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All Internal Segmental Bone Transport and Optional Lengthening With a Newly Developed Universal Cylinder-Kombi-Tube Module for Motorized Nails—Description of a Surgical Technique

Krettek, Christian MD, FRACS, FRCSEd; El Naga, Ashraf MD

Journal of Orthopaedic Trauma: October 2017 - Volume 31 - Issue - p S39–S41
doi: 10.1097/BOT.0000000000000986
Supplement Article

Summary: Segmental transport is an effective method of treatment for segmental defects, but the need for external fixation during the transport phase is a disadvantage. To avoid external fixation, we have developed a Cylinder-Kombi-Tube Segmental Transport (CKTST) module for combination with a commercially available motorized lengthening nail. This CKTST module allows for an all-internal segmental bone transport and also allows for optional lengthening if needed. The concept and surgical technique of CKTST are described and illustrated with a clinical case.

Supplemental Digital Content is Available in the Text.

Trauma Department, Medizinische Hochschule Hannover (MHH), Hannover, Germany.

Reprints: Christian Krettek, MD, FRACS, FRCSEd, Trauma Department, Medizinische Hochschule Hannover (MHH), Carl-Neuberg-Straße 1, 30625 Hannover, Germany (e-mail:

The authors report no conflict of interest.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (

Accepted September 01, 2017

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Various reasons can lead to complete segmental bone defects (open high-energy fractures with bone lost at the scene, surgical osseous debridement for devitalized or infected bone, tumors, and other pathology). Methods of treatment include bone grafting, the use of bone substitutes, shortening, shortening with secondary lengthening, the use of bridging implants, and segmental bone transport (SBT).

Segmental bone transport (SBT) can be performed with a complete external fixation and transport system,1,2 or as an external segmental transport along a bridging internal device such as an intramedullary nail3 or a plate.4

External fixation has been a great addition to the treatment of musculoskeletal bone defects but external fixators are related to a variety of problems and complications. These include pain, pin tract infection, joint stiffness, interference with gait, discomfort, and a host of aesthetic and psychological problems. When external segmental transport is performed over an internal device such as a nail or plate, the time needed for the external fixator is reduced to about 30 percent when compared with only using an external system.

Recently, motorized nails have been described for limb lengthening.5–7 The motor of the nail can be activated with mechanical energy by gait or with electrical energy either from a battery or magnetically induced with an actuating device. A custom-made motorized nail for segmental transport has been described in the past in a single case.8 Since then, other applications in humans have been rarely described in the literature.

In this article, we describe the treatment of bone defects with a recently developed simple universal implant module, the CKTST module (K-Implant, Hannover, Germany), which can be attached to any motorized lengthening nail (see Figures, Supplemental Digital Content 1 and 2, and This module uses the driving force and control (forward, stop, backward, and speed control) of a motorized lengthening nail for SBT and allows for optional additional bone lengthening in cases where there is some shortening. Since both SBT and bone lengthening is internal, the risks, disadvantages and negative side effects of external transport systems can be avoided.

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A 74-year-old patient sustained a distal open Grade IIIA fracture of his right tibia (AO/OTA42A) and fibula fracture, which was initially debrided and stabilized with open reduction and internal fixation (tibia: medial 14-hole titanium compression plate and lag screw, fibula: lateral 1/3 tubular titanium plate) (see Figure, Supplemental Digital Content 3, One year later, he presented to our institution with pain [visual analog scale (VAS), 6–8] and inability to walk without crutches. There was no history of infection or wound healing problems in this otherwise healthy, nondiabetic, and nonsmoking patient. Radiographs and CT scans showed an atrophic nonunion of the tibia with sclerotic fracture lines and the fibula was healed. There was malalignment of the tibia with a 3° valgus deformity and a 25° external torsion compared with the other uninjured side. The soft tissues were extremely tight, strongly adherent to the underlying bone, and with a dark change in skin color at the level of the fracture. The foot had normal pulses with intact sensory and motor function. There was limited dorsiflexion at the ankle joint (dorsi-/plantarflexion 0°/10°/30°). Knee range of motion was normal.

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Medico-Legal Aspects

After several extensive discussion of various treatment options, the patient opted for the CKTST module system (see Table, Supplemental Digital Content 6, The CKTST module is not an FDA-approved implant module (patent pending EP17184283.4). Production, storage, and implantation complies with German and European medical implant regulations. Local ethics committee approval was obtained.

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Surgical Technique

In the first surgery, the patient underwent thorough soft tissue and osseous debridement. After removal of all necrotic bone, a tibia defect of 90 mm remained. This defect was filled with a gentamicin cement spacer and the wound was closed with a negative pressure wound system. Several days later, a free vascularized latissimus dorsi flap transfer was performed. Wound healing was uneventful and the patient was mobilized with a below knee brace and allowed partial weight bearing (15–20 kg) with very mild pain (VAS 1–2).

