Osseous and ligamentous scaphoid anatomy: Part I. A systematic literature review highlighting controversies

The "Standing Peanut" Scaphoid View: A Semi-supinated Radiographic View for Intraoperative Evaluation of Screw Placement in Scaphoid Waist Fractures

Scaphoid waist fractures are the most common fracture of the scaphoid. Operative management is indicated with unstable fractures and often for nondisplaced waist fractures to decrease time to union and return to work/sport. Screw placement within the central axis of the scaphoid is paramount and correlates with outcomes. Assessment of intrascaphoid screw placement is classically done via intraoperative fluoroscopy. An additional fluoroscopic view is presented to assist in confirming implant positioning. Along with the standard anterioposterior, lateral, pronated oblique, and "scaphoid" view we obtain a "standing peanut" view for assessment of central screw placement. This view also allows for further evaluation of center/center positioning and better assessment of fixation crossing the fracture into the proximal pole. The "standing peanut" view is best obtained in a sequential manner beginning with the forearm in neutral rotation. First, the forearm is then supinated 30 degrees; next, the wrist is placed at 45 degrees of ulnar deviation. Then finally, 10 degrees of wrist extension. We utilize this additional intraoperative view in conjunction with the standard fluoroscopic views for assessing and ensuring center-center implant positioning, particularly within the proximal pole. When ensuring center-center positioning, we prefer this view as an adjunct view to the standard fluoroscopic views intraoperatively. It provides a beneficial view of the proximal pole delineating the number of screw threads that have obtained proximal pole purchase. We have found it particularly useful in the setting of scaphoid waist fracture nonunion with the classic 'humpback' deformity after correction with volar interposition grafting. Standard radiographic views may be misinterpreted regarding implant positioning if there remains any residual flexion. The view requires little in the way of training to obtain once appreciated and exposes the patient to minimal additional radiation.

The Lateral-W Construct: An Anatomical Variant of the Dorsal Wrist Ligaments

Background  The dorsal intercarpal ligament (DIC) is an elegant dorsal stabilizer of the proximal carpal row, including the scaphoid's proximal pole and scapholunate joint. Along with the dorsal radiocarpal (DRC) ligament, it acts as a dorsal radioscaphoid stabilizer, with dynamism due to its ability to modify its length up to threefold by changing the angles between its V-shaped bundle morphology. The DIC ligament consistently originates from the dorsal tubercle of the triquetrum on the ulnar side. It spans transversely, attaching to the dorsal groove of the scaphoid (97-100%), lunate (75-90%), and proximal rim of the trapezium (12.5-50%), and overlapping the lunotriquetral interosseous ligament and the scapholunate interosseous ligament. Together with the DRC, Viegas et al (Viegas SF, Yamaguchi S, Boyd NL, Patterson RM. The dorsal ligaments of the wrist: anatomy, mechanical properties, and function. J Hand Surg Am 1999;24(3):456-468) proposed that this ligament complex should be called the "lateral-V construct." Anatomical Variant  The authors present a unique type C variant of the DIC ligament, showing a distinct thick bundle directed at the dorsal aspect of the second metacarpal base that thus creates a "lateral-W construct." This dorsal triquetro-metacarpal 2 (dTqMC2) ligament acts as restraint to the body of the capitate and will provide enhanced stability of the dorsal midcarpal joint by limiting dorsal translation of the capitate in relation to the lunate. Clinical Relevance  Our finding may contribute to the increasing knowledge of the dorsal ligament complex and its role in dorsal midcarpal instability, as well as surgical repair techniques.

Scaphoid Length Loss Following Nonunion Is Associated with Dorsal Intercalated Segment Instability

Background  Dorsal intercalated segment instability (DISI) in scaphoid nonunions is frequently attributed to fracture location relative to ligamentous attachments onto the scaphoid apex. We hypothesize scaphoid length loss to have a stronger correlation with DISI deformity than fracture location in patients with scaphoid nonunion. Questions/Purposes  To investigate the correlation between (1) scaphoid length loss, (2) fracture location relative to the scaphoid apex, and (3) type of nonunion (Herbert classification) and DISI deformity in skeletally mature patients with scaphoid nonunion. Patients and Methods  Twenty-seven cases of computed tomography (CT)-confirmed scaphoid nonunion (>6 months) were retrospectively included. Our primary outcome was the degree of DISI as measured by the radiolunate (RL) angle on CT. Scaphoid length loss was expressed as height-to-length (H/L) ratio. Fracture location was classified as proximal or distal to the scaphoid apex. Nonunions were classified as fibrous unions (type D1) or pseudoarthrosis (type D2). The correlation between RL angle, H/L ratio, fracture location, and nonunion type was evaluated. Results  H/L ratio was the only factor associated with the degree of DISI as measured by RL angle. As scaphoid length loss increased (increasing H/L ratio), the RL angle increased. There was no significant difference in RL angle between fractures located proximal (30 degrees) or distal (28 degrees) to the scaphoid apex, or type D1 (31 degrees) versus type D2 (28 degrees) nonunions. There was no correlation between patient age, sex, or wrist side affected and RL angle. Conclusions  Scaphoid length loss, rather than fracture location, is correlated to the degree of DISI deformity in patients with scaphoid nonunion. This highlights the importance of restoring scaphoid height when planning scaphoid nonunion reconstruction. Level of Evidence  Level III, diagnostic study.

