Influence of tibial slope asymmetry on femoral rotation in patients with lateral patellar instability

Association of tibial slope alterations with anterior cruciate ligament (ACL) injury and mucoid degeneration

OBJECTIVE

To compare radiographic measurements of lateral tibial slope (LTS), medial TS (MTS), and coronal TS (CTS) in MRI-defined intact, injured, and mucoid-degenerated native ACL knees and determine inter-reader reliability.

MATERIALS AND METHODS

Patient records from 2 years at tertiary care hospitals were reviewed for individuals aged 18-100 undergoing 3-Tesla knee MRI and radiographs. Two randomly selected cohorts, control, and pathologic ACLs on MRI with 86 patients each, were age, gender, and BMI-matched. A fellowship-trained musculoskeletal radiologist reevaluated curated images, characterizing ACL status. Two trained medical students independently collected clinical data and measured slopes on blinded radiographs. ICC, Cohen's kappa, and case-control matching were performed using SPSS statistical package, with ICC and ANOVA used for comparisons.

RESULTS

Among 172 patients with 172 MRIs and radiographs, there were 86 controls and 86 ACL lesions. There were 108/172 (62.79%) males and 64/172 (37.21%) females. ICCs were 0.966 for MTS, 0.975 for LTS, and 0.978 for CTS. Mucoid degeneration patients had a higher BMI and were older than control (p < .05) or completely torn (p < .001) ACL patients. There was no difference in TS between normal and pathologic ACLs; however, LTS-MTS differences were larger with partial tears (2.5 ± 4.9) than normal ACLs by 4.5° (± 1.2, p < .001), complete tears by 4.5° (± 1.3, p < .001), and mucoid degeneration by 4.9° (± 1.5, p = .001).

CONCLUSION

Various TS measurements are reliable. LTS-MTS differences are associated with different ACL lesions compared to normal ACLs.

Implications for Femoral Tunnel Placement in Medial Patellofemoral Ligament Reconstruction Considering the Sagittal Trochlear Groove Curvature in Severe Trochlear Dysplasia Before and After Deepening Trochleoplasty

BACKGROUND

Medial patellofemoral ligament reconstruction (MPFL-R) aims to restore proper ligament function with minimal changes in length during range of motion, yet the ideal area for femoral fixation of the graft remains controversial.

PURPOSE

To determine the region where the isometric circular path of a simulated MPFL graft (best-fit circle) follows the sagittal radius curvature of the trochlea in normal (nontrochlear dysplastic) knees and to evaluate the best-fit circle coverage of different femoral fixation points in knees with severe trochlear dysplasia (TD) and after deepening trochleoplasty.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twelve patients (4 male, 8 female; mean age, 24 ± 8 years) who underwent surgical treatment for recurrent lateral patellar instability due to severe TD were prospectively enrolled in this study. Four previously defined reference points for the femoral MPFL-R (Schöttle, Fujino, Stephen, and Oka) were identified, and the best-fit circle was drawn along the sagittal trochlear groove curvature. The divergence between each best-fit circle and the trochlear groove was calculated, with negative values indicating relative slackening and positive values indicating relative tightening of the simulated MPFL graft. Measurements were made on true-lateral fluoroscopic images before and after deepening trochleoplasty and compared with those of a sex-matched control group.

RESULTS

The best-fit circle of the Schöttle point followed the sagittal curvature of the trochlea most closely in both the control and trochlear dysplastic knees, followed by the Fujino, Stephen, and Oka points. As the radius of the trochlear groove curvature increased, the divergence of all best-fit circles to the trochlear groove became negative (all P < .05). This effect was most pronounced at the Stephen and Oka points, followed by the Fujino and Schöttle points (all P < .05). After deepening trochleoplasty, the divergence of the Schöttle point changed toward positive values (11.6% at 40°; P < .001). Concurrently, the best-fit circle divergence of all other reference points improved toward baseline (all P < .05).

CONCLUSION

The isometric circle of the Schöttle point provides the best congruence with the sagittal trochlear groove curvature in both the normal trochlea and the dysplastic trochlea. After trochleoplasty, the best-fit circles of more distal femoral fixation points resulted in better congruence with the deepened trochlear groove, whereas the best-fit circle of Schöttle indicated graft tension during flexion.

CLINICAL RELEVANCE

According to the present study, different femoral fixation points should be considered depending on whether the TD is corrected.

Assessment of the reliability and validity of imaging measurements for patellofemoral instability: an updated systematic review

OBJECTIVE

To provide an update on the reliability and validity of all radiological measures used to assess patients presenting with patellofemoral instability.

METHODS

A search of the CINHAL, EMBASE, MEDLINE, and SCOPUS databases and the Cochrane library was conducted. All studies assessing the validity, reliability, sensitivity, and specificity of radiological measures of the patellofemoral joints of patients with patellofemoral instability from 2010 onwards were considered for inclusion. Discrimination validity, inter- and intra-observer reliability, and the sensitivity and specificity of specific imaging measures were evaluated.

RESULTS

Seventy-three studies met the selection criteria and were included for analysis. We identified eight radiological measures in four categories with good reliability and validity: the tibial tubercle to trochlear groove distance, specific measures of patellar height (Blackburne-Peel index, Caton-Deschamps index and Insall-Salvati ratios), three measures of trochlear dysplasia (sulcus angle, trochlear depth, and lateral trochlear inclination), and the tibial tubercle to posterior cruciate ligament distance. No included studies examined the reliability and validity of patellofemoral instability ultrasound measures.

CONCLUSION

Our updated review demonstrated good inter- and intra-observer reliability and discrimination validity for the tibial tubercle-trochlear groove distance, specific patellar height, and trochlear dysplasia measures on MRI. The tibial tubercle to posterior cruciate ligament distance, an indirect measure of rotational asymmetry, was a valid and reliable measure on MRI. Due to a lack of assessments across more than one study, there are a variety of proposed measures with insufficient evidence to determine their validity, reliability, sensitivity, and specificity.

