Bone Marrow Needle Redesign

Bone marrow core biopsy and aspiration are two procedures clinicians utilize to diagnose hematological disorders. Core biopsy is the collection of an intact bone marrow sample for analysis of the tissue structure. Aspiration, on the other hand, is the retrieval of a fluid and cell sample for lab tests such as chromosomal & cell surface protein analyses and identification of the presence of viruses, bacteria, or fungi. The most popular device used for these two procedures is the Jamshidi bone marrow needle pictured below.

IMG: Jamshidi bone marrow needle

The inspiration for redesigning the bone marrow needle was based on feedback that the current devices on the market are highly uncomfortable to use. This is due to the high amount of force and torsion required to penetrate a patient's skin and bone tissue to access the bone marrow. Clinicians can develop long-term wrist and shoulder pain through repeated bone marrow biopsy & aspiration procedures. This led to the redesign, which allows users to utilize a one-handed grip for precision or two-handed grip for strength when collecting bone marrow samples.

Bone Marrow Needle Redesign - Sketch

Several ideas for the bone marrow needle redesign were sketched with two main considerations in mind: the device must be capable of both core biopsy & aspiration and must allow the user to more easily access the bone marrow. Some of the original design exploration sketches are shown below.

IMG: Bone Marrow Needle Redesign Exploration Sketches

These initial sketches led to the final bone marrow needle design shown below, which includes an attachment point for accessories necessary for core biopsy and aspiration as well as two side bicycle-like handle grips.

IMG: Bone Marrow Needle Final Design Intent

Bone Marrow Needle Redesign - Model

The bone marrow needle redesign was created in Fusion 360 and consists of the main extractor handle and needle along with four accessories including a safety cap, drilling attachment, aspiration attachment, and a core sample extractor.

IMG: Bone Marrow Needle Redesign Components

The user utilizes a one-handed grip to precisely and accurately align the main extractor needle and drilling attachment on the patient. The one-handed grip is used to initially pierce the patient's skin.

IMG: Bone Marrow Needle Redesign One-Handed Grip

The user utilizes a two-handed grip to apply more driving force to the main extractor needle and drilling attachment to easily pierce all the way through the patient's skin and bone tissue into the bone marrow for completion of the bone marrow biopsy and aspiration procedures.

IMG: Bone Marrow Needle Redesign Two-Handed Grip

IMG: Bone Marrow Needle Redesign Aspiration Procedure

Bone Marrow Needle Redesign Demo

VID: Removal of safety cap and insertion of drilling attachment

VID: Removal of drilling attachment and insertion of aspiration attachment

VID: Core biopsy sample retrieval after biopsy is complete

Main Extractor Handle & Needle

The main extractor handle was designed out of ABS plastic with a main body for single-handed use and protruding bodies for two-handed use. The protruding bodies are covered by four rubber segments each for improved grip and reduced chance of slippage during usage. A stainless steel extractor needle was designed to attach to the main extractor handle and is utilized in bone marrow core biopsy procedures to collect a bone marrow tissue sample.

IMG: Main Extractor Handle & Needle

The handle contains an exterior-threaded cylinder at the top that serves as a connection point for the accessories. The handle was designed to be secured together with self-tapping screws which are inserted through concentric bosses. An upstanding rib was added to the lining of the interior of the handle to prevent the two plastic halves from rubbing together.

IMG: Main Extractor Handle Connection Points & Upstanding Rib

The stainless steel main extractor needle inserts into the base of the handle and contains several protruding cylinders which were designed to be securely held in place by bosses extending from both handle halves.

IMG: Main Extractor Needle Attachment Points

Markings were added at half-inch intervals to the body of the main extraction needle for depth guidance. The distal cutting end of the extraction needle was designed to taper inwards and has a serrated tip for core biopsy sample retrieval. A ledge was added to the interior of the cutting end so a bone marrow tissue sample could be obtained with a straight pull of the main extraction handle and needle out of the body. This is referred to as "core-retention" technology in existing bone marrow biopsy devices.

IMG: Extractor Needle Depth Guidance Markings

IMG: Extractor Needle Distal Cutting End

Safety Cap & Drilling Attachment

The safety cap & drilling attachment both have an identically designed ABS plastic handle body. The safety cap was designed to be connected to the main extractor handle when it is either not in use or when collecting a bone marrow core biopsy tissue sample. The drilling attachment differs from the safety cap in that it contains a stainless steel drilling component utilized in bone marrow biopsy and aspiration procedures to initially access a patient's bone marrow.

IMG: Safety Cap & Drilling Attachment

An internally-threaded cylinder was added to both the safety cap & drilling attachment handles as a connection point to the main extractor handle. Concentric screw bosses were added to the handles for insertion of self-tapping screws to secure the two handle halves together. An upstanding rib was also added to prevent the two plastic halves from rubbing together.

IMG: Safety Cap Handle Connection Points & Upstanding Rib

IMG: Drilling Attachment Handle Connection Points & Upstanding Rib

The stainless steel drilling component inserts into the base of the drilling attachment handle. The drilling component contains a protruding cylinder which was designed to be securely held in place by bosses extending from both handle halves.

