Patellar maltracking: an update on the diagnosis and treatment strategies

MR imaging after patellar MACI and MPFL reconstruction: a comparison of isolated versus combined procedures

OBJECTIVE

To qualitatively and quantitatively evaluate the 2.5-year MRI outcome after Matrix-associated autologous chondrocyte implantation (MACI) at the patella, reconstruction of the medial patellofemoral ligament (MPFL), and combined procedures.

METHODS

In 66 consecutive patients (age 22.8 ± 6.4years) with MACI at the patella (n = 16), MPFL reconstruction (MPFL; n = 31), or combined procedures (n = 19) 3T MRI was performed 2.5 years after surgery. For morphological MRI evaluation WORMS and MOCART scores were obtained. In addition quantitative cartilage T2 and T1rho relaxation times were acquired. Several clinical scores were obtained. Statistical analyses included descriptive statistics, Mann-Whitney-U-tests and Pearson correlations.

RESULTS

WORMS scores at follow-up (FU) were significantly worse after combined procedures (8.7 ± 4.9) than after isolated MACI (4.3 ± 3.6, P = 0.005) and after isolated MPFL reconstruction (5.3 ± 5.7, P = 0.004). Bone marrow edema at the patella in the combined group was the only (non-significantly) worsening WORMS parameter from pre- to postoperatively. MOCART scores were significantly worse in the combined group than in the isolated MACI group (57 ± 3 vs 88 ± 9, P < 0.001). Perfect defect filling was achieved in 26% and 69% of cases in the combined and MACI group, respectively (P = 0.031). Global and patellar T2 values were higher in the combined group (Global T2: 34.0 ± 2.8ms) and MACI group (35.5 ± 3.1ms) as compared to the MPFL group (31.1 ± 3.2ms, P < 0.05). T2 values correlated significantly with clinical scores (P < 0.005). Clinical Cincinnati scores were significantly worse in the combined group (P < 0.05).

CONCLUSION

After combined surgery with patellar MACI and MPFL reconstruction inferior MRI outcomes were observed than after isolated procedures. Therefore, patients with need for combined surgery may be at particular risk for osteoarthritis.

Supratrochlear Rim is Correlated with Isolated Patellar Chondromalacia on Magnetic Resonance Imaging of the Knee

Purpose

To investigate the relationship between the supratrochlear rim and isolated patellar chondromalacia (PC) using magnetic resonance imaging (MRI) scans of the knee.

Methods

Patients without patellofemoral pain (control group) and patients with patellofemoral pain and diagnosed with stage III or IV PC based on MRI (defect group) were retrospectively identified. Patients with a history of patellar subluxation were excluded. We used patient MRI scans to perform 20 anatomical measurements of the patellofemoral joint. We also performed 2 measurements of the anterior femoral curvature. A total of 30 patients (29 ± 8.7 years) were in the control group, and 20 patients were in the defect group (29.4 ± 9.7 years).

Results

The maximum curvature (P < .001) and mean curvature (P < .001) of the anterior femoral condyle were found statistically significantly different between the groups. Patellotrochlear index (P = .03) and Insall-Salvati index (P < .001) were also found statistically significantly different between the 2 groups. Patella type III and trochlear dysplasia grade B were found more common in the defect group.

Conclusions

In this Level III prognostic, case-control study, we have shown through MRI knee measurements that the isolated patellar chondromalacia in patients without a history of patellar subluxation and dislocation is correlated with the increased anterior femoral curvature in combination with patella alta.

Patellar tilt, congruence angle, and tibial tubercle-trochlear groove distance are correlated with positive J-sign in adolescents

PURPOSE

The J-sign is a clinical evaluation tool that assesses for patellar maltracking and is considered positive if lateral translation of the patella in extension, in the pattern of an inverted J is observed. This study aims to determine the association of clinical J-sign with imaging features noted on dynamic kinematic computed tomography (DKCT).

METHODS

A retrospective review was conducted by reviewing the clinical records of all patients aged 18 years or younger who had a CT patellar tracking scan done between 1 January 2005 to 31 December 2016 in a single institution. Patients who had the presence or absence of a 'J-sign' evaluated clinically were included. Radiographic parameters evaluated using the axial cuts include the patellar tilt angle, congruence angle, Dejour's classification, femoral sulcus angle, trochlear groove depth, and Wiberg's classification. Patients were then divided into two groups based on the presence or absence of J-sign on clinical examination. The radiographic measurements were then analyzed for association with the presence or absence of J-sign on clinical examination.

RESULTS

Patients with a positive J-sign had an increased patellar tilt of 23.3° ± 14.2° and an increased congruence angle of 47.1° ± 28.5° when measured in extension as compared to a patellar tilt of 18.3° ± 10.8° and a congruence angle of 32.1° ± 20.8° in patients with a negative J-sign (p = 0.024 and 0.004, respectively). Comparisons of the change in congruence angles with the knee in full extension and at 20° flexion also yielded significantly higher change of 28.0° ± 20.4° in patients with a positive J-sign as compared to 11.9° ± 17.5° in patients with a negative J-sign. Patients with a positive J-sign also had an increased TT-TG distance of 17.6 ± 5.6 mm as compared to a TT-TG distance of 14.7 ± 6.9 mm in patients with a negative J-sign (p = 0.01).

CONCLUSION

Patients with a positive J-sign had an increased patellar tilt and an increased congruence angle when measured in extension. Increased TT-TG distance was also significantly associated with positive J-sign. Patients with a positive J-sign also had a greater change in their congruence angle when measured with the knee in full extension and at 20° of flexion.

Association between the most superior point of patella-entrance of femoral trochlea distance ratio (SP-ET index) and chondromalacia patella: an investigation via magnetic resonance imaging

Purpose

In this study, the effect of the most superior point of patella-entrance of femoral trochlea distance ratio (SP-ET index) on chondromalacia patella (CP) was investigated with 2 reviewers.

Material and methods

A total of 348 knees of 308 patients were analysed retrospectively with magnetic resonance imaging (MRI). Patients with or without CP constituted the study and the control groups in this cross-sectional investigation. Two reviewers interpreted the dataset regarding the SP-ET index. This ratio was calculated as the distance between the most superior point of patella and the entrance of femoral trochlea (β) divided by the patellar articular surface length (α). The relationship between the SP-ET index and CP was presented using independent samples T-tests, and the intraclass correlation coefficient (ICC) was calculated to reveal the interobserver differences.

Results

There was excellent agreement between the reviewers regarding α, β, and SP-ET values (ICC was 0.971, 0.964, and 0.943, respectively). Higher SP-ET values were obtained for patients with CP, in comparison with patients without any chondral lesion (p < 0.001). A significant, positive, and moderate level of correlation was revealed between SP-ET measurements and CP grades for the total study population.

Conclusions

SP-ET index showed high interobserver agreement and indicated a significant difference between patients with and without CP. Both reviewers' results indicated positive and significant correlation between the measured SP-ET values and different grades of CP for females, males, and the total study population.

Patella Fracture After Total Knee Arthroplasty: A Review

The management and underlying causes of patellar periprosthetic fractures (PPF) after total knee arthroplasty (TKA) constitute an issue of growing importance given the rising frequency of these procedures. Patella periprosthetic fractures, though relatively rare, pose significant challenges and are a frequent indication for revision surgeries. Despite a decrease in overall incidence, PPFs remain the second most common type of periprosthetic fractures after TKA. Several factors have been identified and associated with patient-specific factors, surgical technique errors, and implant-related causes. Currently extensor apparatus integrity, bone stock, and component loosening are the major concerns and indications for the selective treatment approach. In this study, a thorough review of the existing literature was performed summarizing the epidemiology, clinical manifestation, treatment approach, and functional outcome of PPF. This review aims to underline the significance of such predisposing factors, point out the severity of PPF, and offer insights into the optimal intra- and post-operative management of the patella.

