Abstract
Objective
This study aims to compare the short-term efficacy of the Mako robot-assisted modified subvastus approach (MA-MSVA) with the conventional medial parapatellar approach (MPA) in total knee arthroplasty (TKA).
Methods
This study included 275 patients who underwent TKA between May 2024 and May 2025, divided into the MA-MSVA group (n = 78), the MSVA group (n = 74), and the MPA group (n = 123). The three groups were compared in terms of early postoperative prosthesis alignment accuracy: mechanical tibiofemoral angle, mechanical lateral distal femoral angle, medial proximal tibial angle, lateral femoral component (the flexion angle of the femoral implant), lateral tibial component (the slope angle of the tibial implant) and outlier rates; clinical outcomes: International Knee Documentation Committee, five-level EuroQol five-dimensional questionnaire (EQ-5D-5 L), knee society score (KSS), visual analog scale (VAS) and range of motion (ROM); quadriceps muscle strength: knee extensors (KE ) and knee flexors (KF), and muscle injury markers: creatine kinase (CK) and lactate dehydrogenase.
Results
The MA-MSVA group demonstrated significantly superior prosthesis alignment accuracy compared with MSVA and MPA groups (P < 0.05), with the lowest outlier rate. On postoperative days (POD) 1 and 14, the MA-MSVA group demonstrated better outcomes in EQ-5D-5 L, KSS, VAS, and ROM than the other two groups (P < 0.05). Muscle injury in POD 1 was less severe (lower CK values), and muscle strength recovery was faster (higher KE and KF) within 30 days postoperatively in the MA-MSVA group. The MSVA group outperformed the MPA group in terms of early functional recovery and muscle strength recovery; however, its alignment accuracy was similar to that of the MPA group.
Conclusion
MA-MSVA significantly enhances prosthesis alignment accuracy, accelerates early functional recovery, reduces pain, and promotes quadriceps strength recovery following TKA. While MSVA provides advantages in functional recovery over MPA, its alignment accuracy remains comparable. MA-MSVA technique, by combining precision with minimally invasive benefits, aligns with the enhanced recovery after surgery concept and merits clinical application.
Level of evidence
Level III, retrospective cohort study.
Supplementary Information
The online version contains supplementary material available at 10.1186/s13018-025-06619-w.
Keywords: Enhanced recovery after surgery, Modified subvastus approach, Mako robotic-assisted, Total knee arthroplasty, Quadriceps strength
Background
End-stage knee osteoarthritis is one of the leading causes of disability among the middle-aged and elderly population globally. In 2021, approximately 607 million people worldwide were affected by osteoarthritis, representing 7.7% of the global population. The age-standardized years lived with disability rate was 244.5, the age-standardized prevalence rate was 6,967.29, and the age-standardized incidence rate was 535 [1]. Its high prevalence, years lived with disability rate, and steadily increasing incidence contribute to substantial health loss and economic burden [2–4].
Total knee arthroplasty (TKA) is the gold standard surgical treatment for end-stage knee osteoarthritis, providing significant improvement in joint function. With the widespread adoption of the enhanced recovery after surgery (ERAS) concept, ERAS protocols for TKA have gained increasing attention [5, 6]. However, some patients continue to experience persistent pain and poor functional recovery following surgery [7], problems may be associated with soft tissue trauma from the traditional medial parapatellar approach (MPA) [8]. Consequently, developing more refined and minimally invasive surgical techniques has become a crucial direction for enhancing TKA outcomes.
As a classic approach, MPA provides excellent surgical exposure but requires a vertical incision on the medial boundary of the quadriceps tendon and patellar eversion, which affects the extensor mechanism and may result in complications, including anterior knee pain and extensor mechanism insufficiency [9–11]. Consequently, the subvastus approach (SVA) [12] and the mini-SVA (Mini-SVA) [13] have been developed to preserve the integrity of the extensor mechanism, thereby reducing early postoperative pain, accelerating recovery of the straight-leg raise, and improving short-term joint mobility [14]. However, these approaches still have limitations, including difficult surgical exposure and a steep learning curve, especially in severely obese patients or those with significant flexion contractures, potentially increasing operative time and revision risk [15–17].
Accordingly, we designed a modified SVA (MSVA) based on the traditional SVA. This approach utilizes a two-segment skin incision design (approximately 12–15 cm in length) with reduced subcutaneous dissection, which enhances exposure efficiency at the inferior border of the vastus medialis muscle while minimizing soft tissue trauma and reinforcing the minimally invasive nature. Furthermore, MSVA involves incising the vastus medialis fascia followed by blunt dissection, retracting the vastus medialis muscle, and adjusting the suprapatellar pouch incision site, thereby improving patellar mobility while fully preserving the integrity of the muscle belly. The application of a dynamic mobile window technique enhances operational feasibility, enabling MSVA to provide adequate exposure without the need for special instruments while effectively protecting the extensor mechanism (Fig. 1).
Fig. 1.
