Effects of sectioning the posterolateral structures on knee kinematics and in situ forces in the posterior cruciate ligament

PCL insufficient patients with increased translational and rotational passive knee joint laxity have no increased range of anterior-posterior and rotational tibiofemoral motion during level walking

Passive translational tibiofemoral laxity has been extensively examined in posterior cruciate ligament (PCL) insufficient patients and belongs to the standard clinical assessment. However, objective measurements of passive rotational knee laxity, as well as range of tibiofemoral motion during active movements, are both not well understood. None of these are currently quantified in clinical evaluations of patients with PCL insufficiency. The objective of this study was to quantify passive translational and rotational knee laxity as well as range of anterior–posterior and rotational tibiofemoral motion during level walking in a PCL insufficient patient cohort as a basis for any later clinical evaluation and therapy. The laxity of 9 patient knees with isolated PCL insufficiency or additionally posterolateral corner (PLC) insufficiency (8 males, 1 female, age 36.78 ± 7.46 years) were analysed and compared to the contralateral (CL) knees. A rotometer device with a C-arm fluoroscope was used to assess the passive tibiofemoral rotational laxity while stress radiography was used to evaluate passive translational tibiofemoral laxity. Functional gait analysis was used to examine the range of anterior–posterior and rotational tibiofemoral motion during level walking. Passive translational laxity was significantly increased in PCL insufficient knees in comparison to the CL sides (15.5 ± 5.9 mm vs. 3.7 ± 1.9 mm, p < 0.01). Also, passive rotational laxity was significantly higher compared to the CL knees (26.1 ± 8.2° vs. 20.6 ± 5.6° at 90° knee flexion, p < 0.01; 19.0 ± 6.9° vs. 15.5 ± 5.9° at 60° knee flexion, p = 0.04). No significant differences were observed for the rotational (16.3 ± 3.7° vs. 15.2 ± 3.6°, p = 0.43) and translational (17.0 ± 5.4 mm vs. 16.1 ± 2.8 mm, p = 0.55) range of anterior–posterior and rotational tibiofemoral motion during level walking conditions for PCL insufficient knees compared to CL knees respectively. The present study illustrates that patients with PCL insufficiency show a substantial increased passive tibiofemoral laxity, not only in tibiofemoral translation but also in tibiofemoral rotation. Our data indicate that this increased passive multiplanar knee joint laxity can be widely compensated during level walking. Further studies should investigate progressive changes in knee joint laxity and kinematics post PCL injury and reconstruction to judge the individual need for therapy and effects of physiotherapy such as quadriceps force training on gait patterns in PCL insufficient patients.

Sequential Changes in Posterior Tibial Translation After Posterior Cruciate Ligament Reconstruction: Risk Factors for Residual Posterior Sagging

Background:

Residual posterior sagging may occur after posterior cruciate ligament (PCL) reconstruction (PCLR), yet when it mainly occurs is not fully understood.

Purpose:

To elucidate sequential changes in radiographic posterior tibial translation (PTT) after PCLR.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

The authors retrospectively investigated the radiographic findings from 22 patients who underwent bisocket double-bundle PCLR for isolated PCL injury with at least 2 years of follow-up (mean, 4.5 years; range, 2-10 years). Injury severity was assessed using PTT on lateral radiographs with gravity sag views and was stratified according to side-to-side difference in the tibial-femoral stepoff: grade 1 (<5 mm), grade 2 (5 to <10 mm), or grade 3 (≥10 mm). Measurements were taken preoperatively and then immediately, 3 months, 6 months, 1 year, and ≥2 years postoperatively. The authors also investigated the risk factors for residual posterior sagging, indicated when PTT was ≥5 mm (grade ≥2) at the minimum 2-year follow-up.

Results:

Preoperatively, 13 patients had a grade 2 injury, and 9 had grade 3 injury. The PTT, restored immediately after PCLR, significantly increased at 3 months (P < .001) but remained unchanged thereafter ≥2 years. There were 7 cases of postoperative PTT ≥5 mm on radiographs. Patients with residual posterior sagging had significantly larger mean PTT than did those without residual posterior sagging at all time points except for immediately postoperatively (preoperatively, 9.1 ± 1.6 vs 12.2 ± 2.3 mm; 3-month follow-up, 2.7 ± 1.6 vs 7.0 ± 1.8 mm; ≥2-year follow-up, 3.4 ± 1.0 vs 6.5 ± 1.4 mm; P < .001 for all). Multivariate logistic regression analysis showed that preoperative grade 3 injury was independently associated with residual posterior sagging (OR, 26.809; 95% CI, 1.257-571.963; P < .001).

Conclusion:

The initially reduced postoperative PTT significantly increased within 3 months using conventional rehabilitation protocols, but no progression was observed up to 4.5 years after PCLR. Preoperative grade 3 injury was independently associated with residual posterior sagging.

Elongation Patterns of the Posterior Cruciate Ligament after Total Knee Arthroplasty

This study aimed to understand the ability of fixed-bearing posterior cruciate ligament (PCL)-retaining implants to maintain functionality of the PCL in vivo. To achieve this, elongation of the PCL was examined in six subjects with good clinical and functional outcomes using 3D kinematics reconstructed from video-fluoroscopy, together with multibody modelling of the knee. Here, length-change patterns of the ligament bundles were tracked throughout complete cycles of level walking and stair descent. Throughout both activities, elongation of the anterolateral bundle exhibited a flexion-dependent pattern with more stretching during swing than stance phase (e.g., at 40° flexion, anterolateral bundle experienced 3.9% strain during stance and 9.1% during swing phase of stair descent). The posteromedial bundle remained shorter than its reference length (defined at heel strike of the level gait cycle) during both activities. Compared with loading patterns of the healthy ligament, postoperative elongation patterns indicate a slackening of the ligament at early flexion followed by peak ligament lengths at considerably smaller flexion angles. The reported data provide a novel insight into in vivo PCL function during activities of daily living that has not been captured previously. The findings support previous investigations reporting difficulties in achieving a balanced tension in the retained PCL.

The Laxity of the Native Knee: A Meta-Analysis of in Vitro Studies

BACKGROUND

Although soft-tissue balancing plays an important role in knee arthroplasty, we are aware of no objective target parameters describing the soft-tissue tension of the native knee. In the present study, we aimed to meta-analyze data from studies investigating native knee laxity to create a guide for creating a naturally balanced knee joint.

METHODS

PubMed and Web of Science were searched for studies with laxity data published from 1996 through 2016. Graphs were digitally segmented in cases in which numerical data were not available in text or table form. Three-level random-effects meta-analyses were conducted.

RESULTS

Seventy-six studies evaluating knee laxity at various flexion angles (0° to 90°) were included. Knee laxity was significantly different between 0° and 90° of flexion (p < 0.001) in all 6 testing directions, with mean differences of 0.94 mm and -0.35 mm for anterior and posterior translation, 1.61° and 4.25° for varus and valgus rotation, and 1.62° and 6.42° for internal and external rotation, respectively.

CONCLUSIONS

Knee laxity was dependent on the flexion angle of the knee joint in all degrees of freedom investigated. Furthermore, asymmetry between anterior-posterior, varus-valgus, and internal-external rotation was substantial and depended on the joint flexion angle.

CLINICAL RELEVANCE

If the goal of knee arthroplasty is to restore the kinematics of the knee as well as possible, pooled laxity data of the intact soft tissue envelope could be useful as a general guide for soft-tissue balancing in total knee arthroplasty.

