Osteoarthritis of the knee is an important public health concern. It leads to reduced functioning and affects the quality of life [1]. It presents with joint pain, inability to bear weight, reduced daily life efficacy in perfo rming routine activities, and noticeable osteophyte growth around the joint [2]. The prevalence of knee joint osteoarthritis in India is higher than worldwide which is 22-39 % [3]. For advanced stages, total knee arthroplasty is the treatment of choice. The total knee arthroplasty also known as total knee replacement [TKR] is a secure procedure in which the joint is replaced by metal components leading to improvement in ambulation and decrease in pain [4]. There are many procedures for this surgery with medial parapatellar approach being the most common one, as it provides exceptional visualization but it compromises the quadriceps muscle and peripatellar blood supply which leads to a complication of pain in anterior part of the knee, reduced extension of the knee joint and avascular necrosis [5]. With the introduction of minimally invasive techniques a hold of these complications is made with promising clinical outcomes. The subvastus approach was first introduced by Erkes in 1929 and made popular by Hoffman in 1991[6]. It has an advantage to keep the quardiceps tenson intact without compromising the blood vessels of patella by avoiding injury to the articular branch of the descending geniculate artery, which connects the patellar plexus with the medial superior geniculate artery, also the need for lateral release is reduced because it maintains the extensor mechanism [7]. There are various researches, these include the study by Abdalrahman et al.(2022) [8], Varela-Egocheaga et al.,[9], Shen et al.,(2007) [10] and Teng et al., which concluded that subvatus approach has better outcomes than parapetallar in terms of noticeable advantage in Knee society scores. In the study by Cila et al., the results have shown that subvatus approach have greater improvement in quadriceps strength in comparison to parapetallar. The objective of our study is to carry out a retrospective study in patients with osteoarthritis, operated with total knee replacement at our tertiary center to compare between subvastus and standard parapatellar approach. The outcome will be compared based on Knee society scores (KSS) of two groups and Straight leg raise, post-operatively at 2 weeks, 1 month and 3 months.

This is a retrospective study performed at our tertiary care center in Punjab, India. We gathered data from patients who were admitted with end-stage knee osteoarthritis for the procedure of total knee replacement, from October 2024 to December 2024. The study comprised 31 patients of either gender, within the age group 50-80 years. Out of 31 patients 16 patients underwent parapatellar approach, out of which 9 had unilateral right TKR and 7 had unilateral left total knee replacement while other 15 cases were managed with subvastus approach, 8 operated on unilateral right knee and 7 on unilateral left. Patients included in the study were (a) aged between 50-80 years with no gender restrictions; (b) cases operated with end-stage osteoarthritis; Exclusion criteria included (a) cases with low ejection fraction <30%; (b) Patients with knee flexion contractures greater than 10 degrees, varus deformities greater than 20 degrees, valgus deformities greater than 10 degrees; (c) body mass index exceeding 40 kg/m²; (d) those who have previously undergone knee surgery; (e) those who had neuroskeletal deformity; (h) cases who had active infection at site of operation or near-by. After applying the necessary criterias, sample size was calculated which is 31. These were divided into two groups, group-1 and group-2. Group-1 consisted of patients who underwent medial parapatellar approach (Control group), while Group-2 included patients who had subvastus approach (MIS group). No differences were found between the groups related to the following preoperative parameters: age, gender, weight, body mass index, preoperative hemoglobin values, preoperative global Knee Society score, objective or functional scores, preoperative range of motion (ROM), and preoperative long-leg knee axis. All procedures were carried out by the same surgeon. Minimally invasive procedures were carried out using the modified subvastus technique as outlined by Boerger and colleagues. The patient was positioned in a standard manner, with a tourniquet applied around the upper thigh. To guarantee hemostasis, the tourniquet was increased at the start of the surgery and removed once the last components were positioned. From the patella's superior pole down to just below the joint line, a longitudinal skin incision was created in the middle of the patella at a small medial angle. Along the lower border of the vastus medialis and the medial side of the patella, an inverted L-shaped arthrotomy was made. Using a specifically made extramedullary guide with a 5-degree posterior slope, the tibial osteotomy was carried out first. A specially made minimally invasive intramedullary guide was then used to prepare the femur, combining the previously measured valgus (from long-leg radiographs) with a 3-degree external rotation. The patients included in the standard surgery group were operated on using the classic medial parapatellar approach with patellar eversion. All patients received prophylaxis to prevent infection by administering 2 g of cefoperazone 1 hour before surgery, followed by 1 g every 8 hours for 24 hours. For deep venous prophylaxis, 40 or 60 mg of enoxaparin was given 12 hours before surgery and then every 24 hours for 1 week. All patients adhered to the same postoperative protocol. Ambulation and knee range of motion exercises began the day after surgery. No rapid recovery protocol was implemented for any patient. Pain medication was provided only if needed, following this protocol: 1 ampoule of tramadol in 100 ml of normal saline every 8 hours. After hospital discharge, the patients were reviewed at 2 weeks, 1 month and 3 months. In assessing early recovery the Straight leg test, strength of quadriceps and range of motion (ROM) was measured. To measure the range of motion, the same goniometer was utilized for all patients. Functional outcomes between the groups were compared using the Knee Society score (KSS), which was assessed at 2 weeks, 1 month, and 3 months. Both the KSS and its components, objective and functional were analyzed. Lastly, the range of motion (ROM), measured by the goniometer, was evaluated independently at 2 weeks, 1 month, and 3 months for its specific relevance to knee function. The data was analyzed using the SPSS 16.0 statistical program. Descriptive statistics such as mean, standard deviation, frequency, and percentage were used to summarize the findings. Using the t-test to compare means, a statistical comparison of quadriceps function will be done between the two groups. A P-value below 0.05 is deemed to be significant.

