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Case Report

Technical Failure of Medial Patellofemoral LigamentReconstruction

Matthew Bollier, M.D., John Fulkerson, M.D., Andy Cosgarea, M.D., and Miho Tanaka, M.D.

Abstract: In patients with chronic patellofemoral instability who have normal alignment anddeficient proximal medial restraints, medial patellofemoral ligament (MPFL) reconstruction is a goodoption to treat patellar instability. However, medial subluxation, medial patellofemoral articularoverload, and recurrent lateral instability are possible when the graft is positioned non-anatomically.The clinical presentation of MPFL femoral tunnel malpositioning has not been highlighted in theliterature. We have had 5 patients referred to us after a malpositioned femoral MPFL graft led todisabling symptoms and a need for revision surgery. This report highlights the effects of amalpositioned graft and describes strategies to identify the anatomic MPFL insertion during surgery.

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The medial patellofemoral ligament (MPFL) guidesthe patella into the trochlear groove during the

first 30° of knee flexion.1-4 In patients with chroniclateral patellofemoral instability who have normalalignment and deficient proximal medial restraints,MPFL reconstruction is a good option to treat patellarinstability. Numerous techniques have been describedwith a variety of graft choices and fixation strate-gies.5-22 Many studies have reported good outcomeswith MPFL reconstruction,12,23-26 but continued insta-ility and cartilage breakdown are possible when theraft is positioned non-anatomically. Servien et al.27

recently analyzed femoral tunnel position on radiog-raphy and magnetic resonance imaging (MRI) 1 yearafter MPFL reconstruction. Of the tunnels, 69% were

From the Department of Orthopaedic Surgery, University ofowa (M.B.), Iowa City, Iowa; Orthopaedic Associates of HartfordJ.F.), Hartford, Connecticut; and Department of Orthopaedicurgery, The Johns Hopkins University (A.C., M.T.), Baltimore,aryland, U.S.A.Received December 30, 2010; accepted February 9, 2011.Address correspondence to Matthew Bollier, M.D., Department ofrthopaedic Surgery, University of Iowa, 200 Hawkins Dr, 01008

PP, Iowa City, IA 52240, U.S.A. E-mail: mattbollier@yahoocom

© 2011 by the Arthroscopy Association of North America0749-8063/10771/$36.00

doi:10.1016/j.arthro.2011.02.014

Arthroscopy: The Journal of Arthroscopic and Related

in good position on radiography and 65% were in properposition on MRI; in contrast, 35% of tunnels werethought to be positioned anterior or proximal. Elias andCosgarea28 reported a 50% increase in peak medialpatellofemoral pressure when an over-tightened MPFLgraft is positioned proximally on the femur.

The clinical presentation of MPFL femoral tunnelmalpositioning has not been highlighted in the literature.We have had 5 patients referred to us after a malposi-tioned femoral MPFL graft led to disabling symptomsand a need for revision surgery. We used the methoddescribed by Schottle et al.29 and modified by Servien etl.27 to determine femoral tunnel positioning on lateral

radiographs (Fig 1). Of the 5 cases, 4 exhibited proximalgraft position, and all 5 cases had an anteriorly posi-tioned graft. Iatrogenic medial patella subluxation devel-oped in 3 patients, and 2 patients had recurrent lateralinstability. Two patients with medial subluxation werefound to have severe medial patellofemoral arthritis.

