Posterior cruciate ligament graft fixation angles, part 1: biomechanical evaluation for anatomic single-bundle reconstruction

Surgical Management and Rehabilitation of Ultra-Low Velocity Bilateral Multi-Ligament Knee Injury: A Case Report

Bilateral low-velocity multi-ligament knee Injury (MLKI) is a rare injury increasing in prevalence along with obesity. Early surgical intervention is indicated to improve long-term outcomes. We describe the surgical and postoperative management of a bilateral MLKI. The patient underwent staged multi-ligament knee reconstruction 17 and 35 days after injury. Return to light-duty was achieved 4 weeks following each procedure and progression to exercise at 6 months. The patient is 2 year postoperative and returned to all activity without complaint. We describe successful surgical and rehabilitation management, which encourages early surgery and rehabilitation strategies to improve long-term outcomes.

Outcomes of Surgical Treatment for Multiligament Knee Injuries in a Cohort Including Competitive Athletes With Long-Term Follow-Up

Background

There is a paucity of outcomes data on surgical reconstruction for multiligament knee injury (MLKI) in the orthopaedic literature.

Purpose

To examine functional and return-to-sports (RTS) outcomes and revision rates after single-stage reconstruction for MLKIs in a cohort containing a large proportion of competitive athletes over a 20-year period.

Study Design

Case series; Level of evidence, 4.

Methods

We identified all patients at our institution who underwent surgical reconstruction for an anterior cruciate ligament (ACL) or bicruciate (ACL-posterior cruciate ligament) MLKI between 2001 and 2020 and had ≥2 years of postoperative outcome data. Patient-reported outcomes were evaluated using the International Knee Documentation Committee (IKDC) form, a surgical satisfaction survey, and questions about subsequent knee surgery and RTS administered via telephone. Summary statistics for all outcomes data were calculated, and predictors of IKDC scores at follow-up were examined using univariable linear regression.

Results

Out of 151 patients eligible for this study, outcomes data were collected in 119 patients (79%). The mean follow-up time was 8.3 ± 4.4 years, and the mean IKDC score at follow-up was 79 ± 17. A total of 83 competitive athletes were included; 62 of these athletes attempted to return to preinjury sport. Among the 62 who attempted RTS, 50 (81%) were successful, and 12 were unable to return due to limitations from their surgery. At follow-up, 112 of the overall cohort of 119 patients (94%) were either satisfied or very satisfied with their surgical outcome, and 91% stated the surgery met or exceeded their expectations. In addition, 24% had subsequent ipsilateral knee operations after their index multiligament knee reconstruction. Older age at surgery and female sex were associated with worse IKDC scores at follow-up.

Conclusion

Despite the severity of the injuries in our cohort, we found high levels of patient-reported function and a high rate of successful RTS in the competitive athletes. Older age and female sex were associated with worse patient-reported knee function at follow-up.

Suture Tape Augmentation Improves Posterior Stability After Isolated Posterior Cruciate Ligament Reconstruction Using Hamstring Tendon Autograft With Single-Bundle Transtibial Technique

PURPOSE

To assess whether posterior cruciate ligament reconstruction (PCLR) with suture tape augmentation can yield more stability after isolated PCLR.

METHODS

A prospective database was retrospectively reviewed to identify patients who underwent primary isolated PCLR (control group) or isolated PCLR with suture tape augmentation (study group) from January 2016 to September 2020. We analyzed subjective International Knee Documentation Committee (IKDC), Lysholm, and Tegner knee scores; posterior drawer test findings; posterior stress radiographs; and return-to-sports activity rates. The minimal clinically important difference (MCID) was used to evaluate clinical relevance (subjective IKDC, Lysholm, and Tegner scores).

RESULTS

A total of 59 patients were included in this analysis (28 in control group and 31 in study group). The average length of follow-up was similar between the study and control groups (48.6 months vs 47.9 months, P = .800). Knee function was significantly improved in the study group in terms of subjective IKDC scores (85.1 ± 6.4 in study group vs 79.8 ± 6.4 in control group, P = .002), Lysholm scores (86.3 ± 7.4 vs 80.8 ± 7.4, P = .005), and Tegner scores (7.0 ± 1.4 vs 5.6 ± 1.7, P = .006). However, the differences between the control and study groups were less than the MCID for the subjective IKDC score and Lysholm score. In the control and study groups, 21.4% of patients (6 of 28) and 48.4% of patients (15 of 31), respectively, returned to their preinjury sports activity levels (P = .031). At last follow-up, the mean side-to-side difference in posterior laxity was significantly improved in the study group compared with the control group (1.52 ± 0.70 mm in study group vs 3.17 ± 2.01 mm in control group, P < .01).

CONCLUSIONS

Primary isolated PCLR with suture tape augmentation provides better posterior stability than PCLR without suture tape augmentation at a minimum of 2 years' follow-up. No differences between the groups were observed in the percentage of patients who met or exceeded the MCID for the subjective IKDC and Lysholm scores.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Rates of Subjective Failure After Both Isolated and Combined Posterior Cruciate Ligament Reconstruction: A Study From the Norwegian Knee Ligament Registry 2004-2021

BACKGROUND

Outcomes after posterior cruciate ligament (PCL) reconstruction (PCLR) have been reported to be inferior to those of anterior cruciate ligament reconstruction. Furthermore, combined ligament injuries have been reported to have inferior outcomes compared with isolated PCLR.

PURPOSE/HYPOTHESIS

The purpose of this study was to report on PCLR outcomes and failure rates and compare these outcomes between isolated PCLR and multiligament knee surgery involving the PCL. The hypothesis was that combined PCL injury reconstruction would have higher rates of subjective failure and revision relative to isolated PCLR.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Patients with primary PCLR with or without concomitant ligament injuries registered in the Norwegian Knee Ligament Registry between 2004 and 2021 were included. Knee injury and Osteoarthritis Outcome Score (KOOS) totals were collected preoperatively and at 2 years and 5 years postoperatively. The primary outcome measure was failure, defined as either a revision surgery or a KOOS Quality of Life (QoL) subscale score <44.

RESULTS

The sample included 631 primary PCLR procedures, with 185 (29%) isolated PCLR procedures and 446 (71%) combined reconstructions, with a median follow-up time of 7.3 and 7.9 years, respectively. The majority of patients had poor preoperative knee function as defined by a KOOS QoL score <44 (90.1% isolated PCLR, 85.7% combined PCL injuries; P = .24). Subjective outcomes improved significantly at 2- and 5-year follow-up compared with preoperative assessments in both groups (P < .001); however, at 2 years, 49.5% and 46.5% had subjective failure (KOOS QoL <44) for isolated PCLR and combined PCLR, respectively (P = .61). At 5 years, the subjective failure rates of isolated and combined PCLR were 46.7% and 34.2%, respectively (P = .04). No significant difference was found in revision rates between the groups at 5 years (1.9% and 4.6%, respectively; P = .07).

CONCLUSION

Patients who underwent PCLR had improved KOOS QoL scores relative to their preoperative state. However, the subjective failure rate was high for both isolated and multiligament PCLR. Within the first 2 years after surgery, patients who undergo isolated PCLR can be expected to have similar failure rates to patients who undergo combined ligament reconstructions.

Altered knee kinematics after posterior cruciate ligament single-bundle reconstruction-a comprehensive prospective biomechanical in vivo analysis

Purpose: Passive tibiofemoral anterior-posterior (AP) laxity has been extensively investigated after posterior cruciate ligament (PCL) single-bundle reconstruction. However, the PCL also plays an important role in providing rotational stability in the knee. Little is known in relation to the effects of PCL single-bundle reconstruction on passive tibiofemoral rotational laxity. Gait biomechanics after PCL reconstruction are even less understood. The aim of this study was a comprehensive prospective biomechanical in vivo analysis of the effect of PCL single-bundle reconstruction on passive tibiofemoral rotational laxity, passive anterior-posterior laxity, and gait pattern. Methods: Eight patients undergoing PCL single-bundle reconstruction (seven male, one female, mean age 35.6 ± 6.6 years, BMI 28.0 ± 3.6 kg/m2) were analyzed preoperatively and 6 months postoperatively. Three of the eight patients received additional posterolateral corner (PLC) reconstruction. Conventional stress radiography was used to evaluate passive translational tibiofemoral laxity. A previously established rotometer device with a C-arm fluoroscope was used to assess passive tibiofemoral rotational laxity. Functional gait analysis was used to examine knee kinematics during level walking. Results: The mean side-to-side difference (SSD) in passive posterior translation was significantly reduced postoperatively (12.1 ± 4.4 mm vs. 4.3 ± 1.8 mm; p < 0.01). A significant reduction in passive tibiofemoral rotational laxity at 90° knee flexion was observed postoperatively (27.8° ± 7.0° vs. 19.9° ± 7.5°; p = 0.02). The range of AP tibiofemoral motion during level walking was significantly reduced in the reconstructed knees when compared to the contralateral knees at 6-month follow-up (16.6 ± 2.4 mm vs. 13.5 ± 1.6 mm; p < 0.01). Conclusion: PCL single-bundle reconstruction with optional PLC reconstruction reduces increased passive tibiofemoral translational and rotational laxity in PCL insufficient knees. However, increased passive tibiofemoral translational laxity could not be fully restored and patients showed altered knee kinematics with a significantly reduced range of tibiofemoral AP translation during level walking at 6-month follow-up. The findings of this study indicate a remaining lack of restoration of biomechanics after PCL single-bundle reconstruction in the active and passive state, which could be a possible cause for joint degeneration after PCL single-bundle reconstruction.

