number.

#### *2.2. Indication*

To be eligible for reconstruction using a custom-made 3D printed intercalary titanium alloy implant with a highly cancellous surface, patients had to meet the following criteria: 


#### *2.3. Pre-Operative Planning and Production*

Custom-made 3D-printed intercalary tibia monobloc titanium aluminum vanadium alloy (TiAl6V4) implants with highly cancellous implant surfaces were planned on preoperative computed tomography (CT) scans (DICOM format, reconstruction matrix 512 × 512, slice thickness ≤ 1 mm). Osteotomy levels were defined using corresponding pre-treatment magnetic resonance imaging (MRI) studies and measured by distance to the adjacent joint line. 3D-CAD of the implants was performed by Implantcast Inc. (Buxtehude, Germany) as specified and approved by the operating surgeon before production using electron beam melting technology (EBM®) commenced (Figure 1). Implants were gamma-sterilized using the same parameters established for off-the-shelf implants. ≤

**Figure 1.** 3D-CADs based on computed tomography datasets (**a**) Patient #1: hollow implant with a highly cancellous implant surface and extracortical plates with supplementary interlocking screw options at proximal and distal implant-bone interface; (**b**) Patient #4: solid implant with a highly cancellous implant surface, small solid proximal and hollow distal stem and plates with interlocking screw options at the proximal and distal implant-bone interface.

#### *2.4. Implant Properties and Highly Cancellous Implant Surface (EPORE ®, Implantcast, Buxtehude, Germany)* plants were designed imitating the individual patient's bone geometry

All custom-made 3D-printed intercalary tibia monobloc titanium alloy (TiAl6V4) implants were designed imitating the individual patient's bone geometry and dimensions (Table 2).

**Table 2.** Mechanical Implant Properties.

