vendex and Bone-Neoplasms

In the presence of a tumor defect, completed humeral shaft fractures continue to be a major surgical challenge since there is no "gold standard" treatment. This is due, in part, to the fact that only one prior biomechanical study exists on the matter, but which only compared 2 repair methods. The current authors measured the humeral torsional performance of 5 fixation constructs for completed pathological fractures. In 40 artificial humeri, a 2-cm hemi-cylindrical cortical defect with a transverse fracture was created in the lateral cortex. Specimens were divided into 5 different constructs and tested in torsion. Construct A was a broad 10-hole 4.5-mm dynamic compression plate (DCP). Construct B was the same as A except that the screw holes and the tumor defect were filled with bone cement and the screws were inserted into soft cement. Construct C was the same as A except that the canal and tumor defect were filled with bone cement and the screws were inserted into dry cement. Construct D was a locked intramedullary nail inserted in the antegrade direction. Construct E was the same as D except that bone cement filled the defect. For torsional stiffness, construct C (4.45 ± 0.20 Nm/deg) was not different than B or E (p > 0.16), but was higher than A and D (p < 0.001). For failure torque, construct C achieved a higher failure torque (69.65 ± 5.35 Nm) than other groups (p < 0.001). For the failure angle, there were no differences between plating constructs A to C (p ≥ 0.11), except for B versus C (p < 0.05), or between nailing groups D versus E (p = 0.97), however, all plating groups had smaller failure angles than both nailing groups (p < 0.05). For failure energy, construct C (17.97 ± 3.59 J) had a higher value than other groups (p < 0.005), except for A (p = 0.057). Torsional failure always occurred in the bone in the classic "spiral" pattern. Construct C provided the highest torsional stability for a completed pathological humeral shaft fracture.

Topics: Adult; Biomechanical Phenomena; Bone Neoplasms; Humans; Humeral Fractures; Humerus; Materials Testing; Mechanical Phenomena; Stress, Mechanical; Torque

Bone sarcomas are the fourth most common cancer in individuals under 25 years. Limb salvage procedures have become increasingly popular for the treatment of osteosarcomas as they have functional and psychological benefits over traditional amputative procedures. The purpose of this paper was to evaluate kinematic and kinetic characteristics of patient's post-limb salvage and examine key predictive factors of gait dysfunction. A retrospective outcome study was undertaken on 20 limb salvage patients (10 females, 10 males) recruited from the Queensland Bone Tumour Registry. Kinematic and kinetic data were collected using a 3D motional analysis system and three force platforms. Loading response knee flexion in the affected lower limb was reduced compared to the unaffected lower limb (P<0.001) and the control group (P<0.001), although, closer examination of results showed two contrasting patterns of knee flexion during loading. Multiple regression analysis showed that muscular integrity (i.e. strength, ROM and residual mass) was the most predictive factor of function following limb salvage surgery. ANOVA showed that patients treated with the Stanmore SIMLES prostheses exhibited superior torque and power production at the ankle during late stance compared to those treated with the Stryker HMRS. In summary, the results showed that limb salvage patients adopted a gait pattern that reduced the moment demand at the knee and hip, suggesting a compensation for pain, reduced stability and/or muscle weakness.

Topics: Adolescent; Analysis of Variance; Artificial Limbs; Biomechanical Phenomena; Bone Neoplasms; Disability Evaluation; Female; Humans; Kinetics; Limb Salvage; Lower Extremity; Osteosarcoma; Postural Balance; Registries; Regression Analysis; Torque; Treatment Outcome

With disseminated malignancies, segmental defects of the humeral diaphysis may occur from surgical resection or as a complication of failed prior internal fixation. This study directly compared the biomechanical properties of a second generation titanium modular intercalary humeral spacer (segmental defect replacement prosthesis) with those of a modern locked humeral nail combined with methylmethacrylate (intramedullary nail) or with an intercalary allograft spacer (allograft nail composite) for fixation of segmental defects of the humeral diaphysis. Eighteen matched pairs (36 specimens) of fresh-frozen humeri were prepared in a standard fashion to create a 5-cm middiaphyseal defect and were divided randomly into three groups of 12 specimens each, using three different reconstructive methods. Specimens were tested in external torsion to failure on a Materials Testing System machine. The segmental defect replacement specimens had statistically greater peak torque (mean, 41.4 N-m) and stiffness (mean, 2.1 N-m/ degrees) than the intramedullary nail specimens (mean peak torque, 23.1 N-m) (mean stiffness, 1.6 N-m/ degrees) or the allograft nail composite specimens (mean peak torque, 12.4 N-m) (mean stiffness, 0.6 N-m/ degrees). The intramedullary nail specimens also had a statistically greater peak torque at failure and stiffness than the allograft nail composite specimens. For segmental defects of the humeral diaphysis, reconstruction with a cemented metallic intercalary spacer provides significantly greater immediate stability than interlocked intramedullary nail fixation supplemented with segmental methylmethacrylate or intercalary allograft reconstruction.

Topics: Biomechanical Phenomena; Bone Nails; Bone Neoplasms; Cementation; Equipment Failure; Humans; Humerus; In Vitro Techniques; Internal Fixators; Methylmethacrylate; Prosthesis Implantation; Radiography; Titanium; Torque