Graft fixation in cruciate ligament reconstruction

Anatomic double-bundle medial patellofemoral ligament reconstruction with aperture fixation using an adjustable-length loop device: a 2-year follow-up study

Background

To assess the clinical availability of an adjustable-length loop device for use in the double-bundle technique with aperture fixation at the patella and femur during anatomic double-bundle medial patellofemoral ligament reconstruction (DB-MPFLR) for recurrent patellar dislocation.

Methods

We retrospectively investigated 11 patients (12 knees) with recurrent patellar dislocation who underwent anatomic DB-MPFLR with an ipsilateral semitendinosus tendon autograft. The graft was folded in half, and its central portion was hanged using the adjustable-length loop device. Both free ends of the graft were fixed at the proximal and distal ends of the medial edge of the patella by using suture anchors, and the hanged graft loop was pulled into the femoral tunnel while maintaining equal tension on both bundles. Manual traction of the suture loops was applied to fix the graft appropriately in full range of motion (ROM) of the knee joint under arthroscopic guidance. Clinical outcomes such as re-dislocation, ROM, clinical scores (Kujala score, Lysholm score, and visual analogue scale score for anterior knee pain), and complications were assessed preoperatively and at 2 years postoperatively. Radiographic parameters indicating patellar position, including congruence angle and lateral patellofemoral angle, were measured at 4 different angles of knee flexion (30°, 45°, 60°, and 90°).

Results

At 4 different flexion angles of the knee joint, the preoperative congruence angle decreased significantly and the lateral patellofemoral angle increased significantly at the final follow-up (P <  0.001). Notably, the improvements in these angles were maintained with no significant differences at the 4 different flexion angles. None of the patients experienced subluxation or re-dislocation after surgery. The patellar instability symptoms improved, as confirmed on the basis of radiographic and other clinical outcomes.

Conclusion

New DB technique with aperture fixation at the patella and femur by using an adjustable-length loop device offers high stability with full ROM of the knee joint, can be considered as a feasible procedure and technique for recurrent patellar dislocation.

Biomechanical analysis of a double fixation method for tendon graft in porcine tibia – using an interference screw plus staple

Objective

The aim of the study was to compare the mechanical behavior of interference screw tibial fixation vs. screw-plus-staple tibial fixation in an animal model.

Methods

Thirty-six pieces of swine knee specimens were selected and divided into two groups: Group 1, tibial fixation with interference screw (n = 17), and Group 2, fixation with interference screw and staple (n = 19). The models were submitted to a single cycle of tension testing. The following variables were measured: graft cross-sectional area, failure point on 10 mm (F₁₀), yield load (F_y), and stiffness.

Results

The mean values of graft cross-sectional area, F₁₀, F_y, and stiffness did not present significant differences between the groups.

Conclusion

The addition of a second staple-type ligament fixation device, complementing the interference screw, did not increase the mechanical safety of the system.

Anterior Laxity at 2 Years After Anterior Cruciate Ligament Reconstruction Is Comparable When Using Adjustable-Loop Suspensory Fixation and Interference Screw Fixation

BACKGROUND

Adjustable-loop suspensory fixation (ALSF) devices are commonly used in anterior cruciate ligament reconstruction (ACLR). However, concern exists regarding the potential for lengthening under cyclical loads.

PURPOSE

To compare the residual anterior laxity of 2 methods of femoral fixation, ALSF versus interference screw fixation, in patients undergoing isolated ACLR in the absence of meniscal injuries. To determine the preoperative risk factors associated with residual postoperative anterior laxity.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A retrospective analysis was performed comparing 2 groups of patients that underwent primary ACLR using ALSF versus bioabsorbable interference screw fixation. Anterior knee laxity was assessed with Telos stress radiography, while functional outcomes were evaluated with the Knee injury and Osteoarthritis Outcome Score (KOOS) and Tegner activity level scale at a minimum of 2 years postoperatively. A multivariate analysis was performed to identify factors associated with residual postoperative laxity >3 mm.

RESULTS

Of the 1136 patients who underwent ACLR during the study period, 363 met the inclusion criteria. A total of 272 patients (75%) (mean age, 31.7 ± 10.7 years) with a mean follow-up of 25.7 ± 4.6 months (range, 24-36 months) consented to participate (screw group: n = 121; ALSF group: n = 151). The 2 groups were statistically comparable in terms of age, sex ratio, time from injury to surgery, graft diameter, preoperative laxity, preoperative objective International Knee Documentation Committee (IKDC) grade, and preoperative Tegner score. The mean postoperative laxity as a continuous variable was significantly different comparing the ALSF and screw groups (1.49 ± 1.98 mm and 2.32 ± 1.97 mm, respectively; P < .001). In the screw group, 76 patients (62.8%) had normal (<3 mm), 40 (33.1%) had nearly normal (3-6 mm), and 5 (4.1%) had abnormal (≥6 mm) postoperative knee laxity according to the IKDC grade, while in the ALSF group, 112 patients (74.2%) had normal, 37 (24.5%) had nearly normal, and 2 (1.3%) had abnormal laxity ( P = .0833). No significant difference was found in KOOS or Tegner scores comparing the 2 femoral fixation methods: KOOS, 90.6 ± 7.5 (ALSF group) and 90.6 ± 7.4 (screw group) ( P = .7631), versus Tegner, 6.5 ± 1.3 (ALSF group) and 6.3 ± 1.4 (screw group) ( P = .2992). A negative correlation was found between postoperative laxity and final Tegner ( r_s = -0.303, P < .001) and KOOS scores ( r_s = -0.168, P = .005). The initial univariate analysis showed differences between groups of patients with residual knee laxity ≥3 mm and <3 mm on preoperative pivot shift, preoperative laxity, age, fixation type, and preoperative objective IKDC grade. The multivariate analysis on these factors showed that the pivot shift remained the only significant predictor for residual laxity ≥3 mm for pivot shift grade 2 compared with grade 1 (odds ratio, 4.689 [95% CI, 2.465-9.286]) and for pivot shift grade 3 compared with grade 1 (odds ratio, 58.025 [95% CI, 12.757-557.741]) ( P < .001).

CONCLUSION

For primary ACLR, the use of an ALSF device for femoral fixation is associated with noninferior postoperative anterior knee laxity results compared with interference screw fixation at a minimum 2 years' follow-up. The preoperative pivot shift is the only significant risk factor for postoperative residual anterior knee laxity >3 mm.

Minimizing Graft-Tunnel Mismatch in Allograft Anterior Cruciate Ligament Reconstruction Using Blumensaat's Line: A Cadaveric Study

PURPOSE

To evaluate the accuracy of Blumensaat's line (BL) in predicting the tendinous graft length and tibial tunnel length (TTL) in an independent-tunnel anterior cruciate ligament reconstruction (ACLR) using a bone-patellar tendon-bone (BTB) allograft.

METHODS

Eighteen ACLRs were performed on cadaveric specimens using an anteromedial portal technique. All knees had no previous surgeries or deformities. Lateral knee radiographs of each specimen were taken prior to the ACLR, and BL was measured. Length-specific allografts for the tendinous portion of the grafts were then ordered by adding 20 mm to the length of BL. The TTL was predicted by subtracting BL and femoral tunnel length (FTL) from the overall graft length. Graft-tunnel mismatch (GTM) was recorded for each specimen. Statistical analysis compared overall results with the gold standard (0 mm) of GTM.

RESULTS

The average lateral femoral condyle width measured in line with the femoral tunnel was 33 ± 3.43 mm. The average FTL was 25 ± 0.54 mm. The average intra-articular distance (IAD) between femoral and tibial tunnel apertures was 31 ± 3.65 mm. The average TTL was 35 ± 2.21 mm. The difference between the predicted TTL and the actual TTL was not statistically significant (P = .3). The mean GTM was -0.9 ± 3.15 mm. There was no statistically significant difference between the BL method and the gold standard (P = .45). The mean percent difference between BL and the IAD was 5.2%.

CONCLUSIONS

The BL method can accurately predict the desired length for the tendinous portion of a BTB allograft as well as the TTL, thereby potentially minimizing GTM during arthroscopic BTB allograft ACLR. Patient-specific allografts can be ordered preoperatively based on BL.

CLINICAL RELEVANCE

This method provides the surgeon a way to avoid GTM preoperatively by ordering patient-specific grafts prior to performing an independent-tunnel BTB allograft ACLR.

