Bone Incorporation of Silicate-Substituted Calcium Phosphate in 2-Stage Revision Anterior Cruciate Ligament Reconstruction: A Histologic and Radiographic Study

Interference Screw versus Cement Fixation in Anterior Cruciate Ligament Soft Tissue Grafts: A Biomechanical Study

Shortcomings of fixation have been reported as a source of graft failure in anterior cruciate ligament (ACL) reconstruction. While interference screws have long been used as fixation devices for ACL reconstruction, they are not without complications. Previous studies have highlighted the use of bone void filler as a fixation method; however, no biomechanical comparisons using soft tissue grafts with interference screws exist to our knowledge. The purpose of this study is to evaluate the fixation strength of a calcium phosphate cement bone void filler compared with screw fixation in an ACL reconstruction bone replica model with human soft tissue grafts. In total, 10 ACL grafts were constructed using semitendinosus and gracilis tendons harvested from 10 donors. Grafts were affixed with either an 8-10 mm × 23 mm polyether ether ketone interference screw (n = 5) or with approximately 8 mL of calcium phosphate cement (n = 5) into open cell polyurethane blocks. Graft constructs were tested to failure in cyclic loading under displacement control at a rate of 1 mm per second. When compared with screw construct, the cement construct showed a 978% higher load at yield, 228% higher load at failure, 181% higher displacement at yield, 233% higher work at failure, and a 545% higher stiffness. Normalized data for the screw constructs relative to the cement constructs from the same donor showed 14 ± 11% load at yield, 54 ± 38% load at failure, and 172 ± 14% graft elongation. The results of this study indicate that cement fixation of ACL grafts may result in a stronger construct compared with the current standard of fixation with interference screws. This method could potentially reduce the incidence of complications associated with interface screw placement such as bone tunnel widening, screw migration, and screw breakage.

Management of anterior cruciate ligament revision in adults: the 2022 ESSKA consensus: part II-surgical strategy

PURPOSE

The aim of this ESSKA consensus is to give recommendations based on scientific evidence and expert opinion to improve the diagnosis, preoperative planning, indication and surgical strategy in Anterior Cruciate Ligament revision.

METHODS

Part 2, presented herein, followed exactly the same methodology as Part 1: the so-called ESSKA formal consensus derived from the Delphi method. Eighteen questions were ultimately asked. The quality of the answers received the following grades of recommendation: Grade A (high level scientific support), Grade B (scientific presumption), Grade C (low level scientific support) or Grade D (expert opinion). All answers were scored from 1 to 9 by the raters. Once a general consensus had been reached between the steering and rating groups, the question-answer sets were submitted to the peer-review group. A final combined meeting of all the members of the consensus was then held to ratify the document.

RESULTS

The review of the literature revealed a rather low scientific quality of studies examining the surgical strategy in cases of ACL reconstruction failure. Of the 18 questions, only 1 received a Grade A rating; 5, a Grade B rating; and 9, grades of C or D. The three remaining complex questions received further evaluations for each portion of the question and were looked at in more detail for the following grades: B and D; A, C and D; or A, B, C and D. The mean rating of all questions by the rating group was 8.0 + - 1.1. The questions and recommendations are listed in the article.

CONCLUSION

ACL revision surgery, especially the surgical strategy, is a widely debated subject with many different opinions and techniques. The literature reveals a poor level of standardization. Therefore, this international European consensus project is of great importance and clinical relevance for guiding the management of ACL revision in adults.

LEVEL OF EVIDENCE

Level II.

Management of Bone Loss and Tunnel Widening in Revision ACL Reconstruction

➤ Both mechanical and biological factors can contribute to bone loss and tunnel widening following primary anterior cruciate ligament (ACL) reconstruction.➤ Revision ACL surgery success is dependent on graft position, fixation, and biological incorporation.➤ Both 1-stage and 2-stage revision ACL reconstructions can be successful in correctly indicated patients.➤ Potential future solutions may involve the incorporation of biological agents to enhance revision ACL surgery, including the use of bone marrow aspirate concentrate, platelet-rich plasma, and bone morphogenetic protein-2.

