DISSERTATIONS | GIDEON REGALADO | ASSESSMENT OF THE PATELLOFEMORAL JOINT IN... | No 57
Dissertations in Health Sciences
PUBLICATIONS OF
THE UNIVERSITY OF EASTERN FINLAND
Patellofemoral disorder is a common problem among children and adolescents. It reflects the complexity in the interaction between anatomy and function of the joint influenced by the dynamic process of growth. The disorder encompasses signs and symptoms ranging from instability, pain and patellar dislocation. For this reason, assessing the patellofemoral joint in children and
adolescents remains a big challenge.
A lot of studies have been done on the adult knee. In contrast, there is a paucity of studies done in children and adolescent knee. The assessment of the knee starts with a good history and physical examination. This is followed
by imaging. The “sine qua non” of imaging for the patellofemoral joint is radiological examination. But static radiological examination alone
is not enough.
The advent of CT and MRI brings along with it the development of dynamic assessment of the patellofemoral joint. Dynamic assessment of the patellofemoral offers the possibility of looking into both the general and most
specially the subtle changes that happen in different phases of movement of the patellofemoral joint from full extension to deep flexion both qualitatively and quantitatively. These subtle findings relate to the effect of the activities of the muscles, ligaments and tendons on the joint during its movement, findings
that are not detectable in static imaging alone.
Although this thesis include the outcome of a long-term follow-up of the conservative and operative treatment for patellar dislocation, on one hand,
on the other hand, it very much focuses on the applicability of KINE-MRI assessment in children and adolescents. In this thesis the proven KINE-MRI
parameters in the adults are applied in children and adolescents.
The TT-TG parameter measurement technique in adults is applied in children and adolescents.
The benefit of MRI imaging in the young knee is based on the fact that it is not invasive and there is no radiation hazard involved. This makes it very suitable for children and adolescents. The weakness of studies included in this
thesis is due to the fact that the samples sizes used are small. On the other hand, because there are not so many studies done on children and adolescents
so far, this thesis serves as a stimulus for further studies in the future.
The prospect of dynamic assessment through KINE-MRI relative to assessment of the patellofemoral joint of children and adolescents is unlimited.
It is an evolving assessment modality.
GIDEON REGALADO
DISSERTATIONS | GIDEON REGALADO | ASSESSMENT OF THE PATELLOFEMORAL JOINT IN... | No 57
Dissertations in Health Sciences
PUBLICATIONS OF
THE UNIVERSITY OF EASTERN FINLAND
Patellofemoral disorder is a common problem among children and adolescents. It reflects the complexity in the interaction between anatomy and function of the joint influenced by the dynamic process of growth. The disorder
encompasses signs and symptoms ranging from instability, pain and patellar dislocation. For this reason, assessing the patellofemoral joint in children and
adolescents remains a big challenge.
A lot of studies have been done on the adult knee. In contrast, there is a paucity of studies done in children and adolescent knee. The assessment of the knee starts with a good history and physical examination. This is followed
by imaging. The “sine qua non” of imaging for the patellofemoral joint is radiological examination. But static radiological examination alone
is not enough.
The advent of CT and MRI brings along with it the development of dynamic assessment of the patellofemoral joint. Dynamic assessment of the patellofemoral offers the possibility of looking into both the general and most
specially the subtle changes that happen in different phases of movement of the patellofemoral joint from full extension to deep flexion both qualitatively and quantitatively. These subtle findings relate to the effect of the activities of the muscles, ligaments and tendons on the joint during its movement, findings
that are not detectable in static imaging alone.
Although this thesis include the outcome of a long-term follow-up of the conservative and operative treatment for patellar dislocation, on one hand,
on the other hand, it very much focuses on the applicability of KINE-MRI assessment in children and adolescents. In this thesis the proven KINE-MRI
parameters in the adults are applied in children and adolescents.
The TT-TG parameter measurement technique in adults is applied in children and adolescents.
The benefit of MRI imaging in the young knee is based on the fact that it is not invasive and there is no radiation hazard involved. This makes it very suitable for children and adolescents. The weakness of studies included in this
thesis is due to the fact that the samples sizes used are small. On the other hand, because there are not so many studies done on children and adolescents
so far, this thesis serves as a stimulus for further studies in the future.
The prospect of dynamic assessment through KINE-MRI relative to assessment of the patellofemoral joint of children and adolescents is unlimited.
It is an evolving assessment modality.
GIDEON REGALADO
ASSESSMENT OF THE PATELLOFEMORAL JOINT IN CHILDREN AND ADOLESCENTS BY
KINEMATIC MRI IMAGING AND BY CLINICAL
EVALUATION
Gideon Regalado
ASSESSMENT OF THE PATELLOFEMORAL JOINT IN CHILDREN AND ADOLESCENTS BY
KINEMATIC MRI IMAGING AND BY CLINICAL EVALUATION
To be presented by permission of the
Faculty of Health Sciences, University of Eastern Finland for pubic examination in Auditorium 1, Kuopio
on September 25, 2020 at 12 o’clock noon.
Publications of the University of Eastern Finland Dissertation in Health Sciences
Number 570
Department of Orthopedics and Traumatology, Institute of Clinical Medicine, Faculty of Health Sciences,
University of Eastern Finland Kuopio
2020
Series Editors
Professor Tomi Laitinen, M.D. Ph.D.
Institute of Clinical Medicine, Clinical Physiology and Nuclear Medicine Faculty of Health Sciences
Associate professor (Tenure Track) Tarja Kvist, Ph.D.
Department of Nursing Science Faculty of Health Sciences Professor Ville Leinonen, M.D., Ph.D.
Institute of Clinical Medicine, Neurosurgery Faculty of Health Sciences
Professor Tarja Malm, Ph.D.
A. I. Virtanen Institute for Molecular Sciences Faculty of Health Sciences
Lecturer Veli-Pekka Ranta, Ph.D.
School of Pharmacy Faculty of Health Sciences
Distributor:
University of Eastern Finland Kuopio Campus Library
P.O. Box 1627 FI-70211 Kuopio, Finland
www.uef.fi/kirjasto Name of printing office/kirjapaino
Grano, 2020
ISBN: 978-952-61-3415-4 (print/nid.) ISBN: 978-952-61-3416-1 (PDF)
ISSNL: 1798-5706 ISSN: 1798-5706 ISSN: 1798-5714 (PDF)
Author’s address: Institute of Clinical Medicine, Surgery
Faculty of Health Sciences, University of Eastern Finland P.O. Box 100
FI-70029
KUOPIO, FINLAND E-mail: gidreg@gmail.com
Doctoral programme: Doctoral programme of Clinical Research Supervisors: Professor Matti Eskelinen, M.D., Ph.D.
Institute of Clinical Medicine, Surgery
Faculty of Health Sciences, University of Eastern Finland KUOPIO, FINLAND
Docent Antti Joukainen, M.D., Ph.D.
Department of Orthopedics and Traumatology Kuopio University Hospital
University of Eastern Finland KUOPIO, FINLAND
Docent Hannu Kokki, M.D., Ph.D.
Institute of Clinical Medicine University of Eastern Finland KUOPIO, FINLAND
Reviewers: Professor Jari Arokoski, M.D., Ph.D.
Department of Physical and Rehabilitation Medicine Helsinki University Hospital
University of Helsinki HELSINKI, FINLAND
Professor Ilkka Kiviranta, M.D., Ph.D.
Department of Orthopaedics and Traumatology University of Helsinki
HELSINKI, FINLAND
Opponent: Professor Ilkka Helenius, M.D. Ph.D.
