Gastrocnemius tightness on joint angle and work of lower extremity during gait

Background

Muscular tightness is a common clinical musculoskeletal disorder and is regarded as a predisposing factor for muscle injuries. In this study, a two-way mixed design ANOVA was applied to investigate the effects of the gastrocnemius tightness on the joint angle and joint work during walking.

Methods

Twenty-two patients with muscular tightness of gastrocnemius muscle (<12° of ankle dorsiflexion with knee extended) and 22 age- and gender-matched subjects with normal gastrocnemius flexibility (>15° of ankle dorsiflexion with knee extended) participated in this study. The joint angle and work at hip, knee, and ankle joints during the stance phase were analyzed at two preset cadences of 100 steps/min and 140 steps/min.

Findings

Significantly greater flexion angles at hip (P = 0.025) and knee (P = 0.001) were found in the tightness group at the time of maximal ankle dorsiflexion. Significantly less work generation at knee (P = 0.034) and greater work absorption at ankle (P = 0.024) were detected in the tightness group.

Interpretation

The subjects with gastrocnemius tightness revealed a compensatory gait pattern, which included the changes in the joint angles and associated work productions. The potential disturbance of the knee control and strain injuries of plantar flexors might be crucial in the clinical considerations for subjects with gastrocnemius tightness.     

Mechanics of the anterior interval of the knee using open dynamic MRI

Background

The anterior interval of the knee has been defined as the space between the infrapatellar fat pad and patellar tendon anteriorly, and the anterior border of the tibia and the transverse meniscal ligament posteriorly. Investigation of the normal kinematics of this region is necessary as we begin to appreciate the significant impact that pathologic processes of the anterior interval have on the knee.

Methods

Non-weight bearing and weight bearing dynamic MRIs of 20 healthy knees were evaluated at 30° intervals from 0° to 120° flexion. The angle subtended by the patellar tendon and the anterior tibia was measured at each interval of flexion by three independent observers. The amount of angular change over each interval of flexion was also evaluated and the differences between the relative weight bearing conditions were statistically evaluated.

Findings

The angle formed by the anterior tibia and the patellar tendon decreases with knee flexion (45.2° (SD 10.1°) at full extension vs. 1.2° (SD 2.1°) at full flexion). The average patellar tendon–tibial angle excursion was significantly reduced with full-weight bearing, 43.1° (SD 11.2°) from 0° to 120° of flexion, compared to non-weight bearing, 30.9° (SD 6.1°) over the same range of motion (P < 0.001). Full-weight bearing decreased the angle excursion by 28% compared to non-weight bearing.

Interpretation

The observed changes in the anterior interval are influenced by multiple factors including load, knee architecture, tendon elasticity and tibio-femoral and patello-femoral kinematics. The impact of load on the mechanics of the anterior interval is most pronounced between 0° and 30° of flexion.     

Guidelines for the Early Restoration of Active Knee Flexion After Total Knee Arthroplasty: Implications for Rehabilitation and Early Intervention

Objectives

To investigate the association between active knee flexion at initial (1–2wk) and final (7wk) outpatient visits after total knee arthroplasty (TKA), and to develop a guide for the expected progression of knee flexion in the subacute postoperative phase.

Design

Prospective case series.

Setting

Rehabilitation clinic.

Participants

Consecutive sample of patients (N=108) who underwent TKA between December 2007 and August 2012.

Intervention

TKA followed by a standardized, 5-week outpatient rehabilitation program (2 sessions per week) immediately after hospital discharge.

Main Outcome Measure

Active knee flexion was recorded on the patient's first outpatient visit (1–2wk) and then biweekly throughout the patient's 5-week outpatient rehabilitation program.

Results

Active knee flexion at initial (1–2wk) and final (7wk) outpatient visits were significantly correlated (r=.86, P<.001). Mean active knee flexion significantly improved (P<.001) across all patients from 90.4° at initial outpatient visit to 110° at final outpatient visit. At 7 weeks postsurgery, a value of 100° was determined as the cut-off point for an acceptable active knee flexion, which corresponded with 80° of active knee flexion at initial outpatient presentation at 1 to 2 weeks.

Conclusions

Active knee flexion at the initial outpatient visit exhibits a strong correlation with knee flexion at 7 weeks after TKA. These knee flexion guidelines may allow for the provision of individualized rehabilitation, allow practitioners to provide patients with realistic goals of progression throughout the subacute phase, and allow the early identification of patients at risk for poor long-term outcomes who may benefit from further intensive care or other early intervention.     

Increasing posterior tibial slope does not raise anterior cruciate ligament strain but decreases tibial rotation ability

Background

It was investigated whether the strain of the anterior cruciate ligament and tibial kinematics are affected by increasing posterior tibial slope.

Methods

9 human cadaveric knee joints were passively moved between full extension and 120° flexion in a motion and loading simulator under various loading conditions and at 0°, 5°, 10° and 15° posterior tibial slope angles. The anterior cruciate ligament strain and the tibial rotation angle were registered. To assess the influence of posterior tibial slope on the anterior cruciate ligament strain at a fixed flexion angle the anterior cruciate ligament strain was recorded at three different flexion angles of 0°, 30° and 90° while continuously increasing the osteotomy angle from 5° to 15°.

