Correction of Large Bilateral Tibia Vara
      with the Ilizarov Method

      by
      S. Robert Rozbruch, MD; Arkady Blyakher, MD; Stephen B. Haas, MD; Robert Hotchkiss, MD

      Limb Lengthening Service, Knee Service
      Department of Orthopaedic Surgery, Hospital for Special Surgery
      Weill Medical College, Cornell University


      Abstract
      An adult patient with massive bilateral tibia vara as a result of neglected infantile Blount's disease is presented. Correction of the deformities was performed with a tibia and fibula osteotomy and gradual correction using circular external fixation. This represents very early American experience with the Ilizarov method. Ten year clinical and radiographic follow up is presented.

      Introduction:
      Blount's Disease in the adult is a sequel of either the infantile, juvenile, or adolescent types depending on the age of onset.1 Disordered growth of the proximal medial physis and metaphysis produces a localized varus deformity. In addition there is usually a medial tibial torsion deformity. In severe neglected cases, there may be ligamentous laxity, a large varus deformity, extreme sloping and depression of the posteromedial plateau of the tibia, and hypermobility of the medial meniscus.14 Extreme medial deviation of the mechanical axis line leads to abnormal stress transmission across the knee, and this is expected to cause knee pain and progressive degenerative arthritis in adulthood. Zayer,19 in a report of 133 knees in 86 patients with Blount's disease, found that in individuals under 30 years of age there was none with degenerative joint disease, whereas in patients over 30 years of age, 41% had radiographic evidence of degenerative changes. Increasing varus deformity predisposed to degenerative change.

      A variety of methods have been used to correct the tibia vara. These include acute correction of the deformity with various oblique or dome shaped osteotomies with a number of different fixation techniques. Review of the literature 2,8,13,17 reveals a high percentage of fair and poor results. Acute angular and rotational correction of a large deformity with internal fixation is subject to imprecision, nerve palsy, and compartment syndrome. Limited weight bearing is also required in the postoperative period. Closing wedge osteotomies often add to preexisting limb shortening and compromise metaphyseal bone stock.

      The gradual correction of deformity using the principles of distraction osteogenesis was introduced by Ilizarov.6 This method has many advantages over more traditional methods. This case represents very early American experience with the Ilizarov method for correction of massive bilateral varus deformities in an adult from neglected BlountŐs disease with a ten-year followup.

      Case Report:
      A 22 year-old woman presented with severe varus deformities of both legs (Fig. 1A). She was able to ambulate but did so with a limp and with pain in the knees. She had surgical treatment as a young child in Africa but was not aware of the details. On physical examination, using a goniometer, the right leg varus measured 70° and the left leg varus measured 75°. Range of motion of both knees was 0° to 130°. There was full mobility of the hips. Preoperative supine radiographs showed a right femorotibial angle of 40° varus (Fig. 1B) and a left femorotibial angle of 48° varus (Fig. 1C). Both sides were consistent with type VI infantile tibia vara according to the classification of Langenskiold and Riska.7 Standing radiographs showed a femorotibial angle on the right of 55° varus and on the left of 62° varus.

      Bilateral proximal tibia osteotomies, proximal fibula resections of 5 centimeters and peroneal nerve decompressions were performed. Bilateral Ilizarov frames were applied to match the varus deformities. A postoperative right-sided extensor hallucis longus palsy was noted. Gradual adjustment of the frames was started on postoperative day seven. The speed of correction was determined so that the bone at the concavity of the deformity was being distracted at 1 mm per day. Weight bearing as tolerated was encouraged throughout the treatment. At the end of the correction she was ambulating full weight-bearing in the bilateral frames. (Fig 2) At three and one-half months after the index procedure, the patient was taken back to the operating room for excision of prominent bone from the left tibia and frame modification. At five and one-half months after the index procedure, the right Ilizarov frame was removed. At six and one-half months, the left Ilizarov frame was removed. The left proximal tibia was subsequently noted to have a stiff nonunion, and further surgical treatment was felt to be necessary. At seven months following the index procedure, the Ilizarov frame was reapplied to the left leg for the purpose of stabilizing and compressing the nonunion site. The nonunion was not surgically exposed and was not bone grafted. Three months later the left sided frame was removed.

