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Abelleyra Lastoria DA, Hutchinson K, Tapadar T, Ahmad S, Smith T, Nicolaou N, Hing CB. Patho-morphology of patellar instability in children and adolescents: A systematic review and meta-analysis. Knee 2024; 48:166-196. [PMID: 38657526 DOI: 10.1016/j.knee.2024.03.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2024] [Revised: 03/25/2024] [Accepted: 03/27/2024] [Indexed: 04/26/2024]
Abstract
BACKGROUND Children and adolescents have the highest incidence of patellar instability among the population. We aimed to identify patho-morphological and epidemiological factors associated with patellar instability, and to identify factors predisposing to recurrence in children and adolescents. METHODS Published and unpublished literature databases, conference proceedings and the reference lists of included studies were searched to the 14th of March 2024. Studies were eligible if they compared history characteristics, examination features and radiological parameters between patients with and without instability, or evaluated risk factors for instability recurrence. A random-effects meta-analysis was performed. Included studies were appraised using tools respective of study design. RESULTS The evidence was moderate to low in quality. Forty-five studies (including 9000 patients) were eligible. Tibial tubercle - tibial groove (TT-TG) distance (weighted mean difference [WMD] 5.96 mm, 95% Confidence Interval [CI]: 4.94 to 6.99 mm), sulcus angle (WMD: 13.93˚, 95% CI: 9.1˚ to 18.8˚), and Insall-Salvati index (WMD: 0.2, 95% CI: 0.16 to 0.23) were greater in patients with patellar instability. Risk factors for recurrent dislocation included age less than 18 years (Odds ratio [OR]: 2.56, 95% CI: 1.63 to 4.0), skeletal immaturity (OR: 1.79, 95% CI: 1.21 to 2.64) and presence of trochlear dysplasia (OR: 3.37, 95% CI: 1.85 to 6.15). CONCLUSION Knowledge of patho-morphological factors associated with patellar instability could help explain its pathophysiological processes, allowing for the design of treatment approaches and the identification of patients at risk.
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Affiliation(s)
| | | | - Thabia Tapadar
- St George's University of London, London SW17 0RE, United Kingdom
| | - Salwa Ahmad
- St George's University of London, London SW17 0RE, United Kingdom
| | - Toby Smith
- University of Warwick, Coventry CV4 7HL, United Kingdom
| | - Nicolas Nicolaou
- Sheffield Children's Hospital, Sheffield S10 2TH, United Kingdom
| | - Caroline Blanca Hing
- St George's University Hospitals NHS Foundation Trust, London SW17 0RE, United Kingdom
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Danielsen O, Poulsen TA, Eysturoy NH, Mortensen ES, Hölmich P, Barfod KW. Trochlea dysplasia, increased TT-TG distance and patella alta are risk factors for developing first-time and recurrent patella dislocation: a systematic review. Knee Surg Sports Traumatol Arthrosc 2023; 31:3806-3846. [PMID: 36854995 DOI: 10.1007/s00167-022-07255-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Accepted: 11/23/2022] [Indexed: 03/02/2023]
Abstract
PURPOSE The aim of the study was to perform a systematic review and best knowledge synthesis of the present literature concerning biomechanical risk factors for developing first-time and recurrent patella dislocation. METHODS The study was performed as a systematic review following PRISMA guidelines. PubMed and EMBASE were systematically searched. Studies investigating participants with risk factors for first-time as well as recurrent patella dislocation were included. The records were screened, and data extracted independently by two researchers supervised by a third independent assessor. The study was registered in PROSPERO. RESULTS A total of 6233 records were screened, and 50 studies met the inclusion criteria. The biomechanical risk factors: trochlear dysplasia, increased tibial tuberosity-trochlear groove distance (TT-TG), and patella alta were found to be statistically significantly associated with patella dislocation in several publications and were thus recognized as risk factors for patella dislocation. The soft-tissue stabilizers: longer and thinner MPFL ligament, increased number of type 2C and decreased number of type 1 muscle fibers, and joint laxity were found to be statistically significantly associated with patella dislocation in a few publications, but due to limited evidence, no conclusion was made on this matter. CONCLUSION There is strong evidence in the literature that abnormalities of bony stabilizers, trochlear dysplasia, increased TT-TG distance, and patella alta are risk factors for patella dislocation. There is less evidence that soft-tissue stabilizers are risk factors. The study emphasizes the importance of a thorough investigation of bony stabilizers in clinical decision-making. LEVEL OF EVIDENCE Level IV.
