Coronal alignment after total knee arthroplasty

et al. 2020

Preprint

Background: Whether neutral alignment brings better clinical outcomes is controversial. Consideration of the preoperative knee condition of patients and some limitations of previous studies, we suggested that other index may be more important than a generic target of 0° ± 3° of a neutral axis to reflect changes in coronal alignment after total knee replacement (TKR). The purpose of this study was to explore the relationship between alignment and functional outcome with a new grouping method and the concept of correction rate. Methods: A new grouping method was adopted to divide patients into three groups based on the degree of correction of mechanical femoral-tibial angle (MFTA): neutral, under and over-correction. Hospital for Special Surgery (HSS) score were compared among the 3 groups. In addition, we also attempt to further explore whether the concept of correction rate can predict postoperative functional score. Results: HSS showed significant improvement in all groups. There was no difference in HSS or incremental scores based on the postoperative alignment category for the degree of correction of MFTA. The correlational analyses also didn’t find any relevant results.Conclusion: TKR is a soft tissue procedure and clinical outcome depends on many factors, only reaching neutral alignment after surgery may not mean a good clinical result. Therefore, categorization of optimal coronal alignment after TKR may be impractical. But we still believe that the concept of correction rate and new grouping method are worthy of research which can reflects the preoperative knee condition and the change of coronal alignment. Perhaps it can be better used in TKR in the future. Level of evidence: III.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Degree of Coronal Alignment Correction Can’t Predict Knee Function in Total Knee Replacement

Zhu

Chen

et al. 2020

Preprint

“…In contrast with patients who receive primary total hip arthroplasty, approximately 20% of those who receive TKA are not satis ed with their outcomes (11,12). Although its underlying reason is not clear, alignment technique of TKA is beginning to be considered to be related to the patient's postoperative outcomes and dissatisfaction (13,14). With the application of more accurate alignment assistant instruments, the conventional MA technique has begun to be challenged in recent years (7,15,16), because MA cannot fully respect the patient's natural alignment of lower extremities and joint line orientation, and a signi cant variation in overall coronal limb alignment and in femoral and tibial joint lines had been proved to exist in osteoarthritic knees (17).…”

Section: Discussionmentioning

confidence: 99%

How joint line orientation affects the amount of bone resection in mechanically aligned TKA: a retrospective clinical-radiographic correlation study

Liang

et al. 2020

Preprint

Abstract Background The discrepancy of bone resections between the medial and the lateral compartment is very common in total knee replacement (TKA) when mechanical alignment (MA) is used. The purpose of this study was to explore whether or how the joint line orientation affects the gross amount of bone resection in mechanically aligned TKA. Methods A total of 112 patients (137 knees) diagnosed with osteoarthritis (OA) were included. Simulated bone cuttings were conducted on the coronal view using full-length weight bearing radiographs according to the technical requirement of MA, and the feasibility of simulated osteotomy was verified by intraoperative calipered measurement. Correlation and regression analyses were conducted between the amounts of bone resection and various parameters, including hip-knee-ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), joint line congruency angle (JLCA), and medial proximal tibial angle (MPTA). Moreover, any intraoperative bone resection adjustments if existed, were retrospectively collected using medical records query system. Results All knees in current case series can be artificially divided into 4 subgroups: 84 varus knees (61.3%) with valgus femur in subgroup 1, 32 varus knees (23.4%) with varus femur in subgroup 2. 14 valgus knees (10.2%) with varus tibia in subgroup 3, 7 valgus knees (5.1%) with valgus tibia in subgroup 4. The amount of simulated bone resection had high consistency with the intraoperative measurement. MPTA and mLDFA had a positive correlation with the bone resection amount in subgroup 1. The regression equation was Bone resection (mm) = 0.556*mLDFA (deg.) + 0.098*MPTA (deg.) -39.74, R2 = 0.808. Similarly, the intraoperative bone cutting adjustments also showed a certain relationship with mLDFA in subgroup 1. Conclusions Deformities of knee OA can be divided into 4 subgroups based on the alignment of extremities and the joint line orientations. When a TKA is performed in varus knee with valgus femur using conventional instrument and mechanical alignment technique, the amount of bone resection on coronal plane is linearly related to the patient’s mLDFA.

“…The traditional opinion is that the postoperative limb alignment should be neutral, which is considered the prerequisite for successful total knee replacement (TKR) [1][2][3]. However, recent studies have challenged the gold standard of neutral alignment, questioning the utility of defining alignment as a dichotomous variable (aligned or malaligned) [4][5].…”

Section: Introductionmentioning

confidence: 99%

Degree of Coronal Alignment Correction Can’t Predict Knee Function in Total Knee Replacement

Zhu

Chen

et al. 2020

Preprint

Background: Whether neutral alignment brings better clinical outcomes is controversial. Consideration of the preoperative knee condition of patients and some limitations of previous studies, we suggested that other index may be more important than a generic target of 0° ± 3° of a neutral axis to reflect changes in coronal alignment after TKR. The purpose of this study was to explore the relationship between alignment and functional outcome with a new grouping method and the concept of correction rate. Methods: A new grouping method was adopted to divide patients into three groups based on the degree of correction of MFTA: neutral, under and over-correction. HSS were compared among the 3 groups. In addition, we also attempt to further explore whether the concept of correction rate can predict postoperative functional score. Results: HSS showed significant improvement in all groups. There was no difference in HSS or incremental scores based on the postoperative alignment category for the degree of correction of MFTA. The correlational analyses also didn’t find any relevant results. Conclusion: TKR is a soft tissue procedure and clinical outcome depends on many factors, only reaching neutral alignment after surgery may not mean a good clinical result. Therefore, categorization of optimal coronal alignment after TKR may be impractical. But we still believe that the concept of correction rate and new grouping method are worthy of research which can reflects the preoperative knee condition and the change of coronal alignment. Perhaps it can be better used in TKR in the future.