Abstract
Background
Treatment of congenital and habitual dislocation of the patella in syndromic adolescents can be difficult due to accompanying soft-tissue and/or osseous abnormalities often present in the knee. The aim of this study was to report the results of surgical treatment of congenital and habitual patellar dislocation with medial patellofemoral ligament (MPFL) reconstruction and tibial tubercle osteotomy (TTO) in adolescents with an underlying syndrome.
Methods
Syndromic adolescent patients with congenital or habitual patellar dislocation treated with MPFL reconstruction and TTO between 2005 and 2019 with a minimum of one year of follow-up were identified. Demographic, clinical, radiographic, and surgical data were recorded, and any complications were noted. Kujala and Lysholm scores were used to quantitate knee function.
Results
Seventeen knees in 11 patients met the criteria for inclusion. The mean age at operation was 14.8 years (range, 13.3–18.3 years). Patients were identified as having Ehlers-Danlos (four), Down (two), trichorhinophalangeal (one), McCune-Albright (one), Klippel-Feil (one), and generalized joint hypermobility (two) syndromes. The mean follow-up was 2.2 years for each individual knee (range, 1–5.9 years). The mean Kujala score increased from 56 ± 10 preoperatively to 86 ± 6 at the most recent postoperative visit (p < 0.001). The mean Lysholm score increased from 53 ± 10 preoperatively to 85 ± 7 at the most recent postoperative visit (p < 0.001). Knee flexion increased significantly from 117° ± 15° preoperatively to 154° ± 13° postoperatively (p < 0.001). However, knee extension was no different pre- and postoperatively (4° ± 8° vs. 1° ± 4°, respectively, p = 0.2).
Conclusions
Congenital and habitual patellar dislocation in adolescent-aged patients with an underlying syndromic diagnosis can be successfully treated with MPFL reconstruction combined with TTO.
Keywords: Patellar dislocation, Dislocation of the patella, Syndromic adolescent, Reconstruction, Tibial tubercle osteotomy, Medial patellofemoral ligament, MPFL
1. Introduction
Patellar dislocation may arise from a variety of etiologies including traumatic, obligatory (also known as habitual), or fixed (congenital). In habitual patellar instability, the patella dislocates each time the knee is flexed, but may return to a reduced position with extension.1 Patients with congenital patellar dislocation exhibit an irreducible, laterally-displaced patella.2 Habitual and congenital patellar dislocations are frequently associated with underlying syndromes, such as Down, nail-patella, DiGeorge, Ehler-Danlos, Larsen, and Rubinstein-Taybi syndromes, as well as chondrodysplasia punctata, arthrogryposis, and fibular hemimelia.3, 4, 5, 6 These types of patellar dislocation are almost always associated with underlying osseous and/or soft-tissue abnormalities, culminating in disruption of the local (knee) and/or global (lower extremity alignment) anatomy.
In the normal knee, the medial patellofemoral ligament (MPFL) plays an important role in patellofemoral stability.7 In patellar dislocation, the MPFL is most often not functional, and its reconstruction is a common surgical technique used to restore patellofemoral stability.8,9 In isolation, however, MPFL reconstruction is at risk of failure if the patellar tendon inserts in an abnormally lateral position.10, 11, 12 In these instances, relocation of the patellar tendon insertion to a more favorable location to neutralize lateralizing forces on the patella is desired. One popular method to achieve this is the anteromedial sliding osteotomy of the tibial tubercle described by Fulkerson in 1983.13
Various techniques for addressing congenital or habitual patellar dislocation have been described, but these rely mainly on soft-tissue rearrangements.4, 5, 6,14, 15, 16, 17, 18, 19 When surgically treating syndromic adolescent patients with this condition at our institution, we routinely perform a MPFL reconstruction combined with a Fulkerson tibial tubercle osteotomy (TTO) (Fig. 1a–f). This treatment strategy has been described in a few publications in the adult population10,11,20; however, the literature concerning this technique in adolescents is quite scarce. The purpose of this study was to present our experience with this combined procedure for treating congenital and habitual dislocation of the patella in syndromic adolescent patients.