Total 31 patients were a part of the study. 16 in Group-1 and 15 in Group-2. Out of 31 participants, the majority were female, 20 in number (64.5%). 32.2% cases belonged to the age group 50-60 years, 48.3% were of 61-70 years and 16.1% were aged 71-80 years. The proportion of females was more in Group-2 in contrast to Group-1. The BMI of all cases in average was 33.35 ± 6.65. During the follow up, 66.7 % of Group-2 cases showed earlier achievement of active straight leg raise (SLR) compared to 43.7% of Group-1 cases by the end of 2-weeks. The results remained significant even at the end of 1 month with 86.66% of Group 2 and 68.7% of Group-1 with active SLR. During the follow up of all cases beyond first two weeks, it was seen that the range of motion and strength of quadriceps was significantly superior in those who under subvastus approach than medial parapettelar approach, due to sparing of quadriceps muscle in subvastus technique. The data obtained had clearly shown that faster recovery is seen in the subvastus group. The Oxford Knee Score (OKS): By the end of 2 weeks, the mean OKS was significantly higher in Group-2 (56.6_+7.45) than Group-1 (49.9_+5.96), p-value = 0.015. At 1 month the difference increased and the trend remained significant, with mean scores of 66.8_+4.13 contrary to 56.8_+3.64 (p-value< 0.001). At 3 months, subvastus group remained significantly superior (75.9_+3.07) compared to medial parapatellar group (66.5_+3.69; p <0.001). Independent Samples T-Test Table 1 OKS T-tests Statistic df p Mean difference SE difference 2 OKS Student's t 2.59 29.0 0.015 6.26 2.41 1 OKS Student's t 7.20 29.0 <0.001 10.05 1.40 3 OKS Student's t 7.66 29.0 <0.001 9.37 1.22 Group Descriptives Table 2 OKS Group N Mean Median SD SE 2 OKS 1 15 56.2 54.0 7.45 1.923 2 16 49.9 49.0 5.96 1.490 1 OKS 1 15 66.8 66.0 4.13 1.065 2 16 56.8 56.0 3.64 0.911 3 OKS 1 15 75.9 76.0 3.07 0.792 2 16 66.5 66.0 3.69 0.922 Plots 2 Week OKS Figure 1: 2 weeks OKS comparison 1 Month OKS Figure 2: 1 month OKS comparison 3 Month OKS Figure 3: 3 months OKS comparison The Functional Knee Score (FKS): At 2 weeks, there was no significant difference between the mean FKS of both the groups. However, at the end of 1 month the subvastus group had superior mean FKS (63.9_+3.81) in contrast to group-1 of medial parapatellar approach (56.5_+3.76; p<0.001). This pattern was maintained at 3 months (75.2_+4.59 vs 65.4_+3.63; p<0.001). Independent Sample T-test Table 3 FAS T-tests Statistic df p Mean difference SE difference 2 FAS Student's t 0.989 29.0 0.331 1.94 1.96 1 FAS Student's t 5.414 29.0 <0.001 7.37 1.36 3 FAS Student's t 6.636 29.0 <0.001 9.83 1.48 Group descriptives Table 4 FAS Group N Mean Median SD SE 2 FAS 1 15 48.1 48.0 6.12 1.581 2 16 46.1 46.0 4.76 1.190 1 FAS 1 15 63.9 64.0 3.81 0.985 2 16 56.5 56.0 3.76 0.940 3 FAS 1 15 75.2 74.0 4.59 1.184 2 16 65.4 64.0 3.63 0.908 Plots 2 Weeks FAS Figure 4: 2 weeks FAS comparison 1 Month FAS Figure 5: 1 month FAS comparison 3 Month FAS Figure 6: 3 months FAS comparison Independent Sample T-Tests Table 5 FAS T-tests Statistic df p 2 FAS Student's t 0.989 29.0 0.331 1 FAS Student's t 5.414 29.0 <0.001 3 FAS Student's t 6.636 29.0 <0.001 Complications Neither group experienced any significant side effects, including infection, implant failure, or deep vein thrombosis (DVT). However, Group 1 patients reported slight anterior knee pain, whereas Group 2 patients did not record any such complaints. Summary of Findings When compared to the conventional medial parapatellar technique (Group 1), the subvastus method (Group 2) was linked to better functional results, faster recovery, increased quadriceps strength, and better range of motion. These findings imply that the subvastus approach is a better choice for patients having total knee arthroplasty (TKA) because it provides notable benefits in the early postoperative phase.

