1 Introduction

Intramedullary (IM) fixation with a nail and locking screws has recently become the gold standard management of intertrochanteric fractures of the proximal femur providing short operating time and minimal soft tissue injury.^1,2 However, in unstable intertrochanteric fractures with lesser trochanter (LT) involvement, the use of IM nailing alone may not be enough since anatomical reduction of the posteromedial fragment is not achieved leading to non-union of the fracture.^3–6 Additionally, the iliopsoas muscle's function is greatly compromised resulting in delayed recovery, groin pain and limited physical mobility post-surgery; both aspects have relevant prognostic consequences on all patients presenting with this type of fracture.

Various techniques have been described in the scientific literature to fix the LT including screw fixation and circumferential wiring,^7–9 nevertheless, these cerclage techniques use traditional monofilament metal wires that are associated with breakage, loss of tension, debris, and increased risk of injury to the surgeon.^10–12

The Sling Fixation Technique is a new surgical technique where traditional IM nailing of the proximal femur is performed in conjunction with fixation of the LT using a polymer-based cerclage wire.

2 Patients and methods

We designed a prospective observational study following for one year after surgery a number of thirty consecutive patients undergoing proximal IM nailing between July 2019 to April 2020. The consecutive patients presented with a similar fracture pattern (unstable intertrochanteric fractures with LT involvement), and were then assigned into 2 groups, each group consisted of 15 patients. The control group was treated with IM nailing alone while the second group was treated with IM nailing followed by LT fixation with the Sling technique.

The primary outcomes of the present study were to compare both the clinical results and the radiological outcomes of the Sling Fixation Technique against isolated IM fixation in the treatment of these unstable intertrochanteric fractures. The secondary outcomes were checking any eventual differences in complication and implant failure rates.

The Institutional Review Board approval was obtained (IRB approval number: 2211/2018). The study was conducted according to the criteria set by the Declaration of Helsinki and each subject signed an informed consent before participating in the study.

2.2

2.2 “Sling” surgical technique

All surgeries were performed by the same senior surgeon (M.V.). All patients underwent spinal anesthesia and then placed in supine position on a traction table with the affected lower limb firmly placed in a traction boot, the contralateral limb was placed in flexion-abduction to facilitate intraoperative fluoroscopy using the C-arm. Closed reduction maneuvers were attempted no more than 3 times under fluoroscopic control. The surgical site was then prepared and draped using a dedicate transparent adhesive sheet. This draping system has a plastic conical shape bag positioned just under the planned surgical incisions. In order to collect the intraoperative blood loss we used a different method compared to Algadiem et al.¹⁶: all the blood that comes out from the patient is therefore kept inside this plastic bag. Every time the surgeon needs to wash the surgical field with NaCl solution, the bag is previously emptied from its bottom where there is a tap to keep the liquid inside the bag. While washing the tap is left open. In case of this procedure is repeated more than once, the total amount of intraoperative bleeding loss is calculated by summing the amount of blood collected in this bag time by time.

The standard IM nail incision above the greater trochanter was distally extended by 4–6 cm, the fascia lata was then incised and the gluteus medius was bluntly split to reach the fracture site. A mini-sub-vastus approach is then performed to gain visualization of the fracture site. Limb traction is applied to bring the displaced LT fragment approximately to the fracture line's level. At this point, a reduction clamp or a narrow Hohmann retractor is used to obtain temporary anatomical reduction of the LT fragment which is then confirmed under fluoroscopy. To maintain this reduction, the cerclage wire is then introduced. A Deschamps wire passer is inserted in an anteromedial-posterolateral fashion just above the LTa and then the proximal cable is inserted. The Deschamps are then placed distally to the LT and the distal cable is inserted. Both ends of the cable are then locked. The cable is manually pre-tensioned and locked with the use of tensioning cleats. The knob is turned in a clockwise fashion to ensure correct tension. For assessing the tension on the wire, the tensioning cleats are labelled LO and HI where “LO” indicates 360 N, while the “HI” indicates 530 N. The wire tension used will greatly depend on the patient's bone quality and its ability to withstand the cable pressure and should be evaluated clinically and radiographically pre-operatively. The Supercable cerclage is then locked in position by rotating the side lever of the tensioning tool that thrusts the cable locking wedge. This system allows easy re-tightening if necessary. The last step before cutting the cable ends is to slightly de-tension the cable by turning the knob. A second Supercable cable might be used if there is distal diaphyseal extension of the LT fracture requiring additional support (Fig. 1).

