Is the clinical outcome after cartilage treatment affected by subchondral bone edema?

Purpose

Subchondral bone edema is a common finding after cartilage treatment, but its interpretation is still debated. The aim of this study is to analyse the presence of edema after matrix-assisted autologous chondrocyte transplantation (MACT) for knee cartilage lesions at different follow-up times and its correlation with the clinical outcome.

Methods

Two hundred and forty-eight magnetic resonance imagings (MRIs) of patients treated with a hyaluronic acid-based MACT for lesions of the knee articular surface were considered. The MRIs belonged to 116 patients (mean age at surgery 28.6 ± 10.3 years, average defect size 2.4 ± 1.0 cm²), 57 affected by degenerative cartilage lesions, 27 traumatic and 32 were osteochondritis dissecans (OCD). MRI follow-up was performed from 6 to 108 months after treatment. Other than its presence or absence, the subchondral bone edema was evaluated using a 3-level grading considering extension and hyperintensity, and with the WORMS score edema classification. The IKDC subjective score was collected at the time of every MRI.

Results

An analysis of the entire MRI group showed that edema is not constantly present through the follow-up, but presents a particular and well-defined trend. Edema was present within the first 2 years and was then markedly reduced or disappeared at 2 and 3 years (p = 0.044). Afterwards the level of edema increased again (p < 0.0005) and remained steadily present at medium/long-term follow-up. Patellar lesions presented significantly lower edema (p = 0.012), whereas OCD lesions presented more edema at all follow-up (p = 0.002) and a different trend, with an increasing level of edema over time. No correlation was found between edema and clinical outcome.

Conclusions

Edema after MACT is present during the first phases of cartilage maturation up to 2 years of follow-up, and then tends to disappear. However, after a few years, it tends to reappear. Less edema was found in the patella, whereas more edema was found in the OCD, where subchondral bone is primarily involved. Interestingly, the presence of edema was not correlated with a poorer clinical outcome. Whether this might be a prognostic factor at longer follow-up remains to be determined, but our results give some indication on what to expect on both MRI edema and clinical outcome after MACT.

Level of evidence

Case series, Level IV.     

The position of the tibia tubercle in 0°–90° flexion: comparing patients with patella dislocation to healthy volunteers

Purpose

The aim of this study was to measure the tibia tubercle trochlea groove distance (TT–TG) as a function of knee flexion. Our hypothesis was that there is a different pattern in healthy volunteers and patients with patella instability (PFI).

Methods

Thirty-six knees of 30 patients with at least one dislocation of the patella and 30 knees of 30 healthy volunteers as control group were analysed with magnetic resonance imaging by three different observers. The TT–TG was measured in steps of 15° between 0° and 90° of knee flexion. Furthermore, the alignment of the leg (MA), the femur torsion (FTor) and the tibia torsion (TTor) was calculated.

Results

The TT–TG was higher in patients compared to volunteers and in extension compared to flexion. This difference was statistically significant (p < 0.05). Most of the patients with a TT–TG above 20 mm in extension showed a high decrease in flexion to normal values. In some patients, this compensating mechanism fails. MA, FTor and TTor were not different in patients and control group (n.s.).

Conclusion

The TT–TG distance is dynamic and decreased significantly during flexion in knees with PFI and healthy volunteers. However, there were a small number of patients in the PFI group where this compensation mechanism did not work. Therefore, the decision to perform a tibia tubercle osteotomy should not be based on one single measurement in extension or 30° of knee flexion.

Level of evidence

II.     

Alignment does not influence cartilage T2 in asymptomatic knee joints

Purpose

To investigate whether the static knee alignment affects articular cartilage ultrastructures when measured using T2 relaxation among asymptomatic subjects.

Methods

Both knee joints (n = 96) of 48 asymptomatic volunteers (26 females, 22 males; 25.4 ± 1.7 years; no history of major knee trauma or surgery) were evaluated clinically (Lysholm, Tegner) and by MRI (hip–knee–ankle angle, standard knee protocol, T2 mapping). Group (n = 4) division was as follows: neutral (<1° varus/valgus), mild varus (2°–4° varus), severe varus (>4° varus) and valgus (2°–4° valgus) deformity with n = 12 subjects/group; n = 24 knees/group. Regions of interest (ROI) for T2 assessment were placed within full-thickness cartilage across the whole joint surface and were divided respecting compartmental as well as functional joint anatomy.

