A Combined Surgical Approach for Recurrent Patellar Dislocation in Adolescents With Patella Alta and Increased Tibial Tuberosity-Trochlear Groove Distance: Improved Clinical Outcomes but Decreased Posterior Tibial Slopes in Skeletally Immature Patients at Minimum 4-Year Follow-Up

PURPOSE

(1) To report the clinical and radiological outcomes of a surgical technique combining anatomic medial patellofemoral ligament reconstruction and tibia tuberosity transfer in adolescents with patella alta and elevated tibial tuberosity-trochlear groove (TT-TG) distance in the treatment of recurrent patellar dislocation; and (2) to investigate the potential risks of growth arrest or developmental deformities associated with this combined technique.

METHODS

Medical records of patients who underwent the combined surgery from 2015 to 2019 were reviewed. This study included adolescents aged between 14 and 18 years with a Caton-Deschamps index (CDI) > 1.30 and TT-TG distance >20 mm, with a minimum follow-up of 4 years. Radiological examinations including lateral views and full-length posteroanterior standing radiographs were investigated to assess patella height by CDI, posterior tibial slope (PTS) angle, side-to-side difference in bone length, and lower extremity alignment by hip-knee-ankle angle; computed tomography scans and magnetic resonance imaging profiles were investigated to evaluate TT-TG distance and staging of growth plate closure. Other evaluations included preoperative and postoperative physical examination, Kujala score, and Tegner activity score. The patients were stratified into 3 subgroups according to an magnetic resonance imaging-based staging system of the growth plate closure, and each outcome was analyzed. A cohort-specific minimal clinically important difference estimation was performed using standard error of measurement.

RESULTS

The average age at the time of surgery was 16.1 years (range, 14.1-17.8). The average follow-up was 5.6 years (range, 4.0-7.6). No recurrent dislocation occurred, and no clinically significant deformity or axis deviation was encountered. Postoperative patellar height by CDI was 1.00 ± 0.11 (range, 0.81-1.15). No significant differences were found in the preoperative and postoperative hip-knee-ankle angle or side-to-side difference in femur/tibia length among all subgroups. A significantly decreased PTS angle was found in patients with open growth plates, from 10.2° ± 1.7° before surgery to 8.1° ± 1.0° after surgery (P = .015). The Kujala score and Tegner score both significantly improved, from 65.5 ± 13.9 before surgery to 90.4 ± 7.2 after surgery in the Kujala score (P < .001) and from 4.0 ± 1.1 before surgery to 4.7 ± 1.3 after surgery in the Tegner score (P < .001). Of the whole cohort, 63.1%, 100%, 47.1%, and 94.1% of patients achieved the minimal clinically important difference for PTS angle, CDI, Tegner score, and Kujala score, respectively.

CONCLUSIONS

This combined technique is safe and effective in treating recurrent patellar dislocation in skeletally mature adolescents with concurrent patella alta (CDI > 1.30) and TT-TG distance >20 mm, permitting patients to have improved knee function and low complication rates. Nonetheless, patients with open growth plates demonstrated a decrease in PTS, which might predispose the knee to recurvatum and osteoarthritis in the long term.

LEVEL OF EVIDENCE

Level IV, controlled case series.

Effect of Patellar Morphology on the Risk of Osteochondral Fracture after Patellar Dislocation: A Cross-sectional Study

OBJECTIVE

The risk of osteochondral fracture (OCF) after patellar dislocation has been shown to be related to patellofemoral anatomy, but its relationship to patellar morphology remains unknown. The aim of this study was to investigate the associations between patellar morphology and the risk of OCF after patellar dislocation.

METHODS

A total of 140 patients with patellar dislocation between January 2018 and June 2023 were enrolled in this study and divided into two groups. Sixty-five patellar dislocation patients with OCF were included in the OCF group, while 75 patellar dislocation patients without OCF were included in the non-OCF group. Computed tomography was used to compare measurements of patellar morphology including Wiberg classification, patellar width and thickness, Wiberg angle, Wiberg index, facet ratio, lateral patellar facet angle, and patellar tilt angle. A logistic regression model was performed to evaluate the correlations between patellar morphology and the risk of OCF after patellar dislocation. Receiver operating characteristic curves were used to calculate the area under the curve (AUC) and determine the diagnostic values of patellar morphology for OCF after patellar dislocation. Subgroup analyses for gender and age were conducted to compare the differences in patellar morphology of PD patients.

RESULTS

Wiberg angle was significantly lower in the OCF group (p = 0.017), while Wiberg index (p = 0.002) and facet ratio (p = 0.023) were significantly higher in the OCF group. According to the results of logistic regression analysis, Wiberg angle (odds ratio [OR] = 0.96, p = 0.022) and Wiberg index (OR = 1.105, p = 0.032) were the final relevant factors for the occurrence of OCF after patellar dislocation. The AUC was 0.622 (95% confidence interval [CI]: 0.529-0.714) for Wiberg angle, 0.65 (95% CI: 0.558-0.742) for Wiberg index, and 0.702 (95% CI: 0.615-0.788) for the combination of Wiberg angle plus Wiberg index.

CONCLUSION

Wiberg angle and Wiberg index were independent risk factors for the occurrence of osteochondral fracture after patellar dislocation. Moreover, Wiberg angle, Wiberg index, and the combination of Wiberg angle plus Wiberg index had good predictive diagnostic value for the occurrence of OCF after patellar dislocation.

Outcomes of surgical treatment of patellar instability in children with Down syndrome

BACKGROUND

patellar instability is a relatively frequent musculoskeletal disorder in children with Down syndrome (DS). However, such a condition has seldom been studied in the literature, even less its surgical treatment. Different techniques have been offered for this condition; the evidence for surgical options is scarce and primarily based on case reports or case series with few patients and heterogeneous techniques. Given this background, we aimed to evaluate the outcomes of a uniform kind of surgical procedure for such a condition that combined lateral soft tissue release, medial patellofemoral ligament (MPFL) reconstruction (using a partial-thickness quadriceps tendon autograft), the Roux-Goldthwait procedure, and V-Y quadricepsplasty (if needed).

MATERIALS AND METHODS

This retrospective study involved 11 skeletally immature patients (12 knees; 9 males and 2 females), 5.5 to 14.1 years of age, with DS who had patellofemoral instability (PFI) and were managed by this technique between October 2018 and March 2020. Preoperative radiography, CT scan, and MRI were performed to evaluate the physis status, lower limb alignment, patellar height, trochlear morphology, and any associated knee pathology. A functional knee assessment was done by using the Kujala score and the modified Lysholm score.

RESULTS

The mean time of follow-up (± SD) was 47.7 ± 5.8 months (range: 39-56). Pre-operatively, the Kujala score (± SD) was 52.6 ± 14.3 (range: (31-74), and at final follow-up, it was 92.2 ± 4.4 (range: (88-98), showing a significant improvement (P < 0.001). The preoperative modified Lysholm score (± SD) was 54.3 ± 8.1 (range: 39-62), and at final follow-up it was 92.4 ± 5.3 (range: 82-96), showing a significant improvement (P < 0.001). All patients had a stable patella without a recurrence of instability and regained full ROM. There was no incidence of a patellar fracture or femoral physis injury.

CONCLUSIONS

Our proposed technique of combined soft tissue procedures, including lateral soft tissue release, MPFL reconstruction (using a partial-thickness quadriceps tendon autograft), the Roux-Goldthwait procedure, and V-Y quadricepsplasty, was an effective method for treating patellar instability in children with DS while avoiding physeal injury and patellar fracture. Functional scores and radiological outcomes were improved.

LEVEL OF EVIDENCE

IV; retrospective case series.

Medial patellar ligament reconstruction in combination with derotational distal femoral osteotomy for treating recurrent patellar dislocation in the presence of increased femoral anteversion: a systematic review

BACKGROUND

Medial patellar ligament reconstruction (MPFL-R) in combination with derotational distal femoral osteotomy (DDFO) for treating recurrent patellar dislocation (RPD) in the presence of increased femoral anteversion is one of the most commonly used surgical techniques in the current clinical practice. However, there are limited studies on the clinical outcomes of MPFL-R in combination with DDFO to treat RPD in the presence of increased femoral anteversion.

PURPOSE

To study the role of MPFL-R in combination with DDFO in the treatment of RPD in the presence of increased femoral anteversion.

METHODS

A systematic review was performed according to the PRISMA guidelines by searching the Medline, Embase, Web of Science, and Cochrane Library databases through June 1, 2023. Studies of patients who received MPFL-R in combination with DDFO after presenting with RPD and increased femoral anteversion were included. Methodological quality was assessed using the MINORS (Methodological Index for Nonrandomized Studies) score. Each study's basic characteristics, including characteristic information, radiological parameters, surgical techniques, patient-reported outcomes, and complications, were recorded and analyzed.

RESULTS

A total of 6 studies with 231 patients (236 knees) were included. Sample sizes ranged from 12 to 162 patients, and the majority of the patients were female (range, 67-100%). The mean age and follow-up ranges were 18 to 24 years and 16 to 49 months, respectively. The mean femoral anteversion decreased significantly from 34° preoperatively to 12° postoperatively. In studies reporting preoperative and postoperative outcomes, significant improvements were found in the Lysholm score, Kujala score, International Knee Documentation Committee score, and visual analog scale for pain. Postoperative complications were reported in all studies, with an overall reported complication rate of 4.7%, but no redislocations occurred during the follow-up period.

CONCLUSION

For RPD with increased femoral anteversion, MPFL-R in combination with DDFO leads to a good clinical outcome and a low redislocation rate. However, there was no consensus among researchers on the indications for MPFL-R combined with DDFO in the treatment of RPD.

Reconstruction of the medial patellofemoral ligament through a double bundle of a single patellar tract and quadriceps tendons combined with medial displacement of lateral hemi-tibial tuberosity for treating low-grade recurrent patella dislocation

PURPOSE

The present study aimed to assess the clinical efficacy and imaging results of reconstruction of the medial patellofemoral ligament through a double bundle of single patellar tract and quadriceps tendons combined with medial displacement of lateral hemi-tibial tuberosity for treating low-grade recurrent patella dislocation.

