Background
Reliable fixation of the soft hamstring grafts in ACL reconstruction has been reported as problematic.
Hypothesis
The biomechanical properties of patellar tendon (PT) grafts fixed with ...biodegradable screws (PTBS) are superior compared to quadrupled hamstring grafts fixed with BioScrew (HBS) or Suture-Disc fixation (HSD).
Study Design
Controlled laboratory study with roentgen stereometric analysis (RSA).
Methods
Ten porcine specimens were prepared for each group. In the PT group, the bone plugs were fixed with a 7 · 25 mm BioScrew. In the hamstring group, four-stranded tendon grafts were anchored within a tibial tunnel of 8 mm diameter either with a 7 · 25 mm BioScrew or eight polyester sutures knotted over a Suture-Disc. The grafts were loaded stepwise, and micromotion of the graft inside the tibial tunnel was measured with RSA.
Results
Hamstring grafts failed at lower loads (HBS: 536 N, HSD 445 N) than the PTBS grafts (658 N). Stiffness in the PTBS group was much greater compared to the hamstring groups (3500 N/mm versus HBS = 517 N/mm and HSD = 111 N/mm). Irreversible graft motion after graft loading with 200 N was measured at 0.03 mm (PTBS), 0.38mm (HBS), and 1.85mm (HSD). Elasticity for the HSD fixation was measured at 0.67 mm at 100 N and 1.32 mm at 200 N load.
Conclusion
Hamstring graft fixation with BioScrew and Suture-Disc displayed less stiffness and early graft motion compared to PTBS fixation. Screw fixation of tendon grafts is superior to Suture-Disc fixation with linkage material since it offers greater stiffness and less graft motion inside the tibial tunnel.
Clinical Relevance
Our results revealed graft motion for hamstring fixation with screw or linkage material at loads that occur during rehabilitation. This, in turn, may lead to graft laxity.
Mathematical relationships have long been used to describe many aspects of muscle function such as the relationship between muscle force and muscle length, muscle force and velocity of contraction or ...the degree of muscle activation during a contraction. During this work various mathematical expressions have been employed in order to gain an insight into different aspects of muscle activity. The first part of the work examined whether performing a strength protocol on a dynamometer can lead to an increase in eccentric strength output as well as in the neuromuscular activation of the quadriceps group of muscles that appears inhibited during slow concentric and fast eccentric contractions. Neuromuscular activation was modelled via a three-parameter sigmoid function that was also tested for robustness to perturbations in the maximum activation values. During the second part of the study the "functional" hamstrings to quadriceps ratio H:Qfun was expressed as a function of two variables i.e., angular velocity and joint angle. Initially nine-parameter torque-angular velocity-angle profiles were obtained for the knee extensors and flexors from a group of participants. A theoretical 17- parameter H:Qfun function was then derived for each dataset. Subsequently, a simpler, 6-parameter function was derived, RE = aexp(bωn + cθm)-dω1/2θ2 that best reproduced the original 17-parameter fit. Finally, a six-segment subject specific torque-driven model of the Snatch lift was developed in order to investigate the optimal mechanics of the lift. The model simulated the lift from its initiation until the end of the second pull when the feet of the athlete momentarily leave the platform. The six-segment model comprised of foot, shank, thigh, torso (head + trunk), arm and forearm segments with torque generators at the ankle, knee, hip and shoulder joints respectively. The torque profiles were obtained using an isokinetic dynamometer.
Summary The objective of this study was to evaluate the clinical and radiological results of a prospective, continuous series of 105 ACL reconstructions using the STG tendons fixed to the femur by an ...EndoButton CL® , with more than 4 years of follow-up. Hypothesis The subjective and objective clinical results as well as the radiological results (tunnel enlargement) obtained by a cortical, extra-anatomic femoral fixation are at least equivalent to the results obtained with other types of femoral fixation systems. Material and methods One hundred and five patients aged with a mean 26 years (range, 12–56 years) were operated on for an anterior cruciate ligament rupture using the same technique and by the same operator: four-strand STG fixed to the tibia by a double fixation – BioRCI-HA screw and staple – and on the femur by an EndoButton CL® (Smith and Nephew). The results were assessed at 6 months, 1 and 2 years and then at a mean follow-up of 51 months, both clinically (IKDC, Lysholm, KT-1000) and radiologically (Telos laximetry, tunnel position, and morphological analysis). Results No complications related to the use of the EndoButton® were observed. No additional interference screw was necessary. According to the IKDC laxity classification, 91.4% of the patients were classified in category A or B, nine knees (8.6%) were classified C or D. Four failures required revision with a patellar tendon graft. On the final IKDC score, 63 patients (60%) were classified grade A, 37 grade B (35.3%), four grade C (3.8%), and one grade D (0.9%). On the Telos laximetry, 62 patients (59%) had a differential laxity less than or equal to 2 mm. The mean value was 1.8 mm (range, 0–11). Tibial tunnel enlargement was constant; femoral tunnel enlargement was significant (> 2 mm) in 27.6% of the knees. No femoral tunnel diameter modification corresponding to the EndoButton® passage was observed. Discussion The results of this series are comparable to the results of other series. Its reproducibility and the absence of iatrogenic complications for this femoral EndoButton CL® fixation make it a top-choice technique, like the corticocancellous graft procedures, but without their disadvantages. No secondary elongation attributable to the EndoButton CL® was observed. This femoral fixation procedure appeared necessary and sufficient to providing good mechanical stability for the graft in the femoral tunnel. Level of evidence Level IV: retrospective therapeutic study.
