The best method of reconstructing osteoarticular defects to maintain joint stability and prevent early degenerative joint disease has yet to be resolved. Buckwalter broadly divided the treatment strategies into two types
1 : those that stimulate repair or regeneration of articular cartilage and those that involve transplantation of an articular surface. However, these methods do not provide the osseous support that may be needed when bone loss has occurred in the epiphysis.
We report the case of a three-year-old patient in whom massive osteoarticular bone loss from the medial tibial plateau of the left leg, due to a lawn-mower injury, was treated with the Ilizarov technique of distraction histogenesis. To our knowledge, this is the first time that this method has been utilized to repair an osteochondral defect. Our patient was informed that data concerning the case would be submitted for publication.
A three-year-old boy sustained an injury to the left leg from a lawn mower. He sustained soft-tissue and bone loss on the medial aspect of the proximal part of the left tibia and knee. The medial tibial plateau, including the articular cartilage, was missing, and there was a fracture through the remaining proximal tibial physis. A gastrocnemius-muscle pedicle graft and a split-thickness skin graft were used to cover the soft-tissue defect. The detached patellar tendon was sutured back in the region of the tibial tubercle. Six months after the initial injury, a nonunion of the proximal tibial physeal fracture (
Fig. 1 ) was treated with open reduction and iliac-crest bone grafting and screw fixation. The bone healed in three months (
Fig. 2 ) but with medial instability at the knee joint, which was controlled with a hinged knee-ankle-foot orthosis. The knee had an extension lag of 20° secondary to quadriceps weakness.
When the patient was examined three years later, 45° of medial instability was noted at the knee, and the involved leg was 3 cm shorter than the right. Radiographic evaluation revealed that the medial tibial plateau was deficient by 50%. It was decided that four problems had to be addressed: (1) the posterolateral subluxation of the knee, (2) the defect of the medial tibial plateau, (3) the medial instability at the knee joint, and (4) the leg-length discrepancy.
First, the Ilizarov apparatus was applied to the left femur and tibia with a fixed link at the joint to correct angular deformity and posterior and lateral subluxation of the tibia by gradual distraction and translation. One month later, an oblique proximal tibial osteotomy was performed in the sagittal plane. Proximally, the osteotomy started medial to the tibial spine, and the distal part of the osteotomy exited at the medial tibial cortex below. Two olive wires were inserted through overdrilled holes in the lateral cortex to abut the inner wall of the osteotomized fragment. These were attached to a medial ring distraction device (
Fig. 3 ). Medially directed distraction (in the coronal plane) of the osteotomized medial plateau fragment was performed gradually until the fragment was completely under the medial femoral condyle. At this point, the Ilizarov apparatus was adjusted to provide hinges at the level of the knee joint so as to allow motion. A distal tibial osteotomy was also performed at that time to lengthen the tibia. Five months after the original application, the desired length was achieved and good healing of the transported medial tibial plateau was noted on radiographs. The femoral and hinge components of the Ilizarov apparatus were removed, and continuous passive motion was initiated. Arthrography of the knee demonstrated an outline of the knee joint with what appeared to be a joint space. Six and one-half months after the initial application of the Ilizarov apparatus, it was completely removed, and measurement of the left tibia showed a 3-cm gain in length. The knee was stable, and a brace was not needed. At the conclusion of this treatment, the patient had 5° to 90° of active range of motion of the knee, and he was able to participate in school sports activity, including basketball.
At the age of nine years and seven months, as a result of overgrowth of the proximal part of the left fibula, the patient underwent an epiphysiodesis of the proximal part of the fibula. Arthroscopic evaluation and biopsy of the articular cartilage were also performed at this time. Initial arthroscopy revealed normal-appearing articular cartilage within the patella and the lateral compartment. The medial tibial plateau was covered with thick fibrous tissue that enveloped the tibial and femoral surfaces, and hyaline-like cartilage was revealed on trocar core biopsy of that plateau. On histological examination of the deeper layers of the articular surface, no tidemark indicative of an abnormal cartilage-bone junction could be seen in the underlying bone.
