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TKR: Surgical Approach


- Discussion:
    - anterior longitudinal incision allows full exposure of the proximal tibia;
          - this incision allows exposure of both medial & lateral aspects of joint w/o the necessity for large skin flaps;
    - this incsion has advantage that it leaves strong cuff of fibrous tissue attached to vastus medialis obliquus muscle;
    - this strong cuff facilitates suture placement and secure closure at the end of the case;
    - straight incisions are less disruptive to the blood supply to knee than curved incisions;
    - a gentle medially curved incision is an alternative which may heal with less prominent scarring and may better facilitate
             knee flexion (because of less scar contraction);
    - hazards:
             - small medial or hockey stick incisions usually do not present a problem;
             - w/ longitudinal parallel scars, it is important to avoid lateral skin flaps, and therefore lateral scars should be re-used; 
             - infra-patellar branch of saphenous nerve:
                     - Neuroma of the infrapatellar branch of the saphenous nerve a cause of reversible knee stiffness after total knee arthroplasty

- Technique:
    - tourniquet considerations:
           - ensure that leg is optimally exsanguinated inorder to reduce residual venous stasis and to reduce the chances of venous thrombosis; 
           - goal is to use the lowest tourniquet pressure possible;
           - references:
                  - Vascular injuries in total knee arthroplasty. A review of the problem with special reference to the possible effects of the tourniquet.
                  - Total knee arthroplasty after ipsilateral peripheral arterial bypass graft: acute arterial occlusion is a risk with or without tourniquet use.
                  - Total knee arthroplasty in patients with peripheral vascular disease

    - incision considerations:
            - expose the knee joint thru a straight longitudinal incision beginning 6-12 cm proximal to superior pole of the patella, extending
                   over patella, & ending at the medial border of tibial tuberosity or approx 6 cmm distal to the inferior pole of the patella;
           - some surgeons prefer to vary the incision w/ a gentle medial curve over the patella, arguing that the curved incision is less likely
                     to scar and contract;
           - consider carrying incision upto 12 cm from superior pole of patella & carry it inferiorly an equal distance below inf margin of patella;
           - this reduces degree of skin retraction and lowers risk of tissue necrosis; 
           - references:
                   - Hypesthesia after Anterolateral versus Midline Skin Incision in TKA: A Randomized Study
                   - Incision stretching in primary TKA: what is the real length of our approach?

      - superficial retinaculum:
           - after incising skin & subQ fat, it is important to sharply dissect down onto superficial retinaculum w/o undermining above this layer;
           - this preserves the subfascial vessels, decreasing risk of skin slough;
           - generally, the surgeons knife will incise thru a portion of the superficial retinaculum while incising thru the subQ layer;
           - at this point, insert curved Mayo's thru this defect and spread underneath both proximally and distally;
           - further mobilize this layer and the gently separate the retinaculum from the underlying deep fascia using the dull end of the scapel;
           - undermining is performed medially until the fascia is elevated 5 mm past the patella;
           - excessive lateral undermining may cause necrosis of skin overlying patella (esp if lateral retinacular release is performed later in case); 

- Quadriceps and Patellar Tendon Incision:
    - at proximal apex of  incision, incise thru medial 1/3 of quadriceps and continue deep incision distally to superior border of patella;
    - continue the incision tightly along the medial border of the patella down to the superior border of the patellar tendon;
           - preserve a narrow margin of capsule on patella to make wound closure easier
    - continue the incision distally thru the medial third of the patella tendon down to the tibial tubercle;
           - this technique offers tremendous exposure of the knee, and allows easy eversion of the patella;
           - it is essential not to disturb the insertion of the medial patellar tendon insertion;
           - lower part of incision should not extend below tibial tubercle inorder, to avoid damaging infrapatellar branch of saphenous nerve;
           - transect the fat pad in line with the primarily capsular incision;
    - mid-vastus arthrotomy:
           - advantage over the standard incision is that the vastus medialis insertion into the medial border of the quadriceps tendon (allows rapid restoration of extensor mechanism);
           - vastus medialis muscle is divided in its mid-substance in the direction of its fibers;
           - incision is made with the knee in flexion (automatically retracts transected tissues and places tension on tissues about to be cut);
           - incise thru the superficial retinaculum but leave a thin layer of fascia over the VMO;
           - w/ the knee in full flexion, split thru the tendon at the superomedial corner of the patella, but do not split more than 4 cm;
           - release the capsular folds of the suprapatellar pouch proximal to the patella, and evert the patella;
    - references:
           - V-Y quadricepsplasty in total knee arthroplasty.
           - Subvastus (Southern) approach for primary total knee arthroplasty.
           - Evolution of the quadriceps snip.
           - Surgical technique of the midvastus arthrotomy.      
           - Comparison of the vastus-splitting and median parapatellar approaches for primary total knee arthroplasty: a prospective, randomized study.
           - A Comparison of Subvastus and Midvastus Approaches in Minimally Invasive Total Knee Arthroplasty
           - Does the length of incision in the quadriceps affect the recovery of strength after total knee replacement? a prospective randomised clinical trial.


- Excision of Fat Pad:  
    - use the back end of the scapel to bluntly separate the potential space between the fat pad and the patellar tendon;
    - once this space has been defined, use to knife to completely remove the fat pad;
    - reference:
           - Scintigraphic determination of patellar viability after excision of infrapatellar fat pad and/or lateral retinacular release in total knee arthroplasty.

- Inverted V Capsular Incision:
    - may be indicated in revision cases or when there is difficulting in everting the patella;
    - inverted V capsular incision w/ 2nd arm of inverted V begins at proximal apex & extends at 45 deg angle across quadriceps tendon, through vastus lateralis
           tendon, & into portion of iliotibial band;
           - incision should stop short of sup. lateral geniculate artery;
           - release decreases tension on patellar ligament & allows eversion of patella in almost all patients, regardless of previous surgery;
           - it is crucial not to avulse the patellar ligament from tubercle

Wound problems in total knee arthroplasty.

A Prospective Randomized Study of Minimally Invasive Total Knee Arthroplasty Compared with Conventional Surgery

Intramuscular Hematoma Following a Midvastus Approach During Primary Total Knee Arthroplasty