Global and Spatial Compartmental Interrelationships of Bone Density, Microstructure, Geometry and Biomechanics in the Distal Radius in a Colles' Fracture Study Using HR-pQCT.

Background: Bone parameters derived from HR-pQCT have been investigated on a parameter-by-parameter basis for different clinical conditions. However, little is known regarding the interrelationships of bone parameters and the spatial distribution of these interrelationships. In this work: 1) we investigate compartmental interrelationships of bone parameters; 2) assess the spatial distribution of interrelationships of bone parameters; and 3) compare interrelationships of bone parameters between postmenopausal women with and without a recent Colles' fracture. Methods: Images from the unaffected radius in fracture cases (n=84), and from the non-dominant radius of controls (n=98) were obtained using HR-pQCT. Trabecular voxel-based maps of local bone volume fraction (L.Tb.BV/TV), homogenized volumetric bone mineral density (H.Tb.BMD), homogenized µFEA-derived strain energy density (H.Tb.SED), and homogenized inter-trabecular distances (H.Tb.1/N) were generated; as well as surface-based maps of apparent cortical bone thickness (Surf.app.Ct.Th), porosity-weighted cortical bone thickness (Surf.Ct.SIT), mean cortical BMD (Surf.Ct.BMD), and mean cortical SED (Surf.Ct.SED). Anatomical correspondences across the parametric maps in the study were established via spatial normalization to a common template. Mean values of the parametric maps before spatial normalization were used to assess compartmental Spearman's rank partial correlations of bone parameters (e.g., between H.Tb.BMD and L.Tb.BV/TV or between Surf.Ct.BMD and Surf.app.Ct.Th). Spearman's rank partial correlations were also assessed for each voxel and vertex of the spatially normalized parametric maps, thus generating maps of Spearman's rank partial correlation coefficients. Correlations were performed independently within each group, and compared between groups using the Fisher's Z transformation. Results: All within-group global trabecular and cortical Spearman's rank partial correlations were significant; and the correlations of H.Tb.BMD-L.Tb.BV/TV, H.Tb.BMD-H.Tb.1/N, L.Tb.BV/TV-H.Tb.1/N, Surf.Ct.BMD-Surf.Ct.SED and Surf.Ct.SIT-Surf.Ct.SED were significantly different between controls and fracture cases. The spatial analyses revealed significant heterogeneous voxel- and surface-based correlation coefficient maps across the distal radius for both groups; and the correlation maps of H.Tb.BMD-L.Tb.BV/TV, H.Tb.BMD-H.Tb.1/N, L.Tb.BV/TV-H.Tb.1/N, H.Tb.1/N-H.Tb.SED and Surf.app.Ct.Th - Surf.Ct.SIT yielded small clusters of significant correlation differences between groups. Discussion: The heterogeneous spatial distribution of interrelationships of bone parameters assessing density, microstructure, geometry and biomechanics, along with their global and local differences between controls and fracture cases, may help us further understand different bone mechanisms of bone fracture.

Carpal Fractures Other than Scaphoid in the Athlete.

Carpal fractures of bones other than the scaphoid occur at a much lower rate than scaphoid fractures. The close relationship between the carpus, intrinsic and extrinsic wrist ligaments, and wrist kinematics makes a thorough history, clinical examination, and interpretation of imaging for carpal malalignment essential. Carpal malalignment should be addressed with reduction and fixation. Nondisplaced fractures are often treated nonoperatively and displaced intraarticular fractures are almost always treatment operatively. The physician should keep in mind the athlete's specific goals and needs. Treatment must be individualized. Options for early return to play should be discussed when possible.

Wrist kinetics after scaphoidectomy.

