Anterior Mobility of the Posterior Horn of the Lateral Meniscus Is Associated With Abnormal Magnetic Resonance Imaging Findings of Anteroinferior Popliteomeniscal Fascicle and Posterosuperior Popliteomeniscal Fascicle as Well as a Clinical History of Catching or Locking Symptoms.

Purpose: To identify predictors of anterior mobility of the posterior horn of the lateral meniscus (PHLM) among patient demographics (age, sex), clinical characteristics (a history of catching or locking symptoms [CLS], body mass index, alignment of limb), and magnetic resonance imaging (MRI) findings of 4 restraints: anteroinferior popliteomeniscal fascicle (aiPMF), posterosuperior popliteomeniscal fascicle (psPMF), posteroinferior popliteomeniscal fascicle (piPMF), and meniscofibular ligament (MFibL). Methods: Between October 2010 and December 2014, patients who underwent arthroscopic measurement of mobility of the PHLM were identified. The Sakai classification was used to classify aiPMF and psPMF on MRI into the following 3 types: type A, the fascicle was depicted with obvious continuity and with a low-intensity band; type B, depicted with continuity but with an ambiguous intensity structure; and type C, depicted with discontinuity or not visible. Magnetic resonance images of the piPMF and MFibL were evaluated as presence or absence. The mobility of the PHLM was measured arthroscopically at traction forces of 10 and 20 N. Results: A total of 73 patients (47 men, mean age 41.8 ± 19.3 years) were included. Multivariate regression analyses revealed aiPMF type C and psPMF types B and C to be independent factors associated with mobility at both traction forces, and CLS was an independent factor at a traction force of 20 N. Compared with that of type A, the increased mobility of aiPMF type C was 5.0 mm (P = .019) and 5.6 mm (P = .011) at 10 and 20 N, respectively; the increased mobility of psPMF type B was 2.5 mm (P = .007) and 3.5 mm (P = .0003), respectively; and the increased mobility of psPMF type C was 3.3 mm (P = .021) and 3.6 mm (P = .014), respectively. The increased mobility associated with CLS was 3.5 mm at 20 N (P = .022). Conclusions: Anterior displacement of the PHLM induced by an external traction force at 90° of flexion of the knee joint was associated with abnormal MRI findings of the anteroinferior popliteomeniscal fascicle and posterosuperior popliteomeniscal fascicle, as well as a history of catching or locking symptoms. Clinical Relevance: Understanding signs and symptoms and associated pathology in patients with symptomatic anterior mobility of the posterior horn of the lateral meniscus may help guide best treatment.

Reconstruction of the Popliteomeniscal Fascicles for Treatment of Recurrent Subluxation of the Lateral Meniscus.

Recurrent subluxation of the lateral meniscus is characterized by episodes of mechanical locking of the knee joint. To completely preclude the posterior segment of the lateral meniscus from undergoing anterior dislocation during deep knee flexion, the structures to which it is attached need to be relatively taut. The posterosuperior popliteomeniscal fascicle retains its tension during deep knee flexion; therefore, reconstruction of the posterosuperior and anteroinferior popliteomeniscal fascicles was performed with an autograft harvested from the iliotibial band. This technique provides stabilization of the posterior segment of the lateral meniscus during deep knee flexion without interfering with the normal movement of the lateral meniscus throughout the range of motion of the knee joint.

A Case of Bilateral Permanent Subluxation of the Lateral Meniscus.

We report a case of bilateral, permanent subluxation of the lateral meniscus. To our knowledge, the present case is the first reported description of bilateral irreducible anterior dislocation of the posterior segment of the lateral meniscus. This disorder is characterized by a flipped meniscus sign of the lateral meniscus on sagittal magnetic resonance images of the knee joint, with no history of trauma or locking symptoms. A detailed examination of serial magnetic resonance images of the lateral meniscus can help differentiate this condition from malformation of the lateral meniscus, that is, a double-layered meniscus. We recommend two-stage treatment for this disorder. First, the knee joint is kept in straight position for 3 weeks after the lateral meniscus is reduced to the normal position. Second, if subluxation of the lateral meniscus recurs, meniscocapsular suture is then performed. Although subluxation of the lateral meniscus without locking symptoms is rare, it is important to be familiar with this condition to diagnose and treat it correctly.

