The cruciate ligaments in knee replacement

Summary The cruciate ligaments were resected with their bony insertions during total knee arthroplasty carried out in 12 patients with severe rheumatoid or osteoarthritis. The ligaments were examined histologically and biomechanically, using ten specimens from healthy adults as a control. A significant difference was found in the tensile stiffness and viscoelastic properties of the ligaments between the arthritic and the control group. The ligaments in the rheumatoid knees had a distinctly inferior tensile strength compared with the osteoarthritic knees. Total knee replacement, which also replaces ligament function, should therefore be considered in severely damaged rheumatoid knees.

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Résumé Les ligaments croisés du genou ont été réséqués avec leurs insertions osseuses au cours d'arthroplasties totales du genou réalisées sur douze sujets atteints de graves lésions d'arthrose ou de polyarthrite rhumatoïde. Les ligaments ont été étudiés sur le plan histologique et biomécanique, et dix spécimens provenant d'adultes sains ont été utilisés comme contrôle. On a mis en évidence des différences significatives de la résistance et des propriétés visco-élastiques des ligaments entre ceux des patients arthrosiques et les autres. Les ligaments des genoux rhumatoïdes présentaient une résistance nettement plus faible comparativement à ceux des genoux arthrosiques. L'arthroplastie totale du genou qui remplace également la fonction ligamentaire, peut donc être efficace dans les genoux rhumatoïdes, grandement endommagés.

     

Tension changes in the collateral ligaments of a cruciate ligament-deficient knee joint: an experimental biomechanical study

BACKGROUND: The biomechanical changes in the cruciate ligament-deficient knee are still widely unexplained. By producing a model of cruciate ligament insufficiency in the knee joint, we wanted to provide an experimental explanation for the great amount of secondary injuries to the knee joint after conservative treatment of an anterior cruciate ligament rupture. METHODS: The forces exerted on the medial and lateral collateral ligament were measured in ten fresh human cadaver knees. While simulating muscle force and body weight, the ligamentous loading patterns were determined before and after the anterior cruciate ligament was transected. The specimens were moved in a special apparatus from 0 degrees extension to 100 degrees flexion. Strain gauges were used to measure the ligament forces. They were fixed at the bony origins and insertions of the examined ligaments. The method allowed all ligamentous and capsular structures to be kept intact, thereby creating nearly physiological conditions by simulating muscular strength and axial force. RESULTS: During the quasistatic measurements, the relative changes of the ligament forces were determined from one angle position to the next. The variability of these relative values were very small among the ten specimens. The method yielded reproducible ligament force data. The values obtained in the intact knee joints were markedly similar to those reported in the literature. Cutting the anterior cruciate ligament led to a general increase of the ligament forces on both collateral ligaments. CONCLUSION: Our results show excess stress of the main ligamentous stabilisers after anterior cruciate ligament transection. This is an explanation for the secondary injuries often seen after conservative treatment of anterior cruciate ligament rupture as a result of impaired knee biomechanics.     

膝后外侧角解剖学特点和力学的稳定机制

目的探讨膝后外侧角(PLC)的结构组成、解剖学和生物力学特点。方法15具30例膝关节尸体标本，解剖观察PLC的位置、组成和形态学特点。在选择性离断PLC部分结构的不同工况下。观察膝内翻加载移位和胫骨上端的后外侧旋转加载移位。结果(1)PLC位于膝关节后外侧区域，邻近上胫腓联合处，由膝外侧副韧带、豆腓韧带、弓状韧带、腘肌腱、腘腓韧带、后外侧关节囊等结构组成。(2)PLC切断后，膝内翻移位增加274％～280％，胫骨上端后外侧旋转移位增大210％～305％。其中膝外侧副韧带离断后膝内翻移位增加比例达78％～87％；而离断腘腓韧带后胫骨上端后外侧旋转移位增幅比例达81％～91％。结论(1)膝外侧副韧带和腘腓韧带是膝后外侧角中主要的稳定结构；(2)膝后外侧角具有明显对抗膝内翻不稳和膝后外侧旋转不稳定的作用。     

