Total Knee Replacement (TKR) - Surgical Steps

PHASE 1 - PATIENT POSITIONING & SETUP

• Patient placed supine on operating table
• Tourniquet applied to the proximal thigh
• Leg positioned in flexion (knee bent over the side of the table or with a leg holder)
• Sterile prep and draping of the entire lower extremity

PHASE 2 - SURGICAL APPROACH

1. Skin incision - Anterior midline incision made with the knee in flexion (allows subcutaneous tissue to fall medially/laterally, improving exposure). The incision must be long enough to avoid skin tension and potential necrosis.
2. Previous scars - Incorporate existing anterior scars if in a usable position. If multiple scars exist, use the most lateral one (blood supply to the anterior knee skin is predominantly medial).
3. Retinacular incision - Medial parapatellar retinacular approach: the incision extends proximally the length of the quadriceps tendon (leaving a 3-4 mm cuff of tendon on the vastus medialis for closure), around the medial side of the patella, then 3-4 cm down the anteromedial tibia along the medial border of the patellar tendon.
4. Medial dissection - Subperiosteally elevate the anteromedial capsule and deep medial collateral ligament off the tibia to the posteromedial corner.
5. Patellar eversion - Extend the knee and evert (or subluxate laterally) the patella, releasing lateral patellofemoral plicae.
6. Joint preparation - Flex the knee and remove the ACL and anterior horns of both menisci along with any osteophytes causing malposition or soft-tissue imbalance. If PCL-substituting, resect PCL now or later. Subluxate and externally rotate the tibia (relaxes extensor mechanism, reduces risk of patellar tendon avulsion).

Alternative approaches: Subvastus ("Southern") approach - bluntly mobilizes the distal medial border of vastus medialis, dislocating the entire extensor mechanism laterally (preserves quadriceps integrity, faster strength recovery but limited exposure in obese patients). Midvastus approach - splits the vastus medialis in line with its fibers rather than subluxating it.

PHASE 3 - BONE RESECTION (Technique 8.2 - Measured Resection)

Distal Femoral Cut

1. Cut the distal femur at a valgus angle of 5-7 degrees (measured perpendicular to the mechanical axis of the femur, confirmed on long-standing radiograph). Amount of bone removed equals that replaced by the femoral component.
   • For preoperative flexion contracture: additional resection may be done, but avoid elevating the joint line >4 mm.
   • For PCL-substituting prosthesis: resect an additional 2 mm distally.

Femoral Component Rotation (Anterior/Posterior Cuts)

1. The anterior and posterior femoral cuts determine rotational alignment of the femoral component, which shapes the flexion gap:
   • Transepicondylar axis: posterior femoral cut parallel to a line connecting medial and lateral epicondyles.
   • AP axis (Whiteside's line): posterior femoral cut perpendicular to a line from the trochlear sulcus to the top of the intercondylar notch.
   • Posterior condylar reference: cut in 3 degrees of external rotation off the posterior condylar line (caution in valgus knees with hypoplastic lateral condyle - risk of internal rotation error).
2. Anterior/posterior femoral sizing:
   • Posterior referencing: measures thickness of posterior condylar resection directly - more accurate in recreating original dimensions, but higher risk of anterior femoral notching.
   • Anterior referencing: measures AP dimension from anterior femoral cortex - more reliable flange seating against anterior femur.
3. Chamfer cuts completed (anterior and posterior) for PCL-retaining design. For PCL-substituting design: intercondylar box cut made to accommodate the post-and-cam housing.

Proximal Tibial Cut

1. Cut the tibia perpendicular to its mechanical axis, using an intramedullary or extramedullary cutting guide. Key points:
   • Posterior slope: 3 degrees (often built into the polyethylene insert in most modern systems).
   • Amount of resection: measured off the less arthritic side - typically 8-10 mm. If measured off the more arthritic side: 2 mm or less.
   • Protect the patellar tendon and collateral ligaments during this cut.
   • The proximal tibia may be cut before or after distal femoral cuts.

