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Ryan Zerega, Carolyn Killelea, Justin Losciale, Mallory Faherty, and Timothy Sell

each year. 3 , 4 ACL reconstruction (ACLR) is the standard of care to reestablish knee joint stability following injury, but it frequently fails, either through reinjury or inability to successfully return to sport. 5 Secondary ACL injury (either ipsilateral surgical graft failure or contralateral

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Troy Blackburn, Kevin M. Guskiewicz, Meredith A. Petschauer, and William E. Prentice

Objectives:

To determine whether proprioception or muscular strength is the dominant factor in balance and joint stability and define what type of ankle rehabilitation is most effective for these purposes.

Setting:

The University of North Carolina Sports Medicine Research Laboratory.

Subjects:

Thirty-two healthy volunteers free of head injury, dominant leg injury, and vestibular deficits.

Design:

Subjects were divided into control, strength-training, proprioceptive-training, and strength-proprioception combination training groups. Balance was assessed before and after 6-week training programs.

Measurements:

Static, semidynamic, and dynamic balance were assessed.

Results:

Subjects showed no improvement for static balance but improved significantly for semidynamic (P = .038) and dynamic (P = .002) balance. No significant differences were observed between groups.

Conclusions:

Enhancement of proprioception and muscular strength are equally effective in promoting joint stability and balance maintenance. In addition, no 1 type of training program is superior to another for these purposes.

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Kathleen A. Swanik, Kellie Huxel Bliven, and Charles Buz Swanik

Context:

There are contradictory data on optimal muscle-activation strategies for restoring shoulder stability. Further investigation of neuromuscular-control strategies for glenohumeral-joint stability will guide clinicians in decisions regarding appropriate rehabilitation exercises.

Objectives:

To determine whether subscapularis, infraspinatus, and teres minor (anteroposterior force couple) muscle activation differ between 4 shoulder exercises and describe coactivation ratios and individual muscle-recruitment characteristics of rotator-cuff muscles throughout each shoulder exercise.

Design:

Crossover.

Setting:

Laboratory.

Participants:

healthy, physically active men, age 20.55 ± 2.0 y.

Interventions:

4 rehabilitation exercises: pitchback, PNF D2 pattern with tubing, push-up plus, and slide board.

Main Outcomes Measures:

Mean coactivation level, coactivation-ratio patterns, and level (area) of muscle-activation patterns of the subscapularis, infraspinatus, and teres minor throughout each exercise.

Results:

Coactivation levels varied throughout each exercise. Subscapularis activity was consistently higher than that of the infraspinatus and teres minor combined at the start of each exercise and in end ranges of motion. Individual muscle-recruitment levels in the subscapularis were also different between exercises.

Conclusion:

Results provide descriptive data for determining normative coactivation-ratio values for muscle recruitment for the functional exercises studied. Differences in subscapularis activation suggest a reliance to resist anteriorly directed forces.

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Michael W.R. Holmes and Peter J. Keir

Understanding joint stiffness and stability is beneficial for assessing injury risk. The purpose of this study was to examine joint rotational stiffness for individual muscles contributing to elbow joint stability. Fifteen male participants maintained combinations of three body orientations (standing, supine, sitting) and three hand preloads (no load, solid tube, fluid filled tube) while a device imposed a sudden elbow extension. Elbow angle and activity from nine muscles were inputs to a biomechanical model to determine relative contributions to elbow joint rotational stiffness, reported as percent of total stiffness. A body orientation by preload interaction was evident for most muscles (P < .001). Brachioradialis had the largest change in contribution while standing (no load, 18.5%; solid, 23.8%; fluid, 26.3%). Across trials, the greatest contributions were brachialis (30.4 ± 1.9%) and brachioradialis (21.7 ± 2.2%). Contributions from the forearm muscles and triceps were 5.5 ± 0.6% and 9.2 ± 1.9%, respectively. Contributions increased at time points closer to the perturbation (baseline to anticipatory), indicating increased neuromuscular response to resist rotation. This study quantified muscle contributions that resist elbow perturbations, found that forearm muscles contribute marginally and showed that orientation and preload should be considered when evaluating elbow joint stiffness and safety.

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Michael A. Samaan, Eric K. Greska, Matthew C. Hoch, Joshua T. Weinhandl, Sebastian Y. Bawab, and Stacie I. Ringleb

Context:

ACL injury may cause a lack of knee joint proprioception and motor control due to knee joint instability. ACL reconstruction restores knee joint stability, yet dynamic postural control may still be affected while performing dynamic tasks.

