Biomechanical and kinematic influences of a total infrapatellar fat pad resection on the knee

BACKGROUND: This biomechanical study was performed to evaluate the consequences of total infrapatellar fat pad resection on knee kinematics and patellar contact pressure. HYPOTHESIS: Resection of the infrapatellar fat pad produces significant changes in knee kinematics and patellar contact pressure. STUDY DESIGN: Biomechanical cadaveric study. METHODS: Isokinetic knee extension was simulated on 10 human knee cadaveric specimens (6 men, 4 women; mean age at death, 44 years). Joint kinematics were evaluated by an ultrasound-based 3D motion analysis system, and retro-patellar contact pressure was measured using an electronic pressure-sensitive film. All data were taken before and after resection of the infrapatellar fat pad and statistically analyzed. RESULTS: A total resection of the infrapatellar fat pad resulted in a significant decrease of the tibial external rotation relative to the femur between 63 degrees of flexion and full knee extension (maximum: 3 degrees rotation difference at 0 degrees knee flexion, P = .011), combined with a significant medial translation of the patella between 29 degrees and 69 degrees of knee flexion (range, 0.9-1.3 mm, P = .017-.028). Retro-patellar contact pressure was significantly reduced (from 20% to 25%, P = .008-.021) at all flexion angles. CONCLUSION: A resection of the infrapatellar fat influences patellar biomechanics and knee kinematics. CLINICAL RELEVANCE: The infrapatellar fat pad may have a biomechanical function and may play a role in anterior knee pain syndrome.     

The influence of patellar bracing on patellar and knee load-distribution and kinematics: an experimental cadaver study

The aim of this study was to analyze the biomechanical consequences of patella bracing in order to evaluate possible mechanisms supporting its clinical application. The hypothesis is that the patellar bracing reduces patellofemoral pressure by influencing patellar and knee kinematics, and load distribution. Physiologic isokinetic knee extension motions were simulated on ten human knee cadaver specimens using a knee kinematic simulator. Joint kinematics were evaluated using an ultrasound-based motion analysis system and patellofemoral contact pressure was measured using a thin-film piezoresistive pressure measuring system. Infrapatellar tissue pressure was analyzed using a closed sensor-cell. Three different patella braces were fitted to the knee cadavers and their influence on the kinematic and kinetic biomechanical parameters were evaluated and compared to the physiologic situation. Patellar bracing resulted in a significant (p = 0.05) proximalization of the patella up to 3 mm. Depending on the type of brace used, a decrease in the infrapatellar fat pad pressure was found and the patellofemoral contact area was decreased significantly (p = 0.05) between 60° of knee flexion and full extension (maximum 22%). Patella bracing significantly (p = 0.05) reduced the patellofemoral contact pressure an average of 10%, as well as the peak contact pressure which occurred. Patellar bracing significantly influences patella biomechanics in a reduction of the patellofemoral contact area and contact pressure as well as a decrease in the infrapatellar tissue pressure. The application of infrapatellar straps is suggested for the treatment and prevention of anterior knee pain, especially in high level sports.     

The anterior cruciate ligament does play a role in controlling axial rotation in the knee

This study deals with the influence of peroperative ligament tension on total tibial rotation at different knee flexion angles. Fourteen human cadaver knees with a mean age of 56 years (range 42–84 years) were examined. The cadaver knees were subjected to internal/external (i/e) rotational torque of 6 Nm, at 10, 30, 50, 70 and 90 deg of knee flexion. The mean total i/e rotation with the anterior cruciate ligament (ACL) intact at 10 deg of knee flexion was 30.4 deg and after removing the ACL, 33.1 deg. At 10 and 30 deg of knee flexion, the increase in i/e rotation was significant, while there was no significant difference in mean values at greater knee flexion. Ligament reconstruction with a tension of 5 N at 30 deg of knee flexion using either the over the top or through the femoral condyle reconstructive procedure restored normal tibial rotation. With increased graft tension the knee motion was increasingly restricted at low angles of knee flexion. Our results indicate that the ACL does play a role in limiting axial rotation, and even minor tensioning forces introduced in any of the two ACL reconstructions used produced restricted knee motion.     

