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

Categorize the existing clamps used for tensile test of human graft- a systematic review

BACKGROUND

The use of tendon allografts for orthopedic repair has gained wide acceptance in recent years, most notably in anterior cruciate tendon reconstruction. Multiple studies support the use of tendon allografts and the benefits of its use are well accepted and understood. One of the important criteria of the use of tendon allografts is statistically similar histological and biomechanical properties to autographs. The aim of this systematic literature review is to investigate and categorize existing clamps used in the determination of the biomechanical properties of tendons such as maximum load, maximum strength, modulus of elasticity, ultimate strain, and stiffness. A variety of clamps for use during the endurance test of tendons were categorized according to the temperature used during the measurement. The clamps are divided into three groups: room temperature, cooled and heated clamps. The second goal of our review is to overview of clamps on the following aspects: name of clamp, author and date, type of clamps, type of endurance test (static or dynamic), type preloading (dynamic or static), type of tendon and measured and calculated parameters, and summarize in Table 3, as a comprehensive catalogue.

METHODS

This systematic review was carried out in keeping with the PRISMA 2020 E&E and the PRISMA-S guidelines and checklists. A search was conducted for publications dating between 1991 and February 28th 2022 through three electronic databases (Web of Science, Scopus, and PubMed). We used Critical Appraisal Skills Program checklist to check the quality of included articles.

RESULTS

The database search and additional sources resulted in 1725 records. 1635 records eliminated during the screening for various reasons (case report, other languages, book chapter, unavailable text/conference abstract, unrelated topic). The number of articles used in the final synthesis was 90. A variety of clamps for use during the endurance test of tendons were identified and categorized according to the temperature used during the measurement. Based on this, the clamps are divided into three groups: room temperature, cooled or heated clamps.

CONCLUSIONS

On the basis of the systematic literature review, mechanical parameters determined by usage with cooled clamps proved to be more reliable than with those at room temperature and with heated clamps. The collected information from the articles included name of clamp, author and date, type of clamps, type of endurance test (static or dynamic), type preloading (dynamic or static), type of tendon and measured and calculated parameters given in Table 3. summarized. The main advantage of the cooled clamps is that there is no limit to the type and length of the tendon. This study provides an overview of clamps and does not represent the modernity of any method.

ACL reconstruction with femoral and tibial adjustable versus fixed-loop suspensory fixation: a retrospective cohort study

Background

Cortical suspensory fixation (CSF) devices gain more and more popularity as a reliable alternative to interference screws for graft fixation in anterior cruciate ligament (ACL) reconstruction. Adjustable-loop fixation may be associated with increased anterior laxity and inferior clinical outcome. The purpose of the study was to compare anterior laxity and clinical outcome after minimally invasive all-inside ACL reconstruction using an adjustable-loop (AL) to a standard technique with a fixed-loop (FL) CSF device.

Methods

Patients who underwent primary single-bundle ACL reconstruction with a quadrupled hamstring autograft at a single institution between 2012 and 2016 were reviewed. In the AL group minimally invasive popliteal tendon harvesting was performed with an all-inside approach (femoral and tibial sockets). In the FL group a traditional anteromedial approach was used for tendon harvesting and a femoral socket and full tibial tunnel were drilled. An objective clinical assessment was performed with Telos x-rays and the International Knee Documentation Committee (IKDC) Objective Score. Patient-reported outcomes (PRO) included the IKDC Subjective Score, the Lysholm Knee Score, the Knee Injury and Osteoarthritis Score (KOOS) and the Tegner Activity Scale.

Results

A total of 67 patients were enrolled in this retrospective study with a mean follow-up of 4 (± 1.5) years. The groups were homogenous at baseline regarding age, gender, and the time to surgery. At follow-up, no statistically significant differences were found regarding anterior laxity (AL: 2.3 ± 3 mm vs. FL: 2.3 ± 2.6 mm, p = 0.981). PRO scores were comparable between the AL and FL groups (IKDC score, 84.8 vs. 88.8, p = 0.185; Lysholm 87.3 vs. 89.9, p = 0.380; KOOS 90.7 vs. 91.4, p = 0.720; Tegner 5.5 vs. 6.2, p = 0.085). The rate of saphenous nerve lesions was significantly lower in the AL group with popliteal harvesting of the tendon (8.3% vs. 35.5%, p = 0.014).

Conclusion

The use of an adjustable-loop device on the femoral and tibial side led to similar stability and clinical results compared to a fixed-loop device.

