Acute locking in revision total knee arthroplasty due to disengagement of the locking screw

Acute locking of the joint in a replaced knee joint is very rare. This report describes an acute locking episode of a revised modular total knee replacement, occurring more than 2 years after surgery. A disengaged screw from the modular femoral component had lodged in the joint at the inferior pole of the patella and required urgent arthroscopic removal. There was no subsequent failure of the stem–condylar junction, nor loosening of the femoral component.     

The effect of posterior tibial slope on knee flexion in posterior-stabilized total knee arthroplasty

Purpose

To evaluate and quantify the effect of the tibial slope on the postoperative maximal knee flexion and stability in the posterior-stabilized total knee arthroplasty (TKA).

Methods

Fifty-six patients (65 knees) who had undergone TKA with the posterior-stabilized prostheses were divided into the following 3 groups according to the measured tibial slopes: Group 1: ≤4°, Group 2: 4°–7° and Group 3: >7°. The preoperative range of the motion, the change in the posterior condylar offset, the elevation of the joint line, the postoperative tibiofemoral angle and the preoperative and postoperative Hospital for Special Surgery (HSS) scores were recorded. The tibial anteroposterior translation was measured using the Kneelax 3 Arthrometer at both the 30° and the 90° flexion angles.

Results

The mean values of the postoperative maximal knee flexion were 101° (SD 5), 106° (SD 5) and 113° (SD 9) in Groups 1, 2 and 3, respectively. A significant difference was found in the postoperative maximal flexion between the 3 groups (P < 0.001). However, no significant differences were found between the 3 groups in the postoperative HSS scores, the changes in the posterior condylar offset, the elevation of the joint line or the tibial anteroposterior translation at either the 30° or the 90° flexion angles. A 1° increase in the tibial slope resulted in a 1.8° flexion increment (r = 1.8, R ² = 0.463, P < 0.001).

Conclusion

An increase in the posterior tibial slope can significantly increase the postoperative maximal knee flexion. The tibial slope with an appropriate flexion and extension gap balance during the operation does not affect the joint stability.

Level of evidence

Retrospective comparative study, Level III.     

Computer-assisted revision of total knee arthroplasty

Revision total knee prosthesis still remains a difficult procedure. Particularly, challenging is the restoration of the joint line to a normal position and the attainment of correct lower limb alignment and healthy bone support for the implants. Computer assistance improves accuracy during the implantation of primary total knees. The goal of this study was to evaluate the usefulness of computer assisted surgery (CAS) in total knee prosthesis revision. We revised 15 NKII total knee arthroplasties with the Navitrack system and compared the mechanical alignment and the joint line level on pre- and postoperative radiographs. After revision, the joint line position was restored. The knee with the revision prosthesis was aligned in the frontal plan with implants fixed perpendicularly to the mechanical axis. It is possible to correctly revise knee prosthesis with computer assistance only and without having to use a conventional ancillary. We had a permanent control of the joint line position and have performed the revision surgery following the same steps as in a primary implantation.     

The influence of tibial slope on maximal flexion after total knee arthroplasty

Many surgeons believe that increasing the tibial slope in total knee arthroplasty (TKA) is beneficial with regard to maximal postoperative flexion. Review of the clinical literature, however, does not confirm this hypothesis, neither does it give an answer to the question of how much flexion gain can be expected per degree extra tibial slope. The purpose of this study was, therefore, to evaluate and quantify the influence of tibial slope on maximal postoperative flexion in contemporary posterior cruciate ligament (PCL)-retaining TKA. Twenty-one cadaver simulations of a standard PCL-retaining TKA were studied while reproducing identical deep flexion femorotibial kinematics as documented by three-dimensional computer-aided videofluoroscopy from patients with well-functioning TKAs of the same design. In each knee the tibial component was consecutively implanted with 0° posterior slope, 4° posterior slope, and 7° posterior slope. Maximal flexion was recorded for each configuration. Average maximal flexion at 0° tibial slope was 104°, and increased significantly to 112° when the same knees were implanted with 4° tibial slope. Increasing the slope further to 7° again significantly improved average maximal flexion to 120°. When postoperative radiographic tibial slope was compared to maximal flexion, an average gain of 1.7° flexion for every degree extra tibial slope was noted. Increasing the tibial slope in PCL-retaining TKA does indeed improve maximal flexion before tibial insert impingement occurs against the femoral bone. The surgeon can expect an average gain of 1.7° flexion for every degree extra tibial slope.     