Fig. 1.
Radiographs of a 16-year-old male with Down syndrome presenting with patellar instability of the left knee. A) and B) demonstrate preoperative plain radiographs. C) shows an axial magnetic resonance image demonstrating characteristic medial patellar facet and lateral femoral condyle bone bruising as well as a shallow trochlea. D) demonstrates fluoroscopic guidance utilized to locate Schottle's point for femoral tunnel drilling. E) (anteroposterior) and F) (lateral) demonstrate tibial tubercle osteotomy with two headless screws for fixation.
2. Material and methods
After institutional review board approval, adolescents between ages 13 and 18 years, with congenital or habitual patella dislocation and closed proximal tibial physes who underwent combined MPFL reconstruction and TTO between 2005 and 2019 with a minimum of one year of follow-up at our institution, were identified. Patients were included if they had an underlying syndrome or if they had a diagnosis of generalized joint hypermobility characterized by excessive joint laxity, hypermobility, and hypotonia. Demographic, clinical, radiographic, and surgical data were recorded. Clinical knee flexion and extension were determined from clinic notes documenting knee range of motion. The Caton-Deschamps index21,22 was measured on preoperative radiographs, with a value of 1.2 or greater signifying patella alta. Functional outcomes were measured via the Kujala23 and Lysholm24 scales, which were collected both pre- and postoperatively. Previous and concomitant surgical procedures to address the patellofemoral pathology were recorded.
2.1. Surgical technique
Diagnostic arthroscopy was first performed to evaluate the condition of the articular cartilage, menisci, and ligamentous structures. Any intraarticular pathology discovered that required treatment was addressed.
After arthroscopic evaluation, the TTO as described by Fulkerson13 was performed. For patients found to have patella alta on preoperative workup, distalization of the tibial tubercle was performed as well. Two headless screws were used for fixation of the osteotomy.
Following completion of the TTO, attention was directed to performing the MPFL reconstruction. A small incision was made along the medial aspect of the patella, which was then exposed with sharp dissection. Under fluoroscopic guidance, the junction of the superior and middle thirds of the patella were identified, and a 5-mm tunnel was drilled from medial to lateral at this location. A semitendinosus allograft was prepared and fixed to the patellar tunnel using a suture anchor. A small medial incision was made on the distal femur, and sharp dissection was used to arrive at the cortex. Under fluoroscopic guidance, a guide pin was placed from medial to lateral at Schottle's point,25 and was overdrilled to cannulate a tunnel in the distal femur. The graft was then tunneled underneath the skin, placed into the femoral tunnel, and secured with an appropriately-sized biocomposite interference screw. After securing the graft, its isometry was verified and the knee was brought through a full range of motion. The wounds were copiously irrigated and closed in a layered fashion, then sterile dressings were applied.
2.2. Postoperative rehabilitation
Toe-touch weight bearing was allowed for the first month. For the first week, the knee was kept in full extension with a locked knee brace. After this, the brace was modified to allow range of motion to 90° of flexion for three weeks. After week four, unlimited range of motion and weight bearing as tolerated was permitted. Patients were generally cleared for gradual return to activity around three months postoperatively.
2.3. Statistical analysis
Descriptive statistics were used to describe the population, and the paired t-test was used to compare pre- and postoperative continuous data. Statistical analysis was performed using SPSS v25 (IBM Corp., Armonk, NY) and statistical significance was defined as p < 0.05.