The tibial tubercle-trochlear groove distance: a comparison study between EOS and MRI in the paediatric population

OBJECTIVE

This study aims to compare the relative reliability and accuracy of TT-TG measurements in EOS with that of MRI in a paediatric population.

METHODS

Patients were included if they underwent both an MRI and EOS scans and were under the age of 16. Two authors recorded the TT-TG distances on each modality at two separate time points. In the EOS images, the distance between the two points was measured in the horizontal 2D plane. In the MRI images, it was done in the plane referenced by posterior femoral condylar axis. The intra- and inter-rater reliability was assessed in each modality and between modalities.

RESULTS

Twenty-seven patients (30 knees), 14 males, and 13 females with an average age of 13 years (range: 7-16 years) were included in the study. The mean TT-TG distance on EOS scan and MRI scan was 14 mm. On inter- and intra-observer analysis, both imaging modalities had excellent reliability (0.97 ICC for EOS and 0.98 ICC for MRI inter-observer) and repeatability (0.98-0.99 ICC for EOS and 0.99 ICC for MRI for intra-observer). However, on comparing the two imaging modalities (EOS vs MRI), the ICC was fair (0.56 ICC for rater 1 and 0.65 ICC for rater 2).

CONCLUSION

While the EOS TT-TG measurements were precise and reproducible, they were only moderately comparable to MRI TT-TG measurements. Consequently, EOS TT-TG measurements should not be used for decision-making without the development of EOS-specific TT-TG values that indicate the need for distal realignment surgery.

LEVEL OF EVIDENCE

Level II.

Evaluation of Anatomical Variations with Morphological Measurements and Their Relationship to Meniscal Injury and Ligament Damage

The purpose of this study was to reveal the anatomical risk factors for anterior and posterior cruciate ligament (ACL and PCL) injuries and menisci injury. We aim to investigate whether there are significant relationships between tibial tubercle-trochlear groove (TT-TG) distance, patella angle, trochlear sulcus angle (TSA), trochlear groove depth (TGD), medial and lateral trochlea length (MT and LT), MT/LT ratio, lateral patellar tilt angle (LPTA), patella-patellar tendon angle (P-PTA), quadriceps-patellar tendon angle (QPA), Insall-Salvati index (ISI), medial and lateral trochlear inclination (MTI and LTI) measurements and important common pathologies such as ACL, PCL, medial and lateral meniscal injuries (MM and LM), peripatellar fat pad edema, chondromalacia, and effusion. Thus, the mechanisms of injury will be better understood by revealing important anatomical variations for meniscus and ligament damage. Three hundred eighty patients with knee magnetic resonance imaging examination were included in this study. Our patients who underwent knee magnetic resonance imaging were divided into groups according to the presence of MM tear, LM tear, ACL tear, PCL tear, peripatellar fat pad edema, chondromalacia and effusion. TT-TG distance, patella angle, TSA, TGD, MT, LT, MT/LT ratio, LPTA, P-PTA, QPA, ISI, MTI, and LTI were measured. In patients with ACL tear, age, LT, ML/LT ratio, and QPA measurements were found to be significantly higher. There was no significant difference between the participants' LPTA value and the presence of ACL tear, MM and LM injury. MT and ML/LT ratio were found to be significantly lower in the group with MM tear (p <0.001). The TT-TG distance was found to be significantly lower in the group with LM tear. Increased age, LT, ML/LT ratio, and QPA are predisposed risk for ACL tear. Decreased MT and ML/LT ratio are among the risk factors for MM tear. The anatomical variations are associated with ligament and meniscal injury.

A rare cause of Hoffa's fat pad impingement: the crossed-doubled patellar tendon

We present an unusual case of Hoffa's fat pad impingement syndrome and chondromalacia patellae in the presence of a rare congenital crossed doubled patellar tendon. The crossed-doubled patellar tendon is exceedingly rare. It's relationship to other conditions involved in anterior knee pain is unclear; however, this case highlights potential pathological associations.

Effect of Patellofemoral Arthroplasty on Patellar Height in Patients with Patellofemoral Osteoarthritis

Osteoarthritis (OA) in the knee is common, painful, and may be uni- or multicompartmental. The compartment affected by arthritis may be due to trauma, malalignment (varus or valgus), or in the case of patellofemoral OA, patella alta. Patellofemoral arthroplasty (PFA) is an effective partial knee replacement surgery for patellofemoral OA. We hypothesized that PFA can decrease patellar height. In addition, we predicted better outcomes for patients with patella alta before PFA and those whose patellar heights decreased after PFA. This is a retrospective cohort study of PFA patients from 2012 to 2020. Before and after PFA, we measured patellar heights on X-ray images and collected patient-reported outcome measures (PROMs) (International Knee Documentation Committee score, Kujala Anterior Knee Pain Score, and Veterans RAND 12-Item Health Survey for mental and physical health). Statistical analyses assessed PROMs and compared outcomes based on pre- and postoperative patella height. Of 133 knees, 73% presented with patella alta and 61% had patellar heights that decreased after PFA. Compared with patients who did not present with patella alta, patients with patella alta reported similar outcomes with respect to knee function, pain, and general physical and mental health. Compared with patients whose patellar heights decreased after PFA, patients whose knees did not decrease in height reported greater improvements in pain and function. Our findings suggest that patella alta is commonly found in patients with patellofemoral OA and that PFA can decrease patellar height. Future studies are needed to assess whether patellofemoral OA patients with greater degrees of patella alta would benefit from staged or concurrent tibial tubercle distalization.

Excessive femoral torsion is not associated with patellofemoral pain or instability if TKA is functionally aligned and the patella denervated

PURPOSE

Recent data suggest that individual morphologic factors should be respected to restore preoperative patellofemoral alignment and thus reduce the likelihood of anterior knee pain. The goal of this study was to investigate the effect of excessive femoral torsion (FT) on clinical outcome of TKA.

METHODS

Patients who underwent TKA and complete preoperative radiographic evaluation including a long-leg radiograph and CT scan were included. 51 patients showed increased FT of > 20° and were matched for age/sex to 51 controls (FT < 20°). Thirteen patients were lost to follow-up. Thirty-eight matched pairs were compared after a 2 year follow-up clinically (Kujala and patellofemoral score for TKA) and radiographically (FT, frontal leg axis, TT-TG, patellar thickness, patellar tilt, and lateral displacement of patella). Functional alignment of TKA was performed (hybrid-technique). All patellae were denervated but no patella was resurfaced.

RESULTS

There was no significant difference between clinical scores two years after surgery between patients with normal and excessive FT (n.s.). Kujala score was 64.3 ± 16.7 versus 64.8 ± 14.4 (n.s.), and patellofemoral score for TKA was 74.3 ± 21 versus 78.5 ± 20.7 (n.s.) for increased FT group and control group, respectively. There was no correlation between preoperative FT and clinical scores. Other radiographic parameters were similar between both groups. No correlations between clinical outcomes and preoperative/postoperative frontal leg axis or total leg axis correction were found (n.s.).

CONCLUSION

If the leg axis deformity is corrected to a roughly neutral alignment during cemented TKA, including patellar denervation, then excessive FT was not associated with patellofemoral pain or instability.

LEVEL OF EVIDENCE

Prospective comparative study, level II.

Association among peripatellar fat pad edema and related patellofemoral maltracking parameters: a case-control magnetic resonance imaging study

BACKGROUND

The peripatellar fat pads are critical for protective cushioning during movement, and their endocrine function has been shown to affect osteoarthritis. Magnetic resonance imaging (MRI) is frequently used to visualize edema of the peripatellar fat pads due to injury. In this study, we aimed to assess the relationship between peripatellar fat pad edema and patellofemoral maltracking MRI parameters and investigate the association among cases of peripatellar fat pad edema.

METHODS

Age- and sex-matched peripatellar fat pad edema cases were identified and divided into superolateral Hoffa, quadriceps, and prefemoral groups. Images were assessed according to tibial tuberosity lateralization, trochlear dysplasia, patellar alta, patellar tilt, and bisect offset. McNemar's test or paired t-tests and Spearman's correlation were used for statistical analysis. Interobserver agreement was assessed with the intraclass correlation coefficient.

