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There are a variety of approaches that one can choose from to lengthen his limbs. Below is a list of known methods along with their advantages and disadvantages.
What is limb lengthening?
Limb lengthening is the gradual elongation of bone and soft tissues (skin, muscle, nerves, blood vessels). Using an external device called an external fixator or one of various internal devices, the bone and soft tissues are slowly pulled apart and gradually lengthened in a process called distraction. The distraction is done at a recommended average of 1 millimeter per day. If the rate of distraction is higher than this, complications such as muscle contracture (tightness), nerve paralysis, and bone non-union can occur. If distraction is done too slowly, premature consolidation (gap between the bones is filled with regenerate bone) is possible, preventing further distraction. The distraction rate of 1 mm per day is not a strict rule, as there are frequently cases that require a slower distraction rate, and occasionally a faster rate. Once the desired length is obtained, distraction stops and the consolidation phase begins. The consolidation phase is the period when newly formed bone calcifies. Once the bone is fully healed, the lengthening device can be removed.
External Methods of Limb Lengthening
Ilizarov Apparatus
The Ilizarov Apparatus was invented in the Soviet Union by Dr. Gavriil Abramovich Ilizarov in 1951 and has been used in North America since 1981 for correction of leg deformities and lengthening. The Ilizarov Apparatus (also known as the Ilizarov fixator or ring fixator) is an assembly of 2 or 3 rings that encircle the leg or arm and are applied to the bone using screws and wires, each ring connected to the other by connecting rods. The Ilizarov Apparatus is applied through surgery, where the wires are threaded through the skin and muscle that lie over the bone which will be corrected or lengthened. The rings are then secured with telescoping rods and a small cut is made in the limb between the rings. Through the cut’s opening, the outer layer of bone is sliced, leaving the inner marrow undamaged. The lengthening phase is started about one week after the initial surgery, where the patient turns screws on the Ilizarov Apparatus that turn to stretch the bones slowly. Once distraction is done, the fixator remains in place for the consolidation phase so as to prevent the regenerate bone from breaking under the weight bearing load. A child will have to wear the external fixator for approximately 1 month for each centimeter lengthened. Adults may require 1.5 to 2 months or longer per centimeter.
Advantages: Cheapest lengthening option. No additional surgery required after frame removal
Disadvantages: Prolonged time wearing Ilizarov Apparatus has a higher chance of health-related complications such as pin tract infection and decreased range of motion in joints. This can also have a negative psychological effect to the patient, leading to frustration and lack of willingness to participate in physiotherapy. Risk of fracture in regenerated bone after frame removal due to the lack of internal stabilization. May require repeated adjustments to avoid bone misalignment. Discomfort and soft tissue tethering due to pin sites.
LON (Lengthening Over Nail)
Lengthening Over Nails combines a ring fixator for lengthening and a regular intramedullary nail. The LON concept was first introduced by F.C. Bost and L.J. Larsen in 1956 but was popularized by Dr. Dror Paley in 1990 in order to reduce the treatment time in EF (external fixation). During the operation, a hole is made through the bone in order to provide space for an intramedullary nail (nail inside the central cavity of a bone shaft where bone marrow is stored). The hole is made to be approximately 1.5 mm larger than that of the nail itself. This process is called reaming. Once the bone is reamed, the intramedullary nail is inserted into the bone’s central cavity and then locked at the proximal end (the end closer to body’s center) of the nail using screws. A corticotomy (cutting of the bone) is then performed, followed by attachment of the external fixator. The lengthening phase is started about one week after the initial surgery, where the patient turns screws on the Ilizarov Apparatus that turn to stretch the bones over the intramedullary nail slowly. Once the desired length is achieved, two distal (the end farther from body’s center) interlocking screws are inserted into the nail and the external fixator is removed. The purpose of the intramedullary nail is to provide weight bearing support during the consolidation phase. Once the bones are fully consolidated, another operation is needed to remove the nails along with a week’s bed rest for the bones to heal from nail removal.
