affixed with markers were implanted into the tibia and femur for kinematic measurement. The EMG data from the rectus femoris, semitendinosus, biceps femoris, and lateral head of the gastrocnemius were integrated for each subject in three separate time periods: 250 ms preceding footstrike and two consecutive 125 ms time intervals following footstrike. RESULTS: With brace, semitendinosus activity significantly decreased 17% prior to footstrike whereas bicep femoris significantly decreased 44% during A2, (P<0.05). Rectus femoris activity significantly increased 21% in A2 (P<0.05). No consistent reductions in anterior translations were evident. CONCLUSION: Our preliminary findings, based on a limited number of subjects, indicate joint stability may result from proprioceptive feedback rather than the mechanical stabilising effect of the brace. Despite a significant increase in rectus femoris activity upon landing, only one subject demonstrated an increase in anterior tibial drawer. RELEVANCE: Studies have shown functional braces do not mechanically stabilise the anterior cruciate ligament deficient knee. Perhaps bracing alters proprioceptive feedback. It has been shown that bracing the anterior cruciate ligament deficient knee may affect hamstring and quadriceps activity. Our findings stresses the importance of functional knee bracing combined with proprioceptive and muscular coordination training in order to increase joint stability.

Adult↗

PubMed2007

The proximal origin of the hamstrings and surrounding anatomy encountered during repair. A cadaveric study.

BACKGROUND: Avulsion of the proximal origin of the hamstrings has become a more frequently recognized athletic injury. Most orthopaedic surgeons rarely operate in this anatomic area. The purpose of the present study was to define the anatomy of the proximal origin of the hamstrings and its relationship to neurovascular and muscular structures encountered during a repair of a complete avulsion. METHODS: Fourteen fresh-frozen hip-to-foot human cadaveric specimens were dissected in the prone position. The proximal origin of the hamstrings and its relationship to the surrounding neurologic and muscular structures were documented and measured with use of digital calipers. RESULTS: Six of the fourteen specimens were from female donors. The average age of the donors at the time of death was 68 +/- 13 years. The average height of the donors was 66 +/- 3.5 in (167 +/- 8.9 cm), and the average weight was 142 +/- 39 lb (64 +/- 17.7 kg). The semitendinosus and biceps femoris have a common tendinous site of origin on the ischium. A number of measurements were obtained. The musculotendinous junctions of the semitendinosus and biceps femoris separated at an average of 9.9 +/- 1.5 cm from the most proximal origin site on the ischium. The average distance from the proximal border of the semitendinosus/biceps femoris origin to the inferior border of the gluteus maximus was 6.3 +/- 1.3 cm. At the lateral border of the ischium, the average distance from the inferior gluteal nerve and artery to the inferior border of the gluteus maximus was 5.0 +/- 0.8 cm. The sciatic nerve was an average of 1.2 +/- 0.2 cm from the most lateral aspect of the ischial tuberosity. The site of origin of the semitendinosus/biceps femoris was oval, with average measurements of 2.7 +/- 0.5 cm from proximal to distal and of 1.8 +/- 0.2 cm from medial to lateral. The site of origin of the semimembranosus was crescent-shaped, with average measurements of 3.1 +/- 0.3 cm from proximal to distal and of 1.1 +/- 0.5 cm from medial to lateral. CONCLUSIONS: The semitendinosus and biceps femoris have a common tendon of origin on the ischium, and the semimembranosus originates just laterally. The proximal origin of the hamstrings has intimate relationships with the inferior gluteal nerve and artery and the sciatic nerve, which may be at risk during surgical dissection and retraction.

Aged↗

PubMed1993

Electromyographic evaluation of closed and open kinetic chain knee rehabilitation exercises.

The use of closed kinetic chain knee rehabilitation exercises has been advocated in recent years. The primary reason cited for employing closed kinetic chain exercises is that these exercises result in less anteroposterior (A/P) shear force at the knee joint, when compared with traditionally used open kinetic chain exercises. The purpose of this study was to determine the electromyographical (EMG) activity ratio of quadriceps to hamstrings occurring in the following exercises: unilateral one quarter squats, leg extensions (N-K Table), lateral step-ups, and movements on the Fitter (Fitter International, Inc), Stair-master 4000 (Randal Sports/Medical Products, Inc), and slideboard. Ten female student-athletes participated in this study. EMG surface electrodes were applied over the rectus femoris and biceps femoris muscles. The subjects completed three maximum isometric contractions for both muscle groups to obtain baseline EMG data. They then performed repetitions of each exercise. These movements were videotaped simultaneously with a stationary shuttered video camera operating at 30 Hz. A computer program was used to analyze the videotaped performances for knee joint range of motion (ROM). Three trials of data were averaged. Baseline EMG activity was used to determine percentage of maximum EMG activity for each exercise. There were significant differences (p.<01) among the exercises for the following dependent variables: ROM, maximum angle, percent of maximum contraction, time of contraction, and total EMG (EMG area under the curve). This study suggests that the five closed kinetic chain exercises studied result in minimal A/P shear forces at the knee joint.

