Surgeon Info

Is there a minimum or maximum patient age?

There is no predetermined age for a JTS extendible implant. One of the key factors is the length of bone that needs to be resected. As the youngster reaches skeletal maturity (girls reach skeletal maturity faster than boys) then other options may also be considered such as an over length definitive (adult implant) or a surgical epiphysiodesis of the contralateral physis (growth plate). As for the upper age, adults with severe leg length discrepancies have been treated.

Osteosarcoma Treatment

What extension can be expected?

The table summarizes the typical length of the extension in respect to the amount of bone resected for proximal femur, distal femur and proximal tibia replacements.

What is the implant made of?

Limb sparing implants are typically made from titanium alloy (Ti 6Al 4V) and cobalt chromium molybdenum (CoCrMo) alloy. The patient specific shaft body and the intramedullary stem are fabricated from titanium alloy. In the case of a distal femoral, total femoral or proximal tibial replacement, the knee joint is produced from CoCrMo. This also applies to a femoral head for a proximal femoral or total femoral replacement. CoCrMo is best for these replacements as it has excellent wear characteristics. Ultra high molecular weight polyethylene is used in the knee joint for bushes and bearing components.

Are they modular?

No. Each implant is designed and manufactured for the recipient patient. Typically the design is configured to achieve the maximum amount of extension possible within the implant length. The design of a modular taper junction requires 40-50mm of length. In difficult reconstructions, such as high resection levels or revisions, when there may need to be options available, a number of stem configurations can be provided. The intramedullary stem is integral with the piston of the extending mechanism thus providing a strong construct.

What imaging is required?

Each extendible implant is custom made to the patient’s specifications. For this, measurements, radiographs and CT scans are required. For more details on the specific requirements download the Radiography Measurement Instructions.

Please explain the lengthening procedure?

The lengthening procedure is very straightforward and is typically undertaken in an outpatient department. The external drive is placed on the couch, where the youngster can sit comfortable with their leg inside the unit. Its very important that the magnet is within the tunnel of the external drive unit. For a distal femur this would be switched to A. Almost instantaneously, the magnet will start spinning and it takes 4 minutes to extend the implant 1mm. The gearbox can be heard turning with the aid of a stethoscope either placed on the knee or the medial malleolus. The youngster should not require any form of sedation or anaesthesia. Many youngsters sit happily playing with electronic games, or reading a magazine. After the desired lengthening has been achieved (this is determined by the length of time), the patient may be assessed to confirm the lengthening using image intensifier or plain radiography.

Osteosarcoma TreatmentWhere is the magnet?

In a distal femur, the magnet is proximal to the knee joint. For proximal femoral replacements, it is a little proximal to the level of resection and for proximal tibial replacements it is a little below the knee joint. The power is switched on to the external drive unit and then the control is switched either to A or B depending on the skeletal location of the device.

How much lengthening per episode?

This is dependent upon the individual’s requirements. Typically patients are lengthened when there is 4-6mm of discrepancy between the two limbs. In a study of over 1,000 lengthening procedures the average amount extended per sitting was 4.3mm. For the taller teenagers, a little more extension may be achievable and in the younger patients, particularly the proximal tibia, a little less. The over stretching of the tissues is not recommended.

How often are the implants lengthened?

This is dependent upon the patient and their specific circumstances. Some patients may not require lengthening for a year or more as they may have had growth arrest during chemotherapy or rare overgrowth of the ipsilateral growth plates. Typically, during the growth spurt patients are being lengthened between 2 and 4 times a year.

What are the points to look out for?

There are a number of points that should be taken into consideration and these are:

  • Ensure the magnet is within the external drive
  • Do not over lengthen the implant
  • Ensure that the direction switch (A or B) is correct for the specific skeletal location and for the direction of expansion. These implants can be be reversed by changing the direction of the current (A to B or B to A).

Where can the lengthening take place?

The lengthening procedures are normally undertaken in out patient departments. There is no need to undertake the procedure in the Operating Room.

Can it be reversed?

Yes – just by switching from A to B or B to A

Does the patient require sedation or anaesthesia?

Many youngsters who have their JTS implants extended report that they experienced no pain during the lengthening procedure and at most only mild discomfit as the tissues are being slowly stretched. Most patients during the lengthening process are happy to play with a games console or read a book. At the first lengthening the youngster may be a little fearful that it will hurt but once the lengthening process starts that become much more relaxed. Only in exceptional cases has there been a need for sedation.



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Copyright 2012 | Stanmore Implants Ltd | Design by Varn Media Privacy | Text Only Version

Surgeon Info

Is there a minimum or maximum patient age?