Postoperative Immobilization of Scaphoid Fractures: A Comprehensive Review of the Literature

The optimal protocol for postoperative immobilization following operative treatment of scaphoid fractures remains controversial. Reports of successful management with brief postoperative immobilization suggest that earlier restoration of function may be achieved by limiting the duration of immobilization. However, the risk of nonunion and its associated complications suggest that a more conservative approach with extended immobilization could optimize fracture healing. This paper presents a thorough review of the relevant literature and summarizes the myriad postoperative immobilization protocols and their reported outcomes. Postoperative immobilization protocols and reported outcomes for displaced, comminuted, and proximal pole fractures are discussed separately. The literature is reviewed following different operative techniques, including open reduction internal fixation and percutaneous screw fixation. Vigilant postoperative care of scaphoid fractures managed surgically is warranted to monitor for signs of nonunion while attempting to regain motion and strength to the injured wrist.

Wrist Arthritis and Arthrodesis: Preserving Function, Minimizing Problems

Wrist arthritis is a common condition with numerous causes and presentations. Several management options exist, and treatment should be individualized based on patient age, comorbidities, occupation, duration of symptoms, and failed treatment modalities. Arthroscopy and denervation are appealing because of shorter recovery time and preservation of motion, but duration of effectiveness varies between patients. Patients who fail these smaller procedures or those with pancarpal arthrosis are treated effectively with total wrist arthrodesis or total wrist arthroplasty in lower-demand patients. This article reviews causes and patterns of wrist arthritis and discusses treatment strategies aimed at preserving function and minimizing complications.

Fixation Techniques for Scaphoid Nonunion

Scaphoid fractures are common injuries with high risk of nonunion. Various fixation techniques exist for managing scaphoid nonunions, including Kirschner wires, single or dual headless compression screws, combination fixation techniques, volar plating, and compressive staple fixation. The indication for each fixation technique varies depending on the patient, type of nonunion, and clinical scenario.

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.

The Dorsal Ligament Complex: A Cadaveric, Histology, and Imaging Study

PURPOSE

The distinction between the dorsal intercarpal (DIC) and dorsal scaphotriquetral (DST) ligaments is imprecise and unclear in the literature. The purpose of our cadaveric study was to define the origins, insertions, and anatomic relationships of the dorsal wrist ligaments and relate these anatomic findings to magnetic resonance imaging (MRI) scans and histology.

METHODS

The study included 17 unmatched fresh-frozen cadaveric specimens (7 male and 10 female), with a mean age of 67.1 years (range, 48-86 years). Wrists with arthritis or carpal malalignment were excluded. Ligaments were dissected and insertion sites were recorded in the radioulnar (width) and proximodistal (length) dimensions, centered at the midpoints of the insertion. Three cadaveric specimens underwent a histologic analysis to demonstrate ligament composition and insertion sites. Three additional cadavers underwent MRI, from which 3-dimensional models were built to model ligament topography.

RESULTS

The conjoined triquetral insertion of the DIC, DST, and dorsal radiocarpal (DRC) measured 88.5 ± 6.4 mm². In each specimen, there were 2 distinct deep and superficial components of intercarpal fibers. The deep component inserted on the lunate with an area of 59.0 ± 5.0 mm². The deep and superficial components diverged as they coursed radially. The superficial component proceeded to the scaphoid ridge, trapezium, and trapezoid, whereas the deep component inserted on the proximal row. The deep fibers blended distally from their lunate insertion with the DST, forming a robust, 2.9 ± 0.8-mm wide extension over the dorsal capitate. The DRC inserted on the lunate, proximal to the DIC and DST insertions, with an area of 23.9 ± 5.4 mm².

CONCLUSIONS

The dorsal ligament complex forms a firm link across the proximal carpal row and the DST provides extension of the proximal row over the capitate.

CLINICAL RELEVANCE

This information can guide surgeons while performing a dorsal approach to the wrist and repairing traumatic ligament disruption.

Histomorphology of the Subregions of the Scapholunate Interosseous Ligament and Its Enthesis

Background  The scapholunate interosseous ligament (SLIL) has three subregions: dorsal, proximal, and volar. The SLIL enthesis has not previously been studied despite its important mechanical function in wrist joint biomechanics. Questions/Purposes  This study aims to compare the histomorphological differences between the SLIL subregions, including at their entheses. Three questions are explored: Do the gross dimensions differ between SLIL subregions? Does the enthesis qualitatively, and its calcified fibrocartilage (CF) quantitatively, differ between (a) SLIL subregions and (b) scaphoid and lunate attachments? Methods  Twelve fresh-frozen human cadaveric wrists were dissected and the gross dimensions of the SLIL subregions measured. Subregions were histologically processed for morphological and compositional analyses, including quantification of enthesis CF area. Results  The dorsal subregion was the thickest. The dorsal and volar subregions had fibrocartilaginous entheses, while the proximal subregion was attached to articular cartilage. The dorsal subregion had significantly more CF than the volar subregion. There was no significant difference in the enthesis CF between scaphoid and lunate attachments in the three subregions. Conclusions  There are significant morphological differences between the SLIL subregions. The dorsal subregion has the largest amount of CF, which is consistent with the greater biomechanical force subjected to this subregion. The similar histomorphology of the ligament at the scaphoid and lunate entheses suggests that similar biomechanical forces are applied to both attachments. Clinical Relevance  The histomorphological results confirm that the dorsal subregion is the strongest of the three subregions. The results from the entheseal region may have important implications in the study of graft incorporation during SLIL reconstruction.