Advantages: Requires only 1/3 of the time wearing an external fixator as compared to the purely external method. Intramedullary nail helps prevent misalignment in regenerate bone. Fewer complications than external method overall.
Disadvantages: Higher rate of pin site infection due to presence of intramedullary nail during lengthening. Requires acute deformity correction which compromises bone healing potential during subsequent lengthening. Comparatively high incidence of deep intramedullary infection. Additional surgery required to remove intramedullary nails years later. Need to be careful of impact on intramedullary nails during consolidation due to risk of re-fracture. Doesn’t appear to reduce the duration needed for bones to heal compared to purely external method. Unlike LATN, LON uses a small diameter nail so bone can regenerate over it, allowing less stability than LATN method. Discomfort and soft tissue tethering due to pin sites.
LATN (Lengthening and then Nailing)
LATN is a newer limb lengthening technique that combines external and internal methods. The Ilizarov Apparatus is applied through surgery, where the wires are threaded through the skin and muscle that lie over the bone which will be corrected or lengthened. The external fixator is prepared so that an intramedullary nail can be placed inside the bone later. The rings are then secured with telescoping rods and a small cut is made in the limb between the rings. Through the cut’s opening, the outer layer of bone is sliced, leaving the inner marrow undamaged. The lengthening phase is started about one week after the initial surgery, where the patient turns screws on the Ilizarov Apparatus that turn to stretch the bones slowly. Once distraction is done, a reamed intramedullary nail is inserted into the bone’s central cavity to support the bone during the consolidation phase, allowing early removal of the external fixator. Once the bones are fully consolidated, another operation is needed to remove the nails along with a week’s bed rest for the bones to heal from nail removal.
Advantages: Requires only 1/3 of the time wearing an external fixator as compared to the purely external method. Quicker bone healing rate than pure external method. Lower rate of infection than LON. Infections can be treated more easily and gradually during lengthening due to absence of intramedullary nail present in LON method during lengthening phase. Larger diameter nail than the one used in LON method is inserted into bone cavity during consolidation, allowing greater stability and increased protection against re-fracture.
Disadvantages: May require repeated adjustments to avoid bone misalignment due to lack of IM nail during lengthening phase. Need to be careful of impact on intramedullary nails during consolidation due to risk of re-fracture. Discomfort and soft tissue tethering due to pin sites.
Unilateral External Fixator (Monorail Fixator)
Monorail Fixators are similar to the standard Ilizarov Apparatus. However, instead of a bulky external frame there is a single bar that runs along the outside of the limb and is attached with between 4 and 6 pins to the bone. It provides more comfort than the Ilizarov fixator and is often used when treating arm deformities. Unilateral lengtheners can be purely external or can be combined with an intramedullary nail as used in the LON method.
Advantages: Fewer scars than standard Ilizarov Apparatus due to less pins, can be worn under clothes, suitable for pediatric patients with smaller limbs.
Disadvantages: Pinhole scars are larger than scars made by the Ilizarov Apparatus due to greater pin size. Pin site infections are common. Less stability than standard Ilizarov Apparatus. Some patients say the larger pinhole sites cause more pain than the standard Ilizarov Apparatus.
Salamehfix (SLDF)
The Salamehfix (SLDF) System is a hinged, Eternal Fixation System developed by Prof. Ghassan Salameh in Syria. It is an arc system rather than a circular system and consists of three small arcs. The arcs are not the same diameter so the system can take the shape of leg.
Advantages: Screws and wires are in minimally painful regions, making it more tolerable than the traditional Ilizarov Apparatus. Provides for stable fixation and early full weight bearing. Device developed to maintain proper alignment during lengthening. Clothes can be worn over it during the lengthening and consolidation phases due to its small size.
Disadvantages: Prolonged time wearing Salamehfix (same as external fixator) can have a negative psychological effect on the patient, leading to frustration and lack of willingness to participate in physiotherapy. Risk of fracture in regenerated bone after frame removal due to the lack of internal stabilization.
Micro-Wound
Developed in Chongqing, China by Dr. Helong Bai, the Micro-Wound is a thin external fixator clip that is attached to one side of the leg and doesn’t have the uncomfortable bulkiness of the classic Ilizarov Apparatus.
