Bioabsorbable Versus Titanium Screws in Anterior Cruciate Ligament Reconstruction Using Hamstring Autograft: A Prospective, Blinded, Randomized Controlled Trial With 5-Year Follow-up

Effect of Different Screw Materials on ACL Reconstruction With the Tape Locking Screw Technique: A Retrospective Study From the FAST Cohort

Background

Screws for graft fixation are available in 3 different materials for anterior cruciate ligament reconstruction (ACLR) with the Tape Locking Screw (TLS) technique: titanium, poly-l-lactic acid bioabsorbable, and polyetheretherketone (PEEK).

Purpose

To compare the effect of the 3 different fixation materials on graft and implant survival after ACLR with the TLS technique.

Study Design

Cohort study; Level of evidence, 3.

Methods

Included were 521 patients from the French Prospective ACL Study (FAST) cohort who underwent primary surgical ACLR with the TLS technique. Patients were divided into 3 groups depending on the type of screw material used: titanium (TLS-T group), poly-l-lactic acid bioabsorbable (TLS-B group), or PEEK (TLS-P group). The primary endpoint was a retear within 2 years after ACLR. The secondary endpoints were complication rate, return to sports rate, and functional scores. Objective and subjective functional scores-including the International Knee Documentation Committee, the Knee injury and Osteoarthritis Outcome Score (KOOS), and the Lysholm score-were evaluated preoperatively and at the 2-year follow-up. Pain was assessed with the KOOS-Pain subscore recorded pre- and postoperatively every 6 months up to 2 years. Patient satisfaction was recorded at the 2-year follow-up.

Results

No significant differences between the study groups were found in retear rates (4.4%, 4.5%, and 4.3% in the TLS-T, TLS-P, and TLS-B groups 2 years after surgery) or subjective and objective outcomes. The TLS-T group had the lowest rate of intraoperative implant-related complications (0.9%) compared with the TLS-P (4.3%) and TLS-B (7.7%) groups. Young age was a significant risk factor for retear in the TLS-T (P = .03) and TLS-B (P = .0001) groups, while a high level of sports was found to be a significant risk factor in the TLS-P (P = .04) group. All functional scores improved significantly at the 2-year follow-up (P < .0001), with no significant group difference. The KOOS-Pain subscore improved continuously with no significant group difference. The rate of return to preinjury sports was between 43.4% and 58.6%. The rate of highly satisfied patients at the final follow-up was between 86.2% and 91.8%.

Conclusion

There was no difference in retear rate or objective and subjective functional scores between implant materials for TLS ACLR in this study.

Comparison of Graft Type and Fixation Method in Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis Based on Randomized Control Studies

BACKGROUND

The anterior cruciate ligament (ACL) is the most commonly injured ligament in the knee. ACL reconstruction (ACLR) proves the standard for treating this injury. However, graft choice and method of fixation remain a heavily debated topic. This study investigates the following: bone-patellar tendon-bone (BPTB) vs. hamstring tendon (HT) autograft, single-bundle vs. double-bundle hamstring graft, and metal vs. bioabsorbable screws in ACLR.

METHODS

A systematic review was performed on PubMed and Google Scholar according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Data were collected on patient demographics, complications, and functionality scores including International Knee Documentation Committee (IKDC) and Lysholm scores. A systematic review and meta-analysis were conducted with Review Manager. Outcome measurements were determined using forest plots with significant differences considered p < 0.05.

RESULTS

Twenty-five studies were included, accounting for 2,170 patients. No statistically significant difference was appreciated when comparing BPTB to hamstring autografts. Patients who received a double bundle HT autograft exhibited significantly superior outcomes in terms of revision (p = 0.05), failure (p = 0.002), normal pivot shift tests (p = 0.04), and normal IKDC (p = 0.008). When comparing screw types, bioabsorbable screws had a greater Lysholm score (p = 0.01) and lower failure rates for copolymer screws (p = 0.03).

CONCLUSION

Overall, the data collected suggested that BPTB and HT autografts display similar postoperative results. However, if an HT autograft is used, the data suggest a double-bundle graft improves both functionality and decreases the possible complications. Finally, bioabsorbable screws prove superior to metal screws when looking at both functionality and failure rates. Further research into the superior graft type is still needed.

LEVEL OF EVIDENCE

Level II. See Instructions for Authors for a complete description of levels of evidence.

Biodegradable biomaterials in orthopedic surgery: A narrative review of the current evidence

BACKGROUND

Biomaterials are routinely used in orthopedic surgery to fill bone defects, improve bone healing, and as degradable fixation material. A wide range of materials are currently in use, and the materials are chosen according to their bioactive properties. Osteoinductive materials stimulate bone healing by promoting osteogenesis. Osteoconductive materials facilitate bone growth on the surface of the material. Despite the many materials in use and an increasing number of published studies, randomized controlled trials on the subject are scarce.

METHODS

This review aims to summarize the history of biodegradable biomaterials and also the published level I evidence currently available on orthopedic biomaterials.