Arthroscopic Reduction and Fixation with Fiber Wire Suture Tape for PCL Avulsion Fractures

Background

The internal and external rotation over 90° of flexion is restricted by posterior cruciate ligament (PCL). PCL also restricts posterior translation of tibia at all angles of flexion. The purpose of this study was to compare preoperative and postoperative functional outcomes (Lysholm scores and IKDC scores) in patients with PCL avulsion injuries managed with fixation by fiber wire suture tape.

Methods

This was a prospective cohort study. The study group included 20 patients with PCL avulsion injuries with a mean age of 49.5 years (12 males and 8 females). All patients underwent treatment with high-strength 2-0 fiber tape tied around the PCL tibial insertion under arthroscopy for reduction and fixation.

Results

There was increase in Lysholm score of 20 follow-up patients, from preoperative 36.9 ± 3.9 to a postoperative score of 96.1 ± 3.5. An increase in IKDC scores to 95.4 ± 3.1 from 52.9 ± 9.2 was also seen. Significant differences were found between preoperative and postoperative values. 19 patients regained function and one patient required manipulation under anesthesia. Satisfactory reduction was showed in X-ray and 3D CT scan for all 20 patients.

Conclusion

If the PCL avulsion fracture injury is not identified and adequately treated, it can cause serious morbidity. Although newer studies demonstrate equivalent functional outcomes with arthroscopic treatment, open reduction with internal fixation (ORIF) with Cortico-Cancellous (CC) screw fixation is still a common treatment option. Improve postoperative functional outcome with minimal complications, author recommends PCL avulsion fracture fixation with arthroscopic fiber wire suture tape.

Safe femoral tunnel drilling angles avoid injury to the medial and posteromedial femoral anatomic structures during single-bundle posterior cruciate ligament reconstruction with the inside-out technique

PURPOSE

To investigate the relationship between the medial and posteromedial femoral anatomic structures and the femoral tunnel exit produced by different tunnel orientations when creating the femoral tunnel for posterior cruciate ligament reconstruction (PCLR) using the inside-out (IO) technique and to estimate safe tunnel orientations to minimize the risk of iatrogenic injury to these structures.

METHODS

Eleven cadaveric knees were used. The medial and posteromedial aspects of each knee joint were dissected to reveal the "safe zone," which is a bony area that avoids the distribution or attachment of at-risk structures (MCL, PMC structures, and articular cartilage), while remaining 10 mm away from the articular cartilage. The hypothesis of this study was that by creating the femoral tunnel at specific angles using the IO technique, the tunnel outlet would be as close to the safe zone as possible, protecting the at-risk structures from damage. Femoral tunnels were drilled at 20 different angle combinations on each specimen: 0°, 15°, 30°, 45°, and 60° relative to a line parallel to the transepicondylar axis in the axial plane, as well as 15°, 30°, 45°, and 60° relative to a line parallel to the femoral axis in the coronal plane. The positional relationship between each tunnel exit and the safe zone was recorded, and the shortest distance between the exit center and the safe zone boundary was measured.

RESULTS

The risk of iatrogenic injury differed depending on the drilling orientation (χ² = 168.880, P < 0.001). Femoral drilling angle combinations of 45/45°, 45/60°, 60/30°, 60/45°, and 60/60° (axial/coronal) were considered relatively safer than other orientations (P < 0.05). The shortest distance between the tunnel exit and the safe zone boundary was negatively correlated with the angle in the axial plane (P < 0.001, r = - 0.810).

CONCLUSIONS

When creating the IO femoral tunnel for single-bundle PCL reconstruction, angle combinations of 45/45°, 45/60°, 60/30°, 60/45°, and 60/60° (axial/oblique coronal) could be utilized to prevent at-risk structures from being damaged. The drilling angles and the safe zone can be employed to optimize the femoral tunnel in PCLR.

Influence of the Tibial Tunnel Angle and Posterior Tibial Slope on "Killer Turn" during Posterior Cruciate Ligament Reconstruction: A Three-Dimensional Finite Element Analysis

This study aimed to evaluate the influence of various posterior tibial slopes (PTSs) and tibial tunnel angles (TTAs) on "killer turn" in posterior cruciate ligament (PCL) reconstruction by using three-dimensional finite element analysis (FEA). The study models were created using computed tomography images of a healthy young Asian male. Using SolidWorks, PCL grafts and tibial bone tunnels at different tibial drilling angles (30°, 45°, 60°) were developed. Anterior opening wedge high tibial osteotomy (aOW-HTO) was performed to evaluate the influence of the PTS (+8°, +4°, native, -4°, -8°). An FEA was performed utilizing the ANSYS software program. In the same PTS model, the peak of the equivalent Von Mises stress in PCL grafts decreased as the angle of the TTA increased. In the same TTA model, the peak of the Von Mises in PCL grafts decreased as the PTS angle increased. The "high-contact stress area" (contact stress greater than 10 MPa) was diminished when the TTA and PTS were increased. aOW-HTO was used to steepen the PTS, and a larger TTA may reduce the stress at the "killer turn" during PCL reconstruction. In conclusion, the study findings suggest that using aOW-HTO to steepen the PTS and a larger TTA may reduce the stress at the "killer turn" during PCL reconstruction. The usefulness and safety of this surgical procedure need to be evaluated in future clinical studies.

Stability of the knee after posterior cruciate ligament reconstruction using peroneus longus tendon graft with three femoral insertion sites. A cadaveric study

Introduction

Many kinds of grafts were used for single-bundle reconstruction of the posterior cruciate ligament (PCL). Recently, the peroneus longus tendon (PLT) was used in some clinical reports. This study aimed to test the best position of the femoral insertion in the case of using PLT for PCL reconstruction.

Methods

Seventeen fresh frozen cadaveric knees were randomized into three groups. Group AL (6 knees): the femoral insertion in PCL reconstruction was at the footprint center of the anterolateral bundle (ALB). Group PM (5 knees): at the footprint center of the posteromedial bundle (PMB). And group MC (6 knees) was at the midpoint of the center of the anterolateral bundle and posteromedial bundle. The PCL of all knees was cut and a PCL reconstruction procedure was performed with autologous peroneus longus tendon (PLT). The stability of each knee was tested in three conditions: PCL was intact, PCL was resected, and PCL was reconstructed. The KT-1000 machine was used to measure the maximum posterior displacement of the tibia under force with the knees at 0, 30, 60, 90, and 120 degrees of flexion.

Results

Average posterior displacement of the tibia under force for intact PCL of group AL was 1.6 mm, group MC was 1.2 mm, and group PM was 1.3 mm. After PCL was resected, the knee laxity was increased remarkably: posterior displacement of the tibia of group AL was 8.9 mm, group MC was 9.4 mm, and group PM was 13.6 mm. After PCL was reconstructed, group AL was 1.5 mm, group MC was 2.0 mm, and group PM was 5.6 mm. The results showed that after PCL reconstruction the group AL and group MC give better stability to the knee (p < 0.05, except knee at 120 degrees of flexion). Group AL got more stability than group MC, but the difference was not significant (p ≥ 0.164).

Conclusion

In a single-bundle reconstruction of the PCL with the graft PLT, the femoral insertion at the footprint center of the ALB and the midpoint of the center of the ALB and PMB showed better stability than that at PMB.

Global variation in isolated posterior cruciate ligament reconstruction

Purpose

In the setting of persistent instability or failed non-operative management, surgical reconstruction is commonly recommended for isolated posterior cruciate ligament (PCL) tears. The purpose of this study was to systematically review published studies to evaluate regional variation in the epidemiology of and surgical approaches to primary, isolated PCL reconstruction.

Methods

A systematic review was performed in June 2022 to identify studies examining operative techniques during primary, isolated PCL reconstruction. Collected variables consisted of reconstruction technique, graft type, graft source, tibial reconstruction technique, femoral and tibial drilling and fixation methods, and whether the remnant PCL was preserved or debrided. Studies were classified into four global regions: Asia, Europe, North America, and South America.

Results

Forty-five studies, consisting of 1461 total patients, were identified. Most of the included studies were from Asia (69%, n = 31/45). Single bundle reconstruction was more commonly reported in studies out of Asia, Europe, and North America. Hamstring autografts were utilized in 51.7% (n = 611/1181) of patients from Asia and 60.8% (n = 124/204) of patients from Europe. Trans-tibial drilling and outside-in femoral drilling were commonly reported in all global regions. The PCL remnant was generally debrided, while remnant preservation was commonly reported in studies from Asia.

Conclusion

Surgical treatment of isolated PCL injuries varies by region, with the majority of published studies coming from Asia. Single-bundle reconstruction with hamstring autograft through a trans-tibial approach is the most commonly reported technique in the literature, with males reported to undergo isolated reconstruction more often than females.

Level of Evidence

Systematic review, Level IV.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40634-022-00541-4.

Single and double bundle posterior cruciate ligament reconstruction yield comparable clinical and functional outcomes: a systematic review and meta-analysis

PURPOSE

To perform a systematic review and compare the functional and objective outcomes after single-bundle (SB) vs. double-bundle (DB) posterior cruciate ligament reconstruction (PCLR). Where possible to pool outcomes and arrive at summary estimates of treatment effect for DB PCLR vs. SB PCLR via an embedded meta-analysis.

