Introduction
Avascular osteonecrosis of the lunate, known as Kienböck’s disease, is a rare condition with a prevalence of less than 5 in 10,000 people [1]. This debilitating disease significantly impacts wrist function and quality of life, affecting daily activities and overall well-being [2]. At Lichtman stage III, the lunate has undergone significant deterioration, presenting complex treatment challenges [3].
Treatment modalities for Kienböck’s disease are delineated according to the Lichtman classification, particularly at stage III characterized by significant lunate collapse [4], the selection of treatment reflects diverse surgical philosophies. Options include joint-leveling procedures such as radial shortening osteotomy [5] and capitate shortening osteotomy [6], as well as revascularization techniques [7] aimed at lunate preservation and restoration of vascularity. Alternatively, some surgeons advocate for salvage procedures [8], encompassing limited carpal fusion—such as scaphocapitate fusion [3,9] or scaphotrapeziotrapezoid fusion [10,11]—or proximal row carpectomy [8] to stabilize the carpus and mitigate pain. According to a meta-analysis conducted by Wang et al. [8], all evaluated treatment modalities provided significant pain relief and functional improvement for patients with stage III Kienböck’s disease.
Recent advancements in arthroscopic techniques for the wrist have enabled intercarpal fusions that reduce surgical damage, shorten recovery periods, and potentially lower the risk of complications, while also preserving joint mobility compared to open procedures [12,13]. Arthroscopic scaphocapitate fusion also offers additional advantages, including preserved soft tissue and blood supply, less pain, and minimal scarring [14]. Despite these advantages, few studies have investigated the clinical outcomes of arthroscopic scaphocapitate fusion in the treatment of Kienböck’s disease [14,15].
This study aims to present our clinical results obtained in arthroscopic limited intercarpal fusion performed without using autobone grafts or complete excision of the lunate in patients with Kienböck’s disease, demonstrating that good outcomes can still be achieved.
Methods
Ethics statement: This study was approved by the Public Institutional Review Board (No. P01-202406-01-022). The study was performed in accordance with the Declaration of Helsinki, and written informed consent was waived due to its retrospective nature.
1. Study design and participants
From January 2017 to October 2022, 12 patients diagnosed with Lichtman stage III Kienböck’s disease who did not respond to an average of 3 months of conservative treatment underwent surgical interventions [16]. Among these 12 patients, nine who underwent arthroscopic scaphocapitate fusion and completed a minimum follow-up period of 12 months were selected for inclusion in this study. All surgeries were conducted by a single hand surgeon. Patients who opted for other surgical interventions, such as one individual who underwent proximal row carpectomy and another who received radial shortening osteotomy, along with one patient with incomplete follow-up data, were excluded. Consequently, the final analysis encompassed nine patients.
Data were collected retrospectively from patient medical records, including demographics (age, gender), disease stage at the time of surgery, detailed surgical procedure notes, postoperative complications, and follow-up clinical outcomes.
2. Arthroscopic scaphocapitate fusion technique
A single, highly experienced surgeon (JKP) (level 4) [17] performed all arthroscopic scaphocapitate fusions. Wrist arthroscopy was performed under general anesthesia using a tourniquet. The hand was suspended using a traction tower set to 5–7 kg. The forearm was wrapped with a compressive elastic bandage. For distension and washout of the joint, continuous saline irrigation was carried out by gravity infusion from an elevated bag.
The 3–4 and 4–5 portals, 6 radial, midcarpal ulnar (MCU), and midcarpal radial (MCR) portals were made for examination of bones, joints, and ligaments. After routine arthroscopic examination, synovial hypertrophy was debrided by shaver and radio frequency probe. The lunate was preserved in all cases. Partial debridement was performed only when there were free fragments or sharp margins, using a 2.7-mm arthroscopic burr and rongeur through the 3–4 and 4–5 portals. The scaphocapitate joint surfaces were burred from the articular surface to the cancellous bone from MCR and MCU portals to prepare scaphocapitate fusion. A guide wire was inserted percutaneously under image intensifier between the scaphoid and capitate bone. A headless compression screw was inserted through the guide wire. Autologous bone grafts were not employed in any of the patients. Instead, a variety of allografts and bone substitutes were utilized to facilitate bone union. Specifically, demineralized bone matrix (DBM), allogenic cancellous bone chips, and a bone substitute composed of hydroxyapatite combined with recombinant human bone morphogenetic protein-2 (rhBMP-2) were employed.
A short-arm splint was applied for the initial 2 weeks after operation, succeeded by a thermoplastic brace for an additional 4 weeks. Graduated mobilization was encouraged, with full activities resumed following confirmation of bone union via radiographs.
