Femoral Intramedullary Nailing - How To Choose The Best Insertion Point?

Introduction

The development of femoral fracture treatment can be traced back to the 1940s when Kuntscher introduced the closed intramedullary nailing technique. The use of intramedullary nails (IMNs) in femoral fractures has become the standard of care over the past few decades, and current improvements in intramedullary nailing and advances in surgical techniques have allowed for a significant increase in the use of intramedullary nailing of the femur.

Conservative treatment of femoral stem fractures is used only in a very small number of patients with significant contraindications to anesthesia and surgery, and the mainstay of treatment remains surgical fixation. With regard to the surgical treatment of these fractures, there are several options available, including intramedullary nailing, plate screw fixation, and external fixation. Compared with other surgical options, intramedullary nailing is the modality with the lowest complication rate and the highest fracture healing rate, and it is becoming more widely used in clinical practice.

A good understanding of the anatomy of the proximal femur, the blood supply to the femoral head and the anatomy of the hip muscles can greatly increase the success rate of intramedullary nailing for femoral fractures. In contrast, the choice of entry point depends on many factors, including intramedullary nail design, fracture site, fracture comminution, and patient factors (e.g., polytrauma, pregnancy, and obesity). Regardless of the entry site chosen, obtaining the correct entry point is essential to maintain adequate reduction during intramedullary nail insertion while reducing the risk of complications.

Femoral Anatomy

1.Blood supply to the femoral head

The femoral head receives vascular supply from 3 major arteries. The lateral rotator femoral artery (with 3-4 branches), the obturator artery, which supplies the round ligament, and the medial rotator femoral artery (Fig. 1), which also gives off an upward ascending vessel that anastomoses with the lateral rotator femoral artery and supplies the greater trochanteric region.

2.Anatomy Of The Hip Muscles

When performing intramedullary nailing of the femur, a good understanding of the muscles in the area surrounding the rotor is essential to prevent unnecessary injury. The gluteus medius muscle originates from the ilium and ends on the lateral aspect of the greater trochanter, while the gluteus minimus muscle also originates from the ilium and passes over the posterior aspect of the hip joint to end on the posterior aspect of the greater trochanter (Figures 2 & 3). Both of these muscles function as adductors of the thigh and internal rotators of the hip. Therefore, damage to these muscles during insertion of a paracentric femoral intramedullary nail will result in adductor weakness and Trendelenburg gait, which has a negative impact on patient recovery and outcome.

Fig. 2. Anatomy of the muscles around the hip joint

Figure 3. proximal femoral muscle attachment area

Parallel Femoral Intramedullary Nail

Several recent studies have explored the optimal entry point for the paracrine femoral nail. Nail entry point options include the greater trochanter and the pyriform fossa, each with its own indications and associated complications (Table 1).

1.Large rotor needle entry point

The greater trochanter has been described as the outermost trapezoidal bony protuberance located on the lateral aspect of the femoral neck, the surface of which provides attachment to the lateral gluteus medius and anterior gluteus minimus muscles (Figures 2 and 3). Although this is a minor bony landmark, localizing the correct starting point when performing a femoral IMN may be the difference between obtaining a satisfactory or poor result when dealing with a femoral stem fracture.

Reviewing the current literature for femoral entry point descriptions, we found a lack of a clearly described anatomical landmark for the femoral rotor IMN entry point.Bharti et al. described the entry point from the apical apex of the greater trochanter as being medial toward the medullary cavity in orthostatic position, and as being the center of the greater trochanter in line with the center of the femoral medullary cavity in lateral position (Fig. 4), and an alternative description of the greater trochanter entry point on the lateral hip view is in the rotor between the anterior between the anterior one-third and posterior two-thirds of the rotor.Georgiadis et al. described the point of needle entry as the most posterior side of the apical superior margin of the rotor.

FIGURE 4. Intraoperative orthostatic and lateral views of the hip show the ideal entry point for the femoral paramedian intramedullary nailing of the greater trochanter. “*” indicates the intramedullary nail entry point.

Recent studies in the literature have shown that the apex of the greater trochanter is the ideal starting point for obtaining an optimal line of force, and that poor alignment due to inversion deformity often occurs when the point of entry is shifted more than 2 mm lateral to the greater trochanter. This study also emphasized that a more posterior entry point leads to distal forward displacement, whereas an intermediate entry point may cause the distal fracture block to be displaced posteriorly. In contrast, another study showed that in intertrochanteric femur fractures, the incidence of intramedullary nail impingement was significantly higher with a pinning point that was lateral to the anterior side than with a pinning point that was closer to the medial and posterior sides.

The greater trochanteric apex pinning point is commonly used in obese patients, and this procedure is less technically demanding, providing less operative time and a lower risk of complications than the pyriform fossa pinning point.

COMPLICATIONS: Intraoperative and postoperative complications of femoral intramedullary nailing with a greater trochanteric approach point have been discussed in several publications. One of these, usually related to the nailing technique, is medically induced fractures. In intertrochanteric femoral fractures, an entry point located lateral and anterior to the greater trochanter is more likely to result in a medial fracture than an entry point closer to the medial side.

