Tibial shaft fracture- Fixation with a Taylor Spatial Frame (TSF) circular external fixator (Smith and Nephew)

This patient suffered multiple injuries and was managed with Damage Control Orthopaedics (DCO) techniques. Initially the leg was decompressed for an acute compartment syndrome and subsequently skin grafted within 72 hours.
The patient was too sick to return to theatre for conversion of the temporary external fixator to an intramedullary nail and as it was over 2 weeks since the ex-fix was applied, the risk of developing a deep infection had therefore increased, so we felt a circular frame would be safer.
Harwood P, Giannoudis PV, Probst C, Grimme K, Krettek C. Risk of local infection following damage control procedures for femoral shaft fractures. Orthopaedic Proceedings. 2018; 88-B: Supp I

The limb is pre-washed with a detergent soap to remove any skin oil.The skin naturally secretes oils and as the antiseptic is water / alcohol based, then the two are immiscible. It is therefore important to remove the layer of oil on the skin, so that the antiseptic can penetrate the skin pores.

The leg is prepared with chlorhexidine antiseptic.
In unstable leg fractures, it is often easier to prep the top half and then lift the leg to prep the lower half. Due to the weight of the leg, if you prep the foot first and then lift the leg, it is difficult for the assistant to hold for a prolonged period.

As the leg is unstable, it is better to lift it up supporting above and below the fracture.
I routinely do a double prep using a dark pink chlorhexidine solution and then wash that off with a lighter pink chlorhexidine solution. I use the colour contrast to clearly see that the whole limb has been painted with antiseptic.

The surgical drapes are applied.
The drapes are applied so that the knee is visible to ensure that the leg rotation can be checked during the operation.
To check the limb rotation, the foot is dorsiflexed into a plantargrade position. A line drawn from the second metatarsal through the mid-calcaneum should align with the tibial tuberosity proximally.

A separate drape with an adhesive edge is stuck to the side of the operating table so that when the C-arm swings under to obtain a lateral view, it is covered and the sterile field is maintained.

The side drape is folded and clipped to the edge of the table. This can then be unclipped and extended to cover the C-arm when in the lateral position.

The fracture level is drawn on to the patient’s skin using fluoroscopy

It is important to identify and draw the fracture on to the patient’s skin from both an AP and lateral view. This shows that the fracture / zone of injury is larger than the AP view alone demonstrated.

The level of the fixator rings is planned. When planning the ring level you need to take into account the extent of the fracture and the previous ex-fix pin sites.
The crosshatch area represents the fracture and the transverse lines above and below are the anticipated ring levels.

A medium length strut is selected and extended to its’ mid-point and compared to the planned ring levels.This is an important step because if the rings are too far apart or too close together, then multiple strut changes may be needed when running a prescription / programme.
It’s important to note that the strut would actually be in a diagonal orientation with respect to the tibia but for the purposes of the photo, it has been held in line with the tibia and hence may appear too long.
There is also another method for determining which size struts and strut lengths and this involves a look up table that is available from the manufacturer. Here you need to know the ring sizes, to decide which struts and strut lengths would be appropriate.

A 1.8mm reference wire is inserted into the tibia perpendicular to the anatomical axis of the bone.This wire is used to mount the first ring.
The anatomical axis of a bone is drawn by first identifying the mid-point between the cortices both proximally and distally (within the same diaphyseal portion of the bone) and then these two points are connected (and extended if required).

The cross sectional anatomy of the limb is essential reading and knowledge for a frame surgeon. You have to have a detailed understanding of where the structures at risk (nerves / vessels) are, so that the frame and points of fixation can be planned appropriately.
With regard to this case, the proximal ring is at the level of cut 2 (see diagram) and the distal ring is at the level of cut 4/5.
This image is from the Smith and Nephew publication on safe soft tissue corridors which is reproduced with permission in the Implants section of this technique, and should be referred to.

