The cyclops lesion: a cause of diminished knee extension after rupture of the anterior cruciate ligament

Comprehensive Clinical Examination of ACL Injuries

A comprehensive clinical examination of the potentially anterior cruciate ligament (ACL)-deficient knee should proceed as follows: inspection; palpation; range of motion; varus and valgus stress; neurovascular status; and finally provocative maneuvers. The Lachman, anterior drawer, Lever, and pivot shift tests are all greater than 90% specific for ACL pathology. Due to the relatively high coincidence of ACL injuries and those to the posterior cruciate ligament, posterolateral corner , posteromedial corner , and menisci, it is critical that the examiner perform provocative maneuvers to evaluate the integrity of these structures as well.

Magnetic Resonance Imaging of Cyclops Lesion in Patients With Non-reconstructed Anterior Cruciate Ligament

Introduction The term cyclops lesion refers to localized anterior fibrosis, which is the abnormal proliferation of fibrous tissue in a joint that develops in the anterior aspect of the intercondylar notch. It is a known cause of extension loss of the knee after anterior cruciate ligament (ACL) reconstruction; however, it can be found in patients who have not undergone any surgical repair of the ACL. The term "cyclops lesion" was given based on the arthroscopic appearance of the fibrous nodule and vessels that resemble an eye. The purpose of this study is to highlight the existence of cyclops lesions in non-operated knees. Methods We conducted a study on 10 patients who were subjected to an MRI knee in a Siemens Magnetom Vida 3 Tesla (Erlangen, Germany) machine. We retrospectively analyzed all 10 cases in our institution from July 2021 to March 2022. These subjects had a previous history of trauma, and they presented with complaints of pain and difficulty in knee extension but no history of previous ligament repair. All patients underwent an MRI examination. When a cyclops lesion was revealed on MR imaging, the signal-intensity characteristics, location, and size were documented. Results There were a total of 10 patients included in the study, of whom eight were males and two were females. The most common clinical presentation in all our cases was difficulty in the extension of the knee, while there was associated instability and difficulty in walking in some patients. There was a demonstrable cyclops lesion near the tibial attachment of ACL in eight (80%) patients, whereas it was found to be located just lateral to the anterior intercondylar notch in the rest of the two (20%) patients. Conclusion MRI is an effective tool to evaluate unexplained pain, functional limitations, and limited range of motion in patients with suspected arthrofibrosis. MRI also helps determine the extent of fibrosis involvement and excludes other complications that may have a similar clinical picture.

Influence of female sex and double-quadruple semitendinosus-gracilis graft on the incidence of postoperative symptomatic cyclops lesions after ACL reconstruction

PURPOSE

Risk factors for the development of symptomatic cyclops lesion after anterior cruciate ligament reconstruction (ACLR) surgery are not entirely identified yet. This study aimed to investigate whether the choice of hamstring graft (semitendinosus-gracilis; STG vs. semitendinosus; ST) affects the risk of developing a symptomatic cyclops lesion after ACLR.

METHODS

This retrospective cohort study included 1416 patients receiving either an ST graft (n = 1209) or an STG graft (n = 207) ACLR with a follow-up of at least 2 years. A persisting extension limitation was clinically determined, and cyclops lesions were confirmed by magnetic resonance imaging (MRI) and second-look arthroscopy. Graft-specific incidence of cyclops lesions was examined with χ2 test and combined with the factors number of graft bundles, graft diameter and sex evaluated with a binominal logistic regression model.

RESULTS

In total, 46 patients developed symptomatic cyclops lesions (3.2%), with 36 having ACLR with an ST graft (3.0%) and 10 with an STG graft (4.8%) (n.s). The mean time from ACLR to the second-look arthroscopy for cyclops removal was 1.1 ± 0.6 years. Female patients were 2.5 times more likely to develop a cyclops lesion than male patients. Patients with an STG graft and larger graft diameters did not have a higher risk of developing cyclops lesions. Patients who received an STG graft with both tendons folded four times (double-quadruple) had significantly higher risk of developing a cyclops compared with all other numbers of graft bundles combined (8.3%, respectively 3.0%; p = 0.014).

CONCLUSION

This study could not prove an increased risk of developing a symptomatic cyclops lesion for patients with an STG graft compared with an ST graft used for ACLR. However, patients with a double-quadruple ACLR had a higher percentage of cyclops lesions compared with all other numbers of graft bundles. Female sex was associated with an increased risk of developing cyclops lesions.

LEVEL OF EVIDENCE

Level III.

Cyclops syndrome following anterior cruciate ligament reconstruction: Can relapse occur after surgery?

Symptomatic cyclops lesions are complications that can be seen at rates of up to approximately 10% after anterior cruciate ligament reconstruction. However, recurrent cyclops lesions have rarely been documented. There are case rare series in the literature regarding the treatment of recurrent cyclops lesion. Future large studies are needed to investigate factors contributing to the development of cyclops lesions and syndrome and treatment options.

Prevention of knee stiffness following ligament reconstruction: Understanding the role of Arthrogenic Muscle Inhibition (AMI)

The knee is a joint that is often injured in sport, with a large and increasing number of ligament tears and repairs; postoperative complications can lead to poor outcome, such as stiffness. Beyond the well-known and well-described intra- and extra-articular causes of postoperative stiffness, the present study introduces the concept of a central reflex motor inhibition mechanism called arthrogenic muscle inhibition (AMI). AMI occurs after trauma and can be defined as active knee extension deficit due to central impairment of Vastus Medialis Obliquus (VMO) contraction, often associated with spinal reflex hamstring contracture. This explains the post-traumatic flexion contracture that is so common after knee sprain. The clinical presentation of AMI is easy to detect in consultation, in 4 grades from simple VMO inhibition to fixed flexion contracture by posterior capsule retraction in chronic cases. After recent anterior cruciate ligament (ACL) tear, more than 55% of patients show AMI, reducible in 80% of cases by simple targeted exercises initiated in consultation. Practically, in patients who have sustained knee sprain, it is essential to screen for this reflex mechanism and assess reducibility, as AMI greatly aggravates the risk of postoperative stiffness. In case of hemarthrosis, we recommend joint aspiration, which provides immediate benefit in terms of pain and motor inhibition. In case of persistent AMI, classical electrostimulation and "cushion crush", as used by all physiotherapists, are ineffective. To reduce the risk of postoperative stiffness, no surgery should be considered until AMI has resolved. LEVEL OF EVIDENCE: expert opinion.

Arthroscopic Lysis of Adhesions for Arthrofibrosis After Anterior Cruciate Ligament Reconstruction

BACKGROUND

Arthrofibrosis (AF) after anterior cruciate ligament reconstruction (ACLR) remains a challenge. There is a paucity of data on arthroscopic interventions for AF after ACLR.

