Tibial Tuberosity To Trochlear Groove Research Articles

The tibial tubercle-to-trochlear groove distance changes in standing weight-bearing condition: An upright weight-bearing computed tomography analysis

BackgroundThe tibial tubercle-to-trochlear groove (TT-TG) distance and Insall-Salvati (I/S) ratio are widely used to determine the need for distal realignment in conjunction with medial patellofemoral ligament (MPFL) reconstruction in patients with recurrent patellar dislocation. A TT-TG distance >20 mm and an I/S ratio >1.3 are significant anatomical risk factors for patellar instability. However, these parameters have traditionally been measured using non-weight-bearing (NWB) imaging modalities. As patellar dislocation occurs during weight-bearing actions, these two parameters should be measured under weight-bearing conditions. Thus, this study aimed to measure the TT-TG distance and I/S ratio using upright full-weight-bearing (FWB) computed tomography (CT) scans and compare the data with NWB CT scans. MethodsThis study included 49 knee joints of 26 healthy volunteers. CT images were obtained under both FWB and NWB standing conditions using a 320-detector row upright CT scanner. TT-TGs in the axial plane and I/S ratios in the sagittal plane were measured and compared. ResultsThe average FWB TT-TG distance was 20.3 ± 3.9 mm, whereas the average NWB TT-TG distance was 12.3 ± 4.7 mm. The TT-TG level was significantly higher in the FWB condition than that in the NWB condition (P < 0.001). The I/S ratios were comparable between the FWB and NWB conditions (P = 0.29). ConclusionsThe TT-TG distance in the standing weight-bearing condition was larger than the conventional TT-TG distance and surpassed the historical cutoff value of TT-TG, which may affect the indication of additional distal realignment in MPFL reconstruction for patellar instability.

Measurement of TT-TG can change with sequential MRIs due to variations in tibiofemoral rotation in patellofemoral instability patients.

There are various anatomic risk factors for patellofemoral instability (PFI) that help guide surgical treatment, including the tibial tubercle to trochlear groove (TT-TG) distance. However, no study has analysed the temporal changes in TT-TG prior to surgical intervention. This study sought to understand the variations in TT-TG over time for pediatric patients suffering from PFI prior to surgical intervention. The authors hypothesised that the TT-TG would substantially change between time points. Patients undergoing medial patellofemoral ligament (MPFL) reconstruction between 2014 and 2019 by one of two fellowship-trained orthopaedic surgeons were identified. Patients were included if they had two preoperative magnetic resonance imaging (MRI) performed on the same knee within 7.5 months of each other prior to any surgical intervention and had an initial TT-TG greater than 10 mm. After considering 251 patients for inclusion, 21 patients met the final inclusion criteria. The mean age was 14.5 ± 2.5 years and 61.9% were female. TT-TG was initially noted to be 15.1 ± 1.8 mm. At mean time aftersequential MRIs of 5.0 ± 1.9 months, TT-TG was noted to be 16.7 ± 3.2 mm. The differences between initial and subsequent TT-TG ranged from a 21.2% decrease to a 61.1% increase, with a mean difference of an 11.3% increase. Comparison between initial and subsequent TT-TG values demonstrated a significant difference (p = 0.017). Change in tibiofemoral rotation ranged from -9.2° to 7.5°. When comparing the change in TT-TG to change in tibiofemoral rotation, a significant correlation was found (p = 0.019). Despite only a mean time between MRIs of 5 months, variations in TT-TG ranged from a decrease of 21.2% to an increase of 61.1%. The significant relationship between the changes in TT-TG and changes in tibiofemoral rotation between MRIs suggest that TT-TG measurements may vary due to variations in tibiofemoral rotation at the time of individual MRIs. Level IV.

Poster 285: MRI Measurement of TT-TG Can Change Without Intervention: An Analysis of Sequential Pre-Operative MRIs in PFI patients

