May 30, 2024

Septic arthritis is an orthopedics emergency that leads to the complete destruction of cartilage in the joint.

in the hip, it destroys the femoral head, neck, and also the acetabulum

Most commonly: Staphylococcus aureus or Streptococcus and others

Incidence

Hip >> Knee >> Elbow

Pathogenesis of Septic arthritis

  • Microorganisms enter joints by bacteremic spread from the subcutaneous abscess, otitis media, pneumonia, tonsilitis, or umbilical infections
  • By extension of local abscess or infections
  • By transfusion through umbilical catheters
  • After a contaminated needle passes to the vein
  • The infected umbilical cord was cut at birth in unhygienic conditions

Joint is inflamed and synovium is thickened, filled with pus, and swollen.

Synovial fluid contains > 50,000 PMNs/mm

Bacterias (seen in gram stain)

WBC breakdown:- release of proteolytic enzymes

Destroy articular cartilage

Once the articular cartilage is destroyed (no or little regeneration occurs), granulation across joint space creates collagen scar

In severely untreated cases

  • Secondary infection to the bone
  • Perforation to capsule
  • Excessive intraarticular pressure (AVN)
  • Destruction of cartilage:- Both subchondral bone exposed, fused –>Bony ankylosis

Clinical Features

  • Irritability, fever, and failure to thrive
  • Pseudoparalysis
  • Swelling
  • An abnormal attitude of joints

Lab Investigations

CRP, WBC Count Increases

ESR > 80mmHg

A blood culture may be positive

Principle of treatment

It should be distinguished from Acute osteomyelitis

  1. Early diagnosis with a high index of suspicion as that early removal of the pus from the joint is performed. Early treatment before extensive articular damage has occurred, can restore the joint to normal
  2. Higher antibiotics should be started and is changed according to culture and sensitivity
  3. Splint the joint to prevent deformity. Eg. In the hip, if not splinted properly in abduction, dislocation can occur
  4. Removal of pus and decompression of joint tension are vital measures to prevent cartilage destruction

Joint drainage

Articular damage begins within 8 hours hence there is real urgency in washing out joints( removing the bacteria and minimizing enzymatic degradation)

A different way of drainage of joints

  • Repeated needle aspiration
  • Arthrotomy
  • Irrigation of Hip joint

In the hip, joint repeated needle aspiration is not indicated as it is difficult to aspirate thick pus and joint tension may not be fully reduced

Instillation of antibiotics directly into joints may cause irritation. So, arthrotomy is preferred

Complications are seen if arthrotomy is delayed more than 3 days

Septic Arthritis in Infants

Etiology and cartilage destruction

  • Spread of infection from metaphysics to epiphysis as metaphysics penetrates growth plate up to age to 1-1/2 years
  • Proteolytic enzymes derived from leukocytes break down

Clinical Features

Two categories

  1. Very ill, febrile, refusing feeds, vomiting, convulsions ( attention is focused on systemic problems)
  2. Mild fever, no constitutional symptoms (Delay in diagnosis occurs)

Radiological Features

  • The first sign is swelling due to the collection of fluid in the joint and edema of soft tissue
  • Periostitis around the femoral shaft
  • Translucency:- Head/ Neck unossified and translucent

Risk Factors for developing sequelae

  • Diagnostic delay and late referral
  • Over-reliance to antibiotics
  • Lack of use of advancing imaging
  • Newborn with comorbidities
  • Increase incidence of CA-MRSA
  • Failure to do complete debridement

Sequelae between osteomyelitis and septic arthritis

Septic ArthritisAcute Osteomyelitis
AVNRecurrent sinus formation
Joint/ Bone deformityPathological fracture
ChondrolysisFocal bone loss
Loss of articular bonesSegmental bone loss
Length discrepancy
Growth plate injury

Choi classification modified by Hunka of post septic sequelae

TypeSub-typeResulting deformitiesRecommended treatment
IIaNormal appearancesObservation
IbAvascular necrotic changes
(mild COXA MAGNA due to hyperemias)
Containment procedure
(Like in Perthes)
II
(Involvement of epiphysis, physics, and metaphysics)
IIa
(Asymmetrical physeal closure)
COXA BREVA with/without head deformationContainment +/- trochanteric apophysiodesis +/- pelvis osteotomy
IIb
(Symmetrical physeal closure)
COXA VALGUS/VARANeck realignment procedure +/- fusion +/- LLD management
III
(Damage to femoral head)
IIIaCOXA VALGUS/VARA and femoral anteversion/retroversionProximal femoral osteotomy
IIIBPseudoarthrosis through the neck due to neck osteomyelitisValgus femoral osteotomy +/- bone grafting
IV
(Damage to femoral head and neck)
IVaPartial loss of neck<6 years: Modofoed Harmons’ operation
>6 years: Pelvic support osteotomy
IVbComplete loss of neck< 6 years: GT arthroplasty +/- pelvic osteotomy
> 6 years: Pelvic support osteotomy +/- lengthening
Choi classification modified by Hunka of post septic sequelae
Choi classification modified by Hunka of post septic sequelae
Choi classification modified by Hunka of post septic sequelae
Choi classification modified by Hunka of post septic sequelae

Surgical Procedures

1. Greater trochanter Arthroplasty

After the head and neck are destroyed, the trochanter can be placed into the acetabulum to function similarly to the femoral head

Femur angulated to create resemblances of the neck-shaft angle

Principles: Trochanteric apophysis that is covered by hyaline cartilage will remodel into a spherical shape

2. Harmon Operation

If the femoral head is destroyed but there is the remnant of the femoral neck covered by unossified hyaline cartilage, remnants are placed into the acetabulum

The upper end of the femur is split and the medial fragment is angulated in order to facilitate the placement of the neck of the femur into the acetabulum

3. Pelvic support osteotomy

In order to restore all the elements of deformity including joint stability, restoring adductor insufficiency and LLD

See also: Acute Hematogenous Osteomyelitis

See also: Chronic Osteomyelitis

See also: Subacute hematogenous osteomyelitis