Knee Arthroplasty

A Retrospective Analysis of the Modified Intervastus Approach

Author Affiliation | Disclosures

Dr. Sartawi is an orthopedic surgeon, Assistant Professor, University of Illinois College of Medicine, Champaign, Illinois. Dr. Rahman is a Postdoctoral Research Fellow, Department of Biomechanics, University of Nebraska at Omaha, Omaha, Nebraska. Dr. Kohlmann is an orthopedic surgeon, Department of Surgery, Sarah Bush Lincoln Health Center, Mattoon, Illinois. Dr. Leighton is orthopedic surgeon, Professor of Surgery at Dalhousie University in Halifax, Nova Scotia, Canada. Dr. Kersh is an Assistant Professor, Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois.

Authors’ Disclosure Statement:  The authors report no actual or potential conflict of interest in relation to this article.

Address correspondence to: Hafizur Rahman, Department of Biomechanics, 6160 University Drive South (tel, 402-554-3228; email,

Am J Orthop. 2018;47(12). Copyright Frontline Medical Communications Inc. 2018. All rights reserved.


The subvastus (SV) approach is a well-known muscle- and tendon-sparing approach for total knee arthroplasty (TKA), which has been shown in some studies to provide better outcomes in the visual analog pain score (VAS), knee range of motion (ROM), straight-leg raise, as well as faster rehabilitation, compared with the standard medial parapatellar (MP) approach. We previously described a new knee replacement technique known as the modified intervastus (MIV) approach. The MIV approach is a muscle- and tendon-sparing approach that is extensile and simple to perform. It may be used in the majority of complex primary cases and revisions. Here we describe the surgical technique for performing the MIV approach and provide functional outcome measures. A total of 127 patients (mean age, 66.75 years) underwent TKA using the MIV approach with 1-year follow-up. Clinical outcomes were assessed by recording both a VAS and knee ROM preoperatively, and again at several postoperative time points when the length of time required to ambulate independently (without assistive devices) was also measured. The VAS decreased significantly from the preoperative period (3.69 ± 2.22) to postoperative day 1 (3.17 ± 1.97) (P < .05). Although knee ROM decreased 1 week after surgery, the ROM increased by 6 weeks after surgery compared with the preoperative ROM, and the trend continued over the 1-year follow-up. One-third (33%) of patients were able to walk independently (without assistive devices) at 2 weeks and 78% at 8 weeks. The MIV approach to the knee is a muscle- and tendon-sparing approach that offers advantages over the SV approach and may be used for complex primary and revision total knee cases.

Take-Home Points

  • The modified intervastus approach to the knee spares the quadriceps tendon and the vastus medialis muscle.
  • The modified intervastus approach is an extensile approach.
  • The modified intersvastus approach is a safe approach to the knee that can be used in total knee arthroplasty and leads to early straight-leg raise and a rapid recovery.
  • The modified intervastus approach can be used on the majority of patients requiring a total knee replacement.
  • The modified intervastus approach utilizes a unique closure that avoids soft tissue strangulation.

Total knee arthroplasty (TKA) is one of the most common orthopedic surgical procedures, with more than 600,000 TKAs performed annually in the United States, and by 2030 the number is expected to reach 3.48 million per year.1 Several approaches have been described for total TKA, and the medial parapatellar (MP) approach to the knee is considered the workhorse of total knee replacements. It is an extensile approach that is easy to perform but may delay active knee extension and straight-leg raise after surgery.2  Alternative approaches such as the subvastus (SV) and midvastus approaches to the knee (Figure 1A) typically allow a more rapid straight-leg raise but may be more challenging to perform and time-consuming in morbidly obese patients, muscular patients, and patients with severe deformities.3

The intervastus approach (Figure 1A) described by Jojima4 and others utilizes the interval between the quadriceps tendon and vastus medialis. Although it is a simple approach to perform that is extensile, it is not considered tendon-sparing since the vastus medialis inserts onto the medial aspect of the quadriceps tendon (Figure 2). Therefore, dissecting through this interval, without elevation of the vastus medialis (Figure 3A), damages the quadriceps tendon, and strangulation of the muscle occurs with repair of the arthrotomy site (Figure 3B).  This situation is even more likely in patients with a low-lying vastus medialis.6

The modified intervastus (MIV) approach described previously,7 may be used in the majority of patients undergoing TKA. The advantages of this approach include its extensile nature, similarities to an MP approach, and preservation of both the extensor mechanism and the vastus medialis, leading to a more rapid return to active knee extension than is traditionally observed.2,7 The approach is simple to perform, easy to close, and is compatible with more extensile approaches such as a quadriceps snip if required in revision scenarios.7 However, functional outcomes of the MIV approach have not been quantified. It is unknown whether these outcomes will offer any advantages compared with the SV approach. Therefore, the objective of this study was to measure functional outcomes of the MIV approach and to compare the results with those previously published for the SV approach. We hypothesized that using the MIV approach for TKA surgery would lead to early straight-leg raise and increase in knee range of motion (ROM) postoperatively.

