Distal tibial fractures (DTFs) are the leading fractures involving the lower extremity, and they account for 10–13% of all tibial fractures [1]. Unfortunately, treating DTFs remains a challenge to this day. An inadequate soft-tissue envelope, adjoining ankle joint, and underlying trauma mechanisms induce complications following fractures [2]. Given these challenges, minimally invasive treatment procedures such as minimally invasive plating (MIPO) and intramedullary nailing (IMN) are preferred, despite certain drawbacks. Multiple reports suggest that MIPO is accompanied by an elevated rate of tissue breakdown, infection, and implant-associated complications [3, 4]. In contrast, IMN is a minimally invasive fixation process that prevents additional soft-tissue damage by promoting endogenous osteosynthesis. Nevertheless, IMN has a tendency towards malalignment [5,6,7,8]. It is yet unknown whether this is due to the inability to maintain reduction during IMN, especially during moments of flexion or extension, or due to a reduction loss owing to the large distal tibia diameter and resulting loss of interference fit with the nail [8].
Traditional tibial nailing is done through entry portal placement via a hyper-flexed infrapatellar (HFIP) approach, whereby either a patellar tendon-splitting or patellar tendon-sparing method is used while the knee remains in hyperflexion. During canal preparation, knee flexion and extension are required for fluoroscopic image-based visualization of the instrument and implant placements. In contrast, the suprapatellar (SP) and parapatellar (PP) IMN techniques forgo extremity manipulations, as the limb is placed in a semi-extended condition during the entire operation. Hence, a DTF can be reduced and persistently maintained during medullary canal preparation and IMN placement [8]. However, the application of these techniques is concerning owing to their intra-articular nature, as they can have complications such as knee cartilage damage [9, 10], septic arthritis [11], and heterotopic ossification [12]. In addition, the application of the SP IMN technique requires special surgical instruments.
Recently, we developed an extra-articular semi-extended infrapatellar (SEIP) approach that utilizes the infrapatellar (IP) space while the knee in a semi-extended position [13]. The aforementioned retrospective study demonstrated that, when treating tibial shaft fractures, the SEIP technique can markedly reduce the intra-surgical fluoroscopy duration, surgical duration, and knee pain and can enhance postsurgical knee function relative to the traditional HFIP technique [13]. However, to date, there are no studies on the safety and efficacy of the SEIP technique in treating DTFs. Thus, the current investigation assessed the performance of the SEIP approach in enhancing DTF alignment relative to the classical HFIP procedure. We speculated that the SEIP approach would enhance DTF alignment in patients treated with IMN. We also compared the intraoperative indicators, foot and ankle functions, and associated complications.
Patients and methods
This randomized clinical trial (RCT) was conducted in a level I trauma center in China. We received ethical approval from the Affiliated Kunshan Hospital of Jiangsu University (approval no. 2020-04-024-K01) and strictly followed the guidelines of the Declaration of Helsinki. All participants provided informed consent prior to the initiation of the study. This work is registered in the Chinese Clinical Trial Registry (ChiCTR2100043673). This study selected adult participants over 18 years of age with an acute closed or Gustilo I DTF occurring between April 2018 and June 2021 who received their final follow-up in July 2022. DTFs were classified based on the Orthopaedic Trauma Association (OTA) stratification system using initial injury films and computed tomography (CT). The following patients were selected for analysis: those with extraarticular fractures (OTA 43-A) and (OTA 43-C1 and C2) with a nondisplaced intraarticular fracture line [8]. Moreover, we only included fractures with major fracture lines located within 12 cm of the distal tibial plafond [14]. The following patients were eliminated from the analysis: those with a fracture occurring too distal to achieve proper fixation of four cortices using distal interlocking screws [5] and those with an ipsilateral proximal tibia fracture or knee injury, prior knee or ankle surgery preexisting ankle arthrodesis, and pathological fracture. In addition, we also eliminated patients with open Gustilo II or III fractures or fractures with a displaced intraarticular fragment. Following consent, the participants were arbitrarily separated into two populations in a 1:1 ratio: those receiving the HFIP IMN (control) or the SEIP IMN (experimental) treatment. The IMN (Tibia Without X-ray-Excellent [TWX-E] instrument system; Sanatmetal Orthopaedic & Traumatologic Equipment Manufacturer Ltd., Hungary) used in this study harbored three proximal and four distal locking possibilities, and the most distal hole was 5 mm from the nail tip, a 15° Herzog curvature was present on the proximal side, and a 3° bend was present on the distal side for simpler introduction.