Surgical technique of MA-MSVA. a The approach utilized a two-segment skin incision design: A midline skin incision from the medial tibial tubercle to the medial midpoint of the patella, and another incision from the medial patellar midpoint parallel to the inferior border of the vastus medialis muscle (approximately 50°). b Retraction of the vastus medialis with incision of the suprapatellar pouch at the midpoint of its inferior border. c, d Femoral and tibial fixation pins and dynamic trackers were inserted extracapsularly on the medial femoral side and below the tibial tubercle. e–j Intraoperative osteotomy was conducted using the MAKO system. k–m Procedure for implant installation. n, o The capsule and fascia were repaired anatomically. p, q An intra-articular injection of 2 g of tranexamic acid was administered, and the incision was closed
Recently, robotic-assisted systems such as Mako have introduced a higher level of precision, minimal invasiveness, and reproducibility to TKA. Studies have indicated that Mako robotic-assisted (MA) TKA can reduce postoperative pain, significantly improve prosthesis alignment accuracy, optimize sagittal alignment, and accelerate postoperative functional recovery [18–24]. Consequently, we attempted to combine the precision of the Mako system with the minimally invasive concept of MSVA, termed MA-MSVA, to systematically compare its outcomes and the differences between MA-MSVA and MPA in prosthesis alignment accuracy and short-term efficacy. This comparison is essential for refining the TKA evaluation system and promoting standardized application of the technique.
Based on the limitations of the current short-term efficacy evaluation system for TKA performed with MA-MSVA, this study proposes the following core hypothesis: Compared to MPA, MA-MSVA achieves a synergistic optimization of precision and minimally invasive surgery, significantly improving early knee flexion range of motion, reducing pain, enhancing prosthesis alignment accuracy, and accelerating quadriceps strength recovery during the early postoperative period.
Therefore, this retrospective cohort study aims to compare the short-term efficacy of MA-MSVA, MSVA, and MPA within 30 days after TKA, focusing on joint function, pain control, quadriceps strength recovery, and prosthesis alignment accuracy, to offer high-level evidence supporting the clinical application of MA-MSVA.
Materials and methods
A retrospective analysis was conducted on patients who underwent TKA at our hospital between May 2024 and May 2025. The inclusion criteria comprised patients undergoing unilateral TKA for end-stage knee osteoarthritis. Exclusion criteria included the following: [1] Neuromuscular dysfunction (paralysis, myolysis, or myasthenia); [2] history of previous knee injury or surgery; [3] posterior cruciate ligament injury or dysfunction, rheumatoid arthritis, traumatic arthritis, or peri-knee tumors; [4] knee infection; [5] poor imaging quality or incomplete data. A total of 275 patients were included and divided into three groups based on the use of MA and the surgical method: The MA-MSVA group (n = 78), the MSVA group (n = 74), and the MPA group (n = 123; Fig. 2).
Fig. 2.
Flowchart for patient analysis
Clinical data and techniques
All surgeries were performed by two experienced TKA surgeons who had completed the learning curve. All patients followed ERAS principles (Supplementary Table 1). A tourniquet was applied before skin incision and released following capsular closure in all cases; no drainage was used. The Triathlon CR fixed-bearing prosthesis (Stryker, USA) was used in all three groups.
MA-MSVA surgical technique
Preoperative CT scans of the knee were obtained, and 3D reconstruction models and preoperative plans were created using Mako Total Knee software. The approach employed a two-segment skin incision design: A midline skin incision from the medial tibial tubercle to the medial midpoint of the patella, and the second incision from the medial patellar midpoint running parallel to the inferior border of the vastus medialis muscle (approximately 50°; Fig. 1a). The vastus medialis fascia was incised, but the muscle belly was left intact; instead, it was separated from the surrounding fascia and retracted laterally. The suprapatellar pouch was then incised at its midpoint, with the vastus medialis retracted (Fig. 1b). The patella and extensor mechanism were retracted laterally without eversion, and the mobile window technique was used to achieve adequate exposure. Femoral and tibial fixation pins and dynamic trackers were inserted extracapsularly at the medial femoral side and below the tibial tubercle (Figs. 1c, d). Intraoperative dynamic tracking, gap calculation, and coronal alignment were performed using the MAKO system software. Planned bone resections were recorded following initial registration, and osteotomy proceeded according to the plan (Figs. 1e–j). Osteotomy completion was confirmed in the navigation interface when the green zone of the planned cut was entirely removed. Additional capsular or ligament releases were performed as needed. Following osteotomy, trial implants were placed to assess knee mobility and stability. The femoral and tibial trackers and pins were removed, and the final implants were inserted (Figs. 1k–m), followed by anatomical repair of the capsule and fascia (Figs. 1n-o). Intra-articular injection of 2 g tranexamic acid was administered, and the incision was closed (Figs. 1p–q).
MSVA surgical technique
The MSVA method was used to obtain adequate surgical exposure, followed by TKA utilizing conventional instruments.
MPA surgical technique
In the MPA group, a standard anterior midline skin incision was made, approximately 12–15 cm long, extending from the tibial tubercle to 4–7 cm proximal to the higher pole of the patella. An arthrotomy was performed proximally along the junction between the vastus medialis obliquus and the quadriceps tendon. The capsule was incised distally along the medial border of the patella and the patellar tendon. Patellar eversion was performed to achieve adequate exposure, and TKA was completed utilizing conventional instruments.
