Distal femur fractures are a significant challenge in orthopedic surgery because of their complex nature and treatment demands. They make up roughly 1% of all skeletal fractures and represent about 6–7% of all femoral fractures(1). Epidemiological data indicate that supracondylar femur fractures occur at an incidence of approximately 37 cases per 100,000 individuals annually. These injuries arise through two primary mechanisms that are related to patient demographics(2). Distal femur fractures are challenging injuries because they often involve multiple complicating factors such as fragment splintering (comminution), extension into the joint surface, extensive soft‑tissue damage, reduced bone density (osteopenia), and an enlarged distal medullary canal. Because of this complexity, managing these fractures is difficult and can lead to serious complications and functional impairment if treatment is inadequate. In the past, non‑operative management with skeletal traction was commonly used for these injuries. However, this method frequently resulted in undesirable outcomes including angular deformities, stiffness of the knee joint, and the development of post‑traumatic osteoarthritis. Consequently, modern treatment emphasizes precise surgical techniques to restore anatomy and function while minimizing such complications(3). In recent times, retrograde intramedullary nailing (RIN) has become a favored surgical choice for managing distal femur fractures, especially when there is associated soft‑tissue injury. This minimally invasive procedure has several benefits: it causes less damage to surrounding tissues, lowers the chance of infection, and promotes quicker bone healing than conventional plate fixation(4,5). Positioning the nail inside the medullary canal gives strong biomechanical support, which decreases the likelihood of varus or valgus misalignment—a problem often seen with lateral plate systems(6). Additionally, retrograde nailing allows patients to start early movement and weight‑bearing, which is essential for restoring function and preventing postoperative issues like knee stiffness(7). Using an intramedullary nail has several benefits compared with traditional lateral fixation plates. The nail technique usually shortens surgery time, decreases blood loss, keeps the fracture hematoma intact, avoids stripping of the periosteum, and requires only limited soft‑tissue dissection. Because the nail shares the load with the bone, patients can begin early mobilization, which improves functional results. The biomechanical advantage of placing the nail inside the medullary canal is that it shortens the lever arm, which helps reduce angular deformity in the coronal plane (8). This study evaluates the radiological outcomes of fracture healing and alignment in patients with distal femur fractures treated with retrograde intramedullary nailing.

A hospital-based prospective study was conducted at Melmaruvathur Adiparasakthi Institute of Medical Sciences, Tamil Nadu, spanning from April 2023 to December 2024, with the primary objective of evaluating radiological outcomes of patients who underwent retrograde nailing for distal femur fractures. The study population consisted of patients aged between 18 and 65 years, diagnosed with distal femur fractures classified under AO categories 33-A1, 33-A2, 33-A3, 33-C1, and 33-C2. Patients with neurovascular injuries, pre-existing knee flexion deformity, and fractures classified as AO 33-C3 and 33-B were excluded from the study. The surgical procedure involved retrograde nailing performed under spinal anesthesia, with patients positioned supine and the knee flexed. A medial preligamentous or transligamentous approach was utilized to access the distal femur, and the nail was inserted following reaming of the medullary canal. Postoperative follow-up assessments were conducted at 1, 3, and 6 months, incorporating both X-ray evaluations and clinical examinations to assess fracture healing, alignment, and functional recovery. The study protocol received approval from the Institutional Research and Ethics Committee, and informed consent was obtained from all participants. Throughout the study, stringent measures were implemented to ensure the confidentiality and privacy of patient data. Data Collection Data were entered into Microsoft Excel 2010 and SPSS version 20. Descriptive statistics included mean and standard deviation for continuous variables, and frequency distributions and percentages for categorical variables. The Chi-square test assessed associations between variables.