METHODS

A comprehensive PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) literature search identified 13 eligible studies evaluating clinical outcomes of both techniques for PCLR. Clinical outcome measures included in the meta-analysis were functional outcomes (Lysholm Score, Tegner Activity Scale) and objective measurements of posterior laxity of the operated knee (arthrometer and stress radiographs).

RESULTS

The meta-analysis included 603 patients. Three hundred and fifteen patients were treated with SB and two hundred and eighty-eight patients with DB PCLR. There were no significant differences between SB and DB PCLR in postoperative functional Lysholm Scores (CI [- 0.18, 0.17]), Tegner Activity Scales (CI [- 0.32, 0.12]) and IKDC objective grades (CI [- 0.13, 1.17]). Regarding posterior stability using KT-1000 and Kneelax III arthrometer measurements, there were no differences between the SB and DB group. However, double-bundle reconstruction provided better objective outcome of measurement of posterior laxity (CI [0.02, 0.46]) when measured with Telos stress radiography.

CONCLUSION

A systematic review was conducted to identify current best evidence pertaining to DB and SB PCLR. An embedded meta-analysis arrived at similar summary estimates of treatment effect for motion, stability and overall function for both techniques. There is no demonstrable clinically relevant difference between techniques based on the currently available evidence.

LEVEL OF EVIDENCE

III.

Single versus double bundle in posterior cruciate ligament (PCL) reconstruction: a meta-analysis

Posterior cruciate ligament (PCL) reconstruction can be performed using single bundle (SB) and double bundle (DB) techniques. The present study investigated whether DB PCL reconstruction is superior to SB reconstruction in terms of patient reported outcome measures (PROMs) and joint stability. In December 2021 Embase, Google Scholar, Pubmed, Scopus databases were accessed. All clinical trials comparing SB versus DB reconstruction to address PCL insufficiency in skeletally mature patients were considered. Data from 483 procedures were retrieved. The mean follow-up was 31.0 (28.0 to 107.6) months, and the mean timespan between injury and surgery was 11.3 (6 to 37) months. The mean age of the patients was 29.3 ± 3.8 years. 85 of 483 patients (18%) were women. At a mean of 31.0 months post reconstruction, ROM (P = 0.03) was slightly greater in the SB group, while the Tegner score (P = 0.03) and the Telos stress (P = 0.04) were more favorable in the DB cohort. Similarity was found in instrumental laxity (P = 0.4) and Lysholm score (P = 0.3). The current evidence does not support the use of DB techniques for PCL reconstruction. Both methods could restore knee stability and motion with satisfactory short term patient reported outcome measures. Further high quality clinical trials are required to validate these results on a larger scale.

Graft position at the femoral condyle affects knee mobility after posterior cruciate ligament replacement

BACKGROUND

In some cases posterior cruciate ligament (PCL) tears require surgical reconstruction. As the femoral footprint of the ligament is quite large, an ideal graft fixation position on the medial notch wall has not yet been identified. The aim of this study was to compare three different graft fixation positions within the anatomical footprint of the PCL and test it for posterior tibial translation at different knee flexion angles.

METHODS

In six human knee specimens a drawer test was simulated on a material testing machine by applying load on the tibia. At three different knee flexion angles (0°, 45°, 90°) knee mobility was examined with respect to tibial posterior translation and stiffness for the following conditions: intact ligaments, detached PCL, three different graft fixation positions on the femoral condyle.

RESULTS

Replacement of the PCL within its femoral footprint restored knee stability in terms of tibial posterior translation. Low graft position showed comparable drawer displacements to the intact condition for all knee flexion angles (p > 0.344). A higher graft position excessively reduced the posterior translation (p < 0.047) and resulted in a restricted knee mobility and a stiffer joint.

CONCLUSIONS

Graft fixation positions on the femoral condyle play a crucial role in post-operative knee mobility and joint functionality after PCL replacement. Even though all graft fixation positions were placed within the femoral footprint of a native PCL, only the lower position on the medial notch wall showed comparable posterior tibial translation to an intact PCL.

Evolving evidence in the treatment of primary and recurrent posterior cruciate ligament injuries, part 2: surgical techniques, outcomes and rehabilitation

Isolated and combined posterior cruciate ligament (PCL) injuries are associated with severe limitations in daily, professional, and sports activities as well as with devastating long-term effects for the knee joint. As the number of primary and recurrent PCL injuries increases, so does the body of literature, with high-quality evidence evolving in recent years. However, the debate about the ideal treatment approach such as; operative vs. non-operative; single-bundle vs. double-bundle reconstruction; transtibial vs. tibial inlay technique, continues. Ultimately, the goal in the treatment of PCL injuries is restoring native knee kinematics and preventing residual posterior and combined rotatory knee laxity through an individualized approach. Certain demographic, anatomical, and surgical risk factors for failures in operative treatment have been identified. Failures after PCL reconstruction are increasing, confronting the treating surgeon with challenges including the need for revision PCL reconstruction. Part 2 of the evidence-based update on the management of primary and recurrent PCL injuries will summarize the outcomes of operative and non-operative treatment including indications, surgical techniques, complications, and risk factors for recurrent PCL deficiency. This paper aims to support surgeons in decision-making for the treatment of PCL injuries by systematically evaluating underlying risk factors, thus preventing postoperative complications and recurrent knee laxity. LEVEL OF EVIDENCE: V.

Evolving evidence in the treatment of primary and recurrent posterior cruciate ligament injuries, part 1: anatomy, biomechanics and diagnostics

The posterior cruciate ligament (PCL) represents an intra-articular structure composed of two distinct bundles. Considering the anterior and posterior meniscofemoral ligaments, a total of four ligamentous fibre bundles of the posterior knee complex act synergistically to restrain posterior and rotatory tibial loads. Injury mechanisms associated with high-energy trauma and accompanying injury patterns may complicate the diagnostic evaluation and accuracy. Therefore, a thorough and systematic diagnostic workup is necessary to assess the severity of the PCL injury and to initiate an appropriate treatment approach. Since structural damage to the PCL occurs in more than one third of trauma patients experiencing acute knee injury with hemarthrosis, background knowledge for management of PCL injuries is important. In Part 1 of the evidence-based update on management of primary and recurrent PCL injuries, the anatomical, biomechanical, and diagnostic principles are presented. This paper aims to convey the anatomical and biomechanical knowledge needed for accurate diagnosis to facilitate subsequent decision-making in the treatment of PCL injuries.Level of evidence V.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

CLINICAL RELEVANCE

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

Posterior Cruciate Ligament

Improved understanding of the anatomy and biomechanics of the posterior cruciate ligament (PCL) has led to the evolution and improvement of anatomic-based reconstructions. The PCL is composed of the larger anterolateral bundle (ALB) and the smaller posteromedial bundle (PMB). On the femoral side, the ALB spans from the trochlear point to the medial arch point on the roof of the notch, while the PMB occupies the medial wall from the medial arch point to the most posterior aspect of the articular cartilage. Because of these broad and distinct attachments, the bundles have a load-sharing, synergistic and codominant relationship. Both restrict posterior translation; however, the ALB has a proportionally larger role in restricting translation throughout flexion, whereas the PMB has a role comparable to that of the ALB in full extension. In addition, the PMB resists internal rotational at greater flexion angles (> 90°). Consequently, it is difficult to restore native kinematics with a single graft. Biomechanical analysis of single- versus double-bundle PCL reconstructions (SB PCLR vs DB PCLR) demonstrates improved restoration of native kinematics with a DB PCLR, including resistance to posterior translation throughout flexion (15°-120°) and internal rotation in deeper flexion (90°-120°). Similarly, clinical research demonstrates excellent outcomes following DB PCLR, including functional outcomes comparable to those of anterior cruciate ligament reconstructions, with no significant differences between isolated and multiligament PCL injuries. Compared to SB PCLR, systematic review has demonstrated the superiority of DB PCLR based on objective postoperative stress radiography and International Knee Documentation Committee scores in randomized trials. In addition to reconstruction techniques, recent research has identified other factors that impact kinematics and PCL forces, including decreased tibial slope, which leads to increased graft stresses, and incidence of native PCL injuries. As the understanding of these other contributing factors evolves, so will surgical and treatment algorithms that will further improve patients' outcomes.

[Damage of the knee posterior cruciate ligament: biomechanics, basic diagnostics, treatment and secondary osteoarthritis prevention directions]

The analysis of literature data was performed on the pathogenesis, diagnosis and treatment of injuries of the posterior cruciate ligament (PCL) of the knee joint. PCL is the largest intra-articular ligament of the knee joint, can withstand the maximum loads compared with other ligaments. It was noted that, in general, in cases of damage to the PCL, it is necessary to use a set of diagnostic methods, and the basic principles for the choice of optimal treatment plan for this patient. It considered the results of the conservative treatment of PCL partial ruptures, and it is indicated that this approach increases the risk of degenerative anatomical structures and functional disorders of the joint. It was noted that it is advisable to conduct surgical treatment to restore the stability of the knee joint and normalize function, while a number of methods for the reconstruction of PCL have been proposed to date. The usage of chondroprotectors for prevention of the secondary osteoarthrosis of the knee joint affected by posterior cruciate ligament rupture was analyzed in the literature data.

Bicruciate lesion biomechanics, Part 2-treatment using a simultaneous tensioning protocol: ACL fixation first is better than PCL fixation first to restore tibiofemoral orientation

PURPOSE

An uncommon technique for bicruciate ligament reconstruction involving simultaneous tensioning of the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) grafts with ACL graft fixation first has been pointed out as superior to the "gold-standard" PCL graft fixation first. The purpose of this study was to compare tibiofemoral biomechanics between ACL fixation first and PCL fixation first in a simultaneous tensioning protocol for bicruciate ligament reconstruction.