Management of Proximal Pole Scaphoid Nonunions: A Critical Analysis Review

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Optimal management of nonunions of the proximal pole of the scaphoid is controversial and dependent on many patient and pathophysiologic considerations.

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If the proximal pole subchondral bone support is sufficient, options include open reduction and internal fixation, either alone or in combination with autologous nonvascularized or vascularized bone graft.

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If the proximal pole is not salvageable, replacement with osteochondral autografts or osteochondral flaps is the only option for reconstruction of the native anatomy.

3D computational anatomy of the scaphoid and its waist for use in fracture treatment

BACKGROUND

A detailed understanding of scaphoid anatomy helps anatomic fracture reduction, and optimal screw position. Therefore, we analysed (1) the size and shape variations of the cartilage and osseous surface, (2) the distribution of volumetric bone mineral density (vBMD) and (3) if the vBMD values differ between a peripheral and a central screw pathway?

METHODS

Forty-three fresh frozen hand specimens (17 females, 26 males) were analysed with high-resolution peripheral quantitative computed tomography (HR-pQCT) and dissected to compute a 3D-statistical osseous and cartilage surface model and a 3D-averaged vBMD model of the scaphoid. 3D patterns were analysed using principal component analysis (PCA). vBMD was analysed via averaging HR-pQCT grey values and virtual bone probing along a central and peripheral pathway.

RESULTS

(1) PCA displayed most notable variation in length ranging from 1.7 cm (- 2SD) to 2.6 cm (mean) and 3.7 cm (+ 2SD) associated with differences of the width and configuration of the dorsal surface (curved and narrow (4 mm) to a wider width (9 mm)). (2) High vBMD was located in the peripheral zone. Lowest vBMD was observed in the centre and waist. (3) Virtual probing along a peripheral pathway near to the cartilage surfaces for the capitate and lunate allowed the center region to be bypassed, resulting in increased vBMD compared to a central pathway.

CONCLUSION

High anatomical variations regarding the osseous and cartilage surfaces were associated with three distinct concentrically arranged zones with notable different vBMD. The complex scaphoid anatomy with its waist might alter the strategy of fracture fixation, education and research.

Current Techniques in Scapholunate Ligament Reconstruction

Scapholunate ligament injuries are common and can lead to a predictable pattern of arthritis (scaphoid lunate advanced collapse wrist) if unrecognized or untreated. This article describes the relevant anatomy, biomechanics, and classification system, and provides an up-to-date literature-based review of treatment options, including acute repair and various reconstruction techniques. It also helps guide surgeons in making decisions regarding a systematic treatment algorithm for these injuries.

The Vascular Anatomy of the Scaphoid: New Discoveries Using Micro-Computed Tomography Imaging

PURPOSE

The purpose of this study was to investigate the intraosseous vascular anatomy of the scaphoid using recent advances in micro-computed tomography (micro-CT) imaging and 3-dimensional reconstruction. We also studied the effect of scaphoid shape and screw position on the intraosseous vascular structure.

METHODS

Thirteen upper extremities were injected with a contrast agent. The scaphoid bones were extracted and scanned using a micro-CT scanner. The vascular impact of screw insertion at various axes through the scaphoid was calculated and compared using the generated 3-dimensional models. The specimens were 3-dimensionally-printed and the morphology was assessed according to bone dimensions. A relationship between the internal vascular patterns and these morphological features was determined.

RESULTS

All specimens received vascular inflow from the dorsal ridge forming a vascular network that supplied an average of 83% of the bone's volume. This network was supplemented in 4 specimens with volar vessels entering at the waist. Another network was identified, created by vessels entering volarly at the tubercle, which supplied the remainder of the scaphoid. One specimen did not receive any vessels at the tubercle. With regards to screw placement, screws placed in the central axis were the least disruptive to the internal vascularity, followed by the antegrade (dorsal) insertion axis. Two morphological bone types were identified: type I or full scaphoids and type II or slender scaphoids. Type I possessed a more robust internal vascular network than type II scaphoids.

CONCLUSIONS

This study identifies 2 distinct types of scaphoid morphology with 1 of them having a less robust blood supply, which may prove to be related to development of nonunion, avascular necrosis, or Preiser disease. Central axis and antegrade (dorsal) screw fixation may be least disruptive to the internal blood supply.

