Joint line position in revision total knee arthroplasty: the role of posterior femoral off-set stems

Clinical Outcomes of Offset Stem Couplers with or without Cone Augmentation in Revision Total Knee Arthroplasty

Intramedullary stems are often required in patients undergoing revision total knee arthroplasty (rTKA) to achieve stable fixation. Significant bone loss may require the addition of a metal cone to maximize fixation and osteointegration. The purpose of this study was to investigate clinical outcomes in rTKA using different fixation techniques. We conducted a single-institution retrospective review of all patients who received a tibial and femoral stem during rTKA between August 2011 and July 2021. Patients were separated into three cohorts based on fixation construct: press-fit stem with an offset coupler (OS), fully cemented straight (CS) stem, and press-fit straight (PFS) stem. A subanalysis of patients who received tibial cone augmentation was also conducted. A total of 358 patients who underwent rTKA were included in this study, of which 102 (28.5%) had a minimum 2-year follow-up and 25 (7.0%) had a minimum 5-year follow-up. In the primary analysis, 194 patients were included in the OS cohort, 72 in the CS cohort, and 92 in the PFS cohort. When stem type alone was considered, there was no significant difference in rerevision rate (p = 0.431) between cohorts. Subanalysis of patients who received augmentation with a tibial cone demonstrated that OS implants led to significantly higher rates of rerevision compared with the other two stem types (OS: 18.2% vs. CS: 2.1% vs. PFS: 11.1%; p = 0.037). The findings of the present analysis demonstrate that CS and cones in rTKA may provide more reliable long-term outcomes compared with press-fit stems with OS. LEVEL III EVIDENCE:  Retrospective Cohort Study.

A Three-dimensional Comparison of Pre- and Post-component Position in a Series of Off-label Robotic-assisted Revision Total Knee Arthroplasties

Background

The application of robotic-assisted arthroplasty in revision knee scenarios continues to evolve. This study compares the pre- and post-revision implant positions in series of revision total knee arthroplasties (TKA) using a robotic arm system.

Methods

Twenty-five consecutive off-label robotic-assisted revision TKA were performed. After virtual revision femoral and tibial components were positioned to achieve "balanced" medial and lateral flexion and extension gaps, the existing primary implants (PI) were removed, and bone cuts were executed with the robotic arm system. Preoperative coronal, sagittal, and axial position of the PI was compared to the final planned positions of the robotic revision implants (RRI) for each subject. A repeated measures ANOVA using the absolute difference in millimeters and degrees between the PI and RRI orientation was completed.

Results

Intra-operatively, the virtual gaps were balanced within the planning software followed by successful execution of the plan. There was a statistically significant difference between posterior condylar offset and tibial component positioning for RRI compared to PI. There was no difference between the distal femoral component values between PI and RRI.

Conclusions

The sagittal alignment of the revision implants, specifically the femoral posterior condylar offset and tibial component slope, are statistically significant considerations for a stable revision TKA with off-label use of a robotic-arm system. Other potential benefits may include appropriate implant sizing which can affect the resultant ligamentous tension important for a functional revision TKA. Future research and software iterations will be needed to determine the overall accuracy and utility of robotic-assisted revision TKA.

The Effect of Joint Line Elevation on Patient-Reported Outcomes After Contemporary Revision Total Knee Arthroplasty

BACKGROUND

Joint line elevation in revision total knee arthroplasty (rTKA) is considered a risk factor for inferior outcomes, engendering a dogmatic protocol of joint line restoration. However, this precedent is based on historical data using rudimentary revision systems and unvalidated outcome measures. This study's purpose was to evaluate the effect of joint line height elevation on validated patient-reported outcome measures (PROMs) using modern revision implants.

METHODS

A total of 327 rTKAs performed at a single institution were reviewed. Surgical technique prioritized flexion-extension gap balancing and accepted joint line elevation if necessary to achieve a balanced flexion space. Radiographic measurements included changes in joint line height (from preoperative and calculated "intended" anatomic/native) and change in posterior condylar offset. Prospectively collected PROMs were evaluated using multivariate regression.

