Abstract
Background
Advanced osteoarthritis of knees with varus deformity consists of attenuation of lateral structures with contracture of the posteromedial structures and formation of medial osteophytes. The conventional step-wise medial and posteromedial release with measured resection may sometimes hinder achievement of perfectly balanced flexion and extension gaps with maintenance of flexion stability, without the use of a constrained prosthesis. Medial femoral epicondylar sliding osteotomy tailors the balancing to the need of the kinematics of the native knee and precludes the use of a constrained implant.
Methods
15 patients with Ahlbäck Grades III through V osteoarthritic changes at Howrah Orthopaedic Hospital were included in a prospective cohort case series with a minimum period of follow-up being 12 months. Physical examination, clinical questionnaire and radiographic evaluation were done post-operatively for objectification by functional Knee Society and Oxford Knee Scores respectively.
Results and Analysis
The mean post-operative femorotibial angulation ameliorated to a value of 3.73 ± 1.58° from 18.67 ± 4.2° in the pre-operative stage. The mean overall Range of Motion of operated knee was 109.87 ± 6.86° with no residual frontal laxity and/or laxity in the coronal plane. The mean amount of resection of tibial plateau in patients with severe varus deformity was kept to a minimum, 6.56 mm from the least deficient portion of the lateral condyle. There were no complications as regards component loosening and/or surgical-site infection.
Conclusion
The main objective of balancing a severely varus-afflicted knee is to preserve as much of the Medial Collateral Ligament as possible, to retain its check rein function and not jeopardise the stability. This is ensured by distalisation and posteriorizing the medial epicondyle by an incomplete osteotomy in addition to modest tibial resection fetching a non-isometric point of knee flexion. All osteotomies united by bony union and restoration of kinematic alignment. The limitation of this study however includes the lack of long-term results, such as late instability and polyethylene wear.
Keywords: Medial epicondylar sliding osteotomy, Varus, Tibial resection, Gap balancing
Introduction
The lifetime risk of developing knee osteoarthritis is 44.7% according to the study conducted in Johnston County [1]. The pathoanatomy in a fixed varus deformity of knee comprises medial tibial osteophyte formation with subtle erosion of the medial tibial bone stock along with contractures of the medial structures and posteromedial capsule with stretching of the Lateral Collateral Ligament, which of course, is a late sequel. The structures to undergo contractures are the Medial Collateral Ligament, Pes Anserinus and Semi-Membranosus muscle.
Varus malalignment defined as a tibiofemoral mechanical angle of 177° or less, or arbitrarily defined as more than 15°–20° varus deviation from the mechanical axis increases the risk of disease progression fourfold [2], as opposed to a normal alignment angulation of 180° ± 3° [3]. Due to a varus adduction moment during gait, there is off-loading of the lateral compartment with increased burden on the medial tibial condyle, thereby accelerating the process of erosion and advancement of secondary changes such as osteophyte formation. In a varus-afflicted medial osteoarthritic knee, the medial facets in flexion and extension are both affected heavily as depicted by reflection on the normal morphometry Fig. 1. Condylar morphometry reveals that axes such as the transepicondylar and posterior condylar ones, used to align the femoral component determine the rotational alignment and contact pressures in an implanted knee [4], whereas the posterior condylar, the condylar centre’s and the tibial tubercle axes are used to align the tibial tray [5] for the same reason. However, these get altered in a varus deformity leading to malalignment and altered biomechanics, if patient-specific implantation is not executed keeping in mind the aforementioned fact.
Fig. 1.
