Rare bone diseases can present to spinal surgeons with issues comprising instability, vertebral fracture, neurological compression and spinal deformity, and any or all can affect all areas of the spine. The management of these spinal issues can be challenging in their own right and is added to by the nuances of the rare bone condition itself. This article covers the specifics of the issues faced, through both an anatomical and pathological lens, to give the basics of the management of the spine aspects of these rare bone diseases to those that will see these conditions uncommonly, or need to know about them for examination purposes. Whilst not intending to cover all possible scenarios, this article provides the basics of knowledge and can be built on if required for those who work with this patient group.
Achondroplasia is the most common skeletal dysplasia, arising from a gain-of-function variant in FGFR3 that disrupts endochondral ossification and results in a highly conserved pattern of skeletal dysmorphology. Although short stature is the most visible feature, the clinical burden extends well beyond growth: a developmentally narrow craniospinal canal, altered vertebral morphology and abnormal limb alignment generate a substantial lifetime surgical burden that begins in infancy and continues into adulthood. This review covers the pathophysiology, diagnostic pathway and principal complications relevant to orthopaedic practice. Foramen magnum stenosis and sleep-disordered breathing require active surveillance from birth and must be formally assessed before any elective intervention. Spinal complications, including thoracolumbar kyphosis and lumbar stenosis, follow a broadly predictable natural history, while lower-limb malalignment and ligamentous laxity contribute to progressive functional limitation across the lifespan. Orthopaedic input in achondroplasia in children primarily focuses on restoration of the mechanical axis via guided growth or osteotomies but limb lengthening in upper and/or lower limbs can also be offered. The therapeutic landscape has shifted considerably with the introduction of disease-modifying pharmacotherapy. These agents are now part of routine care for many children with achondroplasia in some countries and have implications for surgical planning that orthopaedic teams need to be aware of. Safe, effective management of achondroplasia requires structured, anticipatory surveillance and close coordination within a specialist medical team throughout life.
Genetic developmental disorders of the skeleton are individually rare but together constitute an important area of orthopaedic practice. The multiple epiphyseal dysplasias represent a subgroup of these conditions in which endochondral ossification is disrupted by defects that are primarily in cartilage metabolism in the developing skeleton. The ends of the tubular bones (epiphyses) and articular cartilage are particularly affected; this is manifest variably as short stature (sometimes disproportionate), abnormal joint structure, angular deformities of the joints and long bones, and premature degenerative arthritis. The genes responsible for most of these conditions have been identified in the past 40 years but current medical treatments are still largely limited to providing symptomatic relief. In childhood, orthopaedic intervention is sometimes required to correct major structural abnormalities of the joints or for limb realignment. Premature osteoarthritis is a common consequence of many of these disorders and joint replacement surgery (particularly hips but also knees) is quite commonly required in early adult life for those with the more severe variants of these conditions. This review provides a framework for distinguishing the various forms of multiple epiphyseal dysplasia, their underlying causes, and the principles of medical and surgical treatment.
Rare bone disorders are just that, rare. Despite this fact, patients with these conditions are a relatively popular inclusion in orthopaedic clinical examinations. This paper aims to elucidate several of these conditions to improve the potential examination candidates' knowledge of their presentation, clinical examination findings, pathology and importantly, up to date principles of management of these conditions in the UK. This article will take the prospective candidate through the approach for a clinical examination, principles of management of skeletal dysplasias in UK practice, followed by more in depth discussion of multiple epiphyseal dysplasia, spondyloepiphyseal dysplasia congenita and tarda, achondroplasia, pseudoachondroplasia, Ollier's disease, multiple hereditary exostosis, osteopetrosis, hypophosphatasia, fibrous dysplasia, osteogenesis imperfecta, cleidocranial dysplasia, X-linked hypophosphataemia, Langerhan's cell hystiocytosis and chronic non-bacterial osteomyelitis/chronic recurrent multifocal osteomyelitis. This work includes clinical photographs and radiographs (published with permission) to illustrate some of the key clinical and radiological findings of these conditions.
Hip and knee arthroplasty is a procedure that presents unique challenges when performed in those with rare bone disease, including assessment of bone quality and strength, prosthesis type and shape, along with techniques of fixation of the implants and subsequent stability. Complications are more common and may be more challenging to resolve. This review highlights the specific issues facing the surgeon when performing lower limb joint replacement in this patient group.
