Tibial tuberosity to trochlear groove distance and its association with patellofemoral osteoarthritis-related structural damage worsening: data from the osteoarthritis initiative

Tibial Tubercle Trochlear Groove Distance Does Not Correlate With Patellar Tendon Length in Patients Who Underwent Anterior Cruciate Ligament Reconstruction

Purpose

To examine the relationship between tibial tubercle-trochlear groove (TT-TG) distance and patellar tendon length.

Methods

All healthy athletes who underwent anterior cruciate ligament reconstruction who had a magnetic resonance imaging (MRI) study of the knee on file between July 2018 and June 2019 at a single institution were retrospectively reviewed. Exclusion criteria included patients without an MRI study of the knee on file or with an MRI of insufficient quality precluding reliable calculation of TT-TG and patellar tendon length. MRIs were reviewed to calculate TT-TG, patellar tendon length, and Caton-Deschamps Index (CDI). Patient charts were reviewed to obtain anthropometric characteristics including sex, concomitant injuries, and previous knee procedures as well as age at time of MRI. Spearman correlations were used to assess the relationship between TT-TG, patellar tendon length, and CDI, with regression analysis performed to assess for relationships between TT-TG, patellar tendon length, and patient-specific factors.

Results

Overall, 235 patients (99 female [42.1%], 136 male [57.9%]; mean age: 30.0 years [23.0; 40.0]) were included. Inter-rater reliability between the 2 reviewers was 0.888 for TT-TG, 0.804 for patellar tendon length, and 0.748 for CDI, indicating strong agreement. The correlation between TT-TG and patellar tendon length was 0.021, indicating no true relationship. The correlation between TT-TG and CDI was -0.048 and that of patellar tendon length and CDI was 0.411, indicating a weak positive relationship. Regression analysis found that male sex is strongly correlated with a longer patellar tendon length (odds ratio 2.65, 95% confidence interval 1.33-3.97, P < .001).

Conclusions

In this study, no correlation was found between TT-TG and patellar tendon length or CDI. Male sex was correlated with a longer patellar length.

Level of Evidence

Level III.

Retro-tubercular Biplanar Medial Opening-Wedge High Tibial Osteotomy Results in Superior Patellofemoral Alignment Versus Supra-tubercular Osteotomy

PURPOSE

To compare the changes in patellofemoral (PF) joint alignment, focusing on multiple planes, between two different types of biplanar medial opening-wedge high tibial osteotomy (OWHTO).

METHODS

Patients who underwent biplanar OWHTO between July 2017 and May 2021 were retrospectively evaluated. They were allocated to either the supra-tubercular (ST)- or retro-tubercular (RT)-OWHTO group. The following radiologic parameters were compared between the two groups: 1) weight-bearing line ratio (WBLR), 2) patellar height, 3) posterior tibial slope (PTS), 4) tibial tubercle-trochlear groove (TT-TG) distance, 5) TT-TG angle, and 6) femoral shaft-patellar tendon (FS-PT) angle. Clinical outcomes and the minimal clinically important difference (MCID) were also evaluated.

RESULTS

In total, 104 knees that underwent ST-OWHTO and 105 knees that underwent RT-OWHTO were evaluated. The patellar height significantly decreased only after ST-OWHTO (P < .001). The TT-TG distance and FS-PT angle significantly increased, more after ST-OWHTO than RT-OWHTO (mean change value: 5.72 mm vs 1.91 mm; P < .001 for TT-TG distance; and 4.72° vs 1.80°; P < .001 for FS-PT angle). The TT-TG angle increased significantly after ST-OWHTO (mean change value: 7.62°; P < .001) but decreased after RT-OWHTO mean change value: -4.30°; P < .001). The PTS more increased after RT-OWHTO than after ST-OWHTO (mean change value: 0.91° vs 1.69°; P = .003). Clinical outcomes in both groups improved postoperatively, and no significant differences were observed between the groups.

