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Comparison of the method using 3D printing model and PACS in preoperative planning for open wedge high tibial osteotomy
Abstracts / Asia-Pacific Journal of Sports Medicine, Arthroscopy, Rehabilitation and Technology 9 (2017) 12e58
Conclusion: HTO techniques can realignment, improve the relationship of knee, and make the repaired/reconstructed ligament healing in normal position and loading normal strain. Keywords: Old knee dislocation, HTO, osteotomy, malalignment
Knee - Osteotomy > High tibial osteotomy OP-003 MID-TERM SURVIVAL ANALYSIS OF HIGH TIBIAL OSTEOTOMY d A COMPARATIVE STUDY OF COMPUTER ASSISTED AND CONVENTIONAL TECHNIQUE Sang Jun Song, Dae Kyung Bae, Kang Il Kim, Cheol Hee Park. Department of Orthopaedic Surgery, College of Medicine, Kyung Hee University, South Korea Background: Various factors have been reported to be associated with the survival of an HTO, including age, gender, BMI, preoperative ROM, OA grade, and postoperative correction angle. To the best of our knowledge, no study has compared survival rates between computer-assisted and conventional HTO. The purpose of the present study was to compare the clinical and radiographic results and survival rates between computerassisted and conventional closing wedge high tibial osteotomy (HTO). Material: Data from a consecutive cohort comprising 132 computerassisted HTOs and 75 conventional HTOs using miniplate staples were retrospectively reviewed. Method: The hospital for special surgery (HSS) score and femorotibial angle (FTA) were compared between the two groups. The survival rates were also compared to procedure failure. Several variables were analyzed to determine the risk factors affecting the survival rate of the HTO. Results: The HSS scores at the postoperative one year were slightly better for the computer-assisted HTOs (87.9 vs.81.8). The average postoperative FTA was greater in the computer-assisted group (valgus 9.0 vs. valgus 7.6 , P < 0.001). The inlier of postoperative FTAs was wider in the computerassisted group (81.1% vs. 58.7%). The overall 5- and 10-year survival rates were 95.4% and 86.3%, respectively. The survival rates did not differ between the groups until 9 years (P ¼ 0.369). The postoperative FTA was the only independent factor that affected the survival rate (P ¼ 0.003). Discussion: The most important finding of the present study was that there were no significant differences in the 9-year survival rate between the computer-assisted and conventional HTO groups although the clinical and radiographic results were better for the computer-assisted group. The difference in the clinical and radiographic results could be caused by the different lengths of follow-up. Therefore, we compared not only the last follow-up results, but also the postoperative 1 year clinical results and the FTA 2 weeks postoperatively between the two groups. Although the shortterm clinical and radiographic results seemed to be better in the computerassisted group, a more sophisticated longer-term survivorship analysis will be required to prove the long-term benefits of computer-assisted HTO. Conclusion: The mid-term clinical and radiographic results of HTO were satisfactory for both computer assisted and conventional HTOs, but the survival rates deteriorated over time. The 9-year survival rate of HTO was not different between the computer-assisted and conventional HTOs. A comparative analysis of a longer-term survival rate is required. It is advisable to correct the FTA to more than 7 valgus, considering the long-term survival rate. Keywords: knee, osteoarthritis, high tibial osteotomy, closing wedge, navigation, survival
Knee - Osteotomy > High tibial osteotomy OP-005 RADIOGRAPHIC DISCREPANCY OF LOWER LIMB ALIGNMENT BETWEEN PREOPERATIVE PLANNING AND POSTOPERATIVE OPENING WEDGE HIGH TIBIAL OSTEOTOMY Kosuke Nakagawa, Shuhei Otsuki, Yoshinori Okamaoto, Tomohiko Murakami, Masashi Neo. Department of orthopedic surgery, Osaka Medical College, Japan Opening wedge high tibial osteotomy (OWHTO) is widely performed for medial osteoarthritis (OA) and osteonecrosis (ON). Concept of HTO for
