Subluxation of the patella. Computed tomography analysis of patellofemoral congruence

Morphology of the knee in adult patients with neglected developmental dysplasia of the hip

BACKGROUND

Although there have been numerous studies on the treatment of developmental dysplasia of the hip, few have focused on its natural history into adulthood. We observed valgus deformity of the knee in a group of adult patients with developmental dysplasia of the hip. To the best of our knowledge, there has been no detailed study of that condition. The purpose of this study was to investigate structural changes of the knee in patients with neglected developmental dysplasia of the hip.

METHODS

Thirty-four adult patients with neglected developmental dysplasia of the hip and ten healthy adults were evaluated. The lower extremities were grouped according to the severity of the dysplasia. The morphology of the knees was evaluated with radiographic measurements, and the groups were compared.

RESULTS

Compared with the control group, the patients with severe developmental dysplasia of the hip had significant valgus deformity of the knee. This finding was associated with an increased vertical dimension of the medial femoral condyle, which led to a valgus inclination of the distal femoral articular surface. Although the femoral sulcus was shallower in the patients with developmental dysplasia of the hip, patellofemoral congruency was not deranged.

CONCLUSIONS

The pathologic condition of the hip joint in patients with developmental dysplasia of the hip results in developmental changes in the osseous anatomy of the knee joint, with the development of a valgus deformity of the lower extremity. If any surgical intervention is planned in a patient with developmental dysplasia of the hip, the whole lower extremity should be carefully analyzed, with special attention to the morphology of the knee, to avoid creating problems of malalignment.

MR imaging of patellar dislocation and relocation

Patellar dislocation and relocation (PDR) typically occurs suddenly after trauma or torsional stress on the extensor mechanism. Clinical evaluation after patellar dislocation/relocation usually reveals a swollen knee that is difficult to examine. Radiographs may show hemathroses and a minority of patients will have a chip fracture of the patella. Magnetic resonance (MR) imaging features seen with PDR include disruption or sprain of the medial retinaculum, lateral patellar tilt or subluxation, lateral femoral condylar and medical patellar osseous contusions, osteochondral injury, damage to Hoffa's fat pad, and joint effusion. Up to one third of patients will also show concomitant injury to the major ligaments of the knee or menisci. Without repair of the primary injury, redislocation occurs in greater than one half of patients. Consequently, surgical correction is often advocated. This article reviews the factors predisposing to PDR, the activities associated with PDR, the clinical, radiographic, and MR imaging features of PDR, and (briefly) therapy for this injury.

Tibial tubercle malposition in patellar joint instability: a computed tomograpy study in full extension and at 30 degree flexion

We evaluated the tibial tubercle position in knees with patellar instability. CT in full extension and at 30 degree flexion was used in 18 knees with instability and 18 control knees. Scans were taken at the level of the femoral epicondyles, tibial tubercle and distal tibia. We found that in full extension, the tibial tubercle was in a more lateral position in the unstable than in the control knees. At 30 degree flexion, the tibial tubercle in the unstable knees rotated internally, but it was never within the normal range. CT scans taken in full extension and at 30 degree flexion seem to be of value for ascertaining the degree of tibial tubercle malposition during knee flexion in patellar instability.

In vivo tracking of the human patella using cine phase contrast magnetic resonance imaging

Improper patellar tracking is often considered to be the cause of patellar-femoral pain. Unfortunately, our knowledge of patellar-femoral-tibial (knee) joint kinematics is severely limited due to a lack of three-dimensional, noninvasive, in vivo measurement techniques. This study presents the first large-scale, dynamic, three-dimensional, noninvasive, in vivo study of nonimpaired knee joint kinematics during volitional leg extensions. Cine-phase contrast magnetic resonance imaging was used to measure the velocity profiles of the patella, femur, and tibia in 18 unimpaired knees during leg extensions, resisted by a 34 N weight. Bone displacements were calculated through integration and then converted into three-dimensional orientation angles. We found that the patella displaced laterally, superiorly, and anteriorly as the knee extended. Further, patellar flexion lagged knee flexion, patellar tilt was variable, and patellar rotation was fairly constant throughout extension.

