Austin Moore’S Prosthesis Surgical Technique

surgical technique of AMP
practical tips

1. Austin Moore’s Prosthesis
Technique
Vinod Naneria
Girish Yeotikar
Arjun Wadhwani
Choithram Hospital & Research Centre,
Indore, India

2. The philosophy
•Proximal fixation of the implant is crucial in the
success of the surgery.
•A tight fixation gives mechanical stability, and
allow the grafts in the fenestration to
consolidate, making it a self-locking device.
•This prevents over-loading of calcar – no
subsidence, no loosening, no failure.

3. Painful AMP
•An AMP fails on the table.
•Almost always the success of the surgery can
be predicted on the table.
•Be prepared for change to plan “B” or “C”.
•Be prepared for peri-operative calcar split.

4. Painful AMP- two primary reasons
•Inadequate Proximal Fixation
–Loose Prosthesis
–Calcar absorption
–Subsidence of the prosthesis
–Loss of varus alignment in the canal
•Acetabular cartilage erosion

5. Inadequate Proximal Fixation
•Not under our control
–Elderly
–Osteoporotic
–Wide canal
•Under our control
–Faulty operative technique
–Over reaming by improper Rasp
–Improper selection of Implant

6. Proximal Fixation
Tips & Tricks
•Pre-operative assessment of the Canal.
•Proper neck cut.
•Avoid comminuting Calcar Femoris.
•Save at least 1cm of neck at Calcar
•Insert canal finder from Piriformis Fossa
•In wider canal, avoid use of rasp.

7. Proximal Fixation
Tips & Tricks
•Select proper Implant which will fill the
proximal femur without increasing
comminution.
•Use a artery forcep in the prosthesis proximal
hole ( originally for extraction), for rotation
control during insertion.

8. Proximal Fixation
Tips & Tricks
•Impaction grafting:
–The most important area is the medial side near calcar.
Graft should be inserted when nearly half of the prosthesis
has gone inside.
–Fill the fenestrations of the prosthesis with bone grafts, as
the prosthesis advances in to the canal.
–The color of the implant should not over-hang on the
calcar.
–If done properly, it should rest on the neck and will
compress the grafts.

10. Posterio-lateral incision in lateral decubitous position

12. Quadratus
Gemeli
Piriformis
Sciatic Nerve
Gluteus Maximus
Cut the rotators close to the bone

13. Incise the capsule in “T” shape

14. Measure the size of the head

15. Superior lateral neck attched to Gr. Troch must be removed

16. Neck Cut

17. Piriformis fossa as entry point

19. Bone grafts harvesting

20. Selection of Implant
•Pre operative planning
•Intra-operative planning
•Correct head diameter
•Correct stem width
•Correct length of collar
•Cement
•Tension band wiring

21. Variables - Implant
•Head size
•Stem size
•Collar width
•Offset
•Neck – shaft angle
•Stem width
•Number & size of stem holes

22. Prosthesis design:
Proper Offset
Stem Diameter
Neck over hang
Fitness at proximal part

23. Half inserted prosthesis

24. Packing of graft in the medial wall

26. Graft in the distal hole

27. Grafts in the proximal hole

28. Final setting

29. Trochanteric index

30. Reduction by gentle pressure

31. Capsular repair

32. Post Op X-ray

33. Bone growth on medial side and in the fenestrations

34. AMP - summary
•Pre operative planning
•key to ensuring success is careful planning
•It’s all in the mind
•If you work on the surgery before hands on
mind in brief you can have both hand free and
brain free surgery

35. AMP - Summary
•Femoral head size
•Neck preparation according to AMP
•Entry point
•Reaming
•Pack the bone grafts in fenestrations.
•Impaction bone grafting

36. AMP - Summary
Post operative Regimen
antibiotic – 24 hrs
Abduction pillow
Bed side sitting – 24 – 48 hrs
Walking with support – 3
rd
– 5
th
day
Weight bearing as tolerated

37. Failure & Success - Amp?
•Most AMP fails on the table
•Subsidence and Loosening depends on
proximal fixation achieved on table
•Once the proximal locking holes filled with
bone – the prosthesis is stable & long lasting.
•Hypertrophy of medial side, lateral wall
hypertrophy, & new bone at the tip ensures
long term success.