Linda J. Askew

A biomechanical study of normal functional elbow motion.

UNLABELLED We studied thirty-three normal patients, eighteen women and fifteen men, for normal motion and the amount of elbow motion required for fifteen activities of daily living. The amounts of elbow flexion and forearm rotation (pronation and supination) were measured simultaneously by means of an electrogoniometer. Activities of dressing and hygiene require elbow positioning from about 140 degrees of flexion needed to reach the occiput to 15 degrees of flexion required to tie a shoe. Most of these activities are performed with the forearm in zero to 50 degrees of supination. Other activities of daily living (such as eating, using a telephone, or opening a door) are accomplished with arcs of motion of varying magnitudes. Most of the activities of daily living that were studied in this project can be accomplished with 100 degrees of elbow flexion (from 30 to 130 degrees) and 100 degrees of forearm rotation (50 degrees of pronation and 50 degrees of supination). CLINICAL RELEVANCE These data, not previously recorded, may be used to provide an objective basis for the determination of disability impairment, to determine the optimum position for elbow splinting or arthrodesis, and to assist in the design of elbow prostheses. The motion needed to perform essential daily activities is obtainable with a successful total elbow arthroplasty.

Rupture of the distal tendon of the biceps brachii. A biomechanical study.

In biomechanical studies on ten patients who had had a rupture of the distal tendon of the biceps brachii, we compared the results of immediate anatomical reattachment, delayed reattachment, and conservative treatment. When the tendon was simply attached to the brachialis muscle (one patient), there was nearly normal strength in elbow flexion but about 50 per cent loss of forearm supination. Late reinsertion (one patient) improved strength of both flexion and supination, but not to normal. Immediate reattachment (four patients) restored normal strength in flexion and supination at one year but not at four months (one patient). With conservative treatment (three patients) there was a mean loss of 40 per cent of supination strength and variable loss of flexion strength, averaging 30 per cent. These data suggest that immediate surgical reinsertion of the biceps tendon into the radial tuberosity, compared with other modes of treatment, restores more strength of flexion and supination.

Functional ranges of motion of the wrist joint.

We have examined 40 normal subjects (20 men and 20 women) to determine the ideal range of motion required to perform activities of daily living. The amount of wrist flexion and extension, as well as radial and ulnar deviation, was measured simultaneously by means of a biaxial wrist electrogoniometer. The entire battery of evaluated tasks could be achieved with 60 degrees of extension, 54 degrees of flexion, 40 degrees of ulnar deviation, and 17 degrees of radial deviation, which reflects the maximum wrist motion required for daily activities. The majority of the hand placement and range of motion tasks that were studied in this project could be accomplished with 70 percent of the maximal range of wrist motion. This converts to 40 degrees each of wrist flexion and extension, and 40 degrees of combined radial-ulnar deviation. This study provides normal standards for the functional range of motion of the wrist.

Silastic prosthetic replacement for the radial head.

Seventeen patients had a Silastic prosthesis for the radial head inserted following fracture of that structure. Follow-up averaged 6.7 years. Nine of the seventeen patients had had an associated dislocation of the elbow or a Monteggia fracture. Six patients received the implant at the time of the treatment for the fracture and all six were doing well, although the implant had failed radiographically in three of the six. There were five failures among the other eleven patients; four of the five had the prosthesis removed. On the basis of these data, we concluded that the indications for use of the Silastic radial-head prosthesis after fracture are extremely limited, and its routine use cannot be justified.

Isometric elbow strength in normal individuals.

Isometric elbow strength was measured with torque cell dynamometers in a group of 104 normal subjects. Their mean age was 43 years (range, 21-79 years). Test functions included elbow flexion and extension, forearm pronation and supination, and grip. In general, the men were twice as strong as the women, and the dominant extremities were 6% stronger than the nondominant. The mean extension strength was 61% of that of flexion, and pronation was 86% of supination.

