Correction of Lower Extremity Deformities by Distraction Osteogenesis

Advances in Orthopaedic Surgery | ORIGINAL ARTICLES

Correction of Lower Extremity Deformities by Distraction Osteogenesis

Mark T. Dahl, M.D.

Gillette Children's Hospital, St. Paul, Minnesota; Fairview Riverside Medical Center, Minneapolis, Minnesota; and Shriners Hospital for Crippled Children, Minneapolis, Minnesota

ABSTRACT

Lower extremities (n = 171) with various deformities were gradually corrected by distraction osteogenesis. One of two fixators (llizarov or DeBastiani) was used depending on the features of the deformity. Careful preoperative planning, patient education, precise surgical technique, and sustained postoperative care were essential for success. Complications were frequent, particularly pin site and soft-tissue sequelae, but they rarely prevented a successful result. Distraction
osteogenesis offers a wide variety of correction possibilities for severe lower extremity deformities.

INTRODUCTION

In recent years, the primary technical advances in limb lengthening and deformity correction have been in the development of external fixators that allow for weightbearing and maintenance of joint function during gradual bone and soft-tissue regeneration. A variety of available devices include Wagner's and DeBastiani's monolateral frames, and the multiplanar systems of Monticelli, Fischer, and Ilizarov.

The introduction of each fixation device adds new principles and operative techniques for treating skeletal deformities. Wagner's fixator provides monolateral fixation for long-bone lengthenings (Wagner, 1978). Ilizarov's transfixion wire/ring system provides for multilevel, multiapical, and juxta-articular corrections (Ilizarov, 1990). DeBastiani's rigid frame has a telescoping feature that allows dynamic loading (DeBastiani et al., 1987). Fischer's fixator combines circular and monolateral features with partial rings and the use of wires or half pins (Fischer, 1983).

The primary biological advancement in limb lengthening is Ilizarov's concept of bone and soft-tissue regeneration in a widening distraction gap under controlled mechanical means through a subperiosteal corticotomy (Aronson, 1990). The creation of bone by intramembranous ossification was pioneered by Ilizarov, and as scientific and clinical knowledge of Ilizarov's methodology grows, a broad spectrum of lower extremity applications is occurring.

This article describes lower extremity applications of the Ilizarov and DeBastiani methods. The case examples describe and illustrate several of these uses, depending on the location of the deformity and the difficulty of the correction.

DEFORMITY CORRECTIONS

Since 1985, distraction osteogenesis has been used by the author to treat 171 various lower extremity orthopedic problems. The most common use of the DeBastiani device was for femoral lengthenings without significant angular deformity. The Ilizarov apparatus was widely used for complex, multilevel, multiangular, and juxta-articular applications. These applications, in order of frequency, involve: limb lengthening, lengthening with angular correction, angular correction alone, treatment of nonunions, and treatment of congenital tibial pseudarthroses. There were a few cases involving recalcitrant club feet and severe foot deformities. Twelve patients were also treated with upper extremity corrections (Coony & Dahl, this issue, p. 150).

INDICATIONS

Indications for using the llizarov or DeBastiani techniques in adults include fracture repair (diaphyseal and juxta-articular); repair of postraumatic problems such as nonunions, malunions, segmental bone defects, and chronic osteomyelitis; and resolution of joint contractures. Indications in children include limb lengthening, limb lengthening with deformity correction, and deformity correction through bone or soft tissue.

THE CLINICAL "PROCESS"

This treatment is not a procedure, but a process, occurring and changing over weeks and months. Understanding the need for careful preoperative planning, meticulous technique, and continued follow-up evaluation during the process of distraction are necessary for successful outcomes. Combining these principles with appropriate expectations on the part of the surgeon and patient is necessary.

When planning a correction, a multitude of factors must be considered, including the patient's age, etiology, and extent of deformity. Deformities must be classified, listed, and their magnitude measured, before initiating the planning process. Comprehensive treatment involving 1) preoperative planning, 2) patient education, 3) precise surgical technique, and 4) postoperative care is essential.

1. Preoperative planning follows a detailed musculoskeletal history and examination. Full-length standing X-rays and multiple views are necessary to analyze mechanical axis. Special studies such as tomography, magnetic resonance imaging, and radioisotope scanning are occasionally necessary. Overlay drawings and computer graphics are also used to assist in apparatus design and preassembly. Before surgery, it is critical to understand the patient's symptoms and expectations.

2. Through patient education, a detailed course of events can be presented that prepares the patient and family both physically and emotionally for the prolonged treatment. Strict patient compliance and rapport throughout this difficult process is vital.