Objectives: Following a patella dislocation event, the patella can remain unstable, leading to patellofemoral instability (PI). There are various anatomic risk factors for PI that help guide surgical treatment including the tibial tubercle to trochlear groove (TT-TG) distance. However, to the authors knowledge, no study has analyzed the temporal changes in TT-TG prior to any surgical intervention. This study, therefore, sought to understand the variations in TT-TG for pediatric patients suffering from patellar instability prior to any surgical intervention. The authors hypothesized that the TT-TG would not substantially change between timepoints. Methods: Patients undergoing medial patellofemoral ligament (MPFL) reconstruction using CPT code 27427 between January 1, 2014 and December 31, 2019 by one of two orthopedic surgeons were identified. Patients were included if they 1) had two pre-operative MRIs performed of the same knee within 8 months of each other prior to any surgical intervention and 2) had an initial TT-TG between 10 mm and 20 mm. Exclusion criteria were previous ipsilateral knee surgery or planned MPFL reconstruction with tibial tubercle osteotomy. Initial and subsequent TT-TG measurements were compared using paired-samples t-tests with two-tailed statistical significance set at p ≤0.05. IBM SPSS Statistics version 22 (Armonk, NY) was used for all statistical analysis. Results: After considering 251 patients for inclusion, 26 patients met inclusion criteria and were analyzed. Mean age of the cohort was 14.5±2.4 years and 42.3% were male. TT-TG was initially noted to be 15.3±1.8 mm. At mean time between sequential MRI’s of 4.8±1.9 months, TT-TG was noted to be 17.1±3.5 mm. The differences between initial and subsequent TT-TG ranged from a 21% decrease to a 61% increase, with a mean difference of a 12.1% increase. Comparison between initial and subsequent TT-TG values demonstrated a significant difference (p=0.006). Conclusions: At a mean time between MRIs of 4.8 months, variations in TT-TG ranged from a decrease of 21% to an increase of 61%. These findings suggest that TT-TG measurements may vary in patients on sequential MRIs and could be due to variations in tibiofemoral rotation during imaging. Surgeons should be aware of these variations when planning surgical correction for patellar instability. [Table: see text]

Poster 141: Does the Traditional TT-TG Distance Accurately Reflect the Relative Position of the Tibial Tubercle to the Trochlear Groove? A Three-Dimensional Analysis

Objectives: The tibial tubercle to trochlear groove (TT-TG) distance often guides surgical decision- making for patellar instability. Traditional TT-TG measurements are limited by interrater reliability and lack of consideration for variable anatomy throughout flexion. The purpose of this study was to compare the traditional TT-TG measurement to three-dimensional measures generated from automated trochlear groove detection with sequential radial slices on magnetic resonance imaging (MRI). Methods: Twenty-four knees (4 healthy controls, 20 patellar instability patients) were segmented into three-dimensional distal femur and tibia models. A custom-designed program was employed to detect the trochlear groove through its course based on the shortest distance to the origin in a polar (radial) axis defined by the distal femoral condyles. The program also identified the surface projection of the tibial tubercle center of mass. The medial-lateral distance between the trochlear groove and tibial tubercle was calculated for the first 45 degrees of the detected groove to generate radial TT-TG (rTT-TG) values. The mean and maximum rTT-TG values were compared to the traditional TT-TG MRI measurement performed by one grader. Results: Mean rTT-TG values were significantly greater than traditional measurements (21.8 mm versus 17.9 mm, p=.003) with moderate correlation between measurements (Pearson r = 0.59, p=.002). In Dejour C and D dysplasia, the mean rTT-TG measurements trended towards being greater than traditional measurements (C: 24.3 mm versus 16.6 mm; D: 28.5 mm versus 21.8 mm; p=0.057 for both comparisons). Dejour C dysplasia demonstrated a significantly greater maximum rTT-TG than the traditional measurement (27.9 mm versus 16.6 mm, p=0.029), and Dejour D dysplasia demonstrated a similar trend (30.2 mm versus 21.8 mm; p=0.057). Conclusions: Traditional TT-TG distances may underestimate the true medial-lateral offset between trochlear groove and tibial tubercle, particularly in patients with high- grade dysplasia. This represents a potential alternative to the current standard measurement techniques which may improve measurement reliability by automation. Our study suggests that utilizing 3D radial TT-TG values via automated measurement may more accurately portray the variable anatomy of the trochlear entrance and offer a standardized alternative to a frequently used measurement to overcome reader reliability.

Poster 296: Incidence and Risk Factors for Contralateral Patellofemoral Instability

Objectives: Background: Patellofemoral joint instability is common in young athletes and often requires surgical intervention. Incidence and risk factors for ipsilateral instability recurrence have been more discussed in the literature than contralateral instability events. Purpose: To evaluate the incidence and risk factors for contralateral patellofemoral instability in patients who have undergone patellar stabilization surgery. Methods: This retrospective study included 543 patients who had undergone medial patellofemoral ligament reconstruction and/or Fulkerson osteotomy as surgical management for lateral patellofemoral instability. The medical records of these patients were examined to evaluate the non-surgical knee. Available imaging of each affected knee was examined to evaluate for patella alta, skeletal maturity, trochlear dysplasia, tibial tubercle to trochlear groove (TT-TG) distance, and tibial tubercle to posterior collateral ligament (TT-PCL) distance. Demographic factors such as BMI, age, and sex were also examined. A second arm was done excluding patients with previous history of bilateral instability, assessing risk factors using the same methods. This yielded information about incidence and risk factors of “new onset” contralateral instability post-stabilization surgery. Results: Of the 543 patients examined, 205 (37.8%) had evidence of contralateral instability. Patella alta (OR, 2.4), skeletal immaturity (OR, 2.67), and younger age (p&lt;0.0001) were associated with increased risk of bilateral instability. Sex, BMI, TT-TG distance, and TT-PCL distance, and trochlear dysplasia were not associated with increased risk of bilateral instability. In the second study, 63 out of 401 (15.71%) of patients had evidence of new onset contralateral instability post-surgery. Skeletal immaturity (OR, 3.65) was found to be associated with increased risk of instability. Conclusions: The incidence of bilateral patellofemoral instability was found to be 37.8%. Lower age, skeletal immaturity, and patella alta were found to be associated with increased risk of bilateral instability. Incidence of new-onset contralateral instability was found to be 15.71% and was only associated with skeletal immaturity.

