Dissociation of polyethylene liners with the Depuy Pinnacle cup: a report of 26 cases.

BACKGROUND: Although the Pinnacle Acetabular Hip System (DePuy Synthes) has demonstrated excellent survivorship results since it was first introduced in 2003, there have been a growing number of cases indicating that Pinnacle liners may be subject to a higher-than-expected rate of early dissociation failure. Between 2006 and 2020, our Centre received 212 retrieved Pinnacle liners from Western Australian hospitals. Of these, 26 were removed due to liner dissociation. METHODS: To better understand the frequency and cause of this complication we assessed all retrieved Pinnacle acetabular components for type, damage modes and patient demographics. The leverage force required to dissociate Pinnacle liners was also measured and compared with another commonly used acetabular system, the Trident (Stryker Orthopaedics). RESULTS: The estimated minimum incidence of liner dissociation from our data was 0.35%. Characterisation of dissociated Pinnacle cases (n = 26) revealed 73% were female with an average age of 59 compared to all retrieved Pinnacle cases (n = 212) where 58% were female with an average age of 66. Retrieval analysis indicated plastic deformation of the liner into an ovoid shape, signs of impingement on the rim postero-superiorly and shearing of the liner's anti-rotation tabs was common. Mechanical testing indicated that the dissociation strength of Pinnacle cups decreases at approximately 6.6 N/year in situ (p = 0.01). CONCLUSION: The survival rate of Pinnacle acetabular cups is exceptional with only 5% revised at 10 years. However, surgeons should be aware of the clinical symptoms and high-risk demographics when assessing patients with polyethylene Pinnacle liners.

Diagnosing neonatal transphyseal fractures of the distal humerus.

A traumatic birth can cause significant upper limb injury; the presenting features are non-specific and the differential diagnosis long. Transphyseal fractures of the distal humerus are a rare but clinically important birth injury. This injury has typical radiographic findings, which due to the un-ossified nature of the distal humeral epiphysis can easily be misinterpreted. This article presents the radiographic appearance correlated with arthrography, ultrasound and MRI obtained from four cases of neonatal transphyseal fracture of the distal humerus. We hope that by demonstrating the appearances for each of these imaging techniques in relation to the underlying pathology will reduce errors of interpretation that may lead to inappropriate diagnosis and management of these children.

Protocol for a randomised control trial of bisphosphonate (zoledronic acid) treatment in childhood femoral head avascular necrosis due to Perthes disease.

INTRODUCTION: Perthes disease (PD) is an idiopathic disorder presenting with avascular necrosis to the femoral head, which frequently results in flattening. Long-term function is directly related to the subsequent femoral head sphericity. Current treatment includes mechanical modalities and surgical procedures, which are therapeutic but are not uniformly able to prevent collapse. The use of the nitrogen-containing bisphosphonate zoledronic acid (ZA) to inhibit osteoclastic bone resorption is aimed at preserving femoral head strength, reducing collapse and thus maintaining shape. The proposed multicentre, prospective, randomised controlled trial intends to evaluate the efficacy of ZA treatment in PD. METHODS AND ANALYSIS: An open-label randomised control trial recruiting 100 children (50 each treatment arm) 5 to 16 years old with unilateral PD. Subjects are randomly assigned to either (a) ZA and standard care or (b) Standard care. The primary outcome measure is deformity index (DI), a radiographic parameter of femoral head roundness assessed at 24 months, following 12 months of ZA treatment (3-monthly doses of ZA 0.025 mg/kg at baseline, 3, 6, 9 and 12 months) plus 12 months observation (group A) or 24 months of observation (group B). Secondary outcome measures are femoral head subluxation, Faces Pain scale, Harris hip score and quality of life. Assessments are made at baseline, 3 monthly during the first year of follow-up and then 6 monthly, until the 24th month. ETHICS AND DISSEMINATION: The study commenced following the written approval from the Human Research Ethics Committee. Safety considerations regarding the effects of ZA are monitored which include the subject's symptomatology, mineral status, bone mass and turnover activity, and metaphyseal modelling. Data handling plan requires that all documents, clinical information, biological samples and investigation results will be held in strict confidence by study investigators to preserve its safety and confidentiality. TRIAL REGISTRATION NUMBER: Australian and New Zealand Clinical Trials ACTRN12610000407099, pre-results.

Predictors of Outcome in Pediatric Osteomyelitis: Five Years Experience in a Single Tertiary Center.

