Wedge-less oblique supracondylar femoral osteotomy and casting for genu valgum in older children and young adults

Abstract

Background

Genu valgum is one of the commonest deformities seen by the orthopaedicians. The most common cause is idiopathic but genu valgum secondary to nutritional deficiency is also fairly common in developing and third world countries. Supracondylar osteotomy and internal fixation with plate and screws, is the treatment of choice in older children and young adults, which is costly, requires a wide exposure, a second surgery for implant removal and risk of infection is more. This study was undertaken to measure the outcome of simple oblique percutaneous wedge-less metaphyseal supracondylar osteotomy of the distal femur and casting in older children and adolescents with Genu Valgum in a small centre catering mostly to patients from middle and low income households.

Patients and methods

Patients aged between 12 and 22 years with genu valgum deformity with a tibiofemoral angle ≥15°, and an intermalleolar distance of more than 7 cm in unilateral and more than 10 cm in bilateral cases, who are not amenable to be treated with guided growth techniques, were included. Patients having knee instability, restriction of knee range of motion, genu recurvatum, tibial deformity component, open physis, were excluded from the study. The correction was undertaken by a simple supracondylar wedge-less metaphyseal short oblique osteotomy of the distal femur followed by immobilization with a long leg plaster of Paris cast. Functional outcome was assessed using Böstman et al. score.

Results

46 limbs in 29 patients with a mean age of 14.5 years were operated. The mean follow-up of patients was 6 months. The preoperative radiological tibiofemoral angle (TFA) had a mean value of 19.89° which improved to a mean of 5.31° postoperatively. Intermalleolar distance (IMD) improved from a mean of 13.81 cm to 3.15 cm post-correction. Mean Lateral distal femoral angle (LDFA) improved from 77.11° to 87.20°. Knee score was excellent in all patients at 3 months and 6 months post intervention. There were no serious complications except superficial plaster sores in 4 patients, which healed uneventfully and temporary restriction of knee range of motion in 5 patients. All patients achieved a full range of knee motion after physical therapy.

Conclusion

Supracondylar wedge-less short oblique metaphyseal distal femoral osteotomy and immobilization with plaster of Paris cast is a simple, cheap, safe & viable option for the correction of genu valgum deformity originating from distal femur, with minimal complications in older children and adolescents with limited growth potential, especially in low income countries and small centres.

1. Introduction

Genu valgum, commonly called “knock-knee” is a fairly common deformity seen by orthopaedic surgeons in outpatient departments. Normal alignment of knee is slight varus at birth which becomes neutral by 2 years and then becomes valgus in the age group of 2–8 years, and the maximal amount of physiologic valgus being in the age group of 2–4 years. In the great majority of children, the normal valgus alignment of 5–7° is achieved by 9 years of age.^{1, 2, 3} The most common cause of genu valgum is idiopathic. Other causes are nutritional (more common in developing and third world countries), metabolic, trauma, infection, tumours, and skeletal dysplasias.⁴ The location of the deformity can be distal femur, knee joint, or proximal tibia. Correction of excessive physiologic or idiopathic genu valgum may be indicated in children older than 8 years when there is anterior knee pain, problems with running, abnormal gait patterns, patellar malalignment, ligamentous instability or excessive cosmetic concern.⁵ In growing children with open physis, hemiepiphysiodesis (temporary with staples or transphyseal screws or permanent via timed hemiepihysiodesis) can be done^{6, 7, 8, 9, 10, 11, 12} Hemiephysiodesis is an attractive option as a lesser procedure with minimal complications, but the growth potential in older children is limited as the distal femur physis fuses by 12 years of age in the majority of children, and, hence there is no role of growth modulation techniques.

These older children or adolescents need corrective osteotomies around the distal femur as distal femur is the most common cause of the deformity. Various types of distal femoral osteotomies have been described in the literature for correction of this deformity, such as medial closing wedge, lateral opening wedge, dome or “V” osteotomy, Ilizarov distraction method, Computer hexapod assisted orthopaedic surgery (CHAOS), each having their advantages and disadvantages.^{13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23}

Children younger than 12 years of age were excluded as physis in these patients were found to be in advanced stage of fusion radiologically whose deformity correction was amenable to growth modulation technique.

We discuss the results of simple wedge-less oblique metaphyseal distal femoral supracondylar osteotomy and plaster of Paris cast in this group of patients.

