Journal of Head Neck & Spine Surgery
Abstract
Professional sport activities or work may exert
considerable stress on the spine. We aimed to assess the effects of
loading on the deformation of the vertebral body of the twelfth thoracic
vertebra (T12) and the lumbar vertebrae (L1-L5), which are subjected to
considerable stress in basketball players. A total of 20 basketball
players were assigned to one of two groups, based on their experience
with playing basketball: under 5 years, junior group; over 5 years,
senior group. All participants underwent magnetic resonance imaging; the
relevant geometric variables were measured using specialized software,
and the outcome measures were calculated using specific formulas; the
outcome measures were compared between the junior and senior groups. The
results indicated a significant difference between the two groups with
respect to the compression deformity ratio at four levels (T12, L1, L2,
and L3), and to the biconcave deformity at one level (L3). Our data
suggest that the mechanical loading on lower spine plays an important
role in the development of degenerative changes of the vertebral body,
which may be considered a risk factor for future injury and low back
pain in basketball players.
Keywords: Vertebral body changes; Magnetic resonance imaging; Basketball
Abbrevations:
T12: Thoracic Vertebra; L1-L5: Lumbar Vertebrae; Ha: Anterior Margin;
Hp: Posterior Margin; Hm: Halfway Between these Margins; Dap:
Anterior-Posterior Diameter; BMI: Body Mass Index
Introduction
During sports activities, several important
musculoskeletal structures are required to perform complex spinal
movement patterns that involve bending and twisting at high speeds.
Therefore, the spine is subject to the action of many forces, due to
both physiological motion (flexion, extension, rotation, lateral
flexion) and accessory motion (shearing tension, compression) [1].
Depending on the direction, magnitude, and point of application of the
forces, the spine may suffer deformation and injury. Abnormalities of
the spine may also cause injury and pain among athletes because of the
unique demands related to each specific sports activity. Lumbar spine
injuries represent a significant concern to the athletes, coaches, and
physicians.
During athletic endeavors, the lumbar spine is
subjected to considerable stress due to unfavorable biomechanical
situations typically occurring during such activities [2]. The
thoracolumbar and lumbar spine are particularly susceptible to injury
due to the large forces exerted in these regions, which are related to:
body
weight; loads created by motions such as flexion, extension, and
rotation [3]; and loads created by accelerating motions especially in
sports demanding high speed movements.
In athletes, independent variables that contribute,
individually or in combination, to lumbar spine injury include poor
technique, poor conditioning, and abnormal anatomy; thus, young athletes
may have a spinal deformity that is incidentally or potentially related
to their sports activities [4].
Heavy physical work can lead to degenerative changes
in the spine [5,6], with body position being a factor that can
dramatically affect the load on the lumbar spine. It was shown that the
vertebral body undergoes a gradual change in shape under the application
of a constant load [7]. Compressive damage arising from repetitive
loading is most likely a common event in life; damage to the vertebral
body causes decompression of the adjacent disc, leading to internal disc
disruption and further degenerative changes [8-10]. Compression
fractures can occur with axial loading in a flexed or vertical position.
The capacity
of the spine to resist injury is decreased if the forces applied
involve flexion and are of long duration [11].
It has been demonstrated that the load on the spine during
physical activity can be measured based on changes in stature
[12]. In analyses of force transmission and in model studies
on the spine in high level athletes, it is necessary to estimate
reference geometric parameters. It is particularly important to
determine the size of the intervertebral discs, the size and shape
of the vertebrae, and the overall shape of the spine [13].
Besides the loads carried or lifted by the upper extremities,
loads caused by specific, frequent movement during sports
activities cause significant loading stress to the vertebral bodies,
inducing continuous remodeling of the vertebrae. This leads to
degeneration and deformities of the vertebral body, which is
associated with increased risk of injury. In the case of the lumbar
spine, loads due to flexion, extension, rotation, and acceleration
are typically associated with deformity of the vertebral body.
To assess the potential deformation, the height of the vertebral
body is measured in three places: at the anterior margin (Ha), at
the posterior margin (Hp), and at halfway between these margins
(Hm). Three types of vertebral deformities can then be defined
based on these heights and on the anterior-posterior diameter
(Dap) of the vertebral body. Thus, an anterior wedge deformity
is characterized by a low Ha/Hp ratio; a biconcave deformity
is characterized by a low Hm/Hp ratio; and a compression
deformity is characterized by a low Hp/Dap ratio [14].