Low re-rupture rate with BPTB autograft and semitendinosus gracilis autograft with preserved insertions in ACL reconstruction surgery in sports persons

PURPOSE

To compare the results of bone-patellar tendon-bone graft (BPTB), semitendinosus-gracilis graft with preserved insertions (STGPI) and semitendinosus-gracilis-free graft (STGF) in terms of graft failure, objective mechanical stability, functional outcome, and return to sports in elite and recreational sports persons. It was hypothesized that the STGPI graft provided superior outcome as compared to the other two grafts.

METHODS

Two hundred and forty-nine elite and recreational players who underwent ACL reconstruction surgery, with BPTB graft (N = 80), STGPI graft (N = 85), and STGF graft (N = 84) with a minimum follow-up of 2 years, were assessed using clinical tests, knee arthrometer (KT 1000™), single-leg hop test, Lysholm knee score, Tegner's activity scale, and return to sports. Groups were matched in terms of age, gender, mode of injury, side involved, the level of sports, associated injuries, and mean follow-up.

RESULTS

The median age of the patients was 24 years (range 16-46 years), with 227 males and 22 females, with a mean follow-up of 61.8 ± 25.9 months. At the final follow-up, the mean side-to-side difference by KT 1000™ was significantly superior in BPTB group (1.4 ± 2.1 mm) as compared to STGPI (1.9 ± 2.0 mm) and STGF group (2.5 ± 2.0 mm) (p = 0.002). The mean Lysholm knee score, Limb symmetry index (LSI) using single-leg hop test and the mean difference in pre-injury and post-surgery level of Tegner's activity scale were not significantly different. The rate of graft failure was significantly higher in STGF group (7.1%) as compared to BPTB (1.2%) and STGPI (1.2%) groups (p = 0.043).

CONCLUSION

BPTB graft is a better graft in terms of mechanical stability than STGPI and STGF grafts. STGPI graft and BPTB graft are superior to STGF graft in terms of graft failure rate. However, there is no statistically significant difference amongst the three grafts in terms of return to sports and clinical tests of instability. STGPI graft is another option in the clinical setting with low graft failure rate like that of BPTB graft and with the added advantage of not having significant donor site morbidity.

LEVEL OF EVIDENCE

III.

Adjustable- Versus Fixed-Loop Devices for Femoral Fixation in ACL Reconstruction: An In Vitro Full-Construct Biomechanical Study of Surgical Technique-Based Tibial Fixation and Graft Preparation

Background

Femoral suspensory fixation for anterior cruciate ligament (ACL) reconstruction has evolved from fixed- to adjustable-loop devices. However, there are still controversies regarding undesired lengthening of adjustable-loop devices.

Hypothesis

Adjustable-loop fixation will achieve similar elongation to that of fixed-loop devices, and intraoperative preconditioning will reduce initial elongation for adjustable-loop constructs.

Study Design

Controlled laboratory study.

Methods

Three adjustable-loop devices (GraftMax, TightRope, and Ultrabutton) and 2 fixed-loop devices (Endobutton and RetroButton) were used in an intraoperative surgical technique workflow according to an in vitro model with porcine bone and bovine tendons (8 specimens per device; N = 40 constructs tested). Each construct underwent 1000 cycles of position- and force-controlled dynamic loading, whereby a total elongation threshold of 3 mm was defined as clinical failure. Constructs were finally pulled to failure at 50 mm/min.

Results

There were no statistically significant differences among the devices for total or dynamic elongation. Total elongation (mean ± SD) for adjustable-loop constructs was 4.13 ± 1.46 mm for GraftMax, 2.78 ± 0.85 mm for TightRope, and 2.76 ± 0.45 mm for Ultrabutton; for the fixed-loop devices, total elongation was 2.85 ± 0.74 mm for Endobutton and 2.85 ± 1.03 mm for RetroButton. The GraftMax had a significantly lower initial force (95.5 ± 58.0 N) after retensioning, with the highest initial elongation (0.99 ± 0.60 mm). The Ultrabutton showed the greatest force loss (-105.9 ± 13.5 N) during position control cycling, which was significantly different from the GraftMax (-22.3 ± 28.2 N), with the smallest force loss (P < .001). The TightRope construct had a significantly smaller initial elongation (-0.36 ± 0.22 mm) and the greatest pull-to-failure load (958 ± 40 N) as compared with all of the other devices.

Conclusion

Adjustable- and fixed-loop configurations achieved statistically comparable fixation strength for total elongation. However, the GraftMax construct exceeded the total elongation threshold of clinical failure. The Ultrabutton produced the greatest loss of force during position control cycling, and the GraftMax button design prevented proper retensioning. The TightRope had a significant greater ultimate strength when compared with all other devices.

Clinical Relevance

Biomechanical testing according to a surgical technique workflow suggests that adjustable-loop devices can be considered a safe alternative to fixed-loop devices in ACL reconstruction.

Pull-out strength of four tibial fixation devices used in anterior cruciate ligament reconstruction

INTRODUCTION

In reconstructions of the anterior cruciate ligament (ACL), tibial fixation can be the weak point in the assembly during the early postoperative period. The present study sought to compare pull-out strength between four tibial fixation systems used in ACL reconstruction.

HYPOTHESIS

The study hypothesis was that all four devices show ≥450N pull-out strength with comparable biomechanical breakage characteristics.

MATERIAL AND METHODS

An experimental study used a mechanical model to perform axial traction on a synthetic ligament (polypropylene cord folded in four) implanted in an artificial tibia (Sawbones Proximal Tibia # 1116-2: model: normal anatomy; solid foam; size: medium) using four tibial fixation systems: Ligafix^® interference screw (SBM™); Bio-Intrafix^® (Mitek™); Translig^® (SBM™); RIGIDfix^® (SBM™). For each system, four models were tested using an Instron 5566^® traction machine, allowing 100mm/min stretching up to breakage. Study parameters comprised: pull-out strength, maximal whole assembly slippage, stiffness at breaking point, and type of break.

RESULTS

Mean pull-out strength was 450±24N (range, 421-488N) for Ligafix^®, 415±60N (327-454N) for Bio-Intrafix^®, 539±66N (449-636N) for RigidFix and 1067±211N (736-1301N) for Translig^®, and was significantly greater for Translig^® than for the other devices (p=0.02), which did not significantly differ from one another. The expected maximal load of 450N was reached in 100% of cases with Translig^® and RIGIDfix^® and in 50% of cases with Bio-Intrafix^® and Ligafix^®. There were no significant differences regarding stiffness. Ligafix^® showed significantly less slippage than the others (p=0.006), with breakage caused by the ligament sliding between bone and implant.

DISCUSSION

In this in-vitro study, the Translig^® fixation device showed better pull-out strength than the other three devices tested.

TYPE OF STUDY AND LEVEL OF EVIDENCE

Comparative laboratory study. Level II.

Cross Pin Versus Interference Screw for Femoral Graft Fixation in Hamstring Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-analysis of Clinical Outcomes

PURPOSE

To compare the effectiveness of a cross pin and interference screw for femoral graft fixation in primary anterior cruciate ligament reconstruction (ACLR) and provide an appropriate reference for orthopaedic surgeons.

METHODS

The Medline, Cochrane Library, Web of Science, Scopus, and PubMed databases were searched in March 2016, and comparative trials using cross-pin and interference screw devices for femoral graft fixation in primary hamstring ACLR with clinical outcome measurements were included in the review. Trials with no controlled groups, hybrid fixation, no clinical outcomes, or follow-up of less than 1 year were excluded. The quality of the included studies was assessed with the Cochrane Back Review Group 12-item scale. Abstracted data were pooled with fixed or random effects depending on the detected heterogeneity. The outcome measures were the scoring system and physical examination findings, including the Lysholm score, International Knee Documentation Committee score or grade, Tegner score, negative Lachman test, negative pivot-shift test, and instrumented side-to-side anterior-posterior laxity difference.

RESULTS

All the studies reviewed were of prospective design. Within the cross-pin group, patients who underwent hamstring ACLR showed a significantly smaller instrumented side-to-side anterior-posterior laxity difference when compared with interference screw fixation (weighted mean difference, 0.38 mm [95% confidence interval, 0.08-0.67 mm]; P = .01), whereas the results of a negative Lachman test and negative pivot-shift test were comparable. Outcomes regarding the scoring system did not reach a significant difference between the 2 groups.

CONCLUSIONS

The statistically decreased instrumented side-to-side anterior-posterior laxity difference achieved by cross-pin transfixation appears to be of limited clinical significance when compared with interference screw fixation in primary hamstring ACLR. Clinically, the performance of cross-pin devices did not show a significant advantage over that of the interference screw for femoral graft fixation in hamstring ACLR.

LEVEL OF EVIDENCE

Level II.

