Bone microarchitecture of the tibial plateau in skeletal health and osteoporosis

High-Resolution Peripheral Quantitative Computed Tomography in Rheumatic Diseases: A New Option for Knee Osteoarthritis

High-resolution peripheral quantitative computed tomography (HR-pQCT) provides a new opportunity for the noninvasive measurement of bone microarchitecture in patient research of rheumatic disease in joints of the extremities. Rheumatoid arthritis of the hand and osteoarthritis of the knee are highly prevalent and there are no cures, so an improved understanding of the etiology of these diseases, particularly when combining HR-pQCT with other imaging modalities, is important to develop new disease management strategies. Analysis of HR-pQCT data is challenging due to the large size of the datasets, but the field continues to rapidly develop, and there is excellent opportunity to integrate sophisticated analyses for this novel research tool.

Double reverse traction repositor assisted closed reduction and internal fixation versus open reduction and internal fixation for treatment of lateral tibial plateau fractures among the elderly

BACKGROUND

In elderly tibial plateau fractures (TPFs), the lateral condyles are involved frequently. This study aimed to compare the outcomes of open reduction and internal fixation (ORIF) and double reverse traction repositor (DRTR) assisted closed reduction and internal fixation (CRIF) in elderly patients with lateral TPFs.

METHODS

From January 2015 to July 2020, we retrospectively reviewed 68 patients treated surgically at our trauma center for lateral TPFs (Schatzker type I-III). 31 patients were eventually assigned to the DRTR assisted CRIF group, whereas 37 patients were assigned to the ORIF group. The primary outcomes included surgical details, radiological assessment, follow-up knee function, and complications.

RESULTS

The DRTR assisted CRIF group experienced a 43.6 mL decrease in intraoperative blood loss (161.3 ml vs 204.9 ml, p = 0.033), and the operation duration was 32.1 min shorter than the ORIF group (83.8 min vs 115.9 min, p < 0.001). There was no statistically significant difference in terms of widening of the tibia plateau (WTP), depth of articular depression (DAD), medial proximal tibial angle (MPTA) and posterior tibial slope angle (PTSA) immediately after surgery and at the last follow-up. No differences in malreduction (p = 0.566) or reduction loss (p = 0.623) were observed between the groups, and Lysholm and HSS scores were similar between the two groups (83.6 ± 15.8 vs 83.4 ± 5.1, p = 0.934; 89.3 ± 7.8 vs 86.9 ± 6.2, p = 0.172; respectively). However, ORIF was associated with a greater increase in postoperative complications than DRTR assisted CRIF (3.2% vs 27%, p = 0.008).

CONCLUSION

Both types of internal fixation provide good radiological outcomes and knee function in the treatment of lateral TPFs in the elderly. However, DRTR assisted CRIF has the advantage of a shorter duration of surgery, less blood loss, and fewer postoperative complications, and appears to be a better treatment option for elderly patients with lateral TPFs.

Periprosthetic tibial fracture as a complication of unicompartmental knee arthroplasty: Current insights

Periprosthetic fracture following knee arthroplasty is a rare but devastating complication associated with significant morbidity. With unicompartmental knee arthroplasty being performed far less frequently than total knee arthroplasty, periprosthetic fracture following unicompartmental knee arthroplasty presents a particular challenge to orthopaedic surgeons, due to clinical unfamiliarity and sparsity of literature. An up-to-date review of the epidemiology, risk factors, and management strategies for PPF after UKA is presented.

Outcomes after ORIF are similar in young and elderly patients with tibial plateau fractures: A minimum 2-year follow-up study

BACKGROUND

This study aimed to compare the outcomes of open reduction internal fixation in young and elderly patients with tibial plateau fractures.

METHODS

A total of 224 patients with tibial plateau fractures treated with open reduction internal fixation at a level I trauma center from 2014 to 2019 were reviewed. The patients with a minimum follow-up of 2 years were divided into two groups, with those aged 60 years and older divided into the elderly group and those under 60 years divided into the young group. The mean follow-up time was 55 months (range: 24-80), and the primary outcomes were quality of reduction and function. The secondary outcomes included complications, fracture healing time, and conversion to total knee arthroplasty.

RESULTS

The elderly group had a higher proportion of women than the young group (61.1% vs. 23.9%, p < 0.001). Diabetes was more prevalent in the elderly cohort than in the young cohort (18.9% vs. 9.0%, p = 0.030). The rate of bone grafts was higher in the elderly group (57.8% vs. 41.8%, p = 0.019), but no significant differences were found between the groups regarding fracture characteristics, the operative time or intraoperative blood loss. The reduction quality, knee function, postoperative complications, healing time, and total knee arthroplasty conversion rate were not significantly different (p > 0.05) between the groups.

