Effect of tibial slope or posterior cruciate ligament release on knee kinematics

An experimental study using fresh human cadaver knees was designed to evaluate the effect of partial posterior cruciate ligament release or posterior tibial slope on knee kinematics after total knee arthroplasty. Varus and valgus laxity, rotational laxity, anteroposterior laxity, femoral rollback, and maximum flexion angle were evaluated in a normal knee, an ideal total knee arthroplasty, and a total knee arthroplasty in which the ligaments were made to be too tight in flexion. The total knee arthroplasty specimens then were subjected to either partial posterior cruciate ligament release or increased posterior tibial slope, and the tests were repeated. Posterior tibial slope increased varus and valgus laxity, anteroposterior laxity, and rotational laxity in the knee that had flexion tightness. Posterior cruciate ligament release corrected only anteroposterior tightness, and had no effect on the abnormal collateral ligament tightness. Increased posterior tibial slope significantly improved varus and valgus laxity and rotational laxity in the knee that was tight in flexion more than with release of the posterior cruciate ligament. Therefore increasing posterior tibial slope is preferable for a knee that is tight in flexion during total knee arthroplasty.     

Unicompartmental arthroplasty of the knee. Cadaver study of the importance of the anterior cruciate ligament

The tibiofemoral articulation on horizontal and 10 degrees tilted tibial components was examined radiographically in 20 cadaver knees after lateral arthroplasty, and after cutting the anterior cruciate ligament in 10 knees with medial and 10 with lateral arthroplasty. Articulation took place more posteriorly on the horizontal components at any degree of flexion examined; a correlation was found between the operation-induced change in the inclination of the lateral tibial plateau and the point of articulation. Based on the regression equations, the expected point of articulation on an arbitrarily chosen component placement could be calculated for any degree of flexion provided the preoperative inclination was known. Cutting the anterior cruciate ligament caused articulation to move posteriorly on the tibial component at both medial and lateral arthroplasty. We concluded that it was possible to estimate the tilt of the tibial component that was required to avoid marginal articulations when the preoperative slope of the tibial plateau was known. Absence of the anterior cruciate ligament seems to contraindicate unicompartmental arthroplasty.     

The radiographic classification of medial gonarthrosis. Correlation with operation methods in 200 knees.

Ahlb?ck's classification of gonarthrosis can be applied with improved precision by careful interpretation of anteroposterior varus stress and lateral radiographs of the knee. The tibial lesion in early gonarthrosis is located in the anterior and middle part of the medial plateau. In more advanced disease, when the anterior cruciate ligament is invariably damaged, the lesion extends to the posterior margin of the medial tibial plateau. We studied the preoperative radiographs of 200 knees with arthrosis. We were able to predict the integrity of the anterior cruciate ligament (and the use of unicompartmental arthroplasty) with 95 percent accuracy and rupture or damage to the anterior cruciate ligament (and the use of total condylar arthroplasty) with 100 percent accuracy. We believe that the Ahlb?ck classification reflects the anatomic and pathologic progression of medial compartment gonarthrosis, and is of value in allowing more accurate comparisons to be made of different methods of treatment.     

Incidence and mechanism of the pivot shift. An in vitro study.

The aim of this study was to determine the incidence and mechanism of the pivot shift phenomenon in the normal and anterior cruciate ligament transected knee in vitro. Fifteen knees were tested under a range of valgus moments and iliotibial tract tensions when intact and after anterior cruciate ligament transection. Knee kinematics were measured and described in terms of tibial rotation as the knee flexed. Eight knees pivoted after anterior cruciate ligament transection. The mean pivot shift motion was an external tibial rotation of 17 degrees (+/- 11 degrees standard deviation) over a range of 27 degrees (+/- 24 degrees) knee flexion, at a mean flexion angle of 56 degrees (+/- 27 degrees). Clinically, this corresponds to a reduction of an anteriorly subluxed lateral tibial plateau as the knee flexes. When intact, pivoting and nonpivoting knees had similar anteroposterior laxity, but after anterior cruciate ligament transection, the pivoting group had significantly greater laxity. The loading required to elicit the pivot shift was critical and variable between knees, which raises questions about comparing clinicians' techniques and results in assessing the buckling instability attributable to anterior cruciate ligament injury.     

