The distribution of cartilage thickness within the joints of the lower limb of elderly individuals

Deep learning and conventional hip MRI for the detection of labral and cartilage abnormalities using arthroscopy as standard of reference

OBJECTIVES

To evaluate the performance of high-resolution deep learning-based hip MR imaging (CSAI) compared to standard-resolution compressed sense (CS) sequences using hip arthroscopy as standard of reference.

METHODS

Thirty-two patients (mean age, 37.5 years (± 11.7), 24 men) with femoroacetabular impingement syndrome underwent 3-T MR imaging prior to hip arthroscopy. Coronal and sagittal intermediate-weighted TSE sequences with fat saturation were obtained using CS (0.6 × 0.8 mm) and high-resolution CSAI (0.3 × 0.4 mm), with 3 mm slice thickness and similar acquisition times (3:55-4:12 min). MR scans were independently assessed by three radiologists and a hip arthroscopy specialist for labral and cartilage abnormalities. Sensitivity, specificity, and accuracy were calculated using arthroscopy as reference standard. Statistical comparisons between CS and CSAI were performed using McNemar's test.

RESULTS

Labral abnormality detection showed excellent sensitivity for radiologists (CS and CSAI: 97-100%) and the surgeon (CS: 81%, CSAI: 90%, p = 0.08), with 100% specificity. Overall cartilage lesion sensitivity was significantly higher with CSAI versus CS (42% vs. 37%, p < 0.001). Highest sensitivity was observed in superolateral acetabular cartilage (CS: 81%, CSAI: 88%, p < 0.001), while highest specificity was found for the anteroinferior acetabular cartilage (CS and CSAI: 99%). Sensitivity was lowest for the assessment of the anteroinferior and posterior acetabular zones, and inferior and posterior femoral zones (CS and CSAI < 6%).

CONCLUSION

CS and CSAI MR imaging showed excellent diagnostic performance for labral abnormalities. Despite CSAI's improved cartilage lesion detection, overall diagnostic performance for cartilage assessment remained suboptimal.

KEY POINTS

Question Accurate preoperative detection of labral and cartilage lesions in femoroacetabular impingement remains challenging, with current MRI protocols showing variable diagnostic performance. Findings High-resolution deep learning-based and standard-resolution compressed sense MRI demonstrate comparable diagnostic performance, with high accuracy for labral defects but limited sensitivity for cartilage lesions. Clinical relevance Current MRI protocols, regardless of resolution optimization, show persistent limitations in cartilage evaluation, indicating the need for further technical advancement to improve diagnostic confidence in presurgical planning.

Is Native Joint Line More Accurately Restored with Robotic Assisted Total Knee Arthroplasty than with Conventional Instruments?

Introduction

Changes in joint line (JL) position after total knee arthroplasty (TKA) have revealed implant failure, diminished knee function, and altered knee biomechanics. The purpose of this study was to compare the joint line restoration of robotic-assisted TKA (RA-TKA) and conventional TKA (c-TKA).

Materials and Methods

In a prospective cohort study trial, trained fellows performed radiographic analyses on patients receiving RA-TKA (group-1) and c-TKA (group-2) to quantify joint line using the adductor tubercle method. Statistical analysis was used using t-tests, with statistical significance defined as a P < 0.005.

Results

The study contained 150 RA-TKAs and 150 total C-TKAs. Both groups were comparable in demographics such as age, gender, and body mass index. On average, RA-TKAs resulted in a 1.65 ± 0.46 mm shift in the JL position, while C-TKAs resulted in a 2.52 ± 0.52 mm change (P = 0.000). The interclass correlation coefficient between the robotic and conventional groups is around 0.992.

Conclusion

RA-TKA restores the JL position better than C-TKA, which appears to depend on precise planning and ligament balancing, which is attainable with robotic-aided surgery. The clinical relevance of this statistically significant difference requires additional investigation.

Impact of treadmill running on distal femoral cartilage thickness: a cross-sectional study of professional athletes and healthy controls

PURPOSE

This present study aimed to assess the impact of treadmill running on distal femoral cartilage thickness.

METHODS

Professional athletes aged 20 to 40 years with a history of treadmill running (minimum 75 min per week for the past three months or more) and age-, sex-, and body mass index (BMI)-matched healthy controls were recruited. Demographics and clinical features of participants were recorded. Athletes were divided into subgroup 1 with less than 12 months of treadmill running and subgroup 2 with 12 months or more of treadmill running. Distal femoral cartilage thicknesses were measured at the midpoints of the right medial condyle (RMC), right intercondylar area (RIA), right lateral condyle (RLC), left medial condyle (LMC), left intercondylar area (LIA), and left lateral condyle (LLC) via ultrasonography.

RESULT

A total of 72 athletes (mean age: 29.6 ± 6.6 years) and 72 controls (mean age: 31.9 ± 6.7 years) were enrolled. Athletes had significantly thinner cartilages in the RLC (2.21 ± 0.38 vs. 2.39 ± 0.31 cm, p = 0.002), LLC (2.28 ± 0.37 vs. 2.46 ± 0.35 cm, p = 0.004), and LMC (2.28 ± 0.42 vs. 2.42 ± 0.36 cm, p = 0.039) compared with the control group. Furthermore, cartilage thickness was significantly thinner in subgroup 2 athletes compared with the control group in the RLC (2.13 ± 0.34 vs. 2.39 ± 0.31 cm, p = 0.001), LLC (2.22 ± 0.31 vs. 2.46 ± 0.35 cm, p = 0.005), and LMC (2.21 ± 0.46 vs. 2.42 ± 0.36 cm, p = 0.027); however, subgroup 1 athletes did not have such differences. There was a weak negative correlation between total months of treadmill running and cartilage thickness in the RLC (r = - 0.0236, p = 0.046) and LLC (r = - 0.0233, p = 0.049). No significant correlation was found between the distal femoral cartilage thickness at different sites and the patients' demographic features, including age, BMI, speed and incline of treadmill running, and minutes of running per session and week (p > 0.05).

CONCLUSION

Compared with healthy controls, professional athletes with a history of long-term high-intensity treadmill running had thinner femoral cartilages. The duration (months) of treadmill running was weakly negatively correlated with distal femoral cartilage thickness. Longitudinal studies with prolonged follow-ups are needed to clarify how treadmill running affects femoral cartilage thickness in athletes.

Does robotic-assisted unicompartmental knee arthroplasty restore native joint line more accurately than with conventional instruments?

The study's primary aim is the restoration of native joint line in patients having robotic-assisted unicondylar knee arthroplasty and conventional unicondylar knee arthroplasty. Literature in the past has demonstrated that reducing the joint line can result in greater failure rates. This is a prospective cohort investigation of patients who had medial UKA between March 2017 and March 2022.All patient's pre-operative and post-operative radiological joint line assessments were examined by two observers by Weber's methods. Robotic-assisted UKA performed with hand-held image-free robots was compared to conventional UKA groups. The distal position of the femoral component was higher in Group B utilizing conventional tools than in Group A employing robotic-assisted UKA. This positional difference was statistically significant. The mean difference among the pre-operative and post-operative joint lines in Group A was 1.6 ± 0.49 (range 0.8 mm-2.4 mm), while it was 2.47 ± 0.51 (range 1.6 mm-3.9 mm) (p 0.005) in Group B. In Group A, a greater percentage of the subjects (64%) attained a femoral component position within two millimeters from the joint line, whereas just 18% in Group B did. When compared with the conventional UKA technique, the meticulous attention to detail and planning for ligament rebalancing when using the robotic-assisted UKA technique not solely enhance surgical precision for implant placing but additionally provides excellent native joint line restoration and balancing. For validation of its longevity and survivability, the cohort must be tracked for a longer period of time.

Designing polymers for cartilage uptake: effects of architecture and molar mass

Osteoarthritis (OA) is a progressive disease, involving the progressive breakdown of cartilage, as well as changes to the synovium and bone. There are currently no disease-modifying treatments available clinically. An increasing understanding of the disease pathophysiology is leading to new potential therapeutics, but improved approaches are needed to deliver these drugs, particularly to cartilage tissue, which is avascular and contains a dense matrix of collagens and negatively charged aggrecan proteoglycans. Cationic delivery vehicles have been shown to effectively penetrate cartilage, but these studies have thus far largely focused on proteins or nanoparticles, and the effects of macromolecular architectures have not yet been explored. Described here is the synthesis of a small library of polycations composed of N-(2-hydroxypropyl)methacrylamide (HPMA) and N-(3-aminopropyl)methacrylamide (APMA) with linear, 4-arm, or 8-arm structures and varying degrees of polymerization (DP) by reversible addition fragmentation chain-transfer (RAFT) polymerization. Uptake and retention of the polycations in bovine articular cartilage was assessed. While all polycations penetrated cartilage, uptake and retention generally increased with DP before decreasing for the highest DP. In addition, uptake and retention were higher for the linear polycations compared to the 4-arm and 8-arm polycations. In general, the polycations were well tolerated by bovine chondrocytes, but the highest DP polycations imparted greater cytotoxicity. Overall, this study reveals that linear polymer architectures may be more favorable for binding to the cartilage matrix and that the DP can be tuned to maximize uptake while minimizing cytotoxicity.