Department of Orthopaedics and Traumatology Helsinki University Hospital
University of Helsinki HELSINKI
FINLAND
Regalado, Gideon
Assessment of the Patellofemoral Joint in Children and Adolescents by Kinematic MRI Imaging and by Clinical Evaluation.
Kuopio: University of Kuopio: Eastern Finland Publication of the University of Eastern Finland Dissertations in Health Sciences. Number. 2020. 09.25.
ISBN: 978-952-61-3415-4 (print):
ISSNL: 1798-5707 ISSN: 1798-5706
ISBN: 978-952-61-3416-1 (pdf):
ISSN: 1798-5714 (pdf):
ABSTRACT
Due to the complexity of the patellofemoral joint problems in children and adolescents, its diagnosis remains a challenge. The introduction of kinetic MRI (KINE-MRI), however, has made it possible to dynamically investigate the patellofemoral joint. This thesis consists of three studies. The 1st study aims to validate the applicability of KINE- MRI in children and adolescents. Of the twenty-nine patients who underwent a KINE- MRI scan, nineteen patients had objective unilateral patellar dislocations and ten had signs and symptoms compatible with patellofemoral instability. Ten healthy subjects aged 11-16 years were recruited for comparison. Both knees of the patients were examined and the study’s parameters included the following: 1) bisect offset (BSO) 2) lateral patellar displacement (LPD) 3) patellar tilt angle (PTA) 4) sulcus angle (SA) and 5) Insall–Salvati Index (ISI) at 0, 10, 20 and 30 degrees of flexion. The subjects were divided into three groups: Group 1: knee with patellar dislocation or affected knee (AKG) (n = 29), Group 2: knee without patellar dislocation or unaffected knees (UAKG) (n=26), and Group 3: healthy knees (HKG) (n=19). The study proved that the KINE- MRI’s parameters are reproducible in children and adolescents. In the 2nd study, thirty- six patients with primary patellar dislocation were randomized into two groupings: a) conservative treatment group and b) operative treatment group. They were followed up prospectively for 6 years. The study proved that there were fewer re-dislocations and better functioning in the primary operative treatment group (33%) than that of the conservative treatment group (73%). The 3rd study consisted of taking a KINE-MRI measurement of TT-TG distances in adolescents. Thirteen healthy, 11-17-year-old subjects (8 boys and 5 girls) were studied using Tesla 3.0 MRI at 30 to 0 degrees angles.
The study proved that the TT-TG distance decreased in greater flexion but increased progressively towards full extension. At 0° of flexion, the mean TT-TG distance was 16.5 mm (SD 4.7) and at 30° of flexion, the mean was 11.2 mm (SD 2.4).
The results of these three studies emphasize the strengths of KINE-MRI in the diagnostic evaluation of the patellofemoral joint and examines the outcomes of different courses of treatment for patellofemoral disorders. First, KINE-MRI parameters are reproducible in children and adolescents with patellofemoral instability and dislocation.
Operative treatment of primary patellar dislocation produces better outcomes than conservative treatment over a long-term period of 6 years. Lastly, the TT-TG distance measurement is reproducible in children and adolescents and proves that the TT-TG distance decreases in full flexion and increases in full extension. These results, along with the dynamic imaging one can attain with the use of KINE-MRI, may inform a new way of evaluating patellofemoral joint disorders in children and adolescents.
Keywords:
Adolescent, Patellar dislocation, Patellar instability, Patellofemoral pain, KINE-MRI
Regalado, Gideon
Assessment of the Patellofemoral Joint in Children and Adolescents by Kinematic MRI Imaging and by Clinical Evaluation.
Kuopio: University of Kuopio: Eastern Finland Publication of the University of Eastern Finland Dissertations in Health Sciences. Number. 2020. 09.25.
ISBN: 978-952-61-3415-4 (print):
ISSNL: 1798-5707 ISSN: 1798-5706
ISBN: 978-952-61-3416-1 (pdf):
ISSN: 1798-5714 (pdf):
TIIVISTELMÄ
Lasten ja nuorten polvilumpio-reisiluunivelen ongelmien monimutkaisuuden vuoksi sen diagnoosi on edelleen haaste. KINE-MRI:n käyttöönotto on mahdollistanut nivelen tutkimisen dynaamisesti. Tämä väitöskirja koostuu kolmesta tutkimuksesta.
Ensimmäinen tutkimus vahvisti KINE-MRI:n soveltuvuuden lapsille ja nuorille.
Tutkimuksessa oli 29 potilasta, joista 19 tutkittavalla oli objektiivinen toispuolinen polvilumpion sijoiltaanmeno ja kymmenellä potilaalla polvilumpio-reisiluunivelen epävakauteen sopivia löydöksiä. Kymmenen tervettä 11-16 vuotiasta tutkittavaa rekrytoitiin vertailuryhmään. Tutkittavien molemmat polvet tutkittiin dynaamisella KINE-MRI-menetelmällä. Tutkimusparametrit olivat: 1) puolipoikkeama (BSO) 2) sivusuuntainen lumpion siirtymä (LPD) 3) lumpion kallistuskulma (PTA) 4) sulcus- kulma (SA) ja 5) Insall-Salvati (ISI) -suhde 0, 10, 20 ja 30 asteen taivutuksessa.
Tutkittavina olivat ryhmä 1: polvi, jossa oli lumpion sijoiltaanmeno, vammautunut polvi (AKG) (n = 29), ryhmä 2: polvi ilman lumpion sijoiltaanmeno, terve polvi (UAKG) (n = 26) ja ryhmä 3: terveet polvet (HKG) (n = 19). Tutkimus osoitti, että KINE-MRI parametrit olivat toistettavissa lapsilla ja murrosikäisillä. Toisessa tutkimuksessa 36 potilasta, joilla oli primaarinen polvilumpion sijoiltaanmeno, satunnaistettiin A) konservatiiviseen hoitoryhmään ja B) operatiiviseen hoitoryhmään, ja heitä seurattiin 6 vuoden ajan. Tutkimus osoitti, että primaarisessa operatiivisessa hoitoryhmässä oli vähemmänn uusia sijoiltaanmenoja (33%) ja toiminnallinen tulos oli parempi verrattuna konservatiivisen hoidon ryhmään, jossa sijoiltaanmenoja oli 73%. Kolmas tutkimus oli dynaaminen kinemaattinen TT-TG-etäisyyksien mittaus murrosikäisillä. Kolmetoista tervettä, 11-17-vuotiasta henkilöä (8 poikaa ja 5 tyttöä) tutkittiin Tesla 3.0 MRI:llä polvinivelen ollessa 30 - 0 asteen kulmassa. Tutkimus osoitti, että TT-TG-etäisyys pieneni polven taivutuskulman kasvaessa ja vastaavasti kasvoi polvea oikaistaessa. Kun polvinivel oli suorassa, TT-TG-etäisyys oli 16,5 mm (SD 4,7) ja 30 ° taivutuksessa 11,2 mm (SD 2,4).
Yhteenvetona voidaan todeta, että KINE-MRI -parametrit olivat toistettavissa lapsilla ja nuorilla, joilla oli polvilumpio-reisiluunivelen epävakaus ja polvilumpion sijoiltaanmeno. Primaarinen polvilumpion sijoiltaanmenon operatiivinen hoito johti parempaan toiminnalliseen lopputulokseen ja pienempään uuden sijoiltaanmenon riskiin kuin konservatiivinen hoito. TT-TG-etäisyyden mittaus oli toistettavissa lapsilla ja murrosikäisillä ja sopi myös heidän tutkimiseensa.