Biomechanical evaluation of the influence of posterolateral corner structures on cruciate ligaments forces during simulated gait and squatting

Posterolateral corner (PLC) structures of the knee joint comprise complex anatomical soft tissues that support static and dynamic functional movements of the knee. Most previous studies analyzed posterolateral stability in vitro under static loading conditions. This study aimed to evaluate the contributions of the lateral (fibular) collateral ligament (LCL), popliteofibular ligament (PFL), and popliteus tendon (PT) to cruciate ligament forces under simulated dynamic loading conditions by using selective individual resection. We combined medical imaging and motion capture of healthy subjects (four males and one female) to develop subject-specific knee models that simulated the 12 degrees of freedom of tibiofemoral and patellofemoral joint behaviors. These computational models were validated by comparing electromyographic (EMG) data with muscle activation data and were based on previous experimental studies. A rigid multi-body dynamics simulation using a lower extremity musculoskeletal model was performed to incorporate intact and selective resection of ligaments, based on a novel force-dependent kinematics method, during gait (walking) and squatting. Deficiency of the PLC structures resulted in increased loading on the posterior cruciate ligament and anterior cruciate ligament. Among PLC structures, the PT is the most influential on cruciate ligament forces under dynamic loading conditions.

Femoral Fixation With Curve Cross-Pin System in Arthroscopic Posterior Cruciate Ligament Reconstruction

Posterior cruciate ligament (PCL) ruptures account for 1% to 44% of all acute ligament injuries of the knee. In this paper we wanted to try out a system for femural fixation. Hamstring tendons are harvested and standard tibial tunnel is prepared using the transtibial PCL guide; by identifying the PCL footprint, the femoral half tunnel 27 to 30 mm with in-out technique is performed. The femoral rod of a curve cross-pin system is inserted into the anterolateral access within the femoral half tunnel. The guide block is placed 2.5 cm anterior (in a coronal plane) and 2.5 cm proximal to the lateral epicondyle. The arc attachment is assembled and the bone stock assessed with the bone gauge pin in contact with the cortex of the medial femoral condyle. Then the first sleeve over trocar is assembled, and the graft is passed through the tunnel and fixed on the femur with the pins and on the tibia with interferential screw. After biomechanical studies we obtained a maximum load at 930.95 N and maximum stiffness at 58.92 N/mm.

Loading Patterns of the Posterior Cruciate Ligament in the Healthy Knee: A Systematic Review

BACKGROUND

The posterior cruciate ligament (PCL) is the strongest ligament of the knee, serving as one of the major passive stabilizers of the tibio-femoral joint. However, despite a number of experimental and modelling approaches to understand the kinematics and kinetics of the ligament, the normal loading conditions of the PCL and its functional bundles are still controversially discussed.

OBJECTIVES

This study aimed to generate science-based evidence for understanding the functional loading of the PCL, including the anterolateral and posteromedial bundles, in the healthy knee joint through systematic review and statistical analysis of the literature.

DATA SOURCES

MEDLINE, EMBASE and CENTRAL.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Databases were searched for articles containing any numerical strain or force data on the healthy PCL and its functional bundles. Studied activities were as follows: passive flexion, flexion under 100N and 134N posterior tibial load, walking, stair ascent and descent, body-weight squatting and forward lunge.

METHOD

Statistical analysis was performed on the reported load data, which was weighted according to the number of knees tested to extract average strain and force trends of the PCL and identify deviations from the norms.

RESULTS

From the 3577 articles retrieved by the initial electronic search, only 66 met all inclusion criteria. The results obtained by aggregating data reported in the eligible studies indicate that the loading patterns of the PCL vary with activity type, knee flexion angle, but importantly also the technique used for assessment. Moreover, different fibres of the PCL exhibit different strain patterns during knee flexion, with higher strain magnitudes reported in the anterolateral bundle. While during passive flexion the posteromedial bundle is either lax or very slightly elongated, it experiences higher strain levels during forward lunge and has a synergetic relationship with the anterolateral bundle. The strain patterns obtained for virtual fibres that connect the origin and insertion of the bundles in a straight line show similar trends to those of the real bundles but with different magnitudes.

CONCLUSION

This review represents what is now the best available understanding of the biomechanics of the PCL, and may help to improve programs for injury prevention, diagnosis methods as well as reconstruction and rehabilitation techniques.

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.

Clinically relevant anatomy and what anatomic reconstruction means

BACKGROUND

Within the past 20 years, knee ligament injuries have been increasingly reported in the literature to be treated with anatomic reconstructions over soft tissue advancements or sling-type procedures to recreate the native anatomy and restore knee function. Historically, early clinician scientists published on the qualitative anatomy of the knee, which provided a foundation for the initial knee biomechanical studies in the nineteenth and twentieth centuries. Similarly, the work of early sports medicine orthopaedic clinician scientists in the late twentieth century formed the basis for the quantitative anatomic and functional robotic biomechanical studies found currently in the sports medicine orthopaedic literature. The development of an anatomic reconstruction first requires an appreciation of the quantitative anatomy and function of each major stabilizing component of the knee.

PURPOSE

This paper provides an overview of the initial qualitative anatomic studies from which the initial knee ligament surgeries were based and expands to recent detailed quantitative studies of the major knee ligaments and the renewed recent focus on anatomic surgical reconstructions.

CONCLUSIONS

Anatomic repairs and reconstructions of the anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament and posterolateral corner attempt to restore knee function by rebuilding or restoring the native anatomy. The basis of anatomic reconstruction techniques is a detailed understanding of quantitative knee anatomy. Additionally, an appreciation of the function of each component is necessary to ensure surgical success.

LEVEL OF EVIDENCE

V.

Biomechanical effect of posterolateral corner sectioning after ACL injury and reconstruction

PURPOSE

Posterolateral corner structures functionally interact with the ACL. The aim of this study was to investigate the capability of an isolated ACL reconstruction control laxity parameters in a knee with combined ACL and PLC and the increase in terms of laxity produced by the resection of the PC in an ACL-deficient knee.

METHOD

An in vitro cadaveric study was performed on seven knees. The joints were analysed in the following conditions: intact, after ACL resection, after popliteus complex resection, after ACL reconstruction and after LCL. Testing laxity parameters were recorded with an intra-operative navigation system and defined as: AP displacement at 30° and 90° of flexion (AP30 and AP90) applying a 130 N load and IE at 30° and 90° of knee flexion with a 5 N load.

RESULTS

Sectioning the ACL significantly increased the AP30 at 30° and 90° of knee flexion (p < 0.05). At 90° of knee flexion, the resection of the LCL determined a significant increase in terms of AP laxity (p < 0.05). At 90° has been found a significant difference for the IE laxity (p < 0.05) after PC resection. Sectioning the LCL produced a significant increase in IE laxity at 30° and 90° of knee flexion (p < 0.05).

CONCLUSION

Isolated ACL reconstruction is able to control the AP laxity with a combined complete lesion of the PLC at 30° of knee flexion, but not at higher angle of knee flexion. Considering the IE rotations, the reconstruction was not sufficient not even to control a partial lesion of the PLC. These findings suggest that additional surgical procedures should be considerate even when facing combined PLC lesion.

The effect of graft strength on knee laxity and graft in-situ forces after posterior cruciate ligament reconstruction

Surgical reconstruction is generally recommended for posterior cruciate ligament (PCL) injuries; however, the use of grafts is still a controversial problem. In this study, a three-dimensional finite element model of the human tibiofemoral joint with articular cartilage layers, menisci, and four main ligaments was constructed to investigate the effects of graft strengths on knee kinematics and in-situ forces of PCL grafts. Nine different graft strengths with stiffness ranging from 0% (PCL rupture) to 200%, in increments of 25%, of an intact PCL's strength were used to simulate the PCL reconstruction. A 100 N posterior tibial drawer load was applied to the knee joint at full extension. Results revealed that the maximum posterior translation of the PCL rupture model (0% stiffness) was 6.77 mm in the medial compartment, which resulted in tibial internal rotation of about 3.01°. After PCL reconstruction with any graft strength, the laxity of the medial tibial compartment was noticeably improved. Tibial translation and rotation were similar to the intact knee after PCL reconstruction with graft strengths ranging from 75% to 125% of an intact PCL. When the graft's strength surpassed 150%, the medial tibia moved forward and external tibial rotation greatly increased. The in-situ forces generated in the PCL grafts ranged from 13.15 N to 75.82 N, depending on the stiffness. In conclusion, the strength of PCL grafts have has a noticeable effect on anterior-posterior translation of the medial tibial compartment and its in-situ force. Similar kinematic response may happen in the models when the PCL graft's strength lies between 75% and 125% of an intact PCL.

