Accidental perforation of the lateral femoral cortex in ACL reconstruction: an investigation of mechanical properties of different fixation techniques

Complications following all-inside anterior cruciate ligament reconstruction

PURPOSE

We conducted a comprehensive analysis of possible perioperative complications following all-inside anterior cruciate ligament reconstruction (ACLR). Additional techniques and tips are proposed to prevent and manage complications.

METHODS

Complications following all-inside ACLR performed between December 2015 and December 2020 were retrospectively analysed. Altogether, 348 operations were performed and 275 patients were enrolled with a minimum 12-month follow-up period. Only semitendinosus autograft was utilised in most patients, and semitendinosus-gracilis autograft and allograft were used in five and 31 patients, respectively. Simultaneous meniscal repair, partial meniscectomy, and chondral surgery were performed in 29.5%, 21.1%, and 4.4% of patients, respectively. Complications were observed based on the patient's clinical condition, plain film, and magnetic resonance imaging. Clinical outcomes were assessed pre-operatively and at 12 months post-operatively, using the International Knee Documentation Committee form, Lysholm and Tegner activity scores, and KT1000 side-to-side difference.

RESULTS

Intraoperative and post-operative complications developed in 65 patients (23.6%). The most common complication was cortical button malposition on the femoral side (19.3%). Intra-operative breakage of the retrograde drill was found in two cases (0.73%), with three cases (1.1%) of over-drilling with destruction of the outer cortex. Post-operatively, four (1.5%), 13 (4.7%), and 16 (5.8%) cases of infection, full-thickness re-rupture, and loss of extension, respectively, were recorded. Functional outcome scales showed significant post-operative improvement.

CONCLUSION

Cortical button malposition was the most common but easily preventable complication. All-inside ACLR could be safe and promising after the suggested additional operative techniques and proper perioperative management which decrease complication rates and improve favourable outcomes.

Posterior wall blowout on computed tomography after anterior cruciate ligament reconstruction

BACKGROUND

During anterior cruciate ligament (ACL) reconstruction, even when a posterior wall of the femoral bone tunnel is identified, computed tomography (CT) occasionally demonstrates a breach of the posterior femoral cortex of the femoral bone tunnel, i.e., posterior wall blowout, after ACL reconstruction (posterior wall blowout-like phenomenon). This study aimed to investigate the influence of the posterior wall blowout-like phenomenon on clinical outcomes after ACL reconstruction using hamstring tendon.

METHODS

A total of 105 patients who underwent CT examination two weeks after ACL reconstruction were enrolled. A cortical suspension device was used for femoral side fixation in all cases. Posterior wall was identified in all cases during the surgery. The side-to-side difference in anterior knee laxity, pivot shift test, Lysholm knee score, the International Knee Documentation Committee (IKDC) subjective form, and the Knee Injury and Osteoarthritis Outcome Score (KOOS) were evaluated one year after the surgery. A second CT examination was performed 6-12 months after the surgery, if a posterior wall blowout-like phenomenon was identified in the first CT examination.

RESULTS

Two weeks after the surgery, 16 of the 105 patients showed a posterior wall blowout-like phenomenon. Twelve of the 16 cases demonstrated a regenerated posterior femoral cortex of the femoral bone tunnel on their second CT images. There were no significant differences between the posterior wall blowout-like phenomenon group and the normal posterior wall group in terms of a side-to-side difference in anterior knee laxity (0.4 ± 1.5 mm and 0.1 ± 1.6 mm, respectively), pivot shift test, Lysholm knee score, IKDC score, and KOOS at one year after surgery. The length and diameter of the femoral bone tunnel were not significantly different between the two groups.

CONCLUSIONS

Posterior wall blowout-like phenomenon after ACL reconstruction using a cortical suspension device did not negatively influence clinical outcomes.

LEVEL OF EVIDENCE

III - retrospective comparative clinical study.

The "Not" Good, the Bad and the Ugly: Prevention and Management of Common Intraoperative and Delayed Complications in Orthopedic Sports Medicine Surgical Procedures

Despite advances in techniques designed to make arthroscopic sports medicine procedures simple, complications still arise in the operating room; even in the most trained hands. However, what marks a skilled surgeon is not just the ability to steer the ship amidst smooth seas, but a knack for getting out of trouble once things deviate from the set course. Each surgical case presents a unique challenge, and no 2 are the same. For this reason, a true expert surgeon must know how to deal with "complications" ranging from a mild swell to a raging storm. In this review we present strategies to prevent and navigate some of the most common, and fearsome complications a sports medicine surgeon may face during surgery. A great surgeon is one that acknowledges that throughout their career it is not a question of "if" these situations will arise, but "when"; and preparation is the key to success.

