What Is the Optimal Method of Fixation for Scaphoid Nonunion Relative to the Location of the Lesion?

INTRODUCTION: Scaphoid nonunion is a typical complication of scaphoid fractures, with the nonunion rate varying by the location of the scaphoid. The current widely used method for treating scaphoid nonunion, which is challenging for surgeons, is the headless compression screw (HCS). Various surgical approaches, such as the scaphoid plate, have been proposed to address the problem of screw fixation; however, no consensus exists regarding the optimal treatment method. This study focused on analyzing appropriate treatment methods based on the anatomical location of the scaphoid nonunion. METHODS: Ninety-seven patients with scaphoid nonunion were treated between 2008 and 2023. All patients underwent treatment using 1 HCS or scaphoid volar locking plate with nonvascularized bone graft from the distal radius depending on the scaphoid's location. The scaphoid angle and bone union were confirmed using radiological examinations. The clinical evaluations included range of motion, pain, grip strength, and functional wrist scores. RESULTS: Fifty-seven patients were included in the final analysis. In the screw group, 26 patients (26/42 [62%]) obtained a bone union, and all 15 patients (15/15 [100%]) in the plate group obtained a union ( P = 0.005). In the waist group, 16 patients with screw (16/25 [64%]) and 8 using a plate (8/8 [100%]) showed bony healing. In the proximal group, 3 patients with HCS (3/9 [33%]) and 4 using plate (4/4 [100%]) showed bone union. In the distal group, 7 patients with a screw (7/8 [87%]) and 3 with the plate (3/3 [100%]) showed bone union. Significant differences were found in the waist ( P = 0.047) and proximal groups ( P = 0.026), but not in the distal group ( P = 0.521). All groups showed improved radiological angles associated with the scaphoid and better clinical outcomes postoperatively. CONCLUSIONS: Plate fixation was overall superior to screw fixation for scaphoid nonunion, especially in the waist and proximal poles, providing better union rates and stability. For the distal group, both methods are effective, with the choice depending on the surgeon's expertise and patient factors. The results highlight the importance of the lesion's anatomical location in selecting the appropriate fixation method.

An Atypically Displaced Scaphoid Fracture With Proximal Fragment in the Flexor Compartment of the Forearm: A Case Report.

CASE: This case report details the rare presentation of a scaphoid waist fracture in a 27-year-old right-hand-dominant man, with an atypical displacement of the proximal fracture fragment into the flexor compartment of the forearm. Urgent open reduction and internal fixation using a Herbert screw were performed, resulting in fracture union and favorable wrist function at the 1-year follow-up. CONCLUSION: This case serves as a reminder that tailored, timely interventions for challenging scaphoid fractures can yield favorable long-term results, underscoring the significance of individualized approaches in fracture management.

Lunate-capitate arthrodesis for scaphoid nonunion: a comparative study.

BACKGROUND: Scaphoid nonunion advanced collapse (SNAC) injuries are frequently associated with irreversible degenerative wrist arthritic changes that necessitate surgical intervention. Midcarpal fusion remains the mainstay of the management of SNAC II and III injuries. A successful four-corner fusion (4CF) relies on a stable lunate-capitate fusion (LCF). There have been reports of management relying solely on LCF. The outcomes of LC- and 4 C-fusions in SNAC injuries were not widely documented. The objective of this research is to provide valuable insights into the effectiveness of both fusion procedures in the management of SNAC II and III wrist injuries, with a focus on reporting associated complications, functional and radiological outcomes. PATIENTS AND METHODS: This retrospective study encompassed 65 patients diagnosed with SNAC II and III wrist injuries who underwent limited wrist fusion procedures between 2015 and 2024, with a minimum of 2 years of postoperative follow-up. Exclusion criteria encompassed patients with carpal instability, prior wrist surgical interventions, and scapholunate advanced collapse. Following the fusion procedure performed, patients were stratified into two groups: the LCF group consisting of 31 patients, and the 4CF group comprising 34 patients. Preoperative and intraoperative data were retrieved from the patient's medical records. At their final follow-up appointments, patients underwent comprehensive radiographic and clinical evaluations. Clinical outcomes including hand grip strength, range of motion, the Disabilities of the Arm, Shoulder, and Hand Score, and the Mayo Modified Wrist Score, were compared between groups. Any associated complications were reported. RESULTS: The average healing time was 74.7 ± 15.6 and 72.2 ± 13.2 days for the LCF and 4CF groups, respectively. At the final visit, all patients showed functional improvement relative to their preoperative status, with comparable wrist range of motions observed in both groups. The functional wrist scores were slightly better in the LCF patients (P > 0.05). The average grip strength was significantly greater in the LCF group (P = 0.04), with mean strength values of 86.8% and 82.1% of the contralateral side, for the LCF and 4CF groups, respectively. CONCLUSION: The LCF is not less efficient than the 4CF in the treatment of SNAC II and III wrist injuries. Through a less time-consuming procedure, LCF can efficiently provide comparable results to 4CF. LEVEL OF EVIDENCE: level IV evidence.

