The Knee and Leg



The Knee and Leg





INJECTIONS AND ASPIRATIONS


Intra-articular Knee Injection/Aspiration



Superomedial/Lateral Approach


Description of Procedure



  • Position the patient supine with the knee in extension.


  • Prepare a wide area of the skin with antibacterial solution.


  • Optional: Mark the entry site with a marking pen. Perform this step before application of antibacterial solution if a nonsterile pen is used.


  • The entry site is typically 1 cm medial or lateral to the respective border of the patella at the superior pole.


  • Optional: Anesthetize the skin overlying the planned entry site with 2 to 3 mL of local anesthetic.


  • Direct the needle through the skin into the suprapatellar pouch, which is between the patella and femur. If bony resistance is met, evaluate both your starting point and the angle of your needle and determine if you are encountering the patella or femur before making adjustments. The thickness of the patella is commonly underestimated (Figs. 6-1 and 6-2).



  • Aspirate synovial fluid to verify that the needle is appropriately positioned.


  • Continue aspirating or inject the desired solution.






FIGURE 6-1






FIGURE 6-2


Anteromedial/Lateral Approach


Description of Procedure



  • Position the knee in 90° of flexion.


  • Prepare a wide area of the skin with antibacterial solution.


  • Palpate medial/lateral joint line and the medial/lateral boarder of the patellar tendon.


  • Optional: Mark the entry site with a marking pen. Perform this step before application of antibacterial solution if a nonsterile pen is used.


  • The entry site is approximately 1.5 cm proximal to the tibial plateau, just medial or lateral to the respective side of the patellar tendon. The joint line is typically palpable; however, the distal pole of the patella is a good landmark for the level of the joint (Fig. 6-3).


  • Optional: Anesthetize the skin overlying the entry site with 2 to 3 mL of local anesthetic.


  • Direct the needle through the skin into the anterolateral/medial area of the knee joint. If bony resistance is met, evaluate your position, withdraw the needle to the skin, and redirect. An entry site or angle too distal will cause you to hit the tibia, and an entry site or angle too proximal will cause you to hit the respective femoral condyle (Figs. 6-4 and 6-5).


  • Aspirate synovial fluid to verify that the needle is appropriately positioned.


  • Continue aspirating or inject the desired solution.


Tips and Other Considerations



  • The use of local anesthetic is debatable. Some physicians feel it is not helpful because only the skin will be anesthetized and a second injection is required.


  • For aspirations, an 18G needle with a large (35 mL or larger) syringe is generally recommended. For injections, a 22G needle with a smaller syringe may be used.


  • Although advantages and disadvantages of the approaches can be debated, we typically perform injections via the anterolateral approach and aspirations via the superolateral approach.




  • Entry into the joint may be facilitated by eversion (superolateral approach) or inversion (superomedial approach) of the patella.


  • If fluid is not initially obtained, redirect the needle. The needle must be withdrawn until it is just within the skin before redirection. Changing the angle of the needle by withdrawing it first will simply push tissue around (not change its path) and may even risk damage to surrounding tissue, as the bevel may act like a knife.


  • When an intra-articular knee injection is performed in the setting of an open wound to evaluate for the presence of a traumatic arthrotomy, it is important to visually inspect the wound first. Consider the location and subcutaneous extension of the wound, which can often be extensive. Select an approach furthest from the wound in order to minimize the risk of a false-positive result. False negatives are typically encountered in the setting of a small arthrotomy where sufficient fluid is not used to maximally distend the joint. If blood or serous fluid is actively draining from the wound, consider injecting with a diluted methylene blue solution to enhance visualization of the injected fluid.






FIGURE 6-3






FIGURE 6-4






FIGURE 6-5


CLOSED REDUCTIONS


Knee Dislocation



Description of Procedure



  • Closed reduction of a true dislocation usually requires conscious sedation or general anesthesia.


  • The knee can dislocate in any direction. However, all closed reductions start with longitudinal traction followed by manipulation of the tibia.


  • Apply in-line traction (Fig. 6-6).


  • Regardless of the direction of dislocation, reduction should be obtained with direct manipulation of the tibia, rather than the femur. The exception to this recommendation is the anterior dislocation when the distal femur should be lifted after the application of axial traction (Fig. 6-7).


  • Splint the knee in approximately 20° of flexion to allow for relaxation of tension on the posterior neurovascular structures. Most knee immobilizers have some flexion built in and therefore can be used as an alternative.


  • Obtain urgent postreduction radiographs to assess reduction.


Tips and Other Considerations



  • Medial dimpling in the setting of the posterolateral knee dislocation signifies piercing of the medial capsule and indicates that a closed reduction may be impossible. However, a closed reduction should still be attempted.


  • Detailed pre- and postreduction neurovascular examinations are critical. Even in the presence of palpable pedal pulses, an ankle-brachial index should still be obtained. An ankle-brachial index of less than 0.9 requires further investigation.



  • Vascular compromise requires emergent surgical intervention.


  • With an intact vascular examination, controversy remains regarding recommendations for traditional angiography versus computed tomography angiography versus serial examinations.






FIGURE 6-6






FIGURE 6-7


Patellar Dislocations



Description of Procedure



  • In the position of greatest comfort, perform an aspiration of the invariably present hemarthrosis and inject 5 to 10 mL of local anesthetic (see “Intra-articular Knee Injection/Aspiration”). Aspiration of the hemarthrosis will decompress the knee and facilitate reduction by allowing the patella to lie within the trochlear groove.


  • Place the knee in extension. Extension of the knee typically results in the most stable position of the patellofemoral joint. Additionally, knee extension relaxes the extensor mechanism if a reduction is required.



  • Often, extension alone will cause reduction of the patella. If not, apply a medially directed force to the laterally dislocated patella.


  • Occasionally, slight flexion (approximately 30°) will be required to maintain the reduction since this allows the patella to sit in the deepest portion of the trochlea.


  • Immobilize the patient with a brace or cast in the position of the greatest stability.


Tips and Other Considerations



  • Rarely, reduction can be achieved but not maintained with positioning alone. In this setting, apply a long leg or cylinder cast (see “Splinting and Casting” section) with a lateral mold over the patella to maintain the reduction.


Tibial Shaft Fractures



Tolerances



  • Varus/valgus angulation < 5° to 10°.


  • Anterior/posterior angulation < 5° to 10°.


  • Translation < 50%.


  • Shortening < 2 cm.


Description of Procedure

Mar 14, 2020 | Posted by in ORTHOPEDIC | Comments Off on The Knee and Leg
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