Bone mineral density around the knee after open wedge high tibial osteotomy measured up to 24 months in 51 patients.

PURPOSE: To evaluate bone mineral density (BMD) and radiographic and clinical outcomes of patients with varus knee osteoarthritis treated with open wedge high tibial osteotomy (OWHTO). We hypothesised that medial condyle BMD would decrease and lateral condyle BMD would increase after OWHTO. METHODS: Overall, 51 patients (mean age: 65.3 years; female: 40, male: 11) treated with OWHTO were prospectively enrolled. Several angles using whole single-leg radiographs were measured preoperatively and up to 24 months postoperatively. Five square tibial regions of interest (ROI) located below the proximal tibia as T1-T5 from medial to lateral regions and two square femoral ROI as F1 and F2 from medial and lateral regions, respectively, were defined. M/L BMD ratio was used to define the medial-to-lateral condyle BMD ratio. Femoral condyle BMD (F1 and F2) around the knee, as well as lumbar spine, and ipsilateral and contralateral femoral neck BMD, were measured before OWHTO and 3, 6, 12 and 24 months after OWHTO using dual-energy X-ray absorptiometry. Furthermore, tibial condyle BMD (T1-T5) around the knee was measured before and 24 months after OWHTO. Clinical outcomes were evaluated using the Knee Society knee and function scores, the Knee Injury and Osteoarthritis Outcome Score, and the Lysholm score preoperatively and 24 months postoperatively. A power analysis was performed. RESULTS: F1 BMD decreased by 19.2% from before to 3 months postoperatively. F2 BMD did not change up to 24 months after OWHTO. Femoral M/L BMD ratio decreased by 22.2% 3 months after OWHTO. T1 BMD and tibial M/L BMD ratio decreased, whilst T3, T4 and T5 BMD increased 24 months after OWHTO. Mean hip-knee-ankle angle (HKA) and weight-bearing line ratio were corrected from - 6.8° to 4.5° and 14.7 to 60.7%, respectively, postoperatively. Lumbar spine BMD did not change up to 12 months postoperatively. Ipsilateral femoral neck BMD decreased up to 6 months after OWHTO. CONCLUSION: Medial femoral condyle BMD decreased rapidly within 3 months and continued to decrease up to 12 months, but lateral femoral condyle BMD did not change after OWHTO. BMD measurements around the knee condyle enabled the evaluation of the changes in stress distribution before and after OWHTO with accelerated rehabilitation. LEVEL OF EVIDENCE: II.

Can double-level osteotomy prevent patellofemoral osteoarthritis progression compared with open wedge high tibial osteotomy?

PURPOSE: To compare radiographic, clinical, and arthroscopic findings in patellofemoral (PF) osteoarthritis (OA) between open wedge high tibial osteotomy (OWHTO) and double-level osteotomy (DLO) with the same operative indication. METHODS: After adjustment for patient age, and coronal alignment, 36 knees with OWHTO alone and 36 knees with DLO were compared. Radiographic, clinical, and arthroscopic findings were documented before osteotomy. Arthroscopic findings were observed 1 year after osteotomy, and clinical and radiographic findings were observed 2 years after osteotomy. Patellar height was evaluated using the Insall-Salvati (IS) ratio, Carton-Deschamps (CD) index, and Blackburne-Peel (BP) index. Lateral patellar tilt and patellar shift were measured. A power analysis was performed. RESULTS: The postoperative CD and BP indices in the OWHTO group were lower than those in the DLO group (p < 0.001 and p = 0.001, respectively). The CD and BP indices in both groups significantly decreased postoperatively (all p < 0.001). Tilting angles in the OWHTO and DLO groups significantly decreased postoperatively (p < 0.001 and p = 0.002, respectively). There were no significant differences in American Knee Society scores, Kujala score, and the Knee Injury and Osteoarthritis Outcome Scores between both groups. The PF OA progression of the trochlear in the OWHTO group was higher than that in the DLO group (p = 0.002), and the PF OA progression of the patellar facet in the DLO group and anterior femoral condyle in both groups on the lateral side were higher than those on the medial side (p = 0.006, 0.032, and 0.041, respectively). CONCLUSIONS: DLO decreased the rate of low patellar height compared with OWHTO. DLO decreased the rate of PF OA progression in the trochlea compared with OWHTO. There were no significant differences in clinical outcomes in both groups. LEVEL OF EVIDENCE: Level III, case-control study.