CONCLUSIONS

Open reduction internal fixation remains a satisfactory technique to treat tibial plateau fractures in the elderly. Although the rate of bone grafts is higher in elderly patients, they had comparable outcomes compared with their younger counterparts.

Biomechanical Comparison of Anatomic Versus Lower of Anteromedial and Anterolateral Tibial Tunnels in Posterior Cruciate Ligament Reconstruction

OBJECTIVE

In order to reduce the "killer turn" effect, various tibial tunnels have been developed. However, few studies investigated the biomechanical effects of different tibial tunnels during PCL reconstruction. This study aims to compare the time-zero biomechanical properties of anteromedial, anterolateral, lower anteromedial, and lower anterolateral tibial tunnels in transtibial posterior cruciate ligament (PCL) reconstruction under load-to-failure loading.

METHODS

Porcine tibias and bovine extensor tendons were used to simulate in vitro transtibial PCL reconstruction. Forty bovine extensor tendons and 40 porcine tibias were randomly divided into four experimental groups: anteromedial tunnel group (AM group, n = 10), anterolateral tunnel group (AL group, n = 10), lower anteromedial tunnel group (L-AM group, n = 10), and lower anterolateral tunnel group (L-AL group, n = 10). The biomechanical test was then carried out in each group using the load-to-failure test. The ultimate load (in newtons), yield load (in newtons), tensile stiffness (in newtons per millimeter), load-elongation curve, failure mode, and tibial tunnel length (in millimeter) were recorded for each specimen. One-way analysis of variance (ANOVA) was used to compare the mean differences among the four groups.

RESULTS

The biomechanical outcomes showed that there were no differences in the mean tensile stiffness and failure mode among four groups. The ultimate load and yield load of the L-AM group were significantly higher than those of other three groups (P < 0.05). For the AM group, its ultimate load is significantly higher than that of the L-AL group (P < 0.05), and its yield load is higher than that of the AL group and L-AL group (P < 0.05). However, we found no significant differences in either ultimate load or yield load between AL group and L-AL group (P > 0.05). There was significant statistical difference in the length of tibial tunnel between anatomic groups (AM and AL) and lower groups (L-AM and L-AL) (P < 0.05).

CONCLUSION

Compared with the anteromedial, anterolateral, and lower anterolateral tibial tunnel, the lower anteromedial tibial tunnel showed better time-zero biomechanical properties including ultimate load and yield load in transtibial PCL reconstruction.

The influence of 3D printing on inter- and intrarater reliability on the classification of tibial plateau fractures

PURPOSE

Tibial plateau fractures continue to be a challenging task in clinical practice and current outcomes seem to provide the potential for further improvement. Especially presurgical understanding of the orientation of fracture lines and fracture severity is an essential key to sufficient surgical treatment. The object of this study was to evaluate the reliability of modern axial CT-based classification systems for tibial plateau fractures. In addition, the diagnostic-added value of 3D printing on the classification systems was investigated.

METHODS

22 raters were asked to classify 22 tibial plateau fractures (11 AO B- and 11 AO C-fractures) with the AO, the 10-Segment and the Revisited Schatzker classification in a three-step evaluation: first only using CT scans, second with 3D volumetric reconstructions and last with 3D-printed fracture models. Inter- and intraobserver agreement and the subjective certainty were analyzed. Statistics were done using kappa values, percentage match and a univariant one-way analysis of variance.

RESULTS

The AO classifications interobserver percentage match and kappa values improved for all raters and recorded an overall value of 0.34, respectively, 43% for the 3D print. The 10-Segment classification interobserver agreement also improved with the 3D-printed models and scored an overall kappa value of 0.18 and a percentage match of 79%. Equally the Revisited Schatzker classification increased its values to 0.31 and 35%. The intraobserver agreement showed a moderate agreement for the AO (0.44) and Revisited Schatzker classification (0.42) whereas the 10-Segment classification showed a fair agreement (0.27). Additionally, the raters changed their classification in 36% of the cases after evaluating the fracture with the 3D-printed models and the subjective certainty regarding the decisions improved as categories of self-reliant diagnostic choices were selected 18% (p < 0.05) more often after using the 3D-printed models.

CONCLUSION

Based on the measured outcomes it was concluded that the new classification systems show an overall slight to fair reliability and the use of 3D printing proved to be beneficial for the preoperative diagnostics of tibial plateau fractures. The 10-Segment classification system showed the highest percentage match evaluation of all classification systems demonstrating its high clinical value across all levels of user experience.