BACKGROUND: The scaphoid cannot be excised without generating substantial carpal dysfunction. The extent and nature of such a destabilizing procedure, however, has never been properly studied in the laboratory. METHODS: We used a six-degrees-of-freedom motion tracking device to quantify the changes in carpal alignment produced by isometric simultaneous loading of five wrist motor tendons in 12 fresh normal cadaver arms, before and after excising the entire scaphoid. FINDINGS: In the intact wrist, tendon loading consistently extended and supinated the capitate while flexing the triquetrum. After scaphoidectomy, the opposite rotations were always found: the capitate collapsed into flexion and pronation, whereas the triquetrum migrated proximally, while extending and radial deviating. All these changes were statistically significant. INTERPRETATION: Unless it is supplemented by some sort of midcarpal stabilization, scaphoidectomy alone is much too aggressive as a procedure to be considered a treatment option for wrist osteoarthritis. LEVEL OF EVIDENCE: Laboratory study. Not applicable.

Does Wrist Laxity Influence Three-Dimensional Carpal Bone Motion?

Previous two-dimensional (2D) studies have shown that there is a spectrum of carpal mechanics that varies between row-type motion and column-type motion as a function of wrist laxity. More recent three-dimensional (3D) studies have suggested instead that carpal bone motion is consistent across individuals. The purpose of this study was to use 3D methods to determine whether carpal kinematics differ between stiffer wrists and wrists with higher laxity. Wrist laxity was quantified using a goniometer in ten subjects by measuring passive wrist flexion-extension (FE) range of motion (ROM). In vivo kinematics of subjects' scaphoid and lunate with respect to the radius were computed from computed tomography (CT) volume images in wrist radial and ulnar deviation positions. Scaphoid and lunate motion was defined as "column-type" if the bones flexed and extended during wrist radial-ulnar deviation (RUD), and "row-type" if the bones radial-ulnar deviated during wrist RUD. We found that through wrist RUD, the scaphoid primarily flexed and extended, but the scaphoids of subjects with decreased laxity had a larger component of RUD (R2 = 0.48, P < 0.05). We also determined that the posture of the scaphoid in the neutral wrist position predicts wrist radial deviation (RD) ROM (R2 = 0.46, P < 0.05). These results suggest that ligament laxity plays a role in affecting carpal bone motion of the proximal row throughout radial and ulnar deviation motions; however, other factors such as bone position may also affect motion. By developing a better understanding of normal carpal kinematics and how they are affected, this will help physicians provide patient-specific approaches to different wrist pathologies.

Prevalence of Os Styloideum in National Hockey League Players.

BACKGROUND: Os styloideum describes an accessory carpal ossicle between the trapezoid, the capitate, and the second and third metacarpals. Injuries to this tissue have been described as part of the carpal boss syndrome. While the etiology of os styloideum remains uncertain, it may represent a physiologic response to altered loading forces in the wrist, similar to the development of cam-type deformity in the hips of ice hockey players or the Bennett lesion in the shoulders of baseball pitchers. HYPOTHESIS: Professional hockey players will have a higher prevalence of os styloideum compared with the general population. STUDY DESIGN: Case series. LEVEL OF EVIDENCE: Level 4. METHODS: A retrospective review of 16 professional hockey players from 4 different National Hockey League (NHL) teams who underwent unilateral imaging of the wrist was performed. Seventeen wrists were reviewed for the presence of os styloideum. RESULTS: Thirteen of 16 players (81%) had an os styloideum, representing an increased prevalence compared with the general population. Previous clinical and cadaveric studies estimated a general prevalence of up to 19% ( P < 0.001). For the 10 players who had their leading wrist scanned, 9 had an os styloideum (90%). Ten of 11 (91%) players demonstrated a bone marrow edema pattern within the metacarpal and the os styloideum on magnetic resonance imaging. There was no significant association between the presence of an os styloideum and the player's position, leading wrist, or years in the league. CONCLUSION: There appears to be an increased prevalence of os styloideum among NHL players, and team physicians should consider this finding while formulating a differential diagnosis for dorsal wrist pain. CLINICAL RELEVANCE: This study identified NHL players as having an increased prevalence of os styloideum compared with the general population. By doing so, these findings represent an opportunity to enhance our understanding of the etiology, clinical significance, and treatment of os styloideum.

