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Pediatric Genu Valgum Workup

  • Author: Peter M Stevens, MD; Chief Editor: Jeffrey D Thomson, MD  more...
 
Updated: Aug 22, 2016
 

Laboratory Studies

When an underlying syndrome is suggested by the physical findings and history, consultation with a geneticist and workup are warranted. If metabolic bone problems are a concern, relevant hematologic and urine studies are warranted, along with consultation with an endocrinologist. In a select few patients, bone densitometry studies may be warranted.

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Imaging Studies

The criterion standard for documentation of genu valgum is a standing anteroposterior (AP) radiograph of the lower extremities, taken with the patellae facing forward. This study permits direct visualization of both the true and the apparent limb lengths and alignment. The length of each femur and tibia is measured, and any diaphyseal deformities (which would be missed on a scanogram) are clearly visible.

The mechanical axis is a line drawn from the center of the head of the femur to the center of the ankle; this line should bisect the knee. In normal variations, this line is still in the central 50% of the knee. Genu valgum is defined by lateral deviation of the axis or deviation toward or beyond the joint margin. The deformity may be in the femur, the tibia, or both. The normal lateral distal femoral angle is 84° (6° of valgus), and the medial proximal tibial angle is 87° (3° of varus).

When physeal abnormalities are suspected, obtain AP and lateral radiographs of the hip or knee (or fluoroscopy) to have better visualization of the physis. If a skeletal dysplasia is suggested, a skeletal survey is warranted.

A sunrise or Merchant view of the patellae may reveal tilt, subluxation, and, occasionally, osteochondral defects or loose bodies. Finally, it may be helpful to obtain an AP radiograph of the left wrist for bone age, to ensure remaining growth (ideally ≥12 months) is adequate to allow for correction of a deformity by growth manipulation.

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Histologic Findings

Depending on the underlying etiology of genu valgum, epiphyseal, physeal, or metaphyseal histologic abnormalities may be present. However, biopsy of the bone rarely is necessary or helpful. Such invasive procedures may have an adverse effect upon physeal growth and the outcome of treatment.

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Contributor Information and Disclosures
Author

Peter M Stevens, MD Professor, Director of Pediatric Orthopedic Fellowship Program, Department of Orthopedics, University of Utah School of Medicine

Peter M Stevens, MD is a member of the following medical societies: Pediatric Orthopaedic Society of North America, Alpha Omega Alpha, American Academy of Orthopaedic Surgeons, American Orthopaedic Association

Disclosure: Received royalty from Orthofix Inc for independent contractor; Received royalty from Orthopediatrics, Inc for independent contractor; Received honoraria from Orthopediatrics, Inc for speaking and teaching.

Coauthor(s)

Michael C Holmstrom, MD Consulting Surgeon, Department of Orthopedics, The Orthopedic Specialty Hospital (TOSH)

Michael C Holmstrom, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, Arthroscopy Association of North America, Pediatric Orthopaedic Society of North America, American Medical Association, Utah Medical Association

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

George H Thompson, MD Director of Pediatric Orthopedic Surgery, Rainbow Babies and Children’s Hospital, University Hospitals Case Medical Center, and MetroHealth Medical Center; Professor of Orthopedic Surgery and Pediatrics, Case Western Reserve University School of Medicine

George H Thompson, MD is a member of the following medical societies: American Orthopaedic Association, Scoliosis Research Society, Pediatric Orthopaedic Society of North America, American Academy of Orthopaedic Surgeons

Disclosure: Received none from OrthoPediatrics for consulting; Received salary from Journal of Pediatric Orthopaedics for management position; Received none from SpineForm for consulting; Received none from SICOT for board membership.

Chief Editor

Jeffrey D Thomson, MD Associate Professor, Department of Orthopedic Surgery, University of Connecticut School of Medicine; Director of Orthopedic Surgery, Department of Pediatric Orthopedic Surgery, Associate Director of Clinical Affairs for the Department of Surgical Subspecialties, Connecticut Children’s Medical Center; President, Connecticut Children's Specialty Group

Jeffrey D Thomson, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons

Disclosure: Nothing to disclose.

Additional Contributors

Mininder S Kocher, MD, MPH Associate Professor of Orthopedic Surgery, Harvard Medical School/Harvard School of Public Health; Associate Director, Division of Sports Medicine, Department of Orthopedic Surgery, Children's Hospital Boston

Mininder S Kocher, MD, MPH is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American College of Sports Medicine, Pediatric Orthopaedic Society of North America, American Association for the History of Medicine, American Orthopaedic Society for Sports Medicine, Massachusetts Medical Society

Disclosure: Received consulting fee from Smith & Nephew Endoscopy for consulting; Received consulting fee from EBI Biomet for consulting; Received consulting fee from OrthoPediatrics for consulting; Received stock from Pivot Medical for consulting; Received consulting fee from pediped for consulting; Received royalty from WB Saunders for none; Received stock from Fixes-4-Kids for consulting.