Effect of knee flexion on the in situ force distribution in the human anterior cruciate ligament

This study was conducted to evaluate the effect of applied load on the magnitude, direction, and point of tibial intersection of the in situ forces of the anteromedial (AM) and posterolateral (PL) bands of the human anterior cruciate ligament (ACL) at 30° and 90° of knee flexion. An Instron was used to apply a 100 N anterior shear force to 11 human cadaver knees, 6 at 30° of knee flexion and 5 at 90° of knee flexion. A Universal Force Sensor (UFS) recorded the resultant 6 degree-of freedom (DOF) forces/moments. Each specimen then underwent serial removal of the AM and PL bands. With the knee limited to 1 DOF (anteroposterior), tests were performed before and after each structure was removed. Because the path was identical in each test, the principle of superposition was applied. Thus, the difference between the resultant forces could be attributed to the force carried by the structure just removed. The magnitudes of force in the ACL at 30° and 90° of knee flexion were 114.1±7.4 N and 90.8±8.3 N, respectively (P<0.05). At 30°, the AM and PL bundles carried 95% and 4% of the total ACL force, respectively. At 90°, the AM and PL bands carried 85% and 13%, respectively (P<0.05). The direction of the in situ force in the whole ACL as well as its two bands correlated with the anatomic orientation of the ligament. The resultant total ACL force intersected the tibial plateau at the posterolateral aspect of the AM band's insertion at 30° of knee flexion, while at 90°, the force intersection moved posteriorly to the AM/PL border. This research provides new insight into the fundamental force relationships of the ACL and its bundles. In response to an anterior tibial shear force, the AM band of the ACL was the predominant load carrier at both 30° and 90° of knee flexion. However, contrary to carlier reports, the in situ force carried in the PL band increased as knee flexion increased. Further, the tibial intersection of the resultant ACL force moved laterally with knee flexion. These findings confirm the dynamic structure of the ACL that in itself has no isometricity and may also indicate that there is no ideal location in which to position a replacement graft. The use of this methodology with more physiologically unconstrained motion should lead to more definitive clinical conclusions.     

The weight-bearing knee after anterior cruciate ligament rupture

Unilateral weight bearing was simulated on 12 cadaver knees to quantitate anterior tibial translation (ATT) after anterior cruciate ligament (ACL) transection and to asses the role of the posteromedial structure and the hamstrings in controlling laxity. With the ACL intact, ATT was 3.5±2.8 mm in extension and 4.3±3.6 mm at 60° flexion. After sectioning the ACL, ATT was 6.5±4.7 mm in extension and 17.5±10 mm at 60° flexion (P=0.001). Applying a force in the hamstrings was unable to correct the pathological ATT observed after ACL section. Partial medial meniscectomy did not increase ATT after the ACL section. Disinsertion of the posterior horn of the medial meniscus and total medial meniscectomy increased ATT significantly compared to isolated ACL section. After ACL transection, sectioning the meniscotibial fibers or posteromedial capsule significantly increased ATT (6.5±0.5 mm in extension). Section of the postero-oblique ligament or popliteus tendon had no effect on ATT.     

Sources of anterior knee pain

The anterior part of the knee consists mainly of structures belonging to the patellofemoral joint, which includes a variety of tissues, such as cartilage, subchondral bone, synovial plicae, infrapatellar fat pad, retinacula, capsule, and tendons. Each of these structures, alone or in combination, can be a source of anterior knee pain. Unphysiologic load or changed metabolic activities can lead to structural failure with loss of homeostatic conditions.     

