A technique for enhancing union of allograft to host bone

A new joint reconstruction technique in the treatment of giant cell tumors around the knee: Structural allograft and unicompartmental arthroplasty

OBJECTIVE

The long-term prognosis of patients who underwent unicompartmental knee arthroplasty (UKA) with a structural allograft or hemiarticular allograft transplantation to treat giant cell tumors (GCTs) around the knee and the prosthesis survival rate were analyzed.

METHODS

We retrospectively reviewed 73 patients who were diagnosed with GCTs around the knee and underwent surgery to restore joint function from 2000 to 2015. Patients were divided into two groups according to the surgical procedure used for functional knee reconstruction: hemiarticular allograft transplantation or structural allograft and UKA. The Knee Society Score (KSS) and Western Ontario and McMaster Universities Arthritis Index (WOMAC) were used to analyze postoperative knee function between the two groups. The Kellgren-Lawrence (K-L) classification system was used to evaluate the progression of osteoarthritis. The incidence of complications and the prosthesis survival rate were also investigated.

RESULTS

Patients who underwent UKA to treat GCT demonstrated significantly improved knee function. The rate of an excellent or good KSS was significantly different between the two groups (p = 0.041 at the 1-year follow-up, p = 0.033 at the last follow-up). The proportion of severe cases according to WOMAC in the two groups was also different (p = 0.030 at the 1-year follow-up, p = 0.021 at the last follow-up). According to the K-L grade of unaffected compartments, UKA better prevented the progression of osteoarthritis (p = 0.034).

CONCLUSIONS

Patients with GCTs around the knee could benefit from UKA. In addition to providing better knee function and range of motion, UKA could also slow the progression of osteoarthritis in the knee joint. This new surgical method could meet the needs of patients wishing to preserve joint integrity and favorable joint function.

Anticancer and bone-enhanced nano-hydroxyapatite/gelatin/polylactic acid fibrous membrane with dual drug delivery and sequential release for osteosarcoma

Surgical resection of osteosarcoma is always accompanied by residual metastasis of tumor cells and bone tissue defects. In this work, a novel kind of gelatin/polylactic acid (PLA) coaxial fiber membrane with a shell layer containing doxorubicin-loaded hydroxyapatite (DOX@nHAp) nanoparticles and a core layer containing Icariin (ICA) was developed for antitumor and bone enhancement at the defect site. Physical evaluation displayed that the composite membrane provided moderate hydrophilicity, enhanced tensile strength (Dry: 2-3 MPa, wet: 1-2 MPa) and elasticity (70-100 %), as well as increased specific surface area and pore volume (19.39 m²/g and 0.16 cm³/g). In SBF, DOX@nHAp in the fibers promoted biomineralization on the fiber surface. In in vitro evaluation, approximately 80 % of DOX had a short-term release during the first 8 days, followed by long-term release behavior of ICA for up to 40 days. CCK-8 results confirmed that the membrane could actively support MC3T3-E1 cells proliferation and was conductive to high alkaline phosphatase expression, while the viability of MG-63 cells was effectively inhibited to 50 %. Thus, the dual-loaded fibrous membrane with a coaxial structure and nHAp is a promising system for anticancer and defects reconstruction after osteosarcoma surgery.

Mechanical strain induces ex vivo expansion of periosteum

Segmental bone defects present complex clinical challenges. Nonunion, malunion, and infection are common sequalae of autogenous bone grafts, allografts, and synthetic bone implants due to poor incorporation with the patient's bone. The current project explores the osteogenic properties of periosteum to facilitate graft incorporation. As tissue area is a natural limitation of autografting, mechanical strain was implemented to expand the periosteum. Freshly harvested, porcine periosteum was strained at 5 and 10% per day for 10 days with non-strained and free-floating samples serving as controls. Total tissue size, viability and histologic examination revealed that strain increased area to a maximum of 1.6-fold in the 10% daily strain. No change in tissue anatomy or viability via MTT or Ki67 staining and quantification was observed among groups. The osteogenic potential of the mechanical expanded periosteum was then examined in vivo. Human cancellous allografts were wrapped with 10% per day strained, fresh, free-floating, or no porcine periosteum and implanted subcutaneously into female, athymic mice. Tissue was collected at 8- and 16-weeks. Gene expression analysis revealed a significant increase in alkaline phosphatase and osteocalcin in the fresh periosteum group at 8-weeks post implantation compared to all other groups. Values among all groups were similar at week 16. Additionally, histological assessment with H&E and Masson-Goldner Trichrome staining showed that all periosteal groups outperformed the non-periosteal allograft, with fresh periosteum demonstrating the highest levels of new tissue mineralization at the periosteum-bone interface. Overall, mechanical expansion of the periosteum can provide increased area for segmental healing via autograft strategies, though further studies are needed to explore culture methodology to optimize osteogenic potential.

