Inclusion Criteria

Inclusion criteria:

1. First condition is that the benign tumor is located deeply in bones of extremities,
or pelvis, so we anticipate the difficulty to find the tumor and to assess the
adequacy of resection without the aid of computer-assisted navigation during
operation.

2. Second condition is when the violation of joint or growth plate is expected during
removal of tumor due to its close proximity to joint or growth plate.

In case of malignant bone tumor, the sufficient preservation of joint anatomy should be
required even with resection margin of 1.5 cm away from reactive zone of tumor. The
sufficient preservation of joint is defined when at least 1 cm subchondral bone is
remained after tumor resection, because 1 cm subchondral bone is required for fixation
with allograft in subsequent reconstruction. The sufficient preservation of joint is also
defined when articular surface is removed, but more than 50% of articular surface has to
be saved.

Exclusion criteria were

1. Patients who denied to perform navigation surgery after explanation of navigation
surgery protocol

2. Medically high-risk patients who could not withstand long surgical time for joint
reconstruction

3. Patients whose feasibility of joint preservation was not fulfill the above inclusion
criteria at initial presentation, although the tumor size was decreased enough to
fulfill the inclusion criteria in MRI after completion of neoadjuvant chemotherapy.