2. Materials and methods

29 Children and young adults (46 Limbs) with genu valgum, aged 12 years–22 years, with unilateral or bilateral Genu Valgum having a tibiofemoral angle (TFA) of more than 15°, the origin of deformity being distal femur, and associated with gait disturbances, knee pain, difficulty in running, excessive cosmetic concern and having an inter-malleolar distance (IMD) of more than 10 cm in bilateral cases and 7 cm in unilateral cases, were included.

A thorough history and physical examination were done. Knee flexion test was done to assess the origin of the deformity.²⁴ IMD and the tibiofemoral angle were measured preoperatively as well as a minimum of 6 months after the surgery. Tibiofemoral angle was drawn by measuring the angle formed between a line connecting center of patella to anterior superior iliac spine and another line from the center of the patella to the center of the ankle. With the patient standing, patella facing forwards and knees in extension and just touching each other, IMD was measured. Lateral distal femoral angle (LDFA) was measured from radiographs, as the angle between the mechanical axis of the femur and the articular surface of the distal femur laterally. Repeat clinical and radiological assessment was done at follow up.

Blood investigations were done in the form of complete blood count, serum calcium, serum phosphate, alkaline phosphate, Kidney function tests, Vitamin D3 levels. Routine radiographs of both the knees were taken preoperatively as well as in immediate postoperative period, at 3 weeks, at 6 weeks, 3 months, and 6 months. Functional outcome was assessed with Bostmann knee score at 3 months and 6 months or next follow up, whichever was later. Scores of 30 to 28 classified as excellent, 27 to 20 good and less than 20 unsatisfactory.

Surgical technique: A complete pre-anaesthetic workup was done. Under General/spinal anaesthesia, patients were prepared with betadine and draped in the supine position. Tourniquet was applied, the knee was flexed and the Adductor tubercle, knee joint line, and patella were marked. A 2–3 cm longitudinal incision was given in the midline over the medial aspect of distal femur. The incision was started 0.5–1 cm distal to the adductor tubercle and extended proximally. Skin and subcutaneous tissue were incised in the line of incision. The medial border of Vastus medialis obliquus was retracted anteriorly with a double hook retractor. The periosteum was split longitudinally and a short oblique osteotomy was made parallel to knee joint line from medial to lateral direction angling inferiorly to superiorly just proximal to distal femur metaphyseal flare with a straight osteotome leaving the lateral cortex intact. The lateral cortex was weakened using a 2 mm osteotome or drill holes. No translation was done. Osteotomy was controlled by leaving the lateral cortex intact and completing the osteotomy laterally with a varus stress with impaction of the cancellous bone medially. This method of osteotomy is suitable for cases of genu valgum with center of rotation angulation (CORA) in the metaphyseal region or distally, seen in idiopathic or metabolic aetiology.

Desired correction was checked by assessing the orientation of knee joint line intraoperatively and alignment of mechanical axis of the limb using electrocautery wire under image intensifier by ensuring that this line was corrected to center of knee or just lateral to the medial tibial spine and by assessment of intermalleolar distance with both limbs in full extension and patella facing anteriorly.

The wound is closed in layers starting with the periosteum on the medial side and a well-molded above-knee plaster of Paris cast extending up to groin was applied with the knee in extension. The osteotomy was noticed to be inherently sable as its a closing compression osteotomy with intact lateral periosteal sleeve with medial beak of proximal fragment impacting the cancellous bone of medial femoral condyle and a well molded cast was applied immediately ensuring at all times with C-arm imaging that the correction was achieved and well maintained. K-wire fixation is used if displacement of distal fragment was noticed mediolaterally, judged by discontinuity of lateral cortical line in C-Arm anteroposterior images or in anteroposterior plane with step off in lateral views. Displacement was seen in one case which needed to be fixed with crossed k-wires.

Bilateral cases were operated in a single sitting and the duration of the entire procedure was less than 30 min in unilateral cases and 45 min to 1 hour in bilateral cases.

3. Results

Quantitative variables were compared using the paired t-test/Wilcoxon's test across follow-ups. Quantitative variables were compared using the independent t-test/Mann-Whitney test between two groups. Qualitative variables were correlated using the chi-square test. A P value of <0.05 was considered statistically significant. The data were entered in Microsoft Excel spreadsheet (Microsoft Corp., Redmond, WA, USA), and analysis was performed using SPSS Version 20.0 (IBM Corp., Armonk, NY, USA).

