Evaluation of a cadaveric wrist motion simulator using marker-based X-ray reconstruction of moving morphology.

Surgical intervention is a common option for the treatment of wrist joint arthritis and traumatic wrist injury. Whether this surgery is arthrodesis or a motion preserving procedure such as arthroplasty, wrist joint biomechanics are inevitably altered. To evaluate effects of surgery on parameters such as range of motion, efficiency and carpal kinematics, repeatable and controlled motion of cadaveric specimens is required. This study describes the development of a device that enables cadaveric wrist motion to be simulated before and after motion preserving surgery in a highly controlled manner. The simulator achieves joint motion through the application of predetermined displacements to the five major tendons of the wrist, and records tendon forces. A pilot experiment using six wrists aimed to evaluate its accuracy and reproducibility. Biplanar X-ray videoradiography (BPVR) and X-Ray Reconstruction of Moving Morphology (XROMM) were used to measure overall wrist angles before and after total wrist arthroplasty. The simulator was able to produce flexion, extension, radioulnar deviation, dart thrower's motion and circumduction within previously reported functional ranges of motion. Pre- and post-surgical wrist angles did not significantly differ. Intra-specimen motion trials were repeatable; root mean square errors between individual trials and average wrist angle and tendon force profiles were below 1° and 2 N respectively. Inter-specimen variation was higher, likely due to anatomical variation and lack of wrist position feedback. In conclusion, combining repeatable intra-specimen cadaveric motion simulation with BPVR and XROMM can be used to determine potential effects of motion preserving surgeries on wrist range of motion and biomechanics.

Safe zones in dorsal portals for wrist arthroscopy: a cadaveric study.

The standard dorsal portals are the most commonly used in wrist arthroscopy. This cadaveric study aims to determine safe zones, by quantitatively describing the neurovascular relationships of the dorsal wrist arthroscopy portals: 1-2, 3-4, midcarpal radial, midcarpal ulnar, 4-5, 6-radial and 6-ulnar. The neurovascular structures of twenty-one fresh frozen human cadaveric upper limbs were exposed, while the aforementioned portals were established with needles through portal sites. The minimum distance between portals and: dorsal carpal branch of radial artery, superficial branch of radial nerve, posterior interosseous nerve and dorsal branch of ulnar nerve, were measured accordingly with a digital caliper, followed by statistical analysis of the data. The median and interquartile range for each portal to structures at risk were determined and a safe zone around each portal was established. Free of any neurovascular structure safe zones surrounding 1-2, 3-4, midcarpal radial, midcarpal ulnar, 4-5, 6-radial and 6-ulnar portals were found at 0.46mm, 2.33mm, 10.73mm, 11.01mm, 10.38mm, 5.95mm and 0.64mm respectively. Results of statistical analysis from comparisons between 1-2, 3-4 and midcarpal radial portals, indicated that 1-2 was the least safe. The same analysis among 3-4, midcarpal radial, midcarpal ulnar and 4-5 portals indicated that midcarpal portals were safer, while 3-4 was the least safe. Results among midcarpal ulnar, 4-5, 6-radial and 6-ulnar portals indicated that 6-radial and specifically 6-ulnar were the least safe. This study provides a safe approach to the dorsal aspect of the wrist, enhancing established measurements and further examining safety of the posterior interosseous nerve.

An anatomic study of the morphologic characteristics of the dorsal capitolunate ligament.

