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| ORIGINAL ARTICLE |
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| Year : 2021 | Volume
: 7
| Issue : 2 | Page : 132-137 |
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New measurements to determine changes after intra-articular high tibial osteotomy
Milind Chaudhary1, Aditya P Apte1, Jitsen Manna1, Ravi Bhadiyadra1, Prafulla Herode2
1 Centre for Ilizarov Techniques, Chaudhary Hospital, Akola, Maharashtra, India
2 Department of Orthopaedics, Rural Medical College, Loni, Maharashtra, India
| Date of Submission | 01-Dec-2021 |
| Date of Decision | 19-Dec-2021 |
| Date of Acceptance | 21-Dec-2021 |
| Date of Web Publication | 30-Dec-2021 |
Correspondence Address:
Dr. Milind Chaudhary
Centre for Ilizarov Techniques in India, Chaudhary Hospital, Civil Lines, Akola - 444 001, Maharashtra
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/jllr.jllr_41_21
Background: Most high tibial osteotomies (HTO), performed for medial compartment osteoarthritis of the knee (MCOA) are extra-articular osteotomies of the upper tibia. Recently, attention has turned to detecting and treating intra-articular deformities of the upper tibia causing MCOA. Chiba introduced the tibial condylar valgus osteotomy (TCVO) in Japan and few English language articles have described indications, surgical techniques of results of these osteotomies. Two angles commonly measure and detect the intra-articular deformity and measure the difference between preoperative and postoperative parameters: Joint line convergence angle (JLCA) and condylar plateau angle (CPA). Aims and Objectives: JLCA is relatively easy to measure as it uses clearly visible landmarks to draw tangents to femoral and tibial condyles to subtend the angle. CPA is a little difficult to measure and we found it to be less reliable in intra-observer as well as interobserver readings. Materials and Methods: We decided to measure the intra-articular deformity by using spine edge angle (SEA) and spine vertical distance (SVD) as two new measurements. These have proved to be reliable in intra as well as interobserver measurements. We compared readings of SEA and SVD in 57 patients each who had an intra-articular TCVO and also an extraarticular medial open wedge HTO (OWHTO). Results: We found a significant change between preoperative and postoperative measurements of SEA and SVD in patients who underwent TCVO, but no change in patients who underwent OWHTO. Conclusions: The two new measurements of SEA and SVD accurately measure the change in intra-articular deformity parameters in patients who undergo TCVO and are more reliable than CPA.
Keywords: Condylar plateau angle, high tibial osteotomy, intraarticular osteotomy, joint line convergence angle, spine edge angle, spine vertical distance, tibial condylar valgus osteotomy
How to cite this article:
Chaudhary M, Apte AP, Manna J, Bhadiyadra R, Herode P. New measurements to determine changes after intra-articular high tibial osteotomy. J Limb Lengthen Reconstr 2021;7:132-7 |
How to cite this URL:
Chaudhary M, Apte AP, Manna J, Bhadiyadra R, Herode P. New measurements to determine changes after intra-articular high tibial osteotomy. J Limb Lengthen Reconstr [serial online] 2021 [cited 2023 Feb 2];7:132-7. Available from: https://www.jlimblengthrecon.org/text.asp?2021/7/2/132/334382 |
| Introduction | |  |
High tibial osteotomy (HTO) is a well understood and time-tested method of treatment for medial compartment osteoarthritis (MCOA) of knee. Most osteotomies described around the knee are extra-articular corrections of mostly upper tibial or lower femoral varus deformities. The medial opening wedge osteotomy (open wedge HTO [OWHTO]) enjoys a surge in popularity lately due to good instrumentation, ability to achieve accurate correction into valgus, early mobilization and preservation of upper tibial anatomy for any future need for total knee arthroplasty. Closing wedge lower femoral osteotomies have been described in combination of upper tibial deformities to preserve the knee joint line orientation when large corrections only through upper tibia could alter it.[1]
