Vilai, Parunyu

Abstract Background Computational modeling is a tool being deployed for orthopaedic solutions but its use in the hand and wrist remains limited. This work used a model to simulate a clinically relevant provocative scaphoid shift maneuver (SSM) with different levels of scapholunate interosseous ligament (SLIL) injuries to observe the effect on different metrics. Methods A personalized model simulated the full SSM motion cycle from ulnar deviation with extension to radial deviation with flexion informed by the participant’s motion obtained from dynamic computed tomography. Models repeated the SSM under different levels of SLIL injury and reported changes in joint kinematics, contact mechanics, and ligament forces. Results The fully injured model increased scaphoid dorsal translation, flexion, and radial deviation compared to the intact condition and caused a subluxation of the scaphoid. Radioscaphoid contact areas were approximately 200% greater in the fully injured model compared with all others and the fully injured model was the only condition where contact force decreased across the motion cycle. Ligament forces in the intact condition were on average 33.0 N and 54.2 N for the volar and dorsal SLIL, respectively. Lastly, the long radiolunate, an extrinsic stabilizer, had forces that increased following SLIL injury. Conclusions Computational models can successfully recreate clinically observed behaviors of an SSM, including scaphoid subluxation, while providing new insights via quantification of contact mechanics and ligament forces. Contact mechanics metrics may be important for understanding the long-term progression of untreated SLIL injuries to osteoarthritis. Additionally, ligament force metrics may explain the progression of SLIL injuries from volar SLIL to dorsal SLIL and highlight the importance of repairing extrinsic stabilizers of the joint, due to increased force sharing following SLIL injury. This work provides a pathway to future studies investigating the effects of SLIL injury and repair, both acutely and chronically.

Abstract Column-type wrists, which exhibit increased scaphoid flexion during radial deviation, often experience greater loss of motion after periscaphoid arthrodesis compared with row-type wrists. Dynamic radiographic series are typically used to differentiate these kinematic patterns. In this study, we evaluate capitate morphology as a means of predicting column- or row-type carpal kinematics. This study investigated whether wrist kinematic patterns could be predicted using simple anteroposterior (AP) radiographs. We hypothesized that capitate morphology, given its close articulation with the scaphoid, influences these patterns. We analyzed 75 wrist motion radiographic series from 45 patients. Capitates were classified as either Type I (rectangular) or Type II (pentagonal) based on their shape. Wrist kinematic patterns were categorized as row- or column-type based on the degree of scaphoid length shortening during radial deviation. Our analysis revealed that a Type II capitate was a significant predictor of column-type wrists, with an odds ratio of 6.01 compared with Type I (p = 0.014). Furthermore, Type II capitates were associated with increased scaphoid flexion and reduced translation. Capitate morphology, as assessed from a plain AP radiograph, can serve as an easily accessible marker and reliable predictor of wrist motion patterns. This could potentially aid in surgical planning and patient counseling, particularly when dynamic radiographic series are not feasible. Diagnostic, Level III.

Introduction: This study investigated the association between capitate morphology and the success rates of non-vascularized bone graft (NVBG) and vascularized bone graft (VBG) operations for scaphoid nonunion. Methods: We retrospectively analysed 213 patients with established scaphoid non-union who underwent either non-vascularized bone graft ( n = 75) or vascularized bone graft ( n = 138). We analysed risk factors, including demographics, medical history, implant type, previous surgery, bone graft donor site and capitate morphology for their association with treatment outcome. We also assessed the relationship between capitate and scaphoid morphology in the uninjured wrists of 31 patients. Results: The overall success rate was 81% for NVBG and 86% for VBG, with no significant difference. For NVBG, Type II capitate, age 40 or older and tobacco use were significant risk factors for failure. For VBG, only previous surgery was a significant risk factor. In uninjured wrists, a Type II capitate was associated with a significantly thinner scaphoid waist and a lower waist index than a Type I capitate. Conclusion: Our study introduces a new radiographic classification of capitate morphology and establishes its significant association with scaphoid morphology. Beyond traditional factors, capitate morphology can help to assess scaphoid morphology and potentially infer vascularity, aiding the selection of the most appropriate bone graft type for treating scaphoid non-union. Level of evidence: III

Abstract Preiser's disease (PD), or idiopathic avascular necrosis of the scaphoid, is a debilitating condition leading to wrist pain, dysfunction, and pan-carpal arthritis. While impaired scaphoid vascularity is central to its pathogenesis, identifying individuals at risk is challenging due to the morphological distortion of the scaphoid as the disease progresses. This study aims to investigate the association between a novel capitate morphology classification, scaphoid morphology, and their impact on PD prevalence and characteristics. We also re-evaluate negative ulnar variance (NUV) as a potential risk factor for PD. This retrospective case–control study included 34 PD patients and 340 age-matched controls. Capitate morphology was classified into Type I/II on anteroposterior (AP) radiographs based on capitotrapezoid–scaphocapitate (CT–SC) joint line angle and ratio. Scaphoid morphology was assessed via the waist index on contralateral healthy wrists. Radiographic measurements of ulnar variance and PD staging were also performed. Statistical analyses compared morphological prevalence and risk factors between groups. Type II capitate was significantly more prevalent in the PD group (35.3%) than in controls (17.1%, p = 0.018). Similarly, NUV was significantly higher in PD patients (29%) compared with controls (6.8%, p < 0.001). We found a strong correlation between Type II capitate and slender (Type II) scaphoid morphology in healthy wrists. No significant differences in age, gender, or affected side were observed. Interobserver and intraobserver agreements for capitate classification were substantial (kappa ≥0.882). Our study introduces a reliable radiographic method for classifying capitate morphology, which strongly correlates with intrinsic scaphoid shape and potential vascular vulnerability. Both Type II capitate morphology and NUV are significant predisposing factors for PD. These findings offer valuable insights for identifying at-risk individuals and improving understanding of PD's multifactorial etiology. Diagnostic Level III.