A point mutation in Fgf9 impedes joint interzone formation leading to multiple synostoses syndrome.

Human multiple synostoses syndrome (SYNS) is an autosomal dominant disorder characterized by multiple joint fusions. We previously identified a point mutation (S99N) in FGF9 that causes human SYNS3. However, the physiological function of FGF9 during joint development and comprehensive molecular portraits of SYNS3 remain elusive. Here, we report that mice harboring the S99N mutation in Fgf9 develop the curly tail phenotype and partially or fully fused caudal vertebrae and limb joints, which mimic the major phenotypes of SYNS3 patients. Further study reveals that the S99N mutation in Fgf9 disrupts joint interzone formation by affecting the chondrogenic differentiation of mesenchymal cells at the early stage of joint development. Consistently, the limb bud micromass culture (LBMMC) assay shows that Fgf9 inhibits mesenchymal cell differentiation into chondrocytes by downregulating the expression of Sox6 and Sox9. However, the mutant protein does not exhibit the same inhibitory effect. We also show that Fgf9 is required for normal expression of Gdf5 in the prospective elbow and knee joints through its activation of Gdf5 promoter activity. Signal transduction assays indicate that the S99N mutation diminishes FGF signaling in developmental limb joints. Finally, we demonstrate that the conformational change in FGF9 resulting from the S99N mutation disrupts FGF9/FGFR/heparin interaction, which impedes FGF signaling in developmental joints. Taken together, we conclude that the S99N mutation in Fgf9 causes SYNS3 via the disturbance of joint interzone formation. These results further implicate the crucial role of Fgf9 during embryonic joint development.

Changes in carpal tunnel compliance with incremental flexor retinaculum release.

BACKGROUND: Flexor retinaculum transection is a routine surgical treatment for carpal tunnel syndrome, yet the biomechanical and clinical sequelae of the procedure remain unclear. We investigated the effects of flexor retinaculum release on carpal tunnel structural compliance using cadaveric hands. METHODS: The flexor retinaculum was incrementally and sequentially released with transections of 25, 50, 75, and 100 % of the transverse carpal ligament, followed by the distal aponeurosis and then the antebrachial fascia. Paired outward 10 N forces were applied to the insertion sites of the transverse carpal ligament at the distal (hamate-trapezium) and proximal (pisiform-scaphoid) levels of the carpal tunnel. Carpal tunnel compliance was defined as the change in carpal arch width normalized to the constant 10 N force. RESULTS: With the flexor retinaculum intact, carpal tunnel compliance at the proximal level, 0.696 ± 0.128 mm/N, was 13.6 times greater than that at the distal level, 0.056 ± 0.020 mm/N. Complete release of the transverse carpal ligament was required to achieve a significant gain in compliance at the distal level (p < 0.05). Subsequent release of the distal aponeurosis resulted in an appreciable additional increase in compliance (43.0 %, p = 0.052) at the distal level, but a minimal increase (1.7 %, p = 0.987) at the proximal level. Complete flexor retinaculum release provided a significant gain in compliance relative to transverse carpal ligament release alone at both proximal and distal levels (p < 0.05). CONCLUSIONS: Overall, complete flexor retinaculum release increased proximal compliance by 52 % and distal compliance by 332 %. The increase in carpal tunnel compliance with complete flexor retinaculum release helps explain the benefit of carpal tunnel release surgery for patients with carpal tunnel syndrome.

Factors associated with improved outcomes following proximal row carpectomy: a long-term outcome study of 144 patients.

