Ten-year survival analysis of the PFC total knee arthroplasty--a surgeon's first 99 replacements

Mid-Flexion Instability After Total Knee Arthroplasty: Diagnosis, Implant Design, and Outcomes

Mid-flexion instability (MFI) in total knee arthroplasty refers to a distinct clinical entity where the knee is stable at full extension and 90° of flexion, but unstable somewhere between these 2 points. The presentation of MFI is often vague, and studies defining objective clinical or intraoperative measurements are limited. In this review, we aim to properly define the condition, describe diagnostic criteria and risk factors contributing to MFI, review current implant design, and present outcomes of revision surgery performed for MFI. [Orthopedics. 2023;46(1):e13-e19.].

Clinical and functional outcomes of primary total knee arthroplasty: a South American perspective

Background

The aim of this study was to report the clinical and functional outcomes as well as complications after primary total knee arthroplasty in a cohort of Chilean patients.

Methods

We retrospectively reviewed 191 total knee arthroplasties performed in 182 patients over an 8-year period, with a minimum follow-up of 2 years. The primary outcome measure was the rate of major complications. Secondary outcomes were minor complications, residual symptoms, level of satisfaction, and the Knee Injury and Osteoarthritis Outcome Score.

Results

Global complication rate was 15.5%, reintervention rate was 9.2%, and revision rate was 2.5%. Major and minor complications were seen in 9.2% and 5.1% of patients, respectively. Average Knee Injury and Osteoarthritis Outcome Score was 77 points (14-100), and 90% of patients reported satisfaction with the procedure. At 2-year follow-up, 45.8% of patients had some degree of range of motion limitations.

Conclusions

Our results show a medium-term follow-up complication rate comparable to those described in the literature. This is the first series to report on the clinical and functional outcomes after primary total knee arthroplasty in a Chilean population.

National Joint Registry of Iran

Joint replacement is currently on the rise with a high community burden. A registry was designed to evaluate the costs, possible complications, and rate of revisions as well as finding the most effective techniques, risk factors associated with poor results, indications for revision surgeries, and also demographic evaluation of patients undergoing joint replacement surgery in Iran.

Iranian Joint Registry (Iranian National Hip and Knee Arthroplasty Registry)

Periodic evaluation and monitoring the health and economic outcome of joint replacement surgery is a common and popular process under the territory of joint registries in many countries. In this article we introduce the methodology used for the foundation of the National Iranian Joint Registry (IJR) with a joint collaboration of the Social Security Organization (SSO) and academic research departments considering the requirements of the Iran's Ministry of Health and Education.

Midflexion instability in primary total knee replacement: a review

Introduction: Midflexion instability in primary total knee replacement (TKR) is an evolving concept. Successful treatment of instability requires an understanding of the different types of instability.

Methods: A literature review was performed to identify information pertinent to midflexion instability in primary total knee replacement, utilising PRISMA guidelines. Databases searched included Embase, Medline, All of the Cochrane Library, PubMed and cross references.

Results: Three factors, i.e., elevated joint line, multiradii femoral component and medial collateral ligament (MCL) laxity, were identified to influence midflexion instability. Literature suggested mediolateral instability at 30–60° of flexion as diagnostic of midflexion instability. Literature search also revealed paucity in clinical studies analysing midflexion instability. Most of the evidence was obtained from cadaveric studies for elevated joint line and MCL laxity. Clinical studies on multiradii femoral component were limited by their small study size and early followup period.

Conclusion: Elevated joint line, multiradii femoral component and MCL laxity have been suggested to cause midflexion laxity in primary TKR. Due to limitations in available evidence, this review was unable to raise the strength of overall evidence. Future well-designed clinical studies are essential to make definitive conclusions. This review serves as a baseline for future researchers and creates awareness for routine assessment of midflexion instability in primary total knee replacement.

Kinematic alignment produces near-normal knee motion but increases contact stress after total knee arthroplasty: A case study on a single implant design

BACKGROUND

Kinematically aligned total knee arthroplasty (TKA) is of increasing interest because this method might improve postoperative patient satisfaction. In kinematic alignment the femoral component is implanted in a slightly more valgus and internally rotated position, and the tibial component is implanted in a slightly more varus and internally rotated position, than in mechanical alignment. However, the biomechanics of kinematically aligned TKA remain largely unknown. The aim of this study was to compare the kinematics and contact stresses of mechanically and kinematically aligned TKAs.

