Abstract
Longstanding un-united scaphoid fractures or scapholunate insufficiency can progress to degenerative wrist osteoarthritis (termed scaphoid non-union advanced collapse (SNAC) or scapho-lunate advanced collapse (SLAC) respectively). Scaphoid excision and partial wrist fusion is a well-established procedure for the surgical treatment of this condition. In this study we present a novel technique and mid-term results, where fusion is reserved for the luno-capitate and triquetro-hamate joints, commonly referred to as bicolumnar fusion. The purpose of this study was to report functional and radiological outcomes in a series of patients who underwent this surgical technique.
This was a prospective study of 23 consecutive patients (25 wrists) who underwent a bicolumnar carpal fusion from January 2014 to January 2017 due to a stage 2 or 3 SNAC/SLAC wrist, with a minimum follow-up of one year. In all cases two retrograde cannulated headless compression screws were used for inter-carpal fixation. The clinical assessment consisted of range of motion, grip and pinch strength that were compared with the unaffected contralateral side where possible. Patient-reported outcome measures, including the DASH and PRWE scores were analysed. The radiographic assessment parameters consisted of fusion state and the appearance of the radio-lunate joint space. We also examined the relationship between the capito-lunate fusion angle and wrist range of motion, comparing wrists fused with a capito-lunate angle greater than 20° of extension with wrists fused in a neutral position.
The average follow-up was 2.9 years. The mean wrist extension was 41°, flexion 36° and radial-ulnar deviation arc was 43° (70%, 52% and 63% of contralateral side respectively). Grip strength was 40 kg and pinch strength was 8.9 kg, both 93% of contralateral side. Residual pain for activities of daily living was 1.4 (VAS). The mean DASH and PRWE scores were 19±16 and 29±18 respectively. There were three cases of non-union (fusion rate of 88%). Two wrists were converted to total wrist arthroplasty and one partial fusion was revised and healed successfully. Patients with an extended capito-lunate fusion angle trended toward more wrist extension but this did not reach statistical significance (P= 0.07). Wrist flexion did not differ between groups. Radio-lunate joint space narrowing progressed in 2 patients but did not affect their functional outcome.
After bicolumnar carpal fusion using retrograde headless screws, patients in this series maintained a functional flexion-extension arc of motion, with grip-pinch strength that was close to normal. These functional outcomes and fusion rates were comparable with standard 4-corner fusion technique. A capito-lunate fusion angle greater than 20° may provide more wrist extension but further investigation is required to establish this effect. This technique has the advantage that compression screws are placed in a retrograde fashion, which does not violate the proximal articular surface of the lunate, preserving the residual load-bearing articulation. Moreover, the hardware is completely contained, with no revision surgery for hardware removal required in this series.