Outcome measures
Clinical outcome assessment
Operative duration and tourniquet duration were reported for all three groups. The International Knee Documentation Committee (IKDC) score was recorded preoperatively and on postoperative day (POD) 30. The five-level EuroQol five-dimensional questionnaire (EQ-5D-5 L), knee society score (KSS), visual analog scale (VAS), and range of motion (ROM) were recorded preoperatively, on POD 1, POD 14, and POD 30 to assess knee function and pain.
Muscle injury and quadriceps strength assessment
The creatine kinase (CK) and lactate dehydrogenase (LDH) levels were measured preoperatively and on POD 1 to assess muscle injury. Quadriceps strength (knee extensors [KE] and knee flexors [KF]) was measured using a Hoggan microFET3 dynamometer (Hoggan Scientific, LLC, Salt Lake City, UT, USA) preoperatively, on POD 1, POD 14, and POD 30 (Fig. 3). The measurement approach for quadriceps strength was based on the report by Mentiplay et al. [25].
Fig. 3.
Schematic diagram of quadriceps muscle strength measurement. a Knee extensors: The patient sits with the hip and knee flexed at 90°. The dynamometer is placed on the anterior aspect of the distal lower leg, 5 cm proximal to the tip of the lateral malleolus. b Knee flexors: The patient sits with the hip and knee flexed at 90°. The dynamometer is placed on the posterior aspect of the distal lower leg, 5 cm proximal to the tip of the lateral malleolus
Radiographic assessment
Preoperative and postoperative full-length weight-bearing radiographs of the lower limbs were obtained for all patients. Images were digitized and analyzed using GE Healthcare Systems (Chicago, USA). Three orthopedic surgeons participated in the reliability test for radiographic measurements. A predetermined set of radiographs was presented in random order by a research assistant who was not involved in the study. Following the reliability assessment, the surgeons measured the radiographic parameters for all patients.
The following radiographic measurements were performed (Fig. 4): [1] mechanical tibiofemoral angle (mTFA, optimal 180°), mechanical lateral distal femoral angle (mLDFA, optimal 90°), and medial proximal tibial angle (MPTA, optimal 90°); [2] lateral femoral component (LFC) angle (optimal 11°, based on the characteristics of the prosthesis used in this trial and after consultation with clinicians); [3] lateral tibial component (LTC) angle (optimal 85°). Outliers were defined as a deviation of ≥ 3° from the optimal value for any of these angles.
Fig. 4.
Schematic diagram of radiological measurement principles [4]. Mechanical tibiofemoral angle (mTFA, optimal 180°), mechanical lateral distal femoral angle (mLDFA, optimal 90°), medial proximal tibial angle (MPTA, optimal 90°) [4]. Lateral femoral component (LFC) angle (optimal 11°, according to the characteristics of the prosthesis employed in this trial and following consultation with clinicians), lateral tibial component (LTC) angle (optimal 85°)
Statistical analysis
All data were analyzed using SPSS software (version 26.0; IBM, Armonk, NY, USA). Under the assumptions of single measurement and absolute agreement, a two-way random-effects model was applied, and the intraclass correlation coefficient (ICC) was employed to assess inter-observer reliability. Measurement data are described as mean ± standard deviation, and count data are described as frequency and percentage. If data followed a normal distribution with homogeneity of variance, one-way analysis of variance (ANOVA) and the LSD post-hoc test were employed to compare differences among three independent samples and between pairs within groups. For non-normally distributed data or data with unequal variances, the Kruskal–Wallis one-way ANOVA by ranks was used. For normally distributed repeated measures parameters within groups, one-way repeated measures ANOVA was used; otherwise, the Friedman test was employed. The chi-square test was used for categorical variables. A P < 0.05 was considered statistically significant.
Results
General information
The study included 275 patients: 78 in the MA-MSVA group, 74 in the MSVA group, and 123 in the MPA group. Non-significant differences were observed among the three groups in terms of age, gender, BMI, operation side, or K and L grade (P > 0.05; Table 1). Regarding inter-observer reliability, all radiographic measurements indicated excellent ICC values (Supplementary Table 2).
Table 1.
