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Serial Assessment of Weight-Bearing Lower Extremity Alignment Radiographs After Open-Wedge High Tibial Osteotomy
Serial Assessment of Weight-Bearing Lower Extremity Alignment Radiographs After Open-Wedge High Tibial Osteotomy Yong Seuk Lee, M.D., Beom Koo Lee, M.D., Jae Ho Kwon, M.D., Jong In Kim, M.D., Francis Joseph V. Reyes, M.D., Dong Won Suh, M.D., and Kyung-Wook Nha, M.D.
Purpose: The purpose of this study was to perform a serial assessment of the radiologic parameters of the mechanical axis (MA) and the weight-bearing line (WBL) using a weight-bearing anteroposterior (AP) long-standing view of the lower extremity to determine whether the postoperative MA and WBL change with time. Methods: A total of 90 consecutive lower limbs were examined retrospectively from a weight-bearing AP long-standing view of the lower extremity obtained from 120 patients who underwent open-wedge high tibial osteotomy (OWHTO). A total of 30 patients were excluded because of (1) complications (7 patients) such as bone graft collapse or broken screws, malunion, or nonunion arising after surgery and (2) no acquisition of a regular series of weight-bearing AP long-standing views of the lower extremity (23 patients). The AP long-standing view of the lower extremity was taken, and weight-bearing AP long-standing views of the lower extremity at 1 month, 6 months, 1 year, and 2 years postoperatively were used for assessment of serial change. The Picture Archiving Communication System (Marotech, Inc, St-Augustin-de-Desmaures, Quebec, Canada) was used for radiologic measurements of the WBL ratio and MA. Serial changes were compared between 1 month, 6 months, 1 year, and 2 years postoperatively. Results: The WBL ratio progressively shifted medially, with significant changes at all time points until 1 year postoperatively (1 month to 6 months, P ¼ .04; 6 months to 1 year, P ¼ .04; 1 year to 2 years, P ¼ .22). Even though the MA angle showed a similar decreasing trend, it showed no statistical difference (P > .05). Conclusions: This study showed that after OWHTO, the WBL shifts progressively medially until 1 year postoperatively. Level of Evidence: Level IV, diagnostic study.
D
uring open-wedge high tibial osteotomy (OWHTO), realignment usually aims toward having a valgus correction, and the overlying superficial medial collateral ligament (MCL) is usually managed in several ways: it is left intact, subperiosteal elevation is performed, or a partial
From Department of Orthopaedic Surgery (Y.S.L.), Seoul National University College of Medicine, Bundang Hospital, Gyeonggi-do; Department of Orthopaedic Surgery (B.K.L.), Gachon University, Gil Hospital, Incheon; Department of Orthopaedic Surgery (D.W.S.), Barunsesang Hospital, Seongnam; and Department of Orthopaedic Surgery (J.H.K., J.I.K., F.J.V.R., K-W.N.), Ilsan Paik Hospital, Inje University, Ilsan, South Korea. Supported by a 2014 Inje University Research Grant. The authors report that they have no conflicts of interest in the authorship and publication of this article. Received March 18, 2013; accepted November 26, 2013. Address correspondence to Kyung-Wook Nha, M.D., Department of Orthopedic Surgery, Ilsan Paik Hospital, Inje University, 2240, Daehwadong, Ilsan-Segu, Koyang-Si, Ilsan 411-706, Korea. E-mail: kwnhamj@ hotmail.com or [email protected] Ó 2014 by the Arthroscopy Association of North America 0749-8063/13188/$36.00 http://dx.doi.org/10.1016/j.arthro.2013.11.028
or complete release from its distal insertion is carried out.1-4 Therefore, it was proposed that the corrected valgus angulation shows an increase after weight bearing in patients who have undergone OWHTO,2 and it was suggested that the MCL release at the time of operation may be an important contributor to the overcorrection of the alignment and postoperative valgus instability.5,6 In addition, biomechanically, it is well known that any release of the MCL can increase the knee laxity when valgus stress is applied.3 However, interestingly, postoperative valgus instability or incremental corrected valgus angulation after OWHTO is an uncommon complication in the clinical situation.4,7,8 Varus, valgus, or neutral alignment is defined on the basis of the hip-knee-ankle angle, which requires visualization of all 3 joints.9-11 The weight-bearing AP long-standing view of the lower extremity is usually checked at weight-bearing conditions and is regarded as an accurate method for restoration of coronal alignment.9,12,13 Among various radiologic parameters, the mechanical axis (MA) and weight-bearing line (WBL)
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 30, No 3 (March), 2014: pp 319-325
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Fig 1. Radiographs showing measurement method of (A) weight-bearing line (WBL) ratio (red line ¼ WBL; green line ¼ total length of tibial plateau; yellow line ¼ length from medial edge of tibial plateau to crossing point of the mechanical axis) and (B) mechanical axis (MA) angle (red line ¼ MA of femur; yellow line ¼ MA of tibia).
ratio are commonly used for assessment of lower extremity alignment.9,12,13 Lee et al.12,13 reported that the WBL ratio was more accurate than the navigation technique and the MA was a better radiologic parameter than the WBL ratio in the navigational OWHTO. The purpose of this study was to perform a serial assessment of the radiologic parameters of MA and WBL using the weight-bearing anteroposterior (AP) long-standing view of the lower extremity to determine whether the postoperative MA and WBL change with time. We hypothesized that the corrected valgus angulation would not deteriorate the postoperative valgus angulation with time even though the superficial MCL was released at the time of the surgery.
