Preoperative Joint Line Convergence Angle Research Articles

The tipping point in medial opening wedge high tibial osteotomy relates to the shape of the proximal tibia more than to lower limb alignment correction.

The tipping point (TP) of the knee joint isthe centre of rotation of the joint in the coronal plane. This study aimed to define the TP in medial opening wedge high tibial osteotomy (MOWHTO). Data from 154 consecutive patients with varus knee malalignment, who underwent MOWHTO between 2017 and 2021, was retrospectively reviewed. The degree of preoperative osteoarthritis (OA), using the Kellgren-Lawrence (KL) grading system,was recorded. Long-leg standing radiographs were used to record the alignment parameters, including the hip-knee-ankle angle (HKA), the mechanical lateral distal femoral angle (mLDFA), the medial proximal tibial angle (MPTA), the joint line convergence angle (JLCA) and the joint line obliquity (JLO) angle. Postoperative Tegner activity scores, Western Ontario and McMaster University Scoresand patients'satisfaction were recorded. To define the TP, the relationship of all variables to Δ JLCA (absolute difference between preoperative to postoperative JLCA values) was analysed. Linear regression was employed for Δ JLCA to preoperative JLCA and postoperative and Δ MPTA (absolute difference between preoperative and postoperative values). K-means clustering was used to partition observations into clusters, in which each observation belongs to the cluster with the nearest mean serving as a prototype of the cluster, and analysed if there was any specific threshold influencing Δ JLCA. After defining the TP, further subanalysis of the TP based on the preoperative KL OA grade and analysis of variance of this TP to the KL OA grade was performed. A total of 154 patients (77.9% males and 22.1% females) were included. The mean age was 48.2 ± 11 years, and the mean body mass index was 27.1 ± 4 kg/m2. Preoperatively, 26 (16.9%) patients had KL grade IV OA. The mean preoperative and postoperative JLCA and the significance of their relation to Δ JLCA were 2.6° ± 1.8° (p < 0.0001) and 1.9° ± 1.8° (p = 0.6), respectively. The mean Δ JLCA was 1.4° ± 1.5°. The mean pre- and postoperative MPTA and the significance of their relation to Δ JLCA were 84.6 ± 2.2 (p = 0.005) and 91.8 ± 2.5 (p < 0.0007), respectively. The mean Δ MPTA was 7.2 ± 2.3 (p = 0.3). The mean preoperative and postoperative HKA and the significance of their relation to Δ JLCA were 174.6 ± 2.5 (p = 0.2) and 181.9 ± 2.4 (p = 0.7), respectively. The overall linear regression for Δ JLCA was statistically significant for preoperative JLCA (R2 = 0.3, p < 0.0001) and postoperative MPTA (R2 = 0.09, p = 0.0001) and statistically insignificant for Δ MPTA (R2 = 0.01, p = 0.2)and postoperative HKA (R2 = 0.04, p = 0.7). MPTA > 91.5° was the optimal threshold dividing this series data set between substantial and nonsignificant Δ JLCA. In this study, the main predictive factors for intra-articular correction (Δ JLCA) after MOWHTO were the preoperative value of JLCA and the postoperative value of MPTA. A value of 92° for postoperative MPTA is potentially the optimal threshold to predict intra-articular correction. Level IV, retrospective cohort study.

Preoperative joint line obliquity, a newly identified factor for overcorrection, can be incorporated into a novel preoperative planning method to optimise alignment in high tibial osteotomy.

The aim of this study was to analyse the factors associated with additional postoperative alignment changes after accurate bony correction by selecting only patients with well-performed bony correction as planned and developa method of incorporating significant factors into preoperative planning. Among 104 consecutive patients who underwent medial open wedge high tibial osteotomy (MOWHTO) between October 2019 and July 2022, 61 with well-performed bony corrections were retrospectively reviewed. The major criterion for well-performed bony correction was a difference of <1° between the simulated medial proximal tibial angle (MPTA) and the actual postoperative MPTA as measured in three dimensions. Radiographic parameters, such as the joint line convergence angle (JLCA) and joint line obliquity (JLO), were measured preoperatively and postoperatively, utilising standing and supine whole lower extremity anteroposterior, valgusand varus stress radiographs. Multiple linear regression analysis identified the factors affecting alignment changes, and a prediction model was developed. A method for applying this prediction model to preoperative planning was proposed. Preoperative JLCA on standing (preJLCAstd ), preoperative JLCA on 0° valgus stress radiograph (vgJLCA0 ), and preoperative JLO (preJLO) were significantly correlated with JLCA change (∆JLCA) (p < 0.001, p < 0.001, p = 0.006). The prediction model was estimated as ∆JLCA = 0.493 × (vgJLCA0 ) - 0.727 × (preJLCAstd ) + 0.189 × (preJLO) - 1.587 in. (R = 0.815, modified R2 = 0.646, p < 0.001). The proposed method resulted in a reduced overcorrection rate (p = 0.003) and an improved proportion of acceptable alignments (p = 0.013). PreJLCAstd , vgJLCA0 and preJLO can be used to estimate ∆JLCA. PreJLO was recently identified as a significant factor associated with additional alignment changes. Utilising the proposed preoperative planning and a prediction model with these factors shows promise in calibrating postoperative alignment after MOWHTO. Level III, retrospective cohort study.