PURPOSE: There is consensus in favor of a description of the dorsal ligaments of the carpus as not including a direct ligament between the lunate and capitate. On the other hand, there is an anatomical formation which, according to the currently accepted description, corresponds to the dorsal midcarpal capsule, itself thickened by the dorsal intercarpal ligament. The question is whether the capsule at this point deserves to be called an individualizable ligament. In our operative experience of the dorsal carpus, we have encountered a stout structure adherent to the lunate and capitate. In this article, we present the anatomic evidence of this structure's existence. METHODS: Seven adult fresh frozen upper extremities were dissected. Three wrists were longitudinally sectioned in line with the middle finger metacarpal. The remaining 4 were dissected dorsally. Two representative samples of the stout structure connecting the lunate to the capitate were sent to pathology for histologic analysis and staining. RESULTS: In all 3 of the longitudinally sectioned wrists, a thick band of tissue could clearly be seen, originating on the lunate, spanning the dorsal interval between the lunate and the capitate, and inserting on the capitate. With this structure intact, dorsal dislocation of the capitate was not possible, but preliminary sectioning of the structure allowed dislocation. In the 4 dorsally dissected wrists, the same connection was observed, palmar to the dorsal intercarpal ligament, in every specimen. The average dimensions of the dorsal capitolunate were: 15.25 ± 1 mm long, 8.75 ± 1 mm wide at the midpoint, and 1.75 ± 1 mm thick. The two specimens sent to pathology after sectioning showed longitudinally oriented collagen fibers. This structure also stained positive for elastin and contained intrasubstance vascular structures. CONCLUSION: There is a stout ligamentous structure connecting the lunate to the capitate, palmar to the dorsal intercarpal ligament. Disruption of this structure appears to be necessary for dorsal dislocation of the capitate. Clinical studies are needed to gain better understanding of the exact function and importance of this structure.

Analysis of Wrist Morphology Through Hamate and Lunate Bone Variations in Anatolian Population Using Plain Radiography / Análisis de la Morfología de la Articulación Radiocarpiana a Través de las Variaciones de los Huesos Hamato y Semilunar en la Población de Anatolia Mediante Radiografía Simple

SUMMARY: The present study aimed to evaluate wrist (lunate) anatomy in terms of the incidence of lunatum morphology on plain-radiographs among the Anatolian (Turkey) population, accompanied by demographic analysis. We obtained all the patients' data regarding demographical features, diagnosis, and posteroanterior (PA) X-ray imaging. Two radiograph-reviewers repeated the analysis twice, one month later, blinded to their findings before the previous review. The lunatum structure was determined as Type-1 (n:293) and Type-2 (n:207) for each radiograph. Most of the 500 wrists' radiographs [n:293 (58.6 %)] were type-I lunate. The mean age was 36.7±13.3 (range:18-90) years. Sex distribution was as follows: 185 (63.1 %) males to 108 (36.9 %) females. Type-2 lunate was seen in 207 participants (41.4 %). The mean age for type-2 was 41.6±15.2 (18-88) years. 142 (68.6 %) participants were male sex, while 65 (31.4 %) were females. The mean age of subjects with type-I showed a difference with type-II (p=0.007). There was no relationship in terms of sex (p=0.206) between the groups. In the Anatolian region, type-1 lunate was dominant compared to type-2. The incidence rate of lunate type in Anatolian population was similar to the Arab population.

El presente estudio tuvo como objetivo evaluar la anatomía de la articulación radiocarpiana en términos de la incidencia de la morfología del hueso semilunar en radiografías simples entre la población de Anatolia (Turquía), acompañado de un análisis demográfico. Obtuvimos todos los datos de los pacientes con respecto a las características demográficas, el diagnóstico y las imágenes de rayos X posteroanteriores (PA). Dos revisores de radiografías repitieron el análisis dos veces, un mes después, sin conocer sus hallazgos antes de la revisión anterior. La estructura del lunatum se determinó como Tipo-1 (n:293) y Tipo-2 (n:207) para cada radiografía. La mayoría de las 500 radiografías de muñecas [n:293 (58,6 %)] fueron semilunar tipo I. La edad media fue de 36,7±13,3 (rango: 18-90) años. La distribución por sexos fue la siguiente: 185 (63,1 %) hombres y 108 (36,9 %) mujeres. El semilunar tipo 2 se observó en 207 participantes (41,4 %). La edad media para el tipo 2 fue de 41,6±15,2 (18-88) años. 142 (68,6 %) participantes eran del sexo masculino, mientras que 65 (31,4 %) eran del sexo femenino. La edad media de los sujetos con tipo I mostró una diferencia con el tipo II (p = 0,007). No hubo relación en cuanto al sexo (p=0,206) entre los grupos. En la región de Anatolia, el semilunar tipo 1 era dominante en comparación con el tipo 2. La tasa de incidencia del tipo semilunar en la población de Anatolia fue similar a la de la población árabe.

Morphology of the triangular fibrocartilage complex of the Vietnamese adult: a cadaveric study.