Poster 139: Utilization of 3D Statistical Shape Modeling of Anatomic Variation Across a Cohort of Patella Instability Patients

Poster 139: Utilization of 3D Statistical Shape Modeling of Anatomic Variation Across a Cohort of Patella Instability Patients

In Vivo Length Changes Between the Attachments of the Medial Patellofemoral Complex Fibers in Knees With Anatomic Risk Factors for Patellar Instability

Background: Medial patellofemoral complex (MPFC) reconstruction plays an important role in the surgical treatment of patellar instability. Anatomic reconstruction is critical in re-creating the native function of the ligament, which includes minimizing length changes that occur in early flexion. Anatomic risk factors for patellar instability such as trochlear dysplasia, patella alta, and increased tibial tuberosity to trochlear groove (TT-TG) distance have been shown to influence the function of the MPFC graft in cadaveric studies, but the native length change patterns of the MPFC fibers in knees with anatomic risk factors have not been described. Purpose: To describe the in vivo length changes of the MPFC fibers in knees with anatomic risk factors for patellar instability and identify the optimal attachment sites for MPFC reconstruction. Study Design: Controlled laboratory study. Methods: Dynamic computed tomography imaging was performed on the asymptomatic knee in patients with contralateral patellar instability. Three-dimensional digital knee models were created to assess knees between 0° and 50° of flexion in 10° increments. MPFC fiber lengths were calculated at each flexion angle between known anatomic attachment points on the extensor mechanism (quadriceps tendon, MPFC midpoint [M], and patella) and femur (1, 2, and 3, representing the proximal to distal femoral footprint). Changes in MPFC fiber length were compared for each condition and assessed for their relationships to morphologic risk factors (trochlear depth, Caton Deschamps Index [CDI], and TT-TG distance). Results: In 22 knees, native MPFC fibers were found to be longer at 0° than at 20° to 50° of flexion. Length changes observed between 0° and 50° increased with the number of risk factors present. In the central fibers of the MPFC (M-2), 1.7% ± 3.1% length change was noted in knees with no anatomic risk factors, which increased to 5.6% ± 4.6%, 17.0% ± 6.4%, and 26.7% ± 6.8% in the setting of 1, 2, and 3 risk factors, respectively. Nonanatomic patella-based attachments were more likely to demonstrate unfavorable length change patterns, in which length was greater at 50° than 0°. In patellar attachments, an independent relationship was found between increasing length changes and TT-TG distance, while in quadriceps tendon attachments, a trend toward a negative relationship between length changes and CDI was noted. All configurations demonstrated a strong relationship between percentage change in length and number of morphologic risk factors present, with the greatest influence found in patella-based attachments. Conclusion: The MPFC fibers demonstrated increased length changes in knees when a greater number of morphological risk factors for patellar instability were present, which worsened in the setting of nonanatomic configurations. This suggests that the function of the intact MPFC in patients with anatomic risk factors may not reflect previously described findings in anatomically normal knees. Further studies are needed to understand the pathoanatomy related to these changes, as well as the implications for graft placement and assessment of length changes during MPFC reconstruction techniques. Clinical Relevance: MPFC length change patterns vary based on the number of morphologic risk factors for patellar instability present and should be considered during reconstructive procedures.

Patellofemoral Instability in the Pediatric Population.