Surgical Technique

The MIV approach preserves the quadriceps tendon and vastus medialis.7 After exposure of the vastus medialis muscle, the interval between the quadriceps tendon and vastus medialis is identified (Figure 4).  The fascia overlying the lateral edge of the vastus medialis is incised where it meets the quadriceps tendon (Figure 5).  The muscle is then bluntly elevated off the underlying capsule just enough to allow for a capsular repair later (Figure 6).  An arthrotomy is then performed from cephalad to caudal (Figure 7).  This interval may be extended proximally between the vastus intermedius and vastus medialis to expose the distal femur if needed. The closure is performed by repairing the capsule with absorbable suture (Figure 8A), and the vastus medialis fascia is repaired back to the medial edge of the quadriceps tendon, restoring the anatomy (Figure 8B).

Patients and Methods

A retrospective review of functional outcomes after TKA using the MIV approach was conducted; the study was approved by the University of Illinois Institutional Review Board. A total of 127 patients of mean age 66.75 years (range, 48–86 years) with primary osteoarthritis of the knee who were indicated for a total knee replacement with 1-year follow-up were included. The patient demographics are shown in Table 1.  All patients underwent TKA using the MIV approach described above by 2 experienced orthopedic surgeons at the same institution. Patients received spinal anesthesia and a periarticular pain block intraoperatively. A measured resection technique was used by 1 surgeon, and a gap-balancing technique by the other. Surgeon 1 used the Persona PS cemented knee system (Zimmer Biomet, and Surgeon 2 used the Sigma PS cemented knee system (Depuy). Patellar resurfacing was done in all cases. Patellar tracking was checked intraoperatively using the ‘no-touch’ technique, and the need for a lateral release was noted. Drains were removed on postoperative day 1. Oral opioids were given as needed. Intravenous antibiotics were continued for 24 hours. Oral anticoagulants were used for thromboembolism prophylaxis for 3 weeks. Patients were mobilized on the day of surgery with full weight-bearing under the supervision of an experienced physical therapist. Static and dynamic quadriceps exercises were started on the same day of surgery along with active knee ROM exercises. Pain score, extensor lag, ROM, walking ability, and complications were recorded in all patients.

The visual analog score (VAS) was obtained preoperatively and recorded on postoperative day 1. Patient walking distance with assistance was measured on the day of surgery, after surgery, and on the day of hospital discharge. Patients were assessed preoperatively and postoperatively at 1 week, 2 weeks, 6 weeks, 3 months, 6 months, and 1 year for knee ROM. A one-way ANOVA was conducted to compare the preoperative and postoperative day 1 VAS with significance set at P < .05 (OriginPro 2015, OriginLab Corporation). Differences in knee ROM between preoperative and postoperative follow-up periods (1 week, 2 weeks, 6 weeks, 3 months, 6 months, and 1 year) were identified using a 1-way ANOVA with a post hoc Tukey test. Significance was set at P < .05.


All patients were able to fully straight-leg raise and demonstrate functional knee ROM by postoperative day 1. The patella tracked centrally in all patients, and none required a lateral retinacular release. The majority of patients were discharged in the first 48 hours after surgery on oral narcotics. None required IV narcotics during their hospital stay or a blood transfusion. Two cases were complicated by severe knee skin blistering postoperatively due to a reaction to an adhesive dressing; one was complicated by skin necrosis leading to a flap reconstruction that became infected, requiring a 2-stage revision. A separate case had an acute postoperative infection that required irrigation and debridement with polyethylene exchange. After a 12-week course of antibiotics, the infection was eradicated. All patients reported a high satisfaction rate during their acute postoperative phase.

Postoperatively, all patients were able to walk on the day of surgery either independently or with some assistance. On the day of surgery, 10% of patients were able to walk >200 feet, and this increased to 65% of patients able to walk >200 feet on the day of discharge (compare Figure 9A and Figure 9B).  Within 2 weeks of surgery, 30% of patients could walk independently (without assistive devices), and this number increased to 78% by 8 weeks after surgery (Figure 10).

Pain assessed using the VAS was lower on postoperative day 1 (3.17 ± 1.97) than the preoperative score (3.69 ± 2.22, P < .05). Overall, knee ROM significantly increased during the follow-up after surgery. Initially, the ROM decreased 1 week after surgery (90.82 ± 10.28) compared with preoperative ROM (101.04 ± 19.48, P < .001) (Figure 10).  At 2 weeks after surgery, knee ROM returned to the preoperative value (100.70 ± 13.36). By 6 weeks after surgery, knee ROM was 17° greater than the preoperative ROM (118.45 ± 11.89, P < .001). Knee ROM remained stable at 3- and 6-month assessments, and showed further improvement by 1 year (126.62 ± 9.81, P < .001) compared with the preoperative state (Figure 10). The net improvement in knee ROM was 25° of increased knee flexion by 1 year.


