A biomechanical analysis of joint contact forces in the posterior cruciate deficient knee

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.

Walking with a Posterior Cruciate Ligament Injury: A Musculoskeletal Model Study

The understanding of the changes induced in the knee's kinematics by a Posterior Cruciate Ligament (PCL) injury is still rather incomplete. This computational study aimed to analyze how the internal loads are redistributed among the remaining ligaments when the PCL is lesioned at different degrees and to understand if there is a possibility to compensate for a PCL lesion by changing the hamstring's contraction in the second half of the swing phase. A musculoskeletal model of the knee joint was used for simulating a progressive PCL injury by gradually reducing the ligament stiffness. Then, in the model with a PCL residual stiffness at 15%, further dynamic simulations of walking were performed by progressively reducing the hamstring's force. In each condition, the ligaments tension, contact force and knee kinematics were analyzed. In the simulated PCL-injured knee, the Medial Collateral Ligament (MCL) became the main passive stabilizer of the tibial posterior translation, with synergistic recruitment of the Lateral Collateral Ligament. This resulted in an enhancement of the tibial-femoral contact force with respect to the intact knee. The reduction in the hamstring's force limited the tibial posterior sliding and, consequently, the tension of the ligaments compensating for PCL injury decreased, as did the tibiofemoral contact force. This study does not pretend to represent any specific population, since our musculoskeletal model represents a single subject. However, the implemented model could allow the non-invasive estimation of load redistribution in cases of PCL injury. Understanding the changes in the knee joint biomechanics could help clinicians to restore patients' joint stability and prevent joint degeneration.

The Transportal Graft Passage in Transtibial Posterior Cruciate Ligament Reconstruction With a Bone-Patellar Tendon-Bone Graft

Posterior cruciate ligament injury is one of the most common problems in sports medicine. The treatment of choice for this injury is posterior cruciate ligament reconstruction, which improves the biomechanical and clinical stabilities of the knee. There are many graft choices, of which the bone-patellar tendon-bone (BPTB) graft is a popular option. In applying the BPTB graft, most surgeons use the transtibial technique by passing the graft from the tibial tunnel to the femoral tunnel, which is normally performed without problems, but there is a chance of patellar tendon fiber damage because of the sharp turn required from the tibial tunnel to the femoral tunnel. To minimize this risk, herein we propose a transportal graft passage technique with which it is easy to pass the BPTB graft and reduce the risk of graft damage.

Anatomy and Biomechanics of the Posterior Cruciate Ligament and Their Surgical Implications

Knowledge and understanding of the complex anatomy and biomechanical function of the native posterior cruciate ligament (PCL) is vitally important when evaluating PCL injury and possible reconstruction. The PCL has important relationships with the anterior cruciate ligament, menisci, tibial spines, ligament of Humphrey, ligament of Wrisberg, and the posterior neurovascular structures. Through various experimental designs, the biomechanical role of the PCL has been elucidated. The PCL has its most well-defined role as a primary restraint/stabilizer to posterior stress and it seems this role is greatest at higher degrees of knee flexion. The natural history of high-grade deficiency leads to increased contact pressures and degeneration of both the medial and patellofemoral compartments. There is still considerable debate regarding whether high-level athletes can return to sport at the same level with conservative treatment of a high-grade PCL tear, and whether greater laxity in the knee correlates with decreased subjective and objective outcomes. Poor surgical outcomes after PCL reconstruction have been attributed to many factors, the most common of which include: additional intra-articular pathology, poor fixation methods, insufficient knowledge of PCL anatomy, improper tunnel placement, and poor surgical candidates.

Lower Limb Biomechanics During Level Walking After an Isolated Posterior Cruciate Ligament Rupture

Background:

The posterior cruciate ligament (PCL) is an important structure in knee stabilization. Knee cartilage degeneration after a PCL injury has been reported in several studies. Understanding the changes in movement patterns of patients with PCL ruptures could help clinicians make specific treatment protocols to restore patients’ sporting ability and prevent joint degeneration. However, the kinematics and kinetics of the lower limb in patients with PCL injuries are still not clear.

Purpose:

To investigate the biomechanical characteristics during level walking in patients with isolated PCL deficiency.

Study Design:

Controlled laboratory study.

Methods:

Three-dimensional videographic and force plate data were collected for 27 healthy male participants (control group) and 25 male patients with isolated PCL-deficiency (PCL-d group) walking at a constant self-selected speed. Paired and independent t tests were performed to determine the differences between the involved and uninvolved legs in the PCL-d group and between the PCL-d and control groups, respectively.

Results:

Compared with the control leg, both legs in the PCL-d group had smaller knee moments of flexion and internal rotation; greater hip angles of flexion and adduction; greater hip moments of internal rotation; greater ankle angles of extension and adduction; and smaller ankle moments of flexion, adduction, and internal rotation. Moreover, compared with the uninvolved leg in the PCL-d group, the involved leg in the PCL-d group had significantly smaller knee extension angles and moments during the terminal stance phase, greater hip external rotation angles and extension moments, and smaller ankle adduction angles and flexion moments.

Conclusion:

PCL ruptures altered walking patterns in both the involved and uninvolved legs, which could affect alignment of the lower limb and loading on the knee, hip, and ankle joints. Patients with PCL injuries adapted their hip and ankle to maintain knee stability.

Clinical Relevance:

The kinematic and kinetic adaptations in the knee, hip, and ankle after a PCL rupture during level walking are likely to be a compensatory strategy for knee instability. The results of this study suggest that these adaptations should be considered in the treatment of patients with PCL ruptures.

Biomechanical evaluation of PCL reconstruction with suture augmentation

PURPOSE

The purpose of this study was to compare kinematics and patellofemoral contact pressures of all inside and transtibial single bundle PCL reconstructions and determine if suture augmentation further improves the biomechanics of either technique.

METHODS

Cadaveric knees were tested with a posterior drawer force, and varus, valgus, internal and external moments at 30, 60, 90, and 120° of flexion. Displacement, rotation, and patellofemoral contact pressures were compared between: Intact, PCL-deficient, All-Inside PCL reconstruction with (AI-SA) and without (AI) suture augmentation, and transtibial PCL reconstruction with (TT-SA) and without (TT) suture augmentation.

RESULTS

Sectioning the PCL increased posterior tibial translation (PTT) from intact at 60° to 120° of flexion, p < 0.001. AI PCL reconstruction improved stability from the deficient-state but had greater PTT than intact at 90° of flexion, p < 0.05. Adding suture augmentation to the AI reconstruction further reduced PTT to levels that were not statistically different from intact at all flexion angles. TT reconstructed knees had greater PTT than intact knees at 60, 90, and 120° of flexion, p < 0.01. Adding suture augmentation (TT-SA) improved posterior stability to PTT levels that were not statistically different from intact knees at 30, 60, and 120° of flexion. Patellofemoral pressures were highest in PCL-deficient knees at increased angles of flexion and were reduced after reconstruction, but this was not significant.

