Oxford Technique

PreoperativeUKA Oxford AP

 

Indications

- anteromedial disease

- patient points to anterior medial joint line only as source of pain

 

Pre-op x-rays

- AP and lateral

- Rosenberg to assess lateral joint

- long leg AP view to assess alignment

 

Pre-op examination

- must correct to neutral

- no releases are performed in a UKR

 

Operation (Oxford Meniscal Bearing)

 

Set up

- leg hangs over thigh bolster

- must be able to flex to 110o

- have bolsters on bed ready to change to TKR if required

 

Incision

- medial border of patella along medial border of patella ligament to medial border of TT

- this gives good exposure of medial compartment

- remove fat pad that is blocking view and meniscus

- inspect ACL, PFJ and lateral compartment to decide whether to proceed

- remove tibial / femoral / notch osteophytes

 

Tibial cut

- tibial EM jig

- centred over crest and second metatarsal

- depth of cut is very important as too much exposes weaker tibial bone and makes any revision more difficult

- usually takes 5 - 6 mm off the preserved posterior portion of the medial compartment

- this will mean that after insertion of a 2 mm tibial prosthesis, the insert should be 4 -5 mm thick

 

Vertical cut

- along the lateral margin of the MFC, medial edge of ACL

- ensure is passed completely posterior

- inferiorly is limited by tibial block

- want to ER the cut, as the mobile bearing will come laterally in extension

 

Horizontal cut

- protect MCL with retractors

- bony cut should come out as one piece

- trial off the inferior aspect of bone piece with opposite side trial

 

Posterior femoral cut

- femoral IM rod I cm anterior to notch and 5 mm medial towards femoral head

- this retracts patella, and guides flex/ext of femoral component and rotation

- insert tibial spacer to reconstitute tibial joint line

- insert femoral jig

- align with crest of tibia for varus / valgus, make parallel with femoral rod for flexion/ extension, and aligned with IM rod for rotation

- insert 2 x drill holes

- attach jig

- cut posterior femoral cut

- can now see better and remove all meniscus

 

Setting flexion / extension gaps and cutting distal femur

- insert 1 sphigot and ream

- in flexion insert spacer block (about 5 - 6 mm)

- in 20o extension insert spacer block (about 1 - 2 mm)

- the difference is how much more you have to remove from the distal femoral cut to balance gaps

- if difference is 3 mm, insert 3 sphigot and ream (has a stop)

- retrial gaps

 

Preparation of femur

- insert trials

- extend knee

- will see that need to remove portion of cartilage above femoral component to prevent poly impingement

- need to remove cartilage below implant

 

Preparation of tibia

- insert appropriate trial

- use special instrument to insure is flush posteriorly

- able to overhang 1 - 2mm antero-medially

- better to oversize than undersize to prevent tibial subsidence

- pin in place

- need to cut for keel

- must not penetrate anterior or posterior cortex or risk of fracture is too high and will need to convert to TKR

 

Cement prosthesis

 

Retrial

- trial spacer blocks to determine final size of meniscal bearing poly

- not too tight as don't want to overcorrect out of varus and overload the lateral compartment