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Affiliation(s)
- Oddrún Danielsen
- National Hospital of the Faroe Islands, J.C. Svabosgøta 41-49, 100, Tórshavn, Faroe Islands.
| | - Turið Akraberg Poulsen
- National Hospital of the Faroe Islands, J.C. Svabosgøta 41-49, 100, Tórshavn, Faroe Islands
| | | | | | - Per Hölmich
- Sports Orthopedic Research Center, Copenhagen, (SORC-C), Department of Orthopedic Surgery, Copenhagen University Hospital, Amager-Hvidovre, Kettegård Allé 30, 2650, Hvidovre, Denmark
| | - Kristoffer Weisskirchner Barfod
- Sports Orthopedic Research Center, Copenhagen, (SORC-C), Department of Orthopedic Surgery, Copenhagen University Hospital, Amager-Hvidovre, Kettegård Allé 30, 2650, Hvidovre, Denmark
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Danielsen O, Poulsen TA, Eysturoy NH, Mortensen ES, Hölmich P, Barfod KW. Familial association and epidemilogical factors as risk factors for developing first time and recurrent patella dislocation: a systematic review and best knowledge synthesis of present literature. Knee Surg Sports Traumatol Arthrosc 2023; 31:3701-3733. [PMID: 36629887 DOI: 10.1007/s00167-022-07265-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2021] [Accepted: 11/28/2022] [Indexed: 01/12/2023]
Abstract
PURPOSE The aim of our study was to perform a systematic review and best knowledge synthesis of the present literature concerning the familial association and epidemiological factors as risk factors for developing first-time and recurrent patella dislocation. METHODS The study was conducted according to the PRISMA guidelines and registered in PROSPERO. EMBASE and PubMed were systematically searched on the 5th of May 2022. Studies investigating participants with genetic and epidemiological risk factors for the first time as well as recurrent patella dislocation were included. The records were screened, and data were extracted independently by two researchers supervised by a third independent assessor. RESULTS A total of 6,649 records were screened, and 67 studies were included. Familial association was described as a risk factor for patella dislocation in 17 studies. One study found that participants with a family history of patella dislocation had a 3.7 higher risk for patella dislocation in the contralateral asymptomatic knee, and another study found a family history of PD in 9% of 74 participants. Eleven studies found an accumulation of patella dislocation across generations in specific families. Additionally, a range of genetic syndromes was associated with patella dislocation. Young age is a well-investigated risk factor for patella dislocation, but the results are inconsistent. Only five and eight studies investigated skeletal immaturity and gender as risk factors for patella dislocation, respectively. CONCLUSION There may be a familial association with patella dislocation, but further investigation is necessary to determine the strength and etiology of the association. There is weak evidence that epidemiological risk factors, such as age, skeletal immaturity, gender, and BMI are risk factors for patella dislocation. LEVEL OF EVIDENCE IV.
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Affiliation(s)
- Oddrún Danielsen
- National Hospital of the Faroe Islands, J.C. Svabosgøta 41-49, 100, Tórshavn, Faroe Islands.
| | - Turið Akraberg Poulsen
- National Hospital of the Faroe Islands, J.C. Svabosgøta 41-49, 100, Tórshavn, Faroe Islands
| | | | | | - Per Hölmich
- Sports Orthopedic Research Center-Copenhagen, (SORC-C), Department of Orthopedic Surgery, Copenhagen University Hospital, Amager-Hvidovre, Kettegård Allé 30, 2650, Hvidovre, Denmark
| | - Kristoffer Weisskirchner Barfod
- Sports Orthopedic Research Center-Copenhagen, (SORC-C), Department of Orthopedic Surgery, Copenhagen University Hospital, Amager-Hvidovre, Kettegård Allé 30, 2650, Hvidovre, Denmark
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Axial orientation of the femoral trochlea is superior to femoral anteversion for predicting patellar instability. Knee Surg Sports Traumatol Arthrosc 2022:10.1007/s00167-022-07259-x. [PMID: 36446909 DOI: 10.1007/s00167-022-07259-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Accepted: 11/25/2022] [Indexed: 12/05/2022]
Abstract
PURPOSE The femoral anteversion angle is considered to be the same as femoral torsion; however, the femoral anteversion angle is strongly influenced by the femoral posterior condylar morphology. It remains unclear whether the femoral anteversion angle and axial orientation of the femoral trochlea can predict patellar instability. This study aimed to redefine the femoral inherent torsion, verify whether the femoral anteversion angle reflects the femoral inherent torsion, and compare the validity and calculate the cut-off values of the femoral anteversion angle and femoral trochlear axial orientation for predicting patellar instability. METHODS Seventy-three patients with patellar instability and 73 matched controls underwent computed tomography to measure the femoral anteversion angle, femoral inherent torsion, and femoral trochlear axial orientation. Pearson's product moment correlation