CONCLUSION

In this time-zero study, both the all-inside and transtibial single bundle PCL reconstructions effectively reduce posterior translation from the deficient-PCL state. In addition, suture augmentation of both techniques provided further anterior-posterior stability.

Modified tibial tunnel placement for single-bundle posterior cruciate ligament reconstruction reduces the "Killer Turn" in a biomechanical model

BACKGROUND

Our previous three-dimensional finite element analysis found that posterior cruciate ligament (PCL) reconstruction in the modified tibial tunneling placement (MTT, 10 mm inferior and 5 mm lateral to the PCL anatomical insertion) could reduce the peak stress of the graft and may reduce the killer turn. The purpose of the current study was to compare the biomechanical results between MTT and traditional tibial tunneling technique (TTT, PCL anatomical insertion) during transtibial PCL reconstruction.

METHODS

Fifty-six 3D-printed tibia models and fresh mature porcine flexor digitorum tendons were studied. The PCL reconstruction specimens were randomly divided into TTT group and MTT group based on tibial tunnel placement. A 50 to 300 N cyclic loading was applied using a material testing system. Each specimen completed 2000 cycles at a rate of 200 mm/min and a loading frequency of 80 cycles/min. Load-displacement curves, failure mode, and graft displacement were recorded. Mean maximum contact pressure was measured using a pressure-sensitive film. After cyclic loading test, the surviving grafts were randomly assigned to load-to-failure group or Scanning Electron Microscopy (SEM) group. Ultimate failure load and the appearance of graft abrasion were recorded and analyzed.

RESULT

During the cyclic loading test, 3 samples in the TTT group, and 2 in the MTT group were excluded because of the graft pullout during the test. Mean maximum contact pressure of killer turn was 9.30 ± 0.29 MPa in the TTT group and 7.27 ± 0.25 MPa in MTT group (P < .05). Mean graft displacement was 4.54 ± 0.23 mm in the TTT group and 3.37 ± 3.56 mm in the MTT group (P < .05). Maximum failure load was 1886.0 ± 41.83 N in the TTT group and 2019.30 ± 20.10 N in the MTT group (P < .05). The SEM analysis showed heavy abrasion and fiber discontinuity in graft in the TTT group, while it showed slight abrasion and fiber arrangement disorders in the MTT group.

CONCLUSIONS

The MTT PCL reconstruction significantly reduced stress concentration and graft abrasion as compared with the TTT PCL reconstruction, and it may be a better choice for the reduction of "killer Turn" effect during transtibial PCL construction.

Posterior cruciate ligament injury is influenced by intercondylar shape and size of tibial eminence

AIMS

Little is known about the risk factors that predispose to a rupture of the posterior cruciate ligament (PCL). Identifying risk factors is the first step in trying to prevent a rupture of the PCL from occurring. The morphology of the knee in patients who rupture their PCL may differ from that of control patients. The purpose of this study was to identify any variations in bone morphology that are related to a PCL.

PATIENTS AND METHODS

We compared the anteroposterior (AP), lateral, and Rosenberg view radiographs of 94 patients with a ruptured PCL to a control group of 168 patients matched by age, sex, and body mass index (BMI), but with an intact PCL after a knee injury. Statistical shape modelling software was used to assess the shape of the knee and determine any difference in anatomical landmarks.

RESULTS

We found shape variants on the AP and Rosenberg view radiographs to be significantly different between patients who tore their PCL and those with an intact PCL after a knee injury. Overall, patients who ruptured their PCL have smaller intercondylar notches and smaller tibial eminences than control patients.

CONCLUSION

This study shows that differences in the shape of the knee are associated with the presence of a PCL rupture after injury. A smaller and more sharply angled intercondylar notch and a more flattened tibial eminence are related to PCL rupture. This suggests that the morphology of the knee is a risk factor for sustaining a PCL rupture. Cite this article: Bone Joint J 2019;101-B:1058-1062.

The Biomechanics of Multiligament Knee Injuries: From Trauma to Treatment

The multiple ligament injured knee is a complex biomechanical environment. When primary stabilizers fail, secondary stabilizers have an increased role. In addition, loss of primary restraints puts undue stress on the remaining intact structures of the knee. Treatment of these injuries requires accurate diagnosis of all injured structures, and careful consideration of repairs and reconstructions that restore the synergistic stability of all ligaments in the knee.

Degenerative changes after posterior cruciate ligament reconstruction are irrespective of posterior knee stability: MRI-based long-term results

INTRODUCTION

Posterior cruciate ligament reconstruction (PCLR) is advocated to prevent an early onset of osteoarthritis. We hypothesized that posterior instability after PCLR correlates with degenerative changes.

MATERIALS AND METHODS

MRIs of 42 (12 female/30 male; 39 ± 9 years) patients were enrolled with a minimum 5-year follow-up (FFU) after PCLR. In addition, 25 contralateral and 15 follow-up MRIs (12 months after baseline) were performed. Degenerative changes were graded using WORMS. Posterior tibial translation (PTT) was measured using posterior stress radiographs. Outcome parameters included WORMS/cartilage subscore for the whole joint, patellofemoral (PFJ), medial (MFTJ), and lateral femorotibial joint (LFTJ).

RESULTS

Final follow-up was 101 (range 68-168) months. WORMS reached 41.5 [18.5-56.8]. Regional WORMS for PFJ was significantly higher than MFTJ and LFTJ. Cartilage subscore yielded 7 [2.8-15]. MFTJ and PFJ were significantly higher than LFTJ. Primary outcome parameters were significantly higher than the contralateral knee (P < 0.0001) and significantly increased within 12 months (P = 0.0002). There was a significant correlation between the intraoperative degree of cartilage injury and WORMS (P < 0.0001 with r = 0.64) and between the number of previous surgery and the cartilage subscore (P = 0.03 with r = 0.32). Meniscal surgery led to a significantly higher WORMS (P = 0.035). Combined risk models revealed that women below the mean age had significantly lower WORMS (P = 0.001) and cartilage subscores (P = 0.003).

CONCLUSIONS

Patients undergo degenerative changes after PCLR, which are significantly higher compared to the contralateral knee. These occur predominantly at PFJ/MFTJ and are irrespective of posterior stability. Concomitant meniscus/cartilage injuries and a high number of previous surgeries are further risk factors.