METHODS

Twenty-three patients with recurrent patellar dislocation, including ten males and 13 females, with 23 knee joints were enrolled according to the relevant criteria. Reconstruction of the medial patellofemoral ligament was performed through a double bundle of a single patellar tract and quadriceps tendons combined with medial displacement of lateral hemi-tibial tuberosity. Knee function was evaluated using visual analog scale (VAS) score, International Knee Documentation Committee (IKDC) score, Lysholm score, Tegner score, and Kujala score at pre- and postoperative stages. Patellar stability was assessed by CT scans measuring tibial tuberosity-trochlear groove (TT-TG) distance, lateral patella displacement (LPD), congruence angle (CA), and patellar tilt angle (PTA).

RESULTS

All 23 patients were effectively followed up for 13-28 months (mean: 21.91 ± 4.14 months). At the last follow-up, the postoperative VAS score, IKDC score, Lysholm score, Tegner score, and Kujala score of 23 patients were 1.13 ± 0.82, 87.35 ± 3.17, 90.22 ± 1.28, 4.35 ± 0.65, and 89.26 ± 1.96, respectively, as compared to the preoperative values of 5.91 ± 1.13, 30.96 ± 5.09, 30.30 ± 2.98, 1.26 ± 0.62, and 27.87 ± 3.46, respectively, and these differences were statistically significant (P < 0.001). At the last follow-up, the postoperative TT-TG, LPD, CA, and PTA values of the 23 patients were 8.80 ± 1.85 mm, 6.01 ± 1.77 mm, 11.32 ± 6.18°, and 9.35 ± 2.88°, respectively, compared to the preoperative values of 18.77 ± 1.74 mm, 14.90 ± 4.07 mm, 37.82 ± 5.71°, and 23.58 ± 3.24°, respectively, and the differences were statistically significant (P < 0.001). No relevant complications were observed in the 23 patients.

CONCLUSIONS

Reconstruction of the medial patellofemoral ligament through a double bundle of a single patellar tract and quadriceps tendons combined with medial displacement of lateral hemi-tibial tuberosity for treating low-grade recurrent patella dislocation showed satisfactory medium-term efficacy, and further investigations are required to confirm the long-term efficacy of this approach.

The Importance of Medial Patellar Shape as a Risk Factor for Recurrent Patellar Dislocation in Adults

BACKGROUND

Research on the cause of lateral patellar dislocation (LPD) has focused on trochlear morphologic parameters, joint alignment, and patellofemoral soft tissue forces. A paucity of information is available regarding how patellar morphologic parameters influence the risk for LPD.

PURPOSE/HYPOTHESIS

The purpose was to assess whether patellar morphology is a risk factor for recurrent LPD. It was hypothesized that (1) patients with recurrent LPD would have decreased patellar width and volume and (2) patellar morphologic parameters would accurately discriminate patients with recurrent LPD from controls.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 3.

METHODS

A total of 21 adults with recurrent LPD (age, 29.7 ± 11.1 years; height, 170.8 ± 9.9 cm; weight, 76.1 ± 17.5 kg; 57% female) were compared with 21 sex- and height-matched controls (age, 27.2 ± 6.7 years; height, 172.0 ± 10.6 cm; weight, 71.1 ± 12.8 kg; 57% female). Three-dimensional axial fat-saturated magnetic resonance imaging scans were used to measure patellar medial, lateral, and total width; patellar volume; patellar medial and lateral facet length; the Wiberg index; and previously validated knee joint alignment and femoral shape measurements (eg, tibial tuberosity to trochlear groove distance, trochlear dysplasia).

RESULTS

The LPD group demonstrated reduced medial patellar width (Δ = -3.6 mm; P < .001) and medial facet length (Δ = -3.7 mm; P < .001) but no change in lateral width or facet length. This resulted in decreased total patellar width (Δ = -3.2 mm; P = .009), decreased patellar volume (Δ = -0.3 cm3; P = .025), and an increased Wiberg index (Δ = 0.05; P < .001). No significant differences were found for all other patellar shape measures between cohorts. Medial patellar width was the strongest single discriminator (83.3% accuracy) for recurrent LPD. Combining medial patellar width, patellofemoral tilt, and trochlear groove length increased the discrimination to 92.9%.

CONCLUSION

The medial patellar width was significantly smaller in patients with recurrent LPD and was the single most accurate discriminator for recurrent LPD, even compared with traditional trochlear shape and joint alignment measures (eg, trochlear dysplasia, patella alta). Therefore, medial patellar morphology should be assessed in patients with LPD as a risk factor for recurrence and a potential means to improve treatment.

Patellar Lateralization, Absence of Joint Hypermobility, and the Mechanism of Injury Are Associated With Osteochondral Fracture After First-time Acute Lateral Patellar Dislocation in Adolescents: An MRI-based Evaluation

BACKGROUND

Although the risk factors for patellofemoral dislocation are clearly defined, risk factors for osteochondral fracture (OCF) after patellar dislocation are not as well defined. The aim of this study was to investigate the risk factors for OCF by evaluating patients with and without OCF after first-time acute patellar dislocation.

METHODS

This multicenter study was conducted as a retrospective examination of the radiologic measurements on the magnetic resonance imaging of 306 patients. The patients were divided into the OCF group and non-OCF group, and OCFs were grouped according to whether the fracture was in the patella or femur. Patellar height, patellar lateralization, trochlear morphology, patellofemoral matching, and patella types were evaluated on patient magnetic resonance imaging. The presence of joint hypermobility in the patients was determined according to the Beighton scale score. The injury mechanisms of the patients were grouped as sports-related injuries, injuries resulting from simple falls, and injuries during daily activities.

RESULTS

A total of 120 OCFs were detected in 108 (35.2%) patients, of which 96 (80%) were in the patella and 24 (20%) in the femur. The rate of OCF after sports-related injuries was found to be significantly higher than in other injury mechanisms ( P =0.001). More joint hypermobility was detected in patients without OCF ( P =0.041). The measurements of tibial tubercle-trochlear groove, tibial tubercle-posterior cruciate ligament distance and lateral patellar displacement were statistically higher in cases with OCF ( P =0.001). In patients with normal joint mobility, the rate of OCF localization in the patella was significantly higher ( P =0.035). No correlation was found between any other parameters and OCF ( P >0.05). The absence of joint hypermobility and the measurements of tibial tubercle-trochlear groove distance, tibial tubercle-posterior cruciate ligament distance, and lateral patellar displacement were independent risk factors for the incidence of OCF according to the logistic regression analysis.

CONCLUSIONS

The absence of joint hypermobility and patellar lateralization are independent risk factors for the occurrence of OCF after first-time patellar dislocation. Sports-related injury is a nonindependent risk factor for the presence of OCF. In patients with normal joint mobility, the incidence of OCF in the patella is higher than in the femur. These important factors should be considered when evaluating patients and starting their treatment.

LEVEL OF EVIDENCE

Level III-retrospective cohort study.

Diagnosis and treatment of recurrent patellar dislocation with knee extensor device combined with rearrangement

OBJECTIVE

This study aimed to investigate the clinical effects of combining knee extension mechanism (EM) with rearrangement in the treatment of recurrent patellar dislocation (RPD).

PATIENTS AND METHODS

Eighty-four patients with RPD admitted to the First Affiliated Hospital of Kunming Medical University were included. In this work, all patients received routine computed tomography (CT) examinations. In addition, the evaluation factors of EM combined with rearrangement therapy in RPD patients were analyzed using logistic regression.

RESULTS

Lysholm and Kujula scores, femoral canal width, patellar canal width, patellar tilt angle (PTA), and lateral patellar displacement (LPD) were significantly increased at 1 and 3 years after treatment (p < 0.05). LPA was significantly decreased, while the tibial tuberosity trochlear groove of the femur (TT-TG) demonstrated no considerable differences (p > 0.05). The good rate of the short-term Insall-Salvati index was 78.6%, and that of the long-term Insall-Salvati index was 76.1%. The combination of the knee extension device and rearrangement therapy has a higher rate of short-term and long-term Insall-Salvati index (ISI) excellence. In addition, the range of motion of the knee joint increased significantly, and the Q Angle decreased significantly (p < 0.05). Logistic regression analysis showed that age and ISI were highly correlated with the evaluation of therapeutic effects in patients with RPD.

CONCLUSIONS

EM combined with rearrangement in the treatment of RPD had positive short-term and long-term efficacy, high application value, and age, which can be popularized in clinical applications and have positive diagnostic value.

Medial Patellofemoral Complex Reconstruction (Combined Reconstruction of Medial Patellofemoral Ligament and Medial Quadriceps Tendon-Femoral Ligament) With Semitendinosus Autograft Resulted in Similar Clinical and Radiographic Outcomes to Medial Patellofemoral Ligament Reconstruction in Treating Recurrent Patellar Dislocation

PURPOSE

To compare clinical and radiographic outcomes of medial patellofemoral ligament reconstruction (MPFL-R) and medial patellofemoral complex reconstruction (MPFC-R) for recurrent patellar dislocation. Outcome measures were compared based on the Insall-Salvati index.

METHODS

Patients who were diagnosed with recurrent patellar dislocation and underwent either MPFL-R or MPFC-R (combined reconstruction of MPFL and medial quadriceps tendon-femoral ligament) were retrospectively analyzed. Group allocation was based on surgical procedure and patient characteristics were collected. Clinical assessments included patient-reported outcome measures (PROMs) and return-to-sports rates. Minimal clinically important difference analysis was performed. A subgroup analysis of PROMs was carried out between patients with an Insall-Salvati index ≤1.2 versus >1.2. The patellar tilt angle, lateral patellar displacement, and bisect offset ratio were measured pre- and postsurgery. Functional failures and complications were assessed.

RESULTS

Overall, 70 patients (72 knees) in the MPFL-R group and 58 patients (61 knees) in the MPFC-R group were included. Patient characteristics were comparable between the groups. At a minimum follow-up of 24 (mean, 50.6 ± 22.1) months, all PROMs were substantially improved (P < .001), without significant intergroup differences. The percentages of patients reaching the minimal clinically important difference were similar after MPFL-R and MPFC-R: 98.6% versus 93.4% (International Knee Documentation Committee), 97.2% versus 98.4% (Lysholm), 98.6% versus 100% (Kujala), and 77.8% versus 72.1% (Tegner). The subgroup analysis based on patellar height and the return-to-sport rates also suggested comparable results. Radiographic evaluation demonstrated significantly smaller lateral patellar displacements (P = .004) and bisect offset ratios (P < .001) but similar patellar tilt angles after MPFC-R. Four (5.6%) patients receiving MPFL-R and 2 (3.3%) patients receiving MPFC-R reported recurrence of functional instability, without statistically significant difference.

