Campanacci III and/or recurrent GCT in the distal radius are characterized by strong invasion and a high recurrence rate. The primary goal of treatment is an oncologic cure. and further functional satisfaction is intensely demanded. The present study is the first to comparing allograft and prosthesis reconstruction for the treatment of GCTs in the distal radius. To highlight differences between the 3D-printed prosthesis and allograft reconstruction, the comparison was performed with regards to functional outcomes and complications. With respect to functional outcome, the MSTS and Mayo score were evaluated; in general, the prosthetic group had a significantly higher scores when compared to the variation of before and after surgery (17.1% vs 28.6%, P<0.01 and 47.3 vs 51.7, P=0.03). In addition, the prosthetic group had a significantly higher score in both MSTS and Mayo, compared to the postoperative evaluation (Table 4).
Comparison of range of motion(ROM)
For the variation of ROM in the Mayo score, there was a significantly higher score in the prosthesis group compared to the allograft group (4.0 vs 6.4, P=0.04). There was no significant difference between groups with regards to the variation of ROM in the MSTS score (0.67 vs 0.60, P=0.84
). This discrepancy in ROM between the Mayo and MSTS scores may be partially explained by the fact that ROM is given a weighting of 25% in the Mayo score compared to 14% in the MSTS system. In addition, most patients received full marks in the MSTS system because the ROM was more than 120 , and included extension, flexion, supination, pronation, and radial and ulnar deviation. However, the ROM score is valued by a percentage of the contralateral side in the Mayo system, which rarely receives gets full marks.
In previous studies, custom-made cemented prosthesis reconstruction obtained reasonable ROM, with different types, including distal radial prosthesis [9, 11, 20], and total wrist joint prosthesis prothesis[22, 27, 28]. For our 3D-printed uncemented prosthesis, not only the individual and precise design, but also the “press-fit” fixation make surgery easy and result in considerable functional outcomes[21]. Our 3D-printed prosthesis has three main advantages. First, a thick and suitable polyethylene liner is made according to the contralateral side; second, the reserved bone crest of the distal radius on the shaft ensure appropriate implantation without any rotation; and third, seven or eight pores, on the distal prosthetic edge, provide a sufficient area for soft tissue reconstruction. For the allograft group, all patients developed grade 2 or 3 degeneration of the wrist joint (Figure 4), and the median degeneration-time was 9 months (95% CI: 8.03-9.97) (Figure 5). There might be an explanation in that creeping substitution, the process through which the allograft is gradually replaced by living bone[29], goes to tide mark under dead articular cartilage, therefore there is a risk of subchondral collapse[30]. With respect to forearm rotation, the distal radioulnar joint (DRUJ) plays a critical role. We reveal that four patients developed separation of the DRUJ (Figure 6) in prosthetic reconstruction. Based on the tumor border, most structures of the triangular fibrocartilage complex (TFCC) were not preserved in the four patients; therefore, there was a tendency for separation of the DRUJ. With respect to the stabilizing structures of the DRUJ, thess includes the TFCC, surrounding ligament, tendon, muscle, interosseous membrane, the bone itself, and the capsule[31]. The TFCC, containing superficial and deep fibers, is the main stabilizer of the DRUJ[32]. Many studies concluded that the dorsal superficial fibers tighten in pronation, as do the deep palmar fibers and vice versa[31]. Therefore, we speculate that the relative decrease in pronation and supination is associated with insufficient reconstruction of the TFCC. When soft tissue reconstruction is achieved, we suggest that the retained fibers of the TFCC should be precisely reconstructed by suturing. No separation of the DRUJ was detected in allograft patients, because of selection bias and longer immobilization postoperatively.
Comparison of Pain
Compared to the postoperative pain, there was a significantly lower level of pain in the prosthesis group in terms of both Mayo (22.3 vs 15.3, P<0.01) and MSTS (5.30 vs 3.13, P=0.04) score. However, the postoperative pain score was not significantly different with VAS evaluation (1.2 vs 1.3, P=0.985). Although the pain was fairly decreased postoperatively in both reconstruction methods, the patients in the prosthesis group complained less of pain compared to those in the allograft group. We speculate that the anatomical and precise design increases the matching of joint compatibility and improved comfort for patients. For prosthesis reconstruction, Zhang et al. reported that only 1 patient complained of moderate pain in a total of 11 patients[9], Wang et al. reported that no patients suffered pain with activity in a total of 10 patients[20]. Secondly, allograft reconstruction has shown a high rate of joint degeneration, which increased the level of pain and decreased the ROM. Rabitsch et al. reported 100% joint degeneration in 4 patients[33], while Duan et al. reported 100% joint degeneration in 15 patients[13].
