scholarly journals Geometry of Torsional Malalignment Syndrom: Trochlear Dysplasia but not Torsion Predicts Lateral Patellar Instability

2019 ◽  
Vol 7 (6_suppl4) ◽  
pp. 2325967119S0022
Author(s):  
Peter Balcarek ◽  
Dennis Vogel
Keyword(s):  
Inclination Angle ◽  
Patellar Instability ◽  
Trochlear Dysplasia ◽  
Patellofemoral Pain ◽  
Tibial Tuberosity ◽  
Patellar Tracking ◽  
Trochlear Groove ◽  
Type B ◽  
Tibial Torsion ◽  
Torsional Malalignment

Aims and Objectives: To analyze parameters of limb malalignment and patellar tracking in patients with torsional malalignment syndrome presenting with clinical symptoms of either patellofemoral pain or patellar instability. Materials and Methods: Between April 2015 and July 2017, 428 patients were treated for lateral patellar instability (LPD), and 333 patients were treated for patellofemoral pain syndrome (PFPS). Sixty-two patients (14.5%) with patellar instability (LPD group) and 29 patients (8.7%) with patellofemoral pain (PFPS group) had additional torsional malalignment and were included in this study. All patients underwent magnetic resonance imaging assessment of torsional alignment and patellar tracking, including femoral antetorsion, tibial torsion, knee rotation, tibial tuberosity-trochlear groove distance, tibial tuberosity-posterior cruciate ligament distance, Dejour’s classification of trochlear dysplasia, lateral trochlear inclination angle, and patellar height Results: Groups differed significantly in terms of trochlear dysplasia (p<0.001), lateral trochlear inclination angle (p<0.001) and tibial tuberosity-trochlear groove distance (p=0.0167) but did not differ in terms of femoral torsion (LPD group 20.02° +/- 8.8°; PFPS group 20.03° +/- 7.91°; p=0.8545), tibial torsion (LPD group 39.53° +/- 9.23°; PFPS group 41.24° +/- 7.28°; p=0.3616), and knee rotation (LPD group 10.42° +/- 5.16°; PFPS group 8.48° +/- 7.81°; p=0.0163). Only measures of coronal alignment were positively correlated. This was also true for the tibial tuberosity-trochlear groove distance and knee rotation but not for any other parameters of torsional limb alignment. Trochlear dysplasia (type B-D) was identified as the only significant predictor of patellar instability. Conclusion: Torsional malalignment syndrome, represented in this study by two clinical entities - PFPS and LPD - is not characterized by a typical constellation of different malalignment parameters. Between groups, parameters differed significantly only in terms of trochlear dysplasia and the tibial tuberosity-trochlear groove distance, with trochlear dysplasia (type B-D), but not torsion, identified as predictor of lateral patellar instability.

scholarly journals Why do MPFL reconstructions fail today?

2020 ◽  
Vol 8 (5_suppl4) ◽  
pp. 2325967120S0029
Author(s):  
Felix Zimmermann ◽  
Peter Balcarek
Keyword(s):  
Risk Factors ◽  
Revision Surgery ◽  
Patellar Instability ◽  
Trochlear Dysplasia ◽  
Valgus Deformity ◽  
Patellar Height ◽  
Tibial Tuberosity ◽  
Mpfl Reconstruction ◽  
Trochlear Groove ◽  
Type B