The relationship between the ''Fujisawa point'' and anatomical femorotibial angle following simulated open wedge high tibial osteotomy.

BACKGROUND: We evaluated the relationship between the weight-bearing line (WBL) ratio and anatomical femorotibial angle (FTA) by simulated open wedge high tibial osteotomy (OWHTO). This study evaluated the correlation between the ''Fujisawa point'' and FTA, and identified factors which caused deviations between the two measurement methods. We hypothesized that the Fujisawa point corresponded with 170° of the FTA. METHODS: Preoperative antero-posterior full-length lower limb radiographs of 82 patients were obtained for the OWHTO to place the WBL ratio at a target of 62.5% of the width of the tibial plateau (Fujisawa point). The coronal alignment was measured pre- and post-planning. The patients were divided into two groups by the post-planning FTA: a correspondence group (168.5°â‰¦FTA≦171.5°) and a non-correspondence group (FTA < 168.5°, 171.5° < FTA). The relationship between the Fujisawa point and the FTA was analyzed with multivariate regression analysis. RESULTS: The post-planning FTA was 169.8 ± 1.1° and within 170 ± 1.5° in 69 cases (84.1%) when the WBL ratio was 62.5%. The neck shaft angle was 128.1 ± 5.2° in the correspondence group, and 122.3 ± 6.3° in the non-correspondence group. The multivariate linear regression analysis revealed that the neck shaft angle was the only factor that predicted the correspondence of the Fujisawa point with the FTA at 170° (p = 0.006, odd 1.28). CONCLUSIONS: The post-planning FTA converged at 170° when the WBL ratio passed through the Fujisawa point and the neck shaft angle was the only predictor.

Joint line obliquity was maintained after double-level osteotomy, but was increased after open-wedge high tibial osteotomy.

PURPOSE: To compare the radiographic, clinical, and arthroscopic outcomes of varus osteoarthritic knees treated with an open-wedge high tibial osteotomy (OWHTO) alone or with a double-level osteotomy (DLO). It was hypothesized that treatment with DLO would maintain the joint line obliquity (JLO) and acquire better arthroscopic and clinical outcomes after surgery than OWHTO alone. METHODS: Knees with predicted medial proximal tibial angle (MPTA) > 95° were treated with OWHTO alone or with DLO. Preoperatively, age, body mass index, and hip-knee-ankle angle (HKA) differed between the two groups. Therefore, after adjustment for those factors, 34 knees with OWHTO alone and 34 knees with DLO were compared. On whole-leg radiographs for a single leg, HKA, weightbearing line (WBL) ratio, lateral distal femoral angle (LDFA), MPTA, and JLO were measured before and 2 years after surgery. Clinical outcomes were evaluated by the Knee Society Score (KSS) knee, KSS function, Lysholm, and Knee injury and Osteoarthritis Outcome Score (KOOS) scores before and 2 years after surgery. Arthroscopic findings were obtained before and 1 year after surgery. Various factors were compared between the two groups. RESULTS: JLO increased significantly from 1.4° to 6.3° in the OWHTO group (p < 0.001) and changed from 1.0° to 1.3° in the DLO group (n.s.). Postoperative MPTA and JLO in the OWHTO group were significantly higher than those in the DLO group (both p < 0.001). There were no significant differences in the KSS knee, KSS function, and KOOS scores between the two groups. Postoperative Lysholm score in the DLO group was higher than that in the OWHTO group (p < 0.025). Femoral and tibial cartilage regeneration in the medial condyles and deterioration in the lateral condyles did not differ between the two groups on second-look arthroscopy. CONCLUSIONS: JLO was not significantly changed after surgery in the DLO group. DLO enabled the acquisition of physiological JLO compared with OWHTO alone. LEVEL OF EVIDENCE: Retrospective comparative study, Level III.

