The major finding of this study is the fact that the true functional outcome after ORIF of both simple and complex ankle fractures is significantly impaired in young and sportive patients. This finding occurs despite a proven anatomical reduction and fixation and no arthritic findings in the radiological assessment.
Contrary to our hypothesis of similar functional outcome in operatively treated simple ankle fractures, a clear impairment in forced dorsal extension compared to the control group was found.
The impairment in forced dorsal extension after ORIF may be caused by the following mechanisms: an altered length-tension relationship and changed neuromuscular mechanisms; scarring of the joint capsule due to the surgical approach; the accompanied soft tissue and ligamentous (deltoid ligament) injury; the postoperative immobilization in a cast or walker boot that may cause a shortening of the gastroc-soleus complex.[16] Furthermore, duration of postoperative immobilization seems to have an impact on how severe impairment of range of motion does occur.[17–19] The impairment in active and forced dorsal extension was greater in the complex group. Complex ankle fractures get a more strict and often longer immobilization than simple ankle fractures, which may be treated with early weight bearing and physiotherapy-supported early movement exercises.[18, 20, 21] Furthermore, complex fractures including ankle fracture dislocations are more often treated with closed reduction and temporary external fixation, which is another cause for impaired postoperative ROM.[6, 22–24] Unfortunately, this impairment in ROM does not decrease even after years.[17]
Interestingly, the ROM of active dorsal extension of the ankle without any weight bearing was higher in both operatively treated groups compared to the control group, for which we do not have a scientific explanation. One could only guess that the postoperative physiotherapy led to an increased ROM as a side effect.
The existing literature focusses on timing and amount of weight bearing, and immobilization after ORIF of ankle fractures and therefore lacks precise information of the functional outcome.[20, 25, 26] Studies investigating functional outcome did not, to our knowledge, examine patients but rather gained their results by questionnaires.[26, 27]
In weight bearing exercises, like in the drop-jump test, the operated leg could not reach the same results compared to the uninjured leg in both postoperative groups. Patients after complex fractures had a significantly worse outcome. This finding might be caused by the initial deltoid ligament injury (in cases without fracture of the medial malleolus) resulting in a more pronounced feeling of ankle instability and the resulting fear of reinjuring the ankle, despite no clinical or radiological signs of instability. Importantly, pain was not the limiting factor. However, in the leg press test, the complex fracture group surprisingly showed the best outcome. This might be caused by a more intense and longer period of postoperative physiotherapy-supported rehabilitation. This is supported by the finding that the operative patients had a larger circumference of the thigh and the lower leg. Obviously, it is not proven whether the difference already existed preoperative, and we did not find any literature investigating forced weight bearing and its correlation with circumferences of the lower leg. The complex group showed worse results in the drop jump test, but better results in the leg press test compared to the simple group. One reason for this might be, that drop jump situations require explosive power and maximum ankle stability, whereas leg press tests create more static load situations for the ankle joint (open versus closed chain exercises) and do not focus on ankle stability.
Concerning the subjective outcome, both groups showed an impairment in quality of life with focus on physical and social functioning as well as some limitations in daily living, while pain was not playing a dominant role. These findings correlate with existing literature and the impairment might even exist two years after surgery, associated with the increasing age of the patient.[28–33]The control group did not reach the maximum values answering the questionnaires, which indicates some psycho-sociological or other distorting influence.[34]
Despite proven impairment in range of motion, limitations in functional testing and impairment in quality of life, most of the patients could participate in postoperative sportive activities. The literature concerning this topic is not only contradicting but also scarce and heterogeneous. Some authors describe a severe impairment in postoperative sportive activities in simple ankle fractures, others showed almost all patients returning to preoperative sports and activity level, even in athletes.[31, 35–40] Factors influencing return to sports are age, talar osteochondral lesions, syndesmotic injury, preoperative activity level as well as motivation e.g. in professional athletes.[41, 42] In addition, the complexity of the ankle fracture plays an important role, as complex fractures are more frequently combined with ankle dislocations, another risk factor for persisting ankle instability and poor outcome.[42–45]
We hypothesized that there will be a discrepancy between radiological outcome and clinical and/or functional outcome. This was confirmed as all the x-rays showed an anatomical reduction and a fully healed fracture. Most patients, including the control group, showed medial and lateral clear spaces symmetrically smaller than 4 mm, which might be one radiological sign of developing arthritis according to van Dijk and Scranton.[15, 46–48] However, no signs of arthritic changes such as osteophyte formation, subchondral sclerosis or subchondral cysts were seen.
Measurements on plain ankle radiographs are still subject of discussion, because they could be influenced by a variety of factors including positioning of the foot and ankle, individual joint spaces depending on age, sex and regarding height as well as inter-observer variability.[48–50]
Concerning the syndesmosis, the simple group showed more patients with a tibio-fibular space wider than 5 mm (40%) compared to the complex group (8%). In complex fractures, the syndesmosis was always treated by a ligamentous and/or osseous stabilization. In type Weber B fractures this stabilization depends on the intraoperative clinical and radiological assessment (hook test, external rotation test). Traditional measurements on X-rays for syndesmotic injury do not correlate with findings on the more sensitive and specific MRI, except for the tibio-fibular overlap.[48] Furthermore, approximately 25% of the patients suffering a supination-external rotation type fracture stage four do have a combination of a medial malleolar fracture and an injury to the deltoid ligament complex.[7–9, 51] This questions the importance of measuring the joint spaces and tibiofibular clear space on plain radiographs in general to evaluate syndesmotic injury.
Several limitations mandate mentioning. First, this study is retrospective, and the surgeons were heterogeneous. However, all surgeons were trained in Switzerland by the AO principles, and thus a 'Unité de doctrine' is present. Second, fractures were grouped only by radiological criteria, summarizing type Weber B fractures without accompanying fracture of the posterior or medial malleolus as simple group. All other malleolar fractures were grouped as complex fractures. One could argue that Weber B fractures may have occult ligamentous injuries and a more sophisticated grouping, e.g. MRI based, would be scientifically more accurate. However, the great majority of surgeons will group according to the Danis-Weber, and thus we used this widely popular classification.
Third, the number of patients is moderate, due to the very strict inclusion and exclusion criteria. Especially the maximum age of 51 years and the requirement of an absence of any injuries of the lower extremity led to the exclusion of many patients. Still, we believe that creating very homogenous groups lead to more precise outcome statements. Furthermore, it was difficult to motivate the patients to undergo the rather excessive testing that also included radiological exams. However, to our knowledge, no other study has assessed the outcome of the specific group of young and active patients with such specific function tests, and the existing literature lacks the necessary homogeneity and thus the true functional outcome. Despite the moderate number of patients, the study reaches enough statistical power to show the differences in the functional outcome of these frequent fractures. Additionally, we present several functional tests that can be used for further studies in this field.
In conclusion, ankle fractures treated with ORIF have a significant and long-lasting impact on functional outcome in young and active patients. A good radiological result does not prove an equally good functional outcome. The results underline the importance of recreating ankle stability by addressing all ligamentous and osseous injuries, especially in high demand patients.