Intercondylar distal femoral fracture. An unreported complication of posterior-stabilized total knee arthroplasty

No Discernible Difference in Revision Rate or Survivorship Between Posterior Cruciate-Retaining and Posterior Cruciate-Substituting TKA

BACKGROUND

Many authors and the data of multiple registries have suggested that the use of posterior cruciate-substituting (posterior stabilized [PS]) total knee arthroplasty (TKA) leads to a higher risk of revision compared with the use of posterior cruciate-retaining (CR) TKA. The aim of the present prospective, randomized, long-term study was to compare PS and CR TKA with regard to the clinical, radiographic, and computed tomography (CT) results; the prevalence of osteolysis; revision rate; and survivorship.

METHODS

This study included a consecutive series of 300 patients (mean age [and standard deviation], 63.6 ± 6 years) who underwent simultaneous, bilateral TKA in the same anesthetic session. Each patient received a NexGen CR-Flex prosthesis on 1 side and a NexGen LPS-Flex prosthesis on the contralateral side. The mean follow-up period was 18 years (range, 17.5 to 19.5 years).

RESULTS

There were no significant differences between the NexGen CR and LPS-Flex TKA groups at the latest follow-up with regard to the mean Knee Society knee score (93 versus 92 points, respectively); the Western Ontario and McMaster Universities Osteoarthritis Index score (19.1 points for both); the University of California Los Angeles activity score (6.1 points for both); range of motion (125° ± 6.1° versus 126° ± 6.5°); radiographic and CT results; and revision rate (6.0% versus 6.3%). No knee had osteolysis. The estimated survival rate at 19.5 years was 94% (95% confidence interval [CI], 91% to 100%) for the NexGen CR-Flex prosthesis and 93.7% (95% CI, 91% to 100%) for the LPS-Flex prosthesis, with revision or aseptic loosening as the end point.

CONCLUSIONS

The findings of the present, long-term (minimum follow-up of 17.5 years) clinical study showed that NexGen CR-Flex and NexGen LPS-Flex implants produced excellent clinical and radiographic results. There was no notable clinical advantage of a NexGen CR-Flex implant over a NexGen LPS-Flex implant.

LEVEL OF EVIDENCE

Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Minimum 19-Year Clinical Results and Patient Satisfaction After Total Knee Arthroplasty

BACKGROUND

Long-term (minimum 19-year) outcome data on clinical results and patient satisfaction after posterior-stabilized total knee arthroplasties (TKAs) are missing in the literature. The purpose of the study was to evaluate the clinical and radiographic results as well as patient satisfaction at a mean of 21.2 years after posterior-stabilized TKAs.

METHODS

This study included 756 patients (1,350 knees) who had undergone TKAs. There were 96 men and 660 women (mean age, 58 years; range, 40 to 84). The mean follow-up was 21.2 years (range, 19 to 23). At each follow-up visit, the patients were assessed radiographically and clinically. Furthermore, patient satisfaction was determined.

RESULTS

The Knee Society total, pain, function, and deformity scores were 42, 18, 33, and 5 points, respectively, at the final follow-up. The mean Western Ontario and McMaster Universities Arthritis Index score was 25 points at the final follow-up. With revision or aseptic loosening as the end point, the 23-year intimated survival for the implant was 96% (95% confidence interval, 91 to 100%). The overall patient satisfaction score at the final follow-up was 83.3 points (range, 81 to 86). Patient satisfaction scores with regard to pain, housework, recreation, and surgery were 84, 81, 82, and 86 points, respectively.

CONCLUSIONS

The findings of the present, mean 21-year follow-up clinical study suggest excellent results with regard to the revision rates and survivorship of the posterior-stabilized total knee implants. However, consistent with the literature, we found that about 80% of patients expressed overall satisfaction with their primary TKAs. About 8% of patients were either somewhat or very dissatisfied with the procedure.

Saw-box osteotomy versus reamer-box osteotomy in posterior stabilized total knee arthroplasty: a retrospective study of an average five year follow-up

PURPOSE

The purpose of this study is to compare the difference of results between two methods of femoral box osteotomy adopted by two designs of posterior stabilized total knee prostheses.

PATIENTS AND METHODS

Retrospective analysis of the results of two groups of patients operated upon using two primary PS TKA systems, PFC Sigma (DePuy Synthes, Johnson and Johnson®) and Genesis II prosthesis (Smith and Nephew®), with an average of five year follow-up was done. Group 1 included 152 knees in 121 patients and group 2 included 122 knees in 111 patients. The average follow-up period in both groups was five years. The box osteotomy method depends on bone saw in group 1, and bone reamer in group 2.

RESULTS

The KSS score of group 2 was better in the first six months postoperatively. Then, no significant differences were seen in the remaining follow-up visits. The risk of periprosthetic fractures was significantly higher in group 1 (p-value 0.040). Survival analysis showed a significantly shorter time for reoperation in group 1 than in group 2 as described by log-rank test, (p < 0.006).

CONCLUSION

The method of box cutting has an impact on the function and longevity of posterior stabilized primary knee implants. The risk of periprosthetic fractures can be reduced by proper patient selection, decreasing the box sizes, and development of more "controlled" box osteotomy instruments.

Clinical relevance of roll-back replacement of ultra congruent total knee arthroplasty: comparison of mid-term outcomes with posterior stabilizing design

INTRODUCTION

The outcomes of total knee arthroplasty (TKA) remain controversial, and we do not know which factors are important for successful outcomes. This study aimed to compare the mid-term outcomes of different conceptual designs by evaluating the radiological and clinical outcomes.

MATERIALS AND METHODS

A total of 478 total knee arthroplasties (TKAs) were enrolled and allocated into groups I [posterior stabilizing (PS) with anterior referencing (AR)], II [PS with posterior referencing (PR), and III [ultra-congruent (UC) TKA)]. Preoperative findings, last follow-up clinical outcomes, and final follow-up radiological and indirect assessments of the femoral rollback were compared between the groups.

RESULTS

The mean follow-up period was 72.6 ± 12.9 months. The tourniquet was used samely applied to every group. Flexion contracture was significantly larger in group III than in groups I and II (3.3 ± 2.7, p < 0.001), and further flexion was significantly smaller in group III (130.0° ± 2.7°, p < 0.001). Among the radiological parameters, posterior osteophyte formation was the most common in group III (67.8%). The rollback distance was significantly smaller in group III than in groups I and II (p < 0.001). The active deep flexion angle was affected by the posterior condylar offset (PCO) ratio, and the contact point changed the distance (p < 0.05).

CONCLUSION

PS TKAs showed better ROMs than UC TKAs; however, no differences were noted in the clinical outcome scales. The flexion angle was affected by the PCOR and rollback at both PS and UC TKAs. However, rollback negatively affected the flexion angle during UC TKAs. An inappropriate femoral rollback was identified, and femoral osteophyte formation was determined to be the most prominent in UC TKAs. Level of evidence Level III comparative study.

Diagnosis and Management of Intraoperative Periprosthetic Fractures in Primary Total Knee Arthroplasty

Intraoperative periprosthetic fracture is an uncommon but notable complication that can occur during primary total knee arthroplasty. These fractures may occur at various stages during the procedure, including surgical exposure, implant preparation, implant trialing, and final implantation. Management of femoral and tibial fractures necessitates intraoperative recognition, including attentiveness of preoperative patient and surgical risk factors. This comprehensive review article focuses on the patient and surgical risk factors, diagnosis, management, and outcomes related to intraoperative fractures during primary total knee arthroplasty.

Favorable outcomes of posterior cruciate-stabilized inserts over ultracongruent inserts in total knee arthroplasty

OBJECTIVE

Posterior cruciate-stabilized (PS) and ultracongruent (UC) inserts are used during total knee arthroplasty (TKA), but superiority in gaining postoperative knee flexion and functionality remains contested. Therefore, this study compared postoperative outcomes between PS and UC inserts.

METHODS

A retrospective review evaluated unilateral or bilateral TKAs with PS or UC inserts from August 2011 to March 2020. Nonparametric statistics were performed to evaluate differences in patient demographics, pre- and postknee flexion and Knee Society Knee (KSS-K) and Function Score (KSS-F). Univariate and multivariable regressions were performed to evaluate the influence on postoperative knee flexion ≥ 120°, presented as odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

Patient demographics were not significantly different between the 577 PS and 399 UC knees evaluated. Postoperatively, a larger proportion of UC knees demonstrated knee flexion < 120° (36.0% vs. 18.6%, p < 0.001) and lower KSS-K (91.0 ± 8.7 vs. 91.6 ± 10.3, p < 0.001) and KSS-F (76.8 ± 21.6 vs. 79.9 ± 21.6, p = 0.007) than the PS group. The PS group had greater improvement in flexion angle (4.9° ± 14.9° vs. 1.0° ± 15.6°, p < 0.001) and KSS-F (27.3 ± 23.3 vs. 23.1 ± 25.3, p = 0.007) as compared to that of UC patients. Patients with preoperative flexion < 120° (OR 2.787, CI 2.066-3.761; p < 0.001), higher body mass index (OR 1.033, CI 1.006-1.061; p = 0.017) and UC insert (OR 2.461, CI 1.832-3.307; p < 0.001) were less likely to achieve flexion ≥ 120°.