The Ideal Cortical Button Location on the Lateral Femur for Anterior Cruciate Ligament Suspensory Fixation is 30 mm Proximal to the Lateral Epicondyle

Purpose

To determine the ideal location for anterior cruciate ligament (ACL) suspensory cortical button placement on the lateral femur with the highest failure load and to establish the relationship of tunnel diameter and cortical thickness on load to failure.

Methods

Computed tomography (CT) data were obtained from 45 cadaveric distal femurs. A Cartesian coordinate system was established along the lateral femur with the lateral epicondyle (LE) as a reference point. Locations 0, 20 and 30 mm from the LE along lines 0°, 25°, 50°, and 75° posterioproximal from the axial plane were created. Tunnels connecting from each location to the center of the ACL footprint were simulated. Cortical thickness and long axis diameter of the oval cortical holes were determined for each location. Based on the CT data, custom drill guides were created and used to drill 4.5 mm tunnels at each lateral femur location to the ACL footprint on the cadaver femurs. Cortical buttons were placed at each location and pulled using a servohydraulic testing system. The correlation of tunnel diameter and cortical thickness to button failure load were analyzed using a regression analysis.

Results

Significant differences were found for failure load (P<.0001) and cortical thickness between the locations tested (P<.0001). The location 30 mm proximal from the LE and 75⁰ from the axial plane had the highest failure load of 573 N. A regression analysis (R² = .15) indicated that the cortical thickness was significantly correlated with load to failure (P <.0001), whereas the long-axis diameter was not (P = .33).

Conclusion

The ideal cortical button location on the lateral femur for ACL suspensory fixation was located 30 mm proximal from the lateral epicondyle, based on this area’s high failure load. Oblique tunnel drilling of this proximal location may cause a larger long-axis diameter cortical hole, but the cortex is also thicker, which is more closely correlated with failure load.

Clinical Relevance

Different ACL suspensory cortical button locations on the lateral femur have different failure loads based on the cortical thickness of the bone supporting the button. It is important for surgeons to understand which drilling techniques place the button in a proximal and posterior location, especially if the bone quality of the patient is of concern.

Estudo biomecânico de diferentes dispositivos de fixação femoral na reconstrução do ligamento patelofemoral medial em joelhos de suínos

Objetivo Avaliar diferentes dispositivos de fixação femoral na reconstrução do ligamento patelofemoral medial para comparar sua eficácia quanto à força de fixação até a falha em joelhos suínos.

Métodos Foram ensaiados 30 joelhos de suínos subdivididos em 3 grupos de 10 joelhos. Os enxertos retirados foram dissecados de tendões extensores das patas dos suínos. Cada grupo teve o enxerto fixado ao fêmur com parafuso de interferência, âncora, ou tenodese no tendão adutor. Os 3 métodos foram submetidos à testes biomecânicos utilizando uma máquina universal de ensaio de tração com uma velocidade de 20 mm/min.

Resultados Verificamos que a média mais elevada da resistência linear sob tração lateral (185,45 ± 41,22 N) ocorreu no grupo 1: “fixação por parafuso,” seguido do grupo 2: “fixação por âncora” (152,97 ± 49,43 N), e a média foi menor no grupo 3: “fixação por tenodese” (76,69 ± 18,90 N). Para a margem de erro fixada (5%), comprovou-se a diferença significativa entre os grupos (p < 0,001) e também através dos testes de comparações múltiplas (entre os pares de grupos) verificou-se a ocorrência de diferenças significativas. A variabilidade expressada por meio do coeficiente de variação mostrou-se reduzida, já que a referida medida foi inferior a 33,3%.

Conclusão O uso de parafusos de interferência no túnel ósseo de joelhos porcinos é suficientemente forte para fixação femoral na reconstrução do ligamento patelofemoral medial, assim como a fixação com âncoras montáveis com fio de alta resistência. Entretanto, a tenodese no tendão adutor mostrou-se frágil para essa finalidade.

