Current management of long bone large segmental defects

Abstract

Large segmental defects of long bones comprise a complex pathology resulting from a variety of aetiologies. Their prolonged, painful and uncertain treatment is usually beset with a range of consequences for the patient, varying from the psychological to the socioeconomic. Trauma, osteomyelitis, bone tumour resections or treatment of congenital deformities are main causes of bone deficiency. Their treatment has been thoroughly studied for the last 35 years and both vascularized bone grafting and distraction osteogenesis with the Ilizarov technique have emerged as gold standards. Novel techniques have arisen during the last 10 years, giving new perspectives to the management of this problem. Intramedullary lengthening devices, bioactive membranes, osteogenic proteins and tissue engineering are the new weapons in the armamentarium of orthopaedic surgeons. This study describes the aforementioned treatment techniques (classic and novel) and elaborates on their indications, advantages/disadvantages and complications. Algorithms for the assessment and treatment of critically size long-bone segmental defects are also proposed.

Introduction

Bone healing and reconstruction after traumatic or non-traumatic lesions are processes involving a cascade of cellular, humoral, and mechanical events culminating in the reestablishment of bone integrity. Surgical intervention, if needed and undertaken, should facilitate timely recovery and may be categorized depending on the nature of the bone lesions being addressed. When these lesions are long-bone segmental defects of the upper or lower limbs specific considerations shall be taken into account, depending on the cause, the grade of the defect and any existing commorbidities.

High energy trauma, diseases, developmental deformities, revision surgery and resection of tumour or osteomyelitis are the main causes of long-bone defects.¹ Based on several animal studies, critically-sized defects are defined as “the smallest osseous defect in a particular bone and species of animal that will not heal spontaneously during the lifetime of the animal”.2, 3 Alternatively they have been defined as segmental bone deficiency of a length exceeding 2–2.5 times the diameter of the affected bone.4, 5 However it is not only the length of the bone defect that may characterize a bone defect as critical, but a number of variables. These variables include location, associated soft tissue and biomechanical problems in the affected limb, age, metabolic and systemic disorders and related co-morbidities that may affect bone healing.2, 5, 6, 7, 8, 9, 10 These factors impede the implementation of an overarching classification pattern for long-bone defects, comparable to those existing for fractures in general. Moreover, the complexity of potential co-morbidities (soft-tissue defects, inflammation) and the variety of predisposing causes (developmental, post-traumatic, tumours, osteomyelitis) have not allowed a single surgical technique to become established as the treatment of choice.

For relatively small bone defects with adequate soft-tissue coverage, the bone gap can usually be bridged with conventional cancellous bone grafts or bone substitutes.¹¹ However, most authors12, 13 do not advocate this technique when the defect exceeds 4–5 cm. Partial resorption of the graft and revascularisation by creeping substitution result in a weakness of the reconstructed segment, predisposing to iterative fractures.¹⁴ Thus, for segmental bone defects larger than 4–5 cm, with or without a soft-tissue defect, the need for more specialized management becomes essential.¹⁵ The two methods that have prevailed lately are vascularized fibular grafting (VFG),16, 17, 18, 19 and distraction osteogenesis or internal bone transport (IBT) with an external fixator (Ilizarov technique).20, 21, 22, 23 Apart from these two well known techniques, several other novel approaches have been examined over the years.

This paper presents the current concepts of management of large, long-bone diaphyseal defects (> 5 cm) and discusses the indications, limitations and complications of each of the commonly used surgical techniques.