Anterior cruciate ligament reconstruction

The two-incision technique

Thomas J. Gill, MDa,*, J. Richard Steadman, MDb,c

aDepartment of Orthopedic Surgery, Harvard Medical School, Massachusetts General Hospital Ambulatory Care Center,

15 Parkman Street Boston, MA 02114, USAbThe Steadman Hawkins Clinic, 181 West Meadow Drive, Vail, CO, USA

cSouthwestern Medical School, Dallas, TX, USA

The anterior cruciate ligament (ACL) can be

successfully reconstructed using a variety of surgical

techniques. Historically, the two-incision technique

was the standard of practice. It allows predictable,

near-anatomic placement of the femoral tunnel and

provides highly reproducible results with few com-

plications. As arthroscopic techniques continue to

advance, the all-endoscopic reconstruction technique

has gained tremendous popularity. Advocates of the

endoscopic method cite the avoidance of a second

lateral incision and decreased operative time as its

major advantages, with the implication that better

functional outcomes result.

There are several major advantages of the two-

incision technique over endoscopic methods. These

include consistent femoral tunnel placement, elimina-

tion of concern for ‘‘blowing out the back wall,’’

elimination of the problem of graft– tunnel mismatch,

elimination of the problem of screw divergence, and

ease of use for revision ACL reconstruction proce-

dures. The angle of the ACL graft is also more

anatomic, matching the angle of the native ACL.

In this chapter we present our technique for

reconstruction of the ACL using the two-incision

approach. Indications for its use are discussed.

Advantages and disadvantages of the two-incision

method compared with the all-endoscopic approach

are reviewed.

Technical considerations of the endoscopic and

two-incision techniques

Femoral tunnel placement

Incorrect placement of the femoral tunnel results

in one of the more common surgical errors made

when reconstructing the ACL. ‘‘Over-the-top’’ place-

ment is nonisometric, producing an increase in graft

length and tension with progressive knee extension.

Anterior displacement of the femoral tunnel causes

an increase in graft strain with increasing knee

flexion, resulting in decreased joint motion and

arthrofibrosis postoperatively and possible graft im-

pingement in extension.

The native ACL changes less than 3 mm in length

with passive knee motion [1,2]. This change in length

occurs because of the cam effect of the femoral

condyles, which causes a change in the position of

the instant center of rotation of the knee in the sagittal

plane. Because the center of rotation is closer to the

femoral attachment than the tibial attachment site,

there is little room for error when placing the femoral

tunnel if knee kinematics are to be optimized [3]. As a

result, it is imperative to place an ACL graft so that

there is less than 3 mm of graft motion from 0� to 90�of knee flexion. In fact, we believe that 2 mm of graft

motion is the maximum amount of motion that should

be permitted when performing an ACL reconstruction.

An isometer may be used before fixation of the graft to

accurately assess the potential degree of graft motion

[4]. In this manner, graft tension can be minimized in

the postoperative rehabilitation period [2,5].

0030-5898/02/$ – see front matter D 2002, Elsevier Science (USA). All rights reserved.

PII: S0030 -5898 (02 )00030 -5

* Corresponding author.

E-mail address: TGILL@partners.org (T.J. Gill).

Orthop Clin N Am 33 (2002) 727–735

Radiographic studies have confirmed the impor-

tance of femoral tunnel placement. Clinical results

correlate positively with femoral tunnels placed at

least 60% posterior to the anterior origin Blumen-

saat’s line [6]. A loss of knee flexion and increased

graft strain results from a femoral tunnel placed

more anteriorly.

The two-incision technique can eliminate the

problem of anterior femoral tunnel placement. The

‘‘rear-entry guide’’ that is available in most surgical

sets does not, in general, permit significantly anterior

graft placement. These guides are designed to be

placed on the back wall of the intercondylar notch,

maximizing posterior placement of the graft. Because

the lateral femoral condyle serves as the conduit for

the femoral bone block, there is no concern about

‘‘blowing out the back wall’’ of the intercondylar

notch. In contrast, the endoscopic technique relies on

this back wall for bone block stability and fixation.

Once disrupted, the endoscopic technique cannot be

used without sacrificing optimal femoral graft place-

ment. It is likely this concern results in some sur-

geons erring on the anterior side when placing an

endoscopic femoral tunnel.