RESULTS

Of 1210 MRI scans, 50, 68, and 42 cases were in the superolateral Hoffa, quadriceps, and prefemoral groups, respectively. Subjects with superolateral Hoffa fat pad edema had a lower lateral trochlear inclination (p = 0.028), higher Insall-Salvati (p < 0.001) and modified Insall-Salvati (p = 0.021) ratios, and lower patellotrochlear index (p < 0.001) than controls. The prefemoral group had a lower lateral trochlear inclination (p = 0.014) and higher Insall-Salvati (p < 0.001) and modified Insall-Salvati (p = 0.004) ratios compared with the control group. In contrast, the patellotrochlear index (p = 0.001) was lower. Mean patellar tilt angle (p = 0.019) and mean bisect offset (p = 0.005) were significantly different between cases and controls. The quadriceps group showed no association. Superolateral Hoffa was positively correlated with prefemoral (p < 0.001, r = 0.408) and negatively correlated with quadriceps (p < 0.001, r = -0.500) fat pad edema.

CONCLUSIONS

Superolateral Hoffa and prefemoral fat pad edemas were associated with patellar maltracking parameters. Quadriceps fat pad edema and maltracking parameters were not associated. Superolateral Hoffa fat pad edema was positively correlated with prefemoral and negatively correlated with quadriceps fat pad edema.

Effect of Adding Kinesio Taping to Exercise Therapy in the Treatment of Patellofemoral Pain Syndrome

Background and objectives: Patellar taping has been widely used for the primary or adjunctive treatment of patellofemoral pain syndrome (PFPS); however, there are limited data in terms of functional outcomes. This study aimed to investigate whether there is any beneficial effect of adding Kinesio Taping^® (KT) to exercise therapy in the treatment of PFPS. Materials and Methods: Twenty patients (27.5 ± 5.4 years) with PFPS who applied KT and 19 patients (27.3 ± 7.4 years) who did not were included in this study. Quadriceps muscle strength and acceleration time (AT) were assessed using an isokinetic device. Patient-reported outcomes were evaluated using the Kujala anterior knee pain scale (AKPS). Both groups underwent one-month exercise therapy. Results: There was no significant difference in quadriceps strength, AT, and AKPS at baseline and at 1 month between the taping and non-taping groups (p > 0.05). However, for quadriceps muscle strength, the effect of time*group interaction was statistically significant (F(1.37) = 4.543, p < 0.05, partial eta squared 0.109), showing that improvement in the quadriceps strength was higher in the non-taping group than that in the taping group. Conclusions: Adding KT to exercise therapy did not elicit extra benefits in quadriceps muscle strength and AT, and AKPS among PFPS with abnormal patellar tracking at one month.

Particularities on Anatomy and Normal Postsurgical Appearances of the Knee

Detailed knowledge of anatomy helps to understand pathologic processes. This article focuses on the anatomy and functionality of the knee, with emphasis on recently studied concepts and anatomic features that have an association with the development of pathology. The most common anatomic variants posing a challenge for diagnosis and other common findings in asymptomatic patients are reviewed. Good understanding of the different surgical procedures helps in providing as much information as possible to guarantee a positive outcome, improving prognosis. We review what are the commonly expected postsurgical appearances and the most common postsurgical complications.

In vivo intra-articular contrast enhanced μCT imaging of mouse knee cartilage

In vivo micro-Computed Tomography (μCT) is commonly used tool in the study of mouse bone architecture. However, in vivo imaging of mouse cartilage has been limited. Intra-articular contrast injection was evaluated for its utility in detecting mouse cartilage in μCT. Clinically used iodinated contrast agent was chosen for its widespread commercial availability. Imaging protocol was developed with wild type C57BL/6 mice for its ability to detect expected cartilage thinning that occurs with sexual maturity. The protocol was then validated with transgenic mouse model with known extracellular matrix loss. μCT findings showed good correspondence with histological assessment. In conclusion, in vivo intra-articular contrast-enhanced μCT arthrography is viable technique for evaluation of mouse cartilage. SUMMARY: In vivo intra-articular contrast enhanced μCT of the mouse knee joint can delineate cartilage thickness and extracellular matrix content. The imaging protocol may be useful for longitudinal evaluation of cartilage anomalies in transgenicmouse model.

Imaging findings and clinical function after combined surgery for recurrent patella dislocation: a comparative study

Background

Limited research has evaluated imaging results following a combination of operations for recurrent patella dislocation (RPD) based on medial patellofemoral ligament (MPFL) reconstruction. Therefore, this study aimed to retrospectively compare the imaging and clinical results of RPD following 2 types of combined surgical techniques.

Methods

Patients who underwent combined surgery for RPD from January 2008 to December 2019 were enrolled in the study and allocated into 2 groups. MPFL reconstruction combined with lateral retinacular release (LRR) was performed in groups A and B, and an additional tibial tuberosity transfer (TTT) was performed in group B only. Patients in group A with a tibial tuberosity trochlear groove (TT-TG) distance greater than 15 mm were included in subgroup A*. Congruence angle (CA), patellar tilt angle (PTA), lateral patellofemoral angle (LPA), lateral patellar displacement (LPD), TT-TG, Insall-Salvati Index (ISI), the Dejour type of trochlear dysplasia, and knee function were assessed. All groups were followed up in the short-term (1-2 years), and group B was also followed up in the mid-term (over 5 years).

Results

A total of 40 knees (36 patients) were included in group A, 26 knees (24 patients) in subgroup A*, and 27 knees (26 patients) in group B. In group A, CA, PTA, and LPD had increased at the short-term follow-up, yet LPA had decreased compared to the results 3 days after surgery. In group B, at the mid-term follow-up, PTA (12.54±6.88 vs. 15.23±6.10; P=0.002) increased while LPD (7.08±6.48 vs. 4.69±6.28; P=0.049) decreased compared with the short-term outcomes. The more severe the femoral trochlear dysplasia, the lower the mid-term Kujala scores in group B (P=0.007). The short-term TT-TG (17.32±4.288 vs. 12.84±3.758; P<0.001) and ISI [1.25 (1.1075, 1.300) vs. 1.06 (1.00, 1.16); P<0.001] in group B were lower than those in group A, who had a higher Kujala score (P<0.001). The CA, LPD, ISI, TT-TG, and Kujala score in subgroup A* were higher than those in group B at the short-term follow-up (P<0.05).

Conclusions

Both types of combination treatments were successful in altering the patellofemoral joint in a satisfactory manner, and the knee function improved in both groups. A TTT might not be necessary for patients with a TT-TG distance greater than 15 mm.

Individual Influence of Trochlear Dysplasia on Patellofemoral Kinematics after Isolated MPFL Reconstruction

INTRODUCTION

The influence of the MPFL graft in cases of patella instability with dysplastic trochlea is a controversial topic. The effect of the MPFL reconstruction as single therapy is under investigation, especially with severely dysplastic trochlea (Dejour types C and D). The purpose of this study was to evaluate the impact of trochlear dysplasia on patellar kinematics in patients suffering from low flexion patellar instability under weight-bearing conditions after isolated MPFL reconstruction.

MATERIAL AND METHODS

Thirteen patients were included in this study, among them were eight patients with mild dysplasia (Dejour type A and B) and five patients with severe dysplasia (Dejour type C and D). By performing a knee MRI with in situ loading, patella kinematics and the patellofemoral cartilage contact area could be measured under the activation of the quadriceps musculature in knee flexion angles of 0°, 15° and 30°. To mitigate MRI motion artefacts, prospective motion correction based on optical tracking was applied. Bone and cartilage segmentation were performed semi-automatically for further data analysis. Cartilage contact area (CCA) and patella tilt were the main outcome measures for this study. Pre- and post-surgery measures were compared for each group.

