Injectable bone substitute aids minimally invasive treatment for insufficiency fractures
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Bone voids, or bone marrow lesions, and other bone defects of the skeletal system are typically non-traumatic, slow-healing injuries that occur below the surface of the bone on weight-bearing joints.
Insufficiency fractures are often undiagnosed by physicians due to not being able to visualize these fractures on normal radiographs, patients often presenting with vague symptoms or physicians attributing the patient’s symptoms to preexisting conditions, such as osteoarthritis. Left untreated, insufficiency fractures often result in acute and/or chronic pain and reduced quality of life for patients. Bone marrow lesions (BML) have been linked with cartilage loss and the progression of OA. These lesions are often caused by either prolonged weight-bearing or repetitive and normal or physiologic stress placed upon weakened bone as opposed to a single traumatic event or injury. BMLs are detectable via fluid-sensitive, fat-suppressed MRI, but are not detectable on radiographs (Figure 1). Studies have also shown patients diagnosed with chronic BMLs are more likely to progress to a total knee arthroplasty.
Source: Wasik Ashraf, DO
Tactoset Injectable Bone Substitute (Anika Therapeutics) is a calcium phosphate-based biocompatible bone substitute material that incorporates proprietary hyaluronic acid (HA) from Anika. It is easily injected during minimally invasive surgery and is intended for filling bone voids or defects of the skeletal system that are not intrinsic to the stability of bony structure. The procedure is typically done in an outpatient setting or performed at an ASC.
Source: Anika
Components
The Tactoset Injectable Bone Substitute mixing kit includes a prefilled syringe of calcium phosphate powder and a glass syringe that contains a HA-based setting solution. The material set also includes four 1-mL Luer lock syringes and one female-female Luer lock connector. The prefilled syringes are combined in a sterile, closed mixing system and their contents form the injectable bone substitute mixture. The female-female Luer lock connector is used to transfer the injectable bone substitute mixture to four 1-mL syringes for use during the procedure.
The injectable bone substitute is injected into the target area via a cannula. The 11-GA cannula set includes three cannulas: one drillable outer cannula with removable drillable stylet (gauge: 3.05 mm or 11 GA; length: 1,100 mm); one inner cannula for end delivery (gauge: 2.41 mm or 13 GA; length: 134.39 mm); and one inner cannula for side delivery (gauge: 2.41 mm or 13 GA; length: 134.39 mm), as well as one push rod used to clear the material from the inner cannula. The cannula set is also available in 15 GA configuration (Figure 2).
Procedure eligibility
The injectable bone substitute provides a minimally invasive treatment option for patients with BMLs via percutaneous skeletal fixation. The goal of the procedure is to improve structural quality of affected subchondral bone and promote local bone remodeling, as well as prevent subchondral bone collapse and OA progression.
TKA is a proven treatment for patients with OA and the pain associated with BMLs, however, it is invasive and irreversible. Especially for younger patients, the long-term efficacy of TKA is often questioned because results may not last and early revision surgery may be necessary. Nonsurgical conservative treatment options should be considered the first line of defense to alleviate joint pain in these scenarios. Treatment options may include lifestyle changes, such as weight loss to protect joints from excess stress, pain relievers, corticosteroid or viscosupplementation injections into the joint space or physical therapy. If nonsurgical conservative treatment fails, physicians may recommend surgery.
The injectable bone substitute provides a minimally invasive alternative to TKA for patients who are diagnosed with a BML.
Enhanced flowability, injectability
The injectable bone substitute is a self-setting calcium phosphate-based injectable osteoconductive, biocompatible material. It is enhanced by HA, which is a naturally occurring substance in the human body.
With the addition of HA, the injectable bone substitute becomes highly flowable and easily injectable during minimally invasive surgery. The consistency of the product provides tactile feedback during injection so the surgeon can confirm filling of the bone defect. Upon injection, the bone substitute interdigitates into trabecular bone architecture to fill closed bone voids. It also supports cell-mediated regeneration of new bone as the material is resorbed.
OR setup
The OR setup should ensure the surgeon can access recent MRI done prior to and during the procedure. It is important for the surgeon to use the appropriate MRI sequences across all three planes (axial, coronal and sagittal) to pinpoint the precise location of the bone void before initiating the procedure.
The OR setup involves placing the patient on a radiolucent table in the supine position. The patient’s operating leg should be elevated to a position that allows for unobstructed radiographic views throughout the procedure. It is also necessary to ensure there is access to standard arthroscopic instruments and preoperative MRI images during the procedure.
Procedure prepping
To begin the procedure, first obtain appropriate fluoroscopic views to visualize the bone void. Then, determine the preferred trajectory to access the treatment area relative to ligamentous structures and prepare accordingly. Based on the location of the bone void, determine whether to select a side- or end-targeted inner cannula from among the delivery cannulas. The patient, who may be administered general anesthesia, is then prepped and draped in a sterile fashion.