Reconstruction of the Medial Patellofemoral Ligament With Arthroscopic Control of Patellofemoral Congruence Using Electrical Stimulation of the Quadriceps.

Reconstruction of the medial patellofemoral ligament (MPFL) for recurrent patellar dislocation provides significant improvements in knee function. However, various complications have been reported, with most attributed to incorrect positioning of anchoring sites for the reconstructed MPFL and inappropriate graft tension. Patellofemoral congruence at 30° of flexion on arthroscopy was therefore controlled using devices able to modify the length of the reconstructed MPFL. This was done under circumstances of external rotation of the knee joint and electrical stimulation of the quadriceps with the purpose of maintaining the patella in a lateral shift. Advantages of this technique include completely controllable correction on arthroscopy under the worst patellofemoral congruence induced by external rotation of the knee joint and electrical stimulation of the quadriceps at 30° of flexion of the knee joint; in other words, voluntary determination of lateral shift during arthroscopy.

Reconstruction of the Medial Patellofemoral Ligament Using a Synthetic Graft With Arthroscopic Control of Patellofemoral Congruence.

PURPOSE: To compare the results of reconstruction of the medial patellofemoral ligament (MPFL) using a synthetic graft (Poly-Tape) between knee joints in which the patella was reduced to the strict center and those in which it was slightly lateral to the center of the trochlea to determine whether patellar position within this range affects the results. METHODS: Forty-six knee joints in 46 patients were examined retrospectively with a minimum follow-up of 2 years. The position of the patellar central ridge in the trochlea on arthroscopy immediately after reconstruction of the MPFL was measured. The joints were classified into group 1 (6 male and 12 female patients), in which the patella was reduced to the strict center of the trochlea, and group 2 (10 male and 18 female patients), in which the patella was reduced slightly lateral to the center. The mean age was 20.7 years in group 1 and 20.3 years in group 2. Knee joints were assessed using the Kujala score and the International Knee Documentation Committee (IKDC) subjective evaluation score. RESULTS: The mean Kujala and IKDC scores improved significantly in both groups after surgery (both P < .001). There was no significant difference between the groups for any assessment before surgery or in the Kujala score after surgery (P = .075). However, the IKDC score after surgery was significantly better in group 2 (91.3 ± 9.1) than in group 1 (82.8 ± 13.1) (P = .012). CONCLUSIONS: When recurrent dislocation of the patella was treated with MPFL reconstruction using a synthetic graft, subjective evaluations were better in knee joints in which the patella was repositioned slightly lateral to the center of the trochlea than in those in which the patella was reduced to the strict center, although there was no significant difference in knee function between them. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Arthroscopic treatment of femoral nerve paresthesia caused by an acetabular paralabral cyst.

This report describes a rare case of femoral nerve paresthesia caused by an acetabular paralabral cyst of the hip joint. A 68-year-old woman presented with a 6-month history of right hip pain and paresthesia along the anterior thigh and radiating down to the anterior aspect of the knee. Radiography showed osteoarthritis with a narrowed joint space in the right hip joint. Magnetic resonance imaging showed a cyst with low T1- and high T2-weighted signal intensity arising from a labral tear at the anterior aspect of the acetabulum. The cyst was connected to the joint space and displaced the femoral nerve to the anteromedial side. The lesion was diagnosed as an acetabular paralabral cyst causing femoral neuropathy. Because the main symptom was femoral nerve paresthesia and the patient desired a less invasive procedure, arthroscopic labral repair was performed to stop synovial fluid flow to the paralabral cyst that was causing the femoral nerve paresthesia. After surgery, the cyst and femoral nerve paresthesia disappeared. At the 18-month follow-up, the patient had no recurrence. There have been several reports of neurovascular compression caused by the cyst around the hip joint. To the authors' knowledge, only 3 cases of acetabular paralabral cysts causing sciatica have been reported. The current patient appears to represent a rare case of an acetabular paralabral cyst causing femoral nerve paresthesia. The authors suggest that arthroscopic labral repair for an acetabular paralabral cyst causing neuropathy can be an option for patients who desire a less invasive procedure.