RESULTS

The mean joint line elevation from preoperative and "intended" to postoperative joint line was 4.9 ± 5.7 mm and 7.2 ± 6.6 mm, respectively. The mean increase in posterior condylar offset was 1.0 ± 4.6 mm. Patients within ±5 mm of preoperative joint line height were 3.88× more likely to achieve the substantial clinical benefit for Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (P = .004). An increase from intended joint line height >5 mm was not associated with differences in any other PROMs (P ≥ .165).

CONCLUSIONS

In contemporary rTKA, recreating the joint line within 5 mm of preoperative improves knee-specific health outcomes. These data support approximating native joint line height as a viable technique to optimize flexion gap balance and subsequent patient outcomes in rTKA.

LEVEL OF EVIDENCE

Level III retrospective cohort study.

The role of joint line position and restoration of posterior condylar offset in revision total knee arthroplasty : a systematic review of 422 revision knees arthroplasty

The aim of this systematic review was to evaluate the evidence on reservation of Posterior Femoral Condylar Offset (PFCO) and Joint Line (JL) after Revision Total Knee Arthroplasty (RTKA) for im- proved functional outcomes. A comprehensive search of PubMed, Medline, Cochrane, CINAHL, and Embase databases was conducted, with papers published from the inception of the database to October 2020 included. All relevant articles were retrieved, and their bibliographies were hand searched for further references on Posterior condylar offset and revision total knee arthroplasty. The search strategy yielded 28 articles. After duplicate titles were excluded, abstracts and full text were reviewed. Nine studies were assessed for eligibility, four studies were excluded because they did not fully comply with the inclusion criteria. Six articles were finally included in this systematic review. Based on this systematic review restoration of the JL and PFCO in RTKR is associated with a significant improvement in the post-operative range of motion, KSS, OKS, patellar function, and SF-36. Reservation of JL should be a major consideration when undertaking RTKA. Of note, increasing PFCO to balance the flexion gap while maintaining joint line should be well assessed intra-operatively. The upper limit of the PFCO that widely accepted is up to 40 % greater than that of the native knee. 4 mm is the upper limit for JL restoration. Level of evidence III.

Rotating Hinge Implants in Knee Arthroplasty

Due to demographic transition an increasing number of primary knee arthroplasty is expected. A consequence is a rise in frequency in revision knee arthroplasty. Rotating hinge prostheses are a development of former hinge prostheses, due to changes in implant design the outcome of modern rotating hinge implants clearly improved in comparison to former models. Interpretation of outcome in present literature is difficult due to the small number of cases and the heterogeneous indications. Nevertheless the use of rotating hinge knee prostheses in primary and revision arthroplasty is associated with good clinical outcomes, when indicated appropriately.

Tibial shaft anatomy differs between Caucasians and East Asian individuals

PURPOSE

The orientation and distance from the shaft of the femur and tibia to the articular surface centre is important for performing total knee arthroplasty (TKA) with cementless stems. It is important to understand anatomic differences between races to match the tibial and femoral shaft axis to the knee articular surface. Thus, the purpose of this study was to compare knee morphology between Caucasian and East Asian individuals to determine the optimal placement of tibial and femoral stems.

METHODS

A retrospective study was conducted on a matched cohort of 50 East Asians (21F, 29M) and 50 Caucasians (21F, 29M) by age and gender. CT scans were obtained in healthy volunteers using < 2-mm slices. The distance from the proximal tibial diaphysis axis to the tibial plateau centre and the distance from the distal femoral diaphysis axis to the centre of distal femoral articular surface were measured separately. Tibial measurements were taken using Akagi's anteroposterior (AP) axis and the widest mediolateral (ML) diameter, and femoral measurements were based on Whiteside's line and the surgical epicondylar axis.

RESULTS

The ML distance between the tibial shaft centre and Akagi's line was significantly higher for Asians (9.9 ± 2.7 mm, Caucasians 7.7 ± 3.1 mm, p < 0.001). The distance between the femoral shaft centre and Whiteside's line was lower, although not significantly different (Asians 1.9 ± 1.0 mm, Caucasians 2.2 ± 1.1 mm, n.s.). However, there were no differences in the AP dimension for the femur or tibia comparing Asians to Caucasians in both tibial side (Asians 10.6 ± 3.3 mm vs. Caucasians 10.9 ± 4.0 mm) and femoral side (Asians 18.1 ± 1.7 mm vs. Caucasians 17.5 ± 1.6 mm).

