Special Considerations for Pediatric Patellar Instability

Initial studies conducted on patellar tendon transfer have positive outcomes.¹⁷⁹ At a mean follow-up of 5.1 years, patients reported a decrease in pain and increased the ROM and activity, and only 1 reported a postoperative redislocation.¹⁷⁹ In more recent studies, both Benoit and colleagues³⁶ and Garin and colleagues⁵⁸ reviewed cases of patellar instability treated with patellar tendon transfer to address concomitant patellar alignment and anatomic abnormalities. They reported good functional, clinical, and radiographic outcomes with 12.5% and 16% recurrence rates, respectively.^36,58 They also noted radiographic improvements in femoral sulcus angle, particularly in younger patients, which indicate this procedure is effective in addressing bony abnormalities that can result from neglected malalignment issues.^36,58,154

QUADRICEPSPLASTY

Quadricepsplasty is a lengthening and remodeling technique not frequently used in the pediatric population. The goal of this procedure in patients with significant amounts of growth remaining is to reposition the patella to ameliorate trochlear remodeling and prevent worsening symptoms and anatomic abnormalities.³⁶ A quadricepsplasty accomplishes this by de-rotating and/or lengthening the extensor mechanism and may or may not involve a concomitant MPFL reconstruction. This procedure is particularly effective in young patients who experience obligatory dislocation.^60,72 Several quadricepsplasty techniques have been described including Thompson, Curtis and Fisher, Judet, Stanisavljevic, and V-Y technique.^180-186 Most techniques initially involve sharp dissection of the vastus medialis and lateralis from the rectus femoral tendon. A tongue is then fashioned out of the rectus femoral tendon. Once the vastus medialis and lateralis are detached from the margins of the patella, the knee is extended, and the distal ends of the vasti are sutured to the tongue of the rectus tendon. Effective extension facilitates flexion to 90°.¹⁸⁴ The authors recommend a modification of this technique in which a Z lengthening of the quadriceps tendon is performed after the vastus lateralis is removed distally from the patella and the quadriceps tendon.

Several series and case reports evaluating quadricepsplasty in adult patients report positive outcomes with most patients achieving good or excellent flexion with minimal complications.^{183,185,187-189} Reports on quadricepsplasty used to treat conditions other than patellofemoral instability in children have reported similar positive outcomes.^190-192 As quadricepsplasty for patellar instability is relatively rare in pediatric patients, there is not much relevant literature. However, Kocon and colleagues¹⁹³ reported results of quadricepsplasty and quadricepsplasty combined with the modified Galeazzi procedure in 8 children (10 knees) with a mean follow-up of 3.25 years. Seventy percent of cases resulted in stabilization and correction of patellar position, and only 2 postoperative redislocations were noted.¹⁹³ Additionally, in a study evaluating 6 patients suffering from patellar instability, 2 of whom were obligate dislocators, quadricepsplasty resulted in patellar stability, satisfaction, and near normal gait patterns.¹⁹⁴

Figure 10 shows the surgical algorithm used for patellar instability characteristics.

CONCLUSION

Patellofemoral joint stability relies on a complex interplay of musculotendinous units, ligaments and the osteocartilaginous morphology of the patellofemoral joint. Patellar instability in pediatric patients is different from adults. Having an in-depth understanding of the remodeling potential, the insertion sites for the MPFL and its relationship to the physis are of utmost importance when planning surgery. Reducing and maintaining the patella within the patellofemoral joint early enough can allow for remodeling of the patella and/or the trochlea to provide for lasting stability. Appropriate surgical principles, such as tensioning, can help both prevent continued pain and minimize future complications.