protrusio

Question 1

what is acetabular protrusio?

Answer 1

proximal and medial migration of the femoral head through the medial acetabular wall into the pelvis

Question 2

what are the causes of protrusio?

Answer 2

primary idiopathic and secondary protrusio
* inflammatory - RA and ank spond
* metabolic - paget’s disease, osteogenesis imperfecta
* genetic - marfan’s, Ehler’s danlos
* trauma - iatrogenic fracture, osteolysis post THR
* infection
* neoplasia - neurofibromatosis, mets, osteonecrosis acetabulum

Question 3

how would you assess a patient with protrusio

Answer 3

1. stiffness - from impingement
2. pain - secondary OA
3. exclude secondary causes and symptoms of them
4. previous management options tried

imaging:
- xray
- ct scan - looking for post and med wall defects and surgical planning

Question 4

Management of protrusio?

Answer 4

exhaust conservative treatments first

preoperative:
* imaging - xray and CT scan
* to evaluate posterior and medial wall defects
* to plan acetabulum placement
* exclude secondary causes
* anaesthetic review
* discussion in hip MDT with colleagues
* templating - to avoid offset and leg length discrepancy - restore proper hip biomechanics

intraoperative:
* performed by senior consultant - technically difficult
* careful hip dislocation - risk of fracture from deep socket.
* consider
* in situ neck osteotomy
* troch osteotomy
* extensive capular incision
* find sciatic nerve early as nearer joint than normal
* peripheral reaming
* minimal medial wall reaming as thin, bone graft floor and lateralise cup
* cementless acetabulum, bone graft and screws
* need to restore anatomy - if cup kept too medial there is impingement and loosening of the cup
* risk of coxa vara - leg length discrepancy

Question 5

why use bone graft instead of cement for protrusio?

Answer 5

• bone graft provides adequate biological buttress after incorporation and reduces the effect of thermal necrosis and osteolysis following exothermic curing of cement
• difficulty pressurizing the cup

Question 6

what are the risks associated with THR for protrusio?

Answer 6

• mot common loosening and medial migration of cup
• dislocation - if external rotators can’t reach GT for repair
• LLD
• acetabular fracture
• NV injury - particularly the sciatic nerve
• visceral injury - reaming thin medial wall - bladder, ureter and external iliac artery

Question 7

what are the results for a THR with protrusio?

Answer 7

Mayo clinic series in 2013 - reported:
* 89% cementless vs 85% cemented at 15yrs
* survivorship decreased when the prosthetic hip centre not restored to the anatomical centre by more than 10mm

Question 8

what is marfan syndrome

Answer 8

a congenital connective tissue syndrome due to a defect in the fibrillin-1 gene

Question 9

how would your treatment differ for marfan patient?

Answer 9

echo - for mitral valve prolapse and aortic root diltation