13
medial OA is to transfer mechanical axis to the lateral compartment of the knee, thereby reduces knee pain, and prevent OA change in medial compartment, suggesting that accurate correction of lower limb alignment is critical for getting the successful outcome after OWHTO. However, postoperative lower limb alignment is sometimes different from preoperative planning. Although several factors might be affected this discrepancy, we focused on soft tissue knee laxity. The current study evaluated the effect of soft tissue around the knee using varus / valgus stress radiography. Materials & Methods: This study involved 26 knees from 23 patients undergoing OWHTO for primary medial OA and ON from March 2014 to November 2016. 10 knees were from 8 males and 16 knees were from 15 females with the average of 65 ± 11 years old (range 35-81 years old) at the time of surgery. Preoperative planning for the degree of correction was assessed on full-length anteroposterior radiograph with the standing position as the mechanical axis passed through the lateral intercondylar eminence of proximal tibia by using softwere (Advanced Caseplan, Trauma CAD, Germany). After medial opening high tibial osteotomy site was performed with two b eTricalciumPhosphate wedges (Osferion60, Olympus Terumo Biomaterials, Tokyo, Japan) and locking plate (TomoFixTM, Synthes, Bettlach, Switzerland, FlexitSystem®, neosteo, France and Tris Medial HTO Plate System, Olympus Terumo Biomaterials, Tokyo, Japan). Radiographs were obtained both pre- and post-operatively (1 month after surgery) and hip knee ankle angle (HKA), medial proximal tibial angle (MPTA), mechanical axis (%MA), and joint line convergence angle (JLCA) were measured. Varus JLCA was defined as JLCA during manual varus stress under fluoroscopy. Valgus JLCA was defined as JLCA during manual valgus stress too. Results: The average HKA angle significantly changed from varus 5.9 ± 2.7 (varus 1 to 12 ) to valgus 3.4 ± 1.6 (valgus 0 to 7,p ˂ 0.001). The average MPTA significantly changed from 84.2 ± 2.7 (79 to 89 ) to valgus 92.6 ± 2.4 (87 to 96 ,p ˂ 0.001). The average JLCA significantly changed from 3.7 ± 1.9 (1 to 8 ) to valgus 2.2 ± 1.4 (-1 to 4 , p ˂ 0.001). The average %MA significantly changed from 22.6% ± 15.3% (-6.8% to 47.5%) to 59.7% ± 10.4% (37% to 79%, p ˂ 0.001). The average planning HKA was valgus 2.5 ± 1.1 (valgus 1 to 5 ) and was significantly different from postoperative HKA (p ¼ 0.038). The average planning MPTA was 92.7 ± 2.6 (87 to 96 ) and was not significantly different from postoperative HKA (p ¼ 0.92). Preoperatively stress tests showed that varus JLCA was 4.1 ± 1.7 (1 to 7 ), valgus JLCA was -0.2 ± 1.5 (-2 to 3 ). DHKA angle showed a moderate correlation with varus HKA angle (r, 0.46) and pre- to post differences in JLCA (r, 0.56). But, DHKA angle showed a poor correlation with valgus JLCA (r, 0.25). Discussion: The most important findings of the present study was that knee laxity which was evaluated with varus JLCA showed a correlation withDHKA angle (over correction) between preoperative planning and postoperative OWHTO. In conclusion, as knee varus laxity was getting increased, the discrepancy between preoperative planning and postoperative alignment was detected, especially with over correction. Keywords: high tibial osteotomy, hip knee ankle angle, preoperative planning, over correction
Knee - Osteotomy > High tibial osteotomy OP-006 COMPARISON OF THE METHOD USING 3D PRINTING MODEL AND PACS IN PREOPERATIVE PLANNING FOR OPEN WEDGE HIGH TIBIAL OSTEOTOMY Hee-June Kim, Hee-Soo Kyung. Department of Orthopaedic Surgery, Kyungpook National University Hospital, Daegu, Republic of Korea Purpose: The purpose was to compare the accuracy of the method using 3D printing model with the method using picture archiving and communication system (PACS) images in high tibial osteotomy (HTO). Materials and Methods: This study analyzed 40 patients with varus deformity and medial osteoarthritis. From 2012 to 2016, patients underwent HTO using either 3D printing model (20 knees) or method based on a PACS image (20 knees). After obtaining the correction angle for the target point (62.5% point of the mediolateral tibial plateau width), in the 3D printing method, the wedge-shaped 3D-printed model was designed with the measured angle and osteotomy section and was produced by the 3D