A Cost-Effective Alternative for Lateral Femoral Wall Perforation in Anterior Cruciate Ligament (ACL) Reconstruction: A Case Report

Lateral femoral wall perforation is a rare intra-operative complication in anterior cruciate ligament (ACL) reconstruction surgery. However, it can be challenging to manage if it occurs. We share our experience on lateral femoral wall perforation managed by a large fragment washer. A 25-year-old man with right ACL injury presented with knee instability despite physiotherapy. Anterior drawer test (ADT) and Lachman test were grade 3, glide on pivot shift was positive. During ACL reconstruction, the lateral femoral wall was perforated. Due to unavailability of the rescue endobutton and budget constraint, we passed the endobutton through a washer and allowed it to sit on the washer over the lateral femoral wall. ADT and Lachman test on post-operative 6, 12 and 24 weeks were grade 1, with a negative pivot shift test. Lysholm knee score improved from 69 pre-operatively to 98 post-operatively. Conventionally, lateral femoral wall perforation can be managed by rescue endobutton, or screw and washer post technique. As this complication is rare, the rescue endobutton may not be available at all times, and the cost of the implant is also another important factor to consider. A washer can be used as an alternative technique to manage lateral femoral wall perforation in ACL reconstruction as it is not only cost-effective but also provides stable fixation with good functional outcome.

Aperture elongation of the femoral tunnel on the lateral cortex in anatomical double-bundle anterior cruciate ligament reconstruction using the outside-in technique

In anatomical anterior cruciate ligament reconstruction surgery using the outside-in technique, the aperture of the femoral lateral cortex may become elliptical.Retrospective cross-sectional studyTo evaluate the extent of elliptical eccentricity in lateral apertures relative to aperture positioning and clinical failure rate in anatomical anterior cruciate ligament double-bundle reconstruction using outside-in technique.In 75 patients, the aperture elongation factor was defined as the ratio of the major axis of the elliptical aperture to the drill size. Using the lateral epicondyle as a reference point, the lateral femur was divided into sections by distance and angle, and the minimum area was evaluated to assess the relationship between the elongation factor and aperture position of the lateral cortex for each bundle. The incidence and associated clinical performance regarding cortical button migration were also investigated.Aperture elongation factors were 120.2 ± 13.3% and 120.0 ± 16.3% on the anteromedial (AM) and posterolateral (PL) sides, respectively. Femoral tunnel elongation was smallest when the entry point axis were both between 30 to 60° and distance was between 10 to 20 mm and 0 to 10 mm on the AM and PL sides, respectively. During the postoperative follow-up period, intra-tunnel migration was confirmed in 4 of 75 cases (5.3%). Fixation failure neither affected clinical scores nor knee laxity.Areas of minimum elongation for each bundle on both AM and PL sides were found anteroproximally to the lateral epicondyle and positioned near each other. Elongation did not directly affect the clinical outcome.Level of evidence grade: prognostic level III.

Assessment of fixation for anterior cruciate ligament reconstruction using oversized suspensory devices on full-length femoral tunnels

BACKGROUND

In ACL repair, full-length single-diameter tunnels facilitate anatomic femoral fixation with suspensory devices, especially with outside-in techniques, and are required after accidental cortical perforation. With tunnel diameters over 6 mm, fixation resistance using regular suspensory devices may not suffice. Oversized cortical footprint devices could be a solution to guarantee fixation performance in larger tunnel diameters. This study aims to assess the biomechanical properties of ACL femoral fixation provided by two enlarged suspensory devices of similar characteristics, a fixed loop (G-Lok™ with G-Lok-XL™) and an adjustable loop (ProCinch™ with G-Lok-XL™), resting on a full-length 9 mm diameter tunnel compared to the widely accepted regular fixed-loop device (G-Lok™) on a socket tunnel.

METHODS

Twenty-seven fresh frozen porcine femurs and flexor digitorum profundus tendons were randomly assigned to a study group depending on the fixation method used (N = 9). Graft-femur constructs were subjected to a traction cyclic test (5000 cycles, [50-250]N load, 1 Hz) followed by a load-to-failure test (v = 1 mm/s). Residual displacement during the cyclic test and stiffness, displacements at physiological loads, ultimate load and corresponding displacement during the load-to-failure test were determined.

FINDINGS

No significant differences could be established for any parameter measured in the comparison between the control with the socket tunnel and the oversized fixations with full-length tunnels.

