A Kinematic Analysis of Shoulder Instability and the Role of Core Stability

Nick Hassler and Will Kerr

Shoulder AnatomyBones

• Scapula (shoulder blade)• Clavicle• Humerus

Joints• AC Joint• Glenohumeral Joint (ball & socket)

• Labrum

Muscles• Rotator Cuff (4 muscles)• Deltoid• Trapezius• Pectorals

Shoulder Instability• What is it?

• The structures that surround the shoulder joint become stretched or torn allowing the humeral head to move away from the shoulder socket

• How does it occur?• Sudden traumatic injury• Previous injuries (dislocations and tears)• Repetitive use

Injuries and Treatment• Resulting injuries

• Subluxation (partial dislocation)• Dislocation• Stretched ligaments and joints puts individual at higher risk for variety of tears and

fractures• Current treatment options

• Physical therapy• Surgical procedures

• Capsule tightening• Ligament repairs• Labral repair (Bankart repair)

ImpactNumber of People

• Instability has a variety of sources• Athletic, workplace, leisure activities

• Number of sports involving shoulder activity

Cost Considerations• Physical therapy ($20-$120 per session)• Surgical cost (upwards of $20,000)• Workers compensation fees

Additional Factors• Easy to overlook due to lack of immediate pain• Heightened risk for more severe injuries• Preventing you from doing things you love

Research GoalsTo analyze the relationship between core strength and shoulder instability in order to provide a novel approach to minimizing shoulder instability.

Hypothesis: Shoulder stability will increase with the implementation of a core strengthening protocol.

Previous StudiesSaeterbakken 2011

• Core stability training program of progressively unstable closed kinetic chain

• Major Findings → Maximal throwing velocity increased (4.9%) in experimental group

• Shortcomings → No difference between core strength and core stability and influence of each on performance variables

Previous Studies• Core stability was found to be lower in

participants with shoulder dysfunction compared to healthy participants

• Major Findings → overhead athletes with shoulder dysfunction had non‐optimal core stability

• Shortcomings → Small sample and potentially drew a false conclusion from the correlations shown

[3] Hazar, et al

Research MethodsMeasured variables:

• Humeral head position• Glenohumeral Joint Forces• Core Activation

Measurement Methods:• X-Ray → Joint Positioning (statically)• Motion Capture → Joint Positioning (dynamically)• Motion Capture/Force Plates → Force• EMG → Core Activation

Proposed Testing ProtocolParticipants:

• 1000 NCAA overhead athletes• 500 male/500 female• Age: 18 - 24• No previous traumatic shoulder injuries• Half of participants will not participate in progressive core protocol (control group)

Length of Study:• 12 months

• Evaluating variables every 3 months• Protocol frequency: 2 times per week

Proposed Testing ProtocolProgressive Core Protocol:

Core Strengthening: (closed kinetic chain)A. unstable sling exerciseB. modified side plank

Core Stability: (open kinetic chain)C. Bosu ball weighted squatD. exercise ball balance

http://www.youtube.com/watch?v=A2OSQx1dK5k

Data Analysis● Humeral Head Position

○ Evaluate changes in glenohumeral positioning and compare to control group

● Joint Forces○ Magnitude and direction of resultant force in the

glenohumeral joint ● Core Activation

○ Percentage of activation of core muscles

Evaluation Tasks● Neutral position (positioning)● Front raise (forces)● Side raise (forces)● Bosu ball balance (core

activation)

Expected ResultsWe expect that the experimental group will experience better shoulder stability compared to the control group:

• Less movement of the humeral head with respect to the glenoid• More optimal glenohumeral positioning• Less variation of force directions• Higher level of core activation

Future ImpactsIncreasing shoulder longevity in overhead sport athletes

• Decreasing chronic shoulder injuries• Providing a low impact means for improving shoulder health • Reduced medical costs

References[1] Brumitt, J., Dale, R.B., 2009. Integrating Shoulder and Core Exercises When Rehabilitating Athletes Performing Overhead Activities. North

American Journal of Sports Physical Therapy 4, 132–138.[2] Emery, C.A., 2005. Effectiveness of a home-based balance-training program in reducing sports-related injuries among healthy adolescents:

a cluster randomized controlled trial. Canadian Medical Association Journal 172, 749–754. doi:10.1503/cmaj.1040805[3] Hazar, Z., Ulug, N., Yuksel, I., 2014. Is There a Relation Between Shoulder Dysfunction and Core Instability? Orthopaedic Journal of Sports

Medicine 2, 8–13. doi:10.1177/2325967114s00173[4] Mısırlıoğlu, T.Ö., 2018. Does a core stabilization exercise program have a role on shoulder rehabilitation? A comparative study in young

females. Turkish Journal of Physical Medicine and Rehabilitation 64, 328–336. doi:10.5606/tftrd.2018.1418[5] Page, P., 2011. SHOULDER MUSCLE IMBALANCE AND SUBACROMIAL IMPINGEMENT SYNDROME IN OVERHEAD ATHLETES.

International Journal of Sports Physical Theraphy 6, 51–58.[6] Saeterbakken, A.H., Tillaar, R.V.D., Seiler, S., 2011. Effect of Core Stability Training on Throwing Velocity in Female Handball Players.

Journal of Strength and Conditioning Research 25, 712–718. doi:10.1519/jsc.0b013e3181cc227e[7] Silfies, S.P., Ebaugh, D., Pontillo, M., Butowicz, C.M., 2015. Critical review of the impact of core stability on upper extremity athletic injury

and performance. Brazilian Journal of Physical Therapy 19, 360–368. doi:10.1590/bjpt-rbf.2014.0108[8] Swanik, K.A., Lephart, S.M., Swanik, C., Lephart, S.P., Stone, D.A., Fu, F.H., 2002. The effects of shoulder plyometric training on

proprioception and selected muscle performance characteristics. Journal of Shoulder and Elbow Surgery 11, 579–586. doi:10.1067/mse.2002.127303

[9] Wilk, K.E., Meister, K., Andrews, J.R., 2002. Current Concepts in the Rehabilitation of the Overhead Throwing Athlete. The American Journal of Sports Medicine 30, 136–151. doi:10.1177/03635465020300011201

[10] Yaggie, J.A., Campbell, B.M., 2006. Effects Of Balance Training On Selected Skills. Journal of Strength and Conditioning Research 20, 422–428. doi:10.1519/00124278-200605000-00031

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