Variables affecting patellar height in patients undergoing primary total knee replacement

Does sex and region affect the patella position? A multi-center study of 2000 cases

PURPOSE

As patella height can affect the outcome of total knee arthroplasty (TKA) in a number of ways, this study aimed to investigate whether factors such as region, sex and age play a role in causing differences in patella height.

METHODS

Between the 1st of March and the 31st of December 2022, 2000 patients from 7 different countries (Turkey, Saudi Arabia, Germany, Austria, Italy, Spain, and the United Kingdom) awaiting elective TKA were enrolled in this study. Lateral radiographs of the knee with the femoral condyles fully overlapped were used to measure the Insall-Salvati index. The patella height measurements were then correlated with age, sex and region to see if there were any patterns of distribution.

RESULTS

From ten different hospitals across seven countries, 2,000 patients were collected. Approximately, 50% of the groups were female and 50% were male with a median age at surgery of 59 years (± 20 years). There were no significant differences in patella position based on age, region or sex between the different study populations, although there were significant differences between patients from different countries.

CONCLUSION

Patella height showed significant variability within our patient cohort, even between different populations within the same country of origin. However, it should be noted that age, sex and country of origin do not appear to influence patella height in the preoperative planning of knee surgery.

Patella Baja with Complete Quadriceps Tendon Rupture

Patella baja is an uncommon yet dangerous condition primarily found in patients who have received knee surgery, but can occur in anyone, more commonly in overweight, middle-aged males. The case presented outlines an instance in which a man with no previous history of knee injury or surgery, yet with other high-risk factors, develops patella baja after a minor injury. The case highlights the importance of testing and awareness of such conditions. The case report outlines the cause, diagnosis, and treatment of the patient's condition.

Modified Z-plasty of the Patellar Ligament with Reinforcement of the Quadriceps Tendon in the Treatment of Patella Baja

Patella baja is an infrequent knee pathology, but it is limiting due to joint stiffness and localized pain in the anterior region of the knee. It may occur after trauma, prolonged immobilization or local surgical intervention. The striking pathological finding is the shortening and increase in thickness of the patellar ligament. Several surgical techniques have been described for its treatment, and there is no standardized treatment. We describe the case of a 73-year-old female patient who presented with knee stiffness, significant functional deficit, and patella baja after total knee arthroplasty. She underwent a recently described soft tissue surgical procedure, with excellent functional evolution, improving from a Lysholm Knee Score of 16 to 81 points, allowing early mobilization and return to daily life activities.

Serial Change in Patellar Height after Tension Band Wiring of Patellar Fractures

Background and Objectives: Patella baja is a common complication after operative treatment for patellar fracture. This study aimed to investigate (1) the serial changes in patellar height and (2) the potential predictive factors for patellar height changes after tension band wiring (TBW) for patellar fractures. Materials and Methods: Forty-one patients who underwent TBW for patellar fracture between March 2019 and September 2022 were enrolled. To identify serial changes in patellar height, modified Blackburne-Peel index (mBPI) was assessed at just after surgery, at 3 months, at 6 months, at 1 year and at the final follow-up. Multiple regression analysis was conducted to identify factors correlated with mBPI difference between the contralateral side (considered as preoperative status) and injured side. Results: The postoperative mBPI exhibited a decline over time (mean mBPI immediately post operation/3 months/6 months/1 year/final follow-up: 0.69/0.63/0.63/0.62/0.61) Specifically, mBPI showed a significant reduction immediately post operation to 3 months (p < 0.001), although comparisons at other time points did not reveal significant differences. A lower position of the fracture was associated with a decrease in patellar height after surgery. Conclusions: Patellar height was mainly decreased from immediately post operation to 3 months. A fracture in a lower position of associated with decreased patellar height after the TBW of the transverse patellar fracture.

Change in patellar height in medial and lateral unicompartmental knee arthroplasty: a clinical trial

INTRODUCTION

Evidence on patellar height changes following unicompartmental knee arthroplasty (UKA) is lacking. Therefore, this study compared the patella height in patients who underwent medial versus lateral UKA. Moreover, a subgroup analysis was conducted to investigate whether sex, age, and BMI of the patients exert an influence on the postoperative patellar height.