METHODS

12 fresh-frozen cadaveric knees (six matched pairs) were tested using a custom testing system. Neutral tibial position representing tibiofemoral orientation, anterior-posterior (AP) tibial translation, varus-valgus laxity, and internal-external rotation were measured using a Microscribe 3DLX at 0°, 30°, 60°, and 90° of knee flexion. The following knee conditions were evaluated: intact, bicruciate deficient and following bicruciate reconstruction. A simultaneous tensioning protocol was used for bicruciate reconstruction and PCL fixation first was compared to ACL fixation first. PCL graft fixation was always performed at 90° of flexion and ACL graft fixation was always performed at full extension.

RESULTS

ACL fixation first achieved a tibiofemoral orientation closer to the intact knee than PCL fixation first at 90° flexion (1.8 ± 1.6 mm versus 6.1 ± 3.2 mm, p = 0.016). PCL fixation first had a larger decrease in AP translation than ACL fixation first at 30° flexion (64.6 ± 3.5% vs. 58.3 ± 2.4%, p = 0.01). No significant differences were found for varus/valgus, external-internal rotation decrements after bicruciate reconstruction nor for AP translation, varus/valgus and internal/external rotation increase after bicruciate lesion comparing ACL fixation first to PCL fixation first.

CONCLUSION

Bicruciate ligament reconstruction using a simultaneous tensioning protocol with ACL fixation first resulted in a closer to normal tibiofemoral orientation. This study will help guide surgeons in decision making for the graft tensioning protocol and fixation sequence in a bicruciate ligament reconstruction.

LEVEL OF EVIDENCE

V therapeutic study.

Anatomic is better than isometric posterior cruciate ligament tunnel placement based upon in vivo simulation

PURPOSE

To elucidate the effects of various tibial and femoral attachment locations on the theoretical length changes and isometry of PCL grafts in healthy knees during in vivo weightbearing motion.

METHODS

The intact knees of 14 patients were imaged using a combined magnetic resonance and dual fluoroscopic imaging technique while the patient performed a quasi-static lunge (0°-120° of flexion). The theoretical end-to-end distances of the 3-dimensional wrapping paths between 165 femoral attachments, including the anatomic anterolateral bundle (ALB), central attachment and posteromedial bundle (PMB) of the PCL, connected to an anterolateral, central, and posteromedial tibial attachment were simulated and measured. A descriptive heatmap was created to demonstrate the length changes on the medial condyle and formal comparisons were made between the length changes of the anatomic PCL and most isometric grafts.

RESULTS

The most isometric graft, with approximately 3% length change between 0° and 120° of flexion, was located proximal to the anatomic femoral PCL attachments. Grafts with femoral attachments proximal to the isometric zone decreased in length with increasing flexion angles, whereas grafts with more distal attachments increased in length with increasing flexion angles. The ALB and central single-bundle graft demonstrated a significant elongation from 0° to 120° of flexion (p < 0.001). The PMB decreased in length between 0° and 60° of flexion after which the bundle increased in length to its maximum length at 120° (p < 0.001). No significant differences in length changes were found between either the ALB or PMB and the central graft, and between the ALB and PMB at flexion angles ≥ 60° (n.s.).

CONCLUSIONS

The most isometric attachment was proximal to the anatomic PCL footprint and resulted in non-physiological length changes. Moving the femoral attachment locations of the PCL significantly affected length change patterns, whereas moving the tibia locations did not. The importance of anatomically positioned (i.e., distal to the isometric area) femoral PCL reconstruction locations to replicate physiological length changes is highlighted. These data can be used to optimize tunnel positioning in either single- or double-bundle and primary or revision PCL reconstruction cases.

LEVEL OF EVIDENCE

IV.

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.

Tibial Slope and Its Effect on Graft Force in Posterior Cruciate Ligament Reconstructions

BACKGROUND

A flattened posterior tibial slope may cause excessive unwanted stress on the posterior cruciate ligament (PCL) reconstruction graft and place patients at risk for PCL reconstruction graft failure. To date, there is a paucity of biomechanical studies evaluating the effect of posterior tibial slope on the loading properties of single-bundle (SB) and double-bundle (DB) PCL grafts.

PURPOSE/HYPOTHESIS

The purpose of this study was to quantify the effect of sagittal plane tibial slope on PCL reconstruction graft force at varying slopes and knee flexion angles for SB and DB PCL reconstructions. The null hypothesis was that there would be no differences in SB or DB PCL graft forces with changes in posterior tibial slope or knee flexion angle.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten male fresh-frozen cadaveric knees had a proximal posterior tibial osteotomy performed and an external fixator placed for tibial slope adjustment. SB (anterolateral bundle [ALB] only) and DB PCL reconstruction procedures were performed and tested consecutively for each specimen. The ALB and posteromedial bundle graft forces were recorded before (unloaded force) and after (loaded force) compression with a 300-N axial load. Unloaded and loaded graft forces were tested at flexion angles of 45°, 60°, 75°, and 90°. Tibial slope was varied between -2° and 16° of posterior slope at 2° increments under these test conditions.

RESULTS

Modeling for unloaded testing revealed that tibial slope had an independently significant and linear decreasing effect on the force of all PCL grafts regardless of flexion angle (coefficient = -1.0, SE = 0.08, P < .001). Higher knee flexion angles were significantly associated with higher unloaded graft force for all PCL grafts ( P < .001). After the graft was subjected to loading, tibial slope also had an independently significant and linear decreasing effect on the loaded force of all PCL grafts regardless of flexion angle (coefficient = -0.70, SE = 0.11, P < .001). The ALB graft of DB reconstructions had a significantly lower loaded graft force than the ALB graft of the SB PCL reconstruction (coefficient = 14.8, SE = 1.62, P < .001). The posteromedial bundle graft had a significantly lower loaded graft force than the ALB graft in both reconstruction states across all flexion angles (both P < .001). Higher knee flexion angles were also significantly associated with higher loaded graft force for all graft constructs ( P < .001).

CONCLUSION

PCL graft forces increased as tibial slope decreased (flattened) in the loaded and unloaded states. An increased posterior tibial slope was protective of PCL reconstruction grafts. The findings of this study support the effect of tibial slope on PCL grafts that has been noted clinically, and a flat tibial slope should be considered a factor when evaluating the cause of failed PCL reconstructions.

CLINICAL RELEVANCE

The authors validated that decreased tibial slope increased the loads on PCL reconstruction grafts. Patients with flat tibial slopes in chronic tears or revision PCL reconstruction cases should be evaluated closely for the possible need of a first-stage or concurrent slope-increasing tibial osteotomy.

Decreased Posterior Tibial Slope Does Not Affect Postoperative Posterior Knee Laxity After Double-Bundle Posterior Cruciate Ligament Reconstruction

BACKGROUND

Recent clinical studies identified sagittal plane posterior tibial slope as a risk factor for increased postoperative laxity after single-bundle posterior cruciate ligament reconstruction (PCLR).

PURPOSE/HYPOTHESIS

To retrospectively compare the degree of posterior tibial slope and its effect on posterior tibial translation (PTT) after double-bundle (DB) PCLR. Our null hypothesis was that preoperative tibial slope would not be associated with graft laxity.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Patients who underwent DB PCLR between 2010 and 2017 by a single surgeon were retrospectively analyzed. Measurements of posterior tibial slope were performed on lateral radiographs, and PTT was measured with pre- and postoperative kneeling stress radiographs. Simple and multiple linear regression was performed to estimate the unadjusted and adjusted effect of tibial slope on postoperative graft laxity, respectively.

RESULTS

A total of 103 patients with posterior cruciate ligament tears and subsequent reconstructions were included. There was a significant reduction of the mean ± SD side-to-side difference in PTT between stress radiographs (preoperative, 10.6 ± 2.7 mm; postoperative, 1.5 ± 2.6 mm; mean difference, 9.1 mm; 95% CI, 8.4-9.8; P < .001). Linear regression analysis revealed no significant correlation between preoperative posterior tibial slope and the amount of side-to-side difference in PTT on postoperative stress radiographs obtained at a mean 18.5 months ( R = -0.115, P = .249). Combined ligament injury (beta = -1.01; 95% CI, -2.00 to -0.01; P = .047) was a significant independent predictor of decreased postoperative side-to-side difference in PTT.

CONCLUSION

Graft laxity, determined by PTT in posterior kneeling stress radiographs, was not influenced by decreased posterior tibial slope after DB PCLRs. The observed results in the current study support the use of DB PCLR. Future studies should be conducted to compare the effect of tibial slope after SB PCLR and DB PCLR at long-term follow-up.

Stereophotogrammetric surface anatomy of the anterior cruciate ligament's tibial footprint: Precise osseous structure and distances to arthroscopically-relevant landmarks

BACKGROUND

While femoral tunnel malposition is widely recognized as the main technical error of failed anterior cruciate ligament (ACL) surgery, tibial tunnel malposition is likely underrecognized and underappreciated.

PURPOSE

To describe more precisely the qualitative and quantitative anatomy of the ACL's tibial attachment in vitro using widely available technology for stereophotogrammetric surface reconstruction, and to test its applicability in vivo.