Objective: This descriptive study aims to describe various anatomical morphological indicators of the triangular fibrocartilage complex (TFCC) in Vietnamese adults. Materials and methods: We analyzed 30 wrist joints from 15 fresh cadavers. To access the components of the TFCC, the wrist joints were dissected and measured, and anatomical morphological indices, inclu-ding length, width, thickness, origin, and insertion, were recorded. Results: Nine of 30 articular discs had central tears. The average length of the articular disc was 10.05±2.26 mm, while the average width was 12.10±1.39 mm. The average thickness of the articular disk on the ulnar side was 1.56±0.42 mm, while the average thickness of the articular disk on the radial side was 2.63±1.04 mm. Most meniscus homologues (86.6%) were of the narrow opening type according to the Ishii classification, with a horizontal dimension of 6.98±2.05 mm, anteroposterior diameter of 8.94±2.46 mm, and thickness of 1.27±0.41 mm. The volar radioulnar ligament averaged 12.75±2.17 mm in length and 2.54±0.77 mm in width, while the dorsal radioulnar ligament ave-raged 12.82±2.63 mm in length and 2.37±0.65 mm in width. The ulnar collateral ligament averaged 13.59±2.79 mm in length, 3.75±0.80 mm in width, and 0.95±0.46 mm in thickness. The ulnolunate and ulnotriquetral ligaments had average lengths of 7.34±2.87 mm and 5.70±2.98 mm, widths of 3.93±1.55 mm and 4.87±1.06 mm, and thicknesses of 0.96±0.61 mm and 1.43±0.98 mm, respectively. Conclusions: There are no differences in the shape or structure of the adult Vietnamese TFCC. No significant differences were noted in any TFCC component according to wrist side or gender.

A study of clinical anatomy of the safe zone for the volar approach for wrist arthroscopy.

OBJECTIVE: The current study was to perform an anatomical observation of the volar approach for wrist arthroscopy and to establish the safe zone for this approach. METHODS: Eight preserved specimens and 2 fresh specimens were used to simulate the medial-to-lateral operation and to mark the volar approach. Based on anatomical measurements of the volar approach, the closest distances from the 1/2, 6R, 6U, VR, VR' and VU approaches to the adjacent important structures were established. RESULTS: The closest distance from the 1/2 approach to the superficial branch of the radial nerve was 2.4±1.5mm. The closest distances from the 6U and 6R approaches to the dorsal carpal branch of the ulnar nerve were 16.2±1.3mm and 9.0±2.4mm, respectively. The closest distances from the VR and VR' approaches to the palmar cutaneous branch of the median nerve were 6.7±1.1mm and 2.8±0.9mm, respectively; the closest distances to the radial artery were 6.3±4.0mm and 10.0±3.4mm, respectively. Moreover, both of the two approaches passed through the base of the flexor carpi radialis tendon. The closest distance from the VU approach to the ulnar artery and flexor digitorum profundus tendon were 3.3±1.4mm and 0.3±2.5mm, respectively. CONCLUSIONS: In conclusion, a safe zone could be located for the establishment of the volar approach for wrist arthroscopy. LEVEL OF EVIDENCE: III; retrospective study with no control group.

Carpal allometry of African apes among mammals.

OBJECTIVES: Morphological variation in African ape carpals has been used to support the idea that Pan and Gorilla evolved knuckle-walking independently. Little work, however, has focused on the effect of body mass on carpal morphology. Here, we compare carpal allometry in Pan and Gorilla to that of other quadrupedal mammals with similar body mass differences. If allometric trends in Pan and Gorilla carpals mirror those of other mammals with similar body mass variation, then body mass differences may provide a more parsimonious explanation for African ape carpal variation than the independent evolution of knuckle-walking. MATERIALS AND METHODS: Three linear measurements were collected on the capitate, hamate, lunate, and scaphoid (or scapholunate) of 39 quadrupedal species from six mammalian families/subfamilies. Relationships between linear measurements and estimated body mass were analyzed using reduced major axis regression. Slopes were compared to 0.33 for isometry. RESULTS: Within Hominidae, higher body mass taxa (Gorilla) have relatively anteroposteriorly wider, mediolaterally wider, and/or proximodistally shorter capitates, hamates, and scaphoids than low body mass taxa (Pan). These allometric relationships are mirrored in most, but not all, mammalian families/subfamilies included in the analysis. CONCLUSIONS: Within most mammalian families/subfamilies, carpals of high body mass taxa are proximodistally shorter, anteroposteriorly wider, and mediolaterally wider than those of low body mass taxa. These distinctions may be caused by the need to accommodate relatively higher forelimb loading associated with greater body mass. Because these trends occur within multiple mammalian families/subfamilies, some carpal variation in Pan and Gorilla is consistent with body mass differences.