Design and Analysis of Biomedical Scaffolds Using TPMS-Based Porous Structures Inspired from Additive Manufacturing

Gyroid (G) and primitive (P) porous structures have multiple application areas, ranging from thermal to mechanical, and fall in the complex triply periodic minimal surface (TPMS) category. Such intricate bioinspired constructs are gaining attention because they meet both biological and mechanical requirements for osseous reconstruction. The study aimed to develop G and P structures with varying porosity levels from 40% to 80% by modulating the strut thickness to proportionally resemble the stiffness of host tissue. The performance characteristics were evaluated using Ti6Al4V and important relationships between feature dimension, strut thickness, porosity, and stiffness were established. Numerical results showed that the studied porous structures could decrease stiffness from 107 GPa (stiffness of Ti6Al4V) to the range between 4.21 GPa to 29.63 GPa of varying porosities, which matches the human bone stiffness range. Furthermore, using this foundation, a subject-specific scaffold (made of P unit cells with an 80% porosity) was developed to reconstruct segmental bone defect (SBD) of the human femur, demonstrating a significant decrease in the stress shielding effect. Stress transfer on the bone surrounded by a P scaffold was compared with a solid implant which showed a net increase of stress transfer of 76% with the use of P scaffold. In the conclusion, future concerns and recommendations are suggested.

A taper-fit junction to improve long bone reconstruction: A parametric In Silico model

PURPOSE

Critical size long bone defects represent a clinical challenge in orthopaedic surgery. Various grafting techniques have been developed through the years, but they all present several downsides. A key requirement of all grafting techniques is the achievement of a continuous interface between host bone and graft to enhance both biological processes and mechanical stability. This study used a parametric in silico model to quantify the biomechanical effect of the inaccuracies inherent to current osteotomy techniques, and to test a new concept of accurate taper-fit junction that may improve the biomechanical parameters of the reconstruction under load.

METHODS

A population-based in-silico 3D model of the reconstruction of a long bone defect was built to represent a defect of the femoral mid-diaphysis. To fix the reconstruction a titanium plate was placed on the lateral aspect of the reconstruction. The model was modified to (i) quantify the biomechanical consequences of actual inaccuracies in the realization of a flat host-graft interface, (ii) compare the contact behaviour and bone strains among different taper angles of the new design and the current host-graft flat interface, (iii) evaluate the robustness of the taper-fit design to inter-subject variability in bone geometry and defect length.

RESULTS

The influence of 2° single-plane misalignments of the host-graft interface is highly dependent on the misalignment orientation with respect to the metal plate. For some misalignment orientations, tangential micromotions of contact interfaces exceeded alert thresholds. When the angle of the taper-fit host-graft junction is changed from 10° to 30° and the results obtained are compared with the planar case, the overall stiffness is almost preserved, the bone strains are almost unchanged with safety factors higher than five, and full contact closure around the host-graft junction is achieved at 20°. Similarly, contact pressures decrease almost linearly with a 20% decrease at 30°. The host-graft micro motions are almost unchanged in both value and distribution up to 20° and never exceed the warning threshold of 50 μm.

CONCLUSIONS

The present in silico study developed quantitative biomechanical evidence that an osteotomy performed with attention to the perpendicularity of the cut planes is needed to reduce the risk of mismatch and possible complications of long bone reconstructions, and that a new concept of a taper-fit junction may improve the biomechanical environment of the interface between the graft and the host bone. The optimal taper-fit configuration is suggested to be around a 20° taper angle. These results will serve as an input to conduct exvivo experiments to further corroborate the proposed taper-fit junction concept and to refine its surgical implementation.

