Tunnel Carpal Syndrome
A review of factors which could be involved in the etiology and a proposed model to analyze it
Agenda
Statistics Carpal tunnel syndrome Hand anatomy Nerve entrapment process Symptoms, signs and electrodiagnostics of CTS Outcomes of CTS Factors studied in relationship with CTS Work activities with high incidence of CTS Results of studies Conclusion based on studies Proposal model of etiology of CTS A case study using proposed model Suggestions of interventions based on model Limitations of the model Questions?
Statistics
The National Ambulatory Medical Care Survey of 1989, ranks Musculoskeletal Disorders second after respiratory conditions as the most common reason for seeking health care. In 1989 it was estimated that there were 2.7 million visits to health care due to hand and wrist pain. (National Ambulatory Medical Care Survey) 14.4 % prevalent CTS (symptoms); 2.7 %prevalent CTS (diagnosis) on 1998 [Atroshi,1999] 1998 National Health Survey Data report a US prevalence of self-reported carpal tunnel syndrome of 1.87 million people, of which over one-third CTS was diagnosed and half were believed to be work-related [Tanaka, et al, 1998]
Carpal Tunnel Syndrome (CTS)
Compression of the median nerve as it passes through the carpal canal in the wrist.
Hand Anatomy
Nerve entrapment
Pathological condition caused by incompatibility between the volume of nerve and the space available to the nerve structure (Lundborg, 1988)
Increase pressure which impairs: a)blood flow b)oxygenation c) axonal transport system
Nerve Compression
Edema (i.e. swelling) of surrounding tissue in canal
Mechanical irritation of surrounding structures such tendons and muscles
From Hagberg, et al, 1995 and Lundborg, 1988
Symptoms, signs and electrodiagnostics of CTS
Physical signs
Symptoms
Pain Paresthesias Numbness in the distribution of median nerve Pain especially at night
Diminished sensibility to vibration and light touch Abnormal two-point discrimination Thenar muscle weakness and atrophy Phalen's sign Tinel's sign
Electrodiagnostics
Nerve conduction test
Outcomes of CTS
Individual level
Discomfort (numbness, tingling) Fatigue Pain (burning pain) Inability to perform Loose of sensitivity to light touch and pressure *at work, *at "some" tasks outside work *at "some" everyday activities Distress
Business level Direct costs
Compensation cost Lost wages Lost productivity
Indirect costs
Training
Definitions
Exposure:
Amount of a factor to which a group or individual is in contact to. Sometimes contrasted with dose, the amount that enters or interact with the organism. Proximity or contact with a factor in such a manner that an injury, disease or illness may occur (Last, 1988
as in Hagberg, et al 1995)
Risk Factor:
Injury:
Damage to individual anatomic, physiologic and/or psychiatric resulting from exposure to termal, mechanical or chemical energy or other stressors or from other essentials as heat or oxygen
An aspect of personal behaviour or lifestyle, an environmental exposure (including work) or an inborn or inherited characteristic, which on the basis of epidemiologic evidence is known to be associated with healthrelated conditions. The term `risk factor is also use with the following meaning: a) An attribute or exposure that is associated with an increased probability of a specified outcome. Not necessarily a causal factor b) An attribute or exposure that increases the probability of occurrence of disease or other especified outcome. A determinant
From Hagberg, et al, 1995
CTS studies/ factors studied