Consistency of serial ultrasonographic joint tissue measurements by the Joint tissueActivity and Damage Exam (JADE) protocol in relation to hemophilic joint health parameters

OBJECTIVES

The Joint _tissueActivity and Damage Exam (JADE) is a point-of-care (POC) musculoskeletal ultrasound (MSKUS) protocol for non-radiologists to evaluate hemophilic arthopathy. Our aim was to determine the consistency of cross-sectional analyses of direct tissue measurements (JADE protocol) and clinical Hemophilia Joint Health Score [HJHS] and functional joint assessments (arc) at three clinic visits.

METHODS

We prospectively studied adults (n = 44) with hemophilia (A or B) of any severity and arthropathy at 3 North American sites. We assessed HJHS, total arc, and JADE parameters (bilateral elbows, ankles, and knees) at study entry, at ≈12-18 months, and at ≈24-36 months, and used MSKUS to evaluate painful episodes between study visits. JADE measurements included osteochondral alterations, cartilage thickness, and soft tissue expansion at sentinel positions. Associations between joint HJHS and total arc with each JADE variable were examined with random intercept models.

RESULTS

At each visit increasing HJHS and decreasing total arc were associated in the expected direction with increasing length of OAs and soft tissue expansion in all joints, and decreasing cartilage thickness in the knee. However, HJHS associations with cartilage thickness were U-shaped for elbow and ankle (i.e. cartilage thinning and thickening). Associations between total arc and cartilage thickness followed a similar curve. (Near) normal levels of both joint parameters (HJHS and total arc) were associated with normal ranges of cartilage thickness. JADE views were also helpful to detect hemarthrosis in association with joint pains.

CONCLUSIONS

POC MSKUS applying direct tissue measurements using the JADE protocol provided reproducible cross-sectional associations with joint health outcomes on three visits. These findings advance protocol validation and enable iterative adaptations resulting in JADE protocol version 2.

Hip joint mechanics in patients with osteonecrosis of the femoral head following treatment by advanced core decompression

BACKGROUND

Osteonecrosis of the femoral head is a serious disease which, if left untreated, leads to destruction of the affected hip joint. For treatment of early stages of this disease, core decompression is the most common procedure. This study investigated the influence of the necrotic lesion and core decompression on the stress pattern in the hip joint using finite element analysis.

METHODS

Subject-specific models were generated from CT scan data of 5 intact hips. For each intact hip, twelve affected hip models were created by imposing a necrotic lesion in the femoral head, and four treated models were then created from four affected ones with central lesion, respectively. Treated models were created by supposing that the defect zone and the drill canal were filled with a bone substitute. Totally 105 hip models from three groups (intact, affected and treated) were simulated during normal walking activity.

FINDINGS

Necrotic lesion modified the stress distribution within the femoral head. Peak stress increased significantly up to 186% in mean in hips with a large lesion indicating an increased risk of femoral head collapse. Additionally, the presence of a medium to large necrosis altered significantly stress values (P < 0.05) and pattern in the articular cartilage. Our study revealed that advanced core decompression can recover normal cartilage stress values and pattern in treated joint.

INTERPRETATION

The presence of a large lesion increased the risk of femoral head collapse. Advanced core decompression with bone grafts can restore normal cartilage mechanics in hip postoperatively.

Acetabular Cartilage Thickness Differs Among Cam, Pincer, or Mixed-Type Femoroacetabular Impingement: A Descriptive Study Using In Vivo Ultrasonic Measurements During Surgical Hip Dislocation

OBJECTIVE

To investigate acetabular cartilage thickness among (1) 8 measurement locations on the lunate surface and (2) different types of femoroacetabular impingement (FAI).

DESIGN

Prospective descriptive study comparing in vivo measured acetabular cartilage thickness using a validated ultrasonic device during surgical hip dislocation in 50 hips. Measurement locations included the anterior/posterior horn and 3 locations on each peripheral and central aspect of the acetabulum. The clock system was used for orientation. Thickness was compared among cam (11 hips), pincer (8 hips), and mixed-type (31 hips) of FAI. Mean age was 31 ± 8 (range, 18-49) years. Hips with no degenerative changes were included (Tönnis stage = 0).

RESULTS

Acetabular cartilage thickness ranged from 1.7 mm to 2.7 mm and differed among the 8 locations (P < 0.001). Thicker cartilage was found on the peripheral aspect at 11 and 1 o'clock positions (mean of 2.4 mm and 2.7 mm, respectively). At 5 out of 8 locations of measurement (anterior and posterior horn, 1 o'clock peripheral, 12 and 2 o'clock central), cartilage thickness was thinner in hips with pincer impingement compared to cam and/or mixed-type of FAI (P ranging from <0.001 to 0.031). No difference in thickness existed between cam and mixed-type of impingement (P = 0.751).

CONCLUSION

Acetabular cartilage thickness varied topographically and among FAI types. This study provides first baseline information about topographical cartilage thickness in FAI measured in vivo. Thinner cartilage thickness in pincer deformities could be misinterpreted as joint degeneration and could therefore have an impact on indication for hip preserving surgery.

Arthroscopic Debridement and Autologous Micronized Adipose Tissue Injection in the Treatment of Advanced-Stage Posttraumatic Osteoarthritis of the Ankle

OBJECTIVE

To evaluate the effect of intra-articular injection of autologous micronized adipose tissue (MAT) with ankle arthroscopic debridement in patients with advanced-stage posttraumatic osteoarthritis (PTOA) of ankle.

DESIGN

A retrospective cohort study investigating patients treated with arthroscopic debridement and autologous MAT injection for ankle PTOA was performed. Patients with Kellgren-Lawrence (KL) grade 3 to 4 were included. Visual analogue scale (VAS), Foot and Ankle Outcome Scores (FAOS), and patient satisfaction were evaluated.

RESULTS

A total of 19 patients (19 ankles) were included (KL grade 3, 8 patients; grade 4, 11 patients). At a mean follow-up time of 14.3 months (range, 7-23 months), the mean FAOS subscales for pain and quality of life significantly increased from 48.8 and 20.1 preoperatively to 61.1 and 30.1 (P = 0.029 and 0.048, respectively). The mean VAS score significantly improved from 6.1 to 3.8 (P = 0.003) at final follow-up. A total of 10.5% (2/19) of patients were very satisfied, 31.6% (6/19) satisfied, 26.3% (5/19) neutral, 21.1% (4/19) unsatisfied, and 10.5% (2/19) very unsatisfied with their outcomes. The overall FAOS score demonstrated a significant difference in pre- to postoperative change with 14.8 for KL grade 3 and 5.9 for KL grade 4 (P = 0.048).

CONCLUSIONS

Autologous MAT injection is a safe and potentially beneficial procedure for advanced-stage ankle PTOA as an adjunct to arthroscopic debridement, although more than one-third of patients were unsatisfied with the procedure. This procedure may be more beneficial for KL grade 3 patients than grade 4 patients. However, future investigations are necessary to define the role of MAT for ankle PTOA.

Accessibility and Thickness of Medial and Lateral Talar Body Cartilage for Treatment of Ankle and Foot Osteochondral Lesions

BACKGROUND

The purposes of this study were to determine (1) if cartilage thicknesses on the talar dome and medial/lateral surfaces of the talus were similar, (2) whether there was sufficient donor cartilage surface area on the medial and lateral talar surfaces to repair talar dome cartilage injuries of the talus, and (3) whether the cartilage surface could be increased following anterior talofibular ligament (ATFL) and sectioning of the tibionavicular and tibiospring portion of the anterior deltoid.

METHODS

Medial and lateral approaches were utilized in 8 cadaveric ankles to identify the accessible medial, lateral, and talar dome cartilage surfaces in 3 conditions: (1) intact, (2) ATFL release, and (3) superficial anterior deltoid ligament release. The talus was explanted, and the cartilage areas were digitized with a coordinate measuring machine. Cartilage thickness was quantified using a laser scanner.

RESULTS

The mean cartilage thickness was 1.0 ± 0.1 mm in all areas tested. In intact ankles, the medial side of the talus showed a larger total area of available cartilage than the lateral side (152 mm² vs 133 mm²). ATFL release increased the available cartilage area on the medial and lateral sides to 167 mm² and 194 mm², respectively. However, only the lateral talar surface had sufficient circular graft donor cartilage available for autologous osteochondral transplantation (AOT) procedures of the talus. After ATFL and deltoid sectioning, there was an increase in available graft donor cartilage available for AOT procedures.

CONCLUSION

The thickness of the medial and lateral talar cartilage surfaces is very similar to that of the talar dome cartilage surface, which provides evidence that the medial and lateral surfaces may serve as acceptable AOT donor cartilage. The surface area available for AOT donor site grafting was sufficient in the intact state; however, sectioning the ATFL and superficial anterior deltoid ligament increased the overall lateral talar surface area available for circular grafting for an AOT procedure that requires a larger graft. These results support the idea that lateral surfaces of the talus may be used as donor cartilage for an AOT procedure since donor and recipient sites are similar in cartilage thickness, and there is sufficient cartilage surface area available for common lesion sizes in the foot and ankle.

