Eiichi Uchiyama

Strain on the Ulnar Nerve at the Elbow and Wrist During Throwing Motion

BACKGROUND It is well known that cubital tunnel syndrome frequently occurs in throwing athletes. The cause of cubital tunnel syndrome is considered to be mechanical stimuli on the ulnar nerve in the cubital tunnel. The hypothesis of the present cadaveric study was that the ulnar nerve is subjected to longitudinal strain in the cubital tunnel during the throwing motion. METHODS Four phases of throwing (stance, wind-up, middle cock-up, and early acceleration) were passively simulated in seven fresh-frozen transthoracic cadaveric specimens that were fixed in an upright position to allow free arm movement. In each throwing phase, the elbow was sequentially flexed from 45 degrees to 90 degrees to 120 degrees to maximum flexion. The longitudinal movement of and strain on the ulnar nerve were measured with use of a caliper and a strain gauge at the proximal aspects of both the cubital tunnel and the canal of Guyon. RESULTS The movement of the ulnar nerve at the proximal aspect of the cubital tunnel was significantly increased during all throwing phases with increased elbow flexion (p < 0.05). An average maximum movement of 12.4 +/- 2.4 mm was recorded during the wind-up phase with maximum elbow flexion. The movement at the proximal aspect of the canal of Guyon was approximately two-thirds of that at the proximal aspect of the cubital tunnel. The strain on the ulnar nerve at the proximal aspect of the cubital tunnel was significantly increased with elbow flexion in the stance, wind-up, and middle cock-up phases (p < 0.05). An average maximum strain of 13.1% +/- 6.1% was recorded during the early acceleration phase with maximum elbow flexion. The strain at the proximal aspect of the canal of Guyon was approximately half of that at the proximal aspect of the cubital tunnel. CONCLUSIONS In the present study, the maximum strain on the ulnar nerve during the acceleration phase was found to be close to the elastic and circulatory limits of the nerve.

Three-Dimensional Analysis of Ankle Instability After Tibiofibular Syndesmosis Injuries: A Biomechanical Experimental Study

Background Rupture of the distal tibiofibular syndesmosis commonly occurs with extreme external rotation. Most studies of syndesmosis injuries have concentrated only on external rotation instability of the ankle joint and have not examined other defects. Hypothesis Syndesmosis injuries cause multidirectional ankle instability. Study Design Controlled laboratory study. Methods Ankle instability caused by distal tibiofibular syndesmosis injuries was examined using 7 normal fresh-frozen cadaveric legs. The anterior tibiofibular ligament, interosseous membrane, and posterior tibiofibular ligament, which compose the distal tibiofibular syndesmosis, were sequentially cut. Anterior, posterior, medial, and lateral traction forces, as well as internal and external rotation torque, were applied to the tibia; the diastasis between the tibia and fibula and the angular motion among the tibia, fibula, and talus were measured using a magnetic tracking system. Results A medial traction force with a cut anterior tibiofibular ligament significantly increased the diastasis from 1.1 to 2.0 mm (P = .001) and talar tilt angles from 9.6° to 15.2° (P < .001). External rotation torque significantly increased the diastasis from 0.5 to 1.8 mm (P= .009) with a complete cut; external rotation torque also significantly increased rotational angles from 7.1° to 9.4° (P = .05) with an anterior tibiofibular ligament cut. Conclusion Syndesmosis injuries caused ankle instability with medial traction force and external rotation torque to the tibia. Clinical Relevance Both physicians and athletes should be aware of inversion instability of the ankle joint caused by tibiofibular syndesmosis injuries.

Pathomechanics of Hallux Valgus: Biomechanical and Immunohistochemical Study

Background: One factor believed to contribute to the development of hallux valgus is an abnormality in collagen structure and makeup of the medial collateral ligament (MCL) of the first metatarsophalangeal joint (MTPJ). We hypothesized that the mechanical properties of the MCL in feet with hallux valgus are significantly different from those in normal feet and that these differences may be related to alterations in the type or distribution of collagen fibers at the interface between the MCL and the bone. Materials and Methods: Seven normal fresh-frozen cadaver feet were compared to four cadaver feet that had hallux valgus deformities. The MCL mechanical properties, structure of collagen fibers, and content proportion of type I and type III collagen were determined. Results: The load-deformation and stress-strain curves were curvilinear with three regions: laxity, toe, and linear regions. Laxity of the MCL in feet with hallux valgus was significantly larger than that of normal feet (p = 0.022). Stiffness and tensile modulus in the toe region in feet with hallux valgus were significantly smaller than those in normal feet (p = 0.004); however, stiffness and tensile modulus in the linear region were not significantly different. The MCL collagen fibrils in the feet with hallux valgus had a more wavy distribution than the fibrils in the normal feet. Conclusions: In general, strong staining for collagen III and to a lesser extent, collagen I was observed at the interface between the MCL and bone in the feet with hallux valgus but not in the normal feet. These results indicate that the abnormal mechanical properties of the MCL in feet with hallux valgus may be related to differences in the organization of collagen I and collagen III fibrils.