Female Tanzer, 1959 Kendall, 1960 Phalen, 1972 Stock, 1991 (no) Birth control pill use Sabour and Fadel 1970 Krom et al, 1990 (no) Pregnancy Massey, 1978 Bilateral oophorectomy Cannon, et al, 1981 Hysterrectomy without oophorectomy Krom, et al 1990
Related to estrogen's levels
Mechanical Stress Tichauer, 1966 Force and repetition Silverstein, et al, 1987 Repetition and cold Chiang, et al, 1990
Force Tanzer, 1959 Nordstrom, et al 1997 Carragee, et al, 1988 CDC, 1989 occup& disease surv. Nathan, et al 1988 Silverstein, 1986; 1987 Weislander, et al 1989 -Armstrong, 1979 Repetitive hand motions Nordstrom, 1997 Birkbeck et al, 1975 Carragee, et al , 1988 CDC, 1989 occup & disease surv. Feldman, et al, 1983 Silverstein, et al, 1986; 1987 Wieslander, et al , 1989 (only after 20 years of exposure!) Cannon, et al, 1981 (no) Moore, 1992 Chiang, et al, 1990 Kuorinka, et al, 1979 Stetson, et al, 1993, Nathan, et al 1988, 1992a Barnhart et al, 1991 Osorio, et al, 1994 Awkward postures CDC, 1989 occup& disease surv. Duncan, et al, 1987 Margolis, et 1987 al, Masear,et al, 1986 Tichauer, 1966 Vibration Juntunen, et al, 1983 CDC, 1989 occup& disease surv. Feldman, et al, 1983 Wieslander, et al, 1989 Cannon, et al, 1981 Bovenzi, 1990; 1994
Use of power tools or machinery Nordstrom, 1997 Diabetes mellitus Comi, et al, 1985 Krom, et al, 1990 (no) Flexed wrist activities Extended Wrist Activities Krom, et al, 1990 Krom, et al, 1990 Age Morgenstern,et al, 1991 Height Krom, et al, 1990 English, et al, 1995 Weight Krom, et al 1990 Nordstrom, 1997 English, et al, 1995 Varicosis (MEN) Krom, et al, 1990 Previous musculoskeletal condition Nordstrom, 1997 Rheumatism Krom, et al 1990 (no) Typing Krom, et al 1990 (no) Autonomy at work Nordstrom, 1997 Quantitative workload Nordstrom, 1997 (no) Perception of importance of occup. Safety and health Nordstrom, 1997 (no)
* Significant (consistent evidence )according to Hales, et al, 1996.
Factors studied
Gender Birth control use Pregnacy Bilateral oophorectomy Histerectomy without oophorectomy
Height Weight Varicosis Rheumatism Diabetes mellitus
Force Repetitive motions Awkward postures Vibration Mechanical Stress Force and repetition Repetition and cold Use of power tools and machinery Flexed/Extended wrists activities Typing Autonomy at work Quantitative workload Perception of importance of safety and health
Work activities studied
Some work areas/ industries with high incidence of CTS
Female garment (Punnet, et al 1985) Ski Manufacturing (Barnhart, 1991) Grocery store (Baron, et al, 1991; Morgenstern,et al, 1991; Osorio, et al, 1994) Postal machine operators (CA, Berkeley) Frozen food factory workers (Chiang, 1990) Oyster, crab and clam packing (Franklin et al 1991; Chiang,et al, 1993) Meat workers (Franklin et al 1991 and Schottland et al, Pork processing plants (Moore and Garg, 1994) Poultry workers (Franklin et al 1991, Schottland, et al, 1991) Slaugterhouses and butchers (Falck and Aario, 1983) Fish canneries and processing grinders Electronic assembly (Feldman, et al, 1987) Air craft engine workers (Cannon, et al, 1981) Textile workers (McCormack, et al, 1990) Clerical Bottlers and canners Automobile assembly workers
Results of studies
Show no concensus on what factors are related with the etiology of CTS Show no consensus on the degree of influence of factors to CTS.
Why? Due to different:
Measures (objective vs. subjective) Type of study Confounding factors Biases (e.g. survivor bias) Tools to measure Case definition Approaches (e.g. no comparable) Industries, job descriptions Sample size (e.g. big enough to see difference) Statistical methods and interpretation
Conclusion of studies
Insufficient evidence
Posture and CTS
Evidence
Highly repetitive work and CTS Force and CTS Vibration and CTS
S...