CONCLUSIONS

RT-OWHTO resulted in lesser changes in multiplane PF joint alignment than ST-OWHTO. However, no difference was observed in clinical outcomes between both groups, and PTS increased after RT-OWHTO. Therefore, these aspects of RT-OWHTO should also be considered.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Development of patellofemoral osteoarthritis with knee joint malalignment and lateral patellar dislocation after hindlimb suspension in growing rats

Knee malalignment is a risk factor for patellar instability and patellofemoral osteoarthritis (PFOA), but etiologies remain unknown. We investigated the potential effects of decreased weight loading during growth on knee alignments and patellofemoral (PF) joint pathology. Hindlimb suspension (HS) was performed in 4-week-old female rats for 2, 4, and 8 weeks (HS groups). Age-matched rats were used as controls. Three-dimensional reconstructed images of the knee were obtained using X-ray computed tomography. Tibial tubercle-trochlear groove (TT-TG) distance, patellar tilt angle, and bisect offset were measured as indices of knee alignment. Histological analysis was also performed to evaluate the changes in cartilage and synovium in the PF joints. At Week 8, TT-TG distance, patella tilt angle, and bisect offset were significantly larger in the HS group than in the control group, respectively, indicating tibial external rotation, outward patellar tilt, and external displacement of the patella. Lateral patellar dislocation was frequently found in the HS group at Week 8 (five of eight knee joints, p < 0.05). Degenerative changes in the cartilage of the trochlear groove were observed at Week 8, and synovial changes such as hypertrophy and synovitis were observed at Weeks 4 and 8. Correlation analyses revealed significant relationships between the Mankin score and bisect offset, and between the OARSI synovitis score and all knee alignments indices. These results suggest that decreased weight loading on the lower extremities in growing rats resulted in knee malalignments characterized by external rotation of tibia and high incidence of lateral patellar dislocation with concomitant PFOA.

Tibial tuberosity-trochlear groove distance is significantly decreased by medial closing wedge distal femoral osteotomy

PURPOSE

While medial closing wedge distal femoral osteotomy (MCWDFO) has been used to address patella instability combined with valgus malalignment, its impact on patellofemoral parameters remains uncharted. Hence, this study seeks to establish a three-dimensional (3D) planning of MCWDFO and measure its effect on the tibial tubercle - trochlear groove distance (TTTG) through simulation and calculation.

METHODS

MCWDFO with a stepwise increment of one-degree varisation (1°-15°) was performed on 3D surface models of 14 lower extremities with valgus malalignment and 24 lower extremities with neutral alignment of the lower limb, resulting in a total of 608 simulations. Anatomic landmarks were employed to measure hip-knee-ankle angle (HKA), TTTG, and femoral torsion for each simulation. A mathematical formula was adopted to calculate TTTG changes following MCWDFO, and subsequently the mean simulated and calculated TTTG values were compared. Following a standardised protocol, MCWDFO was performed without rotational changes.

RESULTS

MCWDFO exhibited an almost linear reduction in TTTG, at a rate of approximately -1.05 ± 0.13 mm per 1° of varisation, demonstrating a strong negative correlation (R = -0.83; p < 0.001). Limb alignment did not exert an influence on TTTG change; however, it correlated with tibial plateau width. The mean difference between the simulated and calculated TTTG values amounted to 0.03 ± 0.03 mm per 1° varisation (p < 0.001).

CONCLUSION

The TTTG distance is linearly reduced by 1.05 mm for every 1° of varisation within the varus correction range of 0°-15° during MCWDFO. Patients with combined valgus and patellar instability may benefit from MCWDFO due to frequently pathological TTTG.

LEVEL OF EVIDENCE

Level III, descriptive laboratory study.

Quadriceps tendon malalignment is an independent anatomical deformity which is the primary abnormality associated with lateral facet patellofemoral joint osteoarthritis

PURPOSE

The purposes of this study are to, firstly, develop techniques to accurately identify extensor mechanism malalignment by measuring the alignment of the quadriceps tendon (QTA) with computerized tomography (CT) scans. Secondly, to investigate correlations between QTA and lower limb bony anatomical variations within a representative normal population. Lastly, to evaluate the clinical significance of QTA by establishing its potential connection with lateral facet patellofemoral joint osteoarthritis (LFPFJOA).

