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abstractFull article available online at Healio.com/Orthopedics. Search: 20131021-25

Medial and Lateral Retinaculum Plasty for Congenital Patellar Dislocation due to Small Patella SyndromeCheng-hai Wang, MD; Lei Shu, MD; Long-fei Ma, MD; Jian-Wei Zhou, MD; gang Ji, MD; fei Wang, MD; Juan Wang, MD

The objective of this study was to explore the clinical effect of medial and lateral retinaculum plasty for congenital patellar dislocation due to small patella syndrome. Twelve patients with congenital patellar dislocation due to small patella syndrome treated at the authors’ hospital between January 2005 and February 2010 were en-rolled in the study. The study group comprised 4 men (4 knees) and 8 women (8 knees) with an average age of 10.5866.91 years. All patients underwent medial and lateral retinaculum plasty. Clinical evaluation included the number of patellar redislo-cations, patellar apprehension sign, Kujala score, subjective questionnaire score, and patella lateral shift and patellar tilt angle measured using a cross-sectional computed tomography scan. All patients were followed up, and the shortest follow-up time was 2 years. Kujala scores improved from 49.2066.20 preoperatively to 80.1065.80 post-operatively. Subjective questionnaire scores indicated that the excellent and good rate was 75%. In addition, a significant difference existed in the patellar tilt angle and patella lateral shift between pre- and postoperative results (P,.05). Medial and lateral retinaculum plasty for patients with congenital patellar dislocation due to small pa-tella syndrome can be effective to correct the tracking of the patellofemoral joint and improve knee function.

The authors are from the Department of Orthopaedic Surgery (CW), Affiliated Hospital of Hebei, University of Engineering; the Department of Orthopaedic Surgery (LS, JZ, GJ, FW, JW), Third Hos-pital of Hebei Medical University, Hebei, China; and the Department of Orthopaedic Surgery (LM), Affiliated Hospital of Jining Medical University, Shandong, China.

Drs Wang (Cheng-hai) and Shu contributed equally to this study.The authors have no relevant financial relationships to disclose.Correspondence should be addressed to: Fei Wang, MD, Department of Orthopaedic Surgery, Third

Hospital of Hebei Medical University, 139 Ziqiang Rd, Shijiazhuang, Hebei, China 050051 (doctorwf@yeah.net).

doi: 10.3928/01477447-20131021-25

Figure: Computed tomography scan showing pa-tella dysplasia and femoral trochlear dysplasia as-sociated with patellar dislocation in a 31-year-old woman who reported the inability to completely extend her left knee joint and occasionally expe-rienced knee pain since childhood but had not received any treatment since birth (A). Computed tomography scan 2.5 years postoperatively (B).

A

B

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Congenital dislocation of the patella is a rela-tively rare clinical dis-

ease. Congenital dislocation of the patella is identified by an irreducible, permanent lateral dislocation. In 1968, Green et al1 described congenital dis-location of the patella for the first time. Previous literature reported that congenital dislo-cation of the patella is often bi-lateral and familial.2 In 1979, Scott and Taor3 first described “small patella syndrome,” which is characterized by pa-tellar aplasia or hypoplasia and pelvic abnormalities.

Between January 2005 to February 2010, twelve pa-tients with congenital patellar dislocation due to small pa-tella syndrome were treated in the author’s hospital us-ing a new surgical technique, which was termed medial and lateral retinaculum plasty. The purpose of this study was to review and evaluate the authors’ experi-ences with surgery for congenital patellar dislocation due to small patella syndrome.

