Quadricepsplasty or quadriceps lengthening is a surgical procedure used to remove the deforming force of a short or malaligned quadriceps mechanism that creates a lateralized patella that tracks outside the trochlear groove in flexion.

It is most commonly used in the pediatric population with congenital or obligatory patellar dislocation in flexion.¹,²

By derotating and/or lengthening the extensor mechanism, this procedure helps to maintain the patella within the trochlea in flexion.

If done in patients with significant growth remaining, quadricepsplasty may even help remodel the trochlea by relocating the patella in the groove in flexion.³

In the child and young adolescent population, this procedure most effectively corrects obligatory patellar dislocations in flexion. This is a relatively uncommon type of presentation where the patella dislocates with every episode of knee flexion.

In such cases, the quadriceps mechanism is typically shortened and its functional axis is laterally deviated. Therefore, it is essential to surgically address both patellar alignment and the deformity of the extensor mechanism. If not, the shortened quadriceps will continue to inhibit proper patellar tracking either by inhibiting full flexion in cases where the patella is surgically stabilized within the patella or by overpowering the reconstructed medial structures and leading to recurrent lateralization of the patella with flexion.

Several quadricepsplasty techniques that accomplish these goals have been described, including Thompson, Judet, Stanisavljevic, Z lengthening, and the V-Y technique (Curtis and Fisher).⁴,⁵,⁶,⁷,⁸,⁹,¹⁰

The basic principles behind these procedures are the lengthening of the quadriceps mechanism and release or lengthening of the lateral retinaculum of the patella. The techniques discussed in this chapter are surgical procedures that address the distal quadriceps mechanism (the V-Y quadriceps tendon lengthening, Z lengthening of the quadriceps tendon) and procedures that address the quadriceps mechanism as a whole, such as the Judet procedure.

Historically, pediatric patellar dislocations were categorized simply as traumatic or congenital; however, recently, more extensive and specific classification systems have been established.

Most classification systems address anatomic, biomechanical, pathophysiologic, and clinical patterns.

The one preferred by the authors is consolidated into three main categories of pediatric patellar dislocation: traumatic (acute or recurrent), obligatory (either in flexion or in extension), and fixed lateral¹,²,¹¹ (Table 13.1).

Traumatic dislocations are acute when they involve a single injury episode with resulting effusion and disability; recurrent dislocations involve repeated events following an initial dislocation that can be traumatic or atraumatic.

Obligatory dislocation of the patella in flexion is the most relevant category of dislocation to this chapter. During these dislocations, the patella slips out of the trochlea into the lateral gutter whenever the knee is
flexed and, subsequently, can only be reduced when the leg is in full extension. Obligatory dislocations occur most often as a result of shortened extensor mechanisms.

Fixed lateral dislocations are rare and occur when the patella cannot be reduced in flexion or extension. These dislocations typically require a quadriceps lengthening procedure as part of the surgical reconstruction.

Both obligatory and fixed lateral dislocations can be syndromic and present with congenital abnormalities, including skeletal dysplasia, Rubinstein-Taybi syndrome, Kabuki syndrome, Down syndrome, nail-patella syndrome, Marfan disease, cerebral palsy, or Ehlers-Danlos syndrome.¹²,¹³,¹⁴

The indications and contraindications for quadricepsplasty are described in Table 13.2.

One of the original quadricepsplasty techniques is known as the V to Y advancement or V-Y lengthening, described by Curtis and Fischer in 1969.¹⁵

This technique involves freeing both the medial and lateral aspects of the extensor mechanism from the quadriceps tendon and its extensive attachment to the underlying femur. To accomplish this, the medial and lateral retinacula are divided. The iliotibial band (ITB) should also be released or lengthened if the tibia is in valgus and external rotation. After sharp dissection of the lateralis and medialis, the quadriceps tendon is cut into a V-shaped manner. The lateral retinaculum is freed from attachments to the femur. With the knee flexed to approximately 60° of flexion, the quadriceps tendon is repaired in its lengthened position, giving the appearance of a V to Y proximal progression. Then, the medialis and lateralis are reattached to the lengthened quadriceps tendon (Figure 13.1A, B).

This technique has been shown to produce positive outcomes. Abdelaziz et al and Tercier et al have published outcomes regarding this technique; however, it is important to note that both of them used it in the context of congenital dislocation of the knee (CDK) rather than congenital patellar dislocation.⁸,¹⁶ In 2011, Abdelaziz et al reported on a cohort of 11 infants who underwent either serial casting, V-Y quadricepsplasty (VYQ), or a percutaneous quadriceps recession for CDK.¹⁶ VYQ was recommended for patients with more severe CDK in which the knee has recurrent dislocations or is dislocated on radiographs and lacks passive flexion greater than 30°. Four knees were initially treated with VYQ. The authors were initially disappointed by the results due to wound breakdown and infection; however, they found VYQ was ultimately the only effective measure to treat severely dislocated knees. Additionally, despite the initial infections, all children were able to walk independently, all parents were satisfied with the outcome, and the majority of knees were rated as “excellent” or “good.”