Superior Bone Microarchitecture in Anatomic Versus Nonanatomic Fibular Drill Tunnels for Reconstruction of the Posterolateral Corner of the Knee

Background:

Several fibula-based reconstruction techniques have been introduced to address ligamentous injuries of the posterolateral corner of the knee. These techniques involve a drill tunnel with auto- or allograft placement through the proximal fibula.

Purpose:

To determine the skeletal microarchitecture of the proximal fibula and its association with age and to compare the microarchitecture within the regions of different drill tunnel techniques for reconstruction of the posterolateral corner.

Study Design:

Descriptive laboratory study.

Methods:

A total of 30 human fibulae were analyzed in this cadaveric imaging study. High-resolution peripheral quantitative computed tomography measurements were performed in a 4.5 cm–long volume of interest at the proximal fibula. Three-dimensional microarchitectural data sets of cortical and trabecular compartments were evaluated using customized scripts. The quadrants representing the entry and exit drill tunnel positions corresponding to anatomic techniques (LaPrade/Arciero) and the Larson technique were analyzed. Linear regression models and group comparisons were applied.

Results:

Trabecular microarchitecture parameters declined significantly with age in women but not men. Analysis of subregions with respect to height revealed stable cortical and decreasing trabecular values from proximal to distal in both sexes. Along with a structural variability in axial slices, superior values were found for the densitometric and microarchitectural parameters corresponding to the fibular drill tunnels in the anatomic versus Larson technique (mean ± SD; bone volume to tissue volume at the entry position, 0.273 ± 0.079 vs 0.175 ± 0.063; P < .0001; cortical thickness at the entry position, 0.501 ± 0.138 vs 0.353 ± 0.081 mm; P < .0001).

Conclusion:

Age represented a relevant risk factor for impaired skeletal microarchitecture in the proximal fibula in women but not men. The region of drill tunnels according to anatomic techniques showed superior bone microarchitecture versus that according to the Larson technique.

Resveratrol Ameliorates High Altitude Hypoxia-Induced Osteoporosis by Suppressing the ROS/HIF Signaling Pathway

Hypoxia at high-altitude leads to osteoporosis. Resveratrol (RES), as an antioxidant, has been reported to promote osteoblastogenesis and suppress osteoclastogenesis. However, the therapeutic effect of RES against osteoporosis induced by high-altitude hypoxia remains unclear. Thus, this study was intended to investigate the potential effects of RES on high-altitude hypoxia-induced osteoporosis both in vivo and in vitro. Male Wistar rats were given RES (400 mg/kg) once daily for nine weeks under hypoxia, while the control was allowed to grow under normoxia. Bone mineral density (BMD), the levels of bone metabolism-related markers, and the changes on a histological level were measured. Bone marrow-derived mesenchymal stem cells (BMSCs) and RAW264.7 were incubated with RES under hypoxia, with a control growing under normoxia, followed by the evaluation of proliferation and differentiation. The results showed that RES inhibited high-altitude hypoxia-induced reduction in BMD, enhanced alkaline phosphatase (ALP), osteocalcin (OCN), calcitonin (CT) and runt-related transcription factor 2 (RUNX2) levels, whereas it reduced cross-linked carboxy-terminal telopeptide of type I collagen (CTX-I) levels and tartrate-resistant acid phosphatase (TRAP) activity in vivo. In addition, RES attenuated histological deteriorations in the femurs. In vitro, RES promoted osteoblastogenesis and mineralization in hypoxia-exposed BMSCs, along with promotion in RUNX2, ALP, OCN and osteopontin (OPN) levels, and inhibited the proliferation and osteoclastogenesis of RAW264.7. The promotion effects of RES on osteoblastogenesis were accompanied by the down-regulation of reactive oxygen species (ROS) and hypoxia inducible factor-1α (HIF-1α) induced by hypoxia. These results demonstrate that RES can alleviate high-altitude hypoxia-induced osteoporosis via promoting osteoblastogenesis by suppressing the ROS/HIF-1α signaling pathway. Thus, we suggest that RES might be a potential treatment with minimal side effects to protect against high-altitude hypoxia-induced osteoporosis.

Periprosthetic fractures after medial unicompartmental knee arthroplasty: a narrative review

INTRODUCTION

On rare occasions, fractures of the tibial plateau may occur after uni-compartmental knee arthroplasty (UKA) and account for 2% of total UKA failures. The purpose of this narrative review is to identify and discuss potential risk factors that might lead to prevention of this invalidating complication.

