we performed a retrospective population - based cohort study to describe the epidemiology and incidence of traumatic tendon injuries occurring in the hand and wrist within olmsted county , mn , united states ( population range , 127,626 to 138,420 citizens during the years of the study period ) during a 10-year period from january 1 , 2001 through december 31 , 2010 . minimal risk study ( 09 - 003826 ) approved on 6/26/2009 .
approval from our hospital and county institutional review board was obtained prior to initiating the study and all patients gave consent for research .
the study was performed using the rochester epidemiology project ( rep ) , a comprehensive database of all medical records of virtually all medical care providers to olmsted county , rochester , mn .
the database has tracked residents since the early 1960's.8 ) olmsted county contains one large urban community ( rochester , mn ) which represents roughly 75% of the overall population , with a surrounding rural and mostly agricultural region .
the majority of workers in olmsted county are in service industries , primarily healthcare and hospitality .
incident cases were defined as patients with an open wound of the hand or wrist with tendon involvement , secondary to acute trauma .
only patients who gave authorization to be included for research and lived in olmsted county at the time of the trauma were included .
exclusion criteria involved all chronic or non - traumatic injuries ( e.g. , secondary to inflammation , congenital malformations or flexion deformities ) . also excluded were avulsion fractures , complete amputations and closed tendon injuries including spontaneous ruptures and closed mallet fingers .
hand and wrist injuries were examined , and forearm injuries proximal to extensor zone 8 and flexor zone 5 were excluded .
patients in the rep database were identified using international classification of diseases ( icd)-9 codes describing open wounds with tendon involvement of wrist , hand , finger or unspecified upper limb .
the icd-9 codes are very reliable as a result of the professional coders of the health care institutions in olmsted county .
the patients ' age , gender , ethnicity , dominant hand , occupation , year of injury , mechanism of injury and the injured tendon and zone were identified and recorded from the patients ' medical records . for analysis of incidence rates , age at diagnosis
was categorized into eight groups : 0 - 9 years , 10 - 19 years , 20 - 29 years , 30 - 39 years , 40 - 49 years , 50 - 59 years , 60 - 69 years , and > 70 years .
additionally , the occupation of any patient who experienced a work - related injury was reviewed and assigned to one of 23 " major groups " as defined by the 2010 standard occupational classification structure ( soc2010 ) , which is used by federal statistical agencies to classify workers into categories for statistical analysis.9 ) incidence rates of tendon injuries were calculated for the years 2001 through 2010 assuming all olmsted county residents were at risk .
rates were calculated as the number of tendon injuries divided by the number of population person - years and reported as per 1,000 person - years , with 95% confidence intervals assuming a poisson distribution .
the denominator age- and sex - specific population person - years were estimated from decennial census figures , with linear interpolation between census years .
age- and sex - adjusted estimates were calculated by direct adjustment to the 2000 us census population.10 ) potential trends in the incidence of tendon injuries in the hand were examined by calculating age- , sex- and calendar - year - specific incidence rates , and evaluating these rates using poisson regression .
we performed a retrospective population - based cohort study to describe the epidemiology and incidence of traumatic tendon injuries occurring in the hand and wrist within olmsted county , mn , united states ( population range , 127,626 to 138,420 citizens during the years of the study period ) during a 10-year period from january 1 , 2001 through december 31 , 2010 . minimal risk study ( 09 - 003826 ) approved on 6/26/2009 .
approval from our hospital and county institutional review board was obtained prior to initiating the study and all patients gave consent for research .
the study was performed using the rochester epidemiology project ( rep ) , a comprehensive database of all medical records of virtually all medical care providers to olmsted county , rochester , mn .
the database has tracked residents since the early 1960's.8 ) olmsted county contains one large urban community ( rochester , mn ) which represents roughly 75% of the overall population , with a surrounding rural and mostly agricultural region .
the majority of workers in olmsted county are in service industries , primarily healthcare and hospitality .
incident cases were defined as patients with an open wound of the hand or wrist with tendon involvement , secondary to acute trauma .
only patients who gave authorization to be included for research and lived in olmsted county at the time of the trauma were included .
exclusion criteria involved all chronic or non - traumatic injuries ( e.g. , secondary to inflammation , congenital malformations or flexion deformities ) .
also excluded were avulsion fractures , complete amputations and closed tendon injuries including spontaneous ruptures and closed mallet fingers .