This review focuses on the etiology, diagnosis, and management of patellar instability in pediatric patients. Radiological outcomes such as tibial-tubercle to trochlear groove (TT-TG) distance used in diagnosis are subject to factors of influence such as femoral anteversion and knee flexion angle, and new measure such as tibial-tubercle to posterior cruciate ligament distance as well as TT-TG/trochlear width (TT-TG/TW) are under investigation. To prevent recurrent instability, surgical intervention for acute patellar dislocations may be advantageous compared to conservative management. Patellar instability is a common pathology found in pediatric cohorts. Diagnosis can be performed via a combination of history, physical examination maneuvers, and radiological risk factors such as patella alta, patellar tilt, trochlear dysplasia, and elevated TT-TG distances. Current literature advocates the usage of additional radiological measures to TT-TG such as TT-TG/TW, especially as TT-TG varies with age in younger patients. Recent literature potentially suggests the utilization of surgical procedures such as MPFL reconstruction or repair for acute dislocations in the hope of preventing recurrent instability. Special indications for pediatric patients include osteochondral fracture identification to help prevent patellofemoral osteoarthritis. A comprehensive workup and understanding of current literature can aid clinicians in aiming to prevent recurrent patellar dislocation in pediatric patients.

Concomitant anterior medializing osteotomy and MPFL reconstruction improves patellar tilt when compared to MPFL reconstruction alone.

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). 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 2years) and pre-operative TT-TG distance (within 2mm) to a comparison cohort of patients who underwent isolated MPFLR (iMPFLR) without osseous procedures. A total of 56 patients were analyzed (28 per group). The mean age of the cohort was 15.5 ± 2.0years and was similar between both groups (15.9 ± 1.9 versus 15.1 ± 2.0years [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). 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. III.

Lateral Patellar Instability.

Patellar instability represents a common problem with an evolving understanding and multifactorial pathoetiology. Treatment plans should be based on the identification of contributing anatomical factors and tailored to each individual patient. Risks for recurrent instability are dependent on several patient-specific factors including patella alta, increased tibial tubercle-to-trochlear groove (TT-TG) distance, trochlear dysplasia, younger skeletal age, and ligamentous laxity. Cartilage or osteochondral lesions and/or fractures are commonly observed in first-time patellar dislocation, and magnetic resonance imaging (MRI) should be strongly considered. Advanced imaging modalities, such as computed tomography (CT) or MRI, should also be obtained preoperatively to identify predisposing factors and guide surgical treatment. Medial patellofemoral ligament (MPFL) reconstruction with anatomical femoral tunnel positioning is associated with lower recurrence rates compared with MPFL repair and has become a common and successful reconstructive surgical option in cases of instability. Lateral retinacular tightness can be addressed with lateral retinacular release or lengthening, but these procedures should not be performed in isolation. Tibial tubercle osteotomy is a powerful reconstructive tool in the setting of underlying skeletal risk factors for instability and can be of particular benefit in the presence of increased TT-TG distance (>20 mm), and/or in the setting of patella alta. The indications for trochleoplasty are still developing along with the clinical evidence, but trochleoplasty may be indicated in some cases of severe trochlear dysplasia. Several surgical techniques have indications in specific clinical scenarios and populations, and indications, risks, and benefits to each are progressing with our understanding. Combined femoral derotational osteotomy and MPFL reconstruction can be considered for patients with a femoral anteversion angle of >30° to improve patient outcomes and reduce recurrence rates.

Tibial Tubercle Osteotomy With Concomitant Medial Patellofemoral Ligament Reconstruction

Background: Patellofemoral anatomy allows for substantial freedom of motion. Medial patellofemoral ligament (MPFL) tears occur in up to 96% of lateral patellar dislocations. Risk factors for subsequent instability include maltracking and increased tibial tubercle to trochlear groove (TT-TG) distance. Indication: Medial patellofemoral ligament reconstruction (MPFLR) with concurrent tibial tubercle osteotomy (TTO) is indicated in patients with recurrent dislocation or unresolved apprehension. Concurrent TTO should be considered for TT-TGs 15-20 mm depending on overall clinical picture and risk factors. We strongly consider TTO for TT-TGs ≥20 mm and for revision procedures. Technique Description: Following diagnostic arthroscopy, a midline incision is made from the inferior patellar pole to 3 cm beyond the tibial tubercle. The anterior compartment is incised and retracted laterally. An osteotomy guide is affixed to the tibia and an osteotomy cut is made with a saw, leaving a small bridge of periosteum distally. The osteotomy is competed proximally with osteotomes, then medialized and held in place with two 4.5-mm screws. An incision is made on the superomedial patella and two 0.045 inch guidewires are placed at the MPFL insertion and overdrilled with a 3.5-mm drill. A 22-cm semitendinosus allograft is prepared and fixed to the patella using two 3.5-mm anchors. An incision is made over the medial epicondyle and a 2.4-mm beath pin is placed at Schöttle point. Isometry is confirmed and the pin is overdrilled with a 6-mm reamer. The allograft is passed just superficial to capsule from the peripatellar incision to the medial incision, docked into the femur, and secured with a 6-mm interference screw at 30° of flexion after confirmation of appropriate graft length. Results: Studies have demonstrated improved outcomes for patients undergoing MPFLR + TTO compared with isolated MPFL in the setting of maltracking and increased TT-TG distance. In addition, a recent meta-analysis demonstrated no negative effect of concurrent TTO on return to sport timeline. Discussion/Conclusion: MPFLR with concurrent TTO is effective, with surgical correction of underlying maltracking and satisfactory return to sport. Consideration to MPFL + TTO should be given to patients with recurrent instability and pathologically increased TT-TG. The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Patellar dislocation recurrence after pediatric MPFL reconstruction: Bone tunnels and soft tissues versus suture anchors and interference screw