Can wedge osteotomy correct depression of the lateral tibial plateau mimicking posterolateral rotatory knee instability?

BACKGROUND

The literature suggests rotatory knee instability (pseudolaxity) can be associated with depressions of the lateral tibial plateau in patients despite an intact arcuate ligament complex. Correcting this bone deformity by an open-wedge osteotomy of the lateral tibia plateau, elevating the depressed bone may restore knee stability.

QUESTIONS/PURPOSES

We therefore asked whether: (1) knee stability is restored after this procedure; (2) Lysholm functional scores improve after this treatment; and (3) the limb alignment changes.

PATIENTS AND METHODS

We retrospectively evaluated 12 patients who underwent a subchondral open-wedge osteotomy of the lateral tibial plateau combined with a knee arthroscopic procedure for the treatment of a knee rotational instability secondary to a lateral compartment bone deficit between 2000 and 2007. Eleven patients with a mean age of 35 years were available for followup at a minimum of 2 years (average, 5.4 years; range, 2-9 years). Preoperatively and at last followup, patients were clinically and radiographically evaluated by the Lysholm score and with comparative knee radiographs. Complications were recorded.

RESULTS

At last followup all patients rated their knees as stable. All osteotomies healed uneventfully. The Lysholm score improved from 62 to 87. Followup radiographs showed no changes in the femorotibial axis as result of the osteotomy.

CONCLUSIONS

Patients with chronic depression of the posterolateral tibial plateau may exhibit symptoms of posterolateral knee instability, a sort of pseudolaxity. In these patients, an open-wedge osteotomy of the lateral tibia plateau, elevating the depressed bone, and tensioning posterolateral structures improves this secondary posterolateral knee instability.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Location and classification of popliteus tendon's origin: cadaveric study

BACKGROUND

In posterolateral insufficiency, many investigators have proposed a lateral tunnel for PT reconstruction. Although they were usually located at the anterior and proximal to the lateral femoral epicondyle, there are still controversies regarding the exact location of PT tunnel. The aim of the present study was to describe our novel findings of femoral attachment of popliteus tendon (PT) and lateral collateral ligament (LCL) and to present an adequate femoral tunnel site, based on the cadaver dissection.

METHODS

Nine embalmed cadavers (18 knees), which were fully extended, were dissected to determine a precise anatomic description of the PT attachment compared to the femoral epicondyle and the LCL. The anatomic variations and attachment of the LCL and PT around the epicondyle were described.

RESULTS

The LCL (mean length: 53 mm, mean width 9 mm) was attached uniformly at the lateral epicondyle of the femur, which was slightly inferior and posterior to the top of the lateral epicondyle, but the PT (mean length: 36 mm, mean width: 8 mm) had the multiform attachments around the epicondyle and our dissection identified three different locations of the PT's attachment; postero-inferior attachment (13 knees), just inferior attachment (2 knees), and double attachment by bifurcate bundles (3 knees). These results demonstrate that the attachment for the PT is mostly located at the postero-inferior site of the epicondyle in the fully extended position and can be seen only when the knee is fully extended because the attachment of the PT shifts anteriorly with regard to the LCL in higher flexion angles.

CONCLUSION

If the original site of the PT's attachment cannot be seen, the recommendation of the femoral tunnel for the PT reconstruction should be located at the postero-inferior site as compared with the LCL attachment in the fully extended position.

Double-bundle reconstruction cannot restore intact knee kinematics in the ACL/LCL-deficient knee

INTRODUCTION

The aim of this study was to evaluate the effect of single-bundle (SB) and anatomic double-bundle (DB) anterior cruciate ligament (ACL) reconstruction on the resulting knee kinematics in a simulated clinical setting with ACL rupture and associated extra-articular damage to the lateral structures. It was hypothesized that anatomic DB ACL reconstruction restores the intact knee kinematics in ACL/LCL-deficient knees, whereas SB ACL reconstruction fails to restore the intact knee kinematics.

MATERIALS AND METHODS

Ten fresh-frozen human cadaver knees were subjected to anterior tibial load of 134 N (simulated KT 1000) and combined rotatory load of 10-Nm valgus and 4-Nm internal tibial torque (simulated pivot shift) using a robotic/UFS testing system. The resulting knee kinematics was determined for intact, ACL/LCL-deficient, SB ACL-reconstructed/LCL-deficient, and DB ACL-reconstructed/LCL-deficient knee. Statistical analysis was performed using a two-way ANOVA test with the level of significance set at P < 0.05.

RESULTS

Under a simulated KT 1000 test, anterior tibial translation (ATT) following SB ACL reconstruction was statistically significant at 0 degrees , 30 degrees and 60 degrees of knee flexion when compared to the intact knee. ATT after DB ACL reconstruction showed no statistically significant difference from the intact knee; however, there was a significant difference in SB reconstruction at 0 degrees and 30 degrees of knee flexion. Under a simulated pivot shift test, both SB and DB ACL reconstruction failed to restore the intact knee kinematics.

CONCLUSION

The results of the study did not support our initial hypothesis. Though DB reconstructions were significantly superior to SB reconstruction under simulated KT 1000 test, SB as well as DB reconstruction failed to restore the intact kinematics under simulated pivot shift loads. The clinical relevance of this study is that caution and precise preoperative diagnostics are needed to avoid failure of intra-articular ACL reconstruction if the extra-articular stabilizers are torn.

Long-term results of isolated anterolateral bundle reconstructions of the posterior cruciate ligament: a 6- to 12-year follow-up study

BACKGROUND

Little is known about the parameters that influence the long-term results of isolated arthroscopically assisted reconstructions of the anterolateral bundle of the posterior cruciate ligament (PCL).

HYPOTHESIS

Chondrosis, time interval from injury to surgery, and graft choice significantly influence the long-term results of single-bundle PCL reconstructions.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Between 1995 and 2001, 22 male and 3 female patients with a mean age of 30.8 years (range, 17-52) underwent an anterolateral bundle reconstruction of the PCL for functional instability and pain. Nine were treated with a bone-patellar tendon-bone autograft (BPTB), 15 with a semitendinosus gracilis (STG) autograft, and 1 with an Achilles tendon allograft. Twenty-two patients were clinically and radiographically reviewed at a mean follow-up of 9.1 years (range, 6.5-12.6). Three patients were interviewed by telephone. Thirteen patients had chondrosis at time of surgery. The mean time from injury to surgery was 1.5 years.

RESULTS

The mean final International Knee Documentation Committee (IKDC), Lysholm, and functional visual analog scale (VAS) scores (65, 75, and 8, respectively) were fair to good and were significantly better than preoperatively (38, 50, and 4, respectively) (P < .001). The final Tegner (5.7) score was significantly lower than the preinjury score (7.2) (P < .001). The mean anteroposterior laxity measured by KT-1000 arthrometer and Telos stress radiographs was significantly increased on the operated side (mean side-to-side difference of 2.1 mm and 4.7 mm, respectively). The functional scores were not significantly different between the BPTB and STG reconstructions. Patients without chondrosis at time of surgery and patients operated within the first year from injury had significantly better functional results at final follow-up (P < .05).

