KNEE

Displaced osteochondral fracture of the lateral femoral condyleassociated with an acute anterior cruciate ligament avulsionfracture: a corollary of ‘‘the lateral femoral notch sign’’

Gaurav Sharma • V. Anand Naik • Amite Pankaj

Received: 25 July 2011 / Accepted: 14 November 2011 / Published online: 24 November 2011

� Springer-Verlag 2011

Abstract Anterior cruciate ligament (ACL) rupture is

usually accompanied by bone contusions resulting from

impact of tibia on femur. The injury sometimes becomes

manifest as a depression on the lateral femoral condyle

giving rise to ‘‘lateral femoral notch’’ sign. The authors

describe a rare case of impaction of the tibia and femur

resulting in an osteochondral fracture rather than the usual

bone contusion, which frequently occurs with ACL rupture.

Open reduction and internal fixation of both the ACL

avulsion fracture and the osteochondral fracture from the

lateral femoral condyle were done, and the patient had a

good outcome at 1-year follow-up.

Level of evidence V.

Keywords Osteochondral fracture � Lateral femoral

condyle � Anterior cruciate ligament

Introduction

The ‘‘lateral femoral notch sign’’ is a radiographic sign that

describes a depression in the lateral femoral condyle

occurring in association with anterior cruciate ligament

(ACL) tear [9, 13]. Disruption of the ACL results in

abnormal translation of tibia on femur causing the posterior

aspect of the lateral tibial plateau and the middle to anterior

portion of the lateral femoral condyle to forcefully impact

against one another [4, 7, 9]. This causes a pattern of

injuries known as ‘‘kissing contusions,’’ which are usually

radiographically occult injuries to the cartilage and bone

demonstrated as bone contusions during MR imaging

[4, 9]. The lateral femoral notch sign and posterior fracture

of the lateral tibial plateau [14] are infrequently seen

radiographic signs corresponding to the kissing contusions

seen at MR imaging [9].

Whereas in most cases the lateral femoral notch has only

radiographic significance with no need for surgical treat-

ment, extreme formations have clinical relevance due to

deformation of the articular surface of the femoral condyle

as possible precursor of osteoarthritis [13]. There have been

attempts to treat osteochondral depression fracture of the

lateral femoral condyle in recent past in order to decrease

the likelihood of long-term osteoarthritis [3, 10, 13].

Although a depression fracture (lateral femoral notch) of

the distal lateral femoral condyle in association with a torn

ACL has been described by several authors [1–3, 9, 10, 13, 17],

a displaced osteochondral fracture of the lateral femoral

condyle, to the best of our knowledge, has not previously

been described.

The authors report on such a case as a corollary to the

lateral femoral notch sign, with an increased force of injury

leading to a shear fracture of the distal femoral condyle at

its impact with the posterior aspect of the lateral tibial

plateau.

Case report

A 30-year-old man sustained a twisting injury to his left

knee in a motorcycle accident (valgus stress on flexed and

externally rotated knee). He felt a pop in his knee at foot

impact with the ground, which was followed by pain and

swelling of the knee. The patient presented to the emer-

gency department 2 h after the injury. Physical examina-

tion revealed a positive Lachman test with no evidence of

G. Sharma (&) � V. A. Naik � A. Pankaj

Department of Orthopedics, University College of Medical

Sciences and GTB Hospital, Delhi 110095, India

e-mail: sharmagaurav850@gmail.com

123

Knee Surg Sports Traumatol Arthrosc (2012) 20:1599–1602

DOI 10.1007/s00167-011-1795-3

abnormal valgus or varus laxity. The range of motion was

limited to 100� of flexion due to pain and articular effusion.

Tenderness was present within the lateral joint line.

Arthrocentesis was performed and 90 ml of blood with fat

droplets was obtained. Radiographs of his left knee dem-

onstrated an ACL tibial avulsion fracture associated with

an osteochondral fracture of the lateral femoral condyle.

The fragment from the anterior aspect of the femoral

condyle was located superiorly and laterally within the

knee joint, adjacent to the patella (Fig. 1). A CT scan was

obtained, which further delineated the ACL avulsion

fracture as well as the osteochondral fragment.

The patient underwent open reduction and internal fix-

ation of both the ACL avulsion fracture and the osteo-

chondral fracture from the lateral femoral condyle. The

procedure was performed under spinal anesthesia under

tourniquet control. A lateral parapatellar arthrotomy was

performed and the fracture surfaces exposed.