Electromyographic analysis of the thumb: A study of isometric forces in pinch and grasp

An electromyographic study of thumb muscles was performed on eight subjects by means of integrated polyelectromyography and simultaneous recordings of isometric flexion-extension, abduction-adduction, and prehensile pinch and grasp of the thumb. The integrated electromyographic signal proved to be an excellent index of thumb muscle activity, with a linear relationship found at low to middle levels of muscle strength. To facilitate understanding of thumb function, thumb muscles can be classified as primary or secondary on the basis of electrical potential activity. In isometric flexion, the flexor pollicis longus (FPL) was primary, whereas in extension, the extensor pollicis longus (EPL) and abductor pollicis longus were primary. In adduction, the adductor pollicis and EPL were primary and the FPL was secondary. In abduction, the abductor pollicis brevis and opponens pollicis were primary. The adductor pollicis, and FPL were nearly equal during pinch and grasp, with significant electrical activity increasing with greater force requirements. The first dorsal interosseous and EPL contributed secondarily in both pinch and grasp. When surgeons consider tendon transfers for nonfunctioning thumb muscles, the primary muscles should be replaced first to best restore pinch and grasp strength.

Prosthetic replacement of the proximal humerus.

Eighteen patients had prosthetic proximal humeral replacement with either a metal or ceramic prosthesis. Three replacements were performed for fracture nonunions, five for benign neoplasms, six for low-grade malignancies, and four for high-grade malignancies. Retention of elbow and hand function was good. In five of the 11 ceramic prostheses, failure occurred at the humeral-prosthetic junction even though it was designed for biologic fixation. Ten of 18 prostheses subluxated or dislocated. Twelve of 18 patients have had revision operations. While the revision rate in this initial series was high, valuable experience was gained for further investigations of shoulder arthroplasty.

Electrogoniometer for the Measurement of Human Elbow Joint Rotation

Since the electrogoniometric method has been justified for the measurement of lower extremity joint motion, a similar device is developed for the measurement of elbow joint and forearm rotations. In this design, the axis of forearm rotation coincides with the anatomical axis which eliminates the cross talk existing in the regular triaxial goniometer. Although the axis of abduction-adduction is still offset from the elbow joint, special linkage arrangement was used to obtain equivalent motion. Experimental method was used to validate the accuracy of the device and model simulation was performed to emphasize the importance of accurate placement of the instrument on test subjects. Application of the present apparatus to normal subjects was studied to illustrate the range of elbow motion required in performing normal activities of daily living. This device is currently used in the functional evaluation of patients with elbow and forearm problems.

Reliability of isometric strength testing. Temporal factors and strength variation

Isometric strength measurements of grip, pronation, supination, and elbow extension and flexion on dominant and nondominant sides were made on 40 normal subjects (age range, 40-70 years) to investigate the variability of isometric strength at different times of the day. Statistically significant differences were found in certain pronation, supination, and grip comparisons. No statistically significant difference was found in extension and flexion. Although significant, the absolute change in strength at different times of the day was small and showed no consistent trend. On the basis of these data, it appears that this variation can probably not be routinely detected in the normal clinical setting. However, the study further defines the reliability of isometric strength testing and should be considered in further attempts at more accurate measurement of elbow function. The small variations of strength, approximately 5%, that can be measured universally with sensitive testing equipment, are clinically relevant. However, when attempting to determine an impairment state in order not to place too much importance on small differences, care should be exercised in interpreting strength measurements. This investigation demonstrates how the application of sophisticated biomechanical techniques may be employed to provide useful objective information in the difficult clinical area of disability assessment. Disability judgments may be made more accurate as more is learned of the normal variables influencing objective measurement.

Strength function after elbow arthroplasty

A prospective study of elbow strength after total elbow joint arthroplasty was conducted in 27 patients (31 procedures). In this overall group, flexion strength improved 92%, pronation, 63%, and supination, 69%. Grip strength improved 35%, but there was no mean improvement in extension strength among these patients. After 27 procedures for rheumatoid arthritis, the average strength improvement of all five functions was 71% compared to a 25% improvement in four patients with nonrheumatoid involvement. Placement of the prosthetic axis of rotation proximal or anterior to the normal axis was associated with consistently poorer strength. The sample was too. small to distinguish performance among prosthetic types, but the triceps-sparing approach showed consistently better strength in extension (averaging 20%) than did the other exposures.