Overlapping allograft for primary or salvage bone tumor reconstruction

BACKGROUND

Compared with end-to-end allograft coaptation, overlapping allograft offer a superior union rate by increasing the contact area. However, reports on overlapping allograft are scarce. Therefore, we attempted to confirm the usefulness of this technique either after primary tumor resection or in salvaging a failed reconstruction.

METHODS

We analyzed the outcome of 35 overlapping allografts reconstructions. Indications were primary reconstruction of a skeletal defect (n = 19) and salvage of a failed reconstruction (n = 16). Graft survival, union rate, and time to union were evaluated as a function of clinical variables such as age, use of chemotherapy, type of junction, method of fixation, length of overlapped bone, and method of overlapping.

RESULTS

All 35 overlapping allografts showed union at a mean of 5.6 months (range, 3-14 months). One allograft was removed with local recurrence at 19 months post-operatively. Average length of overlapped bone was 3.5 cm (range, 1.4-6.5 cm). Patient age <15-years (P = 0.001) and circumferential overlapping (P = 0.011) shortened the time to union.

CONCLUSIONS

In terms of graft failure rate, union rate, and time to union, overlapping allograft is an excellent technique, which overcomes the limitations of end-to-end fixation.

Periosteal adventitia is a valuable bone graft alternative

BACKGROUND

Periosteal adventitia is believed to consist of fibrous tissue without any regenerative potential. This theory results in the assumption that surgically stripped periosteum which is also adventitial has no bone regeneration potential. We decided to test whether the periosteal adventitia is osteoinductive and whether it is suitable for a commonly faced clinical situation in an animal model.

METHODS

This study used 24 femurs from 12 rabbits, which were separated into 3 groups. Lateral femoral condylar cavitary defects were created with a 5 mm drill bit. In group I, the defects were left empty as the control. In group II, the defects were only filled with ceramic graft particles. In group III, the defects were filled with a mixture of ceramic graft particles and autogenous, adventitial, periosteal particles. All animals were sacrificed at the end of the 6th week and were evaluated histologically.

RESULTS

The microscopy of 3 different histologists suggested that group III had far superior healing when compared to the control group and group II. The statistical evaluation of the histomorphometrically gathered quantitative results revealed a meaningful increase in woven bone and a decrease in fibrous tissue in group III, confirming the histological analysis.

CONCLUSIONS

In this study we observed that the composite graft obtained by mixing ceramics and free adventitial periosteal grafts offers healing potential surpassing both the ceramic-only group as well as the control group. We conclude that adventitial periosteal graft greatly facilitates new bone formation.

Overlapping allograft in reconstructive surgery for malignant bone tumours in paediatric patients

The use of allografts for the treatment of bone tumours in children is limited by nonunion and the difficulty of finding a suitable graft. Furthermore, appositional growth can’t be expected of an allograft.

We used an overlapping allograft in 11 children, with a mean age of ten years (4 to 15), with a mean follow-up of 24.1 months (20 to 33). There were five intercalary and six intra-articular resections, and the tumours were in the femur in six cases and the humerus in five. Rates of union, times to union, remodelling patterns and allograft-associated complications were evaluated.

No allograft was removed due to a complication. Of the 16 junctional sites, 15 (94%) showed union at a mean of 3.1 months (2 to 5). Remodelling between host and allograft was seen at 14 junctions at a mean of five months (4 to 7). The mean Musculoskeletal Tumor Society score was 26.5 of 30 (88.3%). One case of nonunion and another with screw protrusion required re-operation.

Overlapping allografts have the potential to shorten time to union, decrease rates of nonunion and have positive appositional growth effect.

Stringent patient selection in bulk allograft reconstructions

We hypothesized that stringent patient selection in the use of large bulk structural allografts for limb preservation would positively affect outcomes and decrease complication rates by eliminating certain comorbid or social factors known to contribute to the most detrimental sources of allograft failure: infection, fracture, and nonunion.Our selection criteria included patients who were younger than 50 years, nonsmokers, non-obese (body mass index <40), who did not receive radiation therapy to the recipient site perioperatively, and who underwent intercalary allograft reconstruction except in the upper extremity where osteoarticular allografts were permitted. Outcomes were assessed using the Musculoskeletal Tumor Society (MSTS) and Toronto Extremity Salvage Score (TESS) scoring systems. Twenty-three patients fulfilled our cohort inclusion criteria. The overall survival rate for the 23 allografts was 91% (21/23). Average MSTS and TESS scores were 76% and 87%, respectively. Eleven of 23 patients experienced at least 1 complication requiring a second procedure. Musculoskeletal Tumor Society scores among patients experiencing no complications averaged 83% vs 71% for patients experiencing at least 1 complication. Average TESS scores were 89% and 86%, respectively.The results of our early experience indicate there is no appreciable difference in complication rates among our series of patients stringently selected for bulk allograft reconstruction compared to other previously reported studies.