Comparison of Radiographic Measurement Parameters of the Wrist in Patients with and without Scaphoid Fracture after Fall on an Outstretched Hand.

PURPOSE OF THE STUDY: To investigate the effects of anatomical variations on the mechanism of scaphoid fracture by comparing the radiologic parameters of the wrist of patients with and without scaphoid fracture after a fall on an outstretched hand. MATERIAL AND METHODS: Cross-sectional comparative retrospective analysis of radiographs of patients with (Group 1, n=169) and without scaphoid fracture (Group 2, n=188). Morphometric data were measured including radial inclination (RI), radial height (RH), ulnar variance (UV), carpal height (CH) ratio, revised carpal height (RCH) ratio and palmar tilt of the distal radius (PT). Receiver operating characteristics (ROC) curve analysis was used to assess the diagnostic performance for each variable with statistically significant difference. RESULTS: The mean RI and PT degrees and RH length were statistically significantly higher, and the mean UV was lower in Group 1 compared to Group 2. No difference was determined between the groups with respect to the CH ratio and RCH ratio. With ROC curve analysis, the cut-off value with the highest odds ratio was determined as RH (Cut-off value=10.77 mm, OR=21.886). CONCLUSIONS: Although higher RI, RH, PT values and more negative ulnar variance were observed in the scaphoid fracture group compared to the non-fracture group, ROC curve analysis showed that only increased RH can be considered as a possible risk factor for scaphoid fractures after fall on an outstretched hand. KEY WORDS: radiographs, risk factor, scaphoid fracture, wrist morphology.

Three-corner arthrodesis for scapholunate and scaphoid nonunion advanced collapsed wrists: outcomes at long term follow-ups.

OBJECTIVES: This study aimed to assess clinical, functional and radiological outcomes after three-corner arthrodesis in patients suffering from symptomatic scapholunate or scaphoid non-union advanced collapsed wrists. We hypothesised that three-corner arthrodesis provided satisfactory clinical and radiological results in the long term. MATERIAL AND METHODS: This was a retrospective study of 13 patients (14 wrists) who underwent a three-corner arthrodesis between March 2004 and January 2019 with a mean follow-up of 6,7 years. Clinical assessment consisted of wrist motion, grip strength, pain and functional scores (Quick-DASH, PRWE, MWS). All complications and surgical revisions were investigated. Radiographic assessment searched for union, evaluated carpal height and ulnar translation, lunate tilt and occurrence of radio-lunate arthritis. RESULTS: At the last follow-up Quick-DASH and PRWE scores were 24,87(± 17.2) and 47.4 (± 26.9) respectively and were significantly improved. Wrist motion was 35°, 32°, 10° et 24° of flexion, extension, radial and ulnar deviation respectively. Union was obtained for 13 (92,9%) wrists. The mean radiolunate angle was 11° (-17°-34°). Three patients needed reintervention, which 2 consisted of total wrist arthrodesis due to persisting pain. Mild signs of radio-lunate arthritis were found in three patients. CONCLUSION: Three-corner arthrodesis seemed to provide satisfactory long-term functional outcomes. The union rate was high and even patients with signs of radio-lunate arthritis still had improved outcomes at the last follow-up. It could be a part of surgical options in wrists with radio- and midcarpal arthritis, among other procedures.