Graft– tunnel mismatch

A major factor in the success of an endoscopic

ACL reconstruction relates to the length of the tibial

tunnel, especially when using fixed-length bone–

patellar tendon–bone autografts. Fixation of the graft

in the femoral tunnel is usually a fixed variable.

Regardless of the length of the femoral bone block,

the end of the bone block is placed at the opening of

the intercondylar notch to allow biomechanically

superior ‘‘articular’’ fixation with interference screws.

This construct minimizes the incidence of the ‘‘wind-

shield wiper effect,’’ tunnel widening, and graft

elongation. Seeding the bone block more proximally

in the femur also exposes the graft to the risk of

abrasion on the tunnel opening or severance while

inserting an endoscopically placed interference screw.

As a result of the fixed variable of femoral graft

placement, the length of the patellar tendon and tibial

bone block become a central concern for endoscopic

reconstructions. Graft – tunnel mismatch can occur

when the length of the graft is too long or too short

with regard to the tibial tunnel. If the tibial tunnel is

placed at too acute an angle, its length is shortened,

and graft extrusion can occur. The ability to achieve

interference screw fixation is compromised if at least

15 to 20 mm of graft is not inside the tunnel. An

excessively long tunnel may result in blind placement

of the interference screw deep inside the tibial tunnel,

with potential problems of screw divergence or articu-

lar penetration.

To avoid problems with graft– tunnel mismatch,

surgeons using the endoscopic technique often use

one of a variety of mathematical formulas to deter-

mine the correct angle to drill or to create the desired

tibial tunnel length [7,8]. An indirect technique,

called the N + 7 rule, adds 7� to the length of the

patellar tendon (N) to calculate the proper angle to

drill the tibial tunnel [9]. Some surgeons add 5 mm

to the length of the tendon in their calculations to

compensate for the obliquity of the tibial tunnel [7].

All such calculations are unimportant when per-

forming the two-incision technique. Because the

femoral bone blocks and tibial bone blocks are placed

and secured under direct vision, the graft can be

advanced or retracted in the femoral and tibial tunnels

as needed to optimize placement near the articular

surface while eliminating the possibility of graft

extrusion at either end. The tibial tunnel can therefore

be drilled at virtually any angle, within reason. This is

an especially important point when combined ACL/

posterior cruciate ligament (PCL) reconstructions are

performed, and a proper bone bridge (about 2 cm) is

desired between the two tibial tunnels to avoid tunnel

overlap and to optimize fixation.

Screw divergence

Screw divergence occurs when graft fixation

screws are not placed parallel to the long axis of

the bone block. It is generally accepted that the

fixation sites of ACL grafts are the weakest points

of an ACL reconstruction in the immediate post-

operative period. Interference screws provide the

most secure fixation when using a bone–patellar

tendon graft [10,11]. If the screws diverge or con-

verge from the graft, fixation strength may be com-

promised or the bone block can be fractured.

Divergence angles exceeding 15� to 30� have been

associated with an increased incidence of graft pull-

out in several in vitro load-to-failure studies [12–14].

Interference screw fixation in the femoral tunnel is

accomplished under direct visualization when using

the two-incision technique, using a cannulated screw

placed over a guide wire. Several studies have dem-

onstrated that endoscopic placement of the screw is not

as accurate as using the two-incision technique [15].

Endoscopic guides such as the ‘‘two-pin passer’’

(Linvatec, Largo, FL) have been developed to aid in

parallel screw placement. A slotted guide pin used for

graft passage is placed through the femoral tunnel,

with the guide wire for the femoral screw placed in

parallel through the slot and out the femur. The

T.J. Gill, J.R. Steadman / Orthop Clin N Am 33 (2002) 727–735728

problem of screw divergence is virtually eliminated

when using such a guide, but it is still essential to use

a graft protector when advancing the interference

screw to prevent injury to the graft from the screw

threads. It is also important to hyperflex the knee

until the guide wire is completely straight to facilitate

screw advancement, protect the graft, and prevent

guide pin breakage.

