Optimization of Anteromedial Portal Femoral Tunnel Drilling With Flexible and Straight Reamers in Anterior Cruciate Ligament Reconstruction: A Cadaveric 3-Dimensional Computed Tomography Analysis

Tsetse fly inspired steerable bone drill-a proof of concept

The fixation strength of pedicle screws could be increased by fixating along the much stronger cortical bone layer, which is not possible with the current rigid and straight bone drills. Inspired by the tsetse fly, a single-plane steerable bone drill was developed. The drill has a flexible transmission using two stacked leaf springs such that the drill is flexible in one plane and can drill along the cortical bone layer utilizing wall guidance. A proof-of-principle experiment was performed which showed that the Tsetse Drill was able to successfully drill through 5, 10 and 15 PCF cancellous bone phantom which has similar mechanical properties to severe osteoporotic, osteoporotic and healthy cancellous bone. Furthermore, the Tsetse Drill was able to successfully steer and drill along the cortical wall utilizing wall guidance for an insertion angle of 5°, 10° and 15°. The experiments conclude that the tsetse fly-inspired drilling method is successful and even allows the drilling along the cortical bone layer. The Tsetse Drill can create curved tunnels utilizing wall guidance which could increase the fixation strength of bone anchors and limit the risk of cortical breach and damage to surrounding anatomy.

Effect of the core bone engaged length on the BASHTI fixation strength, an in-vitro study on bovine tendons using identical-density surrogate bones

BACKGROUND

BASHTI is an implant-less anterior cruciate ligament (ACL) reconstruction technique, which resolves the problems caused by implants such as interference screws. This study aims to investigate the effect of the drill bit and tendon's diameter on the Core Bone Engaged Length (CBEL) and the fixation strength. CBEL is the length of core bone which has a full engagement with both tunnel and graft at the same time.

METHODS

60 in-vitro tests were conducted for 6, 7, 8, and 9 mm tendon sizes with a 10 mm bone tunnel. In this study bovine tendons and dummy bone blocks were used to model the fixation. Drill bits were used to extract the core bone for securing the auto-graft. A three-stage tensile test including a force-controlled cyclical preloading of 10-50 N with a frequency of 0.1 Hz for 10 cycles, followed by the main force-controlled cyclical loading of 50-200 N with a frequency of 0.5 Hz for 150 cycles, and immediately a displacement-controlled single cycle pull-out load with a rate of 20 mm/min were carried out to discover the fixation strength of each sample.

RESULTS

The 6 mm group had the greatest CBEL. However, all cases in this group failed in loadings below 200 N, which is the minimum required strength after ACL reconstruction. The fixation strength of cases with more than 200 N fixation strength for 7, 8, and 9 mm tendon diameters were 275 ± 42, 330 ± 110, and 348 ± 93 N, respectively, showing insignificant difference between groups (P-value = 0.45). Nevertheless, CBELs for these groups were 16.6 ± 3.4, 9.6 ± 2.4, and 11.7 ± 3.8 mm, respectively, implying a significant increase in CBEL in the 7 mm group than that for 8 and 9 mm groups (P-value = 0.002 and 0.049, respectively).

CONCLUSION

Results showed that CBEL could assess the quality of BASHTI technique. However, CBEL was an inverse function of tendon compression, so it was not an independent parameter to determine BASHTI strength. Also, the CBEL of 7 mm group which fulfilled the 200 N threshold was higher than that of 8 and 9 mm groups, so its healing process speed may be higher, which is recommended for a future study in this field.

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.

Flexible Versus Rigid Reaming Systems for Independent Femoral Tunnel Reaming During ACL Reconstruction: Minimum 2-Year Clinical Outcomes

Background:

Radiographic and cadaveric studies have suggested that anatomic anterior cruciate ligament reconstruction (ACLR) femoral tunnel drilling with the use of a flexible reaming system through an anteromedial portal (AM-FR) may result in a different graft and femoral tunnel position compared with using a rigid reamer through an accessory anteromedial portal with hyperflexion (AAM-RR). No prior studies have directly compared clinical outcomes between the use of these 2 techniques for femoral tunnel creation during ACLR.