CONCLUSION

Favorable clinical and functional outcomes were noted in the PS group as compared to UC inserts in TKA. The greater improvement in overall knee flexion may suggest the PS insert may be especially appropriate for patients with lower preoperative range of motion.

LEVEL OF EVIDENCE

III, retrospective comparative study.

Intraoperative Fractures Sustained During Total Knee Arthroplasty: A Critical Analysis Review

» While the occurrence of postoperative periprosthetic fractures around total knee arthroplasties (TKAs) are well reported, little is known about intraoperative fractures that occur during TKA. Intraoperative fractures during TKA can occur in femur, tibia, or patella. It is a rare complication with an incidence of 0.2% to 4.4%.» Risk factors of periprosthetic fractures include osteoporosis, anterior cortical notching, chronic corticosteroid use, advanced age, female sex, neurologic disorders, and surgical technique.» Fractures can potentially occur at any stage of the TKA including exposure, bone preparation, placement of trial components, cementation, insertion of the final components, and seating of the polyethylene insert. Forced flexion during trialing increases the risk for patella fracture, tibial plateau, or tubercle fractures especially when there is under resection of the bone.» Management guidelines for these fractures are lacking with current options being observation, internal fixation, the use of stems and augments, increasing constraint of the prosthesis, implant revision, and modifying the postoperative rehabilitation.» Finally, the outcomes of intraoperative fractures are not well reported in the literature.

Intraoperative Periprosthetic Fractures during primary Total knee arthroplasty: Experience from an Asian high-volume arthroplasty centre

BACKGROUND

Intraoperative periprosthetic fracture (IF) is an under-reported complication in primary total knee arthroplasty (TKA). This study aimed to audit the outcomes and complication rates in patients encountering IF during primary TKA and propose a new classification for its management.

METHODS

A nested case-control study was performed at a tertiary referral hospital where 50 patients encountering IF during primary TKA operated by a single surgeon team between January 2016 to May 2021, were compared with 150 (3:1) age-, gender- and implant-matched patients not encountering IF. Demographic data, risk factors, outcomes and complications of both groups were compared at a minimum follow up of 1 year.

RESULTS

The incidence of IF was 0.45%, with 44 fractures in the femur (88%), six (12%) in the tibia and none in the patella. Medial collateral ligament avulsion fracture (54.54%) in the femur and medial plateau fracture (66.66%) in the tibia were the most common fracture types. At final follow up, the fracture group had higher rates of 90-day re-admissions (8% vs. 2.66%, P = 0.095), deep infection (4% vs. 0.66%, P = 0.15) and revisions (6% vs. 1.33%, P = 0.06). The mean Knee Society Score was not significantly different between the two groups (152.22 ± 9.25 vs. 161.68 ± 11.22, P = 0.642) with union being achieved in all but one patient at a mean duration of 9.6 weeks.

CONCLUSIONS

Patients with severe and fixed deformities have a higher risk for IF. The occurrence of fracture and the complexity of surgery equally contribute to the higher complication rates. Appropriately managed fractures have comparable functional outcomes.

Early Femoral Insufficiency Fractures After Primary Total Knee Arthroplasty

Background

Periprosthetic femur fracture following total knee arthroplasty (TKA) is a devastating complication. Although trauma-related periprosthetic femur fractures have been well studied, early atraumatic insufficiency periprosthetic fractures (IPFs) are gaining attention. We present the largest IPF series to date to better understand and prevent this complication.

Methods

A retrospective study of all patients who underwent a revision surgery for periprosthetic fracture within 6 months of primary TKA between 2007 and 2020 was performed. Patient demographics, preoperative radiographs, implant details, and fracture radiographs were reviewed. Alignment measurements and fracture characteristics were assessed.

Results

Sixteen patients met criteria (rate 0.05%), and 11 had posterior-stabilized TKAs. The mean age was 79 years, mean body mass index was 31 kg/m², and 94% (15/16) were female. Seven (47%) patients had a confirmed history of osteoporosis. IPF occurred on average 4 weeks (range, 4 days-13 weeks) after the index TKA. Overall, 12 of 16 (73%) had preoperative valgus deformities, and 11 patients (10 valgus, 1 varus) had preoperative deformities >10 degrees. A characteristic radiographic appearance of femoral condylar impaction and collapse was noted in 12 of 16 cases (75%); 11 of these 12 fractures (92%) involved the unloaded compartment based on preoperative varus/valgus deformity.

Conclusions

Patients who developed IPFs were most commonly elderly, obese women with osteoporosis and severe preoperative valgus deformities. The apparent mechanism of failure was overloading of previously unloaded osteopenic femoral condyle. In high-risk patients, the use of a cruciate-retaining femoral component or a femoral stem for a posterior-stabilized femur may be considered to help avoid this catastrophic complication.

Risk Factors and Preventive Strategies for Perioperative Distal Femoral Fracture in Patients Undergoing Total Knee Arthroplasty

Background and Objectives Perioperative distal femoral fracture is rare in patients undergoing total knee arthroplasty (TKA). In such rare cases, additional fixation might be required, and recovery can be delayed. Several studies have focused on perioperative distal femoral fractures in TKA, but there remains a lack of information on risk factors. The purpose of this study was to investigate risk factors for perioperative distal femoral fractures in patients undergoing TKA and suggest preventive strategies. Materials and Methods: This retrospective study included a total of 5364 TKA cases in a single institution from 2011 to 2022. Twenty-four distal femoral fractures occurred during TKA or within one month postoperatively (0.45%). Patient demographics, intraoperative findings, and postoperative progress were obtained from patient medical records and radiographs. Risk factors for fractures were analyzed using multivariate Firth logistic regression analysis. Results: Although all 24 distal femoral fractures occurred in female patients (24 of 4819 patients, 0.50%), the incidence rate of fracture between male and female patients was not significantly different (p = 0.165). The presence of osteoporosis and insertion of a polyethylene (PE) insert with knee dislocation were statistically significant risk factors (p = 0.009 and p = 0.046, respectively). However, multivariate logistic regression analysis showed that only osteoporosis with bone mineral density (BMD) < -2.8 (odds ratio (2.30), 95% CI (1.03-5.54), p = 0.043) was an independent risk factor for perioperative distal femoral fracture in TKA patients. Conclusions: Our results suggest that osteoporosis with BMD < -2.8 is a risk factor for distal femoral fractures in patients undergoing TKA. In these patients, careful bone cutting, adequate gap balancing, and especially the use of the sliding method for insertion of a PE insert are recommended as preventive strategies.

Intraoperative Fractures of the Tibia and Femur in Knee Revision Surgery

Intra-operative fractures in knee revision surgery are relatively rare and have not been well studied. They may occur during joint exposition, removal of the prosthesis or cement, or implantation of trial or original components. The fractures affect both the metaphyseal area and diaphysis of the tibia and femur. Tibial fractures are slightly more common than femur fractures. On the femur, the medial condyle is most frequently affected, followed by the femur diaphysis. The use of non-cemented stems is associated with a greater risk of intra-operative diaphyseal fractures than that of cemented stems. Overall, women and patients with an osteopenic bone structure have a higher risk of fractures. It is common that fractures are diagnosed post-operatively. In these cases, conservative therapy may be successful, depending on the stability of the prosthesis and bones. The most common surgical fixation options are cerclages and screws, followed by stem extensions for bridging the fracture. Plate fixation or use of strut grafts are also sensible therapy options. Overall, intraoperative fractures have a high healing potential with stable and good joint function. The revision rate is still 15%, which is most often caused by peri-prosthetic infection.

Revision Risk for Total Knee Arthroplasty Polyethylene Designs in Patients 65 Years of Age or Older: An Analysis from the American Joint Replacement Registry

BACKGROUND

Polyethylene bearing design may influence the risk of revision after total knee arthroplasty (TKA). Previous investigations from outside of the United States have suggested the potential for an increased risk of all-cause revision and revision for infection with the use of posterior-stabilized bearings. We examine the risk of revision based on the polyethylene bearing design selection for primary TKA.

