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Retzky JS, Palhares GM, Uppstrom TJ, Hinkley P, Fletcher C, Gomoll AH, Strickland SM. Risk Factors for Atraumatic Medial Patellar Facet Lesions. Orthop J Sports Med 2024; 12:23259671241255681. [PMID: 38881850 PMCID: PMC11179489 DOI: 10.1177/23259671241255681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Accepted: 10/24/2023] [Indexed: 06/18/2024] Open
Abstract
Background Medial patellar facet lesions have been well-described in the setting of patellar instability. However, relatively little is known about risk factors for atraumatic medial patellar facet lesions. Purpose/Hypothesis To identify clinical and radiographic risk factors for medial patellar facet lesions in patients without a history of trauma or patellar instability. It was hypothesized that a posterior tibial tubercle relative to the trochlear groove would be a risk factor for atraumatic medial patellar facet lesions. Study Design Case-control study; Level of evidence, 3. Methods A total of 37 patients with atraumatic medial patellar facet lesions were matched by age, sex, and body mass index with 37 control patients without a history of patellofemoral dysplasia. Demographic and imaging characteristics were compared between groups. Plain radiography was used to evaluate Wiberg type, and magnetic resonance imaging was used to calculate Caton-Deschamps index, tibial tubercle-trochlear groove distance, trochlear facet asymmetry ratio, patellotrochlear index, sulcus depth, patellar bisect ratio, and tibial tubercle height. Statistically significant variables from univariate analysis were used as inputs to the multivariate regression model to assess independent risk factors. Results There were no differences between groups with respect to Wiberg type, Caton-Deschamps index, tibial tubercle-trochlear groove distance, sulcus depth, or patellotrochlear index (P > .05 for all). The medial facet lesion group had a larger medial trochlear facet (trochlear facet asymmetry ratio, 0.72 ± 0.11 vs 0.60 ± 0.09; P < .001), a more medial-lying patella in the trochlear groove (patellar bisect ratio, 0.57 ± 0.06 vs 0.55 ± 0.07; P = .035), and a more posterior tibial tubercle relative to the trochlear groove (tibial tubercle height, -3.13 ± 5.21 vs -0.23 ± 5.93 mm; P = .030) compared with the control group. Multivariate regression analysis identified trochlear facet asymmetry and tibial tubercle height as independent risk factors for medial patellar facet lesions (relative risk = 97.3 [95% CI, 14.9-635.1], P < .001 and relative risk = 0.95 [95% CI, 0.92-0.98], P = .004, respectively). Conclusion A relatively larger medial trochlear facet and a more posterior tibial tubercle relative to the trochlear groove were found to be risk factors for medial patellar facet lesions in patients without a history of trauma or patellar instability.
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Affiliation(s)
- Julia S Retzky
- Hospital for Special Surgery, Sports Medicine Institute, New York, New York, USA
| | - Guilherme M Palhares
- Hospital for Special Surgery, Sports Medicine Institute, New York, New York, USA
| | - Tyler J Uppstrom
- Hospital for Special Surgery, Sports Medicine Institute, New York, New York, USA
| | - Paige Hinkley
- Hospital for Special Surgery, Sports Medicine Institute, New York, New York, USA
| | - Connor Fletcher
- Hospital for Special Surgery, Sports Medicine Institute, New York, New York, USA
| | - Andreas H Gomoll
- Hospital for Special Surgery, Sports Medicine Institute, New York, New York, USA
| | - Sabrina M Strickland
- Hospital for Special Surgery, Sports Medicine Institute, New York, New York, USA
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Jud L, Hartmann M, Vlachopoulos L, Zimmermann SM, Ackermann J, Fucentese SF. Increased tibial tuberosity torsion has the greatest predictive value in patients with patellofemoral instability compared to other commonly assessed parameters. Knee Surg Sports Traumatol Arthrosc 2024; 32:1179-1186. [PMID: 38504510 DOI: 10.1002/ksa.12151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 02/29/2024] [Accepted: 03/04/2024] [Indexed: 03/21/2024]
Abstract
PURPOSE The multifactorial nature of patellofemoral instability requires a comprehensive assessment of the affected patients. While an association between tibial tuberosity (TT) torsion and patellofemoral instability is known, its specific effect has not yet been investigated. This study investigated the effect of TT torsion on patellofemoral instability. METHODS This retrospective cohort study compared patients who underwent surgical intervention for patellofemoral instability and asymptomatic controls. TT torsion was measured in addition to other commonly assessed risk factors for patellofemoral instability using standardised computed tomography (CT) data of the lower extremities. The diagnostic performances of the assessed parameters were evaluated using receiver operating characteristic curve analysis and odds ratios (ORs) were calculated. RESULTS The patellofemoral instability group consisted of 79 knees, compared to 72 knees in the asymptomatic control group. Both groups differed significantly in all assessed parameters (p < 0.001), except for tibial torsion (n.s.). Among all parameters, TT torsion presented the best diagnostic performance for predicting patellar instability with an area under the curve of 0.95 (95% confidence interval [CI], 0.91-0.98; p < 0.001). A cut-off value of 17.7° yielded a 0.87 sensitivity and 0.89 specificity to predict patellar instability (OR, 55.2; 95% CI, 20.5-148.6; p < 0.001). CONCLUSION Among the evaluated risk factors, TT torsion had the highest predictive value for patellofemoral instability. Patients with TT torsions ≥ 17.7° showed a 55-fold increased probability of patellofemoral instability. Therefore, TT torsion should be included in the assessment of patients with patellofemoral instability. LEVEL OF EVIDENCE Level III.