CLINICAL RELEVANCE

This anatomical study investigates the feasibility of talar osteochondral autografts from the medial or lateral talar surfaces exposed with standard approaches. It confirms the similar cartilage thickness of the talar dome and the ability to access up to an 8- to 10-mm donor graft from the lateral side of the talus after ligament release. This knowledge may allow better operative planning for use of these surfaces for osteochondral lesions within the foot and ankle, particularly in certain circumstances of a revision microfracture.

Robotic-assisted Unicompartmental knee Arthroplasty optimizes joint line restitution better than conventional surgery

Purpose

To compare joint line restoration after unicompartmental knee arthroplasty (UKA) between conventional and robotic-assisted surgery. Previous studies have shown that joint line distalization can lead to higher failure rates. The hypothesis was that robotic-assisted UKA is associated with less femoral component distalization and a precise tibial cut, which allows a more anatomical restitution of the knee joint line.

Methods

Retrospective cohort study of patients undergoing medial or lateral UKA between May 2018 and March 2020. Preoperative and postoperative radiologic assessment of the joint line was performed by two observers, using three different methods, one for tibial slope and one for tibial resection. Robotic assisted UKA and conventional UKA groups were compared.

Results

Sixty UKA were included, of which 48 (77.42%) were medial. Robotic-assisted UKA were 40 (64.52%) and 22(35.48%) were conventional

The distalization of the femoral component was higher in the conventional group despite the method of measurement used In both Weber methods, the difference was statistically different: Conventional 2.3 (0.9 to 5.6) v/s Robotic 1.5 (− 1.1 to 4.1) (p =0.0025*). A higher proportion of patients achieved a femoral component position ≤ two millimeters from the joint line using robotic-assisted UKA compared to the conventional technique .

No statistical difference between robotic-assisted and conventional UKA was found in tibial resection and slope.

Conclusion

Robotic-assisted UKA shows a better rate of joint line restoration due to less femoral component distalization than conventional UKA. No difference was found in the amount of tibial resection between groups in this study.

Level of evidence

III

A Combined Geometric Morphometric and Discrete Element Modeling Approach for Hip Cartilage Contact Mechanics

Finite element analysis (FEA) provides the current reference standard for numerical simulation of hip cartilage contact mechanics. Unfortunately, the development of subject-specific FEA models is a laborious process. Owed to its simplicity, Discrete Element Analysis (DEA) provides an attractive alternative to FEA. Advancements in computational morphometrics, specifically statistical shape modeling (SSM), provide the opportunity to predict cartilage anatomy without image segmentation, which could be integrated with DEA to provide an efficient platform to predict cartilage contact stresses in large populations. The objective of this study was, first, to validate linear and non-linear DEA against a previously validated FEA model and, second, to present and evaluate the applicability of a novel population-averaged cartilage geometry prediction method against previously used methods to estimate cartilage anatomy. The population-averaged method is based on average cartilage thickness maps and therefore allows for a more accurate and individualized cartilage geometry estimation when combined with SSM. The root mean squared error of the population-averaged cartilage geometry predicted by SSM as compared to the manually segmented cartilage geometry was 0.31 ± 0.08 mm. Identical boundary and loading conditions were applied to the DEA and FEA models. Predicted DEA stress distribution patterns and magnitude of peak stresses were in better agreement with FEA for the novel cartilage anatomy prediction method as compared to commonly used parametric methods based on the estimation of acetabular and femoral head radius. Still, contact stress was overestimated and contact area was underestimated for all cartilage anatomy prediction methods. Linear and non-linear DEA methods differed mainly in peak stress results with the non-linear definition being more sensitive to detection of high peak stresses. In conclusion, DEA in combination with the novel population-averaged cartilage anatomy prediction method provided accurate predictions while offering an efficient platform to conduct population-wide analyses of hip contact mechanics.

Variation in the Thickness of Knee Cartilage. The Use of a Novel Machine Learning Algorithm for Cartilage Segmentation of Magnetic Resonance Images

BACKGROUND

The variation in articular cartilage thickness (ACT) in healthy knees is difficult to quantify and therefore poorly documented. Our aims are to (1) define how machine learning (ML) algorithms can automate the segmentation and measurement of ACT on magnetic resonance imaging (MRI) (2) use ML to provide reference data on ACT in healthy knees, and (3) identify whether demographic variables impact these results.

METHODS

Patients recruited into the Osteoarthritis Initiative with a radiographic Kellgren-Lawrence grade of 0 or 1 with 3D double-echo steady-state MRIs were included and their gender, age, and body mass index were collected. Using a validated ML algorithm, 2 orthogonal points on each femoral condyle were identified (distal and posterior) and ACT was measured on each MRI. Site-specific ACT was compared using paired t-tests, and multivariate regression was used to investigate the risk-adjusted effect of each demographic variable on ACT.

RESULTS

A total of 3910 MRI were included. The average femoral ACT was 2.34 mm (standard deviation, 0.71; 95% confidence interval, 0.95-3.73). In multivariate analysis, distal-medial (-0.17 mm) and distal-lateral cartilage (-0.32 mm) were found to be thinner than posterior-lateral cartilage, while posterior-medial cartilage was found to be thicker (0.21 mm). In addition, female sex was found to negatively impact cartilage thickness (OR, -0.36; all values: P < .001).

CONCLUSION

ML was effectively used to automate the segmentation and measurement of cartilage thickness on a large number of MRIs of healthy knees to provide normative data on the variation in ACT in this population. We further report patient variables that can influence ACT. Further validation will determine whether this technique represents a powerful new tool for tracking the impact of medical intervention on the progression of articular cartilage degeneration.

Protocol development for synchrotron contrast-enhanced CT of human hip cartilage

Understanding hip osteoarthritis requires new investigational tools for quantitative studies of biophysical and biomechanical properties as well as for determination of structure. Three new protocols to study pathological changes in cartilage and to measure cartilage thickness in intact human hips are described using synchrotron contrast enhanced computed tomography (sCECT) with the iodinated contrast agent CA4+. Ten human cadaver hips were prepared and injected with CA4+ using three different methods, all of which included rotation and distraction of the joint. CA4+ diffusion into cartilage was monitored using sCECT. The thickness of acetabular and femoral cartilage was also measured. Diffusion times ranged from 2 h to 75 h, depending on the injection protocol and the cartilage region. Direct single injection of the contrast through the labrum resulted in the fastest diffusion times. The iodine attenuation coefficient, which reflects the contrast agent distribution in the cartilage, ranged from 0.0142/cm to 0.1457/cm. Three injections at the head/neck conjunction area yielded the highest iodine attenuation coefficients in cartilage. The femoral cartilage in the Superior-Medial compartment was significantly thicker than in the other 3 femoral compartments, and femoral cartilage in the Superior-Anterior compartment was significantly thinner than the other 3 femoral compartments. The acetabular cartilage in the Superior compartment was significantly thicker than that in the Superior-Posterior compartment. sCECT with CA4+ allows assessment of hip cartilage thickness with 0.1 mm isotropic voxel size, sufficient for evaluating cartilage pathology and biomechanics.

Suitability of Using the Hamate for Reconstruction of the Finger Middle Phalanx Base: An Assessment of Cartilage Thickness

Background

Osteochondral grafts are indicated for reconstructing the finger middle phalanx base when there is greater than 50% involvement of the articular surface and significant comminution. This study aims to compare the cartilage thickness of the distal surface of the hamate to the finger middle phalanx base to assess its suitability as an osteochondral graft.

Methods

A 3-dimensional laser scanner and computer modelling techniques were utilized to determine the cartilage thickness of the distal surface of the hamate, and finger middle phalanx base using cadaver specimens. The mean, maximum, and coefficient of variation (CV%; a measure of uniformity of cartilage distribution), as well as cartilage distribution maps were determined.

Results

The mean cartilage thickness of the hamate was 0.73 ± 0.08 mm compared to the average mean thickness of the finger middle phalanx base of 0.40 ± 0.12 mm. The maximum cartilage thickness of the hamate was 1.27 ± 0.14 mm compared to the average maximum of the finger middle phalanx base of 0.67 ± 0.14 mm. The CV% of the hamate was 27.8 ± 4.2 compared to the average CV% for the finger middle phalanx base of 26.6 ± 8.1. The hamate and finger middle phalanx base have maximum areas that were most frequently at or spanning the median ridge; however, this was more consistently observed with the hamate.

Conclusion

The distal surface of the hamate is a suitable osteochondral graft with respect to cartilage thickness and distribution providing sufficient cartilage for reconstruction of the finger middle phalanx base.

Regional Distribution of Articular Cartilage Thickness in the Elbow Joint: A 3-Dimensional Study in Elderly Humans

During elbow procedures, reconstruction of the joint (including the articular cartilage) is important in order to restore elbow function; however, the regional distribution of elbow cartilage is not completely understood. The purpose of the present study was to investigate the 3-dimensional (3-D) distribution patterns of cartilage thickness of elbow bones (including the distal part of the humerus, proximal part of the ulna, and radial head) in order to elucidate the morphological relationship among them.

