MRI of the pediatric elbow: Assessment of ligaments, plicae, and cartilage in the clinical setting

Vavken Patrick MD^1,2, Vavken Julia MD³, Camathias Carlo MD^4,5
1 Alphaclinic Zurich, Kraftstrasse 29, 8044 Zurich, Switzerland
² Division of Sports Medicine/Department of Orthopedic Surgery, Boston Children’s Hospital, Harvard Medical School, Boston, MA, United States
³ Spine Unit, Kantonsspital Baden, Baden, Switzerland
⁴ Praxis Zeppelin, Brauerstrasse 95, 9016 St. Gallen
⁵ Medizinische Fakultät der Universität Basel, Klingelbergstrasse 6, 4056 Basel

Abstract

Elbow injuries in young athletes are becoming an increasing concern for orthopedic sports medicine specialists, but imaging is frequently complicated. The purpose of this study was to assess MRI in imaging ligaments, plicae, and cartilage in 65 pediatric and adolescent patients. 9 MRIs (13%) did not allow assessment because of poor quality. In skeletally mature patients, the radial and ulnar collateral ligament were clearly discernable in 94% and 77%, measuring 1.5 ± 0.6 mm and 1.9 ± 0.6, compared to 55% and 59% in the immature patients with a mean thickness of 1.1 ± 0.6 and 1.4 ± 0.6 mm (p<0.05). 12 patients (18%) revealed a cartilaginous pseudodefects, 5 (8%) had a true OCD. 23 (35%) showed a posterolateral plica with a maximum extension of 1.6 ± 1.7 mm. In OCD the plica was significantly larger compared to patients without OCD (p=0.001). While MRI is a helpful tool in assessing elbow injuries, its usefulness is restricted in pediatric and adolescent patients. 1 in 10 MRI studies was too distorted to be read. However, ligaments ad plicae could be well discerned in most patients. At 18% pseudodefects are much less common than in adults (85%).

Zusammenfassung

Ellbogenverletzungen bei Kindern und Jugendlichen sind eine zunehmende Problematik für Sportmediziner, aber Bildgebung ist oft kompliziert. Für diese Studie wurden 65 Ellbogen MRTs von Kindern und Jugendlichen nach Bändern, Plicae und Knorpel untersucht. 9 MRTs (13%) konnten wegen Artefakten nicht verwertet werden. In den skeletal reifen Patienten konnten das radiale und ulnare kollaterale Ligament bei 94% resp. 77% klar abgegrenzt werden (1.5 ± 0.6 mm und 1.9 ± 0.6), im Vergleich dazu bei skeletal unreifen Patienten bei 55% und 59% (1.1 ± 0.6 und 1.4 ± 0.6 mm (p<0.05)). 12 Patienten (18%) zeigten kartilaginäre Pseudodefekte, 5 (8%) hatten eine OCD. 23 (35%) zeigten eine Plica von 1.6 ± 1.7 mm. Bei OCD war die Plica signifikant grösser (p=0.001). Die Verwertbarkeit von pädiatrischen MRTs ist damit limitiert, aber Bänder und Plica können gut abgegrenzt werden. Pseudodefekte sind mit 18% deutlich geringer als bei Erwachsenen (85%).

