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Chapter in film

BASICS - starting at 0:16

GUIDELINE 1 - starting at 2:38

GUIDELINE 2 - starting at 3:50

GUIDELINE 3 - starting at 5:06


The BETZBONE® is an internal limb-lengthening system which was invented by Dr. Betz on the basis of his experience with over 2,000 limb lengthening patients. The BETZBONE® is based on a similar technical principle as the Albizzia®-Nail - a manual, mechanical clicking mechanism. In contrast to the Albizzia®-Nail, the clicking mechanism of the BETZBONE® operates very smoothly and, hence, after a period of adjustment, is very easy for the patient to handle. In regards to its most important features, like the stability, the lengthening capacity, and the ease with which it's controlled, in combination with the fact that the patient maintains good mobility throughout the process, the BETZBONE®, by far, outmatches every other internal system available on the market. Furthermore, the dangerous formation of rust, which is possible with every other lengthening system, is impossible for the BETZBONE®. Because all of its components are made of the same noncorrosive material, there is no need to encapsulate the BETZBONE®'s driving components in order to protect them from the bodily fluids. For patients who live at greater altitudes or who need to fly home, there is another feature of great importance: in systems with encapsulated components, there is often extreme pain triggered by gases which leak from the encapsulated parts of the nail when subjected to atmospheric changes. Because the BETZBONE® doesn't require its driving components to be encapsulated, there is no extreme pain due to this fluctuation of atmospheric pressure.


Bilateral lengthening of both thigh bones with newly built bone tissue (pink)

Basics of limb-lengthening

(Chapter in movie starting at minute 0:16) - The basis of every limb lengthening procedure is the lengthening of the bones. The bones are cut through and the lengthening nails are implanted. The body fills the gap that arises from the cutting with soft connective tissue. Afterwards, the ends of the bones are extended by approximately 1 mm or 0.04 inches per day. At this rate, the body continuously fills the expanding gap with soft tissue. Thus, a lengthening of 9 cm or 3.5 inches takes approximately 3 months. During the consolidation phase, which takes a minimum of another 9 months, the body converts the newly built soft tissue into bone tissue. In this way, a longer bone made of the body's own natural bone tissue is created.
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bilaterale verlaengerung

Bilateral lengthening of both thigh bones (left) and both shin lower legs (right)

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Positions of bone cutting in bilateral limb lengthening (left: thigh bones - right: lower legs)

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Positions of the BETZBONE®-medullary nails in bilateral limb lengthening (left: thigh bones - right: lower legs)


X-ray of a patient with bilateral lengthening of both thigh bones

Guideline 1: Bilateral lengthening of one segment

(Chapter in film starting at 2:38) - Bilateral lengthening means the lengthening either of both thigh bones or both shin bones at the same time. It is the more comfortable treatment procedure with the shortest treatment time, because it meets the particular needs of the soft tissue, which needs to be stretched and, thereby, adapted to the elongated bone. With the increasing length of the bone, the soft tissue, like muscles, ligaments and nerves, which are partly fixed at the bone, are more and more stretched. The increasing stretch leads to pain and the patient can ease this pain by bending his or her legs, a characteristic relief action. The higher the lengthening distance in each leg, the higher the discomfort.
A suitable treatment consists of special stretching exercises, physiotherapy, machine workouts (like those at a gym), and hydrotherapy by exercising in a warm pool, all of which allow the soft tissue to be slowly stretched and thus adapted to the elongated bone.
With bilateral lengthening - of either both thighs or both lower legs at the same time - this is achieved in the quickest and easiest way. The stretching of the soft tissue is limited to one segment in each leg (thigh or lower leg) and thus kept to a comfortable level. Furthermore, the lengthening and stretching is divided symmetrically along both sides - left and right - of the body and thus the orientation of the biomechanical axis of the body is undisturbed as much as possible. Under these conditions, the stretching of the soft tissue can be achieved in a comparably less uncomfortable and shorter treatment time.
In 1999, Dr. Betz performed the first ever simultaneous four-fold lengthening, meaning the lengthening of both thigh- and both shin-bones at the same time. But when comparing the level of discomfort and the complete treatment time (until the achievement of a normal gait pattern) of simultaneous four-fold lengthening and consecutive bilateral two-fold lengthening, the bilateral two-fold lengthening proved to be the superior method, giving better results in a shorter time.
The simultaneous lengthening of thigh- and shin bone in one leg only, also titled "Rapid Lengthening," has also been shown to be inferior. The intention of Rapid Lengthening, billed as an innovative idea, is to overcome the insufficient lengthening capacity of the nails used. Because of its discomfort, we don't recommend this method to our patients either.