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Affiliation(s)
- Lukas Jud
- Department of Orthopedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
| | - Martin Hartmann
- Department of Orthopedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
| | - Lazaros Vlachopoulos
- Department of Orthopedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
| | - Stefan M Zimmermann
- Department of Orthopedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
| | - Jakob Ackermann
- Department of Orthopedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
| | - Sandro F Fucentese
- Department of Orthopedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
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Li K, Xu C, Dong Z, Ji G, Wang F. Reliability of Tibial Tubercle-Trochlear Groove Distance for Assessing Tibial Tubercle Lateralization: A Study Comparing Different Anatomic References. Orthop J Sports Med 2024; 12:23259671241239965. [PMID: 38601189 PMCID: PMC11005510 DOI: 10.1177/23259671241239965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Accepted: 10/05/2023] [Indexed: 04/12/2024] Open
Abstract
Background The tibial tubercle-trochlear groove (TT-TG) distance is a measurement used to quantitatively assess tibial tubercle lateralization (TTL), and it has important reference value for the treatment of patellar dislocation (PD). However, TT-TG distance accuracy has been questioned, so many new parameters have been proposed. Purpose To compare which of the TT-TG, tibial tubercle-midepicondyle (TT-ME), tibial tubercle-Roman arch (TT-RA), tibial tubercle-tibial intercondylar midpoint (TT-TIM), and tibial tubercle-mid inter-epicondyle trochlea intersection (TT-MIELTI) distances better reflect TTL in patients with PD. Study Design Cohort study (diagnosis); Level of evidence, 3. Methods A total of 96 patients who had undergone surgery for PD and 96 patients without PD (controls) were included in the study. The patients had all undergone computed tomography examination. The TT-TG, TT-ME, TT-RA, TT-TIM, TT-MIELTI distances and the TTL distance were measured independently by 2 surgeons in a blinded and randomized fashion. The t test was used to detect whether the parameters were significantly different between the 2 groups. The TTL distance was used as a reference value for lateralization of tibial tubercle. Pearson correlation coefficients were calculated to determine correlations between the defined measurements. Results The intra- and interobserver reliability of the defined measurements was excellent. All parameters except for TT-TIM distance were significantly larger in the PD group than the control group (P < .01 for all). There was a moderate correlation (r = 0.601) between the TT-TG distance and TTL, and other parameters were less correlated with TTL. Conclusion Among 5 the parameters tested, the TT-TG distance still had the highest correlation with TTL and was able to reflect TTL better in patients with PD. The role of TT-TIM distance in the assessment of PD needs further study.
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Affiliation(s)
- Kehan Li
- Third Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
| | - Chenyue Xu
- Third Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
| | - Zhenyue Dong
- Third Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
| | - Gang Ji
- Third Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
| | - Fei Wang
- Third Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
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Irarrázaval S, Besa P, Fernández T, Fernández F, Donoso R, Tuca MJ, Lira MJ, Orrego M. Tibial tubercle to trochlear groove and the roman arch method for tibial tubercle lateralisation are reliable and distinguish between subjects with and without major patellar instability. J ISAKOS 2024:S2059-7754(24)00006-3. [PMID: 38228271 DOI: 10.1016/j.jisako.2024.01.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Revised: 12/20/2023] [Accepted: 01/08/2024] [Indexed: 01/18/2024]
Abstract
PURPOSE Patellofemoral (PF) instability recurrence depends on several factors including the relative lateralisation of tibial tubercle (TT) regarding the trochlear groove (TG). TT relative lateralisation quantification has long been a topic of debate. Multiple measuring techniques have been described including TT-trochlear groove (TT-TG), TT-posterior cruciate ligament (TT-PCL) and TT-roman arch (TT-RA), with no clear consensus regarding the most reliable index or pathologic threshold. We set out to determine the normal value range of each index and their association with age, sex and PF instability status. Also, this study aims to determine a reliable pathologic distance threshold to effectively predict patellar dislocation. METHODS Skeletally mature patients up to 45 years of age who presented a CT Scan and an MRI of the same knee between 2014 and 2018 were included and divided into subgroups based on history of PF instability. Three indexes (TT-TG, TT-PCL and TT-RA) were assessed by two independent observers blinded to instability history. ROC curves were performed for each index to obtain the cut point that better predicts instability. Univariate and multivariate models adjusted by age, sex, instability history and type of imaging technique were performed to test the influence of these variables. RESULTS 208 patients were included. Mean age was 27.93 ± 8.48 years, 67.3% were female and 71 patients (34.1%) presented major instability history. Good or excellent inter and intraobserver reliability was found for all three indexes. All indexes presented significantly different distributions between subjects with and without major instability (p < 0.001), except for TT-PCL. Different cut point values differing between imaging modalities were found: 11.4 mm for MRI TT-TG, 17 mm for CT TT-TG, 15.6 mm for MRI TT-RA and 18.2 mm for CT TT-RA. CONCLUSIONS All indexes studied had good or excellent inter and intraobserver reliability. Measurements between imaging techniques (CT and MR) are not interchangeable. Both TT-TG and TT-RA correctly distinguish between subjects with and without major instability, while TT-PCL does not, recommending caution when evaluated on its own. Specific threshold values depending on imaging technique should be considered for surgical decision-making. LEVEL OF EVIDENCE Level IV, Diagnostic Test.
