1. IntroductionAnkle fractures (FX), common injuries constituting about 9% of all FX [1] of the human skeleton, are considered the third most common FX in geriatric patients [2,3]. In recent years, an increasing number of elderly patients have suffered from ankle FX [4,5]. The majority of these elderly patients already suffered from numerous comorbidities at the time of the accident [6]. The focus of fracture treatment in the elderly population is to achieve as much freedom as possible, in combination with maintaining quality of life comparable to the pre-accidental level. Nevertheless, operative treatment is associated with typical complications, such as mal- or nonunion, and especially skin problems ranging from delayed wound healing to severe skin defects [7,8,9,10,11,12].Open reduction and internal fixation (ORIF) has become the standard of care for displaced ankle FX in adults [13,14]. Several techniques for internal ankle fixation are commonly used, ranging from simple lag screw fixation to plate osteosynthesis with non-locking to locking screw systems up to biodegradable systems [15,16,17,18,19,20]. In this context, several studies in the common literature focus on intramedullary (IM) fixation of the distal fibula FX, fracture stabilization, and the appearance of soft tissue-related complications in the older population [21,22,23,24,25,26,27].In addition to fracture healing and the complications related to the surgery itself, postoperative therapy is a prognostic factor for the patient’s satisfaction, functional outcome, and return to normal daily activities [28,29,30,31]. For older patients suffering from an ankle fracture, returning to their normal daily life is important in terms of their quality of life and freedom [32,33,34]. In older patients with preexisting comorbidities, surgical treatment must not only respect the soft tissue conditions, but should also have the goal of a shortened pre- and post-operative therapy time window, shortened hospital stay, faster time of recovery, and achievement of full resilience as quickly as possible [6,35]. Therefore, the main goal of any post-operative therapy is to reduce time of recovery to a minimum and to achieve full physical capacity as early as possible. In the past, a few clinical trials have shown that early weight bearing and functional treatment avoiding a plaster cast may shorten the immobilization period, but it also may provoke a loss of reduction, depending on morphology and initial stability of the FX, as well as patients’ age and comorbidities [28,32,36,37,38,39]. A few clinical trials have demonstrated that IM ankle FX fixation might be a good method to preserve the soft tissue, but it could lead to fibula shortening and loosening of the implant [21,22,26,27,40,41].Thus far, surgical treatment of FX with IM nailing has already shown promising results in the treatment of various complex fractures of the femur [42], tibial shaft [43], and clavicle [44]; hence, IM nailing has become a standard implant. To the best of our knowledge, there still exists no prospective randomized trial assessing the treatment of distal fibula FX using these modern implants.In this context, surgical treatment of ankle fractures using IM fixation systems were controversially discussed because of their biomechanical performance and implant costs [45,46].

The aim of this study was to analyze whether open reduction internal fixation (ORIF) of distal fibula FX, using a standard semitubular plate or closed reduction and IM fixation using a new minimally invasive intramedullary Photodynamic Bone Stabilization System (IlluminOss®), allows for a better outcome for immediate postoperative weight bearing and the reduction of complications in older patients with a wide range of comorbidities.