METHODS

An analysis of the American Joint Replacement Registry (AJRR) data from 2012 to 2019 was performed. We identified all primary TKAs over the study period and linked cases to supplemental U.S. Centers for Medicare & Medicaid Services (CMS) data where available. Patient demographic characteristics, polyethylene characteristics, procedure dates, and cause for revision were recorded. Analysis was performed to compare minimally stabilized implants (cruciate-retaining, anterior-stabilized, or pivot bearing designs) with posterior-stabilized implants. Cumulative incidence function (CIF) curves and Cox proportional hazard ratios (HRs) were created for all-cause revision and revision for infection in each group.

RESULTS

We identified 305,279 cases with reported minimally stabilized or posterior-stabilized implant characteristics. There were 161,486 cases (52.9%) that utilized posterior-stabilized bearings compared with 143,793 cases (47.1%) with minimally stabilized bearings. For minimally stabilized bearings, 1,693 cases (1.18%) had all-cause revision and 334 cases (0.23%) had revision for infection. For posterior-stabilized bearings, 2,406 cases (1.49%) had all-cause revision and 446 cases (0.28%) had revision for infection. The use of posterior-stabilized bearings had HRs of 1.25 (95% confidence interval [CI], 1.2 to 1.3; p < 0.0001) for all-cause revision and 1.18 (95% CI, 1.0 to 1.4; p = 0.02) for revision for infection.

CONCLUSIONS

Similar to investigations from international registries, we found an increased risk of all-cause revision and revision for infection when using posterior-stabilized bearings in TKA in the United States. Surgeons should consider this finding when considering bearing selection for primary TKA.

LEVEL OF EVIDENCE

Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

The Effect of Posterior Cruciate Ligament Release on Kinematics and Outcomes in Primary Total Knee Arthroplasty With a Dual-Pivot Conforming Polyethylene

BACKGROUND

Ultracongruent bearings are increasingly utilized in total knee arthroplasty (TKA); however, implications of surgical technique on knee kinematics and outcomes with these bearings are not well understood. This study's purpose was to evaluate the relationship of 3-dimensional knee kinematics and patient-reported outcome measures (PROMs) in a dual-pivot congruent bearing TKA with and without posterior cruciate ligament (PCL) release.

METHODS

Forty patients undergoing TKA with an asymmetric ultracongruent bearing were prospectively enrolled for gait analysis preoperatively and 4 months postoperatively. Three-dimensional gait analysis was performed utilizing infrared motion capture. Knee kinematic data and PCL disposition were analyzed for correlations with PROMs.

RESULTS

The PCL was fully released in 52.5% (21/40) of cases. Greater maximum anteroposterior femoral translation correlated with lower Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (rho = -0.596, P = .012), greater Knee Society Score pain with level walking (rho = 0.411, P = .101), and greater Knee Society Score pain while climbing stairs (rho = 0.469, P = .058) at 4-month follow-up. The PCL-release group was associated with greater maximum femoral anteroposterior translation (9.8 vs 5.5 mm, P = .053) and greater maximum internal tibial rotation (-6.2° vs -3.0°, P = .040), supporting a more anterior-based position of the medial condyle. The PCL released group had lower median Knee Injury and Osteoarthritis Outcome Score for Joint Replacement scores (70.7 vs 76.3, P = .031) and reported that their knees "sometimes or always" feel normal less frequently (81.8% vs 92.3%, P = .576).

CONCLUSION

With this asymmetric ultracongruent bearing TKA, preservation or partial titration release of the PCL, as opposed to full PCL release, appears to minimize deleterious anterior femoral translation and internal tibial rotation, which is correlated with optimized patient-reported outcomes.

LEVEL OF EVIDENCE

II.

Posterior stabilized total knee arthroplasty increases the risk of postoperative periprosthetic fractures

Background

The Insall-Burstein posterior-stabilized knee design was first developed in 1978 by adding a central cam mechanism to the articular surface geometry of the total condylar prosthesis to correct its problems being not “rolling back”. Since then, the use of posterior-stabilized (PS) implants in total knee arthroplasty (TKA) is becoming increasingly popular. However, one of the main disadvantages of PS designs is related to the amount of bone removed during femoral box osteotomy to create the housing of the PS mechanism, the clinical value of removing more or less bone during primary TKA remains to be fully established. The objective of this study was to compare the incidence of early postoperative periprosthetic fractures in the cruciate retaining (CR) and posterior stabilized (PS) knee prosthesis.

Methods

An institutional high volume arthroplasty unit database was reviewed to identify all patients who sustained a postoperative periprosthetic fracture following primary TKA between January 2014 and May 2018. A retrospective chart review was performed to collect clinical, radiographic, and operative report data. A total of 352 patients with 600 primary TKAs were identified. (300 cases of cruciate retaining TKAs from 178 patients and 300 cases of posterior stabilized TKAs from 174 patients) were retrospectively reviewed.

Results

Eleven patients (1.83%) sustained periprosthetic fractures in the postoperative setting following primary TKA. All of the fractures were located on the femur and were treated surgically. Only one knee (one patient) from the CR group sustained a periprosthetic fracture, while 10 knees (from 10 patients) from the PS group sustained a fracture. The relative risk of sustaining a fracture in the CR group was 0.10 times relative to the PS group (RR   =   0.10, 95% CI 0.0129 – 0.776).

Conclusion

Posterior stabilized total knee arthroplasties (TKAs) significantly increase the risk of periprosthetic fractures in obese Asian patients compared to cruciate retaining TKAs.

Cruciate Substituting Implants in Primary Total Knee Arthroplasty

The use of cruciate substituting (CS) total knee replacement has been increasing in popularity. There are numerous factors that have likely contributed to this expansion. The CS philosophy incorporates the ease of use commonly cited by advocates of the posterior stabilized (PS) total knee design with the bone preservation associated with a cruciate retaining (CR) design. The ultra-congruent highly cross-linked polyethylene liner increases stability without an appreciable change in wear. Furthermore, balancing the flexion and extension gaps does not require “titrating” the posterior cruciate ligament, improving the user-friendliness. This paper reviews the nuances of this implant design compared to PS and CR designs as well as provides surgical technique recommendations/considerations.

Team Approach: Preoperative Management of Metabolic Conditions in Total Joint Replacement

»

Total joint arthroplasties (TJAs) of the knee and hip have been considered 2 of the most successful surgical procedures performed to date.

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Frailty is defined as increased vulnerability to adverse outcomes with physiologic stress.

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Preoperative optimization of frailty and metabolic bone conditions, including osteoporosis, vitamin D deficiency, and diabetes, through a multidisciplinary approach can help improve outcomes and minimize costs after TJA.

3D Geometric Shape Reconstruction for Revision TKA and UKA Knees Using Gaussian Process Regression

Revision knee surgery is complicated by distortion of previous components and removal of additional bone, potentially causing misalignment and inappropriate selection of implants. In this study, we reconstructed the native femoral and tibial surface shapes in simulated total/unicompartmental knee arthroplasty (TKA/UKA) for 20 femurs and 20 tibias using a statistical inference method based on Gaussian Process regression. Compared to the true geometry, the average absolute errors (mean absolute distances) in the prediction of resected femur bones in TKA, medial UKA, and lateral UKA were 1.0 ± 0.3 mm, 1.0 ± 0.3 mm, and 0.8 ± 0.2 mm, respectively, while those in the prediction of tibia resections in the corresponding surgeries were 1.0 ± 0.4 mm, 0.8 ± 0.2 mm, and 0.7 ± 0.2 mm, respectively. Furthermore, it was found that the prediction accuracy depends on the size and gender of the resected bone. For example, the prediction accuracy for UKA cuts was significantly better than that for TKA cuts (p < 0.05). The female and male cuts were often overfit and underfit, respectively. The data indicated that this reconstruction approach can be a viable option for planning of revision surgeries, especially when contralateral anatomy is pathological or cannot be available.

Tibial baseplate position and posterior cruciate ligament status impact patient-reported outcomes in conforming dual-pivot bearing total knee arthroplasty

Background

In an effort to optimize clinical outcomes and enhance stability, ultracongruent bearings have been increasingly used in primary total knee arthroplasty (TKA). The importance of the posterior cruciate ligament (PCL) and optimal sagittal tibial baseplate position in ultracongruent bearing TKA remains unknown. This study sought to determine whether these modifiable, surgical-technique-dependent variables meaningfully impact patient-reported outcome measures.

Methods

A total of 759 primary TKAs of the same dual-pivot design performed using a consistent surgical technique between January 2016 and April 2019 were retrospectively reviewed. PCL status was recorded, and anteroposterior (AP) tibial baseplate position and posterior tibial slope were measured by two independent blinded raters. Patient-reported outcomes related to pain, function, satisfaction, and activity level were analyzed in relationship to PCL status, posterior tibial slope, and AP tibial baseplate position, in addition to other pertinent covariates.

