Use of novel and inexpensive radiolucent soft tissue protector for insertion of proximal locking screws in femoral retrograde intramedullary nailing

Abstract

We use a straightforward technique for insertion of proximal interlocking screw fixation during retrograde intramedullary nailing of the femur utilizing a common 3 cc syringe as a radiolucent soft tissue protector. Following insertion of the implant and distal interlock insertion, the distal Luer-Lok tip of a 3 cc syringe is cut off to create a hollow tube. Once the correct location of the proximal locking holes is confirmed fluoroscopically, the syringe is inserted through the incision into the soft tissue over the long drill sleeve and trochar. The inner drill guide and trochar is then removed, leaving only the syringe. Through this syringe, the proximal interlocking hole is drilled and measured, and the screw is inserted. The syringe establishes a safe pathway for passage of instrumentation, mitigating damage to the surrounding soft tissues, and allowing for unobstructed fluoroscopic visualization throughout insertion of the locking screws. This technique is safe, inexpensive and reproducible; utilizing common equipment available in most operative settings.

1. Introduction

Intramedullary (IM) nailing has become the preferred method of treating femoral shaft fractures.¹ It is associated with high union rates and low complication rates.² Multiple factors must be taken into account when performing this seemingly straightforward procedure, including fracture characteristics, associated musculoskeletal and/or visceral injuries, local soft-tissue injury, and the technical familiarity of the surgeon with each nailing method.¹ Patient body habitus, particularly, large soft tissue profiles in the proximal thigh can make free-handed insertion of proximal interlocking screws challenging in retrograde femoral nailing.

As the population continues to expand, both in number and thigh circumference, surgeons may more frequently encounter technical challenges related to patients’ body habitus. The prevalence of adult obesity in the United States in 2016, as defined by Body Mass Index (BMI) greater than 30 was 39.6%.³ This represents a 9.1% increase from just 15 years prior and encompasses over 98 million Americans over 18 years of age. Instrumentation and technical innovation should evolve to consider this issue.

We describe a novel and inexpensive technique to help establish and maintain a safe start site and trajectory for drilling the proximal interlock holes during femoral retrograde nailing. A clear and preserved path for insertion of the proximal interlock screw is created using standard equipment and a common 3 cc syringe.

2. Technique

The standard technique for retrograde femoral intramedullary nailing is performed up until proximal interlock screw fixation. Most intramedullary femoral nails on the market have anterior-posterior as well as medial-lateral locking options, which are typically utilized with a freehand technique. Our technique was performed with the Stryker (Kalamazoo, MI) T2 Femoral Nailing System.⁴

The critical step with any free-hand locking technique, proximal or distal, requires the visualization of a perfectly round locking hole, or oblong locking hole with the use of C-Arm. The C-Arm is gently manipulated to ensure the beam is in plane with the implant. The X-ray beam is arranged to obtain a ‘perfect circle’ with the locking hole. Care is taken to ensure the intramedullary device and limb remain in acceptable anatomic rotation.

On the back table, a sterile 3 cc syringe is opened. The plunger removed and discarded. The tip of the syringe was then cut, leaving a clear, hollow, radiolucent tube (Fig. 1).

• Step 2

Fig. 1.

(a) Materials: 3 cc syringe, Stryker long tissue protection sleeve, long drill sleeve and long trocar. (b) Tip of syringe is cut with a pair of heavy scissors. The cut syringe measures 7cm in length. (c) Components prior to assembly (d) Stryker trochar, drill guide and 3 cc syringe “sheath”. The diameter of the Stryker drill guide is 8mm compared to the 9mm diameter of the 3 cc syringe.

• Step 1

“Perfect-circle” technique⁵ was performed in the usual fashion, first with radiographic approximation of the incision using the handle of a Schnidt Tonsil Forceps and a 15-blade. Once localized, the skin is incised and the deeper tissues are bluntly dissected using a “nick and spread” technique.

• Step 3

Blunt dissection was carried down to the anterior cortex of the femur with a straight Schnidt Tonsil Forceps. The periosteum is roughened slightly to facilitate drill stability.

• Step 4

The hollow 3 cc syringe is then inserted as a sheath over the long drill sleeve and long trocar. This is then introduced through the incision to the anterior cortex of the femur, taking care to ensure that the 3 cc syringe is inserted as deeply as possible to the incision. The metal guide is removed leaving the 3 cc syringe.

• Step 5

The center-tipped 4.2 × 230mm drill is inserted through the 3 cc syringe down to cortical bone, and the location of the drill hole for either the static or dynamic Anterior-Posterior proximal locking hole of the nail is determined in the usual fashion. Upon x-ray verification, the drill is placed perpendicular to the nail and image intensifier receiver. A hole is drilled through the anterior and posterior cortex. Confirmation with xray may be obtained ensuring the drill passes through the hole in the nail in the A/P, M/L or both planes (Fig. 2a–b).

