Bioabsorbable polyglyconate interference screw fixation in anterior cruciate ligament reconstruction: a prospective computed tomography-controlled 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.

Fiber-reinforced fixation implant for proximal interphalangeal joint arthrodesis shows advanced implant bio-integration at 2-year follow-up

BACKGROUND

A bio-integrative fiber-reinforced implant (OSSIOfiber® Hammertoe Fixation Implant, OSSIO Ltd., Caesarea, Israel) for proximal interphalangeal joint (PIPJ) correction-arthrodesis showed partial bio-integration at 1-year follow-up (1FU) in a previous study. The study was prolonged to assess the bio-integration at 2-year-follow-up (2FU).

METHODS

Twenty-four patients with proximal interphalangeal joint (PIPJ) correction-arthrodesis using the fiber-reinforced implant and analysed at 1FU, completed 2FU. Follow-up included clinical examination, patient reported outcomes, radiographs, MRI and bio-integration scoring. Results were compared between the 1FU and 2FU (paired t-test).

RESULTS

Radiographs confirmed fusion in 96 % (n = 23) at 2FU (1FU, 92 % (n = 22)). Implant was no longer visible in 21 % (n = 5), partially visible in 33 % (n = 8), and fully visible in 46 % (n = 11)(1FU, fully visible 100 % (n = 24)). The border between implant and surrounding bone was scored not visible in 88 % (n = 21) and partially visible in 12 % (n = 3) (1FU, border partially visible 100 % (n = 24)). There were no cyst formation or fluid accumulation findings 1FU/2FU. Mild bone edema was detected in 4 % (n = 1) (1FU, 29 % (n = 7)). None of the edema findings were considered as adverse implant related. The mean bio-integration score was 9.71 ± 0.69 at 2FU (1FU, 7.71 ± 0.46). The parameters of border between implant and bone and bone edema further improved at the 2FU compared to the 1FU, total bio-integration score was also higher at 2FU than 1FU (each p < 0.05).

CONCLUSIONS

This study demonstrates 96 % PIPJ fusion rate and increased bio-integration from 1FU to 2FU, reaching advanced bio-integration of the fiber-reinforced implant at 2FU.

Fiber-reinforced fixation implant for proximal interphalangeal joint arthrodesis shows implant bio-integration at 1-year follow-up

BACKGROUND

A new bio-integrative fiber-reinforced implant (OSSIOfiber® Hammertoe Fixation Implant, OSSIO Ltd., Caesarea, Israel) was developed for proximal interphalangeal joint (PIPJ) correction-arthrodesis. The main purpose of this clinical study was to assess implant bio-integration at 1-year follow-up.

METHODS

Twenty-four patients, previously treated for a Hammertoe deformity using the bio-integrative, fiber-reinforced implant, were enrolled in this follow-up study. One-year follow-up included clinical examination, patient reported outcomes, radiographs, Magnetic Resonance Imaging (MRI) and bio-integration scoring.

RESULTS

Proximal interphalangeal joint (PIPJ) radiographic fusion rate was 92% (n = 22). MRI was analyzed for 24 (100%) patients. In 100% of patients (n = 24), the border between implant and surrounding tissue was scored as partially visible. There were no cyst formation or fluid accumulation findings. Mild bone edema was detected in 29% (n = 7) and is attributed to the chronic distribution of forces due to chronic abnormal gait and pasture. None of the edema findings were considered as adverse implant-related finding. The mean bio-integration score was 7.71 ± 0.46.

CONCLUSIONS

This study demonstrates safe bio-integration of the newly developed fiber-reinforced implant at 1-year follow-up without negative side effects.

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.

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.

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.

Timeline for Maximal Subjective Outcome Improvement After Anterior Cruciate Ligament Reconstruction

BACKGROUND

Anterior cruciate ligament (ACL) tears are one of the most common traumatic knee injuries experienced by athletes. Return to sport is considered the pinnacle endpoint among patients receiving ACL reconstruction. However, at the time of return to sport, patients may not be participating at their previous levels of function, as defined by clinical metrics.

PURPOSE

To establish when patients perceive maximal subjective medical improvement according to patient-reported outcome measures (PROMs).

STUDY DESIGN

Systematic review.

METHODS

A systematic review of the PubMed database was conducted to identify studies that reported sequential PROMs up to a minimum of 2 years after ACL reconstruction. Pooled analysis was conducted for PROMs at follow-up points of 3 months, 6 months, 1 year, and 2 years. Clinically significant improvement was determined between pairs of intervals with the minimal clinically important difference.

RESULTS

This review contains 30 studies including 2253 patients who underwent ACL reconstruction. Clinically significant improvement in the KOOS (Knee injury and Osteoarthritis Outcome Score) was seen up to 1 year after ACL reconstruction, but no clinical significance was noted from 1 to 2 years. Clinically significant improvement in the IKDC (International Knee Documentation Committee) and Lysholm questionnaires was seen up to 6 months postoperatively, but no clinical significance was noted beyond that.

CONCLUSION

After ACL reconstruction, maximal subjective medical improvement is established 1 year postoperatively, with no further perceived clinical improvement beyond this time point according to current PROMs. The KOOS may be a more responsive metric to subjective improvements in this patient cohort than other patient-reported outcomes, such as the IKDC and Lysholm.

CLINICAL RELEVANCE

After ACL reconstruction, patients perceive interval subjective improvements until 1 year postoperatively.

Bone-to-bone integrations were complete within 5 months after anatomical rectangular tunnel anterior cruciate ligament reconstruction using a bone-patellar tendon-bone graft

PURPOSE

Anterior cruciate ligament (ACL) reconstruction using a bone-patellar tendon-bone (BTB) graft is known to provide secure fixation due to the direct bone-to-bone integration of the bone plug and bone tunnel. It is important to know the time required for bone integration when designing the postoperative rehabilitation protocol or deciding when the patient can return to competition-level activity, especially if the patient is an athlete. However, because reports are scarce, the period necessary for bone-to-bone integration after ACL reconstruction using a BTB graft remains unclear. The purpose of this study was to clarify this issue. It was hypothesised that ACL reconstruction using a BTB graft via an anatomical rectangular tunnel would help in the integration between bone plugs and bone tunnels on both the femoral and tibial sides after at least 6 months, at which point basic exercises similar to pre-injury sporting activity levels can be resumed.

METHODS

This study included 40 knees treated with ACL reconstruction using a BTB graft via anatomical rectangular tunnel reconstruction between 2013 and 2014 in a single institute. The integration between bone plugs and bone tunnels was evaluated using multi-slice tomosynthesis, which is a technique for producing slice images using conventional radiographic systems, at 1, 3, and 5 months postoperatively. All procedures were performed by two experienced surgeons. Bone integration was evaluated by two orthopaedic doctors.

RESULTS

The rates of integration of the bone plug and femoral bone tunnel on tomosynthesis at 1, 3, and 5 months postoperatively were 0, 55, and 100%, respectively. On the tibial side, the corresponding rates were 0, 75, and 100%, respectively. The rate of integration on the tibial side was significantly higher than that on the femoral side at 3 months postoperatively (p = 0.031).

CONCLUSIONS

Bone-to-bone integration on the femoral and tibial sides was complete within 5 months after surgery in all cases. Since the time required for bone integration is important in designing the postoperative rehabilitation approach, these results will serve as a useful guideline for planning rehabilitation protocols.

LEVEL OF EVIDENCE

IV.

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.