Quantitative MR measures of three-dimensional patellar kinematics as a research and diagnostic tool

PURPOSE

A three-dimensional (3D) study of normal patellar-femoral-tibial (knee) joint kinematics was performed using Cine Phase Contrast Magnetic resonance imaging (Cine-PC MRI) to determine the utility of this technique as a diagnostic tool in defining alterations in patellar tracking.

METHODS

Cine-PC MRI was originally developed to measure heart motion and blood flow and has now been adapted to the study of the musculoskeletal system. Thus, for the first time knee joint kinematics can be studied three-dimensionally, noninvasively, and in vivo during dynamic volitional leg extensions under load. Cine-PC MRI provides one anatomic and three orthogonal velocity images (vx, vy, and vz) for each time frame within the motion cycle. Bone displacements are calculated using integration and are then converted into both 3D orientation angles and 2D clinical angles.

RESULTS

The 3D patellar tilt and 2D clinical patellar tilt angle were nearly identical, even though these two angles have distinct mathematical definitions. The precision of the 2D clinical patellar tilt angle (N = 3) was approximately 2.4 degrees.

CONCLUSIONS

Since the overall subject (N = 18) variability for clinical patellar tilt angle and medial/lateral patellar displacement was low (SD = 2.9 degrees and 3.3 mm, respectively), Cine-PC MRI could prove to be a valuable tool in studying subtle changes in patellar tracking.

Patellar alignment evaluated by MRI

We analyzed the congruence of the articular cartilage surfaces and the corresponding subchondral bone in the patellar joint. 20 volunteers underwent MRI investigations of the right patellar joint in 20 degree and 45 degree flexion in the axial plane. The sulcus, congruence, and lateral patellofemoral angles, measured on MRI slices centered through the midtransverse patella, were recorded. In 20 degree and 45 degree knee flexion, the bony sulcus and lateral patellofemoral angles were significantly different from the respective cartilagineous angle. We conclude that 1) measurement of the bony sulcus and lateral patellofemoral angles does not allow conclusions about the articular cartilage surface and its thickness, 2) the bony congruence angle corresponds well to the articular cartilage surface as an indicator of patellar centralization.

Open or arthroscopic lateral release. Indications, techniques, and rehabilitation

Careful patient selection, accurate surgical technique, and careful postoperative rehabilitation are all equally important to success in lateral release surgery. Whether the surgery is performed by open or arthroscopic technique, one must release all layers of the retinaculum, spare the vastus lateralis, extend the release far enough distally, check intraoperative patellar mobility, and obtain absolute hemostasis. Postoperative rehabilitation must stress pain control, early quadriceps contraction, patellar mobility, and knee motion. With attention to these details, successful lateral release surgery is likely in most patients with pathologic lateral patellar tilt and minimal patellofemoral arthrosis.

Patellofemoral malalignment

Anterior knee pain represents one of the most common musculoskeletal complaints of adolescents. It is a disorder in which there is broad clinical experience and yet it represents a difficult and frustrating entity for the athlete to endure and for the physician to treat. An appropriate clinical examination and selected diagnostic studies can define the diagnosis and the introduction of conservative therapy usually will correct the problem. Occasionally, surgical intervention is required, and debate remains as to the optimal techniques that should be used.