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bilaterale verlaengerung3

Stretching of the soft tissue in bilateral lengthening of both thigh bones (left) and both shin lower legs (right): The stretching is limited to one segment in each leg (thigh or lower leg) and thus kept to a comfortable level. Lengthening and stretching is divided symmetrically along both sides - left and right - and thus the orientation of the biomechanical axis of the body is undisturbed as much as possible. The distances in centimeter are just examples.


Mobilization of a patient with bilateral lengthening of both thigh bones 2 hours after surgery


Two patients with bilateral lengthening of both thigh bones mobile on crutches 4 and 8 days after surgery respectively

Guideline 2: immediate mobilization of the patient on crutches

(Chapter in film starting at 2:38) - The, by far, best general follow-up treatment for limb-lengthening patients is walking and climbing stairs. The sooner the patients are mobilized, the easier and faster they get used to their daily lengthening progress. Because with bilateral lengthening, both legs were lengthened simultaneously, crutches can be used only if the lengthening system is able to hold the full weight of the body without any problems with the implant system that results from that burden.
If the full body weight can't be supported, the preferred method of bilateral lengthening can't be performed, or can only be performed if the patient is immobilized in a wheelchair during the complete phases of lengthening and consolidation, which would total 9 months for a lengthening distance of 9 cm/3.54 inch. This complicates the process and extends the treatment time because the patients can't use their muscles and ligaments properly for a long time. They can't train their legs under everyday conditions and, therefore, are not able to gain confidence in the stability of the lengthened legs.
The BETZBONE®-limb-lengthening-nail was the first and for many years the only available limb lengthening system worldwide that can bear the whole body weight of even heavy patients. (Moreover, it remains the only internal lengthening system that can be made visible on magnetic resonance tomography (MRT) scans). Betzbone lengthening patients, therefore, are not immobilized at any time, but can be mobilized on crutches as quickly as 2 hours after the surgical procedure. They train their "growing" legs from the first day onward during the entire lengthening- and consolidation-phases and, thus, get used to them much more easily and quickly.

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Patient managing his lengthening with the clicking mechanism in a rehab center without assistance 6 weeks after surgery

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Daily documentation of the number of clicks and, thus, the lengthening distance by the patient

Guideline 3: Easy and safe lengthening control

(Chapter in film starting at 5:06) - The lengthening of the BETZBONE® is enabled with a manual, mechanical clicking mechanism, which is triggered from a slight twisting of telescopic rods against each other. Complex and cost-intensive electronic components are not necessary. Every twist generates a characteristic clicking sound. The clicking mechanism is much smoother than with the old Albizzia nail and, hence, much more comfortable and acceptable for the patient. Every click is equivalent to a precisely defined lengthening distance of 0.052 or 0.07 mm/0.002 or 0.0027 inch, depending on the nail. With the documentation of the clicking numbers, for example as a tally sheet in a table, the lengthening process can be managed and controlled extremely easily and absolutely reliably. Weekly x-ray scans or even daily appointments with a doctor, which necessarily accompany the use of some other internal systems, can be forgone. Because the patient is able to manage his lengthening without intensive assistance, he is absolutely free to choose the place where he wants to successfully complete this phase. Many patients choose a rehab center in their home countries in order to go to work and live their everyday lives there. This is absolutely recommended by us. Other patients choose a rehab center, a homestay or a hotel with training facilities near the BETZ INSTITUTE® in Germany.

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Bears the whole body weight of even heavy patients

betzbone vorteile

Due to the easy-to-handle clicking mechanism, the patients are able to manage the lengthening without intensive assistance

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Dr. Betz demonstrating the BETZBONE®

Advantages of the BETZBONE®


12,5 cm/4.92 inch maximum lengthening capacity per nail respective of the segment

  • High flexibility in regards to height increase


Bears the whole body weight of even heavy patients

  • Shorter treatment time with bilateral lengthening - both thighs or both lower legs at the same time - due to immediate postoperative mobilization on crutches
  • No immobilization in a wheelchair for several months as happens with other systems


Easy and safe lengthening control

  • Easy and conveniently managed by the patient without intensive assistance
  • Fewer appointments with the doctor
  • Fewer x-ray scans at only once a month
  • Can lengthen in rehab centers worldwide or even at home
  • Release from the BETZ INSTITUTE® usually occurs 2 weeks after the operation


Nail consists of absolutely corrosion-free material inside and outside

  • No corrosion and therefor no problems with rust
  • No seals necessary
  • No problem with gases coming out of the encapsulated parts of the nail during variations in atmospheric pressure








Comparison of internal limb lengthening nails


Lengthening capacity


12.5 CM/4.92 INCH




  6 CM/2.36 INCH

  8 CM/3.15 INCH

  8 CM/3.15 INCH