A clinical review of bioabsorbable interference screws and their adverse effects in anterior cruciate ligament reconstruction surgery

Talar and fibular histiocytic-driven massive expansile osteolysis following polyetheretherketone interference screw implantation: a case report

Numerous interference screws of different compositions exist including titanium screws, bioabsorbable screws, and polyetheretherketone (PEEK) screws. PEEK-based implants are frequently used in orthopaedic surgery due to their biocompatibility, similar elastic modulus to cortical bone, and purported negligible risk of osteolysis compared with bioabsorbable screws. In this case report, we present the case of a 48-year-old healthy female who experienced a massive osteolytic reaction in the talus and fibula after 11 weeks following implantation of PEEK-based interference screws during lateral ankle ligament reconstruction. The patient subsequently underwent removal of the PEEK screws and specimens were sent for microbiological and histopathological analysis. The specimens report demonstrated fibrotic tenosynovial soft tissue with patchy chronic inflammation, oedematous reactive changes, and histiocytic reaction, with no evidence of any significant acute inflammation. The patient recovered well and was asymptomatic at 6 months postoperatively. To our knowledge, this is the first case report of a massive osteolytic reaction to PEEK-based interference screws.

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.

Angiogenic Modification of Microfibrous Polycaprolactone by pCMV-VEGF165 Plasmid Promotes Local Vascular Growth after Implantation in Rats

Insufficient vascular growth in the area of artificial-material implantation contributes to ischemia, fibrosis, the development of bacterial infections, and tissue necrosis around the graft. The purpose of this study was to evaluate angiogenesis after implantation of polycaprolactone microfiber scaffolds modified by a pCMV-VEGF165-plasmid in rats. Influence of vascularization on scaffold degradation was also examined. We investigated flat microfibrous scaffolds obtained by electrospinning polycaprolactone with incorporation of the pCMV-VEGF-165 plasmid into the microfibers at concentrations of 0.005 ng of plasmid per 1 mg of polycaprolactone (0.005 ng/mg) (LCGroup) and 0.05 ng/mg (HCGroup). The samples were subcutaneously implanted in the interscapular area of rats. On days 7, 16, 33, 46, and 64, the scaffolds were removed, and a histological study with a morphometric evaluation of the density and diameter of the vessels and microfiber diameter was performed. The number of vessels was increased in all groups, as well as the resorption of the scaffold. On day 33, the vascular density in the HCGroup was 42% higher compared to the control group (p = 0.0344). The dose-dependent effect of the pCMV-VEGF165-plasmid was confirmed by enhanced angiogenesis in the HCGroup compared to the LCGroup on day 33 (p-value = 0.0259). We did not find a statistically significant correlation between scaffold degradation rate and vessel growth (the Pearson correlation coefficient was ρ = 0.20, p-value = 0.6134). Functionalization of polycaprolactone by incorporation of the pCMV-VEGF165 plasmid provided improved vascularization within 33 days after implantation, however, vessel growth did not seem to correlate with scaffold degradation rate.

Evaluation of the degradation of two bioabsorbable interference screws: an in-vivo study in sheep

PURPOSE

To evaluate in-vivo degradation of two bioabsorbable interference screws.

METHODS

Twenty-two crossbred Santa Inês ewes were used. A poly-DL-lactide (PDLLA) screw (70%/30%) was inserted in the right pelvic limb, and a PDLLA screw (70%) + β-tri-calcium phosphate (β-TCP) (30%) in the left pelvic limb. Animals were euthanized at one, four, seven and a half and 18 months after surgery. Plain radiography, computed tomography (CT), microCT, and histological analysis were accomplished.

RESULTS

PDLLA screw was hypodense at all evaluation moments, but with progressive density increase along the central axis, whereas PDLLA/β-TCP was initially hyperdense and progressively lost this characteristic. No adverse reactions were observed on histological evaluation.

CONCLUSIONS

The inclusion of β-TCP favors screw degradation since the PDLLA/β-TCP screws evidenced a more intense degradation process than the PDLLA screws at the last evaluation. PDLLA screws showed higher bone production, evident around the screw thread, inside the lateral perforations, and in the central canal, whereas the PDLLA/β-TCP screws presented less bone tissue at the implantation site.

Bone density may affect primary stability of anterior cruciate ligament reconstruction when organic core bone plug fixation technique used

Purpose

Core Bone Plug Fixation (CBPF) technique is an implant-less methodology for ACL reconstruction. This study investigates the effect of bone density on CBPF stability to identify the bone quality that is likely to benefit from this technique.

Methods

Artificial blocks with 160 (Group 1), 240 (Group 2), and 320 (Group 3) kg/m³ densities were used to simulate human bone with diverse qualities. These groups are representative of the elderly, middle age and young people, respectively. A tunnel was made in each test sample using a cannulated drill bit which enabled harvesting the core bone plug intact. Fresh animal tendon grafts were prepared and passed through the tunnel, so the core bone was pushed in to secure the tendon. The fixation stability was tested by applying a cyclic load following by a pullout load until the failure occurred. The selected group was compared with interference screw fixation technique as a gold standard method in ACL reconstruction.

Results

The Group 2 stiffness and yield strength were significantly larger than Group 1. The graft slippage of Group 1 was significantly less than Group 3. The ultimate strengths were 310 N and 363 N, in Groups 2 and 3, significantly larger than that of Group 1. The ultimate strength in fixation by interference screw was 693.18 N, significantly larger than the bone plug method.

Conclusions

The stability of CBPF was greatly affected by bone density. This technique is more suitable for young and middle-aged people. With further improvements, the CBPF might be an alternative ACL reconstruction technique for patients with good bone quality.

Clinical relevance

The CBPF technique offers an implant-less organic ACL reconstruction technique with numerous advantages and likely would speed up the healing process by using the patient’s own bones and tissues rather than any non-biologic fixations.

Evaluation of the in vitro cytotoxicity and modulation of the inflammatory response by the bioresorbable polymers poly(D,L-lactide-co-glycolide) and poly(L-lactide-co-glycolide)

Bioresorbable polymers composed of poly(D,L-lactide-co-glycolide) (PDLLGA) and poly(L-lactide-co-glycolide) (PLLGA) have become increasingly popular for the preparation of bone substitute constructs. However, there are reports of a delayed inflammatory reaction occurring months or years after implantation. Due to the long polymer degradation times, in vitro tests carried out at physiological temperature, 37°C, tend to assess only the short-term biocompatibility of these materials. The aim of this work is to develop an in vitro protocol that can be used to assess the long-term cytotoxicity of bioresorbable polymers in a time efficient manner. This study used a previously developed and validated accelerated degradation protocol to obtain samples of PDLLGA and PLLGA at increasing levels of degradation. Samples were then applied to standard ISO 10993-5 direct contact cytotoxicity testing and it was found that PDLLGA samples showed increasing levels of cytotoxicity at the later stages of degradation, with PLLGA samples demonstrating significantly less cytotoxic behaviour. Following concern that accumulation of acidic degradation products in a closed multi-well culture environment could overestimate cytotoxicity, we developed and validated a new dynamic flow culture methodology, for testing the cytotoxicity of these degradable materials, by adapting a commercial "organ on a chip" flow culture system, Quasi Vivo®. In addition to cytotoxicity testing, we have carried out profiling of inflammatory cytokines released by cells in response to degraded PDLLGA and PLLGA, and have suggested mechanism by which lactide-based bioresorbable materials could modulate the inflammatory response through the G-protein coupled receptor (GPCR), hydroxycarboxylic acid receptor 1 (HCA₁). STATEMENT OF SIGNIFICANCE: Bioresorbable materials naturally disintegrate over time when implanted into the body. They are often used to make screws and clips for repair of broken bones. Unfortunately, some patients can react badly to the material, resulting in painful inflammation. Biomaterials scientists are interested in developing materials that are more compatible with the body. However, it is very difficult to predict the long-term compatibility of bioresorbable materials in the lab. In our study, we have developed a method that will allow us to study the effects of the materials as they continue to break down. This will help us understand why the materials may cause inflammation, and will support research into the development of new and improved materials for bone repair.

