All data were assessed using SPSS version 20.0 (IBM). Binary data were entered into contingency tables to allow cross-tabulation of the results. For data cells of >5, differences were tested using the chi-square test; otherwise, the Fisher exact test was used. Numerical data were tested using a Student t test if parametric or a Mann-Whitney test if nonparametric. A 1-way analysis of variance (ANOVA) test was used for groupwise analysis of parametric data.
Of 61 patients included in this study, 1-year patient-related outcome measures were obtained for 50 patients (82%). The dropout rate was a consequence of the major trauma setting and large tertiary referral base. There were 22 male patients and 28 female patients. According to the Mason and Molloy classification, there were 17 type-1 fractures (34%), 12 type-2A fractures (24%), 10 type-2B fractures (20%), and 11 type-3 fractures (22%). The mean age of this cohort of patients was 46.8 years (range, 21 to 87 years). Categorizing by the Mason and Molloy classification, the mean age was 46.8 years for patients with type-1 fractures, 55.0 years for patients with type-2A fractures, 49.7 years for patients with type-2B fractures, and 43.3 years for patients with type-3 fractures. Using nonparametric group statistical analysis, there was no significant difference in age among the groups.
The overall Olerud-Molander Ankle Score for all posterior malleolar fractures in this cohort was 74.1 points (95% confidence interval [CI], 69.1 to 79.1 points). Comparing this study’s functional results with the functional results of our previous multicenter trial11, in which posterior malleolar fractures were treated using the traditional method (ankle fracture fixation using OTA/AO principles, in which posterior malleolar fractures were not fixed if they were <25%), there was an improvement in outcome (Table II). The categorizing of the outcomes by the Mason classification is illustrated in Table III. Using a 1-way ANOVA test, there was no significant difference (p = 0.886) between groups or within groups. However, there was a trend that a lower Mason and Molloy classification had higher Olerud-Molander Ankle Score outcomes.
TABLE II -
Functional Results of Posterior Malleolar Fixation Techniques, Comparing the Current Study with Our Previous Multicenter Ankle Fracture Outcome Study
||No. of Patients
||Olerud-Molander Ankle Score†(points)
||52.9 (20 to 69)‡
||54.3 (33.9 to 74.7)
||46.8 (21 to 87)‡
||74.1 (69.1 to 79.1)
The values are given as the mean, with the range in parentheses.
The values are given as the mean, with the 95% CI in parentheses.
The comparison of the means was significant at p < 0.05.
TABLE III -
Comparison of 1-Year Olerud-Molander Ankle Scores Between the Mason Classification Groups
||No. of Patients
||Olerud-Molander Ankle Score*(points)
||74.1 (69.1 to 79.1)
||75.9 (66.4 to 85.3)
||75.0 (61.5 to 88.5)
||74.0 (64.2 to 83.8)
||70.5 (59.0 to 81.9)
The values are given as the mean, with the 95% CI in parentheses.
The overall mean 1-year EQ-5D index for this cohort of patients was 0.88 (95% CI, 0.82 to 0.95). The mean visual analog scale score for this patient group was 77.5 points (95% CI, 70.0 to 84.9 points). Categorizing the outcomes by the Mason and Molloy classification, the mean EQ-5D index was 0.88 (95% CI, 0.77 to 0.99) for patients with type-1 fractures, 0.79 (95% CI, 0.57 to 1.0) for patients with type-2A fractures, 0.91 (95% CI, 0.80 to 1) for patients with type-2B fractures, and 0.96 (95% CI, 0.90 to 1) for patients with type-3 fractures. The mean visual analog scale score for health was 83.3 points (95% CI, 72.0 to 94.6 points) for patients with type-1 fractures, 69.2 (95% CI, 47.0 to 91.3 points) for patients with type-2A fractures, 80.8 points (95% CI, 64.2 to 97.4 points) for patients with type-2B fractures, and 74.5 points (95% CI, 57.8 to 91.3 points) for patients with type-3 fractures. Using nonparametric group statistical analysis, there was no significant difference in the EQ-5D or the visual analog scale score either within or between the groups.
The functional outcomes of posterior malleolar fractures are reported to be significantly worse than the outcomes for unimalleolar and bimalleolar ankle fractures2. In our previous study, we presented a significant clinical difference between unimalleolar fractures and their trimalleolar counterparts, with a difference between them of >20 points on Olerud-Molander Ankle Score functional outcomes11. In that study by Roberts et al.11, true posterior Pilon fractures (Mason and Molloy classification type 3) were not included. In their study, Roberts et al. reported Olerud-Molander Ankle Score functional outcomes that were equivalent to those reported in the literature in other large outcomes studies, with mean Olerud-Molander Ankle Score functional results ranging from 75 to 95 points for unimalleolar fractures and 56 to 85 points for bimalleolar fractures12-16. In the current study, posterior pilon fractures were included, which makes the 20-point increase in functional outcomes, to near unimalleolar fracture functional results, even more dramatic. There were no other differences in treatment between the previous study and the current study, as all included fractures underwent surgical fixation of the medial and lateral malleolar fractures.
