A novel capitate bone Ilizarov external fixator for treating Kienböck's disease: an anatomical and biomechanical study.

This study aims to measure anatomical data of the capitate bone, develop an external fixator for treating late-stage osteonecrosis of lunate through Ilizarov technique, and evaluate its biomechanical performance. We selected eight wrist joint specimens to measure various parameters of the capitate bone, including its length, the distance from the junction of capitate head and body to the proximal end, as well as the width of its proximal head and distal body. Additionally, we measured these same indicators in 107 patients who had undergone wrist X-ray examination. Based on our measurements, we categorized the capitate bone into two groups and designed two types of capitate bone Ilizarov external fixator (CIEF) for it. Then, we compared it with the orthofix external fixator (OEF) through dynamic fatigue biomechanical experiments and pull-out resistance experiments. The results of the measurement revealed two categories of general patterns in the capitate bone. The first type maintains a consistent longitudinal axis between the proximal and distal ends. The second type is characterized by its proximal end being close to the radial side and its distal end being close to the ulnar side. In the dynamic tensile fatigue test, CIEF-A and CIEF-B had smaller maximum displacement values compared to the OEF (P < 0.05). In the anti-pull-out experiment, both CIEF-A and CIEF-B exhibited higher maximum pull-out force than the OEF (P < 0.05). CIFE is a treatment for advanced osteonecrosis of the lunate bone. It is specifically designed to align with the anatomical characteristics of the capitate bone, providing excellent biomechanical properties and a simple clinical procedure. However, additional clinical experiments are needed to confirm its effectiveness in the future.

One-Year Outcomes of the Anatomical Front and Back Reconstruction for Scapholunate Dissociation.

PURPOSE: Anatomical front and back (ANAFAB) reconstruction addresses the critical volar and dorsal ligaments associated with scapholunate dissociation. We hypothesized that patients with symptomatic, chronic, late-stage scapholunate dissociation would demonstrate improvements in all radiographic parameters and patient-reported outcomes (PROMs) after ANAFAB reconstruction. METHODS: From 2018 to 2021, 21 ANAFAB reconstructions performed by a single surgeon were followed prospectively, with 20 patients having a minimum follow-up of 12 months. In total, 17 men and four women were included, with an average age of 49 years. Three patients had modified Garcia-Elias stage 3 disease, eight stage 4, seven stage 5, and three stage 7. ANAFAB reconstruction of intrinsic and extrinsic ligament stabilizers was performed using a hybrid synthetic tape/tendon graft in a transosseous reconstruction. Pre- and postoperative radiographic parameters, grip, pinch strength, the Patient-Rated Wrist Evaluation, PROMIS Upper Extremity Function, and PROMIS Pain Interference outcome measures were compared. RESULTS: Mean follow-up was 17.9 months (range: 12-38). Radiographic parameters were improved at follow-up, including the following: scapholunate angle (mean 75.3° preoperatively to 69.2°), scapholunate gap (5.9-4.2 mm), dorsal scaphoid translation (1.2-0.2 mm), and radiolunate angle (13.5° to 1.8°). Mean Patient-Rated Wrist Evaluation scores for pain and function decreased from 40.6 before surgery to 10.4. We were unable to detect a significant difference in grip or pinch strength or radioscaphoid angle with the numbers tested. There were two minor complications, and two complications required re-operations, one patient who was converted to a proximal row carpectomy for failure of fixation, and one who required tenolysis/arthrolysis for arthrofibrosis. CONCLUSIONS: At 17.9-month average follow-up, radiographic and patient-reported outcome parameters improved after reconstruction of the critical dorsal and volar ligament stabilizers of the proximal carpal row with the ANAFAB technique. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

Ligamentoplasty in scapholunate instability: short-term results of the "all dorsal scapholunate repair" technique.