CASE REPORTS

Case 1

A 39-year-old woman underwent an Elmslie-Trillatprocedure, lateral retinacular release, and vastus me-

dialis oblique advancement in 2008 for chronic lateral

1Surgery, Vol xx, No x (Month), 2011: pp xxx

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2 M. BOLLIER ET AL.

patellofemoral instability. Recurrent lateral instabilitydeveloped within 6 months. In 2009 a semitendinosusallograft MPFL reconstruction was performed. Onreferral to our office, the patient complained ofchronic medial patellofemoral aching and acute epi-sodes of patella shifting and popping, causing severepain. Examination showed a positive medial patellasubluxation test and a tight MPFL graft with medial tilt.Plain radiographs and computed tomography showedan anteriorly and proximally positioned femoral tunnel(Fig 2). The patient again underwent surgery, and ar-throscopic examination showed medial patella facet ar-thritis, overload, and medial tilt (Fig 3). Arthroscopicrelease of the MPFL graft, patella chondroplasty, andopen lateral imbrication were performed. This allowedthe patella to track centrally and unloaded the arthriticmedial facet. Postoperatively, the patient reported painrelief and resolution of her shifting and popping symp-toms.

Case 2

A 33-year-old woman had an anteromedial tibialtubercle transfer and allograft MPFL reconstruction in2008 for chronic lateral patellofemoral instability. In-creasing pain developed postoperatively. When the pa-tient presented to our office in 2009, she had a positivemedial patella subluxation test, gross medial tracking ofthe patella, medial tilt, and significant medial retinacu-lum tenderness. Radiography and MRI showed an an-

FIGURE 1. Femoral tunnel positioning. The normal femoral inser-tion of the MPFL is represented by the blue circle as described bySchottle et al.29 This is found by the intersection of line x (tangen-ial to posterior condyle) and line y (perpendicular to line x atosterior aspect of Blumensaat line). The green circle representsodification of the anatomic zone to �7 mm because of the

iameter of the femoral tunnel. (Reprinted with permission.27)

teriorly positioned femoral tunnel (Fig 4). Repeat ar-

throscopy showed extensive medial patella facetcartilage loss, medial tilt, and a tight MPFL graft.Arthroscopic medial release and patella chondroplastywere performed, and patella tracking improved. Un-fortunately, the patient continued to have disablingpain and limitation of daily activities. An isolatedpatellofemoral arthroplasty was performed, whichgave her considerable pain relief and allowed her toreturn to low-demand activities (Fig 5).

Case 3

A 16-year-old female gymnast began having bilat-eral patellofemoral dislocations at age 13 years. Shetried physical therapy but continued to have left kneepatellofemoral dislocations with activities of daily liv-ing. In 2007 she underwent an Elmslie-Trillat proce-dure, lateral retinacular release, and MPFL repair tothe femur with suture anchors. She subsequently hadredislocation at 4 months postoperatively. In 2008 sheunderwent an MPFL reconstruction with a semitendi-

FIGURE 2. Lateral radiograph showing an anteriorly and proxi-mally positioned femoral tunnel in a 39-year-old woman after anallograft MPFL reconstruction was performed (case 1). Medialpatella subluxation and medial patella tilt developed from her

malpositioned MPFL graft.

3TECHNICAL FAILURE OF MPFL RECONSTRUCTION

nosus autograft. The femoral tunnel was anterior andproximal to the normal insertion site (Fig 6). Unfor-tunately, left knee recurrent lateral dislocations againdeveloped 3 months postoperatively. The patient be-came extremely disabled and had intolerable spasmsas a result of the dislocations. Despite bracing and adedicated physical therapy program, she began havingdislocations on a regular basis and was referred to ouroffice for evaluation and treatment. In 2010 we per-formed a revision MPFL reconstruction with semiten-dinosus allograft, and the patient has not had anyfurther patella dislocations.

Case 4

A 20-year-old woman had a lateral retinacular re-lease in 1999 for chronic patellofemoral instability. In2000 she underwent a medial tibial tubercle transferfor recurrent dislocation. She did well for 6 years butsubsequently had recurrent instability events. In 2006she had an MPFL reconstruction with semitendinosusautograft. She presented to our office in 2007 withcomplaints of daily subluxation episodes and an in-ability to run. On examination, she had positive lateralpatella apprehension and hyperlaxity. Plain radio-graphs showed evidence of trochlear dysplasia and ananteriorly malpositioned femoral tunnel (Fig 7). In2008 we performed a revision MPFL reconstructionwith semitendinosus allograft, and the patient’s con-

FIGURE 3. Intraoperative arthroscopic picture showing medialpatellofemoral overload and medial patellar tilt in a 39-year-oldwoman with a malpositioned MPFL graft (case 1). The arthroscopeis in the inferior-lateral arthroscopy portal looking up at the patella.The patient is supine.

dition has been stable since.