Demographic data for four groups
| Parameter | MA-MSVA(n = 78) | MSVA (n = 74) | MPA(n = 123) | P value |
|---|---|---|---|---|
| Age(y) | 71.45 ± 6.41(53–87) | 72.08 ± 6.76(48–88) | 73.07 ± 7.19(52–91) | 0.168 |
| Gender | ||||
| Male | 23(29.5%) | 24(32.4%) | 39(31.7%) | 0.917 |
| Female | 55(70.5%) | 50(67.6%) | 84(68.3%) | |
| BMI (kg/m2) | 25.94 ± 3.86 | 26.28 ± 3.93 | 25.95 ± 4.18 | 0.830 |
| Operation side | ||||
| Right | 41(52.6%) | 41(55.4%) | 66(53.7%) | 0.939 |
| Left | 37(47.4%) | 33(44.6%) | 57(46.3%) | |
| K-L grade | ||||
| Ⅲ | 32(41.0%) | 27(36.5%) | 48(39.0%) | 0.848 |
| Ⅳ | 46(59.0%) | 47(63.5%) | 75(61.0%) |
MA-MSVA, mako-robotic assisted modified subvastus approach; MPA, medial parapatellar approach; BMI, body mass index; K-L grade, Kellgren–Lawrence grade
Comparison of radiographic and prosthesis alignment accuracy
Preoperatively, non-significant differences were found among the three groups in mTFA, mLDFA, MPTA, or LTC (P > 0.05). Postoperatively, significant differences were observed among the groups (mTFA: 179.52 ± 2.04, 178.62 ± 2.45, and 178.45 ± 2.68, P = 0.008; mLDFA: 89.81 ± 1.29, 91.21 ± 2.02, and 91.06 ± 1.71, P < 0.001; MPTA: 90.27 ± 1.50, 89.17 ± 1.97, and 89.47 ± 2.18, P = 0.001; LFC: 11.70 ± 2.27, 9.95 ± 2.96, and 10.34 ± 3.35, P < 0.001; LTC: 85.34 ± 1.76, 83.26 ± 2.26, and 83.08 ± 2.46, P < 0.001). Moreover, the number of outliers postoperatively differed significantly among the groups (P < 0.05), with the MA-MSVA group having significantly fewer outliers compared to the other two groups (P < 0.05), while a non-significant difference was found between MSVA and MPA groups (P > 0.05; Table 2). In the MA-MSVA group, significant differences were found both pre- and postoperatively for mTFA, mLDFA, and MPTA (P < 0.001), but not for LTC (P > 0.05). In MSVA and MPA groups, significant differences were observed pre- and postoperatively for mTFA, mLDFA, MPTA, and LTC (P < 0.05; Supplementary Table 3). Pairwise comparisons of all postoperative radiographic parameters demonstrated significant differences between the MA-MSVA group and the other two groups (P < 0.05), but non-significant difference between MSVA and MPA groups (P > 0.05; Table 3). These findings indicate that the MA-MSVA group exhibits the best prosthesis alignment accuracy, while MSVA and MPA were similar.
Table 2.
Comparison of radiological and osteotomy accuracy among the three groups of patients
| Parameter | MA-MSVA(n = 78) | MSVA (n = 74) | MPA(n = 123) | P value |
|---|---|---|---|---|
| Preoperative | ||||
| mTFA(°) | 176.35 ± 6.45 | 176.23 ± 6.25 | 176.58 ± 6.36 | 0.951 |
| mLDFA(°) | 87.62 ± 3.12 | 88.32 ± 3.04 | 88.08 ± 9.27 | 0.095 |
| MPTA(°) | 86.61 ± 3.59 | 86.90 ± 3.52 | 86.42 ± 3.25 | 0.639 |
| LTC(°) | 85.15 ± 3.12 | 85.29 ± 2.93 | 85.23 ± 3.15 | 0.987 |
| Postoperative | ||||
| mTFA(°) | 179.52 ± 2.04 | 178.62 ± 2.45 | 178.45 ± 2.68 | 0.008 |
| Outlier(≥ 3°) | 5a(6.4%) | 20b(27.0%) | 34b(27.6%) | 0.001 |
| mLDFA(°) | 89.81 ± 1.29 | 91.21 ± 2.02 | 91.06 ± 1.71 | < 0.001 |
| Outlier(≥ 3°) | 4a(5.1%) | 14b(18.9%) | 21b(17.1%) | 0.024 |
| MPTA(°) | 90.27 ± 1.50 | 89.17 ± 1.97 | 89.47 ± 2.18 | 0.001 |
| Outlier(≥ 3°) | 4a(5.1%) | 15b(20.3%) | 24b(19.5%) | 0.010 |
| LFC (°) | 11.70 ± 2.27 | 9.95 ± 2.96 | 10.34 ± 3.35 | < 0.001 |
| Outlier(≥ 3°) | 8a(10.3%) | 23b(31.1%) | 43b(35.0%) | < 0.001 |
| LTC (°) | 85.34 ± 1.76 | 83.26 ± 2.26 | 83.08 ± 2.46 | < 0.001 |
| Outlier(≥ 3°) | 7a(9.0%) | 24b(32.4%) | 46b(37.4%) | < 0.001 |
MA-MSVA, mako-robotic assisted modified subvastus approach; MPA, medial parapatellar approach; mTFA, mechanical tibiofemoral angle; mLDFA, mechanical lateral distal femoral angle; MPTA, medial proximal tibial angle; LTC, lateral tibial component; LFC, lateral femoral component
a, b, If two subscript letters are the same, it indicates that there is a significant difference of 0.05 level among these categories; if they are different, there is no significant difference
Table 3.