We operated 46 limbs in 29 patients with a mean age of 14.5 years(12–22years) in 12 males and 17 females.12 patients had unilateral deformity, 17 had a bilateral deformity. The bilateral deformities were operated simultaneously. The patients had a mean height of 159.1 cm (149–168 cm), weight of 48.41 kg (42–55 kg) and BMI of 19.1(16.9–21) (Table 1).We have not evaluated the correlation of height and weight with outcome parameters.

Table 1.

Demographic data.

Number	29(46limbs)
Age(mean) in years	14.55 ± 1.7(12–22)
Gender	Males-12 Females-17
Side	Bilateral-17 Unilateral-12
Height(cm)	159.1 ± 4.8 (149–168)
Weight(kg)	48.41 ± 3.76 (42–55)
BMI	19.1 ± 1.2 (16.9–21)

Preoperative radiological tibiofemoral angle had a mean value of 19.89° (range; 15°–30°) which improved to a mean value of 5.31° (range; 0°–8°) postoperatively. The difference was statistically significant (P-value <0.0001). Mean LDFA improved from 77.11° to 87.20°. All patients had an excellent knee scores at 3 months and 6 months post intervention. None of the patients had an unsatisfactory knee score. The mean IMD before the correction was 13.81 cm which improved to a mean of 3.15 cm post-correction. The difference was statistically significant. (P-value <0.0001). The preoperative mean mechanical axis deviation (MAD) was 11.96 mm which improved to 6.10 mm postoperatively (Table 2). All patients except one, were immobilized with an above knee plaster of Paris cast. One patient had a postoperative displacement of osteotomy, which was reduced and fixed with k-wires.

Table 2.

Comparison of preoperative and postoperative (at 6months) outcome parameters.

Parameter(mean)	Preoperative	Postoperative	P-value
TFA	19.89 ± 1.9	5.31 ± 1.2	<0.0001
IMD	13.8 ± 1.9	3.15 ± 1.0	<0.0001
BKS		29.83 ± 0.47
LDFA	77.11 ± 2.71	87.20 ± 0.86	<0.0001
MAD (mm)	11.96+/- 3.24	6.10 ± 2.10	<0.0001

Static quadriceps, hamstring and static abduction exercises were started from the second postoperative day when patient is comfortable. Plaster immobilization continued for 6–8 weeks based on radiographic and clinical union at the osteotomy site with usual nursing care and static quadriceps/hamstring/abduction exercises. Knee, ankle range of motion exercises were started immediately following cast removal, followed by toe touch weight bearing with a walking frame 1–2 weeks later, which was gradually discontinued as per comfort of the patients. All patients returned to full weight bearing 10–12 weeks post-surgery (Fig. 1, Fig. 2, Fig. 3).

Fig. 1.

Serial radiographs in a 16 year old pre-operatively, immediate post op in a cast and at 6 weeks when osteotomy has healed.

Fig. 2.

Radiographs of the same patient at 6 months post procedure, and clinical picture with Patient standing, sitting cross legged and squatting.

Fig. 3.

Radiographs of a 15 year old preoperatively, at 6 weeks and at 6 months post op with standing clinical picture.

The main complications noted were knee stiffness in immediate post cast removal period, in 5 patients, which was managed with physical therapy and all patients went on to achieve full range of motion. Under-correction was noticed in two cases which were revised after few days but no case of overcorrection or failure of correction, infection, non-union of the osteotomy site, shortening, and permanent knee stiffness were noted in any patient.

We did not study the correlation of demographic variables with clinical and radiological variables.

4. Discussion

Genu Valgum continues to be a common deformity seen by orthopaedic surgeons. The most common cause is physiological or idiopathic but in third world countries and developing countries nutritional deficiency as a cause is also very common. In younger children having excessive genu valgum with anterior knee discomfort, patellar malalignment, difficulty in running, or having cosmetic concern, hemiepiphysiodesis is done. In older children and adolescents, due to limited growth potential because of distal physeal closure around 14 years of age, growth modulation is not amenable and hence these patients require corrective osteotomies. Since the distal femur is the most common cause of the deformity, various forms of distal femoral osteotomies have been described in the literature. We have done a very simple, quick, easy to perform, reproducible short oblique metaphyseal wedge-less supracondylar osteotomy which can be very useful in small centres especially in low income areas.

