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[A 20-year follow-up study of internal gonarthrosis after tibial valgus osteotomy. Single versus repeated osteotomy].

PURPOSE OF THE STUDY
The study defines the conditions in which valgus osteotomy can produce satisfactory 20-year results in cases of medial unicompartmental gonarthrosis.


MATERIAL AND METHODS
Among a series of 93 osteotomies, 35 knees were followed up for 20 years. Changes to the medial and lateral femorotibial compartments were identified on forced varus and valgus radiographs and on foot standing Xray. The condition of the patellofemoral articulation was defined on patellofemoral aspect at 30 degrees flexion. Frontal axial deviation was monitored by preoperative and postoperative standing film (first year, 10 years and 20 years).


RESULTS
Only 25 knees still had a satisfactory functional result (no mechanical pain). However, among these 25 knees, 13 good functional results were obtained after a new osteotomy performed between the 7th and 15th year after initial surgery. There were therefore only 12 knees which managed to reach 20 years with their original tibial osteotomy. Radiologically, in absence of adverse hypercorrection (greater than 6 degrees valgus), there was no deterioration or only small deterioration of the lateral femorotibial compartment at 20 years even among the knees which had undergone two tibial osteotomies.


DISCUSSION
Osteotomy rarely avoids the problem of recurrent deformity which appears fairly rapidly (before 10 years) when initial correction is poor (below 3 degrees valgus). However, even correction of between 3 and 6 degrees valgus was not immune to recurrent varus deformity at long term (20 years): among knees with goniometry between 3 degrees and 6 degrees at the one-year postoperative review, 20 were still within this group by the 10th year; but only 9 knees were still in this range at 20 years.


CONCLUSION
Whilst longevity of a tibial osteotomy seems limited, a second valgus tibial osteotomy can reproduce the same effects as the first (no pain and preservation of the medial femorotibial compartment): 13 repeated tibial osteotomies produced a good result at 20 years follow-up which suggests that medial femorotibial gonarthroses in younger patients can be treated conservatively.