Steep lateral tibial slope measured on magnetic resonance imaging is the best radiological predictor of anterior cruciate ligament reconstruction failure

PURPOSE

To identify the radiological predictive risk factors for anterior cruciate ligament reconstruction (ACLR) failure, compare the diagnostic accuracies of different parameters of conventional radiographs and magnetic resonance imaging (MRI), and determine the cutoff values for patients at higher risk.

METHODS

Twenty-eight patients who were diagnosed as ACLR failure via MRI or arthroscopic examination were included in the study group. They were matched to 56 patients who underwent primary ACLR with the same surgical technique and without graft failure at the minimum 24-month follow-up by age, sex, and body mass index. On true lateral whole-leg radiographs, the posterior tibial slope (PTS) referenced to the tibial mechanical axis (PTS-mechanical), PTS referenced to the tibial proximal anatomical axis (PTS-anatomical), and anterior tibial translation (ATT) were measured. On the sagittal slices of MRI, the medial tibial slope (MTS), medial tibial plateau (MTP) subluxation (MTPsublx), lateral tibial slope (LTS), and lateral tibial plateau (LTP) subluxation (LTPsublx) were obtained. Receiver operator characteristic (ROC) curves were constructed to compare the diagnostic performance and determine the cutoff values of different radiological parameters.

RESULTS

The study group demonstrated higher values of PTS-mechanical (10.7° ± 2.9° vs 8.7° ± 1.9°, p = 0.003), PTS-anatomical (13.2° ± 2.8° vs 10.5° ± 2.5°, p < 0.001), ATT (10.7 ± 3.3 mm vs 8.9 ± 2.2 mm, p = 0.014), LTS (9.4° ± 2.1° vs 5.5° ± 2.5°, p < 0.001), and LTPsublx (8.2 ± 2.8 mm vs 6.8 ± 1.9 mm, p = 0.009) as compared with the control group. The area under the ROC curve of LTS was significantly larger than that of PTS-mechanical (p = 0.006) and PTS-anatomical (p = 0.020). Based on the maximum Youden indexes, the cutoff values of PTS-mechanical, PTS-anatomical, and LTS were 10.1° (sensitivity, 64.3%; specificity, 78.6%), 12.0° (sensitivity, 71.4%; specificity, 71.4%), and 7.7° (sensitivity, 85.7%; specificity, 80.4%), respectively.

CONCLUSION

Due to the morphological asymmetry of the MTP and LTP, steep LTS measured on MRI is the best radiological predictor of ACLR failure. Detailed measurement of the LTS on MRI is recommended to evaluate the risk of ACLR failure prior to the surgery.

LEVEL OF EVIDENCE

III.

Influence of Bone Morphology on In Vivo Tibio-Femoral Kinematics in Healthy Knees during Gait Activities

An improved understanding of the relationships between bone morphology and in vivo tibio-femoral kinematics potentially enhances functional outcomes in patients with knee disorders. The aim of this study was to quantify the influence of femoral and tibial bony morphology on tibio-femoral kinematics throughout complete gait cycles in healthy subjects. Twenty-six volunteers underwent clinical examination, radiographic assessment, and dynamic video-fluoroscopy during level walking, downhill walking, and stair descent. Femoral computer-tomography (CT) measurements included medial condylar (MC) and lateral condylar (LC) width, MC and LC flexion circle, and lateral femoral condyle index (LFCI). Tibial CT measurements included both medial (MTP) and lateral tibial plateau (LTP) slopes, depths, lengths, and widths. The influence of bony morphology on tibial internal/external rotation and anteroposterior (AP)-translation of the lateral and medial compartments were analyzed in a multiple regression model. An increase in tibial internal/external rotation could be demonstrated with decreasing MC width β: −0.30 (95% CI: −0.58 to −0.03) (p = 0.03) during the loaded stance phase of level walking. An increased lateral AP-translation occurred with both a smaller LC flexion circle β: −0.16 (95% CI: −0.28 to −0.05) (p = 0.007) and a deeper MTP β: 0.90 (95% CI: 0.23 to 1.56) (p = 0.01) during the loaded stance phase of level walking. The identified relationship between in vivo tibio-femoral kinematics and bone morphology supports a customized approach and individual assessment of these factors in patients with knee disorders and potentially enhances functional outcomes in anterior cruciate ligament injuries and total knee arthroplasty.

Relationship between Anatomical Risk Factors, Articular Cartilage Lesions, and Patient Outcomes Following Medial Patellofemoral Ligament Reconstruction

OBJECTIVE

The purpose of this study was (1) to determine which risk factors for patellar instability were associated with the presence of patellofemoral cartilage lesions and (2) to determine how cartilage lesion presence, size, and grade affect postoperative disease-specific quality of life.

DESIGN

Preoperative, intraoperative, and postoperative demographic, anthropometric (body mass index, Beighton score, hip rotation), radiographic (crossover sign, trochlear bump), cartilage lesion morphology (presence, size, location, grade), and outcomes data (Banff Patella Instability Instrument 2.0 [BPII 2.0]) were prospectively collected from patients undergoing isolated medial patellofemoral ligament reconstruction. For all knees (n = 264), single and multivariable logistic regression was used to determine if any patellar instability risk factors affected the odds of having a cartilage lesion. In patients with unilateral symptoms (n = 121), single variable linear regression was used to determine if the presence, size, or ICRS (International Cartilage Regeneration & Joint Preservation Society) grade of cartilage lesions could predict the 12 or 24+ month postoperative BPII 2.0 score.

RESULTS

A total of 84.5% of knees had patellofemoral cartilage lesions (88.3% involved the distal-medial patella). Trochlear dysplasia (high grade: odds ratio = 15.7, P < 0.001; low grade: odds ratio = 2.9, P = 0.015) was associated with the presence of a cartilage lesion. The presence, size, and grade of cartilage lesions were not associated with 12 or 24+ month postoperative BPII 2.0 scores.

CONCLUSIONS

Trochlear dysplasia was a risk factor for the development of patellofemoral cartilage lesions in this patient population. Cartilage lesions most commonly involve the distal-medial patella. There was no significant relationship between patellofemoral cartilage lesion presence, size, or grade and postoperative BPII 2.0 scores in short-term follow-up.

