Coronal laxity in extension in vivo after total knee arthroplasty

We performed stress arthrometric studies on 77 knees (71 patients) with total knee arthroplasty to determine the presence and magnitude of femoral abduction and adduction in knee extension. A total of 53 knees (49 patients) had posterior cruciate ligament-retaining (PCLR) prostheses, and 24 (22 patients) had PCL-substituting (PCLS) prostheses. The selected patients had successful arthroplasties with no clinical complications a minimum of 5 years after primary surgery. Each patient was subjected to a successive abduction and adduction stress test at 0°–20° of flexion using a Telos arthrometer. The mean values for abduction and adduction were 4.8° and 4.5° with a PCLR prosthesis, respectively, and 4.6° and 4.0° with a PCLS prosthesis. There were no statistical differences between PCLR and PCLS knees. The results suggest that approximately 4° of laxity in these directions is suitable in total knee arthroplasty for a satisfactory clinical outcome 5–9 years after surgery.     

Sagittal laxity in vivo after total knee arthroplasty

Introduction A stress arthrometry study of 77 knees undergoing total knee arthroplasty was performed to determine the difference in anteroposterior (AP) laxity between posterior cruciate ligament (PCL)-retaining (PCLR) and PCL-substituting (PCLS) prostheses using the Genesis I TKA.Materials and methods Fifty-three knees had PCLR and 24 had PCLS prostheses. The selected patients had successful arthroplasties after a minimum follow-up of 5 years. AP laxity was measured with a KT-2000 arthrometer (Medmetric, San Diego, CA, USA) using standard protocols.Results At 30° of flexion, there was no statistical difference in anterior (PCLR: 4.7 mm, PCLS: 4.5 mm), posterior (PCLR: 1.1 mm, PCLS: 0.7 mm), or total (PCLR: 5.8 mm, PCLS: 5.3 mm) displacement. At 75°, significant differences were seen in both anterior (PCLR: 3.3 mm, PCLS: 2.3 mm) and total (PCLR: 4.8 mm, PCLS: 3.4 mm) displacement (p=0.001 and p=0.009, respectively), although there was no statistical difference in posterior displacement (PCLR: 1.5 mm, PCLS: 1.1 mm).Conclusion The above values are considered the suitable degree of AP laxity in total knee arthroplasty for a satisfactory clinical outcome 5–9 years after surgery. The PCL in a PCLR prosthesis and the central tibial spine and femoral cam in a PCLS prosthesis might play comparable roles in determining the laxity in the posterior direction in these prostheses.     

In vivo laxity of low contact stress mobile-bearing prostheses

A stress arthrometric study was done on 60 knees in 54 patients with total knee arthroplasties using a Telos arthrometer, to determine anteroposterior and abduction and adduction laxity and to evaluate the relationship between laxity and retention of the posterior cruciate ligament using low contact stress mobile-bearing prostheses. Thirty knees had posterior cruciate ligament-retaining and 30 had posterior cruciate ligament-sacrificing prostheses. The selected patients had successful knee arthroplasty 6 months previously. Anteroposterior displacement was measured at 30 degree and 90 degree flexion; there were no statistically significant differences between the posterior cruciate ligament-retaining (10.5 mm at 30 degree, 9.3 mm at 90 degree) and posterior cuciate ligament-sacrificing (9.8 mm at 30 degree, 9.7 mm at 90 degree) groups. Abduction and adduction were between 0 degree and 20 degree flexion, there were no significant differences between the two groups. Because all the patients in this study had good clinical results, approximately 10 mm anteroposterior displacement and 4 degree laxity in the coronal direction are considered favorable in low contact stress mobile-bearing prostheses of both designs.     

Range of motion during the perioperative period in total knee arthroplasty

INTRODUCTION: This study focused on the change in the range of motion (ROM) during the perioperative period, i.e., the preoperative and intraoperative ROM, and that on discharge, and compared the difference between posterior cruciate ligament-retaining (PCLR) and -sacrificing (PCLS) prostheses. MATERIALS AND METHODS: In this prospectively randomized study, we compared the changes in the ROM in PCLR (n = 50) and PCLS (n = 50) total knee arthroplasties. RESULTS: The mean flexion in PCLR prostheses was 130.0 degrees preoperatively, 120.0 degrees intraoperatively, and 105.0 degrees at discharge, and 125.0 degrees , 120.0 degrees , and 100.0 degrees , respectively, in PCLS. The designs did not differ statistically in each period (P > 0.05). Both designs showed significant correlations between the preoperative and intraoperative ROM, and between the preoperative and discharge ROM. Only the PCLS showed a significant correlation between the intraoperative and discharge ROM, and a significant difference was observed in correlation of rank coefficient between the two prostheses (P < 0.001). CONCLUSIONS: The PCLS design has an advantage in rehabilitation planning because of the predictable changes in the ROM during the perioperative period, although the acquired average ROM at discharge did not differ statistically.     