It is important to carefully time the preparation of the injectable bone substitute mixture that will be used during the surgery. The bone substitute mixture should be readied by a surgical technician or scrub nurse at the start of the procedure when the surgeon is about 10 minutes out from needing the product. Another nurse should record the time as soon as mixing the substance begins.
The steps for mixing are as follows:
1) Open the packaging and transfer the contents to a sterile field using sterile technique. Loosen the stopper on each 1-mL syringe to break the seal;
2) Remove cap from the prefilled mixing syringe that contains the powder, but do not discard it. Remove cap from the glass syringe. Using the female-female Luer lock connector, attach the glass syringe containing the setting solution to the mixing syringe that contains the powder;
3) Hold the syringes vertically with the glass syringe on top. Inject the entire contents of the setting solution into the mixing syringe that contains the powder. Pull back the powder syringe plunger rod to ensure the contents are fully transferred;
4) Start a timer as soon as the powder and setting solution make contact with one another;
5) Remove the solution syringe and Luer lock connector. Recap the mixing syringe. Remove the plunger rod sleeve (do not discard it) and use the integrated mixing handle to mix the solution and powder by pressing and rotating the handle in and out of the material from top to bottom. Mix for 1 minute to ensure complete mixing;
6) Reattach the plunger rod sleeve over the integrated mixing handle. Remove the tip cap and attach a Luer lock connector to the mixing syringe. Expel residual air from the mixing syringe until a small drop of the injectable bone substitute mixture is ejected; and
7) Attach a 1-mL Luer lock syringe. Hold and pull back on the plunger rod of the 1-mL syringe to aid in transferring the bone substitute material. Fill the syringe to 0.9 mL and do not overfill the syringe. Fill any remaining syringes and repeat, as needed (Table).
Cannula placement, injection
While the bone substitute mixture is being prepped, the surgeon should drill the outer cannula into position under fluoroscopic guidance and confirm its positioning. It is important to avoid multiple drill attempts, which could result in extravasation of the material. Once the outer cannula is in place, remove the stylet and insert the appropriate inner cannula for side- or end-targeted delivery (Figure 3).
Source: Wasik Ashraf, DO
With the inner cannula in place, attach a 1-mL Luer lock syringe that contains the bone substitute mixture and inject the material into the bone void using constant pressure and rotating the cannula, if necessary. Repeat this process with as many of the remaining 1-mL Luer lock syringes as are needed to fill the bone void. Do not overfill the defect. Once the injectable bone substitute has been injected, inspect for extrusion and remove any excess material within 2 minutes following implantation (Figure 4). Next, remove the inner cannula and reinsert the stylet. Leave the cannula in place while the material sets for approximately 10 minutes, after which the cannula can be removed. Once this is complete, irrigate and close the incision site (Figure 5).
Postoperative care
Many surgeons provide their patients with crutches to use the first 3 to 5 days after the procedure and recommend weight-bearing as tolerated. Pain medication is often prescribed for up to the first 5 days after surgery. Commencement of physical therapy is typically recommended 7 to 10 days after the procedure to improve quadricep function and it should focus on core strengthening.
The injectable bone substitute offers some distinct advantages for treatment of BMLs. The closed mixing system allows for enhanced ease of use via reproducible steps and for a consistent formulation to be injected into the bone. The cannula system design allows a surgeon to easily switch intraoperatively between side-targeted or end-targeted delivery without having to remove and reinsert the outer cannula, which achieves increased intraoperative flexibility. The addition of HA to the material increases the injectability and flowability of the product within the patient’s existing bone structure, thus enhancing the intraoperative efficiency and user experience.
Injectable bone substitute provides patients who have BMLs with a minimally invasive treatment option that can improve their quality of life and allow them to return to normal activities quickly.
- References:
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- Tactoset injectable bone substitute; Anika Therapeutics Inc., AML 500-335_F_1UP PDF.pdf. Available at: www.anikaifu.com/wp-content/uploads/2020/06/Tactoset-IFU-Rev.F.pdf. Accessed April 16, 2021.
- Tactoset instructions for use; Anika Therapeutics Inc., AML 500-335. Available at: www.anikaifu.com/wp-content/uploads/2020/06/Tactoset-IFU-Rev.F.pdf. Accessed April 16, 2021.
- Tanamas SK, et al. Rheumatology. 2010;doi:10.1093/rheumatology/keq286.
- For more information:
- Wasik Ashraf, DO, is a fellowship trained orthopedic surgeon and director of sports medicine at Montefiore St. Luke’s Cornwall Hospital. He can be reached at Crystal Tun Healthcare, 219 Blooming Grove Turnpike, New Windsor, NY 12553; email: achristoforos@greenough.biz.
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