Durability and strength of Steinmann pin augmentation in cemented tibial defects

Acetabular Screws With Cement Augment for Tibial Plateau Defects in Dynamic Spacer Implantation: A Case of Recalcitrant Native Knee Septic Arthritis

Treating tibial bone defects in the setting of recalcitrant native knee arthritis presents a challenging biomechanical problem for orthopaedic surgeons. A dynamic antibiotic spacer offers an effective solution to preserve patient function and manage infection. However, severe bone loss may compromise the fixation of the dynamic spacer. We describe the application of acetabular screws as rebar in a case of an Anderson Orthopaedic Research Institute type 3 defect of the medial tibial plateau. Additionally, we outline a facile method for fabricating the tibial stem component to ensure optimal fit within the intramedullary canal. Short-term follow-up (8 months) indicates successful fixation of the tibial component, absence of knee pain, and a knee range of motion up to 100 degrees.

Screw inserting in different phase of cement affect the pull-out strength of cement augmented screws

BACKGROUND

For large bone defects, after curettage of aggressive bone tumors; such as giant-cell tumors, cementation with supplement internal fixation was used to prevent subsequent collapse of the cement-bone constructs. The purpose of this study is to compare the pull-out strength of cement augmented screws between inserting screws in the working phase or hard phase of bone cement.

HYPOTHESIS

Timing at which completed screw insertion takes place affecting the pull-out strength of cement augmented screws.

METHODS

Pull-out strength was compared between screws; inserted within the working phases of cement, and after the cement was hardened in high viscos cement blocks. Each group consists of 10 cortex screws, 10 cancellous screws and 10 locking screws. The pull-out strength test was followed using the instructions of ASTM F543-13e1 Standard Specification and Test Methods, for Metallic Medical Bone Screws.

RESULTS

Screws that were inserted in the working phases of cement had significantly higher pull-out strength, than those inserted in hard cement (p=0.021). The pull-out strength was statistically significant in difference among the types of screws (p<0.001), with locking screws having the highest pull-out strength. Furthermore, the pull-out strength of locking screws revealed no significant difference when either; inserted during the working or hardened phases of bone cement.

CONCLUSION

Insertion of screws during the working periods of PMMA cement had higher pull out strength compared to the hard phase of cement. Hence, we recommend performing internal fixation before cementation after curettage of aggressive bone tumors. However, if the surgeon prefers to pack the cement first, for the benefit of avoiding residual bone defects, we suggest using a locking plate system to achieve comparable pull-out strength.

LEVEL OF EVIDENCE

In-vitro study.

Fibular strut allograft or bone cement for reconstruction after curettage of a giant cell tumour of the proximal femur : a retrospective cohort study

AIMS

Giant cell tumours (GCTs) of the proximal femur are rare, and there is no consensus about the best method of filling the defect left by curettage. In this study, we compared the outcome of using a fibular strut allograft and bone cement to reconstruct the bone defect after extended curettage of a GCT of the proximal femur.

METHODS

In a retrospective study, we reviewed 26 patients with a GCT of the proximal femur in whom the bone defect had been filled with either a fibular strut allograft (n = 12) or bone cement (n = 14). Their demographic details and oncological and nononcological complications were retrieved from their medical records. Limb function was assessed using the Musculoskeletal Tumor Society (MSTS) score.

RESULTS

Mean follow-up was 116 months (SD 59.2; 48 to 240) for the fibular strut allograft group and 113 months (SD 43.7; 60 to 192) for the bone cement group (p = 0.391). The rate of recurrence was not significantly different between the two groups (25% vs 21.4%). The rate of nononcological complications was 16.7% in the strut allograft group and 42.8% in the bone cement group. Degenerative joint disease was the most frequent nononcological complication in the cement group. The mean MSTS score of the patients was 92.4% (SD 11.5%; 73.3% to 100.0%) in the fibular strut allograft group and 74.2% (SD 10.5%; 66.7% to 96.7%) in the bone cement group (p < 0.001).

CONCLUSION

Given the similar rate of recurrence and a lower rate of nononcological complications, fibular strut grafting could be recommended as a method of reconstructing the bone defect left by curettage of a GCT of the proximal femur. Cite this article: Bone Joint J 2022;104-B(2):297-301.

Post-operative fracture risk assessment following tumor curettage in the distal femur: a hybrid in vitro and in silico biomechanical approach

The distal femur is the predominant site for benign bone tumours and a common site for fracture following tumour removal or cementation. However, the lack of conclusive assessment criterion for post-operative fracture risk and appropriate devices for cement augmentation are serious concerns. Hence, a validated biomechanical tool was developed to assess bone strength, depending on the size and location of artificially created tumorous defects in the distal femora. The mechanics of the bone–cement interface was investigated to determine the main causes of reconstruction failure. Based on quantitative-CT images, non-linear and heterogeneous finite element (FE) models of human cadaveric distal femora with simulated tumourous defects were created and validated using in vitro mechanical tests from 14 cadaveric samples. Statistical analyses demonstrated a strong linear relationship (R² = 0.95, slope = 1.12) with no significant difference between bone strengths predicted by in silico analyses and in vitro tests (P = 0.174). FE analyses showed little reduction in bone strength until the defect was 35% or more of epiphyseal volume, and reduction in bone strength was less pronounced for laterally located defects than medial side defects. Moreover, the proximal end of the cortical window and the most interior wall of the bone–cement interface were the most vulnerable sites for reconstruction failure.