Comparison of Bioabsorbable and Metallic Interference Screws for Graft Fixation During ACL Reconstruction: A Meta-analysis of Randomized Controlled Trials

Background

Bioabsorbable interference screws and metallic interference screws are both widely used for graft fixation, but it remains unclear which screw type is superior.

Purpose

To compare clinical outcomes and complications between bioabsorbable and metallic interference screws for anterior cruciate ligament reconstruction (ACLR).

Study Design

Systematic review; Level of evidence, 1.

Methods

The literature was searched for relevant randomized controlled trials published between 1966 and 2020. Two investigators independently assessed risk of bias in the included studies, and data were pooled to calculate mean differences (MDs) for continuous outcomes and risk ratios (RRs) for dichotomous outcomes, together with 95% CIs. Meta-analysis was performed using a random- or fixed-effects model, depending on the heterogeneity in the data.

Results

Included were 14 randomized controlled trials involving 1032 patients who underwent ACLR: 528 patients with bioabsorbable screws and 504 patients with metallic screws. The 2 groups did not differ significantly in International Knee Documentation Committee score (RR, 1.04; 95% CI, 0.97 to 1.11), Lysholm score (MD, 0.59; 95% CI, -0.46 to 1.63), range of motion deficit (RR, 0.95; 95% CI, 0.67 to 1.34), positive pivot-shift test (RR, 0.87; 95% CI, 0.61 to 1.24), positive Lachman test (RR, 0.82; 95% CI, 0.48 to 1.39), or KT-1000 arthrometer value (MD, 0.01; 95% CI, -0.16 to 0.18). However, bioabsorbable screws were associated with a significantly higher risk of complications (RR, 1.70; 95% CI, 1.16 to 2.50), such as graft rupture, joint effusion, and infection.

Conclusion

The results of this review showed that there was no difference between metallic and bioabsorbable screws for ACLR in terms of subjective knee function or knee laxity, but metallic interference screws had fewer complications.

Stacked Biocomposite Screws in a Single-Stage Revision Anterior Cruciate Ligament Reconstruction Has Acceptable Fixation Strength in a Porcine Cadaveric Model

BACKGROUND

Stacked screws is a commonly used technique in single-stage revision anterior cruciate ligament (ACL) reconstruction in the setting of bone loss, but there are limited data to support its use.

HYPOTHESIS

Two configurations of a biocomposite stacked screws construct have similar fixation strength and linear stiffness as a primary ACL reconstruction construct in a biomechanical model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 30 porcine legs were divided into 3 groups. Group 1 underwent primary ACL reconstruction with a patellar tendon graft fixed into the femur, with an 8-mm biocomposite interference screw of beta-tricalcium phosphate and poly lactide-co-glycolide. For a revision ACL reconstruction model, groups 2 and 3 had bone tunnels created and subsequently filled with 12-mm biocomposite screws. New bone tunnels were drilled through the filler screw and the surrounding bone, and the patellar bone plug was inserted. Group 2 was fixed with 8-mm biocomposite screws on the side of the graft opposite the filler screw, while group 3 had the interference screw interposed between the graft and the filler screw. The construct was loaded at 1.5 mm/s in line with the tunnel until failure. Load to failure, linear stiffness, and mode of failure were recorded.

RESULTS

The mean pullout strength for groups 1, 2, and 3 was 626 ± 145 N, 653 ± 152 N, and 720 ± 125 N, respectively (P = .328). The mean linear stiffness of the construct in groups 1, 2, and 3 was 71.4 ± 9.9 N/mm, 84.1 ± 11.1 N/mm, and 82.0 ± 10.8 N/mm, respectively. Group 2 was significantly stiffer than group 1 (P = .037).

CONCLUSION

Two configurations of a biocomposite stacked screws construct for a single-stage revision ACL reconstruction in the setting of bone loss show a similar fixation strength and linear stiffness to a primary ACL reconstruction at time zero in a porcine model.

CLINICAL RELEVANCE

In the setting of bone loss from tunnel malpositioning, a single-stage revision ACL reconstruction using a stacked screws construct may provide adequate fixation strength and linear stiffness.

A comprehensive scoping review of tibial cysts after anterior cruciate ligament reconstruction

Purpose

The purpose of this study was to perform a scoping review of published literature reporting on surgical management of tibial cysts which developed after ACLR.

Methods

A scoping review was conducted following the Arksey and O’Malley framework for scoping studies and Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) extension for scoping reviews (PRISMA-ScR) guidelines. A search strategy using the terms [“Tibial Cyst” AND “ACL”], [“Pretibial Cyst” AND “ACL”] was applied to the PUBMED database.

Results

Thirty-seven studies published between 1990 and 2019 were a part of this scoping review. Non-absorbable implants for tibial graft fixation were used in 10 studies (comprising a total 21 patients), while bio-absorbable implants were used in 27 studies (comprising a total 115 patients). Incidence of tibial cyst was reported in 3 studies (434 primary ACLRs) from whom 3.9% (n = 17) developed tibial cyst. Tibial cyst development in relation to use of bio-absorbable screws for tibial ACL graft fixation was reported in 16 studies (42.1%). Use of bio-absorbable screws with another factor was found to be related to tibial cyst development in another 1 study (2.6%). Most common symptoms were presence of mass or swelling, pain, tenderness, drainage, instability and effusion.

Conclusion

This scoping review demonstrated that tibial cysts is more frequently related to bioabsorbable screws, however it can also occur due to other causes. Current literature on tibial cyst after ACLR is of low-quality evidence. Future research is required to better understand aetiology, risk factors for cyst formation and the best possible mode of management.

Level of evidence

IV

Supplementary Information

The online version contains supplementary material available at 10.1186/s40634-021-00356-9.

Computed Tomography Imaging of BioComposite Interference Screw After ACL Reconstruction With Bone-Patellar Tendon-Bone Graft

Background:

Bioabsorbable interference screws tend to have high resorption rates after anterior cruciate ligament (ACL) reconstruction; however, no studies have examined screws composed of 30% biphasic calcium phosphate and 70% poly-d-lactide (30% BCP/70% PLDLA).

Purpose:

To evaluate femoral and tibial tunnel widening and resorption of 30% BCP/70% PLDLA interference screws and replacement with bone at 2 to 5 years after ACL reconstruction using bone–patellar tendon–bone (BTB) autograft.

Study Design:

Case series; Level of evidence, 4.

Methods:

Included were 20 patients who had undergone ACL reconstruction using BTB autograft and were reevaluated 2 to 5 years after surgery using computed tomography scans. Tunnel measurements were obtained from computed tomography scans in the sagittal and coronal planes and were compared with known tunnel measurements based on operative reports. These images and measurements were used to assess tunnel widening, resorption of the 30% BCP/70% PLDLA screw, its replacement with bone, and possible cyst formation. Paired t tests were used to compare initial and final femoral and tibial tunnel measurements.

Results:

The cross-sectional area of the femoral tunnel decreased at the aperture (P = .03), middle (P = .0002), and exit (P < .0001) of the tunnel compared with the initial femoral tunnel size, and the tibial tunnel cross-sectional area decreased at the aperture (P < .0001) and exit (P = .01) of the tunnel compared with the initial tibial tunnel size. Bone formation was observed in 100% of femoral tunnels and 94.7% of tibial tunnels. Screw resorption was 100% in the femur and 94.7% in the tibia at the final follow-up. Cysts were noted around the femoral tunnel in 2 patients (5.1%).

Conclusion:

The 30% BCP/70% PLDLA interference screws used for ACL reconstruction using BTB autograft had high rates of resorption and replacement with bone, and there were no increases in tunnel size at 2 to 5 years postoperatively. The authors observed a low rate of cyst formation and no other adverse events stemming from the use of this specific biointerference screw, suggesting that this type of screw is a reasonable option for graft fixation with minimal unfavorable events and a reliable resorption profile.