Patient Age and Hip Morphology Alter Joint Mechanics in Computational Models of Patients With Hip Dysplasia

BACKGROUND

Older patients (> 30 years) undergoing periacetabular osteotomy (PAO) to delay THA often have inferior patient-reported outcomes than younger adult patients (< 30 years). It is unclear how patient age affects hip morphology, mechanics, or patient-reported outcome scores.

QUESTIONS/PURPOSES

(1) Is increased patient age associated with computationally derived elevations in joint contact stresses? (2) Does hip shape affect computationally derived joint contact stresses? (3) Do computationally derived joint contact stresses correlate with visual analog scale (VAS) pain scores evaluated at rest in the clinic at a minimum of 1 year after surgery?

METHODS

A minimum of 1 year of clinical followup was required for inclusion. The first 15 patients younger than 30 years of age, and the first 15 patients older than 30 years of age, who underwent PAO for treatment of classic dysplasia (lateral center-edge angle < 25°) who met the minimum followup were selected from a historical database of patients treated by a single surgeon between April 2003 and April 2010. The older cohort consisted of 14 females and one male with a median age of 41 years (range, 31-54 years). The younger cohort consisted of 10 females and five males with a median age of 19 years (range, 12-29 years). Median followup for the older than 30 years versus younger than 30 years cohort was 19 months (range, 12-37 months) versus 24 months (range, 13-38 months). Pre- and postoperative hip models were created from CT scans for discrete element analysis (DEA) contact stress computations. DEA treats contacting articular surfaces as rigid bodies (bones) separated by a bed of compressive springs (cartilage), the deformation of which governs computation of joint contact stresses. This technique greatly simplifies computational complexity compared with other modeling techniques, which permits patient-specific modeling of larger cohorts. Articular surface shape was assessed by total root mean square deviation of each patient's acetabular and femoral cartilage geometry from sphericity. Preoperative and postoperative VAS pain scores evaluated at rest in the clinic were correlated with computed contact stresses.

RESULTS

Patients older than 30 years had higher predicted median peak contact stress preoperatively (13 MPa [range, 9-23 MPa; 95% confidence interval {CI}, 11-15 MPa] versus 7 MPa [range, 6-14 MPa; 95% CI, 6-8 MPa], p < 0.001) but not postoperatively (10 MPa [range, 6-18 MPa; 95% CI, 8-12 MPa] versus 8 MPa [range, 6-13 MPa; 95% CI, 7-9 MPa], p = 0.137). Deviation from acetabular sphericity positively correlated with preoperative peak contact stress (R = 0.326, p = 0.002) and was greater in the older cohort (0.9 mm [range, 0.8-1.5 mm; 95% CI, 0.8-1.0 mm] versus 0.8 mm [range, 0.6-0.9 mm; 95% CI, 0.7-0.9 mm], p = 0.014). Peak preoperative contact stress did not correlate with preoperative VAS pain score (R = 0.072, p = 0.229), and no correlation was found between change in peak contact stress and change in VAS score (R = 0.019, p = 0.280).

CONCLUSIONS

Patients over the age of 30 years with dysplasia had less spherical acetabula and higher predicted preoperative contact stress than those younger than 30 years of age. Future studies with larger numbers of patients and longer term functional outcomes will be needed to determine the role of altered mechanics in the long-term success of PAO varying with patient age.

CLINICAL RELEVANCE

These findings suggest that long-term exposure to abnormal joint loading may have deleterious effects on the hip geometry and may render the joint less amenable to joint preservation procedures. Given the lack of a direct relationship between mechanics and pain, orthopaedic surgeons should be particularly critical when evaluating three-dimensional dysplastic hip morphology in patients older than 30 years of age to ensure beneficial joint reorientation.

Joint contact stresses calculated for acetabular dysplasia patients using discrete element analysis are significantly influenced by the applied gait pattern

Gait modifications in acetabular dysplasia patients may influence cartilage contact stress patterns within the hip joint, with serious implications for clinical outcomes and the risk of developing osteoarthritis. The objective of this study was to understand how the gait pattern used to load computational models of dysplastic hips influences computed joint mechanics. Three-dimensional pre- and post-operative hip models of thirty patients previously treated for hip dysplasia with periacetabular osteotomy (PAO) were developed for performing discrete element analysis (DEA). Using DEA, contact stress patterns were calculated for each pre- and post-operative hip model when loaded with an instrumented total hip, a dysplastic, a matched control, and a normal gait pattern. DEA models loaded with the dysplastic and matched control gait patterns had significantly higher (p = 0.012 and p < 0.001) average pre-operative maximum contact stress than models loaded with the normal gait. Models loaded with the dysplastic and matched control gait patterns had nearly significantly higher (p = 0.051) and significantly higher (p = 0.008) average pre-operative contact stress, respectively, than models loaded with the instrumented hip gait. Following PAO, the average maximum contact stress for DEA models loaded with the dysplastic and matched control patterns decreased, which was significantly different (p < 0.001) from observed increases in maximum contact stress calculated when utilizing the instrumented hip and normal gait patterns. The correlation between change in DEA-computed maximum contact stress and the change in radiographic measurements of lateral center-edge angle were greatest (R2 = 0.330) when utilizing the dysplastic gait pattern. These results indicate that utilizing a dysplastic gait pattern to load DEA models may be a crucial element to capturing contact stress patterns most representative of this patient population.

In-Vitro Detection of Small Isolated Cartilage Defects: Intravascular Ultrasound Vs. Optical Coherence Tomography

This experimental work focused on the sensor selection for the development of a needle-like instrument to treat small isolated cartilage defects with hydrogels. The aim was to identify the most accurate and sensitive imaging method to determine the location and size of defects compared to a gold standard (µCT). Only intravascular ultrasound imaging (IVUS) vs. optical coherent tomography (OCT) were looked at, as they fulfilled the criteria for integration in the needle design. An in-vitro study was conducted on six human cadaveric tali that were dissected and submerged in saline. To simulate the natural appearance of cartilage defects, three types of defects were created via a standardised protocol: osteochondral defects (OCD), chondral defects (CD) and cartilage surface fibrillation (CSF), all sized between 0.1 and 3 mm in diameter. The detection rate by two observers for all diameters of OCD were 80, 92 and 100% with IVUS, OCT and µCT, for CD these were 60, 83 and 97%, and for CSF 0, 29 and 24%. Both IVUS and OCT can detect the presence of OCD and CD accurately if they are larger than 2 mm in diameter, and OCT can detect fibrillated cartilage defects larger than 3 mm in diameter. A significant difference between OCT–µCT and IVUS–µCT was found for the diameter error (p = 0.004) and insertion depth error (p = 0.002), indicating that OCT gives values closer to reference µCT. The OCT imaging technique is more sensitive to various types and sizes of defects and has a smaller diameter, and is therefore preferred for the intended application.

Discrete element analysis is a valid method for computing joint contact stress in the hip before and after acetabular fracture

Evaluation of abnormalities in joint contact stress that develop after inaccurate reduction of an acetabular fracture may provide a potential means for predicting the risk of developing post-traumatic osteoarthritis. Discrete element analysis (DEA) is a computational technique for calculating intra-articular contact stress distributions in a fraction of the time required to obtain the same information using the more commonly employed finite element analysis technique. The goal of this work was to validate the accuracy of DEA-computed contact stress against physical measurements of contact stress made in cadaveric hips using Tekscan sensors. Four static loading tests in a variety of poses from heel-strike to toe-off were performed in two different cadaveric hip specimens with the acetabulum intact and again with an intentionally malreduced posterior wall acetabular fracture. DEA-computed contact stress was compared on a point-by-point basis to stress measured from the physical experiments. There was good agreement between computed and measured contact stress over the entire contact area (correlation coefficients ranged from 0.88 to 0.99). DEA-computed peak contact stress was within an average of 0.5 MPa (range 0.2-0.8 MPa) of the Tekscan peak stress for intact hips, and within an average of 0.6 MPa (range 0-1.6 MPa) for fractured cases. DEA-computed contact areas were within an average of 33% of the Tekscan-measured areas (range: 1.4-60%). These results indicate that the DEA methodology is a valid method for accurately estimating contact stress in both intact and fractured hips.

Anatomically Standardized Maps Reveal Distinct Patterns of Cartilage Thickness With Increasing Severity of Medial Compartment Knee Osteoarthritis

While cartilage thickness alterations are a central element of knee osteoarthritis (OA), differences among disease stages are still incompletely understood. This study aimed to quantify the spatial-variations in cartilage thickness using anatomically standardized thickness maps and test if there are characteristic patterns in patients with different stages of medial compartment knee OA. Magnetic resonance images were acquired for 75 non-OA and 100 OA knees of varying severities (Kellgren and Lawrence (KL) scores 1-4). Three-dimensional cartilage models were reconstructed and a shape matching technique was applied to convert the models into two-dimensional anatomically standardized thickness maps. Difference thickness maps and statistical parametric mapping were used to compare the four OA and the non-OA subgroups. This analysis showed distinct thickness patterns for each clinical stage that formed a coherent succession from the non-OA to the KL 4 subgroups. Interestingly, the only significant difference for early stage (KL 1) was thicker femoral cartilage. With increase in disease severity, typical patterns developed, including thinner cartilage in the anterior area of the medial condyle (significant for KL 3 and 4) and thicker cartilage in the posterior area of the medial and lateral condyles (significant for all OA subgroups). The tibial patterns mainly consisted of thinner cartilage for both medial and lateral compartments (significant for KL 2-4). Comparing anatomically standardized maps allowed identifying patterns of thickening and thinning over the entire cartilage surface, consequently improving the characterization of thickness differences associated with OA. The results also highlighted the value of anatomically standardized maps to analyze spatial variations in cartilage thickness. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2442-2451, 2017.

