A review of wear debris in thumb base joint implants

AIM

Polymers and metals, such as polyethylene (PE) and cobalt chrome (CoCr), are common materials used in thumb-based joint implants, also known as CMC (Carpometacarpal) arthroplasty. The purpose of this review was to investigate the reported failure modes related to wear debris from these type of materials in CMC implants. The impact of wear debris on clinical outcomes of CMC implants was also examined. Potential adverse wear conditions and inflammatory particle characteristics were also considered.

METHOD

A literature search was performed using PRISMA guidelines and 55 studies were reviewed including 49 cohort studies and 6 case studies. Of the 55 studies, 38/55 (69%) focused on metal-on-polyethylene devices, followed by metal-on-metal (35%), and metal-on-bone (4%).

RESULTS

The summarized data was used to determine the frequency of failure modes potentially related to wear debris from metals and/or polymers. The most commonly reported incidents potentially relating to debris were implant loosening (7.1%), osteolysis (1.2%) and metallosis (0.6%). Interestingly the reported mechanisms behind osteolysis and loosening greatly varied. Inflammatory reactions, while rare, were generally attributed to metallic debris from metal-on-metal devices. Mechanisms of adverse wear conditions included implant malpositioning, over-tensioning, high loading for active patients, third-body debris, and polyethylene wear-through. No specific examination of debris particle characterization was found, pointing to a gap in the literature.

CONCLUSION

This review underscores the types of failure modes associated with wear debris in CMC implants. It was found that failure rates and adverse wear conditions of CMC implants of any design are low and the exact relationship between wear debris and implant incidences, such as osteolysis and loosening remains uncertain. The authors note that further research and specific characterization is required to understand the relationship between debris and implant failure.

Impact of bone and cartilage segmentation from CT and MRI on both bone forearm osteotomy planning

INTRODUCTION

The use of MRI scans for pre-operative surgical planning of forearm osteotomies provides additional information of joint cartilage and soft tissue structures and reduces radiation exposure in comparison with the use of CT scans. In this study, we investigated whether using 3D information obtained from MRI with and without cartilage information leads to a different outcome of pre-operative planning.

METHODS

Bilateral CT and MRI scans of the forearms of 10 adolescent and young adult patients with a unilateral bone deformation were acquired in a prospective study. The bones were segmented from CT and MRI, and cartilage only from MRI. The deformed bones were virtually reconstructed, by registering the joint ends to the healthy contralateral side. An optimal osteotomy plane was determined that minimized the distance between the resulting fragments. This process was performed in threefold: using the CT and MRI bone segmentations, and the MRI cartilage segmentations.

RESULTS

Comparison of bone segmentation from MRI and CT scan resulted in a 0.95 ± 0.02 Dice Similarity Coefficient and 0.42 ± 0.07 mm Mean Absolute Surface Distance. All realignment parameters showed excellent reliability across the different segmentations. However, the mean differences in translational realignment between CT and MRI bone segmentations (4.5 ± 2.1 mm) and between MRI bone and MRI bone and cartilage segmentations (2.8 ± 2.1 mm) were shown to be clinically and statistically significant. A significant positive correlation was found between the translational realignment and the relative amount of cartilage.

CONCLUSION

This study indicates that although bone realignment remained largely similar when using MRI with and without cartilage information compared to using CT, the small differences in segmentation could induce statistically and clinically significant differences in the osteotomy planning. We also showed that endochondral cartilage might be a non-negligible factor when planning osteotomies for young patients.

Corrective Osteotomy in a Patient With Congenital Absence of Pronation Based on Three-Dimensional Statistical Shape Modeling

We present a new indication of a three-dimensional statistical shape model (SSM): a patient with bilateral impaired forearm rotation due to a congenital variance in bone shape. A corrective osteotomy was planned and performed to best match the SSM created by computed tomography (CT) scans of 18 peers. Postoperatively, pronation increased by 70°, and the patient was pain-free. A CT scan showed accurate correction of the deformity and union of all osteotomies. This technique offers opportunities for patients with bilateral nontraumatic osseous forearm pathology.

Reconstruction of the cervical ligament in patients with chronic subtalar instability

PURPOSE

Diagnosis and treatment of subtalar instability (STI) remains complicated and challenging. The purpose of this study was to investigate the outcome of an anatomical reconstruction of the cervical ligament in patients with suspected chronic STI.

METHODS

This prospective study assessed the results of a surgical reconstruction of the cervical ligament using a gracilis tendon graft in a group of 14 patients (16 feet). Diagnosis of STI was performed using a predefined algorithm including clinical signs, MRI and peroperative evaluation. All patients had symptoms of chronic hindfoot instability despite prolonged non-surgical treatment. At final follow-up the outcome was assessed using the Karlsson score, the Foot and Ankle Outcome Score and the American Orthopaedic Foot and Ankle Society score.

RESULTS

After an average follow up of 22.6 months (range, 15-36), all patients reported significant improvement compared to their preoperative symptoms. The mean preoperative Karlsson score improved from 36.4 ± 13.5 (median 37, range 10-55) to a mean postoperative Karlsson score was 89.6 ± 8.5 (median 90, range 72-100) (P < 0.0001). The cervical ligament reconstruction was combined with other procedures in 13 cases: calcaneofibular ligament (CFL) reconstruction (3), CFL and anterior talofibular ligament reconstruction (7), bifurcate ligament reconstruction (3).

CONCLUSION

Anatomical reconstruction of the cervical ligament is a valid technique to treat patients with STI. It is a safe procedure and produces good clinical results with minimal complications. This technique can be considered in more complex cases and can be combined with other procedures according to the specific location of the instability.

LEVEL OF EVIDENCE

Level III.

The different subtalar ligaments show significant differences in their mechanical properties

BACKGROUND

Today, the relative contribution of each ligamentous structure in the stability of the subtalar joint is still unclear. The purpose of this study is to assess the material properties of the different ligamentous structures of the subtalar joint.

METHODS

Eighteen paired fresh-frozen cadaveric feet were used to obtain bone-ligament-bone complexes of the calcaneofibular ligament (CFL), the cervical ligament (CL) and the anterior capsular ligament-interosseous talocalcaneal ligament complex (ACaL-ITCL). The samples were subjected to uniaxial testing to calculate their respective stiffness and failure load.

RESULTS

The stiffness of ACaL-ITCL complex (mean: 150 ± 51 N/mm, 95% confidence interval (CI): 125.0-176.6 N/mm) was significantly higher than both CFL (mean: 55.8 ± 23.0 N/mm, CI: 43.8-67.7 N/mm) and CL (mean: 63.9 ± 38.0 N/mm, CI: 44.4-83.3 N/mm). The failure load of both the ACaL-ITCL complex (mean:382.5 ± 158 N, CI: 304.1-460.8 N) and the CFL (mean:320.4 ± 122.0 N, CI: 257.5-383.2 N) were significantly higher than that of the CL (mean:163.5 ± 58.0 N, CI: 131.3-195.7 N). The injury pattern demonstrated a partial rupture in all CFL and ACaL-ITCL specimens and in 60% of the CL specimens.

CONCLUSION

The CFL, CL and ACaL-ITCL show significant differences in their intrinsic mechanical properties. Both the CFL and CL are more compliant ligaments and seem to be involved in the development of subtalar instability. Based on the material properties, a gracilis tendon graft seems more appropriate than a synthetic ligament to reconstruct a CL or CFL. A partial rupture was the most commonly seen injury pattern in all ligaments. A fibular avulsion of the CFL was only rarely seen. The injury patterns need further investigation as they are important to optimize diagnosis and treatment.