Introduction

Increased sports participation, both overall and in high-level competition, has produced an increase in elbow injuries in pediatric and adolescent patients [16,17]. Fortunately, the evidence base for treatment of such injuries has also grown considerably in the last year, be it for osseous trauma [3], sports medicine and elbow arthroscopy in pediatric patients [19], or ligament reconstruction [10]. In parallel to traumatic injury, overuse injuries such as (osteochondritis dissecans) OCD are a frequently encountered problem in the young athlete complaining of elbow pain [12]. Again, treatment strategies for such defects are evolving, and outcomes are improving [6,14].
With injury incidence increasing and effective treatments available, the challenge in managing pediatric patients with elbow pain is to link the right patient with the right treatment. However, the clinical exam of the painful elbow is a difficult task [2,18]. This is particularly true in pediatric and adolescent patients [5]. Ligamentous instability can be masked by contractures or changes in activity [11]. The clinical exam for OCD is based on a history of lateral elbow pain, with tenderness to palpation over the capitellum [6,14] Synovial plicae of sufficient size and thickness can cause locking and mechanical irritation [13,15], but again the ability of the physical exam to confirm this diagnosis is limited.
In the face of these shortcomings of the physical exam, MR imaging is a mainstay in the diagnosis of elbow pain. There is some data in the literature on normal values for the elbow anatomy, but these values have been obtained from adult populations. [8,9] While ample studies offer guidelines for the pediatric knee [4], shoulder [1], or hip [7], there is a paucity of data on the pediatric elbow.
The purpose of this study was to review the anatomy of the elbow on 65 consecutive MRIs in patients younger than 18 years seen at a tertiary pediatric hospital. Our special focus was on the assessment of ligaments, plicae, and cartilage. Of note, we chose to assess a clinical population rather than volunteering controls to be able to present a representative assessment of a clinical situation, including pain, emotional distress, and compliance issues.

Materials and Methods

MRI images of patients that were worked up for elbow pain and read as normal for ligamentous injury by a board-certified, musculoskeletal radiologist were obtained from 65 patients seen at a tertiary pediatric hospital over a 6 month period. Patients were excluded if they had a prior history of elbow trauma or septic arthritis or a history of prior elbow surgery. The mean age of the included patients was 11 ± 4 years (range 2 to 18). 32 were male and 33 were female. 29 patients had open physes (19 male and 10 female) at an average age of 9.2 ± 3.3 years, compared to a mean age of 14.2 ± 2.2 years in the skeletally mature group.
All studies were blinded and given to two orthopedic surgeons with fellowship training in sports medicine and multiple years of clinical experience in treating pediatric elbow injuries.
The first endpoint was the discernability of collateral ligaments as a binary (visible/not visible) variable, i.e. visibility over the entire course. The second endpoint was measurement of their size in mm at their thickest point in the three planes of the MRI at the level of the joint line. The second endpoint was cartilage damage and pseudodefects. Pseudodefects were defined as those cartilage defects on MRI that were not substantiated in further diagnostics and treatment. Third, we assessed for the presence and size of posterior/posterolateral plicae. Again, their size in mm was measured at their thickest point in the three planes of the MRI. Last, we tested if these endpoints differ between patients with open and closed physes. All assessments were done in independent duplicate using a clinical imaging software.
For statistical analysis, we assessed all patients as one group, as well as comparing the subgroups skeletally mature and immature. Between group differences were compared using student’s t-test. Inter-observer agreement was assessed using kappa values. All analyses were done using Stata 12 (StataCorp LP, College Station. Tx).

Results

9 MRIs (13%) did not allow unequivocal assessment of any of the endpoints because of poor quality or artefacts. (Fig. 1) 7 patients (78%) were skeletally immature, 2 were mature (22%).

The assessment of the collateral ligaments in the total population revealed that the ulnar collateral was discernable in 51% (95%CI 39 to 63) and the radial ligament complex in 45% (95%CI 33 to 57). The average size was 1.7 ± 0.9 mm for the ulnar and 1.3 ± 0.6 mm for the radial ligament complex. Comparing the discernability of the collateral ligaments across skeletally mature and immature patients, results were better for both ligaments in the mature group. Discernability was significantly better for the ulnar ligament in the mature group (p=0.007), whereas the difference was not statistically significant for the radial ligaments (p=0.188). The ligaments also were bigger in the mature patients (p=0.017 ulnar, p=0.028 radial). (Table 1)