Accuracy of wrist fracture detection on radiographs by artificial intelligence compared to human clinicians. A systematic review and meta-analysis.

PURPOSE: The aim of the study is to perform a systematic review and meta-analysis comparing the diagnostic performance of artificial intelligence (AI) and human readers in the detection of wrist fractures. METHOD: This study conducted a systematic review following PRISMA guidelines. Medline and Embase databases were searched for relevant articles published up to August 14, 2023. All included studies reported the diagnostic performance of AI to detect wrist fractures, with or without comparison to human readers. A meta-analysis was performed to calculate the pooled sensitivity and specificity of AI and human experts in detecting distal radius, and scaphoid fractures respectively. RESULTS: Of 213 identified records, 20 studies were included after abstract screening and full-text review. Nine articles examined distal radius fractures, while eight studies examined scaphoid fractures. One study included distal radius and scaphoid fractures, and two studies examined paediatric distal radius fractures. The pooled sensitivity and specificity for AI in detecting distal radius fractures were 0.92 (95% CI 0.88-0.95) and 0.89 (0.84-0.92), respectively. The corresponding values for human readers were 0.95 (0.91-0.97) and 0.94 (0.91-0.96). For scaphoid fractures, pooled sensitivity and specificity for AI were 0.85 (0.73-0.92) and 0.83 (0.76-0.89), while human experts exhibited 0.71 (0.66-0.76) and 0.93 (0.90-0.95), respectively. CONCLUSION: The results indicate comparable diagnostic accuracy between AI and human readers, especially for distal radius fractures. For the detection of scaphoid fractures, the human readers were similarly sensitive but more specific. These findings underscore the potential of AI to enhance fracture detection accuracy and improve clinical workflow, rather than to replace human intelligence.

[Trans-scapho-perilunar fracture-dislocation: a case report]. / Fractura-luxación transescafo-perilunar: reporte de un caso clínico.

Trans-scaphoid perilunate fractures-dislocations are rare injuries caused by high-energy trauma of the wrist. Diagnosis is based on medical history, physical examination, and tools such as radiographs, computed tomography scan, and magnetic resonance imaging. Early treatment consists of closed reduction and casting to stabilize the limb. Definitive treatment is surgical and includes bone and soft tissue repair. A case of trans-scaphoid perilunate fracture-dislocation is presented, along with diagnosis, management and outcome.

Las fracturas-luxaciones transescafo-perilunares son lesiones infrecuentes causadas por impactos de alta energía hacia la muñeca. El diagnóstico se basa en la historia clínica, exploración física y herramientas como la radiografía, la tomografía computarizada y la resonancia magnética. El manejo inmediato consiste en una reducción cerrada e inmovilización para estabilizar la extremidad. El tratamiento definitivo es de carácter quirúrgico e incluye la reparación ósea y de tejidos blandos. Se presenta un caso de fractura-luxación transescafo-perilunar, su diagnóstico, manejo y evolución.

In vivo non-contact regions of proximal scaphoid in six extreme wrist positions.

INTRODUCTION: Fractures of the scaphoid are the most common carpal injuries, account for 80-90% of all carpal fractures. 5-15% nonunion of scaphoid fractures were reported even with adequate primary treatment, which probably progresses to osteoarthritic changes several decades later. Researches regarding to scaphoid physiological characteristic in vitro and in vivo and kinds of trials in clinical practice are being kept on going, which contribute much to our clinical practice. With the advancing wrist arthroscopy, 3D-print patient-specific drill guide, and intraoperative fluoroscopic guidance, dorsal approach (mini-invasive and percutaneous technique) is being popular, through which we can implant the screw in good coincidence with biomechanics and with less disturbing tenuous blood supply of the scaphoid. Investigating the noncontact area of the dorsal proximal scaphoid in different wrist positions can facilitate preoperatively estimating insert point of the screw. MATERIALS AND METHODS: Eight volunteers were recruited to accept CT scans in six extreme wrist positions. The images of DICOM mode were imput into the Mimics analytical system, the segmented scaphoid, lunate and radius were exported in mode of ASCII STL and were opened in the software of Geomagic studio. We created four planes based on anatomic markers on the surface of the radius and scaphoid to confine the proximal scaphoid to form the so-called non-contact regions. We measured and compared the areas in six targeted positions. RESULTS: Amidst six extreme wrist positions, area of the non-contact region in extreme dorsal extension (59.81 ± 26.46 mm2) was significantly the smallest, and it in extreme palmar flexion significantly was largest (170.51 ± 30.44 mm2). The non-contact regions increased in order of dorsal extension, supination, ulnar deviation, radial deviation, pronation and palmar flexion. As for two-group comparison, the non-contact region showed significantly larger (p < 0.05) in palmar flexion than the others except for in pronation individually, and in radial deviation (p < 0.05) than in dorsal extension. CONCLUSIONS: Sufficient space was available for the screw started from the dorsal approach despite the wrist positions.