PURPOSE

To (1) describe the patient, injury, and surgical characteristics and patient-reported outcomes (PROs) of those requiring an arthroscopic intervention for loss of motion after ACLR and (2) compare outcomes between patients undergoing an early intervention (within 3 months) versus those undergoing a late intervention (after 3 months).

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Patients with a history of ACLR and a subsequent operative procedure for postoperative AF at a single institution between 2000 and 2018 were retrospectively identified. Arthroscopic interventions included lysis of adhesions, capsular release with or without manipulation under anesthesia, and excision of cyclops lesions. Patients were excluded if they had a knee dislocation or multiple-ligament injury, a periarticular fracture, or less than 2-year follow-up from the arthroscopic intervention. PROs including the Tegner activity score, visual analog scale pain score, and International Knee Documentation Committee score as well as knee range of motion (ROM) were recorded.

RESULTS

A total of 40 patients were included with a mean age of 27.2 years (range, 11.0-63.8 years) at surgery and a mean follow-up of 10.0 years (range, 2.9-20.7 years). The mean preoperative flexion and extension were 102° (range, 40°-150°) and 8° (range, 0°-25°), respectively. The mean postoperative flexion and extension were 131° (range, 110° to 150°) and 0° (range, -10° to 5°), respectively. After the arthroscopic intervention, the mean ROM improved from 94° (range, 40°-140°) preoperatively to 131° (range, 107°-152°) at final follow-up (P < .001), and the visual analog scale pain score improved from 3.0 preoperatively to 1.2 postoperatively (P = .001). Overall, 13 patients (32.5%) underwent an intervention within 3 months and 27 (67.5%) after 3 months. The early intervention group had a higher postoperative International Knee Documentation Committee score compared with the late intervention group (86.8 vs 71.7, respectively; P = .035).

CONCLUSION

An arthroscopic intervention for AF after ACLR successfully improved knee ROM and pain. Patients who underwent either early or late surgery obtained satisfactory motion and function, although improved PROs were observed when the intervention occurred within 3 months of the primary procedure.

Comparison of Clinical, Magnetic Resonance Imaging (MRI) and Arthroscopic Findings in Assessment of Cartilage Defects and Internal Derangement of Knee

BACKGROUND

The knee is the most commonly injured joint because of its anatomical structure, its exposure to external forces, and its functional demands. Orthopaedic surgeons previously relied on clinical evaluation for diagnosing any internal derangement of the knee joint. With the advent of new clinical methods for diagnosing ligament injuries and cartilage defects, there are very less studies comparing the accuracy of all three methods, clinical examination, magnetic resonance imaging (MRI) and arthroscopy to reach a definitive diagnosis.

OBJECTIVE

This study aims to compare the sensitivity, specificity, accuracy and predictive values of clinical examination and MRI with that of arthroscopy which is the ideal investigation of choice for cartilage defects and internal derangements of the knee.

MATERIAL AND METHODS

A prospective, observational and hospital-based study was done on patients with internal derangement of knee and cartilage defects. Clinical examination (based on the clinical tests for each ligament), MRI (1.5 T) and arthroscopy were done on all patients, the findings of which were compared using the Chi-square test. The following parameters were assessed while using arthroscopy as the gold standard of reference: accuracy, specificity, sensitivity, positive predictive value (PPV), and negative predictive value (NPV).

RESULTS

Anterior cruciate ligament (ACL) was the most common ligament to be injured followed by the medial meniscus. The overall accuracy of clinical evaluation and MRI to diagnose meniscal injuries was found to be 94% and 91% respectively. The clinical examination had sensitivity and specificity of 96% and 82% in diagnosing ACL tears, respectively, whereas MRI had sensitivity and specificity of 88% and 76% respectively. For the medial meniscus, the clinical examination had sensitivity and specificity of 93% and 96% respectively whereas MRI had a sensitivity of 100% and specificity of 89%. We observed that the accuracy of MRI for grading ACL and meniscal tears was similar i.e. 79% and 78% respectively, but was slightly low (70%) for grading of chondromalacia patellae.

CONCLUSION

This study supports the use of MRI and clinical assessment in the diagnosis of chondral defects and internal knee derangement. Clinical tests are reliable and have high sensitivity in diagnosing ACL tears and chondral defects when compared to MRI. Not all lesions should routinely undergo MRI for diagnostic purposes; only a few circumstances warrant its usage. MRI is less reliable in grading ACL tears, meniscal tears and chondral injuries.

Occurrence Rate of Cyclops Lesion After Anatomic Double-Bundle ACL Reconstruction: Comparison Between Remnant Tissue Preservation and Resection Methods

Background

The occurrence rate of cyclops lesion after anatomic double-bundle anterior cruciate ligament (ACL) reconstruction with remnant tissue preservation remains unclear.

Hypothesis

The study hypotheses were as follows: (1) the occurrence rate of cyclops lesion will be comparable between the remnant-preserving and remnant-resecting ACL reconstruction methods, and (2) there will be no significant differences in clinical outcomes between the remnant-preserving and remnant-resecting procedures.

Methods

This retrospective comparative study involved 177 patients who underwent unilateral anatomic double-bundle ACL reconstruction using hamstring tendon autografts from 2014 to 2018 at our hospital. According to the Crain classification of ACL remnant tissue, 98 patients with remnant types I, II, or III underwent the remnant-preserving procedure (group A), and the remaining 79 patients with remnant type IV underwent the remnant-resecting procedure (group B). All patients underwent second-look arthroscopy. Patients were evaluated according to arthroscopic and clinical results at postoperative 15.2 ± 8.4 months (mean ± SD). Statistical comparisons between groups were made using the paired Student t test, chi-square test, and Fisher exact test.

Study Design

Cohort study; Level of evidence, 3.

Results

At second-look arthroscopy, the incidence of cyclops lesions was significantly higher in group B than in group A (29.1% vs 13.3%; P = .0139). Cyclops lesions were divided into 4 locations: femoral side (type 1), midsubstance (type 2), tibial side (type 3), and anterior (type 4) of the ACL graft. The ratio of the tibial-side cyclops lesion (type 3) was significantly higher in group B than in group A (P = .0354). There were no significant differences in the clinical evaluation scores between the procedures. Side-to-side anterior laxity was significantly less in group A than in group B (0.7 vs 1.6 mm; P = .0035). Concerning postoperative laceration and synovium coverage of the grafts, group A was significantly better than group B (P < .0001).

Conclusion

In this cohort of patients undergoing double-bundle ACL reconstruction, resection of the ACL remnant was associated with a significantly higher rate of cyclops lesion formation when compared with preservation of the remnant.

Femoral intercondylar notch: Accuracy of a novel MRI measurement protocol

OBJECTIVE

The most common mechanical complication following an anterior cruciate ligament (ACL) reconstruction is joint stiffness, due in part to cyclops syndrome. A narrow intercondylar notch is an anatomical risk factor. A reliable preoperative notch measurement would help anticipate proper graft size, or plan a notchplasty during the ligament reconstruction, if necessary. No study has yet assessed the accuracy of the methods used to measure notch size.

