Interference screw divergence in endoscopic anterior cruciate ligament reconstruction

Femoral interference screw divergence as a result of anteromedial portal insertion and outside-in FlipCutter femoral tunnel drilling: A cadaveric study

Aims and objectives

To investigate whether interference screw fixation through an anteromedial portal into an outside-in drilled femoral tunnel via a flip cutter results in acceptable hardware position.

Materials & methods

10 cadaveric knees underwent ACL-reconstruction with patellar BTB autograft. Femoral tunnel drilling was performed utilizing an outside-in flip cutter drill and interference screws for femoral fixation. Lateral and anterior-posterior (AP) fluoroscopic images were taken to measure screw divergence within the femoral tunnel. The means of AP and lateral divergence angles were compared using two-tailed t-tests.

Results

Using the flip cutter, the AP and lateral divergence angles were 7.3° ± 4.5° and 9.3° ± 9.3°, respectively, while the total divergence angles were 16.6° ± 11.8°. Divergence angles using a cannulated reamer were found to be 14.4° ± 2.5° and 6.8° ± 2.8° for AP and lateral, respectively and 21.1° ± 5.2° for the total divergence. The AP divergence angles using the flip cutter were significantly less than those reported using a cannulated reamer (p = 0.001).

Conclusions

The flip cutter method resulted in significantly reduced divergence angle between the screw and graft when compared to previous cadaveric studies in the coronal plane. There was no significant difference in divergence angle in the sagittal plane. Both methods appear to result in divergence angles below the threshold which would be considered to significantly decrease pull-out strength. Large standard deviations also reflect limited sample size but may also suggest more variability in divergence when compared to historical control set. This study clearly establishes the outside-in technique using a retrograde reamer as a viable independent femoral drilling solution for ACL reconstruction when using a BTB autograft with a femoral interference screw.

Evaluation of Failed ACL Reconstruction: An Updated Review

Failure rates among primary Anterior Cruciate Ligament Reconstruction (ACLR) range from 3.2% to 11.1%. Recently, there has been increased focus on surgical and anatomic considerations which predispose patients to failure, including excessive posterior tibial slope (PTS), unaddressed high-grade pivot shift, and improper tunnel placement. The purpose of this review was to provide a current summary and analysis of the literature regarding patient-related and technical factors surrounding revision ACLR, rehabilitation considerations, overall outcomes and return to sport (RTS) for patients who undergo revision ACLR. There is a convincingly higher re-tear and revision rate in patients who undergo ACLR with allograft than autograft, especially amongst the young, athletic population. Unrecognized Posterior Cruciate Ligament (PLC) injury is a common cause of ACLR failure and current literature suggests concurrent operative management of high-grade PLC injuries. Given the high rates of revision surgery in young active patients who return to pivoting sports, the authors recommend strong consideration of a combined ACLR + Anterolateral Ligament (ALL) or Lateral extra-articular tenodesis (LET) procedure in this population. Excessive PTS has been identified as an independent risk factor for ACL graft failure. Careful consideration of patient-specific factors such as age and activity level may influence the success of ACL reconstruction. Additional technical considerations including graft choice and fixation method, tunnel position, evaluation of concomitant posterolateral corner and high-grade pivot shift injuries, and the role of excessive posterior tibial slope may play a significant role in preventing failure.

Anatomical rectangular tunnel anterior cruciate ligament reconstruction provides excellent clinical outcomes

PURPOSE

The purpose of this study was to prospectively evaluate the clinical outcomes following anatomical rectangular tunnel anterior cruciate ligament (ACL) reconstruction with a bone-patellar tendon-bone (BTB) graft using an adjustable-length femoral cortical fixation device with enough patients and a high follow-up rate.

METHODS

This study included 125 patients who underwent anatomical rectangular tunnel ACL reconstruction with a BTB graft. A BTB TightRope^® was used for femoral graft fixation. Clinical evaluations were performed more than 2 years after surgery using the International Knee Documentation Committee (IKDC) Form. Patients interviewed by telephone were only subjectively evaluated. The side-to-side difference in anterior laxity at a manual maximum force was measured using the KT-2000 Arthrometer^®.