3. Results
Seventeen knees in 11 patients underwent MPFL reconstruction with TTO and were included in this study. Three patients were found to have patella alta preoperatively and distalization of their TTO was included in their surgical management. The mean age at operation was 14.8 years (range, 13.3–18.3 years). Nine patients had a diagnosis of an underlying syndrome including Ehlers-Danlos syndrome in four patients, Down syndrome in two patients, trichorhinophalangeal syndrome in one patient, McCune Albright syndrome in one patient, and Klippel-Feil syndrome in one patient (Table 1). Two patients who had generalized joint hypermobility were included. The mean follow-up time was 2.2 years for each individual knee (range, 1–5.9 years). The type of dislocation was habitual (obligatory) for all cases except for two knees of one patient with generalized joint hypermobility who had congenital patellar dislocations. The physes of all patients were closed.
Table 1.
Patient characteristics, complications, and associated procedures in addition to MPFL reconstruction with TTO.
| Patient No. |
Sex | Patellar Dislocation Type | Age at Operation (yrs) | Syndrome | Involved Knee | Complications | Previous Procedures | Concomitant Procedures |
|---|---|---|---|---|---|---|---|---|
| 1 | F | Habitual | 18 | Ehlers-Danlos | Left | None | None | Chondroplasty, loose body removal, partial meniscectomy, plica excision, microfracture |
| 2 | F | Habitual | 17 | Ehlers-Danlos | Bilateral | None | None | Lateral retinacular release (bilateral) |
| 3 | M | Habitual | 16 | Ehlers-Danlos | Left | None | VMO plication | Chondroplasty, microfracture, lateral retinacular release |
| 4 | F | Habitual | 17 | Ehlers-Danlos | Bilateral | Surgical site infection (unilateral) | None | Lateral retinacular release (bilateral) |
| 5 | M | Habitual | 16 | Down | Bilateral | TT avulsion with loss of fixation (bilateral) | VMO plication (bilateral) | Lateral retinacular release (bilateral) |
| 6 | F | Habitual | 17 | Down | Left | Arthrofibrosis, tendonitis | VMO plication | Chondroplasty, lateral retinacular release, microfracture |
| 7 | M | Habitual | 18 | Klippel-Feil | Left | None | Distal femoral varus osteotomy, proximal femoral derotation osteotomy | None |
| 8 | M | Habitual | 17 | McCune Albright | Left | None | Excision of peri-genu osteochondromas, distal femoral varus osteotomy | None |
| 9 | F | Habitual | 15 | Trichorhinophalangeal | Bilateral | None | VMO plication (bilateral) | Plica excision (unilateral) |
| 10 | F | Congenital | 13 | Generalized joint hypermobility | Bilateral | None | VMO plication (bilateral) | Lateral retinacular release (bilateral), quadricepsplasty (unilateral) |
| 11 | F | Habitual | 14 | Generalized joint hypermobility | Bilateral | Arthrofibrosis, tendonitis (unilateral) | VMO plication (bilateral) | Lateral retinacular release (bilateral) |
F, female; M, male; MPEL, medical patellofemoral ligament; TT, tibial tubercle; TTO, tibial tubercle osteotomy; VMO, vastus medialis obliquus.
Previous procedures performed included vastus medialis obliquus advancement, medial distal femoral hemiepiphysiodesis, distal femoral varus osteotomy, proximal femoral derotation osteotomy, and peri-genu osteochondroma excision. Concomitant procedures performed included lateral retinacular release, plica excision, chondroplasty, partial meniscectomy, quadricepsplasty, and loose body removal with patellar chondral microfracture (Table 1).
Complications were observed in five knees of four patients (Table 1). One patient with Down syndrome and bilateral knee involvement underwent revision tibial tubercle fixation to both knees for tibial tubercle avulsion and loss of fixation, Fig. 2a–d. One patient developed a deep infection due to coagulase negative staphylococcus at the osteotomy site, which resolved after surgical debridement and intravenous cefazolin therapy. Two patients developed arthrofibrosis and tendonitis due to prominent hardware over the TTO site, which resolved with removal of hardware and manipulation of the knee under anesthesia.
Fig. 2.