3. The surgical techniques of frame design and application, subperiosteal corticotomy, and proper pin and wire insertion, all require instruction and practice.

4. Postoperative care during the gradual correction process requires a coordinated approach between the surgeon and a multidisciplinary team that includes the limb-fixator nurse, physical therapist, and many other team members. Weekly clinic visits during lengthening or deformity correction are necessary. Monthly visits occur during the healing phase. Physical therapy and graded return to normal function are continued throughout treatment.

The fixators are removed on an outpatient basis. Anesthesia is not used during removal of the DeBastiani device, but a general anesthesia is used when removing the Ilizarov device.

LIMB LENGTHENING

The DeBastiani and Ilizarov methods utilize similar biological principles for stimulating bone growth. The variations in design and surgical application make the devices technically quite different. The Ilizarov fixator appears to have greater versatility in correcting complex deformities, while the DeBastiani device offers greater application simplicity and patient tolerance.

In discrepancies greater than 5 cm, or less than 5 cm when associated with an angular deformity or in a short-statured individual, limb lengthening is considered. There were 117 such lengthenings performed; 65 of these were femora and 52 were tibiae. Of these, 39 were completed using the DeBastiani device, while 78 were corrected with the Ilizarov apparatus.

Case 1 A 17-year-old girl with an acquired 9-cm discrepancy was treated with a lengthening of 8 cm (Fig. 1). Treatment time was 7 months. The slight varus deviation is not evident clinically. Articular function has been maintained and the discrepancy reduced to 1 cm.

Figure 1.

Case 2 An 8-year-old boy with congenital posteromedial bow of the tibia and a discrepancy of 5 cm was treated with a single-level tibial angular correction and lengthening (Fig. 2). Treatment time was 24 weeks. The 3-year follow up X-ray shows complete lengthening remodeling.

Figure 2.

ANGULAR DEFORMITY CORRECTION

Conventional subtraction osteotomy is usually preferred for moderate angular deformities but limits of safety and lack of adjustability exist. Gradual distraction osteotomies with external fixation offer certain advantages: the deformities of length, translation, and rotation can also be corrected; nerves and surrounding soft tissues can slowly accommodate to the new position; and progressive clinical evaluation "fine-tuning" of the correction is possible. Twenty-seven segments with deformities secondary to Blount's disease, dysplasias, degenerative knee arthrosis, and partial growth plate arrest about the knee or ankle were treated.

Case 3 A 6-year-old boy with infantile tibia vara, resulting in severe angular and rotational deformity, was treated bilaterally (Fig. 3). Fixation time was 10 weeks followed by 4 weeks of casting.

Figure 3.

Case 4 A 22-year-old woman with a posttraumatic tibial malunion was corrected with oblique planar
hinges (Fig. 4).

Figure 4.

NONUNIONS

llizarov has introduced new concepts in the diagnosis and management of nonunions. Catagni and associates have further described these concepts for practical applications (Catagni, 1991). Twenty-three nonunion/malunions have been treated including five with massive bone loss, seven hypertrophic, five atrophic, and six congenital tibial pseudarthrosis. Union was achieved in all but one, a 29-year-old female with multiply-operated, congenital tibial pseudarthrosis.

Case 5 A 28-year-old woman with bilateral tibial nonunions, following a boating accident, was treated with compression-distraction osteosynthesis (Fig. 5). Twenty-four weeks of fixation were required.

Figure 5.

Case 6 A 13-year-old girl with multiply-operated, congenital tibial pseudarthrosis was treated with resection and compression of the nonunion and proximal lengthening (Fig. 6). A length of 7 cm was achieved and union was present at 2 years posttreatment.

Figure 6.

COMPLICATIONS

A spectrum of complications with varying frequencies and severity occur with distraction osteogenesis techniques (Dahl, in press; Paley. 1990). Pin-site inflammations, the most common minor complication, occur at 5% of the sites once skill at insertion techniques is achieved. In limb-length surgery, the major complications of axial deviation, delayed union, fracture, joint subluxation, and contracture were prevalent in the first 40 applications.

This complication rate and severity decreases slowly with experience, as demonstrated in the author's learning curve (Fig. 7) for limb-lengthening complications (Dahl, in press).

CONCLUSION

Current principles of distraction osteogenesis are built upon the observations and experiences of llizarov. The complexity of the deformities treated are high; however, the continued application and evolution of these methodologies is occurring. In the applications mentioned, the course of treatment has been rewarding and has satisfied the patient and surgeon in all but a few cases. Despite early enthusiasm, these difficult techniques require a cautionary approach as their role in the management of severe lower extremity deformities is still being defined.