Evaluation of joint laxity against distal traction force upon flexion in cruciate-retaining and posterior-stabilized total knee arthroplasty

Background  Several studies have reported varus-valgus stability in the extension position after total knee arthroplasty (TKA). However, few studies have evaluated joint laxity in the flexion position postoperatively. The purpose of the study was to evaluate joint laxity against distal traction force on flexion after cruciate-retaining and posterior-stabilized total knee arthroplasties. Methods  A total of 44 knees (22 knees cruciate-retaining, 22 knees posterior-stabilized) in 40 patients with osteoarthritis were tested in this study. The subjects were seated at a table and their knee joints were fixed at 80° of flexion to avoid overlapping images of condyles and the femoral shaft. Tibial shafts were adjusted to be parallel to the radiographic films, and posteroanterior radiographs were obtained. Flexion stress tests were performed with a distal traction of 100 N at a neutral foot position. Radiographs were obtained at neutral and traction positions. The distance from the perpendicular line of the top of the polyethylene insert to the midpoint on the tangential line of the femoral condyle was measured (joint space distance) at each side. Results  In the flexion-neutral position, average joint space distances were 0.1 ± 0.2 mm in cruciate-retaining (CR) TKA knees and 0.2 ± 0.3 mm in posterior-stabilized (PS) TKA knees. With flexion-traction stress tests, the average joint space distances were 0.5 ± 0. 5 mm in CR TKA knees 2.4 ± 1.2 mm in PS TKA knees. Average changes of joint space distances between the two positions were 0.3 ± 0.4 mm (CR TKA) and 2.2 ± 1.5 mm (PS TKA). The changes in joint space distances between neutral and traction positions of PS TKA knees were significantly larger than those of CR TKA knees in flexion stress tests (P < 0.01). Conclusion  The posterior cruciate ligament acted as a stabilizer against distal traction force in the CR-TKA knees. However, the laxity of PS-TKA knees against distal force differed among individual cases.     

Relationship between outcome scores and knee laxity following total knee arthroplasty: a systematic review

Background and purpose — Instability following primary total knee arthroplasty (TKA) is, according to all national registries, one of the major failure mechanisms leading to revision surgery. However, the range of soft-tissue laxity that favors both pain relief and optimal knee function following TKA remains unclear. We reviewed current evidence on the relationship between instrumented knee laxity measured postoperatively and outcome scores following primary TKA.

Patients and methods — We conducted a systematic search of PubMed, Embase, and Cochrane databases to identify relevant studies, which were cross-referenced using Web of Science.

Results — 14 eligible studies were identified; all were methodologically similar. Both sagittal and coronal laxity measurement were reported; 6 studies reported on measurement in both extension and flexion. In knee extension from 0° to 30° none of 11 studies could establish statistically significant association between laxity and outcome scores. In flexion from 60° to 90° 6 of 9 studies found statistically significant association. Favorable results were reported for posterior cruciate retaining (CR) knees with sagittal laxity between 5 and 10?mm at 75–80° and for knees with medial coronal laxity below 4° in 80–90° of flexion.

Interpretation — In order to improve outcome following TKA careful measuring and adjusting of ligament laxity intraoperatively seems important. Future studies using newer outcome scores supplemented by performance-based scores may complement current evidence.     

Partial and Combined Partial Knee Arthroplasty: Greater Anterior-Posterior Stability Than Posterior Cruciate–Retaining Total Knee Arthroplasty

BackgroundLittle is known regarding anterior-posterior stability after anterior cruciate ligament–preserving partial (PKA) and combined partial knee arthroplasty (CPKA) compared to standard posterior cruciate–retaining total knee arthroplasty (TKA).MethodsThe anterior-posterior tibial translation of twenty-four cadaveric knees was measured, with optical tracking, while under 90N drawer with the knee flexed 0-90°. Knees were tested before and after PKA, CPKA (medial and lateral bicompartmental and bi-unicondylar), and then posterior cruciate–retaining TKA. The anterior-posterior tibial translations of the arthroplasty states, at each flexion angle, were compared to the native knee and each other with repeated measures analyses of variance and post-hoc t-tests.ResultsUnicompartmental and bicompartmental arthroplasty states had similar laxities to the native knee and to each other, with ≤1-mm differences throughout the flexion range (P ≥ .199). Bi-unicondylar arthroplasty resulted in 6- to 8-mm increase of anterior tibial translation at high flexion angles compared to the native knee (P ≤ .023 at 80-90°). Meanwhile, TKA exhibited increased laxity across all flexion angles, with increased anterior tibial translation of up to 18 ± 6 mm (P < .001) and increased posterior translation of up to 4 ± 2 mm (P < .001).ConclusionsIn a cadaveric study, anterior-posterior tibial translation did not differ from native laxity after PKA and CPKA. Posterior cruciate ligament–preserving TKA demonstrated increased laxity, particularly in anterior tibial translation.     