INTERPRETATION

ACL femoral fixation achieved in full-length single diameter tunnels by using an enlarged suspension device, both with a fixed or an adjustable loop, provide similar biomechanical properties to the gold-standard fixed-loop device in a socket tunnel. Therefore, its clinical use may be safe.

Techniques for Femoral Socket Creation in ACL Reconstruction

Anterior cruciate ligament (ACL) injury is common and affects a wide variety of individuals. An ACL reconstruction is the treatment of choice for patients with subjective and objective symptoms of instability and is of particular importance to cutting or pivoting athletes. With many variables involved in ACL reconstruction, femoral tunnel placement has been found to affect clinical outcomes with nonanatomic placement being identified as the most common technical error. Traditionally the femoral tunnel was created through the tibial tunnel or transtibial with the use of a guide and a rigid reaming system. Because of proximal, nonanatomic tunnel placement using the transtibial technique, the use of the anteromedial portal and outside-in drilling techniques has allowed placement of the tunnel over the femoral footprint. In this paper, we discuss the difference between the 3 techniques and the advantages and disadvantages of each. The authors then explore the clinical differences and outcomes in techniques by reviewing the relevant literature.

Anterior cruciate ligament graft fixation first in anterior and posterior cruciate ligament reconstruction best restores knee kinematics

PURPOSE

To evaluate the effect of different graft fixation sequences in one-stage anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) reconstruction on (1) knee biomechanics and (2) tibiofemoral alignment.

METHODS

Twelve porcine knees were used in this study. Five fixation sequences were performed (angle indicating knee flexion): (a) PCL at 30° and ACL at 30°, (b) PCL at 90° and ACL at 30°, (c) ACL at 30° and PCL at 30°, (d) ACL at 30° and PCL at 90°, and (e) ACL and PCL simultaneous fixation at 30°. Anterior and posterior tibial translation was measured under an 89 N load. A 3-D digitizer was used to measure the change in anteroposterior (AP) tibiofemoral position.

RESULTS

None of the graft fixation sequences restored the AP laxity of the intact knee, and there are minimal differences in the in situ tissue forces in the ACL and PCL grafts. The reconstructions with fixation of the PCL graft first resulted in a significantly larger change in AP tibiofemoral position from the intact knee at 60° and 90° of knee flexion than the reconstructions with fixation of the ACL graft first (p < 0.05).

CONCLUSION

Fixation of the ACL graft at 30° of knee flexion followed by fixation of the PCL graft can best restore the tibiofemoral position of the intact knee. This study has clinical relevance in regard to the effect of graft fixation sequence on the position of the tibia relative to the femur in one-stage ACL and PCL reconstruction.

Converting round tendons to flat tendon constructs: Does the preparation process have an influence on the structural properties?

PURPOSE

The structural properties of hamstring tendon grafts were evaluated in a porcine model, after processing it to a flat shape, to better replace or augment anatomic flat structures (e.g. ACL, MPFL or MCL).

METHODS

In this biomechanical study, porcine flexor tendons were used which have a comparable shape to semitendinosus and gracilis tendons. One part of the tendon was prepared to a flat tendon construct by splitting the tendon longitudinally with a knife to half of the diameter of the tendon. The semi-split tendon was scratched out to a flat shape. The other matched part was tested in its original round shape. The tendons (n = 40) have been fixed in a uniaxial testing machine (Zwick/Roell) by cryo-clamps after preparing the fixed ends by 2-0 polyester sutures (2-0 Ethibond^® EXCEL, Ethicon, Somerville, NJ). In every specimen, there was a free 60-mm tendon part between both clamps. The tendons have been loaded to failure to evaluate typical biomechanical parameters such as stiffness, yield load and maximum load.

RESULTS

No statistically significant differences (n.s.) regarding stiffness, yield load and maximum load between natively round and processed flat tendons could be detected.

CONCLUSION

A prepared flat-shaped tendon does not show any different structural properties compared with an original round tendon. Therefore, a flat tendon seems to be a biomechanical stable graft option for anatomic reconstruction or augmentation of injured natively flat-shaped structures such as MCL, MPFL or ACL.

Knee joint kinematics after dynamic intraligamentary stabilization: cadaveric study on a novel anterior cruciate ligament repair technique

PURPOSE

Dynamic intraligamentary stabilization (DIS) has been introduced for the repair of acute anterior cruciate ligament (ACL) tears as an alternative to delayed reconstruction. The aim of the present study was to compare knee joint kinematics after DIS to those of the ACL-intact and ACL-deficient knee under simulated Lachman/KT-1000 and pivot-shift tests. We hypothesized that DIS provides knee joint kinematics equivalent to an intact ACL.

