R

A

VUr

AA

KPDATT

1

cl

au

g[

2

osap

t

1

Orthopaedics & Traumatology: Surgery & Research 101 (2015) S59–S67

Available online at

ScienceDirectwww.sciencedirect.com

eview article

cute traumatic patellar dislocation

.B. Duthon ∗

nité d’orthopédie et traumatologie du sport, service de chirurgie orthopédique et traumatologie de l’appareil moteur, hôpitaux universitaires de Genève, 4,ue Gabrielle-Perret-Gentil, 1211 Genève 14, Switzerland

a r t i c l e i n f o

rticle history:ccepted 1st December 2014

eywords:atellaislocationcuteraumaticreatment

a b s t r a c t

Inaugural traumatic patellar dislocation is most often due to trauma sustained during physical or sportsactivity. Two-thirds of acute patellar dislocations occur in young active patients (less than 20 years old).Non-contact knee sprain in flexion and valgus is the leading mechanism in patellar dislocation, accountingfor as many as 93% of all cases. The strong displacement of the patella tears the medial stabilizing struc-tures, and notably the medial patellofemoral ligament (MPFL), which is almost always injured in acutepatellar dislocation, most frequently at its femoral attachment. Lateral patellar glide can be assessed withthe knee in extension or 20◦ flexion. Displacement by more than 50% of the patellar width is consideredabnormal and may induce apprehension. Plain X-ray and CT are mandatory to diagnose bony risk factors

for patellar dislocation, such as trochlear dysplasia or increased tibial tubercle-trochlear groove distance(TT-TG), and plan correction. MRI gives information on cartilage and capsulo-ligamentous status for treat-ment planning: free bodies or osteochondral fracture have to be treated surgically. If patellar dislocationoccurs in an anatomically normal knee and osteochondral fracture is ruled out on MRI, non-operativetreatment is usually recommended.

© 2014 Elsevier Masson SAS. All rights reserved.

. Introduction

Acute traumatic patellar dislocation is the second most frequentause of traumatic hemarthrosis of the knee, after anterior cruciateigament tear, and accounts for 3% of all traumatic knee lesions [1,2].

It is usually due to trauma sustained during physical or sportsctivity. In two-thirds of cases, it concerns young active subjectsnder 20 years of age [3–5].

It may have long-term consequences: instability of patellar ori-in, pain, recurrent dislocation and patellofemoral osteoarthritis6].

. Anatomy

The patellofemoral joint is complex; stability depends onsteoarticular conformation and static and dynamic stabilizationtructures. Any change in anatomy, such as extensor apparatuslignment defect, patellofemoral dysplasia or trauma, can induce

atellar instability.

The embryonic patella develops during the 7th week of gesta-ion. Cells develop in the deep layer of the patellar tendon, forming

∗ Tel.: +41 22 372 79 06; fax: +41 22 372 77 99.E-mail address: victoria.duthon@hcuge.ch

http://dx.doi.org/10.1016/j.otsr.2014.12.001877-0568/© 2014 Elsevier Masson SAS. All rights reserved.

a nascent cartilage structure, which ossifies only at the age of4–6 years [7]. Six centers of patellar ossification develop then fuseto form a single nucleus of ossification.

Normally, the two patellar joint surfaces, medial and lateral,are symmetric and congruent with the femoral trochlea. Trochlearmorphology remains relatively constant but, with growth, the thicktrochlear cartilage thins in the middle, creating an illusion of atrochlear “hollow” [8]. The peripatellar soft tissue and particularlythe medial patellofemoral ligament (MPFL) and vastus medialisobliquus (VMO) muscle contribute significantly to joint stability[9]. The MPFL inserts to the femur between the medial epicondyleand the adductor tubercle, and to the superomedial edge of thepatella (Fig. 1).

3. Biomechanics

The MPFL provides 50–80% of the mechanisms counteractinglateral patellar glide [10,11]. Lateral patellar dislocation renders itincompetent, promoting recurrence of dislocation [12].

Neighboring structures, such as the patellomeniscal or patel-

lotibial ligaments and the superficial medial retinaculum, makelesser contributions to patellar stability.

The VMO muscle is very important, acting as a dynamic stabi-lizer, and is intimately related to the MPFL [8].

S60 V.B. Duthon / Orthopaedics & Traumatology: S

F

czi

bieck

4

lik

ddmsgp“mb

5

ld1iit

wa

Fig. 1. Anatomic diagram showing MPFL position.

rom Maîtrise orthopédique No. 186–2009.

Patellar tracking and patellofemoral stability result from highlyomplex interactions between these static and dynamic stabili-ers. Patellar trajectory in the femoral trochlea is not straight, butncludes tilt, glide and rotation.

With the knee in complete extension, the patella lies above andeyond the femoral sulcus. It enters the trochlea when the knee is

n 10–30◦ flexion, depending on patellar tendon length: trochlearntry is later in case of patella alta or of “short” trochlea, in whichase osteoarticular stabilization of the patellar is lacking when thenee is in extension or slight flexion [8,13].