Lateral knee laxity increases the risk of excessive joint line obliquity after medial opening-wedge high tibial osteotomy

BackgroundMedial opening-wedge high tibial osteotomy (HTO) is a well-recognized treatment for patient with varus knee osteoarthritis. Joint line obliquity has recently been suggested to negatively impact clinical outcomes following HTO, but little is known about what factors lead to increased joint line obliquity. The purpose of the current study was (1) to evaluate whether increased preoperative lateral knee laxity, represented by the joint line convergence angle, results in increased joint line obliquity in a consecutive series of patients treated with HTO and (2) to determine the effect of advanced arthritic changes on joint line obliquity. HypothesisIncreased joint line convergence angle would be associated with increased joint line obliquity. Patients and methodsAll HTOs performed at our center between 2010–2017 were retrospectively reviewed. Patients were excluded if pre- and postoperative standing alignment radiographs were not available. Varus-producing osteotomies were excluded. Patients were subdivided according to their preoperative joint line convergence angle (≤3° or >3°) and the degree of radiographic arthritic change. The primary outcome measure was the postoperative joint line obliquity. Categorical variables were compared using the paired samples t-test. Survival analysis was performed for failure and overall rate of reoperation. ResultsDuring the study period, 90 HTO were performed, and 38 patients (42 knees; M/F: 32/6; mean age: 41.6; mean follow-up: 4.72 years) met the inclusion criteria. The most common surgical indications were varus knee osteoarthritis (n=27, 64.3%) and osteochondritis dissecans (n=7, 8.2%). Patients with a preoperative joint line convergence angle >3° demonstrated significantly greater joint line obliquity postoperatively as compared to those with a joint line convergence angle ≤3° (6.4°±4.6° vs. 2.5°±5.7°, respectively; p=0.02). Patients with advanced arthritic changes had significantly lower preoperative (–3°±3.4° vs. –5.6°±4.1°; p=0.03) and greater postoperative (5.8°±4° vs. 2.2°±6.4°; p=0.04) joint line obliquity as compared to those with minimal arthritic changes. There were 12 complications among the 42 procedures: one conversion to total knee replacement (TKR), one hardware failure (fixation revised), one infection, and 9 hardware removals. Overall survival using conversion to TKR was 96.23% (95% CI 0.92–1.0) at 10 years. DiscussionLateral knee laxity, as defined by a preoperative joint line convergence angle >3°, and advanced arthritic changes are associated with increased postoperative joint line obliquity following medial opening-wedge high tibial osteotomy. Soft-tissue adaptation should be accounted for in order to avoid excessive joint line obliquity following high tibial osteotomy, and the planned correction should be reduced by 25% in patients with a preoperative joint line convergence angle >3° when templating using standing alignment radiographs. Level of evidenceIV.

Potential anatomic risk factors resulting oversized postoperative medial proximal tibial angle after double level osteotomy

BackgroundDouble level osteotomy (DLO) has been introduced to prevent increased postoperative joint line obliquity. However, although DLO is planned, knees with postoperative medial proximal tibial angle (MPTA) > 95° in preoperative surgical planning are present. This retrospective study aimed to evaluate risk factors for an MPTA > 95° in preoperative surgical planning for DLO in patients with varus knee osteoarthritis (OA).MethodsA total of 168 knees that underwent osteotomies around the knee for varus knee OA were enrolled. The hip-knee-ankle angle (HKA), weight-bearing line (WBL) ratio, mechanical lateral distal femoral angle (mLDFA), joint line convergence angle (JLCA) and mechanical medial proximal tibial angle (mMPTA) were measured on preoperative radiographs. The postoperative WBL ratio was planned to be 62.5%. When the postoperative mMPTA was more than 95° in isolated high tibial osteotomy (HTO), (DLO) was planned so that the postoperative mLDFA was 85°, and residual deformity was corrected by HTO. Knees with postoperative mMPTA ≤ 95° and > 95° were classified into the correctable group and uncorrectable group, respectively.ResultsDLO was required in 101 knees (60.1%). Among them, 41 knees (40.6%) were classified into the uncorrectable group. Binomial logistic regression analysis showed that preoperative JLCA and mMPTA were independent predictors in the uncorrectable group.ConclusionsEven with DLO, postoperative mMPTA was more than 95° in approximately 40% of cases. Preoperative increased JLCA and decreased mMPTA were risk factors for a postoperative mMPTA of > 95° after DLO.

