Minimally Invasive Surgical Approaches In Total Knee Arthroplasty
Condition: Knee Osteoarthritis
MeSH terms: Osteoarthritis; Osteoarthritis, Knee
Study type: Interventional

Summary: 
      The hypothesis of the proposed study is that performing total knee arthroplasty through a
      mini subvastus approach results in statistically significant differences in one or more of
      the above functional outcome measures, when compared in a blinded, prospective, controlled,
      randomized manner to mini-medial arthrotomy approach.

        1. Analyses of lower extremity functional activities (gait and stairs)

        2. Strength of thigh musculature

        3. Self-assessment of the functional outcomes

        4. Return to the activities of daily living and sports activities
    

Detailed description: 
      In order to assign patients to specific treatment groups in an unbiased manner, randomization
      will occur prior to surgery. The assigned treatment codes for patients in each group will be
      generated by a computerized randomization program developed by the department of
      biostatistics, taking into account factors such age, sex and BMI. After the patient has met
      the entrance criteria, and given their full informed consent to participate in the study,
      they will be randomly assigned to one treatment group. Patient randomization will be
      performed during the clinic visit at which the surgery is scheduled, which typically occurs
      1-3 days prior to surgery. The patients enrolled in the functional recovery measurement
      subset will be a consecutive series of the randomly assigned patients until 20 patients are
      assigned in each of the two study arms.

      Operative Procedures The mini-subvastus approach and the medial parapatellar approach are the
      two surgical approaches that will be studied with respect to gait analysis, activity level
      and thigh strength. A cemented condylar implant, FDA approved devices, will be used for all
      cases in this study. The only difference between the two treatment groups will be the
      surgical approach for inserting these components. These two surgical approaches comprise the
      two study arms and are described in detail below.

      Minisubvastus approach :

      The skin incision is made from the superior pole of the patella to the top of the tibial
      tubercle and typically measures 3.5 inches in extension. The MIS subvastus approach is
      amenable to stepwise surgeon learning, and it is recommended that surgeons start with a
      traditional 6- to 8-in incision and then shorten the incision length as they gain familiarity
      with the subvastus exposure. The medial skin flap is elevated to clearly delineate the
      inferior border of the vastus medialis obliquus (VMO) muscle. The inferior border of the VMO
      is almost always found more inferior and more medial than most surgeons anticipate. This
      anatomy is very consistent, and the tendon at the inferior edge of the VMO attaches at a 50
      degrees angle and attaches to the midpole of the patella. It is very important to save this
      edge of tendon as that is where the retractor will rest so that the VMO muscle itself is
      protected throughout the case. Incise with cautery along the inferior edge of the VMO over to
      the midpole of the patella (do not be tempted to cheat this superiorly as that will hinder,
      not help, the ultimate exposure). The proximal limb of the incision, which parallels the
      inferior edge of the VMO, is made at a 508 angle relative to the long axis of the femur.
      After intersecting the midpole of the patella the incision is directed straight distally
      along the medial border of the patellar tendon down to the inferior border of the tibial
      tubercle. A narrow 90 degrees bent Homan retractor is placed in the lateral gutter and rests
      against the robust edge of VMO tendon that was preserved during the exposure. The patella is
      completely retracted, with surprisingly little force, into the lateral gutter. The knee is
      then flexed to 90 degrees providing excellent exposure of the distal femur. If the patella
      does not slide easily into the lateral gutter with this maneuver it is typically because a
      portion of the medial patellofemoral ligament remains attached to the patella usually because
      the proximal limb of the arthrotomy was made in too horizontal a fashion rather than at the
      50 degrees angle that parallels the VMO. The distal femur is prepared with a narrow version
      of a standard intramedullary resection guide. By bringing the knee out to 60 degrees of
      flexion the anterior portion of the distal femur can be visualized well. This position also
      relaxes the skin over the anterior femur making it easier to retract. If a very small skin
      incision is to be used, then the distal femur is cut one condyle at a time with the
      intramedullary portion of the cutting guide left in place for added stability. If a slightly
      longer skin incision is used, the distal cutting guide can be pinned in place and both
      condyles cut in a standard fashion. The tibia is prepared next and that is done to provide
      more working room for subsequently sizing and rotating the femoral component (the most
      difficult part of any MIS TKA). Good exposure of the entire surface of the tibia is
      accomplished with 3 retractors placed precisely: a pickle-fork retractor posteriorly to
      provide an anterior drawer and bent Homan retractors medially and laterally to protect the
      collaterals and define the perimeter of the tibial bone. The tibial resection is carried out
      with an extramedullary guide that is positioned under the skin but on top of the patellar
      tendon anteriorly. Because of this positioning, care must be taken to protect the patellar
      tendon during proximal tibial resection. The tibia is cut in one piece using a narrow but
      thick saw blade that fits the captured guide. The narrow blade allows sufficient
      maneuverability to work around the patellar tendon and sufficient tactile feedback for the
      surgeon to sense when the posterior and lateral tibial cortex has been cut. The femoral
      sizing and rotation guide is designed to be pinned to the distal femur and is thin enough
      that the knee can subsequently be brought out to 60 degrees of flexion to visualize the
      anterior femur for accurate sizing. By bringing the knee to 60 degrees of flexion and placing
      a retractor anteriorly the surgeon can confirm that the femoral cortex will not be notched.
      It is appropriate to clear some of the synovium overlying the anterior femoral cortex to be
      sure that femoral sizing is accurate and that the femur is not going to be notched. The
      femoral finishing guide can be translated medially or laterally and femoral rotation can be
      confirmed by referencing the posterior condyles, Whiteside's line, or the transepicondylar
      axis, all of which can be clearly defined with this subvastus approach. Before cutting the
      anterior femoral cortex the surgeon should confirm that the guide is placed appropriately to
      avoid notching. Trial components can be assembled and the knee reduced with a trial tibial
      insert to check overall limb alignment and flexion/ extension gap balance. Patellar
      preparation with this surgical approach can be saved until the end. Cutting the patella is
      not required for exposure, and by leaving the patella until the end the risk of inadvertent
      damage to the cut surface of the patella is minimized. The patella can be prepared freehand
      or with the surgeon's choice of cutting or reaming guides. If a cutting guide is used it is
      useful to remove the trial components before patellar preparation as then the entire limb can
      shorten, taking tension off the extensor mechanism and allowing easier access to the patella
      for preparation. The modular tibial tray is cemented first followed by the femur and then the
      patella. The tibia is subluxed forward with the aid of the pickle-fork retractor and the
      medial and lateral margins of the tibia are exposed well with 90 degrees bent Homan
      retractors. Care is taken to remove excess cement from around the tibial base plate,
      particularly posterolaterally, before moving on to cementing of the femur. The tibia is then
      repositioned under the femur at 90 degrees of flexion and the femur is exposed for cementing
      by placing bent Homan retractors on the medial and lateral sides above the collateral
      ligament insertions on the femur. A third retractor is placed under the VMO where it overlies
      the anterior femur. Cement is applied to both the posterior femoral condyles and the anterior
      femoral flange of the femoral implant and then cement is applied directly to the bone of the
      distal femur and anterior chamfer cuts. Alternately, the entire undersurface of femoral
      implant can be coated with cement before impaction. Care is again taken to remove all excess
      cement with special attention paid to the distal lateral surface of the femur where cement
      can extrude and be difficult to visualize once the patella is cemented. At this point the
      real tibial insert can be placed or a trial insert can be used as the surgeon sees fit. The
      patella is cemented last. Once the cement has hardened, patellar tracking is readily
      assessed. One should see centrally tracking without tilt or subluxation and contact of the
      patellar component with the medial femoral condyle with the knee in 908 of flexion. The
      tourniquet should be let down and any small bleeders in the subvastus space should be
      cauterized. The closure is begun by first reap proximating the corner of capsule at the
      midpole of the patella. Then, 3 interrupted 0-vicryl sutures are placed along the proximal
      limb of the arthrotomy. Care is taken to place those sutures deep to the VMO muscle itself
      and instead to grasp the underlying synovium attached to the VMO instead of the muscle
      itself. These first 4 sutures are then tied with the knee at 90 degrees of flexion to avoid
      oversewing the medial side and creating an iatrogenic patella baja postoperatively. A deep
      drain is placed in the knee joint and the distal/vertical limb of the arthrotomy is closed
      with multiple interrupted 0-vicryl sutures placed with the knee in 90 degrees of flexion. The
      skin is closed in layers. Staples are preferred over a subcuticular suture for the final
      closure. There is unquestionably more tension placed on the skin during any MIS TKA surgery
      than is the case in standard open surgery and, in our experience, the potential for wound
      healing problems is magnified if the skin is handled multiple times as is the case with a
      running subcuticular closure.

