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Radial Head Volume Measurements using Quantitative Three Dimensional CT images for Radial Head Deformation following missed Monteggia lesions

  • Lisette C. Langenberg
    Correspondence
    Corresponding author: Lisette C Langenberg, MD, Department of orthopaedic surgery and sports medicine, Erasmus MC university Medical Center, PO box 2040, 3000 CA Rotterdam, the Netherlands.
    Affiliations
    Department of orthopaedic surgery and sports medicine, Erasmus MC university Medical Center, PO box 2040, 3000 CA Rotterdam, the Netherlands

    Department of orthopaedic surgery, Noordwest Ziekenhuisgroep, Alkmaar, the Netherlands

    Department of orthopaedic surgery, Amphia, Breda, the Netherlands
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  • Stein J. Janssen
    Affiliations
    Department of Orthopaedic Surgery and Sports Medicine, Amsterdam Movement Sciences (AMS), Amsterdam University Medical Centre, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
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  • Denise Eygendaal
    Affiliations
    Department of orthopaedic surgery and sports medicine, Erasmus MC university Medical Center, PO box 2040, 3000 CA Rotterdam, the Netherlands

    Department of orthopaedic surgery, Amphia, Breda, the Netherlands
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Open AccessPublished:November 21, 2022DOI:https://doi.org/10.1016/j.jseint.2022.10.011

      Abstract

      Introduction

      In chronic radial head dislocation, the radial head may enlarge and become dome-shaped. To date there is no validated tool to quantify radial head deformation and predict its influence on surgical outcome. This study assesses the potential value of volume and surface calculations obtained by quantitative three dimensional CT scanning (Q3DCT) in the workup for corrective surgery in pediatric patients with missed Monteggia lesions.

      Material and methods

      Ten consecutive pediatric patients with a missed Monteggia lesion were included (2012-2020). The volume and the articular surface size of the radial head were calculated using Q3DCT and a three dimensional reconstruction of the articular surface relief was depicted in a heat map. The head/neck ratio was calculated and compared to Q3DCT data of missed Monteggia patients and their age/sex matched controls.

      Results

      The radial head volume and radial articular surface size did not differ significantly between patients with missed Monteggia lesions and age/sex matched controls (volume 1487 mm3 versus 1163 mm3, p=0,32; articular surface size 282 mm3 versus 236 mm3 ,p=0,33). Optically, heat maps of the articular surface of missed Monteggia patients did not differ notably from control heat maps.. A higher head/neck ratio correlated to a larger radial head volume (Pearson r=0,73; p=0,02).

      Discussion and conclusion

      Q3DCT may be an interesting tool in the preoperative workup of pediatric missed Monteggia lesions. Prospective research with larger cohort sizes and data that compares the affected side to the contralateral elbow is needed to assess its true clinical potential.

      Keywords

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      ,
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      , arthrography
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      or lateral X-rays with calculation of the head-neck ratio
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      . No threshold is known for any of the imaging techniques named above to distinguish between a “normal” or a “deformed” radial head. Most authors compare to the unaffected side, but clinical implications for the amount of radial head deformation remain vague. Currently, the head/neck ratio is often used to objectify radial head deformation. It was conceived based on the typical formation of a slender radial neck and radial head widening in posttraumatic radial head dislocation, compared to the contralateral elbow
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      and there have been no validation studies to identify a threshold that indicates a higher risk for postoperative complications. In a small cohort study from our clinic, the intraoperative aspect of the radial head, noted by the operating surgeon deviated substantially from the estimated dysplastic changes by preoperative head-neck ratio on lateral X-rays
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      This study aimed to measure and visualize the following dysplastic features: (1) radial head volume, (2) articular surface size of the radial head and (3) concavity of the radial head using Q3DCT of chronic missed Monteggia lesions. Radial head Q3DCT features were then correlated to radial head redislocation rate.
      It was hypothesized that the articular surface shape would deform due to repetitive radial head dislocations.

      Material and methods

      All consecutive patients that reported to the Amphia hospital in Breda, the Netherlands, between January 2012 and January 2020 with a chronic radial head dislocation following a missed Monteggia lesion were approached to participate in this retrospective study. A fellowship trained musculoskeletal radiologist and the senior author identified missed Monteggia lesions. Inclusion criteria were a trauma to presentation interval of at least four weeks, age under 18 years, and workup that included a preoperative Computed Tomography (CT) scan of adequate quality. Congenital dislocations and acute presentations were excluded. Postoperative follow-up was following hospital protocol; all patients were followed up with plain radiographs of the elbow at six weeks and one year postoperatively. Several patients had longer follow-up at the surgeons’ or parents’ preference.
      Our institutional Medical Ethics Review Committee approved our research protocol and all patients agreed on anonymous use of their data for scientific purposes.
      Given the retrospective study design, it was impossible to obtain a CT scan from the non-affected elbow at the moment of presentation. Therefore, each patient with a missed Monteggia lesion (cases) was 1:1 matched to a patient without a Monteggia lesion (hereafter referred to as “control patients”). Subjects were matched based on age (within 0,4 years) and sex.

