The Influence of Iliotibial Tract on Patellar Tracking Chi-Chuan Wu, MD* Chun-Hsiung Shih, MD†

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FEATURE ARTICLE

Abstract

Thirty patients with 49 snapping hips and patellar Significant improvements in the congruence angle and malalignment underwent surgical release of the iliotibial lateral patellofemoral angle were noted on Merchant tract contracture over the trochanteric area. Minimal fol- radiograph for all knees (PϽ.01). On CT, at 20° and 45° low-up was 2 years (average 4.6 years, range: 2-9 years). knee bending, all congruence, lateral patellofemoral, and Eight patients underwent computed tomography (CT) patellar tilt angles significantly improved postoperatively preoperatively and 1 month postoperatively to investigate in 8 knees (PϽ.01). Iliotibial tract affects patellar tracking the patellar location in the patellofemoral articulation with and dominates lateral patellar supporting structures. knee bending at 0°, 20°, 45°, 60°, and 90°.

Anterior knee pain is common in orthope- patellar supporting structures have not yet examined regardless of the presence or dics and patellar malalignment is a com- been defined. absence of snapping hip.22,24,25 The clini- mon disorder that causes this pain.1-10 The Snapping hip, an uncommon disorder, cal features of patellofemoral pain syn- cause of patellar malalignment has been is caused by iliotibial tract contracture drome included aggravated anterior knee investigated and predisposing factors (external type).20-23 Snapping hip usually pain during stair climbing, knee soreness include an abnormal patellofemoral artic- is diagnosed because of discomfort or after prolonged sitting, and positive ulation, abnormal lower extremity align- snapping in the upper thigh. The senior grinding tenderness in the patellofemoral ment, and abnormal patellar supporting author (C.-C.W.) created a hypothesis that joint.7,19,26-28 When external snapping hip structures.11-13 Patellar tracking is most iliotibial tract contracture may cause was combined in the ipsilateral knee, commonly affected by abnormal patellar external snapping hip and patellar anteroposterior (AP) pelvic, AP and lat- supporting structures.11-13 malalignment. Therefore, treatment of eral knee, and Merchant tangential view Patellar malalignment usually occurs such a contracture could concomitantly radiographs were obtained.24 as lateral tilting or lateral patellar sublux- correct both disorders. If so, the impor- Patients who had both clinical disor- ation, which is due to weakened medial tance of the iliotibial tract related to patel- ders, malaligned patella on the Merchant soft tissues or tight lateral soft tissues lar tracking could be assessed. view, and normal patellofemoral articula- around the patella.7,14,15 Iliotibial tract also To test this hypothesis, a prospective tion and lower extremity alignment on affects patellar tracking.1,16-19 However, study was performed. A pilot clinical plain radiograph were candidates for sur- its role and importance regarding lateral study investigated the validity of the con- gical release of the iliotibial tract contrac- cept and computed tomography (CT) ture. Patients who had patellofemoral was supplemented to test the hypothesis. pain syndrome and snapping hip but no From the *Department of Orthopedics, Chang malaligned patellae on the Merchant Gung Memorial Hospital, Chang Gung Institute of Technology, Taoyuan; and the †Department of MATERIALS AND METHODS radiograph were excluded due to the Orthopedics, Kang Ning General Hospital, Pilot Study inability to objectively evaluate the Taipei, Taiwan. From February 1993 to July 2000, improvement quantitatively. This study was supported by the National all consecutive patients (aged Ͻ40 The 7-year pilot study included 37 Science Council (NSC 88-2314-B-182A-062), years) who presented to the senior patients and 60 hips. Average patient age Executive Yuan, China. Reprint requests: Chi-Chuan Wu, MD, Dept of author’s (C.-C.W.) orthopedic out- was 28 years (range: 21-35 years) with a Orthopedics, Chang Gung Memorial Hospital, 5 patient department due to patello- 1:2 male to female ratio. Twenty-three Fu-Hsin St, 333, Kweishan, Taoyuan, Taiwan. femoral pain syndrome were routinely patients had bilateral disorders and 14

