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Abstract

Purpose:

Presently, there is no publication combining clinical follow-up with magnetic resonance imaging (MRI) to determine possible post-traumatic alterations following paediatric intra-articular fractures of the medial malleolus. Therefore, the aims of this study were to retrospectively analyze a cohort of patients with Salter–Harris (SH) III and IV fractures of the medial malleolus and to evaluate their long-term outcome. MRI was used to assess possible changes of the articular surface that cannot be diagnosed on native radiographs.

Patients and Methods:

Fifty-four patients with SH III (n = 38) or IV fractures (n = 17) of the medial malleolus treated between 2001 and 2011 were invited for a follow-up examination. Clinical outcome was assessed with the Weber score and osteoarthritis with the Kellgren and Lawrence classification. MRI was rated by the Outerbridge classification. Correlations between the clinical and radiological outcomes were calculated.

Results:

Seventeen patients were recruited for long-term follow-up at a mean of 112 (range, 65–184) months. The Weber score was very good for 5 patients, good for 10 patients and poor for 2 patients; the Kellgren and Lawrence score revealed a favourable grade 0 in 15 patients and grade 1 in 2 patients. The MRI-based Outerbridge classification yielded grade 0 for 12 patients, grade 1 for 1 patient, grade 2 for 2 patients and grade 3 for 1 patient. The Outerbridge score significantly (p < 0.05) correlated with the Weber score.

Conclusion:

This study shows excellent and good outcome of SH III and IV fractures of the medial malleolus. Worse clinical outcome correlated with post-traumatic changes of the articular cartilage seen on MRI.

Keywords

adolescents ankle children fracture magnetic resonance imaging medial malleolus outcome Salter–Harris III Salter–Harris IV

Introduction

Fractures of the distal tibia are rare lesions accounting for 2.5% of fractures in children and adolescents.¹ However, 18–30% of these fractures affect the growth plate, thereby representing the third most common growth plate injury.^2
–4

Conservative treatment consists of immobilization with or without reduction and is the standard procedure for all extra-articular distal tibia fractures.⁵ Especially, in younger patients, a certain amount of displacement can be tolerated and will be corrected in the remodelling process typical for this age.^5,6 Fractures with intra-articular involvement, however, require special attention even in children because inappropriate treatment and inaccuracy of reduction are associated with devastating long-term sequelae such as joint incongruity, osteoarthritis, angular deformity and premature physeal closure with subsequent leg-length discrepancy.^5,7,8 Therefore, anatomic reduction is of pivotal importance in these cases.⁹ To minimize the complication rate, articular incongruities of more than 2 mm that cannot be maintained by closed means are considered an indication for open reduction and fixation.^5,10,11

Due to the low incidence of intra-articular fractures of the distal tibia in children, there is only a limited number of studies reporting their long-term outcome.^12
–14 All of these include clinical assessment and radiologic examinations with plain radiographs. This design, however, neglects possible alterations of the articular cartilage, which could be detected by magnetic resonance imaging (MRI).^15,16 Presently, there is no publication combining clinical long-term follow-up with MRI to determine possible post-traumatic alterations following paediatric intra-articular fractures of the distal tibia.

Therefore, the aims of this study were to analyze a cohort of paediatric patients with intra-articular medial malleolar fractures (Salter–Harris (SH) III and IV) and to evaluate their clinical and radiological long-term outcome. Our hypothesis was that MRI reveals changes of the articular surface that cannot be seen in native radiological imaging.

Patients and methods

Following the approval of the local ethics committee (EK 28-127 ex 15/16), all patients with SH III or IV fractures of the medial malleolus treated between 2001 and 2011 at the Department of Paediatric and Adolescent Surgery at the Medical University of Graz were included. Patients with transitional fractures or pathological fractures were excluded.

