Abstract
Purpose
This study aimed to evaluate the clinical and radiological outcomes of lunate excision scaphocapitate fusion (LESCF) using a single headless cannulated compression screw in patients with advanced Kienböck disease (Lichtman IIIb–IV). The hypothesis was that this technique would provide significant pain relief, functional improvement, and comparable union rates to multi-screw methods while reducing implant-related morbidity.
Methods
A retrospective single-center case series included 24 patients (8 males, 16 females; mean age 37.3 ± 8.5 years) who underwent LESCF between June 2021 and June 2023. Minimum follow-up was 24 months (mean 33.6 ± 4.1). Clinical evaluation included pain (VAS), wrist function (Modified Mayo Wrist Score), grip strength, and range of motion. Radiological assessment involved union rate and time, radioscaphoid angle (RSA), carpal height ratio (CHR), Modified Carpal Ulnar Distance Ratio (modified-CUDR) and ulnar variance.
Results
Radiographic union was achieved in all cases (100%) at a mean of 3.5 ± 1.2 months. Mean VAS score decreased from 7.2 ± 1.1 to 2.1 ± 1.0 (p < 0.001), and Modified Mayo Wrist Score improved from 47 ± 12 to 74 ± 10 (p < 0.001). Grip strength increased from 55 ± 15% to 75 ± 18% of the contralateral hand (p < 0.01). Flexion–extension arc slightly decreased (81° ± 10 to 76° ± 9; p < 0.05), while radioulnar deviation changes were minimal. RSA improved from 48° ± 7 to 41° ± 6 (p < 0.01), with no significant change in CHR or ulnar variance. Modified CUDR values were found to be 0.834 ± 0.104 in the preoperative period and 0.804 ± 0.116 in the postoperative period. One patient (4.2%) reported mild screw irritation without surgical intervention; no other complications occurred.
Conclusion
Single-screw scapho-capitate fusion and lunate excision can be considered a suitable treatment option for advanced Kienböck’s disease, offering pain reduction, positive effects on functional recovery, acceptable healing rates, and a low risk of complications. However, larger, prospective studies are needed to demonstrate the long-term results of this method and its comparative effectiveness with other surgical techniques.
Introduction
Kienböck’s disease is a pathology characterized by progressive carpal collapse and wrist pain resulting from avascular necrosis of the lunate bone.1–4 In advanced stages (Lichtman IIIb–IV) of Kienböck’s disease, limited carpal fusions such as scaphocapitate fusion (SCF) and proximal row carpectomy (PRC) are considered the main salvage surgical options.1–7 LESCF reduces the axial load at the radiolunate joint line by redirecting load transmission to the scaphocapitate and radioscaphoid joints. This biomechanical adjustment can reduce pain, increase grip strength, and maintain acceptable range of motion.1–3,8–11 Although high union rates after LESCF have been reported in the literature, patient information is important due to the complication profile (20–30%) and the heterogeneity of outcomes.1,2,8,9 Single-screw LESCF techniques have been studied in limited numbers, and the current level of evidence is generally low.1,2,8–13 Views on carpal load distribution after lunate excision remain controversial; some studies suggest that lunate excision reduces pain, while others suggest that preserving the lunate increases joint stability.3,10,12,14 This study evaluated the retrospective clinical and radiological outcomes of scaphocapitate fusion performed with a single headless cannulated compression screw accompanied by lunate excision in patients with advanced-stage Kienböck’s disease. The primary outcome measures in the study were determined as union rate and union time, and the secondary outcomes were defined as pain level (VAS), wrist function (Modified Mayo Score), grip strength, range of motion (flexion–extension and radial/ulnar deviation) and radiological parameters (radioscaphoid angle (RSA), CHR, Youm method) and ulnar variance).1,2,8–11,13,15 Our hypothesis is that SCF performed using a single headless cannulated screw accompanied by lunate excision will significantly improve pain and wrist function, the union rate will be comparable to multi-screw techniques, and the use of a single implant may provide an advantage in terms of surgical technique and reduce the number of implants.1,2,8–14
Materials and methods
This study was designed as a single-center retrospective case series with a level of evidence of IV. Consecutive patients diagnosed with advanced Kienböck disease (Lichtman IIIb–IV) between June 2021 and June 2023 were retrospectively analyzed. For radiological assessment, preoperative direct radiographs and magnetic resonance imaging techniques were utilized.