Radiologic Measurements in the Assessment of Patellar Instability: A Systematic Review and Meta-analysis

Background:

Numerous diagnostic imaging measurements related to patellar instability have been evaluated in the literature; however, little has been done to compare these findings across multiple studies.

Purpose:

To review the different imaging measurements used to evaluate patellar instability and to assess the prevalence of each measure and its utility in predicting instability. We focused on reliability across imaging modalities and between patients with and without patellar instability.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

We performed a systematic review of the literature using the PubMed, SCOPUS, and Cochrane databases. Each database was searched for variations of the terms “patellar instability,” “patellar dislocation,” “trochlear dysplasia,” “radiographic measures,” “computed tomography,” and “magnetic resonance imaging.” Studies were included if they were published after May 1, 2009, and before May 1, 2019. A meta-analysis using a random effects model was performed on several measurements, comparing instability and control groups to generate pooled values.

Results:

A total of 813 articles were identified, and 96 articles comprising 7912 patients and 106 unique metrics were included in the analysis. The mean patient age was 23.1 years (95% CI, 21.1-24.5), and 41% were male. The tibial tubercle–trochlear groove (TT-TG) distance was the most frequently included metric (59 studies), followed by the Insall-Salvati ratio and Caton-Deschamps index (both 26 studies). The interobserver intraclass correlation coefficients were excellent or good for the TT-TG distance and Insall-Salvati ratio in 100% of studies reporting them; however, for the Caton-Deschamps index and Blackburne-Peel ratio, they were excellent or good in only 43% and 40% of studies. Pooled magnetic resonance imaging values for TT-TG distance (P < .01), Insall-Salvati ratio (P = .01), and femoral sulcus angle (P = .02) were significantly different between the instability and control groups. Values for tibial tubercle–posterior cruciate ligament distance (P = .36) and Caton-Deschamps index (P = .09) were not significantly different between groups.

Conclusion:

The most commonly reported measurements for evaluating patellar instability assessed patellar tracking and trochlear morphology. The TT-TG distance was the most common measurement and was greater in the patellar instability group as compared with the control group. In addition, the TT-TG, tibial tubercle–posterior cruciate ligament, and patellar tendon–trochlear groove distances were highly reproducible measurements for patellar tracking, and the Insall-Salvati ratio had superior reproducibility for assessing patellar height.

Predictors of Pediatric Anterior Cruciate Ligament Injury: The Influence of Steep Lateral Posterior Tibial Slope and Its Relationship to the Lateral Meniscus

PURPOSE

To examine the relationship between posterior tibial slope and lateral meniscal bone angle (LMBA) on anterior cruciate ligament (ACL) tear risk in a pediatric population.

METHODS

In this case-control study, non-contact ACL-injured pediatric patients with no significant lateral meniscal lesions were matched by age and sex in a 1:1 ratio to a group of radiologically normal controls. Knee magnetic resonance imaging (MRI) studies were analyzed by 3 independent, blinded observers measuring the medial posterior tibial slope (MTS), lateral posterior tibial slope (LTS), and LMBA. Sagittal slope asymmetry was calculated as the absolute difference in degrees between slopes, and the relationship between LMBA and LTS was calculated as a ratio. Binary logistic regressions identified independent predictors of ACL injury. Receiver operator characteristics were performed to determine predictive accuracy.

RESULTS

20 study patients were compared with 20 sex- and age-matched controls (age 14.8 ± 2.42, mean ± standard deviation). LTS was significantly higher in the ACL-injured group (11.30° ± 3.52° versus 7.00° ± 2.63°, P = .0001), as were the absolute slope difference (7.10 ± 2.92° versus 3.14 ± 3.25°, P = .0002) and LTS:LMBA ratio (0.46 ± 0.17 versus 0.26 ± 0.12, P = .0001). No significant differences were observed for MTS or LMBA. Independent predictors were LTS (odds ratio [OR] 1.58, 95% confidence interval [CI] 1.18 to 2.13, P = .002), LTS:LMBA ratio (OR 3.13, 95% CI 1.48 to 6.62, P = .003), and absolute slope difference (OR 1.65, 95% CI 1.17 to 2.32, P = .005). LTS:LMBA ratio was the strongest predictor variable (area under the curve 0.86).

CONCLUSION

This study suggests that LTS, absolute slope difference, and LTS:LMBA ratio are significant pediatric ACL-injury risk factors. All 3 demonstrate good predictive accuracy; however, the relationship between steep LTS and shallow LMBA was the strongest predictor.

LEVEL OF EVIDENCE

III, case-control study.

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.

Neither lateral patellar facet nor patellar size are altered in patellofemoral unstable patients: a comparative magnetic resonance imaging analysis

PURPOSE

It remains unclear if morphologic patterns of the patella itself predispose to patellar instability. This study examined established patellar landmarks in relation to the femoral condyle width to clarify differences of patellar morphologies in patellofemoral stable and unstable patients.

METHODS

Magnetic Resonance Imaging of 50 subjects (20.7 ± 4.4 years; 17 males, 33 females) with patellofemoral instability (study group, SG) and 50 subjects (25.3 ± 5.8 years; 31 males, 19 females) with anterior cruciate ligament rupture (control group, CG) were analyzed. Corresponding patellar value indices (PW-I; LPF-I 1; LPF-I 2) in relation to the femoral condyle width (FCW) were evaluated after the measurement of absolute patellar dimension [patellar width (PW); direct length of the lateral patellar facet (LPF-1); projected length of the lateral patellar facet (LPF-2)]. The patellar shape according to Wiberg, trochlear dysplasia, patellar height, and tibial tubercle-trochlear groove (TT-TG) distance were determined.

RESULTS

The SG showed a significantly longer absolute (LPF 2) (P = 0.041) and relative (LPF-I 1, LPF-I 2) (P < 0.001) lateral facet of the patella. No significant differences were evaluable for the relative patellar width (PW-I) (ns). A patellar shape type 3 (P = 0.001) as well as a higher position of the patella and TT-TG-distance (P < 0.001) were significantly more often present in the SG.

CONCLUSION

There are several bony alterations associated with patellofemoral instability, but our data did not show a significantly smaller lateral patellar facet or relative patellar width that could facilitate a patellar dislocation. This helps surgeons, that are considering to surgically address the patella in cases of patellofemoral instability, to better understand its morphologic pattern.

