Stephanie Benoit May 12, 2016

For patients with early stages of osteoarthritis, high tibial osteotomy (HTO) can be a useful treatment option. In the closing-wedge version of this operation, a wedge of bone is cut out of the lateral side of the tibia, whereas with the opening-wedge osteotomy, a bone graft is inserted in a cut made on the medial side. Both realign the knee and relieve pressure from the joint. The closing-wedge technique is more common, but recently, the opening-wedge osteotomy has become more popular since it is less invasive and possibly results in less deformity of the proximal tibia.

Analyzing the degree of proximal tibial deformity

Although HTO can be very effective in many patients, it sometimes becomes necessary to convert to a total knee replacement (TKR) procedure later on when the patient outgrows the effects of the HTO. However, due to the anatomical changes resulting from HTO, there may be difficulties when performing TKR afterwards.

Dr. Yasutaka Tashiro and his team at the Kyushu University, Japan wanted to investigate the differences in proximal tibial deformity caused by the two techniques used for HTOs, and how these effects could interfere in later TKR procedures. In 2015, Dr. Tashiro received a Mimics Innovation Award for this research.

In order to research the effects of each technique, they used Materialise Mimics to analyze the amount of proximal deformity in a range of virtual 3D knee models in patients with medial osteoarthritis or osteonecrosis. In particular, they looked at the angle between the anatomical and mechanical axis, the distance between the anatomical axis and the surface center of the cut in the proximal tibia, as well as the distance between the lateral cortex of the tibia and the stem of the tibia implant.

Closing- vs opening-wedge osteotomy: angle between anatomical axis and mechanical axis

The angle between anatomical axis (AA) and mechanical axis (MA) after the HTO simulation was measured. A positive angle represents varus alignment.

Closing-wedge versus opening-wedge osteotomy

The team noticed that in general, the risk of interference between the total knee replacement implant and the cortical bone was higher after a closing-wedge procedure, as opposed to an opening-wedge procedure, due to a lateral shift of the mechanical axis. The difference of the angle between the mechanical axis and the anatomical axis was negligible between both procedures. Overall, the differences between both osteotomies would likely be small with regards to later conversion to total knee replacement. Since the two surgical techniques could not be compared in identical cases in-vivo, using simulations of the procedures in Materialise Mimics was a major advantage in performing this study.

Closing- vs opening-wedge osteotomy: nearest points of tibial implant and inside wall of lateral cortical bone

The distance between the nearest point of tibial implant and inside wall of cortical bone was measured on the 3D software. In this model, the red area means the distance is under 5mm and the green area means the distance is over 8 mm.

About the author

Yasutaka Tashiro

Dr. Yasutaka Tashiro graduated as an MD from Kyushu University, Faculty of Medicine and obtained his PhD degree at Kyushu University in 2009. He then took on the role of a research assistant professor and in 2014 became a research scholar at the Department of Orthopaedic Surgery. His research focuses on orthopaedic surgery, sport and rehabilitation medicine and biomechanics. In 2015, Dr. Tashiro won a Mimics Innovation Award for his research on “Head to head analysis of closing-wedge versus opening-wedge high tibial osteotomy on tibia deformity using computer simulation”. Read more publications from Dr. Yasutaka Tashiro on ResearchGate.

Reference Kuwashima U, Tashiro Y, et al. Comparison of the impact of closing wedge versus opening wedge high tibial osteotomy on proximal tibial deformity and subsequent revision to total knee arthroplasty. Knee Surg Sports Traumatol Arthrosc. E-pub ahead of print on 26 March 2016.