Results

Leg alignment was 0.7° ± 0.5° varus among neutral, 3.0° ± 0.6° varus among mild varus, 5.0° ± 1.1° varus among severe varus and 2.5° ± 0.7° valgus among valgus group subjects and thus significantly different. No differences between the groups emerged from clinical measures. No morphological pathology was detected in any knee joint. Global T2 values (42.3 ± 2.3; 37.7–47.9 ms) of ROIs placed within every knee joint per subject were not different between alignment groups or between genders, respectively.

Conclusion

Static frontal plane leg malalignment does not affect cartilage ultrastructure among young, asymptomatic individuals as measured by T2 quantitative imaging.

Level of evidence

Cross-sectional study, Level II-III.     

Osteoarthritis of the patella, lateral femoral condyle and posterior medial femoral condyle correlate with range of motion

Purpose

The type of osteoarthritis and the degree of severity which causes restriction of knee range of motion (ROM) is still largely unknown. The objective of this study was to analyse the location and the degree of cartilage degeneration that affect knee range of motion and the connection, if any, between femorotibial angle (FTA) and knee ROM restriction.

Methods

Four hundreds and fifty-six knees in 230 subjects with knee osteoarthritis undergoing knee arthroplasty were included. Articular surface was divided into eight sections, and cartilage degeneration was evaluated macroscopically during the operation. Cartilage degeneration was classified into four grades based on the degree of exposure of subchondral bone. A Pearson correlation was conducted between FTA and knee flexion angle to determine whether high a degree of FTA caused knee flexion restriction. A logistic regression analysis was also conducted to detect the locations and levels of cartilage degeneration causing knee flexion restriction.

Results

No correlation was found between FTA and flexion angle (r = ?0.08). Flexion angle was not restricted with increasing FTA. Logistic regression analysis showed significant correlation between restricted knee ROM and levels of knee cartilage degeneration in the patella (odds ratio (OR) = 1.77; P = 0.01), the lateral femoral condyle (OR = 1.62; P = 0.03) and the posterior medial femoral condyle (OR = 1.80; P = 0.03).

Conclusion

For clinical relevance, soft tissue release and osteophyte resection around the patella, lateral femoral condyle and posterior medial femoral condyle might be indicated to obtain a higher degree of knee flexion angle.

Level of evidence

Case–control study, Level III.     

Effects of four different surgical approaches on intra-operative joint gap in posterior-stabilized total knee arthroplasty

Purpose

The effects of surgical approaches and patellar positions on joint gap measurement during total knee arthroplasty (TKA) remain unclear. We hypothesized that joint gap changes with different knee flexion angles would not be consistent within four different approaches and two different patellar positions.

Methods

This study enrolled 80 knees undergoing posterior-stabilized TKA. For 60 varus knees, parapatellar, midvastus, and subvastus approaches were used in 20 knees each. For 20 valgus knees, a lateral subvastus approach was used. Component gap length and inclination were measured intra-operatively using a specific tensor device under 40 lb with the patella reduced or shifted laterally, at 0°, 45°, 90°, and 135° of knee flexion.

Results

Mean gap lengths at 45° and 90° of knee flexion were significantly larger with the parapatellar approach than with midvastus or lateral subvastus approaches (P < 0.05). Regarding gap inclination, varus angle increased linearly through the entire arc of flexion in all four approaches. When the patella was shifted laterally, gap lengths at 45°, 90°, and 135° were significantly reduced compared with those for the patella reduced in the subvastus approach, whereas gap length was constant in the parapatellar approach, regardless of patellar position.

Conclusion

Joint gap kinematics was not consistent within four different approaches and two different patellar positions. Relatively large gaps at 45° and 90° were unique features for the parapatellar approach. Surgeons should be aware that the flexion gap is reduced when the patella is shifted laterally in vastus medialis-preserving approaches such as the subvastus approach.

Level of evidence

II.     