CONCLUSIONS

MPFC-R resulted in similar overall clinical and radiographic outcomes to MPFL-R in treating recurrent patellar dislocation. MPFC-R might not provide additional benefits for patients with an Insall-Salvati index >1.2.

LEVEL OF EVIDENCE

Level IV, therapeutic, retrospective cohort study.

Exploring osteochondral damage patterns in acute patellar dislocation: insights into morphological associations and risk factors

Osteochondral damage (OD) is a significant outcome following acute patellar dislocation (APD), yet the factors contributing to its susceptibility remain unclear. The primary objective of this study was to assess the association between demographic characteristics, patellofemoral (PF) joint morphology, and the occurrence of OD. A retrospective analysis identified 74 patients with APD who underwent treatment in our unit between 2019 and 2022. All patients received MRI within a week of injury to assess OD, subsequently categorized according to the injury pattern. The Caton-Deschamps index (CDI), tibial tuberosity-trochlear groove distance (TT-TG), lateral trochlear inclination (LTI), sulcus angle (SA), patellar width (PW), patellar thickness (PT), and femoral condyle geometry were calculated from the MRI scans and compared between groups. The findings revealed that OD predominantly manifested in the lateral femoral condyle (LFC) region and the medial patella (MP) region. In our patient cohort, this study identified a significant association between sulcus angle and the incidence of OD in both MP and LFC regions. Additionally, a significant correlation was discerned between skeletal maturity and the incidence of OD in the LFC region within demographic characteristics.

Acute patellar dislocation: how skeletal maturity affects patterns of injury

OBJECTIVE

The main objective of this study was to understand the role of skeletal maturity in the different patterns of osteochondral and ligamentous injuries after an acute lateral patellar dislocation.

MATERIALS AND METHODS

Two radiologists independently reviewed MRIs of 212 knees performed after an acute lateral patellar dislocation to evaluate the presence of high-grade patellar osteochondral injury, femoral osteochondral injury, and medial patellofemoral ligament injury. The association of skeletal maturity (indicated by a closed distal femoral physis), age, sex, and first-time versus recurrent dislocation with each of these various lesions was analyzed using Chi-square or T test, and multivariable logistic regression with estimation of odds ratios (OR).

RESULTS

Skeletal maturity was significantly associated with high-grade patellar osteochondral injury [OR=2.72 (95% CI 1.00, 7.36); p=0.049] and femoral-side MPFL tear [OR=2.34 (95% CI 1.05, 5.25); p=0.039]. Skeletal immaturity was significantly associated with patellar-side MPFL tear [OR=0.35 (95% CI 0.14, 0.90); p=0.029].

CONCLUSION

Patterns of injury to the patella and medial patellofemoral ligament vary notably between the skeletally immature and mature, and these variations may be explained by the inherent weakness of the patellar secondary physis.

MRI of patellar stabilizers: Anatomic visibility, inter-reader reliability, and intra-reader reproducibility of primary and secondary ligament anatomy

OBJECTIVE

To compare MRI features of medial and lateral patellar stabilizers in patients with and without patellar instability.

METHODS

Retrospective study of 196 patients (mean age, 33.1 ± 18.5 years; 119 women) after diagnosis of patellar instability (cohort-1, acute patellar dislocation; cohort-2, chronic patellar maltracking) or no patellar instability (cohort-3, acute ACL rupture; cohort-4, chronic medial meniscus tear). On MRI, four medial and four lateral stabilizers were evaluated for visibility and injury by three readers independently. Inter- and intra-reader agreement was determined.

RESULTS

Medial and lateral patellofemoral ligaments (MPFL and LPFL) were mostly or fully visualized in all cases (100%). Of the secondary patellar stabilizers, the medial patellotibial ligament was mostly or fully visualized in 166 cases (84.7%). Other secondary stabilizers were mostly or fully visualized in only a minority of cases (range, 0.5-32.1%). Injury scores for all four medial stabilizers were higher in patients with acute patellar dislocation than the other 3 cohorts (p < .05). Visibility inter- and intra-reader agreement was good for medial stabilizers (κ 0.61-0.78) and moderate-to-good for lateral stabilizers (κ 0.40-0.72). Injury inter- and intra-reader agreement was moderate-to-excellent for medial stabilizers (κ 0.43-0.90) and poor-to-moderate for lateral stabilizers (κ 0-0.50).

CONCLUSION

The MPFL and LPFL were well visualized on MRI while the secondary stabilizers were less frequently visualized. The secondary stabilizers were more frequently visualized medially than laterally, and patellotibial ligaments were more frequently visualized compared to the other secondary stabilizers. Injury to the medial stabilizers was more common with acute patellar dislocation than with chronic patellar maltracking or other knee injuries.

MPFL Reconstruction Combined with a Modified Elmslie-Trillat Procedure for Recurrent Patellofemoral Instability

Several combined procedures have been reported for treating recurrent patellofemoral instability (RPI) with various types and severity of morphological abnormalities, but none have identified absolute threshold values as indications for surgery. We performed medial patellofemoral ligament (MPFL) reconstruction combined with a modified Elmslie-Trillat (ET) procedure on 24 knees (10 male and 11 female patients) to treat RPI with morphological abnormalities corresponding to elevated tibial tubercle-trochlear groove (TT-TG) distance, significant patella alta, and trochlear dysplasia. The inclusion criteria were RPI with morphological abnormalities corresponding to one or more of the following: sulcus angle > 160 degrees, trochlear dysplasia of Dejour classification C or D, Caton-Deschamps index > 1.5, lateral shift ratio > 50%, congruence angle > 15 degrees, or TT-TG distance > 20 mm, including habitual dislocation of the patella. Skeletally immature patients and those with congenital dislocation of the patella were excluded. The Kujala score, International Knee Documentation Committee subjective score, Knee Injury and Osteoarthritis Outcome score (KOOS), and each item of the KOOS improved significantly after surgery. Patellar apprehension sign was present preoperatively in all cases, but all disappeared postoperatively. No instance of postoperative redislocation was observed. On radiographic examination, the mean Q angle, tilting angle, lateral shift ratio, congruence angle, Caton-Deschamps index, Insall-Salvati index, and TT-TG distance improved significantly after surgery. There were no significant differences in sulcus angle after surgery. These results suggest MPFL reconstruction combined with a modified ET procedure provides satisfactory outcomes based on radiological and clinical evaluations for RPI with morphological abnormalities corresponding to elevated TT-TG distance, significant patella alta, and trochlear dysplasia.

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

PURPOSE

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.

METHODS

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.

RESULTS

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 after sequential 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).

CONCLUSION

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 OF EVIDENCE

Level IV.

Epidemiology of Lateral Patellar Dislocation Including Bone Bruise Incidence: Five Years of Data from a Trauma Center

OBJECTIVE

Systematic summary of the epidemiology of patellar dislocation is rare. This study aims to investigate sex-, age-, type-, injury causing events-, incidence of bone bruise and time from last injury (TFLI)-specific characteristics, and detail the epidemiological characteristics of patellar dislocation.

METHOD

In this descriptive epidemiological study, a total of 743 patients who have a history of lateral patellar dislocation with either first-time patellar dislocation (FPD) or recurrent patellar dislocation (RPD) between August 2017 and June 2022 at our institution met the inclusion criteria and were selected in this study. Patient characteristics including the type, gender, age, events leading to patellar dislocation, incidence of patellar bone bruise, and the time from last injury (TFLI) of patellar dislocation were retrospectively obtained and described. Magnetic resonance imaging scans (MRI) of the knee were reviewed for insuring bone bruise.

RESULTS

Among the 743 patients with patellar dislocation who required surgical reconstruction of the medial retinaculum, 418 (56.2%) had RPD and 325 (43.8%) had FPD. There were more females (65.0%) than males (35.0%) in patellar dislocation patients. Among the female patients, those aged <18 years had higher incidence (31.4%) of patellar dislocation. Among the male patients, those aged <18 and 19-28 years had higher incidence (16.8%) of patellar dislocation. Of all age groups, the prevalence rate of patellar dislocation was high in juvenile population and females, but with no statistical significance. The most common patellar dislocation-causing event was sport accidents (40.1%), followed by life accidents (23.2%). The incidence of left-knee patellar dislocation was slightly higher than that of right-knee patellar dislocation. The incidence of patellar bone bruise of RPD (63.2%) was significantly lower (p < 0.05) than that of FPD (82.2%). Patellar dislocation patients with bone bruise had shorter time from last injury (TFLI) than those without patellar bone bruise (p < 0.05).

CONCLUSIONS

The incidence of bone bruise of RPD was lower than that of FPD, and patients with patellar bone bruise may have a shorter time from last injury than those without bone bruise.

Medial Patellofemoral Ligament Reconstruction With or Without Tibial Tubercle Osteotomy in Carefully Selected Patients Results in a 5% Revision Rate: A Preliminary Analysis

PURPOSE

The purpose was to assess the outcomes of medial patellofemoral ligament (MPFL) allograft reconstruction with or without tibial tubercle osteotomy (TTO) in adolescents, with a focus on evaluating demographic and imaging characteristics on outcomes.

METHODS

A single-institution retrospective study was performed of patients ages 12 to 19 years who underwent MPFL reconstruction +/- TTO for the treatment of lateral patellar instability. Demographic, clinical, surgical, and postoperative information was collected. All x-ray and magnetic resonance imaging measurements were completed independently by 2 surgeons. Patients were contacted to complete patient-reported outcomes at a minimum of 2 years following surgery. The primary outcome measure was recurrent instability resulting in revision surgery.

RESULTS

Seventy-eight knees in 74 patients, with a median age of 15.3 years (interquartile range: 14.4, 16.1), were included. Forty-five knees underwent isolated MPFL reconstruction and 33 knees had a combined MPFL + TTO. The knees that underwent MPFL + TTO had significantly greater tibial tubercle-trochlear groove distance (19.0 mm vs. 15.4 mm, P =0.015) and patellar tendon-lateral trochlear ridge distance (10.9 mm vs. 5.9 mm, P =0.018) than the knees treated with isolated MPFL reconstruction. Four knees (5.1%) underwent revision stabilization surgery, including 3 knees in the MPFL cohort (6.7%) and 1 knee in the MPFL + TTO cohort (3.0%). The rate of failure between the MPFL and MPFL + TTO knees was not significantly different, P =0.634. There were no differences in age, sex, body mass index, number of dislocations, or any imaging characteristics in patients who underwent revision versus those who did not. Patient-reported outcomes were collected on 50 knees at a median of 36 months (interquartile range: 24, 54) after surgery, and no differences were noted between cohorts.