Postoperative Anteroposterior Laxity Influences Subjective Outcome After Total Knee Arthroplasty

Background

We hypothesized that postoperative anteroposterior (AP) stability of the knee correlates with patient-reported clinical outcome and knee function after total knee arthroplasty (TKA).

Laxity characteristics of normal and pathological murine knee joints in vitro

The aim of this study was to validate a device developed previously to measure laxity of murine knee joints and to investigate whether experimentally induced pathological conditions result in measurable laxity. The laxity characteristics of normal murine knee joints were derived from measurements of 25 left knees of normal mice. Reporducible, nonlinear s-shaped load-displacement curves were determined, and parameters of anterior-posterior translation, varus-valgus rotation, and compliance were calculated from the curves. No differences were found between the left and right knee joints of eight mice. The average displacement between 0.8 N of anterior force and 0.8 N of posterior force was 0.47 ± 0.10 mm. The endpoint compliances for anterior and posterior displacements were 0.16 ± 0.03 and 0.16 ± 0.04 mm/N, respectively. The average rotation between a 4 Nmm valgus moment and a 4 Nmm varus moment was 17.4 ± 3.3°. The endpoint compliances for varsus and valgus rotations were 1.1 ± 0.7 and 1.0 ± 0.3°/Nmm, respectively. Storage of the joints at ?70°C had no effect on laxity. We also studied the parameters of laxity after pathology of the knee joint was induced. Zymosan-induced or antigen-induced arthritis did not increase laxity of the joint. In an osteoarthritis model induced by injection of collagenase, laxity was markedly increased. In conclusion, laxity in the knees of mice can be measured reproducibly, and changes in the characteristics of laxity due to pathological conditions can be quantified.     

固定平台全膝关节置换术后10年以上临床随访研究

 目的 总结固定平台全膝关节置换的长期临床疗效,分析随访10年以上患者的假体生存情况及相关影响因素。方法 1993年6月至2002年5月期间施行全膝关节置换手术285例,其中226例患者(246例膝)纳入研究,男47例,女179例;年龄(62.2±9.4)岁(32~78岁)。其中类风湿关节炎36例43膝,骨关节炎188例201膝。统计假体生存时间10年以上者的膝关节HSS评分、活动度及术后影像学改变,分析假体生存情况及影响假体生存的因素。结果 160例(177膝)随访10年以上,术后平均随访11.9年(10~18年),总的10年假体生存率为93.6%,15年假体生存率为92.8%。后十字韧带保留假体与后稳定型假体长期生存率的差异无统计学意义。髌骨置换与不置换、类风湿关节炎与骨关节炎患者假体生存率的差异无统计学意义。术前膝关节HSS评分平均为(56.58±11.05)分,末次随访为(92.29±10.95)分;术前膝关节活动度平均为84.8°±24.0°,末次随访为99.7°±17.6°,膝关节伸直迟滞由术前平均8.4°±9.1°改善为0.5°±2°。翻修手术15例,原因为感染10例、无菌松动3例、关节僵硬1例、髌骨原因1例。结论 固定平台全膝关节置换可获得满意的长期临床疗效,10年假体生存率可达90%以上。是否保留后十字韧带、是否行髌骨置换、类风湿关节炎与骨关节炎患者长期假体生存率的差异无统计学意义。     

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.     