Methods Evaluation A total of 90 consecutive lower limbs were examined retrospectively using the AP long-standing view of the lower extremity obtained from 120 patients who underwent OWHTO from 2007 to 2011. The OWHTO was performed on patients with unicompartmental arthritis with a varus deformity. The exclusion criteria were as follows: (1) complications (7 patients) such as bone graft collapse or broken screws, malunion, or nonunion arising after surgery and (2) no acquisition of a regular series of weight-bearing AP long-standing views of the lower extremity (23 patients). Approval was obtained from the institutional review board and all patients provided
informed consent for participation. The weight-bearing AP long-standing view of the lower extremity was taken and standardized with the knee in full extension, the patella facing forward, and both feet facing forward at shoulder width in a weight-bearing state using a custommade foot plate.9 Weight-bearing AP long-standing views of the lower extremity were also taken 1 month, 6 months, 1 year, and 2 years postoperatively and were used for assessment of serial change. The Picture Archiving Communication System (Marotech, Inc, St-Augustin-de-Desmaures, Quebec, Canada), which can automatically measure to 2 decimal points, was used for radiologic measurements of the WBL ratio and MA. The WBL was drawn from the center of the femoral head to the center of the superior articular surface of the talus. For calculation of the WBL ratio, the denominator was the width of the tibia, as measured using a ruler, and the numerator was the tibial intersection of the WBL (with medial tibial edge at 0% and the lateral tibial edge at 100%) (Fig 1A).14 We used the degree that was rounded off the numbers to 2 decimal points. For calculation of the MA angle, we used the angle between a line drawn from the center of the femoral head to the center of the knee and a line drawn from the center of the knee to the center of the talus (Fig 1B). Serial changes were compared between views taken 1 month, 6 months, 1 year, and 2 years postoperatively. Surgical Technique Preoperatively, weight-bearing AP long-standing views of the lower extremity were obtained in all patients. A
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full-sized (100%) image of the radiograph was then printed on paper. Using this full-sized paper printout, the MA of the lower limb was plotted and the WBL percentage at the tibia was calculated. At the approximate site of the osteotomy at the proximal tibia, the paper was cut using scissors and a medial opening wedge was created such that the WBL passed through the lateral tibial plateau at 62% of the width of the plateau, which was the correction goal. Subsequently, the thickness of the wedge required to achieve a 62% WBL was determined using a ruler. However, in cases of WBL that passed medial to the medial tibial cortex, we aimed the WBL point to 50% to 60% if the preoperative plan of the osteotomy gap was more than 18 mm.12 Diagnostic knee arthroscopy was performed, at which time the menisci, ligaments, and articular cartilage were inspected, and debridement or meniscal surgery was carried out if necessary. The contralateral anterior iliac crest was prepared. The tricortical iliac crest bone was harvested by osteotomy or with an oscillating saw. The graft size was delineated on the bone by electrocautery with the mean graft dimensions of 30 mm in length, 10 to 15 mm in width, and 50 mm in depth. In smaller patients, the graft might be smaller in width, approximately 7 to 10 mm. The graft was fashioned into the appropriate size and shape using an oscillating saw to give an AP tricortical graft width ratio of 0.68 and to maintain the posterior slope.12,14,15 The anterior portion of the superficial MCL was partially released for reduction of pressure and exposure of the posteromedial cortex. In each case, the osteotomy was planned to originate at the medial tibial cortex along the metaphyseal flare (approximately 3 cm distal to the joint line) and terminated at the lateral tibial cortex (approximately 1 cm distal to the joint line, the fibular tip). The osteotomy was propagated through the proximal aspect of the insertion of the patellar ligament, leaving most of the ligament attached to the distal tibial fragment. Thin osteotomies were used to complete the osteotomy immediately short of the lateral cortex, keeping the lateral cortex and lateral capsular hinge intact. The previously fashioned triangular tricortical bone segment that was determined on the preoperative weight-bearing AP long-standing view of the lower extremity was inserted to be aligned with the opening gap shape and impacted into the osteotomy site. Once the stability, posterior slope, and final alignment had been confirmed by the cable method using an image intensifier, the bone graft was fixed in place using a Locking Compression Plate System (TomoFix, De Puy Synthes, Raynham, MA) with 6.5 mm screws. After removal of the drainage on postoperative day 1, isometric quadriceps, active ankle, and straightlegeraising exercises were initiated. The patients were allowed range of motion from 0 to 100 at 2 weeks
Table 1. Demographic Data of the Patients Variable No. cases Sex (male/female) Age, y, median (range) Height, cm, median (range) Body mass index, kg/m2 (median SD) Follow-up, mo (mean SD)
Data 90 24 of 66 53.4 (38-65) 162 (146-180) 26.9 3.8 34 18.7
P Value
Clinical Scores
Preoperative
Final Follow-up
Oxford (mean SD) Hospital for Special Surgery (mean SD)
21.3 7.9 63.8 7.1
40.7 9.5 89.7 4.7
.016 .003
SD, standard deviation.
after operation. Toe-touch weight bearing was allowed for 2 weeks after surgery followed by partial weight bearing for the next 4 weeks. Full weight bearing was allowed 6 weeks after radiographic evaluation for bone consolidation at the osteotomy site. No cast or brace was given postoperatively. Statistical Analysis PASW Statistics, version 18.0 (SPSS Inc, Chicago, IL), was used. P < .05 was considered significant. The reliability of the measurements was assessed by examining the intrarater and inter-rater reliability using the intraclass correlation coefficient (ICC). Two orthopaedic surgeons who are in our clinical fellowship working in the orthopaedic department performed the measurements twice at 2-week intervals. For evaluation of serial changes in the WBL ratio and the MA, statistical significance was tested using a paired t test.
