Repair of the arthrotomy is a performed at the end of every total knee arthroplasty (TKA). After the arthrotomy is performed, most surgeons attempt to close the arthrotomy with the medial and lateral edges anatomically approximated. If no landmarks are made prior to performing the arthrotomy however, there is a risk that anatomic approximation may not be obtained. This study looked into the biomechanical changes in stiffness of the knee before and after a medial parapatellar approach repaired with an anatomic, and shifted capsular repair with the medial side of the arthrotomy shifted up or down when repaired to determine if capsular closure may have an effect on the stiffness of the joint. Fourteen cadaveric TKA specimens were retrieved through the Medical Education and Research Institute (Memphis TN). For each specimen tested, the skin and muscle tissue was removed, and the femur and tibia were cut transversely 180 mm from the joint center. Specimens were fixed in extension in a custom knee testing platform (Little Rock AR) and subjected to a 10 Nm varus and valgus torque and a 1.5 Nm internal and external rotational torque. The angle at which these moments occurred was recorded, and each test was repeated for 0, 30, 60, and 90 degrees of flexion. After tests were performed on retrieved TKA specimens, a fellowship trained orthopedic surgeon vented the knee capsule by making an incision with a number 10 scalpel blade in a horizontal nature to provide a landmark for anatomic reapproximation. Tests were repeated as before, after which the surgeon performed a standard arthrotomy and repaired it using #0 suture and a neutral alignment. Sutures were cut and the repair was repeated using upward 5 mm shift and downward 5 mm shift of the medial side of the arthrotomy during the repair. All tests were repeated after each repair technique. Any increase or decrease in laxity after capsule repair was referenced to the TKA laxity tested prior to an arthrotomy being performed.Introduction:
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Soft tissue balancing is a part of every total knee arthroplasty (TKA) surgery. Traditionally, balancing the varus knee has been approached by releasing portions of the medial soft tissue sleeve in a sub-periosteal nature off of the proximal tibia, but this may lead to undue laxity or residual pain about the area the release was performed. More recently, “pie crusting” of the medial soft tissue sleeve has been used to balance the varus knee without compromising the structural integrity of the ligament. This technique may provide advantages over a sub-periosteal release by targeting only medial tight bands that can be palpated with the capsule distracted in 90 degrees of flexion and full extension. This study aims to biomechanically validate the pie crusting technique of the medial soft tissue sleeve and compare the results to those of standard medial releases that have been previously reported. Six cadaveric TKA specimens were retrieved through the Medical Education and Research Institute (Memphis TN). For each specimen tested, the skin and muscle tissue was removed, and the femur and tibia were cut transversely 180 mm from the joint center. Specimens were fixed in extension in a custom knee testing platform (Little Rock AR) and subjected to a 10 Nm varus and valgus torque. The angle at which these moments occurred was recorded, and each test was repeated for 0, 30, 60, and 90 degrees of flexion. After tests were performed on TKA specimens, a fellowship trained orthopedic surgeon performed “pie crusting,” making alternating stab patterns with a number 11 scalpel blade along the anterior half of the superficial medial collateral ligament (SMCL) or posterior half of the SMCL including the posterior oblique ligament (POL). Three specimens had the anterior capsule pie crusted first and three had the posterior pie crusting performed first, followed by complete pie crusting. After two stages of pie crusting, the medial soft tissue sleeve was released off of the proximal tibia in a sub-periosteal fashion for comparison. Laxity was defined as the angles at which valgus torque equaled 10 Nm. Any increase or decrease in laxity was referenced to the normal TKA laxity.Introduction:
Methods
