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Erica M. Willadsen, Andrea B. Zahn and Chris J. Durall

Clinical Scenario The high prevalence of noncontact anterior cruciate ligament (ACL) injuries in adolescent female athletes is thought to originate from hormonal, neuromuscular, and structural differences between sexes. 1 Although hormonal and structural factors are nonmodifiable, neuromuscular

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Takayuki Hasegawa, Toshiro Otani, Kentaro Takeda, Hideo Matsumoto, Kengo Harato, Yoshiaki Toyama and Takeo Nagura

The purpose of the current study was to longitudinally evaluate how preoperative knee kinematics change after ACL reconstruction. Three-dimensional gait analysis using the point cluster method was undertaken on the same subjects preoperatively and at 3, 6, and 12 months after ACL reconstructive surgery. Thirteen subjects (7 males, 6 females) were examined while performing 2 different activities at self-selected speeds: walking and walk-pivoting (walking, pivoting toward the landed limb side and walking away). The contralateral knees of subjects at 12 months postoperatively were selected as control knees. Flexion range in the stance phase increased with time after surgery, but remained lower than in the contralateral knee, even at 12 months postoperatively (P < .05) during walking and walk-pivoting. The rotation pattern during walking and walk-pivoting showed an offset toward external rotation by 6 months postoperatively compared with control knees, while at 12 months postoperatively the offset had nearly disappeared and the movement pattern resembled that in control knees. These findings suggest that a return to sport participation by 6 months after ACL reconstruction requires careful consideration. Depending on the type of sport, activity restriction even after 12 months may need to be considered to allow complete kinematic restoration.

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Luke M. Mueller, Ben A. Bloomer and Chris J. Durall

Clinical Scenario:

Anterior cruciate ligament (ACL) injuries are associated with a lengthy recovery time, decreased performance, and an increased rate of reinjury. To improve performance of the injured knee, affected athletes often undergo surgical reconstruction and rehabilitation. Determining when an athlete is ready to safely return to play (RTP), however, can be challenging for clinicians. Although various outcome measures have been recommended, their ability to predict a safe RTP is questionable.

Focused Clinical Question:

Which outcome measures should be used to determine readiness to return to play after ACL reconstruction?

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Alasdair R. Dempsey, Bruce C. Elliott, Bridget J. Munro, Julie R. Steele and David G. Lloyd

Anterior cruciate ligament (ACL) injuries are costly. Sidestep technique training reduces knee moments that load the ACL. This study examined whether landing technique training alters knee moments. Nineteen team sport athletes completed the study. Motion analysis and ground reaction forces were recorded before and after 6 weeks of technique modification. An inverse dynamic model was used to calculate three-dimensional knee loading. Pre- and postintervention scores were compared using paired t tests. Maximal knee flexion angle during landing was increased following training. There was no change in valgus or flexion moments, but an increase in peak internal rotation moment. This increase in internal rotation moment may increase the risk of ACL injury. However, the increased angle at which the peak internal rotation moment occurred at follow up may mitigate any increase in injury risk by reducing load transmission.

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J. Craig Garrison, Joe M. Hart, Riann M. Palmieri, D. Casey Kerrigan and Christopher D. Ingersoll

Context:

Gender differences in muscle activity during landing have been studied as a possible contributing factor to the greater incidence of anterior cruciate ligament injuries in women.

Objective:

To compare root-mean-square (RMS) electromyography (EMG) of selected lower extremity muscles at initial contact (IC) and at peak knee internal-rotation (IR) moment in men and women during landing.

Design:

Preexperimental design static-group comparison.

Setting:

Motion-analysis laboratory.

Participants:

16 varsity college soccer players (8 men, 8 women).

Main Outcome Measures:

EMG activity of the gluteus medius, lateral hamstrings, vastus lateralis, and rectus femoris during landing.

Results:

When RMS EMG of all muscles was considered simultaneously, no significant differences were detected between genders at IC or at peak knee IR moment.

Conclusion:

Male and female college soccer players display similar relative muscle activities of the lower extremity during landing. Gender landing-control parameters might vary depending on the technique used to analyze muscle activity.

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Christopher Carcia, Jim Eggen and Sandra Shultz

Context:

The influence of hip-muscle function on knee-joint kinematics during landing has been inadequately investigated.

Objective:

To determine the effect of bilateral hip-abductor fatigue on frontal-plane tibiofemoral landing characteristics and vertical ground-reaction force (vGRF) during the landing phase of a drop jump.

Design:

Experimental, pretest–posttest.

Setting:

Research laboratory.

Participants:

20 recreationally active college-age students.

Intervention:

Isometric bilateral hip-abductor-fatigue protocol.

Main Outcome Measures:

Frontal-plane tibiofemoral landing angle, excursion, and vGRF during landing from a drop jump under prefatigue, postfatigue, and recovery conditions.

Results:

After the fatigue protocol, participants landed in a greater valgus orientation than in the prefatigued state. No differences in frontal-plane excursion or vGRF were noted.

Conclusions:

Isolated bilateral hip-abductor fatigue alters frontal-plane lower extremity orientation during a double-leg landing. Because an increase in valgus orientation has been observed at or near the time of noncontact anterior cruciate ligament injuries, we recommend improving hip-abductor muscle performance to lessen the risk of such injuries.