Large varus deformities with a significant deviation of the mechanical axis may have an intra-articular component to the varus deformity.[2] Blount's disease has a depression of the medial tibial plateau and a large varus. Hemi-plateau elevation is a well-known treatment for Blount's disease.[3] Intra-articular HTO is akin to the Hemiplateau elevation. Chiba described an intra-articular osteotomy called the tibial condylar valgus osteotomy (TCVO) in 1989.[4] Few articles in English describe its indications, surgical technique and compare it with extra-articular osteotomies[4],[5],[6],[7],[8],[9],[10],[11],[12] Joint line convergence angle (JLCA) and condylar plateau angle (CPA) help in detecting an intra-articular deformity, along with a large deviation of mechanical axis and presence of lateral thrust gait. JLCA is easy to measure as it describes the angle subtended by tangents to lower femoral and upper tibial condyles. A range of 0°–5° is considered normal. Angles larger than 5° suggest an intra-articular deformity. CPA is described by some as medial tibial plateau depression angle (MTPD).[4],[5],[6] It is, however, poorly described and has indistinct or ambiguous landmarks for measurement. It measures the angle between the two condyles of the upper tibia. Ideally, the two condyles are collinear. Kuwashima et al.[9] have described three types of upper tibial shapes. Flat, pagoda, and depression types. A “flat” shape describes a normal upper tibia. When the intercondylar eminences are prominent upward and tibial condyles slope downward, it shows a “pagoda” tibia. A depressed medial tibial condyle may cause the pagoda shape. This is an ideal indication for an intra-articular correction using the TCVO. The third type of upper tibial shape is the depression type where the tangents to the tibial condyles converge and slope downward toward the center. Here, the intercondylar eminences are not higher than the edges of the two tibial condyles. A TCVO will not work for this shape of the upper tibia.
Extra-articular osteotomies can reduce JLCA, though indirectly. Heijens[11] has described the phenomenon of the coronal hypomochlion where the tipping point to correction of JLCA in extra-articular osteotomies is at hip knee ankle (HKA) angle of 2° valgus. A combination of osseous deformity and capsuloligamentous laxity cause intra-articular deformity. Therefore, it may be difficult to assess efficacy of correction of the intra-articular deformity by JLCA alone. The main difficulty in measuring MTPD or CPA is dearth of literature and a lack of clearly defined landmarks to draw tangents to the medial and lateral tibial condyles.
While the literature on this subject is scant, we found significant difficulties in measuring CPA in our analysis of intra-articular osteotomies that we have performed over the last 7 years at our institute. We found that landmarks to determine the perfect tangents to the medial and lateral tibial condyles varied significantly between observations [Figure 1] and [Figure 2]. | Figure 1: Condylar plateau angle as measured by Observer 1. Normally medial and lateral tibial condyles are collinear. The medial tibial condyle is frequently depressed in medial compartment osteoarthritis. Tangent to the broadest convex part of medial and lateral condyles is drawn and acute angle is measured. Here it is measured as 12.8°
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 | Figure 2: Condylar plateau angle (CPA) of the same patient as measured by Observer 2. As the perception of the broadest convex part of tibial plateau varies from observer-to-observer CPA measurement can differ significantly. Here it is measured as 30.5°
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We aimed to analyze the variability and lack of reliability of estimation of CPA. We aimed also to establish a new set of measurements which reliably measure the intraarticular deformity and its correction after surgery. We describe a new angle called the spine-edge angle (SEA) and a measurement called the spine vertical distance (SVD). We aimed to study the intra-observer and inter-observer variability using intraclass correlation coefficients for these two measurements. We also compared the change in these two measurements in 57 knees with TCVO and 57 knees which underwent an extra-articular OWHTO.
| Materials and Methods | | |
We have performed 57 intra-articular HTOs in 49 patients since the last 7 years at our institute. Thirty-three of them were only intra-articular osteotomies and were fixed with a medial locking plate. 24 of them had a combination of intra and extra-articular osteotomies and were fixed using an Ilizarov external fixator. In these patients, the second dome osteotomy achieved additional extra-articular correction to improve correction of mechanical axis into valgus. It was performed in the upper diaphysis, about an inch below the lower extent of the intra-articular osteotomy.
We used full length X-rays to measure the mechanical axis deviation (MAD), JLCA, CPA before (bo) and after (po) surgery. We also measured the SEA and SVD before and after surgery. Two observers (trained clinical fellows) performed the measurements at least 3 weeks apart each. We used Carestream Image Suite 4.1 mini-PACS system for the measurements.