Robotic Total Knee Arthroplasty with a Cruciate-Retaining Implant: A 10-Year Follow-up Study

Background

This study compared clinical and radiological results between robotic total knee arthroplasty (TKA) and conventional TKA with a cruciate-retaining implant at 10-year follow-up. The hypothesis was that robotic TKA would allow for more accurate leg alignment and component placement, and thus enhance clinical and radiological results and long-term survival rates.

Methods

A total of 113 primary TKAs performed using a cruciate-retaining implant in 102 patients from 2004 to 2007 were reviewed retrospectively. Of the 113 TKAs, 71 were robotic TKAs and 42 were conventional TKAs. Clinical outcomes (visual analogue scale pain score, Hospital for Special Surgery score, Western Ontario and McMaster University score, range of motion, and complications), radiological outcomes, and long-term survival rates were evaluated at a mean follow-up of 10 years.

Results

Clinical outcomes and long-term survival rates were similar between the two groups. Regarding the radiological outcomes, the robotic TKA group had significantly fewer postoperative leg alignment outliers (femoral coronal inclination, tibial coronal inclination, femoral sagittal inclination, tibial sagittal inclination, and mechanical axis) and fewer radiolucent lines than the conventional TKA group.

Conclusions

Both robotic and conventional TKAs resulted in good clinical outcomes and postoperative leg alignments. Robotic TKA appeared to reduce the incidence of leg alignment outliers and radiolucent lines compared to conventional TKA.

Cartilage thickness of distal humerus and its relationships with bone dimensions: magnetic resonance imaging bilateral study in healthy elbows

BACKGROUND

Little is known about the cartilage thickness of the distal humerus and how it affects the shape of the articular surface. Our aims were to assess cartilage thickness and to determine the extent to which it affects the true profile of the distal humerus.

METHODS

We assessed 78 healthy elbows (39 subjects, 19 women and 20 men) with a mean age of 28 years (range, 21-32 years). Cartilage thickness was measured by use of high-definition magnetic resonance imaging scans at 19 different points of the articular surface, 13 on the trochlea and 6 on the capitellum, on the axial and coronal views. Bone diameters at the medial and lateral trochlear ridges, trochlear groove, and capitellum, as well as the articular surface width, were measured. Subject height was used as an indirect measurement of humerus length. Pearson correlation coefficients and the Student t test were used.

RESULTS

Cartilage thickness showed a significant variation (range, 0.4-1.8 mm) independent of sex and side. It appeared thinner at the medial and lateral edges, whereas it increased at the level of the trochleocapitellar and trochlear grooves, the lateral trochlear ridges, and the center of the capitellum. The mean bone diameters of the medial ridge, lateral ridge, trochlear groove, and capitellum measured 25.1 mm, 21 mm, 16.9 mm, and 19.6 mm, respectively. The mean width of the articular surface was 42.9 mm (range, 35.8-50.2 mm). No significant correlation was found between cartilage thickness and bone dimensions.

CONCLUSION

Cartilage thickness is not uniform and modifies the morphologic shape and diameters of the humeral articular surface. These findings may be relevant to anatomic prosthesis design.

MRI-based hip cartilage measures in osteoarthritic and non-osteoarthritic individuals: a systematic review

Osteoarthritis is a common hip joint disease, involving loss of articular cartilage. The prevalence and prognosis of hip osteoarthritis have been difficult to determine, with various clinical and radiological methods used to derive epidemiological estimates exhibiting significant heterogeneity. MRI-based methods directly visualise hip joint cartilage, and offer potential to more reliably define presence and severity of osteoarthritis, but have been underused. We performed a systematic review of MRI-based estimates of hip articular cartilage in the general population and in patients with established osteoarthritis, using MEDLINE, EMBASE and SCOPUS current to June 2016, with search terms such as ‘hip’, ‘femoral head’, ‘cartilage’, ‘volume’, ‘thickness’, ‘MRI’, etc. Ultimately, 11 studies were found appropriate for inclusion, but they were heterogeneous in osteoarthritis assessment methodology and composition. Overall, the studies consistently demonstrate the reliability and potential clinical utility of MRI-based estimates. However, no longitudinal data or reference values for hip cartilage thickness or volume have been published, limiting the ability of MRI to define or risk-stratify hip osteoarthritis. MRI-based techniques are available to quantify articular cartilage signal, volume, thickness and defects, which could establish the sequence and rate of articular cartilage changes at the hip that yield symptomatic osteoarthritis. However, prevalence and rates of progression of hip osteoarthritis have not been established in any MRI studies in the general population. Future investigations could fill this important knowledge gap using robust MRI methods in population-based cross-sectional and longitudinal studies.

Post-traumatic osteoarthritis of the ankle: A distinct clinical entity requiring new research approaches

The diagnosis of ankle osteoarthritis (OA) is increasing as a result of advancements in non-invasive imaging modalities such as magnetic resonance imaging, improved arthroscopic surgical technology and heightened awareness among clinicians. Unlike OA of the knee, primary or age-related ankle OA is rare, with the majority of ankle OA classified as post-traumatic (PTOA). Ankle trauma, more specifically ankle sprain, is the single most common athletic injury, and no effective therapies are available to prevent or slow progression of PTOA. Despite the high incidence of ankle trauma and OA, ankle-related OA research is sparse, with the majority of clinical and basic studies pertaining to the knee joint. Fundamental differences exist between joints including their structure and molecular composition, response to trauma, susceptibility to OA, clinical manifestations of disease, and response to treatment. Considerable evidence suggests that research findings from knee should not be extrapolated to the ankle, however few ankle-specific preclinical models of PTOA are currently available. The objective of this article is to review the current state of ankle OA investigation, highlighting important differences between the ankle and knee that may limit the extent to which research findings from knee models are applicable to the ankle joint. Considerations for the development of new ankle-specific, clinically relevant animal models are discussed. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:440-453, 2017.

Ultrasonographic evaluation of the femoral cartilage thickness in patients with chronic renal failure

OBJECTIVE

To investigate the effects of chronic renal failure (CRF) on the distal femoral cartilage thickness by using ultrasonography and to determine the relationship between cartilage thickness and certain disease-related parameters.

DESIGN

Fifty-seven CRF patients (41 male and 16 female) (mean [SD] age, 44.7 [12.1] years) and 60 healthy controls (41 male and 19 female) (mean [SD] age, 43.5 [13.3] years) were enrolled in this study. Demographic and clinical characteristics were recorded. Cartilage thickness measurements were taken from the medial and lateral condyles, and intercondylar areas of both knees.

RESULTS

Groups were similar in terms of age, weight, height, body mass index and gender (all p>0.05). The mean cartilage thickness was found to be less in CRF patients than in controls (statistically significant for medial condyles and intercondylar areas both in right and the left knees [all p<0.05]). Cartilage thickness showed no correlation with eGFR, and with the levels of serum urea, creatinine, calcium, magnesium, phosphor, hemoglobin, uric acid and as well as steroid use (all p>0.05) in CRF patients.

CONCLUSION

In the light of our findings, we imply that patients with CRF have thinner femoral cartilage than healthy controls. This result may support the view that patients with CRF are at increased risk for developing early knee osteoarthritis. Last but not least, clinicians should be aware of the importance of rehabilitation strategies aimed at decreasing onset and progression of knee osteoarthritis in patients with CRF.

Is a "sulcus cut" technique effective for determining the level of distal femoral resection in total knee arthroplasty?

PURPOSE

Determining the level of distal femoral resection is crucial when performing total knee arthroplasty (TKA). However, variations in distal femoral resection are encountered unexpectedly. A "sulcus cut" technique is sometimes used to determine the level of distal femoral resection, but its effectiveness has not been evaluated. The aim of this study was to examine the reliability of the sulcus cut technique using computer simulation for preoperative planning.

METHODS

This study group comprised 40 knees in 34 patients (22 women, 12 men) scheduled for TKA. The preoperative planning software of a computed tomography (CT)-based navigation system was used. We determined the resected level of the femur so that the bone-implant interface of the femoral component was adjusted to the deepest subchondral bone of the trochlear groove in coronal CT images. We then measured each perpendicular distance from the resected surface of the proximal femur to the most distal point of the lateral and medial femoral condyles.

RESULTS

The mean distances of the distal-lateral and distal-medial condylar resections from the femoral sulcus were 7 mm (±1 mm) and 8 mm (±1 mm), respectively. The resection level did not differ significantly between men and women or between different component sizes. There was a slightly positive correlation between the femoral mechanical and anatomical axis angle and the distance of the distal-lateral condylar resection from the femoral sulcus.