METHODS

With the use of a robotic knee simulator, knee kinematics were determined in simulated Lachman/KT-1000 and pivot-shift tests at 0°, 15°, 30°, 60°, and 90° of flexion in eight cadaveric knees under the following conditions: (1) intact ACL, (2) ACL deficiency, (3) DIS with a preload of 60 N, and (4) DIS with a preload of 80 N. Statistical analyses were performed using two-factor repeated-measures analysis of variance. The significance level was set at a p value of <0.05.

RESULTS

After DIS with a preload of either 60 N or 80 N, the anterior translation was significantly reduced in the simulated Lachman/KT-1000 and pivot-shift tests when compared to the ACL-deficient knee (p < 0.05). No significant differences were observed between the DIS reconstruction with a preload of 80 N and the intact ACL with regard to anterior laxity in either test. However, DIS with a preload of only 60 N was not able to restore knee joint kinematics to that of an intact knee in all degrees of flexion.

CONCLUSION

DIS with a preload of 80 N restores knee joint kinematics comparable to that of an ACL-intact knee and is therefore capable of providing knee joint stability during ACL healing. DIS therefore provides a new technique for primary ACL repair with superior biomechanical properties in comparison with other techniques that have been described previously, although further clinical studies are required to determine its usefulness in clinical settings.

The effect of anterior cruciate ligament graft rotation on knee biomechanics

PURPOSE

The purpose of this study was to evaluate the effects on knee biomechanics of rotating the distal end of the bone-patellar tendon graft 90° in anatomic single-bundle (SB) anterior cruciate ligament (ACL) reconstruction with a porcine model.

METHODS

Twenty (n = 20) porcine knees were evaluated using a robotic testing system. Two groups and three knee states were compared: (1) intact ACL, (2) deficient ACL and (3) anatomic SB ACL reconstruction with (a) non-rotated graft or (b) rotated graft (anatomic external fibre rotation). Anterior tibial translation (ATT), internal (IR) and external rotation (ER) and the in situ tissue force were measured under an 89-N anterior tibial (AT) load and 4-N m internal and external tibial torques.

RESULTS

A significant difference from the intact ACL was found in ATT at 60° and 90° of knee flexion for rotated and non-rotated graft reconstructions (p < 0.05). There was a significant difference in the in situ force from the intact ACL with AT loading for rotated and non-rotated graft reconstructions at 60° and 90° of knee flexion (p < 0.05). Under IR loading, the in situ force was significantly different from the intact ACL at 30° and 60° of knee flexion for rotated and non-rotated graft reconstructions (p < 0.05). There were no significant differences in ATT, IR, ER and the in situ force between rotated and non-rotated reconstructions.

CONCLUSION

Graft rotation can be used with anatomic SB ACL reconstruction and not have a deleterious effect on knee anterior and rotational biomechanics. This study has clinical relevance in regard to the use of graft rotation to better reproduce the native ACL fibre orientation in ACL reconstruction.

The influence of femoral tunnel length on graft rupture after anterior cruciate ligament reconstruction

Background

For ACL reconstruction, the minimum length of the femoral tunnel and the flexor tendon graft length needed within the tunnel for proper integration have not been defined. The aim of this study was to assess whether a short tunnel is a risk factor for poor prognosis and re-rupture by comparing the outcomes of patients with short femoral tunnels to those of patients with longer tunnels.

Materials and methods

A retrospective observational study of 80 patients who underwent ACL reconstruction using flexor tendons via the medial transportal or transtibial technique was performed. Patients were categorized according to the amount of graft within the tunnel: ≤1.5 versus >1.5 cm; ≤2 versus >2 cm; ≤2.5 versus >2.5 cm; and ≤1.5 versus >2.5 cm. Patients were evaluated 2 years after surgery by performing a physical examination (Lachman, pivot shift and anterior drawer tests), using a KT1000 arthrometer, calculating objective and subjective International Knee Documentation Committee scores, conducting the Lysholm score, and recording re-ruptures.