Femoral press-fit fixation versus interference screw fixation in anterior cruciate ligament reconstruction with bone-patellar tendon-bone autograft: 20-year follow-up

INTRODUCTION

The aim of this paper is to present our experience with femoral press-fit fixation in anterior cruciate ligament reconstruction using bone-patellar tendon-bone autograft.

METHODS

The patient population was randomly placed in two groups: group A (58 patients), who underwent femoral screw fixation; group B (62 patients), who underwent femoral press-fit fixation.

RESULTS

At last follow-up 9.2% of patients were lost; 28% of patients in group A and 64% of patients in group B had excellent International Knee Documentation Committee score (grade A); 66% of patients in group A and 32% of patients in group B had good International Knee Documentation Committee scores (grade B). The difference was statistically significant (p < 0.05).

CONCLUSIONS

Femoral press-fit fixation of bone- patellar tendon- bone autograft provides stable fixation at low cost, it ensures unlimited bone-to-bone healing and high primary stability, avoiding the disadvantages of hardware and the need for removal in case of revision.

Risk of Revision Was Not Reduced by a Double-bundle ACL Reconstruction Technique: Results From the Scandinavian Registers

BACKGROUND

Double-bundle anterior cruciate ligament (ACL) reconstruction has demonstrated improved biomechanical properties and moderately better objective outcomes compared with single-bundle reconstructions. This could make an impact on the rerupture rate and reduce the risk of revisions in patients undergoing double-bundle ACL reconstruction compared with patients reconstructed with a traditional single-bundle technique. The National Knee Ligament Registers in Scandinavia provide information that can be used to evaluate the revision outcome after ACL reconstructions.

QUESTIONS/PURPOSES

The purposes of the study were (1) to compare the risk of revision between double-bundle and single-bundle reconstructions, reconstructed with autologous hamstring tendon grafts; (2) to compare the risk of revision between double-bundle hamstring tendon and single-bundle bone-patellar tendon-bone autografts; and (3) to compare the hazard ratios for the same two research questions after Cox regression analysis was performed.

METHODS

Data collection of primary ACL reconstructions from the National Knee Ligament Registers in Denmark, Norway, and Sweden from July 1, 2005, to December 31, 2014, was retrospectively analyzed. A total of 60,775 patients were included in the study; 994 patients were reconstructed with double-bundle hamstring tendon grafts, 51,991 with single-bundle hamstring tendon grafts, and 7790 with single-bundle bone-patellar tendon-bone grafts. The double-bundle ACL-reconstructed patients were compared with the two other groups. The risk of revision for each research question was detected by the risk ratio, hazard ratio, and the corresponding 95% confidence intervals. Kaplan-Meier analysis was used to estimate survival at 1, 2, and 5 years for the three different groups. Furthermore, a Cox proportional hazard regression model was applied and the hazard ratios were adjusted for country, age, sex, meniscal or chondral injury, and utilized fixation devices on the femoral and tibial sides.

RESULTS

There were no differences in the crude risk of revision between the patients undergoing the double-bundle technique and the two other groups. A total of 3.7% patients were revised in the double-bundle group (37 of 994 patients) versus 3.8% in the single-bundle hamstring tendon group (1952 of 51,991; risk ratio, 1.01; 95% confidence interval (CI), 0.73-1.39; p = 0.96), and 2.8% of the patients were revised in the bone-patellar tendon-bone group (219 of the 7790 bone-patellar tendon-bone patients; risk ratio, 0.76; 95% CI, 0.54-1.06; p = 0.11). Cox regression analysis with adjustment for country, age, sex, menisci or cartilage injury, and utilized fixation device on the femoral and tibial sides, did not reveal any further difference in the risk of revision between the single-bundle hamstring tendon and double-bundle hamstring tendon groups (hazard ratio, 1.18; 95% CI, 0.85-1.62; p = 0.33), but the adjusted hazard ratio showed a lower risk of revision in the single-bundle bone-patellar tendon-bone group compared with the double-bundle group (hazard ratio, 0.62; 95% CI, 0.43-0.90; p = 0.01). Comparisons of the graft revision rates reported separately for each country revealed that double-bundle hamstring tendon reconstructions in Sweden had a lower hazard ratio compared with the single-bundle hamstring tendon reconstructions (hazard ratio, 1.00 versus 1.89; 95% CI, 1.09-3.29; p = 0.02). Survival at 5 years after index surgery was 96.0% for the double-bundle group, 95.4% for the single-bundle hamstring tendon group, and 97.0% for the single-bundle bone-patellar tendon-bone group.

CONCLUSIONS

Based on the data from all three national registers, the risk of revision was not influenced by the reconstruction technique in terms of using single- or double-bundle hamstring tendons, although national differences in survival existed. Using bone-patellar tendon-bone grafts lowered the risk of revision compared with double-bundle hamstring tendon grafts. These findings should be considered when deciding what reconstruction technique to use in ACL-deficient knees. Future studies identifying the reasons for graft rerupture in single- and double-bundle reconstructions would be of interest to understand the findings of the present study.

LEVEL OF EVIDENCE

Level III, therapeutic study.

A new femoral fixation device for anterior cruciate ligament reconstruction using the outside-in technique and hamstring tendon graft: A comparison between two devices in cadaveric human knee models

BACKGROUND

A new device (T-anchor) was developed for ACL reconstruction and is implanted via the outside-in technique using hamstring grafts. The purpose of this study was to compare the T-anchor with the EndoButton Direct.

METHODS

This study was conducted on 30 cadaveric knees (15 matched pairs). There were two groups of 15 each in the T-anchor and EndoButton Direct groups. After the harvest of grafts, fixation site profile and graft length were measured by loading the grafts onto both devices. They were then tested on a universal testing machine to assess elongation after cyclic loading, load to failure, ultimate load, and mode of failure.

RESULTS

The fixation site profile was lower in the T-anchor group than in the EndoButton Direct group (2.3±0.4mm vs. 4.7±1.0mm, P<0.001). The length of the graft-device complex of the T-anchor specimens was longer than that of the EndoButton Direct specimens (125.0±8.9mm vs. 115.0±8.7mm, P<0.001). The mean cyclic elongation was lower for the T-anchor group when compared with the EndoButton Direct group (2.4±0.6mm vs. 3.9±2.6mm, P=0.015). There was no statistically significant difference in ultimate load and load to failure between the T-anchor and EndoButton Direct groups. For mode of failure, the T-anchor fared better (P=0.013) with all failures attributed to specimens.

CONCLUSIONS

In this cadaveric study, the new device, T-anchor, performed better than the EndoButton Direct with respect to the above-mentioned study parameters except for ultimate load and load to failure.

ACL reconstruction using femoral Rigid-fix and tibial Bio-intrafix devices

OBJECTIVES

The objective of this study is to report the clinical and functional outcomes of Hamstring graft ACL reconstruction fixed with femoral Rigid-fix and tibial Bio-intrafix devices.

METHODS

In a prospective study, the clinical (Lysholm score) and functional outcomes (International Knee Documentation Committee, IKDC) of 44 patients who underwent autologus hamstring graft ACL reconstruction using femoral Rigid-fix and tibial Bio-intrafix devices, were evaluated at the end of one year. Joint laxity was assessed with KT-1000 arthrometer (MEDmetric, San Diego, CA).

RESULTS

None of the patients complained of instability, joint swelling or severe pain in the postoperative period. The IKDC score improved from 66.62 + 5.36 to 92.36 + 5.30 (P < 0.001). Lysholm scores in the preoperative and follow up period were 68.28 + 5.54 and 93.87 + 4.75 respectively; the improvement was statistically significant with P value < 0.001. Similarly, the mean anterior translation of tibia improved from 7.45 mm in the preoperative period to 3.89 mm after one year of ACL reconstruction. Associated meniscus injury didn't have significant impact on the overall outcome. No intraoperative or postoperative complications were documented.

CONCLUSION

Hamstring graft fixation using femoral Rigid-fix and tibial Bio-intrafix devices provide secure graft fixation and allows aggressive rehabilitation. The clinical and functional outcome of this hybrid fixation technique is rewarding.

Pullout strength of a novel hybrid fixation technique (Tape Locking Screw™) in soft-tissue ACL reconstruction: A biomechanical study in human and porcine bone

INTRODUCTION

A novel hybrid anterior cruciate ligament (ACL) reconstruction technique known as Tape Locking Screw™ (TLS) is gaining popularity. Utilizing a suspension-type construct in conjunction with an interference screw, this technique has demonstrated successful initial clinical results with the use of quadruple hamstring graft. However, there is currently limited data available on the biomechanical strength of this fixation. This study investigates the pullout strength of the construct in human distal femora as well as in a porcine model. The construct is tested in isolation, without the use of any graft. We hypothesized that the pullout strength of this construct would be similar to or better than current fixation systems available.