Injury to the scapholunate complex is the cause of scapholunate instability which can lead to radiocarpal and medio-carpal osteoarthritis. Several ligamentoplasty techniques have been reported for the treatment of chronic scapholunate instability before the osteoarthritis stage. The objective of this study was to assess the short-term results of an "all dorsal scapholunate repair" ligamentoplasty. We report the clinical, radiological and functional results of a retrospective study including 21 patients, operated between June 2019 and December 2020 for a stage 3 or 4 scapholunate instability according to the Garcia Elias classification. With a follow-up of 14.2 months, the pain was 0.1/10 according to the VAS at rest and 4/10 during exercise. Wrist strength was measured at 65% of the opposite side. The flexion-extension range of motion was 105°. Radiologically, there was a reduction of the diastasis and scapholunate angle. Osteolysis areas around the anchors were described in 47% of patients. The mean QuickDASH was 29.2/100, PRWE 24/100 and Mayo wrist score 67.8/100. Eighty-one percent of patients were satisfied. Seventeen patients had returned to work 5.2 months postoperatively. In the case of work-related injury, the functional scores were poorer, with a delayed return to work. This technique provides encouraging results in the short term. Most patients were improved compared to preoperative state. The work-related injury appears to be a poor prognostic factor. A longer-term study is imperative to confirm the maintenance over time of the correction of carpal malalignment and the evolution of the osteolysis areas.Level of evidence: Level IV Retrospective study.

Radiographic evaluation of radial flexion osteotomy effect on static scapholunate instability: a preliminary cadaveric study.

INTRODUCTION: The optimal treatment of chronic scapholunate instability has yet to be established. Scapholunate ligament grafts are still far from being the ideal solution. We conducted an experimental study to evaluate whether flexion-opening wedge osteotomy of the distal radius improves misalignment and avoids rotatory subluxation of the scaphoid in a cadaveric model of static scapholunate dissociative instability. MATERIALS AND METHODS: Radiographic studies were performed on 15 cryopreserved specimens after recreating a model of scapholunate instability by division of the scapholunate interosseous ligament (SLIL) and secondary stabilizers, taking radiographs at baseline, after the instability model, and after distal radius osteotomy. Static and dynamic (under controlled tendon traction) anteroposterior and lateral views were obtained to measure the length (in mm) of the carpal scaphoid and scapholunate interval, scapholunate angle, radio-lunate angle, and palmar tilt of the distal joint surface of the radius and to measure the dorsal scaphoid translation by the concentric circles method. The Wilcoxon test was used for statistical comparisons. RESULTS: The scapholunate interval was significantly decreased after osteotomy in all static anteroposterior views and in all lateral views under tendon traction. Dorsal scaphoid translation was significantly reduced in static lateral view in extension and in dynamic lateral view under 5-pound flexor carpi radialis tendon tension controlled by a digital dynamometer. CONCLUSIONS: Flexion-addition osteotomy of the distal radius appears to improve carpal alignment parameters in a cadaveric model of static scapholunate instability, achieving similar values to those obtained before instability.

An Evaluation of the Reliability of Manual Landmark Identification on 3D Segmented Wrists.

BACKGROUND: Three-dimensional (3D) preoperative planning is increasingly used in orthopaedic surgery. Two-dimensional (2D) characterization of distal radial deformities remains inaccurate, and 3D planning requires a reliable reference frame at the wrist. We aim to evaluate the reliability of the determination of anatomical points placed manually on 3D models of the radius to determine which of those points allow reliable morphometric measurements. METHODS: Twenty-three radial scans were reconstructed in 3D. Five operators specialized in the upper limb manually positioned 8 anatomical points on each model. One of the operators repeated the operation 6 times. The anatomical points were based on previously published 3D models used for radial inclination and dorsopalmar tilt measurements. The repeatability and reproducibility of the measurements derived using this manual landmarking were calculated using different measurement methods based on the identified points. An error of ≤2° was considered clinically acceptable. RESULTS: This study of intraobserver and interobserver variability of the anatomic points allowed us to determine the least variable and most accurately defined points. The middle of the ulnar border of the radius, the radial styloid, and the midpoint of the ulnar incisura of the radius were the least variable. The palmar and dorsal ends of the ridge delineating the scaphoid and lunate facets were the most variable. Only 1 of the radial inclination measurement methods was clinically acceptable; the others had a repeatability and reproducibility limit of >2°, making those measurements clinically unacceptable. CONCLUSIONS: The use of isolated points seems insufficient for the development of a wrist reference frame, especially for the purpose of measuring dorsopalmar tilt. If one concurs that an error of 2° is unacceptable for all distal radial measurements, then clinicians should avoid using 3D landmarked points, due to their unreliability, except for radial inclination measured using the radial styloid and the midpoint of the ulnar edge of the radius. A characterization of the wrist using 3D shapes that fit the articular surface of the radius should be considered. LEVEL OF EVIDENCE: Diagnostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Correlation between dorsal capsulo-scapholunate septum (DCSS) lesion and predynamic scapholunate instability.

