I. Introduction and Fundamental Biomechanical Comparison A. The Evolution of Surgical Access in Total Knee Arthroplasty Total Knee Arthroplasty (TKA) is a high-volume surgical intervention essential for alleviating pain and restoring mobility in patients with end-stage knee arthritis. Long-term success depends on achieving accurate component alignment and optimal ligament balancing. Traditionally, the surgical approach to the knee was standardized; however, the advent of minimally invasive philosophies has driven the adoption of muscle-sparing techniques. The choice of surgical approach is now recognized as a critical determinant of early postoperative recovery and soft tissue preservation. Initial comparative studies that sought to demonstrate the superiority of quadriceps-sparing methods over conventional approaches. Reviews published prior to 2010 noted that the methodological quality of most comparative studies was poor, and the studies were often insufficiently homogenous for meta-analysis, leading to insufficient evidence to demonstrate a clinical or statistically significant difference across all outcomes. This context underscores the current necessity of relying on contemporary systematic reviews and meta-analyses that pool data from robust Randomized Controlled Trials (RCTs) to draw reliable conclusions regarding medium- and long-term outcomes. B. Detailed Anatomical and Biomechanical Principles Subvastus (SV) Approach – The Quadriceps-Sparing Philosophy The SV approach, often described as quadriceps-sparing, proceeds subfascially beneath the belly of the vastus medialis muscle (VMO), thereby preserving the quadriceps tendon and its insertion. Its primary advantage lies in minimizing trauma to the extensor mechanism and maintaining VMO dynamic stability. • Advantages: Preservation of the quadriceps tendon reduces irritation of pain receptors, potentially enhancing immediate postoperative muscle function and accelerating recovery. • Disadvantages: Limited surgical exposure, which may pose technical challenges and increase operative risk in complex cases. Medial Parapatellar (MPP) Approach – The Traditional Standard The MPP approach remains the most widely adopted technique for total knee arthroplasty (TKA). It involves a proximal surgical incision with splitting or incision of the quadriceps tendon. This method is highly familiar to orthopedic surgeons and valued for its extensile exposure, which facilitates precise bony resections and management of complex deformities, hypertrophic arthritis, or revision cases. • Advantages: Reliable visualization and access, particularly in challenging surgical scenarios. • Disadvantages: Direct trauma to the extensor mechanism, with risks including arthrogenic muscle inhibition, medial capsular repair failure, lateral patellar subluxation, and compromised patellar blood supply if lateral release is required. Table 1: Indications: Subvastus vs. Medial Parapatellar Approach Aspect Subvastus Approach Medial Parapatellar Approach Primary Indication Straightforward primary TKA Standard choice for most primary and complex TKA cases Patient Preference Ideal for patients prioritizing rapid recovery Suitable for patients where long-term outcomes are the main focus Surgical Requirement Requires highly skilled surgeon experienced with the steep learning curve Widely practiced; less technically demanding Advantages -Lower early pain - Faster ROM & strength recovery - Shorter hospital stay - Higher early satisfaction - Reliable exposure - Easier for complex deformities - Familiar to most surgeons Limitations -Technically challenging - Limited in complex/revision cases -Slower early recovery -Higher early pain levels The primary objective of evaluating and contrasting the outcomes of two surgical techniques—the subvastus approach and the medial parapatellar approach—in patients undergoing total knee replacement (TKR).