MATERIALS AND METHODS

Electronic database of Pubmed, Scopus, Cochrane and Google Scholar were searched. A total of 457 articles related to the topic were found. Of those, 86 references were included in this narrative review.

RESULTS

UKA implantation acts as a stress riser in the medial compartment. To avoid fractures, surgeons need to balance load and bone stock. Post-operative lower limb alignment, implant positioning, level of resection and sizing of the tibial tray have a strong influence on load distribution of the tibial bone. Pain on weight-bearing signals bone-load imbalance and acts as an indicator of bone remodeling and should be a trigger for unloading. The first three months after surgery are critical because of transient post-operative osteoporosis and local biomechanical changes. Acquired osteoporosis is a growing concern in the arthroplasty population. Split fractures require internal fixation, while subsidence fractures differ in their management depending of the amount of bone impaction. Loose implants require revision knee arthroplasty.

CONCLUSION

Peri-prosthetic fracture is a rare, but troublesome event, which can lead to implant failure and revision surgery. Better knowledge of the multifactorial risk factors in association with a thorough surgical technique is key for prevention.

Tibial plateau fractures: three dimensional fracture mapping and morphologic measurements

Purpose

The injury mechanisms and classifications of tibial plateau fractures (TPFs) are still controversial. The aim of this study is to show 3D fracture mapping of different types of tibial plateau fractures. Moreover, combined with Schatzker and ten-segment classification, we aimed to analyze the injury frequency and characteristics of different segments.

Methods

In total, 346 patients with TPFs treated at level I trauma centres from 2017 to 2021 were reviewed. The CT files of the included cases were typed and categorized. 3D reconstruction of TPFs patients’ CT files were performed using software. All fracture lines were superimposed on the standard model by the software to create TPFs 3D fracture mapping.

Results

This study included 204 male and 142 female patients (average age, 47 years [range, 18 to 83 years]) with a tibial plateau fracture. Using the Schatzker classification, we found 39 type I (11.27%), 103 type II (29.77%), nine type III (2.60%), 71 type IV (20.52%), 52 type V (15.03%), 59 type VI (17.05%) fractures, and 13 others (3.76%). The density areas of fracture lines are mainly located in the ALC and PLC segments (74.3%, 69.1%). In different views, fracture lines of different Schatzker types showed distinct distribution characteristics.

Conclusions

Schatzker classification combined with 3D fracture mapping provides a new presentation of tibial plateau fracture morphology. According to the 3D fracture mapping, different types of TPFs have distinctly different distribution characteristics of fracture lines. There are significant differences between different types of fracture injury segments.

Analysis of Effects of PTEN-Mediated TGF-β/Smad2 Pathway on Osteogenic Differentiation in Osteoporotic Tibial Fracture Rats and Bone Marrow Mesenchymal Stem Cell under Tension

Purpose. To discuss effects of phosphatase and tensin homolog protein (PTEN)-mediated transforming growth factor-β (TGF-β)/Smad homologue 2 (Smad2) pathway on osteogenic differentiation in osteoporotic (OP) tibial fracture rats and bone marrow mesenchymal stem cell (BMSC) under tension. Methods. A tibial fracture model was established. The rats were divided into sham-operated group and model group, and tibia tissue was collected. Purchase well-grown cultured rat BMSC, and use the Flexercell in vitro cell mechanics loading device to apply tension. The expression of PTEN was detected by qRT-PCR. After the BMSCs were transfected with si-PTEN and oe-PTEN, the force was applied to detect cell differentiation. The expression of TGF-β/Smad2 protein was detected by Western blot. The formation of calcium nodules in BMSC was detected by alkaline phosphatase (ALP) staining and alizarin red (AR) staining. Results. The expression of PTEN was higher in the model group and tension MSC group, and the expression of TGF-β and Smad2 protein was lower. The expression of TGF-β and Smad2 protein in oe-PTEN group was lower than the oe-NC group and control group. The expression of TGF-β and Smad2 protein in si-PTEN group was higher than the si-NC group and control group. The results of ALP staining and AR staining also confirmed the above results. Conclusion. PTEN-mediated TGF-β/Smad2 pathway may play a key role in the osteogenic differentiation of OP tibial fracture rats. Downregulation of PTEN and upregulation of TGF-β/Smad2 signal can promote the osteogenic differentiation of BMSC under tension.

[Change in the treatment of tibial plateau fractures]

BACKGROUND

The treatment of tibial plateau fractures has experienced a number of very different conceptual developments in recent years, not only with respect to technical innovations but also against the background of changing fracture patterns and the growing requirements of patients.