Less invasive procedures are becoming accessible nowadays for total knee replacement. The quadriceps sparing method in TKR was first introduced by Tria et al., this technique is minimally invasive without affecting eversion of patella and functioning of quadriceps[11]. Many studies including Scuderi et al. [12], Roysam and Oakley [13], and Schroer et al. [14] justified that subvastus is truly quadriceps sparing. However, in contrast to our study there are researches by Kim et al., Chiang et al., Varnell et al. and Lin et al. which favored medial parapatellar approach. [15,16,17,18]. Our study showed significant advantages in FKS, OKS, SLR and ROM among subvastus operated cases over the standard technique. Another study by Fauré et al. reported that subvastus approach has greater postoperative muscle strength [19]. A blinded study by Boerger et al., on nonrandomised 120 cases concluded that minimally invasive methods had better outcomes in terms of postoperative pain and recovery [20]. Post-operative satisfaction of patient depends on the strength of the muscle that is related in the surgery. As the conventional surgical approach deals with incision of the quadriceps tendon to expose the inner side of knee joint, this procedure hampers the function of knee extension. Whereas, it is preserved in subvastus approach.[21] The later saves the blood supply of patella, stability of patellofemoral joint, and decreases the damage to capsule by not everting the patella. This also helps in alleviating the pain. [22] In our study we reported similar results in regard to knee functioning post-operatively. There is also decreased damage to muscles, collateral ligaments, soft tissues, and bursas in group-2 cases thus increasing the satisfaction of patient. The subvastus approach is associated with early recovery surgery since the patient has better ability to perform functional activities because of good muscle strength and better range of motion which further enhances blood circulation and decreases the cardiovascular complications. To further decrease the incidence of deep vein thrombosis and pulmonary embolus, anticoagulants are added after the surgery.[23] This surgery is a success only if performed by experienced and expert surgeons else it has some disadvantages as reported by Shang et al., [24] which includes violent traction, injury to collateral ligaments, injury to subpatellar bursa and soft tissues, misplacement of prosthesis, and increase risk of infection if performed by a inexperienced surgeon. Our study adds contribution to the literature data available of parapatellar vs subvastus approach for total knee replacement surgery, especially in North India.

The subvastus approach deals with quicker recovery, gain of function of knee, and reduction in hospital stay duration in comparison to traditional parapatellar approach in Total knee arthroplasty.

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