Mechanisms of injury Flashcards
What is a muscle strain?
Overstretching of a muscle in which muscle fibres tear - usually near muscle tendon junction
Highest in eccentric contraction where under linear contraction force but lengthening
What muscles often experience muscle strain?
Hamstring
Quadriceps
Hip flexors
Hip adductors
What is the grading of muscle strains?
Grade 1- some fibres involved
Grade 2 - signficant number of fibres invovled
Grade 3 - complete tear or rupture- usually in already tendinopathic sufferers
Whats the challenge about muscle strains?
High incidence rate
High re injury rate
Slow healing
Persistent symptoms
Of the hamstrings which is most at risk and why?
Biceps femoris
Thought to occur in terminal phase of gait cycle - 2nd half hamstring are active and lengthened - reaches 110% of its length in upright position.
What was loughborough’s research in relation to Hamstring strains?
Aponeurosis size - disproportionately small biceps femoris long head aponeurosis suggested as a risk factor as the mechanical strain is concentrated to a small area
Found - high variation in aponeurosis size but not related to muscle size and knee flexor strength
What are the signs and symptoms of a hamstring strain?
Usually occur during sprinting - limb suddenly after a brief bout of explosive sprinting and would be forced to stop and fall to ground
localised stfiffness, tightness, discolouration, swelling, redness and bruising
May have a stiff leg gait as cannot use hamstring to initiate movement
Broad discoloration may indicate high grade myotendionous injury or avulsion #
Explain the examination of a suspected hamstring strain
Palpate to check for muscle belly rupture - precise location may be hard to identify as deep
- Hurdle test
- Bent knee stretch test
Increased posterior thigh pain with extension indicates possible hamstring strain or tendinopathy
What imaging may be used in suspected hamstring strains?
XR - negative results unless ischial tuberosity avulsion #
Dynamic ultrasonography - identify fluid collections - oedema and internal bleeding
MRI/ CT- precisely define injury location, degrees of damage, number of involved tendons, extent of retraction and chronicity.
How can we assess knee strength?
Maximal torques generated by hamstrings and quadriceps and ratio is isokinetic dynamometer test - flexion and extension speed fixed- resistant depends on torque participant can generate leading to no harm.
What are the different types of strength ratio hamstring to quads?
- Conventional H:Q ratio - concentric to concentric
- Functional H:Q ratio - eccentric to concentric
- Concentric - Eccentric
- Eccentric - Eccentric
Which ratio is usually used and why?
Functional H:Q - Hamstring usually lengthened when working
Should be at least 60% - more preferable to at least 75%
What is the issue with resting time from a muscle strain?
Too long hamstring would shrink and scar tissue form around the tear
Too little time risks reinjury
Explain the management of a total hamstring tear
Surgical repair and braced with a hip orthosis in 30-40 degrees of flexion to limit stress to surgical site
Followed by rehab
Will need DVT prevention
Weight bearing with crutches > RoM development > isotonic exercise > dynamic hip training / isometric stretching > sports specific > full isotonic evaluation.
Post a complete hamstring tear when can people return to sport?
When injured side is 80% strength of non operative leg
6-10 months
What exercises are recommended by the NHS for hamstring strains?
Hamstring stretch Buttock stretch Supine Walk out bridge Supine single limb chair bridge exercise single limb balance windmill touches with dumbbells
Explain the principles of the Nordic hamstring exercise
Partner exercise - leaning forward with someone resting on ankles. Asked to use their arms to buffer the fall and let their chest touch the surface and immediately push up to minimise concentric phase.
What are the advantages of the Nordic hamstring exercise ?
Can be done anywhere
Can be done entire team at once
Reduced injury risk- more effective
In the meta-analysis what were identified as the RFs - Hamstring strains?
Older age, previous injury of hamstring strain and increased quadriceps peak torque.
Explain model based image matching in relation to ACLs and its findings?
Excessive secondary movement - rotation and tertiary joint motion - AB and AD duction within 40ms of footstrike
- Abduction neutral at strike and then increased 10-13 degrees at 40ms
- External rotation of 5 degrees at footstrike and internally rotated to 8 degrees at 40ms
- knee externally rotated again 17 degrees afterwards
Explain the theory about subluxation - cause or effect?
- valgus strain on MCL and lateral meniscus
2, Compression and quadriceps contraction - posteriort translation of lateral femoral condyle and rupture of ACL at 40ms - Without ACL- medial femoral condyle translated posteriorly–> tibial external rotation.
Explain the relationship between hamstrings, quadriceps and the strain on the ACL
Movement of the knee through a flexed to extended position - passively or actively increases ACL strain
When knee is almost fully extended strain on the ACL is greatest.
- At this orientation - isolated quadricep contraction increases strain
- Isolated hamstring contraction neither increases or decreased strain
Quadriceps contracting and hamstrings not - ACL is experiencing highest strain making it vunerable to injury
Explain the principles behind an ACL repair
Injured ACL is removed
Drill holes in femur and tibia
Pass graft through the tunnels
Fix graft with screws
Explain the double bundle and its repair technique
Anteriomedial bundle - translational,
Posteriomedial bundle - rotational
Can use a hamstring graft for repair
Double bundle repair can be done arthroscopically leaving very little scars.
Explain the difference between stability and laxity
How can each be tested?
Stability involves the contribution from muscles
Laxity - just testing the function of the ligaments
- can be rotational or linear
Laxity can be tested using Arthrometer KT100- given a certain fixed amount of stress and then measure the displacement - higher displacement higher laxity
Stability can be tested using a dynamic functional test- good for gross evaluation but not for in vivo motions
How is the BPB graft obtained and what are the potiental consequences of this?
Open knee surgery - wound at anterior knee may cause loss of sensation numbness or discomfort in knealing
What are the methods that can be employed to help healing of a hamstring graft?
Bone morphogenic proteins Mesechymal stem cells Calcuim phosphate cement Low intensity pulsed ultrasound Shock wave therapy US guided shock wave therapy
What is the main mechanism for ACL injury and what is injured in this?
How does this vary from the unhappy triad?
Knee in toe out
MCL, ACL and lateral meniscus
~Unhappy triad is medial meniscus and ligament and ACL
What percent of ankle sprains are each type and what is injured in each?
- Lateral (85%) - Anterior talofibular ligament, posterior talofibular ligament and calofibular ligament
- Medial (5%) - Deltoid ligament
- High ankle sprain (10%) - interosseus membrane and sydesmotic ligament.
What is the issue with high ankle sprains?
Rarely diagnosed
How are each of the ankle sprains caused?
Lateral - inversion and supination
Medial sprain - eversion and pronation
High ankle sprain - Dorsiflexion and inversion
What muscles should aim to be strengthened during ankle sprain rehab?
Fibularis brevis and longus - main evertors of the ankle
What is the grading for ankle sprains?
Anatomical - based on the ligaments involved
1) AFTL only
2) AFTL and PFTL
3) AFTL, PFTL and CFL
Severity
- Mild/ partially stretched
- Partial tear
- Completely torn
Why are eversion sprains more rare?
Fibular extends down to lower position in the form of the lateral malleolus providing an actual block
What is used to decide when to XR a ankle or foot?
What is good about these?
Ottowa Ankle/foot rules
They have a high sensitivity and good specificity - sensitivity means few false negatives - picks up most #s
What is important to remember about the diagnosis of ankle sprains?
Cannot give a specific diagnosis for 5 days post injury