CONCLUSIONS

The sulcus cut technique can be used to determine the desirable level of the distal femoral resection in TKA.

LEVEL OF EVIDENCE

Case series, Level IV.

Patterns of femoral cartilage thickness are different in asymptomatic and osteoarthritic knees and can be used to detect disease-related differences between samples

Measures of mean cartilage thickness over predefined regions in the femoral plate using magnetic resonance imaging have provided important insights into the characteristics of knee osteoarthritis (OA), however, this quantification method suffers from the limited ability to detect OA-related differences between knees and loses potentially important information regarding spatial variations in cartilage thickness. The objectives of this study were to develop a new method for analyzing patterns of femoral cartilage thickness and to test the following hypotheses: (1) asymptomatic knees have similar thickness patterns, (2) thickness patterns differ with knee OA, and (3) thickness patterns are more sensitive than mean thicknesses to differences between OA conditions. Bi-orthogonal thickness patterns were extracted from thickness maps of segmented magnetic resonance images in the medial, lateral, and trochlea compartments. Fifty asymptomatic knees were used to develop the method and establish reference asymptomatic patterns. Another subgroup of 20 asymptomatic knees and three subgroups of 20 OA knees each with a Kellgren/Lawrence grade (KLG) of 1, 2, and 3, respectively, were selected for hypotheses testing. The thickness patterns were similar between asymptomatic knees (coefficient of multiple determination between 0.8 and 0.9). The thickness pattern alterations, i.e., the differences between the thickness patterns of an individual knee and reference asymptomatic thickness patterns, increased with increasing OA severity (Kendall correlation between 0.23 and 0.47) and KLG 2 and 3 knees had significantly larger thickness pattern alterations than asymptomatic knees in the three compartments. On average, the number of significant differences detected between the four subgroups was 4.5 times greater with thickness pattern alterations than mean thicknesses. The increase was particularly marked in the medial compartment, where the number of significant differences between subgroups was 10 times greater with thickness pattern alterations than mean thickness measurements. Asymptomatic knees had characteristic regional thickness patterns and these patterns were different in medial OA knees. Assessing the thickness patterns, which account for the spatial variations in cartilage thickness and capture both cartilage thinning and swelling, could enhance the capacity to detect OA-related differences between knees.

[Malleolar osteotomy--osteotomy as approach]

Both arthroscopic and open surgical techniques may be used for treatment of osteochondral lesions of the ankle joint. Osteotomy around the ankle joint is a well established technique to extend the approach in cases where the osteochondral lesions are located more posteriorly. Medial, oblique, monoplanar malleolar osteotomy should be used in patients with lesions of the medial talus shoulder. The posterolateral ostechondral lesions are less frequent and in such cases distal fibular osteotomy is recommended. In this study the indications for different forms of osteotomy are discussed and the surgical techniques are described.

Avidin as a model for charge driven transport into cartilage and drug delivery for treating early stage post-traumatic osteoarthritis

Local drug delivery into cartilage remains a challenge due to its dense extracellular matrix of negatively charged proteoglycans enmeshed within a collagen fibril network. The high negative fixed charge density of cartilage offers the unique opportunity to utilize electrostatic interactions to augment transport, binding and retention of drug carriers. With the goal of developing particle-based drug delivery mechanisms for treating post-traumatic osteoarthritis, our objectives were, first, to determine the size range of a variety of solutes that could penetrate and diffuse through normal cartilage and enzymatically treated cartilage to mimic early stages of OA, and second, to investigate the effects of electrostatic interactions on particle partitioning, uptake and binding within cartilage using the highly positively charged protein, Avidin, as a model. Results showed that solutes having a hydrodynamic diameter ≤10 nm can penetrate into the full thickness of cartilage explants while larger sized solutes were trapped in the tissue's superficial zone. Avidin had a 400-fold higher uptake than its neutral same-sized counterpart, NeutrAvidin, and >90% of the absorbed Avidin remained within cartilage explants for at least 15 days. We report reversible, weak binding (K(D) ~ 150 μM) of Avidin to intratissue sites in cartilage. The large effective binding site density (N(T) ~ 2920 μM) within cartilage matrix facilitates Avidin's retention, making its structure suitable for particle based drug delivery into cartilage.

Histomorphometric, CT arthrographic, and biomechanical mapping of the human ankle

BACKGROUND

The specific morphological and biomechanical characteristics of the osteochondral unit of the ankle joint are not yet fully understood. This anatomical study aimed to map regional thickness of the articular hyaline uncalcified cartilage and its adjacent layers of mineralized cartilage and subchondral bone as well as to measure the regional indentation stiffness of human ankle joint cartilage.

MATERIALS AND METHODS

A total of 20 pairs of human cadaver ankle joints (median age: 78 years) were evaluated by histomorphometry and multidetector row double-contrast CT arthrography for cartilage thickness in 17 distinct anatomical regions. In addition, regional distribution of the subchondral bone plate and of the mineralized cartilage was scrutinized histologically. Cartilage indentation stiffness was measured using an arthroscopic handheld device (Artscan200), especially validated for use in thin cartilage. The correlation between the thickness of different components of the osteochondral unit and the cartilage indentation stiffness was evaluated.

RESULTS

The thinnest uncalcified cartilage was measured at the anterior talar dome and the distal fibula. The thickest uncalcified cartilage was found in the mid and posterior talar dome, as well as in the tibial plafond. Mineralized cartilage and subchondral bone showed highest values at the anteromedial talar dome. Cartilage indentation stiffness showed a bicentric distribution pattern in 14/20 ankle pairs and was highest in regions with thin cartilage. Positive correlation between the thickness of the mineralized cartilage and the subchondral bone plate was found. No correlation between the thickness of the uncalcified and the mineralized cartilage could be identified.

CONCLUSION

This anatomical study provides a comprehensive mapping of the osteochondral unit of the human ankle joint in elderly people. Articular hyaline uncalcified cartilage and the subchondral bone plate showed clear regional differences and were reciprocally distributed. Cartilage indentation stiffness was inversely correlated to cartilage thickness in elderly people.

CLINICAL RELEVANCE

Thorough understanding of the osteochondral unit of the ankle joint could be helpful for clinicians and researchers in the development of improved operative repair techniques for osteochondral defects in the ankle joint, for example, in constructing specific tissue-engineered osteochondral plugs.

Assessment of early tibiofemoral joint space width changes after anterior cruciate ligament injury and reconstruction: a matched case-control study

BACKGROUND

Progression of primary knee osteoarthritis (OA) is often quantified by measuring structural alterations of the joint such as those in tibiofemoral joint space width (JSW) over time. Limited information is available regarding changes that occur during the onset and progression of posttraumatic OA (PTOA) that are often associated with anterior cruciate ligament (ACL) injury. Furthermore, there is a paucity of information regarding JSW changes in healthy patients, making JSW interpretation challenging during early PTOA progression.

PURPOSE

To evaluate tibiofemoral JSW after ACL injury, ACL reconstruction, and rehabilitation compared with healthy, matched controls.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

A total of 39 ACL-injured patients and 32 matched controls were evaluated. Injured patients were assessed at presurgical baseline and after ACL reconstruction (mean follow-up, 46 months), as were controls. Bilateral, standing, fluoroscopy-assisted, and posterior-anterior metatarsal-phalangeal view knee radiographs were obtained at each visit and JSW was measured.

RESULTS

The JSW differences between knees in control patients were not significantly different and did not change over time. Baseline JSW differences in the ACL group were significantly different than in controls. Three patients (7.9% of total) had an increased JSW difference, and 1 patient (2.6%) had a decreased medial JSW difference. In the lateral compartment, 6 patients (15.8%) had a decreased JSW difference. At follow-up, 2 patients in the ACL group (5%) had a decreased medial JSW difference, and 3 (7.9%) had a significantly increased difference in relation to controls. Lateral compartment analyses revealed 7 (18.4%) patients with a significantly decreased JSW difference and no patients with an increased difference compared with controls.

CONCLUSION

One third of ACL-injured knees underwent significant JSW change soon after injury; consequently, evaluation of within-knee JSW changes over time in ACL-injured patients may not be appropriate with a study based on case-control analysis. The JSWs in the healthy knee of ACL-injured patients do not change over time, allowing this knee to be used as a control for the injured knee. This is important when evaluating the earliest stages of PTOA after ACL injury, when patients are asymptomatic and intervention may be most beneficial.

A nonlinear QCT-based finite element model validation study for the human femur tested in two configurations in vitro

PURPOSE

Femoral fracture is a common medical problem in osteoporotic individuals. Bone mineral density (BMD) is the gold standard measure to evaluate fracture risk in vivo. Quantitative computed tomography (QCT)-based homogenized voxel finite element (hvFE) models have been proved to be more accurate predictors of femoral strength than BMD by adding geometrical and material properties. The aim of this study was to evaluate the ability of hvFE models in predicting femoral stiffness, strength and failure location for a large number of pairs of human femora tested in two different loading scenarios.