BACKGROUND: Acute haematogenous osteomyelitis is a bacterial infection of bone, which occurs most frequently in children. Outcomes are excellent for the majority of children, but a minority develop complicated osteomyelitis. Predicting which children will develop complicated osteomyelitis remains a challenge, particularly in developed countries where most patients are discharged home after a relatively short period in hospital. METHODS: We conducted a 5-year retrospective case note review of all children aged 3 months to 16 years admitted with a diagnosis of acute haematogenous osteomyelitis. We compared standardized clinical and laboratory parameters in those who developed simple and complicated osteomyelitis. RESULTS: Of the 299 children who met inclusion, 241 (80.6%) had simple and 58 (19.4%) had complicated osteomyelitis. The major predictors of complicated disease were older age, a temperature greater than 38.5°C and a higher C-reactive protein at admission. CONCLUSIONS: A risk prediction model, utilizing information available shortly after hospitalization, allows early identification of children at greatest risk of developing complicated osteomyelitis.

Simultaneous bilateral elbow dislocation with bilateral medial epicondyle fractures in a 13-year-old female gymnast with hyperlaxity.

Bilateral simultaneous elbow dislocations are extremely rare and have only been described in 12 cases. In the paediatric population unilateral elbow dislocations are rare with 3-6% of all elbow injuries and there are only few studies describing this injury exclusively in children. There is only one case report of a paediatric patient who sustained a simultaneous bilateral elbow dislocation with medial epicondyle fractures. We present a second paediatric case of simultaneous bilateral elbow dislocation with associated displaced bilateral medial epicondyle fractures in a gymnast with joint hyperlaxity (3 of 5 Wynne-Davies criteria) treated with closed reduction and short-term immobilisation (3 weeks). The patient returned to full trampoline gymnastics between 4 and 5 months postinjury and made an uneventful recovery.

Delayed diagnosis of developmental dislocation of the hip: the Western Australian experience.

BACKGROUND: A delay in the diagnosis of developmental dislocation of the hip has many long-term consequences. This retrospective study was undertaken in order to establish an incidence of late-presenting developmental dislocation of the hip in Western Australia, and investigate possible causes for missed diagnoses. METHOD: Data were collected retrospectively from 1 January to 31 December 2010. Theatre records were searched for operative descriptions including the words 'arthrogram hip', 'EUA hip', 'closed reduction hip', 'open reduction hip' and 'spica'. Medical records were checked to establish the demographic details and background history of cases identified. Delayed diagnosis of developmental dysplasia of the hip (DDH) was defined as a dislocated hip requiring operative reduction, diagnosed at age greater than 3 months. RESULTS: Seventeen children with 21 dislocated hips were identified. Age at diagnosis ranged from 6 months to 5 years. Girls accounted for 88.2% (15/17) and the left hip was involved two-thirds of the time (14/21). Bilateral dislocations were found in four children. CONCLUSION: This study has identified an incidence of late-presenting developmental hip dislocation of approximately three times the previously established rate. Possible reasons for this are explored. Additional retrospective audit is now underway, and changes are already in place to ensure that infants with DDH born in Western Australia are identified and treated as early as possible.

Inherited multicentric osteolysis: case report of three siblings treated with bisphosphonate.

Inherited Multicentric Osteolysis (IMO) is an uncommon familial condition of idiopathic pathophysiology causing bone osteolysis and dysplasia. These patients present with common rheumatologic complaints of pain, dysfunction and disability, and are often initially misdiagnosed as a chronic rheumatic disease of childhood such as juvenile idiopathic arthritis. We report a case of three siblings diagnosed with IMO. Diagnosis was made during childhood, with each sibling having different manifestations and course of disease. One had a previous history of bilateral hip dysplasia. Two had osteolysis of the foot, distal tibia and femur (lower limb bones), whilst one had osteolysis of the rib and unusual clavicular fractures. Unusually, all siblings appear to experience decreased pain sensation compared to norms. All siblings were treated with bisphosphonates and experienced a rapid improvement in pain symptoms, decreased analgesic requirements. Two had bone mineral density testing performed and both had increases post-bisphosphonate. In all three, there was subjective evidence of stabilisation of bone disease. Testing for matrix metalloproteinase-2 (MMP2) gene was negative.

Damage of oxinium femoral heads subsequent to hip arthroplasty dislocation three retrieval case studies.

Oxinium exhibits 4900 times less volumetric wear and 640 times less deep scratches in laboratory wear testing compared with traditional cobalt-chromium alloys. Despite the superior wear resistance because of the thin ceramic surface, the zirconium alloy substrate is relatively soft (Hv = 285) when compared with cobalt-chrome alloy femoral heads (ISO 5832-12; Hv = ~420,) and may deform in contact with acetabular shell materials (ISO5832-3; Hv = 350) in the case of dislocation. Three retrieval cases highlight the damage that may occur during dislocation and/or when performing closed reduction maneuvers. It is recommended that closed reduction be attempted with caution because significant head damage can occur. This may lead to accelerated polyethylene wear. In the case of successful reduction, close patient follow-up is recommended. Open reduction with femoral head inspection and exchange may be preferable if difficulty is encountered in closed reduction maneuvers.