Special Considerations for Pediatric Patellar Instability

QUADRICEPS TENDON TRANSFER OUTCOMES

Studies specifically evaluating the quadriceps tendon transfer technique for MPFL reconstruction in children are sparse, but authors have reported positive clinical outcomes and low complication rates in adults. After following 32 young adults who underwent this MPFL reconstruction technique for 3 years, Goyal¹⁰⁹ reported a significant increase in mean Kujala scores from 49.31 to 91.25 and no complications or redislocation. He argues this type of quadriceps graft has a high success rate because it is anatomically more similar to the MPFL than other grafts and does not require additional patellar fixation.^101,109 Similar positive Kujala scores and minimal complications have been reported in adult patient populations.¹⁴⁸ Abouelsoud and colleagues¹⁴⁹ conducted one of the few studies in skeletally immature patients and reported similarly positive results with no redislocations and significantly improved Kujala scores at a mean follow-up of 29.25 months in their 16-patient cohorts.

ADDUCTOR MAGNUS TENDON TRANSFER

After initially describing this technique in 14 adult patients, Avikainen and colleagues⁹⁶ followed this cohort and reported positive subjective results and only 1 redislocation. In a more recent study in which the adductor tendon transfer technique was compared with the quadriceps tendon transfer described above and the bone-patellar tendon allograft, Steiner and colleagues⁶⁹ reported similarly significant improvement in all cohorts in Lysholm, Kujala, and Tegner scores with no redislocations. Additionally, Malecki and colleagues¹⁵⁰ followed a cohort of 33 children with 39 knees diagnosed with recurrent patellar dislocation, who underwent MPFL reconstruction using the adductor magnus tendon. After evaluating this cohort functionally and radiographically, the authors reported improvements in Lysholm and Kujala scores, patellar tilt and congruence angles, and peak torque of the quadriceps muscle and flexor.¹⁵⁰ However, this cohort did report postoperative redislocations in 36.4% of patients (4 of 11).¹⁵⁰

HEMI-PATELLA TENDON TRANSFER

In 2012, in the first randomized controlled trial, Bitar and colleagues⁶⁷ compared the outcomes of patients who underwent MPFL reconstruction via the hemi-patellar tendon technique with those who were managed nonoperatively with immobilization and physiotherapy after first-time patellar dislocation. At 2-year follow-up, the surgical cohort presented positive results with a significantly higher mean Kujala score (88.9 to 70.8) and no redislocations or subluxations. In contrast, 35% of nonoperative cases presented with recurrences and subluxations over the 2-year period.⁶⁷

MCL OR ADDUCTOR TENDON AS A PULLEY

Studies have reported good postoperative results and low complication rates for these dynamic techniques.^128,129 In terms of kinematics, while hypermobility and patellar height were not fully corrected, improvements in patellar tilt and lateral shift were reported in a cohort of 6 patients with a minimum 4-year follow-up.¹²⁹ To further evaluate whether the more dynamic pulley reconstruction technique resulted in better outcomes, Gomes and colleagues¹²⁸ compared the subjective reports, clinical evaluations, and complication rates of patients who underwent MPFL reconstruction with a rigid adductor magnus fixation vs a semitendinosus tendon dynamic femoral fixation. One case in the rigid cohort experienced a subsequent subluxation, while patients in the semitendinosus group had better subjective reports and a higher rate of return to sport.¹²⁸ More recently, Kumahashi and colleagues¹⁵¹ specifically studied the outcomes of the MCL tendon as a pulley in 5 patients aged 14 to 15 years. They reported similar successful results as no patients experienced recurrence, and all patients exhibited improvement in radiographic measures of patellar tilt and congruence angle, lateral shift ratio, and both Kujala and Lysholm scores.¹⁵¹

While there has yet to be a randomized controlled trial comparing all of these different techniques, there is a general consensus in the literature that patients tend to perform better following MPFL reconstruction vs MPFL repair.

OTHER STABILIZATION PROCEDURES, INCLUDING DISTAL REALIGNMENT

Patients with additional underlying deficits and malalignment issues such as significant trochlear dysplasia, increased TT-TG distance, patella alta, increased Q angle, and/or positive J sign may require stabilization procedures beyond MPFL reconstruction.^152,153 TT osteotomies are often used to correct alignment issues in the adult patient population; however, these procedures are typically contraindicated in skeletally immature patients. Alternative realignment procedures for the pediatric population include both proximal and distal realignment, with proximal realignment performed primarily in children under the age of 12 years.¹⁵³ Many variations on these procedures exist, some of which are no longer regularly performed due to poor reported outcomes. In this article, we discuss several of the techniques, focusing primarily on those that have demonstrated higher success rates.

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