Title: Complications of High Tibial Osteotomy
Reference: Handal, E.G., Morawski, D.R., Santore, R.F., in Knee Surgery, 1993, Chapter 57
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
– 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, ï¿½undercorrectionï¿½ can be considered if less than 5 degrees have been achieved. ï¿½Excessive valgusï¿½ 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 ï¿½overcorrectedï¿½ by 3 degrees if you achieve 10.
– there is some rationale for overcorrecting ï¿½a bitï¿½ – 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 ï¿½overcorrectionï¿½ 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! Coventryï¿½s 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
– 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.
– 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