Morphometric analysis to define flexion and extension facets in the distal femur with the one in extension reaching upto the medial sulcus terminalis (dotted line) and being divided into four zones [4]
In the femur, Puthumanapully et al. [6] showed diminished femoral anteversion with external rotation of the tibial tubercle axis and increased slope in the coronal plane. The Medial Collateral ligament is, not actually shortened in length; rather some contributing factors such as the fibrosis of posteromedial complex including the posterior oblique ligament, impingement by medial osteophytes and extrusion of medial meniscus provoke deformation of the most pivotal medial structure with posterior bowstringing. Proper soft tissue balancing in this regard will pave way for the long survivorship of an implanted knee. Some are proponents of the measured resection technique relying on the axes, while others are focussed on obtaining the equal tensioning of the soft tissue restraints on either side of the knee joint centre, by placing parallel cuts on the femur and tibia respectively. Primary or secondary osteoarthritis with varus deformity is a menace to deal with, when proper kinematic alignment is compromised in a desperate attempt to balance by measured resection technique and the good old classical order of medial release (Figs. 2, 3, 4 and 5). There are three components of the superficial MCL for release, namely the femoral origin, the mid-substance and the tibial insertion. Inadvertent release at the cost of stability of the joint can cause condylar lift off. However, knees with rigid varus deformities may necessitate sub-periosteal elevation of the tibial attachment of superficial MCL, perhaps requiring a more constrained implant [7]. Also, the mid-substance of the ligament can be pie-crusted or pierced by hypodermic needle for release. On the contrary, inadequate medial release may lead to polyethylene wear, and potential component loosening due to persistent adductor thrust [8]. The Medial Condylar Sliding Osteotomy is performed only when, despite adequate soft tissue releases from femur and tibia and subsequent medial tibial reduction osteotomy, the medial joint space still remains tight and does not allow trial tibial baseplate with the insert to go in on the medial side (whereas the lateral joint space is adequate to allow the same insert easily without much effort). Engh and Ammeen et al. [9] demonstrated a technique of detachment of MCL with a sliver of medial epicondyle including the insertion of Adductor Magnus tendon and allowed to fall back and behind without any internal fixation. Broadly speaking, this sort of procedure is employed when medio-lateral soft tissue gap difference exceeds 2 mm in full extension and at 90° flexion, or flexion extension gap difference exceeds 2 mm with or without a residual varus deformity of 3° despite extensive soft tissue release and medial tibial reduction osteotomy [10]. Mullaji et al. [11] in his landmark paper employing computer navigation to execute a sliding medial epicondylar osteotomy demonstrated that the degree of medio-lateral laxity improved from Grade 3 in eight knees and Grade 2 in four knees to Grade I (< 5 mm) in all the knees post-operatively with improvement of mean Knee Society Score from 30 (10–54) to 92 (86–100) and that of mean knee flexion from 106° to 112° with no extensor lag or residual flexion deformity by more than 5°. Sim et al. [12] in his article of short-term follow-up of the procedure showed an improvement of femorotibial angle from pre-operative varus of 8. 2 ± 5° to post-operative valgus of 5.6 ± 1.5° with change of mechanical axis from varus of 13.9 ± 4.5° to varus of 0.7 ± 1.6° (P-value < 0.001). Gabriel Stan et al. [13] in his comparative study between sliding osteotomy and additional tibial medial plateau resection illustrated a statistically significant lesser amount of bone resection in the former group (1.63 ± 0.96 mm vs 4.73 ± 2.7 mm; P value < 0.001) with the requirement of a lower thickness of polyethylene insert. The main aim of the osteotomy deployed is to detension the MCL without damaging the same. The osteotomised fragment is well positioned due to attachment of posterior cortex and surrounding soft tissue attachments. The surface area of osteotomy is more important than size of the fragment. The larger surface area, the better and quicker chance of bony healing (Figs. 6, 7).
Fig. 2.
Osteotome used to subperiosteally strip medial supporting structure while maintaining a continuous soft tissue sleeve [7]
Fig. 3.
Subperiosteal sleeve dissection off anteromedial tibia, comprising Superficial and deep fibres of MCL with/without Pes Anserinus [7]
Fig. 4.
Semimembranosus insertion sharply dissected with tibia externally rotated [7]
Fig. 5.
Depicting the sequential order of medial and posteromedial soft tissue releases in order to balance a varus knee. [GAP BALANCING METHOD]
Fig. 6.
Schematic free hand diagram of distal femur with trial implant in position; The red line segments represents proposed Osteotomy line; SB SAW BLADE
Fig. 7.
Schematic free hand diagram depicting the distalisation and posteriorisation of the osteotomised medial condyle
Materials and Methods
Study Design
Fifteen patients between 2018 and 2023 having Grade III to V Ahlback classification of knee osteoarthritis arriving at Howrah Orthopaedic Hospital were operated on for fixed varus deformities with sliding medial condylar osteotomy as a method to balance the knee, when medial structures were tight despite a medial tibial reduction osteotomy. The inclusion criteria were primary osteoarthritis with varus > 15° and the exclusion criteria being post-traumatic secondary osteoarthritis, neuromuscular disease, congenital deformities and BMI > 30. The mean length of follow-up of patients was 18 months with the minimum being 12 months. None of the patients were lost to our follow-up. The mean age of patients was found to be 57.2 and the mean BMI 27.4 kg/m2.
