4: Anterior and Medial Thigh and Knee Flashcards
femoral shaft fractures
- in previously healthy and young adults, femoral shaft fractures normally due to high-velocity trauma
- in elderly, w osteoporotic bones or in pt w bone metastases/other bone lesions e.g. bone cysts, fractures can occur following low-velocity injuries
- musculature acts as deforming force following fracture
- proximal fragment often abducted due to pull of gluteus medius/minimus on greater trochanter and flexed due to action of iliopsoas on lesser trochanter
- distal segment adducted into varus deformity (action of adductors e.g. magnus and gracilis) and extended due to pull of gastrocnemius on posterior femur
how can a patient with a femoral shaft fracture present
- tight swollen thigh
- blood loss in closed femoral shaft fracture is 1000-1500ml and the patient may develop hypovolaemic shock
- blood loss in open fem fratures can be double amount
- complications due to involvement of neurovasculature is rare
how are femoral shaft fractures treated
surgical fixation
causes of distal femoral fractures and consequences
- younger pt = high-energy sporting injuries often w significant displacement of fracture fragments
- elder pt = in association w osteoporotic bone; usually a fall from standing
-
popliteal artery may become involved if there is significant displacement of fracture
- therefore careful assessment of neurovascular status of limb before and after reduction of fracture = essential
tibial plateau fractures
- tend to be high-energy injuries
- usual mechanism is axial (top to bottom) loading w varus or valgus angulation (abnormal medial or lateral flexion load) of knee
what do tibial plateau fractures affect
articulating surface of the tibia within the knee joint
- unicondylar or bicondylar
- fractures affecting lateral tibial condyle = most common
- articular cartilage is always damaged and despite careful approximation of fracture fragments, most pt = degree of post-traumatic OA in affected joint
what can tibial plateau fractures be associated with
meniscal tears and ACL injuries
what can cause patellar fractures
- direct impact injury e.g. knee against dashboard in car crash
- eccentric contraction of quads
- mostly occur in pt 20-50
consequences of patellar fracture
- patella = largest seasmoid bone and its most important blood supply is via inferior pole
- on examination = palpable defect in patella and haemarthrosis (blood in joint)
- if extensor mechanism is disrupted meaning fracture completely splits the patella distal to the insertion of quads, patient will be unable to perform a straight leg raise
how are patella fractures treated
- displaced patellar fractures require reduction and surgical fixation
- undisplaced fractures can be protected whilst healing using splinting and crutches (usually do not require surgery)
what can be mistaken for patellar fracture
- in some people , patella is bipartite meaning in 2 parts
- this develops because there is a failure of union of secondary ossification centre w main body of patella
- normal anatomical variant
patella dislocation and subluxation
refers to the patella being completely displaced out of normal alignment
- sublaxation = partial displacement
what is the most common direction for patella to dislocate and why
laterally
- due to ‘Q’ angle between line of pull of quadriceps tendon and patellar ligament
how is patella usually held in correct position
- by contraction of inferior, almost horixontal fibres of vastus medialis (vastus medialis obliquus or VMO)
- specific role of VMO is to stabilise patella within trochlear groove and control tracking of patella when knee is flexed and extended
common cause of patella dislocation and affected populations
trauma: often twisting injury in slight flexion or direct blow to knee
- age group most commonly affected are athletic teenagers and the usual mechanism is internal rotation of the femur on a planted foot whilst flexing the knee (e.g. in a sudden change of direction during sports)
what factors can predispose patellar dislocation
- Generalised ligamentous laxity
- Weakness of the quadriceps muscles, especially the VMO
- Shallow trochlear (patellofemoral) groove with a flat lateral lip
- Long patellar ligament
- Previous dislocations
what does treatment of patellar dislocation involve
- extending knee and manually reducing patella
- immobilisation used whilst healing
- followed by physio to strengthen VMO
meniscal injuries
- most common type of knee injury
- typically occur during sudden twisting motion of weight-bearing knee in high degree of flexion
how would a patient with a meniscal injury present
- intermittent pain localised to joint line + knee clicking, catching, locking or sensation of giving way
-
swelling occurs as delayed symptom due to reactive effusion or none as menisci largely avascular (except at periphery)
- therefore, acute haemarthrosis is therefore rare and if present, indicates a tear in the peripheral vascular aspect of the meniscus or an associated injury to the anterior cruciate ligament - chronic effusion (increased synovial fluid) can occur due to synovitis (inflammation of the synovial membrane)
what would you find on examination of a patient with meniscal injury
- joint line tenderness and restricted motion due to pain or swelling
- mechanical block to motion or locking can occur w displaces tear due to loose meniscal fragments becoming trapped between articular surfaces
how are meniscal injuries repaired
- acute traumatic meniscal tears are usually treated surgically by either meniscectomy or meniscal repair
- increasing evidence that meniscal tears that result from a chronic degenerative process within the knee have a similar prognosis with conservative management as with surgery
varus
medial angulation of the distal segment
valgus
lateral angulation of the distal segment
collateral ligament injury
- common sporting injury e.g. in football usually resulting from acute varus or valgus angulation of knee
- also work together w PCL to prevent excessive posterior motion of tibia on femur
is MCL or LCL injured more commonly
- MCL injured more commonly than LCL but torn LCL has higher chance of causing knee instability because medial tibial plateau forms deeper more stable socket for femoral condyle than lateral tibial plateau
- so intact LCL = more critical role in maintaining stability of knee
what will a patient suffering collateral ligament injury experience
- pain and swelling of knee
- as initial pain and stiffness subside, knee joint may feel unstable and pt may complain of it giving way
unhappy triad
injury to the anterior cruciate ligament, medial collateral ligament and medial meniscus
- results from a** strong force applied to the lateral aspect**of the knee
- medial meniscus is firmly adherent to the medial collateral ligament, which is why it is also injured
which is injured more commonly ACL or PCL
ACL as it is weaker
how is ACL usually injured
as result of quick deceleration, hyperextension or rotational injury e.g. following a sudden change of direction during sport
- can also be torn by the application of a large force to the back of the knee with the joint partly flexed
how will a patient with ACL injury present
popping sensation in their knee with immediate swelling
- When the swelling has subsided, the patient experiences instability of the knee as the tibia slides anteriorly under the femur
how can a PCL injury occur
- ‘dashboard injury’ where the knee is flexed and a large force is applied to upper tibia, displacing it posteriorly (seen in collisions when proximal leg collides w dashboard
- can also be torn during football when player falls on flexed knee w ankkle plantarflexed
- tibia hits the ground first and is displaced posteriorly, avulsing the PCL - severe hyperextension injury can also avulse the PCL from its insertion on the posterior aspect of the intercondylar area
how can ACL and PCL injuries be detected
using the anterior and posterior drawer tests
- Lachman’s test = ACL