The Risk of Transphyseal Drilling in Skeletally Immature Patients With Anterior Cruciate Ligament Injury
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The Risk of Transphyseal Drilling in Skeletally Immature Patients With Anterior Cruciate Ligament Injury
Peter Faunø 0
Lone Rømer 0
Torsten Nielsen 0
Martin Lind 0
0 Investigation performed at Department of Sports Traumatology, Aarhus University Hospital , Aarhus , Denmark
Background: Anterior cruciate ligament reconstruction (ACLR) in skeletally immature patients can result in growth plate injury, which can cause growth disturbances. Purpose: To evaluate radiological tibial and femoral length and axis growth disturbances as well as clinical outcomes in skeletally immature ACLR patients treated with a transphyseal drilling technique. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 39 pediatric patients with ACL injury and open physes at time of surgery, as diagnosed clinically and with magnetic resonance imaging (MRI), were treated using transphyseal ACLR using hamstring graft. Mean patient age was 11.7 years (range, 9.0-14.0 years). Patients were evaluated with full extremity radiographs measuring leg length discrepancy and malalignment, as well as clinical evaluation with KT-1000 arthrometer measurements and Tegner activity scale and Knee injury and Osteoarthritis Outcome Score (KOOS) outcomes after follow-up of 68 months (range, 29-148 months). Results: Of the 39 initial patients, 33 were evaluated both clinically and radiographically. We found a mean femoral length shortening of 3.5 mm (P ¼ .01) on the operated leg. Eight patients (24%) had a more than 10-mm shortening of the operated leg, whereas only 1 patient (3%) had a 10-mm shortening of the nonoperated leg. In 27 of 33 patients (82%; P < .001), the anatomic femoral axes of the operated leg were found to be more than 2 of valgus compared with the nonoperated leg. The tibial anatomic axes changed into a less pronounced varus angulation (P ¼ .02). The femoral-tibial anatomic axes were not significantly different when comparing the 2 legs. We did not find any statistical difference in growth arrest comparing patients treated surgically at the ages of 13 to 14 years to patients younger than 13 years. Tegner and KOOS scores were significantly lower among girls compared with boys. Side-to-side KT-1000 arthrometer difference improved from 5.2 mm preoperatively to 1.6 mm at follow-up. Conclusion: This study shows that transphyseal ACLR in children results in minor length growth disturbances in 24% of patients. The surgically induced distal femoral valgus angulation is counterbalanced by a proximal tibial varus angulation. Growth disturbance after surgery is not associated with a certain pediatric age group. Otherwise, transphyseal ACLR has satisfactory clinical outcomes, with good subjective outcomes, function level, and knee stability.
anterior cruciate ligament; open physis; pediatric; transphyseal drilling; knee instability
over the past few years.12,31 According to the Danish ACL
register, 6% of all ACL reconstructions (ACLRs) are
performed in patients younger than 15 years.25
The main reason for the existing controversy regarding
optimal treatment of children with ACL injury is the
concern of surgically induced physeal growth disturbance.
Nonoperative treatment may not sufficiently prevent knee
instability and can lead to further meniscal and cartilage
damage due to recurrent instability episodes.13,24,29
Operative treatment, on the other hand, may cause growth
disturbances of the involved leg due to involvement of the
physis.22 However, the literature regarding outcome after
surgical treatment of ACL injury in children demonstrates
good clinical results comparable to ACLR in adults. In a
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meta-analysis of children and adolescents, only 1.9% had
leg length discrepancies after transphyseal ACLR.9 These
results were, however, based on clinical judgment or
standard radiographs, and the mean patient age was 13 years.