4. DiscussionTo the best of our knowledge, this is the first randomized controlled study to compare semitubular plates with the presented new intramedullary stabilization system in distal fibula fracture treatment with an immediate postoperative weight bearing regime in the intramedullary stabilization patient group. With increasing age, the probability of fracture occurrence rises, and also the number of ankle fractures (9% of all human skeleton fractures [1]) increases; thus, ankle fractures are considered the third most common FX in geriatric patients [2,3]. Usually, many of these elderly patients with ankle FX already suffer from numerous comorbidities at the time of the accident [6]. In this context, treatment of ankle fractures in the elderly population should result in achieving as much freedom as possible, in combination with quality of life comparable to before the accident. Nevertheless, operative treatment is usually associated with typical complications, such as mal- or nonunion, and especially skin problems ranging from delayed wound healing to severe skin defects [7,8,9,10,11,12]. Commonly known open reduction and internal fixation (ORIF) using various techniques is the standard of care for displaced ankle FX in adults [15,16,17]. Generally speaking, a recent advance in the treatment of fractures of different bones was the introduction of intramedullary nails [43,44]. Thus far, the use of intramedullary nailing systems in distal fibula fractures has been investigated under the aspects of FX stabilization, soft tissue management, and complication rates [25,26,27]. The majority of these studies were of retrospective character. The presented prospective randomized study focused on the comparison of treating ankle fractures of patients at an age over 65 years either using a rather established semitubular plate AO-system or an intramedullary Photodynamic Bone Stabilization System (IlluminOss®). Our results show that the IlluminOss® system allows for a progressive postoperative rehabilitation protocol performing full weight bearing immediately after surgery, leading to reliable results along with a good functional outcome.In the general literature, complication rates of up to 25% have been reported for ankle fractures, especially in geriatric patients [10,13]. These complications include wound healing problems, redness, hyperthermia, superficial and deep infections, deep leg vein thrombosis, and loosening of the material resulting in a loss of reposition. Previous studies in elderly patients with preexisting comorbidities demonstrated that intramedullary nailing systems in distal fibula FX have a significantly lower incidence of soft tissue complications and lead to adequate FX stability compared to conventional plate osteosynthesis [26,28,29,30]. White et al. described in their prospective randomized study on 100 patients (n = 50 ORIF, n = 50 IM nailing) no superficial wound infections in the IM group compared to eight (16%) superficial wound infections in the ORIF group [22]. Similar results for wound infections following IM nailing were described by Cofiman et al. [27]. In their study, only 1 deep infection occurred in the 34 patients available for follow-up after IM nailing [27]. Both studies consider small incisions as beneficial for soft tissue healing [22,27]. In the actual study, the rate of postoperative complications was lower in the Photodynamic Bone Stabilization System group (Group II). Similar to White et al. and Cofiman et al., no single minor complication (superficial wound infection, delayed union etc.) was detected in this treatment Group II. In contrast, in Group I treated with the DePuy Synthes® one-third semitubular plate with a rather greater incision, four minor complications (22%) occurred. In terms of major complications, such as secondary loss of reduction, non-union, major wound infections, etc., only one major complication was detected in both groups without reaching significance (Group I 5.5%, Group II 4.7%. See Table 3).Considering the consistently low complication rates in the above mentioned studies (White et al., Cofiman et al. [22,27]) as well as in the presented study for the patients treated with the IM IlluminOss® Photodynamic Bone Stabilization System, we are convinced that the significantly reduced size of the surgical incision wound plays a decisive role in the reduction of wound healing disorders, especially in older patients with significant comorbidities. Moreover, our data suggest that the small surgical incision allows for an overlook of the posttraumatic soft-tissue swelling and is not considered as a contraindication to a potentially earlier surgery, along with earlier mobilization and an earlier discharge from the hospital.Early weight bearing and postoperative mobilization are very controversially discussed in the literature. In this context, patient-related factors, such as age, comorbidities, and fracture morphology, have a strong impact on the postoperative treatment [14,33,45,48,59].Smeeing et al. showed in a normal-aged patient population (18–65 y) without comorbidities suffering from Lauge-Hansen supination external rotation type 2–4 ankle fractures treated with ORIF that a postoperative unlimited weight-bearing and mobilization regimen improved short-term functional outcome after six weeks, shortened the absence from work, and improved the time to return to sports compared to the patients who only followed a limited weight-bearing or unprotected non-weight-bearing therapy regimen. The mean OMAS (61.2 ± 19.0) after six weeks was up to 10 to 15 points higher compared to the two other groups [35].In this context, we were able to prove in the actual study that treatment of distal fibula fractures with IM stabilization using the innovative IlluminOss® Photodynamic Bone Stabilization System allowing for an immediate weight bearing in elder patients with a wide range of comorbidities leads to similar good functional results six weeks postoperatively, as described by Smeeing in patients under 65 (see Table 4). Therefore, the actual data present a significant better outcome at the first two follow-up exams (6 and 12 weeks postoperatively) compared to the ORIF group who followed a restricted postoperative rehabilitation protocol including partial weight bearing (see Table 1).

We believe this new IM implant used in the presented study allows for a safe and stable fracture fixation, and it is the key to the early full weight bearing and good clinical outcome in the enrolled elderly patients with significant comorbidities.