Between 2001 and 2011, 54 patients (n = 21 females; n = 33 males) were treated with 55 SH III (n = 38) or IV fractures (n = 17) of the medial malleolus. One male patient sustained a refracture of an SH III fracture 2 months following the initial injury. The mean age of the patients was 11 (range, 3–15) years; 39 fractures were non-displaced and, therefore, treated conservatively with cast immobilization. In three cases, closed reduction under general anaesthesia was performed. The remaining 13 fractures underwent open reduction and internal fixation (ORIF; screw osteosynthesis in 12 cases and a combination of screw and K-wire in 1 case). One case was initially treated conservatively in another hospital. Due to secondary displacement, ORIF with screw osteosynthesis was performed 3 weeks later. All patients were immobilized in a cast for a mean of 5 (range, 1.5–6) weeks. Implants were removed after a mean of 145 (range, 73–299) days.

Long-term follow-up

All patients were invited for a clinical and radiological follow-up. Signed informed consent was obtained prior to examination. At the clinical functional examination, the range of motion (ROM) of both ankle joints, knee joints and hip joints was recorded with a goniometer. Leg lengths and axes were determined. Additionally, the Weber¹⁷ and the Olerud and Molander scores¹⁸ were assessed. Overall patient satisfaction was evaluated using a visual analogue scale (VAS; 0–100). Plain digital radiographs (mortise and lateral view) of the formerly injured ankle joint were taken. The grade of osteoarthritis was assessed according to the Kellgren and Lawrence classification system.¹⁹

Additionally, patients underwent MRI scans of both ankle joints to assess post-traumatic and degenerative changes in more detail. All respective scans were performed on a 3 Tesla (T) PRISMA (Siemens Healthineers, Erlangen, Germany) scanner with a dedicated 16-channel ankle coil. Patients were scanned in supine position. Fields of view, as well as repetition and echo times, were automatically adapted to the respective joint by the scanner software. Spin echo proton density-weighted sequences with fat suppression were acquired in axial, coronal and sagittal imaging planes, with an in-plane resolution of about 0.4 mm. Moreover, a sagittal spin echo T1-weighted sequence (image resolution of approximately 0.4 mm) and a gradient-echo T2-weighted ‘Double Echo Steady State’ sequence (isotropic resolution of about 0.6 mm) were acquired. Based on the Outerbridge classification,²⁰ the MRI examinations were graded using certified radiological reading equipment by a paediatric radiologist with 5 years of experience in musculoskeletal MRI. The radiologist was blinded to the clinical results.

Statistical analysis

Data are displayed as absolute numbers, percentages and means and standard deviations as appropriate. Leg lengths at follow-up were compared using the Wilcoxon test. Correlations between the different clinical and radiological scores were calculated using Pearson’s correlations. A p < 0.05 was considered statistically significant.

Results

We were able to recruit 17 patients (n = 5 females, n =12 males) for the clinical and radiological long-term follow-up. The mean follow-up time was 112 (range, 65–184) months. Four (n = 2 SH III, n = 2 SH IV fractures) of these patients initially underwent ORIF; the remaining 13 (n = 9 SH III, n = 4 SH IV fractures) were initially treated conservatively due to a non-displaced fracture. Anatomical reduction was established in all cases.

The majority of the patients (n = 13) were skeletally mature at follow-up. The average total active ROM of the ankle joint was 61 ± 14° for the formerly injured side and 62 ± 11° for the contralateral side.

The Weber score was very good for 5 patients, good for 10 patients and poor for 2 patients. The Olerud and Molander score was excellent for 15 patients and good for 2 patients. There were no cases with satisfactory or poor outcome.

The VAS was ≥90 in 15 patients, between 80 and 89 in 1 patient and between 70 and 79 in 1 patient. No patient stated a VAS <70.

The X-ray-based Kellgren and Lawrence score yielded grade 0 in 15 patients and grade 1 in 2 patients. No grade 2, 3 or 4 changes were seen.

A total of 16 patients underwent MRI examination of both ankle joints (Figures 1 and 2). One patient refused to take part at the MRI examination. The MRI-based Outerbridge classification of the affected side yielded grade 0 for 12 patients, grade 1 for 1 patient, grade 2 for 2 patients and grade 3 for 1 patient. Grade 4 lesions were not encountered.

Figure 1.

(a) Initial radiograph of the right ankle showing an SH III fracture of a 7-year-old girl. (b) Unremarkable follow-up radiograph 70 months after conservative treatment. (c) Follow-up MRI (proton density-weighted coronal image with fat saturation) without signs of post-traumatic changes. MRI: magnetic resonance imaging; SH: Salter–Harris.