Medial epicondyle osteotomy: a method of choice in severe varus knee arthroplasty

The purpose of this study was to evaluate the results of total knee arthroplasty (TKA) after using medial epicondyle osteotomy (MEO) as a balancing method for severe varus deformity and also to compare these results with those of TKA after using additional resection of the tibial medial plateau to correct this deformity. A total of 60 knees with severe varus deformity underwent TKA between 2006 and 2010. In 30 cases, we used MEO as a balancing method, and in other 30, additional medial tibial plateau resection was performed. The clinical outcomes were measured with the Knee Society score (KSS), the range of the motion and frontal laxity of the knee. The radiological outcomes were measured by anteroposterior simple radiographs to assess: the union state of the osteotomy site, the amount of resected tibial medial plateau bone and the femorotibial angle. The findings of the study show that in the MEO group the KSS improved from 21.13?±?13.6 to 92.1?±?7.6 points (P?<?0.001). Moreover, the range of motion increased from 70.3°?±?25.3° to 109.3°?±?12.7° (P?<?0.001). The femorotibial angle was corrected from a 22.6°?±?5.71° varus to a 4.0°?±?1.38° valgus (P?<?0.001) and frontal laxity decreased from 10.83°?±?3.9° to 0.33°?±?1.2° (P?<?0.001). No statistically significant differences were found between groups regarding the postoperative outcomes of KSS, range of motion, femorotibial angle and frontal laxity. The amount of resected tibial medial plateau bone was statistically significantly smaller in the MEO group (1.63?±?0.96?mm in the MEO group and 4.73?±?2.7?mm in the other group; P?<?0.001). In the MEO group, the mean thickness of the polyethylene insert was 12.66?±?1.21?mm, while in the second group, it was 13.73?±?1.59?mm, with statistically significant P?=?0.005. Fibrous union occurred in all knees in the MEO group. Using medial epicondyle osteotomy for varus knee when performing total knee arthroplasty could be a useful ligament-balancing technique to achieve medial stability of the knee. In addition, it could have considerable advantages towards the additional resection of the tibial medial plateau.     

Abnormal kinematics of the artificial knee: Roentgen stereophotogrammetric analysis of 10 Miller-Galante and five New Jersey LCS knees

The in vivo kinematics of two types of unconstrained, posterior cruciate ligament retaining knee prostheses were analyzed 1 year postoperatively using roentgen stereophotogrammetric analysis. Ten knees had the Miller-Galante and five the New Jersey LCS design. the Miller-Galante knees displayed decreased adduction during active flexion when compared with normal knees. in both types of prostheses, there was decreased medial and increased proximal and posterior displacement. the abnormal kinematics probably reflect the design of the articular surfaces, the absence of the anterior cruciate ligament, and the dysfunction of the posterior cruciate ligament.     

Asymmetry of mediolateral laxity of the normal knee

Background Understanding the normal kinematics of the joints is important for reconstructive surgery. However, only a few extensive studies have been done on medial and lateral laxity of the normal knee. Methods Radiographs of 50 normal knees were obtained under varus and valgus stress in both extension and flexion and the relative angle of the articular surface was measured. Results In extension, the mean angle was 4.9° in varus stress and 2.4° in valgus stress. In flexion, the mean angle was 4.8° in varus stress and 1.7° in valgus stress. Lateral laxity was significantly greater than medial laxity in both extension and flexion. Conclusions Lateral laxity may be necessary for the medial pivot movement of the normal knee. There is some disagreement regarding the importance of pursuing the perfect rectangular gaps during total knee arthroplasty (TKA). The methods for measuring the tension of soft tissues during the operation are not accurate and do not always reflect the postoperative tensions of dynamic phases, such as walking and standing. Slight lateral laxity can be accepted with TKA, and further studies are necessary to determine whether prosthesis lift-off occurs in the replaced knee with slight lateral laxity similar to that in the normal knee.     

Abnormal kinematics of the artificial knee. Roentgen stereophotogrammetric analysis of 10 Miller-Galante and five New Jersey LCS knees

The in vivo kinematics of two types of unconstrained, posterior cruciate ligament retaining knee prostheses were analyzed 1 year postoperatively using roentgen stereophotogrammetric analysis. Ten knees had the Miller-Galante and five the New Jersey LCS design. The Miller-Galante knees displayed decreased adduction during active flexion when compared with normal knees. In both types of prostheses, there was decreased medial and increased proximal and posterior displacement. The abnormal kinematics probably reflect the design of the articular surfaces, the absence of the anterior cruciate ligament, and the dysfunction of the posterior cruciate ligament.     