The effect of constitutive representations and structural constituents of ligaments on knee joint mechanics

Ligaments provide stability to the human knee joint and play an essential role in restraining motion during daily activities. Compression-tension nonlinearity is a well-known characteristic of ligaments. Moreover, simpler material representations without this feature might give reasonable results because ligaments are primarily in tension during loading. However, the biomechanical role of different constitutive representations and their fibril-reinforced poroelastic properties is unknown. A numerical knee model which considers geometric and material nonlinearities of meniscus and cartilages was applied. Five different constitutive models for the ligaments (spring, elastic, hyperelastic, porohyperelastic, and fibril-reinforced porohyperelastic (FRPHE)) were implemented. Knee joint forces for the models with elastic, hyperelastic and porohyperelastic properties showed similar behavior throughout the stance, while the model with FRPHE properties exhibited lower joint forces during the last 50% of the stance phase. The model with ligaments as springs produced the lowest joint forces at this same stance phase. The results also showed that the fibril network contributed substantially to the knee joint forces, while the nonfibrillar matrix and fluid had small effects. Our results indicate that simpler material models of ligaments with similar properties in compression and tension can be used when the loading is directed primarily along the ligament axis in tension.

Multiple looping technique for tibial fixation in posterior cruciate ligament reconstruction using free tendon Achilles allograft

PURPOSE

This study was conducted to evaluate case series outcomes of a new tibial fixation technique using a free tendon graft during posterior cruciate ligament (PCL) reconstruction which is less affected by tibial metaphysis bone density.

METHODS

Thirty-two subjects underwent single-bundle PCL reconstruction using a free tendon Achilles allograft. The graft was looped to be double stranded. The free ends of the graft were fixed to the femoral side using suture washer, and the looped end was fixed to the tibial side using the multiple looping technique. Range of motion of the knee and side-to-side difference were assessed at the last follow-up. The Lysholm Knee score was evaluated preoperatively and at the last follow-up. The Tegner Activity Scale score was evaluated before injury and at the last follow-up.

RESULTS

Twenty-eight subjects were followed up for at least 18 months. Mean follow-up was 27.7 ± 4.8 months. All subjects showed normal range of motion at the last follow-up. The mean side-to-side difference was 10.4 ± 2.8 mm preoperatively and 2.3 ± 1.8 mm at the last follow-up (p < 0.001). The mean Lysholm Knee score was 58 ± 9 preoperatively and 91 ± 5 at the last follow-up (p < 0.001). The median Tegner Activity Scale score was 7 (range 5-9) before injury and 6 (range 4-8) at the last follow-up (p = 0.001).

CONCLUSIONS

The multiple looping technique for tibial fixation resulted in satisfactory outcomes from single-bundle PCL reconstruction without any significant complications.

LEVEL OF EVIDENCE

Therapeutic case series, Level IV.

The effect of a dynamic PCL brace on patellofemoral compartment pressures in PCL-and PCL/PLC-deficient knees

Background

The natural history of posterior cruciate ligament (PCL) deficiency includes the development of arthrosis in the patellofemoral joint (PFJ). The purpose of this biomechanical study was to evaluate the hypothesis that dynamic bracing reduces PFJ pressures in PCL- and combined PCL/posterolateral corner (PLC)-deficient knees. Study Design: Controlled Laboratory Study.

Methods

Eight fresh frozen cadaveric knees with intact cruciate and collateral ligaments were included. PFJ pressures and force were measured using a pressure mapping system via a lateral arthrotomy at knee flexion angles of 30°, 60°, 90°, and 120° in intact, PCL-deficient, and PCL/PLC-deficient knees under a combined quadriceps/hamstrings load of 400 N/200 N. Testing was then repeated in PCL- and PCL/PLC-deficient knees after application of a dynamic PCL brace.

Results

Application of a dynamic PCL brace led to a reduction in peak PFJ pressures in PCL-deficient knees. In addition, the brace led to a significant reduction in peak pressures in PCL/PLC-deficient knees at 60°, 90°, and 120° of flexion. Application of the dynamic brace also led to a reduction in total PFJ force across all flexion angles for both PCL- and PCL/PLC-deficient knees.

Conclusion

Dynamic bracing reduces PFJ pressures in PCL- and combined PCL/PLC-deficient knees, particularly at high degrees of knee flexion.

Distinctions of introarticular force distribution between genesis-II posterior stabilized and cruciate retaining total knee arthroplasty: An intraoperative comparative study of 45 patients

BACKGROUND

Although both the posterior stabilized and cruciate retaining total knee arthroplasty have been proven to effectively relieve pain and restore basic functions, the joint gap width during flexion was reported to be different due to the presence or absence of posterior cruciate ligament, which may lead to different intra-articular force distribution. In this study, we investigated the distinctions in intra-articular force distribution between the two types of TKA designs in patients with varus knee osteoarthritis.

METHODS

Forty five patients (50 knees) with varus knee osteoarthritis were prospectively included, with each 25 knees receiving cruciate retaining and posterior stabilized total knee arthroplasty, respectively. With an intra-articular force measurement system, the intra-articular force distribution with knee flexion at 0°, 30°, 45°, 60°, 90°, and 120° were recorded in all patients.

FINDINGS

The total force was similar for posterior stabilized and cruciate retaining knees at all flexion degrees. However, force in the medial compartment accounted for 59.8%-84.0% of total force in posterior stabilized knees, while 27.4%-65.7% in cruciate retaining knees. In cruciate retaining knees, no significant difference was found between forces in the two compartments at 30° flexion (P=0.444), but force was significantly concentrated in the lateral side during 45°-120° flexion (P=0.000-0.028).

INTERPRETATION

Although the entire intra-articular forces were similar between CR and PS knees at different flexion angles, medial part had higher force than lateral part when PS knee was used. The posterior cruciate ligament do a role in soft balance, and make the force more evenly distributed.

The effects of posterior cruciate ligament deficiency on posterolateral corner structures under gait- and squat-loading conditions: A computational knee model

Objectives

The aim of the current study was to analyse the effects of posterior cruciate ligament (PCL) deficiency on forces of the posterolateral corner structure and on tibiofemoral (TF) and patellofemoral (PF) contact force under dynamic-loading conditions.

Methods

A subject-specific knee model was validated using a passive flexion experiment, electromyography data, muscle activation, and previous experimental studies. The simulation was performed on the musculoskeletal models with and without PCL deficiency using a novel force-dependent kinematics method under gait- and squat-loading conditions, followed by probabilistic analysis for material uncertain to be considered.