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Affiliation(s)
- Sebastián Irarrázaval
- Department of Orthopedic Surgery, School of Medicine, Pontificia Universidad Católica de Chile, 8330077, Chile
| | - Pablo Besa
- Department of Orthopedic Surgery, School of Medicine, Pontificia Universidad Católica de Chile, 8330077, Chile.
| | - Tomás Fernández
- Department of Orthopedic Surgery, School of Medicine, Pontificia Universidad Católica de Chile, 8330077, Chile
| | - Francisco Fernández
- Department of Orthopedic Surgery, School of Medicine, Pontificia Universidad Católica de Chile, 8330077, Chile
| | - Rodrigo Donoso
- Department of Orthopedic Surgery, School of Medicine, Pontificia Universidad Católica de Chile, 8330077, Chile
| | - María Jesús Tuca
- Department of Orthopedic Surgery, School of Medicine, Pontificia Universidad Católica de Chile, 8330077, Chile
| | - María Jesús Lira
- Department of Orthopedic Surgery, School of Medicine, Pontificia Universidad Católica de Chile, 8330077, Chile
| | - Mario Orrego
- Department of Orthopedic Surgery, School of Medicine, Pontificia Universidad Católica de Chile, 8330077, Chile
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Murphy GT, Rudraraju R, Mathews T, Sidhu V, Miller A, Brown K, Nicholls A. The tibial tubercle-trochlear groove distance: a comparison study between EOS and MRI in the paediatric population. Skeletal Radiol 2024; 53:85-91. [PMID: 37300708 DOI: 10.1007/s00256-023-04385-6] [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: 12/16/2022] [Revised: 06/04/2023] [Accepted: 06/04/2023] [Indexed: 06/12/2023]
Abstract
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.
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Affiliation(s)
- Geoffrey T Murphy
- Sydney Orthopaedic Research Institute, Level 2, 500 Pacific Highway, St. Leonards, Sydney, 2065, Australia.
| | - Ravi Rudraraju
- Sydney Orthopaedic Research Institute, Level 2, 500 Pacific Highway, St. Leonards, Sydney, 2065, Australia
| | | | | | | | - Kylie Brown
- Westmead Children's Hospital, Westmead, Australia
| | - Alex Nicholls
- Sydney Orthopaedic Research Institute, Level 2, 500 Pacific Highway, St. Leonards, Sydney, 2065, Australia
- Westmead Children's Hospital, Westmead, Australia
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Pineda T, Dejour D. Inconsistent repeatability of the Dejour classification of trochlear dysplasia due to the variability of imaging modalities: a systematic review. Knee Surg Sports Traumatol Arthrosc 2023; 31:5707-5720. [PMID: 37919443 DOI: 10.1007/s00167-023-07612-8] [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: 08/08/2023] [Accepted: 09/28/2023] [Indexed: 11/04/2023]
Abstract
PURPOSE The purpose of this systematic review was to critically assess the quality of papers that report on the intra- and inter-observer repeatability of the Dejour classification for trochlear dysplasia, and to identify the possible causes for poor repeatability. METHODS Two authors independently conducted an electronic search (four databases) on 8 February 2023 for studies (English or French) that assessed trochlear dysplasia classifications on imaging of skeletally mature participants. Exclusion criteria were reviews of clinical studies, conference proceedings, or editorials. After title, abstract, and full-text screening, characteristics of eligible studies were tabulated (author, year, journal, study design, cohort characteristics, and intra- and/or inter-observer agreement coefficients). The methodological quality of studies was assessed using the Joanna Briggs Institute (JBI) checklist for analytical cross-sectional studies. Authors analysed three components of the included studies: (1) classifications based on true lateral radiographs and slice imaging; (2) dysplasia graded into Type A vs B vs C vs D and 3) coefficients of intra- and/or inter-observer agreement. RESULTS The electronic search returned 3,178 references, and after removal of duplicates and irrelevant studies, ten were eligible for data extraction. A second search (31 July 2023) yielded one additional study. Eight studies did not include lateral radiographs, two studies did not explicitly state if radiographs were true lateral views, and one used true lateral radiographs in isolation. Classification of trochlear dysplasia into A vs B vs C vs D using different imaging modalities resulted in moderate to near-perfect intra-observer agreement, and slight to near-perfect inter-observer agreement. Studies distinguished between moderate and severe dysplasia using a variety of combinations: A vs B/C/D, A/B vs C/D and A/C vs B/D. CONCLUSION This systematic review revealed that the Dejour classification remains the most widely used to assess trochlear dysplasia and that the majority of studies that assessed the reliability of the Dejour classification, reported moderate to near-perfect inter-observer agreement; however, pooling of results for comparison among the included studies was inappropriate due to substantial variation in imaging protocols and non-standardised criteria to distinguish severe from moderate dysplasia. LEVEL OF EVIDENCE Level IV. TRIAL REGISTRY The PROSPERO registration number is CRD42023386731.