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unilateral. Duration of anterior knee graphs were recorded. Quadriceps angle, and patellar tilt angle was evalu- pain was intermittent for several months strengthening and hamstring stretching ated using two-tailed paired Student’s t to several years. Conservative treatment exercises were encouraged. test. PϽ.05 was considered statistically did not improve pain. Trochanteric area Knee function was evaluated using significant. soreness was noted in 22 hips, with sev- Micheli’s grading and four grades were The correlation of lateral patello- eral months’ to several years’ intermit- divided. A satisfactory result included femoral angle and patellar tilt angle tent duration. an excellent or good outcome.18 Patellar was evaluated using Pearson correla- No abnormal patellofemoral articula- tracking was evaluated by congruence tion coefficient (r). tions or lower extremity malalignments angle and lateral patellofemoral angle. were noted in these patients. Twenty-six RESULTS knees had lateral patellar subluxation Computed Tomography Study Pilot Study and 34 knees had simple lateral patellar From August 1998 to July 2000, all Thirty patients with 49 knees under- tilting. In this study, patellar malalign- consecutive new patients were exam- went minimum 2-year follow-up (aver- ment was defined as lateral patellar sub- ined with CT (HiSpeed Advantage; GE age, 4.6 years; range: 2-9 years). Knee luxation with an abnormal congruence Medical Systems, Milwaukee, Wis) function improved in 41 knees (P=.001). angle (Ͼ0°)29,30 and lateral patellar tilt- over the upper, middle, and lower Seven patients could not be contacted. ing with a normal congruence angle but patella with knee bending at 0°, 20°, Congruence angle improved from abnormal lateral patellofemoral angle 45°, 60°, and 90°. 8°Ϯ9.6° to 1.6°Ϯ7.8° (P=.004). Lateral (Ͻ0°).18,31,32 Eight patients were included in this patellofemoral angle improved from study. Average patient age was 29 years Ϫ1.3°Ϯ5.8° to 7.5°Ϯ4.9° (PϽ.001) Operative Technique (range: 22-34 years) with a 1:2 male to (Figure 1). Under spinal anesthesia, patients female ratio. All patients had bilateral No wound infection or other compli- were placed in the supine position with disorders, and no abnormal patello- cations were noted. the affected hip elevated. With the hip in femoral articulation or lower extremity full flexion and adduction, a 2-cm skin malalignment was noted. Computed Tomography Study incision was made longitudinally along Computed tomography was obtained All 8 patients (16 knees) underwent the posterior border of the femur, just preoperatively and 1 month postopera- CT. Preoperatively, patellae were later- distal to the greater trochanter. The skin tively. Further CT could not be obtained ally subluxed (congruence angle Ͼ0°) was extracted and the underlying fascia due to monetary expense. Consequently, with 0°, 20°, or 45° knee bending (Table was exposed. The fascia was transverse- only a Merchant radiograph was regular- 1). However, because the femoral artic- ly dissected with a scalpel from the pos- ly taken at follow-up. Daily activity was ular surface was partly blurred, patellar terior toward the anterior aspect of the not restricted postoperatively. location could not be measured with 60° thigh. The hip was gradually extended, Patellar location in the patello- or 90° knee bending. allowing the contracted fascia to slide femoral articulation was investigated. One month postoperatively, patellar backward. Dissection continued until all The best (clearest) of three scans over subluxation was not significantly snapping resolved. different levels of the patella was cho- improved with 0° knee bending. With index finger palpation, only sen. In addition to the congruence and However, significant improvement was involved contracted soft tissues were lateral patellofemoral angles, patellar noted with 20° and 45° knee bending released. Contracted soft tissues that did tilt angle also was measured. Patellar (PϽ.01), and the laterally subluxed not contribute to the snapping hip were lateral subluxation was determined by patellae had been reduced to normal preserved without release. The hip was congruence angle and patellar lateral location (Figure 2). tested in adduction-flexion to adduc- tilting, lateral patellofemoral, or patel- With 0° knee bending, lateral patello- tion-extension and back and forth to lar tilt angles (Ͻ8°).30 femoral angle and patellar tilt angle was ensure complete release. After hemo- positive pre- and postoperatively. The stasis was achieved, the wound was Statistical Analysis improvement was not significantly sig- closed with absorbable sutures. A closed In the pilot study, knee function nificant. drain was inserted according to the improvement was evaluated using With 20° knee bending, lateral amount of bleeding.25 Fisher’s exact test and change of con- patellofemoral angle was negative pre- Postoperatively, patients were permit- gruence angle and lateral patello- operatively and improved postopera- ted to ambulate without aids as early as femoral angle was evaluated using two- tively (PϽ.01). Patellar tilt angle was possible. Daily activity was increased as tailed paired Student’s t test. Statistical positive preoperatively and significant- tolerated. Patients underwent 1-month, significance was considered PϽ.05. ly improved postoperatively (PϽ.01). 6-month, 1-year, and annual follow-up. In the CT study, change of congru- With 45° knee bending, lateral Clinical features and Merchant radio- ence angle, lateral patellofemoral patellofemoral angle and patellar tilt

