JII BCS Exam: Knee Design And Function! Quiz

Which of the following statements regarding the JBCS knee system are true? 

• Over 40,500 JBCS knees have been implanted globally by over 250 surgeons. 2300 of these were implanted in Australia

• Over 65,000 JBCS knees have been implanted globally by over 600 surgeons. 3346 of these were implanted in Australia

• The global full market release took place in March 2006 at the AAOS where it won the most innovative product award

The JBCS Knee System restored normal knee function by…

• Increasing anterior-posterior stability throughout knee flexion

• Promoting a normal kinematic pattern

• Placing the femur more posteriorly during full extension to reduce paradoxical motion

• A & B

The JBCS knee system was designed to restore normal knee function by increasing A-P stability through a range of motion & promoting a normal kinematic pattern. This was made possible through which of the following novel design features?

• Anatomically correct joint line and articulating surface

• Anterior and internally rotated position of the femur in extension

• Dual cam - ACL & PCL replication

• All of the above

Consistent with the articular surface of a normal knee, the JBCS design had a larger lateral than medial femoral condyle and higher lateral than medial tibial plateau resulting in an anatomically correct 3-degree joint line.

• True

• False

Which features of the JBCS tibial insert design mimic the native articular surfaces to provide medial stability and increased posterior translation of the lateral condyle during flexion?

• The JBCS tibial insert was designed to be symmetrical in shape to mimic the native tibial plateau

• As with the native tibial plateau the tibial insert was designed with a concave medial and convex lateral shape

• As with the native tibial plateau the tibial insert was designed with a concave lateral and convex medial shape

• A & C

In the JBCS the posterior femoral condylar surfaces were extended with minimal bone resection through a ____ degree flexed cut, completely replacing the articular surfaces and restoring the original posterior offsets.

In the JBCS the restoration of the posterior femoral condylar articular surfaces and offsets in combination with the lateral femoral rollback allowed for deep flexion up to…?

• 145 degrees

• 155 degrees

• 160 degrees

• 150 degrees

Studies have shown that conventional knee replacements routinely experience paradoxical motion – the anterior sliding of the femoral component on the tibia as the knee goes into flexion. How did the JBCS knee resist this paradoxical motion?

• The cam post construct which replicated both anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) function

• An inherent screw-home mechanism supporting a relative posterior and externally rotated position of the femur in extension

• An inherent screw-home mechanism supporting a relative anterior and internally rotated position of the femur in extension

• A & C

The normal screw home position of the JBCS allowed the knee to rest in its normal anatomical position and thus as in the normal knee the quadriceps muscle was not required to maintain stability in extension.

• True

• False

As the JBCS knee moved out of screw home the external rotation of the femur resulted in… 

• Straightening of the quadriceps mechanism (increasing the Q angle) thereby increasing anterior femoral translation in deep flexion

• Straightening of the quadriceps mechanism (reduction of the Q angle to 0) thereby increasing patella-femoral shear forces in deep flexion

• Straightening of the quadriceps mechanism (reduction of Q angle to 0) thereby reducing patella-femoral shear forces in deep flexion

• A & B

The JBCS Knee system featured an anterior and posterior cam. Which of the following statements are correct? 

• The anterior cam and post replicated the function of the ACL preventing posterior tibial translation (anterior femoral translation) and providing stability early in gait

• The anterior cam and post replicated the function of the ACL preventing anterior tibial translation (posterior femoral translation) and providing stability early in gait

• The posterior cam and post replicated the function of the PCL, providing posterior stability and limiting posterior translation of tibia (femoral anterior translation)

According to published literature by Morra et al (2004) which knee system most closely replicated the kinematics of a healthy un-operated Knee?

• PFC Rotating Platform

• Vanguard PS

• Triathlon CR

• JBCS

• ADVANCE Medial-Pivot Knee

In published literature by Cantani et al (2009) Knee joint kinematics were assessed in 16 JBCS patients using video-fluoroscopy and electromyography (EMG) during activities of daily-living including stair climbing, chair rising and sitting, and step up/down test. What did the results of this study show? 

• All JBCS patients demonstrated femoral external rotation and translation similar to that of other conventional knee designs

• This more physiological knee motion resulted in recovery of normal extensor and flexor muscle function which was attributed to the more anatomical knee design

• All patients demonstrated a combination of relatively normal locomotion and gait, coupled with clear femoral external rotation and translation