BackgroundSeveral Medial Patellofemoral Ligament (MPFL) reconstruction techniques have been developed, and those with soft tissue fixation are often preferred in children because they allow the growth cartilage to be preserved. Nevertheless, the recurrence rate of patellar dislocation varies widely from one series to another, with no clear superiority of one technique in the pediatric setting. The objectives of this study were to compare the results of two tendon graft fixation techniques (tendon-tendon fixation and anchor-screw fixation) by analyzing: 1) the rate of patellar dislocation recurrence, 2) clinical outcomes, 3) tourniquet time and 4) complication rate. HypothesisThe two tendon graft fixation techniques used in MPFL reconstruction are equivalent in terms of the patellar dislocation recurrence rate. Patients and methodsThis is a retrospective comparative study including 57 patients with a median age of 14 years (12–15 years) who underwent MPFL reconstruction between 2016 and 2020. The tendon graft was fixed upon itself, after passing through a patellar tunnel (Group A: tendon-tendon fixation; n=29) or by two anchors and an interference screw (Group B: anchor-screw fixation; n=28). The preoperative radiographic data were comparable in the two groups: patellar height [A: 1.3 (interquartile range (IQR): 1.2–1.4) / B: 1.2 (IQR: 1–1.4) (p=0.21)], tibial tuberosity to trochlear groove (TTTG) distance [A: 16 (IQR: 13–19) / B: 13.5 (IQR: 11.5–18.8) (p=0.12)], patellar tilt [A: 25 (IQR: 20–35) / B: 24.5 (IQR: 21–32) (p=0.93)]. For each technique, the rate of patellar dislocation recurrence, clinical and functional results (Kujala score, Marx activity score, Lille patellofemoral score), complications (pain, stiffness, revision) were analyzed. In addition to MPFL repair, 13 patients (2 in Group A, 11 in Group B) underwent additional orthopedic procedures to enhance patellar stability. Resultsno patients were lost to follow-up and the median follow-up was 30 months (IQR: 20–38). The dislocation recurrence rate was higher in Group A, 6.9% (2/29) compared to none in Group B. The clinical results were comparable for the two groups with a Kujala score [A: 94 (IQR: 89–100) / B: 92 (IQR: 87.5–94.5) (p=0.12)]; Marx score [A: 10 (IQR: 7–11) / B: 9.5 (IQR: 7.5–12) (p=0.89)] and Lille patellofemoral score [A: 97 (IQR: 91–100) / B: 94 (IQR: 90–98) (p=0.21)]. The tourniquet time was shorter in Group A than in Group B, 61minutes (IQR: 52-71) versus 85minutes (IQR: 55-115) (p=0.024) excluding additional orthopedic procedures. The complication rate was 17.2% (5/29) in Group A (dislocation n=2, stiffness n=2, ATT (anterior tibial tuberosity) revision with screw removal n=1) and 10.7% (3/28) in B (pain n=1, ATT revision with screw removal n=2) (p=0.35). ConclusionClinically, anchor-screw fixation appears to reduce the risk of patellar dislocation recurrence but this could not be statistically tested. On the other hand, the two techniques are comparable in terms of the functional results. Level of evidenceIII; retrospective case-control study.