METHODS

Radiographs and hospital records of patients undergoing UKA were prospectively collected. Surgeries were performed by one author with long experience in UKA in a highly standardised fashion. The implants were fixed-bearing medial PPK (Zimmer Biomet, Warsaw, Indiana, USA) and fixed-bearing lateral ZUK (Lima Corporate, Udine, Italy). The patellar height was measured using the Insall-Salvati and Caton-Deschamps indices.

RESULTS

A total of 203 patients were included: 119 patients were included in the medial and 84 in the lateral UKA. The mean age of the patients was 68.9 ± 6.7 years, and the mean BMI was 28.1 ± 4.1 kg/m2. 54% (110 of 203 patients) were women. On admission, between-group comparability was found in age, BMI, sex, and length of the follow-up. No between-group and within-group difference was detected pre- and post-operatively in the Insall-Salvati and Caton-Deschamps indices in patients who have undergone medial versus lateral UKA. Concerning the subgroup analyses, no between-group and within-group difference was detected pre- and post-operatively in all comparisons according to sex, age, and BMI.

CONCLUSION

No difference was found in patella height in patients who have undergone medial compared to lateral UKA. Furthermore, there was no evidence of an association between patient characteristics (sex, age, BMI) and patella height between medial and lateral UKA.

A new and simple method for patellar height measurement: Fibula-condyle-patella angle

OBJECTIVES

This study aims to evaluate the inter-observer reliability of fibula-condyle-patella angle measurements and to compare it with other measurement techniques.

PATIENTS AND METHODS

Between January 01, 2023 and January 31, 2023, a total of 108 patients (20 males, 88 females; mean age: 47.5±12.0 years; range, 18 to 72 years) who underwent X-rays using the fibula-condyle-patella angle, Insall-Salvati, Caton-Deschamps, Blackburne-Pell, and plateau-patella angle (PPA) methods were retrospectively analyzed. Knee lateral radiographs taken in at least 30 degrees of flexion and appropriate rotation were scanned. All measurements were made by two orthopedic surgeons who were blinded to measurement methods.

RESULTS

Right knee patellar height measurements were conducted in 56 patients, while left knee patellar heights were assessed in 52 patients. The highest inter-observer concordance was found in the fibula-condyle-patella angle. The second highest concordance was found in the Insall-Salvati. The highest concordance correlation was found with PPA in the measurements of both researchers.

CONCLUSION

The fibula-condyle-patella angle is a reliable technique with a good inter-observer reliability for measuring patellar height. We believe that this study will inspire future research to establish comprehensive reference values for clinical applications.

Simultaneous Evaluation of Tibiofemoral and Patellofemoral Mechanics in Total Knee Arthroplasty: A Combined Experimental and Computational Approach

Contemporary total knee arthroplasty (TKA) has not fully restored natural patellofemoral (P-F) mechanics across the patient population. Previous experimental simulations have been limited in their ability to create dynamic, unconstrained, muscle-driven P-F articulation while simultaneously controlling tibiofemoral (T-F) contact mechanics. The purpose of this study was to develop a novel experimental simulation and validate a corresponding finite element model to evaluate T-F and P-F mechanics. A commercially available wear simulator was retrofitted with custom fixturing to evaluate whole-knee TKA mechanics with varying patella heights during a simulated deep knee bend. A corresponding dynamic finite element model was developed to validate kinematic and kinetic predictions against experimental measurements. Patella alta reduced P-F reaction forces in early and midflexion, corresponding with an increase in T-F forces that indicated an increase in extensor mechanism efficiency. Due to reduced wrapping of the extensor mechanism in deeper flexion for the alta condition, peak P-F forces in flexion increased from 101% to 135% of the applied quadriceps load for the baja and alta conditions, respectively. Strong agreement was observed between the experiment and model predictions with root-mean-square errors (RMSE) for P-F kinematics ranging from 0.8 deg to 3.3 deg and 0.7 mm to 1.4 mm. RMSE for P-F forces ranged from 7.4 N to 53.6 N. By simultaneously controlling dynamic, physiological loading of the T-F and P-F joint, this novel experimental simulation and validated model will be a valuable tool for investigation of future TKA designs and surgical techniques.

Can Anterior Knee Pain Be Explained by Patella Position After Infrapatellar Tibia Intramedullary Nailing?