METHODS

A musculoskeletal computer simulation was used to determine the effects of mechanically or kinematically aligned TKA. Knee kinematics were examined for mechanically aligned, kinematically aligned, and kinematically aligned outlier models. Patellofemoral and tibiofemoral contact forces were measured using finite element analysis.

RESULTS

Greater femoral rollback and more external rotation of the femoral component were observed with kinematically aligned TKA than mechanically aligned TKA. However, patellofemoral and tibiofemoral contact stresses were increased in kinematically aligned TKA.

CONCLUSIONS

These findings suggest that kinematically aligned TKA produces near-normal knee kinematics, but that concerns for long-term outcome might arise because of high contact stresses.

Five year survival analysis of an oxidised zirconium total knee arthroplasty

BACKGROUND

Zirconium total knee arthroplasties theoretically have a low incidence of failure as they are low friction, hard wearing and hypoallergenic. We report the five year survival of 213 Profix zirconium total knee arthroplasties with a conforming all polyethylene tibial component.

METHODS

Data was collected prospectively and multiple strict end points were used. SF12 and WOMAC scores were recorded pre-operatively, at three months, at twelve months, at 3 years and at 5 years.

RESULTS

Eight patients died and six were "lost to follow-up". The remaining 199 knees were followed up for five years. The mean WOMAC score improved from 56 to 35 and the mean SF12 physical component score improved from 28 to 34. The five year survival for failure due to implant related reasons was 99.5% (95% CI 97.4-100). This was due to one tibial component becoming loose aseptically in year zero.

CONCLUSIONS

Our results demonstrate that the Profix zirconium total knee arthroplasty has a low medium term failure rate comparable to the best implants. Further research is needed to establish if the beneficial properties of zirconium improve long term implant survival.

Impact of change of knee prosthesis on early clinical outcomes in a large volume arthroplasty centre

Introduction

The aim of our study was to investigate the effect of changing the default knee prosthesis in a high volume dedicated arthroplasty unit from DePuy’s PFC® Sigma® to Smith & Nephew’s Genesis™ II.

Methods

A retrospective analysis was performed of prospective data on primary total knee replacements (TKRs) from January 2009 until December 2011. This provided information on the operative time, length of stay, pain at mobilisation, radiography analysis, any complications, and readmission at 30 and 60 days.

Results

The total numbers of primary TKRs using the PFC® and Genesis™ II prostheses were 1,061 and 1,268 respectively. The results showed a slight increase (maximum of five minutes) in the operative time for all the surgeons except one surgeon, whose operative time reduced by an average of seven minutes. There was no significant adverse outcome after the change in the knee implant. There was no clinically significant increase in the length of stay, pain at mobilisation or complication rates. There was a twofold increase in the wastage of the implant in the Genesis™ II group in the initial learning period.

Conclusions

Through a competitive process of implant tendering, we have successfully introduced a new implant into a large elective orthopaedic unit. This has resulted in significant financial savings without adversely affecting our clinical practice or patient outcome.

Impact of change of knee prosthesis on early clinical outcomes in a large volume arthroplasty centre

INTRODUCTION

The aim of our study was to investigate the effect of changing the default knee prosthesis in a high volume dedicated arthroplasty unit from DePuy's PFC(®) Sigma(®) to Smith & Nephew's Genesis™ II.

METHODS

A retrospective analysis was performed of prospective data on primary total knee replacements (TKRs) from January 2009 until December 2011. This provided information on the operative time, length of stay, pain at mobilisation, radiography analysis, any complications, and readmission at 30 and 60 days.

RESULTS

The total numbers of primary TKRs using the PFC(®) and Genesis™ II prostheses were 1,061 and 1,268 respectively. The results showed a slight increase (maximum of five minutes) in the operative time for all the surgeons except one surgeon, whose operative time reduced by an average of seven minutes. There was no significant adverse outcome after the change in the knee implant. There was no clinically significant increase in the length of stay, pain at mobilisation or complication rates. There was a twofold increase in the wastage of the implant in the Genesis™ II group in the initial learning period.

CONCLUSIONS

Through a competitive process of implant tendering, we have successfully introduced a new implant into a large elective orthopaedic unit. This has resulted in significant financial savings without adversely affecting our clinical practice or patient outcome.