RESULTS

Most of the studies have been superiority trials with non-significant differences compared to conventional treatment options, confirming that several biomaterials are suitable treatment options for multiple indications including bone and/or tendon fixation, filling bone defects, and spinal fusion. Biomaterials help to avoid donor site complications associated with autogenous bone grafts and often eliminate the need for implant removal. However, the surgical technique may in some cases be more demanding than with conventional methods. Careful consideration of the pros and cons is therefore recommended in clinical practice.

CONCLUSION

Biodegradable biomaterials complement the range of available treatment options in several fields of orthopedic surgery. However, some biomaterials performed worse than expected and were not recommended for clinical use, emphasizing the need for high-quality randomized trials. It is also noteworthy that several trials included only a limited number of patients, rendering the interpretation of the results of these underpowered studies challenging.

Smaller diameter femoral tunnel biocomposite interference screws provide adequate fixation strength in anterior cruciate ligament reconstruction

PURPOSE

The purpose of this study was to evaluate the effect of bioabsorbable interference screw diameter on the pullout strength and failure mode for femoral tunnel fixation in primary anterior cruciate ligament reconstruction (ACLR) at time zero fixation using bone-patellar tendon-bone (BTB) autograft in a cadaveric model.

METHODS

Twenty-four fresh-frozen cadaveric knees were obtained from 17 different donors. Specimens were allocated to three different treatment groups (n = 8 per group) based on interference screw diameter: 6 mm, 7 mm, or 8 mm biocomposite interference screw. All specimens underwent dual energy X-ray absorptiometry (DEXA) scanning prior to allocation to ensure no difference in bone mineral density among groups (n.s.). All specimens underwent femoral-sided ACLR with BTB autograft. Specimens subsequently underwent mechanical testing under monotonic loading conditions to failure. The load to failure and failure mechanism were recorded.

RESULTS

The mean pullout force (N) at time zero for each group was 309 ± 213 N, 518 ± 313 N, and 541 ± 267 N for 6 mm, 7 mm, and 8 mm biocomposite interference screw diameter, respectively (n.s.). One specimen in the 6 mm group, two specimens in the 7 mm group, and one specimen in the 8 mm group failed by screw pullout. The remainder in each group failed by graft failure (n.s.).

CONCLUSION

Biocomposite interference screw diameter did not have a significant influence on fixation pullout strength or failure mode following femoral tunnel fixation using BTB autograft at time zero. A 6 mm interference screw can improve preservation of native bone stock, increase potential for biologic healing, and decrease the risk of damage to the graft during insertion without significantly compromising fixation strength. This study supports the use of smaller 6 mm interference screw diameter options for femoral tunnel fixation in ACLR.

Anterior Screw Insertion Results in Greater Tibial Tunnel Enlargement Rates after Single-Bundle Anterior Cruciate Ligament Reconstruction than Posterior Insertion: A Retrospective Study

Background and Objectives: Tunnel enlargement (TE) is a widely reported phenomenon after anterior cruciate ligament reconstruction (ACLR). Given the paucity of knowledge in the literature, it remains unclear whether screw position in the tunnel affects TE. This retrospective cohort study evaluated differences in postoperative tunnel enlargement rates (TER) and clinical results between anterior and posterior tibial interference screw insertion during single-bundle ACLR using autologous hamstring grafts. Materials and Methods: A group of consecutive patients that underwent primary arthroscopic single-bundle ACLR in our hospital were screened and divided into two groups based on the position of the tibial interference screw (determined by Computer Tomography within 3 days after surgery): anterior screw position group (A) and posterior screw position group (B). The bone tunnel size was measured using magnetic resonance imaging (MRI) performed 1 year after surgery. International Knee Documentation Committee (IKDC) score and the Knee Injury and Osteoarthritis Outcome Score (KOOS) were used for clinical results 1 year postoperatively. Results: 87 patients were included. The TER of Group A is higher than that of Group B (43.17% vs. 33.80%, p = 0.024). Group A showed a significant increase (12.1%) in enlargement rates at the joint line level than group B (43.77% vs. 31.67%, p = 0.004). Moreover, KOOS and IKDC scores improved in both groups. There were no significant differences in clinical outcomes between the two groups. Conclusions: One year after ACLR, patients with posterior screw showed significantly lower TE than patients with anterior screw. However, the position of screw did not lead to differences in clinical results over our follow-up period. Posterior screw position in the tibial tunnel maybe a better choice in terms of reducing TE. Whether the different screw positions affect the long-term TE and long-term clinical outcomes needs to be confirmed by further studies.

Clinical and radiological comparison of bioactive glass and poly-L-lactic acid/hydroxyapatite bioabsorbable interference screws for tibial graft fixation in anterior cruciate ligament reconstruction

BACKGROUND

Ligament reconstruction is still the main treatment modality for patients with a complete ligament rupture. The semitendinosus tendon, alone quadrupled or double folded and combined with the gracilis tendon, is still the most frequently used autologous graft for a reconstructive procedure. Absorbable interference screw usage has gained popularity in the past decade because they create less artifacts during MR imaging and tend to osteointegrate over the years, arguably leading to a more anatomic fixation. The purpose of this study was to compare the 5-year radiological and clinical results of two different tibial graft fixation screws.