. Definitions

Patellar dislocation, if not otherwise specified, is lateral dis-ocation; medial dislocation, which is exclusively iatrogenic, andntra-articular dislocation are very rare, but exist and need to benown.

There is an important distinction between inaugural traumaticislocation (single), recurrent dislocation (several) and habitualislocation, as definitions and treatments differ. Inaugural trau-atic dislocation ruptures previously intact medial para-patellar

tructures [5,14,15], and may remain single. In common to all inau-ural traumatic dislocations is knee hemarthrosis, due to medialara-patellar stabilization structure rupture. Dislocation becomesrecurrent” if repeated several times following the inaugural trau-atic dislocation. Habitual dislocation is a complex entity defined

y patellar dislocation on each movement of flexion of the knee.

. Incidence and risk factors

There have been several studies of incidence of inaugural patel-ar dislocation in adults [3–5,14]. Mean annual incidence of patellarislocation varies with age group: it is between 5.8 and 7.0 per00,000 person-years in the general population, but 29 per 100,000

n 10–17 year-olds; It reaches 69 per 100,000 person-years in mil-tary personnel undergoing aptitude testing and very demanding

raining [14].

Women are at greater risk than men, as are young subjects,hether military or in the general population; risk decreases with

ge [3–5,14]. This may be due to young subjects’ more intense

urgery & Research 101 (2015) S59–S67

physical activity and/or to morphologic and tissue-related factorsthat make some adolescents more vulnerable.

6. Traumatic mechanism and predisposing factors

The typical mechanism underlying patellar dislocation is amovement of the knee in flexion and valgus without direct con-tact, accounting for 93% of traumatic patellar dislocations [3]. Mostpatients report a sensation of slippage, intense pain and secondaryeffusion, often suggestive of knee sprain. True traumatic dislo-cation, caused by direct tangential shock dislocating the patellalaterally, also occurs. History taking can determine the traumamechanism.

Whatever the mechanism, according to Sillanpaa et al., almostall patients with traumatic patellar dislocation show hemarthro-sis, MPFL lesion and medial patellar wing fracture. Osteochondralfracture occurs in 25% of traumatic patellar dislocations [3].

Recurrence risk is increased 6-fold in case of history of ipsi- orcontralateral patellar dislocation [4]. Dejour and Walch, in 1987,attributed patellar predisposition toward dislocation and instabil-ity with recurrence to four principal and certain secondary factors.

6.1. Principal predisposing factors

6.1.1. Trochlear dysplasiaTrochlear dysplasia [16,17] is a determining factor, consisting

in progressive filling of the trochlear floor, resulting in greater orlesser smoothing out of the trochlear groove, which becomes flator convex. There are several associated signs on strict lateral kneeX-ray (Fig. 2):

• crossing sign: crossing between the deep line of the trochlea andthe anterior edge of the two condyles (which would normally bemore anterior), at and below which point the trochlea is com-pletely flat;

• supra-trochlear spur: a spur above the trochlea, resulting fromoverall trochlear pre-eminence;

• double contour: projection of the subchondral bone of thehypoplastic medial edge of the trochlea;

• trochlear projection: measured with respect to the tangent to thelast 10 cm of the anterior femoral cortex; the floor of the trochleamay lie forward, flush or backward with the cortex (positive, zeroor negative projection, respectively);

• trochlear depth: mainly of prognostic value. Maldague and Frot[18] measured trochlear depth at 1 cm from the summit. Dejouret al. [16,19] suggested a variant: a tangent to the last 10 cm of theposterior femoral cortex and a perpendicular through the summitof the posterior condyles cross at a point through which a line isdrawn subtending an open angle of 15◦ forward and downward;this line crosses the line of the floor of the trochlea at point Band the bicondylar line at point A. It is the distance AB that is tobe measured, with a threshold of 4 mm, values less than whichsignifying pathology.

Dejour and Lecoultre classified trochlear dysplasia in 4 grades[20] (Fig. 3):

• grade A: crossing sign with normal morphology of the sides of thetrochlea on CT;

• grade B: crossing sign, supra-trochlear spur, trochlea flat on CT;• grade C: double contour ending below the crossing sign, medial

hypoplasia and lateral convexity on CT;• grade D: double contour ending below the crossing sign, supra-

trochlear spur, medial hypoplasia and lateral convexity on CT,with the two sides joining in a “cliff”.

V.B. Duthon / Orthopaedics & Traumatology: Surgery & Research 101 (2015) S59–S67 S61

he 4 tr

F

6

gsno1

6

ptteir>

FsF

Fig. 2. Diagram showing t

rom Maîtrise orthopédique No. 176–2008.

.1.2. Elevated TT-TG distanceThe distance between the tibial tubercle and the trochlear

roove (TT-TG) [21] (Fig. 4) is measured from 2 superimposed CTlices, one through the floor of the groove where the intercondylarotch has a Norman arch shape, and the other through the middlef the tibial tubercle. Normal values depend on degree of flexion:6 ± 4 mm in extension to 9 ± 4 mm in flexion.