Materials and MethodsTwelve patients with congenital pa-

tellar dislocation due to small patella syndrome treated at the authors’ hospital between January 2005 and February 2010 were enrolled in the study. The study group comprised 4 men (4 knees) and 8 women (8 knees) with an average age of 10.5866.91 years. All patients underwent medial and lateral retinaculum plasty. Patients’ demographic data are shown in Table 1. All patients reported pain around the knee. Patellar crepitus was positive in all patients. Knee radiography and com-puted tomography (CT) scan verified the occurrence of patellar dislocation. Knee CT images indicating dislocation of the patella in the family for 3 generations were obtained (Figures 1-3).

surgical techniqueThe same senior surgeon conducted the

surgery in all patients. Patients were placed in the supine position and spinal anesthesia was administered. Anteromedial, antero-lateral, and superolateral portals were rou-tinely adopted. Diagnostic arthroscopy was performed to evaluate the patellar trajectory, cartilage degeneration of the patellofemoral joint, and associated concomitant injuries and to deal with intra-articular lesions (such as meniscectomy, repair, cartilage trim-ming, and removal of loose bodies).

For the withdrawal of the arthroscope, a 3-cm longitudinal incision in the medial edge of the patella was made, cutting the skin, subcutaneous tissue, and deep fascia and exposing the vastus medialis and me-dial patellar retinaculum. A transverse dis-section was made along the junction of the vastus medialis and medial retinaculum to the medial femoral condyle with the aim of dividing both. The medial retinaculum was pulled proximally and laterally near the up-per pole of the patella with temporary fixa-tion. Finally, the vastus medialis was pulled

distally and laterally near the middle line of the patella with temporary fixation.

A 3-cm longitudinal incision in the lat-eral edge of the patella was made, and the skin was dissected, subcutaneous tissue and deep fascia in turn that would expose the lateral patellar retinaculum. A section with a 1-cm width in the lateral patellar retinaculum along the line from the lateral upper margin of the patella to the lateral femoral condyle was grafted to the junc-tion of the lateral patellar retinaculum and the tensor fasciae latae. The free end of the lateral patellar retinaculum was pulled to the center of the patellar lateral edge and temporarily fixed on the lateral edge of the patella. Assessment of patellar ac-tivity by hand, static observation of the patellofemoral joint relationship, and dy-namic observation of the patella trajectory in flexion and extension activities through the arthroscope were performed. Finally, the vastus medialis and the medial patel-lar retinaculum were sutured and fixed on the prepatellar and patellar medial mar-gin with #1 PDS sutures (Ethicon, Inc,

Table 1

Demographic Data

Patient No. Sex Side

Preop Treatment

Age at Diagnosis,

y

Age at Operation,

y ComplicationsFollow-up, mo

1 Female Right None 6 8 None 24

2 Female Right None 5 9 None 24

3 Male Right None 9 11 None 30

4 Female Left None 8 12 None 36

5 Male Right None 6 9 None 30

6 Female Left None 5 11 None 24

7 Female Right None 9 9 None 36

8 Male Left None 8 9 None 30

9 Female Right None 31 31 None 30

10 Female Right None 3 3 None 24

11 Male Left None 5 5 None 24

12 Female Left None 7 10 None 42

Abbreviation: preop, preoperative.

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Somerville, New Jersey), and the free end of the lateral patellar retinaculum was re-sutured on the patellar lateral border with #1 PDS sutures (Figures 4, 5).

Postoperative RehabilitationThis surgery does not require that pa-

tients wear a brace for external fixation. Two days postoperatively, patients began to per-

form exercises such as isometric contraction of the quadriceps femoris muscle, straight-leg raising, patella traction, and mild knee flexion. Two weeks postoperatively, patients began continuous passive motion exercises and active and assisted knee range of motion exercises and could perform knee flexion to 60°. Four weeks postoperatively, patients could flex the knee to 90° and were able to achieve partial weight bearing on the af-fected limb. Six weeks postoperatively, pa-tients could flex the knee to 120°, achieve full weight bearing on the affected limb, and perform jogging exercises. Six months post-operatively, patients were able to return to their normal physical activities.

Follow-upKnee range of motion was recorded.

The patella lateral shift and patellar tilt an-gle were measured using a cross-sectional CT scan with 20° of knee flexion. The Ku-jala score4 and a subjective questionnaire score5 were used to assess knee function.