The Great Need of a Biomechanical-Based Approach for Surgical Methods of Giant Cell Tumor: A Critical Review

There are many unanswered questions about giant cell tumor (GCT) treatment and not enough attention is paid to the biomechanics of the current treatment methods. Treatment methods have not changed much, and the best method remains controversial to some degree, due to the lack of adequate clinical and biomechanical investigations. Biomechanical tests, including in vitro mechanical experiments combined with finite element analysis, are very helpful in assessing the efficiency of the surgical methods employed and in determining the optimal method of surgery. Tests can be tailored to meet a patient’s needs, while limiting postoperative complications. One of the complications, following tumor surgery, is the frequency of postoperative fractures. In order to prevent postoperative fractures, defect reconstruction is recommended. The reconstruction usually consists of defect infilling with bone cement, and in the case of large defects cement augmentation is employed. Whether cement augmentation is essential and offers enough mechanical strength and what is the best fixation device for cement augmentation are areas of debate. In this article, the biomechanical studies comparing different methods of tumor surgery and cement augmentation, highlighting the areas needing more attention to advance GCT treatment, are critically reviewed. Based on our review, we recommend a biomechanical criterion for the essence of defect reconstruction, which must include patient specific factors, in addition to the tumor geometrical properties.

Steinmann pin augmentation versus locking plate constructs

BACKGROUND

Aggressive bone neoplasms, such as giant cell tumors, often affect the proximal tibia warranting bony resection via curettage leaving behind massive defects that require extensive reconstruction. Reconstruction is usually accomplished with poly(methyl methacrylate) (PMMA) packing supplemented with an internal fixation construct. The purpose of this study is to compare Steinmann pin augmentation to locking plate constructs to determine which offers the stiffer reconstruction option.

MATERIALS AND METHODS

Large defects were created below the lateral condyle of fresh frozen tibias. The defects extended for an average of 35 mm beneath the lateral plateau in the frontal plane, and from the anterior to posterior cortex in the sagittal plane. Distally the defect extended for an average of 35 mm to the metadiaphyseal junction. In the Pin group, the tibias were reconstructed with three 4-mm diameter Steinmann pins placed in the medullary canal and PMMA packing. In the Plate group, the tibias were reconstructed with a 6-hole 3.5-mm LCP Proximal locking plate fixed to the proximal-lateral tibia utilizing seven 3.5-mm screws and PMMA packing. The tibias were tested for stiffness on a MTS machine by applying up to 400 N to the tibial plateau in force control at 5 N/s. Fatigue properties were tested by applying a haversine loading waveform between 200 N and 1,200 N at 3 Hz simulating walking upstairs/downstairs.

RESULTS

Locking plate constructs (801.8 ± 78 N/mm) had greater (p = 0.041) stiffness than tibial constructs fixed with Steinmann pins (646.5 ± 206.3 N/mm).

CONCLUSIONS

Permanent deformation was similar between the Pin and Plate group; however, two tibia from the Pin group exhibited displacements >5 mm which we considered failure.

LEVEL OF EVIDENCE

n/a.

Distal femur defects reconstructed with polymethylmethacrylate and internal fixation devices: a biomechanical study

Benign aggressive distal femur tumors are treated with curettage, adjuvant phenol or argon, and polymethylmethacrylate (PMMA) packing. For large defects, an internal fixation device is added to reduce the fracture risk. The purpose of this study is to compare the strength of locking plates to other fixation devices for stabilization of these defects. Lateral condyle defects in young, fresh frozen femurs were packed with PMMA and augmented by internal fixation. Three groups of 4 matched pairs of femurs were organized for the following comparisons: (1) stacked Steinmann pins vs crossed screws; (2) stacked pins vs locking plates; and (3) crossed screws vs locking plates. Specimens were subjected to axial load-to-failure testing on an MTS machine. There was no difference in load-to-failure strength (P=.177) using Steinmann pins or crossed screws. Locking plate constructs were stronger (P=.028) than Steinmann pin constructs. Locking plate constructs were also stronger (P<.001) than crossed-screw constructs. Steinmann pin constructs failed with severe intra-articular fractures; crossed screw constructs failed with bulging of the defects, articular impaction, and minimal fracture propagation. Locking plate constructs failed with extra-articular spiral shaft fractures.