Pairwise comparisons of three groups of radiological changes
| Parameter | Group | Group | P |
|---|---|---|---|
| Postoperative | |||
| mTFA(°) | MA-MSVA | MSVA | 0.008 |
| MA-MSVA | MPA | 0.005 | |
| MSVA | MPA | 0.886 | |
| mLDFA(°) | MA-MSVA | MSVA | < 0.001 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | 0.595 | |
| MPTA(°) | MA-MSVA | MSVA | < 0.001 |
| MA-MSVA | MPA | 0.005 | |
| MSVA | MPA | 0.196 | |
| LFC (°) | MA-MSVA | MSVA | < 0.001 |
| MA-MSVA | MPA | 0.001 | |
| MSVA | MPA | 0.521 | |
| LTC (°) | MA-MSVA | MSVA | < 0.001 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | 0.866 |
MA-MSVA, mako-robotic assisted modified subvastus approach; MPA, medial parapatellar approach; mTFA, mechanical tibiofemoral angle; mLDFA, mechanical lateral distal femoral angle; MPTA, medial proximal tibial angle; LTC, lateral tibial component; LFC, lateral femoral component
Comparison of surgical data and clinical outcomes
Significant differences were found among the three groups in operative duration and tourniquet duration (operative duration: 125.06 ± 24.94, 103.31 ± 19.01, and 106.04 ± 17.26, P < 0.001; tourniquet duration: 69.35 ± 14.60, 58.53 ± 12.54, and 59.89 ± 13.37, P < 0.001). Preoperatively, non-significant differences were identified among the groups in IKDC, EQ-5D-5 L, KSS, VAS, or ROM (P > 0.05). On POD 1, significant differences were observed in EQ-5D-5 L, KSS, VAS, and ROM (EQ-5D-5 L: 0.64 ± 0.09, 0.60 ± 0.10, and 0.56 ± 0.09, P < 0.001; KSS: 63.65 ± 11.52, 57.39 ± 8.67, and 51.88 ± 11.89, P < 0.001; VAS: 2.10 ± 0.64, 2.50 ± 1.01, and 2.96 ± 0.83, P < 0.001; ROM: 108.54 ± 10.34, 104.55 ± 8.94, and 99.47 ± 11.40, P < 0.001). Similarly, on POD 14, significant differences were found in EQ-5D-5 L, KSS, VAS, and ROM (EQ-5D-5 L: 0.82 ± 0.08, 0.75 ± 0.10, and 0.71 ± 0.11, P < 0.001; KSS: 77.64 ± 9.29, 72.67 ± 5.89, and 68.74 ± 6.44, P < 0.001; VAS: 0.90 ± 0.73, 1.24 ± 0.70, and 1.69 ± 0.78, P < 0.001; ROM: 116.15 ± 10.99, 110.95 ± 9.19, and 105.36 ± 12.42, P < 0.001). At the one-month postoperative follow-up, non-significant differences were observed among the groups (P > 0.05; Table 4; Fig. 5). Significant differences were found within each group between preoperative and postoperative clinical outcomes (P < 0.001; Supplementary Table 4). Pairwise comparisons of surgical data demonstrated that the MA-MSVA group exhibited significantly longer operative and tourniquet durations than the other two groups (P < 0.001), while no difference was found between MSVA and MPA groups (P > 0.05), indicating that MSVA did not increase operative or tourniquet time. For clinical outcomes on POD1 and 14, pairwise comparisons indicated significant differences among all three groups (P < 0.05; Table 5). The MA-MSVA group revealed the best recovery in clinical outcomes, followed by the MSVA group, with the MPA group exhibiting the slowest recovery.
Table 4.
Surgical data and clinical outcomes among the three groups
| Parameter | MA-MSVA(n = 78) | MSVA (n = 74) | MPA(n = 123) | P value |
|---|---|---|---|---|
| Operative duration(min) | 125.06 ± 24.94 | 103.31 ± 19.01 | 106.04 ± 17.26 | < 0.001 |
| Tourniquet duration(min) | 69.35 ± 14.60 | 58.53 ± 12.54 | 59.89 ± 13.37 | < 0.001 |
| Preoperative | ||||
| IKDC | 34.28 ± 7.28 | 35.01 ± 8.03 | 34.45 ± 9.61 | 0.872 |
| EQ-5D-5 L | 0.22 ± 0.15 | 0.22 ± 0.14 | 0.25 ± 0.13 | 0.302 |
| KSS | 38.90 ± 13.81 | 37.64 ± 11.55 | 36.15 ± 13.40 | 0.203 |
| VAS | 5.85 ± 1.08 | 6.00 ± 1.09 | 5.81 ± 1.07 | 0.530 |
| ROM | 96.94 ± 9.95 | 95.50 ± 9.02 | 95.40 ± 13.02 | 0.372 |
| POD 1 | ||||
| EQ-5D-5 L | 0.64 ± 0.09 | 0.60 ± 0.10 | 0.56 ± 0.09 | < 0.001 |
| KSS | 63.65 ± 11.52 | 57.39 ± 8.67 | 51.88 ± 11.89 | < 0.001 |
| VAS | 2.10 ± 0.64 | 2.50 ± 1.01 | 2.96 ± 0.83 | < 0.001 |
| ROM | 108.54 ± 10.34 | 104.55 ± 8.94 | 99.47 ± 11.40 | < 0.001 |
| POD 14 | ||||
| EQ-5D-5 L | 0.82 ± 0.08 | 0.75 ± 0.10 | 0.71 ± 0.11 | < 0.001 |
| KSS | 77.64 ± 9.29 | 72.67 ± 5.89 | 68.74 ± 6.44 | < 0.001 |
| VAS | 0.90 ± 0.73 | 1.24 ± 0.70 | 1.69 ± 0.78 | < 0.001 |
| ROM | 116.15 ± 10.99 | 110.95 ± 9.19 | 105.36 ± 12.42 | < 0.001 |
| POD 30 | ||||
| IKDC | 79.03 ± 7.39 | 77.28 ± 8.85 | 76.75 ± 9.68 | 0.349 |
| EQ-5D-5 L | 0.83 ± 0.07 | 0.82 ± 0.09 | 0.82 ± 0.08 | 0.441 |
| KSS | 86.35 ± 6.40 | 85.66 ± 4.35 | 85.00 ± 5.75 | 0.221 |
| VAS | 0.22 ± 0.42 | 0.31 ± 0.47 | 0.33 ± 0.47 | 0.204 |
| ROM | 124.72 ± 10.70 | 123.31 ± 9.06 | 122.45 ± 13.31 | 0.329 |
MA-MSVA, mako-robotic assisted modified subvastus approach; MPA, medial parapatellar approach; IKDC, international knee documentation committee; EQ-5D-5 L, five-level EuroQol five-dimensional questionnaire; KSS, knee society score; VAS, visual analog scale; ROM, range of motion; POD, postoperative day
Fig. 5.