Examining the Efficacy of Arthroscopic Scaphocapitate Arthrodesis for Advanced Kienbock's Disease: Clinical and Radiological Outcomes.

Background: Altering wrist biomechanics, Kienbock's disease leads to progressive carpal collapse that results in early arthritis and degenerative changes. By shifting the loading axis toward the radioscaphoid joint, scaphocapitate arthrodesis (SCA) has been reported as a salvage procedure effective in treating symptomatic patients with advanced Kienbock's disease. In this study, we aimed to evaluate the clinical and radiological outcomes of arthroscopic SCA in symptomatic patients with advanced stages of Kienbock's disease. Methods: Between March 2010 and February 2021, we included 15 patients with symptomatic stage IIIA (n=2) and stage IIIB (n=13) Kienbock's disease who were followed up for a minimum of 24 months after arthroscopic SCA with or without lunate excision. The lunate was excised in 6 patients and retained in 9. Visual analog scale (VAS) pain score, grip strength, range of motion (ROM), active flexion-extension arc, and modified Mayo wrist score (MMWS) were measured preoperatively and at each follow-up examination after surgery. Operation-related complications and radiographic changes were also assessed. Results: There were 13 women and 2 men, with a mean age of 57.6 years (range, 21-74 years) at the time of undergoing arthroscopic SCA. Follow-up ranged from 24 to 116 months, with an average of 56.9 ± 32.3 months. Bony union was achieved in all patients. At preoperative examination, wrist ROM (67%) and grip strength (48%) significantly decreased, compared to the contralateral wrist. At the final follow-up, there were significant improvements in VAS, grip strength, and MMWS, whereas the active wrist ROM showed no significant change. Radioscaphoid angle recovered after surgery, while radiographic carpal collapse and ulnar translation of the carpus occurred. In subgroup analysis according to excision of the lunate, there were no significant differences in VAS, MMWS, grip strength, or total ROM. However, increased ulnar translation and decreased radial deviation were noted in the lunate excision group. Conclusions: Arthroscopic SCA achieved significant improvements in pain and wrist function in patients with advanced Kienbock's disease without any complications. Excision of the lunate when performing arthroscopic SCA seemed to induce progressive carpal ulnar translation, with no apparent clinical benefits over retaining it.

Post-processing of quantitative 4D-CT for initial evaluation of scapholunate Instability: Assessment of simplified approaches to data analysis.

OBJECTIVES: To evaluate the diagnostic performance of simplified post-processing approaches for quantitative wrist 4D-CT in the assessment of scapholunate instability (SLI). METHODS: A prospective monocentric case-control study included 60 patients with suspected post-traumatic scapholunate ligament (SLL) tears and persistent pain. Of these, 40 patients exhibited SLL tears, subdivided into two groups of 20 each: one group with completely torn ligaments and the other with partially torn ligaments. The remaining 20 patients, whose SLLs were intact, served as controls. 4D-CT and CT arthrography were performed, and post-processed by two readers using three approaches: the standard method with full data assessment and dedicated software, partial data assessment with post-processing software (bone locking), and partial data assessment without post-processing software (no bone locking). The scapholunate gap (SLG) parameter was measured in millimeters to evaluate scapholunate diastasis during radioulnar deviation (RUD). The scapholunate ligament status on CT arthrography was considered the gold standard. RESULTS: The SLG-derived parameters (range, mean, and maximal values) were significantly increased in patients with both intact and torn scapholunate ligaments across all post-processing approaches (P values ranging from 0.001 to 0.004). SLG range was the best parameter for diagnosing SLL tears, with ROC AUC values ranging from 0.7 to 0.88 across the three post-processing methods. The interobserver reproducibility was better with the alternative approaches (ICC values 0.93-0.96) compared to the standard approach (ICC values 0.65-0.72). Additionally, post-processing time was shorter with the alternative approaches, especially when specific software was not used (reduced from 10 to three minutes). CONCLUSION: Simpler approaches to wrist 4D-CT data analysis yielded acceptable diagnostic performances and improved interobserver reproducibility compared to the standard approach.

