Sprains and Strains The Biomechanics of Injury Janus D. Butcher UMD School of Medicine June 2007

Sprains and Strains Biomechanical Model History and Physical Initial Treatment Rehabilitative Treatment Illustrative Cases/Complications

Definitions A sprain is?

Definitions A sprain is? Ligament Injury

Definitions A strain is?

Definitions A strain is? Musculotendinous Injury

Biomechanical Model of Acute Ligament/tendon Injury Acute injury occurs when a ligament or tendon is subjected to tensile stress (load) that exceeds it’s tensile strength.

Biomechanical Model of Overuse Injury to Ligament or Tendon Overuse injury occurs when ligament or tendon is subjected to repetitive tensile stress at a frequency, duration, and intensity that exceed its capacity for recovery or repair.

Concentric Contraction/Load Muscle shortens as it exerts force.

Eccentric Contraction/Load Muscles are forced to lengthen while exerting a force

Biomechanical Model Factors That Increase Risk of Injury Increased tensile stress Decreased tensile strength Decrease capacity for repair

Increased Tensile Stress Eccentric overload Ballistic velocity Weak supporting dynamic stabilizers Proprioceptive deficit

Proprioception is….. Balance

Decreased Tensile Strength Prior injury Disuse atrophy Degenerative disease Aging Connective tissue disease Medications

Decreased Capacity for Repair Recurrent injury Aging Connective tissue disease Vascular disease Diabetes Smoking Medications Other

Biomechanical Model Injury Prevention Decrease tensile load (stress) Increase tensile strength Enhance ability for repair

Decrease Tensile Load Extrinsic Factors Proper equipment Proper technique Bracing/taping Orthotics

Increase Tensile Strength Intrinsic Factors Resistance exercise (eccentric loading) Balanced strengthening of dynamic stabilizers General conditioning Proprioception training

Enhance Capacity for Repair Conditioning Lifestyle Drugs

Sprains and Strains Mechanism of Injury Deformation injury produced by stress Musculotendinous injuries usually eccentric overload Ligament injuries usually non-anatomic stress

Musculotendinous Injury Eccentric overload

Ligamentous Injury Non-Anatomic Stress

Grading Severity Grade 1: Micro-tears (stretch) Grade 2: Macrotears (partial tear) Grade 3: Complete disruption

Joint Laxity vs. Joint Instability

Joint Stability Musculotendinous unit and ligaments are symbiotic in joint stability Static stabilizer vs. dynamic stabilizers

Functional Instability Not the same as joint laxity Frequently describes “giving out” Unable to do certain activities Jump Pivot Decelerate Cut

Functional Instability Possible Causes Ligamentous laxity Motion deficit Strength or endurance deficit Proprioception issues Internal derangement (fracture/loose body)

Sprains and Strains Physical Exam Inspection Swelling Bruising Pain Provocation Motion Palpation

Physical Exam Palpation Crepitance Weakness Palpable defect

Physical Exam Stress Testing Laxity End Point

Modifiers of Endpoint Muscle tone Muscle guarding Joint effusion Soft tissue swelling Mechanical block Ligamentous endpoint

Physical Exam Caveats 1.The patient will tell you what’s wrong 2.The exam may or may not be confirmatory

Initial Treatment PProtection Ractive Rest Iintermittent Ice CCompression EElevation Manti-inflammatory Medication Manti-inflammatory Modalities

Rest

A four letter word

Rest A four letter word Relative rest implies ACTIVE rest

Active Rest Treatment Implications Stimulates healing of tissue Allows maintenance of general conditioning Prevents loss of strength in supporting structures Maintains joint ROM Addresses proprioception retraining

Active Rest Activity is performed in a biomechanically normal position Protected from abnormal motion No pain with activity No pain or swelling after activity

Rehabilitative Exercise Goals Control immediate inflammatory response Promote normal tissue healing Increase tensile strength Address collateral joint effectors Maximize functional stability

Who Gets Therapy? Everyone!

Return to Sport Absence of pain is not appropriate end- point of treatment-Webb Strength >80% on normal ROM normal Proprioception normal

Return to Sport Bracing Almost everyone Functions Support Joint Enhance proprioception Ensure Appropriate fit Use with specified activities

Case 24 year old student hockey athlete slid feet first into the boards. He saw it coming and tried to stop his crash. Felt a ripping sensation in his left thigh and was unable to bear weight.

Physical Exam

Swelling Bruising Palpable defect in the vastus lateralis Negative extensor lag

Imaging Xray- none initially MRI

Treatment PKnee immobilizer RKnee immobilizer/flexion block splint IIce CAce Wrap EElevation MNo MNSAIDS (Indocin)

Therapy 1.Initial rest until able to weight bear 2.Gentle stretching 3.Gradual eccentric exercise (2-4 weeks) 4.Dynamic flexibility and strengthening 5.Return to sport 4 to 8 weeks

Complications Re-injury Complete tear MO

Prevention of Myositis Ossificans Avoid repeat injury Avoid aggressive activity early Indocin 50mg t.i.d.

Case 33 year old runner sprained ankle 1 year ago. Was very bruised and swollen but symptoms subsided without treatment Now has had multiple ankle sprains over the past year and ankle feels very unstable.

Physical exam Inspection: Normal Tender in the anterio- lateral corner Weakness in peroneus brevis ROM: diminished dorsiflexion

Physical exam Anterior drawer/talar tilt are normal Proprioception: Poor balance on injured side

Diagnosis? 1.Ankle sprain (recurrent grade 2 or less) 2.Synovitis 3.Functional instability

Treatment Brace Strengthing ROM Proprioception

Questions?