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Affiliation(s)
- Tomas Pineda
- Lyon-Ortho-Clinic, Clinique de La Sauvegarde, 29 Avenue des Sources, 69009, Ramsay Santé, Lyon, France
| | - David Dejour
- Lyon-Ortho-Clinic, Clinique de La Sauvegarde, 29 Avenue des Sources, 69009, Ramsay Santé, Lyon, France
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Bae K, Aldosari AM, Kang MS. The Difference in Tibial Tuberosity to Trochlear Groove Distance Between CT and MRI Arises From the Degree of Knee Flexion During Imaging. J Pediatr Orthop 2023; 43:e761-e768. [PMID: 37493032 DOI: 10.1097/bpo.0000000000002481] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 07/27/2023]
Abstract
BACKGROUND Tibial tuberosity to trochlear groove distance (TT-TG) has been reported to have different values according to imaging modalities, usually higher in computed tomography (CT) than in magnetic resonance imaging (MRI). This difference is thought to be caused by the degree of knee flexion during imaging, but few studies have aimed to elucidate the cause. METHODS Five hundred eight patients with knee CT or MRI performed between ages of 6 to 16 years without underlying diseases affecting the musculoskeletal system were included. This study was conducted in 2 statistical ways. (1) Propensity score matching was performed for the imaging modality, and the bony TT-TG was compared between the 2 matched groups. (2) A regression model was fitted with 484 patients with either CT or MRI (a training set), and validation of the fitted model was performed with 24 patients with both CT and MRI simultaneously taken within a week (a test set). The predicted TT-TG values were compared with the measured values. RESULTS (1) Eighty-one patients were successfully matched by propensity score (all the standardized mean differences < 0.1) for each modality. In the matched patients, there was no significant difference in TT-TG according to the imaging modality (11.3 ± 3.7 mm for CT, 10.4 ± 3.8 mm for MRI, P = 0.126). (2) For the model fitting, different linear models were fitted before and after 10 degrees of knee flexion angle because there was a sharp change in TT-TG when the knee flexion angle was <10 degrees. The predicted TT-TG values did not significantly differ from the measured values (10.2 ± 4.3 mm vs. 9.0 ± 5.1 mm, P = 0.124). CONCLUSIONS This study is the first to statistically prove that the difference between TT-TG in MRI and CT originates from the different degrees of knee flexion. In addition, although more studies are needed, authors recommend imaging to be performed with the knee flexed at least 10 degrees for more reliable measurements because TT-TG changes sharply if the knee flexion angle is <10 degrees. LEVEL OF EVIDENCE III.
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Affiliation(s)
- Kunhyung Bae
- Department of Orthopedic Surgery, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Songpa-gu
- Department of Orthopedic Surgery, Hanyang University Hospital, Hanyang University College of Medicine, Seongdong-gu, Seoul, Republic of Korea
| | - Amaal Mohammed Aldosari
- Department of Orthopedic Surgery, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Songpa-gu
- Department of Orthopedic Surgery, Alnoor Specialist Hospital, Makkah, Makkah, Saudi Arabia
| | - Michael Seungcheol Kang
- Department of Orthopedic Surgery, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Songpa-gu
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Pascual-Leone N, Chipman DE, Meza BC, Mintz DN, Fabricant PD, Green DW. Concomitant anterior medializing osteotomy and MPFL reconstruction improves patellar tilt when compared to MPFL reconstruction alone. Knee Surg Sports Traumatol Arthrosc 2023:10.1007/s00167-023-07396-x. [PMID: 37062043 DOI: 10.1007/s00167-023-07396-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Accepted: 03/17/2023] [Indexed: 04/17/2023]
Abstract
PURPOSE Understanding how surgical procedures influence anatomic factors associated with patellofemoral instability can help guide surgeons when planning treatments for individual patients. This study sought to understand how patellar tilt is affected in adolescent patients with elevated pre-operative tibial tuberosity to trochlear groove (TT-TG) values undergoing medial patellofemoral ligament reconstruction (MPFLR) with or without an anterior medializing osteotomy (AMZ). METHODS Utilizing a prospective database of 274 patellofemoral instability patients who underwent MPFLR ± AMZ by one of two orthopedic surgeons at a single institution, those who underwent MPFLR + AMZ were identified. Pre-operative and post-operative magnetic resonance imaging (MRI) were used to measure TT-TG distance, while radiographs were used to measure patellar tilt (tilt). Patients were matched based on age at surgery (within 2 years) and pre-operative TT-TG distance (within 2 mm) to a comparison cohort of patients who underwent isolated MPFLR (iMPFLR) without osseous procedures. RESULTS A total of 56 patients were analyzed (28 per group). The mean age of the cohort was 15.5 ± 2.0 years and was similar between both groups (15.9 ± 1.9 versus 15.1 ± 2.0 years [n.s]). When comparing the two cohorts, significant pre- to post-operative decreases in patellar tilt for both MPFLR + AMZ (6.6 degrees, p < 0.001) and iMPFLR (3.9 degrees, p = 0.013) were noted. While there were no differences in pre-operative patellar tilt (21.2 ± 3.5 versus 21.1 ± 3.4 [n.s]), post-operatively, MPFLR + AMZ had significantly less patellar tilt than iMPFLR (13.2 ± 5.5 versus 16.5 ± 4.4, p = 0.017). CONCLUSIONS This study found that patellar tilt significantly improved in participants undergoing either MPFLR + AMZ or iMPFLR. In addition, those undergoing MPFLR + AMZ were found to have significantly lower post-operative tilt than those undergoing iMPFLR. If patellar tilt is found pre-operatively to be significantly elevated and a risk for future dislocations, these findings suggest that surgeons might strongly consider MPFLR with AMZ to further address the increased tilt. LEVEL OF EVIDENCE III.