HYPOTHESIS

We hypothesized that bioabsorbable interference screws made of bioactive glass would lead to higher rates of osteointegration, better overall clinical results, less foreign body reaction rates and less tibial tunnel widening when compared to the poly-L-lactic acid/hydroxyapatite (PLLA-HA) screws.

PATIENTS AND METHODS

Fifty-one patients treated with an anatomic single bundle ACL reconstruction between June 2015 and July 2016 at our institution were included in the study. The tibial graft was fixed with a bioactive glass screw in 24, and with a PLLA-HA in 27 patients. Tibial tunnel widening, foreign body reaction, osteointegration and resorption rates were evaluated and compared on a magnetic resonance scan at a minimum of 5 year postoperatively. Overall clinical results and side-to-side difference on KT-1000 were also analyzed in-between groups.

RESULTS

Tibial tunnel widening was similar for both groups. Foreign body reaction, while not statistically significant, was less aggressive when bioactive glass screws were used. Osteointegration and resorption rates of the bioactive glass screws were significantly higher than the PLLA-HA group (p=0.000). While all patients showed an overall improvement on postoperative scores (p=0.000), patients with a bioactive glass interference screw had statistically higher translational stability with KT-1000, compared to the poly-L-lactic acid/hydroxyapatite group (p=0.001).

DISCUSSION

At a minimum of 5 years, compared to conventional PLLA-HA interference screws, 45S5 bioactive glass screw provide higher resorption rates, are more highly biodegradable and provide overall good clinical results.

LEVEL OF EVIDENCE

III.

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.

Tibial-graft fixation methods on anterior cruciate ligament reconstructions: a literature review

Introduction

Anterior cruciate ligament (ACL) reconstruction is the most performed orthopedic surgical procedure. The result of ACL reconstructions depends on multiple technical variables, including tension to be applied to the graft for fixation, knee-flexion angle during fixation and the type of fixation to the bone.

Objective

To carry out a survey of the literature with the best evidence on these themes.

Methods

Literature review about methods of tibial-graft fixation in ACL reconstructions – tension applied at the time of fixation, type of graft fixation, and knee-flexion degree during tibial fixation.

Results

Thirty studies on the selected topics were found. Most studies point to graft-tension levels close to 90 N to obtain the best results. Regarding the knee-flexion angle, multiple studies suggest that fixation at a 30° angle would bring superior biomechanical advantages. Regarding the type of implant for fixation, it is not possible to affirm the superiority of one method over another in clinical outcomes.

Conclusions

There is no consensus on the best method for tibial fixation of the grafts in ACL reconstructions regarding tension, type of implant and knee-flexion angle. However, the analysis of the studies pointed to certain trends and allowed the drawing of specific conclusions.

Systematic Review of Silk Scaffolds in Musculoskeletal Tissue Engineering Applications in the Recent Decade

During the past decade, various novel tissue engineering (TE) strategies have been developed to maintain, repair, and restore the biomechanical functions of the musculoskeletal system. Silk fibroins are natural polymers with numerous advantageous properties such as good biocompatibility, high mechanical strength, and low degradation rate and are increasingly being recognized as a scaffolding material of choice in musculoskeletal TE applications. This current systematic review examines and summarizes the latest research on silk scaffolds in musculoskeletal TE applications within the past decade. Scientific databases searched include PubMed, Web of Science, Medline, Cochrane library, and Embase. The following keywords and search terms were used: musculoskeletal, tendon, ligament, intervertebral disc, muscle, cartilage, bone, silk, and tissue engineering. Our Review was limited to articles on musculoskeletal TE, which were published in English from 2010 to September 2019. The eligibility of the articles was assessed by two reviewers according to prespecified inclusion and exclusion criteria, after which an independent reviewer performed data extraction and a second independent reviewer validated the data obtained. A total of 1120 articles were reviewed from the databases. According to inclusion and exclusion criteria, 480 articles were considered as relevant for the purpose of this systematic review. Tissue engineering is an effective modality for repairing or replacing injured or damaged tissues and organs with artificial materials. This Review is intended to reveal the research status of silk-based scaffolds in the musculoskeletal system within the recent decade. In addition, a comprehensive translational research route for silk biomaterial from bench to bedside is described in this Review.

Comparative Risk-Benefit Profiles of Individual Devices for Graft Fixation in Anterior Cruciate Ligament Reconstruction: A Systematic Review and Network Meta-analysis

PURPOSE

To compare the efficacy and safety of individual devices for femoral and/or tibial graft fixation in anterior cruciate ligament (ACL) reconstruction.

METHODS

The PubMed, Embase, Cochrane Library, and Web of Science databases were searched from inception to December 12, 2018. Randomized controlled trials comparing individual devices for ACL graft fixation were included. Bayesian network meta-analysis was performed to assess the efficacy profile using the following outcomes: Lysholm score, International Knee Documentation Committee (IKDC) category, laxity, range of motion, and Tegner score. The incidence of infection, effusion, and graft rupture for each device was reported.