CLINICAL RELEVANCE

Safer fixation of the scaphoid bone may be achieved by knowledge of intraosseous vascular patterns.

Role of Ligament Stabilizers of the Proximal Carpal Row in Preventing Dorsal Intercalated Segment Instability: A Cadaveric Study

BACKGROUND

Isolated injuries of the scapholunate interosseous ligament (SLIL) are insufficient to produce dorsal intercalated segment instability. There is no consensus about which additional ligamentous stabilizers are critical determinants of dorsal intercalated segment instability. The aim of this study was to evaluate the role of the long radiolunate (LRL), scaphotrapeziotrapezoid (STT), and dorsal intercarpal (DIC) ligaments in preventing dorsal intercalated segment instability.

METHODS

Thirty fresh-frozen forearms were randomized to 5 ligament section sequences to study the SLIL, LRL, STT, and DIC ligaments. The DIC-lunate insertion (DIC) and scaphoid insertion (DIC) were studied separately; the DIC insertions on the trapezium and triquetrum were left intact. Loaded posteroanterior and lateral fluoroscopic images were obtained at baseline and repeated after each ligament was sectioned. After each sequence, the wrists were loaded cyclically (71 N). The radiolunate angle was measured with load. Dorsal intercalated segment instability was defined as an increase of >15° in the radiolunate angle compared with baseline.

RESULTS

Division of the SLIL did not increase the radiolunate angle. Section of the SLIL+LRL or SLIL+DIC significantly increased the radiolunate angle but did not produce dorsal intercalated segment instability. Section of the SLIL+STT or SLIL+DIC+DIC produced dorsal intercalated segment instability.

CONCLUSIONS

In order to produce dorsal intercalated segment instability, complete scapholunate injuries require the disruption of at least 1 critical ligament stabilizer of the scaphoid or lunate (the STT or DIC+DIC).

CLINICAL RELEVANCE

When treating SLIL tears with dorsal intercalated segment instability, techniques to evaluate the volar and dorsal critical stabilizers of the proximal carpal row should be considered.

Three-dimensional geometric morphometric analysis of the distal radius insertion sites of the palmar radiocarpal ligaments in hominoid primates

OBJECTIVES

To identify anatomic differences in the insertion sites of the palmar radiocarpal ligaments in different species of hominoid primates that may be related to their different types of locomotion.

MATERIALS AND METHODS

We have used three-dimensional geometric morphometrics (3D GM) to analyze the distal radius ligament insertion sites in 31 Homo sapiens, 25 Pan troglodytes, 31 Gorilla gorilla, and 15 Pongo pygmaeus. We have also dissected the radioscaphocapitate (RSC), long radiolunate (LRL) and short radiolunate (SRL) ligaments in six H. sapiens and five P. troglodytes to obtain quantitative values that were then compared with the results of the 3D GM analysis.

RESULTS

H. sapiens had a relatively larger insertion site of the RSC + LRL ligament than the other hominoid primates. P. pygmaeus and P. troglodytes had a relatively large SRL ligament insertion site with a palmar orientation. In G. gorilla, the two ligament insertion sites were relatively smaller and the SRL insertion site had an ulnopalmar orientation.

DISCUSSION

The morphological differences observed can be related to the types of locomotion used by the different species and to quantitative data obtained from the dissection of ligaments in H. sapiens and P. troglodytes. 3D GM analysis of ligament insertion sites can help in interpreting the types of locomotion used by extinct hominoid primates through the analysis of preserved fossilized fragments of the distal radius.

Volar Approach to Percutaneous Fixation of Acute Nondisplaced Fractures of the Scaphoid

Scaphoid fractures typically occur in young, healthy males at the peak of their employment and productivity, and left untreated or inadequately treated will ultimately progress to nonunion and a "predictable" pattern of wrist arthritis and carpal collapse. Nonoperative treatment of these fractures requires prolonged cast immobilization, which can lead to wrist stiffness, loss of grip strength, muscle atrophy, and protracted loss of economic productivity. To prevent these devastating sequelae, percutaneous techniques for scaphoid fixation have been described and popularized; however, these techniques are technically demanding as optimal position of the compression screw is required to achieve bony union. The focus of this paper is to describe the indications, contraindications, and a series of reproducible, practical pearls to achieve ideal percutaneous scaphoid compression screw fixation of scaphoid waist and distal pole fractures.

Management of Scaphoid Fractures

LEARNING OBJECTIVES

After reading this article, the participant should be able to: 1. Understand the epidemiology, classification, and anatomy pertinent to the scaphoid. 2. Appropriately evaluate a patient with suspected scaphoid fracture, including appropriate imaging. 3. Understand the indications for operative treatment of scaphoid fractures, and be familiar with the various surgical approaches. 4. Describe the treatment options for scaphoid nonunion and avascular necrosis of the proximal pole.

SUMMARY

The goal of this continuing medical education module is to present the preoperative assessment and the formation and execution of a surgical treatment plan for acute fractures of the scaphoid. In addition, secondary surgical options for treatment of scaphoid nonunion and avascular necrosis are discussed.