Results

Comparison of predicted passive flexion, posterior drawer kinematics and muscle activation with experimental measurements showed good agreement. Forces of the posterolateral corner structure, and TF and PF contact forces increased with PCL deficiency under gait- and squat-loading conditions. The rate of increase in PF contact force was the greatest during the squat-loading condition. The TF contact forces increased on both medial and lateral compartments during gait-loading conditions. However, during the squat-loading condition, the medial TF contact force tended to increase, while the lateral TF contact forces decreased. The posterolateral corner structure, which showed the greatest increase in force with deficiency of PCL under both gait- and squat-loading conditions, was the popliteus tendon (PT).

Conclusion

PCL deficiency is a factor affecting the variability of force on the PT in dynamic-loading conditions, and it could lead to degeneration of the PF joint.

Cite this article: K-T. Kang, Y-G. Koh, M. Jung, J-H. Nam, J. Son, Y.H. Lee, S-J. Kim, S-H. Kim. The effects of posterior cruciate ligament deficiency on posterolateral corner structures under gait- and squat-loading conditions: A computational knee model. Bone Joint Res 2017;6:31–42. DOI: 10.1302/2046-3758.61.BJR-2016-0184.R1.

Is the all-arthroscopic tibial inlay double-bundle PCL reconstruction a viable option in multiligament knee injuries?

BACKGROUND

All-arthroscopic tibial inlay double-bundle (DB) posterior cruciate ligament (PCL) reconstruction avoids an open dissection and the "killer turn" while maintaining the advantage of an anatomic graft. However, clinical data on the viability of this surgical technique in multiligamentous knee injuries are lacking.

QUESTIONS/PURPOSES

At greater than 2 years of followup, we evaluated (1) validated outcomes scores; (2) range of motion; and (3) side-to-side stability on PCL stress radiographs of a small group of patients who underwent all-arthroscopic tibial inlay DB PCL reconstruction in multiligamentous knee injuries, either shortly after injury or late.

METHODS

All patients sustaining an operative multiligamentous knee injury between August 2007 and March 2009 underwent PCL reconstruction with the all-arthroscopic tibial inlay DB PCL reconstruction. Twelve patients sustained such injuries and were reconstructed during the study period and all 12 returned for followup with a minimum of 2 years (mean 3 ± 0.8 years). There were nine males and three females, with a mean age of 30 years; four patients had a subacute reconstruction (≥ 3 weeks, but < 3 months), and eight patients had chronic reconstructions (> 3 months). Mean time from injury to PCL reconstruction was 7 ± 12 months. Demographics, ROM, outcome scores (Lysholm and International Knee Documentation Committee [IKDC] scores), and PCL stress views were obtained.

RESULTS

At final followup, mean Lysholm and IKDC subjective scores were 79 ± 16 and 72 ± 19, respectively. IKDC objective scores included eight nearly normal knees, three abnormal knees, and one severely abnormal knee. Mean flexion and extension losses compared with the contralateral were 10 ± 9 and 1 ± 2, respectively. Mean ± SD final side-to-side difference on PCL stress radiographs was 5 ± 3 mm.

CONCLUSIONS

The clinical and radiographic results of the all-arthroscopic tibial inlay DB PCL reconstruction appear comparable to the same technique in isolated PCL injuries and, based on similar published case series, comparable to results of multiligamentous knee reconstructions using other PCL reconstruction techniques.

LEVEL OF EVIDENCE

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

Surgical management of PCL injuries: indications, techniques, and outcomes

The ideal treatment for posterior cruciate ligament (PCL) injuries is controversial and remains an active area of orthopedic research. The indications for surgery and the ideal method of reconstruction continue to be evaluated in biomechanical and clinical studies. Recent research has provided information on the anatomy and biomechanics of the PCL, and the merits and drawbacks of the transtibial compared with the tibial inlay technique, the use of single vs double-bundle reconstruction, and different graft options for reconstruction. This review discusses important factors in the surgical treatment of PCL injuries, with attention to the most current literature on these topics.

Arthroscopic transtibial single-bundle posterior cruciate ligament reconstruction using patellar tendon graft compared with hamstring tendon graft

PURPOSE

The purpose of this study was to compare the outcomes of arthroscopic transtibial single-bundle posterior cruciate ligament reconstruction using autologous patellar tendon and hamstring tendon grafts.

METHODS

From 1998 to 2007, 59 patients with symptomatic isolated posterior cruciate ligament injury were included in this retrospective study. Twenty-five knees were reconstructed using bone-patellar tendon-bone graft, and 34 knees were reconstructed using hamstring graft. In both groups, surgical techniques were similar, except material of fixation screws. Patients were evaluated pre-operatively and post-operatively at the latest follow-up with several parameters, including symptoms, physical examination, outcome satisfaction, functional scores, radiography and complications.

RESULTS

Average follow-up period was 51.6 months in patellar tendon group and 51.1 months in hamstring tendon group. Significantly more kneeling pain (32 vs. 3 %), squatting pain (24 vs. 3 %), anterior knee pain (36 vs. 3 %), posterior drawer laxity and osteoarthritic change were shown in patellar tendon group than in hamstring tendon group post-operatively. No significant differences were found in other parameters between both groups.

CONCLUSIONS

Several shortcomings, including anterior knee pain, squatting pain, kneeling pain and osteoarthritic change, have to be concerned when using patellar tendon autograft. In conclusion, hamstring tendon autograft may be a better choice for transtibial tunnel PCL reconstruction.

A review of the anatomical, biomechanical and kinematic findings of posterior cruciate ligament injury with respect to non-operative management

An understanding of the kinematics of posterior cruciate ligament (PCL) deficiency is important for the diagnosis and management of patients with isolated PCL injury. The kinematics of PCL injury has been analysed through cadaveric and in vivo imaging studies. Cadaveric studies have detailed the anatomy of the PCL. It consists of two functional bundles, anterolateral and posteromedial, which exhibit different tensioning patterns through the arc of knee flexion. Isolated sectioning of the PCL and its related structures in cadaveric specimens has defined its primary and secondary restraining functions. The PCL is the primary restraint to posterior tibia translation above 30° and is a secondary restraint below 30° of knee flexion. Furthermore, sectioning of the PCL produces increased chondral deformation forces in the medial compartment as the knee flexes. However, the drawback of cadaveric studies is that they can not replicate the contribution of surrounding neuromuscular structures to joint stability that occurs in the clinical setting. To address this, there have been in vivo studies that have examined the kinematics of the PCL deficient knee using imaging modalities whilst subjects perform dynamic manoeuvres. These studies demonstrate significant posterior subluxation of the medial tibia as the knee flexes. The results of these experimental studies are in line with clinical consequences of PCL deficiency. In particular, arthroscopic evaluation of subjects with isolated PCL injuries demonstrate an increased incidence of chondral lesions in the medial compartment. Yet despite the altered kinematics with PCL injury only a minority of patients require surgery for persistent instability and the majority of athletes are able to return to sport following a period of non-operative rehabilitation. Specifically, non-operative management centres on a programme of quadriceps strengthening and hamstring inhibition to minimise posterior tibial load. The mechanism behind the neuromuscular adaptation that allows the majority of athletes to return to sport has been investigated but not clearly elucidated. The purpose of this review paper is to draw together the findings of experimental studies on the anatomical and kinematic effects of PCL injury and summarise their relevance with respect to non-operative management and functional outcome in patients with isolated PCL deficiency.

