Cruciate injury patterns in knee hyperextension: a cadaveric model

Establishing a Consensus Definition of a Knee Fracture-Dislocation (Schenck Knee Dislocation V) Using a Global Modified Delphi Method

BACKGROUND

Knee fracture-dislocations are complex injuries; however, there is no universally accepted definition of what constitutes a fracture-dislocation within the Schenck Knee Dislocation (KD) V subcategory. The purpose of this study was to establish a more precise definition for fracture patterns included within the Schenck KD V subcategory.

METHODS

A series of clinical scenarios encompassing various fracture patterns in association with a bicruciate knee ligament injury was created by a working group of 8 surgeons. Utilizing a modified Delphi technique, 46 surgeons from 18 countries and 6 continents with clinical and academic expertise in multiligamentous knee injuries undertook 3 rounds of online surveys to establish consensus. Consensus was defined as ≥70% agreement with responses of either "strongly agree" or "agree" for a positive consensus or "strongly disagree" or "disagree" for a negative consensus.

RESULTS

There was a 100% response rate for Rounds 1 and 2 and a 96% response rate for Round 3. A total of 11 fracture patterns reached consensus for inclusion: (1) nondisplaced articular fracture of the femur; (2) displaced articular fracture of the femur; (3) tibial plateau fracture involving the weight-bearing surface (with or without tibial spine involvement); (4) tibial plateau peripheral rim compression fracture; (5) posterolateral tibial plateau compression fracture, Bernholt type IIB; (6) posterolateral tibial plateau compression fracture, Bernholt type IIIA; (7) posterolateral tibial plateau compression fracture, Bernholt type IIIB; (8) Gerdy's tubercle avulsion fracture with weight-bearing surface involvement; (9) displaced tibial tubercle fracture; (10) displaced patellar body fracture; and (11) displaced patellar inferior pole fracture. Fourteen fracture patterns reached consensus for exclusion from the definition. Two fracture patterns failed to reach consensus for either inclusion or exclusion from the definition.

CONCLUSIONS

Using a modified Delphi technique, this study established consensus for specific fracture patterns to include within or exclude from the Schenck KD V subcategory.

LEVEL OF EVIDENCE

Prognostic Level V . See Instructions for Authors for a complete description of levels of evidence.

Radiographic Measurements Correlate to Isolated Posterolateral Corner (PLC) Injury in a Novel Cadaveric Model

INTRODUCTION

 Injury to the posterolateral corner (PLC) of the knee often requires surgical reconstruction. There remains no consensus on treatment for PLC injury, and, therefore, it is imperative to have a reproducible injury model to improve the general knowledge of PLC injuries. A novel cadaveric model of isolated PLC injury is proposed and evaluated using radiographic parameters as well as gross dissection.

MATERIAL AND METHODS

 All protocols were reviewed by the Human Investigation and Research Committee of the home institution and were approved. Translational force in a defined posterior and lateral direction was applied to cadaveric native knees to induce PLC injury. Varus and recurvatum stress fluoroscopic imaging was obtained of each specimen before and after the injury model. Lateral joint distance and recurvatum angle after stress was measured on each image via picture archiving and communication software (PACS) imaging software. After the injury model, injured structures were assessed via saline loading and gross dissection. Any specimens found to be fractured were excluded from the analysis of stress radiography.

RESULTS

 A total of 12 knees underwent testing and 6/12 successfully induced PLC injury without fracture. The lateral capsule was torn in every specimen. The popliteofibular ligament (PFL) was torn in 83% of specimens and the fibular collateral ligament (FCL) in 66.7% of specimens. The median lateral gapping after injury under varus stress radiography was 5.39 mm and the median recurvatum angle after injury was 14.25°. Radiographic parameters had a direct relationship with a number of structures injured.

CONCLUSIONS

 This is the first successful cadaver model of PLC injury. The lateral capsule was injured in every specimen emphasizing the importance of this structure to the PLC.

Functional Interaction of the Cruciate Ligaments, Posteromedial and Posterolateral Capsule, Oblique Popliteal Ligament, and Other Structures in Preventing Abnormal Knee Hyperextension

BACKGROUND

The ligaments and soft tissue capsular structures of the knee joint that provide a resisting force to prevent abnormal knee hyperextension have not been determined. This knowledge is required for the diagnosis and treatment of knee hyperextension abnormalities.

PURPOSE

To determine the resisting moment of knee ligament and capsular structures that resist knee hyperextension.