METHOD

CT scans were orientated to a mechanical axis reference frame and three techniques developed to measure the alignment of the quadriceps tendon. Multiple measurement of bony alignment from the hip to the ankle were performed on each scan. A series of 110 cadaveric CT scans were measured to determine normal values, reproducibility, and correlations with bony anatomy. Secondly, a comparison between 2 groups of 25 patients, 1 group with LFPFJOA and 1 group with isolated medial OA and no LFPFJOA.

RESULTS

From the cadaveric study, it was determined that the alignment of the quadriceps tendon is on average 4.3° (SD 3.9) varus and the apex of the tendon is 9.1 mm (SD 7.7 mm) lateral to the trochlear groove and externally rotated 1.9° (SD 12.4°) from the centre of the femoral shaft. There was no association between the quadriceps tendon alignment and any other bony measurements including tibial tubercle trochlear groove distance (TTTG), coronal alignment, trochlear groove alignment and femoral neck anteversion. A lateralized QTA was significantly associated with LFPFJOA. QTA in the LFPFJOA group was 9.6° varus (SD 2.8°), 21.3 mm (SD 6.6) lateralised and 17.3° ER (SD 11°) compared to 5.5° (SD 2.3°), 10.7 mm (SD 4.9) and 3.3° (SD 7.2°), respectively, in the control group (p < 0.001). A significant association with LFPFJOA was also found for TTTG (17.2 mm (SD 5.7) vs 12.1 mm (SD 4.3), p < 0.01). Logistic regression analysis confirmed the QTA as having the stronger association with LFPFJOA than TTTG (AUC 0.87 to 0.92 for QTA vs 0.79 for TTTG).

CONCLUSION

These studies have confirmed the ability to accurately determine QTA on CT scans. The normal values indicate that the QTA is highly variable and unrelated to bony anatomy. The comparative study has determined that QTA is clinically relevant and a lateralised QTA is the dominant predictor of severe LFPFJOA. This deformity should be considered when assessing patella maltracking associated with patella osteoarthritis, patella instability and arthroplasty.

LEVEL OF EVIDENCE

III (retrospective cohort study).

A More Posterior Tibial Tubercle (Decreased Sagittal Tibial Tubercle-Trochlear Groove Distance) Is Significantly Associated With Patellofemoral Joint Degenerative Cartilage Change: A Deep Learning Analysis

PURPOSE

To perform patellofemoral joint (PFJ) geometric measurements on knee magnetic resonance imaging scans and determine their relations with chondral lesions in a multicenter cohort using deep learning.

METHODS

The sagittal tibial tubercle-trochlear groove (sTTTG) distance, tibial tubercle-trochlear groove distance, trochlear sulcus angle, trochlear depth, Caton-Deschamps Index (CDI), and flexion angle were measured by use of deep learning-generated segmentations on a subset of the Osteoarthritis Initiative study with radiologist-graded PFJ cartilage grades (n = 2,461). Kruskal-Wallis H tests were performed to compare differences in PFJ morphology between subjects without PFJ osteoarthritis (OA) and those with PFJ OA. PFJ morphology was correlated with secondary outcomes of mean patellar cartilage thickness and mean patellar cartilage T2 relaxation time using linear regression models controlling for age, sex, and body mass index.

