How to perform an elbow spanning external fixation
Source
Surgeon:
Thomas Ibounig (orthopedic surgeon)
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Summary
Focus: Temporary fixation of an unstable elbow joint.
Key elements: Pin placement planning, radial nerve protection, humeral and ulnar pin insertion, frame assembly, aftercare, pitfalls, and complications.
Indications and Clinical Context
General
Medical experts: Thomas Ibounig (orthopedic surgeon), Robert Björkenheim (orthopedic surgeon), Lauri Kavaja (orthopedic resident)
Name(s) of procedure: Elbow spanning external fixation, elbow ex-fix
Goal of Operation
Temporary fixation of an unstable elbow joint.
Problem
Traumatic elbow joint instability or a fracture with severely compromised soft tissue.
Diagnosis
S53.1 Subluxation and dislocation of ulnohumeral joint
In case of an elbow fracture:
S42.4 Distal humerus fracture
S52.0 Proximal ulna fracture
Short Pathophysiological Description
The stabilizing structures in the elbow are divided into primary and secondary structures. Stability of the elbow joint is primarily provided by the ulnohumeral joint, the medial and lateral collateral ligaments, the radiocapitellar joint, the joint capsule, and the origins of the extensor and flexor muscles of the forearm. The secondary stabilizing structures are the muscles crossing the elbow joint, namely the anconeus, the brachialis, the biceps, and the triceps brachii muscles.
If the injury to the primary and/or secondary structures is extensive, the elbow joint might not be stabilized by their repair and additional procedures may become necessary.
Key Anatomical Structures
Radial nerve
Humerus
Ulna
Radius
Step-by-Step Technique
Preparations and Anesthesia
The patient is in a supine position, with the upper limb on the arm table.
Plexus block or general anesthesia.
The plexus block will anesthetize deeper layers, but sometimes there is residual skin sensation around the posterior distal humerus, which can be treated with local anesthesia.
Landmarks and Pin Placement Planning
The aim is to first place two pins in the humerus and two in the ulna. The pins will then be joined together by rods and form the external fixator, which in turn will stabilize the elbow joint.
In terms of stability, it is recommended to place one pin as close to the joint as possible and the other one as far away from the first pin as possible in both the humerus and the ulna.
While placing the pins, keep in mind possible further/definitive treatments. The pins should not interfere with planned incision sites used for future definitive care (i.e. plates, screws, etc.).To plan the pin placement, palpate the humerus epicondyles, the olecranon, the ulnar diaphysis, and the proximal radius. The proximal radius is best palpated during pronation/supination movement.
The radial nerve can also be palpable, particularly in slim patients. You may use a soft marker to trace the outlines of the bones and the radial nerve on the skin. Using a soft marker will prevent damaging the skin.
Humeral pin sites:
The radial nerve runs along the distal humerus, which means that percutaneous placement of humeral pins is not recommended, and a proper incision is needed to avoid damaging the nerve.
The flat anatomy of the olecranon fossa limits placing the distal humeral pin too distally; thus, the best site is a bit proximal from the olecranon fossa. You can use fluoroscopy to find a suitable site to avoid hitting the olecranon fossa.
The skin incision should be just long enough for safe placement of the pins. There is no need for a very large incision because the pins should be placed about 8-10 cm apart to achieve sufficient stability.Ulnar pin sites:
The forearm pins should be placed in the proximal ulna. The ulnar pins can be inserted through pinhole incisions of the skin as there are no critical neurovascular structures between the skin and the ulna.
We do not recommend placing the pins in the proximal radius because the pronation/supination movement will then be lost. Additionally, with drilling the proximal radius, damage to the posterior interosseous nerve (PIN) is possible.
Note that the ulna is broader proximally and narrows distally, which slightly limits the placement of the distal ulnar pin.
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Humeral Incision
Make a lateral skin incision, approximately 10 cm, in the lower third of the humerus down to about 2-3 cm proximal to the lateral epicondyle.
Open the fascia and advance through the muscle parallel to the muscle fibers with scissors or a knife.