      Surgical procedure

      All surgical procedures were performed by this study’s principal investigator (DE) and included an open reduction of the radiocapitellar joint, a corrective osteotomy of the ulna, and a reconstruction of the annular ligament. Before repositioning the radial head, the surgeon judged the optical dysplastic features of the radial head (concavity, widening of the radial head) and the effort that was required for radial head repositioning. Postoperatively, a cast in 90 degrees flexion and neutral forearm rotation was applied for the duration of four weeks. After cast removal, physiotherapy was started for all patients.

      Outcome measures and explanatory variables

      Medical records were reviewed to extract the baseline CT scan and data at presentation, details of the performed surgery, peroperative aspect of the radial head, and the postoperative radiograph at follow-up consultation.
      The outcome measures for Q3DCT analysis were: radial head volume, radial head articular surface size, and heat map depiction of radial head articular surface concavity. CT scans were saved as Digital Imaging and Communications in Medicine files and uploaded in 3D Slicer (version 4.10.2; Slicer Community, Boston, MA, USA). Cortical outline of the radial head was manually marked on transverse, sagittal, and coronal CT slides using a cut-off of 200 to 250 Hounsfield units in 3D Slicer. The radial head was defined as all bone proximal to the physis or physeal scar. 3D Slicer renders a 3D polygon mesh model, which was imported into Rhinoceros (Rhinoceros 5.0; McNeel, Seattle, WA, USA). The volume of the radial tuberosity was measured in mm3 (mm = millimeter) and the articular surface area in mm2, standard features in Rhinoceros. Assessment of radial head concavity was a visual assessment using heatmap projected over the radial head articular surface.
      The head/neck ratio as described by Kim et al was calculated on plain radiographs for both missed Monteggia patients and their controls
      • Kim H.T.
      • Conjares J.N.V.
      • Suh J.T.
      • Yoo C Il
      Chronic radial head dislocation in children, Part 1: Pathologic changes preventing stable reduction and surgical correction.
      , and then compared to Q3DCT data.

      Statistical analysis

      Categorical variables are reported as frequencies and percentages, and continuous variables as mean with standard deviation (SD). We used a paired t-test to assess differences in outcome measures between cases and controls. A two-tailed p-value below 0.05 was considered statistically significant. To assess correlation, a Pearson correlation coefficient was calculated. IBM SPSS Statistics 25 (IBM Corp., Armonk, NY, USA) was used for all statistical analysis and there were no missing values for any of the variables.

      Results

      Fourteen pediatric patients with a missed Monteggia lesion were eligible for inclusion. One patient denied participation, one patient had a potential congenital component (dysmorph radial head on the contralateral side) and two patients had preoperative CT scans of insufficient quality. Hence, ten patients could be included for Q3DCT analysis.
      Average age of included patients was 11 years, range (5,9 to 15,5 years), there were six girls and four boys. The mean time between trauma and the CT-scan at presentation was 3,2 years (0,3 - 9,3) (table 1). Mean follow-up was 1,7 years (0,8-5,8 years).
      Table 1Patient characteristics
      Case noSideM/FTrauma-CT(y)Age at CT(y)H/N

      MM
      Age at Surg(y)Peroperative

      Aspect
      RepositioningComplicationsH/N C
      1RF2.29,31,819,4530-40% def.easy1.20
      2LF2.17,71,417,59Mild def. cap. overgr.Impossible1.33
      3LFns5,92,2115,55Slight def.Easynon-union with redislocation1.38
      4RF0.311,31,411,69Bipolar def.1.73
      5LF5.412,01,4312,18Some def.Impossible1.34
      6LM5.812,51,5213,04Slight def.Easy1.27
      7RM0.412,31,512,58Slight def.Easysubluxation1.29
      8LF1.17,71,538,07Slight def.Easy1.36
      ALM9,315,41.971.55
      BRM2,015,51.641.56
      Mean3.29.81.6411.31.40
      M/F = Male/Female; Trauma-CT=time between trauma and CT scan in years; H/N MM=Head/Neck ratio; def=deformed; cap. overgr.=caput overgrowth; H/N C: Head/Neck ratio Control; ns=Not specified. Note: case A and B are patients that were treated conservatively.
      Indications for elbow CT-scan in control patients were: olecranon trauma (n=3), medial extraarticular calcifications (n=2), medial condyle fractures (n=1), supracondylar fracture (n=2), radial neck fracture (n=1) and Osteochondritis Dissecans of the capitellum (n=1).
      The mean age difference between the included patients and their age/sex matches was 0,02 year (range 0 - 0,4 year). (table 2).
      Table 2Radial head volume and articular surface area of the radial head in Missed Monteggia lesion patients versus age and sex matched control cases
      Missed Monteggia Cases (n=10)Controls (n=10)p-value
      Mean (±SD)Mean (±SD)
      Volume of the radial head in mm31487 (±1180)1163 (±836)0.317
      Articular surface area of the radial head in mm2282 (±143)236 (±128)0.331
      Eight patients underwent a surgical correction of the chronic radial head dislocation (cases 1-8 in table 1). There were two complications (case 3: ulna non-union and redislocation of the radial head, and case 7: subluxation of the radial head). Two patients were treated conservatively (case A and B) because the surgeon considered the radial head too dysplastic on preoperative radiographs and CT-scans.