CONCLUSIONS

Patellar stabilization surgery, including MPFL reconstruction and TTO in carefully selected patients, had excellent revision-free outcomes in 95% of this adolescent cohort. In this case series, those patients whose treatment included TTO had greater tibial tubercle-trochlear groove and patellar tendon-lateral trochlear ridge as compared to the isolated MPFL cohort. Despite previous literature suggesting demographic and imaging characteristics as risks for recurrent instability, we identified no characteristics within these two distinct surgical treatment groups to be predictive of the need for revision stabilization, regardless of the treatment group.

LEVEL OF EVIDENCE

Level III-retrospective comparison study.

High prevalence of patellar dislocation and trochlear dysplasia in a geographically and genetically isolated society: an observational national cohort study from the Faroese Knee Cohort

BACKGROUND AND PURPOSE

We aimed to calculate the prevalence of patellar dislocation (PD) and trochlear dysplasia (TD) in a national cohort aged 15-19 years in the Faroe Island.

PATIENTS AND METHODS

All inhabitants in the Faroe Islands aged 15-19 years were invited to answer an online survey, including demographics and questions regarding prior PD. Participants with prior PD were invited for radiographs and MRI of both knees to be taken. Trochlear dysplasia was defined as one of the following: Dejour type A-D on radiographs, lateral trochlear inclination angle (LTI) < 11°, or trochlear depth < 3 mm on MRI.

RESULTS

3,749 individuals were contacted, 41 were excluded, and 1,638 (44%) completed the survey. 146 reported a prior PD (the PD cohort) and 100 accepted to participate and have radiographs and MRI taken of both knees (the clinical PD cohort), 76 of whom were diagnosed with TD. The national prevalence of PD was 8.9%. The national prevalence of symptomatic TD was 6.8%. The prevalence of TD in the clinical PD cohort was 76%. TD was bilateral in 78% of TD patients, but only 27% of patients with bilateral TD had PD in both knees.

CONCLUSION

The prevalence of PD in the Faroe Islands is found to be very high. The national prevalence of TD and the prevalence of TD in participants with prior PD is high, indicating a potential genetic influence.

Open lateral condyle Hoffa's fracture with intra-articular patella dislocation, quadriceps tendon rupture and PCL avulsion

We present a rare case of open lateral condyle Hoffa's fracture with concurrent patellar intra-articular dislocation, quadriceps rupture and posterior cruciate ligament (PCL) avulsion. The early adolescent male sustained these injuries in a road traffic accident. Diagnostic evaluation and a multidisciplinary approach guided treatment decisions. The patient underwent single-stage open reduction and internal fixation for the lateral condyle Hoffa's fracture and quadriceps tendon repair, while conservative management was chosen for the PCL avulsion. At the 1-year follow-up, the patient exhibited improved knee function.This case underscores the management of complex knee injuries and contributes to understanding unique injury patterns, enhancing patient care.

Patients with bilateral patellar instability have multiple and symmetric risk factors in each knee

PURPOSE

Bilateral involvement is common in patients with patellar instability. The management of bilateral patellar instability is associated with increased complication rate. The higher complication rate in this cohort may be related to the presence of underlying anatomic risk factors. The purpose of the study was to evaluate the presence and side-to-side differences in risk factors between knees in bilateral patellar instability.

METHODS

In a retrospective study (2008-2017), demographic information, characteristics of patellar dislocation and anatomic risk factors on MRI (trochlear dysplasia, patellar height, tibial tubercle lateralization, patellar tilt, sulcus angle, bump height) were evaluated in both knees of all patients (n = 32, 15 males and 17 females) with bilateral patellar instability. The risk factors were analyzed based on established cut off values and were compared between gender, laterality and more symptomatic (index) knee. Knee symmetry and absolute differences between risk factors for both knees were analyzed.

RESULTS

The mean age of 32 patients was 14.6 ± 2.3 years. Of the 4 major anatomic risk factors, the most common were trochlear dysplasia in 59/64 (92.1%) knees and patella alta in 51/64 (79.7%) knees. Tibial tubercle lateralization was the least common risk factor being present in 8/64 (12.5%) knees. Of 64 knees, 55 (85.9%) had 2 or more risk factors and 30 (46.8%) had 3 or all 4 risk factors present. There were no significant differences in risk factors based on gender, laterality or index knee. There was symmetry between paired knees for 31/32 (96.8%) patients for trochlear depth, 29/32 (90.6%) for patellar tilt, 27/32 (84.3%) for TT-TG distance and 25/32 (78.1%) for patellar height. There were no significant differences in absolute measurements between knees for any of the risk factors.

CONCLUSION

Patients with bilateral instability had multiple risk factors, with trochlear dysplasia being the most common and increased TT-TG distance being the least common. Majority of patients had 2 or more risk factors and about half had 3 or 4 risk factors in each knee. There was symmetry between paired knees for each risk factor without any significant differences between the index knee compared to the contralateral knee.

LEVEL OF EVIDENCE

Level III.

The larger patellar tilt angle and lower intercondylar notch angle might increase posterior cruciate ligament injury risk: a retrospective comparative study

BACKGROUND

Posterior cruciate ligament (PCL) injuries are common ligament injuries of the knee, and previous studies often focused on the associations between the morphology of the knee and PCL injuries. Studies on the correlation between PCL injuries and patellofemoral alignment are limited.

METHODS

This retrospective study included 92 patients with PCL injured and 92 patients with PCL intact. Measurement parameters were compared between the two groups, including patellar tilt angle, congruence angle, patellar height, hip-knee-ankle angle, lateral trochlear inclination, femoral condyle ratio, bicondylar width, intercondylar notch width and index, notch angle, trochlear facet asymmetry, and trochlear sulcus depth and angle. Independent risk factors associated with PCL injuries were identified by logistic regression analyses.

RESULTS

In the PCL injured group, the patellar tilt angle was significantly larger (13.19 ± 5.90° vs. 10.02 ± 4.95°, P = 0.04); the intercondylar notch angle was significantly lower (60.97 ± 7.83° vs. 67.01 ± 6.00°, P = 0.004); the medial and lateral femoral condyle ratio were significantly larger (0.63 ± 0.64 vs. 0.60 ± 0.56, P = 0.031; 0.65 ± 0.60 vs. 0.58 ± 0.53, P = 0.005) than in the PCL intact group. There were 11 patients with patellar dislocation in the PCL injured group, accounting for 12%. In these patients, the patellar height was higher (1.39 ± 0.17 vs. 1.09 ± 0.25, P = 0.009); the trochlear sulcus angle was larger (157.70 ± 8.7° vs. 141.80 ± 8.78°, P < 0.001); and the trochlear sulcus depth was shallower (3.10 ± 1.20mm vs. 5.11 ± 1.48mm, P = 0.003) than those in the patients without patellar dislocation. Multivariate analyses showed that patellar tilt angle (each increase 1 degree, OR = 1.14) and intercondylar notch angle (each increase 1 degree, OR = 0.90) were independent risk factors for PCL injuries.

CONCLUSION

The patients with PCL injuries had larger patellar tilt angles, lower intercondylar notch angles, and longer posterior femoral condyles than patients with PCL intact. The larger patellar tilt angle and lower intercondylar notch angle might be risk factors for PCL injuries.

Patellar Dislocation in Adolescent Patients: Influence on Cartilage Properties Based on T1ρ Relaxation Times

BACKGROUND

Adolescents who experience a patellar dislocation have an elevated risk of patellofemoral posttraumatic osteoarthritis. Magnetic resonance imaging (MRI)-based T1ρ relaxation times were measured for adolescents to evaluate patellofemoral cartilage after patellar dislocation. Long T1ρ relaxation times are an indicator of cartilage degradation.

HYPOTHESIS

The primary hypothesis is that patellofemoral cartilage T1ρ relaxation times will be elevated in the acute phase after patellar dislocation. The secondary hypothesis is that T1ρ relaxation times will be higher for knees with multiple rather than single dislocations due to repeated traumatic injury.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

In total, 23 adolescents being treated for a recent patellar dislocation, 13 for a first-time dislocation (47 ± 38 days since most recent dislocation) and 10 for multiple dislocations (55 ± 24 days since most recent dislocation), and 10 healthy controls participated in MRI-based T1ρ relaxation time mapping. For multiple regions of the patellofemoral joint, mean T1ρ values were compared between the 3 groups with multiple group comparisons and post hoc tests. T1ρ relaxation times were also correlated against measures of patellofemoral anatomy and alignment for single and multiple dislocations. Statistical significance was set at P < .05.

RESULTS

T1ρ relaxation times were significantly longer for injured knees (single and multiple dislocations) than controls at the medial and central patella and central trochlear groove. For the regions on the patella, significant differences between injured and control knees exceeded 15%. No significant differences were identified between single and multiple dislocations. For the initial dislocation group, T1ρ relaxation times within multiple regions of the patellofemoral joint were significantly correlated with lateral patellar alignment or patellar height.

CONCLUSION

Elevated patellofemoral cartilage T1ρ relaxation times are consistent with a high risk of long-term patellofemoral osteoarthritis for adolescents who experience patellar dislocations. T1ρ relaxation times were elevated for multiple regions of patellofemoral cartilage. T1ρ relaxation times were expected to increase with additional dislocation episodes, but relaxation times after single and multiple dislocations were similar. After a first dislocation, parameters related to patellar maltracking were correlated with cartilage degradation.

Distal femoral torsion is correlated with higher-grade trochlear dysplasia and shorter anterior condyles in patients with patellar dislocation and increased femoral torsion

PURPOSE

To describe the characteristics of femoral torsion in patients with different segmental torsion types and to evaluate the correlations between segmental torsion and the morphology of the femoral condyles and trochlea in patients with patellar dislocation and increased femoral torsion.

METHODS

Between January 2021 and March 2023, 69 patients were included and classified into two groups according to the femoral segment contributing the most to total torsion: 32 patients in Group A (femoral neck and shaft torsion) and 37 patients in Group B (distal torsion). Trochlear dysplasia was evaluated using Dejour's classification and sulcus angle. The morphology of the femoral condyles was evaluated using the lengths and ratios of the medial and lateral condyles. Correlations between femoral torsion and morphology were evaluated.