Arthroscopic evaluation of patellofemoral congruence with rotation of the knee joint and electrical stimulation of the quadriceps.

PURPOSE: The aim of this study was to investigate the pathoanatomic features of patellar instability by arthroscopically comparing patellofemoral congruence with rotation of the knee joint and/or electrical stimulation of the quadriceps (ESQ) between knees with and without patellar instability. METHODS: We retrospectively examined 83 knee joints in 83 patients. The joints were classified into 2 groups: group 1 comprised those without a history of patellar dislocation and included 59 patients (25 male and 34 female patients), and group 2 comprised those with a history of patellar dislocation and included 24 patients (9 male and 15 female patients). Evaluation of patellofemoral congruence at 30° of flexion of the knee joint was conducted based on an axial radiograph and arthroscopic findings. The congruence angle was measured on the radiograph. The position of the patellar central ridge (PPCR) on the trochlear groove during arthroscopy was measured using still video frames of knee joints with rotational stress and/or ESQ. Statistical differences in the measurements between the 2 groups were assessed with the unpaired t test and the area under the receiver operating characteristic curve of each measurement. RESULTS: There were significant differences (P < .0001) between the 2 groups in the congruence angle on radiographs and PPCR in knee joints with rotational stress and/or ESQ on arthroscopy. External and internal rotation of the knee joint caused lateral and medial patellar shift, respectively, in both groups, but the shift was significantly larger in group 2. ESQ in addition to rotation caused further patellar shift in group 2 but reduced patellar shift in group 1. Measurement of PPCR with external rotation of the knee and ESQ was the only method to show an area under the receiver operating characteristic curve of 1. CONCLUSIONS: There were significant differences in the effects of rotation of the knee joint and/or ESQ on patellofemoral congruence at 30° of flexion of the knee joint on arthroscopy between knees with and without patellar instability. LEVEL OF EVIDENCE: Level III, diagnostic study of nonconsecutive patients.

Fracture of an osteochondroma of the femoral neck caused by impingement against the ischium.

This article describes 2 cases of osteochondroma emanating from the posterior aspect of the femoral neck with a fracture at the base of its stalk caused by impingement between the tumor and the ischium. A 44-year-old man and a 57-year-old man presented with left hip pain. Radiographs revealed a mass at the posterior aspect of the femoral neck. Computed tomography and magnetic resonance imaging revealed that the mass was fractured at the stalk. The relationship between the tumor and the ischium was examined with an image intensifier. The tumor impinged on the ischium with slight flexion and external rotation of the hip joint. In both patients, the tumor was excised, and the pathological report was osteochondroma. At follow-up, the patients had full hip joint range of motion, and lateral radiographs of the left hip joint showed complete resection of the tumor without recurrence. To the authors' knowledge, the current cases are the first reports of fracture of an osteochondroma with confirmed impingement using an image intensifier pre- and intraoperatively. Both patients had histories of restricted hip range of motion and a sudden onset of pain. After excision, the patients recovered to activities of daily living with no complications. An osteochondroma at the posterior aspect of the femoral neck can impinge on the ischium and fracture at its base with a sudden onset of pain. Awareness of this mechanism of impingement may lead to a better understanding of patient symptoms caused by osteochondroma of the femoral neck.

Magnetic resonance imaging and arthroscopic findings of the popliteomeniscal fascicles with and without recurrent subluxation of the lateral meniscus.