OBJECTIVE

What developments in recent years have had a significant impact on current treatment strategies for tibial plateau fractures?

METHODS

Narrative review of publications listed in PubMed on the topic of treatment of complex tibial plateau fractures.

RESULTS

While the two-dimensional classifications are becoming less important, computed tomography (CT)-based three-dimensional assessment of fracture progression and an access strategy based on it are coming to the fore. Direct dorsal approaches have been shown to be superior, particularly in the case of relevant posteromedial and/or posterolateral fracture involvement. The step-by-step approach extension via specific osteotomies of ligamentous attachments also enables a needs-dependent and fracture-dependent complete joint visualization and reduction control. In the treatment of geriatric tibial plateau fractures, primary treatment with endoprostheses is becoming increasingly more important to enable early mobilization under full load bearing with significantly shorter rehabilitation times.

CONCLUSION

Modern developments in the context of fracture treatment around the tibial plateau have led to a relevant reduction of infections and improved surgical outcomes; however, the high demands and the improved understanding of fractures still underline the great challenge in the treatment of complex fracture patterns.

Intra- and inter-observer reliability assessment of widely used classifications and the "Ten-segment classification" of tibial plateau fractures

BACKGROUND

Ten-segment classification provides a different approach to the evaluation of tibial plateau fractures. The purpose of this study was to assess the intra- and inter-observer reliability of three widely used classification systems (Schatzker, Arbeitsgemeinschaft für Osteosynthesefragen (AO/OTA), and the updated three-column concept (uTCC)) with ten-segment classification in two-dimensional computed tomography (2D-CT) and three-dimensional computed tomography (3D-CT).

METHOD

Ninety 2D-CT and 3D-CT scans of patients with tibial plateau fractures were included in this retrospective cohort study. The included data were independently classified by six observers of different years of seniority and were independently observed and classified again after eight weeks. Inter-observer and intra-observer reliability of the four fracture classifications made by the six observers was analyzed using the kappa statistic. Kappa values were interpreted according to the categorical rating by Landis and Koch.

RESULTS

When the inter-observer reliability was based on 2D-CT/3D-CT analysis, the mean Kappa values for the Schatzker, AO/OTA, uTCC, and ten-segment classification were 0.64/0.66, 0.56/0.59, 0.53/0.65, and 0.60/0.73, respectively. When intra-observer reliability was based on 2D-CT/3D-CT, the mean Kappa values for the Schatzker, AO/OTA, uTCC, and ten-segment classification were 0.68/0.83, 0.69/0.83, 0.74/0.85, and 0.80/0.91, respectively.

CONCLUSIONS

The use of 3D-CT is important for the reliable diagnosis and recognition of tibial plateau fracture features compared to 2D-CT. When using 3D-CT, ten-segment classification showed high intra- and inter-observer agreement.

Radiological Outcome Measures Indicate Advantages of Precontoured Locking Compression Plates in Elderly Patients With Split-Depression Fractures to the Lateral Tibial Plateau (AO41B3)

Background

Split-depression fractures to the lateral tibial plateau (AO41B3) often feature severe joint surface destructions. Precontoured locking compression plates (LCPs) are designed for optimum support of the reduced joint surface and have especially been emphasized in reduced bone quality. A lack of evidence still inhibits their broad utilization in elderly patients. Thus, aim of the present study was to investigate the implant-specific radiological outcomes of AO41B3-fractures in young versus elderly patients.

Methods

The hospital’s database was screened for isolated AO41B3-factures, open reduction and internal fixation (ORIF), and radiological follow-up ≥12 months. CT-scans, radiographs, and patients’ records were analyzed. Patients were attributed as young (18–49) or elderly (≥50 years). Additional subgrouping was carried out into precontoured LCP and conventional implants. The Rasmussen Radiological Score (RRS) after 12 months was set as primary outcome parameter. The RRS postoperatively and the medial proximal tibial angle (MPTA) postoperatively and after 12 months were secondary outcome parameters.