Interestingly, in the same study, the use of hamstring
grafts was shown to be less prone to provoke growth
disturbance than the use of patellar tendon graft.9
The purpose of this study was to quantify the degree of
growth disturbances in the operated leg compared with the
nonoperated leg after transphyseal hamstring ACLR in
children using an accurate digital radiographic
The study was approved by the regional ethics committee
(j-36534). In the period from 2001 to 2010, a total of 39
children with ACL lesions diagnosed clinically and on
magnetic resonance imaging (MRI) were treated with
transphyseal ACLR; hamstring grafts and an Endobutton (Smith &
Nephew) were used as the femoral fixation and bicortical
screw and washer as the tibial fixation (Figure 1). All
patients showed a clear open epiphysis in the distal femur
and proximal tibia on preoperative radiographs.
Preoperative Tanner staging and bone age radiographs were not
done. The patients were evaluated preoperatively and at
final follow-up. All patients were skeletally mature at the
time of follow-up. Mean age at surgery was 11.7 ± 1.4 years
(range, 9-14 years; boys: 11.6 ± 1.3 years, girls: 11.9 ± 1.5
years). The observation time was 68.0 ± 33.9 months
(range, 29-148 months). Five patients did not respond to
the request for a final follow-up and 1 patient was
pregnant, leaving the fully accessible number of patients at 33.
At final follow-up, a clinical outcome evaluation was
performed using a subjective evaluation: the Knee injury and
Osteoarthritis Outcome Score (KOOS).30 The functional level
was evaluated using the Tegner activity scale,5 and objective
knee stability was evaluated using side-to-side KT-1000
arthrometer measurements. Furthermore, patients were
evaluated using full-extremity radiographs assessing leg length
discrepancy and angular malalignment.
In all 33 patients, ACLR was performed using 4-stranded
hamstring autografts and an Endobutton as femoral
fixation. For tibial fixation, the graft ends were locked under a
spiked washer (Arthrotek) secured with a bicortical screw
(Arthrotek) placed distally to the tibial epiphysis. The tibial
tunnel was placed close to the tibial tuberosity, and the
femoral tunnel was drilled transtibially to achieve a steep graft
orientation. The diameters of the drilled tunnels were the
same as for the graft within 0.5-mm increments (Figure 1).
The postoperative radiological examinations were
performed using the MultiDiagnost Eleva 3D-RX system
(Philips Medical Systems) with an optional application
designed for measurement of lower limb geometry. A run
of radiographic images used for leg measurements was
obtained using the normal acquisition protocol with the
patient in the standing position with their back against
the tabletop and full body weight on the leg displayed. The
image dataset was transferred to a ViewForum R6.3
workstation (Philips Medical Systems) with the ‘‘Leg
Measurement Package’’ installed. The algorithm for leg composite
image reconstruction is specifically designed for a series of
images of the lower limb skeleton taking specific features of
these images into account. The package reconstructs a
single composite image from a run of radiographic images
made for this purpose. The composite image was used for
length of femur and tibia and angle measurements around
the knee (Figure 2). The angle and length measurements
are performed by defining specific anatomic landmarks in
the composite image. Thereafter, the software program
automatically calculates the measurements.
All radiological measurements were performed by a senior
radiologist (L.R.). There was no previous relevant validating
of the MultiDiagnost Eleva system, so we performed an
inter- and intraobserver study on 10 radiographs from the
study patients. Intra- and interobserver variation were
assessed by interclass correlation analysis. Three individual
observers (P.F., M.L., T.N.) measured all radiological
parameters from 10 study patients for interobserver variation
analysis. Measurements were repeated after 2 weeks for
intraobserver variation analysis. Measurement variations
were calculated by interclass correlation coefficient (ICC)
statistics for both length and angulation parameters.
Interobserver ICC for length and angular measurements
was 1.00 for both. The intraobserver ICC for length and
angular measurements was 0.98 and 0.95, respectively.
We found these precision data satisfactory for our
radiological analysis. We defined a leg length discrepancy of more
than 10 mm as clinically relevant.