OBJECTIVE: Scapholunate instability is the most common ligament injury of the wrist. In case of predynamic instability, diagnosis can be difficult, even under arthroscopy. Scapholunate instability is not the result of an isolated injury to the scapholunate interosseous ligament. Scapholunate stability is dependent not only on the scapholunate ligament, but on a complex that is comprising intrinsic and extrinsic ligaments. The dorsal capsule-scapholunate septum (DCSS) is one of the secondary stabilizers of the scapholunate complex. The objective of the present study was to investigate the correlation between DCSS lesion and predynamic scapholunate instability. METHOD: A prospective multicenter study included patients who underwent wrist arthroscopy for traumatic wrist. Arthroscopic DCSS lesion stage and instability according to European Wrist Arthroscopy Society stage were assessed. RESULTS: Twenty-seven subjects were included. We found a significant correlation between pathological DCSS and predynamic scapholunate instability and a correlation between DCSS lesion severity and instability level. CONCLUSION: Isolated DCSS lesion should be considered a predictive factor for predynamic instability.

Reverse Wafer Procedure for Ulnar Impaction Syndrome.

Ulnar impaction syndrome occurs when excessive load across the ulnocarpal joints results in pathologic changes, especially over the articular surface of the ulnar head and proximal ulnar corner of the lunate. The 2 main surgical options in ulnar impaction syndrome are ulnar shortening osteotomy and wafer procedure, whether open or arthroscopically, to decompress the ulnocarpal joint load. However, all of these techniques have their shortcomings and drawbacks. The current study demonstrates a novel technique to decompress the ulnocarpal joint load: the "reverse wafer procedure" for ulnar impaction syndrome. In this surgical technique, we resected the proximal ulnar side of the lunate instead of partial resection of the thin wafer of the distal ulnar head dome in the standard wafer procedure. This technique avoids iatrogenic central tear of triangular fibrocartilage and distal radioulnar joint portal arthroscopy, which is technically demanding while preserving the distal radioulnar joint.

Anatomical front and back reconstruction sustains radiographic alignment: a comparison to three-ligament tenodesis.

Multiple techniques exist to reconstruct the scapholunate interosseous ligament, though none have demonstrated superiority. This study compares 1-year radiographic outcomes of the three-ligament tenodesis and the anatomical front and back reconstruction. All patients who underwent reconstruction of their scapholunate interosseous ligament at one institution with either anatomical front and back reconstruction or three-ligament tenodesis between 2011 and 2020 were retrospectively reviewed. At 52-week follow-up, anatomical front and back reconstruction maintained a statistically significant improvement in scapholunate gap, corrected radiolunate angle and dorsal scaphoid translation, while three-ligament tenodesis demonstrated no sustained improvement in any parameter. The improvement in dorsal scaphoid translation was significantly greater for patients undergoing anatomical front and back reconstruction compared with three-ligament tenodesis at the 16-weeks postoperative timepoint (-1.0 mm, -0.3 mm). Anatomical front and back reconstruction demonstrates sustained improvement in radiographic outcomes at 1 year when compared with three-ligament tenodesis. By addressing both volar and dorsal critical ligament restraints, adoption of anatomical front and back reconstruction for advanced stage scapholunate interosseous ligament injuries should be considered.Level of evidence: IV.

Carpal instability after partial trapeziectomy, total trapeziectomy and the resection of the distal scaphoid pole: a cadaveric study.