CONCLUSION

Arthroscopically assisted reconstructions of the anterolateral bundle of the PCL in patients with symptomatic isolated grade II to IV PCL-deficient knees lead to significantly improved functional results at long term if there is no cartilage damage at time of surgery. Nonoperative treatment should not be extended more than 1 year from injury. Graft choice did not significantly influence the functional outcome at long term.

The influence of tibial positioning on the diagnostic accuracy of combined posterior cruciate ligament and posterolateral rotatory instability of the knee

Background

To determine if tibial positioning affects the external rotation of the tibia in a dial test for posterolateral rotatory instability combined with posterior cruciate ligament (PCL) injuries.

Methods

Between April 2007 and October 2007, 16 patients with a PCL tear and posterolateral rotatory instability were diagnosed using a dial test. The thigh-foot angle was measured at both 30° and 90° of knee flexion with an external rotation stress applied to the tibia in 2 different positions (reduction and posterior subluxation). The measurements were performed twice by 2 orthopedic surgeons.

Results

In posterior subluxation, the mean side-to-side difference in the thigh-foot angle was 11.56 ± 3.01° at 30° of knee flexion and 11.88 ± 4.03° at 90° of knee flexion. In the sequential dial test performed with the tibia reduced, the mean side-to-side difference was 15.94 ± 4.17° (p < 0.05) at 30° of knee flexion and 16.88 ± 4.42° (p = 0.001) at 90° of knee flexion. The mean tibial external rotation was 5.31 ± 2.86° and 6.87 ± 3.59° higher in the reduced position than in the posterior subluxation at both 30° and 90° of knee flexion.

Conclusions

In the dial test, reducing the tibia with an anterior force increases the ability of an examiner to detect posterolateral rotary instability of the knee combined with PCL injuries.

Double-bundle PCL and posterolateral corner reconstruction components are codominant

A more complete biomechanical understanding of a combined posterior cruciate ligament and posterolateral corner knee reconstruction may help surgeons develop uniformly accepted clinical surgical techniques that restore normal anatomy and protect the knee from premature arthritic changes. We identified the in situ force patterns of the individual components of a combined double-bundle posterior cruciate ligament and posterolateral corner knee reconstruction. We tested 10 human cadaveric knees using a robotic testing system by sequentially cutting and reconstructing the posterior cruciate ligament and posterolateral corner. The knees were subjected to a 134-N posterior tibial load and 5-Nm external tibial torque. The posterior cruciate ligament was reconstructed with a double-bundle technique. The posterolateral corner reconstruction included reattaching the popliteus tendon to its femoral origin and reconstructing the popliteofibular ligament. The in situ forces in the anterolateral bundle were greater in the posterolateral corner-deficient state than in the posterolateral corner-reconstructed state at 30 degrees under the posterior tibial load and at 90 degrees under the external tibial torque. We observed no differences in the in situ forces between the anterolateral and posteromedial bundles under any loading condition. The popliteus tendon and popliteofibular ligament had similar in situ forces at all flexion angles. The data suggest the two bundles protect each other by functioning in a load-sharing, codominant fashion, with no component dominating at any flexion angle. We believe the findings support reconstructing both posterior cruciate ligament bundles and both posterolateral corner components.

The role of the posterior oblique ligament in controlling posterior tibial translation in the posterior cruciate ligament-deficient knee

BACKGROUND

Posterior cruciate ligament injuries are often associated with injuries to other structures. The role of the posteromedial structures of the knee in these injuries has received little attention.

HYPOTHESIS

The posterior oblique ligament is an important restraint to posterior tibial translation in the posterior cruciate ligament-deficient knee.

STUDY DESIGN

Controlled laboratory study.

METHODS

Kinematic studies were performed on 10 cadaveric knees to test 3 external loading conditions at 0 degrees , 30 degrees , 60 degrees , and 90 degrees of flexion (134 N posterior tibial load, 10 N x m valgus rotation, and 5 N x m internal rotation). Resulting posterior tibial translation was determined by using a robotic/universal force-moment sensor testing system for (1) intact, (2) posterior cruciate ligament-deficient, (3) posterior cruciate ligament/superficial medial collateral ligament-deficient, (4) posterior cruciate ligament/superficial medial collateral ligament/deep medial collateral ligament/posterior oblique ligament-deficient, and (5) posterior cruciate ligament/superficial medial collateral ligament/deep medial collateral ligament/posterior oblique ligament/posteromedial capsule-deficient knee.

RESULTS

When both the superficial medial collateral ligament and deep medial collateral ligament were cut in the posterior cruciate ligament-deficient knee, posterior tibial translation did not increase significantly at any flexion grade under all external loading conditions (P > .05). Additional cutting of the posterior oblique ligament increased posterior tibial translation significantly at 0 degrees , 30 degrees , 60 degrees , and 90 degrees of flexion under posterior tibial load and at all flexion angles tested under valgus or internal tibial load (P < .05). Additional cutting of the posteromedial capsule increased posterior tibial translation only at 0 degrees and 30 degrees in response to a valgus and internal tibial load (P < .05).

CONCLUSION

The posterior oblique ligament and posteromedial capsule have a significant role in the prevention of additional posterior tibial translation in the knee with posterior cruciate ligament injury.

CLINICAL RELEVANCE

The posterior oblique ligament should be addressed in the patient with combined injuries to the posterior cruciate ligament and the posteromedial structures.

Anterolateral rotational knee instability: role of posterolateral structures. Winner of the AGA-DonJoy Award 2006

INTRODUCTION

The aim of this study was to determine the anterolateral rotational instability (ALRI) of the human knee after rupture of the anterior cruciate ligament (ACL) and after additional injury of the different components of the posterolateral structures (PLS). It was hypothesized that a transsection of the ACL will significantly increase the ALRI of the knee and furthermore that sectioning the PLS [lateral collateral ligament (LCL), popliteus complex (PC)] will additionally significantly increase the ALRI.

MATERIALS AND METHODS

Five human cadaveric knees were used for dissection to study the appearance and behaviour of the structures of the posterolateral corner under anterior tibial load. Ten fresh-frozen human cadaver knees were subjected to anterior tibial load of 134 N and combined rotatory load of 10 Nm valgus and 4 Nm internal tibial torque using a robotic/universal force moment sensor (UFS) testing system and the resulting knee kinematics were determined for intact, ACL-, LCL- and PC-deficient (popliteus tendon and popliteofibular ligament) knee. Statistical analyses were performed using a two-way ANOVA test with the level of significance set at P < 0.05.

RESULTS

Sectioning the ACL significantly increased the anterior tibial translation (ATT) and internal tibial rotation under a combined rotatory load at 0 and 30 degrees flexion (P < 0.05). Sectioning the LCL further increased the ALRI significantly at 0 degrees , 30 degrees and 60 degrees of flexion (P < 0.05). Subsequent cutting of the PC increased the ATT under anterior tibial load (P < 0.05), but did not increase the ALRI (P > 0.05).

CONCLUSION

The results of the current study confirm the concept that the rupture of the ACL is associated with ALRI. Current reconstruction techniques should focus on restoring the anterolateral rotational knee instability to the intact knee. Additional injury to the LCL further increases the anterior rotational instability significantly, while the PC is less important. Cautions should be taken when examining a patient with ACL rupture to diagnose injuries to the primary restraints of tibial rotation such as the LCL. If an additional extraarticular stabilisation technique is needed for severe ALRI, the technique should be able to restore the function of the LCL and not the PC.

Function of posterior cruciate ligament bundles during in vivo knee flexion

BACKGROUND

The biomechanical functions of the anterolateral and posteromedial bundles of the posterior cruciate ligament over the range of flexion of the knee joint remain unclear.