Results The demographics of the included population are listed in Table 1. There were 66 women and 24 men (mean age, 54.5 and 50.8 years, respectively), with a mean followup period of 34 18.7 months. ICCs for the intra- and inter-rater agreement ranged from 0.973 to 0.991. Values for each of the 5 testing periods and their statistical results are listed in Tables 2 and 3. The preoperative WBL ratio and MA angle was 20.0 17.0 and varus was 7.2 4.4 . For the WBL ratio, statistical differences were observed between preoperatively and 1 month postoperatively (64.6 11.9) (P ¼ .00), 1 month and 6 months postoperatively (63.1 13.8) (P ¼ .04), 6 months and 1 year postoperatively (61.6 14.9) (P ¼ .04), and 1 month and 1 year postoperatively (P ¼ .01). However, no statistical significance was observed between 1 year and 2 years postoperatively (61.3 15.9) (P ¼ .22). The WBL was shifted medially with statistical significance until 1 year postoperatively. However, no statistically significant change was observed after 1 year (Fig 2).
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6 Mo Postoperatively 3.5y,z 3.9
Discussion
Mean SD
Each paired letter (a, b, c, d) shows statistical significance between the measures (P < .05). Each paired symbol (*,y,z,x) shows no statistical significant between the measures (P > .05). Negative measure indicates varus measure. MA, mechanical axis; SD, standard deviation; WBL, weight-bearing line.
1 Yr Postoperatively 61.6c,* 14.9 6 Mo Postoperatively 63.1b,c 13.8 1 Mo Postoperatively 64.6a,b 11.9 Preoperatively 20.0a 17.1
WBL Ratio (%)
Table 2. Serial Changes of the WBL Ratio and MA Angle
2 Yr Postoperatively 61.3* 15.9
Preoperatively 7.2d 4.4
1 Mo Postoperatively 3.9d,y 3.5
MA Angle ( )
1 Yr Postoperatively 3.3z,x 4.5
2 Yr Postoperatively 2.9x 4.5
For the MA angle, statistical differences were observed when the preoperative and postoperative 1-month radiographs were compared (3.9 3.5 ) (P ¼ .00) However, no statistical differences were observed between the postoperative views at 1 month and 6 months (3.5 3.9 ) (P ¼ .08), at 6 months and 1 year (3.3 4.5 ) (P ¼ .42), at 1 year and 2 years (2.9 4.5 ) (P ¼ .28), and at 1 month and 1 year (P ¼ .08). However, even though the absolute value showed a similar decreasing trend with time, the MA angle showed no statistical difference (P > .05) (Tables 2 and 3, Fig 3). The principal findings of this study were as follows: (1) the WBL was shifted medially with statistical significance until 1 year postoperatively and showed a steady state from 1 year postoperatively and (2) the absolute value of the MA valgus angle showed a decrease with time, although no statistical differences were observed. These results could imply that postoperative deviation of valgus angulation was not observed even though valgus angulation was achieved immediately postoperatively and MCL release was performed at the time of the operation. From these results, it was thought that union of the bony gap and healing of medial soft tissue would be related to these changes. The most expected scenario in OWHTO is that the line of the MA will be shifted laterally, after the abduction of the lower leg and the foot, leading to the reduction of the adduction moment that acts during the weight acceptance phase of the gait, which may contribute to the load acting on the medial compartment of the knee. However, the issue of where this MA should be positioned and where it crosses the knee is critical.1 Most surgeons usually aim toward having a valgus correction and perform MCL release during the operation.1-4,16 Therefore, previous studies have reported that postoperative deviation of valgus angulation17 and valgus instability could be accentuated, and a harmful effect could occur in the lateral tibiofemoral compartment.1-3 However, in another study, postoperative valgus instability was uncommon and valgus instability was decreased.7 In addition, undercorrection showed the worst results among undercorrection (<50% WBL), acceptable correction (50% to 70% WBL), and overcorrection (>70% WBL).18 In an evaluation of the lateral compartment after OWHTO using a sheep model, standard correction and overcorrection were reported to be safe procedures for the intact lateral compartment.19,20 The WBL ratio of the weight-bearing AP longstanding view of the lower extremity is regarded as an accurate assessment tool for restoration of coronal alignment in OWHTO.12 Pitfalls in determination of
SERIAL ASSESSMENT OF WBL AFTER OWHTO Table 3. Results of Statistical Analysis of the Data P Values (< .05) WBL Ratio (%) MA Angle ( ) Preoperatively v 1 mo postoperatively 0.00 0.00 1 mo v 6 mo postoperatively 0.04 0.08 6 mo v 1 yr postoperatively 0.04 0.42 1 yr v 2 yr postoperatively 0.22 0.28 1 mo v 1yr postoperatively 0.01 0.08
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by Marx et al.,23 who reported a correlation coefficient of 0.93 to 0.99. Rauh et al.24 reported significant interrater and intrarater reliability in determining lower extremity alignment; however, an average deviation of approximately 1 between measured and actual alignment was suggested. Our ICCs ranged from 0.973 to 0.991, similar to those reported by Marx et al.23
MA, mechanical axis; WBL, weight-bearing line.
knee alignment using a weight-bearing AP longstanding view of the lower extremity were reported by Brouwer et al.,21,22 who stated that isolated flexion or rotation has little effect, and simultaneous flexion of the knee and rotation of the leg cause large changes in projected angles. The reliability of a weight-bearing AP long-standing view of the lower extremity was assessed
Fig 2. The weight-bearing line (WBL) ratio was decreased with time until 1 year postoperatively and showed a steady state at 2 years postoperatively. (A) One month postoperatively. (B) Six months postoperatively. (C) One year postoperatively. (D) Two years postoperatively.
Limitations Our study has some limitations that must be considered. First, direct evaluation of the state of the collateral ligament was not performed, and the effect of pre- and postoperative ligamentous laxity is questionable. Second, only coronal alignment was evaluated, and it is influenced by flexion and axial rotation of the limb.9,21 Third, a precise explanation of the direct cause of these changes could not be determined.