Table 1: Demographic Profile of the Study Population Demographic characteristics Frequency percentage Age group 18 to 25 yrs 4 14.8 25 to 34 yrs 11 40.7 35 to 44 yrs 7 25.9 45 to 54 yrs 3 11.1 55 to 65 yrs 2 7.4 Gender Male 17 63 Female 10 37 The study population consisted of 27 patients, with the majority (40.7%) aged 25-34 years, followed by 35-44 years (25.9%). Males accounted for 63% of the patients, while females accounted for 37%. Table 2: AO classification of fractures undergone Retrograde Intramedullary Nailing in the study. AO Classification of fractures Number of participants Percentage A1 12 45 A2 10 38 A3 3 11 C1 1 3 C2 1 3 Total 27 100 The table shows the AO classification of fractures treated with Retrograde Intramedullary Nailing (n=27). Most fractures were Type A1 (45%), followed by A2 (38%), A3 (11%), and C1 and C2 (3% each). Table 3: Fracture Characteristics and Mechanism of Injury Characteristic Frequency Percentage Type of Fracture Open 2 7.4 Closed 25 92.6 Mechanism of Injury Road Traffic Accidents 23 85.2 Fall 4 14.8 The table shows the distribution of fracture types and mechanisms of injury. Most fractures were closed (92.6%) and resulted from Road Traffic Accidents (85.2%). Table 4: Distribution of Time taken for radiographic healing of fracture among the study participants. Time taken for radiographic healing Frequency Percent less than 3 months 13 48.1 3 to 6 months 11 40.7 >6 months 3 11.1 The above table shows distribution of Time taken for radiographic healing of fracture among the study participants. About 48.1 % of study participants took less than 3 months for radiographic healing of fracture while 40.7 % took 3 to 6 months. Only 11.1 % of study participants took a longer period of more than 6 months. Table 5: Association between Age group of the participants and post operative complication. Age group in years Post-operative complications No Complication (%) Infection (%) Knee pain (%) Knee stiffness (%) Chi square value P value 18 to 25 4 (14.8%) 0 0 0 34.57 0.005 25 to 34 10 (37.0%) 0 1 (3.7%) 0 35 to 44 2 (7.4%) 0 2 (7.4%) 3 (11.1%) 45 to 54 1 (3.7%) 2 (7.4%) 0 0 55 to 65 0 0 1 (3.7%) 1 (3.7%) The table shows that most participants (64.1%) had no complications. Knee stiffness and knee pain were reported in 14.8% and 11.1% of participants, respectively, particularly in the 35-44 age group. Infections were reported in 7.4% of participants, primarily in the 45-54 age group. The chi-square value (34.57) indicates a significant association between age group and post-operative complications. Table 6: Association between Age group of the participants and Time to radiographic healing Age group in years Time to radiographic healing less than 3 months 3 to 6 months >6 months Chi square value P value 18 to 25 4 (14.8%) 0 0 32.59 0.001 25 to 34 8 (29.6%) 3 (11.1%) 0 35 to 44 1 (3.7%) 6 (22.2%) 0 45 to 54 0 2 (7.4%) 1 (3.7%) 55 to 65 0 0 2 (7.4%) The table shows a significant association between age group and time to radiographic healing (p=0.001). Most participants (44.4%) healed within 3 months, primarily in the 25-34 age group. Healing took 3-6 months for 40.7% of participants, mainly in the 35-44 age group. 11.1% took >6 months to heal, mostly in older age groups. Table 7: Association between Gender of the participants and Time to radiographic healing: Gender Time to radiographic healing in months less than 3 months 3 to 6 months >6 months Chi square value P value Male 7 (25.9 %) 8 (29.6 %) 2 (7.4 %) 0.931 0.628 Female 6 (22.2 %) 3 (11.1%) 1 (3.7%) The table shows no significant association between gender and time to radiographic healing (p=0.628). Males took 3-6 months to heal in 29.6% of cases, while females healed within 3 months in 22.2% of cases. Healing took >6 months in 11.1% of males and 3.7% of females. Table 8: Association between Post operative complications and Time to radiographic healing: Post operative complications Time to radiographic healing in months less than 3 3 to 6 >6 Chi square value P value No Complications 17 (44.4 %) 4 (14.8 %) 1 (3.7%) 12.292 0.139 Infection 0 2 (7.4 %) 0 Knee pain 1 (3.7%) 2 (7.4 %) 1 (3.7%) Knee stiffness 0 3 (11.1%) 1 (3.7%) The table shows no significant association between post-operative complications and time to radiographic healing (p=0.139). Most participants with no complications healed within 3 months (44.4%). Those with knee stiffness took 3-6 months to heal in 11.1% of cases. Infections and knee pain were reported in a few cases, but the association is not statistically significant. Table 9: Association between Injury mechanism and Time to radiographic healing: Injury mechanism Time to radiographic healing less than 5 6 to 10 10 to 12 Chi square value P value RTA 12 44.4 %) 8 (29.6%) 3 (11.1 %) 2.39 0.302 Fall 1 (3.7%) 3 (11.1 %) 0 The table shows no significant association between injury mechanism and time to radiographic healing (p=0.302). Most participants with Road Traffic Accidents (RTA) healed within 3 months (44.4%), while 29.6% took 3-6 months. Falls were reported in a few cases, with healing times varying from <3 months to 3-6 month. Radiological Investigation CASE 1 Figure 1: Pre op xray Figure 2: Intra op Figure 3: POST OP X-RAY Figure 4: POST OP X-RAY 1st MONTH FOLLOW UP Figure 5: POST OP X-RAY 4thMONTH FOLLOW UP Figure 6: POST OP X-RAY 8 MONTHS FOLLOW UP Figure 7: POST OP X-RAY 2 YEARS FOLLOW UP

