Fixation Stability and Bony Healing Following Open Wedge High Tibial Osteotomy
Condition: Opening Wedge High Tibial Osteotomy
Study type: Interventional

Summary: 
      Patients undergoing opening wedge high tibial osteotomy (HTO) will be randomized to standard
      or locking screw fixation of the osteotomy plate. Tantalum beads will be implanted around the
      osteotomy site in all subjects to facilitate RSA imaging which will then allow micromotion at
      the osteotomy site to be quantified.

      Primary Objectives and Hypothesis

        1. a)to determine fixation stability of the Puddu opening wedge osteotomy plate secured
           with non-locking compared to locking screws. We hypothesize that plate fixation with
           locking screws will result in a significant reduction of micromotion between tibial
           segments prior to bony healing compared to the non-locking screw fixation.

           b)To determine the progress of bony healing. We hypothesize that increased fixation
           stability in patients with locking screws will facilitate early bone healing reflected
           by smaller micromotion over time compared to the non-locking screw patients.

        2. a)If there is improved stability with the use of locking screws, rehabilitation
           protocols following opening wedge HTO will be modified accordingly. We hypothesize that
           decreasing micromotion will reach the detection limit of the RSA setup (0.4 mm) earlier
           in the locking screw group than in the non-locking screw group.

           b)To evaluate the effect of the osteotomy on proximal tibial anatomy. We hypothesize
           that an open-wedge procedure might increase rather than decrease the tibial slope.
    

Detailed description: 
      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
    

Intervention name(s): High tibial osteotomy
Intervention type(s): Procedure
Intervention description(s): HTO
Other intervention name(s): open wedge
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Participant)
Primary purpose: Treatment
Keywords: Opening wedge high tibial osteotomy; Radio Sterometric Analysis; Locking screw fixation