Advantages: More comfortable than the Ilizarov Apparatus. Fewer pinhole sites and scars.
Disadvantages: Only one surgeon seems to use this method. Risk of fracture in regenerated bone after frame removal due to the lack of internal stabilization. Not as stable as standard Ilizarov Apparatus. Minimal peer-reviewed research on this method. Very mixed results from former patients. More costly than other options in China that already have a good track record.
Internal Methods of Limb Lengthening
The advancement of limb lengthening technology has led to internal options for lengthening that avoid the use of uncomfortable external fixators.
Albizzia Nail and its updated nails - Guichet Nail and Betzbone
The Albizzia nail was invented by Dr. Jean-Marc Guichet with assistance from his professor, Paul Marie Grammont. It is a fully implantable nail that is locked into the bone with screws. The nail distracts when the patient rotates the foot or ankle until it makes a clicking noise, alerting the patient that distraction has taken place. The patient can determine the rate of distraction by performing a set number of “clicks” per day. The Albizzia nail has an automatic 'dynamization' system in its mechanism. During weight-bearing and walking, as the nail supports more weight, more bone formation is stimulated. When the bone strengthens, the loading force is gradually transferred to the bone and the load on the nail decreases. With the bone becoming stronger, it eliminates the need to remove screws to remove axial load from the nail to the bone.
The original Albizzia nail is no longer in production, however Dr. Guichet and Dr. Betz have developed the Guichet Nail and Betz Bone respectively. Both are reportedly more sturdy and reliable than the original Albizzia.
Advantages: Reduced risk of joint stiffness, infection, and pain than external methods. Greater comfort and tolerance compared to externals. Fewer scars. No soft tissue tethering as with external methods. Weight bearing permitted during distraction phase. Only two operations needed.
Disadvantages: Costly. Requires considerable movement at the hip to initiate lengthening, making it more uncomfortable than other internal methods. Need to be careful of impact on internal nails during consolidation for risk of refracture.
Bliskunov Nail
The Bliskunov Nail was invented by the late Professor Alexander Bliskunov. The Bliskunov Nail is similar to the Albizzia Nail and its successors, but with some notable differences. In addition to the internal nail set inside the bone cavity, the Bliskunov Nail includes a part in the pelvis that connects the femur to the pelvis. The patient uses lateral movements of the whole limb to distract the nail.
Advantages: Reduced risk of joint stiffness, infection, and pain. Greater comfort and tolerance compared to externals. Fewer scars than externals. No soft tissue tethering as with external methods.
Disadvantages: More costly than external methods. Longer scars than other internal methods, including a scar on the pelvis. Dynamization (removal of upper or lower femoral screws to allow loading through newly formed bone rather than through nail) can cause between a 2 to 7 mm loss in height gain.
Intramedullary Skeletal Kinetic Distractor (ISKD)
The ISKD was invented by Dr. J Dean Cole, orthopedic surgeon and President of Orthodyne Inc. The ISKD uses a kinetic clutch mechanism to lengthen the limb. One end of a rod is screwed onto another and the rod is inserted into the bone cavity. Small rotational movements by the patient cause the telescopic nail to lengthen. The clutch ensures that the rod can rotate only in one direction and a monitor is included to track how much the leg has distracted at any point in time.
Advantages: Reduced risk of joint stiffness, infection, and pain. Greater comfort and tolerance compared to externals. Fewer scars. No soft tissue tethering as with external methods.
Disadvantages: High rate of mechanical failure requiring additional surgery to replace. Device is not full weight bearing which leads to weakening of muscles. Distraction rate difficult to control due to small degree of rotation required for lengthening, allowing one to possibly lengthen even 5 mm in a single day. Difficulty in controlling lengthening rate can cause trouble when trying to quicken lengthening in the face of premature consolidation or when trying to slow lengthening in the face of weak ossification. The only way to neutralize the implant and stop it from gaining length in an emergency situation is to perform additional surgery to set an external fixator around the nail to lock rotation. Additional complications can lead to much higher cost. Dynamization (removal of upper or lower femoral screws to allow loading through newly formed bone rather than through nail) can cause between a 2 to 7 mm loss in height gain.