Effects of Two Melt Extrusion Based Additive Manufacturing Technologies and Common Sterilization Methods on the Properties of a Medical Grade PLGA Copolymer

Although bioabsorbable polymers have garnered increasing attention because of their potential in tissue engineering applications, to our knowledge there are only a few bioabsorbable 3D printed medical devices on the market thus far. In this study, we assessed the processability of medical grade Poly(lactic-co-glycolic) Acid (PLGA)85:15 via two additive manufacturing technologies: Fused Filament Fabrication (FFF) and Direct Pellet Printing (DPP) to highlight the least destructive technology towards PLGA. To quantify PLGA degradation, its molecular weight (gel permeation chromatography (GPC)) as well as its thermal properties (differential scanning calorimetry (DSC)) were evaluated at each processing step, including sterilization with conventional methods (ethylene oxide, gamma, and beta irradiation). Results show that 3D printing of PLGA on a DPP printer significantly decreased the number-average molecular weight (Mn) to the greatest extent (26% Mn loss, p < 0.0001) as it applies a longer residence time and higher shear stress compared to classic FFF (19% Mn loss, p < 0.0001). Among all sterilization methods tested, ethylene oxide seems to be the most appropriate, as it leads to no significant changes in PLGA properties. After sterilization, all samples were considered to be non-toxic, as cell viability was above 70% compared to the control, indicating that this manufacturing route could be used for the development of bioabsorbable medical devices. Based on our observations, we recommend using FFF printing and ethylene oxide sterilization to produce PLGA medical devices.

ACL reconstruction with adjustable-length loop cortical button fixation results in less tibial tunnel widening compared with interference screw fixation

PURPOSE

To compare tunnel widening and clinical outcome after anterior cruciate ligament reconstruction (ACLR) with interference screw fixation and all-inside reconstruction using button fixation.

METHODS

Tunnel widening was assessed using tunnel volume and diameter measurements on computed tomography (CT) scans after surgery and 6 months and 2 years later, and compared between the two groups. The clinical outcome was assessed after 2 years with instrumented tibial anteroposterior translation measurements, hop testing and International Knee Documentation Committee (IKDC), Lysholm and Tegner activity scores.

RESULTS

The study population at the final follow-up was 14 patients with screw fixation and 16 patients with button fixation. Tibial tunnels with screw fixation showed significantly larger increase in tunnel volume over time (P = 0.021) and larger tunnel diameters after 2 years in comparison with button fixation (P < 0.001). There were no significant differences in femoral tunnel volume changes over time or in tunnel diameters after 2 years. No significant differences were found in the clinical outcome scores.

CONCLUSIONS

All-inside ACLR using button fixation was associated with less tibial tunnel widening and smaller tunnels after 2 years in comparison with ACLR using screw fixation. The need for staged revision ACLRs may be greater with interference screws in comparison with button fixation at the tibial tunnel. The clinical outcomes in the two groups were comparable.

LEVEL OF EVIDENCE

II. RCT: Consort NCT01755819.

Femoral Interference Screw Fixation in ACL Reconstruction Using Bone-Patellar Tendon-Bone Grafts

» Anterior cruciate ligament (ACL) reconstruction is a commonly performed orthopaedic procedure with numerous reconstructive graft and fixation options. Interference screws have become one of the most commonly utilized methods of securing ACL grafts such as bone-patellar tendon-bone (BPTB) autografts. » The composition of interference screws has undergone substantial evolution over the past several decades, and numerous advantages and disadvantages are associated with each design. » The composition, geometry, and insertional torque of interference screws have important implications for screw biomechanics and may ultimately influence the strength, stability of graft fixation, and biologic healing in ACL reconstruction. » This article reviews the development and biomechanical properties of interference screws while examining outcomes, complications, and gaps in knowledge that are associated with the use of femoral interference screws during BPTB ACL reconstruction.

Long-term study on the osteogenetic capability and mechanical behavior of a new resorbable biocomposite anchor in a canine model

Background

Biodegradable suture anchors are commonly used for repairing torn rotator cuffs, but these biodegradable materials still suffer from low mechanical strength, poor osteointegration, and the generation of acidic degradation byproducts.

Method

The purpose of this study was to evaluate the long-term mechanical behavior and osteogenetic capabilities of a biocomposite anchor injection molded with 30% β-tricalcium phosphate microparticles blended with 70% poly (L-lactide-co-glycolide) (85/15). This study investigated in vitro degradation and in vivo bone formation in a canine model. The initial mechanical behavior, mechanical strength retention with degradation time, and degradation features were investigated.

Results

The results showed that the biocomposite anchor had sufficient initial mechanical stability confirmed by comparing the initial shear load on the anchor with the minimum shear load borne by an ankle fracture fixation screw, which is considered a worst-case implantation site for mechanical loading. The maximum shear load retention of the biocomposite anchor was 83% at 12 weeks, which is desirable, as it aligns with the rate of bone healing. The β-tricalcium phosphate fillers were evenly dispersed in the polymeric matrix and acted to slow the degradation rate and improve the mechanical strength of the anchor. The interface characteristics between the β-tricalcium phosphate particles and the polymeric matrix changed the degradation behavior of the biocomposite. Phosphate buffer saline was shown to diffuse through the interface into the biocomposite to inhibit the core accelerated degradation rate. In vivo, the addition of β-tricalcium phosphate induced new bone formation. The biocomposite material developed in this study demonstrated improved osteogenesis in comparison to a plain poly (L-lactide-co-glycolide) material. Neither anchor produced adverse tissue reactions, indicating that the biocomposite had favorable biocompatibility following long-term implantation.

Conclusion

In summary, the new biocomposite anchor presented in this study had favorable osteogenetic capability, mechanical property, and controlled degradation rate for bone fixation.

Translational potential of this article

The new biocomposite anchor had sufficient initial and long-term fixation stability and bone formation capability in the canine model. It is indicated that the new biocomposite anchor has a ​potential for orthopedic application.

Long-term radiographic appearance of a bioabsorbable biocomposite tibial tuberosity advancement cage implant

OBJECTIVE

To report the radiographic appearance of a bioabsorbable biocomposite tibial tuberosity advancement cage at least 1 year after implantation. Design Retrospective case series.

METHODS

Medical records (February 2014-March 2015) of dogs receiving a biocomposite tibial tuberosity advancement cage were reviewed. Cases were selected if they had undergone surgery at least 1 year before the selection, no additional surgeries were performed, and no known surgical site infection had occurred. Medical record information assessed included signalment, body weight (kg), affected stifle joint (left or right), date of original surgery and the size of biocomposite cage used (9 or 12 mm). Radiographs were evaluated by two blinded radiologists who calculated percentages of osteolucency present in five zones around the cage and assigned a numerical score based on these calculations. Variables were evaluated statistically for effect on lucency percentage and numerical score.

RESULTS

Fifty dogs were included. Zone 5 (caudoproximal area) was found to have the lowest lucency percentage and score and zone 3 (distal area) had the highest lucency percentage and score. Twelve-millimetre cages were significantly associated with a higher lucency numerical score than 9 mm cages.

CONCLUSION

A biocomposite tibial tuberosity advancement cage was found to have variable amounts of radiographically apparent osseous integration at least 1 year after implantation.

Editorial Commentary: Fill It up: The Fate of "Absorbable" Implants

Surgeons make conscious decisions daily regarding implants. But do they really know what happens in the body to "absorbable anchors?" How long does it take to resorb, and what fills the space left behind? Absorbable materials can be very different, and well-done studies are important to help us understand the process and to guide our decisions.