Relevance of the Tibial Slope on Functional Outcomes in ACL-Deficient and ACL Intact Fixed-Bearing Medial Unicompartmental Knee Arthroplasty

BackgroundExcessive posterior tibial slope in medial unicompartmental knee arthroplasty (UKA) has been implicated in early failure. The purpose of this study was to evaluate the relationship between preoperative posterior tibial slope and postoperative slope of the implant (PSI) on outcomes in patients with anterior cruciate ligament (ACL) intact and ACL-deficient knees after fixed-bearing medial UKA.MethodsPatients who underwent a medial UKA between 2002 and 2017 with a minimum 3-year follow-up were included. Preoperative posterior tibial slope and postoperative PSI were measured. Outcomes measures included Knee Injury and Osteoarthritis Outcomes Score (KOOS) subscales, Lysholm, and VR-12. Failure was defined as conversion to total knee arthroplasty.ResultsOf 241 knees undergoing UKA, 131 patients (70 women, 61 men; average age of 65 ± 10 years (average BMI of 27.9 ± 4) were included. For all patients, survivorship was 98% at 5 years and 96% at 10 years with a mean survival time for UKA was 15.2 years [95% CI: 14.6-15.7]. No failure had a PSI >7°. There were no superficial or deep infections. There were no significant differences in outcome scores between the ACL intact and the ACL-deficient group; therefore, the data were combined for analysis. At mean 8-year follow-up, KOOS pain scores were better in patients with PSI ≤7° (87 ± 16) than those with PSI >7° (81 ± 15). 76% of patients with PSI ≤7° reached the Patient Acceptable Symptom State for KOOS pain; whereas, 59% of patients with PSI >7° reached PASS for KOOS pain (P = .015).ConclusionPatients with postoperative posterior slope of the tibial implant >7° had significantly worse postoperative pain, without conversion to TKA, and with maintenance of high function. In ACL deficient and intact knees, nonrobotically-assisted, fixed-bearing medial UKA had a 96% survivorship at 10 years.     

Combined anterior cruciate reconstruction and Oxford unicompartmental knee arthroplasty

The options for treatment of the young active patient with isolated symptomatic osteoarthritis of the medial compartment and pre-existing deficiency of the anterior cruciate ligament are limited. The potential longevity of the implant and levels of activity of the patient may preclude total knee replacement, and tibial osteotomy and unicompartmental knee arthroplasty are unreliable because of the ligamentous instability. Unicompartmental knee arthroplasties tend to fail because of wear or tibial loosening resulting from eccentric loading. Therefore, we combined reconstruction of the anterior cruciate ligament with unicompartmental arthroplasty of the knee in 15 patients (ACLR group), and matched them with 15 patients who had undergone Oxford unicompartmental knee arthroplasty with an intact anterior cruciate ligament (ACLI group). The clinical and radiological data at a minimum of 2.5 years were compared for both groups. The groups were well matched for age, gender and length of follow-up and had no significant differences in their pre-operative scores. At the last follow-up, the mean outcome scores for both the ACLR and ACLI groups were high (Oxford knee scores of 46 (37 to 48) and 43 (38 to 46), respectively, objective Knee Society scores of 99 (95 to 100) and 94 (82 to 100), and functional Knee Society scores of 96 and 96 (both 85 to 100). One patient in the ACLR group needed revision to a total knee replacement because of infection. No patient in either group had radiological evidence of component loosening. The radiological study showed no difference in the pattern of tibial loading between the groups. The short-term clinical results of combined anterior cruciate ligament reconstruction and unicompartmental knee arthroplasty are excellent. The previous shortcomings of unicompartmental knee arthroplasty in the presence of deficiency of the anterior cruciate ligament appear to have been addressed with the combined procedure. This operation seems to be a viable treatment option for young active patients with symptomatic arthritis of the medial compartment, in whom the anterior cruciate ligament has been ruptured.     

