ARTHROSCOPY AND SPORTS MEDICINE

Hybrid hamstring graft tibial fixation in anterior cruciateligament reconstruction

Miroslav Z. Milankov • Natasa Miljkovic •

Natasa Janjic

Received: 16 January 2010 / Published online: 4 June 2010

� Springer-Verlag 2010

Abstract Tibial fixation of the anterior cruciate ligament

hamstring tendon graft is commonly considered more

problematic than femoral fixation. When interference screws

are used for tibial hamstring tendon graft fixation, graft

sometimes looses its tension, so a hybrid fixation (more than

one method of fixation) must be applied. Biomechanical

studies show that an implementation of interference screws

combined with different indirect distal hamstring tendon

fixation techniques can withstand much higher tearing forces

when compared with one type of fixation. We made a tech-

nique of hybrid tibial fixation of the hamstring graft using

round interference screws and an additional bi-cortical

4.5-mm diameter screw with a modified head that allows

control over the initial tension of the graft.

Keywords Anterior cruciate ligament reconstruction �Hamstring tendon graft � Tibial graft fixation

Introduction

The use of hamstring grafts in anterior cruciate ligament

(ACL) reconstruction has becoming more popular in the

last 10 years. Rigid fixation of the hamstring tendon graft

which is strongly associated with the long-term clinical

success of the ACL reconstruction may be the reason for

this. The tricky part of the hamstring graft fixation is at the

tibial side and many different direct and indirect method of

fixation have been developed to make it more easy and

reproducible.

A suture interwoven into the graft and tied around the

screws, so-called whipstitch, was one of the first methods

of indirect graft fixation. In the 1980s, this technique was

overshadowed by the use of bone-patellar tendon-bone

(BPTB) graft and interference screws. Most of the ham-

string graft tibial fixation techniques also utilize interfer-

ence screw, although there are some indirect ones such as:

sutures tied over a post or a bony bridge, a suture button,

EndoPearl device, washers (AO, WasherLock, spiced

washer) Fastlok device, double-spike plate, barbed liga-

ment staple, and several types of tibial screws.

When interference screws are used for tibial graft fixa-

tion, graft sometimes looses its tension, so a hybrid fixation

(more than one method of fixation) must be applied. Bio-

mechanical studies show that an implementation of inter-

ference screws combined with different indirect distal

hamstring tendon fixation techniques can withstand much

higher tearing forces as compared to one type of fixation

[2, 5, 8, 10]. This paper is describing a technique of hybrid

tibial fixation of the hamstring graft using round interfer-

ence screws and an additional bi-cortical screw with a

modified head which allows control over the initial tension

of the graft.

Technical report

A standard anterolateral portal was used as a viewing portal

and an anteromedial one was used as a working portal. The

M. Z. Milankov (&) � N. Janjic

Department of Orthopaedic Surgery and Traumatology,

Clinical Center Vojvodina, Medical Faculty,

University of Novi Sad, Hajduk Veljkova 1,

21 000 Novi Sad, Serbia

e-mail: milankom@eunet.rs

N. Miljkovic

Plastic Surgery Research Laboratory,

University of Pittsburgh, 200 Lothrop Street,

BST 1608E, Pittsburgh, PA 15261, USA

e-mail: miljkovicnd@upmc.edu

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Arch Orthop Trauma Surg (2010) 130:1033–1036