Line graph indicating comparisons of EQ-5D-5 L, KSS, ROM, and VAS scores among the three groups at different time points
Table 5.
Pairwise comparisons of three groups of surgical data and clinical outcomes
| Parameter | Group | Group | P |
|---|---|---|---|
| Operative duration(min) | MA-MSVA | MSVA | < 0.001 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | 0.171 | |
| Tourniquet duration(min) | MA-MSVA | MSVA | < 0.001 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | 0.465 | |
| POD 1 | |||
| EQ-5D-5 L | MA-MSVA | MSVA | 0.006 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | 0.004 | |
| KSS | MA-MSVA | MSVA | 0.005 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | < 0.001 | |
| VAS | MA-MSVA | MSVA | 0.003 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | 0.001 | |
| ROM | MA-MSVA | MSVA | 0.006 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | 0.011 | |
| POD 14 | |||
| EQ-5D-5 L | MA-MSVA | MSVA | < 0.001 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | 0.012 | |
| KSS | MA-MSVA | MSVA | 0.005 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | < 0.001 | |
| VAS | MA-MSVA | MSVA | 0.011 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | < 0.001 | |
| ROM | MA-MSVA | MSVA | 0.002 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | 0.008 |
MA-MSVA, mako-robotic assisted modified subvastus approach; MPA, medial parapatellar approach; IKDC, international knee documentation committee; EQ-5D-5 L, five-level EuroQol five-dimensional questionnaire; KSS, knee society score; VAS, visual analog scale; ROM, range of motion; POD, postoperative day
Comparison of muscle injury and quadriceps strength changes
Preoperatively, non-significant differences were found among the three groups in CK, LDH, KE, or KF (P > 0.05). On POD 1, significant differences were observed in CK, KE, and KF (CK: 179.27 ± 48.19, 212.78 ± 67.37, and 251.24 ± 105.20, P < 0.001; KE: 0.61 ± 0.14, 0.54 ± 0.15, and 0.43 ± 0.19, P < 0.001; KF: 0.37 ± 0.17, 0.30 ± 0.14, and 0.22 ± 0.12, P < 0.001), but not in LDH (P > 0.05). On POD 14, significant differences were found in KE and KF (KE: 0.78 ± 0.14, 0.69 ± 0.15, and 0.53 ± 0.20, P < 0.001; KF: 0.53 ± 0.18, 0.43 ± 0.15, and 0.32 ± 0.12, P < 0.001). On POD 30, significant differences persisted in KE and KF (KE: 0.89 ± 0.14, 0.79 ± 0.16, and 0.62 ± 0.20, P < 0.001; KF: 0.63 ± 0.17, 0.52 ± 0.15, and 0.38 ± 0.13, P < 0.001; Table 6; Fig. 6). Significant differences were found within each group between preoperative and postoperative values for muscle injury markers and quadriceps strength (P < 0.001; Supplementary Table 5). Pairwise comparisons on POD1 indicated significant differences in CK, KE, and KF among all three groups (P < 0.05). On POD14 and 30, pairwise comparisons indicated significant differences in KE and KF among all three groups (P < 0.05; Table 7). The MA-MSVA group experienced the least muscle injury and the fastest recovery of quadriceps strength, followed by the MSVA group, with the MPA group exhibiting the worst results.
Table 6.