Regarding the hospital length of stay, a significant difference between the two groups was identified in favor of Group II (p = 0.05, see Table 6). This result confirmed the significant differences between patients from Group I and Group II in terms of range of motion and the assessed outcome scores (see Table 4). In addition, patients in Group II had a significantly shorter preoperative delay caused by posttraumatic swelling of the ankle compared to patients in Group I (p = 0.01, see Table 6).The outcome scores assessed in the presented study are self-assessment questionnaires that reflect the subjective physical well-being and clinical outcome of the individual patients [60]. All used outcome scores have a graduation divided into five scales, ranging from poor to fair over good to excellent. Especially in the early follow-up exams after 6 and 12 weeks of the postoperative treatment, functional ankle scoring results showed a very significant difference (OMAS p = 0.01, KPSS p = 0.01 and 0.02 see Table 4) for the used scores in favor of Group II (see Table 4). No statistical differences regarding the used outcome scores were detected in the follow up examination after 6 and 12 months (OMAS p = 0.06/0.07, KPSS p = 0.06/0.06, see Table 4).The distinct lack of comparability due to different applied postoperative treatment regimens is considered a basic limitation. While Group I patients (semitubular plate) were treated with partial weight bearing for 6 weeks, Group II patients (IlluminOss® Photodynamic Bone Stabilization System) started full weight bearing right after surgery. However, recommendations for patients treated with the new intramedullary implant are still missing the guidelines of the DGOU, as well as of the AO, for patients treated with semitubular plates involving partial weight bearing [59]. The allowance of full weight bearing led to an improved clinical outcome in patients treated with the intramedullary Photodynamic Bone Stabilization System. The presented results seem to be reliable and safe, and they should be considered an important contribution of our research.

Due to the small number of patients, the influence of implant removal was not analyzed. However, the presented follow-up rate of 86.5%, the wide assessment of functional parameters, and the prospective randomized character of the study certainly present the strengths of the presented work.

Studies with higher sample sizes are necessary in the future to demonstrate the benefits and possible disadvantages of these novel implant systems in the treatment of ankle fractures. Although we were able to show in our clinical prospective study for the first time a comparison of outcomes in geriatric patients for both implant groups, this study has its limitations. The fact that in our population, no fracture-related or implant-related infection occurred in the Photodynamic Bone Stabilization System, thus there was no necessity for implant removal in this group, does not mean that this complication is impossible. The used blue light might have antibacterial effects that must be investigated in future studies. Nevertheless, there is still the question to answer of how to remove this implant. An implant removal kit is provided on the market by the manufacturer, but still only a few cases of implant removal are known. Further investigations of possible complications in the usage of this novel implant have to be done in the future.

Although the current literature shows a trend towards the use of locking plate systems in distal fibula FX, and especially in osteoporotic FX, we showed that the use of this new intramedullary system provides a benefit for the geriatric population regarding postoperative clinical outcome, as well as shorter time period to full recovery and full weight bearing, plus very gentle soft tissue management due to the small incision site as compared to the locking plate treatment [49,61,62]. For this study, the use of locking one-third semitubular plates instead of the applied non-locking one-third semitubular plates could have been beneficial for patients randomized in Group I. Thus far, it could be shown that the use of locking plates allows an early weight bearing in younger patients suffering from a distal fibula fracture [20,35]. Nevertheless, the extended surgical approach and operative soft tissue stress can pose a disadvantage in geriatric patients and lead to soft tissue problems as compared to minimally invasive surgical methods; hence, minimally invasive surgical treatment should experience a renaissance [63,64,65]. Overall, all geriatric patients will benefit individually from a faster recovery, but also the cost of medical care could be reduced in general due to shorter hospital stays. Nevertheless, this study focused on the patient’s outcome; therefore, an additional economic analysis could provide supplementary information regarding cost effectiveness. In addition, an analysis of the assumed reduction of health-related costs is advisable.

In general, adding two more groups to the study—e.g., (a) conservative treatment and (b) current intramedullary fibular nail—would add an interesting additional aspect regarding the treatment of distal fibula fractures in geriatric patients, as well as provide broader coverage of all aspects in the treatment of such fractures.