HYPOTHESIS

The novel measurement protocol proposed in this study would be more reproducible than the reference technique.

METHODS

A total of 20 preoperative knee MRIs performed during the assessment of an ACL rupture were randomly selected. The notch size was measured using 2 methods: traditional (ratio of the notch and metaphyseal widths measured on a line drawn through the popliteal groove) and novel. The latter was measured using the same ratio but took into account the notch width in its proximal third, according to a coronal slice that passes through the ACL tibial attachment. Three orthopedic surgeons with different levels of experience (senior surgeon, junior surgeon and surgical resident) performed these measurement protocols twice on anonymized MRI scans, 10days apart. Spearman's rank correlation coefficient was used to assess the intraobserver correlations and a concordance index was used to assess the interobserver correlations. The influence of the second MRI reading was analyzed with a bootstrap test.

RESULTS

The mean intraobserver reliability was 0.73 for the reference method and 0.83 for the proposed method. The values of the bootstrap tests were higher for the proposed method (0.45 vs. 0.45 and 0.70; p<05 for interobserver; 0.49 vs. 0.69 and 0.62; p<05 for intraobserver).

CONCLUSION

The proposed measurement protocol showed a higher reproducibility in assessing notch size than the traditional method. This technique therefore provides a reliable assessment of the intercondylar notch width.

LEVEL OF EVIDENCE

IV; retrospective study.

Significant risk of arthrolysis after simultaneous anterior cruciate ligament reconstruction and treatment of dislocated bucket-handle meniscal tear

INTRODUCTION

Postoperative stiffness is a feared complication after anterior cruciate ligament (ACL) reconstruction. In case of associated dislocated bucket-handle meniscal tear (BHMT), reduction is urgent, with ligament reconstruction in the same surgical step.

HYPOTHESIS

Treatment of associated dislocated BHMT in ACL reconstruction incurs increased risk of arthrolysis for stiffness in flexion and/or extension.

MATERIAL AND METHODS

A retrospective exposure/non-exposure study included 208 patients undergoing ACL reconstruction between January 2009 and December 2018. Those showing dislocated medial or lateral BHMT at surgery (group A) were compared versus those free of meniscal lesions (group B). The main objective was to assess the risk of surgical revision for arthrolysis within 12 months. Group A included 69 patients: 40 male (58%), 29 female (42%); mean age, 29.0±11.2 years. Group B included 139 patients: 68 male (49%), 71 female (51%); mean age, 30.0±10.4 years. Patients were classified according to age of ACL tear, as acute (<6 weeks), subacute (6 weeks to 6 months), or chronic (>6 months).

RESULTS

Risk of revision surgery for arthrolysis was greater in Group A than in Group B, with 7 (10.1%) and 4 (2.9%) cases respectively (p=0.044), with 12-month arthrolysis-free survival of 89.7% (95% CI, 82.7-97.2) and 97.1% (95% CI, 94.3-99.9) respectively (p=0.023). Stiffness in flexion and extension was more frequent in Group A at 6 weeks and at 6 months (p>0.05). Risk of arthrolysis did not significantly differ according to accident-to-surgery time in the overall series (p=0.421) or specifically in Group A (p=0.887). The BHMT was sutured in 39 cases (56.5%), including 3 failures (7.7%) at 12 months' follow-up. Arthrolysis was required in 6 patients treated by meniscal suture (15.4%) and just 1 patient treated by meniscectomy (3.3%) (p=0.128).

CONCLUSION

The present study confirmed increased risk of surgical revision for arthrolysis after ACL reconstruction in case of dislocated BHMT treated in the same surgical step. Age of ACL tear and type of BHMT treatment (suture or meniscectomy) showed no impact on postoperative stiffness.

LEVEL OF EVIDENCE

IV, retrospective exposure/non-exposure cohort study.

Preservation of the Tibial Stump During Anterior Cruciate Ligament Reconstruction Surgery Did Not Increase the Rate of Surgery for Symptomatic Cyclops Lesions

Background

Preservation of the tibial stump during anterior cruciate ligament reconstruction (ACLR) is controversial. While proposed benefits include enhanced graft revascularization, improved proprioception, and decreased graft rupture rates, a potential complication is the development of a symptomatic cyclops lesion. It is therefore important to determine whether any benefits outweigh potential complications.

Purpose

To determine whether greater preservation of the tibial stump remnant would be associated with a decreased graft rupture rate without a concomitant increase in the rate of surgery for symptomatic cyclops lesions at 2 years after ACLR.

Study Design

Cohort study; Level of evidence, 3.

Methods

A cohort of 658 patients in whom the amount of tibial stump preserved was classified as no stump (n = 228), <50% (n = 342), or >50% (n = 88) was followed up for 2 years, with graft ruptures and surgical treatment for cyclops lesions recorded. Contingency and Kaplan-Meier survival analyses were used to determine trends among the 3 remnant preservation groups in terms of graft rupture rates and surgery for cyclops lesions. Subgroup analysis was also conducted to examine sex-based differences.

Results

There was no significant association between graft rupture rates and remnant preservation. There was a significant trend for fewer operations for symptomatic cyclops lesions with greater remnant preservation when the entire cohort was analyzed (P = .04) and also when only female patients were analyzed (P = .04).

Conclusion

Although preservation of the tibial stump remnant was not associated with a reduced graft rupture rate, it was also not associated with increased rates of surgery for symptomatic cyclops lesions.

Cyclops Lesions of the Knee: A Narrative Review of the Literature

Cyclops lesion is a known complication of anterior cruciate ligament reconstruction (ACLR). Although the incidence of cyclops lesion appears to be decreasing, it remains an important cause of restriction of extension after ACLR. We reviewed the available literature regarding the cyclops lesion and syndrome and cyclops-like lesions to analyze available evidence on cyclops lesions and variants of cyclops lesions. A keyword search in PubMed, Scopus, Web of Science, and EMBASE, Ovid Medline, and Ovid journals provided 47 relevant articles in the English literature, which were used to create this review. We classified cyclops lesions based on clinical presentation, pathology, and location. Risk factors, management options, tips to reduce the condition, and controversies related to the condition have been discussed. Female sex, greater graft volume, bony avulsion injuries, excessively anterior tibial tunnel, double-bundle ACLR, and bicruciate-retaining arthroplasty appear to predispose patients to cyclops lesions. Cyclops syndrome is a cyclops lesion that causes a loss of terminal extension. Arthroscopic debridement is an effective treatment for cyclops syndrome, whereas cyclops lesions are usually managed conservatively. It is important to distinguish between cyclops lesion and cyclops syndrome, as management differs based on symptoms. Cyclops lesion is diagnosed using magnetic resonance imaging. The management of choice for symptomatic lesions is surgical excision. Outcomes after excision are very good, and recurrence is rare.

