There are different fixation methods for traumatic lower limb fractures in orthopaedics, both surgical and non surgical. Specifically focusing on the tibia treatment options range from above knee circular pop, open reduction and internal fixation with plate fixation, intra medullary fixation as well as external fixators.

External fixators can be used as a form of temporary fixation or definitive fixation depending on the fracture pattern, soft tissue around the limb and available resources. Two types of external fixators are monolateral (in this wiki platform called ‘external fixator’) and ring fixator. Each has its advantages of use and disadvantages.  

This document will be focusing on ring external fixators, its applications, components, applications, and usage.

Terminology & components

• Circular fixator/frame or ring fixator - These terms are used interchangeably. Also often Ilizarov frame is used as a term, but this means a specific ring fixator with fixed struts. For this text we will use ring fixator as the standard term. 
• Wires - 1.8mm diameter, smooth and ideally with a bayonet eccentric tip. Olive wires come with a stop at the bone interface.

• Half pins - Pins that can be inserted in bone and attached to a ring fixator. In general 5-6mm diameter, with different thread lengths available. Modern pins are hydroxyapatite coated. Hydroxyapatite (HA) is a bioactive calcium phosphate ceramic that’s similar to the mineral component of bone. This coating enhances their biological and mechanical performance at the bone–pin interface, leading to better fixation and reduces pin tract infections.

Ring block - Consists of two rings and four connecting rods and is used to stabilise each bone segment. To optimize stability the distance between both rings should be maximum possible, allowing safe distance from the adjacent joints and from the fracture site. 

Virtual ring block - One ring at one limb segment with pins or wires that equals/approximate the stability of a ring block (further reading under ‘How to use Virtual ringblocks & Half pins’).

Dummy ring - An extra ring for improved stability, that is placed in between two rings in a segment when the distance between 2 rings in a segment that is greater than 160mm.

Wire tensioning - Applied by the wire tensioner instrument coming with the set. The steps of tensioning are: 

1 Tighten the wire fixation bolt at one side (always the side of the olive if present). 

2 On the other side the wire fixation bolt is only finger-tightened. 

3 Apply the tensioner on this side.

4 Tension while keeping the tensioner straight withstanding the forces. General rules of maximum tensioning forces: 

• Closed/full ring 130kg (N/m2)
• ⅝  or open ring 110kg
• Post - also known as Rancho; can be attached with a bolt to a ring to enable the creation of virtual ringblocks inserting half-pins on different levels in the bone segment. It often needs to be used in combination with half-pin fixation bolts depending on specific brands.

Indications & conceptualisation

In theory every fracture of a long bone that requires stabilisation and benefits from axial loading is suitable for fixation with some kind of a ring fixator. In reality it depends on several factors whether you would consider choosing this technique above others. These include fracture pattern and location, soft tissue integrity and cover, wound size &contamination as well as patient host factors.

Ring fixation is a biological fixation method that only allows axial micromotion and eliminates shear motions at the fracture site if applied correctly. It leads to a stable yet dynamic frame that allows the surgeon the options of acute and gradual correction, frame modularity to build as complex a frame as needed, and the ability of the patient to bear weight and move adjacent joints as tolerated. Other advantages include fracture reduction and stabilisation can be performed percutaneously; soft tissue resuscitation by ligamentotaxis; it can assist in soft tissue and bone defect management.¹

Ring fixation is considered an advanced technique nowadays mainly applied in tertiary referral centers in high-resource settings. There exist many different brandspecific variations and instruments. However, the principles go back to basic fracture healing, that with proper training, a basic instrument set and the right case selection could be applied in a lower-resource setting. Ring fixator components can be reused and repurposed safely which can be cost saving in the long run.

We will try to describe these basic principles focusing on lower leg fractures in this chapter. We do not pretend to be complete in any way. In the references we will add more in depth further reading. In comment boxes are considerations and alternatives added.

How to apply a basic ring fixator on a tibial shaft fracture?

Here we describe the technique to apply a basic ring fixator for the stabilisation of a midshaft (open) tibia fracture using classic ringblocks and rigid struts. We go into detail of every step, that is basic knowledge for other paragraphs. In the successive paragraphs we describe the sometimes easier and more forgiving alternative techniques with virtual ringblocks, halfpins and rapid adjustment struts. Aspects of both techniques can be combined for specific indications.

1 Preparation

Surgical planning

“you plan to fail if you fail to plan”.

