Abstract
Background
Ankle fractures are highly prevalent orthopaedic injuries frequently involving the posterior malleolus, affecting ankle stability and function.
Methods
This study evaluated functional outcomes and return to sport following operative fixation of posterior malleolus fractures. The study included all consecutive patients with posterior malleolus fracture, who underwent operative fixation in a single institution in the UK. Patient demographics, fracture pattern based on Mason classification, operative details, postoperative radiographs and complications were extracted and analysed. Primary outcome was functional outcome assessed using the Olerud and Molander (OM) score and secondary outcomes were return to sport, union rates, complications and Visual Analogue Pain Score (VAS).
Results
Between May 2019 and May 2021, n = 52 patients were eligible for inclusion. Mean age was 45.2 ± 14.5 with mean follow up of 14.2 ± 4.3 months. The mean OM score was 79.3 ± 16.9 and mean VAS score was 1.2 ± 1.7. Residual symptoms were frequent: 55 % reported some level of ongoing pain, 35 % stiffness, 23 % swelling. Out of 43 patients doing sports pre-injury, 28 (65 %) returned to the same sport level, 11 (26 %) to a lower level, and 4 (9 %) were unable to return. No significant differences in outcome were observed between Mason fracture types.
Conclusions
Functional recovery was achieved in the majority of patients, with 42 % excellent and 52 % fair outcomes, though residual symptoms remained common. Residual symptoms and functional limitations must be emphasised to patients to manage postoperative expectations.
1
Introduction
Ankle fractures are common traumatic injuries affecting 107–184 per 100,000 of the population per year , . Unimalleolar fractures are most common, followed by bimalleolar fractures , . The exact incidence of ankle fractures with posterior malleolus involvement varies from 7 % to 44 % , .
Historically, management was based on fragment size (>1/3 articular surface), but recent reviews suggest fragment size alone does not determine outcome. ,,,,, Posterior malleolus fractures are closely linked with Posterior Inferior Tibio-Fibular Ligament injury, syndesmotic instability, and poorer outcomes, including residual symptoms and early arthritis ,, .
Anatomic reduction of posterior malleolar fractures is critical. Biomechanical studies confirm that malreduction alters talar contact mechanics and contributes to post-traumatic arthritis ,,, . The indications and outcomes of operative management for posterior malleolar fractures remains an area of interest. In particular, there is a lack of studies reviewing the functional outcomes following surgical management of posterior malleolar fractures with regards to return to sporting activities.
Aim: To evaluate functional outcomes and return to sport following operative fixation of posterior malleolar ankle fractures using plate and screw fixation with or without syndesmotic stabilisation, with minimum 12-month follow-up.
Based on existing literature and our clinical experience, we hypothesised that operative fixation of posterior malleolar fractures allows the majority of patients to achieve satisfactory postoperative function at 12 months, defined by an Olerud–Molander (OM) score of ≥ 80 and minimal residual pain (VAS ≤2). We further hypothesised that functional outcomes and return-to-sport rates would not significantly differ between fracture morphologies classified according to the Mason system.
2
Methods
2.1
Study design and setting
This is a retrospective review of consecutive patients who underwent operative fixation of a posterior malleolus fracture between May 2019 and May 2021 at a single UK district general hospital. All operations were performed by two senior foot and ankle surgeons. The study was reported in line with the STROBE guidelines for observational studies .
2.2
Participants
The study included adults with posterior malleolus fractures managed operatively with ≥ 12 months follow-up. Exclusion criteria were: fractures without posterior malleolus involvement, pilon fractures (distinguished on CT by metaphyseal extension, comminution, or >2/3 articular surface involvement), open fractures, polytrauma, pathological fractures, neurovascular injuries, and skeletally immature patients. No high-energy or complex soft tissue injuries requiring plastics input were included.
2.3
Fracture classification, operative technique and postoperative protocol
All ankle fractures presented in our institution were discussed in a multidisciplinary trauma meeting where decision regarding management options was made based on patient and fracture characteristics. All included patients underwent preoperative computed tomography (CT) of the ankle to characterise the posterior malleolar morphology and enable classification according to the Mason system. The decision making process involved consideration of patient age, past medical and surgical history, social history and pre-injury level of function. Fracture characteristics that were considered included involvement of malleoli, site, size and comminution of fragments, integrity of articular surface, evidence of syndesmotic injury (either clinical or radiological) and soft tissue condition.