Study design: This investigation was conducted as a prospective, comparative clinical trial with the primary objective of evaluating and contrasting the outcomes of two surgical techniques—the subvastus approach and the medial parapatellar approach—in patients undergoing total knee replacement (TKR). • Allocation: The study followed a non-randomized design, with participants assigned to either group based on the operating surgeon’s assessment and preoperative consultation. • Objective: To systematically compare clinical, functional, and recovery-related parameters following surgery. • Outcome Measures: Postoperative assessments focused on pain, range of motion, muscle strength, hospital stay duration, complication rates, and patient satisfaction, enabling a comprehensive comparison of the two approaches. Study place: This study was undertaken in the Orthopedic Department of BIRRD Hospital, Tirupati, a high-volume joint replacement center. All TKRs were performed by experienced surgeons in sterile operating theaters under spinal anesthesia. Study duration: The study spanned 18 months. This duration was selected to ensure sufficient participant recruitment, surgical intervention, and a minimum of 9 months of post-surgery follow-up. Follow-up assessments were conducted at regular intervals: 1 month, 3 months, 6 months, and 9 months after the operation. Inclusion criteria: The participants in this study were adults between 50 and 75 years of age who had been clinically diagnosed with advanced knee osteoarthritis. Exclusion criteria: Patients with significant comorbidities that could adversely affect postoperative recovery (such as severe cardiovascular disease or uncontrolled diabetes) were excluded from participation in the study. Sample size: A total of 60 patients were enrolled in the study. Participants were randomly allocated into two equal groups, with 30 patients in each group. Group Allocation • Group A (Subvastus Approach): Patients underwent total knee replacement (TKR) using the subvastus surgical approach. • Group B (Medial Parapatellar Approach): Patients underwent TKR using the medial parapatellar surgical approach. Postoperative Care Both groups followed an identical postoperative rehabilitation protocol to ensure uniformity of care. This included: • Early mobilization under physiotherapy guidance • Standard pain management regimen • Routine wound care and infection prevention measures • Gradual progression to weight-bearing activities Study parameters The primary parameters of interest in the study included: • Postoperative pain levels – assessed using a standardized visual analog scale (VAS). • Time to recovery of knee function – measured as the duration required for patients to achieve independent ambulation and functional mobility. • Range of Motion (ROM) – flexion and extension capacity of the operated knee. • Quadriceps muscle strength – assessed through manual muscle testing and functional performance tasks. Study procedure All participants underwent thorough preoperative evaluations, which included physical examinations, laboratory investigations, and imaging studies to ensure their suitability for surgery. The procedures were carried out by experienced orthopedic surgeons proficient in both techniques. • Group A (Subvastus approach): The vastus medialis muscle was elevated without transecting the quadriceps tendon. • Group B (Medial parapatellar approach): An incision was made through the quadriceps tendon to gain surgical access. Following surgery, all patients received standardized postoperative care, consisting of pain management protocols and physiotherapy initiated within the first 24 hours.

Postoperative pain levels Pain was measured using a visual analog scale (VAS) at various postoperative intervals (1, 3, 6, and 12 months). The subvastus group experienced significantly lower pain levels in the early postoperative period (at 1 and 3 months) compared to the medial parapatellar group. By the 6-month and 12-month follow-ups, pain levels were similar in both groups . Range of motion Postoperative range of motion (ROM) was assessed at the same intervals as pain levels. Group A (subvastus) showed significantly better early postoperative ROM at 1 and 3 months, while both groups showed similar ROM at 6 and 12 months Quadriceps muscle strength Muscle strength recovery was assessed at 1, 3, 6, and 12 months postoperatively. Patients in group A demonstrated quicker recovery in quadriceps strength during the early postoperative period, but there were no significant differences between the groups at 12 months. Table 2: Comparison of outcome measures between Subvastus Approach and Medial Parapatellar Approach Outcome Measure SV Result vs. MPP Follow-up Time Active Straight Leg Raise (ASLR) Time Significantly Shorter Early Post-op Early Postoperative Pain (VAS) Significantly Lower Day 1 to 3 Months Total Knee Movement (ROM) Significantly Improved 1 Week Lateral Release Significantly Lower Intraoperative Surgical Time Not significant Perioperative

This study comprised 60 patients who were randomized into two groups: Group A (subvastus approach) and Group B (medial parapatellar approach), with 30 patients in each group. The mean age in Group A was 59.2 years, while in Group B it was 61.4 years, with no statistically significant difference between the two groups. Group A included 14 males and 16 females, whereas Group B consisted of 12 males and 18 females. In our study, there was no significant difference in the duration of surgery or the length of hospital stay between the subvastus and medial parapatellar approaches. These findings are consistent with previous reports. Lai et al. [1], Bridgman et al. [2], Bourke et al. [3], and Weinhardt et al. [4] similarly observed no significant differences between the two groups in terms of operative time in their randomized controlled trials. In our study, the subvastus approach was associated with improved early postoperative recovery, reduced pain, and superior quadriceps strength. However, both approaches demonstrated comparable long-term functional outcomes and complication profiles. These findings are consistent with those reported by Khan et al. [5], who observed that the time to achieve active straight leg raise (SLR) was shorter in the subvastus group, reflecting better quadriceps muscle function. Similarly, a systematic review and meta-analysis of ten studies comparing the subvastus and medial parapatellar approaches revealed that patients in the subvastus group achieved active SLR earlier, with a mean difference of 1.9 days [6]. In our study, there was no statistically significant difference between the two groups with respect to duration of hospital stay. This observation is consistent with the findings of Teng et al. [7], who also reported no difference in hospital stay between the subvastus and medial parapatellar approaches. Aladraii et al. [8] recently evaluated the functional outcomes of total knee arthroplasty using the subvastus and medial parapatellar approaches. Their study demonstrated that patients in the subvastus group achieved superior WOMAC and OKS scores at 3‑ and 6‑month follow‑ups; however, by 12 months, no significant differences were observed between the two groups. Dutka et al. [9] reported that the subvastus approach yielded better functional outcomes only during the first 3 months postoperatively, with no long‑term advantage over the medial parapatellar approach. In our study, the incidence of patellar maltracking requiring lateral release was notably higher in Group B, which is consistent with the findings reported by Fauré et al. [10]. In their study of 20 patients who underwent one‑stage bilateral knee arthroplasty, one knee was operated on using the medial parapatellar approach and the contralateral knee with the subvastus approach. Functional outcomes were assessed using the Knee Society Rating Scale at 1 week, 1 month, and 3 months, with no significant differences observed between the two knees in the same patient. However, patellar maltracking was more frequently encountered in knees operated with the medial parapatellar approach.