We measured JLCA and CPA as described above. SEA was measured as follows. Apex of the angle was at the zenith of the medial tibial spine. Two arms extended to the upper edges of the medial and lateral tibial plateau. This angle ranged from 145° to 165°, with its apex cephalad [Figure 3] and [Figure 4]. SVD was measured as follows. A horizontal line connected the proximal-most points of the edges of the medial and lateral tibial condyles. A perpendicular dropped from the apex of the medial tibial spine to this line was measured in millimeters [Figure 5] and [Figure 6]. Similar measurements were made for 57 knees who underwent an extra-articular OWHTO, and we aimed to compare the difference between these two disparate types of osteotomies. | Figure 3: Preoperative measurement of spine edge angle in a 58-year-old female with medial compartment osteoarthritis. Apex of the angle is at the zenith of the medial tibial spine. One arm is extended to the medial most edge of the medial tibial plateau and another arm is extended to the outermost point of the lateral tibial plateau. Here it is measured as 147.1°
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 | Figure 4: Postoperative measurement of spine edge angle. Measured as 162.2
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 | Figure 5: Preoperative measurement of spine vertical distance (SVD). The innermost and outermost points of the tibial plateaus are connected with a straight line. A vertical is dropped from the apex of the medial tibial spine to this line and the distance is calculated as SVD. Measured as 11.29 mm
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 | Figure 6: Postoperative measurement of spine vertical distance. Measured here as 7.03 mm
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We entered data and calculated means, and intra-observer and inter-observer variability in MS Excel. P < 0.05 was considered statistically significant.
Surgical technique
We used regional anesthesia with tourniquet control to perform TCVO intra-articular osteotomy. We used fluoroscopy and a video camera to record the mediolateral, antero-posterior, and rotational laxity. A vertical incision extends from upper pole of patella to 2 inches below tibial tuberosity. Medial and lateral patellar retinacular releases[12],[13] were performed on all patients as they had patella-femoral joint line tenderness. We elevated the pes anserinus along with the superficial medial collateral ligament from the medial tibia. An L-shaped osteotomy was performed with its vertical limb medial to the patellar ligament from the joint line extending down for 3.5 cm. A horizontal limb extending medially was outlined with a sharp osteotome and the posterior cortices at both limbs were carefully cut under Image intensifier control. Care was taken not to plunge the osteotomes posteriorly. Before starting correction, a thin 1.8 mm wires were inserted subchondrally with stoppers on either side to prevent separation of the tibial condyles. The osteotomy was spread apart by a valgus directed force applied to the leg and then using an arthrodesis spreader.
Adequate correction was achieved when mediolateral laxity was eliminated and good alignment into valgus was achieved. The osteotomy was fixed with a medial locking plate.
In 28 cases with a large preoperative varus deformity with MAD <0%, we chose to perform a double osteotomy. The second osteotomy was performed one inch distal to the first one and was a diaphyseal focal dome osteotomya performed by drill hole technique. In these patients, a proximal fibulectomy was also performed. The upper intra-articular osteotomy was fixed with a cancellous screw. Two tapering (thread taper of five to four mm) half pins were inserted, one from medial and lateral side each crossing the vertical osteotomy line. Two thin (thread taper of 4 to 3 mm) half pins were inserted in anteroposterior direction just below the upper osteotomy. All four pins were fixed with an Ilizarov ring. Fixation distal to the distal osteotomy was achieved with two rings having one half-pin each. These rings were separated by at least 15 cm and gave a stable fixation [Figure 7]. More half pins and wires can be added to distal block depending on height and weight of the patient to enhance stability. The distal dome osteotomy was analogous to the Ilizarov Focal Dome or the Subtubercle osteotomy described by Warner.[14],[15] | Figure 7: 50-year-old with a large varus with a high JLCA and CPA was treated by an Ilizarov fixator and a double osteotomy in the tibia. The Intra-articular osteotomy was acutely corrected and fixed with pins attached to upper ring. The second extra-articular dome osteotomy is corrected gradually between first and second rings.
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The distal osteotomy was completed, and the distal fragment was minimally laterally translated. Good bony contact in the dome or arcuate osteotomy was maintained. The correction of extra-articular varus through this osteotomy was fine-tuned with help of hinges. Some correction was also done after surgery to ensure that mechanical axis passed around the Fujisawa point.
| Results | | |
There were 15 male and 34 female patients (total of 49 patients) with 24 left and 33 right knees.