PURPOSE: The aim of this study was to examine the posterosuperior popliteomeniscal fascicle (sPMF) and anteroinferior popliteomeniscal fascicle (iPMF) by use of magnetic resonance imaging in control knee joints and joints with recurrent subluxation of the lateral meniscus (RSLM) to determine the incidence of abnormal popliteomeniscal fascicles (PMFs) in these groups. METHODS: Knee joints were diagnosed with RSLM when there was a history of mechanical locking episodes and when subluxation of the lateral meniscus was recognized on arthroscopy. In this study 238 knee joints were evaluated. The joints were classified into a control group (215 joints), RSLM group (16 joints), and contralateral RSLM group (7 joints). Classification of the sPMF (iPMF) on magnetic resonance imaging was as follows: type I, a tense, low-intensity band ran from the superior (inferior) border of the lateral meniscus to the popliteus tendon; type II, an unclear band ran from the superior (inferior) border of the lateral meniscus; and type III, no band was observed. Types II and III were thought to exhibit abnormal PMFs. The distribution of knee joints among the 3 groups and PMF types was examined. RESULTS: Percentages of abnormal sPMFs and iPMFs were 40% and 26%, respectively, in the control group; 100% and 29%, respectively, in the contralateral RSLM group; and 100% and 100%, respectively, in the RSLM group. A significant difference in the distribution of knee joints by classification of sPMFs was recognized between the control and contralateral RSLM groups (P < .0001). A significant difference in iPMFs was also recognized between the contralateral RSLM and RSLM groups (P = .0005). CONCLUSIONS: A significantly high incidence of abnormal sPMFs was found in RSLM and contralateral knees. Thus abnormal sPMFs existed in both knee joints before patients had locking symptoms, suggesting that abnormal sPMFs may be required for locking symptoms. A significantly high incidence of abnormal iPMFs was found only in the knee joints with RSLM. An abnormal iPMF is thus the essential lesion to allow the at-risk lateral meniscus to become unstable beyond the rate of control knees. LEVEL OF EVIDENCE: Level III, case-control study.

Association of internal rotation of the knee joint with recurrent subluxation of the lateral meniscus.

PURPOSE: To compare the arc of rotation of the knee joint at 90° of flexion in control knee joints and those affected by recurrent subluxation of the lateral meniscus (RSLM), in determining whether rotatory instability of the knee joint is a risk factor for RSLM. METHODS: Knee joints were diagnosed with RSLM when there was a history of mechanical locking episodes and when subluxation of the lateral meniscus with the peripheral margin of the posterior segment moving anteriorly beyond the lateral femoral condyle was recognized on arthroscopy. In this study 288 knee joints in 270 subjects were evaluated. The joints were classified into a control group (252 joints), an RSLM group (24 joints), and a contralateral RSLM group (12 joints). The arcs of external and internal rotation at 90° of flexion of the knee joint induced by 7 Nm of torque under non-weight-bearing conditions were measured with a Biodex System 3 (Biodex Medical Systems, Shirley, NY). RESULTS: There were no significant differences in mean values of external rotation among the 3 groups. The mean values of internal rotation of both the RSLM and contralateral RSLM groups were significantly larger than that of the control group, by about 15° (P < .0001). The mean value of internal rotation was slightly higher than that of external rotation in the RSLM and contralateral RSLM groups, although the mean value of internal rotation was smaller than that of external rotation by 10.1° in the control group. CONCLUSIONS: RSLM was found to be strongly related to bilateral increase in the arc of internal rotation at 90° of flexion of the knee joint, suggesting that internal rotatory instability of the flexed knee joint can be considered one of the risk factors for and diagnostic parameters of RSLM. LEVEL OF EVIDENCE: Level III, diagnostic study of nonconsecutive patients.

Cam impingement of the posterior femoral condyle in medial meniscal tears.

