Postoperative excessive external femoral rotation in revision total hip arthroplasty is associated with muscle weakness in iliopsoas and gluteus medius and risk for hip dislocation

Background Excessive external femoral rotation (FR) can functionally increase stem anteversion (SA) and is often observed at an early stage after surgery in revision total hip arthroplasty (THA). This study was conducted to investigate the prevalence of external FR, identify the factors associated with external FR, and determine the association of FR and other factors with hip dislocation in revision THA. Methods We enrolled 51 revision THA patients (55 hip cases). The patient background, angle of anatomical and functional SA, FR angle, sizes and densities of muscles around the hip joint, impingement distance, and consequence of postoperative hip dislocation were assessed by reviewing their medical history and imaging data that includes computed tomography (CT) scans before and after surgery. Results Forty-five hip cases (81.8%) showed external FR (mean 13.0°). External FR was significantly correlated with anatomical SA (r = − 0.54) and increase in functional SA (r = 0.36), which was significantly correlated with impingement distance (r = 0.46). The independent factors associated with external FR in multivariate analysis were the anatomical SA, CT densities of the psoas, gluteus medius and maximus muscles, and 2-stage revision (R2 = 0.559). During follow-up period, eight cases of revision THA showed hip dislocation. FR, functional SA, impingement distance, CT density of psoas and gluteus medius muscle, body mass index, number of past operation, and ratio of 2-stage revision THA were significantly different between cases with dislocation and non-dislocation. The odds ratio of FR and impingement distance for hip dislocation was identified as 1.061(95% confidence interval (CI): 1.011–1.114) and 0.901 (95% CI 0.820–0.991), respectively. Conclusions Revision THA frequently causes an external FR that functionally increases the SA and impingement risk, particularly in hips with 2-stage revision with psoas and gluteus medius muscle atrophy. Patients who have undergone revision THA and have an excessive external FR may require careful monitoring for possible hip dislocation due to hip joint instability and impingement.

The Effect of Femoral Malrotation in Offset Templating for Total Hip Arthroplasty: A Cadaveric Study and Curvilinear Analysis

Techniques allow assessment of preoperative offset in hip arthroplasty. This study assessed femoral rotation in preoperative offset templating using a cadaveric model. Ten femurs were imaged at degrees of rotation. Offset was measured. A generalizable equation predicting change in offset was derived with a curvilinear model. Statistically significant differences at rotational positions were found. For 30 degrees of internal rotation, 2.1 mm change in adjusted mean offset existed; for 30 degrees of external rotation, 8.4 mm change existed. Improved awareness of malrotation of the proximal femur and templating adjustments may improve total hip arthroplasty outcomes. This study reflects level of evidence III.

Clinical impact of component placement in manually instrumented total knee arthroplasty

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.

Total knee replacement wear during simulated gait with mechanical and anatomic alignments

Total knee replacements (TKR) have historically been implanted perpendicular to the mechanical axis of the knee joint, with a commensurate external rotation of the femur in flexion relative to the posterior condylar axis (PCA). Although this mechanical alignment (MA) method has typically offered good long-term survivorship of implants, it may result in alignment of the implant that departs significantly from the native Joint Line (JL) in extension and flexion for a considerable portion of the patient population. There is a growing interest with surgeons to implant TKR components more closely aligned to the natural JL (Anatomic Alignment-AA) of the patient’s knee joint to reduce the need for soft tissue releases during surgery, potentially improving knee function and patient satisfaction. Using a previously-validated finite element model of the lower extremity, implant- and alignment-specific loading conditions were developed and applied in a wear experiment via a six-degree-of-freedom joint simulator. MA was defined as 0° Joint Line (JL), 0° varus hip-knee-ankle (HKA) angle, and 3° external femoral rotation. AA was defined as 5° varus JL, 3° varus HKA, and 0° femoral rotation. The experiment returned wear rates of 3.76 ± 0.51 mg/million cycles (Mcyc) and 2.59 ± 2.11 mg/Mcyc for ATTUNE® cruciate-retaining (CR) fixed bearing (FB) in MA and AA, respectively. For ATTUNE posterior-stabilized (PS) FB in AA, the wear rate was 0.97 ± 1.11 mg/Mcyc. For ATTUNE CR rotating platform (RP), the wear rates were 0.23 ± 0.19 mg/Mcyc, 0.48 ± 1.02 mg/Mcyc in MA and AA respectively. Using a two-way ANOVA, it was determined that there was no significantly difference in the wear rates between AA and MA ( p = 0.144) nor the wear rate of ATTUNE PS FB in AA significantly different from either ATTUNE CR FB or ATTUNE CR RP.

Kinematic Analysis of Total Knee Arthroplasty(TKA) using Orthosensor system: Externally rotated femoral prosthesis versus Traditional design prosthesis

Purpose The purpose of this study was to elucidate kinematic change according to the implant’s specific femoral rotation by using orthosensor implant with three degrees external rotation of femoral rotation rebuilt and traditional TKA implant without rebuilt of the femoral rotation .Methods Twenty-eight patients (34 knees) underwent TKA using traditional TKA implant and 16 patients (22 knees) underwent TKA using implant with three degrees external rotation of femoral rotation. Patients were followed up for at least 1 year. Mean age of patients was 71.1 years (range, 60 to 80 years) at the time of surgery. After implantation of femur and tibial components, we applied the orthosensor system, to evaluate femoral rollback of the new artificial joint. Femoral rollback was analyzed using digitized screenshot function of orthosensor system.Results Overall femoral tracking proportion regardless of implants was significantly higher on the medial compartment compared to that on the lateral compartment (13.3 ± 8.4% vs. 6.3 ± 5.0%, p < 0.001). Regarding femoral tracking according to each compartment, externally rotated femoral prosthesis and traditional prosthesis showed 12.1 ± 8.2% and 14.2 ± 8.6% (p = 0.371) on the medial compartment and 8.0 ± 5.8% and 5.2 ± 4.2% (p = 0.059) on the lateral compartment, respectively.Conclusion Our study showed reverse femoral roll-back movement with higher tracking distance on the lateral compartment during TKA. externally rotated femoral prosthesis TKA system with femoral component 3-degree rebuilt showed less roll-back difference between medial and lateral compartments compared to traditional TKA system. Fortunately, both TKA systems had excellent short-term clinical outcomes without having significant difference between the two. With longer follow-up and larger cohort, the advantage and effectiveness of femoral component rotation can be elucidated in the future.