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Feldman, David S. MD1,2; Rand, Troy J. PhD1; Deszczynski, Jaroslaw MD3; Albrewczynski, Tomasz MD2; Paley, Droll MD1,2; Huser, Aaron J. DO1,a
1Paley Advanced Body Lengthening Institute, St. Mary's Hospital, West Palm Beach, Florida
2Paley Institute for European Studies, Medicoover Hospital, Warsaw, Poland
3 Department of Orthopedics and Rehabilitation, Warsaw Medical University, Warsaw, Poland
Corresponding author’s email: [Email Protection]
Investigation conducted at the Paley Advanced Body Lengthening Institute at St. Mary's Hospital in West Palm Beach, Florida
Disclosure: A disclosure form for potential conflicts of interest is provided with the online version of the article (https://links.lww.com/JBJS/G668).
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Multiple hereditary exogenous osteosarcoma (MHE) is a rare bone disease that can lead to the growth of benign cartilage cap tumors and many bone deformities. As many as 60% of MHE patients have forearm deformities, and 20% to 30% of patients have subluxation or dislocation of the radial head. Radial head subluxation/dislocation causes shortening of the forearm and loss of movement. The purpose of this study is to determine the radiological variables that best predict subluxation/dislocation of the radial head to determine whether preventive treatment is needed.
We retrospectively reviewed the cases of consecutive MHE patients treated in our center from April 2007 to December 2019. Radiological measurements include the presence or absence of distal ulnar chondroma, total ulnar arch, total radial arch, and percentage of ulna length. Participants were divided into 3 groups according to the state of the radial head: localization, subluxation and dislocation. The Kruskal-Wallis H test and Dunn's post-hoc analysis were used to compare radiographic measurements. Use binomial logistic regression to run the predictive model and create a predictive matrix.
The study included 88 patients. Compared with the dislocation group, the positioning group had significant differences in pronation, supination and extension. There were significant differences in the percentage of ulnar length, total ulnar arch, and total radial arch between the fixation group and the dislocation group (p <0.0001); however, in the binomial regression analysis, only the percentage of ulnar length and total ulnar arch can be used Distinguish between positioning group and subluxation/dislocation group. Both of these measures are important predictors of subluxation/dislocation. Patients with ulnar arch <17° do not have subluxation/dislocation of the radial head.
The data shows that the total ulna arch and the percentage of ulna length are good predictors of subluxation/dislocation of the radial head. These two parameters can be used to monitor forearm deformities and guide the timing of preventive treatment.
Prognosis grade III. For a complete description of the level of evidence, please refer to the Author's Notes.
Multiple hereditary exostoses (MHE) is an autosomal dominant genetic disease that affects 1 in 50,000 newborns1. This condition can lead to the growth of benign cartilage cap tumors, which are most commonly found in the growth plates of long bones. Common deformities in patients with MHE include subluxation or dislocation of the radial head joint, and shortening of the forearm 1-4.
According to reports, the prevalence of forearm deformities in MHE2 patients is as high as 60%. If these deformities are not treated, they may cause subluxation/dislocation of the radial head (Figure 1). Later management, after dislocation, function cannot usually be restored, especially supination and pronation5. If the dislocation of the radial head is prevented, the loss of function can be reduced. It is important to determine which patients are at risk for subluxation/dislocation of the radial head because it gives the surgeon the opportunity to intervene before it occurs.
Previous studies have determined that the location/number of osteochondromas, the length of the ulna and the radius of the radius are risk factors for dislocation of the radial head3,6,7. Another condition that causes dislocation of the radial head is a Monteggia fracture. Ulnar malunion is associated with chronic dislocation of the radial head in patients with Monteggia fractures8. Ulnar deformity is considered to be a contributing factor to dislocation of the radial head in patients with MHE; however, we are not aware of any published studies that provide evidence for this recommendation9.
The purpose of this study is to determine which radiological measurements may be risk factors for subluxation/dislocation of the radial head. We hypothesize that the ulnar arch is an important risk factor for this pathological condition.
This study has been approved by the institutional review board. A retrospective chart review was performed on all MHE patients treated in our clinic from April 2007 to December 2019. A total of 248 patients were admitted. If they have anteroposterior and lateral radiographs of the radius and ulna, they are included in the study. If the 2 x-rays of the forearm were not orthogonal, the patient was excluded from the study. Each patient includes an arm to eliminate the influence of related data in the group. For patients in the positioning group, one side is randomly selected and the nearest X-ray is selected, unless they have undergone surgery, in which case the last X-ray before surgery is used. For patients in the subluxation or dislocation group, use the subluxation or dislocation side for analysis, and use the first X-ray showing the subluxation/dislocation. Basic demographic data and range of motion data are collected from the chart. The range of motion includes supination, pronation, elbow flexion and elbow extension. Measurements are made on X-rays, including the percentage of ulna length, total radius of the radius, total ulna, the presence of osteochondroma of the distal ulna, and the state of the radial head joint (localization, subluxation, or dislocation).