The distance between the distal margin of the flexor retinaculum and the radiocarpal joint as a landmark in CTS surgery: A cadaver study.

BACKGROUND: The most frequent peripheral entrapment neuropathy is compression of the median nerve in the carpal tunnel, known as carpal tunnel syndrome. The most effective treatment is surgery, where the flexor retinaculum (FR) is divided. Nevertheless, after this operation, a significant number of patients suffer from persistent symptoms due to incomplete FR distal release. It may be difficult to identify the distal boundary of the FR due to the minimal skin incision. We aimed to identify an anatomical landmark to avoid incomplete distal FR release. The radiocarpal (RC) joint can be palpated, and lies in close proximity to the boundaries of the FR. Thus, the distance between the RC joint space and the distal FR margin - the RC-FR distance - could be a reliable and individual morphologic measurement from easily acquired regional anthropological measurements. METHODS: During this study, 39 radiocarpal regions of 23 embalmed cadavers were dissected, and measurements were taken. Linear regression corresponding to the ulnar length and the RC-FR distance was established. RESULTS: The mean RC-FR distance from the RC joint space to the distal FR margin was 3.8 cm (95 % CI 3.5-4.0), and the range was 2.3-5.1 cm. This distance was 1.1 cm (95 % CI 0.8-1.4) longer in males than in females (p < 0.00001), and there were no side-specific differences. The individual projection of the distal FR margin in centimeters can be calculated by measurement of the ipsilateral ulnar length divided by 4 and reduced by 2.9, p < 0.005. CONCLUSIONS: The side-equal and sex-specific position of the distal flexor retinaculum margin could be calculated from the palpable radiocarpal joint space based on the ipsilateral ulnar length.

Bone Morphology in Ulnar Impaction Syndrome: A Radiographic Evaluation.

Background: Positive ulnar variance (UV) may be associated with a higher incidence of ulnar impaction syndrome (UIS). However, neutral and/or negative UV has also been associated with the development of UIS; therefore, other risk factors may be involved. The purpose of this study was to compare radiological bone morphology in patients with UIS and asymptomatic controls. Methods: Between 2009 and 2018, posteroanterior wrist radiographs of 47 wrists in 45 patients diagnosed with UIS were compared with those of 163 wrists in 93 asymptomatic patients from the control group. The following parameters were obtained: ulnar variance (UV); ulnar head top-fovea distance (UTFD); capitate-triquetrum distance (CTD); radio-lunate distance (RLD) and lunate coverage ratio (LCR). The morphology of the lunate was classified based on the absence (type I) or presence (type II) of a medial facet that articulates with the hamate. The radiographic parameters and lunate types were compared between the two groups. We then divided the groups into two subgroups: the positive UV subgroup and the neutral/negative UV subgroup. In each subgroup, the radiographic parameters and lunate types were compared between the UIS and control groups. Results: In the UIS group, the UV and UTFD were significantly increased compared to those in the control group. The proportion of type II lunates was significantly higher in the UIS group than in the control group. In addition, the type II lunate was more common in the UIS group in both the positive UV and negative UV groups. Conclusions: Our study suggests that in addition to positive UV, ulnar head morphology with an increased UTFD and type II lunate morphology may be associated with the development of ulnar impaction syndrome. Level of Evidence: Level III (Diagnostic).

An Anatomical Study of the Palmaris Brevis, Transverse Carpal Ligament, and the Recurrent Motor Branch of the Median Nerve.