A computer-generated stratified block-randomized number series classified by the OTA stratification was used to determine treatment allocation. A single senior trauma surgeon conducted or supervised all surgeries. Fibula fixation and supplementary reduction techniques including blocking screws, percutaneous clamps, and temporary plating were used, based on the surgeon’s preference. Owing to our study design, double blinding was not possible. Data processing, statistical analyses, and assessments were conducted by staff who were unaware of the treatment assignments.
Surgical technique
The HFIP technique was carried out with the patellar-tendon-split approach while placing the knee in 90° flexion. The SEIP technique was detailed in a previously published paper [13]. The primary unique elements of the SEIP technique include the following (Fig. 1): (a) a more distal tibial entry point; (b) modern IMN designs, including suitable Herzog curvature on the proximal side, curvature on the distal side, and a short proximal jig; (c) an extra-articular approach with the knees flexed approximately 30°, and (d) the use of a protective soft pad on the femoral side.
In brief, the patient was laid supine on a radiolucent table with the affected leg flexed ~ 30° using a roll under the knee joint. An incision was made ~ 4–5 cm lateral to the patellar tendon (Fig. 2). Next, the patellar tendon was medially pulled to visualize the tibial tuberosity slope. Hemostatic forceps were used to position the tibial entry point, which was then confirmed using intraoperative fluoroscopy (Fig. 3A, B). The ideal entry point seen on the anteroposterior (AP) view was immediately medial to the lateral tibial spine, with perfect alignment with the tibial shaft. On the lateral view, the entry point was at the tibial tuberosity slope ~ 10 mm distal to the anterior articular margin (Fig. 3C, D). Once the entry point was identified, reduction, reaming, nail insertion, and locking were performed similar to the traditional HFIP technique except that the injured leg remained in the semi-extended position at all times (Fig. 4). In order to prevent intraoperative compression of the proximal IMN jig on the skin, a compression protective pad was placed on the femoral side.
Post-surgical management and follow-ups
The post-surgical management and follow-ups were the same for both cohorts. For close fractures, first-generation cephalosporin was intravenously injected pre-operation and 24 h post-operation. For the Gustilo type I open fracture, the antibiotic usage duration was appropriately extended. The knee and ankle ranges of motion were supported. Moreover, the quadriceps were gradually strengthened using physical therapy. Weightbearing advancements were typically performed prior to the complete unification of bone fractures. The patients were clinically and radiologically followed up once every four weeks until union occurred. Lastly, additional follow-ups occurred at 3, 6, and 12 months after surgery.
Outcomes
The primary outcome for this study was malalignment. At each follow-up, coronal and sagittal plane radiographs of the entire knee, tibia, and ankle were obtained. Postsurgical AP and lateral tibial radiographs were assessed via the Paley technique for deformity evaluation [15]. Satisfactory radiographic alignment was described as < 5° in either the coronal or sagittal plane [8]. Figure 5 illustrates a case of malalignment following IMN. All measurements were taken by a trained senior radiologist who was unaware of the treatment assignments.
We prespecified several secondary outcomes, including intraoperative fluoroscopy time, operation time, blood loss, hospital length of stay, the functional ankle score, and complications. If the fracture healing duration was between 6 and 9 months, then it was deemed as delayed union [16]. Nonunion was a failure to unite the fracture by the ninth month post operation [17]. The functional ankle score was assessed via the American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Scale score [16]. To restrict bias in all clinical and manual evaluations, the last follow-up, performed at 1 year post operation, was conducted by an independent physician not involved in treating the study participants.
Statistics
The data distribution was assessed via the Kolmogorov–Smirnoff test. Normally distributed continuous data are presented as mean (standard deviation [SD]), whilst the rest are provided as median (interquartile range [IQR]). Normally distributed data were evaluated via an independent two-tailed t-test. Non-normally distributed data were assessed via the Mann–Whitney U test. To assess categorical information, provided as frequency (%), the chi-squared test was employed. If the chi-squared test assumptions were violated, a Fisher’s exact test was employed instead. Multivariate analysis was performed for malalignment (binary data) information, which yielded the predicted adjusted risk ratio (RR) and 95% confidence interval (CI). The adjusted confounding factors were as follows: age, gender, fracture type, and OTA stratification. Two-sided P values < 0.05 were deemed as significant. The R package (http://www.R-project.org, R Foundation) was employed for all data analyses.
Sample size
Our definition of the primary outcome (malalignment rate) was based on our preliminary examinations and a prior report [6, 18], and it was predicted to be 0.04 in the treated population (SEIP) and 0.25 in the control population (HFIP). The ratio of the number of participants in both study populations was 1:1. With an α value of 0.1 (one tail) and a β value of 0.2 (power of 0.80) in the G Power statistical analysis program, version 3.1, our patient size was determined to be 40 patients per group.