Modular augmentation in revision total knee arthroplasty

Purpose

Controversy exists about the real effectiveness of modular augmentation to manage bone defects in revision total knee arthroplasty. The purpose of this study was to determine whether use of modular augmentation to reconstruct severe defects (1) significantly increased overall outcomes, (2) caused radiolucency or osteolysis and (3) affected mid-term survivorship of knee revisions. The hypothesis was that modular augmentation provides a good survivorship of knee revisions.

Methods

Thirty-eight consecutive revision knee arthroplasties were followed for a median follow-up period of 7 (4.5–9) years. Type 2 and 3 defects were treated with metal augments, tantalum cones and modular cementless stems. Patients were assessed using the IKS knee and function scores and the HSS score.

Results

The median IKS knee and function scores and HSS score were 34 (15–58), 19.5 (13–39) and 30 (24–60) points before the operation, respectively, and 78 (49–97), 76 (58–90) and 80.5 (64–98) points (p < 0.001) at the latest follow-up. The median knee flexion increased from 82° (31°–110°) to 116° (100°–129°) (p < 0.01). Tibial radiolucencies were observed in 2 (5.2 %) cases. Re-revision was necessary in three (7.9 %) patients.

Conclusions

Modular augmentation may reduce the need for allografting to treat severe bone defects, providing a well-functioning and durable knee joint reconstruction.

Level of evidence

Case-series study, Level IV.     

Increasing financial burden of revision total knee arthroplasty

We reviewed the peri-operative and financial data of patients who underwent revision total knee arthroplasty in our institution between 1997 and 2006. The aims were to compare difference in cost between aseptic and septic cases and to identify the sources of preventable cost increase in revision knee procedure. The study group comprised 117 women (65%) and 62 men (35%). The median age of patients decreased from 73 years (37–83 years) in 1997–2001 to 70 years (15–91 years) in 2002–2006, a decline of 4% (P < 0.05). The mean ASA scores also dropped from 3 to 2 between the two periods. Despite this, the mean total cost of revision knee procedure continued to increase. Patients undergoing revision arthroplasty because of infection had much higher (P = 0.0001) cost compared to their aseptic counterpart. Increase in the costs of investigations (P < 0.05) and implant (P < 0.05) was the major contributing factors. The cost of implants increased by 32–35% (P < 0.05) depending on implant selection. Changing demographics will increase the requirement for this surgery and thus increase its overall cost to society. Cost increases associated with unnecessary investigations, prolonged hospital stay and use of expensive implants should be avoided.     

Posterior tibial slope impacts intraoperatively measured mid-flexion anteroposterior kinematics during cruciate-retaining total knee arthroplasty

Purpose

Posterior tibial slope (PTS) for cruciate-retaining (CR) total knee arthroplasty (TKA) is usually pre-determined by the surgeon. Limited information is available comparing different choices of PTS on the kinematics of the CR TKA, independent of the balancing of the extension gap. This study hypothesized that with the same balanced extension gap, the choice of PTS significantly impacts the intraoperatively measured kinematics of CR TKA.

Methods

Navigated CR TKAs were performed on seven fresh-frozen cadavers with healthy knees and intact posterior cruciate ligament (PCL). A custom designed tibial baseplate was implanted to allow in situ modification of the PTS, which altered the flexion gap but maintained the extension gap. Knee kinematics were measured by performing passive range of motion (ROM) tests from full extension to 120° of flexion on the intact knee and CR TKAs with four different PTSs (1°, 4°, 7°, and 10°). The measured kinematics were compared across test conditions to assess the impact of PTS.

Results

With a consistent extension gap, the change of PTS had significant impact on the anteroposterior (AP) kinematics of the CR TKA knees in mid-flexion range (45°–90°), but not so much for the high-flexion range (90°–120°). No considerable impacts were found on internal/external (I/E) rotation and hip–knee–ankle (HKA) angle. However, the findings on the individual basis suggested the impact of PTS on I/E rotation and HKA angle may be patient-specific.

Conclusions

The data suggested that the choice of PTS had the greatest impact on the mid-flexion AP translation among the intraoperatively measured kinematics. This impact may be considered while making surgical decisions in the context of AP kinematics. When using a tibial component designed with “center” pivoting PTS, a surgeon may be able to fine tune the PTS to achieve proper mid-flexion AP stability.

