Subvastus approach versus medial parapatellar approach in total knee arthroplasty – A prospective comparative study of functional outcome

Praveen Dileep; Vinod Padmanabhan; CP Krishnaraj

doi:10.4103/joasis.joasis_5_22

ORIGINAL ARTICLE

Year : 2022 | Volume : 19 | Issue : 1 | Page : 2-6

Subvastus approach versus medial parapatellar approach in total knee arthroplasty – A prospective comparative study of functional outcome

Praveen Dileep, Vinod Padmanabhan, CP Krishnaraj
Department of Orthopedics, Sree Sudheendra Medical Mission, Ernakulam, Kerala, India

Date of Submission	05-Mar-2022
Date of Acceptance	08-Mar-2022
Date of Web Publication	26-Jun-2022

Correspondence Address:
Praveen Dileep
Department of Orthopaedics, Sree Sudheendra Medical Mission, Ernakulam - 622 018, Kerala
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/joasis.joasis_5_22

Abstract

Introduction: For late stages of arthritis of knee, total knee arthroplasty (TKA) is the most successful joint replacement surgery for the patients to achieve good function. The medial parapatellar (MPP) approach is most often used, whereas the subvastus approach (SV) is a suitable alternative. Patients and Methods: This is a prospective, observational, comparative study. Results: It has been demonstrated that the approach (SV) is advantageous in the early postoperative period compared to the MPP surgical approach (MPP). The SV group was able to perform straight leg raising earlier, had good pain scores, and experienced better range of motion when compared to the MPP group. The Knee Society Knee Score for pain was also better in the SV group in the immediate postoperative period. Conclusion: The SV approach, which is based on avoidance damage to extensor mechanism and peripatellar plexus of vessels, helps in early rehabilitation after TKA.

Keywords: Knee society score, medial parapatellar, subvastus, total knee arthroplasty

How to cite this article:
Dileep P, Padmanabhan V, Krishnaraj C P. Subvastus approach versus medial parapatellar approach in total knee arthroplasty – A prospective comparative study of functional outcome. J Orthop Assoc South Indian States 2022;19:2-6

How to cite this URL:
Dileep P, Padmanabhan V, Krishnaraj C P. Subvastus approach versus medial parapatellar approach in total knee arthroplasty – A prospective comparative study of functional outcome. J Orthop Assoc South Indian States [serial online] 2022 [cited 2023 Apr 1];19:2-6. Available from: https://www.joasis.org/text.asp?2022/19/1/2/348318

Introduction

Total knee arthroplasty (TKA) is a common and efficient surgical procedure for improving function and pain relief in patients with primary or secondary arthritis. TKA has a very high patient satisfaction rate.^[1] The conventional medial parapatellar (MPP) approach requires an incision through the quadriceps tendon, which may impair the extensor mechanism of the knee postoperatively. Alternatives to the standard MPP approach for TKA have been developed with the aim of improving postoperative recovery and shortening hospital stay.^[2],[3] Such approaches include the subvastus (SV), mid-vastus, and minimal incision surgical techniques.^[4],[5] The SV approach was described by Erkes in 1929^[6] and popularized by Hoffman^[2] in 1991. The SV approach leaves the quadriceps intact and completely attached to the medial patellar border, which theoretically reduces the pain associated with violating the extensor mechanism and lessens the risk of blood supply damage to the patella and subsequent avascular necrosis and fractures of the patella.^[7],[8] Such benefits may improve the range of movement and functional outcomes of patients after TKA surgery.^[9] This approach also helps in improved patellar tracking,^[10] expedited rehabilitation,^[11] and reduced postoperative pain resulting in shorter hospital stays.^[12]

Patients and Methods

From January 2017 to December 2020, a retrospective observational comparative study was undertaken to compare the early functional results of TKA done through the SV and MPP approaches in 54 primary TKA cases. Patients were divided into two Groups with 27 patients in each: group A included patients with TKA done through the SV approach and Group B included patients with TKA done through the MPP approach. Inclusion criteria included patients with primary knee osteoarthritis who underwent total knee replacement. Exclusion criteria included prior knee surgeries, fixed flexion deformity >20°, valgus deformity, axial deformity >20°, previous bony injuries around the knee, previous deep-knee scars, body mass index >30, and damage of the extensor mechanism. All procedures were performed by the same surgical team under spinal anesthesia through an anterior midline skin incision. All surgeries were posterior stabilizing TKA. The implants used were Buechel-Pappas total knee system. We excluded all other cases done with other implants systems, cruciate-retaining TKA and other complex deformities which require revision systems. All procedures were performed under tourniquet, which was released after closure. In all cases, patella was not resurfaced. Drains were used in all knees for 48 h. The primary outcome evaluated was postoperative knee range of motion (ROM). The evaluated secondary outcome variables included postoperative pain severity assessed through visual analog score (VAS), knee society score (KSS) objective and functional scores, and extensor mechanism integrity assessed through days to Straight Leg Raise functional knee outcome scores and number of lateral releases performed. ROM and KSS Objective and Functional scores in both groups were assessed preoperatively and postoperatively at 3 days, 2 weeks, 6 weeks, 3 months, and at 1 year. Days to straight leg raising (SLR) and VAS scores were calculated preoperatively and at postoperative days 1, 2, and 3.

