Anatomical study of the first dorsal extensor compartment for the treatment of de Quervain's disease

Introduction: Anatomical variations of the first dorsal extensor compartment (1st EC) are commonly noted. Materials and methods: Forty cadaver hands were dissected to define the 1st EC. Through the gross findings, we classified the contents according to the presence of septation, subcompartment, and variation of tendons. Bony cross-section of the wrist was performed to reveal any bony pattern within the 1st EC. We also measured the anatomical structures of the 1st EC. Results: A septum that results in subcompartments was present in 24, complete in 2 and incomplete in 22 hands distally. The mean size of the 1st EC was 20.69 ± 12 mm in length, and 8.65 ± 0.67 mm in width. The mean length of the septum was 11.18 ± 5.18 mm, while the mean width of the subcompartment was 3.18 ± 0.40 mm. All the subcompartments enclosed only extensor pollicis brevis (EPB) tendons. The mean number of abductor pollicis longus and EPB tendon slips was 2.6 ± 0.5 and 1.1 ± 0.2, respectively. The bony floor of the 1st EC was classified into five types. Two distinctive grooves separating two tendons with protruding osseous ridge (type I, n = 9), two distinctive grooves separating two tendons without protruding osseous ridge (type II, n = 10), a single distinct groove with osteophytes (type III, n = 16), indistinct groove with fibrous septum separating two tendons (type IV, n = 4), and indistinct groove without fibrous septum (type V, n = 1). Conclusion: Knowledge about the 1st EC abnormality is mandatory for the successful treatment of de Quervain's disease.