Surgical Management of Patellofemoral Instability in the Skeletally Immature Patient

Lauren H. Redler, MD; Margaret L. Wright, MD

Disclosures

J Am Acad Orthop Surg. 2018;26(19):e405-e415. 

In This Article

Implant-mediated Guided Growth

Indications

Guided growth techniques have been used for many years to correct genu valgum in children with open physes. The goals of these procedures are to maximize growth potential and to avoid osteotomies after growth is complete. Genu valgum is a known risk factor for patellar instability, and correction of genu valgum in isolation or in addition to medial soft-tissue procedures decreases the risk of recurrent instability.[45] Radiographs should be obtained to confirm bone age; a three-joint standing radiograph of the lower extremities should be obtained to assess remaining growth and the degree of deformity. Guided growth techniques are typically indicated in patients with genu valgum >10° (defined by the lateral distal femoral angle <79°) that is associated with patellar instability, who have at least 6 months to 1 year of remaining growth. Temporary hemiepiphysiodesis through the application of an extraphyseal tension band plate is a safe, effective, and minimally invasive technique. However, it should not be used in children aged <8 years because spontaneous correction of the deformity is likely in children this young.[46]

Technique

Temporary hemiepiphysiodesis, or tension band plating, is most often done at the distal medial femur but can also be applied to the proximal medial tibia in cases in which both the femur and tibia contribute to the deformity. The surgical site is identified with fluoroscopy, and the procedure is performed through a 2-cm skin incision or through the incision over the femoral insertion of the MPFL if the procedure is done concurrently with a medial soft-tissue procedure. Using blunt dissection, the periosteum over the physis is identified but not violated. The figure-of-8 plate is placed and held provisionally with a hypodermic needle or K-wire fixation. Fluoroscopy is used to confirm the position of the plate over the midsagittal line of the distal femoral physis on the lateral view, with one hole of the plate on each side of the physis. When position is confirmed, K-wires are placed in each hole, and cannulated screws are placed for definitive fixation. Weight bearing as tolerated may be permitted or weight bearing within the limitations of any other procedures that were performed concurrently.[46] Patients are followed at 3- to 4-month intervals with standing three-joint radiographs to measure correction of the deformity (Figure 9). The plates are removed when correction is complete, and the patient should continue to be followed at 4- to 6-month intervals until skeletal maturity with standing radiographs to confirm that no overcorrection or other deformity develops.

Figure 9.

A, Preoperative standing AP three-joint radiograph of the lower extremities showing genu valgum of the left knee. B, Postoperative standing AP three-joint radiograph of the lower extremities showing correction of genu valgum with distal medial femoral and proximal medial tibial hemiepiphysiodesis.

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