Fitbone
The Fitbone was invented by Dr. Augustin Betz and Dr. Rainer Baumgart in 1989 and has been continuously developed with improvements since then. It is a telescopic nail that is driven by a small electric motor located at the end of it. Distraction is caused by forces from the motor that transmit to the internal nail and force it to lengthen. The energy for the fitbone motor is transmitted through the skin from an external transmitter controlled by the patient to the receiver under the skin.
Link to a demonstration of the Fitbone:
Advantages: Minimal scarring. No pin sites. Reduced risk of joint stiffness, infection, and pain. Greater comfort and tolerance compared to externals and other internal methods. No soft tissue tethering due to lack of pin sites.
Disadvantages: Far more costly than external methods and other internal methods. Not weight bearing, leading to muscle weakness and prolonging recovery. Additional surgery required for consolidation phase to add stronger nail. More complications than other internals due to mechanical nature of the device. Dynamization (removal of upper or lower femoral screws to allow loading through newly formed bone rather than through nail) can cause between a 2 to 7 mm loss in height gain.
PRECISE System
The Precise System is an internal limb lengthening device that is controlled externally by a magnetic field generator called an External remote Controller (ERC). The internal device consists of a telescopic titanium rod that is placed into the bone cavity of the limb being lengthened and held by screws. Within the rod is a small magnetic motor and gear box that creates force needed to lengthen the rod. The external magnetic field generator powers the internal motor and is pressed onto the skin outside the leg for few minute intervals several times a day. that is held on the skin next to the leg several times a day.
Link to a CGI demonstration of the PRECISE:
Advantages: Reduced risk of joint stiffness, infection, and pain. Greater comfort and tolerance compared to externals. Fewer scars. No soft tissue tethering as with external methods. More reliable than Fitbone or ISKD.
Disadvantages: Very costly. Not full weight-bearing, leading to muscle weakness. Current nail can lengthen a maximum of 6.5 cm.
What is limb lengthening?
Limb lengthening is the gradual elongation of bone and soft tissues (skin, muscle, nerves, blood vessels). Using an external device called an external fixator or one of various internal devices, the bone and soft tissues are slowly pulled apart and gradually lengthened in a process called distraction. The distraction is done at a recommended average of 1 millimeter per day. If the rate of distraction is higher than this, complications such as muscle contracture (tightness), nerve paralysis, and bone non-union can occur. If distraction is done too slowly, premature consolidation (gap between the bones is filled with regenerate bone) is possible, preventing further distraction. The distraction rate of 1 mm per day is not a strict rule, as there are frequently cases that require a slower distraction rate, and occasionally a faster rate. Once the desired length is obtained, distraction stops and the consolidation phase begins. The consolidation phase is the period when newly formed bone calcifies. Once the bone is fully healed, the lengthening device can be removed.
External Methods of Limb Lengthening
Ilizarov Apparatus
The Ilizarov Apparatus was invented in the Soviet Union by Dr. Gavriil Abramovich Ilizarov in 1951 and has been used in North America since 1981 for correction of leg deformities and lengthening. The Ilizarov Apparatus (also known as the Ilizarov fixator or ring fixator) is an assembly of 2 or 3 rings that encircle the leg or arm and are applied to the bone using screws and wires, each ring connected to the other by connecting rods. The Ilizarov Apparatus is applied through surgery, where the wires are threaded through the skin and muscle that lie over the bone which will be corrected or lengthened. The rings are then secured with telescoping rods and a small cut is made in the limb between the rings. Through the cut’s opening, the outer layer of bone is sliced, leaving the inner marrow undamaged. The lengthening phase is started about one week after the initial surgery, where the patient turns screws on the Ilizarov Apparatus that turn to stretch the bones slowly. Once distraction is done, the fixator remains in place for the consolidation phase so as to prevent the regenerate bone from breaking under the weight bearing load. A child will have to wear the external fixator for approximately 1 month for each centimeter lengthened. Adults may require 1.5 to 2 months or longer per centimeter.