LEVEL OF EVIDENCE

III.

Femoral Anteversion Is Related to Tibial Tubercle-Trochlear Groove Distance in Patients with Patellar Dislocation

PURPOSE

To evaluate the potential relationship between the tibial tubercle-trochlear groove (TT-TG) distance and the femoral anteversion of different segments of the femur in patients with patellar dislocation.

METHODS

A total of 60 patients with a diagnosis of patellar dislocation were included in our study. Patients with previous knee surgeries, previous fractures, or lack of necessary radiologic examinations were excluded from our study. The data of computed tomography scanning within a week before the surgery was used to measure the TT-TG distance, total anteversion, proximal anteversion, diaphyseal anteversion, distal anteversion, and tibial torsion. All the data were obtained from the picture archiving and communication system (PACS) workstation. The Pearson correlation analysis was performed to confirm the potential relationship between TT-TG distance and femoral anteversion of different segments. The intraclass correlation coefficient was used to assess the interobserver reliability of measurements.

RESULTS

The TT-TG distance was significantly correlated with the diaphyseal anteversion (r = -0.305, P = 0.008) and distal anteversion (r = 0.365, P = 0.004). The total anteversion was associated with proximal anteversion (r = 0.392, P = 0.02) and diaphyseal anteversion (r = 0.631, P < 0.001). The intraclass correlation coefficient showed the measurements of included parameters were presented with excellent agreement.

CONCLUSION

Our study showed that patients with high diaphyseal anteversion and distal anteversion tend to had a higher TT-TG distance but the value of total and proximal femoral anteversion were independent of the value of TT-TG distance.

LEVEL OF EVIDENCE

Level IV therapeutic case series.

Static patella tilt and axial engagement in knee extension are mainly influenced by knee torsion, the tibial tubercle-trochlear groove distance (TTTG), and trochlear dysplasia but not by femoral or tibial torsion

PURPOSE

The aim of this study was to investigate the association of femoral (FT), tibial (TT), and knee torsion (KT) on the patella tilt (PT), the axial engagement index (AEI), and the tibial tuberosity-trochlear groove distance (TTTG).

METHODS

Femoral torsion, tibial torsion, knee torsion, patella tilt, the axial engagement index, the TTTG, and trochlear dysplasia were retrospectively evaluated on 59 patients suffering from recurrent patella instability or anterior knee pain with 118 torsional lower limb magnetic resonance imaging studies.

RESULTS

FT and TT did not show any significant associations with TTTG, PT, and AEI (n.s.). KT was significantly associated with a higher TTTG, higher PT, and lower AEI (all, p < 0.001). Higher grade trochlear dysplasia was associated with a higher PT and lower AEI (both, p < 0.001). The Dejour classification showed no significant association with FT, TT, KT, and TTTG (n.s.). All measurement parameters showed an excellent interrater agreement (ICC 0.89-0.97).

CONCLUSIONS

Static patella tilt and patellofemoral axial engagement in knee extension are mainly influenced by knee torsion, TTTG, and trochlear dysplasia but not by femoral or tibial torsion. These findings help to understand the underlying reasons for the patella position in knee extensions in CT and MRI investigations in patients suffering from patella instability and patellofemoral pain syndrome.

LEVEL OF EVIDENCE

III.

When does the patella dislocate? A systematic review of biomechanical & kinematic studies

Background

Patellar dislocations are a significant injury with the potential for long term problems. Little work has been done on establishing the mechanism by which this injury occurs.

Objectives

To determine the mechanism of injury of a patella dislocation based on the available published literature and compare them to already proposed theories.

Methods

A systematic review of the literature was conducted following searches performed on MEDLINE, EMBASE and ProQuest from the earliest year of indexing using the following search terms in any combination: "patella", "dislocation", "mechanism of injury", "anatomy", "biomechanical" and "risk factor". A broad inclusion criteria was used that included studies that looked at patellar dislocations and instability with respect to the patellofemoral joint (PFJ) kinematics or altered kinematics of the PFJ. Studies that did not address the kinematics or biomechanics of the PFJ were excluded. Studies were appraised based on their methodology using a combination of the Critical Appraisal Skills Programme tool and the Quality Appraisal for Cadaveric Studies.

Results

113 studies were identified from a search of MEDLINE, EMBASE and ProQuest databases. Following application of our inclusion criteria, a total of 23 studies were included in our review. 18 of these studies were cadaveric biomechanical studies. The remaining studies were anatomical, imaging based, and a computer simulation based study.

Conclusions

These biomechanical and kinematic studies provide some evidence that a dislocation is likely to occur during early knee flexion with external rotation of the tibia and contraction of the quadriceps. There is limited evidence to support other elements of proposed mechanisms of dislocation.

Steep lateral tibial slope and lateral-to-medial slope asymmetry are risk factors for concomitant posterolateral meniscus root tears in anterior cruciate ligament injuries

PURPOSE

To compare sagittal and coronal tibial slopes between anterior cruciate ligament (ACL) injured subjects with and without posterolateral meniscus root tear (PLRT).

METHODS

A chart review was conducted to identify patients with isolated ACL tears and patients with an associated PLRT. Patients with other concomitant injuries and patients who underwent surgery > 6 months after the injury were excluded. Magnetic resonance image data were used to compare the medial and lateral sagittal tibial slope (MTS and LTS), lateral-to-medial slope asymmetry (LTS-MTS), and coronal slope of the tibial plateau between both groups. Mean LTS and standard deviation (SD) of the control group were calculated, and a value of > mean + 1 SD was considered an abnormal LTS. Interobserver reproducibility was assessed by calculating interclass correlation coefficients (ICCs) of measurements independently obtained by two reviewers.

RESULTS

Fifty-nine patients met the in- and exclusion criteria. Thirty nine (66%) had an isolated ACL tear and 20 (34%) had an associated PLRT. Interrater ICCs for LTS, MTS, and coronal slope were 0.930, 0.884 and 0.825, respectively, representing good to excellent interobserver reproducibility. Patients with a PLRT had significantly steeper LTS (8.0 ± 3.2 vs. 4.0 ± 2.0; p < 0.001) and significantly greater difference of LTS-MTS (3.7 ± 2.9 vs. - 0.6 ± 2.0; p < 0.001). Furthermore, patients with abnormal LTS were significantly overrepresented among patients with PLRT (70% vs. 18%; p < 0.001). No significant difference between both groups was found for MTS and coronal slope.