A sensory role for the cruciate ligaments

Morphologic, physiologic, and clinical evidence for the sensory role of the cruciate ligaments is reviewed. The cruciate ligaments accommodate morphologically different sensory nerve endings (Ruffini endings, Pacinian corpuscles, Golgi tendon organlike endings, and free nerve endings) with different capabilities of providing the central nervous system with information not only about noxious and chemical events but also about characteristics of movements and position-related stretches of these ligaments. A survey of available data reveals that low threshold joint-ligament receptor (i.e., mechanoreceptor) afferents evoke only weak and rare effects in skeletomotor neurons (alpha-motor neurons), while they frequently and powerfully influence fusimotor neurons (gamma-motor neurons). The effects on the gamma-muscle-spindle system in the muscles around the knee are so potent that even stretches of the cruciate ligaments at relatively moderate loads (not noxious) may induce major changes in responses of the muscle spindle afferents. As the activity in the primary muscle spindle afferents modifies the stiffness in the muscles, the cruciate ligament receptors, via the gamma-muscle-spindle system, may participate in the regulation and preprogramming of the muscular stiffness around the knee joint and thereby of the knee joint stiffness. Thus, the sensory system of the cruciate ligaments is able to significantly contribute to the functional stability of the knee joint.     

Posterior cruciate function following total knee arthroplasty: A biomechanical study

The strain developed in the posterior cruciate ligament (PCL) of eight fresh cadaveric knees was measured before and after total knee arthroplasty using a loading technique that simulated stair ascent and descent. Each knee was instrumented with a Hall Effect strain gauge (Micro-Strain, Burlington, VT) in the PCL, a load cell in the quadriceps tendon, an electrogoniometer, and an array of linear displacement transducers to measure femoral rollback. Testing was undertaken with each knee in its normal state with the anterior cruciate cut and with a cruciate-retaining prosthesis, a cruciate-excising prosthesis, and a cruciate-substituting prosthesis. Normal PCL strain levels were produced in only 37% of the trials following implantation of the cruciate-retaining knee arthroplasties. With a cruciate-retaining prosthesis, femoral rollback decreased by an average of 36% and was associated with a 15% loss in extensor efficiency. In the procedures performed with excision of the PCL, rollback decreased by 70% and extensor efficiency by 19%. Cruciate substitution resulted in a 12% loss in rollback and an 11% decrease in extensor efficiency. The strain developed within the PCL during knee flexion was found to be extremely sensitive to the thickness of the polymeric tibial insert. In the majority of cases, it was not possible to restore normal ligament loading with flexion while simultaneously maintaining acceptable varus/valgus stability of the knee joint. Using a range of contemporary knee arthroplasties, the authors were unable to consistently reproduce normal function of the PCL.     

Excision of the cruciate ligaments in total knee replacement

The cruciate ligaments (and the intercondylar eminence of the tibia) should be removed when the knee is replaced. A mechanically unlinked prosthesis can be designed which will then be capable of restoring "cruciate" stability, i.e., anteroposterior stability of the tibia in the flexed knee. A knee replaced with such a prosthesis will only be stable if the prosthesis is inserted using the correct instruments and technique. Stability depends as much on precise surgical technique as it does on prosthetic design.     

Limits of movement in the human knee. Effect of sectioning the posterior cruciate ligament and posterolateral structures