14
Abstracts / Asia-Pacific Journal of Sports Medicine, Arthroscopy, Rehabilitation and Technology 9 (2017) 12e58
printer. The PACS method used preoperative radiographs to shift the weight bearing axis. The accuracy of the HTO and the proportion of acceptable range (62.5 ± 5%) at each method was compared using the fulllength lower limb radiographs at the sixth postoperative week. The preand postoperative posterior tibial slope angle was also compared at each method. Results: The weight bearing line on the tibial plateau was corrected from a preoperative 21.1 ± 11.8% to a postoperative 61.6 ± 3.4% in the 3D group and from 19.5 ± 12.3% to 61.4 ± 8.0% in the PACS group. The patients in an acceptable range were more in 3D printing group (80%) than in PACS group (60%) (p¼0.028). The mean of absolute difference with the target point was less in 3D printing groups (2.4 ± 2.5) than PACS group (6.2 ± 5.1) (p¼0.006). The posterior tibial slope was not significantly different in 3D printing group (8.6 ⋄ 8.9 , p¼0.073), whereas different in PACS group (9.9 ⋄ 10.5 , p¼0.042). Conclusions: In HTO, correction based on the 3D printing method was more accurate than correction using the PACS method.. Keywords: HTO, 3D printing, PACS, accuracy
Knee - Osteotomy > High tibial osteotomy OP-007 A NOVEL TECHNIQUE IN OPEN WEDGE HTO TO PRESERVE THE TIBIAL SLOPE (BASIC STUDY ON CADAVER AND RECONSTRUCTION CT SCANNING) Hamidreza Yazdi 1, Masoud Hosseiny 2, Mehran Radi 1. 1 Department of Knee Surgery, Iran University of Medical Science, Iran; 2 Department of Biomechanics, School of Mechanical Engineering, Iran University of Science and Technology, Iran Background: High tibial osteotomy (HTO) is a well-established treatment option for uni-compartmental osteoarthritis associated with coronal deformity of the lower limb . Clinical indications for an HTO include varus alignment of the knee associated with medial compartment arthritis, knee instability, medial compartment overload following meniscectomy, and osteochondral lesions requiring resurfacing procedures. Many techniques have been described for HTO. The goal of the procedure is to realign the lower extremity and redistribute the joint forces applied to each compartment of the knee, thereby decreasing pain and improving overall function . The technique used for proximal tibia osteotomy has typically been the lateral closing wedge. In recent years, the medial opening wedge technique has gained popularity. The primary focus of both is to alter the weight-bearing axis in the coronal plane. Both methods have been shown to produce satisfactory clinical results in both the short- and long-term . Lateral closing wedge HTO was once considered to be the standard of care; however, this technique is associated with fibular osteotomy or proximal tibiofibular joint disruption, peroneal nerve injury, more demanding subsequent total knee arthroplasty (TKA), and loss of bone stock . Recently, medial opening wedge HTO has become the primary surgical technique . Disadvantages associated with medial opening wedge HTO include the need for bone grafting and the risk of collapse or loss of correction . It is very important in a high tibial open wedge osteotomy to keep the slope unchanged in the sagittal plane; it should mimic the proximal tibial joint slope. Noyes et al. showed that in order for the tibial slope to remain unchanged, the osteotomy line must be parallel to the tibial slope, and the most anterior gap of the osteotomy wedge at the tibial tubercle should be onehalf the posteromedial gap. Every millimeter of gap error at the tibial tubercles results in approximately 2 of change in the tibial slope . In some conditions, however, during the open wedge HTO, the osteotomy line may not be parallel to the tibial plateau. In such cases, it is necessary to find a method to keep the slope unchanged. This study aimed to introduce a quantitative method of open wedge HTO to preserve the tibial slope without considering the osteotomy line. To the best of our knowledge, this is the first study to introduce a method for
