Current trends in the anterior cruciate ligament part 1: biology and biomechanics.

A trend within the orthopedic community is rejection of the belief that "one size fits all." Freddie Fu, among others, strived to individualize the treatment of anterior cruciate ligament (ACL) injuries based on the patient's anatomy. Further, during the last two decades, greater emphasis has been placed on improving the outcomes of ACL reconstruction (ACL-R). Accordingly, anatomic tunnel placement is paramount in preventing graft impingement and restoring knee kinematics. Additionally, identification and management of concomitant knee injuries help to re-establish knee kinematics and prevent lower outcomes and registry studies continue to determine which graft yields the best outcomes. The utilization of registry studies has provided several large-scale epidemiologic studies that have bolstered outcomes data, such as avoiding allografts in pediatric populations and incorporating extra-articular stabilizing procedures in younger athletes to prevent re-rupture. In describing the anatomic and biomechanical understanding of the ACL and the resulting improvements in terms of surgical reconstruction, the purpose of this article is to illustrate how basic science advancements have directly led to improvements in clinical outcomes for ACL-injured patients.Level of evidenceV.

The posteromedial corner of the knee: an international expert consensus statement on diagnosis, classification, treatment, and rehabilitation.

PURPOSE: To establish recommendations for diagnosis, classification, treatment, and rehabilitation of posteromedial corner (PMC) knee injuries using a modified Delphi technique. METHODS: A list of statements concerning the diagnosis, classification, treatment and rehabilitation of PMC injuries was created by a working group of four individuals. Using a modified Delphi technique, a group of 35 surgeons with expertise in PMC injuries was surveyed, on three occasions, to establish consensus on the inclusion or exclusion of each statement. Experts were encouraged to propose further suggestions or modifications following each round. Pre-defined criteria were used to refine item lists after each survey. The final document included statements reaching consensus in round three. RESULTS: Thirty-five experts had a 100% response rate for all three rounds. A total of 53 items achieved over 75% consensus. The overall rate of consensus was 82.8%. Statements pertaining to PMC reconstruction and those regarding the treatment of combined cruciate and PMC injuries reached 100% consensus. Consensus was reached for 85.7% of the statements on anatomy of the PMC, 90% for those relating to diagnosis, 70% relating to classification, 64.3% relating to the treatment of isolated PMC injuries, and 83.3% relating to rehabilitation after PMC reconstruction. CONCLUSION: A modified Delphi technique was applied to generate an expert consensus statement concerning the diagnosis, classification, treatment, and rehabilitation practices for PMC injuries of the knee with high levels of expert agreement. Though the majority of statements pertaining to anatomy, diagnosis, and rehabilitation reached consensus, there remains inconsistency as to the optimal approach to treating isolated PMC injuries. Additionally, there is a need for improved PMC injury classification. LEVEL OF EVIDENCE: Level V.

Large variability exists in the management of posterolateral corner injuries in the global surgical community.

PURPOSE: The management of posterolateral corner (PLC) injuries has significantly evolved over the past 2 decades. The purpose of this study was to determine the current worldview of key concepts on the diagnosis, treatment strategy, and rehabilitation for patients presenting with PLC injuries. METHODS: A 12-question multiple-choice online survey was designed to address key questions in the diagnosis, treatment, and rehabilitation of PLC injuries. The survey was distributed to the most important international sports medicine societies worldwide. Clinical agreement was defined as > 80% of agreement in responses and general agreement was defined as > 60% of agreement in responses. RESULTS: 975 surgeons completed the survey with 49% from Europe, 21% from North America, 12% from Latin America, 12% from Asia, and smaller percentages from Africa and Oceania. Less than 14% of respondents manage more than ten PCL injuries yearly. Clinical agreement of > 80% was only evident in the use of MRI in the diagnosis of PLC injury. Responses for surgical treatment were split between isometric fibular-based reconstruction techniques and anatomically based fibular and tibial-based reconstructions. A general agreement of > 60% was present for the use of a post-operative brace in the early rehabilitation. CONCLUSION: In the global surgical community, there remains a significant variability in the diagnosis, treatment, and postoperative management of PLC injuries. The number of PLC injuries treated yearly by most surgeons remains low. As global clinical consensus for PLC remains elusive, societies will need to play an important role in the dissemination of evidence-based practices for PLC injuries. LEVEL OF EVIDENCE: IV.