Aims and Objectives: The medial patellofemoral ligament (MPFL) is the most important passive stabilizer of the patella. In recurrent lateral patellar dislocations reconstruction of the MPFL with an autologous tendon transplant is a frequently performed surgical procedure that shows a low redislocation rate between 1%-7%. However, a complication rate of up to 26% and a reoperation rate of 4% has also been observed. The question, therefore, arises which parameter determines MPFL reconstruction failure. Thus, the purpose of this study was to identify reasons for MPFL reconstruction failure with regard to patients’ complaints leading to reoperation. Materials and Methods: Between July 2015 and May 2019 28 patients (M/F 9/19; mean age 27 ± 8 years) with postoperative complaints after MPFL reconstructive surgery had to undergo revision surgery. Preoperative failure analysis included clinical examination (ROM, ReDPAT, J-sign, and Patella-Glide Test) and radiological imaging with regard to anatomical risk factors of patellar instability and MPFL tunnel positioning. Anatomical predisposition was assessed according to Dejour’s classification of trochlear dysplasia, tibial tuberosity-trochlear groove distance, tibial tuberosity-posterior cruciate ligament distance, patellar height, varus/valgus malalignment and torsional profile. Results: Three major reasons for revision surgery were identified: (1) patellar redislocation, (2) limited range of motion (ROM), and (3) anterior knee pain (AKP). Sixteen of the 28 patients (57%) suffered from recurrent patellar dislocation. Severe trochlear dysplasia (type B/D according to Dejour) (44%), valgus deformity (19%), increased patellar height (19%), and misplaced femoral drill channels (31%) could be identified as risk factors for redislocation. An increased TT-TG (>20mm) or TT-PCL (>24mm) distance could not be observed in any patient in this group. Limited ROM with an average maximum flexion ability of about 92 ± 26° was observed in 10 of the 28 patients (36%), of which 9 patients additionally complained of AKP. Misplaced femoral drill channels (80%), severe trochlear dysplasia (type B/D according to Dejour) (20%) and postoperative decreased patellar height (20%) could be identified as risk factors for postoperative limited ROM. Other reasons for postoperative AKP were increased femoral antetorsion (n=1) and retropatellar cartilage damage (n=2) without any loss of ROM. Conclusion: Recurrent dislocation of the patella, limited ROM and AKP were identified as most common complications after MPFL reconstruction leading to revision surgery. Failures are mainly due to neglected bony risk factors of patellar instability (trochlear dysplasia, patella alta and valgus deformity) and to misplaced femoral drill channels. Appropriate patient selection and an accurate surgical technique appear mandatory for a good clinical outcome when patellar instability is treated solely with an MPFL reconstruction.

scholarly journals Identifying Patients With Patella Alta and/or Severe Trochlear Dysplasia Through the Presence of Patellar Apprehension in Higher Degrees of Flexion

2020 ◽  
Vol 8 (6) ◽  
pp. 232596712092548
Author(s):  
Matthew Colatruglio ◽  
David C. Flanigan ◽  
Sarah Harangody ◽  
Robert A. Duerr ◽  
Christopher C. Kaeding ◽  
...  
Keyword(s):  
Knee Flexion ◽  
Patellar Instability ◽  
Trochlear Dysplasia ◽  
Patella Alta ◽  
Tibial Tubercle ◽  
Trochlear Groove ◽  
Type B ◽  
Level Of Evidence ◽  
Sulcus Angle ◽  
Recurrent Patellar Instability

