Femoral and tibial insert downsizing increases the laxity envelope in TKA.

Purpose: This study examines the effect of component downsizing in a modern total knee arthroplasty (TKA) system on the laxity envelope of the knee throughout flexion.

Methods: A robotic testing system was utilized to measure laxity envelopes in the implanted knee by in the anterior-posterior (AP), medial-lateral (ML), internal-external (IE) and varus-valgus (VV) directions. Five fresh-frozen cadavers were tested with a modern cruciate retaining TKA implantation, a 1-mm thinner polyethylene insert and a femoral component 2 mm smaller in the AP dimension.

The role of the oblique popliteal ligament and other structures in preventing knee hyperextension.

Background: Ligament restraints to terminal knee extension are poorly understood.

Hypotheses: (1) As with other motions of the knee, genu recurvatum is limited primarily by a named, identifiable structure. (2) As the largest static structure of the posterior knee, the oblique popliteal ligament is uniquely suited to act as a checkrein to knee hyperextension.

The effect of a proximal tibial medial opening wedge osteotomy on posterolateral knee instability: a biomechanical study.

Background: Increased stability of posterolateral corner knee injuries has been observed clinically after proximal tibial medial opening wedge osteotomies.

Hypothesis: Static varus and external rotatory stability will be significantly improved in a knee with a grade 3 posterolateral knee injury after a proximal tibial medial opening wedge osteotomy.

Study Design: Controlled laboratory study.

A prospective magnetic resonance imaging study of the incidence of posterolateral and multiple ligament injuries in acute knee injuries presenting with a hemarthrosis.

Purpose: The purpose of this study was to determine whether the incidence of posterolateral knee injuries, as well as other concurrent knee ligament injuries, could be obtained from a prospective evaluation of magnetic resonance imaging scans in patients with an acute knee injury with a hemarthrosis.

Methods: We prospectively documented all patients with acute (within 30 days) knee injuries with a hemarthrosis over a 90-day period who underwent 1.5-T magnetic resonance imaging at a large referral imaging facility with 6 sites, effectively covering a large metropolitan area.

Assessment of a goat model of posterolateral knee instability.

The development of an in vivo animal model of posterolateral knee instability is desired for devising effective interventions for this injury. Sequential sectioning of the popliteus tendon, lateral collateral ligament, and lateral capsule was done in cadaveric goat knees to create knee joint instability, followed by in vivo studies (Studies 1 and 2) of 7 and 3 months duration, respectively. In Study 1, the popliteus tendon and lateral collateral ligament were sectioned; in Study 2, these structures as well as the lateral joint capsule were sectioned.

The anatomy of the medial part of the knee.

Background: While the anatomy of the medial part of the knee has been described qualitatively, quantitative descriptions of the attachment sites of the main medial knee structures have not been reported. The purpose of the present study was to verify the qualitative anatomy of medial knee structures and to perform a quantitative evaluation of their anatomic attachment sites as well as their relationships to pertinent osseous landmarks.

Methods: Dissections were performed and measurements were made for eight nonpaired fresh-frozen cadaveric knees with use of an electromagnetic three-dimensional tracking sensor system.

The anatomy of the posterior aspect of the knee. An anatomic study.

Background: The orthopaedic literature contains relatively little quantitative information regarding the anatomy of the posterior aspect of the knee. The purpose of the present study was to provide a detailed description of, and to propose a standard nomenclature for, the anatomy of the posterior aspect of the knee.

Methods: Detailed dissection of twenty nonpaired, fresh-frozen knees was performed.

The effects of estrogen on material and mechanical properties of the intra- and extra-articular knee structures.

Background: Female athletes have a higher incidence of anterior cruciate ligament injuries than do male athletes in similar sports. Hormones, particularly estrogen, have been indicated by some studies to be correlated with the disproportionate number of anterior cruciate ligament injuries in female athletes.

Hypothesis: Estrogen does not affect the mechanical or material properties of primate anterior cruciate ligaments or patellar tendons.

An in vivo injury model of posterolateral knee instability.

Background: Posterolateral knee instability is a difficult clinical problem to diagnose and treat. To best evaluate its natural history and the effects of interventional treatments, it is important to develop an in vivo model in an attempt to validate human cadaveric and clinical observational studies.