3. Evaluation
Preoperative and postoperative clinical and radiological assessments were conducted for all patients. At each visit during the regular follow-up examinations conducted by the surgeon, the range of motion (ROM) of the wrist, pain visual analogue scale (VAS) score, grip strength, Patient-Rated Wrist Evaluation (PRWE) score, and Disabilities of the Arm, Shoulder, and Hand (DASH) score were evaluated. The criteria for union involved the presence of bridging trabeculae crossing the joint, as observed on anteroposterior plain radiographs [14]. The modified carpal height ratio (MCHR) was calculated by dividing the longitudinal length of the capitate by the distance from the articular surface of the third metacarpal base to the articular surface of the distal radius (Fig. 1), as observed in the 1-year follow-up plain radiograph [18].
4. Statistical analysis
Statistical analyses of the data obtained in the present study were conducted using IBM SPSS Statistics ver. 22 (IBM Corp., Armonk, NY, USA). Descriptive statistical methods (mean, median, standard deviation, interquartile ranges [IQRs], and frequency) were used to evaluate the study data. The Wilcoxon sign test was used to compare within-group parameters both preoperative and postoperative treatment. A p-value of <0.05 was accepted as statistically significant.
Results
1. Study sample and surgical outcomes
The study included nine patients, with a mean age of 29.6 years and a median age of 26 years (range, 21–46 years; IQR, 22–35 years). Two patients were at stage IIIA, and seven patients were at stage IIIB. The number of screws used for fixation was two for four patients and one for five patients. No autologous bone grafts were used; DBM was employed in five cases, while two cases utilized allogenic cancellous bone chips, and the remaining two cases employed a bone substitute composed of hydroxyapatite combined with rhBMP-2. The mean operation time was 102.4 minutes, and the median operation time was 100 minutes (range, 90–120 minutes; IQR, 95–110 minutes). Both the mean and median fusion durations were 8 weeks (range, 6–10 weeks; IQR, 8.5–8 weeks). Union was achieved in all patients. The mean of 22.7 months, with a median follow-up period was 24 months (range, 12–36 months; IQR, 20–24 months).
Anatomical outcome evaluations revealed that the mean MCHR significantly decreased from 1.41 preoperatively to 1.39 at the final follow-up (p<0.001). Similarly, the median decreased from 1.40 preoperatively to 1.39 at the final follow-up, and the IQR narrowed from 1.43–1.40 preoperatively to 1.41–1.37 at the final follow-up (Table 1, Figs. 2, 3).
2. Functional outcome and complications at final follow-up
Wrist flexion/extension arc motion demonstrated a mean increase from 58.3° to 75.6° (p=0.001), with the median increasing from 60° preoperatively to 80° postoperatively and IQRs from 50°–60° to 70°–80° (Fig. 4). Grip strength as a percentage of the healthy side showed a mean increase from 29.4% to 71.8% (p<0.001), with the median improving from 30% preoperatively to 70% postoperatively, and IQRs moving from 29.44–30 preoperatively to 70–80 postoperatively. DASH scores decreased from a mean of 43.9 to 17.5 (p<0.001), with the median decreasing from 44.2 preoperatively to 17.5 postoperatively, and IQRs narrowing from 43.3–50 preoperatively to 15.8–19.2 postoperatively. PRWE scores decreased from a mean of 45.2 to 18 (p<0.001), with the median decreasing from 43 preoperatively to 17 postoperatively, and IQRs narrowing from 40–50 preoperatively to 16–20.5 postoperatively. VAS for pain at activity decreased from a mean of 5.7 to 2.9 (p < 0.001), with the median decreasing from 6 preoperatively to 3 postoperatively, and IQRs narrowing from 5–6 preoperatively to 3–4 postoperatively (Table 2). Postoperative scars were observed only at the openings for arthroscopy portals and screw insertions (Fig. 5).
Discussion
This study suggests that arthroscopic scaphocapitate fusion with lunate preservation can improve pain, function, and anatomical outcomes for patients with stage III Kienböck’s disease. The results are noteworthy, given the advantages of the arthroscopic approach over traditional open surgical methods.
The minimally invasive nature of arthroscopic scaphocapitate fusion offers several benefits over traditional open surgery. Open surgical methods typically result in larger scars and longer rehabilitation periods [14]. In contrast, the arthroscopic technique results in minimal scarring, which is advantageous for patients concerned about cosmetic outcomes. Although our study did not specifically measure return-to-work times, the less invasive procedure may contribute to faster recovery and earlier return to daily activities, as suggested by previous literature [12]. Furthermore, previous studies have reported that the time to fusion for arthroscopic scaphocapitate fusion ranges from 7.2 to 8 weeks [14,15], whereas open scaphocapitate fusion procedures have reported times of 14 weeks [8,10] and even up to 22 weeks [19]. There was also a difference in nonunion rates, with open procedures reporting rates ranging from 0% to 23%, while arthroscopic procedures reported nonunion rates of 0% to 10% [10,14,15,19-22]. Based on these findings, it can be inferred that arthroscopic scaphocapitate fusion may lead to shorter fusion times and lower rates of nonunion. Koh et al. [15] have hypothesized that these outcomes are possible due to the preservation of surrounding soft tissue attachments and the blood supply to the carpal bones during arthroscopic surgery.
