Biomechanical evaluation of a 1-stage revision anterior cruciate ligament reconstruction technique using a structural bone void filler for femoral fixation

Clinical Outcomes of Single-Stage Revision Anterior Cruciate Ligament Reconstruction Using a Fast-Setting Bone Graft Substitute

Revision anterior cruciate ligament reconstruction (ACLR) can be achieved in a single-stage or two-stage approach. Single-stage revisions have several advantages, including one less operation, decreased cost, and a quicker recovery for patients. Revision ACLR can be complicated by malpositioned or dilated bone tunnels, which makes a single-stage revision more challenging or sometimes necessitates a two-stage approach. The use of fast-setting bone graft substitutes (BGS) has been described in recent literature as a strategy to potentially help address this problem in the setting of single-stage revision ACLR. The aim of this study was to evaluate patient-reported clinical outcomes of patients who have undergone single-stage revision ACLR using fast-setting BGS to address prior malpositioned or dilated tunnels. A retrospective review was conducted of the first nine consecutive patients who had undergone single-stage revision ACLR using a fast-setting BGS by a single surgeon between May 2017 and February 2020 with a minimum of 2-year follow-up. Patient-reported clinical outcomes, including the International Knee Documentation Committee (IKDC) questionnaire, the Tegner Lysholm Knee Scoring Scale, patient satisfaction questions, and the need for additional surgery were evaluated for this group between 26 and 49 months postoperative. Of the nine patients eligible for inclusion, eight patients (88.9%) were evaluated, and one was lost to follow-up. At an average follow-up of 37.9 months (range: 27.8-55.7), the mean postoperative IKDC score was 75.0 ± 11.3, and the mean postoperative Tegner Lysholm Knee Score was 83.0 ± 17.6. None of the patients required additional revision surgery or experienced construct failure at the time of follow-up. Seven of eight respondents (87.5%) had their preoperative expectations met with the surgery, and 100% of patients stated they would have the surgery again. Single-stage revision ACLR using fast-setting BGS showed overall positive clinical outcomes for this pilot group of patients at a minimum 2-year follow-up. In select revision scenarios, these materials may be a valuable option to allow the filling of defects without compromising fixation or clinical outcomes.

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

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

Tunnel Management in Revision Anterior Cruciate Ligament Reconstruction: Current Concepts

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

Prevalence and Incidence of Chondral and Meniscal Lesions in Patients Undergoing Primary and Subsequent Revision Anterior Cruciate Ligament Reconstruction: An Analysis of 213 Patients From the SANTI Group

BACKGROUND

Previous studies have shown a higher prevalence of meniscal and chondral lesions at the time of revision anterior cruciate ligament reconstruction (R-ACLR) compared with primary ACLR procedures. However, studies that follow the development of meniscal and chondral status through primary and subsequent R-ACLR are scarce.

PURPOSE

To compare the prevalence of meniscal and chondral injuries in patients undergoing primary ACLR and subsequent R-ACLR.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Patients who underwent ACLR and subsequently needed R-ACLR between January 2009 and February 2018 in a single center were included. A retrospective analysis of prospectively collected data was conducted.

RESULTS

A total of 213 patients were included, with a mean follow-up of 59.7 months. The mean age was 22 years at primary ACLR and 26.1 years at the time of revision. The proportion of meniscal tears was higher at the time of R-ACLR compared with the time of primary reconstruction (70.0% vs 44.6%, respectively; P < .001). Similarly, the prevalence of chondral lesions was significantly higher at the time of revision versus the primary reconstruction (15.5% vs 7.0%, respectively; P = .003).

CONCLUSION

R-ACLR is associated with a higher rate of concomitant meniscal and chondral lesions than primary ACLR.

One-Stage ACL Revision Using a Bone Allograft Plug for a Semianatomic Tibial Tunnel That Is Too Anterior

Revision of an anterior cruciate ligament (ACL) reconstruction can be performed as a one-stage or two-stage surgery. Several factors must be taken into consideration when making this choice, especially the size and position of the existing tunnels. When the tibial tunnel is semianatomic, it is difficult to make a new tunnel in the correct position without overlapping the existing tunnel. For this reason, we have developed a one-stage ACL revision surgery that uses a bone allograft plug. When it comes to choosing a reconstruction technique, we believe that combined intra-articular and extra-articular reconstruction with the iliotibial band is suitable when the hamstring tendons are not available, combined with clinical findings of translational and rotational instability. Because the existing tunnels require reorientation, a new femoral tunnel can be created by outside-in drilling to eliminate the risk of overlap, while an allograft bone plug can be used to fill the overly anterior tibial tunnel and allow us to drill the correct tibial tunnel right away. In our hands, this is a safe and effective technique, but longer follow-up is needed to validate its indications.