IMG: Drilling Component Attachment Points

The distal cutting end of the stainless steel drilling component was specially designed with a beveled tip to provide the user with improved piercing ability to more easily access a patient's bone marrow.

IMG: Drilling Component Distal Cutting End

Aspiration Attachment

The aspiration attachment was designed out of ABS plastic and has a cylindrical handle shape. A mount for a female luer lock was included for connection to a syringe. A stainless steel needle component was designed and attaches to the female luer lock mounted inside the main aspiration handle body and is utilized to collect fluid and cell samples during bone marrow aspiration procedures.

IMG: Aspiration Attachment

An internally threaded cylinder was added to the aspiration attachment handle as a connection point to the main extractor handle. A hole was placed at the top of the aspiration handle to allow for mounting of a female luer lock. Concentric screw bosses were designed for accommodation of self-tapping screws to secure the two handle halves together. An upstanding rib was also added to prevent the two plastic handle halves from rubbing together.

IMG: Aspiration Attachment Handle Connection Points & Upstanding Rib

The distal tip of the stainless steel aspiration needle was specially designed with three separate small holes to collect fluid and cell samples without retaining unwanted components of the bone marrow.

IMG: Aspiration Attachment Distal Needle Tip

Core Sample Extractor

The stainless steel core sample extractor was designed with a rubber tip for gripping and prevention of self-laceration on the main extractor needle distal cutting end. The opposite end of the core sample extractor has a specially designed smooth tip that is utilized to safely push a bone marrow tissue sample out of the main extractor needle after core biopsy has been performed.

IMG: Core Sample Extractor Attachment

IMG: Rubber Safety Tip

IMG: Smooth Distal End

Bone Marrow Needle Redesign - Design for Manufacturing

Design for Manufacturing (DFM) principles were applied throughout the creation of the bone marrow needle redesign. For all plastic parts, draft angles of three degrees were added to all surfaces, material thickness was kept consistent to reduce potential for sink and/or short fill, and the need for side-actions was removed to ensure the components could be manufactured in a cheap and quick manner during injection molding. The draft analysis for all plastic components is shown below.

IMG: Draft Analysis for Main Extractor Handle, Safety Cap, Drilling Attachment, and Aspiration Attachment

Bone Marrow Needle Redesign - Finite Element Analysis

Finite Element Analysis (FEA) was performed on the bone marrow needle redesign, specifically the main extractor handle and needle, to ensure the device could withstand stresses associated with use. Safety factors above 1.2 were considered acceptable.

The first study was performed to analyze whether or not the main extractor handle and needle could withstand forces applied with a one-handed grip. An extreme load case of 20 lbs of force was applied to the center portion of the main extractor handle while keeping the main extractor needle tip and body constrained in all directions.

IMG: FEA Main Extractor Handle One-Handed Grip Load Case

The resultant minimum safety factor of the first study was 4.93 with the main stress areas being concentrated around the lower extractor needle mounts. Since this is an extreme load case and the resultant minimum safety factor is well above the acceptable threshold, the bone marrow needle redesign will withstand any forces associated with the single-handed use case.

IMG: FEA Main Extractor Handle One-Handed Grip Safety Factor Results

IMG: FEA Main Extractor Handle One-Handed Grip Stress Results

The second study was performed to analyze whether or not the main extractor handle and needle could withstand forces applied with a two-handed grip. An extreme load case of 10 lbs of force was applied to each side handle while keeping the main extractor needle tip and body constrained in all directions.

IMG: FEA Main Extractor Handle Two-Handed Grip Load Case

The resultant minimum safety factor of the second study was 1.45 with the main stress areas being concentrated around the lower extractor needle mounts. There were other stress areas throughout the main extractor handle as well. Since this is an extreme load case and the resultant minimum safety factor is still above the acceptable threshold, the bone marrow needle redesign will withstand any forces associated with the two-handed use case.

IMG: FEA Main Extractor Handle Two-Handed Grip Safety Factor Results

IMG: FEA Main Extractor Handle Two-Handed Grip Stress Results

Bone Marrow Needle Redesign - Labor, Burden, and Materials Cost Analysis

A Labor, Burden, and Materials (LBM) cost analysis was performed on all components of the bone marrow needle redesign including packaging to determine the cost to manufacture the device. The cost of screws was obtained from McMaster-Carr, and the cost of the silicone rubber pieces was obtained from a silicone rubber wholesale company. The cost of cardboard for packaging was found from a cardboard wholesale company. The cost to injection mold all plastic parts, including packaging, and to machine all stainless steel parts was estimated using custompartnet.com. The LBM cost analysis for the main extractor handle and needle along with the four accessories and packaging is shown below.

IMG: Main Extractor Handle & Needle LBM

IMG: Safety Cap LBM

IMG: Drilling Attachment LBM

IMG: Aspiration Attachment LBM

IMG: Core Sample Extractor LBM

IMG: Packaging LBM

After completing the Labor, Burden, and Materials cost analysis of all of the components of the bone marrow needle redesign device, the total cost of the device was estimated to be $21.55.

IMG: Bone Marrow Needle Redesign Total Cost