Medial Patellofemoral Ligament Reconstruction

Background: Recurrentlateral patellar dislocation is a devastating condition associated with different pathologies, including medial patellofemoral ligament (MPFL) injury, increased tibial tubercle to trochlear groove (TT-TG) distance, and trochlear dysplasia. This video aims to provide an overview of isolated MPFL reconstruction in a patient with recurrent patellar dislocation and chronic MPFL injury. Indications: Isolated MPFL reconstruction is indicated for patients with recurrent lateral patellar instability following an initial trial of nonoperative management, in the absence of other contributing anatomic factors. Candidates for isolated MPFL reconstruction should have a TT-TG distance of &lt;20 mm, and normal or Dejour type A trochlear morphology. Technique Description: Semitendinosus allograft is used to reconstruct the torn or attenuated MPFL. Following diagnostic arthroscopy, an incision is made over the medial border of the patella and dissection is carried through the skin and subcutaneous tissue to the fascia. Two K-wires are over-drilled and two 3.5-mm Arthrex SwiveLock anchors are placed. The allograft is prepared and whipstitched on both sides. The central portion of the graft is tide down to the anchors. A second incision is then made on the medial side of the knee over the epicondyle. Dissection is carried down to the fascia, and palpation is used to identify Schottles’ point. This is confirmed with fluoroscopy. An 8-mm drill bit is then used to drill to a depth of 60 mm on the femoral side. The grafts are passed one at a time through the femoral tunnel. The femoral side is fixed with an Arthrex BioComposite Interference Screw and the incisions are subsequently irrigated and closed in a layered fashion. Results: MPFL reconstruction demonstrates good functional and clinical outcomes with high rates of patient satisfaction and low rates of failure. A recent systematic review demonstrated an 84% rate of return to sport, improved postoperative outcomes, and pooled risks of recurrent instability and reoperation of less than 5% following isolated MPFL reconstruction. Conclusion: Isolated MPFL reconstruction should be considered for patients with recurrent patellar instability in the absence of other clinical risk factors. The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Unpacking the Tibial Tubercle–Trochlear Groove Distance: Evaluation of Rotational Factors, Trochlear Groove and Tibial Tubercle Position, and Role of Trochlear Dysplasia

Background: The tibial tubercle to trochlear groove (TT-TG) distance is often utilized for determining the surgical treatment for patients with patellar instability (PI). It is thought to directly represent the position of the TT on the tibia. Recent work has shown that the measurement of the TT-TG distance is multifactorial. Purpose: To investigate the relationship between relative tibial external rotation (rTER) and trochlear dysplasia (TD), as well as the location of the TG and TT in patients with and without PI, and to correlate these and other anatomic measurements with the TT-TG distance. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 89 patients with PI who underwent magnetic resonance imaging were identified with 92 matched control patients. A standardized measurement protocol on axial magnetic resonance imaging determined rTER, the proximal and distal TG lateralization (pTGL and dTGL, respectively) ratios, and the TT lateralization (TTL) ratio. Other measures of interest included the lateral trochlear inclination angle, sulcus angle, and lateral patellar inclination angle. Univariate regression was used to determine the associations of TD (lateral trochlear inclination angle, sulcus angle) with rTER and the TG position, and multivariate regression was used to model associations among all the variables with the proximal and distal TT-TG distances. Results: rTER was significantly higher in the study group (P < .001), and univariate regression showed a significant association between dysplasia measures and rTER (P < .001). The pTGL ratio was lower in the study group (P = .025), but there was no difference in the dTGL ratio (P = .090) or the TTL ratio (P = .098) between the groups. There were no associations between dysplasia measures and the pTGL and dTGL ratios (P > .05). Multivariate regression showed that the proximal TT-TG distance is predicted by the sulcus angle, pTGL ratio, rTER, and TTL ratio (P < .05) and that the distal TT-TG distance is predicted by the lateral patellar inclination angle, dTGL ratio, sulcus angle, rTER, and TTL ratio (P < .05). Conclusion: rTER had a significant association with TD. The position of the proximal TG was more medial in patients with PI. There was no significant difference in the TTL ratio between patients with and without PI. The TT-TG distance was associated with multiple anatomic measures and was not solely predicated on the position of the TT.

Tibial Tubercle to Trochlear Groove Distance Measured by Posterior Condylar Reference Line on MRI Can Over-Evaluate Lateralization Deformity of Tibial Tubercle in Patients with Recurrent Patellar Dislocation.

Background: The tibial tubercle to trochlear groove (TT-TG) distance is currently considered as an indication for tibial tubercle osteotomy. While the influence of femoral condylar morphology on such measurement remains unclear. Methods: A total of 86 patients with patellar dislocation (PD) and 86 healthy individuals were enrolled. Femoral condylar morphology and the TT-TG distance measured by anatomical transepicondylar axis (TT-TGa), by surgical transepicondylar axis (TT-TGs), and by posterior condylar reference line (TT-TGp) were assessed by MRI. Unpaired t-test, Spearman, and Pearson correlation analysis were conducted. We determined the pathological value of the parameters and established a binary regression model. Results: The interclass correlation coefficients of all the TT-TG distances were greater than 0.75 in all types of trochlear dysplasia. The lateral/posterior femoral condyle was shorter and the medial/posterior condyle was longer in the study group (28.5 ± 3.3 and 35.2 ± 2.8, respectively) than in the control group (30.9 ± 2.7 and 33.5 ± 2.3, respectively). In the study group, the TT-TGp distance was greater than TT-TGs and TT-TGa distance (p < 0.001). The pathological value of the TT-TG distance was 13.0 mm. Each TT-TG distance revealed a significant OR with regard to PD. Conclusion: The TT-TGa, TT-TGs, and TT-TGp distance can be reliably measured by MRI even in patients with trochlear dysplasia. While the TT-TGp distance may overestimate the lateralization deformity of the tibial tubercle. Posterior femoral condylar dysplasia may be a reason for such overestimating. These findings have not been correlated to clinical outcomes and further studies are required.