DOI 10.1007/s00402-010-1124-1

hamstring tendon with its periosteal attachments was har-

vested through a short oblique skin incision. The ACL

stump was debrided and a limited notchplasty was per-

formed. The femoral tunnel was created first to avoid

excess fluid loss. The knee was placed in full flexion

between 120� and 130�. The femoral guide (Karl Storz,

Tutlingen, Germany) with an appropriate offset was

introduced into the joint through the anteromedial portal

and drill-wire was placed into the center of the anatomic

insertion of the ACL and was over-drilled with a reamer. A

suture was retrieved and a guide pin was drilled into the

joint followed by a cannulated reamer with an equal

diameter to the graft to create the tibial tunnel. A grasper

was then placed through the tibial tunnel to retrieve the

suture. After a precise graft preparation on a side table by

an assistant, the graft was passed through the tibia into the

femoral socket, properly positioned in the tunnel and fixed

with RCI—round cannulated interference screws (Grujic &

Upyjb�h, Novi Sad, Serbia). While performing full range of

knee motion, firm traction was applied to the graft to

pretense the graft and observe if the full extension causes

any impingement. The graft was tensioned using 60 N

force (Karl Storz, Tutlingen, Germany) and fixed with

round cannulated interference screws. In addition, bi-cor-

tical 4.5-mm diameter, custom-made screw, with a modi-

fied head was placed immediately below the tibial tunnel

opening (Fig. 1). The screw was tightened completely at

first and then untightened for half of a circle. Graft’s

sutures were placed through the slots on the head of the

screw (Fig. 2), three knots were tied (Fig. 3) and the screw

was retightened completely for 1/4 of a circle (Fig. 4). The

knee stability was checked using Lachman and anterior

drawer tests and operative wound was closed in a usual

fashion. Postoperative X-ray control made 2 days later

after removing drains (Fig. 5).

Fig. 1 Bi-cortical 4.5-mm diameter screw with a modified head

placed immediately below the tibial tunnel opening

Fig. 2 Graft’s sutures placed through the slots on the head of the

screw

Fig. 3 Three knots tied

Fig. 4 Screw retightened completely for 1/4 of a circle

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This technique was used in about 200 cases, with no

intra- or postoperative complications except in one case,

where the sharp edge of the slot cut off the suture. From

that time onwards, our slots have rounded edges.

Discussion

Although the fixation technique for patellar tendon grafts is

a pretty much straightforward procedure, no consensus has

been found on the fixation of hamstring tendon grafts.

Tibial fixation of the ACL graft is commonly considered

more problematic than femoral fixation because interfer-

ence screw with sharp edges may damage the integrity of a

soft tissue graft, forces acting on the ACL substitute are

parallel to the tibial drill hole, the bone quality of the tibial

metaphysis is inferior to that of the femur and the four-

tailed end of the hamstring tendon graft that is fixed to the

tibia is more difficult to secure [1, 11]. When interference

screws are used in tibia, they are inserted from the outside-in,

producing forces that are counter to the direction of the

tension on the graft, as opposed to the femoral side, where

the screw is placed from the inside-out, thus wedging the

graft during screw insertion.

A novel hybrid fixation method which compiles two

fixation techniques at the tibial site was developed. This

method of tibial hamstring tendon graft fixation provides

good initial fixation strength together with the biome-

chanical and biologic advantages of joint line interference

fit fixation. Ishibashi et al. [3] showed that an increase in

the length of the graft construct will likely reduced the

stiffness, and the site of graft fixation at the tibia which

may affect the long-term success of ACL reconstruction.

While Weimann et al. [9.] showed the benefit hybrid fix-

ation on the femoral side, Scheffler et al. [7] demonstrated

that direct soft tissue fixation with the interference screw

still allows considerable graft slippage which can be pre-

vented using a bone block or application of a backup or

hybrid fixation, especially on the tibial fixation site. Bio-

mechanical testing showed that a interference screw (RCI)

and additional fixation to the distal hamstring tendon

resulted in higher load at failure and stiffness as compared

to either interference screw (RCI), cortical screw, double-

spike plate, spike washer or WasherLoc fixation alone

[2, 5, 8, 10].

All previously described indirect tibial hamstring tendon

graft fixation techniques did not allow full and precise

control over the initial graft tension, except the use of

double-spike plate, which allowed partial, but unprecise

control of the graft tension. The pretension technique

influences the initial graft strength in response to repetitive

loading. Intra-articular or in vivo pretension of the graft

during ACL reconstruction before final fixation at tibial

side provides the least displacement loads when compared

with manual and extra-articular pretension [4]. Biome-

chanical and clinical study showed that the increased initial

graft tension in the knee leads to the decreased antero-

posterior laxity, but the underlying mechanism is not

clearly understood. On the other hand, excessive initial

tension should be avoided, because it may cause abnormal

join stiffness, loss of extension, graft failure, and degen-

eration of the articular cartilage [6].

Secure initial fixation of the graft is essential for a

successful early rehabilitation before the graft fully incor-

porates into the host’s bone. We believe that our hybrid

technique of tibial fixation of the hamstring graft allows

simple, precise, strong early fixation and by doing that

promotes biological incorporation. That said, we are aware

that further biomechanical studies to compare our hybrid

tibial fixation technique of the hamstring graft to other

contemporary methods are needed to objectively evaluate

this technique.

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