Case 5

A 19-year-old woman with a history of Ehlers–Danlos syndrome had bilateral lateral retinacular re-leases for chronic bilateral patellofemoral instabilityin 2005. Recurrent left knee patellofemoral instabilitydeveloped, and she underwent an MPFL reconstruc-tion with semitendinosus autograft in 2007. She didwell for 1 year, but then increasing medial retinacularpain and acute dramatic patella popping developed.On presentation to our office in 2009, the patient wasfound to have a positive medial patella subluxationtest and a tight MPFL graft. Plain radiographs showedan anteriorly positioned femoral tunnel (Fig 8). Sheunderwent surgery including release of the MPFLgraft, lateral patella stabilization, and debridement of amedial patella chondral lesion. The lateral one-third ofher patella tendon was sutured to the iliotibial band asa restraint to medial subluxation. Although she con-tinued to have occasional anterior knee discomfort

FIGURE 4. Axial MRI scan showing an anteriorly positionedfemoral tunnel in a 33-year-old woman after an allograft MPFLreconstruction (case 2). Significant medial patella facet arthritisand medial tilt developed from her over-tightened and malposi-

tioned MPFL graft.

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postoperatively, she had no further episodes of painfulpatella popping.

DISCUSSION

Patellofemoral stability involves the coordinatednteraction between static, dynamic, and osseous struc-

FIGURE 5. Lateral radiograph of isolated patellofemoral arthro-plasty performed in a 33-year-old woman for severe arthritis anddisabling pain after failed MPFL reconstruction (case 2).

FIGURE 6. Lateral radiograph showing an anteriorly and proxi-ally positioned femoral tunnel in a 16-year-old female gymnast

fter an autograft MPFL reconstruction (case 3). Recurrent lateralnstability developed. The arrow points to the anatomic MPFL

temoral insertion.

tures (Table 1). In full extension the patella is proxi-mal to the trochlear groove and is dependent on soft-tissue restraints for stability. The MPFL is responsiblefor guiding the patella into the trochlear groove duringthe first 30° of knee flexion.1 Correct patella centeringin the groove during early knee flexion is essential forpatellofemoral stability and is largely determined bythe dynamic and static soft-tissue structures. Withknee flexion beyond 30°, a non-dysplastic trochleargroove is the primary restraint to lateral patellar trans-lation.1 With increasing knee flexion, tension in the

PFL decreases considerably. In the setting of aormal trochlear groove and patellar height, thePFL has been found to be isometric between full

xtension and 70° of flexion.30 It provides restraint tolateral patella translation largely in the first 30° ofknee flexion with no measurable MPFL tension indeeper flexion.28 It is important to understand thattudies looking at MPFL tension have been performedn patients with normal anatomy and these biome-hanical relations may change when patella alta orrochlear dysplasia is present.

In these referred patients, anterior and proximallacement of the MPFL femoral graft insertion ledo 3 possible outcomes: medial patellofemoral ar-

FIGURE 7. Lateral radiograph showing an anteriorly and proxi-mally positioned femoral tunnel in a 20-year-old woman after anautograft MPFL reconstruction (case 4). Recurrent lateral instabil-ity developed. (malpos, malpositioned.)