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Affiliation(s)
- Nicolas Pascual-Leone
- Department of Pediatric Orthopaedic Surgery, Hospital for Special Surgery, New York, NY, USA
| | - Danielle E Chipman
- Department of Pediatric Orthopaedic Surgery, Hospital for Special Surgery, New York, NY, USA
| | - Blake C Meza
- Department of Pediatric Orthopaedic Surgery, Hospital for Special Surgery, New York, NY, USA
| | - Douglas N Mintz
- Department of Radiology & Imaging, Hospital for Special Surgery, New York, NY, USA
| | - Peter D Fabricant
- Department of Pediatric Orthopaedic Surgery, Hospital for Special Surgery, New York, NY, USA
| | - Daniel W Green
- Department of Pediatric Orthopaedic Surgery, Hospital for Special Surgery, New York, NY, USA.
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Huettner F, Lutter C, Zuehlke C, Kfuri M, Tischer T, Harrer J. Determination of Standard Values for Knee Version in a Healthy Population. Am J Sports Med 2023; 51:949-956. [PMID: 36803062 DOI: 10.1177/03635465231152475] [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] [Indexed: 02/23/2023]
Abstract
BACKGROUND Different measures are used to describe relevant anatomic variations that can result in patellofemoral instability and disorders. Knee version, the relative rotational alignment between the femur and tibia in the axial plane at the level of the knee, may have a decisive effect on the kinematics of the patellofemoral joint. However, data regarding the values of knee version are currently lacking. PURPOSE This study aimed to determine standard values for knee version in a healthy population. STUDY DESIGN Cross-sectional study; Level of evidence, 3. METHODS A total of 100 healthy volunteers (50 male and 50 female) without patellofemoral disorders or lower extremity malalignment were included in this study and underwent knee magnetic resonance imaging. The torsion values of the femur and tibia were independently measured using the Waidelich and Strecker method. Knee version, defined as static rotation of the tibia with respect to the femur in full extension, was determined by measuring the angle between the tangent lines to the dorsal femoral condyle (DFC) and the dorsal tibial head (DTH; defined by the posterior point of the proximal tibial plateau). Supplementary measurements were obtained as follows: (1) femoral epicondylar line (FEL), (2) tibial ellipse center line (TECL), (3) tibial tuberosity-trochlear groove (TT-TG) distance, and (4) tibial tuberosity-posterior cruciate ligament (TT-PCL) distance. RESULTS In 200 analyzed legs of 100 volunteers (mean age, 26.5 ± 5.8 years [range, 18 to 40 years]), we identified a mean internal femoral torsion of -23.8°± 9.7° (range, -46.2° to 1.6°), external tibial torsion of 33.2°± 7.4° (range, 16.4° to 50.3°), and external knee version (DFC to DTH) of 1.3°± 3.9° (range, -8.7° to 11.7°). Other measurements were as follows: FEL to TECL, -0.9°± 4.9° (range, -16.8° to 12.1°); FEL to DTH, -3.6°± 4.0° (range, -12.6° to 6.8°); and DFC to TECL, 4.0°± 4.9° (range, -12.7° to 14.7°). The mean TT-TG distance was 13.4 ± 3.7 mm (range, 5.3-23.5 mm), and the mean TT-PCL distance was 11.5 ± 3.5 mm (range, 6.0-20.9 mm). Female participants had significantly greater external knee version than male participants. CONCLUSION Coronal- and sagittal-plane alignments of the knee have a well-known effect on the biomechanics of this joint. Additional information about the axial plane may result in new decision-making algorithms for managing knee disorders. This study is the first to report standard values of knee version in a healthy population. As a subsequent step building on this work, we advocate for the measurement of knee version in patients with patellofemoral disorders, as this parameter may assist with new treatment guidelines in the future.