Patellofemoral Instability: Evaluation and Management

Patellofemoral disorders are a common cause of knee pain and disability. A thorough history and a careful physical examination are essential to accurate diagnosis, and imaging modalities play an important role. Magnetic resonance imaging can provide information on malalignment and soft-tissue injuries. Although there is a continuum of diagnoses, most patellofemoral disorders can be divided into three distinct categories: soft-tissue abnormalities, patellar instability due to subluxation and dislocation, and patellofemoral arthritis. Many patellofemoral disorders respond to nonoperative therapy. When surgical intervention is necessary, patellar tilt can be successfully treated by a lateral release. Lateral patellar subluxation associated with malalignment can be corrected by a distal realignment procedure such as the anteromedial tibial tubercle transfer. Repair of the medial patellofemoral ligament in cases of patellar dislocation has considerably lowered the incidence of recurrent instability. Although no ideal treatment exists for patellofemoral arthritis, mechanical symptoms may be alleviated by arthroscopic debridement of delamination lesions. Articular cartilage-wear disorders may be stabilized by addressing the primary causative disorder.

Recurrent dislocation of the patella and the Goldthwait operation

In this study 17 patients with recurrent dislocation of the patella were followed up 10 years after their Goldthwait operation. The subjective and clinical findings were excellent or good in 70%. X-radiographs indicated osteoarthritis of the femoropatellar joint in 60%. Concerning the aetiopathological factors, we found an increased external torsion of the afflicted extremity (measured by computed tomography).

Axial radiography or CT in the measurement of patellofemoral malalignment indices in children and adolescents?

The present study compares the repeatability of patellofemoral malalignment (PFM) indices obtained by 20 degree flexion axial radiography (AR) and computerized tomography (CT) with 0 degree and 20 degree flexion of the knees in children and adolescents. Thirty-one patients with a mean age of 14.2 years (range 8 to 19.2 years) suffering from PFM were examined using these two radiographic techniques. The lateral patellofemoral angle (LPA), the lateral patellar tilt (LPT), and the lateral patellar displacement (LPD) were measured by by two different investigators on different occasions, and the agreement of these indices between CT and AR was evaluated according to Bland and Altman's statistical method. LPT and LPD obtained by AR were more reliable and repeatable than those obtained by CT. The quadriceps muscle contraction exacerbates PFM indices significantly with the knees in full extension (P = 0.0001). LPT and LPD measured at 20 degrees AR show reliably the two pathological components (the patellar tilt and the lateral patellar displacement) of PFM which are necessary for diagnosis and treatment planning. CT with quadriceps contractions is better in qualitative screening of more subtle cases of PFM.

Patellofemoral alignment: reliability

Clinical assessment of the patellofemoral alignment is frequently performed, yet the repeatability of these measurements has not been previously investigated. This study examined the reliability of measuring patellofemoral alignment. The Q angle, A angle, and patellar orientation (mediolateral tilt, mediolateral position, superoinferior tilt, and rotation) of 27 healthy subjects were measured over three trials using standardized positioning and operationally defined goniometric, pluri-cal caliper, and visual estimation measurement techniques. Intratester and intertester intraclass correlation coefficients of measurements obtained with the pluri-cal caliper and goniometer ranged from .52 to .86 and .003 to .61, respectively. Intratester and intertester standard errors of the instrumented measurements ranged from 1.6 to 3.5 degrees and 3.2 to 6.8 degrees (.28 and .55 cm for mediolateral position), respectively. Intratester kappa's of visually estimating patellar orientation ranged from .40 to .57. Intertester kappa's were between .03 and .30. The results suggest that both clinical estimation and instrumented measurement of patellofemoral alignment may be unreliable.

Importance of soft tissue integrity on biomechanical studies of the patella after TKA

This study evaluated the effects of soft tissue integrity on patellar tracking and patellofemoral joint force after total knee arthroplasty. The results indicate that partial dissection of the soft tissue integrity in the in vitro biomechanical studies of the patellofemoral joint can alter patellar tracking and joint force significantly, leading to improper conclusions.