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

BACKGROUND

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

HYPOTHESIS

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

STUDY DESIGN

Controlled laboratory study.

METHODS

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

RESULTS

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

CONCLUSION

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

CLINICAL RELEVANCE

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

Influence of Preoperative Tunnel Widening On the Outcomes of a Single Stage-Only Approach to Every Revision Anterior Cruciate Ligament Reconstruction: An Analysis of 409 Consecutive Patients From the SANTI Study Group

BACKGROUND

Preoperative tunnel widening is a frequently reported indication for performing a 2-stage revision anterior cruciate ligament reconstruction (ACLR) instead of a single-stage procedure. However, the strength of the available evidence to support a 2-stage strategy is low.

PURPOSE/HYPOTHESIS

The purpose was to evaluate the clinical outcomes of a single stage-only approach to revision ACLR. It was hypothesized that this approach would be associated with significant improvements from baseline in patient-reported outcome measures (PROMs) and knee stability and that there would be no significant differences in any postoperative outcomes between patients with and without preoperative tunnel widening.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A retrospective analysis was conducted of a large series of consecutive patients undergoing revision ACLR with a minimum follow-up of 2 years. Preoperative tunnel widening was assessed using digital radiographs. All patients underwent single-stage surgery with an outside-in technique, regardless of the degree of tunnel widening. Clinical outcomes were compared according to whether tunnel widening was present (either tunnel ≥12 mm) or not (both tunnels <12 mm).

RESULTS

The study included 409 patients with a mean ± SD follow-up of 69.6 ± 29.0 months. After revision ACLR, there was a significant reduction in the side-to-side anteroposterior laxity difference, from 7.7 ± 2.2 mm preoperatively to 1.2 ± 1.1 mm at 2 years (P < .001). The mean International Knee Documentation Committee (IKDC) and all subscales of the Knee injury and Osteoarthritis Outcome Score (KOOS) exceeded the thresholds for the Patient Acceptable Symptom State defined for primary ACLR. An overall 358 patients had retrievable preoperative radiographs. According to the tunnel diameter measurements, 111 patients were allocated to group A (both tunnels <12 mm) and 247 patients to group B (either/both tunnels ≥12 mm). There were no significant differences between groups with respect to anteroposterior side-to-side laxity difference, graft rupture rates, non-graft rupture related reoperations, or contralateral anterior cruciate ligament injury rates. There was also no significant difference between groups that exceeded minimal detectable change thresholds for any of the PROMs recorded (ACL-RSI [Anterior Cruciate Ligament-Return to Sports After Injury], Lysholm, Tegner, IKDC, KOOS).

CONCLUSION

A single-stage approach to revision ACLR is associated with excellent clinical results when an outside-in drilling technique is utilized. The presence of preoperative tunnel widening does not significantly influence PROMs, knee stability, graft rupture rates, or non-graft rupture related reoperation rates.

One-Stage Anatomical Revision Anterior Cruciate Ligament Reconstruction: Results According to Tunnel Overlaps

PURPOSE

To present clinical results according to tunnel overlap in 1-stage anatomical revision anterior cruciate ligament reconstruction (ACLR).

METHODS

All patients who underwent revision ACLR performed by a single surgeon (J.H.A.) from 2012 to 2017 and were followed up for >24 months were retrospectively evaluated. The exclusion criteria were concomitant ligament injury, including medial collateral ligament injury, modified Outerbridge grade ≥3 cartilage lesion, and severe meniscus defects. Tunnel overlap was measured on 3-dimensionally reconstructed computed tomography images. Patients in the nonoverlapped femoral tunnel group (group NO, n = 52) were treated with new tunnel drilling that completely avoided previous tunnels, and those in the overlapped femoral tunnel group (group O, n = 41) were treated with a new tunnel that overlapped with previous tunnels. Clinical outcomes were evaluated using the subjective International Knee Documentation Committee (IKDC) and Lysholm scores. Knee joint stability was measured using the Lachman and pivot shift tests. Patients with femoral tunnel widening of ≥14 mm underwent 2-stage ACLR.