UNLABELLED: We conducted a review of 144 consecutive patients who underwent proximal row carpectomy from 1967 to 2010 for the diagnosis of wrist arthritis. At a mean follow-up of 13.4 years, patients experienced good pain relief with preservation (but not improvement) of wrist motion. A total of 17 patients (12%) required revision surgery at an average of 44.6 months. Improved pain, function, and survival outcomes were seen in those who underwent proximal row carpectomy after the age of 40, had a preoperative diagnosis of Kienbock's disease, who underwent a concomitant neurectomy procedure, patients who were non-labourers, and patients who underwent surgery after 1990. Although 45% of patients developed moderate to severe radiocapitate arthrosis postoperatively, these findings did not correlate with clinical outcomes or risk of revision surgery. Patients with type II lunate and type II and III capitate shapes had higher rates of postoperative radiocapitate arthrosis. LEVEL OF EVIDENCE: III, Prognostic.

[RESEARCH PROGRESS OF BIOMECHANICS OF PROXIMAL ROW CARPAL INSTABILITY].

OBJECTIVE: To review the research progress of the biomechanics of proximal row carpal instability (IPRC). METHODS: The related literature concerning IPRC was extensively reviewed. The biomechanical mechanism of the surrounding soft tissue in maintaining the stability of the proximal row carpal (PRC) was analyzed, and the methods to repair or reconstruct the stability and function of the PRC were summarized from two aspects including basic biomechanics and clinical biomechanics. RESULTS: The muscles and ligaments of the PRC are critical to its stability. Most scholars have reached a consensus about biomechanical mechanism of the PRC, but there are still controversial conclusions on the biomechanics mechanism of the surrounding soft tissue to stability of distal radioulnar joint when the triangular fibrocartilage complex are damaged and the biomechanics mechanism of the scapholunate ligament. At present, there is no unified standard about the methods to repair or reconstruct the stability and function of the PRC. So, it is difficult for clinical practice. CONCLUSION: Some strides have been made in the basic biomechanical study on muscle and ligament and clinical biomechanical study on the methods to repair or reconstruct the stability and function of PRC, but it will be needed to further study the morphology of carpal articular surface and the adjacent articular surface, the pressure of distal carpals to proximal carpal and so on.

The Effect of Midcarpal Versus Total Wrist Fusion on the Hand's Load Distribution During Gripping.

PURPOSE: To analyze the total grip force and load distribution of the hand with midcarpal fusion (MCF) and total wrist fusion (TWF). METHODS: Twelve patients with unilateral TWF and 12 patients with unilateral MCF were assessed at an average 64 months (range, 19-100 months) postoperatively. The total grip force and load distribution of both hands were measured by the Manugraphy system using 3 cylinder sizes. The load applied to 7 anatomical areas of the hand during cylinder grip was analyzed, comparing the operated and the nonsurgical hands. RESULTS: For the 100 mm and 150 mm cylinders, a significantly lower total grip force was found in hands operated with either TWF or MCF. For the 200 mm cylinder, there was a significant difference between nonsurgical hands and those with MCF but not between nonsurgical hands and those with TWF. For the 100 mm cylinder, the difference between nonsurgical and operated hands was greater in hands with TWF than those with MCF. For the load distribution of the hand, no differences between the operated and the nonsurgical hand were found for either MCF or TWF. CONCLUSIONS: MFC and TWF resulted in a reduced cylinder grip force. With respect to the load distribution, neither procedure influenced the relative contribution that each area of the hand produced during cylinder grip. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic III.

Carpal Ligament Injuries, Pathomechanics, and Classification.

Carpal instability is a complex array of maladaptive and posttraumatic conditions that lead to the inability of the wrist to maintain anatomic relationships under normal loads. Many different classification schemes have evolved to explain the mechanistic evolution and pathophysiology of carpal instability, including 2 of the most common malalignment patterns: volar intercalated segment instability and the more common dorsal intercalated segment instability. Recent classifications emphasize the relationships within and between the rows of carpal bones. Future research is likely to unify the disparate paradigms used to describe wrist instability.

Midcarpal Instability: A Comprehensive Review and Update.

Midcarpal instability has been well described as a clinical entity but the pathokinematics and pathologic anatomy continue to be poorly understood. This article presents a comprehensive review of the existing knowledge and literature-based evidence for the diagnosis and management of the various entities comprising midcarpal instability. It discusses the limitations of the current understanding of midcarpal instability and proposes new directions for furthering knowledge of the causes and treatment of midcarpal instability and wrist pathomechanics in general.