Knee Extension Deficit in the Early Postoperative Period Predisposes to Cyclops Syndrome After Anterior Cruciate Ligament Reconstruction: A Risk Factor Analysis in 3633 Patients From the SANTI Study Group Database

BACKGROUND

Cyclops syndrome is characterized by a symptomatic extension deficit attributed to impingement of a cyclops lesion within the intercondylar notch. The syndrome is an important cause of reoperation after anterior cruciate ligament reconstruction (ACLR). It has been suggested that remnant-preserving ACLR techniques may predispose to cyclops syndrome, but there is very limited evidence to support this. In general terms, risk factors for cyclops syndrome are not well-understood.

PURPOSE

To determine the frequency of and risk factors for reoperation for cyclops syndrome in a large series of patients after ACLR.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

A retrospective analysis of prospectively collected data was performed, including all patients who underwent primary ACLR between January 2011 to December 2017. Patients undergoing major concomitant procedures were excluded. Demographic data, intraoperative findings (including the size of preserved remnants), and postoperative outcomes were recorded. Those patients who underwent reoperation for cyclops syndrome were identified, and potential risk factors were evaluated in multivariate analysis.

RESULTS

A total of 3633 patients were included in the study, among whom 65 (1.8%) underwent reoperation for cyclops syndrome. Multivariate analysis demonstrated that preservation of large remnants did not predispose to cyclops lesions (odds ratio [OR], 1.11; 95% CI, 0.63-1.93). The most important risk factor was extension deficit in the early postoperative period. If present at 3 weeks postoperatively, it was associated with a >2-fold increased risk of cyclops syndrome (OR, 2.302; 95% CI, 1.268-4.239; P < .01), which was increased to 8-fold if present 6 weeks after ACLR (OR, 7.959; 95% CI, 4.442-14.405; P < .0001). None of the other potential risk factors evaluated were found to be significantly associated with an increased frequency of cyclops syndrome.

CONCLUSION

Failure to regain full extension in the early postoperative period was the only significant risk factor for cyclops syndrome after ACLR in a large cohort of patients. Other previously hypothesized risk factors, such as preservation of a large anterior cruciate ligament remnant, did not predispose to the development of this debilitating postoperative complication.

Incidence and risk factors for cyclops syndrome after anterior cruciate ligament reconstruction: A systematic literature review

BACKGROUND

Cyclops syndrome after anterior cruciate ligament (ACL) reconstruction is due to a fibrous nodule that develops in the anterior part of the intercondylar notch and prevents full knee extension. The primary objective of this systematic literature review was to evaluate the incidence of symptomatic cyclops lesion after ACL reconstruction. The secondary objective was to identify risk factors for cyclops syndrome.

HYPOTHESIS

Cyclops syndrome is common after ACL reconstruction and has several risk factors reported in the literature.

METHODS

A systematic literature review was performed by searching the PubMed, Medline, CINAHL, Cochrane, and Embase databases with the key terms 'cyclops' and 'ACL reconstruction'. The data thus retrieved were evaluated independently by two investigators. All articles in English or French that reported the incidence and risk factors of cyclops syndrome after ACL reconstruction were included.

RESULTS

The search retrieved the titles and abstracts of 79 articles, of which 20 were selected to be read in full; among these, 10 were included in the study. The incidence of symptomatic cyclops lesion ranged from 1.9% to 10.9%. Identified risk factors were as follows: pre-operatively, knee inflammation and/or motion restriction at the time of ACL reconstruction; intra-operatively, narrow intercondylar notch and excessively anterior position of the tibial tunnel; and post-operatively, persistent hamstring muscle spasm.

DISCUSSION

Development of a cyclops lesion is common after ACL reconstruction, occurs early, and may require further surgery. The knowledge of the risk factors provided by this study may improve the ability to devise effective preventive measures.

LEVEL OF EVIDENCE

II, systematic literature review.

Flexion contracture due to cyclops lesion after bicruciate-retaining total knee arthroplasty

Flexion contracture may develop after total knee arthroplasty (TKA) and is usually associated with soft tissue contracture in the posterior compartment or hamstrings. A cyclops lesion is a soft tissue mass which can form in the anterior compartment usually after anterior cruciate ligament reconstruction and has been observed after bicruciate-retaining TKA. We have treated a patient who developed progressive loss of full extension from 0° to 20° after bicruciate-retaining TKA. A large fibrous tissue mass (cyclops lesion) was identified in the anterior compartment during arthrotomy 1 year after TKA. Excision of the mass resulted in complete resolution of the flexion contracture.

Complications After Anterior Cruciate Ligament Reconstruction and Their Relation to the Type of Graft: A Prospective Study of 958 Cases

BACKGROUND

Complications and adverse events after anterior cruciate ligament (ACL) reconstruction are well known, but they have been underestimated in previous studies.

PURPOSE

To describe the complications and adverse events after ACL reconstruction within a 2-year follow-up and analyze them in relation to the type of graft.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

From 2000 to 2012, 958 patients with an isolated ACL injury underwent surgery by a single knee surgeon. ACL reconstruction was performed with the medial portal technique for the femoral tunnel and the use of bone-patellar tendon-bone (BPTB) or hamstring tendon graft. Patients were reviewed at 6 weeks and 3, 6, 12, and 24 months after surgery with the International Knee Documentation Committee score, plain radiographs, and the KT-1000 arthrometer.

RESULTS

Of 958 patients enrolled, 147 (15%) were lost at last follow-up. The 2 groups (bone-patellar tendon-bone [n = 257] and hamstring [n = 554]) were similar regarding the mean age at the time of surgery and preoperative anterior laxity. The main complications were as follows: anterior knee pain (n = 130 of 811, 16%), stiffness (n = 72, 8.8%), secondary meniscal lesions (n = 59, 7.2%), pain attributed to fixation (n = 79, 9.7%), ACL rerupture (n = 47, 5.7%), contralateral ACL ruptures (n = 24, 3%), patellar fractures (n = 3, 0.3%), infections (n = 9, 1%), and thromboembolic complications (n = 5, 0.6%). There was no significant difference between the grafts with respect to the frequency of joint stiffness, secondary meniscal lesions, or anterior knee pain. During the first 2 postoperative years, the percentage of patients with anterior knee pain was higher in the patellar tendon group (23.3% vs 12.6%, P < .001); however, this difference was not significant after the 2-year interval (3.1% vs 2.5%, P = .63). The percentage of patients with a rerupture of the graft was significantly lower in the patellar tendon group than in the hamstring group (25 of 811 [3.1%] vs 57 of 811 [7%], P = .023). Similar results were recorded regarding the pain related to the hardware material (7 of 811 [0.8%] in the BPTB group vs 113 of 811 [13.9%] in the hamstring group, P = .001). The percentage of ACL ruptures contralateral to the repair was higher in the patellar tendon group (41 of 811 [5%] vs 17 of 811 [2%], P = .016).

