The Effects of Interlocking a Universal Hip Cementless Stem on Implant Subsidence and Mechanical Properties of Cadaveric Canine Femora

OBJECTIVE: To determine if an interlocking bolt would limit subsidence of the biological fixation universal hip (BFX(®)) femoral stem under cyclic loading and enhance construct stiffness, yield, and failure properties. STUDY DESIGN: Ex vivo biomechanical study. ANIMALS: Cadaveric canine femora (10 pairs). METHODS: Paired femora implanted with a traditional stem or an interlocking stem (constructs) were cyclically loaded at walk, trot, and gallop loads while implant and bone motions were captured using kinematic markers and high‐speed video. Constructs were then loaded to failure to evaluate failure mechanical properties. RESULTS: Implant subsidence was greater (P = .037) for the traditional implant (4.19 mm) than the interlocking implant (0.78 mm) only after gallop cyclic loading, and cumulatively after walk, trot, and gallop cyclic loads (5.20 mm vs. 1.28 mm, P = .038). Yield and failure loads were greater (P = .029 and .002, respectively) for the interlocking stem construct (1155 N and 2337 N) than the traditional stem construct (816 N and 1405 N). Version angle change after cyclic loading was greater (P = .020) for the traditional implant (3.89 degrees) than for the interlocking implant (0.16 degrees), whereas stem varus displacement at failure was greater (P = .008) for the interlocking implant (1.5 degrees) than the traditional implant (0.17 degrees). CONCLUSION: Addition of a stabilizing bolt enhanced construct stability and limited subsidence of a BFX(®) femoral stem. Use of the interlocking implant may decrease postoperative subsidence. However, in vivo effects of the interlocking bolt on osseointegration, bone remodeling, and stress shielding are unknown

Avaliação funcional retrospectiva de pacientes com fratura proximal de úmero fixada com placa com parafusos de ângulo fixo para região proximal no úmero Retrospective functional assessment of patients with humerus proximal fractures internally fixed with a fixed-angle plate for proximal humerus area

As fraturas do úmero proximal são lesões comuns, levando seus pacientes a importantes limitações funcionais além de algumas complicações. Atualmente existem algumas opções de tratamentos cirúrgicos visando à melhor estabilização da lesão através de técnicas de ostessíntese, dependendo do grau de gravidade da lesão. Dentre eles, tem-se utilizado a placa com parafusos de ângulo fixo para região proximal do úmero, a qual possui o intuito de preservar a integridade biológica da cabeça umeral associada à redução anatômica segura utilizando múltiplos parafusos de fixação com estabilidade angular, permitindo assim a mobilização precoce do membro fraturado. Foram estudados retrospectivamente 11 pacientes com fratura proximal do úmero, tratados com esse modelo de placa entre os anos de 2004 e 2005. Na avaliação funcional foram utilizados o questionário de Constant e o índice DASH. Os resultados sugerem o aparecimento de perda funcional residual no membro superior após esse tipo de trauma, apesar da fixação estável e o tratamento fisioterapêutico.<br>Proximal humeral fractures are common injuries leading to severe functional restrictions and complications for patients. Today, there are several surgical alternatives aimed at achieving better injury stabilization by means of osteosynthesis techniques, depending on injury severity. One of these is the fixed-angle plate fixation of the proximal humerus. This bone fixation system is intended to preserve the biologic integrity of the humeral head associated with a safe anatomical reduction, employing several fixating screws with angle stability, thereby allowing an early mobilization of the fractured limb. Eleven patients with proximal humeral fractures treated with the method of fixed-angle plate fixation of the proximal humerus in the period of 2004 to 2005 were retrospectively studied. The patients were subjected to the Constant questionnaire and the DASH index for functional assessment. The results showed some residual dysfunction at the upper end after this type of trauma, even using a fixed-angle plate fixation of the proximal humerus, which notably provides a safe fixation, associated to physical therapy