Delayed onset bioabsorbable screw reaction, intact screw extrusion and Pseudomonas aeruginosa tibial tunnel osteomyelitis years after arthroscopic anterior cruciate ligament reconstruction using hamstring graft

Postoperative reaction and infection after anterior cruciate ligament (ACL) reconstruction is a rare complication. We report two cases of bioabsorbable screw extrusion and Pseudomonas aeruginosa tibial tunnel infection in 17/18-year-old men, 2 and 4 years after ACL reconstruction, respectively. They underwent tibial tunnel debridement, removal of the still intact poly-L-D-lactic acid bioabsorbable screw and subsequent wound closure. Physical examination findings confirmed patency of the hamstring graft. Culture guided antibiotics were completed, and wounds healed unremarkably. Both returned to previous level of activity. Successful treatment is achieved through a logical sequence of management, as well as a multidisciplinary approach to prevent unnecessary secondary procedures and morbidity.

Bioabsorbable screws, whatever the composition, can result in symptomatic intra-osseous tibial tunnel cysts after ACL reconstruction

PURPOSE

To describe the clinical results of patients who underwent surgical treatment for a intra-osseous tibial tunnel cyst on a bioabsorbable interference screw following anterior cruciate ligament reconstruction (ACL).

METHODS

This retrospective study included all patients who underwent surgery between 2004 and 2016 for an intra-osseous tibial tunnel cyst on bioabsorbable interference screw following ACL reconstruction. The diagnosis was suggested clinically by pretibial pain at the incision site, sometimes associated with a palpable subcutaneous nodule and then confirmed on MRI. The first stage of surgery included exploratory arthroscopy followed by open excision/curettage of the cyst and then the tunnel was filled. The main criterion for outcome was a clinically normal knee (no pain, 0-120 range of motion, stable, with no effusion) at 6 months of follow-up.

RESULTS

This series included 53 patients, mean age 35.3 ± 9.9 years old w ith a mean 4.6 ± 3.1 years (between 3.1 months and 19 years) of follow-up after ligament reconstruction. The tibial screw was completely absorbed in 9/53 (17%) of patients, and fragmented in 22/53 (41.5%). At the 6-month follow-up, 42/53 (79.2%) patients had a normal knee, 11/53 (20.8%) persistent pain in the cyst area, 52/53 (98.1%) normal range of motion and 53 (100%) a stable knee. A recurrent cyst developed at 2 years of follow-up in one patient.

CONCLUSION

Complete absorption of a bioabsorbable interference screw is long, increasing the risk of developing intra-osseous tibial cysts during this period. The development of new materials with improved absorption properties is needed.

LEVEL OF EVIDENCE

IV-Retrospective study.

Adjustable-length loop cortical button versus interference screw fixation in quadriceps tendon anterior cruciate ligament reconstruction - A biomechanical in vitro study

BACKGROUND

This biomechanical cadaveric in vitro study aimed to evaluate and compare the dynamic elongation behavior and ultimate failure strength of tibial adjustable-length loop cortical button versus interference screw fixation in quadriceps tendon-based anterior cruciate ligament reconstruction.

METHODS

Sixteen human quadriceps tendons were harvested and fixed into porcine tibiae using either biodegradable interference screw (n = 8) or adjustable loop device (n = 8) fixation. An acrylic block was utilized for femoral adjustable loop device fixation for both groups. All constructs were precycled for 10 times at 0.5 Hz and manually retensioned before tested in position and force control mode each for 1000 cycles at 0.75 Hz according to in vitro loading conditions replicating the in vivo ACL environment. Subsequently, an ultimate failure test at 50 mm/min was performed with mode of failure noted.

FINDINGS

Tibial IS fixation showed no statistically significant differences in the initial (-0.46 vs. -0.47 mm; P = 0.9780), dynamic (2.18 mm vs. 2.89 mm; P = 0,0661), and total elongation (1.72 mm vs. 2.42 mm; P = 0,0997) compared to adjustable loop device fixation. The tibial button fixation revealed an increased ultimate failure load (743.3 N vs. 606.3 N; P = 0.0027), while stiffness was decreased in comparison to screw fixation (133.2 N/mm vs. 153.5 N/mm; P = 0,0045).

INTERPRETATION

Anterior cruciate ligament reconstruction for quadriceps tendon graft using a tibial adjustable-length loop cortical button provides for comparable dynamic stabilization of the knee with increased ultimate failure load at decreased stiffness compared to screw fixation.

Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction with Hamstring Tendon Autograft through Single Femoral Tunnel and Single Branched Tibial Tunnel

Conventional single-bundle anterior cruciate ligament (ACL) reconstruction cannot improve the rotational stability of the knee. Traditional double-bundle ACL reconstruction requires is demanding, complex, time- and implant consuming, and associated with a high incidence of complications. Double-bundle ACL reconstruction using a free quadriceps tendon autograft through 3 independent tunnels provides some advantage, but the antegrade graft passage, tibial tunnel confluence, and graft site morbidity represent disadvantages. This Technical Note describes a modification of double-bundle ACL reconstruction using the hamstring tendon autograft through a single branched tibial tunnel and a single femoral tunnel using 2 interference screws (Arthrex, Naples, FL). The gracilis tendon autograft is passed through tibial tunnel stem to the posterolateral tibial tunnel branch to the posterolateral position in the femoral tunnel. The semitendinosus tendon autograft is passed through the tibial tunnel stem to the anteromedial tibial tunnel branch to the anteromedial position in the femoral tunnel. Both grafts are fixed by 2 interference screws: 1 at the femoral tunnel and 1 at the tibial tunnel stem with the knee at 20° flexion.

Biocompatibility, biodegradation and excretion of polylactic acid (PLA) in medical implants and theranostic systems

Polylactic acid (PLA) is the most commonly used biodegradable polymer in clinical applications today. Examples range from drug delivery systems, tissue engineering, temporary and long-term implantable devices; constantly expanding to new fields. This is owed greatly to the polymer's favorable biocompatibility and to its safe degradation products. Once coming in contact with biological media, the polymer begins breaking down, usually by hydrolysis, into lactic acid (LA) or to carbon dioxide and water. These products are metabolized intracellularly or excreted in the urine and breath. Bacterial infection and foreign-body inflammation enhance the breakdown of PLA, through the secretion of enzymes that degrade the polymeric matrix. The biodegradation occurs both on the surface of the polymeric device and inside the polymer body, by diffusion of water between the polymer chains. The median half-life of the polymer is 30 weeks; however, this can be lengthened or shortened to address the clinical needs. Degradation kinetics can be tuned by determining the molecular composition and the physical architecture of the device. Using L- or D- chirality of the LA will greatly slow or lengthen the degradation rates, respectively. Despite the fact that this polymer is more than 150 years old, PLA remains a fertile platform for biomedical innovation and fundamental understanding of how artificial polymers can safely coexist with biological systems.

Rehabilitation of Tibial Plateau Fracture Following Anterior Cruciate Ligament Reconstruction: A Case Report

Objective

The purpose of this case report was to describe the management of a tibial plateau fracture in a patient who had undergone anterior cruciate ligament (ACL) reconstruction 3.5 years earlier.

Clinical Features

A 36-year-old man presented with pain and edema following a fall from a height of approximately 2 m while skateboarding. The patient reported having undergone arthroscopic ACL reconstruction with allograft and bioabsorbable screws 3.5 years earlier. Computed tomography scan revealed a comminuted fracture extending through the graft tunnel, as well as evidence of tunnel widening and incomplete bone resorption and generation within the tibial tunnel.

Intervention and Outcome

A trauma surgeon repaired the plateau fracture with internal fixation. The patient was non-weight bearing for 8 weeks while undergoing rehabilitation in a chiropractic clinic (spinal manipulation, physiotherapy, nutritional support) twice per week and returned to full activity within 3 months.

Conclusions

The patient responded favorably to the treatment protocol, which included rehabilitation by a doctor of chiropractic and co-management with a trauma surgeon.