open wedge HTO that keeps the tibial slope unchanged despite the osteotomy line. Methods: At first , mathematical calculations were concentrated, and the relations ,formulas and tables were extracted . The results of formulas and tables were examined using software on reconstruction CT scanning of two intact tibiae. Then the results of the calculations were tested on five fresh cadavers. Results: Software results showed that the changes in slope angle using the simplified formulas and tables are less than 0.5 in both subjects. Based on the p-value, the simplified formula or the tables can be used to correct the varus with minimal change in the slope and without considering osteotomy line. Results from osteotomies on 5 bones showed that changes in slope angle were significantly small. In 3 subjects, the change was less than 0.6 . Discussion: Performing the osteotomy parallel to the proximal tibial plateau is an important step in the osteotomy method(19), but it is sometimes difficult to find the tibial plateau during the osteotomy. In the current study, a new osteotomy technique was considered in which a proximal tibial osteotomy was performed regardless of the proximal tibial plateau. Based on the mathematical formula, a table was introduced to facilitate the technique. Based on this study ,the surgeon can measure two different lengths (L1 and L2) of proximal tibia intraoperatively, and using the table’s data, the desired amount of correction can be achieved with less than 1.4 . The most important advantages of the method of the current study are that it does not need to consider the osteotomy line parallel to the tibial plateau and changes in the slope are minimal (mean ¼ 0.6). Conclusion: Use of this new technique in open wedge HTO can result in good varus correction with minimal changes to the tibial slope, regardless of the orientation of the osteotomy line. Keywords: high tibial osteotomy, open wedge, tibial slope
Knee - Osteotomy > High tibial osteotomy OP-008 FEEDBACK FROM A CONSECUTIVE 100 CASES OF MEDIAL OPEN WEDGE HTO USING A CUMULATIVE SUMMATION TEST FOR LEARNING CURVE Kwang Jun Oh, Do Kyung Lee. Department of Orthopaedic Surgery, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, South Korea Background: Achievement of planned correction, prevention of excessive posterior slope and avoidance of lateral hinge fracture are important factors for successful surgical outcomes in biplane medial open wedge high tibial osteotomy (biplane-OWHTO). However, there was no report for these factors could be improved by surgical experience. The purpose of this study was to elucidate the feedback from surgical outcomes of biplaneOWHTO using the cumulative summation test for learning curve (LCCUSUM) which is a useful method for self-monitoring and continuous quality improvement for the surgical procedure. Material & Method: A consecutive 100 cases of biplane-OWHTO were evaluated. Treatment failure in terms of correction were defined as undercorrection when the weight bearing line(WBL) pass the point less than 50% and as over-correction over 70% of width of tibia plateau respectively. A change more than 5 degrees of posterior slope compared with non-operated knee and presence of lateral hinge fracture were also defined as treatment failure. These defined failures were separately evaluated the learning curve using the LC-CUSUM score. Results: The LC-CUSUM test signaled competency after 53 procedures for the change of posterior slope, after 38 procedures for lateral hinge fracture, and after 27 procedures for under-correction. However, the LC-CUSUM test does not signaled competency after 100 procedures for the over-correction. Therefore, the surgeon could reach and maintain competency as increased surgical experience for the maintenance of posterior slope, and prevention of lateral hinge fracture and under-correction respectively. However, surgical experience could not reveal the competency for reduced over-correction in biplane-OWHTO.
