SURGICAL TECHNIQUES PEDIATRIC 2022, Dec, 22 | 12:00 am

Repair of Congenital Pseudarthrosis of the Tibia With the Williams Rod

 

Chapter 33

Repair of Congenital Pseudarthrosis of the Tibia With the Williams Rod

Perry L. Schoenecker and Margaret M. Rich

 

DEFINITION

  • Congenital pseudarthrosis of the tibia follows pathologic fracture of a tibia.2,4

  • In most cases, the pseudarthrosis is preceded by increasing anterolateral bowing of the tibia.8

  • Spontaneous healing does not occur; shortening and angulation with instability are progressive and impair ambulation.

  • Surgical treatment with a solid intramedullary rod and bone graft and long-term protection with a total-contact orthosis can provide lasting consolidation and minimize secondary de-formity.1,3,5,7,9

  • Inability to achieve stable union may necessitate amputa-tion.5,7

     

    ANATOMY

  • The tibia is abnormal from birth; however, this may not become apparent until weight bearing begins. The remainder of the extremity is normal.

  • Most patients will have anterolateral bowing that increases to the point of pathologic fracture.

  • Shortening is common and tends to increase after fracture.

  • As the anterior bowing increases, the foot may assume a dorsiflexed position to maintain contact with the floor.

  • Involvement of the fibula is variable and may worsen as the tibial pseudarthrosis progresses.

  • Nearly all cases are unilateral.

     

    PATHOGENESIS

  • Anterolateral bowing, when present, increases with weight bearing as the mechanical axis falls farther behind the axis of the tibia. Additionally, the calf musculature acts like a bowstring and increases tension within the tibia, leading to failure.

  • Most pseudarthroses occur in the middle to distal third of the tibia.

  • The pseudarthrosis comprises hamartomatous fibrous tissue, not neurofibroma.

  • Fibular bowing or pseudarthrosis compounds the deformity and further compromises stability.7,8

     

    NATURAL HISTORY

  • Rarely, bowing or sclerosis is present and does not progress to fracture and pseudarthrosis.

  • Once established, the pseudarthrosis remains and does not resolve spontaneously. The resultant instability and shortening interferes with normal ambulation.

  • Use of a total-contact orthosis may slow the progression and postpone but not eliminate the need for surgical intervention.

  • More severe deformities become symptomatic at an earlier age, occasionally presenting in infancy.

PATIENT HISTORY AND PHYSICAL FINDINGS

  • The most common presenting complaint is anterolateral bowing of the tibia (FIG 1).2,4 Shortening of the involved extremity may not be apparent at presentation.

  • Pain is absent unless the tibia has fractured acutely.

  • Limp or dull aching may precede pathologic fracture.

  • Over half of these patients have neurofibromatosis (NF) type I.4,8

  • The skin should be closely inspected for café-au-lait spots, axillary or inguinal freckles, or neurofibromas as signs of underlying NF.

  • A family history of NF may be present.

  • Referral to a geneticist is recommended for confirmation of the diagnosis and genetic counseling.

     

    IMAGING AND OTHER DIAGNOSTIC STUDIES

  • Anteroposterior (AP) and lateral plane radiographs of the affected tibia are sufficient for diagnosis (FIG 2).

  • The radiographic appearance of the tibia is variable: it may be cystic, sclerotic, or atrophic. There may be involvement throughout the tibia.2–4

     

     

     

     

     

    FIG 1 • Standing AP photo of lower extremities. Anterior and lateral bowing is present in the left tibia of this 4-year-old girl. Shortening is minimal. The foot, knee, and thigh appear normal. Note multiple café-au-lait spots on the thighs and lateral side of the right leg, one of the major criteria of type I neurofibromatosis.

     

    1251

     

     

     

    A
    B

     

    FIG 2 • A. AP radiograph of the tibia at age 13 months demonstrates lateral bowing of the tibia and fibula. The medullary canal of the tibia is widened and has a cystic appearance. B. The accompanying lateral view shows the anterior bow with a mixed cystic and sclerotic medullary canal of the tibia. Note the relative dorsiflexed position of the foot as compensation for the anterior angulation of the distal tibia. A total-contact orthosis is used to support the extremity and slow progression of the deformity.