Preoperative joint line convergence angle correction is a key factor in optimising accuracy in varus knee correction osteotomy

PurposeThis study aimed to identify and prevent preoperative factors that can be influenced in preoperative planning to reduce postoperative malcorrections.MethodsThe method used in this study was a retrospective two-centre analysis of 78 pre and postoperative fully weight-bearing radiographs of patients who underwent valgus osteotomy correction due to symptomatic medial compartment osteoarthritis. A computer software (TraumaCad®) was used to aim for an intersection point of the mechanical tibiofemoral axis (mTFA) with the tibia plateau at 55–60% (medial = 0%, lateral = 100%). Postoperative divergence ± 5% of this point was defined as over- and undercorrection. Preoperative joint geometry factors were correlated with postoperative malcorrection. Planning was conducted using the established method described by Miniaci (Group A) and with additional correction of the joint line convergence angle (JLCA) using the formula JLCA-2/2 (Group B). Additionally, in a small clinical case series, planning was conducted with JLCA correction. Statistical analysis was performed using (multiple) linear regression analysis and analysis of variance (ANOVA) with p < 0.05 considered significant.ResultsIn 78 analysed cases, postoperative malcorrection was detected in 37.2% (5.1% undercorrection, 32.1% overcorrection). Linear regression analysis revealed preoperative body mass index (BMI, p = 0.04), JLCA (p = 0.0001), and osteotomy level divergence (p = 0.0005) as factors correlated with overcorrection. In a multiple regression analysis, JLCA and osteotomy level divergence remained significant factors. Preoperative JLCA correction reduced the planned osteotomy gap (A 9.7 ± 2.8 mm vs B 8.3 ± 2.4 mm; p > 0.05) and postoperative medial proximal tibial angle (MPTA: A 94.3 ± 2.1° vs B 92.3 ± 1.5°; p < .05) in patients with preoperative JLCA ≥ 4°. The results were validated using a virtual postoperative correction of cases with overcorrection. A case series (n = 8) with a preoperative JLCA > 4 revealed a postoperative accuracy using the JLCA correction of 3.4 ± 1.9%.ConclusionPreoperative JLCA ≥ 4° and tibial osteotomy level divergence were identified as risk factors for postoperative overcorrection. Preoperative JLCA correction using the formula JLCA-2/2 is proposed to better control ideal postoperative correction and reduce MPTA. The intraoperatively realised osteotomy level should be precisely in accordance with preoperative planning.Level of evidenceIII, cross-sectional study.

Effects of proximal fibular partial excision on medial compartment knee osteoarthritis.

This study aimed to investigate the clinical and radiological progression of the patients who underwent proximal fibular partial excision (PFPE) for medial compartment knee osteoarthritis. Patients with medial compartment knee osteoarthritis who did not benefit from conservative treatment and accepted the PFPE surgery were involved in this study. Patients with traumatic arthritis, inflammatory arthritis, previous lower extremity fractures, valgus malalignment of the knee, and infection at the planned surgical site, however, were kept apart. Patients were assessed both clinically by Visual Analog Scale (VAS) and American Knee Society Score (AKSS), radiologically by Kellgren Lawrence classification, tibiofemoral angle, and joint-line convergence angle (JLCA). The patients were systematically assessed especially in the sixth month and first, second, and third years of the post-operative period. A total of 35 patients (mean age: 56.5, min: 45, max: 79) were involved in this study. The mean follow-up period was 22.4months (min: 6, max: 36). It has been observed that: Statistically significant decrease in VAS and increase in AKSS after PFPE (p < 0.001) No statistically significant improvement in preoperative and postoperative tibiofemoral angle and JLCA measurements CONCLUSIONS: The PFPE is a safe and effective surgical treatment for pain relief and functional improvement in medial compartment knee osteoarthritis. More studies are needed on its mechanism of action, long-term effects, and comparison with other treatment options.

Factors Associated with Postoperative Knee Joint Line Obliquity After Medial Open Wedge High Tibial Osteotomy

Background: There are still few reports on factors associated with postoperative knee joint line obliquity (KJLO). Purpose: The purpose was to determine preoperative radiographic factors that are associated with KJLO postoperatively after open wedge high tibial osteotomy (OWHTO) using multivariable linear regression analysis and multivariable logistic regression analysis. Study Design: Case-control study; Level of evidence, 3. Methods: A total of 60 patients with 65 varus knees who underwent OWHTO between December 2012 and June 2018 at a single institution were retrospectively enrolled in this study. The authors evaluated radiologic parameters including the weightbearing line ratio, femorotibial angle, medial proximal tibial angle, mechanical lateral distal femoral angle (LDFA), lateral distal tibial angle, joint line convergence angle (JLCA), KJLO, and ankle joint obliquity. They also categorized these radiographic parameters as preoperative and postoperative and calculated the difference (Δ) between preoperative and postoperative values. To determine which of the radiographic parameters were most associated with postoperative KJLO, multivariable linear regression analysis was performed using the stepwise method. Multivariable logistic regression analysis was used to examine the relative contribution of the preoperative radiographic parameters to an abnormal postoperative KJLO (>4°). Results: In the multivariable linear regression analysis, the preoperative LDFA and JLCA showed a statistically significant correlation. Multivariable logistic regression analysis revealed that the mean preoperative LDFA was significantly larger in the group with abnormal KJLO than in the group with the control group (odds ratio, 1.84; 95% CI, 1.12-3.02; P = .02), while preoperative JLCA tended to be larger in the abnormal KJLO group than the control group but not statistically significantly different. Conclusion: KJLO after OWHTO was associated with preoperative LDFA and JLCA in multivariable linear regression analysis, and preoperative LDFA was the most important factor associated with abnormal KJLO after OWHTO in multivariable logistic regression analysis.