HYPOTHESIS

The combined posteromedial and posterolateral capsular structures function to provide a major restraint to prevent abnormal knee hyperextension. The anterior and posterior cruciate ligaments resist knee hyperextension but function as secondary restraints.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A 6 degrees of freedom robotic system determined intact laxity limits in 24 cadaveric knees from 0° to 100° of knee flexion for anteroposterior limits at ±135 N, abduction-adduction limits at ±7 N·m, and external-internal limits at ±5 N·m. One loading method (n = 14 knees) used a static loading sequence with knee hyperextension to 27-N·m torque while maintaining all other degrees of freedom at zero load during sequential soft tissue cutting. The second method (n = 10 knees) used a cyclic loading sequence to decrease viscoelastic effects with soft tissue cutting at 0° of extension, followed by knee hyperextension to 27-N·m torque and cycled back to 0°. Selective soft tissue cuttings were performed of the following: oblique popliteal ligament, fabellofibular ligament, posterolateral capsule, posteromedial capsule with posterior oblique ligament, cruciate ligaments, lateral collateral ligament, popliteus, anterolateral ligament and iliotibial band, and superficial plus deep medial collateral ligaments. The sequential loss in the restraining moment with sectioning provides the function of that structure in resisting knee hyperextension.

RESULTS

The median resisting force to knee hyperextension, in descending order, was the posteromedial capsule and posterior oblique ligament (21.7%), posterorolateral ligament and fabellofibular ligament (17.1%), anterior and posterior cruciate ligaments (13% and 12.9%, respectively), superior and deep medial collateral ligament (9.6%), oblique popliteal ligament (7.7%), and lateral collateral ligament (5.4%). The combined posterior capsular structures provided 54.7% and the anterior and posterior cruciate ligaments 25.3% of the total resisting moment to prevent knee hyperextension.

CONCLUSION

Diagnosis of abnormal knee hyperextension involves a combination of multiple ligament and soft tissue structures without 1 primary restraint. The posteromedial and posterolateral capsular structures provided the major resisting moment to prevent knee hyperextension. The cruciate ligaments produced a lesser resisting moment to knee hyperextension.

CLINICAL RELEVANCE

This is the first study to comprehensively measure all of the knee ligaments and capsular structures providing a resisting moment to abnormal knee hyperextension. These data are required for diagnostic and treatment strategies on the pathomechanics of abnormal knee hyperextension in patients after injury or developmental cases.

Cartilage and Meniscus Injuries Are More Common in Patients Undergoing Delayed Multiligament Reconstruction

The purpose of this study was to describe the pattern of meniscus and cartilage pathology in multiligament knee injuries (MLKIs) and determine the relationship between surgical timing and injury mechanism with degree of intra-articular injury. Patients with surgically treated MLKIs over a 15-year period were retrospectively reviewed and grouped based on surgical intervention, time to intervention, and injury mechanism. The presence or absence of meniscus and chondral injury were recorded at the time of surgery. Surgical intervention within 6 weeks of injury was deemed acute, while surgery occurring more than 6 weeks from injury was classified as delayed. Over the 15-year study period, 207 patients with MLKIs were identified. Compared with acutely managed patients, the delayed intervention group had significantly more meniscus (p = 0.03) and cartilage (p < 0.01) pathology. Meniscus injury rates in MLKIs sustained during sporting activity did not differ from nonsporting injuries (p = 0.63). However, the nonsporting group had significantly more chondral injuries (p < 0.01). High-energy injury mechanism was associated with increased cartilage (p = 0.02), but not meniscus (p = 0.61) injury rates. In conclusion, surgical reconstruction of MLKIs delayed for more than 6 weeks was associated with increased meniscus and cartilage pathology.

The Effect of Enzymatic Crosslink Degradation on the Mechanics of the Anterior Cruciate Ligament: A Hybrid Multi-Domain Model

The anterior cruciate ligament’s (ACL) mechanics is an important factor governing the ligament’s integrity and, hence, the knee joint’s response. Despite many investigations in this area, the cause and effect of injuries remain unclear or unknown. This may be due to the complexity of the direct link between macro- and micro-scale damage mechanisms. In the first part of this investigation, a three-dimensional coarse-grained model of collagen fibril (type I) was developed using a bottom-up approach to investigate deformation mechanisms under tensile testing. The output of this molecular level was used later to calibrate the parameters of a hierarchical multi-scale fibril-reinforced hyper-elastoplastic model of the ACL. Our model enabled us to determine the mechanical behavior of the ACL as a function of the basic response of the collagen molecules. Modeled elastic response and damage distribution were in good agreement with the reported measurements and computational investigations. Our results suggest that degradation of crosslink content dictates the loss of the stiffness of the fibrils and, hence, damage to the ACL. Therefore, the proposed computational frame is a promising tool that will allow new insights into the biomechanics of the ACL.

Complications associated with hyperextension bicondylar tibial plateau fractures: a retrospective study

Background

Hyperextension bicondylar tibial plateau fracture (HBTPF) is a particular form of tibial plateau fracture which has gained increasing interest recently but were rarely documented. In this study, we reported the characteristics, clinical intervention, and therapeutic outcomes of HBTPF patients.