The presence of persistent symptoms 12 months following a first lateral ankle sprain: A systematic review and meta-analysis

BACKGROUND

A lateral ankle sprain (LAS) is the most common musculoskeletal injury in the physically active population. It is uncertain what percentage of these patients develop persisting symptoms including pain, recurrent sprains and subjective instability. This systematic review was conducted to assess the presence and duration of persistent symptoms after a first LAS.

METHODS

A systematic review of the Medline, Web of Sciences, Embase, CINAHL and Pedro databases was performed to identify peer-reviewed articles concerning the occurrence and duration of remaining symptoms after a first LAS. Inclusion criteria focused on selection of patients without previous ankle injuries and study quality. One of the following outcomes had to be described: subjective instability, resprains, remaining symptoms.

RESULTS

In total, 15 studies were included. The occurrence of patients with subjective instability decreased from 37.9% (95%CI [6.0-69.7]) at 3 months to 16.1% (95%CI [7.8-24.3]) at 6 months and 8.1% (95%CI [3.3-13.3]) at 12 months. The occurrence of patients with a recurrent LAS was 15.8% (95%CI [6.3-25.3]) at 12 months. The occurrence of patients with residual pain decreased from 48.6% (95%CI [23.6-73.5]) at 3 months, to 21.5% (95%CI [2.8-40.2]) at 6 months and 6.7% (95%CI [3.2-10.1]) at 12 months.

CONCLUSION

This study offers new insights in the presence of remaining symptoms after a first LAS and the development of chronic ankle instability. Twelve months following an initial LAS, a significant number of patients may still have symptoms. The incidence of subjective instability, and pain, continues to decrease until 12 months post-injury. This new information may suggest that a longer period of non-operative treatment may be warranted before recommending surgical intervention in patients with a first LAS.

Outcomes of 3-D corrective osteotomies for paediatric malunited both-bone forearm fractures

Closed treatment of paediatric diaphyseal forearm fractures carries the risk of re-displacement, which can lead to symptomatic malunions. This is because growth will not correct angulation deformity as it does in metaphyseal fractures. The purpose of this prospective cohort study was to evaluate the outcomes after 3-D-planned corrective osteotomy with patient-specific surgical guides for paediatric malunited forearm fractures causing impaired pro-supination. Our primary outcome measure was the gain in pro-supination at 12 months follow-up. Fifteen patients with a mean age at trauma of 9.6 years and time until osteotomy of 5.9 years were included. Preoperatively, patients displayed a mean pro-supination of 67° corresponding to 44% of the contralateral forearm. At final follow-up, this improved to 128°, achieving 85% of the contralateral side. Multivariate linear regression analysis revealed that predictors of greater functional gain after 3-D corrective osteotomy are severe preoperative impairment in pro-supination, shorter interval until 3-D corrective osteotomy and greater angulation of the radius.Level of evidence: III.

Adaptive local thresholding can enhance the accuracy of HR-pQCT-based trabecular bone morphology assessment

High-resolution peripheral quantitative computed tomography (HR-pQCT) devices can scan extremities at bone microstructural level in vivo and are used mainly in research of bone diseases. Two HR-pQCT scanners are commercially available to date: XtremeCT (first generation) and XtremeCT-II (second generation) from Scanco Medical AG (Switzerland). Recently, we have proposed an adaptive local thresholding (AT) technique and showed that it can improve quantification accuracy of bone microstructural parameters, with visually less sharp cone-beam CT (CBCT) images providing a similar accuracy than XtremeCT. The aim of this study was to evaluate whether the AT segmentation technique could enhance the accuracy of HR-pQCT in quantifying bone microstructural images and to assess whether the agreement between XtremeCT and XtremeCT-II could be improved. Nineteen radii were scanned with three scanners from Scanco Medical AG: (1) XtremeCT at 82 μm, (2) XtremeCT-II at 60.7 μm and (3) the small animal microCT scanner VivaCT40 at 19 μm voxel size. The scans were segmented applying two different methods, once following the manufacturer standard technique (ST), and once by means of AT. Three-dimensional (3D) morphological analysis was performed on the trabecular volume of the segmented images using the manufacturer's standard software to calculate bone volume fraction (BV/TV), trabecular thickness (Tb.Th), separation (Tb.Sp) and number (Tb.N). The average accuracy of XtremeCT improved from R² = 0.76 (ST) to 0.85 (AT) and reached the same level of accuracy as XtremeCT-II with ST (R² = 0.86). The largest improvements were obtained for BV/TV and Tb.Th. For XtremeCT-II, mean accuracy improved slightly from R² = 0.86 (ST) to 0.89 (AT). For both segmentations and both scanners, the standard section was quantified slightly more accurate than the subchondral section. The agreement between the scanners was enhanced from R² = 0.89 (ST) to 0.98 (AT). In conclusion, AT can enhance the accuracy of XtremeCT to quantify distal radius bone microstructural parameters close to XtremeCT-II level and increases the agreement between the two HR-pQCT scanners. High-resolution peripheral quantitative computed tomography, segmentation, bone microstructural parameters.

A calcaneal tunnel for CFL reconstruction should be directed to the posterior inferior medial edge of the calcaneal tuberosity

PURPOSE

Anatomical reconstruction of the calcaneofibular ligament (CFL) is a common technique to treat chronic lateral ankle instability. A bone tunnel is used to fix the graft in the calcaneus. The purpose of this study is to provide some recommendations about tunnel entrance and tunnel direction based on anatomical landmarks.

METHODS

The study consisted of two parts. The first part assessed the lateral tunnel entrance for location and safety. The second part addressed the tunnel direction and safety upon exiting the calcaneum on the medial side. In the first part, 29 specimens were used to locate the anatomical insertion of the CFL based on the intersection of two lines related to the fibular axis and specific landmarks on the lateral malleolus. In the second part, 22 specimens were dissected to determine the position of the neurovascular structures at risk during tunnel drilling. Therefore, a method based on four imaginary squares using external anatomical landmarks was developed.

RESULTS

For the tunnel entrance on the lateral side, the mean distance to the centre of the CFL footprint was 2.8 ± 3.0 mm (0-10.4 mm). The mean distance between both observers was 4.2 ± 3.2 mm (0-10.3 mm). The mean distance to the sural nerve was 1.4 ± 2 mm (0-5.8 mm). The mean distance to the peroneal tendons was 7.3 ± 3.1 mm (1.2-12.4 mm). For the tunnel exit on the medial side, the two anterior squares always contained the neurovascular bundle. A safe zone without important neurovascular structures was found and corresponded to the two posterior squares.

CONCLUSION

Lateral landmarks enabled to locate the CFL footprint. Precautions should be taken to protect the nearby sural nerve. A safe zone on the medial side could be determined to guide safe tunnel direction. A calcaneal tunnel should be directed to the posterior inferior medial edge of the calcaneal tuberosity.