INTRODUCTION: Non-dissociative carpal instability (CIND) may lead to severe functional impairment. Destabilisation of the scapho-trapezial-trapezoidal (STT) ligament complex seems to result in a CIND. MATERIALS AND METHODS: In one group with eight cadaver arms, distal scaphoid pole was resected with the adjacent ligaments. In the other eight cadavers, hemitrapeziectomy was performed followed by total trapeziectomy. CT scans were performed in different wrist positions, and the changed positions of the scaphoid, lunate and capitate were measured in comparison to non-operated wrists. RESULTS: Mainly in clenched fist position, dissociation between proximal and distal row can be determined after total trapeziectomy and resection of distal scaphoid pole. Capitate rotates dorsally up to 24°, the scaphoid up to 17° and the lunate up to 7° compared to the non-operated wrists. Resection of the distal scaphoid pole results in dorsal rotation of capitate and scaphoid of about 14° and the lunate 8°. Relative scapholunate and capitolunate angle increased significantly after total trapeziectomy, especially in clenched fist position. After scaphoid pole resection, significant SL and CL angles changes could be seen in almost every wrist position. CONCLUSION: Destabilisation of the STT ligament complex by total trapeziectomy or distal scaphoid pole resection results in dissociation of the proximal and distal carpal row without instability within the proximal or distal row, corresponding to a CIND. LEVEL OF EVIDENCE: III.

Osteolysis After Augmented Scapholunate Ligament Reconstruction: A Report of 3 Cases.

CASE: Augmented scapholunate ligament reconstruction using polyether ether ketone anchors and ultra-high molecular weight polyethylene synthetic tape has the theoretical advantage of improved stability, avoidance of K-wire fixation, and the potential for earlier mobilization. We present 3 cases of scaphoid and lunate osteolysis/fragmentation, operative and histologic findings at reoperation, and the sequelae of this technique. CONCLUSION: If planning to use suture anchors and synthetic tapes in small carpal bones, we recommend advising patients about the risk of osteolysis and monitoring closely patients who complain of pain with motion after surgery.

Volar Locking Plate Fixation for Distal Radius Fractures Distal to the Watershed Line with an Intact Lunate Volar Rim.

Background: We treated distal radius fractures (DRFs) beyond the watershed line without fracture of the lunate volar rim using a volar locking plate (VLP) and report the radiological and clinical outcomes at least 3 years after surgery. Methods: In 41 consecutive patients between January 2012 and August 2017, the fragment was composed of the radial styloid process (distal to the watershed line) and the lunate volar rim was intact. We evaluated demographic factors, radiological features and radiological/clinical outcomes at the final follow-up. Results: Twenty-nine patients were followed and evaluated. The mean follow-up period was 5.7 years. The mean patient age was 52.7 years and 24 patients had intracapsular intra-articular fractures. The fracture line was present in the lunate fossa in all patients. Twenty patients were classified as Soong grade 2, and five and four patients were grades 1 and 0, respectively. No radiological parameter (volar tilt, radial inclination, step-off and ulnar variance) was significantly different between the affected and contralateral normal sides. The mean visual analogue scale pain score and Disabilities of the Arm, Shoulder and Hand score, as well as the range of movement of the wrist, were not different between the affected and contralateral normal wrists. Finally, the grip strength on the affected side was 92% of the contralateral value. Major complications, such as nonunion, malunion and tendon rupture, were absent. Conclusions: DRFs distal to the watershed line with an intact lunate volar rim are rare and easy to miss. Careful inspection of 3D-CT images is necessary to determine these injuries, and the optimal choice for proper fixation of the fragment amongst the commercial VLPs would result in satisfactory radiological and clinical outcomes. Level of Evidence: Level IV (Therapeutic).

Anterior dislocation of the lunate due to a high-energy trauma.