      Standard Approach:

      A medial parapatellar approach will be performed in the control group; this is a contemporary
      modification to the standard approach for total knee arthroplasty.

      Postoperative Course Hospitalization Patients will come into the hospital on the day of their
      surgery. Hospitalization of 2 to 3 nights is routine for these patients, although
      complications may prolong that time. The patient will receive one preoperative dose and three
      postoperative doses of IV antibiotics over a 24 hour period. All patients will receive
      appropriate anticoagulation for deep venous thrombosis prophylaxis.

      Postoperative Physical Therapy

      Both treatment groups will have identical postoperative care via standard postoperative
      clinical pathways. Structured physical therapy will begin the day after surgery and continued
      during the hospitalization. Patients are encouraged to sit up at the bedside the evening of
      their surgery. A home therapy program will be given to the patient, although formal physical
      therapy will not continue on an outpatient basis. The following general principles will be
      followed and the patient instructed accordingly:

        -  Post-op Day 1, transfer from bed to chair with assist

        -  Active ROM to begin within first 24 hours postoperatively

        -  Weight bearing status and progression as tolerated

        -  Progress ambulation from walker to crutches/cane(s) as tolerated

        -  Patients should be encouraged to maximize independent ambulation and increase distance
           ambulated daily

      Discharge Criteria

        -  Patient is independent and safe with aids

        -  Patient is able to transfer out of and into bed from a standing position

        -  Is able to rise from a chair to a standing position

        -  Ambulate 100 feet
    

Intervention name(s): Minimally invasive total knee replacement; Standard approach total knee replacement
Intervention type(s): Procedure; Procedure
Intervention description(s): A cemented tricompartmental total knee replacement will be performed using a minimally invasive surgical approach.; A cemented tricompartmental total knee replacement will be performed using a traditional medial parapatellar surgical approach.
Other intervention name(s): Posterior stabilzed total knee replacement.; Minimally invasive total knee replacement.; Posterior stabilized total knee replacement.; Minimally invasive total knee replacment.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Treatment