Methods

From May 2015 to October 2017, clinical data of consecutive patients with bicondylar tibial plateau fractures (BTPF) who underwent surgical treatment in our hospital were retrospectively studied. The patients were allocated to either the HBTPF group (study group) or the non-HBTPF group (control group) based on the radiological features, and inclusion and exclusion criteria. Demographics, characteristics of knee joint injuries, complications, and outcomes were compared between the two groups.

Results

In total, 59 patients were included in this study. Among them, 17 patients with HBTPF were identified and 42 patients were diagnosed as non-HBTPF. No differences in age, sex, cause of injury, side of injury, site of injury, nerve injury, operation time, and treatment time and incision complication between HBTPF and non-HBTPF group. The incidence rate of popliteal artery injury in HBTPF group was 29.4 %, which was significantly higher than that of non-HBTPF group. Small bone chips on the lateral film were found in 94.1 % of the patients in HBTPF group, which was significantly higher than that of non-HBTPF group. The range of motion (ROM) and hospital for special surgery (HSS) score of HBTPF group were significantly lower than those of non-HBTPF group.

Conclusions

HBTPF is a severe injury with a higher incidence rate of popliteal artery injury and worse outcomes than non-HBTPF. Small bone chips at the anterior margin of the proximal tibia on the lateral plain film might be a characteristic of HBTPF.

Isolated Partial Femoral Avulsion Fracture of the Posterior Cruciate Ligament in Adults

Objective

To investigate the manifestation, mechanisms, and treatment of isolated partial femoral avulsion fractures of the posterior cruciate ligament (PCL) in adults.

Methods

From January 2011 to December 2018, we retrospectively reviewed the clinical data of three patients with isolated partial femoral avulsion fractures of the PCL who were admitted to our institution. All of these patients were admitted to our emergency department within 24 h after injury. After physical examination and radiographs were taken and reviewed, all patients were admitted and underwent surgical treatment. In a 26‐year‐old man who underwent arthroscopic surgery through the traditional medial and lateral approach before finally converting to open surgery with the posterior approach, the fragment that was finally removed was partially attached to the PCL. In the other two patients, women aged 63 and 68 years, who underwent arthroscopic surgery via the traditional medial and lateral approach, the fragments were large and attached to most fibers of the PCL. We fixed the fragments using hollow screws in arthroscopic view. In addition, in the 63‐year‐old patient, an anchor was embedded to restore the tension of the PCL. Four weeks after surgery, the patients started to wear long leg braces in full extension with the tibia blocked up by cushion. Physical examinations were conducted and radiographs were taken preoperatively and at 4 weeks and 3 months after surgery to evaluate the condition of the injury. The range of motion and the Lysholm knee scoring scale for the knee joint were compared before and after the surgery.

Results

For the three patients, the radiographs taken at 3 months postoperatively showed that the fixation of the screws did not fail, and the subchondral bone was generally normal compared to the preoperative radiographs. CT scanning at 3 months after surgery showed that the fracture healed in the original position of the avulsion site. For all patients, the affected knees presented as stable at physical examination 3 months after surgery; the Lachmann test and the anterior drawer test results were negative. In addition, the flexion–extension, internal rotation, and external rotation were approximately 0°–130°, 0°–30°, and 0°–40° in the 26‐year‐old patient, respectively. The flexion–extension, internal rotation, and external rotation were approximately 0°–100°, 0°–20°, and 0°–35° for the 63‐year‐old patient, respectively. The flexion–extension, internal rotation, and external rotation were approximately 0°–100°, 0°–15°, and 0°–20° for the 68‐year‐old patient, respectively. There was no pain or only little pain 3 months after surgery. There was no swelling or discomfort at the 3‐month follow up. The Lysholm knee scores of the 68‐year‐old, 63‐year‐old, and 26‐year‐old patient were 80, 87, and 95 at 3 months after surgery, respectively, which were obviously improved postoperatively.

Conclusion

The manifestation of isolated partial femoral avulsion fractures of the PCL in adults is often related to the injury mechanism, and surgery is essential for the treatment of these patients. Most of these fractures can be repaired by arthroscopic surgery, but some have to be treated by open surgery.

Asymptomatic Genu Recurvatum reshapes lower limb sagittal joint and elevation angles during gait at different speeds

BACKGROUND

Kinematic characteristics of walking with an asymptomatic genu recurvatum are currently unknown. The objective of this study is to characterize the lower limb sagittal joint and elevation angles during walking in participants with asymptomatic genu recurvatum and compare it with control participants without knee deformation at different speeds.

METHODS

The spatio-temporal parameters and kinematics of the lower limb were recorded using an optoelectronic motion capture system in 26 participants (n = 13 with genu recurvatum and n = 13 controls). The participants walked on an instrumented treadmill during five minutes at three different speeds: slow, medium and fast.

RESULTS

Participants with genu recurvatum showed several significant differences with controls: a narrower step width, a greater maximum hip joint extension angle, a greater knee joint extension angle at mid stance, a lower maximum knee joint flexion angle during the swing phase, and a greater ankle joint extension angle at the end of the gait cycle. Participants with genu recurvatum had a greater minimum thigh elevation angle, a greater maximum foot elevation angle, and a change in the orientation of the covariance plane. Walking speed had a significant effect on nearly all lower limb joint and elevation angles, and covariance plane parameters.