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Affiliation(s)
- Felix Huettner
- Department of Orthopaedic Surgery, REGIOMED Klinikum Lichtenfels, Lichtenfels, Germany
- Department of Orthopaedic Surgery, Rostock University Medical Center, Rostock, Germany
| | - Christoph Lutter
- Department of Orthopaedic Surgery, Rostock University Medical Center, Rostock, Germany
| | - Constantin Zuehlke
- Department of Radiology, REGIOMED Klinikum Lichtenfels, Lichtenfels, Germany
| | - Mauricio Kfuri
- Department of Orthopaedic Surgery, University of Missouri, Columbia, Missouri, USA
| | - Thomas Tischer
- Department of Orthopaedic Surgery, Rostock University Medical Center, Rostock, Germany
- Department of Orthopaedic Surgery, Malteser Waldkrankenhaus St Marien, Erlangen, Germany
| | - Joerg Harrer
- Department of Orthopaedic Surgery, REGIOMED Klinikum Lichtenfels, Lichtenfels, Germany
- Committee Osteotomy, German Knee Society (DKG), Germany
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Xu Z, Song Y, Deng R, Ye J, Wang X, Wang H, Yu JK. CT and MRI measurements of tibial tubercle lateralization in patients with patellar dislocation were not equivalent but could be interchangeable. Knee Surg Sports Traumatol Arthrosc 2023; 31:349-357. [PMID: 36088618 DOI: 10.1007/s00167-022-07119-8] [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: 05/10/2022] [Accepted: 08/10/2022] [Indexed: 01/25/2023]
Abstract
PURPOSE To compare the values and the relationship of tibial tubercle lateralization measurements between computerized tomography (CT) and magnetic resonance imaging (MRI). METHODS Sixty patients with patellar dislocation who underwent both CT and MRI of the same knee joint from November 2021 to February 2022 were included in our study. The intraclass correlation coefficient (ICC) and Bland-Altman analysis were performed to evaluate the reliability of tibial tubercle-trochlear groove (TT-TG), tibial tubercle-Roman arch (TT-RA), and tibial tubercle-posterior cruciate ligament (TT-PCL) distance measurements. The values of CT and MRI measurements using the same bony landmarks were compared for the difference. Pearson correlation analysis and linear regression analysis were performed to assess the correlation between CT and MRI measurements. Finally, the estimated values obtained from the regression equation were compared with the actual values obtained from the radiological measurement to evaluate the accuracy of the equations. RESULTS A total of 60 patients with patellar dislocation who underwent both CT and MRI of the same knee joint were included in this study. The included measurements showed excellent agreement with ICCs > 0.9. TT-TG distance measured on CT (19.5 ± 5.1 mm) had a mean of 7.1 mm higher than that on MRI (12.4 ± 4.7 mm) (P < 0.001). The mean value of TT-RA distance was 22.5 ± 3.7 mm on CT and 16.7 ± 4.9 mm on MRI (P < 0.001), showing a mean difference of 5.8 mm. The values of TT-TG distance measured by CT and MRI were significantly correlated (R = 0.5, P < 0.001). The values of TT-RA distance between these two modalities showed a better correlation than that of TT-TG distance (R = 0.6, P < 0.001). The interchange values of TT-TG distance and TT-RA distance between CT and MRI can be obtained using regression equations (TT-TG distance: y = 0.6x + 12.3; TT-RA distance: y = 0.5x + 14.4). CONCLUSION The values of tibial tubercle lateralization measured by MRI may be underestimated compared with those measured by CT. Although the values measured on CT and MRI are not equivalent, the value in the other modality can be estimated. Therefore, an additional CT scan for tibial tubercle lateralization evaluation may not be necessary. LEVEL OF EVIDENCE Level II.
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Affiliation(s)
- Zijie Xu
- Sports Medicine Department, Beijing Key Laboratory of Sports Injuries, Peking University Third Hospital, Beijing, China.,Institute of Sports Medicine, Peking University, Beijing, China
| | - Yifan Song
- Sports Medicine Department, Beijing Key Laboratory of Sports Injuries, Peking University Third Hospital, Beijing, China.,Institute of Sports Medicine, Peking University, Beijing, China
| | - Ronghui Deng
- Sports Medicine Department, Beijing Key Laboratory of Sports Injuries, Peking University Third Hospital, Beijing, China.,Institute of Sports Medicine, Peking University, Beijing, China
| | - Jing Ye
- Sports Medicine Department, Beijing Key Laboratory of Sports Injuries, Peking University Third Hospital, Beijing, China.,Institute of Sports Medicine, Peking University, Beijing, China
| | - Xinjie Wang
- Sports Medicine Department, Beijing Key Laboratory of Sports Injuries, Peking University Third Hospital, Beijing, China.,Institute of Sports Medicine, Peking University, Beijing, China
| | - Haijun Wang
- Sports Medicine Department, Beijing Key Laboratory of Sports Injuries, Peking University Third Hospital, Beijing, China. .,Institute of Sports Medicine, Peking University, Beijing, China.
| | - Jia-Kuo Yu
- Sports Medicine Department, Beijing Key Laboratory of Sports Injuries, Peking University Third Hospital, Beijing, China. .,Institute of Sports Medicine, Peking University, Beijing, China.
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11
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Kim TJ, Lee TJ, Song HS, Bae JH. The Tibial Tuberosity-Rotational Angle as a Novel Predisposing Parameter for Patellar Dislocation. Orthop J Sports Med 2022; 10:23259671221142626. [PMID: 36582930 PMCID: PMC9793030 DOI: 10.1177/23259671221142626] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Accepted: 09/15/2022] [Indexed: 12/24/2022] Open
Abstract
Background The tibial tuberosity (TT) in the axial plane is located on a curved line along the anterior cortex of the proximal tibia. Therefore, the linear measurement of TT position may not fully reflect TT malposition. Purpose To introduce TT-rotational angle (TT-RA) as a new anatomical parameter, which means the rotation of the TT relative to the dorsal condylar line of the tibia, and to validate its predictive value for patellar dislocation. Study Design Cross-sectional study; Level of evidence, 3. Methods Included were 46 patients with a history of patellar dislocation and 46 age- and sex-matched controls who underwent axial magnetic resonance imaging. Seven radiological parameters were measured and compared between the 2 groups, including TT-trochlear groove (TT-TG) distance, tibial tubercle-posterior cruciate ligament (TT-PCL) distance, TT-PCL ratio, TT lateralization (TTL), trochlear groove medialization (TGM), TT-RA, trochlear groove-posterior condylar axis angle (TG-PCA), and knee rotation. The predictive values of parameters for patellar dislocation were assessed using multiple logistic regression analysis. Results The intra- and interobserver correlation coefficients for measuring the radiographic parameters showed good to excellent values., respectively. There were significant differences in the TT-TG distance (13.9 vs 6.8 mm; P < .001), TT-RA (16.0° vs 9.1°; P < .001), TG-PCA (93.7° vs 95.4°; P = .017), and knee rotation (0.9° vs 5.3°; P < .001) between the 2 groups. However, there was no significant difference in TT-PCL distance (20.7 vs 19.4 mm; P = .075), TT-PCL ratio (28.0% vs 26.6%; P = .136), TTL (65.7% vs 64.9%; P = .270), or TGM (54.9% vs 55.0%; P = .923). Multivariable analysis showed that 3 parameters were significantly associated with patellar dislocation: TT-RA (OR, 1.57; P < .001), TT-TG distance (OR, 1.52; P = .002), and knee rotation (OR, 0.75; P = .022). Conclusion The TT-RA was a reliable predisposing parameter of patellar instability. It can be an alternative method of measurement when the TT-TG distance is not clearly defined.