An MRI-based Study to Investigate If the Patella is Truly Centred between the Femoral Condyles in the Coronal Plane

BackgroundAn AP knee radiograph is considered adequate if the patella is centred between the femoral condyles. Our previous studies demonstrated a tendency for lateral patellar deviation on an AP view orthogonal to the posterior femoral condyles. However, findings were based on cadaveric samples limited by the lack of soft tissue effects on patellar positioning.Materials and methodsAfter excluding those with deformity or damage to osseous or ligamentous structures, 106 knee MRI scans were randomly selected. Patellar centring was calculated as a percentage of total distal femoral intercondylar width and represented how lateral the centre of the patella is located with respect to the midpoint of the femoral condyles. Multiple regression analysis was performed to determine the relationship between patellar centring and age, gender, anatomic lateral distal femoral angle (aLDFA), medial proximal tibial angle (MPTA) and tibial tuberosity to trochlear groove (TT-TG) distance.ResultsThere were 35 males and 71 females included in the study with a mean age of 29 ± 14 years. Mean patellar centring was 8 ± 4%. There was a statistically significant correlation between TT-TG distance and positive (lateral) patellar centring (standardised β = 0.36, p <0.01). There were no associations between aLDFA and MPTA with patellar centring.ConclusionThis study demonstrates that the patella is rarely perfectly centred and is usually positioned slightly laterally within the femoral condyles in an AP view orthogonal to the posterior aspect of the femoral condyles. The use of supine MRI scans makes this data relevant to a patient on the operating room table.How to cite this articleShah NS, Kyriakedes JC, Liu RW. An MRI-based Study to Investigate If the Patella is Truly Centred between the Femoral Condyles in the Coronal Plane. Strategies Trauma Limb Reconstr 2022;17(2):63–67.

A Case of Patellar Instability and Lateral Facet Cartilage Defect

Background: Concomitant cartilage injury is commonly associated with patellofemoral instability. While nonoperative treatment remains the gold standard for first time dislocators, there has been an increased trend toward addressing patellar instability when symptomatic cartilage disease is present. Indications: A healthy active 29-year-old woman &gt;2 years of patellar instability and pain symptoms in the right knee. Imaging revealed tibial tubercle to trochlear groove (TT-TG) distance of 19.8 mm, and a Caton Deschamps Ratio of 1.54. Initial staging arthroscopy demonstrated a near full thickness cartilage defect of the lateral patellar facet measuring 2x2 cm. Technique Description: In the index procedure, a staging diagnostic arthroscopy is performed to evaluate the extent of the cartilage defect. Given the size of the lesion, a matrix-induced autologous chondrocyte implantation (MACI) biopsy is performed for later implantation. At the second stage procedure, a midline approach to the patella and tibial tubercle is performed. A 45° osteotomy is initiated with a cutting jig. The osteotomy is detached distally to allow for both anteromedialization and distalization to offload the cartilage defect and improve patellar articulation. The lateral patellar facet cartilage defect is prepared, and a combination of fibrin sealant and digital pressure is used to implant the pre-shaped MACI transplant. The osteotomy is then secured with 2 bicortical screws. A semitendinosus allograft is secured to the upper half of the medial border of the patellar and secured to its anatomometric point on the femur to reconstruct the medial patellofemoral ligament (MPFL). Results: Patient successfully returned to running and is currently working on return to other sports with no anterior knee pain or instability. Recent studies have demonstrated overall good clinical outcomes following MACI for patellofemoral lesions. Addressing underlying bony deformity and offloading patellofemoral cartilage lesions with tibial tubercle osteotomy in combination with MPFL reconstruction has improved patellar stability and good patient satisfaction. Discussion/Conclusion: Combined tibial tubercle osteotomy, MPFL reconstruction, and MACI in a comprehensive approach can successfully address symptomatic patellofemoral cartilage disease in the setting of patellar instability with underlying bony abnormalities.

Combined MPFL Reconstruction with Tibial Tubercle Osteotomy and Repair of Patellar Cartilage Defect with Particulated Juvenile Articular Cartilage.

Combined MPFL Reconstruction with Tibial Tubercle Osteotomy and Repair of Patellar Cartilage Defect with Particulated Juvenile Articular Cartilage.

