The minimally invasive surgical local osteo-enhancement procedure (LOEP) to deliver a resorbable, tri-phasic calcium-based implant material to address bone loss and strengthen the proximal femur

Abstract

With global population growth and advancing age, fragility fractures present a major healthcare challenge that current approaches have not resolved. Although pharmacological agents have been shown to reduce fragility fracture risk, there remain unmet needs in clinical care, especially for patients at imminent risk of hip fracture, given the delay between treatment initiation and observed protective effect. This gap suggests a need for novel approaches, including hip procedures that strengthen bone locally and quickly. The purpose of this report is to describe a procedural technique that has been shown in ex vivo and clinical studies to rapidly enhance proximal femur biomechanical properties and leads to new bone formation. Local osteo-enhancement procedure (LOEP) is a minimally invasive surgical procedure to address bone voids in the pelvis and extremities, including in the proximal femur, due to trauma and disease such as osteoporosis. After surgical preparation of voids within the femoral neck and intertrochanteric regions of the proximal femur, a resorbable, triphasic, calcium-based implant material, AGN1, is delivered to that site. Clinical studies demonstrate consistent implant material resorption, concurrent replacement of the material with bone, and a significant, durable increase in areal bone mineral density (aBMD). The procedural technique has been studied as a standalone procedure and as concomitant surgery taking place in the same operative session as the surgical treatment of a contralateral index hip fragility fracture. In the study of concomitant use, LOEP was reported not to disrupt the standard of care for mobilization and rehabilitation for hip fracture. The clinical studies completed suggest that the procedure demonstrates an acceptable safety profile and has the potential to reduce the incidence of hip fragility fractures.

Keywords: LOEP; augmentation; biomechanics; femoroplasty; hip fracture; osteo-enhancement; osteoporosis; prevention.

Figure 1

Illustration of the instruments and implant material components provided in the AGN1 LOEP kit. The instruments are used to access and prepare the site for treatment as well as to mix and inject the AGN1 implant material.

Figure 2

The left image (A) displays the patient in the supine position on the fracture table with internal rotation of the operative leg by approximately 20°. The right image (B) displays the setup after preparation, draping, and positioning for a fluoroscopy-guided AP image.

Figure 3

The left image (A) displays the patient in the supine position on the fracture table. A metallic, non-sterile instrument is being used to identify and mark the central trajectory in the AP plane, and the right image (B) marks the central position in the lateral plane. Both marks are prepared before prep and drape.

Figure 4

A local anesthesia injection is performed after prep and drape to localize and confirm the proper skin incision that is colinear with the projected lateral cortical entry. The fluoroscopic image confirms needle entry through the skin to the lateral femur, above the level of the most proximal portion of the lesser trochanter.

Figure 5

The guide pin is introduced through the obturator and tissue protector above the level of the lesser trochanter and towards the center-center position in both planes, as demonstrated by the fluoroscopic images.

Figure 6

The cannulated drill is introduced over the guide pin under direct fluoroscopic visualization and advanced to the base of the femoral head.

Figure 7

The working trough is introduced through the tissue protector, and the cutout tip is seated within the lateral cortical access portal, as demonstrated by the red arrow on the fluoroscopic image.

Figure 8

The debridement tool is introduced over the working trough and into the apex of the enhancement site. The fluoroscopic image shows the debridement tool positioned within the proximal femur.

Figure 9

The illustration sequence demonstrates the debridement steps from central loosening (A) to peripheral roughening (B,C) and to the final probing step to define the boundaries of the enhancement site to be injected (D).

Figure 10

The suction/irrigation device is inserted over the working trough, and the location within the enhancement site is confirmed by fluoroscopy.

Figure 11

The suction/irrigation device is inserted over the working trough and confirmed within the enhancement site by fluoroscopy. During two cycles of suction and irrigation, the fat and loose nonstructural bone elements are removed.

Figure 12

The prefilled injection cannula is inserted over the working trough, and its position within the enhancement site is confirmed by fluoroscopy. Once confirmed, the working trough is removed prior to beginning to fill the enhancement site to facilitate venting.

Figure 13

The sequence of illustrations and fluoroscopic images demonstrates the filling of the enhancement site with AGN1 from proximal to distal gradually over several minutes.

Figure 14

Demonstrates the guide pin and drill entering the lateral cortex above the level of the most proximal portion of the lesser trochanter in the lower risk area for stress risers.

Figure 15

Illustration of positioning techniques to obtain the lateral fluoroscopy views for patients undergoing contralateral hip replacement for fracture repair prior to LOEP. Lateral views can be achieved via the frog leg position (A) or a cross-table acquisition with the contralateral hip flexed at 90° (B).