Injury, Int. J. Care Injured (2005) 36, 862—865

www.elsevier.com/locate/injury

CASE REPORT

Transverse Hoffa’s or deep osteochondral fracture?An unusual fracture of the lateral femoralcondyle in a child

D.J.M. Biau, P.J. Schranz *

Princess Elizabeth Orthopaedic Centre, Royal Devon and Exeter Hospital,Barrack Road, Exeter, EX2 5DW Devon, UK

Accepted 25 November 2004

Introduction

Fractures of the distal femur are more frequent inyoung people, mainly men, sustaining high energytrauma, and in elderly sustaining low energy traumato osteoporotic bones.2,12 These fractures are veryuncommon in children.9 Fractures limited to thearticular surface of the lateral femoral condyle areeither coronal fractures (Hoffa’s fracture, AO B3)1,3,8,10,11,14,18 or small osteochondral fractures.7,15

Although non-union of a lateral femoral condylefracture has been previously reported in children inthe literature,13,17 it has, however, to the best of ourknowledge, never been reported as an acute injury.We report the case of a 13-year-old boy successfullytreated with open reduction and minimal internalfixation of an unusual lateral femoral condyle frac-ture.

Case report

A 13-year-old boy sustained a twisting injury to hisright knee whilst playing cricket (a right handed

* Corresponding author. Tel.: +44 1392 403576;fax: +44 1392 403505.

E-mail address: Peter.Schranz@rdehc-tr.swest.nhs.uk(P.J. Schranz).

0020–1383/$ — see front matter # 2004 Elsevier Ltd. All rights resedoi:10.1016/j.injury.2004.11.028

batsman). As he twisted onto his right knee (weightbearing) to hit the ball, he felt his knee opening upin valgus, and a sharp pain around the joint.

Unable to bear weight, he presented to theemergency department within 2 h. The knee washeld in 408 of flexion, and swollen. On examina-tion, the joint was globally tender, and range ofmovement restricted by the pain. AP and lateral X-rays of the knee revealed a posterior fracture ofthe lateral femoral condyle with the fragmentsubluxed in the intercondylar notch (Fig. 1aand b).

Examination under anaesthetic revealed a stableknee, locked in flexion.

Arthroscopy revealed a tense haemarthrosis,with the displaced lateral femoral condyle fragmentjammed in the intercondylar notch, blocking fullextension. The ACL, deep lateral and medial col-lateral ligament and menisci were intact. As thefragment was not reducible arthroscopically, anopen reduction was performed.

Arthrotomy revealed a large osteochondral frac-ture of the lateral femoral condyle extendingthroughout the entire width of the condyle. Thefragment was reduced and fixed with three Herbertscrews. Stable anatomical reduction was obtained,the wound was closed in layers and the knee wassplinted in extension for 2 weeks.

rved.

Transverse Hoffa’s or deep osteochondral fracture? 863

Figure 1 AP and lateral X-ray showing the displacedlateral femoral condyle fracture.

Figure 2 AP and lateral X-ray showing the appearanceone year after surgery.

Partialweightbearingwasallowedafter6weeksandfullweightat12weeks.Kneemotionwasstartedafter2weeks and the brace was discarded after 6 weeks.

Full range of motion was obtained at 6 weeks, andthe X-rays showed no displacement of the fracture.

Clinical and radiological followup at 1 yearrevealed no pain, a full range of motion, with nosigns of avascular necrosis (Fig. 2a and b).

Discussion

Fracture of a femoral condyle in the coronal plane isan unusual injury, first described by Hoffa in 1904.6 A

high energy trauma is always the cause of the injury,and capsular, ligaments and bony injuries are fre-quently associated.3,8,10 Valgus or varus stressdetermines the condyle injured, the lateral condylebeing the most commonly fractured. The posteriorcondyle is sheared off from the epiphysis followingaxial compression on a flexed knee. Although avul-sion by the capsule or cruciate ligaments have beenadvocated as a possible mechanism, most of thesefractures are free from any soft tissue attachment atsurgery. The typical Hoffa’s fracture is frontal, in theplane of the posterior cortex of the femur. Leten-neur’s classification of fractures of the posteriorcondyle includes more posterior (type II), or more

864 D.J.M. Biau, P.J. Schranz

oblique fracture planes (type III).10 In this case, thefracture lies in a distal and almost transverse plane,and therefore, can neither be denominated as aHoffa’s fracture nor be included in Letenneur’sclassification.

