Locomotor System Flashcards
What is the pathophysiology of septic arthritis?
Damage occurs within hours from cartilage degradation by enzymes and bone ischaemia from increased pressure
What is the cause of septic arthritis?
Most commonly is haematogenous spread of s aureus
Also can develop from osteomyelitis (esp neonates) infection spreads from metaphysis via transphyseal vessels
or direct inoculation
What are the most common causative organisms in septic arthritis?
S aureus (most)
Group B strep Gram -ve bacilli Group A step Strep pneumonia Neisseria gonorrhoea
Give examples of gram -ve bacilli
E Coli Salmonella Shigella Leigonella Pseudomonas
What is group A strep?
Streptococcus pyogenes
cause strep throat, impetigo
What is group B strep?
Streptococcus agalactiae
How does septic arthritis present in children?
Easily missed! Infants characteristically do not appear ill and may be confused with more common conditions eg transient synovitis and trauma
Fever (but 50% do not have)
Joint pain
Unwillingness to move affected join (eg limp / refusal to weight bear)
Hot, warm, swollen joint
What age group / sex does septic arthritis most commonly affect in children?
Preschool infants
Toddlers
Half present in first 2 years
Twice as common in M
Group A and B streptococcus are both beta-haemolytic. What are alpha-haemolytic streptococcus?
Streptococcus pneumoniae
Streptococcus viridans
(gamma- haemolytic = enterococcus)
What joints are most commonly affected in children with septic arthritis?
75% = lower limb
Knee > hip > ankle
Other 25% = upper limb
What investigations are performed for septic arthritis?
CRP, synovial WCC, and % of polymorphonuclear cells and lactate = best markers
FBC Synovial fluid examination Synovial tissue culture Blood culture PCR Tests for Lyme disease Immunology Imaging - plain radiographs, US, CT or MRI
What is the medical and surgical management of septic arthritis?
Surgical drainage and lavage of the joint
High dose IV abx
- Start before results of cultures are known
- IV for 2-3 weeks then switch PO for 2-4 weeks
1st line : flucloxicillin (clindamycin if allergy)
If MRSA suspected = vancomycin (or teicoplanan)
What would a plain XR show of a septic joint?
Usually normal initially
Widened joint spaces suggest effusion
Later signs:
- Subluxation / dislocation
- Space narrowing
- Erosive changes
When would an MRI be used in septic arthritis?
If diagnosis in doubt to exclude osteomyelitis
When would a CT be used in septic arthritis?
To image sternoclavicular and sacroiliac joints
What other management may improve recovery from septic arthritis?
Splintage
- In position of function
- Improves pain
- Allow inflammation to settle
Physiotherapy
Which joint has the worst prognosis in septic arthritis?
Septic hip - potential complication is complete destruction of femoral head and capsule, dislocation and 30% loss of growth of potential femur
What is developmental dysplasia of this hip (DDH)?
Previously called congenital dislocation of the hip (CDH)
The acetabulum is shallow and does not adequately cover the femoral head, leading to the hip joint being dislocatable or dislocated
What is the spectrum of DDH?
Wide spectrum of severity ranging from mild acetabular dysplasia with a stable hip, through more severe forms of dysplasia with neonatal hip instability, to established hip dysplasia with or without later subluxation or dislocation
Not always detectable at birth
Which hip is more commonly dislocated in DDH?
Left hip
Possibly due to more common left occiput anterior position in utero, limiting abduction of the left hip
What % of DDH are bilateral?
20%
List some RF for DDH (6)
1) Breech position (17x inc risk)
2) FH
3) Female sex (80% F)
4) Impaired limb movement eg oligohydraminous or multiple pregnancies
5) Prematurity
6) Neuromuscular disorders eg CP
How common is DDH? When is DDH usually picked up?
1-3% newborns
6-8 week baby checks
What is DDH associated with?
Tallipes
What is important to include in an examination for DDH?
1) Observation of symmetrical skin creases and leg length
2) Ortolani test
3) Barlow test
What is the Barlow test?