Technique

The subvastus approach

With the patient in supine position, a midline incision starting 4 –5 cm above upper limit of patella is continued along the center of patella to the medial limit of the tibial tuberosity after keeping the knee in 30° of flexion. Skin and subcutaneous tissue are carefully elevated from the quadriceps muscle, more from the medial side [Figure 1]a. Arthrotomy at the site of upper medial pole of the patella is done and no 1 vicryl suture tags are placed on either edge for uniform approximation during closure. Arthrotomy is extended along the medial edge of vastus medialis and distally just below the tibial tuberosity. Blunt dissection is done until the medial intermuscular septum and the vastus medialis is then elevated with Z retractor [Figure 1]b. Without everting the patella, vastus medialis is retracted laterally. The femur and tibia cuts are taken, and original implants fixed with bone cement after trailing [Figure 1]c. While assessing the patellar tracking, if patellar tilt or subluxation is noticed, a lateral release is performed. The Arthrotomy is closed with continuous sutures [Figure 1]d. In all cases, a wound drain is exited laterally and removed after 48–72 h. For all cases, subcutaneous enoxaparin is given for thromboprophylaxis till discharge and oral aspirin 75 mg OD for 6 weeks is given at the time of discharge.

Figure 1: (a) Dissection along the inferior edge of vastus medialis. (b) Elevating the vastus medialis with Z retractor. (c) After prosthesis insertion. (d) After closure of arthrotomy

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Rehabilitation

The patient is encouraged to sit up in bed as early as on the night of the surgery. Full weight-bearing mobilization with support is started on postoperative day 1. From the same day onward, under the supervision of an experienced physiotherapist, gait training, static and dynamic exercises of hip and knee are done twice daily. Wound inspection is done on postoperative day 2 and day 4. Discharge is done with advice of continuing full weight-bearing ambulation with support knee and hip ROM exercises.

Sample size calculation

Assuming from the previous study conducted by Roysam GS^[13] in which the mean standard deviation (SD) of days to regain active straight leg raise in Group I of patients undergoing TKA through the parapatellar approach and Group II of patients undergoing TKA through SV approach were 3.2 (1.4) and 5.8 (1.7), respectively, at 95% continuous integration and 80% power of the study, the sample size of this study was derived as 27 in each group with a total sample size of 54.

Total sample = n × 2 = 54.5 ≈ 54

Data analysis

Data analysis was performed with SPSS Inc. (Released 2008. SPSS Statistics for Windows, Version 17.0. SPSS Inc., Chicago., USA) for windows. Alpha value was set as 0.05. Descriptive statistics were performed to find mean, SD for the demographic variable and outcome variables. Unpaired t-test was used to find significant differences among variables such as age and days to SLR. Chi-square test was used to find gender distribution and performed among both groups. Mann–Whitney U-test was used to find significant differences among baseline data of the outcome variable such as KSS pain, KSS function, and VAS. Mann–Whitney U-test was used to find difference in scores between groups for KSS pain, KSS function, and VAS. Unpaired t-test was used to find difference in scores between groups for ROM.

Results

After considering the inclusion and exclusion criteria, 27 patients were included in Group A (SV) and 27 patients were included in Group B (MPP). Baseline data for demographic variable such as age and gender were homogenous among both groups. Mean age of Group A was 66.48 ± 5.74 years and Group B was 65.30 ± 5.17 years.

ROM was significantly more in Group A (SV) at 3-day, 2-week, and 6-week postoperative. ROM was comparable between both the groups from 3-month postoperative with no significant statistical difference [Table 1].

Table 1: Range of motion

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The KSS objective score of Group A was significantly higher at 3-day, 2-week, and 6-week postoperative. No significant statistical difference was noted in the KSS objective score in both groups at 3-month and 1-year postoperative [Table 2] and [Figure 2].