RESULTS

Total torsion was significantly correlated with femoral neck and shaft torsion (r = 0.882, P < 0.001) and distal torsion (r  = 0.262, P = 0.030). Femoral neck and shaft torsion was significantly increased with increasing total torsion. The trochlear sulcus was flatter and more dysplastic, and the anterior condyles were shorter in Group B. Distal torsion was significantly correlated with the lengths of the medial and lateral anterior condyles (r  = - 0.567, P < 0.001; r = -0.701, P < 0.001), sulcus angle (r  = 0.611, P < 0.001) and Dejour trochlea type (r  = 0.512, P = 0.001), while femoral neck and shaft torsion showed no correlations.

CONCLUSION

Femoral torsion is a complex of femoral neck and shaft torsion and distal torsion, especially femoral neck and shaft torsion. Distal torsion was significantly correlated with a flatter trochlear sulcus, higher-grade trochlear dysplasia, and shorter anterior condyles. The new findings highlighted the importance of the segmental evaluation of femoral torsion, which would facilitate understanding of the anatomical characteristics of femoral torsion in patients with patellar dislocation and increased femoral torsion and may lead to improvement in the surgical options regarding femoral torsion.

LEVEL OF EVIDENCE

Level III.

Lateral trochlear inclination measured by the transepicondylar axis holds potential for evaluating trochlear dysplasia in patients with lateral patellar dislocation

PURPOSE

To verify that lateral trochlear inclination (LTI) measured by the transepicondylar axis can reliably be used to evaluate trochlear dysplasia (TD) on MRI and can serve as an objective indication of trochleoplasty for patients with lateral patellar dislocation (LPD).

METHODS

Eighty patients with recurrent LPD and eighty healthy subjects were included. TD, posterior condylar angle (PCA), and LTI measured by the posterior condylar reference line (LTIp), surgical transepicondylar axis (LTIs), and anatomical transepicondylar axis (LTIa) were assessed on MRI. The intraclass correlation coefficient (ICC) and Bland-Altman analysis were performed, the correlations and differences amongst the parameters were identified, and a binary logistic regression model was established.

RESULTS

Each measurement had excellent inter- and intra-observer agreement. The LTIp, LTIs and LTIa were smaller in the study group than in the control group, with mean differences of 9.0°, 7.2° and 7.0°, respectively (P < 0.001). The PCA was larger in patients with LPD than in the control group (P < 0.001). LTIp was associated with PCA in the study group (r = - 0.41, P < 0.001). The pathological values of LTIp, LTIs and LTIa were 11.7°, 15.3° and 17.4°, respectively. LTIs and LTIa were independent risk factors for LPD, with ORs of 7.33 (95% CI [1.06-52.90], P = 0.048) and 10.29 (95% CI [1.38-76.96], P = 0.023), respectively.

CONCLUSION

The LTI can be reliably measured by MRI, but LTIp could potentially decrease the recorded value from the actual inclination angle. LTIs and LTIa are more appropriate to serve as trochleoplasty indications for patients with LPD, which could help orthopedists with surgical decision-making.

LEVEL OF EVIDENCE

Level III.

Patellar Tilt and Patellar Tendon-Trochlear Groove Angle Present the Optimum Magnetic Resonance Imaging Diagnostic Reliability for Patients With Patellar Instability

PURPOSE

To describe, in controls and in a population with patellar instability, magnetic resonance imaging values of measurements representing major associated factors for patellar instability (patellar height, trochlear dysplasia, and extensor mechanism alignment), as well as their cutoff values.

METHODS

In total, 323 knee magnetic resonance imaging scans, 142 with patellar instability and 181 controls without patellofemoral complaints (anterior cruciate, medial collateral ligament, meniscus ruptures or normal) were evaluated. Means, normality values in the control population, ideal cutoff values through receiver operating characteristic curves analysis, and interobserver reliability (intraclass correlation coefficient) were described for a series of measurements.

RESULTS

All measurements were statistically different in control and instability patients, except for the patellotrochlear index and tibial tuberosity to posterior cruciate ligament distance. The interobserver intraclass correlation coefficient was good or excellent (above 0.75) only for the patellotrochlear index, patellar tendon-trochlear groove (PTTG) angle, and patellar tilt. The optimal cutoff value for each measurement was: PTTG angle ≥25.3o with sensitivity (S) of 70% and specificity (E) of 89%, patellar tilt ≥16o (S: 69% and E: 84%), trochlear sulcus angle ≥153o (S: 75% and E: 76%), Carrillon ≤12.8o (S: 62% and E: 87%), PTTG distance ≥11mm (S: 71% and E: 78%), Caton-Deschamps index ≥1.23 (S: 72% and E: 76%) and trochlear bump ≥3.95 mm (S: 76% and E: 65%).

CONCLUSIONS

Caton-Deschamps index (≥1.23), trochlear sulcus angle (≥153o), ventral prominence of the trochlea (≥3.95 mm), PTTG distance (≥11 mm), PTTG angle (≥25.3o), Carrillon angle (≤12.8o), and patellar tilt (≥16o) presented better diagnostic performance for patellar instability. Patellotrochlear index and tibial tuberosity to posterior cruciate ligament distance were not related to patellar instability. The interobserver reliability of the factors related to patellar instability was excellent only for the PTTG angle and lateral patellar tilt.

LEVEL OF EVIDENCE

Level III, retrospective case-control study.

Editorial Commentary: Evaluation of Patellofemoral Instability Is Complex and Multifactorial

The work-up of patellofemoral instability is complex and multifactorial. Patient factors (i.e., age, activity demand, goals/expectations), clinical presentation (pain, instability, or both), and physical examination (i.e., J-sign, apprehension into flexion), must be correlated with imaging findings (radiographs, magnetic resonance imaging, computed tomography) and anatomic risk factors, including patella alta, trochlear dysplasia, patellar tilt, lateralized force vector, valgus, femoral anteversion, and tibial torsion. Thus, developing a standard battery of reliable and reproducible radiographic measures of patellofemoral instability is a challenge. Imaging cut-offs provide insight into relative risk of recurrent instability. We still fall short in using imaging parameters to predict when to operate, what procedure(s) to perform, and how the patient might do. Future directions include the use of artificial intelligence and 3-dimensional measurements to help simplify a complex problem.

Bilateral Patellofemoral Ligament Reconstruction for Patellar Instability in Ehlers-Danlos Syndrome: A Case Report

CASE

We report the case of an 11-year-old boy with Ehlers-Danlos syndrome (EDC) who exhibited simultaneous medial and lateral patellar instability. The patient presented with a medial patellar dislocation, and subsequently, the patella became very unstable both medially and laterally. Despite distal realignment, the patellar instability was so significant that he underwent simultaneous reconstruction of the medial and lateral patellofemoral ligament using the semitendinosus tendon, with a good result.

CONCLUSION

Simultaneous reconstruction of the medial and lateral patellofemoral ligament is an effective method in cases of extreme patellar instability, such as the EDS case.

Derotational distal femur osteotomy combined with medial patellofemoral ligament reconstruction yields satisfactory results in recurrent patellar dislocation with excessive femoral anteversion angle and trochlear dysplasia

PURPOSE

The purpose of this study was to evaluate the clinical outcomes of medial patellofemoral ligament (MPFL) reconstruction combined with derotational distal femur osteotomy in patients with recurrent patellar dislocation who had excessive femoral anteversion angle and trochlear dysplasia.

METHODS

Between 2015 and 2020, 64 patients (64 knees) with recurrent patellar dislocation, who had excessive femoral anteversion angle (≥ 25°) and trochlear dysplasia and were surgically treated using derotational distal femur osteotomy and MPFL reconstruction, were eligible for this retrospective study. These patients were assigned to two groups according to the grade of trochlear dysplasia. Group A (type A trochlear dysplasia, n = 33) and Group B (type B, C, D trochlear dysplasia, n = 31). Preoperative and postoperative patellar tilt angle (PTA), Caton-Deschamps index (CD-I), tibial tubercle-trochlear groove (TT-TG) distance and femoral anteversion angle were evaluated. Patient outcomes were assessed using the preoperative and postoperative International Knee Documentation Committee (IKDC) score, Kujala score, Lysholm score, Tegner score, and visual analog scale (VAS) score.

RESULTS

A total of 64 patients (64 knees) were evaluated in this study, with a mean follow-up period of 28.4 ± 3.6 months. There were no cases of wound infection, osteotomy site fractures, deep venous thrombosis of the lower extremities, or re-dislocation in the two groups during the postoperative follow-up period. All patients returned to full extension and flexion. The postoperative Tegner score, Lysholm score, Kujala score, IKDC score, VAS score, PTA, CD-I, TT-TG distance, and femoral anteversion angle were significantly improved compared with the preoperative status (P < 0.05). There was no significant difference between the two groups (n.s.).

CONCLUSION

MPFL reconstruction combined with derotational distal femur osteotomy showed satisfactory clinical outcomes during follow-up in patients with recurrent patellar dislocation who had excessive femoral anteversion angle and trochlear dysplasia. Even patients with high-grade trochlear dysplasia showed satisfactory results. For those patients, additional surgery is not necessary.

LEVEL OF EVIDENCE

Level III.

Reconstruction of medial patellofemoral ligament with adductor magnus tendon for recurrent patellar dislocation in children: a retrospective comparative cohort study

BACKGROUND

The purpose of current retrospective study was to explore the outcomes of using the adductor magnus tendon to reconstruct the medial patellofemoral ligament in the treatment of recurrent patellar dislocation in children.

METHOD

Thirty-two children with recurrent patellar dislocation were selected. Sixteen cases in the conservative group, seven males and nine females, with an average age of 11.81 ± 1.28 years; sixteen cases in the surgical group, eight males and eight females, with an average age of 11.56 ± 1.15 years. All patients had no surgery history. The IS index (> 1.2), Q angle (> 20°) and tibial tubercle-femoral trochlear groove (TT-TG) distance (> 20 mm) were measured by X-ray and MRI. The conservative group was treated with closed reduction and a brace, and the surgical group received surgical treatment. Two years after surgery, congruence angle (CA) (- 6° to 6°) and lateral patellofemoral angle (LPFA) (7.7°-18.7°) were measured by X-ray image and all children were evaluated based on Kujala and Lysholm scores. The re-dislocation rate was recorded. Analysis was performed by t test and chi-square with the statistical SPSS software. P < 0.05 was considered a statistically significant difference. Furthermore, we measured the length (mm) of the adductor tendon and MPFL in three knee cadaveric specimens, and also observed the positional relationship between the two structures.