Identify the radial nerve, which can be found on the posterior side of the humerus before crossing to the anterior side at the border of the distal third of the bone. The nerve is often palpable before it can be visualized. You will first see the fatty streak and/or veins that run alongside the nerve.
Make sure to always be aware of the location of the radial nerve. You may use a retractor or a vessel loop to pull the nerve gently away from the operating field.
When you are certain the nerve is protected, you may proceed to the bone surface with a knife or blunt dissection with a Semb rasp, for example.
Placing the Humeral Pins
Use 5 mm pins for the humerus. The aim is to place the proximal pin proximal/anterior to the radial nerve and the distal pin distal/posterior to the nerve.
Make sure to protect the radial nerve at all times and also try not to stretch the nerve. The radial nerve is easily affected by stretching, which may result in temporary paralysis.
Establish the pin location in the middle of the humerus. The pins should be placed in the middle of the medullary canal. If the pins are placed too close to the cortices, there is a risk of fracture and the pins becoming loose.
The cortices of the diaphysis area are strong. We recommend drilling the lateral cortex first and then inserting the pin using the manual handle to get a better feel of the resistance of the medial cortex. Remember: if the bone is osteoporotic, there may be no resistance at the second cortex.
Pay attention to the correct depth when inserting the pin. To help with the assessment, it may be helpful to know that the humerus is about 2-2.5 cm wide here at the distal part. You can check pin placement by using a finger, but nevertheless, you need to take a fluoroscopy image to make sure that the pins are inserted correctly.
Placing the Ulnar Pins
Use the 4 mm pins for the ulna through small puncture-type incisions of the skin.
Use blunt dissection to reach the bone surface.
By using a trocar or a pin, place the pin laterally on the ulna and make sure that it is in the middle of the bone.
The pins should be placed in the middle of the medullary canal. If the pins are placed too close to the cortices, there is a risk of fracture and the pins becoming loose.In the diaphysis of the bone, the cortices are strong. It is best to drill into the lateral cortex first and then insert the pin using a manual handle to get a better feel of the resistance of the medial cortex and to control the insertion of the pin.
Make sure the ulnar pins are aligned. When the external fixator is later assembled, any twisting of the pins can cause tension and possibly even break the ulna.
Check with fluoroscopy that the pins are inserted correctly.
Humeral Wound Closure
Close the humeral wound before the frame assembly; otherwise, the frame will be in the way and the skin closure will become more difficult.
Take generous bites of the skin and the subcutis with individual sutures. If the skin around the pin is stretched, it may be necessary to make a small additional incision.
Frame Assembly
The closer to the bone the frame is, the more stable the fixator. On the other hand, if the frame is placed too close to the skin, it may cause soft tissue issues and complicate wound care. In most cases, a middle ground is called for, i.e. allowing the wound and pin-site care while not compromising the stability of the ex-fix.
Before tightening the screws, reduce the joint and/or fracture. When the joint seems congruent, perform a preliminary tightening of the screws and take fluoroscopic images of the joint.Finally, make sure that all the screws have been tightened. You can “wiggle” the ex-fix gently to make sure nothing comes loose. Once the patient is awake, the ex-fix will be subjected to movement, and testing the frame in the OR is always a good idea.
Take final fluoroscopy images. There should be a lateral and an AP image to help make sure that the joint is in place. In case of a fracture, make sure that there is no shortening or malalignment of the bones to help minimize damage to the soft tissues. Elbow joint congruency is confirmed using fluoroscopy.
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Piftalls and Complications
Pitfalls
Incorrect Pin Position
While placing the pins, adequate stability should be achieved while at the same time keeping in mind possible further/definitive treatments. The pins should not interfere with planned incision sites used for future definitive care (i.e. plates, screws, etc.).
When placing the pins, it is important to make sure that the pin will go through the medullary canal and not just perforate the cortices. If the pins are placed incorrectly, they may come loose.
Furthermore, the depth of the pins should be evaluated by using a finger and fluoroscopic images. Keep in mind not to drill the pins too deep past the second cortex as it may cause unnecessary soft-tissue damage.