Proper preoperative planning was undertaken by employing standing orthoscanograms of bilateral lower limbs and true size AP and Lateral skiagrams of the affected knees. Posterior Stabilised Knee implants were used in all patients and the criterion for going forward with an osteotomy was more than 4 mm of medio-lateral imbalance despite adequate posteromedial release and medial tibial reduction osteotomy with modest amount of release of the superficial MCL fibres from its proximal tibial attachment. The functional outcome was assessed using the Knee Society Score and Oxford knee questionnaire while the radiographic outcome was assessed in terms of bony union, emergence of osteolysis and any subtle changes in the tibial slope.
Surgical Technique
First, proximal tibial cut was performed perpendicular to mechanical axis of tibia. Next, distal femoral cut was performed parallel to the proximal tibial cut. The preliminary estimations for stability and tightness in extension were performed. Medial side osteophytes were excised and deep MCL was elevated in all cases. If the medial side still was tight in extension, medial and posteromedial capsule and soft tissue including the semimembranosus were released. If the correction was made, the anterior–posterior and chamfers cuts were performed, PCL removed, and the femoral trial was created with an appropriate insertion in the extension.. In cases where the medial side was tight in flexion, a small segment of the posteromedial edge of tibial plateau was excised (Fig. 8). After this, a trial spacer was inserted to assess the balance (Fig. 9). If in this situation, the medial joint space was still unaccepting of the spacer block in contrast to a lax lateral joint space, an incomplete sliding femoral osteotomy with a narrow saw was done to ensure cutting of 85% of the condylar cross section. The main trick of MCSO is to mark the osteotomy site all around with marking pen with the femoral trial implant in proper place (Fig. 10). The osteotomy is performed along the marking keeping the femoral trial seated on femur (Fig. 11). This femoral trial component gives protection of osteotomy (to avoid saw/Osteotome inadvertently go laterally into the medial condyle). The plane of osteotomy starts 5 mm lateral to the medial edge of the bony femoral condyle and extending superomedially to exit distal to the adductor tubercle. The osteotome was used thereafter to open up the osteotomy. The length of osteotomy was determined by the medio-lateral imbalance and the difference between the medial and lateral gaps quantified to assess the medial tightness necessitating a sliding osteotomy. The thin wafer of bone was removed after assessing the lateral joint space in extension followed by calibrating the tension in the medial gap by a laminar spreader to render a perfectly rectangular extension gap (Fig. 12). Thereafter, a rectangular flexion gap was achieved by tensioning in the laminar spreaders with the knee in 90° flexion. The osteotomised segment was then distalised and posteriorized after placement of the implant to relax the anteromedial part of Superficial MCL ( Figs. 13, 14). Trial implants were placed and stability assessed in extension by giving a valgus stress, followed by assessment of stability in flexion (Figs. 15, 16).
Fig. 8.
Reduction osteotomy of medial tibial condyle done
Fig. 9.
Lax lateral joint space allowing a 9 mm insert while the medial space is still tight despite extensive medial release and a reduction osteotomy of the medial tibial condyle
Fig. 10.
Marking of the osteotomy site
Fig. 11.
Incomplete osteotomy of the medial femoral condyle
Fig. 12.
Opening up of the osteotomy site
Fig. 13.
After osteotomy, medial joint space allows easy insertion of tibial insert and the arrow pointing to opened up osteotomy site. Also note that the soft tissue attachment of the osteotomised fragment is completely intact at the base and proximally
Fig. 14.
Medial epicondyle has moved distally and posteriorly to relax the anteromedial portion of Superficial MCL
Fig. 15.
Valgus stress to assess stability of osteotomy in extension
Fig. 16.
Stability of osteotomy in flexion
Then, cement preparation was done and the bone bed prepared for the final implantation. The condylar block was fixed to the distal femur at its translocated position with cancellous screws with washers after definitive implant incorporation. Because the osteotomised fragment is distalised, a portion of the osteotomised condylar fragment might be seen coming down at the joint level. In this situation, the overhanging portion should be nibbled out.