.1.3. Patella alta [22,23]Isolated high patella or “patella alta” may be found in recurrent

atellar dislocation and may be the cause of recurrence. Normally,he patella enters the trochlea as of the first degrees of flexion, beinghereby stabilized: if it is too high with respect to the trochlea,

ntry is delayed, with a risk of dislocation. The Caton-Deschampsndex [24] is used to measure patellar height on lateral knee X-ay; the normal value is 1, and patella alta is defined by an index1.2. Patellar tendon length is also relevant, and can be measured

ig. 3. Lateral knee radiograph showing signs of trochlear dysplasia: double shape,upra-trochlear spur (éperon supra-trochléen), crossing sign (signe du croisement).rom Maîtrise orthopédique No. 176–2008.

ochlear dysplasia grades.

on lateral X-ray, or more precisely on MRI or CT; length >52 mm isabnormal [25], although the threshold may be modulated accordingto the patient’s height.

6.1.4. Patellar tiltPatellar tilt is measured by superimposing two CT slices, one

through the long axis of the patella and the other through thetrochlear reference slice (where the notch has a Norman archshape). It is the angle subtended by the long axis of the patella andthe posterior bicondylar plane (Fig. 5). It corresponds to quadricepsdysplasia, especially of the vastus medialis, but also to trochleardysplasia. Measurement is taken with the quadriceps relaxed andthen contracted, giving a dynamic assessment of tilt. Normal valueslie between 10 and 20◦.

6.2. Secondary predisposing factors

The secondary predisposing factors are described as follows:

• elevated Q angle with tibial tubercle lateralization and genu val-gum [26,27];

Fig. 4. Diagram showing measurement of TT-TG distance [TT-GT] (tibial tubercle[TTA] – trochlear groove) [AE: anterolateral; AI: anteromedial].

S62 V.B. Duthon / Orthopaedics & Traumatology: Surgery & Research 101 (2015) S59–S67

•

•••

tl

7

o

otltaptilvnmt

sid

•

•

oltep

CT assesses osseous risk factors: patellofemoral malalignment,osteochondral defects, patellar tilt and lateral subluxation, elevatedTT-TG distance and trochlear dysplasia [36].

Fig. 5. CT measurement of patellar tilt.

elevated femoral anteversion with compensatory lateral tibialtorsion [28];vastus medialis hypoplasia;ligament hyperlaxity [29,30] with genu recurvatum;patellar dysplasia: Wiberg defined 3 patellar types according toaxial aspect in 30◦ flexion [31], and Baumgartl added a 4th type[32]:◦ type 1: concave medial facet almost as long as the lateral face,◦ type 2: short concave medial facet,◦ type 3: short convex medial facet (dysplastic patella),◦ type 4: absence of medial crest or medial facet.

Patellar dysplasia was investigated by Servien et al. in the sagi-tal plane, based on analysis of the patellar tip, which is shorter theonger the patellar ligament [33].

. Clinical examination

In fresh trauma, clinical examination is essential for diagnosisf patellar dislocation [8].

Patellar dislocation usually resolves spontaneously. Only 20%f patients require reduction of persistent dislocation. Diagnosis ishen clear: the patient is in great pain, the knee is deformed by theateral dislocation of the patella, and there is often flexion contrac-ure. Analgesia or even anesthesia is essential, for the patient to beble to relax. The knee is brought into complete extension and theatella is reduced by lateral medializing pressure to slip it back intohe femoral trochlea. Voluminous hemarthrosis can be withdrawnn the same step, to relieve pain and facilitate clinical and radio-ogical examination: the Merchant view in 45◦ flexion and lateraliew in 30◦ flexion are difficult to take in patients with volumi-ous hemarthrosis under tension. Fatty lobules in the joint fluiday indicate osteochondral fracture or simply bone impaction of

he medial patellar facet onto the lateral femoral condyle (Fig. 2).In spontaneous reduction, other diagnoses may be considered:

evere sprain, joint fracture, etc. The trauma circumstances andmmediate post-trauma aspect (lateralized patella?) should beetermined, with examination for:

patellar hypermobility and apprehension when the patella isshifted laterally;pain on palpation of the MPFL.

Loss of tendon and muscle substance at the patellar insertionf the vastus medialis and/or MPFL and a patella that is easily dis-

ocated are prognostic factors of poor outcome for non-operativereatment [8]. Valgus and abnormal lower-limb rotation, contralat-ral patellar hypermobility [34], hyperlaxity and familial history ofatellar dislocation should also be explored for.

Fig. 6. Merchant view of patella, showing lateral patellar subluxation, increasedpatellar tilt and a bone fragment from the medial edge corresponding to MPFLavulsion.

8. Imaging

8.1. Plain X-ray

Radiography should comprise an AP weight-bearing view inextension, Merchant view (weight-bearing in 45◦ flexion), alsoknown as a femoropatellar axial view, and lateral view in 30◦ flex-ion.