Biomechanical characteristics of bioabsorbable magnesium-based (MgYREZr-alloy) interference screws with different threads

PURPOSE

Degradable magnesium implants have received increasing interest in recent years. In anterior cruciate ligament reconstruction surgery, the well-known osteoconductive effects of biodegradable magnesium alloys may be useful. The aim of this study was to examine whether interference screws made of MgYREZr have comparable biomechanical properties to commonly used biodegradable screws and whether a different thread on the magnesium screw has an influence on the fixation strength.

METHODS

Five magnesium (MgYREZr-alloy) screws were tested per group. Three different groups with variable thread designs (Designs 1, 2, and 3) were produced and compared with the commercially available bioabsorbable Bioacryl rapid polylactic-co-glycolic acid screw Milagro^®. In vitro testing was performed in synthetic bone using artificial ligament fixed by an interference screw. The constructs were pretensioned with a constant load of 60 N for 30 s followed by 500 cycles between 60 N and 250 N at 1 Hz. Construct displacements between the 1st and 20th and the 21st and 500th cycles were recorded. After a 30 s break, a maximum load to failure test was performed at 1 mm/s measuring the maximum pull-out force.

RESULTS

The maximum loads to failure of all three types of magnesium interference screws (Design 1: 1,092 ± 133.7 N; Design 2: 1,014 ± 103.3 N; Design 3: 1,001 ± 124 N) were significantly larger than that of the bioabsorbable Milagro^® interference screw (786.8 ± 62.5 N) (p < 0.05). However, the greatest maximum load was found with magnesium screw Design 1. Except for a significant difference between Designs 1 and 2, there were no further significant differences among the four groups in displacement after the 20th cycle.

CONCLUSIONS

Biomechanical testing showed higher pull-out forces for magnesium compared with a commercial polymer screw. Hence, they suggest better stability and are a potential alternative. The thread geometry does not significantly influence the stability provided by the magnesium implants. This study shows the first promising results of a degradable material, which may be a clinical alternative in the future.

Magnetic resonance imaging after anterior cruciate ligament reconstruction: A practical guide

Anterior cruciate ligament (ACL) reconstruction is one of the most common orthopedic procedures performed worldwide. In this regard, magnetic resonance imaging (MRI) represents a useful pre-operative tool to confirm a disruption of the ACL and to assess for potential associated injuries. However, MRI is also valuable post-operatively, as it is able to identify, in a non-invasive way, a number of aspects and situations that could suggest potential problems to clinicians. Graft signal and integrity, correct tunnel placement, tunnel widening, and problems with fixation devices or the donor site could all compromise the surgical outcomes and potentially predict the failure of the ACL reconstruction. Furthermore, several anatomical features of the knee could be associated to worst outcomes or higher risk of failure. This review provides a practical guide for the clinician to evaluate the post-surgical ACL through MRI, and to analyze all the parameters and features directly or indirectly related to ACL reconstruction, in order to assess for normal or pathologic conditions.

Synthesis of Pendent Carbonate Ester Groups onto Aliphatic Polycarbonates

The reactions of mono- -bromo ethyl carbonate with carboxylic acids, amines, and alcohols were investigated as a model tool for the preparation of novel aliphatic polycarbonate esters. The formation of the corresponding carbonate ester, carbamate, and carbonate derivatives, showed that of the three types of groups chosen to react with -bromo ethyl carbonate, only the carboxylate anions displaced the bromo group to form the corresponding -carbonate ester bond (R—COO—CH(CH3)—O—CO—CH2—CH3). This approach was applied to the synthesis of pendent carbonate ester groups onto aliphatic polycarbonates. The synthetic pathway involved partial bromination of polytrimethylene carbonate (PTMC) to Br-PTMC, which was then reacted with benzoic acid or acetic acid to form the corresponding benzoate and acetate pendent polycarbonate, respectively. The hydrolysis of Br-PTMC and its derivatives as possible biodegradable polymers were investigated. The benzoate group was more susceptible to hydrolysis than the carbonate group hence degradation of the ester catalyzed the hydrolysis of the polymer and improved its biodegradability. The decrease in molecular weight, the release profile for benzoic acid from the grafted polymer and the degradation of Br-PTMC, ACPTMC and PTMC, in terms of the change in pH, were evaluated.

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.

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

BACKGROUND

Longer-term results of bioabsorbable screws for anterior cruciate ligament reconstruction (ACLR) have been reported, but results are specific to the exact screw material and design. Titanium and poly-L-lactic acid with hydroxyapatite (PLLA-HA) screw outcomes have been compared only to 2 years.

PURPOSE/HYPOTHESIS

The purpose of this study was to compare the clinical and radiologic outcomes of the PLLA-HA screw versus titanium screw for hamstring tendon ACLR over a 5-year follow-up period. The hypothesis was that there are no differences in clinical scores or tunnel widening between the PLLA-HA and the titanium screws and that the PLLA-HA screw as seen on magnetic resonance imaging (MRI) should show high-grade resorption and ossification response over 5 years.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

METHODS

A total of 40 patients undergoing ACLR were randomized to receive either a PLLA-HA screw (PLLA-HA group) or a titanium screw (titanium group) for ACL fixation. Blinded evaluation was performed at 2 and 5 years with the International Knee Documentation Committee and Lysholm knee score, KT-1000 arthrometer, single-legged hop test, and MRI to evaluate tunnel and screw volumes, periscrew ossification, graft integration, and cyst formation.

RESULTS

There was no difference in any clinical outcome measure at 2- or 5-year follow-up between the 2 groups. At 2 years, the femoral tunnel in the PLLA-HA group was smaller than that in the titanium group (P = .02); at 5 years, there was no difference. At 2 years, the femoral PLLA-HA screw was a mean 76% of its original volume, and by 5 years, it was 36%. At 2 years, the tibial PLLA-HA screw mean volume was 68% of its original volume, and by 5 years, it was 46%. At 5 years in the PLLA-HA group, 88% of femoral tunnels and 56% of tibial tunnels demonstrated a significant ossification response. There was no increase in cyst formation in the PLLA-HA group and no screw breakages.

CONCLUSION

There were equivalent clinical results between the PLLA-HA and titanium groups at 2- and 5-year follow-ups. The PLLA-HA screw was not associated with increased tunnel widening or cyst formation when compared with the titanium screw. The PLLA-HA screw demonstrated progressive screw resorption and gradual but incomplete ossification over 5 years.

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.

Tibial and Femoral Tunnel Changes After ACL Reconstruction: A Prospective 2-Year Longitudinal MRI Study

BACKGROUND

Tunnel widening after anterior cruciate ligament reconstruction (ACL-R) is a well-accepted and frequent phenomenon, yet little is known regarding its origin or natural history.

PURPOSE

To prospectively evaluate the cross-sectional area (CSA) changes in tibial and femoral bone tunnels after ACL-R with serial MRI.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Patients underwent arthroscopic ACL-R with the same surgeon, surgical technique, and rehabilitation protocol. Each patient underwent preoperative dual-energy x-ray absorptiometry and clinical evaluation, as well as postoperative time zero MRI followed by subsequent MRI and clinical examination, including functional and subjective outcome tests, at 6, 12, 24, 52, and 104 weeks. Tibial and femoral tunnel CSA was measured on each MRI at tunnel aperture (ttA and ftA), midsection (ttM and ftM), and exit (ttE and ftE). Logistic regression modeling was used to examine the predictive value of demographic data and preoperative bone quality (as measured by dual-energy x-ray absorptiometry) on functional outcome scores, manual and instrumented laxity measurements, and changes in tunnel area over time.