Application of a three-dimensional computational wrist model to proximal row carpectomy.

A three-dimensional (3D) computational model of the wrist examined the biomechanical effects of the proximal row carpectomy (PRC), a surgical treatment of certain wrist degenerative conditions but with functional consequences. Model simulations, replicating the 3D bony anatomy, soft tissue restraints, muscle loading, and applied perturbations, demonstrated quantitatively accurate responses for the decreased motions subsequent to the surgical procedure. It also yielded some knowledge of alterations in radiocarpal contact force which likely increase contact pressure as well as additional insight into the importance of the triangular fibrocartilage complex and retinacular/capsular structures for stabilizing the deficient wrist. As better understanding of the wrist joint is achieved, this model could serve as a useful clinical tool.

Wrist osteoarthritis.

Painful wrist osteoarthritis can result in major functional impairment. Most cases are related to posttraumatic sequel, metabolic arthropathies, or inflammatory joint disease, although wrist osteoarthritis occurs as an idiopathic condition in a small minority of cases. Surgery is indicated only when conservative treatment fails. The main objective is to ensure pain relief while restoring strength. Motion-preserving procedures are usually preferred, although residual wrist mobility is not crucial to good function. The vast array of available surgical techniques includes excisional arthroplasty, limited and total fusion, total wrist denervation, partial and total arthroplasty, and rib-cartilage graft implantation. Surgical decisions rest on the cause and extent of the degenerative wrist lesions, degree of residual mobility, and patient's wishes and functional demand. Proximal row carpectomy and four-corner fusion with scaphoid bone excision are the most widely used surgical procedures for stage II wrist osteoarthritis secondary to scapho-lunate advanced collapse (SLAC) or scaphoid non-union advanced collapse (SNAC) wrist. Proximal row carpectomy is not indicated in patients with stage III disease. Total wrist denervation is a satisfactory treatment option in patients of any age who have good range of motion and low functional demands; furthermore, the low morbidity associated with this procedure makes it a good option for elderly patients regardless of their range of motion. Total wrist fusion can be used not only as a revision procedure, but also as the primary surgical treatment in heavy manual labourers with wrist stiffness or generalised wrist-joint involvement. The role for pyrocarbon implants, rib-cartilage graft implantation, and total wrist arthroplasty remains to be determined, given the short follow-ups in available studies.

A method for carpal motion hysteresis quantification in 4-dimensional imaging of the wrist.

INTRODUCTION: Carpal bones motions exhibit hysteresis that is dependent on the direction of wrist motion, which can be seen during 4-dimensional (3D plus time) imaging of the wrist. In vitro studies have demonstrated the phenomenon of carpal hysteresis and have reported that hysteresis area increases with carpal instabilities. However, their techniques required implantation of bone markers and thus cannot be used clinically. The objective of this study is to use noninvasive 4-dimensional computed tomography (4 DCT) technique to quantify carpal hysteresis, and to determine the reliability of this method. METHOD: A cadaveric wrist mounted on a custom motion simulator was imaged using a dual-source CT scanner while undergoing periodic radioulnar deviation. Ten image phases of this motion was reconstructed through retrospective cardiac gating. The rotational angles of scaphoid, lunate and triquetrum in each phase were derived through manual registration using Matlab after segmenting the bones in Analyze 8.1. These angles were then plotted against global wrist positional angles to produce the hysteresis curves and the area was calculated. The image segmentation and measurements were repeated by 2 raters to derive intra- and inter-rater reliability assessments. RESULTS: The hysteresis area was found to be larger in the lunate (96.5 deg(2)) followed by triquetrum (92.3 deg(2)) and scaphoid (67.5 deg(2)). The measurement of the total hysteresis area of the scaphoid had the highest reliability with intra- and inter-rater reliability of 95.5% and 95.4% respectively. DISCUSSION: We have demonstrated that our approach of using 4 DCT imaging can be used to assess and quantify the hysteresis of the carpal motion with good reliability.