Muscle injuries and quadriceps strength among the three groups
| Parameter | MA-MSVA(n = 78) | MSVA (n = 74) | MPA(n = 123) | P value |
|---|---|---|---|---|
| Preoperative | ||||
| CK | 109.04 ± 46.07 | 115.30 ± 77.74 | 109.17 ± 67.70 | 0.601 |
| LDH | 196.40 ± 41.62 | 196.51 ± 33.43 | 206.16 ± 42.96 | 0.149 |
| KE | 0.77 ± 0.14 | 0.76 ± 0.16 | 0.77 ± 0.19 | 0.734 |
| KF | 0.52 ± 0.19 | 0.51 ± 0.18 | 0.51 ± 0.22 | 0.749 |
| POD 1 | ||||
| CK | 179.27 ± 48.19 | 212.78 ± 67.37 | 251.24 ± 105.20 | < 0.001 |
| LDH | 224.24 ± 44.02 | 227.58 ± 34.65 | 233.92 ± 42.78 | 0.242 |
| KE | 0.61 ± 0.14 | 0.54 ± 0.15 | 0.43 ± 0.19 | < 0.001 |
| KF | 0.37 ± 0.17 | 0.30 ± 0.14 | 0.22 ± 0.12 | < 0.001 |
| POD 14 | ||||
| KE | 0.78 ± 0.14 | 0.69 ± 0.15 | 0.53 ± 0. 20 | < 0.001 |
| KF | 0.53 ± 0.18 | 0.43 ± 0.15 | 0.32 ± 0.12 | < 0.001 |
| POD 30 | ||||
| KE | 0.89 ± 0.14 | 0.79 ± 0.16 | 0.62 ± 0.20 | < 0.001 |
| KF | 0.63 ± 0.17 | 0.52 ± 0.15 | 0.38 ± 0.13 | < 0.001 |
MA-MSVA, mako-robotic assisted modified subvastus approach; MPA, medial parapatellar approach; CK, creatine kinase; LDH, lactate dehydrogenase; KE, knee extensors; KF, knee flexors; POD, postoperative day
Fig. 6.
Line graph comparing KE and KF among the three groups at different time points
Table 7.
Pairwise comparisons of muscle injuries and quadriceps femoris strength in three groups
| Parameter | Group | Group | P |
|---|---|---|---|
| POD 1 | |||
| CK | MA-MSVA | MSVA | 0.006 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | 0.010 | |
| KE | MA-MSVA | MSVA | 0.016 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | < 0.001 | |
| KF | MA-MSVA | MSVA | 0.024 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | < 0.001 | |
| POD 14 | |||
| KE | MA-MSVA | MSVA | 0.002 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | < 0.001 | |
| KF | MA-MSVA | MSVA | 0.003 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | < 0.001 | |
| POD 30 | |||
| KE | MA-MSVA | MSVA | 0.001 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | < 0.001 | |
| KF | MA-MSVA | MSVA | 0.002 |
| MA-MSVA | MPA | < 0.001 | |
| MSVA | MPA | < 0.001 |
MA-MSVA, mako-robotic assisted modified subvastus approach; MPA, medial parapatellar approach; CK, creatine kinase; KE, knee extensors; KF, knee flexors
Complications
Superficial wound exudation occurred in three patients in each of MA-MSVA and MSVA groups (incidence rates 3.8% and 4.1%, respectively) and in four patients in the MPA group (incidence rate 3.3%). The exudation stopped within three days after the local dressing was applied. The difference among the three groups was non-statistically significant (P = 0.952). No infections were identified during the one-month postoperative follow-up.
Discussion
This single-center retrospective cohort study compared the short-term efficacy of MA-MSVA, MSVA, and MPA in TKA. The results indicated that the MA-MSVA group exhibited the best in terms of prosthesis alignment accuracy, early functional recovery, pain control, and muscle strength recovery, without increasing perioperative risks. Additionally, while MSVA was comparable to MPA in alignment accuracy, it demonstrated advantages in early functional recovery, pain control, and muscle strength recovery. These results offer essential clinical evidence for the progress of precise and minimally invasive TKA.
Prosthesis alignment accuracy
MA-TKA can enhance precision, offer better prosthesis positioning and limb alignment, and achieve superior radiographic outcomes [19, 26–28]. Moreover, this study found that the MA-MSVA group exhibited better alignment accuracy compared to the MSVA and MPA groups (Tables 2 and 3), clearly demonstrating the core value of the Mako robotic system’s precision technology. However, our results also indicated that MSVA, although minimally invasive, was comparable to MPA in operative time, tourniquet time, and alignment accuracy (P > 0.05; Tables 2 and 3). In all TKA methods, MSVA did not present issues with inadequate exposure or prolonged operative time. By combining MA with MSVA, this study achieved synergistic optimization of precision and minimally invasive, significantly improving prosthesis alignment accuracy.
Early functional recovery
Studies have indicated that mini-SVA can facilitate early recovery of knee ROM and straight-leg raise, reduce postoperative pain, and enhance early satisfaction and clinical outcomes [14, 29]. MA-TKA can significantly reduce postoperative pain, shorten hospital stay, and result in better clinical function scores [20, 30–32]. Can the combination of both accelerate functional recovery? Our study found that the MA-MSVA group exhibited significantly better EQ-5D-5 L, KSS, VAS, and ROM scores on POD1 and POD14 compared to the other two groups (P < 0.05; Tables 4 and 5; Fig. 5). MA-MSVA preserves the integrity of the vastus medialis muscle belly, reduces intraoperative tissue retraction, and minimizes soft tissue trauma. This indicates that the precision and minimally invasive mechanism can facilitate early functional rehabilitation, aligning with the core goals of ERAS.