Purpose: To develop an in vivo model of posterolateral knee instability in the rabbit and to determine the natural history of untreated posterolateral knee injuries at 6 months postoperatively.

Anatomy of the posterolateral aspect of the goat knee.

The purpose of this study was to determine the anatomy of the posterolateral aspect of the goat knee for future in vivo studies using a goat model to examine the natural history of posterolateral knee injuries. Twelve non-paired, fresh-frozen, adult goat knees were dissected to determine the anatomy of the posterolateral corner. The main posterolateral structures identified in the goat knee were the lateral collateral ligament, the popliteus muscle and tendon, popliteomeniscal fascicles, and the lateral gastrocnemius muscle.

Mechanical properties of the posterolateral structures of the knee.

Background: The individual biomechanical strength properties of the fibular collateral ligament, popliteofibular ligament, and popliteus tendon have not been well elucidated by previous studies. To define the necessary strength requirements for a posterolateral knee reconstruction, these properties for the main individual structures of the posterolateral knee need to be defined.

Hypothesis: The biomechanical failure properties of the fibular collateral ligament, popliteofibular ligament, and popliteus tendon can be determined by cadaveric testing.

Force measurements on the fibular collateral ligament, popliteofibular ligament, and popliteus tendon to applied loads.

Background: Little information is known about the forces seen on the main individual structures of the posterolateral knee to applied loads. This information is needed to determine which structures should be reconstructed and also the relative strengths needed for reconstruction grafts.

Purpose: To determine in vitro forces in the fibular collateral ligament, popliteofibular ligament, and popliteus tendon for various posterolateral knee loading conditions.

An analysis of an anatomical posterolateral knee reconstruction: an in vitro biomechanical study and development of a surgical technique.

Background: To date, no surgical technique to treat posterolateral knee instability anatomically reconstructs the 3 major static stabilizing structures of the posterolateral knee: the fibular collateral ligament, the popliteus tendon, and the popliteofibular ligament.

Hypothesis: Static varus and external rotatory stability would be restored to the reconstructed knee with a posterolateral knee injury.

Methods: The anatomical locations of the original fibular collateral ligament, popliteus tendon, and popliteofibular ligament were reconstructed using a 2-graft technique.

Assessment of healing of grade III posterolateral corner injuries: an in vivo model.

The primary purpose of this study was to test the hypothesis that an in vivo model of posterolateral knee instability could be created in the rabbit and to develop a natural history model in animals. The biomechanical and gross features of the rabbit knee 12 weeks after rupture of the fibular collateral ligament (FCL) and popliteus tendon were investigated in 14 skeletally mature New Zealand white rabbits. In the operated leg both the FCL and popliteus tendon were traumatically ruptured near their respective femoral insertions and the contralateral leg served as the control.

The posterolateral attachments of the knee: a qualitative and quantitative morphologic analysis of the fibular collateral ligament, popliteus tendon, popliteofibular ligament, and lateral gastrocnemius tendon.

Background: Quantitative descriptions of the attachment sites of the main posterolateral knee structures have not been performed.

Purpose: To qualitatively and quantitatively determine the anatomic attachment sites of these structures and their relationships to pertinent bony landmarks.

Study Type: Cadaveric study.

The anatomy of the posterolateral aspect of the rabbit knee.

The purpose of this study was to determine the anatomy of the posterolateral aspect of the rabbit knee to serve as a basis for future in vitro and in vivo posterolateral knee biomechanical and injury studies. Twelve nonpaired fresh-frozen New Zealand white rabbit knees were dissected to determine the anatomy of the posterolateral corner. The following main structures were consistently identified in the rabbit posterolateral knee: the gastrocnemius muscles, biceps femoris muscle, popliteus muscle and tendon, fibular collateral ligament, posterior capsule, ligament of Wrisberg, and posterior meniscotibial ligament.

The influence of the integrity of posterolateral structures on tibiofemoral orientation when an anterior cruciate ligament graft is tensioned.

Background: The effect of injury to the posterolateral structures of the knee on the success of an anterior cruciate ligament reconstruction is not well known.

Hypothesis: Increasing graft tension increases the amount of external rotation of the tibia if the posterolateral structures are deficient.

Study Design: Laboratory study.