RESULTS

The mean follow-up duration of 93 patients was 46.9 months (range, 24-97 months). All preoperative subjective and objective IKDC (P<0.001) and Telos stress test scores (P = .016) were significantly improved at the last follow-up. Forty-one patients had overlapping femoral tunnels, whereas 87 had overlapping tibial tunnels. At the last follow-up, subjective IKDC and Lysholm scores (73.6 ± 15.3 vs 74.9 ± 12.1, P = .799 and 80.0 ± 19.2 vs 81.44 ± 13.5, P = .505, respectively) and objective pivot shift (IKDC grade) in the Lachman test (P = .183 and P = .450, respectively) did not differ significantly between groups NO and O, respectively.

CONCLUSIONS

One-stage anatomical revision ACLR significantly improved the clinical results. Most tibial tunnels (94%) and approximately one-half (44%) of the femoral tunnels overlapped. The overlapped femoral tunnel group did not show inferior outcomes or stability.

LEVEL OF EVIDENCE

Level III, cohort study.

The posteromedial corner of the knee: an international expert consensus statement on diagnosis, classification, treatment, and rehabilitation

PURPOSE

To establish recommendations for diagnosis, classification, treatment, and rehabilitation of posteromedial corner (PMC) knee injuries using a modified Delphi technique.

METHODS

A list of statements concerning the diagnosis, classification, treatment and rehabilitation of PMC injuries was created by a working group of four individuals. Using a modified Delphi technique, a group of 35 surgeons with expertise in PMC injuries was surveyed, on three occasions, to establish consensus on the inclusion or exclusion of each statement. Experts were encouraged to propose further suggestions or modifications following each round. Pre-defined criteria were used to refine item lists after each survey. The final document included statements reaching consensus in round three.

RESULTS

Thirty-five experts had a 100% response rate for all three rounds. A total of 53 items achieved over 75% consensus. The overall rate of consensus was 82.8%. Statements pertaining to PMC reconstruction and those regarding the treatment of combined cruciate and PMC injuries reached 100% consensus. Consensus was reached for 85.7% of the statements on anatomy of the PMC, 90% for those relating to diagnosis, 70% relating to classification, 64.3% relating to the treatment of isolated PMC injuries, and 83.3% relating to rehabilitation after PMC reconstruction.

CONCLUSION

A modified Delphi technique was applied to generate an expert consensus statement concerning the diagnosis, classification, treatment, and rehabilitation practices for PMC injuries of the knee with high levels of expert agreement. Though the majority of statements pertaining to anatomy, diagnosis, and rehabilitation reached consensus, there remains inconsistency as to the optimal approach to treating isolated PMC injuries. Additionally, there is a need for improved PMC injury classification.

LEVEL OF EVIDENCE

Level V.

Single-Stage Revision Anterior Cruciate Ligament Reconstruction Using Fast-Setting Bone Graft Substitutes

Revision anterior cruciate ligament reconstructions can be performed using either a single-stage or 2-stage technique. There are several benefits to using a single-stage approach when technically possible. Although not always feasible, eliminating the necessity of a 2-stage approach for certain indications is clearly preferable because it requires fewer operative procedures, leads to a more rapid recovery, and is cost effective. Here, we describe the use of fast-setting bone graft substitutes in the setting of single-stage revision anterior cruciate ligament reconstruction. The authors have found this technique useful in converting what would sometimes otherwise be approached using 2 stages into a single-stage procedure.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

LEVEL OF EVIDENCE

Level I, prospective, randomized controlled clinical trial.

Single-stage revision anterior cruciate ligament reconstruction using bone grafting for posterior or widening tibial tunnels restores stability of the knee and improves clinical outcomes

PURPOSE

Revision ACL surgery may be complicated by tunnel malposition and/or tunnel widening and often requires a staged treatment approach that includes bone grafting, a period of several months to allow bone graft incorporation and then definitive revision ACL reconstruction. The purpose of this study was to evaluate the results of a single-staged ACL revision reconstruction technique using a cylindrical dowel bone graft for patients who have existing posteriorly placed and/or widened tibial tunnels in the tibia at a minimum of 2 years follow-up.