Advantages: Cheapest lengthening option. No additional surgery required after frame removal
Disadvantages: Prolonged time wearing Ilizarov Apparatus has a higher chance of health-related complications such as pin tract infection and decreased range of motion in joints. This can also have a negative psychological effect to the patient, leading to frustration and lack of willingness to participate in physiotherapy. Risk of fracture in regenerated bone after frame removal due to the lack of internal stabilization. May require repeated adjustments to avoid bone misalignment. Discomfort and soft tissue tethering due to pin sites.
LON (Lengthening Over Nail)
Lengthening Over Nails combines a ring fixator for lengthening and a regular intramedullary nail. The LON concept was first introduced by F.C. Bost and L.J. Larsen in 1956 but was popularized by Dr. Dror Paley in 1990 in order to reduce the treatment time in EF (external fixation). During the operation, a hole is made through the bone in order to provide space for an intramedullary nail (nail inside the central cavity of a bone shaft where bone marrow is stored). The hole is made to be approximately 1.5 mm larger than that of the nail itself. This process is called reaming. Once the bone is reamed, the intramedullary nail is inserted into the bone’s central cavity and then locked at the proximal end (the end closer to body’s center) of the nail using screws. A corticotomy (cutting of the bone) is then performed, followed by attachment of the external fixator. The lengthening phase is started about one week after the initial surgery, where the patient turns screws on the Ilizarov Apparatus that turn to stretch the bones over the intramedullary nail slowly. Once the desired length is achieved, two distal (the end farther from body’s center) interlocking screws are inserted into the nail and the external fixator is removed. The purpose of the intramedullary nail is to provide weight bearing support during the consolidation phase. Once the bones are fully consolidated, another operation is needed to remove the nails along with a week’s bed rest for the bones to heal from nail removal.
Advantages: Requires only 1/3 of the time wearing an external fixator as compared to the purely external method. Intramedullary nail helps prevent misalignment in regenerate bone. Fewer complications than external method overall.
Disadvantages: Higher rate of pin site infection due to presence of intramedullary nail during lengthening. Requires acute deformity correction which compromises bone healing potential during subsequent lengthening. Comparatively high incidence of deep intramedullary infection. Additional surgery required to remove intramedullary nails years later. Need to be careful of impact on intramedullary nails during consolidation due to risk of re-fracture. Doesn’t appear to reduce the duration needed for bones to heal compared to purely external method. Unlike LATN, LON uses a small diameter nail so bone can regenerate over it, allowing less stability than LATN method. Discomfort and soft tissue tethering due to pin sites.
LATN (Lengthening and then Nailing)
LATN is a newer limb lengthening technique that combines external and internal methods. The Ilizarov Apparatus is applied through surgery, where the wires are threaded through the skin and muscle that lie over the bone which will be corrected or lengthened. The external fixator is prepared so that an intramedullary nail can be placed inside the bone later. The rings are then secured with telescoping rods and a small cut is made in the limb between the rings. Through the cut’s opening, the outer layer of bone is sliced, leaving the inner marrow undamaged. The lengthening phase is started about one week after the initial surgery, where the patient turns screws on the Ilizarov Apparatus that turn to stretch the bones slowly. Once distraction is done, a reamed intramedullary nail is inserted into the bone’s central cavity to support the bone during the consolidation phase, allowing early removal of the external fixator. Once the bones are fully consolidated, another operation is needed to remove the nails along with a week’s bed rest for the bones to heal from nail removal.
Advantages: Requires only 1/3 of the time wearing an external fixator as compared to the purely external method. Quicker bone healing rate than pure external method. Lower rate of infection than LON. Infections can be treated more easily and gradually during lengthening due to absence of intramedullary nail present in LON method during lengthening phase. Larger diameter nail than the one used in LON method is inserted into bone cavity during consolidation, allowing greater stability and increased protection against re-fracture.
