Sagittal patellar tilt and concomitant quadriceps hypotrophy after tibial nailing

Abnormal sagittal patellar tilt during active knee flexion and extension on 4DCT might be associated with patellofemoral pain

BACKGROUND

The quadriceps during activities mainly affect patellar movement in the sagittal plane. This study was to analyze the pattern of sagittal patellar tilt in patellofemoral pain (PFP) patients by four-dimensional computed tomography (4DCT).

METHODS

Thirty-four knees of PFP patients and 34 control knees were scanned with 4DCT. Patella-patellar tendon angle (P-PTA), patella-lateral tibial plateau angle (P-LTPA), patella-screen horizontal line angle (P-SHLA), articular facet of the patella-lateral tibial plateau angle (PA-LTPA), articular facet of the patella-screen horizontal line angle (PA-SHLA), and upper margin of the patella-quadriceps tendon angle (PU-QTA) were used to evaluate the sagittal patellar tilt. Two-factor repeated-measures ANOVA was used to compare all parameters between the two groups.

RESULTS

At 30°-40° of flexion, P-PTA was significantly lower in PFP group than in control group (p = 0.004). At 0°-10°, PU-QTA was significantly higher in PFP group than in control group (p = 0.027). During flexion and extension, P-SHLA and PA-SHLA were significantly higher in PFP group than in control group, but there were no significant differences in P-LTPA and PA-LTPA. From - 10° to 30°, P-PTA decreased as the knee flexion angle increased. PU-QTA, P-LTPA, and PA-LTPA also decreased as the knee flexion angle increased, but P-SHLA and PA-SHLA increased.

CONCLUSIONS

In PFP group, sagittal patellar tilt was abnormal, and patella showed anterior tilt relative to the screen horizontal line during active knee flexion and extension. The pattern of patellar sagittal motion during dynamic process was consistent between PFP and control groups. The characteristics of patellofemoral sagittal alignment should not be ignored when analyzing patellofemoral stability.

Differences in Patellofemoral Alignment Between Static and Dynamic Extension Positions in Patients With Patellofemoral Pain

Background

Considering that patellofemoral pain (PFP) is related to dynamic factors, dynamic extension on 4-dimensional computed tomography (4-DCT) may better reflect the influence of muscles and surrounding soft tissue than static extension.

Purpose

To compare the characteristics of patellofemoral alignment between the static and dynamic knee extension position in patients with PFP and controls via 4-DCT.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

Included were 39 knees (25 patients) with PFP and 37 control knees (24 participants). For each knee, an image of the dynamic extension position (a single frame of the knee in full extension [flexion angle of -5° to 0°] selected from 21 frames of continuous images acquired by 4-DCT during active flexion and extension) and an image of the static extension position (acquired using the same equipment with the knee fully extended and the muscles relaxed) were selected. Patellofemoral alignment was evaluated between the dynamic and static extension positions and between the PFP and control groups with the following parameters: patella-patellar tendon angle (P-PTA), Blackburne-Peel ratio, bisect-offset (BO) index, lateral patellar tilt (LPT), and tibial tuberosity-trochlear groove (TT-TG) distance.

Results

In both PFP patients and controls, the P-PTA, Blackburne-Peel ratio, and BO index in the static extension position were significantly lower (P < .001 for all), while the LPT and TT-TG distance in the static extension position were significantly higher (P ≤ .034 and P < .001, respectively) compared with values in the dynamic extension position. In the comparison between groups, only P-PTA in the static extension position was significantly different (134.97° ± 4.51° [PFP] vs 137.82° ± 5.63° [control]; P = .027). No difference was found in the rate of change from the static to the dynamic extension position of any parameter between the study groups.

Conclusion

The study results revealed significant differences in patellofemoral alignment characteristics between the static and dynamic extension positions of PFP patients and controls. Multiplanar measurements may have a role in subsequent patellofemoral alignment evaluation.

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.

Patella-patellar tendon angle in relation to the medial patellar plica syndrome, chondromalacia patella, and infrapatellar fat pad syndrome