Abstract A cadaver knee simulator has been developed to model surgical transfer of the rectus femoris. The simulator allows knee specimens six degrees of freedom and is capable of modeling both the ...swing and stance phases of human gait. Experiments were conducted using a mechanical hinge analog of the knee to verify that time, flexion angle, and knee extension force measurements recorded when using the simulator were not influenced by its design or operation. A ballistic double pendulum model was used to model the swing phase of gait, and the contributions of hip and ankle torques and hamstrings cocontraction were included when modeling the stance phase of gait. When modeling swing, range of motion and time to peak knee flexion in swing for the hinge knee were similar to those of in vivo test subjects. Measurements of hinge knee extension force when modeling stance under various biomechanical conditions matched those predicted using an analytical model. Future studies using cadaver knee specimens will apply techniques described in this paper to further our understanding of changes in knee biomechanics caused by rectus femoris transfer surgery.
Type of study
This study investigates whether the amount of tibial and femoral bone tunnel enlargement following anterior cruciate ligament (ACL) reconstruction with hamstrings can be reduced by ...compaction bone tunnel drilling.
Methods
Patients undergoing primary ACL reconstruction with four-strand hamstrings (
n
= 26) were matched to either extraction drilling (
n
= 13) or compaction drilling (
n
= 13). Extracortical femoral fixation was by means of a 20 mm Endobutton CL and tibial fixation was by resorbable interference screw. A CT scan was performed on the second postoperative day and an average of 4 months (range 3.8–5 months) postoperatively in all patients. Tunnel enlargement was determined by digitally measuring the widths perpendicular to the long axis of the tunnels on an oblique coronal and axial plane. The CT measurements were compared to the intraoperative drill diameter.
Results
With extraction drilling the average tibial tunnel diameter proximal to the interference screw increased from 8.5 to 10.4 mm (
P
< 0.0001) and the average femoral tunnel from 8.0 to 10.6 mm (
P
< 0.0001). With compaction drilling it increased from 8.2 to 10.0 mm (
P
< 0.0001) and from 7.6 to 9.7 mm (
P
< 0.002), respectively. Tunnel widening was 22% on the tibial side for both groups and 33 versus 28% on the femoral side (
P
= 0.09) for extraction versus compaction drilling.
Conclusion
There was a significant tibial and femoral tunnel widening on CT an average of only 4 months following ACL reconstruction with hamstrings. Compaction drilling with a stepped router did not prove to reduce the postoperative tunnel widening significantly. Tunnel widening was higher on the femoral side which could be related to the extracortical femoral fixation technique.
Level of evidence
Level 4.
The anterior cruciate ligament (ACL) consists of two primal functional bundles, anteromedial bundle and posterolateral bundles. Those two bundles play different functional roles and contribute ...differently to knee stability throughout the range of motion. Recent advancement in studies of anatomy and biomechanics of ACL has led surgeons to perform double-bundle ACL reconstruction to obtain better stability and kinematics. Consequently, variable surgical techniques of double-bundle ACL reconstruction have been reported to replicate native ACL. In addition, various surgical key points and problems in double-bundle ACL reconstruction techniques have also been reported. There has been a trend to more anatomically replicate native ACL bundles, not simply creating two bundles. We summarize the basic knowledge and current concepts of anatomic double-bundle ACL reconstruction using hamstrings tendons.
Imaging of the hamstrings Davis, Kirkland W
Seminars in musculoskeletal radiology
12, Številka:
1
Journal Article
Recenzirano
The hamstring muscles, located in the posterior thigh, include the biceps femoris, the semimembranosus, and the semitendinosus. The proximal portions of the hamstring muscles are subject to a variety ...of injuries and pathology. Many of these entities affect the origin of the hamstrings, including the tendinous enthesis, the underlying ischial tuberosity, and the surrounding tissues. Tendinosis and small partial tears at the origin are the result of chronic attrition. They may be accompanied by bursitis or hamstring syndrome. Apophysitis occurs in teenagers prior to complete fusion of the ischial apophysis and results from repeated traction injuries on the apophysis without discrete displacement. Abrupt injury at the origin from forced flexion of the hip results in osseous avulsions of the apophysis in teenagers and proximal tendon ruptures in adults. Other entities affect the muscles distal to the tendon origins. These injuries include strains and partial tears of the musculotendinous junction from acute indirect trauma, delayed onset muscle soreness from overuse of the muscle group without discrete remembered injury, and contusions and myositis ossificans from direct blunt impact. The imaging features of these injuries and pathology are fairly specific and diagnostic, with the exception of some cases of myositis ossificans and chronic ischial avulsions.