Conversion of failed modern unicompartmental arthroplasty to total knee arthroplasty

Between January 1983 and January 1991, 29 patients (31 knees) with a failed Robert Brigham metal-backed knee arthroplasty (Johnson & Johnson, Raynham, MA) underwent revision to a total knee arthroplasty (TKA). Twenty-five patients had osteoarthritis, three avascular necrosis, and one rheumatoid arthritis. The average patient age was 72.3 years (range, 49–88 years), and the average weight was 179 lb. (range, 112–242 lb.). The interval between the primary and secondary index procedures averaged 62 months (range, 7–106 months), and mean postrevision follow-up period was 45 months (range, 24–104 months). The primary mechanism of failure of the UKA was tibial polyethylene wear in 21 knees and opposite compartment progression of arthritis in 10 knees. Sixteen knees had particulate synovitis with dense metallic staining of the synovium. At revision, the posterior cruciate ligament was spared in 30 knees and substituted in 1 knee. Restoration of bony deficiency at revision required cancellous bone—graft for contained defects in seven knees, tibial wedges in four knees, and femoral wedges in two knees. No defects received structural allografts. The data suggest that failed, modern unicompartmental knee arthroplasty can successfully be converted to TKA. In most cases, the posterior cruciate ligament can be spared and bone defects corrected with simple wedges or cancellous grafts. Moreover, the results of revision of failed unicompartmental knee arthroplasty are superior to those of failed TKA and failed high tibial osteotomy and comparable to the authors' results of primary TKA with similar-length follow-up periods. Although these results are encouraging, longer-term follow-up evaluation is required to determine survivorship of these revision arthroplasties.     

Anterior cruciate ligament deficiency alters the in vivo motion of the tibiofemoral cartilage contact points in both the anteroposterior and mediolateral directions

BACKGROUND: Quantifying the effects of anterior cruciate ligament deficiency on joint biomechanics is critical in order to better understand the mechanisms of joint degeneration in anterior cruciate ligament-deficient knees and to improve the surgical treatment of anterior cruciate ligament injuries. We investigated the changes in position of the in vivo tibiofemoral articular cartilage contact points in anterior cruciate ligament-deficient and intact contralateral knees with use of a newly developed dual orthogonal fluoroscopic and magnetic resonance imaging technique. METHODS: Nine patients with an anterior cruciate ligament rupture in one knee and a normal contralateral knee were recruited. Magnetic resonance images were acquired for both the intact and anterior cruciate ligament-deficient knees to construct computer knee models of the surfaces of the bone and cartilage. Each patient performed a single-leg weight-bearing lunge as images were recorded with use of a dual fluoroscopic system at full extension and at 15 degrees , 30 degrees , 60 degrees , and 90 degrees of flexion. The in vivo knee position at each flexion angle was then reproduced with use of the knee models and fluoroscopic images. The contact points were defined as the centroids of the areas of intersection of the tibial and femoral articular cartilage surfaces. RESULTS: The contact points moved not only in the anteroposterior direction but also in the mediolateral direction in both the anterior cruciate ligament-deficient and intact knees. In the anteroposterior direction, the contact points in the medial compartment of the tibia were more posterior in the anterior cruciate ligament-deficient knees than in the intact knees at full extension and 15 degrees of flexion (p < 0.05). No significant differences were observed with regard to the anteroposterior motion of the contact points in the lateral compartment of the tibia. In the mediolateral direction, there was a significant lateral shift of the contact points in the medial compartment of the tibia toward the medial tibial spine between full extension and 60 degrees of flexion (p < 0.05). The contact points in the lateral compartment of the tibia shifted laterally, away from the lateral tibial spine, at 15 degrees and 30 degrees of flexion (p < 0.05). CONCLUSIONS: In the presence of anterior cruciate ligament injury, the contact points shift both posteriorly and laterally on the surface of the tibial plateau. In the medial compartment, the contact points shift toward the medial tibial spine, a region where degeneration is observed in patients with chronic anterior cruciate ligament injuries.     

Total knee arthroplasty with retention of both cruciate ligaments. A nine to eleven-year follow-up study.