Distal Fibular Length Needed for Ankle Stability

Background: The fibula is commonly used for bone grafts. Previous clinical and biomechanical studies have suggested that the length of the residual portion of the distal part of the fibula has an important effect on the long-term stability of the ankle joint. However, we cannot find clear-cut guidelines for the amount of bone that can be harvested safely. Methods: Using six normal fresh-frozen cadaver legs, motions of the tibia, talus and calcaneus were measured. The fibula was cut sequentially 3 cm from the proximal tip of the fibula and distally 10 cm, 6 cm, and 4 cm from the distal tip of the lateral malleolus. The angular motion of each bone was measured while a medial and lateral traction force of 19.6 N was applied to the proximal tibia. Angles of the tibia, talus, and calcaneus were measured. Results: Sequential resection of the fibula increased the inversion angles of the ankle joint. The proximal 3-cm cut increased the inversion angle from 42.1 ± 6.2 degrees to 49.6 ± 3.6 degrees, and the distal 4-cm cut increased the angle from 57.6 ± 6.6 degrees to 67.4 ± 5.9 degrees. The rotational angles were almost constant with sequential resections of the fibula; however, the distal 4-cm cut increased the rotational angle from 11.3 ± 25.1 degrees to 78.7 ± 37.5 degrees. Conclusions: The whole fibula including the head is essential for the stability of the ankle joint complex, and the distal fibula is responsible for stabilizing the ankle mortise during external rotation and inversion. We recommend fixation of the syndesmosis or bracing to prevent ankle joint instability with rotation of the talus in the mortise, especially when the distal fibula is shortened 6 cm or more.

Does distal tibiofibular joint mobilization decrease limitation of ankle dorsiflexion

Limitation of ankle motion is in many cases treated by joint mobilization (JM), a kind of manual physical therapy technique. Until now, the JM approach has mainly focused on the talocrural joint, with less attention to the distal tibiofibular joint. We applied cyclic loading to the lateral malleolus as in JM in order to clarify the relationship between the dorsiflexion angle and the excursion of the lateral malleolus. Seven normal, fresh-frozen cadaver legs were used. To each specimen, cyclic loading with a 30N force was applied 1000 times to the lateral malleolus at a speed of 15N/s. The displacement of the lateral malleolus was measured with a magnetic tracking system. The maximum dorsiflexion angle was measured before and after cyclic loading. After the first 100 and 1000 times of cyclic loading, the tibia was displaced 0.44+/-0.30mm and 0.75+/-0.36mm, respectively, and the fibula was displaced 0.44+/-0.28mm and 0.92+/-0.39mm, respectively. The average dorsiflexion angle increased from 14.36+/-7.51 degrees to 16.74+/-7.21 degrees after cyclic loading (P<0.05). Movement of the distal tibiofibular joint led to a significant increase in the range of ankle dorsiflexion. These results suggest that tibiofibular JM would be effective for limitation of ankle dorsiflexion.

Mechanical Stability of the Subtalar Joint After Lateral Ligament Sectioning and Ankle Brace Application: A Biomechanical Experimental Study

Background The roles of each ligament supporting the subtalar joint have not been clarified despite several biomechanical studies. The effects of ankle braces on subtalar instability have not been shown. Hypothesis The ankle brace has a partial effect on restricting excessive motion of the subtalar joint. Study Design Controlled laboratory study. Methods Ten normal fresh-frozen cadaveric specimens were used. The angular motions of the talus were measured via a magnetic tracking system. The specimens were tested while inversion and eversion forces, as well as internal and external rotation torques, were applied. The calcaneofibular ligament, cervical ligament, and interosseous talocalcaneal ligament were sectioned sequentially, and the roles of each ligament, as well as the stabilizing effects of the ankle brace, were examined. Results Complete sectioning of the ligaments increased the angle between the talus and calcaneus in the frontal plane to 51.7° ± 11.8° compared with 35.7° ± 6.0° in the intact state when inversion force was applied. There was a statistically significant difference in the angles between complete sectioning of the ligaments and after application of the brace (34.1° ± 7.3°) when inversion force was applied. On the other hand, significant differences in subtalar rotation were not found between complete sectioning of the ligaments and application of the brace when internal and external rotational torques were applied. Conclusion The ankle brace limited inversion of the subtalar joint, but it did not restrict motion after application of internal or external rotational torques. Clinical Relevance In cases of severe ankle sprains involving the calcaneofibular ligament, cervical ligament, and interosseous talocalcaneal ligament injuries, application of an ankle brace might be less effective in limiting internal-external rotational instabilities than in cases of inversion instabilities in the subtalar joint. An improvement in the design of the brace is needed to restore better rotational stability in the subtalar joint.