Figure 2.

(a) Initial radiograph of the left ankle with an SH III fracture of a 10-year-old boy. (b) Initial right ankle CT in coronal reconstruction showing the non-displaced fracture. (c) Follow-up radiograph with pronounced subcortical sclerosis and irregularities (black arrow) in keeping with post-traumatic changes 82 months after conservative treatment. (d) MRI (proton density-weighted sequence with fat suppression) in coronal imaging plane showing a cartilaginous defect (white arrow). MRI: magnetic resonance imaging; CT: computerized tomography; SH: Salter–Harris.

At follow-up, leg lengths did not differ between the formerly injured compared to the uninjured side (injured side 91.8 ± 5.7 cm; uninjured side 91.8 ± 5.9 cm, p = 1.0).

An overview of the clinical and radiological findings at follow-up is presented in Table 1. Correlations of the different clinical and radiological scores are presented in Table 2. The Outerbridge classification significantly correlated with the Weber score and the Kellgren and Lawrence score.

Table 1.

Clinical and radiological findings at follow-up (mean follow-up time 112 months; range, 65–184) of 17 patients with SH III and IV fractures of the medial malleolus.

Age	Fracture	Treatment	F/U (months)	VAS	Weber	Olerud and Molander	Kellgren and Lawrence	Outerbridge
10	SH IV	Cons.	122	95	Good	Good	0	0
14	SH IV	Cons.	131	80	Good	Excellent	0	0
3	SH IV	ORIF	184	100	Good	Excellent	0	0
11	SH IV	ORIF	119	100	Good	Excellent	0	2
14	SH IV	Cons.	104	95	Good	Excellent	0	0
12	SH IV	Cons.	71	95	Very good	Excellent	0	0
10	SH III	Cons.	82	100	Poor	Excellent	1	3
7	SH III	Cons.	70	100	Very good	Excellent	0	0
11	SH III	Cons.	69	100	Very good	Excellent	0	1
12	SH III	Cons.	68	100	Very good	Excellent	0	N/A
9	SH III	Cons.	67	100	Good	Excellent	0	0
11	SH III	Cons.	65	100	Very good	Excellent	0	0
7	SH III	ORIF	65	90	Good	Excellent	0	0
8	SH III	Cons.	181	100	Good	Excellent	0	0
9	SH III	Cons.	179	90	Good	Excellent	0	0
9	SH III	ORIF	174	70	Poor	Good	1	2
12	SH III	Cons.	157	90	Good	Excellent	0	0

Cons.: conservative; ORIF: open reduction and internal fixation; N/A: not available; VAS: visual analogue scale; SH: Salter–Harris.

Table 2.

Correlation coefficients (Pearson’s R) of the different clinical and radiological scores at follow-up.^a

	VAS	Weber	Olerud–Molander	Kellgren–Lawrence	Outerbridge
VAS	–	−0.424	0.656	−0.412	−0.100
Weber	−0.424	–	−0.425	0.676	0.621
Olerud–Molander	0.656	−0.425	–	−0.501	−0.234
Kellgren–Lawrence	−0.412	0.676	−0.501	–	0.808
Outerbridge	−0.100	0.621	−0.234	0.808	–

VAS: visual analogue scale.

^a Statistically significant correlations (p < 0.05) are displayed in bold.

Discussion

The present study reports clinical and radiological outcome of 17 patients with SH III and IV fractures of the medial malleolus at a mean follow-up of 112 months. For the first time, MRI was used to display post-traumatic changes of the articular surface in such patients. The MRI-based Outerbridge classification significantly correlated with both clinical and radiological outcome.

In children, fractures of the ankle joint represent only 6% of the total number of tibial fractures.²¹ The majority of studies reporting fractures of the distal tibia have included the whole range of possible lesions including SH I–V, juvenile Tillaux and two/triplane fractures.^8,11,22 Fewer studies, however, have solely concentrated on intra-articular fractures, that is, SH III and IV fractures, of patients with completely open physes.¹⁴ Since these fractures occur in younger children when compared to transitional fractures, which occur during closure of the growth plate, they carry a higher risk of long-term complications such as premature physeal closure with subsequent leg length discrepancies or angular deformities.²³ Therefore, only SH III and IV fractures were included in the present study.