The Merchant view may reveal bone avulsion of the medial facetof the patella (Fig. 6) and enables analysis of patellofemoral cen-tering. The avulsion involves either the patellar insertion of theMPFL or the more distal patellomeniscal ligament insertion. Osteo-chondral fractures of the inferomedial pole of the patella are highlysuggestive of traumatic patellar dislocation (Fig. 7), but are over-looked on 30–40% of initial radiographs [11,35].

8.2. CT

Fig. 7. Intraoperative photograph of fracture-avulsion of the inferomedial pole ofthe patella after inaugural traumatic dislocation.

V.B. Duthon / Orthopaedics & Traumatology: S

Fig. 8. MRI axial slice in a patient who had sustained inaugural traumatic lateralpatellar dislocation the previous day. The bone edema of the medial facet of thepatella and lateral facet of the lateral femoral condyle corresponds to impactionddi

a

oXtol

8

tpl[

ooaol

9

i

rpr

1

p

uring dislocation. Effusion shows 2 levels and corresponds to lipo-hemarthrosisue to medial capsulo-ligamentous complex tear and patellofemoral bone fracture-

mpaction.

It is also useful to screen for lower-limb rotational abnormalitynd to measure TT-TG distance in various degrees of flexion [8].

Cartilage cover makes the trochlear groove shallower than thesseous groove, especially in subjects under 18 years of age. CT or-ray measurements using the trochlear groove as landmark are

herefore less contributive than those on MRI, which take accountf the cartilage [37]. Neither does CT analyze the medial capsulo-igamentous stabilizing structures with precision.

.3. MRI

MRI is more specific in precisely determining involved struc-ures and thus guiding treatment decision-making. It assesses theatellofemoral joint cartilage surfaces and also the medial patel-

ar stabilizing structures (medial retinaculum, MPFL and VMO)38–40].

In patellar dislocation, MRI reveals: hemarthrosis, bone edemaf the medial patellar facet and lateral femoral condyle (Fig. 8),steochondral lesions of the medial patellar facet (Fig. 9) and thenterolateral part of the lateral femoral condyle. Concave deformityf the inferomedial patella, due to impaction, is a specific sign ofateral patellar dislocation [15,41].

. Natural history

The sequelae of inaugural patellar dislocation are well describedn the literature [33,34], and may be serious.

More than 50% of patients present symptoms after inaugu-al patellar dislocation [42], with a risk of more or less severeatellofemoral osteoarthritis in the long-term [43]. Moreover,ecurrence rates may be as high as 40% [44].

0. Treatment

Adapted treatment is essential to limit recurrence of dislocation,ainful subluxation and osteoarthritis.

urgery & Research 101 (2015) S59–S67 S63

The preventive impact of primary stabilization surgery on sec-ondary instability is a matter of debate.

Treatment guidelines and results are highly variable, with lowlevel of evidence.

Series reporting results on various treatment options combinedacute traumatic dislocation and recurrent dislocation [42,45–48].Non-operative and surgical management have been compared in afew studies [47,49], but with only 2 randomized prospective stud-ies [50,51]. Recurrence rates are high, ranging from 10 to 30% insurgery [1,26,48,49,52] and 13 to 52% for non-operative treatment[42,45–47,49].

10.1. Non-operative treatment

Several teams favor non-operative management of inauguraltraumatic patellar dislocation [13,51,53]. Stefancin and Parker rec-ommended this attitude in a review of 70 articles, except in caseof chondral lesion, osteochondral fracture or major lesions of themedial stabilizing structures on clinical and radiological (CT andMRI) assessment [2].

The precise modalities, however, have been little studied:

• there is agreement that patients should initially be immobilizedfor 2–3 weeks, to control pain; immobilization in some 20◦ flex-ion approximates the two extremities of the torn medial wing.Knee braces are used to stabilize the patella as soon as painallows;

• weight-bearing is authorized as soon as possible, depending onpain;

• early mobilization is important to maintain joint cartilagetrophicity [8]; closed-chain exercises and passive mobilizationare then initiated [5].

Rehabilitation following inaugural traumatic patellar disloca-tion seeks to restore normal range of knee motion (full flexionand extension) and to reinforce the quadriceps to restore dynamicpatellar balance. The medialis vastus was for some years atarget for reinforcement, insufficiency being thought to con-tribute to lateral dislocation, but the literature fails to confirmthis hypothesis [54]; it is thus just one element of rehabili-tation among others: muscle reinforcement, electrotherapy andproprioception.

In a literature review, Smith et al. [55] showed that one-third ofpatients suffered recurrence of dislocation after rehabilitation, andwere unable to identify the ideal protocol.

10.2. Surgical treatment

10.2.1. Chondral and osteochondral fractureArthroscopy is indispensable in case of intra-articular free body

released by chondral lesion or osteochondral fracture. When osteo-chondral fracture involves more than 10% of the patellar jointsurface or involves the weight-bearing surface of the lateral femoralcondyle, the osteochondral fragment should so far as possible befixed by open surgery, for instance using resorbable pins (Fig. 10);if this is not possible, micro-fracturing may stimulate cartilageregrowth.