Results

Fifty nine consecutive patients were included (26 young, 38.2 ± 7.8 years; 33 elderly, 61.3 ± 9.4 years). There were no significant differences regarding mean size and depression depth of the lateral joint surface fragments. Prior to implant-specific subgrouping, the radiological outcome measures revealed no significant differences between young (RRS = 7.7 ± 1.7; MPTA = 90.3 ± 2.3°) and elderly (RRS = 7.2 ± 1.7; MPTA = 90.5 ± 3.3°). After implant-specific subgrouping, the radiological outcome revealed significantly impaired results in young patients with conventional implants (RRS_(C) = 6.9 ± 1.6, RRS_(LCP) = 8.5 ± 1.5, P = .015; MPTA_(C) = 91.5 ± 1.9°, MPTA_(LCP) = 89.1 ± 2.1°, P = .01). The effect was even more pronounced in elderly patients, with highly significant deterioration of the radiological outcome measures for conventional implants compared to precontoured LCP (RRS_(C) = 5.7 ± 1.6, RRS_(LCP) = 8.2 ± .8, P < .001; MPTA_(C) = 92.6 ± 4.2°, MPTA_(LCP) = 89.2 ± 1.4°, P = .002).

Conclusion

Utilizing precontoured LCP in the treatment of AO41B3-fractures is associated with improved radiological outcomes. This effect is significant in young but even more pronounced in elderly patients. Consequently, precontoured LCP should closely be considered in any AO41B3-fracture, but especially in elderly patients.

Architecture of the cancellous bone in human proximal tibia based on P45 sectional plastinated specimens

PURPOSE

To reveal differences in the pattern of trabecular architecture in the epiphysis and metaphysis of the proximal tibia.

METHODS

The trabecular architecture of the proximal tibia was observed in 27 P45 plastinated knee specimens.

RESULTS

In the medial and lateral condyles, under the articular cartilage surrounded by the medial or lateral meniscus, the cancellous bone is formed by thick and dense trabecular bands, which run longitudinally in the epiphysis and then pass through the epiphyseal line to terminate on the slanted cortex of the metaphysis. In the intercondylar eminence, the trabeculae are arranged basically in a network. In the central portion of the tibial metaphysis, cancellous bone consists of fine arcuate trabeculae, which extend to the anterior and posterior cortices, respectively. These trabeculae are intersected sparsely and form trusses over the medullary cavity. Near the areas of attachment of the iliotibial tract, tibial collateral ligament, anterior and posterior cruciate ligaments, and patellar ligament, the cancellous bone is locally reinforced with patchy trabeculae, dense radiating trabeculae, or two orthotropic trabecular bands.

CONCLUSION

This study provides further accurate anatomical information on the trabeculae of the proximal tibia. The soft structures of knee joint, including the articular cartilage, menisci, and ligaments, and the slanted cortices of the metaphysis are important landmarks for the location of different arrangements of the cancellous architecture. The present results are beneficial for clinical diagnosis and treatment of pathologies of the knee joint, or the establishment of a finite element analysis model of the knee joint.

Validation of Bone Density and Microarchitecture Measurements of the Load-Bearing Femur in the Human Knee Obtained Using In Vivo HR-pQCT Protocol

High resolution peripheral quantitative computed tomography (HR-pQCT) was designed to study bone mineral density (BMD) and microarchitecture in peripheral sites at the distal radius and tibia. With the introduction of the second generation HR-pQCT scanner (XtremeCT II, Scanco Medical) that has a larger, longer gantry it is now possible to study the human knee in vivo using HR-pQCT. Previous validation of HR-pQCT measurements at the distal radius and tibia against micro-CT is not representative of the knee because the increased cross-sectional area, greater amount of soft tissue surrounding the scan region, and different imaging protocol result in potentially increased beam hardening effects and photon scatter and different signal-to-noise ratio. The objective of this study is to determine the accuracy of density and microarchitecture measurements in the human knee measured by HR-pQCT using an in vivo protocol. Twelve fresh-frozen cadaver knees were imaged using in vivo HR-pQCT (60.7 µm) protocol. Subsequentially, distal femurs were extracted and imaged using a higher resolution (30.3 µm) ex vivo protocol, replicating micro-CT imaging. Scans were registered so that agreement of density and bone microarchitecture measurements could be determined using linear regression and Bland-Altman plots. All density and microarchitecture outcomes were highly correlated between the 2 protocols (R² > 0.89) albeit with statistically significant differences between absolute measures based on paired t tests. All parameters showed accuracy between 4.5% and 8.7%, and errors were highly systematic, particularly for trabecular BMD and trabecular thickness (R² > 0.93). We found that BMD and microarchitecture measurements in the distal femur obtained using an in vivo HR-pQCT knee protocol contained systematic errors, and accurately represented measurements obtained using a micro-CT equivalent imaging protocol. This work establishes the validity and limitations of using HR-pQCT to study the BMD and microarchitecture of human knees in future clinical studies.