METHODS

Stereophotogrammetric surface reconstruction was obtained from fourteen proximal tibias of cadaver donors. Measurements of areas and distances from the center of the ACL footprint and the footprint of the obtained bundles to selected arthroscopically-relevant anatomic landmarks were carried out using a three-dimensional design software program, and means and 95% confidence intervals were calculated for these measurements. Reference landmarks were tested in three-dimensional models obtained with arthroscopic videos.

MAIN FINDINGS

The osseous footprint of the ACL was described in detail, including its precise elevated limits, size, and shape, with its elevation pattern described as a quarter-turn-staircase-like ridge. Its internal indentations were related to inter-spaces identified as bundle divisions. Distances from the footprint center to arthroscopically relevant landmarks were obtained and compared to its internal structure, yielding a useful X-like landmark pointing to the most accurate placeholder for the ACL footprint's "anatomic" center. Certain structures and reference landmarks described were readily recognized in three-dimensional models from arthroscopic videos.

CONCLUSIONS

Stereophotogrammetric surface reconstruction is an accessible technique for the investigation of anatomic structures in vitro, offering a detailed three-dimensional depiction of the ACL's osseous footprint.

Graft sources do not affect to the outcome of transtibial posterior cruciate ligament reconstruction: a systematic review

INTRODUCTION

Despite numerous published reports on posterior cruciate ligament (PCL) reconstruction in the past 30 years, the ideal graft source remains unclear, and few objective scientific data have been published that thoroughly evaluate the long-term outcomes according to the graft source. We, therefore, conducted a systematic review of available high-quality comparative studies that evaluated clinical and objective stability testing to compare the different graft sources for PCL reconstruction.

MATERIALS AND METHODS

Eight articles were included in the final analysis. There were two level II and six level III studies. Autograft included 4-strand hamstring grafts (SHGs), 7-SHGs, quadriceps tendon, and patellar tendon. Allografts included Achilles tendon and tibialis anterior tendon. Hybrid graft and a ligament advanced reinforcement system (LARS) were used in one study each. Comparison was performed between autografts and allografts in three studies, between different autografts in two studies, between autograft and LARS in one study, among three different grafts in one study, and between 4 and 7-SHGs in one study.

RESULTS

Most studies reported no statistically significant differences in the clinical results, except for one study that compared 4- and 7-SHG. Stability was similar or superior in a comparison between autografts and allografts, and was not statistically different between different autografts or between 4-SHG and LARS. However, more-stranded HG showed better stability than that of the less-stranded HG. Complications were more frequent with autografts.

CONCLUSION

Using a comprehensive analysis of the current literature, the authors could not identify an individual graft source with clearly superior clinical results, compared with other graft sources. However, autografts, especially 4-SHGs, showed similar or superior stability to irradiated allografts. Therefore, the graft source has a minimal effect on the clinical outcome, but it could have some effects on stability in single bundle transtibial PCL reconstruction.

Double-Bundle Posterior Cruciate Ligament Reconstruction in 100 Patients at a Mean 3 Years' Follow-up: Outcomes Were Comparable to Anterior Cruciate Ligament Reconstructions

BACKGROUND

Historically, outcomes of posterior cruciate ligament (PCL) reconstructions have been less predictable and reported to yield inferior results when compared with those for anterior cruciate ligament (ACL) reconstructions.

PURPOSE

To report on the outcomes of double-bundle PCL reconstructions (DB PCLRs) in isolated versus combined injuries and acute versus chronic PCL reconstructions. To compare the outcomes of isolated DB PCLR with isolated ACL reconstruction.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

All patients who underwent a primary endoscopic DB PCLR for complete PCL tears (grade III) between May 2010 and March 2015 were reviewed. Patient-reported outcome scores (Tegner, Lysholm, WOMAC [Western Ontario and McMaster Universities Osteoarthritis Index], SF-12 [12-item Short Form Health Survey]) and objective posterior stress radiographs were collected preoperatively and at a minimum 2 years postoperatively. A cohort subanalysis was additionally performed between isolated and combined PCL reconstruction and acute versus chronic PCL reconstruction. Patients who underwent isolated ACL reconstructions over the same inclusion period (2010-2015) were selected as a comparison group.

RESULTS

One hundred patients who underwent DB PCLR were included in this study. There were 31 isolated PCL injuries, and 69 patients had concurrent combined PCL injuries requiring surgery. The mean follow-up for the PCL cohort was 2.9 years (range, 2-6 years). The median Tegner activity score improved from 2 to 5, Lysholm from 48 to 86, WOMAC from 35.5 to 5, and SF-12 Physical Component Summary from 34 to 54.8 (all P values <.001). The mean side-to-side difference in posterior tibial translation on kneeling stress radiographs improved from 11.0 ± 3.5 mm preoperatively to 1.6 ± 2.0 mm postoperatively ( P < .001). There were no differences in postoperative functional scores between isolated PCL reconstructions and PCL-based multiligament reconstructions (all P values >.229). There was no significant difference in the reported outcome scores between acute and chronic reconstructions (all P values >.087) except for Tegner scores ( P < .001) and patient satisfaction ( P = .011) favoring acutely treated PCL injuries. There were no significant differences between patients who had an isolated DB PCLR and patients who underwent an isolated ACL reconstruction (n = 141) in postoperative outcome scores (all P values >.064).

CONCLUSION

Significantly improved functional and objective outcomes were observed after anatomic DB PCLR at a mean 3 years' follow-up, with low complication rates, regardless of concomitant ligamentous injury or timing to surgery. Additionally, contrary to previous reports, comparable subjective and functional clinical outcomes were achieved compared with an isolated ACL reconstruction control cohort.

Biomechanical Comparison of Single-Bundle and Double-Bundle Posterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-Analysis

BACKGROUND

Of the many issues regarding surgical techniques for posterior cruciate ligament (PCL) reconstruction, the choice between single-bundle (SB) and double-bundle (DB) reconstruction is one of the most debated. However, it is unclear which of the reconstruction techniques yields better outcomes in knees with a PCL injury. The purpose of this meta-analysis was to compare the benefits of SB and DB PCL reconstruction in terms of biomechanical outcomes.

METHODS

The MEDLINE, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science, and SCOPUS electronic databases were searched for relevant articles comparing the outcomes of SB and DB PCL reconstruction that were published up until August 2016. Data searching, extraction, analysis, and quality assessment were performed on the basis of the Cochrane Collaboration guidelines. Biomechanical outcomes of both techniques were evaluated using various outcomes. Results involving continuous outcomes are presented as standardized mean differences (SMDs) with 95% confidence intervals (CIs).

RESULTS

Ten biomechanical studies were included. There were no significant biomechanical differences between the groups with respect to external rotation, varus rotation, or coupled external rotation of the tibia with posterior drawer force at any knee flexion angle. However, posterior laxity measured using the posterior drawer test showed significantly better results after DB compared with SB reconstruction at low flexion (SMD = -0.90, 95% CI = -1.24 to -0.56, I = 0%), 30° (SMD = -0.79, 95% CI = -1.28 to -0.31, I = 48%), 60° (SMD = -0.87, 95% CI = -1.33 to -0.40, I = 33%), and 90° (SMD = -0.73, 95% CI = -1.11 to -0.35, I = 27%).

CONCLUSIONS

Anatomic DB reconstruction of the PCL is superior to anatomic SB reconstruction in terms of restoration of anteroposterior stability. However, it remains unclear which technique yields better improvement in terms of external rotation laxity, varus laxity, and coupled external rotation of the tibia with posterior drawer force. High-quality randomized controlled trials are required to confirm and expand on these results.

Posterior Cruciate Ligament: Anatomy and Biomechanics

PURPOSE OF REVIEW

The purpose of this review is to present an in-depth look at the most recent literature regarding pertinent posterior cruciate ligament (PCL) anatomy and biomechanics.

RECENT FINDINGS

The PCL is an important restraint of posterior tibial translation relative to the femur. In addition, the PCL acts as a secondary restraint to resist varus, valgus, and external rotation moments about the knee. While less common than ACL injuries, injuries to the PCL can occur from a posterior force directed on the tibia, most common with the knee in a flexed position. The PCL is composed of two functional bundles and has important implications for knee stability. The anterolateral and posteromedial bundles have different patterns of tensioning throughout knee range of motion. The two bundles therefore contribute to resisting posterior tibial translation and rotation at different angles of knee flexion.

Both isolated and multi-ligament posterior cruciate ligament reconstruction results in improved subjective outcome: results from the Danish Knee Ligament Reconstruction Registry

PURPOSE

There are few descriptions of outcomes after posterior cruciate ligament (PCL) reconstruction in the literature due to the rarity of this type of knee injury. Since 2005, the Danish Knee Ligament Reconstruction Registry (DKRR) has monitored outcomes of PCL reconstructions. This study describes the epidemiology of PCL reconstruction and subsequent outcomes in a Danish population.

METHODS

Of 23,253 knee ligament reconstructions performed in 2005-2015, 581 were registered as PCL reconstructions in the DKRR. The types of reconstruction were classified as isolated (n = 237) or multi-ligament (n = 344), and the cause of injury and concomitant meniscus and cartilage injury data were extracted. The outcome at 1-year follow-up was based on the Knee Injury and Osteoarthritis Outcome Score (KOOS) and Tegner activity level. The outcome data were compared with data on 21.820 primary anterior cruciate ligament (ACL) reconstructions.