RESULTS

We included 57 randomized controlled trials involving 4,304 patients aged 23.8 to 40.9 years. The female proportion ranged from 0% to 100%. The length of follow-up ranged from 6 to 144 months. Of the 13 studied femoral fixation devices, none was significantly different from the others regarding the Lysholm score, IKDC category, range of motion, and Tegner score. Bioabsorbable interference screws (standardized mean difference, 1.3; 95% credible interval, 0.0-2.5) showed higher laxity than the EndoPearl at a borderline level of statistical significance, but the difference varied substantially within multiple sensitivity analyses. Infection (2.0%) was most commonly seen with the EndoPearl, whereas the bone mulch screw had the highest incidence of effusion (5.5%) and graft rupture (5.5%). For the 9 studied tibial fixation devices, no significant difference was observed in the aforementioned efficacy measurements. Bioabsorbable interference screws with staples had the highest incidence of infection (11.1%) and effusion (15.6%), whereas graft rupture was most commonly seen with the bone plug (4.0%).

CONCLUSIONS

Graft fixation devices in ACL reconstruction share a similar efficacy profile in terms of the Lysholm score, IKDC category, range of motion, and Tegner score but not laxity. On the other hand, safety profiles seem to vary among different devices. These findings can support surgeons, alongside their experience and preference, as well as the relative cost of each device, in delivering an individualized plan for an optimal operation.

LEVEL OF EVIDENCE

Level II, meta-analysis of Level I and II studies.

Three-Dimensional Printed Porous Titanium Screw with Bioactive Surface Modification for Bone-Tendon Healing: A Rabbit Animal Model

The interference screw fixation method is used to secure a graft in the tibial tunnel during anterior cruciate ligament reconstruction surgery. However, several complications have been reported, such as biodegradable screw breakage, inflammatory or foreign body reaction, tunnel enlargement, and delayed graft healing. Using additive manufacturing (AM) technology, we developed a titanium alloy (Ti₆Al₄V) interference screw with chemically calcium phosphate surface modification technology to improve bone integration in the tibial tunnel. After chemical and heat treatment, the titanium screw formed a dense apatite layer on the metal surface in simulated body fluid. Twenty-seven New Zealand white rabbits were randomly divided into control and additive manufactured (AMD) screw groups. The long digital extensor tendon was detached and translated into a tibial plateau tunnel (diameter: 2.0 mm) and transfixed with an interference screw while the paw was in dorsiflexion. Biomechanical analyses, histological analyses, and an imaging study were performed at 1, 3, and 6 months. The biomechanical test showed that the ultimate pull-out load failure was significantly higher in the AMD screw group in all tested periods. Micro-computed tomography analyses revealed early woven bone formation in the AMD screw group at 1 and 3 months. In conclusion, AMD screws with bioactive surface modification improved bone ingrowth and enhanced biomechanical performance in a rabbit model.

Biocomposite Interference Screws in Anterior Cruciate Ligament Reconstruction: Osteoconductivity and Degradation

Purpose

To evaluate the long-term in vivo degradation of an amorphous stereoisomer combined with micro β-tricalcium phosphate poly levo (96%)/dextro (4%) lactide beta-tricalcium phosphate biocomposite interference screw.

Methods

A study approved by the institutional review board of in vivo biologic behavior of the screw was initiated in 2011 using an anterior cruciate ligament (ACL) reconstruction model. Twenty patients undergoing bone–patellar tendon–bone ACL reconstruction fixed at the femur and tibia with these biocomposite screws followed at least 36 months were evaluated by physical, radiographic, and computed tomography (CT) evaluations. Lysholm, Tegner, Cincinnati, and International Knee Documentation Committee scores were obtained. CT Hounsfield unit (HU) data were obtained at the femoral and tibial screw and other bone sites. An ossification quality score (range 1-4) was used to determine osteoconductivity at the screw sites.

Results

In total, 11 male and 9 female patients evaluated by CT scan and radiographs a mean of 41 months postsurgery (range, 37-51) showed bone plug healing to the tunnel wall and the screw replaced with calcified and nontrabecular material. Osteoconductivity was present in 34 of 40 tunnels (85%) and nearly complete or complete (type 3 or 4 ossification) in 10 of 40 (25%). Mean screw-site densities (femoral 239 HU; tibial 290 HU) were consistent with cancellous bone density. One positive pivot-shift test was found. Lysholm, Cincinnati, Tegner, and International Knee Documentation Committee activity scores improved from 46.9, 43.5, 1.9, and 1.7 preoperatively to 92, 90.2, 6.0, and 3.2 at follow-up, respectively. The average postoperative Single Assessment Numeric Evaluation score was 86 and mean KT-1000 arthrometer difference was 0.32 mm.

Conclusions

The micro β-tricalcium phosphate poly levo (96%)/dextro (4%) lactide beta-tricalcium phosphate interference screw was replaced by calcified, nontrabecular material a mean of 42 months after implantation in a bone–patellar tendon–bone ACL reconstruction model. Osteoconductivity was confirmed.

Level of Evidence

Level IV (therapeutic case series).

Bioabsorbable Versus Titanium Screws in Anterior Cruciate Ligament Reconstruction Using Hamstring Autograft: A Prospective, Randomized Controlled Trial With 13-Year Follow-up

BACKGROUND

Bioabsorbable screws for anterior cruciate ligament reconstruction (ACLR) have been a popular choice, with theoretical advantages in imaging and surgery. Titanium and poly-L-lactic acid with hydroxyapatite (PLLA-HA) screws have been compared, but with less than a decade of follow-up.