In the ensuing year, the patient continued to do well except for an increasing leg-length discrepancy. When the patient was thirteen years of age, the knee could be extended fully and flexed to 100°. The leg-length discrepancy had increased to 6 cm, with a predicted discrepancy of >8 cm at skeletal maturity. To compensate for this projected discrepancy, proximal epiphysiodesis of the right tibia was performed, and the Ilizarov method was used again to achieve 7-cm of lengthening of the distal part of the left tibia. Arthroscopic evaluation as well as articular biopsy with fluoroscopic guidance revealed extensive fibrous scarring. The articular cartilage within the lateral compartment was normal in appearance and consistency. The medial tibial plateau had a cupped appearance; the anterior portion was covered with fibrocartilage-like tissue while the posterior portion appeared to contain hyaline cartilage. The medial femoral condyle appeared normal. Trocar needle biopsies of the anterior medial plateau revealed mainly fibrocartilage with small areas of hyaline-appearing cartilage. Biopsy of the posterior tibial plateau revealed primarily hyaline-appearing cartilage.
Five months later, the Ilizarov apparatus was removed. The regenerated segment had healed. At the six-month follow-up examination, the range of motion of the knee was 10° to 110°. Clinically, the knee was straight in the coronal plane and was stable. Quadriceps power was 4 of 5. The patient had returned to full school and sports activity without difficulty. When examined at the age of sixteen years, the patient still had a 10° to 110° range of motion, and the strength of the hamstrings and quadriceps muscles was graded 5 of 5. Standing radiographs showed a well-maintained joint space (
Fig. 4 ). Patella alta had persisted but did not interfere with quadriceps strength.
Magnetic resonance imaging of the knee when the patient was eighteen years of age revealed a narrow yet congruent medial femoral condyle and medial tibial plateau. The magnetic resonance imaging signal of the articular surface of the medial compartment was similar to, albeit thicker than, that of the hyaline cartilage of the lateral compartment of the knee. The range of motion of the knee and muscle strength in the leg had been maintained.
Power lawn-mower accidents are frequent causes of mutilating injuries in children
2,3 . In one series, amputations occurred in 46% (sixty-seven) of 144 children involved in such accidents
3 . Lawn-mower injuries often result in open fractures of the proximal tibial epiphysis, which are associated with the worst prognosis
4 , with considerable deformity and growth disturbances as common sequelae
3 .
Osteochondral defects occur more commonly in adolescents and young adults, whereas chondral defects occur mostly in young and middle-aged adults
1 . Within the last two decades, researchers have developed various methods to repair osteoarticular defects in human and animal models. These methods include subchondral drilling of bone
5 ; perichondrial, osteoperiosteal
6 , and periosteal
7 interposition flaps; tendon autografts
8 ; osteotomies; implantation of an artificial matrix
9-12 ; allogeneic tissue-engineered cartilage implants
13 ; autologous chondrocyte transplantation
14,15 ; autogenous callo-osseous graft
16 ; growth factors
17 ; and osteoarticular autograft
18 and allograft
19,20 transplantation. Despite the intense research, no reliable and reproducible method to restore hyaline cartilage has been developed. In addition, the above-mentioned techniques do not address repair of a large bone defect, which may be needed to support the articular surface.
The Ilizarov principle of distraction histogenesis has been used for limb-lengthening, correction of limb deformities, and treatment of nonunion and bone loss secondary to trauma, tumor, or infection
21 . To our knowledge, it has not been described for treatment of massive posttraumatic osteoarticular loss, especially in patients with open growth plates. We applied the Ilizarov principle of distraction histogenesis with osteochondral distraction to restore the tibial plateau in the coronal plane, reduce and maintain stability of the knee joint, and achieve leg-length equality.
Patella alta developed in our patient after the injury. Initially, we did not consider correction of the patella alta because of the extent of the injury and the lack of full flexion of the knee. At a later stage, the patellar surface was observed to be no longer congruent with the femoral groove. We believed that relocation of the patella might result in a loss of flexion and in patellofemoral arthritis. Therefore, as the patient had adequate knee function, no further attempt at patellar realignment was considered necessary.
In young children with severe injuries resulting in large articular defects, reconstruction of the articular surface is possible with use of the Ilizarov technique. In our patient, although the regenerated cartilage was not completely hyaline-like, it did provide joint-surface integrity and stability. This technique may prove to be an effective alternative to knee fusion, osteoarticular allografting, or early total joint arthroplasty in children with a devastating injury such as that sustained by our patient.