Varus and valgus flexion laxity of total knee alignment methods in loaded cadaveric knees.

Both total knee alignment methods, the anatomic and classic, seek to achieve stability in flexion and extension. However, posterior femoral condyle referencing (anatomic alignment) combined with perpendicular tibial resection (classic alignment) results in a 3 degree relative internal rotation of the femoral component with lateral joint opening. The current cadaver study investigated the influence of total knee alignment methods and femoral component malrotation (3 degrees and 6 degrees internal and external malrotation) on femorotibial laxity. Varus and valgus excursion tests were done at 0 degrees, 30 degrees, 60 degrees, and 90 degrees knee flexion under vertical loading conditions of 150 N. None of the alignments produced increased laxity in extension. The largest laxity was found on the varus test at 60 degrees flexion with the femoral component at 6 degrees internal rotation. A 3 degree internal rotation of the femoral component showed increased varus laxity only for the combined alignment method. This finding shows that the femoral component position of the combined alignment method is a 3 degree relative internal malrotation and that an additional internal malrotation may compromise varus stability. Posterior femoral condyle referencing did not provide proper femoral component rotation. A ligament tensor may be helpful in determining femoral component rotation after soft tissue release in extension is performed.     

Transfer of forearm muscles according to steindler to restore elbow flexion after paralyses

Objective Restoration of active elbow flexion through transfer of the origin of the intact forearm muscles (medial and/or lateral epicondyle) to the distal humerus. This procedure will improve the function of the paralyzed arm. Indications Absent or inadequate function of elbow flexors in instances of plexus damage. Absent elbow flexion after peripheral nerve lesions or poliomyelitis. Contraindications Possibility of improvement through reinnervation, either spontaneous or after neurosurgical procedures. Inadequate strength of forearm flexors or extensors. Ankylosed elbow joint secondary to trauma or degenerative changes (osteoarthritis). Surgical Technique The medial and/or lateral epicondyle is osteotomized with the attached muscles, transferred to the distal humerus and attached to freshened bone with mini cortex screws. Results Results of 6 patients operated by us were compared to those reported in the literature. They showed that an elbow flexion of at least 90° can be obtained and that the strength is sufficient to bend the elbow against gravity. Complications are rare.     

A mathematical analysis of the effect of flexion and rotation on apparent varus/valgus alignment at the knee

The quantitative effect of flexion and rotation on apparent varus/valgus deformity was analyzed, and the expected amount of deformity as a function of flexion rotational artifact determined, as shown by use of formulae and tabulated computational results. These results were calculated first when no deformity was present initially, and also for varying amounts of initial deformity.     

The role of the musculocutaneous and radial nerves in elbow flexion and forearm supination: a biomechanical study

The intention of this prospective study was to evaluate the role of the musculocutaneous and radial nerves in elbow flexion and forearm supination. The study included 29 patients having loco-regional anaesthesia for minor hand surgery. Elbow flexion and forearm supination forces were evaluated before and after an isolated musculocutaneous nerve block in one group and an isolated radial nerve block in another group. The results showed that the biceps tendon is responsible for 47% of the forearm supination force and the combination of brachioradialis and the supinator for 64% of this force. It showed also that the musculocutaneous and radial nerves contribute by 42% and 27.5%, respectively, to the flexion force of the elbow. These results are intended to help surgeons in decision making when treating chronic biceps tendon rupture, in repair of traumatic brachial plexus neuropathy and in using tendon transfers, such as the Steindler transfer, around the elbow.     

Effects of forearm rotation on the clinical evaluation of ulnar variance

Neutral rotation radiographs of the wrist are recommended to standardize the measurement of ulnar variance because it is known that changes in forearm rotation result in changes of this measurement. The purpose of this study was to examine whether there are clinically measurable differences in ulnar variance between radiographs in various degrees of forearm rotation in human subjects. Forty-five wrist radiographs of 15 normal adults were obtained in 3 positions: maximum forearm pronation, neutral rotation, and maximum supination. The ulnar variance on each view was measured by 3 independent observers using a standard millimeter ruler. The average absolute difference in ulnar variance was 0.4 mm between pronation, 0.6 mm between pronation and supination, and 0.2 mm between neutral and supination. Although we found a statistically significant difference in ulnar variance between the pronated and neutral positions, this difference may not be clinically significant and may not justify concerns of forearm position during the radiographic evaluation of ulnar variance.     

Kinematics and laxity of the Souter-Strathclyde total elbow prosthesis

The motion pattern and laxity of 8 cadaveric elbows were recorded with a 3-dimensional electromagnetic tracking device before and after the Souter-Strathclyde total elbow prosthesis was implanted. The Souter-Strathclyde prosthesis replicates the valgus-varus motion pattern of the intact elbow but causes a significant internal rotation of the ulnar shaft of 8.9 degrees +/- 4.1 degrees (P < .0005) at 110 degrees of elbow flexion. One of the reasons for this unphysiological motion pattern is positioning of the humeral component in a mean of 5.4 degrees +/- 6.4 degrees of external rotation compared with the intact elbow (P = .05). This positioning is related to the design of this device. The Souter-Strathclyde elbow prosthesis has a mean maximum valgus-varus laxity of 6.5 degrees +/- 1.5 degrees compared with 4.3 degrees +/- 2.3 degrees for the intact elbow (P = .004). This implant is more constrained than previously tested devices, which may explain its relatively higher loosening rate.     

Lateral laxity in flexion increases the postoperative flexion angle in cruciate-retaining total knee arthroplasty

Thirty-eight patients diagnosed with osteoarthritis underwent 41 cruciate-retaining total knee arthroplasties. In varus and valgus tests at flexion, subjects were seated on a table at 80° of knee flexion; 50 N was applied perpendicular to the lower leg. The factors affecting the postoperative flexion angle were investigated in a multiregression analysis. The mean joint angles of the flexion-valgus and flexion-varus tests were 3.4° ± 1.4° and 6.2° ± 2.5°, respectively. The flexion-varus angle was correlated with the postoperative flexion angle (P < .01). The mean postoperative flexion angles were 110.8° ± 9.6° and 118.1° ± 8.0° in the groups with the flexion-varus angle of 6° or less and more than 6°, respectively (P = .02). Slack lateral laxity in flexion had a significant effect during knee flexion in cruciate-retaining total knee arthroplasty.     

Nerve entrapment syndrome of the elbow and forearm

In this study we will discuss entrapment of the median, ulnair, radial and lateral antebrachial nerves of the elbow and the forearm. Compression of the nerves may occur when they traverse a tunnel and an incompatibility exists between the diameter of the tunnel and its contents (e.g. nerves, tendons,...). However, at the elbow and the forearm the nerves are also exposed to particularly dynamic compressions. This is due to anatomical relationships changing between the nerve and its surrounding muscles, tendons and aponevroses during the motion of flexion-extension of the elbow and the prono-supination of the forearm. The possibility of this dynamic factor should be thoroughly explored during the examination through appropriate dynamic tests as described in this study.