The patella-patellar tendon angle (PPTA) assessing the sagittal patellar tilt was reported to be related with anterior knee pain. Herein, clinical effect of PPTA in patients with medial patellar plica (MPP) syndrome, chondromalacia patella, and infrapatellar fat pad (IPFP) syndrome, the most common causes of anterior knee pain, was evaluated. In this retrospective study, 156 patients with anterior knee pain who underwent magnetic resonance imaging (MRI) and arthroscopic surgery that confirmed isolated MPP syndrome, chondromalacia patella, or IPFP syndrome from June 2011 to January 2021 were included in the study group and 118 patients without knee pathology on MRI during the same period were included in the control group. The PPTA was measured on knee MRI and compared between the two groups. A receiver operating characteristic (ROC) analysis was used to evaluate the value of PPTA for predicting the risk of patellofemoral joint disorder. The mean PPTA was significantly smaller in study group (138.1 ± 4.2°) than control group (142.1 ± 4.3°) (p < 0.001). However, there was no significant difference in PPTA among the patients with MPP syndrome, chondromalacia patella, and IPFP syndrome. Furthermore, the ROC analysis revealed that the area under curve, sensitivity, and specificity for predicting the risk of patellofemoral joint disorders were 0.696, 70.3% and 57.6%, respectively, at a PPTA cutoff of 138.3°. Therefore, the smaller PPTA may be associated with MPP syndrome, chondromalacia patella, and IPFP syndrome. Furthermore, PPTA could be a predictive factor for the risk of patellofemoral joint disease in patients with anterior knee pain.

Sagittal patellar flexion angle measurement determines greater incidence of patella alta in patellar tendinopathy patients

PURPOSE

The objective of this study was to compare patellar height and patella alta between a control cohort and patients with patellar tendinopathy by the sagittal patellar flexion angle (SPFA) measurement.

METHODS

Magnetic resonance imaging (MRI) scans of the knee were obtained from a sports imaging facility and screened to select patients with anterior knee pain. This symptomatic group was divided into two patient cohorts: those with and without MRI features of patellar tendinopathy. Lateral knee radiographs were reviewed and SPFA, knee flexion angle and Insall-Salvati ratio (IS) were measured from the radiographs by two independent reviewers.

RESULTS

A total of 99 patients consisting of 48 patellar tendinopathy patients and 51 control patients were included. There was a significantly higher mean patellar height (p = 0.002, d = 0.639) and a greater patella alta incidence in the patellar tendinopathy cohort (25.0%) compared to the controls (3.9%) (p = 0.022, d = 0.312). Insall-Salvati ratio measurements showed no difference in patella alta incidence between tendinopathy and control cohorts. There was excellent inter- and intra-observer reliability of SPFA measurements (ICC 0.99).

CONCLUSION

This is the first study to demonstrate a greater incidence of patella alta in patellar tendinopathy patients compared to controls. A greater patella alta incidence amongst patellar tendinopathy patients as defined by SPFA was found to be clinically relevant, as it suggests these patients may comprise the recalcitrant patient subgroup who do not improve with current surgical intervention and may therefore benefit from a biomechanical surgical solution.

LEVEL OF EVIDENCE

III.

Effects of morphological changes in the patellar tendon on the development of anterior knee pain after intramedullary nailing for tibial shaft fractures: A retrospective comparative study

OBJECTIVE

This study aimed to investigate the effects of morphological changes of the patellar tendon (length, width, and thickness) on the development of anterior knee pain (AKP) after intramedullary nailing (IMN) of tibial shaft fractures.

METHODS

A total of 39 patients, treated by IMN using the transpatellar approach for tibial shaft fractures, were retrospectively reviewed and included in the study. The patients were then divided into 2 groups based on the presence of AKP: group A, patients who developed AKP (9 men, 9 women; mean age=35.39±9.32 years), and group B, patients without AKP (13 men, 8 women; mean age=41.38±14.78 years). To assess the morphological changes in the patellar tendon, magnetic resonance imaging was performed on the operated and unoperated, contralateral knees of the patients. The patellar tendon index (PTI) was calculated using the length, width, and thickness of the patellar tendon, and a set of variables was established to be a proportion of the measurements of the operated knees to those of the unoperated ones (operated/healthy PTI ratio). PTI ratios were compared between both the groups. Furthermore, the morphological features of the patellar tendon, including the length, width, and thickness, were examined within the groups as independent variables. To assess pain intensity in group A, a 10-cm visual analogue scale (VAS) was used. To evaluate functional status, the Lysholm knee scoring system was used.

RESULTS

The PTI ratio was significantly higher in group A (1.37±0.12) than in group B (1.03±0.08) (p<0.001). In group A, the mean VAS score was 5.35±1.11, and a moderate linear correlation was found between PTI ratios and VAS scores (r=0.494, p=0.044). The mean Lysholm score was significantly lower in group A (80.17±3.05) than in group B (89.76±3.05) (p<0.001). In group A, the width and thickness of the patellar tendon were found to be significantly different between the operated and unoperated knees (p=0.024 and p=0.002, respectively). In group B, there was no difference between the operated and unoperated knees in terms of the 3 measurements (length, width, and thickness) (p=0.762, p=0.753, and p=0.118, respectively).