Results

Median age and body mass index of the cohort were 68.3 years and 33.4 kg/m², respectively, with 73% being female. In multivariate analysis, partial or full release of the PCL was predictive of a knee “always” feeling normal (odds ratio 1.42, P = .041). Furthermore, tibial baseplate position closer to the middle of the tibia was associated with greater improvements in pain with level walking, pain while climbing stairs, and Knee Injury and Osteoarthritis Outcome Score for Joint Replacement total scores (P ≤ .079).

Conclusion

In congruent dual-pivot bearing TKA, partially or fully releasing the PCL and AP tibial baseplate position closer to the middle of the tibia may provide greater improvement in pain and function scores at minimum 1-year follow-up.

Midterm Outcomes and Survivorship of Anterior Stabilized Versus Cruciate Retaining Bearing in Primary Total Knee Arthroplasty

BACKGROUND

There has been increasing utilization of ultracongruent bearings with a cruciate retaining (CR) femoral component in primary total knee arthroplasty. The purpose of this study is to compare outcomes and survivorship between an ultracongruent anterior stabilized (AS) and CR bearing.

METHODS

A retrospective review was performed from 2010 through 2014 of all primary total knee arthroplasties with a single knee systems identical CR femur and AS or CR bearing with minimum 2-year follow-up yielding a study cohort of 3323 patients (4164 knees). Knee range of motion, Knee Society pain scores, Knee Society clinical scores, Knee Society functional scores, and University of California Los Angeles activity scores were evaluated. The need for manipulation under anesthesia (MUA), nonrevision surgery and revisions were assessed.

RESULTS

AS bearing was used in 1471 knees (35%) and CR bearing used in 2693 knees (65%). Mean follow-up was 5.4 years. The AS group had significantly higher improvements in knee range of motion, Knee Society clinical, Knee Society functional, and Knee Society pain scores. MUAs were performed on 120 knees (8.2%) in the AS group compared with 158 knees (5.9%) in the CR group (P = .005). The AS group had significantly less all-cause failure, aseptic failures, revisions for instability, and revisions for isolated polyethylene wear. The 10-year aseptic survival for AS was 98.3% and for 92.3% for the CR group (P = .002).

CONCLUSION

These mid-term results demonstrate the AS bearing had significantly higher improvements in clinical and functional outcomes as well as greater survivorship. Knees in which an AS bearing was used did have a higher incidence of MUA.

Sister, Sister! Siblings With Simultaneous Early Femoral Insufficiency Fractures After Total Knee Arthroplasty

Early periprosthetic fractures after total knee arthroplasty are rare but devastating complications which require revision surgery and lead to poor patient satisfaction. We present 2 siblings who underwent primary total knee arthroplasty on the same day and then both presented 2 weeks after surgery with atraumatic periprosthetic femur fractures. The first patient underwent revision for a cemented distal femoral replacement with stemmed tibial fixation. The second patient underwent an isolated femoral component revision with a stemmed femoral component and distal augment. Histological evaluation identified significant peri-implant osteoporosis. The variation in complexity associated with early periprosthetic femoral insufficiency fractures is highlighted by these 2 cases. Surgeons may consider using stemmed femoral components in similar patients if poor distal femoral bone stock is encountered intraoperatively.

Intraoperative Femoral Condyle Fracture during Bone Preparation in a Cruciate-retaining Primary Total Knee Arthroplasty

Introduction

Intraoperative fracture in revision knee arthroplasty is commonly described. Intraoperative fracture during primary total knee arthroplasty (TKA) is a significant yet infrequently reported complication. The literature about intraoperative fractures during primary TKA is limited. It is usually seen in posterior-stabilized prosthesis during primary TKA, however, its occurrence in cruciate-retaining (CR) primary TKA is rarely reported.

Case Report

The authors describe a unique case of intraoperative medial femoral condyle fracture in primary CR TKA during bone preparation. The fracture was managed successfully by fixation with a 3.5 mm screw followed by cemented primary CRTKA. Bony union was achieved with a good clinical outcome as shown by the Knee Society Knee Score of 86 and a Function Score of 90 without any signs of prosthesis failure/loosening at 2 years' follow-up.

Discussion

Careful pre-operative evaluation and planning are necessary for patients with risk factors to avoid poor outcome. A stable internal fixation abiding the standard principles of fracture fixation and arthroplasty is needed to achieve a satisfactory functional and radiographic outcome, thus avoids early prosthetic failure.

Bilateral Posterior-Stabilized Total Knee Arthroplasty in a Patient With Osteopetrosis and Literature Review

We present a case report of a patient with osteopetrosis and refractory bilateral knees osteoarthritis who underwent bilateral total knee arthroplasties (TKAs). After conservative management has failed, surgical treatment with arthroplasty is an excellent alternative with satisfactory outcomes. TKA in patients with osteopetrosis has only been described in 6 other case studies, none of which underwent bilateral TKA. To perform this procedure, additional attention should be directed toward the presurgical planning because of the amplified difficulty of the procedure and the altered bone biology that increases the risks of intraoperative fractures and markedly extends the time of surgery. This report describes a case of osteopetrosis with refractory osteoarthritis managed with bilateral TKA, the surgical technique and special considerations, complications, and future recommendations.

Anterior-stabilized TKA is inferior to posterior-stabilized TKA in terms of postoperative posterior stability and knee flexion in osteoarthritic knees: a prospective randomized controlled trial with bilateral TKA

PURPOSE

To determine whether knee stability, range of motion (ROM) and clinical scores differ between anterior-stabilized (AS) and posterior-stabilized (PS) total knee arthroplasty (TKA).

METHODS

This prospective randomized controlled trial included 34 patients with severe bilateral knee osteoarthritis who underwent bilateral TKA between June 2010 and July 2011 using AS and PS designs of a single-implant system. AS TKA with ultracongruent inserts was performed in one knee and PS TKA with a cam-post mechanism was performed in the other knee in each patient. Clinical and radiological data from a mean follow-up period of 5 years, including ROM, clinical scores, peak knee torque determined by isokinetic test, knee joint laxity determined by Telos stress views, tourniquet time and subjects' preference were analyzed.

RESULTS

The mean postoperative knee flexion angle did not differ between groups until 1 year. Beginning 2 years postoperatively, the knee flexion angle decreased slightly in the AS group and was smaller than that in the PS group (p = 0.004). The mean Knee Society knee score was higher in the PS group than in the AS group after 2 years. The quadriceps strength did not differ between groups. The mean posterior laxity after TKA was 6-8 mm greater in the AS group than in the PS group. No radiological loosening was observed in either group. More subjects preferred PS knees to AS knees. However, this difference was not significant.

CONCLUSION

AS primary TKA was inferior to PS TKA in terms of posterior knee stability, postoperative knee flexion and clinical scores after 2 years.

LEVEL OF EVIDENCE

Therapeutic study, Level 1.

Intra-operative fractures in primary total knee arthroplasty - a systematic review

BACKGROUND

One of the rare complications of primary total knee arthroplasty is intra-operative fracture. Intra-operative fracture during revision knee arthroplasty has been well-documented but there is limited literature on fractures occurring during primary knee arthroplasty. We conducted a systematic review of the literature to compare and contrast the various studies to clearly define the predisposing factors, incidence, and characteristics of the fracture itself and to arrive at a consensus on the management and prevention of intra-operative fractures during primary knee arthroplasty.

METHODS

The PubMed/Medline, Cochrane, Scopus and Embase databases were searched using keywords "intra-operative fracture", "distal femoral fracture", "tibial fracture", "patella fracture" and "primary total knee arthroplasty". A total of 158 articles were retrieved and after further filtration and exclusion processing, 10 articles that evaluated intra-operative fractures in primary total knee arthroplasty were included for the review.

RESULTS

The reported incidence of intra-operative fractures varied from 0.2% to 4.4%. A higher incidence in female patients with a male to female ratio of 0.4 was reported. Posterior stabilized (PS) total knee arthroplasty was associated with higher risk of intra-operative femoral fractures by many authors in this review. Timing of occurrence and location of the intra-operative fractures can vary widely, with femoral fractures occurring more commonly during bone preparation, trialing and impaction of the final implant and tibial fractures occurring during preparation for the tibial keel and impaction of the tibial component.