We applied specific forces and moments to the knees of fifteen whole lower limbs of cadavera and measured, with a six degrees-of-freedom electrogoniometer, the position of the tibia at which the ligaments and the geometry of the joint limited motion. The limits were determined for anterior and posterior tibial translation, internal and external rotation, and varus and valgus angulation from zero to 90 degrees of flexion. The limits were measured in the intact knee and then the changes that occurred with removal of the posterior cruciate ligament, the lateral collateral ligament, the popliteus tendon at its femoral attachment, and the arcuate complex were measured. The cutting order was varied, allowing us to determine the changes in the limits that occurred when each structure was cut alone and the amount of motion of the joint that was required for each structure to become taut and to limit additional motion when the other supporting structures had been removed. Removal of only the posterior cruciate ligament increased the limit for posterior tibial translation, with no change in the limits for tibial rotation or varus and valgus angulation. The additional posterior translation was least at full extension and increased progressively, reaching 11.4 millimeters at 90 degrees of flexion. The progressive increase in posterior translation with flexion was apparently due to slackening of the posterior portion of the capsule, as the translation nearly doubled when the posterolateral structures subsequently were removed. Removal of only the posterolateral extra-articular restraints increased the amount of external rotation and varus angulation. The average increase in external rotation depended on the angle of flexion; it was greatest at 30 degrees of flexion and decreased with additional flexion. At 90 degrees of flexion, the intact posterior cruciate ligament limited the increase in external rotation to only 5.3 degrees, less than one-half of the 13.0-degree increase that occurred at 30 degrees of flexion. Subsequent removal of the posterior cruciate ligament markedly increased external rotation at 90 degrees of flexion, resulting in a total increase of 20.9 degrees. The limit for varus angulation was normal as long as the lateral collateral ligament was intact. When the lateral collateral ligament was cut, the limit increased 4.5 degrees (approximately 4.5 millimeters of additional joint opening) when the knee was partially flexed (to 15 degrees).(ABSTRACT TRUNCATED AT 400 WORDS)     

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.     

Dynamic reconstruction of the cruciate ligaments of the knee

Summary This paper reports the long term results of dynamic gracilis or semitendinosus transfer in chronic cruciate ligament instability of the knee. During the period 1968–1983, 76 dynamic reconstructions were performed. Sixty-one patients (63 knees) were evaluated. There were 42 males and 19 females. The mean age at operation was 29.5 years and the average time before operation was 3.7 years. The anterior cruciate ligament was reconstructed in 54 cases, the posterior in 7 and the anterior and posterior in 2. Altogether 32 ligaments (12 cruciates) had been repaired and 28 menisci removed at previous operations. A scoring system (up to 50 points, with 16 parameters) was used. An excellent result was achieved in 21 cases, good in 15, fair in 18 and poor in 19 cases at an average follow-up of 7.4 years. The average score was 33.2 points. Subjectively only 4 patients described the end result as poor. The anterior cruciate alone was reconstructed in 25 patients with an average score of 35.4 points. In 12 cases the operative delay was less than one year and in these the average score was 41.2. In 6 cases three ligaments were reconstructed and the average score was 24.0. There were advanced degenerative changes in 6 knees (average score 24.3).

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Résumé Cet article rapporte les résultats éloignés du transfert du droit interne ou du demi-tendineux dans les instabilités chroniques du genou par lésion des ligaments croisés. De 1968 à 1983, 76 reconstructions dynamiques ont été réalisées. 61 patients, 42 hommes et 19 femmes, représentant 63 genoux, ont été examinés. L'âge moyen lors de l'opération était de 29,5 ans et le délai moyen entre l'accident et l'opération était de 3,7 ans. La reconstruction a porté 54 fois sur le ligament croisé antérieur, 7 fois sur le postérieur et 2 fois sur les deux. 32 ligaments (dont 12 croisés) avaient été réparés et 28 ménisques excisés préalablement à l'intervention. On a utilisé une évaluation chiffrée, allant jusqu'à 50 points et comportant 16 paramètres. Les résultats ont été jugés excellents dans 21 cas, bons dans 15, passables dans 18 et mauvais dans 9, avec un recul moyen de 7,4 ans. Le score moyen était de 33,2 points. Le résultat n'était subjectivement considéré comme mauvais que par 4 malades. Le ligament croisé antérieur a été le seul reconstruit chez 25 opérés avec un score moyen de 35,4. Dans 12 cas le délai entre l'accident et l'intervention était inférieur à un an, et dans ces cas le score moyen était de 41,2. Chez 6 malades trois ligaments ont été reconstruits et le score moyen était de 24. Il existait de notables lésions dégénératives au niveau de 6 genoux, avec un score moven de 23,3.