Advancements in Bone Fixation Utilizing Novel Biointegrative Fixation Technology

Advancement in orthopedics have been increasing rapidly. The most important advances have been in fixation. With time, metallic hardware will begin to be replaced by materials that become one with the body. This progress will not only aid in the repair process it will allow permanent and improved reinforcement of the fixated region. Biointegrative technology is a promising new generation of materials capable of achieving this goal. Over time, it is expected that plates, screws, pins, interference screws, and even possibly joint replacements will incorporate into patients' bodies, negating the need for hardware removal and adding structure and stability to an iatrogenically weakened area.

Editorial Commentary: The Acrid Bioscrew in Anterior Cruciate Ligament Reconstruction of the Knee

Bioresorbable screws have been widely adopted for graft fixation in knee anterior cruciate ligament (ACL) reconstruction on the promise of screw resorbtion and replacement by bone. When considering the value of bioresorbable screws, it is imperative to understand that the "A" in PGA and PLA, the base ingredient of all bioscrews, is for Acid. All resorb by a process of hydrolysis; the speed and extent of resorbtion is determined by both the acidity of the screw and the environment in which it is placed. Regrettably, the promise of reliable, predictable screw resorbtion and replacement by bone remains elusive, despite the addition of "osteoconductive" materials. For the most part, bioresorbables are associated with good clinical outcomes for ACL reconstruction; they are not "dangerous," just disappointing with respect to bony replacement. We propose that nonresorbing inert plastics such as PEEK (polyether ether ketone) may be better suited for the purpose of graft fixation devices for ACL reconstruction.

A novel, hydroxyapatite-based screw-like device for anterior cruciate ligament (ACL) reconstructions

BACKGROUND

Rupture of the anterior cruciate ligament (ACL) is one of the most common injuries of the knee. Common techniques for ACL reconstruction require a graft fixation using interference screws. Nowadays, these interference screws are normally made of titanium or polymer/ceramic composites. The main challenge of application of a fixation device made entirely of bioactive ceramic is in relation to the low strength of such materials. The purpose of this study was to evaluate a novel geometry for a fixation device made of pure hydroxyapatite for ACL reconstructions that can overcome some problems of the titanium and the polymer/ceramic screws.

METHODS

Finite Element Analysis was used for optimization of the stress distribution in conventional interference screw geometry. For experimental evaluation of the new fixation device, ex vivo tests were performed.

RESULTS

The innovative screw-like fixation device is characterized by multiple threads with a large thread pitch. The novel design enabled the insertion of the screw into the bone without the application of an external torque or a screwdriver. In turn, it also allowed for the use of low-strength and high-bioactivity materials, like hydroxyapatite. Ex vivo tests showed that the novel screw can sustain pull-out forces up to 476 N, which is comparable to that of the commercially available BioComposite™ interference screws (Arthrex Inc., Germany), as a reference.

CONCLUSIONS

In summary, the novel screw design is a promising strategy to develop all-ceramic fixation devices for ACL reconstructions, which may eliminate some drawbacks of the current interference screws.

Femoral and Tibial Tunnel Diameter and Bioabsorbable Screw Findings After Double-Bundle ACL Reconstruction in 5-Year Clinical and MRI Follow-up

Background:

Tunnel enlargement is frequently seen in short-term follow-up after anterior cruciate ligament reconstruction (ACLR). According to new evidence, tunnel enlargement may be followed by tunnel narrowing, but the long-term evolution of the tunnels is currently unknown.

Hypothesis/Purpose:

The hypothesis was that tunnel enlargement is followed by tunnel narrowing caused by ossification as seen in follow-up using magnetic resonance imaging (MRI). The purpose of this study was to evaluate the ossification pattern of the tunnels, the communication of the 2 femoral and 2 tibial tunnels, and screw absorption findings in MRI.

Study Design:

Case series; Level of evidence, 4.

Methods:

Thirty-one patients underwent anatomic double-bundle ACLR with hamstring grafts and bioabsorbable interference screw fixation and were followed with MRI and clinical evaluation at 2 and 5 years postoperatively.

Results:

The mean tunnel enlargement at 2 years was 58% and reduced to 46% at 5 years. Tunnel ossification resulted in evenly narrowed tunnels in 44%, in conical tunnels in 48%, and fully ossified tunnels in 8%. Tunnel communication increased from 13% to 23% in the femur and from 19% to 23% in the tibia between 2 and 5 years and was not associated with knee laxity. At 5 years, 54% of the screws were not visible, with 35% of the screws replaced by a cyst and 19% fully ossified. Tunnel cysts were not associated with worse patient-reported outcomes or knee laxity. Patients with a tibial anteromedial tunnel cyst had higher Lysholm scores than patients without a cyst (93 and 84, P = .03).

Conclusion:

Tunnel enlargement was followed by tunnel narrowing in 5-year follow-up after double-bundle ACLR. Tunnel communication and tunnel cysts were frequent MRI findings and not associated with adverse clinical evaluation results.

Flexor Hallucis Longus Tendon Transfer Fixation

INTRODUCTION

Flexor hallucis longus (FHL) tendon transfer to the calcaneus is commonly used in the surgical treatment of chronic Achilles tendinopathy. This study assesses the integrity of FHL tendon biotenodesis screw fixation with respect to 2 variables: incorporation of a terminal whipstitch and tunnel depth.

MATERIALS AND METHODS

A total of 60 fresh-frozen cadaver FHL tendons and 28 calcanei were harvested for analysis in 4 sets of fixation constructs; 14 whipstitched tendons were compared against their nonwhipstitched paired tendon via pull-out strength load testing, and 16 tendon pairs were randomized for fixation in either a full-depth tunnel (bicortical) or a 25-mm partial tunnel (unicortical). All comparisons were carried out in native bone and synthetic models.

RESULTS

Whipstitched tendons demonstrated significantly stronger mean clinical load (253.68 vs 177.24 N, P = .008) and maximum load to failure (294.31N vs 194.57 N, P = .001) compared with the nonwhipstitched tendons in synthetic bone. There were no statistical differences in mean clinical load (200.96 vs 228.31 N, P = .63) and maximum load to failure (192.69 vs 217.74 N, P = .73) between full and partial tunnel groups. There were no significant differences found in trials carried out in cadaveric bone.

CONCLUSION

Use of a terminal whipstitch achieves greater fixation strength in FHL tendon biotenodesis transfers. Complete and partial tunnel constructs are equivocal in their pull-out strength. Data produced in a homogeneous bone substitute model demonstrate the biomechanical superiority of the whipstitch as well as the noninferiority of the partial tunnel technique.

LEVELS OF EVIDENCE

Level IIb.

Bioabsorbable versus metallic interference screws for graft fixation in anterior cruciate ligament reconstruction

BACKGROUND

Anterior cruciate ligament (ACL) tears are frequently treated with surgical reconstruction with grafts, frequently patella tendon or hamstrings. Interference screws are often used to secure the graft in bone tunnels in the femur and tibia. This review examines whether bioabsorbable interference screws give better results than metal interference screws when used for graft fixation in ACL reconstruction.

OBJECTIVES

To assess the effects (benefits and harms) of bioabsorbable versus metallic interference screws for graft fixation in ACL reconstruction.

SEARCH METHODS

We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register, CENTRAL (the Cochrane Library), MEDLINE, Embase, LILACS, trial registers and reference lists of articles. Date of search: January 2016.

SELECTION CRITERIA

We included randomised controlled trials and quasi-randomised trials comparing bioabsorbable with metallic interferences screws in ACL reconstruction. The main outcomes sought were subjective-rated knee function, failure of treatment, and activity level.

DATA COLLECTION AND ANALYSIS

At least two review authors selected eligible trials, independently assessed risk of bias, and cross-checked data. Data were pooled whenever relevant and possible. Requests for further information were sent to the original study authors.