      At one year and five month follow-up following the index procedure, she was ambulating well. She complained of a mild occasional ache in the right knee. Range of motion (ROM) of the right knee was 0° — 135° and the left knee was -3° — 135°. At two-year followup, the patient complained of no pain. ROM of the right knee was 0° — 130° and the left knee was -5° to 125°. A mild lateral thrust was noted bilaterally, but the left side was more pronounced. Erect leg radiograph demonstrated complete bony healing of the osteotomies. The left leg was noted to be 8 mm longer than the right leg. Mechanical axis deviation was 31 mm medial to the midline on the right side and 44 mm medial to the midline on the left side. Lateral distal femoral angle was 83° on the right and 77° on the left. Medial proximal tibial angle was 74° on the right side and 65° on the left side11 (Fig 3A).

      At ten-year followup from the index procedure is ambulating without assistance. She complains of mild and intermittent pain in both knees that responds to the occasional short-term use of non-steroidal anti-inflammatory medications. Knee alignment is visibly normal. (Fig. 3B) No significant coronal or sagittal plane instability is noted. Standing radiographs (Fig. 3C) demonstrate a femorotibial angle of 2° varus of both right and left sides. Knee joint spaces are maintained, and bony remodeling has occurred. Lateral radiographs (Fig. 3D, Fig. 3E) demonstrate the absence of deformity and advanced bony remodeling.

      Discussion:

      This patient is an example of a young adult presentation of a neglected case of bilateral infantile Blount's disease. Oyemande10 reported 25 Nigerian adolescent patients with advanced tibia vara. Fifteen of the patients had bilateral deformities. They were treated with closing wedge osteotomies, acute correction through an open technique, and casting. Complications reported were 4 residual deformities, one osteomyelitis, one wound necrosis, and several large keloid scars. The closing wedge osteotomies led to further shortening.

      Medial mechanical axis deviation and increased stress on the medial joint compartment is thought to be the etiology of Blount's disease and a contributing factor to progressive medial compartment degeneration. Zayer19 found that 11 of 27 knees in patients with Blount's disease over age 30 had osteoarthritic changes. Increasing varus predisposed to degenerative change, but the relationship was not constant. The legs with smaller medial proximal tibial angles were predisposed to degenerative change, and medial proximal tibial angles less than 73° were only seen in knees with osteoarthritis. The patient in the current report had severe sloping and depression of the medial plateau. While this was not addressed in this patient, there are authors who have advocated elevation of the plateau. Zayer18 reported hemicondylar osteotomy in two 15 year-old patients with neglected Blount's disease. At 6 year follow up, he reported good results and recommended this technique for late neglected cases.

      Gregosiewicz et al5 advocated a double elevating osteotomy for severe cases of tibia vara. They performed an acute closing wedge osteotomy in the metaphysis and used this wedge of bone to fill an opening wedge osteotomy through the medial physis. This was done in children, average age 8, and was stabilized with crossed wires and a long leg cast. This improvement of the congruence of the articular surface in addition to mechanical axis realignment may help protect the knee from future degeneration.

      Disadvantages of internal fixation after proximal tibial osteotomy include the lack of postoperative adjustability, difficulty in translating the distal fragment laterally, and the need for limited weight bearing or casting. The inability to obtain a standing hip to ankle radiograph during surgery limits the precision of an intraoperative correction. With external fixation stabilization, the position can be changed acutely or gradually after a standing hip to ankle radiograph is obtained and the appropriate mechanical axis analysis is performed.11

      Acute deformity corrections and stabilization with external fixation has been reported by several authors. Miller et al9 reported the use of an inverted arcuate osteotomy, acute correction, and stabilization with a hybrid external fixator in 12 patients. The average deformity correction obtained was 21.7°. They reported no nerve palsies or compartment syndromes. Smith et al15 reported on the use of a gigli saw percutaneous osteotomy, acute correction, and stabilization with an Orthofix unilateral external fixator in 19 patients with an average weight of 258 lbs. The average correction performed was 27.6° and the time to healing was 141 days. At union the average mechanical axis was 1.9° of varus. Four of their patients had adjustment of the fixator in the postoperative period. One patient had a peroneal nerve palsy that resolved.

      Disadvantages of acute deformity correction may include an increased risk of neurovascular insult and compartment syndrome, particularly with large deformities. Several authors have reported the use of gradual deformity correction with external fixation for tibia vara. Price et al12 reported on the use of dynamic axial external fixation in a group of 23 patients obtaining an average of 20° of correction. De Plabos et al4 reported on the use of gradual correction in 10 patients. An average of 15° of angular correction was obtained at the proximal tibia osteotomy. The average time in the frame was 12 weeks. Stanitski et al16 reported on the use of gradual correction with circular external fixation for 17 obese children. The average preoperative angular deformity was 27° of varus and all patients achieved alignment within 5° of normal. Three patients had leg length discrepancy and underwent an average of 3.5 cm of simultaneous lengthening. The time in frame was 12 weeks for those patients treated without lengthening and 16.9 weeks in those requiring lengthening. There were no nerve palsies or compartment syndromes.