Posterolateral corner of the knee: an expert consensus statement on diagnosis, classification, treatment, and rehabilitation.

PURPOSE: To develop a statement on the diagnosis, classification, treatment, and rehabilitation concepts of posterolateral corner (PLC) injuries of the knee using a modified Delphi technique. METHODS: A working group of three individuals generated a list of statements relating to the diagnosis, classification, treatment, and rehabilitation of PLC injuries to form the basis of an initial survey for rating by an international group of experts. The PLC expert group (composed of 27 experts throughout the world) was surveyed on three occasions to establish consensus on the inclusion/exclusion of each item. In addition to rating agreement, experts were invited to propose further items for inclusion or to suggest modifications of existing items at each round. Pre-defined criteria were used to refine item lists after each survey. Statements reaching consensus in round three were included within the final consensus document. RESULTS: Twenty-seven experts (100% response rate) completed three rounds of surveys. After three rounds, 29 items achieved consensus with over 75% agreement and less than 5% disagreement. Consensus was reached in 92% of the statements relating to diagnosis of PLC injuries, 100% relating to classification, 70% relating to treatment and in 88% of items relating to rehabilitation statements, with an overall consensus of 81%. CONCLUSIONS: This study has established a consensus statement relating to the diagnosis, classification, treatment, and rehabilitation of PLC injuries. Further research is needed to develop updated classification systems, and better understand the role of non-invasive and minimally invasive approaches along with standardized rehabilitation protocols. LEVEL OF EVIDENCE: Consensus of expert opinion, Level V.

Reliability of wearable sensors-based parameters for the assessment of knee stability.

Anterior cruciate ligament (ACL) rupture represents one of the most recurrent knee injuries in soccer players. To allow a safe return to sport after ACL reconstruction, standardised and reliable procedures/criteria are needed. In this context, wearable sensors are gaining momentum as they allow obtaining objective information during sport-specific and in-the-field tasks. This paper aims at proposing a sensor-based protocol for the assessment of knee stability and at quantifying its reliability. Seventeen soccer players performed a single leg squat and a cross over hop test. Each participant was equipped with two magnetic-inertial measurement units located on the tibia and foot. Parameters related to the knee stability were obtained from linear acceleration and angular velocity signals. The intraclass correlation coefficient (ICC) and minimum detectable change (MDC) were calculated to evaluate each parameter reliability. The ICC ranged from 0.29 to 0.84 according to the considered parameter. Specifically, angular velocity-based parameters proved to be more reliable than acceleration-based counterparts, particularly in the cross over hop test (average ICC values of 0.46 and 0.63 for acceleration- and angular velocity-based parameters, respectively). An exception was represented, in the single leg squat, by parameters extracted from the acceleration trajectory on the tibial transverse plane (0.60≤ICC≤0.76), which can be considered as promising candidates for ACL injury risk assessment. Overall, greater ICC values were found for the dominant limb, with respect to the non-dominant one (average ICC: 0.64 and 0.53, respectively). Interestingly, this between-limb difference in variability was not always mirrored by LSI results. MDC values provide useful information in the perspective of applying the proposed protocol on athletes with ACL reconstruction. Thus, The outcome of this study sets the basis for the definition of reliable and objective criteria for return to sport clearance after ACL injury.

Posterior cruciate ligament reconstruction using an arthroscopic femoral inlay technique.

Several techniques for posterior cruciate ligament reconstruction have been developed. The purpose of this paper is to present a new surgical technique that provides greater anatomical femoral fixation avoiding the sharp angle made by the graft at the exit of the femoral tunnel.

Release of growth factors after arthroscopic acromioplasty.

It has recently been postulated that a variety of growth factors may be released from cancellous bone after an acromioplasty. The aim of this study was to demonstrate the presence of growth factors in the subacromial space after acromioplasty. Between October 2006 and March 2007, 23 patients underwent arthroscopic acromioplasty. A sample of at least 3 ml of fluid from the shoulder was obtained 15 min after the end of the procedure. At the same time another sample of 3 ml of the patient's venous blood was obtained as a control. The concentrations of growth factors in the fluids collected were determined using enzyme-linked immunosorbent assay (ELISA). The growth factors assayed were platelet-derived growth factor-AB (PDGF-AB), basic fibroblast growth factor basic (bFGF) and transforming growth factor beta 1 (TGF-beta1). The concentrations of TGF-beta1 (p = 0.0001), PDGF-AB (p = 0.02), and bFGF (p < 0.0001) were significantly higher in the fluid from the subacromial space than in the blood sample. There are high concentrations of several growth factors in the subacromial space after acromioplasty.