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Fig 3. The mechanical axis (MA) angle was decreased with time until postoperative year 2, without statistical significance. (A) One month postoperatively. (B) Six months postoperatively. (C) One year postoperatively. (D) Two years postoperatively.
Conclusions This study showed that after OWHTO, the WBL shifts progressively medially until 1 year postoperatively.
References 1. Amis AA. Biomechanics of high tibial osteotomy. Knee Surg Sports Traumatol Arthrosc 2012;21:197-205. 2. Sim JA, Kwak JH, Yang SH, Choi ES, Lee BK. Effect of weight-bearing on the alignment after open wedge high tibial osteotomy. Knee Surg Sports Traumatol Arthrosc 2010;18:874-878. 3. Pape D, Duchow J, Rupp S, Seil R, Kohn D. Partial release of the superficial medial collateral ligament for openwedge high tibial osteotomy. A human cadaver study evaluating medial joint opening by stress radiography. Knee Surg Sports Traumatol Arthrosc 2006;14:141-148. 4. Lobenhoffer P, Agneskirchner JD. Improvements in surgical technique of valgus high tibial osteotomy. Knee Surg Sports Traumatol Arthrosc 2003;11:132-138.
5. Bito H, Takeuchi R, Kumagai K, et al. A predictive factor for acquiring an ideal lower limb realignment after opening-wedge high tibial osteotomy. Knee Surg Sports Traumatol Arthrosc 2009;17:382-389. 6. Birmingham TB, Giffin JR, Chesworth BM, et al. Medial opening wedge high tibial osteotomy: a prospective cohort study of gait, radiographic, and patient-reported outcomes. Arthritis Rheum 2009;61:648-657. 7. Gaasbeek RD, Nicolaas L, Rijnberg WJ, van Loon CJ, van Kampen A. Correction accuracy and collateral laxity in open versus closed wedge high tibial osteotomy. A one-year randomised controlled study. Int Orthop 2009;34:201-207. 8. Brouwer RW, Bierma-Zeinstra SM, van Raaij TM, Verhaar JA. Osteotomy for medial compartment arthritis of the knee using a closing wedge or an opening wedge controlled by a Puddu plate. A one-year randomised, controlled study. J Bone Joint Surg Br 2006;88:1454-1459. 9. Lee YS, Lee BK, Lee SH, Park HG, Jun DS, Moon DH. Effect of foot rotation on the mechanical axis and correlation between knee and whole leg
SERIAL ASSESSMENT OF WBL AFTER OWHTO
10.
11.
12.
13.
14.
15.
16.
17.
radiographs. Knee Surg Sports Traumatol Arthrosc 2013;21:2542-2547. Kraus VB, Vail TP, Worrell T, McDaniel G. A comparative assessment of alignment angle of the knee by radiographic and physical examination methods. Arthritis Rheum 2005;52:1730-1735. Sharma L, Song J, Felson DT, Cahue S, Shamiyeh E, Dunlop DD. The role of knee alignment in disease progression and functional decline in knee osteoarthritis. JAMA 2001;286:188-195. Lee DH, Han SB, Oh KJ, et al. The weight-bearing scanogram technique provides better coronal limb alignment than the navigation technique in open high tibial osteotomy. Knee. October 5, 2012. [Epub ahead of print.] Lee DH, Nha KW, Park SJ, Han SB. Preoperative and postoperative comparisons of navigation and radiologic limb alignment measurements after high tibial osteotomy. Arthroscopy 2012;28:1842-1850. Nha KW, Lee YS, Hwang DH, et al. Second-look arthroscopic findings after open-wedge high tibia osteotomy focusing on the posterior root tears of the medial meniscus. Arthroscopy 2013;29:226-231. Chae DJ, Shetty GM, Lee DB, Choi HW, Han SB, Nha KW. Tibial slope and patellar height after opening wedge high tibia osteotomy using autologous tricortical iliac bone graft. Knee 2008;15:128-133. Smith TO, Sexton D, Mitchell P, Hing CB. Opening- or closing-wedged high tibial osteotomy: a meta-analysis of clinical and radiological outcomes. Knee 2011;18:361-368. Brosset T, Pasquier G, Migaud H, Gougeon F. Opening wedge high tibial osteotomy performed without filling the defect but with locking plate fixation (TomoFix) and early
18.
19.
20.
21.
22.
23.
24.
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weight-bearing: Prospective evaluation of bone union, precision and maintenance of correction in 51 cases. Orthop Traumatol Surg Res 2011;97:705-711. El-Azab HM, Morgenstern M, Ahrens P, Schuster T, Imhoff AB, Lorenz SG. Limb alignment after open-wedge high tibial osteotomy and its effect on the clinical outcome. Orthopedics 2011;34:e622-e628. Madry H, Ziegler R, Orth P, et al. Effect of open wedge high tibial osteotomy on the lateral compartment in sheep. Part I: Analysis of the lateral meniscus. Knee Surg Sports Traumatol Arthrosc 2012;21:39-48. Ziegler R, Goebel L, Cucchiarini M, Pape D, Madry H. Effect of open wedge high tibial osteotomy on the lateral tibiofemoral compartment in sheep. Part II: Standard and overcorrection do not cause articular cartilage degeneration. Knee Surg Sports Traumatol Arthrosc. January 23, 2013. [Epub ahead of print.] Brouwer RW, Jakma TS, Bierma-Zeinstra SM, Ginai AZ, Verhaar JA. The whole leg radiograph: standing versus supine for determining axial alignment. Acta Orthop Scand 2003;74:565-568. Brouwer RW, Jakma TS, Brouwer KH, Verhaar JA. Pitfalls in determining knee alignment: a radiographic cadaver study. J Knee Surg 2007;20:210-215. Marx RG, Grimm P, Lillemoe KA, et al. Reliability of lower extremity alignment measurement using radiographs and PACS. Knee Surg Sports Traumatol Arthrosc 2011;19:1693-1698. Rauh MA, Boyle J, Mihalko WM, Phillips MJ, BayersThering M, Krackow KA. Reliability of measuring longstanding lower extremity radiographs. Orthopedics 2007; 30:299-303.