Deciphering the Relevance of Bone ECM Signaling

Bone mineral density, a bone matrix parameter frequently used to predict fracture risk, is not the only one to affect bone fragility. Other factors, including the extracellular matrix (ECM) composition and microarchitecture, are of paramount relevance in this process. The bone ECM is a noncellular three-dimensional structure secreted by cells into the extracellular space, which comprises inorganic and organic compounds. The main inorganic components of the ECM are calcium-deficient apatite and trace elements, while the organic ECM consists of collagen type I and noncollagenous proteins. Bone ECM dynamically interacts with osteoblasts and osteoclasts to regulate the formation of new bone during regeneration. Thus, the composition and structure of inorganic and organic bone matrix may directly affect bone quality. Moreover, proteins that compose ECM, beyond their structural role have other crucial biological functions, thanks to their ability to bind multiple interacting partners like other ECM proteins, growth factors, signal receptors and adhesion molecules. Thus, ECM proteins provide a complex network of biochemical and physiological signals. Herein, we summarize different ECM factors that are essential to bone strength besides, discussing how these parameters are altered in pathological conditions related with bone fragility.

In vivo analysis of subchondral trabecular bone in patients with osteoarthritis of the knee using second-generation high-resolution peripheral quantitative computed tomography (HR-pQCT)

OBJECTIVE

Subchondral bone plays an important role in the pathological mechanisms of knee osteoarthritis (OA). High-resolution peripheral quantitative computed tomography (HR-pQCT) is an imaging modality allowing noninvasive microstructural analysis of human bone, and the second generation enables scanning of the knee. The purpose of this study was to perform in vivo analysis of subchondral trabecular bone in patients with medial knee OA, to elucidate features of bone microstructure in medial knee OA, and to investigate relationships between bone microstructure and both stage of disease and lower limb alignment.

METHODS

Subjects were 20 women, including both patients with medial knee OA (Kellgren-Lawrence (KL) grade 2, n = 5, KL grade 3, n = 7, and KL grade 4, n = 4; mean age: 63.0 years; body mass index (BMI): 23.8 kg/m²) and volunteers without knee OA (KL grade 1, n = 4, mean age: 66.0 years; BMI: 23.8 kg/m²). The proximal tibia (20-mm length) was scanned by second-generation HR-pQCT at a voxel size of 60.7 μm. A subchondral trabecular bone volume of 5 mm length was extracted from the medial and lateral plateaus. They were then divided into 4 regions: anterior, central, medial or lateral, and posterior. Finally, subchondral bone microstructure parameters were analyzed and compared, between each plateau and region. Relationships between microstructural parameters and disease stage (KL grade, minimum joint space width), and between those parameters and lower limb alignment (femorotibial angle: FTA, mechanical axis deviation: MAD) were also investigated.

RESULTS

In the medial plateau, volumetric bone mineral density (vBMD), bone volume fraction (BV/TV), and trabecular thickness were significantly higher and structure model index (SMI) was significantly lower than in the lateral plateau, particularly in the anterior, central, and medial regions (p < .01 each). In the anterior region of the medial plateau, vBMD, BV/TV, and connectivity density showed strong positive correlations with KL grade, FTA, and MAD (r-range: 0.61 to 0.83), while trabecular separation and SMI exhibited strong negative correlations with KL grade, FTA, and MAD (r-range: -0.60 to -0.83).

CONCLUSIONS

Higher bone volume, trabecular thickness, and a more plate-like structure were observed in the medial tibial plateau than in the lateral. Subchondral bone microstructure at the anterior region in the medial plateau showed strong relationships with KL grade and lower limb alignment. These results indicate that subchondral bone microstructure in this region may provide representative indices, particularly in medial knee OA. Although this study involved a specifically Asian cohort with a lower BMI distribution than other ethnic groups, the technique presented may be useful in studying the pathogenesis of OA or evaluating treatment effects.

Seltene Gefahr eines Kompartmentsyndroms bei arthroskopischer Versorgung der Tibiaplateaufraktur

Frakturen des Tibiaplateaus gehen häufig mit Begleitverletzungen (z. B. vorderes Kreuzband, Seitenbänder, Meniskus) sowie einer komplexen Beteiligung der Gelenkflächen einher. Die Therapie erfolgt in der Regel durch eine operative Versorgung mittels winkelstabiler Platten. In diesem Beitrag wird der Fall einer 61-jährigen Patientin nach Sturz in der häuslichen Umgebung beschrieben, bei dem sie sich eine Fraktur des vorderen Tibiakopfes und der medialen Femurkondyle mit einer multiligamentären Ruptur sowie eine Lappenruptur des lateralen Meniskus zuzog, sodass die Indikation für eine arthroskopische Operation bestand. Aufgrund der Gefahr eines Kompartmentsyndroms musste der Eingriff jedoch vorzeitig abgebrochen werden. Im Anschluss wurde die Patientin erfolgreich mit einer Knietotalendoprothese versorgt. Das Kompartmentsyndrom stellt eine sehr seltene, aber ernsthafte Komplikation der Arthroskopie dar. Eine gute invasive Therapieoption ist die Fasziotomie, wobei deren Indikation u. a. vom Druck des Kompartiments abhängt. Genaue Richtlinien bezüglich der Behandlung des Kompartmentsyndroms liegen noch nicht vor. Die Therapie sollte in erster Linie patientenorientiert erfolgen.