Background: Recurrent patellar instability is frequently treated surgically with reconstruction of the medial patellofemoral ligament (MPFL). Patients with significant patella alta, trochlear dysplasia, and/or an elevated tibial tubercle–trochlear groove (TT-TG) distance may benefit from a concurrent bony procedure such as tibial tubercle osteotomy or trochleoplasty. The indications to perform such procedures are traditionally based on imaging criteria but remain controversial. Patellar apprehension is common in patients with patellar instability but typically resolves in higher degrees of knee flexion. Hypothesis: The persistence of patellar apprehension at greater than 60° of knee flexion is associated with patella alta, an increased TT-TG distance, and trochlear dysplasia. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 76 patients with recurrent patellar instability were prospectively identified in a sports medicine clinic. Patellar apprehension was evaluated in each patient. Apprehension was defined as the patient reporting that the patella felt unstable to lateral patellar translation. Apprehension was first assessed at full knee extension and repeatedly assessed as the knee was flexed in 10° intervals, as measured using a goniometer. The degree of flexion at which patellar apprehension disappeared was recorded. Plain radiographs and magnetic resonance imaging (MRI) scans were obtained for all patients. Patellar height was assessed with the Caton-Deschamps (CD) index, and trochlear morphology was assessed through measurements of the sulcus angle and depth on MRI and classified using the Dejour classification system. Imaging measurements of patients in whom apprehension resolved by 60° of knee flexion were compared with measurements for those with apprehension that persisted deeper into flexion. Results: Apprehension resolved by 60° of flexion in 56 patients and persisted into deeper flexion in 20 patients. The patients with a delayed resolution of apprehension demonstrated a higher CD index; elevated TT-TG distance; increased sulcus angle; decreased sulcus depth; and higher incidence of Dejour type B, C, or D dysplasia (all P < .05). Of the 20 patients with a delayed resolution of apprehension, 18 had either Dejour type B, C, or D dysplasia or a CD index of at least 1.30. A delayed resolution of apprehension was present in 11 of the 16 patients with Dejour type B, C, or D dysplasia. Conclusion: Overall, 90% of patients with significant patella alta and the majority of patients with high-grade trochlear dysplasia demonstrated patellar apprehension that persisted beyond 60° of knee flexion. Additionally, 90% of patients with persistent apprehension had significant patella alta and/or trochlear dysplasia. Further work is needed to evaluate the utility of these findings to inform surgical decision-making in this population.

scholarly journals Accuracy of tibial tuberosity-trochlear groove distance and tibial tuberosity-posterior cruciate ligament distance in terms of the severity of trochlear dysplasia

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Conglei Dong ◽  
Chao Zhao ◽  
Ming Li ◽  
Chongyi Fan ◽  
Xunkai Feng ◽  
...  
Keyword(s):  
Trochlear Dysplasia ◽  
Cruciate Ligament ◽  
Pearson Correlation ◽  
Tibial Tuberosity ◽  
Tibial Tubercle ◽  
Trochlear Groove ◽  
Pearson Correlation Coefficient ◽  
Type B ◽  
Group Type ◽  
Severe Group

Abstract Purpose Increased tibial tubercle-trochlear groove distance (TT-TG) was proposed as one of the main risk factors for patellofemoral instability (PFI). The increased TT-TG distance indicated externalization of the tibial tubercle with the reference of the trochlear groove. However, in the case of severe trochlear dysplasia, the reference point on the trochlear groove was indistinct, and the accuracy of TT-TG was controversial. The purpose of this study was to evaluate the accuracy of TT-TG and TT-PCL in consideration of the mild and severe trochlear dysplasia. Methods From 2015 to 2020, MRI findings of consecutive knee joints with PFI symptoms diagnosed in our hospital were retrospectively analyzed. All knees with trochlear dysplasia were diagnosed by longitudinal MRI scan and lateral radiograph. The knees were classified according to the four-type classification system described by Dejour et al. Twenty cases of type A (mild trochlear dysplasia); 20 cases of type B, C, and D (severe trochlear dysplasia); and 20 cases of normal type were selected and divided into normal group (normal trochlea), mild group (type A), and severe group (type B, type C, type D). Tibial tubercle-trochlear groove distance (TT-TG), tibial tubercle-posterior cruciate ligament distance (TT-PCL), and the Dejour classification of trochlear dysplasia were assessed by 2 experienced orthopedics. The reliability of TT-TG distance and TT-PCL distance was tested by intraclass correlation coefficients (ICCs). Results Comparing the differences between TT-TG and TT-PCL in the normal, mild, and severe groups, the TT-TG and TT-PCL in the mild and severe groups show different meanings (normal, 8.83 ± 3.62 mm vs. 8.44 ± 4.57 mm, P > 0.05; mild, 17.30 ± 4.81 mm vs. 20.09 ± 5.05 mm, P < 0.05; severe, 10.79 ± 4.24 mm vs. 12.31 ± 5.43 mm, P > 0.05). The Pearson correlation coefficient of TT-TG and TT-PCL measurements of trochlear dysplasia were r = 0.480 (mild group, P = 0.032) and r = 0.585 (severe group, P < 0.001). The intra-observer ICCs of TT-TG were r = 0.814 (mild group) and r = 0.739 (severe group). The inter-observer ICCs of TT-TG were r = 0.810 (mild group) and r = 0.713 (severe group). In the normal knee, the Pearson correlation coefficient of TT-TG and TT-PCL was r = 0.787(P < 0.001), the intra-observer ICC of TT-TG was r = 0.989, and the inter-observer ICC of TT-TG was r = 0.978. Conclusion Compared with the mild trochlear dysplasia, the inter-observer and intra-observer correlations of TT-TG measurements decreased in the group of severe dysplastic trochlea (inter-observer ICC, 0.810 vs. 0.713; intra-observer ICC, 0.814 vs. 0.739). In the present study, the determination of TT-TG and TT-PCL distance are of great significance for patients with low-grade trochlear dysplasia. And TT-PCL, without referring to the abnormal trochlear groove, is an effective indicator to measure the lateralization of tibial tuberosity in patients with severe dysplastic trochlea.