MATERIALS AND METHODS

The Tape Locking Screw hybrid fixation system was implanted into twenty-two fresh frozen human distal femora (50-89 years old) randomized to 10×20mm titanium or polyether ether ketone (PEEK) screws by a single sports fellowship trained orthopedic surgeon. Given that the graft is secured to polyethylene terephthalate tape within the construct, the construct was implanted without any graft in order to isolate the device for biomechanical testing. After implantation, a tensile force was applied directly to the loop of tape at a loading rate of 5mm/min using an electromechanical testing system. The failure load was calculated from the resultant load-displacement curve. Specimens were then visually examined for mode of failure. Similar biomechanical tests were performed on sixteen porcine femora.

RESULTS

In the human model, the mean pullout strength was 523±269N with the PEEK screw and 578±245N with the titanium screw. In the porcine femur model, mean strength was 616±177N with PEEK, 584±245N with titanium. There was no statistically significant difference in failure loads between these four groups. Tape slippage at the screw bone interface was the primary mode of failure in all the groups tested.

DISCUSSION

Our results demonstrate that the hybrid technique provides excellent pullout strength in comparison to other soft-tissue ACL fixation methods, with tape slippage being the mode of failure in all specimens tested. This data, in addition to the advantages of the TLS system, support its consideration in the armamentarium of constructs available for soft-tissue ACL reconstruction.

LEVEL OF EVIDENCE

Laboratory controlled study level 2.

Femoral interference screw fixation of hamstring and quadriceps tendons for ACL reconstruction

PURPOSE

This cadaveric study compares the biomechanical properties of femoral graft fixation in ACL reconstruction of either quadriceps or hamstring tendon grafts with four different interference screws. The hypothesis was that quadriceps tendon grafts provide at least equal results concerning gap formation during cyclic loading and ultimate failure load compared to hamstring tendon grafts with four different interference screws.

METHODS

Eighty porcine femora underwent interference screw fixation of human tendon grafts for ACL reconstruction. Either quadriceps (Q) or hamstring (H) tendon grafts and four different bioabsorbable interference (Wolf (W), Storz (S), Mitek (M), Arthrex (A)) screws were used, resulting in 8 groups with 10 specimens per groups (WQ, WH, SQ, SH, MQ, MH, AQ, AH). Biomechanical analysis included pretensioning the constructs with 60 N for 30 s, then cyclic loading of 500 cycles between 60 and 250 N at 1 Hz in a servohydraulic testing machine, with measurement of elongation and stiffness including video measurements. After this, ultimate failure load and failure mode analysis were performed.

RESULTS

No statistically significant difference could be noted between the groups regarding gap formation during cyclic loading [Cycles 21-500 (mm): WQ 3.6 ± 0.8, WH 3.9 ± 1.4, SQ 3.6 ± 0.8, SH 3.3 ± 1.5, MQ 4.3 ± 0.8, MH 4.6 ± 1.0, AQ 4.8 ± 0.8, AH 4.3 ± 1.5, n.s.], stiffness during cyclic loading [Cycles 21-500 (N/mm): WQ 72.9 ± 16.9, WH 71.6 ± 20.7, SQ 69.5 ± 23.9, SH 77.4 ± 25.1, MQ 59.6 ± 11.2, MH 48.4 ± 15.4, AQ 48.8 ± 12.7, AH 51.9 ± 22.2, n.s.], and ultimate failure load [(N): WQ 474.4 ± 88.0, WH 579.3 ± 124.2, SQ 493.9 ± 105.2, SH 576.0 ± 90.4, MQ 478.6 ± 59.0, MH 543.9 ± 119.7, AQ 480.2 ± 93.8, AH 497.8 ± 74.2, n.s.].

CONCLUSIONS

Quadriceps tendon grafts yield comparable biomechanical results for femoral interference screw fixation in ACL reconstruction compared to hamstring tendon grafts. From a clinical perspective, quadriceps tendon grafts should therefore be considered as a good option in ACL reconstruction in the future.

Resorbable screw and sheath versus resorbable interference screw and staples for ACL reconstruction: a comparison of two tibial fixation methods

PURPOSE

The anterior cruciate ligament (ACL) reconstruction is one of the most performed and successful orthopaedic procedures. The results are considered independent by the choice of the graft and the fixation devices. A growing interest on resorbable non-metallic fixation devices versus standard metallic fixation devices has been noted over recent years with few clinical experiences reported in the literature. The aim of this study is to compare the clinical and radiological outcomes of patients undergoing ACL reconstruction using autologous hamstring tendons with tibial fixation by a centrally placed resorbable screw and sheath to a combination of an eccentrically placed resorbable interference screw and supplementary staple fixation.

METHODS

Ninety patients undergoing an isolated, single-bundle, primary ACL reconstruction with autologous hamstring tendons, using the same femoral fixation, were randomized to a tibial fixation with a centrally placed resorbable screw and sheath, BioIntrafix (group A), or an eccentrically placed resorbable interference screw, BioRCI, and two non-resorbable staples (group B). The latter has represented for many years our standard fixation method. Clinical evaluations (KOOS, IKDC, KT-2000™ side-to-side difference) and radiological analyses were conducted in both groups with a minimum follow-up of 2 years.

RESULTS

We assisted in a satisfactory pain relief and functional improvements, without significant clinical and radiological differences in both groups. No further surgery was needed in patients with the screw/sheath tibial fixation. Seven patients with the screw/staples tibial fixation needed the surgical removal of the fixation devices due to pes anserinus irritation or local infection years after the index operation. Other parameters such as the tunnel enlargement were not statistically different in the two groups.

CONCLUSIONS

Good clinical and radiological outcomes of ACL reconstruction by a screw/sheath tibial fixation have been reported showing comparable results with respect to screw/staples fixation. There were no failures associated with loss of fixation with either of tibial fixation methods. A fewer number of surgical removals of tibial devices were also recorded in patients treated by the screw/sheath fixation system, related to the absence of local intolerance or infection compared to subjects with a standard tibial fixation.

Outcomes of ACL Reconstruction With Fixed Versus Variable Loop Button Fixation

Suspensory femoral fixation of anterior cruciate ligament (ACL) grafts with fixed loop button and variable loop button devices has gained popularity for ACL reconstruction. This study examined these 2 methods of fixation to determine their effect on graft laxity and patient-reported outcome scores. A database search was performed to identify patients who had undergone ACL reconstruction with either a fixed loop or a variable loop button technique performed by the primary surgeon. Lysholm, Tegner, and 12-Item Short Form Health Survey scores were obtained, and KT-1000 knee ligament arthrometer (MEDmetric, San Diego, California) mechanical knee testing was performed. Results were compared with the uninjured knee. Of the 112 patients who were identified, 91 met the study criteria. Of these patients, 57 completed KT-1000 knee testing, 33 in the variable group and 24 in the fixed group. The average KT-1000 value for the variable group was 0.38 mm, and the average for the closed group was 0.92 mm (P=.19; 95% confidence interval, -0.28 to 1.35). Among the 19 patients in the variable group and the 13 in the closed group who completed the subjective outcomes questionnaires, no statistically significant difference was found. Clinically lax knees (KT-1000>3 mm) were found in 6.1% and 12.5% of patients in the variable group and the fixed group, respectively (P=.2). The variable group had a rerupture rate of 4.7%, whereas the fixed group had a rerupture rate of 8.7% (P=.21). The study found no statistical difference in ACL graft laxity or postoperative functional outcomes between grafts fixed with the variable loop or fixed loop button technique. [Orthopedics. 2017; 40(2):e275-e280.].

Anterior cruciate ligament reconstruction: MR imaging findings

More than two million people tear their anterior cruciate ligament (ACL) each year, and ACL reconstruction occupies a significant proportion of everyday orthopedic practice, being one of the most commonly performed sports medicine surgical procedures. Patients with postoperative symptoms are frequently imaged to monitor ligament grafts and to identify complications. Given the number of patients undergoing ACL reconstruction, knowledge of the potential complications of this surgery is essential for radiologists. This article provides a review of imaging of ACL reconstruction procedures and the potential complications specific to this surgery.

Tibial fixation in anterior cruciate ligament reconstruction

OBJECTIVE

To determine whether supplementary tibial graft fixation with a staple is routinely necessary for anterior cruciate ligament (ACL) reconstructions.