Purpose:

To compare revision rates at a minimum of 2 years postoperatively for patients who underwent ACLR with AM-FR versus AAM-RR. The secondary objectives were to compare functional testing and patient-reported outcomes between the cohorts.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Included were consecutive patients at a single academic institution between 2013 and 2018 who underwent primary ACLR without additional ligamentous reconstruction. Patients were separated into 2 groups based on the type of anatomic femoral tunnel drilling: AM-FR or AAM-RR. Graft failure, determined by revision ACLR, was assessed with a minimum 2 years of postoperative follow-up. The authors also compared patient-reported outcome scores (International Knee Documentation Committee [IKDC] and Knee injury and Osteoarthritis Outcome Score [KOOS]) and functional performance testing performed at 6 months postoperatively.

Results:

A total of 284 (AAM-RR, 232; AM-FR, 52) patients were included. The mean follow-up time was 3.7 ± 1.5 years, with a minimum 2-year follow-up rate of 90%. There was no significant difference in the rate of revision ACLR between the AAM-RR and AM-FR groups (10.8% vs 9.6%, respectively; P = .806). At 6 months postoperatively, there were no significant between-group differences in peak knee extension strength, peak knee flexion strength, limb symmetry indices, or hop testing, as well as no significant differences in IKDC (AAM-RR, 81.1; AM-FR, 78.9; P = .269) or KOOS (AAM-RR, 89.0; AM-FR, 86.7; P = .104).

Conclusion:

In this limited study, independent femoral tunnel drilling for ACLR using rigid or flexible reaming systems resulted in comparable rates of revision ACLR at a minimum of 2 years postoperatively, with no significant differences in strength assessments or patient-reported outcomes at 6 months postoperatively.

Comparing the Use of Flexible and Rigid Reaming Systems Through an Anteromedial Portal for Femoral Tunnel Creation During Anterior Cruciate Ligament Reconstruction: A Systematic Review

Background

Recent studies have suggested that femoral tunnel drilling during anterior cruciate ligament (ACL) reconstruction (ACLR) with the use of a flexible reaming system through a standard anteromedial portal (AM-FR) may result in a different tunnel geometry compared with a rigid reamer through an accessory anteromedial portal with hyperflexion (AM-RR).

Purpose

To summarize radiologic, anatomic, and clinical outcomes from available studies that directly compared the use of AM-FR versus AM-RR for independent femoral tunnel creation during ACLR.

Study Design

Systematic review; Level of evidence, 4.

Methods

A literature search was performed using the MEDLINE (PubMed) and Web of Science databases to identify all studies that directly compared radiologic, anatomic, and clinical outcomes between the use of AM-FR and AM-RR. The literature search, data recording, and methodological quality assessment was performed by 2 independent reviewers. The outcomes analyzed included resultant ACL graft positioning and graft bending angle; femoral tunnel positioning, aperture morphology, length, and widening; posterior wall breakage; and distance from various posterolateral knee structures.

Results

A total of 13 studies met the eligibility criteria for inclusion. There was no difference in femoral tunnel aperture location between techniques. There were conflicting findings among studies regarding which technique resulted in a more acute graft bending angle. One study reported greater femoral tunnel widening upon follow-up with the use of AM-FR. AM-FR produced longer and more anteverted femoral tunnels than did AM-RR. The difference in tunnel length was significant and more prominent in lesser degrees of knee flexion. With AM-FR, femoral tunnels were farther from the lateral collateral ligament and peroneal nerve, and 1 of 5 studies had fewer reports of posterior wall breakage. There has been no literature comparing the clinical or functional outcomes of these techniques.

Conclusion

Although no clinical studies exist comparing AM-FR and AM-RR for femoral tunnel creation during ACLR, both systems allow for reproducible positioning of an anatomic femoral tunnel aperture. The use of AM-FR results in longer and more anteverted femoral tunnels than using AM-RR, with exit points on the lateral femur that are different but safe. Surgeons should be aware of the technical differences with each method; however, further study is needed to identify any clinically important difference that results.

All Inside Intraepiphyseal ACL Reconstruction Using Flexible Curved Instrumentation and Intraoperative Fluoroscopy in a Skeletally Immature Patient

Case

A 13-year-old skeletally immature female presenting with an anterior cruciate ligament (ACL) rupture after a noncontact injury was treated with an intraepiphyseal ACL reconstruction. Flexible instrumentation was utilized to drill a femoral tunnel with an anatomic starting point, with a trajectory that curved inferolaterally away from the physis. At three years postoperatively, she had returned to her preinjury functioning and did not display any lower limb length growth abnormalities.

