As per our knowledge, this study is the first report to describe the infrapatellar approach-based method for semi-extended tibial nailing, combining the advantages of both semi-extended (parapatellar or suprapatellar) approach and the infrapatellar approach while avoiding the disadvantages of both the methods. This study demonstrated that the SEIP approach significantly reduced intraoperative fluoroscopy time, operation time, VAS score, and the incidence of AKP and improved postoperative knee function compared with the HFIP approach. Moreover, there was an insignificant difference in malalignment, nonunion, delayed union, infection, and other complications.
One of the main advantages of semi-extended tibial nailing is that it can support the tibia in a resting position on a horizontal surface throughout the surgical process, facilitating tibial stabilization and imaging (16). The SEIP method retains these benefits as it helps surgeons in reducing proximal and distal fractures, fluoroscopic imaging, as well as the application of supplemental fixation, percutaneous clamps, and blocking screws.
Based on the study by Tornetta and Collins (12), the traditional method of semi-extended tibial nailing involves a lateral/medial knee arthrotomy or a suprapatellar approach using special cannulas. However, the application of these techniques to other tibial fractures, especially using the suprapatellar approach has raised some concerns due to their intra-articular nature. In a cadaver study, semi-extended nailing was done using the parapatellar/suprapatellar approach on paired legs from 10 freshly frozen cadavers. In the case of parapatellar approach, three legs had intra-articular disruption, one leg had cartilage damage. In legs with a suprapatellar approach, two legs showed damaged patellar cartilage and trochlea cartilage, respectively, and one incidence of ACL injury was reported (29). There were no meniscal injuries and partial laceration of the intermeniscal ligament was observed in three legs in each group. Gelbke et al. studied the contact pressure in the infrapatellar and suprapatellar nailing methods and found that compared with the traditional approach, the suprapatellar approach exposed the knee cartilage to significantly higher pressure; however, this pressure was still lower than the pressure required to cause chondrocyte death (30). Thus, the extra-articular parapatellar approach was developed to minimize the additional risk of abrasive injury while inserting trocars and reamers through the knee joint. However, the study by Kubiak et al. (16) observed the occurrence of small capsular tears that required additional repair either due to inadequate irrigation during reaming or nail insertion or due to limited patellar mobility that causes capsular tear because of insufficient retinacular release. Additionally, there is a risk of postoperative patellar instability secondary to the failure of the retinacular repair (16). Minoughan et al. reported iatrogenic injuries following suprapatellar nailing of an open tibial fracture, along with septic arthritis (23). Recently, Rehman et al. reported a case of heterotopic ossification following suprapatellar nailing (24). Despite these individual cases, the use of intra-articular techniques requires in-depth irrigation of the joint cavity (15). Thus, we developed a modified parapatellar approach-based method, which could be performed through the infrapatellar space. Patella obstruction was solved by appropriately shifting the entry point distally. Compared with the conventional semi-extended and infrapatellar method, the operative area was further away from the knee joint, indicating that it was a safe, simple, and convenient extra-articular technique. We hypothesized that this could have caused a higher functional score and a lower incidence of anterior knee pain of the SEIP group.
A specific potential disadvantage of the suprapatellar nail is the perceived need for a second incision for removing the nail, which is cosmetically displeasing and can cause more scarring and therefore more pain (31). Leary et al. developed a novel percutaneous technique for the suprapatellar intramedullary nailing removal using the same instruments and incision (31). The suprapatellar technique requires constant fluoroscopy, which is highly technical and cost intensive. The SEIP technique directly exposes the end cap similar to the traditional HFIP approach and does not require a second incision.
It is vital that the tibia enters the medullary canal at the right point, which theoretically allows the nail to be introduced in line with the tibial axis in both the coronal and sagittal planes. The lateral incision of SEIP technique on the coronal plane is mainly based on two reasons: (1) Lateral incisions reduce the risk of injury to the infrapatellar branch of the saphenous nerve injury compared with anteromedial knee surgery (32); (2) Hernigou and Cohen (6) have reported that the best position for the entry of a nail of maximum diameter in the transverse plane is 18.7 ± 4.5 mm lateral to the midline or 2.5 ± 1.8 mm lateral to the center of the tibial tubercle. A slightly lateral entry point could reduce the risk of iatrogenic injury to the knee. Moreover, the height of the entry point on the sagittal plane is also important. If the entry point is too high and the Herzog curvature of the nail is too small, patella obstruction increases the difficulty of the surgical procedure. Intramedullary nail and proximal targeting arm outside the medullary cavity push back on the skin accordingly. Additionally, there is an increase in the pressure of the nail in the medullary cavity that pushes forward on the anterior tibial cortex. If the entry point is too low and the Herzog curvature of the nail is too large, the posterior surface of the proximal tibia is endangered, particularly with a thick inflexible nail. Future studies could design intramedullary nails more suitable for SEIP technique.
While using the SEIP technique, especially on a patient who is obese or has a swollen knee, the surgeon needs to consider the mechanical pressure of the intramedullary nail and proximal targeting arm on the skin. In the first three patients with this technique, we observed an indentation at the proximal end of the incision. However, the wound healed normally after the operation without any necrosis or infection. Later, in order to reduce the squeezing effect on the soft tissue, we took two measures. First, we increased the knee flexation angle to minimum 30 degrees. Second, we used special dressings, as previously described, to avoid this defect. The Mepilex Border Post-Op is a highly conformable self-adherent dressing that absorbs exudate and minimizes the risk of maceration (33). This dressing has stable viscosity in the surgical hemorrhage conditions, offers flexible protection without occupying the operating space, and is more friendly to soft tissue injuries.
However, this study had several limitations. First, this study conducted a retrospective analysis of the earliest cases to establish the novelty of this method. Due to their inherent inadequacy, retrospective cohort studies are considered low evidence level studies and require further randomized controlled trials. Second, since it is a relatively newer technique, there were fewer cases in the single trauma center. In the future, multi-center large sample studies are needed. Third, since it is not a double-blind trial, surgeons were aware of the procedures to be used and were more careful when applying new techniques. Fourth, conventional semi-extended approaches were not used for comparison.
An important strength of this research was its strict inclusion and exclusion criteria, which resulted in good consistency in demographics, fracture types, as well as other aspects, and the baseline levels were comparable. Additionally, all surgical procedures were either performed or supervised by a senior trauma surgeon. The 12-month follow-up data were collected prospectively.