Avainsanat:
Adolescent, Patellar dislocation, Patellar instability, Patellofemoral pain, KINE-MRI
ACKNOWLEDGMENTS
The present study and thesis were carried out in the Departments of Orthopedics and Traumatology in Kuopio University Hospital and University of Eastern Finland. First of all, I am indebted to Docent Juhani Merikanto, MD, PhD, for inviting me to study the subject of dynamic kinematic application in the patellofemoral joint of children and adolescents during my surgical residency in Kuopio University Hospital. I am also indebted to the late Professor Esko Alhava, MD, PhD, who gave me his unwavering support for the project during his tenure as Head of the Department of Surgery in the Kuopio University Hospital. I express my thanks to Professor H.
Kröger, MD, PhD, Head of the Department of Orthopedics, Kuopio University Hospital for supporting the project. I am filled with gratitude for my mentor Docent Urho Väätäinen, MD, PhD, who stressed the value of this project. Also, thank you to the nurses who helped me to both collect information and follow-up with my patients in The Kuopio University Hospital Out-patient Clinic.
I am deeply indebted to my Chief Supervisor Professor Matti Eskelinen, MD, PhD, who prodded and encouraged me to continue and finish the project. His warm brotherly affection to the team speaks of his being a true Carelian. I express my sincere thanks to Antti Joukainen, MD, PhD, my second supervisor for his guidance in moving the project forward. I thank my co-researchers. I am truly grateful to my supervisor, Professor Hannu Kokki, MD, PhD, who encouraged me to do research even before this project was conceived.
I am grateful to my co-researcher, Hannu Lintula, MD, PhD, who rebuilt the project and brought clarity during a critical stage in its development. I give my thanks to Docent Kari Vanamo, MD, PhD, who reinforced my conviction to study the patellofemoral joint of children dynamically and kinematically. I also would like to thank Erkki Svedström, MD, PhD, who introduced me to the promising prospects of radiologic investigation of the knee joint. I also thank the Departments of Surgery, Orthopedics, Trauma and Hand Surgery and Radiology for taking ownership over the project. I express my sincere thanks co-researchers, Dr. Juha-Sampo Suomalainen and Physicist, Mervi Könönen, as well as all the research associates for their outstanding teamwork and commitment to the completion of our third article. To all my colleagues, friends and relatives who stood by me, supported me, and helped see this project to the end—my sincere thanks. Special thanks to Mrs. Jessica Grenier for checking the English grammar of the manuscript.
Last, but certainly not least, I thank my wife, Sisko, for her faithful devotion to me and the family. I also thank my children, Anne and Peter, who are my inspiration as a father. I thank God who gives me strength and endurance in adverse circumstances.
He appoints the right time and season for all things in His creation (Ecclesiastes 3:11).
In dedication to the loving memory of my Father, whose USAF veteran’s benefit sent me to medical school. And to my Mother, who likes to tell the world that her son is a surgeon. Additionally, I dedicate this work to my Alma Maters Central Philippine University and University of Sto. Tomas Faculty of Medicine and Surgery and my class of 1977.
Kuopio, 25 September 2020
LIST OF THE ORIGINAL PUBLICATIONS
This dissertation is based on the following publications:
1 Regalado G, Lintula H, Eskelinen M, Kokki H, Kröger H, Svedström E, Vahlberg T, Väätäinen U. Dynamic KINE-MRI in patellofemoral instability in adolescents.
Knee Surg Sports Traumatol Arthrosc. 2014 Nov;22(11):2795-802.
2 Regalado G, Lintula H, Kokki H, Kröger H, Väätäinen U, Eskelinen M. Six-year outcome after non-surgical versus surgical treatment of acute primary patellar dislocation in adolescents: a prospective randomized trial. Knee Surg Sports Traumatol Arthrosc. 2016 Jan;24(1):6-11.
3 Suomalainen JS, Regalado G, Joukainen A, Kääriäinen T, Könönen M, Manninen H, Sipola P, Kokki H. Effects of knee flexion and extension on the tibial tuberosity–trochlear groove (TT–TG) distance in adolescents. J Exp Orthop. 2018 Aug 16;5(1):31.
The publications were adapted with the permission of the copyright owners.
CONTENTS
ABSTRACT ... 7
ACKNOWLEDGMENTS ... 11
1 INTRODUCTION ... 21
2 REVIEW OF THE LITERATURE ... 23
2.1 ANATOMY ... 23
2.2 BIOMECHANICS OF THE PATELLOFEMORAL JOINT ... 28
2.3 PARAMETERS FOR THE INVESTIGATIONS OF THE PATELLOFEMORMAL JOINT ... 28
2.3.1 Patellar tilt angle (PTA) ... 28
2.2.1 Congruency angle (CA) ... 29
2.2.2 Sulcus angle (SA) ... 30
2.2.3 Lateral Patellofemoral or Lateral Patellar angle (LPFA or LPA). ... 31
2.2.4 Lateral patellar displacement (LPD) ... 31
2.2.5 Quadriceps angle (Q angle) ... 32
2.2.6 Tibial Tubercle Trochlear Groove (TT-TG) Distance ... 33
2.2.7 Bisect offset (BSO) ... 34
2.4 DISORDERS OF THE PATELLOFEMORAL JOINT ... 36
2.4.1 Epidemiology ... 36
2.4.2 Patellofemoral pain ... 36
2.4.3 Instability ... 36
2.4.4 Patellofemoral malalignment and tracking abnormalities ... 37
2.5 DEFINITION OF DYNAMIC KINE-MRI ... 37
2.6 MANAGEMENT OF PATELLOFEMORAL INSTABILITY ... 38
2.7 STATUS AND FUTURE OF DYNAMIC KINE-MRI TODAY ... 39
2.8 THE RATIONALE OF THE USE OF KINEMATIC INVESTIGATION IN PATELLOFEMORAL INSTABILITY ... 40
2.9 QUALITATIVE ASSESSMENT IN KINE-MRI ... 41
2.10 QUANTITATIVE ASSESSMENT IN KINE-MRI ... 41
2.10.1Patellar Height Indices ... 42
2.10.2Insall-Salvati Index ... 42
2.10.3Modified Insall-Salvati Index ... 43
2.10.4Caton-Deschamps Index ... 43
2.10.5Blackburn-Peel Index ... 43
2.10.6Patellar Engagement Indices ... 43
2.10.7Trochlear Dysplasia Classification ... 45
2.11 AXIAL IMAGING PARAMETERS ... 46
2.11.1Merchant view. ... 46
2.11.2Laurin view. ... 46
2.12 THE HAZARDS AND LIMITATIONS OF KINE MRI ... 47
2.13 ADVANTAGES OF MRI ... 48
3 AIMS OF THE STUDY ... 49
4 STUDY 1: DYNAMIC KINE-MRI IN PATELLOFEMORAL INSTABILITY IN ADOLESCENTS ... 51
4.2 MATERIALS AND METHODS ... 52
4.3 THE PARAMETERS MEASURED IN THE STUDY WERE: ... 54
4.3.1 BSO- Bisect offset ... 54
4.3.2 LPD- Lateral patellar displacement ... 54
4.3.3 PTA– Patellar Tilt Angle ... 54
4.3.4 SA – Sulcus angle ... 55
4.3.5 Insall–Salvati ratio ... 55
4.4 RESULTS ... 56
4.5 DISCUSSION ... 58
4.6 CONCLUSION ... 61
5 STUDY 2: SIX-YEAR RESULTS OF COMPARISON BETWEEN CLOSED AND OPERATIVE TREATMENT OF ACUTE DISLOCATION OF THE PATELLA IN 36 PATIENTS. A PROSPECTIVE RANDOMIZED STUDY. ... 63
5.4 DISCUSSION ... 68
5.5 CONCLUSION ... 70
6 STUDY 3: EFFECTS OF KNEE FLEXION AND EXTENSION ON THE TIBIAL TUBEROSITY-TROCHLEAR GROOVE (TT-TG) DISTANCE IN ADOLESCENTS .... 71
6.1 INTRODUCTION ... 71
6.2 MATERIALS AND METHODS ... 71
6.3 IMAGING ... 74
6.4 RESULTS ... 76
6.5 DISCUSSION ... 77
6.6 CONCLUSION ... 78
7 GENERAL DISCUSSION ... 79
8 STRENGTHS AND LIMITATIONS ... 80
9 FUTURE PERSPERSPECTIVES ... 80
10 CONCLUSION ... 81
REFERENCES ... 83
ABBREVIATIONS
AKG – Affected Knee Group BPI – Blackburn and Peel Index BSO- Bisect Offset
CA – Congruency Angle