Distribution of substance-P nerve fibers in the knee joint in patients with anterior knee pain syndrome A preliminary report

The etiology of pain in anterior knee pain syndrome is a matter of controversy. The normal, articular cartilage is aneural, so defects in the surface are not thought to produce pain. Some authors have sought the origin of the pain in soft tissue structures around the knee. Knowledge of the distribution of nociceptive nerve fibers around the knee would provide insight for treating anterior knee pain syndrome. Twenty consecutive patients (28 knees), all women, with anterior knee pain syndrome (group I) participated in the study. For comparison we used two groups of patients: 20 patients with an osteoarthritic knee (group II) and 20 patients with anterior cruciate ligament rupture or meniscal lesion with no history of pain in the anterior compartment (group III). Immunohistochemical techniques using a monoclonal antibody to substance-P (SP) were employed to identify nociceptive fibers. For statistical analyses we used the one-way ANOVA test, which was corrected with the LSD test, at the level of significance P < 0.05. Results of the study demonstrate that SP-immunoreactive nerve fibers are widespread within the soft tissues around the knee. These tissues include the retinaculum, synovium, fat pad and, in some circumstances, bone. In cases of anterior knee pain, the presence of neuropeptide-containing fibers was statistically significant in the medial retinaculum (P < 0.005) and in the fat pad (P < 0.001) compared to group III, and compared to group II (P < 0.05 and P < 0.007, respectively). For lateral retinaculum this relationship was not so statistically strong (P < 0.02) and was equal in comparison between anterior knee pain patients (group I) and group II or group III. There were no statistically significant differences in the distribution of substance-P nerve fibers in the fat pad, lateral and medial retinaculum or synovium between groups II and III. The results of this study provide immunohistochemical evidence suggesting that pain may originate in the fat pad and medial retinaculum of many patients with anterior knee pain syndrome. Received: 17 December 1997 Accepted: 20 October 1998     

Infrapatellar plica of the knee: revisited with MR arthrographies undertaken in the knee flexion position mimicking operative arthroscopic posture

Purpose

To describe the appearance of the infrapatellar plica (IPP) on magnetic resonance arthrography (MRA) taken in 70° knee flexion, corresponding to the arthroscopic posture.

Materials and methods

Twenty-two patients (23 knee joints) who underwent MRA with 70° knee flexion were enrolled. All patients underwent MRA with 70° knee flexion to simulate operative arthroscopy. The images included fat-suppressed T1-weighted spin echo axial, sagittal, and coronal images. The visualization and morphology of the IPP were retrospectively assessed by two musculoskeletal radiologists.

Results

The IPP was demonstrated in 78.3% (n = 18/23) and was best visualized on the sagittal section through the intercondylar notch. The IPP manifested as a linear hypointense structure with variable thicknesses. The intercondylar component was delineated clearly, arising from the anterior intercondylar notch in parallel with the ACL and curving gently downward to attach to the infrapatellar fat pad. On the other hand, the Hoffa's fat pad component was not depicted clearly. The morphology of the IPP was either a separate type (60.9%) or a split type (17.4%).

Conclusion

The IPPs can be visualized with a high rate of detection and various morphologic appearances must be appreciated under the review of a flexed knee MRA.     

Results of surgical treatment of arthrofibrosis after ACL reconstruction

We prospectively studied 31 knee arthrolyses performed for loss of motion after intra-articular anterior cruciate ligament (ACL) reconstruction. The arthrolysis was performed on average 10.6 months after the reconstruction (range 4–25). Seven knees were localized forms. They were treated with arthroscopic removal of a fibrous nodule and scar tissue anterior to the ACL, which was preserved. Twenty-four knees were global forms and treated arthroscopically (14) or in open procedure (10). Suprapatellar, medial, and lateral gutter adhesions were sectioned, and fibrous tissue was removed from the anterior compartment. A posteromedial and/or posterolateral capsulotomy was necessary in 7 knees. The ACL graft was nonfunctional and/or malpositioned in 19 knees. The results were evaluated with the IKDC form with an average follow-up of 3.5 years (range 1.5–7). Preoperatively the localized forms had an average extension loss of 11° and an average flexion loss of 14° compared to the opposite knee. At follow-up all the knees were satisfactory for symptoms. All except one achieved a satisfactory motion (within 5° of extension loss and 15° of flexion loss) and a satisfactory final result. Global forms had a greater preoperative flexion loss (average 34°) and extension loss (average 17°). At follow-up 58% were satisfactory for symptoms and 71% for arc of motion. However, the final result was satisfactory in only 37%. In conclusion, local forms have a good prognosis. In global forms motion may be improved by surgery, but the final result is downgraded by symptoms. Arthrolyses performed within 8 months from index operation had a better outcome.     