The calculation method for determining the percentage of ulna length is similar to the method described by Jo et al.6: the length of the ulna from the tip of the styloid process to the edge of the olecranon divided by the length of the ulna. The radius measured from the center of the proximal bone to the center of the distal bone, and the quotient is multiplied by 100 to get a percentage. The length measurement is obtained from the front and rear X-rays. The total ulnar arch and total radial arch are determined by measuring the angles of the proximal and distal diaphyseal midlines of the corresponding bones on orthogonal X-rays. Apply the Pythagorean Theorem to determine the true oblique deformity. Figure 2 shows an example of how to perform these measurements. Some of the ulna analyzed had a deformity of the distal third (Figure 3). For these ulna, the midline of the distal diaphysis was just close to the apex of the distal third of the arch. In addition, the presence or absence of osteochondroma of the distal ulna was also recorded.
The intra-class correlation coefficient (ICC) of the bow measurement subset completed by the attending surgeon and clinical scientist is calculated, and the result has good reliability, and the ICC is 0.77.
According to the state of the radial head, the forearm is divided into 3 groups: positioning, subluxation and dislocation. Subluxation and dislocation are determined by intraoperative arthrography or from X-rays using the method outlined by Souder et al. 11. The Kruskal-Wallis H test was used to compare the range of motion and radiographic measurements between groups to determine differences in group distribution. The post-hoc analysis used Dunn's test for multiple comparisons. All p-values reported after the fact are adjusted for multiplicity. Determine the Pearson correlation coefficient for radiographic measurements.
Binomial logistic regression analysis was performed to predict subluxation/dislocation of the radial head. Binomial regression analysis uses any number of independent variables and creates a probability function that can be used to predict binary outcomes. The subluxation group and the dislocation group were combined into one subluxation/dislocation group, because it is important to prevent these two pathological conditions. Regression analysis was initially performed using the percentage of ulna length, total ulnar arch, total radial arch, and the presence/absence of osteochondroma of the distal ulna to determine which are important risk factors. Important risk factors are used to create the final probability function, which is then analyzed in a series of values. For each value of total ulna arc and percentage of ulna length, the probability of subluxation/dislocation of the radial head is determined. A matrix was created showing the predicted state of the radial head joint (localization and subluxation/dislocation) in relation to the important variables analyzed.
The significance of all tests is set to α = 0.05. Binomial regression analysis was performed using R (R Core Team 2020; R Statistical Computing Project, www.R-project.org/), and other statistical analysis using GraphPad Prism, MacOS version 8.4.2 (www.R-project.org/ )conduct. graphpad.com).
There is no external funding related to this research. However, the MHE Research Foundation (www.mherf.org) in Brooklyn, New York provided financial support to obtain the publication's open access.
A total of 88 patients were enrolled in this study, including 52 males and 36 females. The median age at radiographic examination was 10.0 years (range = 2.5 to 43.8 years). Patients were divided into 3 groups: localization (n = 70; 80%), subluxation (n = 10; 11%), and dislocation (n = 8; 9%).
The range of motion measurement can be used on 63 forearms, and the Kruskal-Wallis H test with Dunn's post hoc analysis was used to compare between the groups (Figure 4, Table I). There are significant differences between the supination and pronation groups (Figure 4-A and 4-B). Post-mortem analysis showed that compared with the dislocation group (median = 38°; range = 0° to 87°), the positioning group (median = 89°; range = 0° to 96°) had greater supination, But with the subluxation group (median = 53°; range = 0° to 93°). With subluxation group (median = 57°; range = 0° to 85°) and dislocation group (median = 50°; range = 15° to 80°). In supination or pronation, there was no difference between the subluxation group and the dislocation group. There was no significant difference in flexion between the groups (Figure 4-C). Post-hoc analysis showed that compared with the positioning group (median = 0°; range = -8), the extent of extension in the dislocation group (median = -8°; range = -35° to 0°) was significantly reduced ( Lack of full extension) ° to 14°), but there was no difference between the subluxation group (median = 0°; range = -30° to 10°) and the positioning or dislocation group (Figure 4-D).