RESULT

There were no significant differences in sex, age, injury site between groups (P > 0.05). Patients in the two groups were followed up for 2 years in average. Among the 16 cases in the conservative group, 7 cases (43.75%) had recurrence of patellar dislocation, while none of recurrence in the surgical group (P < 0.05). The Lysholm score of the surgical group (94.63 ± 8.99) was significantly better than that of the conservative group (79.31 ± 18.90), and the Kujala score of the surgery group (95.25 ± 10.32) was also significantly better than that of the conservative group (77.06° ± 14.34°) (P < 0.05). The CA and LPFA of the two groups of patients after treatment were significantly recovered. The CA (- 5.81° ± 7.90°) in the surgical group was significantly better than that in the conservative group (20.94° ± 8.21°), and the LPFA (6.44° ± 3.22°) was also significantly better than that in the conservative group (- 9.18 ± 11.08), and the difference is statistically significant (P < 0.05). We found it through autopsy that adductor magnus tendon was 124.33 ± 1.53 mm long, MPFL was 48.67 ± 2.08 mm, and the femoral insertion of the adductor magnus tendon was adjacent to the MPFL femoral insertion.

CONCLUSION

Reconstruction of Medial patellofemoral ligament with the adductor magnus tendon, fixing with PEEK suture anchors on the patellar side, can achieve satisfactory results in the treatment of children with recurrent patellar dislocation. Compared with conservative treatment, the rate of recurrence is lower and the stability of the patella is better.

Computer-aided design combined with 3D-printed osteotomy guide-assisted derotational distal femoral osteotomy for treating recurrent patellar dislocation with increased femoral anteversion angle: a retrospective study

PURPOSE

Derotational distal femoral osteotomy (DDFO) has good clinical outcomes for the treatment of the recurrent patellar dislocation combined with increased femoral anteversion angle (FAA). Currently, there is no uniform surgical technique. The purpose of this study was to evaluate the safety and efficacy of computer-aided design (CAD) combined 3D-printed osteotomy guide-assisted DDFO for treating these patients.

METHODS

In a retrospective study of 36 patients with recurrent patellar dislocation (RPD) from December 2017 to December 2020, all patients had increased FAA and underwent DDFO assisted by CAD combined with a 3D-printed osteotomy guide. Patients' radiological parameters were used to assess the correction of increased femoral torsion and preoperative and postoperative subjective scores were recorded to evaluate the knee function. Complications were recorded to determine the safety of the surgery.

RESULT

A total of 36 knees were included in this study, with a mean follow-up time of 32.6 ± 8.1 months. The mean age of the patients was 24.9±4.4 years and all patients experienced patellar dislocation preoperatively with a mean of 5.7±3.2 times. The patients' femoral anteversion angle decreased from 35.03±3.05° preoperatively to 14.80±0.87°, and the TT-TG distance decreased from 20.03±1.27 mm preoperatively to 19.22±1.22 mm. The hip-knee-ankle (HKA) angle and Insall-Salvatti index were not significantly different postoperatively compared to preoperatively. The knee function scores and visual analogue scale at the last follow-up were significantly improved compared to the preoperative scores. No major complications such as redislocation, nonunion, fixation or graft failure, or infection were observed in any patients.

CONCLUSION

Computer-aided design combined with 3D-printed osteotomy guide-assisted derotational distal femoral osteotomy could correct the increased anterior femoral torsion and demonstrate good results. There were no patients experienced re-dislocation during follow-up period and the overall complication rate is low.

Tibial Tubercle-Trochlear Groove Distance Has Better Diagnostic Reliability Than Tubercle-Posterior Cruciate Ligament Distance For Predicting Patellar Instability: A Systematic Review

OBJECTIVE

The tibial tubercle-trochlear groove (TT-TG) distance is now routinely utilized to help determine whether a realignment procedure is necessary for patients with patellar instability. The tibial tubercle-posterior cruciate ligament (TT-PCL) distance has been explored as an alternative measurement. The aim of this study is to compare the reliability of TT-TG and TT-PCL; to explore whether there is a relationship between the TT-PCL and the TT-TG distance; to determine whether there is a relationship between the TT-TG and TT-PCL distances and knee rotation; and to compare the abilities of the TT-PCL distance and the TT-TG distance with predicted patellar instability.

METHOD

This systematic review was performed in accordance with PRISMA guidelines. Three databases, PubMed, EMBASE, and Cochrane Central Register of Controlled Trials, were searched from inception to September 2021 to identify clinical studies comparing TT-TG and TT-PCL distances to patellar instability. Data on patient baseline characteristics, TT-TG and TT-PCL distances, inter-observer reliability, and area under the receiver-operating characteristic curve (AUC) were recorded. The methodological quality of the studies was assessed using the quality assessment form recommended by the Agency for Healthcare Research and Quality (AHRQ).

RESULT

Twenty studies were included in the final analysis, comprising 2330 knees from 2260 patients. The current study showed that TT-TG and TT-PCL have similar observer reliability. The inter- and intra-observer reliability of TT-TG ranged from 0.807 to 0.98 and 0.553 to 0.99, respectively. The inter- and intra-observer reliability of TT-PCL ranged from 0.553 to 0.99 and 0.88 to 0.981, respectively. Six studies compared the AUC for predicting patellar instability and showed that TT-TG had better predictive performance than TT-PCL. Three studies reported a correlation between TT-TG and knee rotation, but no such relationship was found for TT-PCL. Eight studies reported a weak or moderate correlation between TT-TG and TT-PCL.

CONCLUSION

TT-TG and TT-PCL have similar inter- and intra-rater reliability (as measured by ICC), but TT-TG has greater discriminatory power to predict patellar instability than TT-PCL (as measured by AUC values and odds ratio). However, considering trochlear dysplasia and individual variations, future studies need to find more accurate and individualized methods to predict patellar instability.

Suprapatellar pouch effusion is associated with an increased risk of neglected osteochondral fractures in primary acute traumatic patellar dislocation: a consecutive series of 113 children

BACKGROUND

The aim of this study was to investigate the risk factors of neglected osteochondral fractures in primary acute traumatic patellar dislocation in the pediatric population.

METHODS

A total of 113 patients with primary acute traumatic patellar dislocation for whom coincident osteochondral fractures could not be confirmed by X-ray examination at initial diagnosis between January 2010 and February 2022 were retrospectively analyzed. Medical history, physical examination, and radiographic images were recorded in detail. The greatest dimension of the suprapatellar pouch (SP) effusion on radiograph was measured. Computed tomography and magnetic resonance imaging were used to confirm the presence of neglected osteochondral fractures and measure the fragment size. Potential risk factors were calculated and correlated with reference to the neglected osteochondral fractures and fragment size using multivariate linear regression analysis.

RESULTS

Weight, walking ability, effusion grade, and SP measurement had a significant correlation with neglected osteochondral fractures in primary acute traumatic patellar dislocation (p = 0.046; p < 0.001; p = 0.048; p < 0.001). The cutoff point was 53.5 kg for weight and 18.45 mm for SP measurement. In the neglected fractures group, SP measurement was statistically significant with larger fragment size (beta value = 0.457; p < 0.001), and the cutoff point was 26.2 mm.

CONCLUSIONS

SP effusion is not only associated with an increased risk of neglected osteochondral fractures in primary acute traumatic patellar dislocation but also with larger fragment size. Knee radiograph, medical history, and physical examination can predict the need for further imaging examination and even surgery in primary acute traumatic patellar dislocation.

Computational comparison of medializing tibial tubercle osteotomy and trochleoplasty in patients with trochlear dysplasia

Medial patellofemoral ligament reconstruction (MPFLR) has emerged as the procedure of choice for recurrent patellar dislocation. This addresses soft tissue injury but does not address underlying anatomic factors, including trochlear dysplasia, that are commonly present and increase risk of dislocation. Quantification of the stability offered by other surgical interventions, namely, medializing tibial tubercle osteotomy (mTTO) and trochleoplasty, with and without MPFLR, may provide insight for surgical choices in patients with trochlear dysplasia. We developed subject-specific finite element models based on magnetic resonance scans from a cohort of 20 patients with trochlear dysplasia and recurrent patellar dislocation. The objectives of this study were (1) to compare patella stability after mTTO and trochleoplasty procedures; (2) to evaluate whether it is necessary to perform an MPFLR in combination with the mTTO or trocheoplasty procedure; and (3) to quantify the robustness of patellar stability to variability in knee kinematics. Trochleoplasty performed better than mTTO at stabilizing the patella between 5° and 30° flexion. For both mTTO and trochleoplasty procedures, it was beneficial to also perform MPFLR-inclusion of MPFLR halved the magnitude of patellar laxity predicted in the simulations. Simulations that did not include any medial patellofemoral ligament restraint were also more sensitive to variation in tibiofemoral internal-external kinematics.

Effect of Lower Extremity Torsion on Clinical Outcomes After Medial Patellofemoral Ligament Reconstruction and Tibial Tubercle Transfer for Recurrent Patellofemoral Instability

BACKGROUND

Increased femoral torsion (FT) or tibial torsion (TT) has been suggested to be a potential risk factor for recurrent patellofemoral instability. However, the influence of increased FT or TT on the postoperative clinical outcomes of recurrent patellofemoral instability has rarely been investigated.

PURPOSE

To assess the effect of increased FT or TT on postoperative results in patients with recurrent patellofemoral instability after combined medial patellofemoral ligament reconstruction (MPFLR) and tibial tubercle transfer, along with the influence of other risk factors.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Out of 91 patients, the study's analyses included 86 patients with recurrent patellofemoral instability who were treated with MPFLR and tibial tubercle transfer and enrolled between April 2020 and January 2021. FT and TT were assessed using preoperative computed tomography images. According to the torsion value of FT or TT, patients were categorized into 3 groups for each of FT and TT: group A (<20°), group B (20°-30°), and group C (>30°). Patellar height, femoral trochlear dysplasia, and the tibial tuberosity-trochlear groove (TT-TG) distance were also assessed. Patient-reported outcome scores (Tegner, Kujala, International Knee Documentation Committee [IKDC], Lysholm, and Knee injury and Osteoarthritis Outcome Score [KOOS]) were evaluated pre- and postoperatively. Clinical failure of MPFLR was recorded. Subgroup analysis was conducted to evaluate the effect of increased FT or TT on the postoperative outcomes.