MAIN RESULTS

We included 12 trials (11 randomised and one quasi-randomised) involving a total of 944 participants, and reporting follow-up results for 774. Participants in the 12 trials underwent ACL reconstruction with either hamstring tendon grafts (five trials) or patellar tendon grafts (seven trials). Trials participants were randomly allocated to bioabsorbable or metallic interference screws for graft fixation in both femur and tibia (seven trials); femur only (three trials); tibia only (one trial); location was not reported in the remaining trial. A variety of materials was used for the bioabsorbable screws, Poly-L-lactic acid (PLLA) being the most common. The metallic screws, where reported, were titanium.All trials were at high risk of bias, which invariably included performance bias. Seven trials were at high risk of attrition bias and eight at high risk of reporting bias. The quasi-randomised trial was assessed as being at high risk for selection bias. Based on these study limitations and insufficiency of the available data, we judged the quality of evidence for all outcomes was very low.The majority of the available data for patient-reported knee function was presented as Lysholm scores (0 to 100; higher scores = better function). There was very low quality but consistent evidence of no clinically important differences between the two groups in Lysholm scores at 12 months follow-up (mean difference (MD) -0.08, 95% confidence interval (CI) -1.48 to 1.32; three trials, 168 participants); 24 months (MD 0.35, 95% CI -1.27 to 1.98; three trials, 113 participants) or five or more years follow-up (MD 1.23, 95% CI -2.00 to 4.47; two trials, 71 participants). This lack of between-group differences was also reported for Lysholm scores in several trials that did not provide sufficient data for pooling as well as for other self-reported knee function scores reported in several trials.Treatment failure was represented by the summed data for implant breakage during surgery and major postoperative complications (implant failure, graft rupture, symptomatic foreign body reactions, effusion and treated arthrofibrosis and related conditions) that were usually described in the trial reports as requiring further substantive treatment. There is very low-quality evidence of greater treatment failure in the bioabsorbable screw group (60/451 versus 29/434; risk ratio (RR) 1.94 favouring metallic screw fixation, 95% CI 1.29 to 2.93; 885 participants, 11 studies). In a population with an assumed risk (based on the median control group risk) of 56 participants per 1000 having treatment failure after metallic screw fixation, this equates to 53 more (95% CI 17 to 108 more) per 1000 participants having treatment failure after bioabsorbable screw fixation. All 16 intraoperative complications in the bioabsorbable screw group were implant breakages upon screw insertion. Treatment failure defined as postoperative complications only still favoured the metallic screw group but the 95% CI also included the potential for a greater risk of treatment failure after metallic screw fixation: 44/451 versus 29/434; RR 1.44, 95% CI 0.93 to 2.23. Based on the assumed risk of 56 participants per 1000 having postoperative treatment failure after metallic screw fixation, this equates to 25 more (95% CI 4 fewer and 69 more) per 1000 participants having this outcome after bioabsorbable screw fixation.There was very low-quality evidence of very similar activity levels in the two groups at 12 and 24 months follow-up measured via the Tegner score (0 to 10; higher scores = greater activity): 12 months (MD 0.08, 95% CI -0.39 to 0.55; 122 participants, two studies); 24 months (MD 0.01, 95% CI -0.54 to 0.57; 72 participants, two studies).

AUTHORS' CONCLUSIONS

There is very low-quality evidence of no difference in self-reported knee function and levels of activity between bioabsorbable and metallic interference screws for graft fixation in ACL reconstruction. There is very low-quality evidence that bioabsorbable screws may be associated with more overall treatment failures, including implant breakage during surgery. Further research does not appear to be a priority, but if undertaken, should also examine costs.

Efficacy of Osteoconductive Ceramics in Bioresorbable Screws for Anterior Cruciate Ligament Reconstruction: A Prospective Intrapatient Comparative Study

Background:

Osteoconductive additives are used in resorbable interference screws for anterior cruciate ligament (ACL) reconstruction to improve graft incorporation and mitigate adverse effects. There are no published studies that compare biological performances of bioresorbable and biocomposite screws without artifacts due to different follow-up times and intrinsic patient characteristics.

Purpose/Hypothesis:

The purpose of this study was to evaluate the efficacy of osteoconductive agents in bioresorbable screws for ACL reconstruction at minimum follow-up of 2 years by intrapatient comparison. The hypothesis was that osteoconductive ceramics would result in slower resorption, improved ossification, and less tunnel widening.

Study Design:

Cohort study; Level of evidence, 2.

Methods:

A total of 28 ACL reconstructions at 2 centers were randomly assigned into 2 comparable groups: (1) the graft was fixed in the tibia using standard bioresorbable screws and in the femur using biocomposite screws with osteoconductive agents (biphasic calcium phosphate), and (2) the graft was fixed in the femur using a standard bioresorbable screw and in the tibia using a biocomposite screw with osteoconductive agents.

Results:

Twenty-seven patients completed evaluations at 29.9 ± 4.0 months. Resorption was complete for more bioresorbable (81%) than biocomposite (37%) screws (P = .0029), whereas satisfactory ossification was observed in more biocomposite (52%) than bioresorbable (15%) screws (P = .0216). The tunnel shape was normal in more biocomposite (81%) than bioresorbable (48%) screws (P = .0126), and marked cortical formation was twice more frequent for biocomposite (78%) than bioresorbable (37%) screws (P = .0012). Bioresorbable screws exhibited faster resorption in the femur (P = .0202) but not in the tibia (not significant). Conversely, biocomposite screws demonstrated better ossification, less tunnel widening, and more cortical formation in the tibia (P < .0001, P = .0227, and P < .0001, respectively) but not in the femur (not significant for all).

Conclusion:

Osteoconductive additives can reduce the extent of resorption while improving ossification, reducing tunnel widening, and increasing cortical formation.

Clinical Relevance:

The benefits of osteoconductive agents justify their associated costs for ACL reconstruction, particularly in the tibia.

Biodegradable Materials: Anchors and Interference Screws

Biodegradable implants allow clarity in postoperative imaging, easier revision, and fewer concerns about associated tissue damage. It is important to appreciate that different biodegradable materials have different properties and different degradation rates. Faster degradation can be associated with a greater inflammatory response. However, inflammation is a normal part of the degradation process. The concern arises when the inflammation is clinically significant.

Quadruple Semitendinosus Graft Construct and Suspensory Button Fixation for Anterior Cruciate Ligament Reconstruction

Surgical techniques for anterior cruciate ligament reconstruction are evolving, becoming less invasive, with fewer and smaller incisions, preservation of knee bone stock and tendons at the donor site, and better graft positioning and fixation. We describe an anterior cruciate ligament reconstruction technique that aims to preserve bone stock and spares the gracilis. The semitendinosus graft construct is prepared in a quadruple way and fixed with a cortical button in both tunnels, with increased stiffness and resistance of the graft construct. The tibial tunnel is filled at the end of the operation with a bone dowel, keeping the bone stock intact. This technique is safe, with a short learning curve; preserves the gracilis; saves bone; and increases the stiffness and resistance of the tibial fixation.

Tibial Tunnel Cyst Formation after Anterior Cruciate Ligament Reconstruction Using a Non-Bioabsorbable Interference Screw

Tibial cyst formation following the use of bioabsorbable interference screws in anterior cruciate ligament (ACL) reconstruction is well-described; however, cyst formation after the use of metallic interference screws is not well-documented. We describe a case of osteolytic lesion of the proximal tibia presenting to us 20 years after ACL reconstruction using an autologous bone-tendon-bone graft. The original graft fixation technique was interference fixation with a metal screw in the tibial and femoral tunnels. A two-stage revision reconstruction of the ACL was undertaken with curettage and bone grafting of the tibial lesion in the first stage and reconstruction using a four-strand hamstring tendon in the second stage. The patient recovered satisfactorily with complete healing of the cyst and returned to pre-injury level of activities. We have reviewed case reports and case series that describe the aetiology of intra-osseous cyst formation following ACL reconstruction.

Bioabsorbable interference screw failure in anterior cruciate ligament reconstruction: A case series and review of the literature

BACKGROUND

To report a case series of failures of bioabsorbable interference screws with possible identification of a novel failure mechanism.