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

INTRODUCTION: 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. MATERIALS AND METHODS: 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. RESULTS: 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). CONCLUSIONS: 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 OF EVIDENCE: Level III, retrospective comparative study.

Relationship between lower limb torsion and coronal morphologies of the femur and tibia in patients with medial knee osteoarthritis.

BACKGROUND: To investigate the relationship between femoral or tibial torsion and hip-knee-ankle angle (HKA), mechanical lateral distal femoral angle (mLDFA), or mechanical medial proximal tibial angle (mMPTA) in patients with medial knee osteoarthritis (OA). METHODS: A total of 75 knees were enrolled. Femoral and tibial torsions were measured by superimposing the axial planes of computed tomography images. The relationship between femoral or tibial torsion and HKA, mLDFA, or mMPTA on radiographs was examined. RESULTS: The mean femoral torsion was 12.2 ± 8.5° internally; femoral internal and external torsions were observed in 70 and 5 knees, respectively. The mean tibial external torsion was 18.0 ± 7.4° externally; tibial external torsion was observed in all 75 knees. Femoral internal and tibial external torsions increased with lower mMPTA (r = 0.33, P = 0.003; r = - 0.32, P = 0.005, respectively) but were not related to HKA or mLDFA. CONCLUSION: Femoral and tibial torsions were correlated with varus inclination of the proximal tibia in patients with medial knee OA.

Joint line convergence angle predicts outliers of coronal alignment in navigated open-wedge high tibial osteotomy.

INTRODUCTION: Using a navigation system in open-wedge high tibial osteotomy (OWHTO) has higher accuracy than using the conventional method. However, unintentional over- and under-correction still exist. This study aimed to compare various factors related to over- and under-correction and to assess their predictive factors in the preoperative radiographs. MATERIALS AND METHODS: This study involved 96 knees. The difference in the hip-knee-ankle angle (HKA) between the intraoperative navigation system and postoperative radiograph was termed navigation correction loss (NCL). Knees with absolute values of NCL (|NCL|) ≦ 1.5° and |NCL| > 1.5° were categorised into acceptable (n = 46) and outlier (n = 50) groups, respectively. The differences in joint line convergence angle (JLCA) between varus and valgus radiographs, varus JLCA, valgus JLCA, standing JLCA and standing HKA were compared between the two groups. Clinical results were evaluated using the American Knee Society (AKS) scores. RESULTS: The mean intraoperative HKA in the navigation system was - 3.8 ± 1.8°, and that in the postoperative standing radiograph was - 4.2 ± 2.5° (p = 0.033). Preoperative varus, valgus and standing JLCA were higher in the outlier group (p = 0.018, p = 0.020 and p = 0.001, respectively). Logistic regression analyses for preoperative factors of |NCL| ≦ 1.5° showed that standing JLCA was a determining factor, with an odds ratio of 1.334 (confidence interval was 1.087-1.637, p = 0.006). AKS score was higher in the acceptable group (p = 0.040) postoperatively. CONCLUSIONS: Higher preoperative standing JLCA was the predictive factor of |NCL| > 1.5°. This factor reduced the rates of under- and over-correction and resulted in better AKS score in OWHTO.

Mosaic Osteochondral Autograft Transplantation Versus Bone Marrow Stimulation Technique as a Concomitant Procedure With Opening-Wedge High Tibial Osteotomy for Spontaneous Osteonecrosis of the Medial Femoral Condyle.