For Mason type 1 fractures, a decision was made to proceed with ligamentotaxis and syndesmotic fixation, irrespectively of any additional injuries, based on the current literature. Mason type 1 fractures of the posterior malleolus, as classified by CT imaging, involve a small, extra-articular posterolateral fragment and are consistently associated with syndesmotic disruption in almost 100 % of cases despite their limited size . According to the Liverpool protocol, developed by Mason at al, type 1 fracture management does not require direct fixation of the posterior fragment due to its lack of articular involvement. Instead, emphasis is placed on assessing the syndesmosis, through intraoperative stress testing such as the dorsiflexion and external rotation test . If instability is detected, fixation is achieved using either syndesmotic screws or suture-button devices, depending on the surgeon’s preference. This approach avoids the need for a posterior surgical approach, thereby reducing operative morbidity. Studies implementing this protocol have demonstrated favourable outcomes, with patients achieving Olerud-Molander Ankle Scores comparable to those with more complex posterior malleolar injuries thus supporting the rationale for indirect management focused on syndesmotic stability , . Postoperative reduction following syndesmotic fixation was confirmed with intraoperative imaging.
A detailed management flow chart is presented in Fig. 1 .
Flowchart of ankle fracture management based on Mason classification.
All patients with posterior malleolar fractures that were managed operatively had a preoperative CT scan and were classified using the Mason classification .
Standard fixation was performed under fluoroscopic guidance, with intraoperative syndesmotic and deltoid stability testing (Cotton’s and talar tilt tests). Fixation was added if instability was present.
Postoperative protocol: All patients followed a uniform rehabilitation protocol. Initially non-weightbearing in a neutral-position backslab for 6 weeks, then transitioned to a walking boot with progressive weightbearing as tolerated. Postoperative assessment included standardised plain radiographs obtained at 2, 6, 12, and 52 weeks to evaluate fracture union and joint congruency. Postoperative CT was not routinely performed but was reserved for selected cases at the discretion of the treating surgeon. Union was defined as cortical bridging without visible fracture line. Metalwork was not routinely removed.
2.4
Outcome measures and study endpoint
The primary outcome was functional outcomes using the Olerud and Molander (OM) score . Secondary outcomes included union rates, pain (assessed using the visual analogue score (VAS)), ability to return to sport and complications. Complications identified by either the patient or surgeon in outpatient clinics were identified from retrospective review of clinical records. We utilised the Clavien-Dindo complication classification for foot and ankle surgery .
The OM score is a validated ankle specific patient reported outcome score commonly used to evaluate ankle specific functional outcomes . It covers 9 different areas that the patients can assess covering the complete spectrum of ankle function. Those include pain, stiffness, swelling, stair-climbing, running, jumping, squatting, supports, and work and activities of daily living. Scores range from a minimum (zero) to a maximum (100) points. In line with our study hypothesis, a postoperative functional outcome was considered satisfactory if patients achieved an Olerud–Molander (OM) score of ≥ 80 and a VAS pain score of ≤ 2 at final follow-up. We also hypothesised that Mason fracture type would not independently influence the likelihood of achieving this satisfactory outcome or returning to sport.
Patients were retrospectively identified using the hospital electronic database and operative code system. Relevant data was collected as part of routine follow up by physical appointment in the fracture clinic or via virtual (telephone) consultation.
2.5
Bias
Efforts to address potential sources of bias were made by organising a single blinded study. The investigators assessing the outcomes were blinded to fracture classification, fixation method, and operating surgeon.
2.6
Study size
We included consecutive patients over the study period to reduce risk of selection bias. We also conducted an a priori study size calculation to confirm that the study is not underpowered. A post hoc power analysis confirmed that our sample size (n = 52) was adequately powered to detect medium to large effects (effect size ≥ 0.5) using the OM score.