Patellar Resection

1. Resect the articular surface of the patella with a specialized saw or burr, resecting only enough to accommodate the patellar component thickness and avoid "overstuffing" the patellofemoral joint.

PHASE 4 - GAP BALANCING & SOFT-TISSUE RELEASES

1. Place spacer blocks or tensioners in the flexion and extension gaps to assess rectangular balance.
2. Remove all osteophytes from the tibial and femoral periphery first (medial, lateral, and posterior condylar osteophytes - posterior osteophytes block flexion and tent posterior soft tissues).

• Anterior half of superficial MCL - primarily affects the flexion gap
• Posterior half of superficial MCL + posterior oblique ligament - primarily affects the extension gap
• Subperiosteal release done with elevator/osteotome off proximal tibia

• Iliotibial band (ITB) - affects extension gap
• Lateral collateral ligament - affects both flexion and extension gaps
• Popliteus tendon - affects flexion gap more
• Posterolateral corner - affects extension gap more
• Posterior capsule off lateral femoral condyle - if still not balanced
• Pie-crusting technique: multiple stab incisions parallel to joint line to elongate tight lateral structures (peroneal nerve is within 1.5 cm of posterolateral corner - flex knee to protect it)

• Balance medial/lateral soft tissues first
• If contracture persists: release posterior structures
• Last resort: elevate joint line with additional distal femoral resection (max 4 mm to avoid midflexion instability)

PHASE 5 - TRIAL REDUCTION

1. Insert trial tibial baseplate, femoral, and patellar components.
2. Reduce the knee and assess:
   • Varus/valgus stability in extension and at 30 degrees flexion
   • Anteroposterior stability in flexion (especially for PCL-retaining designs)
   • Range of motion (target: full extension to >90 degrees flexion minimum)
   • Patellar tracking through the full arc of motion ("no touch" test - patella should track centrally without thumb pressure on the lateral retinaculum)
3. Adjust gap balance, implant sizing, or releases as needed before final cementation.

PHASE 6 - CEMENTATION & FINAL IMPLANTATION

1. Pulsatile lavage and drying of all bone surfaces to maximize cement interdigitation.
2. Lateral retinacular release performed if needed for patellar tracking (inside-out or outside-in technique).
3. Tibial component cemented first: apply PMMA in the initial "sticky" phase to the tibial baseplate (including the keel), pressurize into cancellous bone (2-5 mm intrusion adequate). A suction drain in a pin site keeps blood and fat from contaminating the cement-prosthesis interface.
4. Femoral component cemented: apply a limited amount of cement to the posterior femoral bone surface (access to posterior recesses is very limited once components are in).
5. Patellar component cemented: use cement in early dough phase for adequate intrusion.
6. Remove excess cement from all component peripheries. Extend the knee with a trial tibial spacer to ensure complete femoral component seating and clear posterior recesses of cement debris.
7. Tibial polyethylene insert locked or screwed into the tibial baseplate.

All three components may be cemented simultaneously with an experienced team, or sequentially with two cement batches (tibia first, then femur/patella).

PHASE 7 - WOUND CLOSURE

1. Irrigate joint thoroughly.
2. Close the retinacular incision (medial parapatellar) with the knee in approximately 45-60 degrees of flexion to avoid overtightening the repair.
3. Close subcutaneous layer.
4. Skin closure with staples or sutures.
5. Apply compressive dressing; tourniquet released.

PHASE 8 - POSTOPERATIVE MANAGEMENT

• Compressive dressing + optional knee immobilizer until adequate quadriceps strength
• Weight bearing as tolerated from postoperative day 1
• Range-of-motion exercises initiated immediately; CPM no longer routinely used
• Passive extension: foot elevated on pillow; active/passive flexion: dangling legs over bed
• Outpatient physical therapy 1-2x/week for 6-8 weeks focusing on quad strengthening and gait training
• DVT prophylaxis per protocol

• Campbell's Operative Orthopaedics, 15th Ed. 2026, Techniques 8.1, 8.2, 8.7, 8.11, 8.12