hand and wrist injuries were examined , and forearm injuries proximal to extensor zone 8 and flexor zone 5 were excluded .
patients in the rep database were identified using international classification of diseases ( icd)-9 codes describing open wounds with tendon involvement of wrist , hand , finger or unspecified upper limb .
the icd-9 codes are very reliable as a result of the professional coders of the health care institutions in olmsted county .
the patients ' age , gender , ethnicity , dominant hand , occupation , year of injury , mechanism of injury and the injured tendon and zone were identified and recorded from the patients ' medical records . for analysis of incidence rates , age at diagnosis
was categorized into eight groups : 0 - 9 years , 10 - 19 years , 20 - 29 years , 30 - 39 years , 40 - 49 years , 50 - 59 years , 60 - 69 years , and > 70 years .
additionally , the occupation of any patient who experienced a work - related injury was reviewed and assigned to one of 23 " major groups " as defined by the 2010 standard occupational classification structure ( soc2010 ) , which is used by federal statistical agencies to classify workers into categories for statistical analysis.9 )
incidence rates of tendon injuries were calculated for the years 2001 through 2010 assuming all olmsted county residents were at risk .
rates were calculated as the number of tendon injuries divided by the number of population person - years and reported as per 1,000 person - years , with 95% confidence intervals assuming a poisson distribution .
the denominator age- and sex - specific population person - years were estimated from decennial census figures , with linear interpolation between census years .
age- and sex - adjusted estimates were calculated by direct adjustment to the 2000 us census population.10 ) potential trends in the incidence of tendon injuries in the hand were examined by calculating age- , sex- and calendar - year - specific incidence rates , and evaluating these rates using poisson regression .
during the 10-year study period , 458 cases of acute traumatic tendon injuries of the hand and wrist were identified .
this involved 692 tendons , of which 184 ( 26.6% ) were reported to be only partially lacerated .
none of the patients had more than one incident of acute traumatic tendon injury during the defined 10-year period .
the overall age- and sex - adjusted incidence rate was 33.2 per 100,000 person - years ( 95% confidence interval [ ci ] , 30.1 to 36.2 ) .
the rate of injuries was significantly associated with gender ( p < 0.001 ) , with an age - adjusted incidence rate of 56.3 per 100,000 person - years for males ( 95% ci , 50.6 to 62.0 ) and 10.7 per 100,000 person - years for females ( 95% ci , 8.3 to 13.2 ) .
most tendon injuries occurred in 2002 , with an incidence rate of 42.9 per 100,000 persons .
overall , the rate of injuries was significantly associated with year ( p = 0.040 ) , with a decreasing trend over the 10-year period .
the mean age at time of injury was 35.9 years ( range , 1 to 91 years ) .
age was significantly associated with the rate of injuries ( p < 0.001 ) , with the highest crude incidence in patients aged 20 - 29 years .
additional patient population characteristics are presented in table 1 . of all patients , 377 patients ( 82% )
had at least one laceration directly located on a digit ( finger and/or thumb ) .
patients with direct digit involvement injured between one to four digits , with the majority of injuries occurring on a single digit ( 75% ) . when the total number of tendon injuries in each digit was compared , injury to the index finger was the most common ( table 2 ) .
extensor tendon injuries accounted for more injuries than flexor tendon injuries ( p < 0.001 ) . in total , 395 extensor tendons and 297 flexor tendons were injured .
patients injured between one to nine tendons in the hand or wrist , the majority having injured one tendon ( 72% ) . of all extensor tendon
injuries , the extensor mechanism in the index finger was injured significantly more often than any other tendon ( 15.6% ) , which remained significant after a bonferroni correction ( bonferroni p < 0.003 ) .
the most commonly injured zone of all extensor tendons was zone three ( 12.6% ) .
extensor tendon zone three was injured more often than zones two and five , although this was not significant ( bonferroni p < 0.004 ) .
the flexor digitorum profundus to the index finger was the most injured flexor tendon ( 9.1% ) . however , after bonferroni adjustment , it was not injured significantly more often than the flexor digitorum profundus tendons to the long , ring and little finger , the flexor digitorum superficialis to the little finger or the flexor pollicis longus ( bonferroni p < 0.004 ) . of all flexor
tendon zones , zone two was injured in 19.1% , which was significantly more often than every other flexor zone ( bonferroni p < 0.006 ) .