coefficients and linear regression were calculated to determine correlations between measurements. Receiver operating characteristic curves and nomograms were plotted to evaluate the predictive validity of the femoral anteversion angle and femoral trochlear axial orientation for patellar instability. RESULTS All measurements showed excellent intra- and inter-observer reliability. Compared with the control group, the patellar instability group had a significantly larger femoral anteversion angle (25.4 ± 6.4° vs. 20.2 ± 4.5°) and femoral inherent torsion (18.3 ± 6.7° vs. 15.8 ± 3.4°), and significantly smaller femoral trochlear axial orientation (58.1 ± 7.3° vs. 66.9 ± 5.1°). The femoral anteversion angle and femoral trochlear axial orientation had area under the receiver operating characteristic curve values of 79 and 84%, respectively, and cut-off values of 24.5° and 62.7°, respectively. The calibration curve and decision curve analysis showed that the femoral trochlear axial orientation performed better than the femoral anteversion angle in predicting patellar instability. There was a strong correlation between the femoral anteversion angle and femoral inherent torsion (r > 0.8). Linear regression analysis of the femoral inherent torsion with the femoral anteversion angle as the prediction variate showed moderate goodness-of-fit (adjusted R2 = 0.69). CONCLUSION The femoral anteversion angle moderately reflects the femoral inherent torsion. The femoral trochlear axial orientation is better than the femoral anteversion in predicting patellar instability in terms of predictive efficiency, consistency with reality, and net clinical benefit. These findings warn orthopaedists against overstating the role of the femoral anteversion angle in patellar instability, and suggest that the femoral trochlear axial orientation could aid in identifying at-risk patients and developing surgical strategies for patellar instability. LEVEL OF EVIDENCE III.
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Dong Z, Zhang X, Xu C, Ji G, Niu Y, Wang F. The tibial tubercle-posterior cruciate ligament (TT-PCL) distance does not truly reflect the lateralization of the tibial tubercle. Knee Surg Sports Traumatol Arthrosc 2022; 30:3470-3479. [PMID: 35366078 DOI: 10.1007/s00167-022-06927-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Accepted: 02/23/2022] [Indexed: 12/01/2022]
Abstract
PURPOSE The role of the tibial tubercle-posterior cruciate ligament (TT-PCL) and tibial tubercle-trochlear groove (TT-TG) in recurrent patellar instability (RPI) remains unclear. This study aims to confirm the validity of the TT-TG and TT-PCL in predicting RPI and to verify whether the TT-PCL can truly reflect the lateralization of the tibial tubercle. METHODS A total of 50 patients with RPI and 50 controls were recruited and underwent magnetic resonance imaging examinations. The TT-TG, TT-PCL, and tibial tubercle lateralization (TTL) were measured independently by two authors in a blinded and randomized fashion. T-test was used for parametric variances and the Mann-Whitney U and Chi-square tests were used for non-parametric variances. Pearson's product moment correlation coefficients were calculated to determine correlations between the defined measurements. The intraclass correlation coefficient was used to assess the reliability of the measurements. RESULTS All defined measurements showed excellent intra- and inter-observer reliability. The TT-TG distance, TT-PCL distance, and TTL were significantly greater in the PI group than in the control group. The AUC was highest for the TT-TG distance compared with that for the TT-PCL distance, and TTL were 0.798, 0.764, and 0.769, with the calculated cut-off value of 12.5 mm, 16.5 mm, and 66.1 percentages. There was a moderate correlation (r = 0.595) between the TT-TG distance and TTL, and a weak correlation (r = 0.430) between the TT-PCL distance and TTL. CONCLUSION Both the TT-TG distance and TT-PCL distance can be measured with excellent reliability on magnetic resonance imaging. The TT-TG distance, rather than the TT-PCL distance, has a better performance in predicting RPI. Most interestingly, the TT-PCL distance cannot reflect the real lateralization of TT. This study provides new information to evaluate TTL in patients with RPI. LEVEL OF EVIDENCE III.
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Affiliation(s)
- Zhenyue Dong
- Department of Orthopaedic Surgery, Third Hospital of Hebei Medical University, Shijiazhuang, 050051, Hebei, China
| | - Xiaoxiao Zhang
- Third Hospital of Hebei Medical University, Shijiazhuang, 050051, Hebei, China
| | - Chenyue Xu
- Department of Orthopaedic Surgery, Third Hospital of Hebei Medical University, Shijiazhuang, 050051, Hebei, China
| | - Gang Ji
- Department of Orthopaedic Surgery, Third Hospital of Hebei Medical University, Shijiazhuang, 050051, Hebei, China
| | - Yingzhen Niu
- Department of Orthopaedic Surgery, Third Hospital of Hebei Medical University, Shijiazhuang, 050051, Hebei, China
| | - Fei Wang
- Department of Orthopaedic Surgery, Third Hospital of Hebei Medical University, Shijiazhuang, 050051, Hebei, China.