RESULTS

A total of 86 patients were enrolled with a median follow-up time of 25 months. At the final follow-up, all functional scores improved significantly. Patella alta, high-grade trochlear dysplasia, and increased TT-TG distance did not have any significant effect on the postoperative functional scores. Regarding FT, subgroup analysis indicated that all functional scores of group C were lower than those of groups A and B except the KOOS knee-related Quality of Life score. For TT, group C had lower scores than group A for all functional outcomes except Tegner and KOOS Quality of Life and lower scores than group B for Kujala, IKDC, KOOS (Symptoms and Sport and Recreation subscales), Tegner, and Lysholm scores. The comparison between group A and group B, whether for FT or TT, revealed no significant differences.

CONCLUSION

For patients with recurrent patellofemoral instability, increased lower extremity torsion (FT or TT >30°) was associated with inferior postoperative clinical outcomes after combined MPFLR and tibial tubercle transfer.

Acute Irreducible Rotational Patellar Dislocation with Patellar Tendon Rupture: A Case Report

CASE

In this report, we present a case of acute patellar dislocation with both vertical and longitudinal rotation of the patella. As a result of rotation in the longitudinal axis, the articular surface of the patella faced outward, and the dorsal surface faced the femoral condyle. The patient underwent open reduction. One year after open reduction and soft-tissue repair, the patient had acceptable knee function and no knee pain.

CONCLUSION

This case shows how similar cases may be treated with an open reduction to properly address the patellar dislocation.

4-in-1 Quadricepsplasty for Habitual and Fixed Lateral Patellar Dislocation in Children

BACKGROUND

Habitual and fixed patellar dislocations represent extreme forms of patellar instability and can lead to significant functional loss. The underlying complex pathoanatomy of a laterally positioned and shortened extensor mechanism poses challenges in its management. The purpose of our study was to evaluate the anatomic risk factors and outcomes of a 4-in-1 quadricepsplasty (wide lateral releases, Insall proximal tube realignment, Roux-Goldthwait patellar tendon hemi-transfer, and step-wise quadriceps lengthening) for stabilization of habitual and fixed patellar dislocation.

METHODS

In a retrospective study, all patients with habitual and fixed patellar dislocation who underwent 4-in-1 quadricepsplasty and had a minimum 2-year follow-up were identified. Preoperative magnetic resonance imagings were evaluated for the presence of anatomic risk factors. As a prospective part of the study, patient-reported outcomes were collected using validated instruments including Pedi-IKDC, HSS-Pedi FABS activity score, BPII 2.0 score, Kujala score, and KOOS score.

RESULTS

Seventeen knees (12 patients) formed the study cohort. Twelve knees had habitual dislocation (9 in extension and 4 in flexion) and 5 had fixed dislocation. Mean age was 9 years. 6/17 (35.3%) knees were associated with syndromes. On magnetic resonance imaging, trochlear dysplasia was the most common anatomic risk factor present in 15/17 (88.2%) knees. 13/17 (76%) knees had presence of 2 or more risk factors. At the mean follow-up of 43.3 months, the mean Pedi-IKDC score was 88.1, the HSS-Pedi FABS activity score was 15.6, the BPII 2.0 score was 78.2, the Kujala score was 90, KOOS score was 93.9, and overall patient satisfaction score was 83.3. For complications, 3/17 knees (17.6%) had recurrent patellar instability, 1 knee had postoperative stiffness that required manipulation under anesthesia and 1 knee had a superficial wound infection.

CONCLUSIONS

Most patients with habitual and fixed patellar dislocation present during the first decade of life. There are several underlying anatomic risk factors, the most common being trochlear dysplasia and patellar tilt. The 4-in-1 quadricepsplasty technique provides reliable patellar stabilization, satisfactory clinical results, and acceptable patient-reported outcomes at a minimum 2-year follow-up, with a 17.6% redislocation rate.

LEVEL OF EVIDENCE

Level IV.

Incidence and concomitant chondral injuries in a consecutive cohort of primary traumatic patellar dislocations examined with sub-acute MRI

PURPOSE

To present age- and sex-specific cumulative annual incidences of primary traumatic lateral patellar dislocation (LPD) and to detail patient characteristics and concomitant chondral injuries including osteochondral fractures, as visualized on magnetic resonance imaging (MRI), in a large consecutive cohort of knee-injured individuals.

METHODS

Data on primary traumatic lateral patellar dislocations were collected from a large consecutive cohort of knee injuries examined with sub-acute MRI in a single centre with a well-defined catchment area. Annual incidences for different age-groups in relation to gender were calculated together with the risk of concomitant chondral and osteochondral injury, during sports and in general.

RESULTS

A total of 184 primary patellar dislocations were identified in the cohort of 1145 acute knee injuries (n=175) and surgical records (n=9). Knee MRI was performed within a median of six days of injury. Median age of patients with primary LPD was 16 years (interquartile range, 14-21; range, 9-47) and 41% were females. Males were significantly older than females at the time of injury (median age 17 vs. 15, P = 0.021) and sustained their primary LPD during sports more often than females (65 vs. 40%, P < 0.001). Primary LPD occurred most frequently at the age of 13 to 15 years where the annual incidence was 125 (95% CI, 96-160) per 100,000 persons. The overall annual incidence of primary LPD was 14 (95% CI, 12-16) per 100,000 persons, with a predominance of males versus females (17 vs. 11, P = 0.01). Concomitant lesions to joint surfaces were displayed on MRI or during surgery in 75 (43%) knees. Osteochondral fractures were seen in 32 knees (18%). We found no statistically significant difference in the risk of osteochondral fracture between those injured during sports or during leisure activity (14 vs. 24%, P = 0.08).

CONCLUSIONS

The annual incidence of first-time patellar dislocation was found to be 14 per 100,000 individuals with the highest incidence found among those aged 13-15 years. Primary LPD was more common among males and was sustained during sports activity in 55% of the cases. Associated injuries to the chondral surfaces should be expected in 43% of knees with primary LPD where 18% represent osteochondral fractures.

Comparison of Hindlimb Conformation in Cats with and without Medial Patellar Luxation

OBJECTIVES

 Medial patellar luxation (MPL) is the most common developmental cause of hindlimb lameness in cats. The association between femoral and tibial conformation and MPL measured on computed tomography (CT) has not been reported in cats. The aims were to report femoral and tibial conformation in cats with and without MPL and to report normal femoral and tibial angles.

METHODS

 Angle of inclination of femoral neck (AI), anatomical lateral distal femoral angle (aLDFA), femoral trochanteric angle (FCT), angle of anteversion of femoral neck (AA), distal and proximal anteversion angle (DAA/PAA), overall tibial valgus (TV), tibial torsion (TT), tibial tuberosity displacement (TTD) and trochlear depth:patellar thickness ratio (T:P) were measured by three observers on CT of cats with and without MPL. Comparisons were made between groups. Inter-observer intraclass correlation coefficient (ICC) was calculated.

RESULTS

 Sixteen cats were recruited: eight control and eight with MPL. The aLDFA, PAA, TT, TTD and T:P were significantly less in cats with high-grade MPL. The AI, FCT, AA, DAA and TV were not significantly different. A high correlation was shown with inter-observer ICC in 33.33% and good correlation in 26.67% when comparing measurements between observers.

CLINICAL SIGNIFICANCE

 This study suggests that cats with high-grade MPL have decreased TT, TTD and T:P and may require tibial tuberosity transposition and femoral trochleoplasty. The PAA, TT and aLDFA were decreased, although clinical significance may vary and these cats may not require correctional osteotomies. Results should be interpreted with caution as high/good levels of inter-observer ICC occurred in less than two-thirds of cases between observers.

Treatment of osteochondral fracture of lateral femoral condyle after patella dislocation with anchor absorbable sutures: A new surgical technique and a case report

RATIONALE

Osteochondral fracture (OCF) in weight-bearing area of lateral femoral condyle (LFC) is a rare combined injury caused by patellar dislocation.

PATIENT CONCERNS

A 15-year-old female student accidentally sprained her right knee while participating in sports activities. The patient felt pain in his right knee and limited movement. After hospitalization, the patients underwent computed tomography scan and magnetic resonance examination.

DIAGNOSIS

According to the imaging results, patellar dislocation combined with OCF of LFC was considered in diagnosis.

INTERVENTIONS

Through the lateral parapatellar approach, we reduced the osteochondral mass and bundled it with absorbable sutures of anchors.

OUTCOMES

The functional and radiographic outcome were satisfactory at 18 months after operation.

LESSONS

Anchor absorbable suture bridge fixation for this kind of OCF is not only effective, but also economical.

[Measurement of external deviation angle of patellar tendon and its application on diagnosis of recurrent patellar dislocation]

OBJECTIVE

To compare computed tomography (CT) measurement results of external deviation angle of patellar tendon and tibia tubercle-trochlea groove (TT-TG), as well as the diagnostic ability and pathology in recurrent patellar dislocation threshold.

METHODS

From January 2015 to March 2020, 46 patients with recurrent patella dislocation and 112 patients with non-patella dislocation were retrospectively analyzed. Forty-six patients with recurrent patella dislocation were divived into 2 groups according to TT-TG value, 11 patients with patellar dislocation with TT-TG≥20 mm(group A), including 7 males and 4 females, aged from 16 to 27 years old with an average of(21.00±3.98) years old; 35 patients with patellar dislocation with TT-TG<20 mm(group B), including 14 males and 21 females, aged from 16 to 37 years old with an average of(22.83±6.09) years old. While 112 patients with non-patella dislocation(group C) included 63 males and 49 females, aged 16 to 36 years old with an average of(22.87±5.69) years old. The measurement data of external deviation angle of patellar tendon and TT-TG value among three groups were compared. Spearman analysis was used to analyze correlation among them. Intraclass correlation coefficient (ICC) was used to determine repeatability within group. Receiver operating characteristic (ROC) area under the curve was used to evaluate diagnostic ability of parameters, and calculate osteotomy parameters of external deviation angle of patellar tendon, as well as external deviation angle of patellar tendon and TT-TG value in the diagnosis of recurrent patella diagnostic parameters of dislocation.