10.2.2. Stabilization surgery

The MPFL and medial retinaculum tend to be torn in acute

traumatic patellar dislocation [50,56,57], so much so that, along-side hemarthrosis, these are genuine symptoms of dislocation[50].

S64 V.B. Duthon / Orthopaedics & Traumatology: Surgery & Research 101 (2015) S59–S67

F l tip o(

at

1dM

t

Ff

ig. 9. MRI sequences showing osteochondral fracture-avulsion of the inferomediacorresponding intraoperative photographs: Figs. 7 and 10).

Patellar dislocation patients can be classified under 3 categoriesccording to whether they show predisposing factors and whetherhe dislocation is inaugural or recurrent.

0.2.2.1. Inaugural dislocation without predisposing factors. Imme-

iate surgical repair of the patellar stabilizing structures (VMO,PFL, medial retinaculum) is recommended in athletic patients.Bone avulsion at the patellar insertion of the MPFL is known not

o show consolidation even with proper immobilization; functional

ig. 10. Intraoperative photographs of 2 × 1 cm free patellar osteochondral bone fragmeragment and 2 resorbable sutures in the purely chondral part.

f the patella in a patient who had previously suffered inaugural patellar dislocation

results of non-operative treatment are unsatisfactory, and fixationis recommended [11,58].

10.2.2.2. Inaugural dislocation with predisposing factors. Surgicalrepair of the patellar stabilizing structures (VMO, MPFL, medial reti-

naculum) is recommended in case of risk factors for recurrence:trochlear dysplasia, patella alta, elevated TT-TG distance.

Repair may consist in suturing the torn structures, with or with-out tendon reinforcement (e.g., Roux-Goldthwait technique, using

nt found within the joint, fixed by resorbable pins in the osteochondral part of the

V.B. Duthon / Orthopaedics & Traumatology: Surgery & Research 101 (2015) S59–S67 S65

Knee instabil ity + Patellofemoral (PF) pain

PF laxity at 0° and 30° flexion, lateral view

Laxity, crossing sign, >4 mm trochlear projec�on

No PF laxity, normal X-ray, no dysplasia

CT No CT

Patel la al ta ind ex >1.2

TT-TG >20 mm

Tilt >20°

MRI

Medialize TT

Lower TT

Ligament bal ance

MPFL reco nstr uc� on

Car�lage fragment

or chondrite

MRI nega �ve

Art hrosco py Conserva�ve treatme nt Differen�al diag nosis

rithm

F

accdsrst

1sdi

tTr

dsa

“a

ctwl

5eht

i

systematically associated, as vastus medialis plasty alone is insuf-ficient to stabilize the patella.

Fig. 11. “À la carte” treatment algo

rom Maîtrise orthopédique No. 186–2009.

strip of patellar tendon), and the predisposing factors should beorrected to limit the risk of recurrence: lowering the tibial tuber-le in patella alta, medializing the tibial tubercle in elevated TT-TGistance (>20 mm in extension). This may be done as a secondtep, consisting not in repairing the stabilizing structures but ineconstructing the MPFL by gracilis tendon autograft associated tourgical correction of predisposing factors. This treatment is closeo that for recurrent dislocation.

0.2.2.3. Recurrent dislocation [2]. In recurrent patellar dislocation,urgery is mandatory due to severe apprehension constituting aisability in everyday life, and to prevent chondral lesions which,

n the long-term, would cause patellofemoral osteoarthritis.The main predisposing factors should be screened for and

reated: patella alta, by lowering the tibial tubercle; elevated TT-G distance, by medializing the tibial tubercle. The MPFL is to beeconstructed.

These procedures are associated, so as to correct as many pre-isposing factors as possible. Trochlear dysplasia can be treated byulcus-deepening trochleoplasty, although this is rarely indicateds first-line treatment.

Treatment in recurrent patellar dislocation is thus personalized,à la carte”, as described by Dejour et al., who drew up a treatmentlgorithm [59] (Fig. 11) based on the following techniques.

10.2.2.3.1. Lowering the tibial tubercle. This technique is indi-ated to correct patella alta. The tibial tubercle is lowered (Fig. 12)o achieve a Caton-Deschamps index approximating 1. Patella altaith index >1.2 is corrected by lowering the tubercle until the index

ies between 0.8 and 1.0.10.2.2.3.2. Patellar tenodesis. If patellar tendon length exceeds

2 mm, lowering the tibial tubercle does not correct the lengthxcess, with a risk of “windscreen-wiper effect” in case of patellar

ypermobility. In such cases, patellar tenodesis can be associatedo tibial tubercle lowering (Fig. 12).

10.2.2.3.3. Tibial tubercle medialization. Tibial tubercle medial-zation, or Elmslie-Trillat osteotomy, is indicated for TT-TG ≥20 mm

for recurrent patellar dislocation.