X-rays in two planes represent the standard first-line diagnostic modality for intra-articular fractures of the distal tibia in children. The necessity of additional computerized tomography (CT) imaging for these fractures is still a matter of controversy in the literature. Lemburg et al. have demonstrated a high rate of disparity comparing conventional radiography and CT-based classification, especially in SH III fracture of the distal tibia.²⁴ However, the authors did not correlate these findings to possible changes in the therapeutic approach. Additionally, another report has presented a diagnostic algorithm for intra-articular distal tibial fractures.²⁵ For patients with completely open physes and non-displaced intra-articular fragments on radiographs, the authors propose to proceed with treatment; on the other hand, presence of intra-articular displacement on radiographs warrants an additional CT scan. In the present study, additional CT scans were performed in a quarter of the patients (n = 14; n = 7 of them with non-displaced fractures and n = 7 with displaced fractures). The radiation exposure associated with CT scanning coupled with the generally excellent to good results of the present study supports a well-considered indication for CT scans.

Paediatric fractures – especially those near the physes – show an enormous remodelling potential. It is undisputable that displaced intra-articular fractures necessitate anatomic reduction in order to avoid devastating long-term sequelae.⁹ However, the exact threshold between conservative and operative treatment is unclear. While the majority of authors recommends cast immobilization (with or without closed reduction) up to an articular gap of 2 mm,^9
–11,14 others state that every displaced intra-articular fracture must be reduced anatomically irrespective of patients age.²⁶ The outcome data of the present report support the 2-mm threshold.

The most devastating complication associated with intra-articular fractures of the distal tibia in paediatric patients is premature physeal closure with subsequent growth arrest, leg length discrepancies and angular deformities. Nevertheless, many studies reporting the outcome of intra-articular ankle fractures in children have included a variety of different distal tibial fractures including transitional fractures with a limited amount of residual growth.^8,11,22 In order to exclude this selection bias, we have decided to include only patients with SH III and IV fractures. Neither in short-time nor in long-term outcome (mean: 112 months), complications associated with premature physeal closure were found in the present study.

While some previous reports have described MRI as a possible imaging modality for preoperative planning of fractures,²⁷ the present study has used MRI for the first time to assess the radiological long-term outcome of paediatric intra-articular fractures of the medial malleolus. Digital radiographs clearly represent the gold standard for radiological assessment of intra-articular fractures in children.⁹ However, the articular cartilage cannot be examined using this method. One of the aims of our study was to investigate whether long-term post-traumatic alterations of the articular surface are present in patients with absent changes on conventional radiographs. In four patients, such alterations could be seen on MRI, while only two patients presented with alterations on conventional radiographs (see Table 1). Additionally, the two patients with an increased Kellgren score also presented with higher grade changes of the articular cartilage as seen on MRI. This combined with the fact that both patients with a poor Weber score showed higher grade alterations of the articular cartilage emphasize the validity of our MRI findings. Correlations between the clinical and radiological scores were calculated, and we were able to show a significant correlation between the MRI-based Outerbridge classification and the clinically based Weber score as well as the Kellgren score which assesses radiological signs of osteoarthritis on plain radiographs. The clinical significance of these findings, however, needs to be addressed in future studies.

The biggest limitation of the present study is the low follow-up rate. Despite all efforts by mail and phone, we were not able to recruit more than a third of the patients. Almost half of the patients (44%) declined to take part because they considered their condition satisfactory. The remaining patients could not be contacted. Migration for job or education can be considered as the most likely factor. Nevertheless, we present the first study that uses MRI imaging to assess the long-term outcome of the relatively rare intra-articular fractures of the medial malleolus in children with completely open physes. In order to confirm our findings, a prospective multicentric approach would be necessary to increase the number of participating patients.

In conclusion, the present study shows excellent to good long-term outcome of SH III and IV fractures of the medial malleolus. Additionally, we were able to demonstrate that changes of the articular cartilage as demonstrated on MRI are associated with a worse clinical outcome.

Footnotes

Acknowledgement

The authors thank the Ralf Loddenkemper-Stiftung.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the Ralf Loddenkemper-Stiftung.

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