Conclusion: HTO techniques can realignment, improve the relationship of knee, and make the repaired/reconstructed ligament healing in normal position and loading normal strain. Keywords: Old knee dislocation, HTO, osteotomy, malalignment
Knee - Osteotomy > High tibial osteotomy OP-003 MID-TERM SURVIVAL ANALYSIS OF HIGH TIBIAL OSTEOTOMY d A COMPARATIVE STUDY OF COMPUTER ASSISTED AND CONVENTIONAL TECHNIQUE Sang Jun Song, Dae Kyung Bae, Kang Il Kim, Cheol Hee Park. Department of Orthopaedic Surgery, College of Medicine, Kyung Hee University, South Korea Background: Various factors have been reported to be associated with the survival of an HTO, including age, gender, BMI, preoperative ROM, OA grade, and postoperative correction angle. To the best of our knowledge, no study has compared survival rates between computer-assisted and conventional HTO. The purpose of the present study was to compare the clinical and radiographic results and survival rates between computerassisted and conventional closing wedge high tibial osteotomy (HTO). Material: Data from a consecutive cohort comprising 132 computerassisted HTOs and 75 conventional HTOs using miniplate staples were retrospectively reviewed. Method: The hospital for special surgery (HSS) score and femorotibial angle (FTA) were compared between the two groups. The survival rates were also compared to procedure failure. Several variables were analyzed to determine the risk factors affecting the survival rate of the HTO. Results: The HSS scores at the postoperative one year were slightly better for the computer-assisted HTOs (87.9 vs.81.8). The average postoperative FTA was greater in the computer-assisted group (valgus 9.0 vs. valgus 7.6 , P < 0.001). The inlier of postoperative FTAs was wider in the computerassisted group (81.1% vs. 58.7%). The overall 5- and 10-year survival rates were 95.4% and 86.3%, respectively. The survival rates did not differ between the groups until 9 years (P ¼ 0.369). The postoperative FTA was the only independent factor that affected the survival rate (P ¼ 0.003). Discussion: The most important finding of the present study was that there were no significant differences in the 9-year survival rate between the computer-assisted and conventional HTO groups although the clinical and radiographic results were better for the computer-assisted group. The difference in the clinical and radiographic results could be caused by the different lengths of follow-up. Therefore, we compared not only the last follow-up results, but also the postoperative 1 year clinical results and the FTA 2 weeks postoperatively between the two groups. Although the shortterm clinical and radiographic results seemed to be better in the computerassisted group, a more sophisticated longer-term survivorship analysis will be required to prove the long-term benefits of computer-assisted HTO. Conclusion: The mid-term clinical and radiographic results of HTO were satisfactory for both computer assisted and conventional HTOs, but the survival rates deteriorated over time. The 9-year survival rate of HTO was not different between the computer-assisted and conventional HTOs. A comparative analysis of a longer-term survival rate is required. It is advisable to correct the FTA to more than 7 valgus, considering the long-term survival rate. Keywords: knee, osteoarthritis, high tibial osteotomy, closing wedge, navigation, survival
Knee - Osteotomy > High tibial osteotomy OP-005 RADIOGRAPHIC DISCREPANCY OF LOWER LIMB ALIGNMENT BETWEEN PREOPERATIVE PLANNING AND POSTOPERATIVE OPENING WEDGE HIGH TIBIAL OSTEOTOMY Kosuke Nakagawa, Shuhei Otsuki, Yoshinori Okamaoto, Tomohiko Murakami, Masashi Neo. Department of orthopedic surgery, Osaka Medical College, Japan Opening wedge high tibial osteotomy (OWHTO) is widely performed for medial osteoarthritis (OA) and osteonecrosis (ON). Concept of HTO for
13