The effect of knee flexion angle and application of an anterior tibial load at the time of graft fixation on the biomechanics of a posterior cruciate ligament-reconstructed knee

Ten knees were studied using a robotic testing system under a 134-N posterior tibial load at five flexion angles. Three knee positions were used to study the effect of flexion angle at the time of graft fixation (full extension, 60 degrees, and 90 degrees) and two were used to study the effect of anterior tibial load (60 degrees and 90 degrees). Knee kinematics and in situ forces were determined for the intact ligament and the graft for each reconstruction. Graft fixation at full extension significantly decreased posterior tibial translation compared with the intact knee by up to 2.9 +/- 2.9 mm at 30 degrees, while in situ forces in the graft were up to 18 +/- 35 N greater than for the intact ligament. Conversely, posterior tibial translation for graft fixation at 90 degrees was significantly greater than that of the intact knee by up to 2.2 +/- 1.1 mm at all flexion angles; in situ forces decreased as much as 33 +/- 30 N. When an anterior tibial load was applied before graft fixation at 90 degrees of flexion, posterior tibial translation did not differ from the intact knee from 30 degrees to 120 degrees, while the in situ force in the graft did not differ from the intact ligament at full extension, 60 degrees, and 120 degrees of flexion. These data suggest that graft fixation at full extension may overconstrain the knee and elevate in situ graft forces. Conversely, fixation with the knee in flexion and an anterior tibial load best restored intact knee biomechanics.     

The effect of femoral attachment location on anterior cruciate ligament reconstruction: graft tension patterns and restoration of normal anterior–posterior laxity patterns

The issue of the best place to attach an anterior cruciate ligament graft to the femur is controversial, and different anatomic or isometric points have been recommended. It was hypothesised that one attachment site could be identified that would be best for restoring normal anterior–posterior laxity throughout the range of knee flexion. It was also hypothesised that these different attachment sites would cause different graft tension patterns during knee flexion. Using six cadaver knees, an isometric point was found 3 mm distal to the posterior edge of Blumensaats line, at the 10:30–11:00 oclock position in right knees, at the antero-proximal edge of the anatomic ACL attachment. Anterior–posterior laxity was measured at ±150 N draw force at 20–120° flexion with the knee intact and after anterior cruciate ligament transection. The graft was placed at the isometric point, and AP laxity was restored to normal at 20° flexion, then measured at other angles. Graft tension was measured throughout, and also during passive flexion–extension. This was repeated for four other graft positions around the isometric point in every knee. Laxity was restored best by grafts tensioned to a mean of 9±14 N, positioned isometrically and 3 mm posterior to the isometric point. Their tension remained low until terminal extension. Grafts 3 mm anterior to the isometric point caused significant overconstraint, and had higher tension beyond 80° knee flexion. Small changes in attachment site had large effects on laxity and tension patterns. These results support an isometric/posterior anatomic femoral graft attachment, which restored knee laxity to normal from 20 to 120° flexion and did not induce high graft tension as the knee flexed. Grafts attached to the roof of the intercondylar notch caused overconstraint and higher tension in the flexed knee.     

