Arthroscopic-assisted bone grafting and SL screw transfixation for the treatment of proximal scaphoid nonunion yielded fracture healing in 19 of 21 patients (90.5%) in this study. These results are encouraging when compared to those of the open bone-grafting method for proximal scaphoid nonunion, in which fracture healing ranged from 90 to 100% [14, 25, 26]. Also, the healing time for our patients, at a mean of 16.3 weeks, was acceptable compared to that for proximal nonunion after open autologous bone grafting, which was reported to be 11.5–17.7 weeks [14, 15, 27].
There could be some intraarticular pathologies coexisting with a scaphoid nonunion. It has been reported in the literature that this constellation is perhaps not uncommon, and if present, the severity of the ligamentous injury is low [6, 28, 29]. With healing rates comparable to open methods, arthroscopic management has the advantages of providing a thorough wrist assessment, a comprehensive approach to address coexisting intraarticular pathologies, and minimal surgical trauma to the structure and vascularity, which is favorable for fracture healing [28, 30].
In treating chronic SL dissociation, RASL could be a treatment option [9, 18]. But in cases of scaphoid nonunion, the SLIL injury would most likely be minor. In our series, we did not see cases with obvious SL dissociation. Also, we did not denudate the SL junctional cartilage, as in the proposed RASL method [17, 18], but performed SL transfixation only. In the follow-ups of the 17 screw-removed patients, we found no further SL separation. So, it seems that screw fixation across the SL joint in proximal scaphoid nonunion treatment would not be harmful to the SL joint. But, as to the benefits for a probable concomitant SL injury after SL fixation, we still cannot draw a clear conclusion.
Rancy et al. reported that the proximal pole of the scaphoid would very likely have impaired vascularity in a fracture nonunion condition, but proximal scaphoid infarction is decidedly rare . The key surgical method is to perform a thorough debriding of the nonunion site and non-vascularized autologous bone grafting. Rancy et al. reported an overall healing rate of 97.1% in treating 35 scaphoid nonunions. However, some surgeons prefer the use of vascularized bone graft, due to the accepted advantages of improved circulation and an enhanced bone healing process [10, 11, 31].
In our study, 2 of the 4 patients who had both vascular compromise of the scaphoid in the MRI and obvious sclerotic density in the radiographs failed to heal. This failure rate is considerable when using this arthroscopy-assisted method for proximal scaphoid nonunion with obvious vascular compromise, although the case number was small. But, in our opinion, if surgeons are familiar with arthroscopic treatment, this method is a minimally invasive surgery that is still worthy of being performed in this patient group, and would not hinder further surgeries too much, even if it fails. However, detailed communication with the patient prior to surgery is necessary and important.
Use of the exaggerated dumbbell-shaped screw in the RASL procedure is suggested (Fig. 2), since a thin part of the screw shaft located at the SL junction seems able to prevent screw loosening; however, the evidence is still inconclusive [17, 18]. We used conical screws in only 3 cases, and they all had fracture healing (Fig. 3). Because of the small number of cases, we cannot conclude that a conical screw could achieve healing success similar to that of a dumbbell-shaped Herbert-like screw for SL transfixation in proximal scaphoid nonunion treatment.
SL screw removal is not routinely suggested if there is no loosening . However, the majority of our patients requested SL screw removal, and this was performed at least 6 months after fixation. This is because, in our culture, people prefer not to leave hardware in the body, if possible. Although we did not encounter complications with screw removal, we do agree that screw removal should be performed only when there is loosening or symptoms related to the screw.
We believe that the use of K-wires instead of the headless screw for SL transfixation would also be a good choice. In our results, the mean fracture healing time was 16.3 weeks. Thus, the fracture healing period with this arthroscopic treatment would not be too long. In addition, K-wires are easier to remove. As their diameter is small, K-wires could possibly be placed with less morbidity than a larger-sized headless screw. However, K-wires could possibly cause skin irritation.
Radial styloidectomy is an acceptable method for treating stage 1 SNAC, but we performed it in only 1 case (case 13). Whether radial styloidectomy will interfere with the results is still unclear. But, according to the study by Vutescu et al., radial styloidectomy should be performed with caution in cases with proximal pole scaphoid nonunion. Their results showed removal of part of the degenerated radial styloid could endanger the carpal extrinsic ligaments and cause carpal instability .
There were some limitations in this study, including its retrospective nature and the small number of cases. The majority of enrolled cases were female, which is not consistent with the reported epidemiology [34, 35]. This is because in the early enrollment period, male patients were still mainly treated with either the open vascularized or non-vascularized bone grafting method. Young female patients would often request treatment due to cosmetic concerns, so the arthroscopic method was performed more with them. Fracture healing was evaluated mainly with radiographs, which are not as precise as a CT scan. Also, the differences in patient characteristics and treatment, such as the use of different types of screws, the differences in the length of follow-up, and operations performed by 2 different surgeons, could also bias this study. The majority of our patients had screw removal, and this would be a drawback of the technique, in that the results would mainly show that the technique included temporary screw fixation across the SL joint for proximal pole scaphoid nonunion.