CONCLUSION

Evidence from this study revealed that morphological changes occurring in the patellar tendon after IMN for tibial shaft fractures using a transpatellar approach may have a significant role in the development of AKP. The increase in the tendon width and thickness may be the cause of pain and insufficient knee function in such patients.

LEVEL OF EVIDENCE

Level III, Therapeutic study.

Patella-patellar tendon angle decreases in patients with infrapatellar fat pad syndrome and medial patellar plica syndrome

PURPOSE

Infrapatellar fat pad (IPFP) syndrome and medial patellar plica (MPP) syndrome are two recognized causes of anterior knee pain. However, diagnosing these syndromes is challenging without arthroscopic examination. The aim of this study was to evaluate sagittal patellar tilt in patients with IPFP syndrome or MPP syndrome by measuring the patella-patellar tendon angle (PPTA) in affected patients.

METHODS

Eighty-three patients with anterior knee pain who underwent diagnostic arthroscopy that confirmed isolated IPFP or MPP syndrome from 2011 to 2016 were included in this retrospective study. Patients were divided into Group A (IPFP syndrome, n = 44) and Group B (MPP syndrome, n = 39). The control group included 78 patients without knee pathology who underwent magnetic resonance imaging (MRI) of the knee during the study period. Radiographic measurements, including PPTA, IPFP area, patellar height, axial patellar alignment, patellar tilt, sulcus angle, and lateral trochlear inclination, were made on MRI images by two experienced sports medicine orthopedists.

RESULTS

The mean PPTA in each knee-pathology group was significantly smaller than that in the control group (Group A: 137.3° ± 4.9°; Group B: 138.1° ± 3.2°; control group, 141.4° ± 2.9°). There was no significant difference between groups for any other radiographic parameter evaluated.

CONCLUSION

The PPTA was significantly smaller in patients with IPFP syndrome or MPP syndrome than in healthy controls. Therefore, sagittal patellar tilt should be included in the routine evaluation of patients with anterior knee pain. Evaluation of PPTA may help to diagnose IPFP syndrome or MPP syndrome.

LEVEL OF EVIDENCE

Level IV.

Patella-patellar tendon angle and lateral patella-tilt angle decrease patients with chondromalacia patella

PURPOSE

The aim of the present study was to evaluate the effect of patellofemoral joint morphology and patellar alignment (lateral patellar tilt and sagittal patellar tilt) on the presence and stage of CP, and identify the differences between sexes.

METHODS

MRI of 243 patients [146 men (60.1%)] were evaluated retrospectively. Patients were grouped as normal group without chondromalacia, group with mild chondromalacia (grades 1-2) and group with severe chondromalacia (grades 3-4). Sagittal patellofemoral alignment was assessed by the angle between the patella and patellar tendon (P-PTA), and the angle between the quadriceps tendon and patella (Q-PA). Patellar tilt was assessed by lateral patellar tilt angle (LPTA). In addition, patellofemoral joint morphology was evaluated by measuring trochlear depth (TD), trochlear sulcus angle (TSA) and patella angle (PA).

RESULTS

P-PTA, Q-PA, LPTA and TD values were significantly lower in patients with severe chondromalacia than in patients with both normal and mild chondromalacia (P < 0.001). TSA values were significantly higher in patients with severe chondromalacia than those with both normal and mild chondromalacia (P < 0.001). TSA was higher and TD was lower in women compared to men (P < 0.001). LPTA and P-PTA were lower in women compared to men, and the difference was significant. There was no difference in PA between the two sexes.

CONCLUSIONS

Patellar cartilage degeneration increases with trochlear dysplasia. There is a strong correlation between patellar malalignment (lateral patellar tilt and sagittal patellar tilt) and chondromalacia patella. Women are more prone to developing CP than men.

Sagittal patellar flexion angle: a novel clinically validated patellar height measurement reflecting patellofemoral kinematics useful throughout knee flexion

PURPOSE

Patellar height measurements on lateral radiographs are dependent on knee flexion which makes standardisation of measurements difficult. This study described a plain radiographic measurement of patellar sagittal height which reflects patellofemoral joint kinematics and can be used at all degrees of flexion.

METHODS

The study had two parts. Part one involved 44 normal subjects to define equations for expected patellar position based on the knee flexion angles for three new patellar height measurements. A mixed model regression with random effect for individual was used to define linear and polynomial equations for expected patellar position relating to three novel measurements of patella height: (1) patellar progression angle (trochlea), (2) patellar progression angle (condyle) and (3) sagittal patellar flexion. Part two was retrospective and involved applying these measurements to a surgical cohort to identify differences between expected and measured patellar position pre- and post-operatively.