RESULTS

Data visualized a trending lower patella tilt after MPFL graft installation in both groups and flexion angles of the knee. There were no significant changes in patella tilt at 0° (unloaded pre-surgery: 22.6 ± 15.2; post-surgery: 17.7 ± 14.3; p = 0.110) and unloaded 15° flexion (pre-surgery: 18.9 ± 12.7; post-surgery: 12.2 ± 13.0; p = 0.052) of the knee in patients with mild dysplasia, whereas in patients with severe dysplasia of the trochlea the results happened not to be significant in the same angles with loading of 5 kg (0° flexion pre-surgery: 34.4 ± 12.1; post-surgery: 31.2 ± 16.1; p = 0.5; 15° flexion pre-surgery: 33.3 ± 6.1; post-surgery: 23.4 ± 8.6; p = 0.068). CCA increased in every flexion angle and group, but significant increase was seen only between 0°-15° (unloaded and loaded) in mild dysplasia of the trochlea, where significant increase in Dejour type C and D group was seen with unloaded full extension of the knee (0° flexion) and 30° flexion (unloaded and loaded).

CONCLUSION

This study proves a significant effect of the MPFL graft to cartilage contact area, as well as an improvement of the patella tilt in patients with mild dysplasia of the trochlea. Thus, the MPFL can be used as a single treatment for patient with Dejour type A and B dysplasia. However, in patients with severe dysplasia the MPFL graft alone does not significantly increase CCA.

The use of cardiac CT acquisition mode for dynamic musculoskeletal imaging

OBJECTIVES

To quantitatively evaluate the impact of a cardiac acquisition CT mode on motion artifacts in comparison to a conventional cine mode for dynamic musculoskeletal (MSK) imaging.

METHODS

A rotating PMMA phantom with air-filled holes drilled at varying distances from the disk center corresponding to linear hole speeds of 0.75 cm/s, 2.0 cm/s, and 3.6 cm/s was designed. Dynamic scans were obtained in cardiac and cine modes while the phantom was rotating at 48°/s in the CT scanner. An automated workflow to compute the Jaccard distance (JD) was established to quantify degree of motion artifacts in the reconstructed phantom images. JD values between the cardiac and cine scan modes were compared using a paired sample t-test. In addition, three healthy volunteers were scanned with both modes during a cyclic flexion-extension motion of the knee and analysed using the proposed metric.

RESULTS

For all hole sizes and speeds, the cardiac scan mode had significantly lower (p-value <0.001) JD values. (0.39 [0.32-0.46]) i.e less motion artifacts in comparison to the cine mode (0.72 [0.68-0.76]). For both modes, a progressive increase in JD was also observed as the linear speed of the holes increased from 0.75 cm/s to 3.6 cm/s. The dynamic images of the three healthy volunteers showed less artifacts when scanned in cardiac mode compared to cine mode, and this was quantitatively confirmed by the JD values.

CONCLUSIONS

A cardiac scan mode could be used to study dynamic musculoskeletal phenomena especially of fast-moving joints since it significantly minimized motion artifacts.

Good patient satisfaction with low complications rate after trochleoplasty in patellofemoral instability

PURPOSE

Trochlear dysplasia has been recognized as the most common factor in patients with patellofemoral dislocation. Trochleoplasty is a surgical procedure whose primary goal is to modify the femoral trochlea's abnormal shape in patients suffering from patellar instability, requiring good surgical skills, correct indication, and accurate patient information.

METHODS

The review aims to describe preoperative planning, patient selection, most common surgical techniques, and clinical results of trochleoplasty in patellar instability in a reproducible manner.

RESULTS

Trochleoplasty can be considered a general term to describe a group of different procedures that reduce trochlear dysplasia's impact on patellar instability, aiming to restore patella-trochlear congruency, remove the supratrochlear bump, allowed a new groove positioning and are generally associated with other procedures. Recent studies showed satisfactory long-term results with the restoration of patellar stability, improving radiological findings of patellofemoral instability.

CONCLUSION

Trochleoplasty is a technically demanding technique, requiring careful patient selection, detailed knowledge, and surgical skills to avoid severe complications. Good patient satisfaction with a low risk of significant complications such as patellofemoral arthritis has been revealed. In conclusion, trochleoplasty should be systematically included in the treatment of patellar dislocation, if indicated.

LEVEL OF EVIDENCE

V.

The SP-ET index is a new index for assessing the vertical position of patella

Background

Some parameters in previous studies did not better reflect the vertical position of the patella relative to the femoral trochlear. This study aimed to assess the value of the most superior point of patella-entrance of femoral trochlea distance ratio (SP-ET index) as a newer index in defining the vertical position of patella relative to the trochlea, correlate it with the Insall–Salvati ratio, and investigate the effect of the new index on patellar cartilage lesions.

Methods

A total of 99 knees of 77 patients with patellar cartilage lesions were retrospectively analyzed using magnetic resonance imaging (MRI) data. The Insall–Salvati ratio and SP-ET index were measured on MR images. Ninety-nine knees just with meniscus rupture were enrolled as the control group. The two parameters of the patellar cartilage lesions were compared with those of the control group.

Results

The Insall–Salvati ratio and SP-ET index in the patellar cartilage lesions group were significantly higher than those in the control group (p < 0.001). The SP-ET index showed a moderate positive correlation with the Insall–Salvati ratio (r = 0.307, p < 0.001). Receiver operating characteristic (ROC) analysis showed that the diagnostic efficiency of the SP-ET index was better than that of the Insall–Salvati ratio in patients with patellar cartilage lesions.

Conclusion

The SP-ET index may be a useful complement parameter to define the vertical position of the patella relative to the femoral trochlear. Increased SP-ET index may be an important risk factor for patellar cartilage lesions.

Predictive Scoring for Recurrent Patellar Instability After a First-time Patellar Dislocation

PURPOSE

Patellofemoral instability is a common acute knee injury seen in the pediatric population. First-time patellar dislocations usually undergo conservative management, but ~15% to 80% of patients experience recurrent instability. This study aims to develop a prediction model using radiographic parameters of the patellofemoral joint seen on computed tomography scans in different degrees of knee flexion, to determine the risk of recurrence after the first episode of patellofemoral instability.

METHODS

A 12-year retrospective case-control study was performed. All patients in a single institution aged 18 years or younger who had a computed tomography patellar tracking scan performed for patellar instability were included. Predictors included in the score were determined through backward logistic regression and compared using receiver operating characteristic curve analysis.

RESULTS

This study revealed that recurrent dislocation in first-time patellofemoral dislocation could be accurately predicted using the prediction score that consisted of age, tibial tubercle-trochlear groove distance and congruence angle at 10- and 20-degree flexion. The sensitivity of the score was 100% and specificity was 73.3%. Three diagnostic zones were identified and used to categorize patients into low-, intermediate-, and high-probability groups.

CONCLUSION

This study presented a scoring system that incorporated radiographic knee kinematics in the risk assessment for recurrent patellofemoral instability for patient stratification. The scoring system could guide the decision for early surgical intervention after the first-episode patellofemoral dislocation for patients at high risk of recurrent patellofemoral dislocation.

Gait Pathology in Subjects with Patellofemoral Instability: A Systematic Review

Identifying potential gait deviations in patellofemoral instability (PI) can help with the development of effective rehabilitation strategies. The purpose of this systematic review was to examine whether there are specific gait alterations in subjects with PI. The present review followed the PRISMA guidelines and was initially registered at PROSPERO (CRD42021236765). The literature search was carried out in the databases of PubMed, the Cochrane library, Web of Science, ClinicalTrials.gov, and Medline. The search strategy resulted in the identification of seven relevant publications. Subjects with PI show decreased walking speed, stride length, and cadence. Some studies reported changes not only in knee kinematics and kinetics but also in hip and ankle kinematics and kinetics. There is evidence that most subjects with PI walk with a quadriceps avoidance gait and show increased genu valgum posture, but there is still great variability in the coping responses within individuals with PI. The discrepancy among the study results might underpin the fact that PI is a multifactorial problem, and subjects cope with the different underlying morphological as well as functional deficits using a variety of gait strategies, which makes the interpretation and understanding of the gait of subjects with PI a clinically challenging task.

