Patients with varus knee osteoarthritis undergoing high tibial osteotomy exhibit more femoral varus but similar tibial morphology compared to non-arthritic varus knees

No clinical outcome difference between varus phenotypes after medial opening-wedge high tibial osteotomy at 2 years follow-up

PURPOSE

Clinical studies regarding medial open-wedge high tibial osteotomy (MOWHTO) often analyse a large group of mechanical varus knees rather than differentiating for its primary varus-inducing component. This study aims to compare the radiological and clinical outcomes of the most prevalent varus malalignment phenotypes using the coronal plane alignment of the knee (CPAK) classification.

METHODS

MOWHTO cases with minimal 2-year clinical follow-up were retrospectively selected from a knee osteotomy database (2016-2020). Based on the medial proximal tibial angle (MPTA) and lateral distal femoral angle (LDFA), subjects were allocated to the correct CPAK phenotype pre- and postoperatively. Clinical outcomes were the numeric rating scale (NRS), the knee injury and osteoarthritis outcome score (KOOS) and the therapeutic response rate (TRR) at 2-year follow-up. Inter-observer correlation coefficient (ICC) and unpaired student t test were performed for cross-phenotype comparison.

RESULTS

One hundred thirty-five (135) subjects were found eligible (53.0 years old ±9.6 [19-77], 72% male, 53% left-sided). The most prevalent preoperative phenotype was CPAK 1 (n = 70 (52%)) and the postoperative phenotype was CPAK 6 (n = 66 (49%)). All CPAK phenotypes improved significantly relative to baseline but cross-phenotype comparison yielded no significant differences in clinical outcome. The TRR at 2 years was 67% for CPAK 1, 69% for CPAK 2 and 87% for CPAK 4. The TRR for CPAK 6 was 64% compared with 80% for CPAK 9, which was not significantly different.

CONCLUSION

At 2-year follow-up, no clinically significant differences are observed between different CPAK phenotypes. Accurate MOWHTO corrections provide significant clinical improvement even in the femoral-driven varus knee and the constitutional varus knee dominated by intra-articular wear. The clinical indication for MOWHTO performance should not be reduced to the medial arthritic varus knee with underlying tibial varus alone.

LEVEL OF EVIDENCE

Level IV, retrospective comparative study.

How Do the Morphological Abnormalities of Femoral Head and Neck, Femoral Shaft and Femoral Condyle Affect the Occurrence and Development of Medial Knee Osteoarthritis

OBJECTIVE

At present, the main viewpoint is that tibial varus is the main reason of medial knee osteoarthritis (OA), and high tibial osteotomy (HTO) is also the main alignment correction method to correct medial knee OA. In contrast, the impact of the anatomical alignment of the femur on medial knee OA is often overlooked. We evaluated the increased risk for medial knee OA because a varus alignment could be attributed to the anatomical reasons that include hip anatomy, femoral shaft bowing (FSB) and femoral condylar dysplasia.

METHODS

The present research adopted a cross-sectional study method. We selected 62 patients with HTO in the Third Hospital of Hebei Medical University from June 2021 to March 2022 as the HTO group and 55 healthy volunteers as the control group. Femoral neck-shaft angle (NSA), lateral FSB, mechanical lateral distal femoral angle (mLDFA) and hip-knee-ankle (HKA) was radiographically examined within the two groups. The femoral neck length and offset were also measured, and the ratio is represented by the ratio of the femoral neck length to off-set (N/O). The 2-tailed Student t-test was used to compare the differences between groups when the data were in accordance with a normal distribution. Otherwise, the Mann-Whitney U tests was used to compare the differences between groups.

RESULT

Compared to the control group, the HTO group had a higher offset (p < 0.05), greater femoral neck length (p < 0.05), and decreased (more varus) NSA (p < 0.05). The HKA in the HTO group was 172.20 ° (3.50°), which was significantly lower than that of the control group 177.00° (3.05°), (p < 0.001), while the medial OA was associated with more varus HKA. The mean mLDFA was 89.10 ° (2.35°) and 87.50° (2.85°) in the HTO and control groups (p < 0.005), respectively. The mean lateral FSB values of the full-length radiographs were larger (p < 0.001) in the HTO group (4.24° ± 3.25°) than that in control group (1.16° ± 2.32°).

CONCLUSION

The reduction of NSA (coxa vara) and the increase of the mLDFA can lead to medial knee OA, while the lateral FSB also affects medial OA. We believe that femoral deformity is also one of the cause of the medial knee OA. Therefore, it is necessary to evaluate the joint deformity of the femur and tibia before surgery in order to determine whether to use HTO alone to correct the lower limb alignment.

A significant rate of tibial overcorrection with an increased JLO occurred after isolated high tibial osteotomy without considering international consensus

PURPOSE

The recent ESSKA consensus recommendations defined indications and outlined parameters for osteotomies around a degenerative varus knee. The consensus collated these guidelines based on the published literature available to answer commonly asked questions including the importance of identifying the site and degree of the lower limb deformity. In the consensus, the authors suggest that a knee joint line obliquity (JLO) greater than 5° or a planned medial proximal tibial angle (MPTA) > 94° preferentially indicates a double level osteotomy (DLO) compared to an isolated opening wedge high tibial osteotomy (OWHTO). This study aimed to analyze the corrections performed on a cohort of isolated opening wedge high tibial osteotomies (OWHTOs) prior to the recent ESSKA recommendations, with a focus on the impact of knee joint line obliquity (JLO) and medial proximal tibial angle (MPTA) on the choice of osteotomy procedure.