      Radial head volume analysis

      The volume of the radial head was not significantly larger in missed Monteggia patients compared to the control group (1487 mm3 vs 1163 mm3, p=0,32). There was no correlation between the trauma-CT interval and radial head volume (Pearson test, r=0,65 p=0,64), or the articular surface size of the RH (r=0,54 p=0,14).

      Articular surface size analysis

      The radial head articular surface size was also not significantly larger in missed Monteggia patients compared to the control group (282 versus 236 mm3, p=0,32). Unfortunately, calculations of the percentage of the articular surface that was concave, turned out unreliable.

      Heat map articular surface analysis

      The articular surface of the radial head was depicted in a heat map using Q3DCT (Figure 1). Some heat maps of patients that were either not operated due to suspicion of radial head dysmorph changes on a plain radiograph (cases A and B); or of patients that sustained a redislocation (case 3 and 7) appeared flattened or convex. However, Q3DCT heat map images could have a similar flattened aspect in the control group. A supplement is available that contains an overview of all MM and C heat maps. Optically, there were no evident differences in articular surface shape for cases versus controls.
      Figure thumbnail gr1
      Figure 1Heat map image of the radial head articular surface relief (case 4). A: Missed Monteggia patient; B: age/sex matched control.

      Comparison to the Head/Neck ratio

      The head-neck (H/N) ratios in patients with missed Monteggia lesions were significantly higher than in the control cases (mean H/N ratio in missed Monteggia was 1,64 and mean H/N ratio for controls was 1,40; p=0,048). We also found a significant correlation between the head-neck ratio and the radial head volume in missed Monteggia patients (Pearson r=0,73; p=0,02).

      Discussion

      This study describes a small cohort of missed Monteggia patients, whose radial head was examined using Q3DCT. Currently, the assessment of preoperative radial head deformation is subjective; Q3DCT seemed a promising and easily accessible method to quantify the amount of radial head deformation.
      Unfortunately, measurements of the concavity of the radial head turned out to be unreliable, and the interpretation of a heat map of the articular surface is highly subjective. Its value is therefore still debatable in individual cases. Our cohort was thereby too small to be able to make any statement regarding the peroperative aspect of the radial head and Q3CT heat map images, and the value of statistic analysis is limited due to the small number of patients. Future research should be prospective and should contain a CT-scan of the contralateral elbow. Also, an inter- or intra observer evaluation would be interesting to assess the clinical value of Q3DCT heat map images.
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      Long-Term Clinical and Radiographic Outcomes After Open Reduction for Missed Monteggia Fracture-Dislocations in Children.
      • Roach J.W.
      • Saltzman H.M.
      The Treatment of chronic Monteggia lesions and chronic traumatic isolated radial head dislocations.
      . In this study, there was no correlation between time since trauma or the age of the child and the volume of the radial head, like in several other publications
      • Eamsobhana P.
      • Chalayon O.
      • Kaewpornsawan K.
      • Ariyawatkul T.
      Missed Monteggia fracture dislocations treated by open reduction of the radial head.
      ,
      • Seel M.J.
      • Peterson H.A.
      Management of chronic posttraumatic radial head dislocation in children.
      ,
      • Song K.S.
      • Ramnani K.
      • Bae K.C.
      • Cho C.H.
      • Lee K.J.
      • Son E.S.
      Indirect reduction of the radial head in children with chronic monteggia lesions.
      ,
      • Stoll T.M.
      • Willis R.B.
      • Paterson D.C.
      Treatment of the missed Monteggia fracture in the child.
      . We advise that in every individual case, an assessment of radial head dysplastic features should be made regardless of the time since trauma or patient age. However a study with a larger cohort is necessary to be able to adequately test this statistically.

      Conclusions

      There were no significant differences in Q3DCT calculations for radial head volume and articular surface size between missed Monteggia patients and age/sex matched control cases. A heat map analysis of the radial head articular surface showed no specific differences in articular surface shape compared to the control group. A higher head-neck ratio was correlated to higher Q3DCT radial head volumes. Q3DCT may still be an interesting tool in the preoperative workup for missed Monteggia patients, but prospective research that combines preoperative, peroperative and postoperative findings in a larger case series that includes contralateral CT scan analysis is mandatory to assess its clinical potential.

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