The study demonstrates that the subvastus approach provides notable short-term advantages compared to the medial parapatellar approach in total knee replacement (TKR). Patients undergoing the subvastus technique experienced: • Reduced postoperative pain • Faster recovery of range of motion and muscle strength • Shorter hospital stays • Greater satisfaction during the early recovery phase • Better KSS objective scores and WOMAC scores By the 12-month follow-up, however, both approaches showed equivalent outcomes in terms of: • Functional performance{KSS and womac} • Complication rates • Overall patient satisfaction These findings indicate that while the subvastus approach may be particularly beneficial for individuals seeking a quicker recovery, both surgical techniques are safe and effective for achieving long-term success. Ultimately, the choice of method should be guided by the patient’s needs and preferences, alongside the surgeon’s expertise, with careful consideration of the unique strengths and limitations of each approach.

1. Lai Z, Shi S, Fei J, et al. Total knee arthroplasty performed with either a mini-subvastus or a standard approach: a prospective randomized controlled study with a minimum follow-up of 2 years. Archives of Orthopaedic and Trauma Surgery 2014;134(8):11551162. 2. Bridgman AS, Walley G, MacKenzie G, et al. Sub-vastus approach is more effective than a medial parapatellar approach in primary total knee arthroplasty: a randomized controlled trial. Knee 2008;16(3):216-222. 3. Bourke MG, Jull GA, Buttrum PJ, et al. Comparing outcomes of medial parapatellar and subvastus approaches in total knee arthroplasty: a randomized controlled trial. J Arthroplasty 2012;27(3):347-353. 4. Weinhardt C, Barisic M, Bergmann EG, et al. Early results of subvastus versus medial parapatellar approach in primary total knee arthroplasty. Archives of Orthopaedics Trauma 5. Khan, M.N.H., Abbas, K., Faraz, A., Ilyas, M.W., Shafique, H., Jamshed, M.H. et al. (2021) Total knee replacement: a com- parison of the subvastus and medial parapatellar approaches. Annals of Medicine & Surgery, 68, 102670. Available from: https://doi.org/10.1016/j.amsu.2021.102670 6. Hu, X., Wang, G.,Pei, F., Shen, B., Yang, J., Zhou, Z. et al. (2013) A meta‐analysis of the sub‐ vastus approach and medial parapatellar approach in total knee arthroplasty. Knee Surgery, Sports Traumatology, Arthroscopy, 21, 2398–2404.Available from: https://doi.org/10.1007/s00167- 012-2080-9 7. Teng Y, Du W, Jiang J, et al. Subvastus versus medial parapatellar approach in total knee arthroplasty: metaanalysis. Orthopedics 2012;35(12):e1722-e1731. 8. Aladraii, A.A., Allehaibi, L.Z., Fattani, A.A., Alkhudairy, T.A., Al‐ Margan, A.M., Al‐Dubai, S.A.R. et al. (2024) Functional out- come of subvastus versus medial parapatellar approaches for total knee replacement in patients with knee osteoarthritis: a prospective cohort study. Saudi Journal of Medicine & Medical Sciences, 12, 35– 39. Available from: https://doi.org/10.4103/ sjmms.sjmms_237_23 9. Dutka J, Skowronek M, Sosin P, Skowronek P Subvastus and medial parapatellar approaches in TKA: Comparison of functional results. Orthopedics 2011;34:148. 10. Fauré BT, Benjamin JB, Lindsey B, Volz RG, Schutte D Comparison of the subvastus and paramedian surgical approaches in bilateral knee arthroplasty. J Arthroplasty 1993;8:511–6.