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The Knee 13 (2006

Tibial plateau fracture after anterior cruciate ligament reconstruction:

Role of the interference screw resorption in the stress riser effect

Mathieu Thaunat a,*, Geoffroy Nourissat b, Pascal Gaudin a, Philippe Beaufils a

a Orthopaedic Surgery Department, Andre Mignot Hospital, 177, rue de Versailles, 78157 Le Chesnay, Franceb Orthopaedic Surgery Department, Saint Antoine Hospital, Paris, France

Received 29 December 2005; received in revised form 31 January 2006; accepted 6 February 2006

Abstract

We report a case of tibial plateau fracture after previous anterior cruciate ligament (ACL) reconstruction using patellar tendon autograft

and bioabsorbable screws 4years previously. The fracture occurred through the tibial tunnel. The interference screw had undergone complete

resorption and the tunnel widening had increased. The resorption of the interference screw did not simultaneously promote and foster the

growth of surrounding bone tissue. Therefore, the area of reactive tissue left by the screw resorption in an enlarged bone tunnel may lead to

vulnerability of the tibial plateau. Stress risers would occur following ACL reconstruction if either resorption is not complete or bony

integration is not complete.

D 2006 Elsevier B.V. All rights reserved.

Keywords: Tibial plateau fracture; Bioabsorbable screw; Anterior cruciate ligament reconstruction; Stress riser

1. Introduction

Currently, the majority of interference screws are made

of partially biodegradable material. The use of a mixture of

bioactive materials and polymers promote small amounts of

tissue growth and cause unwanted debris responsible for

adverse reaction to the material [1]. The aetiology of the

tunnel enlargement remains uncertain but is likely to be

multifactorial with both biological and mechanical factors

playing a part. As the screw degrades, the diameter of the

tunnel increases, and the tissue that replaces the screw in the

first place is either fatty or fibrous but not bone [2].

Although it has been shown that bone tunnel enlargement

does not appear to adversely affect graft laxity or failure

rates [3], it may favour the occurrence of a post traumatic

fracture, by worsening the bony defect. Stress risers would

preferably occur during the first years following the

operation, if either screw resorption is not complete or

bony integration is not complete.

0968-0160/$ - see front matter D 2006 Elsevier B.V. All rights reserved.

doi:10.1016/j.knee.2006.02.001

* Corresponding author. Tel.: +33 6 61 48 01 12; fax: +33 1 39 63 87 38.

E-mail address: mathieuthaunat@yahoo.fr (M. Thaunat).

2. Report

A 24-year-old man fell from 4ft high to the floor and

described a valgus-compression trauma of his knee. This

patient had undergone ACL reconstruction using patellar

graft 4years previously with a good result. The surgery was

performed in the same centre using a standardised, single

incision, bone–patellar tendon–bone (BPTB) ‘‘arthroscop-

ic’’ technique. Placement of the tibial tunnel was performed

in accordance with recent recommendations. Fixation of the

graft in the 11-mm tibial tunnel had been performed with a

9-mm-diameter polyglycolide-co-trimethylencarbonate

(PGA-co-TMC) screw (Endofix, Acufex Inc, Mansfield,

MA, USA). The patient had recovered well and had returned

to his regular athletic activities.

After he fell down, the patient complained of knee pain

with inability to bear weight. Clinically, a haemarthrosis

combined with tenderness on pressure at the medial tibial

condyle was found. The CT scan demonstrated a fracture

which occurred at the tibial fixation site. There was no

displacement of the bone–patellar tendon–bone (BPTB)

graft in the tibial tunnel. The bioabsorbable screw was not

) 241 – 243

Fig. 1. CT scan imaging of the surgical graft after the screw has completely

degraded 4years after the operation. New tissue that formed around the

bone plug is fibrous and fatty. The fracture occurred at the tibial fixation site

(arrowhead). Tunnel widening increases in diameter with the resorption of

the interference screw (arrow) which do not simultaneously promote and

foster the growth of surrounding bone tissue while the screw degrades.

M. Thaunat et al. / The Knee 13 (2006) 241–243242

clearly identifiable, and appeared to have undergone

resorption whereas the diameter of the tunnel was found

to be increased (Fig 1). The absence of displacement led us

to treat the fracture non operatively. Complete union was

obtained following 6weeks of a long-leg plaster cast,

preserving knee stability without need for revision anterior

cruciate ligament reconstruction. Afterwards, the knee was

actively trained in a cast brace and protected weight-bearing

maintained for 2weeks more. At 3months follow-up, the

patient walked without limitation, and got back full range

of motion of his knee and complete stability. The Lachman

and pivot shift test were negative with a firm endpoint.

There was no subjective feeling of knee instability. At

7months follow-up, the patient had resumed his normal

recreational activities.

3. Discussion

The aetiology of the tunnel enlargement remains uncertain

but is likely to be multifactorial. The bioabsorbable screw

resorption plays amajor part in this phenomenon [4,5]. As the

screws break down, they release composite molecules that

can cause inflammatory foreign-body reactions responsible

for osteolysis around these screws [6]. Moreover, previous

authors have reported that the presence of cyst-like for-

mations at the bioabsorbable screw site has to be regarded as a

normal feature of the screw degradation process [7],

especially for the highly crystalline polyglycolide implants.

