Jeremy Kalma - Academia.edu (original) (raw)

Papers by Jeremy Kalma

Research paper thumbnail of Failure Modes of 433 Metal-on-Metal Hip Implants: How, Why, and Wear

Orthopedic Clinics of North America, 2011

Modern metal on metal hip replacement bearings are often seen as a durable option for younger pat... more Modern metal on metal hip replacement bearings are often seen as a durable option for younger patients because they are stronger and considered to produce lower rates of wear and osteolysis. 1 The use of metal-on-metal bearings has increased since the introduction of largediameter components for hip replacements and hip resurfacings, which offer protection against dislocation. Consequently, metal-on-metal bearings are reported to be second in popularity to polyethylene-on-metal bearings. 2 However, concerns remain regarding the potential biologic reactivity and long-term effects of cobaltchromium alloy metal particles and ions, particularly in light of recent reports of soft tissue masses, 3,4 necrosis, 5,6 and systemic effects 7 of elevated ion levels. Although the incidence of these problems is thought to be relatively low, 8 there have been calls to severely limit the use of metal-on-metal bearings. Our research center has collected a large number of failed metal-on-metal implants, including firstgeneration McKee-Farrar total hip replacements (THRs), early generation hip resurfacings (McMinn; Corin Group, PLC, Cirencester, UK and Wagner; Sulzer, Winterthur, Switzerland), 11 and a range of contemporary large-diameter modular THRs and hip resurfacings. In 2006, we published a retrieval study of implant failure modes in metal-on-metal surface arthroplasties and reported that aseptic loosening and femoral neck fracture comprised most failures. We also reported that revision directly attributed to wear of the bearings was relatively rare.

Research paper thumbnail of Biomechanical Testing of Pin Configurations in Supracondylar Humeral Fractures

Journal of Orthopaedic Trauma, 2013

We measured biomechanical stability in simulated supracondylar humeral fractures fixed with each ... more We measured biomechanical stability in simulated supracondylar humeral fractures fixed with each of 6 pin configurations, 2 with associated medial comminution, and developed a technique for reproducible pin placement and divergence. A transverse supracondylar osteotomy was performed on 36 biomechanical humerus models. Of these, 24 (4 groups of 6 specimens each) were fixed with pins in 1 of 4 lateral entry configurations. The remaining 12 (2 groups of 6 specimens each) had a 30-degree medial wedge removed from the distal humerus and were fixed with 1 of 2 configurations. Half of each group was tested under axial rotation and the other half under varus bending. The distal humerus was divided into 4 equal regions from lateral to medial (1-4). Lateral entry pins were inserted through regions 1-3, whereas the medial pin was inserted through region 4. Without comminution, 3 widely spaced, divergent lateral entry pins resulted in higher torsional stiffness (0.36 Nm/degree) than 2 pins in adjacent regions (P < 0.055), but similar to 2 pins in nonadjacent regions (P = 0.57). Three lateral entry pins had higher bending stiffness (79.6 N/mm) than 2 pins, which ranged from 46.7 N/mm (P < 0.01) to 62.5 N/mm (P = 0.21). With comminution, adding a third medial entry pin increased torsional stiffness (0.13-0.24 Nm/degree, P < 0.01) and increased bending stiffness (38.7-44.7 N/mm, P = 0.10). For fractures without medial column comminution, fixation using 3 lateral entry pins may provide the greatest combination of torsional and bending stiffness. With medial comminution, adding a third medial pin increased torsional stiffness (P < 0.01) and bending stiffness (P = 0.10).

Research paper thumbnail of Fixation of Non-Cemented Total Hip Arthroplasty Femoral Components in a Simulated Proximal Bone Defect Model

The Journal of Arthroplasty, 2013

An accelerated sequential proximal femoral bone loss model was used to measure the initial stabil... more An accelerated sequential proximal femoral bone loss model was used to measure the initial stability of three noncemented femoral stem designs: fully porous-coated, proximally porous-coated, and dual-tapered, diaphyseal press-fit (N=18). Only dual-tapered, diaphyseal press-fit stems remained stable with as much as 105 mm of bone loss, with average cyclic micromotion remaining below 25 μm in ML and below 10 μm in AP planes. In contrast, with proximally coated and fully coated stem designs with circular or oval cross-sections, 60mm of bone loss, resulting in lower than 10 cm of diaphyseal bone contact length, led to gross instability, increasing average cyclic micromotions to greater than 100 μm prior to failure. Therefore, the results provide support for using a dual-tapered stem in revision cases with proximal bone loss.