METHODS

Between 2010 and 2014, patients undergoing single-stage revision ACL reconstruction with the described technique were prospectively enrolled and evaluated. At a minimum of 24 months, patients were evaluated by physical examination, multiple clinical outcome instruments including KOOS, Tegner and Lysholm, and preoperative and postoperative MRIs.

RESULTS

At a mean of 35.1 months, 18 consecutive patients had no revision surgery and no subjective knee instability. There were statistically significant improvements in the Tegner (median 2, interquartile range 2.25; p < 0.01), Lysholm (20.0 ± 15.0; p < 0.01), KOOS symptoms scale (12.9 ± 11.8; p < 0.01), KOOS pain scale (15.4 ± 18.7; p < 0.01), KOOS ADL scale (13.5 ± 19.0; p < 0.01), KOOS sports scale (32.8 ± 26.4; p < 0.01), and KOOS QoL scale (18.1 ± 16.9; p < 0.01). Postoperative MRI demonstrated statistically significant anteriorization of the tibial tunnel and a statistically significant decrease in tunnel widening.

CONCLUSION

Revision ACL reconstruction utilizing a single-staged tibial tunnel grafting technique resulted in improved knee pain, function, and stability at a minimum of 24-month follow-up.

LEVEL OF EVIDENCE

IV.

One-Stage Revision Anterior Cruciate Ligament Reconstruction: Results According to Preoperative Bone Tunnel Diameter: Five to Fifteen-Year Follow-up

BACKGROUND

Bone tunnel enlargement is one of the important factors that determine whether a revision anterior cruciate ligament reconstruction (ACLR) should be performed in 1 or 2 stages. The goal of this retrospective cohort study was to compare the mid-term to long-term outcomes of 1-stage revision ACLR according to the amount of preoperative tunnel enlargement.

METHODS

Between January 2002 and January 2012, 88 patients who underwent revision ACLR were enrolled. The patients were divided into 2 groups based on the tunnel diameter (group A, <12 mm; group B, ≥12 mm). Clinical scores (International Knee Documentation Committee [IKDC] subjective score, Lysholm score, and Tegner score) and knee joint stability (as measured with the anterior drawer test, Lachman test, pivot-shift test, and measurement of the side-to-side difference in anterior tibial translation on Telos stress radiographs) were evaluated preoperatively and 5 to 15 years postoperatively. The failure rate and survivorship were compared between groups A and B.

RESULTS

The mean time to final follow-up was 7.9 ± 2.6 years. There were 44 patients in each of the 2 groups. There were no significant differences in the postoperative IKDC subjective scores, Lysholm scores, or Tegner activity scores between the groups. However, group A showed superior results on all knee joint stability tests except for the anterior drawer test. There were 3 failures in group A (7%) and 6 in group B (14%). The overall survival rates with failure as the end point were 93.1% and 84.6%, respectively, at 15 years.

CONCLUSIONS

The 5 to 15-year clinical scores following revision ACLR did not differ significantly according to the preoperative amount of tunnel widening. However, the results of the postoperative Lachman and pivot-shift tests as well as the side-to-side difference in anterior tibial translation on Telos stress radiographs were significantly superior in the group with a preoperative tunnel diameter of <12 mm compared with the group with a tunnel diameter of ≥12 mm.

LEVEL OF EVIDENCE

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

Outcomes After 1-Stage Versus 2-Stage Revision Anterior Cruciate Ligament Reconstruction

BACKGROUND

Revision anterior cruciate ligament reconstruction (ACLR) is becoming increasingly common as the number of primary ACLR cases continues to rise. Despite this, there are limited data on the outcomes of revision ACLR and even less information specifically addressing the differences in 1-stage revision reconstruction versus those performed in a 2-stage fashion after primary reconstruction.