Objective:

To examine the effects of ACL injury and reconstruction on dynamic postural control using the Star Excursion Balance Test (SEBT) and single leg hop (SLH).

Participant:

One Division I female athlete.

Main Outcome Measure:

The athlete’s dynamic postural control, both pre- and postreconstruction, was compared with preinjury data using the method of minimal detectable change using reach distances obtained from the SEBT and hop distances from the SLH.

Results:

ACL injury and reconstruction affected the anterior, posteromedial, and posterolateral reach distances of the SEBT. Despite restoration of joint stability, anterior reach distance in the SEBT did not return to preinjury levels 27 months after ACL reconstruction. SLH distances decreased following injury but returned to preinjury levels 27 months after ACL reconstruction.

Conclusion:

Dynamic postural control and performance during the SEBT and SLH were affected by ACL injury and for extended periods of time after ACL reconstruction. Quadriceps inhibition and muscle strength of the involved limb may affect dynamic postural control both after ACL injury and reconstruction while performing the SEBT. Compensatory mechanisms at the hip and ankle may aid in performance of the SLH after reconstruction. Using baseline measurements, where possible, may help researchers better understand the effects of ACL injury and reconstruction on dynamic postural control.

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Kyoungyoun Park-Braswell, Sandra J. Shultz, and Randy J. Schmitz

individuals with greater AKL have decreased joint stability during physical movement (functional stability) due to poor proprioception and resultant altered movement patterns. 3 This diminished functional stability in individuals with greater knee laxity may result in increased risk factors of ACL injury

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Jung-Hoon Choi, Heon-Seock Cynn, Chung-Hwi Yi, Tae-Lim Yoon, and Seung-Min Baik

injury, but it also causes ankle and foot injuries, such as chronic ankle sprain and plantar fasciitis. 4 , 13 , 15 Therefore, the improvement of hip joint stability through the strengthening of hip muscles can have a significant impact on knee and rearfoot mechanics, which can ultimately improve the

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Paul A. Borsa, Eric L. Sauers, and Scott M. Lephart

Functional training for the purpose of restoring dynamic joint stability has received considerable interest in recent years. Contemporary functional training programs are being designed to complement, rather than replace, traditional rehabilitation protocols. The purpose of this clinical commentary is to present a management strategy for restoring dynamic stability in the posterior cruciate ligament (PCL)-injured knee. The strategy presented integrates five key concepts: (a) planned variation of exercise, (b) outcomes-based assessment, (c) kinetic chain exercise, (d) proprioception and neuromuscular control, and (e) specificity of activity. Pertinent research findings and a clinical rationale are provided for using functional training in the restoration of dynamic stability in the PCL-injured knee.

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Matthew B.A. McCullough, Brian D. Adams, and Nicole M. Grosland

Third-generation total wrist arthroplasty devices have provided joint stability, relief from pain and increased wrist motion for patients suffering from severe arthritis. While reports of clinical follow-up appointments describe improved wrist function, the improvement in overall upper extremity function and patient perception remains a question. Therefore, the purpose of this study was to assess the upper extremity function in patients that received the Universal 2 total implant system. Eight patients participated in the complete protocol, which included testing activities of daily living as well as surveys to assess patient perception. The findings of the current study suggest that although patients exhibit motion that exceeds the needed amount, many still have a perceived disability.

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Carly May Green, Paul Comfort, and Lee Herrington

Context:

A reduction in joint position sense (JPS) is sometimes a consequence of shoulder injury that may adversely affect the ability to maintain dynamic joint stability.

Objective:

To compare shoulder JPS between previously injured and noninjured judokas.

Design:

Cohort study.

Participants:

Twenty-nine noninjured subjects (10.93 ± 3.45 years) and eleven injured subjects (15.09 ± 3.39 years).

Main Outcome Measures:

JPS was tested at 45° and 80°of shoulder external rotation at 90° of abduction.

Results:

No signifcant difference in JPS was found between previously injured and noninjured judokas at either joint position.

Conclusion:

Despite evidence that JPS acuity decreases following shoulder injury, this study did not demonstrate a difference in average error between previously injured and noninjured judokas. Uncontrolled confounding factors, such as age and time since injury, may have affected the results. Sport-specifc shoulder joint loading patterns may also be an important factor that affects JPS.