Evaluation and management of posterior cruciate ligament injuries

BACKGROUND

Posterior cruciate ligament injuries are increasingly recognized, the result of various sports activities, and while most athletes return to sports the development degenerative joint changes is common.

OBJECTIVE

To provide a synopsis of the current best evidence regarding the recognition and treatment of posterior cruciate ligament injuries.

DESIGN

Structured narrative review.

METHODS

Keyword search of Medline, CINAHL, and PEDro databases for studies published in English from January 1975 to July 2011. Additionally, the reference lists from articles obtained were manually searched for relevant literature.

SUMMARY

The manuscript provides an overview of posterior cruciate ligament injury, discusses diagnostic methods to include radiographic examination techniques, and presents information on surgical and conservative management of PCL injuries.

CONCLUSION

Understanding the mechanism of injuries and most effective examination methods can aide in effective early recognition of PCL injuries. Appropriate management of the patient with PCL deficiency or reconstructed knee will optimize outcomes and potentially affect long term knee function.

MRI-based modeling for radiocarpal joint mechanics: validation criteria and results for four specimen-specific models

The objective of this study was to validate the MRI-based joint contact modeling methodology in the radiocarpal joints by comparison of model results with invasive specimen-specific radiocarpal contact measurements from four cadaver experiments. We used a single validation criterion for multiple outcome measures to characterize the utility and overall validity of the modeling approach. For each experiment, a Pressurex film and a Tekscan sensor were sequentially placed into the radiocarpal joints during simulated grasp. Computer models were constructed based on MRI visualization of the cadaver specimens without load. Images were also acquired during the loaded configuration used with the direct experimental measurements. Geometric surface models of the radius, scaphoid and lunate (including cartilage) were constructed from the images acquired without the load. The carpal bone motions from the unloaded state to the loaded state were determined using a series of 3D image registrations. Cartilage thickness was assumed uniform at 1.0 mm with an effective compressive modulus of 4 MPa. Validation was based on experimental versus model contact area, contact force, average contact pressure and peak contact pressure for the radioscaphoid and radiolunate articulations. Contact area was also measured directly from images acquired under load and compared to the experimental and model data. Qualitatively, there was good correspondence between the MRI-based model data and experimental data, with consistent relative size, shape and location of radioscaphoid and radiolunate contact regions. Quantitative data from the model generally compared well with the experimental data for all specimens. Contact area from the MRI-based model was very similar to the contact area measured directly from the images. For all outcome measures except average and peak pressures, at least two specimen models met the validation criteria with respect to experimental measurements for both articulations. Only the model for one specimen met the validation criteria for average and peak pressure of both articulations; however the experimental measures for peak pressure also exhibited high variability. MRI-based modeling can reliably be used for evaluating the contact area and contact force with similar confidence as in currently available experimental techniques. Average contact pressure, and peak contact pressure were more variable from all measurement techniques, and these measures from MRI-based modeling should be used with some caution.

PRELIMINARY VALIDATION OF MRI-BASED MODELING FOR EVALUATION OF JOINT MECHANICS

The objective of this study was to perform preliminary validation of MRI-based joint contact modeling methodology in the radiocarpal joints by comparison with the results of invasive radiocarpal contact measurements in three cadaver experiments. For each experiment, either Pressurex film or a Tekscan sensor was placed into the radiocarpal joints during a simulated grasp. Computer models were based on magnetic resonance imaging (MRI) of the cadaver specimens without load as well as on images acquired with the same loading used for the direct measurements. Geometric surface models of the radius, scaphoid, and lunate (including cartilage) were constructed from the images acquired without load. The carpal bone motions from the unloaded to the loaded state were determined using three-dimensional (3D) voxel image registration. Cartilage thickness was assumed to be uniform at 1.0 mm with an effective compressive modulus of 4 MPa. Resulting data included peak contact pressure, contact area, and contact force in the radioscaphoid and radiolunate joints. Contact area was also measured directly from MR images acquired with load and compared to model data. Qualitatively, there was good correspondence between the MRI-based model data and experimental data, with consistent relative size, shape, and location of radioscaphoid and radiolunate contact areas. Quantitative comparison of model and experimental data was reasonable, but less consistent. Contact area from the MRI-based model was always similar to the contact area measured directly from the MR images. With additional experiments, we believe that MRI-based joint contact modeling will soon be fully validated in the radiocarpal joints.

Clinical results of arthroscopic single-bundle transtibial posterior cruciate ligament reconstruction: a systematic review

BACKGROUND

Reconstruction of the posterior cruciate ligament has traditionally been performed using an arthroscopically assisted single-bundle transtibial technique. Unfortunately, clinical studies evaluating this procedure are rare. In addition, there are no pooled analyses evaluating the effectiveness of this procedure for isolated posterior cruciate ligament tears.

HYPOTHESIS

Patients who undergo arthroscopically assisted, single-bundle, transtibial posterior cruciate ligament reconstruction will exhibit subjective improvement in knee function despite persistent objective knee laxity.

STUDY DESIGN

Systematic review.

METHODS

A structured literature search was performed to identify those clinical studies assessing the results of an arthroscopically assisted single-bundle transtibial posterior cruciate ligament reconstruction for isolated posterior cruciate ligament tears. The published data meeting the inclusion criteria were systematically reviewed with an emphasis on residual posterior laxity, subjective and objective functional outcome, activity level, patient satisfaction, incidence of osteoarthritis, and postoperative complications.

RESULTS

A total of 10 studies were identified that met the inclusion criteria. Mean postoperative instrumented posterior knee laxity varied from 1.96 mm to 5.90 mm, which was considerably improved from preoperative values (range, 8.38-12.3 mm). The range of mean values of the Lysholm knee scores was 81 to 100 points. The overall International Knee Documentation Committee rating was categorized as "normal" or "nearly normal" in 75% of patients and the mean Tegner activity score varied from 4.7 to 6.3 points. Degenerative osteoarthritis was frequently noted at the time of the most recent follow-up. There were few complications reported.

CONCLUSION

Arthroscopically assisted single-bundle transtibial posterior cruciate ligament reconstruction for isolated posterior cruciate ligament tears can improve posterior knee laxity by 1 grade, although this procedure does not reliably restore normal knee stability. Return to recreational and athletic activity was predictable, with 75% of patients exhibiting a normal or nearly normal objective outcome, although degenerative osteoarthritis was not prevented by this procedure.