icular overload, iatrogenic medial subluxation, or

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5TECHNICAL FAILURE OF MPFL RECONSTRUCTION

recurrent lateral instability (Table 2). When anMPFL graft is placed proximally on the femur,there is increased graft tension when the knee isflexed.28 As observed in 2 of our cases, patellaarticular destruction can occur from the very highcompressive force generated by a non-isometricMPFL reconstruction graft. When a malpositionedand over-tightened MPFL graft is combined with alateral retinacular release, iatrogenic medial sublux-ation and medial tilt can develop. When the graft is3 mm shorter than the intact MPFL and positioned5 mm proximal to the normal femoral attachmentsite, medial patellar tilt and peak medial patel-lofemoral pressure are dramatically increased.28

FIGURE 8. Lateral radiograph showing an anteriorly positionedfemoral tunnel in a 19-year-old woman after autograft MPFLreconstruction. Medial patella subluxation and medial patella tiltdeveloped from her malpositioned MPFL graft.

TABLE 1. Considerations in Evaluation of Patients WithPatellofemoral Instability

Dynamic Factors Static Factors

uadriceps/vastus medialisoblique

MPFL

Hip abductor strength Trochlear grooveCore stability Alignment (q angle, TT-TG

distance)Patella alta

Abbreviation: TT-TG, tibial tubercle-trochlear groove distance.

Medial patella subluxation is often overlooked as aause of symptoms because patients will complain ofhe patella moving laterally when the knee is flexed.atients often complain of pain and rapid lateral pa-

ella translation with early knee flexion. The medialatella subluxation test is easily performed by flexinghe knee as a medial translation force is maintained onhe patella. Patients will typically have dramatic re-roduction of symptoms.The third outcome was recurrent lateral patellofemo-

al instability. Nonanatomic femoral MPFL graft inser-ion leads to increased graft tension as the knee isexed. Over time, this can lead to stretching of theraft and failure. It is interesting that tendon graftssed for MPFL reconstruction are typically substantiallytouter than the native MPFL yet can be completelyestroyed by the extreme force generated by improperositioning.Proper femoral placement of an MPFL reconstruc-

ion graft is difficult and requires a thorough under-tanding of medial knee anatomy (Table 3). The in-

sertion site of the MPFL, in the saddle between themedial epicondyle and the adductor tubercle, is typi-cally more posterior than expected.31 Palpating thedductor magnus tendon insertion can help with ori-ntation during surgery because the normal MPFLnsertion is anterior and distal to this. We like to maken incision large enough to clearly identify the adduc-or tendon and the medial collateral ligament. Weecommend inserting a guidewire into the desiredemoral location and then confirming accurate place-ent by checking graft isometry and using fluoros-

opy. If the graft is fixed first in the patella and

TABLE 2. Adverse Outcomes Associated WithMalpositioned MPFL Femoral Tunnel

1. Medial patellofemoral articular overload2. Iatrogenic medial subluxation3. Recurrent lateral instability (from excessive graft tension and

failure)

TABLE 3. Pearls for Confirming Appropriate MPFLGraft Insertion Intraoperatively

1. Use a large enough skin incision to identify anatomy andclearly palpate the saddle between the medial epicondyle andthe adductor tubercle.

2. Palpate the adductor magnus tendon to help with orientation:the MPFL femoral insertion is anterior and distal to this.

3. Confirm guidewire placement with fluoroscopy.

4. Check graft isometry with a free suture.

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tunneled posteriorly, it can be wrapped around theguide pin to check isometry during knee motion. Ide-ally, graft isometry should be maintained during thefirst 50° to 70° of flexion and loosen slightly in ter-minal flexion. If the graft tightens during flexion, thefemoral attachment point is likely too proximal. Onradiographs, the optimal guide pin position is 1 to 2mm anterior to the posterior cortical extension lineand 1 mm proximal to the posterior aspect of theBlumensaat line (Fig 8).29,32