Obtain radiographs - X-ray images of the AP and lateral including adjacent joints should be available prior to the start of surgery to prepare the surgical steps you are planning to take. 

Planning pin placement - It is paramount for the surgeon to go over the anatomy of the lower leg and understand the safe zones for pin placement as well as the location of the perforating arteries which are essential for lower limb flap options. The aforementioned factors may influence pin placement by the surgeon, ring configuration and struts placement. Being aware of the blood supply to the lower limb and location of the perforating arteries will influence the surgeon's debridement plan, any fasciotomies that may be needed and soft-tissue coverage techniques.

The essential perforators come from the posterior tibial artery 10 & 15cm proximal to the medial malleoulus at the posterior tibial border as illustrated

Performing surgical debridement

Prebuilding the frame

For this technique we advise to prebuild the frame based on preoperative x-rays. The prebuilt frame should consist of the rings and struts including its nuts & bolts. 

The prebuilt frame should consist of a ringblock in the proximal segment. The proximal ring is preferably a ⅝ ring with opening at the posterior side to allow the knee to flex and a full distal ring in the proximal segment. Four long connecting rods that exceed in length to reach the proximal ring of the distal segment are different placed through the ring (figure 3). Some surplus length is advised to allow intra-operative adjustment of the distance between the ring blocks and inter-fragmentary compression. In the distal segment the ringblock consists of two full rings. The proximal ring is placed at 3cm below the fracture zone and the distal ring is placed 1cm above the ankle joint. They are connected with rods at other position then the rods of the proximal segment.. A little excess length is useful to allow length adjustment during surgery. 

Preoperative building of the frame

Example of position of rods in the proximal ring. In essence the rods can be placed anywhere. Also does not need to be symmetrical, as long as the weight bearing axis falls within the 'area of support.²

Positioning of the patient

Supine position with small pillow/elevation under the ipsilateral thigh to neutralize the position of the tibial plateau. 

Some doctors prefer the use of a surgical assist device to securely position the leg and allow room for circular frame application such as the Russell Frame (Innovision copyright)], or a frame can be self-build of a modular external fixation set. 

Minimal equipment needed

Check before the surgical checklist procedure (before the patient received anesthesia) the presence of all materials. Check for adjoining sizes of rings. Make sure the application set matches the brand of the circular frame and has instruments that function properly. Sufficient half pins and wires (both with and without olive) should be sterilized. A general orthopedic trauma set for debridement and reduction is on the table. Prepare material to take at least 4 deep cultures in case of suspicion of a fracture-related infection. 

Pre-wash and sterilize the leg according to local protocol

For a tibia fracture sterilize the field from above the knee and the entire foot. Take into consideration possible soft-tissue reconstructions that may be needed for coverage. 

Marking key-points on the leg

Mark/draw a line along the joint line proximally and distally; Proximal line representing mechanical axis of the tibia and it represents the direction of the reference wire. Draw another vertical line to mark the posterior cortex of tibia.

2 Wound and fracture debridement

Perform a full wound and fracture debridementIncluding deep tissue cultures if indicated.

Performing surgical debridement
Surgical debridement in FRI
FRI treatment plan

3 Preliminary reduction

Perform a preliminary reduction. In principle this should be performed closed. In some cases there is an indication or opportunity (open fractures with soft tissue defect over the fracture) to perform an open reduction.

4 Proximal reference wire

Place the proximal reference non-olive wire transverse in the coronal plane lateral-medial direction, parallel to and 1,3-1,5cm distal from the tibial plateau articular surface. Stab incision at the lateral side, drill wire through first cortex using a powerdrill, to steer hold the wire with the lift hand using an alcohol soaked sponge (which will dissipate the heat generated from drilling), use a mallet to pass wires through the remaining soft tissues and skin till it has equal length on both sides, apply alcohol soaked gauzes around base of each wire.

Each ring block must have 4 fixation points. Usually this is 2 per ring, but in theory could by 1 on a ring and 3 on the other ring of the ringblock.

5 Frame placement

Place the prebuilt frame around the leg and attach the reference wire to the proximal ring, place the wire fixation bolts so that the leg will be centered in the ring. Tension the wire to the  5/8th ring to 110kg.

6 Distal reference wire

The distal reference wire is then inserted distal from the most distal ring. It is placed in the coronal plane, and parallel and at least 1cm proximal to distal tibia articular surface using the technique described above under 3.