However, such screws even of the same composition, have

high variability in degradation rates [2] and biological tissue

regeneration remains a slow and asynchronous process in

relation to the degradation. Screws that take longer to break

down inside the body elicit fewer foreign body reactions, but

at the same time require longer for complete bone regener-

ation. Thus, the resorbability of the fixation device deter-

mines the amount of tunnel widening [4,5]. Tunnel widening

is minimal with a metal interference screw and increases in

diameter with the bioresorbable interference screw. The

maximum tunnel width occurs at the time the screw is no

longer visible on MRI [4]. Different studies have shown that

the screws were completely reabsorbed within 1year of

implant, leaving new fibrous and fatty tissue in the graft site

[2,5,8], whereas the first bone regeneration occurred only

2years later [2].

Few cases of tibial tunnel fractures have been published

after ACL reconstruction [9–13]. In all previous cases, the

tibial plateau fracture occurred less than 2years after the

operation, through the transosseous tibial tunnel. The region

of the starting point of the tibial tunnel is known to support

additional stress concentration because of the geometry of the

tibia at the metaphyseal–diaphyseal junction. It has been

shown that the presence of the tunnel was the main factor in

predisposing patients for this type of fracture [9,11]. Indeed,

the anatomical location of the cortical defect is the fracture

initiation site and depending on the geometry and the size of

the cortical defect, strength reductions of up to 90% have

been reported [14,15]. Although no biomechanical studies

have specifically addressed the mechanical effect of bone

tunnels, it seems that the bony defect left by the screw

resorption appears to have a significant effect on the risk for

fracture, especially when the tunnel width is maximum. Thus,

stress risers would only occur following ACL reconstruction

if either resorption is not complete or bony integration is not

complete.

References

[1] Stahelin AC, Weiler A, Rufenacht H, Hoffmann R, Geissmann A,

Feinstein R. Clinical degradation and biocompatibility of different

bioabsorbable interference screws: a report of six cases. Arthroscopy

1997;13(2):238–44.

[2] Bach FD, Carlier RY, Elis JB, Mompoint DM, Feydy A, Judet O, et al.

Anterior cruciate ligament reconstruction with bioabsorbable poly-

glycolic acid interference screws: MR imaging follow-up. Radiology

2002;225(2):541–50.

[3] Wilson TC, Kantaras A, Atay A, Johnson DL. Tunnel enlargement

after anterior cruciate ligament surgery. Am J Sports Med 2004;32:

543–9.

[4] Clatworthy MG, Annear P, Bulow JU, Bartlett RJ. Tunnel widening in

anterior cruciate ligament reconstruction: a prospective evaluation of

hamstring and patella tendon grafts. Knee Surg Sports Traumatol

Arthrosc 1999;7:138–45.

[5] Lajtai G, Noszian I, Humer K, Unger F, Aitzetmuller G, Orthner E.

Serial magnetic resonance imaging evaluation of operative site after

fixation of patellar tendon graft with bioabsorbable interference screws

in anterior cruciate ligament reconstruction. Arthroscopy 1999;15:

709–18.

[6] Weiler A, Hoffmann RF, Stahelin AC, Helling HJ, Sudkamp NP.

Biodegradable implants in sports medicine: the biological base.

Arthroscopy 2000;16(3):305–21.

M. Thaunat et al. / The Knee 13 (2006) 241–243 243

[7] Macarani L, Murrone M, Marini S, Mocci A, Ettore GC. MRI in

ACL reconstructive surgery with PDLLA bioabsorbable interfe-

rence screws: evaluation of degradation and osteointegration pro-

cesses of bioabsorbable screws. Radiol Med (Torino) 2004;107:

47–57.

[8] Fink C, Benedetto KP, Hackl W, Hoser C, Freund MC, Rieger M.

Bioabsorbable polyglyconate interference screw fixation in anterior

cruciate ligament reconstruction: a prospective computed tomography-

controlled study. Arthroscopy 2000;16(5):491–8.

[9] Mithofer K, Gill TJ, Vrahas MS. Tibial plateau fracture following

anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol

Arthrosc 2004;12(4):325–8.

[10] Delcogliano A, Chiossi S, Caporaso A, Franzese S, Menghi A. Tibial

plateau fracture after arthroscopic anterior cruciate ligament recon-

struction. Arthroscopy 2001;17(4):E16.

[11] el-Hage ZM, Mohammed A, Griffiths D, Richardson JB. Tibial

plateau fracture following allograft anterior cruciate ligament (ACL)

reconstruction. Injury 1998;29(1):73–4.

[12] Morgan E, Steensen RN. Traumatic proximal tibial fracture following

anterior cruciate ligament reconstruction. Am J Knee Surg 1998;11(3):

193–4.

[13] Thietje R, Faschingbauer M, Nurnberg HJ. Spontaneous fracture of

the tibia after replacement of the anterior cruciate ligament with

absorbable interference screws. A case report and review of the

Literature. Unfallchirurg 2000;103(7):594–6.

[14] Clark C.R, Morgan C, Sonstegard DA, Matthews LS. The effect of

biopsy-hole shape and size on bone strength. J Bone Joint Surg Am

1977;59(2):213–7.

[15] Johnson B.A, Fallat LM. The effect of screw holes on bone strength. J

Foot Ankle Surg 1997;36(6):446–51.