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TABLE 1 Change of Relative Patellar Location Pre- and Postoperatively*

Knee Bending Measurement Preoperatively Postoperatively P Value 0° Congruence angle 26.5±18.4/14Ϯ21.8 10.3Ϯ17.1/10.4Ϯ7.9 .048/.33 Lateral patellofemoral angle 4Ϯ4.2/5Ϯ3.8 6.5Ϯ4.9/5.6Ϯ4.2 .11/.38 Patellar tilt angle 8.8Ϯ4.4/10Ϯ3.8 11.9Ϯ4.6/12.5Ϯ2.7 .07/.052 20° Congruence angle 5Ϯ9.7/6.8Ϯ7.9 Ϫ11.5Ϯ14.6/Ϫ8.6Ϯ7 .002/.001 Lateral patellofemoral angle Ϫ1.3Ϯ4.4/Ϫ0.3Ϯ7.9 8.1Ϯ4.6/9.4Ϯ3.2 .003/.008 Patellar tilt angle 5Ϯ3.8/6.6Ϯ6.9 13.1Ϯ4.6/14.4Ϯ3.2 .007/.02 45° Congruence angle 5.8Ϯ6.2/4.8Ϯ10.8 Ϫ10.6Ϯ9.4/Ϫ6.9Ϯ4.9 .002/.01 Lateral patellofemoral angle 2.5Ϯ2.7/1.9Ϯ7 11.3Ϯ3.5/13.1Ϯ2.6 .001/.003 Patellar tilt angle 8.1Ϯ3.7/7.5Ϯ6.5 15.6Ϯ3.2/17.9Ϯ2.5 .003/.003

*Represented as right side/left side.