Statistical AnalysisStatistical analysis was performed using

the paired t test, and P values less than .05 were defined as significantly different.

resultsOne case was treated with medial and

lateral retinaculum plasty combined with medial translocation of the tibial tuberos-

Figure 1: Computed tomography scan showing patella dysplasia and femoral trochlear dysplasia associated with patellar dislocation in a 31-year-old woman who reported the inability to completely extend her left knee joint and occasionally experienced knee pain since childhood but had not received any treatment since birth (A). Computed tomography scan 2.5 years postoperatively (B).

1A 1B

2Figure 2: Computed tomography scan of the mother (aged 56 years) of the patient in Figure 1 showing femoral trochlear dysplasia associated with patellar dislocation.

3Figure 3: Computed tomography scan of the son (aged 3 years) of the patient in Figure 1 showing femoral trochlear dysplasia associated with patellar tilt.

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ity. The wound healed in time and had no effect on the recovery of joint function. The shortest follow-up time was 2 years. Kujala scores improved from 49.2066.20 preop-eratively to 80.1065.80 postoperatively. Six patients had excellent results, 3 had good results, and 3 had fair results; the ex-cellent and good rate was 75%. Postopera-tively, the patellar tilt angle and patella lat-eral shift were restored to the normal range with statistical significance (P,.05) com-pared with preoperative values. Follow-up data are presented in Table 2.

discussionThe etiology of congenital patellar

dislocation due to small patella syndrome

is still unknown but may be related to ge-netic issues or trochlear dysplasia and pa-tellar retinaculum. Congenital permanent dislocation of the patella is a disorder of the knee joint in which the patella is per-manently displaced. Even in the process of knee extension, the patella is fixed on the lateral aspect of the femoral condyle. Early diagnosis and definitive treatment are generally recommended to prevent subsequent degenerative changes of the knee joint and to attempt to restore partial knee function.

The pathological changes of patellar congenital dislocation consisted of patel-lar dysplasia, patellar dislocation in the superior and lateral aspect of the trochlea,

trochlear dysplasia, lateral insertion of the patellar tendon, iliotibial tubular hypertro-phy, short and deformed quadriceps, vas-tus lateralis adherent to the iliotibial band and tensor fasciae latae, thin and stretched vastus medialis, knee valgus, and tibial external rotation.6-8 Abnormal anatomic and biomechanical characteristics of the patellofemoral joint may result in abnor-mal contact of the patellofemoral joint and increased or reduced local stress of the articular surface, resulting in damage to the articular cartilage.

This study found that the medial and lateral patellar retinacula of the knee were closely associated with patellofemoral joint stability. The medial patellar retinac-

Figure 4: Schematic diagram of the surgical procedure. A longitudinal incision was made following the medial border of the patella to dissect the vastus medialis and medial patellar retinaculum, and then a transverse dissection was made along the junction of the vastus medialis and medial patellar retinaculum to the medial femoral condyle with the aim of dividing both (A). The vastus medialis and medial patellar retinaculum were divided (B). The medial patellar retinaculum was pulled proximally and laterally near the upper pole of the patella with fixation (C). The vastus medialis was pulled distally and laterally near the middle line of the patella with fixation, and then the 2 overlapping tissues were sutured together (D).

4D4C4B4A

Figure 5: Schematic diagram of the surgical procedure. A section with a 1-cm width of the lateral patellar reti-naculum along the line from the lateral upper margin of the patella to the lat-eral femoral condyle was grafted to the junction of the lateral patellar reti-naculum and the tensor fasciae latae (A). The free end of the lateral patellar retinaculum is shown (B). The free end of the lateral patellar retinaculum was fixed on the patellar lateral border (C).

5A 5B 5C

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ulum consisted of the medial patellofemo-ral ligament, medial patellotibial ligament, and medial patellomeniscal ligament.9-11 The lateral patellar retinaculum consisted of the lateral patellofemoral ligament, lateral patellotibial ligament, and lateral epicondylopatellar ligament.12-15 The me-dial and lateral patellofemoral ligament may influence the patellar lateral shift. Patellar instability often occurred on the basis of knee dysplasia, medial soft tissue relaxation, medial muscle weakness, and tensive lateral retinaculum. Because of the long-term bad cacothesis of the patello-femoral joint, patellar medial retinacular relaxation and the development of lesions will be further accelerated.16 Ghanem et al8 found that the patella was underdevel-oped because it was not placed in the nor-mal femoral trochlea and was dislocated superiorly and posteriorly with reference to the trochlea; it was fixed laterally at the level of the lateral condyle.