Outcome of distal femoral osteotomy for the correction of varus deformities originating in the distal femur: a prospective study

Background: The authors hypothesized that implication of distal femur osteotomy (DFO) in patients with varus deformities that originated in the distal femur will reduce the rate of joint-line obliquity, thereby improving the radiographic, clinical, and functional outcomes of the patients. Here, the authors aimed to evaluate the outcome of DFO in the correction of varus deformities that originated in the distal femur. Methods: In a prospective study, 27 patients (31 knees) with varus deformities located in the distal femur who underwent a lateral biplane closed wedge DFO were included. Radiographic evaluations included the joint-line obliquity, medial proximal tibial angle (MPTA), lateral distal femoral angle (LDFA), and joint-line convergence angle (JLCA). Lysholm-Tegner score and Knee Injury and Osteoarthritis Outcome Score (KOOS) were used for the evaluation of functional outcome. The union of the osteotomy site was assessed radiographically. Results: At the final evaluation session, the mean preoperative varus angle significantly improved from 12.7±3.4 degrees to 1.6±1.6 degrees (P&lt;0.001). The mean preoperative LDFA significantly improved from 96±2.1 degrees to 87.9±1.1 degrees (P&lt;0.001). The mean preoperative JLCA significantly improved from 3.1±0.4 degrees to 2±0.3 degrees (P&lt;0.001). The mean preoperative Lysholm-Tegner scores also improved considerably from 66.4±2 degrees to 88.9±2.6 degrees (P&lt;0.001). The mean KOOS of the patients improved from 63.9±4.1 degrees to 86.1±4.6 degrees. Only one patient (3.2%) was observed to have joint-line obliquity (greater than±4 degrees). Bone union was seen in all patients at an average period of 9±1.9 wk. Conclusions: DFO results in small rate of joint-line obliquity, as well as acceptable radiographic, clinical, and functional outcomes in patients with varus deformities located in the distal femur. Level of Evidence: Level III.

Knee-ankle joint line angle: a significant contributor to high-degree knee joint line obliquity in medial opening wedge high tibial osteotomy

BackgroundMedial opening wedge high tibial osteotomy (MOWHTO) changes the knee joint inclination in the coronal plane, which can be compensated by the ankle joint. Once there is a decompensated knee joint obliquity, it can induce excessive shear force on the articular cartilage. This study aimed to investigate the capacity of the compensation by analyzing the correlation of the knee-ankle joint line angle (KAJA) and the knee joint line obliquity (KJLO).Patients and MethodsNinety-six patients undergoing MOWHTO were included. We measured potential predictors including preoperative or postoperative body mass index (BMI), weight-bearing line (WBL) ratio/correction amount, knee-ankle joint line angle(KAJA), mechanical lateral distal femoral angle (mLDFA), medial proximal tibia angle (MPTA), ankle joint line obliquity (AJLO), mechanical hip-knee-ankle angle (mHKA) and joint line convergence angle (JLCA). The correlations of these predictors and postoperative KJLO were determined using Pearson correlation coefficient. The contribution of significant predictors was further analyzed using multiple linear regression. Finally, the cutoff value of the most contributing factor resulting in decompensated KJLO was derived with receiver operating characteristic (ROC) curve analysis.ResultsPreoperative AJLO, JLCA, MPTA, mHKA and KJLO and postoperative KAJA and MPTA correlated with postoperative KJLO. After multiple linear regression, only preoperative AJLO and JLCA and postoperative KAJA still showed significant contribution to postoperative KJLO. Postoperative KAJA made the greatest contribution. The cutoff value of postoperative KAJA was at 9.6° after ROC analysis. The incidence rate of high-grade KJLO was 69.6% when postoperative KAJA exceeded 9.6°.ConclusionsPostoperative KAJA is a significant contributor to high-grade KJLO after MOWHTO. The incidence was increased at angles greater than 9.6°. The results suggest that KAJA should be carefully assessed during preoperative planning or intraoperative evaluation. Postoperative KAJA < 9.6° can lower the rate of early high-degree KJLO.

High rates of outliers in computer-assisted high tibial osteotomy with excellent mid-term outcomes.