CT – Computerized Tomography HKG - Healthy Knee Group ISI – Insall-Salvati Index
KINE MRI – Kinematic Magnetic Resonance Imaging
LCI – Lateral Condylar Index LPD- Lateral Patellar Displacement LPFA – Lateral Patellofemoral Angle LPL – Lateral Patellar Length LPT – Lateral Patellar Tilt
LRR - Lateral Retinacular Release LPTAB - Lateral Patellar Tilt Angle Bone
LPTAC - Lateral Patellar Tilt Angle Cartilage
MPFC - Medial Patellofemoral Complex MPFL – Medial Patellofemoral Ligament
MPML - Medial Patellomeniscal Complex
MPR - Multiplanar Reconstructions MPTL - Medial Patellotibial Complex MRC - Medial Retinacular Complex MRI – Magnetic Resonance Imaging NRI – Nuclear Magnetic Resonance NPS – Nail Patella Syndrome PA - Patellar Axis
PACS – Picture Archiving and Communication System
PFM - Patellofemoral Malalignment PFPS - Patellofemoral Pain Syndrome PTA - Patellar Tilt Angle
PTI - Patellotrochlear Index Q angle - Quadriceps Angle
X-ray - Electromagnetic radiation with wavelengths 10−8 - 10−12 meter and frequencies 1016 - 1020 hertz.
SA – Sulcus Angle SD - Standard Deviation T - Tesla
3D - Three Dimensional
TL-PL ratio – Tendon Length Patellar Length
TT–TG – Tibial Tubercle Trochlear Groove
UAKG - Unaffected Knee Group
1 INTRODUCTION
Pain, instability, malalignment and tracking disorders altogether represent a spectrum of patellofemoral problems that affect young people. This spectrum of disorders directly relates to the complex biomechanics of the knee joint. That is why the patellofemoral joint, as a field of research, is a prolific and dynamic one. The study of the patellofemoral joint in children and adolescents involves a thorough of understanding how the joint behaves and functions at different stages of its movement—from full extension to deep flexion. As a clinician, it is only through this understanding of the biomechanics of the knee that one can effectively treat and manage the problems of the patellofemoral joint (1, 2) .
The assessment of the knee joint begins with a thorough history and physical examination. The next step is to undergo radiological assessment, prescribing the appropriate study needed to obtain the best information radiography can offer (3) . X- ray remains to be the mainstay of radiological assessment of the patellofemoral joint.
However, X-ray alone is not enough to understand the pathomechanism of patellofemoral disorder, especially in an adolescent knee. With the advancement of computerized tomography (CT) and magnetic resonance imaging (MRI) technologies in the form of the KINE-MRI, clinicians are now able to see what goes on at different stages of movement in the patellofemoral joint. This imaging, in conjunction to other imaging modalities, will better inform our investigation of the patellofemoral joint.
The clinical application of KINE-MRI was introduced by Shellock et. al. (4) in 1988.
Since then, its principles and applications have developed to the extent of becoming a valuable adjunct to the clinical and radiological assessment of the patellofemoral joint.
KINE-MRI, as an investigative tool, is highly effective in the assessment of pain, instability, and malalignment, as well as in tracking abnormalities of the patellofemoral joint in all ages. It provides the possibility to specifically observe the essential pathology behind the diverse problems of the patellofemoral joint in both bone and soft tissue levels and offers possibilities for the development of more novel imaging methods. Its application, therefore, continues to grow and widen. New parameters have been added to the original methods (5-8).
Due to the spectrum of disorders affecting the patellofemoral joint in young people, the current limitations of diagnostic technology used today, and the complexities involved in the assessment of young knees—the need for new, innovative forms of imaging is ever-increasing. This thesis and its three studies aim to establish KINE-MRI as an essential modality for the dynamic assessment of the knee and to highlight its clinical significance. Secondly, this thesis will compare the outcomes of conservative treatment to operative treatment of lateral patellar dislocation in young patients over the course of 6 years. Lastly, this thesis will aim to reproduce the method of Tibial
Tubercle-Trochlear Groove (TT-TG) measurement in healthy, young subjects. The data acquired by these studies aims to better inform one’s evaluation of the patellofemoral joint in children and adolescents.
2 REVIEW OF THE LITERATURE
2.1 ANATOMY
The knee is a biomechanically complex joint consisting of the tibiofemoral and the patellofemoral joints (5). It is not a simple hinge joint. Its movement is the interaction of its static and dynamic stabilizers operating together. The knee joint extends and flexes, bends medially and laterally, rotates and translates anteriorly and posteriorly. The patellofemoral joint is composed of the patella and the trochlea. The patella is the largest sesamoid bone of the body. It consolidates at 7.5 weeks of gestation (6, 7). The patella is triangular in shape with its apex situated inferiorly. It has two main facets, the medial and the lateral. The medial facet is subdivided into two facets with the most medial one being called the odd facet. There are also superior and inferior facets and, on occasion, two more minor ones. Altogether, the patella has 7 facets (8, 9). In 1941, Wiberg (10) classified the shape of the patella into three main types (Figure 1).
Figure 1. The three main types of patella according to Wiberg’s classification are: 1) Type I patella which has equal lateral and medial facets, 2) Type II patella which has a shorter medial facet and longer lateral facet and 3) Type III patella which has a much shorter medial than lateral facet. The medial facet of Type III patella is the shortest of all three types.
The abnormal shape and development of the patella are influenced by genetic factors, which is found in 1) Nail Patella Syndrome (NPS), 2) Down’s Syndrome and 3) Ehlers- Danlos Syndrome. Nail Patella Syndrome is an autosomal dominant genetic abnormality. Hallmark signs of NPS include small fingernails and a small patella which is associated with kidney function derangement. In NPS, the patella is affected in 90%
of its cases; wherein 20% of these cases exhibit a complete absence of the patella. NPS is also known as a hyperactivity syndrome (11, 12) . In Down’s syndrome, there is a generalized joint laxity which also affects the patellofemoral joint. In some cases of Down’s syndrome, there is evidence of trochlear dysplasia. Ehler-Danlos syndrome is a congenital connective tissue disorder with multi-organ involvements. Its main characteristics are generalized joint laxity, skin hyper-extensibility, hypertrophic scarring, peripheral neuropathy and patellar instability and dislocation. The operations due to patellar instability in both NPS and Down’s Syndrome have been performed with good results (13-18) . The treatment of patellar dislocation for congenital Ehlers Danlos Syndrome, however, is conservative (19, 20).
