This study presents the largest cohort on surgically treated LPT fractures. Hawkins Type 1 fractures were treated by open reduction and screw fixation, Type 2 and 3 fractures by resection of the fracture fragments. Furthermore, all concomitant injuries were addressed. Despite this progressive treatment approach, after more than three years after the surgery, the patient rated outcome revealed only moderate to good scores. Twelve (55%) patients suffered from posttraumatic symptomatic subtalar osteoarthritis. Although Hawkins Type 1 fractures resulted in better VAS FA Overall scores than Type 2 fractures, the only independent factor associated to an impaired patient rated outcome was posttraumatic symptomatic subtalar osteoarthritis.
The authors are only aware of eight case series (> 6 patients) reporting on the outcome of LPTFs [4,5,6,7, 10, 17, 18]. Out of those, only two studies applied a standardized treatment algorithm and evaluated the surgical outcome using PROMs [7, 15]. Valderrabano et al. reported excellent results for 14 operatively treated Hawkins Type I fractures. Their mean AOFAS score was 97 (1) and a VAS of 0.2 (0.6) points [7]. However, no data was reported for operatively treated Type II fractures. Von Knoch et al. reported good to moderate AOFAS scores of 93 (82 to 100) points for operatively treated displaced Type I (n = 11) and Type II (n = 5) fractures [15]. Still, various studies have questioned the validity of the AOFAS [19, 20, 22]. As outlined in the introduction, the fractures included in the study by Valderrabano et al. [7] and von Knoch et al. [15] were transformed to the Hawkins classification to increase the comparability.
The herein presented 22 operatively treated LPTFs resulted in only moderate to good PROMs. The VAS FA and Karlsson Score revealed residual impairment. The VAS FA Overall Score (77 ± 21 (20 to 100)) was lower than the published reference values for healthy individuals (86 to 100) but comparable to patients with an isolated hallux valgus (45 to 83) [32]. Similar results were found for the Karlsson Score (72 ± 21 (34 to 97)) with scores above 80 points representing good to very good results [30]. The patients’ quality of life (SF-12: PCS 53 ± 8 (36 to 64), MCS 53 ± 7 (32 to 63)) was in the range of a healthy population. Overall, operatively treated displaced Type I or II fractures result in good to moderate results.
The observed residual impairment was also reflected in the return to sports rate. Only half of the patients reached a sport activity level ≥ 90% after on average 8.2 ± 4.9 (3 to 24) months. A surprisingly high rate (100%) of return to sports in operatively treated patients was found by Valderrabano et al. [7] Von Knoch et al. [15] and Klein et al. [17] reported rates of return to sports comparable to the herein presented study (63% / 59%).
The secondary aim of this study was to identify factors associated to a poor patient rated outcome. Although Hawkins Type 1 fractures resulted in superior results compared to Type 2 fractures (VAS FA Overall: p = 0.018 and -Other: p = 0.002) the strongest independent factor for impairment was posttraumatic symptomatic subtalar osteoarthritis (VAS FA and Karlsson Score). In the current study, 50% of patients suffered from symptomatic subtalar osteoarthritis, which compares well to literature with reported rates of 15 to 45% [6, 7, 10]. On the contrary, neither the occurrence nor the number of concomitant injuries affected the patient rated outcome. Only five studies have previously reported on concomitant injuries following LPTFs [6, 10, 15, 17, 18]. Von Knoch et al. reported a rate of concomitant injuries of 88% [15]. Klein et al. reported on peroneal tendon displacement in 46% of patients suffering a Type 2 LPTF [17]. Both studies did not further analyze the influence of these concomitant injuries. These figures are in the range of the herein observed rate of 82% of patients suffering concomitant injuries. This number might even underestimate the actual occurrence of concomitant injuries accompanying LPTFs, as several of these injuries are only detectable on MRI, and MRI was available for just 46% of patients in this study. On the contrary, the high number of concomitant injuries could have hindered sufficient statistical analysis.
The high incidence of symptomatic posttraumatic subtalar osteoarthritis and the concomitant injuries observed (osteochondral lesion to the posterolateral calcaneal facet, bony avulsion of the medial talocalcaneal ligament, lesion to the plantolateral aspect of the talar head), might have implications for the actual trauma mechanism (Fig. 4). Up to now, most authors discuss a combination of axial compression, dorsal extension, inversion and external rotation of the foot [4,5,6, 12, 13, 33]. Taking into consideration the above outlined combination of concomitant injuries, the mechanism of injury could also be a subluxation of the subtalar joint with external rotation and pronation (Fig. 4).
Several limitations of the herein presented study need to be discussed. First, no sample size calculation was conducted due to the observational study design and the low incidence of LPTF. Second, the study was retrospective, which again is in line with most other studies and again attributable to the low fracture incidence [4,5,6, 10, 15, 17, 18]. A further limitation could be the small number of patients (n = 22). Still, this is the largest published cohort on surgically treatment of LPTF [5,6,7, 10, 15]. The most pronounce limitation is a missing control group. Up to now, extensive comparative studies are missing completely. Although Valderrabano et al. and von Knoch et al. reported on the AOFAS of conservatively treated LPTF, they did not compare different treatment regimes in similar fracture patterns and reported conflicting results [7, 15]. It would be of great interest to prospectively asses the PROM of conservatively treated, displaced LPTF Type I and II according to Hawkins. Finally, the herein used PROMs are not fully validated per the COSMIN group recommendations [26,27,28] and the normative data available for the VAS-FA have not been validated in a foot and ankle trauma population [32]. Future studies should be even more aware of the PROMs chosen and consider scores such as the Self-reported Foot and Ankle Score (SEFAS) [21, 34], Manchester-Oxford foot questionnaire (MOXFQ) [35,36,37].
Despite the above outlined limitations, several strengths of this study are noteworthy. First the intermediate follow-up of more than three years. Second, a follow-up of 96% of patients. Third, the detailed fracture assessment based on CT and MRI imaging. The authors are not aware of any work that has investigated the concomitant injuries and fracture patterns in such detail. Finally, this is the first study to clearly show, that despite consequent treatment of all concomitant injuries, posttraumatic symptomatic subtalar osteoarthritis is the independent factor associated to an impaired patient rated outcome.