The debate over whether to excise or preserve the lunate during limited carpal fusion for Kienböck’s disease remains unresolved. Some authors advocate for lunate excision, arguing that a collapsed lunate can be a source of persistent pain and may require subsequent removal [23]. Studies like that of Özdemir et al. [21] have reported good outcomes with lunate excision combined with scaphocapitate fusion. Conversely, others caution against lunate removal due to the risk of ulnar translation of the scaphoid, which can lead to arthritis [15,20]. Koh et al. [15] and Hegazy et al. [22] also reported successful outcomes while preserving the lunate, thereby minimizing potential complications associated with its excision. This preservation can reduce surgical injury to surrounding tissues [20] and decrease the overall surgery time by the amount typically required for lunate excision [15]. In our study, we chose to preserve the lunate or perform only partial debridement of problematic lesions to reduce surgical time and avoid additional morbidity associated with lunate excision.
Although autologous bone grafting is known as the gold standard, limited harvest quantities and donor site morbidity have led to the consideration of various substitutes [24]. Excellent outcomes using alternative materials have also been reported in the field of hand surgery [25]. In a study on arthroscopic partial wrist fusion, Ho [12] utilized both autologous bone grafts and bone substitutes. The results were similar in both groups; however, the group using bone substitutes experienced less donor site morbidity and reduced total operation time due to the elimination of graft harvesting, highlighting the relative advantages of bone substitutes. Ertem et al. [14] even reported successful outcomes in arthroscopic scaphocapitate fusion without performing any bone grafting. They attributed this success to the minimal damage to osseous vascularization during the surgical procedure. In our study, we also refrained from using autologous bone grafts to avoid donor site morbidity. Instead, we employed materials that could aid bone formation to promote fusion. We employed DBM, allogenic cancellous bone chips, and bone substitutes, and achieved union in all cases. These results suggest that successful fusion can be achieved without using autologous bone grafts.
The method of fixation in scaphocapitate fusion is a crucial factor influencing the success of the procedure. While most previous studies have utilized two screws for fixation due to the larger size of the carpal bones involved [15,20,26], Ertem et al. [14] reported successful fusion using a single screw, suggesting that one screw might suffice in certain cases. In our study, we employed one or two screws based on the need for stiffer fixation. All cases where a single screw was used resulted in successful union, indicating that with proper technique and patient selection, single-screw fixation can be effective.
While some previous studies have reported a decrease in wrist ROM following scaphocapitate fusion [19,21,27], the findings of our study suggest a potential increase in the wrist flexion-extension arc postoperatively. This observation aligns with the results reported by Hegazy et al. [20] and Koh et al. [15], who noted improvements in ROM with procedures that preserved the lunate. Additionally, a cadaveric study by Got et al. [28], suggested that partial carpal fusion of two bones could facilitate a motion equivalent to that of an intact wrist, which might help explain our observations. Although scaphocapitate fusion was achieved, some patients were initially unable to have their ROM effectively assessed postoperatively due to pain. As their pain decreased, these patients demonstrated a smoother and more complete ROM, which could appear as an improvement in the recorded ROM. This suggests that the preservation of the lunate and its surrounding ligaments likely contributed to maintaining necessary wrist biomechanics. Furthermore, the minimally invasive nature of the arthroscopic approach likely helped minimize damage to soft tissues, potentially preserving motion more effectively than traditional open techniques [12].
This study has limitations, including a small sample size and retrospective design, which may introduce selection bias. The lack of a control group and potential confounders limit the generalizability of the findings. Therefore, while the results are promising, they should be interpreted with caution. Future research should include larger, prospective studies with control groups to validate these results and investigate the long-term outcomes of this technique. Comparative studies between arthroscopic and traditional open surgical methods would also be beneficial to confirm the advantages observed in this study.
Conclusion
This study suggests that arthroscopic scaphocapitate fusion with lunate preservation may be an effective surgical option for patients with stage III Kienböck’s disease, potentially improving pain, function, and anatomical outcomes. The minimally invasive nature of the arthroscopic approach offers benefits over traditional open surgery, such as reduced scarring and possibly quicker recovery times. Additionally, the use of DBM, allogenic cancellous bone chips, and bone substitutes instead of autologous bone grafts avoided donor site morbidity and achieved successful fusion in all cases. However, given the small sample size of nine cases and the retrospective design of this study, these findings should be interpreted with caution. Further research involving larger, prospective studies with control groups is necessary to validate these results and to explore the long-term outcomes of this surgical technique.
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