PURPOSE/HYPOTHESIS

The purpose was to compare long-term outcomes of hamstring autograft ACLR using either PLLA-HA screws or titanium screws. We hypothesized there would be no difference at 13 years in clinical scores or tunnel widening between PLLA-HA and titanium screw types, along with high-grade resorption and ossification of PLLA-HA screws.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

Forty patients undergoing ACLR were randomized to receive either a PLLA-HA screw or a titanium screw for ACL hamstring autograft fixation. Blinded evaluation was performed at 2, 5, and 13 years using the International Knee Documentation Committee score, Lysholm knee score, and KT-1000 arthrometer. Magnetic resonance imaging (MRI) was performed at 2 or 5 years and 13 years to evaluate tunnel volumes, ossification around the screw, graft integration, and cyst formation. Computed tomography (CT) of patients with PLLA-HA was performed at 13 years to evaluate tunnel volumes and intratunnel ossification.

RESULTS

No differences were seen in clinical outcomes at 2, 5, or 13 years between the 2 groups. At 13 years, tibial tunnel volumes were smaller for the PLLA-HA group (2.17 cm³) compared with the titanium group (3.33 cm³; P = .004). By 13 years, the PLLA-HA group had complete or nearly complete resorption on MRI or CT scan.

CONCLUSION

Equivalent clinical results were found between PLLA-HA and titanium groups at 2, 5, and 13 years. Although PLLA-HA screws had complete or nearly complete resorption by 13 years, tunnel volumes remained largely unchanged, with minimal ossification.

Complications of Bioabsorbable Tibial Interference Screws After Anterior Cruciate Ligament Reconstruction in Pediatric and Adolescent Athletes

Background:

Interference screw fixation using bioabsorbable implants has become the most common form of tibial-sided graft fixation in anterior cruciate ligament reconstruction (ACLR). Complications related to implant use in the pediatric and adolescent population have not been well studied.

Purpose/Hypothesis:

The purpose of this study was to retrospectively analyze the complications associated with tibial bioabsorbable interference screw use in adolescents after ACLR. We hypothesized that complication rates would be low (<5%) and that different screw types would have similar complication rates and clinical outcomes.

Study Design:

Case series; Level of evidence, 4.

Methods:

Included in this study were patients aged ≤18 years who underwent ACLR with a bioabsorbable tibial interference screw between 2000 and 2011 at a single institution. The subpopulation with screw-related symptoms or complications were identified through chart review. The following 2 outcomes were considered: screw-related symptoms and secondary surgery related to the screw. Multivariable logistic regression was used for adjusted analysis of any screw-related problem.

Results:

There were 925 ACLR procedures in 858 patients (mean age, 15.7 years; range, 10-18 years) who met inclusion criteria. The median follow-up period was 32.0 months. Of the 925 knees, 89 (9.6%) developed a screw-related problem. In 44 (4.8%) cases, no surgery was required; in 45 (4.9%) cases, surgery for a screw-related problem occurred at a median of 24 months postoperatively. The most common surgical indication was pain at the tibial screw site (42/45, 93%), followed by intra-articular screw issues (3/45, 7%). In adjusted analysis, ACLR procedure performed by a “low-volume” ACL surgeon was the only significant predictor identified. After screw removal surgery, 25 of 27 (93%) patients with at least 12 months of follow-up had complete resolution of screw site symptoms, 18 of 23 (78%) evaluable patients returned to sports, while 8 of 27 (30%) patients underwent additional surgeries, 7 of which were unrelated to the screw procedure.

Conclusion:

The rate of clinical sequelae from bioabsorbable tibial interference screws was surprisingly high, with symptoms arising after approximately 1 of 10 ACLRs in adolescents. Reoperation for these symptoms was performed in approximately 5% of the knees in the study, at a median 2 years postoperatively. Most patients were able to return to sports after screw removal surgery.

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.

Femoral-tibial fixation affects risk of revision and reoperation after anterior cruciate ligament reconstruction using hamstring autograft

PURPOSE

Newer fixation devices for hamstring (HS) autograft have been introduced over the years, yet the impact of these devices on ACLR outcomes requiring surgical intervention remains unclear. We sought to evaluate the risk of aseptic revision and reoperation after HS autograft ACLR according to various femoral-tibial fixation methods.

METHODS

A cohort study was conducted using the Kaiser Permanente ACLR Registry. Primary isolated unilateral ACLR patients who received a HS autograft were identified (2007-2014). Fixation devices were categorized as crosspin, interference, suspensory, or combination (defined as more than one fixation device used on the same side) and femoral-tibial fixation groups used in more than 500 ACLR were evaluated. Cox proportional-hazard regression was used to evaluate the association between femoral-tibial fixation method and outcomes while adjusting for confounders.

