The outcome of biphasic calcium phosphate bone substitute in a medial opening wedge high tibial osteotomy

Bone Healing and Clinical Outcome Following Medial Opening-wedge High Tibial Osteotomy Using Wedge-Shaped Cancellous Allograft

OBJECTIVE

Medial opening-wedge high tibial osteotomy (MOWHTO) is considered to be an effective treatment for symptomatic knee osteoarthritis (KOA) of isolated the medial compartment with varus alignment of the lower extremity. However, the choice of material to fill the void remains controversial. This study aims to evaluate the bone union of the osteotomy gap using a novel wedge-shaped cancellous allograft after MOWHTO and its effect on clinical outcomes.

METHODS

All patients who underwent MOWHTO using a novel wedge-shaped cancellous allograft combined with TomoFix locking compression plate (LCP) fixation between January 2016 and July 2020 were enrolled. The radiographic parameters including hip-knee-ankle angle (HKAA), medial proximal tibial angle (MPTA), femorotibial angle (FTA) and posterior tibial slope angle (PTSA) were measured between pre-operative and post-operative radiographs. Knee Society score (KSS) and range of motion (ROM) were assessed preoperatively and at last follow-up. Patients included in this study were divided into two groups according to the correction angle: small correction group (< 10°; SC group) and large correction group (≥ 10°; LC group). The modified Radiographic Union score for tibial fractures (mRUST) was used to assess the difference in bone healing between the two groups at 1, 3, 6, and 12 months postoperatively and at the final follow-up. A paired student's t test was conducted for comparison of differences of the relevant data pre-operatively and post-operatively.

RESULTS

A total of 82 patients (88 knees) were included in this study. The HKAA, MPTA, FTA and PTSA increased from -6.4° ± 3.0°, 85.1° ± 2.6°, 180.1° ± 3.2° and 7.7° ± 4.4° preoperatively to 1.2° ± 4.3° (p < 0.001), 94.4° ± 3.3° (p < 0.001), 171.0° ± 2.8° and 11.8° ± 5.8° (p < 0.001) immediately postoperatively, respectively. However, no significant statistic difference was found in above-mentioned parameters at last follow-up compared to immediate postoperative data (p > 0.05). All patients in this study achieved good bone healing at the final follow-up and no significant differences in mRUST scores were seen between the SC group and LC group. The KSS-Knee score and KSS-Function score improved significantly from 55.4 ± 3.7 and 63.3 ± 4.6 preoperatively to 86.4 ± 2.8 (p < 0.001) and 89.6 ± 2.9 (p < 0.001) at last follow-up, respectively. Nevertheless, there was no significant difference in ROM between pre-operation and last follow-up (p > 0.05).

CONCLUSION

For MOWHTO, the wedge-shaped cancellous allograft was a reliable choice for providing good bone healing and clinical outcomes.

The best position of bone grafts in the medial open-wedge high tibial osteotomy: A finite element analysis

BACKGROUND AND OBJECTIVE

The application of wedge-shaped bone grafts can increase the biomechanical stability of knee during the medial open-wedge high tibial osteotomy (MOWHTO) by reducing the von Mises stress of the medial plate and lateral cortical hinge area. However, the optimal position of bone grafts it remains unclear, so we aimed to determine search for the optimal position of the bone grafts in MOWHTO by using finite element analysis.

METHODS

In the finite element analysis, MOWHTO models were established with three different osteotomy distraction heights and assembled into four groups according to different conditions, including the no bone grafts (NBG) group, the anterior bone grafts (ABG) group, the middle bone grafts (MBG) group, and the posterior bone grafts (PBG) group. Based on previous studies, 600 N and 1800 N loads were applied to the knee joint to simulate the static forces during a double and single leg stance to measure the von Mises stress of the medial implant area and lateral hinge area, the maximum displacement of different models, the relative displacement of the osteotomy area and the stress distribution in the bone grafts.

RESULTS

Compared to the NBG and ABG groups, the stress of the lateral cortical hinge area and the medial implate area was significantly lower in the PBG group. For example, under the 600N force load, when the height of the osteotomy area was 10 mm, 15 mm, and 20 mm, the maximum von Mises stress of the medial implate area and lateral cortical hinge area in the NBG group were 140, 141, 172, and 53, 57, 60 MPa, respectively. Compared with the NBG group, the maximum von Mises stress of the medial implate area and lateral cortical hinge area in the PBG group were reduced by 45%, 56%, 63% and 14%, 39%, 68% at distraction height of 10 mm, 15 mm, and 20 mm, respectively. The bone grafts in the posterior parts provide the best stability,with the stress of the middle and posterior bone grafts are mainly concentrated in the edge.

