Carson D. Schneck

The Three-Dimensional Kinematics and Flexibility Characteristics of the Human Ankle and Subtalar Joints—Part I: Kinematics

The in-vitro, three dimensional kinematic characteristics of the human ankle and subtalar joint were investigated in this study. The main goals of this investigation were: 1) To determine the range of motion of the foot-shank complex and the associated range of motion of the ankle and subtalar joints; 2) To determine the kinematic coupling characteristics of the foot-shank complex, and 3) To identify the relationship between movements at the ankle and subtalar joints and the resulting motion produced between the foot and the shank. The tests were conducted on fifteen fresh amputated lower limbs and consisted of incrementally displacing the foot with respect to the shank while the motion of the articulating bones was measured through a three dimensional position data acquisition system. The kinematic analysis was based on the helical axis parameters describing the incremental displacements between any two of the three articulating bones and on a joint coordinate system used to describe the relative position between the bones. From the results of this investigation it was concluded that: 1) The range of motion of the foot-shank complex in any direction (dorsiflexion/plantarflexion, inversion/eversion and internal rotation/external rotation) is larger than that of either the ankle joint or the subtalar joint.; 2) Large kinematic coupling values are present at the foot-shank complex in inversion/eversion and in internal rotation/external rotation. However, only a slight amount of coupling was observed to occur in dorsiflexion/plantarflexion.; 3) Neither the ankle joint nor the subtalar joint are acting as ideal hinge joints with a fixed axis of rotation.; 4) Motion of the foot-shank complex in any direction is the result of rotations at both the ankle and the subtalar joints. However, the contribution of the ankle joint to dorsiflexion/plantarflexion of the foot-shank complex is larger than that of the subtalar joint and the contribution of the subtalar joint to inversion/eversion is larger than that of the ankle joint.; 5) The ankle and the subtalar joints have an approximately equal contribution to internal rotation/external rotation movements of the foot-shank complex.

The Mechanical Characteristics of the Collateral Ligaments of the Human Ankle Joint

In the present study, the tensile mechanical properties of all of the collateral ligaments of the human ankle joint were determined, in vitro, from tensile tests conducted on 120 ligaments obtained from 20 fresh lower limbs. The ultimate load of the lateral collateral ligaments increased in an anteroposterior sequence, with the anterior fibulotalar ligament less than the fibulocalcaneal ligament and less than the posterior fibulotalar ligament. For the medial collateral ligaments, the increasing order of ultimate load was found to be tibiocalcaneal ligament, tibionavicular ligament, tibiospring ligament, posterior tibiotalar ligament. The posterior tibiotalar ligament and tibiospring ligament, so frequently neglected in the anatomical and orthopaedic literature, demonstrated the highest yield force and ultimate load of all of the collateral ligaments of the ankle. Additionally, the tibiospring ligament showed high yield and ultimate elongation properties probably related to its distal attachment to the spring ligament. The fibulocalcaneal ligament was found to have high linear elastic modulus suggesting some type of unique material properties or internal fiber organization. Knowledge of the mechanical characteristics of the ligaments of the ankle joint contributes to an understanding of their normal function, pathomechanics of injury, and their optimal surgical reparative procedure and reconstructive material. A knowledge of the normal mechanical properties of the ankle ligaments provides a data base to evaluate which of the multiplicity of present tendon graft materials has mechanical properties similar to those of the ligaments to be replaced. Those tendon grafts will be the most suitable for replacement of specific ligaments. Finally, data on the mechanical properties of these ligaments offer the possibility for evaluating any future biological or prosthetic grafts.

Testing for isometry during reconstruction of the anterior cruciate ligament. Anatomical and biomechanical considerations.

Instrumented tibiofemoral (bone-to-bone) excursion wires were implanted in the mid-substance of the anteromedial, central, and posterior fiber-regions of the anterior cruciate ligament through limited anterior and posterior arthrotomies in eight fresh knees from cadavera. The change in the distance of linear separation between each pair of osseous fiber-insertion sites was measured and was plotted against the angle of flexion of the knee as the knee was cycled through a 120-degree range of motion. Testing conditions likely to be present during intraoperative testing for isometry were used (anterior cruciate fibers transected, quadriceps relaxed, femur stabilized with the patient in the supine position and the leg freely dependent, and motion of the knee induced in neutral rotation by force applied at the level of the foot). In no instance did the insertion-site centers of any fiber-region exhibit isometric behavior (change in the distance of linear separation of 1.0 millimeter or less). The least deviations from isometry (range, 1.4 to 3.1 millimeters) were observed for the anteromedial sites, under conditions when the gravitational dependency of the lower leg was constrained. When the leg hung in a dependent manner during passive motion, the deviation from isometry of the anteromedial sites of insertion increased significantly (range, 2.8 to 5.6 millimeters). The central sites of insertion were generally less isometric than the anteromedial sites, and the posterior sites were the least isometric, regardless of testing conditions.