RESULTS

A total of 1,626 knees did not have PFJ OA, whereas 835 knees had PFJ OA. Knees without PFJ OA had an increased (anterior) sTTTG distance (mean ± standard deviation, 11.1 ± 12.8 mm) compared with knees with PFJ OA (8.4 ± 12.7 mm) (P < .001), indicating a more posterior tibial tubercle in subjects with PFJ OA. Knees without PFJ OA had a decreased sulcus angle (127.4° ± 7.1° vs 128.0° ± 8.4°, P = .01) and increased trochlear depth (9.1 ± 1.7 mm vs 9.0 ± 2.0 mm, P = .03) compared with knees with PFJ OA. Decreased patellar cartilage thickness was associated with decreased trochlear depth (β = 0.12, P = .002) and increased CDI (β = -0.07, P < .001). Increased patellar cartilage T2 relaxation time was correlated with decreased sTTTG distance (β = -0.08, P = .01), decreased sulcus angle (β = -0.12, P = .04), and decreased CDI (β = -0.12, P < .001).

CONCLUSIONS

PFJ OA, patellar cartilage thickness, and patellar cartilage T2 relaxation time were shown to be associated with the underlying geometries within the PFJ. This large longitudinal study highlights that a decreased sTTTG distance (i.e., a more posterior tibial tubercle) is significantly associated with PFJ degenerative cartilage change.

LEVEL OF EVIDENCE

Level III, retrospective comparative prognostic trial.

Comparison of post-operative outcomes following anterior cruciate ligament reconstruction between patients with vs. without elevated tibial tubercle-trochlear groove (TT-TG) distance

PURPOSE

It is unclear if an elevated tibial tubercle-trochlear groove (TT-TG) distance is a risk factor for poor outcomes following ACLR. Therefore, the purpose of this study was to determine whether patients with an elevated TT-TG have an increased risk of retear following primary ACLR compared to controls with a normal TT-TG.

METHODS

All patients who underwent primary ACLR between July 2018 and June 2019 with an available preoperative magnetic resonance imaging (MRI) were eligible for inclusion. TT-TG distance was measured on preoperative MRI scans by two independent investigators. Clinical outcomes, return-to-sport rates, and Lysholm scores were compared between patients with a TT-TG < 12.5 mm (normal) and those with a TT-TG ≥ 12.5 mm (elevated).

RESULTS

Overall, 159 patients were included, 98 with normal TT-TG distance and 61 with elevated TT-TG distance. Patients with an elevated TT-TG distance had worse post-operative Lysholm scores than patients with a normal TT-TG distance (83.0 vs. 95.0, p = 0.010). In patients who received a bone-patellar tendon-bone (BTB) graft, an elevated TT-TG distance was associated with higher rates of subjective instability (13.0% vs. 3.0%, p = 0.041), reoperation (13.0% vs. 1.5%, p = 0.012), and post-operative complications (25.0% vs. 8.2%, p = 0.026), as well as lower ACL psychological readiness scores (324.1 vs. 446.7, p = 0.015).

CONCLUSION

Patients with an elevated pre-operative TT-TG distance have worse Lysholm scores than patients with normal TT-TG distance. Patients with an elevated pre-operative TT-TG distance who underwent ACLR with BTB grafts had significantly higher rates of subjective instability, reoperation, and post-operative complications.

LEVEL OF EVIDENCE

III.

Tibial tubercle-Roman arch (TT-RA) distance is superior to tibial tubercle-trochlear groove (TT-TG) distance when evaluating coronal malalignment in patients with knee osteoarthritis

OBJECTIVES

To verify tibial tubercle-Roman arch (TT-RA) distance is superior to tibial tubercle-trochlear groove (TT-TG) distance in preoperative assessment of patellofemoral joints in patients with knee osteoarthritis.

METHODS

Patients with knee osteoarthritis from 2016 to 2020 were considered eligible for inclusion in this study. We divided the patients into valgus group and varus group and did 1:1 matching for the two groups. We measured the TT-TG distance, TT-RA distance, patellar height, patella tilt, hip-knee-ankle (HKA) angle, and Iwano's classification of patellofemoral osteoarthritis (PFOA) by computed tomography images or radiographs. The intraclass correlation coefficient (ICC) of each measurement, the correlations and differences among the parameters, and binary logistic regression analysis were conducted.

