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Medial opening wedge high tibial osteotomy (OWHTO) offers an alternative to total knee arthroplasty (TKA) for patients with varus knee deformity. This report describes a novel, modular implant intended to occupy the wedge osteotomy space via a small medial incision to reduce surgical complications associated with patients having a BMI of 40 or greater (morbidly obese). The wedge-shaped, 3-D laser-sintered titanium alloy implant consists of interlocked components to be assembled in situ. Components were fabricated with a continuous laser-sintered surface lattice structure for bone ingrowth. The sliding resistance of a range of geometrically scaled lattices was assessed to determine the optimal lattice structure for initial implantation. The lattice structure had a 550mm surface opening (150mm internal pore size). Finite element models were created to evaluate three OWHTO scenarios including a medial restraining T-plate and implant combination, a T-plate alone as commonly seen clinically, and a model of only the implant within the osteotomy. Axially loaded models revealed implant stresses to be well below titanium fatigue strength, but the model of the T-plate alone indicated large plate and screw stresses comparable to the fatigue strength. Investigations are ongoing to assess multifunctional loading and experimental strain measurement. These results suggest this modular implant design may provide BMI > 40 patients an effective treatment option to early TKA.