The two-incision surgical technique

Graft harvest

A longitudinal incision is made along the medial

border of the patellar tendon between the inferior pole

of the patella and the tibial tubercle. The subcuta-

neous tissue is dissected down to the level of the

paratenon. The paratenon is incised and elevated as a

distinct layer to allow closure after harvesting of the

tendon is completed. The medial and lateral borders

of the tendon are defined, and the width of the tendon

measured. One third of the tendon is harvested, with a

10-mm graft generally chosen. If the width is less

than 27 mm, a 9-mm graft is used.

A 2-mm drill bit is used to weaken the distal

attachments of the bone blocks rather than using an

oscillating saw, which could ‘‘past point’’ and leave a

stress riser. On the patellar side, the drill enters at a

30� angle to make a more bullet-shaped graft that is

easier to pass into the femoral tunnel. Lateral saw cuts

are made at a 20� angle to make a more trapezoidal

graft. A pick is used to weaken the patella at the

inferior pole so that the patellar bone block does not

break into the joint upon harvest.

Graft sizers are used to trim the bone plugs.

Maximizing the size of the bone plugs within the

respective tunnels is important to obtain rigid fixation

of the graft. Leaving a large gap for the passage of

instruments between the tibial bone plug and the wall

of the tunnel decreases the interference fit and results

in less optimal fixation [11]. Two number 5 Ethibond

sutures are placed at either end of the bone blocks.

We do not typically ‘‘tube’’ the graft. The tibial block

is generally 35 mm by 10 mm, and the patellar block

is usually 25 mm by 10 mm. If 25 mm represents

more than one third the longitudinal length of the

patella, a 20-mm graft is generally harvested instead.

Tibial tunnel placement

Although early studies stressed a more anterior

placement of the tibial tunnel within the ACL tibial

footprint, we use a more posterior placement. The

anterior aspect of the native ACL is concave and

accommodates the anterior aspect of the intercondylar

roof to avoid ligamentous impingement [16]. Placing

the tibial tunnel too far anteriorly increases graft

tension in flexion and results in impingement of the

graft on the intercondylar roof as the knee moves into

extension. Although it is not common to place the

graft too posteriorly, excessively posterior placement

of the graft theoretically increases graft tension in

extension and may damage the tibial attachment of

the PCL during tunnel drilling [3,17]. A more pos-

terior placement orients the graft more vertically with

respect to the tibial joint surface. This orientation can

decrease the ability of the ACL to resist anterior

displacement of the tibia.

We typically use a landmark for the ACL guide

pin that is 7 to 9 mm anterior to the PCL and 7 mm

lateral to the medial femoral condyle on the down-

slope of the medial tibial spine (Fig. 1). Such

placement minimizes the risk of impingement on

the intercondylar roof and the lateral wall. This

placement is supported by the work of Morgan et

al [18]. They reported that at 90� of knee flexion, thedistance from the central insertion site of the ACL to

the anterior margin of the PCL is a constant 7 mm,

independent of variations in knee dimensions. The

guide pin should enter the joint on a line drawn

parallel to the anterior edge of the femoral condyles

from the edge of the femoral condyles. Because

individual anatomy may vary, this secondary guide

confirms correct placement of the guide pin.

Medial– lateral placement is equally important to

prevent graft impingement on the lateral femoral

condyle and in general should be 6 to 7 mm from

the medial femoral condyle.

A tibial tunnel guide with a variable arm is used.

In general, an angle of 55� is chosen. Creating a tibial

Fig. 1. Tibial tunnel placement 7 mm anterior to the PCL on

the downslope of medial tibial spine.

T.J. Gill, J.R. Steadman / Orthop Clin N Am 33 (2002) 727–735 729

tunnel at a constant angle without regard to the

patellar tendon length can lead to a higher incidence

of graft– tunnel mismatch when using the endoscopic

method [19]. This is a nonissue when using the two-

incision technique. A point is chosen for the entrance

to the tibial tunnel at a position at least 1 cm medial to

the tibial tubercle.

After the guide pin is passed, placement is con-

firmed by lifting the heel to passively extend the knee

while arthroscopically observing for pin impinge-

ment on the intercondylar roof. Yaru et al reported

that the anterior tibial displacement caused by the

active pull of the quadriceps tendon results in graft

impingement an average of 9� earlier than that

obtained from passive extension of the knee. They

recommended a more extensive notchplasty to ac-

count for this difference [20]. We recommend a notch

width of at least 18 mm to help avoid lateral wall

impingement. Most arthroscopic pituitary rongeurs

are 17 mm in width when fully opened and can be

used as a guide for notch size. A stenotic notch is

widened using a curved osteotome and motorized

burr. Because the posterior notch can also contribute

to impingement, this area should be made into an

oval to ovoid lateral impingement.