scholarly journals MPFL reconstruction and tibial tuberosity transposition in patients with patellar instability: May it troubleshots also trochlear dysplasia?

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
A. Castelli ◽  
E. Jannelli ◽  
E. Ferranti Calderoni ◽  
G. Galanzino ◽  
A. Ivone ◽  
...  
Keyword(s):  
Patellar Instability ◽  
Trochlear Dysplasia ◽  
Functional Results ◽  
Activity Level ◽  
Tibial Tuberosity ◽  
Mpfl Reconstruction ◽  
Trochlear Groove ◽  
Patellar Tilt ◽  
Sulcus Angle

Abstract Purpose This study aimed to highlight short- and medium-term outcomes of combined medial patello-femoral ligament (MPFL) reconstruction and anterior tibial tuberosity (ATT) transposition surgery in patients with recurrent patellar instability and different degrees of trochlear dysplasia. Methods Between January 2014 and May 2019, 25 patients with patellar instability underwent a surgical procedure combining the lowering/transposition of the ATT and the MPFL reconstruction. Each patient were preoperative assessed by Kujala score, International Knee Documentation Committee (IKDC), Tegner activity level scale. The assessment of instability predisposing factors was carried out with patellar height, tibial tuberosity-trochlear groove (TT-TG) distance, trochlear dysplasia, sulcus angle, patellar tilt and MPFL injuries. Functional outcomes were evaluated with Kujala, IKDC and Tegner scores at 3, 6 and 12 months after surgery. Results The average age of the patients was 20 years (range 13–43 years). Pre- operative Caton–Deschamps index was pathological in 10 (40%). Sulcus angle was elevated in 13 patients (52%) and TT-TG distance was irregular in 17 patients (68%). Trochlear dysplasia was present in 13 patients (9 type A, 3 type B, 1 type C according to Dejour’s Classification). No re-dislocation occurred during the follow-up. There was a significant increase in the Kujala, IKDC and Lysholm scores after 3, 6 and 12 months, and the results were compared for the different follow-up times and patient’s trochlear dysplasia degree. Conclusion This prospective observational longitudinal study identified good clinical outcomes in patients who underwent MPFL reconstruction and ATT transposition for patellar instability. Finally, the different risk factors for patellar instability examined, particularly the presence of trochlear dysplasia, did not significantly influence the final functional results, which range from good to excellent without re-dislocation episodes.

scholarly journals Accuracy of Tibial Tuberosity-Trochlear Groove Distance, Tibial Tuberosity-Posterior Cruciate Ligament Distance In Terms of The Severeity of Trochlear Dysplasia

