What is Cubitus Varus (Gunstock Deformity)?
Elbow injuries often happen in children. Due to the unique structure of a child’s elbow, especially the lower part of their upper arm bone (distal humerus), it’s more prone to fractures. This area shifts from a pipe-like shape to a flatter triangular shape and coupled with a higher flexibility in their ligaments, children between 4 to 8 years can suffer from a specific type of fracture known as supracondylar humerus fractures.
If these fractures don’t heal properly, they can result in a condition known as “gunstock deformity”. This condition misaligns the elbow in three different ways, which can cause issues apart from just appearance. It may result in elbow pain, instability in the movement of the elbow, snapping in the tricep muscles, changes in the alignment of the elbow and lower arm bone, nerve issues in the lower arm, or even an increased likelihood of fractures at the outer part of the elbow.
Therefore, for most cases of gunstock deformity, surgical treatment is suggested. Various treatment options range from watchful waiting to procedures that alter bone growth and ultimately correct the alignment of the bone. The last option, known as corrective osteotomy, is preferred as it has the best probabilities of being successful.
What Causes Cubitus Varus (Gunstock Deformity)?
In the past, up to 30% of people who suffered a specific type of elbow fracture, called supracondylar humerus fractures, also developed a deformity. Thanks to modern surgical treatments, this percentage has significantly dropped. This deformity can also occur, though less frequently, after another type of elbow fracture, known as lateral condyle humeral fractures.
This deformity can also be caused by growth plate injuries, bone death (osteonecrosis), infections, and in rare instances, by conditions related to tumors.
Risk Factors and Frequency for Cubitus Varus (Gunstock Deformity)
Congenital cubitus varus, a rare deformity of the arm, can occur due to a condition called epiphyseal dysplasia of the humerus. In this condition, the part of the humerus (arm bone) called the epiphysis angles towards the middle of the body, which shrinks the carrying angle of the elbow joint. The elbow joint starts to solidify during the 12th week of pregnancy in the womb. If epiphyseal dysplasia happens during this time, it can result in congenital cubitus varus.
Signs and Symptoms of Cubitus Varus (Gunstock Deformity)
For a patient showing symptoms of a cubitus varus deformity, a detailed examination and patient history review are important considerations. The initial visit should include checking for the presence of open wounds, stiffness, scarring, and completing a full nerve and blood circulation assessment. By comparing the ability of the shoulder to rotate in extension between the affected arm and the healthy one, doctors can identify if there’s a rotational misalignment. If the deformity seems to be progressing in a child who’s still growing, further detailed assessment, like x-ray checks and possibly more in-depth scans, are necessary to identify abnormalities in bone growth.
Generally, the cubitus varus deformity is identified 6 to 10 weeks after a fracture has healed and full movement of the elbow has returned. The deformation of the elbow is mostly responsible for its abnormal look, while a certain amount of bend contraction or rearward angling can lessen the visibility of the deformity. Torsional malrotation can make the deformity seem more pronounced. Without treatment, the deformation generally remains stable and usually doesn’t worsen. However, if the growth disturbance in the lower arm bone (distal humeral physis) is uneven, the deformity can progress. If left unaddressed, or if the condition is severe, cubitus varus might cause the ulnar nerve to become trapped and lead to posterolateral rotatory instability due to weakening of the LUCL. Very occasionally, posterolateral rotatory instability becomes evident after surgery has been performed to correct the condition.
Testing for Cubitus Varus (Gunstock Deformity)
To understand the extent of injury in an upper extremity (like your arm), doctors need to take full-length x-ray images of both the injured and healthy arms. These images help estimate certain angles called humeral-elbow-wrist (HEW) angles, which give the most accurate method for assessing the injury. If the arm alignment is angled away from the body, that’s indicated with a (+) sign and called ‘valgus’. If the alignment is towards the body, it’s denoted with a (-) sign, known as ‘varus’.
An alternative to the HEW angle measurement is the Baumann’s angle; however, the HEW angle measurement is preferred because it can be applied to both adults and children who are still growing.
Without these full-length x-ray images, doctors can still estimate the HEW angle by measuring a particular angle from the middle of the bone shaft to the elbow’s center and the center of two forearm bones (radius and ulna).
The main aim of any surgical treatment, known as osteotomies, should be to bring back the HEW angle as close as possible to what it is in the healthy arm. This means the desired correction is determined by the difference in angles between the two arms. Other measurements from x-rays will also help in evaluating and planning the surgical correction.
Doctors also classify the severity of a specific arm deformity, called cubitus varus, into four grades: Grade I involves a loss of the typical outward bend of the arm, Grade II indicates inward bending (varus) of 0 to 10 degrees, Grade III refers to varus of 11 to 20 degrees, and Grade IV is for varus greater than 20 degrees.
Treatment Options for Cubitus Varus (Gunstock Deformity)
A corrective surgery known as osteotomy, which is performed on the lower part of the arm bone (distal humerus), is the preferred treatment option to relieve the symptoms and prevent the recurrence of cubitus varus deformity, or “gunstock deformity.” The aim of this operation is to correct the angle of the elbow joint to between 5 and 15 degrees and provide stability. There are several methods used for this surgery, and none have proved to be more successful or safer than the others. It is also unclear whether it is necessary to correct axial rotational malunion, a rotational misalignment, to achieve better outcomes.
In pediatric patients, pins, screws, staples, and wires are typically used to secure the area after surgery. A recent study with children found external devices to be more cost-effective and easier to remove after surgery than internal ones. However, in adults and sometimes in adolescents, plates are often needed for stable fixation and early motion, to minimize stiffness. Unstable fixation, frequently seen in adults, lets the corrected angle drift back into the deformity, leading to poor cosmetic results.
Recently, some surgeons have started using 3-D printed guides to simplify the process and smoothly correct the three-dimensional deformity, although the costs of these templates can be high. In some long-standing cases, collateral ligament reconstruction may be necessary alongside the main surgery, but this is rarely required for children or adolescents.
There are no specific guidelines for selecting the type of osteotomy, but complex corrections can be technically challenging in children compared to adults. None of the techniques has been found safer or more effective based on a review of multiple studies. Some techniques like step-cut and reverse step-cut are popular due to their increased surface area and inherent stability. Others, like multiplanar osteotomy, can correct the rotational component of the deformity, but they require more intensive planning.
The technique most commonly performed is the lateral closing wedge osteotomy (LCWO) as it is less technically demanding and can have fewer complications. However, unsightly scarring on the side of the elbow can sometimes be a problem with this procedure, and some believe that recurrence can occur if done on patients under 12 years.
Osteotomy techniques that are considered complex, such as the dome osteotomy, can avoid certain complications but may cause stretching of the ulnar nerve, a nerve running along the arm. Other techniques, like distraction osteogenesis, which forms bone gradually by gradually stretching the surgical site, have lower recurrent rates compared to other techniques but are commonly used for the treatment of cubitus varus.
What else can Cubitus Varus (Gunstock Deformity) be?
“Cubitus varus,” or a bent elbow, generally happens because of improper healing of a specific type of fracture just above the elbow. However, there are other possibilities that could cause this condition. These include previous fractures near the outside of the elbow, a decay of a particular bone in the elbow due to reduced blood supply, or an injury to the growth plate of the bone in the lower part of the upper arm.
What to expect with Cubitus Varus (Gunstock Deformity)
If cubitus varus, a condition affecting the elbow, is not treated, it generally doesn’t lead to loss of function. The main reason to correct the deformity through surgery, known as corrective osteotomy, is for aesthetic purposes. However, if the deformity has been present for a long time and is accompanied by instability and ulnar neuropathy (a condition that affects the nerve in the arm), surgery becomes necessary.
Possible Complications When Diagnosed with Cubitus Varus (Gunstock Deformity)
According to reports, about 15% of people who undergo these surgical procedures could experience complications. These complications could involve injuries to the radial and ulnar nerves (nerves in the forearm), lateral condylar prominence (a bony bump on the side of the elbow), infection, stiffness, scarring, and inaccurate correction of the original problem. However, it’s important to note that roughly 75% of the nerve injuries reported with these procedures are temporary and are often related to the surgical approach taken from the backside of the body.
Potential Complications:
- Injuries to the radial and ulnar nerves
- Lateral condylar prominence
- Infection
- Stiffness
- Scarring
- Inaccurate correction of the original problem (under- or overcorrection)
Recovery from Cubitus Varus (Gunstock Deformity)
The after-surgery care differs based on the specific corrective surgery that was done. Usually, a posterior above-elbow splint is used for 2 to 3 weeks, and then the patient begins exercises to regain a full range of motion. Depending on how quickly the patient heals, the K wires (a type of medical pin) are taken out after 4 to 6 weeks.
Preventing Cubitus Varus (Gunstock Deformity)
The main reason for performing an osteotomy on a cubitus varus, which is a medical term for a certain type of elbow deformity, is for improved appearance. This means that the function of the arm or elbow is usually not seriously affected or not affected at all. However, surgery may be recommended for patients who experience symptoms such as a feeling of instability or weakness in the ulnar nerve, which runs down the arm and controls various movements and sensations.