Outcome Measurement
Clinical and radiographic assessments were done preoperatively and at the latest follow-up visit to the OPD. All patients were followed up for a length of 12 months minimum and the functional outcome was assessed by means of Knee Society Score and Oxford Knee questionnaire. Active Range of Motion was measured using a goniometer. Post-operative radiographic outcome was assessed by doing a full length standing AP scanogram of the bilateral lower limbs to evaluate the mechanical axis and Macquet’s line. Valgus and Varus stress X-Rays were also done in extension and 30° of flexion to evaluate any instability. At the latest follow-up, union of the osteotomised segment was assessed by skiagrams and classified either as a bony bridging callus formation or a fibrous union.
Results and Analysis
Fifteen patients were enrolled in this prospective study with a minimum duration of post-operative follow-up and radiological assessment being 12 months, to demonstrate the midterm results of sliding osteotomy, precluding the use of constrained prosthesis and/or sacrificing more bone. These included patients with Grade III or IV osteoarthritis having concerns of performing activities of daily living and/or experiencing volatility of confidence akin to progressive deformity in the knees. Apart from those patients with osteoarthritis, we had two patients of rheumatoid arthritis having varus and fixed flexion deformity in the concerned knee. One of our patients in this series was having osteonecrosis of the knee and another developing arthritis secondary to previous trauma. The first patient enrolled in this series of data is having a 5-years period of follow-up owing to his surgery being performed in 2018, while the last patient to be included, is having a one year of follow-up. The sequential clinical assessments were done at 2 weeks post-surgery and then at 6 weeks, 3 months, 6 months and 12 months respectively. The radiological assessment of union of the osteotomized site was done at 6 months and then at 12 months with skiagrams. Clinical assessment was recorded using the clinical and functional Knee Society Scores and the Oxford Knee Questionnaire respectively at 6 weeks, 3 months, 6 months and 12 months. The clinical and functional scores were found to have ameliorated gradually till 1 year post-surgery and the final outcome assessment tabulation was done at 12 months.
The mean age of patients with primary tricompartmental osteoarthritis as the etiology of varus deformity was 59.82, while patients with rheumatoid arthritis were having a mean age of 46.5. Patients with secondary arthritis were having a mean age of 53.5. A significantly lower mean age for patients with rheumatoid arthritis and secondary causes was evident when compared to patients with primary tri-compartmental osteoarthritis (P = 0.0019, t = − 3.885). The average BMI of patients was in the overweight band (Mean = 27.4) and the gender distribution of the BMI categories is depicted in 233.33% of our study population were males and the rest 66.67% were females. Full-length anteroposterior standing orthoscanograms were done for all patients to assess the mechanical axis deviation whose calculated population mean was 14.96 ± 2.04 mm. In all patients, the origin of varus was intra-articular at the level of proximal tibial plateau. The calculated mean of pre-operative varus angulation measured by goniometer and corroborated with measurement on a true size anteroposterior knee skiagram, was found to be 18.67 ± 4.22°. The mean post-operative mechanical axis deviation was found to be 4.4 ± 0.93 mm, (Fig. 17) whereas the mean post-operative femoro-tibial angulation after correction was 3.73 ± 1.58°.
Fig. 17.
Depicting Gaussian distribution of the measurement of post operative mechanical axis deviation in favour of modest amount of varus and preventing over correction into valgus disposition
Out of 15 patients in our study, seven patients complained of moderate pain in the affected knee occasionally while eight of them experienced mild pain during walks and/or on climbing or alighting a flight of stairs. In contrast, post-operatively, eleven patients were essentially pain-free at normal walks and/or during use of staircases except having occasional mild pain, whereas four patients were completely pain-free (P value < 0.0001) (Table 1).
Table 1.
Table depicting the grades of improvement of different parameters of the functional component of Knee Society Scores and comparison between the pre-operative and post-operative distribution
| Pre-operative functional knee society score parameters | Post-operative functional knee society score parameters | ||||
|---|---|---|---|---|---|
| Walks | < 5 blocks = 80% | 5–10 blocks = 20% | 5–10 blocks = 33.33% | > 10 blocks = 66.67% | |
| Stairs | Using railing for both climbing and alighting = 86.67% | Climbing using railing, but unable to alight = 13.33% | Normal climbing, but using railing while alighting = 86.67% | Normal climbing and alighting = 13.33% | |
| Use of aids | No canes = 40% | Single cane = 53.33% | Two canes = 6.67% | No Canes = 100% | |
Eight patients (53.33%) were found to have used a single cane during ambulation preoperatively while one of them had to deport to use of two canes preoperatively. Post-operatively, all patients were able to ambulate independent of any aids. Majority of patients were able to walk more than 10 blocks and climb stairs normally and used a railing during alighting. Two patients were able to even alight staircases without using a railing (Table 1).