METHODS

We retrospectively reviewed a series of consecutive patients who underwent ACL reconstruction at our institution from April 2012 to July 2013. Patients who fulfilled the inclusion and exclusion criteria were divided into two groups, of which one with tibial fixation of the graft with a biointerference screw alone (biointerference screw group) and the other with tibial fixation of the graft with a biointerference screw and supplementary extra tunnel staple fixation (biointerference screw and staple group). All the surgeries were performed by a single fellowship-trained sports surgeon, using a standardized transportal technique and rehabilitation protocol. Both well-matched groups were evaluated at 1-year follow-up objectively for ligament laxity using instrumented testing with KT-2000 arthrometer and clinical tests as well as subjectively with the validated International Knee Documentation Committee 2000 (IKDC) and Lysholm knee score. All complications were reported.

RESULTS

A total of 64 patients (31 in the only biointerference screw group and 33 in the biointerference screw and staple group) were included in the study. At 1 year, there was no significant difference in the objective and subjective outcome assessments between the two groups. However, four patients from the group with supplementary staple experienced symptomatic hardware on kneeling of which two necessitated removal of hardware.

CONCLUSION

Our study showed that supplementary tibial graft fixation with a staple is not routinely necessary for ACL reconstructions. It confers no additional benefits when compared with the use of biointerference screw alone for tibial graft fixation but may increase the risks of symptomatic hardware.

Incorporation of Hamstring Grafts Within the Tibial Tunnel After Anterior Cruciate Ligament Reconstruction: Magnetic Resonance Imaging of Suspensory Fixation Versus Interference Screws

BACKGROUND

The success of anterior cruciate ligament (ACL) reconstruction requires solid graft incorporation within the tunnels to enable graft remodeling. Resorbable interference screws (RIS) provide limited tendon-bone contact because much of the tunnel circumference is occupied by the screw itself, while adjustable suspensory fixation (ASF) systems provide larger contact zones, which favor ligamentization.

PURPOSE

To evaluate ligamentization of a 4-strand semitendinosus (4ST) graft fixed with ASF compared with RIS within the tibial bone tunnel at 6 months postoperatively using magnetic resonance imaging (MRI).

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

We prospectively enrolled 121 consecutive patients undergoing primary ACL reconstruction using a single-bundle 4ST graft. The femoral end of the graft was fixed using suspensory fixation in all knees. The tibial end of the graft was fixed using ASF in 67 knees and RIS in 54 knees. Six months postoperatively, knee laxity measurements were taken, and MRI was performed to assess graft incorporation within the tibial tunnel.

RESULTS

At 6-month follow-up, MRI scans of 109 knees were available for analysis. The mean tibial tunnel enlargement in the ASF group was 2.3 ± 1.1 mm (range, 0.5-6.0 mm), while in the RIS group, it was 4.7 ± 2.8 mm (range, 0.5-19.0 mm) (P < .001). The Howell graft signal assessment findings were excellent in 97% of knees in the ASF group and in 25% of knees in the RIS group (P < .001). The mean signal-to-noise quotient (SNQ) was 0.078 ± 0.62 in the ASF group and 0.671 ± 0.83 in the RIS group (P < .001).

CONCLUSION

ASF provides more favorable conditions than RIS for the incorporation and ligamentization of 4ST grafts within the tibial tunnel. The ASF system used showed very little tunnel widening, which suggests that it grants stabilization. The SNQ was also considerably better in the ASF group.

The ACL Fixation

ACL rupture frequently occurs due to a pivotal movement between the tibia and femur. In lack of reconstruction surgery of the ligament, osteoarthritis appears. The ACL graft can be fitted through different systems: compression, expansion and suspension. Although different in technique, the clinical end-results show little differences.

Evaluation of biomechanical properties: are porcine flexor tendons and bovine extensor tendons eligible surrogates for human tendons in in vitro studies?

INTRODUCTION

Porcine flexor tendons, bovine extensor tendons, and human (semitendinosus) tendons are frequently used as substitutes for human ACL grafts in biomechanical in vitro studies. This study compares the biomechanical properties and structural differences of these tendons.

MATERIALS AND METHODS

In this biomechanical study, fresh-frozen porcine flexor tendons, bovine extensor tendons, and human semitendinosus tendons were used (n = 36). The tendons were mounted in a uniaxial testing machine (Zwick/Roell) with cryo-clamps, leaving a 60 mm tendon part free between the two clamps. Specimens have been loaded to failure to evaluate the biomechanical parameters stiffness, yield load, and maximum load. A Total Collagen Assay Kit was used to detect differences in the total collagen type I concentration (n = 30). A one-way ANOVA was performed to detect differences in the means. The significance level was set at p < 0.05.

RESULTS

There were no significant differences in the stiffness between the groups (bovine 194 ± 43 N/mm, porcine 211 ± 63 N/mm, and human cadaveric 208 ± 58 N/mm). The yield and maximum loads were high (>1000 N) in all groups, but they were significantly increased in both animal specimens (means of 1681-1795 N) compared with human cadaveric specimen (means of 1289-1406 N; p < 0.01). No difference in the collagen type I concentration was detected (N.S.).

CONCLUSION

Porcine flexor and bovine extensor tendons are eligible substitutes with similar stiffness and high failure loads compared with human cadaveric semitendinosus tendons in in vitro studies.

Hybrid Tibia Fixation of Soft Tissue Grafts in Anterior Cruciate Ligament Reconstruction: A Systematic Review

BACKGROUND

Optimal fixation of soft tissue grafts in anterior cruciate ligament (ACL) reconstruction remains a controversial topic, and tibial-sided fixation is frequently cited as the "weak point" of the femur-graft-tibia construct. Some studies have recommended the use of hybrid fixation (combining intratunnel aperture fixation and extracortical suspensory fixation) on the tibial side to increase the strength of the reconstructed ACL and decrease the risk of graft slippage and subsequent failure. However, no consensus has emerged on the necessity or suitability of this technique, relative to single modes of fixation.

PURPOSE

This study sought answers to the following questions: (1) Does hybrid fixation result in stronger, stiffer initial fixation of soft tissue grafts? (2) Does hybrid fixation reduce side-to-side laxity differences in clinical practice? (3) Does hybrid fixation increase complication rates when compared with a single mode of tibial fixation?

STUDY DESIGN

Systematic review.

METHODS

A systematic keyword search of PubMed, EMBASE, the Cochrane Library of Systematic Reviews, and the PROSPERO International Prospective Register of Systematic Reviews was performed. Candidate articles were included if they compared biomechanical or clinical characteristics of tibial-sided hybrid fixation (defined as a combination of aperture and suspensory fixation methods) with single-mode fixation of soft tissue grafts in ACL reconstruction.

RESULTS

A total of 21 studies (15 biomechanical, 6 clinical) met criteria for inclusion. Most biomechanical studies reported significantly increased strength and stiffness with hybrid fixation versus single modes of fixation. Among clinical studies, 66% reported significantly decreased anterior-posterior laxity when hybrid fixation methods were employed, with the remainder showing no difference.

CONCLUSION

Hybrid methods of tibial-sided graft fixation in ACL reconstruction result in stronger initial fixation and less side-to-side laxity after healing but do not change patient-reported outcomes at 1- to 3-year follow-up.

REGISTRATION

PROSPERO International Prospective Register of Systematic Reviews No. 42014015464.

Can an adjustable-loop length suspensory fixation device reduce femoral tunnel enlargement in anterior cruciate ligament reconstruction? A prospective computer tomography study

BACKGROUND

The aim of this study was to compare bone femoral tunnel enlargement in patients who underwent anterior cruciate ligament (ACL) transtibial reconstruction using an adjustable-loop length suspensory fixation device and a fixed-loop length suspensory fixation device.

METHODS

All patients treated for ACL reconstruction with an ipsilateral hamstring between March 2013 and March 2014 were evaluated. Subjects were assigned to Group A (TightRope™ (TR) femoral fixation) or Group B (EndoButton® (EB) femoral fixation). All patients were evaluated with the Lachman test, pivot-shift test, 2000 International Knee Documentation Committee (IKDC) knee examination and KT1000 arthrometer. The subjective evaluation was performed using the 2000 IKDC Subjective Knee score, the Lysholm knee score, and the Tegner activity scale. CT examination was performed to evaluate femoral tunnel enlargement at four different levels. All patients were assessed at a 12month follow-up visit. Power analysis was performed a priori in accordance with the femoral tunnel enlargement values from the CT scans. Differences with P-values of ≤0.05 were considered to be statistically significant.

RESULTS

The groups were homogenous at baseline with regard to age, gender, BMI, dominance and disease duration. At the final follow-up, no statistically significant differences (P>0.05) were found according to subjective and objective clinical outcome measures. According to the femoral tunnel enlargement, no statistically significant difference was found between the two groups (P>0.05).

