High tibial osteotomy (HTO) is an established treatment for varus osteoarthritis of the knee. The correction can be achieved by lateral closed wedge HTO or medial open wedge HTO techniques. Both techniques can change the patella position which influences alignment of the patella. Patella infera may compromise the result of secondary total knee prosthesis. An analysis of the current literature was carried out focusing on changes of patella position after HTO.
A literature search was performed in PubMed which identified 15 relevant publications and the Insall-Salvati-index, the Blackburne-Peel-index and the Caton-Deschamps-index were analyzed.
Results after closed wedge HTO: the Insall-Salvati-index decreased in 7 papers, increased in 3 papers and was unchanged in 1 paper. The Blackburne-Peel-index increased in 5 papers and decreased in 2. The Caton-Deschamps-index decreased in 4 papers and increased in 2 papers. Results after open wedge HTO: the InsalI-Salvati-index decreased in 5 papers and increased in 2. The Blackburne-Peel-index decreased in all 7 papers and the Caton-Deschamps-index decreased in all 5 papers. The results of these studies vary significantly and there was a tendency to patella infera in both techniques. The Blackburne-Peel-index and the Caton-Deschamps-index may be biased by slope changes but the exact effect is not yet known. The Insall-Salvati-index seems to be independent of slope changes. The effect of different rehabilitation concepts on patella height is not known.
The clinical relevance of the observed changes in patella position must be clarified by prospective studies with strict criteria.