Anterior Knee Pain: State of the Art

Anterior knee pain (AKP) is one of the most common conditions to bring active young patients to a sports injury clinic. It is a heterogeneous condition related to multiple causative factors. Compared to the general population, there appears to be a higher risk of development of patellofemoral osteoarthritis in patients with AKP. AKP can be detrimental to the patient’s quality of life and, in the larger context, significantly burdens the economy with high healthcare costs. This study aims to present a comprehensive evaluation of AKP to improve clinical daily practice. The causes of AKP can be traced not only to structures within and around the knee, but also to factors outside the knee, such as limb malalignment, weakness of specific hip muscle groups, and core and ligamentous laxity. Hence, AKP warrants a pointed evaluation of history and thorough clinical examination, complemented with relevant radiological investigations to identify its origin in the knee and its cause. Conservative management of the condition achieves good results in a majority of patients with AKP. Surgical management becomes necessary only when it is deemed to provide benefit—when the patient has well-characterized structural abnormalities of the knee or limb that correlate with the AKP clinically or in situations where the patient does not obtain significant or sustained relief from symptoms. AKP has a multifactorial etiology. The treatment strategy must be individualized to the patient based on the patient profile and specific cause identified. Hence, treatment of AKP warrants a pointed evaluation of history and thorough clinical examination complemented with relevant radiological investigations to identify the condition’s origin and its cause. A holistic approach focused on the patient as a whole will ensure a good clinical outcome, as much as a focus on the joint as the therapeutic target.

Changes in Anatomic Risk Factors for Patellar Instability During Skeletal Growth and Maturation

BACKGROUND

Several anatomic risk factors have been identified in the pathogenesis of patellofemoral instability. The literature is sparce regarding how these anatomic risk factors change during skeletal growth and development.

HYPOTHESIS

The anatomic risk factors associated with patellar instability change significantly during skeletal growth and maturation with different patterns in male versus female patients.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Magnetic resonance imaging data from 240 unique, asymptomatic knees (7-18 years of age; 50% female) were used to measure patellar height (Caton-Deschamps index), lateral patellar tilt angle, trochlear height, trochlear groove depth, trochlear sulcus angle, and tibial tubercle-trochlear groove (TT-TG) distance. Linear regression was used to test the associations between age and anatomic findings. Two-way analysis of variance with Holm-Šídák post hoc test was used to compare anatomic characteristics between sexes in 3 age groups: prepubertal school-aged children (7-10 years old), early adolescents (11-14 years old), and late adolescents (15-18 years old).

RESULTS

Patellar height (female sex), lateral patellar tilt angle (male sex), and trochlear sulcus angle (both sexes) decreased with age (P < .001). Trochlear height, depth, and TT-TG distance increased with age in both male and female participants (P < .02). Male participants had a larger sulcus angle (by 5.3°± 1.6° at age 11-14 years) and greater trochlear height (by >5 mm across medial, central, and lateral regions at age 15-18 years) than age-matched female participants (P < .01). We found no other sex-related differences in quantified anatomic features (P > .1).

CONCLUSION

The findings partially support our hypothesis indicating significant age-related changes in all quantified features, which were not different between male and female participants except for trochlear sulcus angle in early adolescence and trochlear height in late adolescence. In general, the majority of anatomic risk factors for patellar instability change with maturity in a direction that assists in reducing the risk of patellar instability and/or dislocation. The only outlier is the TT-TG distance, which increased by age, and in our oldest cohort of patients, the mean fell below the normal adult range. The current observations highlight the importance of age in the interpretation of risk for injury as well as the need for further studies to identify intrinsic and extrinsic factors that may result in abnormal development of these anatomic features during skeletal growth and maturation.

The Increased Tibiofemoral Rotation: A Potential Contributing Factor for Patellar Maltracking in Patients with Recurrent Patellar Dislocation

OBJECTIVE

The purpose of this study was to analyze the relationship between tibiofemoral rotation and patellar maltracking in patients with recurrent patellar dislocation.

METHODS

A total of 143 consecutive knees (118 patients) with clinically diagnosed recurrent patellar dislocation from January 2018 to December 2019 were retrospectively analyzed. Patellar tilt angle and bisect offset index were recorded on axial CT to assesses the severity of patellar maltracking. Tibiofemoral rotation angle is measured by comparing the angle between the posterior femoral and tibial condylar lines on three-dimensional CT. The Pearson correlation was calculated to investigate the association between tibiofemoral rotation angle and patellar maltracking. Patients were divided into the rotation group (≥15°) and control group (<15°) based on the value of tibiofemoral rotation and a further comparison was performed. To further clarify the complicated relationship among tibial tubercle-trochlear groove (TT-TG), tibial tubercle-posterior cruciate ligament distance (TT-PCL), tibiofemoral rotation, and patellar maltracking, patients were divided into four subgroups according to the value of TT-TG and TT-PCL.

RESULTS

The mean preoperative tibiofemoral rotation angle was 12° ± 6° (range, 0°-31°). Pearson correlation between patellar maltracking parameters (bisect offset index, patellar tilt angle) and various bony deformities found that the tibiofemoral rotation angle was moderately correlated with bisect offset index (r = 0.451, p < 0.001) and patellar tilt angle (r = 0.462, p < 0.001). Further results demonstrated that bisect offset index (152.1 vs 121.2, p < 0.001) and patellar tilt angle (41.2° vs 33.5°, p < 0.001) were significantly higher in the rotation group than that in control group. For patients with a TT-TG distance of >20 mm, the increased TT-TG distance was mainly caused by tibiofemoral rotation angle in group C (TT-TG > 20 mm, TT-PCL < 24 mm) and predominantly induced by tibial tubercle lateralization in group D (TT-TG > 20 mm, TT-PCL > 24 mm). Bisect offset index and patellar tilt angle were significantly higher in the group C than group D.

CONCLUSION

The increased tibiofemoral rotation angle is associated with patellar maltracking in patients with recurrent patellar dislocation. Patients with increased tibiofemoral rotation angle usually have more severe patellar maltracking.

Osgood-Schlatter Disease: Appearance, Diagnosis and Treatment: A Narrative Review

Osgood-Schlatter disease is the most common osteochondritis of the lower limb in sport-practicing children and adolescents. Its manifestation usually coincides with the appearance of the secondary ossification center of the tibia and is linked to the practice of sports with an explosive component. In the present study, a review of the factors related to its appearance, diagnosis and treatment was carried out. Its appearance seems to be multifactorial and related to multiple morphological, functional, mechanical and environmental factors. Given all the above, risk factor reduction and prevention seem the most logical strategies to effectively prevent the appearance of the condition. In addition, it is essential to create prevention programs that can be objectively assessed and would allow to stop the progress of the pathology, particularly in those sports where high forces are generated on the insertion zone of the patellar tendon at sensitive ages. More studies are needed to clarify which type of treatment is the most appropriate—specific exercises or the usual care treatment.

Patellofemoral Instability in Children: Imaging Findings and Therapeutic Approaches

Patellofemoral instability (PFI) is common in pediatric knee injuries. PFI results from loss of balance in the dynamic relationship of the patella in the femoral trochlear groove. Patellar lateral dislocation, which is at the extreme of the PFI, results from medial stabilizer injury and leads to the patella hitting the lateral femoral condyle. Multiple contributing factors to PFI have been described, including anatomical variants and altered biomechanics. Femoral condyle dysplasia is a major risk factor for PFI. Medial stabilizer injury contributes to PFI by creating an imbalance in dynamic vectors of the patella. Increased Q angle, femoral anteversion, and lateral insertion of the patellar tendon are additional contributing factors that affect dynamic vectors on the patella. An imbalance in the dynamics results in patellofemoral malalignment, which can be recognized by the presence of patella alta, patellar lateral tilt, and lateral subluxation. Dynamic cross-sectional images are useful for in vivo tracking of the patella in patients with PFI. Therapeutic approaches aim to restore normal patellofemoral dynamics and prevent persistent PFI. In this article, the imaging findings of PFI, including risk factors and characteristic findings of acute lateral patellar dislocation, are reviewed. Non-surgical and surgical approaches to PFI in pediatric patients are discussed.