medial OA is to transfer mechanical axis to the lateral compartment of the knee, thereby reduces knee pain, and prevent OA change in medial compartment, suggesting that accurate correction of lower limb alignment is critical for getting the successful outcome after OWHTO. However, postoperative lower limb alignment is sometimes different from preoperative planning. Although several factors might be affected this discrepancy, we focused on soft tissue knee laxity. The current study evaluated the effect of soft tissue around the knee using varus / valgus stress radiography. Materials & Methods: This study involved 26 knees from 23 patients undergoing OWHTO for primary medial OA and ON from March 2014 to November 2016. 10 knees were from 8 males and 16 knees were from 15 females with the average of 65 ± 11 years old (range 35-81 years old) at the time of surgery. Preoperative planning for the degree of correction was assessed on full-length anteroposterior radiograph with the standing position as the mechanical axis passed through the lateral intercondylar eminence of proximal tibia by using softwere (Advanced Caseplan, Trauma CAD, Germany). After medial opening high tibial osteotomy site was performed with two b eTricalciumPhosphate wedges (Osferion60, Olympus Terumo Biomaterials, Tokyo, Japan) and locking plate (TomoFixTM, Synthes, Bettlach, Switzerland, FlexitSystem®, neosteo, France and Tris Medial HTO Plate System, Olympus Terumo Biomaterials, Tokyo, Japan). Radiographs were obtained both pre- and post-operatively (1 month after surgery) and hip knee ankle angle (HKA), medial proximal tibial angle (MPTA), mechanical axis (%MA), and joint line convergence angle (JLCA) were measured. Varus JLCA was defined as JLCA during manual varus stress under fluoroscopy. Valgus JLCA was defined as JLCA during manual valgus stress too. Results: The average HKA angle significantly changed from varus 5.9 ± 2.7 (varus 1 to 12 ) to valgus 3.4 ± 1.6 (valgus 0 to 7,p ˂ 0.001). The average MPTA significantly changed from 84.2 ± 2.7 (79 to 89 ) to valgus 92.6 ± 2.4 (87 to 96 ,p ˂ 0.001). The average JLCA significantly changed from 3.7 ± 1.9 (1 to 8 ) to valgus 2.2 ± 1.4 (-1 to 4 , p ˂ 0.001). The average %MA significantly changed from 22.6% ± 15.3% (-6.8% to 47.5%) to 59.7% ± 10.4% (37% to 79%, p ˂ 0.001). The average planning HKA was valgus 2.5 ± 1.1 (valgus 1 to 5 ) and was significantly different from postoperative HKA (p ¼ 0.038). The average planning MPTA was 92.7 ± 2.6 (87 to 96 ) and was not significantly different from postoperative HKA (p ¼ 0.92). Preoperatively stress tests showed that varus JLCA was 4.1 ± 1.7 (1 to 7 ), valgus JLCA was -0.2 ± 1.5 (-2 to 3 ). DHKA angle showed a moderate correlation with varus HKA angle (r, 0.46) and pre- to post differences in JLCA (r, 0.56). But, DHKA angle showed a poor correlation with valgus JLCA (r, 0.25). Discussion: The most important findings of the present study was that knee laxity which was evaluated with varus JLCA showed a correlation withDHKA angle (over correction) between preoperative planning and postoperative OWHTO. In conclusion, as knee varus laxity was getting increased, the discrepancy between preoperative planning and postoperative alignment was detected, especially with over correction. Keywords: high tibial osteotomy, hip knee ankle angle, preoperative planning, over correction
Knee - Osteotomy > High tibial osteotomy OP-006 COMPARISON OF THE METHOD USING 3D PRINTING MODEL AND PACS IN PREOPERATIVE PLANNING FOR OPEN WEDGE HIGH TIBIAL OSTEOTOMY Hee-June Kim, Hee-Soo Kyung. Department of Orthopaedic Surgery, Kyungpook National University Hospital, Daegu, Republic of Korea Purpose: The purpose was to compare the accuracy of the method using 3D printing model with the method using picture archiving and communication system (PACS) images in high tibial osteotomy (HTO). Materials and Methods: This study analyzed 40 patients with varus deformity and medial osteoarthritis. From 2012 to 2016, patients underwent HTO using either 3D printing model (20 knees) or method based on a PACS image (20 knees). After obtaining the correction angle for the target point (62.5% point of the mediolateral tibial plateau width), in the 3D printing method, the wedge-shaped 3D-printed model was designed with the measured angle and osteotomy section and was produced by the 3D