CONCLUSIONS

Intra-operative fractures during primary total knee arthroplasty are rare with higher risk associated with osteoporosis, rheumatoid arthritis, advanced age, female gender, chronic steroid use, metabolic bone disorders, PS type of femoral implant and difficult surgical exposure of the knee joint due to severe deformities. A plethora of management options have been utilized according to surgeon preference. Standard principles of fracture fixation and arthroplasty principles should be followed to achieve stable internal fixation and any unstable fracture site should be bypassed with the utilization of stemmed components. Satisfactory radiographic and functional outcome can be expected with appropriate treatment.

Intraoperative femoral condyle fracture in primary total knee arthroplasty - a case-control study in Asian population

PURPOSE

Intraoperative femoral condyle fracture is a significant but rarely reported complication during primary total knee arthroplasty (TKA). This is the first study to identify the incidence, risk factors, location and outcome of these fractures in an Asian population with modern posterior-stabilized (PS) TKA.

MATERIALS AND METHODS

We reviewed 2682 consecutive primary TKAs performed between 2011 and 2017 in a single centre; 23 femoral condyle fractures were identified and analysed.

RESULTS

Fractures were managed conservatively with screw fixation or revision arthroplasty. Mean follow up was 3.0 years (range 3 months to 5.9 years). All patients achieved bone union and good functional outcome. The mean Knee Society Knee score was 89.4 (range 71-100) and the function score was 80.2 (range 60-95) at a mean of 3.0 years post-operation. Bilateral surgery was found to be a significant risk factor for femoral condyle fracture, while there was a higher trend of fracture in female patients and Stryker articular surface mounted (ASM) navigation.

CONCLUSIONS

Intraoperative fracture is not uncommon with modern PS TKA. Postulated risk factors for fracture were discussed. Early identification of risk factors and a rigorous surgical technique may reduce risk of fracture. A good functional result was expected after proper treatment.

Increased Intercondylar Femoral Box Cut-to-Femur Size Ratio During Posterior-Stabilized Total Knee Arthroplasty Increases Risk for Intraoperative Fracture

Background

Iatrogenic intraoperative fractures are preventable complications in total knee arthroplasty. As press-fit fixation becomes more popular, further investigation into risk factors is needed. Some authors have suggested that smaller femurs may be at higher risk in posterior-stabilized constructs owing to industry designs trending toward larger, constant box sizes that increase the amount of bone resection relative to bone stock.

Methods

Finite element analysis (FEA) was used to investigate the effect of insertion of posterior-stabilized femoral components on stress distributions in small femurs and whether common bony preparation techniques could further affect risk for intraoperative fracture. The FEA results were validated with mechanical testing by loading to failure with varying resection depths of the distal femur and varying lateralization of the box cut.

Results

With a standard distal resection depth and neutral box position, a decrease in femur size led to an increase in maximal von Mises stresses by 43.6% medially and 44.3% laterally. Box lateralization and increased distal resection depth had minimal changes on the maximal stresses (3.3% medially and −0.4% laterally) on average-sized femurs while having a much larger effect on the stress distribution in small femurs (118.3% medially and 6.7% laterally).

Conclusions

A subset of intraoperative femur fractures is potentially preventable. Small femur sizes, especially ones that would require increased distal resection or change in implant positioning, may benefit from an alternative design without the need for a cam/post mechanism.

Does Recession of the Posterior Cruciate Ligament Influence Outcome in Total Knee Arthroplasty?

BACKGROUND

For a PCL-retaining (posterior cruciate ligament) total knee arthroplasty (TKA) to function suitably, proper soft tissue balancing, including PCL recession, is required. Yet, when the recession of the PCL is needed, there is still a debate as to whether a cruciate-retaining (CR) TKA should be converted to a posterior-stabilized TKA due to the concern of instability and poorer clinical outcomes. The purpose of this study is to determine whether recession of the PCL adversely affects clinical outcomes in patients who undergo CR TKA.

METHODS

CR TKAs of the same design performed by the senior author (J.M.) were identified between December 2006 and July 2015. Clinical outcome measurements were collected and included the Western Ontario and McMaster Universities Osteoarthritis Index score, the Knee Society Clinical Rating System, Short Form-12 Physical Composite Score/Mental Health Composite Score, and revision rates.

RESULTS

There were no significant differences in clinical outcome when the PCL was retained, partially recessed, or completely released during PCL-retaining TKA (Western Ontario and McMaster Universities Osteoarthritis Index: P = .54, Knee Society Clinical Rating System: P = .42, Short Form-12 Mental Health Composite Score: P = .89, Short Form-12 Physical Composite Score: P = .527).

CONCLUSION

This study presents evidence of similar clinical outcomes when the PCL is retained or released during PCL-retaining TKA, provided attention is paid to appropriate soft tissue balancing. CR TKA undergoing partial or complete release of the PCL should not routinely be converted to a posterior-stabilized knee design.

LEVEL OF EVIDENCE

Level II, Prognostic study.

Comparison of Anterior-Stabilized and Posterior-Stabilized Total Knee Arthroplasty in the Same Patients: A Prospective Randomized Study

BACKGROUND

A highly conforming, anterior-stabilized (AS) insert is designed to provide anteroposterior (AP) stability of the posterior-stabilized (PS) insert without a post. The purpose of this study was to compare the static and dynamic stability and function of AS and PS total knee arthroplasty (TKA) in the same patients.

METHODS

A prospective, randomized controlled trial was performed in 45 patients scheduled to undergo same-day bilateral TKA. One knee was randomly assigned to receive an AS TKA, and the other knee was scheduled for a PS TKA from the same knee system. At 2 years postoperatively, the static AP stability was compared using anterior and posterior drawer stress radiographs at 90° knee flexion. Dynamic AP stability was evaluated using one-leg standing lateral fluoroscopic images throughout the range of motion. Knee function was compared using the Knee Society Score and Western Ontario and McMaster Universities Osteoarthritis Index score.

RESULTS

At 2 years postoperatively, there was a significant difference in knee AP laxity at 90° of flexion between the two groups (7.6 ± 3.9 mm in the AS group vs 2.2 ± 2.3 in the PS group, P < .001). However, there were no differences in dynamic AP stability under one-leg standing fluoroscopic lateral images at 30°, 60°, and 90° knee flexion (P = .732, P = .764, and P = .679, respectively). The Knee Society Score and Western Ontario and McMaster Universities Osteoarthritis Index scores were not significantly different between the two groups (P = .641 and P = .582, respectively).

CONCLUSION

Despite the fact that the AS TKA group showed significantly more static posterior displacement than the PS TKA group at 90° of knee flexion, both the AS and PS TKA groups showed similar dynamic stability under weight-bearing conditions and knee function at 2 years postoperatively.

New mobile-bearing TKA with unique ball and socket post-cam mechanism offers similar function and stability with better prosthesis fit and gap balancing compared to an established fixed-bearing prosthesis

PURPOSE

A mobile-bearing (MB) posterior-stabilized total knee arthroplasty (TKA) system with ball and socket post-cam mechanism has been developed with the aims of better prosthesis fit and enhanced stability. However, the data are limited to compare its clinical outcomes with an already established fixed-bearing (FB) implant design.

METHODS

This is a prospective randomized study comparing 260 patients in the MB group and 133 patients in FB group with a minimum 2 years of follow-up. Intraoperative variables, post-operative functional outcomes and incidence of adverse events were compared.

RESULTS

MB group showed better prosthesis fit as the incidence of over-hang of femoral component at junction (medial: 1% vs. 5% and lateral: 2% vs 4%, p < 0.001) and trochlea (medial: 2% vs 30%, p = 0.042 and lateral: 13% vs 21%, p = 0.015) was less than FB group. MB group also showed better gap balancing as the incidence of medio-lateral gap difference more than 2 mm was less in flexion (2.3% vs. 16%, p < 0.001) and extension (3.1% vs. 9.8%, p = 0.005). Post-operative functional outcomes and incidence of adverse events showed no difference between the two groups at 2 years.

CONCLUSIONS

New MB design offers similar functional outcomes and stability along with better intraoperative prosthesis fit and gap balancing compared to an established fixed-bearing design. Hence, this new MB design could be an alternative prosthesis of choice for posterior-stabilized TKA.

LEVEL OF EVIDENCE

I.

Effect of polyethylene conformity on total knee arthroplasty early clinical outcomes

PURPOSE

Total knee arthroplasty is a successful procedure in treating subjects with end-stage knee osteoarthritis. The objective of this matched study was to evaluate subjective patient satisfaction and clinical and radiological outcomes in two groups of patients undergoing primary TKA using an identical third-generation design with different conformity in the polyethylene insert.