The primary aim was to evaluate the accuracy of navigation in opening wedge high tibial osteotomy (HTO). The secondary aim was to examine mid-term outcomes after HTO. Inclusion criteria were patients with medial compartment knee osteoarthritis who underwent computer-assisted HTOs. Mechanical axis (MA), percentage MA (%MA), and change in posterior tibial slope (ΔPTS) were displayed on the navigation screen. Radiographic examinations included hip-knee-ankle (HKA) angle, medial proximal tibial angle (MPTA), joint line convergence angle (JLCA), and PTS. Preoperative and 5weeks postoperative standing radiographs of the whole lower extremity and knee were used. Clinical evaluations were performed using American Knee Society knee score and function score both preoperatively and at last follow-up. Radiographic evaluations were performed by orthopedic surgeons. Intraoperative navigation after osteotomy and postoperative standing radiograph were compared. MA (HKA), %MA, and ΔPTS were compared. Outliers were defined as > 3° in MA, > 10% in %MA, and > 10° in ΔPTS. Outlier and non-outlier groups were compared. The rate of conversion to arthroplasty was examined. This study involved 38 patients (44 knees) and last follow-up was at a mean of 5years (range, 1-9years). Mean American Knee Society knee score and function score improved significantly from 59 to 69 preoperatively to 95 and 85 at last follow-up, respectively. Absolute values of mean errors for MA, %MA, and ΔPTS were 2.1°, 9.3%, 1.2°, respectively. Outlier rates were 18% in MA, 39% in %MA, and 5% in ΔPTS. No significant factors were found in MA and ΔPTS. In %MA, preoperative JLCA was significantly higher in the outlier group compared to the non-outlier group. No knees underwent conversion to total knee arthroplasty. No differences in outcomes were found between outlier and non-outlier groups. Although rates of outlier values in computer-assisted opening wedge HTO were high, mid-term outcomes were excellent. IV.

Joint Space Width Increases Medially and Decreases Laterally at Different Time Points After Medial Open-Wedge High Tibial Osteotomy

To evaluate the serial changes in the joint space width (JSW) of the medial and lateral compartments after medial open-wedge high tibial osteotomy (MOWHTO) and its associated factors. The medial and lateral weight-bearing JSWs were measured on serial radiographs and analyzed preoperatively and postoperatively within 2 weeks, as well as at 3 months, 6 months, 1 year, and 2 years. Associations between the medial and lateral JSWs and age, body mass index, mechanical axis, correction angle, lateral distal femoral angle, medial proximal tibial angle, joint line convergence angle (JLCA), JLCA on stress radiographs, and arthroscopic cartilage status were examined. Clinical outcome was measured according to the Knee Society objective and functional scores. Seventy-one patients who underwent MOWHTO with locking-plate fixation were analyzed. The respective mean medial and lateral JSWs on serial radiographs were as follows: 3.08 mm and 5.14 mm preoperatively, 3.10 mm and 4.63 mm postoperatively, 3.37 mm and 4.57 mm at 3 months, 3.40 mm and 4.59 mm at 6 months, 3.44 mm and 4.57 mm at 1 year, and 3.42 mm and 4.64 mm at 2 years. At 3 months, the medial JSW increased (P < .001), whereas the lateral JSW decreased immediately (P < .001). JSW showed no significant differences at other time points. Preoperative and postoperative JLCAs and medial femoral and tibial cartilage grades were associated with medial JSW changes (P= .021). However, no significant parameters were associated with decreases in the lateral JSW (P > .05). The postoperative Knee Society objective and functional scores improved and were maintained. After MOWHTO, the medial JSW increased at 3 months postoperatively and the lateral JSW decreased immediately. The preoperative and postoperative JLCAs and the medial femoral and tibial cartilage grades were associated with the change in the medial JSW. However, no significant parameters were associated with the decrease in the lateral JSW. Level IV, case series of therapeutic study.

Change of joint-line convergence angle should be considered for accurate alignment correction in high tibial osteotomy

BackgroundThe alignment correction after high tibial osteotomy (HTO) is made both by bony correction and soft-tissue correction around the knee. Change of the joint-line convergence angle (JLCA) represents the soft-tissue correction after HTO, which is the angle made by a tangential line between the femoral condyles and the tibial plateau. We described the patterns of JLCA change and related factors after HTO and investigated the appropriate preoperative planning method.MethodsEighty patients who underwent HTO between 2013 and 2016 were included for this retrospective study. Standing, whole-limb radiograph, supine knee anteroposterior (AP) and lateral were measured on the preoperative and postoperative radiographs. The patterns of JLCA changes and related factors were analyzed.ResultsJLCA decreased by a mean of 0.9° ± 1.2° (P < 0.001) after HTO. Sixteen patients (20%, group II) showed a greater JLCA decrease ≥ 2°, while 64 (80%, group I) patients remained in a narrow range of JLCA change < 2°. Group II showed more varus deformity (varus 8.1° vs. varus 4.7° in the mechanical femorotibial angle, P < 0.001), greater JLCA on standing (4.9° vs. 2.1°, P < 0.001), and the difference of JLCA in the standing and supine positions (2.8° vs. 0.7°, P < 0.001) preoperatively compared to group I. The risk of a greater JLCA decrease ≥ 2° was associated with greater preoperative JLCA in the standing position and the difference between the JLCA in the standing and supine positions. Postoperative JLCA correlated better with preoperative JLCA in the supine position than those in the standing position. A preoperative JLCA ≥ 4° or the difference of preoperative JLCA in the standing and supine positions ≥ 1.7° was the cut-off value to predict a large JLCA decrease ≥ 2° after HTO in the receiver operating characteristic (ROC) curve analysis.ConclusionsSurgeons should consider the effect of the JLCA change during the preoperative planning and intraoperative procedure to avoid unintended overcorrection.