Radiographic outcome was analyzed using the Student
paired t test and the chi-square test. The patient-reported
outcome scores and the KT-1000 arthrometer
measurements comparing preoperative with final follow-up were
evaluated using the Student t test. Analyses were made
comparing age groups and sex. P < .05 was considered
statistically significant. Tests were 1-sided and were not
adjusted for multiple comparisons.
The effect of ACLR on KOOS and Tegner scores is
outlined in Table 1. All KOOS subscores, in particular the
Sport and the Quality of Life (QoL) subscores, improved
significantly. This finding is supported by a significant
improvement in activity level as measured with Tegner
score improvement from 2.8 (boys, 5.0; girls, 2.2) to 6.1
(boys, 7.0; girls, 6.2). Postoperative Tegner and KOOS
scores were significantly lower among girls compared
with boys. KT-1000 arthrometer measurements improved
from 5.2 mm preoperatively to 1.6 mm at follow-up.
There was 1 patient with a more than 4-mm
We found a mean femoral shortening of 3.5 mm (P < .01) for
the operated leg. The tibial length was not significantly
different (Table 2). Eight patients (24%) had a more than
10-mm shortening on the operated leg (mechanical axis),
whereas only 1 patient (3%) had a 10-mm shortening on
the nonoperated leg (Table 3). The femoral-tibial angle (the
valgus angle measured between the axis drawn from the
center of femur head to the intercondylar notch and
the anatomic axis for the tibia) was not significantly
different between knees, whereas the femoral transcondylar
angle was significantly more valgus (100.1 ) than the
opposite knee (98.5 ) (P < .01). The tibial transcondylar angle
was significantly more varus (87.2 ) compared with the
opposite knee (88.2 ) (P < .01) (Table 2).
Comparing patients younger than 12 years at the time of
surgery with patients aged 12 to 14 years, there was no
significant difference in leg length inequality or
femoraltibial axis (Table 4). Similarly, when patients with graft
sizes 7 mm or less (n ¼ 14) were compared with patients
with graft diameters greater than 7 mm (n ¼ 19), no
significant differences were found.
In 27 of 33 patients (82%) (P < .001), the anatomic
femoral axis of the operated leg was found to be 2 or more
valgus compared with the nonoperated leg. Tibial
transcondylar angle changed into significant varus angulation (P <
.01). The overall femoral-tibial anatomic axes were not
significantly different comparing the legs (Table 5).
Leg length D
Femoral length D
Tibial length D
Femoral-tibial anatomic axis D
aData are reported as mean ± SD.
bStudent t test used for comparison.
Our study demonstrates that transphyseal-placed soft
tissue grafts without intraosseous-placed fixation implants
affect both length and angular growth around the knee. This
is in contrast to earlier publications, where no growth
disturbances were seen.8,16,17,22,23 This could be explained by
different diagnostic measures, as several previous studies
have based their evaluation of limb alignment on clinical
measurements, plain radiograph evaluation, small patient
groups, or greater age of the studied patients. However,
Koch et al20 found growth disturbances after pediatric ACLR
in 2 of 12 patients. In contrast to our results, they found an
overgrowth in the operated limp. In a recent study by Calvo
et al,6 no radiological changes were seen in 27 patients 10
years postoperatively. The mean patient age in this group
was greater (13 years) than in our patient group, which could
explain why no changes could be registered. Furthermore, a
different diagnostic tool used in our study with computerized
measurements of length and angle measurement of legs
could explain the difference between the studies.
While we found a significant shortening of operated
limbs, we found no length difference of more than 2 cm. Leg
length inequality is relatively common in the adult
population.15,32 Minor leg length differences have not been found
to cause changes in gait.11 Only when the leg length
discrepancy exceeds 2 cm is a notable gait asymmetry seen.19
It is believed that the risk of leg length inequality is
greatest after ACLR in patients close to skeletal maturity
because of decreased growth rate.2,7 This could not be
confirmed in our study.