Thirty-Three-Year Follow-up Following Silicone Scaphoid Arthroplasty: A Case Report.

CASE: A 64-year-old man presented with a 3-year history of right wrist pain and swelling 33 years after a silicone scaphoid arthroplasty for chronic scaphoid nonunion. Radiographs demonstrated a deformed scaphoid implant, carpal and distal radius cysts, and mild carpal collapse. He elected to undergo a wrist arthrodesis with a dorsal fusion plate after failing conservative management. CONCLUSION: Although carpal bone silicone implant arthroplasties of the wrist have long been abandoned, our patient was pain free and fully functional for 3 decades. He was pleased to undergo serial examinations with radiographs for 30 years without any therapeutic intervention.

A comparative study of volar locking-plate fixation with corticocancellous and pure cancellous bone grafts for scaphoid nonunion with dorsal intercalated segmental instability secondary to scaphoid humpback deformity.

INTRODUCTION: Bone grafts for scaphoid nonunion with deformity include cortcicocancellous or pure cancellous bone grafts. This study compared the outcomes between two types of bone grafts when employing a volar locking-plate in patients with scaphoid nonunion with dorsal intercalated segmental instability (DISI). PATIENTS AND METHODS: This retrospective study included 34 patients with scaphoid nonunion and DISI due to humpback deformity treated between March 2017 and January 2022. Two types of bone grafts were obtained from iliac crest. Twenty of the corticocancellous (CC) group underwent a wedge-shaped graft, while 14 patients of the pure cancellous (C-only) group received graft chips. In both groups, a 1.5-mm anatomically pre-contoured locking plate was used for fixation. Radiographic evaluations included the union rate and carpal alignment including scapholunate angle (SLA), radiolunate angle (RLA), intrascaphoid angle (ISA) and scaphoid height to length ratio (HLR). Clinical assessments encompassed wrist range-of-motion, grip strength, and patient-reported outcomes. RESULTS: Nineteen of the 20 patients in the CC group and 12 of the 14 patients in the C-only group respectively, achieving osseous union. The mean follow-up period in CC group was 14.7 (range, 12 ∼ 24) months and that in C-only group was 12.6 (range, 12 ∼ 15) months. Postoperatively, there were no significant intergroup differences of radiographic parameters including SLA (CC; 49.9° ± 6.7° vs. C-only; 48.9° ± 3.5°, P = 0.676), RLA (1.7° ± 6.4° vs. 2.4° ± 3.3°, P = 0.74), ISA (36° ± 7.5° vs. 36.6° ± 12.2°, P = 0.881), and HLR (0.54 ± 0.09 vs. 0.53 ± 0.05, P = 0.587). Clinical outcomes, including the flexion-extension arc (137° ± 30° vs. 158° ± 33°, P = 0.122), grip strength (93.4 % ± 15.4% vs. 99.5 % ± 16.7 %, P = 0.39), Quick Disabilities of the Arm, Shoulder, and Hand scores (11.2 ± 8.3 vs. 12.5 ± 7.7, P = 0.74) and Mayo Wrist Scores (81.2 ± 13.1 vs. 89 ± 11.4, P = 0.242) also showed no significant intergroup differences. CONCLUSIONS: Volar locking-plate fixation with pure cancellous bone grafts achieved outcomes comparable to those achieved with corticocancellous bone grafts in scaphoid nonunion with deformity, possibly due to the biomechanical advantages of the volar plate to provide structural supports.