To address some of the complications associated with VYQ, including wound dehiscence and insufficient lengthening of the quadriceps, Tercier et al performed a modified VYQ on 20 children (33 knees).⁸ In this technique, the rectus femoris was raised and mobilized from the underlying vasti intermedius. With this method, the authors were able to obtain positive outcomes while avoiding the abovementioned complications. The majority of children became community walkers and gained improvement in the range of motion with flexion to 90°. Additionally, nonsyndromic CDK had grade 5 quadriceps power with only minimal extensor lag.⁸

The Judet procedure, first described by Judet¹⁷ in 1956 and more recently by Bellemans and Daoud, is an extended quadricepsplasty performed in three main steps.⁴,¹⁸ First, both the medial and lateral retinacula are released through a longitudinal lateral and/or medial parapatellar incision. A long lateral incision is then made to allow the division of the vastus lateralis
from the linea aspera, and the vastus intermedius is released and lifted off of the anterior and lateral surfaces of the femur. Once this has been completed, the outer half of the vastus lateralis is interposed and sutured between the extensor mechanism and the anterior femoral cortex.¹⁹

For cases in which the knee is blocked in hyperextension (genu recurvatum), Burnei et al have described an additional release of the adductor muscles, an axial dissection of the femoral nerve, and complete division of the vastus intermedius tendon.²⁰

To limit the length of the incision and subsequent scar, a modified Judet procedure has also been described. Instead of a long lateral incision, a distal posterolateral approach is used to expose the distal third of the femur. Then, the overlying ITB is dissected away, so that the vastus lateralis can be separated and lifted up from the lateral intermuscular septum. The vastus intermedius and quadriceps tendon are then released from the underlying femur, after which the knee can be flexed. In the next stage, the medial expansion, vastus medialis, and medial retinaculum are elevated from the medial condyle, after which the vastus medialis is released from linea aspera. Via another lateral incision, the vastus lateralis is released from its origin at the intertrochanteric line. Finally, a Z-plasty of the ITB is performed in which the anterior and posterior flaps of the incised ITB are sutured together with the knee in maximum flexion.²¹

Because the Judet procedure is more commonly performed in adults, there is little literature reporting outcomes in younger patients. However, both early and more recent literature indicate that this procedure gives reproducibly good results and minimal complications in adults.¹⁹,²² In study cohorts, the majority of patients gained an average of approximately 70° in range of motion and reported “excellent” or “good” results.¹⁹,²² No patients developed extensor lag or reported “poor” results.

Mahran et al reported on results from 19 cases of modified Judet quadricepsplasty, after which patients obtained good range of flexion (average gained: 93.5°) and reported minimal complications.²¹

The distal quadricepsplasty technique has been described by Payr²³,²⁴ and Thompson.²⁵,²⁶ This procedure starts with a lateral approach, after which the medial and lateral vasti are released from the patella and the quadriceps tendon. The rectus femoris is then released from the femur and the vastus intermedius. The vastus intermedius is then dissected from its proximal origin on the femur at which point flexion is tested. If satisfactory flexion is not achieved (<100°), a Z-plasty can be performed to lengthen the rectus femoris tendon. Finally, the medial and lateral vasti tendons are sutured to the rectus femoris tendon with the knee flexed to 90°.20 Several modifications of this procedure have also been described because the original technique is often associated with high rates of morbidity, including skin necrosis and extension lag.²⁰,²⁷,²⁸

Burnei et al compared outcomes for a cohort of 76 patients with severe iatrogenic infantile quadriceps retraction who underwent either the Thompson-Payr distal quadricepsplasty (34 cases) or the modified Judet (94 cases). The investigators modified the Judet with an adductor muscle release, axial dissection of the femoral nerve, and incision of the crural fascia above the patella.²⁰ Both groups obtained above acceptable ranges of motion—the Thompson-Payr technique was used in patients with lesser limitations in ranges of motion, and so this cohort showed an improvement from an average of 37° to 115°. The modified Judet, used in more severe cases, resulted in average improvement of −3° to 80°.20 Reoperations were performed in 14.9% (14 cases) of the Judet cohort and in 5.9% (2 cases) of the Thompson-Payr cohort. Frequency and type of complication differed for the two procedures as well, with the majority of Judet complications being skin necrosis (12.8%) and femoral nerve injuries (4.25%). Contrarily, Thompson-Payr more often resulted in loss of active extension (11.8%). Based on these results, Burnei et al concluded that the modified Judet was ultimately a better technique because it allowed increased intraoperative flexion and resulted in fewer mechanical complications.²⁰

There is minimal literature regarding the Thompson procedure to correct habitual dislocation in pediatric patients; however, there are reports of this technique for quadriceps contracture and fracture-related stiff knees.²⁷,²⁹ Muteti et al reported outcomes of Thompson quadricepsplasty in pediatric patients with quadriceps femoris contracture, and although they found an average gain in flexion of 94.7°, opening the knee did result in some postoperative patellar instability.²⁹