Open-wedge high tibial osteotomy using intraoperative control of joint line convergence angle with reference to preoperative supine radiograph.

Preoperative supine joint line convergence angle (JLCA) correlates with postoperative standing JLCA. Here, we compared the radiographic and clinical outcomes of knees with preoperative JLCAs of ≥ 4° and < 4° in open-wedge high tibial osteotomy (OWHTO). We hypothesized that the postoperative coronal alignment in both groups would not be affected by a change in JLCA if this change could predict before surgery. Eighty-four patients with medial knee osteoarthritis who underwent OWHTO were enrolled retrospectively. A weight-bearing line (WBL) ratio of 62% and a JCLA equivalent to the preoperative supine JLCA were anticipated in preoperative planning. These were intraoperatively set using an alignment rod and a radiolucent protractor under fluoroscopy. Soft tissue correction was defined as correction angle minus bone correction. The participants with preoperative JLCAs of < 4° (low-JLCA group) and ≥ 4° (high-JLCA group) were compared. No significant difference in the coronal alignment was found between the groups after OWHTO. No significant differences in correction angle or bone correction were found between the groups, but the soft tissue correction in the high-JLCA group was higher than that in the low-JLCA group after OWHTO (p = 0.013). When we controlled intraoperative JLCA, the postoperative coronal alignment was not affected by the change in JLCA and the differences in soft tissue correction between the low-JLCA and high-JLCA groups. However, overcorrection compared with the target coronal alignment remained in both groups. Level III, retrospective comparative study.

Posterior tibial slope is a modifiable predictor of relatively large extension gaps in total knee arthroplasty for degenerative osteoarthritis.

During total knee arthroplasty (TKA) for osteoarthritis, the sagittal gap imbalance (SGI) with a relatively large extension gap is an important surgical challenge. We determined the predictors of SGI with a relatively large extension gap and evaluated the surgical outcomes of knees with SGI. 551 consecutive cases of primary TKA for osteoarthritis were retrospectively reviewed. The cohort was divided into two groups according to the SGI and statistically matched according to baseline characteristics via the inverse probability of treatment weighting method. Multiple linear and logistic regression analyses were performed to determine the predictors of sagittal gap difference (SGD) and SGI. Intergroup differences in clinical and radiological outcomes were analyzed. Of all the knees included, 8.5% (n = 45) presented with SGI with a relatively large extension gap and required femoral sagittal balancing to manage SGI. The hyperextension angle (HA), preoperative joint line convergence angle (JLCA), and the change in posterior tibial slope (PTS) significantly correlated to SGD and predicted SGI with a relatively large extension gap. SGI group showed significant changes in femoral posterior condylar offset and joint line height compared to those without SGI (1.48 vs -0.45, 1.37 vs -0.51, respectively). Postoperative ROM and knee society knee scores were lower in SGI group. Knees requiring sagittal balancing to manage SGI with a relatively large extension gap is not uncommon in TKA for osteoarthritic knees. The change in PTS is an independent and modifiable predictor of SGI.

Risk factors and preventive strategy for excessive coronal inclination of tibial plateau following medial opening-wedge high tibial osteotomy.

To investigate risk factors and suggest preventive strategy for excessive coronal inclination of tibial plateau following medial opening-wedge high tibial osteotomy (MOWHTO). A total of 133 consecutive patients who underwent MOWHTO were retrospectively enrolled. Patients were divided into two groups based on postoperative medial proximal tibial angle (post-MPTA) of 95°: control group (n = 111, 83.5%) with post-MPTA less than 95° and excessive MPTA group (n = 22, 16.5%) with post-MPTA 95° or more. Demographics, radiographic parameters [mechanical lateral distal femoral angle (mLDFA), MPTA, posterior tibial slope, joint line obliquity (JLO), hip-knee-ankle angle, joint line convergence angle (JLCA), weight bearing line ratio, and correction angle], and clinical outcomes of patients were compared. Multiple logistic regression analysis was performed to determine risk factors for post-MPTA 95° or more. Multiple logistic regression analysis showed that preoperative JLO ≥ 3° [odds ratio (OR) 6.940, 95% confidence interval (CI) 2.373-20.296, p < 0.001] and preoperative JLCA ≥ 5° (OR 5.723, 95% CI 1.833-17.865, p = 0.008) were statistically significant risk factors for post-MPTA ≥ 95°. Incidences of excessive MPTA following MOWHTO in patients with none, one, and two risk factors preoperatively were 3.7%, 26.7%, and 77.8%, respectively. Preoperative JLO ≥ 3° and JLCA ≥ 5° were two significant risk factors for excessive MPTA following MOWHTO. Thus, surgeon should consider other types of osteotomy if these two risk factors are present together preoperatively in MOWHTO candidates. Level III.