Automatic analysis of the scapholunate distance using 4DCT imaging: normal values in the healthy wrist.

AIM: Early diagnosis of scapholunate ligament (SLL) injuries is crucial to prevent progression to debilitating osteoarthritis. Four-Dimensional Computed Tomography (4DCT) is a promising dynamic imaging modality for assessing such injuries. Capitalizing on the known correlation between SLL injuries and an increased scapholunate distance (SLD), this study aims to develop a fully automatic approach to evaluate the SLD continuously during wrist motion and to apply it to a dataset of healthy wrists to establish reference values. MATERIALS AND METHODS: 50 healthy wrists were analysed in this study. All subjects performed radioulnar deviation (RUD), flexion-extension (FE), and clenching fist (CF) movements during 4DCT acquisition. A novel, automatic method was developed to continuously compute the SLD at five distinct locations within the scapholunate joint, encompassing a centre, volar, dorsal, proximal, and distal measurement. RESULTS: The developed algorithm successfully processed datasets from all subjects. Our results showed that the SLD remained below 2 mm and exhibited minimal changes (median ranges between 0.3 mm and 0.65 mm) during RUD and CF at all measured locations. During FE, the volar and dorsal SLD changed significantly, with median ranges of 0.90 and 1.27 mm, respectively. CONCLUSION: This study establishes a unique database of normal SLD values in healthy wrists during wrist motion. Our results indicate that, aside from RUD and CF, FE may also be important in assessing wrist kinematics. Given the labour-intensive and time-consuming nature of manual analysis of 4DCT images, the introduction of this automated algorithm enhances the clinical utility of 4DCT in diagnosing dynamic wrist injuries.

Detection of scapholunate interosseous ligament injury using dynamic computed tomography-derived arthrokinematics: A prospective clinical trial.

Scapholunate interosseous ligament injuries are a major cause of wrist instability and can be difficult to diagnose radiographically. To improve early diagnosis of scapholunate ligament injuries, we compared injury detection between bilateral routine clinical radiographs, static CT, and dynamic four-dimensional CT (4DCT) during wrist flexion-extension and radioulnar deviation. Participants with unilateral scapholunate ligament injuries were recruited to a prospective clinical trial investigating the diagnostic utility of 4DCT imaging for ligamentous wrist injury. Twenty-one participants underwent arthroscopic surgery to confirm scapholunate ligament injury. Arthrokinematics, defined as distributions of interosseous proximities across radioscaphoid and scapholunate articular surfaces at different positions within the motion cycle, were used as CT-derived biomarkers. Preoperative radiographs, static CT, and extrema of 4DCT were compared between uninjured and injured wrists using Wilcoxon signed rank or Kolmogorov-Smirnov tests. Median interosseous proximities at the scapholunate interval were significantly greater in the injured versus the uninjured wrists at static-neutral and maximum flexion, extension, radial deviation, and ulnar deviation. Mean cumulative distribution functions at the radioscaphoid joint were not significantly different between wrists but were significantly shifted at the scapholunate interval towards increased interosseous proximities in injured versus uninjured wrists in all positions. Median and cumulative distribution scapholunate proximities from static-neutral and 4DCT-derived extrema reflect injury status.

Retrospective analysis of scaphoid trapezium pyrocarbon implant intervention in STT arthritis: a 3-year follow-up study.

AIM: The purpose of this study was to evaluate clinical, patient rated and radiological outcome of the scaphoid trapezium pyrocarbon implant (STPI) at a minimum of three years follow-up. METHODS: Consecutive patients operated with the STPI due to scaphotrapeziotrapezoidal (STT) arthritis between 2012 and 2019 were included. Patients were evaluated preoperatively and annually after surgery for range of motion, grip strength, key pinch, quick-DASH, pain, and satisfaction. Radiographs were evaluated for implant position, signs of dorsal intercalated segment instability (DISI), capitolunate (CL) angle, scapholunate (SL) distance, and presence of osteophytes. RESULTS: Twenty-six patients (29 implants) were included. Seven implants were revised during the follow up, mainly due to pain: three implants were removed, four patients received a new STPI of a different size, leaving 22 implants in 20 patients available for follow up, 9 males and 11 females. Median age was 61.7 years (51-78 years). Median follow-up time was 68 months (37-105 months). Comparing preoperative status to the last follow-up, wrist extension and deviation, thumb abduction, and grip strength did not change. Key Pinch, quick DASH, pain, and patient satisfaction improved significantly at last follow-up. Radiographic signs of DISI were seen in six cases preoperatively and in 12 cases at last follow-up. CONLUSION: At a minimum of three years follow-up, the STPI used for STT-arthritis improve pain, quick-DASH result, and patient satisfaction significantly. ROM and grip strength did not change compared to preoperative values. Radiographic signs of carpal instability were common at the follow-up and the revision rate was high.