High-Resolution Cone-Beam Computed Tomography is a Fast and Promising Technique to Quantify Bone Microstructure and Mechanics of the Distal Radius

Obtaining high-resolution scans of bones and joints for clinical applications is challenging. HR-pQCT is considered the best technology to acquire high-resolution images of the peripheral skeleton in vivo, but a breakthrough for widespread clinical applications is still lacking. Recently, we showed on trapezia that CBCT is a promising alternative providing a larger FOV at a shorter scanning time. The goals of this study were to evaluate the accuracy of CBCT in quantifying trabecular bone microstructural and predicted mechanical parameters of the distal radius, the most often investigated skeletal site with HR-pQCT, and to compare it with HR-pQCT. Nineteen radii were scanned with four scanners: (1) HR-pQCT (XtremeCT, Scanco Medical AG, @ (voxel size) 82 μm), (2) HR-pQCT (XtremeCT-II, Scanco, @60.7 μm), (3) CBCT (NewTom 5G, Cefla, @75 μm) reconstructed and segmented using in-house developed software and (4) microCT (VivaCT40, Scanco, @19 μm-gold standard). The following parameters were evaluated: predicted stiffness, strength, bone volume fraction (BV/TV) and trabecular thickness (Tb.Th), separation (Tb.Sp) and number (Tb.N). The overall accuracy of CBCT with in-house optimized algorithms in quantifying bone microstructural parameters was comparable (R² = 0.79) to XtremeCT (R² = 0.76) and slightly worse than XtremeCT-II (R² = 0.86) which were both processed with the standard manufacturer's technique. CBCT had higher accuracy for BV/TV and Tb.Th but lower for Tb.Sp and Tb.N compared to XtremeCT. Regarding the mechanical parameters, all scanners had high accuracy (R² [Formula: see text] 0.96). While HR-pQCT is optimized for research, the fast scanning time and good accuracy renders CBCT a promising technique for high-resolution clinical scanning.

The effect of orthoses on the kinematics of the trapeziometacarpal, scaphotrapeziotrapezoidal, and radioscaphoid joints

The in vivo effect of four different types of thumb and thumb-wrist orthoses on the three-dimensional kinematics of the trapeziometacarpal (TMC), scaphotrapeziotrapezoidal (STT) and radioscaphoid joints was quantified using computed tomography (CT). Eighteen healthy female volunteers were recruited. The dominant hand of each subject was scanned in four thumb and wrist positions, each in three conditions: without orthosis, with a thumb orthosis (Push Ortho and immediate fitting, IMF) and with a thumb-wrist orthosis (Ligaflex Manu and IMF). CT images were analyzed and rotations relative to the more proximal bone were expressed in a joint-specific coordinate system. Without orthosis, the largest STT rotations were observed during radioulnar deviation of the wrist and the STT range of motion (ROM) was significantly lower during wrist flexion-extension. All tested orthoses caused a significant reduction of the ROM at each joint compared to free motion. Significant differences in movement reduction were observed between prefabricated and IMF orthoses.The IMF thumb-wrist outperformed the Ligaflex Manu in terms of immobilization of the radioscaphoid joint. In addition, the IMF thumb orthosis immobilized the TMC joint significantly better during thumb abduction and adduction than the Push Ortho. We found that different types of thumb and thumb-wrist orthotics are effective in reducing joint mobility. While this reduction tends to be higher using IMF compared to prefabricated orthoses, this effect is only significant for the radioscaphoid and TMC joint. The finding that thumb movements do not induce large STT rotations suggests that the thumb does not need to be immobilized in case of isolated STT osteoarthritis.

The intrinsic subtalar ligaments have a consistent presence, location and morphology

BACKGROUND

Chronic subtalar instability is a disabling complication after acute ankle sprains. Currently, the literature describing the anatomy of the intrinsic subtalar ligaments is limited and equivocal which causes difficulties in diagnosis and treatment of subtalar instability. The purpose of this study is to assess the anatomical characteristics of the subtalar ligaments and to clarify some points of confusion.

METHODS

In 16 cadaveric feet, the dimensions and locations of the subtalar ankle ligaments were assessed and measured. CT-scans before dissection and after indication of the footprints with radio-opaque paint allowed to generate 3D models and assess the footprint characteristics.

RESULTS

The cervical ligament (CL) had similar dimensions as the lateral ligaments: anterior length 13.9 ± 1.5 mm, posterior length 18.5 ± 2.9 mm, talar width 13.6 ± 2.2 mm, calcaneal width 15.8 ± 3.7 mm. The anterior capsular ligament (ACaL) and interosseous talocalcaneal ligament (ITCL) were found to be smaller structures with consistent dimensions and locations.

CONCLUSION

This study identified consistent characteristics of the intrinsic subtalar ligaments and clarifies the local anatomical situation. The dimensions and footprints of the intrinsic ligaments of the subtalar joint suggest a more important role of the CL and ACaL in the stability of the subtalar joint. The results of this study are relevant to improve diagnostic tools and offer some guidelines when reconstructing the injured ligaments.

Quantification of 3D microstructural parameters of trabecular bone is affected by the analysis software

Over the last decades, the use of high-resolution imaging systems to assess bone microstructural parameters has grown immensely. Yet, no standard defining the quantification of these parameters exists. It has been reported that different voxel size and/or segmentation techniques lead to different results. However, the effect of the evaluation software has not been investigated so far. Therefore, the aim of this study was to compare the bone microstructural parameters obtained with two commonly used commercial software packages, namely IPL (Scanco, Switzerland) and CTan (Bruker, Belgium). We hypothesized that even when starting from the same segmented scans, different software packages will report different results. Nineteen trapezia and nineteen distal radii were scanned at two resolutions (20 μm voxel size with microCT and HR-pQCT 60 μm). The scans were segmented using the scanners' default protocol. The segmented images were analyzed twice, once with IPL and once with CTan, to quantify bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), trabecular number (Tb.N) and specific bone surface (BS/BV). Only small differences between IPL and CTan were found for BV/TV. For Tb.Th, Tb.Sp and BS/BV high correlations (R² ≥ 0.99) were observed between the two software packages, but important relative offsets were observed. For microCT scans, the offsets were relative constant, e.g., around 15% for Tb.Th. However, for the HR-pQCT scans the mean relative offsets ranged over the different bone samples (e.g., for Tb.Th from 14.5% to 19.8%). For Tb.N, poor correlations (0.43 ≤ R² ≤ 0.81) for all tested cases were observed. We conclude that trabecular bone microstructural parameters obtained with IPL and CTan cannot be directly compared except for BV/TV. For Tb.Th, Tb.Sp and BS/BV, correction factors can be determined, but these depend on both the image voxel size and specific anatomic location. The two software packages did not produce consistent data on Tb.N. The development of a universal standard seems desirable.

Does subtalar instability really exist? A systematic review

BACKGROUND

Subtalar joint instability (STI) is considered as a potential source of chronic lateral hindfoot instability. However, clinical diagnosis of STI is still challenging. This systematic review was conducted to assess the consistency of the clinical entity "subtalar instability", to investigate the reliability of available diagnostic tools and to provide a critical overview of related studies.

METHODS

A systematic review of the Medline, Web of Sciences and EMBASE databases was performed for studies reporting on tests to investigate subtalar instability or lesions of the subtalar ligaments. To investigate the relation with chronic STI, studies focusing on sinus tarsi syndrome (STS) or acute lesions of the subtalar ligaments were also included in the search strategy and were assessed separately.

RESULTS

This review identified 25 studies focusing on different topics: chronic STI (16), acute lesions of the subtalar ligaments (5) and STS (4). Twelve studies, assessing STI, demonstrated the existence of a subgroup with instability complaints related to abnormal increased subtalar motion (7) or abnormalities of the subtalar ligaments (6). We found insufficient evidence for measuring subtalar tilting using stress radiographs. MRI was able to assess abnormalities of the ligaments and stress-MRI detected abnormally increased motion.