RESULTS

Among the 125 patients, 99 were ultimately included and 26 were lost to follow-up (follow-up rate: 79%). Eight patients had re-tear (re-tear rate: 8%) and six patients had ACL injuries to the contralateral knee. Three patients did not follow our rehabilitation programme. One patient suffered septic arthritis. These 18 patients were considered ineligible for clinical evaluations. Therefore, clinical evaluations were performed in 81 of the 99 patients (64 were available for direct follow-up and 17 were available for a telephone interview). The follow-up period was 30 ± 10 months (range 24-68 months). According to the IKDC subjective assessment, 48 (59%) and 33 (41%) knees were graded as normal and nearly normal, respectively. A loss of extension (3°-5°) was observed in five patients (8%), whereas one patient (2%) exhibited a loss of flexion (3°-5°). The Lachman test was negative in 63 patients (98%). The pivot shift test was negative in 59 patients (92%). The side-to-side difference in KT value was 0.4 ± 0.7 mm (range - 1-4 mm).

CONCLUSION

Anatomical rectangular tunnel ACL reconstruction with a BTB graft using an adjustable-length femoral cortical fixation device provided excellent clinical outcomes both subjectively and objectively more than 2 years after surgery, whereas 8 of the 99 patients had re-tear of the graft. The adjustable-length femoral cortical fixation device could be safely used in anatomical rectangular tunnel ACL reconstruction with a BTB graft.

LEVEL OF EVIDENCE

III.

Femoral Interference Screw Fixation in ACL Reconstruction Using Bone-Patellar Tendon-Bone Grafts

» Anterior cruciate ligament (ACL) reconstruction is a commonly performed orthopaedic procedure with numerous reconstructive graft and fixation options. Interference screws have become one of the most commonly utilized methods of securing ACL grafts such as bone-patellar tendon-bone (BPTB) autografts. » The composition of interference screws has undergone substantial evolution over the past several decades, and numerous advantages and disadvantages are associated with each design. » The composition, geometry, and insertional torque of interference screws have important implications for screw biomechanics and may ultimately influence the strength, stability of graft fixation, and biologic healing in ACL reconstruction. » This article reviews the development and biomechanical properties of interference screws while examining outcomes, complications, and gaps in knowledge that are associated with the use of femoral interference screws during BPTB ACL reconstruction.

Design of a new magnesium-based anterior cruciate ligament interference screw using finite element analysis

Background/objective

In anterior cruciate ligament ​reconstruction, a tendon graft, anchored by interference screws (IFSs), is frequently used as a replacement for the damaged ligament. Generally, IFSs are classified as being either metallic or polymeric. Metallic screws have sharp threads that lacerate the graft, preventing solid fixation. These constructs are difficult to image ​and can limit bone--screw integration because of the higher stiffness of the screw. Polymeric materials are often a better match to bone's material properties, but lack the strength needed to hold grafts in place. Magnesium (Mg) is a material of great promise for orthopaedic applications. Mg has mechanical properties similar to bone, ability to be seen on magnetic resonance imagings, and promotes bone healing. However, questions still remain regarding the strength of Mg-based screws. Previous ex vivo ​animal experiments found stripping of the screw drive when the full torque was applied to Mg screws during surgery, preventing full insertion and poor graft fixation. The similar design of the Mg screw led to questions regarding the relationship between material properties and design, and the ultimate impact on mechanical behaviour. Thus, the objective of this study was to analyze the stresses in the screw head, a key factor in the stripping mechanism of IFS, then use that information to improve screw design, for this material.

Methods

Using finite element analysis, a comparison study of six drive designs (hexagonal, quadrangle, torx, trigonal, trilobe, and turbine) was performed. This was followed by a parametric analysis to determine appropriate drive depth and drive width.