We did not find graft size to be of importance for later
growth disturbances. This could be explained by a possible
correlation between the diameter of the graft and knee
In our study, the distal femur was affected more than
the proximal tibia after ACLR. This is likely explained by
the fact that the contribution of the total limb growth is 37%
for the distal femur and only 28% for the proximal tibial
physis.33 We saw a significant number of femoral valgus
deformities, which may be caused by restricted growth in
the lateral part of the epiphyseal plate induced by drilling
or graft placement. There were also a significant number of
tibial varus malformations in the operated leg, probably
due to the medially placed tunnel. This growth arresting
phenomenon was demonstrated in an animal study in 1950,
when Haas14 found that placement of pins across the
epiphyseal plate caused restriction of bone growth. The same
growth arrest has been seen when using
epiphysealplaced biodegradable implants.27
The significant femoral valgus deformity was partly
counterbalanced by the less significant tibial varus
deformity, leading to a nonsignificant increased number
of patients with valgus of the femur-tibia axis (Figure 3).
The significance of these changes in the biomechanics
around the knee is not clear and has not yet been
described in the literature. Patients in our study
responded well to surgical reconstruction based on
functional and subjective outcome scores. One can speculate
whether patients with hanged knee kinematics are more
prone to later knee injury or overuse injuries. This needs
The patients included in this study underwent surgery
several years ago. Therefore, ACLR was performed using
the transtibial technique, which was standard at that time.
Within the past few years, use of the anteromedial portal
for femoral drilling has been advocated to place a more
anatomic femoral tunnel.28 This in turn will lead to a more
oblique femoral tunnel, resulting in a more peripherally
located drill tunnel through the distal femoral epiphysis.
In animal studies, peripherally placed tunnels have shown
to cause more growth disturbance compared with more
centrally placed tunnels.32 Furthermore, a more oblique course
of the femoral tunnel compared with the steeper tunnel will
lead to a more ovular and thereby larger effect on the
physis, which could compromise growth even more.
Consequently, one could fear that the growth disturbances seen
in our study would be increased in skeletally immature
patients operated on using a more anatomic
reconstruction.18 This calls for further study.
Epiphyseal-sparing ACLR techniques have now been
developed and gained interest. There are many different
techniques described.1,4,10,21 These techniques should
theoretically reduce the growth disturbances seen in this
study. In a meta-analysis, Frosch et al9 reported a greater
incidence of growth disturbances in studies with
physealsparing techniques compared with studies where
transphyseal reconstructions were used.
In this study, we only analyzed malformation registered as
leg length discrepancy and varus-valgus direction. We did
not measure any growth disturbance in the sagittal plane.
The tunnels, as seen in the sagittal plane, are also placed
asymmetrically in the anterior part of the tibial growth
plate and the posterior part of the femoral growth plate.
Therefore, one could expect an impact on growth in the
In theory, one cannot exclude the impact of the trauma
itself. Posttraumatic MRI often shows bone bruise changes
around the knee extend up to the epiphysis. We did not obtain
preoperative long-leg films so it is unclear whether the
discrepancies we saw occurred prior to surgery. The
malformation around the knee seen in this study could have been
influenced by the initial trauma. Studies of ACL patients who
did not receive surgery are needed to clarify this issue.
Five of the original 39 patients did not respond to the
invitation to participate in this study (13%). This is
concerning, as the results of the nonresponding patients could
have changed those of this study. The drilling angle with
respect to the epiphyseal line was not documented in this
study. The drilling angle could differ among patients and
thereby the area of the affected growth plate. This could
result in different growth disturbances among patients.
This study shows that transphyseal ACLR in children
results in minor length growth disturbances in 24% of
patients. The surgically induced distal femoral valgus
angulation is counterbalanced by a proximal tibial varus
angulation. Age was not found to be associated with growth
disturbance after surgery. Transphyseal ACLR has
satisfactory clinical outcomes, with good subjective outcomes,
function level, and knee stability despite the growth
changes induced by transphyseal drilling.
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