     

    • Mild deformities present with bowing and mild sclerosis at the apex. The medullary canal can be narrow or expanded, with a cystic appearance.

    • After fracture, little callus forms and the bone tends to become more atrophic in appearance.

    • Severe deformities show resorption of bone at the pseudarthrosis, increasing fibular deformity, and tapering of the bone ends (the “pulled taffy” appearance).

      DIFFERENTIAL DIAGNOSIS

    • Ring constriction or amniotic band syndrome

    • Fibrous dysplasia

    • Osteofibrous dysplasia

    • Osteomyelitis

    • Fibrosarcoma of infancy

    • Fibular hemimelia (total absence of the fibula)

      NONOPERATIVE MANAGEMENT

    • Use of a total-contact ankle–foot orthosis (AFO) or knee–ankle–foot orthosis (KAFO) provides mechanical support for the tibia, particularly in toddlers and young children.8

    • Pathologic fracture in a very young child can be treated with cast immobilization if the bowing deformity is mild.

    • Nonoperative measures are useful to postpone the age for surgical treatment, allowing the use of a larger intramedullary rod and greater volume of available autologous bone graft.

      SURGICAL MANAGEMENT

    • The presence of a pseudarthrosis warrants operative treatment to stabilize the tibia and provide a sufficient biologic framework for healing.1,3,5–9

  • The intramedullary rod is designed to provide long-term stabilization of the tibial pseudarthrosis as the child grows. The rod remains in place, anchored by press fit in the medullary canal. The proximal tibia and the distal tibia grow away from the ends of the rod.10

  • Younger children may require exchange with a longer rod if needed to maintain support of the tibia and stabilization of the pseudarthrosis.

     

    Preoperative Planning

  • The dimensions of an appropriate-size rod can be determined from the plain films. The width of the medullary canal adjacent to the pseudarthrosis dictates the diameter of rod to be used. The length of the rod is determined from the lateral film.6

  • The anticipated length of tibia to be resected to healthy bone is also measured; it is usually 1 to 2 cm.

  • In young children (less than 8 years) and in those with a very distal pseudarthrosis, the intramedullary rod should cross the ankle and subtalar joints to provide maximum stabilization because of the short distal tibial segment. The distance from the proximal tibial physis to the bottom of the calcaneus is measured. That length minus the amount to be resected is the length of intramedullary rod to be used.

  • In older children (more than 8 years), the rod can be placed within the tibia and does not need to remain across the ankle or subtalar joints. The distance from the proximal tibial physis to the distal tibial physis minus the amount of tibia to be resected is the length of rod that will be needed.

  • The Williams rod is made up of two sections: the section with the female coupling remains within the tibia and the piece with the male coupling is used as an introducer or pusher rod and is not considered in the selection of rod length (FIG 3). The rod can be cut or trimmed intraoperatively if needed to adjust the length.6

  • If additional angular deformity is present in the tibia, an osteotomy may be needed to allow passage of the straight rod within the medullary canal.

  • If a fibular pseudarthrosis is also present, it should also be stabilized using an intramedullary Kirschner wire. If the fibula is intact, osteotomy may be needed to facilitate preparation of the tibia and introduction of the intramedullary rod.7,8

     

    Positioning

  • The patient is supine for preparation and rodding of the tibia. Before this, an iliac bone graft is obtained.

    • For small children, the graft should be obtained from the posterior iliac crest. In those cases, the child is positioned in the lateral decubitus position and is prepared from the waist to the toes.

    • For larger children, a bump can be placed under the buttock to facilitate positioning for an anterior iliac crest graft. It is removed before proceeding with the tibial exposure.

       

      Approach

  • The tibia is approached directly along the anterior subcutaneous border. The incision is centered over the pseudarthrosis and extends 3 to 4 cm above and below that level.

  • The fibula is approached through a longitudinal incision, centered over the fibular pseudarthrosis, anterior to the peroneal muscles.