Nonunion scaphoid bone shape prediction using iterative kernel principal polynomial shape analysis.

BACKGROUND: The scaphoid is an important mechanical stabilizer for both the proximal and distal carpal columns. The precise estimation of the complete scaphoid bone based on partial bone geometric information is a crucial factor in the effective management of scaphoid nonunion. Statistical shape model (SSM) could be utilized to predict the complete scaphoid shape based on the defective scaphoid. However, traditional principal component analysis (PCA) based SSM is limited by its linearity and the inability to adjust the number of modes used for prediction. PURPOSE: This study proposes an iterative kernel principal polynomial shape analysis (iKPPSA)-based SSM to predict the pre-morbid shape of the scaphoid, aiming at enhancing the accuracy as well as the robustness of the model. METHODS: Sixty-five sets of scaphoid images were used to train SSM and nine sets of scaphoid images were used for validation. For each validation image set, three defect types (tubercle, proximal pole, and avascular necrosis) were virtually created. The predicted shapes of the scaphoid by PCA, PPSA, KPCA, and iKPPSA-based SSM were evaluated against the original shape in terms of mean error, Hausdorff distance error, and Dice coefficient. RESULTS: The proposed iKPPSA-based scaphoid SSM demonstrates significant robustness, with a generality of 0.264 mm and a specificity of 0.260 mm. It accounts for 99% of variability with the first seven principal modes of variation. Compared to the traditional PCA-based model, the iKPPSA-based scaphoid model prediction demonstrated superior performance for the proximal pole type fracture, with significant reductions of 25.2%, 24.7%, and 24.6% in mean error, Hausdorff distance, and root mean square error (RMSE), respectively, and a 0.35% improvement in Dice coefficient. CONCLUSION: This study showed that the iKPPSA-based SSM exploits the nonlinearity of data features and delivers high reconstruction accuracy. It can be effectively integrated into preoperative planning for scaphoid fracture management or morphology-based biomechanical modeling of the scaphoid.

Capitate Proximal Fragment Migration Compressing the Median Nerve in Scaphocapitate Fracture: A Case Report.

BACKGROUND Scaphocapitate syndrome is a rare clinical entity consisting of a combined scaphoid and capitate fracture along with a 90- or 180-degrees rotation of the proximal capitate fragment. The syndrome is scarcely described in the literature, with proximal migration of the capitate fragment being reported only by Mudgal et al in 1995. Concurrent compression of the median nerve is a highly unfortunate event, suggesting a unique case presented here. CASE REPORT We present a unique case of scaphocapitate fracture-dislocation in a 25-year-old man with volar dislocation of the capitate's fragment deep to the median nerve. X-rays and CT scan were performed and the patient was treated few hours after the injury by a hand specialist, in order to prevent median neuropathy and avascular necrosis of the fragment. Open reduction and internal fixation utilizing a Herbert screw for the scaphoid fracture and 3 additional K-wires was performed. Immediately post-operatively, the acute neurological symptoms had subsided and good reduction was acquired radiologically. One year post-operatively the patient had regained good hand and wrist functionality, with no extension or flexion ROM deficits. CONCLUSIONS Immediate intervention in a specialized center with reduction and fixation utilizing a Herbert screw and K-wires showed favorable 1-year results in our case of scaphocapitate syndrome. The impending complications of median neuropathy and capitate avascular necrosis were avoided despite the high-risk injury pattern.