     

Significant effect of the posterior tibial slope and medial/lateral ligament balance on knee flexion in total knee arthroplasty

Purpose

The intra-operative femorotibial joint gap and ligament balance, the predictors affecting these gaps and their balances, as well as the postoperative knee flexion, were examined. These factors were assessed radiographically after a posterior cruciate-retaining total knee arthroplasty (TKA). The posterior condylar offset and posterior tibial slope have been reported as the most important intra-operative factors affecting cruciate-retaining-type TKAs. The joint gap and balance have not been investigated in assessments of the posterior condylar offset and the posterior tibial slope.

Methods

The femorotibial gap and medial/lateral ligament balance were measured with an offset-type tensor. The femorotibial gaps were measured at 0°, 45°, 90° and 135° of knee flexion, and various gap changes were calculated at 0°–90° and 0°–135°. Cruciate-retaining-type arthroplasties were performed in 98 knees with varus osteoarthritis.

Results

The 0°–90° femorotibial gap change was strongly affected by the posterior condylar offset value (postoperative posterior condylar offset subtracted by the preoperative posterior condylar offset). The 0°–135° femorotibial gap change was significantly correlated with the posterior tibial slope and the 135° medial/lateral ligament balance. The postoperative flexion angle was positively correlated with the preoperative flexion angle, γ angle and the posterior tibial slope. Multiple-regression analysis demonstrated that the preoperative flexion angle, γ angle, posterior tibial slope and 90° medial/lateral ligament balance were significant independent factors for the postoperative knee flexion angle. The flexion angle change (postoperative flexion angle subtracted by the preoperative flexion angle) was also strongly correlated with the preoperative flexion angle, posterior tibial slope and 90° medial/lateral ligament balance.

Conclusion

The postoperative flexion angle is affected by multiple factors, especially in cruciate-retaining-type TKAs. However, it is important to pay attention not only to the posterior tibial slope, but also to the flexion medial/lateral ligament balance during surgery. A cruciate-retaining-type TKA has the potential to achieve both stability and a wide range of motion and to improve the patients’ activities of daily living.     

Sonography of polyethylene liners used in total knee arthroplasty

OBJECTIVE: We investigated the ability of sonography to reveal the polyethylene liner used in total knee arthroplasty with the hopes of establishing a possible relationship between the sonographic measurement of the actual thickness of the polyethylene liner and the estimated thickness based on conventional radiography. MATERIALS AND METHODS: Twenty-four consecutive patients who were referred for Doppler screening for deep venous thrombosis after total knee arthroplasty were evaluated. The polyethylene liner was identified on sonography, and three measurements were obtained from four locations: anteromedial joint line (just medial to the midline incision), along the medial joint line, anterolateral joint line (just lateral to the midline incision), and along the lateral joint line. These sonographic measurements were compared with radiographic measurements of the radiolucent polyethylene liner and with the manufacturers' stated size of the polyethylene liner. Linear regression analyses were then performed. RESULTS: The polyethylene liner is seen on sonography as a strong linear echogenic interface with posterior acoustic shadowing. Linear regression analyses showed a high correlation (r = 0.8) between the sonographic measurements and the radiographic measurements. A relatively poor correlation (r = 0.2) was noted between the manufacturers' stated size of the liner and the sonographic measurements. CONCLUSION: We found that the polyethylene liner used in total knee arthroplasty can be clearly identified during sonographic evaluation of the knee. We also found a high correlation between the longitudinal measurement of the polyethylene liner with the thickness of the radiolucent polyethylene as measured on conventional radiographs. We propose that sonography could potentially be a useful noninvasive imaging modality to screen for subtle cases of polyethylene wear.     

In vitro investigation of the influence of tibial slope on quadriceps extension force after total knee arthroplasty