RESULTS

Isolated PCL reconstruction was performed in 43% of cases. Meniscus lesions and cartilage lesions were seen in 19 and 15% of cases, respectively. The main causes of PCL injuries were sports (43%) and traffic accidents (33%). The KOOS improved from pre-operative to 1-year follow-up for both isolated PCL reconstructions and multi-ligament PCL reconstructions but did not reach the levels of those recorded in ACL reconstructions. Multi-ligament reconstructions showed the highest improvement in KOOS. The Tegner activity levels for isolated and multi-ligament PCL reconstructions were 4 (0-7) and 4 (0-8), respectively.

CONCLUSIONS

PCL reconstructions represented only 2.6% of all knee ligament reconstructions in Denmark. Sports and traffic accidents were the main causes of injury. Meniscus and cartilage injuries were less frequent in PCL injuries as compared to ACL injuries. Isolated PCL and multi-ligament PCL reconstructions showed significant improvements in subjective outcomes but did not reach those observed in ACL reconstructions. Patients should be counselled about expected outcomes after PCL reconstruction.

LEVEL OF EVIDENCE

III.

Single-Bundle and Double-Bundle Posterior Cruciate Ligament Reconstructions: A Systematic Review and Meta-analysis of 441 Patients at a Minimum 2 Years' Follow-up

PURPOSE

To perform a systematic review on the techniques and a meta-analysis on the functional and objective outcomes after single-bundle (SB) versus double-bundle (DB) posterior cruciate ligament (PCL) reconstructions.

METHODS

A systematic review of the techniques, as well as functional and objective outcomes of clinical studies comparing SB versus DB PCL reconstruction with a mean follow-up of at least 24 months and minimum level of evidence of III were performed. After review of the literature, a quality analysis of the studies (Detsky score) and a meta-analysis comparing raw mean differences in data between SB and DB PCL groups were performed. Clinical outcome measures included in the meta-analysis were functional outcomes (Lysholm, Tegner, and objective International Knee Documentation Committee [IKDC] scores) and objective measurements (arthrometer and stress radiographs).

RESULTS

The systematic search identified 11 studies (441 patients). Three studies were prospective randomized controlled trials and the other 8 studies were case-control studies. Two hundred thirty-two patients were treated with SB PCL reconstruction, whereas 209 were treated with DB PCL reconstruction. Only 4 studies satisfied the threshold for a satisfactory level of methodologic quality (>75%). There were no significant differences between SB and DB PCL reconstructions in postoperative Lysholm (P = .6, 95% confidence interval [CI], -0.98, 2.18) or Tegner scores (P = .37, 95% CI, -0.19, 0.92). DB PCL reconstruction provided significantly better objective posterior tibial translation stability than the SB technique using the Telos technique at 90° (P = -.58, 95% CI, -1.06, -0.10).

CONCLUSIONS

Improved patient-reported outcomes and knee stability were achieved with both SB and DB PCL reconstruction surgery. DB PCL reconstruction provided significantly improved objective posterior tibial stability and objective IKDC scores when compared with SB PCL reconstruction in randomized clinical trials. No significant difference was found for the other patient-reported outcomes.

LEVEL OF EVIDENCE

Level III, systematic review and meta-analysis of Level II and III studies.

Double-bundle posterior cruciate ligament reconstruction: a biomechanical analysis of simulated early motion and partial and full weightbearing on common reconstruction grafts

PURPOSE

The purpose of this study was to determine the biomechanical effects of simulated immediate motion and weightbearing during rehabilitation on different double-bundle posterior cruciate ligament reconstruction (DB-PCLR) graft options.

METHODS

Nine each of commercially prepared (allograft) Achilles tendon allografts, fresh-frozen (autograft) bone-patellar tendon-bone grafts, and fresh-frozen quadriceps tendon grafts were paired with commercially prepared anterior tibialis allografts, fresh-frozen semitendinosus grafts, and fresh-frozen semitendinosus grafts, respectively. Graft pairs were loaded to simulate early range of motion on a stationary bicycle, partial weightbearing (30 %), and full weightbearing.

RESULTS

Acquired laxity (displacement, mm) between graft pairs was not significantly different during simulated early range of motion. However, during simulated partial weightbearing, the median acquired laxity of the patellar tendon/semitendinosus pair (1.06 mm) was significantly less than that of the quadriceps tendon/semitendinosus (1.50 mm, p = 0.01) and Achilles/anterior tibialis (1.44 mm, p = 0.003) graft pairs. During simulated full weightbearing, significantly less acquired laxity was observed for the patellar tendon/semitendinosus graft pair (2.38 mm) compared to the Achilles/anterior tibialis pair (4.85 mm, p = 0.04), but a significant difference was not observed compared to the QT/semitendinosus graft pair (3.91 mm, n.s.). There were no significant differences in the ultimate loads between any of the graft pairs.

CONCLUSIONS

Simulated early range of motion and early partial weightbearing did not result in clinically significant acquired graft laxity in common graft options utilized for DB-PCLR. However, simulated full weightbearing did result in clinically significant acquired graft laxity, and therefore, early rehabilitation protocols should avoid implementing full weightbearing that could contribute to graft failure.

Outcomes After Posterior Cruciate Ligament (PCL) Reconstruction in Patients With Isolated and Combined PCL Tears

Background:

Posterior cruciate ligament (PCL) reconstructions are rarely performed compared with that for the anterior cruciate ligament (ACL).

Purpose:

To evaluate the clinical and functional outcome after isolated or multiligament PCL reconstruction.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Patients who underwent PCL reconstruction between 2002 and 2010 were included. Standardized follow-up was performed between 2012 and 2013 and consisted of subjective scores (Tegner activity score, Knee injury and Osteoarthritis Outcome Score [KOOS], and subjective International Knee Documentation Committee [IKDC] score) and objective measures, including knee laxity (KT-1000), extension strength, and overall IKDC score.

Results:

One hundred ninety-six patients were identified, of which 172 were available for postoperative follow-up: 39.3% with isolated PCL and 60.7% with multiligament injury. One hundred ten patients were available to complete both clinical follow-up and subjective questionnaires; 62 patients returned the subjective questionnaires. Mean follow-up was 5.9 years (range, 3.1-9.7 years). KOOS scores at follow-up in the isolated PCL group by subscale were 74 (symptoms), 76 (pain), 80 (activities of daily living), 55 (sport), and 55 (quality of life). Scores for patients in the multiligament group were 73 (symptoms), 79 (pain), 82 (activities of daily living), 53 (sport), and 56 (quality of life). Tegner scores were 4.5 and 4.4, respectively, and subjective IKDC scores were 63.8 and 65.0. The mean side-to-side difference in knee laxity was 2.7 mm in the isolated PCL group compared with 2.8 mm in the multiligament group. At 1-year follow-up there were significant differences in KOOS outcome scores between the isolated PCL subgroup and the multiligament subgroup, but no differences at final follow-up. Twelve patients (5%) had PCL revision surgery within the follow-up period.

Conclusion:

Despite the type of injury, there were only minor differences in knee laxity and subjective outcome scores between the isolated PCL group and the multiligament group. The overall revision rate in this study was 5.2%.

Anatomic Double-Bundle Posterior Cruciate Ligament Reconstruction

The posterior cruciate ligament (PCL) is the main posterior stabilizer of the knee. It is composed of 2 bundles, the larger anterolateral bundle (ALB) and the smaller posteromedial bundle (PMB). The 2 bundles were historically believed to function independently, with the ALB predominantly being an important stabilizer in flexion and the PMB being a stabilizer mainly in extension. However, a recent biomechanical study¹ noted a codominant relationship between these 2 bundles. The anatomic single-bundle PCL reconstruction, focusing on reconstruction of the larger ALB, is the most commonly performed procedure. Because of the residual posterior and rotational tibial instability after a single-bundle reconstruction and the inability to restore the normal knee kinematics, an anatomic double-bundle PCL reconstruction has been proposed in an effort to recreate both bundles using the native footprint, thereby restoring the normal knee kinematics. The anatomic double-bundle PCL reconstruction has demonstrated improved subjective and objective patient outcomes with a low complication rate. Indications for PCL reconstruction are isolated symptomatic acute grade-III PCL tears, combined multiligament lesions, or acute grade-III PCL tears combined with repairable meniscal body or root tears. For chronic PCL tears, indications include functional limitations due to the PCL tear (e.g., difficulty with deceleration, incline descent, or stairs) and comparative PCL stress radiographic laxity of >8 mm in a symptomatic patient. The steps of this procedure include (1) correct patient positioning to allow for good accessibility of both sides of the joint; (2) graft preparation (Achilles tendon [ALB] and tibialis anterior [PMB] allografts are used); (3) creation of femoral tunnels (11 mm for the ALB adjacent to the cartilage and 7 mm for the PMB with a 2-mm bone bridge); (4) tibial tunnel creation (12-mm diameter, 7 mm anterior to the so-called champagne-glass drop-off); (5) graft fixation and tibial graft passage (a metal screw for the ALB and a bioabsorbable screw for the PMB, with the screws away from the bone bridge to avoid bone bridge breakage); and (6) tibial fixation (the grafts are independently fixed with the knee at 90° of flexion (ALB) and extension (PMB) with screws and washers on the medial side of the tibia. Three prospective randomized studies^18,19,23 suggested that, while clinical outcomes are similar between both isolated transtibial reconstruction techniques, the objective measures of postoperative side-to-side posterior translation and objective International Knee Documentation Committee scores were significantly improved with double-bundle compared with single-bundle PCL reconstructions.