The effect of tibial tuberosity realignment procedures on the patellofemoral pressure distribution

Purpose

The study was performed to characterize the influence of tibial tuberosity realignment on the pressure applied to cartilage on the patella in the intact condition and with lesions on the lateral and medial facets.

Methods

Ten knees were loaded in vitro through the quadriceps (586 N) and hamstrings (200 N) at 40°, 60°, and 80° of flexion while measuring patellofemoral contact pressures with a pressure sensor. The tibial tuberosity was positioned 5 mm lateral of the normal position to represent lateral malalignment, 5 mm medial of the normal position to represent tuberosity medialization, and 10 mm anterior of the medial position to represent tuberosity anteromedialization. The knees were tested with intact cartilage, with a 12-mm-diameter lesion created within the lateral patellar cartilage, and with the lateral lesion repaired with silicone combined with a medial lesion. A repeated measures ANOVA and post hoc tests were used to identify significant (P < 0.05) differences in the maximum lateral and medial pressure between the tuberosity positions.

Results

Tuberosity medialization and anteromedialization significantly decreased the maximum lateral pressure by approximately 15% at 60° and 80° for intact cartilage and cartilage with a lateral lesion. Tuberosity medialization significantly increased the maximum medial pressure for intact cartilage at 80°, but the maximum medial pressure did not exceed the maximum lateral pressure for any testing condition.

Conclusions

The results indicate that medializing the tibial tuberosity by 10 mm reduces the pressure applied to lateral patellar cartilage for intact cartilage and cartilage with lateral lesions, but does not overload medial cartilage.     

End-stage extension of the knee and its influence on tibial tuberosity-trochlear groove distance (TTTG) in asymptomatic volunteers

Purpose

Increased tibial tuberosity-trochlear groove distance (TTTG) is one potential correcting parameter in patients suffering from lateral patellar instability. It was hypothesized that end-stage extension of the knee might influence the TTTG distance on MR images.

Methods

Transverse T1-weighted MR images of the knee were acquired at full extension, 15° and 30° flexion of the knee in 30 asymptomatic volunteers. MRI parameters: slice thickness: 3 mm, matrix: 256 × 384, FOV: 150 × 150 mm. Two observers independently measured the TTTG at all positions.

Results

Mean TTTG for observer 1 was 15.1 ± 3.2 mm at full extension, 10.0 ± 3.5 mm at 15° flexion and 8.1 ± 3.4 mm at 30° flexion. Mean TTTG for observer 2: 14.8 ± 3.3 mm at full extension, 9.4 ± 3.0 mm at 15° flexion, 8.6 ± 3.4 mm at 30° flexion. Mean values were significantly different (p < 0.001) between full extension and 15° as well as 30° flexion for both observers. Mean values were significantly different (p < 0.001) between 15° and 30° for observer 1, but not for observer 2 (n.s.). Interobserver agreement was very good (intraclass correlation coefficient: 0.87–0.88; p < 0.001).

Conclusions

The TTTG increases significantly at the end-stage extension of the knee. Therefore, the comparability of published TTTG values measured on radiographs, CT and MRI at various flexion/extension angles of the knee are limited.

Level of evidence

Development of diagnostic criteria in a consecutive series of patients and a universally applied ‘gold’ standard, Level II.     

Increased patellofemoral pressure after TKA: an in vitro study

Purpose

Considering the discrepant results of the recent biomechanical studies, the purpose of this study was to simulate dynamic muscle-loaded knee flexion with a large number of specimens and to analyse the influence of total knee arthroplasty (TKA) without and with patellar resurfacing on the patellofemoral pressure distribution.

Methods

In 22 cadaver knee specimens, dynamic muscle-loaded knee flexion (15°–90°) was simulated with a specially developed knee simulator applying variable muscle forces on the quadriceps muscles to maintain a constant ankle force. Patellofemoral pressures were measured with flexible, pressure-sensitive sensor foils (TEKSCAN) and patellofemoral offset with an ultrasound motion-tracking system (ZEBRIS). Measurements were taken on the native knee, after total knee arthroplasty and after patellar resurfacing. Correct positioning of the patellar implant was examined radiologically.

