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In a large cohort of osteogenesis imperfecta type V (OI type V) patients (17 individuals from 12 families), we identified the same mutation in the 5′ untranslated region (5′UTR) of the interferon-induced transmembrane protein 5 (IFITM5) gene by whole exome and Sanger sequencing (IFITM5 c.–14C > T) and provide a detailed description of their phenotype. This mutation leads to the creation of a novel start codon adding five residues to IFITM5 and was recently reported in several other OI type V families. The variability of the phenotype was quite large even within families. Whereas some patients presented with the typical calcification of the forearm interosseous membrane, radial head dislocation and hyperplastic callus (HPC) formation following fractures, others had only some of the typical OI type V findings. Thirteen had calcification of interosseous membranes, 14 had radial head dislocations, 10 had HPC, 9 had long bone bowing, 11 could ambulate without assistance, and 1 had mild unilateral mixed hearing loss. The bone mineral density varied greatly, even within families. Our study thus highlights the phenotypic variability of OI type V caused by the IFITM5 mutation.

Langerhans cell histiocytosis is a rare group of disorders without a well-understood etiology. Known formerly as histiocytosis X, the disease has a wide spectrum of clinical presentations, including eosinophilic granuloma (solitary bone lesion), diabetes insipidus, and exophthalmos. It is also known by several eponyms, including Hand-Schüller-Christian disease when it manifests as a triad of cranial bone lesions and Letterer-Siwe disease when it is found in infantile patients with severely disseminated disease. Children aged 5 to 15 years are most commonly affected. Many of these patients initially present to orthopaedic surgeons, and misdiagnosis is frequent. To accurately diagnosis and treat these patients, the orthopaedic surgeon must be familiar with the clinical manifestations and pathophysiology of the disease as well as the treatment guidelines and outcomes for Langerhans cell histiocytosis.

IV.

Osteogenesis imperfecta is a heritable group of collagen-related disorders that affects up to 50,000 people in the United States. Although the disease is most symptomatic in childhood, adults with osteogenesis imperfecta also are affected by the sequelae of the disease. Orthopaedic manifestations include posttraumatic and accelerated degenerative joint disease, kyphoscoliosis, and spondylolisthesis. Other manifestations of abnormal collagen include brittle dentition, hearing loss, cardiac valve abnormalities, and basilar invagination. In general, nonsurgical treatment is preferred for management of acute fractures. High rates of malunion, nonunion, and subsequent deformity have been reported with both closed and open treatment. When surgery is necessary, surgeons should opt for load-sharing intramedullary devices that span the entire length of the bone; locking plates and excessively rigid fixation generally should be avoided. Arthroplasty may be considered for active patients, but the procedure frequently is associated with complications in this patient population. Underlying deformities, such as malunion, bowing, rotational malalignment, coxa vara, and acetabular protrusio, pose specific surgical challenges and underscore the importance of preoperative planning.

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Allergic or hypersensitivity reactions to orthopaedic implants can pose diagnostic and therapeutic challenges. Although 10% to 15% of the population exhibits cutaneous sensitivity to metals, deep-tissue reactions to metal implants are comparatively rare. Nevertheless, the link between cutaneous sensitivity and clinically relevant deep-tissue reactions is unclear. Most reactions to orthopaedic devices are type IV, or delayed-type hypersensitivity reactions. The most commonly implicated allergens are nickel, cobalt, and chromium; however, reactions to nonmetal compounds, such as polymethyl methacrylate, antibiotic spacers, and suture materials, have also been reported. Symptoms of hypersensitivity to implants are nonspecific and include pain, swelling, stiffness, and localized skin reactions. Following arthroplasty, internal fixation, or implantation of similarly allergenic devices, the persistence or early reappearance of inflammatory symptoms should raise suspicions for hypersensitivity. However, hypersensitivity is a diagnosis of exclusion. Infection, as well as aseptic loosening, particulate synovitis, instability, and other causes of failure must first be eliminated.