Comparison of Low and High Temperature Sintering for Processing of Bovine Bone as Block Grafts for Oral Use: A Biological and Mechanical In Vitro Study

Large oral bone defects require grafting of bone blocks rather than granules to give physically robust, biocompatible and osteoconductive regeneration. Bovine bone is widely accepted as a source of clinically appropriate xenograft material. However, the manufacturing process often results in both reduced mechanical strength and biological compatibility. The aim of this study was to assess bovine bone blocks at different sintering temperatures and measure the effects on mechanical properties and biocompatibility. Bone blocks were divided into four groups; Group 1: Control (Untreated); Group 2: Initial boil for 6 h; Group 3: Boil 6 h followed by sintering at 550 °C for 6 h; Group 4: Boil 6 h followed by sintering at 1100 °C for 6 h. Samples were assessed for their purity, crystallinity, mechanical strength, surface morphology, chemical composition, biocompatibility and clinical handling properties. Statistical analysis was performed using one-way ANOVA and post-hoc Tukey's tests for normally distributed and Friedman test for abnormally distributed quantitative data from compression tests and PrestoBlue™ metabolic activity tests. The threshold for statistical significance was set at p < 0.05. The results showed that higher temperature sintering (Group 4) removed all organic material (0.02% organic components and 0.02% residual organic components remained) and increased crystallinity (95.33%) compared to Groups 1-3. All test groups (Group 2-4) showed decreased mechanical strength (MPa: 4.21 ± 1.97, 3.07 ± 1.21, 5.14 ± 1.86, respectively) compared with raw bone (Group 1) (MPa: 23.22 ± 5.24, p <0.05), with micro-cracks seen under SEM in Groups 3 and 4. Group 4 had the highest biocompatibility (p < 0.05) with osteoblasts as compared to Group 3 at all time points in vitro. Clinical handling tests indicated that Group 4 samples could better withstand drilling and screw placement but still demonstrated brittleness compared to Group 1. Hence, bovine bone blocks sintered at 1100 °C for 6 h resulted in highly pure bone with acceptable mechanical strength and clinical handling, suggesting it is a viable option as a block grafting material.

Tunnel Management in Revision Anterior Cruciate Ligament Reconstruction: Current Concepts

Bone tunnel-related complications are frequently encountered during revision anterior cruciate ligament reconstruction (ACLR). Issues with tunnel positioning, enlargement, containment, and hardware interference may complicate surgery and compromise outcomes. As a result, several strategies have emerged to address these issues and optimize results. However, a systematic, unified approach to tunnel pathology in revision ACLR is lacking. The purpose of this review is to highlight the current state of the literature on bone tunnel complications and, although extensive literature on the subject is lacking, present an updated approach to the evaluation and management of tunnel-related issues in revision ACLR.

Arthroscopic Revision of Attenuated Anterior Cruciate Ligament Graft With Enlarged Bone Tunnels Using Injectable Bone Graft Substitute

Revision anterior cruciate ligament (ACL) reconstruction is a technically demanding procedure, and the surgeon should be prepared to address bone tunnel osteolysis, concurrent meniscal, ligamentous, or cartilage lesions, and limb malalignment. ACL revision can typically be done in one procedure, but it may need to be staged if there is poor previous tunnel positioning or excessive tunnel osteolysis. Bone grafting of the tunnels can be accomplished in several ways, including autograft, allograft, or bone substitutes. Currently, no consensus is available regarding the optimal choice of bone graft material for bone tunnel augmentation in revision ACL reconstruction. Bone graft substitute for tunnel augmentation has been showed to have good histologic, radiographic, and intraoperative integration, comparable to that of autologous bone. In this Technical Note, the technical details of arthroscopic treatment of attenuated anterior cruciate ligament graft with enlarged bone tunnels are described. The tunnels are debrided arthroscopically and filled up with PRO-DENSE injectable regenerative graft.