In eleven of our patients, there was moderate amount of medio-lateral instability (6–9 mm) preoperatively when measured clinically in full knee extension, while three patients were having severe amount of medio-lateral instability (10–14 mm). On the contrary, pre-operatively, none of our patients were having any moderate or severe amount of anteroposterior instability when measured clinically at 90 degrees of knee flexion. Nine patients (60%) were found to have a fixed flexion deformity between 5° and 10° with an extension lag of < 10° in all of them except one patient. Three patients with primary osteoarthritis were found to have between 10° and 15° of FFD with an extension lag of 10°–20° in two of these patients. Two patients in our study were found to have rheumatoid arthritis as the etiology of deformity presenting with over 15° of FFD and extension lag of 10°–20°(Fig. 18). In Figure 19 both these parameters, statistically significant relationship was established (p value < 0.0001). Eight patients with primary osteoarthritis and cent percent of patients with secondary osteoarthritis were found to have > 15° of Varus deformity preoperatively when measured with a goniometer. As regards Range of Motion of the diseased knees, five patients in the series were having < 90° of flexion, out of which one patient had rheumatoid arthritis. None of the patients were having beyond 110° of flexion prior to surgery. Following surgical correction of severe varus deformities, the modest amount of varus alignment was kept in order to ensure kinematic alignment and patient satisfaction precluding overcorrection into valgus alignment. The maximum varus alignment obtained post-operatively was 5° with neutral alignment being the most ambitious correction. Post-operatively, the range of motion of flexion in the operated knees was significantly ameliorated as depicted in Fig. 20. There was one patient with extension lag of < 10° due to inadequate physical rehabilitation. There were no patient with residual medio-lateral instability and/or secondary fixed flexion deformity. All patients were found to have evidence of bony union of the osteotomized fragment. Nevertheless, one of the patient was having features of delayed union, which was still not incorporated up until 6 months post-operatively. However, at the subsequent visit, the osteotomy was found to be satisfactorily consolidated, thereby eliminating any unforeseen cases of non-union. There were no adverse events complicating the surgical and functional outcome in the immediate, early and delayed period following surgery. An inverse relationship was established between the degree of varus and the amount of tibial bone resection with reference to the least deficient portion of the lateral tibial condyle Fig. 21. The mean amount of tibial bone resection was found to be 6.56 ± 0.53 mm. There was a statistically significant relationship between the degree of varus deformity and the amount of tibial bone resection (P < 0.0001) (r = − 0.915) [Correlation is significant at the 0.01 level (2-tailed)] (Tables 2 and 3)
Fig. 18.
Chart depicting the fixed flexion and varus deformities, mediolateral instabilities and range of motion scale among the primary and secondary pathologies prior to surgical intervention
Fig. 19.
Normal Gaussian distribution of post operative alignment with the mean being in slight deliberate varus to preclude patient dissatisfaction
Fig. 20.
Depicting that majority of patients were having above 110 degrees of flexion in the operated knee
Fig. 21.
Illustrating inverse relationship between the ascending values of Varus deformity and the corresponding descending values of tibia bone resection with reference to the least deficient portion of the lateral tibial condyle
Table 2.
Paired t-test table
| Parameters (pre-operative vs post-operative) | ‘t’ | Significance (2-tailed) |
|---|---|---|
| Mechanical axis deviation | 27.757 | P < 0.0001 |
| Femorotibial angulation | 20.546 | P < 0.0001 |
| Range of Motion of flexion | − 11.014 | P < 0.0001 |
| Pain Score | − 13.596 | P < 0.0001 |
| Oxford Knee Score | − 28.611 | P < 0.0001 |
| Knee Society Score (Clinical) | − 17.893 | P < 0.0001 |
| Knee Society Score (Functional) | − 18.244 | P < 0.0001 |
Table 3.