RESULTS

6,593 primary ACLR were included. Four femoral-tibial fixation groups had more than 500 ACLR: suspensory-interference (n = 3004, 45.6%), interference-interference (n = 1659, 25.2%), suspensory-combination (n = 1103, 16.7%), and crosspin-interference (n = 827, 12.5%). After adjusting for covariates, revision risk was lower for crosspin-interference (HR = 0.43, 95% CI 0.29-0.65) and interference-interference (HR = 0.63, 95% CI 0.41-0.95) methods compared to the suspensory-interference. In contrast, reoperation risk was higher for crosspin-interference (HR = 2.13, 95% CI 1.37-3.32) and suspensory-combination (HR = 1.68, 95% CI 1.04-2.69) methods compared to suspensory-interference.

CONCLUSIONS

ACLR using HS autograft appears to have the lowest risk of aseptic revision when crosspin or interference fixation is used on the femoral side and is coupled with an interference screw on the tibial side.

LEVEL OF EVIDENCE

III.

Does thread shape affect the fixation strength of the bioabsorbable interference screws for anterior cruciate ligament reconstructions? A biomechanical study

Background

The purpose of this study was to compare the biomechanical behaviour of two bioabsorbable interference screws with different geometries.

Methods

Two different pitch (2.5 and 5 mm) bioabsorbable interference screws, both 9 × 30 mm, were tested. Tests were performed with forty bovine digital extensor tendons and skeletally mature porcine tibiae. Two protocols of cyclic tests at 1 Hz were performed: 1000 cycles from 50 to 250 N, and 5000 cycles from 100 to 300 N (n = 10 for each type of test and screw). After the cyclic loading, a final ramp displacement until failure at 0.5 mm/s was applied.

Results

The stiffness after the cyclic phase of the tests was not statistically different between the two screws (1000th cycle: 2.5 mm pitch 280.3 ± 56.4 N/mm, 5 mm pitch 275.2 ± 65.0 N/mm, P = .965; 5000th cycle: 2.5 mm pitch 281.3 ± 66.4 N/mm, 5 mm pitch 286.1 ± 79.4 N/mm, P = .814). The yield load was not significantly different between the screws (1000 cycle tests: 2.5 mm pitch 482.2 ± 120.2 N, 5 mm pitch 495.9 ± 131.3 N, P = .508; 5000 cycle tests: 2.5 mm pitch 476.4 ± 65.3 N, 5 mm pitch 494.3 ± 39.2 N, P = .391). No correlation was found between the insertion torque and yield load (1000 cycle tests, R² = 0.013; 5000 cycle tests, R² = 0.006).

Conclusions

The pitch of bioabsorbable interference screws does not seem to affect fixation strength. Also, the authors recommend not to use insertion torque alone to estimate the fixation strength.

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.

Implantable composite devices of unsintered hydroxyapatite and poly-l-lactide with dispersive marbling morphology to enhance in vivo bioactivity and bioresorbability

A bone fixation device made of unsintered hydroxyapatite (u-HA) particles uniformly dispersed in a poly-l-lactide matrix and reinforced by compressive forging (uniformly dispersed composite; UDC) has been clinically applied in several fields. However, it has reported some foreign body reactions over a long implantation period due to its slow bioresorbability. To further enhance its bioresorbability, we developed devices comprising a fibrous assembly of poly-l-lactide only three-dimensionally intertwined with particulate hydroxyapatite/poly-l-lactide composite. The biological behavior of the proposed material, provisionally referred to as complementarily reinforced composite (CRC), was compared with that of UDC in vivo. Cylindrical rods of UDC and CRC with 3.2-mm diameters were inserted bilaterally into the intramedullary distal femurs of 32 male Japanese white rabbits. Eight rabbits were euthanized at four, eight, 12, and 25 weeks after insertion. There were no significant differences between the mechanical properties of UDC and CRC over time. However, the results from histological analyses, surface characterization, radiological analyses, and push-out mechanical testing substantiated CRC's superior affinity to bone and enhanced bioactivity and bioresorbability in comparison with UDC. These characteristics were attributed to the dispersive marbling morphology produced by the CRC material's successive connectivity of u-HA particles throughout the PLLA matrix, which would accelerate PLLA hydrolysis degradation by H₂O intrusion and enhance the bioactivity of u-HA particles exposed on the interface soon after implantation.

Does the graft-tunnel friction influence knee joint kinematics and biomechanics after anterior cruciate ligament reconstruction? A finite element study

Graft tissues within bone tunnels remain mobile for a long time after anterior cruciate ligament (ACL) reconstruction. However, whether the graft-tunnel friction affects the finite element (FE) simulation of the ACL reconstruction is still unclear. Four friction coefficients (from 0 to 0.3) were simulated in the ACL-reconstructed joint model as well as two loading levels of anterior tibial drawer. The graft-tunnel friction did not affect joint kinematics and the maximal principal strain of the graft. By contrast, both the relative graft-tunnel motion and equivalent strain for the bone tunnels were altered, which corresponded to different processes of graft-tunnel integration and bone remodeling, respectively. It implies that the graft-tunnel friction should be defined properly for studying the graft-tunnel integration or bone remodeling after ACL reconstruction using numerical simulation.

The Influence of Graft Fixation Methods on Revision Rates After Primary Anterior Cruciate Ligament Reconstruction

BACKGROUND

The method of graft fixation in primary anterior cruciate ligament (ACL) reconstruction is important for initial stability of the graft. Poor graft fixation can result in failure of the reconstruction. The effect of ACL graft fixation principles and fixation implant combinations on the risk of revision after ACL reconstruction is not well understood.