CONCLUSION

The total rate of complications after an ACL reconstruction was 39%, and the surgical revision rate for any reason was 28%. Problems with the hardware material were more frequent in the hamstring group, leading to an increased rate of surgical revision. Anterior knee pain was initially higher in the patellar tendon group, but there was no significant difference in a 2-year interval. The rerupture rate was statistically higher in the hamstring group.

Remnant preservation technique versus standard technique for anterior cruciate ligament reconstruction: a meta-analysis of randomized controlled trials

Background

This meta-analysis was performed to compare the clinical outcomes of primary anterior cruciate ligament (ACL) reconstruction using the ACL remnant preservation technique versus the standard technique.

Methods

PubMed, Embase, and the Cochrane Library were searched through December 24, 2017, to identify randomized controlled studies that compared the use of the ACL remnant preservation technique versus the standard technique for primary ACL reconstruction. Statistical heterogeneity among the trials was evaluated with chi-square and I-square tests. A sensitivity analysis was conducted to explore sources of heterogeneity. Subgroup analysis was performed to identify potential differences according to type of ACL remnant tissue (remnant bundle or remnant fibers).

Results

Seven studies with a combined 412 patients (208 in the remnant preservation technique group and 204 in the standard technique group) were included in the meta-analysis. There was a significant difference between the groups in Lysholm score (mean difference (MD), 2.20; 95% confidence interval (CI), 0.95–3.45; P = 0.0006) and side-to-side difference (MD, − 0.71; 95% CI, − 0.87 to − 0.55; P < 0.01). There was no significant difference between the groups in subjective International Knee Documentation Committee (IKDC) score, complications, pivot shift test, Lachman test, or overall IKDC score. Subgroup analysis demonstrated that for primary ACL reconstruction with preservation of remnant fibers, the remnant preservation technique was superior to the standard technique based on Lysholm scores (P < 0.01) and side-to-side difference (P < 0.01).

Conclusions

Based on the current literature, using the remnant preservation technique showed a better clinical outcome than using the standard technique for patients undergoing primary ACL reconstruction with respect to Lysholm score and side-to-side difference. However, it remains unclear that there is a definite advantage to use the remnant preservation technique compared with the standard technique.

Electronic supplementary material

The online version of this article (10.1186/s13018-018-0937-4) contains supplementary material, which is available to authorized users.

Anterior Knee Impingement in a High-Level Football Punter: A Case Report and Description of the Active-Passive Knee Extension Test

A 22-year-old football punter complained of anterior knee pain deep to his patellar tendon that occurred every time the knee of his kicking leg reached full extension during a punt. Arthroscopy confirmed anterior impingement between a fibrous tissue eminence directly anterior to his anterior cruciate ligament (ACL) and the intercondylar roof in full extension. With the eminence removed, full extension no longer caused impingement as demonstrated arthroscopically. He resumed punting at maximal effort 6 weeks postoperatively without pain. We report the active-passive knee extension test, a physical examination maneuver designed to identify patients with anterior knee impingement between tissue anterior to the ACL and the intercondylar roof. This test is a helpful part of the clinical examination in detecting these lesions.

The cyclops lesion after bicruciate-retaining total knee replacement

The cyclops lesion is a localized anterior arthrofibrosis most commonly seen following anterior cruciate ligament reconstruction. The lesion forms at the anterior cruciate ligament insertion creating a painful extension block between femoral intercondylar notch and tibial plateau. We present 2 cases (3 knees) in which cyclops lesions appeared atypically following bicruciate-retaining total knee replacement. Two lesions occurred in a single patient following bilateral knee replacement. One lesion occurred in an active sportswoman. All 3 resolved following arthroscopic debridement. We describe the presentation of this unusual complication and suggest keys to its diagnosis, treatment, and prevention.

Hamstring Contracture After ACL Reconstruction Is Associated With an Increased Risk of Cyclops Syndrome

Background:

Cyclops syndrome is characterized by loss of terminal knee extension due to proliferative fibrous nodule formation in the intercondylar notch. This complication occurs in the early postoperative period after anterior cruciate ligament reconstruction (ACLR). The pathogenesis of Cyclops syndrome is not well understood.

Hypothesis:

Persistent hamstring contracture after ACLR is associated with an increased risk of subsequent Cyclops syndrome.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

The files of 45 patients who underwent arthroscopic debridement of a Cyclops lesion after ACLR were analyzed. Recorded data included demographic information and technical details of surgery. Preoperative magnetic resonance images were also analyzed, and patients with femoral bone bruising were identified. Passive and active range of motion were recorded in all patients preoperatively and at 3 and 6 weeks after surgery to address the Cyclops lesion. Passive extension deficit was evaluated in comparison with the contralateral limb and classified as secondary to hamstring contracture when contracture was observed and palpated in the prone position and when the extension deficit was reversed after exercises performed to fatigue the hamstrings. A control group was selected using a random numbers table among our entire ACLR cohort. Statistical analysis was performed to analyze differences between the 2 groups.

Results:

There was no significant difference between the groups with regard to age at ACLR, sex distribution, time from injury to surgery (P > .05), proportion of professional athletes, presence of femoral bone bruise, or technical aspects of surgery. The overall extension deficit incidence was significantly higher in the Cyclops group at 3 weeks (Cyclops, 71%; control, 22%) (P < .001) and at 6 weeks (Cyclops, 60%; control, 7%) (P < .001). The extension deficit related to hamstring contracture was significantly higher in the Cyclops group at 3 weeks (Cyclops, 58%; control, 22%) (P < .001) and at 6 weeks (Cyclops, 29%; control, 2%) (P < .001).

Conclusion:

The Cyclops lesion is associated with a persistent hamstring contracture at 3 and 6 weeks after ACLR.

Stump Entrapment of the Torn Anterior Cruciate Ligament

We present a case of anterior cruciate ligament stump entrapment in a 24-year-old gentleman who traumatically injured his knee. The anterior stump became entrapped in the intercondylar notch and after a process of inflammation and fibrosis, produced a mass similar to the more familiar cyclops lesion that may complicate anterior cruciate ligament reconstruction.

Significant associated MRI findings in patients with anterior cruciate ligament stump entrapment

OBJECTIVE

Objective of this study was to determine the relationship between development of stump entrapment (SE) lesions and associated injuries in patients with knee extension deficits who underwent anterior cruciate ligament (ACL) reconstruction surgery.

MATERIALS AND METHODS

This retrospective study included 79 patients who had an arthroscopy-proven ACL rupture causing knee extension loss. Presence and type of the SE lesions, injuries of collateral-cruciate ligaments and bones, and tears of the menisci were evaluated and recorded on magnetic resonance imaging.