     

     

     

     

     

     

    A B

    FIG 3 • A. This assortment of Williams rods includes the female rod, which will remain within the tibia, and the complementary male rod used for insertion. Ideally, variable lengths and widths should be available. Selection of the appropriate-sized rod is based on the width of the medullary canal on the AP and lateral plane films. The length is estimated using the lateral film, measuring from the proximal tibial physis to the distal physis or bottom of the calcaneus, depending on the need to include the ankle and subtalar joints, and subtracting the length of the pseudarthrosis to be resected. The rod is to be coaxial with the tibia and of maximum length to minimize recurrent bowing above and below the rod as growth continues. B. Close-up view of the ends of the male and female sections. The male rod with the knurled end is the distal section and will be removed. The female flat, threaded end will be left in place. If the rod chosen is too long, it can be shortened using a bolt cutter and the tip of the rod removed, leaving the threaded end intact.

     

     

    TECHNIQUES

     

    OBTAINING THE ILIAC CREST BONE GRAFT

    Posterior Iliac Graft

    • A 6-cm incision is made following the contour of the posterior medial corner of the iliac crest.

    • The incision is carried down through the subcutaneous tissue, exposing the fascia overlying the iliac crest and abductor musculature.

    • The apophyseal cartilage is exposed along the ilium and is split in half, sharply, along the course of the iliac crest. The lateral (superficial) half of the apophyseal cartilage and attached periosteum is elevated to expose the outer table of the ilium, subperiosteally.

    • An osteotome is used to cut the outer table. Cortical and cancellous strips are obtained.

    • The apophysis is reapproximated with interrupted sutures. A drain is used at the surgeon’s discretion. The subcutaneous layer and skin are closed, and the patient is then rolled to the supine position.

      Anterior Iliac Crest Graft

    • In larger children, the anterior iliac crest can be used.

    • The approach is similar except the incision is centered over the anterolateral ilium.

       

      PREPARATION OF THE TIBIA

      • A sterile thigh tourniquet is applied and inflated.

      • A 6- to 8-cm longitudinal incision is made over the tibial pseudarthrosis, along the subcutaneous border.

      • The tibia is exposed subperiosteally and circumferentially around the pseudarthrosis.

        • The plane for subperiosteal dissection is more readily identified proximal and distal to the pseudarthrosis rather than directly over it.

        • The fibrous tissue within the pseudarthrosis is removed to expose the bone. A combination of sharp dissection, rongeur, and curettage is used.

        • The pseudarthrosis must be excised in addition to the abnormal dense, sclerotic bone adjacent to it.

        • The medullary canal can be probed and identified with a small curette.

      • A drill bit, smaller in diameter than the intramedullary rod to be inserted, is used to open and enlarge the medullary canal above and below the pseudarthrosis (TECH FIG 1A).

         

    • The C-arm image is used to ensure that the canal preparation is not eccentric.

  • If secondary bowing is present, it may not be possible to remain within the central medullary canal. Osteotomy of the tibia at that level should allow passage of the drill bit, remaining central in the medullary canal.

  • Distally, the drill bit is passed through the tibia, stopping at the physis.

  • If the rod will be left across the ankle and subtalar joints, a similar-sized smooth Kirschner wire is used to perforate the talus and calcaneus. Care must be taken to hold the foot and ankle in a neutral position during this process.

  • Preparation of the tibia is complete when the drill bit can be passed through the proximal fragment up to the physis and distally to the physis.

    • The drill bit should be centered within the tibia in both the AP and lateral images (TECH FIG 1B).

       

      TECHNIQUES

       

      A

       

      B

       

      TECH FIG 1 • Preparation of the tibia. A. A drill bit is used to open the medullary canal proximal and distal to the pseudarthrosis. C-arm image intensification is used to maintain central positioning within the medullary canal on the AP and lateral views. If there is severe bowing of the tibia, an osteotomy may be needed to prevent eccentric reaming, as in this patient. B. Lateral C-arm image of the distal tibia showing central position of the drill bit, stopping just above the distal physis. A similar-size Kirschner wire can be used to cross the physis, talus, and calcaneus if needed prior to rod insertion.

      PREPARATION OF THE FIBULA
       

      incision, anterior to the peroneals. The fibula is exposed the proximal fibula. In some cases this cannot be accom-

      subperiosteally and the fibrous tissue and adjacent

      plished because the fibula is too atrophic.

      pathologic bone are removed, as in the tibia. ■ An intact fibula may interfere with preparation of the
       

      branches of the peroneal nerve, just medial to the tal fragments. It can also prevent contact of the tibial

      fibula. fragments. Osteotomy of the fibula will resolve the issue.
       