CONCLUSION

In transtibial ACL reconstruction, the use of a fixed or adjustable-loop length device products, on the femoral side, led to similar clinical and radiological results.

Quantitative assessment of patellar vascularity following bone-patellar tendon-bone autograft harvest for ACL reconstruction

PURPOSE

Recent anatomic studies have suggested that the dominant arterial supply of the patella enters through the inferior pole. Based upon these findings, we hypothesized that bone-patellar tendon-bone graft harvest can significantly diminish patellar vascularity.

METHODS

Nine matched pair cadaveric knee specimens (mean age 47.4 years) were dissected and cannulated. A single knee was selected to undergo routine graft harvest, and the contralateral knee was left intact to serve as a control. Gadolinium was injected, and magnetic resonance imaging (MRI) signal enhancement was quantified to determine differences in uptake. Each matched pair was subsequently injected with a urethane polymer compound and dissected to correlate vessel disruption with MRI findings.

RESULTS

We identified two predominating patterns of vessel entry. In one pattern, the vessel entered the inferomedial aspect (five o'clock/right, seven o'clock/left) of the patella and was disrupted by graft harvest in 2/9 (22.2 %) pairs. In the second pattern, the vessel entered further medial (four o'clock/right, eight o'clock/left) and was not disrupted (7/9, 78.8 %). The mean decrease in gadolinium uptake following disruption of the predominant vessel measured 56.2 % (range 42.6-69.5 %) compared to an average decrease of 18.3 % (range 7.1-29.1 %) when the dominant arterial supply to the inferior pole remained intact (p < 0.04).

CONCLUSION

Medial entry of the predominant vessel precluded vessel disruption. Disruption of the dominant arterial supply can result in a significant decrease in patellar vascularity. Modification of graft harvest techniques and areas of surgical dissection should be explored to minimize vascular insult. Further correlation with clinical studies/outcomes is necessary to determine a potential association between vascular insult and anterior knee pain.

Temporal Changes in Cellular Repopulation and Collagen Fibril Remodeling and Regeneration After Allograft Anterior Cruciate Ligament Reconstruction: An Experimental Study Using Kusabira-Orange Transgenic Pigs

BACKGROUND

Distinguishing recipient cells from donor ligament cells is difficult in the early graft-healing phase after anterior cruciate ligament (ACL) reconstruction. The ability to track the distribution and differentiation of recipient cells using genetically engineered transgenic (Tg) animals would have significant clinical and research effects on graft healing after ACL reconstruction.

HYPOTHESIS

Kusabira-Orange Tg pigs may allow the tracking of recipient cells infiltrating the graft after ACL reconstruction. The repopulation of recipient cells within the graft would be apparent even in the early graft-healing phase when necrotic donor cells are still present.

STUDY DESIGN

Descriptive laboratory study.

METHODS

In 17 genetically engineered Tg pigs, which carried the red fluorescent protein Kusabira-Orange, ACL reconstruction was performed on the right knee using a digital flexor tendon harvested from wild-type pigs. Tissue samples harvested at different time points were subjected to histological, immunohistochemical, and electron microscopic analyses.

RESULTS

At 3 weeks postoperatively, recipient cells expressing red fluorescence embraced the graft and were infiltrating the central part of the graft. These cells with oval nuclei gradually infiltrated the gap of collagen fibers, losing their regular orientation. At 6 weeks, cellularity within the graft had doubled to match that of the native ACL, while acellular necrotic regions still existed centrally. Ubiquitous cellular distributions resembling the native ACL were observed at 24 weeks. Electron microscopic analysis showed that the mean collagen fibril diameter and density gradually decreased over 24 weeks.

CONCLUSION

Genetically engineered pigs carrying the Kusabira-Orange gene were useful animal models for analyzing intrinsic and extrinsic cellular dynamics during the course of graft healing after ACL reconstruction. Cellular repopulation by recipient cells occurred in the very early stage, and the cellular distribution within the graft resembled that in the native ACL by 24 weeks, but the reconstructed graft had not restored the ultrastructure of the native ACL by that stage.

CLINICAL RELEVANCE

In allograft ACL reconstruction in a pig model, cellular repopulation was completed by 24 weeks after surgery, but the collagen matrix had not resumed the ultrastructure of the native ACL. Surgeons should be aware that risks may remain with returning to sports activities at 24 weeks after surgery.

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

Background:

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

Purpose/Hypothesis:

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

Study Design:

Cohort study; Level of evidence, 2.

Methods:

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

Results:

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

Conclusion:

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

Clinical Relevance:

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

Magnesium inference screw supports early graft incorporation with inhibition of graft degradation in anterior cruciate ligament reconstruction

Patients after anterior cruciate ligament (ACL) reconstruction surgery commonly encounters graft failure in the initial phase of rehabilitation. The inhibition of graft degradation is crucial for the successful reconstruction of the ACL. Here, we used biodegradable high-purity magnesium (HP Mg) screws in the rabbit model of ACL reconstruction with titanium (Ti) screws as a control and analyzed the graft degradation and screw corrosion using direct pull-out tests, microCT scanning, and histological and immunohistochemical staining. The most noteworthy finding was that tendon graft fixed by HP Mg screws exhibited biomechanical properties substantially superior to that by Ti screws and the relative area of collagen fiber at the tendon-bone interface was much larger in the Mg group, when severe graft degradation was identified in the histological analysis at 3 weeks. Semi-quantitative immunohistochemical results further elucidated that the MMP-13 expression significantly decreased surrounding HP Mg screws with relatively higher Collagen II expression. And HP Mg screws exhibited uniform corrosion behavior without displacement or loosening in the femoral tunnel. Therefore, our results demonstrated that Mg screw inhibited graft degradation and improved biomechanical properties of tendon graft during the early phase of graft healing and highlighted its potential in ACL reconstruction.

Anterior Cruciate Ligament: Structure, Injuries and Regenerative Treatments

Anterior cruciate ligament (ACL) is one of the most vulnerable ligaments of the knee. ACL impairment results in episodic instability, chondral and meniscal injury and early osteoarthritis. The poor self-healing capacity of ACL makes surgical treatment inevitable. Current ACL reconstructions include a substitution of torn ACL via biological grafts such as autograft, allograft. This review provides an insight of ACL structure, orientation and properties followed by comparing the performance of various constructs that have been used for ACL replacement. New approaches, undertaken to induce ACL regeneration and fabricate biomimetic scaffolds, are also discussed.

Anterior cruciate ligament reconstruction in adolescents (Tanner stages 2 and 3)

PURPOSE

Management of anterior cruciate ligament injuries in skeletally immature patients (in Tanner stages 2 and 3) is controversial. Conventional reconstruction used in adults can cause iatrogenic growth disturbance due to physeal damage, and studies that report long-term results using a specific technique are scarce. The aim of this study is to evaluate in a large series the mid- and long-term results of a partial transphyseal technique and define the safe percentage of lesions of the femoral growth plate.

METHODS

Between 1989 and 2012, 42 adolescents at risk of growth disturbances (growth prediction of lower limbs >5 cm-Tanner 2, 3) underwent reconstruction of the anterior cruciate ligament using the semitendinosus and gracilis tendons. Growth characteristics of all the patients were assessed preoperatively, and the percentage of damage that would be produced in the femoral physis by the drilling of a 6-mm-diameter tunnel was determined. The technique used achieved graft fixation at both insertion sites, drilling the femoral physis and avoiding the tibial physis. We distinguished two groups: (a) long-term follow-up (mean 13 years 7 months, min 10.9, max 16.2) and (b) medium follow-up (mean 6 years 3 months, min 3.7, max 9.9). All knees were evaluated subjectively by history and objectively by KT2000 testing, and X-rays of both knees were compared for osteoarthritis using the Kellgren-Lawrence classification.

RESULTS

In group A (12 patients) one osteoarthritis grade 2, one instability, and ten good stability and function were observed. The mean KT2000 arthrometer values at 30 lb showed a difference of +2.4 mm (range 1-4 mm) between the operated and non-operated sides (p < 0.05). In group B (21 patients) no growth disturbance of the lower limbs, two failures (reinjury while participating in pivoting sports), and 19 good stability and function were observed. The mean KT2000 arthrometer values at 30 lb showed a difference of +1.9 mm (range 1-5 mm) between the operated and non-operated sides (p < 0.05). The average IKDC score of all the patients was 90 (min: 68, max: 97). None of the adolescents had consequences on growth after an eccentric damage passing tendons less than 7% on the frontal plane and of 1% on cross-sectional area of the femoral physis, and after an oblique tunnel passing 6-mm-diameter tendons of the tibial epiphyseal nucleus.