TKA is a successful procedure that restores knee function with pain relief in osteoarthritis patients. The SV approach for TKA has better outcomes in terms of the VAS, ROM, straight-leg raise with faster rehabilitation compared with the standard MP approach;8–12 however, it can be challenging and time-consuming when used in morbidly obese and muscular patients.3 The SV approach can also increase the risk of complications such as patellar tendon avulsion or medial collateral injury because of the difficulty in exposure specifically for knees with limited ROM.13 Here we introduce the MIV approach as an alternative to the SV approach, overcoming most of these difficulties.

With the prevalence of morbid obesity and the market demand for minimally invasive techniques, we believe the MIV approach represents a good approach for surgeons since it is easy to perform, does not require specialized instrumentation, and is a reproducible approach even on the most complex deformities. The minimal time added to ensure blunt elevation of the vastus medialis muscle and an anatomic repair of the underlying knee capsule and vastus medialis fascia to the medial edge of the quadriceps tendon allows restoration of the anatomy and a robust double-layered watertight seal closure with no strangulation of soft tissues. We believe this reproducible muscle- and tendon-sparing approach that allows gentle, soft tissue handling even in the most complex primary total knee cases may lead to less soft tissue swelling, and therefore, less postoperative pain resulting in an accelerated recovery.

The pain level in this group of patients was reduced after the MIV approach as indicated by the VAS. The VAS was significantly decreased on postoperative day 1 compared with the VAS recorded preoperatively (P < .05), indicating patients felt less pain on the day after surgery. The average VAS on postoperative day 1 from other studies for SV approach ranged from 2.1 to 5,9,12,14–19 whereas our MIV approach value was 3.17. Periarticular blocks were available for this study group, and no peripheral nerve blocks were used. Some studies of the SV approach mention the use of peripheral nerve blocks, while others did not describe the method used for treatment or control of postoperative pain. The decreased reported pain levels and the observed increased knee ROM seen in the MIV and SV approach study groups might be attributable to the treatment of postoperative pain.

Patient ambulation also increased from the day of surgery to the day of discharge for the MIV approach. Only 10% of patients were able to walk with assistance >200 feet on the day of surgery; however, this percentage increased to 65% on the discharge day showing an excellent recovery of walking ability within 2 days of surgery. Mehta and colleagues20 reported that 95% of patients undergoing subvastus/midvastus approaches could walk >10 blocks at 6 months follow-up. For the MIV approach, 78% of patients were able to walk independently within 8 weeks of surgery.

The MIV approach shows improvement in functional outcomes in terms of knee ROM from preoperative to postoperative. Although knee ROM decreased significantly at postoperative week 1, which is most likely because of a peak in postoperative pain and swelling; the ROM started to increase significantly at postoperative week 6. After 1 year, the knee ROM increased by 25% compared with preoperative ROM for the MIV approach. We found the average knee ROM at postoperative 3 months using the MIV approach to be 120.4°. Knee ROM at postoperative 3 months using the SV approach reported by other studies ranged from 87.1° to 120°.19,21–23 Similarly, after 1 year, the average ROM by MIV approach was 126.62°, whereas average knee ROM from other studies using the SV approach was 114.1°.2,10,19,21 Achieving a knee ROM of 120° allows patients to return to their baseline function and perform activities of daily living without limitation. With the prevalence of knee osteoarthritis in the younger population, the need for increased knee ROM post-TKA becomes more important so patients can return to work and function at their baseline.

In addition to being both a muscle- and tendon-sparing approach, other advantages of the MIV approach are that it is simple to perform and gives similar exposure to the MP approach even in difficult primary cases. It is also as extensile as the medial parapatellar approach, and it can be converted to a quadriceps snip if required. There is also minimal, if any, muscle retraction preventing muscle injury that may be seen with some other muscle-sparing approaches to the knee, especially in more difficult primary total knee cases. Another advantage to this approach, as opposed to the other approaches to the knee described here, is that it allows a double-layered closure, decreasing the possibility of arthrotomy dehiscence. Because of this double-layered closure, there is no muscle strangulation with repair of the arthrotomy site as seen in some other approaches to the knee, and both vascularity and innervation to the vastus medialis are preserved.

One limitation of this study is that it is a retrospective analysis. Future studies of the consequences of using this approach need to include quantitative assessment of muscle function using electromyography or dynamometer measurements, utilization of any number of validated knee score systems to measure functional outcomes, and incorporation of a randomized controlled trial.

In summary, the new MIV approach is easy to perform and is compatible with more extensile approaches such as a quadriceps snip, if required in revision scenarios. The MIV approach preserves the extensor mechanism, vascularity, and innervation to the vastus medialis. Our study documents both safety and good clinical outcomes using the MIV approach in TKA. Therefore, the MIV approach may be used in the majority of patients undergoing TKA.

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Table 1. Patient Demographics

Total no. of patients







Age (years)

Mean ± Standard deviation

66.75 ± 9.12


48 – 86

Weight (lb)

Mean ± Standard deviation

218.38 ± 54.47


125 – 364

BMI (kg/m2)

Mean ± Standard deviation

34.10 ± 7.22


21.1 – 62.5





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