METHODS

One hundred consecutive patients undergoing TKA because of knee osteoarthritis were randomized in two matched groups. Group A included 50 Posterior-Stabilized (PS) implants, while group B included 50 Medially Congruent (MC) implants. The surgical technique was identical: gap balancing in extension and measured resection in flexion; cruciate ligaments were always removed; the coronal alignment followed the mechanical axis and the tibial slope was set at 3° in the PS group and 5° in the MC. Oxford Knee Score (OKS) and Knee Society Score (KSS) were assessed preoperatively and at 2 year minimum follow-up. Two-sample T test statistical analysis was performed.

RESULTS

All patients were available at final follow-up: there were no preoperative statistical differences between the two groups in the average preoperative ROM (PS 112°, MC 108°; n.s.), average preoperative KSS (PS 64.4, MC 63.7; n.s.), average preoperative OKS (PS 19.6; MC 19.0; n.s.), and average BMI (PS 34.40, MC 34.60; n.s.). At final follow-up, there were no statistical differences between the two groups in the average OKS (PS 40,5; MC 41.1; n.s.) and in the average KSS (PS 161,5, MC 165,7; n.s.). We found a statistically but not clinically significant difference at final ROM: the average maximum active flexion was 120° in the PS group and 123° in the MC group (s.s.).

CONCLUSION

This study evaluated two biomechanically different polyethylene inserts in the same TKA design, showing that reducing the level of intra-articular conformity had minimal effects on PROMs and objective short-term clinical results but a potentially beneficial effect on ROM. This study suggests that, once a satisfactory intra-operative stability is obtained, the minimal level of constraint should be used.

LEVEL OF EVIDENCE

III.

Intra- operative fractures in primary Total Knee Arthroplasty

BACKGROUND

Intraoperative fracture during primary Total Knee Arthroplasty (TKA) is very rare and there is little literature available which has defined the possible reasons for the occurrence of these fractures. Further, no study till date has defined the various management options available to treat these fractures. This study aims to define (1) the possible reasons for different fracture patterns occurring intraoperatively, (2) the ideal management options for each type of fracture geometry, (3) whether this intraoperative complication affects the physiotherapy protocol and long term outcomes.

METHODS

Out of 3168 primary TKA done between 2010 and 2017, 19 patients developed intraoperative fracture, whose data was evaluated retrospectively. Patients were assessed radiologically to determine the time to union and clinical outcomes were assessed using Knee Society Score.

RESULTS

Out of the 19 intraoperative fractures, 19 were in Tibia and 4 in Femur. Majority of fractures occurred during cementing and final implantation (8 cases), followed by exposure and bone preparation (6 cases) and the least during trialing (4 cases). Out of 15 Tibia fracture, 9 fractures involved the Tibial cortex which were managed with screws (4 cases), sutures and bone cement (5 cases). Stemmed tibial component was used for all Plateau type fracture patterns (6 cases). Out of 4 distal femur fractures, condylar type fracture pattern were fixed with plates and screws (3 cases) and epicondyle avulsion with screws alone (1 case). All the cases showed union (average union time 8.9 weeks) and good KSS scores which remained till their last follow-up. None of the patient developed any other complications or required revision surgery.

CONCLUSIONS

Intraoperative fracture during TKA, although rare but a significant complication which can affect the outcome, if not managed properly. We have shown methods of management for such cases, which have given excellent results.

Early femoral condyle insufficiency fractures after total knee arthroplasty: treatment with delayed surgery and femoral component revision

Background

Periprosthetic fracture following total knee arthroplasty (TKA) is usually associated with a traumatic event and typically treated with fracture fixation techniques. However, we report on a series of patients with early atraumatic condyle fractures that occurred as a result of insufficiency of the unloaded preoperative femoral condyle treated with delayed reconstruction.

Methods

We retrospectively reviewed a series of 7 patients who sustained femoral condyle fractures following TKA and evaluated risk factors for insufficiency.

Results

There were 6 females and 1 male with an average age of 65.5 (range, 63-75) years and an average body mass index of 29.4 (range, 27-32). Fracture occurred on average 24.9 days from the index surgery and secondary to a low energy mechanism. Five patients had valgus alignment (mean, 15.2°) preoperatively and sustained fracture of the unloaded medial femoral condyle. Two patients had varus alignment (mean, 7.0°) preoperatively and both fractured the unloaded lateral condyle. One patient underwent early intervention requiring distal femoral replacement secondary to femoral bone loss. The remaining 6 patients underwent delayed surgery for an average of 6 weeks to allow for fracture healing followed by femoral component revision. At last follow-up (average, 48.5 months), 1 patient required a tibial component revision; however, no revision of the femoral component was required.

Conclusions

Early femoral condyle insufficiency fractures following TKA may be a risk in females with poor bone quality and preoperative valgus alignment. Delayed surgery and femoral component revision is a treatment strategy that prevented the need for other tertiary reconstruction.

Total and intercondylar notch bone resection in posterior stabilized knee arthroplasty: analysis of five manufacturer designs

PURPOSE

The study aimed to volumetrically measure and compare the bone amount removed through the intercondylar femoral notch and the total bone amount removed through five different brands of implant design in order to provide orthopaedic surgeons with opinions in respect of implant selection.

METHODS

Ten implants from five different total knee arthroplasty implant manufacturers, namely Nex-Gen Legacy, Genesis 2 PS, Vanguard, Sigma PS and Scorpio NRG PS, were applied to a total of 50 sawbone models. Equal or the closest sizes of each brand on the anteroposterior plane were selected, and cuts were made following the standard technique. The removed bone pieces were measured in terms of volume and length in three planes, and were statistically analysed.

RESULTS

The comparison made by excluding femoral notch cuts did not produce any statistically significant difference between the amounts of bone removed. The following data were volumetrically obtained from the intercondylar femoral notch cut: Vanguard (3.6 ± 0.4 cm³), Nex-Gen (3.7 ± 0.5 cm³), Sigma (5.7 ± 0.4 cm³), Genesis 2 (6.3 ± 0.3 cm³) and Scorpio NRG (6.7 ± 0.7 cm³). There was no statistical difference between Genesis 2 and Scorpio NRG (n.s.), or between Nex-Gen and Vanguard (n.s.). The smallest volumetric value measured in the removed intercondylar femoral notch cut was obtained using Vanguard.

CONCLUSION

There are significant differences between implant designs in terms of preserving bone stock, and a large proportion of the difference arises from the intercondylar femoral notch cut.

Different intraoperative kinematics with comparable clinical outcomes of ultracongruent and posterior stabilized mobile-bearing total knee arthroplasty

PURPOSE

There remains no consensus as to whether mobile total knee arthroplasty (TKA) should use a posterior cruciate ligament-sacrificing ultracongruent (UC) or a posterior cruciate ligament-substituting posterior stabilized (PS) prosthesis. The purpose of this study was to assess intraoperative kinematics and clinical outcomes of UC and PS rotating platform mobile-bearing TKA.

METHODS

In this randomized controlled study, mobile UC TKA prostheses (n = 45) were compared with mobile PS TKA prostheses (n = 45) with regard to intraoperative kinematics and clinical outcomes. The passive kinematic study using intraoperative navigation system included anterior/posterior translation, varus/valgus alignment and rotation of femur during flexion. The patients were clinically and radiographically evaluated over a 3-year follow-up.

RESULTS

Paradoxical anterior translation of the femur was 10.8 ± 5.2 mm in the UC knee from 0° to 82° of knee flexion and 8.7 ± 3.0 mm in the PS knee from 0° to 70° of knee flexion (p = 0.027). Paradoxical internal rotation of the femur was 5.8° in the UC knees and 9.9° in the PS knees (p = 0.003). But, there was no significant difference between the groups in regard to the coronal alignment. There was no significant difference in the range of motion, KS knee scores, KS function scores, and WOMAC index scores.

CONCLUSIONS

Despite different intraoperative kinematics between mobile UC and mobile PS TKA, neither design reproduced physiologic knee kinematics and there was no difference in clinical outcomes between the two groups. The clinical relevance of the study is that despite different intraoperative kinematics, UC design can be a considerable alternative to PS design in mobile-bearing TKA in respect of clinical outcomes.

LEVEL OF EVIDENCE

II.

Cruciate retaining and cruciate substituting ultra-congruent insert

The posterior cruciate ligament (PCL) conservation and the polyethylene insert constraint in total knee arthroplasty (TKA) are still debated. The PCL is one of the primary stabilizers of the joint, but cruciate retaining (CR) implants have the disadvantage of a difficult balancing of the PCL. Postero-stabilized (PS) implants were introduced to reduce this problem. However, also the PS implants have some disadvantages, due to the cam-mechanism, such as high risk of cam-mechanism polyethylene wear. To minimize the polyethylene wear of the cam-mechanism and the bone sacrifice due to the intercondylar box, different types of inserts were developed, trying to increase the implant conformity and to reduce stresses on the bone-implant interface. In this scenario ultra-congruent (UC) inserts were developed. Those inserts are characterized by a high anterior wall and a deep-dished plate. This conformation should guarantee a good stability without the posterior cam. Few studies on both kinematic and clinical outcomes of UC inserts are available. Clinical and radiological outcomes, as well as kinematic data are similar between UC mobile bearing (MB) and standard PS MB inserts at short to mid-term follow-up. In this manuscript biomechanics and clinical outcomes of UC inserts will be described, and they will be compared to standard PS or CR inserts.