CONCLUSION

Our findings show that genu recurvatum reshapes lower limb sagittal joint and elevation angles during walking at different speeds but preserves the covariation of elevation angles along a plane during both stance and swing phases and the rotation of this plane with increasing speed.

Multiscale modeling of knee ligament biomechanics

Knee connective tissues are mainly responsible for joint stability and play a crucial role in restraining excessive motion during regular activities. The damage mechanism of these tissues is directly linked to the microscale collagen level. However, this mechanical connection is still unclear. During this investigation, a multiscale fibril-reinforced hyper-elastoplastic model was developed and statistically calibrated. The model is accounting for the structural architecture of the soft tissue, starting from the tropocollagen molecule that forms fibrils to the whole soft tissue. Model predictions are in agreement with the results of experimental and numerical studies. Further, damage initiation and propagation in the collagen fiber were computed at knee ligaments and located mainly in the superficial layers. Results indicated higher crosslink density required higher tensile stress to elicit fibril damage. This approach is aligned with a realistic simulation of a damaging process and repair attempt. To the best of our knowledge, this is the first model published in which the connective tissue stiffness is simultaneously predicted by encompassing the mesoscopic scales between the molecular and macroscopic levels.

The Pathoanatomy of Posterolateral Corner Ligamentous Disruption in Multiligament Knee Injuries Is Predictive of Peroneal Nerve Injury

BACKGROUND

A description of the precise locations of ligamentous and myotendinous injury patterns of acute posterolateral corner (PLC) injuries and their associated osseous and neurovascular injuries is lacking in the literature.

PURPOSE

To characterize the ligamentous and myotendinous injury patterns and zones of injury that occur in acute PLC injuries and determine associated rates of peroneal nerve palsies and vascular injuries, as well as fracture and dislocation.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

We retrospectively identified all patients treated for an acute multiligament knee injury (MLKI) at our level 1 trauma center from 2001 to 2018. From this cohort, all patients with PLC injuries were identified. Demographics, involved ligaments and tendons, neurovascular injury, and presence of fracture and dislocation were compared with the larger multiligament knee cohort. Incidence and location of injury of PLC structures-from proximal to midsubstance and distal injury-were recorded.

RESULTS

A total of 100 knees in 100 patients were identified as having MLKIs. A total of 74 patients (74%) had lateral-sided ligament injuries. Of these, 23 (31%) had a peroneal nerve palsy associated with their injury; 10 (14%), a vascular injury; and 23 (31%), a fracture. Patients with PLC injuries had higher rates of peroneal nerve injury as compared with those having acute MLKIs without a PLC injury (31% vs 4%; P = .005). Patients with a complete peroneal nerve palsy (n = 17) were less likely to regain function than those with a partial peroneal nerve palsy (n = 6; 12% vs 100%; P < .0001). Complete injury to the lateral collateral ligament (LCL) occurred in 71 of 74 (96%) PLC injuries, with 3 distinct patterns of injury demonstrated. Fibular avulsion of the LCL was the most common zone of injury (65%), followed by femoral avulsion (20%) and midsubstance tear (15%). Location of injury to the LCL was associated with the rate of peroneal nerve injury, with midsubstance tears and fibular avulsions associated with higher rates of peroneal nerve injury.

CONCLUSION

MLKIs with involvement of the PLC are more likely to suffer peroneal nerve injury. The LCL is nearly always involved, and its location of injury is predictive of peroneal nerve injury. Patients with a complete peroneal nerve palsy at presentation are much less likely to regain function.

[Research progress on hyperextension tibial plateau fractures]

Objective

To summarize the progress in the treatment of hyperextension tibial plateau fractures.

Methods

Related literature concerning hyperextension tibial plateau fractures was reviewed and analyzed in terms of injury mechanisms, clinical patterns, and treatment outcomes.

Results

Hyperextension tibial plateau fractures is a specific type of hyperextension knee injuries, which is happened with the knee in over-extended position (<0°) and characterized by fracture and concomitant ligament injury. It can be classified into 4 patterns: marginal avulsion fractures, unicondylar anteromedial fractures, anterolateral fractures, and bicondylar fractures. The failure of structures occurs according to the diagonal injury mechanism characterized by anterior compression fractures and posterior tension ruptures. It is noted as a rule that a smaller anterior fragment is more likely to accompany by a posterior ligament rupture. Unicondylar anteromedial fracture pattern is caused by hyperextension varus mechanism and usually accompanied by posterolateral corner rupture. Bicondylar hyperextension injury is characterized by posterior metaphyseal cortical tension rupture, anterior articular depression, and reversed posterior slope.