全膝关节表面置换治疗严重膝关节畸形

目的探讨人工全膝关节表面置换术(TKA)治疗严重膝关节畸形临床疗效。方法应用全膝关节表面置换治疗严重膝关节畸形36例(48膝)。使用HSS评分标准评估分析术前、术后膝关节功能及术后疼痛、膝关节活动度的改善情况。43膝采用后稳定型人工全膝关节假体,5膝采用CCK型人工全膝关节假体。结果术后早期均无感染等并发症发生。术后X线片示假体位置良好,下肢力线良好。患者均获得随访,时间6～18个月。HSS评分术前为(41±5.3)分,术后6个月为(87.7±6.5)分。手术优良率为83.3%。患者疼痛、功能方面及活动度均有明显改善。结论全膝关节置换术对严重膝关节畸形的治疗效果满意。但应严格掌握手术适应证。     

Effect of rotational malposition of the femoral component on knee stability kinematics after total knee arthroplasty

Excessive external rotation of the femoral component can cause an abnormally tight popliteus tendon complex, which induces loss of rotational laxity of the knee in the late phase of knee flexion after total knee arthroplasty. This study evaluated the effect of popliteus tendon release on rotational and varus—valgus laxity of implanted knees with an excessively externally rotated femoral component. Rotational and varus—valgus laxity was measured with a knee kinematics testing device before and after total knee arthroplasty. External rotational positions of the femoral component of 5° and 8° were compared, and the effects of popliteus tendon release on rotational and varus—valgus laxity were evaluated. To further investigate this question, the effect of a conforming articular design was compared with that of a flat tibial surface. External rotational position of 5° did not change rotational or varus—valgus laxity of the knee. With an 8° external rotational position, however, external rotational laxity significantly decreased in knees with a conforming surface at angles of 30°, 45°, 60°, and 90°. After popliteus tendon release, external rotational laxity significantly improved at 90° flexion and was identical to that of the normal knee. Internal rotational range was similar before and after popliteus tendon release. Popliteus tendon release did not affect the varus—valgus laxity (stability) with either articular surface.     

Changes in ligamentous laxity after posterior stabilized total knee replacement and factors correlated with postoperative laxity

Instruction

Total knee arthroplasty (TKA) performed with the gap technique can achieve rectangular gaps during flexion and extension by proper bone resection and subsequent soft tissue release. Acquisition of appropriate soft tissue balance is important for successful TKA. It is unknown, however, whether the intraoperative well-balanced ligamentous laxity changes postoperatively over time. We hypothesized that even if good soft tissue balance was achieved intraoperatively the lateral ligamentous laxity would increase with time postoperatively. This phenomenon depends on preoperative background factors.

Methods

We used the angle between the component surfaces of the tibia and femur to define ligamentous laxity. Changes in ligamentous laxity after posterior stabilized minimally invasive surgery (MIS)-TKA were analyzed retrospectively in 150 knees based on radiographic measurements. At 12 months after the operation, the cases were divided into two groups in which the lateral ligamentous laxity in flexion was either ≤3° (balanced group) or >3° (unbalanced group). Factors with a potential to encourage postoperative ligamentous laxity were analyzed.

Results

Our data show that the postoperative ligamentous laxity in extension did not change, whereas the lateral ligamentous laxity in flexion increased with time. This change was significantly related to the preoperative lateral ligamentous laxity, body weight, body mass index, and age.

Conclusion

The results of this study should be taken into account by surgeons performing MIS-TKA with the gap technique.     

The relationship between postoperative ligament balance and preoperative varus deformity in total knee arthroplasty.

We hypothesize that in knees with severe varus deformities, varus-valgus ligament imbalance tends to remain postoperatively after total knee arthroplasty. The purpose of this study was to evaluate the correlation between preoperative varus deformity and postoperative ligament balance quantitatively measured by stress radiograph using Telos SE in total knee arthroplasty. In this study, 44 knee arthroplasties in 32 patients were evaluated. We defined the angle in varus and valgus stress as "varus angle" and "valgus angle," and the sum of varus angle and valgus angle as "sum of varus-valgus angle." There was a significant correlation between preoperative lateral femoral angle and varus angle (p < 0.0001, r = 0.56), which means that postoperative ligament imbalance tends to remain in knees with preoperative varus deformities. There was a significant correlation between the postoperative period and the sum of varus-valgus angle, which suggests that knees with total knee arthroplasty have potential to increase laxity postoperatively.     

Dislocation of a posterior stabilized total knee prosthesis. A report of two cases

Posterior stabilized knee prostheses have been recommended for knees with posterior cruciate deficiency, as well as for knees with prior patellectomy. Two cases are presented in which a complete dislocation of a Kinematic II Stabilizer prosthesis occurred after primary knee arthroplasty. The mechanism of dislocation was a varus or valgus stress while the knee was flexed. This previously unreported complication of dislocation after primary knee arthroplasty with a posterior stabilized knee prosthesis was, we believe, due, in part, to the design of this prosthesis, which provides little mediolateral stability in flexion, in combination with a mild degree of laxity of the collateral ligaments. This complication could be prevented by use of a prosthesis with greater inherent mediolateral stability.