2021 ◽  
Author(s):  
Conglei Dong ◽  
Chao Zhao ◽  
Ming Li ◽  
Chongyi Fan ◽  
Xunkai Feng ◽  
...  
Keyword(s):  
Trochlear Dysplasia ◽  
Cruciate Ligament ◽  
Pearson Correlation ◽  
Tibial Tuberosity ◽  
Tibial Tubercle ◽  
Trochlear Groove ◽  
Pearson Correlation Coefficient ◽  
Type B ◽  
Group Type ◽  
Severe Group

Abstract Purpose Increased Tibial Tubercle-Trochlear Groove Distance (TT-TG) was proposed as one of the main risk factors for patellofemoral instability (PFI). The increased TT-TG distance indicated externalization of the tibial tubercle with the reference of the trochlear groove. However, in the case of severe trochlear dysplasia, the reference point on the trochlear groove was indistinct, and the accuracy of TT-TG was controversial. The purpose of this study was to evaluate the accuracy of TT-TG and TT-PCL in consideration of the mild and sereve trochlear dysplasia . Methods From 2015 to 2020, MRI findings of consecutive knee joints with PFI symptoms diagnosed in our hospital was retrospectively analyzed. All knees with trochlear dysplasia were diagnosed by longitudinal MRI scan and lateral radiograph. The knees were classified according to the four-type classification system described by Dejour et al. 20 cases of type A (mild trochlear dysplasia), 20 cases of type B, C, and D (severe trochlear dysplasia), and 20 cases of normal type were selected and divided into normal group (normal trohlea), mild group (type A) and severe group (type B, type C, type D). Tibial Tubercle-Trochlear Groove Distance (TT-TG), Tibial Tubercle-Posterior Cruciate Ligament Distance (TT-PCL), and the Dejour classification of trochlear dysplasia was assessed by 2 experience orthopaedics. The the reliability of TT-TG diatance and TT-PCL distance was tested by intraclass correlation coefficients (ICC).Results Comparing the differences between TT-TG and TT-PCL in the normal, mild and severe groups, the TT-TG and TT-PCL in the mild and severe group show different meanings. (normal, 8.83±3.62 mm vs. 8.44±4.57mm, P>0.05；mild, 17.30±4.81 mm vs. 20.09±5.05mm, P<0.05；severe, 10.79±4.24 mm vs. 12.31±5.43mm, P>0.05). The Pearson correlation coefficient of TT-TG and TT-PCL measurements of trochlear dysplasia were r=0.480 (mild group, P=0.032), r=0.585 (severe group, P<0.001). The Intra-observer ICC of TT-TG were r=0.814 (mild group), r=0.739 (severe group). The Inter-observer ICC of TT-TG were r=0.810 (mild group), r=0.713 (severe group). In the normal knee, the Pearson correlation coefficient of TT-TG and TT-PCL was r=0.787(P<0.001), the Intra-observer ICC of TT-TG was r=0.989, and the Inter-observer ICC of TT-TG was r=0.978. Conclusion Compared with the mild trchlear dysplasia, the inter-observer and intra-observer correlations of TT-TG measurements decreased in group of sereve dysplastic trochlea (Inter-observer ICC, 0.810 vs. 0.713; Intra-observer ICC , 0.814 vs. 0.739). In the present study, the determination of TT-TG and TT-PCL distance are of great significance for patients with low grade trochlear dysplasia. And TT-PCL, without referring to the abnormal trochlear groove, is an effective indicator to measure the lateraltization of tibial tuberosity in patients with sereve dysplastic trochlea.

scholarly journals Patellofemoral Kinematics and Tibial Tuberosity–Trochlear Groove Distances in Female Adolescents With Patellofemoral Pain

