Predicting Allograft Volume in Orthopedic Oncology: Hemielipsoid Formula vs Intraoperative Fluid-Fill Measurement

Condition(s) studied

Investigational drug(s) / intervention(s)

Hemielipsoid Formula-Based Preoperative and Intraoperative Bone Defect Volume Estimation: Preoperative bone defect volume is estimated by the operating surgeon using the hemielipsoid formula (V = 4/3 × π × a × b × c / 2) applied to routine preoperative CT imaging. The three principal dimensions of the anticipated resection defect are measured on axial, coronal, and sagittal CT reconstructions. Intraoperative defect volume is measured by saline cavity fill displacement as the reference standard. No additional procedures beyond standard surgical care are performed.

Study summary

Bone defects following primary musculoskeletal tumor resection are frequently reconstructed using structural allografts. Allograft availability is limited, and intraoperative waste due to oversized graft selection remains a practical challenge in orthopedic oncology. Accurate preoperative estimation of the expected defect volume is therefore critical not only for surgical planning but also for minimizing unnecessary allograft use.

This prospective study aims to evaluate the accuracy of the preoperative hemielipsoid formula in estimating bone defect volume after primary musculoskeletal tumor resection, using intraoperative fluid displacement as the reference standard. A secondary aim is to determine whether preoperative CT-based hemielipsoid volume calculation can reliably guide allograft selection and reduce intraoperative graft waste.

Patients scheduled for primary musculoskeletal tumor resection with structural allograft reconstruction at Sakarya University Training and Research Hospital will be enrolled. Preoperative defect volume will be estimated using the hemielipsoid formula (V = 4/3 × π × a × b × c / 2) derived from preoperative CT measurements. Intraoperative defect volume will be measured by fluid displacement as the reference standard. Agreement between methods will be assessed by Bland-Altman analysis and intraclass correlation coefficient (ICC).

Eligibility

Primary outcome measure(s)

• Agreement between preoperative hemielipsoid-estimated and intraoperative fluid displacement-measured bone defect volume — Intraoperative (Day 1)
  Assessed by Bland-Altman analysis and intraclass correlation coefficient (ICC) between the two volumetric measurement methods

Trial sites (1)

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