Allograft Bone Dowels Show Better Incorporation in Femoral Versus Tibial Tunnels in 2-Stage Revision Anterior Cruciate Ligament Reconstruction: A Computed Tomography-Based Analysis

PURPOSE

The purpose of this study was to quantitatively evaluate the radiographic outcomes of allograft dowels used in 2-stage revision anterior cruciate ligament reconstruction (ACLR) and to compare the incorporation rates of dowels placed in tibial and femoral tunnels.

METHODS

Prospective review of patients who underwent 2-stage revision ACLR with allograft bone dowels. Inclusion criteria were tibial/femoral tunnel diameter of ≥14 mm on preoperative computed tomography (CT) or overlapping of prior tunnels with planned tunnels. Second-stage timing was determined based on qualitative dowel integration on CT obtained at ∼3 months after the first stage. Quantitative analysis of incorporation rates was performed with the union ratio (UR) and occupying ratio (OR) on postoperative CT scans.

RESULTS

Twenty-one patients, with a mean (SD) age of 32.1 (11.4; range, 18-50) years, were included. Second-stage procedures were performed at a mean (SD) of 6.5 (2.1; range, 2.4-11.5) months after first-stage revision. All dowels showed no signs of degradation at the host bone/graft junction at the second-stage procedure. The mean (SD) diameter of the dowels placed in tibial tunnels was greater than those placed in femoral tunnels (16.1 [2.3] mm vs 12.4 [1.6] mm; P < .05). CT was obtained at a mean (SD) of 121 (28; range, 59-192) days after the first-stage surgery. There was no difference between the OR of femoral and tibial tunnels (mean [SD], 87.6% [4.8%] vs 85.7% [10.1%]; P = .484), but the UR was significantly higher in femoral tunnels (mean [SD], 83% [6.2%] vs 74% [10.5%], P = .005). The intraclass correlation coefficients of OR and UR measurements indicated good reliability.

CONCLUSIONS

Allograft bone dowels are a viable graft choice to replenish bone stock in the setting of a staged revision ACL reconstruction. Allograft dowels placed in femoral tunnels had a higher healing union ratio than tibial tunnel allografts and no evidence of degradation at the bone/graft junction, with no difference seen in occupying ratio.

LEVEL OF EVIDENCE

Level IV, case series.

Economic Reliable Technique for Tunnel Grafting Using Iliac Crest Bone Graft in Two-Staged Revision Anterior Cruciate Ligament Surgery

Revision anterior cruciate ligament surgery is a technically demanding procedure. Mal-positioned tunnels together with bone loss and its management are some of the difficulties and challenges faced. Two-staged procedures have successfully been used to tackle those challenges. We present a technique that is safe, reliable, reproducible, and economic in the management of bone defects faced in anterior cruciate ligament revision surgery by using iliac crest bone graft. Preoperative assessment of tunnel position and size is done by computed tomography. Tri-cortical iliac crest bone graft is harvested through a trap door. It is then shaped to fit the tunnels to be filled. It is tapered at the advancing end to facilitate introduction. Mounted on a passing pin and a drill bit, the graft is arthroscopically introduced into the femoral and tibial tunnels. The second stage is performed after the graft has incorporated, as seen on postoperative computed tomography, done at approximately 3 months after the first stage. Iliac crest provides a natural abundant reservoir for bone graft and has all the advantages of being an autograft. With good meticulous technique, complications can be avoided with less donor-site morbidity. This technique is safe, reliable, and reproducible. It provides an ample amount of graft and harvest does not rely on implants; hence, it is economic.

Bioinorganic supplementation of calcium phosphate-based bone substitutes to improve in vivo performance: a systematic review and meta-analysis of animal studies