Complex Patellofemoral Reconstruction for Recurrent Instability

Background: Patellofemoral instability is due to a combination of bony and soft tissue factors. While recurrent patellar dislocations are rare, evaluation and treatment of these conditions require addressing patellar height and lateralization of the tibial tubercle (TT), restraint to lateral patellar subluxation, and trochlear dysplasia. Other factors to consider are coronal limb-length alignment outside of the physiologic 5 to 8° of valgus, which may significantly alter the Q angle and contribute to lateral instability. Other ligaments around the patella contribute to soft-tissue restraint, including the medial and lateral patellotibial ligaments, patellomeniscal ligaments, and the medial quadriceps tendon femoral ligament. Patellar tilt is assessed with and without quadriceps contraction to further evaluate the patella’s relationship to the trochlear groove. The Caton-Deschamps Index, as well as patellar trochlear index (PTI), are used to measure patellar height for patella alta or baja. Technique Description: The technique is to surgically manage a patient in neutral mechanical alignment on standing limb radiographs, with moderate-to-severe DeJour type B trochlear dysplasia and a trochlear sulcus angle of around 145°, patella alta with a Caton-Deschamps Index of 1.6 and PTI of 0.22, a TT to trochlear groove (TT-TG) distance of 8 mm, and a deficient medial patellofemoral ligament (MPFL). The MPFL reconstruction is done first, with harvesting of the ipsilateral quadriceps tendon and maintenance of its distal attachment on the superior patellar pole. The quadriceps tendon graft is folded medially upon its distal attachment and fixed in this position with suture anchors. Tibial tubercle osteotomy is accomplished by spacing drill holes 2 mm apart, medially and laterally, on the TT and connecting the drill holes with an osteotome and reciprocating saw. A distalized location to secure the TT is selected and superficial bone is excised. A medial parapatellar arthrotomy is performed, and bur attachments are used to drill into the subchondral bone beneath the femoral articular surface to create a V-shaped flap of trochlear cartilage. An arthroscope is inserted under the trochlear flap during this process to visualize the appropriate depth. The trochlear flap is then secured with screws passed over guide pins to secure the flap to the desired location. Cannulated screws and washers are then used to secure the TT to its distalized and/or medialized position, with fluoroscopic verification of screw depth and location. The arthrotomy is then closed with the knee at 45°. The quadriceps graft is passed through a subretinacular channel and secured with suture anchors, adjacent to the adductor tubercle, to complete the MPFL reconstruction. Before closure, appropriate tracking and translation of the patella is verified. Results: Sulcus-deepening trochleoplasty, with or without MPFL reconstruction, has been reported to obtain satisfactory outcomes at 2 years, with close to 85% return to sport and 100% return to work, with improvements in International Knee Documentation Committee (IKDC) scores from 50.8 to 79.1 in some studies. MPFL reconstruction with tibial tubercle osteotomy (TTO) has yielded a 94.5% patient satisfaction rate in the literature. Discussion/Conclusion: In patients with recurrent patellar instability and DeJour types B-D trochlear dysplasia, MPFL reconstruction with TTO and sulcus-deepening trochleoplasty provides excellent subjective outcomes and restores patellar tracking with elimination of recurrent subluxation.

Technical Considerations for an Anteromedializing Tibial Tubercle Osteotomy

Background: Tibial tubercle osteotomy and distal realignment allows for adjustment to the patellofemoral articulation in order to improve patellar tracking and redistribute patellar contract pressures. Indications: A healthy, active 39-year-old woman status post right knee tibial tubercle osteotomy presented with &gt;2 years of patellar instability symptoms in the left knee. Imaging revealed a tibial tubercle to trochlear groove (TT-TG) distance of 21 mm and patellar tendon lateral trochlear ridge (PT-LTR) distance of 14 mm. Technique Description: After knee arthroscopy is performed, an open incision is made along the inferomedial patellar tendon. Two pilot holes are created before a sagittal saw is used to make the tibial tubercle osteotomy, before completing it with an osteotome. Anteromedialization and/or distalization of the osteotomy is performed relative to templated values in order to improve patellar articulation. After correction, 3 bicortical screws are placed to achieve stable fixation. Results: There were no immediate complications following surgery. Surgical management led to improvement of the patient’s patellofemoral pain, which allowed return to prior baseline level of function. Discussion/Conclusion: The preferred technique for an anteromedialzing tibial tubercle osteotomy is presented. An anteromedializing tibial tubercle osteotomy is an effective surgical option for patients with evidence of patellar maltracking or central or lateral patellar chondromalacia whom have failed conservative management. This case demonstrates the efficacy of an anteromedializing tibial tubercle osteotomy to provide pain relief by improving patellar tracking and offloading patellar contact pressures on areas of prominent chondral wear.