# Personalizing core decompression grafting technique for osteonecrosis of the femoral head: calculating the volume of bone resected and adjunct volume required to fill the defect

## TL;DR

This paper introduces a mathematical method to calculate the volume of bone removed during core decompression surgery for osteonecrosis of the femoral head, helping surgeons personalize the amount of graft material used.

## Contribution

A novel intraoperative mathematical method is introduced to calculate resected bone volume and required adjunct volume for core decompression.

## Key findings

- A mathematical method approximates the core decompression defect as two cylinders for intraoperative volume calculation.
- The method can be adapted for use with various expandable reamer systems currently available.
- A simple worksheet is provided to help surgeons determine the appropriate amount of adjunct material to use.

## Abstract

Osteonecrosis of the femoral head can be a debilitating disease leading to collapse of the femoral head and the subsequent need for a hip arthroplasty. Core decompression has emerged as a leading treatment to prevent collapse. Adjunctive therapies, such as bone graft, bone marrow aspirate concentrates, or synthetic bone substitutes are utilized to promote native bone regeneration. Determining the amount of bone resected and the volume of adjunct required is challenging, especially with newer minimally invasive reamers. Under- or over-filling the defect may impact progression of the disease or cause morbidity.

We introduce a mathematical method to be utilized intraoperatively to calculate the volume of bone resected during core decompression with an expandable reamer. This method approximates the core decompression defect as two cylinders using measurements that can be easily taken during the procedure and can be adapted for use with any of the expandable reamer systems available. Using this technique, surgeons can calculate the size of the defect created, which can be used to personalize the amount of adjunct delivered to each patient.

When adjunctive therapies are used with core decompression to treat ONFH, care must be taken when filling the core decompression defect to avoid under- or over-filling the defect, potentially increasing the risk of complications or reducing the efficacy of the procedure. We provide a simple worksheet that can be used by surgeons to help determine how much adjunct should be used.