Results

The maximal patellofemoral peak pressure partly increased from the native knee to the knee with TKA with intact patella (35°–90°, p < 0.012) and highly increased (twofold to threefold) after patellar resurfacing (20°–90°, p < 0.001). Concurrently, the patellofemoral contact area decreased and changed from a wide area distribution in the native knee, to a punctate area after TKA with intact patella and a line-shaped area after patellar resurfacing. Patellar resurfacing led to no increase in patellar thickness and patellofemoral offset.

Conclusions

Despite correct implantation of the patellar implants and largely unchanged patellofemoral offset, a highly significant increase in pressure after patellar resurfacing was measured. Therefore, from a biomechanical point of view, the preservation of the native patella seems reasonable if there is no higher grade patellar cartilage damage.     

Feasibility of in vivo diffusion tensor imaging of articular cartilage with coverage of all cartilage regions

Objectives

To investigate the value of diffusion tensor imaging (DTI) of articular cartilage to differentiate healthy from osteoarthritis (OA) subjects in all cartilage regions.

Methods

DTI was acquired sagittally at 7 T in ten healthy and five OA (Kellgren-Lawrence grade 2) subjects with a line scan diffusion tensor sequence (LSDTI). Three healthy volunteers and two OA subjects were examined twice to assess the test-retest reproducibility. Averaged mean diffusivity (MD) and fractional anisotropy (FA) were calculated in each cartilage region (femoral trochlea, lateral and medial femoral condyles, patella, and lateral and medial tibia).

Results

The test-retest reproducibility was 2.9 % for MD and 5.6 % for FA. Averaged MD was significantly increased (+20 %, p?<?0.05) in the OA subjects in the lateral femoral condyle, lateral tibia and the femoral trochlea compartments. Averaged FA presented a trend of lower values in the OA subjects (-12 %), which was only significant for the lateral tibia.

Conclusions

In vivo DTI of articular cartilage with coverage of all cartilage regions using an LSDTI sequence is feasible, shows excellent reproducibility for MD and FA, and holds potential for the diagnosis of OA.

Key points

? DTI of articular cartilage is feasible at 7 T in all cartilage regions ? DTI of articular cartilage can potentially differentiate healthy and OA subjects     

T2* mapping and delayed gadolinium-enhanced magnetic resonance imaging in cartilage (dGEMRIC) of glenohumeral cartilage in asymptomatic volunteers at 3 T

Objectives

To establish baseline T2* and T1_Gd values of glenohumeral cartilage at 3 T.

Methods

Forty asymptomatic volunteers (mean age: 24.8?±?2.2 years) without shoulder abnormalities were included. The MRI protocol comprised a double-echo steady-state (DESS) sequence for morphological cartilage evaluation, a gradient-echo multiecho sequence for T2* assessment, and a gradient-echo dual-flip-angle sequence for T1_Gd mapping. Statistical assessment involved a one-way analysis of variance (ANOVA) to identify the differences between various regions of the glenohumeral joint and intraclass correlation (ICC) analysis comparing repetitive T2* and T1_Gd measures to assess intra- and interobserver reliability.

Results

Both techniques revealed significant differences between superior and inferior glenohumeral cartilage demonstrating higher T2* (26.2 ms vs. 23.2 ms, P value?<?0.001) and T1_Gd (750.1 ms vs. 720.2 ms, P value?=?0.014) values in the superior regions. No trend was observed in the anterior-posterior measurement (P value range: 0.279–1.000). High intra- and interobserver agreement (ICC value range: 0.895–0.983) was noted for both T2* and T1_Gd mapping.

Conclusions

T2* and T1_Gd mapping are reliable in the assessment of glenohumeral cartilage. The values from this study can be used for comparison to identify cartilage degeneration in patients suffering from shoulder joint abnormalities.

Key Points

? T2* mapping and dGEMRIC are sensitive to collagen degeneration and proteoglycan depletion. ? This study aimed to establish baseline T2*/dGEMRIC values of glenohumeral cartilage. ? Both techniques revealed significant differences between superior and inferior glenohumeral cartilage. ? High intra-/interreader agreement was noted for both T2* mapping and dGEMRIC. ? These baseline normal values should be useful when identifying potential degeneration.     