      Kirschner wire. This is inserted through the distal frag-

      sion across the tibia.

      ment, exiting the skin at the tip of the fibula. After

      STABILIZATION WITH THE WILLIAMS ROD
       

      ducing the tibia, laying the rod next to the leg, and not- across the pseudarthrosis into the proximal tibia, stop-

      ing the position of the rod proximally and distally.

      ping adjacent to the tibial physis (TECH FIG 2D,E).
       

      tibial physis.

      of the rod within the tibia (TECH FIG 2F,G).
       

      tibial physis (if the rod is to remain within the tibia) drill on reverse, the pusher rod will disengage the female

      or within the calcaneus (if the rod will stabilize the section (TECH FIG 2H). Spot C-arm images are used to

      ankle and subtalar joints). confirm satisfactory position of the rod before the
       

      pusher is completely removed.

      an angle to the appropriate length. ■ Contact of the tibial fragments is confirmed visually. If
       

      the fragments are distracted, the surgeon should

      tions together. A power drill is used to insert the pusher osteotomize or remove more fibula to ensure contact

      section into the distal fragment and it is advanced ante-

      is made.

      grade, across the ankle and subtalar joints, exiting the ■ The fibular Kirschner wire is advanced into the proximal

      bottom of the foot through the heelpad (TECH FIG 2A).

      fibula and cut flush with the tip of the fibula.
       

      plantarflexion and dorsiflexion as well as varus– (TECH FIG 2I). Cortical strips can be secured with loops

      valgus alignment. of suture placed around the tibia. Cancellous bone is
       

      placed within and across the pseudarthrosis.

      tension around the rod (TECH FIG 2B). ■ The tourniquet is deflated and circulation assessed
       

      around the repair and in the foot.

      reattached to the distal rod, exiting the foot. The rod is ■ The periosteum usually cannot be closed over the bone

      drawn into the distal fragment (TECH FIG 2C).

      graft. The wound is closed in layers over a drain.

      • A fibular pseudarthrosis is approached through a lateral insertion of the tibial rod, the wire is then drilled into

      • Care must be taken to avoid injury to the deep motor tibia as it can limit mobilization of the proximal and dis-

      • Ideally, the fibula is stabilized with an intramedullary It may be necessary to resect a portion to allow compres-

      • The length of the rod is checked before insertion by re- ■ The tibia is reduced and the rod advanced retrograde

      • The proximal point should be just below the proximal ■ C-arm imaging is used to ensure concentric location

      • The flat, distal end (female) should be at the distal ■ The rod is grasped through the pseudarthrosis; with the

      • If the rod is too long, the pointed end can be cut on

      • The rod sections are assembled by twisting the two sec-

      • The foot must be kept in a neutral position both in ■ The bone graft is placed circumferentially about the tibia

      • A small incision may be needed to relieve the skin

      • The drill is detached from the proximal rod section and

       

       

       

       

       

       

       

       

       

       

      A

      B

       

       

      TECHNIQUES

       

      C

      E

      H

      I

       

       

      D

       

       

       

       

       

       

       

       

      F G

      TECH FIG 2 • A. The male section of the Williams rod is inserted antegrade into the distal segment and advanced through the talus and calcaneus. The foot must be held in neutral flexion and mediolateral angulation as the rod is passed. B. The Williams rod is pushed through the heelpad as it exits the foot. A small incision may be needed to relieve the skin tension around the rod. C. The Williams rod is assembled by twisting the male and female sections together. The drill is attached to the exposed tip of the male section and the rod is drawn into the distal fragment. Note the neutral position of the foot relative to the tibia. D,E. The tibial fragments are approximated and the rod is advanced retrograde into the proximal tibia. F. As the rod is advanced, C-arm images are used to confirm satisfactory coaxial positioning of the rod in both planes. This AP view shows satisfactory position. The rod fills the middle of the canal. A fibular shortening osteotomy has also been completed to allow contact of the tibial fragments. This is usually necessary to avoid distraction by an intact fibula after resection of the pseudarthrosis.