RESULTS

Eighteen patients (including 12 men), mean age 35.5±8.7 years, underwent ACL-R. There was significant tunnel expansion at ttA and ftA sites 6 weeks postoperatively (P=.024 and .0045, respectively). Expansion continued for 24 weeks, with progressive tunnel narrowing thereafter. Average ttA CSA was significantly larger than ftA CSA at all times. The ttM significantly expanded after 6 weeks (P=.06); continued expansion to week 12 was followed by 21 months of reduction in tunnel diameter. The ftM and both ttE and ftE sites decreased in CSA over the 2 years. Median Lysholm and International Knee Documentation Committee scores significantly improved at final follow-up (P=.0083 and <.0001, respectively), and patients returned to preoperative activity levels. Pivot shift significantly decreased (P<.0001). Younger age (<30 years), male sex, and delayed ACL-R (>1 year from time of injury) predicted increased tunnel widening and accelerated expansion in CSA (P<.005).

CONCLUSION

Tunnel expansion after ACL-R occurs early and primarily at the tunnel apertures. Expansion may not affect clinical outcome. Younger age, male sex, and delay from injury to ACL-R may be potential risks for enlargement.

Bioabsorbable versus metallic interference screws in anterior cruciate ligament reconstruction: a systematic review of overlapping meta-analyses

PURPOSE

Multiple meta-analyses of randomized controlled trials have been conducted to compare clinical and functional outcomes after anterior cruciate ligament (ACL) reconstruction using metallic interference screw (MIS) versus bioabsorbable interference screw (BIS) fixation, but discrepancies in their findings have prevented a consensus conclusion. The purposes of this study were (1) to conduct a systematic review of meta-analyses comparing MISs and BISs in ACL reconstruction, (2) to provide surgical treatment recommendations for ACL graft fixation based on the highest available evidence, and (3) to propose future research avenues in areas of practice lacking high-level evidence.

METHODS

The literature was systematically reviewed to identify meta-analyses comparing MISs and BISs in ACL reconstruction. Data were extracted for clinical and functional outcomes, and methodologic quality was assessed using the validated Quality of Reporting of Meta-analyses and Oxman-Guyatt systems. To determine which meta-analyses provided the current best available evidence, the Jadad decision algorithm was used.

RESULTS

One Level I and 2 Level II meta-analyses were included. None showed differences between BISs and MISs in validated outcome scores, pivot-shift testing, KT arthrometry (MEDmetric, San Diego, CA), or loss of knee motion. Subgroup analyses found no differences in clinical outcomes or knee stability across biomaterials. All meta-analyses were of high quality according to the Quality of Reporting of Meta-analyses and Oxman-Guyatt systems. Two meta-analyses were determined by the Jadad algorithm to represent the current best available evidence. Both studies showed prolonged knee effusion with BIS use, with 1 also showing an increased incidence of femoral tunnel widening and screw breakage with BIS use.

CONCLUSIONS

Whereas clinical and functional outcomes are similar with MISs and BISs, prolonged knee effusion, femoral tunnel widening, and screw breakage are more common with BIS use. Future cost-effectiveness analyses may help weigh the known advantages of BISs against their costs and adverse-event profile.

LEVEL OF EVIDENCE

Level II, systematic review of Level I and II studies.

Myth busters: an AOA symposium: AOA critical issues

One of the goals of the annual American Orthopaedic Association (AOA) meeting is to address controversy, both in leadership and clinical practice. A panel of experts in their respective fields presented the background and literature behind three "myths" in orthopaedic management and made conclusions as to their validity. First, Dr. Kocher took on the myth of prophylactic pinning on the contralateral "normal" side for a patient with a slipped capital femoral epiphysis. Second, Dr. Probe evaluated the myth that all intertrochanteric fractures are best treated with intramedullary devices. Last, Dr. Foster and Dr. Silvestri tackled the myth that autograft is always the best choice for anterior cruciate ligament (ACL) reconstruction. All three of these topics are subjects of current debate. The panel's careful examination of the available data along with their expertise in the management of these problems is presented in this thought-provoking JBJS Critical Issues article.

Degradation of poly-D-L-lactide (PDLLA) interference screws (Megafix ®)

INTRODUCTION

Interference screw fixation is a standard procedure in anterior cruciate ligament (ACL) replacement. Aim of this study was to evaluate the degradation process of Poly-D-L-lactide (PDLLA) interference screws used for tibial ACL graft fixation.

MATERIALS AND METHODS

We evaluated magnetic resonance imaging (MRI) scans of 18 patients who underwent ACL revision surgery at different time points after anatomic ACL reconstruction. At primary surgery, a tibial hybrid fixation was performed with a degradable interference (IF) screw made of PDLLA (Megafix(®)) and a button.

RESULTS

MRI revealed three different phases of degradation of the PDLLA screw. 6-8 months after surgery the IF screw was clearly visible as a well-defined structure on MRI and CT scan. After 12-16 months, the screws appeared less defined with central ingrowths' of connective tissue. In some cases only fragmented screw material was visible. At these time points, there was a slight edema surrounding the tunnel visible on MRI. After 22 months and later, the mean screw site densities were comparable with the surrounding bone density. There was no edema or signs of inflammation around the bone tunnels visible. Presence of cystic or osteolytic changes was not detected.

CONCLUSION

After 22 months, a PDLLA screw may not interfere with ACL revision surgery. Regarding the degradation process of PDLLA screws, we noted three different phases. Furthermore, the degradation process observed by MRI resembles to that described by animal studies. The PDLLA screws fully absorb and are partially replaced by bone. The degradation process in humans seems to be longer than that described in animals.

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.

Metallic or bioabsorbable interference screw for graft fixation in anterior cruciate ligament (ACL) reconstruction?

BACKGROUND

Approximately 100,000 anterior cruciate ligament (ACL) reconstructions are performed in the USA each year. Interference screw fixation is considered the standard for rigid fixation of the graft and provides higher fixation strength compared with other devices such as staples or buttons. The present study summarizes the latest evidence comparing the effectiveness of the available classes of interference screws for fixation of ACL grafts.

SOURCES

A comprehensive search of the CINAHL, PubMed, Google Scholar, Embase Biomedical databases and the Cochrane Central Registry of Controlled Trials was performed in March 2013. Twelve studies met our inclusion criteria.

AREAS OF AGREEMENT

Most studies showed no intergroup difference in terms of outcomes measured with validated clinical scores such as IKDC (International Knee Documentation Committee), Lysholm score and Tegner activity level. There was no significant difference regarding range of motion. Knee stability as evaluated with pivot shift and KT arthrometer showed a significant difference only in one study, favouring metallic interference screws. Tunnel widening is much more evident and marked patients who underwent ACL reconstruction with bioabsorbable screws, with no influence on the final clinical results achieved. Complication rates between the two screw classes were similar. The average modified Coleman methodology score was 74.67. AREAS OF UNCERTAINTY/RESEARCH NEED: The data comparing the outcomes achieved by two different materials for fixation, bioabsorbable and metallic, to be used during single-bundle ACL reconstruction, showed no significant difference in the final patient outcomes, in terms of clinical scores, clinical evaluation and imaging.

Risk factors for recurrent anterior cruciate ligament reconstruction: a population study in Ontario, Canada, with 5-year follow-up

BACKGROUND

Anterior cruciate ligament reconstruction (ACLR) is routinely performed for symptomatic instability. Although it is a common procedure, there remain differences in surgical technique. Hospital administrative records in a public health care system were used to investigate the effect of patient, provider, and surgical factors on the risk of revision ACLR.

PURPOSE

To define the rate and risk factors for ACL reoperation in Ontario, Canada, including both ipsilateral revision and contralateral primary procedures.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

All primary elective ACLR procedures performed in Ontario (July 2003 to March 2008) in patients aged 15 to 60 years were identified via physician billing and hospital databases. Revision and contralateral ACLR were sought until January 2012. Patient factors (age, sex, comorbidity, income quintile, length of index hospital admission), provider factors (surgeon volume, academic hospital status), and surgical factors (allograft vs autograft; fixation type [screw, button, staple]; concomitant operative procedures) were used as covariates in a Cox proportional hazards survivorship model to generate hazard ratios (HRs) with confidence intervals (CIs) (α = .05). Kaplan-Meier survivorship curves with ACL revision as the end point were generated.

