Sagittal plane imaging parameters for computer-assisted fluoroscopic anterior cruciate ligament reconstruction.

Reproducible graft placement in anterior cruciate ligament (ACL) reconstructions is considered to be a critical factor affecting the successful clinical outcome of the procedure. Many current ACL instrument systems rely on intra-articular landmarks to guide the ACL tunnel placement. However, most of these instrument systems use mobile soft tissues as landmarks. We hypothesize that consistently identifiable radiographic contour landmarks can be established that can be used to improve the reproducibility of graft tunnel placement in fluoroscopically and computer-assisted ACL reconstructions. For the tibia, magnetic resonance imaging (MRI) scans showed the average ACL attachment site to be projected at 46% on a line extending from the anterior to the posterior cortices. Intraoperative fluoroscopic images were checked for the reproducibility of this line and its clinical use. For the femur, lateral radiographs demonstrated a consistent relationship between the intercondylar roof line (Blumensaat's line) and the nearly circular profile of the posterior and inferior contour of the lateral femoral condyle. The middle of this circular profile is consistently projected on Blumensaat's line at 66% of its anterior-to-posterior direction. Intraoperative images were used, which showed the aiming drill at the point of entering the lateral femoral condyle. Instead of determining the femoral attachment site relative to Blumensaat's line, we can thus determine its position relative to the center of the circle. Based on intraoperative x-rays, the proposed femoral ACL attachment site can be projected on a line parallel with the Blumensaat's line from the circle center in the posterior direction. Our results indicate that there are consistently identifiable radiographic features on the tibia and femur contours that can be used for fluoroscopic and computer-assisted guidance of ACL graft placement.

Patellar tendon graft position after anterior cruciate ligament reconstruction. Interobserver variability on lateral radiographs.

We compared the reliability and validity of graft position measurements made by 4 orthopedic surgeons on intraoperative radiographs obtained using fluoroscopic control and postoperative radiographs obtained from the same 17 patients 6 weeks after ACL reconstruction. Measurements from postoperative radiographs varied significantly more than those from intraoperative radiographs. There was little agreement between the postoperative and intraoperative measurements of the tibial and femoral graft position. We conclude that postoperative radiographs are not a sufficient tool for assessing graft placement after ACL reconstruction using patellar tendon autografts. In order to consider graft position in follow-up studies and to compare results from various surgeons, we suggest intraoperative fluoroscopy to produce radiographs for accurate and reliable measurements.

Computer assistance in arthroscopic anterior cruciate ligament reconstruction.

Accurate placement of the graft is considered one of the most important factors in anterior cruciate ligament surgery. However, reconstruction with contemporary guiding systems still can result in unacceptable graft placement variability. To improve the reproducibility of graft placement, intraoperative visual feedback was added to the arthroscopic technique. First, fluoroscopic visualization was added to evaluate guidewire placement before tunnel drilling. Second, computer graphic overlays were added to the fluoroscopic view. Three groups of patients were treated: 29 patients with arthroscopy, 53 patients with fluoroscopy added, and 50 patients with computer overlays added. Graft placement variability was reduced significantly with fluoroscopic visualization. Computer overlays resulted in additional significant reductions in graft placement variability. Simple visual enhancements seem to be useful in improving the accuracy of arthroscopic anterior cruciate ligament reconstruction.

Hitting a baseball: a biomechanical description.

A tremendous amount of time and energy has been dedicated to the development of conditioning programs, mechanics drills, and rehabilitation protocols for the throwing athlete. In comparison, a significantly smaller amount has been spent on the needs of the hitting athlete. Before these needs can be addressed, an understanding of mechanics and the demands placed on the body during the swing must be developed. This study uses three-dimensional kinematic and kinetic data to define and quantify biomechanics during the baseball swing. The results show that a hitter starts the swing with a weight shift toward the rear foot and the generation of trunk coil. As the hitter strides forward, force applied by the front foot equal to 123% of body weight promotes segment acceleration around the axis of the trunk. The hip segment rotates to a maximum speed of 714 degrees/sec followed by a maximum shoulder segment velocity of 937 degrees/sec. The product of this kinetic link is a maximum linear bat velocity of 31 m/sec. By quantifying the hitting motion, a more educated approach can be made in developing rehabilitation, strength, and conditioning programs for the hitting athlete.