tables 3 and 4 summarize the frequency and percentages of individual tendons injured and the percentage of tendon injuries by zone , respectively . a variety of mechanisms accounted for acute traumatic tendon injuries and included : knife ( n = 129 ) , glass or mirror ( n = 71 ) , any kind of saw ( n = 68 ) , crush injury ( n = 27 ) , degloving injury ( n = 5 ) , and bite injury ( n = 3 ) .
mechanism was not recorded in 40 cases , tendon injury was caused by sharp objects too diverse to specify in 105 cases .
these cases were mainly due to sharp metal ( e.g. , sheet metal , blades of lawn mower , snow blower ) , work instruments ( e.g. , scissor , chisel ) or ceramic splinters .
thirty - four patients ( 7.4% ) were reported to be moderately to severely intoxicated with alcohol , of which one case involved bilateral injury .
tendon injuries related to violence or physical altercations were seen in 27 cases ( 6.4% ) .
of these 27 , alcohol was involved in 16 cases ( 59.3% ) , and the most common mechanism involved a knife ( n = 10 , 37.0% ) .
nineteen patients ( 4.5% ) had self - inflicted or purposely imposed wounds that were obtained in a variety of circumstances .
six patients ( 1.4% ) had self - inflicted wounds secondary to attempted suicide , of which one case involved bilateral injury .
ten cases which were self - inflicted were the result of punching / hitting something ( most commonly glass ) , all while intoxicated with alcohol , and not related to violence or physical altercation .
pediatric cases ( defined at our institution as < 15 years of age ) of acute traumatic tendon injury occurred in 24 patients ( 5.2% ) with a mean age of 9.0 years of age ( range , 1 to 14 years ) ( table 1 ) . of these patients ,
work - related injuries accounted for 24.9% ( n = 104 ) of acute traumatic tendon injuries . after assigning these patients ' occupations to respective soc2010 major groupings , the groups with the highest work - related injuries occurred in construction and extraction occupations ( n = 46 , 44.2% ) , food preparation and serving related occupations ( n = 15 , 14.4% ) , and transportation and material moving occupations ( n = 13 , 12.5% ) ( table 5 ) .
during the 10-year study period , 458 cases of acute traumatic tendon injuries of the hand and wrist were identified .
this involved 692 tendons , of which 184 ( 26.6% ) were reported to be only partially lacerated .
none of the patients had more than one incident of acute traumatic tendon injury during the defined 10-year period .
the overall age- and sex - adjusted incidence rate was 33.2 per 100,000 person - years ( 95% confidence interval [ ci ] , 30.1 to 36.2 ) .
the rate of injuries was significantly associated with gender ( p < 0.001 ) , with an age - adjusted incidence rate of 56.3 per 100,000 person - years for males ( 95% ci , 50.6 to 62.0 ) and 10.7 per 100,000 person - years for females ( 95% ci , 8.3 to 13.2 ) .
most tendon injuries occurred in 2002 , with an incidence rate of 42.9 per 100,000 persons .
overall , the rate of injuries was significantly associated with year ( p = 0.040 ) , with a decreasing trend over the 10-year period .
the mean age at time of injury was 35.9 years ( range , 1 to 91 years ) .
age was significantly associated with the rate of injuries ( p < 0.001 ) , with the highest crude incidence in patients aged 20 - 29 years .
of all patients , 377 patients ( 82% ) had at least one laceration directly located on a digit ( finger and/or thumb ) .
patients with direct digit involvement injured between one to four digits , with the majority of injuries occurring on a single digit ( 75% ) . when the total number of tendon injuries in each digit was compared , injury to the index finger was the most common ( table 2 ) .
extensor tendon injuries accounted for more injuries than flexor tendon injuries ( p < 0.001 ) . in total , 395 extensor tendons and 297 flexor tendons were injured .
patients injured between one to nine tendons in the hand or wrist , the majority having injured one tendon ( 72% ) . of all extensor tendon
injuries , the extensor mechanism in the index finger was injured significantly more often than any other tendon ( 15.6% ) , which remained significant after a bonferroni correction ( bonferroni p < 0.003 ) .
the most commonly injured zone of all extensor tendons was zone three ( 12.6% ) .
extensor tendon zone three was injured more often than zones two and five , although this was not significant ( bonferroni p < 0.004 ) .
