REX Cement Stop™

Downloads:
	Demonstration Video: Insertion Instrument
	Instructions for Use (NL-EN)
	Surgical Technique
	Operatietechniek
	Reprocessing of reusable medical devices
	CE Certificate
	EC Design Examination Certificate
	Literature
	Brochure (EN) (revision is under construction)
	Declaration of conformity
	Product list
	Declaration of conformity (instrumentation)
	Product list (instrumentation)

Introduction: The REX Cement Stop™ is more than a cement restrictor. It is a cement stop, absolutely sealing the intramedullary canal before bone cement is introduced during surgery. This perfect cement restriction is the result of a newly developed technique, featuring a highly deformable gelatine bushing that adapts to any irregularities of the intramedullary canal. The gelatine bushing is centred by a PMMA locking device and expands under axial compression when the insertion instrument is positioned and activated in the intramedullary canal.
Producer: The REX Cement Stop™ is developed and produced by Spierings Orthopaedics B.V., Nijmegen, the Netherlands.
No cement leakage: Due to its unique design, the REX Cement Stop™ demonstrates an optimal performance. As a result of the expandability of the gelatine bushing the REX Cement Stop™ adapts to any irregular shape and forms a press fit within the intramedullary canal. The REX Cement Stop™ allows no cement leakage. Resists high cement pressures without migration: To achieve maximal interface strength, an optimal penetration of cement into the trabecular bone is needed. This increases the longevity of the joint reconstruction. The necessary pressure to achieve this penetration demands a considerable level of resistance of the implanted cement restrictor. The REX Cement Stop™ can resist high pressures without migration and therefore enables optimal penetration. No foreign material at revision: The REX Cement Stop™ features a new, advanced technology, but uses materials that are proven to be effective in thousands of patients; - Resorbable gelatine bushing: The traditional gelatine used in the bushing is highly biocompatible and resorbs fully within four weeks. - PMMA serrated pin, washer and locking rings: The PMMA locking device will integrate with the PMMA cement mantle, assuring easy removal under revision and no extra foreign material.
Three sizes cover all diameters: An exact, time consuming measurement of the intramedullary canal diameter is usually not necessary. The REX Cement Stop™ expands and fully adapts to any irregularity of the intramedullary canal, enabling surgeons to easily select the appropriate size. The REX Cement Stop™ covers all diameters from ø10 to ø20 mm, with only three sizes of plugs. Safety mechanism: The REX Cement Stop™ has a built-in safety mechanism. When the maximum allowable pressure on the femur has been reached (20 bar), the coupling head of the cement stop breaks off. Can be installed distally to the isthmus: The REX Cement Stop™ is inserted in its initial shape and can be inserted below the isthmus, because of its expandability after passing the narrow isthmus.

Ordering information:

FAQ

Q: What is the function of an intramedullary cement restrictor?
A: An intramedullary cement restrictor is used to seal off the intramedullary femur canal of patients requiring cemented artificial joint prosthesis.

Q: Why should the intramedullary canal be sealed off?
A: Sealing off the intramedullary canal enables you to put pressure on the bone cement inserted prior to femoral stem placement. Additionally, a cement restrictor prevents distal leakage of bone cement. 

Q: Why should the bone cement be pressurized?
A: Pressure on the injected bone cement will lead to a better penetration of the bone cement into the surrounding cancellous bone. This will lead to a stronger interface between the host bone and the inserted bone cement, which will increase the longevity of the implant.

Q: How much pressure can the REX Cement Stop resist?
A: In laboratory testing the REX Cement Stop has proven to resist axial pressures up to 11 bar. This means that no distal migration occurred before pressures of 11 bar had been reached. The tests have been performed in regular shaped, tubes, meaning that the pressures can be even higher in vivo because of the irregularities of the intramedullary canal. 

Q: How much pressure does the REX Cement Stop put on the surrounding bone?
A: Laboratory testing has proven that, because of the built-in safety mechanism, the pressure of the REX Cement Stop on the surrounding bone reaches a maximum of 20 bar (depending on the expansion of the gelatine). However, the actual pressure that the gelatine has on the femoral bone is lower than this 20 bars. At the time of expansion, the pressure can be maximally 20 bars on the femoral bone. As soon as this maximum has been reached, the head of the REX Cement Stop breaks off. This results in a relaxation of the tightened lock mechanism, which results in a pressure on the femoral bone of 5 – 7 bars. With reference to the critical pressure of 24  bar - the maximum pressure that can be put on the femoral shaft before fractures occur - the REX Cement Stop is completely safe.