Telomere length is independently associated with age, oxidative biomarkers, and sport training in skeletal muscle of healthy adult males.

In skeletal muscle, which mainly contains postmitotic myonuclei, it has been suggested that telomere length remains roughly constant throughout adult life, or shortens in response to physiopathological conditions in muscle diseases or in the elderly. However, telomere length results from both the replicative history of a specific tissue and the exposure to environmental, DNA damage-related factors, therefore the predictive biological significance of telomere measures should combine the analysis of the various interactive factors. In the present study, we analysed any relationship between telomere length [mean and minimum terminal restriction fragment (TRF) length] chronological age, oxidative damage (4-HNE, protein carbonyls), catalase activity, and heat shock proteins expression (αB-crystallin, Hsp27, Hsp90) in semitendinous muscle biopsies of 26 healthy adult males between 20 and 50 years of age, also exploring the influence of regular exercise participation. The multiple linear regression analysis identified age, 4-HNE, catalase, and training status as significant independent variables associated with telomere length and jointly accounting for ∼30-36% of interindividual variation in mean and/or minimum TRF length. No association has been identified between telomere length and protein carbonyl, αB-crystallin, Hsp27, and Hsp90, as well as between age and the variables related to stress response. Our results showed that skeletal muscle from healthy adults displays an age-dependent telomere attrition and that oxidised environment plays an age-independent contribution, partially influenced by exercise training.

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.

Arthroscopic diagnosis of the snapping popliteus tendon.

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

Evaluation of posterior cruciate ligament healing: a study using magnetic resonance imaging and stress radiography.

PURPOSE: To review a series of tears of the posterior cruciate ligament (PCL) in order to understand its healing process, as well as to identify prognostic factors. TYPE OF STUDY: Prospective study. METHODS: Eighteen patients with isolated or combined PCL tears were evaluated and followed-up for 1 year after their initial injury. Magnetic resonance imaging (MRI) scans and stress radiographs were obtained serially at the time of injury, at 6 months, and at 12 months. RESULTS: Twelve of 18 PCL tears were found to have regained continuity at the 1-year follow-up. These patients complained of an isolated or combined PCL/medial collateral ligament injury at time 0 and all presented a posterior subluxation of less than 8 mm, detected with stress radiographs. The remaining 6 patients had posterior subluxations greater than 12 mm and presented with combined posterolateral corner injuries. CONCLUSIONS: This study underlines the importance of a complete MRI evaluation used in combination with stress radiography to adequately assess the healing process. The results obtained suggest that complete PCL tears with greater than 12 mm of posterior subluxation, as well as combined PLC injuries, are less likely to heal completely. These factors could further aid the surgeon in deciding the need and timing for surgical intervention in the acute setting of a PCL tear. LEVEL OF EVIDENCE: Level II.

Biomechanics of initial tibial fixation in posterior cruciate ligament reconstruction.

PURPOSE: Clinical success of posterior cruciate ligament (PCL) reconstruction continues to lag behind that of its anterior counterpart. The tibial site of PCL graft fixation has been a focus of recent research. This study examined the effect of combined distal and proximal tibial fixation on the ability of a transtibial PCL reconstruction to restore intact knee kinematics and in situ forces of the intact PCL. TYPE OF STUDY: Biomechanical study. METHODS: Ten human cadaveric knees were tested. A 134-N posterior tibial load was applied using a robotic/universal force moment sensor testing system at 0 degrees, 30 degrees, 60 degrees, 90 degrees, and 120 degrees of knee flexion. Each knee was tested under 4 conditions: intact, PCL-deficient, single-bundle transtibial reconstruction with distal tibial fixation, and single-bundle transtibial reconstruction with combined distal and proximal tibial fixation. Knee kinematics in 5 degrees of freedom for each condition were recorded and in situ forces of the intact PCL and the PCL grafts were determined. RESULTS: Reconstruction with combined fixation resulted in significantly less posterior tibial translation than reconstruction with distal fixation at 30 degrees, 90 degrees, and 120 degrees (P < .05), and restored intact knee kinematics at 90 degrees and 120 degrees (P > .05). Reconstruction with combined fixation more closely restored intact PCL in situ forces at 90 degrees (P < .05). CONCLUSIONS: Transtibial reconstruction with combined fixation more closely restores intact knee kinematics and in situ forces in the PCL at initial fixation than does reconstruction with distal tibial fixation. The improved kinematics and in situ forces seen with the combined fixation may be attributed to decreased functional graft length and increased stiffness of the PCL graft. CLINICAL RELEVANCE: Combined tibial fixation may provide a more stable reconstruction at initial fixation.