PURPOSE

To compare the outcomes, patient satisfaction, and failure rates of 1-stage versus 2-stage revision ACLR.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

All patients who underwent revision ACLR between 2010 and 2014 by a single surgeon were collected, and skeletally mature patients over the age of 17 years were included. Patients were excluded if they were skeletally immature; had a previous intra-articular infection in the ipsilateral knee; underwent a prior alignment correction procedure, cartilage repair or transplant procedure, or meniscal allograft transplantation; or had an intra-articular fracture. An ipsilateral or contralateral bone-patellar tendon-bone (BPTB) autograft was the graft of choice. A BPTB allograft was considered for patients aged ≥50 years, for any patient with an insufficient ipsilateral or contralateral patellar tendon, or for those who chose not to have the contralateral patellar tendon graft harvested. Patients completed a subjective questionnaire preoperatively and at a minimum of 2 years postoperatively. Magnetic resonance imaging and computed tomography of all knees were performed preoperatively to assess for associated injuries and to evaluate the ACLR tunnel size and location. Patients with malpositioned tunnels that would critically overlap with an anatomically placed tunnel or those with tunnels ≥14 mm in size underwent bone grafting.

RESULTS

A total of 88 patients met the inclusion criteria for this study. There were 39 patients in the 1-stage revision surgery group (19 male, 20 female) and 49 patients in the 2-stage revision surgery group who underwent tunnel bone grafting first (27 male, 22 female). In both groups, the 12-item Short Form Health Survey (SF-12) Physical Component Summary, Western Ontario and McMaster Universities Arthritis Index, Lysholm, and Tegner activity scale scores significantly improved from preoperatively to postoperatively. There was no significant difference in the SF-12 Mental Component Summary score before and after surgery in either group. Furthermore, there was no significant difference in failure rates or other demographic data between the groups. We observed 4 failures in the 1-stage reconstruction group (10.3%) and 3 failures in the 2-stage reconstruction group (6.1%).

CONCLUSION

In this study, objective outcomes and subjective patient scores and satisfaction were not significantly different between 1-stage and 2-stage revision ACLRs. Both groups had significantly improved objective outcomes and patient subjective outcomes without notable differences in failure rates. Further longitudinal studies comparing 1-stage and 2-stage revision ACLRs over a longer time frame are recommended.

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

PURPOSE

To evaluate the histologic and radiographic outcomes of using silicate-substituted calcium phosphate (Si-CaP) as bone graft substitute for the augmentation of tunnel defects in 2-stage revision anterior cruciate ligament (ACL) reconstruction.

METHODS

Forty patients undergoing 2-stage revision ACL reconstruction were included in a prospective, randomized controlled clinical trial between 2012 and 2015. The inclusion criteria were tunnel diameter of the tibial and/or femoral tunnel of 10 mm or greater after failed ACL reconstruction. Twenty patients received autologous bone from the iliac crest and 20 patients received Si-CaP as a bone graft substitute for tunnel grafting at the first-stage procedure. Punch biopsy specimens of the augmented tunnels were taken at the second-stage procedure, and histologic examination included quantitative analysis of the area of immature bone formation, lamellar bone, and bone marrow. Radiographic analysis included determination of the filling rates of the tunnels on postoperative computed tomography scans.

RESULTS

Forty patients with a mean age of 32 years (standard deviation [SD], 11.0 years) were analyzed. Histologic examination of the tunnels filled with Si-CaP showed that 15% (SD, 14%) of the area was covered with immature bone formation, 41% (SD, 10%) with well-organized lamellar bone, and 44% (SD, 8%) with bone marrow. In the control group (autologous bone), 58% (SD, 3%) of the area was covered with well-organized lamellar bone and 42% (SD, 3%) with bone marrow. Quantitative evaluation of the postoperative computed tomography scans showed a trend of better filling rates in patients with Si-CaP for the tibial tunnel (86% [SD, 17%] vs 78% [SD, 14%]; P = .131). Intraoperatively, Si-CaP was completely integrated into the original bone tunnel providing good stability for tunnel placement and tendon graft fixation comparable to autologous bone.

CONCLUSIONS

Si-CaP as bone graft substitute for tunnel augmentation in 2-stage revision ACL reconstruction shows good histologic, radiographic, and intraoperative integration comparable to autologous bone.

LEVEL OF EVIDENCE

Level I, prospective randomized controlled trial.

Biomechanical Strength and Elongation of the T-Block Modification for Bone-Patella Tendon-Bone Allografts

PURPOSE

To assess the biomechanical performance of 2 different T-block modifications of bone-patella tendon-bone (BPTB) allografts.

