Uniplanar medial opening wedge osteotomy
Equipment
Arthrex Locking Puddhu plate PDF
Arthrex ContourLock system PDF
Technique
Vumedi uniplanar Arthrex Puddhu plate technique
Vumedi uniplanar Arthrex Puddhu plate technique
Position
- patient supine on radiolucent table
Approach
- medial incision close to midline to incorporate into later TKA
- between tibial tuberosity and MCL
- L shaped incision of sartorius fascia
- identify and elevate pes anserinus, as may have to slide plate under
- identify and elevate MCL posteriorly
Exposure
- must expose and protect entire posterior tibia subperiosteally
- should be able to place finger entirely across tibia to proximal tibio-fibular joint
- must expose and protect patella tendon above tibial tuberosity
- place Langenbeck / Homan retractors anteriorly and posteriorly
Consider lateral hinge 2 mm K wire
- 10 mm from lateral cortex
- distal to proximal
Oblique Osteotomy
- entry is 4 cm distal to joint line
- osteotomy must pass above tibial tuberosity
- aiming for just above tip fibula head
- to 10 mm of lateral cortex to avoid lateral hinge fracture
- stay 2 cm below the tibial plateau to avoid intra-articular fracture
- ensure osteotomy is parallel to joint line to avoid altering slope
- ensure complete posterior cortex
Guide pins for osteotomy and checking posterior slope
Osteotomy to within 1cm of the lateral cortex
Opening of wedge
- slow
- stacked osteotomes / lamina spreader / wedged osteotomes
- ensure no change of posterior slope on lateral
Arthrex wedged osteotomes
Opening osteotomy with laminar spreader
Check correct alignment with drop rod
- goal lateral tibial spine
- Fujisawa point / 62% of the tibial plateau / lateral tibial spine
Stabilisation
- locking plates
- +/- autograft / allograft / synthetic bone graft
Arthrex Locking Puddhu plate PDF
Arthrex ContourLock system PDF
Biplanar medial opening wedge osteotomy
Retro-tubercle osteotomy
Advantage
- preserves patella tendon
- ? increases bony contact for healing
Disadvantage
- ? increases incidence of lateral hinge fracture
Technique
Vumedi biplanar medial opening wedge
Vumedi biplanar medial opening wedge
Complications
Infection 1%
Lateral hinge fracture 25%
Intra-articular fracture 3%
Delayed / nonunion
Compartment syndrome
Infection
- database of 822 osteotomies around the knee
- overall infection rate 2.8%
- superficial infection 1.6%
- deep infection 1.2%
- all successfully treated with debridement +/- plate removal
Lateral hinge fracture
Definition
Extension of the osteotomy into far cortex
May be associated with instability / delayed union / nonunion
Incidence
- 48 opening wedge HTO
- xray: incidence lateral hinge fracture 15%
- CT: incidence lateral hinge fracture 50%
Causes
- systematic review hinge fracture after OW HTO
- incidence 25%
- increased with opening > 11 mm
- 55 lateral hinge fracture
- Type I associated with lateral distance < 6 mm
- Type II associated with lateral distance > 9 mm
Classification lateral hinge fracture after OW HTO
Takeuchi classfication
- type I: extend into lateral cortex above proximal tibio-fibular joint
- type II: extend into lateral cortex below proximal tibio-fibular joint
- type III: extend into lateral tibial plateau
Delayed union / Nonunion
Nakamura et al Bone Joint J 2015
- 15 HTO with lateral hinge fracture
- increased delayed union with Type II
- increased delayed union / loss of position with Type III
Song et al Arch Orthop Trauma Surg 2020
- 132 OW HTO
- 24% incidence lateral hinge fractures
- time to union no hinge fracture: 5 months
- time to union hinge fracture: 7 months
- no difference in outcome
Prevention
10 mm from lateral cortex
Aim for tibio-fibular joint
Slow correction
Lateral 2 mm K wire - inserted distal to proximal 10 mm from lateral cortex
? Biplanar osteotomy
- 206 OW HTO, 71 had lateral K wire
- no K wire: hinge fracture 40%
- K wire: hinge fracture 17%
- 59 uniplanar osteotomy versus 44 biplanar osteotomy
- uniplanar osteotomy: hinge fracture 12%, plate irritation 19%
- biplanar osteotomy: hinge fracture 27%, plate irritation 32%
Management
Type I: limit weight bearing 6 weeks
Type II / displacement: lateral plate
Instability
- place a Richards staple / plate over lateral fracture site
Intra-articular fracture
Incidence
- 323 OW HTO
- intra-articular lateral tibial plateau fractures 3%
Causes
- proximal fragment too thin
- osteotomy too short / trying to preserve far cortex for stability
Osteotomy too close to articular surface
Prevention
- proximal fragment minimum 15 mm thick
- osteotomy within 10 mm of far cortex
- slow correction to allow stress relaxation
- ? keep in proximal K wires
Non union
Bone grafting and locking plates
- systematic review of 3000 OW HTO
- autograft: delayed / nonunion 2.6%
- allograft: delayed / nonunion 4.6%
- synthetic bone graft: delayed / nonunion 4.5%
- non locking plates: delayed / nonunion 3.7%
- locking plates: delayed / nonunion 2.6%
Other
Undercorrection / loss of correction
DVT/PE
Patella baja
Compartment syndrome
Harware removal