Acute patellofemoral dislocation is the most common acute knee disorder in children and adolescents. The predisposing factors for acute patellar dislocation are multifactorial.
Treatment of a first-time acute patellofemoral dislocation in the skeletally immature athlete is typically nonsurgical unless associated with substantial articular cartilage damage. In the setting of recurrent instability, surgical reconstruction is usually recommended. Patellofemoral instability is a difficult condition to treat. Surgical treatment of patellofemoral instability in the skeletally immature athlete is evolving from nonanatomic extensor mechanism surgical procedures to anatomic restorative procedures based on reconstitution of the medial patellofemoral ligament. The current goal of surgery is to restore the normal anatomy of the patellofemoral joint. Proper patient selection and attention to technical details are key to good outcomes.
Treatment of the skeletally immature athlete with an acute patellofemoral dislocation remains controversial with long-term outcomes not well understood. In children, the incidence of patellofemoral dislocation is approximately forty-three per 100,000 individuals, with a peak incidence at the age of fifteen years1-3. The risk of acute dislocation and recurrent instability is particularly high in females from ten to seventeen years old4,5. After a first-time dislocation, young athletes may feel a sense of giving-way, pain, or anxiety. Recurrent patellar dislocations often substantially impair their athletic performance. In 1952, MacNab reported a 15% redislocation rate following a first-time dislocation, with 33% of patients reporting pain and weakness following a dislocation6. Additional studies have noted a redislocation rate ranging from 20% to 44%4,7,8. Treatment is complicated by the presence of open growth plates, which precludes utilization of osteotomies9-11. The goal of this paper is to summarize the pathoanatomy and natural history of this patellofemoral instability in the skeletally immature athlete and to discuss both nonoperative and operative treatment options for this injury.
The role of lateral release in the treatment of patellofemoral instability has undergone reevaluation46-48. An isolated lateral release is not recommended for the treatment of patellar instability37,46,49. Lateral release alone does not align the patella more medially46,50. In cases of patellofemoral instability with normal alignment and no evidence of excessive patellar tilt, medial reefing without routine lateral release can be performed51. The current indications for performing a lateral release are (1) abnormal patellar tilt by examination or imaging in the setting of anterior knee pain that has had unsuccessful conservative treatment or (2) recurrent patellofemoral instability in combination with other surgical procedures46. Potential morbidity following lateral release includes hemarthrosis and medial instability47,49,52. For the uncommon patients with anterolateral knee pain and symptoms of medial patellar instability after lateral release, open lateral retinacular closure surgery has been described53.
Distal Realignment
Distal realignment surgical procedures in skeletally immature patients aim to modify the proximal-distal and medial-lateral positions of the patella by soft-tissue transfer distal to the inferior pole of the patella54. Stanitski recommended that a soft-tissue realignment procedure should include releasing the abnormal tethering vector, balancing the medial vector, and aligning the quadriceps-patellar-tibial mechanism55. Distal realignment procedures include transfer of the semitendinosus tendon to the patella54,56,57, transfer of part or all of the patellar tendon medially to the periosteum or to the sartorius tendon58-60, and combination procedures including distal and proximal soft-tissue transfers58,61,62. The Galeazzi procedure (Fig. 6) includes a lateral release combined with transfer of the semitendinosus tendon to the medial patellar retinaculum or directly to the patella via an oblique drill-hole through the patella56,57,63. Success rates for preventing subsequent patellar instability of >80% have been reported with the Galeazzi procedure56. The modified Roux-Goldthwait procedure is a combination distal and proximal soft-tissue transfer that includes a lateral release, plication of the medial retinaculum, advancement of the vastus medialis muscle, and medial transfer of the lateral half of the patellar tendon beneath the intact medial half to the sartorius insertion58,62 (Fig. 7). Success rates for preventing subsequent patellar instability of >80% have been reported with the modified Roux-Goldthwait procedure62. Most recently, Joo et al. reported excellent results in a small case series of patients treated with the “four-in-one” procedure61. The four-in-one procedure includes a lateral release, a vastus medialis muscle advancement, transfer of the semitendinosus tendon to the patella, and transfer of the lateral half of the patellar tendon to the medial tibial periosteum61. These proximal and distal realignment procedures involve shifting extensor mechanism tissue in various nonanatomic directions. Recently, the primary stabilizing role of the medial patellofemoral ligament has been emphasized as the key factor for patellar instability. The current trend in the treatment of patellofemoral instability in young athletes has evolved from nonanatomic extensor mechanism realignments to more anatomic procedures centered on reconstruction of the medial patellofemoral ligament12,13,39,64,65.
