2.1 Selection criteria

Studies published from the inception of data until September 2019 that assess the effectiveness of HFN in patients with osteoporotic ankle fractures were included. Inclusion and Exclusion criteria are outlined in Table 2. Articles meeting the inclusion criteria were read in full and assessed against the eligibility criteria.

2.2 Source of material and search terms

Search terms used with Boolean operators were applied in different online search engines to obtain studies that address the topic of this review (Table 3). The search began in December 2016 and was regularly updated up to September 2019. Manual review of the lists of references from retrieved publications was carried out to include studies potentially meeting the inclusion criteria that were not accessed by our online search. The full paper was retrieved when the title or abstract revealed insufficient information to determine suitability for inclusion. Replicas of the obtained studies from our search strategy were eliminated. All studies were assessed by two independent reviewers against the inclusion criteria for inclusion in our systematic review. Disagreements between the researchers were resolved by a consensus meeting.

Our primary search revealed 48 studies. After carefully evaluating their titles, 9 studies were selected for abstract review. Of these nine abstracts, two further papers were excluded as they did not meet our inclusion criteria (Fig. 1 Summarise search process). Seven articles met our criteria and used in the review (Table 4). The reviewers then agreed on the nature of data to be collected from the included studies on spreadsheets to determine the answers for the primary questions. Collected data included participants’ demographics, details of intervention, outcomes, union rates, follow-up, and complications.

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Fig. 1 Flow chart of the search process. HFN: Hindfoot Nail.

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The pooling of the overall outcome could not be achieved because of the heterogeneity in findings. This heterogeneity originated from the fact that not all papers commented on the same clinical or functional outcomes. For instance, union rate, pain level, functional scores or weight-bearing status were mentioned in most but not all the included papers. Furthermore, between the selected studies there were differences in the nail type utilized (short versus long; locked versus expandable) and different structure of studies (6 prospective or retrospective case series, and one randomized controlled trial).

2.3 Ethical issues

The authors of this review have no conflict of interests to declare.

4.1 Surgical indications

Most of the studies in this systematic review investigating HFN have outlined their indications to insert TTC nail for ankle fragility fractures. The indications included: Frail elderly patients (more than 60 years), poor soft tissue or bone quality (osteopenia and/or history of fragility fractures), and salvage procedure for failed previous operative fixation.

Given that six papers out of seven assessed in the current review are case series, the patient cohort will be prone to selection bias, which is the surgeon's choice directed the nature of treatment in these cases. With the absence of a randomized treatment allocation and defined selection criteria, the case-control studies would prove difficult to reproduce. The authors were aware of the limitations of the study design and have recommended that further idealized studies should be undertaken in the shape of a prospective randomized controlled trial with long term follow-up.

Lemon et al. & Jonas et al. found a correlation between the level of mobility before the injury and the application of HFN as an implant for treatment of fragility ankle fractures in their cohort of patients.^2,5 In addition, the authors recommended the use of HFN nail for less active patients with limited weight-bearing potential. Surgeons who treat fragility ankle fractures often use HFN/IM nail devices for elderly less active patients and use internal fixation implants for younger active patients.¹⁷

4.2 Type of nail

All seven studies used different types of intramedullary nails for surgical fixation of ankle fractures. Each possessing slightly different physical properties and mechanical principles. Each different nail may have its own advantages and disadvantages, and often surgeon preference and equipment availability play a role. One of the more contentious issues associated with the use of short locking nails is the diaphyseal stress riser effect and associated risk of periprosthetic fracture.² Jonas et al. reported three cases in their cohort suffered periprosthetic fractures, yet, no periprosthetic fractures have been reported in any of the earlier two studies which applied short locking nails (Lemon et al., 2003; Amirfyz et al., 2008).^2,5,8 However, small sample sizes and short follow-up periods could attribute to the low reported rates of periprosthetic fracture in both studies.

Al-Nammari et al. and Baker, Mayne, & Andrews in their retrospective study utilized long-locked nails to avoid stress riser effects and periprosthetic fractures. No periprosthetic fracture reported during the follow-up period.^11,12

4.3 Surgical approaches and intra-operative issues

The percutaneous minimally invasive technique used with HFN has several intraoperative benefits in comparison to open reduction techniques. The HFN technique allows a shorter operative time, reduced intraoperative blood loss and reduced soft tissue dissection when compared to open reduction.¹³

4.4 Union

Al-Nammari et al.; Amirfyz et al.; Lemon et al.; and Jonas et al. reported a 100% union rate among all patients in their groups treated with HFN technique based on clinical examination and X-ray evidence.^2,5,8,11 Taylor et al. reported the incidence of non-union to be at 10% in their case series of patients treat with HFN.¹³ The authors failed to report on any potential causes of non-union or further ongoing management. Nevertheless, in cases of asymptomatic non-union, revision is rarely indicated as it is believed that the nail will continue to splint the fracture.¹⁸

The rate of union reported to be 86.7% in a systematic review included 651 cases treated with HFN by Jehan et al., in 2011, ¹⁹with an average time to union of 4.5 months. However, the remaining patients who had non-union, only 26% required a revision, as the majority of patients with non-union either remained asymptomatic or were able to coup with their symptoms.¹⁹ This suggests that, in the event of non-union, HFN can continue to maintain stability across the fracture.