The in vivo effects of unloading and compression on T1-Gd (dGEMRIC) relaxation times in healthy articular knee cartilage at 3.0 Tesla

Purpose

The purpose was to investigate the in vivo effects of unloading and compression on T1-Gd relaxation times in healthy articular knee cartilage.

Materials and methods

Ten volunteers were enrolled, and dGEMRIC images of their right knee joints were obtained using 3.0-T MR at three timepoints: directly following exercise (“baseline”), approximately 15 min after unloading (“unloading”) and during application of a compressive force (50% of the body weight) generated by a loading device via a footplate (“compression”).

Results

Our analysis of variance of pooled data from all cartilage zones demonstrated a significant mean T1-Gd decrease of 56.6 ms between baseline and compression (p?<?0.001), and a significant mean decrease of 42.1 ms between unloading and compression (p?<?0.001). No significant difference was found between baseline and unloading. Higher mean T1-Gd values were observed in the cartilage contact zone (central femoral and tibial zones; 698.3?±?162.2 ms) than in the non-contact zone (anterior and posterior femoral and tibial zones, and dorsal femoral zone; 662.9?±?149.3 ms; p?<?0.01).

Conclusion

T1-Gd times appear to be sensitive to mechanical cartilage stress, and thus, further studies are warranted that investigate the relationship between the biochemical load response and the biomechanical properties of articular cartilage.     

Magnetic resonance imaging and histology of ovine hip joint cartilage in two age populations: a sheep model with assumed healthy cartilage

Objective

To compare morphologically normal appearing cartilage in two age groups with delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) and correlate magnetic resonance imaging (MRI) findings with histology.

Materials and methods

Twenty femoral head specimens collected from ten lambs (group I) and ten young adult sheep (group II) underwent dGEMRIC and histological assessment. A region of 2 cm² with morphologically normal-appearing cartilage was marked with a surgical suture for subsequent matching of MRI and histological sections. The MRI protocol included a three-dimensional (3D) double-echo steady-state sequence for morphological cartilage assessment, a B1 pre-scan with various flip angles for B1 field heterogeneity correction, and 3D volumetric interpolated breathhold examination for T1_Gd mapping (dGEMRIC). Histological analysis was performed according to the Mankin scoring system.

Results

A total of 303 regions of interest (ROI; 101 MRI reformats matching 101 histological sections) was assessed. Twenty-six ROIs were excluded owing to morphologically apparent cartilage damage or insufficient MR image quality. Therefore, 277 ROIs were analyzed. Histological analyses revealed distinct degenerative changes in various cartilage samples of group II (young adult sheep). Corresponding T1_Gd values were significantly lower in the group of sheep (mean T1_Gd?=?540.4 ms) compared with the group of lambs (mean T1_Gd?=?623.6 ms; p?<?0.001).

Conclusions

Although morphologically normal, distinct cartilage degeneration may be present in young adult sheep cartilage. dGEMRIC can reveal these changes and may be a tool for the assessment of early cartilage degeneration.     

The relationship between patellofemoral and tibiofemoral morphology and gait biomechanics following arthroscopic partial medial meniscectomy

Purpose

To examine the relationship between tibiofemoral and patellofemoral joint articular cartilage and subchondral bone in the medial and gait biomechanics following partial medial meniscectomy.

Methods

For this cross-sectional study, 122 patients aged 30–55 years, without evidence of knee osteoarthritis at arthroscopic partial medial meniscectomy, underwent gait analysis and MRI on the operated knee once for each sub-cohort of 3 months, 2 years, or 4 years post-surgery. Cartilage volume, cartilage defects, and bone size were assessed from the MRI using validated methods. The 1st peak in the knee adduction moment, knee adduction moment impulse, 1st peak in the knee flexion moment, knee extension range of motion, and the heel strike transient from the vertical ground reaction force trace were identified from the gait data.

Results

Increased knee stance phase range of motion was associated with decreased patella cartilage volume (B = ?17.9 (95 % CI ?35.4, ?0.4) p = 0.045) while knee adduction moment impulse was associated with increased medial tibial plateau area (B = 7.7 (95 % CI 0.9, 13.3) p = 0.025). A number of other variables approached significance.

