osteotomies for osteoarthritis

Valgus high tibial osteotomy

principles

·      assumes

·      primary cause of unicompartmental OA is mechanical

·      due to alteration of normal tibiofemoral alignment with overload

·      involves

·      realignment of deformity with reversal of excessive load onto unaffected compartment

·      usually indicated for medial compartment OA with varus deformity

·      involves creation of valgus alignment with lateral closing wedge

·      transfers weight to lateral compartment

indications
Patient

·      age < 65

·      physiological rather than chronological

·      not overweight

·      < 1.3 times ideal body weight

·      physically active

Knee

·      pain localised to involved compartment

·      relative preservation of ROM

·      flexion to at least 90o

·      maximum of 15o FFD

·      relative stability

·      minor lateral thrust not important

·      varus deformity not excessive

·      should be less than 15o

·      no internal derangement

X-ray

·      normal appearance of uninvolved compartment

·      severity of changes in involved compartment unimportant

contraindications
Absolute

·      inflammatory arthritis

·      multicompartment symptomatic disease

·      lateral subluxation of tibia > 1 cm

Relative

·      elderly

·      age > 70 yrs

·      overweight

·      > 1.3 times ideal body weight

·      excessive deformity

·      > 15o FFD or > 15o varus

·      severe patellofemoral arthritis

preoperative planning
X-ray

·      perform long standing AP film

·      extends from hip joint to ankle joint

Angles

·      use anatomical or mechanical method

Anatomical

·      draw anatomical axes of femur and tibia

·      centre of femoral shaft to centre of knee joint

·      centre of knee joint to centre of ankle joint

·      measure angle between them

·      calculate required correction

·      aim for 8-10o valgus

Mechanical

·      draw mechanical axes of femur and tibia

·      centre of femoral head to centre of knee joint

·      centre of knee joint to centre of ankle joint

·      measure angle between them

·      calculate required correction

·      aim for 2-4o valgus

Wedge

·      calculate size of wedge required

1.   rule of thumb

·      rough rule is 1 mm = 1o

·      assumes that tibia is 56 mm wide at site of wedge

·      must take magnification into account

2.   calculation

·      wedge height = tibial width x tan (angle required)

3.   x-ray

·      direct measurements can be transposed from x-ray

technique

·      closing wedge osteotomy between joint and tibial tuberosity

Incision

·      vertical incision

·      6 cm from lateral epicondyle

·      half-way between tibial tuberosity and fibula

Approach

·      proximal tibia exposed

·      involves detachment from tibia of lateral structures

·      tibialis anterior anteriorly

·      extensor digitorum longus posteriorly

·      deep fascia

·      extension of biceps insertion into deep fascia

·      exposure continued deep to patellar tendon

·      retractor inserted to visualise anterior tibia proximal to tuberosity and protect patellar tendon

·      proximal tibiofibular joint exposed

·      anterior capsule opened

·      common peroneal nerve protected

·      crosses neck of fibula 5 cm below proximal tip of fibula

·      may be formally exposed

Proximal tibio-fibular joint

·      prevents valgus correction

·      may be addressed by

1.   oblique transection of proximal third to allow overlap

·      may lead to damage to branches to EHL or TA

·      more commonly leads to compartment syndrome

2.   excision of segment of proximal fibula

·      similar drawbacks to above

3.   resection of fibular head

·      gives good acess

·      allows visualisation of nerve

·      requires reattachment of biceps and LCL

·      indicated for large wedge

4.   excision of tibiofibular joint

·      does not require reattachment of structures

·      indicated for smaller wedge

Wedge

·      osteotomy made 2 cm distal to joint line

·      too proximal with thin fragment may lead to fracture and AVN

·      too distal interferes with extensor mechanism

·      guide wire inserted across proximal tibia

·      parallel to joint

·      second guide wire inserted more distally

·      at predetermined distance from proximal wire

·      just contacting proximal wire at medial cortex

·      may use jig for this

·      positions checked with image intensifier

·      lateral wedge osteotomy performed

·      using oscillating saw

·      on ‘inside’ of guide wires

·      medial cortex should be left intact

·      wedge removed

·      using osteotome and curette

·      bone carefully removed posteriorly

·      wedge closed

·      may need to perforate medial cortex with drill

Fixation

·      may use

1.   cast only

2.   stepped staples

3.   plate and screws

4.   external fixator

·      cast or brace applied

·      depends on stability of fixation

Postoperative

·      immobilisation and partial weight bearing for 6 weeks

·      union checked with x-ray

·      gradual ROM and strengthening

·      return to activities at 3 months

Arthroscopy

·      no role in routine osteotomy

·      lateral compartment assessed radiologically

·      degree of medial compartment OA does not influence procedure or outcome

·      useful to assess and treat internal derangements

·      most common is meniscal tear

results
Functional

·      good pain relief

·      no loss of ROM

·      no restriction of activity

Long-term

·      survival is

·      75-90% at 5 yrs

·      60-75% at 10 yrs

·      survival can be predicted by

·      correction greater than or equal to 8o

·      patient’s weight less than or equal to 1.3 x ideal weight

·      if both these present, survivorship predicted to be 95%

Regenerative

·      regular arthroscopy post HTO has shown regeneration of normal-appearing hyaline cartilage once affected area unloaded

complications
Leg

Neurovascular

Peroneal nerve palsy

·      common (5-10%)

·      due to

·      pressure from cast

·      direct injury during operation

·      most recover

Vascular injury

·      injury to

·      popliteal artery

·      anterior tibial artery

·      uncommon

·      minimised by

·      keeping knee flexed

·      not dissecting into interosseous region

Soft tissue

·      wound haematoma

·      wound infection

·      compartment syndrome

Osteotomy

Infection

·      increased with plate or external fixator

·      minimised with staples

Fracture into joint

·      occurs because

·      proximal fragment too small

·      osteotomy incomplete medially

·      oblique proximal cut

Avascular necrosis of proximal fragment

·      uncommon

·      because proximal fragment too small

Union problems

·      delayed union or nonunion

·      may need

Failure to achieve desired correction

·      most common problem

·      desired correction rarely achieved if performed ‘by eye’

Progressive loss of correction

·      over number of years

·      does not necessarily cause pain

·      usually due to

·      undercorrection

·      progressive OA

Varus osteotomies

high tibial osteotomy

·      can be performed for lateral compartment OA

·      varus osteotomy to correct valgus deformity

·      medial closing wedge

·      problems

·      inherent valgus angulation of femur continues to exert valgus deformities on knee

·      resulting medial tilt of joint

·      may be indicated if valgus < 12o

·      otherwise supracondylar femoral osteotomy performed

·      indications and technique as above

·      medial approach with no need to address TF jt

·      aim to produce 0-2o valgus of tibiofemoral anatomical angle

·      results comparable

·      75% relief of symptoms at 10 yrs

·      complications similar

distal femoral osteotomy

·      indicated if valgus deformity > 12o

·      recreates horizontal joint line

·      approach varies

·      medial most often used

·      rigid fixation with blade plate indicated

·      similar results to tibial osteotomy