THA
Heterotopic Ossification
Definition
Extraskeletal bone formation in periarticular tissues
- HA crystals within osteoid matrix
Different to calcification
- osteoid matrix laid down
Types
1. Myositis Ossificans
- post traumatic
DVT / PE
ANZ Working Party on the Management and Prevention of Venous Thromboembolism 2007
Note
Top 6 conditions associated with DVT
- stroke
- THR
- multi trauma
- TKR
- hip fracture
- spinal cord injury
Not one of the 12 doctors was an orthopaedic surgeon
Agents
Heparin / LMWH / fondaparinux
- confirmed effectiveness
Consent
THR Complications
Early
Infection (1% risk deep infection)
Wound Haematoma
Bleeding / Transfusion
Dislocation (2 - 3% recurrent)
NVI
Fracture
DVT/PE (Fatal PE 1/1000 with chemoprophylaxis)
LLD (average 1cm, stability more important)
Medical complications
- pneumonia, UTI, CVA. IHD
Death
Late
Limp (LLD, 1 year with anterolateral approach)
Painful THA
Aetiology
Intrinsic
Infection
Loosening
Thigh pain in uncemented
- micro motion at distal end of stem
- modulus mismatch
Stress fracture / insufficiency fracture
- pubic rami, sacral
Intra-operative fracture
Prosthesis failure
Subtle instability
Extrinsic
Nerve Injury
Epidemiology
Primary THR 1%
Revision THR 3%
DDH 5%
Sciatic nerve 90% of nerve palsy
Other
- femoral nerve
- CPN
- ulna / radial nerve from positioning
Aetiology
Direct
Laceration
- exposure / sciatic and superior gluteal nerve
- drill reamer / obturator nerve
- spike of cement / obturator nerve
Leg Length Discrepancy
Issue
Most common reason for litigation against orthopaedic surgeons in THR
Usually from lengthening
Complications of LLD
1. Nerve palsy
Sciatic nerve - tolerate average 4.4cm lengthening
Common peroneal nerve - tolerate average 2.7 cm lengthening
Lengthen by up to 15-20% of the resting nerve length
- but in reality is unknown and multifactorial
Infection
Risk factors
Patient
Advanced age
Immunosuppression - steroids / Rheumatoid / DM
Malnutrition - Lymphocyte count / Transferrin / Albumin
Vascular disease
Obesity
Poor skin i.e. psoriasis
Previous infection in joint
Infection elsewhere - i.e. UTi
Prolonged hospital admission
Revision surgery
Operative Factors
Preoperative
Intra-operative fracture
THR Acetabular Fracture
Incidence
Increased incidence with press-fit component
- especially if under ream
Prevention
Don't under-ream >1mm
In osteopenic bone
- line to line reaming
- i.e. ream to outer diameter of cup
This also avoids leaving gaps at floor
- very common if under-ream by 2mm
Dislocation
Incidence
2-3% of cases
- doubles with infrequent operator
- second most common reason for revision after loosening
Australian Joint Registry
- dislocation accounts for 14.8% of revisions
Positions
Posterior dislocation
- hip flexed, adducted, IR