Conclusions

Knee joint biomechanics exhibited by persons who had undergone arthroscopic partial meniscectomy gait may go some way to explaining the morphological degeneration observed at the patellofemoral and tibiofemoral compartments of the knee as patients progress from surgery.

Level of evidence

III.     

Clinical outcome after medial patellofemoral ligament reconstruction and autologous chondrocyte implantation following recurrent patella dislocation

Purpose

Medial patellofemoral ligament (MPFL) reconstruction is a well-established treatment option in recurrent patella dislocation. The combination with associated retropatellar cartilage lesions are severe injuries and very difficult to treat. The purpose of this study was to evaluate our clinical results of MPFL reconstruction and autologous chondrocyte implantation (ACI).

Methods

Thirteen patients with recurrent patella dislocation were treated with a combination of MPFL reconstruction and ACI at our institution between 2010 and 2014. All patients had at least 2 patella dislocations. The posttraumatic cartilage lesions were grade IV according to the ICRS and were localized retropatellar in 8 cases and at the lateral femoral condyle in 2 cases. The mean defect size was 7.2 ± 3.5 cm² (3–12 cm²). Subjective and objective scores were assessed before surgery and at f/u, as well as radiologic parameters and cartilage status on magnetic resonance imaging (MRI).

Results

Ten patients (5 male, 5 female) with a mean follow-up of 2 years (minimum 1 year to 4 years) were enrolled in the study. At latest clinical follow-up, all patients had a stable patella with no signs of instability and all patients showed improved subjective and objective scores. Lysholm score increased to 74.1 ± 18.7 (48–99), KOOS score to 74.4 ± 16.9 (57–95), IKDC subjective to 63.9 ± 22.1 (34–93) and Kujala score to 73.8 ± 25.1 (50–100). The post-operative modified MOCART score for quality assessment of the ACI on MRI was an average of 13.7 ± 1.8 points (11–16), with a complete fill of the defect in 80 % of lesions.

Conclusion

Medial patellofemoral ligament reconstruction with simultaneous ACI showed good clinical results in recurrent patella dislocation with traumatic cartilage lesions grade IV. No patella re-dislocation occurred and the ACI was successful in 80 % of patients according to MRI. Subjective and objective scores improved but combined surgery is inferior to reports from the literature on MPFL reconstruction alone without cartilage damage.

Level of evidence

Therapeutic case series, Level IV.     

An in vitro comparative study of T2 and T2* mappings of human articular cartilage at 3-Tesla MRI using histology as the standard of reference

Objective

The aim of this study was to evaluate the correlations between T2 value, T2* value, and histological grades of degenerated human articular cartilage.

Materials and methods

T2 mapping and T2* mapping of nine tibial osteochondral specimens were obtained using a 3-T MRI after total knee arthroplasty. A total of 94 ROIs were analyzed. Histological grades were assessed using the David–Vaudey scale. Spearman’s rho correlation analysis and Pearson’s correlation analysis were performed.

Results

The mean relaxation values in T2 map with different histological grades (0, 1, 2) of the cartilage were 51.9?±?9.2 ms, 55.8?±?12.8 ms, and 59.6?±?10.2 ms, respectively. The mean relaxation values in T2* map with different histological grades (0, 1, 2) of the cartilage were 20.3?±?10.3 ms, 21.1?±?12.4 ms, and 15.4?±?8.5 ms, respectively. Spearman’s rho correlation analysis confirmed a positive correlation between T2 value and histological grade (ρ?=?0.313, p?<?0.05). Pearson’s correlation analysis revealed a significant negative correlation between T2 and T2* (r?=??0.322, p?<?0.05). Although T2* values showed a decreasing trend with an increase in cartilage degeneration, this correlation was not statistically significant in this study (ρ?=??0.192, p?=?0.129).

Conclusions

T2 mapping was correlated with histological degeneration, and it may be a good biomarker for osteoarthritis in human articular cartilage. However, the strength of the correlation was weak (ρ?=?0.313). Although T2* values showed a decreasing trend with an increase in cartilage degeneration, the correlation was not statistically significant. Therefore, T2 mapping may be more appropriate for the initial diagnosis of articular cartilage degeneration in the knee joint. Further studies on T2* mapping are needed to confirm its reliability and mechanism in cartilage degeneration.     