CONCLUSION

Complaints of instability can be related to subtalar ligaments injuries and an abnormally increased motion of the subtalar joint. Stress radiographs should be interpreted with caution and should not have the status of a reference test. Clinical diagnosis should rely on several parameters including MRI.

An oblique fibular tunnel is recommended when reconstructing the ATFL and CFL

PURPOSE

A bone tunnel is often used during the reconstruction of the anterior talofibular ligament (ATFL) and calcaneofibular ligament (CFL). The purpose of this study is to compare proposed directions for drilling this fibular tunnel and to assess potential tunnel length, using a 5-mm-diameter tunnel and surrounding bone.

METHODS

Anonymous DICOM data from spiral CT-scan images of the ankle were obtained from 12 Caucasian patients: 6 females and 6 males. Virtual tunnels were generated in a 3D bone model with angles of 30°, 45°, 60° and 90° in relation to the fibular long axis. Several measurements were performed: distance from entrance to perforation of opposing cortex, shortening of the tunnel, distance from tunnel centre to bone surface.

RESULTS

A tunnel in a perpendicular direction resulted in an average possible tunnel length of 16.8 (± 2.7) mm in the female group and 20.3 (± 3.4) mm in the male group. A tunnel directed at 30° offered the longest length: 30.9 (± 2.5) mm in the female group and 34.4 (± 2.9) mm in the male group. The use of a 5-mm-diameter tunnel in a perpendicular direction caused important shortening of the tunnel at the entrance in some cases. The perpendicular tunnel was very near to the digital fossa while the most obliquely directed tunnels avoided this region.

CONCLUSION

An oblique tunnel allows for a longer tunnel and avoids the region of the digital fossa, thereby retaining more surrounding bone. In addition, absolute values of tunnel length are given, which can be useful when considering the use of certain implants. We recommend drilling an oblique fibular tunnel when reconstructing the ATFL and CFL.

Correlation Between Cone-Beam Computed Tomography and High-Resolution Peripheral Computed Tomography for Assessment of Wrist Bone Microstructure

High-resolution peripheral quantitative computed tomography (HR-pQCT) is considered as the best technique to measure bone microarchitecture in vivo. However, a breakthrough for medical applications is inhibited because of the restricted field of view (∼9 mm) and a relatively long acquisition time (∼3 minutes). The goal of this study was to compare the accuracy of cone-beam computed tomography (CBCT) and HR-pQCT and to determine the agreement between CBCT and HR-pQCT in quantifying bone structural parameters. Nineteen trapezia of arthritic patients were scanned four times ex vivo: 1) CBCT (NewTom 5G, Cefla, at 75 μm); 2) HR-pQCT (XTremeCT-I, Scanco, at 82 μm); 3) HR-pQCT (XTremeCT-II, Scanco, at 60.7 μm); and 4) microCT (SkyScan1172, Bruker, at 19.84 μm). XTremeCT-I and XtremeCT-II were reconstructed, segmented, and analyzed following the manufacturer's guidelines. CBCT was reconstructed with in-house developed software and analyzed twice: once with an adaptive segmentation technique combined with a direct analysis method (AT-DM) and once with a Laplace-Hamming filtering technique combined with an indirect analysis method (LH-IM). Parameters of interest included bone volume fraction (BV/TV) and trabecular thickness (Tb.Th), separation (Tb.Sp), and number (Tb.N). The analyses of the CBCT data showed that the AT-DM analysis correlated better with microCT for BV/TV, Tb.Sp, and Tb.N, whereas the LH-IM technique correlated better for Tb.Th. Evaluated over all parameters, the coefficient of determination for XtremeCT-I, XtremeCT-II, and CBCT were higher as R²  = 0.68, 0.72, and 0.67, respectively. For CBCT, the correlations improved when three samples with very thin trabeculae close to each other were excluded and became similar to those for XtremeCT-I and XtremeCT-II. Interesting for clinical practice is that those bones could be identified automatically with the CBCT scanner. We conclude that CBCT produced similar accuracy as HR-pQCT in bone morphometric analyses of trapezia. The broader range of application, larger field of view, and shorter acquisition time make CBCT a valuable alternative to HR-pQCT. © 2019 American Society for Bone and Mineral Research.

Trapeziometacarpal stabilization through dorsoradial ligament reconstruction: An early post-surgery in vivo biomechanical analyses

Ligament reconstruction can provide pain relief in patients with a painful, unstable, pre-arthritic trapeziometacarpal (TMC) joint. Imbrication of the dorsoradial ligament (DRL) has been proposed as a minimal invasive stabilization technique. It requires less invasive surgery than an Eaton-Littler technique and shows promising long-term clinical outcome. We used dynamic CT to objectively review the effects of the imbrication. Four patients with pain and laxity at the TMC joint, but without radiographic signs of osteoarthritis, were recruited. Dynamic CT scans were made during active thumb abduction-adduction, flexion-extension, and two functional grip tasks using a radiolucent jig. Scans of the patients were acquired before and 3 to 6 months after DRL reconstruction. Motion of each bone in the articular chain of the thumb was quantified. In addition, we mapped changes in the contact patterns between the articular facets during the entire thumb motion. After DRL imbrication, we found no overall decrease in MC1 movement in three out of four patients. Furthermore, no increase in TMC joint congruency, defined as proximity area size, was found for three out of four patients. Pre- and post-operative differences in congruency across different tasks were patient-dependent and relatively small. We demonstrated that, from a biomechanical perspective, there is high variability in post-operative outcome between patients that undergo identical surgical procedures performed by the same surgeon. A post-operative decrease in range of motion, increase in joint congruency or decrease in proximity area shift during thumb motion is not omnipresent. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2851-2864, 2018.

Quantification of bone microstructure in the wrist using cone-beam computed tomography

Due to the rising life expectancy, bone diseases (e.g. osteoporosis, osteoarthritis) and trauma (e.g. fracture) have become an important socio-economic burden. Accurate visualization and quantification of the bone microstructure in vivo is seen as an important step to enhance diagnosis and treatment. Micro-computed tomography (microCT) has become the gold standard in three-dimensional (3D) imaging of trabecular bone structure. Yet, usage is limited to ex vivo analyses, hence, it cannot be used to evaluate bone and bone adaptive responses in a patient. High-resolution peripheral computed tomography (HR-pQCT) is considered the best technique to measure the bone microarchitecture in vivo. By design HR-pQCT is limited to scanning extremities, such as the distal radius and distal tibia with a limited field of view and long scanning time (~2 à 3 min. for a stack of 0.9 cm). Cone-beam computed tomography (CBCT) is a promising alternative with a much larger field of view. Yet, CBCT is challenged by artefacts that reduce image contrast, such that it is currently being used for qualitative evaluation only. Therefore, the aims of this work were first to enhance image contrast and second to determine the accuracy of high-resolution CBCT for bone microarchitectural assessment. Trapezia of nineteen female arthritic patients were scanned twice ex vivo; once using CBCT (NewTom 5G, Cefla, Verona, Italy) at a nominal voxel size of 75 μm and once using microCT (SkyScan 1172, Bruker, Kontich, Belgium) at a voxel size of 19.84 μm. The CBCT-scans were reconstructed following 2 protocols: (1) using the commercial software delivered with the scanner and (2) using in-house developed software. After reconstruction and image processing, the images were segmented using adaptive thresholding. Bone morphometric parameters including bone volume (BV), total tissue volume (TV), bone volume fraction (BV/TV), bone surface density (BS/TV), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp) and trabecular number (Tb.N) were calculated. Statistical evaluations were made at a significance level of 5%. Significant correlations were found between the CBCT-based bone parameters and the microCT-based parameters with R² > 0.68 The in-house reconstructed software outperformed the commercial software. Smaller bias (overestimation of Tb.Th decreased from 114.24% to 59.96%) as well as higher correlations were observed for the in-house processed images. Still, a significant overestimation was observed for BV/TV and Tb. Th and an underestimation for Tb.N. We conclude that our CBCT image reconstruction improved image contrast which allowed for an accurate quantification of trabecular bone microarchitecture.

