Compressive osseointegration for endoprosthetic reconstruction

Femoral Magnetic Lengthening After Distal Femur Endoprosthetic Reconstruction in a Pediatric Patient: A Case Report

CASE

A 10-year-old boy with osteosarcoma of the left distal femur underwent resection with compressive osseointegration endoprosthetic reconstruction, gradually resulting in a 4.5-cm leg-length difference with significant predicted progression. Two years after resection, he underwent right distal femur and proximal tibia epiphysiodesis and placement of a left femoral magnetic lengthening nail. At 2 years after lengthening and skeletal maturity, the patient has symmetric limb lengths, no pain, and returned to sports.

CONCLUSION

A magnetic lengthening nail with contralateral epiphysiodesis is a viable option for correcting limb-length discrepancy after distal femur endoprosthetic reconstruction in a pediatric patient.

Novel axial compressive endoprosthesis ACE can enhance metaphyseal fixation and facilitate osseointegration: A biomechanical study

Background: Metaphyseal fixation for endoprosthetic reconstruction after bone tumor resection is difficult due to the short residual bone length and reverse funnel shape of the metaphysis. In the current study, 3D-printed axial compressive endoprosthesis (ACE) with a short stem and intramedullary axial compressive mechanism is proposed to improve metaphyseal fixation. The rationales of ACE are that 1) intramedullary axial compress enhances the stability of endoprosthesis and facilitates bone ingrowth at the osteotomy site; 2) 3D printed porous metallic surface at osteotomy surface and stem allows bone ingrowth to achieve osseointegration.

Methods: A biomechanical study was performed to explore the initial stability using Sawbones. A diaphysis and metaphyseal segmental defect were created and four fixation structures were simulated: 1) ACE; 2) ACE + lateral plate; 3) stem prosthesis + unilateral plate; 4) stem prosthesis + bilateral plates. Bending and torsional stiffness were determined with a material testing machine. The relationship between the torque of the compression nut and the axial compression force of the bone-implant surface was measured using a round gasket load sensor.

Results: ACE + lateral plate was the stiffest in the bending test (sagittal 324.3 ± 110.8 N/mm, coronal 307.7 ± 8.7 N/mm). ACE + lateral plate and stem prosthesis + bilateral plates had the highest torsional stiffness (10.9 ± 1.3 Nm/° and 10.7 ± 0.2 Nm/° respectively). The bending stiffness of ACE was equivalent to stem prosthesis + bilateral plates (sagittal 196 ± 10 N/mm vs. 200 ± 7 N/mm, coronal 197 ± 14 N/mm vs. 209 ± 3 N/mm), but the torsional stiffness of ACE was inferior to stem prosthesis + bilateral plates (6.1 ± 1.3 Nm/° vs. 10.7 ± 0.2 Nm/°). Stem prosthesis + unilateral plate was the least stiff both in bending and torsion. The relationship between torque (T/Nm) and axial pressure (F/N) was F = 233.5T.

Conclusion: The axial compressive design of ACE enhances primary stability and facilitates osseointegration, which provides an alternative option of metaphyseal fixation for endoprosthetic reconstruction.

Survival and failure modes of the Compress® spindle and expandable distal femur endoprosthesis among pediatric patients: A multi‐institutional study

BACKGROUND

Expandable endoprostheses can be used to equalize limb length for pediatric patients requiring reconstruction following large bony oncologic resections. Outcomes of the Compress® Compliant Pre-Stress (CPS) spindle paired with an Orthopedic Salvage System expandable distal femur endoprosthesis have not been reported.

METHODS

We conducted a multi-institutional retrospective study of pediatric patients with distal femoral bone sarcomas reconstructed with the above endoprostheses. Statistical analysis utilized Kaplan-Meier survival technique and competing risk analysis.