All wires are inserted using power and are lubricated / held with a chlorhexidine soaked swab. This gives only a little bit of directional control. The key technique is to start with the wire in exactly the right place and pointing in the correct direction. Then when inserting the wire, the power tool does not push the wire forward, it simply rotates the wire and allows it to gently advance.
Some surgeons advocate starting the wire rotation at a low velocity and then building up the speed. Others prefer to use pulses of high speed. Personally I prefer to use pulses of high speed and this allows the wire Bayonet tip / bone interface to cool intermittently and reduces the incidence of thermal necrosis to the bone.
To insert a wire, here is my recommended technique:
Identify a safe zone for wire entry and exit
Ensure the muscle compartment contents are in their elongated state, so that they aren’t tethered by the wire
Push the wire through the skin and down to the bone
Check with fluoroscopy the wire position on the bone
Check the wire alignment either fluoroscopically or that the wire is correctly aligned with the ring
Pulse the wire on high speed to drill a hole into the bone and gently advance the wire (do not bend the wire)
On exiting the far cortex of the bone, you can either manually advance the wire with a mallet or use oscillate (this prevents soft tissues from wrapping around the wire)

The first ring is positioned on to the reference wire.When mounting the ring, it is important to check that the ring is firstly the correct size, typically a gap of 2 finger’s width (at least 2 cm) should be available circumferentially around the leg. If there is a slight excess gap and the next size down ring would be too small; the excess is best positioned posteriorly over the muscles, which can swell with muscle contraction or infection.
The TSF can use rings of different sizes, so the proximal ring can be larger than the one around the ankle (which is narrower than the calf). In Ilizarov fixators, the rings should be the same size.
The proximal ring should be rotated around the leg until the ‘master tab’ is directly anterior to the bone. The master tab is where struts 1 & 2 will connect to the proximal ring. The measurements for frame position in relation to the bone are taken from this point (mounting parameters).
In our unit we use syringe bungs to hold down the wire dressings, so these must be placed on to the wire before it is connected to the ring.
If the proximal ring is close to the knee joint, then a 2/3 circumference ring can be used instead and this will permit knee flexion without the ring touching the posterior thigh.

The reference wire is fastened on to the ring.To fasten a wire to the ring, there is a specific technique to follow. Depending on where the wire passes over the ring hole will determine whether you require a ‘cannulated’ wire fixation bolt (wire passes centrally over the ring hole) or a ‘slotted’ wire fixation bolt (the wire passes towards the side of the ring hole).
Select either a slotted or cannulated wire fixation bolt.
Insert a washer (if required) in between the wire and the ring, to prevent the wire from distorting or being pulled on to the frame.
Loosely tighten both wire fixation bolts, so that the wire cannot escape.
Determine which side is preferable to tension from (or if using an olive wire, then tighten the striped side to the ring and tension from the non-striped side).
The wire is tensioned (usually around 90-110 ft lbs)
Tighten the 10 mm nut on the wire fixation bolt, so that the wire is firmly gripped and cannot move. To do this, hold the bolt with the ‘fixation bolt wrench’. The bolt should be kept in perfect alignment with the wire and should not rotate at all. The nut is tightened.

The C-arm is rotated to give a lateral view. A little bit of horizontal plane rotation of the C-arm is used, to ensure that both medial and lateral aspects of the ring perfectly overlap with each other (i.e. the C-arm beam is aligned with the reference wire).
Once the correct C-arm view has been obtained, the ring is tilted up and down on the reference wire until it is perpendicular with the anatomical axis of the tibia (in the lateral view).

A 1.6mm standard K-wire is used to fix the proximal ring to the anterior tibia and maintain the sagittal plane orientation.Now the proximal ring is orientated perpendicularly to the tibia’s anatomic axis in both the AP and Lateral view.

A position for a half pin is planned so that it is in a safe corridor and avoids the fracture and previous ex-fix half pin holes.A safe corridor avoids potential structures at risk e.g. nerves, vessels, joint capsule (can lead to septic arthritis), tethering too much muscle.
To site a half pin, follow these steps:
Palpate the tibia, so that the anterior / posterior or medial / lateral borders are identified.
Select an appropriate size rancho cube (1 – 5 holes are available) or pin clamp
Connect this to the ring using a 16mm bolt but leave it slightly loose so that the assembly will allow a few degrees of rotation.
Insert the drill tissue protector and gently apply pressure so that a faint mark is made on the skin surface where the half pin is intended to be inserted.
Using a scalpel make an incision halfway between the tibia’s borders. Only incise the skin and deep dermis. I prefer to make an oblique incision because if I’m too close to one edge of the tibia, it is easier to adjust the pin placement without having to extend the wound.
Use a clip or pair of scissors to bluntly dissect down to the bone and scrape the periosteum and soft tissues off the bone. Open the clip / scissors and pull back to create a clear path from the skin to the bone surface.