Figure 2: Comparison of knee society score objective score in two approaches. The knee society score objective score of Group A was significantly higher at 3-day, 2-week, and 6-week postoperative. No significant statistical difference was noted in the knee society score objective score in both groups at 3-month and 1-year postoperative

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Table 2: Knee society score objective score

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The KSS functional score showed no significant statistical difference between the 2 groups in the postoperative period [Table 3].

Table 3: Knee society score functional score

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VAS showed significantly lower values in SV group in initial postoperative days [Table 4] and [Figure 3].

Figure 3: Comparison of visual analog score between two approaches. Visual analog score showed significantly lower values in subvastus approach group in initial postoperative days

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Table 4: Visual analog score

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Group A patients achieved SLR in 1.81 ± 0.88 days whereas Group B patients took 2.85 ± 0.91 days for SLR, with a P < 0.00008 [Figure 4].

Figure 4: Comparison of days to straight leg raising in two approaches. Group A patients achieved straight leg raising in 1.81 ± 0.88 days whereas Group B patients took 2.85 ± 0.91 days for straight leg raising, with a P < 0.00008

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Lateral release

The requirement of lateral release was significantly less in Group A. Only six patients in Group A required lateral release while 14 patients out of the total 27 patients in Group B required lateral release with a P < 0.024.

Discussion

The surgical approach for arthrotomy is a deciding factor for better postoperative results and knee joint function. In earlier days, the conventional approach for TKA was MPP. However, due to its intratendinous incision and increased incidences of abnormal patellar tracking associated with the approach, concerns were raised regarding the disruption of extensor function, which in turn can cause severe postoperative complications including patellar dislocation or subluxation, patellar fractures, osteonecrosis, and component erosion.^[14] To deal with the above concerns, SV (southern) approach was proposed by Hofmann et al.^[2] in 1991 for primary TKA. The more recent SV approach has gained popularity, as it preserves the quadriceps integrity and is associated with earlier resumption of extensor mechanism as compared to the MPP approach.

Our study included 54 patients divided into two groups of 27 each. The patients who underwent surgery through the SV and MPP approaches were included under Group A and Group B, respectively. The mean age group of the patients in Group A was 66.5 and in Group B was 65.3.

The study showed that ROM and KSS objective scores were significantly more in Group A (SV) at 3-day postoperative, 2-week postoprative, and 6-week postoprative. From the 3^rd month onward, ROM and KSS objective scores were comparable between the two groups with no statistical difference. During the postoperative period, pain was accessed using VAS, which showed significantly lower values in SV group from postoperative day 1 onward. Better integrity of extensor mechanism in the form of significantly lesser days to SLR was seen in Group A as compared to Group B. The requirement of lateral release was significantly less in Group A with a total of 6 and 14 patients requiring it in Groups A and B, respectively.

Systematic review and meta-analysis done by Berstock et al.^[15] demonstrated earlier return of straight leg raise, lower visual analog pain scores on day 1 and improved ROM at 1 week following the SV approach as compared to the MPP approach. However, no significant statistical difference in incidence of adverse events or in KSS at 6-week and 1-year postoperatively was noted between the SV and MPP approaches.

In a meta-analysis done by Liu et al.^[16] of 32 randomized controlled trials (RCTs) with 2451 TKAs in 2129 patients, comparison between the three most commonly used surgical approaches of TKA, namely MPP, midvastus, and SV was done. The study concluded that the SV approach had better knee ROM at postoperative 1^st week, straight leg raise, and lateral retinacular release.

A meta analyses by Bouché et al.^[17] concluded that no differences were found between various approaches of TKA with respect to functional outcomes, but the SV approach showed higher mean ROM at 6-month postsurgery as compared to all the other surgical approaches of TKA.

A comparison study of MPP and midvastus approach by Song et al.^[18] shows significantly higher incidences of lateral release noted in MPP approach. The incidence of lateral release in MPP was about 40%, which was comparable with this study.

Limitations of the study were lack of true randomization which may have affected the integrity of currently available data, limited sample size, and lack of radiological assessment. There is huge scope for further research on a larger scale and with additional quantitative assessment of quadriceps strength using dynamometer, which was not performed in this study.

Conclusion

The study was conducted with the aim of comparing the early functional outcomes of SV and MPP approaches in primary TKA cases. The ROM and KSS objective score in patients undergoing surgery through the SV approach was significantly better as compared to MPP approach till 6-week postsurgery. Lesser requirement of lateral releases and better extensor mechanism integrity in the form of significantly lesser days to SLR was also seen with the SV approach. Thus, quicker functional recovery and earlier resumption of daily activities are enabled in SV approach.

Ethical clearance

The Institutional Ethics Committee, Sree Sudheendra Medical Mission, Chittoor road, Ernakulam has approved the study.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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