RESULTS

Each group in this study included 75 knees. The inter-observer and intra-observer reliability of the TT-TG distance decreased with the increasing degree of PFOA (ICC < 0.75). The reliability of the TT-RA distance showed excellent agreement in different stages of Iwano's classification. The HKA angle was poorly correlated with the TT-TG distance (r = 0.34, p = 0.003) and the TT-RA distance (r = 0.39, p = 0.001) in valgus knees. As the HKA angle increased by 1 degree, the TT-TG and TT-RA distance increased by nearly 0.45 mm and 0.61 mm, respectively. Valgus malalignment and severe PFOA revealed significant ORs of 3.26 (95% CI [1.06-10.03], p = 0.036) and 3.10 (95% CI [1.01-9.54], p = 0.048) with regard to pathological TT-RA distance, respectively.

CONCLUSION

The TT-RA distance was more reliable than the TT-TG distance in patients with knee osteoarthritis. Valgus malalignment and severe PFOA were risk factors for pathological TT-RA distance.

KEY POINTS

• The TT-RA distance is a reliable and repeatable alternative to the TT-TG distance in evaluating coronal malalignment, especially in patients with severe PFOA. • We validated the significant relationships between TT-TG distance or TT-RA distance and HKA angle in valgus knees, while the correlations among such parameters were not significant in varus knees. • Pathological lateralization of the tibial tubercle was prone to be traced in patients with valgus malalignment or severe PFOA, which could contribute to the patellofemoral malalignment.

Medialization of the mechanical axis of the tibia is related to lateralization of the tibial tuberosity in knee osteoarthritis

PURPOSE

To determine whether medialization of the proximal tibia due to a varus deformity is related to lateralization of the tibial tuberosity in varus knee osteoarthritis (OA).

METHODS

A total of 120 knees that underwent osteotomies around the knee for varus knee OA were enrolled. Mechanical medial proximal tibial angle (mMPTA) was measured on radiographs. The angle between the mechanical and anatomical axes of the tibia (angle MA) and the distance between the centre of the tibial plateau and the anatomical axis (distance MA) were measured in the coronal plane on computed tomography images. The tibial tuberosity-posterior cruciate ligament (TT-PCL) distance, the distance between the midpoint of the tibial tuberosity and the centre of the tibial plateau (TT-centre distance), and the angle between the line through the midpoint of the tibial tuberosity and the centre of the tibial plateau and the anteroposterior axis (TT-centre angle) were measured in the axial plane. The correlations of these parameters were evaluated.

RESULTS

mMPTA correlated negatively with angle MA (r = -0.37, P < 0.01) and distance MA (r = -0.55, P < 0.01). Angle MA and distance MA correlated with TT-PCL distance (r = 0.39, P < 0.01, r = 0.42, P < 0.01), TT-centre distance (r = 0.35, P < 0.01, r = 0.38, P < 0.01) and TT-centre angle (r = 0.36, P < 0.01, r = 0.36, P < 0.01).

CONCLUSIONS

Medialization of the proximal tibia due to a varus deformity may induce lateralization of the tibial tuberosity.

Influence of medial open wedge high tibial osteotomy on tibial tuberosity-trochlear groove distance

PURPOSE

Medial open wedge high tibial osteotomy (MOWHTO) is an effective treatment option for realignment of a varus knee. However, a simple supra-tuberositary osteotomy can lead to patella baja and potentially increases the tibial tuberosity-trochlear groove distance (TTTG). The purpose of this study was to quantify the influence of MOWHTO on TTTG.

METHODS

Three-dimensional (3D) surface models of five lower extremities with a varus hip-knee-ankle angle (HKA) and a borderline TTTG (≥ 15 mm), five lower extremities with a varus HKA and a normal TTTG (< 15 mm) and a 3D statistical shape model (SSM) of a neutrally aligned healthy knee were analysed by simulating MOWHTO with a stepwise increment of one degree of valgisation from the preoperative coronal deformity (0°-15°) for each patient, resulting in a total of 165 simulations. Postoperative 3D TTTG and tibial torsion (TT) were measured for each simulation. A mathematical formula was developed to calculate the increase of TTTG after MOWHTO. Mean differences between simulated and calculated TTTG were analysed.