14
Abstracts / Asia-Pacific Journal of Sports Medicine, Arthroscopy, Rehabilitation and Technology 9 (2017) 12e58
printer. The PACS method used preoperative radiographs to shift the weight bearing axis. The accuracy of the HTO and the proportion of acceptable range (62.5 ± 5%) at each method was compared using the fulllength lower limb radiographs at the sixth postoperative week. The preand postoperative posterior tibial slope angle was also compared at each method. Results: The weight bearing line on the tibial plateau was corrected from a preoperative 21.1 ± 11.8% to a postoperative 61.6 ± 3.4% in the 3D group and from 19.5 ± 12.3% to 61.4 ± 8.0% in the PACS group. The patients in an acceptable range were more in 3D printing group (80%) than in PACS group (60%) (p¼0.028). The mean of absolute difference with the target point was less in 3D printing groups (2.4 ± 2.5) than PACS group (6.2 ± 5.1) (p¼0.006). The posterior tibial slope was not significantly different in 3D printing group (8.6 ⋄ 8.9 , p¼0.073), whereas different in PACS group (9.9 ⋄ 10.5 , p¼0.042). Conclusions: In HTO, correction based on the 3D printing method was more accurate than correction using the PACS method.. Keywords: HTO, 3D printing, PACS, accuracy
Knee - Osteotomy > High tibial osteotomy OP-007 A NOVEL TECHNIQUE IN OPEN WEDGE HTO TO PRESERVE THE TIBIAL SLOPE (BASIC STUDY ON CADAVER AND RECONSTRUCTION CT SCANNING) Hamidreza Yazdi 1, Masoud Hosseiny 2, Mehran Radi 1. 1 Department of Knee Surgery, Iran University of Medical Science, Iran; 2 Department of Biomechanics, School of Mechanical Engineering, Iran University of Science and Technology, Iran Background: High tibial osteotomy (HTO) is a well-established treatment option for uni-compartmental osteoarthritis associated with coronal deformity of the lower limb . Clinical indications for an HTO include varus alignment of the knee associated with medial compartment arthritis, knee instability, medial compartment overload following meniscectomy, and osteochondral lesions requiring resurfacing procedures. Many techniques have been described for HTO. The goal of the procedure is to realign the lower extremity and redistribute the joint forces applied to each compartment of the knee, thereby decreasing pain and improving overall function . The technique used for proximal tibia osteotomy has typically been the lateral closing wedge. In recent years, the medial opening wedge technique has gained popularity. The primary focus of both is to alter the weight-bearing axis in the coronal plane. Both methods have been shown to produce satisfactory clinical results in both the short- and long-term . Lateral closing wedge HTO was once considered to be the standard of care; however, this technique is associated with fibular osteotomy or proximal tibiofibular joint disruption, peroneal nerve injury, more demanding subsequent total knee arthroplasty (TKA), and loss of bone stock . Recently, medial opening wedge HTO has become the primary surgical technique . Disadvantages associated with medial opening wedge HTO include the need for bone grafting and the risk of collapse or loss of correction . It is very important in a high tibial open wedge osteotomy to keep the slope unchanged in the sagittal plane; it should mimic the proximal tibial joint slope. Noyes et al. showed that in order for the tibial slope to remain unchanged, the osteotomy line must be parallel to the tibial slope, and the most anterior gap of the osteotomy wedge at the tibial tubercle should be onehalf the posteromedial gap. Every millimeter of gap error at the tibial tubercles results in approximately 2 of change in the tibial slope . In some conditions, however, during the open wedge HTO, the osteotomy line may not be parallel to the tibial plateau. In such cases, it is necessary to find a method to keep the slope unchanged. This study aimed to introduce a quantitative method of open wedge HTO to preserve the tibial slope without considering the osteotomy line. To the best of our knowledge, this is the first study to introduce a method for