Purpose: The purpose of this study was to perform a serial assessment of the radiologic parameters of the mechanical axis (MA) and the weight-bearing line (WBL) using a weight-bearing anteroposterior (AP) long-standing view of the lower extremity to determine whether the postoperative MA and WBL change with time. Methods: A total of 90 consecutive lower limbs were examined retrospectively from a weight-bearing AP long-standing view of the lower extremity obtained from 120 patients who underwent open-wedge high tibial osteotomy (OWHTO). A total of 30 patients were excluded because of (1) complications (7 patients) such as bone graft collapse or broken screws, malunion, or nonunion arising after surgery and (2) no acquisition of a regular series of weight-bearing AP long-standing views of the lower extremity (23 patients). The AP long-standing view of the lower extremity was taken, and weight-bearing AP long-standing views of the lower extremity at 1 month, 6 months, 1 year, and 2 years postoperatively were used for assessment of serial change. The Picture Archiving Communication System (Marotech, Inc, St-Augustin-de-Desmaures, Quebec, Canada) was used for radiologic measurements of the WBL ratio and MA. Serial changes were compared between 1 month, 6 months, 1 year, and 2 years postoperatively. Results: The WBL ratio progressively shifted medially, with significant changes at all time points until 1 year postoperatively (1 month to 6 months, P ¼ .04; 6 months to 1 year, P ¼ .04; 1 year to 2 years, P ¼ .22). Even though the MA angle showed a similar decreasing trend, it showed no statistical difference (P > .05). Conclusions: This study showed that after OWHTO, the WBL shifts progressively medially until 1 year postoperatively. Level of Evidence: Level IV, diagnostic study.
D
uring open-wedge high tibial osteotomy (OWHTO), realignment usually aims toward having a valgus correction, and the overlying superficial medial collateral ligament (MCL) is usually managed in several ways: it is left intact, subperiosteal elevation is performed, or a partial
From Department of Orthopaedic Surgery (Y.S.L.), Seoul National University College of Medicine, Bundang Hospital, Gyeonggi-do; Department of Orthopaedic Surgery (B.K.L.), Gachon University, Gil Hospital, Incheon; Department of Orthopaedic Surgery (D.W.S.), Barunsesang Hospital, Seongnam; and Department of Orthopaedic Surgery (J.H.K., J.I.K., F.J.V.R., K-W.N.), Ilsan Paik Hospital, Inje University, Ilsan, South Korea. Supported by a 2014 Inje University Research Grant. The authors report that they have no conflicts of interest in the authorship and publication of this article. Received March 18, 2013; accepted November 26, 2013. Address correspondence to Kyung-Wook Nha, M.D., Department of Orthopedic Surgery, Ilsan Paik Hospital, Inje University, 2240, Daehwadong, Ilsan-Segu, Koyang-Si, Ilsan 411-706, Korea. E-mail: kwnhamj@ hotmail.com or [email protected] Ó 2014 by the Arthroscopy Association of North America 0749-8063/13188/$36.00 http://dx.doi.org/10.1016/j.arthro.2013.11.028
or complete release from its distal insertion is carried out.1-4 Therefore, it was proposed that the corrected valgus angulation shows an increase after weight bearing in patients who have undergone OWHTO,2 and it was suggested that the MCL release at the time of operation may be an important contributor to the overcorrection of the alignment and postoperative valgus instability.5,6 In addition, biomechanically, it is well known that any release of the MCL can increase the knee laxity when valgus stress is applied.3 However, interestingly, postoperative valgus instability or incremental corrected valgus angulation after OWHTO is an uncommon complication in the clinical situation.4,7,8 Varus, valgus, or neutral alignment is defined on the basis of the hip-knee-ankle angle, which requires visualization of all 3 joints.9-11 The weight-bearing AP long-standing view of the lower extremity is usually checked at weight-bearing conditions and is regarded as an accurate method for restoration of coronal alignment.9,12,13 Among various radiologic parameters, the mechanical axis (MA) and weight-bearing line (WBL)
Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 30, No 3 (March), 2014: pp 319-325
319
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Y. S. LEE ET AL.
Fig 1. Radiographs showing measurement method of (A) weight-bearing line (WBL) ratio (red line ¼ WBL; green line ¼ total length of tibial plateau; yellow line ¼ length from medial edge of tibial plateau to crossing point of the mechanical axis) and (B) mechanical axis (MA) angle (red line ¼ MA of femur; yellow line ¼ MA of tibia).
ratio are commonly used for assessment of lower extremity alignment.9,12,13 Lee et al.12,13 reported that the WBL ratio was more accurate than the navigation technique and the MA was a better radiologic parameter than the WBL ratio in the navigational OWHTO. The purpose of this study was to perform a serial assessment of the radiologic parameters of MA and WBL using the weight-bearing anteroposterior (AP) long-standing view of the lower extremity to determine whether the postoperative MA and WBL change with time. We hypothesized that the corrected valgus angulation would not deteriorate the postoperative valgus angulation with time even though the superficial MCL was released at the time of the surgery.