METHODS

This monocentric, retrospective study included 129 patients undergoing medial OWHTO for symptomatic isolated medial knee osteoarthritis (Ahlbäck grade I or II) and a global varus malalignment (hip-knee-ankle angle ≤ 177°). An automated software trained to automatically detect lower limb deformity was implemented using patients preoperative long leg alignment X-rays to identify suitability for an isolated HTO in knee varus deformity. Based on the ESSKA recommendations, the site of the osteotomy was identified as well as the degree of correction required. The ESSKA consensus considers avoiding an isolated high tibial osteotomy if the planned resultant knee joint line orientation exceeds 5 ̊ or MPTA exceeds 94°. A preoperative abnormal MPTA was defined by a value lower than 85° and a preoperative abnormal LDFA by a value greater than 90°. The cases of DLO or DFO suggested by the software and the number of extra-tibial anomalies were collected. Multiple linear regression models were developed to establish a relationship between preoperative values and the risk of being outside of ESSKA recommendations postoperatively.

RESULTS

Based on ESSKA recommendations and on threshold values considered abnormal, the software suggested a DLO in 17.8% (n = 23/129) of cases, a distal femoral osteotomy in 27.9% (n = 36/129) of cases and advised against an osteotomy procedure in 24% (n = 31/129) of cases. The software detected a femoral anomaly in 34.9% (n = 45/129) of cases and an JLCA > 6° in 9.3% (n = 12/129). Postoperatively, the MPTA exceeds 94° in 41.1% (n = 53/129) and the JLO exceeds 5° in 29.4% (n = 38/129). On multivariate analysis, a high preoperative MPTA was associated with higher risk of postoperative MPTA > 94° (R2 = 0.36; p < 0.001). Similarly, the probability of the software advising a DLO or DFO was associated with the presence of an "normal" preoperative MPTA (R2 = 0.42; p < 0.001) or an abnormal preoperative LDFA (R2 = 0.48; p < 0.001) or a planned JLO > 5° (R2 = 0.27; p < 0.001).

CONCLUSIONS

Analysis of patients who underwent an isolated OWHTO prior to the ESSKA guidelines, demonstrated a significant rate of post-operative tibial overcorrection and a resultant increased JLO. Pre-operative planning that considers the ESSKA guidelines, allows for better identification of those patients requiring a DFO or DLO and avoidance of resultant post-operative deformities.

LEVEL OF EVIDENCE

IV, case-series.

Hip abduction angle after open-wedge high tibial osteotomy is associated with the timed up & go test and recurrence of varus alignment

The aim of this study is to investigate the association between the hip abduction angle (HAA) and lower limb alignment as well as the clinical assessments in open-wedge high tibial osteotomy (OWHTO) patients. A total of 90 patients who underwent OWHTO were included. The demographic characteristics and clinical assessments (the Visual Analogue Scale for activities of daily living, the Japanese knee osteoarthritis measure, the Knee injury and Osteoarthritis Outcome Score, the Knee Society score, the Timed Up & Go (TUG) test, the single standing (SLS) test and muscle strength) were recorded. The patients were divided into two groups according to the HAA at 1 month after operation: the HAA (-) group (HAA < 0°) and the HAA (+) group (HAA ≥ 0°). Clinical scores except for the SLS test and radiographic parameters except for the posterior tibia slope (PTS), lateral distal femoral angle (LDFA) and lateral distal tibial angle (LDTA) were significantly improved at 2 years postoperatively. Regarding the two groups, scores on the TUG test in the HAA (-) group were significantly lower than those in the HAA (+) group (p = 0.011). The hip-knee-ankle angle (HKA), weight bearing line (WBLR) and knee joint line obliquity (KJLO) in the HAA (-) group were significantly higher than those in the HAA (+) group (p < 0.001, 0.001 and p = 0.025). In contrast, the LDFA in the HAA (-) group were significantly lower than those in the HAA (+) group (p < 0.001). The TUG test and the LDFA were weakly positively correlated with the HAA (r = 0.34, 0.42, p < 0.001 and 0.001). In contrast, the HKA, WBLR and KJLO had a weak negative correlation with the HAA (r = - 0.43, - 0.38 and - 0.37, p < 0.001, 0.001 and 0.001). This study showed the postoperative HAA was significantly associated with the TUG test and the HKA, WBLR, LDFA, and KJLO. A higher postoperative HAA might induce varus recurrence and poor outcomes of the gait parameter.

Impact of the diaphyseal femoral deformity on the lower limb alignment in osteoarthritic varus knees

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. 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/m² (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). 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). The impact of the diaphyseal femoral deformity on the mechanical femoral axis is measured by the C'KS angle, a reliable and reproducible measurement.