open wedge HTO that keeps the tibial slope unchanged despite the osteotomy line. Methods: At first , mathematical calculations were concentrated, and the relations ,formulas and tables were extracted . The results of formulas and tables were examined using software on reconstruction CT scanning of two intact tibiae. Then the results of the calculations were tested on five fresh cadavers. Results: Software results showed that the changes in slope angle using the simplified formulas and tables are less than 0.5 in both subjects. Based on the p-value, the simplified formula or the tables can be used to correct the varus with minimal change in the slope and without considering osteotomy line. Results from osteotomies on 5 bones showed that changes in slope angle were significantly small. In 3 subjects, the change was less than 0.6 . Discussion: Performing the osteotomy parallel to the proximal tibial plateau is an important step in the osteotomy method(19), but it is sometimes difficult to find the tibial plateau during the osteotomy. In the current study, a new osteotomy technique was considered in which a proximal tibial osteotomy was performed regardless of the proximal tibial plateau. Based on the mathematical formula, a table was introduced to facilitate the technique. Based on this study ,the surgeon can measure two different lengths (L1 and L2) of proximal tibia intraoperatively, and using the table’s data, the desired amount of correction can be achieved with less than 1.4 . The most important advantages of the method of the current study are that it does not need to consider the osteotomy line parallel to the tibial plateau and changes in the slope are minimal (mean ¼ 0.6). Conclusion: Use of this new technique in open wedge HTO can result in good varus correction with minimal changes to the tibial slope, regardless of the orientation of the osteotomy line. Keywords: high tibial osteotomy, open wedge, tibial slope
Knee - Osteotomy > High tibial osteotomy OP-008 FEEDBACK FROM A CONSECUTIVE 100 CASES OF MEDIAL OPEN WEDGE HTO USING A CUMULATIVE SUMMATION TEST FOR LEARNING CURVE Kwang Jun Oh, Do Kyung Lee. Department of Orthopaedic Surgery, Konkuk University Medical Center, Konkuk University School of Medicine, Seoul, South Korea Background: Achievement of planned correction, prevention of excessive posterior slope and avoidance of lateral hinge fracture are important factors for successful surgical outcomes in biplane medial open wedge high tibial osteotomy (biplane-OWHTO). However, there was no report for these factors could be improved by surgical experience. The purpose of this study was to elucidate the feedback from surgical outcomes of biplaneOWHTO using the cumulative summation test for learning curve (LCCUSUM) which is a useful method for self-monitoring and continuous quality improvement for the surgical procedure. Material & Method: A consecutive 100 cases of biplane-OWHTO were evaluated. Treatment failure in terms of correction were defined as undercorrection when the weight bearing line(WBL) pass the point less than 50% and as over-correction over 70% of width of tibia plateau respectively. A change more than 5 degrees of posterior slope compared with non-operated knee and presence of lateral hinge fracture were also defined as treatment failure. These defined failures were separately evaluated the learning curve using the LC-CUSUM score. Results: The LC-CUSUM test signaled competency after 53 procedures for the change of posterior slope, after 38 procedures for lateral hinge fracture, and after 27 procedures for under-correction. However, the LC-CUSUM test does not signaled competency after 100 procedures for the over-correction. Therefore, the surgeon could reach and maintain competency as increased surgical experience for the maintenance of posterior slope, and prevention of lateral hinge fracture and under-correction respectively. However, surgical experience could not reveal the competency for reduced over-correction in biplane-OWHTO.