Inclusion criteria: (1) Age ≥18 years (2) Primary lunate excision with scaphocapitate fusion using a single headless cannulated compression screw (3) Availability of at least 24 months of clinical and radiological follow-up data
Exclusion criteria: (1) Previous surgery on the same wrist (2) Concomitant carpal fracture/instability or rheumatic joint disease (3) Active wrist infection (4) Another intercarpal fusion or PRC performed in the same session (5) Insufficient clinical or radiological records.
Demographic and clinical characteristics of the patients.
One patient was excluded from the study due to a previous surgery on the same wrist, two patients due to insufficient clinical and radiological records, and three patients due to insufficient follow-up time. Of these six excluded patients, two were male and four were female; five had right wrist involvement and one had left wrist involvement. The Lichtman stage distribution was stage IIIb in one case, stage IIIc in one case, and stage IV in four cases.
Sugical technique
All surgeries were performed by an experienced hand surgeon using an open dorsal approach.2,3,8–11 The operating arm was held under a tourniquet, with the wrist in a neutral position. Transverse incisions were made on the dorsal skin between the 2nd and 4th extensor compartments, retracting the extensor tendons laterally and excising the terminal branch of the posterior interosseous nerve. A Z-capsulotomy was then performed on the dorsal capsule to widen the radiocarpal and midcarpal joint space.9,10 The lunate bone was meticulously excised using the piecemeal technique, preserving the surrounding soft tissues and volar ligamentous structures; ligamentous continuity in the volar processes of the capitate, scaphoid, and triquetrum was preserved as much as possible. Following lunate excision, the scaphoid and capitate cartilage tissue was removed with curettes to prepare parallel fusion surfaces.2,3,8–11 To achieve temporary alignment, the wrist was maintained in a neutral position, and the scaphoid–capitate junction was stabilized with percutaneous K-wires while the scaphoid was positioned in a neutral or slightly extended alignment relative to the long axis of the radius; when necessary, scaphoid flexion was corrected and maintained in the appropriate position.
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In the following stage, a single headless, 3.5 mm cannulated compression screw was placed from the scaphoid to the capitate.8–11,13 The screw position was confirmed with fluoroscopy to confirm that the cortex had not slipped and that contact with the radioscaphoid joint was maintained.8–11 Post-implantation joint stability was assessed with fluoroscopy-guided stress maneuvers (Figures 1 and 2). The capsule and associated pathologies were repaired; the extensor retinaculum and skin were closed in the anatomical plane. Postoperatively, immobilization was achieved in a short arm cast for 4 weeks, during which time finger and shoulder exercises were permitted. The cast was removed in the fourth week, and active wrist motion therapy with a removable splint was initiated. Strengthening exercises were incorporated into the program starting in the twelfth week.8–10,12 Patients were followed up for follow-up at 2 and 4 weeks, 3 and 6 months, and annually thereafter. Anteroposterior direct radiograph obtained after lunate excision and scaphocapitate fusion. Lateral direct radiograph obtained after lunate excision and scaphocapitate fusion.
Clinical and radiological evaluation
The evaluation of clinical and radiological results was performed by an independent observer who was not directly involved in the study.
Radiographic fusion was defined by the presence of continuous trabeculation and disappearance of the lucent line at the fusion line on posteroanterior (PA) and lateral radiographs.1,2,8–12 When necessary, fusion was confirmed by computed tomography (CT). The time to union was recorded based on the date these criteria were first observed. A representative radiographic appearance when union was confirmed by CT is shown in Figures 3 and 4. Demonstration of scaphocapitate fusion on axial computed tomography images. The arrow indicates the fusion site. Demonstration of scaphocapitate fusion on sagittal computed tomography images. The arrow indicates the fusion site.
Clinical evaluation parameters included Modified Mayo Wrist Score (0–100),1–3,8–11 VAS pain score (0–10), grip strength (measured with a Jamar dynamometer and expressed as a percentage of the contralateral healthy hand), and wrist joint range of motion (flexion–extension arc and radial and ulnar deviation).
