Association of HSS score and mechanical alignment after primary TKA of patients suffering from constitutional varus knee that caused by combined deformities: a retrospective study

For pre-operative osteoarthritis (OA) patients with varus knee, previous studies showed inconsistent results. Therefore, we conducted this study to better identify the association of Hospital for Special Surgery (HSS) score and mechanical alignment. 44 patients (51 knees) with constitutional varus knee caused by combined deformities (LDFA (lateral distal femoral angle) > 90°and MPTA (medial proximal tibial angle) < 85°)) were selected and analyzed with a mean follow-up period of 14 months after total knee arthroplasty (TKA). From January 2015 to December 2016, patients were collected consecutively after primary TKA. After filtering, fifty-one knees (44patients) were analyzed with a mean follow-up period of 14 months. All patients were divided into two groups based on post-operative hip-knee-ankle (HKA) acute angle: varus mechanical alignment (VMA) group (HKA < − 3°) and neutral mechanical axis (NMA) group (− 3° ≤ HKA ≤ 3°). 30 knees were included in the NMA group, and 21 knees in the VMA group. Comparisons of HSS between NMA group and VMA group were performed. After adjusting for age and Body Mass Index (BMI) confounders, Compared with NMA group, the HSS score in VMA group decreased by 0.81 units (95% CI, − 3.37 to 1.75) p = 0.5370). For pre-operative constitutional varus knee caused by combined deformities in chinese populations, no significant association between post-operative lower limb mechanical alignment and HSS score was found.

Restoration of Constitutional Alignment in TKA with a Novel Osteotomy Technique

Many studies have shown that restoration of the preoperative constitutional varus may lead to a normal knee status in total knee arthroplasty (TKA). It is also known that coronal femoral lateral bowing contributes to constitutional varus of the femoral shaft, and bilateral femoral lateral bowing (BFLB) can decelerate medial knee osteoarthritis progression. In this sense, the BFLB should be reserved in TKA. To date, no study has yet reported the technique to reserve BFLB in TKA. Our study showed that the proximal and distal femur had no significant geometric difference between patients with varus knees and BFLB (> 5°) and volunteers with healthy knees and straight femoral shaft. So, the virtual center of femoral head fell on the distal femoral mechanical axis (DMA) after accurate correction of the bowing, indicating that the DMA should be the femoral original constitutional mechanical axis (CA). Subsequently, the distal femoral osteotomy was performed perpendicular to DMA in TKA, and the postoperative angle formed by DMA and tibial mechanical axis (TMA) was measured to assess whether CA was restored successfully. In this study, the gap balance was achieved without medial collateral ligaments release, and the patient's CA was successfully restored (range of DMA–TMA angle 178.2°–179.9°). This study provides a novel technique to restore preoperative CA in patients with varus knees and BFLB. It is found that the distal femur should be cut perpendicular to DMA, so the lower limb alignment and soft tissue strains can be restored to the preoperative state, and the knees would be stable and in a natural status after TKA.

Coronal Alignment in TKA: Traditional Principles Versus New Concepts

Background: Up to 20% of total knee arthroplasty (TKA) patients are not satisfied with their outcome, and coronal alignment is considered an important variable in attaining a well-functioning TKA. Neutral mechanical alignment is not necessarily the anatomic norm and has led some surgeons to advocate a shift in defining and attaining the optimal coronal component alignment. Our aim was to review the different coronal alignment paradigms of TKA and summarize the historical and contemporary outcomes of different alignment techniques.Methods: A systematic review was performed in March 2017 via PubMed using the search terms: coronal alignment, kinematic alignment, and total knee replacement using Boolean “and” in-between terms. Relevant results were then reviewed, analyzed and summarized Conclusions: Early clinical outcomes of kinematically aligned TKAs are promising, but long-term clinical results are unknown. Clinical, laboratory, and retrieval studies suggest that mechanical varus in TKA, especially involving the tibial component, may result in earlier failure. Kinematic alignment with boundaries may be an optimal strategy for patients with pre-operative constitutional varus or congenital tibia vara.