While ACL reconstruction using single-tunnel and single-bundle techniques generally yields good clinical results, more and more studies are now reporting results that are not entirely satisfactory, ...as this type of reconstruction only exerts control over forward tibial shifting, not tibial rotation, when activities that exert high functional demands are undertaken. As a result, recent years have seen the appearance of numerous techniques for anatomic ACL reconstruction that reproduce both the anteromedial and posterolateral bundles of the ligament and therefore offer potentially improved rotational control. This article outlines a technique for anatomic ACL reconstruction. Said technique uses central and anteromedial portals, which afford a better perspective of the intercondylar notch. The main features of this technique are: (1) Double bone tunnels in the femur and tibia. The femoral tunnels are created using the out-in technique. (2) Double bundles with hamstring tendon grafts. (3) Tibial fixation by means of interference screws. (4) Femoral fixation in which the graft is supported by a cortical bone bridge and an interference screw in one of the tunnels. We feel that the main advantage of this technique is precisely that it introduces a new feature (a cortical femoral bone bridge) and is not necessarily dependent on specific double-bundle instrumentation, using only regular drill guides to create out-in femoral tunnels. This enables said tunnels to be located with ease and precision. The femoral fixation model itself, with the support provided by the cortical bone bridge, potentially guarantees a level of resistance that can be further increased with the aid of one or two interference screws, thus avoiding the need for post fixation techniques that require the use of screws or buttons.
The purpose of this study was to come across an exercise that increases the Hamstring contraction levels so that it may protect the anterior cruciate ligament (ACL). Previous studies have postulated ...that changing the projection of the center of gravity behind the feet will decrease the translation of the tibia, therefore protect the ACL. Muscle activity of the quadriceps, hamstring and soleus muscles in healthy subjects was measured with an EMG during three different squat tasks with differences of support of body weight and the center of gravity. The subjects were nine healthy female recreational athletes with no history of any pathological knee condition or musculoskeletal system disorder. There was no significant difference in the activities of the four muscles (Vastus Medialis; Hamstring: Semitendinosus and Biceps Femoris; and Soleus); and there was a similar pattern in the activity between those muscles in the exercises. In addition, VM values were considerably higher than the Hamstring and soleus activity levels. There was no significant difference between one squat from another and among the phases (0-30°, 30-60° or 60-90°) of knee flexion. These results suggest that even when changing the projection of the center of gravity, the activity of the quadriceps is high compared to the hamstring and soleus muscles.
The main aim of this thesis was to examine hamstrings anatomy and its influence on knee flexor muscle function in healthy young men. A secondary aim was to better understand the implications of ...hamstrings anatomy and function, and their variability, in relation to the risk of strain injury. The functional and conventional H:Q ratios (examined up to high angular velocities) as well as the knee joint angle-specific isometric H:Q ratio exhibited good test-retest reliability at joint positions that closely replicated the conditions of high injury risk. Football players did not exhibit any differences in angle-specific or peak torque H:Q ratios compared to recreationally active controls. Knee extensor and flexor strength, relative to body mass, of footballers and controls was similar for all velocities, except concentric knee flexor strength at 400° s-1 (footballers +40%; P < 0.01). Muscle volume explained 30-71% and 38-58% of the differences between individuals in knee extensors and flexors torque respectively across a range of velocities. A moderate correlation was also found between the volume of these antagonistic muscle groups (R2= 0.41). The relative volume of the knee extensors and flexors explained ~20% of the variance in the isometric H:Q ratio and ~31% in the high velocity functional H:Q ratio. Biceps femoris long head exhibited a balanced myosin heavy chain isoform distribution (47.1% type I and 52.9 % total type II) in young healthy men, while BFlh muscle composition was not related to any measure of knee flexor maximal or explosive strength. Biceps femoris long head proximal aponeurosis area varied considerably between participants (>4-fold) and was not related to biceps femoris long head maximal anatomical cross-sectional area (r= 0.04, P= 0.83). Consequently, the aponeurosis:muscle area ratio exhibited 6-fold variability (range, 0.53 to 3.09; CV= 32.5%). Aponeurosis size was not related to isometric or eccentric knee flexion strength. The findings of this thesis suggest that the main anatomical factor that contributes to knee flexors function in vivo is hamstrings muscle size, while muscle composition and aponeurosis size do not seem to have a significant influence. The high inter-individual variability of the biceps femoris long head proximal aponeurosis size suggests that a disproportionately small aponeurosis may be a risk factor for strain injury. In contrast, biceps femoris long head muscle composition does not seem to explain the high incidence of strain injuries in this muscle. Quadriceps and hamstrings muscle size imbalances contribute to functional imbalances that may predispose to strain injury and correction of any size imbalance may be a useful injury prevention tool. Finally, regular exposure to football training and match-play does not seem to influence the balance of muscle strength around the knee joint.
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