The Kruskal-Wallis H test and Dunn's post-hoc analysis (Figure 5, Table I) were used to compare the radiographic measurements of each group. There was a significant difference in the percentage of ulna length between the two groups (Figure 5-A). Post-hoc analysis showed that compared with the subluxation group (median = 98%; range = 92% to 104%), the positioning group (median = 109%; range = 98% to 119%) had a higher percentage of ulnar length Large and dislocated group (median = 92%; range = 72% to 100%). There was no significant difference in the percentage of ulna length between the subluxation group and the dislocation group. There are significant differences in total ruler bows between the groups (Figure 5-B). Post-hoc analysis showed that the total ruler bow of the positioning group (median = 13°; range = 4° to 25°) compared with the subluxation group (median = 22°; range = 17° to 30°) The degree is small, and the dislocation group (median = 22°; range = 19° to 28°). There was no difference between the subluxation group and the dislocation group. Post hoc analysis showed that the total radial bow of the dislocation group (median = 28°; range = 21° to 47°) compared with the fixed group (median = 15°; range = 7° to 41°) Significantly larger, but there was no difference between the subluxation group (median = 17°; range = 13° to 30°) and the dislocation group or the localization group (Figure 5-C).
The three radiographic parameters showed a significant correlation with each other, with different intensities (Figure 6). The percentage of ulna length is moderately to strongly negatively correlated with the total ulnar arch and the total radius. There is also a moderate positive correlation between the ulnar and radial arches.
Figure 7 illustrates the relationship between the total ulna arch and the percentage of ulna length in all three groups. The ulna in the positioning group tends to be long and straight, while the total ulna arch in the subluxation and dislocation groups increases, and the percentage of ulna length decreases. There is no ruler ulnar arm (total ulnar arch <17°) with radial head subluxation/dislocation. In addition, arms with no ulnar length (>104% of ulna length) have subluxation/dislocation of the radial head.
A binomial regression model was developed to predict subluxation/dislocation of the radial head (Table II). The radial head dislocation group and subluxation group were combined into one cohort for regression analysis, because preventive treatment will be based on the prevention of subluxation and dislocation. The initial model used the percentage of ulna length, total ulnar arch, total radius arch, and the presence of distal ulnar osteochondroma; however, the presence of total radius arch and distal ulna osteochondroma was not a significant risk factor and was therefore deleted. The final model was established using only the percentage of ulna length and the total ulnar arch, because both are important risk factors for subluxation/dislocation of the radial head. The model is then used to predict the state of the radius head within the range of the ulnar length percentage and the total ulnar arch value to generate a prediction matrix (Figure 8).
Using the percentage of total ulnar arch and ulna length to predict whether the radial head is located or subluxed/dislocated, the prediction matrix can correctly identify 97% of the cases in our series. The model emphasizes several interesting relationships. First, we found that the ulna is longer than the radius. This seems to give a protective mechanism to the radial head joint. Second, the model predicts that when the length of the ulna is the same as that of the radius (percentage of ulna length = 100), the total ulna arch of >20° will result in subluxation/dislocation of the radial head. Finally, as the percentage of ulna length decreases, the tolerance of the common ulnar arch before subluxation/dislocation of the radial head also decreases; however, in our series of studies, there was no radius small in patients with a total ulnar arch of <17° Head joint subluxation or dislocation. The model can be used as a tool to indicate which patients will benefit from preventive treatment to prevent subluxation/dislocation of the radial head.
MHE is a rare bone disease with a variety of upper limb deformities, including instability of the radial head1. Radioactive head dislocation is associated with loss of function and movement12,13. In our study, individuals with dislocation or subluxation of the radial head showed impaired range of motion. Compared with the fixed group, the supination and pronation of the dislocation group were reduced. The lack of complete elbow extension was also found in the dislocation group. Compared with the positioning group, the elbow extension was significantly less. There was no difference in elbow flexion between the groups. In addition, compared with the positioning group, the subluxation group had less pronation. These findings are important because they indicate that loss of motion occurs in the undislocated elbow, so preventive treatment should be provided before it reaches the subluxation stage. In addition, these findings support the decision to combine subluxation and dislocation groups for regression analysis.
In addition, the range of motion results are consistent with the findings of Noonan et al. Because patients with MHE and dislocation of the radial head have dyskinesias12. However, the investigation conducted by Noonan et al. It was found that these patients had no pain or limitations in their daily lives. Peterson cited multiple sources to suggest that surgeons should actively try to prevent these deformities9. Based on our own experience, we found that family members/patients wish to prevent dislocation of the radial head due to loss of function and movement and cosmetic reasons. Parents with MHE told us that although they “learned to live with the deformity”, they don’t want their children to do the same. This is one of our motivations for this research.