A Higher Initial Tensioning Force of an ACL Graft Results in a Higher Graft Force After Screw Fixation Irrespective of the Screw Diameter: A Biomechanical Study

BACKGROUND

The intra-articular graft force (IAGF) in anterior cruciate ligament reconstruction decreases quickly over the first hours after surgery. Nevertheless, little is known about whether the initial extra-articular tensioning force (EATF) and screw diameter affect the graft force after fixation.

PURPOSE

To investigate the effects of different EATFs on the IAGF of a soft tissue graft fixated via a bioabsorbable interference screw over 100 minutes after fixation and to evaluate the effects of different screw diameters within 1 mm of the tunnel width during this process.

STUDY DESIGN

Controlled laboratory study.

METHODS

In this biomechanical study, a porcine quadruple-strand soft tissue graft was inserted into the tibial anterior cruciate ligament tunnel. On the extra-articular side, 3 loads were applied during retrograde insertion of the bioabsorbable interference screw (6, 7, and 8 mm): 20 N, 80 N, and maximum manual EATF (N_max). Nine study groups consisting of 10 tibiae each were created to test the effects of different EATFs and screw sizes. The IAGF was measured up to 100 minutes after the EATF was released.

RESULTS

An EATF ≥80 N resulted in a larger IAGF for all screw sizes at 100 minutes. There were no significant associations between the IAGF at 100 minutes and different screw diameters. Inserting the tibial screw significantly increased the IAGF in all groups, with the exception of N_max applied in groups with 7- or 8-mm screws. When compared with the end of screw insertion, after the release of the EATF, the IAGF dropped by 55% to 77 % at 100 minutes.

CONCLUSION

An initial EATF ≥80 N is associated with a significantly larger IAGF at 100 minutes in this cadaveric simulation. The IAGF in soft tissue grafts decreased substantially after the retrograde placement of an interference screw. A recommendation regarding screw diameter with respect to the IAGF cannot be given.

CLINICAL RELEVANCE

To obtain a higher residual graft force after bioabsorbable interference screw fixation, an initial EATF ≥80 N should be applied according to this model. The significant decrease in graft force after the release of the EATF indicates that the reconstructed knee cannot be mechanically stabilized after the surgery.

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

BACKGROUND

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

HYPOTHESIS

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

STUDY DESIGN

Controlled laboratory study.

METHODS

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

RESULTS

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

CONCLUSION

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

CLINICAL RELEVANCE

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

Improvement of bone-tendon fixation by porous titanium interference screw: A rabbit animal model

The interference screw is a widely used fixation device in the anterior cruciate ligament (ACL) reconstruction surgeries. Despite the generally satisfactory results, problems of using interference screws were reported. By using additive manufacturing (AM) technology, we developed an innovative titanium alloy (Ti₆ Al₄ V) interference screw with rough surface and inter-connected porous structure designs to improve the bone-tendon fixation. An innovative Ti₆ Al₄ V interference screws were manufactured by AM technology. In vitro mechanical tests were performed to validate its mechanical properties. Twenty-seven New Zealand white rabbits were randomly divided into control and AM screw groups for biomechanical analyses and histological analysis at 4, 8, and 12 weeks postoperatively; while micro-CT analysis was performed at 12 weeks postoperatively. The biomechanical tests showed that the ultimate failure load in the AM interference screw group was significantly higher than that in the control group at all tested periods. These results were also compatible with the findings of micro-CT and histological analyses. In micro-CT analysis, the bone-screw gap was larger in the control group; while for the additive manufactured screw, the screw and bone growth was in close contact. In histological study, the bone-screw gaps were wider in the control group and were almost invisible in the AM screw group. The innovative AM interference screws with surface roughness and inter-connected porous architectures demonstrated better bone-tendon-implant integration, and resulted in stronger biomechanical characteristics when compared to traditional screws. These advantages can be transferred to future interference screw designs to improve their clinical performance. The AM interference screw could improve graft fixation and eventually result in better biomechanical performance of the bone-tendon-screw construct. The innovative AM interference screws can be transferred to future interference screw designs to improve the performance of implants. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2633-2640, 2018.

Screw oversizing for anterior cruciate ligament graft fixation in primary and enlarged tibial tunnels: A biomechanical study in a porcine model

BACKGROUND

Ideal diameter for tibial interference screw fixation of the anterior cruciate ligament (ACL) graft remains controversial. Tibial graft fixation with screws matching the tunnel diameter vs. one-millimetre oversized screws were compared.

METHODS

In 32 cadaveric porcine tibiae, bovine extensor tendons with a diameter of eight millimetres were fixed in (I) a primary ACL reconstruction scenario with eight-millimetre tibial tunnels (pACL), with eight-millimetre (pACL-8) vs. nine-millimetre (pACL-9) screws, and (II) a revision ACL reconstruction scenario with enlarged tunnels of 10 mm (rACL), with 10-mm (rACL-10) vs. 11-mm (rACL-11) screws. Specimens underwent cyclic loading with low and high load magnitudes followed by a load-to-failure test. Graft slippage and ultimate failure load were recorded.