Results

Of the 80 operated patients, nine were lost to follow-up. Comparative assessment of the patients with different amounts of graft within the tunnel indicated no significant differences in the evaluated outcomes, except for positive Lachman test results, which were more frequent in patients with tunnels with ≤2 cm of graft than in those with tunnels with >2 cm of graft.

Conclusion

The amount of graft within the femoral tunnel does not appear to be a risk factor for clinical instability of the knee or re-rupture of the graft. Level of evidence: case series, level IV.

Level of evidence

Case series, level IV.

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.

Biomechanical and histological comparison between the cryopreserved and the lyophilized Gracilis tendon allograft for MPFL reconstruction, a cadaveric experimental study

BACKGROUND

Medial patellofemoral ligament (MPFL) is the main restrictor of lateral shifting of the patella, contributing by 60 % in the first 20° flexion of the knee. MPFL reconstruction has been performed in order to restore the stability of the patella with good results.Lyophilized Gracilis tendon allograft (LGA) compared to Cryopreserved Gracilis tendon allograft (CGA) has a lower cost, does not require to maintain cooling chain or preparation. The purpose of this study is to compare the histological and biomechanical characteristics of an experimental model of reconstruction of the MPFL in porcine patellas with LGA versus CGA.

METHODS

Randomized controlled experimental study in porcine model conducted on 36 porcine patellas in which 18 were intervened with LGA and 18 were intervened with CGA. The confluent tunnel technique was used for MPFL reconstruction. Maximum tensile force, allograft elongation and stiffness of the construct were measured. The cellularity and collagen tissue distribution were evaluated in the allografts. The histological and biomechanical characteristics of the LGA were compared to those of the CGA.

RESULTS

The median of the maximum tensile force for the LGA group was 299.63 N and 280.86 N for the CGA group (p = 0.45). The median of the stiffness was 57.86 N/mm for the LGA and 54.23 N/mm for the CGA (p = 0.2). The median of the elongation for the LGA was 5.95 mm and 6.12 mm for the CGA (p = 0,29). The bone bridge failed in 88.88 % of the constructs with LGA and 94.44 % in those with CGA (p = 0.5).

CONCLUSIONS

No differences were observed between the LGA group and the CGA group in maximum tensile force, elongation, stiffness, site of rupture and histological characteristics. The use of a lyophilized Gracilis tendon allograft for MPFL reconstruction confers the same histological and biomechanical characteristics as a cryopreserved Gracilis tendon allograft.

Posterior Wall Blowout in Anterior Cruciate Ligament Reconstruction: A Review of Anatomic and Surgical Considerations

Violation of the posterior femoral cortex, commonly referred to as posterior wall blowout, can be a devastating intraoperative complication in anterior cruciate ligament (ACL) reconstruction and lead to loss of graft fixation or early graft failure. If cortical blowout occurs despite careful planning and adherence to proper surgical technique, a thorough knowledge of the anatomy and alternative fixation techniques is imperative to ensure optimal patient outcomes. This article highlights anatomic considerations for femoral tunnel placement in ACL reconstruction and techniques for avoidance and salvage of a posterior wall blowout.

Biomechanical Properties of Different Fixation Techniques for Posterior Cruciate Ligament Avulsion Fractures

PURPOSE

To analyze the ultimate failure load, yield load, stiffness, and cyclic elongation of 4 different fixation techniques for posterior cruciate ligament avulsion fractures under cyclic loading and load-to-failure conditions.

METHODS

In 40 porcine knees, a standardized bony avulsion of the posterior cruciate ligament was generated. The osseous avulsion was fixed by the following techniques through an open approach: (1) direct anterograde screw fixation (3.5 mm with washer), (2) retrograde screw fixation (3.5 mm with washer), (3) cortical suspension button fixation (with No. 2 braided suture), and (4) direct suture cerclage (with No. 2 braided suture). The constructs were cyclically loaded 500 times (10 to 100 N) to measure the maximum elongation. Subsequently, loading to failure was performed, and stiffness, yield load, and maximum load were measured. A 1-way analysis-of-variance test was performed with significance set at P < .05.

RESULTS

Button fixation resulted in lower elongation (1.25 ± 0.27 mm) than anterograde screw fixation (2.17 ± 0.74 mm, P = .0058) and the cerclage technique (2.02 ± 0.24 mm, P = .0290). The cerclage technique showed a lower yield load (493.55 ± 88.86 N) than anterograde screw fixation (720.39 ± 139.0 N, P = .0012) and retrograde screw fixation (668.58 ± 147.59 N, P = .0145); it also had lower stiffness and maximum load values (51.2 ± 6.11 N/mm and 631.22 ± 101.22 N, respectively) than the anterograde screw fixation technique (65.6 ± 12.74 N/mm, P = .041, for stiffness and 817.5 ± 145.9 N, P = .008, for maximum load). None of the other results were significantly different (P > .05).

