Austin Moores Hip Hemiarthroplasty Surgical technique

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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.