RESULTS

The SE lesions were significantly more common in patients who had compressive posterior lateral tibial plateau fractures, tibia medial plateau edema and medial collateral ligament (MCL) injuries compared to the patients without stump lesions (p < 0.05). Posterior cruciate ligament (PCL) partial tears or sprains were significantly more common in patients with SE 1 lesions compared to the patients with SE 2 lesions (OR = 6.72; 95 % CI: 1.56-28.93).

CONCLUSION

SE is significantly more common in patients with compressive posterior lateral tibial plateau fractures, tibia medial plateau edemas and MCL injuries. PCL injury is more common in patients with type 1 SE.

Sonographic and Magnetic Resonance Imaging Examination of a Cyclops Lesion After Anterior Cruciate Ligament Reconstruction: A Case Report

OBJECTIVE

This case report describes magnetic resonance imaging (MRI) and diagnostic ultrasound (US) findings for a patient with arthrofibrosis related to a complication of anterior cruciate ligament (ACL) reconstruction.

CLINICAL FEATURES

A 25-year old man presented with right knee pain and loss of extension 5 years after ACL reconstruction. MRI and sonographic examination revealed a soft tissue mass anterolateral to the ACL graft consistent with a cyclops lesion. The lesion was surgically resected and physical therapy was followed postoperatively.

INTERVENTION AND OUTCOME

The patient reported that full range of motion was restored 6 weeks after resection and a course of physical therapy. MRI is the modality of choice for diagnosis, but US may be useful in the diagnosis of this condition.

CONCLUSION

Cyclops lesions may complicate ACL reconstruction or acute ACL injuries. The patient may present with pain and loss of extension, which can be debilitating. MRI and US can be used to diagnose this condition in a timely manner, ensuring optimal clinical outcomes.

The difference in clinical outcome of single-bundle anterior cruciate ligament reconstructions with and without remnant preservation: A meta-analysis

BACKGROUND

The aim of this study was to compare the clinical performance and complications between an ACL reconstruction with a remnant-preserving single-bundle technique and a standard single-bundle technique.

METHODS

A search was performed of RCTs comparing the clinical outcomes and complications of ACL reconstruction with remnant-preserving and standard single-bundle techniques during October 2014. Relevant data were extracted and CONSORT was used to assess the methodological quality. Stata/SE 12.0 was used to perform a meta-analysis of the clinical outcomes.

RESULTS

Six RCTs were included, with a total of 378 patients: 190 in the remnant-preservation technique group and 188 patients in standard-technique group. Assessing anterior stability, no difference was found between the groups for the KT arthrometer, negative rate of Lachman, and the pivot shift test. Assessing functional outcome, there was no significant difference in IKCD scores and grades or Lysholm score. In terms of complications, the percentage of tibial tunnel enlargement in the group of the remnant-preservation technique was significantly lower, despite no significant difference in the incidence of cyclops lesions.

CONCLUSIONS

The outcome of single-bundle ACL reconstruction with the remnant-preservation technique is similar to that with the standard technique in terms of anterior stability and functional recovery of the knee. Remnant preservation in ACL reconstruction decreases the percentage of tibial tunnel enlargement. Level of evidence is II.

Diagnosis of ligamentous and meniscal pathologies in patients with anterior cruciate ligament injury: comparison of magnetic resonance imaging and arthroscopic findings

BACKGROUND

Magnetic resonance imaging (MRI) is routinely used to diagnose or support clinical diagnoses for meniscal or ligamentous injuries prior to offering patients arthroscopic treatment. However, the sensitivity of MRI for the detection of meniscal injury is not yet 100%. Sportsmen have occasionally returned to play with undiagnosed meniscal lesions on the basis of a normal MRI examination. This study was designed to assess the diagnostic parameters of MRI in patients with acute anterior cruciate ligament (ACL) injury.

METHODS

MRI and arthroscopic findings of 320 patients with acute ACL injury were included in this retrospective review. Patients belonged to a single surgeon from a high volume tertiary healthcare institution. All patients had either a MRI or an arthroscopic diagnosis of an acute ACL injury of one knee or both. All patients underwent therapeutic arthroscopy by the senior author routinely as part of arthroscopy-aided ACL reconstruction. Arthroscopic findings were the diagnostic reference based on which the positive predictive value (PPV), negative predictive value (NPV), sensitivity, specificity and concordance strength of association of MRI were calculated for ACL, posterior cruciate ligament (PCL), medial meniscus (MM) and lateral meniscus (LM) injuries.

RESULTS

MRI was most accurate in diagnosing cruciate ligament injuries with a PPV approaching 100%. The PPV of MRI in diagnosing meniscal injuries was approximately 60%. MRI was almost 100% sensitive and specific in diagnosing ACL injuries and 82% sensitive and 100% specific in diagnosing PCL injuries. Conversely, MRI was 77% sensitive and 90% specific in diagnosing MM injuries; and 57% sensitive and 95% specific in diagnosing LM injuries.

CONCLUSIONS

MRI remains the gold standard for diagnosing soft tissue injuries of the knee. However, there is a false positive rate ranging from 6% to 11% for meniscal tears.

Sensitivity and specificity of bell-hammer tear as an indirect sign of partial anterior cruciate ligament rupture on magnetic resonance imaging

PURPOSE

The main purpose of this study was to evaluate the usefulness of the bell-hammer sign in the diagnosis of partial tears of the anterior cruciate ligament (ACL) of the knee on MRI.

METHODS

A retrospective study was performed including all patients who underwent ACL reconstruction for partial or complete tears from 2008 to 2009. The diagnosis of partial or complete ACL tears was based on the appearance of the ligament bundles and the signal quality on MRI. On arthroscopy, which is considered the gold standard, each bundle was classified as normal, partially or completely torn depending on the extent of the rupture and the quality of the remaining fibres. The study included 312 patients, 83 women and 229 men (mean age 33.3 ± 19.6 years). A diagnosis of a tear was made in all patients on preoperative MRI. Arthroscopy did not show any normal ACL, 247/312 (79.2 %) complete tears and 65/312 (20.8%) partial tears, 50/65 (76.9%) on the anteromedial bundle (AM) and 15/65 (23.1%) the posterolateral bundle.

RESULTS

The bell-hammer sign was found on MRI in 13/312 patients (4.5%). It involved 9/65 (13.8%) partial tears, all in the AM bundle, and 4/247 (1.6%) complete tears, significantly more frequent in cases of partial rupture (p < 0.0001). MRI diagnosed a partial tear in 15/65 cases without the bell-hammer sign (sensitivity CI 95% = 23.1 ± 10%, specificity CI 95% = 95.9 ± 2.5%) and with the bell-hammer sign in 23/65 cases (sensitivity CI 95% = 35.4 ± 11%, specificity CI 95% = 93.9 ± 3%). The association of the bell-hammer sign with conventional radiological diagnostic criteria has improved diagnosis performance of MRI for partial tears but not significantly (ns).

CONCLUSION

The most important interest of the bell-hammer sign in the day-to-day clinical work is to suggest partial tears on MRI. It aids making a diagnosis, but its absence does not exclude partial ACL rupture.