Functional Outcomes of a New Mobile-Bearing Ultra-Congruent TKA System: Comparison With the Posterior Stabilized System

We determined whether a new mobile-bearing ultra-congruent (UC) TKA system provides better functional outcomes than an established posterior-stabilized (PS) prosthesis. The functional outcomes (motion arc, AKS scores, WOMAC Index, and SForm-36 scores evaluated at 1 and 2 years postoperatively), satisfaction and incidences of adverse events were compared between the knees implanted with mobile-bearing UC prosthesis (n=103) and the mobile-bearing PS prosthesis (n=99). At 2 years, mobile-bearing UC TKAs showed similar functional outcomes and satisfaction, but smaller motion arc compared to mobile-bearing PS TKAs (126° vs. 131°). There were no differences in the incidence of adverse events. Mobile-bearing UC prosthesis can be considered a safe and viable alternative to the PS design, with an expectation of smaller postoperative maximum flexion.

Distal femoral fracture during primary total knee arthroplasty

PURPOSE

To review 6 cases of periprosthetic distal femoral fracture during total knee arthroplasty (TKA).

METHODS

Of 778 women and 691 men who underwent primary TKAs using posterior-stabilised (n=1240), cruciate-retaining (n=165), or semiconstrained (n=64) implant, 5 women and one man with a mean age of 73.3 years and a mean body mass index of 31.6 kg/m(2) sustained an intra-operative periprosthetic distal femoral fracture and were followed up for a mean of 12.8 (range, 2-39) months.

RESULTS

Respectively in patients with a posterior-stabilised, cruciate-retaining, or semi-constrained implant, the intra-operative fracture rates were 0.32%, 0%, and 3.13%. For women, the respective rates were 0.46%, 0%, and 5.10%. Intra-operative fracture was 9.69 times (p=0.03) more likely to occur in patients with a semi-constrained implant than those with a posterior-stabilised implant, and was 4.44 times (p=0.22) more likely to occur in women than in men. Half of the fractures occurred during the trial phase when the tibia was reduced onto the femur, and half during final prosthesis implantation.

CONCLUSION

Distal femoral fracture during primary TKA is rare and associated with the use of a semiconstrained implant. Preserving as much bone in the distal femur is advised.

Preservation of the posterior cruciate ligament is not helpful in highly conforming mobile-bearing total knee arthroplasty: a randomized controlled study

PURPOSE

The purpose of this study is to investigate whether the preservation of the posterior cruciate ligament (PCL) can be helpful for improving kinematics and clinical outcome in highly conforming mobile-bearing total knee arthroplasty (TKA).

METHODS

Ninety osteoarthritic knees were randomly allocated to either the PCL-preserving group or the PCL-sacrificing group. Passive kinematics was recorded with a navigation system immediately after implantation. Three parameters (anterior/posterior translation, varus/valgus rotation, and internal/external rotation) were analysed from 0° to 120° flexion.

RESULTS

The PCL-preserving group (42 knees) had more varus rotation over 90° flexion (p < 0.05) and more anterior translation of the femur in all ranges of flexion (p < 0.05) than those in the PCL-sacrificing group (44 knees). There was no difference in the internal/external rotation (p > 0.05). The range of motion, functional scores, and radiographic results did not significantly differ between the two groups at the final follow-up. Three knees in the PCL-preserving group were revised: two presented with instability caused by traumatic attenuation of the PCL and one with subluxation of the insert due to a tight PCL.

CONCLUSION

The preservation of the PCL was not helpful for improving kinematics and clinical outcome in highly conforming mobile-bearing TKA.

Reduction in bone volume resection with a newer posterior stabilized total knee arthroplasty design

BACKGROUND

Posterior stabilized total knee arthroplasty requires an intercondylar notch to accommodate the cam housing that articulates with the tibial post to create femoral rollback required for deep flexion. The volume of bone resected for the intercondylar notch varies with implant design, and newer designs may accommodate high flexion with less bone resection.

QUESTIONS/PURPOSES

This study aims to analyze the bone volume and density resected from the intercondylar notch for three posterior stabilized implants from a single company: a Posterior Stabilized (PS) system, a Hi-Flex system (HF), and a rounded new box-reamer (RB) system and to further assess whether the newer RB with a cylindrical cutting tool would preserve more native bone.

MATERIALS AND METHODS

Using a computer model, the PS, HF, and RB femoral components were digitally implanted into CT scans of 19 cadaver femurs. Nine cadavers were fit with a size 4 implant, six with size 3, and four with a size 2. The volume of intercondylar bone resected digitally for femoral preparation was measured. Bone density was measured by CT scans in Hounsfield units (HU). A paired t test was used to compare the mean volume of bone resected for each implant.

RESULTS

For the size 4 femurs, the newer RB design removed 8% less intercondylar bone than the PS design (7,832 ± 501 vs. 8,547 ± 377 mm(3), p < 0.001) and 28% less bone than the HF design (7,832 ± 501 vs. 10,897 ± 444 mm(3), p < 0.001). The average HU for size 4 femurs for RB design was 427 ± 72 (PS = 399 ± 69, p < 0.001; HF = 379 ± 66, p < 0.001). For the size 3 femurs, the RB design removed 12% less intercondylar bone than the PS (6,664 ± 786 vs. 7,516 ± 648 mm(3), p < 0.001) and 27% less bone than the HF (6,664 ± 786 vs. 9,078 ± 713 mm(3), p < 0.001). HU for size 3 femurs for the RB design was 452 ± 70 (PS = 422 ± 53, p < 0.1; HF = 410 ± 59, p < 0.01). For the size 2 femurs, the RB design removed 5% less intercondylar bone than the PS (5,730 ± 552 vs. 6,009 ± 472 mm(3), p < 0.01) and 22% less bone than the HF (5,730 ± 552 vs. 7,380 ± 532 mm(3), p < 0.001). HU for size 2 femurs for the RB design was 430 ± 48 (PS = 408 ± 55, p < 0.01; HF = 385 ± 56, p < 0.01).

CONCLUSIONS

The newer RB design removes less bone from the intercondylar notch than the classic PS and HF designs in all sizes tested. The bone-conserving cuts incorporated into this newer implant design appear to preserve native bone without compromising design objectives.

Periprosthetic femoral condyle fracture after total knee arthroplasty and saline-coupled bipolar sealing technology

Saline-cooled bipolar radiofrequency technology has emerged as an effective method to reduce bleeding during total knee arthroplasty (TKA). No significant osseous complications have been previously reported, and animal studies have revealed no difference in bone healing, strength, or osteonecrosis compared to conventional monopolar electrocautery. This article presents 4 cases of early postoperative periprosthetic femoral condyle fractures after extensive use of saline-cooled bipolar radiofrequency requiring revision TKA. Preoperative, intraoperative, and postoperative details from 4 patients who underwent early TKA revision for periprosthetic femoral condyle fractures were retrospectively reviewed. The senior author (M.M.) had not experienced similar condyle fractures postoperatively in over 2,500 primary TKAs performed over 2 decades. The cases described here were performed between July 2009 and November 2009, shortly after increasing the usage of saline-cooled bipolar radiofrequency on the synovium overlying the femoral condyles for hemostasis. No other change in surgical technique or implant that occurred during this time was observed. The senior author has significantly decreased his use of saline-cooled bipolar radiofrequency and has seen no recurrence of these complications.

The Hazards of Total Knee Arthroplasty: A Case Report in Illustration

Infections and periprosthetic fractures are uncommon but dreaded complications of total knee arthroplasty which carry attendant morbidity and prolonged hospitalization and necessitate repeat surgery. We present a patient with a total knee arthroplasty who had both intra-operative and post-operative periprosthetic fractures who subsequently developed infection of the prosthesis necessitating revision surgery. This was complicated too by positive intra-operative tissue cultures. The clinical course, presentation and management are discussed. Total knee arthroplasty is a frequently performed and successful operation and its complications are challenging to address and require early recognition by the surgeon with appropriate referral to a dedicated arthroplasty surgeon as needed.