CONCLUSIONS

The posterior part of the osteotomy area is the best position for bone graft placement since it provides optimal stability and reduces von Mises stress in the medial plate and lateral cortex hinge area, with the stress of the posterior bone grafts mainly concentrated in the edge. These findings guide bone graft placement sites in clinical surgery and are a basis for future research on bone graft materials and structures in MOWHTO.

Effectiveness of bone substitute materials in opening wedge high tibial osteotomy: a systematic review and meta-analysis

BACKGROUND

A meta-analysis of eligible studies was performed to evaluate the effectiveness of bone substitute materials (BSMs) in opening wedge high tibial osteotomy (OWHTO) for knee osteoarthritis.

METHODS

A systematic review and meta-analysis were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). A comprehensive literature search was performed, and studies comparing BSM with bone graft (BG) and without bone graft (WG) were included. The Cochrane risk of bias tool (version 1.0) and Risk of Bias in Non-randomized Studies of Interventions (ROBINS-I) tool were used to assess the risk of bias for randomized controlled trials (RCTs) and non-randomized studies (NRSs), respectively. The outcomes measured were the osteotomy gap size, the occurrence rates of non-union and lateral hinge fractures, knee functional score, infection and the Visual Analogue Scale (VAS). The quality of evidences was evaluated by Grades of Recommendation, Assessment, Development and Evaluation (GRADE) Working Group system.

RESULTS

Five RCTs and eight NRS including 769 participants were included in our meta-analysis. The BSM group had a larger osteotomy gap size than the control group (MD: 0.41 mm, 95% confidence interval (CI): [0.06, 0.76], p=.02, I²=0%), with a significant difference. No significant difference was found between BSM and control group in main analysis in terms of bone non-union, but with a higher non-union rate when BSM combined with long locking plate was used. No significant differences were found in other outcome measures except for VAS from NRS subgroup. The quality of evidence for outcomes was low.

CONCLUSIONS

BSM combined with locking plate techniques offers a safe and efficient alternative option in OWHTO for osteotomy gap larger than 10 mm, but be aware of the possibility of bone non-union. Given the inherent heterogeneity and low quality of the included studies, future well-designed RCTs are essential to verify the findings.KEY MESSAGEThe treatment of the osteotomy gap is still controversial.BSM combined with a locking plate offers a safe and efficient alternative option for OWHTO with an over 10 mm of osteotomy gap over 10 mm.Due to the inherent heterogeneity and low quality of the included studies, the results should be cautiously interpreted in clinical practice.

Reinforcement strategy for medial open-wedge high tibial osteotomy: a finite element evaluation of the additional opposite screw technique and bone grafts

BACKGROUND AND OBJECTIVE

bone grafts (bgs) and the opposite screw insertion technique are reported to enhance initial stability after medial open-wedge high tibial osteotomy (OWHTO); however, it is unclear how the general and local biomechanical stability of the proximal tibia is affected by these reinforcement strategies. In this study, we aimed to assess the biomechanical differences among different fixation configurations for OWHTO under two loading conditions using finite element analysis, and to assess the biomechanical contribution of an opposite screw insertion.

METHODS

Models of the proximal tibia with three different gap defects were created to simulate different distraction heights in OWHTO. Four groups of models were then assembled with different fixation configurations, including the no BG (NBG) group, BG group, partially threaded screw (PT) group, and fully threaded screw (FT) group. Testing loads were applied to simulate the static forces on the knee joint during double-limb and single-limb standing. For each group, the stresses of the lateral hinge area (LHA) and the medial implant area (MIA), the maximum displacement of the tibia and the relative displacement (RD) of the medial gap were evaluated.

RESULTS

Compared to NBG group, bone block grafting effectively reduced the stress of the tibia and implant, as well as the maximum displacement of the tibia and the RD of the medial gap. The opposite screw group showed similar trends in alleviating the stress concentration on the LHA and MIA, and contributing to the maintaining the medial gap reduction, especially in the FT group; however, additional stresses were concentrated on the opposite screw itself, which indicated the potential risk of screw breakage.

CONCLUSIONS

Compared to NBG group, the BG group bone graft showed superior biomechanical advantages in decreasing the risk of implant failure and lateral hinge fracture, and maintaining the reduction in OWHTO. The additional opposite screw provided an extra support to the proximal tibia, with similar contributions to improve the structural stability after osteotomy, especially in the FT group.

Bone Scaffolds: An Incorporation of Biomaterials, Cells, and Biofactors

Large injuries to bones are still one of the most challenging musculoskeletal problems. Tissue engineering can combine stem cells, scaffold biomaterials, and biofactors to aid in resolving this complication. Therefore, this review aims to provide information on the recent advances made to utilize the potential of biomaterials for making bone scaffolds and the assisted stem cell therapy and use of biofactors for bone tissue engineering. The requirements and different types of biomaterials used for making scaffolds are reviewed. Furthermore, the importance of stem cells and biofactors (growth factors and extracellular vesicles) in bone regeneration and their use in bone scaffolds and the key findings are discussed. Lastly, some of the main obstacles in bone tissue engineering and future trends are highlighted.