LEVEL OF EVIDENCE

Diagnostic study, Level II.

Serial MRI and clinical assessment of cyclops lesions

PURPOSE

'Clinical cyclops syndrome' is associated with pain and a palpable 'clunk' at terminal extension with the loss of full extension. The aims of this prospective controlled study were: (1) to assess whether the minimal debridement of the ACL stump and notch is associated with an increased incidence of clinical cyclops lesions, (2) to look at the incidence and natural history of 'MRI cyclops' lesions using serial MRI's and (3) to assess whether 'MRI cyclops' lesions are associated with the loss of extension.

METHODS

Forty-eight patients were randomized for ACL reconstruction into standard (23) and minimal debridement (24) techniques. One patient was excluded from the study. All patients underwent MR scanning postoperatively at 2, 6 and 12 months, together with the clinical assessment using a KT-1000 arthrometer and International Knee Documentation Committee evaluation. All observations were made by investigators blinded to the surgical technique.

RESULTS

There was no statistical difference in the incidence of cyclops lesions between the two groups (n.s.). The overall incidence of cyclops lesions was 46.8% (22 of 47). The natural history is variable with some getting larger, smaller or remaining static in size. Of patients with cyclops lesions, 17 patients (77%) had cyclops lesions in the setting of full extension. Five patients (23%) had loss of extension at 12 months with no MRI cyclops detected at 2 months.

CONCLUSIONS

The natural history is variable; although once present, the majority of cyclops remain static or regress in size. The onset of cyclops lesions is usually between 6- and 12-month post-ACL reconstruction. Minimal debridement does not lead to an increased incidence of clinical cyclops lesions. The authors conclude that loss of extension is multi-factorial, and there is a discrepancy between what we term 'MRI cyclops' and true 'clinical cyclops'.

LEVEL OF EVIDENCE

Case-control study, Level II.

Sparing the anterior cruciate ligament remnant: is it worth the hassle?

INTRODUCTION

Anterior cruciate ligament (ACL) rupture is the most common surgically treated ligament injury. Many efforts have been taken to reconstruct it as anatomically as possible to restore knee stability and, possibly, prevent knee osteoarthritis.

SOURCES OF DATA

A literature search was performed using the isolated or combined keywords 'ACL augmentation remnant', 'ACL reconstruction and remnant and stump', 'ACL reconstruction and remnant and stump preserving and stability' and 'ACL remnant complete tear' with no limit regarding the year of publication. We identified seven published studies.

AREAS OF AGREEMENT

The ACL remnant might accelerate the vascularization and the ligamentization of the graft and contribute to faster graft innervation leading to a better proprioception.

AREAS OF CONTROVERSY

The role of the ACL remnant is debated, because, although it may increase the risk of impingement and the formation of cyclops lesion, its preservation can improve proprioception, biomechanical functions and vascularity. However, the current assessment methods to assess proprioception, vascularization and the ligamentization do not lead to hard evidence that preservation of the remnant confers clinically relevant advantages over its excision.

GROWING POINTS

The ACL remnant has been demonstrated in experimental studies to have a role in improving revascularization, ligamentization and reinnervation of the graft, but these findings are still not supported by clinical findings. A more direct way to assess proprioceptive function after ACL reconstruction and appropriately conducted powered and rigorously prospective randomized double-blind studies comparing the clinical outcomes of excising the remnant to leaving it in situ are necessary.

Stump entrapment of the anterior cruciate ligament in late childhood and adolescence

Displacement of a portion of the torn anterior cruciate ligament (ACL) into the intercondylar notch can cause a focal fibrotic reaction similar to that seen following ACL reconstruction. This displacement, which can result in locking or limitation of knee extension, is termed stump entrapment and is described in adult MR imaging literature. We present a pictorial essay of the etiology and appearance of stump entrapment on MR imaging of the knee in an older child and adolescents and review the significance of this finding.

Arthroscopic identification of isolated tear of the posterolateral bundle of the anterior cruciate ligament

PURPOSE

The goal of this study was to arthroscopically identify and assess the progressive changes in isolated ruptures of the posterolateral bundle of the anterior cruciate ligament (ACL) over time.

METHODS

This prospective study investigated 174 patients for isolated posterolateral bundle tears during arthroscopic ACL reconstruction. The preoperative side-to-side anterior laxity was measured in all patients. The torn ACLs were inspected and analyzed arthroscopically to determine the tear pattern.

RESULTS

Complete ACL tears were identified in 78.7% of patients and partial ACL tears in 21.3%. Isolated anteromedial bundle tears were identified in 22 patients and posterolateral bundle tears in 15 patients. Statistical analysis showed a significant difference in preoperative differential knee laxity between the group with complete ACL rupture and the group with partial ACL rupture. On arthroscopic evaluation, the posterolateral bundle had retracted distally toward the tibial surface over time. The amount of retraction was correlated to the time period from injury to reconstruction.

CONCLUSIONS

In this study the exact diagnosis of an ACL partial tear was made at arthroscopy in all cases. Our observations confirm the evolution of the ruptured posterolateral bundle, which shows a retraction toward the tibia over time.

LEVEL OF EVIDENCE

Level II, development of diagnostic criteria based on consecutive patients with a universally applied gold standard.

Analysis of different kinds of cyclops lesions with or without extension loss

PURPOSE

The purpose of this study was to retrospectively evaluate patients after anterior cruciate ligament (ACL) reconstruction in whom a cyclops lesion developed to seek the etiologic factors.

METHODS

From 1999 to 2005, we observed 48 cases of cyclops lesions in 311 cases arthroscopically while removing the internal fixation devices after ACL reconstruction. Before removing the hardware, the function of the knee was evaluated through symptoms, signs, radiography, and KT-2000 measurement (MEDmetric, San Diego, CA) in 311 cases. Histologic examination was performed on some of the resected lesions.

RESULTS

Of the 311 patients, 45 were found to have nodular formations in the anterior part of the knee; this caused extension loss in 6 patients. Extension loss occurred at 2 to 3 months after ACL reconstruction. Histologic results were available in 18 patients (6 complained of a loss of extension and 12 were asymptomatic). Microscopic examination of the resected fibrous nodules showed disorganized fibrous connective tissue. We found that 8 nodules (4 with extension loss and 4 without extension loss) contained chondroid tissues, but we did not find osseous tissue in the nodules. The histologic appearance was similar to hypertrophic, degenerative granulation tissue.