CONCLUSION

A steep lateral tibial slope and lateral-to-medial slope asymmetry are risk factors for concomitant PLRT in ACL-injured subjects.

LEVEL OF EVIDENCE

IV, retrospective cohort study.

Computed Tomography-based Analysis of Tibial Tuberosity-Trochlear Groove Distance in Indian Population

Aim To study the tibial tuberosity-trochlear groove distance (TT-TG) in normal Indian population and the variation of the same in relation to tibial size using computed tomography (CT) of knee. Methods CT of 100 knees (62 males and 38 females) were assessed. TT-TG distance and maximal medio-lateral (MML) distance of tibia was measured on axial CT scans. The modified TT-TG (mTT-TG) was calculated as the ratio of TT-TG and MML. Results The average TT-TG distance was 13.01 (±2.84) mm for the entire group with males and females having 12.82 (±2.95) and 13.32 (±2.66) mm, respectively (p > 0.05). The MML distance was 75.99 (±3.78) and 66.77 (±4.33) mm for males and females, respectively (p < 0.05). The average modified TT-TG was 0.18 ± 0.04. The TT-TG distance of Indian knees was similar to values obtained in Caucasian knees and higher than other Asian knees (p < 0.05). Conclusion The average TT-TG distance in Indian population is 13.01 mm, with no difference between males and females. The ML/TT-TG ratio was 0.18. The TT-TG distance in Indian population is found to be similar to the Western population and significantly higher than other Asian population.

Knee Deformities in Children With Down Syndrome: A Focus on Knee Malalignment

BACKGROUND

Patellofemoral instability (PFI) has been the most reported knee abnormality in people with Down syndrome. Other reported knee abnormalities have been associated with PFI and different management approaches have been described with variable outcomes. The aim of this study was to describe the anatomic variations of the knee in children with Down syndrome. A comparison between knees with and without PFI was performed and our experience in treating knee abnormalities in Down syndrome was also reported.

METHODS

Records of all children with Down syndrome were reviewed. Two groups were identified (knees with and without PFI). Radiographic measurements included the mechanical and anatomic lateral distal femoral angles, medial proximal tibial angle, angle of depression of medial tibial plateau, lateral tibial translation, and distal femoral physis-joint angle. On the lateral view, Insall-Salvati and Blackburne-Peel ratios were measured. The sulcus angle was measured on the tangential view. Measurements were compared between the 2 groups (with and without PFI).Knees with PFI were divided into 3 subgroups based on their treatment (group A: surgical valgus correction, group B: surgical soft tissue procedures for PFI, and group C: conservative treatment). Preoperative radiographs were used for the surgical group and last available radiographs were used for the conservative group. Clinical and radiographic data were compared between the groups. For groups A and B, clinical and radiographic data were also compared between preoperative and last visits.

RESULTS

Of the 581 children with Down syndrome, 5% (31 children: 22 females, 9 males) had PFI in 56 knees. Mean age at diagnosis was 11.5±3.5 years. Of the remaining 550 children, 75 children had radiographs for 130 knees. Knees with PFI had significantly more valgus and a larger distal femoral physis-joint angle. Depression of the medial tibial plateau and lateral tibial translation were noted in knees with PFI. Insall-Salvati ratio was higher and the sulcus angle was larger in the PFI group.Of the 56 knees with PFI; 10 knees were in group A, 11 knees in group B, 33 knees in group C, and the remaining 2 knees had combined procedures. Preoperative mechanical and anatomic lateral distal femoral angles were smaller in group A than in group B or C. Grades of PFI improved in group B after surgery. This improvement was not noted in group A.

CONCLUSIONS

In children with Down syndrome, different variations of the knee anatomy can be found. Although PFI might be the most evident knee abnormality, other underlying deformities are common. Treatment of the PFI should be planned through a comprehensive anatomic approach that addresses all aspects of knee deformity.

LEVEL OF EVIDENCE

Level IV-prognostic and therapeutic study.

MPFL in First-Time Dislocators

PURPOSE OF REVIEW

Historically, the standard of care for patients with an acute patella dislocation has been non-operative with the exception being those with a loose body or osteochondral fracture requiring fixation or removal.

RECENT FINDINGS

Recent literature has brought into question this standard of care approach and defined a higher risk subset of first-time dislocators who may benefit from early operative treatment. In addition, these studies suggest that operative treatment not only reduces the risk of recurrence but may improve outcomes overall and specifically in the pediatric population. Though the "high risk" population of first-time dislocators has been more clearly defined, how we treat them remains controversial. We continue to need more evidence-based guidelines to help us manage who we should be fixing and how we should be fixing them. We currently have several multi-center studies in progress, including one specifically looking at the question of medial patellofemoral ligament reconstruction in first-time pediatric and adolescent dislocators.

Anatomic patellar instability risk factors in primary lateral patellar dislocations do not predict injury patterns: an MRI-based study

PURPOSE

The primary goal was to describe the injury patterns in a population of primary (first time) lateral patellar dislocators (LPD) to lend clarity to commonly held notions about injury patterns in this population.

METHODS

A prospective study identifying patients presenting with LPD between 2008 and 2012. Inclusion criteria were a history and physical exam consistent with primary LPD, and an MRI consistent with the diagnosis without other significant ligamentous injury. On MRI, location of cartilage, medial patellofemoral ligament (MPFL) injury, and bone bruising were noted. Severity was categorized as partial or complete for MPFL and cartilage lesions. Anatomic patellar instability risk factors (patella alta, trochlear dysplasia, increased TT-TG, and lateral patella tilt) were recorded and compared to the injury patterns.