     

Tension studies of human knee ligaments. Yield point, ultimate failure, and disruption of the cruciate and tibial collateral ligaments.

Ultimate failure strengths of human tibial collateral and anterior and posterior cruciate ligaments were determined at two different loading rates (12.5 and fifty centimeters per minute) using an Instron Tension Analyzer. The posterior cruciate ligament was significantly stronger than the tibial collateral and anterior cruciate ligaments, which were of equal strength. At ultimate failure the ligaments were intact macroscopically but electron microscopy revealed widespread disruption of the collagen fibrils. Only after further application of stress did actual macroscopic disruption occur, suggesting that microscopic failure of the collagen fibrils in grossly intact ligaments may be a significant cause of clinical instability.     

The distal radioulnar ligaments: a biomechanical study.

The mechanical roles of the triangular fibrocartilage have been examined in three experiments. Kinematic analysis by a stereophotogrammetric method revealed that the palmar radioulnar ligament was taut in supination and that the dorsal radioulnar ligament was taut in pronation. In full pronation, the palmar radioulnar ligament decreased to an average of 71% of its length in tension. In full supination, the dorsal radioulnar ligament decreased to an average of 90% of its length. Mechanical testing of the triangular fibrocartilage under axial load disclosed a significant laxity (mean: 10.4 mm), which was decreased in pronation. Transverse loading tests demonstrated that the triangular fibrocartilage is less stiff in neutral forearm rotation. Study of the material properties of the palmar and dorsal parts of the triangular fibrocartilage showed these structures to be strong ligaments with material properties similar to those of the radiocarpal ligaments.     

The role of the dorsal vertebral cortex in the stability of transpedicular screws. A biomechanical study in human cadaveric vertebrae

The aim of this biomechanical study was to investigate the role of the dorsal vertebral cortex in transpedicular screw fixation. Moss transpedicular screws were introduced into both pedicles of each vertebra in 25 human cadaver vertebrae. The dorsal vertebral cortex and subcortical bone corresponding to the entrance site of the screw were removed on one side and preserved on the other. Biomechanical testing showed that the mean peak pull-out strength for the inserted screws, following removal of the dorsal cortex, was 956.16 N. If the dorsal cortex was preserved, the mean peak pullout strength was 1295.64 N. The mean increase was 339.48 N (26.13%; p = 0.033). The bone mineral density correlated positively with peak pull-out strength. Preservation of the dorsal vertebral cortex at the site of insertion of the screw offers a significant increase in peak pull-out strength. This may result from engagement by the final screw threads in the denser bone of the dorsal cortex and the underlying subcortical area. Every effort should be made to preserve the dorsal vertebral cortex during insertion of transpedicular screws.     

Posterior cruciate ligament and coupled posterolateral instability of the knee

We wanted to investigate the role of the posterior cruciate ligament (PCL) in the knee's posterolateral stability and the magnitude of the coupled posterolateral instability with the knee examined at 90 degrees of flexion. The coupled posterolateral instability of the knee was studied by selective ligament cutting in cadaver knees set at 90 degrees. The coupled posterolateral displacement after cutting the PCL was 173% of the intact knee. With an intact PCL, the coupled posterolateral displacement after cutting the popliteus tendon and lateral collateral ligament with the knee at 90 degrees of flexion was 299% of the intact knee. When the PCL was cut together with the popliteus tendon and lateral collateral ligament, the coupled posterolateral displacement was 367%. The PCL plays an important role in the posterolateral stability of the knee, and its injury may cause mild (< 5 mm) to moderate (5-10 mm) posterolateral instability. Thus, in a knee with posterolateral instability, injury of the PCL must be considered. With an intact PCL, the posterolateral instability was very recognizable with the knee at 90 degrees of flexion, and injury to the PCL further increased the posterolateral instability and caused posterior translation of the knee. Therefore, examination for posterolateral instability of the knee should also be performed with the knee at 90 degrees of flexion, which is much easier to perform in a clinical setting. A positive posterior translation rather than posterolateral instability at different knee positions differentiates knees with combined PCL and posterolateral instability from knees with isolated posterolateral instability.