Tunnel Intersection in Combined Anatomic Reconstruction ... - Healio

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Section Editor: Bennie G.P. Lindeque, MD 

Tunnel Intersection in Combined 

Anatomic Reconstruction of the ACL 

and Posterolateral Corner 

Steven J. Narvy, MD; Michael P. Hall, MD; Ronald S. Kvitne, MD; James E. Tibone, MD 

Abstract: Femoral tunnel intersection in combined anterior cruciate 

ligament and posterolateral corner reconstruction has been 

reported to be high. The purpose of this study was to examine the 

risk of intersection between an anatomic femoral anterior cruciate 

ligament tunnel created with a retrograde reaming device and 

femoral lateral collateral ligament reconstruction tunnels of varying 

trajectory in a synthetic femur model. 

Injuries to the posterolateral 

corner (PLC) of the knee are 

infrequent but can cause severe 

disability due to damage 

to the articular cartilage and 

persistent instability. 1 Although 

injury to the posterolateral 

structures can occur in isolation, 

coexisting injury to other 

structures, such as the menisci 

or the cruciate ligaments, is 

common. 2-4 Unrecognized 

posterolateral rotatory instability 

has been shown to be a 

major cause of anterior cruciate 

ligament (ACL) reconstruction 

failure. 1,5,6 This has led to an increased 

awareness of combined 

injuries and increased numbers 

of combined ACL and PLC reconstructions. 

Numerous authors have 

published various surgical 

techniques for PLC reconstruction. 

3,7-18 Many tunnel configurations 

have been proposed, 

including a neutral lateral tunnel 

originating at the isometric point 

of the lateral epicondyle 14,15 and 

tunnels originating from the anatomic 

origin of the lateral collateral 

ligament (LCL). 19 

The authors are from the Department of Orthopaedic Surgery (SJN, 

JET), Keck School of Medicine, University of Southern California; and the 

Kerlan-Jobe Orthopaedic Clinic (MPH, RSK, JET), Los Angeles, California. 

The authors have no relevant financial relationships to disclose. 

Correspondence should be addressed to: Ronald S. Kvitne, MD, Kerlan- 

Jobe Orthopaedic Clinic, 6801 Park Terrace, Los Angeles, CA 90045 

(drkvitne@aol.com). 

doi: 10.3928/01477447-20130624-07 

In the setting of combined 

ligament reconstruction procedures, 

the close proximity of 

ACL and LCL tunnels in the 

lateral femoral condyle can 

cause bone weakening and tunnel 

collision, particularly when 

performing double-bundle 

ACL reconstruction. 20,21 This 

can compromise graft function. 

Accordingly, the safest LCL 

tunnel trajectory has been recommended 

to avoid any proximal 

angulation in the coronal 

plane. 4,6 However, when creating 

a concomitant, parallel 

tunnel for a popliteal tendon 

reconstruction, this trajectory 

may risk damage to the articular 

cartilage of the lateral femoral 

condyle or trochlea. 6 In addition, 

this contradicts several 

popular PLC reconstruction 

techniques that recommend 

proximal and anterior angulation 

of both tunnels. 7,22 

The accuracy of ACL tunnel 

placement is also important in 

combined ligament reconstruction. 

Gaditoka et al 23 recently 

compared transtibial ACL tunnel 

creation to outside-in and 

anteromedial portal techniques 

in a cadaver model and noted 

statistically significant improvements 

in the percentage of 

coverage of the ACL footprint 

by the femoral tunnel with the 

anteromedial portal and outsidein 

techniques. The center of the 

outside-in tunnel was found to 

most closely replicate the center 

of the ACL footprint. In addition, 

the exit point of outside-in 

tunnels on the lateral femoral 

condyle was farther away from 

the LCL origin (particularly in 

the anterior direction) than the 

anteromedial portal tunnels. 

This increased ability of outside-in 

tunnel creation to replicate 

the center of the ACL footprint 

and to better control tunnel 

trajectory relative to the lateral 

epicondyle may be clinically 

relevant in the reconstruction of 

a multiligament-injured knee. 

The purpose of this study 

was to examine the risk of intersection 

between an anatomic 

femoral ACL tunnel created 

with an outside-in reaming device 

(FlipCutter; Arthrex, Inc, 

Naples, Florida) and femoral 

LCL reconstruction tunnels of 

varying trajectory in a synthetic 

femur model and to identify the 

best trajectory for safe tunnel 

JULY 2013 | Volume 36 • Number 7 529


2A 

Figure 2: Anterior (axial) (A) and proximal (coronal) (B) angulation of the lateral collateral ligament tunnel. 

2B 

Figure 1: Photograph showing the anterior cruciate 

ligament tunnel. 

placement. The authors hypothesized 

that using a retrograde 

ACL tunnel creation technique 

would reduce the risk of tunnel 

intersection and allow for a 

greater range of acceptable tunnel 

positions. 