Posterior cruciate ligament deficiency: biomechanical and biological consequences and the outcomes of conservative treatment. A systematic review

The objective of the study was to evaluate the biomechanical and biological consequences of posterior cruciate ligament deficiency, determine compensatory mechanisms and assess the efficacy of non-operative treatment. Medline, CINAHL, SPORTdiscus, Cochrane Central Register of Controlled Trials and the Cochrane Database of Systematic Reviews were searched at 30th October 2006 for the terms "PCL" and "posterior cruciate ligament" both independently and including the terms "injury", "deficiency" and "insufficiency". Literature searches identified 598 potentially relevant articles, after exclusions there were 47 articles that fulfilled the inclusion criteria: 30 articles analyzing PCL deficiency and 17 studies on the outcomes for non-operative treatment. The authors reviewed all selected articles and abstracted data into predetermined tables depending upon classification. Studies indicate that posterior cruciate ligament deficiency results in posterior tibial translation with combined injuries displaying greater laxity. Results were inconsistent for rotational stability but deficiency increases joint contact pressure and may result in articular damage. A loss of proprioception occurs but the effect on strength and kinetics is inconclusive. There is a lack of evidence for compensatory muscle activity. Return to activity is possible for the majority of non-operatively treated grade I and II isolated injuries. Comparative analysis was not possible in many instances due to study design or experimental protocols. Further research is required to establish the compensatory mechanisms stabilizing the posterior cruciate ligament deficient knee and to investigate the outcomes for non-operatively treated patients.

Importance of tibial slope for stability of the posterior cruciate ligament deficient knee

BACKGROUND

Previous studies have shown that increasing tibial slope can shift the resting position of the tibia anteriorly. As a result, sagittal osteotomies that alter slope have recently been proposed for treatment of posterior cruciate ligament (PCL) injuries.

HYPOTHESES

Increasing tibial slope with an osteotomy shifts the resting position anteriorly in a PCL-deficient knee, thereby partially reducing the posterior tibial "sag" associated with PCL injury. This shift in resting position from the increased slope causes a decrease in posterior tibial translation compared with the PCL-deficient knee in response to posterior tibial and axial compressive loads.

STUDY DESIGN

Controlled laboratory study.

METHODS

Three knee conditions were tested with a robotic universal force-moment sensor testing system: intact, PCL-deficient, and PCL-deficient with increased tibial slope. Tibial slope was increased via a 5-mm anterior opening wedge osteotomy. Three external loading conditions were applied to each knee condition at 0 degrees, 30 degrees, 60 degrees, 90 degrees, and 120 degrees of knee flexion: (1) 134-N anterior-posterior (A-P) tibial load, (2) 200-N axial compressive load, and (3) combined 134-N A-P and 200-N axial loads. For each loading condition, kinematics of the intact knee were recorded for the remaining 5 degrees of freedom (ie, A-P, medial-lateral, and proximal-distal translations, internal-external and varus-valgus rotations).

RESULTS

Posterior cruciate ligament deficiency resulted in a posterior shift of the tibial resting position to 8.4 +/- 2.6 mm at 90 degrees compared with the intact knee. After osteotomy, tibial slope increased from 9.2 degrees +/- 1.0 degrees in the intact knee to 13.8 degrees +/- 0.9 degrees. This increase in slope reduced the posterior sag of the PCL-deficient knee, shifting the resting position anteriorly to 4.0 +/- 2.0 mm at 90 degrees. Under a 200-N axial compressive load with the osteotomy, an additional increase in anterior tibial translation to 2.7 +/- 1.7 mm at 30 degrees was observed. Under a 134-N A-P load, the osteotomy did not significantly affect total A-P translation when compared with the PCL-deficient knee. However, because of the anterior shift in resting position, there was a relative decrease in posterior tibial translation and increase in anterior tibial translation.

CONCLUSION

Increasing tibial slope in a PCL-deficient knee reduces tibial sag by shifting the resting position of the tibia anteriorly. This sag is even further reduced when the knee is subjected to axial compressive loads.

CLINICAL RELEVANCE

These data suggest that increasing tibial slope may be beneficial for patients with PCL-deficient knees.

The role of the high tibial osteotomy in the unstable knee

High tibial osteotomy is an accepted treatment option for knee arthrosis in association with coronal malalignment. However, the effect of this procedure on the sagittal balance of the knee has until recently been largely ignored. Basic science research over the past several years and some small clinical series have introduced a "novel" concept whereby the sagittal balance of a ligament deficient knee can be restored to some degree by altering the posterior tibial slope. This review summarizes the available evidence supporting the role of selective high tibial osteotomy in the treatment of both the acute and chronic ligament deficient knee.

Anatomical posterior cruciate ligament transplantation: a biomechanical analysis

BACKGROUND

Although current techniques of posterior cruciate ligament reconstruction may successfully stabilize the posterior cruciate ligament-deficient knee, no studies have demonstrated restoration of intact-knee kinematics.

HYPOTHESIS

Posterior cruciate ligament transplantation will successfully restore posterior stability and kinematics to the posterior cruciate ligament-deficient knee.

STUDY DESIGN

Controlled laboratory study.

METHODS

Seven pairs (donor/recipient) of size-matched cadaveric knees underwent a novel technique for posterior cruciate ligament transplantation. The grafts were fixed at the femoral origin and tibial insertion using an inlay technique with rigid fixation. The knees were tested in the intact (intact group), posterior cruciate ligament-deficient (deficient group), and posterior cruciate ligament-transplanted (transplant group) states. A 3-dimensional electromagnetic tracking system during an active knee extension and passive knee flexion maneuver was used to quantify kinematics, specifically looking at femoral rollback. KT ligament arthrometry was used to quantify posterior stability at the quadriceps neutral angle (70 degrees ).

RESULTS

For femoral rollback, the intact versus deficient groups was significantly different (P = .045) as was deficient versus transplant groups (P = .008) but not intact versus transplant groups. Similar differences were noted with the measurements of posterior stability (P < .001). Total posterior laxity between the intact versus deficient groups was significantly different (means, 1.32 mm vs 11.1 mm; P < .0001), as was deficient versus transplant groups (means, 11.1 mm vs 2.04 mm; P < .126) but not intact versus transplant groups.

CONCLUSION

In a posterior cruciate ligament-deficient cadaveric model, we demonstrated the technical feasibility and efficacy of posterior cruciate ligament transplantation for restoring femoral rollback and posterior stability at the quadriceps neutral angle.