RESULTS

A total of 12,967 ACLR procedures with a mean follow-up of 5.2 years were eligible for study using preset criteria. The revision rate was 2.6% (mean ± SD, 2.91 ± 1.71 years to revision). The rate of primary contralateral ACLR was 4.6% (mean, 2.95 ± 1.81 years). In the Cox model, younger age (15-19 years) (HR, 2.1; 95% CI, 1.5-2.9; P < .001), ACLR performed at an academic hospital (HR, 1.6; 95% CI, 1.2-2.1; P < .001), and the use of allograft (HR, 1.7; 95% CI, 1.1-2.6; P = .02) significantly increased the risk of revision ACLR. Only younger age (HR, 2.1; 95% CI, 1.6-2.7; P < .001) was associated with an increased risk of contralateral ACLR.

CONCLUSION

Contralateral ACLR was more frequent than revision ACLR in this population, while both surgical procedures were most common in patients younger than 20 years. Academic hospital status, but not surgeon volume, as well as the use of allograft also increased the risk for revision ACLR.

Migration of "bioabsorbable" screws in ACL repair. How much do we know? A systematic review

PURPOSE

Although bioabsorbable screws promise to degrade within months up to several years after implantation, often this does not happen. In fact, other problems such as screw breakage, tunnel enlargement, allergic or foreign body reactions, cyst or abscess formation, and delayed migration of "biodegradable" screws have been reported. This study aims to provide relevant basic science knowledge and recent insights concerning "biomaterials" currently used in fixation devices for anterior cruciate ligament (ACL) repair. A systematic review on the topic of screw "migration" is provided.

METHODS

A PubMed search combining all the key terms was done looking for complications related to late migration of "bioabsorbable" screws used in ACL reconstruction without inferior time limitation up to January 2012. Only clinical reports were included. Reference lists of reports were checked to detect others not identified by the original search. A pre-publication search was performed to identify the most recent relevant articles.

RESULTS

A total of ten articles referred to migration of "bioabsorbable" interference screws. Most cases reported on poly-L-lactic acid-based screws. Migration was noticed between 3 and 22 months postoperatively. It was noticed both in the tibia and the femur and with the application of several types of graft.

CONCLUSION

Migration is a possible complication of "bioabsorbable" interference screws. The information related to all clinical implications of the so-called "biodegradable screws" remains scarce and probably suffers from the phenomenon of publication bias. The complexity of possible reactions occurring in the human body is difficult to reproduce under controlled laboratory conditions.

Bio-interference screw cyst formation in anterior cruciate ligament reconstruction--10-year follow up

PURPOSE

This study used serial MRI to assess the absorption of a poly l-lactide Bioabsorbable interference screw used in the anterior cruciate ligament reconstruction with a 4-strand hamstring technique.

METHODS

A consecutive series of ten patients undergoing anterior cruciate ligament reconstruction a 4-strand hamstring technique were assessed with magnetic resonance imaging (MRI) scans at 1, 2, 4, 7 and 10 years postoperatively.

RESULTS

No resorption had occurred after 4 years in any of the patients. By 7 years screw absorption was complete in seven patients and had progressed in three. New cyst formation occurred in 3 patients between 5 and 7 years. Half the patients displayed small fluid collections within the tibial tunnels. At 10 years all screws were fully absorbed; however cyst formation was common, including the development of a new cyst in the period between 7 and 10 years in one patient. None of the patients had instability, persistent effusions, or clinically detectable adverse reactions to the screws.

CONCLUSIONS

This study has shown that poly l-lactide bioabsorbable screws take longer to resorb than initial in vitro data suggested. It is unclear whether ganglion formation within the tibial tunnel is related to screw resorption or the hamstring graft. The theoretical advantages of bioabsorbable screws must be weighed against these findings.

Early integration of a bone plug in the femoral tunnel in rectangular tunnel ACL reconstruction with a bone-patellar tendon-bone graft: a prospective computed tomography analysis

PURPOSE

The purpose of this prospective study was to evaluate how early the bone plug was integrated into the rectangular femoral tunnel after anatomical ACL reconstruction using a bone-patellar tendon-bone (BTB) graft via a rectangular tunnel (RT BTB ACL-R).

METHODS

Twenty consecutive patients who had undergone the reconstruction procedure were evaluated by CT scans at 4 and 8 weeks postoperatively. In each scan, 30 slices for multiplanar reconstruction were collected parallel to the long axis of the parallelepiped femoral tunnel and perpendicular to the tendinous plane of the bone plug. Each slice was classified as "complete," indicating no visible gap between the plug and the tunnel wall or trabecular continuity or "incomplete," showing a visible gap. Bone plug-tunnel integration was evaluated as "excellent," "good," "fair," or "poor" for >20, 11-20, 5-10, and <4 "complete" slices, respectively.

RESULTS

In this evaluation, 55% of the patients were rated as "excellent" on the first scan, and 80% were "excellent" on the second scan, showing healing over time. The CT values at the anterior interface between the bone plug and the tunnel wall were also measured on both scans. The mean changes in CT value at 8 weeks were significantly lower than those at 4 weeks.

CONCLUSION

This study shows that bone plug-femoral tunnel integration was almost complete by 8 weeks after surgery using RT BTB ACL-R.

A biomechanical evaluation of bicortical metal screw fixation versus absorbable interference screw fixation after coracoid transfer for anterior shoulder instability

PURPOSE

The purpose was to evaluate the load to failure of 2 coracoid fixation techniques after transfer of the coracoid to the anterior glenoid neck.

METHODS

Ten cadavers (mean age, 87 years; range, 74 to 96 years) underwent the Bristow conjoined tendon tenodesis technique as described by Boileau et al. (bioabsorbable interference screw fixation of a coracoid bone plug) in 1 shoulder and the Latarjet-Patte coracoid transfer popularized by Walch (fixation with 2 screws through a larger piece of the coracoid) in the opposite shoulder. The force on the conjoined tendon required to pull the coracoid off of the anterior glenoid was recorded, along with the mode of construct failure.

RESULTS

The median ultimate failure load was 110 N (range, 35 to 170 N) in the interference screw group and 202 N (range, 95 to 300 N) in the bicortical screw group (P = .002). The mode of failure of the interference screw technique was complete avulsion of the bone plug from the socket in 6 cases (60%) and fracture of the bone plug in 4 (40%). The mode of failure of the bone block technique was a vertical fracture through both screw holes in 7 cases (70%), a horizontal fracture through the distal screw hole in 2 (20%), and an intratendinous rupture of the conjoined tendon in 1 (10%).

CONCLUSIONS

Fixation of a coracoid bone block to the anterior glenoid neck with 2 bicortical metal screws is stronger than fixation of a coracoid bone plug with an absorbable interference screw.

CLINICAL RELEVANCE

These data may influence surgeons' decisions regarding coracoid fixation as well as postoperative rehabilitation after coracoid transfer.

Graft fixation alternatives in anterior cruciate ligament reconstruction

Reconstruction of the anterior cruciate ligament is a frequently performed procedure that has had outstanding results. Outcomes are dependent upon an early postoperative physical therapy program that stresses early motion. Early rehabilitation demands rigid intraoperative mechanical fixation of the graft since therapy begins before biologic incorporation of the graft in the bone tunnels. Regardless of the graft substitute chosen, many methods of fixation are available. The best fixation technique depends on several factors, including graft choice and surgeon comfort. The figures are not documented in this paper. We review current methods available for graft fixation in anterior cruciate ligament surgery.