CONCLUSIONS

Among 311 second-look arthroscopies after ACL reconstruction, 45 cyclops lesions were found with a typical histology indicating an inflammatory proliferation with disorganized fibrous tissue, with some having chondroid tissue. Clinically, 10 patients had not returned to sporting activities: 6 of 6 who had extension loss and 4 of 39 who had full range of motion. All 6 patients with extension loss had full motion after resection of the cyclops lesion.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Knee and Ankle Ligaments: Magnetic Resonance Imaging Findings of Normal Anatomy and at Injury

Ligamentous injuries of the lower limb are a common entity sustained during sports activities and military training. Magnetic resonance (MR) imaging of the knee and ankle is playing an increasingly important role in the detection, diagnosis and prognosis of these injuries and their associated complications. MR imaging with its exquisite soft tissue contrast resolution and multiplanar capability is increasingly seen as the modality of choice for evaluating ligamentous injuries of the knee and ankle. Representative knee and ankle MR studies from a tertiary referral hospital are used to illustrate both the normal appearance and typical radiological features of common ligamentous injuries of the knee and ankle. A thorough understanding of the MR appearances of these injuries is crucial to the radiologist and clinicians involved in the management of these patients. Key words: Anterior cruciate ligament, Anterior talofibular ligament, Sports injury, Sprain

Complications of anterior cruciate ligament reconstruction with bone-patellar tendon-bone constructs: care and prevention

Rupture of the anterior cruciate ligament is a common injury. Correct diagnosis and patient selection, along with proper surgical technique, with careful attention to anatomic graft placement, followed by attention to proper rehabilitation, leads to predictably good to excellent results. This article reviews the recognition and avoidance of complications associated with bone-patellar tendon-bone constructs of anterior cruciate ligament reconstruction.

Cyclops Lesions That Occur in the Absence of Prior Anterior Ligament Reconstruction1

Loss of full extension after anterior cruciate ligament (ACL) reconstruction, with development of an audible and palpable "clunk" with terminal extension was first described by Jackson and Schaefer as "cyclops syndrome." This syndrome, which is the result of a fibrous nodule (termed a cyclops nodule), has recently been described in patients who have sustained ACL injury but have not undergone reconstructive surgery. From 2001 to 2006, the authors identified 10 patients (five women and five men, ages 27-76 years) with cyclops nodules seen at magnetic resonance (MR) imaging. All patients had a history of trauma but no history of ACL reconstruction. The cyclops lesions had a mean size of 16 x 12 x 11 mm, with 90% of them located just anterior to the distal ACL. MR imaging showed a well-defined, somewhat heterogeneous soft-tissue nodule with a signal intensity typically similar to that of skeletal muscle. The authors suspect that the cause of cyclops lesions that occur in the absence of ACL reconstruction is similar to that suggested in the classic postoperative patient. Cyclops syndrome should be suspected in any patient in whom an ACL nodule is identified at MR imaging, and similarly a cyclops nodule should be considered as a possible cause of loss of extension in any patient who has sustained ACL injury. Movies available at http://radiographics.rsnajnls.org/cgi/content/full/e26/DC1.

Cyclops syndrome occurring after chronic partial rupture of the anterior cruciate ligament without surgical reconstruction

Cyclops syndrome is one of the specific causes of loss of extension of the knee following anterior cruciate ligament (ACL) reconstruction. This syndrome is manifest by progressive loss of knee extension associated with pain and audible clunk at terminal extension caused by a pedunculated nodule of fibrovascular proliferative tissue usually arising from a graft. Recent published reports, however, have described Cyclops syndrome also developing after a partial ACL rupture without surgical reconstruction. In most cases, Cyclops syndrome generally occurred within 2 months after reconstruction surgery or rupture. Here we report on the case of a patient with symptoms and arthroscopic and histological findings compatible with Cyclops syndrome that developed after a chronic partial ACL rupture that occurred 23 years ago. To our knowledge, this is the first case report of Cyclops syndrome occurring after chronic partial ACL rupture.

MR Arthrography of the Knee: How, Why, When

MR arthrography combines the techniques of arthrography with MR imaging to benefit from the added imaging information afforded by intra-articular distention. This article reviews technical considerations for MR arthrography, potential complications, indications, pitfalls in imaging diagnosis, and commonly encountered pathology. It is an elegant study that can offer precise diagnostic information in the appropriate clinical setting.

Differential diagnosis of tumours and tumour-like lesions of the infrapatellar (Hoffa?s) fat pad: pictorial review with an emphasis on MR imaging

A variety of intrinsic and extrinsic tumours and tumour-like conditions may affect the infrapatellar (Hoffa's) fat pad (IFP). MR imaging is the technique of choice in evaluating these conditions, but correlation with radiographs is important to identify those lesions producing mineralization. This pictorial review illustrates the spectrum of mass-like lesions that can affect the IFP, emphasizing the radiographic and MR findings that suggest a specific diagnosis.

Acute anterior cruciate ligament stump entrapment in anterior cruciate ligament tears: MR imaging appearance

PURPOSE

To describe the magnetic resonance (MR) imaging appearance of anterior cruciate ligament (ACL) stump entrapment in patients who presented with decreased knee extension after rupturing the ACL.

MATERIALS AND METHODS

MR images in 15 patients who had presented with a block to terminal knee extension after sustaining an ACL tear were retrospectively reviewed. The MR imaging appearances of entrapped ACL stumps were defined and correlated with arthroscopic and histologic findings.

RESULTS

The entrapped ACL stumps had two distinct appearances. Type 1 stumps (n = 11) were characterized by a nodular mass located at the anterior aspect of the intercondylar notch, interposed between the lateral femoral condyle and tibia. Type 2 stumps (n = 4) were characterized by a tonguelike free end and angulation of the stump. Histologic evaluation of the resected specimens showed distorted ACL fibers intermixed with variable fibrosis and inflammation.

CONCLUSION

Entrapment of an ACL stump can limit knee extension. The two observed appearances of entrapped ACL stumps likely represent two points along a spectrum of appearances, which possibly includes the cyclops lesion.

Progressive loss of knee extension after injury. Cyclops syndrome due to a lesion of the anterior cruciate ligament

Cyclops syndrome has been defined as a loss of knee extension due to impingement of a pedunculated proliferative tissue mass after anterior cruciate ligament reconstruction. We describe four patients who were operated on for progressive loss of knee extension after minor knee injury. During the arthroscopic procedure, the consistent finding was a fibrous pedunculated nodule adhering to the anterolateral aspect of the original anterior cruciate ligament, obstructing extension by impingement in the anterior aspect of the knee. At least part of the anterior cruciate ligament was intact in all cases. These patients were compared with seven patients who developed cyclops syndrome after anterior cruciate ligament reconstruction. Clinical and arthroscopic findings were the same in both groups. An arthroscopic excision of the nodule, performed an average of 12 weeks after knee trauma or after reconstruction, gave very good results. Histologic examination of the excised nodules from both groups showed fibroelastic connective tissue proliferation, thromboangiitis, and areas of necrotic bone and foreign body giant cell granuloma. On the basis of our observations, we conclude that formation of a fibrous pedunculated nodule may occur after an anterior cruciate ligament injury as well as after surgical reconstruction of the anterior cruciate ligament.