The trochlea, which is a grooved extension of the distal femur, accommodates the patella and is bordered by the medial and the lateral condyles. The groove serves as a bony restraint that prevents the patella from falling off the tract as it moves up and down the longitudinal axis. The lateral part of the groove is higher and wider and extends further forward than the medial part (21) . The quadriceps tendon invests the upper pole of the patella, pulling it cranially in congruence with the anterior aspect of the femur.
The medial and lateral retinacula reinforce the capsule on both sides and form part of the capsule. The patellar tendon synchronizes with the quadriceps tendon in its cranio- caudal movement of the patella. The MPFL (medial patellofemoral ligament) is a thin but strong structure with its insertion at the superomedial aspect of the patella inferior to the insertion of the vastus medialis obliquus (Figure 2).
Figure 2. Shown are the medial ligaments that include the medial patellofemoral ligament (MPFL), the medial patellomeniscal ligament (MPML), and the medial patellotibial (MPTL). Copied with permission: High resolution magnetic resonance imaging of the patellar retinaculum: normal anatomy, common injury patterns, and pathologies. Thawait, Shrey K., et al., Skeletal Radiology, 41, 137-148, 211. Springer Nature.
Recent advances in anatomical studies have identified a proximal component of the MPFL called the medial quadriceps tendon femoral ligament (MQTFL). Tanaka et al.
(22) identified MPFL and MQTFL as parts of the MPFC (medial patellofemoral complex). The MPFL represents only half of the medial restraint to lateral patellar displacement. Other medial soft tissue restraints are the MRC (medial retinacular complex), MPML (medial patellomeniscal ligament) and MPTL (medial patellotibial complex (Figure 3). Along with the MPFC, the MRC, MPML and the MPT ligaments must have equal considerations in the management of patellofemoral instability (21-24).
Figure 3. Shown above is the Medial Patellofemoral Complex (MPFC), which is composed of the medial quadriceps tendon femoral ligament (MQTFL) superiorly and the medial patellofemoral ligament (MPFL) inferiorly. Copied and adapted with permission: Advances in Patellofemoral Surgery (L. Redler, Section Editor). The medial patellofemoral complex. Alexander E. Loeb & Miho J. Tanaka. Current Reviews in Musculoskeletal Medicine volume 11, pages 201-208 (2018).
Springer Link.
The hyaline cartilage of the articular surface of the patellofemoral joint is made up of collagen, glycosaminoglycans and water. The articular cartilage is thicker in the central part of the concave trochlea where it could reach up to 6 mm in thickness and thickest in the loading zones of the patella (25). During the weight bearing stage, the joint fluid distributes itself throughout the cartilage matrix resulting in a balanced state of pressure.
If the cartilage is damaged, there is a loss of fluid pressure within the cartilage matrix which leads to degenerative changes in the joint. The cartilage provides an insensitive aneural and avascular tissue adapted to bearing a high compression load.
In dealing with the young patellofemoral joint, we refer to the classic quote of Professor Mercer Rang, “the child is not a young adult” (26). The growing skeleton is porous, plastic and elastic. Due to the fact that the Haversian canals are wider, and the periosteal sleeve is thicker, fracture of the bone in a young person has greater capacity to heal than that of an adult. The leg grows at around 23 mm per year with most of the growth coming from the knee, which is around 15mm per year (30). This rate of growth usually continues up to the age of 16 years for boys and 14 years for girls, corresponding to the age of menarche. The distal femur alone may grow at 9 mm per year. The
and the possibility of an ensuing growth disturbance presents a dilemma to the treatment of instability in the immature knee.
The three most common pathologies behind patellar instability are a high-riding patella (better known as Patella alta), a tibial tuberosity-trochlear groove distance (TT- TG) distance of more than 20 mm and an underdeveloped trochlea, better known as trochlear dysplasia. Trochlear dysplasia alone is a common problem in the immature knee (27). In 1987, Henri Dejour classified trochlear dysplasia into four types according to the bumps and crossing sign (28-31) (Figure 4).
Figure 4. The Dejour of trochlear dysplasia classification emphasizes the crossing sign that determines the degree of dysplasia. 1) Type A: Crossing sign with preserved trochlear morphology (fairly shallow trochlea 145 degrees); Type B: Crossing sign with supratrochlear hump/(spur) and flat or convex trochlea; Type C: Crossing sign with double contour (projection on the lateral view of the hypoplastic medial facet); and Type D: Crossing sign with double contour, asymmetry of trochlear facets. Adapted with permission from Patellar instability in children and adolescents. F. Chotel, J. Berards, S. Rausx. https://doi.org/10.1016/j.otsr.
2013.06.014. Elsevier.
2.2 BIOMECHANICS OF THE PATELLOFEMORAL JOINT
The patella serves both as a lever arm and pulley. It is a floating bone and is innately unstable if not for the fact that it is tethered to the distal anterocaudal aspect of the femur by an intricate system of soft tissue support. This system of support cannot be rigid;
instead, it must give allowance to the patella to move while maintaining stability.
Stability is defined as relating to the property of the body to resist displacement away from the stable position of equilibrium when all forces are in balance. This definition relates with the patellofemoral joint in equilibrium. The patella also helps in proprioception. The hyaline cartilage provides an insensitive aneural avascular tissue adapted to bearing a high compression load. It has a low coefficient of friction which is essential in transmitting quadriceps power around the distal femur to the tibia (7, 10, 25, 32-34).
In the normal patellofemoral joint the contact stress progressively increases from extension to a maximum of 90 degrees flexion after which it is progressively reduced at deeper flexion.
In order to understand and quantify the anatomy and function of the patellofemoral joint, several radiological parameters are used. These are: 1) Patellar Tilt Angle (PTA), 2) Congruency Angle (CA), 3) Sulcus Angle (SA), 4) Lateral patellofemoral Angle or Lateral Patellar Angle (LPFA or LPA), 5) Bisect Offset (BSO), 6) Lateral Patellar Displacement (LPD), 7) Q angle, and Tibial Tubercle Trochlear Groove (TT-TG) Distance. This thesis looks into these known parameters only.
2.3 PARAMETERS FOR THE INVESTIGATIONS OF THE PATELLOFEMORMAL JOINT
2.3.1 Patellar tilt angle (PTA)
Patellar tilt angle as described by Dejour (30) (35, 36) (30) (Figure 5) is the angle formed by the line running along the lateral facet of the patella and the line that is drawn parallel to the posterior femoral condyles. These lines tend to either bisect or diverge from each other at the lateral patellofemoral side. The angle produced by the two lines from zero to positive (+) degree is abnormal and the angle produced from zero to negative (-) degree is normal. The parameter is used to determine lateral patellar tilt. A positive angle suggests the extent of lateral patellar tilt and instability.
Figure 5. In order to determine the Patellar Tilt Angle, a line drawn parallel to the posterior condylar line (bottom line). This corresponds to the anterior condylar line which either converge with or diverge from the line drawn along the articular surface of the lateral facet of the patella.
The angle produced (double arrow) maybe situated above the anterior condylar line (positive) or below it (negative). An angle on the positive side suggests the presence of lateral patellar tilt and instability.
2.2.1 Congruency angle (CA)
The Congruency Angle was introduced by Merchant in 1974 (37). It is the angle formed by drawing five lines. Two lines (1st and 2nd) are drawn tangent to the articular surfaces of the femoral trochlea converging at the deepest part of the sulcus. A perpendicular line (4th line) is drawn from the posterior condylar line (3rd line) bisecting the deepest part of the sulcus as the reference line. The fifth (5th) line is drawn from the deepest part of the sulcus to bisect the thickest part of the patella through its deepest intra-articular point.