Methods Evaluation A total of 90 consecutive lower limbs were examined retrospectively using the AP long-standing view of the lower extremity obtained from 120 patients who underwent OWHTO from 2007 to 2011. The OWHTO was performed on patients with unicompartmental arthritis with a varus deformity. The exclusion criteria were as follows: (1) complications (7 patients) such as bone graft collapse or broken screws, malunion, or nonunion arising after surgery and (2) no acquisition of a regular series of weight-bearing AP long-standing views of the lower extremity (23 patients). Approval was obtained from the institutional review board and all patients provided
informed consent for participation. The weight-bearing AP long-standing view of the lower extremity was taken and standardized with the knee in full extension, the patella facing forward, and both feet facing forward at shoulder width in a weight-bearing state using a custommade foot plate.9 Weight-bearing AP long-standing views of the lower extremity were also taken 1 month, 6 months, 1 year, and 2 years postoperatively and were used for assessment of serial change. The Picture Archiving Communication System (Marotech, Inc, St-Augustin-de-Desmaures, Quebec, Canada), which can automatically measure to 2 decimal points, was used for radiologic measurements of the WBL ratio and MA. The WBL was drawn from the center of the femoral head to the center of the superior articular surface of the talus. For calculation of the WBL ratio, the denominator was the width of the tibia, as measured using a ruler, and the numerator was the tibial intersection of the WBL (with medial tibial edge at 0% and the lateral tibial edge at 100%) (Fig 1A).14 We used the degree that was rounded off the numbers to 2 decimal points. For calculation of the MA angle, we used the angle between a line drawn from the center of the femoral head to the center of the knee and a line drawn from the center of the knee to the center of the talus (Fig 1B). Serial changes were compared between views taken 1 month, 6 months, 1 year, and 2 years postoperatively. Surgical Technique Preoperatively, weight-bearing AP long-standing views of the lower extremity were obtained in all patients. A
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SERIAL ASSESSMENT OF WBL AFTER OWHTO
full-sized (100%) image of the radiograph was then printed on paper. Using this full-sized paper printout, the MA of the lower limb was plotted and the WBL percentage at the tibia was calculated. At the approximate site of the osteotomy at the proximal tibia, the paper was cut using scissors and a medial opening wedge was created such that the WBL passed through the lateral tibial plateau at 62% of the width of the plateau, which was the correction goal. Subsequently, the thickness of the wedge required to achieve a 62% WBL was determined using a ruler. However, in cases of WBL that passed medial to the medial tibial cortex, we aimed the WBL point to 50% to 60% if the preoperative plan of the osteotomy gap was more than 18 mm.12 Diagnostic knee arthroscopy was performed, at which time the menisci, ligaments, and articular cartilage were inspected, and debridement or meniscal surgery was carried out if necessary. The contralateral anterior iliac crest was prepared. The tricortical iliac crest bone was harvested by osteotomy or with an oscillating saw. The graft size was delineated on the bone by electrocautery with the mean graft dimensions of 30 mm in length, 10 to 15 mm in width, and 50 mm in depth. In smaller patients, the graft might be smaller in width, approximately 7 to 10 mm. The graft was fashioned into the appropriate size and shape using an oscillating saw to give an AP tricortical graft width ratio of 0.68 and to maintain the posterior slope.12,14,15 The anterior portion of the superficial MCL was partially released for reduction of pressure and exposure of the posteromedial cortex. In each case, the osteotomy was planned to originate at the medial tibial cortex along the metaphyseal flare (approximately 3 cm distal to the joint line) and terminated at the lateral tibial cortex (approximately 1 cm distal to the joint line, the fibular tip). The osteotomy was propagated through the proximal aspect of the insertion of the patellar ligament, leaving most of the ligament attached to the distal tibial fragment. Thin osteotomies were used to complete the osteotomy immediately short of the lateral cortex, keeping the lateral cortex and lateral capsular hinge intact. The previously fashioned triangular tricortical bone segment that was determined on the preoperative weight-bearing AP long-standing view of the lower extremity was inserted to be aligned with the opening gap shape and impacted into the osteotomy site. Once the stability, posterior slope, and final alignment had been confirmed by the cable method using an image intensifier, the bone graft was fixed in place using a Locking Compression Plate System (TomoFix, De Puy Synthes, Raynham, MA) with 6.5 mm screws. After removal of the drainage on postoperative day 1, isometric quadriceps, active ankle, and straightlegeraising exercises were initiated. The patients were allowed range of motion from 0 to 100 at 2 weeks
Table 1. Demographic Data of the Patients Variable No. cases Sex (male/female) Age, y, median (range) Height, cm, median (range) Body mass index, kg/m2 (median SD) Follow-up, mo (mean SD)
Data 90 24 of 66 53.4 (38-65) 162 (146-180) 26.9 3.8 34 18.7
P Value
Clinical Scores
Preoperative
Final Follow-up
Oxford (mean SD) Hospital for Special Surgery (mean SD)
21.3 7.9 63.8 7.1
40.7 9.5 89.7 4.7
.016 .003
SD, standard deviation.
after operation. Toe-touch weight bearing was allowed for 2 weeks after surgery followed by partial weight bearing for the next 4 weeks. Full weight bearing was allowed 6 weeks after radiographic evaluation for bone consolidation at the osteotomy site. No cast or brace was given postoperatively. Statistical Analysis PASW Statistics, version 18.0 (SPSS Inc, Chicago, IL), was used. P < .05 was considered significant. The reliability of the measurements was assessed by examining the intrarater and inter-rater reliability using the intraclass correlation coefficient (ICC). Two orthopaedic surgeons who are in our clinical fellowship working in the orthopaedic department performed the measurements twice at 2-week intervals. For evaluation of serial changes in the WBL ratio and the MA, statistical significance was tested using a paired t test.
Results The demographics of the included population are listed in Table 1. There were 66 women and 24 men (mean age, 54.5 and 50.8 years, respectively), with a mean followup period of 34 18.7 months. ICCs for the intra- and inter-rater agreement ranged from 0.973 to 0.991. Values for each of the 5 testing periods and their statistical results are listed in Tables 2 and 3. The preoperative WBL ratio and MA angle was 20.0 17.0 and varus was 7.2 4.4 . For the WBL ratio, statistical differences were observed between preoperatively and 1 month postoperatively (64.6 11.9) (P ¼ .00), 1 month and 6 months postoperatively (63.1 13.8) (P ¼ .04), 6 months and 1 year postoperatively (61.6 14.9) (P ¼ .04), and 1 month and 1 year postoperatively (P ¼ .01). However, no statistical significance was observed between 1 year and 2 years postoperatively (61.3 15.9) (P ¼ .22). The WBL was shifted medially with statistical significance until 1 year postoperatively. However, no statistically significant change was observed after 1 year (Fig 2).
