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Imaging of physeal stress in the upper extremity
(Ab)normal redefined
Kraan, R.B.J.
Publication date
2020
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Citation for published version (APA):
Kraan, R. B. J. (2020). Imaging of physeal stress in the upper extremity: (Ab)normal
redefined.
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Chapter 1
Introduction
Nowadays, prize-winning athletes are portrayed as role model and receive substantial (financial) recognition for their performances. Athletes represent their country in international competitions and governments invest an increasing amount of money to facilitate the development of talented young athletes into successful (Olympic) athletes.1 As a result, children are progressively involved
in organized sports participation and young athletes are often encouraged to specialize in a single sport at an early age and to participate in high intensity year-round training programs.2
These intensive training regimes result in a high prevalence of sports-related overuse injuries of the musculoskeletal system among young athletes 3, often in periods with sudden increases
in training intensity.4 Injuries related to overuse are in general characterized by a gradual onset
and the absence of an identifiable event 5,6, although some overuse injuries (e.g. stress fractures)
can appear to be acute.6 These injuries occur if repetitive stress is applied to the musculoskeletal
system and insufficient time is scheduled for the body to repair the micro-damage and adapt to the workload.7
Physeal injuries…
In young athletes, overuse injuries regularly involve the cartilage of the unfused physis.8
Physeal cartilage is prone to stress-related damage because it is less resistant to stress than other musculoskeletal structures.9,10 The healthy physis is responsible for the growth of long
bones and consists of multiple layers in which chondrocytes mature and eventually ossify.10
The vascularization at the metaphyseal side of the physis plays an important role in this ossification process.11 If repetitive stress is applied to the physis, both the multilayered physis
and the metaphyseal vascularization are easily damaged.12 Damage inflicted to these areas
can cause an impairment of the normal ossification process and disturbance of the normal physeal architecture.11,13 Although these changes appear to be reversible if the injuring stresses
are discontinued in time 13, physeal injuries have been associated with serious long-term
consequences such as growth disturbances.14
… of the shoulder, elbow …
The physis can thus be considered as the weakest link in the musculoskeletal chain.9,10 The
anatomical location of physes at risk for stress-related damage is primarily determined by the biomechanical characteristics of the sport in which an athlete is participating. For example physeal overuse injury of the shoulder and elbow are common in athletes involved in extensive overhead throwing such as baseball pitchers.15 The proximal physis of the humerus is prone to
overuse as a result of the excessive rotational and traction forces during throwing.15,16 In the
elbow the apophysis of the medial epicondyle is vulnerable for the repetitive valgus stress occurring during the overhead throwing motion.17
BNW_Rik_V1.indd 8
… and wrist
Physeal overuse injuries of the wrist are common in young wrist-loading athletes as for example rowers, tennis players and gymnasts.18 Gymnastics is one of the most popular sports in the
Netherlands, especially among young girls 19, and often involves high intensity training regimes.20
Elite gymnasts are reaching peak performance at an increasing younger age; 20 during the 2012
summer Olympics the mean age of female gymnasts was lowest of all sports.21 Consequently,
the prevalence of wrist injuries as a result of overuse among young gymnasts is high with 32-73% reporting wrist pain and 10-28% actually having a stress-related injury of the wrist.18 As physeal
injury of the distal radius is common among young gymnasts it is also referred to as ‘Gymnast wrist’. However, exact prevalence is unknown with studies reporting between 8 and 85% of gymnasts demonstrating signs of physeal injury on radiographs.22
Prevention
Athletes with a physeal injury of the shoulder, elbow or wrist often present themselves with pain increasing during sports activities without a history of acute trauma.15,23 However, pain during or
after sports activities is to some extent regarded as part of the game by most young athletes; these athletes rather compete while taking painkillers than stop training.24 Especially during
important periods of the season or if the injury is in an early stage, athletes and their coaches may decide to continue training despite the presence of pain, risking injury progression. This highlights the importance to develop effective preventive guidelines in order to ensure healthy sports participation among young athletes.
