Aims. The impact of a diaphyseal femoral deformity on knee alignment varies according to its severity and localization. The aims of this study were to determine a method of assessing the impact of diaphyseal femoral deformities on knee alignment for the varus knee, and to evaluate the reliability and the reproducibility of this method in a large cohort of osteoarthritic patients. Methods. All patients who underwent a knee arthroplasty from 2019 to 2021 were included. Exclusion criteria were genu valgus, flexion contracture (> 5°), previous femoral osteotomy or fracture, total hip arthroplasty, and femoral rotational disorder. A total of 205 patients met the inclusion criteria. The mean age was 62.2 years (SD 8.4). The mean BMI was 33.1 kg/m. 2. (SD 5.5). The radiological measurements were performed twice by two independent reviewers, and included hip knee ankle (HKA) angle, mechanical medial distal femoral angle (mMDFA), anatomical medial distal femoral angle (aMDFA), femoral neck shaft angle (NSA), femoral bowing angle (FBow), the distance between the knee centre and the top of the FBow (DK), and the angle representing the FBow impact on the knee (C’KS angle). Results. The FBow impact on the mMDFA can be measured by the C’KS angle. The C’KS angle took the localization (length DK) and the importance (FBow angle) of the FBow into consideration. The mean FBow angle was 4.4° (SD 2.4; 0 to 12.5). The mean C’KS angle was 1.8° (SD 1.1; 0 to 5.8). Overall, 84 knees (41%) had a severe FBow (> 5°). The radiological measurements showed very good to excellent intraobserver and interobserver agreements. The C’KS increased significantly when the length DK decreased and the FBow angle increased (p < 0.001). Conclusion. The impact of the diaphyseal femoral deformity on the mechanical femoral axis is measured by the C’KS angle, a reliable and reproducible measurement. Cite this article: Bone Jt Open 2023;4(4):262–272

Introduction. Deformity influences the weight bearing stresses on the knee joint. Correction of mechanical alignment is performed to offload the knee and slow the rate of degenerative change. Fixator assisted deformity correction facilitates accurate correction prior to internal fixation. We present our results with standard Ilizarov and UNYCO system assisted deformity correction of the lower limb. Materials and Methods. Retrospective analysis of adult surgical cases of mechanical re-alignment performed between 2010 and 2019 in a tertiary referral centre. We recorded standard demographics and operative time from the electronic patient record. We analysed digitalised radiographs to record pre- and post-operative measurements of: Mechanical axis deviation (MAD), femoral tibial angle (FTA), Medial Proximal tibial angle (MPTA) and Mechanical lateral distal femoral angle (mLDFA). The accuracy of the correction was analysed. Time to healing, secondary interventions and complications were also recorded. Results. 7 patients underwent fixator assisted deformity correction with the UNYCO system and 11 with a standard Ilizarov frame. Mean pre-op MAD was 45.8mm in the UNYCO group and 43.4mm in Ilazrov; Mean post-op MAD was 9.5mm in the UNYCO group (5–15) and 12.3 in the Ilizarov group (1–25) p=0.07. The average surgical time in the UNYCO group was 200 minutes (128–325) and 252 minutes (203–301) in the Ilizarov group p=0.07. The mean post op MPTA was 90.2 (87–96) in the UNYCO group and 87.4 (81–94) in the Ilizarov group. The mean mLDFA was 90.0(81–93.5) in the UNYCO group and 87.3(82.2–93.9) in the Ilizarov group. All the corrections involved a plate or nail fixation and mean time to union was 76.3 days in the UNYCO and 117.3 in the Ilizarov group. Conclusions. Both systems allowed accurate correction of deformity and limb alignment. In this small series we were unable to show a difference in theatre time. The application of the principles of deformity correction are as important as the surgical methods

Aims

The aims of this study were: 1) to describe extended restricted kinematic alignment (E-rKA), a novel alignment strategy during robotic-assisted total knee arthroplasty (RA-TKA); 2) to compare residual medial compartment tightness following virtual surgical planning during RA-TKA using mechanical alignment (MA) and E-rKA, in the same set of osteoarthritic varus knees; 3) to assess the requirement of soft-tissue releases during RA-TKA using E-rKA; and 4) to compare the accuracy of surgical plan execution between knees managed with adjustments in component positioning alone, and those which require additional soft-tissue releases.