CONCLUSIONS

The cortical suspension button and retrograde screw fixation techniques showed comparable structural properties to the direct screw fixation technique. The raw structural properties of suture cerclage still seem eligible enough to consider using this technique for fixation.

CLINICAL RELEVANCE

In this in vitro model, all techniques appear to constitute a biomechanically stable alternative to traditional anterograde screw fixation. In contrast to anterograde screw fixation, these techniques can be performed minimally invasively.

Posterior Wall Blowout During Anterior Cruciate Ligament Reconstruction: Suspensory Cortical Fixation With a Screw and Washer Post

Posterior wall blowout can be a devastating intraoperative complication in anterior cruciate ligament reconstruction. This loss of osseous containment can cause difficulty with graft fixation and can potentially lead to early graft failure if unrecognized and left untreated. If cortical blowout occurs despite careful planning and proper surgical technique, a thorough knowledge of the local anatomy and surgical salvage options is paramount to ensure positive patient outcomes. This article highlights our preferred salvage technique using suspensory cortical fixation with a screw and washer construct.

Biomechanical evaluation of knee kinematics after anatomic single- and anatomic double-bundle ACL reconstructions with medial meniscal repair

PURPOSE

To evaluate knee laxity after anatomic ACL reconstruction with additional suture repair of a medial meniscus tear.

METHODS

Kinematics of the intact knee were determined in 12 human cadaver specimens in response to a 134-N anterior tibial load (aTT) and a combined rotatory load of 10 Nm valgus and 4 Nm internal tibial rotation (aTTPS) using a robotic/universal force moment sensor testing system. Subsequently, the ACL was resected following the creation of a standardized tear of the medial meniscus, a standard meniscus repair and an ACL reconstruction using an anatomic single-bundle (6) or an anatomic double-bundle technique (6). Knee kinematics were determined following every sub-step.

RESULTS

Significant increase of aTT in the ACL-deficient knee was found (p ≤ 0.001) with a further increase in the ACL-deficient knee with additional medial meniscal rupture (p ≤ 0.001). ACL reconstructions significantly decreased aTT compared with the ACL and meniscus-ruptured knee. No significant differences were seen between the intact knee and the ACL-reconstructed knee with additional meniscal repair (p < 0.05). In response to a simulated pivot shift, aTTPS in the intact knee significantly increased in the ACL-deficient knee and meniscus-ruptured knee (p = 0.005). No significant differences in knee kinematics were found between SB as well as DB ACL reconstruction with additional medial meniscal repair compared with the intact knee. Comparison of SB versus DB ACL reconstruction did not reveal any significant differences in a simulated Lachman test or simulated pivot shift test (n.s.).

CONCLUSIONS

aTT as well as aTTPS significantly increased with ACL deficiency compared with the intact knee; additional medial meniscal rupture further increased aTT. Anatomic ACL reconstruction with medial meniscal repair did not reveal significant differences in knee kinematics compared with the intact knee. Comparison of anatomic SB versus DB ACL reconstruction with additional repair of the medial meniscus did not show significant differences neither in a simulated Lachman nor in a simulated pivot shift test.

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.

Comparison of outside-in and inside-out technique for tibial fixation of a soft-tissue graft in ACL reconstruction using the Shim technique

INTRODUCTION

The aim of this study was to compare the biomechanical properties of tibial fixation of a free tendon graft in ACL reconstruction using the Shim, a new wedge-shaped implant, in an outside-in technique to fixation by the Shim used in an inside-out technique and fixation by interference screw in a porcine model.

MATERIALS AND METHODS

Porcine tibia and flexor tendons were used. In Group 1, the Shim was applied outside-in. In Group 2, the Shim was inserted inside-out. In the Group 3, an 8-mm interference screw was used. Ten specimens were tested in each group. Load-to-failure, elongation, stiffness and failure mode were recorded. Cyclic loading was performed between 5 and 250 N for 1,000 cycles, followed by a load to failure testing.