Three-Dimensional Compared with Two-Dimensional Preoperative Planning of Corrective Osteotomy for Extra-Articular Distal Radial Malunion: A Multicenter Randomized Controlled Trial

BACKGROUND

Malunion is the most frequent complication seen after a fracture of the distal end of the radius. The primary aim of this study was to compare patient-reported outcome measures (PROMs) after corrective osteotomy for malunited distal radial fractures with and without 3-dimensional (3D) planning and use of patient-specific surgical guides.

METHODS

From September 2010 to May 2015, 40 adult patients with a symptomatic extra-articular malunited distal radial fracture were randomized to 3D computer-assisted planning or conventional 2-dimensional (2D) planning for corrective osteotomy. The primary outcome was the Disabilities of the Arm, Shoulder and Hand (DASH) score. Secondary outcomes included the Patient-Rated Wrist Evaluation (PRWE) score, pain and satisfaction scores, grip strength, and radiographic measurements at 3, 6, and 12 months postoperatively.

RESULTS

From baseline to 12 months of follow-up, the reduction in the mean DASH score was -30.7 ± 18.7 points for the 3D planning group compared with -20.1 ± 17.8 points for 2D planning (p = 0.103). Secondary functional outcome by means of the PRWE resulted in a similar reduction of -34.4 ± 22.9 points for the 3D planning group compared with -26.6 ± 18.3 points for the 2D planning group (p = 0.226). There were no significant differences in pain, satisfaction, range of motion, and grip strength. Radiographic analysis showed significant differences in the mean residual volar angulation (by 3.3°; p = 0.04) and radial inclination (by 2.7°; p = 0.028) compared with the templated side, in favor of 3D planning and guidance. The duration of preoperative planning and surgery as well as complication rates were comparable.

CONCLUSIONS

Although there was a trend toward a minimal clinically important difference in PROMs in favor of 3D computer-assisted guidance for corrective osteotomy of extra-articular distal radial malunion, it did not attain significance because of (post hoc) insufficient power. Despite the challenge of feasibility, a trial of large magnitude is warranted to draw definitive conclusions regarding clinical advantages of this advanced, more expensive technology.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Continuous Quantitative Monitoring of Mural, Platelet-Dependent, Thrombus Kinetics in the Crushed Rat Femoral Vein

A new in vivo method to study the size and dynamics of a growing mural thrombus was set up in the rat femoral vein. The method uses a standardized crush injury to induce a thrombus, and a newly developed transilluminator combined with digital analysis of video recordings. Thrombi in this model formed rapidly, reaching a maximum size 391 ± 35 sec following injury, after which they degraded with a half-life of 197 ± 31 sec. Histological examination indicated that the thrombi consisted mainly of platelets. The quantitative nature of the transillumination technique was demonstrated by simultaneous measurement of the incorporation of 111In labeled platelets into the thrombus. Thrombus formation, studied at 30 min interval in both femoral veins, showed satisfactory reproducibility overall and within a given animal

With this method we were able to induce a thrombus using a clinically relevant injury and to monitor continuously and reproducibly the kinetics of thrombus formation in a vessel of clinically and surgically relevant size

Impact of Osteoarthritis and Total Joint Arthroplasty on the Kinematics of the Trapeziometacarpal Joint: A Pilot Study

PURPOSE

To quantify the effect of osteoarthritis (OA) and total trapeziometacarpal (TMC) joint replacement on thumb kinematics during the primary physiological motions of the thumb.

METHODS

We included 4 female patients with stage III TMC OA. A computed tomography-based markerless method was used to quantify the 3-dimensional thumb kinematics in patients before and after TMC joint replacement surgery with the Arpe implant.

RESULTS

Trapeziometacarpal OA led to a marked decrease of internal rotation and abduction of the first metacarpal (MC1) during thumb flexion and a decrease of MC1 adduction during thumb adduction. As a compensatory phenomenon, the trapezium displayed increased abduction. The absence of MC1 translation in the ball-and-socket implant seems to induce a decrease of MC1 adduction as well as a decrease of trapezium adduction during thumb adduction, compared with OA and healthy joints. Implant replacement displayed an unchanged MC1 flexion during thumb flexion and seemed to slightly increase MC1 axial rotation during thumb flexion and adduction. Abduction and adduction of the MC1 are limited and compensated by this somewhat increased axial rotation, allowing more efficient thumb opposition.

CONCLUSIONS

The study highlights that advanced TMC OA mainly restricts the MC1 mobility. We also showed that, whereas total joint arthroplasty is able to restore thumb function, it cannot fully replicate the kinematics of the healthy TMC joint.

CLINICAL RELEVANCE

The quantification of TMC joint kinematics in OA and implanted patients is essential to improve our understanding of TMC OA as well as to enhance the functionality of implant designs.

Inhibitory Effect of Piracetam on Platelet-rich Thrombus Formation in an Animal Model

Intravenous administration of piracetam to hamsters reduced the formation of a platelet-rich venous thrombus induced by a standardised crush injury, in a dose-dependent fashion with an IC50 of 68 ± 8 mg/kg. 200 mg/kg piracetam also significantly reduced in vivo thrombus formation in rats. However, in vitro aggregation of rat platelets was only inhibited with piracetam-concentrations at least 10-fold higher than plasma concentrations (6.2 ± 1.1 mM) obtained in the treated animals. No effects were seen on clotting tests.

In vitro human platelet aggregation, induced by a variety of agonists, was inhibited by piracetam, with IC50’s of 25-60 mM. The broad inhibition spectrum could be explained by the capacity of piracetam to prevent fibrinogen binding to activated human platelets. Ex vivo aggregations and bleeding times were only minimally affected after administration of 400 mg/kg piracetam i.v. to healthy male volunteers, resulting in peak plasma levels of 5.8 ± 0.3 mM.

A possible antiplatelet effect of piracetam could be due to the documented beneficial effect on red blood cell deformability leading to a putative reduction of ADP release by damaged erythrocytes. However similarly high concentrations were needed to prevent stirring-induced “spontaneous” platelet aggregation in human whole blood.

It is concluded that the observed antithrombotic action of piracetam cannot satisfactorily be explained by an isolated direct effect on platelets. An additional influence of piracetam on the rheology of the circulating blood and/or on the vessel wall itself must therefore be taken into consideration.

In vivo biomechanical behavior of the trapeziometacarpal joint in healthy and osteoarthritic subjects

BACKGROUND

The contact biomechanics of the trapeziometacarpal joint have been investigated in several studies. However, these led to conflicting results and were mostly performed in vitro. The purpose of this study was to provide further insight on the contact biomechanics of the trapeziometacarpal joint by in vivo assessment of healthy and osteoarthritic subjects.