Semilunate and perilunate dislocation is an injury that mostly occurs when the subject is exposed to a high-energy trauma. Considered severe, it compromises the stability and function of the wrist. The case presented is that of a 50-year-old male patient who after having a motorcycle accident arrived at the ER with neurovascular affectation, swelling, deformity and a considerable decrease of the wrist joint movement. He was also referring severe pain. A Henry (Volar) intervention was done with the help of external fixation of the lunate, followed by K-wire fixation, once a prior closed reduction was unsuccessfully attempted. The scaphoid was connected to the semilunate, and then the latter with the capitate. Ligament reconstruction followed, and stability was clinically confirmed with an X-ray. Although improvement of symptomatology was observed during the follow-up analysis, motion of the wrist remained limited. Even with the best treatment, in terms of functionality, this type of injury presents a poor prognosis.

La luxación semilunar y perilunar es una lesión que se produce principalmente cuando el sujeto está expuesto a un traumatismo de alta energía. Considerada grave, compromete la estabilidad y la función de la muñeca. El caso presentado es el de un paciente varón de 50 años que tras sufrir un accidente de motocicleta llegó a urgencias con afectación neurovascular, tumefacción, deformidad y una considerable disminución del movimiento articular de la muñeca. También refería fuertes dolores. Se realizó una intervención de Henry (Volar) con la ayuda de fijación externa del lunar, seguida de fijación con agujas de Kirschner, una vez que se había intentado sin éxito una reducción cerrada previa. El escafoides se conectó con el semilunar y luego éste con el capitado. A continuación se reconstruyó el ligamento y se confirmó clínicamente la estabilidad con una radiografía. Aunque se observó una mejora de la sintomatología durante el análisis de seguimiento, el movimiento de la muñeca seguía siendo limitado. Incluso con el mejor tratamiento, en términos de funcionalidad, este tipo de lesión presenta un mal pronóstico.

Introducing the Foveola lunata, an anatomical landmark of the wrist.

The lunate foveola is often the starting point of a cystic swelling called a "ganglion". To make the anatomy of this region more relevant to the needs of clinicians and more accessible to students, we propose to introduce the term lunate foveola (Foveola lunata) on the dorsal side of the wrist just distal to the os lunatum. The easily located foveola will help in the examination of the wrist to more easily understand the anatomy of the wrist and facilitate the examination of patients with wrist injuries when an injury to the lunate (Os lunatum) is suspected.

Evaluation of a newly designed deep learning-based algorithm for automated assessment of scapholunate distance in wrist radiography as a surrogate parameter for scapholunate ligament rupture and the correlation with arthroscopy.

PURPOSE: Not diagnosed or mistreated scapholunate ligament (SL) tears represent a frequent cause of degenerative wrist arthritis. A newly developed deep learning (DL)-based automated assessment of the SL distance on radiographs may support clinicians in initial image interpretation. MATERIALS AND METHODS: A pre-trained DL algorithm was specifically fine-tuned on static and dynamic dorsopalmar wrist radiography (training data set n = 201) for the automated assessment of the SL distance. Afterwards the DL algorithm was evaluated (evaluation data set n = 364 patients with n = 1604 radiographs) and correlated with results of an experienced human reader and with arthroscopic findings. RESULTS: The evaluation data set comprised arthroscopically diagnosed SL insufficiency according to Geissler's stages 0-4 (56.5%, 2.5%, 5.5%, 7.5%, 28.0%). Diagnostic accuracy of the DL algorithm on dorsopalmar radiography regarding SL integrity was close to that of the human reader (e.g. differentiation of Geissler's stages ≤ 2 versus > 2 with a sensitivity of 74% and a specificity of 78% compared to 77% and 80%) with a correlation coefficient of 0.81 (P < 0.01). CONCLUSION: A DL algorithm like this might become a valuable tool supporting clinicians' initial decision making on radiography regarding SL integrity and consequential triage for further patient management.

Scaphoid, lunate and capitate kinematics in the normal and ligament deficient wrist: A bi-plane X-ray fluoroscopy study.