The coronal plane lower limb alignment plays an important role in the occurrence and progression in knee osteoarthritis. There have been reports of the valgus knee in patients with unilateral developmental hip dislocation (UDHD) with the relatively small sample size. Besides, few studies have analyzed the lower limb alignment of the contralateral side. The purpose of our study was to identify the coronal plane alignment of both the ipsilateral and the contralateral lower limb in patients with UDHD and find out the difference between patients with Hartofilakidis type II and III. The radiographic data of all UDHD patients who met the inclusion criteria from March 2011 to February 2017 were retrospectively reviewed, including the hip-knee-ankle angle (HKA), mechanical lateral distal femoral angle (mLDFA), anatomical lateral distal femoral angle (aLDFA), mechanical proximal tibial angle (MPTA) and the lateral distal tibial angle (LDTA). Besides, the femoral torsion angle was measured on the images of CT scan. The average HKA was 3.42°(range: −4.3–12.8°) on the affected side, and −2.11°(range: −11.4–5.4°) on the contralateral side (P?0.0001). The valgus lower limb alignment on ipsilateral side was most frequently seen in both Hartofilakidis type II (20cases, 51.3%) and type III groups (25cases, 67.6%), whereas for the contralateral side, the neutral alignment in type II group (27 cases, 69.2%) and varus alignment in type III group (19 cases, 51.4%) were most commonly observed. Both the mLDFA (P?0.001) and aLDFA (P?0.001) of ipsilateral side were significantly smaller than those of contralateral side. The average femoral torsion angle was 37.9°(range: 10.4–64.4°) on the affected side, and 27.1°(range: 9.7–45.5°) on the contralateral side (P?0.001). In conclusion, UDHD patients may present with lower limb malalignment on both sides. The valgus lower limb alignment is the most common deformity on ipsilateral side, which is caused by increased femoral torsion angle as well as the decreased aLDFA. The patients with Hartofilakidis type III UDHD may be more prone to present varus alignment deformity than those with Hartofilakidis type II on the contralateral side. The lower limb malalignment and deformity of ipsilateral distal femur should be considered during any surgery involving hip, knee or femur

With observed success and increased popularity of growth modulation techniques, there has been a trend towards use in progressively younger patients. Younger age at growth modulation increases the likelihood of complete deformity correction and need for implant removal prior to skeletal maturity introducing the risk of rebound deformity. The purpose of this study was to quantify magnitude and identify risk factors for rebound deformity after growth modulation. We performed a retrospective review of all patients undergoing growth modulation with a tension band plate for coronal plane deformity about the knee with subsequent implant removal. Exclusion criteria included completion epiphysiodesis or osteotomy at implant removal, ongoing growth modulation, and less than one year radiographic follow-up without rebound deformity. Mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), hip-knee-ankle angle (HKA), and mechanical axis station were measured prior to growth modulation, prior to implant removal, and at final follow-up. Sixty-seven limbs in 45 patients met the inclusion criteria. Mean age at growth modulation was 9.8 years (range 3.4–15.4 years) and mean age at implant removal was 11.4 years (range 5.3–16.4 years). Mean change in HKA after implant removal was 6.9O (range 0O–23 O). Fifty-two percent of patients had greater than 5O rebound and 30% had greater than 10O rebound in HKA after implant removal. Females less than ten years and males less than 12 years at time of growth modulation had greater mean change in HKA after implant removal compared to older patients (8.4O vs 4.7O, p=0.012). Patients with initial deformity greater than 20O degrees had an increased frequency of rebound greater than 10O compared to patients with less severe initial deformity (78% vs 22%, p=0.002). Rebound deformity after growth modulation is common. Growth modulation at a young age and large initial deformity increases risk of rebound. However, rebound does not occur in all at risk patients, therefore, we caution against routine overcorrection. Patients and their families should be informed about the risk of rebound deformity after growth modulation and the potential for multiple surgical interventions prior to skeletal maturity

