History
It is important to identify and document the natural history of genu valgum. On rare occasions, this condition may be noted in the nursery, indicating the presence of some type of localized or generalized skeletal malformation or dysplasia. Congenital lateral dislocation of the patella has been described. The extensor mechanism of the knee is displaced laterally so that every time the child contracts the quadriceps, the knee is flexed (rather than extended) and rotates outward, accentuating the valgus deformity. Another example is postaxial hypoplasia of the limb, sometimes first manifested by the absence of a lateral ray (or two rays) of the foot. [11]
More commonly, genu valgum does not become apparent until after the child reaches walking age. A normal variant of the disorder in toddlers (physiologic valgus) typically is symmetrical and pain-free, but it should resolve spontaneously by the time the child reaches the age of 6 years. If the valgus is unilateral or symptomatic, referral to an orthopedist and radiographic evaluation are warranted.
Family history may be important because certain heritable conditions, such as hereditary multiple exostoses, Marfan syndrome, osteogenesis imperfecta, or vitamin D–resistant rickets may predispose a patient to this condition.
Physical Examination
The physical examination should include assessment of the gait pattern, including the propensity for circumduction, and evaluation of lower-extremity lengths. Stature, craniofacial features, the spine, and the upper extremities should be evaluated. Various genetic conditions and skeletal dysplasias may be documented in this manner; consultation with a geneticist may be warranted.
With the child standing, the relative limb lengths should be compared by leveling the pelvis with blocks and measuring and recording the intermalleolar distance (IMD). Torsional deformities of the femur, tibia, or both should be documented. Often, genu valgum is observed in association with outward torsion of the femur, the tibia, or both. It is important to look for retropatellar crepitus and tenderness and to note patellar tilt, tracking, and stability. For situations other than the aforementioned physiologic genu valgum, medical imaging is warranted.
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This diagram depicts genu valgum involving right leg (lighter shade), where mechanical axis falls outside knee. Goal of treatment is to realign limb and neutralize mechanical axis (dotted red line), thereby mitigating effects of gravity through guided growth of femur and/or tibia (whatever is required to maintain horizontal knee joint axis). Darker shade depicts normal alignment, with mechanical axis now bisecting knee.
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This 9-year-old patient has symmetrical and progressive genu valgum caused by hereditary form of metaphyseal dysplasia. One method of treatment is to undertake bilateral femoral and tibial/fibular osteotomies, securing these with internal plates or external frames. However, hospitalization and attendant cost and risks, including peroneal nerve palsy and compartment syndrome, make this daunting for surgeon and family alike. Furthermore, mobilization and weightbearing may require physical therapy but must be delayed pending initial healing of bones.
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Heretofore, stapling was viable option. This outpatient procedure permitted simultaneous and multiple deformity correction, without casts or delayed weightbearing. However, concept of compressing and overpowering the physes has drawbacks of slower correction because fulcrum is within physis. Provided that rigid staples did not dislodge or fatigue, satisfactory correction could be realized. If hardware failed prematurely, either correction was abandoned or hardware was exchanged. Compared with osteotomies, this was risk worth taking--that is, until advent of better option.
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Application of single eight-Plate per physis permits same correction as stapling, without potential drawbacks of implant migration or fatigue failure. Based on principle of facilitating rather than compressing physes, correction occurs more rapidly, and rebound growth, though possible, may be less frequent. When mechanical axis has been restored to neutral, plates (or metaphyseal screws) are removed (and replaced as necessary if recurrent deformity ensues).
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This 14-year-old boy, weighing 132 kg, presented with activity-related anterior knee pain, circumduction gait, and difficulty with running and sports. Symptoms had been progressive over 18 months despite nonoperative measures that included physical therapy, activity restrictions, and nonsteroidal anti-inflammatory drug (NSAID) therapy.
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At 9 months after insertion of eight-Plates in distal femora (1 per knee), patient's mechanical axis is approaching neutral, and his symptoms have abated. Plates were removed 2 months later, allowing full correction of his valgus deformities. Patient has not had recurrence.
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This 14-year-old boy broke his distal femur 1 year previously. He was treated with internal fixation using condylar plate, and fracture healed uneventfully. However, he developed medial overgrowth of femur, which caused progressive and painful genu valgum. Note lateral displacement of mechanical axis into zone 2. One alternative is to perform supracondylar osteotomy with exchange of plate; this was declined.
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Two options for instrumented and reversible hemiepiphysiodesis are (1) multiple staples and (2) tension-band plate. The latter, being flexible yet secure, avoids potential risks of hardware breakage or migration. Furthermore, growth is facilitated rather than restricted, and alignment is restored more rapidly.
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At 1 year after guided growth of femur with eight-Plate, patient's mechanical axis is neutral, limb lengths are equal, and symptoms have abated; plate was then removed. Neither procedure required hospitalization or immobilization. Each time, patient was able to rapidly resume sports participation.
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17-year-old male underwent arthroscopic reconstruction of left anterior cruciate ligament utilizing braided semitendinosis 1 year prior to this film. With ensuing growth, he developed progressive genu valgum with medial and anterior knee pain and difficulty running.
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Fluoroscopic close-up view of patient's left knee demonstrates that despite chronologic age of 17 years, he has significant growth remaining. (Note arrows pointing to physis = growth plate). It was felt that most expedient and safe treatment would be guided growth. In consideration of his relative skeletal maturity, decision was made to apply tension-band plates to femur and tibia simultaneously, for sake of time.
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Patient's legs are straight 11 months after pan-genu guided growth of medial femur and tibia. Pain has resolved, and he has resumed a fully active lifestyle. Limb lengths are equal, and knee remains stable.
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Standing anteroposterior radiograph of legs confirms clinical findings; plates were therefore removed.
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This 6-year-old girl, born with tibial dysplasia, underwent foot ablation at age 2 years, combined with surgical synostosis of distal fibula to tibial stump. She developed progressive genu valgum necessitating that prosthetist move post medially. However, she then experienced medial knee pain and stump irritation. Full-length weightbearing radiograph demonstrates lateral displacement of mechanical axis (red dotted line) to joint margin.
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Treatment options are limited to osteotomy and guided growth. Osteotomy would require "down time"--out of her prosthesis and nonweightbearing while cut bone is healing.
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Family chose option of guided growth, and plates were applied to distal medial femur and proximal medial tibia. Patient resumed full activities in her prosthesis, and this full-length radiograph, taken 1 year later, demonstrates normalization of mechanical axis. At this point, prosthetist moved post laterally. Knee pain and stump irritation have abated.
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Close-up view demonstrates neutral mechanical axis and open growth plates. Note divergence of screws. At this point, plate was removed. Further growth will be monitored, and guided growth will be repeated if needed.
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Clinical photograph shows her alignment just prior to hardware removal.
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After guided growth for idiopathic genu valgum, this girl's parents sent periodic photos of her legs, documenting full correction over 8 months, whereupon they returned for implant removal. No "routine" office visits and x-rays were required in interim.
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Shown is gross overcorrection of genu valgum. Because there is substantial growth remaining, even this deformity may be corrected by removing medial implant and placing a lateral tension band. The overcorrection was potentially preventable with smartphone monitoring. It is important to educate parents as to what to expect from guided growth and to encourage them to use their smartphones to document improvement with monthly pictures.