[Extended medial and extended lateral approach for tibial plateau fractures]

OBJECTIVE

Complete visualization of the articular surface in comminuted uni- or bicondylar tibial plateau fractures as a prerequisite for anatomical reconstruction to reduce the risk of posttraumatic osteoarthritis.

INDICATIONS

Unicondylar lateral or medial as well as bicondylar intra-articular tibial plateau fractures with central and/or dorsal fracture lines; comminuted destruction of the medial or lateral tibial plateau with dislocation of >2 mm.

CONTRAINDICATIONS

Critical soft tissue in the approach area, femoral condylar fracture, intraligamentous ruptures of the medial or lateral ligaments or the posterolateral corner.

SURGICAL TECHNIQUE

Medial: via the medial or anteromedial approach; lateral: via the antero- or posterolateral approach for open reduction and internal fixation of the tibial plateau fracture. Sharp dissection down to the medial/lateral ligamentous accompanying structures with subsequent presentation of the medial/lateral femoral epicondyle. Medial: approximately 2 × 2 cm osteotomy of the medial femoral epicondyle. Lateral: osteotomy of an approximately 1 × 1 × 0.5 cm bone block of the lateral femoral epicondyle either with protection or including the popliteus tendon running ventrally in the sulcus popliteus. In this case, a violation of the articular condyle should be avoided.

POSTOPERATIVE MANAGEMENT

Early functional posttreatment with full mobilization and 10-20 kg partial load bearing on forearm crutches, fracture-dependent for 6-12 weeks.

RESULTS

Very good visualization of the comminuted articular surface with postoperatively anatomical reconstruction of complex fracture patterns without postoperative concomitant instabilities.

[Osteosynthesis of bicondylar tibial plateau fracture in a prone position : Video article]

OBJECTIVE

The aim of the surgical treatment of intra-articular bicondylar tibial plateau fractures is the anatomical reconstruction and direct biomechanical optimal fixation of the fractured articular surface and the leg axis, taking the frequently associated soft tissue damage into account.

INDICATIONS

This article presents a cadaver model of a simulated complex bicondylar tibial plateau fracture 41C3 according to the AO classification with fracture involvement of all 10 segments and indications for surgery due to a posteromedial shearing fracture and lateral articular destruction with posterolaterocentral impaction.

CONTRAINDICATIONS

Pronounced soft tissue damage with acute or incompletely healed infections in the area of the surgical approach.

SURGICAL TECHNIQUE

In the presented video of the operation, which is available online, the direct treatment of an intra-articular complex tibial plateau fracture from dorsal in a prone position is shown in detail: posterolateral ca. 13 cm long skin incision immediately above the fibular head with subsequent gentle preparation of the peroneal nerve at the medial border of the biceps femoris muscle. Retraction of the lateral head of the gastrocnemius muscle medially. Proximal detachment of the soleus muscle from the fibular head and retraction of the popliteus muscle medially. Horizontal capsule incision for fracture visualization. Opening of the lateral window ventral to the lateral collateral ligament. If necessary, osteotomy of the lateral femoral epicondyle for improved posterolaterocentral fracture visualization. Angular stable osteosynthetic fixation. Posteromedial approach medial to the medial gastrocnemius head. Retraction of the medial head of the gastrocnemius muscle laterally, horizontal capsular incision with sparing of the semimembranosus muscle medially and posterior cruciate ligaments laterally, fracture reduction, fixation with posteromedial support plate, image converter control, wound closure.

FOLLOW-UP

Postoperative cooling and elevation of the operated limb. Depending on the fracture 6-10 weeks partial loading of maximum 20 kg. Prior to full load bearing clinical radiological follow-up checks to determine the bony consolidation and material positioning.

RESULTS

This is an established and safe delivery strategy for complex fracture patterns with dorsally running fractures. The risk of intraoperative malreduction is low. Postoperative reduction losses depend on fracture, operation and especially patient-specific characteristics.