Stress radiographs of the patellofemoral joint

Patellar instability is usually diagnosed on the basis of the clinical presentation without radiographic confirmation. In the present report, we describe a new radiographic method to demonstrate patellar instability. Axial radiographs were made of the patellofemoral joint of ninety individuals (180 knees) and were then repeated while a medial or lateral force was applied to the patella. The applied force was kept constant with use of a specially designed instrument. The ninety individuals were divided into four groups on the basis of the clinical findings: normal, lateral instability, medial instability, and multidirectional instability. Stress radiographs differentiated the four groups and confirmed the clinical diagnosis in all patients who had unilateral symptoms. A four-millimeter increase in medial or lateral excursion of the patella excursion of the asymptomatic knee was significant (p < 0.0001). Stress radiographs offer a simple method for the measurement of force-displacement relationships in the patellofemoral joint and for the demonstration of patellofemoral instability.

Kinematic and dynamic axial computed tomography of the patello-femoral joint in patients with anterior knee pain

Thirty-eight knees of 26 patients with anterior knee pain (12 bilateral) were included in the study. There were 22 women and 4 men, and their average age was 29 years. Axial computed tomography (CT) examination of both knees were done at 0 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees and 60 degrees of flexion with and without muscle contraction. Images were always taken at the mid-patellar level. Patellar tilt angle (PTA), congruence angle (CA) and sulcus angle (SA) were measured at each knee position. Normal values were also obtained from 14 healthy volunteers (28 knees). Thus, the types of patello-femoral incongruence were determined at each knee position: 1, tilt + lateralisation (TL: 12 knees); 2, lateralisation (L: 4 knees); 3, medialisation (M: 5 knees); 4, lateral to medial instability (LM: 1 knee); 5, tilt (T: 1 knee). Fifteen knees were classified as normal. When the groups were analysed separately, in the TL group the T or L component would have been missed in nine cases if the images were taken only at 30 degrees or only in the first 30 degrees of flexion. In the L group two patellae were reduced at 30 degrees. In three knees in the M group, medialisation began at 10 degrees, 20 degrees and 30 degrees. One patella was reduced at 40 degrees. In the LM case, the patella was lateralised at 0 degrees, 10 degrees, 20 degrees and medialised at 30 degrees and 40 degrees. In the T case, the patella was tilted only at 20 degrees, 40 degrees and 60 degrees.(ABSTRACT TRUNCATED AT 250 WORDS)

Computerized tomographic analysis of tibial tubercle position in the painful female patellofemoral joint

We used computerized tomography to evaluate the position of the tibial tubercle and to determine if the tibial tubercle is positioned more laterally in female patients with patellofemoral pain. We also wanted to determine the relationship of the tibial tubercle to tibial external rotation and patellar tilt. Sixty female patients and 19 healthy female controls were evaluated. To evaluate the position of the tibial tubercle, the tibial tubercle rotation angle (the angle formed by the line between the posteriormost edges of the medial and lateral femoral condyle and the line between the central point of the intercondylar space and the central point of the patellar tendon at the level of the tibial tubercle) was measured by superimposing the images from the level of the distal femoral condyle and the tibial tubercle. The relationship between the tibial tubercle rotation angle and patellar tilt was then assessed by dividing the patients into 3 subgroups according to the patellar tilt. The tibial tubercle rotation angle was significantly different between the patellofemoral pain patients and the controls. There were also significant differences between the patients with moderate patellar tilt (10 degrees to 20 degrees) and the controls, and between the patients with high patellar tilt (> 20 degrees) and the controls.

Patellofemoral malalignment in adolescents. Computerized tomographic assessment with or without quadriceps contraction

Twenty-seven adolescents with anterior knee pain with or without patellar instability were studied by computerized tomography to detect patellofemoral malalignment. The examination was performed with and without quadriceps contraction with the knee flexed to 15 degrees. Congruence angle, patellar tilt angle, sulcus angle, and trochlear depth were measured. This investigation showed the well-known types of patellofemoral malalignment with quadriceps relaxed (tilted, lateralized, lateralized, and titled patella) and, in 52% of cases, revealed changes in type and severity with quadriceps contraction (in 41%, lateralization and tilting were markedly more evident; in 11%, the type of malalignment changed). The results demonstrate that, in addition to assessment with quadriceps relaxed, computerized tomography with quadriceps contraction is a useful adjunct to diagnose and define the type of malalignment in particularly difficult circumstances.