In vivo elongation of the anterior cruciate ligament and posterior cruciate ligament during knee flexion

BACKGROUND: Most knowledge regarding cruciate ligament function is based on in vitro experiments. PURPOSE: To investigate the in vivo elongation of the functional bundles of the anterior cruciate ligament and posterior cruciate ligament during weightbearing flexion. HYPOTHESIS: The biomechanical role of functional bundles of the anterior cruciate ligament and posterior cruciate ligament under in vivo loading is different from that measured in cadavers. STUDY DESIGN: In vivo biomechanical study. METHODS: Elongation of the anterior cruciate ligament and posterior cruciate ligament was measured during a quasi-static lunge using imaging and 3-dimensional computer-modeling techniques. RESULTS: The anterior-medial bundle of the anterior cruciate ligament had a relatively constant length from full extension to 90 degrees of flexion. The posterior-lateral bundle of the anterior cruciate ligament decreased in length with flexion. Both bundles of the posterior cruciate ligament had increased lengths with flexion. CONCLUSION: The data did not demonstrate the reciprocal function of the 2 bundles of the anterior cruciate ligament or the posterior cruciate ligament with flexion observed in previous studies. Instead, the data suggest that there is a reciprocal function between the anterior cruciate ligament and posterior cruciate ligament with flexion. The anterior cruciate ligament plays a more important role in low-flexion angles, whereas the posterior cruciate ligament plays a more important role in high flexion. CLINICAL RELEVANCE: Understanding the biomechanical role of the knee ligaments in vivo is essential to reproduce the structural behavior of the ligament after injury (especially for 2-bundle reconstructions) and thus improve surgical outcomes.     

Arthroscopic posteromedial capsular release for knee flexion contractures

Extension deficits of the knee can cause functional limitations in patients after knee surgery or injury. Most frequently, they are treated with manipulations, arthroscopic anterior compartment debridements, or open posterior capsular releases once nonoperative treatment fails. However, an arthroscopic posteromedial capsular release to manage flexion deficits has yet to be studied comprehensively. Arthroscopic posteromedial capsular releases of the knee can result in improved knee motion postoperatively. An arthroscopic posteromedial capsular release involves sectioning the posteromedial capsule at its meniscofemoral portion, midway between its femoral attachment and its posterior horn medial meniscus junction. A review of 15 patients who underwent this operation was performed. Passive knee extension and flexion was measured in patients in the supine position using a goniometer at preoperative evaluations, under anesthesia prior to and immediately after the posteromedial capsular release, and at postoperative follow-up evaluations. The average time from the arthroscopic posteromedial capsular release to the final postoperative follow-up was 24.1 months. Preoperative knee extension averaged 14.7° in 15 patients. The average immediate postoperative knee extension averaged −0.9°. At the final postoperative follow-up, knee extension averaged 0.7°. Overall knee motion improved from an average arc of motion of 101.6°–129.4°. Arthroscopic posteromedial capsular releases and the concurrent postoperative rehabilitation program were effective in the treatment of knee extension deficits. The encouraging results of this study compare well to data presented in open posterior capsular release studies. We believe that arthroscopic posteromedial capsular releases are an effective means to address symptomatic knee extension deficits.     

Intra-articular ganglion cysts of the knee: clinical and MR imaging features

The purpose of this study was to present clinical and MR imaging features of intra-articular ganglion cysts of the knee. Retrospective review of 1685 consecutive medical records and MR examinations of the knee performed at three imaging centers allowed identification of 20 patients (13 men and 7 women; mean age 35 years), in whom evidence of intra-articular ganglion cyst was seen. Of the 20 ganglion cysts, 5 were found in the infrapatellar fat pad, 10 arose from the posterior cruciate ligament, and 5 from the anterior cruciate ligament. Three of five patients with ganglion cyst in the infrapatellar fat pad had a palpable mass. In 7 of 15 patients with ganglion cyst in the intercondylar notch, exacerbation of pain occurred in a squatting position. On four MR arthrographies, ganglion cysts were an intra-articular round, lobulated, low signal intensity lesion. Five cases of fat-suppressed contrast-enhanced T1-weighted SE images demonstrated peripheral thin rim enhancement. The clinical presentation of intra-articular ganglion cyst is varied according to its intra-articular location. The MR appearance of intra-articular ganglion cyst is characteristic and usually associated with the cruciate ligament or the infrapatellar fat pad. Magnetic resonance arthrography has no definite advantage over conventional MR in the evaluation of the lesion. For intra-articular ganglion cyst in the infrapatellar fat pad, fat-suppressed contrast-enhanced MR imaging could be useful, because a thin, rim-enhancing feature of intra-articular ganglion cyst allows it to be distinguished from synovial hemangioma and synovial sarcoma. Received: 29 June 2000 Revised: 13 September 2000 Accepted: 15 September 2000     