References
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This diagram depicts genu valgum involving the right leg (lighter shade), where the mechanical axis falls outside the knee. The goal of treatment is to realign the limb and neutralize the mechanical axis (dotted red line), thereby mitigating the effects of gravity through guided growth of the femur and/or tibia (whatever is required to maintain a horizontal knee joint axis). The darker shade depicts normal alignment with the mechanical axis now bisecting the knee.
This 9-year-old patient has symmetrical and progressive genu valgum caused by a 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, the hospitalization and the attendant cost and risks, including peroneal nerve palsy and compartment syndrome, make this a daunting task for the surgeon and family alike. Furthermore, mobilization and weightbearing may require physical therapy but must be delayed pending initial healing of the bones.
Heretofore, stapling was a viable option. This outpatient procedure permitted simultaneous and multiple deformity correction, without casts or delayed weightbearing. However, the concept of compressing and overpowering the physes has the drawbacks of slower correction because the fulcrum is within the physis. Provided the rigid staples did not dislodge or fatigue, satisfactory correction could be realized. If the hardware failed prematurely, the correction was either abandoned or the hardware exchanged. Compared with osteotomies, it was a risk worth taking, that is, until the advent of a better option.
The application of a single 8-plate per physis permits the same correction as stapling, without the potential drawbacks of implant migration or fatigue failure. Based on the principle of facilitating rather than compressing the physes, the correction occurs more rapidly and rebound growth, though possible, may be less frequent. When the mechanical axis has been restored to neutral, the plates (or metaphyseal screws) are removed (and replaced as necessary if recurrent deformity ensues).
This 14-year-old boy, weighing 132 kg, presented with activity-related anterior knee pain, circumduction gait, and difficulty with running and sports. His symptoms had been progressive over a period of 18 months despite nonoperative measures including physical therapy, activity restrictions, and nonsteroidal anti-inflammatory drug therapy.
Nine months following the insertion of 8-plates in the distal femora (1 per knee), the mechanical axis is approaching neutral and his symptoms abated. The plates were removed 2 months later, allowing for full correction of his valgus deformities. He has not had recurrence.
This 14-year-old boy broke his distal femur 1 year previously. He was treated with internal fixation using a condylar plate, and the fracture healed uneventfully. However, he developed medial overgrowth of the femur, which caused progressive and painful genu valgum. Note the lateral displacement of the mechanical axis into zone 2. One alternative is to perform a supracondylar osteotomy with exchange of the plate; this was declined.
Two options for instrumented and reversible hemi-epiphysiodesis are multiple staples versus a tension band plate. The latter, being flexible yet secure, avoids the potential risks of hardware breakage or migration. Furthermore, growth is facilitated rather than restricted and the alignment is restored more rapidly.
One year following guided growth of the femur with an 8-plate, his mechanical axis is neutral, his limb lengths are equal, and his symptoms have abated; the plate was then removed. Neither procedure required hospitalization or immobilization. Each time he was able to rapidly resume sports participation.
A 17-year-old male who underwent an arthroscopic reconstruction of his 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.
A fluoroscopic close-up view of the left knee demonstrates, despite his chronologic age of 17, that he has significant growth remaining. (Note arrows pointing to the physis = growth plate). It was felt that the most expedient and safe treatment would be guided growth. Considering his relative skeletal maturity, it was elected to apply tension band plates to the femur and tibia simultaneously, for the sake of time.
The patient's legs are straight 11 months following pan-genu guided growth of the medial femur and tibia. His pain has resolved and he has resumed a fully active lifestyle. His limb lengths are equal and his knee remains stable.
A standing AP radiograph of the legs confirms the clinical findings; the plates were therefore removed.
This 6-year-old girl, born with tibial dysplasia, underwent foot ablation at age 2 years, combined with surgical synostosis of the distal fibula to the tibial stump. She developed progressive genu valgum necessitating that the prosthetist move the post medially. However, she then experienced medial knee pain and stump irritation. This full-length weight-bearing radiograph demonstrates lateral displacement of the mechanical axis (red dotted line) to the joint margin.
Treatment options are limited to osteotomy or guided growth. An osteotomy would require "down time" - out of her prosthesis and non weight-bearing while the cut bone is healing.
The family chose the option of guided growth, and plates were applied to the distal medial femur and proximal medial tibia. She resumed full activities in her prosthesis and this full-length radiograph, taken one year later, demonstrates normalization of the mechanical axis. At this point the prosthetist moved her post laterally. Her knee pain and stump irritation have abated.
A close-up view demonstrating the neutral mechanical axis and open growth plates. Note the divergence of the screws. At this point, the plate was removed. Further growth will be monitored, repeating guided growth if needed.
A clinical photograph showing her alignment just prior to hardware removal.
 
 
 
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