OrthoNet

HTO-complications1
Title: Complications of High Tibial Osteotomy

Reference: Handal, E.G., Morawski, D.R., Santore, R.F., in Knee Surgery, 1993, Chapter 57

Main Message

The complication rate of this surgery is high, and is often cited as a reason NOT to do it! These authors, however, believe that it is still a good operation.

Points of Interest

There is a long list of complications in the chapter - most significant are: peroneal nerve injury, vascular injury, malalignment, nonunion, and loss of correction

Malalignment
- the most frequent complication is related to malalignment secondary to undercorrection or overcorrection in the coronal plane.
- the MINIMAL alignment goal is 5o of anatomic valgus, although others would suggest that this is too little and you need to go for 8-10. At least, �undercorrection� can be considered if less than 5 degrees have been achieved. �Excessive valgus� is probably beyond 15 degrees. If you do buy into the idea that 10o of valgus is needed, then a patient who is normally about 7 degrees of valgus is going to be �overcorrected� by 3 degrees if you achieve 10.

- there is some rationale for overcorrecting �a bit� - the lateral ligaments are loose, and overcorrection overcomes this laxity; undercorrection leads to some subluxation of the medial compartment and continued destruction; and most importantly, the literature has consistently shown that knees corrected to neutral or undercorrected have poorer results and recurrent deformity as compared to those that were overcorrected.

* these authors suggest a final anatomic valgus of 8-10o, which represents a 3-5 degree �overcorrection� and correlates with a mechanical axis that falls lateral to the midline of the knee in most patients.

- valgus beyond 15o is associated with cosmetic deformity, patellofemoral tracking problems, gait disturbance, increased lateral compartment loading, and increased difficulty in converting to a TKA

- the most common complication of HTO is UNDERcorrection
- the degree of articular degeneration in the knee varies inversely with the ability to provide lasting pain relief and correction of the mechanical axis.
- people are beginning to see, however, that too much overcorrection is a bad thing too, and that there is a narrow zone of overcorrection that is optimal.
- it should also be noted that some authors have had good results despite only averaging 5 degrees of anatomic valgus! Coventry�s results are terrible in those with only this much correction though.

Johnson, Waugh - gait analysis
- showed that a valgus angle of 5 degrees still had 75% of the force going through the medial compartment.
- 5o of varus had 100% going through the medial compartment
- even at valgus angles of 25o, only a 50% reduction in medial loading occurred!
- ie. in a dynamic sense, we may have no clue as to what the realignment is really doing!

- the overly corrected knee is difficult to convert to TKA - this relates often to the change in length of the extensor mechanism - patella infera. Some have attributed the infera to the osteotomy being behind the tendon, leading to adhesions and contracture during immobilization in extension.

Common Peroneal Nerve Injury
- maintain the knee in flexion to allow it to fall back
- injury to the deep peroneal nerve is most common - safe zone 160 mm from the head.
- superficial peroneal nerve is more vulnerable distally

Vascular Injury
- either direct trauma or embolic phenomena in a vasculopath. Beware the patient with fem-pop calcification. These patients are probably best done without a tourniquet.

Compartment Syndrome

Delayed Union
- ensure that the medial osseo-periosteal hinge is intact
- there is a lower rate of nonunion when the osteotomy is performed proximal to the tibial tuberosity

DVT

Infection

Postop instability