PURPOSE: The aim of this study was to compare the results of meniscal repair of the medial meniscus with or without decompression of the posterior segment of the medial meniscus for the treatment of posteromedial tibiofemoral incongruence at full flexion (PMTFI), which induces deformation of the posterior segment on sagittal magnetic resonance imaging (MRI). METHODS: For more than 2 years, we followed up 27 patients with PMTFI who were classified into the following 2 groups. Group 1 included 8 patients (5 male joints and 3 female joints) with a medial meniscal tear with instability at the site of the tear who underwent meniscal repair. The mean age was 23.6 years. Group 2 included 19 patients (16 male joints and 3 female joints) who had a meniscal tear with instability at the site of the tear and underwent meniscal repair and decompression. The mean age was 26.5 years. In decompression of the posterior segment, redundant bone tissue on the most proximal part of the medial femoral condyle was excised. The patients were assessed by use of the Lysholm score, sagittal MRI at full flexion, and arthroscopic examination. RESULTS: There were no statistical differences in mean Lysholm score between the 2 groups before surgery, but the mean score in group 2 was significantly higher than that in group 1 after surgery. Meniscal deformation of the posterior segment at full flexion on MRI disappeared in all cases after decompression. On second-look arthroscopy, the rate of complete healing at the site of the tear was 0% in group 1 but 57% in group 2, and it was significantly different between these groups. CONCLUSIONS: The addition of decompression of the posterior segment of the medial meniscus to meniscal repair of knee joints with PMTFI allowed more room for the medial meniscus to accommodate and improved both function of the knee joint and the rate of success of repair of isolated medial meniscal tears in patients who regularly performed full knee flexion.

Arthroscopically assisted treatment of tibial plateau fractures.

Abstract We present a new technique for arthroscopically assisted treatment of tibial plateau fractures using custom-made instruments designed for this technique. An impactor was modified so that its tip was concave to enable grasping of the cancellous bone; thus, there is always relatively thick, compressed cancellous bone between a depressed fragment and the tip of the impactor throughout the reduction maneuver. In this way, the risk of the tip of the impactor protruding into the joint space by mistake is eliminated and an accurate and quick reduction of depressed fragments is possible without using fluoroscopy.

Measurement of tension of tendon tissue based on electrical impedance.

The objective of this study was to examine whether the tension of tendon tissue could be measured using electrical impedance and, if so, whether the errors in measurement of the initial tension of a reconstructed anterior cruciate ligament obtained using electrical impedance were small enough to allow its use in clinical practice. The patella-patellar tendon-tibia complex from 35 pig knees was dissected. The relationship between the impedance of the patellar tendon and the traction stress loaded on the patellar tendon, and the repeatability of stress-impedance curves was examined in 15 knees. The relationship between impedance and strain was examined in 5, the influence of the tendon traction direction on tendon impedance was examined in 5, and the influence of the axial torsional deformation of the tendon on tendon impedance was examined in 5. Moreover, the relationship between the initial tension of a reconstructed ligament measured using electrical impedance and the load applied to the reconstructed ligament was examined in the remaining 5 knees. The change in electrical impedance of the patellar tendon due to traction was mostly caused by the strain of the tendon. The mean repeatability was 9.1%, the mean error due to differences in traction direction was 9.7%, and the mean error due to axial torsional deformation was 6.8%. There was a very strong correlation between the tension of the reconstructed ligament measured using electrical impedance and the force applied to the reconstructed ligament. Therefore, electrical impedance can be used to measure tendon tension, and it serves to measure the initial tension of a reconstructed ligament consisting of tendon tissue.

Lack of posteromedial tibiofemoral congruence at full flexion as a causative factor in isolated medial meniscal tears.

The aim of the current study was to investigate posteromedial tibiofemoral congruence at full flexion of the knee in control knee joints and those affected by an isolated medial meniscal tear, to examine whether lack of such congruence was a causative factor in isolated medial meniscal tears. In this study, 1677 knee joints in 875 subjects were evaluated. The joints were classified as a control group (1345 joints), an isolated medial meniscal tear group (224 joints), and a contralateral isolated medial meniscal tear group (108 joints). Posteromedial tibiofemoral congruence was examined on a lateral radiograph of the knee joint at full flexion. The tangent touching the anterior and posterior parts of the articular surface of the medial tibial condyle was assumed to be the X-axis. To evaluate posteromedial tibiofemoral congruence, we measured the angle formed by the tangent that maximized the gradient of the tangent on the articular surface of the medial femoral condyle, and the tangent that maximized the gradient of the tangent on the articular surface of the medial tibial condyle. The mean angle differed significantly between the control and the isolated medial meniscal tear groups, regardless of sex. Isolated medial meniscal tears were found to be strongly related to an abnormally decreased angle, and, therefore, incongruence of the posteromedial tibiofemoral articulation at full flexion was considered to be one of the causes of isolated medial meniscal tears.