Postoperative radiographs of the same 16-year-old male with Down syndrome. A) demonstrates increased pain at the tibial tubercle site 2 months after surgery. Revision surgery demonstrated an inadvertent extension of the osteotomy requiring more screws. B) shows radiographic view at 4 weeks after revision. C) demonstrates slight loss of fixation but a largely reduced osteotomy site. D) shows that the osteotomy site had healed completely with slight proximal migration of the tubercle at 8 months after revision.
At latest follow-up, a significant increase in mean knee flexion compared with preoperative values (117° ± 15° preoperatively to 154° ± 13° postoperatively, p < 0.001) was observed. However, knee extension was no different pre- and postoperatively (4° ± 8° vs. 1° ± 4°, respectively, p = 0.2). Significant improvements were observed in the functional outcomes measured. The mean Kujala score increased from 56 ± 10 preoperatively to 86 ± 6 at the most recent postoperative visit (p < 0.001). The mean Lysholm score increased from 53 ± 10 preoperatively to 85 ± 7 at the most recent postoperative visit (p < 0.001).
4. Discussion
Our data demonstrate that reconstruction of the MPFL and concomitant TTO is an effective surgical strategy for adolescent patients with underlying syndromic conditions. Dislocation of the patella in syndromic children is often the result of a variety of underlying derangements affecting patellofemoral alignment and stability. Isolated or combined ligamentous laxity, hypotonia, angular and/or rotational limb malalignment, and derangement of local anatomy (lateral condyle hypoplasia, osteochondromas, etc.) are usually present. These vary both among different syndromes and within patients with the same underlying syndrome, underlining the importance of an individual treatment approach for each patient to alter the natural history of the patellofemoral affliction.
Development of a cogent surgical strategy begins with a thorough understanding of the forces acting upon the patellofemoral joint and awareness of the presence of all underlying conditions affecting patellofemoral joint stability, which must be addressed. For example, MPFL reconstruction in the knee with underlying valgus deformity is ill-advised due to the increased lateral force vector placed upon the extensor mechanism through the patella.2 Genu valgum may be treated with corrective osteotomies or guided growth, depending on the degree of correction needed and state of the physes. Simultaneous acute valgus correction osteotomies with concomitant TTO and soft-tissue rearrangement have been used for adults with congenital patella dislocation.3 However, in our series, patients with genu valgum were treated with either acute valgus correction osteotomy or medial distal femoral hemiepiphysiodesis at a separate and prior surgical encounter before MPFL reconstruction and TTO (Table 1).
Rotational malalignment from an abnormal increase in femoral anteversion and/or external tibial torsion also predisposes the patella to lateral dislocation and negatively affects outcomes after patella realignment surgery.11,19,20,26 Evaluation for rotational deformities should be routine in the preoperative examination and addressed in the treatment plan, if present. In our series, one patient with Klippel-Fiel syndrome exhibited unilateral abnormal femoral anteversion and was treated with a proximal femoral derotation osteotomy prior to surgically treating the patellofemoral joint (Table 1).
Traditionally, a combination of soft-tissue rearrangements for the surgical treatment of congenital and habitual patellofemoral dislocations in the pediatric population have been described.4, 5, 6,14, 15, 16, 17,19 Sever et al. report favorable results after surgical treatment of 15 knees in 12 skeletally immature children (nine of whom had an underlying syndromic diagnosis) with a modified Stanisavljevic14 soft-tissue procedure.4 In their series of six syndromic children treated with V–Y elongation of the quadriceps, patellar tendon transfer, posterior capsular release, and lateral retinacular release, Wada et al. report improvement in knee range of motion and limping at an average of 3.9 years postoperatively.27 These studies do not, however, include any adolescent patients in their cohorts, making direct comparison with the current investigation difficult. Gordon et al. describe a comprehensive procedure including lateral release and advancement of the vastus medialis obliquus in patients with congenital patellar dislocation, with the addition of either medial transfer of the patellar tendon in skeletally immature children, or medial transfer of the tibial tubercle in skeletally mature patients.19 In their series of 17 knees, they found significant increase in activity tolerance and knee strength and range of motion at a mean follow-up of 5.1 years. However, only one patient in their series was skeletally mature, and no patient-reported outcomes were reported.
