RECONSTRUCTION 2023, Jan, 08 | 12:00 am

Minimally Invasive Total Knee Arthroplasty with Limited Medial Parapatellar Arthrotomy

Introduction

  • Minimally invasive surgery (MIS) for knee arthroplasty began with work on unicondylar knee replacement (Romanowski and Repicci, 2002), and its successful application has encouraged the use of a limited surgical approach in total knee arthroplasty (TKA). The principles of MIS surgery have gained popularity over the last several years, with several approaches evolving from traditional extensile approaches to the knee.

  • This chapter focuses on the limited medial parapatellar arthrotomy and limited quadriceps splitting incision, one of a continuum of modified approaches with limited access and visibility that can be converted to a more traditional approach if necessary.

  • MIS TKA with a limited skin incision and limited medial parapatellar arthrotomy is a familiar and versatile exposure that has evolved with the addition of smaller and more efficient instrumentation. This MIS approach, in particular, is adaptable to the limited operative field in the knee, allowing limited surgical dissection without compromising the procedure and outcome.

  • MIS TKA with a limited medial parapatellar arthrotomy is a similar approach to a traditional, extensile technique, though operating in a field with more limited visibility; consequently, the technique offers a short learning curve. Experienced knee surgeons must be comfortable with operating with limited observation, and with recognizing anatomic landmarks, in order to do the procedure.

     

    P ITFALLS

    • Patients with severe angular deformities

       

    • Patients with compromised soft tissue envelope

       

    • Muscular male patients with large femurs

       

    • Patients with rheumatoid or inflammatory arthritis

     

    Indications

  • Optimizing patient selection and paying specific attention to operative details ensures clinical success, as experience has demonstrated that not all patients are candidates for less invasive total knee surgery.

    • Shorter, thinner women with lower body mass index and more narrow femurs appear to be better candidates for this approach (Scuderi et al., 2004).

    • We have observed that, the wider the femur, as measured by the epicondylar width, the longer the incision. This is intuitive because the bigger the femur, the greater the exposure needed for implantation of a larger femoral component.

    • Patients should also have a minimum range of motion of 90°, with deformity limited to less than

       

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      15° of varus, less than 20° of valgus, and a flexion contracture less than 10° (Scuderi, 2006).

      • Patients with deformities more severe than the aforementioned and/or those with a compromised soft tissue envelope will require greater soft tissue dissection and release to correct the deformities, which will limit the ability to do a mini-incision technique.

      • Other less favorable candidates for this approach include patients with rheumatoid or inflammatory arthritis, patients with diabetes mellitus, patients on chronic steroids, patients with limited preoperative range of motion or severe fixed angular deformity, obese patients, and those with previous skin incisions and arthrotomies (Tenholder et al., 2005).

      • We have also observed that a short patellar tendon requires a longer incision and longer arthrotomy. When the patellar tendon is shortened, it is more difficult to subluxate the patella laterally with a limited arthrotomy without compromising the insertion on the tibial tubercle. Therefore, we measure the Insall-Salvati ratio on the preoperative lateral radiograph and determine the preoperative length of the patellar tendon (Insall, 1971).

      • Finally, muscular patients, especially men with a prominent vastus medialis, require a longer incision because of the bulk of the quadriceps muscle.

        Treatment Options

        • Traditional total knee approach

        • Subvastus approach

        • Midvastus approach

        • Quadriceps-sparing approach

         

        Examination/Imaging

      • Anteroposterior (Fig. 1A) and lateral (Fig. 1B) radiographs are obtained.

       

       

       

      FIGURE 1 A B

       

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      Positioning

      • The patient should be positioned in a standard supine position, with a thigh tourniquet high on the operative thigh.

      • A bump may be placed under the ipsilateral hip, if necessary. In addition, a foot holder or bump may be used to help rest the foot while flexing the leg during the operative procedure.

      • The leg should be prepped and draped in normal sterile fashion.

        Portals/Exposures

        Skin Incision

      • A straight anterior midline incision is made from the superior pole of the patella extending 10–14 cm distally to the superior aspect of the tibial tubercle (Fig. 2).

      • Minimal medial and lateral subcutaneous dissection creates flaps that expose the extensor mechanism, and proximal dissection with release of the deep fascia beneath the skin, superficial to the quadriceps tendon, facilitates exposure (Fig. 3). This dissection allows mobilization of the skin and subcutaneous tissue as needed during the procedure.