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Affiliation(s)
- Tae Jin Kim
- Department of Orthopaedic Surgery, Korea University Guro Hospital,
Seoul, Republic of Korea
| | - Tae Jin Lee
- Department of Orthopaedic Surgery, Korea University Guro Hospital,
Seoul, Republic of Korea
| | - Hyun-Sub Song
- Department of Orthopaedic Surgery, Korea University Guro Hospital,
Seoul, Republic of Korea
| | - Ji Hoon Bae
- Department of Orthopaedic Surgery, Korea University Guro Hospital,
Seoul, Republic of Korea.,Ji Hoon Bae, MD, PhD, Department of Orthopaedic Surgery, Korea
University College of Medicine, Guro Hospital, 80 Guro-dong, Guro-gu, Seoul
152-703, Republic of Korea ()
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12
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Individualized tibial tubercle-trochlear groove distance-to-patellar length ratio (TT-TG/PL) is a more reliable measurement than TT-TG alone for evaluating patellar instability. Knee Surg Sports Traumatol Arthrosc 2022; 30:3644-3650. [PMID: 35437608 DOI: 10.1007/s00167-022-06979-4] [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: 08/24/2021] [Accepted: 04/01/2022] [Indexed: 10/18/2022]
Abstract
PURPOSE To evaluate the intra/inter-rater and diagnostic reliability of the sagittal plane adjusted patellar instability ratios (PIRs) compared to tibial tubercle-trochlear groove (TT-TG) distance alone while employing a matched case-control analysis for age and sex to minimize a potential confounding effect. METHODS A retrospective case-control study was performed of all knee MRI studies of patients diagnosed with patellar instability, between 2005 and 2020 at a regional tertiary medical centre. Using a 1:1 case-control matching of sex and age at the time of the diagnosis, one control subject was assigned to each case of patellar instability. Measurements of TT-TG distance, sagittal patellar length (PL), sagittal patellar tendon length (PTL), TT-TG/PL ratio, and TT-TG/PTL ratio were conducted. Two orthopaedic surgery residents and a senior musculoskeletal radiologist were assigned to assess the intra- and inter-rater reliability. Inter-class coefficients were calculated (ICC). The receiver operating characteristic (ROC) curve and area under curve (AUC) for each parameter were compared to evaluate for diagnostic reliability. Odds ratios (OR) and their 95% confidence intervals (CI) were calculated and a multivariable logistic regression model was performed to control for possible confounders. RESULTS The study included 324 individuals (162 case-control matched pairs). In terms of intra- and inter-rater reliability, TT-TG/PL and TT-TG/PTL ratios showed an excellent correlation within and between readers (TT-TG/PL; intra-rater ICC 0.94 and inter-rater ICC 0.92, TT-TG/PTL; intra-rater ICC 0.91 and inter-rater ICC 0.88). The ROC curve showed a slightly greater AUC of the TT-TG/PL ratio compared to TT-TG distance alone (0.75 vs 0.73, p < 0.001). When applying the pathologic cutoff of TT-TG ≥ 20 mm and TT-TG/PL ≥ 0.5; the calculated odds ratios for the above cutoff were as follows; TT-TG distance alone had an OR of 14 (95% CI 1.8-106.5, p = 0.011) and OR for TT-TG/PL ratio was 23 (95% CI 3.1-170.3, p = 0.002). In the multivariable analysis, while controlling for height and weight, only the association between TT-TG/PL ratio and patellar dislocation remained statistically significant with an adjusted OR of 2.7 (CI 1.3-5.4, p = 0.006), compared to TTTG distance alone (OR = 1.9, n.s.). CONCLUSIONS Patellar instability ratios are significantly more reliable compared to TT-TG distance alone for the evaluation of patellar instability. Patellar instability ratios present superior diagnostic reliability, sensitivity and specificity, and intra\inter rater reliability. Thus, patellar instability ratios could function as a valuable diagnostic tool for the evaluation of patellar instability. LEVEL OF EVIDENCE III.