The MPFL is the main restraint to lateral displacement of the patella between 0° and 30°of knee flexion.7 Because this restraint is lost in patients with patellar dislocation, MPFL reconstruction can be used to restore patellofemoral stability.8,9 In the treatment of habitual patellar dislocation, MPFL reconstruction in isolation may not provide complete correction for patients with patella alta and hypermobility, and risks treatment failure if the patellar tendon insertion is too lateral.10,11,28 To address these concerns, the TTO can be combined with MPFL reconstruction, and has not been shown to increase complication rates in the adult literature.10,11,20,29 Thus, in the present series, due to the skeletal maturity of our patients and prevalence of underlying ligamentous laxity and/or hypotonia seen in these syndromic individuals, MPFL reconstruction is combined with TTO to further combat the lateral pull on the patella.
Direct comparison of functional outcome scores from the current study with the published literature is difficult due to the paucity of reports on this procedure in syndromic adolescents elsewhere. In a systematic review of 92 knees in non-syndromic results with chronic patellar instability, the mean postoperative Kujala score with average follow-up of 38 months was reported as 76.30 Neri et al. reported on 133 adult knees treated with MPFL, either in isolation or with TTO, and found a significant improvement in Kujala scores to around 85 postoperatively.31 In the present series, MPFL reconstruction and TTO were associated with a significant increase in patient-reported outcomes and knee function as measured by the Kujala and Lysholm scores.
Surgeons must be aware of the potential complications as well. In this series, there were two cases of tibial tubercle avulsion and subsequent loss of fixation (bilateral knees in the same patient), one case of surgical site infection, and two cases of arthrofibrosis and tendonitis as a result of prominent hardware over the TTO site. All of these complications resolved–the avulsions were successfully treated with revision fixation, the infection resolved with surgical debridement and intravenous antibiotic treatment, and the two cases of arthrofibrosis and tendonitis resolved with removal of hardware and manipulation of the knee under anesthesia. Surgical treatment in these syndromic patients with underlying soft-tissue disorders is complex, and surgeons must be prepared to address any complications. Headless screws are used to reduce the hardware prominence that may lead to overlying soft-tissue irritation, and keen judgement must be used when sizing the screw to the size of the TTO fragment to minimize the creation of a stress riser.
This study is not without limitations, the first of which is its retrospective nature. Second, having only 11 patients, and with varying underlying diagnoses, can weaken the generalizability of conclusions drawn from any one outcome. While a minimum follow-up length was set at one year for this study, in an attempt to capture any perioperative complications, surgical site infections, and early outcome results, a follow-up range of only 1–5.9 years precludes the ability to comment on anything other than the short-term results of this procedure. Further studies are needed to follow this patient population into adulthood.
The main finding of this study is that in adolescent-aged patients with an underlying syndromic diagnosis, MPFL reconstruction combined with TTO is an effective treatment in those suffering from congenital or habitual patella dislocation. A reliable increase in knee range of motion as well as patient-reported function measured by Lysholm and Kujala scores can be expected.
Level of Evidence
Level IV—therapeutic.
Source of funding
None declared.
Declaration of competing interest
None declared.
Contributor Information
Ahmet Imerci, Email: ahmetimerci@hotmail.com.
Tyler C. McDonald, Email: tyler.mcdonald@nemours.org.
Kenneth J. Rogers, Email: kenneth.rogers@nemours.org.
Mihir M. Thacker, Email: mihir.thacker@nemours.org.
Alfred Atanda, Jr., Email: alfred.atanda@nemours.org.
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