CLINICAL RELEVANCE

Future studies in posterior cruciate ligament reconstruction should not only address stability but also restoration of normal knee kinematics in assessing the success of a given technique.

Injuries of the posterior cruciate ligament and posterolateral corner of the knee

Injuries of the posterior cruciate ligament (PCL) and posterolateral corner (PLC) of the knee are less common than those of the anterior cruciate ligament (ACL) and their significance is often under-appreciated in the acute setting. Even when recognised, knowledge of the natural history and outcome of treatment has lagged behind that of the ACL and has led to confusion over the indications for operative treatment. Recent developments in the understanding of the anatomy and biomechanics of this area of the knee have led to improvements in management and a renewed interest in these potentially disabling injuries. The aim of this review is to bring the trauma generalist abreast of these recent developments and to improve diagnosis through a heightened index of suspicion and use of appropriate special investigations. The principles of management of both isolated and combined injuries to the PCL and PLC, in the acute and chronic settings, are described.

Neuromuscular and biomechanical adaptations of patients with isolated deficiency of the posterior cruciate ligament

BACKGROUND

Functional adaptations of patients with posterior cruciate ligament deficiency (grade II) are largely unknown despite increased recognition of this injury.

HYPOTHESIS

Posterior cruciate ligament-deficient subjects (grade II, 6- to 10-mm bilateral difference in posterior translation) will present with neuromuscular and biomechanical adaptations to overcome significant mechanical instability during gait and drop-landing tasks.

STUDY DESIGN

Controlled laboratory study.

METHODS

Bilateral comparisons were made among 10 posterior cruciate ligament-deficient subjects using radiographic, instrumented laxity, and range of motion examinations. Biomechanical and neuromuscular characteristics of the involved limb of the posterior cruciate ligament-deficient subjects were compared to their uninvolved limb and to 10 matched control subjects performing gait and drop-landing tasks.

RESULTS

Radiographic (15.3 +/- 2.9 to 5.6 +/- 3.7 mm; P = .008) and instrumented laxity (6.3 +/- 2.0 to 1.4 +/- 0.5 mm; P < .001) examinations demonstrated significantly greater posterior displacement of the involved knee within the posterior cruciate ligament-deficient group. The posterior cruciate ligament-deficient group had a significantly decreased maximum knee valgus moment and greater vertical ground reaction force at midstance during gait compared to the control group. During vertical landings, the posterior cruciate ligament-deficient group demonstrated a significantly decreased vertical ground reaction force loading rate. All other analyses reported no significant differences within or between groups.

CONCLUSION

Posterior cruciate ligament-deficient subjects demonstrate minimal biomechanical and neuromuscular differences despite significant clinical laxity.

CLINICAL RELEVANCE

The findings of this study indicate that individuals with grade II posterior cruciate ligament injuries are able to perform gait and drop-landing activities similar to a control group without surgical intervention.

Imaging evaluation of the postoperative knee ligaments

Until the advent of magnetic resonance imaging (MRI), evaluation of ligament reconstruction of the knee was largely based on clinical examination and radiographs. MRI is the modality of choice for noninvasive evaluation of reconstructed ligaments, menisco-capsular structures and soft tissues. This article reviews the surgical techniques, normal and abnormal appearances of the ACL and PCL grafts and common complications following ligament reconstruction.

Osteoarthritis after Sports Knee Injuries

Recent advances in the knowledge of tissue homeostasis, including the tissue homeostasis theory and the envelope of function theory as proposed by Dye, have greatly increased our knowledge of the pathophysiology of osteoarthrosis after sports knee injuries. The development of these two theories has not only advanced our understanding of the treatment and prevention of osteoarthrosis after acute injuries to the knee, but has also given us guidance as to directions for future research.

Joint contact characteristics in agility total ankle arthroplasty

High component contact pressures in total joint prostheses can lead to particle wear debris and prosthesis loosening. The contact pressures in the Agility total ankle prosthesis have not been investigated. In the current study, a cadaveric model was used to evaluate contact characteristics (average contact area, contact pressure, and contact peak pressures) for the Agility total ankle system. Ten cadaveric specimens were implanted with the Agility total ankle and axially loaded to 700 N. The average contact pressure of the system was 5.6 MPa with mean peak pressures of 21.2 MPa. In a separate phase of the study, contact characteristics with applied loads for each of the six component sizes showed a significant effect of component size on contact characteristics. When physiologic ankle forces are considered for normal patient activity, peak pressures observed in the current study may exceed recommended contact pressures (10 MPa) and the compressive yield point (13-22 MPa) for polyethylene. A heavy patient with a small ankle would not be expected to have a good outcome based on the current contact pressures data, whereas a heavy patient with a larger ankle might be a better candidate for surgery.

Measuring the pressure pattern of the joint surface in the uninjured knee

PURPOSE

Testing an applicable intraoperative system for measuring surface pressure in knee joints, simulating as accurately as possible operating theatre conditions.

TYPE OF STUDY

Cadaver study.

METHODS

Pressure probes were introduced into the knee joints medially and laterally (K 6900 quad probes) in five cadavers, providing real-time data with computerized data recording (K-scan system, manuf. Tekscan Inc., South Boston, MA). The initial position of the knee was flexed and hanging, as in a leg holder. In simulation of usual operating theatre procedures, the knee was manually extended to 0 degrees and again brought to hanging position. The data are given as relative-pressure values and should serve as the basis for intraoperative use. During arthroscopy, absolute-pressure values would then be influenced by the pressure of the arthroscopy pump.

RESULTS

In 90 degrees flexion the average pressure ratio between the medial and lateral joint compartments was initially 1:1.5. When the leg was brought to full extension the pressure in the medial compartment increased, giving a pressure ratio of 1:1 at about 15 degrees and 1.8:1 at full extension. When bringing the leg back again to 90 degrees a similar pressure ratio curve was recorded.

CONCLUSIONS

The pressure relationship between the medial and lateral knee compartments could be recorded and was found reproducible in simulated operating-theatre conditions. The measurement of joint surface pressure during implantation of an anterior cruciate ligament graft could provide data for individual intraoperative quality control, thus improving surgical results.

The effect of posterior cruciate ligament reconstruction on patellofemoral contact pressures in the knee joint under simulated muscle loads

BACKGROUND

The mechanism of cartilage degeneration in the patellofemoral joint (PFJ) and medial compartment of the knee following posterior cruciate ligament (PCL) injury remains unclear. PCL reconstruction has been recommended to restore kinematics and prevent long-term degeneration. The effect of current reconstruction techniques on PFJ contact pressures is unknown.

PURPOSE

To measure PFJ contact pressures after PCL deficiency and reconstruction.