Radiological evaluations included the following: • RSA: Angle between the long axis of the radius and the long axis of the scaphoid on the PA radiograph,1,2,8–11 • CHR: Ratio of carpal height to the length of the third metacarpal using the method of Youm et al.,
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• The Modified Carpal Ulnar Distance Ratio (modified-CUDR) is calculated by dividing the distance between the ulnar edge of the distal ulna and the most ulnar border of the carpal bones in a neutral-position PA wrist X-ray by the transverse width of the ulnar head.
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• Ulnar variance: Distance between the distal radius articular surface and the ulnar head on the neutral PA radiograph.
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Statistical analysis
Data were collected retrospectively and anonymized. The distribution of continuous variables was assessed using the Shapiro–Wilk test. The paired t-test was used to compare preoperative and final follow-up values for normally distributed variables, and the Wilcoxon signed-rank test was used for non-normally distributed variables. Results are reported as mean ± standard deviation (Mean ± SD) or median [interquartile range]. Where necessary, absolute preoperative–postoperative difference values were also reported to emphasize clinical significance. Categorical data are presented as numbers (%).
Statistical significance was set at p < 0.05, and analyses were conducted using SPSS v29 software. No correction (e.g., Bonferroni) was applied for multiple comparisons; this was considered a limitation of the study. Furthermore, due to the retrospective design, inter- and intra-observer reliability analyses were not conducted; the fact that the measurements were performed by a single surgeon should be taken into account in this context.
Local ethics committee approval was obtained for the study (SBÜ Gazi Yaşargil EAH, 26/04/2024, 35), and all processes adhered to the Declaration of Helsinki.
Findings
Radiographic union was achieved postoperatively in all patients studied (n = 24). The mean time to union was 3.5 ± 1.2 months (range, 2–6 months); the fusion rate was 100%.
The mean Modified Mayo Score increased from 47 ± 12 preoperatively to 74 ± 10 postoperatively (mean increase +27 points; 95% CI: 20.4–33.6; p < 0.001; Cohen’s d ˜ 2.4). The mean VAS pain score decreased from 7.2 ± 1.1 preoperatively to 2.1 ± 1.0 postoperatively (mean decrease −5.1 points; 95% CI: −5.7 to −4.5; p < 0.001; Cohen’s d ˜ 4.9).
Flexion–extension range of motion decreased from 81° ± 10 to 76° ± 9 (mean decrease −5°; 95% CI: −9.2 to −0.8; p < 0.05). Radial deviation was slightly limited, decreasing from 12° ± 5 to 9° ± 4 (mean −3°; 95% CI: approximately −4.9 to −1.1; p < 0.01). Ulnar deviation increased minimally from 25° ± 8 to 26° ± 7 (mean + 1°; 95% CI: −2.8 to +4.8; p > 0.05). Grip strength improved from 55 ± 15% of the contralateral hand to 75 ± 18% in the surgical hand (mean increase +20 percentage points; 95% CI: 10.1–29.9; p < 0.01; Cohen’s d ˜ 1.2), which was considered clinically significant for functional gain.
Comparison of clinical outcomes (Preoperative vs. Final Follow-up).
Radiological outcomes and fusion success.
Discussion
In this retrospective study, we evaluated the clinical and radiographic outcomes of lunate excision scaphocapitate fusion (LESCF) performed using a single headless compression screw in patients with advanced-stage Kienböck disease. The findings obtained over a mean follow-up period of 33.6 ± 4.1 months indicate that this surgical approach may be an effective option for reducing pain, enhancing functional recovery, and achieving reliable fusion. Radiographic union was achieved in all cases, accompanied by significant improvements in VAS pain scores and the Modified Mayo Wrist Score, as well as an approximately 20% increase in grip strength. These results are consistent with previous reports supporting the potential of LESCF to provide meaningful clinical and radiological improvement in advanced Kienböck disease.2–4,12
These results obtained with LESCF are particularly noteworthy from a clinical perspective, as series using single headless screws are limited in the literature. Collon et al. reported that after SCF in Lichtman stage III patients, the VAS score decreased from 8 to 4, the flexion-extension range of motion was maintained at approximately 91°, and grip strength reached 76% of the contralateral hand. 2 Gezer et al. reported a VAS score of 2.9 and grip strength of 60.9% in advanced-stage patients. 4 In our series, the decrease in VAS score from 7.2 to 2.1 and the increase in grip strength from 55% to 75% are consistent with the literature and indicate a relatively greater improvement in grip strength. Charre et al. reported a 94% union rate and significant functional gain in their series of SKF combined with lunate excision at a mean follow-up of 10.7 years. 3 The 100% union rate achieved in our study supports these findings.