RESULTS

In comparison with matched-sized screws (pACL-8), fixation with oversized screws (pACL-9) showed with significantly increased graft slippage during cyclic loading at higher load magnitudes (1.19 ± 0.23 vs. 1.98 ± 0.67 mm; P = 0.007). There were no significant differences between the two screw sizes in the revision scenario (rACL-10 vs. rACL-11; P = 0.38). Graft fixation in the revision scenario resulted in significantly increased graft slippage in comparison with fixation in primary tunnels at higher loads (pACL vs. rACL; P = 0.004). Pull-out strengths were comparable for both scenarios and all screw sizes (P > 0.316).

CONCLUSIONS

Matched-sized interference screws provided better ACL graft fixation in comparison with an oversized screw diameter. In revision cases, the fixation strength of interference screws in enlarged tunnels was inferior to the fixation strength in primary tunnels.

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.

Are porcine flexor digitorum profundus tendons suitable graft substitutes for human hamstring tendons in biomechanical in vitro-studies?

INTRODUCTION

Although a plenty of studies exist assessing the strength of ligamentous fixation techniques using porcine flexor digitorum profundus tendons as graft substitutes for human hamstring tendons, there is no biomechanical study comparing these two tendons. To interpret the results obtained with porcine flexor digitorum profundus tendons, knowledge of their biomechanical properties is essential. The purpose of this study was to compare the biomechanical properties of human hamstring tendons and porcine flexor digitorum profundus tendons.

MATERIALS AND METHODS

A total of six human hamstring tendons and six porcine flexor digitorum profundus tendons were analysed in this study. Quadruple-bundle human hamstring tendons and double-bundle porcine flexor digitorum profundus tendons with a diameter of 9 mm were used. Specimens were placed into a tensile loading fixation of a servohydraulic testing machine. Biomechanical analysis included pretensioning of the constructs at 50 N for 10 min following cyclic loading of 1500 cycles between 50 and 200 N at 0.5 Hz for measurement of elongation. Subsequently, ultimate failure load and failure mode analysis were performed with a ramp speed of 20 mm/min.

RESULTS

Human hamstring tendons showed significantly higher maximum load to failure values compared to porcine flexor digitorum profundus tendons (1597 ± 179.6 N vs. 1109 ± 101.9 N; p = 0.035). Human hamstring tendons yielded significantly lower initial elongation during preload, but not during cyclical loading.

CONCLUSIONS

When porcine flexor digitorum profundus tendons are used as graft substitutes for human hamstring tendons in biomechanical studies, maximum load to failure is underestimated while elongation is comparable to that of human hamstring tendons. Transferring results of biomechanical studies into clinical practice, the lower maximum load to failure of porcine flexor digitorum profundus tendons needs to be taken into consideration.

Biomechanical comparison of 2 anterior cruciate ligament graft preparation techniques for tibial fixation: adjustable-length loop cortical button or interference screw

BACKGROUND

Cortical button fixation at the femoral side and interference screws within the tibial bone tunnel are widely used for anterior cruciate ligament graft fixation. Using a bone socket instead of a full tunnel allows cortical button fixation on the tibial side as well. If adjustable-length loop cortical button devices are used for femoral and tibial fixation, the tendon graft has to be secured with sutures in a closed tendon loop. The increased distance of fixation points and potential slippage of the tendon strands at the securing sutures might lead to greater risk of postoperative graft elongation when compared with conventional graft preparation with tibial interference screw fixation.

HYPOTHESIS

Compared with an anterior cruciate ligament graft with tibial adjustable-length loop cortical button fixation, a graft with tibial interference screw fixation will show less graft elongation during cyclic loading and lower ultimate failure loads.

STUDY DESIGN

Controlled laboratory study.

METHODS

Grafts with tibial adjustable-length loop cortical button fixation and grafts with tibial interference screw fixation were biomechanically tested in calf tibiae (n = 10 per group). Femoral fixation was equivalent for both groups, using an adjustable-length loop cortical button. Specimens underwent cyclic loading followed by a load-to-failure test.

