In vitro determination of the passive knee flexion axis: Effects of axis alignment on coupled tibiofemoral motions.

The natural passive flexion axis of human cadaveric knees was determined using a technique that minimized coupled tibiofemoral motions (translations and rotations), and the kinematic effects of mal-positioned flexion axes were determined. The femur was clamped in an apparatus that allowed unconstrained tibial motions as the knee was flexed from 0° to 90°. To establish the natural flexion axis, the femur's position was adjusted such that coupled tibiofemoral motions were minimized. Tests were repeated, first with the femur rotated internally and externally from its original position, and again after positioning the femur to flex the knee about the transepicondylar axis. Compared to the transepicondylar axis, flexion about the natural axis significantly reduced mean tibial translation by 66.4% (p < 0.01) and varus-valgus rotation by 70.1% (p <0.01). Mean varus-valgus rotation increased by 3.4° (factor of 4) when the femur was rotated 3° internally or externally from the optimum position. Differences in condylar location coordinates between the transepicondylar and natural flexion axes most likely indistinguishable clinically. Knee flexion about an axis that minimizes coupled tibiofemoral motions could be important for placement and orientation of a femoral total knee component and for specimen alignment during biomechanical knee testing.

Dorsal Radiocarpal Joint Fracture-Dislocation: A Case Report.

CASE: A 19-year-old right-hand-dominant man sustained a right dorsal radiocarpal dislocation. He presented with instability secondary to displacement of the volar ligamentous structures and an avulsed fragment of the distal aspect of the radius within the radiocarpal articulation. The patient was treated with open reduction and internal fixation, as well as a capsuloligamentous repair. At the 18-month follow-up, he had no pain and excellent functional recovery. CONCLUSION: Our experience emphasizes the importance of looking critically at the radiographs when there is an irreducible radiocarpal fracture-dislocation. A volar distal radial fragment and attached ligamentous structures can be the main blocks to closed reduction.

Location of the natural knee axis for internal-external tibial rotation.

BACKGROUND: Rotating hinge and mobile bearing tray knee replacement designs utilize a single fixed axis for tibial rotation, yet there is little published information regarding the natural internal-external axis (IEA) for tibial rotation. Identifying the IEA should provide an opportunity for reproducing normal knee kinematics and maintaining the balance of forces in the soft tissues that help control rotation of the tibia. METHODS: The location and orientation of the IEA relative to the tibial plateau were calculated in 46 fresh frozen human cadaveric specimens using an instant center of rotation analysis at fixed knee flexion angles ranging from five degrees to 105°. RESULTS: IEA location ranged from 4.0 to 4.9mm medial and 1.7 to 5.5mm posterior to the center of the tibial plateau (from 5° to 105° of knee flexion). IEA orientation was reported relative to a reference axis perpendicular to the plane of the tibial plateau. In the frontal plane, the IEA was not significantly different from the reference axis from five degrees to 45° flexion, and 2.0° to 2.7° valgus to the reference axis from 60° to 105° flexion. In the sagittal plane, the IEA was not significantly different from the reference axis from 5° to 15° flexion, and 3.0° to 7.0° extended from the reference axis from 30° to 105° flexion. CONCLUSIONS: The IEA moves posteriorly with increasing knee flexion on the tibial plateau. Placement of the IEA relative to the tibial plateau for a rotating hinge or mobile bearing tray implant may represent a compromise between design objectives for moderate and deeper knee flexion. CLINICAL RELEVANCE: This study has relevance for future knee implant designs.

Use of inertial sensors to predict pivot-shift grade and diagnose an ACL injury during preoperative testing.

BACKGROUND: The pivot-shift (PS) examination is used to demonstrate knee instability and detect anterior cruciate ligament (ACL) injury. Prior studies using inertial sensors identified the ACL-deficient knee with reasonable accuracy, but none addressed the more difficult problem of using these sensors to determine whether a subject has an ACL deficiency and to correctly assign a PS grade to a patient's knee. HYPOTHESIS: Inertial sensor data recorded during a PS examination can accurately predict ACL deficiency and the PS score assigned by the examining physician. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 2. METHODS: A total of 32 patients with unilateral ACL deficiency and 29 with intact ACLs in both knees had inertial sensor modules strapped to the tibia and femur of each limb for preoperative PS testing under anesthesia. Support vector machine (SVM) methods assessed PS grades on the basis of these data, with the examiner's clinical grading shift used as ground truth. A fusion of regression and SVM classification techniques diagnosed ACL deficiency. RESULTS: The clinically determined PS grades of all 122 knees were as follows: 0 (n = 69), +1 (n = 23), +2 (n = 27), and +3 (n = 3). The SVM classification analysis was 77% accurate in correctly classifying these grades, with 98% of computed PS grades falling within ±1 grade of the clinically determined value. The system fusion algorithm diagnosed ACL deficiency in an individual with an overall accuracy of 97%. This method yielded 6% false negatives and 0% false positives. CONCLUSION: This study used inertial sensor technology with SVM algorithms to accurately determine clinically assigned PS grades in ACL-intact and ACL-deficient knees. By extending the assessment to a separate group of patients without ACL injury, the inertial sensor data demonstrated highly accurate diagnosis of ACL deficiency.

Double fascicular nerve transfer for elbow flexion and extension.

Traumatic brachial plexus injuries are life changing, often leaving affected individuals with severe functional deficits. Recent advances in nerve transfers have allowed surgeons to improve elbow flexion, shoulder abduction, and prehension of the hand in some patients. We hypothesize that in a patient who lacks both biceps and triceps function, a double fascicular transfer may be the key to restore elbow flexion and extension. In three cadaver upper limbs, we transferred the expendable motor fascicle of the ulnar nerve to the biceps branch of the musculocutaneous nerve, and the expendable motor fascicle of the median nerve to the triceps (ulnar collateral) branch of the radial nerve. We evaluated the feasibility of this double nerve transfer via a medial approach, and elucidated the anatomy. The transfers were easily performed and were tension-free throughout full range of motion at the elbow. The triceps branch of the radial nerve that we utilized has a length of approximately 4.9 cm, and is best found between 3.5 and 6 cm from the anterior axillary line. We consistently identified a relatively avascular plane in the region between 7.5 and 11 cm from the anterior axillary line, which corresponds with the recipient sites of the medial head of the triceps. The distance between the triceps branch to the median nerve was an average of 2.5 cm. Transfer of expendable motor fascicles from the ulnar and median nerves to the biceps and triceps nerve branches can be successfully and consistently performed through a medial approach in a cadaver.

How to establish an interactive eConference and eJournal Club.

With our hand team scattered across several different locations, it is difficult to find a time to get together for our weekly didactic hand conference and monthly hand journal club. In addition, traffic and tight clinical schedules sometimes force conferences to start late or be canceled. Our solution was to set up an on-line conference. Using TeamViewer to host our conference and Skype to host our journal clubs, we experienced increased attendance by both faculty and residents in our meetings. In this article, we establish a method of hosting effective on-line videoconferences to facilitate nearly universal participation of our hand team, and we hope to assist others who wish to establish similar setups in their communities.