Supracondylar corrective osteotomy for cubitus varus--the internal rotation component and its importance. An unique bone experiment.TR Jimulia, SK Sabnis
Dept. of Orthopaedics, Seth GS Medical College, Parel, Bombay, Maharashtra.
In 20 patients with cubitus varus, a clinical test suggested by Yamamoto et al (1985) was carried out to measure the internal rotation. Average internal rotation was found to be 37.5 +/- 9.390. A correction for internal rotation was carried out for all the patients having angle more than 20 degrees. Following osteotomy, post-operative Yamamoto's angle was measured and was found to be 8.85 +/- 6.5. An experiment was carried out on postmortem human humerus with cubitus varus. The internal rotation was measured with Kirschner wires and was found to be 30 degrees. Osteotomy was carried out to eliminate varus and correct internal rotation. Radiographs taken before and after the osteotomy confirmed the correction. We conclude that this derotation has to be corrected and Yamamoto's test should be used to assess the correction.
Keywords: Adolescent, Biomechanics, Cadaver, Child, Female, Human, Humerus, Male, Osteotomy, methods,Rotation,
Cubitus varus is a commonly faced deformity following a supracondylar fracture of the humerus in children, especially when displaced.
According to Dowd and Mopcroft, 54% of the displaced fractures show a loss of carrying angle greater than 5? and of these, 23% developed cubitus varus deformity. Of the cases with a loss of carrying angle greater than 100, 85% show either residual tilt or internal rotation on the post-reduction radiograph. All cases in which there is residual tilt after manipulation and 40% of those with internal rotation on the post-reduction radiograph, develop cubitus varus deformity.
This deformity exists in 3 planes, viz. horizontal, coronal and vertical can only be assessed in 2 planes by plain radiography. To measure the internal rotation, one would have to depend upon computed tomography, which is quite expensive.
We have used the clinical test as suggested by Yamamoto et al  to measure the rotational element.
Over the last 4 years, 20 patients (13 M: 7F; average age 10.2 years) with cubitus varus were assessed using this clinical technique. Of these 12 had a right-sided deformity. The test described by Yamamoto, et al is as follows:
Measurement method of internal rotation:
"With the subject bending slightly forward, the upper limb is held at the side and then positioned behind the back with the elbow at 900 flexion and the shoulder held at the maximum extension position. In this position the midline of the forearm gets exposed for inspection by the examiner, who stands behind the subject, applying maximum internal rotation to the subject's upper limb around the long axis of the humerus. When no internal rotation deformity of the humerus is present, there is no change in the forearm position. The horizontal plane of the back is parallel with the midline of the forearm. Conversely, in children with the internal rotation deformity of cubitus varus, a certain abnormal angle is formed between the horizontal plane of the back and the midline of the forearm. The angle is designated the internal rotation angle."
We use this clinical test to measure the internal rotation deformity, and considered 20? as the minimum requisite for considering correction. Following this, supracondylar corrective osteotomy was carried out as described below:
A lateral approach to the lower end of the humerus was used. Once the lower end of the humerus was exposed subperiosteally, one Kirschner wire was inserted in the proximal and the distal portion of the osteotomy at the measured angle. The osteotomy was then cut after checking the placement of the wires with an x-ray. The medial cortex was left intact and used as a hinge. The wires were replaced by cortical screws. The osteotomy was then closed and the distal fragment derotated by making the screw heads parallel, which were connected with a stainless steel wire. The correction was checked clinically and radiologically, and the wound was closed in layers. A plaster cast was applied in 90? flexion of the elbow and full supination for 6 weeks and then mobilisation started. The post-operative Yamamoto angle was measured, once the elbow motion was regained.
Experiment on isolated humerus
A post mortem specimen of human humerus having cubitus varus was procured on which the above mentioned osteotomy was carried out. An examination of the abnormal humerus, as compared to the normal humerus, revealed that the lower end of the humerus was in varus and internal rotation.
The deformity was measured with the help of Kirschner wires. The proximal wire was passed to define the coronal axis of the humerus along the borders of the humerus, and the distal wire along the axis of the capitulum, which revealed the varus deformity in the AP plane. An end-on view to compare both the humerii showed the internal rotation deformity of the distal fragment to be 30?, which could have been measured clinically in a alive patient by the Yamamoto's test.
Osteotomy as described above was performed on this humerus.
The average interval between injury and osteotomy was 25.2 months. The average pre-operative Yamamcto's angle was 37.5?.
[Table - 1] presents the detailed data for individual patient. It can be seen from the table that using this simple technique nearly in all the cases excellent correction was obtained as regards the internal rotation deformity. The average post-operative Yamamoto's angle was 8.85 + 6.5? [Figure - 1] and [Figure - 2].
An experiment on isolated humerus also revealed complete correction, with varus eliminated and internal rotation fully corrected as seen on end - on view.
Everyone agrees that the varus component needs to be corrected in a cubitus varus deformity. The hypertension deformity usually moulds with time. It is the correction of the internal rotation deformity, which is still controversial.
The loss of external rotation that occurs at the elbow following a cubitus varus deformity is usually well compensated for by the shoulder, thus leading to the belief that this deformity has no significance,. However, now there is a statistical evidence that the internal rotation deformity is significant. There is up to 30% failure to correct the varus component in series where the internal rotation deformity is not corrected.
If one considers the morphology and function of the lower end of the humerus, along with cosmesis, correction is desirable in all the 3 components of the deformity. A correction of rotational deformity is essential for the correction of the total deformity as the lateral tilt of the distal fragment may increase with the rotational deformity.
We have proven experimentally that derotation does occur in the French osteotomy, and the amount of derotation can be controlled clinically, which should be determined pre-operatively.
A comparison of the radiographs before and after the osteotomy also confirmed that the deformity was eliminated, including the rotational component.
Thus, we conclude that correction of internal rotation deformity above 200 is a must for correction of the deformity and also that the Yamamoto's clinical test is a satisfactory mode of assessment.
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4][Table - 1]