RESULTS

This study involved 157 patients; 107 patients were skeletally mature. Of the 157 patients, 26 had surgery for this injury due to clinician-perceived need for cartilage debridement. MPFL injury severity was complete rupture (N = 69, 44%), partial (N = 67, 43%), and none (N = 19, 13%). MPFL injury location was isolated femoral (N = 16, 10%), isolated patella (N = 26, 17%), isolated mid-substance (0%), multiple locations (N = 95, 61%), and none (N = 20, 13%). Chondral injury location was patella (N = 67, 43%), lateral femoral condyle (N = 11, 7%), multiple locations (N = 53, 34%), and none (N = 26, 17%). A majority (61%) of patellar chondral lesions were at its inferomedial aspect; all medial patellar retinacular partial injuries involved the inferomedial aspect of the patella, consistent with the insertion of the medial patellotibial ligament (MPTL). Skeletally immature patients had a greater risk of isolated patellar MPFL and chondral injury. No clear relationship was found between/across the location and/or severity of bone bruising, MPFL, or chondral injury.

CLINICAL RELEVANCE

Underlying anatomic patellar instability risk factors defined by MRI, do not predict injury patterns. MPFL and chondral injury, as well as bone bruising, are common following LPD. The medial patellotibial ligament is torn in patellar-based medial retinacular injuries, based on MRI injury location. Skeletal immaturity plays a role in the location of the injury pattern with isolated patellar-based MPFL/chondral injury being more common in the skeletally immature patient. Sex does not appear to be a factor in injury patterns after primary LPD. Knowledge of these injury trends will help focus the clinician in injury evaluation when managing primary patellar dislocations.

LEVEL OF EVIDENCE

Case series, Level IV.

Ratio of the tibial tuberosity-trochlear groove distance to the tibial maximal mediolateral axis: A more reliable and standardized way to measure the tibial tuberosity-trochlear groove distance

BACKGROUND

Tibial tuberosity-trochlear groove distance(TT-TG) is a measurement to assist in the diagnosis and treatment of patellar instability, however it still has some limitations. Our study was to modify the accepted measurement method and seek a more reliable and standardized method.

METHODS

The data of 65 healthy controls and 49 patients with bilateral patellar instability from 2010 to 2016 were collected and analyzed by CT. The TT-TG, tibial maximal mediolateral axis (MML), and their ratio [i.e., the modified-TT-TG (M-TT-TG)] were compared between the two groups.

RESULTS

The MML (71.9±12.0 vs. 71.3±10.9) was not significantly different between the two groups (P>0.05). However, the TT-TG(18.1±6.0 vs. 13.1±2.9) and M-TT-TG (0.25±0.08 vs. 0.19±0.04) were significantly different between the two groups (P<0.05). A TT-TG of >15mm was found in 24.5% of healthy controls and 71.5% of patients. The healthy controls with a TT-TG of >15mm were compared with the patients; although no significant difference was found in the TT-TG (16.8±1.5 vs. 18.1±6.0), the healthy controls had a significantly larger MML (76.9±12.7 vs. 71.9±10.9) and significantly smaller M-TT-TG (0.22±0.04 vs. 0.25±0.08). A total of 53.1% of patients but only 6.9% of healthy controls had an M-TT-TG of >0.25.

CONCLUSION

The M-TT-TG is a more reliable and standardized way to measure the effect of the TT-TG with the goal of reducing the false-positive rate associated with the standard measurement technique. The normal M-TT-TG ranges from 0.11 to 0.25, with an M-TT-TG of >0.25 being associated with patellofemoral malalignment.

LEVEL OF EVIDENCE

III.

Assessment of demographic and pathoanatomic risk factors in recurrent patellofemoral instability

PURPOSE

The WARPS/STAID classification employs clinical assessment of presenting features and anatomic characteristics to identify two distinct subsets of patients within the patellofemoral instability population. The purpose of this study was to further define the specific demographics and the prevalence of risky pathoanatomies in patients classified as either WARPS or STAID presenting with recurrent patellofemoral instability. A secondary purpose was to further validate the WARPS/STAID classification with the Banff Patella Instability Instrument (BPII), the Marx activity scale and the Patellar Instability Severity Score (ISS).

METHODS

A convenience sample of 50 patients with recurrent patellofemoral instability, including 25 WARPS and 25 STAID subtype patients, were assessed. Clinical data were collected including assessment of demographic risk factors (sex, BMI, bilaterality of symptoms, affected limb side and age at first dislocation) and pathoanatomic risk factors (TT-TG distance, patella height, patellar tilt, grade of trochlear dysplasia, Beighton score and rotational abnormalities of the tibia or femur). Patients completed the BPII and the Marx activity scale. The ISS was calculated from the clinical assessment data. Patients were stratified into the WARPS or STAID subtypes for comparative analysis. An independent t test was used to compare demographics, the pathoanatomic risk factors and subjective measures between the groups. Convergent validity was tested with a Pearson r correlation coefficient between the WARPS/STAID and ISS scores.

RESULTS

Demographic risk factors statistically associated with a WARPS subtype included female sex, age at first dislocation and bilaterality. Pathoanatomic risk factors statistically associated with a WARPS subtype included trochlear dysplasia, TT-TG distance, generalized ligamentous laxity, patellar tilt and rotational abnormalities. The independent t test revealed a significant difference between the ISS scores: WARPS subtype (M = 4.4, SD = 1.1) and STAID subtype (M = 2.5, SD = 1.5); t(48) = 5.2, p < 0.001. The relationship between the WARPS/STAID and the ISS scores, measured using a Pearson r correlation coefficient, demonstrated a strong relationship: r = -0.61, n = 50, p < 0.001.

CONCLUSIONS

This study has demonstrated statistically significant evidence that certain demographics and pathoanatomies are more prevalent in each of the WARPS and STAID patellofemoral instability subtypes. There was no difference in quality-of-life or activity level between the subtypes. The WARPS/STAID score demonstrated convergent validity to the ISS and divergent validity to the BPII score and the Marx activity scale. This study has further validated both the WARPS/STAID classification and the ISS of patients that present with recurrent patellofemoral instability.

LEVEL OF EVIDENCE

III.

Relationship between tibial spine size and the occurrence of osteochondritis dissecans: an argument in favour of the impingement theory

PURPOSE

Pathophysiology of osteochondritis dissecans (OCD) of the medial femoral condyle remains uncertain. Specifically, the relationship between the size of the anterior tibial spine (ATS) and the presence of OCD has not been explored. The purpose of this study was to evaluate the relationship between ATS size and the occurrence of OCD.

