Femoral Lengthening with External Fixation

Shawn C. Standard and John E. Herzenberg

Indications

Femoral shortening with or without concurrent limb deformity

• Acute deformity correction can be performed with subsequent gradual distraction for lengthening at the same osteotomy site.

• Double femoral osteotomies can be performed for deformity correction at one site and lengthening at the second site.

• Figure 1 shows an example of a patient with congenital femoral deficiency that is undergoing a femoral lengthening. A double-level osteotomy has been performed for acute deformity correction both proximally and distally with concurrent lengthening at the distal osteotomy site.

Femoral shortening greater than 7–8 cm will require sequential lengthenings or a combination of lengthening and epiphysiodesis.

Femoral shortening greater than 3 cm that cannot be treated with more conservative methods (shoe lifts or epiphysiodesis)

• Contraindications to epiphysiodesis:

Abnormal predicted overall height

Inadequate growth remaining

Etiologies

Congenital

• Congenital femoral deficiency

Proximal femoral focal deficiency

Congenital short femur

Postaxial hypoplasia of the limb

• Fibular hemimelia with concurrent femoral shortening

• Hemihypertrophy

Neurofibromatosis

Beckwith-Wiedemann syndrome

Idiopathic

Proteus syndrome

Klippel-Trénaunay syndrome

• Hemiatrophy

• Congenital banding syndrome (Streeter’s dysplasia)

Neuromuscular

• Hemiplegic cerebral palsy

• Polio

• Myelomeningocele

• Sciatic nerve injury

Growth arrest or bone loss

Neonatal

• Osteomyelitis

Growth arrest or bone loss

• Meningococcal septicemia

Developmental

• Developmental dysplasia/dislocation of the hip

• Slipped capital femoral epiphysis

• Legg-Calvé-Perthes disease

• Ollier’s enchondromatosis

• Multiple hereditary exostosis

• Russell-Silver syndrome

• Melorheostosis

• Rickets

• Renal osteodystrophy

• Skeletal dysplasia/achondroplasia

• Osteogenesis imperfecta

• Juvenile rheumatoid arthritis

Pitfalls

• Congenital femoral deficiency

Severe concurrent deformities of the hip and knee—Joint realignment and reconstruction prior to lengthening.

Intrinsic soft tissue contractures—Release of the rectus femoris tendon and excision of the ITB prior to lengthening.

Concurrent instability of the hip and knee joints—The hip joint requires correction of the concurrent acetabular dysplasia with a pelvic osteotomy prior to lengthening. The knee joint should always be bridged with a hinged external fixation component during the lengthening of the congenitally deficient femur.

• Russell-Silver syndrome

Difficult to predict the final limb-length inequality during growth.

Wait until skeletal maturity to equalize limb lengths. May proceed with initial lengthening if leg length discrepancy (LLD) is greater than 5 cm; parents must be warned to expect possible recurrence and need for further treatment.

• Juvenile rheumatoid arthritis

Type V growth pattern with upward slope–plateau–downward slope with improvement without intervention.

Final LLD should be assessed at skeletal maturity and then corrected.

• Achondroplasia

Premature limb lengthening at ages less than 8 years can result in growth inhibition.

Greater than 6–7 cm of femoral lengthening in a skeletally immature patient can result in growth inhibition.

• Hemihypertrophy: Klippel-Trénaunay syndrome

Avoid acute shortening of the involved side secondary to potential venous malformations.

• Polio

Delayed regenerate bone formation and healing—Consider decreased rate of distraction.

Must maintain full knee extension or slight hyperextension for patients with decreased quadriceps strength. Residual knee flexion contractures eliminate the patient’s ability to lock the knee during ambulation and result in brace requirement for supported ambulation.

• Developmental dysplasia/dislocation of the hip, slipped capital femoral epiphysis, and Legg-Calvé-Perthes disease

LLD resulting from residual hip deformity may be treated with proximal femoral/hip osteotomies that impart length with concurrent realignment: proximal femoral valgus osteotomy (Wagner osteotomy); femoral neck lengthening osteotomy (Morscher osteotomy); surgical hip dislocation with subcapital osteotomy.

Controversies

• LLD less than 2 cm

Considered within normal variation

Easily treated with internal shoe lift

No evidence of long-term sequelae

• Severe deformities requiring extensive lengthening

Reconstruction with lengthening should be performed at specialized centers.

Limb ablation with prosthetic reconstruction can be considered if total predicted LLD is greater than 30–35 cm. Associated joints are not amendable to reconstruction.

• LLD less than 5 cm in the skeletally immature patient

Long-leg epiphysiodesis if adequate growth remains and height prediction is within normal range

• LLD less than 5 cm in the skeletally mature patient

Femoral shortening of long leg; requires significant rehabilitation for quadriceps strength recovery

Examination/Imaging

Physical Examination

Range of motion of the hip, knee, and ankle joints

• Concurrent contractures or joint/bony abnormalities must be documented.