PURPOSE

The study aimed to compare the risk of revision among 4 categories of femoral fixation divided by their principle of function using a hamstring tendon (HT) graft only. Furthermore, this study aimed to compare the risk of revision among the most frequently used combinations (tibia and femur) of graft fixation implants in a national patient cohort.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

The authors divided the femoral fixation constructs into 4 categories by their principle of function: cortical suspensory fixation, adjustable cortical suspensory fixation, intratunnel transfixation, and interference screw (aperture) fixation. Data on revision rates and graft fixation methods were extracted from the Danish ACL Reconstruction Registry. The study included patients who underwent primary ACL reconstruction with either an HT or patellar tendon (PT) graft and were followed up at 2 to 10 years. Revision rates at 2-year and full follow-up were extracted for the category of graft fixation in the femur as well as for the most common implant combinations (those involving >175 patients). Patients with infrequently used fixation devices were excluded from this analysis. The HT group included 14 frequently used combinations (n > 175), and there were 2 such combinations in the PT group. A total of 13,200 ACL reconstructions were included in the study. For ACL reconstruction with an HT graft, there were 4680 with cortical suspensory fixation, 577 with adjustable cortical suspensory fixation, 5921 with intratunnel transfixation, and 617 with interference screw fixation. There were 1405 ACL reconstructions with a PT graft.

RESULTS

When only comparing primary ACL reconstructions using an HT graft, cortical suspensory fixation exhibited a significantly higher risk of revision at 2-year follow-up than the other categories of femoral fixation (hazard ratio [HR], 1.24 [95% CI, 1.07-1.44]; P < .05). Intratunnel transfixation exhibited a significantly lower risk of revision (HR, 0.83 [95% CI, 0.73-0.94]; P < .05). Comparing the most frequently used femoral/tibial fixation implant combinations with the mean risk of revision, Endobutton/Intrafix and Endobutton/Biosure PEEK for HT grafts exhibited an increased risk of revision, with an relative risk (RR) of 1.36 (95% CI, 1.03-1.81; P < .05) and 1.55 (95% CI, 1.15-2.09; P < .05), respectively. The Atlantech metal screw/metal screw and Softsilk/Softsilk combinations (both for PT grafts) exhibited a significantly decreased risk of revision, with an RR of 0.41 (95% CI, 0.18-0.91; P < .05) and 0.36 (95% CI, 0.15-0.87; P < .05), respectively.

CONCLUSION

When comparing ACL graft fixation methods in the 4 categories using an HT graft, cortical suspensory fixation was found to have a significantly increased risk of revision, while intratunnel transfixation exhibited a lower risk of revision. Both Endobutton/Intrafix and Endobutton/Biosure PEEK implant combinations exhibited a significantly higher risk of revision. For PT grafts, Atlantech metal screw/metal screw and Softsilk/Softsilk exhibited a significantly lower risk of revision.

Radiographic Tibial Tunnel Assessment After Anterior Cruciate Ligament Reconstruction Using Hamstring Tendon Autografts and Biocomposite Screws: A Prospective Study With 5-Year Follow-Up

PURPOSE

To radiographically assess the tibial tunnel up to 5 years after anterior cruciate ligament (ACL) reconstruction using hamstring tendon autografts and biocomposite interference screws.

METHODS

Fifty-one patients underwent anatomic single-bundle ACL reconstruction with metal interference screws in the femur and biocomposite interference screws in the tibia. Standardized digital radiographs with weight-bearing anteroposterior and lateral views of the index knee were taken in the early postoperative period and at 2 and 5 years postoperatively. Of 51 patients, 40 (78%) underwent radiographic assessment on all 3 occasions. Subjective and objective clinical assessments were obtained preoperatively and at the 5-year follow-up.

RESULTS

The mean follow-up period was 65 months (±3.9 months), with a minimum of 59 months. The width of the tibial tunnel on the anteroposterior view was 9.4 mm (±1.4 mm) in the early postoperative period and 9.2 mm (±1.5 mm) at 5 years (P = .64). The corresponding widths on the lateral view were 9.6 mm (±1.5 mm) in the early postoperative period and 9.0 mm (±1.4 mm) at 5 years (P = .014). In 33 of 40 patients (83%) the width of the tibial tunnel had decreased on 1 or both views at 5 years compared with the early postoperative period. The study group had improved significantly at the 5-year follow-up compared with the preoperative assessments in terms of the KT-1000 arthrometer laxity tests (MEDmetric, San Diego, CA), pivot-shift test, Tegner activity scale, and Lysholm knee score (P < .001). No correlations were found between the tunnel widths and the KT-1000 assessment.

CONCLUSIONS

In 83% of patients, the width of the tibial tunnel had decreased on 1 or both radiographic views at 5 years compared with the early postoperative period after ACL reconstruction using biocomposite interference screws.

LEVEL OF EVIDENCE

Level II, prospective study.

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.

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.