2.7
Ethical approval
This project was registered with the institutional audit and governance department as a service evaluation (registration no. 7277), and formal Research Ethics Committee approval was not required according to national guidelines (UK Health Research Authority). The study was conducted in accordance with the Declaration of Helsinki and the Guidelines for Good Clinical Practice.
2.8
Statistical analysis
Frequency tables and descriptive statistics (mean, standard deviation or median where appropriate) were reported for continuous variables. ANOVA testing was carried out for between group comparisons. All analysis was performed with SPSS. A p value of < 0.05 was considered statistically significant
3
Results
Between May 2019 and May 2021, 284 patients underwent operative management of ankle fractures in our institution; 61 (21 %) had posterior malleolus involvement and were eligible to be included in the study. Nine were lost to follow-up, leaving 52 patients (85 % follow-up) with ≥ 12 months review (mean 14 months). There were 21 men (40 %) and 31 women (60 %), with a mean age of 45 years (range 20–80).
According to Mason classification, there were 10 Type 1 (19 %), 23 Type 2 A (44 %), 12 Type 2B (23 %), and 7 Type 3 (14 %) fractures. All fractures involved ≥ 2 malleoli; no isolated posterior malleolus fractures were observed. Of the 52 cases, 42 (81 %) were trimalleolar and 10 (19 %) were bimalleolar (involving the medial or the lateral malleolus and the posterior malleolus). A flow chart and details of fracture configuration can be seen in Fig. 2 .
Flow diagram showing patient inclusion and fracture configuration. Mason classification: type 1 = posterolateral small fragment; 2 A = posterolateral large fragment; 2B = posteromedial extension; 3 = posteromedial and posterolateral involvement.
Regarding fixation methods, 31 patients (60 %) underwent ORIF via posterolateral plating, 10 (19 %) had ligamentotaxis with syndesmotic fixation, 6 (11 %) had combined posterolateral and posteromedial plating, and 5 (10 %) underwent anterior-to-posterior screw fixation.
3.1
Primary Outcome
Functional recovery was achieved in the majority of patients, with 42 % excellent and 52 % fair outcomes, with a mean OM score of 79.3 ± 16.9. There were 22 patients with excellent outcome (OM > 90), 27 patients with fair outcomes (OM 60–89) and 3 patients with poor outcome (OM<59). Functional outcomes based on Mason classification, between different fracture types, are depicted in Fig. 3 . Comparison using a one-way ANOVA test, showed no significant difference ( p = 0.80) between groups or within groups.
Bar graph demonstrating functional outcomes based on Mason classification, between different fracture types.
A comparison of 1-Year Olerud-Molander Ankle Scores Between different fracture types, based on Mason Classification, can be seen in Fig. 4 .
Comparison of 1-Year Olerud-Molander Ankle Scores Between different fracture types based on Mason Classification.
Secondary Outcomes:The mean visual analogue scale score was 1.3 (SD: 1.7), with 28 (54 %) of patients having some degree of residual pain (VAS>1), which however was in most cases, low in intensity and well controlled. Only one patient described severe constant pain (VAS 8/10) and only 5 patients had moderate pain (VAS > 4). Using a 1-way ANOVA test, there was no significant difference ( p = 0.603) between groups or within groups regarding pain (p > 0.05). 18 (35 %) patients reported some degree of stiffness and 12 (23 %) patients described getting some degree of swelling over one year following surgery. Rates of residual pain, stiffness and swelling can be seen in Table 1 .
Table 1
Comparison of outcomes between different groups based on Mason and Molloy posterior malleolar classification. Values are n (%).
| Type 1 (n = 10) | Type 2 A (n = 23) | Type 2B (n = 12) | Type 3 (n = 7) | |
|---|---|---|---|---|
| Residual pain n (%) | 5 (50 %) | 13 (57 %) | 5 (42 %) | 3(53 %) |
| Residual stiffness | 2 (20 %) | 8 (35 %) | 6 (50 %) | 2 (29 %) |
| Residual swelling | 1 (10 %) | 6 (26 %) | 3 (25 %) | 2 (29 %) |
| Mean VAS | 1 | 1.1 | 1.8 | 1 |
| Mean OM score | 80 | 76 | 70 | 80 |
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