A comparison of the results of anterior cruciate ligament reconstruction using bioabsorbable versus metal interference screws: a meta-analysis

BACKGROUND

Graft fixation during anterior cruciate ligament (ACL) reconstruction can be achieved with use of either bioabsorbable screws or metal screws. Although bioabsorbable screws and metal screws have similar fixation strengths, bioabsorbable screws eliminate the need for removal. In addition, postoperative imaging is easier to interpret when bioabsorbable screws are used. Bioabsorbable screws may be associated with an increased inflammatory response, an increased risk of screw breakage, incomplete screw absorption, or tunnel widening. We investigated the outcomes associated with the use of bioabsorbable screws as compared with metal screws for ACL reconstruction. Our hypothesis was that there is no significant difference in outcomes between these screw types for ACL reconstruction.

METHODS

We systematically searched electronic databases to identify randomized controlled trials in which bioabsorbable screws were compared with metal screws for ACL reconstruction. Therapeutic studies with a minimum twelve-month mean follow-up were considered for inclusion. Clinical outcomes (International Knee Documentation Committee [IKDC], Lysholm, Tegner activity scores), laxity testing, and reported complications were evaluated in the meta-analysis. Additionally, imaging assessment of tunnel widening was evaluated.

RESULTS

Eight studies matched the inclusion criteria. These studies comprised a total of 745 patients undergoing ACL reconstruction (including 378 patients managed with bioabsorbable screws and 367 patients managed with metal screws). No significant differences were identified between the two screw types with respect to IKDC, Lysholm, or Tegner activity scores or with respect to the results of laxity testing with arthrometry. The complication rates were also statistically similar in the two groups. The variability in imaging assessment of tunnel widening among the studies precluded meta-analysis.

CONCLUSIONS

The clinical results associated with bioabsorbable screws and metal screws are statistically similar. Laxity evaluation demonstrated no significant differences between bioabsorbable screws and metal screws. The complication rates associated with bioabsorbable screws and metal screws were also similar. The results of this meta-analysis support the hypothesis that there are no significant differences in the outcomes associated with bioabsorbable screws as compared with metal screws for ACL reconstruction.

LEVEL OF EVIDENCE

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

A prospective randomized study of ACL-reconstructions using bone-patellar tendon-bone grafts fixed with bioabsorbable or metal interference screws

INTRODUCTION

Bioabsorbable screws are, at the expense of metal screws, increasingly used as fixation device in ACL-reconstructions. The possible advantages with bioabsorbable screws are better postoperative MRI evaluations and easier revision surgery.

PURPOSE

The aim of this study was to compare the clinical outcome after ACL-reconstructions with BPTB-grafts fixed with metal interference screws or bioabsorbable screws 7 years postoperatively. The resorption of the bioabsorbable screws was also analyzed.

METHODS

Between 2000 and 2001, 41 patients with ACL deficient knees were randomized for the use of BPTB-graft fixed with either metal interference screws or bioabsorbable poly-L: -lactic acid screws. This is a 7-year follow-up with clinical examinations of both groups and, MRI of the patients with bioabsorbable screws.

RESULTS

The clinical and functional results were satisfactory in both groups. There were no significant differences between the groups in any parameter measured, except for better Pivot shift results in the bioscrew group (P = 0.04). The MRI evaluation showed degradation of the bioscrews. A residual screw tract which appeared threaded was seen in the tibia in 11 of the 16 patients. There was no sign of bony ingrowth in the previous screw site in the tibia in any of the patients.

CONCLUSION

The potential advantages of using PLLA-screws compared to metal screws are not sufficient to warrant the routine use of PLLA-screws in ACL-reconstructions.

LEVEL OF EVIDENCE

I.

Painful knee joint after ACL reconstruction using biodegradable interference screws- SPECT/CT a valuable diagnostic tool? A case report

With the presented case we strive to introduce combined single photon emission computerized tomography and conventional computer tomography (SPECT/CT) as new diagnostic imaging modality and illustrate the possible clinical value in patients after ACL reconstruction. We report the case of a painful knee due to a foreign body reaction and delayed degradation of the biodegradable interference screws after ACL reconstruction. The MRI showed an intact ACL graft, a possible tibial cyclops lesion and a patella infera. There was no increased fluid collection within the bone tunnels. The 99mTc-HDP-SPECT/CT clearly identified a highly increased tracer uptake around and within the tibial and femoral tunnels and the patellofemoral joint. On 3D-CT out of the SPECT/CT data the femoral graft attachment was shallow (50% along the Blumensaat's line) and high in the notch. At revision arthroscopy a diffuse hypertrophy of the synovium, scarring of the Hoffa fat pad and a cyclops lesion of the former ACL graft was found. The interference screws were partially degraded and under palpation and pressure a grey fluid-like substance drained into the joint. The interference screws and the ACL graft were removed and an arthrolysis performed.

In the case presented it was most likely a combination of improper graft placement, delayed degradation of the interference screws and unknown biological factors. The too shallow and high ACL graft placement might have led to roof impingement, chronic intraarticular inflammation and hence the delayed degradation of the screws.

SPECT/CT has facilitated the establishment of diagnosis, process of decision making and further treatment in patients with knee pain after ACL reconstruction. From the combination of structural (tunnel position in 3D-CT) and metabolic information (tracer uptake in SPECT/CT) the patient's cause of the pain was established.

Bioabsorbable versus metallic interference screw fixation in anterior cruciate ligament reconstruction: a meta-analysis of randomized controlled trials

PURPOSE

The aim of the study was to investigate the outcomes between bioabsorbable and metallic screw fixation in anterior cruciate ligament (ACL) reconstruction.

METHODS

Randomized controlled trials (RCTs) comparing bioabsorbable versus metallic screw fixation in single-bundle ACL reconstruction were identified systematically, and the outcomes were analyzed in terms of infection rate, knee joint effusion, Lysholm score, International Knee Documentation Committee final score, pivot-shift test, and KT-1000/-2000 arthrometer (MEDmetric, San Diego, CA) measurements. The type of grafts was ignored in the meta-analysis. Standard mean difference (SMD) or risk ratio (RR) with 95% confidence interval (CI) was calculated by a fixed-effects or random-effects model. Heterogeneity across the studies was also assessed.

RESULTS

We included 10 studies comprising 790 patients who were treated by bioabsorbable versus metallic screw fixation for single-bundle ACL reconstruction. The meta-analyzed results of these studies showed that there was no statistically significant difference between bioabsorbable and metallic screw fixation in infection rate (RR, 0.91; P = .87; 320 patients in 5 studies), KT-1000/2000 arthrometer testing (SMD, -0.01; P = .95; 438 patients in 7 studies), pivot-shift testing (RR, 1.06; P = .82; 260 patients in 4 studies), International Knee Documentation Committee final score (RR, 0.87; P = .63; 300 patients in 5 studies), and Lysholm score (SMD, 0.03; P = .89; 204 patients in 4 studies). The incidence of knee effusion was higher in the bioabsorbable screw group (RR, 2.57; P = .04; 421 patients in 4 studies).

CONCLUSIONS

There was no significant difference in measurement results of knee joint stability or knee joint function outcome between bioabsorbable and metallic interference screws. Knee joint effusion is more common after ACL reconstruction with bioabsorbable interference screw fixation than with metallic interference screw fixation. More high-methodologic quality randomized controlled trials would be helpful in further meta-analysis.

LEVEL OF EVIDENCE

Level I, meta-analysis.