METHODS

Thirty-six pairs of femora were scanned with QCT and total proximal BMD and BMC were evaluated. For each pair, one femur was positioned in one-legged stance configuration (STANCE) and the other in a sideways configuration (SIDE). Nonlinear hvFE models were generated from QCT images by reproducing the same loading configurations imposed in the experiments. For experiments and models, the structural properties (stiffness and ultimate load), the failure location and the motion of the femoral head were computed and compared.

RESULTS

In both configurations, hvFE models predicted both stiffness (R(2)=0.82 for STANCE and R(2)=0.74 for SIDE) and femoral ultimate load (R(2)=0.80 for STANCE and R(2)=0.85 for SIDE) better than BMD and BMC. Moreover, the models predicted qualitatively well the failure location (66% of cases) and the motion of the femoral head.

CONCLUSIONS

The subject specific QCT-based nonlinear hvFE model cannot only predict femoral apparent mechanical properties better than densitometric measures, but can additionally provide useful qualitative information about failure location.

Robotic-assisted TKA reduces postoperative alignment outliers and improves gap balance compared to conventional TKA

BACKGROUND

Several studies have shown mechanical alignment influences the outcome of TKA. Robotic systems have been developed to improve the precision and accuracy of achieving component position and mechanical alignment.

QUESTIONS/PURPOSES

We determined whether robotic-assisted implantation for TKA (1) improved clinical outcome; (2) improved mechanical axis alignment and implant inclination in the coronal and sagittal planes; (3) improved the balance (flexion and extension gaps); and (4) reduced complications, postoperative drainage, and operative time when compared to conventionally implanted TKA over an intermediate-term (minimum 3-year) followup period.

METHODS

We prospectively randomized 100 patients who underwent unilateral TKA into one of two groups: 50 using a robotic-assisted procedure and 50 using conventional manual techniques. Outcome variables considered were postoperative ROM, WOMAC scores, Hospital for Special Surgery (HSS) knee scores, mechanical axis alignment, flexion/extension gap balance, complications, postoperative drainage, and operative time. Minimum followup was 41 months (mean, 65 months; range, 41-81 months).

RESULTS

There were no differences in postoperative ROM, WOMAC scores, and HSS knee scores. The robotic-assisted group resulted in no mechanical axis outliers (> ± 3° from neutral) compared to 24% in the conventional group. There were fewer robotic-assisted knees where the flexion gap exceeded the extension gap by 2 mm. The robotic-assisted procedures took an average of 25 minutes longer than the conventional procedures but had less postoperative blood drainage. There were no differences in complications between groups.

CONCLUSIONS

Robotic-assisted TKA appears to reduce the number of mechanical axis alignment outliers and improve the ability to achieve flexion-extension gap balance, without any differences in clinical scores or complications when compared to conventional manual techniques.

Comparison of third toe joint cartilage thickness to that of the finger proximal interphalangeal (PIP) joint to determine suitability for transplantation in PIP joint reconstruction

PURPOSE

To compare the cartilage thickness of the third toe joints to the finger proximal interphalangeal (PIP) joints to assess the appropriateness of using third toe osteochondral grafts for finger PIP joint reconstruction.

METHODS

A laser scanner was used to construct 3-dimensional computer models of 6 matched cadaver right third toe PIP joints, condyles of the third toe middle phalanx, and finger PIP joints with and without cartilage. Cartilage distribution patterns were computed and analyzed for each surface. The cartilage thickness of both sides of the third toe PIP joint and the third toe middle phalanx condyles were compared to the PIP joint of the fingers. A total of 18 third toe and 48 finger joint surfaces were analyzed.

RESULTS

For the third toe middle phalanx condyles, the mean thickness was 0.20 ± 0.09 mm with a maximum of 0.52 ± 0.18 mm, and a coefficient of variation (CV%; a measure of uniformity of cartilage distribution) of 62. For the third toe proximal phalanx condyles, the mean cartilage thickness was 0.26 ± 0.10 mm with a maximum thickness of 0.56 ± 0.14 mm and a CV% of 44. The mean thickness, maximum thickness, and CV% of the finger proximal phalanx condyles was 0.43 ± 0.11 mm, 0.79 ± 0.16 mm, and 31, respectively. For the third toe middle phalanx base, the mean thickness was 0.28 ± 0.06 mm with a maximum of 0.47 ± 0.09 mm and a CV% of 34, compared to the finger middle phalanx base mean of 0.40 ± 0.12 mm with a maximum of 0.67 ± 0.14 mm and a CV% of 27.

CONCLUSIONS

There were significant differences in cartilage thickness between the third toe and the fingers in this study. However, fewer differences were observed with the third toe middle phalanx base cartilage thickness than with the third toe condyles in comparison to the fingers.

Arthroscopic fixation of matrix-associated autologous chondrocyte implantation: importance of fixation pin angle on joint compression forces

PURPOSE

The aim of the study was to investigate the effect of pin fixation perpendicular and 30° tilted to the matrix surface on the joint compression forces.

METHODS

In a porcine knee model, joint compression forces were recorded with a digital pressure sensor above the medial meniscus and with axial compression of 100 N by use of a material testing machine. The forces were recorded for an intact femoral condyle, as well as a standardized cartilage defect of 25 × 20 mm, after matrix-associated autologous chondrocyte implantation (m-ACI) (BioSeed C; Biotissue Technologies, Freiburg, Germany), fixed by use of a conventional suture technique and pin fixation with a biodegradable pin perpendicular and 30° tilted to the matrix surface.

RESULTS

In knees with cartilage defects, the peak compression forces (mean, 824 kPa) were significantly increased compared with the intact knee joint (564 kPa). After m-ACI implantation with a chondral suture (581.3 kPa) and perpendicular pin fixation, the joint compression forces of the cartilage defect were significantly decreased (630.7 kPa). There were no significant differences compared with the intact knee. After 30° tilted pin insertion, mean joint compression forces were significantly increased (1,740 kPa).

CONCLUSIONS

This study shows that after chondral suture and perpendicular pin fixation, there are no increased compression forces in the knee joint in comparison to an intact knee. Thirty degree tilted pin insertion contributes to increased joint compression forces.

CLINICAL RELEVANCE

A tilted insertion during pin fixation in m-ACI should be avoided because it may lead to increased joint compression forces, especially after cartilage defect lesions on the tibial side.

The medial-lateral force distribution in the ovine stifle joint during walking

Knowledge of the load distribution in the knee is essential for understanding the interaction between mechanics and biology in both the healthy and diseased joint. While the sheep stifle joint is a predominant model for better understanding regeneration after injury, little is known about the compartmental force distribution between the medial and lateral condyles. By including sheep specific anatomy and gait analyses, we used computational musculoskeletal analyses to estimate the medial-lateral joint contact force distribution in ovine stifle joints during walking by simplifying the system of equations into a 2D problem that was solved directly. Gait analysis was conducted using bone markers in three female Merino-mix sheep. Joint contact forces were computed with respect to the specific anatomy of the ovine tibia, resulting in low (<0.13 bodyweight) mean anteroposterior shear forces throughout the gait cycle, with mean peak contact forces perpendicular to the tibial plateau of 2.2 times bodyweight. The medial-lateral compartmental load distribution across the tibial condyles was determined and revealed loading predominantly on the medial condyle, bearing approximately 75% of the total load during phases of peak loading. By considering the anatomical characteristics of the ovine stifle joint, together with the dynamic forces during gait, this study provides evidence for predominantly medial loading in sheep, somewhat similar to the distribution reported in man. However, the exact conditions under which the loading in the ovine stifle joint is representative of the human situation will need to be elucidated in further studies.

A human knee joint model considering fluid pressure and fiber orientation in cartilages and menisci

Articular cartilages and menisci are generally considered to be elastic in the published human knee models, and thus the fluid-flow dependent response of the knee has not been explored using finite element analysis. In the present study, the fluid pressure and site-specific collagen fiber orientation in the cartilages and menisci were implemented into a finite element model of the knee using fibril-reinforced modeling previously proposed for articular cartilage. The geometry of the knee was obtained from magnetic resonance imaging of a healthy young male. The bones were considered to be elastic due to their greater stiffness compared to that of the cartilages and menisci. The displacements obtained for fast ramp compression were essentially same as those for instantaneous compression of equal magnitude with the fluid being trapped in the tissues, which was expected. However, a clearly different pattern of displacements was predicted by an elastic model using a greater Young's modulus and a Poisson's ratio for nearly incompressible material. The results indicated the influence of fluid pressure and fiber orientation on the deformation of articular cartilage in the knee. The fluid pressurization in the femoral cartilage was somehow affected by the site-specific fiber directions. The peak fluid pressure in the femoral condyles was reduced by three quarters when no fibril reinforcement was assumed. The present study indicates the necessity of implementing the fluid pressure and anisotropic fibril reinforcement in articular cartilage for a more accurate understanding of the mechanics of the knee.

