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Harry E. Rubash, MD
Second Session
Moderator: Harry E. Rubash, MD

Susan S. Jordan, MD Scott Martin, MD
In-vivo Kinematics of the Anteromedial and Posterolateral Bundles of the Anterior Cruciate Ligament During Weight-bearing Knee Flexion
Susan S. Jordan, MD
Advisor: Thomas Gill, MD and Guoan Li, PhD
Discussor: Scott Martin, MD

Over 100,000 ACL reconstructions are performed annually in the United States. The current techniques of single-bundle ACL reconstruction restore anterior stability of the knee, but fail to restore rotational stability. Because of this, recent attention has been focused on the development of a doublebundle technique to reproduce the double-bundle anatomy of the actual ACL. As a future sports medicine specialist, Dr. Jordan sought to better understand the in-vivo kinematics of the ACL in order to further refine double-bundle reconstruction techniques. Based on a computer model generated from fluoroscopic imaging of the knees of six different subjects performing a forward lunge, Dr. Jordan suggests that, contrary to classic teaching, the anteromedial and posterolateral bundles are parallel at low flexion angles and have similar elevation, deviation and twist. Therefore, two tibial and two femoral tunnels are necessary in order to restore appropriate anatomy. Dr. Jordan’s findings further suggest that both bundles should be fixed in near extension.

Dr. Jordan suggested that her work would be strengthened by looking at other loading conditions on the knee beyond forward flexion and by taking into account ligament slack. Dr. Scott Martin noted that there is nothing anatomic about our current single bundle endoscopically assisted technique for ACL reconstruction. He applauded Dr. Jordan for not being like many others who have become complacent with our current techniques, as she has sought to provide important kinematic information to those who are working to refine the double bundle technique. Dr. Martin agreed with Dr. Jordan that one of the study’s limitations was not being able to measure strain/ligament slacking. He also suggested that it would be very worthwhile to compare non-reconstructed ACLs with single versus double bundle reconstruction techniques.

Jennifer M. Ty, MD Philip Blazar, MD
The Use of CT Scanning For Triage of Suspected Scaphoid Fractures
Jennifer M. Ty, MD
Advisor: David Ring, MD
Discussor: Philip Blazar, MD

Through her thesis project, Dr. Ty sought to address the difficulty of diagnosing scaphoid fractures in the acute trauma patient. Physical exam tests for scaphoid fractures have low specificity and plain x-rays of the hand miss as many as 7-26% of scaphoid fractures. Knowing this, many doctors in the ER will splint a patient who they suspect may have a scaphoid fracture even if the radiographs do not show one. Consequently, many patients in emergency room/urgent care settings are treated for a scaphoid fracture even though they may not have a fracture. This tendency to overtreat leads to a potentially significant burden both on the patient and society given the period of immobilization, lost work-hours and lost wages. Recognizing the benefit of a more sensitive and specific test for diagnosing scaphoid fractures, Dr. Ty evaluated the use of computed tomography to triage suspected scaphoid fractures. In a prospective study, 28 patients with suspected scaphoid fractures were evaluated with a CT scan at time of injury and on plain film x-ray at their sixth week follow-up appointment. It was found with utilizing a CT scan, no fractures of the scaphoid were missed or undertreated. Further, the CT scan identified that 43% of patients had other fractures of less concern such as non-displaced distal radius fractures or carpal bone fractures. Dr. Ty concluded that CT scans of suspected scaphoid fractures in the ER have the potential to reduce unnecessary immobilization and lessen overall costs associated with treatment and disability.

Dr. Blazar noted that the early diagnosis of scaphoid fractures is a very real clinical problem. He commended Dr. Ty’s efforts as this work speaks to many different careproviders since scaphoid fractures are often seen by doctors of different specialties. Dr. Blazar did note that failure of eight of the 28 patients to follow-up limits the conclusions that can be drawn from the study, but notes that this study helps to advance our knowledge in assessing scaphoid fractures.

Benjamin C. Bengs, MD William W. Tomford, MD
Intraoperative Range of Motion with Varying Patella And Femoral Resection Levels in Total Knee Arthroplasty
Benjamin C. Bengs, MD
Advisor: Richard Scott, MD
Discussor: William W. Tomford, MD

Full passive extension in total knee arthroplasty is predicated on creating a large enough extension gap to accommodate any given combined thickness of femoral and tibial components. Theoretically, greater femoral resection can achieve more passive knee extension. Dr. Scott recognized that the effect of further distal femoral resection has never been studied and enlisted Dr. Bengs to help study this effect. Through a simple intraoperative study of a series of patients undergoing routine PCL-preserving TKA, Dr. Bengs sought to quantify the effect of distal femoral resection on flexion contractures. In this study, femoral and tibial resections were made as they normally would be in order to yield full passive extension with trial components. Distal femoral augments were then sequentially added to the back of the femoral trial component and passive knee extension was measured. The data showed that an average value of 9 degrees of femoral contracture is corrected for every 2mm of distal femoral resection. Additionally Dr. Bengs utilized patella button augments to show that for every 2mm of additional patella thickness, three degrees of flexion is lost.

Dr. Tomford pointed out some of the limitations of this study, namely that it was done using a single goniometer measurement taken by one surgeon intraoperatively. He also queried Dr. Bengs about what he thought the outcome would be if this was done in a series of PCL-sacrificing knees. Dr. Rubash suggested that it would make the paper stronger to acknowledge the effect of PCL and explain how the PCL was handled.

Links of interest: