A preliminary modeling investigation into the safe correction zone for high tibial osteotomy

High Tibial Osteotomy for Joint Preservation

High tibial osteotomy shifts the weight-bearing axis of the lower limb away from a diseased medial compartment. It has been associated with high rates of return to work and sport and high midterm to long-term survivorship. However, appropriate patient selection is paramount for achieving optimal outcomes. Factors that can affect outcomes include severity of medial cartilage damage, age, body mass index, and smoking status.

Surgical planning in HTO - alternative approaches to the Fujisawa gold-standard

BackgroundPresurgical planning of the correction angle plays a decisive role in a high tibial osteotomy, affecting the loading situation in the knee affected by osteoarthritis. The planning approach by Fujisawa et al. aims to adjust the weight-bearing line to achieve an optimal knee joint load distribution. While this method is accessible, it may not fully consider the complexity of individual dynamic knee-loading profiles. This review aims to disclose existing alternative HTO planning methods that do not follow Fujisawa's standard.MethodsPubMed, Web of Science and CENTRAL databases were screened, focusing on HTO research in combination with alternative planning approaches.ResultsEight out of 828 studies were included, with seven simulation studies based on finite element analysis and multi-body dynamics. The planning approaches incorporated gradual degrees of realignment parameters (weight-bearing line shift, medial proximal tibial angle, hip-knee-ankle, knee joint line orientation), simulating their effect on knee kinematics, contact force/stress, Von Mises and shear stress. Two studies proposed implementing individual correction magnitudes derived from preoperatively predicted knee adduction moments.ConclusionMost planning methods depend on static alignment assessments, neglecting an adequate loading-depending profile. They are confined to their conceptual phases, making the associated planning methods unviable for current clinical use.

Achieving Sufficient Valgus Alignment is Essential to Ensure Low Residual Pain in Short- to Midterm Follow-up After High Tibial Osteotomy in KL Grade 4 Osteoarthritis Patients

Background

Severe osteoarthritis (OA) has been identified as a risk factor for inferior outcomes following high tibial osteotomy (HTO).

Purpose

To investigate the effectiveness of HTO in patients with advanced OA, particularly those with Kellgren-Lawrence (KL) grade 4 (KL4), and to compare clinical outcomes based on OA severity and the effect of postoperative alignment in each group.

Study Design

Cohort study; Level of evidence, 3.

Methods

A retrospective review was conducted on patients who underwent biplanar medial opening-wedge HTO from 2010 to 2022, with a follow-up period of 2 to 5 years. Patients were divided into 2 groups based on preoperative KL grades: non-KL4 and KL4. Clinical outcomes were compared using patient-reported outcome (PRO) measures: pain visual analog scale (VAS), Lysholm Knee Score, and Knee injury and Osteoarthritis Outcome Score (KOOS) between the groups. Subgroup analyses were conducted to ascertain whether outcomes differed based on postoperative weightbearing line (WBL) ratio within each group.

Results

Out of 324 patients, 141 were eligible: 110 in the non-KL4 group and 31 in the KL4 group, with a mean follow-up of 37.5 months (overall mean age, 56.9 years; mean body mass index, 26.9 kg/m2). Baseline demographics were similar between the groups. The KL4 group had more severe preoperative conditions (larger defect size and more varus). However, both groups showed significant improvements in PROs (P < .001), with no significant differences between them. In the KL4 group, patients with a postoperative WBL ratio ≥62.5% showed better scores in certain PRO measures, while other PRO data showed no significant differences (VAS: 17.1 ± 19.1 vs 33.9 ± 18.3, P = .03; KOOS Activities of Daily Living subscale: 78.7 ± 9.9 vs 69.3 ± 13.8, P = .04). In contrast, the non-KL4 group showed no difference in PROs based on WBL ratio. In the KL4 group, the final VAS was most correlated with the WBL ratio (r = -0.545; P = .002). A WBL ratio of 62.2% to 67.3% was the cutoff value to predict the achievement of low residual pain (VAS < 18; median of KL4 group) in KL4 patients.

Conclusion

HTO can yield comparable clinical outcomes in KL4 OA patients to those with lower-grade OA. However, achieving sufficient valgus alignment (WBL ratio > 62.2%-67.3%) correlates with less residual pain in the short- to midterm follow-up in high-grade OA patients.

Correction to at least neutral alignment during high tibial osteotomy is sufficient in reducing the knee adduction moment

High tibial osteotomy (HTO) for varus knee osteoarthritis traditionally aims to overcorrect the mechanical tibiofemoral angle (mTFA) to become valgus. However, valgus overcorrection in HTO increases problems such as knee joint line abnormality, hinge fracture, and patellar height change. Thus, there is a trend to avoid overcorrection, but biomechanical basis for abandoning the overcorrection is lacking. From a dynamic perspective, medial-to-lateral knee joint load distribution during gait can be reflected by knee adduction moment (KAM), and the main purpose of HTO is to reduce the KAM increased during gait due to varus alignment. We tried to reveal the association between the KAM obtained from three-dimensional gait analysis and various static alignment parameters, including mTFA, measured from the standing whole limb anteroposterior radiograph and through this, to suggest a dynamically optimal target for HTO. When grouped according to the alignment by the interval of 1°, lower extremities with 3° to 8° of varus had greater KAM values than those with 0° to 5° of valgus. However, within groups of 0° to 5° of valgus, there were no significant differences. Therefore, the varus must be corrected to at least neutral alignment during HTO, but valgus overcorrection does not further reduce the KAM.

Comparison of the clinical and radiological outcomes of Puddu and TomoFix plates for medial opening-wedge high tibial osteotomy: A two-year follow-up of a randomized controlled trial

PURPOSE

Opening-wedge high tibial osteotomy (OWHTO) requires fixation devices for stabilization of the osteotomy gap. The two most commonly used fixation devices are the Puddu and the TomoFix plates. Based on its design, each implant generates a characteristic stability profile. The aim of this randomized controlled trial (RCT) was to investigate the short-term clinical and radiological outcomes of OWHTO using the Puddu and TomoFix plating systems. We hypothesized that the TomoFix plate would achieve superior clinical and radiographic results compared to the Puddu plate.

METHODS

A total of 60 patients were randomly allocated to undergo OWHTO either using the Puddu plate or the TomoFix plate if conservative treatment failed with symptomatic medial compartment knee osteoarthritis (OA) stage I or II according to Ahlbäck classification, and varus malalignment. All patients underwent clinical and radiological assessment preoperatively, and at 3, 6, 12, and 24months postoperatively. Radiological measurement of the hip-knee-ankle (HKA) angle, and posterior tibial slope (PTS) was performed. Functional assessment was carried out using the Hospital for Special Surgery Knee-Rating Scale (HSS) and the Western Ontario McMaster Universities (WOMAC) Osteoarthritis Index. Patients were also evaluated for intraoperative and postoperative complications throughout the follow-up period.

RESULTS

The mean angular correction was 9.6±4°, and 10.5±4.8° in the Puddu and TomoFix groups, respectively (p=0.488). The mean PTS change was significantly higher in the Puddu group (3.4±1.1°) compared to the TomoFix group (0.8±0.7°) (p<0.001). There was a statistically significant improvement in the mean HSS and WOMAC in both groups until one year postoperatively. Neither HSS nor WOMAC showed a statistically significant difference between the Puddu and TomoFix groups at any time during the first two postoperative years. The overall complication rate was not significantly different between the Puddu and TomoFix groups. However, the TomoFix group demonstrated higher incidence of symptomatic hardware (23% vs. 3.3%) and removal of metalwork (17% vs. 0%) than the Puddu group (p=0.023 and 0.020, respectively).

CONCLUSION

This RCT suggests that the implant choice for OWHTO has no significant impact on functional outcomes during the first 2years postoperatively. While the Puddu plate was associated with an unintentional increase in the PTS during the surgery, both implants allowed coronal and sagittal plane corrections to be preserved postoperatively. The overall complication rates were similar, but the TomoFix required more material to be removed because it is more cumbersome. However, these results need to be confirmed on a larger scale.

LEVEL OF EVIDENCE

II; randomized controlled trial.

Association of Undercorrection With Residual Proinflammatory Gene Expressions and Clinical Outcomes After Medial Open Wedge Proximal Tibial Osteotomy

BACKGROUND

Accumulating evidence suggests that synovial inflammation plays a pivotal role in knee osteoarthritis. Although biomechanical findings have shown that medial open-wedge proximal tibial osteotomy (OWPTO) decreases medial compartment loading by correcting knee alignment, the relationship between knee alignment and synovial inflammation in the biological microenvironment has not yet been elucidated.

PURPOSES

To investigate the relationship between preoperative and postoperative knee alignment and synovial gene expression and to determine the cutoff point of postoperative knee alignment at which gene expression of synovial inflammation improves.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 36 patients with osteoarthritis who underwent OWPTO between June 2018 and May 2020 were enrolled. Synovial tissue was collected from affected knees during initial OWPTO and plate removal surgeries, and gene expression associated with the pathogenesis of osteoarthritis in the synovial tissue was investigated using real-time polymerase chain reaction. The correlation between weightbearing line ratio (WBLR) and synovial gene expression was determined. Receiver operating characteristic curve analysis was used to determine the cutoff values of WBLR for improving gene expression. The participants were divided into 2 groups, according to the cutoff values of their WBLR, and compared according to Knee injury and Osteoarthritis Outcome Score (KOOS) and synovial gene expression.

RESULTS

Postoperative WBLR was correlated with gene expression of interleukin 1β (IL1B) (ρ = -0.43; P = .008) and of interleukin 6 (IL6) (ρ = -0.41; P = .01). The cutoff value to predict improvement of IL6 was postoperative WBLR of 52%, with an area under the curve of 0.74 (P = .03). Patients with WBLR of <52% showed higher postoperative inflammatory gene (IL1B [P = .04] and IL6 [P = .03]) and inferior postoperative KOOS values compared with those with WBLR of >52%.

CONCLUSION

The novel cutoff alignment for biological improvement after OWPTO in patients with medial compartment osteoarthritis was determined to be WBLR of 52%, and WBLR of <52% was associated with higher residual intra-articular inflammation and poor clinical outcomes. After accounting for surgical errors, the surgeon should set the target surgical alignment so that the postoperative WBLR does not fall below 52%.

Simultaneous Meniscal Repair and Temporary Guided Growth Using a Tension Band Plate to Correct Alignment in Pediatric Discoid Lateral Meniscus Patients With Valgus Knee

Meniscal stabilization with saucerization has recently been recommended for discoid lateral meniscus (DLM) to preserve the meniscus shape and prevent the progression of osteoarthritis. However, axial alignment of the lower limb causes a significant valgus change after arthroscopic partial meniscectomy and can lead to progressive lateral osteoarthritic changes. Thus, valgus knees in patients with DLM are a suspected predictive factor for poor outcomes after DLM surgery. Valgus malalignment in pediatric patients can be corrected by temporarily tethering one side of the open physis using implant-mediated guided growth to generate differential growth in the coronal plane. This Technical Note describes simultaneous arthroscopic meniscal surgery and temporary hemiepiphysiodesis to treat DLM with valgus deformities to reduce the risk of future chondral damage to the lateral knee compartment.

Around-the-knee osteotomies part 1: definitions, rationale and planning-state of the art

Knee osteotomies are essential orthopedic procedures with the ability to preserve the joint and correct ligament instabilities. Literature supports the correlation between lower limb malalignment and outcomes after knee ligament reconstruction and cartilage procedures. Concepts such as joint line obliquity, posterior tibial slope angle, and intra-articular deformity correction are integral components of both preoperative planning and postoperative evaluations. The concept of preserving and/or restoring joint line congruence during simultaneous correction of varus or valgus deformity can be achieved through several different approaches. With advancements in osteotomy research and surgical planning technology, the surgical decision-making has increased in complexity. Based upon a patient's specific deformity, decisions need to be made whether to perform a single-level (proximal tibia or distal femur) versus double-level (both proximal tibia and distal femur) osteotomy, and whether to correct deformity in a single plane (coronal or sagittal) or perform a biplanar osteotomy, correcting two of the malalignments in either coronal, sagittal, or axial planes. Osteotomy procedures prioritize safety, reproducibility, precision, and meticulous planning. Equally important is the proactive management of possible complications and the implementation of preventive strategies for complications such as hinge fractures and unintentional changes to alignment in other planes. This review navigates the intricate landscape of lower limb alignment, commencing with foundational definitions and rationale for performing osteotomies, progressing through the planning phase, and addressing the critical aspect of complication prevention, all while looking ahead to anticipate future advancements in this field. However, rotational osteotomies and tibial tubercle osteotomies in isolation or as an adjunct procedure are beyond the scope of this review.

Postoperative improvement in patient-reported outcomes after neutral alignment medial open wedge high tibial osteotomy for medial compartment knee osteoarthritis in patients aged ≥70 years versus younger patients

Purpose

To compare the postoperative clinical and radiological outcomes in patients aged ≥70 years following neutral alignment medial opening-wedge high tibial osteotomy (NA-MOWHTO) for medial compartment knee osteoarthritis (KOA) to those observed in younger patients.

Methods

The data of patients who underwent NA-MOWHTO for medial compartment KOA between September 2018 and June 2022 were retrospectively analysed. The patients were categorised into groups Y (<70 years) and O (≥70 years). Age, sex, Kellgren-Lawrence classification, pre- and postoperative mechanical axis, weight-bearing line ratio, medial proximal tibial angle, preoperative Tegner Activity Score and pre- and postoperative Lysholm scores were compared between the groups.

Results

Overall, 81 patients (60 and 21 in groups Y and O, respectively) who underwent NA-MOWHTO were included in this study. No significant differences were found in patient characteristics between the two groups, except for the preoperative Tegner Activity Score, which was significantly higher in group Y than in group O (3 [2-4] vs. 2 [2-2], respectively; p = 0.011). The two groups exhibited no significant differences in pre- and postoperative knee alignments. Postoperatively, Lysholm scores improved significantly in both groups without significant differences. Additionally, no correlation was found between age and pre- and postoperative Lysholm scores.

Conclusions

The postoperative improvement following NA-MOWHTO for medial compartment KOA is comparable in patients aged ≥70 and younger.

Level of Evidence

Level III, Retrospective comparative study.

Clinical and Radiological Outcomes of Medial Meniscal Allograft Transplantation Combined With Realignment Surgery

BACKGROUND

The outcomes of medial meniscal allograft transplantation (MMAT) combined with high tibial osteotomy (HTO) compared with isolated MMAT remain unclear.

PURPOSE

To compare the clinical and radiological results of MMAT combined with HTO and isolated MMAT.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

This retrospective study included 42 consecutive patients, who were divided into group M (isolated MMAT; n = 22) and group H (MMAT combined with HTO with a varus angle >3°; n = 20). Group differences in subjective knee scores, isokinetic muscle strength test, and radiological outcomes (Kellgren-Lawrence grade, mechanical axis, graft extrusion, graft status, and articular cartilage loss) were compared.

RESULTS

The mean follow-up period was 29.2 ± 4.9 months and 27.4 ± 5.3 months for groups M and H, respectively. The Lysholm score improved from 55.4 ± 9.5 to 81.3 ± 9.7 and from 52.6 ± 8.9 to 84.2 ± 10.2 in groups M and H, respectively (both P < .001). The International Knee Documentation Committee subjective score improved from 51.4 ± 10.3 to 79.6 ± 9.4 and from 49.3 ± 11.4 to 81.4 ± 8.3 in groups M and H, respectively (both P < .001). Both groups showed no significant differences in subjective knee scores and isokinetic extensor strength at the final follow-up. The rate of preoperative and postoperative high International Cartilage Regeneration & Joint Preservation Society grade (≥3) did not differ between the 2 groups. Group M showed greater coronal graft extrusion than did group H (3.3 ± 0.7 mm vs 2.7 ± 0.8 mm; P = .014); the rate of pathologic graft extrusion (≥3 mm) was not higher in group M (40.9%) than in group H (20%) with the number of patients available (P = .143). Both groups showed no significant difference in the graft status. Graft tears were observed in 2 patients (9%) in group M and 1 patient (5%) in group H (P = .607).

CONCLUSION

Clinical scores significantly improved after isolated MMAT and MMAT combined with HTO compared with preoperative values, and their short-term outcomes were similar. Postoperative graft extrusion was greater in patients who underwent isolated MMAT, implying that active correction of varus alignment during MMAT may help in intra-articular biomechanics.

Less risk of patellofemoral degeneration without significant clinical and survivorship difference for distal tibial tuberosity high tibial osteotomy compared to biplanar high tibial osteotomy over a mid-term follow-up

PURPOSE

This study aims to compare the mid-term radiographic, clinical results and survivorship between distal tibial tuberosity high tibial osteotomy (DTT-HTO) and conventional biplanar medial open-wedge high tibial osteotomy (cOW-HTO).

METHODS

The weight-bearing line ratio (WBL%) and medial proximal tibial angle (MPTA) were evaluated using a standing anteroposterior view of lower extremity. The posterior tibial slope (PTS), Caton-Deschamps index (CDI), tilting angle (TT) and lateral shift ratio (LSR) were evaluated using the lateral views and Merchant views. The Knee Society (KS) knee and function score, Lysholm score, and Anterior Knee Pain Scale (Kujala score) were were used to evaluate the functional outcomes. All parameters were evaluated preoperatively and at the final follow-up. The postoperative complications and survivorship for both groups were also evaluated during the follow-up period.

RESULTS

The WBL% and MPTA exhibited no significant differences between the two groups preoperatively and at the final follow-up. The postoperative CDI and TT in the cOW group decreased significantly compared with the DTT group (p = .037 and .041, respectively). The PF grade showed a significant increase after DTT-HTO and cOW-HTO (p = .036 and <0.001, respectively). Furthermore, the postoperative PF grade of cOW group was significantly higher than that of DTT group (p = .039). The KS knee and function score, Lysholm score, and Kujala score for both groups improved similarly at the final follow-up. The survivorship free of revision was 92.7 % in the DTT group and 94.2% in the OW group.

CONCLUSIONS

Despite observing a lower risk of PF joint progression in DTT-HTO compared to cOW-HTO, the clinical outcomes and survivorship after DTT-HTO and cOWHTO were comparable over a mid-term follow-up.

Advancements in health informatics: finite element insights into medial open-wedge high tibial osteotomy and lateral meniscal tears

Knee medial compartment osteoarthritis is effectively treated by a medial open-wedge high tibial osteotomy (MOWHTO). The feasibility and safety of MOWHTO for mild lateral meniscal tears are unknown. This study examined the feasibility and safety of knee joint weight-bearing line ratio (WBLr) adjustment during MOWHTO with lateral meniscal injuries. We used a healthy adult male's lower extremities computed tomography scans and knee joint magnetic resonance imaging images to create a normal fine element (FE) model. Based on this model, we generated nine FE models for the MOWHTO operation (WBLr: 40-80%) and 15 models for various lateral meniscal injuries. A compressive load of 650N was applied to all cases to calculate the von Mises stress (VMS), and the intact lateral meniscus' maximal VMS at 77.5% WBLr was accepted as the corrective upper limit stress. Our experimental results show that mild lateral meniscal tears can withstand MOWHTO, while severe tears cannot. Our findings expand the use of MOWHTO and provide a theoretical direction for practical decisions in patients with lateral meniscal injuries.

Comparison of clinical, imaging and second-look arthroscopic outcomes between varus knee patients with and without preoperative tibial varus deformity after medial opening-wedge high tibial osteotomy

PURPOSE

This study aimed to compare the regeneration status of articular cartilage, clinical, and radiologic outcomes between varus knee patients with and without preoperative tibial varus deformity (PTVD) after medial opening-wedge high tibial osteotomy (OWHTO) METHODS: Varus knee patients who had undergone OWHTO were divided into two groups according to preoperative medial proximal tibial angle (MPTA): a great varus (GV) group (MPTA <85°) and a mild varus (MV) group (85°≤preoperative MPTA <87°). The hip-knee-ankle (HKA) angle, weight-bearing line ratio (WBL%), MPTA, joint line convergence angle and joint line obliquity were measured. Second-look arthroscopy was undertaken 24 months after HTO. The Knee Society (KS) function score and knee score, and Lysholm score were used to evaluate the functional outcomes. All parameters were evaluated preoperatively and 24 months after HTO.

RESULTS

The GV group had greater varus than the MV group in HKA and WBL% before surgery, but greater valgus after surgery. The arthroscopic probe before HTO revealed the advanced chondral damage in the GV group and lighter chondral damage in the MV group. The regeneration of medial femoral condyle was considerably more frequent in the GV group (72.5%, 45/62) than in the MV group (50.0%, 27/54) (P = 0.030). No significant differences were observed in all functional outcomes preoperatively and 24 months after HTO.

CONCLUSION

The extent of cartilage regeneration in patients without PTVD was inferior to that in those with PTVD, but the functional outcomes were comparable. OWHTO may be a treatment option in a selected subset of varus knee patients without PTVD.

Effect of limb alignment correction on medial meniscus extrusion under loading condition in high tibial osteotomy

Background

This study aimed to investigate the effect of high tibial osteotomy (HTO) on medial meniscus extrusion (MME) and the association between the changes in limb alignment and MME under weight-bearing (WB) conditions after HTO.

Methods

We included 17 patients with knee osteoarthritis (OA) who underwent HTO. MME was evaluated using ultrasonography in supine and unipedal standing positions. Knee alignment was evaluated radiographically using WB, whole-leg radiographs with the hip-knee-ankle angle (HKAA), percentage of the mechanical axis (%MA), medial proximal tibial angle (MPTA), and joint line convergence angle (JLCA). All measurements were performed serially at four time points: preoperative and 3, 6, and 12 months postoperative. Clinical outcomes were assessed by knee injury and osteoarthrosis outcome score (KOOS) and visual analogue scale (VAS) value for pain.

Results

Mean MME in the WB position was significantly greater than that in the supine position in the preoperative condition; however, MME in both supine and WB positions was significantly lowered postoperatively. The ΔMME, difference of MME between supine and WB positions, was significantly lowered postoperatively and maintained for up to 1 year. MME change in the WB position between preop and postoperative conditions was significantly correlated with change in HKAA and %MA at 1 year postoperative. KOOS and VAS score were significantly improved after HTO.

Conclusions

HTO correcting varus alignment can decrease MME in WB position and minimise the change in MME between supine and WB positions. The changes in MME after HTO were correlated with changes in the mechanical alignments.

Comparison of the clinical effects for different positions of the weight-bearing axis after high tibial osteotomy

PURPOSE

To analyze the clinical effects of different positions of the weight-bearing axis (WBA) after high tibial osteotomy (HTO).

METHODS

The clinical data of 90 patients who underwent HTO in the Department of Orthopedics at our hospital from June 2018 to June 2021 were retrospectively analyzed. Patients were divided into groups A and B (n = 45 per group) according to different post-HTO WBA positions of the affected side. WBAs in both groups were at 50-60% and 62-66% of the tibial plateau, from inside to outside, respectively. American Hospital for Special Surgery Knee Score (HSS), visual analog scale (VAS) score, femorotibial angle (FTA), and medial proximal tibial angle (MPTA) were recorded and analyzed.

RESULTS

All patients were followed up with for 12 months. HSS scores increased gradually and VAS scores decreased gradually in both groups preoperatively, and at 3 months, 6 months, and 1 year postoperatively (P < 0.05). Compared to group A, group B had better HHS scores at 6 months and 1 year postoperatively (P < 0.05). There was no significant between-group difference in VAS scores at all aforementioned timepoints (P > 0.05). Postoperative MPTA and FTA were 89.56° ± 2.18° and 177.11° ± 2.63° in group A, and 89.07° ± 1.98° and 177.07° ± 2.36° in group B, respectively, with no significant between-group difference (P > 0.05).

CONCLUSION

Patients with post-HTO WBA ranges of 50-60% and 62-66% achieved knee joint function improvement and pain relief. Half a year later, those with a WBA range of 62-66% had better knee joint function scores. However, a comparison of long-term effects warrants further investigation.

The position of the lateral tibial spine and the implications for high tibial osteotomy planning

The lateral tibial spine (LTS) is frequently proposed as a correction target in high tibial osteotomy (HTO), although little is known about its exact radiographic position. This study primarily aims to define the position and variance of the LTS. Secondly, this study wants to investigate the relevance of the LTS position on the mechanical tibiofemoral angle (mTFA°) while planning and postoperatively landing the weight-bearing line (WBL) on this landmark. The LTS position was studied on preoperative full-leg standing radiographs (FLSR) and computed tomography (CT) scans in 70 cases. 3D models of the tibia were created in Mimics 23.0 and measurements were conducted in 3-matic 15.0 (Materialise, Leuven®). Next, 100 HTO cases were retrospectively planned with the WBL through the LTS according to Dugdale's method on FLSR. Finally, 55 postoperative FLSR which had the WBL on the LTS (±2%) were assessed for mTFA° outcome. Statistics were conducted in GraphPad 8.0. The LTS was located at 58.3%±1.9 [55-63%] in 2D and 57.3%±2.2 [53-63%] in 3D showing a high correlation (r=0.77 [0.65 to 0.85]). The planned mTFA on the LTS was 181.8°±0.3 (181.3°-182.5°). On postoperative FLSR, the mTFA was 182.2°±0.6 (180.9°-183.1°). The lateral tibial spine is located at 57-58% on the tibial plateau with a 10% maximal variation range. Good agreement was found between 2D and 3D imaging modalities while evaluating its position in the coronal plane. When aiming the WBL through the LTS during valgus-producing HTO, a consistent realignment of 181-183° mTFA can be expected when performing accurate surgery.

Mid-term results of medial open-wedge high tibial osteotomy based on radiological grading of osteoarthritis

PURPOSE

To evaluate the mid-term results of medial open-wedge high tibial osteotomy (OWHTO) based on Kellgren-Lawrence (KL) grades.

MATERIALS AND METHODS

We retrospectively evaluated clinical and radiographic outcomes of 93 patients (mean age 61.4 years, mean follow-up 64.2 months, 109 consecutive knees) who underwent OWHTO for medial compartment osteoarthritis (OA). KL grade was used to evaluate knee OA (KL-1 22 cases; KL-2, 51 cases; KL-3, 36 cases). The clinical outcomes were assessed using Japanese Orthopaedic Association (JOA) and Lysholm scores. Radiographic outcomes were assessed using pre- and post-operative mechanical axis percentage, femorotibial angle, medial proximal tibial angle, and joint line convergence angle. Hinge fracture frequency and OA progression were also evaluated based on KL grades.

RESULTS

The JOA score improved significantly from 70.3 ± 14.9 to 96.2 ± 4.4, 64.1 ± 12.5 to 95.1 ± 5.1, and 68.6 ± 11.4 to 92.1 ± 6.1 in the KL-1, KL-2, and KL-3 groups, respectively. The JOA score in the KL-3 group was significantly lower than in the other groups. The Lysholm score improved significantly from 62.6 ± 8.8 to 97.7 ± 4.7, 62.1 ± 8.1 to 96.7 ± 4.2, and 59.2 ± 9.2 to 95.8 ± 4.6 in the KL-1, KL-2, and KL-3 groups, respectively. The post-operative Lysholm scores were not significantly different among the groups. There were significant differences in radiographic parameters pre-operatively, but not post-operatively, among the groups. Although there were no significant differences in hinge fracture frequency and OA progression, the KL-3 grade predicted OA progression on multivariate analysis.

CONCLUSIONS

Mid-term results of OWHTO significantly improved. However, clinical score in the KL-3 group was lower than that in the KL-1 and KL-2 groups; radiological OA progression was a risk factor in KL-3.

Early surgical outcomes and influencing factors of high tibial osteotomy

Objective

To investigate the influencing factors of functional recovery after high tibial osteotomy (HTO).

Methods

A retrospective research was carried on 98 patients who underwent HTO between January 2018 and December 2020. In each case, the medial proximal tibial angle (MPTA), joint line convergence angle (JLCA), femoral tibial angle (FTA), hip-knee-ankle (HKA), weight bearing line (WBL) ratio of the knee joint, opening gap, opening angle, American knee society knee score (KSS), US Hospital for Special Surgery (HSS) score, Lysholm score, and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were measured to determine postoperative function and influential factors of pain through logistic regression analysis.

Results

The follow-up time was between 18 and 42 months after operation with an average of 27.66 ± 12.9 per month. Overall functional scores were significantly improved. The influencing factors that may affect the postoperative effect of HTO include age and preoperative WBL ratio of the knee joint (WBL%). After incorporating these two factors into the multivariate logistic regression analysis, for every 1 unit increase in the preoperative WBL%, the probability of postoperative HSS being superior is 1.06 times higher than before [Exp(β): 1.062, 95% CI: 1.01-1.1, p = 0.018]. For every year increase in age, the probability of an excellent HSS score after surgery was 0.84 times higher than that before surgery [Exp(β): 0.843, 95% CI: 0.718-0.989, p = 0.036]. Preoperative WBL% ≥ 14.37 was 17.4 times more likely to be rated as excellent postoperative HSS than that <14.37 [Exp(β): 17.406, 95% CI: 1.621-186.927, p = 0.018].

Conclusion

The postoperative functional scores of the patients significantly improved. Patients with preoperative WBL% ≥ 14.37% had better function after surgery.

Comparison of Clinical and Radiological Outcomes between Calibratable Patient-Specific Instrumentation and Conventional Operation for Medial Open-Wedge High Tibial Osteotomy: A Randomized Controlled Trial

BACKGROUND

High tibial osteotomy (HTO) is an effective surgery in treating medial compartment knee osteoarthritis (KOA) combined with varus deformity. An accurate orthopaedy is the key and challenge to the success of HTO. Therefore, we designed a calibratable patient-specific instrumentation (PSI) to assist surgery and evaluated its accuracy and clinical outcomes by comparing with conventional operation (CO).

MATERIALS AND METHODS

37 patients (39 knees) with medial compartment KOA were randomly divided into the PSI and CO groups and underwent medial open-wedge high tibial osteotomy (MOWHTO) from September 2020 to May 2021. The postoperative radiological outcomes were compared with the preoperative measurements or target values to evaluate the accuracy of correction in the two groups. The American Knee Society Score (AKSS), complication rate, number of intraoperative radiation exposures, blood loss volume, and operative duration were analysed to evaluate the clinical outcomes in the two groups.

RESULTS

The designed target values were better achieved in the PSI group than in the CO group. The mean absolute difference between the postoperative measurements and preoperative targets was significantly lower in the PSI group than in the CO group (weight-bearing line (WBL) ratio, 1.97 ± 1.83% vs.5.42 ± 4.41%, P = 0.002; hip-knee-ankle (HKA) angle, 1.12 ± 0.86° vs. 2.27 ± 1.97°, P = 0.018). The operative duration was significantly shorter (P = 0.014), and the number of radiation exposures (P < 0.001) and volume of intraoperative blood loss (P = 0.003) were significantly lower in the PSI group than in the CO group. The clinical AKSS score at 3 and 6 months postoperatively and the functional AKSS score at 3 months postoperatively were significantly higher in the PSI group than in the CO group (P = 0.042, 0.040, and 0.034, respectively).

CONCLUSION

For patients with medial compartment KOA, calibratable PSI can assist the surgeon in MOWHTO with superior accuracy and clinical efficacy. This study was conducted under Randomized Controlled Trial Details (RCT) with Registry Number ChiCTR2000038619.

[Short-term effectiveness of high tibial osteotomy combined with arthroscopic surgery for knee varus arthritis and the results of secondary arthroscopic exploration]

OBJECTIVE

To investigate the effectiveness of high tibial osteotomy (HTO) combined with arthroscopic surgery to treat medial compartment knee osteoarthritis (KOA) and secondary arthroscopic exploration to evaluate the outcome of cartilage and meniscus.

METHODS

A clinical data of 57 patients with medial compartment KOA with varus deformity of lower extremities admitted between August 2014 and October 2018 were retrospectively analyzed. There were 23 males and 34 females with an average age of 51.2 years (range, 41-63 years). The disease duration ranged from 2 to 8 years, with an average of 4.7 years. The preoperative femorotibial angle was (179.86±4.69)°, the relative position of the lower limb mechanical axis passing through the tibial plateau was 24.21%±6.98%, and the posterior slope of the tibial plateau was (5.23±1.45)°. The Kellgren-Lawrence grade of knee joint was grade Ⅱ in 22 cases and grade Ⅲ in 35 cases. The preoperative Hospital for Special Surgery (HSS) score, Lysholm score, and visual analogue scale (VAS) score were 59.1±7.3, 48.8±7.6, and 6.2±1.1, respectively. Arthroscopic exploration was performed during the operation to record the articular cartilage degeneration in the weight-bearing area of the medial compartment (Outerbridge grade Ⅰ in 18 cases, grade Ⅱ in 30 cases, and grade Ⅲ in 9 cases) and the condition of the medial meniscus injury, and the corresponding treatment was performed. The coronal force line was adjusted according to the preoperative Kellgren-Lawrence grade of the knee joint during the operation. After operation, the relative position of the lower limb mechanical axis passing through the tibial plateau, the femorotibial angle, and the posterior slope of the tibial plateau were measured; the Kellgren-Lawrence grade of the knee joint was recorded; the Outerbridge grade of articular cartilage degeneration and the meniscus outcome were evaluated by combining with the MRI of the knee joint at 1 year after operation and the second arthroscopic exploration when the internal fixator was removed. The function and pain of the knee were evaluated by Lysholm score, HSS score, and VAS score.

RESULTS

All the 57 patients were followed up 36-58 months with an average of 42.1 months. Incisions healed by first intention, and no neurovascular injury, intraarticular or hinge fractures occurred during operation, and no postoperative complications such as deep vein thrombosis of lower limbs and internal fixation failure occurred. All the osteotomy sites healed at 3 months after operation. At 1 year after operation, the internal fixator was removed, and the second arthroscopic exploration showed that there were 15 cases of Outerbridge grade Ⅰ, 31 cases of grade Ⅱ, and 11 cases of grade Ⅲ in the weight-bearing area of the medial compartment, and there was no significant difference when compared with preoperative grade ( Z=31.992, P=0.997); there was no cartilage degeneration in other compartments. Meniscus healing was seen in the injured meniscus, and no injury was seen in the normal meniscus. At last follow-up, there were 19 cases of Kellgren-Lawrence grade Ⅱ and 38 cases of grade Ⅲ, and there was no significant difference when compared with preoperative grade ( Z=49.049, P=0.764). The relative position of the lower limb mechanical axis passing through the tibial plateau was 59.16%±2.87%, and the femorotibial angle was (171.54±3.39)°, which significantly improved when compared with those before operation ( P<0.001). The posterior slope of the tibial plateau was (5.65±1.22)°, which was not significantly different from that before operation ( t=-1.673, P=0.096). The HSS score, Lysholm score, and VAS score were 82.3±7.7, 83.4±6.4, and 1.6±1.1 respectively, which were significantly different from those before operation ( P<0.001).

CONCLUSION

HTO combined with arthroscopic surgery for medial compartment KOA with varus deformity of lower extremities can effectively improve the force line of lower extremities, relieve pain symptoms, and improve joint function, with satisfactory short-term effectiveness, and without significant progress in articular cartilage or meniscus injury after operation.

Undercorrection: the undesired effect of compression on the osteotomy gap of the medial opening wedge high tibial osteotomy and its clinical significance

INTRODUCTION

Undercorrection is a common problem in opening wedge high tibial osteotomy (OWHTO). We investigated the compression effect of cortex screw on the osteotomy gap and its clinical significance.

MATERIALS AND METHODS

A standard OWHTO using the TomoFix plate was conducted on 20 bone models in two groups to get a 10-mm medial osteotomy gap. A cortex screw was used temporarily in a neutral (at the center) and an eccentric position (near the inclined plane) of the dynamic hole in group 1 and group 2, respectively. The mean of undercorrection observed in the two groups was compared using an independent t test. Also, the effect of compression on the gap between the plate and medial tibial cortex, and the osteotomy gap was evaluated using a Sine rule. Besides, the mean undercorrection observed was assessed for clinical significance based on the effect on the weight-bearing axis (WBA) using a Cosine Rule.

RESULTS

The mean undercorrection was 1.3 ± 0.6 mm and 2.6 ± 0.6 mm in group 1 and group 2, respectively. A significantly greater undercorrection was observed in group 2 (p < 0.001). The correction loss in group 2 has resulted from combinations of the sliding effect of the dynamic hole and oblique compression effect over the gap between the plate and medial tibial cortex whereas in group 1 it has only resulted from the oblique compression effect. The observed undercorrection in group 2 has resulted in clinically significant WBA shift (10%) over the width of the tibial plateau.

CONCLUSIONS

In OWHTO, compression is important for the stability and healing of osteotomy, but it can also cause loss of correction. In patients requiring large correction, the surgeon should control the amount of compression required and consider making extra osteotomy gap to avoid undercorrection. Furthermore, the placement of cortex screws in neutral is essential to lower the risk of undercorrection.

Is the lateral tibial spine a reliable landmark for planning tibial or femoral valgus osteotomies?

INTRODUCTION

A valgus osteotomy around the knee is a conservative procedure performed to unload the medial tibiofemoral compartment. However, the optimal postoperative alignment target remains controversial. Many studies have applied a "Fujisawa point" at 62.5%. The results of recent studies suggest decreasing the range of the mechanical axis target correction to 50-55%. The primary purpose of this study was to define the mean position of the lateral tibial spine in healthy patients from a reproducible 3-dimensional (3D) analysis. The study hypothesis was that the apex of the lateral tibial spine was a reliable and reproducible landmark for planning valgus osteotomies and preventing overcorrections.

MATERIALS AND METHODS

The study included 1140 patients: 560 women and 580 men, with a mean age of 61.7±16.5 years (18-98) and a mean body mass index (BMI) of 24.9±4.9kg/m² (13.3-54.6). This analysis was done with the Stryker Orthopaedics Modeling and Analytics (SOMA) system which uses a database of computed tomography (CT) scans and 3D bone models. A statistical assessment was performed to determine the mean position of the lateral tibial spine. These measurements were then compared according to ethnicity, sex, age, BMI, knee side (right and left) and the overall mechanical axis of the leg.

RESULTS

The mean tibial plateau width was 72.9±5.7mm (59.1-91.1). The mean position of the lateral tibial spine was 53.6±1.1% (48.9-57.2). The mean position of the medial tibial spine was 48.4±2.5% (43.6-56.1) while the center of the tibial spines was 51.0±1.5% (46.4-56.1). Africans had a significantly more lateral mean tibial spine position than Asians (54.7% vs. 53.3%, p=0.001), Caucasians (54.7% vs. 53.7%, p=0.002) and Middle Easterners (54.7% vs. 53.6%, p=0.034).

CONCLUSION

The lateral tibial spine is a simple and reproducible bony landmark. This landmark can be used when planning valgus osteotomies aiming for a "Fujisawa point" at 54%.

LEVEL OF EVIDENCE

IV.

A novel 3D-printed patient-specific instrument based on "H-point" for medial opening wedge high tibial osteotomy: a cadaver study

BACKGROUND

Opening wedge high tibial osteotomy (OWHTO) is an effective surgical treatment for knee osteoarthritis. This study aimed to explore the feasibility and accuracy of a novel 3D-printed patient-specific instrument (PSI) based on "H-point" for medial OWHTO in a prospective cadaver study.

METHODS

Twenty-six fresh-frozen lower limbs were collected and randomly divided into two groups: PSI group treated with 3D virtual preoperative planning and a novel 3D-printed PSI; control group with the standard technique. 3D models were reversely reconstructed for preoperative surgical planning, guide plate design, and simulated osteotomy. Anatomic features of "H-point," surgical time, fluoroscopic dose, correction accuracy including tibiofemoral angle (FTA) and posterior tibial slope (TS) angle were measured.

RESULTS

First, H-point was always described as a bony bulge in the posteromedial to the proximal tibia and had a relatively constant relationship with the osteotomy site. Second, the absolute correction error of mFTA and TS were significantly smaller in the PSI group. The effective rate of TS in the PSI group was more concentrated with absolute correction error within 1° and within 2° for 53.3% and 93.3%, compared to 9.1% and 45.5% in the control group. The total operation time, positioning osteotomy time, distraction correction time and fluoroscopy dose in the PSI group were significantly less than those in the control group.

CONCLUSIONS

The novel 3D-printed PSI based on H-point is feasibility and accuracy with advantages in terms of TS, surgery time and radiation dose for OWHTO.

How to achieve an optimal alignment in medial opening wedge high tibial osteotomy?

Medial opening wedge high tibial osteotomy (MOWHTO) is a widely used surgical treatment option for medial compartmental osteoarthritis with varus deformity. It is important that proper lower limb alignment is achieved. However, there has been no consensus about an optimal alignment in MOWHTO. Most studies suggest that achieving valgus alignment is necessary, and recent studies support slight valgus mechanical alignment of less than 3° of mechanical femorotibial angle. Overcorrection and undercorrection is not recommended for achieving good surgical outcomes. To prevent undercorrection and overcorrection in MOWHTO, the method of placing the weight-bearing line in the target range must be precise. There are several ways to place a weight-bearing line within the target range. While the most important factor for a successful MOWHTO is achieving an ideal mechanical axis correction, there are a few other factors to consider, including joint line obliquity, posterior tibial slope, ligament balancing, and patellar height. Several factors exist that lead to undercorrection and overcorrection. Preoperative amount of varus deformity, lateral hinge fracture, and fixation failure can result in undercorrection, while medial soft tissue laxity and the amount of correction angle and target point beyond hypomochlion can result in overcorrection. This study aimed to review the literature on optimal alignment in MOWHTO and report on the factors to be considered to prevent correction errors and how to achieve an optimal alignment.

COMPARISON OF CHANGES IN THE ANKLE AFTER UNICONDYLAR KNEE ARTHROPLASTY AND HIGH TIBIAL OSTEOTOMY

Objectives:

We aimed to compare the changes in the coronal alignment of the ankle joints and their clinical effects after high tibial osteotomy (HTO) and unicondylar knee arthroplasty (UKA).

Methods:

50 HTO and 54 UKA patients who were operated on for medial knee osteoarthritis between 2013 and 2018 were retrospectively evaluated. The hip-knee-ankle angle (HKA), the medial proximal tibial angle (MPTA), the tibial plafond inclination (TPI) and the talar inclination (TI) angles were measured before and after operation. Visual analog scale (VAS), short form 36 (SF-36), and ankle-hindfoot scale (AHS) scores of both groups were evaluated and recorded.

Results:

Angular changes in the HKA, MPTA, TPI and TI values showed significantly greater values in the HTO group (p<0.001). When asymptomatic and symptomatic cases were compared, it was found that changes in the HKA, TPI and TI values were significantly greater in symptomatic cases in the HTO group (p<0.05). A significant decline was observed in the VAS, SF-36 and AHS scores in the HTO group in the postoperative period (p<0.05). In intergroup evaluations, a significant decline was detected in pain and functional scores of the HTO group when compared to the UKA group (p<0.05).

Conclusion:

Unicondylar knee arthroplasty can be a good alternative to HTO in selected cases for postoperative ankle complaints. Level of Evidence III; Therapeutic Studies Investigating the Results of Treatment.

Feasibility and 3D Planning of a Novel Patient-Specific Instrumentation Technique in Medial Opening-Wedge High Tibial Osteotomy

A novel approach for opening-wedge high tibial osteotomy (OWHTO) with patient-specific instrumentation (PSI) was evaluated for its safety, feasibility, and accuracy. Next, the mechanical medial proximal tibial angle (mMPTA) was assessed as a potential planning angle by investigating the relation with the mechanical femorotibial angle (mFTA). Ten OWHTO cases were 3D planned using the mMPTA and operated with a customized 3D-printed wedge and cast which resembled the intended osteotomy opening. Patients were closely monitored for intraoperative and postoperative complications up to 1 year after surgery. Radiological assessment was conducted on full leg standing radiographs and supine lower limb computed tomography-scans preoperatively and 3 months after surgery. No intraoperative complications or logistical issues during PSI processing were observed. Absolute accuracy outcomes showed a correction error of 1.3° ± 1.1 mMPTA and 0.9° ± 0.6 mFTA with all osteotomies falling in (-2°; + 2°) mFTA around the target. The mMPTA and mFTA were found to have a strong correlation in both 3D (r = 0.842, p = 0.002) and 2D (r = 0.766, p = 0.01) imaging for effective correction. The study confirmed the development of a safe and feasible PSI technique in OWHTO with excellent accuracy outcomes. The strong correlation between the mMPTA and mFTA indicated that soft tissue changes after OWHTO are of minor significance to the final alignment in ligament-stable patients. Finally, the mMPTA was found to be a reliable planning angle in 3D software for obtaining the intended lower limb realignment and its use can therefore be recommended in modern OWHTO planning.

A Systematic Review on Selected Complications of Open-Wedge High Tibial Osteotomy from Clinical and Biomechanical Perspectives

BACKGROUND

The wedge opened during high tibial osteotomy defines the alignment correction in different body planes and alters soft tissue insertions. Although multiple complications of the surgery can be correlated to this, there is still a lack of consensus on the occurrence of those complications and their cause. The current study is aimed at clarifying this problem using a combined medical and biomechanical perspective.

METHODS

We conducted a systematic review of the literature on selective complications of the surgery correlated with the angles of the opened wedge. Search topics covered tibial slope alteration, patellar height alteration, medial collateral ligament release, and model-based biomechanical simulations related to surgical planning or complications. Findings. The selection process with the defined inclusion/exclusion criteria led to the collection of qualitative and quantitative data from 38 articles. Medial collateral ligament tightness can be a valid complication of this surgery; however, further information about its preoperative condition seems required for better interpreting the results. The posterior tibial slope significantly increases, and the patellar height (using the Blackburne-Peel ratio) significantly decreases in the majority of the selected studies. Model-based biomechanical studies targeting surgical planning are mostly focused on the lower-limb alignment principles and tibiofemoral contact balancing rather than surgical complications. Interpretation. Increased posterior tibial slope, patellar height decrease, and medial collateral ligament tightness can occur due to alterations in different body planes and in soft tissue insertions after wedge opening. This study clarified that information about preoperative alignment in all body planes and soft-tissue conditions should be considered in order to avoid and anticipate these complications and to improve per surgery wedge adaptation. The findings and perspective of this review can contribute to improving the design of future clinical and biomechanical studies.

[Clinical application of split three-dimensional printing patient-specific instrumentation in medial open-wedge high tibial osteotomy]

Objective

To investigate the accuracy of split three-dimensional (3D) printing patient-specific instrumentation (PSI) in medial open-wedge high tibial osteotomy (MOWHTO) and its effectiveness in treating medial knee osteoarthritis.

Methods

Clinical data of 14 patients with medial knee osteoarthritis and treated with split 3D printing PSI-assisted MOWHTO between August 2019 and August 2020 were retrospectively analyzed. There were 5 males and 9 females with an average age of 61 years (range, 43-68 years). The disease duration ranged from 1 to 16 years, with an average of 4.7 years. Preoperative Kellgren-Lawrence grading of knee osteoarthritis included grade Ⅰ in 2 cases, grade Ⅱ in 6 cases, and grade Ⅲ in 6 cases. The Hospital for Special Surgery (HSS) score was 59.1±4.9. The weight bearing line ratio (WBL), hip-knee-ankle angle (HKA), medial proximal tibial angle (MPTA), posterior tibial slope angle (PTSA), and actual correction angle of the lower limbs were measured on postoperative imaging data, and compared with the preoperative measurements and the designed target values to evaluate the accuracy of the PSI-assisted surgery. The patients' knee function were evaluated with the HSS score at 3 and 6 months postoperatively, and at last follow-up.

Results

One patient suffered from an incision exudation at 2 weeks postoperatively, and the incision healed after symptomatic treatment. The incisions of other patients healed by first intention. All patients were followed up 7-19 months (mean, 14.8 months). There was no neural injuries, hinge fracture, plate or screw fractures, loosening, or other complications. The WBL was maintained at the postoperative level according to the X-ray examination during the follow-up period. The WBL, HKA, MPTA, and PTSA were all within a satisfactory range after operation. The WBL, HKA, and MPTA were significantly improved when compared with the preoperative measurements ( P<0.05). There was no significant difference between preoperative and postoperative PTSA ( P>0.05). The differences in postoperative WBL, HKA, MPTA, and correction angle compared with the preoperative designed target values were not significant ( P>0.05). The HSS scores were 69.2±4.7, 77.7±4.3, and 88.1±5.4 at 3 and 6 months postoperatively, and last follow-up, respectively. The differences between time points were significant ( P<0.05).

Conclusion

For patients with medial knee osteoarthritis, the split 3D printing PSI can assist the surgeon in MOWHTO with accurate osteotomy orthopedics and achieve favorable effectiveness.

Lateral tibial intercondylar eminence is a reliable reference for alignment correction in high tibial osteotomy

PURPOSE

The purpose of the study is to determine whether the lateral tibial intercondylar eminence (LTIE) is a reliable reference for alignment correction in high tibial osteotomy (HTO).

METHODS

A total of 1954 consecutive standing whole-leg radiography (WLR) examinations of 1373 adult patients with knee osteoarthritis between 2012 and 2019 were reviewed retrospectively; 145 patients were included, 53 males and 92 females, with a mean age of 63.3 years. Virtual simulation of HTO was performed to measure weight-bearing line (WBL) percentages and hip-knee-ankle (HKA) angles when the WBL passed through the Fujisawa, top, bottom, upper 1/3, and middle points of the lateral slope of the LTIE, and the positional relationship between the Fujisawa point and the lateral slope of the LTIE was determined.

RESULTS

When the WBL passed through the top, bottom, upper 1/3, and middle points of the lateral slope of the LTIE, the mean WBL percentages were 57.7% ± 2.1%, 74.6% ± 3.3%, 63.4% ± 2.1%, and 66.2% ± 2.3%, respectively, and the mean HKA angles were 182.1° ± 0.5°, 185.9° ± 0.8°, 183.3° ± 0.5°, and 184.0° ± 0.5°, respectively. When the WBL passed through the Fujisawa point, it was passing through 28.6% ± 12.7% of the width of the lateral slope (the top and bottom points were defined as 0% and 100%, respectively). When the WBL passed through the middle and upper 1/3 points of the lateral slope of the LTIE, the majority of cases (96.1%-100%) were within the limits of acceptability, as defined by the widely accepted standard of a postoperative HKA angle ranging from 183° to 186°.

CONCLUSION

The upper 1/3 and middle points of the lateral slope of the LTIE are reliable references for guiding the alignment correction in HTO. In clinical application, if 62%-66% of the postoperative WBL percentage is the acceptable target range, the upper 1/3 point of the lateral slope of the LTIE may be a better alternative than the midpoint. If the postoperative HKA angle between 183° and 186° is acceptable, the midpoint of the lateral slope of the LTIE may be better than the upper 1/3 point. These findings are crucial for the accuracy of the traditional intraoperative alignment assessment techniques.

LEVEL OF EVIDENCE

IV.

Towards planning of osteotomy around the knee with quantitative inclusion of the adduction moment: a biomechanical approach

PURPOSE

Despite practised for decades, the planning of osteotomy around the knee, commonly using the Mikulicz-Line, is only empirically based, clinical outcome inconsistent and the target angle still controversial. A better target than the angle of frontal-plane static leg alignment might be the external frontal-plane lever arm (EFL) of the knee adduction moment. Hypothetically assessable from frontal-plane-radiograph skeleton dimensions, it might depend on the leg-alignment angle, the hip-centre-to-hip-centre distance, the femur- and tibia-length.

METHODS

The target EFL to achieve a medial compartment force ratio of 50% during level-walking was identified by relating in-vivo-measurement data of knee-internal loads from nine subjects with instrumented prostheses to the same subjects' EFLs computed from frontal-plane skeleton dimensions. Adduction moments derived from these calculated EFLs were compared to the subjects' adduction moments measured during gait analysis.

RESULTS

Highly significant relationships (0.88 ≤ R2 ≤ 0.90) were found for both the peak adduction moment measured during gait analysis and the medial compartment force ratio measured in vivo to EFL calculated from frontal-plane skeleton dimensions. Both correlations exceed the respective correlations with the leg alignment angle, EFL even predicts the adduction moment's first peak. The guideline EFL for planning osteotomy was identified to 0.349 times the epicondyle distance, hence deducing formulas for individualized target angles and Mikulicz-Line positions based on full-leg radiograph skeleton dimensions. Applied to realistic skeleton geometries, widespread results explain the inconsistency regarding correction recommendations, whereas results for average geometries exactly meet the most-consented "Fujisawa-Point".

CONCLUSION

Osteotomy outcome might be improved by planning re-alignment based on the provided formulas exploiting full-leg-radiograph skeleton dimensions.

Hinge location and apical drill holes in opening wedge high tibial osteotomy: A finite element analysis

At the time of medial opening wedge high tibial osteotomy (HTO) to realign the lower limb and offload medial compartment knee osteoarthritis, unwanted fractures can propagate from the osteotomy apex. The aim of this study was to use finite element (FE) analysis to determine the effect of hinge location and apical drill holes on cortical stresses and strains in HTO. A monoplanar medial opening wedge HTO was created above the tibial tuberosity in a composite tibia. Using the FE method, intact lateral hinges of different widths were considered (5, 7.5, and 10 mm). Additional apical drill holes (2, 4, and 6 mm diameters) were then incorporated into the 10 mm hinge model. The primary outcome measure was the maximum principal strain in the cortical bone surrounding the hinge axis. Secondary outcomes included the force required for osteotomy opening, minimum principal strain, and mean cortical bone stresses (maximum principal/minimum principal/von Mises). Larger intact hinges (10 mm) were associated with higher cortical bone maximum principal strain and stress, lower minimum principal strain/stress, and required greater force to open. Lateral cortex strain concentrations were present in all scenarios, but extended to the joint surface with the 10 mm hinge. Apical drill holes reduced the mean cortical bone maximum principal strain adjacent to the hinge axis: 2 mm hole 6% reduction; 4 mm 35% reduction; and 6 mm 55% reduction. Incorporating a 4-mm apical drill hole centered 10 mm from the intact lateral cortex maintains a cortical bone hinge, minimizes cortical bone strains and reduces the force required to open the HTO; thus improving control.

