Prevalence of a Septated First Dorsal Compartment Among Patients With and Without De Quervain Tenosynovitis: An In Vivo Anatomical Study.

Background: The reported prevalence of a subcompartment housing the extensor pollicis brevis (EPB) tendon within the first dorsal compartment varies widely in the literature, especially regarding the rates of occurrence between genders and among those with and without De Quervain. Based on direct intraoperative observation, we hypothesized that the prevalence of a septated compartment is far greater than previously reported, particularly in those with De Quervain disease. Methods: A prospective analysis of consecutive patients who underwent first dorsal compartment release was carried out. Patients were divided into 2 groups: those with De Quervain tenosynovitis ("De Quervain" group) and a control cohort without a primary diagnosis of De Quervain ("non-De Quervain" group). The intraoperative findings of a single compartment or a separate subcompartment were recorded. The prevalence of a septated compartment was calculated and compared between genders and both patient groups. Results: A total of 102 consecutive patients were included, with a female predominance (74.5%). Overall, 79.4% of patients had a separate subcompartment for the EPB. In the De Quervain cohort, 89.1% had 2 compartments, while 71.4% of non-De Quervain patients had a subcompartment. Men and women had a similar rate of double compartments (80% and 82.4%, respectively). Conclusions: The prevalence of a septated first dorsal compartment is considerably higher than previously reported, most notably in patients afflicted with De Quervain tenosynovitis. This higher rate of septation occurs with a similar prevalence in both men and women. Owing to its consistent presence, the dual first dorsal compartment should be regarded as an expectant anatomical component of the normal wrist.