Journal Article↗

PubMed2005

Orientation of tendons in vivo with active and passive knee muscles.

Tendon orientations in knee models are often taken from cadaver studies. The aim of this study was to investigate the effect of muscle activation on tendon orientation in vivo. Magnetic resonance imaging (MRI) images of the knee were made during relaxation and isometric knee extensions and flexions with 0 degrees , 15 degrees and 30 degrees of knee joint flexion. For six tendons, the orientation angles in sagittal and frontal plane were calculated. In the sagittal plane, muscle activation pulled the patellar tendon to a more vertical orientation and the semitendinosus and sartorius tendons to a more posterior orientation. In the frontal plane, the semitendinosus had a less lateral orientation, the biceps femoris a more medial orientation and the patellar tendon less medial orientation in loaded compared to unloaded conditions. The knee joint angle also influenced the tendon orientations. In the sagittal plane, the patellar tendon had a more anterior orientation near full extension and the biceps femoris had an anterior orientation with 0 degrees and 15 degrees flexions and neutral with 30 degrees flexions. Within 0 degrees to 30 degrees of flexion, the biceps femoris cannot produce a posterior shear force and the anterior angle of the patellar tendon is always larger than the hamstring tendons. Therefore, co-contraction of the hamstring and quadriceps is unlikely to reduce anterior shear forces in knee angles up to 30 degrees . Finally, inter-individual variation in tendon angles was large. This suggests that the amount of shear force produced and the potential to counteract shear forces by co-contraction is subject-specific.

Adult↗

PubMedDate not supplied

Quantitative evaluation of knee instability and muscle strength after anterior cruciate ligament reconstruction using patellar and quadriceps tendon.

Anterior cruciate ligament reconstruction using an autologous graft harvested from the central one-third of the patellar and quadriceps tendon was performed in 65 knees of 65 patients who were followed from 3 to 7 years. Mean anterior laxity of both knees was measured before and after surgery in each patient using the Styker Knee Laxity Tester. At 30 degrees of knee flexion, 58 patients (89%) had differences of less than 2.5 mm between the operated and unoperated knees. Quadriceps strength was measured with the Cybex II and was less than 50% of the uninjured knee at 3 months after surgery. In men, quadriceps strength returned to 78% of normal at 1 year and 85% at final followup. These values were equal to the preoperative level. In women, the quadriceps strength at final followup was 70%, significantly lower than preoperative strength. Hamstring strength recovered to equal the normal strength. Although anterior cruciate ligament reconstruction using one-third of the patellar and quadriceps tendon achieves stability, postoperative quadriceps weakness is a disadvantage. This weakness may be caused by impairment of the knee extensor mechanism resulting from harvesting the graft. We do not currently recommend this technique for anterior cruciate ligament reconstruction.

Adolescent↗

PubMed1989

Hamstring/quadriceps strength ratios in knees with medial collateral ligament insufficiency. Isokinetic and isometric results and their relation to patients' long-term recovery.

The purpose of this study was to investigate the peak torque and total work hamstring/quadriceps strength ratios (HQ-ratios) of 25 knees with medial collateral ligament (MCL) insufficiency and to find out the possible relation between different HQ-ratios and the long-term outcome of the patients. The isokinetic (speed 60 and 180 degrees/sec) and isometric muscle strengths were measured by a Cybex II dynamometer. Three standardized knee scoring scales were used to determine the subjective, clinical, and radiological outcome of the knees with MCL insufficiency. All tests showed great interpersonal variation in HQ-ratios even in the healthy knees (range from 23% to 183%). The average HQ-ratios between the uninjured and injured legs did not differ significantly from each other (range from 40% to 82%). The mean peak torques and total work of hamstrings as well as of quadriceps were slightly, but not significantly lower in the injured leg than on the uninjured side. The follow-up scores did not differ significantly between patient groups with low (less than or equal to 50%), optimal (50-80%), or high (greater than or equal to 80%) absolute HQ-ratios of the MCL insufficient knee. However, in every test the scores were significantly better for patients with an HQ-ratio difference of less than or equal to 15% between the injured and the uninjured side than for those with a clear difference (greater than 15%). The findings suggest that the HQ-ratio is a patient-specific parameter and that any general recommendation on its optimal value is difficult to give.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2006

Clinical measurements of proprioception, muscle strength and laxity in relation to function in the ACL-injured knee.