Results

It was observed that with a typical torque (2 ​Nm) used for screw insertion during anterior cruciate ligament reconstruction, the maximum von Mises and shear stress values were concentrated in the corners or turns of the drive, which could lead to stripping if the values were greater than the yield stress of Mg (193 ​MPa). With a four-time ​increase in drive depth to be fully driven and a 30% greater drive width, these maximum stress values were significantly decreased by more than 75%.

Conclusion

It was concluded that improving the design of a Mg-based screw may increase surgical success rates, by decreasing device failure at insertion.

The translational potential of this article

The results of this work have the potential to improve designs of degradable IFSs, allowing for greater torque to be applied and thus greater screw fixation between host bone and the graft. Such a fixation will allow greater integration, better patient healing, and ultimately improved patient outcomes.

Loop Length Change of an Adjustable-Length Femoral Cortical Suspension Device in Anatomic Rectangular Tunnel Anterior Cruciate Ligament Reconstruction With a Bone-Patellar Tendon-Bone Graft and Associated Clinical Outcomes

PURPOSE

To evaluate loop length changes of an adjustable femoral cortical suspensory fixation device and assess the clinical results after anatomic rectangular tunnel anterior cruciate ligament (ART-ACL) reconstruction with a bone-tendon-bone (BTB) graft.

METHODS

The study included 50 patients who underwent ART-ACL reconstruction with a BTB graft fixed using the adjustable-length device BTB TightRope for femoral fixation between July 2013 and December 2014. Computed tomography examinations were performed at 1 and 12 weeks after the surgery. Loop length was measured in the reconstructed plane just parallel to the femoral tunnel, including the bone plug and the button. Measurement was performed thrice, and the mean value was used. Loop length change was defined as the difference in loop length between 1 and 12 weeks after the surgery. A paired t test was conducted with the effect size for statistical analysis. At 2 years postoperatively, clinical evaluations, including subjective and objective assessments, were performed.

RESULTS

The mean loop lengths at 1 and 12 weeks were 25.77 ± 3.88 mm and 25.81 ± 3.89 mm, respectively, with a significant difference (P = .01). However, the effect size was 0.01, suggesting that the difference was not meaningful. The mean individual loop length change was 0.04 ± 0.13 mm. All individual loop length changes were within the measurement error range. At 2 years postoperatively, 49 patients (98%) were graded as normal or nearly normal according to the International Knee Documentation Committee form. The mean side-to-side difference in anterior laxity at manual maximum force was 0.2 ± 0.5 mm.

CONCLUSIONS

The loop length change of an adjustable-length femoral cortical suspension device was negligible after ART-ACL reconstruction with a BTB graft. This ART-ACL reconstruction with a BTB graft using an adjustable-length device could safely provide sufficient stability to the operated knee.

LEVEL OF EVIDENCE

Level Ⅳ, therapeutic case series.

Hyperflexion and Femoral Interference Screw Insertion in ACL Reconstruction

Background:

In anatomic anterior cruciate ligament (ACL) reconstructions produced with flexible reamers and no knee hyperflexion, it is unknown whether knee hyperflexion is necessary for femoral interference screw insertion.

Purpose:

To compare femoral screw-graft divergence in anatomic ACL reconstructions with endoscopic interference screws placed without knee hyperflexion and with the use of flexible versus rigid screwdrivers.

Study Design:

Controlled laboratory study.

Methods:

Ten matched pairs of cadaveric knees had bone-tendon-bone graft ACL reconstructions with anatomic femoral tunnels. The knees were flexed to 90°. Femoral interference screws (7 × 20 mm) were placed in pairs of knees: in 1 knee with a flexible screwdriver and in the opposite knee with a rigid screwdriver. Graft-screw divergence was imaged with computed tomography scans and tested with cyclic and static biomechanical tests.