Supplementation of CaP-based bone graft substitutes with bioinorganics such as strontium, zinc or silicon is an interesting approach to increase the biological performance in terms of bone regenerative potential of calcium phosphate (CaP)-based bone substitutes. However, the in vivo efficacy of this approach has not been systematically analyzed, yet. Consequently, we performed a systematic review using the available literature regarding the effect of bioinorganic supplementation in CaP-based biomaterials on new bone formation and material degradation in preclinical animal bone defect models and studied this effect quantitatively by performing a meta-analysis. Additional subgroup analyses were used to study the effect of different bioinorganics, animal model, or phase category of CaP-based biomaterial on bone formation or material degradation. Results show that bioinorganic supplementation increases new bone formation (standardized mean difference [SMD]: 1.43 SD, confidence interval [CI]: 1.13-1.73). Additional subgroup analysis showed that strontium, magnesium and silica significantly enhanced bone formation, while zinc did not have any effect. This effect of bioinorganic supplementation on new bone formation was stronger for DCPD or β-TCP and biphasic CaPs than for HA or α-TCP (p < 0.001). In general, material degradation was slightly hindered by bioinorganic supplementation (mean difference [MD]: 0.84%, CI: 0.01-1.66), with the exception of strontium that significantly enhanced degradation. Overall, bioinorganic supplementation represents an effective approach to enhance the biological performance of CaP-based bone substitutes.

Two-Stage Revision Anterior Cruciate Ligament Reconstruction: A Systematic Review of Bone Graft Options for Tunnel Augmentation

BACKGROUND

No consensus is available regarding the optimal choice of bone graft material for bone tunnel augmentation in revision anterior cruciate ligament (ACL) surgery.

PURPOSE

To compare the outcomes of different bone graft materials for staged revision ACL reconstruction.

STUDY DESIGN

Systematic review.

METHODS

A systematic review using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines was performed. PubMed, EMBASE, and the Cochrane Library were queried through use of the terms anterior cruciate ligament and revision to identify all studies reporting outcomes of bone tunnel grafting in 2-stage revision ACL reconstruction. Data extracted included indications for 2-stage surgery, surgical technique, graft material, time between surgeries, rehabilitation protocols, physical examination findings, patient-reported outcomes, and radiographic and histologic findings.

RESULTS

The analysis included 7 studies with a total of 234 patients. The primary outcome in 2 studies was graft incorporation (mean follow-up, 8.8 months), whereas the other 5 studies reported clinical outcomes with follow-up mean ± SD of 4.2 ± 2.1 years. The indication for bone grafting and between-stage protocol varied among studies. Autograft was used in 4 studies: iliac crest bone autograft (ICBG, n = 3) and tibial bone autograft (TBA, n = 1). In 2 studies, the authors investigated the outcomes of allograft: allograft bone matrix (ABM) and allograft bone chips (AC). Finally, 1 study compared ICBG to a synthetic bone substitute. Radiographic evaluation of bone graft integration after the first stage was reported in 4 studies, with an average duration of 4.9 months. In 4 studies, the authors reported the time interval between first and second surgeries, with an average of 6.1 months for ICBG compared with 8.7 months for allogenic and synthetic grafts. Revision ACL graft failure rates were reported by 5 studies, including 1 study with ABM (6.1%), 1 study with AC (8.3%), 1 study with TBA (0%), and 2 studies with ICBG (0% and 2%).

CONCLUSION

The indications for staged ACL reconstruction and the rehabilitation protocol between stages need to be clearly established. The available data indicate that autograft for bone tunnel grafting in 2-stage ACL revision may be associated with a lower risk of revision ACL reconstruction graft failure compared with allograft bone.

Cancellous allogenic and autologous bone grafting ensure comparable tunnel filling results in two-staged revision ACL surgery

OBJECTIVES

Patients with recurrent instability after anterior cruciate ligament (ACL) reconstruction often present with enlarged or misplaced tunnels and bone grafting is required prior to the actual revision reconstruction. Autologous bone grafting features limited quantity and donor site morbidity. These problems may be eliminated utilizing cancellous bone allografts, but their efficiency and reliability have not been investigated systematically. The aim of the present study was to compare tunnel filling rates attained by utilizing either allogenic or autologous cancellous bone grafts.