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Fig. 1 Fig. 1 (A) SuperCable® Iso-Elastic™ wire and tensioning tool. (B) Possible patterns of fracture with intact posteromedial wall that is the fundamental requirement for this technique. “Sling” fashion cerclage with Supercable wire is also represented.

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Following the LT fixation, a standard IM nailing procedure is performed. At the preference of the surgeon, the cerclage wire placemen can also be performed after the IM nailing to directly stabilize the fracture and bring the LT fragment to the level of the fracture line.

Post-operative medical treatment generally consisted of anti-thromboembolic prophylaxis for 1 month and antibiotic treatment with cephalosporins for 24 h post-op.

Patients were directly enrolled in a physical rehabilitation program consisting of passive hip mobilization and progressive weight-bearing by walking with crutches for 2 weeks, after which, all patients were encouraged to perform weight bearing exercises.

3 Results

All the patients survived to reach the one-year follow-up mark and no patients were lost during follow-up. The 2 groups were considered homogenous since there was no significant difference in terms of age distribution (p = 0.402), BMI (p = 0.137), gender (p = 0.841), ASA grading and AO classification of the fracture (Table 1).

Minimal differences were observed in terms of patient comorbidities: hypertension (p = 0.25), diabetes (p = 0.724), heart disease (p = 0.322) and other diseases (p = 0.117).

The Sling group showed slightly higher but non-significant intraoperative blood loss (p = 0.217) and longer operation time (p = 0.067). On the other hand, the Sling group demonstrated significantly shorter times to achieve weight-bearing (p = 0.001) and fracture healing (p = 0.001) (Table 2).

The HHS, BI and RUSH scores were significantly improved at 3 months after surgery for both groups; although the Sling group showed better improvement in terms of HHS and RUSH score compared to the IM group at every point during the follow-up.

No major surgery related postoperative complications were reported. One case of non-evolving Brooker type 1 heterotopic ossifications was observed at 3 months follow-up in the Sling group. In the IM group, fracture nonunion was seen in one case and was treated with a total hip replacement.

4 Discussion

In this study, we describe a new method of treating unstable intertrochanteric fracture using a polymer-based cerclage wire to first achieve LT fixation followed by IM nailing to achieve fixation of the fracture. The clinical and radiological outcomes are reported and compared to treatment with isolated IM nailing. Our results show superiority of the Sling Technique + IM nailing in the treatment of unstable intertrochanteric fractures with LT involvement when compared to IM nailing along. The Sling group when compared to the control group showed significantly shorter time for fracture healing, time to achieve weight-bearing (p = 0.001) and significantly better outcomes in terms of functional recovery and radiographic assessment at 3, 6, and 12 months post-op compared to the IM group (p < 0.001) (Fig. 2).

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Fig. 2 A) 31A1.3 fracture with the LT fragment that is approximately at the same level of the main fracture line after closed reduction maneuvers. Pre-op and intra-op radiographs. (B) 31A1.3 fracture with distal extension. Pre-op and 1 month post-op radiographs. Two wires were used to fix the LT fragment.

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Multiple LT fixation techniques have been previously described in the scientific literature. In a recent study, Gao et al.¹⁷ described cerclage wiring technique to further stabilize intertrochanteric proximal femur fractures (AO/OTA 31-A2.2 and 31-A2.3) used in association with IM fixation. They reported healing time of 14 weeks without any complications such as cable breakage, implant irritation or infection. However, their technique did not consider fixation of the LT.

