During recent years, only four retrospective studies on the non-operative treatment of Lisfranc injury have been published (Crates et al., 2015; Curtis et al., 1993; Nunley
& Vertullo, 2002; Shapiro et al., 1994). All of these previous studies share the same flaws. First, the diagnosis of the injury was based on plain radiographs. Second, the
evaluation of the outcomes had been conducted without using properly validated outcome measures. Third, the non-operative treatment protocol varied between none to six weeks of cast immobilization followed by four weeks of orthosis (Crates et al., 2015; Faciszewski et al., 1990; Myerson et al., 1986; Nunley & Vertullo, 2002;
Shapiro et al., 1994). Non-weightbearing during the immobilization was only used by a few studies (Faciszewski et al., 1990; Nunley & Vertullo, 2002). Moreover, some authors have suggested that only stable injuries without any displacement should be treated non-operatively (Nunley & Vertullo, 2002). Nevertheless, there is no consensus on which techniques should be used to determine whether an injury is stable or not, and therefore this statement needs to be considered carefully (Naguib
& Meyr, 2018; Preidler et al., 1999). Moreover, after completing our study, another retrospective case series was published by Chen et al. (2020). They reported that 54%
of 26 patients developed an instability during the conservative treatment, and were converted to operative treatment Surprisingly, they also reported that the functional outcomes were comparable in both groups, regardless of the timing of the surgery.
After all, there are no RCTs in the literature that have compared operative with non- operative treatment.
The literature provides at least 15 different classification systems for Lisfranc injuries (Hardcastle et al., 1982; Lau et al., 2017; Myerson et al., 1986; Nunley &
Vertullo, 2002; Schepers & Rammelt, 2018; Sivakumar et al., 2018). Ideally, injury classifications should be developed as tools to help doctors in decision making and in choosing the optimal treatment for each patient (Burstein, 1993). Accurately working classifications should also provide estimates of the outcomes after the chosen treatment (Burstein, 1993). The original classification by Schepers and Rammelt (2018) was developed to patch the flaws of the previous radiograph-based classifications that do not take into account all TMT injuries (Hardcastle et al., 1982;
Myerson et al., 1986; Nunley & Vertullo, 2002). This latest classification classifies these injuries based on fracture type (avulsion, simple, or comminuted) and the columns affected, resulting in dozens of different groups. Although this classification seems to be the most suitable classification system for Lisfranc injuries, it would benefit from a reduction in the number of different groups and further studies to guide the treatment of these injuries. Additionally, the classification does not take into account displacement or stability, which seem to be the factors that have an influence on the treatment. Although the results of the surgery might not be dependent on the primary dislocation, it is an important factor when non-operative treatment is considered. As this classification takes all bony injuries into account, it results in multiple classes of injuries. Since it is important to evaluate the results after
treatment of these injuries, the large number of classes makes it impossible to compare them. Therefore, we deemed it necessary to reduce the number of classes to three main groups. Moreover, the inter- and intraobserver reliability of the classification should also be evaluated to assess its reliability.
The main finding of the retrospective case series was that nondisplaced Lisfranc injuries affecting up to three TMT joints can be treated non-operatively with good functional outcomes. More than half of the patients in all groups scored over 90 points in both the Pain and Function subscales and more than 60% scored over 90 points overall. The mean VAS-FA scores for patients without previous foot injuries have been reported in a previous study as follows: 94.5 for Overall, 92.5 for Pain, 95.4 for Function, and 75.6 for Other Complaints (Faciszewski et al., 1990).
Therefore, the results of this series show that most of the non-operatively treated patients in our study recovered close to the level of healthy patients after 2 to 6 years of follow-up. The VAS-FA scores seemed to be following a similar distribution between bony avulsions and simple intra-articular fractures.
In the largest previous study investigating the non-operative treatment of Lisfranc injuries (Crates et al., 2015), up to 20 out of 36 patients underwent secondary surgery during the three-year follow-up period. The non-operative protocol in their study was conducted with 6 weeks of orthosis and weightbearing was allowed as tolerated.
In addition, the diagnosis of subtle Lisfranc injury was based on standard radiographs and patients with remarkable clinical symptoms (even without findings in the radiographs) were included in the study. Moreover, “failed nonoperative treatment” was determined by a surgeon, but no further details of the reasons behind the conversion to operative treatment were given. Due to these flaws, the results of this previous study can be questioned.
The non-operative protocol in our study was more careful than the one used by Crates et al. (Crates et al., 2015). Our protocol with non-weightbearing and longer immobilization was adopted from a previous study by Nunley and Vertullo (2002).
With this non-operative treatment, our secondary operation rate was low, as only 1 of the 60 patients underwent an arthrodesis performed 10 months after the injury.
As our outcomes suggest, the results of non-operative treatment may be better if the non-operative protocol is started with non-weightbearing and the immobilization lasts for 6 to 10 weeks.