The substance of the ACL was intact as were both the

menisci. The ACL tibial avulsion fracture was reduced and

fixed with two Herbert screws. The osteochondral fragment

from the anterior aspect of the distal femoral condyle was

localized and accurately reduced in its native location. It

was provisionally stabilized with smooth Kirschner wires

placed from the osteochondral fragment into the lateral

femoral condyle. Definitive fixation was done using three

Herbert screws that were countersunk 2–3 mm beneath the

articular surface. The knee was stable through full range

of motion. Final radiographs demonstrated satisfactory

reduction and hardware position (Fig. 2).

Postoperatively, the knee was placed in a long-leg hin-

ged knee brace, and the patient was mobilized with the help

of a pair of crutches with the brace locked in extension. He

was kept non–weight bearing for 6 weeks in an effort to

protect the osteochondral fracture fixation. Knee was

mobilized with CPM machine and progressive range of

motion exercises as tolerated. He gained 0–90� of ROM

after 2 weeks that improved to 0–120� at 4 weeks. After

3 months and radiographic evidence of union of fractures,

the patient was started on full weight bearing. After 1 year,

the patient had 0–130� of knee flexion (marginally less than

the opposite side), had no anterior knee laxity (Lachman

and anterior drawer tests were negative as was the pivot

shift test) and had returned to his pre-injury activity level.

Discussion

The most important finding of the present study was the

presence of a displaced osteochondral fracture of the lat-

eral femoral condyle in association with an ACL tibial

avulsion fracture. The most common mechanism of an

ACL tear is an indirect injury resulting from abnormal

rotation in a loaded knee leading to abnormal anterior

translation of tibia on femur that causes the posterior aspect

of the lateral tibial plateau and the middle to anterior

portion of the lateral femoral condyle to forcefully impact

against one another [4, 9] (Fig. 3). This causes a pattern of

injuries known as ‘‘kissing lesions,’’ which are usually

radiographically occult injuries to the cartilage and bone

demonstrated as bone contusions at MR imaging [4, 9].

Bone bruises are present in the lateral compartment of the

knee in up to 80% of ACL ruptures [6–8, 12, 15, 16] and

represent a ‘‘footprint’’ of the mechanism of injury [11].

More severe form of impaction results in depression of the

lateral femoral condyle that becomes evident even on

radiographs and has been described as the ‘‘lateral femoral

Fig. 1 Radiograph and CT scan images of the knee showing avulsion

of the tibial eminence (white arrow) and osteochondral fracture of the

lateral femoral condyle (black arrows)

Fig. 2 Follow-up radiographs at 1 year showing good healing of the

fractures and lack of any degenerative changes

1600 Knee Surg Sports Traumatol Arthrosc (2012) 20:1599–1602

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notch sign’’ [9]. First reports in literature attributed the

lateral femoral notch to chronic ACL insufficiency [5, 17],

which later on was reported to occur also in acute cases [2].

To our knowledge, there are three case reports concerning

fracture management of a lateral femoral notch. One

reported on open reduction, autologous cancellous bone

grafting and secondary ACL reconstruction using a bone-

patellar tendon-bone graft [3]. The second patient was

treated arthroscopically using a bioabsorbable interference

screw to fill up the intracondylar bone defect with con-

temporaneous ACL reconstruction using hamstring tendon

[10]. The third patient was treated as a one-stage procedure

with arthroscopically assisted reduction of a large lateral

femoral notch, cancellous bone allografting and primary

ACL reconstruction [13].

Although a depression fracture (lateral femoral notch) of

the distal lateral femoral condyle has been described in

association with a torn ACL by several authors, a displaced

osteochondral fracture of the lateral femoral condyle has

not previously been described. This perhaps represents the

most severe form of an injury associated with ACL dis-

ruption and bony impaction. In the present case, a shear

fracture of the anterior part of the distal lateral femoral

condyle occurred presumably during the initial rotary

subluxation or when the lateral femoral condyle recoiled to

its anatomic alignment.

Conclusion

A case of a displaced osteochondral fracture of the lateral

femoral condyle associated with an ACL tibial avulsion

fracture is reported. This injury was thought to result from

impaction between the lateral femoral condyle and the

posterior aspect of the lateral tibial plateau at the time of

ACL disruption.

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