METHODS

The matched knee pairs from 10 human cadavers (mean age 49 years) were fashioned into 30 BPTB allografts and divided into 3 groups (10 each): group 1, standard patella tendon-tibial attachment; group 2, T-block tibial attachment with 10 mm of unattached bone proximal to the patella tendon insertion with 15 mm of tendon attached; group 3, T-block tibial attachment with 15 mm of unattached bone proximal to the patella tendon insertion and 10 mm of tendon attached. A biocomposite interference screw secured each graft into a 10-mm tunnel in 15 pcf polyurethane foam. A 10-N preload was applied followed by 500 cycles of 10- to 150-N loading at 0.5 Hz. Grafts completing cyclic loading were destructively tested at 200 mm/min. Failure load, stiffness, elongation, and failure mode were recorded.

RESULTS

Failure loads and elongation for groups 1, 2, and 3 (790, 729, and 700 N; 0.15, 0.16, and 0.19 mm, respectively) were not statistically different (P > .1). Graft stiffness for groups 1 and 2 (214 and 186 N/mm) were not statistically different, but group 3 (170 N/mm) was different from group 1. All group 1 and 2 tests failed by graft pullout as did 8 of 10 from group 3. The other 2 failed by tendon tearing from bone.

CONCLUSIONS

A T-block BPTB allograft harvested with 10 or 15 mm of unattached bone proximal to the tibial patella tendon insertion has no ultimate failure strength difference after cyclic loading compared with the standard BPTB allograft. The 15-mm T-block showed lower stiffness and more elongation at failure than the standard BPTB allograft whereas the 10-mm T-block exhibited comparable stiffness and elongation measurements to the standard BPTB allograft control specimens.

CLINICAL RELEVANCE

The T-block BPTB allograft construct should increase the availability of BPTB allografts for anterior cruciate ligament reconstruction and facilitate the use of grafts possessing longer tendon segments that are currently being discarded.

Influence of Different Tibial Fixation Techniques on Initial Stability in Single-Stage Anterior Cruciate Ligament Revision With Confluent Tibial Tunnels: A Biomechanical Laboratory Study

PURPOSE

To kinematically and biomechanically compare 4 different types of tibial tunnel management in single-stage anterior cruciate ligament (ACL) revision reconstruction with the control: primary ACL reconstruction using a robotic-based knee testing setup.

METHODS

Porcine knees and flexor tendons were used. One hundred specimens were randomly assigned to 5 testing groups: (1) open tibial tunnel, (2) bone plug technique, (3) biodegradable interference screw, (4) dilatation technique, and (5) primary ACL reconstruction. A robotic/universal force-moment sensor testing system was used to simulate the KT-1000 (MEDmetric, San Diego, CA) and pivot-shift tests. Cyclic loading and load-to-failure testing were performed.

RESULTS

Anterior tibial translation increased significantly with all of the techniques compared with the intact ACL (P < .05). In the simulated KT-1000 test, groups 2 and 3 achieved results equal to those of primary ACL reconstruction (P > .05). The open tunnel and dilated tunnel techniques showed significantly greater anterior tibial translation (P < .05). The results of the simulated pivot-shift test were in accordance with those of the KT-1000 test. No significant differences could be observed regarding stiffness or maximum load to failure. However, elongation was significantly lower in the primary ACL reconstruction group compared with groups 1 and 3 (P = .02 and P = .03, respectively).

CONCLUSIONS

Filling an incomplete and incorrect tibial tunnel with a press-fit bone plug or a biodegradable interference screw in a standardized laboratory situation provided initial biomechanical properties and knee stability comparable with those of primary ACL reconstruction. In contrast, the dilatation technique or leaving the malplaced tunnel open did not restore knee kinematics adequately in this model. Backup extracortical fixation should be considered because the load to failure depends on the extracortical fixation when an undersized interference screw is used for aperture fixation.

CLINICAL RELEVANCE

Our biomechanical results could help orthopaedic surgeons to optimize the results of primary ACL revision with incomplete, incorrect tunnel placement.

Pullout strength of bone-patellar tendon-bone allograft bone plugs: a comparison of cadaver tibia and rigid polyurethane foam

PURPOSE

To compare the load-to-failure pullout strength of bone-patellar tendon-bone (BPTB) allografts in human cadaver tibias and rigid polyurethane foam blocks.