Another relevant complication is due to soft-tissue injuries, especially to the branches of the medial rotator femoral artery and the adductor muscles, but these injuries are less common compared with the pyriform fossa entry nail. In addition, the incidence of ischemic necrosis of the femoral head with the apex of the greater trochanter as the entry point is thought to be significantly lower, with studies reporting it as low as 0.3%.

Considering intraoperative time and fluoroscopic exposure, the mean operative time was 90.7 minutes for the greater trochanteric entry point compared with 112.7 minutes for the pear-shaped fossa entry point group, whereas fluoroscopic time was 5.88 seconds for the greater trochanteric entry point group and 10.08 seconds for the pear-shaped fossa entry point group, compared with the pear-shaped fossa entry point.

Patient prognosis was also an important factor when deciding on the intramedullary nail entry point, as early functional recovery (as assessed by the chair-seat test and timed elevation test) was significantly better in patients at 6 months postoperatively for the greater trochanteric entry point compared with the pyriform fossa entry point nail, but this difference was not significant at 12 months postoperatively. Although the greater trochanteric access point is usually associated with less soft tissue stripping due to its location, it can still lead to injury to the abductor muscle group, as has been demonstrated by Ergiş et al. They found that dynamic balance and hip abductor strength were decreased in patients with the greater trochanteric entry peg compared to healthy controls. In addition, their study reported a significant decrease in strength of the hip abductors, flexors and internal/external rotators compared to the non-operated side.

2. Pearly fossa entry point

The fossa of the pyriformis muscle is an important anatomical landmark identified as one of the entry points for a paracentesis femoral intramedullary nail.In their autopsy cadaveric study, Lakhwani et al. noted that the fossa of the pyriformis muscle was neither a “pear” shaped nor a pyriformis muscle attachment. The muscle attaches to a small area at the tip of the greater trochanter, whereas the pyriform fossa is a depression on the medial side of the greater trochanter and is an attachment of the extensor carpi radialis brevis muscle. The authors concluded that the pyriform muscle and the pyriform fossa are two different entities and that the so-called pyriform fossa should be referred to as the “rotor” or the “occlusal” fossa for clarity and anatomical correctness. They suggested that after studying the cis-femoral They suggested that the original term “rotor fossa” be reintroduced in the literature instead of “pyriform fossa” after studying the terminology of the parafemoral entry point. Although the points of these two studies are highly regarded, for ease of description and to prevent confusion with the greater trochanteric entry point, we will still refer to this entry point as the pyriform fossa entry point.

Several studies in the current literature accurately describe the exact entry point of the pearly fossa for intramedullary femoral nails.Georgiadis et al. describe the pearly fossa entry point as the area of attachment of the extensor carpi radialis brevis muscle in the depression at the base of the femoral neck (Fig. 5). The authors also emphasized that an entry point that is too far forward or too far inward may increase the risk of femoral neck fracture, and when the entry point is too far backward, there may be a high risk of ischemic necrosis, which is higher in adolescent patients.

Figure 5. Intraoperative frontolateral view of the hip showing the ideal entry point for a pyriform fossa retrograde femoral intramedullary nail. The “*” indicates the intramedullary nail starting point.

Harper et al. published a study of 14 groups of human cadaveric femurs in 1987 in which they evaluated the location of the intramedullary guide pin and the exit point of the intramedullary nail introduced distally and proximally in a retrograde fashion from the intercondylar notch of the femur. They concluded that the point of entry of the pyriformis paramedian intramedullary nail was located at the junction of the greater trochanter with the femoral neck, slightly anterior to the pyriformis occulta.The insertion site was reconfirmed by Gausepohl et al. In another cadaveric study, they localized the ideal entry point for the femoral intramedullary nail along the medial edge of the greater trochanter overlying the pyriformis tendon. Furthermore, in the cadaveric study by Labronici et al. the fossa of the pyriformis muscle was described as a pear-shaped luminal region that coincided with the central axis of the femoral intramedullary cavity in the coronal plane.

The pyriform fossa access point has some specific disadvantages because it is technically more challenging compared to the greater trochanter access point, especially in obese patients. In addition, the optimal entry site for the pear-shaped fossa needle entry point is a narrow area, making it more challenging to localize. For example, an overly anterior starting point on the femoral neck will result in excessive circumferential stress and increase the risk of anterior cortical burst, especially if the starting point is more than 6 mm anterior to the fossa. In addition, morphologic contrast may impede the correct entry site, especially if the short external rotator is bulky or the rotor is protruding, leading to an entry site that is too medial and a risk of femoral neck fracture.

COMPLICATIONS: By comparing 38 greater trochanteric entry sites with 53 pearly fossa entry sites for femoral intramedullary nailing, Ricci et al found that the pearly fossa group had a 30% longer operative time and a 73% longer fluoroscopy time. These findings were confirmed by Bhatti et al. when comparing the 2 needle entry points.