Conclusion

Currently there is no consensus on the treatment of hyperextension tibial plateau fractures. Further basic and clinical studies are needed.

Revision Multiligament Knee Reconstruction: Clinical Outcomes and Proposed Treatment Algorithm

PURPOSE

To (1) assess clinical outcomes of revision multiligament knee injury (MLKI) reconstruction at a minimum of 2 years' follow-up and (2) present a standardized treatment algorithm used in treating revision MLKI patients.

METHODS

A retrospective review of our institution's MLKI database was performed to identify all patients who underwent revision MLKI reconstructions (≥2 ligaments reconstructed) after implementation of a standardized treatment algorithm in 2000 and had a minimum of 2 years' follow-up. Patient demographic information, injury description (mechanism of injury, neurovascular status, knee dislocation grade, associated chondral or meniscal injury), surgical technique (repair vs reconstruction, staged vs nonstaged, concomitant procedures), mechanism of failure, knee stability, and range of motion, as well as International Knee Documentation Committee and Lysholm scores, were obtained.

RESULTS

We assessed 23 patients (8 female and 15 male patients), with an average age of 26.7 ± 11.5 years at primary surgery and 30.8 ± 11.0 years at revision surgery. The mean follow-up period was 7.5 ± 5.3 years. Of the 23 patients, 10 (43.4%) underwent staged revision procedures: isolated bone grafting in 3, osteotomy in 4, hardware removal with osteochondral allograft in 1, hardware removal with bone grafting in 1, and meniscus repair for a locked knee in 1. The average International Knee Documentation Committee and Lysholm scores were 74.5 ± 22.3 and 79.4 ± 20.2, respectively. High-energy injury and increasing age at revision surgery were the only risk factors found to be associated with significantly worse outcomes (P < .05).

CONCLUSIONS

Patients with recurrent instability after MLKI reconstruction present with many concomitant pathologies, including limb malalignment, bone tunnel widening, retained hardware, meniscal incompetence, and cartilage defects. Revision MLKI reconstruction can provide these patients with modest functional outcomes when a standardized treatment algorithm is used focusing on identification and treatment of the concomitant pathology, often in a staged manner.

LEVEL OF EVIDENCE

Level IV, case series.

Joint loads resulting in ACL rupture: Effects of age, sex, and body mass on injury load and mode of failure in a mouse model

Anterior cruciate ligament (ACL) tears are a common knee injury with a known but poorly understood association with secondary joint injuries and post-traumatic osteoarthritis (OA). Female sex and age are known risk factors for ACL injury but these variables are rarely explored in mouse models of injury. This study aimed to further characterize a non-surgical ACL injury model to determine its clinical relevance across a wider range of mouse specifications. Cadaveric and anesthetized C57BL/6 mice (9-52 weeks of age) underwent joint loading to investigate the effects of age, sex, and body mass on ACL injury mechanisms. The ACL injury load (whole joint load required to rupture the ACL) was measured from force-displacement data, and mode of failure was assessed using micro-dissection and histology. ACL injury load was found to increase with body mass and age (p < 0.001) but age was not significant when controlling for mass. Sex had no effect. In contrast, the mode of ACL failure varied with both age and sex groups. Avulsion fractures (complete or mixed with mid-substance tears) were common in all age groups but the proportion of mixed and mid-substance failures increased with age. Females were more likely than males to have a major avulsion relative to a mid-substance tear (p < 0.01). This data compliments studies in human cadaveric knees, and provides a basis for determining the severity of joint injury relative to a major ACL tear in mice, and for selecting joint loading conditions in future experiments using this model. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1754-1763, 2017.

Tissue Strain Reorganizes Collagen With a Switchlike Response That Regulates Neuronal Extracellular Signal-Regulated Kinase Phosphorylation In Vitro: Implications for Ligamentous Injury and Mechanotransduction

Excessive loading of ligaments can activate the neural afferents that innervate the collagenous tissue, leading to a host of pathologies including pain. An integrated experimental and modeling approach was used to define the responses of neurons and the surrounding collagen fibers to the ligamentous matrix loading and to begin to understand how macroscopic deformation is translated to neuronal loading and signaling. A neuron-collagen construct (NCC) developed to mimic innervation of collagenous tissue underwent tension to strains simulating nonpainful (8%) or painful ligament loading (16%). Both neuronal phosphorylation of extracellular signal-regulated kinase (ERK), which is related to neuroplasticity (R2 ≥ 0.041; p ≤ 0.0171) and neuronal aspect ratio (AR) (R2 ≥ 0.250; p < 0.0001), were significantly correlated with tissue-level strains. As NCC strains increased during a slowly applied loading (1%/s), a "switchlike" fiber realignment response was detected with collagen reorganization occurring only above a transition point of 11.3% strain. A finite-element based discrete fiber network (DFN) model predicted that at bulk strains above the transition point, heterogeneous fiber strains were both tensile and compressive and increased, with strains in some fibers along the loading direction exceeding the applied bulk strain. The transition point identified for changes in collagen fiber realignment was consistent with the measured strain threshold (11.7% with a 95% confidence interval of 10.2-13.4%) for elevating ERK phosphorylation after loading. As with collagen fiber realignment, the greatest degree of neuronal reorientation toward the loading direction was observed at the NCC distraction corresponding to painful loading. Because activation of neuronal ERK occurred only at strains that produced evident collagen fiber realignment, findings suggest that tissue strain-induced changes in the micromechanical environment, especially altered local collagen fiber kinematics, may be associated with mechanotransduction signaling in neurons.