The mean EQ-5D index in the current study is equivalent to the general population results reported in both the United Kingdom and the United States17,18. There was no significant difference either within or between the groups; nevertheless, there was a trend of reduced health markers in the type-2A fracture group. This is likely to represent the increase in the mean age in this group compared with the other fracture groups in our study. Similarly, the Olerud-Molander Ankle Score functional outcomes did not have a significant difference either within or between the groups of the fracture classification. However, there was a trend that indicated a possible prognostic application of the Mason and Molloy classification, with an increasing type indicating an increase in complexity and a decreasing functional result. Type-3 fractures have a larger impaction injury to the tibial plafond, and it makes logical sense that the cartilage injury is likely to be more substantial. The lack of significant difference between the groups is likely to represent the sample size of this study, although it could also represent the general improvement in outcomes across all of the groups.
As shown in previous literature, there are clear indicators that posterior malleolar fractures are variable in their nature, and as such should not be grouped together for analysis2,3,7. Each fracture type has its own injury associations, which in themselves can determine the management and final outcomes of these fractures. This study has illustrated the value of the Mason and Molloy classification system and the subsequent treatment algorithm in its guidance of treatment. The knowledge of the mechanism and its associated injury patterns allows thorough treatment planning. Our algorithm has developed over the treatment of many previous posterior malleolar fractures and is established in our unit, although every fracture pattern should be taken on its own merit.
All of the type-1 fractures represented in this study were confirmed to have a syndesmotic injury on live screening intraoperatively. As indicated in the study by Mason et al., a proportion of these injuries will be partial syndesmotic injuries with the avulsion of the posterior inferior tibiofibular ligament7. This is not apparent on the commonly reported syndesmotic tests used, and an internal rotation test should be undertaken under live screening. In type-2 and 3 fractures, syndesmotic stabilization clinically can be achieved with reduction and fixation of the posterior malleolar fragment if the anterior-inferior tibiofibular ligament has remained intact. Miller et al. reported a rate of 2.1% for syndesmotic instability after fixation of the posterior malleolar fracture fragment with the patient prone compared with a rate of 48.3% for ankle fractures treated without posterior fixation and with the patient in a supine position19. This has also been demonstrated in a cadaveric study by Gardner et al.20, who reported that posterior malleolar fixation resulted in 70% of cases of syndesmotic stability compared with 40% of cases that achieved syndesmotic stability with screw fixation. However, caution should be used because any elevation of the posterior-inferior tibiofibular ligament on approach to the posterior malleolar fragment may eliminate some of the stabilizing force. As reported by Kim and Lee, posterior-inferior tibiofibular ligament release is often required, sometimes only partially, to reduce the posterior malleolar fragment21.
The approach to the posterior malleolar fracture has been included in our treatment algorithm, as a means to guide others who are unfamiliar with posterior hindfoot approaches. The preoperative CT imaging is helpful in determining the optimal surgical approach. The posterolateral and posteromedial approaches have both been reported to be safe in terms of both wound management and radiographic follow-up22,23. Our experience is that the direct approach to the posterior malleolar fracture should be performed where possible, rather than the indirect approach and anterior-to-posterior fixation. This direct approach has been shown by Shi et al. to be superior in terms of both anatomical fixation and functional outcomes24.
We acknowledge a number of limitations to this study. First, this study showed the functional outcomes to a minimum of 1 year after the injury. However, these functional outcomes may change with time. Second, postoperative management using non-weight-bearing was employed, in theory to allow better regeneration of the tibial cartilage. This is in contrast to an increasing practice to allow early weight-bearing and a functional orthosis in an attempt to allow quicker rehabilitation and earlier return to work. There is limited clinical evidence regarding early weight-bearing in the treatment of posterior malleolar fractures, although, in a small study including a joint model, Papachristou et al. reported good functional return by 3 months25. Their joint model illustrated minimal load passing through the posterior malleolar fracture fragment with weight-bearing. Third, a proportion of our type-1 fracture patterns displayed only partial syndesmotic disruptions. In a randomized controlled trial, Andersen et al. reported on suture button and screw fixation for syndesmotic injury and showed an improved functional result with the use of suture button syndesmotic fixation26. Interestingly, their screw fixation group had a higher proportion of posterior malleolar fractures, which displayed a worse functional outcome.
In conclusion, we demonstrated an improvement in the Olerud-Molander Ankle Score for all posterior malleolar fractures with the treatment algorithm applied using the Mason and Molloy classification compared with our previous study. Mason and Molloy classification type-3 fractures have marginally poorer outcomes, which correlates with a more substantial injury. However, this difference did not reach significance.
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