Findings

The anterior cruciate ligament strain was either not affected by the posterior tibial slope angle or, in some load cases, was decreased for increasing posterior tibial slope (P < 0.05). There was a significant decrease of tibial rotation when the posterior tibial slope was increased to 15° for many of the load cases tested (P < 0.05). The mean maximum decrease was from 17.4° (SD 5.7°) to 11.2° (SD 4.7°) observed for flexion-extension motion under 30 N axial load in combination with an internal rotation moment.

Interpretation

The hypothesis that increasing posterior tibial slope results in higher anterior cruciate ligament strain was not confirmed. However, knee kinematics were affected in terms of a reduced tibial rotation. From a biomechanical point of view the data do not support the efficacy of sagittal osteotomies as performed to stabilize anterior cruciate ligament deficient knees.     

Human spastic Gracilis muscle isometric forces measured intraoperatively as a function of knee angle show no abnormal muscular mechanics

Background

To show whether mechanics of activated spastic muscle are representative of the functional deficiencies clearly apparent in the joints, our goal was to test the following hypotheses: (1) The muscle's joint range of force exertion is narrow, and (2) high muscle forces are available at low muscle length.

Methods

During remedial surgery, we measured the forces of the Gracilis muscle of spastic cerebral palsy patients (n = 7, 10 limbs tested) as a function of knee joint angle from flexion (120°) to full extension (0°).

Findings

The spastic Gracilis exerted non-zero forces for the entire knee angles studied. For four limbs, the peak force was exerted at the highest length. For the remainder limbs, the closest knee angle of peak force exertion to 120° was 66°. Maximally 79.1%, and for most limbs only a much lower percentage (minimally 22.4%) of peak Gracilis force (mean 41.59 N (SD 41.76 N)) was available at 120° knee flexion. Moreover, a clinical metric was obtained showing that the occurrence of a contracture was not correlated significantly with key determinants of knee angle-Gracilis force characteristics.

Interpretation

Our hypotheses are rejected: the spastic Gracilis has no narrow operational joint range of force exertion and no supreme active resistance capacity to stretch at low length. We conclude that if activated alone, spastic muscle shows no abnormal mechanics representative of joint movement disorder. Simultaneous stimulation of other muscles as in daily activities may change this situation.     

A rotating inlay decreases contact pressure on inlay post after posterior cruciate substituting total knee arthroplasty

Background

The post/cam mechanism of posterior cruciate substituting total knee arthroplasty, which is intended to achieve maximum range of flexion, offers the risk of failure due to mechanical overload. The purpose of this in vitro study was to investigate load and contact pressure on the inlay post of posterior substituting knee prosthesis with different designs.

Methods

Isokinetic extension/flexion motions of seven fresh frozen left knee specimens were simulated dynamically in a specially designed knee simulator with an extension moment of 31 N m. After implantation of the knee prosthesis system, which provides a fixed and a rotating posterior cruciate substituting inlay, a pressure sensitive film was fixed on the inlay post surface to measure maximum load and contact pressure.

Findings

Both types of inlays showed nearly the same contact load of up to 480 N on the posterior surface of the inlay post at 120° knee flexion. Contact pressure was measured to be up to 19.7 MPa at 120° flexion on the posterior surface of the post of the fixed inlay, whereas contact pressure was measured to be significantly lower (6.8 MPa, p = 0.04) on the inlay post of the rotating inlay.

Interpretation

The modification of a rotating posterior cruciate substituting inlay could not decrease the horizontal load, but offers the possibility to decrease contact pressure on the inlay post to avoid mechanical overload of the polyethylene inlay.     

Limited hip and knee flexion during landing is associated with increased frontal plane knee motion and moments

Background

It has been proposed that female athletes who limit knee and hip flexion during athletic tasks rely more on the passive restraints in the frontal plane to deceleration their body center of mass. This biomechanical pattern is thought to increase the risk for anterior cruciate ligament injury. To date, the relationship between sagittal plane kinematics and frontal plane knee motion and moments has not been explored.

Methods

Subjects consisted of 58 female club soccer players (age range: 11–20 years) with no history of knee injury. Kinematics, ground reaction forces, and surface electromyography were collected while each subject performed a drop landing task. Subjects were divided into two groups based on combined sagittal plane knee and hip flexion angles during the deceleration phase of landing (high flexion and low flexion).

Findings

Subjects in the low flexion group demonstrated increased knee valgus angles (P = 0.02, effect size 0.27), increased knee adductor moments (P = 0.03, effect size 0.24), decreased energy absorption at the knee and hip (P = 0.02, effect size 0.25; and P < 0.001, effect size 0.59), and increased vastus lateralis EMG when compared to subjects in the high flexion group (P = 0.005, effect size 0.35).