BACKGROUND: Although many early designs of total knee arthroplasty allowed the retention of both cruciate ligaments, in most current designs of knee replacement systems, either both cruciate ligaments are removed or the posterior cruciate ligament alone is retained. This report is a review of a series of total knee arthroplasties in which both cruciate ligaments were retained. METHODS: The results of 163 total knee arthroplasties (130 patients) in which both cruciate ligaments were retained were assessed prospectively. One hundred and seven knees (eighty-nine patients) were followed for an average of ten years. There were thirty-four men and ninety-six women, and the average age at the time of the index arthroplasty was sixty-seven years (range, forty-two to eighty-four years). The diagnosis was osteoarthritis in 122 (75 percent) of the knees and rheumatoid arthritis in forty-one (25 percent). Twenty-six knees had a valgus deformity, 109 had a varus deformity, and twenty-eight had a normal alignment of 5 to 10 degrees of valgus. The anterior cruciate ligament was relatively normal in ninety-six knees and was partly degenerated in sixty-seven knees. With use of the rating system of the Knee Society, all 163 knees were prospectively evaluated at yearly intervals; fifty-six of these knees (in forty-one patients) were followed in this manner until the patient died or was lost to follow-up. RESULTS: One hundred and four (97 percent) of the 107 knees available for study at an average of ten years had an excellent or good result. At the time of the latest follow-up, pain was adequately relieved in ninety-seven knees (91 percent) and the average range of flexion was 107+/-12.6 degrees (range, 65 to 135 degrees). Ninety-five knees (89 percent) had normal anteroposterior stability (less than five millimeters of movement in this plane), and twelve knees (11 percent) had five to ten millimeters of movement as demonstrated by the drawer sign. Ninety-six knees (90 percent) had normal mediolateral stability, and eleven (10 percent) had 5 to 10 degrees of laxity. Ninety-four knees (88 percent) had valgus alignment of 5 to 10 degrees. The average knee score was 91+/-8.4 points (range, 54 to 100 points), and the average functional score was 82+/-21 (range, 10 to 100 points). The survival rate at ten years, with revision as the end point, was 95+/-2.0 percent. Seven (4 percent) of the 163 knees in this series were revised. There were no revisions for patellar problems or aseptic loosening of the tibial component. CONCLUSIONS: The good anteroposterior stability in this series after an average follow-up period of ten years indicates that both the anterior and the posterior cruciate ligaments, even when partly degenerated, remain functional when they are preserved in a total knee arthroplasty.     

Knee stability in posterior cruciate ligament retaining total knee arthroplasty

Anteroposterior knee laxity was evaluated in 14 patients (19 knees) who had posterior cruciate ligament retaining total knee arthroplasty using the Miller Galante I prosthesis. The followup ranged from 87 to 118 months (average, 105.9 months), and the measurements were done using the KT-2000 arthrometer. The mean anteroposterior displacement with the knees with Miller Galante I prostheses was 10.1 mm at 30 degrees flexion and 8.1 mm at 75 degrees flexion. In the 15 knees with Miller Galante I prostheses with flexion greater than 90 degrees, seven had less stability at 75 degrees than at 30 degrees flexion. These knees were considered to have a nonfunctional posterior cruciate ligament, and they had a worse Knee Society score (81.1) than did the other eight knees with Miller Galante I prostheses (89.9). There were four knees in which the flexion was less than 90 degrees. In this study, approximately half of the knees with posterior cruciate ligament retaining total knee arthroplasty did not have good anteroposterior stability in flexion an average of 9 years after surgery.     

Anteroposterior stability in posterior cruciate ligament-retaining total knee arthroplasty

Anteroposterior stability was evaluated using a KT-2000 arthrometer in 18 patients (21 knees) continuously for up to 5 years after posterior cruciate ligament-retaining total knee arthroplasty. The Knee Society score, functional score, and the maximum flexion angle did not change significantly during the postoperative period. The mean anteroposterior displacement of all joints studied at both 30 degrees and 75 degrees of flexion did not change significantly during the 5-year period of observation, but 4 individual knees did exhibit increases in anteroposterior displacement of 3 mm or more. One of the 4 knees exhibited osteolysis beneath the tibial component. Three of these knees had undergone high tibial osteotomy at some time before the total knee arthroplasty.     

An anteroposterior axis of the tibia for total knee arthroplasty

The objective of the current study was to identify a new extraarticular anatomic landmark indicating the anteroposterior orientation of the tibia using computed tomography. In 39 volunteers (20 males, 19 females), computed tomography scans for healthy right knees in extension were done perpendicular to the tibial shaft axis. The anteroposterior axis of the tibia was defined as a line perpendicular to the transepicondylar axis and passing through the middle of the posterior cruciate ligament. At the level of the tibial plateau and the patellar tendon attachment, the mean medial percentage width of intersecting point of the patellar tendon and the anteroposterior axis was 10.8% +/- 9.8% (range, -9.3% - +30.0%) and -0.2% +/- 10.4% (range, -23.6% -+23.0%), respectively. The mean angle between the anteroposterior axis and a line connecting the middle of the posterior cruciate ligament to the medial border of the patellar tendon attachment was 0.0 degrees +/- 2.8 degrees (range, -6.3 degrees -+5.2 degrees). The medial border of this attachment therefore can serve as a reliable anterior anatomic landmark to determine the anteroposterior axis of the tibia, and the line connecting the middle of the posterior cruciate ligament and the medial border of the attachment may be useful as a reference axis indicating the anteroposterior orientation of the tibia.     