Does age predict outcome after multiligament knee reconstruction for the dislocated knee? 2- to 22-year follow-up

PURPOSE

The purpose of this study is to determine whether age is a predictor of clinical and functional outcomes in patients who sustained a knee dislocation (KD) and underwent multiligament knee reconstruction. It was hypothesized that increasing age will negatively affect patient outcome.

METHODS

In total, 125 multiligament knee injuries (MLKI) associated with KD were surgically reconstructed between 1992 and 2013 and evaluated with IKDC and Lysholm scores at a median follow-up of 5 (range 2-22) years. Patient demographics including age were then analysed with respect to IKDC and Lysholm scores using rank sums and pair-wise rank sums analysis for continuous variables and Chi-square analysis for categorical variables.

RESULTS

In total, 125 patients (96 males and 29 females) with a median age of 31 (range 11-62) years at the time of surgery were included. At final follow-up, patients ≤30 years old compared to >30 years old obtained higher IKDC (73.3 vs. 61.9; p = 0.01) and Lysholm scores (76.9 vs. 68.5; p = 0.04). No confounding variables including gender, injury mechanism, injury pattern, injuries to the peroneal nerve, popliteal artery, meniscus, or cartilage accounted for differences in outcome scores between the two groups.

CONCLUSION

Based on current available literature, this study represents the largest cohort with the longest follow-up reported on MLKI to date. At intermediate- to long-term follow-up, patients >30 years of age that undergo multiligament knee reconstruction for KD have inferior IKDC and Lysholm scores compared to those ≤30 years of age. However, successful multiligament knee reconstruction can still be obtained in this age group.

LEVEL OF EVIDENCE

IV.

Strain-rate sensitivity of the lateral collateral ligament of the knee

The material properties of ligaments are not well characterized at rates of deformation that occur during high-speed injuries. The aim of this study was to measure the material properties of lateral collateral ligament of the porcine stifle joint in a uniaxial tension model through strain rates in the range from 0.01 to 100/s. Failure strain, tensile modulus and failure stress were calculated. Across the range of strain rates, tensile modulus increased from 288 to 905 MPa and failure stress increased from 39.9 to 77.3 MPa. The strain-rate sensitivity of the material properties decreased as deformation rates increased, and reached a limit at approximately 1/s, beyond which there was no further significant change. In addition, time resolved microfocus small angle X-ray scattering was used to measure the effective fibril modulus (stress/fibril strain) and fibril to tissue strain ratio. The nanoscale data suggest that the contribution of the collagen fibrils towards the observed tissue-level deformation of ligaments diminishes as the loading rate increases. These findings help to predict the patterns of limb injuries that occur at different speeds and improve computational models used to assess and develop mitigation technology.

Case report: Osteochondral avulsion fracture of the posteromedial bundle of the PCL in knee hyperflexion

BACKGROUND

Injury of the PCL of the knee in adults usually results in rupture rather than avulsion fracture and avulsions usually occur at the tibial insertion.

CASE DESCRIPTION

We report an avulsion of the PCL with a femoral origin in a 22-year-old man who was injured by hyperflexion of the knee and was treated with arthroscopy. There were two parts in the partial osteochondral avulsion fracture of the PCL posteromedial (PM) bundle. One part was fixed with polydioxanone suture through drill holes and the other was removed. The fracture healed after 3 months and the knee was stable. At 11 months postoperatively the patient had returned to full-time work without pain or restrictions. The Lysholm II knee score was 95 points. Physical examination showed a negative posterior drawer sign.

LITERATURE REVIEW

We identified four other reported cases of PCL femoral origin avulsion fractures in adults. The subjects were 20 to 25 years old in four of five reports, including our patient. Three of the five patients had involvement of only the lateral cortex of the medial femoral condyle whereas two other patients including our patient, had an osteochondral fracture. The mechanism of PCL avulsion seems to be similar to that of a PCL rupture.

PURPOSES AND CLINICAL RELEVANCE

The hyperflexion injury may result in injury of the PM bundle of the PCL. Our case and one other in the literature suggest such avulsions need not involve the entire PCL.

ACL graft re-rupture after double-bundle reconstruction: factors that influence the intra-articular pattern of injury

PURPOSE

To determine the most common rupture patterns of previously reconstructed DB-ACL cases, seen at the time of revision surgery, and to determine the influence of age, gender, time between the initial ACL reconstruction and re-injury, tunnel angle and etiology of failure.