Special consideration must be given to knee fixed flexion deformity. The cause (soft tissue contracture vs. bony deformity) must be determined.

• Concurrent joint instabilities and ligamentous deficiencies must be documented.

The majority of congenital femoral deficiencies have concurrent absence of anterior and posterior cruciate ligaments.

Clinical alignment

• Coronal plane: varus deformity vs. valgus deformity

• Sagittal plane: recurvatum vs. procurvatum

Rotational profile

• The presence of internal or external femoral torsion must be determined.

Clinical limb-length assessment

• One-centimeter blocks are placed under the short leg until the pelvis is level.

Neurologic examination

• The patient’s strength, sensation, and reflexes should be noted.

Radiographic Examination

Anteroposterior (AP) and lateral standing long-leg radiographs are obtained (taken at a distance of 10 feet using a 51-inch cassette) (Figs. 2 and 3).

• Malalignment and malorientation tests are performed to determine concurrent deformity and location of deformity.

• Limb lengths are assessed (the pelvis should be leveled with blocks and the number of blocks noted on the radiograph).

Standing long-leg lateral radiographs (with maximum knee extension) are obtained (Fig. 4).

• The radiographs are checked for fixed flexion deformity of the knee.

• A malorientation test is performed to determine the presence and location of sagittal plane deformity.

• The radiographs are checked for joint subluxation (significant anterior-posterior instability).

Significant joint or limb deformity should be assessed on a separate radiograph centered on the joint or limb segment of interest.

A supine AP pelvis radiograph should be obtained prior to lengthening to assess the integrity of the hip joint (center-edge angle and appearance of the sourcil).

Treatment Options

Limb ablation with prosthetic reconstruction: used when LLD predicted to be greater than 30–35 cm, or with severe dysplasia or absence of associated joints (hip and knee)

Surgical Anatomy

Acetabulum

• Significant dysplasia will result in increased risk of hip dislocation.

Up-slanting sourcil

Abnormal center-edge angle

• Significant dysplasia requires pelvic osteotomy prior to femoral lengthening (Dega osteotomy, triple osteotomy, periacetabular osteotomy).

Tensor fascia lata/iliotibial band (ITB)

• This structure will be penetrated by the laterally placed half-pins.

At the end of the procedure, the knee must be maximally flexed to stretch/tear the fascia lata around the half-pins.

If the fascia lata is not stretched, a postoperative knee extension contracture will result with minimal knee flexion.

• If a preoperative contracture is present, then a prophylactic release is required at the time of surgery.

Congenital femoral deficiency lengthening requires an excision of the ITB prior to lengthening.

Achondroplasia requires a prophylactic release of the distal ITB prior to the second femoral lengthening (if performed).

Sciatic nerve/peroneal nerve

• These nerves are not directly at risk during the external fixation application or osteotomy.

• Rapid lengthening or concurrent deformity correction can place tension on the neural elements.

The sciatic nerve is tethered as the common peroneal nerve enters the lateral compartment of the lower leg.

Peroneal nerve tension or irritation initially will result in pain on the anterior aspect of the lower leg and dorsum of the foot and altered sensation in the first web space. Late findings include weakness of dorsiflexors or footdrop. Young patients will often hold the toes up with their hands or continuously rub their foot. Treatment involves slowing the rate of distraction, allowing the hip to extend and the knee to flex, and decompression of the peroneal nerve.

Knee joint

• Significant instability will result in increased risk of joint subluxation or dislocation.

A contracted ITB will result in rotatory subluxation of the knee joint with concurrent knee flexion contracture and patella dislocation.

Contracted hamstrings will result in posterior subluxation/dislocation of the knee joint.

• Severe knee instability should be addressed with ligamentous reconstruction and patella realignment prior to femoral lengthening.

Figure 5 illustrates the neurovascular structures of the proximal anterior thigh region that are located medial to the sartorius muscle (Fig. 5A) and the typical placement of the monolateral external fixator for femoral lenghthening (Fig. 5B). Note that the external fixation pins are placed from the lateral position posterior to the tensor fascia lata muscle and away from the neurovascular elements.

Positioning

The patient is placed supine on a radiolucent table that allows visualization from the hips to the ankles.

The fluoroscopy machine is placed on the opposite side of the operating room (OR) table and perpendicular to the involved extremity.

A small bump is placed under the ipsilateral sacrum to allow the lower extremity to rest in a patella-forward position.

The entire lower extremity is prepped and draped to include the groin area, gluteal region, and iliac crest to the subcostal margin.

• This allows the extremity to be manipulated during the procedure.

• All aspects of the hip, femur, and knee are accessible.

Figure 6 shows a patient with fibular hemimelia with significant concurrent congenital femoral deficiency (Fig. 6A). The patient’s lower extremity is draped to allow entire access from the pelvis to the foot (Fig. 6B and 6C).