PURPOSE: To evaluate the effects of osteochondral autograft transplantation (OAT) mosaicplasty as a concomitant procedure with opening-wedge valgus high tibial osteotomy (HTO) for spontaneous osteonecrosis of the medial femoral condyle (MFC) on clinical outcomes and cartilage status in comparison with bone marrow stimulation (BMS) by drilling, and to assess the relation between lesion size and postoperative cartilage status. METHODS: Fifty-eight patients with spontaneous osteonecrosis of the MFC were treated with opening-wedge HTO and a concomitant procedure of BMS (28 patients) or OAT (30 patients). Clinical evaluation was carried out using the Knee Society Score at postoperative 2 years. Postoperative status of articular cartilage was assessed by arthroscopy according to the International Cartilage Repair Society (ICRS) grade at the time of plate removal. RESULTS: The Knee Society Score objective score and function score were improved at postoperative 2 years compared with preoperative value in both groups, but no significant difference was found between the 2 groups. According to the ICRS overall repair grade, cartilage status was rated as normal or nearly normal (ICRS overall score ≥8) in 41% of the BMS group and 90% of the OAT group. The results suggested that cartilage repair in OAT was significantly better than that in BMS (P = .0015). Furthermore, the BMS group revealed that repair with normal or nearly normal was observed in all less than 4 cm2 of lesion size, whereas the OAT group exhibited that repair with normal or nearly normal was independent of lesion size. CONCLUSIONS: This study suggested that OAT is superior to BMS as a concomitant procedure with opening-wedge valgus HTO for spontaneous osteonecrosis of the MFC in the success of cartilage repair. However, clinical outcomes were not significantly different between these 2 procedures. When treating the lesion larger than 4 cm2 by joint-preserving surgery, OAT mosaicplasty is recommended as a concomitant procedure with HTO. LEVEL OF EVIDENCE: Level III, therapeutic case-control study.

Effect of Increased Coronal Inclination of the Tibial Plateau After Opening-Wedge High Tibial Osteotomy.

PURPOSE: To assess whether the increased inclination of the tibial plateau on the coronal view after opening-wedge high tibial osteotomy affects radiographic coronal alignment, clinical outcomes, and cartilage findings. METHODS: After adjustment for the preoperative medial proximal tibial angle (MPTA), patients who underwent opening-wedge high tibial osteotomy were retrospectively divided into those with postoperative MPTA values of 95° or less (normal group) and greater than 95° (increased group), with each group containing 43 knees. The 2 groups were compared regarding their arthroscopic cartilage findings at 1 year postoperatively and radiographic coronal alignment and clinical outcomes at 2 years postoperatively. Cartilage regeneration in the medial condyles and cartilage deterioration in the lateral condyles were evaluated at the time of second-look arthroscopy. Clinical outcomes were evaluated by the American Knee Society knee and function scores, Lysholm knee scoring scale, and Knee Injury and Osteoarthritis Outcome Score (KOOS). RESULTS: The postoperative anatomic femorotibial angle in the increased group was lower than that in the normal group (P < .001), and the amount of overcorrection in the increased group was higher than that in the normal group (P < .001). The postoperative joint line obliquity in the increased group was higher than that in the normal group (P < .001). Cartilage regeneration in the medial condyles and deterioration in the lateral condyles did not differ significantly on the femoral and tibial sides between the groups. The postoperative American Knee Society knee score and KOOS sports and recreational function subscale score in the normal group were higher than those in the increased group (both P < .001). CONCLUSIONS: There were no significant differences in the changes in the appearance of the articular surfaces between the 2 groups at 1 year postoperatively. Patients with a postoperative MPTA greater than 95° had more valgus alignment and higher joint line obliquity and had a lower KOOS sports and recreational function subscale score than patients with a postoperative MPTA of 95° or less at 2 years postoperatively. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Combined CT-based and image-free navigation systems in TKA reduces postoperative outliers of rotational alignment of the tibial component.

INTRODUCTION: Rotational malpositioning of the tibial component can lead to poor functional outcome in TKA. Although various surgical techniques have been proposed, precise rotational placement of the tibial component was difficult to accomplish even with the use of a navigation system. The purpose of this study is to assess whether combined CT-based and image-free navigation systems replicate accurately the rotational alignment of tibial component that was preoperatively planned on CT, compared with the conventional method. MATERIALS AND METHODS: We compared the number of outliers for rotational alignment of the tibial component using combined CT-based and image-free navigation systems (navigated group) with those of conventional method (conventional group). Seventy-two TKAs were performed between May 2012 and December 2014. In the navigated group, the anteroposterior axis was prepared using CT-based navigation system and the tibial component was positioned under control of the navigation. In the conventional group, the tibial component was placed with reference to the Akagi line that was determined visually. Fisher's exact probability test was performed to evaluate the results. RESULTS: There was a significant difference between the two groups with regard to the number of outliers: 3 outliers in the navigated group compared with 12 outliers in the conventional group (P < 0.01). CONCLUSIONS: We concluded that combined CT-based and image-free navigation systems decreased the number of rotational outliers of tibial component, and was helpful for the replication of the accurate rotational alignment of the tibial component that was preoperatively planned.

Factors affecting cartilage repair after medial opening-wedge high tibial osteotomy.

PURPOSE: This study documented the healing potential of degenerated articular cartilage after opening-wedge valgus high tibial osteotomy (HTO) in patients with osteoarthritis of the knee. It was hypothesized that regeneration of articular cartilage is affected by several factors, including preoperative cartilage degeneration grade, difference between the medial femoral condyle (MFC) and the medial tibial condyle (MTC), and postoperative knee alignment. METHODS: Medial opening-wedge valgus HTO was performed in 131 knees of 100 patients (mean age 66 ± 7.7 years). Initial arthroscopy was performed at the time of HTO, and a second-look arthroscopy was performed at the time of plate removal (20.8 ± 6.5 months after HTO). Status of articular cartilage was assessed according to the ICRS grade. Cartilage regeneration was also evaluated by the presence of newly formed cartilaginous tissue. All subjects were followed up postoperatively at 2 years for assessment of clinical and radiographic outcomes. RESULTS: The number of subjects in ICRS grade 1/2/3/4 was significantly altered from 0/11/53/67 preoperatively to 14/21/56/40 postoperatively in the MFC (P < 0.05) and 0/12/62/57 preoperatively to 9/24/64/34 postoperatively in the MTC (P < 0.05). Newly formed cartilaginous tissue was found in 71 % of MFCs and 51 % of MTCs. Incidence of cartilage regeneration was significantly higher in lower BMI cases, MFC, preoperatively advanced ICRS grade and overcorrected knees. Age, gender and clinical outcomes did not affect cartilage regeneration. CONCLUSION: Cartilage regeneration in degenerated articular cartilage is induced after opening-wedge valgus HTO, which is affected by BMI, the difference between the MFC and MTC, preoperative cartilage degeneration grade, and postoperative limb alignment. Therefore, patient selection by BMI rather than age, and surgical techniques maintaining valgus knee alignment should be considered for cartilage regeneration. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

The use of factor Xa inhibitors following opening-wedge high tibial osteotomy for venous thromboembolism prophylaxis.

PURPOSE: This study aimed to investigate the incidence of venous thromboembolism (VTE) after medial opening-wedge high tibial osteotomy (OWHTO) and evaluate the efficacy and safety of edoxaban for the prevention of VTE in patients undergoing OWHTO. METHODS: A total of 139 patients with osteoarthritis or osteonecrosis undergoing OWHTO were enrolled in this prospective, randomized study. Four patients were excluded because of preoperatively diagnosed VTE, and 135 patients were divided into two groups-an edoxaban group and a non-edoxaban group-and underwent computed tomography venography on day 7 to check for postoperative VTE. Blood samples were taken on the day before OWHTO and on postoperative days 1, 3, 7, and 14. RESULTS: Treatment with edoxaban reduced the incidence of VTE after OWHTO; however, there was no statistically significant difference between the two groups. No major bleeding was noted in the edoxaban group. There were significant differences in the D-dimer level, prothrombin time, fibrinogen level, and thrombin antithrombin complex levels between the groups. CONCLUSIONS: Edoxaban is an oral, once-daily, selective, direct factor Xa inhibitor that is safe and easy to handle. It may offer a new option for preventing VTE after OWHTO. LEVEL OF EVIDENCE: I.

Comparative Study of Opening-Wedge High Tibial Osteotomy With and Without a Combined Computed Tomography-Based and Image-Free Navigation System.

PURPOSE: To assess whether a combined computed tomography (CT)-based and image-free navigation system results in better coronal and sagittal alignment than the conventional method for performing opening-wedge high tibial osteotomy (OWHTO) and whether CT-based navigation results in acquisition of an accurate osteotomy plane. METHODS: Sixty-two consecutive knees were randomly divided into navigated and conventional groups. The intraoperative correction angle was determined by the change in hip-knee-ankle angle in the navigated group and by the predicted medial opening width in the conventional group. Outliers of femorotibial angle (FTA) and tibial posterior slope (TPS) were defined as angles of >175° or <165° and angles of >2.5° or <-2.5°, respectively. Radiographic and clinical data were compared between the 2 groups at 2 years postoperatively. RESULTS: Mean postoperative FTAs were 168.5° in the navigated group and 168.1° in the conventional group. Mean change in TPS of -0.2° in the navigated group was significantly lower than that of 1.6° in the conventional group (P = .005). On postoperative CT, mean angle between the tibial plateau and osteotomy planes in the sagittal plane showed a significantly higher anterior opening of 12° in the conventional than in the navigated group (P < .001). There was a significantly greater proportion of TPS outliers in the conventional (51.6%) than in the navigated group (12.9%) (P = .001), and a significantly greater proportion within the normal range in both planes in the navigated (74.2%) than in the conventional group (48.4%) (P = .037). CONCLUSIONS: Combined CT-based and image-free navigation in OWHTO better preserves the original TPS and more frequently restores normal coronal and sagittal plane knee joint alignment. CT-based navigation also enabled acquisition of our target osteotomy plane in the sagittal plan. The navigation system in OWHTO was helpful for simultaneous control of the alignment in 2 planes. LEVEL OF EVIDENCE: Level II, lesser-quality prospective randomized trial.

Femoral shaft bowing in the coronal and sagittal planes on reconstructed computed tomography in women with medial compartment knee osteoarthritis: a comparison with radiograph and its predictive factors.

PURPOSE: To show the differences in lateral and anterior femoral shaft bowing (FSB) between radiographic and computed tomography (CT) images and to assess whether FSB is associated with various predictive factors in women with knee osteoarthritis (OA) using CT images. METHODS: We enrolled 135 Japanese women with medial compartment knee OA. Lateral and anterior FSB were measured by radiography and reconstructed CT. Age, body mass index (BMI), femorotibial angle (FTA), femoral length, and lumbar spine and femoral neck bone mineral density (BMD) were set as predictive factors for progression of knee OA. We compared predictive factors in the lateral FSB group having lateral angulations of >5° with those in the nonbowing group and compared predictive factors in the anterior FSB group having anterior angulations of >11° with those in the nonbowing group. Binomial logistic regression modeling was applied to determine independent predictors of both FSB. RESULTS: There were significant differences in both FSB between the radiographic and reconstructed CT images (P = 0.005 and P = 0.047, respectively). In binomial logistic regression analyses for lateral FSB on CT, age, BMI, and lumbar spine BMD were significant predictors, with odds ratios of 1.16, 1.22, and 0.03, respectively; for anterior FSB on CT, age was a significant predictor, with an odds ratio of 1.06. CONCLUSIONS: It is preferable to measure both FSB on reconstructed CT when planning reconstructive knee surgeries. Age, BMI, and lumbar spine BMD were predictors of lateral FSB progression, and age was a predictor of anterior FSB progression. Level of evidence Level III.

Is the surgical epicondylar axis the center of rotation in the osteoarthritic knee?

The relationship between the surgical epicondylar axis (SEA) and the rotational axis of the distal femur remains unclear. We investigated the relationship between the SEA and the distal femur and whether the SEA can be used as the rotational axis of the knee. Angular and linear measurements of 70 femora at 0°, 30°, 60°, 90°, and 120° of flexion were recorded. Results showed that the SEA was a logical and appropriate parameter as a principal axis for knee flexion at least between 0° and 60° of flexion. The study has important implications for the design and positioning of femoral components in total knee arthroplasty.

Clinical results of unicompartmental arthroplasty for knee osteoarthritis using a tibial component with screw fixation.

PURPOSE: Unicompartmental knee prostheses with screw fixation into the proximal tibia were employed and postoperative clinical results for osteoarthritis of the knee, especially regarding relief of pain, range of motion and satisfactory limb alignment are reported and discussed. METHODS: A total of 140 knees (131 medial and 9 lateral) of 85 patients (21 men and 64 women) were followed up for two to 17 years with an average of 7.0 ± 3.0 years. RESULTS: In spite of loss to follow-up in three knees of two patients and revision to total knee arthroplasty in one knee of one patient, in the remaining 136 knees (82 patients) the mean knee score of the Knee Society Clinical Rating System was 41.0 ± 14.7 pre-operatively, which improved to 93.1 ± 5.7 at follow-up, while the mean functional score similarly improved from 36.9 ± 8.1 to 88.5 ± 6.3 (p < 0.001 respectively). One knee developed a fracture in the medial proximal part of the tibia, but no knee developed loosening of the prosthesis or infection. The mean pre-operative knee flexion was 122.6 ± 15.9°, which improved to 132.9 ± 13.4° (p < 0.001) at follow-up. The limb alignment showed 4.8 ± 4.5° anatomical varus angulation pre-operatively, which was corrected to 5.8 ± 3.3° valgus at follow-up in the medial unicompartmental replacement group (127 knees), and 19 ± 6.1° valgus pre-operatively, which was corrected to 6.7 ± 3.0° valgus at follow-up in the lateral unicompartmental replacement group (nine knees). CONCLUSIONS: The clinical results of arthroplasty with screw fixation were concluded to be promising.

The surgical epicondylar axis is a consistent reference of the distal femur in the coronal and axial planes.

PURPOSE: Various rotational landmarks including the surgical epicondylar axis (SEA) are used for preoperative planning and intra-operative reference of total knee arthroplasty (TKA) in the axial plane. The aim of the study was to elucidate the relationships between the SEA and other femoral anatomical landmarks, including the mechanical axis, distal and posterior knee joints, the trochlear groove, and the anterior femoral condyle, in both the coronal and axial planes. METHODS: Angular and linear measurements were taken of sixty femora using Orthomap3D, which has a tool to analyse computed tomography image data that makes it possible to measure three-dimensional distances and angles precisely. The inter- and intra-observer reliabilities of these measurements were evaluated. Comparisons were made according to height, weight, body mass index, and gender. RESULTS: The angle between the mechanical axis and the SEA was 90.2° (95% CI 90.0°-90.4°). There was a significant correlation for each linear measurement between the SEA and the distal/posterior knee joint line and for each linear measurement between the SEA and the anterior medial/lateral femoral condyle. A significant difference was observed between genders in the linear measurements. Significant correlations were found between height and weight and linear parameters. CONCLUSION: Knowledge of the relationships between the SEA and other femoral anatomical landmarks is useful in preoperative planning, intra-operative landmark, and postoperative assessment of TKA. The SEA is a consistent parameter of femoral alignment in the coronal plane and a stable reference for femoral rotation in the axial plane. LEVEL OF EVIDENCE: III.

Fractures around the lateral cortical hinge after a medial opening-wedge high tibial osteotomy: a new classification of lateral hinge fracture.

PURPOSE: The purpose of this study was to determine the frequency of lateral hinge fractures after opening-wedge high tibial osteotomy and investigate the patterns of fracture and their clinical outcome. METHODS: We analyzed 104 knees in 93 patients with a mean age of 68 ± 7 years. Of the knees, 74 were diagnosed as having primary osteoarthritis and 30 with osteonecrosis. The mean follow-up period was 41 months. Lateral hinge fractures were classified as follows: type I, the fracture reaches just proximal to or within the tibiofibular joint; type II, the fracture reaches the distal portion of the proximal tibiofibular joint; and type III, a lateral plateau fracture. A standard postoperative rehabilitation protocol was used for type I fractures, 3 of 5 patients with type II fractures were treated with non-weight bearing, and type III fractures were treated with non-weight bearing until visible callus formation. RESULTS: The Knee Society scores for the knee and for function showed improvement from 49 ± 11 to 91 ± 7.7 points and from 62 ± 13 to 95 ± 8.2 points, respectively. Lateral cortex fractures were observed in 26 knees (25%): 19 type I, 5 type II, and 2 type III. In the type II fracture group, 2 of 5 patients were judged to have a delayed bone union. There were 2 cases of infection (2%) and 1 case of traumatic neuroma (1%) but no instances of implant failure, nonunion, or deep vein thrombosis among our patient cohort. CONCLUSIONS: High tibial osteotomy patients treated with a combination of TomoFix (Synthes, Bettlach, Switzerland) and bone substitute were able to walk with full weight bearing 2 weeks after surgery. No complications were seen in 19 patients with type I fractures. Of 5 patients with type II fractures, 2 had delayed unions with a correction loss of 3° and 7°, respectively. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Change in pelvic tilt angle 2 to 4 years after total hip arthroplasty.

The purpose of this study was to evaluate the change in pelvic tilt angle (PA) in the sagittal plane in the standing and supine positions for 2 to 4 years after total hip arthroplasty (THA). Anteroposterior pelvic radiographs of 21 male and 65 female patients were investigated before and after THA yearly over 2 to 4 years. Both the standing and supine PA significantly posteriorly tilted after THA. The difference in PA between the standing and supine positions (dPA) significantly increased after THA. Although the PA in the standing and supine positions plateaued 1 year after THA, the dPA gradually increased. In addition, the percentage of patients who showed a difference of more than 10° in dPA tended to increase yearly. In particular, elderly female patients who showed posterior tilt in PA in the standing or supine positions or a large dPA before THA tended to show a dPA of more than 10° after THA.

Low bone mineral density is associated with the onset of spontaneous osteonecrosis of the knee.

BACKGROUND AND PURPOSE: The primary event preceding the onset of symptoms in spontaneous osteonecrosis in the medial femoral condyle (SONK) may be a subchondral insufficiency fracture, which may be associated with underlying low bone mineral density (BMD). However, the pathogenesis of SONK is considered to be multifactorial. Women over 60 years of age tend to have higher incidence of SONK and low BMD. We investigated whether there may be an association between low BMD and SONK in women who are more than 60 years old. METHODS: We compared the BMD of 26 women with SONK within 3 months after the onset of symptoms to that of 26 control women with medial knee osteoarthritis (OA). All the SONK patients had typical clinical presentations and met specified criteria on MRI. The BMDs measured at the lumbar spine, ipsilateral femoral neck, and knee condyles and the ratios of medial condyle BMD to lateral condyle BMD (medial-lateral ratios) in the femur and tibia were compared between the two groups. The medial-lateral ratios were used as parameters for comparisons of the BMDs at both condyles. RESULTS: The mean femoral neck, lateral femoral condyle, and lateral tibial condyle BMDs were between x% and y% lower in the SONK patients than in the OA patients (p < 0.001). The mean femoral and tibial medial-lateral ratios were statistically significantly higher in the SONK patients than in the OA patients. INTERPRETATION: A proportion of women over 60 years of age have low BMD that progresses rapidly after menopause and can precipitate a microfracture. These findings support the subchondral insufficiency fracture theory for the onset of SONK based on low BMD.