In 1987, Van Mechelen et al. described the ‘sequence of prevention’; a model illustrating the four steps necessary for the successful (primary) prevention of sports-injuries.25 The first
step of this model includes establishing the incidence and severity of the injury. Subsequently, mechanisms of injury have to be explored in order to introduce preventive measures and assess the effectiveness of the introduced measures.25 To prevent physeal injuries, according to Van
Mechelen’s model, a diagnostic tool able to accurately assess the presence and severity of physeal injuries is essential to successfully take the first steps in the model. In addition, such a diagnostic tool may be able to identify athletes with or at risk for injury as early as possible to prevent further damage and thus essentially function as a secondary prevention tool for physeal injuries.26,27
Diagnostic imaging …
Traditionally, clinical information and conventional radiographs have been used to evaluate the presence of physeal injury in the wrist.28 In contrast to radiographs, magnetic resonance
imaging (MRI) is able to depict the actual physeal cartilage and therefore valuable for detecting imaging abnormalities of the physis.29,30 As a result of the increasing availability of high-field
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Chapter 1
strength MR-scanners providing high resolution images, MRI nowadays has a prominent role in the diagnostic workup of stress-related physeal injuries.
The healthy physis is characterized by a flat and undulating shape.31 On water-sensitive MR
images, it demonstrates a multilayered architecture reflecting the histologic configuration of the physis.27 In these images, the layers in which the chondrocytes rest, proliferate and hypertrophy
appear as a uniform hyper-intense line, the zone of calcification has a low signal intensity and the newly formed bone is hyper-intense again.27
*
A
B
C
Figure 1. MR images of a gymnast with stress-related injury of the distal radial physis characterized by bone-marrow edema of the distal radius and ulna visible on PD TSE SPAIR (A) and T2 Dixon water-only (B) images and irregularity of the physis, intrusion of physeal cartilage into the metaphysis (white arrowhead) and an increase in physeal thickness compared to the physis of the first metacarpal bone (white asterisk) best visible on an image obtained with a cartilage specific sequence (C)
… what is (ab)normal?
The appearance of the injured distal radial physis on MRI is well established in medical literature. Abnormalities associated with stress-related injury include physeal widening, irregularity of the metaphyseal border, periphyseal bone marrow edema and metaphyseal intrusions of physeal cartilage.8,9,29,30 However, the presence of these abnormalities in the distal radius of
asymptomatic wrist-loading athletes as a result of their sport participation has never been established. Consequently, it is unclear which of the aforementioned MR characteristics truly reflect physeal pathology and which are the consequence of physiologic adaptations of the body to high training intensity. This makes interpretation of diagnostic images challenging; temporary sports cessation for asymptomatic athletes with minor imaging abnormalities might be redundant.
As mentioned before, an accurate diagnostic (imaging) method is valuable for the steps that eventually lead to successful prevention of physeal injuries. However, the unclear significance of imaging characteristics associated with physeal injuries may introduce a variance in interpretation among observers. This suggests that the diagnostic accuracy of image interpretation may
BNW_Rik_V1.indd 10
benefit from evaluating the pathologic significance of these characteristics and exploring a more objective and quantitative diagnostic approach.
A
B
C
*
Figure 2. MR images demonstrating the challenge in diagnostic interpretation; physeal widening and intrusions of physeal cartilage in the metaphysis (white arrowheads) on cartilage specific MR images (A & B) of a gymnast without any symptoms. In addition, bone marrow edema (white asterisks) on PD TSE SPAIR images of an adolescent not involved in extensive wrist-loading sports.
Thesis outline
The main objective of this thesis is to develop an imaging-based strategy for accurate assessment of stress-related physeal injuries of the upper extremity. This strategy can aid in the development of preventive measures and provide reliable diagnostic and preferably prognostic information for young athletes and their coaches.