Comparison of 1.5- and 3-T MR imaging for evaluating the articular cartilage of the knee

Purpose

The aim of this prospective study was to compare routine MRI scans of the knee at 1.5 and 3 T obtained in the same individuals in terms of their performance in the diagnosis of cartilage lesions.

Methods

One hundred patients underwent MRI of the knee at 1.5 and 3 T and subsequent knee arthroscopy. All MR examinations consisted of multiplanar 2D turbo spin-echo sequences. Three radiologists independently graded all articular surfaces of the knee joint seen at MRI. With arthroscopy as the reference standard, the sensitivity, specificity, and accuracy of 1.5- and 3-T MRI for detecting cartilage lesions and the proportion of correctly graded cartilage lesions within the knee joint were determined and compared using resampling statistics.

Results

For all readers and surfaces combined, the respective sensitivity, specificity, and accuracy for detecting all grades of cartilage lesions in the knee joint using MRI were 60, 96, and 87 % at 1.5 T and 69, 96, and 90 % at 3 T. There was a statistically significant improvement in sensitivity (p < 0.05), but not specificity or accuracy (n.s.) for the detection of cartilage lesions at 3 T. There was also a statistically significant (p < 0.05) improvement in the proportion of correctly graded cartilage lesions at 3 T as compared to 1.5 T.

Conclusion

A 3-T MR protocol significantly improves diagnostic performance for the purpose of detecting cartilage lesions within the knee joint, when compared with a similar protocol performed at 1.5 T.

Level of evidence

III.     

Delayed gadolinium-enhanced MRI of the meniscus (dGEMRIM) in patients with knee osteoarthritis: relation with meniscal degeneration on conventional MRI,reproducibility, and correlation with dGEMRIC

Objectives

To assess (1) whether normal and degenerated menisci exhibit different T1_GD on delayed gadolinium-enhanced MRI of the meniscus (dGEMRIM), (2) the reproducibility of dGEMRIM and (3) the correlation between meniscus and cartilage T1_GD in knee osteoarthritis (OA) patients.

Methods

In 17 OA patients who underwent dGEMRIM twice within 7 days, meniscus and cartilage T1_GD was calculated. Meniscus pathology was evaluated on conventional MRI. T1_GD in normal and degenerated menisci were compared using a Student’s t-test. Reproducibility was assessed using ICCs. Pearson’s correlation was calculated between meniscus and cartilage T1_GD.

Results

A trend towards lower T1_GD in degenerated menisci (mean: 402 ms; 95 % CI: 359–444 ms) compared to normal menisci (mean: 448 ms; 95 % CI: 423–473 ms) was observed (p?=?0.05). Meniscus T1_GD ICCs were 0.85–0.90. The correlation between meniscus and cartilage T1_GD was moderate in the lateral (r?=?0.52–0.75) and strong in the medial compartment (r?=?0.78–0.94).

Conclusions

Our results show that degenerated menisci have a clear trend towards lower T1_GD compared to normal menisci. Since these results are highly reproducible, meniscus degeneration may be assessed within one delayed gadolinium-enhanced MRI simultaneously with cartilage. The strong correlation between meniscus and cartilage T1_GD suggests concomitant degeneration in both tissues in OA, but also suggests that dGEMRIC may not be regarded entirely as sulphated glycosaminoglycan specific.

Key Points

? dGEMRIM T1 _GD can possibly be used to assess meniscal degeneration; ? dGEMRIM yields highly reproducible meniscal T1 _GD in early stage osteoarthritic patients; ? Concomitant degeneration of cartilage and meniscus tissue occurs in early stage osteoarthritis; ? dGEMRIC cannot be regarded as entirely sulphated glycosaminoglycan specific.     

Influence of knee flexion angle and weight bearing on the Tibial Tuberosity-Trochlear Groove (TTTG) distance for evaluation of patellofemoral alignment

Purpose

The aim of the present study was to investigate the influence of knee flexion and weight bearing on the Tibial Tuberosity-Trochlear Groove (TTTG) distance.