OBJECTIVE

The objective of this study is to investigate the postoperative position of the patella and its relationship with anterior knee pain in patients operated with infrapatellar reamed tibia intramedullary nailing (IMN).

MATERIALS AND METHODS

 Patients who underwent tibia IMN between 2019 and 2022 and who had anterior knee pain in their postoperative follow-up at least two outpatient clinic controls with an interval of at least one month were examined. Patellar height indices (Insall-Salvati, Blackburne-Peel, Caton-Deschamps, and modified Insall-Salvati) and sagittal angulation (patella-patellar tendon angles) were measured on the lateral direct radiographs of the patients in semi-flexion. As a control group, measurements were made on the contralateral intact extremity radiographs of the same patients.

RESULTS

 There was no significant difference in patellar height indices between the fractured and intact sides in any of the patients (p = 0.588; p = 0.747; p = 0.446; p = 0.573, respectively). When the sagittal angulations were analyzed, a significant difference was found between the fractured and intact sides of the patients (p = 0.048), resulting in an approximate three-degree change.

CONCLUSION

 Patellar sagittal balance has been identified as one of the contributing factors to the development of anterior knee pain following reamed tibial IMN. Further biomechanical and comprehensive clinical studies are needed on this subject.

Effect of Patellofemoral Arthroplasty on Patellar Height in Patients with Patellofemoral Osteoarthritis

Osteoarthritis (OA) in the knee is common, painful, and may be uni- or multicompartmental. The compartment affected by arthritis may be due to trauma, malalignment (varus or valgus), or in the case of patellofemoral OA, patella alta. Patellofemoral arthroplasty (PFA) is an effective partial knee replacement surgery for patellofemoral OA. We hypothesized that PFA can decrease patellar height. In addition, we predicted better outcomes for patients with patella alta before PFA and those whose patellar heights decreased after PFA. This is a retrospective cohort study of PFA patients from 2012 to 2020. Before and after PFA, we measured patellar heights on X-ray images and collected patient-reported outcome measures (PROMs) (International Knee Documentation Committee score, Kujala Anterior Knee Pain Score, and Veterans RAND 12-Item Health Survey for mental and physical health). Statistical analyses assessed PROMs and compared outcomes based on pre- and postoperative patella height. Of 133 knees, 73% presented with patella alta and 61% had patellar heights that decreased after PFA. Compared with patients who did not present with patella alta, patients with patella alta reported similar outcomes with respect to knee function, pain, and general physical and mental health. Compared with patients whose patellar heights decreased after PFA, patients whose knees did not decrease in height reported greater improvements in pain and function. Our findings suggest that patella alta is commonly found in patients with patellofemoral OA and that PFA can decrease patellar height. Future studies are needed to assess whether patellofemoral OA patients with greater degrees of patella alta would benefit from staged or concurrent tibial tubercle distalization.

Automated patellar height assessment on high-resolution radiographs with a novel deep learning-based approach

BACKGROUND

Artificial intelligence and deep learning have shown promising results in medical imaging and interpreting radiographs. Moreover, medical community shows a gaining interest in automating routine diagnostics issues and orthopedic measurements.

AIM

To verify the accuracy of automated patellar height assessment using deep learning-based bone segmentation and detection approach on high resolution radiographs.

METHODS

218 Lateral knee radiographs were included in the analysis. 82 radiographs were utilized for training and 10 other radiographs for validation of a U-Net neural network to achieve required Dice score. 92 other radiographs were used for automatic (U-Net) and manual measurements of the patellar height, quantified by Caton-Deschamps (CD) and Blackburne-Peel (BP) indexes. The detection of required bones regions on high-resolution images was done using a You Only Look Once (YOLO) neural network. The agreement between manual and automatic measurements was calculated using the interclass correlation coefficient (ICC) and the standard error for single measurement (SEM). To check U-Net's generalization the segmentation accuracy on the test set was also calculated.