METHODS

The hands of 16 healthy women and 6 women with trapeziometacarpal osteoarthritis were scanned in positions of maximal thumb extension, flexion, abduction and adduction during three isometric tasks (lateral key pinch, power grasp and jar twist) and in thumb rest posture (relaxed neutral). Three-dimensional surface models of the trapezium and first metacarpal were created for each thumb configuration. The articular surface of each bone was measured in the neutral posture. A computed tomography-based proximity mapping algorithm was developed to calculate the distance between opposing joint surfaces, which was used as a surrogate for intra-articular stress.

FINDINGS

Distinct proximity patterns were observed across tasks with a recurrent pattern reported on the volar aspect of the first metacarpal. The comparison between healthy and arthritic subjects showed a significantly larger articular area, in parallel with a significant joint space narrowing and an increase in proximity area in arthritic subjects. We also observed severe articular deformations in subjects with late stage osteoarthritis.

INTERPRETATION

This study has increased our insight in the contact biomechanics of the trapeziometacarpal joint during tasks and positions of daily life in healthy and arthritic subjects, which might contribute to a better understanding of the occurrence mechanisms of degenerative diseases such as osteoarthritis.

Joint Survival Analysis and Clinical Outcome of Total Joint Arthroplasties With the ARPE Implant in the Treatment of Trapeziometacarpal Osteoarthritis With a Minimal Follow-Up of 5 Years

PURPOSE

The ARPE joint arthroplasty was introduced in 1991 for the treatment of symptomatic trapeziometacarpal (TMC) osteoarthritis. The primary outcome of this prospective study is to report the medium- to long-term joint survival of this prosthesis. Our secondary outcomes are the clinical and functional results.

METHODS

A prospective, consecutive case series study was done at our hand unit. Patients included in the study had at least 5 years follow-up after a total joint arthroplasty for osteoarthritis of the TMC joint using the ARPE implant. The Kaplan-Meier method was used to estimate implant survival over time. Clinical and radiological assessment was recorded prospectively: before surgery and at 1 year and 5 years or more after surgery. We compared the means of the Kapandji index (assessing the thumb range of motion and opposition), the grip strength, and the pinch strength before surgery and at the latest follow-up.

RESULTS

We included all 166 prostheses in the survival analysis with a mean follow-up of 80 months. Five prostheses (3%) required revision surgery and 1 implant (0.6%) failed. Therefore, Kaplan-Meier survival probability was 96% with a mean follow-up of 80 months (95% confidence interval, 91-98). A total of 120 arthroplasties from 115 patients were included in the clinical analysis. At 5 years' follow-up, the median Disabilities of the Arm, Shoulder, and Hand (DASH) score was 4.6 (range, 0-86.6). There was a significant improvement of the mean opposition and grip strength of the affected thumb at final follow-up in comparison with the preoperative values. There was also a significant improvement in the mean pinch strength at 1 year and 5 years after surgery compared with preoperative measurements.

CONCLUSIONS

In our series, the ARPE prosthesis of the thumb TMC joint has proven to be a reliable and effective implant. Mean motion and strength increased whereas pain decreased after surgery and these results remained constant within the follow-up period.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

In vivo kinematics of the thumb during flexion and adduction motion: Evidence for a screw-home mechanism

The thumb plays a crucial role in basic hand function. However, the kinematics of its entire articular chain have not yet been quantified. Such investigation is essential to improve our understanding of thumb function and to develop better strategies to treat thumb joint pathologies. The primary objective of this study is to quantify the in vivo kinematics of the trapeziometacarpal (TMC) and scaphotrapezial (ST) joints during flexion and adduction of the thumb. In addition, we want to evaluate the potential coupling between the TMC and ST joints during these tasks. The hand of 16 asymptomatic women without signs of thumb osteoarthritis were CT scanned in positions of maximal thumb extension, flexion, abduction, and adduction. The CT images were segmented and three-dimensional surface models of the radius, scaphoid, trapezium, and the first metacarpal were created for each thumb motion. The corresponding rotations angles, translations, and helical axes were calculated for each sequence. The analysis shows that flexion and adduction of the thumb result in a three-dimensional rotation and translation of the entire articular chain, including the trapezium and scaphoid. A wider range of motion is observed for the first metacarpal, which displays a clear axial rotation. The coupling of axial rotation of the first metacarpal with flexion and abduction during thumb flexion supports the existence of a screw-home mechanism in the TMC joint. In addition, our results point to a potential motion coupling between the TMC and ST joints and underline the complexity of thumb kinematics. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1556-1564, 2017.

Influence of wrist position on maximum grip force in a post-operative orthosis

BACKGROUND

Flexor tendon repair in the hand remains challenging in avoiding tendon rupture and adhesion formation. Post-operative mobilization has been shown to be critical in regaining functional range of motion.

OBJECTIVES

The objective of this study is 2-fold: to assess the influence of wrist position on maximum grip force generated in a post-operative orthosis and to determine the correlation between this maximum grip force and an individual's grip strength.

STUDY DESIGN

Clinical measurement Methods: A total of 30 uninjured wrists of right-handed men were given a post-operative orthosis with an incorporated Caroli-hinge. The maximum grip force was measured according to a different wrist position ranging from -30° extension until 80° of flexion using a 10° interval. These measurements were plotted out on a graph for regression analysis. A correlation was determined between measurements in a neutral wrist position and maximum grip strength generated without an orthosis. To assess the coherence of the measurements, a mean intraclass correlation coefficient was used.

RESULTS

The maximum grip force values were statistically significantly different in every wrist position and decreased progressively with an increasing flexion angle ( p < 0.05). This relationship is expressed in a logistic regression curve f( x) = -4.98 + 16.92/(1 + (x/8.59))^2.24. A wrist position of 4.4° of flexion was derived from this function to cause a maximum grip force reduction of 33%. Further analysis showed a force decrease of 50% at 23.2° and 66% at 51.8° of wrist flexion. The grip strength measured without an orthosis showed a positive correlation with previous measurements (Spearman's correlation coefficient = 0.74 for the right hand and 0.72 for the left hand ( p < 0.001)).

CONCLUSIONS

The obtained logistic function allowed to derive the wrist position needed in a post-operative orthosis to obtain a desired amount of maximum grip force reduction. Clinical relevance Measuring a high grip force in a clinical setting of flexor tendon repair on the contralateral non-affected hand could indicate the use of an increased flexion angle in a post-operative orthosis. This reduces the load transferred on the tendon repair when involuntary contractions take place, for example, during sleeping when positioned in a post-operative orthosis.

Endoscopic Ankle Lateral Ligament Graft Anatomic Reconstruction

Chronic instability is a common complication of lateral ankle sprains. If nonoperative treatment fails, a surgical repair or reconstruction may be indicated. Today, endoscopic techniques to treat ankle instability are becoming more popular. This article describes an endoscopic technique, using a step-by-step approach, to reconstruct the ATFL and CFL with a gracilis graft. The endoscopic technique is reproducible and safe with regard to the surrounding anatomic structures. Short and midterm results confirm the benefits of this technique.