Insert the drill tissue protector and trocar into the wound and down to the bone.

Remove the trocar and insert the 4.8mm drill bitGently rotate the assembly to feel the edges of the bone and then stop when you are at the midpoint between the two edges. Please note that due to the tibia’s triangular cross section, at some levels and positions, it may be necessary to be slightly off centre but so that the best position is selected within the bone.

Drill on full speed but carefully maintain the drills position so that it doesn’t slip on the bone and also do not distort the frame or its’ relationship to the bone.I use pulses of high speed to allow the drill bit / bone to cool and prevent any thermal necrosis.
I irrigate the drill bit with saline to help decrease its’ temperature.
I also only drill one cortex and then remove the drill bit for cleaning, before re-inserting and drilling the far cortex.
When reaching the far cortex, drilling should be stopped, so that the depth can be read from the side of the calibrated drill bit. Often adding between 5-10mm so that the appropriate thread length half pin can be selected.

After drilling one cortex, the drill bit has lots of bone swarf clogging the flutes. I like to clean the drill bit with a damp swab. I feel this ‘sharpens’ the drill and allows it to work better. It also allows the drill bit to cool down.

The half pin drill hole is irrigated with saline using a syringe and blunt needle.This washes any residual bone swarf out of the hole which could contribute to an infection.

A hydroxyapatite coated half pin is selected and inserted using the T-handle.The half pins are available in 4.5mm and 6.0mm diameters. I routinely use 6.0mm diameter half pins in adults.
The half pins are described as two measurements. The first measurement is the length of the threaded section of the half pin that is hydroxyapatite (HA) coated. The second measurement is the overall length of the half pin (including the HA coated portion). For example, a 35mm x 150mm half pin has a 35mm threaded section which is HA coated and the overall pin length is 150mm.
When inserting a half pin, it is important to select one with an appropriate thread length so that bi-cortical fixation can be achieved. Also it is important that you don’t advance it too far, as this will damage the near cortex bone thread and when withdrawn, it will be loose.
In a randomised trial using HA coated and uncoated pins during bilateral leg lengthening procedures, Piza et al. found that the rate of pin loosening was statistically less for the HA coated pins (4% vs 80%). However, there was no statistical difference in the incidence of pin track infections.
Piza G, Caja VL, Gonzalez-Veijo MA, Navarro A. Hydroxyapatite-coated external-fixation pins – the effect on pin loosening and pin-track infection in leg lengthening for short stature. J Bone Joint Surg [Br]. 2004; 86-B: 892-897.

The half pin insertion depth is checked using fluoroscopy.Note the near cortex is within the threaded portion of the half pin and the HA coated threaded portion is also below the skin surface.

The half pin is secured into the rancho using a grub screw and a 6mm diameter centering sleeve.The grub screw requires a 3mm hexagonal Allen key or screwdriver to tighten it.
A 10mm bolt could be used instead of a grub screw.
The centering sleeves are available in different diameters and are matched to the diameter of the half pin that is used. Also on the top of the centering sleeve, there is a line which indicates where the aperture is, for the grub screw to go through and hold the half pin.
When tightening the grub screw / bolt, it is really important to ensure that the half pin is rotated so that a flat surface is perpendicular to the grub screw / bolt. Note the half pins have a triangular cross section within the shaft. If the pin isn’t correctly aligned with the grub screw, it could slip and loosen the attachment between the half pin and the frame.

The rancho is held with a 13mm spanner and tightened onto the ring using a 10mm spanner on to the 16mm bolt.Again it is important to hold the rancho still and only move the spanner that is tightening the bolt.

The wires can either be broken off or they can be cut and curled over the ring.
If breaking the wires, it is important to flex them up and down in the same plane as the ring. If you do it in the wrong direction, the wire will be slightly longer and it leaves a prominent sharp edge which the patient could scratch themselves on.
The rationale for curling the wire, is that some surgeon’s feel that if the wire loses its’ tension, then it can be re-tensioned. However, there is another method to re-tension a wire (even if it has been broken off). By rotating the wire fixation bolt and nut together away from the limb, this will re-tension the wire.