(in extension). The aim is to medialize the tubercle to achieve aTT-TG distance of 12 mm. For example, if TT-TG = 20 mm, a 9-mmmedialization is needed, adding 1 mm to compensate for possi-ble correction loss on fixation. The distal part of tubercle is left incontinuity with the anterior tibial cortex, and a 4.5-mm screw issufficient for fixation.

10.2.2.3.4. Sulcus-deepening trochleoplasty. The principleswere established by Dejour and Walch in 1987 [60] (Fig. 13). It isa demanding technique and difficult to transmit; indications arethus exceptional. It is indicated in recurrent dislocation with largetrochlear protrusion exceeding 6 mm (especially in grade B and Ddysplasia) or after failure of other techniques.

10.2.2.3.5. Vastus medialis plasty. This technique is indicatedfor dysplasia of the vastus medialis, specifically in the oblique part(VMO). This dysplasia contributes to patellar tilt measured on CT(>20◦). Lateral wing sectioning may be associated. Bone surgery is

Fig. 12. Diagram showing distalization of the tibial tubercle, isolated (center) orassociated with patellar tenodesis (right).

S66 V.B. Duthon / Orthopaedics & Traumatology: S

F

ias

1

opD

•

•

•

p

1

a

b

b

g

s

ubp

D

i

R

[

[

[

[

[

[

[

[

[

[

[

[

[

[

[

[

[

[

[

[

[

[

[[

[

[

[

[

[

[

Fig. 13. Diagram of sulcus-deepening trochleoplasty.

rom Maîtrise orthopédique No. 176–2008.

10.2.2.3.6. MFPL reconstruction. MFPL reconstruction isncreasingly replacing vastus medialis plasty to correct patellar tiltnd limit dislocation of lateral glide of the patella [61]. It moreovereems to reduce or abolish apprehension on the Smillie test.

0.2.3. ResultsTo identify the optimal treatment (surgical versus non-

perative) for inaugural patellar dislocation, Hing et al. [62]erformed a literature review of 5 studies for the Cochraneatabase. No significant difference emerged for:

risk of recurrent dislocation (47/182 versus 53/157; relative risk:0.81; 95% confidence interval: 0.56–1.17);Kujala patellofemoral score (mean difference: 3.13; 95% CI: −7.34to 13.59);or need for surgical revision (RR: 1.09; 95% CI: 0.72–1.65[3 studies]).

There have been no randomized controlled studies to identifyatient groups at risk of recurrent dislocation.

1. Conclusion

Inaugural traumatic patellar dislocation is frequent in youngctive subjects.

Initial assessment requires MRI, which makes a crucial contri-ution to decision-making.

Surgical stabilization of medial patellar bone avulsion providesenefit in patients with risk factors for patellar dislocation.

In dislocation in a normal joint, non-operative management isenerally indicated.

In case of joint abnormality or recurrent dislocation, “à la carte”urgery is usually indicated.

Further prospective randomized studies with longer follow-p will be needed to identify risk factors for patellar dislocation:ehavioral factors, quadriceps force, neuromuscular control, andostural stability in high-risk subjects.

isclosure of interest

The author declares that he has no conflicts of interest concern-ng this article.

eferences

[1] Harilainen A, Myllynen P, Antila H, et al. The significance of arthroscopy andexamination under anaesthesia in the diagnosis of fresh injury haemarthrosisof the knee joint. Injury 1988;19(1):21–4.

[2] Stefancin JJ, Parker RD. First-time traumatic patellar dislocation: a systematic

review. Clin Orthop Relat Res 2007;455:93–101.

[3] Sillanpaa P, Mattila VM, Iivonen T, et al. Incidence and risk factors of acute trau-matic primary patellar dislocation. Med Sci Sports Exerc 2008;40(4):606–11.

[4] Fithian DC, Paxton EW, Stone ML, et al. Epidemiology and natural history ofacute patellar dislocation. Am J Sports Med 2004;32(5):1114–21.

[

urgery & Research 101 (2015) S59–S67

[5] Atkin DM, Fithian DC, Marangi KS, et al. Characteristics of patients with primaryacute lateral patellar dislocation and their recovery within the first 6 monthsof injury. Am J Sports Med 2000;28(4):472–9.

[6] Riedel A, Hartig W, Seeger G, et al. Principles of rat subcortical forebrainorganization: a study using histological techniques and multiple fluorescencelabeling. J Chem Neuroanat 2002;23(2):75–104.

[7] Gardner E, O’Rahilly R. The early development of the knee joint in staged humanembryos. J Anat 1968;102(Pt 2):289–99.

[8] Hinton RY, Sharma KM. Acute and recurrent patellar instability in the youngathlete. Orthop Clin North Am 2003;34(3):385–96.

[9] Smirk C, Morris H. The anatomy and reconstruction of the medialpatellofemoral ligament. Knee 2003;10(3):221–7.

10] Burks RT, Desio SM, Bachus KN, et al. Biomechanical evaluation of lateral patel-lar dislocations. Am J Knee Surg 1998;11(1):24–31.