RESULTS

Proximal tibia and patella was segmented with accuracy 95.9% (Dice score) by U-Net neural network on lateral knee subimages automatically detected by the YOLO network (mean Average Precision mAP greater than 0.96). The mean values of CD and BP indexes calculated by orthopedic surgeons (R#1 and R#2) was 0.93 (± 0.19) and 0.89 (± 0.19) for CD and 0.80 (± 0.17) and 0.78 (± 0.17) for BP. Automatic measurements performed by our algorithm for CD and BP indexes were 0.92 (± 0.21) and 0.75 (± 0.19), respectively. Excellent agreement between the orthopedic surgeons’ measurements and results of the algorithm has been achieved (ICC > 0.75, SEM < 0.014).

CONCLUSION

Automatic patellar height assessment can be achieved on high-resolution radiographs with the required accuracy. Determining patellar end-points and the joint line-fitting to the proximal tibia joint surface allows for accurate CD and BP index calculations. The obtained results indicate that this approach can be valuable tool in a medical practice.

Patellar height changes after treatment of tibia plateau fractures: A radiological analysis

OBJECTIVES

To determine the impact of tibial plateau fractures on patellar height and the factors affecting this impact.

METHODS

A total of 40 patients treated for plateau fractures between 2017-2021 were evaluated in this retrospective prognostic study. The patient group consisted of lateral radiographs of the operated knees, whereas the control group consisted of lateral radiographs of the healthy sides of the same patients. Insall-Salvati, Caton-Deschamps, Blackburne-Peel, and modified Insall-Salvati indices were measured for both groups. In addition, Schaztker and Luo classifications, as well as the demographic profiles of the patients, were analyzed.

RESULTS

There was no significant difference between the groups in terms of patellar height indices (p>0.05). A significant relationship was found between the Insall-Salvati (p=0.046) and Blackburne-Pell (p=0.011) indices and Luo classification. Post hoc analyses revealed a significant relationship between the Insall-Salvati index and "One Column" fractures and between the Blackburne-Peel index and "Two Column" fractures.

CONCLUSION

Long-term functions of tibial plateau fractures should be evaluated not only with a painless range of motion but also with patellar height. It should be noted that the Luo classification, which evaluates the plateau 3-dimensionally, may be associated with changes in postoperative patellar height values.

Patellar height after unicompartmental knee arthroplasty: comparison between fixed and mobile bearing

PURPOSE

The purpose of this study was to determine the changes in patellar heights by comparing standardised pre- and post-operative radiographs in a consecutive series of patients undergoing unicompartmental knee arthroplasty (UKA) with two different approaches and implant designs [fixed bearing (FB) vs mobile bearing (MB)] and to correlate the patellar heights with clinical outcomes.

METHODS

One hundred and seventy-two UKA patients were prospectively enrolled in the study. 75 patients underwent a minimally invasive FB medial UKA (referred to hereinafter as the 'FB group'); 97 patients were treated with a minimally invasive MB medial UKA. The pre-operative and mid-term (1-year) post-operative patellar heights and clinical scores of these groups of patients were compared using the Insall-Salvati (IS) and Caton-Deschamps (CD) indices and the Oxford Knee Score (OKS).

RESULTS

No differences were found between the two groups either with regard to the pre-operative data (p > 0.05) or between pre- and post-operative radiographic scores at the time of each follow-up (p > 0.05). Both the groups reported a significant clinical improvement (p<0.05) as did all the sub-groups (p < 0.05). In the MB group, a higher CD index in females was found at the final follow-up stage (p = 0.043) and a higher pre-operative CD index was found in patients with BMI ≥ 28 (p = 0.040). A statistically negative correlation was found between the pre-operative OKS and pre-operative IS index (rho=- 0.165; p=0.031).

CONCLUSIONS

Both FB and MB arthroplastys with different surgical approaches did not change the patellar height regardless of the age, gender and BMI at short-medium-term follow-up. The post-operative patellar height seems not to be correlated with the clinical outcomes. A higher pre-operative IS index was correlated with knee pain and function.

LEVEL OF EVIDENCE

Level II-prospective comparative study.

STUDY REGISTRATION

Researchregistry6433- www.researchregistry.com .