The process is repeated to apply the second ring below the fracture.A smooth reference wire is inserted perpendicular to the axis of the tibia under fluoroscopic guidance.

The second ring is mounted on to the reference wire ensuring adequate clearance circumferentially around the leg.As this construct will be using a combination of wires and half pins, then only 2 rings will be required.
In an all wire Ilizarov fixator, then 2 rings are used per block (segment of bone above / below the fracture) and each ring needs at least 2 points of fixation (i.e. 2 wires).

The second ring is orientated in the lateral plane to ensure it is perpendicular with the axis of the tibia and secured with a short 1.6mm K-wire.

Safe corridors and locations for the half pins are planned and the ring is secured to the distal fragment.Remember to use the correct method for drilling and siting half pins, as even small variations can lead to suboptimal outcomes e.g. pin loosening etc…
The choice of whether to use a wire or a half pin will be determined by the operating surgeon. The principles are:
To use a safe corridor and avoid any neurovascular structure. If a wire is going to be used, then it should be inserted from a dangerous position to a safe position. What this means, is that the structure at risk is identified and the insertion point of the wire is carefully positioned to account for it. If the exit point were to be close to a structure at risk, then there is much less control of an exit point versus an entry point and this puts the structure in question at risk.
Wires and half pins should be planned taking into account where the struts will go, so that they don’t block or interfere with them.
Wires and half pins should not be too close to joint capsules (there’s a risk of septic arthritis).
Wires and half pins should not tether too much muscle; or skin/muscle that has a long excursion because during the normal gait cycle, the soft tissues will get irritated and may become infected.
When transfixing through a muscle, it should be performed with the muscle in its’ elongated state.
Depending on the type of motion that is desired at the fracture site, this will affect whether an all wire construct or a hybrid (wires and half pins) construct will be used. An all wire construct has axial motion at the fracture site (like a trampoline), whereas a hybrid construct has a cantilever bend type motion.

The half pins are shortened using the half pin bolt croppers.

It is important to select the correct diameter half pin and lower the bolt cropper all the way down the ring.
When using the bolt cropper, a simple error is to not extend the handles. This means much greater force is required to cut the bolt.
Once the rings are secured, the 1.6mm K-wires can also be removed from both rings.

The rings are connected using the six struts.I prefer to have the black numbered section connecting to the proximal ring, so that the numbers are the correct way up when viewed from the patient’s perspective. This makes it easier for the patient to adjust them when running a programme / prescription.
The struts must connect to the designated areas (i.e. the outer holes of the tab). There is sometimes a mark on the ring to help show you. If the strut connects to the wrong location, then the computer will not be able to account for this and any programme / prescription will have an undesirable outcome.

The struts connect to the rings using shoulder bolts. These are torqued to prevent them from coming loose but also allow the strut to rotate, so that the numbered side can be easily seen.
Each strut is numbered from 1 to 6. In this example the master tab is on the proximal ring and directly anterior to the tibia. The struts are therefore number 1 & 2 on this tab and from a patient’s perspective, they count anti-clockwise around the leg. Therefore strut 1 will be on the right, with 2 on the left and so on around the leg.

An acute reduction is performed under fluoroscopic guidance.The fast fx struts have the shoulder clamp (grey section) down towards the numbered black section. This allows the strut to rapidly telescope and shorten / lengthen. The distal ring is held and traction is applied to the fracture and it is manipulated to reduce it. Once satisfied that the position is acceptable, then the shoulder clamp on the strut is moved to grip the threaded portion of the strut and lock it in position.

The leg is imaged in the lateral plane to confirm the reduction.It is often unsatisfactory and further adjustment is necessary.
The distal section needs to be distracted, so that the segment can be posteriorly translated.

Manual adjustment of the strut lengths is used to fine tune the reduction.There is a really good paper by Professor Roger Atkins from Bristol that describes how to adjust the struts to achieve the desired correction. Professor Atkins was one of the early adopters of the frame in the UK and his insights are all worthwhile ones.
An alternative would be to use the computer software instead, but this will increase the anaesthetic time or if done post-operatively, it will increase the frame time.
Heidari N, Hughes A, Atkins RM. Intra-operative correction of the Taylor Spatial Frame without a computer. J Orthop Trauma. 2013; 27(2): e42-e44.