Osteochondral fracture of the femoral condylesusually occurs in young adults following a trivialinjury. They have been classified as endogenousfractures resulting from combined rotary and com-pression forces, and exogenous fractures resultingfrom a direct blow.7,15 Endogenous fractures of thelateral margin of the lateral femoral condyle aredue to the shearing force transmitted by patella.Small osteochondral fractures of the weight bearingarea of the condyle following a twisting injury havebeen advocated, but failed to be reproduced experi-mentally.7 More recent imaging findings suggest thatas the knee flexes and rotates, shearing forcesconcentrate on the posterior half of the femoralcondyle. The more the knee is flexed, the moreposterior the injury.5,16 Despite the similar mechan-ism of injury in this case, osteochondral fragmentsare usually much smaller, although in the adoles-cent, where there is no tide mark between calcifiedand uncalcified cartilage, the fracture may extenddeeper into the subchondral bone.7

OCD of the femoral condyle is a widely recognisedlesion developing in the second decade of life, andcan present in the late stage as an intra-articularloose body. However, in this case, the absence ofpre-injury symptoms, involvement of a weight bear-ing part of the lateral femoral condyle, and a sig-nificant injury to the knee are in favour of afracture. Arthroscopic findings confirm the diagno-sis. A haemarthrosis is unusual in OCD and usuallyassociated with a fresh fracture.4 Moreover, on thefemoral condyle, the ‘flat surface of fresh cancel-lous bone’ of the osteochondral fracture is easilydistinguished from the ‘concave defect of thefemoral condyle with steeply sloping edges’ of thelate OCD. Just as the convex surface covered withcartilage is opposed to the corticated fragment withno cancellous bone exposed of the loose body in thelate OCD.4

The clinical picture of posterior femoral condylefractures is non-specific, and AP and lateral X-raysare required to make the diagnosis. Although it hasbeen reported that undisplaced frontal fracturescould be missed,11 the oblique fracture line anddisplaced fragment easily confirmed the diagnosisin this case. CT-scan is helpful to precisely deter-mine the fracture line and the displacement, and MRimaging for evaluating the extent of soft tissueinjuries, but need not be performed routinely.1,3

Examination under anaesthetic and arthroscopy arenecessary to assess the extent of soft tissue injuries.

As the patient presented with an acutely lockedknee, with the displaced fracture line being easilyseen on X-rays, CT-scan was not required in thiscase. Soft tissue injuries were assessed with carefulexamination under anaesthetic and arthroscopy.

Anatomic reduction and fixation of these frac-tures is mandatory to allow early mobilisation and toprovide good long-term functional results. Undis-placed fractures of the posterior femoral condyleare unstable and should be treated operatively.11

Although antero-posterior lag screws are relevant tofix large fragments, smaller fragments can be accu-rately fixed with Herbert screws, without unduedamage to the articular surface.

Despite the posterior capsule being attached tosome fragments (types I and III), which thereforeremain perfused even after many years,13,17 osteo-necrosis of free fragments is an issue and patientsshould be followed up consequently.10,19 Radiologi-cal signs of necrosis usually appear within the firstfew months.10 We would advise that X-rays andclinical evaluation should be sought 1 year afterthe operation. In this case, no signs of avascularnecrosis were found at the 1 year review and thepatient made a full recovery.

Conclusion

This unusual case of lateral femoral condyle facturein a child reminds us that despite clear cut classi-fication systems, drawn from observation and pro-viding useful tools for teaching and reporting,sometimes nature generates unusual fracture pat-terns that are not easily classified.

References

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