Pearson correlation coefficient table
| Parameters | ‘r’ | Significance (2-tailed) |
|---|---|---|
| • Pre-Operative KSS (Clinical and Functional) | 0.564 | P < 0.028 |
| • Pre-Operative vs Post-Operative KSS (Functional) | 0.590 | P < 0.021 |
| • Amount of tibial bone resection and Pre-operative Varus angulation | − 0.915 | P < 0.0001 |
| • Difference in Joint line opening on Varus–Valgus Stress (post-operative) and amount of tibial bone resection | − 0.631 | P < 0.012 |
Paired t-tests between the pre- and post-operative femorotibial angle as regards correction of varus angulation provided a statistically significant relationship (P < 0.0001). Moreover, post-operative range of motion score was found to have statistically significant improvement over its pre-operative counterpart (P < 0.0001). The opening of corresponding joint lines on Varus and Valgus stresses and their difference was assessed at post-operative follow-up. The mean value was 1.11 ± 0.26 mm. An interesting inverse correlation was evident between the amount of tibial bone resection and the difference in joint line opening on varus and valgus stresses (r = − 0.631) [Correlation is significant at the 0.05 level (2-tailed).]. The mean Oxford knee questionnaire score preoperatively was 18.67 ± 3.68, which improved to a value of 43.4 ± 2.44 (P < 0.0001) (Figs. 22, 23).
Fig. 22.
A through D: A: Pre-operative bilateral varus deformity due to primary osteoarthritis. B: demonstrating Varus thrust gait. C: Kellgren–Lawrence Grade IV Osteoarthritic changes in bilateral knee joints with lateral tibial subluxation and significant deviation of the Macquet’s line. D: Immediate post-operative radiographic result of the left knee undergoing sliding femoral condylar osteotomy with modular fluted rod in tibia
Fig. 23.
A through C: A: Pre-operative anteroposterior and lateral skiagrams of a severe varus afflicted knees B: Immediate post operative skiagrams in anteroposterior and lateral projections with restoration of alignment C: 12 months follow up skiagram in anteroposterior and lateral projections of the same patient showing evidence of bony union with no secondary complications as regards implant loosening and/or mid-flexion instability
Discussion
Conventionally, soft tissue gap balancing with rendering of an equal flexion and extension rectangular shaped gaps is the cornerstone of a successful total knee arthroplasty. Therefore, in severe varus-afflicted knees, the contracted medial soft tissue structures are sequentially released with conversion to a cruciate sacrificing femoral bone cut to achieve optimal gap balancing. However, such releases must be judicious and tailored to preclude the possibilities of incorporation of some degree of constraint in the implant or using of a thicker polyethylene insert. It may also lead to alteration of the joint line and thereby jeopardize the kinematic alignment. Traditionally, the sequential order of release of the medial structures is as follows: deep fibres of MCL, posterior oblique ligament, release of semimembranosus tendon, sub-periosteal proximal medial tibial plateau denudation, posterior capsule release, conversion to cruciate sacrificing femoral bone resection and limited superficial MCL release with or without medial epicondylar osteotomy. Out of all these structures, the superficial MCL plays the pivotal role in influencing the amount of balance in the coronal plane. There are three ways of releasing the superficial MCL. The classical one described by Insall et al. is the release on the tibial attachment of MCL, which nevertheless bears the potential for a harbinger of iatrogenic Grade III MCL tear. The second method deployed is the intra-substance selective release by pie crusting with a spacer block in-sit, resulting in a modest amount of release in the range of 6–8 mm. The third method is the release on the femoral attachment side in the form of medial epicondylar osteotomy. Although it has the merits of safeguarding the iatrogenic MCL injuries and or precludes use of a constrained prosthesis, nevertheless, it has its own demerits in the form of non-union of the thin wafer of bone and/or fibrous union of the osteotomy and also development of complications like heterotopic ossification.