Pushing backwards to try and dislocate the hip
Feeling a clink as dislocatable hip slips out of the acetabulum
What is the Ortolani test?
Abduct the hips to try to relocate hip
Fingers push femur forwards into acetabulum
A dislocated hip will not abduct fully, and ‘clunks’ as it relocates into the acetabulu
What investigations may be performed in DDH?
Dynamic USS to assess hip stability and acetabular development in infants
US used in <4.5 months but pelvic X-rays used more in older infants and children - once femoral head ossification centre as developed
+/- CT / MRI
Athrography used peri-operatively when deciding between open and closed reduction
What is the Galeazzi sign?
Child lies supine with hips and knees flexed to 90 degrees and the height of each knee compared
How may DDH present in an older child?
Limited abduction when fully flexed
May walk on toes on affected side or present with a painless limp
How may bilateral DDH present?
Often a waddling gait with hyperlordosis
Difficult to diagnosis as:
- Absent Galeazzi sign
- Absent asymmetrical thigh and skin folds
- Absent asymmetrical decreased abduction
What is the management of DDH?
Early diagnosis important for good prognosis
Most unstable hips stabilise spontaneously by 2-6 weeks of age and any hip that remains dislocatable or pathologically unstable after this time requires prompt treatment
1st line = bracing
Surgery for those where bracing fails or in children diagnosed >6 months
What bracing is used for DDH?
A dynamic flexion-abduction orthosis (Pavlik harness) and splinting - used to maintain hip reduction
Start ASAP
Adjust harness as child grows and hip stabilises
How successful is bracing for DDH?
Very effective
If started within 90 days of age, only approx 5% need any further treatment
What are some risks of bracing for DDH?
Avascular necrosis
Temporary femoral nerve palsy
Pavlik harness contraindicated if child >4.5-6 months and when hip irreducible
What is the surgical management of DDH?
Closed reduction with adductor or psoas tenotomy (to decrease adduction contracture)
Followed by 3-4 months in a plaster cast or abduction brace
What are potential long term complications of DDH?
Premature degenerative joint disease and low back pain
DDH accounts for 9% of all primary hip replacements and 29% of those 60yr or over
Follow up required until hip clinically stable and normal imaging
List some causes of leg pain and limp in children
Organic:
- Transient synovitis
- Septic arthritis
- Legg-Calvé-Perthes disease
- Slipped capital femoral epipysis
- Trauma
- Osteomyelitis
- Neoplastic disease
- Systemic disease
Non-organic:
- Growing pains
What is the most common cause of a limp?
Transient synovitis
Important to distinguish from septic arthritis which can lead to obstruction of joint
What is transient synovitis?
Self-limiting condition in which there is inflammation in the synovial of the capsule of the hip joint
What age group / sex is transient synovitis more common in?
Boys aged 2-8 years
How does transient synovitis present?
Sudden onset of limp
No systemic symptoms
Single joint pain
No pain on passive movement
Often preceded by URTI
What do investigations show in transient synovitis?
Diagnosis of exclusion
Normal investigations and radiographs
Infection screen and joint aspiration performed to exclude bacterial infection
May show signs of preceding infection eg raised WCC, CRP, pyrexia
What does fever, swelling, erythema and tenderness in a child presenting with a limp?
Osteomyelitis
What may investigations show in osteomyelitis?
High CRP and WCC
Diagnosis using radiography, bone scan or MRI
What is Legg-Perthes disease?
Osteochondritis leading to avascular necrosis of femoral head
In which population is Legg-Perthes disease more common?
4:1 M:F
Ages 4-11 years, peak 4-7 years
What can Legg-Perthes disease follow?
Transient synovitis
How does Legg-Perthes disease present?
Initially painless
Pain and limp when feature occurs
How is Legg-Perthes disease diagnosed?
Radiography or MRI
In which population do slipped capital femoral epiphysis tend to occur?
Overweight teenage boys
How do slipped capital femoral epiphysis present?