Posterior cruciate ligament injuries in the athlete: an anatomical, biomechanical and clinical review.

Recently, the posterior cruciate ligament (PCL) has become an increasingly popular subject of orthopaedic research and debate. In the past several years, anatomic and biomechanical studies have provided invaluable information concerning the structure and function of the PCL. However, many aspects of PCL injury are still not fully understood. Diagnosis of the injury is often missed because of subtlety of symptoms and clinical findings, and current management strategies of PCL injury have experienced relatively poor clinical outcomes. Controversy exists concerning the most appropriate treatment, especially in cases of isolated PCL injury. The purpose of this review is to present a complete overview of the current knowledge regarding the basic science and clinical aspects of PCL injuries, with a specific focus on the athletic population.

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

BACKGROUND: The tibial inlay technique for posterior cruciate ligament reconstruction has been proposed to provide a more anatomic reconstruction because it eliminates the sharp turn in the graft as it exits the proximal margin of the tibial tunnel in the transtibial technique. HYPOTHESIS: Reconstruction of the posterior cruciate ligament using the tibial inlay technique would more closely restore intact knee kinematics and in situ forces in the posterior cruciate ligament than would reconstruction using the transtibial technique. METHODS: Ten human cadaveric knees were tested in a controlled laboratory study. A robotic/universal force-moment sensor testing system was used to apply a 134-N posterior tibial load at 5 knee flexion angles: 0 masculine, 30 masculine, 60 masculine, 90 masculine, and 120 masculine. Four knee conditions were tested: intact, posterior cruciate ligament-deficient, and the single-bundle tibial inlay reconstruction and transtibial posterior cruciate ligament reconstruction. RESULTS: Both reconstruction techniques restored posterior tibial translations to 1.7 to 2.1 mm of the intact knee, with no statistical differences between the techniques. In response to the posterior tibial load, in situ forces in both grafts were between 7 and 39 N less than those in the intact posterior cruciate ligament, with no significant differences between the grafts. CLINICAL RELEVANCE: The study suggests that either technique may be performed with similar biomechanical results at initial fixation under these loading conditions.

A modified bone-tendon-bone harvesting technique for avoiding tibial tunnel-graft mismatch in anterior cruciate ligament reconstruction.

Anatomic graft fixation in anterior cruciate ligament reconstruction has been shown to be extremely important for achieving acceptable postoperative knee stability. Different methods have been proposed for customizing graft length, so that anatomic graft fixation is obtained at the native anterior cruciate ligament site. A technique has been described for avoiding potential complications during the insertion of an interference screw at femoral tunnel and, ultimately, reducing the mismatch within the femoral tunnel. The aim of this article is to present a modified application to the tibial tunnel of a previously described technique for avoiding graft-tunnel mismatch. The advantages are related to the increase in graft complex stiffness, achievement of a more anatomic fixation, and the reduction in synovial fluid leakage.

Serial magnetic resonance imaging evaluation of the patellar tendon after posterior cruciate ligament reconstruction.

