Effect of posterior condylar offset on clinical results after posterior-stabilized total knee arthroplasty

Sexual dimorphism of the posterior condylar offset of the femur and the medial posterior slope of the tibia in non-arthritic knees of Egyptian adults: an MRI study

BACKGROUND

The aim of this magnetic resonance imaging (MRI) study was to investigate controversial sexual dimorphism of the posterior condylar offset of the femur (the offset) and the posterior slope of the tibia (the slope) in non-arthritic knees of Egyptian adults.

METHODS

On 100 male and 100 female MRIs of non-arthritic knees, linear measurements of the distal part of the femur (the offset) and the angular measurements of the proximal part of the tibia (the slope) were performed and compared regarding sex and ethnicity. The intraclass correlation coefficient (ICC) was used to test the interrater agreement.

RESULTS

Both offsets and the lateral offset ratio were larger in males (p < 0.001), the medial offset ratio, and the medial slope in females (p from < 0.001 to 0.007), whereas the lateral slope was sex-free (p = 0.41). Irrespective of sex, however, the medial offset with its ratio, and the medial slope were larger than their counterparts (p < 0.001). Our means of the offsets, their ratios, and the slopes mostly differed from those of other ethnicities (p from ≤ 0.001 to 0.004). ICCs > 0.8 proved MRI's precision was high.

CONCLUSION

There was a sexual dimorphism of both the offset and the medial slope in non-arthritic knees of Egyptian adults. We believe future designs of knee implants should consider these differences in order to improve postoperative range of motion and patients' satisfaction after total knee arthroplasty. Level of evidence Level III Retrospective Cohort Study. Trial registration ClinicalTrials.gov identifier: NCT03622034, registered on July 28, 2018.

The role of posterior condylar offset ratio on clinical and functional outcome of posterior stabilized total knee arthroplasty: a retrospective cohort study

BACKGROUND

Postoperative Range of Motion (ROM) is an important measurement of the success of a Total Knee Arthroplasty (TKA). Much enthusiasm has been recently directed toward the posterior femoral condylar offset (PFCO), with some authors reporting increasing postoperative knee flexion when increasing PFCO. The aim of this study is to retrospectively determine the effect of the PFCO on the clinical and functional outcome of a cohort of patients who underwent a Posterior Stabilized (PS) TKA.

METHODS

Clinical and radiological data of all patients who underwent TKA with PS implant for primary osteoarthritis were retrospectively reviewed. Knee Society Score (KSS), knee ROM, PFCO ratio (PFCOR), and tibial slope (TS) were measured pre and postoperatively.

RESULTS

One hundred and twenty-one patients (141 knees) met the inclusion criteria. The mean knee flexion increased from 98 ± 20.2° (range 30-130) to 123 ± 12.1° (range 70-140) and the mean KSS increased from 74.0 ± 3.3 (range 27-130) to 203.9 ± 8.1 (range 26-249). Postoperative PFCOR and TS were 0.492 ± 0.005 (range 0.40-0.57) and 2.36 ± 0.56° (range - 10.9-12.15°), respectively. Neither maximal flexion angle nor KSS showed a significant correlation with postoperative PFCOR (Pearsons'r = - 0.057, p = 0.5 for flexion angle and Pearsons'r = - 0.073, p = 0.5 for KSS) or with postoperative TS (Pearsons'r = 0.042, p = 0.62 for flexion angle and Pearsons'r = 0.002, p = 0.98 for KSS).

CONCLUSION

Posterior femoral condylar offset remains an important parameter and, especially when using anterior femoral referencing TKA, care must be taken to prevent excessive resection of the posterior femoral condyles.

The Impact of a Gap Balancing or Measured Resection Surgical Technique on Posterior Condylar Offset and Patient-Reported Outcome Measures

Background

To increase total knee arthroplasty procedure satisfaction, surgeons are exploring improvements in surgical technique. The impact of gap balancing or measured resection approach on posterior condylar offset (PCO) is not well understood.

Methods

We reviewed the clinical and radiographic results of 498 unilateral posterior stabilized total knee arthroplasties. Radiographs were assessed to measure the primary endpoints of anterior-posterior width, PCO, and anterior condylar offset. Clinical outcome measures were used to assess patient improvement measures. Multiple linear regression analyses were performed to determine the clinical factors related to our primary endpoints.

Results

No significant difference was observed between groups in anterior-posterior width (P = .24) and PCO (P = .78). Significant positive correlations were observed between postoperative PCO and knee range of motion (r = 0.12, P = .04) and total Knee Society Scores (r = 0.14, P = .02).

Conclusion

No impact of surgical technique on PCO was observed. Correlations were observed between postoperative PCO and the functional subscore and total Knee Society Score. All patients reported clinical improvements at 1 year postoperatively.