Results:

The mean screw-graft divergence was 12.07° ± 4.04° with the rigid screwdriver and 10.68° ± 3.23° with the flexible screwdriver (P = .35). The cyclic tests with screws placed by a rigid screwdriver had a mean increase in displacement of 0.56 ± 0.20 mm. For screws placed with the flexible screwdriver, the mean increase in displacement was 0.58 ± 0.32 mm (P = .66). Yield load was 393.3 ± 95.1 N for screws placed by a rigid screwdriver and 408.2 ± 119.0 N for screws inserted with the flexible screwdriver (P = .78). Maximum load was 523.1 ± 88.7 N for screws placed by a rigid screwdriver and 467.1 ± 107.3 N for screws inserted with the flexible screwdriver (P = .09).

Conclusion:

With either a rigid or a flexible screwdriver, there were no significant effects on screw divergence or fixation strength.

Clinical Relevance:

Knees can be kept at 90° during endoscopic femoral interference screw insertion. The use of a traditional rigid or flexible screwdriver will not affect screw-graft divergence or fixation strength.

Femoral Screw Divergence via the Anteromedial Portal Using an Outside-In Retrograde Drill in Bone-Patella Tendon-Bone Anterior Cruciate Ligament Reconstruction: A Cadaveric Study

PURPOSE

To assess screw divergence when inserting an interference screw for a bone-patellar tendon-bone graft using an outside-in technique with a retrograde drill to create the femoral tunnel.

METHODS

Ten cadaver specimens underwent anterior cruciate ligament reconstruction with a bone-patellar tendon-bone autograft, with 23-mm-deep tunnels created by a retrograde drill outside-in technique. Drilling angles were based on a previous study that established the optimal angles to recreate the anterior cruciate ligament footprint. To ensure that screw insertion angles matched the angle of socket drilling, a marking pen was used to transpose 2 lines on the skin of the anterior knee corresponding to the drill in both the coronal and axial planes with the knee held at 90° of flexion. The femoral-sided bone plug was affixed with a 7 × 23 mm interference screw through an anteromedial portal. Computed tomography scans were used to calculate coronal and sagittal screw-tunnel divergence.

RESULTS

The median screw divergence in the coronal plane was 2.79°, with a range of 1.1° to 17.2°. Of 10 specimens, 8 had no divergence (0° to 5°), 0 screws were between 5° and 10°, 1 screw was between 10° and 15°, and 1 screw was between 15° and 20°. The 95% confidence interval was 3.73° to 11.69°. No screws had ≥20° of divergence. In the sagittal plane, the median screw divergence was 5.68°, with a range of 1.2° to 18.7°. Five specimens had no divergence (0° to 5°), 3 screws were between 5° and 10°, 0 screws were between 10° and 15°, and 2 screws were between 15° and 20° of divergence. The 95% confidence interval was 3.73° to 11.69°. No screws had ≥20° of divergence.

CONCLUSIONS

The results of this study showed that 80% of screws diverted less than 5° in the coronal plane. In the sagittal plane, only 50% of screws were found to have divergence of 5° or less. No screw in either plane had divergence of greater than or equal to 20°.

CLINICAL RELEVANCE

When using a retrograde drill, a skin marking technique is a useful aid in placing interference screws with acceptable angles of divergence when using an inside-out technique.

Can an expansion device be used in anterior cruciate ligament reconstruction? An in vitro study of soft tissue graft tibial fixation

BACKGROUND

The purpose of this study was to compare the mechanical properties of an interference screw with an expansion device in anterior cruciate ligament (ACL) reconstruction.

METHODS

A total of 52 porcine tibia and 20 polyurethane foam blocks (0.16g/cm³) were used. Forty pullout tests were carried out to combine the two types of bones - surrogate and porcine - with the two fixation systems: interference screw and expansion device (n=10 per group). Thirty-two cyclic tests (n=8 per group) were carried out with both fixation devices in porcine bone at two different force amplitudes (100N and 200N).

RESULTS

Stiffness and load values (mean±SD) at six millimeters of displacement for the expansion device and the interference screw were 74±33N/mm, 318±135N, and 52±28N/mm, 205±70N, respectively, showing a difference in stiffness (P=0.016) and load at six millimeters of displacement (P=0.001). No correlation between insertion torque and the ultimate failure load was found for both fixation devices tested. In cyclic tests, significantly higher (P<0.001) numbers of cycles (mean±SD) were reached with the expansion device (81,014±30,291 at 100N; 13,462±11,351 at 200N) than with the interference screw (15,100±8623 at 100N; 343±113 at 200N) at six millimeters of displacement.