17 patients (26%) had a cartilage defect on MRI (6 immature/11 mature). All patients were followed with a CT-arthrogram and/or elbow arthroscopy. No patient showed evidence on loose bodies on MRI. 12 patients (18% of all patients, 71% of all cartilage defects on MRI) revealed normal cartilage on further assessment, i.e. were defined as pseudodefects. 7 pseudodefects (58%) occurred in the skeletally immature group, compared to 5 in the mature group (42%, p=0.08). With MRI findings of cartilage defects less common in the skeletally immature, the relative occurrence of pseudodefects was higher in this group (83%) than the mature group (64%).
Lastly, 23 patients (35%, 95% CI 24 to 47) revealed a discernable posterior/posterolateral plica. The average size was 1.6 ± 1.7 mm. Plicae were both more common and larger in the mature group (Table 2). Interestingly, plicae were significantly more common and substantially bigger in patients with OCD. In these patients plicae were seen in 100% and their average size was 4.0 ± 0.7 mm (p=0.001). (Figure 2)

Discussion

The clinical exam of the elbow can be challenging, even for experienced physicians, and especially in the pediatric and adolescent patient [2,18]. Hence, diagnostic aids such as MRI are crucial. However, to date, there are no assessments of the performance of MRI in the young athlete, compared to a least some such studies in adults [8,9]. This study found evidence that MRI should be used with caution in decision-making in pediatric and adolescent elbow disorders since its findings can be misleading.
Most importantly, we found that elbow MRI, especially in the very young, will produce uninterpretable results in approximately 10% of cases. Treating a child with unclear clinical symptoms and exam one should consider this, and, instead of ordering an expensive yet eventually useless study, maybe chose a more readily available and more cost-effective imaging modality such as ultrasound. These authors know of no comparative study on MRI versus ultrasound for pediatric elbow disorders, but from personal experience, as well as a standpoint of biological plausibility, a dynamic, high-resolution, noise-free exam that can be done with parents or care givers present seems to be a good choice in treating children. Alternatively, sedation for MRI can be considered, however, this renders these studies even more logistically complex.
As for the appreciation of collateral ligaments, we saw that even in the youngest patients they could be well discerned in the majority of patients. Interestingly, the medial ligaments, even if thicker than their lateral partners, were less discernable. This finding is corroborated by the adult literature [8,9]. It seemed that the normal, stable, ulnar collateral has a more striated appearance in young patients than in older ones, but this only an incidental finding of this study and not a formally assessed endpoint. (Figure 3) As for ligament thickness, we found a consistent difference in thickness in favor ölof the ulnar collateral being 25% thicker than the radial collateral across age groups. Interestingly a similar, 20%, can be seen in adult studies [8,9]. Of note, all patients in this study had clinically and radiographically intact collaterals since reliability of ligamentous injury on MRI was not an endpoint of this study.

We did find a fairly high prevalence of posterior/posterolateral plicae in this population. Since all patients presented for elbow pain, we were not able to differentiate painful and painless plicae in our analysis. However, we found a strong association between the presence of a large plica and a capitellar OCD lesion. Ex post we are not able to determine if the OCD caused a secondary thickening of a plica or if a larger than usual plica caused an OCD lesion through repetitive impingement. The prevalence of pseudodefects in our population was not higher than the one described for adults (85%) [8]. As opposed to adults however, cartilage defects in this population were more commonly real than pseudodefects, suggesting that any such findings should not be dismissed in young patients.
Our study was some shortcomings. First, we were not able to calculate estimates for specificity and sensitivity – simply due to the fact that there are no gold standards. Even arthroscopy cannot assess the collateral ligaments. Second we did not study a volunteer population of healthy children, but a clinical sample that did present for elbow pain. The reason for this was that we considered patient anxiety, claustrophobia, and pain paramount confounders of MRI readings, compared to a relaxed, well-prepared patients that volunteered to MRI after due consideration. This assumption was supported by the fact that 10% of the included studies produced results of such poor quality that they could not be read. Last, our assessment is fairly simple. However, given the lack of prior data on this topic we aimed at establishing a baseline of facts before embarking on more complex analyses.

Conclusion

While MRI is a helpful tool in assessing elbow injuries, its usefulness is restricted in pediatric and adolescent patients. 1 in 10 MRI studies was too distorted to be read. However, ligaments ad plicae could be well discerned in most patients. At 18% pseudodefects are much less common than in adults (85%).

Acknowledgments, conflict of interest and ­funding

The authors have no conflict of interest.
No funding was obtained for this study.