RESULTS

Mean preoperative HKA was 6.5 ± 3.0° varus (range 0.8°-11.5°). Mean TTTG increased from 14.2 ± 3.2 mm (range 9.6-19.1) preoperatively to 18.8 ± 3.8 mm (range 14.5-25.0) postoperatively (p = 0.001). TTTG increased approximately linear by + 0.5 ± 0.2° (range 0.3-0.8) per 1° of valgisation with a high positive correlation (0.99, p = 0.001) from 0° to 15°. Mean difference between simulated and calculated TTTG was 0.03 ± 0.02 mm (range 0.01-0.07) per 1° of valgisation (p < 0.001).

CONCLUSION

MOWHTO results in an approximately linear increase in TTTG of + 0.5 mm per 1° of valgisation in the range from 0° to 15° and the lateralisation of the tibial tuberosity can be calculated reliably using the described formula. Preoperative analysis of TTTG in patients undergoing MOWHTO may prevent unintentional patellofemoral malalignment.

LEVEL OF EVIDENCE

III.

Varus inclination of the tibia is related to patellofemoral osteoarthritis in Japanese female patients with moderate knee osteoarthritis

PURPOSE

The aim of this study was to investigate whether the tibial tuberosity-trochlear groove (TT-TG) distance and lateral patellar tilt, which induce patellofemoral osteoarthritis (OA), are related to the coronal deformity of the lower limb in varus knee OA. It was hypothesized that varus inclination of the tibia was negatively correlated with the TT-TG distance and lateral patellar tilt in Japanese female patients with moderate knee OA.

METHODS

A total of 104 female patients (139 knees) scheduled to undergo knee osteotomy for varus knee OA were enrolled. The coronal lower limb alignment was measured on anteroposterior whole-leg radiographs. The TT-TG distance, patellar tilt angle, and the patellofemoral joint space were measured both medially and laterally on computed tomography images. The correlations between coronal lower limb alignment and the TT-TG distance or patellar tilt angle, and the correlations between the TT-TG distance or patellar tilt angle and patellofemoral joint space were evaluated.

RESULTS

The medial proximal tibial angle was negatively correlated with the TT-TG distance (r =  - 0.383, P < 0.01) and patellar tilt angle (r =  - 0.34, P < 0.01). Lateral patellofemoral joint space was negatively correlated with the TT-TG distance (r =  - 0.256, P = 0.002) and patellar tilt angle (r =  - 0.205, P = 0.016).

CONCLUSIONS

Varus inclination of the proximal tibia may induce lateralization of the tibial tuberosity and lateral patellar tilt. The tibial tuberosity lateralization and lateral patellar tilt may induce lateral patellofemoral OA in patients with varus knee OA.

LEVEL OF EVIDENCE

III.

Lateral patellar tilt and its longitudinal association with patellofemoral osteoarthritis-related structural damage: Analysis of the osteoarthritis initiative data

BACKGROUND

Increase in lateral patellar tilt-(LPT) can cause increased pressure on the lateral facet of the knee and can lead to patellar or femoral cartilage damage and further osseous changes. This study aims to test the hypothesis whether there is an association between increased LPT and MRI-based patellofemoral osteoarthritis-(OA) features at baseline and their worsening over a 2-year follow-up in participants of the Osteoarthritis Initiative-(OAI).

METHODS

Recorded clinical and imaging data of 600 participants in the FNIH-OA biomarkers consortium was extracted from its database. The LPT-(as the angle betweenthe longest patella diameter and posterior aspect of condyles) was measured using theaxial knee MRI. Associations of LPT (every 5° increase) with MRI OA Knee Scoring-(MOAKS) for OA-related features, including cartilage and bone marrow lesions (BMLs) in addition to knee cartilage volume at baseline and their worsening after 2-year follow-up were assessed using regression models adjusted for several possible confounders.