HYPOTHESIS

The posterior cruciate ligament bundles have minimal length at low flexion angles and maximal length at high flexion angles.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Seven knees from normal, healthy subjects were scanned with magnetic resonance, and 3-dimensional models of the femur, tibia, and posterior cruciate ligament attachment sites were created. The lines connecting the centroids of the corresponding bundle attachment sites on the femur and tibia represented the anterolateral and posteromedial bundles of the posterior cruciate ligament. Each knee was imaged during weightbearing flexion (from 0 degrees to maximal flexion) using a dual-orthogonal fluoroscopic system. The length, elevation, deviation, and twist of the posterior cruciate ligament bundles were measured as a function of flexion.

RESULTS

The lengths of the anterolateral and posteromedial bundles increased with flexion from 0 degrees to 120 degrees and decreased beyond 120 degrees of flexion. The posteromedial bundle had a lower elevation angle than the anterolateral bundle beyond 60 degrees of flexion. The anterolateral bundle had a larger deviation angle than the posteromedial bundle beyond 75 degrees of flexion. The femoral attachment of the posterior cruciate ligament twisted externally with increasing flexion and reached a maximum of 86.4 degrees +/- 14.7 degrees at 135 degrees of flexion (P < .05).

CONCLUSION

These data suggest that there is no reciprocal function of the bundles with flexion, which is contrary to previous findings. The orientation of the anterolateral and posteromedial bundles suggests that at high flexion, the anterolateral bundle might play an important role in constraining the mediolateral translation, whereas the posteromedial bundle might play an important role in constraining the anteroposterior translation of the tibia.

CLINICAL RELEVANCE

These data provide a better understanding of the biomechanical function of the posterior cruciate ligament bundles and may help to improve the design of the 2-bundle reconstruction techniques of the ruptured posterior cruciate ligament.

Effect of tibial positioning on the diagnosis of posterolateral rotatory instability in the posterior cruciate ligament-deficient knee

OBJECTIVE

To determine whether positioning of the tibia affects the degree of tibial external rotation seen during a dial test in the posterior cruciate ligament (PCL)-posterolateral corner (PLC)-deficient knee.

DESIGN

Laboratory investigation.

SETTING

Biomechanics laboratory.

HYPOTHESIS

An anterior force applied to the tibia in the combined PCL-PLC-deficient knee will yield increased tibial external rotation during a dial test.

METHODS

The degree of tibial external rotation was measured with 5 Nm of external rotation torque applied to the tibia at both 30 degrees and 90 degrees of knee flexion. Before the torque was applied, an anterior force, a posterior force, or neutral (normal, reduced control) force was applied to the tibia. External rotation measurements were repeated after sequential sectioning of the PCL, the posterolateral structures and the fibular collateral ligament (FCL).

RESULTS

Baseline testing of the intact specimens demonstrated a mean external rotation of 18.6 degrees with the knee flexed to 30 degrees (range 16.1-21.0 degrees ), and a mean external rotation of 17.3 degrees with the knee flexed to 90 degrees (range 13.8-20.0 degrees ). Sequential sectioning of the PCL, popliteus and popliteofibular ligament, and the FCL led to a significant increase in tibial external rotation compared with the intact knee for all testing scenarios. After sectioning of the popliteus and popliteofibular ligament, the application of an anterior force during testing led to a mean tibial external rotation that was 5 degrees greater than during testing in the neutral position and 7.5 degrees greater than during testing with a posterior force. In the PCL, popliteus/popliteofibular ligament and FCL-deficient knee, external rotation was 9 degrees and 12 degrees greater with the application of an anterior force during testing compared with neutral positioning and the application of a posterior force, respectively.

CONCLUSION

An anterior force applied to the tibia during the dial test in a combined PCL-PLC-injured knee increased the overall amount of observed tibial external rotation during the dial test. The anterior force reduced the posterior tibial subluxation associated with PCL injury, which is analogous to what is observed when the dial test is performed with the patient in the prone position. Reducing the tibia with either an anterior force when the patient is supine or performing the dial test with the patient in the prone position increases the ability of an examiner to detect a concomitant PLC injury in the setting of a PCL-deficient knee.

MR imaging of the posterolateral corner of the knee

The posterolateral corner (PLC) is a complex functional unit, consisting of several structures, which is responsible for posterolateral stabilization. The PLC is not consistently defined in the literature. However, most descriptions include the popliteal tendon (PT), the lateral collateral ligament (LCL), the popliteofibular ligament (PFL) and the posterolateral capsule, which is reinforced by the arcuate ligament (AL) and the fabellofibular ligament (FFL). Knowledge of PLC anatomy, including its variations, and understanding of the biomechanics is important for correct diagnosis of PLC injuries. An overlooked PLC injury can result in chronic instability, chronic pain, and, eventually, in secondary osteoarthritis. Damage to the PLC also has an adverse effect on the outcome of cruciate ligament repair. Isolated lesions of the PLC are rare. PLC lesions are typically associated with injuries of the cruciate ligaments, the menisci, bone and soft tissue. In the acute phase, clinical findings can be difficult to interpret due to pain and swelling. Magnetic resonance (MR) imaging potentially demonstrates the entire spectrum of PLC injuries and associated lesions of the knee, including those that may be overlooked during clinical examination or arthroscopy.

Popliteus bypass and popliteofibular ligament reconstructions reduce posterior tibial translations and forces in a posterior cruciate ligament graft

PURPOSE

To measure the abilities of popliteus tendon (POP) and popliteofibular ligament (PFL) graft reconstructions to limit posterior tibial translations and alter forces in a PCL graft reconstruction after posterior cruciate ligament (PCL) and lateral collateral ligament (LCL) reconstruction.

METHODS

Fifteen fresh frozen cadaveric knees underwent anterior-posterior (AP) laxity testing with 200 N of applied anterior and posterior tibial force. Forces in the native PCL were recorded during passive extension from 120 degrees to 0 degrees with an applied 100-N posterior tibial force. The popliteus tendon was released at its femoral origin, the PFL and LCL were cut, and the PCL was sectioned, creating a combined grade 3 PCL and posterolateral corner injury. The PCL was reconstructed with a single-bundle inlay graft tensioned to restore intact knee laxity to within 1 mm at 90 degrees , and the LCL was reconstructed with an anatomically placed graft. Testing was repeated with POP and PFL posterolateral reconstructions in addition to the PCL and LCL reconstructions.

RESULTS

PCL + LCL grafts alone matched intact knee laxities between 20 degrees and 90 degrees of flexion; mean laxity was 3.5 mm greater than intact at 0 degrees and 2.2 mm greater at 10 degrees. The addition of a POP reconstruction to PCL + LCL reconstructions significantly reduced AP laxities from -2.4 mm (0 degrees flexion) to -1.4 mm (90 degrees flexion). Mean laxities with POP and PFL grafts were not significantly different from the intact knee or from each other. Mean PCL graft forces with the PCL + LCL reconstructions alone were not significantly different than those with the native PCL. Mean PCL graft forces with POP and PFL reconstructions were not significantly different from each other; both means were significantly less than those for the PCL + LCL reconstructions alone at flexion angles greater than 55 degrees.

CONCLUSIONS

After PCL and LCL reconstruction, the popliteus bypass and popliteofibular ligament reconstructions not only eliminated excessive posterior laxity and returned the knee to a normal laxity profile but also resulted in substantial decreases in PCL graft forces.

CLINICAL RELEVANCE

These results provide further rationale for reconstructing torn posterolateral structures with a grade 3 posterolateral injury in combination with a PCL reconstruction.

Distraction forces on repaired bucket-handle lesions in the medial meniscus

BACKGROUND

Numerous studies have investigated the biomechanical properties of meniscal repair techniques. One of the most commonly discussed parameters is the failure load in the axis of insertion, although little is known about the distraction forces actually occurring at repaired bucket-handle lesions.