11] Desio SM, Burks RT, Bachus KN. Soft tissue restraints to lateral patellar trans-lation in the human knee. Am J Sports Med 1998;26(1):59–65.

12] O’Reilly MA, O’Reilly PM, Bell J. Sonographic appearances of medialretinacular complex injury in transient patellar dislocation. Clin Radiol2003;58(8):636–41.

13] Arendt EA, Fithian DC, Cohen E. Current concepts of lateral patella dislocation.Clin Sports Med 2002;21(3):499–519.

14] Hsiao M, Owens BD, Burks R, et al. Incidence of acute traumatic patellar dislo-cation among active-duty United States military service members. Am J SportsMed 2010;38(10):1997–2004.

15] Virolainen H, Visuri T, Kuusela T. Acute dislocation of the patella: MR findings.Radiology 1993;189(1):243–6.

16] Dejour H, Walch G, Nove-Josserand L, et al. Factors of patellar instabil-ity: an anatomic radiographic study. Knee Surg Sports Traumatol Arthrosc1994;2(1):19–26.

17] Malghem J, Maldague B. Depth insufficiency of the proximal trochlear grooveon lateral radiographs of the knee: relation to patellar dislocation. Radiology1989;170(2):507–10.

18] Maldague BMJ, Frot B. Articulation fémoro-patellaire. Imagerie en orthopédieet traumatologie du genou. Cahiers d’enseignement de la SOFCOT Expansionscientifique franc aise 1988;29:242–59.

19] Dejour HNP, Walch G. Factors in patellar instability. In: Cahiers d’enseignementde la SOFCOT. Elsevier; 1999.

20] Dejour DRP, Lecoultre B. Douleur et instabilité rotulienne : essai de classifica-tion. Med Hyg 1998;5:1466–70.

21] Goutallier D, Bernageau J, Lecudonnec B. The measurement of the tibial tuberos-ity. Patella groove distanced technique and results. Rev Chir Orthop ReparatriceAppar Mot 1978;64(5):423–8 [author’s translation].

22] Insall J, Goldberg V, Salvati E. Recurrent dislocation and the high-riding patella.Clin Orthop Relat Res 1972;88:67–9.

23] Blackburne JS, Peel TE. A new method of measuring patellar height. J Bone JointSurg Br 1977;59(2):241–2.

24] Caton J. Method of measuring the height of the patella. Acta Orthop Belg1989;55(3):385–6.

25] Neyret P, Robinson AH, Le Coultre B, et al. Patellar tendon length – the factor inpatellar instability? Knee 2002;9(1):3–6.

26] Hawkins RJ, Bell RH, Anisette G. Acute patellar dislocations. The natural history.Am J Sports Med 1986;14(2):117–20.

27] Rorabeck CH, Bobechko WP. Acute dislocation of the patella with osteochondralfracture: a review of eighteen cases. J Bone Joint Surg Br 1976;58(2):237–40.

28] Elgafy H, El-Kawy S, Elsafy M, et al. Internal torsion of the distal femur as acause of habitual dislocation of the patella: a case report and a review of causesof patellar dislocation. Am J Orthop 2005;34(5):246–8.

29] Maenpaa H, Lehto MU. Patellar dislocation has predisposing factors. Aroentgenographic study on lateral and tangential views in patients and healthycontrols. Knee Surg Sports Traumatol Arthrosc 1996;4(4):212–6.

30] Runow A. The dislocating patella. Etiology and prognosis in relation to gener-alized joint laxity and anatomy of the patellar articulation. Acta Orthop ScandSuppl 1983;201:1–53.

31] Wiberg G. Roentgenographic and anatomic studies on the patellofemoral joint.Acta Orthop Scand 1941;12:319–410.

32] F.B. Das Kniegelenk. F. Baumgartl. Editor Springer, Berlin; 1944.33] Servien E, Ait Si Selmi T, Neyret P. Study of the patellar apex in objective patellar

dislocation. Rev Chir Orthop Reparatrice Appar Mot 2003;89(7):605–12.34] Stanitski CL. Articular hypermobility and chondral injury in patients with acute

patellar dislocation. Am J Sports Med 1995;23(2):146–50.35] Stanitski CL, Paletta Jr GA. Articular cartilage injury with acute patellar dislo-

cation in adolescents. Arthroscopic and radiographic correlation. Am J SportsMed 1998;26(1):52–5.

36] Hing CB, Shepstone L, Marshall T, et al. A laterally positioned concave trochleargroove prevents patellar dislocation. Clin Orthop Relat Res 2006;447:187–94.

37] Nietosvaara Y, Aalto K. The cartilaginous femoral sulcus in children with patel-lar dislocation: an ultrasonographic study. J Pediatr Orthop 1997;17(1):50–3.

38] Spritzer CE, Courneya DL, Burk Jr DL, et al. Medial retinacular complex injuryin acute patellar dislocation: MR findings and surgical implications. AJR Am JRoentgenol 1997;168(1):117–22.