The risk factors for instability of the radial head in patients with MHE have been previously described3,4,6,7,14. These risk factors include the proportional length of the ulna (related to the radius on the X-ray and the clinical height of the ulna), radius arches, and the number/location of osteochondroma (especially at the distal end of the ulna). We chose to re-examine the radius arch, the length of the ulna, and the presence/absence of osteochondroma of the distal ulna on radiology. In addition, we studied the influence of the ruler bow. The motivation for evaluating the ulnar arch comes from our understanding of the deformed Monteggia fracture and its relationship with the instability of the radial head15. Classically, in a Monteggia fracture, the radial head is dislocated toward the ulnar arch16. In MHE patients, we noticed that the radial head dislocation follows the same pattern, and we want to study its radiological measurement as a potential risk factor for radial head subluxation/dislocation.
Recently, Hreha et al. The normal ruler bow 17 on two planes was studied using distance measurement. They determined that a bow of 7 ± 2 mm in the coronal plane is normal, and 6 ± 3 mm in the sagittal plane is normal. We chose to use the angle method for two reasons. First of all, the degree of deformity of the ulna in MHE patients is different, the radial and ulnar sides are convex; using the method described by Hreha et al., the convex ulnar arch of the same angle has a greater distance measurement value than the convex radial arch. Second, we did not include the distal ulnar arch because it does not simulate Monteggia's deformity, as well as the method described by Hreha et al. Can't adapt to this.
We found that the total ulna arch and the percentage of ulna length are independent predictors of subluxation/dislocation of the radial head. Our preliminary data analysis showed that there were significant differences in total ulnar arch, percentage of ulnar length, and total radial arch between the dislocation/subluxation group and the positioning group. However, in the binomial regression analysis, the total arch of the radial head is not an important predictor of subluxation/dislocation of the radial head. This is different from the findings proposed by Jo et al.6 and can be explained by including total ulnar arch variables, measurement methods, and including patients with radial head subluxation in our study. In short, the more growth retardation of the ulna, the smaller the curvature associated with subluxation/dislocation. However, regardless of the relative length of the ulna, patients with an ulnar arch <17° do not have subluxation or dislocation of the radial head joint. This finding raises questions about the necessity of ulna lengthening and leads us to believe that treatment of ulnar arch deformities (correction of the total ulnar arch) may eliminate the need for ulnar lengthening (percentage correction of ulna length).
This study is a retrospective, cross-sectional review. Ideally, prospective longitudinal studies will be conducted to follow patients and observe the progress of forearm deformities. In addition, our study included a small number of subluxed/dislocated elbows compared to the positioning cohort. However, we believe that the differences observed between the groups will help guide clinical prognosis.
We excluded patients because of insufficient X-rays-for example, if 2 views were obtained but they were the same view (2 coronal images of the ulna). We have now changed our protocol to obtain coronal and lateral views of the elbow centered on the forearm, with the forearm in a neutral position. This allows us to ensure 2 orthogonal views of the forearm.
Finally, our 3 cases did not meet our predictions. Two patients were predicted to be dislocated, but the radial head was located radiologically. One patient had a total curvature of 24° and a percentage of ulna length of 98%. The other patient had a total curvature of 25° and a percentage of ulna length of 101%. Two possible reasons why these patients are not suitable for the model are (1) our analysis did not consider the directionality of the bow, which may change the threshold of subluxation/dislocation of the radial head, and (2) the radiographic measurement error in these cases is located On the boundary between positioning and subluxation/dislocation of the radial head. The third patient had a total ulna arch of 18° and a percentage of ulna length of 98%. The radial head was expected to be positioned, but a radiological dislocation was found. Again, this may be due to radiographic measurement errors, because this condition is also on the boundary between positioning and subluxation/dislocation, or there may be other factors that cause this dislocation. Previous studies have shown that the burden of osteochondroma on the forearm may affect the radial head joint7,14. Our analysis included the presence of osteochondroma of the distal ulna, but did not consider the other location of the osteochondroma or the severity of the involvement.
In summary, there are two radiological measurements that can be used to determine the stability of the radial head joint in patients with MHE. The common ulnar arch is a new radiological measurement that can help predict radial head dislocation and may have an impact on the preventive treatment of radial head subluxation/dislocation. We recommend a series of clinical and radiological examinations to monitor subluxation/dislocation of the radial head. Our predictive model (Figure 8) can help determine which patients are at risk for subluxation/dislocation of the radial head. Such predictions can help surgeons identify patients who can benefit from preventive treatment.
Note: We would like to thank the MHE Research Foundation (www.mherf.org) in Brooklyn, New York, an admirable organization dedicated to education, biomedical research, and advocacy on behalf of patients with multiple hereditary exogenous osteosarcoma Public awareness provides the ability to make this publication open access.
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