Conclusions

The novel application of curved guides and flexible instruments, with intraoperative fluoroscopy, facilitated growth plate avoidance and a successful outcome of ACL reconstruction in a skeletally immature patient.

Anterior Cruciate Ligament Femoral Socket Preparation Using a Cannulated, Calibrated Drill With Adjustable Stop and Slotted Cannula

Anteromedial portal-guided femoral tunnel preparation during anterior cruciate ligament reconstruction can be difficult owing to poor visualization. This may cause iatrogenic damage to the medial femoral condyle cartilage and the posterior cruciate ligament fibers or overdrilling through the lateral femoral cortex, creating difficulties in the use of femoral suspensory devices during anterior cruciate ligament reconstruction. We describe an accurate and safe technique for femoral graft socket preparation using a cannulated, calibrated drill with an adjustable stop and slotted cannula. This easy and reproducible technique uses simple additional instruments and effectively addresses concerns related to femoral graft socket preparation, without requiring additional surgical time.

Dynamic Three-Dimensional Computed Tomography Mapping of Isometric Posterior Cruciate Ligament Attachment Sites on the Tibia and Femur: Single- Versus Double-Bundle Analysis

PURPOSE

(1) To determine the area of posterior cruciate ligament (PCL) insertion sites on the lateral wall of the medial femoral condyle (LWMFC) that demonstrates the least amount of length change through full range of motion (ROM) and (2) to identify a range of flexion that would be favorable for graft tensioning for single-bundle (SB) and double-bundle (DB) PCL reconstruction.

METHODS

Six fresh-frozen cadaveric knees were obtained. Three-dimensional computed tomography point-cloud models were obtained from 0° to 135°. A point grid was placed on the LWMFC and the tibial PCL facet. Intra-articular length was calculated for each point on the femur to the tibia at all flexion angles and grouped to represent areas for bone tunnels of SB and DB PCLR. Normalized length changes were evaluated.

RESULTS

Femoral tunnel location and angle of graft fixation were significant contributors to mean, minimum, and maximum normalized length of the PCL (all p < .001). Tibial tunnel location was not significant in any case (all p < .22). A femoral tunnel in the location of the posteromedial bundle of the PCL resulted in the least length change at all tibial positions (maximum change 13%). Fixation of the anterolateral bundle in extension or at 30° flexion resulted in significant overconstraint of the PCL graft. The femoral tunnel location for a SB PCLR resulted in significant laxity at lower ranges of flexion.

CONCLUSION

PCL length was significantly dependent on femoral tunnel position and angle of fixation, whereas tibial tunnel position did not significantly contribute to observed differences. All PCL grafts demonstrated anisometry, with the anterolateral bundle being more anisometric than the posteromedial bundle. For DB PCLR, the posteromedial bundle demonstrated the highest degree of isometry throughout ROM, although no area of the LWMFC was truly isometric. The anterolateral bundle should be fixed at 90° to avoid overconstraint, and SB PCLR demonstrated significant laxity at lower ranges of flexion.

CLINICAL RELEVANCE

Surgeons can apply the results of this investigation to surgical planning in PCLR to optimize isometry, which may ultimately reduce graft strain and the risk of graft failure. Additionally, DB PCLR demonstrated superiority compared with SB PCLR regarding graft isometry, as significant laxity was encountered at lower ranges of flexion in SB PCLRs. Fixation of the ALB at 90° flexion should be performed to avoid overconstraint in knee extension.

Flexible reamers create comparable anterior cruciate ligament reconstruction femoral tunnels without the hyperflexion required with rigid reamers: 3D-CT analysis of tunnel morphology in a randomised clinical trial

PURPOSE

The hyperflexion required for femoral tunnel drilling in anterior cruciate ligament reconstruction can be challenging in patients with increased body habitus or musculature. Whilst allowing femoral tunnel creation without hyperflexion, additional benefits of flexible reamers have been proposed in terms of tunnel dimensions. The purpose of this study was to examine whether these theoretical benefits are seen in a clinical study.

METHODS

Fifty adult patients (with isolated anterior cruciate ligament rupture) were randomised to reconstruction with either flexible or rigid femoral reamers. Femoral tunnel drilling was performed at 100° flexion (flexible system) or maximal hyperflexion (rigid system). Otherwise, the procedure was standardised. Femoral tunnel measurements were performed by a consultant musculoskeletal radiologist who was blinded to the method of femoral drilling. Tunnel position, length and angles (axial and coronal) were measured alongside aperture shape and exit point using three-dimensional computed tomography 3-6 months post-operatively.