      G. Lateral C-arm image of the advancing rod. The rod is slightly anterior and can be withdrawn and redirected posteriorly to achieve a satisfactory position. In the presence of more severe bowing, an osteotomy would be needed to achieve satisfactory alignment. H. Once the rod is in satisfactory position within the proximal tibia, the male section is partially untwisted from the female section. It may be necessary to grasp the rod through the pseudarthrosis to disengage the two sections. The lateral C-arm image reveals the position of the distal end of the rod before the sections are completely disengaged. The separation of the sections is shown at the arrow. The proximal–distal position of the rod can easily be adjusted if needed. Once contact of the tibial fragments is also confirmed by direct vision and C-arm, the male end is detached and removed. I. The medullary canal is packed with cancellous bone. The cor-ticocancellous strips are placed circumferentially about the pseudarthrosis. These can be secured by loops of suture passed around the tibia.

       

      PEARLS AND PITFALLS

       

       

       

      Patient selection ■ This procedure should be considered only for patients with an established pseudarthrosis. Infants and young children with anterolateral bowing (prepseudarthrosis) should be observed and treated with a total-contact orthosis.

      Alignment and centering of the rod ■ Residual anterior angulation increases the potential for recurrent bowing and

      refracture. Placement of the rod in a colinear fashion within the tibia—that is, a straight rod within a straight tibia—optimizes protection of the tibia from deformity and fracture (FIG 4A). As the tibia grows away from the ends of the rod, bowing may increase through this unprotected segment.

      Foot position ■ If the ankle and subtalar joints are transfixed by the rod, it is important to maintain neutral alignment and a plantigrade foot (FIG 4B). Because of the anterior bow, the foot tends to assume a dorsiflexed position; the lateral bow promotes a valgus deformity at the ankle. A calcaneus foot position further weakens the posterior musculature of the leg. Angular deformity may require treatment by hemiepiphysiodesis or guided growth.

      Distraction ■ An intact or overly long fibula may distract the tibia and compromise consolidation. Osteotomy with shortening as needed to permit contact of the tibial fragments resolves the issue.

      Rod selection ■ Ideally the rod spans enough of the tibia to provide long-term mechanical support and protection of the pseudarthrosis. As growth occurs, more of the tibia is exposed to stresses that promote recurrence of bowing. Selection of the longest and greatest-diameter rod is best. Preoperative measurements from plain films provide a reliable guide for the length and width needed. An assortment of rod sizes are available (Zimmer) and may need to be modified—that is, cut to an appropriate length— before surgery.

      Orthotic management ■ Use of a total-contact orthosis is essential throughout growth to reduce stress

      through the pseudarthrosis and maintain consolidation. A solid AFO is used if the rod transfixes the ankle and subtalar joints. A KAFO is used in young children (less than 5 years).

       

      FIG 4 • A. AP view of tibia after rodding in this 5.5-year-old girl shows ideal rod placement centrally within the tibia. The proximal tip of the rod is just below the physis, the fragments are in contact, and the distal rod is central within the tibia and also fills the medullary canal. The ankle is in neutral varus–valgus alignment. The fibula is very atrophic and could not be stabilized even with a small-diameter Kirschner wire. B. Lateral view of the same patient. The rod crosses the ankle, which is held in neutral flexion. The rod controls a maximum length of the tibia and centers the proximal

      A B tibia over the plafond.

       

      POSTOPERATIVE CARE

      • Cast immobilization is used postoperatively until consolidation of the pseudarthrosis occurs, usually at least 12 weeks. A one-and-a-half spica cast is used for infants and young children (less than 6 years) to minimize stress across the pseudarthrosis. A long-leg, non-weight-bearing cast is used in older children.

         

      • A total-contact orthosis is used long term to protect the area of consolidation and reduce mechanical stresses on the lower leg that promote anterior bowing. Initially a nonarticulated KAFO is used in young children and in those with the rod across the ankle and subtalar joints. This is changed to an articulated AFO when the rod is positioned within the tibia, no longer transfixing the ankle.

         

        A
        B

         

        FIG 5 • Follow-up AP (A) and lateral (B) views of another child 2 years after Williams rod placement and bone graft. The rod now lies within the tibia. The proximal and distal tibial physes have grown away from the ends of the rod. Bowing has not recurred and the consolidation is stable. An articulated total-contact ankle–foot orthosis is used as additional support and protection. Refracture is common but manageable with cast immobilization if deformity is minimal. Supplemental bone graft can be used if healing is delayed. In the presence of recurrent deformity, revision surgery using a larger-diameter, longer rod, bone graft, and osteotomy, if needed, is recommended.