Clinical impact of component placement in manually instrumented total knee arthroplasty : a systematic review

AIMS

The goal of the current systematic review was to assess the impact of implant placement accuracy on outcomes following total knee arthroplasty (TKA).

METHODS

A systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines using the Ovid Medline, Embase, Cochrane Central, and Web of Science databases in order to assess the impact of the patient-reported outcomes measures (PROMs) and implant placement accuracy on outcomes following TKA. Studies assessing the impact of implant alignment, rotation, size, overhang, or condylar offset were included. Study quality was assessed, evidence was graded (one-star: no evidence, two-star: limited evidence, three-star: moderate evidence, four-star: strong evidence), and recommendations were made based on the available evidence.

RESULTS

A total of 49 studies were identified for inclusion. With respect to PROMs, there was two-star evidence in support of mechanical axis alignment (MAA), femorotibial angle (FTA), femoral coronal angle (FCA), tibial coronal angle (TCA), femoral sagittal angle (FSA), femoral rotation, tibial and combined rotation/mismatch, and implant size/overhang or offset on PROMs, and one-star evidence in support of tibial sagittal angle (TSA), impacting PROMs. With respect to survival, there was three- to four-star evidence in support FTA, FCA, TCA, and TSA, moderate evidence in support of femoral rotation, tibial and combined rotation/mismatch, and limited evidence in support of MAA, FSA, and implant size/overhang or offset impacting survival.

CONCLUSION

Overall, there is limited evidence to suggest that PROMs are impacted by the accuracy of implant placement, and malalignment does not appear to be a significant driver of the observed high rates of patient dissatisfaction following TKA. However, FTA, FCA, TCA, TSA, and implant rotation demonstrate a moderate-strong relationship with implant survival. Efforts should be made to improve the accuracy of these parameters in order to improve TKA survival. Cite this article: Bone Joint J 2021;103-B(9):1449-1456.

Effect of femoral posterior condyle offset on knee joint function after total knee replacement: a network meta-analysis and a sequential retrospective cohort study

BACKGROUND

This study was conducted with the aim to compare the effect of posterior condyle offset (PCO) changes on knee joint function of patients following total knee replacement (TKR).

METHODS

Electronic and manual searches were performed in the PubMed, Embase, and Cochrane Library databases from inception to September 2019. Network meta-analysis combined direct and indirect evidence to assess the weighted mean difference (WMD) and surface under the cumulative ranking curves (SUCRA) of different PCO changes (PCO ≤ - 2 mm, - 2 mm < PCO < 0 mm, 0 mm ≤ PCO < 2 mm and PCO ≥ 2 mm) on knee joint function after TKR. Then 103 OA patients undergoing unilateral TKR were included and the effect of PCO on the postoperative knee function was examined.

RESULTS

Totally, 5 cohort studies meeting the inclusion criteria were enrolled in this analysis. The results of meta-analysis showed that patients with 0 mm ≤ PCO < 2 mm after TKR had a better recovery of joint function (flexion contracture: 28.67%; KS functional score: 78.67%; KS knee score: 75.00%) than the remaining three groups. However, the knee flexion (77.00%) of patients with PCO ≤ - 2 mm after TKR was superior to the other three groups. Retrospective study also revealed a significant correlation between PCO changes and the flexion contracture, further flexion and KS functional score of patients after TKR, in which each functional knee score of patients with 0 mm ≤ PCO < 2 mm was better than the others.

CONCLUSION

These findings suggest a close correlation between PCO magnitude and knee joint function after TKR and that 0 mm ≤ PCO < 2 mm is superior to other changes for joint function after TKR.

Total Knee Arthroplasty Using a Medial Pivot or Posterior Cruciate-Stabilizing Prosthesis in Chinese Patients

There is an unmet need for a prosthesis designed according to the anatomical parameters of the Chinese population. This study aims to compare the use of a medial pivot (MP) implant or posterior cruciate ligament (PCL) substitution (posterior-stabilized [PS]) prosthesis for unilateral total knee arthroplasty (TKA) in a Chinese population. The medical records of patients undergoing unilateral TKA with an MP implant (Group A) or a PS prosthesis (Group B) at our institution between January 2010 and December 2011 were retrospectively reviewed. Patients were followed up for 5 years. Preoperatively and at the December 2016 postoperative follow-up, the Hospital for Special Surgery scoring system (HSS knee score) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score were measured to evaluate TKA outcomes. This study included 49 patients in Group A and 51 in Group B. As of December 2016, there were no significant differences in the preoperative/postoperative changes in any category of the HSS knee score or WOMAC score between the groups. There were no postoperative complications in either group during the 5-year follow-up. There were no periprosthetic infections or need for revision surgery. One patient in Group A experienced aching and a small amount of effusion in the articular cavity that was attributed to overexertion. In conclusion, there were no significant differences in midterm outcomes in Chinese patients receiving an MP implant or a PS prosthesis for unilateral TKA. These data suggest that the MP and PCL substitution design are safe and effective for unilateral TKA in China.