METHOD

Eight cadaveric knees were tested with the PCL intact, deficient, and reconstructed. Contact pressures were measured at 30 degrees, 60 degrees, 90 degrees, and 120 degrees of flexion under simulated muscle loads. Knee kinematics were measured by a robotic testing system, and the PFJ contact pressures were measured using a thin film transducer. A single bundle achilles tendon allograft was used in the reconstruction.

RESULTS

PCL deficiency significantly increased the peak contact pressures measured in the PFJ relative to the intact knee under both an isolated quadriceps load of 400 N and a combined quadriceps/hamstrings load of 400 N/200 N. Reconstruction did not significantly reduce the increased contact pressures observed in the PCL-deficient knee.

CONCLUSION

The elevated contact pressures observed in the PCL-deficient knee and reconstructed knee might contribute to the long-term degeneration observed in both the non-operatively treated and PCL-reconstructed knees.

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.

Vascular adaptation of intact joint stabilizing structures in the posterior cruciate ligament deficient rabbit knee

Loss of the posterior cruciate ligament (PCL) of the knee has a significant impact on joint stability and biomechanical function. Changes in joint biomechanics may result in mal-adaptive tissue degeneration and functional alteration of supporting ligaments. This study examines the effects of joint laxity on the vascular physiology of the intact anterior cruciate (ACL) and medial collateral (MCL) ligaments after PCL transection in rabbits.One-year-old female New Zealand white rabbits were assigned to control (n=12), sham-operated (n=12) or PCL transected (2, 6 or 16 weeks, n=12 per time point) groups. Half of the animals (n=6 per group) were used for ACL and MCL blood flow determination using coloured microsphere infusion (ml/min/100 g), and half were used for vascular volume determination (given as vascular index, micro l/g). In the MCL, PCL transection induced large, significant (4-5-fold) increases in blood flow (peak at 2 weeks) and vascular index (peak at 6 weeks) compared to sham-operated animals that returned towards control values by 16 weeks. In contrast, the ACL showed no increase in blood flow in lax joints, and a relatively small (2-fold) increase in vascular index at 6 weeks only. The wet weight and water content of both the MCL and ACL were significantly increased in PCL-deficient joints. We conclude that joint laxity (instability) subsequent to loss of the PCL in rabbits impacts the vascular physiology of intact supporting ligaments, inducing both vasomotor and angiogenic responses in the MCL. Changes in wet weight and water content of both the MCL and ACL demonstrate prolonged physiological adaptation of intact structures in lax joints.

Chondral injury associated with acute isolated posterior cruciate ligament injury

SUMMARY

To evaluate associated cartilaginous damage with acute isolated posterior cruciate ligament (PCL) injury without other concomitant ligamentous injury, arthroscopic evaluations were performed on 61 consecutive patients. Meniscal tear was found in 17 cases (28%). Of these, 3 had medial meniscal tear, 11 had lateral meniscal tear, and 3 had both medial and lateral meniscal tears. Longitudinal tears of anterior segment in lateral menisci were the most common (10 cases). Thirty-two patients (52%) had articular cartilage injury. Of these, 7 had damage greater than one half of the thickness of the articular cartilage, and 3 had erosion that extended to the subchondral bone. The most frequently injured location was the medial femoral condyle (19 cases, 31%). Significant cartilaginous injury could be combined in acute isolated PCL injury. Therefore, it is unreasonable to manage every acute isolated PCL-injured knee using a single treatment modality. Concomitant meniscal and articular cartilaginous lesions should be evaluated when treatment for acute PCL injury is planned.

Rehabilitation Programs for the PCL-Injured and Reconstructed Knee

Treatment of posterior cruciate ligament (PCL) injuries has changed considerably in recent years. This article discusses current rehabilitation for PCL disruptions in athletes. The treatment of PCL injuries varies somewhat based on the chronicity (acute vs. chronic) of injury and associated pathologies. The authors provide their treatment algorithm for the acute and chronic PCL-injured-knee patient. Nonoperative rehabilitation is discussed with a focus on immediate motion, quadriceps muscle strengthening, and functional rehabilitation. A discussion of the biomechanics of exercise is provided, with a focus on tibiofemoral shear forces and PCL strains. Surgical treatment is also discussed, with the current surgical approach being either the two-tunnel or the one-tunnel patellar tendon autograft procedure. The rehabilitation program after surgery is based on the healing constraints, surgical technique, biomechanics of the PCL during functional activities, and exercise. With the new changes in surgical technique and in the rehabilitation process, the authors believe that the outcome after PCL reconstruction will be enhanced.

The natural history of acute, isolated, nonoperatively treated posterior cruciate ligament injuries. A prospective study

We sought to determine prospectively the natural history of acute, isolated, nonoperatively treated posterior cruciate ligament injuries in athletically active patients. The study population consisted of 133 patients (average age, 25.2 years at time of injury). All patients completed a subjective questionnaire each year for an average of 5.4 years (range, 2.3 to 11.4). Sixty-eight of the 133 patients returned to the clinic for long-term follow-up evaluation. Objectively, physical examination revealed no change in laxity from initial injury to follow-up. No correlation was found between radiographic joint space narrowing and grade of laxity. The mean modified Noyes knee score was 84.2 points, the mean Lysholm score was 83.4, and the mean Tegner activity score was 5.7. Patients with greater laxity did not have worse subjective scores. No correlation was found between subjective knee scores and time from injury. Regardless of the amount of laxity, half of the patients returned to the same sport at the same or higher level, one-third returned to the same sport at a lower level, and one-sixth did not return to the same sport. Results of this study suggest that athletically active patients with acute isolated posterior cruciate ligament tears treated nonoperatively achieved a level of objective and subjective knee function that was independent of the grade of laxity.

Load sharing between solid and fluid phases in articular cartilage: I--Experimental determination of in situ mechanical conditions in a porcine knee

The in situ mechanical conditions of cartilage in the articulated knee were quantified during joint loading. Six porcine knees were subjected to a 445 N compressive load while cartilage deformations and contact pressures were measured. From roentgenograms, cartilage thickness before and during loading allowed the calculation of tissue deformation on the lateral femoral condyle at different times during the loading process. Contact pressures on the articular surface were measured with miniature fiber-optic pressure transducers. Results showed that the medial side of the lateral femoral condyle had higher contact pressures, as well as deformations. To begin to correlate the pressures and resulting deformations, the intrinsic material properties of the cartilage on the lateral condyle were obtained from indentation tests. Data from four normal control specimens indicated that the aggregate modulus of the medial side was significantly higher than in other areas of the condyle. These experimental measures of the in situ mechanical conditions of articular cartilage can be combined with theoretical modeling to obtain valuable information about the relative contributions of the solid and fluid phases to supporting the applied load on the cartilage surface (see Part II).