Functional medical ligament balancing in total knee arthroplasty

Function of the anterior and posterior oblique portions of the medial collateral ligament and the posterior capsule in flexion and extension was evaluated in eight knee specimens after posterior cruciate retaining total knee arthroplasty. The posterior oblique portion of the medial collateral ligament was released subperiosteally in four specimens, and the anterior portion was released in four specimens. The medial posterior capsule was released in each group, then the remaining portion of the medial collateral ligament was released. Release of the posterior oblique portion produced moderate laxity at full extension and at 30 degrees flexion, and posterior capsule release produced additional laxity in full extension. Release of the anterior portion produced major laxity at 60 degrees and 90 degrees flexion. Complete medial collateral ligament release increased laxity significantly in both groups in flexion and extension. This rationale was tested in a clinical study of 82 knees (76 patients) in which 62 (76%) required medial collateral ligament release to correct varus deformity during posterior cruciate retaining total knee arthroplasty. Twenty-two knees (35.5%) were tight medially in extension only, and were corrected by releasing the posterior oblique portion. Thirty-one knees (50%) were tight medially in flexion only, and were corrected by releasing the anterior portion. Nine knees (14.5%) were tight medially in flexion and extension and required complete medial collateral ligament release, but three knees (4.8%) remained tight in extension and required medial posterior capsule release to correct flexion contracture and medial ligament contracture. Seventeen (27%) had partial posterior cruciate ligament release to correct excessive rollback of the femoral component on the tibial surface.     

Multiparameter quantitative computer-assisted tomography assessment of unicompartmental knee arthroplasties

BACKGROUND: Unicompartmental knee arthroplasty is a popular alternative to total knee replacement in selected patients. Component alignment has not yet been described by computer-assisted tomography (CAT) imaging techniques; these have been developed for total knee arthroplasty analysis. The aims of this study were to report two new technologies; a new unicompartmental knee arthroplasty system was radiographically assessed with a new CAT scan protocol. METHODS: In a consecutive cohort study, 60 knees were analysed by the 'UniCAT Protocol'. Patients were implanted with a unicompartmental knee arthroplasty system that uses a unique ligament tensor for femoral component alignment. The uniCAT protocol requires a long anteroposterior and lateral scout scan to measure limb alignment and component orientation. A spiral computer-assisted tomography at the knee is used to measure component rotation. The total scan time was 20 s with a calculated unshielded radiation dose of 1 mSv or less. RESULTS: The mechanical axis had a mean of 2.7 degrees varus. Femoral components were implanted with a mean of 0.37 degrees valgus and 1.3 degrees flexion. Tibial components were implanted with a mean 3.47 degrees varus and 5.1 degrees posterior slope. Femoral components were externally rotated a mean of 3.36 degrees, tibial components were externally rotated 6.59 degrees from the posterior tibia and 5.68 degrees from the transepicondylar axis. CONCLUSION: The UniCAT protocol uses less radiation than whole-limb spiral scans and is a method that can be used with all modern computer-assisted tomography machines. The coronal and sagital alignment results compare favourably with previous published reports without computer-assisted tomography. Component rotation has not previously been reported and its implications are yet to be defined.     

Lateral unicompartmental knee arthroplasty: survivorship and technical considerations at an average follow-up of 12.4 years

Successful medial unicompartmental knee arthroplasty is becoming standard; however, the "screw-home" mechanism, internal femoral rotation on a fixed tibia as the knee is fully extended, should be taken into account with lateral compartment arthroplasty. Twenty-nine consecutive lateral unicompartmental arthroplasties were performed with our unique tibial component positioning in 10 degrees to 15 degrees of internal rotation to compensate for the "screw-home" mechanism. The Hospital for Special Surgery knee score and serial radiographs were used in the evaluation of each patient. The mean duration of follow-up was 12.4 years with no revisions. The HSS score was excellent or good in all knees. The average postoperative femoral-tibial alignment was 5 degrees of valgus, and the average posterior tibial slope was 6 degrees . Lateral unicompartmental arthroplasty can provide excellent long-term results with modified positioning of the tibial component.     