The mean age was 54.2 years (17–77 years). There were 25 KL Grade III and 32 Grade IV knees.
There was near perfect correlation of MAD readings before (0.999879) and after surgery (0.999852) between the observers.
There was poor reliability of the intra-observer correlation coefficients for CPA. There was poor correlation of preoperative measurements of CPA (0.37) between the observers and moderate correlation (0.54) for the postoperative readings of CPA.
The new measurements of SEA had moderately good correlation in intra-observer readings but excellent in the inter-observer readings. The results were similar for SVD [Table 1].
The means of all measurements are given in [Table 2].
The intraclass correlation coefficient of these two measurements in extraarticular osteotomies [Table 3] between the two observers is high. | Table 3: Inter observer intraclass corelation coefficient of extra-articular osteotomies
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The values of t-test to compare the change between preoperative and postoperative measurements of SEA and SVD in extra-articular OWHTO showed no significant change [Table 4]. | Table 4: Change in measurements of extraarticular osteotomies before and after surgery
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| Discussion | | |
Intraarticular HTOs are a relatively new method of reparative surgery for MCOA. Knowledge about the indications, surgical technique, results, and complications is gradually increasing.[4],[5],[6],[7] Two accepted radiological measurements point to an intra-articular deformity, namely JLCA and CPA.[8] This is analogous to the MTPD angle described in Blount's disease.[3]
JLCA is easy to measure as the anatomic landmarks are relatively reliable [Table 1] as seen in good interobserver reliability in our series. CPA measures the lack of collinearity of the two condyles of the tibia. When the two condyles are not collinear, it leads to point loading of the medial condyles giving rise to excessive pressure in the medial compartment of knee.
However, we experienced difficulties in accurately measuring the CPA. There are no clear guidelines in the literature about how to measure the angle. While MTPD in Blount disease is easy to measure because of the large deformity, the osseous deformity in MCOA is usually smaller and therefore difficult to measure. Even three to five degrees of medial condylar depression may be enough to cause point loading of the medial condyle and cause pain. We found remarkable lack of reliability in both interobserver or intra-observer readings of CPA.
Therefore, we created two new measurements using reliable anatomical landmarks. Apex of the medial tibial spine and edges of the medial and lateral tibial condyles helped draw both the SEA and the SVD. Both these parameters have shown to be reliable in repeat measurements and between observers [Table 1]. We found no change in these parameters in patients who underwent an extraarticular OWHTO. This proves that both SEA and SVD are reliable to measure the change in the intra-articular anatomy or deformity of the upper tibia when performing an intra-articular osteotomy like the TCVO.
There are several limitations to our study. SEA and SVD merely record the change in the anatomy after surgery reliably. We have not proved these measurements can diagnose an intra-articular deformity of the upper tibia. Both bony deformities and capsuloligamentous changes contribute to the intra-articular deformity. Clinical findings of increased medio-lateral laxity and a dynamic varus gait additionally help decide the need for an intra-articular osteotomy.[9] A large deviation of the mechanical axis points[2] to the possible presence of an intra-articular deformity as was seen in the high deviation of MAD in our TCVO cases [Table 1].
We ideally need to compare SEA and SVD in patients with small and large deviations of the mechanical axis to establish if they are diagnostic of an intra-articular deformity. In the worst-case scenario, we may find no difference in SEA and SVD with mild or severe deviation of the Mechanical Axis. As a limited goal, we find that our study succeeds in establishing two new measurements to gauge the difference between preoperative and postoperative measurements of deformity parameters used in intra-articular HTOs.
Perhaps, cineradiographic measurements of increased medio-lateral laxity would help differentiate intra- and extraarticular deformities. Perhaps, more sophisticated measurements such as statistical shape analysis of the tibial condyles using 3-dimensional data using CT scans may be more accurate.
| Conclusions | | |
We did not find the CPA to be a reliable measurement of intra-articular deformity in surgeries of TCVO. We propose a new set of measurements: The SEA and the SVD to measure the difference in preoperative and postoperative deformity arising from the upper tibia, within the joint.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient (s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
[Table 1], [Table 2], [Table 3], [Table 4]
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