Corresponding author

PD Dr. med. Patrick Vavken
Alphaclinic Zurich
Kraftstrasse 29, 8044 Zürich
Phone: 044 446 10 00
Email: Vavken@alphaclinic.ch

References

1. Chauvin NA, Jaimes C, Laor T, et al. Magnetic resonance imaging of the pediatric shoulder. Magn Reson Imaging Clin N Am. May 2012;20(2):327-347, xi.
2. Colman WW, Strauch RJ. Physical examination of the elbow. Orthop Clin North Am. Jan 1999;30(1):15-20.
3. Flynn JM, Sarwark JF, Waters PM, et al. The surgical management of pediatric fractures of the upper extremity. Instr Course Lect. 2003;52:635-645.
4. Gill KG, Nemeth BA, Davis KW. Magnetic resonance imaging of the pediatric knee. Magn Reson Imaging Clin N Am. Nov 2014;22(4):743-763.
5. Hammoud S, Sgromolo N, Atanda A, Jr. The approach to elbow pain in the pediatric and adolescent throwing athlete. Phys Sportsmed. Feb 2014;42(1):52-68.
6. Hennrikus WP, Miller PE, Micheli LJ, et al. Internal Fixation of Unstable In Situ Osteochondritis Dissecans Lesions of the Capitellum. J Pediatr Orthop. Jul-Aug 2014;35(5):467-473.
7. Huber H, Mainard-Simard L, Lascombes P, et al. Normal values of bony, cartilaginous, and labral coverage of the infant hip in MR imaging. J Pediatr Orthop. Oct-Nov 2014;34(7):674-678.
8. Husarik DB, Saupe N, Pfirrmann CW, et al. Elbow nerves: MR findings in 60 asymptomatic subjects–normal anatomy, variants, and pitfalls. Radiology. Jul 2009;252(1):148-156.
9. Husarik DB, Saupe N, Pfirrmann CW, et al. Ligaments and plicae of the elbow: normal MR imaging variability in 60 asymptomatic subjects. Radiology. Oct 2010;257(1):185-194.
10. Jones KJ, Dines JS, Rebolledo BJ, et al. Operative management of ulnar collateral ligament insufficiency in adolescent athletes. Am J Sports Med. Jan 2013;42(1):117-121.
11. Lattanza LL, Goldfarb CA, Smucny M, et al. Clinical presentation of posterolateral rotatory instability of the elbow in children. J Bone Joint Surg Am. Aug 7 2013;95(15):e105.
12. Makhni EC, Jegede KA, Ahmad CS. Pediatric elbow injuries in athletes. Sports Med Arthrosc. Sep 2014;22(3):e16-24.
13. Meyers AB, Kim HK, Emery KH. Elbow plica syndrome: presenting with elbow locking in a pediatric patient. Pediatr Radiol. Oct 2012;42(10):1263-1266.
14. Shi LL, Bae DS, Kocher MS, et al. Contained versus uncontained lesions in juvenile elbow osteochondritis dissecans. J Pediatr Orthop. Apr-May 2012;32(3):221-225.
15. Steinert AF, Goebel S, Rucker A, et al. Snapping elbow caused by hypertrophic synovial plica in the radiohumeral joint: a report of three cases and review of literature. Arch Orthop Trauma Surg. Mar 2008;130(3):347-351.
16. Stracciolini A, Casciano R, Friedman HL, et al. A closer look at overuse injuries in the pediatric athlete. Clin J Sport Med. Jan 2014;25(1):30-35.
17. Stracciolini A, Casciano R, Levey Friedman H, et al. Pediatric sports injuries: an age comparison of children versus adolescents. Am J Sports Med. Aug 2013;41(8):1922-1929.
18. Valdes K, LaStayo P. The value of provocative tests for the wrist and elbow: a literature review. J Hand Ther. Jan-Mar 2012;26(1):32-42; quiz 43.
19. Vavken P, Muller AM, Camathias C. First 50 Pediatric and Adolescent Elbow Arthroscopies: Analysis of Indications and Complications. J Pediatr Orthop. Mar 3 2015.