Background

The tibia is the most commonly broken major bone in the leg. In younger patients, fractures of the tibia typically occur during sporting activity or road traffic accidents, but in older patients they can happen during simple falls. Injuries usually require hospital admission and surgery, resulting in prolonged periods (months) away from work and social activities.

The treatment of displaced, extra-articular fractures of the distal tibia (lower third) remains controversial. These injuries are difficult to manage because of the limited soft-tissue cover, poor vascularity of the area and proximity of the fracture to the ankle joint. Infections, non-union and malunion are well-recognised complications.

Non-operative treatment is one option and avoids the risks associated with surgery. Sarmiento et al.,² in 2003, reviewed 450 closed fractures of the distal tibia following functional bracing: 13.1% developed a malunion (defined as > 7° of angulation or 12 mm of shortening). Another study,³ using a more robust definition of 10 mm of shortening and 5° of angulation, found a higher rate of malunion (26.4%). In this study, Böstman et al.³ treated patients using a long leg cast, and failure to maintain reduction led to surgical treatment with an intramedullary (IM) nail. Thirty-two out of 103 cases required nailing at a mean of 9 days following injury. Two patients in this group, and three in the non-operative group, went on to have a non-union.³ Union rates were faster with IM nailing than with conservative treatment and median values were 12.5 and 14.5 weeks, respectively (p < 0.001).³ Digby et al.⁴ also found that non-operative treatment for tibial fractures in the metaphyseal region leads to unacceptable deformity and ankle stiffness. Therefore, operative treatment is now the treatment of choice for the majority of patients with a fracture of the distal tibia.

Surgical treatment options are expanding and include locked IM nails, plate and screw fixation, as well as external fixator systems, including the Ilizarov frame and hybrid fixators. External fixators may be beneficial in selected cases, particularly those involving severe soft-tissue injuries, but, in the UK, the IM nail and ‘locking’ plate options are most commonly used for extra-articular fractures. Mid-shaft fractures of the tibia are generally successfully treated with locked IM nails. However, in the more distal metaphyseal region of the tibia, the fixation may be less stable.⁵ The bolts or screws that are inserted into the nail may break,⁶ malalignment may occur⁷ and there is a risk that the nail will penetrate into the ankle joint.^8,9

The development of locking plates, in which a thread on the head of the screws locks into the holes in the plate to create a ‘fixed-angle’ construct, has led to a recent increase in the use of locking plate fixation. However, locking plates are not without risks and they require greater soft tissue dissection, which carries a risk of infection, wound breakdown and damage to the surrounding structures.¹⁰

In a retrospective study¹¹ of 111 patients with extra-articular fractures of the distal tibia (4 to 11 cm proximal to the plafond), a comparison was made between IM nail and locking plate fixation. Seventy-six fractures were treated with an IM nail and 37 were treated with a medial plate.¹¹ Nine patients (12%) had a delayed union or non-union in the IM nail fixation group and one patient (2.7%) had a non-union after locking plate fixation (p = 0.10). Angular malalignment of ≥ 5° occurred in 22 patients with IM nails (29%) and two with locking plates (5.4%; p = 0.003). The authors concluded that fractures of the distal tibia may be treated successfully with locking plates or IM nails, but that delayed union, malunion and secondary procedures were more frequent after IM nailing. Janssen et al.¹² found similar results: delayed union was higher in the IM nail fixation group (25%) than in the locking plate fixation group (16.7%) and rotational malalignment was also higher in the IM nail fixation group (16.7%) than in the locking plate group (0%). However, this was not a randomised controlled trial (RCT) and the results do need to be interpreted with some caution. Randomised prospective assessment are necessary to further clarify these issues and provide information about costs associated with these fractures.¹¹

Only two prospective RCTs had been published when this trial began.^13,14 In the first,¹³ 64 patients were randomised to either IM nail or plate fixation for the treatment of a closed extra-articular fracture. The time to union was found to be similar for the two groups and there was no difference in terms of Olerud–Molander Ankle Score (OMAS) at 2 years. However, a significant difference was observed in the number of wound complications: one in the IM nail fixation group versus seven in the plate group. This paper concluded that IM nailing is the treatment of choice for this injury. However, the method of randomisation was poorly described and so bias in group assignment may have occurred. The study used traditional (non-locking plates) rather than the newer fixed-angle devices. Furthermore, the study included patients with Tschene classification C2 soft-tissue injuries, which may have influenced the results. The second trial¹⁴ randomised 111 patients to either IM nail fixation or ‘locking’ plate fixation. This trial also showed no difference in the time to union but, 1 year after the injury, there was some evidence of improved American Orthopaedic Foot and Ankle Society functional scores in the IM nail fixation group. However, this was a single-centre investigation and > 20% of the patients in the trial were lost to follow-up.

In a meta-analysis, Zelle et al.¹⁵ reviewed 1125 extra-articular fractures of the distal tibia. They reported that non-union, malunion and infection rates were similar for patients undergoing IM nailing and locking plate fixation. It must be noted that none of the studies in the review was a RCT.

Pre-pilot trial

We performed a pilot study involving 24 patients with extra-articular fractures of the distal tibia that were closed or Gustilo and Anderson grade 1.¹⁶ The study was a RCT with clinical assessment, functional outcomes and radiological images performed at baseline and at 6 weeks, and 3, 6 and 12 months post surgery. The study was performed to obtain an estimate of the potential effect size to inform the sample size calculation for a larger definitive trial and to assess recruitment rates and study feasibility.

The study had 12 patients in each group. There was no statistically significant difference between the groups 6 months after the injury but there was a 10-point difference [standard deviation (SD) 20 points] in the Disability Rating Index (DRI)¹⁷ in favour of the IM nail group. More secondary procedures were required in the ‘locking’ plate fixation group. There was also a difference in the cost of the implants.

This pilot study, combined with the literature review, provided compelling evidence to support the development of a definitive RCT in multiple centres.

Null hypothesis

There was no difference in the DRI score between adults with a displaced fracture of the distal tibia treated with locking plate fixation versus IM nail fixation.

Objectives

The primary objective was to estimate the difference in the DRI scores between the trial treatment groups at 6 months after injury.

The secondary objectives were to:

1. estimate the difference in early functional status at 3 months and later functional status at 12 months
2. estimate the difference in health-related quality of life between the trial treatment groups in the first year after injury
3. determine the complication rate of IM nail fixation versus locking plate fixation in the first year after injury, including radiological complications – non-union and malunion
4. investigate, using appropriate statistical and economic analytical methods, the resource use, costs and comparative cost-effectiveness of IM nail fixation versus locking plate fixation.