Epidemiology of surgically treated posterior cruciate ligament injuries in Scandinavia

PURPOSE

The main purpose of the study was to provide an overview of injury mechanisms, concomitant injuries, and other relevant epidemiological data for patients treated in Scandinavia with posterior cruciate ligament reconstruction (PCLR) following a posterior cruciate ligament (PCL) injury.

METHODS

A total number of 1287 patients who underwent PCLR from 2004 to 2013 in the Scandinavian counties were included from the national ligament registries. The variables such as age, sex, activity, and graft used for reconstruction were collected. Then, injuries were sorted based on concomitant injuries. Finally, data from the different registries were compared.

RESULTS

Average age of the treated patients was 32.7 years. Sex distribution ratio of male to female was 858:429 (66.7 %:33.3 %). Depending on definition, 26-37 % of the injuries treated were isolated PCL injuries. PCL injuries were most commonly encountered in sports with 35.4 % of the total number of PCL injuries in the study population. Soccer was the sport with the highest number of injuries (13.1 %). Cartilage lesions occurred in 26.1 % of PCL injuries and meniscal lesions in 21.0 %. Minimum one other additional ligament was injured in 62.2 %.

CONCLUSION

Isolated PCL injuries are common, although the injury is most commonly associated with other ligament injuries. There is a high prevalence of cartilage injuries and meniscal lesions associated with PCL injuries. Sports are the leading cause of PCL injuries treated operatively. Epidemiological data are a necessary part of the basis for injury prevention in the future. The prevalence of concomitant injuries is also relevant and clinically important for the choice of surgical procedure and for the expected outcomes following surgery.

LEVEL OF EVIDENCE

II.

Microstructural and Mechanical Properties of the Posterior Cruciate Ligament: A Comparison of the Anterolateral and Posteromedial Bundles

BACKGROUND

The microstructural organization (collagen fiber alignment) of the posterior cruciate ligament (PCL), which likely corresponds with its functional properties, has only been described qualitatively in the literature, to our knowledge. The goal of this study was to quantify the tensile mechanical and microstructural properties of the PCL and compare these qualities between the anterolateral and posteromedial bundles.

METHODS

Twenty-two knee specimens from 13 donors (8 male and 5 female; mean age [and standard deviation] at the time of death, 43.0 ± 4.1 years; mean body mass index, 30.0 ± 6.7 kg/m²) were dissected to isolate the PCL, and each bundle was split into 3 regions. Mechanical testing of each regional sample consisted of preconditioning followed by a ramp-and-hold stress-relaxation test and a quasi-static ramp-to-failure test. Microstructural analysis was performed with use of a high-resolution, division-of-focal-plane polarization camera to evaluate the average direction of collagen orientation and the degree to which the collagen fibers were aligned in that direction. Results were compared between the anterolateral and posteromedial bundles and across the regions of each bundle.

RESULTS

The anterolateral and posteromedial bundles demonstrated largely equivalent mechanical and microstructural properties. Elastic moduli in the toe and linear regions were not different; however, the posteromedial bundle did show significantly more stress relaxation (p = 0.004). There were also few differences in microstructural properties between bundles, which again were seen only in stress relaxation. Comparing regions within each bundle, several mechanical and microstructural parameters showed significant relationships across the posteromedial bundle, following a gradient of decreasing strength and alignment from anterior to posterior.

CONCLUSIONS

The PCL has relatively homogenous microstructural and mechanical properties, with few differences between the anterolateral and posteromedial bundles. This finding suggests that distinct functions of the PCL bundles result primarily from size and anatomical location rather than from differences in these properties.

CLINICAL RELEVANCE

These properties of the PCL can be used to assess the utility of graft choices and operative techniques for PCL reconstruction and may partly explain limited differences in the outcomes of single-bundle compared with double-bundle reconstruction techniques for the PCL.

Differences of Intra-Articular Graft Length between Sandwich-Style Reconstruction and Zhao-Style Non-Remnant-Preserving Double-Bundle Reconstruction of Posterior Cruciate Ligament

Appropriate graft length within the joint and inside the osseous tunnel is essential for achieving posterior stability and adequate anchorage strength. Because of the curving path and thickness of the graft in double-bundle posterior cruciate ligament (PCL) reconstruction, especially in double-bundle PCL augmentation (with remnant preservation), the actual intra-articular length of PCL grafts, which remains unknown, may be longer than previously published values. The main purpose of the current study is to measure the actual intra-articular graft length required in sandwich-style PCL reconstruction (remnant-preserving double-bundle PCL augmentation) and Zhao-style non-remnant-preserving double-bundle PCL reconstruction (semi-anatomic double-bundle PCL reconstruction using double-double tunnel with tibial medial and lateral arrangement). Nine matched pairs of intact cadaveric knees were randomized between two groups and respectively received sandwich-style PCL reconstruction (remnant-preserving group) and Zhao-style non-remnant-preserving double-bundle PCL reconstruction (non-remnant-preserving group). The tunnel positions were exactly the same in two groups. The anterolateral (AL) bundle was reconstructed with four-stranded semitendinosus tendon, and the posteromedial (PM) bundle was reconstructed with four-stranded gracilis tendon. For each bundle, the length of the graft portion within the joint was measured. The current study indicated that in remnant-preserving group, the average intra-articular exposed portion was 42.0 mm (SD, 1.3 mm; range, 40.0 mm to 43.4 mm) for the AL bundle and 32.5 mm (SD, 2.9 mm; range, 27.8 mm to 35.8 mm) for the PM bundle. In non-remnant-preserving group, the intra-articular exposed portion was 34.5 mm (SD, 1.0 mm; range, 32.7 mm to 36.0 mm) for the AL bundle and 29.1 mm (SD, 2.1 mm; range, 25.2 mm to 31.9 mm) for the PM bundle. For both the AL and PM bundles, significant differences were found in average intra-articular graft length between the two groups. The current study, whose methodology is more rigorous and accurate by measuring the actual intra-articular graft length, has direct applications to clinical practice. When considering the total graft lengths during reconstruction, it is necessary to recognize that remnant PCL has a space occupation effect on graft and that remnant preservation requires longer intra-articular graft lengths than non-remnant preservation.

An In Vitro Robotic Assessment of the Anterolateral Ligament, Part 1: Secondary Role of the Anterolateral Ligament in the Setting of an Anterior Cruciate Ligament Injury

BACKGROUND

Recent investigations have described the structural and functional behavior of the anterolateral ligament (ALL) of the knee through pull-apart and isolated sectioning studies. However, the secondary stabilizing role of the ALL in the setting of a complete anterior cruciate ligament (ACL) tear has not been fully defined for common simulated clinical examinations, such as the pivot-shift, anterior drawer, and internal rotation tests.

HYPOTHESIS

Combined sectioning of the ALL and ACL would lead to increased internal rotation and increased axial plane translation during a pivot-shift test when compared with isolated sectioning of the ACL.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten fresh-frozen human cadaveric knees were subjected to a simulated pivot-shift test with coupled 10-N·m valgus and 5-N·m internal rotation torques from 0° to 60° of knee flexion and a 5-N·m internal rotation torque and an 88-N anterior tibial load, both from 0° to 120° of knee flexion via a 6 degrees of freedom robotic system. Kinematic changes were measured and compared with the intact state for isolated sectioning of the ACL and combined sectioning of the ACL and ALL.

RESULTS

Combined sectioning of the ACL and ALL resulted in a significant increase in axial plane tibial translation during a simulated pivot shift at 0°, 15°, 30°, and 60° of knee flexion and a significant increase in internal rotation at 0°, 15°, 30°, 45°, 60°, 75°, 90°, 105°, and 120° when compared with the intact and ACL-deficient states. Based on the model results, ALL sectioning resulted in an additional 2.1 mm (95% CI, 1.4-2.9 mm; P < .001) of axial plane translation during the pivot shift when compared with ACL-only sectioning, when pooling evidence over all flexion angles. Likewise, when subjected to IR torque, the ACL+ALL-deficient state resulted in an additional 3.2° of internal rotation (95% CI, 2.4°-4.1°; P < .001) versus the intact state, and the additional sectioning of the ALL increased internal rotation by 2.7° (95% CI, 1.8°-3.6°; P < .001) versus the ACL-deficient state.

CONCLUSION

The results of this study confirm the ALL as an important lateral knee structure that provides rotatory stability to the knee. Specifically, the ALL was a significant secondary stabilizer throughout flexion during an applied internal rotation torque and simulated pivot-shift test in the context of an ACL-deficient knee.

CLINICAL RELEVANCE

Residual internal rotation and a positive pivot shift after ACL reconstruction may be attributed to ALL injury. For these patients, surgical treatment of an ALL tear may be considered.

Anatomic Double-Bundle Posterior Cruciate Ligament Reconstruction

The posterior cruciate ligament (PCL) is known to be the main posterior stabilizer of the knee. Anatomic single-bundle PCL reconstruction, focusing on reconstruction of the larger anterolateral bundle, is the most commonly performed procedure. Because of the residual posterior and rotational tibial instability after the single-bundle procedure and the inability to restore the normal knee kinematics, an anatomic double-bundle PCL reconstruction has been proposed in an effort to re-create the native PCL footprint more closely and to restore normal knee kinematics. We detail our technique for an anatomic double-bundle PCL reconstruction using Achilles and anterior tibialis tendon allografts.

