Fixation Stability and Bony Healing Following Open Wedge High Tibial Osteotomy

For this pilot study, a total of 24 patients scheduled for opening wedge HTO who meet the inclusion criteria, have read the study letter of information and signed the informed consent will be randomized to osteotomy plate fixation with either non-locking screws (12 subjects) or locking screws (12 subjects). See flow chart 1.

Pre-operative Assessment

All subjects will undergo routine pre-operative assessment for opening wedge high tibial osteotomy which includes:

• Documentation of demographic data and medical history
• Subjective assessment of knee function using the Knee Injury and Osteoarthritis Outcome Score (KOOS)(11)
• Standard physical evaluation of the lower limb assessing range of motion, alignment, knee-related signs and symptoms
• Radiographs: standing anteroposterior hip-to-ankle;(2) lateral view; skyline patellar view at 30° of knee flexion; bilateral weight-bearing posteroanterior (PA) tunnel view at 45° of knee flexion
• Radiographic classification of arthrosis using the Kellgren scale(4)
• Measurements of mechanical and anatomical axes of the lower limb and calculation of proposed correction angles

Surgery In the operating room all subjects will undergo the following steps.

• Induction of general anaesthesia
• Percutaenous insertion into the proximal tibia surrounding the proposed osteotomy site under fluoroscopic guidance of 6 to 9 radio-opaque 0.8mm tantalum beads using a specifically designed gun. A standardized pattern of widespread tantalum bead distribution will be used. To avoid bead loosening caused by postoperative bone resorption, they will be placed a distance of at least 0.5 cm from the osteotomy line.
• RSA imaging to evaluate bead position
• Standard opening wedge HTO with the only variable being locking or non-locking screw fixation of the Puddu plate according to the randomization schedule. This procedure is routinely carried out under fluoroscopic and or radiographic control
• Second RSA imaging to obtain a reference film to assess stability
• Standard wound closure and application of hinged brace

Postoperative Treatment All subjects will undergo the routine opening wedge HTO post-operative rehabilitation protocol.

Follow-up Visits The times, number and content of follow-up visits for study subjects will not differ from the standard post-operative visits scheduled for all patients who have undergone HTO. However, because RSA imaging is specialized, this will be done at LHSC University Campus rather than at the Fowler Kennedy Sport Medicine Clinic (FKSMC). This will be communicated to patients in the letter of information. Study follow-up visits are at 2, 6,12 weeks, and 6 months after surgery.

At each study follow-up visit subjects will undergo:

• A subjective assessment of knee function using the KOOS
• A standard physical evaluation of the lower limb assessing range of motion, alignment, knee-related signs and symptoms
• Radiographs: standing anteroposterior hip-to-ankle
• RSA imaging in the AP and lateral planes simultaneously

Radiographs from each follow-up visit will be evaluated for classification of arthrosis using the Kellgren scale(4) and for measurements of mechanical and anatomical axes of the lower limb and calculation of the correction angle obtained with HTO. Translations between tibial segments will be calculated as previously described on the RSA images