Quantitative, objective tests can be helpful, especially to track progress over time. However, there is significant variability in results due to factors that are not necessarily clinically meaningful, including simple variation over time, inter-tester variability, fatiguing, degree of effort, etc.
Common quantitative tests used in patients with nerve injury provide objective data.
Pinch Testing (Pinch Meter):
• Useful to track pinch strength (a measure of hand intrinsic function) over time.
• Both pulp-to-pulp and key pinch can be measured.
• Examiner holds meter lightly (avoid rigid stabilization that might falsely inflate values).
• For pulp-to-pulp, the patient grasps the end of the pinch meter with the tip of the thumb on top and the tip of the index finger on the bottom.
• For key pinch, the patient grasps the end of the pinch meter with the tip of the thumb on top and the radial aspect of the flexed index finger on the bottom.
Grip testing (Jamar Dynamometer):
• These can be useful to track grip strength (a measure of hand extrinsic and intrinsic strength) over time.
• Patient is seated, feet on floor, arms adducted and not supported, elbow at 90 degrees flexion, and forearm/wrist in neutral position.
• Patient holds the dynamometer level and facing outward with thumb on one side and fingers on other to grasp the device.
• There are five levels of testing that measure grip in slightly different handle positions -- these vary the relative contributions of intrinsic and extrinsic muscle function.
• Normally, a bell curve of grip measurements occurs over the five levels (an abnormal or flat curve can indicate submaximal effort).
Rapid simultaneous/exchange grip testing can also be useful to detect submaximal effort:
• To assess the sincerity of effort in conjunction with the history, degree of reported pain, degree of atrophy or lack thereof, degree of calluses and other signs of vigorous hand use not in keeping with the stated level of disability.
• Rapid simultaneous grip: patient grasps two dynamometers (one in each hand) simultaneously or with rapid alternation. If submaximal effort is an issue there will be more variation between this method and static testing. This is because with the static test the patient has time to think about providing less effort. With the rapid simultaneous grip, they have less time to ‘think’ through their response and are forced to give more effort. With suboptimal effort, the strong ‘normal’ side gets weaker and the ‘fake’ weak side gets stronger. True malingerers often refuse to do the test or refuse to speed up. Sometimes in these cases, it is useful to demonstrate how quickly you want them to grip.
• Rapid Exchange: Patient grips alternating rapidly between one hand and the other -- if submaximal effort is an issue then the rapid alternating grip is usually significantly greater than that seen with the static grip testing. This is less effective then rapid simultaneous grip at figuring out submaximal effort because there is time between exchanges for the patient to remember which hand is being tested and plan the effort they will provide.
Other measurements include the following:
• Active and passive range of motion of joints (discussed in the Joint Range of Motion Section).
• Circumferential measurements -- measurement of the circumference of the arm, forearm, etc. can provide some information on atrophy and recovery over time.