2016 ◽  
Vol 45 (5) ◽  
pp. 1102-1109 ◽  
Author(s):  
Victor R. Carlson ◽  
Barry P. Boden ◽  
Frances T. Sheehan
Keyword(s):  
Athletic Training ◽  
Lateral Displacement ◽  
Patellofemoral Pain ◽  
Female Adolescent ◽  
Tibial Tuberosity ◽  
Female Adolescents ◽  
Patellar Tracking ◽  
Trochlear Groove ◽  
Control Cohort ◽  
Patellofemoral Kinematics

Background: Patellofemoral pain (PFP) is a prevalent disorder among female adolescents. Overuse is frequently cited as the cause of pain for this population. What is currently unclear, however, is if the patella demonstrates abnormal tracking patterns relative to the femoral trochlear groove in female adolescents with PFP. Purpose: The aim of this case-control study was to determine if abnormal patellar tracking patterns are present in female adolescents with PFP. The secondary aim was to identify if an increased tibial tuberosity–trochlear groove (TT-TG) distance is associated with the observed kinematic patterns. Study Design: Controlled laboratory study. Methods: Twenty female adolescent knees from 12 patients with PFP and 20 age-matched female knees from 13 healthy controls were recruited for this study. Patellofemoral kinematics (eg, lateral patellar displacement) during a repetitive knee extension-flexion maneuver was quantified by dynamic cine phase-contrast magnetic resonance imaging (MRI). Static MRI scans were used to determine the TT-TG distance. Results: Relative to the control cohort, female adolescents with PFP demonstrated significantly greater lateral displacement at 10° (3.2 mm; P < .001), 20° (2.3 mm; P < .001), and 30° (1.7 mm; P = .014) of knee flexion. A subgroup within this cohort (7 knees from 5 patients) demonstrated extreme lateral maltracking >2 SDs of the mean of the control cohort. This subgroup also demonstrated a greater TT-TG distance relative to the controls (Δ = 4.2 mm; P = .001). Conclusion: This study demonstrates abnormal lateral patellar displacement in the absence of patellar tilt in female adolescents with PFP. Because all adolescents from both cohorts participated in impact sports, it appears that rigorous athletic training alone is inadequate to produce symptoms in this population. Rather, PFP may derive from a combination of physical activity in the context of pathological kinematics. Clinical Relevance: Abnormal patellar tracking patterns and abnormal static alignment have been shown to contribute to the etiology of patellofemoral pain in adults. This study demonstrates that pathologic patellar tracking patterns are present in adolescent females with patellofemoral pain.

FULL WEIGHT BEARING KINEMATIC MRI STUDY OF TT-TG DISTANCE: COMPARING PATIENTS WITH PATELLOFEMORAL PAIN TO HEALTHY INDIVIDUALS

2015 ◽  
Vol 21 (4.1) ◽  
pp. 638-642
Author(s):  
Andrius Brazaitis ◽  
Algirdas Tamosiunas ◽  
Janina Tutkuviene
Keyword(s):  
Patellar Instability ◽  
Weight Bearing ◽  
Patellofemoral Pain ◽  
Full Weight Bearing ◽  
Trochlear Groove ◽  
Patellar Tilt ◽  
Full Extension ◽  
Low Degrees ◽  
Mri Study ◽  
Kinematic Magnetic Resonance Imaging

Purpose. The aim of the present study was to investigate tibial tuberosity-trochlear groove (TT-TG) distance dynamics in patients with patellofemoral pain (PFP) and pain free individuals by using full weight bearing kinematic magnetic resonance imaging (MRI) And correlation with patellar instability. Materials and methods. 51 female individuals with PFP and 26 pain free female individuals participated in the study. The kinematic MRI was performed with 1,5 T MRI unit and full-weight bearing. TT-TG distance, bissect offset (BSO) and patellar tilt angle (PTA) were measured in steps of 10° between 50° of flexion to full extension. Results. The TT–TG was higher in PFP patients compared to volunteers’ from 40° to full extension. This difference was statistically significant (p<0.01). PFP patients demonstrated statistically significantly greater TT-TG distance increase from 30° to full extension. BSO and PTA were moderately correlated to TT-TG from 20° of flexion to full extension. Conclusion. TT-TG distance is dynamic and increases significantly during extension in patients with PFP and pain free individuals, depending on knee flexion angle. It shows different pattern of dynamics in PFP group. TT-TG distance is associated with patellar instability (BSO and PTA) at low degrees of flexion.