Lateral and patellofemoral compartment osteoarthritis progression after medial unicompartmental knee arthroplasty: A five- to 10-year follow-up study

BackgroundThe purpose of the study was to evaluate lateral and patellofemoral osteoarthritis (OA) progression after medial unicompartmental knee arthroplasty (UKA) and identify factors affecting the progression that were not identified previously. MethodsWe evaluated 146 patients who underwent medial UKA between 2009 and 2014. Kellgren–Lawrence grading of lateral and patellofemoral OA was performed on preoperative and final follow-up knee radiographs. Radiographic and clinical characteristics, SF-36, and Oxford knee scores were compared between the OA progressed and non-progressed groups. Risk factors for lateral and patellofemoral OA progression were evaluated. ResultsThe lateral OA progressed and non-progressed groups significantly differed in side, preoperative flexion contracture, preoperative joint line convergence angle, postoperative tibiofemoral angle, insert size, revision status (P < 0.05), and the patellofemoral OA progressed and non-progressed groups significantly differed in age, pre- and postoperative flexion contracture, postoperative tibiofemoral angle and pre- and postoperative patellofemoral OA grade (P < 0.05). At the final follow-up, Visual Analogue Scale, Oxford Knee Scores, and SF-36 sub-scores were significantly better in the lateral OA non-progressed group (P < 0.001).Dominant leg (odds ratio (OR): 2.759), insert size (>4, OR: 2.219), revision status (+, OR: 6.692), and postoperative tibiofemoral angle (>5.5°, OR: 1.177) were independent risk factors for lateral OA progression, whereas age (>60 years, OR: 3.222), preoperative patellofemoral OA grade (>1, OR: 2.085), and postoperative flexion contracture (>10°, OR: 1.919) were those for patellofemoral OA progression. ConclusionsMild radiographic progression of 1 KL grade is frequently seen five to 10 years after medial UKA. Postoperative outcomes are significantly affected by lateral compartment OA progression but not by patellofemoral OA progression.

Increased preoperative medial and lateral laxity is a predictor of overcorrection in open wedge high tibial osteotomy.

This study aimed at determining whether overcorrection after open wedge high tibial osteotomy (OWHTO) would be predicted by the magnitude of preoperative medial and lateral coronal soft tissue laxity around the knee joint. Overall, 68 knees of 62 patients who underwent OWHTO for primary medial osteoarthritis were retrospectively reviewed. The mechanical hip-knee-ankle (HKA) axis, weight-bearing line (WBL) ratio, medial proximal tibial angle (MPTA), joint line obliquity, coronal subluxation, and joint line convergence angle (JLCA) were measured on full-weight-bearing long-standing HKA radiographs preoperatively and at 1year postoperatively. The varus valgus stress angle was measured on preoperative radiographs. The correction amount due to soft tissue factors was calculated as the difference between the WBL ratio on postoperative 1-year radiographs and that on virtually corrected preoperative radiographs with the same amount of MPTA at 1year postoperatively. The patients were grouped according to the presence or absence of a ≥ 10% overcorrection of WBL ratio (overcorrection or expected correction). Multiple logistic regression analysis was performed to identify the preoperative risk factors of overcorrection. The average WBL ratio was corrected from 19.0 ± 13.5% preoperatively to 61.6 ± 9.1% postoperatively (P < 0.001). The average MPTA changed from 85.1 ± 1.7° preoperatively to 93.6 ± 2.6° postoperatively, resulting in an average tibia correction angle of 8.6 ± 3.1°. The average estimated correction from soft tissue factors was 5.8 ± 7.4% of the WBL ratio. Soft tissue correction of the WBL ratio > 10% was confirmed in 17 patients (28%). The preoperative JLCA and valgus stress angle were significantly greater in the overcorrection group than in the expected correction group: 5.0 ± 1.7° vs. 3.4 ± 1.9° (P = 0.003) and 2.4 ± 1.0° vs. 1.3 ± 1.2° (P = 0.002), respectively. Among the radiologic parameters, the presence of both ≥ 4° JLCA and ≥ 1.5° valgus stress angle was the only significant risk factor for overcorrection from soft tissue factors (P = 0.006; odds ratio, 30.2). The magnitude of both medial and lateral coronal soft tissue laxity was a predictor of overcorrection from soft tissue factors after OWHTO. Overcorrection was more likely to occur in cases with both ≥ 4° JLCA and ≥ 1.5° valgus stress angle. III.

A residual intra-articular varus after medial opening wedge high tibial osteotomy (HTO) for varus osteoarthritis of the knee.