A knee injury with anterior cruciate ligament (ACL) rupture may cause deficits in proprioception, increased laxity and decreased muscle strength. Although it may be common knowledge that these factors affect knee function, only a few studies have been performed where this has been investigated in the clinical situation, and the results are not conclusive. The purpose of this study was therefore to investigate how and to what extent proprioception, laxity and strength affect knee joint function and evaluate if the methods commonly used for estimating these factors clinically seem to be relevant. The study encompassed 36 patients with ACL deficiency. A single-leg hop test for distance and subjective rating of knee function were defined as dependent variables and analyzed separately in stepwise linear regression models where proprioception, knee joint laxity, hamstrings and quadriceps strength, age and sex were defined as independent variables. Higher threshold values (poorer proprioception), increased side-to-side difference of anterior laxity and poorer strength significantly predicted shorter length of the hop test. Higher rating of subjective function corresponded to female gender, lesser side-to-side difference of anterior laxity and better proprioception.

Adolescent↗

PubMed2003

The effect of screw length and position on fixation of four-stranded hamstring grafts for anterior cruciate ligament reconstruction.

The aim of this study was to examine interference screw fixation of four strand hamstring grafts for anterior cruciate ligament reconstruction in vitro. Bovine tibiae and cannon tendons were used. Screws were introduced from 'outside-in'. The tendons were loaded cyclically to 150 N to simulate walking and 450 N to simulate jogging. Slippage of the tendon from the anchorage was recorded after 100, 300 and 1000 cycles. Cortico-cancellous and cancellous only fixations were compared using a 7-mm screw in an 8-mm tunnel with a 7-mm graft. The effect of screw length was studied by comparing 8 x 25 and 8 x 45 mm screws. Graft slippage with cancellous only fixation was significantly greater than with cortico-cancellous screw fixation (P 0.105), the longer screws gave more consistent behaviour. We concluded that the screw should be placed so that its head engages the cortex, while increasing screw length within cancellous bone did not significantly improve graft fixation. Cyclical load testing reflects the repetitive forces imposed in the early post-operative period following hamstring anterior cruciate ligament reconstruction and is important for the evaluation of graft fixations.

Animals↗

PubMedDate not supplied

Evaluation of hamstring strength and tendon regrowth after harvesting for anterior cruciate ligament reconstruction.

BACKGROUND: It is generally thought that tissue regeneration and good functional recovery can be expected after anterior cruciate ligament reconstruction using the hamstring tendons. However, persistent strength deficit in deep knee flexion has also been reported. HYPOTHESIS: Morphologic regeneration of the harvested hamstring tendon is not necessarily associated with its functional recovery. STUDY DESIGN: Retrospective follow-up study. METHOD: Twenty-eight patients who underwent anterior cruciate ligament reconstruction with hamstring graft were evaluated after a minimum period of 2 years. Status of tendon regrowth was assessed by magnetic resonance imaging. To specifically analyze the functional deficit after graft harvest, the isometric hamstring strength was examined in a sitting position at 90 degrees of flexion and a prone position at 90 degrees and 110 degrees of flexion. Then, the strength data were correlated with the extent of tendon regeneration. RESULTS: In 22 of the 28 patients, a regrowth of the semitendinosus tendon was found, whereas regeneration of the gracilis tendon was observed in 13 patients. In the evaluation of hamstring strength, the isometric peak torque was reduced to 86.2%, 54.6%, and 49.1%, respectively, in the aforementioned 3 postures as compared with the contralateral side. CONCLUSIONS: Significant functional deficit of hamstring strength remains regardless of morphologic regeneration.

Adolescent↗

PubMed2001

Swing- and support-related muscle actions differentially trigger human walk-run and run-walk transitions.

There has been no consistent explanation as to why humans prefer changing their gait from walking to running and from running to walking at increasing and decreasing speeds, respectively. This study examined muscle activation as a possible determinant of these gait transitions. Seven subjects walked and ran on a motor-driven treadmill for 40s at speeds of 55, 70, 85, 100, 115, 130 and 145% of the preferred transition speed. The movements of subjects were videotaped, and surface electromyographic activity was recorded from seven major leg muscles. Resultant moments at the leg joints during the swing phase were calculated. During the swing phase of locomotion at preferred running speeds (115, 130, 145%), swing-related activation of the ankle, knee and hip flexors and peaks of flexion moments were typically lower (P<0.05) during running than during walking. At preferred walking speeds (55, 70, 85%), support-related activation of the ankle and knee extensors was typically lower during stance of walking than during stance of running (P<0.05). These results support the hypothesis that the preferred walk-run transition might be triggered by the increased sense of effort due to the exaggerated swing-related activation of the tibialis anterior, rectus femoris and hamstrings; this increased activation is necessary to meet the higher joint moment demands to move the swing leg during fast walking. The preferred run-walk transition might be similarly triggered by the sense of effort due to the higher support-related activation of the soleus, gastrocnemius and vastii that must generate higher forces during slow running than during walking at the same speed.

Adult↗