Abstract
Current opinion is divided as to whether carpal tunnel syndrome requiring operative decompression can be caused by an occupation.
The aims of this study were to define the lamb freezing worker population who acquire carpal tunnel syndrome and to confirm or refute lamb boning as an occupational cause for carpal tunnel syndrome.
Roles, gender age and exposure periods of all workers who had carpal tunnel decompressions over the past six seasons at the largest lamb Freezing Works in the world were examined. Kaplan-Meier survival analysis for boners, slaughter men and non-knife labourers was performed and tested for significance. Chi-square analysis and ANOVA were performed for gender and age. Age and gender-adjusted Cox regression analysis was performed to establish relative risks/hazard ratios for each of the three groups developing carpal tunnel syndrome. Incidences for boners and non-knife hands were calculated. Comparison of this population and a standard carpal tunnel population was performed.
Two hundred and eighty five carpal tunnel decompressions were performed in workers who failed conservative management at the largest lamb freezing works in the world by a single surgeon after neurophyiological-test confirmation of the diagnosis. Of those having surgery 79% were men: 21% female and this was significant with Chi square testing (p< 0.01). At decompression boners were significantly younger than non-knife hands (p< 0.01). Adjusting for age and gender boners were 120% more likely to need decompression than non-knife labourers (p< 0.01). The median survival for a lamb boner’s carpal tunnel at five years was 44%. The incidence of carpal tunnel syndrome in lamb boners was 10% (person-seasons). This population is entirely different to the published idiopathic population requiring carpal tunnel decompression which is predominantly female with meanage of 55.
To our knowledge this is the first study to provide sound evidence that carpal tunnel syndrome can be caused by an occupation. We have quantified this and welcome ideas for further work in this fascinating a uniquely New Zealand population.
Correspondence should be addressed to Associate Professor N. Susan Stott, Orthopaedic Department, Starship Children’s Hospital, Private Bag 92024, Auckland, New Zealand.