Kinematic and dynamic axial computerized tomography of the normal patellofemoral joint

Fourteen normal volunteers with no history suggesting previous or current knee pathology underwent axial computed tomographic examination of the patellofemoral joint. There were 11 men and 3 women, whose ages ranged from 10 to 46 years (average 25 years). Axial images were obtained at 0 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees, and 60 degrees flexion both with and without contraction of the thigh muscles. Thus, 12 images were obtained for each individual. The CT scanner was focused at the midpatellar level prior to each image. Three measurements were made on 24 knees for each individual: congruence angle (CA), patellar tilt angle (PTA), and sulcus angle (SA). PTA increased slightly from 0 degrees to 20 degrees, and decreased slightly with more flexion (not significant, NS). The lower limit of PTA was usually 9 degrees-10 degrees; it was not lower than 7 degrees in any knee position. Muscle contraction increased PTA slightly at each degree of flexion (NS). Mean CA was +18.3 degrees (SD 20.8 degrees) at 0 degrees, which means that normal individuals may have CAs as high as +39 degrees at full extension. There was a gradual decrease in CAs with knee flexion. The mean values became negative between 20 degrees and 60 degrees flexion. Contraction of the thigh muscles caused lateralisation of the patella except at 30 degrees and 40 degrees flexion. This lateral pull was statistically significant at full extension (P < 0.01) and at 10 degrees flexion (P < 0.05). The SA decreased gradually as the flexion of the knee increased.(ABSTRACT TRUNCATED AT 250 WORDS)

The quantitative measurement of normal passive medial and lateral patellar motion limits

To quantify normal motion, medial and lateral passive patellar motion limits were measured in 67 high school athletes randomly selected from a group of 1340 athletes undergoing preseason physical examinations. Patellar displacement was measured at knee flexion angles of 0 degree and 35 degrees, using both a Patella Pusher (a hand-held force gauge) and a manual technique, and the results were compared. Demographic data and physical examination of the deceleration mechanism (Q angle, vastus medialis obliquus dysplasia, patella alta and baja, and valgus and varus alignment) were correlated with patellar motion limits. With the knee in extension, passive displacement of the patella averaged 9.6 mm medially and 5.4 mm laterally. In flexion, medial displacement averaged 9.4 mm and lateral displacement averaged 10.0 mm. No positive correlations were found between demographic data or deceleration mechanism examination parameters and patellar motion limits, suggesting that motion produced by the displacement force was limited by ligamentous restraints only. The clinical assessment of the passive limits of patellar motion should include examination at knee flexion angles of 0 degree and 35 degrees. The manually produced displacement was found to be more reproducible than displacement by the Patella Pusher (P < 0.05).

Magnetic resonance imaging of patellofemoral relationships

Patellofemoral relationships were analyzed in 11 patients (13 knees) with patellar dislocation and 15 asymptomatic subjects (15 knees) at 0 degree and 20 degrees of flexion. The measurements were made from five consecutive axial images through the patellofemoral joint. The six indices measured were lateral patellar tilt (LPT), lateral patellofemoral angle (LPA), lateral patellar displacement (LPD), patella-lateral condyle index (L/PW), congruence angle (CA), and sulcus angle (SA). The reproducibility of the method was evaluated. The difference between the two study groups was more evident at 0 degree than at 20 degrees of knee flexion. Significant differences were noted between measurements made at different levels of the joint, particularly in the controls. Isometric contraction of the quadriceps muscle lateralized and tilted the patella slightly in both groups. L/PW with and without quadriceps muscle contraction, and LPA with reference to the anterior condyles differentiated between the two study groups most clearly. LPT and LPA with reference to the anterior condyles differentiated the study groups better than LPT and LPA with reference to the posterior condyles. The reproducibility was good except for inter-observer comparison of CA and SA. The use of an imaging plane selected at the midpoint of the patellar articular cartilage increases the sensitivity of the measurements, since it takes into account both the height of the patella and the tendency towards lateralization. These results indicate that patellar tilt is best measured with the LPA index and patellar lateralization with the L/PW index at 0 degree knee flexion. This study should always include isometric contraction of the quadriceps muscle.