Effect of the angle of the femoral and tibial tunnels in the coronal plane and incremental excision of the posterior cruciate ligament on tension of an anterior cruciate ligament graft: an in vitro study

BACKGROUND: High tension in an anterior cruciate ligament graft adversely affects both the graft and the knee; however, it is unknown why high graft tension in flexion occurs in association with a posterior femoral tunnel. The purpose of the present study was to determine the effect of the angle of the femoral and tibial tunnels in the coronal plane and incremental excision of the posterior cruciate ligament on the tension of an anterior cruciate ligament graft during passive flexion. METHODS: Eight cadaveric knees were tested. The angle of the tibial tunnel was varied to 60 degrees, 70 degrees, and 80 degrees in the coronal plane with use of three interchangeable, low-friction bushings. The femoral tunnel, with a 1-mm-thick posterior wall, was drilled through the tibial tunnel bushing with use of the transtibial technique. After the graft had been tested in all three tibial bushings with one femoral tunnel, the femoral tunnel was filled with bone cement and the tunnel combinations were tested. Lastly, the graft was replaced in the 80 degrees femoral and tibial tunnels, and the tests were repeated with excision of the lateral edge of the posterior cruciate ligament in 2-mm increments. Graft tension, the flexion angle, and anteroposterior laxity were recorded in a six-degrees-of-freedom load-application system that passively moved the knee from 0 degrees to 120 degrees of flexion. RESULTS: The graft tension at 120 degrees of flexion was affected by the angle of the femoral tunnel and by incremental excision of the posterior cruciate ligament. The highest graft tension at 120 degrees of flexion was 169 +/- 9 N, which was detected with the graft in the 80 degrees femoral and 80 degrees tibial tunnels. The lowest graft tension at 120 degrees of flexion was 76 +/- 8 N, which was detected with the graft in the 60 degrees femoral and 60 degrees tibial tunnels. The graft tension of 76 N at 120 degrees of flexion with the graft in the 60 degrees femoral and 60 degrees tibial tunnels was closer to the tension in the intact anterior cruciate ligament. Excision of the lateral edge of the posterior cruciate ligament in 2 and 4-mm increments significantly lowered the graft tension at 120 degrees of flexion without changing the anteroposterior position of the tibia. CONCLUSIONS: Placing the femoral tunnel at 60 degrees in the coronal plane lowers graft tension in flexion. Our results suggest that high graft tension in flexion is caused by impingement of the graft against the posterior cruciate ligament, which results from placing the femoral tunnel medially at the apex of the notch in the coronal plane.     

Unicompartmental arthroplasty of the knee: Cadaver study of the importance of the anterior cruciate ligament

The tibiofemoral articulation on horizontal and 10° tilted tibial components was examined radiographically in 20 cadaver knees after lateral arthroplasty, and after cutting the anterior cruciate ligament in 10 knees with medial and 10 with lateral arthroplasty. Articulation took place more posteriorly on the horizontal components at any degree of flexion examined; a correlation was found between the operation-induced change in the inclination of the lateral tibial plateau and the point of articulation. Based on the regression equations, the expected point of articulation on an arbitrarily chosen component placement could be calculated for any degree of flexion provided the preoperative inclination was known. Cutting the anterior cruciate ligament caused articulation to move posteriorly on the tibial component at both medial and lateral arthroplasty. We concluded that it was possible to estimate the tilt of the tibial component that was required to avoid marginal articulations when the preoperative slope of the tibial plateau was known. Absence of the anterior cruciate ligament seems to contraindicate unicornpartmental arthroplasty.     