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6 Mo Postoperatively 3.5y,z 3.9
Discussion
Mean SD
Each paired letter (a, b, c, d) shows statistical significance between the measures (P < .05). Each paired symbol (*,y,z,x) shows no statistical significant between the measures (P > .05). Negative measure indicates varus measure. MA, mechanical axis; SD, standard deviation; WBL, weight-bearing line.
1 Yr Postoperatively 61.6c,* 14.9 6 Mo Postoperatively 63.1b,c 13.8 1 Mo Postoperatively 64.6a,b 11.9 Preoperatively 20.0a 17.1
WBL Ratio (%)
Table 2. Serial Changes of the WBL Ratio and MA Angle
2 Yr Postoperatively 61.3* 15.9
Preoperatively 7.2d 4.4
1 Mo Postoperatively 3.9d,y 3.5
MA Angle ( )
1 Yr Postoperatively 3.3z,x 4.5
2 Yr Postoperatively 2.9x 4.5
For the MA angle, statistical differences were observed when the preoperative and postoperative 1-month radiographs were compared (3.9 3.5 ) (P ¼ .00) However, no statistical differences were observed between the postoperative views at 1 month and 6 months (3.5 3.9 ) (P ¼ .08), at 6 months and 1 year (3.3 4.5 ) (P ¼ .42), at 1 year and 2 years (2.9 4.5 ) (P ¼ .28), and at 1 month and 1 year (P ¼ .08). However, even though the absolute value showed a similar decreasing trend with time, the MA angle showed no statistical difference (P > .05) (Tables 2 and 3, Fig 3). The principal findings of this study were as follows: (1) the WBL was shifted medially with statistical significance until 1 year postoperatively and showed a steady state from 1 year postoperatively and (2) the absolute value of the MA valgus angle showed a decrease with time, although no statistical differences were observed. These results could imply that postoperative deviation of valgus angulation was not observed even though valgus angulation was achieved immediately postoperatively and MCL release was performed at the time of the operation. From these results, it was thought that union of the bony gap and healing of medial soft tissue would be related to these changes. The most expected scenario in OWHTO is that the line of the MA will be shifted laterally, after the abduction of the lower leg and the foot, leading to the reduction of the adduction moment that acts during the weight acceptance phase of the gait, which may contribute to the load acting on the medial compartment of the knee. However, the issue of where this MA should be positioned and where it crosses the knee is critical.1 Most surgeons usually aim toward having a valgus correction and perform MCL release during the operation.1-4,16 Therefore, previous studies have reported that postoperative deviation of valgus angulation17 and valgus instability could be accentuated, and a harmful effect could occur in the lateral tibiofemoral compartment.1-3 However, in another study, postoperative valgus instability was uncommon and valgus instability was decreased.7 In addition, undercorrection showed the worst results among undercorrection (<50% WBL), acceptable correction (50% to 70% WBL), and overcorrection (>70% WBL).18 In an evaluation of the lateral compartment after OWHTO using a sheep model, standard correction and overcorrection were reported to be safe procedures for the intact lateral compartment.19,20 The WBL ratio of the weight-bearing AP longstanding view of the lower extremity is regarded as an accurate assessment tool for restoration of coronal alignment in OWHTO.12 Pitfalls in determination of
SERIAL ASSESSMENT OF WBL AFTER OWHTO Table 3. Results of Statistical Analysis of the Data P Values (< .05) WBL Ratio (%) MA Angle ( ) Preoperatively v 1 mo postoperatively 0.00 0.00 1 mo v 6 mo postoperatively 0.04 0.08 6 mo v 1 yr postoperatively 0.04 0.42 1 yr v 2 yr postoperatively 0.22 0.28 1 mo v 1yr postoperatively 0.01 0.08
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by Marx et al.,23 who reported a correlation coefficient of 0.93 to 0.99. Rauh et al.24 reported significant interrater and intrarater reliability in determining lower extremity alignment; however, an average deviation of approximately 1 between measured and actual alignment was suggested. Our ICCs ranged from 0.973 to 0.991, similar to those reported by Marx et al.23
MA, mechanical axis; WBL, weight-bearing line.
knee alignment using a weight-bearing AP longstanding view of the lower extremity were reported by Brouwer et al.,21,22 who stated that isolated flexion or rotation has little effect, and simultaneous flexion of the knee and rotation of the leg cause large changes in projected angles. The reliability of a weight-bearing AP long-standing view of the lower extremity was assessed
Fig 2. The weight-bearing line (WBL) ratio was decreased with time until 1 year postoperatively and showed a steady state at 2 years postoperatively. (A) One month postoperatively. (B) Six months postoperatively. (C) One year postoperatively. (D) Two years postoperatively.
Limitations Our study has some limitations that must be considered. First, direct evaluation of the state of the collateral ligament was not performed, and the effect of pre- and postoperative ligamentous laxity is questionable. Second, only coronal alignment was evaluated, and it is influenced by flexion and axial rotation of the limb.9,21 Third, a precise explanation of the direct cause of these changes could not be determined.
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Fig 3. The mechanical axis (MA) angle was decreased with time until postoperative year 2, without statistical significance. (A) One month postoperatively. (B) Six months postoperatively. (C) One year postoperatively. (D) Two years postoperatively.