      • In addition, because of the elasticity of the skin, with the knee in flexion, the incision will stretch 2–4 cm, creating a “mobile window” that can be utilized throughout the procedure to permit broader exposure.

         

        P EARLS

        • Release deep fascia beneath skin to get better mobilization.

           

        • Pay careful attention to skin integrity.

           

        • Inject planned arthrotomy with lidocaine plus epinephrine to help reduce postoperative blood loss.

         

        Arthrotomy

      • The planned arthrotomy path is next injected with 30 ml of 1% lidocaine with epinephrine, which we have found to significantly decrease peri- and postoperative blood loss (Cushner et al., 2007).

      • The limited medial parapatellar arthrotomy initially extends 2–4 cm into the quadriceps tendon along its medial third, proximal to the superior pole of the patella (Fig. 4). The arthrotomy can then curve around the medial border of the patella, or can be taken straight over the medial aspect of the patella, peeling the quadriceps expansion from the patella, as described by Insall (1971).

    • Insall preferred the straight midline arthrotomy because it minimizes the disruption of the vastus medialis attachment to the patella, resulting in a straight pull of the extensor mechanism with less tension on the closure.

       

       

       

       

      MIS TKA with Parapatellar Arthrotomy

       

       

       

       

       

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      FIGURE 2

       

      FIGURE 3

       

      FIGURE 4

       

       

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    • If there is difficulty displacing the patella laterally or if the patellar tendon is at risk of tearing, the arthrotomy should be extended proximally to a more traditional approach by gradual lengthening into the quadriceps tendon and skin until adequate exposure is achieved.

      • Once the arthrotomy is made and the appropriate releases are done, the patella is everted and the knee is flexed (Fig. 5).

      • The deep medial collateral ligament, posteromedial capsule, and semimebranosus tendon are elevated subperiosteally from the proximal tibia while the knee is flexed, and the tibia then is externally rotated.

      • Careful placement of retractors protects the supporting soft tissue structures.

    • Specialized retractors are not required, but by using differential force, the arthrotomy can be moved as a mobile window from medial to lateral and from superior to inferior as necessary (Scuderi, 2006). This aids in observation of the joint without applying undue tension to the skin and capsular tissues.

       

       

       

       

      FIGURE 5

       

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      • Struggling to gain exposure by pulling or retracting a limited skin incision will cause unnecessary soft tissue trauma, including tearing and bruising. It is simpler to extend the incision 1–2 cm proximally or distally as needed to gain exposure.

        Procedure

         

        P EARLS

        • Removing tibia bone first enlarges flexion and extension gaps and exposes more of the knee.

           

        • Utilize mobile window created by arthrotomy with selective positioning of knee retractors.

           

        • Specialized and modified instruments can accommodate a smaller incision.

           

        • Careful placement of retractors is needed to protect the collateral ligaments and patellar tendon.

         

        Step 1: Tibial Resection

        • The order of bone resection is dependent on the surgeon’s preference, but we recommend cutting the tibia first.

        • An extramedullary guide is used for tibial resection, and intramedullary instrumentation is used for the distal femoral resection. Although instrumentation is modified to fit in a smaller space, there is no difference in the amount of bone resection.

        • With the knee in 90° of flexion, the tibia is resected perpendicular to the mechanical axis with an extramedullary cutting guide set at the appropriate depth and slope (Fig. 6).

      • The patellar tendon tends to push the proximal resection block medially; adjusting the distal aspect

         

         

         

        FIGURE 6

         

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        of the alignment guide toward the medial malleolus will compensate for this position and prevent a varus resection of the proximal tibia.

    • The retractors are strategically placed to protect the collateral ligaments and the patellar tendon. This mobile window is moved medially when the medial side is resected and laterally when the lateral aspect of the tibia is cut because pulling on both the medial and the lateral retractors at the same time limits exposure (Fig. 7).

    • To remove the resected proximal tibial bone, it may be necessary to bring the knee to 60–70° of flexion. The bone is then brought forward through the arthrotomy with external rotation as the soft tissue attachments are released.

      • Once the proximal tibia bone is removed, there is laxity of the joint in both flexion and extension, permitting easier exposure of the knee and placement of the femoral instrumentation (Fig. 8).

      • With an MIS approach, modified instruments must be used to complete the procedure.