Materials and Methods 

Eighteen solid foam synthetic 

femurs (Pacific Research 

Laboratories, Inc, Vachon, 

Washington) were used as the 

model for tunnel creation. Nine 

were size large (36-mm lateral 

femoral condyle), and 9 were 

size medium (28-mm lateral 

femoral condyle). These synthetic 

femurs were mounted 

proximally to a custom-made 

frame, and anatomic ACL tunnels 

were drilled retrograde 

from the ACL footprint using 

the FlipCutter set at 110° 

and angled 45° anterior in the 

axial plane (Figure 1). Entry 

points on the lateral femoral 

cortex were standardized at 

4 cm proximal to the articular 

surface in the midpoint in 

1 

the anteroposterior 

plane of the femur 

(just anterior to the 

superiormost aspect 

of the lateral 

epicondyle), and 

drilling angle was 

confirmed using a goniometer. 

Several studies have noted increased 

tunnel collision with 

30 mm ACL tunnels compared 

with 25 mm tunnels 4,6 ; a 10-mm 

tunnel was therefore reamed 

to 25 mm deep using the calibration 

mechanism on the 

FlipCutter to prevent confounding 

due to tunnel depth. 

Lateral collateral ligament 

tunnels were then created at the 

anatomic proximal attachment 

of the LCL (1.4 mm proximal 

and 3.1 mm posterior to the 

lateral epicondyle). 19 Previous 

studies have shown that lateral 

tunnel trajectories greater than 

40° in either the axial plane or 

coronal plane can result in elliptical 

tunnels and thinned cortices 

about the tunnel opening 4 ; 

accordingly, tunnel trajectories 

were limited to this range. From 

the LCL starting point, 8-mm 

tunnels were drilled to a depth of 

25 mm at either 0°, 20°, or 40° 

of angulation in either the proximal 

plane or the anterior plane 

(Figure 2). Specimens without 

obvious tunnel convergence underwent 

computed tomography 

(CT) scan with 3-dimensional 

reconstruction (2-mm cuts) 

(Aquilion16; Toshiba Medical 

Systems, Tustin, California) to 

determine the distance between 

the created tunnels or to determine 

whether an occult tunnel 

collision existed (Figures 3, 4). 

Radiographic measurements 

were conducted using the computer’s 

straight-line measuring 

tool to determine the tangent 

distance between the created 

tunnels. 

Results 

Overall frequency of tunnel 

intersection was 3/9 (33%) 

in large femur specimens and 

5/9 (56%) in medium femur 

specimens (P5.34; x 2 ). Among 

specimens without tunnel intersection, 

mean tunnel separation 

was 4.862.5 mm. Mean tunnel 

separation was 5.162.8 mm 

for the large-sized femora and 

4.362.0 mm for the mediumsized 

femora (P5.64; Student’s 

t test). 

At 0° of anterior angulation 

in the axial plane, 5 (83%) 

of 6 specimens were noted to 

have tunnel intersection. At 

20° of anterior angulation, 3 

(50%) of 6 tunnels intersected. 

Mean tunnel separation among 

the remaining specimens was 

4.261.5 mm. No intersection 

occurred with LCL tunnels created 

with 40° of anterior angulation, 

with a mean separation of 

5.762.6 mm. 

At 0° of proximal angulation, 

1 (17%) of 6 specimens 

experienced tunnel intersection. 

Increasing degrees of 

proximal angulation to 20° and 

40° produced a 50% and 66% 

rate of tunnel intersection, respectively. 

At these higher degrees 

of proximal angulation, 

high concomitant anterior angulation 

to 40° prevented tunnel 

intersection in both medium 

and large specimens. 

Maximum tunnel separation 

was noted at 40° of anterior 

angulation and 0° of proximal 

angulation (9.6 mm in the 

large femur and 7.2 mm in the 

medium femur). However, the 

guide pin used to drill the LCL 

tunnel at this trajectory violated 

the trochlea in both medium and 

large specimens (Table). 

Discussion 

This study demonstrates a 

decreased risk of tunnel intersection 

with greater anterior 

angulation and an increased 

risk of tunnel intersection with 

530 ORTHOPEDICS | Healio.com/Orthopedics


Table 

Tunnel Trajectory Results 

Figure 3: Computed tomography scan showing 

divergent tunnels. 

Figure 4: Computed tomography scan showing 

tunnel collision. 

3 

4 

Specimen 

No. 

Femur 

Size 

PLC Angle, deg 

Anterior 

Proximal 

Collision 

Separation 

on CT, mm 

1 Large 0 0 No 1.8 

2 Large 0 20 Yes 


4 Large 20 0 No 5.9 

5 Large 20 20 No 3.4 


Notes 

7 Large 40 0 No 9.6 Trochlea 

violated 

8 Large 40 20 No 6.7 

9 Large 40 40 No 3.4 

10 Medium 0 0 Yes 



13 Medium 20 0 No 3.2 



16 Medium 40 0 No 7.2 Trochlea 

violated 

17 Medium 40 20 No 4.4 

18 Medium 40 40 No 2.6 

Abbreviation: CT, computed tomography; deg, degrees; PLC, posterolateral corner. 

greater proximal angulation. 

