The tibial diaphyseal fractures are usually caused by high-energy trauma4, 10, 21, and the relatively superficial location makes the tibia more susceptible to open fractures associated with significant soft tissue damage and bone loss, resulting in nonunion and deep infection15. Optimal management remains a controversial problem. Previous studies have emphasized the stable fixation and minimal soft tissue disruption for these complex fractures, thereby maintaining the biomechanical microenvironment which is beneficial to bone healing8, 22–24. Preventing infection, obtaining union, and returning the normal daily life is the ultimate goal.
Although intramedullary nail is the gold standard in the management of tibial diaphyseal fractures, external fixation has a clear role in most cases due to the advantage of stabilization with limiting soft tissue dissection, especially for high-energy injuries with poor surrounding soft tissues3, 4, 6, 8, 10, 14, 17, 21. Intramedullary nails work best in managing diaphyseal transverse fractures, but there are challenges in unstable oblique, spiral, and comminuted fractures25. Fortunately, kinds of external fixators provide a stable frame for the varying patterns of tibial fractures. Liu et al.4 conducted hexapod external fixation treatment in 34 high-energy tibial shaft fractures, and the results manifested that the HEF is an alternative and effective method, including various technical advantages. Mangukiya et al.17 achieved satisfactory clinical outcomes in the treatment of 40 patients with compound tibia diaphyseal fracture using an AO monolateral external fixator or Limb reconstruction system. Dickson, D R et al.15 reported on the surgical and functional outcomes of 22 patients with Grade 3 open tibial fractures treated with a circular frame. All cases united, and there were no re-fractures or amputations.
Both circular and monolateral external fixation have been well described in treating tibial shaft fractures with success4, 14, 15, 17, 26, 27. For trauma-control and definitive management, the monolateral external fixators are more likely to be accepted by patients due to wearing-convenient, as well as the treating surgeons because of more accessible application with fewer parts and modifications. Still, they are limited in deformity correction due to the inherent characteristic of uniplanar fixation. The circular external fixators tend to be discommodious to patients, but are more versatile in treatment procedures. Although the superior circular fixator patterns remain uncertain, the HEF, which allows immediate trauma-control and accurate fracture reduction without frame alteration, has become an attractive option as more general orthopedic surgeons are familiar with this device in recent years.
The current study reported a group of 53 high-energy tibial diaphyseal fractures treated by HEF or MEF. Several complications in external fixation treatment, such as pin tract infection, loss of reduction, delayed union, nonunion, and joint stiffness, have been well reported4, 10, 28. In reviewing our data, pin tract infection was the most common complication, as expected. The total pin tract infection rate was 35.8%, matching the previous literature of Francesco et al.29 (35%) and Antoci et al. (33%).30. The differences between the HEF group (41.9%) and the MEF group (27.3%) may be explained due to the more wires and half pins in the HEF group.
We also noted a high reduction loss rate leading to return to the operating room for remanipulation in the MEF group (18.2%), but none was observed in the HEF group. Furthermore, reduction loss was commonly occurred in cases with a relatively small contact area and had relatively little inherent stability. With the substantial difference in design between the HEF and MEF, we do not think that the MEF should not be used to manage tibial diaphyseal fractures, but rather, a circular fixation should be considered in unstable fracture patterns. Alternatively, if a MEF is used for oblique or comminuted fractures, the fracture alignment should be particularly concerned by the treating surgeon.
Although there was a similar delayed union rate between the HEF group (9.7%) and the MEF group (9.1%), the external fixation time in the HEF group (24.2 ± 3.1 weeks) was shorter than that in the MEF group (26.3 ± 3.8 weeks). Additionally, the joint stiffness rate in the HEF group (6.5%) was lower than that in the MEF group (9.1%). The fewer external fixation duration in the HEF group may explain this problem. Furthermore, in the MEF group, nonunion was observed in one case and successfully treated by autogenous iliac crest bone grafting. Compared with uniplanar fixation in MEF treatment, we speculate that the HEF with multiplanar fixation provides a more stable mechanical microenvironment which is beneficial to fracture healing. Another patient in the MEF group was also observed to suffer osteomyelitis and resolved by bone transport technique. The complication rate was 35.5% in the HEF group, while 45.5% in the MEF group. Statistically significant differences were not observed in the ASAMI scores as the sample size was insufficient to reach adequate power, but the observed clear trend implies that there was shorter surgical duration and external fixation time in the HEF treatment, as well as fewer complications.
The hexapod external fixator provides the ability to achieve excellent alignment postoperatively, resulting in a rapid installation and less duration in the operating room even in inexperienced hands without worrying about the accuracy of fracture reduction. Although all the 53 patients in this study achieved functional reduction, there was statistical significance in the residual deformities on the sagittal plane between the two groups. This may be explained that the treating surgeons may subjectively overlook deformities in the sagittal plane during the surgical procedures, while these residual deformities can be salvaged by the postoperative adjustment using a hexapod external fixator. The other possible explanation for these differences could be the relatively unstable eccentric fixation in the MEF group resulting in some deformity recurrence.
Our study preliminary compared the clinical outcomes between hexapod external fixator and monolateral external fixator in the definitive treatment of high-energy tibial diaphyseal fractures. The results manifested that the hexapod external fixation is a superior effective treatment for the high-energy tibial diaphyseal fractures with the advantages of stable fixation, less surgical duration, postoperatively satisfactory fracture reduction, and fewer complications. However, the high cost and long learning curve, we think, maybe the significant limitations of the hexapod external fixation.
The present study has several limitations. Firstly, the selection bias may derive from the retrospective nature. In addition, a conservative attitude should be adopted regarding the interpretations of our results due to single-center small sample size. A further study with multi-center large sample size is needed. Furthermore, statistically significant differences based on smaller differences are most likely clinically not relevant and therefore meaningless. Despite these limitations, this study directly compares the clinical outcomes between the HEF and MEF in the definitive treatment of high-energy tibial diaphyseal fractures and preliminarily draws a conclusion.