RESULTS

All three measurements provided insight into patellofemoral kinematics. Sagittal patellar flexion was the most useful with the least residual error, was the most reliable, and demonstrated the greatest detection clinically.

CONCLUSIONS

Clinically applied radiographic measurements have been described for patellar height which reflect the sagittal motion of the patella and can be used regardless of the degree of flexion in which the radiograph was taken. The expected sagittal patellar flexion linear equation should be used to calculate expected patellar height.

LEVEL OF EVIDENCE

IV.

Suprapatellar versus infrapatellar approaches in the treatment of tibia intramedullary nailing: a retrospective cohort study

Background

Tibial shaft fractures are routinely managed with intramedullary nailing (IMN). An increasingly accepted technique is the suprapatellar (SP) approach. The purpose of this study was to compare the clinical and functional outcomes of knee joint after tibia IMN through an suprapatellar (SP) or traditional infrapatellar (IP) approach.

Methods

Retrospective analysis was performed in patients with tibial shaft fractures that were treated with IMN through a SP or IP approach between 01/01/2014 and 31/12/2016. The clinical and functional outcomes of the knee were assessed with the Hospital for Special Surgery (HSS) Knee Score. Secondary outcomes included the operation time and intraoperative blood loss.

Results

A total of 50 patients/fractures (26 IP and 24 SP) with a minimum follow-up of 15 months were evaluated. All fractures were OTA 42. No significant differences were found between the two groups in age, gender, side of fractures, operation time, intra-operative blood loss, and follow-up time. No significant difference was seen in HSS score (P = 0.62) between them. Sub analysis of all the HSS components scores revealed no significant differences between pain (P = 0.57), the stand and walk (P = 0.54), the need for walking stick (P = 0.60) and extension lag (P = 0.60). The other HSS components showed full scores (IP 10 vs. SP 10) in both approaches, including muscle force, flexion deformity and stability components. The range of motion (ROM) component score was superior in the IP group (P = 0.04) suggesting a higher ROM.

Conclusions

Both SP and IP approach results in equivalent overall HSS knee scores. However, for the HSS component, the IP approach was superior to SP approach regarding the ROM.

Sagittal plane tilting deformity of the patellofemoral joint: a new concept in patients with chondromalacia patella

PURPOSE

The aims of this study were to evaluate sagittal plane alignment in patients with chondromalacia patella via magnetic resonance imaging (MRI), analyse the relationships between the location of the patellar cartilaginous lesions and sagittal alignment and finally investigate the relationships between the sagittal plane malalignment and patellofemoral loadings using by finite element analysis.

METHODS

Fifty-one patients who were diagnosed with isolated modified Outerbridge grade 3-4 patellar chondromalacia based on MRI evaluation and 51 control subjects were evaluated. Chondromalacia patella patients were divided into three subgroups according to the chondral lesion location as superior, middle and inferior. The patella-patellar tendon angle (P-PT) was used for evaluation of sagittal alignment of patellofemoral joint. Each subgroup was compared with control group by using P-PT angle. To investigate the biomechanical effects of sagittal plane malpositioning on patellofemoral joint, bone models were created at 30°, 60° and 90° knee flexion by using mean P-PT angles, which obtained from patients with chondromalacia patellae and control subjects. The total loading and contact area values of the patellofemoral joints were investigated by finite element analysis.

RESULTS

The mean age of all participants was 52.9 ± 8.2 years. The mean P-PT angle was significantly lower in chondromalacia group (142.1° ± 3.6°) compared to control group (144.5° ± 5.3°) (p = 0.008). Chondral lesions were located in superior, middle and inferior zones in 16, 20 and 15 patients, respectively. The mean P-PT angles in patients with superior (141.8 ± 2.7) and inferior subgroups (139.2 ± 2.3) were significantly lower than the values in the control group (p < 0.05). The contact area values were detected higher in models with chondromalacia than in the control models at the same flexion degrees. There were increased loadings at 30° and 90° flexions in the sagittal patellar tilt models.

CONCLUSION

This study revealed that sagittal plain malpositioning of the patellofemoral joint might be related to chondromalacia, especially in the presence of lesions in the upper and lower part of the patella. This condition leads to supraphysiological loadings on the patellofemoral joint. Sagittal patellar tilt should be considered in the evaluation and management of patellar cartilage defects. Taking sagittal plane malalignment into consideration in patellofemoral joint evaluation will enable us to design new physical and surgical modalities.

LEVEL OF EVIDENCE

IV.