Stanisavljevic et al17 described a com-prehensive surgery technique to treat con-genital, irreducible permanent lateral dis-location of the patella, and the results at 2-year follow-up indicated that the clini-cal effect was good. The same procedure was used by McCall and Lessenberry18 in 2 cases of congenital dislocation of the patella; they also achieved good clinical

results. Other authors adopted the Conn procedure for congenital dislocation of the patella and also obtained satisfactory results.19,20 Storen21 used medial trans-fer of the tibial tubercle with release of the lateral capsule of the knee to treat 2 children with congenital permanent irre-ducible lateral patellar dislocations, and clinical results were good. However, the current authors believe that tibial tuber-cle transfer surgery should be avoided in younger patients because of the high risks associated with this procedure.

Most of the patients with congenital dislocation of the patella were adolescents with immature bone structure. Tibial tu-berosity transfer or medial patellofemoral ligament reconstruction may damage the epiphyseal plate, leading to knee dyspla-sia. Therefore, the soft tissue surgery was the best choice for these patients. In the current study, all 12 patients had patellar medial soft tissue laxity and lateral soft tissue contracture. Medial and lateral reti-naculum plasty were necessary for them. In 1 of the 12 patients, a limited procedure was performed by medial translocation of the tibial tuberosity combined with medial and lateral retinaculum plasty; a good out-come was obtained with this procedure.

Medial patellofemoral ligament recon-struction for these patients may increase

the risk of patellar fracture. In this study, the authors adopted medial and lateral retinaculum plasty for 12 patients with congenital dislocation of the small patella in the clinic. No recurrent dislocation oc-curred postoperatively. Kujala score in-creased from 49.2066.20 preoperatively to 80.1065.80 postoperatively. Medial and lateral retinaculum plasty could markedly improve knee function and quality of life.

Patellar tracking was guided by the patellar tendon, patellar lateral retinacu-lum, and patellar medial retinaculum in the process of knee flexion and exten-sion. The authors adopted medial and lateral retinaculum plasty for the patients with congenital dislocation of the small patella to change the tension and attach-ment point of the patellar retinaculum. This operation may change the patella trochlear from the abnormal position to the center of the femoral trochlea. Abnor-mal patellar tracking was modified to the normal position. Mean patellar tilt angle decreased from 13.80°63.65° preop-eratively to 7.60°61.71° postoperatively. Mean patellar lateral shift decreased from 22.7060.65 mm preoperatively to 8.2060.42 mm postoperatively. The dif-ference was statistically significant be-tween the pre- and postoperative results.

Medial and lateral soft tissue structure reconstruction could adjust the position of the patella and reduce lateral patellofemo-ral joint pressure. Lateral release and me-dial tightening of the retinaculum at the same time could move the patella to the normal position and prevent the tilting of the patella to the medial position.

conclusionMedial and lateral retinaculum plasty

surgery could improve knee function and quality of life for patients with congenital patellar dislocation due to small patella syndrome. Early surgical treatment could prevent subsequent degenerative changes of the knee and patient disability. This technique needs further clinical study and application.

Table 2

Paired t Test Preoperatively and 24 Months Postoperatively

Variable Preop 24 mo Postop t P

Kujala score 49.2066.20 80.1065.80 213.598 .000

Patellar tilt angle, deg 13.8063.65 7.6061.71 11.431 .000

Patella lateral shift, mm 22.7060.65 8.2060.42 15.241 .000

Knee flexion, deg 126.3366.33 125.9266.57 0.532 0.605

Subjective questionnaire, No. (%)

Excellent 6 (50)

Good 3 (25)

Fair 3 (25)

Abbreviations: deg, degrees; postop, postoperatively; preop, preoperatively.

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