    • Alignment guides and cutting blocks modified from standard instrumentation are reduced in size and have slightly altered and contoured geometry to facilitate placement within a smaller soft tissue envelope. This is especially helpful when the patella cannot be everted. The skin edges do need to be watched while the bone is being resected.

    • Careful placement of retractors will prevent the saw blade from inadvertently coming in contact with the skin and causing an undue laceration. Excessive retraction can lead to patellar tendon compromise or even to patellar tendon avulsion.

    • Extending the medial parapatellar arthrotomy as necessary is a quick and simple, yet essential solution to preserve soft tissue integrity and ensure a good postoperative result.

 

P EARLS

  • Use anteroposterior or epicondylar axis to select rotational positioning of the component.

 

Step 2: Femoral Resection

  • After removal of the proximal tibial bone, attention is directed to the femur.

  • The knee is once again brought to 90° of flexion, and a limited amount of synovial tissue and fat is resected from the anterior cortex. Very little dissection is performed in the suprapatellar pouch in an effort to reduce bleeding and scar tissue formation. The infrapatellar fat pad is also preserved for the same reasons.

  • The distal end of the femur is resected with a modified intramedullary cutting guide set at the appropriate valgus alignment (Fig. 9).

     

     

     

     

     

    MIS TKA with Parapatellar Arthrotomy

     

     

     

     

     

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    FIGURE 7

     

    FIGURE 8

     

    FIGURE 9

     

     

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  • The next step is to identify either the anteroposterior axis of the distal femur or the transepicondylar axis, which can be done with the knee flexed and careful positioning of the retractors (Fig. 10). Once the femoral rotation is determined, the femur is sized, and the appropriately sized component is selected (Fig. 11).

  • After resection of the anterior and posterior portions of the femur, the menisci are removed, and if a posterior-stabilized prosthesis is being implanted, the posterior cruciate ligament is completely resected.

     

     

     

     

     

    FIGURE 10

     

    FIGURE 11

     

     

    P EARLS

    • Well-established principles still followed.

       

    • Use spacer block to check balance of knees in both flexion and extension.

       

    • Soft tissue releases are performed as needed.

       

    • Miniaturized instruments are used to prepare femur for final components.

     

    Step 3: Balancing and Finishing the Tibia and Femur

    • Standard techniques using spacer blocks are critical steps to help assess alignment and ligament balancing (Fig. 12A and 12B).

       

       

       

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      A

       

       

       

      B

      FIGURE 12

       

  • Total knee arthroplasty is essentially a soft tissue operation focused on balancing the knee. After balancing the knee, the final finishing cuts are made on the distal femur (Fig. 13), and the tibia is sized and prepared to accept the final component

    (Fig. 14).

     

     

     

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    FIGURE 13

     

     

     

    FIGURE 14

     

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    Step 4: Patellar Preparation

    • The patella is prepared last. With the knee in extension or slight flexion, the patella is everted and resected at the appropriate depth.

    • With the proximal tibial and distal femoral resections completed, the additional laxity and space in the knee joint cavity allows the patella to be prepared with minimal extensor mechanism disruption.

       

      P EARLS

      • For trialing, it is easier to insert tibia first, then femur, then trial polyethylene insert.

         

      • In similar fashion, cement tibia, then femur and patella.

         

      • Front-loading tibial trays are useful to lock in articular surface.

       

      Step 5: Trial and Final Components

    • After bone preparation and soft tissue releases, the provisional components are implanted.

      • The tibial tray is implanted first. The knee is hyperflexed and externally rotated so that the tibia is introduced forward through the arthrotomy. The tibial tray is then seated in place.

      • The knee is brought back to 90° of flexion, and with distraction of the joint, the flexion space opens and the femoral component is impacted in place.

      • With a front-loading tibial component, the tibial articular surface is then inserted.

      • A trial reduction is done and the knee is assessed for balance and range of motion. If the trial tests are satisfactory, the provisional components are removed and the bone surfaces are cleaned with pulsatile lavage.

    • The final components are cemented in a sequential manner as described above (Fig. 15).

 

 

 

FIGURE 15

 

 

 

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A B

FIGURE 16

 

  • All excess cement is removed, and the knee is reduced (Fig. 16A and 16B). We have not found it necessary to apply any special techniques or additional incisions for cement removal.

  • The wound is then irrigated with an antibiotic solution.