Interpretation

Female athletes with limited sagittal plane motion during landing exhibit a biomechanical profile that may put these individuals at greater risk for anterior cruciate ligament injury.     

In-vivo evaluation of the kinematic behavior of an artificial medial meniscus implant: A pilot study using open-MRI

Background

In this pilot study we wanted to evaluate the kinematics of a knee implanted with an artificial polycarbonate-urethane meniscus device, designed for medial meniscus replacement. The static kinematic behavior of the implant was compared to the natural medial meniscus of the non-operated knee. A second goal was to evaluate the motion pattern, the radial displacement and the deformation of the meniscal implant.

Methods

Three patients with a polycarbonate-urethane implant were included in this prospective study. An open-MRI was used to track the location of the implant during static weight-bearing conditions, within a range of motion of 0° to 120° knee flexion. Knee kinematics were evaluated by measuring the tibiofemoral contact points and femoral roll-back. Meniscus measurements (both natural and artificial) included anterior–posterior meniscal movement, radial displacement, and meniscal height.

Findings

No difference (P > 0.05) was demonstrated in femoral roll-back and tibiofemoral contact points during knee flexion between the implanted and the non-operated knees. Meniscal measurements showed no significant difference in radial displacement and meniscal height (P > 0.05) at all flexion angles, in both the implanted and non-operated knees. A significant difference (P ≤ 0.05) in anterior–posterior movement during flexion was observed between the two groups.

Interpretation

In this pilot study, the artificial polycarbonate-urethane implant, indicated for medial meniscus replacement, had no influence on femoral roll-back and tibiofemoral contact points, thus suggesting that the joint maintains its static kinematic properties after implantation. Radial displacement and meniscal height were not different, but anterior–posterior movement was slightly different between the implant and the normal meniscus.     

A pilot study to investigate the combined use of Botulinum toxin type-a and ankle foot orthosis for the treatment of spastic foot in chronic hemiplegic patients

Background

Botulinum toxin is commonly used to treat spastic equinus foot. This treatment seems to improve gait in hemiplegic patients when used alone or combined with an ankle-foot orthosis. However, the nature and effects of this improvement have until now rarely been studied. The aim of this study was to quantify the impact of a Botulinum toxin injection in the triceps surae of hemiplegic patients with equinus foot, used either alone or in combination with an ankle-foot orthosis, on the kinematics and dynamics of the paretic lower limb, and to determine the advantage of combining an ankle-foot orthosis with this pharmacological treatment.

Methods

Patients were assessed using gait analysis to measure spatio-temporal, kinematic and dynamic parameters of the gait cycle before Botulinum toxin injection and then 3 and 6 weeks after injection. Eight chronic hemiplegics following central nervous system lesion were included.

Findings

Botulinum toxin injection led to an increase in velocity, peak ankle dorsiflexion during stance phase, and peak knee flexion during swing phase. It also resulted in an increased peak plantarflexion moment. Use of ankle-foot orthosis led to a specific increase in peak ankle dorsiflexion during swing phase and also increased peak plantarflexion moment.

Interpretation

The results indicate that combined Botulinum toxin injection of the triceps surae and wearing an ankle-foot orthosis is more effective than the use of Botulinum toxin only. Use of an ankle-foot orthosis increases ankle dorsiflexion during the swing phase and does not reduce the benefits gained by the use of Botulinum toxin in stance phase.     

Increase of tibial slope reduces backside wear in medial mobile bearing unicompartmental knee arthroplasty

Background

Unicondylar knee arthroplasty is a good alternative for patients in monocompartmental osteoarthritis. The revision rate in unicondylar knee arthroplasty is higher than in total knee arthroplasty. The influence of the tibial slope on wear in unicondylar knee arthroplasty has not been investigated so far.

Methods

The influence of the tibial slope on wear was investigated in mobile bearing unicondylar knee prosthesis. This was positioned with four different tibial slopes (− 4°, 0°, 4°, 8°) in a knee wear simulator simulating the human gait in a plane according to ISO 14243-2:2002(E). After this a kinematic analysis was performed and the inlays were observed under reflected-light-microscopy.

Findings

Wear was significantly reduced with an increasing tibial slope (0°: 3.46 mg/million cycles, SD: 0.59, 4° slope: 1.52 mg/million cycles, SD: 0.06, 8° slope group: 0.99 mg/million cycles, SD: 0.42). An anterior slope of − 4° also reduced wear (2.08 mg/million cycles, SD: 0.37). Kinematic analysis revealed a reduced translation between the inlay and the tibia with an increasing tibial slope. The backside of the inlays of the 4° and 8° slope group showed less wear pattern when observed under reflected-light microscopy.

Interpretation

Increasing the tibial slope led to a reduced translation between the inlay and the prosthesis in the analysed mobile-bearing unicondylar knee arthroplasty and with this to a reduced backside wear. A tibial slope between 4 and 8° can be recommended in mobile UKA to reduce wear, however, the influence on the ligaments has to be considered and needs to be investigated in further studies.