CONCLUSION

East Asian individuals have more offset in the ML dimension for the tibia. This finding is clinical relevant, as this dimensional difference should be taken into consideration when designing primary and revision TKA stemmed tibial implants for East Asian individuals.

LEVEL OF EVIDENCE

Case-control study, Level III.

Snapping Phenomenon after Revisional Total Knee Arthroplasty

The cases of revision total knee arthroplasty (TKA) are increasing. In this report, snapping phenomenon after final implantation of revision TKA has been presented. Snapping was caused by adhered iliotibial band (ITB) impinging against the lateral part of femoral component. Fractional lengthening the ITB by puncture resolved the snapping phenomenon. Surgeons should be aware of the presence of such a case which should be identified during operation to avoid secondary operations.

A Study to Assess the Accuracy of Adductor Tubercle as a Reliable Landmark Used to Determine the Joint Line of the Knee in a Chinese Population

BACKGROUND

Restoring the joint line (JL) is a key element of performing joint arthroplasty, which is a challenging proposition during revision surgeries. We investigated the accuracy of 2 different methods of identifying the JL using the adductor tubercle (AT) as the reference landmark.

METHODS

Standardized protocols for measurements from 50 knee radiographs were established. Femoral width (FW) and the distance from the AT to the JL (ATJL) were measured on anteroposterior radiographs, and the femoral diameter (FD) was measured on true lateral views. The individual ratio of FW and FD to ATJL was calculated using linear regression analysis. Intraobserver and interobserver reliability was assessed. In order to test the accuracy of the ratio calculated, we also recorded the FW and ATJL of 20 additional knees by magnetic resonance images.

RESULTS

There are significant differences between genders with these parameters. A linear correlation was found between FW and ATJL (r² = 0.7201), which was more reliable than the correlation between FD and ATJL (r² = 0.3918). Interobserver repeatability was better for ATJL and FW than for FD. The mean ratio of ATJL/FW was 0.560 ± 0.03, and there was no statistical difference between men and women. After using this ratio formulas in those data measured from knee magnetic resonance imaging, all cases revealed reliability with 100% cases lying in a 4-mm error margin.

CONCLUSION

The AT can be used as a reliable landmark to determine the knee JL position, and the formulas for calculating the ATJL with FW can be applied, making intraoperative identification and judgment easier.

Revision knee surgery techniques

Revision total knee arthroplasty (rTKA) is a challenging, complex procedure. A comprehensive understanding of the anatomy, challenges and pitfalls is essential to achieve a good outcome for the patient.This review discusses the determinants of good outcomes of rTKA. These include, among other factors, the choice of the surgical approach, removal of the components, adequate reconstruction of the joint line and posterior condylar offset and the use of offset stems, as well as choosing the appropriate level of constraint.The modularity of many modern knee revision systems can help to address such issues as anatomical mismatch, gap balancing and malalignment.A well-planned surgical approach must be used in rTKA. A thorough understanding of related knee anatomy is essential.The incidence of joint-line elevation after rTKA is high. Contralateral radiographs, as well as algorithms based on the relationship between bony landmarks and the joint line, can help to reconstruct a physiological joint line during rTKA.Modularity added to systems, such as offset stems, are useful enhancements that may further improve the reconstruction of the anatomy.There are several options for managing the patella, with the best choice depending on the status of the patellar component and residual bone stock. Cite this article: Thienpont E. Revision knee surgery techniques. EFORT Open Rev 2016;1: 233-238. DOI: 10.1302/2058-5241.1.000024.

The role of offset stems in revision knee arthroplasty

Revision total knee arthroplasty (TKA) represents a technically challenging procedure. The use of an offset stem extension can help in addressing some of the difficulties that can be encountered during surgery and, in particular, anatomical mismatch, malalignment, and gap balancing. Different offset stem extensions are available and can be classified according to four parameters: modularity, location of the offset, direction, and size of the displacement. Offset stem extensions can assist with implant alignment on the metaphysis if there is an offset diaphysis, can avoid medial-lateral or anterior-posterior component overhang, can reduce the incidence of coronal or sagittal malalignment, and can help in balancing the flexion and extension spaces by effectively translating the components. The aim of this study is to give an overview of the currently available evidence regarding the use of offset stem extensions in revision TKA as well as some useful surgical tips.