Modular versus all-polyethylene tibial components: comparison of pre- and early post-operative patient scores in total knee replacement

INTRODUCTION

All-polyethylene (AP) tibial components of total knee replacement (TKR) are substantially cheaper than their modular counterparts. It is well established that their survivorship and radiographic outcomes are comparable. In this study, patient-derived outcome measures were used to compare these two implant types.

METHODS

A cohort of 456 primary TKRs (142 AP, 314 modular) were assessed with preoperative and 1-year post-operative Oxford Knee Score, Western Ontario and McMaster Universities Arthritis Index and Short Form - 12 scores.

RESULTS

Both groups performed well with no significant difference in improvement and final scores at 1 year. Although there was a significant difference in mean age among the groups (P < 0.001) age-adjusted scores continued to show no significant difference between the two groups.

DISCUSSION

Our results support the more frequent use of AP tibial components for uncomplicated TKR.

Early migration of tibial components is associated with late revision: a systematic review and meta-analysis of 21,000 knee arthroplasties

PURPOSE

We performed two parallel systematic reviews and meta-analyses to determine the association between early migration of tibial components and late aseptic revision.

METHODS

One review comprised early migration data from radiostereometric analysis (RSA) studies, while the other focused on revision rates for aseptic loosening from long-term survival studies. Thresholds for acceptable and unacceptable migration were determined according to that of several national joint registries: < 5% revision at 10 years.

RESULTS

Following an elaborate literature search, 50 studies (involving 847 total knee prostheses (TKPs)) were included in the RSA review and 56 studies (20,599 TKPs) were included in the survival review. The results showed that for every mm increase in migration there was an 8% increase in revision rate, which remained after correction for age, sex, diagnosis, hospital type, continent, and study quality. Consequently, migration up to 0.5 mm was considered acceptable during the first postoperative year, while migration of 1.6 mm or more was unacceptable. TKPs with migration of between 0.5 and 1.6 mm were considered to be at risk of having revision rates higher than 5% at 10 years.

INTERPRETATION

There was a clinically relevant association between early migration of TKPs and late revision for loosening. The proposed migration thresholds can be implemented in a phased, evidence-based introduction of new types of knee prostheses, since they allow early detection of high-risk TKPs while exposing only a small number of patients.

Is computer-assisted total knee replacement for beginners or experts? Prospective study among three groups of patients treated by surgeons with different levels of experience

Background

Computer-assisted total knee replacement (TKR) has been shown to improve radiographic alignment and therefore the clinical outcome. Outliers with greater than 3° of varus or valgus malalignment in TKR can suffer higher failure rates. The aim of this study was to determine the impact of experience with both computer navigation and knee replacement surgery on the frequency of errors in intraoperative bone cuts and implant alignment, as well as the actual learning curve.

Materials and methods

Three homogeneous groups who underwent computer-assisted TKR were included in the study: group A [surgery performed by a surgeon experienced in both TKR and computer-assisted surgery (CAS)], B [surgery performed by a surgeon experienced in TKR but not CAS], and C [surgery performed by a general orthopedic surgeon]. In other words, all of the surgeons had different levels of experience in TKR and CAS, and each group was treated by only one of the surgeons. Cutting errors, number of re-cuts, complications, and mean surgical times were recorded. Frontal femoral component angle, frontal tibial component angle, hip–knee–ankle angle, and component slopes were evaluated.

Results

The number of cutting errors varied significantly: the lowest number was recorded for TKR performed by the surgeon with experience in CAS. Superior results were achieved in relation to final mechanical axis alignment by the surgeon experienced in CAS compared to the other surgeons. However, the total number of outliers showed no statistically significant difference among the three surgeons. After 11 cases, there were no differences in the number of re-cuts between groups A and C, and after 9 cases there were no differences in surgical time between groups A and B.

Conclusion

A beginner can reproduce the results of an expert TKR surgeon by means of navigation (i.e., CAS) after a learning curve of 16 cases; this represents the break-even point after which no statistically significant difference is observed between the expert surgeon and the beginner utilizing CAS.

Comparison of cross-sections of different femoral components for revision total knee replacement

PURPOSE. To compare the inner contour of the femoral component of 10 total knee replacement (TKR) designs for possible exchange in use.