METHODS

A retrospective review of ACL reconstructions by the senior author utilizing BioComposite™ Interference Screws (Arthrex, Inc., Naples, FL) was performed. Complications related to screw placement, including fracture, breakage or bending were examined. Our rate and methods of failure were compared to those quoted in the current literature.

RESULTS

Eighty-seven patients of average age 23.8 years met inclusion criteria. There were eight screw failures in six patients, with femoral failure in seven and tibial failure in one. The femoral screw fractured halfway between the tip and head in five, while the head of the screw broke in one and the screw bent in another. In the case of tibial interference screw fracture, failure occurred halfway between the tip and head. The insertion device that was used was replaced after recognition of material deformation and considered a potential contributor to the breakage risk as no further screw failures have occurred since.

CONCLUSIONS

We demonstrate a unique failure mechanism of bio-absorbable interference screws. In each case, the reconstruction was salvaged. Regular inspection of materials and implants can ensure optimal outcomes and decrease complications intra-operatively.

The past, present and future in scaffold-based tendon treatments

Tendon injuries represent a significant clinical burden on healthcare systems worldwide. As the human population ages and the life expectancy increases, tendon injuries will become more prevalent, especially among young individuals with long life ahead of them. Advancements in engineering, chemistry and biology have made available an array of three-dimensional scaffold-based intervention strategies, natural or synthetic in origin. Further, functionalisation strategies, based on biophysical, biochemical and biological cues, offer control over cellular functions; localisation and sustained release of therapeutics/biologics; and the ability to positively interact with the host to promote repair and regeneration. Herein, we critically discuss current therapies and emerging technologies that aim to transform tendon treatments in the years to come.

Magnetic resonance appearance of bioabsorbable anchor screws for double row arthroscopic rotator cuff repairs

BACKGROUND

Little is known about the bioabsorbable, anchor related postoperative changes in rotator cuff surgery, which has become more popular recently. The purpose of the present study was to use magnetic resonance imaging (MRI) to analyze the degradation of bioabsorbable anchors and to determine the incidences and characteristics of early postoperative reactions around the anchors and their mechanical failures.

MATERIALS AND METHODS

Postoperative MRIs of 200 patients who underwent arthroscopic rotator cuff repair were retrospectively analyzed. The tissue reactions around the bioanchors included fluid accumulations around the anchor, granulation tissue formation and changes in the condition of the surrounding osseous structure. The condition of the bioanchor itself was also examined, including whether the bioanchor failed mechanically. In the case of mechanical failure, the location of the failure was noted. Serial MRIs of 18 patients were available for analysis.

RESULTS

The total number of medial row bioanchors was 124, while that of the lateral row was 338. A low signal intensity rim suggestive of sclerosis surrounded all lateral row bioanchors. Ninety three lateral row bioanchors (27%) showed a rim with signal intensity similar to or less than that of surrounding bone, which was granulation tissue or foreign body reaction (FBR). Similar signal intensity was seen around nine medial row bioanchors (7%). Fluid accumulation was seen around 4 lateral row bioanchors (1%) and around 14 medial row bioanchors (11%). Five lateral row bioanchors showed the breakage, while there was none in the medial row bioanchors. There were nine cases with a cuff re-tear (4.5%). There was no evidence of affection of glenohumeral articular surfaces or of osteolysis around any bioanchor. In serial MRI, there was no change in appearance of the bioanchors, but the granulation tissue or FBR around four bioanchors and the fluid around one bioanchor showed a decrease in successive MRI.

CONCLUSION

This study highlights the normal and adverse reactions to Bioabsorbable anchors that surgeons can expect to see on MRI after rotator cuff repairs.

Foreign body reaction after PLC reconstruction caused by a broken PLLA screw

Foreign body reactions may occur in patients who receive bioabsorbable implants during orthopedic surgery for fractures and ligament repair. The authors describe a 34-year-old man who presented with a palpable tender mass on the lateral aspect of the left knee of 1 month's duration. He underwent posterior cruciate ligament and posterolateral corner reconstruction 3 years earlier. Physical examination showed a 1×1-cm soft, nontender mass without localized warmth on the lateral epicondyle of the distal femur. Magnetic resonance imaging showed a broken screw fragment surrounded by a cyst-like mass. Under general anesthesia, the surgeon excised the screw fragment and the fibrotic mass, enclosing it in the subcutaneous tissue at the lateral epicondyle, the site at which a poly-L-lactic acid bioabsorbable screw had been inserted to fix the graft for posterolateral corner reconstruction. Histologic evaluation showed a foreign body reaction to the degraded screw particles. To the authors' knowledge, this report is the first description of a patient presenting with a delayed foreign body reaction to a broken poly-L-lactic acid bioabsorbable screw at the lateral femoral epicondyle after posterolateral corner reconstruction. Because delayed foreign body reactions can occur at any site of poly-L-lactic acid bioabsorbable screw insertion, care should be taken to avoid screw protrusion during ligament reconstruction because it can lead to screw breakage and delayed foreign body reaction.

Painful pretibial pseudocyst at bioabsorbable interference screw aperture two years after anterior cruciate ligament reconstruction

We report the case of a patient with a painful subcutaneous nodule, measuring 13 mm × 17 mm, at the pretibial graft aperture site, which presented two years after a successful anterior cruciate ligament reconstruction with an autologous hamstring graft. A bioabsorbable poly-L-lactide interference screw was used for graft fixation at the tibial aperture. The patient underwent surgical excision of the lesion and curettage at the tunnel aperture. Grossly, extruded fragments of the screw and a thick pseudocapsule of surrounding tissue were excised. There was no communication between the tunnel aperture and the knee joint. The graft was also intact. Histological analysis revealed fragments of the bioabsorbable material in association with fibrous and granulomatous chronic inflammatory cells. This was consistent with a foreign body reaction. The patient subsequently recovered and resumed preinjury level of activity. To the best of our knowledge, this is the first report describing a nodular granulomatous type reaction to foreign bioabsorbable poly-L-lactide screw material subsequent to an anterior cruciate reconstruction surgery.

Biodegradation of a magnesium alloy implant in the intercondylar femoral notch showed an appropriate response to the synovial membrane in a rabbit model in vivo

Degradable magnesium alloys are promising biomaterials for orthopedic applications. The aim of this study was to evaluate the potential effects on both the synovial membrane (synovialis) and the synovial fluid (synovia) of the degradation products of a MgYREZr-pin implanted in the intercondylar femoral notch in a rabbit model. Thirty-six animals were randomized into two groups (MgYREZr or Ti6Al4V alloy) of 18 animals each. Each group was then divided into three subgroups with implantation periods of 1, 4, and 12 weeks, with six animals in each subgroup. The initial inflammatory reaction caused by the surgical trauma declined after 12 weeks of implantation, and elucidated a progressive recovery of the synovial membrane. Compared with control Ti6Al4V pins, there were no significant differences between the groups. However, after 12 weeks, recovery of the synovial membrane was more advanced in the titanium group, in which 92% showed no signs of synovitis, than in the magnesium group. A cytotoxicity test with L929 cells and human osteoblasts (HOB) was also conducted, according to EN ISO 10993-5/12, and no toxic leachable products were observed after 24 h of incubation. In conclusion, the MgYREZr alloy seems to be a suitable material for intra-articular degradable implants.

Do newer-generation bioabsorbable screws become incorporated into bone at two years after ACL reconstruction with patellar tendon graft?: A cohort study

BACKGROUND

Bioabsorbable interference screws are used frequently for graft fixation in ACL (anterior cruciate ligament) reconstruction. The resorption properties of many available screws that are marketed as bioabsorbable are not well defined. The CALAXO (Smith & Nephew Endoscopy) and MILAGRO (DePuy Synthes) bioabsorbable screws contain polymers of poly(lactic-co-glycolic acid) (PLGA) plus additives to encourage osseointegration over time. The purpose of this study was to evaluate radiographic and magnetic resonance imaging (MRI) properties and compare patient-reported outcomes at a minimum of two years of follow-up after ACL reconstruction using CALAXO or MILAGRO bioabsorbable interference screws.

