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TKA - Parapatellar Approach

Preoperative Patient Care

A

Outpatient Evaluation and Management

1

Obtain focused history and performs focused exam

  • identify medical issues that may impact surgical care
  • knee specific exam should include assessment of soft tissues, range of motion, laxity, and distal neurovascular exam

2

Interprets basic imaging studies (radiographs)

  • AP, including weight bearing views
  • lateral
  • tunnel view/sunrise view

3

Prescribes and manages nonoperative treatment

  • NSAIDs
  • physical therapy
  • assistive devices
  • injections

4

Makes informed decision to proceed with operative treatment

  • documents failure of non-operative management
  • describes accepted indications and contraindications for surgical intervention

5

Provides post-operative management and rehabilitation

  • postop: 2-3 week postoperative visit
  • wound check
  • remove sutures/staples
  • check radiographs
  • continue physical therapy
  • diagnose and management of early complications
  • postop: 3 month postoperative visit
  • check radiographs
  • diagnosis and management of early/late complications
  • postop: 1 year postoperative visit
  • check radiographs
  • diagnosis and management of late complications
B

Advanced Evaluation and Management

1

Appropriately orders and interprets advanced imaging studies

  • Advanced radiographic views, MRI, CT, nuclear medicine imaging, etc.

2

Appropriately recommends surgical intervention

3

Modifies and adjusts post-operative treatment plan as needed

C

Preoperative H & P

1

Obtains history and performs physical exam

  • identify medical issues that may impact surgical care
  • knee specific exam should include assessment of soft tissues, range of motion, laxity, and distal neurovascular exam

2

Order basic imaging studies

  • multiplanar radiographs of the knee, preferably weight bearing
  • 3-foot standing films for leg alignment (optional)

3

Perform operative consent

  • describe complications of surgery
  • infections
  • thromboembolic events
  • peri-prosthetic fracture
  • neurovascular compromise
  • malalignment
  • patellar maltracking

Operative Techniques

E

Preoperative Plan

1

Radiographic templating

  • template implant sizes

2

Execute surgical walkthrough

  • describe steps of the procedure to the attending prior to the case
  • describe potential complications and steps to avoid them
F

Room Preparation

1

Surgical instrumentation

  • knowledge of the particular implant system and instrumentation

2

Room setup and equipment

  • standard OR table
  • leg holder (optional)

3

Patient positioning

  • supine position
  • bump under the operative hip to minimize hip external rotation if needed (goal is to have patella facing straight up)
  • leg holder can be used to hold the knee at 90 degrees or more of flexion during certain parts of the procedure
  • hip tourniquet should be placed as proximal as possible to allow adequate room for prepping and draping (ideally placed in hip crease)
G

Medial Parapatellar Approach to the Knee

1

Draw incision and identify anatomy

  • identify tibial tubercle, patella, and patellar ligament
  • draw a straight midline incision starting several centimeters (generally two finger breadths) proximal to the proximal pole of the patella and continuing just distal to the tibial tubercle

2

Incise to extensor mechanism

  • carry the skin incision straight down to the deep fascia which marks the extensor mechanism (quad tendon, patella, and patellar ligament)

3

Create skin flaps

  • elevate skin flaps just deep to the fascia
  • the perforating arteries which supply the skin run just superficial to the deep fascia
H

Arthrotomy & Deep Exposure

1

Identify medial aspect of patellar tendon and quadriceps tendon

  • identify the medial aspect of the patellar ligament, medial aspect of the patella and the quad tendon lateral to the vastus medialis oblique (VMO).

2

Perform arthrotomy

  • start from the proximal aspect in a longitudinal manner curving medially around the patella,
  • leave 3-5 mm of soft tissue on the patella to assist with arthrotomy closure later in the case
  • complete the arthrotomy by a straight distal cut along the medial border of the patellar ligament
  • avoid any disruption of the tendon insertion on the tibial tubercle
  • the main danger of the approach is avulsion of the patellar ligament.

3

Perform proximal tibia soft tissue release

  • sharply dissect enough of the medial capsular sleeve off of the tibia to provide exposure of the joint
  • the amount of dissection is variable, depending on the particular knee, but a good rule of thumb is to dissect the tibia posteriorly to the mid-coronal plane
  • in cases of severe fixed varus deformity
  • dissection may need to be carried even more posteriorly to provide exposure
  • medial tibial osteophytes are often present, and removal of them will provide more release of the medial collateral ligament/capsular sleeve
  • in the case of a severe valgus deformity
  • medial laxity may already be present, so a conservative medial dissection is advisable to start

4

Flex knee, evert patella, and prepare joint space

  • flex the knee to at least 90 degrees and evert the patella
  • resect fat pad
  • resect ACL remnant
  • resect meniscus
  • the anterior horn of the lateral meniscus, (the medial meniscus is usually dissected with the medial capsular flap)
  • place retractors
  • a lateral retractor is then placed under the lateral meniscus near the mid-coronal plane
  • a medial retractor retracts the medial sleeve
  • posterior retractor (PCL or Hohmann style) is placed in front to the PCL to push the tibia anteriorly
I