Characterization of bone remodeling of two different porous types of β-tricalcium phosphates: a quantitative site-by-site analysis using computed tomography

This study compared the process of bone remodeling using spherical porous β-tricalcium phosphate (SPTCP) and unidirectional porous β-tricalcium phosphate (UDPTCP) by quantitative computed tomography (CT) analysis. We retrospectively analyzed the data of 16 patients (4 men, 12 women; age, 43-78 years) who underwent medial opening wedge high tibial osteotomy (MOWHTO) and were followed up for 1 year postoperatively. Nine patients used SPTCP spacers and seven patients used UDPTCP spacers. CT was performed at 1 week, 6 months, and 1 year postoperatively. CT attenuation values were measured at three sites on the axial slice and sagittal slice, i.e., the superior, center, and inferior sites and the lateral, center, and medial sites for UDPTCP and SPTCP, respectively. CT attenuation values were lower for UDPTCP than for SPTCP in all sites at 6 months and 1 year postoperatively (p < 0.05). CT attenuation values decreased in the superior and inferior sites for UDPTCP (p < 0.05), and CT attenuation values decreased in the lateral site for both SPTCP and UDPTCP (p < 0.05). The process of bone remodeling differed between the two over a short-term follow-up of 1 year postoperatively.

Silicate/zinc-substituted strontium apatite coating improves the osteoinductive properties of β-tricalcium phosphate bone graft substitute

Background

β-Tricalcium phosphate (β-TCP) is a popular synthetic bone graft substitute with excellent osteoconductive properties and bioabsorbability. However, its osteoinductive properties are inferior to those of autologous or allogeneic bone. Trace elements such as strontium (Sr), silica (Si), and zinc (Zn) have been reported to promote osteogenesis in materials. In this study, we aimed to determine whether a Si/Zn-substituted Sr apatite coating of β-TCP could enhance osteoinductive properties.

Methods

The apatite-coated β-TCP disks were prepared using nanoparticle suspensions of silicate-substituted Sr apatite (SrSiP) or silicate- and Zn-co-substituted Sr apatite (SrZnSiP).

Bone marrow mesenchymal cells (BMSCs) from rat femur were cultured and subsequently seeded at a density of 1.0 × 10⁶/cm² onto apatite-coated and non-coated β-TCP disks.

In vitro, the β-TCP disks were then placed in osteogenic medium, and lactate dehydrogenase (LDH) activity was measured from supernatants after culture for 2 days. Additionally, after culture for 14 days, the mRNA expression of genes encoding osteocalcin (OC), alkaline phosphatase (ALP), bone morphogenetic protein-2 (BMP-2), and vascular endothelial growth factor (VEGF) was evaluated by qRT-PCR. In vivo, the β-TCP disks were transplanted subcutaneously into rats that were sacrificed after 4 weeks. Then, the harvested disks were evaluated biochemically (ALP activity, OC content, mRNA expression of OC, ALP, BMP-2, and VEGF measured by qRT-PCR), radiologically, and histologically.

Results

Significantly higher mRNA expression of almost all evaluated osteogenic and angiogenic genes was observed in the SrZnSiP and SrSiP groups than in the non-coated group, with no significant cytotoxicity elicited by the apatite coating in vitro. Moreover, in vivo, the SrZnSiP and SrSiP groups showed significantly higher osteogenic and angiogenic gene expression and higher ALP activity and OC content than the non-coated group (P < 0.05). Radiological and histopathological findings revealed abundant bone formation in the apatite-coated group.

Conclusions

Our findings indicate that apatite coating of β-TCP improves osteoinductive properties without inducing significant cytotoxicity.

Combination of Cylindrical Autologous Bone Grafting Technique With a Metallic Block Insertion in Open-Wedge High Tibial Osteotomy

Open-wedge high tibial osteotomy (OW-HTO) is an effective surgical intervention for medial-compartment knee osteoarthritis. However, the osteotomized gap might be a disadvantage in OW-HTO because it can cause problems such as delayed bone union or loss of correction. These issues can be minimized by using autologous bone graft in the osteotomized gap, which is known to be the fastest and most clinically satisfactory gap filler. The primary mechanical stability of the osteotomy site in OW-HTO is essential for early weight bearing after surgery. Therefore, we introduce the combination of a cylindrical autologous bone grafting technique and a metallic block insertion for faster bone union and better primary stability of the site in OW-HTO. We expect that the described procedure will enable early postoperative weight bearing and, thereby, allow an early return to normal function.