[Anatomy and biomechanics of the scaphoid]

The scaphoid is biomechanically and clinically of great importance for function of the wrist. In the literature, its anatomy and biomechanics are clearly underrepresented as well as underestimated. In the following review the scaphoid will be presented in more detail, according to recent information and findings. Not only will the origin of the name and the history of previous names, such as cotyloid or navicular, be introduced, but also for the first time in medical literature the significant phylogeny and ontogeny of the scaphoid will be shown. Moreover, the clinically very important blood supply, the ligaments of the scaphoid and relevant biomechanical details will be described.

The Anatomy of the Dorsal Capsulo-Scapholunate Septum: A Cadaveric Study

Background  Tears of the dorsal radiocarpal capsule at the level of the scapholunate interosseous ligament (SLIL) have recently been described in association with predynamic scapholunate instability. Purpose  The aim of this anatomical study of the dorsal capsulo-scapholunate septum (DCSS) was to examine the connection of the dorsal capsule on the SLIL and dorsal intercarpal ligament (DICL). Methods  Fourteen fresh frozen wrists from seven adult cadavers were dissected through a dorsal approach. Any dorsal attachment of the DICL on the dorsal surface of the SLIL, that is, the DCSS, was identified and measured (height and width). Results  The DCSS was consistently found connecting the DICL, the dorsal radiocarpal capsule, and the dorsal aspect of the SLIL. It was formed by the confluence of three arches like intersecting ribs in gothic architecture. The mean dimensions of the DCSS were 5.8 mm in height and 4.0 mm in maximum width. Conclusion  The DCSS that connects the SLIL with the dorsal capsule and DICL could be a constant structure of dorsal wrist. Further investigation is required to study the histology of the DCSS and its biomechanical properties in isolation to know whether the DCSS can be considered a secondary stabilizer of the scapholunate ligament complex. Clinical Relevance  A better anatomical knowledge of scapholunate ligament complex could help understand and manage instability of the wrist.

Acute Scaphoid Fractures: A Critical Analysis Review

Nondisplaced scaphoid fractures can be effectively treated nonoperatively, with union rates approaching or, in some series, exceeding the rates attained with operative intervention. The evidence supports equal outcomes when using a short arm or long arm cast for the closed treatment of nondisplaced scaphoid fractures. Also, equivalent outcomes have been demonstrated with or without a thumb spica component to the cast. Operative intervention is the recommended treatment for displaced scaphoid fractures. Advanced imaging should be obtained if clinical suspicion is present for a scaphoid fracture with negative radiographs more than 2 weeks after the injury. In some settings, it may even be more cost-effective to obtain advanced imaging sooner.

Estimating Scaphoid Lengths Using Anatomical Measurements in the Wrist

PURPOSE

In reconstructive surgery of scaphoid nonunions with humpback deformity, some surgeons recommend restoration of the normal scaphoid length whereas others overexpand the normal length to ensure carpal realignment and prevent late collapse. To be able to define overexpansion and investigate which levels of overexpansion yield optimal clinical results, a precise method for estimating the original scaphoid length is required. The purpose of this anatomic study was to investigate the precision of estimating normal scaphoid lengths based on intact adjacent bone dimensions, compared with using the contralateral scaphoid length.

METHODS

From bilateral computed tomographic scans of 28 healthy wrist pairs, 3-dimensional virtual bone models were created. The left and right scaphoid lengths were determined at the central axis. The capitate length at the central axis and the distal radius width served to derive an ipsilateral scaphoid length estimate. Estimation precision for individual cases was based on the 95% range (±1.96 × SD) of the observed differences between the actual and estimated lengths.

RESULTS

On average, the capitate length was 10% smaller than the scaphoid length; the radius width was 9% larger. Consequently, we averaged the capitate length and radius width for ipsilateral estimations. The average difference between the scaphoid length and the latter ipsilateral estimate was 0.1 mm. The average contralateral scaphoid length difference was also 0.1 mm. Estimation precisions, however, were ±2.2 and ±1.4 mm, respectively.

CONCLUSIONS

Scaphoid length estimation based on the contralateral scaphoid is more precise than the estimating scaphoid length using the ipsilateral radius and capitate.

CLINICAL RELEVANCE

Scaphoid overexpansion can be ensured if the restored length is at least 1.4 mm longer than the contralateral length. This may be valuable information when establishing a target length for reconstruction and investigating the consequences of scaphoid overexpansion on clinical function, such as range of motion, which are currently unknown.

Impact of Different Screw Designs on Durability of Fracture Fixation: In Vitro Study with Cyclic Loading of Scaphoid Bones

PURPOSE

The use of new headless compression screws (HCSs) for scaphoid fixation is growing, but the nonunion rate has remained constant. The aim of this study was to compare the stability of fixation resulting from four modern HCSs using a simulated fracture model to determine the optimal screw design(s).

METHODS

We tested 40 fresh-frozen cadaver scaphoids treated with the Acumed Acutrak 2 mini (AA), the KLS Martin HBS2 midi (MH), the Stryker TwinFix (ST) and the Synthes HCS 3.0 with a long thread (SH). The bones with simulated fractures and implanted screws were loaded uniaxially into flexion for 2000 cycles with a constant bending moment of 800 Nmm. The angulation of the fracture fragments was measured continuously. Data were assessed statistically using the univariate ANOVA test and linear regression analysis, and the significance level was set at p < 0.05.