METHODS

Seventy-nine children between 8 and 17 years of age were included in two groups: OCD (n = 37) and control (n = 42). The groups were matched in terms of age, gender, BMI and weight. Two independent observers performed an MRI analysis of the size of the tibial spine and intercondylar notch relative to the size of the respective epiphyses. For this study, the "S ratio" was calculated by dividing the height of the tibial spine by the height of the tibial epiphysis. The "N ratio" was calculated by dividing the height of the notch by the height of the femoral epiphysis. These two ratios for both groups were compared using Student's t test.

RESULTS

The mean value of the S ratio in the OCD group was 0.39 ± 0.06; the mean value of the S ratio in the control group was 0.32 ± 0.03 (P = 0.004). The mean value of the N ratio in the OCD group was 0.70 ± 0.08; the mean value of the N ratio in the control group was 0.70 ± 0.07 (n.s.).

CONCLUSION

This study's findings confirm our hypothesis that patients with OCD have a more prominent tibial spine than in patients without OCD.

LEVEL OF EVIDENCE

IV.

Evaluation of a modified knee rotation angle in MRI scans with and without trochlear dysplasia: a parameter independent of knee size and trochlear morphology

PURPOSE

Regarding TT-TG in knee realignment surgery, two aspects have to be considered: first, there might be flaws in using absolute values for TT-TG, ignoring the knee size of the individual. Second, in high-grade trochlear dysplasia with a dome-shaped trochlea, measurement of TT-TG has proven to lack precision and reliability. The purpose of this examination was to establish a knee rotation angle, independent of the size of the individual knee and unaffected by a dysplastic trochlea.

METHODS

A total of 114 consecutive MRI scans of knee joints were analysed by two observers, retrospectively. Of these, 59 were obtained from patients with trochlear dysplasia, and another 55 were obtained from patients presenting with a different pathology of the knee joint. Trochlear dysplasia was classified into low grade and high grade. TT-TG was measured according to the method described by Schoettle et al. In addition, a modified knee rotation angle was assessed. Interobserver reliability of the knee rotation angle and its correlation with TT-TG was calculated.

RESULTS

The knee rotation angle showed good correlation with TT-TG in the readings of observer 1 and observer 2. Interobserver correlation of the parameter showed excellent values for the scans with normal trochlea, low-grade and high-grade trochlear dysplasia, respectively. All calculations were statistically significant (p < 0.05).

CONCLUSION

The knee rotation angle might meet the requirements for precise diagnostics in knee realignment surgery. Unlike TT-TG, this parameter seems not to be affected by a dysplastic trochlea. In addition, the dimensionless parameter is independent of the knee size of the individual.

LEVEL OF EVIDENCE

II.

Risk Factors Associated With Grade 3 Pivot Shift After Acute Anterior Cruciate Ligament Injuries

BACKGROUND

Recent literature has demonstrated that involvement in pivoting sports at the time of injury, increased posterior-inferior tibial slope (PITS), anterolateral capsular ligament (ALCL) disruptions, and combined lateral meniscal lesions all contribute to a higher grade of pivot shift after acute anterior cruciate ligament (ACL) injuries.

PURPOSE

To identify risk factors associated with grade 3 pivot shift after acute ACL injuries.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

A database of patients undergoing primary ACL reconstruction from 2009 to 2015 after acute ACL injuries was retrospectively reviewed. A total of 30 patients (30 knees) with grade 3 pivot shift were identified as the study group. Moreover, 30 patients (30 knees) with grade 1 and 30 patients (30 knees) with grade 2 pivot shift were randomly chosen as the 2 control groups. All pivot-shift tests were performed with the patients under anesthesia. Predictors of grade 3 pivot shift that were explored included patient age, sex, time from injury to surgery, pivoting sports involvement at the time of injury, lateral PITS, medial PITS, ALCL disruptions, preoperative KT-1000 arthrometer side-to-side difference, and combined lateral or medial meniscal lesions. Comparisons were performed between the study group and the 2 control groups. Univariable and multivariable logistic regressions were used to identify independent risk factors that were associated with grade 3 pivot shift.

RESULTS

Univariable and multivariable logistic regressions between the study group and the 2 control groups showed that pivoting sports involvement at the time of injury (odds ratio1 [OR1; grade 3 vs grade 1 pivot shift with grade 1 = reference], 11.88; 95% CI, 1.94-149.91; OR2 [grade 3 vs grade 2 pivot shift with grade 2 = reference], 3.41; 95% CI, 1.92-22.60), abnormal degree of lateral PITS (OR1, 14.41; 95% CI, 1.69-174.78; OR2, 6.41; 95% CI, 1.48-47.70), ALCL disruptions (OR1, 8.28; 95% CI, 1.71-117.14; OR2, 4.96; 95% CI, 1.07-28.75), and combined lateral meniscal lesions (OR1, 27.56; 95% CI, 5.48-240.52; OR2, 5.83; 95% CI, 1.21-38.56) were independent risk factors of grade 3 pivot shift after acute ACL injuries.

CONCLUSION

For acute ACL injuries, the best set of predictors of grade 3 pivot shift were pivoting sports involvement at the time of injury, abnormal lateral PITS, ALCL disruptions, and combined lateral meniscal lesions. These results may provide additional information for counseling patients on residual laxity and risks for graft rerupture after ACL reconstruction.

Proximal tibial morphology and its correlation with osteochondritis dissecans of the knee

PURPOSE

The relationship of proximal tibial morphology to the presence of femoral osteochondritis dissecans (OCD) lesions is unknown. This radiographic study tested the null hypothesis that knees with unilateral medial or lateral OCD lesions would have no difference in the slope of their medial, lateral, or posterior tibial plateau compared with unaffected knees.

METHODS

There were 72 patients with unilateral OCD lesions of the medial or lateral femoral condyle seen at our institution from 2005 to 2011. On AP and lateral radiographs of the knee, three examiners conducted independent measurements of the tibial plateau posterior slope, as well as medial and lateral slope as measured from the peak of the tibial spine to the edge of the plateau on the side of the corresponding OCD lesion. Measurements were repeated on normal contralateral and matched control knees.