We primarily focused on stress-related injuries of the distal radial physis in young gymnasts for practical reasons; gymnastics is a popular sport among children in the Netherlands providing a large population of possible participants. However, as the aforementioned physeal injuries in the elbow and shoulder are characterized by similar MR features 30, the result of this thesis can
be used to kick start the development of a similar diagnostic strategy for these injuries as well. Through including both symptomatic and asymptomatic athletes, we aim to detect which MR characteristics reflect true pathology and redefine the normal appearance of the asymptomatic athlete’s wrist. To ensure optimal accuracy of our imaging-based strategy we aimed at elite level athletes as we assumed most severe imaging abnormalities could be identified among athletes with a high training intensity. Of course, we aimed to provide a diagnostic method that is applicable in daily clinical practice for recreational athletes as well.
Imaging of physeal stress in the upper extremity: (ab)normal redefined covers three
complementary parts; Part I focuses on the development of a structured tool for the evaluation
of morphologic MR characteristics associated with distal radial physeal injury. Furthermore, it utilizes the tool to describe the appearance of the distal radius and ulna in symptomatic and asymptomatic gymnasts and non-gymnasts. Part II highlights several of these morphological
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Chapter 1
characteristics and explores methods for reliable and (semi-)quantitative evaluation of physeal pathology among gymnasts suspected of having distal radial physeal injury. Finally, Part III
illustrates future perspectives through identifying in which sports young athletes are at risk for overuse injuries of the elbow and shoulder and should be focused on in forthcoming research projects.
Part I – Morphology
Chapter 2 aims at the development of a systematic MR-imaging based protocol for assessment
of the morphology of the distal radius and ulna. Development of the protocol is based on imaging characteristics described in medical literature and in consensus with several experts in the field. Reproducibility of the protocol is tested using MR images of symptomatic and asymptomatic gymnasts and healthy non-gymnasts. Eventually an MR-based tool is provided which can be readily used for the evaluation of the adolescent’s distal radius and ulna in daily clinical practice.
The developed protocol for evaluation of the distal radius and ulna is used in Chapters 3 and 4 for the structured assessment of MR images used in the studies. Chapter 3 evaluates
the presence, characteristics and effect of maturation on areas of bone marrow edema-like signal intensity in the forearm of healthy adolescents to facilitate diagnostic interpretation of the adolescent’s forearm. Chapter 4 describes the occurrence of the morphologic imaging
characteristics in gymnasts with suspected distal radial physeal injury, asymptomatic gymnasts and healthy non-gymnasts. It aims to establish which characteristics appear in the healthy distal radius and ulna, which are the result of extensive wrist-loading and which truly reflect pathology. This enables to distinguish between healthy and injured physes in daily clinical practice.
Part II – Quantification
The second part of this thesis explores the feasibility of using (semi-)quantitative methods to increase reliability and diagnostic accuracy of physeal injury detection. Chapter 5 focuses on
quantification of the water-signal fraction of the bone marrow of the distal radius and ulna in gymnasts with a suspected injury of the distal radial physis, asymptomatic gymnasts and non-gymnasts. The use of a Dixon chemical shift imaging sequence is illustrated which aims to explore if changes in bone marrow water content can be used as a diagnostic tool to detect physeal injury.
Chapter 6 and 7 are both centered around quantification of physeal thickness by
composing three-dimensional segmentation of the distal radial physis. Chapter 6 studies the
value of assessment of distal radial physeal volume in the diagnostic work-up of physeal wrist injury by comparing the volume of the physis segmentations between symptomatic gymnasts, asymptomatic gymnasts and non-gymnasts. Chapter 7 utilizes the same segmentations to
explore the anatomy of the normal distal radial physis. It identifies the distribution of
stress-BNW_Rik_V1.indd 12
related thickness increase as a result of wrist-loading in asymptomatic gymnasts and suspected physeal injury in symptomatic gymnasts.
Part III – Future perspectives
The first two parts of this thesis describe both morphologic and (semi-)quantitative methods to aid in the imaging based diagnostic approach of physeal wrist injuries in young athletes. Although these methods are evaluated for distal radial physeal injury, validation of these methods for other physeal injuries in the upper extremity may be valuable. Chapter 8 describes
a systematic literature review that aims to identify sports in which young athletes are at risk for obtaining overuse injuries of the elbow and shoulder in order to determine sports to focus on in future research projects.
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Chapter 1
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