Understanding the possible errors in femoral tunnelositioning during MPFL reconstruction, as well asheir complications, is key to performing the proce-ure successfully. The femoral tunnel can be posi-ioned too proximally or too distally, with proximalunnels causing grafts to become increasingly tight inexion and distal tunnels causing tightness in exten-ion. Femoral tunnels can also be placed too anteriorlyr too posteriorly. In addition to tunnel position, therere other factors that contribute to a successful MPFLeconstruction. The position of the patellar tunnel andhe presence of patella alta can also affect the functionf the graft. Perhaps the most important issue, how-ver, is how the graft is tensioned. Even a perfectlyositioned graft can cause serious problems if it isxed too tightly.Regardless of the tunnel positions, a key factor inPFL reconstruction is to maintain appropriate ten-

ion of the graft throughout knee range of motion.haunat and Erasmus33 reported on 2 patients withnterior knee pain and decreased range of motion afterver-tightened MPFL reconstructions. Beck et al.34

showed that 2 N of graft tension restored normalatellar translation. Higher loads (10 and 40 N) sig-ificantly restricted motion and increased medialatellofemoral contact pressure. After confirmation ofnatomic positioning of the tunnels, it is important toension the graft with the patella centered in the troch-ea (Table 4). Securing fixation without maintainingorrect patellar position can over-constrain the patelland lead to symptoms of medial overload and possiblyubluxation. In addition, it is also possible to make theraft too loose even if the tunnels are positionedppropriately.

It is likely that none of the MPFL reconstructionshat are currently being performed are truly anatomic,r precisely reproduce the normal knee biomechanics.ost techniques use a single or double cord-shaped

raft, much thicker and stronger than the ribbon-haped native MPFL. In fact, one could argue that it isot necessary to reproduce normal biomechanics to

revent further patellar instability episodes and r

achieve seemingly good clinical results. In a recentstudy of 29 patients who underwent successful MPFLreconstruction with a minimum follow-up of 2 years,9 of 29 were believed to have improperly positionedfemoral tunnels by radiographic analysis and 10 of 29were believed to have improper placement by MRIanalysis.27 The authors found no correlation betweenunnel position and clinical outcome. They did urgeaution in interpreting their study results, suggestinghat the outcome measurement tools may not haveeen sensitive enough to identify differences betweenroups, and noted their concern that patients withalpositioned tunnels “may have an increased inci-

ence of osteoarthritis in the long term.”27 We sharehis concern and advocate anatomic placement of theemoral and patellar ends of the graft with fixation thateproduces the normal tension characteristics of theative MPFL.MPFL reconstruction is a challenging procedure inhich many factors can affect the outcome. Graftosition in both the femur and the patella, as well asraft tensioning, contribute to the overall outcome ofhe reconstruction. Whereas malpositioning of theemoral tunnel may not necessarily always lead toailure of an MPFL reconstruction or be the sole causef failure, tunnel positioning does play an importantole in maximizing the function of the graft. Weelieve that malpositioning of the MPFL femoral graftnsertion in these cases contributed to iatrogenic me-ial subluxation, medial patellofemoral articular over-oad, and recurrent lateral instability. Similar to thevolution of anterior cruciate ligament reconstruction,e believe that anatomic positioning is more impor-

ant than graft choice or fixation method in MPFL

TABLE 4. Pearls for Setting Appropriate MPFLGraft Tension

1. In full extension, the patella is not centered in the trochleargroove and estimating correct MPFL tension/length isdifficult.

2. Have an assistant hold the lateral border of the patella flushwith the lateral trochlea in 30° of knee flexion while the graftis tensioned. This prevents overtightening the MPFL graft.

3. Tension the MPFL with the knee in 60° of knee flexion, with thepatella fully centered in the trochlear groove. This is when theMPFL is at its maximal length. A checkrein to lateraltranslation will exist without overtensioning the patella.

4. The goal is not to over-tighten the MPFL graft. The MPFLgraft should guide the patella into the trochlear during earlyknee flexion. The patella should engage and center in thetrochlea at 20° to 30° of knee flexion.

econstruction surgery.

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7TECHNICAL FAILURE OF MPFL RECONSTRUCTION

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