Outcome of Patellar Tendon Versus 4-Strand Hamstring Tendon Autografts for Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis of Prospective Randomized Trials

PURPOSE

To compare clinical outcomes of anterior cruciate ligament (ACL) reconstruction and investigate whether the clinical results of 4-strand hamstring tendon (HT) reconstruction are still inferior to that of the patellar tendon (PT).

METHODS

We performed a comprehensive systematic review and meta-analysis of the English literature on PubMed, Scopus, Web of Science, and the Cochrane register for papers that compared clinical outcomes of PT versus HT for ACL reconstruction. Outcome measures analyzed included rate of rerupture, KT-1000, International Knee Documentation Committee grade, Lachman, pivot shift, Lysholm score, Tegner Activity Scale, anterior knee pain, and discomfort on kneeling.

RESULTS

We included 19 studies from an initial 1,168 abstracts for the systematic review, and, eventually, 19 studies were included in the meta-analysis. The study population consisted of a total of 1784 patients. The average follow-up duration was 58.8 months. We found significant differences in favor of the HT technique in the domains of anterior knee pain, kneeling pain, and restriction in the range of active extension ("extension deficit"). We found no differences between the PT and HT technique in terms of rerupture rate. There were no clinically significant differences for the outcomes of Lysholm score and Tegner Activity Scale as well as the KT-1000 side-to-side at maximum manual force.

CONCLUSIONS

Contemporary 4-strand HT ACL reconstruction is comparable with the PT technique in terms of clinical stability and postoperative functional status across most parameters studied. The HT technique carries lower risk of postoperative complications such as anterior knee pain, kneeling discomfort, and extension deficit. Primary ACL reconstruction using the 4-strand HT technique achieves clinical results that are comparable with the PT technique with significantly less postoperative complications.

LEVEL OF EVIDENCE

Level I, systemic review and meta-analysis of Level I studies.

Femoral Aperture Fixation Improves Anterior Cruciate Ligament Graft Function When Added to Cortical Suspensory Fixation: An In Vivo Computer Navigation Study

Background:

Recommendations for bone tunnel placement during anterior cruciate ligament (ACL) reconstruction have become more precise. However, these recommendations differ neither with the choice of graft nor with the method of fixation used. The influence of the method of femoral fixation used on the biomechanical function of a soft tissue ACL graft remains unknown.

Hypothesis:

Our null hypothesis was that adding femoral aperture fixation to femoral cortical fixation, using the same bone tunnels, will not alter the control of anterior translation (AT) and internal rotation (IR) during ACL reconstruction using a hamstring graft.

Study Design:

Controlled laboratory study.

Methods:

A total of 22 patients with an acute isolated ACL rupture underwent reconstruction using a single-bundle autologous hamstring graft. Computer navigation was used intraoperatively to plot the AT and IR during the pivot-shift test before reconstruction, after ACL reconstruction using cortical suspensory fixation, and after the addition of femoral aperture fixation. Statistical analysis (analysis of variance) was used to compare the AT and IR during the pivot shift at each stage in the procedure.

Results:

Before ACL reconstruction, the mean (±SD) AT was 14.2 ± 7.3 mm and mean IR was 17.2° ± 5.5°. After reconstruction using femoral cortical suspension, these figures were significantly reduced to 6.2 ± 3.5 mm and 12.5° ± 3.20°, respectively (P < .001). The addition of the aperture fixation was associated with a further significant reduction to 4.6 ± 3.2 mm and 10.4° ± 2.7°, respectively (P < .001).

Conclusion:

The addition of femoral aperture fixation to suspensory fixation results in a significant reduction in both the AT and IR that occurs during the pivot-shift assessment immediately after ACL reconstruction using autologous hamstring graft.

Clinical Relevance:

The most precise positioning of bone tunnels during soft tissue ACL reconstruction needs to take into consideration the type of fixation being used.

Functional regeneration of ligament-bone interface using a triphasic silk-based graft

The biodegradable silk-based scaffold with unique mechanical property and biocompatibility represents a favorable ligamentous graft for tissue-engineering anterior cruciate ligament (ACL) reconstruction. However, the low efficiency of ligament-bone interface restoration barriers the isotropic silk graft to common ACL therapeutics. To enhance the regeneration of the silk-mediated interface, we developed a specialized stratification approach implementing a sequential modification on isotropic silk to constitute a triphasic silk-based graft in which three regions respectively referring to ligament, cartilage and bone layers of interface were divided, followed by respective biomaterial coating. Furthermore, three types of cells including bone marrow mesenchymal stem cells (BMSCs), chondrocytes and osteoblasts were respectively seeded on the ligament, cartilage and bone region of the triphasic silk graft, and the cell/scaffold complex was rolled up as a multilayered graft mimicking the stratified structure of native ligament-bone interface. In vitro, the trilineage cells loaded on the triphasic silk scaffold revealed a high proliferative capacity as well as enhanced differentiation ability into their corresponding cell lineage. 24 weeks postoperatively after the construct was implanted to repair the ACL defect in rabbit model, the silk-based ligamentous graft exhibited the enhancement of osseointegration detected by a robust pullout force and formation of three-layered structure along with conspicuously corresponding matrix deposition via micro-CT and histological analysis. These findings potentially broaden the application of silk-based ligamentous graft for ACL reconstruction and further large animal study.

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.