Femoral tunnel placement

The femoral tunnel is established from the outside

in using the two-incision technique. A longitudinal

incision is made along the lateral aspect of the distal

femur. The incision is begun at a level 2 cm proximal

to the superior pole of the patella and extended

proximally for a distance of 3 to 4 cm (Fig. 2). The

iliotibial band is split longitudinally, exposing the

vastus lateralis. The vastus lateralis is dissected off of

the intermuscular septum and retracted anteriorly to

expose the lateral aspect of the distal femoral meta-

physis (Fig. 3). Cauterize the perforating veins

through the intermuscular septum to avoid a post-

operative hematoma. The septum is divided distally.

After the femur has been exposed, a 70� arthroscopeis inserted through the anterior inferior lateral portal.

The torn ACL remnant is debrided, exposing the

lateral wall of the intercondylar notch. The notch-

plasty is examined, and an oval posterior wall is

confirmed. A long, curved vascular clamp is inserted

through the inferomedial portal. It is passed around

the posterior aspect of the lateral femoral tunnel,

through the over-the-top position. The clamp is used

to perforate a hole in the posterior capsule to allow

passage of the rear-entry femoral guide. As long as

the clamp is passed laterally, adhering closely to the

posterior aspect of the femur, there is no danger to the

neurovascular structures. Once the septum has been

perforated by the clamp, a curved hook passer is

inserted through the inferomedial portal, along the

over-the-top position (Fig. 4), and through the inter-

muscular septum into the lateral operative field. At

this point, the rear-entry guide is hooked onto the

eyelet at the distal tip of the curved passer. The passer

is then withdrawn, pulling the rear-entry guide into

the joint without danger to the neurovascular struc-

tures (Fig. 5A, B).

The femoral tunnel can then be established. The

tip of the rear-entry drill guide is positioned at the

back wall of the notch, 2 mm anterior to the back wall

Fig. 2. Location of skin incision.

Fig. 3. Elevation of vastus lateralis.

Fig. 4. Passing of rear-entry guide retriever through over the

top position.

T.J. Gill, J.R. Steadman / Orthop Clin N Am 33 (2002) 727–735730

(Fig. 5C). The two-incision technique permits maxi-

mal posterior placement of the femoral tunnel

because there is no concern over blow out of the

posterior wall. The lateral incision site is planned so

that it is 1cm medial to the lateral epicondyle. This

allows the guide pin to enter at a 45� angle to the

femur, allowing the graft to enter at a near anatomic

angle. Endoscopic guides tend to place the femoral

tunnel significantly more anteriorly [21]. The two-

incision technique does not rely on the posterior

intercondylar notch for fixation of the graft. Instead,

the graft is fixed within the cancellous bone of the

lateral femoral condyle. A guide pin is drilled from

the lateral aspect of the femur into the tip of the drill

guide in the joint. A cannulated drill is used to create

the femoral tunnel from the outside in (Fig. 6).

Placement of the tunnels can then be checked

using an isometer. The knee is put through a range of

motion from 0� to 90�. An isometer reading that

changes less than 2 mm is considered acceptable

tunnel placement. If there is greater than 2 mm of

isometer motion, the back wall of the tibial tunnel or

the anterior wall of the femoral tunnel can be shaped

to reduce the motion of the graft by moving the wall

anteriorly with a curette.

Graft passage

Passage of the graft can be accomplished using

several different methods. We find it helpful to use a

commercially available ‘‘graft-passer.’’ A suture or

wire is inserted through the tibial tunnel into the knee

joint. An arthroscopic grasper is used to retrieve the

suture through the femoral tunnel. The plastic graft-

passer is tied to the suture and pulled through the

tunnels. The graft is then placed inside the plastic

sleeve and reduced in the tunnels, and the plastic is

removed. The graft can be pulled either proximally or

distally to maximize graft– tunnel contact (Fig. 7). In

this manner, the possibility of any graft – tunnel

mismatch is eliminated.