the flexor digitorum profundus to the index finger was the most injured flexor tendon ( 9.1% ) . however , after bonferroni adjustment , it was not injured significantly more often than the flexor digitorum profundus tendons to the long , ring and little finger , the flexor digitorum superficialis to the little finger or the flexor pollicis longus ( bonferroni p < 0.004 ) . of all flexor
tendon zones , zone two was injured in 19.1% , which was significantly more often than every other flexor zone ( bonferroni p < 0.006 ) .
tables 3 and 4 summarize the frequency and percentages of individual tendons injured and the percentage of tendon injuries by zone , respectively . a variety of mechanisms accounted for acute traumatic tendon injuries and included : knife ( n = 129 ) , glass or mirror ( n = 71 ) , any kind of saw ( n = 68 ) , crush injury ( n = 27 ) , degloving injury ( n = 5 ) , and bite injury ( n = 3 ) .
mechanism was not recorded in 40 cases , tendon injury was caused by sharp objects too diverse to specify in 105 cases .
these cases were mainly due to sharp metal ( e.g. , sheet metal , blades of lawn mower , snow blower ) , work instruments ( e.g. , scissor , chisel ) or ceramic splinters .
thirty - four patients ( 7.4% ) were reported to be moderately to severely intoxicated with alcohol , of which one case involved bilateral injury .
tendon injuries related to violence or physical altercations were seen in 27 cases ( 6.4% ) .
of these 27 , alcohol was involved in 16 cases ( 59.3% ) , and the most common mechanism involved a knife ( n = 10 , 37.0% ) .
nineteen patients ( 4.5% ) had self - inflicted or purposely imposed wounds that were obtained in a variety of circumstances .
six patients ( 1.4% ) had self - inflicted wounds secondary to attempted suicide , of which one case involved bilateral injury .
ten cases which were self - inflicted were the result of punching / hitting something ( most commonly glass ) , all while intoxicated with alcohol , and not related to violence or physical altercation .
pediatric cases ( defined at our institution as < 15 years of age ) of acute traumatic tendon injury occurred in 24 patients ( 5.2% ) with a mean age of 9.0 years of age ( range , 1 to 14 years ) ( table 1 ) . of these patients
work - related injuries accounted for 24.9% ( n = 104 ) of acute traumatic tendon injuries . after assigning these patients ' occupations to respective soc2010 major groupings , the groups with the highest work - related injuries occurred in construction and extraction occupations ( n = 46 , 44.2% ) , food preparation and serving related occupations ( n = 15 , 14.4% ) , and transportation and material moving occupations ( n = 13 , 12.5% ) ( table 5 ) .
hand injuries account for up to 20% of all treated injuries in an emergency department.1 ) furthermore , acute hand injuries are the most common occupational injury evaluated in emergency departments within the united state.11 ) the spectrum of traumatic hand injuries includes minor soft tissue injuries and fractures to complex injuries requiring nerve , tendon , or artery repair . within this spectrum , tendon injuries are quite common and were reported in 54.8% of patients with a small laceration and 92.5% of patients with a deep injury through a small laceration.2 ) thus , it is important for the treating physician to recognize that even a small laceration to the hand may involve the flexor or extensor mechanism ; however , the incidence of such injuries has not been extensively studied in the literature . without adequate epidemiologic data ,
it is difficult for one to predict the economic burden of these injuries on society , which is of particular relevance in the current setting of growing healthcare costs and limited available economic resources.3,4,5,6,7 ) our data from a mixed urban and rural population show tendon injury in the hand or wrist to occur at a rate of 33.2 injuries per 100,000 person - years .
males have a significantly higher incidence of traumatic tendon injuries to the hand or wrist compared to females ; a finding in accordance with previous studies.12 ) this may be partly due to the nature of gender - related professional work and recreational activities .
previous reports have suggested that most hand injuries appear to occur while performing manual labor either on - the - job or at home.13 ) it was also noted that traumatic tendon injuries in the hand occur most frequently in the 20 - 29 year old age group .