METHODS

Inner contours of the femoral components of 10 cemented, cruciate-retaining TKR designs (e.motion, Genesis, Genia, Innex, LCS, Multigen Plus, NexGen, PFC, Scorpio, Vanguard) were scanned and reconstructed to 2-dimensional contours. Their cross-sections were compared by superimposition and aligning at the distal and anterior cuts. The patellar notch and outer contour were not analysed.

RESULTS

The maximum deviation was 5 mm in the posterior and posterior oblique cuts and 10 mm in the anterior oblique cut. Based on similarity of the inner contour, LCS and Innex was classified as group I, e.motion, Genesis, Scorpio, Vanguard, and Multigen Plus as group II, and Genia, NexGen, and PFC as group III. All 2 designs in group I were not compatible with the other 8 designs. Four of the 5 designs in group II showed good compatibility. All 3 designs in group III significantly differed in the posterior and oblique cuts.

CONCLUSION

A standardised inner contour of the femoral component can increase compatibility of different TKR systems in revision surgery and reduces the extent of bone resection.

Is there a learning curve in foot and ankle surgery?

BACKGROUND

Previous studies of orthopaedic learning curves have largely described the introduction of new techniques to experienced consultants. End points have usually involved technical considerations. A paucity of evidence surrounds foot and ankle surgery. This study investigates the learning curve during a foot and ankle surgeon's first year, defined by functional outcome.

METHODS

150 patients underwent elective foot or ankle surgery during the whole period. Preoperative and 6 month postoperative functional scores were compared between the first and second 6 month groups.

RESULTS

Functional improvement was greater, approaching significance, in the second group (p=0.0605). There was no difference for forefoot cases (p=0.345). Functional improvement was significantly greater in the second group with forefoot cases removed (p=0.0333).

CONCLUSIONS

A learning curve exists in the first year of practice of foot and ankle surgery, demonstrated by functional outcome. This is confined to ankle, hindfoot and midfoot, but not forefoot surgery.

The Genesis II in primary total knee replacement: a systematic literature review of clinical outcomes

Since its introduction in 1996, the Genesis II Total Knee System has produced good clinical results in patients undergoing primary total knee replacement. A systematic review of the literature-the first of its kind for this device-was undertaken to collect data on the Genesis II in order to provide a better understanding of its medium- to long-term performance. Of 124 Genesis II-related studies published in the literature, 11 met the eligibility criteria and were included in the final analysis. The included studies had a mean follow-up length of 38.1 months. Data from 1201 knees were available for review. Patients were an average of 70.5 years of age and predominantly female (63%). Findings indicated that the revision rate with this implant is low with up to 11.9 years of follow-up, with 14 revisions in total. The survival rate ranged from 100% at 1 and 2 years to 96.0% at 11.9 years. The mean Knee Society knee score improved 51.0 points from preoperative to postoperative evaluation. In conclusion, the Genesis II exhibited good clinical performance with up to 11 years follow-up, with an encouraging rate of survival and improvement in function. Additional studies with larger sample sizes and longer follow-up periods are needed to better understand the long-term performance of this implant.

Similar TKA designs with differences in clinical outcome: a randomized, controlled trial of 77 knees with a mean follow-up of 6 years

BACKGROUND AND PURPOSE

To try to improve the outcome of our TKAs, we started to use the CKS prosthesis. However, in a retrospective analysis this design tended to give worse results. We therefore conducted a randomized, controlled trial comparing this CKS prosthesis and our standard PFC prosthesis. Because many randomized studies between different TKA concepts generally fail to show superiority of a particular design, we hypothesized that these seemingly similar designs would not lead to any difference in clinical outcome.

PATIENTS AND METHODS

82 patients (90 knees) were randomly allocated to one or other prosthesis, and 39 CKS prostheses and 38 PFC prostheses could be followed for mean 5.6 years. No patients were lost to follow-up. At each follow-up, patients were evaluated clinically and radiographically, and the KSS, WOMAC, VAS patient satisfaction scores and VAS for pain were recorded.

RESULTS

With total Knee Society score (KSS) as primary endpoint, there was a difference in favor of the PFC group at final follow-up (p = 0.04). Whereas there was one revision in the PFC group, there were 6 revisions in the CKS group (p = 0.1). The survival analysis with any reoperation as endpoint showed better survival in the PFC group (97% (95% CI: 92-100) for the PFC group vs. 79% (95% CI: 66-92) for the CKS group) (p = 0.02).