Background: The anatomical structures in relation to the carpal tunnel release are the palmaris brevis muscle (PBM), transverse carpal ligament (TCL), and the recurrent motor branch of the median nerve (RMBMN). Our aim is to describe the gross morphology in the Korean population of the PBM, TCL, and RMBMN specifically looking for anomalies, and to determine the muscles encountered during a standard carpal tunnel release. Material and Methods: A total of 30 cadaveric hands were dissected. A longitudinal line drawn from the third web space to the midpoint of the distal wrist crease served as the reference line (RL). The PBM and TCL were classified according to its shape and location. The length, width, and thickness of the TCL were measured. The ratio of the lengths of PBM and TCL to RL was calculated. The course of the RMBMN was dissected specifically looking for anomalies. We also looked at the muscle fibers encountered during a standard carpal tunnel release to identify the muscle. Results: PBM was classified into three different types based on the shape. The average thickness of the PBM and TCL were 0.89 ± 0.16 mm and 1.43 ± 0.40 mm, respectively. The distal border of the TCL was thicker than the proximal border. The average ratio of the length of the PBM to the RL was 25.65 ± 8.62% and TCL to the RL was 24.00 ± 3.37%. The distribution of the RMBMN was classified into three different types. A few accessory branches of the RMBMN were also noted. And 36 muscle fibers were noted within the TCL in line with the RL. Conclusion: We clarified findings and added quantitative information about the anatomical structures surrounding carpal tunnel. A thorough knowledge of the anatomy and anomalies around the carpal tunnel is helpful for surgeons to ensure optimal surgical results.

3D geometric morphometric analysis of the distal radius insertion sites of the palmar radiocarpal ligaments indicates a relationship between wrist anatomy and unique locomotor behavior in hylobatids.

OBJECTIVES: The objective of this study is to explore the anatomical differences in the insertion sites of the palmar radiocarpal ligaments between hylobatids and other hominoids that may be related to their different locomotor behaviors. MATERIALS AND METHODS: The morphology of the insertion sites of the palmar radiocarpal ligaments was analyzed with three-dimensional geometric morphometrics (3D GM) in the distal radial epiphysis of 44 hylobatids, 25 Pan, 31 Gorilla and 15 Pongo. RESULTS: Relative to other hominoids, hylobatid insertion sites of the palmar radiocarpal ligaments were relatively larger and the insertion site of the short radiolunate ligament had a palmar orientation. DISCUSSION: Larger palmar radiocarpal ligaments in hylobatids can help stabilize the wrist during the radial and ulnar displacement that occurs in ricochetal brachiation, the characteristic locomotor behavior of hylobatids, and compensate for the large traction loads on the wrist during extended-elbow vertical climbing.

Functional signals and covariation in triquetrum and hamate shape of extant primates using 3D geometric morphometrics.

In this study, we want to investigate the covariation in the shape of two carpal bones, the triquetrum and hamate, and the possible association with locomotor behavior in a broad range of primate taxa. We applied 3D Geometric Morphometrics on a large data set comprising 309 anthropoid primates of 12 different genera. Principal component analyses were performed on the covariance matrix of 18 (triquetrum) and 23 (hamate) Procrustes-aligned surface landmarks. A two-block partial least square analysis was done to test the covariance between triquetrum and hamate shape, without relying on the predictive models implicit in regression analyses. The results show that the carpal shape of quadrupedal anthropoids, which mainly use their wrist under compressive conditions, differs from that of suspensory primates as their wrist is possibly subjected to tensile and torsional forces. Within the hominids, differences in shape also distinguish more terrestrial from more arboreal species. Even within the great apes, we are able to capture shape differences between species of the same genus. In combination with behavioral and biomechanical studies, the results of this research can be used to establish form-function relationships of the primate hand which will aid the functional interpretation of primate fossil remains.

Ulnar-Sided Wrist Pain in the Athlete: Sport-Specific Demands, Clinical Presentation, and Management Options.

ABSTRACT: Ulnar-sided wrist injuries are common in sports that require repeated pronosupination, wrist radial/ulnar deviation, axial loading, and gripping equipment. Common anatomic structures affected include the triangular fibrocartilage complex, extensor carpi ulnaris tendon, distal radioulnar and ulnocarpal joints, and hamate bone. Presenting symptoms include pain with activity, swelling, possible snapping or clicking, and reproduction of symptoms with provocative maneuvers. Imaging may confirm or rule out pathologies, but abnormal findings also may present in asymptomatic athletes. Initial treatment is usually nonoperative with splinting, load management, activity modification, strengthening the components of the kinetic chain of the particular sport, and pain management. Surgery is usually indicated in ulnar-wrist pain pathology such as hook of hamate fractures and required in associated instability. Future research should address specific treatment and rehabilitation protocols, emphasizing the complete kinetic chain along with the injured wrist.

