Surgical Technique

ApproachRevision TKR Tibial Lysis

 

Incision

 

Always use the most lateral scar

- blood supply comes from medial aspect

- want to avoid a large lateral flap of dubious quality

- cross transverse scars at 90o

- minimum 7 cm skin bridge

 

Options

- can do trial / sham incision down to capsule

- can perform skin expansion prior to surgery

- consider plastic surgical review for muscle flap

(medial gastrocnemius rotation flap)

 

Approach

 

Excise scar tissue

- recreate medial and lateral gutters

- recreate suprapatellar bursa

 

Patella eversion

- can just slide patella off laterally rather than evert

- put pin in tibial tuberosity to protect patella tendon insertion

 

Extensile exposures

 

1.  Quadriceps snip

 

2.  Quadriceps turndown

 

Rarely used

- risk AVN of patella

 

May consider if limited flexion

- lengthen quadriceps tendon

 

3.  Tibial tuberosity osteotomy 

- 6-10 cm long, 2 cm wide, 1 cm thick

- lateral periosteum intact / lever open laterally

- bypass osteotomy with stem

- need to wire back around the tibial stem

- place wires before definitive stem

- drill holes medially and laterally

- can use diverging screws as well

 

Removal of components

 

Remove poly

- implant specific tools

 

Careful removal implants to minimise bone loss

- thin, flexible osteotomes, micro-sagittal saw

- gigli saw

- can cut metal with carbide burr

 

Cemented femur / tibia

- separate at cement-implant interface

- remove cement later

 

Uncemented femur / tibia

- rarely have to cut base plate from keel (carbide burr)

- can perform TT osteotomy

- stacked osteotomes

 

Prepare Tibia

 

Reason

- sets joint line

- enables flexion extension balancing

 

Insert trial intramedullary stem

 

Find IM canal

- ream until appropriate diameter

- desired length

- place trial 

- set proximal cutting jigs off IM stem

 

Proximal tibial cut

 

Minimal tibial cut

- cut 1 - 2 mm off high side to preserve bone

- usually lateral side

- make resection for desired augment (5 or 10 mm) other condyle

- use jig

 

Insert trial tibia

 

Use offset as required

- ensures tibial component good fit on tibia

- tibial component not dependent on stem position

- ensure not internally rotated

- attach required augments

 

Recreate Joint line

 

Importance

- if rebuild tibial with augments and poly to correct joint line

- can rebuild distal and posterior femur to match

 

Revision TKR Severe Loss Tibial Bone StockRevision TKR Tibial Augments

 

Markers

- scar from meniscal remnant

- 10 mm above fibula head

- 30 mm below medial epicondyle

- use templated distance from medial epicondyle on other knee

 

Restore joint line with appropriate sized poly

 

Prepare Femur

 

Insert trial intramedullary stem

 

Find IM canal

- entry point important

- if too posterior will flex femur

- if too anterior will extend femur

 

Revision TKR Anterior Femoral Stem Entry

 

Ream until press fit

- insert desired length of stem

 

Distal femoral Cut

 

Distal cutting block on stem

- want to freshen surfaces minimally

- 1-2 mm off distal surface only

- consider distal femoral augments

- wait to trial extension gap to decide distal femoral augments

 

AP sizing

 

Posterior femoral condyles frequently deficient

- require augment posteriorly

- use anatomically sized femoral component

- template from other knee or use previous size from primary

- add augments posteriorly as

 

May need offset so femoral component sits on IM stem

 

Revision TKR Offset Femoral Stem

 

Rotation

 

Trans-epicondylar axis most reliable

- posterior femoral condyles may be more deficient laterally than medially

- set correct rotation

- freshen AP and chamfer cuts

 

Balancing

 

1.  Loose flexion and extension

- ensure poly thickness restores correct joint line

- increase distal and posterior femoral augments

 

2.  Loose flexion gap

- most common

- add posterior femoral augments

- use appropriate sized femoral implant

 

Revision TKR Posterior Femoral Augments

 

3.  Loose extension gap

- increase distal femoral augments

 

Distal Femoral Augment

 

4.  Tight flexion gap

 

A.  Reduce femoral distal augments / femoral component size

B.  Lower joint line by reducing poly thickness

- becomes loose in extension

- increase distal femoral augments

 

5.  Tight extension gap

 

A.  Correct joint line

- decrease distal femoral augments

B.  Joint line too high

- reduce poly to joint level

- create loose flexion gap, posterior femoral augments 

 

6.  Tight flexion and extension

- reduce poly thickness

 

Constraint

 

Usually determine constraint after bone defects dealt with and flexion / extension gaps balanced

 

1.  Collaterals Intact

 

Posterior stabilised sufficient

 

Revision TKR Posterior Stabilisation APRevision TKR Posterior Stabilised Lateral.jpg

 

2.  MCL deficient

 

Option A

 

Young patient MCL deficient

- High Post / Condylar constrained implant

- will eventually fail if don't reconstruct MCL

- young patient use CCK as internal splint and reconstruct MCL

 

MCL reconstruction

- achilles tendon allograft

- semitendinosus left attached distally

 

Option B

 

Rotating hinge 

- elderly patient MCL deficient

 

Revison TKR Hinge APRevision TKR Hinged Lateral

 

TKR HingeTKR Hinge

 

3.  Lateral instability

 

Causes

 

1.  Femoral component malrotation

 

2.  ITB deficient

- VVC

- brace for 3/12

 

3.  LCL deficient

- VVC + reconstruction

- semitendinosus / lars / allograft

- find centre of rotation on femur

- pass through drill hole in fibula

 

Patella 

 

Options

 

1.  > 10 mm bone remaining

- can resurface

 

2.  Ignore

 

Revision TKR Non Resurfaced PatellaRevision Patella

 

Patella tendon avulsion

 

1.  Repair

- Krackow suture secured around tibial post and washer

- staples

 

2.  Biological augmentation

- semitendinosus graft and gracilis

- achilles allograft

- LARS
 

3.  Immobilise in extension for 6 weeks

 

Revision TKR Staple Patella Tendon Insertion