CONCLUSION

The use of an expansion device for ACL reconstructions seemed to be a promising alternative to an interference screw. Insertion torque alone was not a useful predictor of graft fixation strength in ACL reconstructions.

Anterior cruciate ligament femoral socket drilling with a retrograde reamer: lessons from the learning curve

Whereas "anatomic" anterior cruciate ligament reconstruction may improve clinical results, the technique has introduced new technical challenges. The purpose of this technical note and video is to explore tips and tricks that improve femoral socket drilling with a retrograde reamer, bone-patellar tendon-bone graft passage, and interference screw fixation. The techniques for retrograde femoral socket drilling in an inside-out direction, bone-patellar tendon-bone graft passage, and interference screw fixation are described and demonstrated. Pitfalls, troubleshooting tips, and possible solutions are discussed. With the retrograde reamer, the femoral socket can be placed in the footprint of the anterior cruciate ligament with a longer and more vertical tunnel. By modifying the size of the patellar bone plug, graft passage is improved. With care and technique, interference screw fixation in the femoral socket over a guidewire is possible.

Graft fixation alternatives in anterior cruciate ligament reconstruction

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

Fixation strength of the interference screw in the femoral tunnel: The effect of screw divergence on the coronal plane

Clinical studies to examine the effect of screw divergence have not been applied to the fixation of hamstring grafts. A few previous reports have addressed the correlations between the loss of pullout strength and divergence on hamstring tendon fixation in biomechanical tests. The purpose of this study was to examine the effect of interference screw divergence on the coronal plane when digital flexor tendons were fixed with an interference screw. Twenty fresh porcine hindlimb specimens were chosen. The grafts were fixed using titanium soft tissue interference screws. The hindlimbs were divided into two groups according to the insertion method of the screw. The screw was placed along the graft parallel to the long axis of the femoral tunnel in 10 specimens (parallel placement group), and the others were placed laterally at a 15° divergent angle from the bone tunnel on the coronal plane (divergence group). The cyclic-loading test was loaded for 1500cycles. Five specimens failed because of a pull-out of the tendon in divergence group. The number of specimens that failed before the completion of cycles in the divergence group was significantly greater than that in the parallel placement group. Although the residual displacement after 1500cycles for the divergence group was greater than that for the parallel placement group, no statistically significant difference was found between the groups. This study suggests that the screw placed laterally at a 15° divergent angle on the coronal plane decreases the fixation strength of the digital flexor tendons fixed with an interference screw.

Improved divergence angles with femoral interference screw placement through the tibial tunnel as measured by multiplanar reconstruction computed tomography

PURPOSE

A modified technique for anterior cruciate ligament (ACL) reconstruction without graft injury by femoral interference screw insertion directly through the tibial tunnel is reported. This study evaluated femur bioabsorbable interference screw divergence and obliquity of the graft and tunnel positions as measured by multiplanar reconstruction computed tomography (MPR-CT) after endoscopic ACL reconstruction.

METHODS

Twenty-five patients who underwent single-incision arthroscopically assisted ACL reconstruction using hamstring tendon autografts were enrolled in this prospective study. All procedures were performed using the same technique: femoral bioabsorbable interference screw insertion directly through the tibial tunnel. Divergence angles of oblique sagittal and oblique axial views of the graft and tunnel positions using MPR-CT evaluation were obtained. CT images were evaluated in a blinded manner by 3 experienced radiologists.