Disadvantages: May require repeated adjustments to avoid bone misalignment due to lack of IM nail during lengthening phase. Need to be careful of impact on intramedullary nails during consolidation due to risk of re-fracture. Discomfort and soft tissue tethering due to pin sites.
Unilateral External Fixator (Monorail Fixator)
Monorail Fixators are similar to the standard Ilizarov Apparatus. However, instead of a bulky external frame there is a single bar that runs along the outside of the limb and is attached with between 4 and 6 pins to the bone. It provides more comfort than the Ilizarov fixator and is often used when treating arm deformities. Unilateral lengtheners can be purely external or can be combined with an intramedullary nail as used in the LON method.
Advantages: Fewer scars than standard Ilizarov Apparatus due to less pins, can be worn under clothes, suitable for pediatric patients with smaller limbs.
Disadvantages: Pinhole scars are larger than scars made by the Ilizarov Apparatus due to greater pin size. Pin site infections are common. Less stability than standard Ilizarov Apparatus. Some patients say the larger pinhole sites cause more pain than the standard Ilizarov Apparatus.
Salamehfix (SLDF)
The Salamehfix (SLDF) System is a hinged, Eternal Fixation System developed by Prof. Ghassan Salameh in Syria. It is an arc system rather than a circular system and consists of three small arcs. The arcs are not the same diameter so the system can take the shape of leg.
Advantages: Screws and wires are in minimally painful regions, making it more tolerable than the traditional Ilizarov Apparatus. Provides for stable fixation and early full weight bearing. Device developed to maintain proper alignment during lengthening. Clothes can be worn over it during the lengthening and consolidation phases due to its small size.
Disadvantages: Prolonged time wearing Salamehfix (same as external fixator) can have a negative psychological effect on the patient, leading to frustration and lack of willingness to participate in physiotherapy. Risk of fracture in regenerated bone after frame removal due to the lack of internal stabilization.
Micro-Wound
Developed in Chongqing, China by Dr. Helong Bai, the Micro-Wound is a thin external fixator clip that is attached to one side of the leg and doesn’t have the uncomfortable bulkiness of the classic Ilizarov Apparatus.
Advantages: More comfortable than the Ilizarov Apparatus. Fewer pinhole sites and scars.
Disadvantages: Only one surgeon seems to use this method. Risk of fracture in regenerated bone after frame removal due to the lack of internal stabilization. Not as stable as standard Ilizarov Apparatus. Minimal peer-reviewed research on this method. Very mixed results from former patients. More costly than other options in China that already have a good track record.
Internal Methods of Limb Lengthening
The advancement of limb lengthening technology has led to internal options for lengthening that avoid the use of uncomfortable external fixators.
Albizzia Nail and its updated nails - Guichet Nail and Betzbone
The Albizzia nail was invented by Dr. Jean-Marc Guichet with assistance from his professor, Paul Marie Grammont. It is a fully implantable nail that is locked into the bone with screws. The nail distracts when the patient rotates the foot or ankle until it makes a clicking noise, alerting the patient that distraction has taken place. The patient can determine the rate of distraction by performing a set number of “clicks” per day. The Albizzia nail has an automatic 'dynamization' system in its mechanism. During weight-bearing and walking, as the nail supports more weight, more bone formation is stimulated. When the bone strengthens, the loading force is gradually transferred to the bone and the load on the nail decreases. With the bone becoming stronger, it eliminates the need to remove screws to remove axial load from the nail to the bone.
The original Albizzia nail is no longer in production, however Dr. Guichet and Dr. Betz have developed the Guichet Nail and Betz Bone respectively. Both are reportedly more sturdy and reliable than the original Albizzia.
Advantages: Reduced risk of joint stiffness, infection, and pain than external methods. Greater comfort and tolerance compared to externals. Fewer scars. No soft tissue tethering as with external methods. Weight bearing permitted during distraction phase. Only two operations needed.
Disadvantages: Costly. Requires considerable movement at the hip to initiate lengthening, making it more uncomfortable than other internal methods. Need to be careful of impact on internal nails during consolidation for risk of refracture.