The present study attempted to assess the effect of sportsrelated
loading on the remodeling of the twelfth thoracic vertebra
and the five lumbar vertebrae in basketball players, as predictive
markers for future injury or lower back pain.
Material and Methods
Participants
For this study, 20 basketball players (mean age = 20.90,
standard deviation = 2.84) with and without symptoms of lumbar
pain underwent a case history and a physical examination. The
participants were classified in two groups: senior players, with
≥ 5 years of experience; and junior players, with < 5 years of
experience. The two groups were matched for sex and age. All
participants provided informed consent before commencing the
experiment. Players who underwent previous operation in their
spine, and players with history of smoking habit were excluded
from the study. The study was approved by the Institutional
Review Board of our university.
Measures
The pain description for each player was identified by a selfreported
questionnaire and a physical examination conducted
by an orthopedic specialist. The age, body height, mass, and the
body mass index (BMI) of all the subjects were documented. No
participant was medicated during the study. A dedicated 1.5 T
MRI was performed by technicians for lateral views of the lumbar
spine and sacral region of all participants (Figure 1).
The whole body of the vertebra was estimated on each
image using Kinovea version 0.8.15 (Kinovea, France) and
syngo fast View version 1.0 (Siemens, Munich, Germany), and all
measurements were performed blinded to any other information
or measurement regarding the subject.
Procedures
After completing the imaging process, geometric variables
were selected using the two referred software, including: lumbar
body index (Hp/Ha ratio) (Smith et al., 1996), anterior wedge
deformity (Ha/Hp ratio), biconcave deformity (Hm/Hp ratio),
and compression deformity (Hp/Dap ratio) [14].
Statistical analysis
Data of outcome variables were tested using independent
t-test for differences between the two selected groups. Data
analysis was performed using SPSS version 17.0 (IBM, Chicago,
Illinois, US), and level of significance was set as 0.05.
Results
Our findings showed that, between the senior and junior
groups, there were no significant differences regarding age,
weight, height, or BMI. This result suggests that these factors did
not affect the results of the study.
The height of the vertebral body was measured in
three places: at the anterior margin (Ha), at the posterior margin (Hp),
and at halfway between
these margins (Hm). Three types of vertebral deformities can be defined
based on these heights and on the anterior-posterior diameter (Dap):
anterior wedge deformity (low Ha/Hp ratio); biconcave deformity (low
Hm/Hp ratio); and compression deformity (low Hp/Dap ratio). SD: standard
deviation; N: number of participants in the group.
The height of the vertebral body was measured in
three places: at the anterior margin (Ha), at the posterior margin (Hp),
and at halfway between
these margins (Hm). Three types of vertebral deformities can be defined
based on these heights and on the anterior-posterior diameter (Dap):
anterior wedge deformity (low Ha/Hp ratio); biconcave deformity (low
Hm/Hp ratio); and compression deformity (low Hp/Dap ratio). P-values
lower than 0.05 were considered significant.
The ratios, for both groups, of Hm/Hp, Ha/Hp ratio, and Hp/
Dap for each level of the lumbar spine, and for the 12th thoracic
vertebral body are shown in Table 1. Further, we observed
significant differences between the senior and junior groups
regarding Hp/Dap ratio at the spine levels T12 (t = 3.67, p =
0.002), L1 (t = 6.65, p ≤ 0.001), L2 (5.34, p ≤ 0.001), and L3 (t
= 3.28, p = 0.004) (Table 2), revealing that senior basketball
players exhibit greater compression deformity in these levels of
the spine when compared to junior basketball players.
Accordingly, we also observed greater compression
deformities in the L4 and L5 levels of the senior basketball
players when compared with junior players; however, those
results were not statistically significant.
Moreover, the senior basketball players had significantly
higher Hm/Hp ratio at L3 level (t = 2.47, p = 0.02) when
compared with the junior basketball players, revealing that
senior basketball players exhibit greater biconcave deformities
in L3 when compared to junior basketball players.
On MRI examination, no significant difference between the
two groups was observed regarding anterior wedge deformity,
or lumbar body index.
Discussion
High level sports participation in adolescents and young
adults is associated with a greater incidence of low back pain and
structural abnormalities, as revealed in imaging studies [15]. Back pain has significant effects on the athletes’ performance
and is estimated to occur in 1.1% to 30% of athletes, with
some variation depending on the type of sports activity. Among
basketball players, low back pain is a common problem [16-20].