Emerging Updates on the Posterior Cruciate Ligament: A Review of the Current Literature

The posterior cruciate ligament (PCL) is recognized as an essential stabilizer of the knee. However, the complexity of the ligament has generated controversy about its definitive role and the recommended treatment after injury. A proper understanding of the functional role of the PCL is necessary to minimize residual instability, osteoarthritic progression, and failure of additional concomitant ligament graft reconstructions or meniscal repairs after treatment. Recent anatomic and biomechanical studies have elucidated the surgically relevant quantitative anatomy and confirmed the codominant role of the anterolateral and posteromedial bundles of the PCL. Although nonoperative treatment has historically been the initial treatment of choice for isolated PCL injury, possibly biased by the historically poorer objective outcomes postoperatively compared with anterior cruciate ligament reconstructions, surgical intervention has been increasingly used for isolated and combined PCL injuries. Recent studies have more clearly elucidated the biomechanical and clinical effects after PCL tears and resultant treatments. This article presents a thorough review of updates on the clinically relevant anatomy, epidemiology, biomechanical function, diagnosis, and current treatments for the PCL, with an emphasis on the emerging clinical and biomechanical evidence regarding each of the treatment choices for PCL reconstruction surgery. It is recommended that future outcomes studies use PCL stress radiographs to determine objective outcomes and that evidence level 1 and 2 studies be performed to assess outcomes between transtibial and tibial inlay reconstructions and also between single- and double-bundle PCL reconstructions.

Validation of a six degree-of-freedom robotic system for hip in vitro biomechanical testing

Currently, there exists a need for a more thorough understanding of native hip joint kinematics to improve the understanding of pathological conditions, injury mechanisms, and surgical interventions. A biomechanical testing system able to accomplish multiple degree-of-freedom (DOF) movements is required to study the complex articulation of the hip joint. Therefore, the purpose of this study was to assess the repeatability and comparative accuracy of a 6 DOF robotic system as a testing platform for range of motion in vitro hip biomechanical analysis. Intact human cadaveric pelvises, complete with full femurs, were prepared, and a coordinate measuring machine collected measurements of pertinent femoral and pelvic bony landmarks used to define the anatomic hip axes. Passive flexion/extension path and simulated clinical exam kinematics were recorded using a 6 DOF robotic system. The results of this study demonstrate that the 6 DOF robotic system was able to identify hip passive paths in a highly repeatable manner (median RMS error of <0.1mm and <0.4°), and the robotically simulated clinical exams were consistent and repeatable (rotational RMS error ≤0.8°) in determining hip ranges of motion. Thus, a 6 DOF robotic system is a valuable and effective tool for range of motion in vitro hip biomechanical analysis.

The Supine Internal Rotation Test: A Pilot Study Evaluating Tibial Internal Rotation in Grade III Posterior Cruciate Ligament Tears

Background:

Biomechanical studies have reported that the posterior cruciate ligament (PCL) functions as a restraint against excessive tibial internal rotation at higher degrees of knee flexion.

Purpose:

To investigate the use of a supine internal rotation (IR) test for the diagnosis of grade III PCL injuries. The hypothesis was that internal rotation would be greater in patients with grade III PCL injuries compared with other knee injuries and that the supine IR test would demonstrate excellent diagnostic accuracy.

Study Design:

Cohort study (diagnosis); Level of evidence, 2.

Methods:

A consecutive series of 309 patients underwent arthroscopic and/or open knee ligament reconstruction surgery. Seven patients were excluded based on the inability to perform a side-to-side comparison of internal rotation. Tibial internal rotation was assessed bilaterally on 302 patients during examination under anesthesia by a single orthopaedic surgeon measuring tibial tubercle excursion (mm) while applying internal rotation torque. Internal rotation was graded from 0 to 4 at 60°, 75°, 90°, 105°, and 120° of knee flexion. Data were collected and stored prospectively. The optimal threshold for the supine IR test was chosen based on maximization of the Youden index. Diagnostic accuracy parameters were calculated. Multiple logistic regression models were constructed to assess the influence of other knee pathologies on diagnostic accuracy.

Results:

Examination of the 22 PCL-deficient knees demonstrated an increase in tibial internal rotation at 60°, 75°, 90°, 105°, and 120° of knee flexion. The supine IR test had a sensitivity of 95.5%, a specificity of 97.1%, a positive predictive value of 72.4%, and a negative predictive value of 99.6% for the diagnosis of grade III PCL injuries. Posterolateral corner injury had a significant interaction with the supine IR test, increasing its sensitivity and decreasing its specificity.

Conclusion:

PCL-deficient knees demonstrated an increase in the side-to-side difference in tibial internal rotation compared with other knee pathologies. The supine IR test offers high sensitivity and specificity for grade III PCL injuries and may represent a useful adjunct for diagnosing PCL injuries.

Quantification of functional brace forces for posterior cruciate ligament injuries on the knee joint: an in vivo investigation

PURPOSE

Counteracting posterior translation of the tibia with an anterior force on the posterior proximal tibia has been demonstrated clinically to improve posterior knee laxity following posterior cruciate ligament (PCL) injury. This study quantified forces applied to the posterior proximal tibia by two knee braces designed for treatment of PCL injuries.

METHODS

The forces applied by two knee braces to the posterior proximal tibia and in vivo three-dimensional knee kinematics of six adult, male, healthy volunteer subjects (mean ± standard deviation: height, 182.5 ± 5.2 cm; body mass, 83.2 ± 9.3 kg; body mass index, 24.9 ± 1.5 kg/m(2); age, 25.8 ± 2.9 years) were measured using a custom pressure mapping technique and traditional surface marker motion capture techniques, while subjects performed three functional activities. The activities included seated unloaded knee flexion, squatting, and stair descent in a new generation dynamic force (DF) PCL brace and a static force (SF) PCL brace.

RESULTS

During unloaded flexion at the lowest force level setting, the force applied by the DF brace increased as a function of flexion angle (slope = 0.7 N/°; p < 0.001) compared to the SF brace effect. Force applied by the SF brace did not significantly change as a function of flexion angle (slope = 0.0 N/°; n.s.). By 45° of flexion, the average force applied by the DF brace (48.1 N) was significantly larger (p < 0.001) than the average force applied by the SF brace (25.0 N). The difference in force continued to increase as flexion angle increased. During stair descent, average force (mean ± standard deviation) at toe off was significantly higher (p = 0.013) for the DF brace (78.7 ± 21.6 N) than the SF brace (37.3 ± 7.2 N). Similar trends were observed for squatting and for the higher force level settings.

CONCLUSIONS

The DF brace applied forces to the posterior proximal tibia that dynamically increased with increased flexion angle. Additionally, the DF brace applied significantly larger forces at higher flexion angles compared to the SF brace where the PCL is known to experience larger in situ forces. Clinical studies are necessary to determine whether the loading characteristics of the DF brace, which more closely replicated the in situ loading profile of the native PCL, results in long-term improved posterior knee laxity following PCL injury.

LEVEL OF EVIDENCE

II.

Clinically relevant biomechanics of the knee capsule and ligaments

The paper describes the concepts of primary and secondary restraints to knee joint stability and explains systematically how the tibia is stabilised against translational forces and rotational torques in different directions and axes, and how those vary across the arc of flexion-extension. It also shows how the menisci act to stabilise the knee, in addition to load carrying across the joint. It compares the properties of the natural stabilising structures with the strength and stiffness of autogenous tissue grafts and relates those strengths to the strength of graft fixation devices. A good understanding of the biomechanical behaviour of these various structures in the knee will help the surgeon in the assessment and treatment of single and multi-ligament injuries.

Biomechanical analysis of simulated clinical testing and reconstruction of the anterolateral ligament of the knee

BACKGROUND

Anatomic anterolateral ligament (ALL) reconstruction has been proposed to assist anterior cruciate ligament (ACL) reconstruction in controlling anterolateral rotational laxity of the knee. However, the biomechanical effects have not been reported.

PURPOSE

(1) To investigate the effect of ALL transection on rotational knee kinematics and (2) to determine the effect on knee biomechanics of ALL reconstruction procedures compared with lateral extra-articular tenodesis (LET).

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 12 cadaveric knee specimens were tested in the following sequence: (1) ACLintact, (2) anteromedial bundle of ACL sectioned (ACLamb), (3) complete ACL sectioned (ACLfull), (4) ALL sectioned (ALLsec), (5) anatomic ALL reconstruction (ALLanat), and (6) LET. Biomechanical anterior drawer and Lachman tests were performed in which a 90-N load was applied to the posterior tibia, and anterior translation was measured. A combined load to simulate the early phase of the pivot-shift test was executed in which a 5-N·m internal rotation moment was applied to a fully extended knee; anterior translation and internal rotation were measured.

RESULTS

Anterior translation increased across conditions for the biomechanical tests. Internal rotation during the simulated early-phase pivot-shift test was significantly different between ACLfull and ALLsec. Anatomic ALL reconstruction did not significantly reduce internal rotation or anterior translation during the simulated early-phase pivot-shift test. After LET, a significant decrease in anterior translation was found. There was no evidence of overconstraint of the knee with either anatomic ALL reconstruction or LET.

CONCLUSION

The ALL demonstrated a role in controlling anterolateral laxity. LET had a composite effect in governing both anterior and rotational laxity. Anatomic ALL reconstruction did not reduce anterolateral rotational laxity.

CLINICAL RELEVANCE

Profiling the biomechanical characteristics of anterolateral reconstruction is integral to understanding the implications and potential benefit of such an additional procedure to ACL reconstruction.