RESULTS

Knees with medial femoral condyle OCD lesions had greater medial tibial slope compared with normal contralateral knees (p = 0.007) and normal controls (p < 0.04). Knees with lateral femoral condyle OCD lesions had no significant difference in lateral tibial slope compared with the contralateral knee or matched controls. Posterior slope was greater in knees with medial OCD lesions than matched controls (p = 0.007). Intraclass correlation coefficients demonstrated consistency between observers for all measurements.

CONCLUSION

An assessment of proximal tibial morphology demonstrated greater medial and posterior tibial slope in knees with medial OCD lesions compared with normal knees. The technique for measuring medial and lateral tibial slope was reliable among evaluators. The clinical relevance is that proximal tibial morphology may have a relationship with OCD lesions.

LEVEL OF EVIDENCE

III.

Increased Lateral Tibial Slope Is a Risk Factor for Pediatric Anterior Cruciate Ligament Injury: An MRI-Based Case-Control Study of 152 Patients

BACKGROUND

Increased posterior tibial slope is associated with increased risk of anterior cruciate ligament (ACL) injury in adults. A similar association has not been rigorously examined in children and adolescents.

PURPOSE

To determine whether alterations in posterior tibial slope are associated with ACL tears in pediatric and adolescent patients and to quantify changes in tibial slope by age.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Magnetic resonance imaging (MRI) studies of the knee were reviewed by 3 raters blinded to each other in a 1:1 sample of cases and age- and sex-matched controls. A total of 76 skeletally immature ACL-injured knees were compared with 76 knees without ACL injury; the mean age of the study population was 14.8 ± 1.3 years. The posterior slope of the articular surface of the medial tibial plateau and lateral tibial plateau was measured by use of a method similar to that used in previous studies in adult populations. The current study technique differed in that the slope was measured on the cartilage surface, not the subchondral bone. Comparisons between knees were made with t tests, and Spearman correlation analysis was used to assess changes in tibial slope with advancing age.

RESULTS

Increased slope of the lateral tibial plateau (LTS) was significantly increased in ACL-injured patients compared with controls (5.7° ± 2.4° vs 3.4° ± 1.7°; P < .001). There was no statistically significant difference in the slope of the medial tibial plateau (MTS) in the ACL-injured and control knees (5.4° ± 2.2° vs 5.1° ± 2.3°; P = .42). There was no difference in LTS between male and female patients (4.46° vs 4.58°; P = .75). Receiver operating characteristic (ROC) analysis of the LTS revealed that a posterior tibial slope cutoff of >4° resulted in a sensitivity of 76% and a specificity of 75% for predicting ACL tears in this cohort. Spearman correlation analysis revealed that MTS and LTS decreased, or flattened, by 0.31° (P = .028, correlation coefficient r = -0.18) and 0.37° (P = .009, correlation coefficient r = -0.21) per year, respectively, as adolescents age.

CONCLUSION

The LTS was significantly associated with an increased risk of ACL injury in pediatric and adolescent patients. The MTS was not associated with risk of injury. Posterior slope was found to decrease, or flatten, with age. A cutoff of >4° for the posterior slope of the lateral compartment is 76% sensitive and 75% specific for predicting ACL injury in this cohort. The LTS did not influence the incidence of ACL injury differently between sexes.

Characteristics of femorotibial joint geometry in the trochlear dysplastic femur

The medial and lateral tibia plateau geometry has been linked with the severity of trochlear dysplasia. The aim of the present study was to evaluate the tibial slope and the femoral posterior condylar offset in a cohort of consecutive subjects with a trochlear dysplastic femur to investigate whether the condylar offset correlates with, and thus potentially compensates for, tibial slope asymmetry. Magnetic resonance imaging was used to assess the severity of trochlear dysplasia as well as the tibial slope and posterior offset of the femoral condyles separately for the medial and lateral compartment of the knee joint in 98 subjects with a trochlear dysplastic femur and 88 control subjects. A significant positive correlation was found for the medial tibial slope and the medial posterior condylar offset in the study group (r(2) = 0.1566; P < 0.001). This relationship was significant for all subtypes of trochlear dysplasia and was most pronounced in the severe trochlear dysplastic femur (Dejour type D) (r(2) = 0.3734; P = 0.04). No correlation was found for the lateral condylar offset and the lateral tibial slope in the study group or for the condylar offset and the tibial slope on both sides in the control group. The positive correlation between the medial femoral condylar offset and the medial tibial slope, that is, a greater degree of the medial tibial slope indicated a larger offset of the medial femoral condyle, appears to represent a general anthropomorphic characteristic of distal femur geometry in patients with a trochlear dysplastic femur.

Increasing lateral tibial slope: is there an association with articular cartilage changes in the knee?

PURPOSE

The geometry of the lateral tibial slope (LTS) plays an important role in the overall biomechanics of the knee. Through this study, we aim to assess the impact of LTS on cartilage degeneration in the knee.

MATERIALS AND METHODS

A retrospective analysis of 93 knee MRI scans (1.5 T or 3 T) for patients aged 20-45 years with no history of trauma or knee surgery, and absence of internal derangement. The LTS was calculated using the circle method. Chondropathy was graded from 0 (normal) to 3 (severe). Linear regression analysis was used for statistical analysis (p < 0.05).

RESULTS

In our cohort of patients, a statistically significant association was seen between increasing LTS and worsening cartilage degenerative changes in the medial patellar articular surface and the lateral tibial articular surface (p < 0.05). There was no statistically significant association between increasing LTS and worsening chondropathy of the lateral patellar, medial trochlea, lateral trochlea, medial femoral, lateral femoral, and medial tibial articular surfaces.

CONCLUSIONS

Our results show a statistically significant association between increasing LTS and worsening cartilage degenerative changes in the medial patella and the lateral tibial plateau. We speculate that increased LTS may result in increased femoral glide over the lateral tibial plateau with subsequent increased external rotation of the femur predisposing to patellofemoral articular changes. Future arthroscopic studies are needed to further confirm our findings.