Wu et al.¹⁸ investigated the biomechanical aspect of fixating the LT using different wiring techniques in conjunction with Dynamic Hip Screw (DHS) system in the treatment of AO/OTA 31-A2.1 unstable intertrochanteric fractures. This study has demonstrated that patients who underwent DHS + LT Fixation have experienced a better prognostic outcome, in comparison to those who underwent only DHS. Among the different fixation techniques used the so-called “candy package” cerclage technique, first described by Lee et al.^19,20 which has shown superiority by exhibiting greater stability and resistance to cut-out failure with minimal displacement of the fragments. Recently, Kim et al.¹⁰ modified the “candy package” and reported a fracture healing time of 16.6 weeks on average in all cases. They reported wire breakage in only two cases and heterotrophic ossification in one case. The authors did not report any other complications.

The “Sling fixation” technique is based on ensuring continuity of the posteromedial fragment and recovery of psoas muscle function after LT fixation. However, a very important aspect for the success of this technique is the continuity of the posterior wall of the LT: proximal and distal fragment extension must be no more than 0.5 cm. A fragment extension that exceeds this limit results in an ineffective fixation yielding an increased risk of non-union and psoas dysfunction. The Sling technique, as the name suggests, involves the passage of the wire in a “sling” fashion. This immediately sets the technique on a pedestal in comparison to other existing techniques, as it eliminates the need of creating a drill hole. On top of that, the use of an iso-elastic polymer-based wire ensures symmetrical load distribution that improves prognosis by establishing long-term dynamic compressive loading across bony fragments. Thus, providing better healing and increased initial construct length. Furthermore, the polymer-based wire furnishes a greater fatigue strength reducing complications such as breakage, fretting wear and metal debris. Finally, these wires are designed with blunt ends which minimize soft tissue irritation and glove tears for the surgeon. Concerns regarding the use of the cerclage wires have arisen particularly due to the potential disruption to the local blood circulation, and the consequent delay in fracture healing. Nevertheless, more benefits have been manifested, thanks to the posteromedial stability, yielding a better fracture union and healing in all patients. Posteromedial stability compensates the lack of support secondary to the unstable fracture. Additionally, preserving the psoas muscle function allows faster functional recovery in most cases especially in the elderly population.

The results of the current study need to be interpreted considering several potential limitations.

The number of treated cases is small, and the patient pool may not provide the exact representation of the general population. However, the incidence of unstable intertrochanteric fractures with displacement of the LT is only about 25% of all femoral neck fractures providing a small number of cases to begin with.²¹

Another limitation of this study was the relatively short follow-up period, even considering that the first-year post-op results are the most crucial in this population due to the early incidence of complications. These patients are still being followed for evaluation of the long-term results of this type of treatment.

5 Conclusion

The “Sling fixation” technique using a polymer-based wire providing iso-elastic features showed promising outcomes when put in conjunction with the traditional proximal IM nailing method in the treatment of unstable intertrochanteric fractures with lesser trochanter involvement. Wiring improved the primary stability of the reduction, and the fracture healing time and postoperative weight-bearing time were significantly reduced. It also provided patients’ a faster functional recovery when compared to IM nailing alone.

Declarations

Ethics approval and consent to participate: IRB approval number: 2211/2018.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Author contributions

Marco Villano: Conceptualization, Investigation. Roberto Civinini: Methodology, supervision. Matteo Innocenti: Writing-Original draft preparation, Software. Christian Carulli: Data curation. Alessandro Civinini: Software, Validation. Andrea Cozzi Lepri: Conceptualization, Writing-Original draft preparation, Writing- Reviewing and Editing. Zyad A. Taha.

Consent for publication

The study was conducted according to the criteria set by the Declaration of Helsinki and each subject signed an informed consent before participating in the study.