Primary posterior stabilized total knee arthroplasty: analysis of different instrumentation

Bone Preservation in Femoral Intercondylar Box Cut - A Comparative Study between Older and Newer Generation Implants

Introduction

This study was conducted to compare the quantity of intercondylar bone removed during femoral box osteotomy for implantation of three contemporary newer generation posterior stabilized (PS) total knee arthroplasty designs Attune PS (DePuy), Anthem (Smith and Nephews), and NexGen Legacy (Zimmer) with the older version from the same manufacturers.

Materials and Methods

We compared the maximum volumetric bone resection required for the housing of the PS mechanism of these six designs. Bone removal by each PS box cutting jig was three-dimensionally measured. The differences between the three designs were analyzed by the Kruskal-Wallis test. The Mann-Whitney U-test was used for pairwise comparisons. The level of significance was set at P < 0.05.

Results

The newer generation implants save approximately 33% of bone that was resected from the box cut as compared to the older versions. DePuys Attune PS saved 27.1% bone as compared to Sigma PS resecting 6.96 cm3 of bone, and Zimmers Persona saved 40.57% bone as compared to NexGen from the intercondylar box cut resecting 6.18 cm3. Smith and Nephew s Anthem and Genesis have no difference in their box volume with both resecting 7.8 cm3 of bone.

Conclusion

Irrespective of implant size, the Attune PS (DePuy) and Nexgen Legacy (Zimmer) cutting jigs always resected significantly less bone than did the jigs of older generations. There was no significant difference in the bone removed during femoral box osteotomy in the newer and older generations of Smith and Nephew.

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 Aseptic Loosening with Increased Presence and Severity of Backside Burnishing in the Optetrak Logic Posterior-Stabilized Total Knee Arthroplasty Femoral Component

Concerns persist that the Optetrak Logic posterior-stabilized (PS) total knee arthroplasty (TKA) femoral component might correlate with early failures due to aseptic loosening. The primary aim of this study was to examine if the use of the Optetrak Logic PS femoral component is associated with early (<5 years) and more extensive aseptic loosening compared with other PS femoral components. This is a single-institution retrieval analysis and revision registry study (based on prospectively collected data) of 27 failed primary PS TKA patients with loose femoral components that underwent revision TKAs between 2016 and 2019. Patients were stratified by components type: Group A (n = 16) received the Optetrak Logic PS femoral component, while Group B (n = 11) received other PS femoral components. Burnishing (macroscopic polishing of the component's backside) was observed and graded as a marker for relative motion at the cement-implant interface. No significant differences were found between the two groups regarding the baseline demographic, radiographic, and clinical characteristics. Mean length of implantation for Group A (3.8 ± 2.9 years) was significantly shorter (p < 0.001) than that of Group B (12.0 ± 6.7 years). A significant difference (p = 0.009) was found in presence of backside femoral burnishing between Group A (15 of 16 patients; 93.8%) and group B (5 of 11 patients; 45.6%). Furthermore, we found a significant difference (p < 0.001) in the severity of burnishing between Group A (13 of 16 patients with severe degree of burnishing; 81.3%) and Group B (1 of 11 patients with severe degree of burnishing; 9.1%). In contrast to Group B, a distinctive macroscopic pattern found in Logic retrieved femoral components (Group A) was the total absence of cement in the backside surface. The use of the Optetrak Logic PS TKA femoral component was associated with early aseptic loosening and increased presence and severity of backside burnishing with early cement-implant interface debonding compared with other commercially available types of PS TKA femoral components. The earlier failure rate with this implant is of concern.

Total Knee Arthroplasty, All-in-One versus Four-in-One Femoral Cutting Jig System: A Comparison Study

Background. Total knee arthroplasty (TKA) is often indicated for end-stage knee osteoarthritis management. The posterior-stabilized (PS) implant is one of the TKA implants with various component designs, including femoral component cutting jigs. However, little is known about how the differences in cutting jig designs affect the outcomes. This study aims to compare the radiographic and functional outcomes of the patients who underwent cemented TKA using all-in-one and four-in-one femoral component PS implants. Methods. A retrospective comparative study assessed patients who underwent cemented TKA using PS implants from 2018 to 2019. The patients were divided into all-in-one and four-in-one groups. Demographic data, surgery duration, postoperative radiological findings after one week, and functional outcomes after two years were collected and compared. Results. A total of 96 patients were included in the study, 55 patients were in all-in-one sample, and 41 patients were in four-in-one sample. The majority of the patients in both groups were female, aged >60 years old, overweight (BMI ≥ 25), and presented with an ASA score of II. We found significantly shorter surgery duration in the all-in-one group compared to the four-in-one group (128.00 ± 36.24 vs. 210.61 ± 57.54, $p=0.000$ ). The four-in-one group and the all-in-one group showed the insignificant difference in α, β, δ, and γ angles ( $p=0.476$ , 0.273, 0.594, and 0.818). The functional outcomes (SF-12, KSS, and KOOS) showed insignificant differences. Conclusion. There is no differentiation for the postsurgery functional and radiological outcomes between all-in-one and four-in-one implants.

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.

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.

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.