      While there is a general consensus that correction of the varus deformity in Blount's disease is desirable, there have been many methods advocated. These include open or percutaneous osteotomy in the metaphysis of the proximal tibia, opening or closing wedge correction, acute or gradual correction, stabilization with internal or external fixation, and opening wedge correction through the proximal tibia physeal area. The use of a percutaneous osteotomy in the metaphysis and gradual correction of a large deformity with an external fixator has many advantages. The osteotomy is minimally invasive and does not require extensive soft-tissue stripping, improving the bony healing potential. Complications of osteomyelitis, wound dehiscence, and large keloid scar formation should be less likely. Benefits of the use of external fixation as the method of stabilization are that it allows increased weight bearing and lateral translation of the distal fragment along with the angular correction. Another benefit is the feature of postoperative adjustability after a standing hip to ankle radiograph is obtained and the mechanical axis analysis is performed. The use of a gradual correction may decrease the likelihood of neurovascular insult and compartment syndrome particularly in a patient with a massive deformity as in the current report. Gradual correction should be relatively safe in a Blount's disease patient with a massive varus deformity along with procurvatum and internal tibial torsion. Another advantage of gradual correction with a frame is the possibility for limb lengthening if needed to correct length discrepancy. Opening wedge correction prevents further shortening and loss of bone stock.

      In the current patient, correction of large varus deformities was performed. The corrections were 53° and 60° on the right and left sides respectively. Simple knee radiographs were used preoperatively and during the correction, limiting a comprehensive deformity analysis11 Anatomic femorotibial measurements were used as a result. Although the corrections were large and the cosmetic and functional result very good, there is still some mechanical axis deviation in both lower limbs. The use of erect leg radiographs that include the hip, knee, and ankle and the use of a mechanical axis analysis of the deformity and correction 11 are currently used. This may result in a more accurate and critical deformity correction and analysis of the result. In the current case, one may consider additional intervention in this now 32-year-old patient. This would be a difficult recommendation since she is pain-free and has excellent function. Surgical options that could correct residual deformity include another bilateral osteotomy to centralize the mechanical axis line may help prevent progression of osteoarthritis. In addition, an elevation of the sloped medial tibial plateau with an acute opening wedge correction may be beneficial for improving the force distribution across the knee.18 Both femora have valgus deformities. The left side is greater with a lateral distal femoral angle of 77° than the right side with a lateral distal femoral angle of 83° (normal is 85° to 89°).11 One might consider a distal femoral osteotomy to correct the femoral valgus particularly on the left in addition to a tibial osteotomy to correct additional varus. This would put the knee joint line perpendicular to the weight-bearing axis and may help prevent progression of arthritis.

      Complications encountered in the present case included a right extensor hallicus longus palsy noted immediately after surgery. This was probably related to surgical technique during the proximal fibula resection and peroneal nerve decompression. The current recommendation would be for a middle fibula resection or oblique osteotomy without nerve decompression. If during the gradual correction, peroneal nerve symptoms and signs occur, a secondary nerve decompression would be performed. A stiff nonunion of the left proximal tibia was encountered which required reapplication of the Ilizarov frame for compression. Uneventful bony union occurred after 3 months. Compression of a stiff nonunion without surgical exposure or open bone grafting is another helpful application of the Ilizarov method.3,6

      This case represents the very early American experience with Ilizarov method for correction of very large bilateral varus deformities in a young adult with neglected Blount's disease and ten year clinical follow up is presented. There has been an evolution in the method of deformity analysis, which may explain the imperfect although greatly improved position.

      Legend of Figures:

      Fig. 1 A-C
      (A) Preoperative front view showing large varus deformities of both legs.
      (B) Preoperative supine radiograph of the right knee.
      (C) Preoperative supine radiograph of the left knee.

      Fig. 2
      Front view of both legs in Ilizarov frames following correction of the deformities.

      Fig. 3 A-E
      (A) Erect leg radiograph two years following surgery.
      (B) Front view of legs ten years following surgery .
      (C) Standing radiograph of both knees ten years following surgery.
      (D) Lateral radiograph of right knee ten years following surgery.
      (E) Lateral radiograph of left knee ten years following surgery.


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