Intra-articular distal femur fracture extending from an expanded femoral tunnel in an anterior cruciate ligament (ACL) reconstructed knee: a case report

Anterior cruciate ligament (ACL) reconstruction is a popular surgery with overall good results. However, postoperative fracture is a serious, albeit, rare complication. Femoral tunnel lysis may cause a stress riser effect leading to distal femur fractures after ACL reconstruction. We report a case in which a patient who underwent ACL reconstruction surgery 18 months before a low-energy twisting mechanism suffered a distal femur fracture requiring open reduction internal fixation.

Does the graft source really matter in the outcome of patients undergoing anterior cruciate ligament reconstruction? An evaluation of autograft versus allograft reconstruction results: a systematic review

BACKGROUND

Despite the large number of anterior cruciate ligament reconstructions performed each year, there remains a significant controversy regarding the effect of the graft source on the functional outcome of patients.

HYPOTHESIS

There is no difference in outcomes of autograft versus allograft anterior cruciate ligament reconstructions.

STUDY DESIGN

Systematic review.

METHODS

The authors systematically identified prospective studies (Oxford level of evidence I or II only) that included autograft patients, allograft patients, or both. Objective outcomes that were reported were meta-analyzed; this included pivot-shift results, KT-1000 arthrometer results, International Knee Documentation Committee (IKDC) scores, Lysholm Scores, graft failures, and postoperative complications. Two statistical analyses were performed. First a primary statistical analysis was performed comparing pooled autograft data (bone-patellar-tendon bone and hamstrings combined) and pooled allograft data (bone-patellar-tendon bone and hamstrings combined). To have a more comprehensive understanding of the differences between each specific graft source, a secondary analysis was performed without pooling the data; this directly compared the 4 types of graft sources that were studied.

RESULTS

Over 400 scientific manuscripts were initially reviewed; 31 manuscripts fulfilled all of the search criteria. There were very few statistically significant differences between autograft and allograft tissue. The KT-1000 arthrometer laxity testing revealed a mean of 1.4 +/- 0.2 mm (weighted mean +/- standard error of the mean) for the allograft group compared with 1.8 +/- 0.1 mm for the autograft group (t = 2.40; P <.02). However, this difference was only for the mean score; there was no statistical significance when considering KT-1000 arthrometer measurements of greater than 3 or 5 mm. The percentage of patients receiving a final IKDC score of "A" (normal knee) was statistically significant for allograft tissue (43.9% +/- 5.5%) versus autograft tissue (28.2% +/- 1.0%) reconstructions. There was no statistically significant difference between the percentages of IKDC scores of A or B for patients receiving pooled allograft (82.9% +/- 4.2%) versus pooled autograft (87.2% +/- 0.9%) anterior cruciate ligament reconstruction (t = 1.01; P > .1). The graft failure rate was 4.7 +/- 0.5 per 100 for autograft reconstructions and 8.2 +/- 2.1 per 100 allograft reconstructions; although this may represent a trend, it is not statistically significant (t = 1.49; P > .1). The complication rate was slightly higher for autograft reconstructions at 3.5 +/- 0.4 complications per 100 autograft reconstructions compared with 2.4 +/- 1.1 complications per 100 allograft reconstructions, but not significant (t = 1.41; P > .1).

CONCLUSION

After a comprehensive examination and statistical analysis of the modern literature, the authors could not identify an individual graft source that was clearly superior to the other graft sources. This led them to believe that, with currently available data, the graft source has a minimal effect on the outcome of patients undergoing anterior cruciate ligament reconstruction.

Femoral fracture following knee ligament reconstruction surgery due to an unpredictable complication of bioabsorbable screw fixation: a case report and review of literature

We report an unusual case of femoral fracture from minimal trauma, due to the rapid disappearance of a bioabsorbable interference screw used for reconstruction of the posterolateral corner of the knee. The literature on bone tunnel fractures following knee ligament reconstruction surgery is also reviewed.

Microporous pure beta-tricalcium phosphate implants for press-fit fixation of anterior cruciate ligament grafts: strength and healing in a sheep model

PURPOSE

A sheep study was conducted to test a press-fit technique using microporous pure beta-tricalcium phosphate (beta-TCP) dowels for fixation of the anterior cruciate ligament (ACL) graft.

METHODS

Microporous (5 mum) cylindrical plugs of beta-TCP (diameter, 7 mm; length, 25 mm) with interconnecting pores were used. The material featured a novel configuration of structure and surface geometry. Implants were tested by use of press-fit fixation of ACL grafts with and without bone blocks in 42 sheep over a period of 24 weeks. Biomechanical, radiologic, histologic, and immunohistochemical evaluations were performed.

RESULTS

In load-to-failure tests at 6, 12, and 24 weeks after surgery, the intra-articular graft always failed, not the fixation. Grafts showed bony fixation in the tunnel at 6 weeks and primary healing at the junction of the tunnel and joint after 24 weeks. Tricalcium phosphate was resorbed and simultaneously replaced by bone. Remodeling was still incomplete at 24 weeks.

CONCLUSIONS

In the sheep model microporous beta-TCP implants used with press-fit fixation of ACL grafts permit early functional rehabilitation. After 6 weeks, the graft is fixed by woven bone or bony integration. Implanted microporous tricalcium phosphate is resorbed and replaced by bone.

CLINICAL RELEVANCE

In a sheep model we showed that primary healing of ACL grafts with resorption and bony replacement of the fixating implant can be achieved by means of press-fit fixation with pure beta-TCP.

Magnetic resonance imaging analysis of the bioabsorbable Milagro interference screw for graft fixation in anterior cruciate ligament reconstruction

Ligament graft fixation with bioabsorbable interference screws is a standard procedure in cruciate ligament replacement. Previous screw designs may resorb incompletely, and can cause osteolysis and sterile cysts despite being implanted for several years. The aim of this study was to examine the in vivo degradation and biocompatibility of the new Milagro™ interference screw (Mitek, Norderstedt, Germany). The Milagro™ interference screw is made of 30% ß-TCP (TriCalcium phosphate) and 70% PLGA (Poly-lactic-co-glycolic acid). In the period between June 2005 and February 2006, 38 patients underwent graft fixation with Milagro™ screws in our hospital. Arthroscopic ACL reconstruction was performed using hamstring tendon grafts in all the patients. MR imaging was performed on 12 randomly selected patients out of the total of 38 at 3, 6 and 12 months after surgery. During the examination, the volume loss of the screw, tunnel enlargement, presence of osteolysis, fluid lines, edema and postoperative screw replacement by bone tissue were evaluated. There was no edema or signs of inflammation around the bone tunnels. At 3, 6 and 12 months, the tibial screws showed an average volume loss of 0, 8.1% (±7.9%) and 82.6% (±17.2%, P < 0.05), respectively. The femoral screws showed volume losses of 2.5% (±2.1%), 31.3% (±21.6%) and 92.02% (±6.3%, P < 0.05), respectively. The femoral tunnel enlargement was 47.4% (±43.8%) of the original bone tunnel volume after 12 months, and the mean tunnel volume of the tibial tunnel was −9.5% (±58.1%) compared to the original tunnel. Bone ingrowth was observed in all the patients. In conclusion, the resorption behaviour of the Milagro™ screw is closely linked to the graft healing process. The screws were rapidly resorbed after 6 months and, at 12 months, only the screw remnants were detectable. Moreover, the Milagro™ screw is biocompatible and osteoconductive, promoting bone ingrowth during resorption. Tunnel enlargement is not prevented in the first months but is reduced by bone ingrowth after 12 months.