Medial Patellofemoral Ligament Reconstruction
The goal of soft-tissue reconstruction of the medial patellofemoral ligament is to reestablish the normal checkrein against lateral motion and create a tether to help restore normal passive motion of the patella, including allowing the patella to glide laterally about 9 mm. Medial patellofemoral ligament reconstruction is recommended for patients with repeat dislocation, whereas medial patellofemoral ligament repair is utilized more often for patients with a first-time dislocation in whom concomitant injuries are also being addressed. Reconstruction is advocated over repair in patients with repeat dislocation because the chronically injured medial retinacular tissues are insufficient to establish a checkrein against lateral dislocation. Various graft choices have been utilized for medial patellofemoral ligament reconstruction including hamstrings66, patellar tendon67, quadriceps68,69, and adductor magnus70. Allograft can be considered if the patient has hyperlaxity.
Techniques that avoid injury to the growth plate should be utilized in the skeletally immature athlete. Two techniques in particular are safe and effective in this young athletic population. Noyes and Albright reported using an 8 × 70-mm strip of the medial part of the quadriceps tendon to reconstruct the medial patellofemoral ligament68 (Fig. 8). The quadriceps graft is left attached to the superomedial border of the patella. The free end of the graft is passed between the synovium and the retinaculum to the medial femoral epicondyle and is sutured to the medial intermuscular septum. The remaining medial retinaculum is imbricated when the quadriceps tendon harvest site is closed. The graft is tensioned at 30° to 45° of knee flexion to allow for lateral patellar movement of up to 25% of the patellar width. They add a lateral release if tightness of the tissues prevents normal medial patellar translation with or without abnormal patellar tilting. Femoral or patellar drill-holes are not utilized in this technique, so the risk of patellar fracture or injury to the distal femoral physis is reduced68.
Sillanpää et al. reported a technique using the adductor magnus tendon autograft that can also be of value when treating skeletally immature athletes with patellofemoral instability70. The medial two-thirds of the adductor tendon are harvested while leaving the distal insertion intact. A 12-cm strip of the medial aspect of the adductor magnus tendon is transferred via a tunnel between the capsule and the retinaculum and is fixed to the medial patellar margin with two suture anchors. The graft is tensioned at 30° of knee flexion with care to avoid overtightening by allowing lateral patellar glide similar to the contralateral knee70. Lateral release is not added to the procedure except in cases in which the patella cannot be medialized to the neutral position in the trochlear groove. The adductor magnus tendon reconstruction also avoids drill-holes and minimizes the risk of a fracture or injury to the distal femoral physis.
The goal of the rehabilitation phase is to protect the patellar reconstruction while knee motion and strength are regained. Rehabilitation protocols vary by surgeon. Most surgeons utilize a brace for three to six weeks and allow a gradual increase in motion during this time. Utilization of ice packs and ice massage may be helpful. Partial weight-bearing is allowed postoperatively and is progressed to full weight-bearing over four to six weeks. Initial isometric exercises are supplemented with proprioceptive exercises, closed kinetic chain exercises, and lastly, open chain exercises. Most patients can be expected to be able to jog by three to four months and return to full sporting activities by about four to six months.
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