Bliskunov Nail
The Bliskunov Nail was invented by the late Professor Alexander Bliskunov. The Bliskunov Nail is similar to the Albizzia Nail and its successors, but with some notable differences. In addition to the internal nail set inside the bone cavity, the Bliskunov Nail includes a part in the pelvis that connects the femur to the pelvis. The patient uses lateral movements of the whole limb to distract the nail.
Advantages: Reduced risk of joint stiffness, infection, and pain. Greater comfort and tolerance compared to externals. Fewer scars than externals. No soft tissue tethering as with external methods.
Disadvantages: More costly than external methods. Longer scars than other internal methods, including a scar on the pelvis. Dynamization (removal of upper or lower femoral screws to allow loading through newly formed bone rather than through nail) can cause between a 2 to 7 mm loss in height gain.
Intramedullary Skeletal Kinetic Distractor (ISKD)
The ISKD was invented by Dr. J Dean Cole, orthopedic surgeon and President of Orthodyne Inc. The ISKD uses a kinetic clutch mechanism to lengthen the limb. One end of a rod is screwed onto another and the rod is inserted into the bone cavity. Small rotational movements by the patient cause the telescopic nail to lengthen. The clutch ensures that the rod can rotate only in one direction and a monitor is included to track how much the leg has distracted at any point in time.
Advantages: Reduced risk of joint stiffness, infection, and pain. Greater comfort and tolerance compared to externals. Fewer scars. No soft tissue tethering as with external methods.
Disadvantages: High rate of mechanical failure requiring additional surgery to replace. Device is not full weight bearing which leads to weakening of muscles. Distraction rate difficult to control due to small degree of rotation required for lengthening, allowing one to possibly lengthen even 5 mm in a single day. Difficulty in controlling lengthening rate can cause trouble when trying to quicken lengthening in the face of premature consolidation or when trying to slow lengthening in the face of weak ossification. The only way to neutralize the implant and stop it from gaining length in an emergency situation is to perform additional surgery to set an external fixator around the nail to lock rotation. Additional complications can lead to much higher cost. Dynamization (removal of upper or lower femoral screws to allow loading through newly formed bone rather than through nail) can cause between a 2 to 7 mm loss in height gain.
Fitbone
The Fitbone was invented by Dr. Augustin Betz and Dr. Rainer Baumgart in 1989 and has been continuously developed with improvements since then. It is a telescopic nail that is driven by a small electric motor located at the end of it. Distraction is caused by forces from the motor that transmit to the internal nail and force it to lengthen. The energy for the fitbone motor is transmitted through the skin from an external transmitter controlled by the patient to the receiver under the skin.
Link to a demonstration of the Fitbone:
Advantages: Minimal scarring. No pin sites. Reduced risk of joint stiffness, infection, and pain. Greater comfort and tolerance compared to externals and other internal methods. No soft tissue tethering due to lack of pin sites.
Disadvantages: Far more costly than external methods and other internal methods. Not weight bearing, leading to muscle weakness and prolonging recovery. Additional surgery required for consolidation phase to add stronger nail. More complications than other internals due to mechanical nature of the device. Dynamization (removal of upper or lower femoral screws to allow loading through newly formed bone rather than through nail) can cause between a 2 to 7 mm loss in height gain.
PRECISE System
The Precise System is an internal limb lengthening device that is controlled externally by a magnetic field generator called an External remote Controller (ERC). The internal device consists of a telescopic titanium rod that is placed into the bone cavity of the limb being lengthened and held by screws. Within the rod is a small magnetic motor and gear box that creates force needed to lengthen the rod. The external magnetic field generator powers the internal motor and is pressed onto the skin outside the leg for few minute intervals several times a day. that is held on the skin next to the leg several times a day.
Link to a CGI demonstration of the PRECISE:
Advantages: Reduced risk of joint stiffness, infection, and pain. Greater comfort and tolerance compared to externals. Fewer scars. No soft tissue tethering as with external methods. More reliable than Fitbone or ISKD.
Disadvantages: Very costly. Not full weight-bearing, leading to muscle weakness. Current nail can lengthen a maximum of 6.5 cm.