Anterior cruciate ligament graft reconstruction: clinical, technical, and imaging overview

The anterior cruciate ligament (ACL) is one of the most frequently torn ligaments of the knee. With more than 100,000 ACL reconstructions performed yearly in the United States, evaluation of ACL grafts with magnetic resonance imaging is a common occurrence in daily clinical practice. Anterior cruciate ligament reconstructions vary from single bundle, double bundle, selective bundle, and physeal-sparing techniques. Complications of ACL graft reconstructions include graft tears, graft laxity, arthrofibrosis, and hardware failure or migration. This article offers a comprehensive review of ACL reconstruction for the consulting radiologist.

Treatment of anterior cruciate ligament injuries with special reference to surgical technique and rehabilitation: an assessment of randomized controlled trials

PURPOSE

The primary aim was to investigate and assess the current evidence of randomized controlled trials (RCTs) on anterior cruciate ligament (ACL) injuries, with special reference to the choice of surgical techniques and aspects of rehabilitation. A secondary aim was to clarify relative strengths and weaknesses of the selected studies, resolve literature conflicts, and finally, evaluate the need for further studies.

METHODS

A PubMed database search using the key words "anterior cruciate ligament" was performed. The search was limited to only RCTs published in English during the period of January 1995 to March 2009. Articles concerning surgical technique and rehabilitation were obtained. After initial screening and subsequent quality appraisal based on the CONSORT (Consolidated Standards of Reporting Trials) Statement, a total of 70 articles were included in this review.

RESULTS

Initial graft tension and the use of a ligament augmentation device do not affect clinical outcome. Bioabsorbable screws and titanium screws produced equal clinical outcome, regardless of graft type. Radiographic signs of osteoarthritis develop in 50% of ACL-injured patients, regardless of treatment. Meniscectomy further increases the risk. Furthermore, the use of a postoperative knee brace does not affect the clinical outcome after ACL reconstruction. Closed kinetic chain exercises produced less pain and laxity while promoting better subjective outcome than open kinetic chain exercises after patellar tendon reconstruction.

CONCLUSIONS

In terms of quality assessment, several weaknesses pertaining to study design were discovered among the included RCTs, which intelligibly stress the need for further high-quality studies.

LEVEL OF EVIDENCE

Level II, systematic review of RCTs.

WITHDRAWN: Bioresorbable fixation devices for musculoskeletal injuries in adults

BACKGROUND

Bioresorbable implants for musculoskeletal injuries involving bone and ligaments in adults might have significant advantages compared to the conventionally used non-resorbable metal implants because they lead to a gradual transfer of the mechanical load from the implant to the healing bone and do not require a secondary removal operation. Tissue reactions may present a problem and bioresorbable screws are mechanically not as strong as their metal counterparts.

OBJECTIVES

To compare bioresorbable implants to non-resorbable implants with respect to functional outcome, wound infections, other complications and reoperation rate,in the fixation of bone fractures or re-attachment of soft tissue to bone.

SEARCH STRATEGY

We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (March 2004), the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 1, 2004), MEDLINE (1966 to February 2004), EMBASE (1988 to February 2004), BL Inside (to February 2004), SIGLE (to February 2004), the metaRegister of Controlled Trials at http//:controlled-trials.com/, and reference lists of articles.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-randomised trials, comparing bioresorbable osteosynthesis with metal osteosynthesis (including titanium and stainless steel implants) were included.

DATA COLLECTION AND ANALYSIS

Review authors independently assessed trial quality and extracted data. Data were pooled where relevant and possible. Sub-analyses for specific type of fractures and for specific type of tissue reactions were performed. Requests for more information were sent to trialists.

MAIN RESULTS

No significant difference between the bioresorbable and other implants could be demonstrated with respect to functional outcome, infections and other complications. Reoperation rates were lower in some of the groups of people treated with bioresorbable implants.

AUTHORS' CONCLUSIONS

In a selected group of compliant patients with simple fractures, the use of bioresorbable fixation devices might be advantageous.

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

Bioabsorbable material screws are widely used in various surgical specialties. One popular application is their use as interference screws in anterior cruciate ligament (ACL) reconstruction surgery. Despite their routine use, a major concern with bioabsorbable materials in surgery has been the incidence of adverse events. Various case reports, series reports and studies in the past years have reported complications specific to the use of bioabsorbable interference screws intra operatively and at different time periods post operatively. The aim of this literature review is to summarize the clinical studies where bioabsorbable screws have been used in ACL reconstruction surgery and in particular to highlight any specific complications and adverse effects related to the use of these materials.

Tibial fixation of bone-patellar tendon-bone grafts in anterior cruciate ligament reconstruction: a cadaveric study of bovine bone screw and biodegradable interference screw

BACKGROUND

The use of interference screw fixation for bone-patellar tendon-bone grafts in anterior cruciate ligament fixation is well established. No previous study has compared bovine bone screws and biodegradable interference screws or demonstrated their efficacy for requirements associated with early rehabilitation.

HYPOTHESIS

There is no difference in tension loss and pull-out strength between bovine bone screws and biodegradable interference screws.

STUDY DESIGN

Controlled laboratory study.

METHODS

Anterior cruciate ligament reconstructions with bone-patellar tendon-bone allografts were performed in 40 human tibiae from 20 donors. A bovine bone screw and a polylevolactide interference screw were used for tibial fixation in each pair. A cyclic testing protocol with varying magnitude and orientation of the graft loading was developed. Cyclic tests were performed at 1 Hz for 5000 cycles with a peak force of 200 N applied to the graft. Survival rate and postcyclic-test pull-out strength were compared.

RESULTS

Fifteen of 20 reconstructions fixed with bovine bone screws and 17 of 20 fixed with biodegradable screws reached 5000 cycles. Graft tension drop after the 5000 cycles averaged 19.7 N ( +/- 12.9) for bovine bone screws and 18.9 N ( +/- 16.3) for biodegradable screws. There were no significant differences in tension loss and pull-out strength between the 2 types of screws.

CONCLUSION

Bovine bone screws are comparable to biodegradable interference screws in providing stable tibial fixation in anterior cruciate ligament reconstruction using bone-patellar tendon-bone allografts.

CLINICAL RELEVANCE

The use of bovine bone screws may be comparable to the popular biodegradable interference screws used for anterior cruciate ligament reconstruction in postsurgery rehabilitation.

MRI evaluation of the tibial tunnel/screw/tendon interface after ACL reconstruction using a bioabsorbable interference screw

This article describes the complex relationship between graft, bone, and biologic interference screw. Orthopedic surgeons have just begun to understand this complex biologic relationship. Clinical outcome measurements tell very little about the biology in bone tunnels.

Peripheral versus aperture fixation for anterior cruciate ligament reconstruction

Because both the young and aging population are showing increasing interest in sports participation, the number of sports related injuries and in particular anterior cruciate ligament (ACL) injuries have been increasing. Because of these injuries much time and energy has been focused on ACL reconstruction in order to return these individuals to their optimal level of participation in their sport. This article explores and reviews the concepts of ACL fixation location and how this affects the ultimate outcome of this reconstructive procedure.

Beta-tricalcium phosphate plugs for press-fit fixation in ACL reconstruction--a mechanical analysis in bovine bone

BACKGROUND

The goal of this study was to test fixation properties of microporous pure beta-tricalcium phosphate (TCP) plugs (porosity 40%) for press-fit fixation of the ACL graft using patellar tendons with and without bone blocks. We set out to establish whether it is possible, in this way, to obtain results comparable with those of interference screw fixation of bone-tendon-bone (BTB) grafts in terms of cyclic loading and load-to-failure.