Medial joint space width and convergence angle change with time after medial opening-wedge high tibial osteotomy

BACKGROUND

Although the medial joint space width (MJSW) is commonly used for radiographic evaluation of knee osteoarthritis, the changes in knee joint space width (JSW) during weight bearing after medial opening-wedge high tibial osteotomy (MOWHTO) remain unclear. This study aimed to depict how medial and lateral JSWs and convergence angles change gradually after MOWHTO.

METHODS

We retrospectively followed up 81 MOWHTO cases for over 45 months on average. Pre- and postoperative mechanical axes were recorded. The JSWs and convergence angles were measured preoperatively, immediately postoperatively, and 3-6, 9-12, and 21-24 months postoperatively. Patient-reported outcomes were measured using a visual analogue scale (VAS).

RESULTS

The mean mechanical femoral-tibial angle improved from 8.1° varus to 2.4° valgus. At the aforementioned times, the respective mean values of MJSW were 2.6, 3.5, 3.8, 4.0, and 4.2 mm; mean convergence angles were 4.8°, 2.9°, 2.2°, 2.1°, and 1.9°; and the mean VAS scores were 7.2, 7.8, 4.8, 1.4, and 1.3. The MJSW continued to increase significantly in the first year postoperatively and then plateaued for a minimum of 2 years follow up after MOWHTO. The convergence angle decreased significantly in the first 6 months postoperatively and was then maintained.

CONCLUSIONS

The MJSW, convergence angle, and VAS scores continued to improve through weight bearing during the first year after MOWHTO and were maintained for at least 2 years. Thus, JSW measurement may be an easy and representative way of radiographically monitoring the effect of MOWHTO.

3D-Printed Patient-Specific Instrumentation Technique Vs. Conventional Technique in Medial Open Wedge High Tibial Osteotomy: A Prospective Comparative Study

Purpose

The purpose of this study was to compare the accuracy and clinical outcomes of the medial open wedge high tibial osteotomy (MOWHTO) using a three-dimensional (3D-) printed patient-specific instrumentation (PSI) with that of conventional surgical techniques.

Methods

A prospective comparative study which included 18 patients who underwent MOWHTO using 3D-printed PSI technique (3D-printed group) and 19 patients with conventional technique was conducted from Jan 2019 to Dec 2019. After the preoperative planning, 3D-printed PSI (cutting guide model) was used in MOWHTO for 3D-printed group, while freehand osteotomies were adopted in the conventional group. The accuracy of MOWHTO for each method was compared using the radiological index obtained preoperatively and postoperatively, including mechanical femorotibial angle (mFTA) and medial mechanical proximal tibial angle (mMPTA), and correction error. Regular clinical outcomes were also compared between the 2 groups.

Results

The correction errors in the 3D-printed group were significantly lower than the conventional group (mFTA, 0.2° ± 0.6° vs. 1.2° ± 1.4°, P = 0.004) (mMPTA, 0.1° ± 0.4° vs. 2.2° ± 1.8°, P < 0.00001). There was a significantly shorter duration (P < 0.00001) and lower radiation exposures (P < 0.00001) for the osteotomy procedure in the 3D-printed group than in the conventional group. There were significantly higher subjective IKDC scores (P = 0.009) and Lysholm scores (P = 0.03) in the 3D-printed group at the 3-month follow-up, but not significantly different at other time points. Fewer complications occurred in the 3D-printed group.

Conclusions

With the assistance of the 3D-printed patient-specific cutting guide model, a safe and feasible MOWHTO can be conducted with superior accuracy than the conventional technique.

Medial opening wedge high tibial osteotomy: more than ten years of experience with Puddu plate technique supports its indication

PURPOSE

To describe the short-term and long-term results of patients who underwent a medial opening wedge high tibial osteotomy (MOW-HTO) for unicompartmental medial knee joint osteoarthritis.

METHODS

A retrospective review was conducted of patients with MOW-HTO using a Puddu plate®, with more than ten year follow-up. The degree of correction, initial chondral damage, number of meniscal lesions, preoperative and 1-year postoperative functional scale scores (IKDC and Lysholm), and arthroplasty conversion rates at the ten year follow-up were registered. We assumed early indication when patients underwent the operation before they were 40 years old and delayed ≥ 40. Functional outcomes were analyzed by adjusting for pre-operative values. Fisher's exact test was used to study the association between the arthroplasty conversion rates and the timing of indication.

RESULTS

Fifty-five patients were included, 37 of whom were male (67%). Twenty-nine patients had early indications for surgery (53%). All patients completed ten year follow-up. All patients improved IKDC (p < 0.01) and Lysholm (p < 0.01) scores compared to their presurgical scores at the one year post-operative evaluation. We had six minor complications, none requiring revision surgery. We had three conversions to arthroplasty, all in the late indication group, not statistically significant different. Linear regression showed that early indication was associated with a higher IKDC score when adjusting for the Outerbridge chondral damage score, the number of meniscal lesions, and sex (p < 0.01).

CONCLUSION

All patients improved functional scores one year after surgery. Early indication (i.e., younger than 40 years of age) was independently associated with better functional outcomes than late indication at one year follow-up.

Predicting the knee adduction moment after high tibial osteotomy in patients with medial knee osteoarthritis using dynamic simulations

BACKGROUND

High tibial osteotomy (HTO) is a surgical treatment for knee osteoarthritis, which alters the load distribution in the tibiofemoral joint. To date, all surgical planning methods are based on radiographs, which do not consider the loading characteristics during ambulation. This study aimed to develop and validate a simulation tool for predicting the knee adduction moment (KAM) expected after a HTO using the patient pre-operative gait analysis data and dynamic simulations.

METHODS

Ten patients selected for a HTO underwent a gait analysis before surgery. Pre-operative gait data along with the planned correction angle were used for simulation of the KAM expected after leg realignment. After surgery, the same procedures of gait analysis were performed and post-operative KAM was compared to the simulation results.

RESULTS

Significant reductions of the KAM were observed after surgery. During gait at 1.2 m/s, means of the 1st peak KAM were 3.19 ± 1.03 (standard deviation), 1.21 ± 0.80 and 1.21 ± 0.71% BW × Ht for the conditions pre-operative, post-operative and simulation, respectively. Mean root-mean-square error for the KAM was 0.45% BW × Ht (range: 0.23-0.78% BW × Ht) and Lin's concordance coefficient for the 1st peak KAM was 0.813. An individual analysis showed high agreement for several patients and lower agreement for others. Possible changes in gait pattern after surgery may explain this variability.

CONCLUSION

A novel approach for surgical planning based on dynamic loading of the knee during ambulation is presented. The simulation tool is based on patient-specific gait characteristics and may improve the surgical planning procedures used to date.

High Tibial Osteotomy: Review of Techniques and Biomechanics

High tibial osteotomy becomes increasingly important in the treatment of cartilage damage or osteoarthritis of the medial compartment with concurrent varus deformity. HTO produces a postoperative valgus limb alignment with shifting the load-bearing axis of the lower limb laterally. However, maximizing procedural success and postoperative knee function still possess many difficulties. The key to improve the postoperative satisfaction and long-term survival is the understanding of the vital biomechanics of HTO in essence. This review article discussed the alignment principles, surgical technique, and fixation plate of HTO as well as the postoperative gait, musculoskeletal dynamics, and contact mechanics of the knee joint. We aimed to highlight the recent findings and progresses on the biomechanics of HTO. The biomechanical studies on HTO are still insufficient in the areas of gait analysis, joint kinematics, and joint contact mechanics. Combining musculoskeletal dynamics modelling and finite element analysis will help comprehensively understand in vivo patient-specific biomechanics after HTO.