Weaker Functional Pinch Strength Is Associated With Early Thumb Carpometacarpal Osteoarthritis

Abstract

Background The thumb carpometacarpal (CMC) joint orchestrates pinch in its various positions, and thumb CMC osteoarthritis (OA) is a major source of orthopaedic morbidity. Self-reported pain, weakness, and physical examination may not correspond to radiographic findings when diagnosing early thumb CMC OA. Weakness is a prominent feature of the disease, but little evidence exists to quantify self-reported loss of strength with time, or to compare weakness with that of a nonarthritic population during early disease. Questions/purposes We asked: (1) Is pinch strength in subjects with early thumb CMC OA less than that in asymptomatic control subjects; and (2) weakness in which pinch position (key, tripod, or tip pinch) has the strongest association with early OA diagnosis? Methods For this case-control study, we recruited 23 subjects who were asymptomatic and 91 with early OA for comprehensive history, physical examination, strength measurements, pain surveys, and radiographic evaluation. We used multivariate logistic regression to quantify the association between declining pinch strength and early OA diagnosis after controlling for age, sex, and BMI. This analysis was performed for three different pinch positions (key, tripod, and tip pinch) to evaluate which measurement was most closely associated with diagnosis. Results Pinch strength was less in patients with early thumb CMC OA. Key pinch had the most robust association with OA diagnosis, in which a 20% decrease in key pinch strength from the control subjects' baseline was associated with a 10% increase in the OA diagnosis (95% CI, 3%-16%; p = 0.004). This had a stronger association with OA diagnosis than tip pinch, in which a 20% decrease in strength was associated with a 6% increase in early CMC OA (95% CI, 1.0%-11%; p = 0.031). Tripod pinch also was associated to a lesser extent; a 20% reduction in tripod pinch led to a 5% increase in OA (95% CI, 1.3%-9%; p = 0.048). Conclusions Decreasing pinch strength, especially key pinch, is associated with early CMC arthritis before the development of extensive radiographic disease.

Reduction in Cylindrical Grasp Strength Is Associated With Early Thumb Carpometacarpal Osteoarthritis

“…Our results further suggest that perhaps cylindrical grasp is a more sensitive test in measuring the decrease in forces during early disease compared with the standard clinical tool of gross grasp with a dynamometer. CMC joints affected by early OA do not yet show signs of instability during functional tasks; however, a decrease in key pinch strength has been documented in the same early stage of disease [8,18]. Our results complement these findings, suggesting that although there may not be changes in joint stability at early disease stages, there may be changes in loading of the thumb that are detectable with certain clinical tools.…”

“…However, to our knowledge, only one study on functional and biomechanical changes in early thumb CMC OA exists, and it does not evaluate grip strength [18]. Although data exist regarding gross grasp in many populations, including a healthy population and a population with advanced thumb CMC OA [1,5,13,17,20,25,26], there have been no studies that examine this grip strength in a population with early thumb CMC OA.…”

Hand osteoarthritis: clinical phenotypes, molecular mechanisms and disease management

“…Notable associations between self-reported pain and function have been reported for these patients. Furthermore, compared with healthy individuals, patients with this condition have reduced grip and pinch strength 32 , including a decrease in cylindrical grasp and key pinch strength that can begin in the early stages of disease 33,34 . Some of these presentations might be due to changes in the structure and composition of the joint and changes in the innervation of the dorsal radial ligament, which has an important proprioceptive and stabilising role for the thumb base 35 .…”

CORR Insights®: What Demographic and Clinical Characteristics Correlate With Expectations With Trapeziometacarpal Arthritis?

“…In order to tailor treatment and rehabilitation, especially to targeted patient populations, we need kinematic and kinetic studies that examine the normal trapeziometacarpal joint in daily and forceful activity, as well as across the disease spectrum. Preliminary studies measuring the kinematics of grasp, pinch, and jar twist with a simulated load cell in subjects with no arthritis [9], and measuring a statistically significant decrease in pinch and grasp with the same load cell in individuals with early arthritis is a start [8,12]. Such functional simulation paves the way for designing devices that simulate, for instance, how we tear off plastic wrap from a vitamin bottle or flip open an Eppendorf tube.…”