4.5 Olerud and Molander scoring system (OMAS) and postoperative functional status

Al-Nammari et al. and Amirfeyz et al. reported that most patients treated with HFN returned to their pre-operative functional level with a slight, but insignificant, decrease in the postoperative OMAS score.^8,11 The authors accounted for this to the obliteration of the tibiotalar and subtalar joint movement. Despite, they reported that 75.6% of patient with HFN returned to their preoperative mobility level, compared to 72.2% in the ORIF group.

4.6 Weight-bearing and hospital stay

HFN is an intramedullary load sharing device. It is recommended that the patient treated with HFN should be allowed to fully weight-bear immediately after surgery. In contrast to the traditional ORIF technique, which usually requires up to 6 weeks of non-weight bearing postoperatively. Georgiannos, Lampridis, & Bisbinas reported that HFN resulted in a shorter duration of hospital stay, earlier rehabilitation, and reduced risk of complications.¹⁴

The aims of treating fragility ankle fractures could be considered similar to managing the elderly neck of femur/hip fractures. Where the key goal is to facilitate early postoperative mobilization, avoid complications, and to restore early postoperative function and daily activities. In contrast to younger patients were restoring the anatomy of the joint is the main goal.^2,20,21

4.7 Complications

The overall complication rate was 16.49% (32 cases) in this systematic review. Table 5 summarises the different complications reported from the 7 papers included in this review. The complication rates are comparable to a systematic literature review conducted by Jehan et al. where complications of HFN ranged from 15% to 50% in the included studies.¹⁹ By adhering to proper soft-tissue handling, using sound surgical technique, ensuring adequate fixation and managing the patients’ medical comorbidities, the complication rates associated with HFN can be drastically reduced.²² It is recommended that patients should be fully counseled about the risks associated with HFN fixation, highlighting the considerable risk of significant complications including amputation and reoperation.

4.8 Mortality rate

The mortality rate reported in the studies included in this review ranged from 25% to 46% at the final follow-up (Table 4). These figures are close to the reported one-year mortality rate following fragility hip fracture (33%).²³

This is believed to be multifactorial: the high rate of medical comorbidities and frailty seen within-population suffering such injuries is believed to be the main cause. Switzer, & Gammon had demonstrated the potential benefit of involving a geriatrician in the in-hospital care of patients suffering from fragility ankle fractures, as this can reduce the length of stay, readmission rates, complication rates, and overall patient mortality.²⁴

4.9 Risk of arthritis

The HFN technique often creates damage to the articular surfaces of the ankle and subtalar joints during insertion. This recognized articular joint damage can theoretically lead to accelerated arthritic changes. Hence, Lemon et al. have suggested that the removal of the nail after achieving bony union may reduce the potential risk of arthritis.⁵ However, Childress in his study after following up 92 patients for around 16 years, have not noticed any radiological evidence of degenerative changes in ankle and subtalar joints.²⁵ However, in his cohort, Childress only utilizes Steinmann pins rather than the wider HFN nails.

There are other factors that can influence the development of posttraumatic osteoarthritis after ankle fractures, including the reduction and alignment of the fracture, stability at the fracture site, fracture mechanism and cartilage damage caused by the initial injury.²⁶ A systematic review by Stufkens et al. reviewed 1822 surgically treated ankle fractures, reporting that 79.3% of optimally reduced fractures have good - excellent long-term results.²⁶ They concluded that malunion is the most important factor determining the long-term outcome after ankle fracture and attributed the development of arthritis in the remaining 20.7% to other factors such as mechanism of injury and initial cartilage lesions.²⁶ In our systematic review, there were only two reported cases who had valgus malunion following fixation with HFN. Based on this, the author would not recommend removing the implant after achieving a union to avoid osteoarthritis as suggest by Lemon et al.⁵

4.10 Nail removal

There were conflicting views among authors included in this review regarding the removal of HFN following bony union. Lemon et al. recommended removal of the nail after establishment of union at the fracture site, while others did not.^2,5,11 The indications for the removal of the nail included avoiding potentially periprosthetic fractures and the potential for accelerated degenerative process.⁵ Despite Lemon et al. recommending the removal of the nail to patients, only 50% agreed to it, and there was on differences in arthritic changes at the final follow-up.⁵

Al-Nammari et al. found that eliminating hindfoot joint movement at the tibiotalar and subtalar joints does not impair the overall foot function.¹¹ Jonas et al. advised against the routine removal of the nails to avoid subjecting these elderly patients to unnecessary surgical risks.²

4.11 Limitations and implications for future researches

One of the limitations of this review is that the studies included have small sample sizes and short periods of follow-up. Although this study does completely eliminate the current controversy and does not establish with confidence the optimal management strategy of fragility ankle fractures, It will form the basis for future prospective randomized controlled trial comparing the outcome of HFN and conventional methods in treating fragility ankle fractures with long term follow-up.