RESULTS

With no difference in tunnel position, tunnel length was found to increase with the use of the flexible system (37.8 ± 3.7 vs 35.0 ± 4.4 mm; p = 0.024). In addition, the exit point and fixation device were more anterior on the lateral femur using the flexible reamers (p = 0.016). No difference was seen in either tunnel angles or aperture shape. One case of incomplete posterior blow-out was seen in each of the study groups.

CONCLUSIONS

This comparative study shows that flexible reamers can reproduce a desired femoral tunnel position with only small improvements of no clinical relevance. As this can be achieved without hyperflexing the knee, these systems can be used for all patients (even when hyperflexion is a challenge).

LEVEL OF EVIDENCE

I.

Dynamic 3-Dimensional Mapping of Isometric Anterior Cruciate Ligament Attachment Sites on the Tibia and Femur: Is Anatomic Also Isometric?

PURPOSE

The purpose of this study was to (1) map the length changes of the medial wall of the lateral femoral condyle (MWLFC) with respect to various points about the tibial anterior cruciate ligament (ACL) footprint to determine the area that demonstrates the least amount of length change through full range of motion and (2) to identify a range of flexion that would be favorable for graft tensioning.

METHODS

Six fresh-frozen cadaveric knees were obtained from screened individuals with no prior history of arthritis, cancer, surgery, or any ligamentous knee injury. For each knee, 3-dimensional computed tomography point-cloud models were obtained in succession from 0° to 135°. A point grid was placed on the MWLFC and the tibia. Intra-articular length was calculated for each point on the femur to the tibia at all flexion angles and grouped to represent areas for bone tunnels. Normalized length changes were compared.

RESULTS

Areas anterior/distal on the MWLFC increased with increasing flexion, and areas proximal/posterior decreased with increasing flexion. The area about the intersection of the lateral intercondylar ridge and the bifurcate ridge was most isometric throughout flexion as no significant change in ligament length was found throughout flexion. The normalized length changes from the central position of the tibia showed no significant difference compared with the anterior or posterior tibial position.

CONCLUSIONS

No area of the MWLFC is truly isometric through flexion. Femoral tunnel placement slightly anterior to the center of the anteromedial and posterolateral bundles was most isometric. Minimal length change occurs between 10° and 40°, which reflects the range where graft tensioning was most often performed. The results of this study provide further support for an anatomic ACL reconstruction. CLINICAL RELEVANCE: The femoral tunnel location for ACL reconstruction with the least amount of length change through range of motion should encompass the direct fibers of the ACL.

Drilling through anteromedial portal with a femoral aiming device ensures a sufficient length and a proper graft position, and prevents posterior wall breakage during anterior cruciate ligament reconstruction

OBJECTIVE

The aim of this study was to evaluate the characteristics of the femoral tunnel (FT) which was drilled through the AM portal by using a femoral aimer device and AP stability of the knee.

METHODS

Thirty-eight patients, with the mean age 29.6 (range: 20-43) years, were evaluated after ACL reconstruction. The mean follow-up time was 31.9 (range: 16-57) months. The FT was drilled using a femoral aimer with different offset according to the graft size measured, through the AM portal. The semitendinous and gracilis tendon autograft was used for reconstruction. The angles of FT and the exit point on the lateral condyle were measured on AP views of the knee. AP stability of the knee was measured with the KT-2000.

RESULTS

The mean angle of FT was 46.5° (± 8.4°), on the AP view. The mean distance between the exit point of FT and the most distal end of the femoral condyles was 46.7 (± 4.9) mm. The mean FT length was 36.1 (± 3.1) mm. The mean difference of anterior translation compared to the intact knee was 1.9 (± 1.6) mm. Except the three patients, with "one positive" pivot shift test, in the remaining 35 knees stability was equal to the healthy knee.

CONCLUSIONS

Femoral drilling by using a femoral aimer device through AM portal provided long enough FT for safe graft fixation and appropriate coronal plan obliquity. The exit point was far proximal from the insertion site of the popliteus tendon and lateral collateral ligament. Furthermore, the AM portal technique significantly improved AP stability of the knee.