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13
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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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14
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Geraghty L, Zordan R, Walker P, Chao TW, Talbot S. Patellar dislocation is associated with increased tibial but not femoral rotational asymmetry. Knee Surg Sports Traumatol Arthrosc 2022; 30:2342-2351. [PMID: 34850247 DOI: 10.1007/s00167-021-06813-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Accepted: 11/17/2021] [Indexed: 11/27/2022]
Abstract
PURPOSE Patellar dislocation is associated with a range of anatomical abnormalities affecting the trochlea, extensor mechanism and the tibia. The relationship between patellofemoral instability and rotational abnormalities of the posterior condyles, trochlear groove and proximal tibia has not been adequately determined. This study aimed to identify the frequency and severity of anatomical risk factors to determine their relative contribution to patellofemoral instability. METHODS A retrospective morphological study was undertaken comparing multiple anatomical measurements with magnetic resonance imaging of 50 patients with patellofemoral instability to an age- and gender-matched Control group (n = 50). Several techniques were assessed measuring both femoral and tibial axial asymmetry. A new measurement, tibial rotational asymmetry, comparing a line between the midpoints of the collateral ligaments to the axis between the patellar tendon and posterior cruciate ligament, was assessed for its association with patellofemoral instability. RESULTS Compared to the controls, the patellofemoral instability group demonstrated a significant difference in tibial rotational asymmetry, with a mean of 2.9° (SD 3.2°) externally rotated vs - 1.6° (SD 2.2°) in the control group. Significant differences were also demonstrated regarding the sulcus angle, tibial tubercle-trochlear groove distance, tibial tubercle-posterior cruciate ligament distance, patellar size and the Insall-Salvati ratio. There were no differences between groups regarding the lengths of the posterior condyles, the heights of the trochlear ridges or lateralisation of the trochlear groove. Further analysis of the patellofemoral instability group revealed a subgroup of males with normal anatomy (7/50) and a subgroup of females with isolated patella alta (7/50). CONCLUSION Patellofemoral instability is associated with tibial rotational asymmetry due to lateralisation of the tibial tubercle. It is also associated with patella alta and reduced trochlear groove depth. The femoral axial shape is otherwise unchanged. LEVEL OF EVIDENCE III.
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Affiliation(s)
- Liam Geraghty
- The Sports Medicine Practice Hobart, 36 Collins Street, Hobart, TAS, 7000, Australia.
- Department of Orthopaedic Surgery, Western Health, 160 Gordon Street, Footscray, VIC, 3011, Australia.
| | - Rachel Zordan
- Simon Talbot, 1/210 Burgundy Street, Heidelberg, VIC, 3084, Australia
- Honorary Senior Fellow, Melbourne Medical School, University of Melbourne, Parkville, VIC, 3052, Australia
| | - Phoebe Walker
- Department of Orthopaedic Surgery, Western Health, 160 Gordon Street, Footscray, VIC, 3011, Australia
| | - Tat Woon Chao
- Department of Orthopaedic Surgery, Western Health, 160 Gordon Street, Footscray, VIC, 3011, Australia
| | - Simon Talbot
- Department of Orthopaedic Surgery, Western Health, 160 Gordon Street, Footscray, VIC, 3011, Australia
- Simon Talbot, 1/210 Burgundy Street, Heidelberg, VIC, 3084, Australia
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15
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The winking sign is an indicator for increased femorotibial rotation in patients with recurrent patellar instability. Knee Surg Sports Traumatol Arthrosc 2022; 30:3651-3658. [PMID: 35438307 PMCID: PMC9568440 DOI: 10.1007/s00167-022-06971-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 03/29/2022] [Indexed: 10/27/2022]
Abstract
PURPOSE Rotation of the tibia relative to the femur was recently identified as a contributing risk factor for patellar instability, and correlated with its severity. The hypothesis was that in patellofemoral dysplastic knees, an increase in femorotibial rotation can be reliably detected on anteroposterior (AP) radiographs by an overlap of the lateral femoral condyle over the lateral tibial eminence. METHODS Sixty patients (77 knees) received low-dose computed tomography (CT) of the lower extremity for assessment of torsional malalignment due to recurrent patellofemoral instability. Three-dimensional (3D) surface models were created to assess femorotibial rotation and its relationship to other morphologic risk factors of patellofemoral instability. On weight-bearing AP knee radiographs, a femoral condyle/lateral tibial eminence superimposition was defined as a positive winking sign. Using digitally reconstructed radiographs of the 3D models, susceptibility of the winking sign to vertical/horizontal AP knee radiograph malrotation was investigated. RESULTS A positive winking sign was present in 30/77 knees (39.0%) and indicated a 6.3 ± 1.4° increase in femorotibial rotation (p < 0.001). Femoral condyle/tibial eminence superimposition of 1.9 mm detected an increased femorotibial rotation (> 15°) with 43% sensitivity and 90% specificity (AUC = 0.72; p = 0.002). A positive winking sign (with 2 mm overlap) disappeared in case of a 10° horizontally or 15° vertically malrotated radiograph, whereas a 4 mm overlap did not disappear at all, regardless of the quality of the radiograph. In absence of a winking sign, on the other hand, no superimposition resulted within 20° of vertical/horizontal image malrotation. Femorotibial rotation was positively correlated to TT-TG (R2 = 0.40, p = 0.001) and patellar tilt (R2 = 0.30, p = 0.001). CONCLUSIONS The winking sign reliably indicates an increased femorotibial rotation on a weight-bearing AP knee radiograph and could prove useful for day-by-day clinical work. Future research needs to investigate whether femorotibial rotation is not only a prognostic factor but a potential surgical target in patients with patellofemoral disorders. LEVEL OF EVIDENCE III.
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