RESULTS

The median angulation of bone fragments φ allowed by each screw was 0.89° for AA, 1.12° for ST, 1.44° for SH and 2.36° for MH. With regards to linear regression, the most reliable curve was achieved by MH, with a coefficient of determination of R2 = 0.827. This was followed by AA (R2 = 0.354), SH (R2 = 0.247) and ST (R2 = 0.019). Data assessed using an adapted ANOVA model showed no statistically significant difference (p = 0.291) between the screws.

CONCLUSIONS

The continuous development of HCSs has resulted in very comparable implants, and thus, at this time, other factors, such as surgeons' experience, ease of handling and price, should be taken into consideration.

Injuries of the Scapholunate Interosseous Ligament: An Update

The scapholunate ligament is both a key ligament in the stability of the carpus and one of the most frequently injured. Thorough understanding of the anatomy, biomechanics, and pathophysiology of the wrist is important in treating injuries to the scapholunate ligament. The presentation of scapholunate instability often includes a vague injury history and pain with grip, wrist extension, and sport or labor. Identified injuries are classified based on dynamic and static radiographic findings, chronicity, and the presence or absence of arthrosis. Surgical options for the treatment of low- and high-grade injuries include both open and arthroscopic procedures and can be broadly classified into four categories: limited arthroscopic procedures, primary ligament repair, reconstructive procedures, and salvage procedures. No strong evidence currently supports any one treatment. Decision making is largely based on expert opinion and surgeon experience. Prognosis is often guarded, and patient expectations should be tempered.

Determination of the Central Axis of the Scaphoid

Purpose Determine the central axis of the scaphoid and its relation to surrounding anatomic landmarks to facilitate internal fixation of the scaphoid. Methods Seventeen cadaveric dissections of the wrist were performed. Measurements of the height and width of the proximal pole, waist, and distal pole were made. The midpoint of the height and width of each measurement were plotted on a scatter plot graph and a forecast line was developed. The formula of the resultant line was used to calculate the position of the central axis at the proximal pole, waist, and distal pole. The inverse tangent of the slope of the line was then used to determine the angle of the line from proximal to distal. Results The average central axis fell along a line measuring at points from the ulnar to the radial border and from the dorsal to the volar border of the proximal pole, waist, and distal pole at 7.86 mm, 7.61 mm, and 7.31 mm respectively; an angle of 13.78 degrees from ulnar to radial and dorsal to volar. The proximal point can be determined by measuring ∼44 mm radially from the ulnar styloid along the watershed line of the radius and 14 mm volar from the dorsal tip of the Lister tubercle. The distal point can be determined by measuring ∼4 mm ulnar from a line extending distally from the volar radial corner, and 7 mm volar from the most dorsal point of the combined surface of the trapezium and triquetrum. No significant difference existed between male and female specimens. Conclusions The central axis of the scaphoid can be described to exist along a line extending from the relative central point of the proximal pole, measured 7.86 mm radial from the scapholunate ligament and 8.31 mm volar of the most dorsal point; through the waist, and extending to the relative central point of the distal pole measured 3.77 mm ulnar of the volar radial corner and 7.36 mm volar of the most dorsal point at an angle directed radially and volarly at 13.78 degrees. Level of Evidence Level III Type of Study Diagnostic/ therapeutic.

Carpal Ligament Anatomy and Biomechanics

A fundamental understanding of the ligamentous anatomy of the wrist is critical for any physician attempting to treat carpal instability. The anatomy of the wrist is complex, not only because of the number of named structures and their geometry but also because of the inconsistencies in describing these ligaments. The complex anatomy of the wrist is described through a review of the carpal ligaments and their effect on normal carpal motion. Mastery of this topic facilitates the physician's understanding of the patterns of instability that are seen clinically.

Appraising the methodological quality of cadaveric studies: validation of the QUACS scale

Although systematic reviews are conducted in the field of anatomical research, no instruments exist for the assessment of study quality. Thus, our objective was to develop a valid tool that reliably assesses the methodological quality of observational cadaveric studies. The QUACS scale (QUality Appraisal for Cadaveric Studies) was developed using an expert consensus process. It consists of a 13-item checklist addressing the design, conduct and report of cadaveric dissection studies. To evaluate inter-rater reliability, a blinded investigator obtained an initial pool of 120 observational cadaveric studies. Sixty-eight of them were selected randomly according to sample size calculations. Three independent researchers rated each publication by means of the QUACS scale. The reliability of the total score was estimated using the intraclass correlation coefficient (ICC). To assess agreement among individual items, margin-free kappa values were calculated. For construct validity, two experts (an anatomist and an experienced physician) categorized the quality of 15 randomly selected studies as 'excellent' (4 points), 'moderate to good' (3 points), poor to moderate' (2 points) or 'poor' (1 point). Kendall's tau rank correlation was used to compare the expert ratings with the scores on the QUACS scale. An evaluation of feasibility was carried out during the reliability analysis. All three raters recorded the duration of quality appraisal for each article. Means were used to describe average time exposure. The ICC for the total score was 0.87 (95% confidence interval: 0.82-0.92; P < 0.0001). For individual items, margin-free kappa values ranged between 0.56 and 0.96 with an agreement of 69-97% among the three raters. Kendall's tau B coefficient of the association between expert ratings and the results obtained with the QUACS scale was 0.69 (P < 0.01). Required rating time per article was 5.4 ± 1.6 min. The QUACS scale is highly reliable and exhibits strong construct validity. Thus, it can confidently be applied in assessing the methodological quality of observational dissection studies.