CONCLUSIONS

This study defines the possibility to perform a partial transphyseal intra-articular ACL reconstruction in patients in Tanner stages 2 and 3 that avoids tibial physis, involves the distal femoral physis, and produces good results at mid- and long-term follow-up without causing growth disturbances.

LEVEL OF EVIDENCE

IV.

In vivo bone tunnel remodeling in symptomatic patients after ACL reconstruction: a retrospective comparison of articular and extra-articular fixation

BACKGROUND

there is only a paucity of studies dealing with bone remodeling within the tunnels after anterior cruciate ligament (ACL) reconstruction. The objective of this study was to evaluate the influence of tendon graft type and surgical fixation technique on bone tunnel remodeling in patients with symptomatic knees after ACL reconstruction.

METHODS

in a retrospective study 99mTc-HDP bone tracer uptake (BTU) in SPECT/CT of 57 knees with symptoms of pain and/or instability after ACL reconstruction was investigated. All 57 knees were subdivided according their anatomy (femur and tibia), fixation (articular versus extra-articular fixation) and graft types into eight groups: femoral-articular versus extra-articular fixation using bone-patellar tendon-bone (BPTB) and hamstring autografts; tibial-articular versus extra-articular fixation using patellar tendon and hamstring autografts; BTU grading for each area of the localisation scheme were recorded. Tunnel diameter and length was measured in the CT scans.

RESULTS

BTU was higher for the articular fixation in the femur and for the extra-articular fixation in the tibial tunnel. Patellar tendon graft fixation showed a significantly higher BTU in the superior-lateral and posterior-central area of the tibia, meaning the areas of the tibial tunnel near the entrance into the joint. Tunnel enlargement correlated significantly with increased BTU (p<0.05).

CONCLUSION

assessment of in vivo bone tunnel remodelling in symptomatic patients after ACL reconstruction revealed different patterns of BTU with regards to graft and fixation method.

Fixation of Soft Tissue to Bone: Techniques and Fundamentals

A myriad of orthopaedic injuries require surgical fixation of torn connective tissue to an osseous insertion site with either direct repair or reconstruction with a soft-tissue graft. Numerous factors influence the strength of a soft-tissue-to-bone fixation construct, including tissue quality, implant strength, contact area and pressure, and tensioning. Each fixation technique differs with respect to biologic integration, biomechanical stability, and failure mechanism. Fixation methods may or may not require an implant, such as interference screws, staples, internal buttons, transfixion pins, or suture anchors. Understanding the optimal method of soft-tissue fixation for a given scenario is crucial for successful repair or reconstruction.

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.

Registry data highlight increased revision rates for endobutton/biosure HA in ACL reconstruction with hamstring tendon autograft: a nationwide cohort study from the Norwegian Knee Ligament Registry, 2004-2013

BACKGROUND

Compared with a patellar tendon autograft (PT), a hamstring tendon autograft (HT) has an increased risk of revision after anterior cruciate ligament reconstruction (ACLR). There are no studies analyzing whether this can be explained by inferior fixation devices used in HT reconstruction or whether the revision risk of ACLR with an HT or a PT is influenced by the graft fixation.

PURPOSE

To compare the risk of revision and the revision rates between the most commonly used combinations of fixation for HTs with PTs.

STUDY DESIGN

Cohort study; Level of evidence, 2.

METHODS

This study included all patients registered in the Norwegian Knee Ligament Registry from 2004 through 2013 who underwent primary PT or HT ACLR with no concomitant ligament injury and known graft fixation. The 2-year revision rates were calculated using the Kaplan-Meier analysis. Hazard ratios (HRs) for revision at 2 years were calculated using multivariate Cox regression models.

RESULTS

A total of 14,034 patients with primary ACLR were identified: 3806 patients with PTs and 10,228 patients with HTs; the mean follow-up time was 4.5 years. In the HT group, 5 different combinations of fixation in the femur/tibia were used in more than 500 patients: Endobutton/RCI screw (n = 2339), EZLoc/WasherLoc (n = 1352), Endobutton/Biosure HA (n = 1209), Endobutton/Intrafix (n = 687), and TransFix II/metal interference screw (MIS) (n = 620). The crude 2-year revision rate for patients with PTs was 0.7% (95% CI, 0.4%-1.0%), and for patients with HTs, it ranged between the groups from 1.5% (95% CI, 0.5%-2.4%) for TransFix II/MIS to 5.5% (95% CI, 4.0%-7.0%) for Endobutton/Biosure HA. When adjusted for detected confounding factors and compared with patients with PTs, the HR for revision at 2 years was increased for all HT combinations used in more than 500 patients, and the combinations Endobutton/Biosure HA and Endobutton/Intrafix had the highest HRs of 7.3 (95% CI, 4.4-12.1) and 5.5 (95% CI, 3.1-9.9), respectively.

CONCLUSION

The choice of fixation after ACLR with an HT has a significant effect on a patient's risk of revision. In this study population, none of the examined combinations of HT fixation had a revision rate as low as that for a PT.

Cortical Suspensory Button Versus Aperture Interference Screw Fixation for Knee Anterior Cruciate Ligament Soft-Tissue Allograft: A Prospective, Randomized Controlled Trial

PURPOSE

To compare anterior cruciate ligament (ACL) soft-tissue allograft reconstruction using suspensory versus aperture fixation.

METHODS

After we performed prospective power analysis and obtained institutional review board approval, as well as patient consent, 64 patients were block randomized among 3 study sites to the aperture fixation group or suspensory fixation group. All patients underwent all-inside ACL reconstruction with soft-tissue allograft using either (1) femoral and tibial joint-line fixation with a femoral cannulated interference screw and a tibial cannulated interference retrograde screw (aperture) or (2) femoral and tibial cortical buttons (suspensory). Our primary outcome measure was knee anteroposterior (AP) stability measured using the KT-1000 device (MEDmetric, San Diego, CA). Secondary outcome measures included change in pain score on a visual analog scale versus preoperatively, narcotic consumption, International Knee Documentation Committee knee examination rating, International Knee Documentation Committee subjective evaluation score, Knee Society Scores, Short Form 12 scores, and radiographic analysis for socket widening.

RESULTS

Ultimately, 6 included patients (9%) were not treated (cancelled surgery), and at 2 years' follow-up, 43 treated patients (74%) completed clinical evaluation. The primary outcome measure, instrumented knee AP stability at 25° of knee flexion, showed no difference between groups (P = .61) at 24 months' follow-up. In addition, no statistically significant difference between groups was observed for secondary measures.

CONCLUSIONS

Our results show no significant differences in knee AP stability or other outcomes comparing all-inside ACL allograft reconstruction using aperture fixation and all-inside ACL allograft reconstruction using suspensory fixation.

LEVEL OF EVIDENCE

Level II, lesser-quality randomized controlled trial with follow-up of less than 80% at 2 years.

Dimensional assessment of continuous loop cortical suspension devices and clinical implications for intraoperative button flipping and intratunnel graft length

Continuous loop cortical suspension devices have been demonstrated to be more consistent and biomechanically superior compared to adjustable loop devices; however, continuous loop devices present unique challenges compared to adjustable loop devices, especially in short tunnel reconstruction applications. Specifically, adjustable loop devices have the advantage of a "one size fits all" approach, and the ability to tension these devices following button flipping allows for the intratunnel graft length to be maximized. Nevertheless, the reliability of continuous loop devices has sustained their widespread use. We hypothesized that continuous loop cortical suspension devices from different manufacturers would exhibit equivalent 15 mm loop lengths, as advertised. Loop length was measured using a tensile testing machine. Contrary to our hypothesis, continuous loop cortical suspension devices with equivalent advertised lengths exhibited different loop lengths (up to 27% discrepancy). Inconsistencies with regards to manufacturers' reported loop lengths for continuous loop devices could have serious clinical implications and additionally complicate technique transferal among devices. Consequently, the manufacturers' accurate and complete disclosure of the dimensions and specifications associated with each continuous loop device is critical. Furthermore, surgeon awareness of true loop length dimensions and inconsistencies among devices is needed to ensure optimal implantation and resultant clinical outcomes.

In vitro comparison between cortical and cortico-cancellous femoral suspension devices for anterior cruciate ligament reconstruction: implications for mobilization

PURPOSE

To analyse the capability of cortical and cortical-cancellous suspension devices to provide a strong fixation in order to follow an aggressive early mobilization protocol.

METHODS

Anterior cruciate ligament (ACL) reconstruction was performed in vitro on 40 porcine femurs employing a high-strength braided cord as a graft. Four femoral suspension devices were analysed: the cortical suspension devices Endobutton and XO Button and the cortical-cancellous suspension devices Biosteon Cross-pin and Cross-pin ACL. Two kinds of biomechanical testing were carried out: static and post-fatigue failure strength tests. Stiffness, failure load, elongation at failure load, elongation after 20 cycles and elongation after 1,000 cycles were assessed. The bones were cut after testing to analyse the failure pattern.