Meta-analyses in the literature report an average increase in grip strength of 13 kg, a slight decrease in CHR, and an approximately 12° improvement in RSA after LESCF. In our study, grip strength increased from 55% to 75% of the contralateral hand in the operated hand, indicating an approximately 20% increase. Although this increase in kilograms is not directly comparable, it is consistent with the 60–80% range reported in the literatüre. 1 It can be considered an improvement close to the upper limit. When calculated using the Youm method, the mean preoperative CHR was 0.54 ± 0.03 and postoperatively 0.52 ± 0.04, and this change was not statistically significant. In contrast, a statistically significant decrease was observed in RSA from 48° to 41°, suggesting that the scaphoid was brought to a more physiological position and the load distribution on the radiocarpal joint became more balance.1,2,8–11
To assess ulnar translocation of the carpus, the modified Carpal Ulnar Distance Ratio (modified-CUDR) measurement was applied, and a statistically significant decrease in modified-CUDR values was detected in the postoperative period (p = 0.001). Ulnar translocation is a defined finding within the carpal instability spectrum, characterized by the displacement of the carpal bones over the radius towards the ulnar direction, and can be assessed radiographically with objective measurements. 17 In this context, it is thought that ratio-based measurements such as modified-CUDR may be useful in quantitatively revealing changes in carpal alignment after surgery; however, larger sample size and prospective studies are needed to more clearly reveal the relationship between the changes detected in modified-CUDR and long-term clinical outcomes and degenerative processes.
In terms of the complication profile, only one patient experienced local tenderness due to screw irritation; no infection, extensor tendon irritation, implant migration, CRPS, or other complications requiring reoperation were observed. This rate is significantly lower than the 24% complication and 14% revision rates reported in a meta-analysis by Bouri et al. Other studies have reported complication rates between 10% and 20%.1–3,8–12 The absence of complications requiring nonunion or revision in our study may be attributable to the standardized and meticulous application of the surgical technique and appropriate immobilization and rehabilitation protocols. The low complication rates achieved with single-screw fixation and lunate excision, comparable to those reported in the literature with multiple-screw series, can be interpreted as supporting the reliability of this technique; however, due to the lack of a direct comparative study, these results should be interpreted with caution.
One of the notable findings of our study is that union was achieved in all cases following LESCF application with a single headless cannulated screw. Many studies in the literature have used LESCF using two or more screws, and additional bone grafting has been preferred in some cases.2,3,8–11 However, in recent years, it has been reported that single-screw techniques can also provide adequate stability, reduce implant costs and surgical time, and achieve results comparable to multi-screw methods in terms of union and clinical outcomes.1–3,8–13 Pisano et al. is one of the pioneering studies defining the LESCF concept. 11 In our series, achieving 100% union with a single screw demonstrates the effectiveness of appropriate patient selection and a standardized surgical technique. The lack of additional channels for the second screw in the single-screw approach may contribute to the preservation of the fusion surface. In cases where screw compression is sufficient, it is possible to achieve stability without the use of additional implants.