The relationship between pre- and postoperative range of motion utilizing three cruciate-retaining total knee prostheses

We prospectively examined the relationship between pre- and postoperative range of motion utilizing three cruciate retaining knees with various mechanical flexion potentials, i.e., two at about 130 degrees -135 degrees (one with posterior lip and the other without) and the third at about 140 degrees -145 degrees . All groups demonstrated mean flexion and range of motion of 116 degrees -122 degrees at one year. Combining data from the three cohorts, patients with the following preoperative flexion values achieved the indicated mean changes (increases) in flexion at one year: < 90 degrees flexion (Delta 23.6 degrees ), 91 degrees -105 degrees flexion (Delta 19.3 degrees ), and > 105 degrees flexion (Delta 1.8 degrees )). Postoperative improvement was inversely related to preoperative flexion. The high flex knee yielded the best improvement in range of motion (9.7 degrees increase) in the highest flex preoperative group compared to that of the other knees (-7.4 degrees to 2.9 degrees ). Hence, a high flex knee design seems to be important in high preoperative range of motion patients obtaining an increase in the postoperative range of motion rather than possible regression.

Intraoperative fracture during primary total knee arthroplasty

While the occurrence of periprosthetic fractures around total knee arthroplasties (TKAs) is well know, little is known about intraoperative fractures that occur during TKA. We describe the incidence, location, and outcomes of iatrogenic intraoperative fracture during primary TKA. We reviewed 17,389 primary TKAs performed between 1985 and 2005 and identified 66 patients with 67 intraoperative fractures including 49 femur fractures, 18 tibia fractures, and no patella fractures. There were 12 men and 54 women with a mean age of 65.2 +/- 16 years. Of the 49 femur fractures, locations included medial condyle (20), lateral condyle (11), supracondylar femur (eight), medial epicondyle (seven), lateral epicondyle (two), and posterior cortex (one). Tibia fractures (18) included lateral plateau (six), anterior cortex (four), medial plateau (three), lateral cortex (three), medial cortex (one), and posterior cortex (one). Twenty-six fractures occurred during exposure and preparation, 22 while trialing, 13 during cementation, and three while inserting the polyethylene spacer. The minimum followup was 0.15 years (mean, 5.1 years; range, 0.15-15.4 years). All fractures healed clinically and radiographically. Knee Society scores and function scores improved from 46.4 and 34.6 to 79.5 and 61, respectively. Fourteen of the 66 (21%) patients were revised at an average of 2.8 years. Intraoperative fracture is an uncommon complication of primary TKA with a prevalence of 0.39%. Intraoperative fracture occurred more commonly in women (80.6%) and in the femur (73.1%). The majority of fractures occurred during exposure and bone preparation and trialing of the components.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Periprosthetic knee fractures

Fractures of the distal femur, proximal tibia, and patella that occur adjacent to a total knee replacement may be very difficult to treat. Fixation options are compromised because of the short articular segment, frequent comminution, pre-existing osteoporosis, previous surgical incisions, and the presence of the knee implant itself. This review article summarizes current concepts regarding the incidence, classification, treatment options, and outcomes for periprosthetic fractures of the knee.

Treatment of acute distal femur fractures above a total knee arthroplasty: systematic review of 415 cases (1981-2006)

BACKGROUND

There is no consensus on the best treatment for periprosthetic supracondylar fracture.

MATERIAL AND METHODS

We systematically summarized and compared results of different fixation techniques in the management of acute distal femur fractures above a total knee arthroplasty (TKA). Several databases were searched (Medline, Cochrane library, OTA and AAOS abstract databases) and baseline and outcome parameters were abstracted.

RESULTS

We extracted data from 29 case series with a total of 415 fractures. The following outcomes were noted: a nonunion rate of 9%, a fixation failure rate of 4%, an infection rate of 3%, and a revision surgery rate of 13%. Retrograde nailing was associated with relative risk reduction (RRR) of 87% (p = 0.01) for developing a nonunion and 70% (p = 0.03) for requiring revision surgery compared to traditional (non-locking) plating methods. Point estimates also suggested risk reductions for locking plates, although these were not statistically significant (57% for nonunion, p = 0.2; 43% for revision surgery, p = 0.23) compared to traditional plating. RRRs for nonunion and revision surgery were also statistically significantly lower for retrograde nailing and locking plates compared to nonoperative treatment.

INTERPRETATION

Modern-day treatment methods are superior to conventional treatment options in the management of distal femur fractures above TKAs. The results should be interpreted with caution, due to the lack of randomized controlled trials and the possible selection bias in case series.

Posterior stability in fixed-bearing versus mobile-bearing total knee replacement: a radiological comparison of two implants

INTRODUCTION

Posterior tibial translation in total knee replacement (TKR) could be one major factor for PE wear, delamination and loosening of the tibial component due to increased shear forces and component-to-bone interface stress. The aim of this study was to assess the posterior stability of two different designs of posterior cruciate ligament (PCL) substituting TKR.

METHOD

In this non-randomised consecutive study 43 patients underwent TKR for primary osteoarthritis. Twenty-six patients in group FB received a deep-dished fixed-bearing Duracon TKR (Howmedica, Rutherford, NJ, USA) and 17 patients in group MB a deep-dished rotating mobile-bearing Duracon TKR. In both groups the PCL was resected. All patients had pre- and postoperative kneeling stress radiographs and were clinically evaluated with the Knee Society Score. Posterior tibial translation was measured by tracing a line along the posterior tibial cortex in relationship to the posterior edge of Blumensaat's line.

RESULTS

The average follow-up was 13 months for group FB and 11 months for group MB. Both groups demonstrated a statistical significant increase of the mean posterior tibial translation on kneeling stress X-ray of 4.1 mm (group FB) (P < 0.001) and of 6.6 mm (group MB) (P < 0.001) compared to pre-operative. Group MB showed a significant higher posterior draw (P < 0.008). Clinical assessment using the Knee Society Score showed comparable short-term results.

CONCLUSION

The deep-dished fixed-bearing TKR as well as the deep-dished rotating mobile-bearing TKR demonstrated significant posterior tibial translation on kneeling stress X-ray. It remains to be determined what amount of joint play is optimal for clinical function and to minimise shear forces and PE wear. Moreover the amount of posterior tibial translation was significantly higher with the mobile-bearing insert, which could be directly related to the asymmetric rotational mobility of the tibial insert. A long-term follow-up is necessary to investigate whether our findings correlate with the survival-rate of these specific implants.

Periprosthetic fractures after total knee arthroplasties

The management of periprosthetic fracture around the knee remains a challenging problem. The objective of this article was to review the general concepts, treatment algorithms, and the overall treatment outcomes of femoral and tibial periprosthetic fractures after total knee arthroplasty. This article aimed to highlight the deficiencies of the current classification systems that fail to provide a guideline for selection of appropriate treatment options. We proposed a new classification system for periprosthetic femoral fractures that takes into account the status of the prosthesis, the quality of distal bone stock, and the reducibility of the fracture. Type I fractures are those occurring in patients with good bone stock with the prosthesis being fixed and well positioned. Type IA fractures are either nondisplaced or easily reducible and can be treated conservatively. Type IB fractures are irreducible and require reduction and internal fixation. Type II fractures are defined as those occurring also in patients with good bone stock and being reducible, but either the components are loose or malpositioned. These fractures are treated by revision arthroplasty. Type III fractures are reducible or irreducible fractures that occur in patients with poor bone stock and in the vicinity of loose or malpositioned components. These fractures are treated by distal femoral replacement.

LEVEL OF EVIDENCE

Therapeutic study, level V (expert opinion). See Guidelines for Authors for a complete description of levels of evidence.

Long-term results of posterior cruciate-substituting total knee arthroplasty

Posterior cruciate ligament-substituting total knee prostheses have been used extensively since the original posterior-stabilized condylar prosthesis was introduced more than 2 decades ago. The key design principle of this prosthesis was the incorporation of a cam and post mechanism on the femoral and tibial components. This mechanism was intended to function as a mechanical substitute for the posterior cruciate ligament, to optimize prosthesis roll back in flexion, and to avoid flexion instability by preventing posterior subluxation. Central to the use of these devices was the surgical technique, which required resection of both cruciate ligaments and creation of symmetric flexion and extension gaps with equal medial and lateral soft tissue tension. Modifications to the original design have been introduced gradually; these include changes to the patellofemoral geometry, and the addition of monoblock and modular metal-backed tibial components. Despite these changes, the key concepts of the prosthesis design and surgical technique have remained constant. The clinical results obtained with the use of these designs have been reported extensively. Long-term results at greater than 10 years continue to duplicate the outstanding early results with prosthesis survivorship exceeding 95% and high levels of patient function.