Anatomy and Kinematics of the Lateral Collateral Ligament of the Knee

The anatomy and kinematics of the lateral collateral ligament were studied in 10 unembalmed limbs and 20 isolated femurs and fibulas. The ligaments average overall length was 66 mm (range, 59 to 74) and the average greatest dimension of its thin middle portion was the anteroposterior dimension of 3.4 mm (range, 3 to 4). The center of the femoral attachment site was 3.7 mm posterior to the ridge of the lateral epicondyle, not at it apex. A potential radiographic technique for operatively locating the femoral attachment site to within 3 mm is described. During knee flexion in neutral rotation the distance between the femoral and fibular attachment sites of the lateral collateral ligament decreased to 88% of its value in full extension. With 6.5 N m of applied external rotation force, beyond 30° of flexion the attachment sites rapidly approximated. With the same internal rotation force, beyond 15° of flexion the attachment sites separated. From 60° to 105° they were greater than 100% of the value in full extension, suggesting significant distraction between the attachment sites. These changes correlated well with the ligaments change from an 11° posterior slope in extension to a 19° anterior slope in flexion with no applied rotation.

The Three-Dimensional Kinematics and Flexibility Characteristics of the Human Ankle and Subtalar Joint—Part II: Flexibility Characteristics

The objective of the present study was to investigate the in-vitro, coupled, three-dimensional load-displacement and flexibility characteristics of the human ankle joint complex consisting of the talocrural and the talocalcaneal joints and to determine the effects that sectioning of the anterior talofibular ligament has on these characteristics. Similar to other anatomical joints such as the knee and the intervertebral joint, the ankle joint complex was found to exhibit highly nonlinear load-displacement characteristics with the angular displacement approaching asymptotic values as the external load was increased. Therefore, a procedure of incremental linearization was used to derive the flexibility characteristics of this structure. According to this procedure, external loads were applied to the calcaneus in small increments and its resulting three dimensional displacements were recorded. The incremental flexibility coefficients were then derived by assuming linear load-displacement relationship for each increment. From the results obtained from fifteen human ankle specimens, it was evident that the ankle joint complex exhibit highly coupled flexibility and load-displacement characteristics. It was further concluded that the ankle joint complex is the most flexible in the neighborhood of the unloaded, neutral position and that all the flexibility coefficients of the structure decrease rapidly toward the extremes of the range of motion. Rupture of the anterior talofibular ligament was found to have a significant effect on the load-displacement and flexibility characteristics of the ankle joint complex. This effect was manifested as a change in the load-displacement characteristics and a large increase in the flexibility coefficients primarily in those corresponding to rotations in the transverse and the coronal plane. The results of the present study can provide the necessary data base for the development of quantitative diagnostic technique for identifying the site and the extent of injury to the collateral ligaments of the ankle.

The Effect of Damage to the Lateral Collateral Ligaments on the Mechanical Characteristics of the Ankle Joint—An In-Vitro Study

Injuries to the lateral collateral ligaments of the ankle joint are among the most frequently occurring injuries at the lower limb. The present study was conducted for the purpose of establishing the basis for the development of a quantitative diagnostic procedure for such injuries. To achieve this goal, the effect of four types of ligament injuries on the three-dimensional mechanical characteristics of the ankle were investigated. These types of injuries consisted of: 1) isolated tear of the anterior talofibular ligament; 2) isolated tear of the calcaneofibular ligament; 3) isolated tear of the posterior talofibular ligament; and 4) combined tear of both the anterior talofibular ligament and the calcaneofibular ligament. The experiments were conducted on 31 amputated lower limbs and consisted of comparing the three-dimensional load-displacement and flexibility characteristics of the ankle joint prior to and following sectioning of selected ligaments. The experimental and analytical procedures used to derive these characteristics was developed previously by the authors. From the results of this study it was concluded that the three-dimensional flexibility characteristics of the ankle joint are strongly influenced by damage to the lateral collateral ligaments. Furthermore, it was found that each type of ligament injury produced unique and identifiably changes in the flexibility characteristics of the ankle. These unique changes, which are described in detail in this paper, can be used to discriminate between the different types of ligament injuries. Consequently, it was concluded that it is feasible to develop a quantitative diagnostic procedure for ankle ligament injuries based on the effect of the injury on the flexibility characteristics of the ankle.