Femoral Cuts

1

Identify proper femoral rotation

  • identify correct femoral rotation judged by 3 landmarks
  • intercondylar sulcus
  • epicondylar axis
  • a line perpendicular to the long axis of the tibia
  • this is perhaps where surgeons have the greatest disagreement - the measured resection technique usually references from the epicondylar axis or the intercondylar sulcus while the gap balancing technique uses the axis perpendicular to the tibia when the knee is distracted at 90 degrees of flexion
  • the femoral rotation axis can be performed before or after the distal femoral cut is made

2

Place femoral intramedullary guide

  • the entry point is in the midline just anterior to the intercondylar notch
  • use a starter reamer for identification of the femoral canal for placement of the distal femoral cutting jig
  • suction the canal to remove the marrow contents

3

Place femoral cutting gig and confirm rotational alignment.

  • place and secure the distal femoral cutting jig
  • place the appropriately sized cut block in the selected rotation and size (careful not to internally rotate the jig)

4

Make femoral cuts

  • options
  • measured resection
  • utilize a jig anchored on the posterior condyles
  • resects an amount of bone equal to the implant thickness
  • gap balancing
  • this is done after the tibia is cut with the joint tensed at 90 degrees of flexion
  • the posterior bone cut is selected to produce the desired flexion gap (femur and tibia)
  • The potential complications during bone cuts are cutting the MCL or, rarely, the popliteal artery

5

Do posterior capsule release and remove posterior osteophytes

  • important in patients with a pre-operative flexion contracture, especially over 10 degrees
J

Tibia Cuts

1

Place tibial retractors

2

Place extramedullary tibial guide

  • maximally flex the knee and expose the proximal tibia
  • place the cutting jig in the desired varus/valgus alignment and posterior slope

3

Determine amount of tibial resection based on diseased side (medial v lateral plateau)

  • fix the jig with multiple pins

4

Make tibial cut

  • saw cut is made and the resected bone is removed
  • remove any remaining meniscus and posterior osteophytes

5

Trial tibial base plate

  • the trial tibial base plate is sized and placed in the proper rotational position (medial 1/3 of patellar ligament)

6

Trial femoral and tibial implants

  • place the trial implants and test the joint for stability and balance in both flexion and extension
K

Confirm Balancing and Trial Components

1

Place tibial base plate trial

2

Place femoral trial component

3

Balance extension gap

  • Knee should be able to fully extend (no flexion contraction)

4

Balance flexion gap

  • Components should not extrude in full flexion ("lift off sign" indicating too tight)

5

Check varus/valgus balance

  • perform soft tissue releases as needed to address any discrepancies

6

Confirm implant sizes and begin preparing cement

L

Patella Preparation and Final Implant Placement

1

Prepare the patella

  • evert patella and make patellar cut
  • goal is reproduce the original patellar thickness (remnant cut patella + patellar component)
  • expose the articular surface of the patella, remove marginal osteophytes, and cut the patella at the appropriate height
  • drill lug holes with a guide
  • check patellar tracking within trochlea without manually guiding patella ("no-hands" technique)

2

Place the cement

  • pulse lavage bone to prepare for cementing and dry as best as possible
  • place cement on tibia and femur

3

Place final implants

  • place tibial, femoral, and patellar components and trial poly liner

4

Confirm final flexion/extension and varus/valgus stability

N

Wound Closure

1

Irrigate and obtain hemostasis once tourniquet is deflated

2

Place drain (optional)

3

Close joint capsule/arthrotomy

  • the joint capsule is closed with interrupted or running suture
  • closing the capsule at the proximal and distal patellar poles works well to line up the remaining capsular closure

4

Perform superficial closure

  • subcutaneous tissue and skin closure per surgeon preference (generally vicryl suture for subcutaneous closure and staples or monocryl suture for skin closure)

5

Dressing is applied

Postoperative Patient Care

O

Perioperative Inpatient Management

1

Write comprehensive admission orders

  • advance diet as tolerated
  • pain control
  • wound management
  • foley out when ambulating
  • check appropriate labs
  • antibiotics
  • prescribe DVT Prophylaxis
  • appropriately orders and interprets basic imaging studies
  • obtain post-op radiographs of the knee
  • inpatient physical therapy
  • initiate physical therapy as soon as possible
  • weight bearing as tolerated
  • immediate range of motion exercises to knee

2

Appropriate medical management and medical consultation

3

Discharges patient appropriately

  • pain meds
  • wound care
  • outpatient physical therapy/rehabilitation
  • generally follow up in 2 weeks
R

Complex Patient Care

1

Develops unique, complex post-operative management plans

2

Diagnosis and management of complex complications

  • infections
  • thromboembolic events
  • dislocations
  • neurovascular compromise
 

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