This study aimed to define the rates of lower limb angular correction using temporary hemiepiphysiodesis in differing skeletal pathologies. A retrospective review of 61 children (36M:25F) with angular deformities about the knee who underwent 8-plate hemiepiphysiodesis (mean age 10.8y) was undertaken. The children were divided into 9 groups based on their underlying pathology (lower limb hypoplasia, Blount's disease, skeletal dysplasia, rickets, metabolic disease, acquired growth disturbance, vascular malformation, steroid use and complex genetic disorders). Radiographic measurements of each limb segment was undertaken using the TraumaCad® digital templating software based on standing long-leg radiographs - mechanical lateral distal femoral angle (mLDFA) and mechanical medial proximal tibial angle (mMPTA). The rate of correction of each parameter was calculated as a function of the time lapse between the operation date and first radiographic evidence of full correction of the mechanical axis (zone 1). A total of 144 limb segments (80 distal femoral, 64 proximal tibial physes) were analysed. 62.5% of children had mechanical axes outside the knee joint at the time of operation; 63.2% achieved full correction. The rate of angular correction at the distal femur (mLDFA) was quickest in those with acquired growth disturbance (1.15°/month), complex genetic disorders (1.12°/month) and rickets (0.93°/month). It was slowest in those with vascular malformation (0.40°/month), lower extremity hypoplasia (0.44°/month) and metabolic disease (0.49°/month). At the proximal tibia, mMPTA correction was quickest in those with acquired growth disturbance (0.77°/month) and skeletal dysplasia (0.57°/month); whilst being slowest in those with metabolic disease (0.22°/month) and Blount's disease (0.29°/month). The rate of angular correction about the knee varies with the underlying pathology with correction rates varying up to 3-fold. This study demonstrated the differential rate of correction of angular deformities in children with different skeletal pathologies, which would help guide the timing of hemiepiphysiodesis

Introduction. Neutral mechanical alignment in TKA has been shown to be an important consideration for survivorship, wear, and aseptic loosening. However, native knee anatomy is described by a joint line in 3° of varus, 2–3° of mechanical distal femoral valgus, and 2–3° of proximal tibia varus. Described kinematic planning methods replicate native joint alignment in extension without changing tibiofemoral alignment, but do not account for native alignment through a range of motion. An asymmetric TKA femoral component with a thicker medial femoral condyle and posterior condylar internal rotation paired with an asymmetric polyethylene insert aligns the joint line in 3° of varus while maintaining distal femoral and proximal tibial cuts perpendicular to mechanical axis. The asymmetric components recreate an anatomic varus joint line while avoiding tibiofemoral malalignment or femoral component internal rotation, a risk factor for patellofemoral maltracking. The study seeks to determine how many patients would be candidates for a kinematically planned knee without violating the principle of a neutral mechanical axis (0° ± 3°). Methods. A cohort comprised of 55 consecutive preoperative THA patients with asymptomatic knees and 55 consecutive preoperative primary unilateral TKA patients underwent simultaneous biplanar radiographic imaging. Full length coronal images from the thoracolumbar junction to the ankles were measured by two independent observers for the following: mechanical tibiofemoral angle (mTFA), mechanical lateral distal femoral angle (mLDFA), and mechanical medial proximal tibial angle (mMPTA). Patients who met the following conditions: mTFA 0°±3°; mLDFA 87°±3°; and mMPTA 87°±3°, were considered candidates for TKA with an asymmetric implant that would achieve a kinematic joint line and neutral mechanical axis. Similarly, patients with the following conditions: mTFA 0°±3°; mLDFA 90°±3°; and mMPTA 90°±3°, were considered candidates for TKA with a symmetric implant that would achieve a kinematic joint line and neutral mechanical axis. Results. In this cohort of 110 patients, the mean mTFA was 1° varus ± 5°, the mean mLDFA was 87° ± 3°, mMPTA 87°± 2°. The comparison of patients meeting each of the three conditions required for a TKA with a neutral mechanical axis and a kinematic joint line are outlined in Table 1. Conclusion. A TKA with kinematic 3° varus joint line and neutral mechanical axis was possible in 52% of patients using an asymmetric implant and 23% of patients using a symmetric implant. Previous descriptions of kinematic planning using standard TKA components required compromise of neutral mechanical axis alignment with detrimental effects on overall survivorship. Knee arthroplasty using an asymmetric implant may achieve the best of both worlds, neutral mechanical axis and a kinematic joint line, in a large percentage of patients

Aims

A comprehensive classification for coronal lower limb alignment with predictive capabilities for knee balance would be beneficial in total knee arthroplasty (TKA). This paper describes the Coronal Plane Alignment of the Knee (CPAK) classification and examines its utility in preoperative soft tissue balance prediction, comparing kinematic alignment (KA) to mechanical alignment (MA).