Results of free vascularized fibula grafting for allograft nonunion after limb salvage surgery for malignant bone tumors

The purpose of this study was to assess the results of free vascularized fibula grafting (FVFG) in the treatment of allograft fracture nonunion after limb salvage surgery for malignant bone tumors.A retrospective study was performed on 8 patients who underwent FVFG for allograft fracture nonunions. All had prior tumor resection and allograft reconstruction for osteosarcoma (n = 6) or Ewing sarcoma (n = 2) of the femur (n = 3), tibia (n = 2), humerus (n = 2), or ulna (n = 1). All patients failed an initial course of immobilization; 4 patients failed prior open reduction and internal fixation with autogenous nonvascularized bone grafting. Average age at the time of FVFG was 14 years. Average follow-up was 44 months. The FVFG resulted in successful bony healing in 7 of 8 patients, providing pain relief, limb preservation, and restoration of function. One patient developed an infection requiring fibula removal and staged prosthetic reconstruction. Additional complications requiring further treatment included limb-length discrepancy, additional allograft fracture, and wound infection. The FVFG is an effective treatment option for allograft nonunion after limb salvage surgery because it provides both the mechanical stability and biological stimulus for bony healing. Attention to internal fixation, limb alignment, and microvascular principles is essential to prevent complications and allow for the best functional outcomes.

Allograft reconstruction for bone sarcoma of the tibia in the growing child

The outcome of tibial allograft reconstruction after resection of a tumour is inconsistent and has a high rate of failure. There are few reports on the use of tibial allografts in children with open growth plates. We performed 21 allograft reconstructions (16 osteoarticular, five intercalary) in 19 consecutive patients between seven and 17 years of age. Two had Ewing’s sarcoma, one an adamantinoma and 16 osteosarcoma, one with multifocal disease.

Five patients have died; the other 14 were free from disease at the time of follow-up. Six surviving patients (eight allograft reconstructions) continue to have good or excellent function at a mean of 59 months (14 to 132). One patient has poor function at 31 months. The other seven patients have a good or excellent function after additional procedures including exchange of the allograft and resurfacing or revision to an endoprosthesis at a mean of 101 months (43 to 198). The additional operations were performed at a mean of 47 months (20 to 84) after the first reconstruction.

With the use of allograft reconstruction in growing children, joints and growth plates may be preserved, at least partially. Although our results remain inconsistent, tibial allograft reconstruction in selected patients may restore complete and durable function of the limb.

Limb salvage using original low heat-treated tumor-bearing bone

Limb salvage, using original low heat-treated tumor-bearing bone and a conventional joint prosthesis, was done in six patients with malignant tumors of the proximal humerus (one patient with chondrosarcoma and five patients with osteosarcoma) and in six patients with tumor of the proximal femur (two patients with malignant spindle cell sarcoma and four patients with osteosarcoma). Wide excision of the lesion was done and the tumor and surrounding soft tissues were removed. The excised bone was treated with heat and the prosthesis was inserted into the treated bone and fixed with cement. This construct was reinserted into the original site and anchored to the host bone with a plate. The overall union rate of the low heat-treated bone with normal host bone was 91.7%, and the mean union time was 4.6 months (range, 3-7 months) after surgery. The functional result of the proximal femur and proximal humerus were 76.7% and 56.8%, respectively, using the Musculoskeletal Tumor Society functional evaluation system. Complications included hip dislocation in one patient, fracture of the low heat-treated bone in two patients, and absorption of the low heat-treated bone of the humerus in four of six patients. The 5-year survival rate of the low heat-treated tumor-bearing bone was 83.3% using Kaplan-Meier survival analysis. Based on the results of this study, limb salvage using original low heat-treated tumor-bearing bone seems to be effective in treating primary bone sarcoma with high survival and acceptable complication rates, circumventing the complications of allograft bone.