RESULTS

The average divergence angles in oblique sagittal and oblique axial views were 0.88 +/- 1.06 and 1.44 +/- 1.17, respectively. Sagittal, axial, and coronal obliquity of the graft in reconstructed patients averaged 64 degrees (range, 46 degrees to 69 degrees ), 19 degrees (range, 17 degrees to 22.5 degrees ), and 73.6 degrees (range, 70 degrees to 77.6 degrees ), respectively. Radiologic analysis of the femoral insertion according to the quadrant technique showed that the femoral center of the anteromedial (grafted) bundle was 18.6% and 23.6% of the depth of Blumensaat's line and the height of the femoral condyle. At the tibia, the tibial ACL attachment at the center of the anteromedial bundle was at 41.1% of the maximal tibial diameter.

CONCLUSIONS

Our study showed that MPR-CT is a useful diagnostic tool for evaluation of the femoral interference screw divergence, obliquity of the graft, and the exact femoral and tibial insertion site of the graft. The screw will have little or no divergence using this novel technique as measured by the very accurate MPR-CT.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Complications of anterior cruciate ligament reconstruction with bone-patellar tendon-bone constructs: care and prevention

Rupture of the anterior cruciate ligament is a common injury. Correct diagnosis and patient selection, along with proper surgical technique, with careful attention to anatomic graft placement, followed by attention to proper rehabilitation, leads to predictably good to excellent results. This article reviews the recognition and avoidance of complications associated with bone-patellar tendon-bone constructs of anterior cruciate ligament reconstruction.

Bone-patella tendon-bone autograft anterior cruciate ligament reconstruction

The anterior cruciate ligament (ACL) serves an important stabilizing and biomechanical function for the knee. Reconstruction of the ACL remains one of the most commonly performed procedures in the field of sports medicine. Reconstruction of the ACL with bone-patella tendon-bone (BPTB) autograft secured with interference screw fixation has been the historical reference standard and remains the benchmark against which other methods are gauged. This article reviews the reconstruction of the ACL with BPTB autograft including the surgical technique, rationale for BTPB use, and outcomes.

Biomechanics of intratunnel anterior cruciate ligament graft fixation

Interference screw fixation of bone-patellar tendon-bone grafts now is considered the standard against which all ACL graft-fixation techniques are compared, but mechanical fixation of the ACL graft in the bone tunnels is the weak link in the early postoperative period. This article discusses some of the limitations of in vitro biomechanical studies and reviews variables that influence the tensile properties of intratunnel fixation methods for bone-tendon-bone and soft tissue grafts.

Intra-articular pull out of an interference screw after anterior cruciate ligament reconstruction

We report a rare case of late femoral interference screw migration in the posterior compartment of the knee after anterior cruciate ligament reconstruction. The graft was intact with no signs of damage. The screw was successfully removed through the posteromedial portal site and the patient regained full function of the knee.

Intra-articular pull out of an interference screw after anterior cruciate ligament reconstruction

We report a rare case of late femoral interference screw migration in the posterior compartment of the knee after anterior cruciate ligament reconstruction. The graft was intact with no signs of damage. The screw was successfully removed through the posteromedial portal site and the patient regained full function of the knee.

Biomechanical evaluation of press-fit femoral fixation technique in ACL reconstruction

In this experimental study, the authors evaluated the biomechanical properties of the femoral press-fit graft fixation technique in ACL reconstruction. 20 fresh frozen distal femurs, patellae and patellar ligaments were used from 10 cadaver specimens. Three bone-patellar tendon grafts of 10 mm width were prepared from each sample; altogether 60 bone-patellar tendon grafts were prepared for the experiment. Three 9 mm wide tunnels were drilled in each distal femur at different angles (0, 15, 30, 45, and 60 degrees). This means that 60 tunnels were drilled into the 20 femurs, 12 at each angle. The trapezoid bone blocks were impacted into the holes. The primary stability and stiffness of this press-fit fixation method were measured with a Zwick 020 computer-controlled testing device using maximum-failure tensile-strength tests. The ultimate tensile strength was the greatest at 45 degrees (534+/-20 N, range 507-554), with 118+/-10 N/mm (range 99-126) stiffness, followed by 485+/-35 N (range 416-510) with 122+/-13 N/mm (range 104-136) stiffness at 30 degrees, 353+/-18 N (range 320-371) with 113+/-13 N/mm (range 83-124) stiffness at 15 degrees, and 312+/-30 N (range 261-343) with 89+/-14 N/mm (ranged:68-103) stiffness at 0 degrees. In the cases of 0, 15, 30 and 45 degrees the bone blocks were pulled out of the drilled holes, but at 60 degrees rupture of the patellar tendon or breakage of the bone block occurred more frequently. It can be seen that the ultimate tensile strength increased with the angle between the loading direction and the bone block. When compared to data in the literature, these data showed similar and satisfying biomechanical properties of femoral press-fit fixation. Because of the known advantages of an implantation-free fixation technique, the femoral press-fit fixation technique can be a good alternative in ACL surgery. These results provide the basis for future studies involving the postoperative healing process of this femoral press-fit fixation technique in porcine knees.

