2: Arthritis, Osteomyelitis & Acutely Swollen Joint Flashcards
what is the pathophysioogy of OA
occurs in the synovial joints
- progressive loss of articular cartilage and remodelling of the underlying bone
- active response of chondrocytes in articular cartilage and inflamm cells in the surrounding tissues
- release of enzymes from above cells break down collagen and proteoglycans = destroy articular cartilage
- exposure of underlying subchondral bone = sclerosis = remodelling = osteophytes and progressive loss of joint space
what are the risk factors of OA
- obesity
- age
- occupation trauma
- female
- FHx
what are commonly affected joints of OA
- Hips
- Knees
- Distal interphalangeal (DIP) joints in the hands
- Carpometacarpal (CMC) joint at the base of the thumb
- Lumbar spine
- Cervical spine (cervical spondylosis)
what are the 4 key X-Ray changes of OA
- L – Loss of joint space
- O – Osteophytes (bone spurs)
- S – Subarticular sclerosis (increased density of the bone along the joint line)
- S – Subchondral cysts (fluid-filled holes in the bone)
what is the typical presentation of OA
- joint pain and stiffness which is worse with activity and at the end of the day
- deformity, instability and reduced function of joint
what are general signs of OA
- bulky, bony enlargement of the joint
- restricted ROM
- crepitus on movement
- effusions around joint
t are
what are signs of OA in the hands
- Heberden’s nodes (in the DIP joints)
- Bouchard’s nodes (in the PIP joints)
- Squaring at the base of the thumb (CMC joint)
- Weak grip
- Reduced range of motion
- CMCJ
what is osteomyelitis
infection of the bone, either acute or chronic
what are the most commonly affected bones of osteomyelitis in adults and children
- adults: vertbrae
- children: long bones
what are the 3 main routes by which osteomyelitis can arise
- Haematogenous spread
- Direct inoculation of micro-organisms into the bone (e.g. following an open fracture)
- Direct spread from nearby infection (e.g. adjacent septic arthritis)
what are the most common causative organisms of osteomyelitis
- S. aureus
- streptococci
- enterobacter
- P.auerginosa (IV drug users)
- Salmonella (hx of sickle cell disease)
explain the pathophysiology of osteomyelitis
- bacteria enter bone tissue and express adhesins to bind to the host tissue proteins
- produce polysaccharide ECM through which pathogens are able to propagate, spread and seed
what can chronic osteomyelitis lead to
- devascularisation of the affected bone = necrosis and resorption of surrounding bone
- leads to sequestrum (floating piece of dead bone) which acts as resevoir for infected
- this cannot be penetrated by abx as it is avascular
- involucrum can also form where the region becomes encased in a thick sheath of new periosteal bone
what are risk factors of osteomyelitis
- DM
- immunosuppression e.g. long term steroids/AIDS
- excessive alcohol
- IV drug use
what is Potts disease
infection of the vertebral body and intervertebral disc by Mycobacterium tuberculosis
how does Potts disease present
- back pain +/- neurological features
- associated low grade fever
- non-specific infective symptoms
how does Potts disease progress
initially start in the intervertebral disc before spreading to the para-discal regions
- typically affecting the thoraco-lumbar region of the spine
what is the gold standard investigation for Potts disease
MRI
what is the management of Potts
- prolonged course of anti-TB medication
- surgical intervention may be required fro abscess drainage in case of extensive spinal destruction
what investigations/imaging will patients with suspected acute osteomyelitis undergo
- urgent blood tests, including a FBC and CRP
- blood cultures
- plain radiographs (poor accuracy and only visible signs from 7-10 days post infection)
what features may be visible on radiography of osteomyelitis
- osteopenia
- periosteal thickening
- endosteal scalloping
- focal cortical bone loss
how is diagnosis of osteomyelitis reached
MRI
- demonstrates bone marrow oedema 1-2 days post infection
- Nuclear medicine bone scans, e.g. PET-CT or scintigraphy, may also be used in diagnosing osteomyelitis, showing evidence of any active infection
what is the gold standard diagnosis of osteomyelitis
culture via bone biopsy at debridement
- ensure culture is checked for mycobacterium and fungal causes especially in susceptible cases e.g. immunosuppressed
what is the management of osteomyelitis
- if pt clinically well: long term IV abx therapy >4 weeks
- if pt deteriorates/progressive bone destruction seen then need surgical debridement and send samples for culture/sensitivity
what needs to be established when a patient presents with an acutely swollen joint
- onset
- site
- timeframe
- precipitating factors e.g. trauma, surgery
- level of pain
- ability to weight bear
- +/- fever, rigors, lethargy
- other joint involvement
- skin changes
- previous episodes
what is involved in the initial assessment of an acutely swollen joint
- A-E
- inspect: redness, swelling, skin changes
- feel: focal tenderness and evidence of joint effusion
- ROM?
- look for signs of other joint involvement or systemic signs
what investigations are done in an acutely swollen joint
- routine bloods: FBC, CRP, ESR (rheum), serum urate (gout)
- plain film radiographs
- joint aspiration!
what are you looking for in joint aspiration
- visual inspection: opacity, colour, presence of frank pus in the syringe
- can also be sent for WCC and microscopy, culture & sensitivity and light microscopy for crystals
what is gout and where does it commonly affect
- inflammatory arthritis caused by collection of mono sodium urate crystals in a joint
- caused by hyperuricaemia which leads to crystallisation of urate in joint
- classically affects 1st MTP joint
How is a diagnosis of gout made
- joint aspiration and microscopy which will show thin, needle shaped mono sodium urate crystals in the synovial fluid
- plain radiographs will often show only a soft tissue swelling
How is acute gout treated
NSAIDs
How are multiple episodes of gout treated
Prophylactic agents e.g. allopurinol for prevention
What is pseudo gout and how does it differ from gout
Inflammatory arthritis caused by deposits of calcium pyrophosphate crystals within the joint
- more likely to affect the proximal joints with knee and wrist being commonly affected
What are risk factors for pseudo gout (3)
- advanced age
- hyperparathyroidism
- hyperphosphatemia
How is pseudo gout diagnosed and treated
Joint aspiration and microscopy
- positively birefringent rhomboid-shaped crystals
- treat acutely with NSAIDs
What is the diagnostic criteria for RA
EULAR classification
- 4 categories: joint distribution, serology, symptom duration, acute phase reactants
- if >6/10 then definite RA
What conditions are included in spondyloarthropathies
- psoriatic arthritis
- ankylosing spondylitis
- reactive arthritis
- enteropathic arthropathy
What are spondylarthropathies classified as and what are they associated with
Seronegative conditions (RF negative) and associated with HLA-B27
How might spondyloarthropathies present
axial arthritis
- or affecting any joint as an oligoarthritis or monoarthritis
- enthesitis and dactylitis