HYPOTHESIS

There are clinically relevant distraction forces on repaired meniscus bucket-handle lesions.

STUDY DESIGN

Controlled laboratory study.

METHODS

Meniscus bucket-handle lesions were created and repaired in human cadaveric knees with a vertical suture made from a braided steel wire. A small-sized load sensor was connected to the wire at the periphery of the meniscus. The distraction forces acting on the lesion were measured at different knee joint angles (0 degrees -120 degrees of flexion) with internal and external rotation and with and without weight loading. Forces in excess of 10 N were considered to have clinical relevance.

RESULTS

Mean forces on the meniscus repair ranged from 1.64 to 4.72 N. Irrespective of the modalities (ie, different flexion angles, weight load, direction of rotation), it was found that the forces were well below the cutoff value of 10 N (P < .01). Increasing flexion angles generally did not cause an increase in distraction forces.

CONCLUSION

The data suggest that distraction forces are not the primary factor in the mechanical stability of meniscal repair. It must therefore be assumed that other factors such as shear forces are of greater significance.

CLINICAL RELEVANCE

The results may help to validate the biomechanical properties of different meniscal repair techniques.

Double-bundle transtibial posterior cruciate ligament reconstruction with a tendon-patellar bone-semitendinosus tendon autograft: clinical results with a minimum of 2 years' follow-up

PURPOSE

The purpose of this study was to evaluate the clinical and subjective outcomes after arthroscopic-assisted double-bundle posterior cruciate ligament (PCL) reconstruction.

METHODS

A series of 15 patients with grade III isolated chronic PCL tears underwent double-bundle PCL reconstruction. Of these patients, 8 (53%) had simultaneous fractures. The mean time from accident to surgery was 10.8 months (range, 8 to 15 months). The mean age at the time of surgery was 28.2 years (range, 17 to 43 years). All of the patients reported knee insecurity during activities of daily living or light sporting activities, with associated anterior knee pain in 5 patients. Preoperatively, posterolateral or posteromedial corner injuries were ruled out through accurate clinical examination. The knees were assessed before surgery and at a mean follow-up of 3.2 years (range, 2 to 5 years) with a physical examination, 4 different rating scales, and stress radiographs obtained with a Telos device (Telos, Marburg, Germany).

RESULTS

Postoperative physical examination revealed a reduction of the posterior drawer and tibial step-off in all cases, although the posterior laxity was not completely normalized. Nevertheless, the patients were subjectively better after surgery. The subjective International Knee Documentation Committee score was significantly ameliorated. With regard to the objective International Knee Documentation Committee score, 6 knees (40%) were graded as abnormal because of posterior displacement of 6 mm or greater on follow-up stress radiographs with the Telos device. On the Lysholm knee scoring scale, the score was excellent in 13% of patients and good in 87%. The mean score on the Hospital for Special Surgery knee ligament rating scale was 85.8. The Tegner activity score showed an amelioration after surgery, but no patient resumed his or her preinjury level of activities. The postoperative stress radiographs revealed an improvement in posterior instability of 50% or more in all but 3 knees (20%).

CONCLUSIONS

Our technique of double-bundle PCL reconstruction produced a significant reduction in knee symptoms and allowed the patients to return to moderate or strenuous activity, although the posterior tibial translation was not completely normalized and our results appear to be no better than the results of single-bundle PCL reconstruction.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Combined reconstruction of chronic posterior cruciate ligament and posterolateral corner deficiency

We report a retrospective analysis of the results of combined arthroscopically-assisted posterior cruciate ligament reconstruction and open reconstruction of the posterolateral corner in 19 patients with chronic (three or more months) symptomatic instability and pain in the knee.

All the operations were performed between 1996 and 2003 and all the patients were assessed pre- and post-operatively by physical examination and by applying three different ligament rating scores. All also had weight-bearing radiographs, MR scans and an examination under anaesthesia and arthroscopy pre-operatively. The posterior cruciate ligament reconstruction was performed using an arthroscopically-assisted single anterolateral bundle technique and the posterolateral corner structures were reconstructed using an open Larson type of tenodesis.

The mean follow up was 66.8 months (24 to 110). Pre-operatively, all the patients had a grade III posterior sag according to Clancy and demonstrated more than 20° of external rotation compared with the opposite normal knee on the Dial test. Post-operatively, seven patients (37%) had no residual posterior sag, 11 (58%) had a grade I posterior sag and one (5%) had a grade II posterior sag. In five patients (26%) there was persistent minimal posterolateral laxity. The Lysholm score improved from a mean of 41.2 (28 to 53) to 76.5 (57 to 100) (p = 0.0001) and the Tegner score from a mean of 2.6 (1 to 4) to 6.4 (4 to 9) (p = 0.0001).

We conclude that while a combined reconstruction of chronic posterior cruciate ligament and posterolateral corner instability improves the function of the knee, it does not restore complete stability.

Joint kinematics and in situ forces after single bundle PCL reconstruction: a graft placed at the center of the femoral attachment does not restore normal posterior laxity

INTRODUCTION

Femoral tunnel placement has a great influence on the clinical outcome after PCL reconstruction.

MATERIALS AND METHODS

Using a robotic/universal force moment sensor (UFS) testing system, we examined joint kinematics and in situ forces of human knees following soft-tissue single bundle PCL reconstruction fixed at the center of the femoral attachment.

RESULTS

Posterior tibial translation significantly increased at all flexion angles after transsection of the posterior cruciate ligament (p<0.05). PCL reconstruction resulted in significantly less posterior tibial translation at all flexion angles when compared to the PCL deficient knee (p<0.05). The differences in the in situ force between the intact ligament and the reconstructed graft were statistical significant (p<0.05).

CONCLUSION

Single bundle PCL reconstruction with a soft-tissue graft fixed at the center of the femoral attachment is able to reduce the posterior tibial translation significantly. However, it cannot restore kinematics of the intact knee and in situ forces of the intact PCL.

Importance of femoral tunnel placement in double-bundle posterior cruciate ligament reconstruction: biomechanical analysis using a robotic/universal force-moment sensor testing system

BACKGROUND

Previous studies have identified the femoral attachment of the posterior cruciate ligament fibers as one of the primary determinants of fiber tension behavior. In addition, a double-bundle posterior cruciate ligament reconstruction has been shown to restore the intact knee kinematics more closely than does a single-bundle reconstruction.

HYPOTHESIS

An anterior tunnel position in double-bundle posterior cruciate ligament reconstruction restores the biomechanics of the normal knee more closely than does a posterior tunnel position.

STUDY DESIGN

Controlled laboratory study.

METHODS

Kinematics and in situ forces of human knees after double-bundle posterior cruciate ligament reconstruction with 2 different femoral tunnel positions (anterior vs posterior) were evaluated using a robotic/universal force-moment sensor testing system. Within the same specimen, the resulting knee kinematics and in situ forces were compared. For statistical analysis, 2-way analysis of variance repeated measures were performed.

RESULTS

The femoral tunnel position of the double-bundle hamstring graft had significant effect on the resulting posterior tibial displacement and in situ forces of the hamstring grafts. The anterior femoral tunnel position provided significantly less posterior tibial translation than did the posterior tunnel position. There was a tendency toward higher in situ forces of grafts fixed in the anterior tunnel when compared to the posterior position, but this difference was statistically not significant.

CONCLUSION

An anterior position of the bone tunnels in double-bundle posterior cruciate ligament reconstruction restores the normal knee kinematics more closely than does a posterior position of the tunnels.

CLINICAL RELEVANCE

In double-bundle posterior cruciate ligament reconstruction, posterior placement of the tunnel should be avoided.