PURPOSE: Our purpose was to prospectively analyze serial changes in magnetic resonance imaging (MRI) signal of the bone-patellar tendon-bone autograft when used for posterior cruciate ligament (PCL) reconstruction and to retrospectively determine at mid-term follow-up the relationship between MRI graft appearance and clinical stability in patients who have undergone arthroscopic PCL reconstruction with a bone-patellar tendon-bone autograft. TYPE OF STUDY: One prospective serial blinded study and 1 retrospective blinded study. METHODS: The first part of the study focused on MRI scans obtained at 3, 6, 9, and 12 months postoperatively in a case series of 10 consecutive patients who underwent arthroscopically assisted PCL reconstruction (group A), and of 10 patients who underwent combined ACL-PCL arthroscopic reconstruction (group B). For the second part of the study, MRI scans were obtained in a retrospective series of 10 patients at mid-term follow-up after PCL arthroscopic reconstruction (group C). Signal intensity of 3 zones, corresponding to the proximal, middle, and distal intra-articular graft zones, was evaluated according to the Howell et al. classification. Fiber continuity assessment was performed using a modified Kühne et al. score. The signal intensity of the 3 zones was independently scored. Knee stability was clinically and instrumentally graded according to the IKDC evaluation form (group 4). A multivariance analysis and grouped t test were used for statistical evaluation. RESULTS: In group A, the average MRI evaluation score was 7.65 +/- 1.6 at 3 months, 3.8 +/- 0.6 at 6 months, 4.75 +/- 1 at 9 months and 6.25 +/- 1.2 at 1 year. The portion of graft exiting the femoral tunnel exhibited increased signal and faster maturation than the tibial tunnel. In group B (combined ACL-PCL reconstruction), the graft showed slower graft healing with an average MRI score of 4.85 +/- 0.7 at 3 months, 1.9 +/- 0.7 at 6 months, 3.9 +/- 0.9 at 9 months, and 5.3 +/- 1.1 at 1 year. At 1 year follow-up, there was no correlation between MRI appearance and stability in group A, even with MRI findings of fiber continuity. However, at long-term evaluation (group C), a strict correlation between MRI appearance and achieved stability was found. CONCLUSIONS: The patellar tendon when used for PCL reconstruction requires more than 1 year to achieve a low-signal intensity over its entire course, and the distal zone near the tibial tunnel shows a slower healing process. MRI graft assessment is useful only 1 year or more following PCL reconstruction.

Stress radiography for quantifying posterior cruciate ligament deficiency.

PURPOSE: The objective of this study was to evaluate the efficacy of different stress radiography techniques in quantifying a posterior cruciate ligament (PCL) lesion. TYPE OF STUDY: Prospective serial study. METHODS: Sixty patients with subacute or chronic PCL injuries, confirmed using magnetic resonance imaging (MRI) or arthroscopic evaluation, were enrolled in this study. The patients underwent a KT-2000 (Medmetric, San Diego, CA) examination and a series of stress radiographs that included a radiographic posterior drawer test with Telos (Telos, Weterstadt, Germany) at 90 degrees and 25 degrees of knee flexion, an active radiograph at 90 degrees of knee flexion, and an axial view radiograph. RESULTS: Stress radiography performed with Telos showed an average posterior tibial displacement of 11.54 +/- 4.93 mm and 7.97 +/- 3.16 mm at 90 degrees and 25 degrees, respectively. The active radiographs showed an average posterior tibial displacement of 11.48 +/- 5.14 mm. CONCLUSIONS: Stress radiographs were shown to be superior to arthrometric evaluation in quantifying posterior tibial translation. The techniques performed with the knee at 90 degrees of knee flexion allowed for greater posterior tibial displacement and, consequently, an easier quantification of the degree of ligament insufficiency. Stress radiographs performed through hamstring contraction gave the same results as those performed with Telos at 90 degrees of knee flexion.

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.

Distal femoral osteotomy.

Osteotomies around the knee are well-recognized treatments for unloading the affected compartment in cases of lower limb malalignment. There are few papers in the literature describing the outcomes of distal femoral osteotomy (DFO), as compared with the studies reporting on high tibial osteotomy (HTO), probably because valgus malalignment is less common than the varus one. There is still debate as to what the correct indication is and which surgical techniques lead to the best outcomes in performing a DFO. Besides, it is still controversial whether patellofemoral arthritis should be considered as a contraindication to performing a DFO, as well as in HTO. In this article, we will summarize the indications for DFO, the surgical techniques reported in the literature, and their outcomes.

Partial isolated rupture of the popliteus tendon in a professional soccer player: a case report.

The complete isolated rupture of the popliteus tendon has been described as a rare injury and this report describes the case of a 31-year-old soccer player who sustained a partial rupture of the popliteus tendon during a game. The injury was suspected clinically and at MRI but confirmed only by the arthroscopic examination. The treatment consisted in open debridment with no tendon repair or augmentation. Seven weeks post-operation the patient was symptom-free and returned to competitive professional soccer at the same preinjury level. The clinical and arthroscopic findings of the case reported suggest a possible overuse disease with degenerative expression.