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Oscar Martel, Juan F. Cárdenes, Gerardo Garcés and José A. Carta

Anterior cruciate ligament (ACL) reconstruction is one of the most important aspects of knee surgery. For this purpose, several fixation devices have been developed, although the interference screw is the most frequently used. The most typical biomechanical test of these devices consists of placing them in a testing machine and subjecting them to a pull-out test. However, insufficient attention has been paid to the influence of the displacement test rate on the mechanical properties of the fixation system. The aim of this study is to compare the influence of the crosshead rate in the biomechanical test of two different devices for the fixation of ACL tendon grafts. One hundred in vitro tests were performed using porcine tibiae and bovine tendons. The fixation devices used were (1) an interference screw and (2) a new expansion device. All ACL reconstructions were subjected to pull-out test to failure. Five crosshead rates were employed in a range from 30 mm/min to 4000 mm/min. Statistical analyses of the results show that, for the two devices, the rate has a significant effect on both maximum force and stiffness. Moreover, the new expansion device showed lesser dependency on the crosshead rate than the interference screw.

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Gulcan Harput, H. Erkan Kilinc, Hamza Ozer, Gul Baltaci and Carl G. Mattacola

Context:

There is lack of information related to quadriceps and hamstring strength recovery during the early period of rehabilitation after anterior cruciate ligament reconstruction (ACLR) using hamstring-tendon graft (HTG).

Objective:

To investigate quadriceps and hamstring isometric strength at 4-, 8-, and 12-wk time points after ACLR and to document the strength changes of these muscles over time.

Design:

Longitudinal study.

Participants:

24 patients (age 28.1 ± 8.1 y) who underwent unilateral single-bundle anatomic ACLR with 4-strand semitendinosus and gracilis tendon graft.

Main Outcome Measures:

The isometric strength of quadriceps and hamstring muscles was measured on an isokinetic dynamometer at a 60° knee-flexion angle 4, 8, and 12 wk after surgery.

Results:

Quadriceps and hamstring strength significantly increased over time for both the involved limb (quadriceps F 2,46 = 58.3, P < .001; hamstring F 2,46 = 35.7, P < .001) and uninvolved limb (quadriceps F 2,46 = 17.9, P < .001; hamstring F 2,46 = 56.9, P = .001). Quadriceps and hamstring indexes significantly changed from 4 wk (QI 57.9, HI 54.4) to 8 wk (QI 78.8, HI 69.9) and from 8 wk to 12 wk (QI 82, HI 75.7) (P < .001); however, there was no difference between indexes at the 12-wk time point (P = .17).

Conclusions:

The results of this study serve as a reference for clinicians while directing a rehabilitation protocol for HTG ACLR patients to better appreciate expected strength changes of the muscles in the early phase of recovery.

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Christopher J. Durall, Thomas W. Kernozek, Melissa Kersten, Maria Nitz, Jonathan Setz and Sara Beck

Context:

Impaired postural control in single-limb stance and aberrant drop-landing mechanics have been implicated separately as risk factors for noncontact anterior cruciate ligament (ACL) injury, but associations between these variables has not been reported.

Objective:

To determine whether there are associations between single-limb postural control and drop-landing mechanics.

Setting:

University motion-analysis laboratory.

Design:

Single-leg-landing kinematic and kinetic data were collected after participants dropped from a hang bar. Postural-control variables COP excursion and velocity were assessed during single-leg barefoot standing on a force platform.

Participants:

A convenience sample of 24 healthy women.

Main Outcome Measures:

Pearson product–moment correlation coefficients.

Results:

Strong associations were measured between maximal knee-abduction moment and COP excursion (r = .529, P = .003) and average COP velocity (r = .529, P = .003). Strong inverse associations were measured between minimum hip-flexion angle and COP excursion (r = −.521, P = .003) and average COP velocity (r = −.519, P = .003).

Conclusions:

Participants with decreased postural control had higher knee-abduction moments and a more extended hip on landing, which have been implicated separately as risk factors for ACL injury. A longitudinal prospective analysis is needed to determine whether force-platform postural-control measures can identify athletes at risk for ACL injury.

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James Onate, Nelson Cortes, Cailee Welch and Bonnie Van Lunen

Context:

A clinical assessment tool that would allow for efficient large-group screening is needed to identify individuals potentially at risk for anterior cruciate ligament (ACL) injury.

Objective:

To assess the criterion validity of a jumplanding assessment tool compared with 3-dimensional (3D) motion analysis and evaluate interrater reliability across an expert vs novice rater using the Landing Error Scoring System (LESS).

Design:

Validity protocol.

Setting:

Controlled, laboratory.

Participants:

Nineteen female (age 19.58 ± .84 y, height 1.67 ± .05 m, mass 63.66 ± 10.11 kg) college soccer athletes volunteered.

Main Outcome Measurement:

Interrater reliability between expert rater (5 y LESS experience) vs novice rater (no LESS experience). LESS scores across 13 items and total score. 3D lower extremity kinematics were reduced to dichotomous values to match LESS items.

Interventions:

Participants performed drop-box landings from a 30-cm height with standard video-camera and 3D kinematic assessment.

Results:

Intrarater item reliability, assessed by kappa correlation, between novice and experienced LESS raters ranged from moderate to excellent (κ = .459–.875). Overall LESS score, assessed by intraclass correlation coefficient, was excellent (ICC2,1 = .835, P < .001). Statistically significant phi correlation (P < .05) was found between rater and 3D scores for knee-valgus range of motion; however, percent agreement between expert rater and 3D scores revealed excellent agreement (range of 84–100%) for ankle flexion at initial contact, knee-flexion range of motion, trunk flexion at maximum knee flexion, and foot position at initial contact for both external and internal rotation of tibia. Moderate agreement was found between rater and 3D scores for trunk flexion at initial contact, stance width less than shoulder width, knee valgus at initial contact, and knee-valgus range of motion.

Conclusions:

Our findings support moderate to excellent validity and excellent expert vs novice interrater reliability of the LESS to accurately assess 3D kinematic motion patterns. Future research should evaluate the efficacy of the LESS to assess individuals at risk for ACL injury.