Reconstruction of noncontained proximal tibial defects with divergent screws and cement

Postoperative fracture is a well described complication following curettage and cementation of aggressive benign bone tumors. We asked whether: (1) the addition of diverging screws that engage the opposite cortex increase the strength and rigidity of the construct in the proximal tibia compared with (a) cement alone and (b) would cement with intramedullary Steinmann pins; and (2) the modes of failure be different for those constructs. The average load to failure for tibias reconstructed with cement augmented with diverging screws (6321 +/- 681 N) was higher than for tibias reconstructed with cement alone (2343 +/- 222 N). The average load to failure for tibias reconstructed with cement augmented with diverging screws (6885 +/- 445 N) was higher than for tibias reconstructed with cement and intramedullary Steinmann pins (5218 +/- 941 N). Furthermore, constructs with cement augmented with diverging screws were less likely to fail by an intraarticular fracture than other types of constructs. Our data support the use of diverging screws that engage the opposite cortex to augment the strength of the construct when using acrylic cement to fill noncontained defects after curettage of the proximal tibia. This more stable, stronger construct might allow earlier mobilization and rehabilitation after curettage, with a decreased risk of fracture.

The risk for fractures after curettage and cryosurgery around the knee

Curettage and cryosurgery have been used successfully for treatment of benign locally aggressive and some low-grade malignant bone tumors. After treating these lesions, we reconstruct residual bone defects around the knee with cement, intramedullary pins, and autogenous bone graft for subchondral augmentation and closure of cortical windows. We questioned the incidence of fractures and the rates of nonunion and malunion and asked whether patients at risk for fractures can be identified. We conducted chart and radio-graphic reviews of 60 consecutive patients who had curettage and cryosurgery of primary bone lesions in the distal femur or proximal tibia. Ten of the 60 patients (17%) sustained postoperative intraarticular fractures. Patients who sustained fractures had (1) more freeze-thaw cycles; (2) metaphyseal defect ratios greater than 0.6 and 0.8 on the anteroposterior and lateral projections, respectively; and (3) 4 mm or less proximity of the defect to the joint. Only one fracture united in good alignment. Radiographic measurements can assist in identifying patients at risk for fractures after curettage and cryosurgery around the knee. We expect the fracture rate to decline by reducing the number of freeze-thaw cycles and improving our reconstruction method.

Complications of cemented long-stem hip arthroplasties in metastatic bone disease

It is controversial whether a cemented long-stem femoral arthroplasty is a safe surgical option for patients with meta-static bone disease of the hip. Cemented long stems increase the risk of embolic cascades and may cause subsequent cardiopulmonary complications, particularly in patients with metastatic disease. We retrospectively reviewed results of 29 long-stem cemented femoral arthroplasties in 27 patients in which surgical techniques that minimized intramedullary debris and canal pressurization were used. The surgical techniques minimized intraoperative cement-related emboli with aggressive medullary lavage, intraoperative canal suctioning during cementation, use of early low-viscosity polymethylmethacrylate, and slow, controlled insertion of the long-stem prosthesis. Cement-associated hypotension occurred in four (14%) patients, sympathomimetics were administered in nine (31%) patients, and a worsening mental status occurred postoperatively in one (3%) patient. There were no cement-associated desaturation events, cardiac arrests, or intraoperative deaths. No patients required prolonged intubation, and there were no postoperative cardiopulmonary events. Cemented long-stem femoral arthroplasty is a safe procedure for patients with high-risk metastatic disease. Increased awareness of cement-related cardiopulmonary pathophysiology, and modifying conventional surgical techniques can minimize cement-associated complications.

LEVEL OF EVIDENCE

Therapeutic study, Level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.

Biomechanical study of pins in cementing of contained proximal tibia defect

Defects from curettage for giant cell tumors of bone frequently have been reconstructed with bone cement with or without reinforcement pins. The biomechanical basis for the addition of reinforcement pins was examined using a model of a contained defect in the proximal tibia. Fifty-four cadaveric proximal tibia in matched pairs were divided into five test groups: intact tibia, medial metaphyseal contained defect, defect reconstructed with cement alone, defect reconstructed with cement and pins inserted within the medullary canal, and defect reconstructed with cement and pins inserted through the cortex. Specimens were tested to failure during one cycle of compressive loading. Defect specimens were significantly weaker and less stiff than intact specimens, establishing the validity of the model-contained defects. For the reconstructions, there was no statistically significant difference in load to failure, stiffness, energy to failure, or displacement for the polymethylmethacrylate treatment alone when compared with matched specimen receiving polymethylmethacrylate and pins treatment. Similarly, there was no statistical difference in biomechanical properties in comparing matched specimens treated with polymethylmethacrylate alone or polymethylmethacrylate/pins (cortex). For contained defects of the proximal tibia that are typical after curettage for giant cell tumor, there appears to be no biomechanical advantage to use of reinforcement pins in the cement.