This study indicated that at an average of 4.5-months post-surgery, patients with trimalleolar fractures showed poor OMAS results, and their injured ankles were swollen, and the passive ROM were decreased. During gait analysis, patients demonstrated abnormal gait compared with healthy controls, and an asymmetrical gait pattern was seen in patients. Compared with healthy controls, the abnormal performance of patients in plantar pressure distribution were concentrated in hindfoot and forefoot, and patients also showed abnormal muscle activity of TA and PL. Furthermore, the passive inversion ROM was highly correlated to symmetry index of step width and walking. This study was the first to indicate remaining detailed gait deficits in patients with trimalleolar fractures. In addition, gait parameters were correlated with clinical outcomes in patients with trimalleolar fractures for the first time.
OMAS are usually used as a reliable and valid outcome measure after an ankle fracture[18], and based on the total score, ankle function of patients could be divided into four grades: excellent (OMAS:100 to 91 points), good (OMAS:90 to 61 points), fair (OMAS:60 to 31 points) and poor (OMAS:30 to 0 points). [19] In this study, the mean OMAS was 56, indicating that patients with trimalleolar fractures reported fair ankle function. According to the study, the disability of running and jumping contributed most to the total score. Several studies also investigated the OMAS of ankle fractures patients, and they showed better results than our study. Oguzhan Tano glu et al. [20]compared the effect of a 1-stage surgery for the unstable malleolar fracture dislocations with the 2-stage surgery. The two group all included patients with isolated malleolar fractures, bimalleolar fractures and trimalleolar fractures. And the duration of follow-up of the two group was 21.7 and 19.2 months respectively. The mean OMAS was 87.8 for the 1-stage surgery group and 83.2 for the 2-stage surgery. Mareen Braunstein et al. [21]demonstrated functional outcomes after 1 year of arthroscopically assisted ankle fracture treatment, and they reported a mean OMAS of 85 for trimalleolar fractures. The poor OMAS results for trimalleolar fractures in this study might be mainly attributed to the short length of the postoperative follow-up period. This study investigated the clinical outcomes after 4.5 months postoperatively, while other studies evaluated the long-term (more than 1 year) clinical outcomes.
This study indicated that patients with trimalleolar fractures remained physical impairments postoperatively. Compared with the noninjured side, patients represented ankle swelling, and a decrease in passive ROM on the injured side. Ankle swelling is a common and long-standing complication after surgery. It was reported that more than half of the patients following unimalleolar and bimalleolar ankle fractures presented stiffness, swelling and pain [1]. 60% or more of the patients 65 years or older reported ankle pain, swelling and problems when using stairs and reduced activities of daily life one year after ankle fractures [22]. Shah et al.[23]demonstrated that around 45% of 69 patients with Weber B and C ankle fractures still had ankle swelling at 5 years after the injury. Our study investigated the passive ROM, and mean (sd) angle of dorsiflexion, plantarflexion, inversion and eversion of the injured leg on the trimalleolar fractures patients was 7.08 (3.91) degrees, 33.33 (8.07) degrees, 13.75 (6.78) degrees and 6.00 (4.17) degrees respectively. Ganit Segal et al. [1] also measured the passive ankle ROM of patients with trimalleolar fractures in the sagittal (dorsiflexion/ plantar flexion) and coronal plane (inversion/eversion), and the ROM was − 0.8 (7.6) degrees, 40.6 (7.5) degrees, 5.6 (3.6) degrees and 2.5 (4.0) degrees respectively. The result was a little different from our study, might due to the assessment point. Ganit Segal et al. [1] measured ROM at 64.5 days from injury, which was earlier than ours (4.5 months). There was also a study evaluated ROM during activities. van Hoeve, S et al. [4] found that compared with the healthy subjects (12.59 ̊ ± 3.73 ̊), the ROM during gait in patients (7.13 ̊ ± 2.55 ̊) with trimalleolar ankle fractures decreased significantly. After ankle fractures, the uncoagulated hemorrhage leads to the rapid increase of intra-articular pressure, which causes abrupt joint swelling, pain and limited mobility [24]. Presence of soft tissue damages such as tendon and ligamental injuries can cause chronic swelling and stiffness therefore resulting in the dismal outcome [3]. These complications might alter the gait.
The present study showed that patients with trimalleolar fractures presented compromised gait pattern. The temporal-spatial parameters of the injured side were significantly different from the noninjured side and healthy subjects, except no difference exist in step width between both sides. This is in line with other research findings. Two studies investigated the gait parameters of patients with trimalleolar fractures, and compared those with healthy group. They found all gait parameters were significantly below the normal range[1, 6]. Andrew F. Tyler et al. [6] also showed that the gait characteristics of ankle fracture patients were more similar to healthy elderly patients. However, these two studies only investigated the differences between patients and healthy subjects, but did not compare the gait parameters of the injured side with the noninjured side. Ganit Segal et al. [1]also examined limb symmetry of the gait patterns, and found significant asymmetry in step length and single limb support. These findings were consistent with this study. And by correlation analysis in this study, step asymmetry might be related to the difference of ankle inversion ROM between two sides. All these results presented that patients with trimalleolar fractures did not achieve restoration of normal physiologic gait in the short-term, and patients adopted a simple security strategy with a reduction of walking speed[7].
The differences of features of plantar pressure distributions and sEMG in both sides also indicated asymmetries in gait in patients with trimalleolar fractures. The plantar pressure in the T345 and the contact area of MF of the injured side were significantly smaller than those of the noninjured side, and this was probably due to a more cautious and compensatory walking pattern, by further biasing the center of gravity to the noninjured side. Sjoerd Kolk et al.[25] also showed subtle asymmetries in gait kinetics and kinematics between the operated and non-operated limbs, and they considered that patients performed a more cautious walking pattern and an integral strategy. Plantar pressures of other type ankle fractures such as pilon fractures, calcaneal fractures were also asymmetry, and adhesion or conduction disorders at the tibia may be causes of abnormal plantar pressure [25, 26].
Compared with normal healthy subjects, patients with trimalleolar fracture performed abnormal gait during walking support period. Patients tended to step more cautiously on the injured heel, showing smaller peak plantar pressure in HF, and this might be due to pain or psychological factors such as fear or worry of reinjury [27]. For patients, the contact time (%) of HF and MF and total contact time were significantly increased, and it might be associated with lower ankle stability: for patients with trimalleolar fractures, the lateral, medial and posterior malleolus were injured, probably impairing the ankle stability, and patients needed more time to maintain ankle stability [1]. The muscle activity on the TA and PL of the injured side was significantly larger than those in the noninjured, also indicating the ankle stability of the injured side decreased, because muscular co-contraction of TA and PL was increased to stabilize the ankle joint [28]. And in this study, the step width was significantly smaller than that of healthy controls, also showing the walk stability decreased in patients. The plantar pressure features (smaller peak plantar pressure and contact area, shorter contact time) in the forefoot demonstrated that the propulsion ability during walking significantly decreased in patient, and this could decrease the walking speed. In this study, the IEMG of PL of patients was significantly increased, indicating the muscle ability decreased. Therefore, it was reasonable to speculate that the abnormal gait features in the forefoot might be related to the decreased ability of PL. During normal walking, the plantar pressure in the first metatarsal head plays a key role in pushing off [29]. And the PL is essential for maintaining ankle stability and plays an important role in the push-off stage. The PL origins at the proximal tibia and fibula, and inserts at the first metatarsal and medial cuneiform [30]. Except for contributing to 63% of eversion strength, the PL is helpful to initiate pronation and stabilize first ray during propulsion phases of gait [30].