Temperature changes in the knee joint during arthroscopic surgery

Normal joint conditions are altered during arthroscopic surgery, and these changes have uncertain ultrastructural and biomechanical effects on articular cartilage. Experimental studies have shown that temperature variations affect the biomechanical properties of articular cartilage. We documented the temperature of the knee joint in 40 patients at the beginning and end of an arthroscopic procedure (anterior cruciate ligament reconstruction or meniscectomy). The intra-articular measurements were obtained using a digital thermometer connected to a sterile stainless steel probe. Correlation coefficients and linear regression techniques were used to determine which variables are independent predictors of joint temperature at the end of surgery. The mean knee joint temperature before surgery was 35.1°±1.0°C and at the end of surgery 24.6°±1.5°C. The joint temperature at the end of surgery was significantly affected by the temperature of the saline irrigant used and the length of arthroscopic procedure. The clinical implications of our findings must be clarified in animal models.     

Evaluation and treatment of disorders of the infrapatellar fat pad

The infrapatellar fat pad (IFP), also known as Hoffa's fat pad, is an intracapsular, extrasynovial structure that fills the anterior knee compartment, and is richly vascularized and innervated. Its degree of innervation, the proportion of substance-P-containing fibres and close relationship to its posterior synovial lining implicates IFP pathologies as a source of infrapatellar knee pain. Though the precise function of the IFP is unknown, studies have shown that it may play a role in the biomechanics of the knee or act as a store for reparative cells after injury. Inflammation and fibrosis within the IFP, caused by trauma and/or surgery can lead to a variety of arthrofibrotic lesions including Hoffa's disease, anterior interval scarring and infrapatellar contracture syndrome. Lesions or mass-like abnormalities rarely occur within the IFP, but their classification can be narrowed down by radiographical appearance. Clinically, patients with IFP pathology present with burning or aching infrapatellar anterior knee pain that can often be reproduced on physical exam with manoeuvres designed to produce impingement. Sagittal MRI is the most common imaging technique used to assess IFP pathology including fibrosis, inflammation, oedema, and mass-like lesions. IFP pathology is often successfully managed with physical therapy. Passive taping is used to unload or shorten an inflamed IFP, and closed chain quadriceps exercises can improve lower limb control and patellar congruence. Training of the gluteus medius and stretching the anterior hip may help to decrease internal rotation of the hip and valgus force at the knee. Gait training and avoiding hyperextension can also be used for long-term management. Injections within the IFP of local anaesthetic plus corticosteroids and IFP ablation with ultrasound guided alcohol injections have been successfully explored as treatments for IFP pain. IFP pathology refractory to physical therapy can be approached through a variety of operative treatments. Arthroscopic partial resection for IFP impingement and Hoffa's disease has showed favourable results; however, total excision of the IFP performed concomitantly with total knee arthroplasty (TKA) resulted in worse results when compared with TKA alone. Arthroscopic debridement of IFP fibrosis has been successfully used to treat extension block following anterior cruciate ligament reconstruction, and arthroscopic anterior interval release has been an effective treatment for pain associated with anterior interval scarring. Arthroscopic resection of infrapatellar plicae and denervation of the inferior pole of the patella have also been shown to be effective treatments for refractory infrapatellar pain.     