Clinical Comparison of Medial Patellofemoral Ligament Reconstruction With or Without Tibial Tuberosity Transfer for Recurrent Patellar Instability

2021 ◽  
pp. 036354652110377
Author(s):  
Jong-Min Kim ◽  
Jae-Ang Sim ◽  
HongYeol Yang ◽  
Young-Mo Kim ◽  
Joon-Ho Wang ◽  
...  
Keyword(s):  
Clinical Outcomes ◽  
Patellar Instability ◽  
Medial Patellofemoral Ligament ◽  
Tibial Tuberosity ◽  
Mpfl Reconstruction ◽  
Trochlear Groove ◽  
Functional Failure ◽  
Radiological Parameters ◽  
Recurrent Patellar Instability

Background: No clear guidelines or widespread consensus has defined a threshold value of tibial tuberosity–trochlear groove (TT-TG) distance for choosing the appropriate surgical procedures when additional tibial tuberosity osteotomy (TTO) should be added to augment medial patellofemoral ligament (MPFL) reconstruction for recurrent patellar instability. Purpose: To compare the clinical outcomes between MPFL reconstruction and MPFL reconstruction with TTO for patients who have patellar instability with a TT-TG distance of 15 to 25 mm. Study Design: Cohort study; Level of evidence, 3. Methods: We retrospectively analyzed 81 patients who underwent surgical treatment using either MPFL reconstruction or MPFL reconstruction with TTO for recurrent patellar instability with a TT-TG distance of 15 to 25 mm; the mean follow-up was 25.2 months (range, 12.0-53.0 months). The patients were divided into 2 groups: isolated MPFL reconstruction (iMPFL group; n = 36) performed by 2 surgeons and MPFL reconstruction with TTO (TTO group; n = 45) performed by another 2 surgeons. Clinical outcomes were assessed using the Kujala score, Knee injury and Osteoarthritis Outcome Score, and Tegner activity score. Radiological parameters, including patellar height, TT-TG distance, patellar tilt, and congruence angle were compared between the 2 groups. Functional failure based on clinical apprehension sign, repeat subluxation or dislocation, and subjective instability and complications was assessed at the final follow-up. We also compared clinical outcomes based on subgroups of preoperative TT-TG distance (15 mm ≤ TT-TG ≤ 20 mm vs 20 mm < TT-TG ≤ 25 mm). Results: All of the clinical outcome parameters significantly improved in both groups at the final follow-up ( P < .001), with no significant differences between groups. The radiological parameters also showed no significant differences between the 2 groups. The incidence of functional failure was similar between the 2 groups (3 failures in the TTO group and 2 failures in the iMPFL group; P = .42). In the TTO group, 1 patient experienced a repeat dislocation postoperatively and 2 patients had subjective instability; in the iMPFL group, 2 patients had subjective instability. The prevalence of complications did not differ between the 2 groups ( P = .410). In the subgroup analysis based on TT-TG distance, we did not note any differences in clinical outcomes between iMPFL and TTO groups in subgroups of 15 mm ≤ TT-TG ≤ 20 mm and 20 mm < TT-TG ≤ 25 mm. Conclusion: MPFL reconstruction with and without TTO provided similar, satisfactory clinical outcomes and low redislocation rates for patients who had patellar instability with a TT-TG distance of 15 to 25 mm, without statistical difference. Thus, our findings suggest that iMPFL reconstruction is a safe and reliable treatment for patients with recurrent patellar dislocation with a TT-TG distance of 15 to 25 mm, without the disadvantages derived from TTO.

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