The angle formed by the reference line and the line that transects the thickest dept of the patella measures the degree of the incongruency between the patella and the femoral trochlea. The value greater than the mean of 2.5 (+/- 8.6) suggests incongruency and patellofemoral instability (Figure 6).
Figure 6. Congruency (indicated by the double arrow) angle is the angle formed between the line perpendicular to the posterior condylar line and the line that bisects the thickest depth of the patella. In the figure the congruency angle is indicated by the double arrow.
2.2.2 Sulcus angle (SA)
The Sulcus angle was introduced by Brattström et al. (38) in 1964. It is the angle formed by the femoral medial condylar facet line and the lateral condylar facet line converging at the deepest point of the sulcus (Figure 7). Generally, an angle that is greater than 38 degrees suggests shallow sulcus and is consistent with femoral trochlear dysplasia. On the other hand, Mulligan et al. (39) found the mean value to defer according to the technique of imaging used. On the Merchant view, the mean is 138.6 (SD 6.9) (Range:
120-155); and on the Laurin view the mean is 141 (SD 6.9), (Range: 125-162).
2.2.3 Lateral Patellofemoral or Lateral Patellar angle (LPFA or LPA).
The Lateral Patellofemoral Angle/Lateral Patellar Angle is formed by the anterior femoral condylar line and the lateral patellar facet line measured from the lateral side.
The angle from 0 and below with negative value suggests lateral tilt and instability. The parameter was introduced by Laurin et al. (40). It is a variation of the patellar tilt angle (PTA). The normal lateral femoral angle is 0-13 degrees. Like PTA, it demonstrates patellar tilt.
Figure 8. The Lateral Patellar Angle is indicated by the double arrow. A positive angle value to within (+) 13 degrees is normal while the negative angle value below zero degree indicates patellar tilt.
2.2.4 Lateral patellar displacement (LPD)
Lateral patellar displacement (LPD) (Figure 9), is a measure of absolute patellar lateralization. It is the distance measured, in mm, from the highest point of the medial condyle on the most medial side of the patella. A line is drawn perpendicular to the posterior condylar line transecting the highest anterior point of the medial condyle, which is the reference line. If the most medial side of the patella is medial to this line, it is regarded as being in the negative zone. If the most medial side of the patella is lateral to the reference line, it is regarded as being in the positive zone.
In adults, the value of +7 mm or more is considered abnormal. The value in children has not yet been established. The normal range is +/- 7 mm (36, 41, 42).
Figure 9. Lateral Patellar Displacement is the distance of the patella (in mm) from the reference line, which is the line drawn perpendicular to the posterior condylar line that transects the highest anterior point of the medial condyle. The medial side of the patella is considered to be in the negative zone if it lies medial to the reference line and considered to be in the positive zone if it lies lateral to the reference line.
2.2.5 Quadriceps angle (Q angle)
The Q angle is formed by the line drawn between the anterior superior iliac spine (ASIS) and the line drawn from the tibial tubercle. Both lines converge at the center of the patella forming an angle (Figure 10). The Q represents the vector of the pull of the quadriceps muscles and the pull of the patellar tendon. The mean Q angle is 14 degrees in men and 17 degrees in women. The Q angle in women is greater than that of the men due to the fact that women tend to have wider pelvises. The greater the Q-angle, the greater the lateral force exerted on the patella which, in turn, results to a greater risk of patellar dislocation (43-46). In evaluating the Q angle, one must take into consideration the distal femoral rotation and the tibial rotation.
According to the radiographic studies done by Wiberg et al. (47), at the beginning of flexion, the patella lies proximally and laterally resting against the suprapatellar fat pad. As flexion proceeds, the tibia rotates inwards and the patella is drawn into the trochlea from the lateral side. Since the Q angle is influenced by the rotations of the femur and the tibia, it is not a very accurate parameter.
Figure 10. The Q angle is formed by the line drawn between the anterior superior iliac spine and the center of the patella (line a) and the line drawn between the tibial tubercle and the center of the patella (line b). In the figure the Q angle is indicated by the double arrow.
2.2.6 Tibial Tubercle Trochlear Groove (TT-TG) Distance
The TT-TG distance represents the vector of the quadriceps pull on the patella. In order to determine the tibial tubercle trochlear groove distance, two lines are drawn. One line is drawn perpendicular to the posterior condyles transecting the deepest portion of the femoral trochlear grove and another line is drawn bisecting the most anterior part of the tibial tuberosity. It is determined by measuring the distance between the center of the patella and the center of the femoral trochlea. In 1978, Goutallier and Bernageau (48, 49) believed that the TT-TG distance is a more accurate parameter than the Q angle as it measures the actual distance between the tibial tuberosity (TT) and the trochlear groove (TG) during flexion and extension.
The measurement of the TT-TG groove distance is performed digitally by moving the cursor upwards and downwards in a manner where the images superimpose each other. The images are scanned forwards and backwards until either of the two lines on the screen is marked digitally and measured. The mean bony TT-TG value is 14.4 mm by CT and 13.9 mm by MRI. At the cartilaginous tendon level, the values are 15.3 mm by CT and 13.5 mm by MRI (41, 50) (Figure 11). The limitation of the TT-TG distance, as a parameter, is that it is influenced by trochlear dysplasia when it is shallow. One must be aware that an abnormal TT-TG distance can be the result of a lateralization of the tibial tuberosity and an excessive knee rotation (51) (48).
Figure 11. The TT-TG distance is represented by two lines. One line is drawn perpendicular to the posterior condylar line and transects the deepest part of the trochlear groove and the second perpendicular line transects the most anterior part of the tibial tubercle. In the actual setting, the digital cursor is move upwards and downwards and the images are scanned forward and backwards until either of the two lines is visualized in the screen. Adapted from Effects of knee flexion and extension on the tibial tuberosity-trochlear groove (TT-TG) distance in adolescents.
Orthopedics (2018) 5:3. https://doi.org/10.1186/s40634-018-0149-1. Journal of Experimental Orthopedics.
2.2.7 Bisect offset (BSO)
The parameter Bisect Offset (BSO) was introduced by Brossman et al. (35, 52) (Figure 12). In order to determine the BSO, a line is drawn perpendicular to the posterior condylar line which must transect the deepest point of the femoral trochlea and the patella. The part of the patella situated on the lateral side of the perpendicular line is compared to its total width. The ratio in an adult is 0.65 (Range: 0.44-0.64). A ratio of more than 0.65 indicates lateral displacement.
Figure 12. In the Bisect Offset, a perpendicular line is drawn from the posterior condylar line to transect the deepest part of the femoral trochlea and the patella. The part of the patella that lies in the lateral side of the perpendicular line (see line A) is compared to its whole width (see line B).
Adapted with permission from Dynamic KINE-MRI in patellofemoral instability in adolescents.
Knee Surg. Sports Traumatol Arthrosc. 2014;22(11): 2795-802.
The patellar tilt angle (PTA), bisect offset (BSO) and lateral patellar displacement (LPD) are parameters that are called the Brossman Indices (53). They were previously used in CT and X-ray imaging and, later on, used in MRI imaging.
According to studies by Kujala et al. (54-56), the most significant parameter values are derived during the first 0-10 degrees of flexion of the knee joint. At the beginning of flexion, the sulcus angle (SA) (Figure 7) and the lateral patellar tilt angle (PTA) (Figure 5) are smaller. The patella is more displaced and tilted laterally. The congruency angle (CA) (Figure 6) is also directed more laterally. At the start of flexion, the patella tracts along the lateral side of the distal femur and enters the trochlea at around ten degrees of the knee flexion. Therefore, according to Kujala et. al., the most critical stage of diagnosis for an abnormal patellofemoral joint is from 0-10 degrees of the knee flexion.