Patellar instability MRI measurements are associated with knee joint degeneration after reconstruction of the medial patellofemoral ligament

OBJECTIVE

To qualitatively and quantitatively evaluate the 2-year magnetic resonance imaging (MRI) outcome after MPFL reconstruction at the knee and to assess MRI-based risk factors that predispose for inferior clinical and imaging outcomes.

MATERIALS AND METHODS

A total of 31 patients with MPFL reconstruction were included (22 ± 6 years, 10 female). MRI was performed preoperatively in 21/31 patients. Two-year follow-up MRI included quantitative cartilage T2 and T1rho relaxation time measurements at the ipsilateral and contralateral knee. T2_relative was calculated as T2_{patellofemoral}/T2_femorotibial. Morphological evaluation was conducted via WORMS scores. Patellar instability parameters and clinical scores were obtained. Statistical analyses included descriptive statistics, t-tests, multivariate regression models, and correlation analyses.

RESULTS

Two years after MPFL reconstruction, all patellae were clinically stable. Mean total WORMS scores improved significantly from baseline to follow-up (mean difference ± SEM, - 4.0 ± 1.3; P = 0.005). As compared to patients with no worsening of WORMS subscores over time (n = 5), patients with worsening of any WORMS subscore (n = 16) had lower trochlear depth, lower facetal ratio, higher tibial-tuberosity to trochlear groove (TTTG) distance, and higher postoperative lateral patellar tilt (P < 0.05). T2_relative was higher at the ipsilateral knee (P = 0.010). T2_relative was associated with preoperatively higher patellar tilt (P = 0.021) and higher TTTG distance (P = 0.034). TTTG distance, global T2 values, and WORMS progression correlated with clinical outcomes (P < 0.05).

CONCLUSION

MPFL reconstruction is an optimal treatment strategy to restore patellar stability. Still, progressive knee joint degeneration and patellofemoral cartilage matrix degeneration may be observed, with patellar instability MRI parameters representing particular risk factors.

Patellar tilt does not affect patient reported outcomes after modern total knee arthroplasty

BACKGROUND

The focus of patella maltracking after total knee arthroplasty (TKA) has traditionally been on patella polyethylene damage and failure mechanisms rather than functional outcomes. The purpose of this study was to evaluate the effect of patellar tilt on patient reported outcomes (PROMS) after primary TKA performed with patellar resurfacing.

METHODS

A retrospective review using a single implant design was performed. Patella tilt was radiographically measured according to a standardized protocol. PROMS related to pain, function, and satisfaction were evaluated preoperatively and at minimum 1-year follow-up.

RESULTS

A total of 468 TKAs were included for analysis. Mean age and BMI were 64 years and 35 kg/m²; respectively while 63% of patients were female. The median follow-up period was 12.7 months. Overall, patellar tilt was corrected from a median of 5.0 degrees preoperatively to a median of 3.0 degrees postoperatively. Preoperative, postoperative, and the change in patellar tilt had no significant effects on PROMS at minimum 1-year follow-up (p ≥ 0.092). Satisfaction in knee function while getting out of bed was higher for patients with approximately the same patellar tilt before and after TKA compared to patients with an increase in lateral patellar tilt (95% vs 80%, p = 0.025).

CONCLUSIONS

The range of patellar tilt studied in this cohort had little to no effect on PROMS. However, suboptimal patellar tracking may potentiate edge loading of the polyethylene and contribute to implant damage in the long-term. These results are helpful to focus efforts on the tibiofemoral articulation as the predominant determinant of patient outcomes.

The Lateral Side: When and How to Release, Lengthen, and Reconstruct

The lateral patellofemoral complex is an important stabilizer to medial and lateral displacement of the patella. Soft tissue abnormalities can range from pathologic tightness to laxity, presenting with symptoms related to patellar instability, anterior knee pain, or arthritis. Clinical evaluation should be performed to confirm patellar dislocation, assess the integrity of the lateral and medial soft tissues, and explore other pathoanatomic factors that may need to be addressed. Lateral retinacular lengthening is recommended over lateral release owing to the potential of iatrogenic medial instability with release, and a lateral patellofemoral ligament reconstruction can be performed to effectively treat medial instability.

Patellar management during total knee arthroplasty: a review

The optimal management of the patella during total knee arthroplasty (TKA) remains controversial and surgeons tend to approach the patella with one of three general mindsets: always resurface the patella, never resurface the patella, or selectively resurface the patella based on specific patient or patellar criteria.

Studies comparing resurfacing and non-resurfacing of the patella during TKA have reported inconsistent and contradictory findings.

When resurfacing the patella is chosen, there are a number of available patellar component designs, materials, and techniques for cutting and fixation.

When patellar non-resurfacing is chosen, several alternatives are available, including patellar denervation, lateral retinacular release, and patelloplasty. Surgeons may choose to perform any of these alone, or together in some combination.

Prospective randomized studies are needed to better understand which patellar management techniques contribute to superior postoperative outcomes. Until then, this remains a controversial topic, and options for patellar management will need to be weighed on an individual basis per patient.

Cite this article: EFORT Open Rev 2021;6:861-871. DOI: 10.1302/2058-5241.6.200156

Suture Tape Augmentation of Screw Fixation Reduces Fragment Migration in Tibial Tubercle Osteotomy: A Biomechanical Study

Background:

Tibial tubercle osteotomy (TTO) is a complex surgical procedure with a significant risk of complications, which include nonunion and tibial fracture.

Purpose:

To determine whether an additional suture tape augmentation can provide better biomechanical stability compared with standard screw fixation.

Study Design:

Controlled laboratory study.

Methods:

Five matched pairs of human cadaveric knees were divided into 2 groups: the first group underwent standard TTO fixation with 2 parallel screws (standard group). The second group underwent a novel fixation technique, in which a nonabsorbable suture tape (FiberTape) in a figure-of-8 construct was added to the standard screw fixation for extra stabilization in the inferior-superior direction (augmented group). The specimens were biomechanically tested using a multistep cyclic loading protocol from 400 N up to 800 N to simulate the rehabilitation process. Tubercular fragment migration of >50% of the initial distalization length was defined as clinical failure. A pull-to-failure test was applied to the specimens that survived cyclic loading. Tubercular fragment displacement during cyclic loading and pull-to-failure force were recorded and compared between the 2 groups.

Results:

Two specimens of the standard group exhibited clinical failure during cyclic loading to 400 N. All other specimens survived cyclic loading to 800 N. The augmented group showed less cyclic tubercular fragment displacement after every load level compared with the standard group, with statistically significant differences starting from 500 N (P < .05; power > 0.8). Mean ± standard deviation tubercular fragment displacement at the end of cyclic loading was 2.56 ± 0.82 mm for the augmented group and 5.21 ± 0.51 mm for the standard group. Mean ultimate failure load after the pull-to-failure test was 2475 ± 554 N for the augmented group and 1475 ± 280 N for the standard group.

Conclusion:

The specimens that underwent suture tape augmentation showed less tubercular fragment displacement during cyclic loading and higher ultimate failure forces compared with those that underwent standard screw fixation.

Clinical Relevance:

The augmentation technique could potentially increase the success of a TTO.