Postoperative Patellar Height After Undergoing Total Knee Arthroplasty: Mechanical Axis Versus Kinematic Axis

Introduction When performing total knee arthroplasty (TKA), surgeons may use either the mechanical alignment (MA) or the kinematic alignment (KA) to guide implant placement and joint balancing. By measuring preoperative and postoperative patellar height (PH), surgeons can predict knee stability after TKA. Improper PH is associated with knee instability which may complicate the postoperative course and lead to patient dissatisfaction or need for revision. The purpose of this study is to measure patellar height using the Insall-Salvati Index (ISI), Caton-Deschamps Index (CDI), and Blackburne-Peel Index (BPI) preoperatively and postoperatively in patients who underwent TKA with either MA or KA to assess for changes in patellar height. Methods We performed a retrospective eight-year review of 256 patients who underwent TKA with either MA or KA by a single surgeon at a single hospital site. We obtained demographic data, including gender, age, and BMI, via the electronic health record. Furthermore, we calculated the ISI, CDI, and BPI using necessary parameters from preoperative and postoperative radiographs. We used these measurements to assess any statistically significant difference in postoperative PH. Results The MA cohort consisted of 104 patients with an average age of 63 years and an average BMI of 34.1 kg/m2. The KA cohort included 152 patients with an average age of 64 years and an average BMI of 34.9 kg/m2.  For the MA population, the average postoperative score with ISI was 1.10 [1.05 to 1.16] (p < 0.001), with CDI was 1.05 [0.98 to 1.11] (p < 0.001), and with BPI was was 0.94 [0.89 to 0.99] (p < 0.001). While for the KA population, the average postoperative score with ISI was 1.03 [0.99 to 1.06] (p = 0.17), with CDI was 0.87 [0.82 to 0.91] (p = 0.15), and with BPI was 0.82 [0.78 to 0.86] (p = 0.34). Conclusion TKA with a KA has a statistically significant improvement in postoperative PH and better postoperative maintenance of preoperative PH. Improved PH may lead to increased patellofemoral stability and superior postoperative outcomes in patients undergoing TKA. Future studies should focus on whether differences in preoperative and postoperative PH measurements result in changes in clinical outcomes in patients with MA versus KA TKA.

MODELING OF PATELLA HEIGHT WITH DISTAL FEMUR AND PROXIMAL TIBIA REFERENCE POINTS WITH ARTIFICIAL NEURAL NETWORK

The patellofemoral joint is one of the parts of the knee extension mechanism that plays a role in the stability of the knee by enlarging the force arm of the quadriceps muscle and changing the direction of the muscle strength. For the entire knee joint to perform its task painlessly and functionally, the positions and strength of the muscles, the strength of the ligaments, and their reaction to movement must be compatible. The Insall–Salvati (Ins-Sal) index is useful for showing changes in patellar height produced by repositioning the tibial plateau, in other words, showing changes in patellar tendon length. Patella height is an important value to be taken into account in knee prosthesis surgery, tibial osteotomy, and anterior cruciate ligament reconstruction. The morphometric relationship between the reference measurements of the distal femur and proximal tibia and the position of the patella will be useful in determining the natural anatomy. In this study, we aimed to determine the relationship between patella height and distal femur and proximal tibia reference areas by using the artificial neural network method as an alternative approach method. In order to assess the performance of the estimation of the Ins-Sal index, the four ANN model with six input combinations which included age, gender and the reference measurements for the right and left sides have been constructed and tested. The MSE and [Formula: see text] values are calculated for every four models for the training and test phase. The results show that the proposed approach for modeling of relation between reference measurements and the Ins-Sal index is a powerful approach.

Better precision of a new robotically assisted system for total knee arthroplasty compared to conventional techniques: A sawbone model study

BACKGROUND

The purpose of this study was to compare the accuracy of this new HURWA robotic-assisted total knee arthroplasty (TKA) technique to the accuracy of the conventional technique in a sawbone model.

METHODS

The HURWA robotic-assisted TKA system was applied in the robotic group. After bone resection, all of these sawbones were scanned by the use of a structured light scanning system. Measurements of bone resections, femoral coronal and sagittal measurements, and tibial coronal and sagittal measurements were recorded.

RESULTS

Compared to the conventional technique, the HURWA robotic-assisted system significantly improved the accuracy of the bone resection levels and angles. In the robotic group, the accuracy of all of the bone resection levels was below 0.6 mm (with standard deviation [SD] below 0.6 mm), and all of the bone resection angles were below 0.6° (with SD below 0.4°).

CONCLUSION

Our data suggest that this novel HURWA robotic-assisted system can significantly improve the accuracy of bone resection levels and angles.