Examination of the Wrist.

LEARNING OBJECTIVES: After reading this article and reviewing the supplemental videos, the participant should be able to: 1. Identify common wrist conditions that may be encountered on evaluation. 2. Describe provocative maneuvers used to confirm a diagnosis of wrist disorder. 3. Develop a systematic approach to examination of the wrist. 4. Determine appropriate diagnostic maneuvers for radial, central, and ulnar wrist pain. SUMMARY: The wrist is a complex structure, and providers caring for hand and upper extremity conditions need to have an understanding of the wrist examination and provocative maneuvers for conditions that are encountered. Fractures, tendonitis, arthritis, and instabilities are all commonly encountered, and the provider should have an idea of the diagnosis based on clinical examination and use imaging as needed to confirm or stage a diagnosis.

Five Wrist Operations That Give the Best Results.

LEARNING OBJECTIVES: After reading this article and viewing the videos, the participant should be able to: 1. Recognize the following five wrist operations as consistent options for different wrist injuries: carpal tunnel release, medial femoral condyle bone flap for scaphoid nonunion associated with carpal collapse and avascular necrosis, scaphocapitate arthrodesis for Kienböck disease, percutaneous screw fixation of nondisplaced scaphoid fracture, and four-corner arthrodesis. 2. Know the state-of-the-art of these five procedures. 3. State the indications of each operation. 4. List the surgical steps of these five procedures. SUMMARY: The wrist is a complex joint that concentrates different types of tissues (e.g., bone, cartilage, ligaments, nerves, vessels) and a broad different spectrum of diseases. Treatment of wrist injuries has improved during recent years, mainly because of improvement in strategy, techniques, microsurgical equipment, understanding anatomy and improvements in technology. In this article, we present the five operations (i.e., carpal tunnel release, medial femoral condyle bone flap for scaphoid nonunion associated with carpal collapse and avascular necrosis, scaphocapitate arthrodesis for Kienböck disease, percutaneous screw fixation of nondisplaced scaphoid fracture, and four-corner arthrodesis) that have consistently given good outcomes in patients suffering from different wrist injuries/maladies.

MRI of the Wrist Ligaments.

Technological advances in magnetic resonance imaging (MRI) have improved radiologists' ability to evaluate wrist ligaments. MRI interpretation often guides clinical management. This article aims to review the normal and pathologic appearance of intrinsic and extrinsic wrist ligaments with a focus on MRI. Variant anatomy, imaging pearls, and clinical significance are also discussed. Special attention is paid to key wrist ligaments that play a role in carpal stability.

Magnetic Resonance Imaging of the Triangular Fibrocartilage Complex.

The imaging evaluation and interpretation of the triangular fibrocartilage complex (TFCC) is both challenging and rewarding for the radiologist and surgeon alike. The TFCC comprises a complicated group of fibrocartilaginous and ligamentous structures at the ulnar aspect of the wrist that plays an important role in wrist biomechanics. It is the main stabilizer of the distal radioulnar and ulnocarpal joints and functions to distribute compressive forces at the ulnocarpal joint during axial loading. Derangement of the TFCC is the most common source of ulnar-sided wrist pain. Imaging plays an important role in the diagnosis and management of these lesions. The TFCC can anatomically be divided into proximal and distal parts to emphasize the role that the proximal TFCC has in stabilizing the distal radioulnar joint. Tears can be divided into traumatic and degenerative categories using the Palmer classification. Further subclassification based on the location for traumatic tears and the degree of derangement in degenerative tears guides clinical management. The vascular anatomy is important in determining management options for various lesions. A detailed understanding of the normal anatomy of the TFCC, imaging limitations and pitfalls, the Palmer classification system, and current treatment options is critical to the accurate and clinically useful interpretation of radiologic examinations of the TFCC.

3T Magnetic Resonance Imaging of the Wrist Tendons.

Magnetic resonance imaging (MRI) is frequently used in the imaging evaluation of wrist pain. The complex anatomy of the wrist can be demonstrated by MRI. Three tesla (3 T) MRI offers increased signal-to-noise ratio relative to 1.5 T MRI allowing for higher soft tissue contrast and better spatial resolution. The resulting increase in conspicuity of fine anatomic detail may improve the detection and characterization of wrist pathology. In this article, we will review the anatomy, normal variants, and common pathologies of the wrist tendons as evaluated on 3 T MRI.