In our series, all patients were assessed intra-operatively for the medio-lateral balance in coronal plane and anteroposterior stability in the sagittal plane. This was accomplished by performing anterior drawer test in 90 degree of knee flexion and Lachman’s test in 30 degrees of knee flexion. A firm end point without translation was the expected outcome of a well-balanced knee. Also, joint line opening on varus and valgus stresses were assessed at 30 degree of knee flexion and their difference computed to ensure coronal balance. The difference in opening if kept below 3 mm, ensured an optimally balanced knee. There was a high threshold for substantial release of the medial structures and initial assessment was done by inserting a trial spacer block with economical release. Then, according to the degree of the tightness, a thin wafer of bone with superficial MCL attachment on the femoral side was posteriorised and distalised to create some medial space and a perfectly balanced knee. Over correction into valgus was deliberately refrained from, in view of rendering requisite patient satisfaction. On comparing the results of the current study with the reported literature, the mean post-operative clinical Knee Society Score in our study, being 89.2 as opposed a pre-operative mean of 38 closely resembled the values of Engh Gerard et al., being respectively 93 post-operatively against 42 preoperatively. The mean ROM pre-operatively was 96.07 ± 7.34 which improved to a value of 109.87 ± 6.86. The values in the current study show a greater rate of improvement of the range of motion when compared to the values of Engh et al. whereby the mean preoperative ROM value of 101° improved to a mean post-operative value of 111°.
In the series of Mullaji et al., the mean preoperative tibiofemoral angle of 22.7° was corrected to a mean of 5.3° valgus, out of which, 86% of the knees were in valgus alignment post-operatively.
In the current study, the mean preoperative and post-operative tibiofemoral angulation was 18.67 and 3.73 degrees respectively, thus supports the fact that over correction into valgus was avoided in order to render more patient satisfaction and restore kinematic alignment keeping in mind the physiological hip knee ankle axes. Similarly in the reported article by Engh et al., these values corresponded to a mean of 6 degrees preoperatively and 7 degrees post-operatively. Comparisons with other reported literature are listed in Table 4. The current series shows 100% bony union, as compared to values of 63.9% bony union and 54% bony union in established literature by Sim et al. and Engh et al. respectively. The mean difference of varus and valgus stress view X-rays was found to bear close resemblance to the data in the series by Sim et al. In the modern era with the advent of many constrained prostheses and with ever increasing reliance on the availability of navigation and/or robotic arms, there is inadvertent medial soft tissue release off the proximal tibia resulting in a lax joint with demand for a thicker insert and perhaps altered knee kinematics. Medial Sliding epicondylar osteotomy is an effective and skillful tool to deploy in essence to combat all the bigger problems and also become a little frugal on the proximal tibial resection. Hence, all these aspects confer a better milieu for a future revision if need be. On the contrary, owing to shifting of the attachment of MCL without releasing it by avoiding pie crusting, there is a non-isometric point of knee flexion which might be a forerunner of late instability. The limitations of this study are that the population size is small owing to this study not being a multicentric one and not having uniform periods of follow-up and heterogeneity of the timing of surgery from the first enrolled and last enrolled patient in the study. The study only included the prospective cohort cases and excluded the retrospective analysis. Second, the long-term assessment to look out for aseptic component loosening and/or residual late instability could not be addressed due to mid-term follow-up results in majority of the patients.
Table 4.
Depicting the comparison of parameters between the current study and some of the reported literature
| Parameters | Mullaji et al. | Engh et al. | Sim et al. | Current study |
|---|---|---|---|---|
| Mean preoperative Tibiofemoral angle | 22.7 | 6 | 10.4 | 18.67 |
| Mean post-operative Tibiofemoral angle | 5.3 degree valgus | 7 degree valgus | 5.5 ± 3.4 ° Valgus | 3.73 degree varus |
| Pre-operative ROM | 116.2 ± 11.5 | 101 | 112 ± 21.8 | 96 ± 7.34 |
| Post-operative ROM | 111.1 8.7 | 111 | 118.9 ± 13.3 | 109.87 ± 6.86 |
| Pre-operative KSS (clinical) | 22.8 | 42 | 35.5 ± 17.1 | 38 ± 9.97 |
| Post-operative KSS (clinical) | 91.1 | 93 | 89.1 ± 8.4 | 89.2 ± 3.63 |
| Mean difference of Varus–Valgus angle on stress radiographs | – | – | 1.6 ± 1.0 (1.0–6.1) | 1.11 ± 0.28 (0.8–1.5) |
Data availability statement
The authors hereby confirm that the data supporting the findings of this study are available within the article and its supplementary material.
Declarations
Conflict of interest
On behalf of all authors, the corresponding author states that there is no conflict of interest.
Ethical Statement
This article does not contain any studies with human or animal subjects performed by the any of the authors.
Informed Consent
For this type of study informed consent is not required.
Footnotes
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Data Availability Statement
The authors hereby confirm that the data supporting the findings of this study are available within the article and its supplementary material.