In vivo contact biomechanics in the trapeziometacarpal joint using finite deformation biphasic theory and mathematical modelling

The assessment of the contact biomechanics in the trapeziometacarpal (TMC) joint during functional tasks represents a relevant way to obtain a better understanding of the onset of osteoarthritis (OA). CT scans of the hand region of 20 female volunteers were taken in relaxed neutral, lateral key pinch and power grasp configuration. 3D models of the first metacarpal (MC1) and the trapezium were created. The articular area of each bone was quantified and a mathematical model was developed in Matlab to evaluate the projected contact area and stress distribution of each bone. The articular areas of the MC1 and the trapezium presented no significant difference. A slightly smaller projected contact area was calculated for the trapezium compared to the MC1. Similar amounts of stress were reported in the neutral and lateral pinch configurations. The highest stress levels were observed during power grasp. Very consistent results for high stress location on the volar/radial articular sub-region were found in the neutral and power grasp configurations. More variation was reported during lateral pinch. The mathematical model presented in this paper offers the possibility to predict contact patterns within the TMC joint based on in vivo CT images.

Airbag-induced thumb avulsion: two case reports

Although airbags are designed to save lives and protect victims from serious injuries, airbag deployment can cause unwanted lesions. In this case report, two cases are presented of young women who sustained an important fracture dislocation of the first carpometacarpal joint (CMC I joint) caused by airbag deployment during a car collision.

Comparison of the anatomical dimensions and mechanical properties of the dorsoradial and anterior oblique ligaments of the trapeziometacarpal joint

PURPOSE

The respective roles of the dorsoradial (DRL) and anterior oblique (AOL) ligaments in stability of the highly mobile trapeziometacarpal (TMC) joint remain disputed. Earlier publications have pointed to the AOL as the key stabilizing structure; yet, more recent publications have challenged the stabilizing role of the AOL, favoring the DRL as the main TMC joint stabilizer. We executed an anatomical study of the ligaments, including detailed dissection to quantify the length, width, and thickness of the AOL and DRL and tested the material properties of these ligaments.

METHODS

Thirteen fresh frozen cadaveric thumbs from 9 specimens were used. Length, width, and thickness of the AOL and DRL were measured on magnetic resonance imaging and/or after dissection. Next, the first metacarpal and trapezium were isolated together with both ligaments, and both bones were cut sagittally to isolate a first metacarpal-AOL-trapezium and first metacarpal-DRL-trapezium complex from each thumb. These samples were subjected to cyclic loading in displacement-controlled tests. The obtained force-displacement curves were used to calculate stiffness and hysteresis of each sample.

RESULTS

Our results showed that the DRL is significantly shorter and thicker than the AOL, which is thin and ill-defined. Our results also indicate that the DRL has a higher stiffness than the AOL, making it a more likely candidate to provide joint stability.

CONCLUSIONS

Although the AOL has been asserted to be the primary restraint to dorsoradial subluxation, this view has been challenged over the past 10 years by several studies. These studies have shown the AOL to be relatively weak and compliant compared with the intermetacarpal and dorsoradial ligaments and have demonstrated that the DRL is the strongest and stiffest ligament of the TMC joint. Our studies confirm these findings.

CLINICAL RELEVANCE

This study indicates that the DRL is relatively stiff and thick, suggesting it should be repaired or reconstructed when disrupted to restore stability of the TMC joint.

Accuracy of 3D Virtual Planning of Corrective Osteotomies of the Distal Radius

Corrective osteotomies of the distal radius for symptomatic malunion are time-tested procedures that rely on accurate corrections. Patients with combined intra- and extra-articular malunions present a challenging deformity. Virtual planning and patient-specific instruments (PSIs) to transfer the planning into the operating room have been used both to simplify the surgery and to make it more accurate. This report focuses on the clinically achieved accuracy in four patients treated between 2008 and 2012 with virtual planning and PSIs for a combined intra- and extraarticular malunion of the distal radius. The accuracy of the correction is quantified by comparing the virtual three-dimensional (3D) planning model with the postoperative 3D bone model. For the extraarticular malunion the 3D volar tilt, 3D radial inclination and 3D ulnar variance are measured. The volar tilt is undercorrected in all cases with an average of -6 ± 6°. The average difference between the postoperative and planned 3D radial inclination was -1 ± 5°. The average difference between the postoperative and planned 3D ulnar variances is 0 ± 1 mm. For the evaluation of the intraarticular malunion, both the arc method of measurement and distance map measurement are used. The average postoperative maximum gap is 2.1 ± 0.9 mm. The average maximum postoperative step-off is 1.3 ± 0.4 mm. The average distance between the postoperative and planned articular surfaces is 1.1 ± 0.6 mm as determined in the distance map measurement. There is a tendency to achieve higher accuracy as experience builds up, both on the surgeon's side and on the design engineering side. We believe this technology holds the potential to achieve consistent accuracy of very complex corrections.

Computer-assisted versus non-computer-assisted preoperative planning of corrective osteotomy for extra-articular distal radius malunions: a randomized controlled trial

Background

Malunion is the most common complication of distal radius fracture. It has previously been demonstrated that there is a correlation between the quality of anatomical correction and overall wrist function. However, surgical correction can be difficult because of the often complex anatomy associated with this condition. Computer assisted surgical planning, combined with patient-specific surgical guides, has the potential to improve pre-operative understanding of patient anatomy as well as intra-operative accuracy. For patients with malunion of the distal radius fracture, this technology could significantly improve clinical outcomes that largely depend on the quality of restoration of normal anatomy. Therefore, the objective of this study is to compare patient outcomes after corrective osteotomy for distal radius malunion with and without preoperative computer-assisted planning and peri-operative patient-specific surgical guides.

Methods/Design

This study is a multi-center randomized controlled trial of conventional planning versus computer-assisted planning for surgical correction of distal radius malunion. Adult patients with extra-articular malunion of the distal radius will be invited to enroll in our study. After providing informed consent, subjects will be randomized to two groups: one group will receive corrective surgery with conventional preoperative planning, while the other will receive corrective surgery with computer-assisted pre-operative planning and peri-operative patient specific surgical guides. In the computer-assisted planning group, a CT scan of the affected forearm as well as the normal, contralateral forearm will be obtained. The images will be used to construct a 3D anatomical model of the defect and patient-specific surgical guides will be manufactured. Outcome will be measured by DASH and PRWE scores, grip strength, radiographic measurements, and patient satisfaction at 3, 6, and 12 months postoperatively.

Discussion

Computer-assisted surgical planning, combined with patient-specific surgical guides, is a powerful new technology that has the potential to improve the accuracy and consistency of orthopaedic surgery. To date, the role of this technology in upper extremity surgery has not been adequately investigated, and it is unclear whether its use provides any significant clinical benefit over traditional preoperative imaging protocols. Our study will represent the first randomized controlled trial investigating the use of computer assisted surgery in corrective osteotomy for distal radius malunions.

Trial registration

NCT01193010

Rapid prototyping of scaphoid and lunate bones

In this study, a novel rapid prototyping technology was used to fabricate scaphoid and lunate bone prostheses, two carpal bones that are prone to avascular necrosis. Carpal prostheses were fabricated with an Envisiontec Perfactory SXGA stereolithography system using Envisiontec eShell 200 photocurable polymer. Fabrication was guided using 3-D models, which were generated using Mimics software (Materialise NV, Leuven, Belgium) from patient computer tomography data. The prostheses were fabricated in a layer-by-layer manner; approximately 50-microm thick layers were observed in the prostheses. Hardness and Young's modulus values of polymerized eShell 200 material were 93.8 +/- 7.25 MPa and 3050 +/- 90 MPa, respectively. The minimum compressive force required for fracture was 1360 N for the scaphoid prosthesis and 1248 N for the lunate prosthesis. Polymerized Envisiontec eShell material exhibited high human neonatal epidermal keratinocyte cell viability rate in an MTT assay. The results of this study indicate that small bone prostheses fabricated by stereolithography using eShell 200 polymer may have suitable geometry, mechanical properties, and cytocompatibility properties for in vivo use.