Imaging of Patellofemoral Instability

Patellar instability is a broad term that encompasses patellar dislocation, patellar subluxation, and patellar instability. Although both functional and anatomic considerations contribute to symptoms of patellar instability, the most important are thought to be patella alta, trochlear dysplasia, and lateralization of the tibial tubercle. In patients with a history suspicious for prior patellar dislocation, careful evaluation of MRI and radiographic studies can reveal characteristic findings. The most common methods to address patellofemoral instability are medial patellofemoral ligament reconstruction and tibial tubercle osteotomy with either anteromedialization or medialization. Less commonly trochleoplasty is indicated as well. Patients may be treated with one of or a combination of these techniques, each of which has specific indications and complications.

Using a 3D handheld scanner to capture trochlear groove shape: proof of concept study

INTRODUCTION

Trochleoplasty is a surgical procedure used to treat patellar instability by modifying the trochlear groove. Analysis of the groove with a handheld scanner would enable accurate real-time planning and facilitate tailormade correction. We aimed to measure trochlear depth, sulcus angle, trochlear facet ratio, trochlear angle and lateral trochlear inclination angle and to establish inter- and intra-rater reliability for knee models to determine reliability and repeatability.

METHODS

The trochlear grooves of three knee models were scanned by two investigators. Three-dimensional reference models were created and surface-matched. Custom software was used to determine the desired parameters. The intraclass correlation coefficient (ICC) was used to determine test-retest reliability and the parameter results for each model that showed best reproducibility.

RESULTS

There was good interobserver reliability (trochlear depth, 1.0mm; sulcus angle, 2.7°; trochlear angle, 4.0°; lateral trochlear inclination angle, 4.0°), except in the trochlear facet ratio (32.0%) of one knee model. With outliers removed, the ICC was moderate to excellent in 73.34% of measurements, with trochlear depth showing the best reproducibility.

DISCUSSION

This feasibility study showed a handheld scanner in conjunction with supporting software can measure trochlear parameters with good to excellent inter- and intra-observer reliability.

Prevalence of lateral patellofemoral maltracking and associated complications in patients with Osgood Schlatter disease

OBJECTIVE

To evaluate adults with history of Osgood Schlatter disease (OSD) for imaging features of lateral patellofemoral maltracking.

METHODS

In a span of four years, 10,181 unique non-contrast knee MRIs were performed on patients aged 20-50. Patients with acute trauma, prior surgery, and synovial pathologies were excluded. 171 exams had imaging findings of OSD, and an age-matched control group of 342 patients without OSD was randomly selected. Two radiologists retrospectively reviewed MRIs for features of lateral patellofemoral maltracking. Maltracking was defined as edema in superolateral Hoffa's fat or a tibial tuberosity-trochlear groove (TT-TG) distance ≥20 mm with either patellar tilt/translation. Binomial logistic regression identified predictors of maltracking in OSD. Optimal TT-TG distance to indicate maltracking was determined by receiver operating characteristic curve.

RESULTS

59% (101/171) of the knees with OSD showed findings of maltracking, with patella alta, trochlear dysplasia, and quadriceps tendinosis as significant predictors of maltracking (p < 0.001). Patellofemoral chondrosis was present in 63% (107/171), with maltracking contributing to higher grade chondrosis more so than increasing age (OR 8.4 versus 1.07). 13 mm was the optimal cut-off TT-TG distance to indicate maltracking (sensitivity 83%, specificity 80%). The prevalence of maltracking in the control group was 15% (p < 0.001 compared with the OSD group).

CONCLUSION

Adults with sequelae of OSD are at high risk of maltracking and are likely to develop patellofemoral chondrosis. A lower threshold for identifying maltracking patients, including a lower cut-off TT-TG distance can help identify those at risk. Radiologists should maintain a high index of suspicion for maltracking in adults with OSD to guide clinical intervention.

Clinical Improvement Is Achieved Following Tibial Tubercle Distomedialization for Patellar Maltracking and Patella Alta Without Instability

Purpose

To determine short-term patient-reported outcomes following distomedial tibial tubercle transfer (TTT) in patients with patellar maltracking and patella alta without instability.

Methods

A single-surgeon case series study was performed on patients receiving distomedial TTT for the indication of patellar maltracking and patella alta without instability, after nonresponse to conservative treatment. Patient-reported outcomes were assessed preoperatively and at 3-, 6-, 12-, and 24-month follow-up using Kujala, Knee injury and Osteoarthritis Outcome Score (KOOS), and visual analog scale (VAS) pain scores. Generalized estimating equations analyses were performed to study improvement over time. Minimal clinically important differences obtained from literature were used to determine clinical relevance.

Results

A total of 40 patients were included. Eight patients were lost to follow-up; thus, outcomes of 32 patients were analyzed. Mean follow-up was 22 months, median age was 21 years, and 75% were female. Mean Kujala score increased pre- to postoperatively from 55 ± 12 to 79 ± 16 (P < .001), KOOS from 48 ± 14 to 79 ± 15 (P < .001), and VAS from 64 ± 17 to 25 ± 21 (P < .001), respectively. Eighty-four percent had clinical improvement of Kujala score, 91% of KOOS, and 78% of VAS score. A plateau phase in pain reduction was reached at 3 months, and in functional improvement at 6 months follow-up, after which no further significant improvement was observed. Complication rate was 3% and removal of hardware rate was 72%. Conclusions: In this case series study, distomedial TTT led to clinically relevant functional improvement and pain reduction in patients with patellar maltracking and patella alta without instability. However, the removal of hardware rate was high (72%).

Level of Evidence

Level IV, therapeutic case series.

Patellar Tracking in Revision Total Knee Arthroplasty: Does Retaining a Patella From a Different Implant System Matter?

BACKGROUND

Patellar maltracking is a potential surgical complication following total knee arthroplasty (TKA) and can result in anterior knee pain, recurrent patellar dislocation, and damage to the medial patellar soft tissue stabilizers. Data remain unclear as to whether the patellar button should be revised during a revision TKA (rTKA) if changing the component implant system. Our study examines whether retaining the original patellar button during an rTKA using a different implant system affects patellar tracking.

METHODS

A retrospective cohort study of rTKA patients between August 2011 and June 2019 was performed at an urban, tertiary referral center. Patients were divided into 2 cohorts depending on whether their retained patella from their primary TKA was of the same (SIM) or different implant manufacturer (DIM) as the revision system used. Radiographic measurements were performed on preoperative and postoperative knee radiographs and differences were compared between the 2 groups. Baseline demographic data were also collected.

RESULTS

Of the 293 consecutive, aseptic rTKA cases identified, 122 underwent revision in the SIM cohort and 171 in the DIM cohort. There were no demographic differences between the groups. No statistical significance was calculated for differences in preoperative and postoperative patellar tilt or Insall-Salvati ratio between the groups. The DIM group was found to have more lateral patellar translation (-0.01 ± 6.09 vs 2.68 ± 7.61 mm, P = .001). However, when calculating differences in the magnitude of the translation (thereby removing differences due to laterality), no difference was observed (0.06 ± 3.69 vs 0.52 ± 4.95 mm, P = .394).

CONCLUSION

No clinically significant differences in patellar tracking were observed when the original patellar component was retained and a different revision implant system was used. Given the inherent risks of bone loss and fracture with patellar component revision, surgeons performing rTKA may retain the primary patella if it is well fixed and can still expect appropriate patellar tracking regardless of the revision implant system used.

LEVEL OF EVIDENCE

III, Retrospective cohort study.

The association of patellar tendinosis with patellar maltracking and Hoffa's fat pad impingement: A case-control MRI study

OBJECTIVES

To assess whether proximal or distal patellar tendinosis is associated with patellar maltracking parameters and superolateral Hoffa's fat pad impingement.

METHODS

Institutional radiology database was reviewed for knee MRI scans performed over a 7-year period identifying cases of unequivocal patellar tendinosis, which were separated into 2 groups: proximal and distal tendinosis. For each group of proximal and distal patellar tendinosis, a control group of age and gender matched subjects was assigned. The scans were evaluated for patellar maltracking parameters including patellar alta, tibial tuberosity lateralization, trochlear dysplasia and lateral patellar tilt and for presence of superolateral Hoffa's fat pad edema. These parameters were compared between the case and control groups.