7 Attaching and tensioning of the distal reference wire

Attaching and tensioning of the distal reference wire to the distal ring will align the proximal and distal fragments in the coronal plane, but not in the rotational plane. Therefore proper rotational alignment must be achieved before attaching the wire. The wire fixation bolts should be placed in the anterior half of the ring to allow proper correction of sagittal plan angulation. The wire can be tensioned 130kg. 

8 Correct translation malalignment

Correct translation in coronal plane, if still present, by sliding the fragments of the wire till aligned. And to correct sagittal angulation, a rolled towel placed under the fracture site can be useful to maintain position temporarily. 

9 Placement of the remaining rings

Place the remaining rings at the correct distance from the fracture (at least two centimeters, depending on fracture fragmentation and obliquity) by adjusting the heights of the nuts on the rods. And place and tighten a transversal wire in both rings.

To fixate the ring perpendicular to the rods, first tighten the nuts above and below the ring on one rod while all other nuts are not close to the ring yet. Next tighten all others while keeping the ring in the same position.

10 Insert remaining wires

Insert the remaining wires in to create stable rings. In reality, perfectly perpendicularly placed wires is hard to achieve, therefore it is suggested to add minimum 2 more wires per ring at 30-90 degrees divergence with two opposing olives at the remaining wires. Always respect the safe zones of wire placement

Alternatively to wires half-pins can be considered to be placed, especially in the tibial diaphysis these hold well. Read the next paragraph about considerations.

Safe zones and advised wire and half pin placement in the left lower leg. For more into detail reading: Ilizarov - Atlas Insertion transoseous Wires Half-Pins.

11 Rods

Tighten the nuts around the rods. Create fracture compression by tightening the nuts of the second and third ring towards each other.

12 Final x-rays

Try to make full bone projections with intraoperative fluoroscopy (if available) in perfect AP and lateral, to measure axis and possible malalignments.

13 Postoperative planning

Depending on soft-tissue treatment direct weight bearing is allowed. Removal of frame once callus is seen on xray and walking without pain and assistance. If no other complications occur generally after 6-12 weeks. 

How to use Virtual ringblocks & Half pins?

Often addition of a second ring in a segment is not possible due to space restrictions, therefore half pins can be added on posts to create virtual ring blocks. A stable virtual ring block consists of: 

• One full ring
• One wire, sometimes added with another wire
• Two half pins on a post at different levels preferably a 7 hole spread on the posts away from each other. Each pin should be placed through divergent orientation

Half pin insertion technique:

1 Longitudinal stab skin incision

2 Spread with a (small artery) clamp till bone

3 Place tissue protector/drill guide on the bare bone

4 Machine drill with 3.5mm drill bit (high speed) while flushing with saline

5 Remove drill and flush through guide to remove debris

6 Insert manually with T-handle the HA-coated 6mm half pin that should be threaded at least the full course through the bone

7 Apply an alcohol swab around the pin at the insertion (or in case available brandspecific protection rubbers) 

All half pins require pre-drilling to minimize thermal necrosis and pin loosening drill no more than 6 seconds and stop to cool the bone, saline irrigation continuously whilst drilling and lastly irrigate drill hole to evacuate debris from the drill hole. Insert a 6mm (HA coated if available) half pin in the hole manually.

The order of application a virtual ring block: 

1 Place a AP half pin on the tibial ridge (when the proximal ring should be placed close to the knee joint a reference wire in the transcondylar transverse plane anterior to the fibula is preferred, as described above) 

2 Connect to a rancho (often with 3 or 4 holes) and attach the ring (5/8th when close to knee) to it loosely. 

3 Adjust the position of the ring till it is perpendicular to the mechanical axis in AP and lateral view (preferably use fluoroscopy confirmation), then tighten the half-pin fixation bolt and the bolt to fixate the post to the ring. 

4 Add a second half pin on the other side of the ring on a post (also often on a post with 3 or 4 holes). First attach the post to the ring. Put the drill guide of the half pin through the hole of the post to determine its position. Insert pin using the technique described above. The safe zone is generally from the anteromedial side of the tibia. Tighten the bolt to the ring first and second the half-pin fixation bolt. 

5 Add a smooth wire in the transverse lateral to medial direction directly onto the ring and tighten it. 

Full half pin constructs

Full half pin constructs can also be used with equivalent mechanical stability by placing three 60° divergent 6mm half pins above and below a ring spanning a large part of the limb segmen (figure 7)t. 

A six-pin two-ring frame with divergent 6mm half pins is equivalent to a four-ring tensioned wire frame in terms of axial stability and bending resistance while allowing axial micromotion. 