RESULTS

The mean LPT angle in this sample was 8.84° ± 5.19. In baseline, higher LPT was associated with lower cartilage volumes and higher cartilage lesions and BMLs MOAKS scores in the lateral trochlear and patellar subregions. Over the follow-ups, subjects with higher LPT measures in the baseline showed higher odds of experiencing BML score worsening in the lateral trochlear subregion-(OR:1.25[1.01-1.56]) over the 2-year follow-ups.

CONCLUSIONS

Increase in LPT measures may be associated with OA-related features in the trochlear subregion. Therefore, aside from its use as an indicator of patellofemoral instability syndrome, LPT may be associated with longitudinal progression of patellofemoral OA.

Tibial tuberosity-tibial intercondylar midpoint distance measured on computed tomography scanner is not biased during knee rotation and could be clinically more relevant than current measurement systems

PURPOSE

The purpose of this retrospective cross-sectional case-control study was to evaluate an alternative imaging test for lateralization of the tibial tuberosity, unbiased towards knee rotation.

METHODS

On axial CT images of 129 knees, classified as cases (two or more patellar luxations) and controls (no patellar luxations), two raters gauged the standard tibial tuberosity-trochlear groove (TT-TG) distance, tibial tuberosity-femoral intercondylar midpoint (TT-FIM) distance, and new tibial tuberosity-tibial intercondylar midpoint (TT-TIM) distance singly, and knee longitudinal rotation angles (LRAs), and the presence of femoral trochlear dysplasia (FTD) jointly.

RESULTS

All imaging tests intercorrelated and discriminated between stability groups. TT-TIM had the lowest values with the highest precision. Though poorly, TT-TG and TT-FIM negatively correlated with age and LRAs regarding femur, but positively with presence of FTD, whereas TT-TIM was unbiased. The accuracy of TT-TG (> 20 mm), TT-FIM (> 20 mm), and TT-TIM (> 13 mm) was good with almost perfect reproducibility. Only TT-TIM was sex-biased (p = 0.009), with > 12 mm cut-off in females and (presumably) > 14 mm in males.

CONCLUSION

TT-TIM is an alternative imaging test for lateralization of the tibial tuberosity, unbiased towards knee rotation.

Osteoarthritis year in review 2019: imaging

OBJECTIVE

To provide a narrative review of original articles on osteoarthritis (OA) imaging published between April 1, 2018 and March 30, 2019.

METHODS

All original research articles on OA imaging published in English between April 1, 2018 and March 30, 2019 were identified using a PubMed database search. The search terms of "Osteoarthritis" or "OA" were combined with the search terms "Radiography", "X-Rays", "Magnetic Resonance Imaging", "MRI", "Ultrasound", "US", "Computed Tomography", "Dual Energy X-Ray Absorptiometry", "DXA", "DEXA", "CT", "Nuclear Medicine", "Scintigraphy", "Single-Photon Emission Computed Tomography", "SPECT", "Positron Emission Tomography", "PET", "PET-CT", or "PET-MRI". Articles were reviewed to determine relevance based upon the following criteria: 1) study involved human subjects with OA or risk factors for OA and 2) study involved imaging to evaluate OA disease status or OA treatment response. Relevant articles were ranked according to scientific merit, with the best publications selected for inclusion in the narrative report.

RESULTS

The PubMed search revealed a total of 1257 articles, of which 256 (20.4%) were considered relevant to OA imaging. Two-hundred twenty-six (87.1%) articles involved the knee joint, while 195 (76.2%) articles involved the use of magnetic resonance imaging (MRI). The proportion of published studies involving the use of MRI was higher than previous years. An increasing number of articles were also published on imaging of subjects with joint injury and on deep learning application in OA imaging.

CONCLUSION

MRI and other imaging modalities continue to play an important role in research studies designed to better understand the pathogenesis, progression, and treatment of OA.