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Wierer G, Krabb N, Kaiser P, Ortmaier R, Schützenberger S, Schlumberger M, Hiller B, Ingruber F, Smekal V, Attal R, Seitlinger G. The Patellar Instability Probability Calculator: A Multivariate-Based Model to Predict the Individual Risk of Recurrent Lateral Patellar Dislocation. Am J Sports Med 2022; 50:471-477. [PMID: 35060768 DOI: 10.1177/03635465211063176] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND Predicting the risk of recurrence is of great interest when counseling patients after primary lateral patellar dislocation (LPD). PURPOSE To investigate a multivariate model to predict the individual risk of recurrent LPD. STUDY DESIGN Case-control study; Level of evidence, 3. METHODS The study population included patients with primary LPD, knee imaging, and a minimum 2-year follow-up after nonoperative treatment. Data including patient characteristics and anatomic patellar instability risk factors were collected retrospectively from 7 national study centers. Bivariate and multivariate regression analyses were carried out to identify risk factors for recurrent LPD and to generate an accuracy-optimized model for out-of-sample prediction. RESULTS In total, 115 of 201 patients (57%) experienced recurrent LPD within 2 years after primary LPD. Age ≤16 years at primary LPD (odds ratio [OR], 5.0), history of contralateral instability (OR, 2.4), and trochlear dysplasia (Dejour type B-D: OR, 2.5; lateral trochlear inclination ≤12°: OR, 2.7) were significant risk factors for recurrent LPD (P < .05). The prediction accuracy including these 3 risk factors was 79%. Patella alta, an increased tibial tubercle to trochlear groove distance, and patellar tilt had neither an association with increased recurrence rates nor an influence on prediction accuracy of recurrent LPD. CONCLUSION Young age and trochlear dysplasia are major risk factors for early recurrent LPD. A multivariate model including age at primary LPD, lateral trochlear inclination, and history of contralateral LPD achieved the highest prediction accuracy. Based on these findings, the patellar instability probability calculator is proposed to estimate the individual risk of early recurrence when counseling patients after primary LPD.
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Affiliation(s)
- Guido Wierer
- Department of Orthopedics and Traumatology, Paracelsus Medical University Salzburg, Austria.,Research Unit for Orthopaedic Sports Medicine and Injury Prevention, Private University for Health Sciences, Medical Informatics and Technology, Hall in Tirol, Austria
| | - Nicole Krabb
- Department of Orthopedics and Traumatology, Paracelsus Medical University Salzburg, Austria
| | - Peter Kaiser
- Department of Orthopaedics and Traumatology, Medical University of Innsbruck, Austria
| | - Reinhold Ortmaier
- Department of Orthopaedic Surgery, Ordensklinikum Barmherzige Schwestern Linz, Teaching Hospital of the Paracelsus Medical University Salzburg, Linz, Austria
| | | | - Michael Schlumberger
- Department of Orthopaedics and Traumatology, Medical University of Innsbruck, Austria.,Center for Sports Orthopedics and Special Joint Surgery, Orthopedic Hospital Markgroeningen, Germany
| | - Bernd Hiller
- AUVA Trauma Center Salzburg, Academic Teaching Hospital of the Paracelsus Medical University, Salzburg, Austria
| | - Florian Ingruber
- AUVA Trauma Hospital Lorenz Boehler-European Hand Trauma Center, Vienna, Austria
| | | | - Rene Attal
- Department of Trauma Surgery and Sports Traumatology, Academic Hospital Feldkirch, LKH Feldkirch, Austria
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Onor GI, Yalcin S, Kaar SG, Pace JL, Ferrua P, Farrow LD. The Evaluation of Trochlear Osseous Morphology: An Epidemiologic Study. Orthop J Sports Med 2021; 9:2325967121994548. [PMID: 33869646 PMCID: PMC8020235 DOI: 10.1177/2325967121994548] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Accepted: 11/18/2020] [Indexed: 01/17/2023] Open
Abstract
Background: The femoral trochlea is considered the most significant osseous factor
affecting stability in the patellofemoral joint. The true prevalence of
trochlear dysplasia in the general population is largely unknown. Purpose/Hypothesis: To investigate the prevalence of trochlear dysplasia in the general
population. Our hypothesis was that, while trochlear dysplasia is not
uncommon, there is a low prevalence of severe dysplasia in the general
population. Study Design: Descriptive epidemiology study. Methods: Five observers were asked to evaluate 692 skeletally mature femoral specimens