39] Sanders TG, Morrison WB, Singleton BA, et al. Medial patellofemoral ligament

injury following acute transient dislocation of the patella: MR findings withsurgical correlation in 14 patients. J Comput Assist Tomogr 2001;25(6):957–62.

40] Nomura E, Horiuchi Y, Inoue M. Correlation of MR imaging findings and openexploration of medial patellofemoral ligament injuries in acute patellar dislo-cations. Knee 2002;9(2):139–43.

logy: S

[

[

[

[

[

[

[

[

[

[

[

[

[

[

[

[

[

[

[

[

V.B. Duthon / Orthopaedics & Traumato

41] Elias DA, White LM, Fithian DC. Acute lateral patellar dislocation atMR imaging: injury patterns of medial patellar soft tissue restraints andosteochondral injuries of the inferomedial patella. Radiology 2002;225(3):736–43.

42] Maenpaa H, Lehto MU. Patellar dislocation. The long-term results of non-operative management in 100 patients. Am J Sports Med 1997;25(2):213–7.

43] Maenpaa H, Lehto MU. Patellofemoral osteoarthritis after patellar dislocation.Clin Orthop Relat Res 1997;339:156–62.

44] Maenpaa H, Huhtala H, Lehto MU. Recurrence after patellar dislocation.Redislocation in 37/75 patients followed for 6–24 years. Acta Orthop Scand1997;68(5):424–6.

45] Cofield RH, Bryan RS. Acute dislocation of the patella: results of conservativetreatment. J Trauma 1977;17(7):526–31.

46] Larsen E, Lauridsen F. Conservative treatment of patellar dislocations. Influenceof evident factors on the tendency to redislocation and the therapeutic result.Clin Orthop Relat Res 1982;171:131–6.

47] Cash JD, Hughston JC. Treatment of acute patellar dislocation. Am J Sports Med1988;16(3):244–9.

48] Vainionpaa S, Laasonen E, Silvennoinen T, et al. Acute dislocation of thepatella. A prospective review of operative treatment. J Bone Joint Surg Br1990;72(3):366–9.

49] Nikku R, Nietosvaara Y, Kallio PE, et al. Operative versus closed treatment ofprimary dislocation of the patella. Similar 2-year results in 125 randomizedpatients. Acta Orthop Scand 1997;68(5):419–23.

50] Sillanpaa PJ, Mattila VM, Maenpaa H, et al. Treatment with and without initialstabilizing surgery for primary traumatic patellar dislocation. A prospectiverandomized study. J Bone Joint Surg Am 2009;91(2):263–73.

51] Nikku R, Nietosvaara Y, Aalto K, et al. Operative treatment of primarypatellar dislocation does not improve medium-term outcome: a 7-year

[

[

urgery & Research 101 (2015) S59–S67 S67

follow-up report and risk analysis of 127 randomized patients. Acta Orthop2005;76(5):699–704.

52] Harilainen A, Sandelin J. Prospective long-term results of operative treatmentin primary dislocation of the patella. Knee Surg Sports Traumatol Arthrosc1993;1(2):100–3.

53] Buchner M, Baudendistel B, Sabo D, et al. Acute traumatic primary patellardislocation: long-term results comparing conservative and surgical treatment.Clin J Sport Med 2005;15(2):62–6.

54] Smith TO, Bowyer D, Dixon J, et al. Can vastus medialis oblique be preferen-tially activated? A systematic review of electromyographic studies. PhysiotherTheory Pract 2009;25(2):69–98.

55] Smith TO, Davies L, Chester R, et al. Clinical outcomes of rehabilitation forpatients following lateral patellar dislocation: a systematic review. Physiother-apy 2010;96(4):269–81.

56] Ahmad CS, Stein BE, Matuz D, et al. Immediate surgical repair of the medialpatellar stabilizers for acute patellar dislocation. A review of eight cases. Am JSports Med 2000;28(6):804–10.

57] Garth Jr WP, DiChristina DG, Holt G. Delayed proximal repair and distal realign-ment after patellar dislocation. Clin Orthop Relat Res 2000;377:132–44.

58] Hautamaa PV, Fithian DC, Kaufman KR, et al. Medial soft tissue restraints inlateral patellar instability and repair. Clin Orthop Relat Res 1998;(349):174–82.

59] Demey G, Servien E, Debarge R, et al. Prise en charge actuelle des luxationsépisodiques de la rotule (place de la reconstruction du ligament fémoro-patellaire médial). Maitr Orthop 2009;186.

60] Dejour HWG. Pathologie fémoro-patellaire. In: 6e Journée lyonnaise de

chirurgie du genou. 1987.

61] Amis AA, Firer P, Mountney J, et al. Anatomy and biomechanics of the medialpatellofemoral ligament. Knee 2003;10(3):215–20.

62] Hing CB, Smith TO, Donell S, et al. Surgical versus non-surgical interventions fortreating patellar dislocation. Cochrane Database Syst Rev 2011;11:CD008106.