Muscle protection and strength recovery
Thigh pain is relatively common following TKA, and iatrogenic quadriceps injury is one of the leading causes [10]. Studies indicate that quadriceps strength can decrease by up to 60% one month after surgery compared to preoperative levels [33] and may remain reduced for months [34]. By dynamically monitoring CK, LDH levels, and quadriceps strength (KE and KF), this study found that the MA-MSVA group exhibited the lowest CK values on POD 1 and the fastest quadriceps strength recovery within 30 days postoperatively, followed by the MSVA group, with the MPA group exhibiting the slowest results (Tables 6 and 7; Fig. 6). Through the precision and minimally invasive mechanism, MA-MSVA maximizes the protection of the extensor apparatus’s physiological function and accelerates quadriceps strength recovery.
Surgical duration, tourniquet use, and early postoperative outcomes
The MA-MSVA procedure resulted in an increase of approximately 20 min in operative duration and about 10 min in tourniquet duration. In this study, pain levels and muscle strength on POD 1 were not affected. It may be necessary to further consider the potential impact of tourniquet use on immediate functional outcomes [35], warranting additional evaluation of functional recovery from the immediate postoperative period to POD 1. The increases in operative duration and tourniquet duration did not influence postoperative complications such as wound exudation or infection.
Research value and clinical significance
This study demonstrates that the MA-MSVA protocol significantly enhances early knee flexion ROM, reduces pain, improves prosthesis alignment accuracy, and accelerates quadriceps strength recovery in the early postoperative period, thereby providing a foundation for advancing ERAS development.
Limitations
This study has several limitations: First, its single-center retrospective design may introduce selection bias, as the choice of surgical technique could be influenced by surgeon preference. The sample originates from a single institution, which limits its generalizability compared to prospective multicenter research. Second, follow-up was limited to 30 days postoperatively, lacking assessment of long-term outcomes such as prosthesis survival, functional results, and complications, thus unable to determine the impact of MA-MSVA on long-term TKA outcomes. Third, no subgroup analysis was performed for severely obese patients or those with significant deformities, making it challenging to clarify the applicability of the techniques in complex populations; subsequent studies are required to address this. Fourthly, to truly determine whether mako robot-assisted surgery itself or MA-MSVA can improve accuracy and functional effects, a control group of MA-MPA needs to be added in future studies. Fifth, it may be necessary to further consider the potential impact of tourniquet use on immediate functional outcomes, warranting additional evaluation of functional recovery from the immediate postoperative period to POD 1.
Conclusion
This study systematically compared the short-term efficacy of MA-MSVA, MSVA, and MPA in TKA. The findings indicate that MA-MSVA significantly improves prosthesis alignment accuracy, accelerates early postoperative knee functional recovery, reduces pain, and promotes early quadriceps strength recovery, without increasing perioperative complication risks. MSVA outperforms the MPA in terms of early functional recovery and muscle protection but is comparable in terms of alignment accuracy. By combining the precision of robotic assistance with the physiological protection advantages of the minimally invasive method, MA-MSVA achieves a synergistic effect of precision and minimality, providing a novel direction for optimizing TKA techniques. It is remarkably consistent with the ERAS concept and warrants clinical promotion.
Supplementary Information
Below is the link to the electronic supplementary material.
Acknowledgements
We would like to give our sincere appreciation to the reviewers for their helpful comments on this article.
Abbreviations
- MA-MSVA
Mako-robotic assisted modified subvastus approach
- MPA
Medial parapatellar approach
- TKA
Total knee arthroplasty
- ERAS
Enhanced recovery after surgery
- SVA
Subvastus approach
- Mini-SVA
Mini-SVA
- mTFA
Mechanical tibiofemoral angle
- mLDFA
Mechanical lateral distal femoral angle
- MPTA
Medial proximal tibial angle
- LTC
Lateral tibial component
- LFC
Lateral femoral component
- IKDC
International Knee Documentation Committee
- EQ-5D-5L
Five-level EuroQol five-dimensional questionnaire
- KSS
Knee Society Score
- VAS
Visual analog scale
- ROM
Range of motion
- POD
Postoperative day
- CK
Creatine kinase
- LDH
Lactate dehydrogenase
- KE
Knee extensors
- KF
Knee flexors
Author contributions
Yongyong Fan: design of investigation and data collection. Lingjun Jiang: data analysis and writing paper. Zhongyi Chen: data collection, data analysis and writing paper. Chenglong Wang: design of investigation, data collection, data analysis and writing paper. All authors read and approved the final manuscript.
Funding
This study was supported by Science and Technology Plan Project of Taizhou (grant number: 25ywb62).
Data availability
The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.
Declarations
Competing interests
The authors declare no competing interests.
Ethics approval and consent to participate
This study has been approved by the Ethics Committee (Taizhou Hospital of Zhejiang Province affiliated to Wenzhou Medical University) (May 19, 2025, Approval number K20250522). All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. Written informed consent was obtained from individual or guardian participants.
Consent for publication
Not applicable.
Informed consent
Written informed consent was obtained from all patients.
Footnotes
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Yongyong Fan and Lingjun Jiang contributed equally to this work.
Contributor Information
Zhongyi Chen, Email: czy@enzemed.com.
Chenglong Wang, Email: wangcl4779@enzemed.com.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Data Availability Statement
The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.