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
- 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
- Higher antibiotics should be started and is changed according to culture and sensitivity
- Splint the joint to prevent deformity. Eg. In the hip, if not splinted properly in abduction, dislocation can occur
- 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
- Very ill, febrile, refusing feeds, vomiting, convulsions ( attention is focused on systemic problems)
- 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 Arthritis | Acute Osteomyelitis |
|---|---|
| AVN | Recurrent sinus formation |
| Joint/ Bone deformity | Pathological fracture |
| Chondrolysis | Focal bone loss |
| Loss of articular bones | Segmental bone loss |
| Length discrepancy | |
| Growth plate injury |
Choi classification modified by Hunka of post septic sequelae
| Type | Sub-type | Resulting deformities | Recommended treatment |
|---|---|---|---|
| I | Ia | Normal appearances | Observation |
| Ib | Avascular 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 deformation | Containment +/- trochanteric apophysiodesis +/- pelvis osteotomy |
| IIb (Symmetrical physeal closure) | COXA VALGUS/VARA | Neck realignment procedure +/- fusion +/- LLD management | |
| III (Damage to femoral head) | IIIa | COXA VALGUS/VARA and femoral anteversion/retroversion | Proximal femoral osteotomy |
| IIIB | Pseudoarthrosis through the neck due to neck osteomyelitis | Valgus femoral osteotomy +/- bone grafting | |
| IV (Damage to femoral head and neck) | IVa | Partial loss of neck | <6 years: Modofoed Harmons’ operation >6 years: Pelvic support osteotomy |
| IVb | Complete loss of neck | < 6 years: GT arthroplasty +/- pelvic osteotomy > 6 years: Pelvic support osteotomy +/- lengthening |
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