from 359 skeletons for trochlear dysplasia at 2 time points. We further
subclassified the dysplastic trochlea in 62 femora with the highest rated
degree of dysplasia. Results: Sex (P = .11) and race (P = .2) had no
effect on the severity of dysplasia. Interobserver reliability was excellent
(0.906 and 0.904), and intraobserver reliability was good to excellent
(0.686 to 0.808). The percentages of trochlea graded as normal, mildly
dysplastic, moderately dysplastic, and severely dysplastic were 61.5%,
21.4%, 12.7%, and 4.4%, respectively, in the first evaluation, and 58.5%,
23.7%, 12.7%, and 5.1% in the second evaluation. Of the 62 trochlea with the
highest scores for dysplasia, 36 had trochlear dysplasia without a
supratrochlear spur, 8 had trochlear dysplasia with medial femoral condyle
hypoplasia, and 18 had trochlear dysplasia with a supratrochlear spur. Conclusion: Observers with differing degrees of clinical experience had similar opinions
on the degree of trochlear dysplasia. Also, our cohort showed that moderate
to severe dysplasia is not uncommon, as it is present in approximately 17%
of knees in our cohort. Our findings also suggest that clinicians are
speaking the same language when identifying and describing trochlear
dysplasia on gross inspection.
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Affiliation(s)
- Gabriel I Onor
- Warren Alpert Medical School, Brown University, Providence, Rhode Island, USA
| | - Sercan Yalcin
- Cleveland Clinic Orthopaedic and Rheumatologic Institute, Cleveland, Ohio, USA
| | - Scott G Kaar
- Department of Orthopaedic Surgery, St. Louis University, St. Louis, Missouri, USA
| | - J Lee Pace
- Elite Sports Medicine, Connecticut Children's Medical Center, Farmington, Connecticut, USA
| | - Paolo Ferrua
- Gaetano Pini Orthopaedic Institute, University of Milan, Milan, Italy
| | - Lutul D Farrow
- Cleveland Clinic Orthopaedic and Rheumatologic Institute, Cleveland, Ohio, USA
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Reliability of a Caton-Deschamps-derived patella height index for knee arthroplasty. INTERNATIONAL ORTHOPAEDICS 2021; 45:2001-2005. [PMID: 33471223 PMCID: PMC8338832 DOI: 10.1007/s00264-020-04931-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/23/2020] [Accepted: 12/29/2020] [Indexed: 12/01/2022]
Abstract
Purpose The original Caton-Deschamps index (oCDI) detects functional patella height. It cannot be used in knees with an implanted endoprosthesis. The “modified Caton-Deschamps index” (mCDI) for knee arthroplasty can miss pseudo-patella-infera (PPI), which is common after TKA. A derivate of the oCDI could be a simple analogue to the index published in 1982 using a modified tibial reference point at the anterior proximal point of the inlay, which can indirectly be located on the lateral knee radiograph. It was the aim of this study to determine the intra- and inter-rater agreement of a derived Caton-Deschamps index (dCDI) for knee arthroplasty. We hypothesized that the derived Caton-Deschamps index (dCDI) is a reliable radiological measure for patella height in knee arthroplasty. Methods Several patella height indices were measured by three independent raters in two passes. The second pass was performed after 6 weeks in random order. Intra- and inter-observer agreements were determined and analyzed using the intraclass correlation coefficient (ICC). For radiographic evaluation, digital lateral radiographs of 150 knees before and after primary TKA were used. Results We found high interrater reliability for all analyzed indices. We found the highest agreements for the ISI preop (ICC = 0.914) and postop (ICC = 0.920), respectively. We also found very good intra-rater reliability for the CDI (ICCpreop = 0.954), dCDI (ICCpostop = 0.945), ISI (ICCpreop = 0.960; ICCpostop=0.940) and BPI (ICCpreop = 0.969; ICCpostop = 0.955). Fourteen cases (9.3%) with insignificant PPI were found. Conclusion The derived Caton-Deschamps index (dCDI) can easily be used in knee arthroplasty and demonstrated high intra- and interrater agreement, which was similar to other commonly used and established patella height indices.
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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. INTERNATIONAL ORTHOPAEDICS 2020; 45:959-970. [PMID: 33037445 DOI: 10.1007/s00264-020-04820-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Accepted: 09/15/2020] [Indexed: 10/23/2022]
Abstract
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.
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