Diagnostik und Therapie von Verletzungen des hinteren Kreuzbandes

Over the last few years, the posterior cruciate ligament (PCL) has taken over from the anterior cruciate ligament (ACL) as the new challenge in knee diagnosis and treatment. PCL injuries are much more frequent than previously thought. Despite increasing experience, we are often still confronted with an inappropriate and delayed diagnosis of this injury and its concomitant lesions. Additionally, the outcome of surgical treatment has not yet reached an acceptable rate of satisfaction. Therefore, the goal of this concept review is to give a comprehensive insight into injury mechanisms, diagnostics and treatment regimes based on our experience and data from the international literature. Furthermore, diagnostic problems with respect to clinical examination and imaging techniques are discussed. We also present a differential concept for the perioperative and conservative management of PCL deficient knees in order to adequately address concomitant injuries such as posterolateral rotatory instability and combined ACL injuries, with the aim of further improving results.

The insertion geometry of the posterolateral corner of the knee

We have quantitatively documented the insertion geometry of the main stabilising structures of the posterolateral corner of the knee in 34 human cadavers. The lateral collateral ligament inserted posterior (4.6 mm, sd 2) and proximal (1.3 mm, sd 3.6) to the lateral epicondyle of the femur and posterior (8.1 mm, sd 3.2) to the anterior point of the head of the fibula. On the femur, the popliteus tendon inserted distally (11 mm, sd 0.8) and either anterior or posterior (mean 0.84 mm anterior, sd 4) to the lateral collateral ligament. The popliteofibular ligament inserted distal (1.3 mm, sd 1.2) and anterior (0.5 mm, sd 2.0) to the tip of the styloid process of the fibula. The ligaments had a consistent pattern of insertion and, despite the variation between specimens, the standard deviations were less than the typical size of drill hole used in reconstruction of the posterolateral corner. The data provided in this study can be used in the anatomical repair and reconstruction of this region of the knee.

Anatomic posterolateral corner knee reconstruction

Injuries to the lateral collateral ligament and posterolateral corner of the knee, particularly when combined with anterior cruciate or posterior cruciate ligament injuries, can result in profound symptomatic knee instability. Although many surgical improvements have been made in reconstruction of anterior and posterior cruciate ligament injuries, reconstruction of the posterolateral corner has had less predictable results, with residual pathologic laxity especially in the chronic situation. This has stimulated many surgeons to recommend acute repair of posterolateral knee injuries. This article describes a more anatomic reconstruction of the posterolateral corner for chronic instability, recreating the lateral collateral ligament and popliteofibular ligament using either autogenous or allograft soft tissue and an interference screw technique. In a small clinical series, this has proven to restore varus rotation and external rotation patholaxities with a high degree of predictability.

Arthroscopic diagnosis of the snapping popliteus tendon

The syndrome of the snapping popliteus tendon is a rare cause of lateral knee pain and may be difficult to diagnose, leading to patients undergoing inappropriate therapy or surgical intervention. In this report, we describe the arthroscopic findings of the snapping popliteus tendon. Two men and 1 woman presented complaining of pain and a snapping sensation at the lateral aspect of the knee. No clear traumatic history was reported by any of the patients. Two patients had previously undergone partial lateral meniscectomy without relief of their symptoms. While the only consistently positive clinical sign was the Cabot sign, the arthroscopic findings confirmed the diagnosis in all cases. We observed in all cases inflammation around the tendon and visualized the portion of popliteus tendon near its insertion that is usually hidden by the femoral condyle. Further, flexion and extension with the limb in the tailor position revealed the snapping popliteus tendon. Successful treatment was achieved by securing the popliteus tendon to its sulcus on the lateral femoral condyle. Arthroscopic examination helps the surgeon to identify the snapping popliteus tendon to better treat this simple, yet oftentimes perplexing, condition.

Biomechanical analysis of a combined double-bundle posterior cruciate ligament and posterolateral corner reconstruction

BACKGROUND

Failure to address both components of a combined posterior cruciate ligament and posterolateral corner injury has been implicated as a reason for abnormal biomechanics and inferior clinical results.

HYPOTHESIS

Combined double-bundle posterior cruciate ligament and posterolateral corner reconstruction restores the kinematics and in situ forces of the intact knee ligaments.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten fresh-frozen human cadaveric knees were tested using a robotic testing system through sequential cutting and reconstructing of the posterior cruciate ligament and posterolateral corner. The knees were subjected to a 134-N posterior tibial load and a 5-N.m external tibial torque at multiple flexion angles. The double-bundle posterior cruciate ligament reconstruction was performed using Achilles and semitendinosus tendons. The posterolateral corner reconstruction consisted of reattaching the popliteus tendon to its femoral origin and reconstructing the popliteofibular ligament with a gracilis tendon.

RESULTS

Under the posterior load, the combined reconstruction reduced posterior translation to within 1.2 +/- 1.5 mm of the intact knee. The in situ forces in the posterior cruciate ligament grafts were significantly less than those in the native posterior cruciate ligament at all angles except full extension. Conversely, the forces in the posterolateral corner grafts were significantly higher than those in the native structures at all angles. Under the external torque with the combined reconstruction, external rotation as well as in situ forces in the posterior cruciate ligament and posterolateral corner grafts were not different from the intact knee.

CONCLUSIONS

A combined posterior cruciate ligament and posterolateral corner reconstruction can restore intact knee kinematics at time zero. In situ forces in the intact posterior cruciate ligament and posterolateral corner were not reproduced by the reconstruction; however, the posterolateral corner reconstruction reduced the loads experienced by the posterior cruciate ligament grafts.

CLINICAL RELEVANCE

By addressing both structures of this combined injury, this technique restores native kinematics under the applied loads at fixed flexion angles and demonstrates load sharing among the grafts creating a potentially protective effect against early failure of the posterior cruciate ligament grafts but with increased force in the posterolateral corner construct.

Soft-tissue graft fixation in posterior cruciate ligament reconstruction: evaluation of the effect of tibial insertion site on joint kinematics and in situ forces using a robotic/UFS testing system

INTRODUCTION

Surgical reconstruction of the posterior cruciate ligament (PCL) is recommended in acute injuries that result in severe tibial subluxation and instability. The surgical outcome level may be affected by the tibial fixation site. In response to a 110-N posterior tibial load, kinematics and in situ forces of anatomical soft-tissue graft fixation in single-bundle PCL reconstruction using an interference screw fixation are significantly closer to those in the intact knee than with extracortical fixation with two staples.

MATERIALS AND METHODS

Using a robotic/universal force moment sensor (UFS) testing system, we examined joint kinematics and in situ forces of porcine knees following single-bundle PCL reconstruction fixed at two different tibial fixation sites: anatomical interference screw and extracortical fixation.

RESULTS

The site of the tibial graft fixation had significant effect on the resulting posterior displacement and in situ forces of the graft. Both PCL reconstruction techniques reduced the posterior tibial translation significantly. Proximal fixation techniques provided significantly less posterior tibial translation than extracortical fixation. Single-bundle PCL reconstruction with an interference screw showed higher in situ forces of the graft than the extracortical fixation.

CONCLUSIONS

The kinematics and in situ forces of a single-bundle PCL reconstruction using an interference screw fixation technique are superior to the primary stability of an extracortical fixation with staples.

Anatomical study of the popliteofibular ligament and surrounding structures

Although the popliteofibular ligament (PFL) is an important posterolateral structure of the knee joint, the anatomical characteristics of this ligament remain unclear. We morphologically classified and measured the PFLs from 78 cadaver knees. The PFL was observed in all knees, and it was classified into type I (with one layer) or type II (with two layers). The mean lengths of the anterior and posterior margins were 12.7 and 6.8 mm, respectively; and the mean width and thickness were 10.4 mm and 2.1 mm, respectively. The PFL inclined forward at a mean sagittal angle of 20.7 degrees, which is similar to the 21.2 degrees of the posterior cruciate ligament, indicating that the PFL contributed to posterolateral rotatory stability.