Pins placed too close to the fracture area may make it prone to infection during subsequent osteosynthesis, as the pin tracks offer a direct connection from the skin to the bone surface. Make sure that the pins are placed far enough from the future operating field so that possible pin-site infection will not prevent the stabilizing procedure.
Inadequate Incision for Inserting the Pins
Do not insert the proximal humeral pins percutaneously: the radial nerve is ALWAYS located close to the pins.
Careless Tissue Handling
Identify the radial nerve and protect it diligently during pin insertion. Establish the course of the radial nerve by palpation if the nerve is not visible. When placing the humeral pins, make sure they do not cause stretching of the radial nerve.
Make sure to relieve any tension on the skin around pins. If there is tension on the skin, it may cause pain or predispose the patient to wound healing problems.
Inadequate Outlining of the Anatomy
Distal pins are inserted into the ulna, not the radius. Placing them in the radius may damage the posterior interosseous nerve (PIN) in the proximal pin area. Also, pronation/supination of the forearm may be lost and, due to the mobile character of the radius, the operation is technically more challenging.
Technical Challenges or Lack of Understanding of Biomechanics
Make sure the ulnar pins are aligned to avoid breaking the ulna due to tension when tightening the external fixator.
Complications
Radial Nerve Injury
The radial nerve may be injured in the procedure if its location and course are not established. Injury can be prevented by making a sufficient incision in the upper arm and carefully exposing and protecting the nerve.
Also be careful not to stretch the nerve too much as the radial nerve is easily damaged by stretching, which may result in temporary paresis.
The Joint Is Incongruent
The external fixator is used to achieve joint stability and/or for temporary fracture management. Assemble the external fixator and make sure to confirm the result by appropriate fluoroscopic images. Check that the joint is congruent or that the fracture is set.
Infection
The pin insertion sites of the external fixator may be infected, which is quite common. However, in many cases, infection of the pin site is rather mild and localized, and bedside wound management without antibiotics is sufficient.
Aftercare
General Guidelines
Pin insertion points should be cared for daily. Usually, saline wipes and a dressing change are enough.
Any sign of infection should be treated as soon as possible. Infection may cause the pins to come loose from the bone.
Tighten the screws daily to make sure that the bolts do not come loose. Loosening may occur particularly when the external fixator is used for a longer period of time.
Immobilizing the limb and elevating it will reduce pain and swelling.
The intact joints should be mobilized straight away. However, the patient should naturally abstain from lifting anything heavy.
If the elbow joint is not stable after the repair surgery and an external fixator is called for, the ex-fix will be kept in place until stability has been achieved, i.e. for 3-4(-6) weeks. On the other hand, if temporary stabilization of the joint is needed in the case of a fracture, the external fixator can usually be removed during the final fracture surgery when the soft tissue status allows it.
FAQ
What is the goal of elbow spanning external fixation?
The goal is temporary fixation of an unstable elbow joint.
Where are the pins placed?
The aim is to first place two pins in the humerus and two in the ulna. The pins are then joined together by rods to form the external fixator, which stabilizes the elbow joint.
Why is percutaneous placement of humeral pins not recommended?
The radial nerve runs along the distal humerus, so percutaneous placement of humeral pins is not recommended. A proper incision is needed to avoid damaging the nerve.
Why are distal pins inserted into the ulna rather than the radius?
Distal pins are inserted into the ulna, not the radius. Placing them in the radius may damage the posterior interosseous nerve in the proximal pin area, pronation/supination of the forearm may be lost, and the operation is technically more challenging because of the mobile character of the radius.
How is pin placement checked?
Pin depth should be evaluated by using a finger and fluoroscopic images. Fluoroscopy is also used to check that the humeral and ulnar pins are inserted correctly.
How long may the external fixator be kept in place?
If the elbow joint is not stable after repair surgery and an external fixator is called for, the ex-fix will be kept in place until stability has been achieved, i.e. for 3-4(-6) weeks.
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