MATERIALS AND METHODS

A total of 103 consecutive patients were enrolled retrospectively. All patients suffered from recurrent instability and underwent either allogenic or autologous cancellous bone grafting. Computed tomography (CT) was carried out before and after the bone grafting procedure. Based on preoperative CT scans, positioning and maximum diameter of the femoral and tibial tunnels were determined. Tunnel filling rates were calculated as a ratio of pre- and postoperative tunnel volumes. Primary outcome was the tibial tunnel filling rate. Femoral filling rates and density of the grafted bone were assessed secondarily.

RESULTS

Preoperative CT scans revealed no significant differences between the two groups regarding distribution of misplacement and widening of the femoral or tibial tunnel. Postoperative CT scans were conducted after an interval of 5.2 months. Tunnel filling rates of 74.5% (± 14.3) femoral and 85.3% (± 10.3) tibial were achieved in the allogenic compared to 74.3% (± 15.9) femoral and 84.9% (± 9.4) tibial in the autologous group. With p values of 0.85 at the femur and 0.83 at the tibia, there were no significant differences between the groups. The density of the grafted bone revealed significantly higher values in the allogenic group.

CONCLUSIONS

Utilizing cancellous bone allografts in two-staged revision ACL surgery provides for sufficient and reproducible filling of enlarged or misplaced tunnels. The filling rates are comparable to those achieved with autologous bone grafting. Advantages of allografts are the unrestricted quantity and the absence of any harvesting procedure.

Autologous Bone Graft Versus Silicate-Substituted Calcium Phosphate in the Treatment of Tunnel Defects in 2-Stage Revision Anterior Cruciate Ligament Reconstruction: A Prospective, Randomized Controlled Study With a Minimum Follow-up of 2 Years

PURPOSE

To compare and evaluate knee laxity and functional outcomes between autologous bone graft and silicate-substituted calcium phosphate (Si-CaP) in the treatment of tunnel defects in 2-stage revision anterior cruciate ligament reconstruction (ACLR).

METHODS

This prospective, randomized controlled trial was conducted between 2012 and 2015 with a total of 40 patients who underwent 2-stage revision ACLR. The tunnels were filled with autologous iliac crest cancellous bone graft in 20 patients (control group) and with Si-CaP in the other 20 patients (intervention group). After a minimum follow-up period of 2 years, functional outcomes were assessed by KT-1000 arthrometry (side-to-side [STS] difference), the Tegner score, the Lysholm score, and the International Knee Documentation Committee score.

RESULTS

A total of 37 patients (follow-up rate, 92.5%) with an average age of 31 years were followed up for 3.4 years (range, 2.2-5.5 years). The KT-1000 measurement did not show any STS difference between the bone graft group (0.9 ± 1.5 mm) and the Si-CaP group (0.7 ± 2.0 mm) (P = .731). One patient in the intervention group (5%) had an STS difference greater than 5 mm. Both groups showed significant improvements in the Tegner score, Lysholm score, and International Knee Documentation Committee score from preoperative assessment to final follow-up (P ≤ .002), without any difference between the 2 groups (P ≥ .396). Complications requiring revision occurred in 4 control patients (22%) and in 2 patients in the intervention group (11%) (P = .660). No complications in relation to Si-CaP were observed.

CONCLUSIONS

Equivalent knee laxity and clinical function outcomes were noted 3 years after surgery in both groups of patients. Si-CaP bone substitute is therefore a safe alternative to autologous bone graft for 2-stage ACLR.

LEVEL OF EVIDENCE

Level I, prospective, randomized controlled clinical trial.

Editorial Commentary: Bone Tunnel Grafting for Two-Stage Anterior Cruciate Ligament Revision and the Meaning of Life for an Arthroscopic Surgeon

Accurate bone tunnel filling in a 2-staged anterior cruciate ligament revision is indubitably fundamental for a successful outcome. Bone autograft is commonly employed and it is usually harvested from the iliac crest: this requires longer surgical time, and donor-site morbidity following bone harvest is a well-known problem. Therefore, strategies to minimize or abolish it have been attempted: the use of allografts may seem promising, but their use is associated with high costs and strict regulatory limitations. Bony substitutes instead represent a new and potentially effective solution: they could help surgeons to fill bone tunnels in an easier and faster way that elicits satisfactory lamellar bone formation within the tunnels, and their use is associated with fewer postoperative complications, such as pain and local hematoma. Evidence from literature suggests that this approach could provide significant advantages over traditional autograft harvesting, with comparable outcomes in terms of bone formation and integration, allowing a correct tunnel placement during revision surgery.