INTERPRETATION

Our hypothesis that there would be no difference in clinical outcome was rejected in this study. The PFC system showed excellent results that were comparable to those in previous reports. The CKS design had differences that had considerable negative consequences clinically. The relatively poor results have discouraged us from using this design.

Do residents perform TKAs using computer navigation as accurately as consultants?

The implantation of a total knee arthroplasty (TKA) is a milestone in a resident's surgical training. Studies demonstrate higher loosening rates after TKA by inexperienced surgeons. Alignment outliers should be avoided to achieve a long implant survival. Therefore, our study questioned whether residents implant knee prostheses using computer navigation as accurately as experienced consultants. The data for 662 consecutive TKAs were analyzed retrospectively. The operations were performed by 4 consultants (n=555) and 5 residents under supervision by a consultant (n=107). Cutting errors were recorded from the navigation data. The postoperative mechanical axis and operation time were recorded. Operation time was significantly prolonged if residents performed the operation vs consultants (139 vs 122 minutes, respectively). The analysis of cutting errors within each surgeon's first 20 navigated operations resulted in no significant difference between residents and consultants. During the subsequent operations, a trend toward a more accurate placement of the prosthesis was detected for consultants. The rate of outliers with a mechanical axis deviation >2° was low and did not significantly differ between residents and consultants (3.7% vs 2.3%, respectively). Our study shows that residents implant their first TKA using computer navigation as accurately as experienced consultants. However, the residents' operations take longer and therefore incur additional costs for the teaching clinic.

Scorpio single radius total knee arthroplasty. A minimal five-year follow-up multicentric study

PURPOSE

Our goal was to evaluate the five-year follow-up results of the Scorpio single radius total knee arthroplasty.

METHOD

We performed a retrospective study based upon a multicentre database to evaluate the minimum five-year follow-up clinical and radiological results of 747 patients (831 knees) who underwent primary Scorpio single radius total knee arthroplasty.

RESULTS

The mean age of the patients was 71.9 years. At a minimal five-year follow-up, 141 patients were lost to follow-up, 83 patients had died, eight patients had undergone revision of a component, and the remaining 589 patients (602 knees) had a complete clinical and radiological evaluation after a median of six years (range, 5-8). The mean clinical component of the knee score was 92.2 points, and the mean functional component of the knee score was 76.9 points. At last follow-up, 530 of the 602 knees were rated as excellent or good. Only four knees developed patellar complications requiring revision. The survival rate at six years was 95.2% ± 1.9% and 98.3% ± 0.6 with revision for any reason and revision for mechanical failure as the end point, respectively.

CONCLUSION

This medium-term study indicates favourable clinical and radiological results for this single flexion-extension radius design arthroplasty, with a low complication rate on the patellar side.

Does minimally invasive surgery improve short-term recovery in total knee arthroplasty?

BACKGROUND

Concerns have been raised regarding minimally invasive surgery (MIS) and its possible effect on postoperative functional recovery, complications, and survival rate after TKA.

QUESTIONS/PURPOSES

We specifically asked whether MIS TKA would be associated with (1) increased operative time, (2) reduced blood loss, (3) shortened hospital stay, (4) faster recovery of ROM, (5) higher knee scores, (6) inferior component positioning, and (7) increased complications.

METHODS

We performed a systematic literature search of randomized controlled trials between minimally invasive and standard approaches in TKA that compared operative time, blood loss, ROM, knee scores, component positioning, and complications. We conducted a systematic review and meta-analysis of 13 trials published from 2007 to 2009 of MIS versus standard TKA.

RESULTS

Patients in the MIS group had longer operating times (10-19 minutes). Mean Knee Society scores were better after MIS than after the standard procedure at 6 and 12 weeks postoperatively, but not after 6 months. Improvement in ROM occurred more rapidly in the MIS group 6 days after TKA but later improvements are not clearly documented. We identified no differences between minimally invasive and standard approaches regarding the short-term overall complications and alignment of femoral and tibial components. However, wound healing problems and infections occurred more frequently in the MIS group.