Conclusions This study showed that after OWHTO, the WBL shifts progressively medially until 1 year postoperatively.
References 1. Amis AA. Biomechanics of high tibial osteotomy. Knee Surg Sports Traumatol Arthrosc 2012;21:197-205. 2. Sim JA, Kwak JH, Yang SH, Choi ES, Lee BK. Effect of weight-bearing on the alignment after open wedge high tibial osteotomy. Knee Surg Sports Traumatol Arthrosc 2010;18:874-878. 3. Pape D, Duchow J, Rupp S, Seil R, Kohn D. Partial release of the superficial medial collateral ligament for openwedge high tibial osteotomy. A human cadaver study evaluating medial joint opening by stress radiography. Knee Surg Sports Traumatol Arthrosc 2006;14:141-148. 4. Lobenhoffer P, Agneskirchner JD. Improvements in surgical technique of valgus high tibial osteotomy. Knee Surg Sports Traumatol Arthrosc 2003;11:132-138.
5. Bito H, Takeuchi R, Kumagai K, et al. A predictive factor for acquiring an ideal lower limb realignment after opening-wedge high tibial osteotomy. Knee Surg Sports Traumatol Arthrosc 2009;17:382-389. 6. Birmingham TB, Giffin JR, Chesworth BM, et al. Medial opening wedge high tibial osteotomy: a prospective cohort study of gait, radiographic, and patient-reported outcomes. Arthritis Rheum 2009;61:648-657. 7. Gaasbeek RD, Nicolaas L, Rijnberg WJ, van Loon CJ, van Kampen A. Correction accuracy and collateral laxity in open versus closed wedge high tibial osteotomy. A one-year randomised controlled study. Int Orthop 2009;34:201-207. 8. Brouwer RW, Bierma-Zeinstra SM, van Raaij TM, Verhaar JA. Osteotomy for medial compartment arthritis of the knee using a closing wedge or an opening wedge controlled by a Puddu plate. A one-year randomised, controlled study. J Bone Joint Surg Br 2006;88:1454-1459. 9. Lee YS, Lee BK, Lee SH, Park HG, Jun DS, Moon DH. Effect of foot rotation on the mechanical axis and correlation between knee and whole leg
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10.
11.
12.
13.
14.
15.
16.
17.
radiographs. Knee Surg Sports Traumatol Arthrosc 2013;21:2542-2547. Kraus VB, Vail TP, Worrell T, McDaniel G. A comparative assessment of alignment angle of the knee by radiographic and physical examination methods. Arthritis Rheum 2005;52:1730-1735. Sharma L, Song J, Felson DT, Cahue S, Shamiyeh E, Dunlop DD. The role of knee alignment in disease progression and functional decline in knee osteoarthritis. JAMA 2001;286:188-195. Lee DH, Han SB, Oh KJ, et al. The weight-bearing scanogram technique provides better coronal limb alignment than the navigation technique in open high tibial osteotomy. Knee. October 5, 2012. [Epub ahead of print.] Lee DH, Nha KW, Park SJ, Han SB. Preoperative and postoperative comparisons of navigation and radiologic limb alignment measurements after high tibial osteotomy. Arthroscopy 2012;28:1842-1850. Nha KW, Lee YS, Hwang DH, et al. Second-look arthroscopic findings after open-wedge high tibia osteotomy focusing on the posterior root tears of the medial meniscus. Arthroscopy 2013;29:226-231. Chae DJ, Shetty GM, Lee DB, Choi HW, Han SB, Nha KW. Tibial slope and patellar height after opening wedge high tibia osteotomy using autologous tricortical iliac bone graft. Knee 2008;15:128-133. Smith TO, Sexton D, Mitchell P, Hing CB. Opening- or closing-wedged high tibial osteotomy: a meta-analysis of clinical and radiological outcomes. Knee 2011;18:361-368. Brosset T, Pasquier G, Migaud H, Gougeon F. Opening wedge high tibial osteotomy performed without filling the defect but with locking plate fixation (TomoFix) and early
18.
19.
20.
21.
22.
23.
24.
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weight-bearing: Prospective evaluation of bone union, precision and maintenance of correction in 51 cases. Orthop Traumatol Surg Res 2011;97:705-711. El-Azab HM, Morgenstern M, Ahrens P, Schuster T, Imhoff AB, Lorenz SG. Limb alignment after open-wedge high tibial osteotomy and its effect on the clinical outcome. Orthopedics 2011;34:e622-e628. Madry H, Ziegler R, Orth P, et al. Effect of open wedge high tibial osteotomy on the lateral compartment in sheep. Part I: Analysis of the lateral meniscus. Knee Surg Sports Traumatol Arthrosc 2012;21:39-48. Ziegler R, Goebel L, Cucchiarini M, Pape D, Madry H. Effect of open wedge high tibial osteotomy on the lateral tibiofemoral compartment in sheep. Part II: Standard and overcorrection do not cause articular cartilage degeneration. Knee Surg Sports Traumatol Arthrosc. January 23, 2013. [Epub ahead of print.] Brouwer RW, Jakma TS, Bierma-Zeinstra SM, Ginai AZ, Verhaar JA. The whole leg radiograph: standing versus supine for determining axial alignment. Acta Orthop Scand 2003;74:565-568. Brouwer RW, Jakma TS, Brouwer KH, Verhaar JA. Pitfalls in determining knee alignment: a radiographic cadaver study. J Knee Surg 2007;20:210-215. Marx RG, Grimm P, Lillemoe KA, et al. Reliability of lower extremity alignment measurement using radiographs and PACS. Knee Surg Sports Traumatol Arthrosc 2011;19:1693-1698. Rauh MA, Boyle J, Mihalko WM, Phillips MJ, BayersThering M, Krackow KA. Reliability of measuring longstanding lower extremity radiographs. Orthopedics 2007; 30:299-303.