RESULTS

External deviation angle of patellar tendon in group A, B and C was (22.04±3.09)°, (17.20±4.43)°and (10.22±3.45)° respectively;while TT-TG value was(21.15±0.71) mm, (15.97±2.69) mm and (11.12±3.77) mm, there were significance among three groups (P<0.01), and had difference between group A and B(P<0.01). There was strong positive correlation between external deviation angle of patellar tendon and TT-TG value (r=0.735, P<0.000 1). The intra-group ICC value(0.980, 0.982) of external deviation angle of patellar tendon in group A and B have better repeatability than TT-TG value (0.594, 0.775). The external deviation angle of patellar tendon in group C(0.956) and repeatability of TT-TG value(0.906) was very good. In the diagnosis of recurrent patellar dislocation, the area under ROC curve of external deviation angle of patellar tendon (0.916) was greater than TT-TG value(0.886), and diagnostic parameters were 13.84°and 14.69 mm, respectively;in tibial osteotomy, the area under ROC curve of external deviation angle of patellar tendon was 0.821, and osteotomy parameter was 20.15°.

CONCLUSION

CT imaging could reliably measure external deviation angle of patellar tendon.There is a strong positive correlation between external deviation angle of patellar tendon and value of TT-TG, which could be used to determine pathological state of recurrent patellar dislocation, and external deviation angle of patellar tendon is superior to the TT-TG value in the diagnosis of recurrent patellar dislocation. The external deviation angle of patellar tendon could also be used to guide the formulation of the tibial osteotomy plan for recurrent patellar dislocation.

Postaxial hypoplasia of the lower extremity associated with congenital dislocation of the patella: A case report

RATIONALE

Evaluation of clinical and radiologic abnormalities in patients with postaxial hypoplasia of the lower extremity (PHLE) for treatment decisions represents a major challenge, which is more complicated when PHLE is associated with congenital dislocation of the patella.

PATIENT CONCERNS

: Herein, we present the case of an 8-year-old female patient with evident length inequality in her left lower extremity and inability to walk.

DIAGNOSES

Radiological evaluation revealed PHLE with fibular hemimelia, proximal femoral focal deficiency, tarsal coalition, and congenital patellar dislocation of the patella. The right lower extremity was also affected by fibular hemimelia.

INTERVENTIONS AND OUTCOMES

Surgical management included the Roux-Goldthwait technique for patellofemoral joint realignment, a medial knee stapled with Blount technique, and femur enlargement using the Wagner technique. The results from surgical intervention included a left femoral elongation of 6.7 cm featuring callus with angulation, displacement, and a discrepancy of 5 cm between femurs with a flexor contraction in the knee of -15° and a centralized knee.

LESSON

PHLE accompanied by congenital dislocation of the patella has not been extensively described in the literature; therefore, there is no established management. Starting reconstruction at an early age, together with an adequate classification of the deformity, are essential factors when opting for limb reconstruction.

Tibial Tubercle-Trochlear Groove/Trochlear Width Is the Optimal Indicator for Diagnosing a Lateralized Tibial Tubercle in Recurrent Patellar Dislocation Requiring Surgical Stabilization

PURPOSE

To identify the individualized method of quantifying lateralization of the tibial tubercle with the best diagnostic effectiveness, as evaluated by measurement repeatability using the intraclass correlation coefficient (ICC), the size of the difference between the case group and the control group, and receiver operating characteristic (ROC) curve analysis.

METHODS

Patients who had undergone surgery for recurrent patellar dislocation (the case group) and patients who had no history of patellar dislocation (the control group) from January 2014 to December 2019 were included in the study. Six indices that describe lateralization of the tibial tubercle were calculated using either computed tomography (CT) or magnetic resonance imaging (MRI): tibial tubercle lateralization (TTL), tibial tubercle-trochlear groove (TT-TG) ratio, tibial tubercle-posterior cruciate ligament (TT-PCL) ratio, TT-TG index, (TT-TG)/patellar width (PW), and (TT-TG)/trochlear width (TW). Diagnostic effectiveness was evaluated by 1) intra-rater reliability (measurements on two occasions) and inter-rater reliability (measurements by two assessors) using the ICC, 2) the size of the difference between the case group and the control group, and 3) ROC curve analysis, measuring the area under the ROC curve (AUC) and the post hoc power.

RESULTS

100 knees in 88 patients who had undergone surgery for recurrent patellar dislocation and 55 knees in 53 patients who had no history of patellar dislocation were analyzed. The ICC for all the methods were higher than .75. The mean differences between the case group and the control group for TTL, TT-TG ratio, TT-PCL ratio, TT-TG index, (TT-TG)/PW, and (TT-TG)/TW were 2%, 8%, 2%, 12%, 24% and 56%, respectively. The mean differences between the case group and the control group for (TT-TG)/TW was significantly greater than those for the other methods (P < .0001, unpaired t-test). AUC of TTL, TT-TG ratio, TT-PCL ratio, TT-TG index, (TT-TG)/PW, and (TT-TG)/TW were .708, .880, .630, .814, .882, and .905. AUC of (TT-TG)/TW was significantly greater than those of TTL and TT-PCL ratio (P < .0001). The post hoc power for TT-PCL ratio, TT-TG index, (TT-TG)/PW, TT-TG ratio, (TT-TG)/TW, and TTL were 78%, 81%, 88%, 88%, 91%, and 71%, respectively.

CONCLUSION

Of the six indices evaluated in this study, (TT-TG)/TW showed the greatest mean difference between the two groups, had the greatest diagnostic utility (as measured by AUC values) and had excellent inter-rater and intra-rater reliability (as measured by ICCs). Thus, it may be the best individualized index for diagnosing a lateralized tibial tubercle in patients with recurrent patellar dislocation requiring surgical stabilization compared to patients with no history of patellar dislocation.

LEVEL OF EVIDENCE

Level III, diagnostic study, retrospective cohort study.

Treatment of Chronic Dislocated Patella in a Skeletally Mature Down Syndrome Patient: A Case Report

CASE

A 55-year-old man with Down syndrome (DS) suffered from chronic irreducible right patellar dislocation. Imaging studies showed an attenuated appearance of the medial patellar retinaculum, and the tibial tubercle to trochlear groove distance measured 1.6 cm. Right medial patellofemoral ligament reconstruction (MPFLR) and lateral lengthening (LL) with proximalization of the tibial tubercle (PTT) were performed with good surgical outcomes.

CONCLUSION

The combination of MPFLR, LL, and PTT is a viable option for treating a skeletally mature DS patient with patellofemoral instability causing recurrent patellar dislocation.

Arthroscopically reduced, irreducible patella dislocation

Acute patella dislocations account for approximately 2%-3% of knee injuries and are therefore a relatively common presentation in the accident and emergency department. The majority of patella dislocations can be reduced with simple manoeuvres or even spontaneously and can be managed conservatively by bracing and rehabilitation. The aim of this study is to identify and review the main causes of the unique and unexpected event of irreducible patella dislocation and their characteristic presentations. Irreducible patella dislocations can happen but are very rare. Currently, a limited number of case reports are available, prompting for a need for research on this topic. This case study can shed light on the possible pathogenesis and pathognomonic features of irreducible patella dislocations and provide insight on the available therapeutic approaches.

Patellar instability: will my patella dislocate again?

PURPOSE OF REVIEW

The incidence of patellar instability in pediatric patients ranges is 50-100 in 100,000 patients per year. Risk of recurrent dislocations however has been cited from 8.6% to 88% depending on individual patient factors. This manuscript highlights the demographical, historical, and anatomic factors associated with recurrent patellar instability following a first-time patella dislocation in the pediatric population.

RECENT FINDINGS

In recent years, various studies have focused on identifying risk factors for recurrent patellar instability following a primary patellar dislocation. A mix of patient factors, including age of first dislocation, patella alta, elevated tibial tubercle to trochlear groove and trochlear dysplasia have all been noted in the literature, which have helped to develop various scoring tools to predict recurrent dislocation following nonoperative treatment.

SUMMARY

Risk of recurrent patellar instability in patients who have previously suffered a patellar dislocation can be due to many factors. These risk factors should be used and applied to a variety of risk scores in order to provide physicians and healthcare providers with a tool to counsel patients and families on their patellar redislocation risk and help guide further management.

Medial Patellofemoral Ligament Repair for Recurrent Patellar Instability: Successful Outcomes Among Patients With Low Coronal Malalignment and Normal Patellar Height

Medial patellofemoral ligament (MPFL) repair is discouraged for the treatment of chronic, recurrent patellar instability (RPI) because of high reported failure rates. However, the senior author uses MPFL repair for chronic RPI in the setting of low tibial tubercle-trochlear groove (TT-TG) distance. In this retrospective case series, we report results and evaluate outcome predictors. We used billing records to identify all patients, 14 years or older, who underwent isolated repair for chronic RPI performed by a single surgeon between September 2010 and February 2019. The TT-TG distance, patellar height (Caton-Deschamps Index [CDI]), and trochlear depth were measured on preoperative magnetic resonance imaging; postoperative reports were reviewed; and post hoc Kuala scores were obtained to extend outcome length. Patellar dislocation or revision surgery was considered a failure. Nonfailures were categorized as excellent or fair, based on the most recent report. Univariable generalized estimating equation models were used to evaluate associations of predictors (radiographic parameters, age, ligamentous laxity, primary presenting complaint) with failure and/or success. A total of 93 isolated MPFL repairs were performed. After exclusions were made for workers' compensation insurance (n=4), substance abuse (n=3), major secondary trauma less than 3 months postoperatively (n=3), and follow-up of less than 12 months (n=42), 41 knees (38 patients) had median follow-up of 32 months (interquartile range, 19-48 months). All repairs were patellar sided. Outcomes for 4 knees were considered failures, 23 were excellent, and 14 were fair. Only increased CDI was associated with increased risk of failure (odds ratio, 1.70; 95% CI, 0.98-2.92; P=.06). Mean CDI was 1.23 mm (SD, 0.13 mm) for failures vs 1.08 mm (SD, 0.16 mm) for nonfailures. Failure rate was less than 10% following patellar-sided MPFL repair for treatment of chronic RPI among patients with low TT-TG distance. Increased patellar height was associated with higher risk of failure. [Orthopedics. 2022;45(1):e23-e29.].