These findings were particularly 

important in the mediumsized 

femora, which had overall 

higher rates of intersection, 

likely due to the smaller available 

volume for traversing tunnels. 

However, proximal angulation 

greater than 20° did not 

produce tunnel collision to the 

same extent as has been previously 

described. Proximal angulation 

of 20° or more was a 

safe configuration in the large 

femur when combined with 20° 

of anterior angulation and was 

safe in both femur sizes when 

combined with 40° of anterior 

angulation. 

Two studies have previously 

evaluated tunnel collision 

in combined ACL–PLC 

reconstruction using synthetic 

femur models with study designs 

similar to that of the current 

study. Shuler et al 4 evaluated 

tunnel placement in 11 

synthetic femurs. The ACL 

tunnel was placed in a standard 

manner but appeared to be nonanatomic 

on imaging, with the 

intra-articular tunnel aperture 

centered over the footprint of 

the anteromedial bundle rather 

than between the anteromedial 

and posterolateral bundle footprints. 

The LCL insertion point 

was anatomically located on 

the synthetic femurs, and then 

tunnels of varying axial and 

coronal angulation (0°-60°) 

were drilled from this starting 

point. The authors found that 

increasing the axial trajectory 

of the lateral tunnel from 0° to 

40° was protective against tunnel 

collision and demonstrated 

that tunnel separation distance 

increased directly with axial 

angulation. Coronal angulation 

greater than 20° produced tunnel 

collision in all specimens. 

In a separate arm of the study, 

the authors compared LCL tunnels 

drilled at 40° anterior/0° 

proximal to control tunnels 

drilled at 0° anterior/0° proximal 

in 7 matched cadaver knees 

and noted a 29% collision rate 

with the more anterior tunnels 

compared with 43% in the control 

group. The authors concluded 

that the safest configuration 

for tunnel placement was 

40° anterior and 0° proximal. 4 

Camarda et al 6 performed a 

similar study of tunnel placement 

when the ACL was reconstructed 

using only the 

posterolateral bundle tunnel of 

a double-bundle technique concomitantly 

with reconstruction 

of the lateral collateral ligament 

in 36 synthetic femurs (18 large 

and 18 medium). As in the current 

study, 9 different guidewire 

JULY 2013 | Volume 36 • Number 7 531


orientations in the anterior and 

proximal planes were created at 

20° intervals for the LCL tunnel. 

6 Similar to Shuler et al, 4 the 

authors demonstrated a significantly 

higher rate of tunnel collision 

with proximal angulation 

greater than 20°. No collisions 

were noted when the LCL tunnel 

was reamed at 0° of proximal 

angulation, irrespective of 

anterior trajectory. 6 

Also similar to Shuler et 

al, 4 the current authors noted 

maximal tunnel separation at 

40° anterior and 0° proximal. 

This configuration resulted in 

violation of the trochlea in both 

medium and large specimens, 

although proximal angulation 

to 20° at the same anterior trajectory 

produced satisfactory 

tunnel separation. This finding 

suggests that proximal angulation 

may be protective of the 

trochlea when combined with 

significant anterior angulation. 

However, the limitations of 

this laboratory model must be 

appreciated in making this determination. 

Variability of human 

femoral condyle size can 

greatly affect the risk of tunnel 

collision, and although 2 sizes 

of synthetic femur were used 

in the current study, in vivo 

tunnel creation may produce 

different findings. Similarly, 

in vivo retrograde reaming is 

based on intra-articular landmarks 

from the footprint of 

the ACL, which was not present 

in this sawbones model. 

Using a handheld goniometer 

for lateral tunnel placement 

may have an increased risk 

of variability compared with 

a well-controlled jig. Most 

importantly, the small sample 

size limits the generalizability 

of the current results to in 

vivo reconstructive procedures. 

Nonetheless, this study demonstrates 

the technical feasibility 

of a combined ACL-PLC reconstruction 

using a retrograde 

reaming device in a laboratory 

model. Increasing anterior angulation 

when combined with 

25-mm LCL tunnels may help 

avoid tunnel intersection when 

performing such combined 

procedures, particularly in 

smaller-sized femora. 

Conclusion 

The results of this study provide 

evidence for safe LCL tunnel 

creation when using retrograde 

ACL reaming techniques 

in combined ACL and PLC reconstruction. 

Forty degrees of 

anterior angulation of the LCL 

tunnel produced the lowest risk 

of tunnel collision but at the risk 

of trochlear violation without 

concomitant proximal angulation. 

Therefore, optimal tunnel 

orientation is recommended at 

40° of anterior angulation and 

20° of proximal angulation. 

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