The femoral trochlea with its unique geometrical configuration provides significant bony stabilization to the patellofemoral joint. The depth of the groove determines the effectiveness of the tracking of the patella. Maltracking of the patella correlates with a shallow trochlear groove (21).
Passive or static stabilization is afforded by ligaments, tendons and the retinacula.
The medial and lateral retinacula restrain the patella on both sides, guiding its entrance to the TG at the beginning of flexion. This action is aided by the MPFL medially and the fibers originating from the iliotibial tract laterally. Dynamic stabilizers are composed of the vastus medialis obliquus muscle on the medial side and vastus lateralis on the lateral side. The vastus medialis obliquus muscle prevents lateral displacement of the patella during its gliding movement up and down along the TG. Its effect is demonstrable
through the measurement of the Q angle (34). The MPFL and its variant, the MPFC, are generally known as the major medial stabilizers of the patella while the patellotibial and patellomeniscal ligaments are the minor medial stabilizers. Damage to the major medial stabilizers inevitably leads to lateral instability (57-60).
2.4 DISORDERS OF THE PATELLOFEMORAL JOINT 2.4.1 Epidemiology
The important issues surrounding the patellofemoral joint are: 1) pain, 2) instability, 3) malalignment and 4) patellar tracking abnormalities and their consequences (21). The most significant end result of instability is patellar dislocation. In the most recent study done by Sanders et al., the incidence of first-time, patellar dislocation is higher than previously reported at 23.2 per 100,000 person-years. The annual incidences of patellar dislocation is highest among adolescents between the ages of 14-21 years old with no difference in the number of occurrences between male or female (61).
2.4.2 Patellofemoral pain
Patellofemoral Pain Syndrome (PFPS) is an enigmatic condition of the knee which is prevalent among the adolescent female population. It is considered a complex issue as it relates to the abnormal kinematics of the patellofemoral joint; for example, in its malalignment and instability (62, 63). The studies of Sanchez-Alonso et al.
(64-68) have shed light on the pathophysiology of patellofemoral pain at the neurovascular level. Sanches-Alonso introduced the “neural theory”
as the pathomechanism of PFPS. He suggests that the biomechanical basis of PFPS is due to the cyclical occurrence of soft tissue and bone overload in conjunction with Patellofemoral Malalignment (PFM). This causes a neuro- microvascular response in the lateral retinaculum leading to the perception of pain. That means that even if there is an abnormality in the patellofemoral joint, pain may only occur when the pathomechanism is triggered (62, 63, 65, 69-76).
Dye et al. (77) suggest that patellofemoral pain signifies a disturbance in the balance of functions of the knee joint.
2.4.3 Instability
Patellofemoral instability can be influenced by 1) trochlear dysplasia, 2) an abnormal
the patella could be the end result of patellofemoral instability (21, 25). However, while trochlear dysplasia is a major factor in instability, not all patellae with trochlear dysplasia dislocate. At the same time, patellae can dislocate without even having trochlear dysplasia. Dye proposed the “Homeostatic Tissue Envelope Theory” which stipulates that in order for the patella to dislocate, the stress it is subjected to must exceed its physiological threshold of function (65, 77, 78).
The classification of patellar instability that is proposed by Lyonnaise School, is so far the most precise and complete. It includes the following: Type 1) trochlear dysplasia, Type 2) pathological TT-TG distance, Type 3) patellar tilt and Type 4) patella alta. Each of these categories has its own parameters (30) (40, 41, 48, 50, 79, 80).
2.4.4 Patellofemoral malalignment and tracking abnormalities
Patellofemoral malalignment correlates locally with the alteration of the Q angle and a TT-TG distance of more than 20 mm, trochlear dysplasia and patella alta. It can also correlate with distal factors such as femoral rotation (anteversion) and tibial torsion (3, 59, 60, 65, 79, 81-83).
The abnormal tracking of the patella can be observed clinically through a “J”
movement of the patella at full extension (59, 84). Due to the shallow TG, the patella tends to fall out of the TG during the end stage towards full extension. Since patellar dislocation is a temporary event, sometimes maltracking cannot be proven by radiography alone. KINE-MRI, on the other hand, has the advantage by its ability to assess the patellofemoral joint through its different degrees of flexion and extension.
Moreover, the kinematic assessment for maltracking can be effectively done in conjunction with the assessment of the bony configuration of the patellofemoral joint and TT-TG distance (62, 63, 69, 85-87).
2.5 DEFINITION OF DYNAMIC KINE-MRI
Magnetic resonance imaging (MRI), as applied in humans, is a technique used to form images of the anatomy and physiologic processes of the human body. It uses strong magnetic fields, magnetic field gradients and radio waves to form images. A radio wave pulse is applied to cause magnetization of the tissue. This causes the hydrogen atom, which is abundantly found in the human body in the form of water and fat, to become excited and to spin. During the relaxation phase of the hydrogen proton, the signal emitted is recorded in the coil as a magnetic resonance image. The type of image produced depends on the density of fat and water in the organ being investigated. It also depends on the T (Tesla) weighting techniques; namely T1 (spin-lattice) and T2 (spin-spin). The RF waves are repeated until the desired images are acquired.
Dynamic MR Imaging of the joint is a process of acquisition and processing of static images at static stages of the movement of the joint and observing the events that occur
in every stage of that movement. The same data that is collected from every static stage of the movement is summarized to obtain a complete picture of what is going on in the joint during its whole range of motion (88).
During the KINE-MRI procedure, the subject lies supine inside the MRI scanner tube.
A support is placed under the knee to allow the leg to cyclically flex and extend. An angle localizer is attached at the side of the machine to determine the angle of the knee joint flexion and extension. The subject is asked to actively extend the knee at 4 graduated steps corresponding to the degree levels of 0, 10, 30 and 40 degrees. They are asked to hold it there for 12 seconds for three-dimensional multiple-phase gradient echo Tesla MRI imaging. Each phase consists of an axial and a sagittal image. From these data measurements, the patellofemoral alignment and kinematics are derived (70, 76, 86, 89).
2.6 MANAGEMENT OF PATELLOFEMORAL INSTABILITY
Whether to treat patellar dislocation conservatively or operatively remains to be controversial. The conservative approach involves physical therapy with the goal of strengthening the quadriceps. The fundamental concerns that dictate this decision include the degree of instability, the onset of the patellar dislocation, dysplasia and the TT-TG distance. Surgical treatment involves reconstruction of either the supporting soft tissues, the bone or both.
Traditionally, the reconstructive procedures of the patella are categorized into proximal and distal realignment and the types of procedures are endless in number. For example, lateral release is a classic procedure, but its role in patellar repair has been questioned and downgraded throughout time. As an adjunct to other procedures, it is one measure that should always be considered with caution. Medial imbrication or reefing is another adjunctive procedure in patellar repair, but its use depends on the best judgement of the surgeon. The categorization of patellar reconstructive procedures into proximal and distal realignment is no longer a sufficient way to describe all the varied types of procedures that have developed over the years. As of late, MPFL repair is considered to be the “sine qua non” for patellar dislocation.