Inhibitory effect of piracetam on platelet-rich thrombus formation in an animal model

Intravenous administration of piracetam to hamsters reduced the formation of a platelet-rich venous thrombus induced by a standardised crush injury, in a dose-dependent fashion with an IC50 of 68 +/- 8 mg/kg. 200 mg/kg piracetam also significantly reduced in vivo thrombus formation in rats. However, in vitro aggregation of rat platelets was only inhibited with piracetam-concentrations at least 10-fold higher than plasma concentrations (6.2 +/- 1.1 mM) obtained in the treated animals. No effects were seen on clotting tests. In vitro human platelet aggregation, induced by a variety of agonists, was inhibited by piracetam, with IC50's of 25-60 mM. The broad inhibition spectrum could be explained by the capacity of piracetam to prevent fibrinogen binding to activated human platelets. Ex vivo aggregations and bleeding times were only minimally affected after administration of 400 mg/kg piracetam i.v. to healthy male volunteers, resulting in peak plasma levels of 5.8 +/- 0.3 mM. A possible antiplatelet effect of piracetam could be due to the documented beneficial effect on red blood cell deformability leading to a putative reduction of ADP release by damaged erythrocytes. However similarly high concentrations were needed to prevent stirring-induced "spontaneous" platelet aggregation in human whole blood. It is concluded that the observed antithrombotic action of piracetam cannot satisfactorily be explained by an isolated direct effect on platelets. An additional influence of piracetam on the rheology of the circulating blood and/or on the vessel wall itself must therefore be taken into consideration.

A technique to investigate microvascular mural thrombus formation in arteries and veins: II. Effects of aspirin, heparin, r-hirudin, and G-4120

After a standardized trauma to carotid arteries or femoral veins of hamsters, the antithrombotic effects of two antiplatelet agents (aspirin and the glycoprotein IIb/IIIa antagonist G4120) and two anticoagulants (heparin and the direct thrombin inhibitor r-hirudin) were studied in vivo. The thrombus area volume was assessed by image analysis of the transilluminated experimental vessels. Heparin, r-hirudin, and G-4120 demonstrated a dose-dependent complete inhibition of arterial and venous thrombosis. In contrast, the antithrombotic effect of aspirin was only partial in both vessel types. A significant correlation between activated partial thromboplastin time (aPTT) at the end of the experiments and the antithrombotic effect was observed with the anticoagulant agents. However, only r-hirudin inhibited thrombus formation at a therapeutical prolongation of aPTT, while heparin required supratherapeutical amounts to achieve the same inhibition. The data confirm that the inhibition of aspirin, heparin, r-hirudin, and G-4120 on the formation of platelet-rich thrombi is independent of the blood flow rate.

A technique to investigate mural thrombus formation in small arteries and veins: I. Comparative morphometric and histological analysis

Numerous clinically relevant animal models exist for thrombosis studies. Few of these are suitable for both arteries and veins. In this investigation, an established venous thrombosis model was adapted through minimal technical adjustments to allow also the study of arterial thrombosis. A standardized subintimal crush injury was performed to carotid arteries or femoral veins of hamsters. Thrombus volumes were then quantified by direct morphometric measurements from serial microscopic sections or by on-line image analysis of light intensity changes from transilluminated vessels. The platelet-rich mural thrombus, which was established within minutes of the trauma, disintegrated during the observation period. The life cycle of the thrombus was different in arteries and veins, but significant linear correlation (p < 0.01) was found in both types of vessel between thrombus volumes measured by the two techniques. The model can consequently be used for comparative in vivo thrombosis studies in small (approximately 1-mm) arteries and veins.

Antithrombotic properties of L-cysteine, N-(mercaptoacetyl)-D-Tyr-Arg-Gly-Asp-sulfoxide (G4120) in a hamster platelet-rich femoral vein thrombosis model

Platelet aggregation plays an important role in the pathogenesis in arterial thrombotic disorders. The binding of fibrinogen via the Arg-Gly-Asp (RGD) recognition sequence to the platelet glycoprotein IIb/IIIa (GPIIb/IIIa) receptor is an essential step of platelet aggregation induced by various physiologic agonists, and RGD-containing peptides that bind to the GPIIb/IIIa receptor inhibit thrombus formation in vivo. L-cysteine, N-(mercaptoacetyl)D-tyrosyl-L-arginylglycyl-L alpha-aspartyl-cyclic (1----5)-sulfide, 5-oxide (G4120), a cyclic RGD-containing synthetic pentapeptide, inhibits adenosine diphosphate (ADP)-induced platelet aggregation with 50% inhibition (IC50) at a concentration of 0.05 microgram/mL in human plasma, 0.12 microgram/mL in hamster plasma, and 11 micrograms/mL in rat plasma. Corresponding values for the linear tetrapeptide Arg-Gly-Asp-Phe (RGDF) were 7 and 100 micrograms/mL in human and hamster plasma. The antithrombotic effects of G4120 and RGDF were evaluated in a hamster model consisting of a mural platelet-rich femoral vein thrombus induced by standardized endothelial cell damage. Bolus intravenous injection of G4120 was followed by a biphasic disappearance of G4120 from plasma with t1/2 alpha of 3.7 minutes and t1/2 beta of 63 minutes, corresponding to a plasma clearance of 5.2 +/- 0.68 mL/min. Bolus intravenous injection of G4120 inhibited ex vivo platelet aggregation with 0.5 mumol/L ADP and in vivo thrombus formation in a dose-dependent manner, with ID50 of 11 and 11 micrograms/kg, respectively. Bolus injection of RGDF inhibited in vivo thrombus formation; 43% inhibition was obtained at a dose of 30 mg/kg. Thus, this hamster platelet-rich femoral vein thrombosis model may be useful for the investigation of the antithrombotic properties of platelet GPIIb/IIIa antagonistic peptides. The cyclic synthetic peptide G4120 appears to have a very potent antithrombotic activity in vivo.

Continuous quantitative monitoring of mural, platelet-dependent, thrombus kinetics in the crushed rat femoral vein

A new in vivo method to study the size and dynamics of a growing mural thrombus was set up in the rat femoral vein. The method uses a standardized crush injury to induce a thrombus, and a newly developed transilluminator combined with digital analysis of video recordings. Thrombi in this model formed rapidly, reaching a maximum size 391 +/- 35 sec following injury, after which they degraded with a half-life of 197 +/- 31 sec. Histological examination indicated that the thrombi consisted mainly of platelets. The quantitative nature of the transillumination technique was demonstrated by simultaneous measurement of the incorporation of 111In labeled platelets into the thrombus. Thrombus formation, studied at 30 min interval in both femoral veins, showed satisfactory reproducibility overall and within a given animal. With this method we were able to induce a thrombus using a clinically relevant injury and to monitor continuously and reproducibly the kinetics of thrombus formation in a vessel of clinically and surgically relevant size.