Preoperative evaluation starts with an assessment of the upper extremity resting posture. This should be completed before attempts at active or passive movement in order to avoid evoking a dynamic deformity or increasing tone with limb manipulation. At rest, the baseline hand deformity or posture can be classified ( Table 1 ). Inspection of the upper extremity continues with an assessment of skin integrity, with special attention paid to the axilla, antecubital fossa, posterior elbow, wrist flexion crease, and palm. Active and passive range of motion (ROM) assessment can then be undertaken, in particular to detect the presence or absence of meaningful volitional motor activation. It is critical to establish which muscles are affected by spasticity, which have volitional control, and if there is dyssynergy or spastic cocontracture, myostatic or joint contracture, or rigidity. ^,

The presence and magnitude of spasticity is commonly assessed using the Modified Ashworth Scale (MAS) as described by Bohannon and Smith. The MAS score is obtained by passively ranging the joint through the entire arc of physiologic motion in 1 second or less ( Table 2 ). Advantages of the MAS are that it is a simple system and does not require additional equipment. However, it is an inherently subjective assessment with studies demonstrating moderate interrater and intrarater reliability when used in the upper extremity. The Modified Tardieu Scale (MTS) evaluates spasticity by passively ranging the joint through a slow (>3 second) and fast (<1 second) velocity arc of physiologic motion, measuring the position in which increased resistance is first detected and assessing for the magnitude of spasticity ( Table 3 ). While the MTS system adds objectivity to spasticity assessment, available systematic reviews have yet to support or reject its utility. ^,

In the absence of spasticity or rigidity, limitations in motion may represent periarticular soft tissue contracture, heterotopic ossification, or structural changes to the joint. As such, plain radiographs are recommended to characterize these potential contributors to the joint deformity. To evaluate volitional motor control, the patient is asked to perform simple, representative movements across each joint. ^, These movements should be observed with the extremity in different positions, and repeated while the examiner palpates surrounding muscle groups to identify motor activation, dyssynergy or cocontraction. Motor control at each joint is classified using a 6 point scale that characterizes movements from hypotonic with no active motion to full voluntary control ( Table 4 ). ^, Volitional hand function is further evaluated with the use of props to determine the patient’s ability to grasp and manipulate objects ( Table 5 ).

In addition to physical examination, dynamic polyelectromyography (dEMG) is an invaluable tool to investigate for the absence or presence of volitional motor control, assess for spasticity, and to identify dyssynergy or cocontraction. This is particularly useful for patients with limited arc of physiologic motion or severe deformities. ^, Surface or fine-wire intramuscular electrodes are placed onto key muscle groups to measure electrophysiologic motor activity combined with motion capture to simultaneous link kinematic data. Dynamic EMG is important when the goals of surgery are to augment upper extremity function since unmasking of unidentified spasticity in antagonist muscles may lead to less than optimal surgical outcomes ( Fig. 1 ). The use of dEMG has been shown to improve accuracy in identifying muscles that contribute to spastic deformity in the upper extremity and produce higher agreement between surgeons in operative planning. ^,

Dynamic electromyography (dEMG) of the Elbow. With slow and fast passive range of the motion of the elbow in a flexion-extension arc, the triceps fires involuntarily ( blue arrow ) during rapid elbow flexion indicating elbow extensor spasticity.

Neuromuscular blockade is useful to assess the contribution of spasticity to a deformity and to simulate the outcomes of addressing spasticity with surgery. After performing a baseline physical examination, local anesthetic is injected near the motor nerve of interest to differentiate spasticity alone from deformity affected by myostatic and/or joint contractures. ^, As spasticity is neurally mediated, no change in the deformity is seen after local anesthetic block suggesting a primary component of muscle and/or joint contracture. Neuromuscular blockade will also unmask concomitant spasticity in other muscles, such as the intrinsics after eliminating the contribution of spastic extrinsic finger flexors in a clenched-fist deformity. Accounting for muscle or periarticular contracture from spasticity is essential to optimal surgical outcomes by selecting the correct surgical procedure for the underlying pathology, thus underscoring the value of neuromuscular blockade to surgical planning. Similarly, long-acting neuromuscular agents to spastic muscles, such as botulinum toxin, can be used to prognosticate improvement in pain, correction of deformity, and enhancement of basic upper extremity function after surgical reconstruction. This allows patients to experience the anticipated benefits and limitations of surgery, supporting shared decision-making.