Subluxation of the patella: evaluation of patellar articular cartilage with MR imaging

In patients with subluxation of the patella, injury of the patellar articular cartilage is frequently observed, and correct evaluation of this cartilage injury is extremely important for the management of these patients. Magnetic Resonance (MR) studies were performed on 102 patellofemoral (PF) joints of 51 patients with subluxation of the patella and 20 PF joints of 10 healthy volunteers. In 77 of the 102 PF joints with subluxation, arthroscopy and/or operation were performed. MR images were obtained with spin-echo and FLASH sequences, and para-axial images were obtained. We retrospectively analysed the MR findings of the 77 joints with special attention to the surface and thickness of the cartilage, and classified them into four grades. These MR grades were compared with the grades on arthroscopy, and the following results were obtained: MR grade 0, normal cartilage (n = 27, sensitivity 90.9%, specificity 74.2%); MR grade 1, thickening of the cartilage (n = 24, sensitivity 50%, specificity 89.1%); MR grade 2, surface irregularity of the cartilage (n = 20, sensitivity 85%, specificity 94.7%); MR grade 3, loss of the cartilage (n = 6, sensitivity 100%, specificity 100%). Although the early changes observed by arthroscopy were underestimated from the MR images, MR imaging proved to be extremely useful for evaluating moderately or advanced patellar cartilage injury.

Patellofemoral stress. A prospective analysis of exercise treatment in adolescents and adults

Thirty patients, 13 skeletally immature individuals and 17 adults, participated in a prospective study designed to evaluate the effect of isometric quadriceps strengthening exercises on patellofemoral pain. Of the 30 patients with anatomically normal lower extremity alignment and no history of previous knee trauma or surgery, there were 34 knees that had a decrease in peripatellar knee pain with a structured exercise program. One additional patient had a decrease in pain after an arthroscopic lateral release and with continued exercises. An equal number of skeletally immature patients and adults had a decrease in peripatellar knee pain. However, 5 of the 17 adults had to limit their activities, while no adolescent patient had to limit activity. Additionally, eight skeletally immature knees had greater than 5 degrees change in their congruence angles, as measured on Merchant tangential radiographs, over the year-long course of this study. Only one adult knee had a similar radiographic improvement. We recommend immediate action to alleviate patellofemoral pain syndrome, even when extremity alignment is normal. An isometric, progressive resistance quadriceps program with iliotibial band and hamstring stretching exercises is the preferred initial treatment.

Relation between speed of reaction and psychometric tests of mental ability in musculoskeletal injury-prone subjects

Long reaction time (RT), long choice reaction time (CRT), and low scores on psychometric tests of mental ability (MA) have in previous studies been related to musculoskeletal injuries. There has been controversy concerning the relation between slow reaction and low-grade MA recently, the old hypothesis of negative correlation between RT and MA being discussed. The aim of this study was to analyze the relation between speed of reaction and MA. For a sample of 123 volunteer healthy young men simple RT, choice RT, and spatial (block design), verbal and arithmetic components of MA were tested. A principal component analysis was performed and the factor matrix was rotated orthogonally using the varimax method. Two factors were extracted accounting for 73% of the total variance in data space. The mental ability factor, which was responsible for 70% of the variance in factor space, was comprised of components of MA and choice RT. The speed of reaction factor accounted for the remaining 30% of the variance in factor space and was comprised of simple and choice RTs. As choice RT had significant loading on the mental ability factor, the subjects having scores in the lowest quartile on both choice RT and MA total score were compared with the independent expected value by using the chi-squared test. The results of low-grade MA and slow choice reaction were not independent. Accordingly, the results do not support the entire distinction between traditional mental ability or convergent thinking and speed of reaction in normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)