The use of intraoperative fluoroscopy to reduce femoral interference screw divergence during endoscopic anterior cruciate ligament reconstruction

Femoral interference screw divergence can potentially have detrimental consequences in the rehabilitation of anterior cruciate ligament (ACL) reconstruction. Several biomechanical studies suggest that divergence angles greater than 15 degrees significantly decrease the pullout strength of the graft. Numerous techniques have been described in the literature that address this issue; however, the use of an image intensifier intraoperatively is not frequently discussed. We describe a technique in which fluoroscopy is used to confirm the proper position of the femoral interference screw at the time of the procedure, and therefore minimizes the incidence of significant screw divergence. Radiographic analysis of 62 patients who underwent endoscopic ACL reconstruction using bone-patellar tendon-bone autograft using this technique revealed significant divergence in only 3% of patients.

Endoscopic anterior cruciate ligament reconstruction with patella tendon autograft

The patella tendon is the most commonly used graft source for ACL reconstruction because of its biomechanical strength and stiffness, the availability of bone-to-bone healing on either end, and the ability to firmly secure the graft within the tunnels. Consistently good results have been reported in the literature, with expectations to return to all activities at pre-injury levels of performance. We outline our technique for endoscopic ACL reconstruction using a patella tendon autograft. The technique is divided into the critical stages of pre-operative assessment, graft harvest, notch preparation, tunnel placement, graft passage, graft fixation, and rehabilitation. Methods for avoiding pitfalls and overcoming mishaps are described.

Interference screw divergence in femoral tunnel fixation during endoscopic anterior cruciate ligament reconstruction using hamstring grafts

PURPOSE

To compare the divergence angles between bioabsorbable interference screws inserted into the femoral tunnel with the screwdriver placed through the anteromedial portal to those inserted with the screwdriver placed through the tibial tunnel and to examine the effect of the femoral tunnel interference screws' divergence angles on fixation strength of hamstring grafts after anterior cruciate ligament (ACL) reconstruction using hamstring grafts.

TYPE OF STUDY

Cadaveric biomechanical pullout study.

METHODS

ACL reconstruction was performed in 8 pairs of fresh-frozen human cadaveric knees using hamstring grafts fixed within the femoral tunnels using bioabsorbable interference screws. Within matched pairs, 1 screw was placed into the femoral tunnel using a screwdriver placed through the tibial tunnel (group 1), and in the other knee it was placed into the femoral tunnel using a screwdriver placed through the anteromedial portal (group 2). Radiographs were taken to measure the degree of divergence between the interference screw and the femoral tunnel. After disarticulation, pullout strength was then measured using a cyclic-loading model.

RESULTS

In group 2, there was significantly more divergence between the screw and the femoral tunnel compared with group 1, particularly in the sagittal plane (average 14.4 degrees compared with 3.4 degrees, P =.00014). With the number of specimens available for comparison, no significant difference was detected between the 2 groups with regard to 3 mm and 5 mm of pullout when cyclically loaded (P =.77 and.74, respectively).

CONCLUSIONS

The increased technical difficulty, combined with the potential risks of tibial tunnel widening and graft damage, with placement of the screwdriver through the tibial tunnel for the purpose of decreasing femoral interference screw divergence in ACL reconstruction using hamstring grafts may not be justified.