angle were positive preoperatively and when external snapping hip is treated, significantly improved postoperatively the incision wound should be proximal (PϽ.01) (Figure 3). to the insertion of the gluteus maximus. The correlation of lateral patello- In this study, the approach wound is just femoral angle and patellar tilt angle distal to the greater trochanter.25 A was high (0.90ϽrϽ1) pre- and postop- Lateral retinacular release also is per- eratively (Table 2). formed for patellar malalignment, with a No wound infection or other com- reported success rate between 63% and plications were noted. 100%.5,12,17,18,39-41 Theoretically, the effect of iliotibial tract release should be DISCUSSION less than lateral retinaculum release, as B The anatomy of lateral patellar sup- the majority of lateral patellar support- porting structures has been described ing structures are divided in the latter. and the iliotibial tract does not directly Although CT investigation of the patel- contact the lateral patellar edge.33-37 lar location in the patellofemoral articu- The connection between the iliotibial lation after lateral retinacular release has tract and lateral patellar edge includes not yet been reported, significant im- C the iliopatellar ligament and lateral provement of the congruence angle has Figure 1: Merchant tangential radiographs of retinaculum. The definite role and been reported using Merchant tangential a 27-year-old woman with left patellar importance of the iliotibial tract for lat- radiographs.41 In this study, release of malalignment syndrome of several years’ eral patellar supporting structures have the contracted iliotibial tract resulted in duration demonstrate patellar lateral sub- not yet been defined. Under common an excellent result. luxation (A). Conservative treatment failed. Because external snapping hip was noted circumstances, directly dividing the Patellar malalignment usually is concomitantly, the iliotibial tract was released iliotibial tract to test the traction effect treated nonoperatively initially with a over the trochanteric area. The subluxed is impractical. In this prospective study, reported success rate as high as patella was reduced to the normal location 1 releasing the iliotibial tract contracture 90%.2,7,8,18,26,41-44 However, when patel- month postoperatively (B). At 8-year follow- to treat snapping hip also corrected lar malalignment is associated with up, the patellar location was normal (C). malaligned patella, which proves that snapping hip, theoretically, conserva- the iliotibial tract dominates lateral tive methods are of no avail. Although effective. It is unnecessary to treat both patellar supporting structures. muscle power can be enforced by disorders at two different areas, which Although snapping hip is uncom- strengthening exercise, the strength of may result in complications.17,39-41 mon, its cause has been studied in detail. the vastus medialis does not surpass the Traditionally, patellofemoral pain Despite the fact that it can be internal or traction power provided by the con- syndrome is diagnosed by clinical fea- external, the latter is more common. tracted iliotibial tract. In other words, tures.4,7,45 Compared with CT or mag- Moreover, the most common cause is when both disorders are present, surgi- netic resonance imaging, the Laurin iliotibial tract contracture. Contracture cal correction is more practical. In this (20° knee bending) and Merchant (45° of the anterior gluteal fascia also causes study, release of the iliotibial tract con- knee bending) views are considered external snapping hip.20-25,38 Therefore, tracture in the trochanteric area was unreliable when detecting patellar loca-

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A B C D Figure 2: A 29-year-old woman with bilateral patellar malalignment syndrome and external snapping hip underwent iliotibial tract release. The subluxed patellae were reduced to the normal location 1 month postoperatively. CT was performed with knee bending pre- (upper image) and postoperatively (lower image) at 0° (A), 20° (B), 45° (C), and 60° (D).

A B C D Figure 3: A 31-year-old man presented with bilateral patellar malalignment syndrome and external snapping hip of Ͼ1 year’s duration. The iliotibial tract was released and tilted patellae were reduced to the normal location 1 month postoperatively. CT was performed with knee bending pre- (upper image) and postoperatively (lower image) at 0° (A), 20° (B), 45° (C), and 60° (D).

tion in various angles.45-48 However, on tion postoperatively. A significant im- compression) precludes evaluation of the contrary, in this study, 20° and 45° provement in patellar location is only true improvement pre- and postopera- knee bending provided excellent views demonstrated postoperatively when the tively. Quantitative measurement with to evaluate the postoperative results. knee is flexed to further stretch the ili- congruence angle, lateral patellofemoral With knee extension (0° bending), otibial tract. angle, and patellar tilt angle has proven surgical correction does not significantly In this study, some patients with effective in this study. alter patellar location. However, in some patellofemoral pain syndrome and snap- Lateral patellofemoral angle and cases, the subluxed patellae can be ping hip were excluded because Mer- patellar tilt angle are useful in evaluating reduced to normal location (Figure 2). chant radiograph did not reveal patellar patellar lateral tilting. Because the corre- The assumption is that in these cases, malalignment. In these patients, altered lation coefficient is high (0.90ϽrϽ1), iliotibial tract contracture is so severe patellar location could not be evaluated either can be used for clinical evaluation. that the tension of the resting vastus by plain radiograph. Series CT is effec- The operative results in this study are medialis fails to maintain peripatellar tive; however, it is costly. better than those of patellar malalignment soft-tissue balance. Once the contracture Clinically, the criteria used to classify treated with lateral patellar retinacular is released, the balance among the rest- patellar malalignment have not been release.5,12,18,39 In the present study, ing muscles is recovered. In some cases, consistent.10,28,29,47-50 Roughly classify- patients were relatively younger (age less severe iliotibial tract contracture ing patellar malalignment as dislocation, range: 21-35 years) and degenerative does not significantly alter patellar loca- subluxation, or tilting (excessive lateral knee change was less likely. Patients

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