Gradual onset of pain in groin or knee
How is slipped capital femoral epiphysis diagnosed?
Frog leg Radiography
What characteristics of pain suggest organic and inorganic causes of leg pain?
Organic:
- Day and night
- Interrupts play
- Unilateral
- Located in joint
- Limp or refusal to walk
Non-organic:
- Only at night
- Primarily school days
- No interference with normal activities
- Located between joints
- Bilateral
- Normal gait
What features of a history suggest organic and inorganic causes of leg pain?
Organic:
- Weight loss
- Fever
- Night sweats
- Rash
- Diarrhoea
Inorganic:
- Otherwise healthy child
What features on examination suggest organic and inorganic causes of leg pain?
Organic:
- Point tenderness
- Redness
- Swelling
- Limitation of movement
- Muscle weakness or atrophy
- Fever, rash, pallor, LN, organomegaly
Inorganic:
- Normal examination or minor changes such as coolness or mottling of leg
Where does pain in the hip refer to?
The knee - so must do full examination of leg and groin
What may children with transient synovitis go on to develop?
Reactive arthritis aka post-infectious arthritis
Form of arthritis that occurs during or shortly after extra-articular infection
How is irritable hip / reactive arthritis / transient synovitis managed?
Symptomatic - paracetamol and NSAIDs
Improvement occurs within days
What does reactive arthritis have a genetic association with?
HLA-B27
When does reactive arthritis occur and is it common in children?
Secondary to a GI or genitourinary infection
Not common in children
What is juvenile idiopathic arthritis (JIA)?
A group of conditions that present in childhood with joint inflammation lasting 6 weeks r which no other cause is found aged <16yr
How common is JIA?
One of the most common rheumatic diseases of children and is a major cause of chronic disability
How is JIA characterised?
Synovitis or peripheral joints with soft tissue swelling and effusion
What are the 3 main patterns of presentation of JIA?
1) Systemic
2) Polyarticular
3) Pauciarticular
How common is systemic JIA?
= Still’s disease
Rarest form of JIA
How may systemic JIA present?
Diagnostic puzzle as may not have joint symptoms initially
Child looks ill with:
- Remitting fever
- Variable rash
- Hepatosplenomegaly
- Anaemia
- Weight loss
- Abdo pain
How is systemic JIA confirmed?
Difficult
No characteristic laboratory findings, RF negative
Sepsis and malignant are often considered as ddx
How do children with polyarticular JIA present?
Painful swelling and restricted movement of both large and small joints
Commonly symmetrically distributed
Systemic features not prominent but poor weight gain and mild anaemia may occur
Morning stiffness common and young children may be irritable
What may be found on bloods of polyarticular JIA?
RF negative
Antinuclear antibodies may be positive
What is the prognosis of polyarticular JIA?
Good
Who does pauciarticular JIA usually affect?
Girls under the age of 4
What joints does pauciarticular JIA involve?
Fewer than 5 joints
Commonly knees, ankles and elbows
How does pauciarticular JIA present?
Joints identical to those in polyarticular JIA
Systemic symptoms minimal
How are polyarticular and pauciarticular JIA distinguished from eachother?
1) Number of joint affected :
- Pauciarticular = <5
2) Risk of chronic iridocyclitis:
- In pauciarticular arthritis, inflammation of the inner structures of the eye can lead to loss of vision and potentially permanent blindness
- Changes are only detectable by slit lamp examination this regular ophthalmological exams necessary
What are the main aims of JIA management? (3)
1) Reduce joint inflammation
2) Maintain funciton
3) Prevent deformity
How is joint inflammation reduced in JIA?
NSAIDs
Corticoseteroids in severe systemic disease unresponsive to other therapies
Steroid injection into selected joints (but should not be routine)
Hydroxychloroquine, penicillamine, gold injections, MTX and immune regulatory drugs in severe disease
How is joint function maintained in JIA?
Physical and occupational therapy
Daily exercises, hydrotherapy, day and night splints