The management of patellar instability though challenging when treating an adolescent is not impossible. It is generally understood that while operating on the distal femur of an adolescent child, one must avoid damaging an open physis because of the possibility of causing a disturbance in growth. However, Nelitz’s et al. (27) studies challenges this particular notion. Nelitz treated eighteen adolescents (18 knees) with open physes and severe trochlear dysplasia using thin flap trochleoplasty. The median age at the time of operation was 12.6 years (range, 12.2-13.3 years) for girls and 14.5 years
score improved significantly from 67 (range, 54-75) preoperatively to 89.5 (range, 78-96) at follow-up (p < .01). The median visual analog scale showed significant pre- to postoperative improvement from 5 (range, 3-7) to 1 (range, 0-3) (p < .01). The activity level, according to the Tegner activity score, did not change significantly. Therefore, they concluded that bony repair for patellofemoral instability in patients with open physis may be considered if there is only less than 2 years of expected growth remaining. In addition to Nelitz’s findings, many other authors found no evidence of clinical or radiological disturbances in growth after trochleoplasty nor did they find reports of recurrent patellar dislocations in adolescents who had less than two years of expected growth remaining (31, 94-99) (100).
For less severe instability in an adolescent’s patellofemoral joint, MPFL and other soft tissue procedures have been recommended. Malagelada et al. (90) performed a 4-in-1 patellar realignment (lateral release, medial reefing, Insall tube realignment and Roux- Goldthwaite patella ligament transfer) in recurrent patellar dislocations on 12 adolescent patients (total of 16 operated knees). All patients underwent the same procedure after attempting a minimum period of 6 months of non-operative treatment with unsatisfactory results. The main outcome measured was recurrent dislocations.
Functional outcomes were assessed using the Kujala score and the Pediatric form of the International Knee Documentation Committee Subjective Knee Form (Pedi-IKDC). The patients were followed up for a minimum of 3 years. None of the patients sustained further patella dislocations following the operation. In three cases, minor patellar maltracking was noted post-operatively, but all three remained asymptomatic. Three patients had a small area of numbness lateral to the operative incision, which coincided with hypertrophic scarring. There was one case of superficial wound infection. The mean Kujala score was 83.4 +/- 11.47 and the mean Pedi-IKDC was 79.5 +/- 12.56 at the latest follow-up (minimum of 36 months). They concluded that the 4-in-1 patellar realignment is a good procedure in pediatric and adolescent patients with recurrent patella instability. Satisfactory results were observed with a minimal complication and re-dislocation rate in their series (90).
For more severe instability, as in trochlear dysplasia, trochleoplasty is considered to be the procedure of choice. In the case of malalignment, the Fulkerson osteotomy, which is the anteromedialization of the patella, is the procedure of choice. Each of these procedures have a lot of variations. Patients must be carefully selected on the basis of history, physical examination and the imaging results (91, 92).
2.7 STATUS AND FUTURE OF DYNAMIC KINE-MRI TODAY
Plain radiography, CT and static MRI can delineate pathology in the knee joint with reasonable sensitivity. Static axial images of the patellofemoral joint at different degrees of flexion reveal only the degree of patellar tilt or subluxation. The accuracy of patellar position on static axial MRI is limited by the absence of muscle contraction, movement,
and loading. Only dynamic kinematic axial images during different stages of the patellofemoral articulation can demonstrate the degree of flexion where, for example, patellar malalignment is maximal and follow the changes relative to the subsequent stages of movement of the joint. Arthroscopy, aside from its diagnostic value, provides the opportunity for treatment of intra-articular changes contributing to knee joint disturbances, but it is an invasive technique with potential risks of complications. The cost-effectiveness of MRI is apparent when it is able to estimate the extent of the intra- articular pathology in the acutely-injured knee during the patellofemoral investigation (43, 80, 93). The total examination time for active movement during the dynamic MRI procedure is approximately 8 to 10 minutes, thus it can be performed during routine MRI examination of the knee. Aside from its ability to detect internal derangement in the patellofemoral joint that cannot be detected by any method of clinical examination, it can detect signs of an incipient or transient patellar dislocation. Dynamic MRI offers a new perspective in the study of both the normal and the abnormal patellofemoral joint.
2.8 THE RATIONALE OF THE USE OF KINEMATIC INVESTIGATION IN PATELLOFEMORAL INSTABILITY
The dynamic imaging of patellofemoral joint movement provides essential diagnostic information in the assessment of joint abnormalities and malformation. In 1997, Dupuy et al. (94) carried out an investigation of 18 patients (20 knees) with knee pain and suspected patellar tracking disorder. They concluded that cine viewing of the patellar motion had better results than single images. They were also able to produce a high grade of quality in their images. In 1999, Muhle et al., compared ultrafast kinematic CT imaging with that of ultrafast KINE-MRI, using ultrafast from 0 – 30 degrees of flexion (95). Though this was a comparison study, their research proved the importance of dynamic imaging of the patellofemoral joint for detecting abnormal tracking patterns.
These studies highlighted the clinical significance and need of dynamic kinematic imaging, both by CT and MRI and propelled the future directions of both for the investigation of patellofemoral instability.
The value of the KINE-MRI as one of the modalities for patellofemoral assessment are summarized as follows: 1) excellent, noninvasive assessment of the patellofemoral joint and 2) detailed three dimensional (3D) capability at the range of motion from 0-30 degrees, with the possibility of imaging of up to 45 degrees (54, 96, 97). These capabilities make the KINE-MRI a very feasible assessment tool, not only for adults, but for children and adolescents.
Dynamic KINE-MRI can enhance one’s investigation of both mild to severe cases of
need to examine one's rotational malalignment. Whatever degree of patellofemoral instability, dynamic KINE-MRI has the potential to greatly improve and enhance our current and future investigations of the patellofemoral joint with all of these concerns in mind (98, 99).
2.9 QUALITATIVE
ASSESSMENT IN KINE-MRI
The methods of KINE-MRI assessment are qualitative and quantitative. The initial focus of an MRI evaluation is to detect anatomical abnormalities of the patellofemoral joint (i.e., cartilaginous pathology, patellar displacement and tilt, patellar height and dysplasia) in a one-time, exposure test. In comparison, Dynamic KINE evaluation involves the observation and measurement of different parameters at different stages inside the range of movement of the joint. Tracking abnormalities of the patellofemoral joint can then be quantified using the stated parameters; from full extension to deeper flexion (100, 101).
The qualitative methods of assessment derived from static data as proposed by Shellock are as follows (102):
1. Normal: the patella is aligned with the TG with both lateral and medial aspects of the trochlea.
2. Lateral subluxation: the apex of the patella is laterally displaced and overlaps the lateral aspect of the femoral trochlea.
3. Excessive Lateral Patellar Syndrome: the lateral facet is tilted toward the lateral aspect of the trochlea with little or no subluxation at all.
4. Medial subluxation: the apex of the patella is medially displaced relative to the femoral trochlea.
5. Lateral to medial subluxation: the patella starts in a laterally displaced position and moves to a medially displaced position concomitantly with increasing knee flexion.
6. Dislocation: the patella is completely displaced from its normal position relative to the femoral trochlea.
2.10 QUANTITATIVE ASSESSMENT IN KINE-MRI
The quantitative assessment of the KINE-MRI was pioneered by Kujala et al., in 1989 (58). The axial and sagittal parameters taken into consideration are as follows:
1) Sulcus Angle (SA), 2) Lateral Patellofemoral Angle (LPFA), 3) Lateral Patellar Tilt (LPT), 4) Congruency Angle (CA), and 5) Lateral Patellar Displacement (LPD) (54) (103). Brossman developed more specific indices: 1) Patellar Tilt Angle (PTA), 2) Bisect Offset (BSO) and 3) Lateral Patellar Displacement (LPD).
