High Tibial Osteotomy

Definition

  • Osteotomy of the proximal tibial metaphysis to redistribute weight away from an affected compartment
    • lateral closing wedge
    • medial opening wedge

History

  • First used by Jackson in 1958 for treatment of Osteoarthritis.

Biomechanics

  • normal load bearing
    • 60% on the medial side
    • 40% on the lateral side.
  • Coventry stated that the rationale was “to transfer the load from the more involved compartment to the less involved contralateral compartment”.
  • Recent change in thinking, because to unload the medial compartment excessive valgus is required – in the order of 25°
  • Coventry felt that articular cartilage could be restored if the medial compartment was unloaded, & there is ↑ in the joint space after osteotomy
    • but
      • biopsies from the medial compartment show that the repair response is consistently fibrocartilage, with little hyaline cartilage.
  • bone density on the medial side decreases post osteotomy, & cysts can regress.

A lateral closing wedge osteotomy

  • Shortens the leg
  • Shortens the distance from the tibial plateau to the tibial tuberosity
  • Create laxity of the lateral collateral ligament
  • Increase the Q angle

A barrel vault (dome) osteotomy

  • Not change leg length
  • Be more stable
  • Possibly scar the extensor mechanism

A medial opening wedge osteotomy

  • Lengthen the leg
  • Tense the medial collateral ligament
  • Move the patella insertion distally
  • Displace the tibial tuberosity laterally
  • fibula does not need to be touched.

Level of Osteotomy

  • usually made above the tibial tubercle
  • Osteotomies below the tibial tubercle
    • lower to heal
    • 3-4 times the nonunion rates of osteotomies than above the tibial tubercle.

Indications

  • Uni-compartmental osteoarthrosis in a young active patient
    • This will theoretically allow unlimited activity.
  • < 12° of valgus
    • >12° of valgus → supracondylar femoral osteotomy
  • A combined HTO & ACL reconstruction
    • can be performed in the rare patient
      • varus deformity,
      • isolated symptomatic medial compartment
      • Osteoarthritis & instability affecting ADLs

Contraindications

  1. Significant disease in other compartments
    • (mild to moderate patellofemoral osteoarthritis is not a contraindication)
    • Includes previous meniscectomy in contralateral compartment
  2. Inflammatory arthritis
  3. Flexion contracture more than 15°
  4. < 90° of knee flexion
  5. > 3 mm of medial bone loss
  6. > 20° correction needed
  7. Patient problems with cosmetic affect of valgus knee – particularly in women

Coventry’s Criteria

  1. Age less than 65/physically active
  2. Pain must correlate with radiological changes
  3. Radiographically normal lateral compartment
  4. Relatively mobile knee – less than 15° FFD, greater than 90° knee flexion
  5. Varus deformity less than 15°
  6. Stable knee
    • “If the tibia shifts laterally more than 1cm in a knee with varus, results are less certain”
  7. Internal derangement eliminated

Preoperative Assessment

  1. Clinical
    • Document adequate ROM
    • Ligament stability
    • Angular deformity
    • Normal ipsilateral hip function
  2. Radiographic
    • Knee
      • Normal weight-bearing knee series to evaluate for disease in other compartments
    • Full-length
      • three joint weight bearing series
        • for measurement of mechanical axis
        • tibiofemoral axis
  3. Arthroscopic
    • assess the other compartments of the knee
    • address meniscal pathology

Operative Technique

  • Operative Technique for Hight Tibial Osteotomy (HTO)

Complications

  • Early
    • Peroneal nerve palsy: 3-13%, overall rate of 10%
    • Under or over correction
    • Intra-articular fracture
    • Compartment syndrome
    • DVT – 1.2-13.5%
  • Late
    • Non-union
    • Early loss of correction
      • Coventry’s commonest complication was recurrence of varus.
      • He felt that in almost every case the cause was failure to overcorrect the varus knee to 7° or more of anatomical valgus
    • Conversion to TKR
      • success rates of conversion
        • approach those of revision TKR
        • with one study of 45 patients showing only 50% excellent results & 29% good results
      • Patella infera
        • commonly encountered
      • infection is higher also
        • around 4-5%

Results

  • Clinical results deteriorate with time
    • 5 year s
      • 80 – 90%
      • Noyes
        • 88% were satisfied at a mean of 58 months postoperatively & would have the operation again
    • 10 years
      • 60% good results
      • Coventry
        • 62% of patients had less pain than before the operation & 65% had better function.
        • No patient felt his function had been compromised by the surgery
        • Coventry felt that pain relief was due to unloading of overstressed subchondral bony trabeculae
      • Insall
        • 38% pain free at 10 years

HTO for lateral compartment Osteoarthritis

  • Poor results

Conversion to TKR

Problems

  • Patella eversion & height
    • tendency towards patella infera
  • Patellar tracking
    • lateral release is more common
  • Ligament balancing
    • Some authors recommend routine use of a PCL substituting design
  • Wound problems/skin incision
  • Proximal tibial deformity
    • may be necessary to use a lateral tibial augment, & if using a stem it may need to be offset.
    • Intramedullary jigging may not be as accurate;
      • consider using extramedullary jigging.
    • Resect minimal amount of lateral bone, by referencing off the medial side
  • Peroneal nerve scarring
  • Hardware removal

Results

  • Results similar to revision TKR.
  • Some authors have found results inferior to primary TKR. (Katz, Mont).
  • Medding, Keating & Ritter found in patients who had bilateral TKR, one side after a HTO, that results were equivalent.