Research paper thumbnail of Failure Modes of 433 Metal-on-Metal Hip Implants: How, Why, and Wear

Orthopedic Clinics of North America, 2011

Modern metal on metal hip replacement bearings are often seen as a durable option for younger pat... more Modern metal on metal hip replacement bearings are often seen as a durable option for younger patients because they are stronger and considered to produce lower rates of wear and osteolysis. 1 The use of metal-on-metal bearings has increased since the introduction of largediameter components for hip replacements and hip resurfacings, which offer protection against dislocation. Consequently, metal-on-metal bearings are reported to be second in popularity to polyethylene-on-metal bearings. 2 However, concerns remain regarding the potential biologic reactivity and long-term effects of cobaltchromium alloy metal particles and ions, particularly in light of recent reports of soft tissue masses, 3,4 necrosis, 5,6 and systemic effects 7 of elevated ion levels. Although the incidence of these problems is thought to be relatively low, 8 there have been calls to severely limit the use of metal-on-metal bearings. Our research center has collected a large number of failed metal-on-metal implants, including firstgeneration McKee-Farrar total hip replacements (THRs), early generation hip resurfacings (McMinn; Corin Group, PLC, Cirencester, UK and Wagner; Sulzer, Winterthur, Switzerland), 11 and a range of contemporary large-diameter modular THRs and hip resurfacings. In 2006, we published a retrieval study of implant failure modes in metal-on-metal surface arthroplasties and reported that aseptic loosening and femoral neck fracture comprised most failures. We also reported that revision directly attributed to wear of the bearings was relatively rare.

Research paper thumbnail of Biomechanical Testing of Pin Configurations in Supracondylar Humeral Fractures

Journal of Orthopaedic Trauma, 2013

We measured biomechanical stability in simulated supracondylar humeral fractures fixed with each ... more We measured biomechanical stability in simulated supracondylar humeral fractures fixed with each of 6 pin configurations, 2 with associated medial comminution, and developed a technique for reproducible pin placement and divergence. A transverse supracondylar osteotomy was performed on 36 biomechanical humerus models. Of these, 24 (4 groups of 6 specimens each) were fixed with pins in 1 of 4 lateral entry configurations. The remaining 12 (2 groups of 6 specimens each) had a 30-degree medial wedge removed from the distal humerus and were fixed with 1 of 2 configurations. Half of each group was tested under axial rotation and the other half under varus bending. The distal humerus was divided into 4 equal regions from lateral to medial (1-4). Lateral entry pins were inserted through regions 1-3, whereas the medial pin was inserted through region 4. Without comminution, 3 widely spaced, divergent lateral entry pins resulted in higher torsional stiffness (0.36 Nm/degree) than 2 pins in adjacent regions (P < 0.055), but similar to 2 pins in nonadjacent regions (P = 0.57). Three lateral entry pins had higher bending stiffness (79.6 N/mm) than 2 pins, which ranged from 46.7 N/mm (P < 0.01) to 62.5 N/mm (P = 0.21). With comminution, adding a third medial entry pin increased torsional stiffness (0.13-0.24 Nm/degree, P < 0.01) and increased bending stiffness (38.7-44.7 N/mm, P = 0.10). For fractures without medial column comminution, fixation using 3 lateral entry pins may provide the greatest combination of torsional and bending stiffness. With medial comminution, adding a third medial pin increased torsional stiffness (P < 0.01) and bending stiffness (P = 0.10).

Research paper thumbnail of Fixation of Non-Cemented Total Hip Arthroplasty Femoral Components in a Simulated Proximal Bone Defect Model

The Journal of Arthroplasty, 2013

An accelerated sequential proximal femoral bone loss model was used to measure the initial stabil... more An accelerated sequential proximal femoral bone loss model was used to measure the initial stability of three noncemented femoral stem designs: fully porous-coated, proximally porous-coated, and dual-tapered, diaphyseal press-fit (N=18). Only dual-tapered, diaphyseal press-fit stems remained stable with as much as 105 mm of bone loss, with average cyclic micromotion remaining below 25 μm in ML and below 10 μm in AP planes. In contrast, with proximally coated and fully coated stem designs with circular or oval cross-sections, 60mm of bone loss, resulting in lower than 10 cm of diaphyseal bone contact length, led to gross instability, increasing average cyclic micromotions to greater than 100 μm prior to failure. Therefore, the results provide support for using a dual-tapered stem in revision cases with proximal bone loss.