The most common surgery done for genu valgum is dome osteotomy and fixation with plate and screws. Difficulties with obtaining a perfect dome and a need for wide exposure, problems with hardware irritation, implant cost, and a separate surgery for implant removal once the correction is achieved, precludes its widespread use. Bansal et al. reported hypertrophic scar formation, superficial wound infection and loss of correction in their study of 21 patients for which dome osteotomy was done and fixed with low-profile proximal humerus locking plate.²⁵ Watanabe et al. have done a similar osteotomy and reported three cases of pin tract infections, three cases of delayed unions, one case of joint contracture, and one case of transient peroneal nerve palsy, but function recovered completely without treatment. Limb lengthening was performed in five patients and they concluded that acute correction with focal dome osteotomy is very useful for cases of alignment correction, but is not indicated for cases of alignment correction with lengthening, due to a high risk of complications related to poor callus formation.²⁶ Kazimi et al. in a study 40 patients have done medial closing wedge osteotomy and fixation was done either with angle blade plate and LCP and they found no significant difference between the two.²⁷ Makhmalbaf et al. found no significant difference in alignment and functional outcome when the distal femoral osteotomy was fixed with a blade plate or immobilized with a long leg cast.²⁸

Ranjan et al. and Agarwal et al. have reported good results with a supracondylar V osteotomy in their studies of 187 and 9 patients respectively. They have reported superficial and deep infections, and hypertrophic scar formation in few patients and partial slippage of distal femoral physis (Agarwal et al.) in one patient with excellent results otherwise. Prakash et al. have done a chevron osteotomy in 115 limbs and have used k wires and plaster of paris cast. They observed superficial infections in K-wire fixations, limb length discrepancy (LLD), and loss of reduction in a few patients. This type of osteotomy has the advantage of not requiring a wedge resection and hence less chances of LLD.^16,17,29

Distraction osteogenesis with the Ilizarov apparatus and Taylor spatial frame (TSF) offers the advantage of simultaneous correction in multiple planes but they have a long learning curve and are time consuming, costly, painful, and cumbersome and there is the risk of pin site infection, neurovascular compromise. Solomin et al. in their retrospective study of 123 patients with femoral deformity have compared ortho SUV frame (OSF) with Ilizarov apparatus (IA). They observed that using OSF simplifies deformity correction and reduces the time period in complex as well as in simple deformities. Accuracy of correction with OSF was significantly higher than correction with IA.³⁰

Elgeuoshy et al. have done a similar transverse osteotomy in 11 patients (15 Limbs) and observed similar results. Their follow up was longer than ours but sample size was small.³¹ We have done it in 29 patients (46 Limbs) with excellent functional and radiological outcomes in short term. The advantages of this procedure are that it is simple, easy to perform and reproduce, requires minimal instrumentation, there is minimal blood loss, hardware irritation and risk of infection is less as a wide exposure is not needed, and can be done in 30 minutes-1 hour. A secondary procedure to remove the implant is not required since all except one were immobilized with a cast. Although few cases had temporary knee stiffness, all of them gained full knee range of motion after physical therapy. There was no infection, non-union, or loss of correction or recurrence of deformity at last follow up. The limitations of the study were short period of follow-up due to which we cannot predict the effects of osteotomy and change in joint orientation on the joint biomechanics in long run and because of its dependence on the clinical and radiological measurements, the reliability and reproducibility require attention.

5. Conclusion

Correction of symptomatic genu valgum deformity of distal femoral origin in older children and young adults with a wedge-less metaphyseal short oblique supracondylar osteotomy and a plaster of Paris cast immobilization is a simple, quick, easy and viable procedure with minimal complications, especially in low income countries & small centres and yields excellent clinical, radiological, and functional outcomes. However, future studies with a larger sample sizes and longer follow-ups comparing various osteotomies and fixation methods are needed.

Ethical standard statement

Clearance was obtained from hospital ethical review board for this study and conformed to the ethical guidelines of the Helsinki declaration (as revised in Tokyo 2004). No studying advertising was made and no remuneration was offered.

Informed consent

We obtained informed consent from all the participants included in this study for the procedure and use of data for publication.

Declaration of competing interest

We have not received any funding for this work and have no conflict of interest to declare.