RESULTS

Grafts with screw fixation showed significantly less initial elongation (cycles 1-5: 1.46 ± 0.26 mm), secondary elongation (cycles 6-1000: 1.87 ± 0.67 mm), and total elongation (cycles 1-1000: 3.33 ± 0.83 mm) in comparison with grafts with button fixation (2.47 ± 0.26, 3.56 ± 0.39, and 6.03 ± 0.61 mm, respectively) (P < .001). While pull-out stiffness was significantly higher for grafts with screw fixation (309.5 ± 33.2 vs 185.6 ± 16.4 N/mm) (P < .001), grafts with button fixation were able to withstand significantly higher ultimate failure loads (908 ± 74 vs 693 ± 119 N) (P < .001).

CONCLUSION

Grafts with tibial adjustable-length loop cortical button fixation resulted in higher graft elongation during cyclic loading and showed higher ultimate failure loads in comparison with conventional graft preparation with tibial interference screw fixation at time zero.

CLINICAL RELEVANCE

The results of this biomechanical study suggest that grafts with tibial interference screw fixation provide better knee stability at time zero because of reduced graft elongation and greater stiffness in comparison with grafts with tibial adjustable-length loop cortical button fixation.

A Comparison of Clinical Outcomes of Two Methods of Femoral Hamstring Graft Pin Fixation in Anterior Cruciate Ligament Reconstruction

The outcome of anterior cruciate ligament (ACL) reconstruction with hamstring grafts depends on early rehabilitation and secure graft fixation. Various devices available for graft fixation at the femoral tunnel have different biomechanical properties as demonstrated on cadaveric studies. The aim of this study was to compare clinical outcomes in patients using either of two methods of transfemoral pin fixation for hamstring grafts in ACL reconstruction. Twenty-eight patients undergoing primary ACL reconstruction with hamstring autograft with either transfemoral expansion fixation (Rigidfix) or cortical-cancellous suspension (Transfix) by a single surgeon were analysed including subjective knee scores and objective measurements including range of motion and arthrometer-measured anterior translation. Transfix was used in 14 (50.0%) patients and Rigidfix was used in 14 (50.0%) patients. There was no significant difference in pre-injury Tegner activity scores, pre-operative Tegner activity scores, Lysholm scores and age or in Tegner post-operative activity scores, Lysholm scores, range of motion, Lachman and pivot scores absolute anterior translation and anterior translation compared to the non-operated knee at two years. There was a significant improvement in Tegner (2.6 ± 2.4, p<0.00) and Lysholm (25.3 ± 21.2, p<0.00) scores at two years with no significant difference between the two groups. One patient had a broken Transfix cross-pin 13 months after surgery which presented as a subcutaneous swelling which was removed. Although the biomechanical properties of Rigidfix and Transfix differ as demonstrated in cadaveric studies, both devices had similar favourable clinical outcomes in our series.

Femoral tunnel-interference screw divergence in anterior cruciate ligament reconstruction using bone-patellar tendon-bone graft: A comparison of two techniques

BACKGROUND

Interference screw is a popular fixation device used to rigidly fix bone-patellar tendon-bone (B-PT-B) graft both in femoral and tibial tunnels in anterior cruciate ligament (ACL) reconstruction. Parallel placement of screw is difficult in transtibially drilled femoral tunnel but always desired as it affects pullout strength of the graft. Commonly, interference screw into the femoral tunnel is inserted through the anteromedial (AM) or accessory AM portal. These portals are not-in-line with the transtibially drilled femoral tunnel. Furthermore, these portals increase the divergence of the interference screw in the femoral tunnel. We hypothesized that interference screw placement through patellar tendon (PT) portal (through donor defect) in transtibially drilled femoral tunnel can be less divergent. We report the prospective randomized study to investigate the difference of divergence of interference screw placed through PT portal and AM portal and its clinical relevance.

MATERIALS AND METHODS

Forty-one patients underwent femoral tunnel B-PT-B graft fixation through AM portal (group 1) and other 41 (group 2) through PT portal. Femoral tunnel-interference screw divergence was measured on postoperative digital lateral X-rays. Ha's method was used to grade divergence. The clinical outcome was assessed by postoperative intervention knee documentation committee grading (IKDC) and Lysholm score at 2 years followup.

RESULTS

Mean tunnel-screw divergence in sagittal plane through AM portal was 13.38° (95% CI: 12.34-14.41) and through PT portal was 7.20° (95% CI: 6.25-8.16) (P<0.0001). In AM portal group, 82.9% patients had divergence in either grade 3 or 4 category, whereas in PT portal group, 82.9% patients were in grade 1 or 2 category (P<0.0001). Mean Lysholm score were 92.8 and 94.5 at two-year follow-up in both groups which were statistically not significant. The International knee documentation committee grades of patients in both groups were similar and had no statistical significance.

CONCLUSION

Femoral interference screw placement through the PT portal leads to significantly less screw divergence as compared with screw placement through the AM portal. However, this difference in divergence is not reflected in clinical outcome.