         

        • Once the ankle is no longer transfixed, an ankle rehabilitation program is implemented that includes range of motion and calf strengthening.

        • Periodic follow-up is necessary throughout growth to monitor the quality of healing and maintenance of good rod position (FIG 5).

        • Ambulation and activities are unrestricted as long as the orthosis is used. Once skeletal maturity is reached, the orthotic use is recommended for sports and high-stress activities.

          OUTCOMES

        • Patients resume independent ambulation with long-term orthotic protection.

        • Consolidation reliably occurs in 90% of cases with this technique.1,3,5,7–9

        • Two long-term studies assessed the quality of maintenance of healing, with variable results. Both studies emphasized the importance of paying attention to details regarding the technique of rod insertion, continued orthotic use, and long-term follow-up care.7,8

      • Anterior bowing may recur and lead to refracture. If the rod is in good position, healing can be obtained by simple cast immobilization. If healing is delayed, the addition of bone graft will generally lead to union.1

      • Valgus angulation may also occur and may need to be managed by guided growth or hemiepiphysiodesis.8

      • Limb-length inequality is variable. It is more common with patients with severe deformity, those requiring greater length of pseudarthrosis resection, and those with recurrent fracture.

      • While most patients realized long-term satisfactory healing and function, some patients ultimately chose amputation after multiple recurrent fractures resulting in loss of function or limb-length inequality.7,8

        COMPLICATIONS

      • Complications include those routinely associated with musculoskeletal procedures, such as swelling, wound healing, and pain, with similar incidence.

      • The most likely intraoperative complication is neurovascu-lar injury, particularly to the deep motor branches of the peroneal nerve. These are at risk during fibular osteotomy.

      • None of the studies have reported occurrence of a compartment syndrome, although this could be produced by overzeal-ous use of bone graft, which may compress the tibial vessels. Fasciotomy is usually incidental with the surgical approach to the tibia.

      • Refracture with progressive shortening and loss of stability may compromise function sufficiently to warrant amputation.

      • Satisfying the primary goal of a healed pseudarthrosis is easier to accomplish than maintaining union, which serves to emphasize the recalcitrant nature of this pathologic process.

 

REFERENCES

  1. Anderson DJ, Schoenecker PL, Sheridan JJ, et al. Use of an intramedullary rod for the treatment of congenital pseudarthrosis of the tibia. J Bone Joint Surg Am 1992;74A:161–168.

  2. Boyd HB. Pathology and natural history of congenital pseudarthrosis of the tibia. Clin Orthop Relat Res 1982;166:5–13.

  3. Charnley J. Congenital pseudarthrosis of the tibia treated by the intramedullary nail. J Bone Joint Surg Am 1956;38A:283–290.

  4. Crawford AH. Anterolateral bowing. Pediatric Orthopedic Society of North America One-Day Course, Orlando, FL, May 16, 1999.

  5. Dobbs MB, Rich MM, Gordon JE, et al. Use of an intramedullary rod for treatment of congenital pseudarthrosis of the tibia: a long-term follow-up study. J Bone Joint Surg Am 2004;86A:1186–1197.

  6. Dobbs MB, Rich MM, Gordon JE, et al. Use of an intramedullary rod for the treatment of congenital pseudarthrosis of the tibia: surgical technique. J Bone Joint Surg Am (Suppl Surg Tech) 2005;87A:33–40.

  7. Johnson CE. Congenital pseudarthrosis of the tibia: results of technical variations in the Charnley-Williams procedure. J Bone Joint Surg Am 2002;84A:1799–1810.

  8. Schoenecker PL, Rich MM. Bowing of the tibia: congenital pseudarthrosis of the tibia. In: Morrissy RT, Weinstein SL, eds. Lovell and Winter’s Pediatric Orthopedics, 6th ed. Philadelphia: Lippincott Williams & Wilkins, 2005:1189–1197.

  9. Umber JS, Moss SW, Coleman SS. Surgical treatment of congenital pseudarthrosis of the tibia. Clin Orthop Relat Res 1982;166:28–33.

  10. Williams PF. Fragmentation and rodding in osteogenesis imperfecta. J Bone Joint Surg Br 1965;47B:23–31.