METHODS

In a bovine model 30 ACL grafts were fixed in tibial drill holes, divided into three groups: 10 BTB grafts fixed with TCP press-fit plugs (7x25 mm), 10 pure patellar tendon grafts with TCP press-fit plugs (7x25 mm), and 10 BTB grafts with metal interference screws (7x25 mm). All grafts were tested by cyclic loading (50-200 N) and loaded until failure in a tensiometer.

RESULTS

Under cyclic loading one interference screw fixation failed. None of the TCP plug fixations failed. After 1500 cycles the displacement of the graft in the drill hole for BTB fixed with screws was 3.6+/-7.8 mm, for BTB/TCP plugs 1.6+/-3.4 mm, and for the pure tendon/TCP grafts 1.4+/-0.4 mm. Regarding cyclic loading the pure tendon/TCP system was significantly superior to BTB (p=0.007). The load-to-failure for the BTB/interference screw group was 908+/-539 N with a stiffness of 94+/-36 N/mm, 936+/-245 N for the BTB/TCP cylinder group with a stiffness of 98+/-12 N/mm, and 673+/-159 N for the pure tendon/TCP group with a stiffness of 117+/-9 N/mm. In terms of pull-out load the BTB/TCP system was significantly better than the pure tendon/TCP group (p=0.011). However, pure tendon/TCP grafts achieved significantly greater stiffness (p=0.002) than the BTB system.

CONCLUSION

Press-fit fixation with microporous pure beta-TCP plugs of BTB grafts or patellar tendon grafts without bone blocks for ACL reconstruction leads to primary stability comparable with that achieved by fixation with metal interference screws in case of BTB grafts.

Prospective evaluation of patellar tendon graft fixation in anterior cruciate ligament reconstruction comparing composite bioabsorbable and allograft interference screws

PURPOSE

Bioabsorbable interference screws have proved to be biologically safe and to provide adequate graft fixation. Metallic interference screws have therefore been continuously replaced over the years. However, degradation times are highly variable, and bony replacement of the screw does not always occur in human beings. Composite interference screws have recently been introduced to enhance bony integration. We evaluated 2 different composite interference screws and compared them with an allograft interference screw over a 2-year period after anterior cruciate ligament (ACL) reconstruction with an autologous bone-patellar tendon-bone graft.

METHODS

Three groups of patients were prospectively evaluated. Poly-L-lactid acid/hydroxyapatite composite screws (BioRCI-HA; Smith & Nephew, Andover, MA) (group A), poly-L-lactid acid/beta-tricalcium phosphate composite screws (Bilok; Atlantech, Radevormwald, Germany) (group B), or allograft interference screws (CorlS; Regeneration Technologies, Alachua, FL) (group C) were used for tibial fixation of a patellar tendon autograft in ACL reconstruction. Each group consisted of 20 patients (mean age, 32.2 +/- 10.9 years in group A, 32.3 +/- 10.6 years in group B, and 31.1 +/- 6.6 years in group C) with no significant (P < .05) differences in age, sex, and time of follow-up. Subjective and clinical International Knee Documentation Committee parameters were evaluated preoperatively and at 3, 12, and 24 months postoperatively; computed tomography scans were obtained postoperatively and at 3, 12, and 24 months; and magnetic resonance imaging (MRI) scans were obtained at 3 and 24 months postoperatively.

RESULTS

Screw breakage during insertion occurred in 2 cases (1 in group A and 1 in group B). There was no significant (P < .05) difference in subjective and clinical results at any time of follow-up. No inflammatory response could be detected on MRI in any of the patients in all groups. Computed tomography scans documented complete bone block incorporation at 3 months in all groups. Both composite interference screws showed signs of degradation but were still clearly visible 24 months after ACL reconstruction. At 12 months, a sclerotic rim around the screw cavity could be outlined in group B only. No bony replacement had taken place up to 24 months postoperatively in group A or B. In group C the allograft bone screw was completely integrated and barely visible after 24 months.

CONCLUSIONS

All 3 screw types provided adequate graft fixation and were associated with excellent clinical results and no inflammatory response on MRI. Ultimately, a resorbable screw has to be replaced by bone to facilitate revision surgery. Formation of a sclerotic rim around the outline of the screw makes later bony replacement (group B) unlikely. After 24 months, complete bony integration had only taken place when allograft screws were used.

CLINICAL RELEVANCE

At 24 months, no advantage of composite screw materials over conventional bioabsorbable screws could be detected. If composite materials will be of any advantage with respect to bony replacement has to be observed with longer-term follow-up. The allograft bone screw was completely incorporated and replaced by cancellous bone after 24 months. Unfortunately, the screw's more complicated handling, higher cost, and limited availability impair the possibilities for its standard clinical use.

Biodegradable Materials in Arthroscopy

The use of biodegradable materials as implants has revolutionized the way medicine is practiced today. This review provides a general description of salient biodegradable polymeric materials currently used in arthroscopy. These materials include polyglycolic acid, self-reinforced polyglycolic acid, poly-L-lactic acid, self-reinforced polylactic-L-acid, poly-D-L-lactic acid, copolymer of poly-D-L-lactic acid polyglycolic acid, and polyglyconate. The mechanical strength, degradation properties, and widespread use of these materials, especially in the knee and shoulder, are discussed individually. Also discussed are the relatively few complications that are related to these materials' arthroscopic use. Future directions in biodegradable materials, including smart polymers, are also considered. In the future, novel techniques to identify the ideal polymer for a particular application will need to be developed to minimize the risk for implant complications.

Biodegradable Composite Implants

Biodegradable implants are established in the field of operative sports medicine. So-called composite implants are increasingly used. The idea to improve biocompatibility and osteoconductivity of biodegradable polymers by modifying them with a ceramic component, has led to the development of these composite implants. Today, an increasing variety of composite implants are available. They have substantially different material characteristics, which depend on matrix polymer choice and the additional ceramic. The material characteristics influence the mechanical properties, in vivo degradation, the osseous replacement and the host-tissue response. It is important to understand their biologic base for a better knowledge of the advantages and risks associated with using composite implants in the field of operative sports medicine. The purpose of this review is to focus on current developments in biodegradable composite implants and their biologic base.

Magnetic resonance imaging analysis of bioabsorbable interference screws used for fixation of bone-patellar tendon-bone autografts in endoscopic reconstruction of the anterior cruciate ligament

BACKGROUND

Metal interference screws can cause problems if revision is needed and can interfere with magnetic resonance imaging. Bioabsorbable screws have been developed to prevent these problems, but the rate of resorption and integration is not well understood.

HYPOTHESIS

Poly-L-lactic acid interference screws will be resorbed 2 years after anterior cruciate ligament reconstruction.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

The study group consisted of 19 patients with isolated anterior cruciate ligament ruptures reconstructed with bone-patellar tendon-bone autografts fixed with poly-L-lactic acid interference screws using an endoscopic technique. Magnetic resonance imaging was used to evaluate resorption of the screws, bony integration of the screws, and integration of the bone blocks after 2 years.

RESULTS

At 2 years, the mean reduction in the volume of the femoral screws was 64% and of the tibial screw was 63%. Bony integration of the femoral bone block was considered good in 17 patients and fair in 2 patients. Integration of the tibial bone block was considered good in 16 patients and fair in 1 patient who demonstrated widening of the tibial tunnel. Osteolysis around the screws was seen in 3 patients in the femur and none in the tibia.

CONCLUSION

The mean reduction in volume of the poly-L-lactic acid screws as measured by magnetic resonance imaging after 2 years was approximately two thirds. The integration of the bone blocks was considered good in 90% of the patients. Osteolysis around the screws was visible in 16% of the patients.

CLINICAL RELEVANCE

Two years after ACL reconstruction using poly-L-lactic acid interference screws, the surgeon can expect to find approximately one third of the volume of the screw remaining in the bone tunnels.