Why adductor magnus muscle is large: The function based on muscle morphology in cadavers

The aim of this study was to examine anatomical properties of the adductor magnus through a detailed classification, and to hypothesize its function and size to gather enough information about morphology. Ten cadaveric specimens of the adductor magnus were used. The muscle was separated into four portios (AM1–AM4) based on the courses of the corresponding perforating arteries, and its volume, muscle length, muscle fiber length and physiological cross‐sectional area were assessed. The architectural characteristics of these four portions of the adductor magnus were then classified with the aid of principal component analysis. The results led us into demarcating the most proximal part of the adductor magnus (AM1) from the remaining parts (AM2, AM3, and AM4). Classification of the adductor magnus in terms of architectural characteristics differed from the more traditional anatomical distinction. The AM2, AM3, and AM4, having longer muscle fiber lengths than the AM1, appear to be designed as displacers for moving the thigh through a large range of motion. The AM1 appears instead to be oriented principally toward stabilizing the hip joint. The large mass of the adductor magnus should thus be regarded as a complex of functionally differentiable muscle portions.

Dynamic effect of the tibialis posterior muscle on the arch of the foot during cyclic axial loading

BACKGROUND The most common cause of acquired flatfoot deformity is tibialis posterior tendon dysfunction. The present study compared the change in medial longitudinal arch height during cyclic axial loading with and without activated tibialis posterior tendon force. METHODS Fourteen normal, fresh frozen cadaveric legs were used. A total of 10,000 cyclic axial loadings of 500 N were applied to the longitudinal axis of the tibia. The 32-N tibialis posterior tendon forces were applied to the specimens of the active group (n=7). Specimens of another group (non-active group, n=7) were investigated without the tibialis posterior tendon force. The bony arch index was calculated from the displacement of the navicular height. FINDINGS The mean initial bony arch indexes with maximal weightbearing were 0.239 (SD 0.009) in active group and 0.239 (SD 0.014) in non-active group. After 7000 cycles, the bony arch indexes with maximal weightbearing were significantly greater in the active group (mean 0.214, SD 0.013) than in the non-active group (mean 0.199, SD 0.013). The mean bony arch indexes with maximal weightbearing after 10,000 cycles were 0.212 (SD 0.011) in the active group and 0.196 (SD 0.015) in the non-active group. INTERPRETATION The passive supportive structures were inadequate, and the tibialis posterior muscle was essential to maintain the medial longitudinal arch of the foot in the dynamic weightbearing condition. The findings underscore that physical therapy and arch supportive equipments are important to prevent flatfoot deformity in the condition of weakness or dysfunction of the tibialis posterior muscle.

Stretching positions for the coracohumeral ligament: Strain measurement during passive motion using fresh/frozen cadaver shoulders

BackgroundContracture of the coracohumeral ligament is reported to restrict external rotation of the shoulder with arm at the side and restrict posterior-inferior shift of the humeral head. The contracture is supposed to restrict range of motion of the glenohumeral joint.MethodsTo obtain stretching position of the coracohumeral ligament, strain on the ligament was measured at the superficial fibers of the ligament using 9 fresh/frozen cadaver shoulders. By sequential measurement using a strain gauge, the ligament strain was measured from reference length (L0). Shoulder positions were determined using a 3 Space Tracker System. Through a combination of previously reported coracohumeral stretching positions and those observed in preliminary measurement, ligament strain were measured by passive external rotation from 10° internal rotation, by adding each 10° external rotation, to maximal external rotation.ResultsStretching positions in which significantly larger strain were obtained compared to the L0 values were 0° elevation in scapula plane with 40°, 50° and maximum external rotation (5.68%, 7.2%, 7.87%), 30° extension with 50°, maximum external rotation (4.20%, 4.79%), and 30° extension + adduction with 30°, 40°, 50° and maximum external rotation (4.09%, 4.67%, 4.78%, 5.05%)(P < 0.05). No positive strain on the coracohumeral ligament was observed for the previously reported stretching positions; ie, 90° abduction with external rotation or flexion with external rotation.ConclusionsSignificant strain of the coracohumeral ligament will be achieved by passive external rotation at lower shoulder elevations, extension, and extension with adduction.

Biomechanical and clinical evaluation of a newly designed polycentric knee of transfemoral prosthesis

We have designed a new polycentric knee adopting a hydraulic unit and an intelligent mechanism. The biomechanical parameters of this prototype, such as the stance duration, peak knee flexion angle in stance and swing, peak hip flexion angle, and peak hip extension moments were analyzed at three different cadences (88, 96, 104 steps/min) in three amputees, and then compared to those of polycentric hydraulic knees currently in use. The same parameters were also measured for 10 healthy volunteers and subsequently analyzed. In the prototype, almost all the values of the parameters showed no significant variety in individuals at the different cadences. The situation was the same with the healthy volunteers. However, the values of the parameter for the conventional knee varied significantly with the individual at the different cadences. The prototype may be of practical use, contributing to a stable walk even at different cadences.