Cartilage and subchondral bone distributions of the distal radius: a 3-dimensional analysis using cadavers.

OBJECTIVE: To quantify the spatial distributions of cartilage and subchondral bone thickness of the distal radius. DESIGN: Using 17 cadaveric wrists, three types of 3-dimensional models were created: a cartilage-bone model, obtained by laser scanning; a bone model, rescanned after dissolving the cartilage; and a subchondral bone model, obtained using computed tomography. By superimposing the bone model onto the cartilage-bone and the subchondral bone models, the cartilage and subchondral bone thickness were determined. Measurements along with the spatial distribution were made at fixed anatomic points including the scaphoid and lunate fossa, sigmoid notch and interfossal ridge, and compared at each of these four regions. RESULTS: Cartilage thickness of the interfossal ridge (0.89 ± 0.23 mm) had a larger average thickness compared to that of the scaphoid fossa (0.70 ± 0.18 mm; p = 0.004), lunate fossa (0.75 ± 0.17 mm; p = 0.044) and sigmoid notch (0.64 ± 0.13 mm; p < 0.001). Subchondral bone was found to be thickest at the scaphoid (2.18 ± 0.72 mm) and lunate fossae (1.94 ± 0.93 mm), which were both thicker than that of sigmoid notch (1.63 ± 1.06 mm: vs scaphoid fossa, p = 0.020) or interfossal ridge (1.54 ± 0.84 mm: vs scaphoid fossa, p = 0.004; vs lunate fossa, p = 0.048). In the volar-ulnar sub-regions of the scaphoid and lunate fossa, the subchondral bone thickened. CONCLUSIONS: Our data can be applied when treating distal radius fractures. Cartilage thickness was less than 1 mm across the articular surface, which may give an insight into threshold for an acceptable range of step-offs. The combined findings of subchondral bone appreciate the importance of the volar-ulnar corner of the distal radius in the volar locking plate fixation.

Anatomical relationship between the morphology of the styloid process of the ulna and the attachment of the radioulnar ligaments.

The radioulnar ligaments are the major stabilizers of the distal radioulnar joint under dynamic loading; however, anatomical detail regarding their attachment on the middle and distal thirds of the styloid process of the ulna remains unclear. Because previous anatomical studies included only old cadavers, their anatomical findings might not reflect the morphological features of younger and healthy specimens. This study investigated the anatomical features of the distal ulna, particularly the styloid process, to determine the attachment of the radioulnar ligaments to the styloid process and verified their direction and attachment to the styloid process in younger and healthy donors using magnetic resonance imaging (MRI). We investigated the morphological features of the distal ulna of 12 cadaveric wrists using micro-computed tomography (micro-CT). We also visualized and measured the distribution of the cortical bone thickness. We histologically analyzed three specimens in the axial plane and macroscopically analyzed seven specimens to examine the attachment of the radioulnar ligaments to the styloid process. In addition, we evaluated five wrists from living volunteers using 3.0 Tesla MRI. The distal ulna has a ridge on the dorsoradial aspect of the styloid process that corresponds to the attachment of the radioulnar ligaments. Micro-CT images after data processing revealed that the cortical thickness of the dorsoradial quadrant was thicker than that of the other quadrant at the proximal slice of the styloid process (p < 0.01), and that of the dorsoulnar (p = 0.021) and ulnopalmar (p < 0.01) quadrants at the middle slice. Histological analyses showed that the radioulnar ligaments were attached to the middle and distal thirds of the styloid process via chondral-apophyseal entheses. The direction of the fiber was dorsal in the middle third of the styloid process and changed to palmar in the distal third of the styloid process. The direction and attachment of the radioulnar ligaments on the styloid process were confirmed using MRI for younger and healthy participants. The radioulnar ligaments were attached to the dorsoradial ridge of the styloid process, which was confirmed by cortical bone thickening, histology at the attachment sites, and in vivo MR imaging. The directions of the radioulnar ligaments sterically intersected, which would satisfy both slipping stability and rotational mobility. These anatomical findings may provide the basis for biomechanical consideration of distal radioulnar joint stabilization.