The hand is not a fixed, static structure but a dynamic sensorimotor organ with an incredible repertoire of motor functions. The primary aim of reconstruction of an injured hand is to restore as much of these lost functions to the hand, and consequently, much of the hand surgery literature has been dedicated to the recovery of sensory and neuromuscular functions.
Objective assessment of both tactile resolution and passive ranges of motion are made possible by the wide availability of normative data [1
]. However, such normative data cannot be generalized for hand strength measurements because of the wide range of demographic and physiologic factors influencing hand strength.
The hand dynamometer and pinch gauges are inexpensive, easy to administer, and are considered to provide repeatable measurements in clinical settings as well as for research purposes [9
]. Such strength measurements, however, are only useful in the presence of normative data derived from the population of concern. Without a pre-existing cross-sectional study providing such data, hand strength measurements can only provide a limited picture of clinical progress in postoperative or medical patients.
In 1975, a study by Oh [17
] provided normative values of grip strength among the South Korean population. Unfortunately, the data from the study were reported in a publication that no longer exists, and extant copies of the publication are not widely available, even among hand surgeons living in Korea.
Additionally, anecdotal experiences of Korean hand surgeons who are familiar with Oh's publication have suggested that the values reported in the study might be outdated. During the ensuing decades since Oh's report, the population in South Korea has experienced an exponential economic growth with a resultant demographic transition as well as drastic improvements in nutrition and overall health outcome measures [18
In this present study, grip strengths peaked in the young adult group (20 to 29), and this outcome most obviously reflects the variations of muscular mass, which peaks during this period, in the normal course of human development [19
]. This result is consistent with the age-related patterns reported by Oh [17
], Schmidt and Toews [20
], and Lunde et al. [21
The mean grip strength values in this study were greater than the values published by Oh [17
]. Taking the male group of 20 to 29 years age, a comparison can be made. In our study, the grip strengths were 46.9 kg and 44.9 kg in the right and left hands. These values are higher than the results reported 35 years ago by Oh [17
], which were 42.1 kg and 38.6 kg, respectively.
It is worth noting that the 20- to 29-year-old participants in this study had all been born after Oh's study [17
]. The epidemiologic significance is that the increased hand strength appears to reflect the dramatic nutritional and public health improvements that the South Korean population has experienced in the past several decades [18
In any given population, the hand strength ratios appear consistent. Among the male participants in this study, the strength ratio between the dominant and non-dominant hand was 1.05±0.08. This is similar to the ratio reported among Caucasian individuals by Schmidt and Toews [20
] (1.03±0.05) and also to the ratio reported earlier in the Korean population (1.02±0.14) [17
]. This overall similarity in strength ratios could also be observed among the female populations from this study, from the study by Oh, and from those reported by Lunde et al. [21
Comparison to previously-published hand strength ratios
Adjusting for sex and age group, however, the absolute normative values from this study are different from those of the Korean population circa 1975 and, also, from those of Caucasian populations [14
]. Thus, we believe that our research data represents more valid and up-to-date normative hand strength data for the population of interest.
An argument could be made as to whether this data holds any clinical utility. Of course, objective measurements of hand strength are not routine parts of a primary-care exam, and an individual who presents to a hand clinic most likely would not have had undergone such measurements prior to an injury. Furthermore, certain types of hand injury do not affect strength outcomes-especially those distal injuries that spare mechanical components such as bones and tendons.
When an injury or a disease process does decrease hand strength, however, the consequent result is a decrease in the overall function of the involved hand. Population-specific normative data is useful in the management of such patients who experience declining hand strength. The normative data validates the intra-individual standard of using the non-injured hand as the control-with the understanding that a dominant hand is only marginally stronger than the non-dominant one.
Normative hand strength data holds an even more significant utility in the management of injuries or disease processes that involve both hands. When both hands are affected, neither of them can serve as a control for the other. In such cases, hand strength data provides the most useful standard for monitoring hand strength. At any point in the management of such patients, a significant deviation from the expected range of hand strengths would certainly warrant a clinical investigation for unrecognized pathology and intervention, if necessary.
In summary, this study presents updated normative data on hand strengths in the South Korean population. The characteristics of hand strength across demographic variables and hand-dominance are consistent with previously published studies. Of special note is that absolute hand strength measurements can neither be used across ethnicity nor populations that have experienced rapid economic development. This is evidenced by the change in hand strength among the South Korean population in the past four decades.
The hand dynamometer and pinch gauge used in this study are inexpensive and easy to use. The measurements obtained from these instruments are reliable and objective. Used in conjunction with available normative data, hand strength exams allow progressive assessment of hand function in both post-surgical and medical patients. The authors believe these strength tests to have a valid clinical and epidemiologic utility for the population studied.