The choice for the use of half-pins, wires or a combination of both can depend on different factors, including location of the fracture (in diaphyseal fractures half-pins are better accepted then wires with less pin irritation/infection), availability of materials and surgeons preference. 

The addition of out-of-plane half pins or wires to any limb segment produces an increase in stability to that particular limb segment. This can be particularly helpful when the segment is short.

Half-pins are often preferred in the diaphysis due to less irritation, loosening and infection.

Rapid adjustable struts instead of rigid rods

Instead of rigid rods, nowadays often adjustable struts are used instead. These are more forgiving in application, a frame does not need to be prebuilt, and some give advanced options such as gradual limb correction. 

Generally there are two types:

• Rapid adjustment struts - These are telescopic struts with multi-angle hinges at both ends which allows quick longitudinal, rotational and angular correction. Three or four of these struts spanning the fracture between two virtual ring blocks will create sufficient stabilisation.

Rapid adjustment struts (Orthofix copyright)

• Hexapod struts - These are six telescopic struts with multi-angle hinges placed in a hexapod form, that are numbered and can be gradually lengthened or shortened to correct alignment or length of a limb. This advanced limb reconstruction process is often supported by computer software of a specific frame brand.

Hexapod struts (Smith & Nephews copyright)

How to apply a spanning ankle frame?

For distal tibia or ankle luxation fractures a stabilisation construct often needs spanning of the ankle joint (figure 10). The primary objective of this strategy is to realign and stabilize the traumatized joint until definitive surgery while facilitating soft-tissue treatment and definitive surgical planning. 

A proximal virtual ring block can be placed on the tibial diaphysis proximal to the fracture using the above described technique with half pins only. The distal virtual ring block is a foot ring. The virtual ringblocks are interconnected with adjustable struts. 

With the knowledge of the abovementioned application principles of a ring fixator, this video can be followed to apply a temporary ankle spanning frame:

This Video and Temporary Circular External Fixation for Spanning the Traumatized Ankle Joint for more information on temporary ankle spanning circular external fixation

A technique to place a foot ring: 

• Draw lines on skin - Horizontal at the height where you plan the ring; divide calcaneus in 3rds, at the posterior 3rd line enter the bone with the olive wire and at the anterior third line exit the bone. 
• First wire - Drill the first calcaneus olive wire from lateral to medial 
• Second wire - Drill metatarsal wire from medial to lateral with the ring in perfect position
• Third wire - Drill second calcaneus olive wire from medial to lateral (at that moment the ring is not movable anymore)
• Attachment - Then attach the long struts to the ring to see how high you want the tibia ring (struts should be half way extended)
• Tibia ring in temporary non-weightbearing ankle spanning frames could suffice with only 2 half pins

An ankle spanning trauma frame

Aftercare of ring fixators

Post-operative care for patients can be divided in the acute setting, intermediate and longterm management.

Acute

0 This is immediately post-operative.

• Patient will have wound care Mx 
• Debulking of any bandage around the frame to access wound
• Frame can be cleaned with saline soaked gauze 
• Opportunity for educating the patient on pin-site care should be taken 
• Patients' pin-site gauze will be changed if it is soaked with blood and alcohol soaked gauze re-applied.
• Patient is do pinsite care. Two different regimes are generally followed: 

1 Daily cleaning and leave open

2 Weekly cleaning and dress with sponge.

• To note skin irritation and rash in the first 72 hours. In this case keep pin sites clean and no direct antibiotics is indicated.
• Patient is allowed to weight bear as tolerated (depending on soft-tissue status, the fracture configuration and if the joint was involved)

Intermediate (> 72 hours post frame insertion)

• Note for infection: pinsites will be red, painful, may see pus draining [ref to “the good, the bad and the ugly pinsite classification system”]

• Re-educate on cleaning pinsites and increase cleaning frequency to twice daily, keep a close eye and see patient weekly
• Consider course of antibiotics for a week when a pinsite infection is suspected

Longterm

• Look out for pinsite infection: Chronic infections seen, pus around pinsites, loose wires and pin, unstable frame and abscess collections
• Note radiological features of fracture related infections
• If infection present patient will need in-patient care with incision and drainage of abscess with re-evaluation of frame stability possibly revision of some pins or wires
• Consider need for deep tissue cultures taken when FRI is suspected. Patient may need a course of antibiotics afterwards.

How to diagnose FRI