Materials and methods

Magnetic resonance imaging of the knee was carried out in 8 healthy volunteers. An open 0.25 T scanner equipped with a C-shaped permanent tilting magnet allowing examinations in weight-bearing conditions was used for the present investigation. A 3D gradient-echo sequence with axial slice orientation was obtained in a lying and an upright position with the knee straight and at 30° of knee flexion. The medial, central and lateral trochlear heights as well as the TTTG were determined.

Results

The mean medial trochlear height was 76.2 ± 4 %, the central trochlear height was 72.2 ± 3 %, and lateral trochlear height was 82.9 ± 3 %. The mean TTTG distance was 11.6 ± 4.4 mm in lying position at 0° knee flexion and 7.3 ± 2.9 mm (n.s.) at 30° knee flexion. Under weight bearing, the mean TTTG was significantly smaller at both 0° knee flexion 6.3 ± 3.2 mm (p = 0.040) and 30° knee flexion 4.9 ± 3.9 mm (p = 0.006) compared to the lying position with 0° knee flexion.

Conclusion

Tibial Tuberosity-Trochlear Groove distance depends on both knee flexion angle and weight bearing. The latter only seems to be of relevance in full extension.     

Patellar thickness and lateral retinacular release affects patellofemoral kinematics in total knee arthroplasty

Purpose

To study the effect of increasing patellar thickness (overstuffing) on patellofemoral kinematics in total knee arthroplasty and whether subsequent lateral retinacular release would restore the change in kinematics.

Methods

The quadriceps of eight fresh-frozen knees were loaded on a custom-made jig. Kinematic data were recorded using an optical tracking device for the native knee, following total knee arthroplasty (TKA), then with patellar thicknesses from ?2 to +4 mm, during knee extension motion. Staged lateral retinacular releases were performed to examine the restoration of normal patellar kinematics.

Results

Compared to the native knee, TKA led to significant changes in patellofemoral kinematics, with significant increases in lateral shift, tilt and rotation. When patellar composite thickness was increased, the patella tilted further laterally. Lateral release partly corrected this lateral tilt but caused abnormal tibial external rotation. With complete release of the lateral retinaculum and capsule, the patella with an increased thickness of 4 mm remained more laterally tilted compared to the TKA with normal patellar thickness between 45° and 55° knee flexion and from 75° onwards. This was on average by 2.4° ± 2.9° (p < 0.05) and 2.°9 ± 3.0° (p < 0.01), respectively. Before the release, for those flexion ranges, the patella was tilted laterally by 4.7° ± 3.2° and 5.4° ± 2.7° more than in the TKA with matched patellar thickness.

Conclusion

Patellar thickness affects patellofemoral kinematics after TKA. Although lateral tilt was partly corrected by lateral retinacular release, this affected the tibiofemoral kinematics.

Level of evidence

IV.     

Magnetic resonance transverse relaxation time T2 of knee cartilage in osteoarthritis at 3-T: a cross-sectional multicentre, multivendor reproducibility study

Objective

The transverse relaxation time (T2) in MR imaging has been identified as a potential biomarker of hyaline cartilage pathology. This study investigates whether MR assessments of T2 are comparable between 3-T scanners from three different vendors.

Design

Twelve subjects with symptoms of knee osteoarthritis and one or more risk factors had their knee scanned on each of the three vendors’ scanners located in three sites in the UK. MR data acquisition was based on the United States National Institutes of Health Osteoarthritis Initiative protocol. Measures of cartilage T2 and R2 (inverse of T2) were computed for precision error assessment. Intrascanner reproducibility was also assessed with a phantom (all three scanners) and a cohort of 5 subjects (one scanner only).

Results

Whole-organ magnetic resonance (WORM) semiquantitative cartilage scores ranged from minimal to advanced degradation. Intrascanner R2 root-mean-square coefficients of variation (RMSCOV) were low, within the range 2.6 to 6.3% for femoral and tibial regions. For one scanner pair, mean T2 differences ranged from ?1.2 to 2.8 ms, with no significant difference observed for the medial tibia and patella regions (p?<?0.05). T2 values from the third scanner were systematically lower, producing interscanner mean T2 differences within the range 5.4 to 10.0 ms.

Conclusion

Significant interscanner cartilage T2 differences were found and should be accounted for before data from scanners of different vendors are compared.