Pain in the spine is often difficult to diagnose. Loading appears
to play an important role in the development of radiographic
changes of the lumbar spine, and one factor that can dramatically
affect the load on the lumbar spine is body position [21]. In
the present study, we used MRI, which is considered the most
accurate imaging modality for assessing the spine [22]. However,
it is important to note that abnormal imaging findings are not
always related to the source of the pain, as pathology can exist
without pain, and vice versa. In the present study, we assessed
degenerative changes related to vertebral body size and shape,
which may be considered predictive markers for future lower
back pain or injury.
Basketball is popular worldwide and creates unique
physiological and physical demands on the players. For example,
playing and dribbling the ball are usually executed in a position
of spinal flexion, Repetitive jumping, landing from height, and
abrupt changes of direction create significant forces acting
on the spine. Such repetitive loading can create microscopic
damage within a material or tissue, which gradually builds up
until gross failure occurs. In living tissues, the process of damage
accumulation is opposed by the process of adaptive remodeling
[1,14]. According to Alexander [3], the type of injury that occurs
in the lumbar spine, which is under significant stress in basketball
players, is dependent on the direction, magnitude, and the point
of application of the forces in the spine. Ruyssen-Witrand et
al. [23] proposed that vertebral size should be considered a
potential independent risk factor for vertebral fracture.
Several studies have compared lumbar spine abnormalities
of elite athletes with those in non-athletic groups with respect to
various sports such as wrestling, soccer, tennis, track and field,
and gymnastics [24-26].
In this study, we focused on two groups with the same sex,
range of age, and range of BMI, but with different experience
with respect to playing basketball. We hypothesized that,
independently of other factors, more years of playing in
basketball-specific body positions and acceleration motions may
cause more abnormalities in the lumbar spine. Indeed, we found
that the vertebrae T12, L1, L2, and L3 showed a significantly
higher compression deformity in senior basketball players.
Likewise, L3 had more biconcave deformities (lower Hm/Hp
ratio) in senior basketball players. Thus, playing basketball for
more years appears to cause more loading on the lumbar spine,
and deformity of the vertebral body.
Our result suggests that, in basketball players, T12 and L1-L3
are at higher risk of degenerative deformities and fractures, as
they may be affected by compression and biconcave deformities
to a higher extent. Schmitt et al. [26] reported that the concavity
index at all levels of the lumbar spine was similar in different
groups of track and field athletes. On the other hand, Reilly &
Seaton [27] observed an average spinal shrinkage rate of 0.4mm/
min in players dribbling a hockey ball. Predisposing factors in
basketball include repetitive spinal flexion, extension, twisting,
and loading. Poor development of abdominal musculature
in conjunction with strong paraspinal muscles may increase
the stress on the lumbar spine during hyperextension, while
repetitive jumping and changing of direction create significant
forces throughout the spine [1]. In basketball, athletes must
bend and rotate their bodies. The specific patterns of loading
experienced by the basketball players during dribbling, frequent
flexion, and hyperextension may explain the higher rate of
radiographic changes we found for the vertebral body of T12, L1,
L2, and L3 in more experienced players.
No other significant differences were observed in our MRI
examination of the lumbar spine with respect to lumbar index at
any level, or compression and biconcave deformity of vertebrae
L4 and L5. We did find slight differences with respect to anterior
wedge deformity, but this observation did not reach statistical
significance, and thus requires more attention before it can be
hypothesized as a risk factor for stress fractures.
The present study is limited due to its small population
sample, and the fact that it did not account for factors like diet,
quality of sleep, or the physical and mental condition of the
participants.
Conclusion
In this study, we focused on loading on the lumbar spine
caused by basketball-specific body positions, which may
translate into vertebral deformities and thus increase the risk of
pain and spinal injury, and ultimately prevent the player from
participating in sport events. Athletes with minor fractures in
the lumbar vertebral body but without neurologic involvement
may be considered to return to the sport competition, but
under the supervision of the coach and physician; however, they
should be made aware of the risks of future injury caused by
the deformities. Coaches and athletes may consider these risk
factors and apply proper training and conditioning to avoid the
development of vertebral body deformities.
In general, athletes and coaches in sports that have an
increased risk of lumbar spine injury should be educated in
preventive techniques. Specific sport training may be considered
to support this part of the spine, with the understanding that
significant forces are transferred to the lumbar vertebrae, and
with knowledge of the sport-specific deformation likely to occur
at various spinal levels.
Acknowledgment
The authors would like to thank the athletes who participated
in this study, as well as the employees of the Orthopedics
Department and the technicians of the MRI Centre at our hospital
for their support with data collection.
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