Finite element simulation of the mechanical impact of computer work on the carpal tunnel syndrome.

Carpal tunnel syndrome (CTS) is a clinical disorder resulting from the compression of the median nerve. The available evidence regarding the association between computer use and CTS is controversial. There is some evidence that computer mouse or keyboard work, or both are associated with the development of CTS. Despite the availability of pressure measurements in the carpal tunnel during computer work (exposure to keyboard or mouse) there are no available data to support a direct effect of the increased intracarpal canal pressure on the median nerve. This study presents an attempt to simulate the direct effects of computer work on the whole carpal area section using finite element analysis. A finite element mesh was produced from computerized tomography scans of the carpal area, involving all tissues present in the carpal tunnel. Two loading scenarios were applied on these models based on biomechanical data measured during computer work. It was found that mouse work can produce large deformation fields on the median nerve region. Also, the high stressing effect of the carpal ligament was verified. Keyboard work produced considerable and heterogeneous elongations along the longitudinal axis of the median nerve. Our study provides evidence that increased intracarpal canal pressures caused by awkward wrist postures imposed during computer work were associated directly with deformation of the median nerve. Despite the limitations of the present study the findings could be considered as a contribution to the understanding of the development of CTS due to exposure to computer work.

CT-based three-dimensional kinematic comparison of dart-throwing motion between wrists with malunited distal radius and contralateral normal wrists.

AIM: To compare motion of the capitate, scaphoid, and lunate in wrists with a malunited distal radius and contralateral normal wrists during dart-throwing motion (DTM) by three-dimensional kinematic studies using computed tomography (CT) images. MATERIALS AND METHODS: CT was performed simultaneously on both wrists in six patients with a unilateral distal radius malunion at three stepwise positions simulating DTM. Using volume registration technique, the kinematic variables of helical axis motion of the capitate, scaphoid, and lunate were calculated and compared between both wrists. The helical motion of the capitate was also evaluated in a scaphoid- and lunate-based coordinate system. RESULTS: Among the average rotation and translation of the scaphoid, lunate, and capitate during DTM, only the average rotation of the capitate was significantly different between the uninjured (88.9°) and the injured (70°) wrist (p = 0.0075). Rotation of the capitate relative to the scaphoid (26.3° versus 37.8°, p = 0.029) or lunate (39.2° versus 59.3°, p = 0.028) was smaller in the malunited wrist. The centres of helical axis motion of the three carpal bones were located more dorsally and radially in the injured wrist. CONCLUSIONS: The present study showed that decreased DTM in wrists with a distal radius malunion resulted from decreased midcarpal motion. The present study of the capitate, scaphoid, and lunate in wrists with distal radius malunion might be the first to present a 3D kinematic analysis of the effect of distal radius malunion on the carpal bones.

The identification of MAFB mutations in eight patients with multicentric carpo-tarsal osteolysis supports genetic homogeneity but clinical variability.

Multicentric carpo-tarsal osteolysis (MCTO) with or without nephropathy is a rare osteolysis disorder beginning in early childhood and involving mainly carpal and tarsal bones. Renal disease appears later in life in the majority of cases and evolves quickly to end stage renal failure. Autosomal dominant (AD) inheritance has been demonstrated, with a high frequency of sporadic cases. Recently, mutations in a highly conserved region of the MAFB gene (v-maf musculoaponeurotic fibrosarcoma oncogene ortholog B) have been identified in MCTO patients by exome sequencing. MafB, known as a regulator of various developmental processes, is essential for osteoclastogenesis and renal development. We report here the molecular screening of MAFB in eight MCTO patients from six families. We identified MAFB mutations in all, including three novel missense mutations clustering within the hot spot mutation region. Among the eight patients, six only presented renal disease. Our report confirms the genetic homogeneity of MCTO and provides data underlying the clinical variability of this disorder.