The purpose of this study was to investigate the influence of tibial base plate angulation on knee kinematics and kinetics during knee arthroplasty. The amount of quadriceps force required to extend the knee and the anteroposterior displacement of a mobile bearing insert as well as tibiofemoral position were measured during an in vitro simulation of an isokinetic knee extension cycle. Human knee specimens (n = 7, mean age 62, range 52–75 years, all male) were tested in a kinematic knee simulating machine after total knee arthroplasty (TKA) with a mobile bearing insert prosthesis (Interax^®, Stryker/Howmedica). During simulation, a hydraulic cylinder applied sufficient force to the quadriceps tendon to produce an extension moment of 31 N m about the knee. The quadriceps load was measured using a load cell attached to the quadriceps tendon, the anteroposterior displacement of the mobile bearing insert as well as the relative tibiofemoral position was measured using an ultrasound base motion analysis system (CMS 100^®, Zebris). Quadriceps load, insert and tibial displacement were first investigated with the tibial base plate implanted with a neutral tibial base plate orientation, and subsequently after 10° posterior angulation. The quadriceps forces needed to produce a 31 N m knee extension moment after TKA with neutral slope reached levels as high as 1,391 N (SD 82 N). After applying a posterior slope of 10°, maximum quadriceps force was measured to be up to 1,303 N (SD 34 N, P = 0.04). The mobile bearing insert was observed to move up to 0.1 mm (SD 4.2 mm) anteriorly relative to the tibial base plate with neutral tibial slope, and up to 1.0 mm (SD 4.5 mm, P = 0.47) with tibial slope. Femoral position relative to the tibia moved from a posterior position of 13.1 mm (SD 4.0 mm) anteriorly up to 0.5 mm (SD 6.3 mm), and from 16.0 mm (SD 6.4 mm, P = 0.67) to 9.5 mm (SD 9.9 mm, P = 0.33) with a 10° tibial slope. Posterior slope of the tibial base plate resulted in a more physiologic insert movement with a more posterior position of the femur and reduced quadriceps force especially in knee flexion angles above 60° compared to TKA with a neutral slope of the tibial base plate. Thus, the data suggest that the quadriceps lever arm was improved, which might have positive effect in mobilization of patients after TKA.     

The influence of the tibial slope on intra-operative soft tissue balance in cruciate-retaining and posterior-stabilized total knee arthroplasty

Purpose

This study aims to make clear the influence of the tibial slope on intra-operative soft tissue balance measurements using a tensor in cruciate-retaining and posterior-stabilized total knee arthroplasty (TKA).

Methods

Forty patients with osteoarthritis of the knee received TKAs (20 cruciate-retaining TKAs and 20 posterior-stabilized TKA). Soft tissue balance was measured using an offset type tensor at 0, 10, 45, 90, 135 degrees of knee flexion. The tibial slopes were measured by post-operative lateral radiograph. The correlation between the tibial slope and values of soft tissue balance were assessed.

Results

Joint component gap at 90° (R = 0.537, p < 0.01) and 135° (R = 0.463, p < 0.05) of flexion and joint component gap change value of 90–0° (R = 0.433, p < 0.05) showed positive correlations with tibial slope in posterior-stabilized TKA. There was no relationship between the tibial slope and the value of soft tissue balances in cruciate-retaining TKA.

Conclusions

In the present study, we confirmed that increasing the tibial slope resulted in a larger flexion gap compared to extension gap in posterior-stabilized TKA. Surgeons should be aware that increasing the tibial slope is one factor responsible for widening the flexion–extension gap difference in posterior-stabilized TKA.

Level of evidence

III.     

Triple fracture during rehabilitation after revision total knee arthroplasty

Purpose

The incidence of periprosthetic fractures after knee-joint implant revisions is increasing in prevalence. We present a method of treatment for a patient who sustained a triple fracture—a periprosthetic femur fracture, a patella fracture, and a tibial shaft fracture.

Methods

The femoral fracture was treated with a specially designed intramedullary nail, the patella fracture with a figure-of-eight suture, and the tibial shaft fracture by a minimal-invasive plate osteosynthesis using a percutaneous plating technique.

Results

Osseous consolidation was confirmed, and the patient presented a satisfying range of movement under full-weight-bearing conditions after mobilisation.

Conclusions

Simultaneous multiple periprosthetic fractures are a special challenge, and in situ coupling of the endoprosthesis with a slotted hollow nail presents a valuable option for the treatment.

Level of evidence

Level V, Expert opinion.     

Modular tibial plate for minimally invasive total knee arthroplasty

Purpose

Aim of the study was to evaluate the clinical and radiological results of a modular tibial plate purposely designed for minimally invasive total knee arthroplasty.

Methods

We prospectively assessed the results of 200 primary total knee replacements performed through a minimally invasive approach using a dedicated modular tibial plate, a posterior stabilized knee prosthesis, and a fixed bearing in 175 patients (139 women and 36 men), undergoing surgery between 2005 and 2009 presenting knee osteoarthritis. Median age at the time of surgery was 69?years (52–88).