Do spacer blocks accurately estimate deformity correction and gap balance in total knee arthroplasty? A prospective study with computer navigation

BACKGROUND

Spacer blocks are used commonly in knee arthroplasty to estimate gaps and ligament balance. Their use continues along with modern technology despite dearth of literature regarding their accuracy and reliability. This prospective study aims to determine the difference in values of gap and balance measurements between spacers and trials in computer assisted TKA.

METHODS

50 patients with moderate varus deformity of <20° undergoing primary TKA were recruited for this prospective study. After navigation assisted cuts and requisite ligament release, gaps and balance were recorded in extension and 90° flexion with spacer block followed by implant trials.

RESULTS

There were 33 females and 17 males with average BMI of 28.2 ± 5kg/m². The average preoperative flexion deformity was 6.5° ± 4.4° and varus deformity was 8.2° ± 3.8°. Average difference of deformity in sagittal plane in extension between spacer and trial was 6.2° which was statistically significant (p = 0.001) implying that knee achieves more extension with spacer blocks as compared to trials because the blocks do not have posterior offset of the condyles. However, there was no difference between values of soft tissue balance and coronal plane correction between spacer blocks and trials in extension and 90° flexion (p > 0.05).

CONCLUSION

Spacer blocks do not estimate extension space accurately with knee achieving 6.2 more flexion with trials as compared to spacer blocks when assessed for sagittal plane correction in extension. Spacer blocks should pass in easily in extension to avoid any flexion deformity when the actual trials are inserted.

Comparison of the biomechanical effect of posterior condylar offset and kinematics between posterior cruciate-retaining and posterior-stabilized total knee arthroplasty

BACKGROUND

The effect of the changes in the femoral posterior condylar offset (PCO) on anterior-posterior (AP) translation and internal-external (IE) rotation in cruciate-retaining (CR) and posterior-stabilized (PS) total knee arthroplasty (TKA) remains unknown. The purpose of this study was to compare the kinematics in CR and PS TKA with respect to the difference in prosthetic design and PCO change through a computational simulation.

METHODS

We developed three-dimensional finite element models with the different PCOs of ±1, ±2 and ±3 mm in the posterior direction using CR and PS TKA. We performed the simulation with different PCOs under a deep knee bend condition and evaluated the kinematics for the AP and IE in CR and PS TKA.

RESULTS

The more tibiofemoral (TF) translation in the posterior direction was found as PCO translated in posterior direction for both CR and PS TKA compared to the neutral position. However, the change of the AP translation with respect to the PCO change in CR TKA was greater than PS TKA. The more TF external rotation was found as PCO translated in the anterior direction for both CR and PS TKA compared to the neutral position. However, unlike the TF translation, the TF rotation was not influenced by the PCO change in both CR and PS TKA.

CONCLUSION

The PCO magnitude was influenced by a postoperative change in the kinematics in CR TKA although a relatively smaller effect was observed in PS TKA. Hence, surgeons should be aware of the PCO change, especially for CR TKA.

Biomechanical Effects of Posterior Condylar Offset and Posterior Tibial Slope on Quadriceps Force and Joint Contact Forces in Posterior-Stabilized Total Knee Arthroplasty

This study aimed to determine the biomechanical effect of the posterior condylar offset (PCO) and posterior tibial slope (PTS) in posterior-stabilized (PS) fixed-bearing total knee arthroplasty (TKA). We developed ±1, ±2, and ±3 mm PCO models in the posterior direction and −3°, 0°, 3°, and 6° PTS models using a previously validated FE model. The influence of changes in the PCO and PTS on the biomechanical effects under deep-knee-bend loading was investigated. The contact stress on the PE insert increased by 14% and decreased by 7% on average as the PCO increased and decreased, respectively, compared to the neutral position. In addition, the contact stress on post in PE insert increased by 18% on average as PTS increased from −3° to 6°. However, the contact stress on the patellar button decreased by 11% on average as PTS increased from −3° to 6° in all different PCO cases. The quadriceps force decreased by 14% as PTS increased from −3° to 6° in all PCO models. The same trend was found in patellar tendon force. Changes in PCO had adverse biomechanical effects whereas PTS increase had positive biomechanical effects. However, excessive PTS should be avoided to prevent knee instability and subsequent failure.