The ligamentous structures of the wrist stabilise and constrain the interactions of the carpal bones during active wrist motion; however, the three-dimensional translations and rotations of the scaphoid, lunate and capitate in the normal and ligament deficient wrist during planar and oblique wrist motions remain poorly understood. This study employed a computer-controlled simulator to replicate physiological wrist motion by dynamic muscle force application, while carpal kinematics were simultaneously measured using bi-plane x-ray fluoroscopy. The aim was to quantify carpal kinematics in the native wrist and after sequential sectioning of the scapholunate interosseous ligament (SLIL) and secondary scapholunate ligament structures. Seven fresh-frozen cadaveric wrist specimens were harvested, and cycles of flexion-extension, radial-ulnar deviation and dart-thrower's motion were simulated. The results showed significant rotational and translational changes to these carpal bones in all stages of disruptions to the supporting ligaments (p < 0.05). Specifically, following the disruption of the dorsal SLIL (Stage II), the scaphoid became significantly more flexed, ulnarly deviated, and pronated relative to the radius, whereas the lunate became more extended, supinated and volarly translated (p < 0.05). Sectioning of the dorsal intercarpal (DIC), dorsal radiocarpal (DRC), and scaphotrapeziotrapezoid (STT) ligaments (Stage IV) caused the scaphoid to collapse further into flexion, ulnar deviation, and pronation. These findings highlight the importance of all the ligamentous attachments that relate to the stability of the scapholunate joint, but more importantly, the dorsal SLIL in maintaining scapholunate stability, and the preservation of the attachments of the DIC and DRC ligaments during dorsal surgical approaches. The findings will be useful in diagnosing wrist pathology and in surgical planning.

Suture Anchor Fixation for Lunate Osteochondral Shear Fracture: A Case Report.

CASE: A 26-year-old right-hand-dominant man sustained a left transradial, translunate perilunate injury after motor vehicle collision. The proximal lunate fractured a primarily cartilaginous 15 × 15 mm osteochondral shear fragment with 40% articular surface involvement. A novel lunate fracture suture anchor fixation technique is described, which led to fracture healing. The radial styloid was treated with a single screw. CONCLUSION: Translunate perilunate injuries involving the lunate proximal articular surface are rare. Treatment recommendations are limited to case reports. Suture anchor fixation led to stable fixation and fracture healing at the final 6-month postoperative follow-up.

[Dorsal plate assisted fixation of dorsal lunate fossa fracture of distal radius].

OBJECTIVE: To explore clinical efficacy of dorsal plate assisted fixation of dorsal lunate fossa fracture block of distal radius. METHODS: From January 2019 to January 2022, 30 patients were treated with dorsal plate assisted fixation of dorsal lunate fossa fracture of distal radius, including 13 males and 17 females, aged from 42 to 68 years old with an average of (48.7±5.6) years old;According to Doi fracture classification, 24 patients were type 3 blocks and 6 patients were type 4 blocks. The degree of palmar angle of anterior and posterior distal radius was fixed by dorsal steel plate during operation. Fracture healing and functional recovery of wrist were observed after operation. Functional evaluation was performed by Gartland and Werley scoring system at 12 months after operation. RESULTS: All patients were followed up from 12 to 13 months with an average of (11.3±0.9) months. All fractures healed for 4 to 5 months with an average of(4.7±0.8) months. Median palpal inclination of anterior and posterior distal radius fixed by dorsal plate was 5.30°(4.85°, 6.03°), 12.45°(11.98°, 13.43°) respectively, and had statistical difference( P<0.01). Gartland and Werley scores was (1.1±0.4) at 12 months afteropertaion, and 27 patients got excellent result and 3 good. CONCLUSION: Dorsal plate assisted fixation of dorsal lunate fossa fractures is beneficial to reduction and stabilization of displaced dorsal fractures and restoration of palmar inclination.

Scapholunate Instability: Diagnosis and Management - Classification and Treatment Considerations - Part 2.

Intervention for scapholunate instability is aimed at halting the degenerative process by restoring ligament integrity and normalizing carpal kinematics. Part 1 of this Current Concepts article reviewed the anatomy, kinematics, and biomechanical properties of the scapholunate ligament as well as its critical stabilizers. In this section, we provide a foundation for understanding the spectrum of scapholunate ligament instability and incorporate meaningful new anatomical insights that influence treatment considerations. These updates clarify the importance of the critical stabilizers of the scapholunate interval, ligament-specific considerations in scapholunate ligament reconstruction, and the risks of ligament disinsertion when surgically exposing the dorsal wrist. We propose a ligament-based treatment algorithm based on the stage of injury, degree and nature of ligament damage, and presence of arthritic changes.