Varus deformity of knee osteoarthritis was formed by both intra-articular and extra-articular pathologies. Such intra-articular deformities could not be fully corrected by a medial open-wedge high tibial osteotomy (HTO), which was performed as an extra-articular procedure. Therefore, the purpose of this study was to investigate whether any residual varus was left inside the joint after HTO in the patients with knee osteoarthritis, and a correlation of the residual varus could be traced. This study involved 66 patients (66 knees) undergoing HTO for medial knee osteoarthritis. The percentage of mechanical axis (%MA), mechanical femorotibial angle (mFTA), mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA) and joint line convergence angle (JLCA) were measured on radiographs of the full-length legs preoperatively and 6 months postoperatively. The relationship between changes in the JLCA and alignment correction was assessed. The postoperative residual JLCA was categorized as the optimal (postoperative JLCA ≤ 2°), the acceptable (2° < postoperative JLCA ≤ 5°), and the unacceptable (postoperative JLCA > 5°) to analyze its correlation with pre- or intra-operative factors. Average %MA and mFTA were improved from 5.5 to 60% and from 190.2° to 176.4°, respectively. There was no change in mLDFA, whereas mMPTA changed from 80.3° to 91.8°. JLCA changed from 4.2° to 2.7°. The analyses of multiple linear regression showed that the preoperative JLCA and postoperative changes in mechanical alignment (%MA, mFTA and mMPTA) were two important variables dependently associated with differences in JLCAs postoperatively. However, postoperative JLCAs showed a stronger correlation to preoperative JLCAs than to changes in mechanical alignment postoperatively. A Chi-square analysis showed a significantly higher percentage of patients achieved acceptable postoperative JLCAs in the preoperative JLCA ≤ 6° group (78.8%) compared to the preoperative JLCA > 6° group (6.1%). Therefore, 6° of JLCA was suggested to be a tipping point. The capability of HTO to correct intra-articular varus deformities, which was represented by JLCAs, is limited. Postoperative residual JLCAs were correlated primarily to preoperative JLCA values and total alignment correction, while the former accounted for most. A preoperative JLCA of 6° was suggested to be a tipping point, and a larger value indicated more than 5° residual JLCA after the HTO.

Physiologic knee joint alignment and orientation can be restored by the minimally invasive double level osteotomy for osteoarthritic knees with severe varus deformity.

The purpose of this study was to examine early radiological and clinical outcomes following minimally invasive double level osteotomy (DLO) procedure performed for osteoarthritic knees with severe varus deformity. Twenty consecutive patients who underwent DLO for varus osteoarthritic knees were included in the study. All patients could be tracked for a minimum of 1year. Periodical radiological and clinical evaluations were performed at 6 and 12months after surgery. In the radiological assessment, the following parameters were measured on full-length weight-bearing radiographs both pre- and postoperatively: mechanical tibiofemoral angle (mTFA), mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), and joint-line convergence angle (JLCA). In addition, subjective clinical results were evaluated using the Knee Injury and Osteoarthritis Outcome Score (KOOS) and the International Knee Documentation Committee (IKDC) Subjective Score. The mean age of the study population was 62.5 ± 6.8years (range 45-76years). In the radiological evaluation, the preoperative mTFA, mLDFA, mMPTA, and JLCA values averaged 13.5° ± 3.1° varus, 91.1° ± 1.4°, 82.3° ± 2.0°, and 5.8° ± 2.3°, respectively. At 6 and 12months, all of the radiological parameters significantly improved and corrected to the values within normal range. In the clinical assessments at the follow-up evaluations, both the KOOS and IKDC subjective scores significantly improved from the preoperative values. No significant changes were noted between the 6 and 12-month results in the radiological and clinical assessments. The minimally invasive DLO technique is a valuable surgical technique accomplishing restoration of physiologic knee joint alignment and orientation with significant improvement in patient-registered clinical outcomes in early postoperative evaluation. Although the follow-up period is still short, the excellent clinical and radiological outcomes shown in the present study support the efficacy of this procedure. Retrospective case series, Level IV.

Predicting the Feasibility of Correcting Mechanical Axis in Large Varus Deformities With Unicompartmental Knee Arthroplasty

BackgroundDue to disappointing historical outcomes of unicompartmental knee arthroplasty (UKA), Kozinn and Scott proposed strict selection criteria, including preoperative varus alignment of ≤15°, to improve the outcomes of UKA. No studies to date, however, have assessed the feasibility of correcting large preoperative varus deformities with UKA surgery. The study goals were therefore to (1) assess to what extent patients with large varus deformities could be corrected and (2) determine radiographic parameters to predict sufficient correction. MethodsIn 200 consecutive robotic-arm assisted medial UKA patients with large preoperative varus deformities (≥7°), the mechanical axis angle (MAA) and joint line convergence angle (JLCA) were measured on hip-knee-ankle radiographs. It was assessed what number of patients were corrected to optimal (≤4°) and acceptable (5°-7°) alignment, and whether the feasibility of this correction could be predicted using an estimated MAA (eMAA, preoperative MAA−JLCA) using regression analyses. ResultsMean preoperative MAA was 10° of varus (range, 7°-18°), JLCA was 5° (1°-12°), postoperative MAA was 4° of varus (−3° to 8°), and correction was 6° (1°-14°). Postoperative optimal alignment was achieved in 62% and acceptable alignment in 36%. The eMAA was a significant predictor for optimal postoperative alignment, when corrected for age and gender (P < .001). ConclusionPatients with large preoperative varus deformities (7°-18°) could be considered candidates for medial UKA, as 98% was corrected to optimal or acceptable alignment, although cautious approach is needed in deformities >15°. Furthermore, it was noted that the feasibility of achieving optimal alignment could be predicted using the preoperative MAA, JLCA, and age.