The pin and wire sites are dressed with chlorhexidine soaked gauze.The dressings are held with red clips on the half pins and rubber syringe bungs on the wires.
The fasciotomy skin grafts are covered with Jelonet (a paraffin coated non-adherent dressing).

It is very difficult to wrap a bandage around a leg under a circular frame, so the area is packed with ‘fluffed up’ gauze.
Note the coloured and numbered clips have also been applied to the struts.
Red
Orange
Yellow
Green
Blue
Purple

The strut lengths and ring sizes are read out and recorded on the operating room white board.I recommend taking a photo of the white board with the strut lengths and ring sizes, as this can be easily read and transcribed into the patient’s operation note.
Wool is also packed under the frame, to hold the dressings in situ.

After the operation a departmental ‘reference’ x-ray is performed.The reference x-ray must be requested specifying which is the reference ring. In this case, it is the proximal ring and this should appear as a single line on the x-ray (not an ellipse like the distal ring).
The x-ray must be a true AP / lateral and both must be perfectly orthogonal.
Ideally the whole bone and joints above / below the fracture should be included. As long as you can draw the anatomical axis of both segments, it will be sufficient.

From the reference x-rays, the following will be measured and inputted into the TSF software to calculate a programme / prescription to correct the deformity.
Deformity parameters
AP angulation (varus / valgus)
AP translation
Lateral angulation (apex anterior / posterior)
Lateral translation
Axial angulation (internal / external rotation)
Axial translation (short / long)
Frame parameters
Ring sizes
Strut sizes and lengths
Mounting parameters
AP frame offset (distance from master tab to the origin)
Lateral frame offset (distance from master tab to the origin)
Axial frame offset (distance from the master tab to the origin)
Axial view frame rotation
The origin is the CORA and distances are perpendicular (not direct measurements at an angle).
The full description on how to use the software is beyond the scope of this technique but the important concepts to note are the deformity parameters, the frame parameters and the mounting parameters. Once the computer has this information, it can calculate the programme to correct the deformity.

The timing of when to remove the frame is often a difficult decision. The patient should have regained a normal gait pattern and have no symptoms of pain at the level of the fracture when fully weightbearing (they sometimes still have discomfort where the wires / pins irritate the soft tissues).
Radiographs are essential and due to the mechanics of the fracture / frame construct, callus should be seen at the fracture site from secondary bone healing. On the radiographs you look for cortical bridging and an absence / resolution of the fracture line. Whelan et al. have also developed a scoring tool for tibial fractures called the Radiographic Union Scale in Tibial fractures (RUST). This was developed for tibial fractures treated with intra-medullary nails however, the findings and principles are useful. Here each cortex (anterior / posterior / medial / lateral) is given a score:
Callus – absent; Fracture line – visible
Callus – present; Fracture line – visible
Callus – present; Fracture line – invisible
The scores of all cortices are combined to give an overall score. The minimum score is 4 (completely unhealed) and the maximum score is 12 (fully healed). A score of 10 or more is considered united.
Once you feel satisfied that the fracture is stable, then you can destabilise the frame. With a hexapod fixator, simply removing one strut will destabilise the whole construct (so if a strut change is required during the programme / prescription, then a 7th strut must be temporarily interposed).
The fracture stiffness can be manually tested by firmly holding the leg and trying to bend it. This shouldn’t be painful for the patient and very little movement / deflection of the frame should be seen. Do not hold the frame and bend this, as there will be movement at the frame / bone interface.
One option is to remove all of the diagonal struts and replace these with 3-4 vertical struts that connect the rings. These should be left loose so that they will allow axial movement. This maintains sagittal and coronal alignment but allows increasing loads to be transferred to the bone. The patient is then reviewed in a few weeks and a final decision is made to remove the frame.
Alternatively struts can be sequentially removed until you are ready to remove the rings.
We routinely take frames off in clinic by infiltrating local anaesthetic around the HA coated half pins and using Entonox. If any olive wires have been used, then these frames are removed in theatre.
Once the frame is off, then either a walking cast or aircast boot is used for the last few weeks of treatment.
Whelan DB, Bhandari M, Stephen D et al. Development of the radiographic union score for tibial fractures for the assessment of tibial fracture healing after intramedullary nail fixation. J Trauma 2010; 68: 629-632.