High Tibial Osteotomy vs Uni Knee Replacement - Gavin Jennings 16/3/2004

1) High Tibial Osteotomy

Aim is to realign the limb and shift weight bearing force from the degenerated tibio-femoral compartment to the healthier one. The following will refer predominantly to medial disease

Historical

First reported in 1958( Jackson- 8 cases-lateral closing wedge ) and popularised by Coventry (Mayo Clinic 1965). Since then there has been much debate over patient selection and the technique likely to give the best outcome in terms of pain free functional knees and as transition to total knee arthroplasty.

Indications

Numerous papers have addressed the factors affecting the surgical outcome of tibial osteotomy. No two papers use the exact operative criteria, nor the same outcome measures nor intervals of assessment, but as a summary of the larger studies, the following criteria are thought to positively influence results:

· Preoperative planning, surgical technique and method of fixation (Jacob, Cass, Berman)

· Age< 50-55years ( Naudie 1999)

· Weight/ BMI less than 1.32 times ideal ( Coventry 1993)

· Preop ROM> 90 degrees

· Preop soft tissue balance and stability

· Remaining compartment disease

· Preop angulation of less than 12 degrees of valgus

· Degree of correction of 5-12 degrees

· Early range of motion, CPM

Techniques

Include the classic lateral closing wedge ( Coventry ) using staples with cylinder immobilisation. Based on concern for altered PFJ mechanics(baja) due to immobilisation, more stable fixations have been employed using screws and plates.

Likewise, different osteotomies have developed including-

Opening wedge ( with fixation methods such as - tricortical iliac crest+ fixation

-uniplanar/ circular ex-fix

-Puddu plate

Dome osteotomy

Percutaneous (giggli saw)

Complications

Over and under correction. Delayed and non union

Peroneal nerve injury ( up to 20%) Vascular injury (rare)

DVT

Outcome

Probably the best-known historical follow-ups with decent numbers are:

Coventry JBJS A 1993 87 cases- 89% 5 year survival, 75% 10 year survival

Insall JBJS A 1984 85% at 5years, 63% at10 years

For medial opening-

Heringou JBJS A 1987 90% 5 year, 45% 10 year survival

Most recent long-term study was by Sprenger( Florida ) JBJS March 2003. Mean follow up of 10.8 years. Similar overall results to previous studies but 90% 10-year survival in those who had a valgus angle of 8 to 16 degrees at one-year post op follow up

Conversion to TKR

Earlier reports have been contradictory in whether previous HTO was deleterious.

However Meding (Indiana) (JBJS September 2000) looked at thirty nine bilateral TKRs with previous unilateral HTO and found no discernible difference at 7.5 years

In summary, over the years the indication for osteotomy has narrowed considerably and now should focus on the active under 50(-60)year olds who are not overweight.

Techniques have also evolved and it has been suggested that this will improve survival.

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