The semimembranosus-tibial collateral ligament bursa : anatomical study and magnetic resonance imaging

A bursa that was deep to the tibial collateral ligament and adjacent to the semimembranosus tendon was studied in fifty cadaveric knees; a vinyl solution was injected into four of the specimens in order to facilitate a study of the relationship between the bursa and its surrounding structures. The bursa had the shape of an inverted U: the superficial arm was an elliptical pocket that was located between the semimembranosus tendon and the tibial collateral ligament, and the deep arm was a triangular pocket that was located between the semimembranosus tendon and the medial tibial condyle. The bursa measured, on the average, twenty-one millimeters in its greatest anteroposterior dimension and ten millimeters in its greatest superoinferior dimension. Magnetic resonance images were made of two patients, and they showed fluid in the bursa.

Venous drainage of the platysma myocutaneous flap

OBJECTIVES: The platysma myocutaneous flap offers a regional reconstruction option for relatively small soft tissue defects in the head and neck area. However, epidermolysis of its skin paddle with resultant fibrosis and tongue tethering has been documented. This has been attributed to arterial and/or venous vascular compromise. We investigated the venous drainage patterns of this flap in a cadaveric study. STUDY DESIGN AND SETTING: We made selective Microfil dye injections into the external and internal jugular veins of 5 cadavers. A wide cervical flap was then raised, and anatomic dissection of the superficial and deep venous systems was performed to identify the dominant draining veins of the platysma flap. RESULTS: Universally, small communicating veins from the internal jugular venous system were noted to drain the platysma flap anteriorly. The external jugular vein was noted to drain the flap posteriorly. CONCLUSIONS: Although it is difficult to preserve the anterior communicating veins with 180° flap rotation, the results of this study suggest a possible benefit of external jugular vein harvest in continuity with the platysma flap. Further clinical studies are needed to assess whether flap venous congestion, epidermolysis, and resultant fibrosis can be minimized with this technique. (Otolaryngol Head Neck Surg 2004;130:357–9.)

Anterior protrusion of retroperitoneal processes a mimic of lesser sac or gastrohepatic masses

The space between the left lobe of the liver and the lesser curvature of the stomach normally contains intraperitoneal structures. These include the gastrohepatic recess of the greater peritoneal cavity, the medial recess of the lesser sac and the interposed gastrohepatic ligament. An anterior protrusion of retroperitoneum can project into this space, dorsal to the posterior reflection of the medial compartment of the lesser sac. Tumors that extend into this fossa are anterior and medial to the fundic and upper body region of the stomach. These tumors may cause confusion regarding their origin if the radiologist is not aware of the existence of this retroperitoneal protrusion. Between 1982, and 1986, 183 patients with pancreatic cancer were hospitalized at our institution, 63 of whom had computed tomography (CT) scans of the abdomen. Four of these patients (6.3%) demonstrated direct tumor extension anterior to the stomach. During this same period, four large benign retroperitoneal tumors also exhibited this finding. Masses in the gastrohepatic interval between the liver and stomach can be extensions of retroperitoneal processes and should not be assumed to represent intraperitoneal involvement.

Development of Auditory Function in the Mongolian Gerbil

The gerbil ear is not mature at birth. The sound‐conducting apparatus as well as inner‐ear structures continue to develop over a period of at least 16 to 20 days postparturition. This circumstance allows a unique opportunity to examine relationships between morphology and function in the auditory apparatus. Mongolian gerbils were vitally perfused at various ages ranging from 20 min to more than 23 days. Serial sections were done and observations made on the developmental status of the external, middle, and inner parts of the ear. Cochlear potentials were recorded from some animals. The presence of reflex activity to sound was noted. Our observations indicate that the earliest reflex response to sound (whole body) occurred at 16 days. Electrical activity could be recorded from the round window niche by day 14. Maturation of the organ of Corti was questionable by day 10, and the limbus and spiral sulci were not well differentiated. By day 16, all parts of the organ of Corti appeared well developed. Ossicula...