Relative contribution of the ACL, MCL, and bony contact to the anterior stability of the knee

Ligaments and other soft tissues, as well as bony contact, all contribute to anterior stability of the knee joint. This study was designed to measure the in situ force in the medial collateral ligament (MCL), anterior cruciate ligament (ACL), posterolateral structures (PLS), and posterior cruciate ligament (PCL) in response to 110 N anterior tibial loading. The changes in knee kinematics associated with ACL deficiency and combined MCL+ACL deficiency were also evaluated. Utilizing a robotic/universal force-moment sensor system, ten human cadaveric knee joints were tested between 0° and 90° of knee flexion. This unique testing system is designed to determine the in situ forces in structures of interest without making mechanical contact with the tissue. More importantly, data for individual structures can be obtained from the same knee specimen since the robotic manipulator can reproduce the motion of the intact knee. The in situ forces in the ACL under anterior tibial loading to 110 N were highest at 15° flexion, 103 ± 14 N (mean ± SD), decreasing to 59.2 ± 30 N at 90° flexion. For the MCL, these forces were 8.0 ± 3.5 N and 38.1 ± 25 N, respectively. Forces due to bony contact were as high as 34.1 ± 23 N at 30° flexion, while those in the PLS were relatively small at all flexion angles. Combined MCL+ACL deficiency was found to significantly increase anterior tibial translation relative to the ACL-deficient knee only above 60° of knee flexion. These findings confirm the hypothesis that there is significant load sharing between various ligaments and bony contact during anterior tibial loading of the knee. For this reason, the MCL and osteochondral surfaces may also be at significant risk during ACL injury. Received: 29 December 1997 Accepted: 16 July 1998     

A biomechanical analysis of two reconstructive approaches to the posterolateral corner of the knee

The objective of this study was to evaluate the effects of the biceps femoris tenodesis and popliteofibular ligament reconstruction on knee biomechanics. Ten human cadaveric knees were tested in the intact, posterolateral corner (PLC)-deficient, and PLC-reconstructed conditions using a robotic/universal force moment sensor testing system. The knees were subjected to: (1) a 134 N posterior tibial load, and (2) a 10 Nm external tibial torque applied to the tibia at full extension, 30° and 90° of flexion. External tibial rotation of the intact knee ranged from 18.3±4.6° at full extension to 27.9±4.6° at 30° under the 10 Nm external tibial torque. These values increased after sectioning the PLC by 2.8°–7.5° at 30° and 90° respectively. After the popliteofibular ligament reconstruction, external tibial rotation values were not significantly different from those for the intact knee at any angle tested, while values following the biceps tenodesis were as much as 5.7° greater than the intact knee. Under the 134 N posterior tibial load, there were minimal decreases in posterior tibial translation of up to 0.9 mm with the biceps tenodesis and up to 1.6 mm with the popliteofibular ligament reconstruction compared to the intact knee. The in situ forces in the biceps tenodesis were not significantly different than the intact PLC at full extension or 30°, while the in situ forces in the popliteofibular graft were not significantly different at any flexion angle. Our data suggests that by restoring external tibial rotation the popliteofibular ligament reconstruction more closely reproduces the primary function of the PLC as compared to the biceps tenodesis.     

膝关节骨性关节炎髌下脂肪垫在中药治疗前后的CT变化研究

目的:通过对比膝骨性关节炎(knee osteoarthritis,KOA)膝关节髌下脂肪垫治疗前后CT图像的变化,探讨中医药治疗KOA的疗效。方法:将130例KOA患者随机分为2组,治疗组65例给予健步通络熏蒸液熏洗,30min/d,10d为1个疗程,共3个疗程;对照组65例每6d关节内注射玻璃酸钠30mg,共5次;2组皆治疗30d。治疗前后均行膝关节CT扫描,观察治疗前后髌下脂肪垫的变化。结果:治疗组经治疗后髌下脂肪垫的前后径、内外径、上下径均有缩小,密度均有降低,优于对照组;治疗组总有效率(83.08%)优于对照组(76.92%),差异有统计学意义(P0.05)。结论:对比膝关节髌下脂肪垫CT图像的变化是评价中医药治疗KOA疗效的有效方法。