[Choice of total knee arthroplasty: posterior cruciate ligament preserved or not]

Total knee arthroplasty is an effective method for the treatment of end-stage knee osteoarthrosis, which can effectively relieve joint pain and reconstruct the integrity of the joint. Whether the posterior cruciate ligament should be preserved during surgery or not, which is still in dispute. In recent years, posterior cruciate-retaining and substituting total knee prostheses are both applied in clinical practice. Both domestic and international studies have shown that there are no significant difference in patient satisfaction, knee flexion, survival rate of the prosthesis and the main clinical manifestations between two prostheses. However, posterior cruciate-retaining total knee prosthesis is more consistent with the normal physiology and biomechanics of the human body. The gait is more balanced and proprioceptive when walking up and down the stairs, but when the joints are buckling, the femur is abnormal to move back to the tibia, resulting in abnormal motion. While posterior cruciate-substituting total knee prosthesis can correct severe deformity of the knee, and keep better balance between flexion and extension of the knee joint, but there is a potential complication of patellar clunk syndrome. Therefore, under the same conditions, the younger patients may prefer to chose posterior cruciate-retaining total knee prosthesis, while elder patients may prefer to chose posterior cruciate-substituting total knee prosthesis. This paper reviews the function of posterior cruciate ligament, as well as the advantages and disadvantages of two prostheses, so as to provide some references for clinic.

Cruciate-retaining total knee arthroplasty: How much of the PCL is really retained?

PURPOSE

It is questionable how much of the PCL is really preserved following a complete transverse tibial cut during a cruciate-retaining (CR) total knee arthroplasty (TKA). It is hypothesized that a complete transverse tibial cut jeopardizes the PCL tibial insertion during a common CR TKA. Thus, the aim of the present study was to assess intraoperatively the amount of PCL tibial attachment damage following a standard complete tibial cut technique.

METHODS

Thirty consecutive female patients suffering from degenerative knee osteoarthritis were included. Two measurements were performed on preoperative MRI images. On sagittal plane, the PCL facet of tibia and the PCL tibial attachment were measured. All 30 patients underwent a TKA using a common CR prosthesis. Postoperatively, the amount of PCL facet resection was measured on the resected tibial plateau using a digital sliding caliper.

RESULTS

In preoperative MRI images, the length of the PCL facet of tibia was found 25.5 ± 2.1 mm and the length of the PCL tibial attachment was 14.5 ± 1.3 mm. The amount of PCL facet resection following TKA was 20.6 ± 2.2 mm on average. This result corresponds to an average resection of 65.1 ± 15.9 % of the PCL tibial attachment following TKA.

CONCLUSION

The hypothesis that a complete transverse tibial cut during a conventional CR TKA jeopardizes the PCL tibial insertion was confirmed. According to measurements performed on preoperative knee MRI scans and surgical specimens of resected tibial plateaus, a significant amount of the PCL insertion on the tibia is actually removed in the majority of cases. Surgeons should be aware that when resecting the tibial plateau without using a technique that spares the PCL tibial attachment, there is a high risk of considerable damage to the PCL that may, in turn, increase the likelihood of potential complications due to PCL deficiency.

LEVEL OF EVIDENCE

IV.

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.

Cross-linked versus conventional polyethylene for total knee arthroplasty: a meta-analysis

BACKGROUND

Highly cross-linked polyethylene (HXLPE) has been reported as an effective material for decreasing polyethylene wear and osteolysis in total knee arthroplasty (TKA). Because no single study to date has been large enough to definitively determine the benefit of HXLPE in TKA, we conducted a meta-analysis to pool the results from randomized controlled trials (RCTs) and non-RCTs to make such a determination.

METHODS

Potential candidate articles were identified by searching the Cochrane Library, Medline (1966-2015.10), PubMed (1966-2015.10), Embase (1980-2015.10), ScienceDirect (1985-2015.10), and other databases. "Gray studies" were identified from the included articles' reference lists. Pooled data were analyzed using RevMan 5.1.

RESULTS

Three RCTs and three non-RCTs were included in the meta-analysis. There were no significant differences between the groups in the total number of reoperations (P = 0.11), reoperations for prosthesis loosening (P = 0.08), radiolucent line (P = 0.20), osteolysis (P = 0.38), prosthesis loosening (P = 0.10), and mechanical failures related to the tibial polyethylene (P = 1.00). Similarly, no significant differences between the two groups were found in postoperative total knee score (P = 0.18) or functional score (P = 0.23).

CONCLUSIONS

The meta-analysis showed that compared with conventional polyethylene, HXLPE did not improve the clinical and radiographic outcomes in mid-term follow-up after TKA. Additional high-quality multicenter prospective RCTs with good design, large study populations and long-term follow-up will be necessary to further clarify the effect of HXLPE in TKA.

Therapeutic effects of segmental resection and decompression combined with joint prosthesis on continuous knee osteoarthritis

OBJECTIVE

To observe the therapeutic effects of segmental resection and decompression combined with joint prosthesis on continuous knee osteoarthritis (OA).

METHODS

A total of 130 patients with knee OA were selected and randomly divided into an observation group and a control group (n=65). The control group was treated by segmental resection in combination with joint prosthesis, and the observation group was treated by segmental resection and decompression combined with joint prosthesis. They were followed-up for three months.

RESULTS

All patients underwent successful surgeries during which no severe complications occurred. During the follow-up period, the overall effective rates of the observation group and the control group were 93.8% and 78.5% respectively, which were not statistically significantly different (p < 0.05). The observation group was significantly less prone to patellar instability, infection and deep vein thrombosis compared with the control group (P < 0.05). On the same day after surgery, the knee joint scores and functional scores of the two groups were similar, which evidently increased three months later, with significant intra-group and inter-group differences (p < 0.05).

CONCLUSION

Combining segmental resection and decompression with joint prosthesis gave rise to satisfactory short-term prognosis by effectively improving the flexion and extension of injured knee and by decreasing complications, thus being worthy of promotion in clinical practice.