RESULTS

Thirty-six patients were included from five institutions. Spindle survivorship was 86.3% (95% confidence interval [CI], 67.7-93.5) at 10 years. Two patients had a failure of osseointegration (5.7%), both within 12 months. Twenty-two (59%) patients had 70 lengthening procedures, with mean expansions of 3.2 cm (range: 1-9) over 3.4 surgeries. The expandable mechanism failed in eight patients with a cumulative incidence of 16.1% (95% CI, 5.6-31.5) at 5 years. Twenty-nine patients sustained International Society of Limb Salvage failures requiring 63 unplanned surgeries. Periprosthetic joint infection occurred in six patients (16.7%). Limb preservation rate was 91% at 10 years.

CONCLUSIONS

There is a high rate of osseointegration of the Compress® spindle among pediatric patients when coupled with an expandable implant. However, there is a high rate of expansion mechanism failure and prosthetic joint infections requiring revision surgery.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

What Are the Long-term Surgical Outcomes of Compressive Endoprosthetic Osseointegration of the Femur with a Minimum 10-year Follow-up Period?

BACKGROUND

Endoprosthetic reconstruction after oncologic resection of bone tumors requires stable fixation between the prosthesis and residual host bone. Compressive osseointegration has been developed as an alternative to traditional stemmed implants to address the challenges and complications of achieving this fixation. Sufficient time has now passed from the advent of compressive implants to allow for an assessment of the intermediate-term and long-term results of this form of fixation.

QUESTIONS/PURPOSES

At a minimum follow-up of 10 years after implantation of a compressive osseointegration device for oncologic reconstruction: (1) What is the risk of periprosthetic fracture, aseptic loosening, or implant breakage resulting in revision surgery for endoprosthesis removal? (2) What is the long-term cortical response at the host-endoprosthesis interface as visualized on plain radiographs?

METHODS

A single-center, retrospective study was performed between 2002 and 2010, in which 110 patients with primary bone sarcoma of the proximal or distal femur were considered for oncologic resection and reconstruction. Patients were considered for a compressive osseointegration endoprosthesis if they were 50 years of age or younger, had not previously received femoral radiation, had no metabolic disease impairing bone healing, were not diagnosed with metastatic disease, and had life expectancy greater than six months. Of the 110 patients, 25 were treated with a compressive osseointegration implant of the proximal or distal femur, and 85 patients were treated with conventional stemmed implants or amputation because of older age, advanced disease, metabolic comorbidities, inability to tolerate a nonweightbearing postoperative period, or in the case of rotationplasty, patient preference. All patients who received this device during the period of study were considered eligible for inclusion in this review. The median (range) age was 18 years (7 to 50), and 13 of 25 patients were men. Five patients died of disease before the minimum follow-up duration of 10 years; two underwent amputation due to local recurrence and three died with the implant in situ, leaving 20 patients for complete analysis. Median follow-up was 144 months, and all 20 surviving patients had a minimum follow-up of 10 years (121 to 230 months). The primary endpoint was reoperation and implant removal for periprosthetic fracture, aseptic loosening, or mechanical breakage of any component of the compressive device in the endoprosthesis. In final analysis, death was considered a competing event to revision surgery, and cumulative incidence was reported after competing-event analysis. A secondary aim was radiographic evaluation of the host-implant interface to assess the long-term cortical response to compressive osseointegration.

RESULTS

Spindle fracture or loosening was noted in three patients, and the remaining 17 patients maintained the compression device until the final follow-up. The risk of reoperation for aseptic loosening, periprosthetic fracture, or mechanical breakage of the implant using a competing risks estimator was 12% at 10 years (95% CI 0% to 26%). These complications occurred within 29 months of the index surgery; no patients had implant loosening or mechanical breakdown after this initial period. On radiographic assessment, 14 patients demonstrated cortical hypertrophy of the bone-implant interface, six patients had maintenance of the native cortical contour, and no patients had cortical atrophy or narrowing at the implant interface.Conclusion Long-term follow-up in patients with compressive osseointegrative endoprosthetic devices demonstrated no late revisions because of periprosthetic fracture, aseptic loosening, or implant breakage in this cohort with a minimum 10-year follow-up. There was no evidence of late-onset cortical atrophy or stress shielding at the host-implant interface. This study supports the long-term stability of the interface between host bone and the endoprosthesis in compressive osseointegration devices.

LEVEL OF EVIDENCE

Level IV, therapeutic study.