this corresponds with the age of the workforce most likely to have more physical labor intensive occupations which may place them at increased risk for injury . in our study , the most common occupations experiencing work - related injury occurred in construction and extraction occupations ( e.g. , carpentry , construction , electrical , textile ) , food preparation and serving related occupations ( e.g. , cooking / chefs , restaurant personnel ) , and transportation and material moving occupations ( e.g. , machinist , manufacturing - related jobs , equipment operators ) . while unable to be calculated in our study , the combination of these work - related injuries surely accounts for an incredible amount of lost work time and overall economic burden to our population .
this study shows that extensor tendon injuries occurred more frequently than flexor tendon injuries , with the index finger representing the most commonly injured finger .
previous reports have noted the predominance of flexor tendon research , but a paucity of outcome studies exists examining the outcomes following extensor tendon repair and its long - term morbidity on young laborers.14,15,16,17,18 ) as such , future research may wish to focus on the treatment and rehabilitation of extensor tendon injuries . with regard to flexor tendon injuries ,
injury was most commonly located in zone two , suggesting that most flexor tendon injuries occur distal to camper 's chiasm .
rosberg et al.7 ) previously reported that isolated injury of the profundus tendon to the small finger was the most common flexor tendon injury during their examination of 135 flexor tendon injuries in a swedish population .
weaknesses of the present study include the retrospective nature of the study and the specific geography of our cohort population
. the incidence of traumatic tendon injuries reported here may not be applicable to large metropolitan areas , but rather be of relevance to smaller urban and mixed communities with agricultural areas within the midwest united states .
we did not examine the socioeconomic factors or the working environment of injured patients , which may have influenced injury patterns .
in addition , no effort was made to examine treatment modalities , outcomes , or health care cost related to the management of these injuries which will be the subject of future analysis .
missed cases in the present database include all neglected injuries and cases of tendon injury not seen within our health care centers .
the chance of missed cases , however , is most likely low , as it is unlikely for patients with an injury in the county studied to seek care outside the large region that this hospital provides . to put the frequency of tendon injuries into perspective
, it is interesting to note that the incidence of scaphoid fractures is 1.47 fractures per 100,000 person - years.19 ) this rate is 23 times smaller than the incidence rate of tendon injuries showed by our study .
although our data demonstrates a significant decrease in incidence over the 10-year period , we believe the present incidence is still of such importance that it should encourage the ongoing study of tendon healing and rehabilitation as a means of decreasing morbidity following these injuries .
the reason for this decrease is a question for further investigation , but could be related to changing occupations and increasing awareness of possible risks.11,13 ) in conclusion , an improved and updated understanding of the epidemiology of acute tendon injuries will hopefully stimulate additional investigation into the prevention and treatment of these injuries .
 backgroundacute traumatic tendon injuries of the hand and wrist are commonly encountered in the emergency department . despite the frequency , few studies have examined the true incidence of acute traumatic tendon injuries in the hand and wrist or compared the incidences of both extensor and flexor tendon injuries.methodswe performed a retrospective population - based cohort study of all acute traumatic tendon injuries of the hand and wrist in a mixed urban and rural midwest county in the united states between 2001 - 2010 . 
 a regional epidemiologic database and medical codes were used to identify index cases . 
 epidemiologic information including occupation , year of injury , mechanism of injury and the injured tendon and zone were recorded.resultsduring the 10-year study period there was an incidence rate of 33.2 injuries per 100,000 person - years . 
 there was a decreasing rate of injury during the study period . 
 highest incidence of injury occurred at 20 - 29 years of age . 
 there was significant association between injury rate and age , and males had a higher incidence than females . 
 the majority of cases involved a single tendon , with extensor tendon injuries occurring more frequently than flexor tendons . typically , extensor tendon injuries involved zone three of the index finger , while flexor tendons involved zone two of the index finger . 
 work - related injuries accounted for 24.9% of acute traumatic tendon injuries . 
 the occupations of work - related injuries were assigned to major groups defined by the 2010 standard occupational classification structure . after assigning these patients ' occupations to respective major groups , the most common groups work - related injuries occurred in construction and extraction occupations ( 44.2% ) , food preparation and serving related occupations ( 14.4% ) , and transportation and material moving occupations ( 12.5%).conclusionsepidemiology data enhances our knowledge of injury patterns and may play a role in the prevention and treatment of future injuries , with an end result of reducing lost work time and economic burden . 
METHODS
Study Design
Study Population
Data Collection
Statistical Analysis
RESULTS
Incidence of Acute Traumatic Tendon Injury
Injury Characteristics and Patterns
DISCUSSION