Q: What should the surgeon do in case he estimates that a lower pressure is adequate. (e.g. in case of osteoporosis)?
A: The REX Cement Stop has a safety mechanism to prevent the pressure on the surrounding bone to become too high. Should the surgeon estimate that a lower pressure is needed, he/she should release the knob of the insertion instrument before the head of the REX Cement Stop breaks off.

Q: How does the safety mechanism work?
A: When maximum pressure of the gelatine bushing on the femur wall has been reached, the knob force of the insertion instrument will sharply rise. If the knob is turned further, the coupling head of the cement stop will break off. The coupling head of the cement stop will remain inside the insertion instrument and the REX Cement Stop will be left in situ.

Q: Is the REX Cement Stop radiopaque?
A: No. No X-ray markers or radiopaque agent have been used in the REX Cement Stop.

Q: Can you see the REX Cement Stop on an X-ray photo?
A: Yes, indirectly: the bottom of the bone cement shows the contour of the top of the REX Cement Stop, which is not radiopaque. Also, there is no leakage of bone cement (which is radiopaque) distally from where the REX Cement Stop has been positioned, so you can indirectly see the REX Cement Stop on the X-ray and verify that it has functioned correctly (see figure).

             
Q: Is the REX Cement Stop biocompatible?
A: Yes, both components (the gelatine bushing and the PMMA locking device) are widely accepted to be biocompatible. They are both accepted as being non-toxical and non pyrogenetic. PMMA is also used in bone cement and the PMMA parts of the REX Cement Stop bond to the inserted bone cement. The gelatine used in the bushing is fully degradable and will be absorbed within 4 weeks time.

Q: Can the REX Cement Stop easily be removed in case of revision?
A: The flexible bushing will fully resorb within 4 weeks time. The PMMA bonds to the bone cement. Therefore, in case of a revision, the REX plug can be removed together with the bone cement.

Q: How can you remove the REX Cement Stop during surgery (e.g. in case the REX Cement Stop has been wrongly positioned)?
A: The REX Cement Stop can be removed by breaking the locking ring of the REX Cement Stop, for instance with a sharp chisel.

Q: How is it prevented that the REX Cement Stop is positioned in the wrong place.
A: Prior to insertion, the surgeon should measure the length of the prosthesis’ stem using the measurement indications on the instrument and reamers. Please make sure the tip of the stem is held at the 0-marking on the instrumentation.

Q: Can the REX Cement Stop be used in all sizes of intramedullary canals?
A: No, their use is limited to canals with a diameter between 10 mm and 20 mm. A fourth size (extra small) is under development for canals smaller than 10mm.

Q: Is it always necessary to measure the canal previous to insertion?
A: Yes. The canal diameter can be determined by using the REX Reamers before inserting the plug. Please make sure the reaming is done with a turning motion to prevent that bone particles locally obstruct or narrow the femur canal.

Q: What size should the surgeon choose when in doubt?
A: The surgeon should choose the size of the largest REX Reamer that can be reamed into the canal.

Q: Should the REX Cement Stop be kept in a refrigerator?
A: No, the REX Cement Stop should be kept in a dry room between 10°C and 30°C.

Q: Is there a risk for BSE (Bovine Spongiform Encephalopathy) in the gelatine used in the bushing of the REX Cement Stop?
A: No, there is no risk for BSE, which is only found in cows. The gelatine of the REX Cement Stop is derived from pigs. Additionally, BSE is never found in the skin of any animal. The gelatine from the REX Cement Stop is derived from pig skin. This results in a double security against BSE.

Q: Is there an increased risk of embolism using the REX Cement Stop?
A: No. Testing in fresh frozen bone (Prof. C. Heisel at the University of West-Virginia, Morgantown ) has shown that inserting cement restrictors (especially oversized restrictors) leads to more extrusion of debris into the circulation. The REX Cement Stop will be inserted in its initial (small) shape and will expand locally. This means that there is no pressure on the intramedullary canal during insertion. This results in a risk of embolism that even is less than with commonly used cement restrictors.

Q: Will the surrounding bone be influenced by the expansion of the REX Cement Stop?
A: No, for two reasons:

• The pressure of the REX Cement Stop on the surrounding bone is very short lasting, because of the quick resorption of the gelatine bushing.
• At the time of expansion, the pressure will be maximally 20 bars on the femoral wall. As soon as this maximum has been reached, the head of the REX Cement Stop snaps off. This results in a slight relaxation of the tightened lock mechanism, and the pressure drops immediately after insertion to 5-7 bars.

Q: Can the REX Cement Stop be used in other joints as well?
A: No, pressures on the bone have only been tested and proven in the femoral canal.

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