Evaluation for fracture patterns around the wrist on three-dimensional extremity computed tomography, especially focused on the triquetrum

INTRODUCTION

To describe fracture patterns of triquetrum and analyse them according to fracture classifications, anatomy of intrinsic carpal ligaments and comparison with other wrist fractures.

METHODS

We retrospectively reviewed 297 three-dimensional extremity computed tomographies (CTs) on wrist fractures from October 2007 to January 2012. We initially classified the fractures according to the involved bones and analyzed them according to the patterns of triquetrum fractures, associated carpal bone fractures and presence of combined distal radius fractures. We also correlated the fracture patterns with the patient's injury patterns.

RESULTS

A total of 297 CTs and 291 patients were included (162 males and 129 females; mean age, 47.8 years). There were a total of 131 carpal bone fractures in 102 patients of 102 CTs. Triquetrum fractures were the most commonly observed cases (36 cases/27.5%). For the triquetrum fractures, the following types were observed: 26 dorsal, five volar, two comminuted fractures are observed in triquetrum. Three other triquetrum fractures show combined forms of other carpal bone fractures. For the combined distal radius fractures, 10 dorsal and two volar fractures were shown. Out of 187 distal radius fractures, 20 showed carpal bone fractures (10.7%). There were no differences in injury patterns according to the fracture patterns. The most common pattern of injury was falling on the outstretched hand, followed by fall from height.

CONCLUSION

The dorsum of triquetrum is more frequently fractured than the volar aspect. The number of carpal bone fractures among the patients who have distal radius fractures is higher than usual expectation.

Scaphoid fractures: a higher order analysis of clinical tests and application of clinical reasoning strategies

INTRODUCTION

The purpose of this study was to identify clinical tests for scaphoid fractures and, using a higher order analysis, to determine their diagnostic accuracy.

METHODS

A literature review of the databases CINAHL, Embase, Medline and PUBMED from 1980 to September 30, 2011 was conducted to obtain applicable literature on clinical tests used in identifying scaphoid fractures. Methodological quality was determined using the criteria for validity suggested by Sackett et al (2000). Using a random effects model, pooled positive likelihood ratios (PPLR) were established for any test evaluated in at least 3 published studies. Moderator analyses provided insight into heterogeneity of results.

RESULTS

Higher order analysis indicated that the scaphoid compression test, anatomical snuffbox tenderness and scaphoid tubercle tenderness demonstrated statistically significant ability to identify scaphoid fractures with PPLR of 2.37 (1.27-4.41), 1.52 (1.12-2.06) and 1.67 (1.33-2.09) respectively. Descriptive factors (gender and mechanism of injury) were also identified but did not demonstrate significant diagnostic ability. Pooled data revealed the existence of heterogeneity for the three clinical tests and descriptive factors, which could not be easily explained.

CONCLUSION

Three clinical tests with statistically significant diagnostic validity were identified. In isolation, the clinical significance of each is questionable. Further studies with description of sample characteristics, blinded assessments, and agreement on a reference standard are recommended.

Comparison of two percutaneous volar approaches for screw fixation of scaphoid waist fractures: radiographic and biomechanical study of an osteotomy-simulated model

BACKGROUND

When a surgeon uses a percutaneous volar approach to treat scaphoid waist fractures, central screw placement is complicated by the shape of the scaphoid and by obstruction by the trapezium. In this study, we used radiographs and biomechanical tests to compare the standard volar percutaneous approach with the transtrapezial approach, with regard to central screw placement at the distal pole of the scaphoid.

METHODS

Fourteen matched pairs of cadaveric wrists were randomly assigned to two treatment groups. Under fluoroscopic control, a guidewire was drilled into the scaphoid, either through a transtrapezial approach or through a standard volar approach that avoided the trapezium. Guidewire position was measured in the coronal and sagittal planes. A transverse osteotomy was performed along the scaphoid waist, and this was followed by the insertion of the longest possible cannulated headless bone screw. Each specimen was placed into a fixture with a pneumatically driven plunger resting on the surface of the distal pole. Load was applied by using a load-controlled test protocol in a hydraulic testing machine.