The posterior condylar offset ratio and femoral anatomy in anterior versus posterior referencing total knee arthroplasty

BACKGROUND

The preservation of joint anatomy is one of the key issues in total knee arthroplasty. The effect of the prosthesis' referencing system, relative to femoral anatomy, remains unknown. It was sought to determine if femoral anatomy, following total knee arthroplasty is better maintained using either anterior referencing or posterior referencing prosthesis. The posterior condylar offset ratio (PCOR) was employed for preoperative and postoperative radiographic comparison of femoral condyles. It was hypothesized that posterior referencing prosthesis would better restore condylar morphology.

METHODS

Sixty-six patients undergoing a total knee arthroplasty with anterior referenced Zimmer(®) NexGen(®) LPS prosthesis and ninety-one with posterior referenced Tornier(®) HLS Noetos(®) were divided into two groups according to the prosthetic model used and retrospectively compared. PCOR was calculated as the quotient of the distance between the posterior condylar border and the tangent to the posterior cortex of the femoral diaphysis, and the distance between the posterior condylar border and the tangent to the anterior cortex of the femoral diaphysis. PCOR was determined preoperatively and postoperatively and compared within each group and between both groups.

RESULTS

An increase in the PCOR (P<0.0001) following surgery was observed in both anterior referencing and posterior referencing models. No difference was noted when the postoperative PCOR was compared between both groups (P=0.61).

CONCLUSION

Both anterior and posterior referencing prosthesis lead to a similar increase of the PCOR following total knee arthroplasty.

LEVEL OF EVIDENCE

Level IV.

Important Differences Exist in Posterior Condylar Offsets in an Osteological Collection of 1,058 Femurs

Posterior condylar offset (PCO) has important implications in total knee arthroplasty (TKA) function and design. In an osteological study of 1,058 femurs, we measured PCO using two separate techniques with a 3D digitizer. Measurements were standardized for the size of the femur. The medial PCO was greater than lateral PCO (32.6mm vs. 31.2mm, P<0.0001). In 53% of individuals, the medial PCO differed between sides by more than 2mm. Age did not affect standardized medial or lateral PCO. Compared with African-Americans, Caucasians had a larger standardized medial (1.3mm vs. 1.2mm, P=0.006) and lateral (1.1mm vs. 1.0mm, P=0.004) PCOs. The standardized medial (1.2mm vs. 1.3mm, P=0.073), and lateral (1.1mm vs. 1.1mm, P=0.098), PCO did not differ between men and women, respectively.

Bone loss management in total knee revision surgery

PURPOSE

Bone stock reconstruction in TKR surgery is one of the biggest challenges for the surgeon. According to some, authors causes of bone stock loosening are multiple, including stress shielding, osteolysis from wear, septic or aseptic loosening, and bone loss caused by a poorly balanced implant. Moreover, bone loss may be iatrogenic at the time of implant removal, indicating that bone preservation during implant removal is critical.

METHODS

Defect localization and extension affect the surgeon's decisions about the choice of the surgical technique and the type of plant to be taken. Today there are several options available for bone deficiency treatment. The treatment choice is undoubtedly linked to the cause of revision, experience and personal philosophy, but it is necessary to consider also the patient's age, expectations of life, functional requirements and bone quality. Many authors prefer bone stock reconstruction techniques in patients with high bone quality and a better quality of life with more prospects. In patients with lower lease on life and lower bone quality the best bone replacement techniques are of modular systems, wedges, and augments. In cases with septic bone loss, more or less extended, different authors recommend reducing bone grafts in favor of modular prostheses to reduce the risk of graft contamination.

RESULTS

All of these techniques have been shown to be durable in midterm outcomes, but concerns exist for a number of reasons, including disease transmission, resorption, fracture, immune reaction to allograft, the cost of custom prostheses, the inability to modify the construct intraoperatively and the overall technical challenge of applying these techniques.

CONCLUSIONS

The choice between different surgical options depends on bone defect dimension and characteristics but are also patient-related. Reestablishment of well-aligned and stable implants is necessary for successful reconstruction, but this can't be accomplished without a sufficient restoration of an eventual bone loss.