METHODS

Forty patients who presented for revision surgery after previous double-bundle ACL reconstruction were enrolled. Three orthopedic surgeons independently reviewed the arthroscopic videos and determined the rupture pattern of both the anteromedial and posterolateral grafts. The graft rupture pattern was then correlated with the previously mentioned factors.

RESULTS

The most common injury pattern seen at the time of revision ACL surgery was mid-substance AM and PL bundle rupture. Factors that influenced the rupture pattern (proximal vs. mid-substance and distal rupture vs. elongated, but in continuity) were months between ACL reconstruction and re-injury (P = 0.002), the etiology of failure (traumatic vs. atraumatic) (P = 0.025) and the measured graft tunnel angle (P = 0.048).

CONCLUSIONS

The most common pattern of graft re-rupture was mid-substance AM and mid-substance PL. As the length of time from the initial DB-ACL reconstruction to revision surgery increased, the pattern of injury more closely resembled that of the native ACL. Evaluation of patients who have undergone double-bundle ACL reconstruction, with a particular focus on graft maturity, mechanism of injury and femoral tunnel angles, and graft rupture pattern assists in preoperative planning for revision surgery.

Pure Passive Hyperextension of the Human Cadaver Knee Generates Simultaneous Bicruciate Ligament Rupture

Knee hyperextension has been described as a mechanism of isolated anterior cruciate ligament (ACL) tears, but clinical and experimental studies have produced contradictory results for the ligament injuries and the injury sequence caused by the hyperextension loading mechanism. The hypothesis of this study was that bicruciate ligament injuries would occur as a result of knee hyperextension by producing high tibio-femoral (TF) compressive forces that would cause anterior translation of the tibia to rupture the ACL, while joint extension would simultaneously induce rupture of the posterior cruciate ligament (PCL). Six human knees were loaded in hyperextension until gross injury, while bending moments and motions were recorded. Pressure sensitive film documented the magnitude and location of TF compressive forces. The peak bending moment at failure was 108 N m±46 N m at a total extension angle of 33.6 deg±11 deg. All joints failed by simultaneous ACL and PCL damages at the time of a sudden drop in the bending moment. High compressive forces were measured in the anterior compartments of the knee and likely produced the anterior tibial subluxation, which contributed to excessive tension in the ACL. The injury to the PCL at the same time may have been due to excessive extension of the joint. These data, and the comparisons with previous experimental studies, may help explain the mechanisms of knee ligament injury during hyperextension. Knowledge of forces and constraints that occur clinically could then help diagnose primary and secondary joint injuries following hyperextension of the human knee.

A 'plane' explanation of anterior cruciate ligament injury mechanisms: a systematic review

Although intrinsic and extrinsic risk factors for anterior cruciate ligament (ACL) injury have been explored extensively, the factors surrounding the inciting event and the biomechanical mechanisms underlying ACL injury remain elusive. This systematic review summarizes all the relevant data and clarifies the strengths and weaknesses of the literature regarding ACL injury mechanisms. The hypothesis is that most ACL injuries do not occur via solely sagittal, frontal or transverse plane mechanisms. Electronic database literature searches of PubMed MEDLINE (1966-2008), CINAHL (1982-2008) and SportDiscus (1985-2008) were used for the systematic review to identify any studies in the literature that examined ACL injury mechanisms. Methodological approaches that describe and evaluate ACL injury mechanisms included athlete interviews, arthroscopic studies, clinical imaging and physical exam tests, video analysis, cadaveric studies, laboratory tests (motion analysis, electromyography) and mathematical modelling studies. One hundred and ninety-eight studies associated with ACL injury mechanisms were identified and provided evidence regarding plane of injury, with evidence supporting sagittal, frontal and/or transverse plane mechanisms of injury. Collectively, the studies indicate that it is highly probable that ACL injuries are more likely to occur during multi-planar rather than single-planar mechanisms of injury.

The role of the oblique popliteal ligament and other structures in preventing knee hyperextension

BACKGROUND

Ligament restraints to terminal knee extension are poorly understood.

HYPOTHESES

(1) As with other motions of the knee, genu recurvatum is limited primarily by a named, identifiable structure. (2) As the largest static structure of the posterior knee, the oblique popliteal ligament is uniquely suited to act as a checkrein to knee hyperextension.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Twenty fresh-frozen human knees were divided into 3 groups for a ligament sectioning study. Extension moments of 14 and 27 N x m were applied before and after sectioning of each ligament, and motion changes were recorded. In group 1, the oblique popliteal ligament was sectioned first, followed by the fabellofibular ligament, ligament of Wrisberg, anterior cruciate ligament, posterolateral structures, and posterior cruciate ligament. In group 2, the order was altered to section the anterior cruciate ligament first; no other changes were made. Similarly, the cutting order for group 3 was altered to section the posterior cruciate ligament first. The sagittal tibial slope of each specimen was documented off a lateral radiograph.

