Isolated proliferative extensor tenosynovitis of the fourth dorsal compartment in non–rheumatoid patients is rare and may lead to tendon degeneration, intratendinous tearing, and functional impairment. Surgical management remains controversial, particularly regarding preservation of extensor retinaculum biomechanics. This study evaluates the clinical outcomes of the Kapandji extensor retinaculum plasty for treatment of advanced fourth-compartment extensor tenosynovitis.

A retrospective case series was conducted including five patients (three men, two women; mean age, 71.2 years) treated surgically between January 2020 and March 2026 for spontaneous proliferative extensor tenosynovitis of the fourth compartment without inflammatory arthritis. All patients failed conservative treatment. Surgical management consisted of synovectomy, tendon debridement and/or repair as indicated, followed by Kapandji extensor retinaculum plasty to enlarge the compartment while preserving pulley function. Clinical outcomes included wrist range of motion, grip strength (Jamar dynamometer), complications, and histopathological findings.

At a mean follow-up of 9.5 months, wrist extension of the affected side improved from a mean of 36.5° (10−50°) preoperatively to 57.2° (40−70°) postoperatively, approaching the contralateral side. However, the mean flexion at the affected wrist changed from 47° (35−60°) to 40.8° (20−62°) at latest follow-up. Grip strength increased from a mean of 21.3 kg to 24.6 kg. No postoperative complications, bowstringing, or loss of finger motion were observed. Histopathological analysis demonstrated chronic non-specific degenerative inflammatory changes without evidence of rheumatoid disease in all cases.

The Kapandji extensor retinaculum plasty is a safe and reproducible technique for treating isolated proliferative extensor tenosynovitis of the fourth compartment. By allowing thorough tendon exposure, debridement, and compartment enlargement while preserving retinacular biomechanics, this approach provides reliable early functional improvement without complications. Larger studies with longer follow-up are needed to confirm long-term durability.