Comparison of Satisfaction
With respect to postoperative satisfaction in terms of MSTS score, there was a significantly higher satisfaction in the prosthesis group compared to allograft group (2.88 vs 4.25, P<0.01). Nevertheless, there was no significant difference between groups 22.19 vs 23.44, P=0.30) with regards to the Mayo score. This discrepancy may be partially explained by the difference in the weighting of satisfaction in the Mayo and MSTS scores. Although the discrepancy was found in the Mayo and MSTS scores evaluating functional outcomes, a comprehensive comparison was performed between groups using the Mayo and MSTS score. Overall, the prosthetic reconstruction had a better functional outcome, compared to the allograft reconstruction.
Comparison of Complications With Henderson Classification
With respect to complications, the main potential problems for the allograft, including nonunion, allograft fracture, wrist osteoarthritis, slow incorporation of the allograft, and rejection, have been reported after en bloc resection (Table 5). Indeed, Bus et al’s compared the complication rates of allograft reconstruction between different sites, and demonstrated that the distal radius showed a significantly lower risk in structural failure and infection compared to the proximal tibia, distal femur, and proximal humerus[38]. Furthermore, the LCP makes reconstructions easy and may be expected to result in fewer complications[13]. As a result, previous authors have suggested that if an intercalary allograft survives the critical 3 to 4 years, it is likely to last for many years[39]. In our study, four patients had palmer subluxation, three of which developed palmer subluxation within the 6 months after surgery. There are three potential reasons for this finding: firstly, the strength of the flexor is greater than that of the extensor[31], developing the tendency of palmer dislocation; secondly, all the patients underwent a dorsal approach, protecting most of the stabilizing structures in the palmar; and thirdly, without the pores in the prosthesis, the retained soft tissue suturing is tedious and unreliable. One patient progressively acquired palmer subluxation in the third year after operation (Figure 7). According to the radiograph, we speculate that the subluxation was subordinate to the carpal degeneration.
The main potential complications associated with prosthesis are subluxation, aseptic loosening, infection, soft-tissue failure and fracture of the prosthesis[9, 11, 20, 22, 40] (Table 6). In the present study, three patients developed palmar subluxation that occurred within 1 month of surgery (Figure 8). In theory, mirroring of the contralateral normal distal radius is the best anatomical match. Accounting for distal radial volar palmar tilt 11-12 [31], the tendency, for volar subluxation for the carpus to slide off the distal radius, is inevitable. However, soft-tissue tension is affected by the expansive growth of the lesion, especially in Campanacci III or recurrent GCTs of bones[42], and the degeneration of proximal row carpal is generally detected in our elderly patients or those with recurring disease. Hence, total mirroring of the contralateral side may be misleading in this respect, and we propose that the degeneration of the proximal row carpal should be religiously considered. Additionally, it is advisable to sequentially reconstruct retained soft tissue for appropriate soft tissue tension[21]. In addition, radius lengthening combined with folding-plasty of soft-tissue reconstruction is an effective method.
The majority of studies report wrist joint degeneration after allograft reconstruction (table 5), while wrist joint degeneration was rarely detected using the prosthesis method. Duan et al. reported that degeneration was revealed in a mean of 4 months postoperatively[13], while we found degeneration with a mean of 9 months. We speculate that the wrist joint degeneration secondary to allograft reconstruction develops in the first year postoperatively. With respect to the comparison of wrist subluxation, although there was no significant difference between the allograft (4 patients) and prosthesis (3 patients) groups, different mechanisms were found in the two groups. For allograft reconstruction, subluxation was subordinate to the gradual carpal degeneration, while subluxation was mostly dependent on the prosthetic design and retained soft tissue.
This study presents several limitations, mainly due to the nature of the disease. Firstly, our study was retrospective with a small size ( 15 patients in each group). As such, our small sample size may be expected to result in low statistical power. Secondly, the follow-up time was significantly different in the two groups, and the follow-up time is insufficient to make conclusions on the long-term implications of the result. Thirdly, no patient was administered denosumab preoperatively. The efficacy of denosumab has been demonstrated in patients with unresectable or recurrent GCT of bone, according to the NCCN guideline and previous studies[43]. However, denosumab did not show any effect on reducing the recurrence rate[44], and complications such as sarcomatous transformation should be considered[45]. Fourthly, our findings are only based on the respective data from our institution, this implies a study selection bias that must be acknowledged, and which might only reflect surgeon or patient preference. As such, this may have had a substantial impact on our observations. Finally, we did not have sufficient reconstruction types such as autograft fibula grafts, for arthrodesis or osteoarticular reconstructions nor did we look at vascularized fibular grafts; as a result, our ability to state that arthrodesis is a superior reconstruction method is limited and we can only show that the results in our patients provided them with reasonable function.