Retrograde intramedullary nailing is favoured due to its minimally invasive nature, use of closed reduction methods, and effective preservation of surrounding soft tissues. Early stabilization surgery is advantageous as it facilitates soft tissue management, enables early movement, and simplifies the treatment process. The present study's patient population was primarily middle-aged, with 41% between 41-50 years and 26% between 51-60 years. Males accounted for 63% of the cohort, while females made up 37%. This demographic pattern is consistent with existing research on distal femur fractures. For instance, Handolin et al. (2004) found a similar male predominance in their study of 46 retrograde intramedullary nailing procedures(9). Our study's age distribution shows a slightly different pattern compared to Hierholzer et al. (2011), who reported an average age of 54 and a broader age range (17-89 years) in their comparison of retrograde nailing and LISS.(10) The larger number of middle-aged participants in our study may indicate a local trend of high-energy trauma affecting working-age individuals. The fracture distribution in our study showed a high prevalence of Type A fractures (94%), primarily A1 (45%) and A2 (38%), with Type C fractures being less frequent (6%). This pattern is consistent with existing research, including Gill et al. (2017) and Markmiller et al. (2004), which reported extra-articular fractures as more common and often treated with retrograde nailing(11,12). Though not statistically significant (p=0.438), our study found road traffic accidents linked to more complications. This aligns with Frischknecht et al. (2011), who reported high-energy trauma causes more severe soft tissue damage, leading to higher complication rates(13). The lack of significant association suggests surgical technique and post-operative care may have reduced risks. Papadokostakis et al. (2005) highlighted proper technique and rehab protocols as key to minimizing complications, regardless of injury mechanism(14). Radiological outcomes were evaluated using the Rust score at 1, 3 and 6 months post-surgery, showing significant improvements over time. Age significantly impacted healing time, with older patients (60-70 years and >70 years) taking longer to heal (p<0.001). This aligns with existing knowledge on age-related bone healing decline. D'sa and Karuppiah (2019) found similar age-dependent healing patterns, attributing delays to reduced osteoblastic activity and vascular supply in older patients(15). Gender wasn't significantly linked to healing time (p=0.628), though males (25.9%) healed slightly faster than females (22.2%). This matches Gao et al. (2013), who found no gender-based healing time differences after retrograde nailing(16). Healing timelines seem more influenced by factors beyond gender. Post-operative complications weren't significantly linked to healing time (p=0.139), with most patients healing within expected times. This contrasts with Hoskins et al. (2016), who found complications like infection and fixation failure delayed healing (17). Our study's findings have key clinical implications. Retrograde nailing shows promise as a versatile treatment option for distal femur fractures, with good radiological outcomes across various patient groups. Its low complication rates, even in older patients, suggest it could be a preferred choice over less invasive plating systems for this population.

The findings of this study demonstrate that retrograde intramedullary nailing (RIN) is a reliable and effective treatment option for distal femur fractures, offering good radiological outcomes and low complication rates across various patient groups. The study's results show that RIN is associated with significant improvements in radiological outcomes, as evaluated by the Rust score, and facilitates early mobilization and weight-bearing, leading to improved functional recovery. The low complication rates, particularly in older patients, suggest that RIN could be a preferred choice over less invasive plating systems for this population. The results of this study can inform clinical decision-making and guide treatment planning for patients with distal femur fractures.

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