Biomechanical comparison of tibial inlay versus transtibial techniques for posterior cruciate ligament reconstruction: analysis of knee kinematics and graft in situ forces

BACKGROUND

The tibial inlay technique for posterior cruciate ligament reconstruction has been proposed to provide a more anatomic reconstruction because it eliminates the sharp turn in the graft as it exits the proximal margin of the tibial tunnel in the transtibial technique.

HYPOTHESIS

Reconstruction of the posterior cruciate ligament using the tibial inlay technique would more closely restore intact knee kinematics and in situ forces in the posterior cruciate ligament than would reconstruction using the transtibial technique.

METHODS

Ten human cadaveric knees were tested in a controlled laboratory study. A robotic/universal force-moment sensor testing system was used to apply a 134-N posterior tibial load at 5 knee flexion angles: 0 masculine, 30 masculine, 60 masculine, 90 masculine, and 120 masculine. Four knee conditions were tested: intact, posterior cruciate ligament-deficient, and the single-bundle tibial inlay reconstruction and transtibial posterior cruciate ligament reconstruction.

RESULTS

Both reconstruction techniques restored posterior tibial translations to 1.7 to 2.1 mm of the intact knee, with no statistical differences between the techniques. In response to the posterior tibial load, in situ forces in both grafts were between 7 and 39 N less than those in the intact posterior cruciate ligament, with no significant differences between the grafts.

CLINICAL RELEVANCE

The study suggests that either technique may be performed with similar biomechanical results at initial fixation under these loading conditions.

[Posterior knee instability]

Due to improved diagnostic methods, posterior knee instabilities are detected more often. Up to now, however, the natural history of isolated ruptures of the posterior cruciate ligament is not known exactly. After conservative treatment, the first degenerative changes occur after about 10-15 years, mainly in the femoropatellar joint and the medial compartment. In complex posterior instabilities with lesions of the secondary stabilizers, the posterolateral structures, the lateral collateral ligament, and the leg alignment play an important role. Conservative or operative treatment of posterior knee instabilities depends on the extent of the lesion, the violated structures, and the impairment of the patient. For replacement of the posterior cruciate ligament, grafts from the patella ligament, the quadriceps tendon, and the hamstrings are used most frequently. In simultaneous lesions of the posterolateral corner of the knee joint, additional ligament-stabilizing methods are necessary.

Surgical treatment of posterior cruciate ligament and posterolateral corner injuries. An anatomical, biomechanical and clinical review

The posterior cruciate ligament has become an increasingly popular subject of orthopaedic research and debate. While biomechanical studies have shown its role as major stabilizer of the knee, clinical studies have shown its increasing incidence. Furthermore, injuries to posterolateral structures are frequently encountered and failure to recognize and treat this associated injury may lead to stretching or failure of the cruciate reconstruction. Surgical reconstruction of isolated/combined injuries is now more effective than before and different technical options are now available for the surgeon, even if much work remains ahead of us as we try to understand how to successfully treat these complex knee injuries.

On the coupling between anterior and posterior cruciate ligaments, and knee joint response under anterior femoral drawer in flexion: a finite element study

OBJECTIVE

To investigate the extent of coupling between the anterior and posterior cruciate ligaments as well as the role of the posterior cruciate ligament in the knee joint response under anterior femoral force at different flexion angles.

DESIGN

A developed finite element model of the tibiofemoral joint is used to perform non-linear elastostatic analyses.

BACKGROUND

The structural properties of the posterior cruciate ligament subsequent to an injury (either left untreated or replaced by a graft) would likely change, an event that alters the function of not only the ligament itself but also the other intact cruciate ligament and the entire joint.

METHODS

The model consists of two bony structures and their articular cartilage layers, menisci and four principal ligaments. Under 100 N anterior femoral load at different flexion angles from 0 degrees to 90 degrees, kinematics, forces in ligaments and contact forces in the fully unconstrained joint were computed in intact cases and following alterations in joint ligaments.

RESULTS

Collateral ligaments were the primary structures to resist the force at full extension under 100 N anterior femoral load with a moderate contribution from the posterior cruciate ligament. With joint flexion up to 90 degrees, however, force in the posterior cruciate ligament substantially increased whereas that in collateral ligaments diminished.

CONCLUSIONS

A remarkable coupling was found between the posterior cruciate ligament and the anterior cruciate ligament in flexion; a structural alteration in one of them significantly influenced the mechanical role of both ligaments and not just the one affected. A tauter or stiffer ligament increased the force in both ligaments while an excessive laxity or rupture in one diminished forces in both.

RELEVANCE

Alterations in ligament stiffness or initial tautness during reconstruction surgery or following injuries markedly influence the normal role of both cruciate ligaments. Consideration of cruciate ligaments coupled together rather than in isolation should be the rule in the management of ligament injuries towards a successful long-term outcome.

Stress radiography for quantifying posterior cruciate ligament deficiency

PURPOSE

The objective of this study was to evaluate the efficacy of different stress radiography techniques in quantifying a posterior cruciate ligament (PCL) lesion.

TYPE OF STUDY

Prospective serial study.

METHODS

Sixty patients with subacute or chronic PCL injuries, confirmed using magnetic resonance imaging (MRI) or arthroscopic evaluation, were enrolled in this study. The patients underwent a KT-2000 (Medmetric, San Diego, CA) examination and a series of stress radiographs that included a radiographic posterior drawer test with Telos (Telos, Weterstadt, Germany) at 90 degrees and 25 degrees of knee flexion, an active radiograph at 90 degrees of knee flexion, and an axial view radiograph.

RESULTS

Stress radiography performed with Telos showed an average posterior tibial displacement of 11.54 +/- 4.93 mm and 7.97 +/- 3.16 mm at 90 degrees and 25 degrees, respectively. The active radiographs showed an average posterior tibial displacement of 11.48 +/- 5.14 mm.

CONCLUSIONS

Stress radiographs were shown to be superior to arthrometric evaluation in quantifying posterior tibial translation. The techniques performed with the knee at 90 degrees of knee flexion allowed for greater posterior tibial displacement and, consequently, an easier quantification of the degree of ligament insufficiency. Stress radiographs performed through hamstring contraction gave the same results as those performed with Telos at 90 degrees of knee flexion.

Graft choice and graft fixation in PCL reconstruction

Several grafts and several fixation techniques have been introduced for PCL reconstruction over the past years. To date, autograft and allograft tissues are recommended for PCL reconstruction, whilst synthetic grafts should be avoided. Autograft tissues include the bone-patellar tendon-bone graft, the hamstrings and the quadriceps tendon. Allograft tissues are increasingly being used for primary PCL reconstruction. The use of allograft tissues requires a number of formal prerequisites to be fulfilled. Besides the previous mentioned graft types allograft tissues include Achilles and tibialis anterior/posterior tendons. To date no superior graft type has been identified. Several techniques and devices have been used for fixation of a PCL replacement graft. Most of these were originally developed for ACL reconstruction and then adapted to PCL reconstruction. However, biomechanical requirements of the PCL differ substantially from those of the ACL. To date, requirements for PCL graft fixations are not known. From a systematic approach femoral graft fixation can either be achieved within the bone tunnel (nearly anatomic) with an interference screw or outside the bone tunnel on the medial femoral condyle using a staple, an endobutton or a screw. Tibial graft fixation can be achieved either with an interference screw in the bone tunnel or with a staple, screw/washer or sutures tied over a bone bridge outside the bone tunnel (extra-anatomic). An alternative fixation on the tibial side is the inlay technique that reduces the acute angulation of the graft at the posterior aspect of the tibia. Further research is necessary to identify the differences between the various fixation techniques.