Site dependence of thickness and speed of sound in articular cartilage of bovine patella

Researchers have made efforts to quantify thickness of articular cartilage as well as its acoustic and mechanical properties using various ultrasound (US) techniques during the last decades, because they are important indicators of articular cartilage degeneration. However, the variation of the thickness and speed of sound of articular cartilage at different anatomical sites would result in the uncertainty of US assessment of degeneration. In this paper, the site dependences of speed of sound and thickness of bovine patellar articular cartilage (n = 10) were investigated using a custom-made US measurement system. The thickness and speed of sound of articular cartilage at different locations of the bovine patella were measured on excised specimens ex situ using a noncontact US approach. A total of 10 patellae were tested. The results showed the overall mean value of the speed of sound in the articular cartilage at the 25 measured sites was 1626 +/- 86 m/s (range, 1507 to 1834 m/s). No statistically significant difference in the speed of sound was observed among the 25 locations or among the four quadrants of the patella. The highest speed of sound (1834 +/- 74 m/s) was obtained at the medial-upper quadrant and the lowest value (1507 +/- 74 m/s) at the medial-lower quadrant. Further grouping of the data revealed that the speed of sound in the central region (1633 +/- 21 m/s) was significantly (p < 0.01) larger than that for the surrounding region (1621 +/- 22 m/s). The overall mean thickness of the patellar articular cartilage was 1.34 +/- 0.34 mm. No significant difference was obtained in the thickness among the 25 locations and also among the four quadrants. However, when the thickness values were divided diagonally, a significant difference (p < 0.01) was observed between the upper region (1.27 +/- 0.11 mm) and the lower region (1.31 +/- 0.41 mm) of the patellae. Although no significant differences in the thickness and speed of sound among the tested sites were observed, it was demonstrated in this study that they did show some degree of site dependence.

Three-dimensional distribution of articular cartilage thickness in the elderly cadaveric acetabulum: a new method using three-dimensional digitizer and CT

OBJECTIVE

The aim of this study was to evaluate the three-dimensional (3D) distribution of the acetabular articular cartilage thickness in cadaveric elderly individuals, measured using a new method with a 3D-digitizer and computed tomography (CT) and to validate this method using a thresholding technique.

DESIGN

Twenty cadaveric hemipelves without fracture, previous hip surgery, or macroscopic degenerative changes were digitized by a 3D-digitizer to make 3D cartilage surface models, and scanned by 3D-CT to create 3D bone surface models. These two surface models were then merged using a surface registration method. Acetabular articular cartilage thickness was evaluated as the distance between the two surface models, and the distribution was mapped. Tests for accuracy and reproducibility were performed by comparing the cartilage thickness of five human femoral heads measured by stereomicroscopy with the distance between the cartilage and bone surface models.

RESULTS

The superolateral cartilage tended to be the thickest in all acetabula. The smallest category (0-0.5 mm) of articular cartilage thickness existed at the posteroinferior lunate surface. In this new method, the mean measurement error was 0.018+/-0.044 mm for the average optimum threshold and the intraclass correlation coefficients were 0.99 in surface registration and 0.94 in data acquisition for reproducibility, indicating high accuracy and reproducibility.

CONCLUSIONS

The proposed method for measuring articular cartilage using a 3D-digitizer and 3D-CT was accurate and reproducible. In the elderly individuals, acetabular articular cartilage tended to be thicker in the superolateral area and there was the thinnest category (0-0.5 mm) on the posteroinferior lunate surface of the acetabulum. The contour generated along 480 Hounsfield units (HU) was closest to the subchondral bone contour in the elderly hip.

Acetabular cartilage thickness: accuracy of three-dimensional reconstructions from multidetector CT arthrograms in a cadaver study

PURPOSE

To prospectively quantify the accuracy of hip cartilage thickness estimated from three-dimensional (3D) surfaces, generated by segmenting multidetector computed tomographic (CT) arthrograms by using direct physical measurements of cartilage thickness as the reference standard.

MATERIALS AND METHODS

Four fresh-frozen cadaver hip joints from two male donors, ages 43 and 46 years, were obtained; institutional review board approval for cadaver research was also obtained. Sixteen holes were drilled perpendicular to the cartilage of four cadaveric acetabula (two specimens). Hip capsules were surgically closed, injected with contrast material, and scanned by using multidetector CT. After scanning, 5.3-mmcores were harvested concentrically at each drill hole and cartilage thickness was measured with a microscope. Cartilage was reconstructed in 3D by using commercial software. Segmentations were repeated by two authors. Reconstructed cartilage thickness was determined by using a published algorithm. Bland-Altman plots and linear regression were used to assess accuracy. Repeatability was quantified by using the coefficient of variation, intraclass correlation coefficient (ICC), repeatability coefficient, and percentage variability.

RESULTS

Cartilage was reconstructed to a bias of -0.13 mm and a repeatability coefficient of + or - 0.46 mm. Regression of the scatterplots indicated a tendency for multidetector CT to overestimate thickness. Intra- and interobserver repeatability were very good. For intraobserver correlation, the coefficient of variation was 14.80%, the ICC was 0.88, the repeatability coefficient was 0.55 mm, and the percentage variability was 11.77%. For interobserver correlation, the coefficient of variation was 13.47%, the ICC was 0.90, the repeatability coefficient was 0.52 mm, and the percentage variability was 11.63%.

CONCLUSION

Assuming that an accuracy of approximately + or - 0.5 mm is sufficient, reconstructions of cartilage geometry from multidetector CT arthrographic data could be used as a preoperative surgical planning tool.

Consideration of the femoral head cartilage thickness in preoperative planning in bipolar hemiarthroplasty

PURPOSE

Bipolar hemiarthroplasty (BH) is one of the commonly performed orthopedic procedures for the treatment of displaced fractures of the femoral neck. However, despite the common use of the BH, little has been written on preoperative planning for this operation. The purpose of this study was to assess the neglected subject which is about the cognition of the femoral head cartilage in planning a BH.

METHODS

We reviewed a group of 62 consecutive patients in whom cemented BH had been performed by one surgeon. A total of 31 patients underwent BH with consideration of the femoral head cartilage thickness in preoperative planning. The anteroposterior radiographs of this group were compared to those of a group of 31 patients who underwent BH without consideration of the femoral head cartilage thickness in preoperative planning. We measured the limb length and offset with reference to the normal contralateral hip and the cartilage thickness of the hip joints postoperatively.

RESULTS

There were significant reduction in the limb-length discrepancy (LLD) (mean 0.4 mm lengthening compared with 1.6 mm shortening; P < 0.001) and improvement of the femoral offset ratios of the operated hips to the normal contralateral hips (mean 99.9% compared with 96.8%; P = 0.032) in the group of patients with consideration of the femoral head cartilage thickness in preoperative planning.

CONCLUSIONS

The femoral head cartilage should be considered when determining the level of femoral neck resection in order to reduce postoperative LLD when planning a bipolar hemiarthroplasty. Accurate and careful preoperative planning can result in balanced hip reconstruction by equalizing limb lengths and restoring the offsets.

A review of the differences between normal and osteoarthritis articular cartilage in human knee and ankle joints

BACKGROUND

Osteoarthritis (OA) is the most common joint disease yet its pathophysiology is still poorly understood. It is more prevalent in some lower limb joints than others; in particular the knee is more commonly affected than the ankle. Research into articular cartilage and OA has primarily focussed on using animal models. However, it is apparent that articular cartilage differs between species, so more research is concentrating on human cartilage.

OBJECTIVE

This paper reviews recent studies that have been undertaken to elucidate the reasons for this, and to discover if the findings would alter the conception that articular cartilage is not capable of repair.

METHOD

Primary research papers into human knee and ankle cartilage published since 1997 have been reviewed.

RESULTS

Differences in the structure, metabolism, physical properties and response to trauma have been found, implying that ankle cartilage may be more resistant to damage.

CONCLUSIONS

More research is needed before definitive conclusions can be reached, but the findings so far suggest that OA should not be accepted as the inevitable outcome of joint injury and individuals and practitioners, such as podiatrists, may be able to use simple measures to prevent or delay its onset.

Comparison of MR-arthrography and CT-arthrography in hyaline cartilage-thickness measurement in radiographically normal cadaver hips with anatomy as gold standard

OBJECTIVE

To compare magnetic resonance (MR)-arthrography and multidetector-spiral-computed-tomography (MDSCT)-arthrography in cartilage-thickness measurement, in hips without cartilage loss, with coronal anatomic slices as gold standard.

METHOD

Institutional review board permission to study cadavers of individuals who willed their bodies to science was obtained. Two independent observers measured femoral and acetabular cartilage thicknesses of 12 radiographically normal hips (six women, five men; age range, 52-98 years; mean age, 76.5 years), on MDSCT-arthrographic and MR-arthrographic reformations, and on coronal anatomic slices, excluding regions of cartilage loss. Inter- and intraobserver reproducibilities were determined. Analysis of variance (ANOVA) was used to test differences between MR-arthrographic and MDSCT-arthrographic measurement errors compared to anatomy.

RESULTS

By MR-arthrography, cartilage was not measurable at approximately 50% of points on sagittal and transverse sections, compared to 0-6% of the points by MDSCT-arthrography. In the coronal plane, the difference between MDSCT-arthrographic and MR-arthrographic measurement errors was not significant (P=0.93).

CONCLUSION

In the coronal plane, MR-arthrography and MDSCT-arthrography were similarly accurate for measuring hip cartilage thickness.