Results

No patients were lost at follow-up. 3 implants underwent revision. At a mean 3?years (1–5?years) follow-up, the HHS and KSS score showed a significant improvement, increasing, respectively, from a median value of 35–95 (78–100) and from 31 points in the “knee” and 45 points in the “function” score to a median of 95 (83–100) and 94 (81–100). Using the Kaplan–Meier method, the survival rate at 5?years was 97.9% with a 95% confidence interval.

Conclusion

The implant showed good results in either clinical or radiological assessment at a short/midterm follow-up with a high survival rate.

Level of evidence

Therapeutic study, Level IV.     

延长的胫骨结节截骨在翻修全膝置换中的应用

目的探讨延长的胫骨结节截骨在全膝置换术中的应用。方法对1998年5月至2002年10月间12例采用延长的胫骨结节截骨的患者进行回顾性研究。结果所有截骨在术后6个月临床和X线片评估均愈合,关节活动度平均从79°增加到95°,平均膝关节评分从60改善至85。结论延长的胫骨结节截骨在翻修全膝关节置换术中能改善手术显露和关节功能。     

Navigation-assisted total knee arthroplasty in knees with osteoarthritis due to extra-articular deformity

Purpose  

Extra-articular post-traumatic deformity may make difficult the implantation of total knee arthroplasty (TKA). Staged surgical procedures, including femoral or tibial osteotomy, can be required to restore proper alignment. These procedures may be inappropriate because of high rate of complications. Intra-articular resection is an alternative procedure, but it is limited by the potential compromise of collateral knee ligaments. Conventional instrumentation cannot be used in patients with previous trauma and residual bone deformity. We want to assess whether computer-assisted surgery may be a good alternative to traditional techniques.     

Accuracy of manual instrumentation of tibial cutting guide in total knee arthroplasty

Purpose

The aim of this study was to evaluate the accuracy of conventional instrumentation for tibial resection in total knee arthroplasty (TKA) as assessed by a computer-based navigation system during each phase of the surgical procedure. The hypothesis is that conventional instrumentation fails to achieve optimal accuracy in final implant positioning, thus leading to surgical errors.

Methods

Forty primary TKAs were performed. The resection guide was placed using an extramedullary guide. Accurate guide positioning was assessed by the navigation system prior to the osteotomy. The alignment measurement was repeated after resection and after component implantation in order to quantify the deviation caused by the manual positioning of the prosthetic components. A deviation ≥2° was considered unsatisfactory.

Results

In the frontal plane, unsatisfactory results observed were as follows: 15 % with reference to manual positioning of the resection guide and 10 % with reference to definition of the resection plane with a tendency towards varus malalignment. In the sagittal plane, unsatisfactory results were as follows: 45 % with reference to manual positioning of the resection guide and 40 % with reference to definition of the resection plane with a trend of decreased tibial slope angle. The deviation between bone resection and subsequent implant placement was ≥2° in none of the cases.

Conclusions

The study confirms the hypothesis that conventional instrumentation fails to achieve optimal accuracy in the positioning of the tibial component. During each phase of the surgical procedure, a tendency towards varus malalignment and a decreased tibial slope angle were observed.

Levels of evidence

II.     

Evaluation of anatomic references for tibial sagittal alignment in total knee arthroplasty

The authors aimed to demonstrate the relationship between the sagittal mechanical axis of the tibia and other reference axes of the tibia and fibula in patients with advanced osteoarthritis of the knee joints, and then to identify a reliable landmark in order to minimize posterior tibial slope measurement errors. We evaluated 133 osteoarthritic knees with neutral or varus deformity in 64 female and 8 male patients. Axial computed tomographic images of whole tibiae including knee and ankle joints were obtained and reconstructed using 3-dimensional imaging software. Angles between the mechanical axis (MA), the tibial anatomical axis (TAA), the anterior tibial cortex (ATC) and the fibular shaft axis (FSA) were measured, and then medial and lateral tibial slope angles were measured using all axes. Mean angles between MA and the other anatomical reference lines (TAA, ATC and FSA) were 0.9, 2.2 and −2.1°, respectively. The mean values of lateral tibial slopes with respect to MA, TAA, ATC and FSA were 8.7, 10, 12 and 7.3, respectively, and their intra- and inter-observer reliabilities were higher than those of medial tibial slopes. Although posterior tibial slope change markedly according to the reference axis used, the axes used in conventional TKA showed significant correlations with each other, and thus, may be used safely if differences with the mechanical axis are considered. Moreover, the lateral tibial slope might have advantages over the medial tibial slope in terms of restoration of the natural tibial slope.