RESULTS

Mean maximum load-to-failure was 629.53 N in Group 1,648.54 N in Group 2 and 749.53 N in Group 3. There was no significant difference between the groups. Stiffness varied between 127.34 N/mm in Group 1, 151.27 N/mm in Group 2 and 182.25 N/mm in Group 3. No significant differences were found between outside-in Shim and interference screw fixation. No significant difference was found for elongation among the three groups. The main failure mode was a rupture of the tendon in the IFS group and a slippage of either the implant or the tendon in both groups using the Shim.

CONCLUSIONS

As no statistically significant difference could be seen concerning load to failure, stiffness and elongation between the inside-out and the outside-in techniques, the Shim can be used for tibial fixation in an outside-in or inside-out technique depending on the preference of the surgeon. To prevent slippage of the graft a hybrid fixation should be considered.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

CLINICAL RELEVANCE

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

The effect of notchplasty in anterior cruciate ligament reconstruction: a biomechanical study in the porcine knee

INTRODUCTION

Notchplasty is frequently performed by many orthopaedic surgeons during anterior cruciate ligament (ACL) reconstruction. The effect of notchplasty on tunnel placement and knee biomechanics with ACL reconstruction is not known.

METHODS

Twelve (n = 12) porcine knees were tested using a robotic testing system. Four knee states were compared: (1) intact ACL, (2) ACL-deficient, (3) anatomic single bundle (SB) ACL reconstruction and (4) anatomic SB ACL reconstruction with a 5-mm notchplasty. The graft was fixed at 60° of flexion (full extension of porcine knee is 30°) with an 80-N tension. The knees were subjected to two loading conditions: an 89-N anterior tibial load (ATT) and 4 Nm internal (IR) and external tibial (ER) rotational torques. The kinematics and in situ force obtained from the different knee conditions were compared.

RESULTS

There were no significant differences between pre- and post-notchplasty in the ER at 30° and 60° of knee flexion (n.s.). However, a significant difference was found between pre- and post-notchplasty in ATT at 30° and 60° of flexion (p < 0.05). The in situ force in the anatomic SB reconstruction with notchplasty was significant lower than the intact and anatomic reconstructed ACL pre-notchplasty at 30°, 60° and 90° of knee flexion (p < 0.05). In response to the IR tibial torque, there were significant differences between pre- and post-notchplasty in IR at 60° (p < 0.05) of knee flexion.

CONCLUSION

Notchplasty had greater effect on anterior stability than rotational stability. This change in knee kinematics could be detrimental to a healing bone graft, ligamentization and could lead to failure of the reconstruction in early post-operative period.

Medial patellofemoral ligament reconstruction: fixation strength of 5 different techniques for graft fixation at the patella

PURPOSE

To compare the structural properties of 5 different fixation strategies for a free tendon graft at the patella in medial patellofemoral ligament (MPFL) reconstruction under cyclic loading and load to failure testing.

METHODS

We used porcine patella and flexor tendons. We tested the following fixation techniques: 3.5-mm titanium anchor, transosseous 1-mm braided polyester suture, interference screw fixation, medial bone bridge, and transpatellar tunnels. We preconditioned each graft between 5 and 20 Nm before cyclic loading with 100 Nm for 1,000 cycles was started, and then performed load to failure testing. We recorded maximum load, stiffness, and elongation.

RESULTS

In the bone bridge group, 60% of all specimens failed during cyclic testing. Fixation by transosseous sutures showed significantly less stiffness compared with all other techniques (P < .05). The bone bridge technique showed significantly lower load to failure compared with all other techniques (P < .05). Differences between the other groups were not significant.

CONCLUSIONS

Fixation of a free tendon graft by transosseous sutures provides similar load to failure and elongation but less stiffness compared with fixation by anchors, interference screws, or transverse tunnels. Load to failure for the bone bridge technique was significantly lower than that for all other techniques. Furthermore, this fixation technique had a lower load to failure than that of the native MPFL.

CLINICAL RELEVANCE

Fixation of soft tissue grafts at the patella by 1-mm braided polyester suture provides adequate fixation strength without implants in the patella, which might cause soft tissue irritation. Further studies will have to show if the lesser stiffness of this technique causes problems in the clinical setting or if this laxity might even be an advantage because it makes this reconstruction more forgiving concerning overtensioning the graft. Significantly lower load to failure of the bone bridge technique should be considered in postoperative treatment.