METHODS

Twenty BPTB allografts were trimmed creating 25 mm × 10 mm × 10 mm tibial plugs. Ten-millimeter tunnels were drilled in 10 human cadaver tibias and 10 rigid polyurethane foam blocks. The BPTB anterior cruciate ligament allografts were inserted into these tunnels and secured with metal interference screws, with placement of 10 of each type in each material. After preloading (10 N), cyclic loading (500 cycles, 10 to 150 N at 200 mm/min) and load-to-failure testing (200 mm/min) were performed. The endpoints were ultimate failure load, cyclic loading elongation, and failure mode.

RESULTS

No difference in ultimate failure load existed between grafts inserted into rigid polyurethane foam blocks (705 N) and those in cadaver tibias (669 N) (P = .69). The mean rigid polyurethane foam block elongation (0.211 mm) was less than that in tibial bone (0.470 mm) (P = .038), with a smaller standard deviation (0.07 mm for foam) than tibial bone (0.34 mm).

CONCLUSIONS

All BPTB grafts successfully completed 500 cycles. The rigid polyurethane foam block showed less variation in test results than human cadaver tibias.

CLINICAL RELEVANCE

Rigid polyurethane foam blocks provide an acceptable substitute for human cadaver bone tibia for biomechanical testing of BPTB allografts and offer near-equivalent results.

Revision anterior cruciate ligament reconstruction: an update

With the rising number of anterior cruciate ligament (ACL) reconstructions performed, revision ACL reconstruction is increasingly common nowadays. A broad variety of primary and revision ACL reconstruction techniques have been described in the literature. Recurrent instability after primary ACL surgery is often due to non-anatomical ACL graft reconstruction and altered biomechanics. Anatomical reconstruction must be the primary goal of this challenging revision procedure. Recently, revision ACL reconstruction has been described using double bundle hamstring graft. Successful revision ACL reconstruction requires an exact understanding of the causes of failure and technical or diagnostic errors. The purpose of this article is to review the causes of failure, preoperative evaluation, graft selection and types of fixation, tunnel placement, various types of surgical techniques and clinical outcome of revision ACL reconstruction.

Evaluation of a one-stage ACL revision technique using bone void filler after cyclic loading

BACKGROUND

Revision anterior cruciate ligament (ACL) reconstruction often requires a two-stage approach. This study analyzes the biomechanical properties after cyclic loading of a one-stage ACL revision technique using a calcium phosphate bone cement.

METHODS

Arthroscopic reconstruction of the ACL was performed in 5 matched pairs of fresh-frozen cadaveric knees separated into two groups. The control group underwent a standard reconstruction with a bone-patellar tendon-bone autograft with bioabsorbable interference screw fixation. The experimental group simulated a failed reconstruction by drilling a 12 mm hole and underwent a revision after filling it with a bioabsorbable calcium phosphate bone cement. The specimens were dissected, scanned for bone mineral density, and cyclically loaded on a mechanical testing system (preload of 250 cycles of 5-75 N at 0.5 Hz followed by 10,000 cycles of 20-150 N at 1 Hz). Intact specifmens underwent a load-to-failure protocol of 50mm/min. Ultimate load, stiffness, and modes of failure were recorded. Data was analyzed using paired t-tests.

FINDINGS

All specimens completed the mechanical testing protocol. The control group had a mean maximum load of 471.33 N (SD 220.73 N) and the experimental group had 453.54 N (SD 152.36; p=0.84). There were no statistically significant differences in maximum load or stiffness. No correlation between bone mineral density (BMD) and maximum load was found.

INTERPRETATION

Using calcium phosphate filler in a single-stage ACL revision is biomechanically viable. Further testing of long-term incorporation of the ACL graft in an animal model, along with human clinical trials, should be performed before there is clinical acceptance of this technique.

Revision anterior cruciate ligament reconstruction

Revision reconstruction of the anterior cruciate ligament (ACL) introduces several diagnostic and technical challenges in comparison with primary ACL reconstruction. With the increasing numbers of original reconstructions combined with the continued expectation of high-level athletic participation, revision ACL reconstruction is likely to become more frequent. The purpose of this article was to summarize the causes of failure and the evaluation of the patient with recurrent instability. A review of the literature regarding results after revision ACL reconstruction was performed to assist in the decision-making process and patient counseling. Good results can be obtained in terms of functional stability after revision reconstruction, but chondral and meniscal injury as well as unrecognized associated pathologic instability may play a role in diminished outcomes. In addition, a wide variety of surgical techniques are reviewed to address problems associated with tunnel malposition, widening, and pre-existing hardware.