Practical considerations in anterior cruciate ligament replacement surgery

The endoscopic method of anterior cruciate ligament (ACL) reconstruction using a patellar tendon graft that is secured with interference screws is a commonly performed procedure. It has many potential pitfalls, the majority of which are secondary to technical errors. Prevention of errors starts with a full knowledge of normal ACL anatomy and any discrepancies with the size and shape of the graft substitute. Accurate tibial and femoral tunnel placement is essential and involves using consistent intra-articular landmarks and achieving specific radiographic criteria. Accurate tunnel placement minimizes graft excursion and impingement against the roof of the intercondylar notch. This will result in maximum knee stability and motion. Much has been written about the principles of graft-tunnel mismatch and interference screw-bone plug divergence. The clinical implications of these potential sources of error remain somewhat controversial and are discussed in this article.

Is screw divergence in femoral bone-tendon-bone graft fixation avoidable in anterior cruciate ligament reconstruction using a single-incision technique? A radiographically controlled cadaver study

Interference screw fixation of patellar tendon bone-tendon-bone grafts for anterior cruciate ligament reconstruction has proven to be a method with high pullout strength if screw divergence is avoided. Twenty-four fresh-frozen cadaveric human knees were used to identify the ideal position for a portal and an optimal knee flexion angle to obtain parallel placement of screw and bone block. On all specimens, anterior cruciate ligament reconstruction was performed using a single-incision technique. In the first part of this study, screw placement was analyzed in the frontal plane. In the second part, screw placement was investigated in the sagittal plane, measuring the additional flexion required between femoral tunnel drilling (at 60 degrees of knee flexion) and screw insertion to obtain parallel screw placement. For both part I and II, image intensification was used. In the third part, femoral screw placement was carried out through a paraligamentous approach and with additional flexion of 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, and 60 degrees. This study shows that screw placement with minimal divergence in the frontal and sagittal planes can be achieved by inserting the screw through a nearly central portal and flexing the knee an additional 35 degrees to 40 degrees.

Graft fixation in cruciate ligament reconstruction

Cruciate ligament reconstruction has progressed dramatically in the last 20 years. Anatomic placement of ligament substitutes has fostered rehabilitation efforts that stress immediate and full range of motion, immediate weightbearing, neuromuscular strength and coordination, and early return to athletic competition (3 months). This has placed extreme importance on secure graft fixation at the time of ligament reconstruction. Current ligament substitutes require a bony or soft tissue component to be fixed within a bone tunnel or on the periosteum at a distance from the normal ligament attachment site. Fixation devices have progressed from metal to biodegradable and from far to near-normal native ligament attachment sites. Ideally, the biomechanical properties of the entire graft construct would approach those of the native ligament and facilitate biologic incorporation of the graft. Fixation should be done at the normal anatomic attachment site of the native ligament (aperture fixation) and, over time, allow the biologic return of the histologic transition zone from ligament to fibrocartilage, to calcified fibrocartilage, to bone. The purpose of this article is to review current fixation devices and techniques in cruciate ligament surgery.

The HAKI technique of femoral interference screw insertion

We describe a simple and reliable technique, the HAKI technique, of femoral interference screw fixation that can reduce surgical complications. In 83 ordinary endoscopic anterior cruciate ligament (ACL) reconstructions and 110 ACL reconstructions with our new technique, surgical complications related to the femoral interference screw fixation were evaluated. With our new technique, only one complication occurred while overall complications of 15.7% occurred in the ordinary group. Compared with the ordinary technique group, which had an average of 12.0 degrees screw divergence on anteroposterior radiographs and 13.5 degrees on lateral radiographs, our new technique had a significantly lower incidence of femoral screw divergence, with 8.0 degrees and 8.3 degrees on the anteroposterior and lateral views, respectively. This new technique could reduce a significant portion of complications that occur during endoscopic (single incision) bone-patellar tendon-bone ACL reconstruction.