A dynamic analysis of a functional brace for anterior cruciate ligament insufficiency.

A dynamic, in vivo, functional analysis of braces designed for ACL insufficiency has never been reported. In this study, 14 athletes who had arthroscopically proven absent ACLs were evaluated in the Biomechanics Laboratory at the Centinela Hospital Medical Center. None of the ligaments were repaired or reconstructed. Footswitch, high speed photography, and force place data were recorded while the athletes performed running and cutting maneuvers with and without their custom fitted C.Ti. braces (Innovation Sports, Irvine, CA). Cybex testing, KT-1000 evaluation, and radiographs were collected for each subject. Statistical analysis showed that while performing cutting maneuvers, braced limbs generated significantly increased shear forces compared to the same limb unbraced. During straight line running, braced limbs generated significantly less lateral and aft shear forces compared to the same limb unbraced. Running velocity increased while wearing a brace for most athletes, but this was not statistically significant. As expected, the sound limb generated significantly greater shear forces than the unbraced involved limb during most cutting maneuvers. Athletes who did not achieve 80% of the Cybex (Cybex, Division of Lumex, Ronkonkoma, NY) quadriceps torque of the sound limb generated significantly more forces during cutting maneuvers while wearing their braces. The cutting angle, approach time to the cut, and time on the force plate showed no significant differences during brace wear. We conclude that the C.Ti brace allows significantly better running and cutting performances for athletes who have torn ACLs. Athletes who have not achieved 80% of quadricep strength as measured by Cybex testing showed even more improvement while wearing their braces.(ABSTRACT TRUNCATED AT 250 WORDS)

The Mumford procedure in athletes. An objective analysis of function.

No report in the English literature exists on objective muscle testing following the Mumford procedure (distal clavicular resection). Twenty-three athletes, including six at the professional level, were evaluated an average 3.7 years after the Mumford procedure was performed for degenerative changes after a Grade I or Grade II dislocation. All athletes were evaluated with an in depth questionnaire, physical examination, and radiographic study. Seventeen performed Cybex testing of both shoulders. All but one were satisfied with the surgery. Sixteen returned to their same level of sports activity, including five of the six professional athletes. The most common complaint of all those not achieving the previous level of sports was the inability to achieve their previous maximum bench press strength. All athletes demonstrated full motion; five exhibited painless crepitation at the acromioclavicular joint. Ten of the twenty-three exhibited increased horizontal clavicular motion. Radiographs demonstrated an average of 1.9 cm of bone resection, with varying amounts of ossification present between the remaining clavicle and acromion in eight athletes. The involved limb performed significantly more work than the sound limb in flexion (P = 0.0133) and internal rotation (P = 0.0575) at 300 deg/sec. The involved limb performed significantly more repetitions at 300 deg/sec than the sound limb in the extension plane (P = 0.0373). The sound limb was significantly stronger during extension (P = 0.0759) and flexion (P = 0.0063) at 60 deg/sec compared to the involved limb. The sound limb performed significantly more total repetitions at 300 deg/sec in the abduction-abduction plane than the involved limb (P = 0.0843).(ABSTRACT TRUNCATED AT 250 WORDS)

The etiology of valgus angulation after metaphyseal fractures of the tibia in children.

We conducted a retrospective study of proximal metaphyseal fractures of the tibia in children who developed valgus deformities. We reviewed the cases in an effort to determine the most likely etiology of post-fracture tibia valga, which occurs despite careful treatment and follow-up. We reviewed seven major theories presented in the literature regarding the etiology of this problem. Our conclusion was that all the theories were not prerequisites for the development of valgus angulation, but rather may be secondary mechanisms. We suggest that the most likely primary mechanism is an increased vascular response causing an asymmetric growth stimulation of the medial metaphysis of the proximal tibia.