CONCLUSIONS

MIS leads to faster recovery than conventional surgery with similar rates of component malalignment but is associated with more frequent delayed wound healing and infections. Potential benefits in long-term survival rate and functional improvement require additional investigation. Level of Evidence Level II, therapeutic study (systematic review). See the Guidelines for Authors for a complete description of levels of evidence.

Activity recommendations after total hip and knee arthroplasty: a survey of the American Association for Hip and Knee Surgeons

There are limited data to guide surgeon recommendations regarding activities after total joint arthroplasty. The present study aims to better clarify the current community standards. A questionnaire was distributed to the members of the American Association for Hip and Knee Surgeons attending the 2007 annual meeting inquiring about recommendations for 15 activities for patients with total hip arthroplasty or total knee arthroplasty. One hundred thirty-nine surveys were returned. Spearman rank correlation was used to analyze the data. More than 95% of the responses placed no limitations on low-impact activities including level surface walking, stair climbing, level surface bicycling, swimming, and golf. Higher-impact activities were more commonly discouraged, although there was considerable variability. Recommendations after total hip arthroplasty were more liberal compared to those after total knee arthroplasty. Higher-volume surgeons tended to be more liberal in their recommendations. No responder indicated that there was strong scientific evidence for their recommendations. Investigations are needed to elucidate the long-term effects of higher load and/or higher cycle activities on total joint arthroplasty.

Relationship between cutting errors and learning curve in computer-assisted total knee replacement

Computer-assisted total knee replacement (TKR) has been shown to improve radiographic alignment. Continuous feedback from the navigation system allows accurate adjustment of the bone cuts, thus reducing errors. The aim of this study was to determine the impact of experience both with computer navigation and knee replacement surgery on the frequency of errors in intraoperative bone cuts and implant alignment. Three homogeneous patient groups undergoing computer assisted TKR were included in the study. Each group was treated by one of three surgeons with varying experience in computer-aided and knee replacement surgery. Surgeon A had extensive experience in knee replacement and computer-assisted surgery. Surgeon B was an experienced knee replacement surgeon. A general orthopaedic surgeon with limited knee replacement surgery experience performed all surgeries in group C. The cutting errors and the number of re-cuts were determined intraoperatively. The complications and mean surgical time were collected for each group. The postoperative frontal femoral component angle, frontal tibial component angle, hip-knee-ankle angle and component slopes were evaluated. The results showed that the number of cutting errors were lowest for TKR performed by the surgeon with experience in navigation. This difference was statistically significant when compared to the general orthopaedic surgeon. A statistically significant superior result was achieved in final mechanical axis alignment for the surgeon experienced in computer-guided surgery compared to the other two groups (179.3 degrees compared to 178.9 degrees and 178.1 degrees ). However, the total number of outliers was similar, with no statistically significant differences among the three surgeons. Experience with navigation significantly reduced the surgical time.

Relationship between cutting errors and learning curve in computer-assisted total knee replacement

Computer-assisted total knee replacement (TKR) has been shown to improve radiographic alignment. Continuous feedback from the navigation system allows accurate adjustment of the bone cuts, thus reducing errors. The aim of this study was to determine the impact of experience both with computer navigation and knee replacement surgery on the frequency of errors in intraoperative bone cuts and implant alignment. Three homogeneous patient groups undergoing computer assisted TKR were included in the study. Each group was treated by one of three surgeons with varying experience in computer-aided and knee replacement surgery. Surgeon A had extensive experience in knee replacement and computer-assisted surgery. Surgeon B was an experienced knee replacement surgeon. A general orthopaedic surgeon with limited knee replacement surgery experience performed all surgeries in group C. The cutting errors and the number of re-cuts were determined intraoperatively. The complications and mean surgical time were collected for each group. The postoperative frontal femoral component angle, frontal tibial component angle, hip-knee-ankle angle and component slopes were evaluated. The results showed that the number of cutting errors were lowest for TKR performed by the surgeon with experience in navigation. This difference was statistically significant when compared to the general orthopaedic surgeon. A statistically significant superior result was achieved in final mechanical axis alignment for the surgeon experienced in computer-guided surgery compared to the other two groups (179.3 degrees compared to 178.9 degrees and 178.1 degrees ). However, the total number of outliers was similar, with no statistically significant differences among the three surgeons. Experience with navigation significantly reduced the surgical time.