Fig. 6. Drilling of femoral tunnel from lateral incision.

Fig. 5. (A) Retrieving rear-entry guide into joint. (B) Rear-

entry guide. (C) Placement for femoral tunnel.

T.J. Gill, J.R. Steadman / Orthop Clin N Am 33 (2002) 727–735 731

We do not twist the graft before fixation. This is

supported by Diduch et al [22], whose study indi-

cated that pre-twisting the patellar tendon autograft

in ACL reconstruction had no significant short-term

effect on knee laxity as determined by instrumented

testing or clinical examination.

Graft fixation

Interference screw fixation is ideal with the two-

incision technique. Interference screws are placed

along guide wires inserted parallel to the bone

blocks. Guide wires decrease the possibility of

screw divergence, which has been shown to weaken

the initial fixation strength of ACL grafts. The

femoral screw is generally placed first (Fig. 8),

leaving the proximal head of the screw at the level

of the lateral femoral cortex. Although there is a

report suggesting stronger fixation with the endo-

scopic versus two-incision technique [23], this dif-

ference does not seem to be clinically relevant. In

the senior author’s series, there have been no fail-

Fig. 8. Placement of femoral interference screw.

Fig. 7. Passage of patellar tendon graft in antegrade fashion.

T.J. Gill, J.R. Steadman / Orthop Clin N Am 33 (2002) 727–735732

ures of fixation using the two-incision technique in

over 2000 cases.

After femoral screw placement is performed, the

knee is cycled with tension applied to the graft. The

tibial inference screw is then placed with the knee in

full extension, and tension is applied to the sutures on

the tibial bone block.

The sutures used to pass the graft are left prom-

inent after screw fixation to allow the screws to be

located in the event of a revision reconstruction, even

if there is bony overgrowth.

Outcomes: endoscopic versus two-incision

Advocates of endoscopic reconstruction tech-

niques frequently cite the avoidance of a lateral

incision and decreased operative time as the major

advantages of the technique when compared with

the two-incision procedure. The suggestion is that

avoiding the lateral incision decreases morbidity,

allows earlier and more aggressive rehabilitation,

and thus improves outcomes. In over 2000 cases

done by the senior author, there have been no

complaints localized to the lateral incision site.

However, to the best of our knowledge, there have

been no studies to date that have demonstrated

improved outcomes using the endoscopic technique.

In contrast, multiple studies have reported no sig-

nificant difference in outcomes between endoscopic

and two-incision techniques [24–37]. Besides the

functional outcomes, there does not seem to be a

difference in proprioception [28] or the ability to

begin early rehabilitation between the two groups

[10,30]. The endoscopic technique does offer advan-

tages with regard to cosmesis [32] and decreased

operative time [27,32]. Hospital stay and cost

may be slightly higher with the two-incision tech-

nique [38].

Complications

The two-incision ACL reconstruction technique

has been used by one of us (JRS) for over 3000 pa-

tients. We have never had an incident in which there

was damage to the popliteal artery, popliteal vein,

or tibial nerve. In contrast to unsubstantiated con-

cerns over the safety of the two-incision technique,

several studies have reported a higher rate of com-

plications when using the endoscopic method [15,25,

33,39–41]. Screw divergence and violation of the

back wall of the femoral tunnel were most commonly

cited. Heterotopic ossification has been reported for

two-incision reconstructions [42].

Conclusion

It is not possible to create a normal cruciate

ligament with ACL reconstruction surgery. Instead,

the surgeon should strive to recreate a functionally

stable knee. Although there are many important

considerations, accurate graft placement and secure

fixation is paramount in achieving a successful recon-

struction, regardless of the technique used. The two-

incision technique eliminates many of the pitfalls of

endoscopic reconstructions, including graft– tunnel

mismatch, violation of the posterior femoral tunnel,

screw-divergence, and anterior placement of the fem-

oral tunnel. Perhaps one of the greatest utilities of the

two-incision technique is its use for revision of a

failed endoscopic reconstruction because the femoral

tunnel placement can be optimized without concern

about overlapping with the previous femoral tunnel or

blowing out the back wall. The two-incision tech-

nique, when performed properly, allows highly pre-

dictable, consistent results with few complications.

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