There is no predetermined age for a JTS extendible implant. One of the key factors is the length of bone that needs to be resected. As the youngster reaches skeletal maturity (girls reach skeletal maturity faster than boys) then other options may also be considered such as an over length definitive (adult implant) or a surgical epiphysiodesis of the contralateral physis (growth plate). As for the upper age, adults with severe leg length discrepancies have been treated.

Osteosarcoma Treatment

What extension can be expected?

The table summarizes the typical length of the extension in respect to the amount of bone resected for proximal femur, distal femur and proximal tibia replacements.

What is the implant made of?

Limb sparing implants are typically made from titanium alloy (Ti 6Al 4V) and cobalt chromium molybdenum (CoCrMo) alloy. The patient specific shaft body and the intramedullary stem are fabricated from titanium alloy. In the case of a distal femoral, total femoral or proximal tibial replacement, the knee joint is produced from CoCrMo. This also applies to a femoral head for a proximal femoral or total femoral replacement. CoCrMo is best for these replacements as it has excellent wear characteristics. Ultra high molecular weight polyethylene is used in the knee joint for bushes and bearing components.

Are they modular?

No. Each implant is designed and manufactured for the recipient patient. Typically the design is configured to achieve the maximum amount of extension possible within the implant length. The design of a modular taper junction requires 40-50mm of length. In difficult reconstructions, such as high resection levels or revisions, when there may need to be options available, a number of stem configurations can be provided. The intramedullary stem is integral with the piston of the extending mechanism thus providing a strong construct.

What imaging is required?

Each extendible implant is custom made to the patient’s specifications. For this, measurements, radiographs and CT scans are required. For more details on the specific requirements download the Radiography Measurement Instructions.

Please explain the lengthening procedure?

The lengthening procedure is very straightforward and is typically undertaken in an outpatient department. The external drive is placed on the couch, where the youngster can sit comfortable with their leg inside the unit. Its very important that the magnet is within the tunnel of the external drive unit. For a distal femur this would be switched to A. Almost instantaneously, the magnet will start spinning and it takes 4 minutes to extend the implant 1mm. The gearbox can be heard turning with the aid of a stethoscope either placed on the knee or the medial malleolus. The youngster should not require any form of sedation or anaesthesia. Many youngsters sit happily playing with electronic games, or reading a magazine. After the desired lengthening has been achieved (this is determined by the length of time), the patient may be assessed to confirm the lengthening using image intensifier or plain radiography.

Osteosarcoma TreatmentWhere is the magnet?

In a distal femur, the magnet is proximal to the knee joint. For proximal femoral replacements, it is a little proximal to the level of resection and for proximal tibial replacements it is a little below the knee joint. The power is switched on to the external drive unit and then the control is switched either to A or B depending on the skeletal location of the device.

How much lengthening per episode?

This is dependent upon the individual’s requirements. Typically patients are lengthened when there is 4-6mm of discrepancy between the two limbs. In a study of over 1,000 lengthening procedures the average amount extended per sitting was 4.3mm. For the taller teenagers, a little more extension may be achievable and in the younger patients, particularly the proximal tibia, a little less. The over stretching of the tissues is not recommended.

How often are the implants lengthened?

This is dependent upon the patient and their specific circumstances. Some patients may not require lengthening for a year or more as they may have had growth arrest during chemotherapy or rare overgrowth of the ipsilateral growth plates. Typically, during the growth spurt patients are being lengthened between 2 and 4 times a year.

What are the points to look out for?

There are a number of points that should be taken into consideration and these are:

  • Ensure the magnet is within the external drive
  • Do not over lengthen the implant
  • Ensure that the direction switch (A or B) is correct for the specific skeletal location and for the direction of expansion. These implants can be be reversed by changing the direction of the current (A to B or B to A).

Where can the lengthening take place?

The lengthening procedures are normally undertaken in out patient departments. There is no need to undertake the procedure in the Operating Room.

Can it be reversed?

Yes – just by switching from A to B or B to A

Does the patient require sedation or anaesthesia?

Many youngsters who have their JTS implants extended report that they experienced no pain during the lengthening procedure and at most only mild discomfit as the tissues are being slowly stretched. Most patients during the lengthening process are happy to play with a games console or read a book. At the first lengthening the youngster may be a little fearful that it will hurt but once the lengthening process starts that become much more relaxed. Only in exceptional cases has there been a need for sedation.



Watch our real life stories about the JTS implant

Copyright © 2017 | Stanmore Implants Ltd | Website by Varn Text Only Version