[Three-dimensional finite element model construction and biomechanical analysis of customized titanium alloy lunate prosthesis].

Objective: To design customized titanium alloy lunate prosthesis, construct three-dimensional finite element model of wrist joint before and after replacement by finite element analysis, and observe the biomechanical changes of wrist joint after replacement, providing biomechanical basis for clinical application of prosthesis. Methods: One fresh frozen human forearm was collected, and the maximum range of motions in flexion, extension, ulnar deviation, and radialis deviation tested by cortex motion capture system were 48.42°, 38.04°, 35.68°, and 26.41°, respectively. The wrist joint data was obtained by CT scan and imported into Mimics21.0 software and Magics21.0 software to construct a wrist joint three-dimensional model and design customized titanium alloy lunate prosthesis. Then Geomagic Studio 2017 software and Solidworks 2017 software were used to construct the three-dimensional finite element models of a normal wrist joint (normal model) and a wrist joint with lunate prosthesis after replacement (replacement model). The stress distribution and deformation of the wrist joint before and after replacement were analyzed for flexion at and 15°, 30°, 48.42°, extension at 15°, 30°, and 38.04°, ulnar deviation at 10°, 20°, and 35.68°, and radial deviation at 5°, 15°, and 26.41° by the ANSYS 17.0 finite element analysis software. And the stress distribution of lunate bone and lunate prosthesis were also observed. Results: The three-dimensional finite element models of wrist joint before and after replacement were successfully constructed. At different range of motion of flexion, extension, ulnar deviation, and radial deviation, there were some differences in the number of nodes and units in the grid models. In the four directions of flexion, extension, ulnar deviation, and radial deviation, the maximum deformation of wrist joint in normal model and replacement model occurred in the radial side, and the values increased gradually with the increase of the range of motion. The maximum stress of the wrist joint increased gradually with the increase of the range of motion, and at maximum range of motion, the stress was concentrated on the proximal radius, showing an overall trend of moving from the radial wrist to the proximal radius. The maximum stress of normal lunate bone increased gradually with the increase of range of motion in different directions, and the stress position also changed. The maximum stress of lunate prosthesis was concentrated on the ulnar side of the prosthesis, which increased gradually with the increase of the range of motion in flexion, and decreased gradually with the increase of the range of motion in extension, ulnar deviation, and radialis deviation. The stress on prosthesis increased significantly when compared with that on normal lunate bone. Conclusion: The customized titanium alloy lunate prosthesis does not change the wrist joint load transfer mode, which provided data support for the clinical application of the prosthesis.

Comminuted lunate fracture combined with distal radius fracture and scaphoid fracture: A case report.

RATIONALE: Incidence of lunate fractures is very low, less than 1% of all fractures. Lunate fractures generally come from high-energy injuries, often combined with other wrist fractures. Simple lunate fractures can be fixed with screws or Kirschner wires. However, Comminuted lunate fractures are difficult to reduce and fixe by conventional methods. PATIENT CONCERNS: Here we report a 42-year-old male construction worker who was crushed by an excavator bucket and presented with comminuted lunate fracture combined with distal radius fracture and scaphoid fracture. DIAGNOSES: Comminuted lunate fracture, distal radius fracture, and scaphoid fracture. INTERVENTIONS: The posterior approach was used to reconstruct the radial lunate bone with polymethylmethacrylate cement, and cannulated screws were used to fix the scaphoid and distal radius fractures. OUTCOMES: At the 3rd month after surgery, the movement of the right wrist joint improved. At the sixth month after surgery, the patient returned to the building site and began working at the same intensity as before the injury. LESSONS: Although the incidence of comminuted lunate fractures is very low, they occur sometimes. For comminuted lunate fractures, early identification and intervention can preserve most of the function of the wrist joint.