RESULTS

The greatest increase in knee hyperextension was observed after sectioning the oblique popliteal ligament. This was independent of cutting order, consistent across groups, and statistically significant. In all groups, the increase in knee hyperextension after sectioning the oblique popliteal ligament approached or exceeded the increases seen after sectioning the anterior and posterior cruciate ligaments combined. Overall, less knee hyperextension was seen in knees with increased posterior tibial slope.

CONCLUSION

The oblique popliteal ligament was found to be the primary ligamentous restraint to knee hyperextension.

CLINICAL RELEVANCE

Further studies are needed to determine if surgical repair or reconstruction of the oblique popliteal ligament can restore normal motion limits in patients with symptomatic genu recurvatum. Patients with decreased posterior tibial slope would have increased recurvatum with posterior structure injury, which increases the likelihood of increased symptoms in this population.

Biomechanical and anatomical assessment after knee hyperextension injury

BACKGROUND

Knee hyperextension can be a serious and disabling injury in both the athletic and general patient population. Understanding the pathoanatomy and pathomechanics is critical for accurate surgical soft tissue reconstructions.

PURPOSE

To quantify the effects of knee hyperextension injury on knee laxity in a human cadaveric model and to qualitatively assess the anatomical injury pattern through surgical dissection.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Six fresh-frozen cadaveric knees were rigidly mounted on a custom knee testing system that simulates clinical laxity tests. The knee laxity measurements consisted of anterior-posterior laxity, internal-external rotational laxity, and varus-valgus laxity using a custom testing setup and a Microscribe 3DLX system. The laxity data were collected at both 30 degrees and 90 degrees of knee flexion for the intact specimens and then after 15 degrees and 30 degrees hyperextension injury. After biomechanical assessment, a detailed dissection was performed to document the injured structures in the knee. Repeated-measures analysis of variance with a Tukey post hoc test (P < .05) was used for statistical comparison.

RESULTS

The results from this study suggest progressive damage to translational and rotational knee soft-tissue restraints with increasing knee hyperextension. Knee hyperextension to 30 degrees caused the most significant increase in anterior-posterior and rotational laxity. Anatomical dissections showed a general injury pattern to the posterolateral corner, partial femoral anterior cruciate ligament avulsion in 4 of 6 specimens, and no gross posterior cruciate ligament injuries.

CONCLUSION

Injuries to the posterolateral corner of the knee can result from isolated knee hyperextension.

CLINICAL RELEVANCE

The clinician should be aware of the potential for posterolateral corner injuries with isolated knee hyperextension. This will allow early surgical planning and primary surgical repair.

Sagittal plane compensations for artificially induced limitation of the first metatarsophalangeal joint: a preliminary study

This study was undertaken to establish whether reduced dorsiflexion at the first metatarsophalangeal joint affects sagittal plane kinematics at the ankle, knee, and hip. Twenty individuals with symptom-free metatarsophalangeal joints were studied as they walked with and without an insole designed to restrict first metatarsophalangeal joint dorsiflexion. Sagittal plane kinematics at the ankle, knee, and hip were compared in the two conditions. When walking with the insole, the ankle was more dorsiflexed during late midstance and less plantarflexed during propulsion, the knee was more flexed during midstance, and the hip was less extended during late midstance. This evidence of a link between the first metatarsophalangeal joint and the kinematics of the proximal joints demonstrates the potential for the clinical entities of hallux rigidus and hallux limitus to influence gait and justifies more detailed study of this relationship.

Modeling of failure mode in knee ligaments depending on the strain rate

BACKGROUND

The failure mechanism of the knee ligament (bone-ligament-bone complex) at different strain rates is an important subject in the biomechanics of the knee. This study reviews and summarizes the literature describing ligament injury as a function of stain rate, which has been published during the last 30 years.

METHODS

Three modes of injury are presented as a function of strain rate, and they are used to analyze the published cases. The number of avulsions is larger than that of ligament tearing in mode I. There is no significant difference between the number of avulsions and ligament tearing in mode II. Ligament tearing happens more frequently than avulsion in mode III.

RESULTS

When the strain rate increases, the order of mode is mode I, II, III, I, and II. Analytical models of ligament behavior as a function of strain rate are also presented and used to provide an integrated framework for describing all of the failure regimes. In addition, this study showed the failure mechanisms with different specimens, ages, and strain rates.

CONCLUSION

There have been several a numbers of studies of ligament failure under various conditions including widely varying strain rates. One issue in these studies is whether ligament failure occurs mid-ligament or at the bone attachment point, with assertions that this is a function of the strain rate. However, over the range of strain rates and other conditions reported, there has appeared to be discrepancies in the conclusions on the effect of strain rate. The analysis and model presented here provides a unifying assessment of the previous disparities, emphasizing the differential effect of strain rate on the relative strengths of the ligament and the attachment.