METHODS

A cohort of patients who underwent ACL reconstruction in which the fixation used was either CALAXO or MILAGRO screws returned for repeat radiographs for evaluation of tunnel widening, repeat MRI for evaluation of graft integrity and screw breakdown, and completion of the pain and symptom items of the KOOS (Knee injury and Osteoarthritis Outcome Score) questionnaire.

RESULTS

At a mean of three years (range, 2.5 to 4.0 years) after surgery, thirty-one patients with sixty-two CALAXO screws and thirty-six patients with seventy-two MILAGRO screws returned for repeat evaluation. Two blinded, independent reviewers found no significant differences between the two screw types when comparing radiographs for tibial or femoral tunnel widening or MRIs for graft integrity, tibial and femoral foreign body reactions, or femoral screw degradation. Both reviewers found a significant difference between the two screw types when comparing tibial screw degradation properties (p < 0.01). All analyzed CALAXO screws were rated as partially intact or degraded; the MILAGRO screws were more likely to be rated as intact. No significant differences were noted between the two screw types when comparing the two KOOS subscales.

CONCLUSIONS

CALAXO screws in the tibial tunnel were more likely to be rated as degraded or partially degraded compared with MILAGRO screws at a mean of three years after implantation for ACL reconstruction. Although these newer-generation bioabsorbable screws were designed to promote osseointegration, no tunnel narrowing was noted, and in the majority of cases the remains of the screws were present at approximately three years.

Long-term degradation of poly-lactic co-glycolide/β-tricalcium phosphate biocomposite anchors in arthroscopic bankart repair: a prospective study

PURPOSE

To evaluate, using magnetic resonance (MR), the biological efficacy of anchors made of 30% β-tricalcium phosphate and 70% poly-lactic co-glycolide (PLGA) used for the repair of Bankart lesions after shoulder instability.

METHODS

Twenty consecutive patients who were candidates for surgical treatment for unidirectional, post-traumatic shoulder instability were treated arthroscopically with anchors made of 70% PLGA plus 30% β-tricalcium phosphate preloaded with OrthoCord suture (DePuy Mitek, Raynham, MA). Fifteen of them were evaluated by MR at least 16 months after the intervention. A second evaluation was performed at least 12 months after the first evaluation in the patients in whom implanted anchors were still visible at the first evaluation (n = 5) with a low-intensity signal in all sequences. Two radiologists, with different amounts of experience (15 and 3 years), separately evaluated the MR patterns of the trabecular glenoid bone, the walls of the bone tunnel, and the signal from the anchors. The following parameters were considered in the MR evaluation: integrity of the tunnel edge (grade 0 to 2), intensity of the signal from the anchor site (grade 1 to 3), and presence of cystic lesions. The normal signal from the glenoid trabecular bone has been used as the reference parameter. The anchors were considered independent variables, and thus each one was analyzed individually, even in the same patient. At the final clinical follow-up, a Rowe questionnaire was filled out for each patient.

RESULTS

Overall, 44 anchors were evaluated (33 anchors at the first follow-up and 11 anchors at the second follow-up). The mean follow-up period was 28.6 months. With the exception of 2 patients (10%), none of the patients had any episodes of dislocation, having satisfactory postoperative results. No cystic lesions were detected by MR imaging. The interobserver concordance between the 2 radiologists calculated with the Cohen κ was substantial (κ = 0.780 and κ = 0.791 for integrity of tunnel edge and for intensity of signal from anchor site, respectively). Both the integrity of the tunnel border and the intensity of the signal at the site of the anchors that had been implanted more than 24 months before the evaluation were significantly different from those of anchors implanted less than 24 months before the evaluation (tunnel border grade of 0 in 41%, 1 in 50%, and 2 in 9% v 0 in 4.5%, 1 in 50%, and 2 in 45.5% [P = .003]; anchor signal grade of 1 in 41%, 2 in 45.5%, and 3 in 13.5% v 1 in 13.5%, 2 in 41%, and 3 in 45.5% [P = .03]). Analysis of the linear contrasts (analysis of variance) showed a linear increase in the mean values for time to increased tunnel border grade (grade 0, 22 ± 4 months; grade 1, 27 ± 8 months; and grade 2, 29 ± 5 months [P = .02]) and grade of intensity of the signal in the anchor site (grade 1, 24 ± 6 months; grade 2, 26 ± 7 months; and grade 3, 29 ± 7 months [P = .05]).

CONCLUSIONS

Anchors made of 30% β-tricalcium phosphate and 70% PLGA showed excellent biological efficacy, without causing significant cystic lesions, producing gradual changes in the MR signal that seems to become equivalent to that of the glenoid trabecular bone at a mean of 29 months after implantation.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Meta-analysis comparing bioabsorbable versus metal interference screw for adverse and clinical outcomes in anterior cruciate ligament reconstruction

PURPOSE

To compare bioabsorbable screw (BS) against metal screw (MS) primarily on adverse effects and secondarily on clinical outcomes after single-bundle primary anterior cruciate ligament reconstruction.

METHODS

Electronic searches were performed using search strategies meeting the mentioned purposes. Retrieved articles were selected for randomised controlled trials (RCTs) reporting at least 1-year follow-up. Potential studies were selected under inclusion and exclusion criteria. Risk of biases and data extraction was completed by two review authors. Discrepancies were resolved through discussion. Mean difference and risk ratio with 95 % confidence interval (CI) were used for continuous and binary outcomes, respectively. Heterogeneity was assessed using I (2). Pooled treatment effects with 95 % CI were estimated using the fixed- or random-effect model where appropriate.

RESULTS

Eleven RCTs with 878 randomly allocated patients were included, and 711 patients (81 %) with eligible follow-up time up to 8 years were analysed. Comparing with the MS group, BS group using medial hamstring graft showed evidence of larger tunnel widening on the femoral side measured from radiographs or magnetic resonance imaging, though data could not be pooled because diverse measurement methods had been used. Significantly higher rates of effusion and screw breakage, and fewer cases of complete tunnel healing were reported in the BS group. Nevertheless, functional and clinical results were not deteriorated by the presence of these adverse effects for both short- and longer-term follow-ups.

CONCLUSION

This is the first systematic review focusing on adverse effects of the BS, such as larger tunnel widening and higher rates of other complications. With these effects, routine use of the BS should be balanced with the advantages claimed. Cost-effectiveness is another issue, and well-designed RCTs are needed to better validate the implication.

Pre-tibial reaction to biointerference screw in anterior cruciate ligament reconstruction

BACKGROUND

We aim to report a series of cases that presented as pre-tibial swelling and pain following anterior cruciate ligament (ACL) reconstruction using bioabsorbable fixation devices.

METHODS

All ACL reconstructions done between 2007 and 2010 were reviewed retrospectively to identify complications related to bioabsorbable fixation devices. We performed 273 ACL reconstructions over a period of three years from 2007 to 2010 using a bioabsorbable screw for tibial fixation of the quadrupled hamstring autograft.

RESULTS

Fourteen patients (5%) at mean age of 30 (range 16-47) years, presented to us at a mean post-operative period of 26 months (range 12-39) with pre-tibial pain and swelling over the tibial screw site. All of them had normal inflammatory markers. All of these patients underwent surgical debridement, which revealed remnants of screw and reactive material. There was no evidence of infection in the intra-operative specimen cultures. Histopathology revealed a reactive appearance and surrounding myxoid changes. Removal of screw debris and curettage of the tunnel resulted in complete recovery of all patients at a mean follow up of 12 (range 8-16) months.

CONCLUSIONS

Pre-tibial cyst along with other adverse biological response should be considered as a possible complication in ACL reconstruction. We report an incidence of 5% of pre-tibial reaction in patients undergoing ACL reconstruction with bio-absorbable interference screw fixation for the proximal tibia.