• Step 6

Fig. 2.

(a) Tissue protector including 3 cc syringe inserted through incision to bone. (b) Appropriate drill position for A/P locking screw verified with fluoroscopic imaging prior to drilling (c) Proximal interlocking screw inserted through 3 cc syringe. (d)Verification of screw through proximal locking hole.

The drill is withdrawn, maintaining the 3 cc syringe in the soft tissues, docked to the anterior femoral cortex with downward pressure to avoid slippage and loss of trajectory. A depth gauge is inserted through the syringe to determine the appropriate length of the locking screw.

• Step 7

An appropriately sized proximal interlocking screw of pre-measured length loaded on the screwdriver is then introduced through the 3 cc syringe down to the drill hole and inserted. Once radiographic confirmation that the screw is seated down to cortical bone, the screwdriver and 3 cc syringe are removed from the incision (Fig. 2c–d).

• Step 8

Steps 2-7 may be repeated for insertion of a second proximal interlock screw, if so indicated.

3. Case Example 1

A 33-year-old female, BMI 34, presented after ejection off a motorcycle with multiple skeletal injuries which included a comminuted midshaft femur fracture (Fig. 3a). Patient was taken to the operating room on hospital day one for a retrograde intramedullary nail for stabilization of the right femur (Fig. 3b). The described technique was utilized to optimized placement of both of the proximal interlocking screws. At one-year follow-up the patient had returned to work and activities without restriction. There were no issues with wound healing or pain at the interlock site.

Fig. 3.

Case Example 1 (a) Radiographs at time of Injury (b) Radiographs at three-month follow-up.

4. Discussion

Though a relatively straightforward procedure in most orthopaedic traumatologists’ hands, retrograde intramedullary nailing of femoral shaft fractures is not without its perils and pitfalls. Often performed as the last step in fixation of these fractures, following reduction, nail insertion, and distal locking, proximal interlocking presents a unique set of challenges and potential complications, which can be exacerbated by the patient’s body habitus.

Difficulty establishing and maintaining drill trajectory and inability to localize the drill hole have been well described in the use of interlocked intramedullary devices.⁶ Historical techniques included the use of an additional nail to line up the holes⁷ for the interlocks, though this is not cost-effective nor practical with the use of modern, single-packed sterilized nails. Other techniques have been described to assist in accurate drill placement through the nail in antegrade femoral nails,^8,9 but there has been little focus on accurate and efficient placement of the screw itself, likely due to the relative ease of placement of interlocks in the distal femur relative to the proximal femur. Loss of the locking screw in the soft tissues, temporary or otherwise, is not reported in the literature but is a potential complication. The risk of drill slippage is reduced in modern with the toothed drill guide. However, once this guide is removed there is no additional device provided for maintaining the corridor for insertion of the screw itself. These experiences can be frustrating and time consuming, particularly in the academic setting. These issues are exaggerated further in patients with BMI >30.

Beyond technical frustrations, complications such as damage to the nearby neurovascular structures are also possible. Riina et al. performed a cadaveric study examining the neurovascular structures at risk during proximal interlocking of retrograde femoral nails and found that the first division of the femoral nerve crossed the femur on average approximately 4cm distal to the piriformis fossa.¹⁰ This anatomy may be further distorted in patients with concomitant acetabular fractures, due to the displacement of the soft tissues caused by the resultant hematoma.¹¹ Thus, it is imperative that the soft tissue be approached with caution. The use of any tool that provides adequate tissue protection and avoids extensive dissection, multiple passes of the drill or depth gauge, or loss of the screw into the thigh would be useful.

By establishing a radiolucent path, from incision to anterior cortex of the femur, the drill trajectory can be maintained following drilling, during measurement with a depth gauge, and ultimate insertion of the interlocking screw. Advantages of this technique include its simplicity, low-cost and reproducibility. Furthermore, as a radiolucent soft tissue projector, radiographs can be taken unobstructed throughout the entire process of proximal interlocking fixation. Technique-specific challenges still remain including drill or syringe slippage, accurate drilling depth, off-axis drilling, and screw loss or stripping. While many of these challenges overlap with standard interlocking techniques, we have found that overall these are less frequent with our technique. While the syringe measures only 7cm in length, we have had success in muscular and obese patients. Considering the pliability of the soft tissue envelope, the syringe can be docked against the anterior femoral cortex with modest downward pressure. However, this technique may be challenging in the severely obese and we are unable to recommend a circumferential size cut-off.

This technique may be applicable to other procedures where a radiolucent soft-tissue protector may be advantageous. Based off of a current review of the literature, no similar techniques have been reported.

Compliance with ethical standards

Funding

This study has no sources of funding to report.

Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. This article does not contain any studies with animals performed by any of the authors. No institutional review board was necessary.

Informed consent

Informed consent was not applicable for this surgical technique report.

Declaration of competing interest

Declare that they have no conflict of interest.