  • The arthrotomy is closed over a suction drain with figure-of-8 absorbable Vicryl sutures placed in oblique fashion to exploit the vector pull of the vastus medialis muscle. The subcutaneous layer and skin are closed in a routine manner.

    Postoperative Care and Expected Outcomes

  • Thigh-high compression stockings, venodynes, and anticoagulation are initiated in the postanesthesia care unit. The reinfusion drain is removed the following morning.

  • Continuous passive motion is started in the recovery room. Physical therapy is initiated on postoperative day 1, with immediate weight bearing as tolerated and active range of motion as soon as the patient is alert and stable.

  • Pharmacologic anticoagulation is augmented with venodynes or pneumatic foot pumps, which the patient wears while in bed during the hospitalization.

  • Patients are discharged either to home or to a rehabilitation center within 2–4 days.

     

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    Clinical Results

    • Total knee arthroplasty has been one of the most successful surgical procedures in medical history, with investigators typically reporting 95% good to excellent results and greater than 94% survival at 10-to 15-year follow-up in conventional fixed-bearing TKA (Cook et al., 2006; Ranawat et al., 1993).

    • MIS in TKA is part of a continuum in modifying surgical technique. The MIS TKA approach discussed here modifies a traditional approach using a limited medial parapatellar arthrotomy to provide sufficient exposure to all three compartments of the knee. Its familiarity and simplicity make this the most popular MIS approach to TKA.

    • In appropriate patients, adhering to meticulous surgical technique and being aware of the limitations can help to avoid complications.

    • The success of MIS in TKA depends on appropriate patient selection and a willingness to extend

      the arthrotomy as needed for exposure. In our experience, the minimally invasive approach to total knee replacement has reduced the average skin incision by approximately 50%, to an average length of 10–14 cm, while use of this technique has not negatively affected our clinical success (Cook et al., 2006).

    • The benefit of MIS is not determined by the incision length or the cosmetic result, but rather in the more limited violation of the anatomic structures about the knee.

  • The addition of modified and smaller instruments has made it easier to access the knee joint via a limited approach with little or no damage to the extensor mechanism.

  • With less violation of the extensor mechanism and suprapatellar pouch, MIS in TKA offers the patient advantages in terms of decreased pain and morbidity, reduced analgesia use, diminished postoperative blood loss, improved quadriceps function, and faster postoperative recovery and return to normal function (Laskin, 2003; Tenholder et al., 2005).

  • The limited medial parapatellar MIS approach is preferred because it can be easily extended to a more extensile approach if there are any difficulties gaining exposure during the procedure.

 

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Evidence

Cook JL, Scuderi GR, Tenholder M. Incidence of lateral release in total knee arthroplasty in standard and mini-incision approaches. Clin Orthop Relat Res. 2006;(452):123-6.

 

Study reporting no correlation between size of incision and incidence of lateral release. (Level III evidence)

 

Cushner FD, Kim R, Scuderi GR, Kelly MA, Scott WN. Use of lidocaine with epinephrine injection to reduce blood loss in minimally invasive total knee arthroplasty. Transfus Altern Transfus Med. 2007;9:59.

 

Reduction in postoperative hemoglobin drop using injections comparing standard incision (3.3 g/dl drop) to mini-incision (2.0 g/dl drop).

Insall JN. A midline approach to the knee. J Bone Joint Surg [Am] 1971;53:1584-6. Laskin RS. New techniques and concepts in total knee replacement. Clin Orthop Relat

Res. 2003;(416):151-3.

 

Diminished analgesia use, improvement in postoperative flexion, improved ability to perform straight leg raise, less blood loss, and reduced hospital stays were acheived while performing TKAs through an 8- to 10-cm incision and mini-midvastus approach with maintained radiographic alignment and without an increase in operative time.

 

Ranawat CS, Flynn WF, Sadler S, Hansraj KK, Maynard MJ. Long-term results of the total condylar knee arthroplasty: a 15-year survivorship study. Clin Orthop Relat Res. 1993;(286):94-102.

 

Romanowski MR, Repicci JA: Minimally invasive unicondylar arthroplasty: eight year follow-up. J Knee Surg 2002;15:17-22.

 

Scuderi GR. Minimally invasive total knee arthroplasty with a limited medial parapatellar arthrotomy. Oper Tech Orthop 2006;16:145-52.

 

Review of minimally invasive primary total knee replacement demonstrates improved postoperative motion and decreased immediate postoperative blood loss and transfusion requirements.