Two-Stage Revision Anterior Cruciate Ligament Reconstruction Using Silicate-Substituted Calcium Phosphate

Revision surgery after failed primary anterior cruciate ligament reconstruction is technically demanding. In cases in which the tunnels of the primary anterior cruciate ligament reconstruction are widened to greater than 10 mm and/or are incorrectly positioned, a 2-stage procedure enables restoration of bone stock and thus free placement of the tunnels during the revision. The gold standard for tunnel augmentation is an autologous iliac crest cancellous bone graft. However, harvesting the graft is associated with high morbidity. This article describes an alternative method for managing bone deficiencies using the synthetic bone graft substitute silicate-substituted calcium phosphate.

Two-stage revision anterior cruciate ligament reconstruction

With the rising number of anterior cruciate ligament (ACL) reconstructions, revision ACL reconstructions are becoming increasingly common. A revision procedure may be performed to improved knee function, correct instability, and facilitate a return to normal activities. When performing a revision reconstruction, the surgeon decides between a single-stage or a two-stage revision. Two-stage revisions are rarely performed, but are particularly useful when addressing substantial tunnel-widening, active infection, and concomitant knee pathology (e.g., malalignment, other ligamentous injuries, meniscal or chondral lesions). Among these potential scenarios requiring a two-stage revision, tunnel-widening is the most common cause; the first stage involves graft removal, tunnel curettage, and bone grafting, followed by revision ACL reconstruction in the second stage. The purpose of this article is to review the preoperative planning, surgical considerations, rehabilitation, and outcomes of two-stage revision ACL reconstructions and summarize the recent literature outlining treatment results.

Supercritical Carbon Dioxide-Sterilized Bone Allograft in the Treatment of Tunnel Defects in 2-Stage Revision Anterior Cruciate Ligament Reconstruction: A Histologic Evaluation

PURPOSE

To examine the histologic properties of supercritical carbon dioxide (sCO₂)-sterilized bone allograft for tunnel grafting and determine in vivo graft quality, as well as graft incorporation and remodeling, in 2-stage revision anterior cruciate ligament (ACL) surgery.

METHODS

Histologic evaluation was performed in 12 subjects undergoing 2-stage revision ACL reconstruction. In the first stage, the femoral and tibial tunnels were debrided, tunnel dimensions were measured, and tunnels were grafted with sCO₂-sterilized bone allograft. In the second stage, revision ACL reconstruction was performed and bone biopsy specimens were taken from the tibia. Tissue, bone, and graft volumes were measured, and histomorphometric analysis was performed.

RESULTS

The mean time between the 2 stages was 8.8 months (range, 5.6-21.3 months). In the second stage, bone graft material was easily identified by its necrotic appearance comprising mature lamellar bone devoid of osteocyte nuclei within osteocyte lacunae. In all tissue samples, host-bone apposition of predominantly mature lamellar bone was noted on the surface of graft fragments in keeping with "creeping substitution." In several regions in 3 cases, osteoblastic and osteoclastic activity was evident in keeping with ongoing creeping substitution and remodeling. The mean bone volume over tissue volume was 68% (range, 33%-92%), and the mean graft volume over bone volume was 41% (range, 19%-70%). The mean graft volume (8 cases) harvested at less than 7 months (44%; 95% confidence interval, 31.4%-56.8%) was not significantly different than the mean graft volume (4 cases) harvested at greater than 10 months (34%; 95% confidence interval, 14.3%-54.2%; P = .214).

CONCLUSIONS

The sCO₂-sterilized bone allograft showed graft incorporation and remodeling through creeping substitution.

CLINICAL RELEVANCE

The initial bone apposition and graft fragment bridging appear to provide a strong environment for ACL graft fixation resulting in technically successful 2-stage revision ACL reconstruction.