RESULTS

All guidewires were inside the central one-third of the proximal pole. The guidewire positions at the distal pole differed significantly between the transtrapezial and standard volar approach groups (p < 0.001). The load to 2 mm of displacement and the load to failure averaged, respectively, 324.4 N (standard error of the mean [SEM] = 73.5 N) and 386.4 N (SEM = 65.6 N) for the transtrapezial approach group compared with 125.7 N (SEM = 22.6 N) (p = 0.002) and 191.4 N (SEM = 36.30 N) (p = 0.005) for the standard volar approach group.

CONCLUSIONS

The data suggest that, in a cadaveric osteotomy-simulated scaphoid waist fracture model, the transtrapezial approach reliably achieves central positioning of a screw in the proximal and distal poles. This position offers a biomechanical advantage compared with central placement in only the proximal pole.

Skeletal anatomy of the hand

The skeletal anatomy of the hand is composed of phalanges, metacarpal bones, and carpal bones. Its function is a product of the complex interactions between the power provided by the intrinsic and extrinsic musculature, the stability provided by the ligaments, and the structure provided by the bones, which serve as insertion and attachment sites for the muscles and ligaments. This article provides a detailed description of the skeletal anatomy of the human hand.

A proposed method of goniometric measurement of the dart-throwers motion

In recent years, the dart-throwing motion (DTM) has been described in the literature as the movement pattern in the wrist where many functional activities occur. As therapists, we are trained in measuring wrist flexion, extension, radial deviation, and ulnar deviation, but measuring the DTM has not been described. This author describes a method for measuring the DTM in the clinic. -Victoria Priganc, PhD, OTR, CHT, CLT, Practice Forum Editor.

Anatomical Description of the Dorsal Capsulo-Scapholunate Septum (DCSS)-Arthroscopic Staging of Scapholunate Instability after DCSS Sectioning

Background The dorsal capsuloligamentous scapholunate septum (DCSS) is a confluence of the dorsal capsule, the dorsal intercarpal ligament (DIC), and the scapholunate interosseous ligament (SLIOL). It appears to play a role in the stability of the scapholunate articulation. The purpose of this study was to describe the anatomical basis for this structure and to investigate its role in scapholunate instability through sectioning of this structure followed by an arthroscopic and fluoroscopic analysis. Material and Methods In the anatomical part of the study we dissected 3 fresh cadaver wrists to examine the anatomy of the DCSS. In the arthroscopic part of the study we assessed the EWAS grade of SL instability before and after sectioning the DCSS and measured the scapholunate and radiolunate angles fluoroscopically. Results Sectioning the DCSS increased the EWAS grade of SL instability but did not affect the scapholunate gap, the scapholunate angle or radiolunate angle. Conclusion We have demonstrated that there is a distinct structure that is separate from the dorsal capsule, which we have labeled the Dorsal Capsuloligamentous Scapholunate Septum. We believe that the DCSS is a previously unreported secondary stabilizer of the SL joint which may have therapeutic and prognostic implications.

The scaphoid

The scaphoid is vitally important for the proper mechanics of wrist function. Its unique morphology from its boat like shape to its retrograde blood supply can present with challenges in the presence of a fracture. Almost completely covered with articular cartilage, this creates precise surface loading demands and intolerance to bony remodeling. Fracture location compounds risk of malunion and non-union. Scaphoid fractures may significantly impair wrist function and activities of daily living, with both individual and economic consequences.

Osseous and ligamentous scaphoid anatomy: Part II. Evaluation of ligament morphology using three-dimensional anatomical imaging

PURPOSE

There are many controversies in the literature regarding the morphology of the scaphoid ligaments. The aim of this study was to provide a more accurate description by quantitatively describing the 3-dimensional, geometrical aspects of the scaphoid ligaments and their attachments, using cryomicrotome images of cadaveric wrists.

METHODS

Eight fresh-frozen human cadaver wrists were examined with computed tomography (CT) and an imaging cryomicrotome. A series of 2-dimensional cryoimages created a 3-dimensional anatomical data set of each test specimen. Detection of ligaments and their surface areas was performed by manually marking the course and attachment points for each ligament, using dedicated visualization software. The 3-dimensional bone surfaces were segmented from the acquired CT images and incorporated in the 3-dimensional anatomical data set of the same anatomical specimen to facilitate the detection procedure. The results of the morphological parameters and attachment areas of the scaphoid ligaments are described 3-dimensionally.

RESULTS

The mean size of the whole scaphoid surface was 1503 ± 17 mm(2), and the mean size of all ligament attachments on the scaphoid was 131 ± 14 mm(2); thus, ligament attachments consist of 9% ± 0.9% of the total scaphoid surface area. Based on the data, a 3-dimensional representation of the wrist was created to present the scaphoid ligament attachment areas and paths. The dorsal intercarpal ligament had the most individual variability between specimens in attachments.

CONCLUSIONS

The quantitative results were almost completely consistent with the findings of previous reports. The only inconsistency in ligament morphology regarded the scaphocapitate ligament, which in this study was found to be the thickest ligament attached to the scaphoid.

CLINICAL RELEVANCE

The results of this study improve our knowledge of scaphoid ligament anatomy, as they corroborate previous findings. This is important for carpal surgery and will pave the way to a better understanding of the biomechanics involved in destabilization of wrist fractures.