RESULTS

Out of 9852 MRI scans, 94 patellar tendinosis cases were included (65 proximal and 29 distal tendinosis) and matched with equal numbers of controls. In the proximal patellar tendinosis group, more subjects had patella alta (22 versus 6, p = 0.0006), lateralization of tibial tuberosity (16 versus 7, p = 0.0495) and superolateral Hoffa's fat pad edema (16 versus 4, p = 0.0073) compared to the control group. In the distal patellar tendinosis group, there was no significant difference in the prevalence of any maltracking indicator or superolateral Hoffa's fat pad edema compared to the control group.

CONCLUSION

Proximal patellar tendinosis was associated with patellar maltracking parameters including patella alta, lateralized tibial tuberosity and superolateral Hoffa's fat pad impingement. No association was demonstrated between distal patellar tendinosis and patellar maltracking indicators or superolateral Hoffa's fat pad impingement.

Clinical Outcomes and Prognostic Factors in Patients With Recurrent Patellar Lateral Dislocation Treated With Isolated Medial Patellofemoral Ligament Reconstruction: A Retrospective Single-Center Analysis

Background

Medial patellofemoral ligament reconstruction (MPFLR) is widely used to treat patellofemoral instability. However, it is still unclear when a concomitant bony procedure is needed.

Purpose

To evaluate the therapeutic efficacy of isolated MPFLR for recurrent patellar lateral dislocation and to identify the prognostic factors for clinical outcomes.

Study Design

Case series; Level of evidence, 4.

Methods

A total of 237 patients who had undergone unilateral isolated MPFLR between January 2011 and December 2016 were included. Patellar tracking (J sign) and radiologic information including patellar height, trochlear dysplasia, tibial tubercle-trochlear groove distance, and patellar tilt was collected preoperatively, and the Kujala and International Knee Documentation Committee (IKDC) functional scores were used to assess postoperative recovery. Failure was defined as redislocation or patient-reported and clinically confirmed patellar instability. The influence of radiologic features and the J sign on knee functional scores was explored via subgroup analysis. Potential prognostic factors were explored using univariate and multivariate regression analyses, and risk factors for a positive J sign were evaluated using Spearman coefficient correlation analysis.

Results

The mean ± SD follow-up period was 70.67 ± 18.05 months (range, 36-108 months). From preoperatively to final follow-up, all patients had statistically and clinically significant improvements in the Kujala score (from 51.43 ± 6.87 to 88.52 ± 4.83; P < .001) and IKDC score (from 49.78 ± 6.05 to 81.16 ± 4.20; P < .001). Subgroup analysis indicated no significant difference in functional score improvements based on radiologic features or the J sign. Overall, 20 knees (8.4%) experienced postoperative failure: 11 with redislocation and 9 with patellar instability. A preoperative positive J sign was shown to be an independent prognostic factor for postoperative failure via logistic regression analyses: univariate (odds ratio, 3.340; 95% CI, 1.316-8.480; P = .011) and multivariate (odds ratio, 3.038; 95% CI, 1.179-7.827; P = .021). In addition, the J sign was closely associated with patellar height (r _S, 0.159; P = .014) and trochlear dysplasia (r _S, 0.235; P < .001).

Conclusion

Isolated MPFLR appears to be an effective strategy for recurrent patellar lateral dislocation, with significant functional improvement and a low failure rate. A preoperative positive J sign was identified as a potential prognostic risk factor for postoperative failure.

Tibial tubercle transfer leads to clinically relevant improvement in patients with patellar maltracking without instability: a systematic review and meta-analysis

PURPOSE

To assess the different surgical techniques and their outcomes following tibial tubercle transfer (TTT) in patients with patellar maltracking.

METHODS

A systematic search of the literature was performed in PubMed, EMBASE and Cochrane Library. Studies reporting patient-reported outcome measures (PROMs) or clinical outcome following: TTT in patients with patellar maltracking were included. Collected PROMs were Lysholm, Kujala, IKDC score, and VAS pain. Clinical outcome included reported clinical success, patient satisfaction, complications and removal of hardware (ROH). Overall pre-, post-operative and change scores were estimated using random-effects meta-analysis models. Results were reported as overall mean and per transfer direction.

RESULTS

A total of 26 studies and 761 patients (818 knees, mean age 35 years, mean follow-up 5.0 years) were included. In 73% of the studies, surgery was performed after failed conservative treatment. Transfer direction was anteromedial in 76% of all procedures. Overall Lysholm score improved from 61 to 91, Kujala from 52 to 85, IKDC from 53 to 81, and VAS from 6.2 to 2.5, respectively. Clinical success was reported in 79% of patients, and 80% of patients reported to have satisfactory results. Rates of complications and ROH were 13% and 29%, respectively.

CONCLUSIONS

TTT for management of patellar maltracking can lead to good results with clinically meaningful improvement, an overall clinical success of 79% and overall patient satisfaction of 80% when appreciating the underlying anatomic condition and using appropriate technique. The level of evidence was low, and large-scale prospective, comparative cohort studies with uniform outcome scales are needed to confirm these findings.

LEVEL OF EVIDENCE

IV.

Literature review of the causes of pain following total knee replacement surgery: prosthesis, inflammation and arthrofibrosis

Adverse knee pain occurs in 10–34% of all total knee replacements (TKR), and 20% of TKR patients experience more pain post-operatively than pre-operatively. Knee pain is amongst the top five reasons for knee replacement revision in the United Kingdom. The number of TKRs is predicted to continue increasing due to the ageing population.

A narrative literature review was performed on the different causes of pain following TKR. A database search on Scopus, PubMed, and Google Scholar was conducted to look for articles related to TKR, pain, and cause. Articles were selected based on relevance, publication date, quality of research and validation. Relevant sections were added to the review.

One hundred and fourteen articles were identified and potential causes of TKR pain included: arthrofibrosis, aseptic loosening, avascular necrosis, central sensitization, component malpositioning, infection, instability, nerve damage, overstuffing, patellar maltracking, polyethylene wear, psychological factors and unresurfaced patella.

It is important to tailor our approach to address the individual causes of pain. Certain controllable risk factors can be managed pre-operatively to minimize post-operative pain. Risk factors help to predict adverse pain outcomes and identify specific causes.

There are multiple causes of pain following TKR. Some factors will require further extensive studies, and as pain is a commonly attributed reason for TKR revision, its underlying aetiologies should be explored. Understanding these factors helps to develop effective methods for diagnosis, prevention and management of TKR pain, which help to improve patient outcomes.

Cite this article: EFORT Open Rev 2020;5:534-543. DOI: 10.1302/2058-5241.5.200031

MPFL reconstruction: indications and results

BACKGROUND AND AIM

The medial patellofemoral ligament (MPFL) is the most important structure commonly injured during lateral patellar dislocation and its rupture accounts for 3% of total knee injuries. MPFL reconstruction (MPFLR) is a reliable procedure with good results but variable rates of recurrent instability. The aim of this study is to underline the proper indications for the MPFLR reconstruction and to explain all the pearls and pitfalls regarding the MPFLR both in our experience and found in the latest literature.

METHODS

A comprehensive search in the latest literature using various combinations of the keywords MPFL, MPFLR, dislocation, treatment was performed. The following data were extracted: diagnosis methods, indications and contraindications for isolated MPFLR, type of management, recurrence of instability, outcomes and complications.

RESULTS

History of multiple patellar dislocations is the most relevant indication for ligament reconstruction especially after a failed course of conservative treatment in presence of persistent patello-femoral instability. Gold standard technique for MPFLR has not been clearly defined yet.

CONCLUSIONS

There is still poor literature about outcome comparisons, therefore it is challenging to decide which technique is the most appropriate as surgical procedures are continuously developing. The ideal candidates for MPFLR have to be decided after a throughout evaluation and careful planning and, with nowadays knowledge, it is possible to put indication for a reconstruction exposing the patient to minimal risks.