RESULTS

All of the devices exceed 50 % of total elongation in the first 20 cycles of fatigue. In the static failure tests, there were significant differences (p < 0.05) in elongation to failure between the cortical-cancellous suspension devices Biosteon Cross-pin and Cross-pin ACL and the cortical suspension device Endobutton. No significant differences were found in the failure tests after 1,000 cycles of loading. The failure mode of the cortical devices comprised breakage of the cortical bone, accompanied by introduction of the device into the tunnel. The failure mode of the cortical-cancellous devices was pin breakage accompanied by tunnel enlargement.

CONCLUSION

The first cycles of mobilization are critical for elongation. This mobilization process does not significantly diminish the mechanical characteristics of the reconstructions. All the fixations support an intensive early mobilization protocol, with loads of over 500 N.

The double-pulley technique for anatomical double-bundled medial patellofemoral ligament reconstruction

INTRODUCTION

Majority of the current medial patellofemoral ligament (MPFL) reconstruction techniques vary with respect to methods of fixation on the patella. In an effort to maximise the area of patellar footprint coverage and minimise the complication of patellar fracture, we developed a procedure that implemented the double-pulley suture anchors technique.

DESIGN

Prospective case series.

SETTING

A primary medical centre in Kaohsiung, Taiwan.

PATIENTS AND METHODS

Eighteen consecutive patients (18 knees) who met the inclusion criteria underwent the aforementioned operation between January 2010 and March 2012. Patients were evaluated using functional scores (Kujala and Tegner-Lysholm scores), apprehension test, and radiographic examination (congruence angle and patellar tilting angle) preoperatively and at the follow-up.

RESULTS

The mean follow-up was 35 months. A firm endpoint to lateral patellar translation was noted in all patients at the last follow-up with a mean lateral translation quadrant of 1.5 (improved from 3.5 preoperatively, p<0.001). Both clinical and radiographic assessment improved significantly (p<0.001); the mean Kujala score improved from 55.3±6.8 preoperatively to 95.2±3.5 at the last follow-up; TegnerLysholm from 43.6±8.1 to 93.6±6.8; the mean congruence angle improved from 20.6°±2.1° preoperatively to -5.2°±2.4° at the last follow-up; and the patellar tilting angle from 23.8°±2.3° to 9.6°±1.3°.

CONCLUSION

The double-pulley patellar fixation technique, by having a result that is comparable with those of other studies that used aperture fixation techniques, can be a promising surgical option for anatomically reconstructing the medial petellofemoral ligament.

Acromioclavicular joint reconstruction: complications and innovations

Minimally invasive anatomic reconstruction of the acromioclavicular joint is a technically challenging procedure. The repair must be sufficiently strong and reconstitute the joint as closely as possible. This includes restoration of both superior-inferior stability, and the often overlooked anterior-posterior stability, of the acromioclavicular joint. There is no gold standard treatment for acromioclavicular joint separation.

[Ligament bracing--augmented cruciate ligament sutures: biomechanical studies of a new treatment concept]

BACKGROUND

In the context of acute knee dislocations, suture repair of ruptured cruciate ligaments leads to good clinical results in 80% of cases. Disadvantages are low primary stability and subsequently secondary elongation of the sutured ligaments. In the present study, we compared primary stability of suture repair, reinforced by different suture augments, to cruciate ligament reconstruction.

OBJECTIVE

The concept of ligament bracing with transosseous suture repair of the cruciate ligaments and additional suture augmentation is biomechanically superior to cruciate ligament reconstruction.

MATERIAL AND METHODS

A total of 42 porcine knee joints divided into seven groups were examined. The stability of four different suture/augmentation combinations were compared to cruciate ligament reconstruction with human hamstring tendons. The investigational setup consisted of testing 1000 cycles with 20 N to 154 N load in a.-p. translation and 60° flexion. Elongation and load to failure were measured.

RESULTS

Neither reconstruction (3.13 ± 1.65 mm; 362 ± 51 N) nor augmented suture repair (1.89-2.5 mm; 464-624 N) achieved the primary stability of the intact cruciate ligament (0.63 ± 0.34 mm, 1012 ± 91 N). In comparison to ligament reconstruction, all four augmented suture repairs showed minor elongation in the cyclic test and a higher load to failure. The isolated suture repair showed poor results (6.79 ± 4.86 mm, 177 ± 73 N).

CONCLUSION

Augmented suture repair provides significantly higher stability compared with isolated suture repair and reconstruction with hamstring tendons. The concept of ligament bracing could be a promising future treatment option in acute knee dislocations. Clinical results remain to be seen.

Anterior cruciate ligament tears: reconstruction and rehabilitation

Tears of the anterior cruciate ligament (ACL) are common knee injuries experienced by athletes and people with active lifestyles. It is important for members of the healthcare team to take an evidence-based approach to the diagnosis, surgical management, and postoperative rehabilitation of patients with an ACL-deficient knee. Mechanism of ACL injury and diagnostic testing is consistent throughout the literature. Patients frequently opt for ACL reconstruction, and many surgical techniques for ACL reconstruction are available with no clear consensus regarding superiority. Surgeon preference dictates the type of reconstruction and graft choice utilized. No standardized pre- and postoperative rehabilitation protocol exists. However, rehabilitation plays an important role in functional outcomes. A comprehensive rehabilitation program is needed pre- and postoperatively to produce positive patient outcomes.

[Knee laxity in anterior cruciate ligament reconstruction : The influence of graft rotation using interference screw fixation]

BACKGROUND

The use of interference screws for femoral graft fixation in anterior cruciate ligament (ACL) reconstruction with hamstring grafts can result in rotation of the graft around the screw leading to changes in the final position of the graft within the bone tunnel.

MATERIAL AND METHODS

In a prospective study 107 patients (54 right and 53 left knees) underwent ACL reconstruction with a hamstring tendon autograft. Femoral fixation of the graft was performed with a standard right-thread screw in all cases. Patients were assessed at 6 months postoperatively with the international knee documentation committee (IKDC) standard evaluation including instrumented laxity measurements and the results were compared between right and left knees.

RESULTS

A significantly higher postoperative anterior laxity was observed in left knees with a negative Lachman test in only 64 % of the cases compared with 87 % in the group of right knees. Accordingly, instrumented laxity measurements of the reconstructed knee compared with the contralateral knee revealed significant differences between left and right knees (left knees 1.8±1.2 mm and right knees 1.0±1.4 mm).

CONCLUSIONS

This study demonstrates the importance of femoral graft positioning and its sensitivity to multiple influencing factors. The use of standard right-thread interference screws for femoral graft fixation in the mirrored situation of right and left knees may produce a systematic error in ACL reconstruction. Due to a possible rotation of the graft around the screw, the final position of the transplant may vary thus leading to significant changes in anterior translation of the operated knee.

Single-Bundle Anterior Cruciate Ligament Reconstruction with Semitendinosus Tendon Using the PINN-ACL CrossPin System: Minimum 4-Year Follow-up

PURPOSE

This study evaluated mid-term results of anterior cruciate ligament (ACL) reconstruction using the PINN-ACL CrossPin system that allowed for short graft fixation.

MATERIALS AND METHODS

Forty-three patients underwent single-bundle ACL reconstruction with a 4-strand semitendinosus tendon graft using the PINN-ACL CrossPin system. Femoral fixation was done using the PINN-ACL CrossPin system, and the tibial side was fixed with post-tie and a bioabsorbable interference screw. The mean follow-up period was 50 months. Evaluation was done using the Lachman test, pivot-shift test, International Knee Documentation Committee (IKDC) score and grade. Anterior displacement was assessed.

RESULTS

There was improvement in the Lachman test and pivot-shift test at final follow-up, form grade II (n=40) or III (n=3) to grade I (n=3) or 0 (n=40) and from grade I (n=20) or II (n=10) to grade I (n=8) or 0 (n=22), respectively. The mean IKDC score was 88.7, and grade A and B were 93.0% at final follow-up. Side-to-side difference was improved from 6.7 mm to 2.1 mm at final follow-up. Complications occurred in 3 patients, a re-ruptured due to trauma at 2 years after surgery and a deep infection and a superficial infection.

CONCLUSIONS

The mid-term follow-up results of ACL reconstruction with the PINN-ACL CrossPin system were satisfactory. The PINN-ACL CrossPin can be considered as a useful instrument for short graft fixation.