Regarding soft-tissue injury, there was a higher risk of soft-tissue injury at the pyriformis inlet compared with the interosseous neuromuscular at the greater trochanteric needle entry point. Dora et al. evaluated 16 adult cadaveric femurs for soft tissue injuries to the pyriformis muscle and rotor entry pin. They found that although the pyriformis fossa was geometrically optimal, it caused more significant damage to the vascular supply to the femoral head and surrounding muscles and tendons. These findings were reconfirmed by cadaveric studies by Ansari Moin et al. WHO also compared two entry points. They noted that internal fixation of the nail starting at the pyriformis muscle was more likely to damage the hip abductors and external rotators. In addition, damage to the medial rotator femoral artery was found in all cases (Table 2).

Recently, Bharti et al. studied the complication risk of femoral intramedullary nailing at the greater trochanteric entry point and the pearly fossa entry point and found the complication risks such as fracture healing rate and summarized them as follows (Table 3).

Retrograde femoral intramedullary nailing

Determining the appropriate entry point for retrograde femoral intramedullary nailing will help to achieve restoration of optimal fracture alignment, length, and rotation while minimizing articular cartilage damage, anterior cruciate ligament (ACL), posterior cruciate ligament (ACL), and soft tissue injury (Table 1). Recently, there has been an increasing interest in retrograde femoral intramedullary nailing with the aim of reducing the complications associated with paracromial nailing, including hip pain, heterotopic ossification, adductor weakness, and pudendal nerve palsy, which is considered minimally invasive when compared with incisional reduction and locking femoral plating for internal fixation, especially in fractures of the distal one-third of the femoral stem. In addition, recent evidence suggests that when these retrograde intramedullary nails are appropriately sized, proximal locking nails may not be required.There was no difference in healing rates, time to healing, or patient-reported outcomes between Meccariello et al. and Bisaccia et al. in the treatment of distal one-third femoral stem fractures using locking and nonlocking retrograde intramedullary nails. Thus, the use of retrograde femoral nailing has become popular and widely accepted.

Many descriptions of the optimal entry point for retrograde femoral intramedullary nailing can be found in the literature. Most studies identify the ideal entry point for the retrograde femoral nail as 1.2 anterior to the femoral origin of the posterior cruciate ligament

cm (in line with the medullary cavity) and the center of the intercondylar fossa (Figure 6).

FIGURE 6. Intraoperative orthostatic and lateral views of the knee showing the ideal entry point for a retrograde femoral intramedullary nail. “*” indicates the intramedullary nail starting point.

Although there is no absolute indication for retrograde femoral intramedullary nailing, multiple relative indications have been described. These include polytrauma patients, morbidly obese patients, pregnant patients, bilateral femoral stem fractures, ipsilateral femoral stem and acetabular/pelvic fractures or femoral neck fractures, and ipsilateral femoral stem and tibial fractures. Most of these indications are related to ease of patient positioning and prevention of multiple surgical wounds in close proximity.

On the other hand, absolute contraindications to retrograde femoral intramedullary nailing include obstruction of the retrograde intramedullary channel by the retained implant and open fractures of the distal femur. Relative contraindications are fractures located within 5 cm of the lesser trochanter, difficulty in accessing the optimal entry point due to a knee flexion of less than 45 degrees, prior knee infection that may lead to a risk of spreading to the femoral stem, severe soft-tissue injuries around the knee, and intra-articular fracture of the inferior pole of the patella and the extreme distal pole.

Complications: Most complications of retrograde femoral nailing are related to improper handling, especially incorrect placement of the entry point. In the sagittal plane, a more anterior entry point will result in posterior fracture translation, articular surface damage, and possibly nail impingement on the patella when the knee is flexed. On the other hand, if the entry point is improperly positioned in the posterior direction, this may result in a higher risk of injury to the posterior cruciate ligament origin and anterior displacement of the fracture site.

Hutchinson et al. described complications associated with improper coronal plane entry points. They found that an overly medial entry point resulted in a posterolateral deformity with posterolateral fracture translation, whereas an overly lateral one resulted in a medial deformity and medial translation.Sanders et al. reported that selecting a medial starting point that was 2 cm or more off the medial axis resulted in a medial cortical fracture that was malunited due to a posterior isthmic bending moment of the fracture resulting in poor posterolateral reduction.

Other complications associated with retrograde femoral follower nailing include knee pain, stiffness, heterotopic knee ossification, and intra-articular knee free body formation.

Conclude

Although each intramedullary nailing technique has a corresponding indication, the choice of which intramedullary nailing technique to use in the treatment of femoral stem fractures usually depends on surgeon preference. When performing intramedullary nailing of the femur, obtaining the correct entry point for the type of nail used for fixation is required for a successful outcome. Knowledge of local anatomy and imaging performance will help the surgeon perform a technically adequate procedure while reducing the risk of associated complications. Additionally, in intramedullary nailing procedures, maintenance of reduction is a critical component in preventing malunion and malunion or nonunion of fractures.