Lunate excision may contribute to pain reduction by altering carpal load distribution during SCF. The high union rate and significant pain reduction achieved after lunate excision in our series support this view. However, there are also studies reporting the potential positive effects of lunate preservation on stability.3,12,14 Therefore, the advantages and disadvantages of both approaches need to be clarified more clearly through prospective and comparative studies. 18
In advanced-stage Kienböck’s disease, LESCF and PRC techniques are frequently compared. The literature reports that both methods are effective in pain control and generally provide similar results in terms of grip strength and range of motion.4–7 Gezer et al., in their study using SCF (VAS: 2.9; grip strength: 61%) and PRC (VAS: 3.2; grip strength: 59%) in advanced-stage patients, found no significant difference between the two groups. 4 Another significant advantage of LESCF over PRC is its applicability as an effective treatment option for patients unsuitable for proximal row carpectomy due to chondral damage developing in the lunocapitate joint. While our study lacks a direct comparative design, the pain control and grip strength results obtained after LESCF are in the range of those reported for PRC in the literature.4–7,19 Therefore, single-screw LESCF can be considered an alternative approach to PRC with appropriate patient selection; however, this conclusion is based on literature comparison rather than direct evidence.
Limited carpal fusion techniques and related arthrodesis approaches, other than LESCF, have been reported in the literature as applicable in various wrist pathologies, primarily Kienböck’s disease. Goyal et al. evaluated the early clinical and functional outcomes of limited carpal fusion, while Elshahhat et al. comparatively examined scapho-capitate and lunato-capitate arthrodesis techniques for different indications and showed that both approaches could provide satisfactory results with appropriate patient selection.20–22 However, there is significant heterogeneity among these studies in terms of surgical technique, preservation or excision of the lunate, fixation methods, and patient populations. This makes it difficult to draw definitive conclusions about which configuration of limited carpal fusion is more advantageous in which patient group. Therefore, while the findings, including the current series, support the potential effectiveness of limited carpal fusion approaches, prospective, comparative, and long-term follow-up studies are needed to reach clear conclusions regarding the superiority or equivalence of techniques based on lunate excision versus lunate preservation.
While the 100% union rate and low complication profile reported in this study are clinically encouraging, the methodological limitations of the study should be considered in interpreting the findings. First, the relatively small sample size and the single-center, retrospective Level IV case series design limit the generalizability of the results. Although the fact that all cases were from consecutive patients can be considered a factor that partially reduces selection bias, the fact that the surgery was performed by a single experienced surgeon may have increased the influence of surgical technique, decision-making process, and perioperative management on the results. This creates uncertainty as to whether similar results can be obtained by different surgeons and centers. Therefore, the findings of this study are hypothetical in nature, and multicenter, larger sample size, prospective comparative studies are needed to more clearly demonstrate the efficacy and safety of the method.
The main limitation of this study is its retrospective design and the lack of a control group (e.g., multi-screw LESCF or PRC). The relatively small sample size (n = 24) and the fact that all cases were operated on by a single surgeon, while ensuring the homogeneity of the surgical technique, partially limit the generalizability of the results. Although the follow-up period was at least 24 months for all patients, long-term results (e.g., ≥10 years) were not available, thus limiting the ability to comment on late degenerative changes and potential revision surgeries.1–3,5–7
Inter-/intra-observer reliability of radiological measurements was not statistically assessed; this presents a limitation that should be considered, particularly when interpreting angle and ratio measurements such as RSA and CHR. Furthermore, the lack of correction for multiple comparisons could theoretically increase the risk of false-positive errors. Despite these limitations, the systematic application of the technique in a homogeneous cohort of advanced Kienböck’s disease patients and the detailed reporting of both clinical and radiological results are among the strengths of the study.
Conclusion
Scaphoid-capitate fusion, performed with a single headless cannulated compression screw and lunate excision, can be considered a suitable treatment option for patients with advanced Kienböck’s disease. Our study demonstrated that this method can reduce pain, achieve positive results in wrist function, and achieve a relatively high union rate with low complication rates. Our findings highlight the importance of technical factors (appropriate scaphoid positioning, adequate compression, and carefully prepared fusion surfaces) that enhance union success in LESCF. Furthermore, it suggests that a single-screw approach may offer potential advantages in terms of surgical time and cost in suitable cases.
However, prospective studies with larger sample sizes are needed to evaluate the long-term outcomes of this method and its comparative effectiveness with other techniques (multiple-screw LESCF, proximal row carpectomy, arthroscopic fusion, etc.).
Footnotes
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
Declaration of conflicting interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.