增加胫骨平台后倾角度、后交叉韧带部分松解对全膝关节置换术后膝关节运动影响的实验研究

目的通过增加胫骨平台后倾角度或后交叉韧带（PCL）部分松解对全膝关节置换术（TKA）中屈曲间隙过紧进行处理,分析这两种方法对TKA术后膝关节运动学的影响。方法测量6例新鲜尸体膝关节标本在完整状态下、正常TKA、屈曲间隙过紧、增加胫骨平台后倾角以及PCL部分松解TKA术后膝关节屈曲0°、30°、60°、90°、120°时的前后松弛度、内外翻松弛度、旋转松弛度及最大屈曲度。结果屈曲过紧TKA与正常TKA相比,在屈曲30°、60°、90°和120°时前后松弛度、内外翻松弛度及旋转松弛度均显著较小（P〈0．05）。与屈曲过紧TKA相比,增加胫骨后倾角后,在屈曲30°、60°、90°和120°时前后松弛度、内外翻松弛度和旋转松弛度均明显增大（P〈0．05）。PCL部分松解与屈曲过紧TKA相比,在屈曲30°、60°、90°和120°时前后松弛度明显增加（P〈0．05）;旋转松弛度在屈曲30°、60°、90°时明显增加（P〈0．05）。与PCL部分松解相比,增加胫骨后倾角的内外翻松弛度在屈曲30°、60°、90°时明显较大（P〈0．05）;旋转松弛度在屈曲0°、30°、60°和90°时明显较大（P〈0．05）。屈曲过紧TKA的最大屈曲度（120．4°）与正常TKA（130．3°）及增加胫骨后倾角（131．1°）相比明显较小（P〈0．05）。增加后倾角与PCL部分松解（124．0°）相比,最大屈曲度较大,但差异无统计学意义（P=0．0816）。结论屈曲间隙过紧TKA术后膝关节的前后松弛度、内外翻松弛度、旋转松弛度和最大屈曲度均减小;增加胫骨平台后倾角后,前后松弛度、内外翻松弛度、旋转松弛度和最大屈曲度均明显增大;PCL部分松解仅能明显增大前后松弛度。因此对于TKA术中屈曲紧张的膝关节,增加胫骨平台后倾角比PCL部分松解能更好地改善膝关节的运动学。     

Medical restraints to anterior-posterior motion of the knee

We investigated the motion of cadaver knees before and after section of the medial structures and anterior cruciate ligament. The knees were tested using a 5-degrees-of-freedom in vitro knee-testing apparatus that measured anterior-posterior, medial-lateral, and axial displacement as well as internal-external and valgus-varus rotation. The flexion angle could be varied but was fixed for each individual test. A 125-newton anterior-posterior force was applied perpendicular to the tibial shaft and the resulting motion of the knee was measured. In five knees the anterior cruciate ligament was cut first, followed by progressive cuts of the structures on the medial side (superficial medial collateral ligament, deep medial ligament, oblique fibers of the superficial medial ligament, and the posteromedial part of the capsule). Conversely, in five knees the medial structures were progressively cut first, followed by section of the anterior cruciate ligament. Tests were performed after each cut. With an intact anterior cruciate ligament, progressive cutting of the medial side had no effect on anterior and posterior displacements. When section of the medial structures followed cutting of the anterior cruciate ligament, anterior displacement exceeded that seen after isolated section of the anterior cruciate ligament. The anterior and posterior load-tests were repeated with the tibia fixed in 5 degrees of internal and 5 degrees of external rotation. Fixed external rotation had no effect on anterior and posterior displacements. Fixed internal rotation significantly decreased anterior displacement only when both the anterior cruciate ligament and the medial structures were cut.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of posterior cruciate sacrifice on durability of the cement-bone interface. A nine-year survivorship study of 100 total condylar knee arthroplasties

This article presents a survivorship analysis of the second conservative 100 primary total-condylar knee arthroplasties in 75 patients performed between 1979 and 1980, with a maximum follow-up of 9 years. With this type of knee arthroplasty, the posterior cruciate ligament is routinely sacrificed. Survivorship results revealed that 98.9 per cent of the knees had good outcome at 9 years of follow-up, using revision surgery for aseptic and septic loosening and radiographic evidence of global radiolucency or shift of the component as endpoint. Radiographic survivorship analysis showed well-fixed components in 87 per cent of implants, using endpoint criteria of appearance and progression of radiolucency under tibial component. Sacrificing the posterior cruciate ligament does not adversely affect durability of fixation of the total-condylar knee arthroplasty. Bone cement provides an excellent fixation of total knee implant.