Once the skin of the free flap was dry and the wound had completely healed, the patient was brought back to the operating room. The free flap was elevated at the anterior margin, the cement spacer was removed and the torsional malalignment was corrected by rotating the tibia and an osteotomy of the fibula. The proximal medullary cavity of the tibia was opened by a trans-ligamentous or infrapatellar approach, and a motorized nail (PRECICE; Nuvasive, San Diego, CA) in combination with the CKTST module was inserted and placed in the very short distal tibia fragment, directly onto a broken plate screw, which was left in place at the initial debridement.

The motorized nail was locked in the proximal tibia. The distal holes of the motorized nail remained at the distal end of the proximal fragment (see Figures, Supplemental Digital Content 4 and 5, and The CKTST module was locked in the distal tibial fragment with 2 locking screws after making sure that (1) the slot of the CKTST module was in line with the distal locking holes of the motorized nail proximally and (2) the tibial torsion was symmetric to the contralateral side. The distal motorized nail screws were then placed passing through the bone, the CKTST module, and the distal nail hole. This locking screw insertion of the transport fragment locking was done before the Gigli saw and hole osteotomy of the transport fragment. The transport was then successfully tested intraoperatively with the magnetic actuator for 1 mm temporarily.

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Postoperative Treatment Course

Wound healing again was uneventful and the patient was mobilized with a below knee brace and partial weight bearing (15–20 kg) with very mild pain (VAS 1–2). Because of the age of the patient (74 years), we delayed starting the transport until 3 weeks after the osteotomy and began at a slow (0.25 mm/d) rate. Weekly radiographs in 2 planes were taken and ultrasound controls were performed. At 4 weeks, we saw that the regenerate demonstrated low density and we then reversed the transport direction for 2 weeks to give the regenerate more opportunities to mature. Three months after osteotomy, the transport rate was increased to 1 mm/d, and radiographs began to show homogenous calcification of the transport callus. Since any motorized nail has a limited transport distance (here 50 mm), a planned so-called “pit stop maneuver” was necessary. Under general anesthesia, the transport segment was temporarily unlocked from the motorized nail while temporarily secured to the distal main fragment. Then the nail was rewinded. After that, the transport segment was relocked at a more proximal position of the transport segment and the temporary fixation was released again. This allowed for the necessary additional transport length. Although the transport segment was entering the distal main fragment, 2 of 3 distal locking screws had to be removed because they would have hindered the docking. A local docking debridement was followed by a small local bone graft. A loosened proximal locking screw was reinserted and secured with a short 3.5-mm 1/3 tubular plate.

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During transport, we observed sequential screw loosening of the proximal interlocking screws in the nail. The screw loosening was addressed with reinsertion and application of a small plate.

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SBT with the use of a simple universal slotted cylindrical transport tube for combination with any motorized lengthening nail is a newly developed tool and described for the first time in the orthopaedic literature. There are several advantages over conventional techniques.

The treatment of segmental bone defects with bone grafting or the use of bone substitutes has significantly improved, especially with the induced membrane concept.9,10 Donor site morbidity and the creation of a rigid full-thickness bone “block” rather than a tube has its related problems such as re-fracture which have been observed in the past.

SBT can be performed either with a complete external fixation and transport system,1,2 or with an external segmental transport along a bridging internal device like an intramedullary nail3 or a plate.4 In general, external fixation is related to a variety of problems and complications. Another disadvantage of partial or complete external segmental transport concepts is the need for the placement of Schanz screws in the static proximal and distal main fragments. This can be difficult or impossible in short segments, as in the presented patient. For these reasons, we prefer to avoid external fixation whenever it is possible.

Recently developed magnetically activated nails11–13 have advantages over gait-activated systems,5 which are difficult to control (speed and stop) and cannot reverse direction. Magnetically activated motorized nails overcome these disadvantages because they allow good control of start and stop as well as the direction and speed. These are preferred by us for use with the CKTST module.

Potential disadvantages are related to the fact that any motorized nail system requires a certain minimum length of the nail which can be problematic in short end fragments. In these circumstances, direct locking of the transport fragment may not be possible and other methods of connection (wire and plate) may need to be considered. Another disadvantage of magnetically motorized nails is the fact that the induction of energy is related to the distance between the external actuator and the internal receiver in the nail. In obese patients and limbs with large soft tissue envelope, the amount of energy transferred is less compared with normal weight patients and slim limbs.

One of the great advantages of the CKTST module is that it allows excellent control of speed, stop, and direction. In the case presented, this was helpful, because the patient's bone regeneration was less reliable than in a younger patient. When the regenerate appeared less sound than expected in a routine ultrasound evaluation, we reversed the SBT for 2 weeks, before advancing it again.

Another important advantage is the fact that the CKTST module allows for additional optional gradual lengthening. Most of these patients with segmental defects also have some shortening. In addition, there is frequently some shortening associated with debridement at the docking site.

Another advantage is that shorter fragments are more amenable to this technique with the module. The fragment opposite the nail entrance can be as short as 3 cm. In case of lengthening over nail or plate, the placement and fixation with additional Schanz screws would be very difficult or impossible.

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The authors thank the Members of the Radiology Department of Medizinische Hochschule Hannover (MHH) for their assistance with patient images.

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bone defect; motorized intramedullary nail; internal segmental bone transport; transport module; femur; tibia

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